Scipedia: Documents published in 2009

A system dynamics energy model for a sustainable transportation system

Scipedia content — Wed, 03 Feb 2021 19:34:40 +0100

The transportation sector is one of the most resilient to the shift away from oil. Policies have been put in place in different regions to introduce alternative fuels and reduce the road transportation heavy dependency on oil products and the related environmental impacts; results, however, are in most cases disappointing. The system is resilient and goes back to the historical dichotomy gasoline-diesel. If from a policy maker perspective, a system dynamics model of the automotive sector can lead to the development of effective policies to achieve sustainable mobility, from an energy company perspective, such a model could be used to analyze possible threats and design optimal adaptation strategies for a highly volatile and market that is always on the edge of starting a new major transition. The model here presented can serve both purposes, and the results obtained show how a similar instrument can really make the difference in highly dynamic sectors with ongoing major transitions. "p"QC 20200518

Eddy Current Sensor Arrays for Pipeline Inspection With and Without Coatings

Scipedia content — Wed, 03 Feb 2021 19:26:37 +0100

Coatings are used on pipelines throughout the oil and gas industry for a variety of applications including corrosion protection, temperature maintenance, and weight control. These coatings also present a barrier to inspections for damage and typically need to be removed prior to inspection with nondestructive evaluation (NDE) methods. This has led to the development of improved NDE methods for detection and characterization of damage without removing the coatings or insulation. This paper describes adaptations of JENTEK’s Meandering Winding Magnetometer (MWM® )-Array technology for improved NDE in pipelines, including rapid and reliable imaging of damage, such as external corrosion, external mechanical damage, and stress corrosion cracking (SCC). The MWM-Array technology uses magnetic field-based sensor arrays and model-based inverse methods to determine electromagnetic and geometric properties of the pipeline material, which are then related to specific damage conditions of interest. This technology has been successfully applied in the aerospace and manufacturing industries and provides substantially improved performance for imaging surface and buried damage through coatings and for curved surfaces compared to conventional NDE methods. Several representative applications are described. These include: 1) imaging of near surface material loss through moderate thickness coatings (less than 1.5-in. (38 mm)); 2) imaging of mechanical damage through thin (less than 0.25-in. (6.35 mm)) coatings; 3) imaging of SCC through very thin (less than 0.030-in. (0.76 mm)) and thin (less than 0.25-in. (6.35 mm)) coatings. For SCC, digital imaging of damage regions and automated analysis tools for assessing individual cracks has the potential to be a replacement for magnetic particle inspection (MPI). Initial work has demonstrated these capabilities in a laboratory environment with some field testing and ongoing work is transitioning this technology into field environments.Copyright © 2010 by ASME

A report on the potentialities of restoration and revitalization of the historical village of Meymand, Iran

Scipedia content — Wed, 03 Feb 2021 19:19:07 +0100

Considering the importance of conservation and in recognition of historical places this paper explains the potential of revitalization of Meymand, while presenting its architecture in generalities. These potentials will be examined in a rural and single-unit architecture scale through applying models. This case study has been made as a field study report. Using previous studies available in Meymand’s cultural heritage base archive, interviewing different people, taking photographs, collecting related information from the village, and processing and gathering them, have been done in order to conduct this study. The whole fabric of Meymand has been examined with regard to general characteristics, understanding different periods of development, and components and elements of the units. The only way to revitalize this village in a correct way is to recover its proper economy and to restore all of its residential units and its past culture in a new form. Reorganizing the fabric of Meymand depends on solving the problems related to its fabric with the least intervention.

A mathematical analysis of conflict prevention information

Scipedia content — Wed, 03 Feb 2021 19:04:14 +0100

In air traffic management, conflict prevention information refers to the guidance maneuvers, which if taken, ensure that an aircraft's path is conflict-free. These guidance maneuvers take the form of changes to track angle or ground speed. Conflict prevention information may be assembled into prevention bands that advise the crew on maneuvers that should not be taken. Unlike conflict resolution systems, which presume that the aircraft already has a conflict, conflict prevention systems show conflicts for any maneuver, giving the pilot confidence that if a maneuver is made, then no near-term conflicts will result. Because near-term conflicts can lead to safety concerns, strong verification of information correctness is required. This paper presents a mathematical framework to analyze the correctness of algorithms that produce conflict prevention information incorporating an arbitrary number of traffic aircraft and with both a near-term and intermediate-term lookahead times. The framework is illustrated with a formally verified algorithm for 2-dimensional track angle prevention bands.

Macroscopic Capacity Model with Individual Sector Closing Speed Estimates

Scipedia content — Wed, 03 Feb 2021 18:59:59 +0100

Reliable airspace capacity estimates are important both for operational air traffic management and for airspace design. Air traffic management relies on manual procedures. Hence, controller workload determines the capacity of most sectors. Yet the current operational model for estimating capacity in United States airspace does not account for workload from conflict avoidance tasks. Aircraft closing speeds and airspace separation standards determine the rate of aircraft conflicts. Numerically, conflict workload intensity is the product of the conflict rate and the mean controller time required to service a conflict. As workload intensity approaches unity, the sector reaches capacity. We determine unknown model parameters by fitting capacity calculations against peak traffic observations for en route sectors. The result is an analytical model for capacity that is more accurate than the current operational model. The mean closing speed of all pairs of aircraft in a volume of airspace determines the conflict rate. This paper reports an effort to refine the conflict component of the model by replacing its original global closing speed estimate with local traffic-based closing speed estimates for individual sectors. Exact calculation of mean closing speed requires full position and velocity information for all flight tracks. The database that we used to obtain the peak traffic counts includes initial heading, speed, and altitude fields for all traffic entering a sector. Without positional coordinates and intersector track information, these data fields provide only crude closing speed estimates. We examined these estimates as possible indicators of sector route and altitude complexity in the New York Center. Individual sector closing speed estimates based on these observations did not improve the model fit for the 30 New York sectors.

Analysis of Automated Aircraft Conflict Resolution and Weather Avoidance

Scipedia content — Wed, 03 Feb 2021 18:52:28 +0100

*† ‡ This paper describes an integrated solution to traffic conflict detection and resolution with weather avoidance in the Center-TRACON Automation System. An automatic conflict resolution algorithm developed and tested to resolve aircraft-to-aircraft conflicts is modified to reroute aircraft around convective weather constraints while avoiding traffic conflicts. The approach extends algorithms which resolve aircraft-to-aircraft conflicts to also resolve aircraft-to-forecast weather conflicts. Alternatively, a separate algorithm that solves aircraft to weather conflicts would have to be integrated with the current method to solve both aircraft and weather conflicts. This evaluation limited conflict resolutions to horizontal maneuvers due to software limitations in the research software that are being addressed. Simulation results show 96 percent of aircraft-to-aircraft conflicts without any weather constraints were successfully resolved. In high traffic scenarios with moderate weather, 91 percent of conflicts were resolved, while in high traffic with bad weather 72 percent of conflicts were resolved.

Airport troughput capacity limits for demand management planning

Scipedia content — Wed, 03 Feb 2021 18:48:50 +0100

The success of demand management approaches to curbing flight delays is predicated on an accurate and reliable a-priori determination of airport arrival and departure capacity. The assignment of declared capacity, completed more than one year in advance, must consider the inherent variability in the actual throughput capacity for each 15 minute period during the day. For airports with large variations in airport capacity, the capacity limit must be set to high enough avoid long periods of under utilization of the airport resources and low enough to avoid extended periods of excessive delays. This paper examines: (i) the variability of throughput capacity at the OEP-35 airports during the convective weather season in 2008, (ii) established the average costs of delays due to reduced capacity and the average profits per flight at each airport, (iii) given the cost of delays and lost profits, an optimum capacity is determined at each airport to minimize both the under-utilization of airport capacity and flight delays due to variability in the available throughput capacity

Transient Simulation of Natural Gas Citygates Stations

Scipedia content — Wed, 03 Feb 2021 18:47:36 +0100

The demand of natural gas in the Brazilian energy market is increasing very fast over the few years and it was necessary to enhance the operational performance and safety of the gas distribution. The perfect operation of the natural gas citygate stations is essential to guarantee the delivery of natural gas for the end users like local distribution companies, thermoelectric power plants and large industrial customers within the contracted marketing conditions. These stations receive natural gas directly from high pressure pipelines and reduce the pressure using regulation valves that provoke a temperature reduction due the Joule-Thompson (JT) behavior, typical of natural gases. This temperature loss is compensated by forcing part of the gas flow through water/glycol bath heaters that use natural gas as fuel in the heating process. Usually the downstream gas temperature condition is controlled above a minimal set point while modifying the three-way valve position that regulates hot and cold streams flows. A numerical tool has been developed to simulate the dynamic process inside the natural gas citygate station, and proved to be a reliable tool to analyze the transient performance of the main equipments (filter, three way valve, heater, JT valve, relief valves) when submitted to abnormal conditions or changes in capacity. The methodology developed is able to handle a variety of citygate design.Copyright © 2010 by ASME

Primary and backup paths optimal design for traffic engineering in hybrid IGP/MPLS networks

Scipedia content — Wed, 03 Feb 2021 18:40:38 +0100

The paper describes an optimization model which aims at minimizing the maximum link utilization of IP telecommunication networks under the joint use of the traditional IGP protocols and the more sophisticated MPLS-TE technology. The survivability of the network is taken into account in the optimization process implementing the path restoration scheme. This scheme benefits of the Fast Re-Route (FRR) capability allowing service providers to offer high availability and high revenue SLAs (Service Level Agreements). The hybrid IGP/MPLS approach relies on the formulation of an innovative Linear Programming mathematical model that, while optimizing the network utilization, provides optimal user performance, efficient use of network resources, and 100% survivability in case of single link failure. The possibility of performing an optimal exploitation of the network resources throughout the joint use of the IGP and MPLS protocols provides a flexible tool for the ISP (Internet Service Provider) networks traffic engineers. The efficiency of the proposed approach is validated by a wide experimentation performed on synthetic and real networks. The obtained results show that a limited number of LSP tunnels have to be set up in order to significantly reduce the congestion level of the network while at the same time guaranteeing the survivability of the network.

Simulation-Based Study to Quantify Data-Communication Benefits in Congested Airport Terminal Area

Scipedia content — Wed, 03 Feb 2021 18:37:01 +0100

Innovative approach to determining railway line capacity

Scipedia content — Wed, 03 Feb 2021 18:32:50 +0100

The contribution deals with critical assessment of used analytical and graphic-analytical methods for determining the lines capacity and of problems connected to the capacity formulation. Negative outcomes from executed case studies force us to investigate new approaches, which would result in more accurate capacity determination. Simulation models appear to be an appropriate tool allowing the investigation of the capacity of transport infrastructure in the interaction with the range of traffic. In case of incongruity between the transport infrastructure and the range of traffic operation, the implementation of various arrangements including the economical assessment can be simulated by means of scenarios. At the end of the paper a short list of the experience with the application of simulation modelling on particular lines in the Czech Republic is presented.

High Speed Rail, a new mode of suburban metropolitan transport

Scipedia content — Wed, 03 Feb 2021 18:26:56 +0100

High Speed Rail (HSR) was conceived as an alternative to air transport to interconnect big cities and metropolises from 400 to 600 km distances. Recently these HSR lines are starting to have stations in traditional cities or new urban developments within the limits of each metropolis (between 20 and 100 km from the centre). The existence of these HSR stations in the periphery of metropolises is opening up two new metropolitan transportation behaviour possibilities. Firstly, the HSR used between central and peripheral metropolitan stations as a special new type of suburban metropolitan transport and secondly, peripheral HSR stations used to travel to/from other faraway places instead of using the central HSR stations. This paper describes this new type of HSR cities, lines, stations and services, and points out several cases in Spain, France, Sweden and Great Britain where this is taking place. Data from two survey campaigns just implemented on the HSR passengers between Madrid and Toledo, and Madrid and Guadalajara is used to describe and analyse their profile. The paper points out the possibilities of this new type of HSR to help the generation of metropolitan sub-centres and to extend the metropolitan influence further away, analyses the HSR travelling patterns and allows indications of the type of processes that are taking place

Precise Worst-Case Execution Time Analysis for Processors with Timing Anomalies

Scipedia content — Wed, 03 Feb 2021 18:05:47 +0100

This paper explores timing anomalies in WCET analysis.Timing anomalies add to the complexity of WCET analysis and make it hard to apply divide-and-conquer strategies to simplify the WCET assessment.So far, timing anomalies have been described as a problem that occurs when the WCET of a control-flow graph is computed from the WCETs of its subgraphs, i.e., from a series decomposition. This paper extends the state of the art by (i) showing that timing anomalies can as well occur in a parallel decomposition of the WCET problem, i.e., when complexity is reduced by splitting the hardware state space and performing a separate WCET analysis for hardware components that work in parallel, (ii) proving that the potential occurrence of parallel timing anomalies makes the parallel decomposition technique unsafe (i.e., one cannot guarantee that the calculated WCET bound does not underestimate the WCET), and (iii) identifying special cases of parallel timing anomalies for which the parallel decomposition technique is safe. The latter provides an important hint to hardware designers on their way to constructing predictable hardware components.

Quantifying ases multiconnectivity using multicast information

Scipedia content — Wed, 03 Feb 2021 17:57:50 +0100

Redundant connectivity (or multiconnectivity) between adjacent autonomous systems (ASes) is important for inter-domain traffic engineering and fast recovery in case of failures. However, the redundancy of ASes business relationship links has not been quantitatively studied, mainly due to the difficulty of obtaining relevant data. In this paper, we show that the mrinfo multicast monitoring tool can provide useful data about the Internet topology and such redundant links in particular. Our analysis relies on more than four years of daily queries to about ten thousand routers mapped into more than two hundred ASes. We demonstrate that peering links between ASes are frequently redundant. In particular, our analysis shows that more than half of the studied ASes pairs are connected through multiple physical links. We then refine our analysis by considering the different types of ASes and their business relationships. A particular result of our analysis is that at least 75% of the peer-to-peer relationships between adjacent Tier-1 ASes are redundant, i.e., the con- nections between these ASes involve several physical links. Our analysis is conservative, providing so a lower bound, as some links might not be seen by mrinfo due to ISPs filtering policies. Peer reviewed

Distributed scheduling in large scale monitoring infrastructures

Scipedia content — Wed, 03 Feb 2021 17:55:09 +0100

Network monitoring is becoming a necessity for network operators, who usually deploy several monitoring applications that aid in tasks such as traffic engineering, capacity planning and the detection of attacks or other anomalies. There is also an increasing interest in large-scale network monitoring infrastructures that can run multiple applications in several network viewpoints [4].

Adaptive Clock Scheduling for pipelined structures

Scipedia content — Wed, 03 Feb 2021 17:53:50 +0100

This paper introduces a technique called Adaptive Inverter Chain Based Clock Scheduling, which can observe and compensate delay variations in pipelined structures. The main idea behind the method is to expose the data and the clock to the same variations such that the register data sampling process is not disturbed by variations. The proposed scheme also includes a mechanism to detect time failures and to take counter actions to recover from such situations. When compared with other state of the art proposals, which require the augmentation of the registers, our proposal requires a relative smaller area overhead due to the fact that it is focussed on clock and not on data. Moreover our simulations indicate that, depending on the specific delay variations and pipeline logic delay sensitivity to input data patterns, it can enable an up to 46% performance improvement.

Analytical Modeling of Pipeline Parallelism

Scipedia content — Wed, 03 Feb 2021 17:46:23 +0100

Parallel programming is a requirement in the multi-core era. One of the most promising techniques to make parallel programming available for the general users is the use of parallel programming patterns. Functional pipeline parallelism is a pattern that is well suited for many emerging applications, such as streaming and "Recognition, Mining and Synthesis" (RMS) workloads. In this paper we develop an analytical model for pipeline parallelism based on queueing theory. The model is useful to both characterize the performance and efficiency of existing implementations and to guide the design of new pipeline algorithms. We demonstrate the usefulness of the model by characterizing and optimizing two of the PARSEC benchmarks, ferret and dedup. We identified two issues with these codes: load imbalance and I/O bottlenecks. We addressed load imbalance using two techniques: i) parallel pipeline stage collapsing; and ii) dynamic scheduling. We implemented these optimizations using Pthreads and the Threading Building Blocks (TBB) libraries. We compare the performance of different alternatives and we note that the TBB implementation based on work stealing outperforms all other variants.

FromDaDy : spreading aircraft trajectories across views to support iterative queries

Scipedia content — Wed, 03 Feb 2021 17:44:47 +0100

International audience; When displaying thousands of aircraft trajectories on a screen, the visualization is spoiled by a tangle of trails. The visual analysis is therefore difficult, especially if a specific class of trajectories in an erroneous dataset has to be studied. We designed FromDaDy, a trajectory visualization tool that tackles the difficulties of exploring the visualization of multiple trails. This multidimensional data exploration is based on scatterplots, brushing, pick and drop, juxtaposed views and rapid visual design. Users can organize the workspace composed of multiple juxtaposed views. They can define the visual configuration of the views by connecting data dimensions from the dataset to Bertin's visual variables. They can then brush trajectories, and with a pick and drop operation they can spread the brushed information across views. They can then repeat these interactions, until they extract a set of relevant data, thus formulating complex queries. Through two real-world scenarios, we show how FromDaDy supports iterative queries and the extraction of trajectories in a dataset that contains up to 5 million data.

Repair of Dents Subjected to Cyclic Pressure Service Using Composite Materials

Scipedia content — Wed, 03 Feb 2021 17:42:49 +0100

For the better part of the past 15 years composite materials have been used to repair corrosion in high pressure gas and liquid transmission pipelines. This method of repair is widely accepted throughout the pipeline industry because of the extensive evaluation efforts performed by composite repair manufacturers, operators, and research organizations. Pipeline damage comes in different forms, one of which involves dents that include plain dents, dents in girth welds and dents in seam welds. An extensive study has been performed over the past several years involving multiple composite manufacturers who installed their repair systems on the above mentioned dent types. The primary focus of the current study was to evaluate the level of reinforcement provided by composite materials in repairing dented pipelines. The test samples were pressure cycled to failure to determine the level of life extension provided by the composite materials relative to a set of unrepaired test samples. Several of the repaired dents in the study did not fail even after 250,000 pressure cycles were applied at a range of 72% SMYS. The results of this study clearly demonstrate the significant potential that composite repair systems have, when properly designed and installed, to restore the integrity of damaged pipelines to ensure long-term service.Copyright © 2010 by ASME

Urban modal shift management in cities: an indicator based approach

Scipedia content — Wed, 03 Feb 2021 17:41:33 +0100

This paper will discuss how increased transport has negative effects on quality of life, welfare and environment, especially in urban areas. Despite the indispensable function of transport in society, reflections on its overall sustainability must be considered. Minimizing congestion and emissions restricts environmental damage, air pollution, noise nuisance and loss of productive time. In composing sustainable transport policy, city authorities should rely on an assessment monitor to direct transportation patterns towards an urban modal shift. This paper proposes a methodology to assess urban transport, based on sustainability indicators. Different ecological, social, economical, and transport indicators are presented to measure current urban transportation patterns. The integration of such assessment instruments in urban modal shift management should improve accessibility and quality of life.

An Automatic Collision Detection and Avoidance Module for Inland Navigation

Scipedia content — Wed, 03 Feb 2021 17:40:07 +0100

Based on the positional data of other inland vessels which is available through the fusion of radar object tracking and AIS (Automatic Identification System) a model-based prediction of their kinematic states is presented. Information about the river shape is fed into the prediction model according to the type of vessel and its navigational situation. Together with the future states of our own vessel, which are known because it is automatically steared along a guiding line, ranges of encounter are calculated. Furthermore, a path planning algorithm based on nonlinear dynamic optimization is presented that is capable of calculating collision-free paths in real-time that account for the vessel's constrained dynamics. Practical results of the discussed automatic collision detection and avoidance module as part of an integrated navigation system for inland vessels are shown concluding the contribution.

The impact of link-layer retransmissions on video streaming in wireless mesh networks

Scipedia content — Wed, 03 Feb 2021 17:35:25 +0100

Link-layer retransmission is a feature of IEEE 802.11 standard protocol that aims to increase the reliability of data communications. However, when successive retransmissions fail, they add to the traffic congestion, raise the collision probability, and increase the end-to-end delay. Using our 4-hop wireless mesh network testbed, we evaluate the impact of link-layer retransmissions on the performance of video streaming in wireless multi-hop environment. Our experimental results show that when the traffic load is near or exceeds the network capacity, retransmissions cause erratic video quality and increase the end-to-end delay tremendously. When the best-effort traffic coexists, increasing the number of retransmissions degrades the goodput of best-effort traffic and increases the end-to-end delay of video streaming. Retransmissions add reliability and increase the video streaming quality only when the traffic volume is far below the network capacity limit.

Moving beyond end-to-end path information to optimize CDN performance

Scipedia content — Wed, 03 Feb 2021 17:27:29 +0100

Replicating content across a geographically distributed set of servers and redirecting clients to the closest server in terms of latency has emerged as a common paradigm for improving client performance. In this paper, we analyze latencies measured from servers in Google's content distribution network (CDN) to clients all across the Internet to study the effectiveness of latency-based server selection. Our main result is that redirecting every client to the server with least latency does not suffice to optimize client latencies. First, even though most clients are served by a geographically nearby CDN node, a sizeable fraction of experience latencies several tens of milliseconds higher than other in the same region. Second, we find that queueing delays often override the benefits of a client interacting with a nearby server. To help the administrators of Google's CDN cope with these problems, we have built a system called WhyHigh. First, WhyHigh measures client latencies across all nodes in the CDN and correlates measurements to identify the prefixes affected by inflated latencies. Second, since clients in several thousand prefixes have poor latencies, WhyHigh prioritizes problems based on the impact that solving them would have, e.g., by identifying either an AS path common to several inflated prefixes or a CDN node where path inflation is widespread. Finally, WhyHigh diagnoses the causes for inflated latencies using active measurements such as traceroutes and pings, in combination with datasets such as BGP paths and flow records. Typical causes discovered include lack of peering, routing misconfigurations, and side-effects of traffic engineering. We have used WhyHigh to diagnose several instances of inflated latencies, and our efforts over the course of a year have significantly helped improve the performance offered to clients by Google's CDN.

Segmented road grade estimation for fuel efficient heavy duty vehicles

Scipedia content — Wed, 03 Feb 2021 17:26:28 +0100

Long haulage road transport consumes considerable amounts of energy in today's world. Predictive control strategies based on digital maps can significantly lower the portion being wasted in traditional cruise control operated highway driving. Such control strategies rely on high quality stored road grade information. This paper describes a newly developed method to estimate the road grade using sensors commonly found on standard heavy duty vehicles. The method utilizes a piecewise linear road model derived from highway design methodologies. The estimation method has been implemented and evaluated experimentally, and is shown to give better results compared to an existing method. © 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. QC 20120213

A generalised prediction model of first person shooter game traffic

Scipedia content — Wed, 03 Feb 2021 17:15:01 +0100

Modelling traffic generated by Internet-based multiplayer computer games has attracted much attention in the past few years. This has been driven by a need to simulate correctly the network impact of highly interactive online game genres such as the first person shooter (FPS). Packet size distributions and autocovariance models are important elements in the creation of realistic traffic generators for network simulators. In this paper we present techniques for creating representative models for N-player FPS games based on empirically measured traffic of 2-player games. The models capture the packet size distribution as well as the time series behaviour of game traffic. We illustrate the likely generality of our approach using data from seven FPS games that have been popular over the past nine years: Half-Life, Half-Life Counterstrike, Half-Life 2, Half-Life 2 Counterstrike, Quake 3 Arena, Quake 4 and Wolfenstein Enemy Territory.

AC Pipe in North America: Rehabilitation/Replacement Methods and Current Practices

Scipedia content — Wed, 03 Feb 2021 17:14:25 +0100

os cement (AC) pipe was first introduced in North America in the late 1920s and became a common choice for potable water main construction from the 1940s to the 1970s. The use of AC pipe was largely discontinued in North America in the early 1980s but AC pipe is still a significant portion of the water distribution systems in many North American cities. As the pipes deteriorate and fail to meet service requirements, appropriate rehabilitation/replacement methods need to be determined. This paper summarizes survey data on the rehabilitation/replacement methods for AC pipes provided by 19 water utilities in the United States and Canada. The paper also reviews current available rehabilitation/replacement methods to provide some background of the current practices used by the utilities. The survey indicates that trenching is the main method used to repair, rehabilitate, and replace AC pipes. Cost was cited as the main reason for utilities to choose a particular repair/rehabilitation/replacement method. Although most of the rehabilitation/replacement methods have potential social and environmental effects because of possible release of asbestos fibers, the effects were generally not given high priority when selecting methods for renewing AC pipes.

Developing Stress Intensification Factors for Composite Repair Systems Used to Repair Damaged Pipe

Scipedia content — Wed, 03 Feb 2021 17:13:25 +0100

For the better part of the past 15 years composite materials have been used to repair corrosion in high pressure gas and liquid transmission pipelines. This method of repair is widely accepted throughout the pipeline industry because of the extensive evaluation efforts performed by composite repair manufacturers, operators, and research organizations. Pipeline damage comes in different forms, one of which involves dents that include plain dents, dents in girth welds and seam welds. An extensive study has been performed over the past several years involving multiple composite manufacturers that installed their repair systems on the above mentioned dent types. The test samples were pressure cycled to failure to determine the level of life extension provided by the composite materials over a set of unrepaired test samples. Several of the repaired dents in the study did not fail even after 250,000 pressure cycles had been applied at a range of 72% SMYS. The primary purpose of this paper is to present details on how Stress Intensification Factors were derived using the empirically-generated data. The results of this study clearly demonstrate the significant potential that composite repair systems have, when properly designed and installed, to restore the integrity of damaged pipelines and piping systems to ensure long-term service.Copyright © 2010 by ASME

UKOPA Dent Assessment Algorithms: A Strategy for Prioritising Pipeline Dents

Scipedia content — Wed, 03 Feb 2021 17:01:45 +0100

in-line inspection tools improve, dents that would have been below the detection and reporting levels of previous inspections are now being detected and reported to pipeline operators. Consequently, operators are being faced with large numbers of dents in ILI reports that require further consideration and are left with the problem of how to prioritize these dents for further investigation and repair. Although code guidance is clear on the relative severity of dents associated with other features or those based on a depth or strain criteria, this may still leave a significant number of dents in the pipeline which fall within codified static dent assessment criteria, but which may still pose a threat, particularly from fatigue. Many transmission pipelines in the UK are now 30–40 years old and fatigue failures at dent locations are starting to be reported. Such occurrences have raised technical concerns with regulators regarding the perceived conservatism of current dent assessment methods as the dents in question were within the code limits and were reported through standard ILI technologies, however, they were not identified as significant. There is therefore a requirement to develop best practice guidance for the safe and economic operation of dented pipelines. The UK Onshore Pipeline Association (UKOPA) recognized that further guidance was needed in order that operators could identify dents which can be safely left in the pipeline and those for which further excavation is required. They have consequently developed a series of algorithms to allow pipeline operators to prioritize the dents for repair based on ILI results. This paper describes the background research to these algorithms as well the algorithms themselves, demonstrating their use with ILI dent data from operators of onshore oil and gas pipelines. The paper concludes with comments on the current conservatisms in the analysis of dent fatigue and proposes a way forward to allow pipeline operators to manage large numbers of dents for which the dent fatigue life is critical.Copyright © 2010 by ASME

Routing Games for Traffic Engineering

Scipedia content — Wed, 03 Feb 2021 16:57:12 +0100

Current data network scenario makes traffic engineering (TE) a very challenging task. The ever growing access rates and new applications running on end-hosts result in more variable and unpredictable traffic patterns. By providing origin-destination pairs with several possible paths, load-balancing has proved itself an excellent tool to face this uncertainty. In particular, mechanisms where routers greedily minimize a path cost function (thus requiring minimum coordination) have been studied from a game-theoretic perspective in what is known as a routing game (RG). The contribution of this paper is twofold. We first propose a new RG specifically designed for elastic traffic, where we maximize the total utility through load-balancing only. Secondly, we consider several important RGs from a TE perspective and, using several real topologies and traffic demands, present a thorough comparison of their performance. This paper brings insight into several RGs, which will help one in choosing an adequate dynamic load-balancing mechanism. The comparison shows that the performance gain of the proposed game can be important.

A Framework for Securing Future eEnabled Aircraft Navigation and Surveillance

Scipedia content — Wed, 03 Feb 2021 16:53:53 +0100

Current air traffic management systems suffer from poor radar coverage and a highly centralized architecture which can under heavy traffic loads overwhelm Air Traffic Control (ATC) centers. Such limitations can lead to inefficient use of the available airspace capacity and insecure scenarios such as low-visibility landings. Future air transportation systems with e-enabled aircraft and networked technologies, such as Automated Dependent Surveillance Broadcast (ADS-B), are cyber-physical systems that promise to help reduce traffic congestion and ATC inefficiencies by enabling exchange of precise surveillance data in shared airspace. This paper focuses on cyber security concerns with highly accurate surveillance of aircraft navigating in a future shared space. A framework is proposed to protect traffic data for both ground and airborne surveillance of aircraft. The framework identifies major threats and vulnerabilities from cyber exploits, specifies security requirements and mitigation solutions. Major security challenges anticipated in supporting networked infrastructure are given along with some open problems.

Link load balancing optimization of telecommunication networks: a column generation based heuristic approach

Scipedia content — Wed, 03 Feb 2021 16:50:34 +0100

This paper deals with optimal load balancing in telecommunication networks. For a capacitated telecommunications network with single path routing and an estimated traffic demand matrix, we wish to determine the routing paths aiming at min-max optimization of link loads. To solve this problem, we propose a column (path) generation based heuristic. In the first step, we use column generation to solve a linear programming relaxation of the basic problem (obtaining a lower bound and a set of paths). In the second step, we apply a multi-start local search heuristic with path-relinking to the search space defined by the paths found in the first step. In order to assess the merits of this approach, we also implemented a search heuristic which is equivalent to the second step of the proposed one but with no constraints on the set of paths that can be used. Through a set of computational results, we show that the proposed heuristic is efficient in obtaining near optimal routing solutions within short running times. Moreover, the comparison of the two heuristics show that constraining the search space to the columns given by column generation gives better results since this solution space contains good quality solutions and, due to its size, enables to find them in short running times.

Performance measures for managing urban traffic signal systems

Scipedia content — Wed, 03 Feb 2021 16:48:47 +0100

This paper will discuss how most urban traffic control systems go through a rather rigorous design phase based upon a set of fixed design volumes that do not capture the stochastic variation in traffic due to weather, incidents, special events, and shifting demand patterns. Once these systems are built, their operation is relatively open loop, with public feedback (complaints) often the primary feedback for assessing operations and initiating changes. This paper describes procedures and case studies that illustrate how fundamental traffic engineering concepts can be integrated with traffic signal system detection and controller status information to provide real time performance measures. These performance measures characterize the operation of a traffic signal system and identify operation improvement opportunities. Several example performance measure graphics are provided to illustrate how these tools can be used for making operations decisions, evaluating field deployments, and preparing reports for decision makers. The paper concludes by discussing how these performance measures can be extended to include other surface transportation modes, particularly pedestrians, railroads, and transit.

Tools for traffic engineering on IP networks

Scipedia content — Wed, 03 Feb 2021 16:45:34 +0100

In this work, an user friendly software application is proposed, built on top of a network optimization framework, aiming to make traffic engineering an easier task for IP network administrators. This framework was developed in the Center of Computer Science and Technology (CCTC) of the University of Minho and allows the improvement of quality of service levels in TCP/IP based networks, by configuring the routing weights of link-state protocols, such as OSPF. This goal is achieved mainly using Evolutionary Algorithms as the optimization engines, while networks are represented using graph-based mathematical models. These methods allow the optimization of distinct cost functions, using penalties that take into account several measures of network performance such as network congestion and average end-to-end delays. The main goal of this work is to create a structured graphical user interface to support the optimization framework, enabling the user to simulate the effects of diferente OSPF settings, to obtain highly optimized configurations and to compare different weight setting optimization methods.

Towards real implementations of dynamic robust routing exploiting path diversity

Scipedia content — Wed, 03 Feb 2021 16:44:13 +0100

In this paper we compare the performance of tree different dynamic traffic engineering algorithms exploiting path diversity in the Internet, TEXCP, TRUMP and MIRTO. We passed through a thorough implementation phase of these algorithms solving a number of issues related to protocol implementation that allows a complete analysis in real traffic settings in real networks. We discuss the performance of such protocols and some difficulties encountered during their implementation. Supported by an already mature standardization framework we conclude that dynamic yet stable traffic engineering is not only feasible but expected with rising interest by network operators.

Network cell routing model for control of throughput and delay of air traffic

Scipedia content — Wed, 03 Feb 2021 16:43:50 +0100

mpts to manage air traffic by either decreasing delay or increasing flow can have the reverse effect on the other. In the National Airspace System (NAS), flights typically depart at their chosen times, and flow management techniques are implemented in the air in an effort to maximize flow, which could lead to delay for individual aircraft. Other areas of the world allow flights to depart only at predetermined slot times knowing that there is a clear unobstructed path, leading to minimal delays but possibly underutilizing airspace. We propose a new approach in leveraging the highway cell transmission model (CTM) to the airspace in the form of a multi-objective optimization that trades between maximizing throughput and minimizing delay. The model is posed as a multi-commodity traffic flow integer program where the constraints are relaxed slightly from the CTM to examine strategies for achieving optimal throughput and delay. In practice, the model is envisioned to initially run offline to determine a preliminary solution to the initial state of the system. Solutions for subsequent changes in actual state can be determined by running the model online for the incremental state change. Stochastic events such as convective weather clearing times or capacities can be included in the model to better see the benefits and impacts of pre-positioning traffic to take advantage of possible future clearing.

A Comparison of Aviation Greenhouse Gas Emission Mitigation Policies for Europe

Scipedia content — Wed, 03 Feb 2021 16:35:30 +0100

This paper integrates the results of a set of studies looking at UK and European aviation environmental policy measures. It uses a model of the European air transport system to assess the economic costs and environmental benefits associated with proposed emission mitigation strategies. In particular, we con centrate on the potential penetration of fuelsaving technologies and operations, lower carbon alternative fuels and high-speed rail in response to the European Union Emissions Trading Scheme, and the effect on CO2 emissions that this has in both the UK and Europe. A special emphasis is placed on the interaction effects of multiple mitigation policies. We find that a combination of policies could potentially allow UK and European lifecycle aviation CO2 emissions in 2050 to be reduced to below year-2005 levels. Although other operational and technological measures can reduce aviation CO2 emissions by up to 15% compared to an unconstrained base case, the largest part of this reduction comes from the interaction between carbon trading and cellulosic biomass fuels.

Investigating the relationships between gaze patterns, dynamic vehicle surround analysis, and driver intentions

Scipedia content — Wed, 03 Feb 2021 16:31:52 +0100

Recent advances in driver behavior analysis for Active Safety have led to the ability to reliably predict certain driver intentions. Specifically, researchers have developed Advanced Driver Assistance Systems that produce an estimate of a driver's intention to change lanes, make an intersection turn, or brake, several seconds before the act itself. One integral feature in these systems is the analysis of driver visual search prior to a maneuver, using head pose and eye gaze as a proxy to determine focus of attention. However it is not clear whether visual distractions during a goal-oriented visual search could change the driver's behavior and thereby cause a degradation in the performance of the behavior analysis systems. In this paper we aim to determine whether it is feasible to use computer vision to determine whether a driver's visual search was affected by an external stimulus. A holistic ethnographic driving dataset is used as a basis to generate a motion-based visual saliency map of the scene. This map is correlated with predetermined eye gaze data in situations where a driver intends to change lanes. Results demonstrate the capability of this methodology to improve driver attention and behavior estimation, as well as intent prediction.

High-speed trains in Sweden – a good idea?

Scipedia content — Wed, 03 Feb 2021 16:18:11 +0100

The demand for both passenger and freight rail transport in Sweden has never before been higher than in the year 2008. There is now serious lack of capacity and big delays, and need for massive investment in rail. High-speed trains may be a way to relieve track congestion, reduce travel times and improve the environment through less air and car travel. The Swedish National Rail Administration has initiated a number of studies on the value of high-speed trains over the last years. The Swedish government has initiated a study that was finished 14 thof September 2009 and suggested to build a separate high speed tracks in Sweden. The paper describes the main findings of the study and the models employed. The latter is of importance since two models gave significantly different results, even though both showed a positive socio-economic net return. The cost-benefit calculations have also been subject to scepticism. These scepticisms are also described and commented. QC 20120229

Estimation of arrival-departure capacity tradeoffs in multi-airport systems

Scipedia content — Wed, 03 Feb 2021 16:03:08 +0100

Proceedings of the 48th IEEE Conference on Decision and Control, 2009 held jointly with the 2009 28th Chinese Control Conference. CDC/CCC 2009.

The accurate estimation of airport capacity is critical for the efficient planning of landing and takeoff operations, and the mitigation of congestion-induced delays. The analysis of tradeoffs between arrival and departure capacity at an airport, represented by the airport capacity envelope, has been the main focus of prior research. The increasing demand for air traffic operations has resulted in the growth of multi-airport systems, in which several major airports that are in close proximity of each other serve the same geographical region. The arrival and departure flows into these airports interact with each other, and it is necessary to consider inter-airport arrival-departure capacity tradeoffs while scheduling operations. This paper proposes a statistical technique based on quantile regression, for systematically analyzing arrival-departure capacity tradeoffs in multi-airport systems using observations of flight operations. The proposed technique enables the identification of key factors (such as, runway configuration geometry, weather conditions, etc.) that influence both the capacity envelopes of individual airports, and the capacity envelope of the multi-airport system as a whole. The approach is demonstrated through an analysis of the capacity envelopes of the New York area multi-airport system (comprising Newark (EWR), John F. Kennedy (JFK) and LaGuardia (LGA) airports).

Document type: Conference object

IP Overhead Comparison in a Test-Bed for Air Traffic Management Services

Scipedia content — Wed, 03 Feb 2021 15:59:59 +0100

This paper presents the comparison of two IPv6 over IPv4 solutions for a laboratory demonstrator within NEWSKY, a project co-funded by the European Commission within its 6th Research Framework Programme (FP6). NEWSKY aims at developing a concept for a global, heterogeneous communication network for aeronautical communications. It assumes IPv6 hosts, but nowadays satellite networks still run over IPv4 links. Two solutions have been tested and investigated over a real satellite link for this project: L2TP tunneling and NAPT-PT modified. Both are implemented and compared in terms of overhead and complexity. Results show that NAPT-PT modified adds less overhead than tunneling, however, L2TP computation is easier and faster than NAPT-PT modified.

Promoting sustainable energy in the New Zealand transport system: policies, programmes and strategic directions

Scipedia content — Wed, 03 Feb 2021 15:58:45 +0100

This paper discusses the promotion of energy efficiency and renewable energy in the New Zealand transport system. The paper begins by examining the characteristics of New Zealand’s transport system that influence energy use, including the age of vehicles, vehicle ownership rates and the total amount of vehicle kilometers traveled. The paper then overviews the range of targets, policies and programs that are being used to promote greater energy efficiency and renewable energy in the New Zealand transport system, in order to reduce carbon emissions and enhance energy security. Two key measures are focused upon: a vehicle fuel economy labeling scheme and a vehicle fleet fuel economy target. The paper concludes by discussing the prospects for adopting electric vehicles in New Zealand, as a strategic step the country could take to further reduce and diversify its future transport energy use.

An Investigation of the Operational Acceptability of Algorithm-Generated Sector Combinations

Scipedia content — Wed, 03 Feb 2021 15:54:21 +0100

In this paper, algorithm-generated airspace sector combinations are analyzed to determine if they are operationally acceptable. Discussions with practitioners identified three desirable characteristics for operational sector combinations. The first is that at each time during a weekly cycle, approximately the same number of sectors are operational. The second is that sector combinations be familiar, and the third is that sector combinations do not change frequently. Methods for visualizing and quantifying these characteristics are proposed. The methods are used to analyze historical sector combinations from the national airspace system and sector combinations generated by a sector-combining algorithm. The results were analyzed by researchers and practitioners. This analysis indicates that changes to the sector-combining algorithm may be required to ensure combinations that are acceptable for current operations. However, the identified characteristics may be less important in a mid-term timeframe (�2018), which is when a sector combining algorithm is being targeted for deployment. I. Introduction In current operations, supervisors in Air Route Traffic Control Centers (ARTCCs or centers) dynamically combine sectors when they are under-utilized (operating below their capacity). This is done primarily so that there are not more controller teams monitoring airspace than are necessary. There are many factors that impact supervisor decisions about when to combine and split sectors, such as air traffic levels, staff availability and capabilities, equipment availability, current and predicted weather, airport configurations, and air traffic demand management initiatives. Currently, these decisions are made based on supervisor experience and judgement. Some previous research has focused on predicting sector combinations and splits based on past supervisor decisions. 1 In Ref. 2, an algorithm to systematically suggest combinations of under-utilized airspace sectors has been proposed. Results suggest that this algorithm may utilize air traffic control resources more efficiently than they are currently utilized. However, feedback from practitioners regarding the sector combination algorithm in Ref. 2 suggests that the proposed sector combinations may not be operationally acceptable due to controller situational awareness and staff planning factors that are not explicitly considered in the algorithm. 3 In this research, the algorithm-suggested sector combinations are compared to historical sector combinations to determine if the algorithm produces operationally acceptable sector combinations. Three desirable characteristics of operational sector combinations specified by practitioners in Ref. 3 are investigated. Quantitative comparisons are designed to study each characteristic in the operational and algorithm-generated sector combinations. Further practitioner feedback on the results of these comparisons is reported.

Multi-leak estimator for pipelines based on an orthogonal collocation model

Scipedia content — Wed, 03 Feb 2021 15:52:46 +0100

International audience; The orthogonal collocation method (OCM) is used to obtain an approximate solution of the water hammer equations which represent one-phase water flow transients in pipeline systems. The OCM provides solutions over the entire spatial domain, therefore it can be used to obtain an accurate model with possible leaks spatially distributed. An estimator can be designed based on the spatially-discretized model in order to detect multiple leaks by identifying their positions and leak coefficients.

Towards optimising distributed data streaming graphs using parallel streams

Scipedia content — Wed, 03 Feb 2021 15:51:56 +0100

Modern scientific collaborations have opened up the opportunity of solving complex problems that involve multi-disciplinary expertise and large-scale computational experiments. These experiments usually involve large amounts of data that are located in distributed data repositories running various software systems, and managed by different organisations. A common strategy to make the experiments more manageable is executing the processing steps as a workflow. In this paper, we look into the implementation of fine-grained data-flow between computational elements in a scientific workflow as streams. We model the distributed computation as a directed acyclic graph where the nodes represent the processing elements that incrementally implement specific subtasks. The processing elements are connected in a pipelined streaming manner, which allows task executions to overlap. We further optimise the execution by splitting pipelines across processes and by introducing extra parallel streams. We identify performance metrics and design a measurement tool to evaluate each enactment. We conducted experiments to evaluate our optimisation strategies with a real world problem in the Life Sciences---EURExpress-II. The paper presents our distributed data-handling model, the optimisation and instrumentation strategies and the evaluation experiments. We demonstrate linear speed up and argue that this use of data-streaming to enable both overlapped pipeline and parallelised enactment is a generally applicable optimisation strategy.

Urban traffic analysis from a large scale floating car data system

Scipedia content — Wed, 03 Feb 2021 15:48:38 +0100

This paper will discuss how the actual knowledge of traffic performances and travel patterns existing in an urban area is crucial to quantify the effects of transportation improvements and of actions that have to be pursued to improve mobility, as well as even an essential input to calibrate land use and traffic simulation models. In this view the use of Floating-Car Data (FCD) is emerging as a reliable and cost-effective way to gather accurate traffic data for a wide-area road network and to improve the analysis of travel conditions. The purpose of this paper is to provide an insight into the potential application of wide scale FCD for improving the traffic analysis process. The reliability of traffic estimates from FCD largely depends not only on the accuracy but also on the size of the input data: until now FCD experiments have been carried out with few equipped vehicles, maximum some dozen; moreover, mostly of them were special vehicles like taxi or bus, with preferential routes, so their behavior cannot be taken as general reference. The originality of this study lies in the large number of private-owned cars involved corresponding to a penetration rate of about 1.3 percent. A full day of FCD related to the city of Florence is examined in this paper to estimate some travel related measures that cannot be readily replicated on a day-by- day basis using other data sources such as user surveys.

Decoupling Dynamic Information Flow Tracking with a dedicated coprocessor

Scipedia content — Wed, 03 Feb 2021 15:42:16 +0100

Dynamic Information Flow Tracking (DIFT) is a promising security technique. With hardware support, DIFT prevents a wide range of attacks on vulnerable software with minimal performance impact. DIFT architectures, however, require significant changes in the processor pipeline that increase design and verification complexity and may affect clock frequency. These complications deter hardware vendors from supporting DIFT. This paper makes hardware support for DIFT cost-effective by decoupling DIFT functionality onto a simple, separate coprocessor. Decoupling is possible because DIFT operations and regular computation need only synchronize on system calls. The coprocessor is a small hardware engine that performs logical operations and caches 4-bit tags. It introduces no changes to the design or layout of the main processor's logic, pipeline, or caches, and can be combined with various processors. Using a full-system hardware prototype and realistic Linux workloads, we show that the DIFT coprocessor provides the same security guarantees as current DIFT architectures with low runtime overheads.

Curve warning driver support systems. A sensitivity analysis to errors in the estimation of car velocity

Scipedia content — Wed, 03 Feb 2021 15:40:19 +0100

Past research projects on intelligent vehicles have already led to the development of a large number of Advanced Driver Assistance Systems. The current research focus is now shifting towards integration and adaptive automation systems that share the control between driver and the machine. Artificial co-drivers can be used for this scope, as tutors to provide holistic support to the driver. However the question of the accuracy and robustness of co-driver evaluations, with respect to perception noise, becomes critical. This work discusses the robustness to perception noise of a Curve Support function, as part of a holistic driver support system based on a co-driver concept. The main objective of the work is to respond to the following question: how accurate should the vehicle state estimation be to design a reliable system? The paper gives a general framework and preliminary results related to noise in the estimation of the vehicle velocity vector.

An empirical evaluation of the Integrated Tower Operations Digital Data System

Scipedia content — Wed, 03 Feb 2021 15:37:06 +0100

The Integrated Tower Operations Digital Data System (I-TODDS), designed for use by ground and local control positions in Airport Traffic Control Towers (ATCTs), combines surface surveillance capabilities with electronic flight data management, weather information, digital taxi clearances, and taxiway conformance monitoring. I-TODDS uses a high-resolution touchscreen to simplify flight data management and reduce the controllers need to shift visual attention among disparate sources of information. I-TODDS reduces display clutter by showing only relevant information when needed but still preserving access to the full complement of flight data. Additional tools assist the controller in recording important information, timing operations, providing memory cues, and maintaining awareness of aircraft positions on the surface. This paper provides a basic description of I-TODDS and presents the results from a recent experiment. The experiment compared I-TODDS to current ATCT operations using paper flight progress strips and surface surveillance in zero-visibility operations. Sixteen current controllers served as participants. The results showed that I-TODDS reduced taxi-out operations by an average of 106 seconds per aircraft and reduced taxi-in operations by 35 seconds per aircraft. I-TODDS also produced an operationally significant reduction in the number and duration of departure delays while increasing the number of departures. Controllers thought that I-TODDS would have a positive effect on their ability to control airport traffic and I-TODDS may be able to support the Staffed NextGen Tower concept. The Federal Aviation Administration currently has a U.S. patent pending for the I-TODDS prototype.

Expanding Regional Airport Usage to Accommodate Increased Air Traffic Demand

Scipedia content — Tue, 02 Feb 2021 08:44:57 +0100

*Small regional airports present an underutilized source of capacity in the national air transportation system. This study sought to determine whether a 50 percent increase in national operations could be achieved by limiting demand growth at large hub airports and instead growing traffic levels at the surrounding regional airports. This demand scenario for future air traffic in the United States was generated and used as input to a 24-hour simulation of the national airspace system. Results of the demand generation process and metrics predicting the simulation results are presented, in addition to the actual simulation results. The demand generation process showed that sufficient runway capacity exists at regional airports to offload a significant portion of traffic from hub airports. Predictive metrics forecast a large reduction of delays at most major airports when demand is shifted. The simulation results then show that offloading hub traffic can significantly reduce nationwide delays.

Symbols for Cockpit Displays of Traffic Information

Scipedia content — Tue, 02 Feb 2021 08:39:44 +0100

web-based study assessed pilots' ability to learn and remember traffic symbols that may be shown on Cockpit Displays of Traffic Information (CDTI). These displays convey data obtained from Automatic Dependent Surveillance-Broadcast (ADS-B) and related Aircraft Surveillance Applications System (ASAS) technologies, as well as other surveillance data sources. We evaluated three aspects of using the traffic symbols when presented in isolation on a static display: intuitiveness, ease of learning, and ease of remembering the symbols. Four symbol sets were tested, each with approximately 22 symbols. Each participant saw only one of the four symbol sets. The sets used different visual features of the traffic symbol to represent the Directionality, Data Quality, Air/Ground Status, Alert Level, Selection Status, and Pairing Status of nearby aircraft. A total of 623 pilots with a broad range of experience participated in the main portion of the study. Results showed that while some conventions are well understood, such as the use of red and yellow for warnings and cautions (respectively), other conventions may be confusing and should be avoided. Two examples of confusing conventions are (a) using more than one visual feature (e.g., two different shapes) to represent the same traffic information, and (b) using similar visual features (e.g., two different outlines) to represent different traffic information. Results of the study were considered by a Federal Advisory Committee that develops standards for these traffic displays (RTCA Special Committee (SC) 186).

Urban intermodality: potentials for connecting the cities’ public transport

Scipedia content — Tue, 02 Feb 2021 08:39:33 +0100

This paper will discuss how intermodality is a well-known element in interurban freight and passenger transport, but has not yet received much attention in the intra-urban environment – even though urban intermodal passenger transport systems gain special importance when energy becomes an expensive resource and when global climatic changes awaken the population’s environmental consciousness. At the same time, the growing urban population together with separated land uses and low-density housing make mobility a daily trial for society. Intermodality, seen here as a seamless connection of different transport modes, contributes to a more sustainable urban mobility pattern, where each transport mode is used in its most efficient way. This challenges the cities to create intermodal transport systems, usable and useful for the biggest possible part of society. The interconnection of different modes seems to have easy solutions, but its implementation involves complex details, such as accessibility, information integration and urban space management. The present study focuses on different European cities’ intermodality schemes. It includes the analysis of all urban transport modes and their interconnections. Factors such as station localization, public transport usage in combination with non-motorized transport modes as well as private vehicle integration in the transportation system are taken into account. As a conclusion, reflections on the present urban intermodality are made and recommendations are given for the future development of intermodal potential in urban environments.

Accomplishing reuse with a simulation conceptual model

Scipedia content — Tue, 02 Feb 2021 08:33:27 +0100

Reuse has been very difficult or in some cases impossible in the modeling and simulation (M&S) discipline. This paper focuses on how reuse can be accomplished by using a conceptual model (CM) in a community of interest (COI). We address the issue of reuse in a multifaceted manner covering many areas (types) of M&S such as discrete, continuous, Monte Carlo, system dynamics, gaming-based, and agent-based. M&S is commonly employed and reuse is critically needed by many COIs such as air traffic control, automobile manufacturing, ballistic missile defense, business process reengineering, emergency response management, military training, network-centric operations and warfare, supply chain management, telecommunications, and transportation. We present how a CM developed for a COI can assist in reuse for the design of any type of large-scale complex M&S application in that COI. A CM becomes an asset for a COI and offers significant economic benefits through its effective reuse.

Development of a New Lateral Stability Control System Enhanced With Accelerometer Based Tire Sensors

Scipedia content — Tue, 02 Feb 2021 08:32:54 +0100

Vehicles are usually equipped with driver assistance systems such as anti-lock brake, traction control and lateral stability control systems. Although the forces maneuvering a vehicle are generated inside the tire contact patch, state of the art control systems have no feedback directly from the tires. Instead, observers based on indirect measurements are employed to close the control loop. Wireless sensors embedded inside the tires can be used to extract valuable information from the tire deformations such as forces. These forces can be used to develop adaptive stability control systems which update their parameters in real-time depending on the road and vehicle conditions. Furthermore, controllers can selectively regulate tire forces by changing brake/drive torques at each tire. This paper examines the integration of accelerometer based tire sensors with lateral stability control system (ESP). Its aim is to present the main components of a smart-tire enabled ESP and a preliminary study on potential performance improvements.Copyright © 2010 by ASME

Velocity trajectory optimization in hybrid electric trucks

Scipedia content — Tue, 02 Feb 2021 08:29:14 +0100

Hybrid Electric Vehicles (HEVs) enable fuel savings by re-using kinetic and potential energy that was recovered and stored in a battery during braking or driving down hill. Besides, the vehicle itself can be seen as a storage device, where kinetic energy can be stored and retrieved by changing the forward velocity. It is beneficial for fuel consumption to optimize the velocity trajectory in two ways; i) to assist the driver in tracking an optimal velocity trajectory (e.g. input to an Adaptive Cruise Controller); ii) to estimate the future power request trajectory which can be used to optimize the hybrid components use. Taking advantage of satellite navigation, together with the vehicles current mass and road load parameters, an optimization problem is formulated, and solved for a driver defined time constraint. Despite tight velocity constraints, this can result in 5% fuel saving compared to a Cruise Controller with constant velocity setpoint. The benefit of velocity trajectory optimization is indicated with experimental results. © 2010 AACC.

A Hydrogen Ignition Mechanism for Explosions in Nuclear Facility Pipe Systems

Scipedia content — Tue, 02 Feb 2021 08:18:26 +0100

Hydrogen and oxygen generation due to the radiolysis of water is a recognized hazard in pipe systems used in the nuclear industry, where the accumulation of hydrogen and oxygen at high points in the pipe system is expected, and explosive conditions exist. Pipe ruptures at nuclear facilities were attributed to hydrogen explosions inside pipelines, in nuclear facilities, i.e., Hamaoka, Nuclear Power Station in Japan, and Brunsbuettel in Germany. Prior to these accidents an ignition source for hydrogen was questionable, but these accidents, demonstrated that a mechanism was, in fact, available to initiate combustion and explosion. Hydrogen explosions may occur simultaneously with water hammer accidents in nuclear facilities, and a theoretical mechanism to relate water hammer to hydrogen deflagrations and explosions is presented herein.

Recent PRCI Guidelines for Pipelines Exposed to Landslide and Ground Subsidence Hazards

Scipedia content — Tue, 02 Feb 2021 08:06:47 +0100

This paper summarizes key considerations in guidelines published in early 2009 that were developed through a Pipeline Research Council International, Inc. (PRCI) supported by PRCI, the Pipeline Hazardous Materials and Safety Administration of the Department of Transportation, and the California Energy Commission. Past practices for pipelines, as well as almost all other construction projects, have focused on avoidance of areas that have a reasonable probability of experiencing geohazards (defined as large ground displacements that may arise from slope failure, slope creep, earthquake triggered slope movement, and subsidence). This approach has been generally successful when there are limited restrictions on selecting a pipeline alignment. Avoiding potential geohazards is becoming increasingly difficult because of the inability to obtain landowner agreements, the lack of space in common utility corridors, environmental restrictions, incompatibility with existing land use, and/or public opposition. In route corridors where geohazards cannot be avoided, the potential risks associated with these hazards must be managed. Pipeline integrity management strategies to mitigate geohazards consist of: (1) design measures that improve the pipeline resistance to the geohazard, (2) measures that limit or control the severity of the geohazard, and (3) operational programs to monitor ground displacement or pipeline response and identify conditions that may warrant further engineering investigations or mitigation activities. Identifying the most appropriate mitigation strategy needs to be based upon specific hazard scenarios and operating circumstances. The PRCI guidelines provide recommendations for the assessment of new and existing natural gas and liquid hydrocarbon pipelines subjected to potential ground displacements resulting from landslides and ground subsidence. One of the most significant benefits of the guidelines is the systematic approach developed for managing pipeline risks from landslide and ground subsidence hazards. It is hoped that this approach, presented in detailed flow charts, will lead to improvements in current practices by providing a common framework for pipeline operators, the local, state, and federal agencies that have regulatory oversight, and the general public to engage in discussions regarding potential risks from pipelines in areas of unstable ground and the most effective and practical means to reduce those risks to an acceptable level.Copyright © 2010 by ASME

Identifying how automation can lose its intended benefit along the development process: A research plan

Scipedia content — Tue, 02 Feb 2021 07:58:10 +0100

Motivation - Automation can fail to deliver the target safety or productivity benefit as intended by those managers and designers advocating its introduction. In a safety critical domain this problem is of significance not only because the unexpected effects of automation might prevent its widespread usage but also because they might turn out to be a contributor to incident and accidents. Originality/value - Research on failures of automation to deliver the intended benefit has focused mainly on human automation interaction. This PhD research plan aims at characterizing decisions - taken under productive pressure - for those involved in the automation development process, to identify where and when the initial intention the automation is supposed to deliver can drift from the initial idea. Expected Finding - The objective is to develop Anti-Drift Principles to identify and compensate proactively for possible sources of drift in the development of new automation. Research Approach - The research is based on case study and is currently entering Year 2.

Document type: Conference object

User requirements for HEO SATCOM for ATM in high latitudes

Scipedia content — Tue, 02 Feb 2021 07:57:10 +0100

It is currently a significant ongoing effort worldwide to develop the future Air Traffic Management (ATM) system. As part of this work, a satellite communication system may ease the congestion problem for ATM services in high density airspace, and in addition provide coverage in oceanic, remote and polar (ORP) areas. For coverage over polar areas, satellites in highly elliptical orbits (HEO) are particularly suitable. In this paper, an overview of user categories is given and the channel characteristics of an aeronautical satellite channel are considered. Both Molniya and Tundra orbits are included. Curves show how parameters like elevation angle, free space path loss and Doppler shift vary as function of satellite movements. In addition, atmospheric effects due to signal propagation through the ionosphere and the troposphere is considered, and finally the effect of multipath propagation due to signal reflections by the aircraft surface and ground.

Vehicle Swarm Rapid Prototyping Testbed

Scipedia content — Tue, 02 Feb 2021 07:26:33 +0100

Increased levels of vehicle collaboration and auton omy are seen as a means to reduce overall mission completion costs while expanding mi ssion capabilities and increasing mission assurance for complex coupled system of systems. Systems health management technologies have made rapid advances that enable systems to know their own condition and capabilities, thus creating the opportunity for unprecedented lev els of adaptive control, real-time reconfiguration, and mission contingency management. Multi-agent task allocation and mission managements systems must account for vehicle- and system-level health-related issues to ensure that these systems are reliable an d cost effective to operate. Boeing’s Vehicle Swarm Technology Lab (VSTL), established in 2004, includes a 100’x50’x20’ testbed equipped with a vision-based motion capture indoor localization system. The testbed provides a cost-effective rapid prototyping capabil ity for integrating health-based adaptive control of subsystems, vehicle, mission, and swarms to guarantee top-level system-of-systems performance metrics. The lab’s heterogeneous fleet includes over 20 heterogeneous air vehicles, including VTOL and fixed wing, along with their ground stations and communication links in addition to heterogeneous ground vehicles and wall climbing robots. This paper discusses the Boeing VSTL design and capabilities, including the indoor localization system, multi-vehicle command and control (C2) and operator interface, realtime virtual environment, and health-based adaptive behaviors. The lab supports rapid prototyping and exploration of various multi-vehicl e operational concept of operations and missions including persistent surveillance, area se arch and tracking, and high density air traffic management. Additionally, the lab supports experimentation tasks for many other platform configuration and collaborative air, groun d, space, and maritime autonomous system of systems concepts.

H=C"sup"3"/sup" (The three C's of Global Harmonization)

Scipedia content — Tue, 02 Feb 2021 07:26:13 +0100

In order to ensure the proper harmonization of the Next Generation Air Transportation System (NextGen) with other systems and air traffic modernization efforts around the world, we must: Collaborate with our global peers and partners, pooling our intellectual talents to develop globally viable standards; Cooperate within and across the regions of the world to ensure synchronized investments and operational improvements; and Coordinate our efforts with any and all stakeholders to implement a truly global Air Traffic Management (ATM) system. The Federal Aviation Administration (FAA) Air Traffic Organization (ATO) International Office is working on the following five key activities to collaborate, cooperate, and coordinate with the global community to harmonize NextGen with other efforts being developed around the world. This paper will elaborate on each and provide insight into the ATO International Strategy document that captures the associated work.

Risk and Reliability Based Fitness for Service (FFS) Assessment for Subsea Pipelines

Scipedia content — Tue, 02 Feb 2021 07:21:16 +0100

The risk and reliability based fitness-for-services (FFS) assessment addressed in this paper is a quantitative risk assessment (QRA) based FFS study on subsea oil or gas pipelines. The main purpose of QRA is to determine the target reliabilities for different pipeline segments. And then, a structure reliability analysis (SRA) method is used to calculate the maximum safe operating pressure, which indicates the pipeline retaining pressure capacity. It has been revealed that the target reliability or target safety level should reflect the consequences of failure, inspection and monitoring scheme etc. But, in the traditional FFS assessment (e.g. B31G and DNV RP F101), the identification of pipeline target reliability is merely based on qualitative judgments and experience. In this paper, however, a quantitative risk assessment will be performed based on abundant data from pipeline inspection and monitoring records, pipeline environmental impact assessment (EIA) study report, pipeline corrosion study report, pipeline emergency response scheme and anything else which can affect the pipeline failure consequences. An example of pipeline FFS assessment performed at four levels has revealed that the risk and reliability based FFS results have much better consistency to the reality.Copyright © 2010 by ASME

Simulating Flight Routing Network Responses to Airport Capacity Constraints in the US

Scipedia content — Tue, 02 Feb 2021 07:00:50 +0100

This paper presents a model which simulates changes in the airline system flight routing network under alternative policy scenarios. The model simulates a game between airlines, in which each airline increases flight frequency in order to maximize its own profit. The underlying modeling framework allows the relationships between changes in fares, passenger demand, infrastructure capacity constraints, flight delays, flight frequencies, and routing network to be simulated. The model is validated for a network of airports in the United States in 2005, before being applied to simulate changes in the same network through 2030 under two policy scenarios. Both scenarios limit airport capacity expansion: (i) in the whole system, and (ii) at Chicago O’Hare International, a primary hub airport, only. Simulated passenger demand, air traffic, flight delays, system CO 2 emissions and Chicago O’Hare NOx emissions are compared to a baseline scenario in which airport capacity is expanded as planned by the FAA. Despite a significant impact on flight delays, the results show little impact of airport capacity constraints on system passenger demand, air traffic growth or CO2 emissions, but show a shift of connecting traffic away from congested hub airports at which capacity is limited to other less congested hub airports, thus reducing traffic growth at these congested airports, and reducing the growth in NOx emissions.

Case Studies on Simulation of Wax Deposition in Pipelines

Scipedia content — Tue, 02 Feb 2021 06:40:02 +0100

The problem cased by wax deposition during production and transportation of waxy oil has been receiving an increasing attention from the industry, especially with the off-shore projects expansion recently. Due to the high cost of those projects, an accurate modelling on wax precipitation and deposition is imperatively required to facilitate the design, development, and operation of those projects.

The risk rate by ADR road transport of dangerous matters

Scipedia content — Tue, 02 Feb 2021 06:37:57 +0100

The paper will be focused on the questions of ADR road transport of dangerous matters, especially on the risks estimation of transport of dangerous goods in the Czech Republic. The risks estimation is the basic presumption for safety increment by this type of risk transport. The aim of the paper is to refer to the risks, which may occur not only in the case of traffic accidents, but also by influence of the various logistics activities. There is also an endeavour to minimization of these risks in the paper.

Robust routing vs dynamic load-balancing a comprehensive study and new directions

Scipedia content — Tue, 02 Feb 2021 06:36:28 +0100

Traffic Engineering (TE) has become a challenging task for network management and resources optimization due to traffic uncertainty and to the difficulty to predict traffic variations. To address this uncertainty in a robust and efficient way, two almost antagonist approaches have emerged during the last years: Robust Routing and Dynamic Load-Balancing. The former copes with traffic uncertainty in an off-line preemptive fashion, computing a stable routing configuration that is optimized for a large set of possible traffic demands. The latter balances traffic among multiple paths in an on-line reactive fashion, adapting to traffic variations in order to optimize a certain cost-function. Much has been said and discussed about the advantages and drawbacks of each approach, but very few works have tried to compare the performance of both mechanisms, particularly in the same network and traffic scenarios. This paper brings insight into several Robust Routing and Dynamic Load-Balancing algorithms, evaluating their virtues and shortcomings and presenting new mechanisms to improve previous proposals. Among others, such a study intends to help network operators in choosing an adequate mechanism to cope with traffic uncertainty.

Logic synthesis for better than worst-case designs

Scipedia content — Tue, 02 Feb 2021 06:35:03 +0100

In this paper we present a novel metric for measuring and optimizing the performance of circuits that operate with the clock period smaller than the worst-case delay. In particular, we developed an efficient logic optimization operation “balance” and a library mapping algorithm named BTWLibMap. Together they are able to reduce the probability of a timing error by 2.3X while only incurring a 4% area overhead.

On Agent Modelling And System Simulation Of Self-Organisation

Scipedia content — Tue, 02 Feb 2021 06:23:43 +0100

Complex, natural, social, technological and economic systems have recently given rise to the need of a new paradigm for computational systems that are adaptive, can self-organise and exhibit emergent behaviour. The design of such systems concerns a homogeneous set of agents in which each agent receives an input and has to map it to a ‘good’ output, and where self-organisation emerges from the interaction between agents. Although general and simple, this concept is representative for a very wide spectrum of applications such as protocol design for large computer networks, design of collective robotics, and automative traffic engineering. Surprisingly, only a handful of recent research is aimed at a domain-independent (or: general) design of such systems. We propose as the solution for the design-problem a framework that tackles the local (agent) level formally and the global (system) level empirically. This allows us to do rigorous formal verification of the behaviour of the individual agents, as well as large-scale empirical validation of the system as a whole. Besides, it exploits the specific advantages of the approaches regarding the scale of the system: formalisation is good for small systems, while simulation works well for (very) large systems. The objective of this paper is to further develop and exploit the idea of combining a formal approach on the agent level and an empirical approach on the system level in self-organisation.

Dimension Calculation Uncertainties in Queuing Models

Scipedia content — Tue, 02 Feb 2021 05:46:33 +0100

In order to conduct traffic quality assessments, queuing models are used for estimating delays and queue lengths. By applying the formulas in existing highway capacity manuals a dimension inconsistence of parameters is determined. This inconsistence of dimension calculations leads to incorrect calculation results if traffic flow volumes are converted from the unit veh/h into the unit pcu/h. Such unit conversion can directly affect the calculation results of delays and queue lengths. Thus, it can also affect the estimated traffic qualities. This problem is addressed and clarified with some examples. It turns out that the queuing models used in traffic engineering are basically correct. But for applications of those models certain preconditions have to be carefully taken into account.

Utility-based joint sensor selection and congestion control for task-oriented WSNs

Scipedia content — Tue, 02 Feb 2021 05:31:39 +0100

Task-centric wireless sensor network environments are often characterized by the simultaneous operation of multiple tasks. Individual tasks compete for constrained resources and thus need resource mediation algorithms at two levels. First, different sensors must be allocated to different tasks based on the combination of sensor attributes and task requirements. Subsequently, sensor data rates on various data routes must be dynamically adapted to share the available wireless bandwidth, especially when links experience traffic congestion. In this paper we investigate heuristics for incrementally modifying the sensor-task matching process to incorporate changes in the transport capacity constraints or feasible task utility values.

Speed Control for Airborne Separation Assistance in Continuous Descent Arrivals

Scipedia content — Tue, 02 Feb 2021 05:12:07 +0100

orne Separation Assistance System (ASAS) is seen as a promising option for the future ATM concept to increase capacity and flight efficiency while maintaining flight safety. One idea of recent interest in ASAS applications is Airborne SPacing Application using enhanced Sequencing and Merging (ASPA-S&M). The S&M is expected to support energy saving arrivals, commonly referred to as Continuous Descent Arrivals (CDA). The motivation for our study is the need to clarify how safety and capacity depend on the setting of spacing criteria and in combination with specific S&M design aspects, and to identify any potential emergent behavior that should be taken into account in the operation design. For this purpose, a preceding study has designed initial mathematical models of the ASAS application for two aircraft trailing. This research develops the models to multiple aircraft trailing under stochastic wind conditions. In this paper, ASAS core components and their interactions are captured to build an integrated model using a Stochastically and Dynamically Colored Petri Net (SDCPN). Through Monte Carlo simulation based on the SDCPN model, we evaluate the performance of ASAS speed control for CDA operation considering the wind effect and multiple trailing aircraft.

PILEP: a contribution to PCE-based interdomain path computation

Scipedia content — Tue, 02 Feb 2021 04:59:24 +0100

The process of computing routes that network traffic must follow throughout Internet has become more complex in the last years. Nowadays, this process is subject to the application of several constraints related to traffic engineering, resources management, quality of the offered services, security or robustness. The application of all these constraints has caused an increase of complexity of those nodes in charge of path computation. Sometimes, the amount of time and resources spent to compute routes is superior to resources used in the main task of these nodes: traffic classification and forwarding. PCE (Path Computation Element) architecture is being developed to diminish that problem in the context of constraint-based path computation for MPLS (Multiprotocol Label Switching). Although research work in relation to this topic is making progress quickly, there are still some unsolved aspects. As a contribution to PCE development, in this work we present a mechanism called PILEP (Procedure for Interdomain Location of External PCEs) that allows the dynamic discovery of routes computation elements in interdomain environments, making use of the existing routing

Resilient Critical Infrastructure Management Using Service Oriented Architecture

Scipedia content — Tue, 02 Feb 2021 04:35:25 +0100

—The SERSCIS project aims to support the use of interconnected systems of services in Critical Infrastructure (CI) applications. The problem of system interconnectedness is aptly demonstrated by ‘Airport Collaborative Decision Making’ (ACDM). Failure or underperformance of any of the interlinked ICT systems may compromise the ability of airports to plan their use of resources to sustain high levels of air traffic, or to provide accurate aircraft movement forecasts to the wider European air traffic management systems. The proposed solution is to introduce further SERSCIS ICT components to manage dependability and interdependency. These use semantic models of the critical infrastructure, including its ICT services, to identify faults and potential risks and to increase human awareness of them. Semantics allows information and services to be described in such a way that makes them understandable to computers. Thus when a failure (or a threat of failure) is detected, SERSCIS components can take action to manage the consequences, including changing the interdependency relationships between services. In some cases, the components will be able to take action autonomously — e.g. to manage ‘local’ issues such as the allocation of CPU time to maintain service performance, or the selection of services where there are redundant sources available. In other cases the components will alert human operators so they can take action instead. The goal of this paper is to describe a Service Oriented Architecture (SOA) that can be used to address the management of ICT components and interdependencies in critical infrastructure systems. Index Terms—resilience; QoS; SOA; critical infrastructure, SLA;

A Study on the Benefit of TCP Packet Prioritisation

Scipedia content — Tue, 02 Feb 2021 04:29:42 +0100

International audience; This paper studies and analyses the benefits of favouring the transfer of packets of a TCP flow over a best-effort network. Specifically, we aim at studying whether we could improve the pace of short data request, such as HTTP request, by giving a high priority to TCP packets that are not previously enqueued inside a core router. Following the idea that long-lived TCP flows greatly increase the routing queue delay, the motivation of this work is to minimise the impact in terms of delay, introduced by long-lived TCP flows over short TCP flows. Thus, this forwarding scheme avoids to delay packets that do not belong to a flow already enqueued inside a router in order to avoid delay penalty to short flow. We define metrics to study the behaviour of such forwarding scheme and run several experiments over a complex and realistic topology. The results obtained present interesting and unexpected property of this forwarding scheme where not only short TCP flows take benefit of such routing mechanism.

Granules: A lightweight, streaming runtime for cloud computing with support, for Map-Reduce

Scipedia content — Tue, 02 Feb 2021 04:25:41 +0100

Cloud computing has gained significant traction in recent years. The Map-Reduce framework is currently the most dominant programming model in cloud computing settings. In this paper, we describe Granules, a lightweight, streaming-based runtime for cloud computing which incorporates support for the Map-Reduce framework. Granules provides rich lifecycle support for developing scientific applications with support for iterative, periodic and data driven semantics for individual computations and pipelines. We describe our support for variants of the Map-Reduce framework. The paper presents a survey of related work in this area. Finally, this paper describes our performance evaluation of various aspects of the system, including (where possible) comparisons with other comparable systems.

A Model for Ontology-Based Scene Description for Context-Aware Driver Assistance Systems

Scipedia content — Tue, 02 Feb 2021 04:24:45 +0100

Driving assistance systems (DAS) offer support in potentially dangerous situations, especially for unexperienced drivers. Co-operative systems improve their performance by sharing information with each other. One key-enabler for describing and exchanging context between intelligent vehicles, which use it for reasoning about their environment, is a common context-model. In this paper, we briefly discuss the influence of the driving context on decision-making and present an OWL-based context-model for abstract scene representation of driving scenarios. We further outline the integration of scene-descriptions with a logic-based reasoning system, based on a set of transformation rules.

Head and gaze dynamics in visual attention and context learning

Scipedia content — Tue, 02 Feb 2021 04:03:51 +0100

Future intelligent environments and systems may need to interact with humans while simultaneously analyzing events and critical situations. Assistive living, advanced driver assistance systems, and intelligent command-and-control centers are just a few of these cases where human interactions play a critical role in situation analysis. In particular, the behavior or body language of the human subject may be a strong indicator of the context of the situation. In this paper we demonstrate how the interaction of a human observer's head pose and eye gaze behaviors can provide significant insight into the context of the event. Such semantic data derived from human behaviors can be used to help interpret and recognize an ongoing event. We present examples from driving and intelligent meeting rooms to support these conclusions, and demonstrate how to use these techniques to improve contextual learning.

Optimization and simulation of operating strategies for container terminals

Scipedia content — Tue, 02 Feb 2021 03:57:15 +0100

TU Dortmund University developed a simulation suite for the Container Terminal Dortmund GmbH seated in the largest inland port in Europe located in Dortmund. This suite focuses on modelling processes, resources and strategies for container terminals and enables to optimize a terminal with simulation. The aim is to optimize the terminal by determining the best mix of operating strategies for crane control, stacking area, handling area and resource management. To achieve this, the current situation of the terminal and different future scenarios for operating the terminal were modelled with the simulation suite.

The LOFAR Known Pulsar Data Pipeline

Scipedia content — Tue, 02 Feb 2021 03:53:32 +0100

Transient radio phenomena and pulsars are one of six LOFAR Key Science Projects (KSPs). As part of the Transients KSP, the Pulsar Working Group (PWG) has been developing the LOFAR Pulsar Data Pipelines to both study known pulsars as well as search for new ones. The pipelines are being developed for the Blue Gene/P (BG/P) supercomputer and a large Linux cluster in order to utilize enormous amounts of computational capabilities (50Tflops) to process data streams of up to 23TB/hour. The LOFAR pipeline output will be using the Hierarchical Data Format 5 (HDF5) to efficiently store large amounts of numerical data, and to manage complex data encompassing a variety of data types, across distributed storage and processing architectures. We present the LOFAR Known Pulsar Data Pipeline overview, the pulsar beam-formed data format, the status of the pipeline processing as well as our future plans for developing the LOFAR Pulsar Search Pipeline. These LOFAR pipelines and software tools are being developed as the next generation toolset for pulsar processing in Radio Astronomy.

Comment: 6 pages, 1 figure. Accepted for publication in proceedings of "ISKAF2010 Science Meeting", PoS(ISKAF2010)60A

Brazilian Gas Network Computational Model for Reliability Analysis

Scipedia content — Tue, 02 Feb 2021 03:26:20 +0100

This paper presents a discussion of the alternatives and strategies used in the thermo-hydraulic simulation of the Brazilian gas pipeline network. It analyses the advantages and disadvantages of each approach and the option used in order to meet the demands of the overall reliability analysis developed by the Gas Reliability Management Sector of PETROBRAS.Copyright © 2010 by ASME

A Framework for Alternative Formulations of the Pipe Network Equations

Scipedia content — Tue, 02 Feb 2021 03:03:19 +0100

The aim of this paper is to revisit the formulations of the equations for flows and heads in water distribution systems and provide clarity for a logical presentation of a framework for the different formulations. Five formulations are described including 1) flow equations where the equations are formulated only in terms of the unknown flows in a network 2) head equations 3) loop flow equations 4) flow and head equations and 5) the Todini and Pilati flow and head formulation. Graph theory is used to show how many unknowns are required to be solved for in each of the five formulations. A Newton solution method is derived for the flow formulation and the Todini and Pilati formulation.

Impact of uncertainty on the prediction of airspace complexity of congested sectors

Scipedia content — Tue, 02 Feb 2021 03:02:00 +0100

The ability of traffic controllers to separate aircraft determines the capacity of the region of airspace under their control, referred to as a sector. Complexity metrics, specifically dynamic density, is used as an estimate for controller workload. The prediction of dynamic density is required for the development of efficient long-term air traffic plans. This paper explores the influence of trajectory errors on the prediction of dynamic density and uses a worst-case analysis to describe the conditions under which forecast errors may lead to excessive complexity. Although the approach has general applicability, it is described using one definition of complexity. Depending on the sector and the complexity function, when a sector is highly congested, the method identifies aircraft entering the sector at certain locations, boundaries and altitudes, whose errors in prediction contribute significantly to the increase in workload. If these errors cannot be reduced, it may be necessary to limit the traffic approaching the sector from these altitudes and boundaries.

Overview of Vehicle-to-Vehicle Radio Channel Measurements for Collision Avoidance Applications

Scipedia content — Tue, 02 Feb 2021 02:50:01 +0100

In this paper we present an overview of a vehicle-to-vehicle radio channel measurement campaign at 5.6GHz. The selected measurement scenarios are based on important safety-related applications. We explain why these scenarios are interesting from the aspect of radio propagation. Further we"br /" describe the power-delay profile and the Doppler spectral density of two situations especially suitable for collision avoidance applications: A traffic congestion situation where one car is overtaking another one, and a general line-of-sight obstruction between the transmitter and the receiver car. The evaluations show that in these situations the radio channel is highly influenced by the rich scattering environment. Most important scatterers are traffic signs, trucks, and bridges, whereas other cars do not significantly contribute to the multipath propagation.

Sustainability and air transport: Zurich airport case study

Scipedia content — Tue, 02 Feb 2021 02:48:35 +0100

An Operator’s Perspective in Evaluating Composite Repairs

Scipedia content — Tue, 02 Feb 2021 02:43:54 +0100

For more than a decade composite materials have been used by pipeline operators to repair damaged pipelines. To validate the performance of composite repair materials, numerous research programs have been conducted. The recent introduction of standards such as ASME PCC-2 and ISO 24817 have provided industry with guidance in using composite materials concerning factors such as the minimum required repair thickness, recommended performance tests, and qualification guidance. Up until now, operators have developed individual requirements for how composite materials can be used and under what circumstances their use is deemed acceptable. To compliment these internal guidance standards, several operators have elected to conduct independent investigations to evaluate the benefits derived in using composite materials for reinforcing specific anomalies such as gouges, dents, girth welds, and wrinkle bends. This paper provides insights that can be used by operators in evaluating the use of composite materials in repairing damaged pipelines with an emphasis on incorporating the current industry standards.

Development of Industry Standards for Composite Repair Systems

Scipedia content — Tue, 02 Feb 2021 02:43:35 +0100

A significant amount of work has transpired over the past several years in generating consensus-based standards that include ASME PCC-2 and ISO 24817 for developing composite repair systems. The intent in developing these standards has been to provide industry with guidelines for designing composite repair systems to ensure that damaged pipelines and piping systems are safely and properly reinforced. With the numerous composite repair systems currently available to pipeline operators, the importance of evaluating the capabilities of each system cannot be overstated. The fundamental design variables available to manufacturers are stiffness, strength, and thickness of the composite. A properly-designed repair system ensures that strains in the reinforced steel and reinforcing composite material do not reach unacceptable levels. This paper provides a basic overview of the design philosophy embedded into the current design codes, as well as presenting results associated with several specific studies that were conducted to evaluate composite repair performance.

An ant-based algorithm for distributed RWA in optical burst switching

Scipedia content — Tue, 02 Feb 2021 02:31:03 +0100

To meet the demanded bandwidth requirements of future optical communication networks, more dynamism, scalability and automatism will need to be provided, which will require, as well, new control plane designs to respond to network changes very rapidly. In this work, we propose the use of an ant colony optimization (ACO) algorithm to support the routing and wavelength assignment in wavelength continuity constraint optical burst-switched networks. The main advantage of the protocol is its distributed nature, which provides higher survivability to network failures or traffic congestion. From the results we see that the new protocol responds effectively to congestion while at the same time providing better performance in comparison to the shortest path routing with random wavelength assignment.

Peer Reviewed

Application Specific Customization and Scalability of Soft Multiprocessors

Scipedia content — Tue, 02 Feb 2021 02:15:46 +0100

hough soft microprocessors are widely used in FPGAs, limited work has been performed regarding how to automatically and efficiently generate soft multiprocessors.In this paper, an automated parallel compilation environment for multiple soft processors which incorporates parallel compilation and inter-processorcommunication structures is described. A total of eight previously-developed parallel processing benchmarks havebeen automatically mapped to a varying number of synthesized soft microprocessors in commercial FPGAs.The new automated infrastructure allows for an evaluation of area, performance, and power tradeoffs for a range of architectural choices. Experiments show that our soft-multiprocessor systems consisting of up to 16 processors can offer up to 5x improvement in application performance against their uniprocessor counterparts.

Sustainable flexible transport services: a solution against social exclusion

Scipedia content — Tue, 02 Feb 2021 02:06:07 +0100

This paper describes how studies have demonstrated that inadequate transport services may create barriers and limit individual and group participation in the normal range of activities. Availability of sustainable transport services can potentially play a very important role in influencing many factors that are enveloped by the concept of social exclusion; in most circumstances inclusion means participation in processes and activities and participation strongly depends on the physical access to facilities. The right to mobility must be guarantee to mobility-impaired people (children, the elderly and the disabled) even in low demand areas and in the presence of a fragmented public transport service. The Public Transport Authorities (PTAs) can and have to influence and encourage the diffusion of IT based flexible transport systems, being able to link and optimize demand and the offer of transport.

Reliability Analysis of Water Distribution Systems Using Graph Decomposition

Scipedia content — Tue, 02 Feb 2021 01:51:56 +0100

Water supply utilities are increasingly being confronted with growing maintenance requirements in order to provide a reliable and cost efficient operation of the water distribution system in order to deliver high standard drinking water. One specific challenge is to find a satisfactory compromise between the contradictory objectives of saving investment cost and meeting the increasing expectations of customers. A valuable tool for the planner is reliability analysis of the system that for instance provides information about the importance of each particular pipe in determining the total reliability of the system. This information can be used to decide which pipes should be replaced next or potentially duplicated to reduce the risk of system isolation. Since structural (topological) reliability only considers the connectivity of the network a new approach for the calculation of structural hydraulic reliability is presented in this paper. The algorithmic implementation is based on a decomposition method of the network graph that greatly enhances both the calculation of pure structural reliability as well as structural hydraulic reliability.

Providing Cost-effective QoS Monitoring in Multiservice Networks

Scipedia content — Tue, 02 Feb 2021 01:49:19 +0100

http://www.ngi2009.eu/ In multiservice networks, QoS monitoring needs to be carried out in a per-class basis so that each service class measuring requirements and behavior are met and sensed properly. Facing the shortage of off-the-shelf class-based monitoring solutions, this work is focused on the development of a flexibly QoS monitoring tool oriented to multiservice networks. In this context, after discussing main QoS monitoring issues, we propose a flexible QoS monitoring Java application, totally user parameterized and supporting service differentiation. Benefiting from an edge-to-edge design perspective, this service-oriented tool is able to make a periodic evaluation of relevant QoS metrics for each service class, on an intra-domain or end-to-end path basis. Monitoring results, stored in a MySQL database, are useful to drive both online and offline traffic engineering and service management tasks.

Multicriteria analysis measurement of the road transport corridor impact on the environment

Scipedia content — Tue, 02 Feb 2021 01:35:17 +0100

This paper describes how transport is one of the main branches of any economy without which the functioning of a modern economy is, in general, impossible. It ensures necessary economic links and joins all industrial units of a country into one whole, thus establishing the conditions for an economy to function coherently and efficiently. Thus, transport is an important branch of an economy. However, its infrastructure expansion needs high levels of investment. This is why investment projects for the development of the transport structure have to be thoroughly selected and their implementation has to ensure sufficient efficiency. Taking into account that transport generates a number of adverse effects from both transport infrastructures and vehicles, the indirect ones – environmental influences might be included into the group – may have even greater consequences on society than its direct effects.

The posssibilities of railway transport utilizing as a backbone network of integrated passenger transport systems

Scipedia content — Tue, 02 Feb 2021 01:11:36 +0100

The aspects of utilizing of railway transport as a backbone network of integrated passenger transport systems are solved in the contribution. The basic requirements on this railway transport service are specified in the contribution. The main attention is focused on creating of line structure of the integrated transport systems. The location of interchange points is also accented in the contribution. The theoretical presumptions are also illustrated in the way of convenient practical examples.

Colorado WAM separations standards targets of opportunity and flight test analysis

Scipedia content — Tue, 02 Feb 2021 00:54:06 +0100

The Federal Aviation Administration (FAA) Surveillance and Broadcast Services (SBS) Program Office and the Colorado Department of Transportation are implementing Wide Area Multilateration (WAM) in Non-Radar Airspace (NRA) to improve air traffic services at and around routes and fixes that support operations at Hayden/Yampa Valley (HDN), Craig-Moffat (CAG), Steamboat Springs/Bob Adams Field (SBS), and Garfield County Regional - Rifle (RIL) airports. In particular, the lack of comprehensive radar surveillance at and below 10,000 ft. in these regions requires controllers to use procedural separation standards for the Instrument Flight Rules (IFR) arriving/departing aircraft. While this is a safe means of providing service, it is inefficient for current traffic and especially for expected demand growth. Wide Area Multilateration is a distributed surveillance technology that utilizes a constellation of ground stations to provide surveillance coverage within a defined region. This technology makes use of signals transmitted from Air Traffic Control Radio Beacon System (ATCRBS) (Modes A and C) and Mode S transponders, in response to interrogations. The Mode S transponders also provide the squitter message once per second. The implementation, certification, and commissioning of WAM would enable air traffic controllers to apply more efficient separation standards for aircraft operating in the affected airspaces. For this operational environment, with WAM as the surveillance technology, the FAA seeks to achieve 5 NMI lateral/longitudinal separations. This paper describes the technical results from the data modeling, controlled flight test, and targets of opportunity analysis for the WAM sensor constellations near HDN and RIL to support separation standards within the Host Computer System (HCS) automation platform environment at Denver Center (ZDV). Comparative analysis was conducted between WAM and Secondary. U.S. Government work not protected by U.S. Copyright. Surveillance Radar (SSR) to evaluate and validate WAM performance to support separation services.

Rural areas, high-speed train accessibility and sustainable development

Scipedia content — Tue, 02 Feb 2021 00:50:51 +0100

This paper analyzes the key steps in the reorganization of demand-responsive transport systems in rural areas that have low population density, and their connection with the high-speed railway network. The deficiencies of public transport in sparsely populated rural areas means that captive users of public transport avoid trips, or even that they move to live near more accessible places, with the consequential abandonment of the poorly served areas towards urban centers where accessibility is not a problem. On the other hand, those who can use private vehicles are forced to do so, consequentially giving up using public transport altogether and thus reducing demand for this type of transport, which increases the environmental impact caused by the private vehicles. To confront these difficulties, demand-responsive transport systems came into use, responding to the needs of low density territories. The study carried out analyses of the territorial experiences of demand-responsive systems and their implications. Results obtained in this investigation, regarding the definition of potential users, the confluence of diverse types of travelers and merchandise and the support points of compatible attraction of activity with the station, among others, are reviewed in this paper. The experience analyzed in the study cases demonstrates the suitability of this type of system as an alternative to regular transport, contributing to a sustainable use of the territory and public services, among which high-speed railway stations are very significan

Decision analysis of Air Traffic Controller in order to propose decision support systems

Scipedia content — Tue, 02 Feb 2021 00:31:43 +0100

The Air Traffic Controller must take important decisions in each moment. They manipulate a lot of data and parameters. With the increase of traffic it is more difficult to take decision rapidly and safely. In this paper we try to provide some tools able to help the Controller in their work. To do that it is necessary to access to their decision-making process. We propose an approach. This approach is composed of a multiple criteria methodology, and interviews to obtain data. We present next an analysis of these interviews. This analysis show what we can extract from this technique: criteria, preferences for the multiple criteria methodology, and how we use it for propose some tools. The following step will be to integrate the results of these analyses to our system.

Dynamical systems complexity with a view towards air traffic management applications

Scipedia content — Tue, 02 Feb 2021 00:18:46 +0100

International audience; The growth of air traffic in future years requires a paradigm shift in the way the aircraft are controlled. Major innovative projects (SESAR in Europe, NexGen in USA) have started in order to define and implement control tools based on time-space constraints on aircraft trajectories. As a consequence, an increasing level of automation is expected. In this framework, it is of primary importance to be able to quantify the hardness to produce conflict free trajectories for a given situation and the robustness of the solution found. In this paper, a characterisation based on the Lyapunov exponents of a dynamical system interpolating the observed data will be presented. A first part will be devoted to vector field fitting, and a second one to efficient lyapunov exponents computation. Then, some practical implementation issues will be discussed.

Electric vehicles: the solution to emissions from transport?

Scipedia content — Tue, 02 Feb 2021 00:17:12 +0100

The environmental impacts of all industry sectors are coming under more and more scrutiny around the world, given the current focus on climate change, environmental impacts and energy security. The transport sector is included in this scrutiny; it is responsible for about14% of Australia's C02 emissions, with about half of this is due to passenger and light commercial vehicles. Furthermore, greenhouse gas emissions from transport have grown by29% since 1990. One technology that can contribute to sustainable transport is that of electric vehicles,including electric-assisted bicycles, electric scooters and motorcycles, and electric passenger vehicles. The main advantage of electric vehicles is that they can be recharged using electricity generated from clean, renewable energy sources, at a lower environmental and monetary cost than a petrol or diesel car. The main disadvantage of electric vehicles is that they have limited range and long recharge times compared to fossil-fuelled vehicles, and so can not match the versatility of conventional cars. However, low-mass electric vehicles aremuch better suited to the short commutes that make up almost all of the trips made by conventional cars. Refereed/Peer-reviewed

Integrated Traffic Flow Management Decision Making

Scipedia content — Mon, 01 Feb 2021 23:47:26 +0100

generalized approach is proposed to support integrated traffic flow management decision making studies at both the U.S. national and regional levels. It can consider trade- offs between alternative optimization and heuristic based models, strategic versus tactical flight controls, and system versus fleet preferences. Preliminary testing was accomplished by implementing thirteen unique traffic flow management models, which included all of the key components of the system and conducting 85, six-hour fast-time simulation experiments. These experiments considered variations in the strategic planning look-ahead times, the re- planning intervals, and the types of traffic flow management control strategies. Initial testing indicates that longer strategic planning look-ahead times and re-planning intervals result in steadily decreasing levels of sector congestion for a fixed delay level. This applies when accurate estimates of the air traffic demand, airport capacities and airspace capacities are available. In general, the distribution of the delays amongst the users was found to be most equitable when scheduling flights using a heuristic scheduling algorithm, such as ration-by-distance. On the other hand, equity was the worst when using scheduling algorithms that took into account the number of seats aboard each flight. Though the scheduling algorithms were effective at alleviating sector congestion, the tactical rerouting algorithm was the primary control for avoiding en route weather hazards. Finally, the modeled levels of sector congestion, the number of weather incursions, and the total system delays, were found to be in fair agreement with the values that were operationally observed on both good and bad weather days.

Wind-Optimal Routing in the National Airspace System

Scipedia content — Mon, 01 Feb 2021 23:17:25 +0100

study analyzing the economic cost and benefit impacts of different flight routing methods in the National Airspace System is presented. It compares wind-optimal routes and filed flight routes for 365 days of traffic, from 2005 to 2007, in class A airspace. Routing differences are measured by flight time, fuel burn, sector loading, conflict counts, and airport arrival rates. From the results, wind-optimal routes exhibit an average per-flight time saving of 2.7 min and an average fuel saving of 210 lb, compared to filed flight routes. In addition, the airport arrival rates at the top 73 U.S. domestic airports do not show notable differences between wind-optimal routing and filed flight routing. The study shows an average of 29% fewer conflicts. Finally, wind-optimal routes have, at most, one high-altitude sector with increased sector workload than filed flight routes at any time instance.

Robust routing mechanisms for intradomain traffic engineering in dynamic networks

Scipedia content — Mon, 01 Feb 2021 22:46:17 +0100

International audience; Internet traffic is highly dynamic and difficult to predict in current network scenarios. This makes of traffic engineering (TE) a very challenging task for network management and resources optimization. We study the problem of intradomain routing optimization under this traffic uncertainty. Recent works have proposed robust optimization techniques to tackle the problem, conceiving the robust routing (RR) approach. RR copes with traffic uncertainty in an off-line preemptive fashion, computing a single static routing configuration that is optimized for traffic variations within some predefined uncertainty set. Despite achieving routing reliability with relatively low performance loss, RR presents various drawbacks and conception problems as it is currently proposed. This paper brings insight into the different robust routing shortcomings, introducing new mechanisms that improve previous proposals and alleviate these problems. Among others, we propose and evaluate new optimization objectives to attain better global performance from an end-to-end quality of service perspective.