Documents published in 2004 : Scipedia

Wide area surveillance using SSR mode S multilateration: Advantages and limitations
M. Leonardi, V. Paciucci, G. Galati, P. Magaro

Collection of open conferences in research transport (2005). Vol. 2005, 11

Abstract
There is an increasing interest on the various applications of the SSR Mode S (secondary surveillance radar - mode selective) for air traffic and airport traffic management. This paper discusses the applications of ICAO standard Mode S signals, in particular in the down link channel around 1090 MHz, to locate and identify cooperating targets in the airport using multilateration (MLAT) and in the terminal area/en route using wide area multilateration (WAM). Performance analyses and some comparison with the more traditional SSR system (ATC radar beacon system : ATCBRS) are carried ou
Abstract
There is an increasing interest on the various applications of the SSR Mode S (secondary surveillance radar - mode selective) for air traffic and airport traffic management. [...]
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Aggregate congestion control for distributed multimedia applications
T. Sparks, K. Mayer-Patel, D. Ott

Collection of open conferences in research transport (2004). Vol. 2004, 15

Abstract
We consider the problem of applying aggregate congestion control to a class of distributed multimedia applications known as Cluster-to-Cluster (C-to-C) applications. Flows in such an application share a common intermediary path that is the primary source of network delay and packet loss. Using the Coordination Protocol (CP) architecture, we show how aggregate congestion control can be achieved with the following properties: Almost any rate-based, single-flow congestion control algorithm may be applied to make aggregate C-to-C traffic congestion responsive. C-to-C applications may use multiple flow bandwidth shares and still exhibit correct aggregate congestion responsiveness. C-to-C applications may implement complex, application-specific adaptation schemes in which the behavior of individual flows is decoupled from the behavior of the congestion responsive aggregate flow. Bandwidth filtered loss detection (BFLD) is presented as a technique for making single-flow loss detection algorithms work when aggregate traffic uses multiple flowshares. The approach is evaluated using both ns2 simulation and an experimental implementation in Free BSD and Linux. Results demonstrate its success for a wide range of network conditions.
Abstract
We consider the problem of applying aggregate congestion control to a class of distributed multimedia applications known as Cluster-to-Cluster (C-to-C) applications. Flows [...]
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Air Traffic Performance by Market Segments
D. Bhadra

Collection of open conferences in research transport (2004). Vol. 2004, 14

Abstract
How is air traffic performance affected by type and location of markets? Is there any pattern to how air traffic performs with respect to the size and structure of markets, type of networks, and size of aircraft? In this paper, an empirical framework has been developed to examine the determinants of air traffic performance. Air traffic performance is defined as the ratio of airborne time to total ramp-to-ramp time. Using quarterly segment traffic data (i.e., T100 segment of Form 41) for the period 1995-2006, an econometric model is constructed to estimate and evaluate performance measures defined over market segments and networks. This econometric framework establishes and evaluates empirical linkages between performance measures and size of the markets, locations, distance, seasons of the year, and aircraft type over time. Statistical estimates indicate that size of market, type of aircraft, industry structure, and distance play important roles in influencing performance measures.
Abstract
How is air traffic performance affected by type and location of markets? Is there any pattern to how air traffic performs with respect to the size and structure of markets, [...]
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Alternate path routing algorithm for traffic engineering in the Internet
S. Subramanian, V. Muthukumar

Collection of open conferences in research transport (2004). Vol. 2004, 13

Abstract
In this paper, a new algorithm to route traffic efficiently is proposed. The proposed algorithm finds additional routes to the destination and identifies the critical links in the network that are responsible for congestion. The traffic in the network is routed through the paths that have no or least number of critical links. This avoids congestion in the critical links and increases the performance of the network. The performance of the algorithm is compared with the shortest path (Dijkstra's) algorithm.
Abstract
In this paper, a new algorithm to route traffic efficiently is proposed. The proposed algorithm finds additional routes to the destination and identifies the critical links [...]
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Mapping sub-flows to p2mp LSPs
R. Fabregat, Y. Donoso, J. Marzo, F. Solano

Collection of open conferences in research transport (2005). Vol. 2005, 9

Abstract
In previous work we proposed a multi-objective traffic engineering scheme (MHDB-S model) using different distribution trees to multicast several flows. In this paper, we propose a heuristic algorithm to create multiple point-to-multipoint (p2mp) LSPs based on the optimum sub-flow values obtained with our MHDB-S model. Moreover, a general problem for supporting multicasting in MPLS networks is the lack of labels. To reduce the number of labels used, a label space reduction algorithm solution is also considered.
Abstract
In previous work we proposed a multi-objective traffic engineering scheme (MHDB-S model) using different distribution trees to multicast several flows. In this paper, we propose [...]
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A 3-Dimensional Continuum ALE Model for Ice Scour: Study of Trench Effects
I. Konuk, R. Gracie, S. Yu

Collection of open conferences in research transport (2005). Vol. 2005, 8

Abstract
new Arbitrary Lagrangian Eulerian (ALE) Finite Element (FE) model of ice scour was recently developed by the authors. It is based on continuum representation of the soil. It was shown in recent papers that such a model can characterize the mechanics of the ice-soil-pipeline interaction without requiring any of the assumptions that the Winkler models depend on. The model utilizes soil properties obtained by conventional laboratory testing. In a recent paper, this model was used to show that the subscour deformations and ice-soil interaction forces are very sensitive to ice ridge geometries for shallow slope ice features. In this paper, the ALE FE ice scour model is utilized to study the effects of the pipeline trench on the scour process and the forces transmitted to the pipeline. Two different infill soil properties and two different ice ridge geometries are analyzed with a 36 inch diameter pipe buried to in a trench of 1.5 m cover. It is shown that the scour process near and in the trench is significantly different than in the ambient seabed soils and the recognition of this may present some potential advantages for the protection of the pipelines not recognized by the Winkler models. It is also shown that the pipeline loads generated during the scour process are cyclic. They build slowly as the ice moves over the trench and then reverse as the ice ridge moves away from the trench. This is in contrast to monotonic and rapidly growing loads predicted by the Winkler models. The paper shows that the loads transferred to the pipeline depend on the infill soil properties placed in the trench. It is shown that loads experienced by the pipeline are less for the softer infill than stiffer soils.Copyright © 2005 by ASME
Abstract
new Arbitrary Lagrangian Eulerian (ALE) Finite Element (FE) model of ice scour was recently developed by the authors. It is based on continuum representation of the soil. [...]
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Importance of SIMD computation reconsidered
W. Meilander, J. Baker, M. Jin

Collection of open conferences in research transport (2004). Vol. 2004, 12

Abstract
In this paper, SIMD and MIMD solutions for the real-time database management problem of air traffic control are compared. A real-time database system is highly constrained in a multiprocessor and access to the common database must be made to a limited number of data elements at a time. This MIMD database access is contrasted with the comparable SIMD common database access, which can be several hundred times greater. This is true because the SIMD can simultaneously access thousands of pertinent records instead of the limited number in the MIMD. A relatively simple example is given of a problem that has a polynomial time solution using a SIMD but for which a polynomial time solution using a MIMD is normally impossible. The fact that SIMD can support a polynomial time solution for the air traffic control problem but this problem is normally considered to be intractable for multiprocessors argues against the common belief that MIMD have greater power than SIMD. SIMD are more efficient and powerful for some critically important application areas.
Abstract
In this paper, SIMD and MIMD solutions for the real-time database management problem of air traffic control are compared. A real-time database system is highly constrained [...]
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Creating scalable traffic simulation on clusters
A. Gourgoulis, S. Winter, P. Kacsuk, G. Terstyansky

Collection of open conferences in research transport (2004). Vol. 2004, 10

Abstract
We describe the implementation of a transport simulation in a parallel environment. The implementation is based on a graphical parallel programming environment called P-GRADE. The transport simulator, called MadCity, simulates a specific road network of a city and shows cars moving on the roads. To achieve scalability of the traffic simulation, the use of templates is necessary. This helps to control the number of participating processes required for the simulation without making modifications to the simulator's source code. Performance results are collected from four, eight and sixteen nodes of the Parsifal cluster and compared with the sequential execution results of the simulator. The implementation of the transport simulator is extended further to support the simulation of multiple cities within the same cluster and on the Grid.
Abstract
We describe the implementation of a transport simulation in a parallel environment. The implementation is based on a graphical parallel programming environment called P-GRADE. [...]
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Dynamically deployed support as a potential solution to negative behavioral adaptation
R. Kovordanyi, K. Ohlsson, T. Alm

Collection of open conferences in research transport (2005). Vol. 2005, 5

Abstract
dvanced driver assistance systems are designed to make driving easier that is, to alleviate the driver's workload, and to increase traffic safety. However, traffic safety is affected by negative behavioral adaptation, meaning that drivers tend to increase speed and pay less attention to driving when supported by an advanced assistance system. We relate behavioral adaptation to reinforcement learning at a subconscious level, and propose that driver assistance is dynamically varied within predetermined safety limits. The aim of employing a dynamic assistance policy is to prevent the driver from noticing a constant improvement in vehicle handling. We conclude by describing ongoing work for empirically evaluating an improved lane departure warning system that uses a dynamic assistance policy. "p"LITH-IKP-CR--05/1267--SE
Abstract
dvanced driver assistance systems are designed to make driving easier that is, to alleviate the driver's workload, and to increase traffic safety. However, traffic safety [...]
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A fuzzy expert system for deterioration modeling of buried metallic pipes
B. Rajani, H. Najjaran, R. Sadiq

Collection of open conferences in research transport (2004). Vol. 2004, 8

Abstract
This paper presents the framework of a proposed expert system that is used to predict the deterioration rate of buried metallic pipes, based on surrounding soil properties. The knowledge base of the expert system is developed using two sources of information available for evaluating the deterioration of pipes: expert knowledge and field data. The novelty of the proposed approach lies in the modeling process and the framework of the expert system, complying with the nature of the information available. The knowledge base is composed of a subjective and an objective model. The former is based upon fuzzy IF-THEN rules representing the expert knowledge obtained from published work and an expert survey. It determines the soil corrosivity potential (CoP). The objective model is a single-input-single-output (SISO) model that relates the deterioration rate (DR) to CoP. The objective model may be developed using either fuzzy modeling or a regression analysis of field data. The result of the latter is based on a set of available field data, used in a previous study, is presented.
Abstract
This paper presents the framework of a proposed expert system that is used to predict the deterioration rate of buried metallic pipes, based on surrounding soil properties. [...]
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Flight technical error analysis of the SATS higher volume operations simulation and flight experiments
J. Murdoch, D. Williams, C. Adams, M. Consiglio

Collection of open conferences in research transport (2005). Vol. 2005, 4

Abstract
This paper provides an analysis of flight technical error (FTE) from recent SATS experiments, called the higher volume operations (HVO) simulation and flight experiments, which NASA conducted to determine pilot acceptability of the HVO concept for normal operating conditions. Reported are FTE results from simulation and flight experiment data indicating the SATS HVO concept is viable and acceptable to low-time instrument rated pilots when compared with today's system (Baseline). Described is the comparative FTE analysis of lateral, vertical, and airspeed deviations from the Baseline and SATS HVO experimental flight procedures. Based on FTE analysis, all evaluation subjects, low-time instrument-rated pilots, flew the HVO procedures safely and proficiently in comparison to today's system (Baseline). In all cases, the results of the flight experiment validated the results of the simulation experiment and confirm the utility of the simulation platform for comparative human in the loop (HITL) studies of SATS HVO and Baseline operations.
Abstract
This paper provides an analysis of flight technical error (FTE) from recent SATS experiments, called the higher volume operations (HVO) simulation and flight experiments, [...]
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Requirements for air traffic management in the en-route environment
R. Apaza, R. Kerczewski

Collection of open conferences in research transport (2004). Vol. 2004, 5

Abstract
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A first comparison between LIGO and Virgo inspiral search pipelines
D. Grosjean, M. Zanolin, A. Viceré, F. Marion, F. Ricci, D. Brown, S. Chatterji, P. Hello, D. Buskulic, L. Blackburn, M. Knight, A. Clapson, S. Fairhurst, G. Guidi, N. Christensen, L. Bosi, E. Katsavounidis, F. Beauville, A. Lazzarini, P. Brady, M. Bizouard, B. Mours, L. Brocco

Collection of open conferences in research transport (2004). Vol. 2004, 3

Abstract
This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral signals. The project involved comparing the analysis pipelines of the two collaborations on data sets prepared by both sides, containing simulated noise and injected events. The ability of the pipelines to detect the injected events was checked, and a first comparison of how the parameters of the events were recovered has been completed. Comment: GWDAW-9 proceeding
Abstract
This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral [...]
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The use of CUBE dynasim and aaSIDRA for the analysis of a signalized intersection /
Collection of open thesis in transport research (2005). Vol. 2005, 13

Abstract
Thesis (MTransportSysEngineering)--University of South Australia, 2005. Transport systems can be modelled and analysed with two techniques namely analytical and simulation. Until recently, aaSIDRA was the leader in the traffic modelling and analysis software based on analytical theory at micro scale. However, it cannot be used for more than one intersection. Meanwhile, the PARAMICS, AIMSUN NG and VISSIM are micro simulation software which are widely used in modelling and analysing transport systems. Further, CUBE Dynasim is also micro simulation software. It is created by Dynalogic in France and integrated in CUBE by Citilabs, UK. However, this software is relatively new compared to PARAMICS, AIMSUN NG or VISSIM. It is able to model multi nodes and multi modals transport system. The version of software used in this research is CUBE Dynasim 1.4.9 released in 2004 aaSIDRA 2.0 version 2.0.0.205.
Abstract
Thesis (MTransportSysEngineering)--University of South Australia, 2005. Transport systems can be modelled and analysed with two techniques namely analytical and simulation. [...]
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Predictive models for accidents on urban links - A focus on vulnerable road users
T. Jonsson

Collection of open thesis in transport research (2005). Vol. 2005, 11

Abstract
Much of earlier work on predictive models for accidents has been focused on rural traffic or urban intersections. This work has aimed at identifying and investigating possible improvements to predictive models for accidents on urban links. A special focus has been on the accidents of vulnerable road users."br /" "br /" The possible improvements investigated have been: a) the use of exposure data for vulnerable road users, b) the use of actual vehicle speeds, c) to separate vehicle accidents into single vehicle and multiple vehicle accidents and model each type separately."br /" "br /" The study involved eight Swedish cities, of which six were included in the development of accident models. In addition to police-reported traffic accidents, data for the models were collected in specific field studies and partly from the cities."br /" "br /" The study shows that the inclusion of exposure data for vulnerable road users in the models for vulnerable road users? accidents greatly improves the predictive ability of the models. Vehicle speeds were found to be very difficult to use in the models as vehicle speeds are highly correlated with most of the other variables and make the model coefficients unstable. The separate modelling of single and multiple vehicle accidents failed partly as the single vehicle accidents were too few for constructing sound models. The models for multiple vehicle accidents developed, however, had a better predictive ability than models for all vehicle accidents. Land use was the next important explanatory variable for most accident types after the exposure variables."br /" "br /" Accident models were developed with one data set and validated with another data set. The models performed very well in prediction by explaining between 71% and 81% of the systematic variation in the validation data. The validation indicated that exponents were 0.5 for both the flows of pedestrians and motor vehicles in models for accidents involving vulnerable road users, and 1.0 for the motor vehicle flow exponent in the models for motor vehicle accidents. For bicyclist accidents the correct exponent for bicyclist flows is likely to be somewhat lower than 0.5, close to 0.35."br /" "br /" The study also recommended practical uses for the models, listed the lessons learned from the modelling as well as proposed a number of topics for further research.
Abstract
Much of earlier work on predictive models for accidents has been focused on rural traffic or urban intersections. This work has aimed at identifying and investigating possible [...]
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Universal incident detection: a Bayesian network approach /
Collection of open thesis in transport research (2005). Vol. 2005, 10

Abstract
Thesis (PhDTransportSystemsEngineering)--University of South Australia, 2005. Road incidents and incident induced traffic congestions are a big threat to the mobility and safety of our daily life. Timely and accurate incident detection using automated incident detection (AID) systems is essential to effectively tackle incident induced congestion problems and to improve traffic management. The core of an AID system is an incident detection algorithm that interprets real time traffic data and makes decision on incidents. Literature review of existing AID algorithms and their applications reveals that 1) there is no single freeway algorithm that can fulfil the universality aspect of incident detection which is required by the advanced traffic management systems, and 2) how to achieve the effective and stable arterial road incident detection remains a big issue of AID research. In addition, there exists a strong need for incorporating existing expert traffic knowledge into AID algorithms to enhance incident detection performance.
Abstract
Thesis (PhDTransportSystemsEngineering)--University of South Australia, 2005. Road incidents and incident induced traffic congestions are a big threat to the mobility and [...]
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Evaluation of Load Balancing Algorithms in IP Networks : A case study at TeliaSonera
E. Hasselström, T. Sjögren

Collection of open thesis in transport research (2005). Vol. 2005, 9

Abstract
The principle of load balancing is to distribute the data load more evenly over the network in order to increase the network performance and efficiency. With dynamic load balancing the routing is undated at certain intervals. This thesis was developed to evaluate load balancing methods in the IP-network of TeliaSonera.Load balancing using short path routing, bottleneck load balancing and load balancing using MPLS have been evaluated. Short path routing is a flow sharing technique that allows routing on paths other than the shortest one. Load balancing using short path routing is achieved by dynamic updates of the link weights. Bottleneck is in its nature a dynamic load balancing algorithm. Unlike load balancing using short path routing it updates the flow sharing, not the metrics. The algorithm uses information about current flow sharing and link loads to detect bottlenecks within the network. The information is used to calculate new flow sharing parameters. When using MPLS, one or more complete routing paths (LSPs) are defined at each edge LSR before sending any traffic. MPLS brings the ability to perform flow sharing by defining the paths to be used and how the outgoing data load is to be shared among these. The model has been built from data about the network supplied by TeliaSonera. The model consists of a topology part, a traffic part, a routing part and cost part. The traffic model consists of a OD demand matrix. The OD demand matrix has been estimated from collected link loads. This was done with estimation models; the gravity model and an optimisation model. The algorithms have been analysed at several scenarios; normal network, core node failure, core link failure and DWDM system failure. A cost function, where the cost increases as the link load increases has been used to evaluate the algorithms. The signalling requirements for implementation of the load balancing algorithm have also been investigated.
Abstract
The principle of load balancing is to distribute the data load more evenly over the network in order to increase the network performance and efficiency. With dynamic load [...]
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Unleashing traffic engineering for IPv6 multihomed sites
C. de Launois

Collection of open thesis in transport research (2005). Vol. 2005, 5

Abstract
Internet connectivity takes a strategic importance for a growing number of companies. Therefore, for reliability and performance reasons, many Internet service providers and corporate networks connect to at least two providers, a practice called multihoming. However, the current multihoming mechanism contributes to the explosive growth of the Internet routing tables. This growth has major implications for routers on storage requirements, protocol overhead and stability, and forwarding performance. As a consequence, the traditional way to be multihomed in IPv4 is prevented in the next generation IPv6 Internet. Many approaches for IPv6 multihoming were proposed, with little consideration for traffic engineering aspects. The aim of the thesis is to bridge this gap. The thesis investigates the way to best provide traffic engineering for IPv6 multihomed sites. It first demonstrates that Host-Centric multihoming, the foreseen approach for IPv6 multihoming, is the most promising in terms of fault-tolerance and traffic engineering capabilities. Compared to traditional multihoming approaches, our simulation results show that Host-Centric IPv6 multihomed sites are able to obtain lower delays by leveraging the path diversity that underlies the Internet. Unfortunately, no traffic engineering mechanism is available for this multihoming approach. Therefore, this thesis next presents a technique to effectively use the multiple interdomain paths that exist between multihomed sites. The proposed mechanism allows the multihomed sites to control how their flows are distributed over the links with their providers. The mechanism is able to take into account complex and very dynamic routing policies. Finally, the thesis proposes the use of synthetic coordinates as a scalable and efficient way to help hosts in selecting the interdomain paths with the lowest delays. Experimental results with real measurements show that this mechanism allows sites to avoid all paths with really bad delays, and to most often select the lowest delay path. (FSA 3)--UCL, 2005
Abstract
Internet connectivity takes a strategic importance for a growing number of companies. Therefore, for reliability and performance reasons, many Internet service providers and [...]
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Human-kinetic multiclass traffic flow theory and modelling with application to advanced driver assistance systems in congestion
C. Tampère

Collection of open thesis in transport research (2004). Vol. 2004, 4

Abstract
Motivated by the desire to explore future traffic flows that will consist of a mixture of classical vehicles and vehicles equipped with advanced driver assistance systems, new mathematical theories and models are developed. The basis for this theory was borrowed from the kinetic description of gas flows, where we replaced the behaviour of the molecules by typical human driving behaviour. From a methodological point of view, this 'human-kinetic' traffic flow theory provides two major improvements with respect to existing theory. Firstly, the model builds exclusively on a mathematical description of individual driver behaviour, whereas traditionally field measurements of traffic flow variables like flow rate and average speed of the flow are needed. This is of major importance for the exploration of future traffic flows with vehicles and equipment that are not yet on the market, and for which at best individual test results from driving simulator experiments or small scale field trials are available. Secondly, the model accounts for the more refined aspects of individual driver behaviour by considering the 'internal' state of the driver (active/passive, aware/unaware,...) and the variations of driving strategy that occur during driving. This is important when the ambition is to capture refined congestion patterns like the occurrence of stop-and-go waves, oscillating congestion and long jams, where the driving strategy may depend for instance on the motivation of the driver to follow closely. This new theory links together the worlds of traffic engineers and behavioural scientists. As such, it is a promising tool that increases the insight in the human behaviour as a basis of various dynamic congestion patterns, and it facilitates the design and evaluation of electronic systems in the vehicle that assist the driver to behave safer, more comfortable and more efficient in busy traffic flows. Herewith, the results of this research are relevant, both for the theoretical interest of the TRAIL research school, and for the more practically oriented work of TNO, who provided financing for this research in the joint T3 research program.
Abstract
Motivated by the desire to explore future traffic flows that will consist of a mixture of classical vehicles and vehicles equipped with advanced driver assistance systems, [...]
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Combined use of prioritized AIMD and flow-based traffic splitting for robust TCP load balancing
O. Alparslan

Collection of open thesis in transport research (2005). Vol. 2005, 3

Abstract
Cataloged from PDF version of article. In this thesis, we propose a multi-path TCP load balancing traffic engineering methodology in IP networks. In this architecture, TCP traffic is split at the flow level between the primary and secondary paths in order to prevent the adverse effect of packet reordering on TCP performance occuring in packet-based load balancing schemes. Traffic splitting is done by using a random early rerouting algorithm that controls the queuing delay difference between the two alternative paths. We apply strict priority queuing in order to prevent the knock-on effect that arises when primary and secondary path queues have equal priority. Probe packets are used for getting congestion information from the output queues of links along the paths and AIMD (Additive Increase/Multiplicative Decrease) based rate control using this congestion information is applied to the traffic routed over these paths. We compare two queuing architectures, namely first-in-first-out (FIFO) and strict priority. We show through simulations that strict priority queuing has higher performance, it is relatively more robust than FIFO queuing and it eliminates the knock-on effect. We show that avoiding packet reordering by flow level splitting significantly improves the performance of long flows. The capabilities of ns-2 simulator is improved bu using optimizations in order to apply the simulator to relatively large networks. We show that incorporating a-priori knowledge of the traffic demand matrix into the proposed architecture can further improve its performance in terms of load balancing and byte rejection ratio. Alparslan, Onur M.S.
Abstract
Cataloged from PDF version of article. In this thesis, we propose a multi-path TCP load balancing traffic engineering methodology in IP networks. In this architecture, TCP [...]
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Techniques d'Optimisation pour le Dimensionnement et la Reconfiguration des Réseaux MPLS
S. Beker

Collection of open thesis in transport research (2004). Vol. 2004, 3

Abstract
The calculation of virtual topologies on mapped onto physical topologies is one of the main techniques in traffic engineering. For a given physical network topology with fixed capacities, and a traffic matrix to route, the problem is the one of finding a virtual topology which will optimally route the given traffic matrix over the physical topology. When the traffic matrix evolves on long timescales, we will need to recalculate such optimal layout. Our first contribution consists in the definition of cost functions which better represent the actual costs of operation from an operator's standpoint. The second contribution consists in taking into account the costs of reconfiguring the layout to adapt it to the new optimal layout. Considering actual operation and maintenance costs, it would be interesting to reduce the layout complexity, measured as a function of the number of virtual paths required by the layout. We have formulated different optimization problems minimizing layout complexity, under QoS constraints. This realistic model results in hard to solve problems. We have developped heuristic methods to approximatelly solve large network topologies. We have shown the interest of reducing the layout complexity compared to results obtained when optimizing the layout with classical cost functions. The layout reconfiguration induces first a cost of operation, and second a cost associated to the service disruption times needed to reconfigure. We have formulated a family of problems which take into account the reconfiguration costs when calculating the new layout. One of the above mentioned heuristics has been adapted to solve the reconfiguration problem.; La superposition de topologies virtuelles à la topologie physique d'un réseau est un des principaux mécanismes de l'ingénierie de trafic. Soit un réseau physique d'une certaine topologie et capacité fixées et une matrice de trafic à véhiculer, il s'agit trouver une topologie logique permettant de mapper de manière optimale la matrice de trafic sur le réseau physique. Lors de l'évolution de la matrice de trafic sur des échelles de temps longues, il faudra agir sur le layout. La première contribution concerne la définition de fonctions de coût mieux adaptées à la réalité d'un opérateur, la deuxième contribution concerne la prise en compte du coût de changement du layout. Il s'avère intéressant d'un point de vue opérateur de réduire la complexité du layout, mesurée comme une fonction du nombre de chemins virtuels. Nous avons donc formulé divers problèmes de minimisation de la complexité du layout sous des contraintes de QoS. Il s'agit d'une modélisation réaliste mais qui engendre des modèles difficiles à résoudre. Nous avons développés des heuristiques qui permet de trouver des solutions approchées pour des réseaux de grande taille. Nous avons montré que la complexité des layouts peut être significativement réduite en comparaison avec celle obtenue suite à l'optimisation des fonctions de coût classiques. Le changement du layout implique d'une part un coût d'opération et d'autre part peut engendrer des coupures de service qui affecteront directement le coût d'opération. Nous avons formulé une famille de problèmes prenant en compte le coût de reconfiguration du layout. L'une des heuristiques citées a été adaptée pour analyser ces nouveaux problèmes.
Abstract
The calculation of virtual topologies on mapped onto physical topologies is one of the main techniques in traffic engineering. For a given physical network topology with fixed [...]
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Regulating on-street parking
S. Proost, E. Calthrop

Collection of open reports in transport research (2004). Vol. 2004, 35

Abstract
Consider the choices available to a shopper driving to a city and trying to park downtown. One option, typical to many cities, is to follow the signposts to an off-street parking facility, which is often privately operated. Another option is to search for an on-street spot. If this proves unsuccessful, it is always possible to return to the off-street facility. We formalise such a setting and examine optimal on-street parking policy in the presence of an off-street market. Not surprisingly, the amount of socially-wasteful searching behaviour is shown to depend on the prices of both the off- and on-street market. If the off-street market is run competitively, optimal on-street policy reduces to a simple and attractive rule: set the on-street price equal to the resource cost of off-street parking supply. Other pricing rules result in either excessive searching behaviour or excessive off-street investment costs. Time restrictions - a common alternative to on-street fees - are also shown to be inefficient. In practice, however, off-street markets are unlikely to be competitive. We examine the case of a single off-street supplier playing as a Stackelberg follower to the government regulated on-street market. Based on a numerical example (calibrated to London), optimal on-street policy is shown to either involve setting a relatively high on-street price, such that the monopolist is induced to undercut and gain the entire parking demand, or setting a relatively low price, while the monopolist maximises profit on the residual demand curve. Which strategy is optimal is shown to be parameter dependent.
Abstract
Consider the choices available to a shopper driving to a city and trying to park downtown. One option, typical to many cities, is to follow the signposts to an off-street [...]
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INTERNAL REPAIR OF PIPELINES REVIEW & EVALUATION OF INTERNAL PIPELINE REPAIR TRIALS REPORT
N. Porter, R. Gordon, I. Harris, M. Sullivan, C. Neary, B. Bruce, G. Ritter, B. Mohr, D. Harwig, M. Boring

Collection of open reports in transport research (2004). Vol. 2004, 34

Abstract
The two broad categories of fiber-reinforced composite liner repair and deposited weld metal repair technologies were reviewed and evaluated for potential application for internal repair of gas transmission pipelines. Both are used to some extent for other applications and could be further developed for internal, local, structural repair of gas transmission pipelines. Evaluation trials were conducted on pipe sections with simulated corrosion damage repaired with glass fiber-reinforced composite liners, carbon fiber-reinforced composite liners, and weld deposition. Additional un-repaired pipe sections were evaluated in the virgin condition and with simulated damage. Hydrostatic failure pressures for pipe sections repaired with glass fiber-reinforced composite liner were only marginally greater than that of pipe sections without liners, indicating that this type of liner is generally ineffective at restoring the pressure containing capabilities of pipelines. Failure pressure for pipe repaired with carbon fiber-reinforced composite liner was greater than that of the un-repaired pipe section with damage, indicating that this type of liner is effective at restoring the pressure containing capability of pipe. Pipe repaired with weld deposition failed at pressures lower than that of un-repaired pipe in both the virgin and damaged conditions, indicating that this repair technology is less effective at restoring the pressuremore » containing capability of pipe than a carbon fiber-reinforced liner repair. Physical testing indicates that carbon fiber-reinforced liner repair is the most promising technology evaluated to-date. Development of a comprehensive test plan for this process is recommended for use in the next phase of this project.« le
Abstract
The two broad categories of fiber-reinforced composite liner repair and deposited weld metal repair technologies were reviewed and evaluated for potential application for [...]
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IMPROVEMENT TO PIPELINE COMPRESSOR ENGINE RELIABILITY THROUGH RETROFIT MICRO-PILOT IGNITION SYSTEM
T. Bestor

Collection of open reports in transport research (2004). Vol. 2004, 33

Abstract
This report documents the second year's effort towards a 3-year program to develop micropilot ignition systems for existing pipeline compressor engines. In essence, all Phase II goals and objectives were met. We intend to proceed with the Phase III research plan, as set forth by the applicable Research Management Plan. The objective for Phase II was to further develop and optimize the micropilot ignition system for large bore, slow speed engines operating at low compression ratios. The primary elements of Micropilot Phase II were to evaluate the results for the 4-cylinder system prototype developed for Phase I, then optimize this system to demonstrate the technology's readiness for the field demonstration phase. In all, there were twelve (12) tasks defined and executed to support objectives in a stepwise fashion. Task-specific approaches and results are documented in this report. Research activities for Micropilot Phase II were conducted with the understanding that the efforts are expected to result in a commercial product to capture and disseminate the efficiency and environmental benefits of this new technology. Commercially-available fuel injection products were identified and applied to the program where appropriate. Modifications to existing engine components were kept to a minimum. This approach will minimize the overall time-to-market requirements, while meeting performance and cost criteria. The optimized four-cylinder system data demonstrated significant progress compared to Phase I results, as well as traditional spark ignition systems. An extensive testing program at the EECL using the GMV-4 test engine demonstrated that: (1) In general, the engine operated more stable fewer misfires and partial combustion events when using the 3-hole injectors compared to the 5-hole injectors used in Phase I. (2) The engine had, in general, a wider range of operation with the 3-hole injectors. Minimum operational boost levels were approximately 5''Hg lower and the minimum pilot quantity that the engine would operate on was roughly cut in half. (3) A successful concept demonstration of engine lube oil pilot injection was performed where the minimum operational boost was reduced by another 5''Hg to a boost level of 3''Hg; this is, depending on altitude, in the range of boost levels of many blower and piston scavenged low BMEP engines. (4) Micropilot ignition compares very favorably to other ignitions systems. The performance of micropilot ignition with mechanical gas admission valves is very similar to the performance of precombustion chamber ignition with high pressure fuel injection. Compared to spark ignition with mechanical gas admission valves the lean limit of operation is extended by about 5''Hg. These laboratory results will be enhanced, demonstrated and commercialized by others, with management and support from CSU, during Phase III of the Micropilot Ignition program.
Abstract
This report documents the second year's effort towards a 3-year program to develop micropilot ignition systems for existing pipeline compressor engines. In essence, all Phase [...]
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Russia's Gas Sector
W. Tompson, R. Ahrend

Collection of open reports in transport research (2004). Vol. 2004, 32

Abstract
The gas industry is perhaps Russia’s least reformed major sector. Prices are regulated, exports are monopolised and the domestic market is dominated by a state-controlled, vertically integrated monopolist, OAO Gazprom. Gazprom combines commercial and regulatory functions, and maintains tight control over the sector’s infrastructure and over information flows within it. The sector as it is currently constituted is highly unlikely to be able to sustain sufficient output growth to satisfy both rising export commitments and domestic demand. There is significant potential for accelerating the growth of non-Gazprom production and making gas supply in Russia more competitive, but this will require fundamental reform. The proposals for reform advanced in the paper address two sets of issues. First, there is an urgent need to increase transparency in the sector and transfer many of the regulatory functions now performed by Gazprom to state bodies. Secondly, there is a longer-term need for a ...
Abstract
The gas industry is perhaps Russia’s least reformed major sector. Prices are regulated, exports are monopolised and the domestic market is dominated by a state-controlled, [...]
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AIRBORNE, OPTICAL REMOTE SENSING OF METHANE AND ETHANE FOR NATURAL GAS PIPLINE LEAK DETECTION
J. Myers

Collection of open reports in transport research (2004). Vol. 2004, 31

Abstract
Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. The third six-month technical report contains a summary of the progress made towards finalizing the design and assembling the airborne, remote methane and ethane sensor. The vendor has been chosen and is on contract to develop the light source with the appropriate linewidth and spectral shape to best utilize the Ophir gas correlation software. Ophir has expanded upon the target reflectance testing begun in the previous performance period by replacing the experimental receiving optics with the proposed airborne large aperture telescope, which is theoretically capable of capturing many times more signal return. The data gathered from these tests has shown the importance of optimizing the fiber optic receiving fiber to the receiving optic and has helped Ophir to optimize the design of the gas cells and narrowband optical filters. Finally, Ophir will discuss remaining project issues that may impact the success of the project.
Abstract
Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing [...]
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REMOTE FIELD EDDY CURRENT INSPECTION OF UNPIGGABLE PIPELINES
A. Teitsma

Collection of open reports in transport research (2004). Vol. 2004, 30

Abstract
The Remote Field Eddy Current (RFEC) technique is ideal for inspecting unpiggable pipelines because all its components can be made much smaller than the diameter of the pipe to be inspected. We reviewed the technique, and used demonstrations from prior work by others in presentations on the technique and how we plan to develop it. Coils were wound; a jig for pulling the coils through the pipe was manufactured; defects were machined in one six-inch diameter, ten-foot long pipe; and the equipment was assembled. After completing first crude pullout test to show that RFEC inspection would work, we repeated the experiment with a proper jig and got excellent results. The test showed the expected behavior, with the direct field dominating the signal to about two pipe diameters from the drive coil, and the remote field dominating for greater separations between the drive coil and the sensing coils. Response of RFEC to a typical defect was measured, as was the sensitivity to defect size. Before manufacturing defects in the pipe, we measured the effect of defect separation and concluded that defects separated by 18 inches or 1/3rd of the pipe diameter did not interfere with each other. We manufactured a set of 13 defects, and measured the RFEC signals. We found a background variation that was eventually attributed to permeability variations in the seamless pipe. We scanned all thirteen defects and got satisfactory results. The two smallest defects did not show a signal, but these were much too small to be reported in a pipeline inspection. We acquired a ten-foot seam welded pipe that has much less background variation. We are measuring the sensitivity of RFEC signals to mechanical variations between the exciter and sensing coils.
Abstract
The Remote Field Eddy Current (RFEC) technique is ideal for inspecting unpiggable pipelines because all its components can be made much smaller than the diameter of the pipe [...]
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INTERNAL REPAIR OF PIPELINES
M. Sullivan, N. Porter, R. Gordon, C. Neary, B. Bruce, D. Harwig, I. Harris

Collection of open reports in transport research (2004). Vol. 2004, 29

Abstract
The two broad categories of deposited weld metal repair and fiber-reinforced composite liner repair technologies were reviewed for potential application for internal repair of gas transmission pipelines. Both are used to some extent for other applications and could be further developed for internal, local, structural repair of gas transmission pipelines. Preliminary test programs were developed for both deposited weld metal repair and for fiber-reinforced composite liner repair. Evaluation trials have been conducted using a modified fiber-reinforced composite liner provided by RolaTube and pipe sections without liners. All pipe section specimens failed in areas of simulated damage. Pipe sections containing fiber-reinforced composite liners failed at pressures marginally greater than the pipe sections without liners. The next step is to evaluate a liner material with a modulus of elasticity approximately 95% of the modulus of elasticity for steel. Preliminary welding parameters were developed for deposited weld metal repair in preparation of the receipt of Pacific Gas & Electric's internal pipeline welding repair system (that was designed specifically for 559 mm (22 in.) diameter pipe) and the receipt of 559 mm (22 in.) pipe sections from Panhandle Eastern. The next steps are to transfer welding parameters to the PGE between 305 m and 610 m (1,000 ft. and 2,000 ft.); and beyond 914 m (3,000 ft.). All three groups require pig-based systems. A despooled umbilical system would suffice for the first two groups which represents 81% of survey respondents. The third group would require an onboard self-contained power unit for propulsion and welding/liner repair energy needs. (4) Pipe diameter sizes range from 50.8 mm (2 in.) through 1,219.2 mm (48 in.). The most common size range for 80% to 90% of operators surveyed is 508 mm to 762 mm (20 in. to 30 in.), with 95% using 558.8 mm (22 in.) pipe. An evaluation of potential repair methods clearly indicates that the project should continue to focus on the development of a repair process involving the use of GMAW welding and on the development of a repair process involving the use of fiber-reinforced composite liners.
Abstract
The two broad categories of deposited weld metal repair and fiber-reinforced composite liner repair technologies were reviewed for potential application for internal repair [...]
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DEVELOPMENT OF AN INSPECTION PLATFORM AND A SUITE OF SENSORS FOR ASSESSING CORROSION AND MECHANICAL DAMAGE ON UNPIGGABLE TRANSMISSION MAINS
W. Leary, G. Vradis

Collection of open reports in transport research (2004). Vol. 2004, 28

Abstract
This development program is a joint effort among the Northeast Gas Association (formerly New York Gas Group), Foster-Miller, Inc., and the US Department of Energy (DOE) through the National Energy Technology Laboratory (NETL). The total cost of the project is $772,525, with the National Energy Technology Laboratory of the US Department of Energy contributing $572,525, and the Northeast Gas Association contributing $200,000. The present report summarizes the accomplishments of the project during its fourth three-month period (from July 2003 through September 2003). The efforts of the project focused during this period in completing the assessment of the tether technology, which is intended to be used as the means of communication between robot and operator, in designing the MFL sensor module, in completing the kinematic studies, and in initiating tractor design. In addition, work on the ovality sensor progressed significantly, while work on system integration was initiated focusing at this point in time on module coupling. Results to date indicate that the robotic system under design will be able to meet most of the design specifications initially specified. Earlier concerns regarding the portability of the system are shown to be a non-issue, with new more detailed analysis showing that from a locomotor point of view an inspection of a 16 inch-24 inch pipe size range with a single platform is most likely possible However, the limitations imposed by the sensor are more restrictive, preliminary results indicating an inspection range of 16 inch-20 inch pipe sizes. In addition, tether use will most likely have to be limited to medium and low flow conditions in order to preserve tether integrity.
Abstract
This development program is a joint effort among the Northeast Gas Association (formerly New York Gas Group), Foster-Miller, Inc., and the US Department of Energy (DOE) through [...]
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Communication from the Commission: a Community aviation policy towards its neighbours
C. Communities

Collection of open reports in transport research (2004). Vol. 2004, 27
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INTERNAL REPAIR OF PIPELINES
M. Sullivan, N. Porter, B. Mohr, G. Ritter, D. Harwig, R. Gordon, I. Harris, M. Boring, C. Neary, B. Bruce

Collection of open reports in transport research (2004). Vol. 2004, 25

Abstract
The two broad categories of fiber-reinforced composite liner repair and deposited weld metal repair technologies were reviewed and evaluated for potential application for internal repair of gas transmission pipelines. Both are used to some extent for other applications and could be further developed for internal, local, structural repair of gas transmission pipelines. Principal conclusions from a survey of natural gas transmission industry pipeline operators can be summarized in terms of the following performance requirements for internal repair: (1) Use of internal repair is most attractive for river crossings, under other bodies of water, in difficult soil conditions, under highways, under congested intersections, and under railway crossings. (2) Internal pipe repair offers a strong potential advantage to the high cost of horizontal direct drilling when a new bore must be created to solve a leak or other problem. (3) Typical travel distances can be divided into three distinct groups: up to 305 m (1,000 ft.); between 305 m and 610 m (1,000 ft. and 2,000 ft.); and beyond 914 m (3,000 ft.). All three groups require pig-based systems. A despooled umbilical system would suffice for the first two groups which represents 81% of survey respondents. The third group would require an onboard self-contained power unit for propulsion and welding/liner repair energy needs. (4) The most common size range for 80% to 90% of operators surveyed is 508 mm (20 in.) to 762 mm (30 in.), with 95% using 558.8 mm (22 in.) pipe. Evaluation trials were conducted on pipe sections with simulated corrosion damage repaired with glass fiber-reinforced composite liners, carbon fiber-reinforced composite liners, and weld deposition. Additional un-repaired pipe sections were evaluated in the virgin condition and with simulated damage. Hydrostatic failure pressures for pipe sections repaired with glass fiber-reinforced composite liner were only marginally greater than that of pipe sections without liners, indicating that this type of liner is only marginally effective at restoring the pressure containing capabilities of pipelines. Failure pressures for larger diameter pipe repaired with a semi-circular patch of carbon fiber-reinforced composite lines were also marginally greater than that of a pipe section with un-repaired simulated damage without a liner. These results indicate that fiber reinforced composite liners have the potential to increase the burst pressure of pipe sections with external damage Carbon fiber based liners are viewed as more promising than glass fiber based liners because of the potential for more closely matching the mechanical properties of steel. Pipe repaired with weld deposition failed at pressures lower than that of un-repaired pipe in both the virgin and damaged conditions, indicating that this repair technology is less effective at restoring the pressure containing capability of pipe than a carbon fiber-reinforced liner repair. Physical testing indicates that carbon fiber-reinforced liner repair is the most promising technology evaluated to-date. The first round of optimization and validation activities for carbon-fiber repairs are complete. Development of a comprehensive test plan for this process is recommended for use in the field trial portion of this program.
Abstract
The two broad categories of fiber-reinforced composite liner repair and deposited weld metal repair technologies were reviewed and evaluated for potential application for [...]
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ADVANCED COMPRESSOR ENGINE CONTROLS TO ENHANCE OPERATION, RELIABILITY AND INTEGRITY
G. Bourn

Collection of open reports in transport research (2004). Vol. 2004, 24

Abstract
This document provides a mid-term update for the ''Advanced Compressor Engine Controls to Enhance Operation, Reliability, and Integrity'' project. SwRI is conducting this project for DOE in conjunction with Cooper Energy Services, under DOE contract number DE-FC26-03NT41859. The objective of this one-year project is to develop, evaluate, and demonstrate advanced engine control technologies and hardware, specifically, closed-loop NO{sub x} emissions control on a two-stroke integral reciprocating engine/compressor used for pipeline gas transmission service. This work uses a Cooper-Bessemer GMVH-6 laboratory engine owned by Cooper Energy Services (CES) and installed in a test facility at Southwest Research Institute (SwRI). The gas transmission industry operates over 4,000 integral engine compressors, the majority being two-stroke, with a median age of 45 years and a median size of 2000 horsepower. These engines have historically exhibited poor performance and high emissions, due in part to poor engine control. The end results are misfires and partial burns that lead to increased fuel usage and exhaust emissions. Many of the slow-speed integral engines in the gas compression industry utilize control systems that are outdated, slow, and suffer from poor resolution. Research into more advanced control systems for integral compressor engines has increased tremendously in recent years. Themore » recent advancements in control logic are being reviewed and analyzed in this program to understand the effectiveness of each. In addition, the application of a real-time NO{sub x} sensor feedback for closed-loop control is being investigated. To date, the strategies involving fuel/air equivalence ratio for a NO{sub x} prediction algorithm have been reviewed and analyzed. A hierarchy of control strategies will be outlined at the conclusion of this program. This hierarchy will range from the simplest and least expensive closed-loop control to an advanced system utilizing individual cylinder control. The ultimate control strategy is thought to be one that integrates both compressor and engine control, with the engine control based on individual power cylinders. The hierarchy of engine control may be desirable for the variety of engines in various locations that are subject to varying regulated levels of NO{sub x} emissions. The engines in non-attainment areas will require the maximum level of complexity in engine controls.« le
Abstract
This document provides a mid-term update for the ''Advanced Compressor Engine Controls to Enhance Operation, Reliability, and Integrity'' project. SwRI is conducting this [...]
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A Data Fusion System for the Nondestructive Evaluation of Non-Piggable Pipes
S. Mandayam, J. Chen, R. Polikar

Collection of open reports in transport research (2004). Vol. 2004, 23

Abstract
The objectives of this research project are: (1) To design sensor data fusion algorithms that can synergistically combine defect related information from heterogeneous sensors used in gas pipeline inspection for reliably and accurately predicting the condition of the pipe-wall. (2) To develop efficient data management techniques for signals obtained during multisensor interrogation of a gas pipeline. During this reporting period, Rowan University fabricated test specimens with simulated defects for nondestructive evaluation (NDE); designed and developed two versions of a test platform for performing multi-sensor interrogation of test specimens under loaded conditions simulating pressurized gas pipelines; and performed magnetic flux leakage (MFL), ultrasonic testing (UT), thermal imaging and acoustic emission (AE) NDE on the test specimens. The data resulting from this work will be employed for designing multi-sensor data fusion algorithms.
Abstract
The objectives of this research project are: (1) To design sensor data fusion algorithms that can synergistically combine defect related information from heterogeneous sensors [...]
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ADVANCED CUTTINGS TRANSPORT STUDY
N. Takach, C. Redden, K. Ashenayi, T. Reed, L. Volk, S. Miska, A. Washington, Z. Chen, M. Pickell, L. Zhou, M. Volk

Collection of open reports in transport research (2004). Vol. 2004, 22

Abstract
Experiments on the flow loop are continuing. Improvements to the software for data acquisition are being made as additional experience with three-phase flow is gained. Modifications are being made to the Cuttings Injection System in order to improve control and the precision of cuttings injection. The design details for a drill-pipe Rotation System have been completed. A US Patent was filed on October 28, 2002 for a new design for an instrument that can generate a variety of foams under elevated pressures and temperatures and then transfer the test foam to a viscometer for measurements of viscosity. Theoretical analyses of cuttings transport phenomena based on a layered model is under development. Calibrations of two nuclear densitometers have been completed. Baseline tests have been run to determine wall roughness in the 4 different tests sections (i.e. 2-in, 3-in, 4-in pipes and 5.76-in by 3.5-in annulus) of the flow loop. Tests have also been conducted with aerated fluids at EPET conditions. Preliminary experiments on the two candidate aqueous foam formulations were conducted which included rheological tests of the base fluid and foam stability reports. These were conducted after acceptance of the proposal on the Study of Cuttings Transport with Foam Under Elevated Pressure and Elevated Temperature Conditions. Preparation of a test matrix for cuttings-transport experiments with foam in the ACTF is also under way. A controller for instrumentation to measure cuttings concentration and distribution has been designed that can control four transceivers at a time. A prototype of the control circuit board was built and tested. Tests showed that there was a problem with radiated noise. AN improved circuit board was designed and sent to an external expert to verify the new design. The new board is being fabricated and will first be tested with static water and gravel in an annulus at elevated temperatures. A series of viscometer tests to measure foam properties have begun using foam generated by the Dynamic Test Facility (DTF). Investigation of techniques to measure foam quality and size, size distribution and shape of bubbles is continuing.
Abstract
Experiments on the flow loop are continuing. Improvements to the software for data acquisition are being made as additional experience with three-phase flow is gained. Modifications [...]
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PRESSURE ACTIVATED SEALANT TECHNOLOGY
M. Romano

Collection of open reports in transport research (2004). Vol. 2004, 17

Abstract
The objective of this project is to develop new, efficient, cost effective methods of internally sealing natural gas pipeline leaks through the application of differential pressure activated sealants. In researching the current state of the art for gas pipeline sealing technologies we concluded that if the project was successful, it appeared that pressure activated sealant technology would provide a cost effective alternative to existing pipeline repair technology. From our analysis of current field data for a 13 year period from 1985 to 1997 we were able to identify 205 leaks that were candidates for pressure activated sealant technology, affirming that pressure activated sealant technology is a viable option to traditional external leak repairs. The data collected included types of defects, areas of defects, pipe sizes and materials, incident and operating pressures, ability of pipeline to be pigged and corrosion states. This data, and subsequent analysis, was utilized as a basis for constructing applicable sealant test modeling.
Abstract
The objective of this project is to develop new, efficient, cost effective methods of internally sealing natural gas pipeline leaks through the application of differential [...]
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OPERATING PROCEDURE FOR THE PORTABLE ACOUSTIC MONITORING PACKAGE (PAMP)
R. Guiler, P. Browning, G. Palmer, G. Morris, J. Loth

Collection of open reports in transport research (2004). Vol. 2004, 16

Abstract
The Portable Acoustic Monitoring Package (PAMP) has been designed to record and monitor acoustic signals in high-pressure natural gas (NG) transmission lines. Of particular interest are the three acoustic signals associated with a pipeline fracture. The system is portable (less than 30 lbm) and can be used at all line pressures up to 1000 psig. The PAMP requires a shut-off valve equipped 1/2 inch NPT access port in the pipeline. It is fully functional over the typical pressure range found in the natural gas transmission pipelines in the West Virginia, Virginia, Pennsylvania, and Ohio areas. With the use of the PAMP, a full spectrum of acoustic signals can be recorded and defined in terms of acoustic energy in decibels. To detect natural gas pipeline infringements and leaks, the acoustic energy generated inside the line is monitored with a sensitive pressure-equalized microphone and a step function type {Delta}p transducer. The assembly is mounted on a 1000 psig pipe fitting-tree called the PAMP. The electronics required to record, store and analyze the data are described within this report in the format of an operating manual.
Abstract
The Portable Acoustic Monitoring Package (PAMP) has been designed to record and monitor acoustic signals in high-pressure natural gas (NG) transmission lines. Of particular [...]
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GAS PIPELINE PIGABILITY
T. Clark, B. Nestleroth

Collection of open reports in transport research (2004). Vol. 2004, 15

Abstract
In-line inspection equipment is commonly used to examine a large portion of the long distance transmission pipeline system that transports natural gas from well gathering points to local distribution companies. A piece of equipment that is inserted into a pipeline and driven by product flow is called a ''pig''. Using this term as a base, a set of terms has evolved. Pigs that are equipped with sensors and data recording devices are called ''intelligent pigs''. Pipelines that cannot be inspected using intelligent pigs are deemed ''unpigable''. But many factors affect the passage of a pig through a pipeline, or the ''pigability''. The pigability pipeline extend well beyond the basic need for a long round hole with a means to enter and exit. An accurate assessment of pigability includes consideration of pipeline length, attributes, pressure, flow rate, deformation, cleanliness, and other factors as well as the availability of inspection technology. All factors must be considered when assessing the appropriateness of ILI to assess specific pipeline threats.
Abstract
In-line inspection equipment is commonly used to examine a large portion of the long distance transmission pipeline system that transports natural gas from well gathering [...]
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PLAINS CO2 REDUCTION PARTNERSHIP
T. Erickson

Collection of open reports in transport research (2004). Vol. 2004, 14

Abstract
The PCOR Partnership continues to make great progress. Task 2 (Deployment Issues) activities have focused on utilizing Dakota Gasification Company (DGC) experience and data with respect to DGC participation in the enhanced oil recovery project at Weyburn, Saskatchewan. A solid line of communication has been developed with the Interstate Oil & Gas Compact Commission (IOGCC) for the mutual benefit of the PCOR Partnership and IOGCC's complementary efforts. Task 3 (Public Education and Outreach) activities have focused on developing a foundation of background materials in order to avoid a duplication of efforts and provide the best outreach and educational materials possible. Progress in Task 4 (Characterization and Evaluation) has included the development of a database format, the preliminary collection of data regarding CO{sub 2} sources and sinks, and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 (Modeling and Phase II Action Plans) activities have resulted in a conceptual model for screening and qualitatively assessing sequestration options. Task 5 activities have also been useful in structuring data collection and other activities in Tasks 2, 3, and 5.
Abstract
The PCOR Partnership continues to make great progress. Task 2 (Deployment Issues) activities have focused on utilizing Dakota Gasification Company (DGC) experience and data [...]
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INSPECTION OF FUSION JOINTS IN PLASTIC PIPE
A. Savitski, J. Coffey, C. Reichert

Collection of open reports in transport research (2004). Vol. 2004, 13

Abstract
The standard method of joining plastic pipe in the field is the butt fusion process. As in any pipeline application, joint quality greatly affects overall operational safety of the system. Currently no simple, reliable, cost effective method of assessing the quality of fusion joints in the field exists. Visual examination and pressure testing are current non-destructive approaches, which do not provide any assurance about the long-term pipeline performance. This project will develop, demonstrate, and validate an in-situ non-destructive inspection method for butt fusion joints in gas distribution plastic pipelines. The inspection system will include a laser based image-recognition system that will automatically generate and interpret digital images of pipe joints and assign them a pass/fail rating, which eliminates operator bias in evaluating joint quality. A Weld Zone Inspection Method (WZIM) is being developed in which local heat is applied to the joint region to relax the residual stresses formed by the original joining operation and reveal the surface condition of the joint. In cases where the joint is not formed under optimal conditions, and the intermolecular forces between contacting surfaces are not strong enough, the relaxation of macromolecules in the surface layer causes the material to pull back, revealing a fusion line. If the joint is sound, the bond line image does not develop. To establish initial feasibility of the approach, welds were performed under standard and non-standard conditions. These welds were subjected to the WZIM and tensile testing. There appears to be a direct correlation between the WZIM and tensile testing results. Although WZIM appears to be more sensitive than tensile testing can verify, the approach appears valid.
Abstract
The standard method of joining plastic pipe in the field is the butt fusion process. As in any pipeline application, joint quality greatly affects overall operational safety [...]
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European Perspectives on a New Fiscal Framework for Transport
G. Parkhurst, B. Lane, S. Potter

Collection of open chapters of books in transport research (2005). Vol. 2005, 37

Abstract
This chapter presents an overview of changes in transport taxation in European countries to promote more sustainable transport. A number of changes in the framework of car taxation have resulted in some useful environmental gains. However, these changes are limited because the transport tax system has been designed to produce a substantial income from internal-combustion-engine vehicles in an easily administered form. A major restructuring of transport taxation is required to fully address a different goal â that of stimulating improvements to environmental performance. A generalised road user charging-based system could be the way forward. Such a system is now seen by several European countries and some USA states as the transport taxation regime for the 21st century. \\ud \\ud Tax regime change is emerging onto the transport policy agenda as a vital long-term strategy. Largely by default, transport policy-makers are coming to realise that road taxation regime change is inevitable if traffic and congestion management is to be a reality. The way we taxed vehicles and fuel in the 20th century is simply not appropriate for the transport challenges we face today.
Abstract
This chapter presents an overview of changes in transport taxation in European countries to promote more sustainable transport. A number of changes in the framework of car [...]
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Towards an Adaptive and Intelligent MPLS Network
R. Rahim-Amoud, L. Merghem-Boulahia, D. Gaiti

Collection of open chapters of books in transport research (2005). Vol. 2005, 36

Abstract
International audience; The Multi-Protocol Label Switching (MPLS) is an Internet Engineering Task Force (IETF) framework. It is a versatile solution to address the problems faced by present-day networks like speed, scalability and traffic engineering. However, the Quality of Service (QoS) management of MPLS is made by static methods. In this paper, we propose a solution based on Multi-Agent Systems (MAS) to manage the QoS into MPLS by adequate adaptive methods.
Abstract
International audience; The Multi-Protocol Label Switching (MPLS) is an Internet Engineering Task Force (IETF) framework. It is a versatile solution to address the problems [...]
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Ambient intelligence:Plenty of challenges by 2010
T. Clerckx, P. Rigole, J. Bergh, K. Bosschere, A. Georges, D. Preuveneers, Y. Berbers, D. Wagelaar, V. Jonckers, K. Coninx

Collection of open chapters of books in transport research (2005). Vol. 2005, 35

Abstract
Keynote.- Ambient Intelligence 2.0: Towards Synergetic Prosperity.- Sensing.- Behavior Analysis Based on Coordinates of Body Tags.- MobiDiC: Context Adaptive Digital Signage with Coupons.- Slice&Dice: Recognizing Food Preparation Activities Using Embedded Accelerometers.- Reasoning and Sensing.- The Ambient Tag Cloud: A New Concept for Topic-Driven Mobile Urban Exploration.- Constructing Topological Maps of Displays with 3-D Positioning Information.- Activity Recognition for Personal Time Management.- Getting Places: Collaborative Predictions from Status.- Ambient Technology.- Place Enrichment by Mining the Web.- Sensor-Based Human Activity Recognition in a Multi-user Scenario.- Amelie: A Recombinant Computing Framework for Ambient Awareness.- Bug-Free Sensors: The Automatic Verification of Context-Aware TinyOS Applications.- Semi-automatic Story Creation System in Ubiquitous Sensor Environment.- SAGE: A Logical Agent-Based Environment Monitoring and Control System.- Using Video with Active Markers.- Ambient Assisted Living.- An Event-Driven Approach to Activity Recognition in Ambient Assisted Living.- EMon: Embodied Monitorization.- Interoperation Modeling for Intelligent Domotic Environments.- Intertwining Implicit and Explicit Awareness of Wellbeing to Support Peace of Mind and Connectedness.- NICA: Natural Interaction with a Caring Agent.- Applications and Studies.- Ambient Rabbits Likeability of Embodied Ambient Displays.- Contextual Interaction Design: The Case of Pause Buddy.- Creating a Development Support Bubble for Children.- I Bet You Look Good on the Wall: Making the Invisible Computer Visible.- AmIQuin - An Ambient Mannequin for the Shopping Environment.- Designing an Awareness Display for Senior Home Care Professionals.- Methods and Tools.- A Framework to Develop Persuasive Smart Environments.- Measuring the Response Bias Induced by an Experience and Application Research Center.- The Assisted User-Centred Generation and Evaluation of Pervasive Interfaces.- Reasoning and Adaptation.- Increased Robustness in Context Detection and Reasoning Using Uncertainty Measures: Concept and Application.- Synthetic Training Data Generation for Activity Monitoring and Behavior Analysis.- Adaptive User Profiles in Pervasive Advertising Environments. Document type: Part of book or chapter of book
Abstract
Keynote.- Ambient Intelligence 2.0: Towards Synergetic Prosperity.- Sensing.- Behavior Analysis Based on Coordinates of Body Tags.- MobiDiC: Context Adaptive Digital Signage [...]
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Improvement of MPLS Performance by Implementation of a Multi-Agent System
L. Merghem-Boulahia, R. Rahim-Amoud, D. Gaiti

Collection of open chapters of books in transport research (2005). Vol. 2005, 34

Abstract
Multi-Protocol Label Switching (MPLS) is a network layer packet forwarding technology that provides flexible circuit switched traffic engineering solutions in packet switched networks by explicit path routing. However, the actual weakness of MPLS resides in its inability to provide application-level routing intelligence, which is a fundamental component especially for voice delivery. In this paper we propose to introduce a Multi-Agent System (MAS) within the MPLS network to improve its performance. The introduction of agents takes place into the decision points in MPLS at the flow level, and distributes traffic based on the quality of service required by the type of traffic. We also propose an intelligent framework for network as well as an architecture of our agent in order to improve the efficiency of the Quality of Service (QoS) within MPLS.
Abstract
Multi-Protocol Label Switching (MPLS) is a network layer packet forwarding technology that provides flexible circuit switched traffic engineering solutions in packet switched [...]
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Simulation of Energy Consumption and Emissions from Rail Traffic
E. Lindgreen, S. Sorenson

Collection of open chapters of books in transport research (2005). Vol. 2005, 31

Abstract
This report describes the methodology used in the ARTEMIS rail emissions model. The approached used is a matrix of operating conditions, speeds and accelerations, for which basic parameters are used to calculated the resistance to motion of trains. Four types of resistance are included: rolling, aerodynamic, gravitational and acceleration. A necessary element in the calculation is the driving pattern, that is, the distribution of speeds and accelerations for typical operation.In the report, data are analyzed to provide operation condition distributions on both a spatial and temporal basis. The calculation procedure is evaluated with respect to resolution of operation conditions, and then evaluated by comparison with experimental data for a variety of passenger and goods trains. The results indicate that the energy consumption from modeling approach is valid to better that 10% for known operating characteristics. Emissions are calculated from the energy consumption using average fuel based emissions factors and electrical production emissions factors.
Abstract
This report describes the methodology used in the ARTEMIS rail emissions model. The approached used is a matrix of operating conditions, speeds and accelerations, for which [...]
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International Organization for Standardization (ISO)
N. Heath-Brown

Collection of open chapters of books in transport research (2004). Vol. 2004, 24

Abstract
Worldwide federation of national standards bodies (ISO members), whereby members (governmental and non-governmental organizations) have the right to be represented on such committees; approval of ISO procedures requires at least 75% approval by the members voting; standards are prepared by technical committees; appropriate standard to apply depends on activities of the company; â see therefore iso 9000, iso 9000-3, iso 9001, iso 9002, iso 9003, iso 10011â2.
Abstract
Worldwide federation of national standards bodies (ISO members), whereby members (governmental and non-governmental organizations) have the right to be represented on such [...]
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Cyclic Behaviour of Soils and Liquefaction Phenomena
P. Foray, D. Bonjean, H. Michallet

Collection of open chapters of books in transport research (2004). Vol. 2004, 23

Abstract
International audience; Coastal or offshore structures such as pipelines installed on the seabed are submitted to the hydrodynamic action of the waves either by a direct application of cyclic wave loads or through the cyclic movement of risers or flow lines transmitted by floating structures. In fine sandy or silty soils the cyclic loads can induce a liquefaction of the surrounding bed which can play an important part in the processes of erosion, trenching or self-burial of the pipes. A large 1 g physical model was built to study the fluid-soil-structure interaction with special emphasis on the conditions of occurrence of liquefaction around a pipe instrumented with pore pressure sensors. The experiments indicate a build up in pore pressure at the pipe-soil interface and a lateral visualisation showed a liquefaction of a soil band in the vicinity of the pipe. The penetration of the structure can be related to the phenomenon of liquefaction. Document type: Book
Abstract
International audience; Coastal or offshore structures such as pipelines installed on the seabed are submitted to the hydrodynamic action of the waves either by a direct application [...]
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Mobile networking
G. Karlsson, J. Roberts, I. Stavrakakis, A. Alves, S. Avallone, F. Boavida, S. D Antonio, M. Esposito, V. Fodor, M. Gargiulo, J. Harju, Y. Koucheryavy, F. Li, I. Marsh, I. Ivars, D. Moltchanov, E. Monteiro, A. Panagakis, A. Pescapè, G. Quadros, S. Romano, G. Ventre

Collection of open chapters of books in transport research (2004). Vol. 2004, 22

Abstract
Traffic engineering encompasses a set of techniques that can be used to control the flow of traffic in data networks. We discuss several of those techniques that have been developed during the last few years. Some techniques are focused on pure IP networks while others have been designed with emerging technologies for scalable Quality of Service (QoS) such as Differentiated Services and MPLS in mind. We first discuss traffic engineering techniques inside a single domain. We show that by using a non-linear programming formulation of the traffic engineering problem it is possible to meet the requirements of demanding customer traffic, while optimising the use of network resources, through the means of an automated provisioning system. We also extend the functionality of the traffic engineering system through policies. In the following, we discuss the techniques that can be used to control the flow of packets between domains. First, we briefly describe interdomain routing and the Border Gateway Protocol (BGP). Second, we summarise the characteristics of interdomain traffic based on measurements with two different Internet Service Providers. We show by simulations the limitations of several BGP-based traffic engineering techniques that are currently used on the Internet. Then, we discuss the utilisation of BGP to exchange QoS information between domains by using the QOS_NLRI attribute to allow BGP to select more optimum paths. Finally, we consider the multi-homing problem and analyse the current proposed IPv6 multi-homing solutions are analysed along with their impact on communication quality.
Abstract
Traffic engineering encompasses a set of techniques that can be used to control the flow of traffic in data networks. We discuss several of those techniques that have been [...]
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Social savings as a measure of the contribution of a new technology to economic growth
N. Crafts

Collection of open chapters of books in transport research (2004). Vol. 2004, 21
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Experiences Implementing Efficient Java Thread Serialization, Mobility and Persistence
S. Bouchenak, D. Hagimont, S. Krakowiak, N. De Palma, F. Boyer

Collection of open reports in transport research (2004). Vol. 2004, 12

Abstract
Today, mobility and persistence are important aspects of distributed computing- . They have many fields of use such as load balancing, fault tolerance and dynamic reconfiguration of applications. In this context, Java provides many useful mechanisms for the mobility of code via dynamic class loading, and the mobility or persistence of data via object serialization. However, Java does not provide any mechanism for the mobility/persistence of computation (i.e., threads). We designed and implemented a new mechanism, called , that is used to build thread mobility or thread persistence. Therefore, a running Java thread can, at an arbitrary state of its execution, migrate to a remote machine where it resumes its execution, or be checkpointed on disk for possible subsequent recovery. With our services, migrating a thread is simply performed by the call of our primitive, and checkpointing/recovering a thread is performed by the call of our and primitives. Several projects have recently addressed the issue of Java thread serialization, e.g., Sumatra, Wasp, JavaGo, Brakes, JavaGoX, Merpati. Some of them have attempted to minimize the overhead incurred by the thread serialization mechanism on thread performance, but none of them has been able to completely avoid this overhead. We propose a generic Java thread serialization mechanism that does not impose any performance overhead on serialized threads. This is achieved thanks to the use of type inference and dynamic de-optimization techniques. In this paper, we describe the design and implementation details of our thread serialization prototype in Sun Microsystems' JDK. We report on experiments conducted with our prototype, present a comparative performance evaluation of the main thread serialization techniques, and confirm the elimination of the performance overhead with our thread serialization mechanism. Document type: Report
Abstract
Today, mobility and persistence are important aspects of distributed computing- . They have many fields of use such as load balancing, fault tolerance and dynamic reconfiguration [...]
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Shared communications volume 1 a summary and literature review
O. Franzese

Collection of open reports in transport research (2004). Vol. 2004, 11

Abstract
This paper provides a review of examples from the literature of shared communication resources and of agencies and/or organizations that share communication resources. The primary emphasis is on rural, intelligent transportation system communications involving transit. Citations will not be limited, however, to rural activities, or to ITS implementation, or even to transit. In addition, the term ''communication'' will be broadly applied to include all information resources. Literature references to issues that contribute to both successful and failed efforts at sharing communication resources are reviewed. The findings of this literature review indicate that: (1) The most frequently shared communication resources are information/data resources, (2) Telecommunications infrastructure and technologies are the next most frequently shared resources, (3) When resources are successfully shared, all parties benefit, (4) A few unsuccessful attempts of sharing resources have been recorded, along with lessons learned, (5) Impediments to sharing include security issues, concerns over system availability and reliability, service quality and performance, and institutional barriers, (6) Advantages of sharing include financial benefits to agencies from using shared resources and benefits to the public in terms of congestion mitigation, information transfer (e.g., traveler information systems), mobility (e.g., welfare-to-work paratransit), and safety (e.g., speed of incident response, incident avoidance),moreÂ Â» (7) Technology-based solutions exist to address technology-based concerns, and (8) Institutional issues can be addressed through leadership, enhanced knowledge and skills, open communication, responsiveness, and attractive pricing structures.Â«Â le Document type: Report
Abstract
This paper provides a review of examples from the literature of shared communication resources and of agencies and/or organizations that share communication resources. The [...]
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Performance Modeling for 3D Visualization in a Heterogeneous Computing Environment
J. Shalf, K. Ma, W. Bethel, I. Bowman

Collection of open reports in transport research (2004). Vol. 2004, 10

Abstract
The visualization of large, remotely located data sets necessitates the development of a distributed computing pipeline in order to reduce the data, in stages, to a manageable size. The required baseline infrastructure for launching such a distributed pipeline is becoming available, but few services support even marginally optimal resource selection and partitioning of the data analysis workflow. We explore a methodology for building a model of overall application performance using a composition of the analytic models of individual components that comprise the pipeline. The analytic models are shown to be accurate on a testbed of distributed heterogeneous systems. The prediction methodology will form the foundation of a more robust resource management service for future Grid-based visualization applications. Document type: Report
Abstract
The visualization of large, remotely located data sets necessitates the development of a distributed computing pipeline in order to reduce the data, in stages, to a manageable [...]
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Applying simple technology accomplishes visual inspection challenges
C. ROBINSON

Collection of open reports in transport research (2004). Vol. 2004, 9

Abstract
This paper discusses the successful implementation of simple video technologies at the Savannah River Site (SRS) to perform complex visual inspection, monitoring, and surveillance tasks. The constraints and challenges associated with remote viewing are discussed, and examples of applications are given. Work at SRS involves many radioactive, hazardous, and remote operations and activities, which require monitoring or surveillance. As well, many facilities, including tanks, cells, and pipelines, require inspections but are inaccessible to humans. SRTC supports SRS in these situations by applying simple remote viewing technologies to address these issues and accomplish monitoring and inspection goals. Document type: Report
Abstract
This paper discusses the successful implementation of simple video technologies at the Savannah River Site (SRS) to perform complex visual inspection, monitoring, and surveillance [...]
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Realtime monitoring of pipelines for third party contact
N. Burkhardt, N. Crouch, N. Fisher

Collection of open reports in transport research (2004). Vol. 2004, 8

Abstract
Third-party contact with pipelines (typically caused by contact with a digging or drilling device) can result in mechanical damage to the pipe, in addition to coating damage that can initiate corrosion. Because this type of damage often goes unreported and can lead to eventual catastrophic failure of the pipe, a reliable, cost-effective method is needed for monitoring and reporting third-party contact events. The impressed alternating cycle current (IACC) pipeline monitoring method consists of impressing electrical signals on the pipe by generating a time-varying voltage between the pipe and the soil at periodic locations where pipeline access is available. The signal voltage between the pipe and ground is monitored continuously at receiving stations located some distance away. Third-party contact to the pipe that breaks through the coating changes the signal received at the receiving stations. In this project, the IACC monitoring method is being developed, tested, and demonstrated. Work performed to date includes (1) a technology assessment, (2) development of an IACC model to predict performance and assist with selection of signal operating parameters, (3) investigation of potential interactions with cathodic protection systems, and (4) experimental measurements on operating pipelines. Based on information recently found in published studies, it is believed that the operation of IACC on a pipeline will cause no interference with CP systems. Initial results on operating pipelines showed that IACC signals could be successfully propagated over a distance of 3.5 miles, and that simulated contact can be detected up to a distance of 1.4 miles, depending on the pipeline and soil conditions. Document type: Report
Abstract
Third-party contact with pipelines (typically caused by contact with a digging or drilling device) can result in mechanical damage to the pipe, in addition to coating damage [...]
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Development of nonlinear harmonic sensors for detection of mechanical damage
A. Dean, N. Dean, N. Aron, A. Crouch, C. Torres, N. Torres, J. Aron, N. Crouch

Collection of open reports in transport research (2004). Vol. 2004, 7

Abstract
In a joint effort with Tuboscope Pipeline Services of Houston, Texas, Southwest Research Institute (SwRI) adapted its nonlinear harmonic (NLH) sensing technology for use on a new in-line inspection system (smart pig). Nonlinear harmonics, an AC magnetic method for detecting local anomalies of stress and plastic deformation, shows promise of improved characterization of mechanical damage defects such as gouged dents, even though the dents may have re-rounded. The SwRI-Tuboscope project produced a sensor design, electronic design, and sensor suspension design that are directly adaptable to a multitechnology ILI system. This report describes the NLH method, the sensor, circuit, and suspension designs, and shows results from the supporting laboratory work. Document type: Report
Abstract
In a joint effort with Tuboscope Pipeline Services of Houston, Texas, Southwest Research Institute (SwRI) adapted its nonlinear harmonic (NLH) sensing technology for use on [...]
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Internal repair of pipelines
N. Bruce, N. Porter, N. Ritter, N. Boring, N. Lozev, N. Harris, N. Mohr, N. Harwig, N. Gordon, N. Neary, N. Sullivan

Collection of open reports in transport research (2004). Vol. 2004, 6

Abstract
The two broad categories of fiber-reinforced composite liner repair and deposited weld metal repair technologies were reviewed and evaluated for potential application for internal repair of gas transmission pipelines. Both are used to some extent for other applications and could be further developed for internal, local, structural repair of gas transmission pipelines. Principal conclusions from a survey of natural gas transmission industry pipeline operators can be summarized in terms of the following performance requirements for internal repair: (1) Use of internal repair is most attractive for river crossings, under other bodies of water, in difficult soil conditions, under highways, under congested intersections, and under railway crossings. (2) Internal pipe repair offers a strong potential advantage to the high cost of horizontal direct drilling when a new bore must be created to solve a leak or other problem. (3) Typical travel distances can be divided into three distinct groups: up to 305 m (1,000 ft.); between 305 m and 610 m (1,000 ft. and 2,000 ft.); and beyond 914 m (3,000 ft.). All three groups require pig-based systems. A despooled umbilical system would suffice for the first two groups which represents 81% of survey respondents. The third group would require an onboard self-contained power unit for propulsion and welding/liner repair energy needs. (4) The most common size range for 80% to 90% of operators surveyed is 508 mm (20 in.) to 762 mm (30 in.), with 95% using 558.8 mm (22 in.) pipe. Evaluation trials were conducted on pipe sections with simulated corrosion damage repaired with glass fiber-reinforced composite liners, carbon fiber-reinforced composite liners, and weld deposition. Additional un-repaired pipe sections were evaluated in the virgin condition and with simulated damage. Hydrostatic failure pressures for pipe sections repaired with glass fiber-reinforced composite liner were only marginally greater than that of pipe sections without liners, indicating that this type of liner is only marginally effective at restoring the pressure containing capabilities of pipelines. Failure pressures for larger diameter pipe repaired with a semi-circular patch of carbon fiber-reinforced composite lines were also marginally greater than that of a pipe section with un-repaired simulated damage without a liner. These results indicate that fiber reinforced composite liners have the potential to increase the burst pressure of pipe sections with external damage Carbon fiber based liners are viewed as more promising than glass fiber based liners because of the potential for more closely matching the mechanical properties of steel. Pipe repaired with weld deposition failed at pressures lower than that of un-repaired pipe in both the virgin and damaged conditions, indicating that this repair technology is less effective at restoring the pressure containing capability of pipe than a carbon fiber-reinforced liner repair. Physical testing indicates that carbon fiber-reinforced liner repair is the most promising technology evaluated to-date. The first round of optimization and validation activities for carbon-fiber repairs are complete. Development of a comprehensive test plan for this process is recommended for use in the field trial portion of this program. Document type: Report
Abstract
The two broad categories of fiber-reinforced composite liner repair and deposited weld metal repair technologies were reviewed and evaluated for potential application for [...]
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FIELD DEMONSTRATION OF A MEMBRANE PROCESS TO RECOVER HEAVY HYDROCARBONS AND TO REMOVE WATER FROM NATURAL GAS
N. Hofmann, R. Baker, K. Lokhandwala, N. Lokhandwala, T. Hofmann, N. Baker, N. Group, N. Kaschemekat, N. Group, N. Group

Collection of open reports in transport research (2004). Vol. 2001, 5

Abstract
The objective of this project is to design, construct and field demonstrate a 3-MMscfd membrane system to recover natural gas liquids (NGL) and remove water from raw natural gas. An extended field test to demonstrate system performance under real-world conditions is required to convince industry users of the efficiency and reliability of the process. The system will be designed and fabricated by Membrane Technology and Research, Inc. (MTR) and then installed and operated at British Petroleum (BP)-Amoco's Pascagoula, MS plant. The Gas Research Institute will partially support the field demonstration and BP-Amoco will help install the unit and provide onsite operators and utilities. The gas processed by the membrane system will meet pipeline specifications for dewpoint and Btu value and can be delivered without further treatment to the pipeline. Based on data from prior membrane module tests, the process is likely to be significantly less expensive than glycol dehydration followed by propane refrigeration, the principal competitive technology. At the end of this demonstration project the process will be ready for commercialization. The route to commercialization will be developed during this project and may involve collaboration with other companies already servicing the natural gas processing industry. Document type: Report
Abstract
The objective of this project is to design, construct and field demonstrate a 3-MMscfd membrane system to recover natural gas liquids (NGL) and remove water from raw natural [...]
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Temporary losses of highway capacity and impacts on performance phase 2
S. Chin, S. Chin

Collection of open reports in transport research (2004). Vol. 2004, 4

Abstract
Traffic congestion and its impacts significantly affect the nation's economic performance and the public's quality of life. In most urban areas, travel demand routinely exceeds highway capacity during peak periods. In addition, events such as crashes, vehicle breakdowns, work zones, adverse weather, railroad crossings, large trucks loading/unloading in urban areas, and other factors such as toll collection facilities and sub-optimal signal timing cause temporary capacity losses, often worsening the conditions on already congested highway networks. The impacts of these temporary capacity losses include delay, reduced mobility, and reduced reliability of the highway system. They can also cause drivers to re-route or reschedule trips. Such information is vital to formulating sound public policies for the highway infrastructure and its operation. In response to this need, Oak Ridge National Laboratory, sponsored by the Federal Highway Administration (FHWA), made an initial attempt to provide nationwide estimates of the capacity losses and delay caused by temporary capacity-reducing events (Chin et al. 2002). This study, called the Temporary Loss of Capacity (TLC) study, estimated capacity loss and delay on freeways and principal arterials resulting from fatal and non-fatal crashes, vehicle breakdowns, and adverse weather, including snow, ice, and fog. In addition, it estimated capacity lossmoreÂ Â» and delay caused by sub-optimal signal timing at intersections on principal arterials. It also included rough estimates of capacity loss and delay on Interstates due to highway construction and maintenance work zones. Capacity loss and delay were estimated for calendar year 1999, except for work zone estimates, which were estimated for May 2001 to May 2002 due to data availability limitations. Prior to the first phase of this study, which was completed in May of 2002, no nationwide estimates of temporary losses of highway capacity by type of capacity-reducing event had been made. This report describes the second phase of the TLC study (TLC2). TLC2 improves upon the first study by expanding the scope to include delays from rain, toll collection facilities, railroad crossings, and commercial truck pickup and delivery (PUD) activities in urban areas. It includes estimates of work zone capacity loss and delay for all freeways and principal arterials, rather than for Interstates only. It also includes improved estimates of delays caused by fog, snow, and ice, which are based on data not available during the initial phase of the study. Finally, computational errors involving crash and breakdown delay in the original TLC report are corrected.Â«Â le Document type: Report
Abstract
Traffic congestion and its impacts significantly affect the nation's economic performance and the public's quality of life. In most urban areas, travel demand routinely exceeds [...]
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Advanced compressor engine controls to enhance operation reliability and integrity
N. Bourn, N. Gingrich, N. Smith

Collection of open reports in transport research (2004). Vol. 2004, 3

Abstract
This document provides a mid-term update for the ''Advanced Compressor Engine Controls to Enhance Operation, Reliability, and Integrity'' project. SwRI is conducting this project for DOE in conjunction with Cooper Energy Services, under DOE contract number DE-FC26-03NT41859. The objective of this one-year project is to develop, evaluate, and demonstrate advanced engine control technologies and hardware, specifically, closed-loop NO{sub x} emissions control on a two-stroke integral reciprocating engine/compressor used for pipeline gas transmission service. This work uses a Cooper-Bessemer GMVH-6 laboratory engine owned by Cooper Energy Services (CES) and installed in a test facility at Southwest Research Institute (SwRI). The gas transmission industry operates over 4,000 integral engine compressors, the majority being two-stroke, with a median age of 45 years and a median size of 2000 horsepower. These engines have historically exhibited poor performance and high emissions, due in part to poor engine control. The end results are misfires and partial burns that lead to increased fuel usage and exhaust emissions. Many of the slow-speed integral engines in the gas compression industry utilize control systems that are outdated, slow, and suffer from poor resolution. Research into more advanced control systems for integral compressor engines has increased tremendously in recent years. ThemoreÂ Â» recent advancements in control logic are being reviewed and analyzed in this program to understand the effectiveness of each. In addition, the application of a real-time NO{sub x} sensor feedback for closed-loop control is being investigated. To date, the strategies involving fuel/air equivalence ratio for a NO{sub x} prediction algorithm have been reviewed and analyzed. A hierarchy of control strategies will be outlined at the conclusion of this program. This hierarchy will range from the simplest and least expensive closed-loop control to an advanced system utilizing individual cylinder control. The ultimate control strategy is thought to be one that integrates both compressor and engine control, with the engine control based on individual power cylinders. The hierarchy of engine control may be desirable for the variety of engines in various locations that are subject to varying regulated levels of NO{sub x} emissions. The engines in non-attainment areas will require the maximum level of complexity in engine controls.Â«Â le Document type: Report
Abstract
This document provides a mid-term update for the ''Advanced Compressor Engine Controls to Enhance Operation, Reliability, and Integrity'' project. SwRI is conducting this [...]
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Sealing simulated leaks
M. Romano, N. Romano

Collection of open reports in transport research (2004). Vol. 2004, 2

Abstract
This report details the testing equipment, procedures and results performed under Task 7.2 Sealing Simulated Leaks. In terms of our ability to seal leaks identified in the technical topical report, Analysis of Current Field Data, we were 100% successful. In regards to maintaining seal integrity after pigging operations we achieved varying degrees of success. Internal Corrosion defects proved to be the most resistant to the effects of pigging while External Corrosion proved to be the least resistant. Overall, with limitations, pressure activated sealant technology would be a viable option under the right circumstances. Document type: Report
Abstract
This report details the testing equipment, procedures and results performed under Task 7.2 Sealing Simulated Leaks. In terms of our ability to seal leaks identified in the [...]
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Introduction to urban simulation design and development of operational models
G. Ulfarsson, P. Waddell

Collection of open chapters of books in transport research (2004). Vol. 2004, 20

Abstract
This chapter has sought to explain the context, policy applications, and major design choices in the process of developing an operational urban simulation model, with specific reference to UrbanSim as a case study. It has been argued that careful design at each stage of the process is needed to make the model sensitive to the policies of principal concern, to make the data and computational requirements manageable, to make the model usable by staff and other users with appropriate levels of training, and to fit into the operational practices of the relevant organizations. To be useful (relevant) in the policy process, model design should carefully integrate the elements discussed in the chapter into a design that fits well into a specific institutional and political context, and evolve to adapt to changing conditions. This introduction to the design process sets the stage for more in-depth discussion of specification and operational issues in model use. The UrbanSim system is being further developed to adapt to varying data availability, different factors influencing agent choices in locations ranging from newer and rapidly growing US metropolitan areas in other parts of the world. Considerable effort is now being devoted to developing environmental components of the system such as land cover change, and to developing a robust interface and tools for visualization and evaluation of policy scenarios. Document type: Part of book or chapter of book
Abstract
This chapter has sought to explain the context, policy applications, and major design choices in the process of developing an operational urban simulation model, with specific [...]
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Wissenschaftlicher Nachwuchs in Europa
J. Enders

Collection of open chapters of books in transport research (2005). Vol. 2005, 26

Abstract
Der Autor beschreibt zunächst die veränderten Rahmenbedingungen und Erwartungen zur Nachwuchsförderung an den europäischen Hochschulen: Es geht dabei "um die Bedingungen der Nachwuchsförderung in der Massenuniversität, Veränderungen auf den Arbeitsmärkten für Nachwuchswissenschaftler, Veränderungen der Erwartungen an die Funktion der Forschung in der 'Wissensgesellschaft', sowie die Internationalisierung der Nachwuchsförderung. In einem zweiten Schritt werden einige Aspekte der Reorganisation der Nachwuchsförderung" und ihrer zunehmenden politischen Steuerung thematisiert. (DIPF/Orig./av) Document type: Part of book or chapter of book
Abstract
Der Autor beschreibt zunächst die veränderten Rahmenbedingungen und Erwartungen zur Nachwuchsförderung an den europäischen Hochschulen: Es geht dabei "um die Bedingungen [...]
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Some Observations of Internet Stream Lifetimes
N. Brownlee

Collection of open chapters of books in transport research (2005). Vol. 2005, 22

Abstract
We present measurements of stream lifetimes for Internet traffic on a backbone link in California and a university link in Auckland. We investigate the consequences of sampling techniques such as ignoring streams with six or fewer packets, since they usually account for less than 10% of the total bytes. We find that we often observe large bursts of small attack' streams, which will diminish the integrity of strategies that focus on the elephants'. Our observations further demonstrate the danger of traffic engineering approaches based on incorrect assumptions about the nature of the traffic. Document type: Part of book or chapter of book
Abstract
We present measurements of stream lifetimes for Internet traffic on a backbone link in California and a university link in Auckland. We investigate the consequences of sampling [...]
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Activities in Space and Time
H. Miller

Collection of open chapters of books in transport research (2004). Vol. 2004, 14

Abstract
This chapter discusses theories and methods for analyzing the interrelationship of human activities in space and time, focusing on time geography; and elegant and powerful framework. The relevance of time geography for analyzing real world transportation and communication systems has improved tremendously in recent years with the rise of geographic information technologies such as geographic information systems (GIS) and the global positioning system (GPS). At the same time, information technologies such the Internet and mobile telephone have drastically altered the relationships between geo-space and time in the real world, creating fascinating and imperative research challenges. The new time geography has great potential for guiding land use and transportation systems toward more livable and sustainable outcomes. Document type: Part of book or chapter of book
Abstract
This chapter discusses theories and methods for analyzing the interrelationship of human activities in space and time, focusing on time geography; and elegant and powerful [...]
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Verkennende ecologische gebiedsvisie van het kanaal Gent-Brugge en omgeving
A. Kerckvoorde, L. Martens, K. Decleer

Collection of open chapters of books in transport research (2005). Vol. 2005, 13

Abstract
Document type: Book
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Spatial equilibration in transport networks
A. Nagurney

Collection of open chapters of books in transport research (2004). Vol. 2004, 12

Abstract
This chapter traced the evolution of the foundations of transport network equilibrium modeling and analysis, with a focus on the principle methodological advances. In particular, an attempt has been made to set out in accessible fashion rigorous approaches to the formulation of a variety of traffic network equilibrium models and to establish relationships between the models as well as those that are closely linked such as spatial price equilibrium models. It should be emphasized that this topic is a very active area of research as well as practice. It should also be highlighted and further emphasized that traffic network equilibrium modeling and analysis provide a powerful framework for decision-making on complex networks. Indeed, given the interrelationships between telecommunications and transportation networks in todays network economy, it can be expected further synergies and advances in the study of such foundational networks. Of particular promise are the areas of multicriteria decision-making on networks, multitiered networks, as well as multilevel networks (in the form of transportation/logistical/financial/informational networks), formally referred to as supernetworks. Document type: Part of book or chapter of book
Abstract
This chapter traced the evolution of the foundations of transport network equilibrium modeling and analysis, with a focus on the principle methodological advances. In particular, [...]
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Processor sharing flows in the internet
M. Kobayashi, N. McKeown, M. Kobayashi, R. Zhang-Shen, N. Dukkipati, N. Dukkipati, N. McKeown, R. Zhang-Shen

Collection of open chapters of books in transport research (2005). Vol. 2005, 9

Abstract
Most congestion control algorithms try to emulate processor sharing (PS) by giving each competing flow an equal share of a bottleneck link. This approach leads to fairness, and prevents long flows from hogging resources. For example, if a set of flows with the same round trip time share a bottleneck link, TCPs congestion control mechanism tries to achieve PS; so do most of the proposed alternatives, such as eXplicit Control Protocol (XCP). But although they emulate PS well in a static scenario when all flows are long-lived, they do not come close to PS when new flows arrive randomly and have a finite amount of data to send, as is the case in todays Internet. Typically, flows take an order of magnitude longer to complete with TCP or XCP than with PS, suggesting large room for improvement. And so in this paper, we explore how a new congestion control algorithm Rate Control Protocol (RCP) comes much closer to emulating PS over a broad range of operating conditions. In RCP, a router assigns a single rate to all flows that pass through it. The router does not keep flow-state, and does no per-packet calculations. Yet we are able to show that under a wide range of traffic characteristics and network conditions, RCPs performance is very close to ideal processor sharing. Document type: Part of book or chapter of book
Abstract
Most congestion control algorithms try to emulate processor sharing (PS) by giving each competing flow an equal share of a bottleneck link. This approach leads to fairness, [...]
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European Perspectives on a New Fiscal Framework for Transport
S. Potter, G. Parkhurst, B. Lane

Collection of open chapters of books in transport research (2005). Vol. 2005, 8

Abstract
This chapter presents an overview of changes in transport taxation in European countries to promote more sustainable transport. A number of changes in the framework of car taxation have resulted in some useful environmental gains. However, these changes are limited because the transport tax system has been designed to produce a substantial income from internal-combustion-engine vehicles in an easily administered form. A major restructuring of transport taxation is required to fully address a different goal that of stimulating improvements to environmental performance. A generalised road user charging-based system could be the way forward. Such a system is now seen by several European countries and some USA states as the transport taxation regime for the 21st century. \\ud \\ud Tax regime change is emerging onto the transport policy agenda as a vital long-term strategy. Largely by default, transport policy-makers are coming to realise that road taxation regime change is inevitable if traffic and congestion management is to be a reality. The way we taxed vehicles and fuel in the 20th century is simply not appropriate for the transport challenges we face today. Document type: Part of book or chapter of book
Abstract
This chapter presents an overview of changes in transport taxation in European countries to promote more sustainable transport. A number of changes in the framework of car [...]
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Intelligent Features Within the J-Sim Simulation Environment
N. Meskaoui, N. Meskaoui, D. Gaiti, K. Kabalan, N. Meskaoui, D. Gaiti, K. Kabalan

Collection of open chapters of books in transport research (2004). Vol. 2004, 4

Abstract
International audience; This paper presents our approach integrating a high level of intelligence within telecommunication networks. Artificial intelligence has proved its efficiency in resolving complex issues in different fields like air traffic control, robotics, and medical diagnosis. However its usage in telecommunication networks is still very moderated. The main objectives of our framework is to encourage the deployment of techniques characterized by a high level of intelligence – inspired from the artificial intelligence domain in networking. For this reason, we build an extension, with intelligent capabilities, to the J-Sim simulation environment. This extension proposes an intelligent package having the essential entities required for simulating intelligent features. Using this intelligent package and the abstract node model (INET) proposed by J-Sim for network simulations, it will be possible to test the efficiency of integrating intelligent techniques in networking. Document type: Part of book or chapter of book
Abstract
International audience; This paper presents our approach integrating a high level of intelligence within telecommunication networks. Artificial intelligence has proved its [...]
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Urban Transport in Chennai and Bangalore
S. Mitric, I. Chatterton

Collection of open chapters of books in transport research (2004). Vol. 2004, 2

Abstract
This report is intended to facilitate the discussions between the World Bank and the Governments of Tamil Nadu and Karnataka, City Governments of Chennai and Bangalore, on possibly expanding the Bank's urban transport assistance in these two cities, and elsewhere in the two states. The report consists of a diagnostic chapter, a discussion of pivotal issues, a reformulated strategy, and a menu of possible Bank-funded projects to support this strategy. Case studies of urban transport in Chennai and Bangalore, the basis for the report, are attached. Document type: Book
Abstract
This report is intended to facilitate the discussions between the World Bank and the Governments of Tamil Nadu and Karnataka, City Governments of Chennai and Bangalore, on [...]
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CFD analysis of the roll movement of a container ship
J. García-Espinosa, E. Oñate, J. Helmers, M. Chakkor

Revista de Ingeniería Naval (2004). Vol. 814, pp. 104-108

Abstract
In the present work a novel approach has been developed for the resolution of this problem of analysis of the movement of roll of a ship. The methodology used for this is based on the modification of the differential equations of the fluid dynamics (RANSE equations), including the movement of the free surface, by applying the finite calculus method. The modified equations are solved using an implicit predictor-corrector scheme and the finite element method (FEM). This resolution scheme is considered optimal for these types of problems, both in accuracy and in calculation time. As an example, it should be noted that for typical problems (more than 1,000,000 finite elements) less than 4 hours of CPU are required to solve several cycles of ship movement (Pentium IV). This allows the analysis of an array of tests in a few days or even hours, having a computer network or sufficient computing power.
Abstract
In the present work a novel approach has been developed for the resolution of this problem of analysis of the movement of roll of a ship. The methodology used for this is [...]
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Accurate upper and lower error bounds by solving flux-free local problems in “stars”
P. Diez, N. Parés, A. Huerta

European Journal of Finite Elements (2004). Vol. 13 (5-7), pp. 497-507

Abstract
Two implicit residual type estimators yielding upper bounds of the error are presented which do not require flux equilibration. One of them is based on the ideas introduced in [MAC 00, CAR 99, MOR 03, PRU 02]. The new approach introduced here is based on using the estimated error function rather than the estimated error norms. Once the upper bounds are computed, also lower bounds for the error are obtained with little supplementary effort.
Abstract
Two implicit residual type estimators yielding upper bounds of the error are presented which do not require flux equilibration. One of them is based on the ideas introduced [...]
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Error estimates for an operator-splitting method for incompressible flows
J. Blasco, R. Codina

Applied Numerical Mathematics (2004). Vol. 51 (1), pp. 1-17

Abstract
In this paper we provide an error analysis of a fractional-step method for the numerical solution of the incompressible Navier–Stokes equations. Under mild regularity assumptions on the continuous solution, we obtain first order error estimates in the time step size, both for the intermediate and the end-of-step velocities of the method; we also give some error estimates for the pressure solution.
Abstract
In this paper we provide an error analysis of a fractional-step method for the numerical solution of the incompressible Navier–Stokes equations. Under mild regularity [...]
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A finite element model for the simulation of lost foam casting
G. Houzeaux, R. Codina

Int. J. Numer. Meth. Fluids (2004). Vol. 46 (2), pp. 203-226

Abstract
In this paper, we present a numerical model to simulate lost foam casting processes. We first introduce this particular casting in order to catch the different physical processes in play during a casting. We also briefly comment on the possible physical and numerical models to envisage the numerical simulation. Next we present a model which aims at solving “part of” the complexities of the casting, together with a simple energy budget that enables to obtain an equation for the velocity of the metal front advance. Once the physical model is established we develop a finite element method to solve the governing equations. The numerical and physical methodologies are then validated through the solution of a two and a three-dimensional example. Finally, we briefly discuss some possible improvements of the numerical model in order to catch more physical phenomena.
Abstract
In this paper, we present a numerical model to simulate lost foam casting processes. We first introduce this particular casting in order to catch the different physical processes [...]
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Approximation of the incompressible Navier–Stokes equations using orthogonal subscale stabilization and pressure segregation on anisotropic finite element meshes
R. Codina, O. Soto

Comput. Methods Appl. Mech. Engrg., (2004). Vol. 193 (15-16), pp. 1403-1419

Abstract
This paper describes a finite element model to solve the incompressible Navier–Stokes equations based on the stabilization with orthogonal subscales and a pressure segregation. The former consists of adding a least-square form of the component orthogonal to the finite element space of the convective and pressure gradient terms; this allows to deal with convection-dominated flows and to use equal velocity–pressure interpolation. The pressure segregation is inspired in fractional step schemes, although the converged solution corresponds to that of a monolithic time integration. Likewise, we put special emphasis on the use of anisotropic grids. In particular, we describe some possible choices for the calculation of the element length that appears in the stabilization parameters and check their behavior in two classical numerical examples. The preconditioning strategy used to solve the resulting algebraic system for very anisotropic meshes is also briefly described.
Abstract
This paper describes a finite element model to solve the incompressible Navier–Stokes equations based on the stabilization with orthogonal subscales and a pressure segregation. [...]
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A stabilized finite element predictor–corrector scheme for the incompressible Navier–Stokes equations using a nodal‐based implementation
R. Codina, A. Folch

Int. J. Numer. Meth. Fluids (2004). Vol. 44 (5), pp. 483-503

Abstract
A finite element model to solve the incompressible Navier–Stokes equations based on the stabilization with orthogonal subscales, a predictor–corrector scheme to segregate the pressure and a nodal based implementation is presented in this paper. The stabilization consists of adding a least‐squares form of the component orthogonal to the finite element space of the convective and pressure gradient terms, which allows to deal with convection‐dominated flows and to use equal velocity–pressure interpolation. The pressure segregation is inspired in fractional step schemes, although the converged solution corresponds to that of a monolithic time integration. Finally, the nodal‐based implementation is based on an a priori calculation of the integrals appearing in the formulation and then the construction of the matrix and right‐hand side vector of the final algebraic system to be solved. After appropriate approximations, this matrix and this vector can be constructed directly for each nodal point, without the need to loop over the elements and thus making the calculations much faster. Some issues related to this implementation for fractional step and our predictor–corrector scheme, which is the main contribution of this paper, are discussed
Abstract
A finite element model to solve the incompressible Navier–Stokes equations based on the stabilization with orthogonal subscales, a predictor–corrector scheme to [...]
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A Dirichlet/Neumann domain decomposition method for incompressible turbulent flows on overlapping subdomains
G. Houzeaux, R. Codina

Computers and Fluids (2004). Vol. 33 (5-6), pp. 771-782

Abstract
When one wants to simulate flows with moving bodies and when there is no possible way of prescribing simple boundary conditions in any frame of reference, one possibility is the use of domain decomposition methods. The domain decomposition method we present in this work aims at coupling overlapping subdomains in relative motion using a Dirichlet/Neumann coupling. The method is applied to the solution of incompressible and turbulent flows.
Abstract
When one wants to simulate flows with moving bodies and when there is no possible way of prescribing simple boundary conditions in any frame of reference, one possibility [...]
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Discrete element modelling and simulation of sand mould manufacture for the lost foam process
J. Rojek, F. Zárate, C. Agelet de Saracibar, C. Gilbourne, P. Verdot

Int. J. Numer. Meth. Engng. (2004). Vol. 62 (11), pp. 1241-1441

Abstract
This paper presents a numerical model of mould manufacture for the lost foam casting process. The process of mould filling with sand and sand compaction by vibration are modelled using spherical (in 3D) or cylindrical (in 2D) discrete elements. The motion of discrete elements is described by means of equations of rigid body dynamics. Rigid particles interact among one another with contact forces, both in normal and tangential directions. Numerical simulation predicts defects of the mould due to insufficient sand compaction around the pattern. Combining the discrete element model of sand with the finite element model of the pattern allows us to detect possible distortion of the pattern during mould filling and compaction. Results of numerical simulation are validated by comparison with experimental data.
Abstract
This paper presents a numerical model of mould manufacture for the lost foam casting process. The process of mould filling with sand and sand compaction by vibration are modelled [...]
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Shear band localization via local J2 continuum damage mechanics
M. Cervera, M. Chiumenti, C. Agelet de Saracibar

Comput. Methods Appl. Mech. Engrg., (2004). Vol. 193 (9-11), pp. 849-880

Abstract
This paper describes a novel formulation for the solution of problems involving shear band localization using a local isotropic J2 continuum damage model and mixed linear simplex (triangles and tetrahedra). Stabilization methods are used to ensure existence and uniqueness of the solution, attaining global and local stability of the corresponding discrete finite element formulation. Consistent residual viscosity is used to enhance robustness and convergence of the formulation. Implementation and computational aspects are also discussed. A simple isotropic local J2 damage constitutive model is considered, either with linear or exponential softening. The softening modulus is regularized according to the material mode II fracture energy and the element size. Numerical examples show that the formulation derived is fully stable and remarkably robust, totally free of volumetric locking and spurious oscillations of the pressure. As a consequence, the results obtained do not suffer from spurious mesh-size or mesh-bias dependence, comparing very favourably with those obtained with the ill-posed standard approaches.
Abstract
This paper describes a novel formulation for the solution of problems involving shear band localization using a local isotropic J2 continuum damage model and mixed linear [...]
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Development of local models and their computational implementation for polymer coated steel sheets
J. Rojek, M. Luege, E. Oñate

(2004). Research Report, Nº PI265

Abstract
This report present review of the state of the art of numerical modelling of polymers and polymer coated metal laminates and gives details of selected numerical models including those that will be used in the work in the project POLYCOAT. The first sections studied in the project. Basic mechanical and thermal properties of the polymers are reviewed. Then constitutive models developed for polymers are reviewed based on literature and own work. Details of selected models are given. Deformation behaviour of polymer coated metal laminates is considered with special attention to the phenomena observed at the polymer-metal interface. The numerical models for the interface are presented finally.
Abstract
This report present review of the state of the art of numerical modelling of polymers and polymer coated metal laminates and gives details of selected numerical models including [...]
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El valor del cálculo en los sistemas de ayuda a la toma de decisiones en ingeniería
E. Oñate

Revista de Obras Públicas (2004). Vol. 151 (3449), pp. 41-48

Abstract
El artículo revindica el valor de los métodos de cálculo que se enseñan en las Escuelas de Ingeniería, como herramientas indispensables en los nuevos sistemas de ayuda a la toma de decisiones (SAD). Los SAD integran base de datos, métodos de cálculo y módulos de inteligencia artificial, y su utilización se extiende cada día más para ayuda al diseño y gestión de infraestructuras y servicios de ingeniería. En el texto se describen varios desarrollos y aplicaciones recientes de SAD en ingeniería civil. El artículo acaba con una reflexión sobre los límites de los SAD. The paper stresses the value of the computational methods taught in engineering faculties as indispensable tools within the new decision support systems (DSS). The DSS integrate data bases, computational methods and artificial intelligence modules. They are increasingly used for supporting the design and management of civil constructions and services in engineering. The paper describes recent developments and applications of DSS in civil engineering. The text ends up with a discussion on the limits of the DSS.
Abstract
El artículo revindica el valor de los métodos de cálculo que se enseñan en las Escuelas de Ingeniería, como herramientas indispensables [...]
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The efects of VaR position limits on endogenous price formation in financial markets
G. Peffer

(2004). Research Report, Nº PI263

Abstract
This paper sets out to study the impact that market risk limits have on the price dynamics in securities markets. We start out from a standard model in which trading patterns are determined for utility-maximising investors in non-clearing markets with a particularly simple price formation mechanism. To make trading conditions more realistic, we add borrowing and short-selling constraints and incorporate a stochastic information arrival process into the standard model. We present a VaR position limit formulation that allows us to integrate market risk limit considerations into our model and solve the respective utility maximization problems. Simulation results are then discussed which show an increase in price instability in a scenario of widespread adoption of VaR as a mechanism to limit portfolio risk.
Abstract
This paper sets out to study the impact that market risk limits have on the price dynamics in securities markets. We start out from a standard model in which trading patterns [...]
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Aplicaciones de algoritmos que conservan la energía-momentum en dinámica no-lineal
W. Matias Silva

(2004). Research Report, Nº PI259

Abstract
En este trabajo se estudia los algoritmos de integración en el tiempo que se basan en el método α generalizado. Para realizar dicho estudio se adoptan los planteamientos desarrollados en KUHL & CRISFIELD [1999]. Por tanto, el principal objetivo es investigar el comportamiento, en el análisis dinámico no-lineal, de los siguientes algoritmos: 1. La regla de trapecio - RT; 2. La regla del punto medio - RPM; 3. El método de Newmark - NM; 4. El método α de Bossak - MαB; 5. El método α de Hilber - MαH; 6. El método α generalizado - MαG; 7. El método de energía-momentum - MEM; 8. El método de energía-momentum modificado - MEM+ξ; 9. El método de energía-momentum generalizado - MEMG; 10. El método de energía-momentum generalizado modificado - MEMG+ξ; Según las siguientes características deseables: 1. Estabilidad numérica; 2. Conservación y decaimiento de la energía total; 3. Mínima disipación de frecuencias bajas; 4. Máxima disipación de frecuencias altas; 5. Convergencia durante el proceso iterativo; Para ello se ha analizado el problema del péndulo simple no-lineal discretizado con el elemento de barra bi-articulado. En la primera simulación numérica se ha tratado el péndulo como rígido mientras que en la segunda simulación se considera el péndulo elástico.
Abstract
En este trabajo se estudia los algoritmos de integración en el tiempo que se basan en el método α generalizado. Para realizar dicho estudio se adoptan [...]
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Stability and robustness issues in numerical modeling of material failure in the strong discontinuity approach
J. Oliver, A. Huespe, S. Blanco, D. Linero

(2004). Research Report, Nº PI258

Abstract
Robustness and stability of the Continuum Strong Discontinuity Approach (CSDA) to material failure are addressed. After identification of lack of symmetry of the finite element formulation and material softening in the constitutive model as possible causes of loss of robustness, two remedies are proposed: 1) a symmetric version of the elementary enriched finite element with embedded discontinuities, and 2) an implicit explicit integration of the internal variable, in the constitutive model, that renders the tangent constitutive algorithmic operator positive definite and constant. The combination of both developments leads to finite element formulations with constant and non-singular tangent structural stiffness, these allowing dramatic improvements in terms of robustness and computational costs. After assessing the convergence properties of the new strategies, three-dimensional numerical simulations of failure problems illustrate the performance of the proposed procedures.
Abstract
Robustness and stability of the Continuum Strong Discontinuity Approach (CSDA) to material failure are addressed. After identification of lack of symmetry of the finite element [...]
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Development of a new FEM code for ship hydrodynamics analysis. Applications to the design of America's Cup yachts.
E. Oñate, J. García-Espinosa

(2004). Research Report, Nº PI257

Abstract
The objective of the project that is presented at the IV Prize Duran i Farell Award for Research and Technology is the development of a new computational code based on the finite element method for the fluid-dynamics analysis of vessels. The code allows to accurately reproduce the model basin tests (MBT) usually used for the experimental evaluation of the hydrodynamic resistance of ships. The new code, called Tdyn, is a much more economical and precise alternative to model basin tests, by allowing the analysis of the behavior of vessels in real scale, thus eliminating the usual scale errors in the experimental tests. Tdyn incorporates new mathematical models and advanced finite elements methods that have led to numerous international publications. Tdyn was jointly developed by researchers from the Technical University of Catalonia (UPC) of the Department of Strength of Materials and Structural Engineering of the Barcelona School of Civil Engineering and of the Department of Nautical Engineering and Science of the Faculty of Nautical Studies of Barcelona in the framework of several European and national projects carried out in collaboration with the research center CIMNE and the company Compass IS, as well as other prestigious companies in the naval architecture sector. Tdyn was applied to the design of several America’s Cup yachts (in particular, of the ALINGHI team, winner of the 2003 edition). Tdyn is currently commercialized worldwide through Compass IS, a spin-off of the UPC.
Abstract
The objective of the project that is presented at the IV Prize Duran i Farell Award for Research and Technology is the development of a new computational code based on the [...]
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Optimization. An attempt at describing the State of the Art
E. Pahl

(2004). Research Report, Nº PI256

Abstract
This paper is an attempt at describing the State of the Art of the vast field of continuous optimization. We will survey deterministic and stochastic methods as well as hybrid approaches in their application to single objective and multiobjective optimization. We study the parameters of optimization algorithms and possibilities for tuning them. Finally, we discuss several methods for using approximate models for computationally expensive problems.
Abstract
This paper is an attempt at describing the State of the Art of the vast field of continuous optimization. We will survey deterministic and stochastic methods as well as hybrid [...]
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El método de Level Set: Revisión y nuevas propuestas
A. Valls, J. García-Espinosa, E. Oñate

(2004). Research Report, Nº PI254

Abstract
El método Level Set utilizado en un amplio espectro de problemas de distinta índole, como la simulación de interfaces entre fluidos, el tratamiento de imágenes, la combustión,…tiene como principal objetivo la simulación numérica de la evolución de interfaces entre distintas regiones en contacto. El presente estudio es una revisión y aportación de nuevas propuestas para el método Level Set, en particular para su aplicación a la interfaz entre fluidos. Este método formulado independiente del tipo de método utilizado para la integración numérica de las ecuaciones en derivadas parciales que gobiernan el fenómeno a simular, disfruta de gran aceptación en el mundo de las diferencias finitas y existe abundante literatura al respecto. En este estudio se ha considerado la combinación del método Level Set y el método de Elementos Finitos no tan usual como en el caso anterior, dotando a este estudio de cierta singularidad. El estudio se ha organizado en 9 secciones o capítulos. En capítulos del 1 al 5 se presenta una introducción teórica al método Level Set con todo el rigor matemático. Se introducen también las últimas ideas desarrolladas en este campo. A lo largo de estos capítulos se propone a modo de ejemplo la aplicación del método Level Set a la interfaz entre dos fluidos. Los capítulos 6 y 7 se presentan los detalles computacionales de este método, así como los detalles de los algoritmos necesarios para la aplicación del método de Level Set. También se hace una revisión de la discretización por el método de los Elementos Finitos estabilizados de la ecuación de transporte, necesaria para la aplicación del método. Los capítulos 8 y 9 recogen varios resultados y conclusiones de la aplicación de este método a distintos ejemplos en dos y tres dimensiones, algunos de ellos presentes en gran parte de la literatura existente.
Abstract
El método Level Set utilizado en un amplio espectro de problemas de distinta índole, como la simulación de interfaces entre fluidos, el tratamiento de [...]
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Neural networks ant the Multilayer Perceptron (with a Software Model)
R. López

(2004). Research Report, Nº PI253

Abstract
In this work we introduce the basic concepts of neural networks, their learning paradigms and learning tasks. We also describe diferent neuron models and network architectures. There are many diferent types of neural networks. Here we study in detail the multilayer perceptron, which is an important class of neural network. Finally we propose a software model for the multilayer perceptron.
Abstract
In this work we introduce the basic concepts of neural networks, their learning paradigms and learning tasks. We also describe diferent neuron models and network architectures. [...]
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On application of robustness test for error estimators to patches near kinked boundaries in three dimensional problems: Part II, Test results for error estimators using SPR and REP
B. Boroomand, F. Mossaiby

(2004). Research Report, Nº PI251

Abstract
In this part of the paper we shall use the formulation given in the first part to assess the quality of recovery based error estimators using two recovery methods, i.e. Superconvergent Patch Recovery (SPR) and Recovery by Equilibrium in Patches (REP). The recovery methods have been shown to be asymptotically robust and superconvergent when applied to two dimensional problems. In this study we shall examine the behavior of the recovery methods on several three dimensional mesh patterns for patches located either inside or at boundaries. This is performed by first finding an asymptotic finite element solution, irrespective of boundary conditions at far ends of the domain, and then applying the recovery methods. The test procedure near kinked boundaries is explained in a step by step manner. The results are given in a series of tables and figures for various cases of three dimensional mesh patterns. It has been experienced that the full superconvergent property is generally lost due to presence of boundary layer solution and the definition of the recoveries near boundaries though the results of the robustness test is still within an acceptable range.
Abstract
In this part of the paper we shall use the formulation given in the first part to assess the quality of recovery based error estimators using two recovery methods, i.e. Superconvergent [...]
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Economical exploitation of polymer coated steel sheet in large-scale production of new can types by the European can industry
J. Rojek, E. Oñate, M. Chiumenti, M. Luege, F. Zarate, O. Fruitos, A. Ferriz, S. Oller

(2004). Research Report, Nº PI252

Abstract
This report presents review of the state of the art of numerical modelling of polymers and polymer coated metal laminates and gives details of selected numerical models including those that will be used in the work in the project POLYCOAT. The first sections of the report contain characteristics of polymers which are important for the application studied in the project. Basic mechanical and thermal properties of the polymers are reviewed. Then constitutive models developed for polymers are reviewed based on literature and own work. Details of selected models are given. Deformation behavior of polymer coated metal laminates is considered with special attention to the phenomena at the polymer-metal interface. The numerical models for the interface are presented finally.
Abstract
This report presents review of the state of the art of numerical modelling of polymers and polymer coated metal laminates and gives details of selected numerical models including [...]
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Desarrollo del código de elementos finitos TDYN para estudio de la hidrodinámica de barcos. Aplicaciones al diseño de veleros de la Copa América.
E. Oñate, J. García-Espinosa

(2004). Research Report, Nº PI246

Abstract
En los últimos años CIMNE ha desarrollado en colaboración con la empresa COMPASS Ingeniería y Sistemas, S.A. (www.compassis.com) un nuevo código de cálculo basado en el método de los elementos finitos para el estudio fluido-dinámico de embarcaciones. El código permite reproducir de forma virtual con fidelidad el denominado “Canal de Ensayos Hidrodinámicos” (CEH) utilizado regularmente para la evaluación experimental de la resistencia hidrodinámica de barcos. El nuevo código, denominado TDYN, es una alternativa a mucho más económica y precisa a los ensayos en el CEH, al permitir analizar el comportamiento de barcos en el agua a escala real, eliminando así los errores de escala usuales en los ensayos experimentales. TDYN incorpora nuevos modelos matemáticos y métodos de elementos finitos avanzados que han llevado a término numerosas publicaciones internacionales. TDYN se desarrolló conjuntamente por investigadores de la Universidad Politécnica de Catalunya (UPC) del Depto. De Resistencia de Materiales y Estructuras de la Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos de Barcelona y del Departamento de Ciencia e Ingenieros Náuticas de la Facultad de Náutica de Barcelona en el marco de diversos proyectos europeos y nacionales llevados a término en colaboración con CIMNE y la empresa COMPASS, además de otras empresas de prestigio en el sector naval. TDYN se aplicó al diseño de diversos veleros de la Copa América (en particular por el equipo del barco ALINGHI ganador de la edición de 2003). TDNY lo comercializa actualmente en todo el mundo la empresa COMPASS, una spin-off de la UPC.
Abstract
En los últimos años CIMNE ha desarrollado en colaboración con la empresa COMPASS Ingeniería y Sistemas, S.A. (www.compassis.com) un nuevo código [...]
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The particle finite element method. An overview
E. Oñate, S. Idelsohn, F. Del Pin, R. Aubry

International Journal of Computational Methods (2004). Vol. 1 (2), pp. 267-307

Abstract
We present a general formulation for analysis of fluid-structure interaction problems using the particle finite element method (PFEM). The key feature of the PFEM is the use of a Lagrangian description to model the motion of nodes (particles) in both the fluid and the structure domains. Nodes are thus viewed as particles which can freely move and even separate from the main analysis domain representing, for instance, the effect of water drops. A mesh connects the nodes defining the discretized domain where the governing equations, expressed in an integral from, are solved as in the standard FEM. The necessary stabilization for dealing with the incompressibility condition in the fluid is introduced via the finite calculus (FIC) method. A fractional step scheme for the transient coupled fluid-structure solution is described. Examples of application of the PFEM method to solve a number of fluid-structure interaction problems involving large motions of the free surface and splashing of waves are presented.
Abstract
We present a general formulation for analysis of fluid-structure interaction problems using the particle finite element method (PFEM). The key feature of the PFEM is the use [...]
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Ship hydrodynamics
E. Oñate, J. García-Espinosa, S. Idelsohn

(2004). Encyclopedia of Computational Mechanics, E. Stein, R. de Borst and T.J.R. Hughes (Eds.), John Wiley & Sons Ltd, Vol. 3, Chapter 18, pp. 579 - 607

Abstract
This chapter presents an overview of some computational methods for analysis of ship hydrodynamics problems. Attention is focused on the description of a stabilized finite element formulation derived via a finite calculus procedure. Both arbitrary Lagrangian-Eulerian (ALE) and fully Lagrangian forms are presented. Details of the treatment of the free-surface waves and the interaction between the ship structure and the sea water are also given. Examples of application to a variety of ship hydrodynamics problems are shown.
Abstract
This chapter presents an overview of some computational methods for analysis of ship hydrodynamics problems. Attention is focused on the description of a stabilized finite [...]
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On the orthogonal subgrid scale pressure stabilization of small and finite deformation J2 Plasticity
C. Agelet de Saracibar, M. Chiumenti, M. Cervera, Q. Valverde

Monograph Series on Computational Modeling of Forming Processes, editor C. Agelet (2004). CMFP2, ISBN: 84-95999-62-5

Abstract
The use of stabilization methods is becoming an increasingly well-accepted technique due to their success in dealing with numerous numerical pathologies that arise in a variety of applications in computational mechanics. In this monograph a multiscale finite element method technique to deal with pressure stabilization of nearly incompressibility problems in nonlinear solid mechanics at small and finite deformations J2 plasticity is presented. A mixed formulation involving pressure and displacement fields is used as starting point. Within the finite element discretization setting, continuous linear interpolation for both fields is considered. To overcome the Babuˇska-Brezzi stability condition, a multiscale stabilization method based on the Orthogonal Subgrid Scale (OSGS) technique is introduced. Suitable nonlinear expression of the stabilization parameters are proposed. The main advantage of the method is the possibility of using linear triangular or tetrahedral finite elements, which are easy to generate and, therefore, very convenient for practical industrial applications. Numerical results obtained using the OSGS stabilization technique are compared with results provided by the P1 standard Galerkin displacements linear triangular/tehrahedral element, P1/P1 standard mixed linear displacements/ linear pressure triangular/tetrahedral element and Q1/P0 mixed bilinear/ trilinear displacements/constant pressure quadrilateral/hexahedral element for 2D/3D nearly incompressible problems in the context of nonlinear small and finite deformation J2 plasticity models.
Abstract
The use of stabilization methods is becoming an increasingly well-accepted technique due to their success in dealing with numerous numerical pathologies that arise in [...]
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Possibilities of the particle finite element method for fluid-structure interaction problems with free surface waves
E. Oñate, S. Idelsohn, F. Del Pin, R. Aubry

Revue Européenne des Éléments Finis (2004). Vol. 13, pp. 637-666

Abstract
We present a general formulation for analysis of fluid-structure interaction problems using the particle finite element method (PFEM). The key feature of the PFEM is the use of a Lagrangian description to model the motion of nodes (particles) in both the fluid and the structure domains. Nodes are thus viewed as particles which can freely move and even separate from the main analysis domain representing, for instance, the effect of water drops. A mesh connects the nodes defining the discretized domain where the governing equations, expressed in an integral from, are solved as in the standard FEM. The necessary stabilization for dealing with the incompressibility condition in the fluid is introduced via the finite calculus (FIC) method. A fractional step scheme for the transient coupled fluid-structure solution is described. Examples of application of the PFEM method to solve a number of fluid-structure interaction problems involving large motions of the free surface and splashing of waves are presented.
Abstract
We present a general formulation for analysis of fluid-structure interaction problems using the particle finite element method (PFEM). The key feature of the PFEM is the use [...]
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Volumetric constraint models for anisotropic elastic solids
C. Felippa, E. Oñate

Journal of Applied Mechanics (2004). Vol. 71 (5), pp. 731-734

Abstract
We study three “incompressibility flavors” of linearly-elastic anisotropic solids that exhibit volumetric constraints: isochoric, hydroisochoric and rigidtropic. An isochoric material deforms without volume change under any stress system. An hydroisochoric material does so under hydrostatic stress. A rigidtropic material undergoes zero deformations under a certain stress pattern. Whereas the three models coalesce for isotropic materials, important differences appear for anisotropic behavior. We find that isochoric and hydroisochoric models under certain conditions may be hampered by unstable physical behavior. Rigidtropic models can represent semistable physical materials of arbitrary anisotropy while including isochoric and hydroisochoric behavior as special cases.
Abstract
We study three “incompressibility flavors” of linearly-elastic anisotropic solids that exhibit volumetric constraints: isochoric, hydroisochoric and rigidtropic. [...]
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Modeling material failure in concrete structures under cyclic actions
R. Faria, M. Cervera, J. Oliver

Journal of Structural Engineering (2004). 130 (12), pp. 1997-2005.

Abstract
A constitutive model devised for the analysis of concrete structures, and suitable for generic two- or three-dimensional applications, is presented and validated. For plain concrete a tension-compression distinguishing stress split is performed, and two scalar damage variables account for the degradation induced by the tensile and compressive stress components. As outcomes the model reproduces the stiffness recovery upon load reversal, and it captures the strength enhancement under multiaxial compression. Besides, the simple formulation as well as the extremely reduced number of parameters involved in the concrete model makes it quite suitable for the analysis of real structures, and constitutes a useful design tool. As regards to the nonlinear performance of the steel reinforcement, the explicit Giuffrè–Menegotto–Pinto model is adopted. Efficiency of the global model is illustrated via two seismic applications: one concerning an arch dam, and the other a six-floor reinforced concrete wall. The latter application is presented for validation purposes.
Abstract
A constitutive model devised for the analysis of concrete structures, and suitable for generic two- or three-dimensional applications, is presented and validated. For plain [...]
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A stabilized formulation for incompressible plasticity using linear triangles and tetrahedra
M. Chiumenti, Q. Valverde, C. Agelet de Saracibar, M. Cervera

International Journal of Plasticity (2004). 20 (8-9), pp. 1487-1504

Abstract
In this paper, a stabilized finite element method to deal with incompressibility in solid mechanics is presented. Both elastic and J2-plastic constitutive behavior have been considered. A mixed formulation involving pressure and displacement fields is used and a continuous linear interpolation is considered for both fields. To circumvent the Babuška–Brezzi condition a stabilization technique based on the orthogonal sub-scale method is introduced. The main advantage of the method is the possibility of using linear triangular or tetrahedral finite elements, which are easy to generate for real industrial applications. Results are compared with standard Galerkin and Q1P0 mixed formulations in either elastic or elasto-plastic incompressible problems.
Abstract
In this paper, a stabilized finite element method to deal with incompressibility in solid mechanics is presented. Both elastic and J2-plastic constitutive behavior have been [...]
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Softening, localization and stabilization: capture of discontinuous solutions in J2 plasticity
M. Cervera, M. Chiumenti, C. Agelet de Saracibar

Int. J. Numer. Anal. Meth. Geomech. (2004). 28 (5), pp. 373-393.

Abstract
This paper exploits the concept of stabilization techniques to improve the behaviour of mixed linear/linear simplicial elements (triangles and tetrahedra) in incompressible or nearly incompressible situations. Elasto‐J2‐plastic constitutive behaviour has been considered with linear and exponential softening. Two different stabilization methods are used to attain global stability of the corresponding discrete finite element formulation. Implementation and computational aspects are also discussed, showing that a robust application of the proposed formulation is feasible. Numerical examples show that the formulation derived is free of volumetric locking and spurious oscillations of the pressure. The results obtained do not suffer from spurious mesh‐size or mesh‐bias dependence, comparing very favourably with those obtained with the standard, non‐stabilized, approaches.
Abstract
This paper exploits the concept of stabilization techniques to improve the behaviour of mixed linear/linear simplicial elements (triangles and tetrahedra) in incompressible [...]
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Red de revistas iberoamericanas
Comunicar. Media Education Research Journal (2004). Vol. 12, (2), 66
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Reseñas
Comunicar. Media Education Research Journal (2004). Vol. 12, (2), 65
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