Scipedia: Documents published in 2006

Towards a Generic “Single-Path Programming” Solution With Reduced Power Consumption

Scipedia content — Tue, 02 Feb 2021 04:02:00 +0100

As embedded designs become more widespread and complex they tend to use more modern processors. Such processors will often include features (such as pipelines, caches, and branch predictors) which help to improve performance. While such performance improvements are welcome, they come at the price of predictability. More specifically, the use of advanced processor hardware makes it difficult to predict the worst-case execution time (WCET) of tasks. As part of an effort to address these problems, Puschner and Burns (Proc. 7th IEEE International Workshop on Object-Oriented Real-Time Dependable Systems, Jan. 2002) proposed the “single path programming paradigm”. As its name implies program code written according to this paradigm has only one execution path: this helps to ensure a constant execution time. Yet there are two problems with the techniques described by Puschner and Burns: (i) they are applicable only to hardware which supports “conditional move” or similar instructions; (ii) their balancing approach increases power consumption. In the present paper, we begin to address both of these problems with a set of novel code-balancing techniques. The effectiveness of these new techniques is explored by means of an empirical study.

Phased-Array Focusing with Longitudinal Guided Waves in a Viscoelastic Coated Hollow Cylinder

Scipedia content — Tue, 02 Feb 2021 03:49:10 +0100

Guided wave phased‐array focusing techniques have been studied and applied in the long‐range guided wave inspection of industrial pipelines. Advantages include longer inspection distance, greater wave penetration power and higher detection sensitivity. For reasons of protection, safety and thermal efficiency, a large percentage of pipes are coated and/or encased and buried underground. A phased‐array focusing study for guided waves is now considered on pipelines with viscoelastic coatings. In this paper, longitudinal guided wave focusing as well as axisymmetric wave propagation is studied in a bare pipe and a pipe with a viscoelastic coating. A finite element model is studied. First, an investigation on whether the coating has an affect on the axisymmetric guided wave propagation is reported. Based on the result of a single channel, phased array focusing with 8‐channel segments is studied. This study provides a very useful tool and guidance for the analysis and examination of guided wave focusing in a real field pipeline under various coating and environmental conditions.

Future news of international freight transport markets — what to expect and how to be prepared

Scipedia content — Tue, 02 Feb 2021 03:24:49 +0100

Transport and logistics have to be understood and analyzed at international and interregional scales because of fast growing international trade, developments in specific transport corridors, and the ongoing concentration process of international, multi-modal logistics providers. This paper describes the current situation of international transport markets, the main trends and driving forces of the process are analyzed, some selected issues are projected into the future, and major impacts on regional and urban levels are derived. The paper finds that freight transport might be growing even faster within the next ten years than generally assumed. New solutions in different elements of the logistics value chain, elimination of current bottlenecks, and enhanced business models of multi-modal, international cooperation, and rational transport policies seem to be the candidate fields of action in this context. Nevertheless, risks of declining environmental qualities around logistics hubs and corridors have to be considered.

Dividing the Traffic Matrix to Approach Optimal Traffic Engineering

Scipedia content — Tue, 02 Feb 2021 03:21:22 +0100

In this paper we propose a new method to approach optimal Traffic Engineering routing. The method consists of dividing the traffic matrix into $N$ sub-matrices, called strata, and route each of these independently. We propose two different implementations of our method in routers. Our method can also be used to compute a very precise approximation of the optimal value of a given objective function for comparison to heuristic Traffic Engineering algorithms. For this application, our algorithm is very efficient on large topologies compared to an LP formulation. Peer reviewed

Cellular automata simulation of traffic flow through a road with a construction zone

Scipedia content — Tue, 02 Feb 2021 02:52:14 +0100

Development of sustainable traffic planning: analysis of Danish planning visions 2005 and 2015

Scipedia content — Tue, 02 Feb 2021 02:39:27 +0100

Traffic and city planning has been a matter of solving actual problems with specific plans rather than by making visionary long-term planning to prevent new problems from occurring. As the amount of traffic increases and congestion problems appear there has, however, been a renewed focus on the interaction between transport and sustainability. To exemplify the advancement of Danish planning methodology this paper reviews a visionary traffic planning report produced by the Danish Ministry of Transport in 1993 called “Trafik 2005”. On this basis a recent set of planning visions for 2015 is examined and by using a simple counting technique the development in Danish transport planning is monitored and conclusions are given.

Tensile Testing of Carbon Steel in High Pressure Hydrogen

Scipedia content — Tue, 02 Feb 2021 02:23:28 +0100

An infrastructure of new and existing pipelines and systems will be required to carry and to deliver hydrogen as an alternative energy source under the hydrogen economy. Carbon and low alloy steels of moderate strength are currently used in hydrogen delivery systems as well as in the existing natural gas systems. It is critical to understand the material response of these standard pipeline materials when they are subjected to pressurized hydrogen environments. The methods and results from a testing program to quantify hydrogen effects on mechanical properties of carbon steel pipeline and pipeline weld materials are provided. Tensile properties of one type of steel (A106 Grade B) in base metal, welded and heat affected zone conditions were tested at room temperature in air and high pressure (10.34 MPa or 1500 psig) hydrogen. A general reduction in the materials ability to plastically deform was noted in this material when specimens were tested in hydrogen. Furthermore, the primary mode of fracture was changed from ductile rupture in air to cleavage with secondary tearing in hydrogen. The mechanical test results will be applied in future analyses to evaluate service life of the pipelines. The results are also envisioned to be part of the bases for construction codes and structural integrity demonstrations for hydrogen service pipeline and vessels.

Asset Management Strategies for Metallic Municipal Transmission Pipelines

Scipedia content — Tue, 02 Feb 2021 02:07:19 +0100

This paper presents strategies for the control of external corrosion on municipal transmission pipelines as part of a comprehensive Asset Management Program. Several Asset Management strategies are available to municipal utility managers including run to failure; run until failure and repair as required; and operate and maintain using preventative maintenance to provide an indefinite life. Examples of these strategies would include operating a water pump to failure, operating a pipeline until a failure occurs and then making repairs as required, and operating and maintaining a facility such that the facility has an indefinite life. Several asset management strategies are currently being used in the municipal transmission pipeline arena. This paper discusses the short term and long term impacts of these strategies.

Internet Traffic Forecasting using Neural Networks

Scipedia content — Tue, 02 Feb 2021 01:49:52 +0100

The forecast of Internet traffic is an important issue that has received few attention from the computer networks field. By improving this task, efficient traffic engineering and anomaly detection tools can be created, resulting in economic gains from better resource management. This paper presents a Neural Network Ensemble (NNE) for the prediction of TCP/IP traffic using a Time Series Forecasting (TSF) point of view. Several experiments were devised by considering real-world data from two large Internet Service Providers. In addition, different time scales (e.g. every five minutes and hourly) and forecasting horizons were analyzed. Overall, the NNE approach is competitive when compared with other TSF methods (e.g. Holt-Winters and ARIMA). Engineering and Physical Sciences Research Council (EP/522885 grant). Portuguese National Conference of Rectors (CRUP)/British Council Portugal (B-53/05 grant). Nuffield Foundation (NAL/001136/A grant).

DVB-S2/DVB-RCS satellite system performance assessment for IFE and ATN aeronautical communications

Scipedia content — Tue, 02 Feb 2021 01:38:49 +0100

This paper presents the PhD work conducted by Na TAO. The director of this thesis is Professor Michel BOUSQUET. The study is supervised by Alain PIROVANO and Jose RADZIK. This PhD work has started January 2006 and will end in December 2008. Two concurrent satellite systems are presently proposed for in-flight entertainment (IFE) communications, thus demonstrating the capability of satellites to provide multimedia access to users on board airplanes. At the same time, an increasing interest for the use of satellite communications for air traffic control has been motivated by the increasing load of traditional radio links, mainly in the VHF band. However, the development of a dedicated satellite system for ATC (Air Traffic Control) and ATN (Aeronautical Telecommunication Network) seems to be a long-term perspective. The objective of the presented system design is to provide both passenger application traffic (Internet, GSM) access and a high-reliability channel for aeronautical applications using the same satellite links. Due to the constraints in capacity and radio bandwidth allocation, very high frequencies (above 20 GHz) are considered here. The corresponding design implications for the air interface are taken into account and access performances are derived using a dedicated simulation model. Some preliminary results are shown in this paper to demonstrate the technical feasibility of such system design with increased capacity, more details and the open issues will be studied in the future of the thesis research.

Bi-level optimal toll design problem solved by the inverse Stackelberg games approach

Scipedia content — Tue, 02 Feb 2021 01:34:40 +0100

This paper considers the special type of Stackelberg games known as inverse (or reverse) Stackelberg games and their application to the problem of bi-level optimal toll design in road traffic systems. On a given strongly connected network the paper assumes a non-cooperative game with two levels of players: the road authority as a leader and travelers as followers. The paper considers the road authority with two possible objectives: It either tries to maximize the total toll revenue or to minimize the total travel time of the network by setting tolls on toll roads, while the travelers minimize their travel costs by choosing their travel behavior. In the analysis of traffic systems, link-travel times are modeled as link performance functions, relating travel time to the volume of traffic on the link. These functions are typically smooth, nonlinear, positive, and strictly increasing with link flow. The paper defines link tolls as functions of one or more link flows of the network. Starting from small networks with several origin-destination pairs we analytically find the optimal toll functions for the road authority with the lower level defined by the deterministic user-equilibrium model. The main contributions of this paper are the application of the new field of inverse Stackelberg games in traffic problems and finding the solution to these problems analytically. In order to define the toll as a function of the link flows seems to be very practical and can help to solve, for example, the congestion problems in densely populated areas.

Airspace block organization with metaheurisitics and partitioning packages

Scipedia content — Tue, 02 Feb 2021 01:00:16 +0100

International audience; In this paper, different metaheuristics applied on an air traffic control problem. This problem is a graph partitioning problem. It can be solved by classical methods which are spectral and multilevel methods. State-of-the-art public-domain graph partitioning packages, CHACO and METIS are used to resolve it. A comparison between results return by these packages and metaheuristics implementations is made for different objective functions of the literature.Metaheuristics used are simulated annealing, ant colony and a new one called fusion fission developed in the LOG laboratory. Experimental results show that metaheuristics find better results than classical packages.

Traction system for electric vehicles using a variable frequency three-phase induction motor driver with regenerative braking

Scipedia content — Tue, 02 Feb 2021 00:16:13 +0100

This paper describes the development and implementation of a traction system, based in the utilization of a three-phase induction motor controlled by a Power Electronics Inverter, to be used in electric vehicles. This system allows the speed control of the vehicle, forwards and backwards, and also permits regenerative braking. The induction motor is fed, through the inverter, by a set of batteries. During the operation in the regenerative braking mode, the induction motor returns, through the inverter, the vehicle kinetic energy to the batteries. Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ESE/41170/2001, POCTI/ESE/48242/2002 Programa de Incentivos à Modernização da Economia (PRIME) - projecto SINUS

Trailing Vortex Wake Encounters at Altitude - A Potential Flight Safety Issue?

Scipedia content — Mon, 01 Feb 2021 23:50:07 +0100

The potential hazard of one aircraft encountering the trailing vortex wake of another aircraft during either take-off or landing is well known. The wake vortex hazard in the terminal area has been virtually eliminated using the operational procedures and aircraft separation criteria mandated by the air traffic authorities. This paper presents arguments that wake encounters at cruise altitude are a potential safety issue that needs to be examined. Wake vortex encounters at cruise altitudes are likely to increase due to three factors. These factors include; the reduction of the minimum vertical separation distances between aircraft, the increased air traffic allowed by the reduced vertical separations, and the large difference in the size of aircraft operating at the cruise altitudes. The arguments are supported by simple analysis and a review of simulation and flight test results obtained from earlier studies of wake encounters at low altitudes. Simple analysis techniques show that the rolling moment induced on a following aircraft is comparable in magnitude to that which could occur during take-off or landing. In addition reported wake encounters at cruise altitude are discussed.

Steel Water Pipe Joint Testing

Scipedia content — Mon, 01 Feb 2021 23:45:18 +0100

Steel water pipe in the municipal industry has typically been designed with either restrained or non-restrained joints, (typically rubber gaskets). Restrained joints are required where thrust is at elbows, tees, laterals, wyes, reducers, valves, and dead ends. These joints are restrained by welding, harnessing and blocking. Most typical is the welded slip joint, because of its flexibility, ease in forming and laying, watertight quality and its ability to make small angle changes at each joint. The efficiency of the welded slip joints and rubber gasket joints has been tested by numerous manufactures for internal pressure. The pipe barrel will usually fail by exceeding the elastic limit of the steel prior to leaking or failure of the joint. This is due to the increased section modulus of the joint configuration and stress orientation. The ASME, recommends applying joint efficiencies of 0.45 and 0.55, respectfully for single and double-fillet lap welds and 0.9 for butt-welded pipe. The full-scale tests done by Thompson Pipe and Steel Company (1984) showed efficiencies in the 0.83 to 0.76 range for lap welded pipe. The unpublished tests at Consolidated Western Steel (1958) revealed efficiencies at nearly 1.0 for lap welded joints. Joint efficiency values are sometimes used to calculate shell thickness for buried pipelines. The question arises, what do these efficiencies mean, and how should they used in design of welded joints?

Air Traffic Control Studies of Small Aircraft Transportation System Operations

Scipedia content — Mon, 01 Feb 2021 23:39:15 +0100

The National Aeronautics and Space Administration's (NASA's) small aircraft transportation system (SATS) higher volume operations (HVO) research team collaborated with the Federal Aviation Administration's (FAA's) William J. Hughes Technical Center to provide a real-time simulation environment for conducting three proof of concept investigations of SATS HVO from an air traffic control (ATC) perspective. For the complete final test report (Magyarits et al., 2005). The main intent of the simulations was to collect data from certified professional controllers (CPCs) on workload and feasibility of SATS HVO in the operational environment from terminal and en route views (Magyarits et al., 2005). CPCs provided feedback on SATS procedures, phraseology, and the display of SATS related information. The information obtained will assist NASA researchers in the continued development and refinement of the SATS HVO concept.

AReViRoad: a virtual reality tool for traffic simulation

Scipedia content — Mon, 01 Feb 2021 23:35:31 +0100

This paper will introduce AReViRoad, a virtual reality tool and a traffic road simulator that enables one to determine the impact of the road network on traffic fluidity. The traffic generation is based on a multi-agent system in which each vehicle (an entity) is a software agent with its own behavior (autonomous). This solution offers a credible traffic road that will be used for testing a road network. With a set of given tools one can create one’s own road network. Thereafter, one can configure one’s own simulation (number of vehicles, tested road network, flow of car generators) and then launch, observe and analyze it with dedicated tools, such as a 3D view, flow meter and timer.

Optimal Control of Air Traffic Networks Using Continuous Flow Models

Scipedia content — Mon, 01 Feb 2021 23:19:00 +0100

n the National Airspace System using an Eulerian description of the network with hyperbolic partial dierential equations. Existence and uniqueness (well-posedness) of a solution to the system of partial dierential equations on a network is established. Subsequently, an optimal control problem is studied with the junction coecients as control variables. We use a fully discretised adjoint approach and we implement it on a network with 16 links and 5 junctions created from the enroute high altitude jetways between the Oakland and Salt Lake City air trac control centers. The aircraft flows on the final link of the network with and without control are compared and the results demonstrate the eciency of the method developed in the article.

A computer simulation scenario analysis approach as a decision support tool for transportation systems planning

Scipedia content — Mon, 01 Feb 2021 23:10:55 +0100

the level of traffic congestion rises and the complexity of traffic networks increases, the development of effective transportation strategies becomes the most challenging task for every transport authority. Meanwhile, advancements in computer technology and especially the technique of computer simulation offer a new effective way for testing plausible solutions prior to their implementation. Based on a microscopic traffic simulation model this paper presents an evaluation of the effectiveness of alternative traffic solution interventions on a main arterial in Nicosia, Cyprus. In particular, computer experiments are carried out to test various plausible scenario solutions. The scenarios under evaluation, involve the use of dedicated bus lanes, high occupancy vehicle lanes and road enhancement interventions. The simulation results show that an attractive scenario such as the use of dedicated bus lanes, if not designed properly, could bring disastrous results not only to the private car transport mode but also to the bus transport mode as coupling effects cause buses to get stuck with the rest of the traffic. By going through a computer experimentation process and scenario analysis a viable solution is derived, where restricted lanes for buses and high occupancy vehicles are introduced in combination with road geometry redesign and traffic re-direction at key points. 96 177 187 "p"Sponsors: WIT Transactions on The Built Environment Conference code: 71376

Assessing the Effects of Impact Forces on Subsea Flowlines and Pipelines

Scipedia content — Mon, 01 Feb 2021 22:58:10 +0100

Damage associated with external impact can be a critical component in operating subsea flowlines and pipelines. External damage typically involves impact with anchors, although consideration of dropped objects is also important. Historically, operators assess damage after it occurs in an attempt to determine and establish mechanical integrity. For more than 30 years research has been performed studying the effects of external damage on subsea pipelines. In recent years there has been an interest in proactively addressing the potential for damage and attempting to quantify the severity of damage in terms of impact energies associated with anchors and dropped objects. This paper presents insights garnered in assessing the severity of pipeline damage in the form of dents and gouges. Additionally, research associated with impact forces including experimental work is included as part of the presentation, as well as limit analysis techniques using finite element methods. The primary purpose of this paper is to communicate to offshore pipeline operators a methodology that can be employed to assess the severity of damage and quantify tolerance levels in terms of impact energy.

Vision Based Following of Locally Linear Structures using an Unmanned Aerial Vehicle

Scipedia content — Mon, 01 Feb 2021 22:56:53 +0100

Inspecting and monitoring oil-gas pipelines, roads, bridges, power generation grids is very important in ensuring the reliability and life expectancy of these civil systems. An autonomous UAV can decrease the operational costs, expedite the monitoring process and be used in situations where manned inspection is not possible. This paper addresses the problem of monitoring these systems using an autonomous unmanned aerial vehicle (UAV) which follows the locally linear structures using visual feedback.

Sustainable regional development and provincial development planning: the case of Bolu

Scipedia content — Mon, 01 Feb 2021 22:50:51 +0100

This paper analyzes the possibilities of a development strategy for realizing sustainable spatial development in Bolu (an important tourism center and transit point of Northwestern Anatolia in Turkey). The paper also analyzes the principles and limitations of the 2023 Provincial Development Plan of Bolu (BIGEP). In Bolu province, where the co-existence of nature protection areas, a rich flora and fauna and historical settlements has provided suitable conditions for the development of mass tourism facilities, the earthquakes in the Eastern Marmara and Duzce in 1999 accelerated the urbanization of agricultural lands for housing needs at the sub-regional level. Both the need for spatial and economic planning of the future development of urban and rural settlements and the priorities of pre-disaster planning in the provincial area made necessary the preparation of a sub-regional development plan in Bolu. The BIGEP plan comprising the economic and spatial development strategies of Bolu province for 2023 can be evaluated as an effort to reveal the sub-regional development dynamics under the heading of a “provincial development plan”. However, the content of the BIGEP requires elaboration in terms of the priorities of sustainable development. The implementation scope of the plan as a region under constant threat from earthquakes means that the discussion of sustainability is far from being a priority. Here, the crucial questions are which priorities, emphases and contents do the policies on spatial and economic structure in a region under threat of earthquake have? Which natural contradictions exist for a strategy on making such a region the focus of economic development? And lastly, can provincial development planning be a planning level for sustainable development of the build environment?

Distributed Explicit Partial Rerouting (DEPR) Scheme for Load Balancing in MPLS Networks

Scipedia content — Mon, 01 Feb 2021 22:34:14 +0100

Traffic engineering is one of the important enhancements introduced by the deployment of Multiprotocol Label Switching (MPLS) into IP-networks. Minimizing congestion is a central goal of traffic engineering as it degrades the overall network performance. We propose the Distributed Explicit Partial Rerouting (DEPR) scheme as a reactive congestion removal for MPLS networks. DEPR removes congestion by rerouting the LSPs crossing the congested link to a partial route set up around the congested link (unlike other methods that re-establish the full route from the source to the destination). The scheme is shown to adapt quickly to network dynamics and to scale well with large networks. It also enhances the overall network throughput and delay performance.

Air to Air Communication Protocol

Scipedia content — Mon, 01 Feb 2021 22:21:05 +0100

We present air to air communication (AAC) a wireless protocol designed for communication among airplanes as well as airplanes and control centers. AAC enables the broadcast of emergency and surveillance information such as realtime video over the network even in presence of adverse conditions such as coordinated terrorist attacks. AAC is very robust. AAC minimizes the number of retransmissions and therefore reduce the collisions, which could considerably delay transmissions and disrupt the communications during emergency situations. AAC performs very well in highly dynamic ad hoc networks of airplane. AAC has the potential to significantly enhance the security of the homeland by closely monitoring the airplane which, if hijacked by terrorists or criminals, could be used as weapons. We have evaluated AAC through analysis and ns-2 simulations.

Making liveable and sustainable major urban streets: the case of Begin Road in Tel-Aviv – Jaffa

Scipedia content — Mon, 01 Feb 2021 21:58:57 +0100

This paper discusses the struggle to create a new major urban street that will help liveability and sustainability in the city of Tel-Aviv. Begin Road used to be a major inter-urban road linking the center of Tel-Aviv with its eastern and northern suburbs. With the construction of the Ayalon Freeway, the new suburban rail system sharing the same corridor, and the planned light rail subway that will run underneath it, Begin Road is undergoing a process of change. It is being transformed into the future main street of the Tel-Aviv CBD. This paper discusses the functions of major urban streets, the detrimental effects of modern traffic engineering practices and the need to revive these streets. This theoretical background guided the design of alternatives for Begin Road. Each alternative has its merits and drawbacks with regard to creating complex major streets and a functioning pedestrian realm. The paper also discusses some of the problems of creating such streets in the current regulatory and professional context.

Role of microsimulation in evaluating intelligent transportation systems applications in urban transportation

Scipedia content — Mon, 01 Feb 2021 21:34:55 +0100

Given the complexity and novel aspects of intelligent transportation system (ITS)-based measures for transportation network improvements, traditional macroscopic travel analysis models are of limited use for assessing project benefits and costs. In order to fully capture the operational-level impacts of such technologies, a microsimulation approach is required. This paper describes the use of microsimulation techniques for studying the relative effectiveness of alternatives that include ITS applications. To illustrate the methodology, a case study involving the transportation network in Ottawa, Canada is presented. The paper is divided into five parts. First, mobility issues and the need for innovative solutions are introduced. Second, the transportation network in Ottawa is described and potential initiatives for addressing traffic congestion are noted, including demand reduction, freeway capacity expansion, and selected ITS measures. Third, the microsimulation-based modeling methodology is defined which was used to test improvement scenarios. Results from the various micro-simulation runs are then presented in terms of selected measures-of-effectiveness. Conclusions drawn from the case study are presented in the final section.

Tradable traffic rights for urban transport

Scipedia content — Mon, 01 Feb 2021 21:32:54 +0100

The objective of this paper is to study the theory of tradable pollution rights applied to urban mobility. The paper will focus on the urban congestion problems and investigates the possibility to keep under control not only urban pollution but congestion through tradable rights applied to traffic management. The introduction of tradable rights in urban mobility is considered in this paper to establish a market system where traffic is kept under control at a given level. Tradable rights are exchanged between different subjects on the basis of their different need to travel and of their consequent willingness to pay. This gives place to a market for rights to circulate at a market price which results from the intersection of supply and demand of tradable certificates. Price is not, therefore, fixed by a policy maker. The paper discusses different schemes of tradable permits markets and focuses on the main effects and problems arising from the application of this tool: fixing circulation level, defining criteria to distribute certificates, preserving market competition and urban development. Furthermore, the paper investigates some possible solutions to emerging problems and analyses the possibility of combining tradable permits and other policies in order to point at an organic governance of urban mobility.

Road pricing versus tradable entry rights: a transaction cost approach

Scipedia content — Mon, 01 Feb 2021 21:32:32 +0100

This paper describes how, with respect to market-based transportation policies, it is a widely held view of transportation professionals that road pricing entails substantial, though far fewer, transaction costs than tradable transportation permit systems. This conclusion seems to hold only if operational costs are singled out and this paper explores all relevant market, managerial and political transaction costs associated with road pricing and tradable entry rights. The two instruments have the same objective, namely to reduce congestion, and, to a lesser degree, noise, safety and environmental externalities. It is argued that the prevalence of transaction costs is largely dependent on the design of the policy instrument and the technology used. Developments in new technology will ensure that transaction costs associated with implementing a network wide, fleet wide road pricing or tradable entry permit system can remain at a low level. Comparative analysis further shows that a cap-and-trade program of entry permits distributed for free (on a smart card), traded on a brokered market and monitored downstream is not only more effective, but also likely to entail fewer transaction costs than road pricing. Any attempt, in turn, to save the huge information and search costs incurred by road pricing impairs its efficacy by severing the link between the externality and the price paid.

On the Design of Integrated Air/Ground Automation

Scipedia content — Mon, 01 Feb 2021 20:32:16 +0100

This paper addresses the design of automation for the primary operators in the air transportation system: air traffic controllers and flight crews. The modernization of the airspace system requires the implementation of extensive integrated automation support in air traffic control facilities and on flight decks. Research in the human factors division at NASA Ames Research Center over the past seven years has focused on prototyping and evaluating both air and ground aspects of envisioned future air traffic management concepts. This paper presents an example of automating an air traffic control task. It expresses lessons learned and views on the process of designing automation for the very complex and distributed air traffic system.

New Method to Minimize Fuel Consumption of Gas Pipeline Using Ant Colony Optimization Algorithms

Scipedia content — Mon, 01 Feb 2021 20:28:26 +0100

International audience; In this paper, ant colony optimization algorithm (ACOA) is proposed to solve the problem of how to efficiently operate a natural gas pipeline under steady state assumptions. The system is composed by compressing stations linked by pipe-legs. For each station, it is necessary to find the operating turbocompressors optimal values and the discharge pressures ones to minimize the total amount of fuel gas consumed in the system by the compressor stations. In the past, several techniques ranging from classical gradient-based procedures to dynamic programming, for solving this no convex problem have been applied. In this paper, we propose the ant colony optimization metaheuristic. This method was applied to the gas pipeline Hassi R' mell- ARZEW (two cities in Algeria) and the results are compared with those obtained by employing dynamic programming method. From these results, we obtain that the ACO technique is an interesting way for the gas pipeline operations optimization.

Data-Centric Air Traffic Management Decision Support Tool Model

Scipedia content — Mon, 01 Feb 2021 20:19:19 +0100

‡This paper describes the differences between a data-centered and an algorithmic design model as it applies to air traffic management software. An example of converting an existing algorithmic software baseline to a data-centric model is discussed. Using the data-centric model, a proof of concept flight deviation tool was developed. The deviation tool received inputs from a real-time data manager and a third party database to supply a list of aircraft identified as off their assigned flight path. The results were displayed using a standard web browser. From the development of this prototype it was determined that the use of a database should be coupled with a data manager to ensure a timely interaction with the data.

Impact of Free Maneuvering Aircraft on Ground-Side Operations in Mixed Airspace

Scipedia content — Mon, 01 Feb 2021 20:12:59 +0100

Numerous concepts aimed at increasing airspace capacity have been proposed to meet the anticipated increase in future air traffic demand. NASA Ames and NASA Langley Research Centers have recently conducted a joint simulation to test the En Route Free Maneuvering concept element of Distributed Air-Ground Traffic Management (DAG-TM), which integrated advanced air and ground decision support tools (DSTs) with Controller-Pilot Data Link Communication (CPDLC). In this concept, controller-"managed" aircraft flying under Instrument Flight Rules (IFR) were mixed with free maneuvering aircraft flying under Autonomous Flight Rules (AFR). Under APR, free maneuvering aircraft were responsible for conflicts with all managed aircraft flying in the same airspace. The results showed a significant potential for capacity gains. The workload correlated primarily with the managed portion of the traffic in mixed operations and the analyses of the controller task load in mixed operations showed a significant reduction of "routine" tasks, such as check-ins and handoffs, as well as route, altitude, and speed clearances. Despite the reduction in workload in mixed operations, controllers had a number of safety concerns, such as over-reliance on automation and lack of situation awareness of APR aircraft. The findings from the study also suggest that integrated ground-side DSTs in themselves have potential to increase capacity without free maneuvering aircraft. DAG-TM research was funded by the Airspace Systems program as part of the Advanced Air Transportation Technologies project. DAG-TM activities were conducted by NASA Ames, NASA Langley, and NASA Glen Research Center.

The Outlook and Challenges of 'IT' Applications for Gas Pipelines Maintenance Operations

Scipedia content — Mon, 01 Feb 2021 19:57:10 +0100

Tokyo Gas Co., ltd, the largest gas company in Japan, supplies city gas to Tokyo Metropolitan area, covering 3000km2 and 9.6million customers. Increasing maintenance cost and damages of underground utilities let Tokyo Gas start the research and development of digital mapping in 1977. Tokyo Gas developed GIS basic software “TUMSY” in 1983 after the several years’ research of foreign GIS products, which could not afford to store huge and dense pipeline-drawings. GIS basic software TUMSY consisted of DBMS and business applications. By using TUMSY, 30,000 manual drawings were digitized into the database. Then for about 20 years, TUMSY has been reinforced and improved on the same architecture, and various applications with utilization of database have been developed. The history tells us that GIS is essential to the company activities, and must be always implemented on the highest level of technology and business expertise.

Fuzzy Decision in Airplane Speed Control

Scipedia content — Mon, 01 Feb 2021 19:38:14 +0100

fuzzy decision system for helping air-traffic experts in controlling airplane velocities and in keeping an airplane flight within several constraints established to air lane sections is proposed in this paper. Automatic systems for air-traffic control are essential due to the ever increasing number of airplanes flying all over the world, the amount of environmental and airplane constraints and the necessity to guarantee the safety both for flights and for air-traffic control operators. The proposed system uses Mamdani direct inference method. Results show the effectiveness of the developed fuzzy system in controlling the airplane velocity to achieve the desired performance and encourage the adequacy of the system to include several different variables usually employed in air-traffic control.

Joint Optimization of Intra- and Inter-Autonomous System Traffic Engineering

Scipedia content — Mon, 01 Feb 2021 19:29:04 +0100

Traffic Engineering (TE) is used to optimize IP operational network performance. The existing literature generally considers intra- and inter-AS (Autonomous System) TE independently. However, the overall network performance may not be truly optimized when these aspects are considered separately. This is due to the interaction between intra- and inter-AS TE, where a solution of intra-AS TE may not be a good input to inter-AS TE and vice versa. To remedy this situation, we propose considering intra-AS aspects during inter-AS TE and vice versa. We propose a joint optimization of intra- and inter-AS TE to further improve the overall network performance by simultaneously finding the best egress points for the inter-AS traffic and the best routing scheme for the intra-AS traffic. Three strategies are presented to attack the problem, namely sequential, nested and integrated optimization. Our simulation study shows that, compared to sequential and nested optimization, integrated optimization can significantly improve the overall network performance by accommodating 30%-60% more traffic demands.

Improved Tank Car Safety Research

Scipedia content — Mon, 01 Feb 2021 16:31:37 +0100

Three recent accidents involving the release of hazardous material have focused attention on the structural integrity of railroad tank cars: (1) Minot, ND, on January 18, 2002; (2) Macdona, TX, on June 28, 2004; and (3) Graniteville, SC, on January 6, 2005. Each of these accidents resulted in fatalities. Research is being conducted to develop strategies for improving railroad tank cars so they can maintain tank integrity in severe accidents. A collaborative effort called the Next Generation Rail Tank Car (NGRTC) Project intends to use these research results to help develop improved tank car designs. Dow Chemical Company, Union Pacific Railroad, and Union Tank Car Company are the industry sponsors of the NGRTC Project. The Federal Railroad Administration (FRA) and Transport Canada participate in the NGRTC project through Memoranda of Cooperation. FRA and the Pipeline and Hazardous Materials Safety Administration intend to use these research results to support rulemaking. The approach taken in performing this research is to define the collision conditions of concern, to evaluate the behavior of current design equipment in these scenarios, and to develop alternative strategies for increasing the maximum impact speed for which tank integrity is maintained. The accident scenarios have been developed from a review of accidents and are intended to bound the range of main-line accidents that can lead to a release of hazardous material from a tank car. The accident scenarios and collision modes have been used to define car-to-car impact scenarios. These car-to-car impact scenarios define the conditions under which the commodity must be contained. The impact scenarios are being used to evaluate the integrity of current design and improved design tank cars. Full-scale impact tests are also being conducted, to help validate modeling of the baseline equipment. The models have been refined based on the test results. The models are now being applied to develop the improved equipment designs. This paper describes the overall research framework and provides an overview of the research done to date, as well as the planned efforts.

Human Behavior Based Predictive Brake Assistance

Scipedia content — Mon, 01 Feb 2021 16:12:34 +0100

Driver assistance systems have both the potential to alert the driver to critical situations and distract or annoy the driver if the driver is already aware of the situation. As systems attempt to preemptively warn drivers more and more in advance, this problem becomes exacerbated. We present a predictive braking assistance system that identifies not only the need for braking action, but also whether or not a braking action is being planned by the driver. Our system uses a Bayesian framework to determine the criticality of the situation by assessing (1) the probability that braking should be performed given observations of the vehicle and surround and (2) the probability that the driver intends to perform a braking action. We train and evaluate our system using over 22 hours of data collected from real driving scenarios with 28 different drivers.

Signal processing techniques for aeronautical communications via satellite

Scipedia content — Mon, 01 Feb 2021 15:51:43 +0100

onautical communications are playing an important role in the air traffic control as well as new passenger communication services. Due to the global coverage required, satellite transponders provide the required links which are traditionally limited to narrowband throughputs (e.g. 64 kb/s) due to the propagation channel characteristics. This paper analyses the reasons that limit the throughput of the aeronautical satellite links and presents advanced signal processing techniques that allow satellite transceivers to break the narrowband barrier

An overview of long-range dependent network traffic engineering and analysis: Characteristics, Simulation, modelling and control

Scipedia content — Fri, 29 Jan 2021 00:08:50 +0100

This paper surveys techniques for the recognition and treatment of self-similar network or internetwork traffic. Various researchers have reported traffic measurements that demonstrate considerable burstiness on a range of time scales with properties of self-similarity. Rapid technological development has widened the scope of network and Internet applications and, in turn, increased traffic volume. The exponential growth of the number of servers, as well as the number of users, causes Internet performance to be problematic as a result of the significant impact that long-range dependent traffic has on buffer requirements. Consequently, accurate and reliable measurement, analysis and control of Internet traffic are vital. The most significant techniques for performance evaluation include theoretical analysis, simulation, and empirical study based on measurement. In this research, we discuss existing and recent developments in performance evaluation and control tools used in network traffic engineering.

A feature-based tracking algorithm for vehicles in intersections

Scipedia content — Thu, 28 Jan 2021 23:59:16 +0100

Intelligent Transportation Systems need methods to automatically monitor the road traffic, and especially track vehicles. Most research has concentrated on highways. Traffic in intersections is more variable, with multiple entrance and exit regions. This paper describes an extension to intersections of the feature-tracking algorithm described in [1]. Vehicle features are rarely tracked from their entrance in the field of view to their exit. Our algorithm can accommodate the problem caused by the disruption of feature tracks. It is evaluated on video sequences recorded on four different intersections.

Automated transport in urban areas: opportunities in the Netherlands

Scipedia content — Thu, 28 Jan 2021 23:07:48 +0100

utomated transport could be one of the options to contribute to the development of sustainable mobility in urban areas. In order to realize sustainable mobility in urban areas transportation planners should invest in collective and space efficient transport. With this purpose in mind, this paper is about nonmechanical guided automated transport on the road with the ambition to participate in conventional traffic in the long term, with the so-called cybernetic transport systems (CTS). As well as a contribution to sustainable mobility, these systems should also contribute to the current transport system and have to answer transportation demands. Since municipalities feel the direct consequences of conventional transport, they also feel the negative impacts of this kind of transport. The effects of these impacts make a municipality one of the most important stakeholders for the problems related to traffic in urban areas. This paper elaborates on the possibilities of CTS to contribute to the current transport system and on the possibilities of municipalities to develop innovative and sustainable transport systems like CTS.

An increase of public transport and accessibility to urban amenities, some limited results: the case of the Lyons conurbation

Scipedia content — Thu, 28 Jan 2021 22:58:29 +0100

http://library.witpress.com/pages/listpapers.asp?q_bid=358&q_subject=Transport%20Engineering; The observable modifications in cities and on the individuals' way of life have impacts on the mobility practices, on the citizens' social conditions and on the capacity to reach activities. These evolutions can create, reduce or amplify chance inequalities to access activities between the different social groups. It leads to considering in the French decision-making processes, some aspects of the social dimension of sustainability, reduced to chances equalities and to the social implications of accessibility. The accessibility to urban amenities is based on the right to transport as a necessary condition for chance inequalities for all. In this context, we analyze whether an urban transportation system could reduce the population's chance inequalities in terms of social access to a basket of goods. We propose, on the Lyons conurbation, for the year 1999, to quantify the accessibility, by car or by public transport, of the rich or poor districts' inhabitants. Then, we explore the effects of an increase of public transport supply, based on the Urban Travel Plan for the Lyons conurbation. Does now provide improved accessibility and to reduce the inequalities between the richest and the poorest districts?

Intelligent monitoring and adaptive competence assignment for driver and vehicle

Scipedia content — Thu, 28 Jan 2021 22:46:14 +0100

This paper presents a concept for achieving higher safety in road traffic by addressing long and short term reduced capability of the driver in regard to his driving task. Pivot point of the proposed concept is the continuous monitoring of the driver and the vehicle's state and their competence assignment. For this purpose, the driver and vehicle will be treated as one system and regarded under cybernetic aspects. For estimation of the driver's condition or capability respectively, an approach is suggested, which combines data of the vehicle sensory equipment with methods for monitoring drivers.

Investigation ofant colonyalgorithm in multiple traffic flow environments

Scipedia content — Thu, 28 Jan 2021 22:22:49 +0100

The conventional approaches to routing and bandwidth allocation, the two major components of traffic engineering, have proved insufficient to address QoS requirements of flows while optimizing utilization for complex communication networks. In this paper we consider ant colony algorithms to address this problem. Our studies show that the ant-based routing models are sensitive to initial parameters settings. Only careful adjustments of these initial parameters results in an acceptable convergence behavior. The robust behavior of the real ant compared to the routing algorithms derived from it inspires us to investigate the reasons behind the shortcomings of these algorithms. We present results from an in-depth study of ant behavior in a quest for a robust algorithm. In this work we consider a realistic environment in which multiple source-destination flows compete for resources. We study the routing and load balancing behavior that emerges and show how the behavior relates to analytical approaches. We show the results using simulations in OPNET and derive recommendations on the improvement of the ant-like algorithm

MPLS traffic engineering in satellite networks

Scipedia content — Thu, 28 Jan 2021 22:15:50 +0100

Broadband satellite constellation networks will be required to carry all types of IP traffic, real time interactive traffic as well as non-real time traffic, warranting the need for appropriate QoS for these different traffic flows. In this paper we investigate the need for MPLS traffic engineering in GEO/MEO/LEO satellite networks to address QoS issues. We compare the service received by TCP and UDP flows when they share a link and when they are routed on explicit MPLS traffic trunks. Since MPLS traffic trunks allow non-shortest path links also to be used, the total network throughput goes up with proper traffic engineering. If UDP and TCP flows are mixed in a trunk, TCP flows receive reduced service as the UDP flows increase their rates. Also, we found that with MPLS traffic engineering we can protect real time traffic and VoIP traffic from packet loss and excessive jitter by separating them from other congestion unresponsive flows

Peer Reviewed

An Investigation into the History and Use of Welded Lap Joints for Steel Water Pipe

Scipedia content — Thu, 28 Jan 2021 22:00:33 +0100

It is common practice to weld joints in water pipe. The practice is more recent than welded joints in pressure vessels. Therefore, it is inevitable that welding standards for pipe welds would have been influenced by the older pressure vessel codes. There are significant differences between high-pressure tanks and pipes for transmission and distribution of water. Successful lap welded pipelines and test programs on welded lap joints provide information on the performance and performance limits of welded lap joints in pipes. Single welded lap joints are adequate for most welded steel water pipe. Double welded lap joints are roughly ten percent stronger (than single). Single welded lap joints can resist longitudinal stresses when valves are closed, i.e., zero flow, (highest pressure and worst case pressure analysis). Longitudinal stress caused by change in temperature must be included if the pipe length is fixed. Design is based on safety factors, which should be ratio of longitudinal weld strength and maximum longitudinal stress. Longitudinal weld strength should be determined by full pipe sections – not coupons cut from a joint. Maximum longitudinal stress is generally less than the hoop stress. Hoop stress is the primary design consideration.

Modeling Mobility with Behavioral Rules: the Case of Incident and Emergency Situations

Scipedia content — Thu, 28 Jan 2021 21:35:10 +0100

International audience; Mobility models must scale accordingly to the application and reflect real scenarios in which wireless devices are deployed. Typical examples of scenarios requiring precise mobility models are critical situations (e.g., vehicular traffic incident, escaping pedestrians in emergency situations) – for which the ad hoc paradigm was first designed for. In these particular situations, autonomous agents of communicating devices will assist mobile users in their displacements either to avoid traffic jam due to incidents or find the closest emergency exit. But, since the environment conditions (i.e., flow of pedestrians or vehicles and incidents) may change during time in part due to mobility itself, autonomous agents assisting mobile users in their displacements must constantly exchange information and dynamically adapt to the perceived situations. This requires to precisely modeling both mobility (vehicular and pedestrian traffic) and communications systems between agents. Unfortunately, these two areas have been treated separately, although mobility and network simulators should be tightly bound. In this paper, we propose a new modeling approach to mobility, namely Behavioral Mobility models (BM), which decomposes mobility into simple atomic individual behaviors. Combined, these behaviors yield realistic displacement patterns by reproducing the mobility observed at small scales in every day life, in both space and time. We also propose to bind mobility and network simulators to run joint simulations in order to push simulations to more realness. This approach combined to BM models is particularly suited to simulate critical situations where mobility is influenced by the changing environment conditions. We demonstrate the feasibility of our approach with two cases studies.

Estimation of Freeway Travel Time Based on Sparsely Distributed Detectors

Scipedia content — Thu, 28 Jan 2021 21:10:57 +0100

This study presents a new approach for estimating travel time information along freeway corridors, which experience recurrent congestions but have only a limited number of available detectors due to budget constraints. The proposed iterative estimation procedure, based on a set of empirically calibrated regression models, intends to rebuild the relations between travel times and accumulated flows within each segment of the target freeway corridor. To evaluate the effectiveness of the proposed methodology, this study has conducted extensive numerical experiments with simulated data from a CORSIM simulator. Experimental results under various traffic volume levels have revealed that the proposed method offers a promising property for use in travel time estimation based on sparsely distributed sensors.

Planning with PlaceMaker: complex indices for sustainable projects

Scipedia content — Thu, 28 Jan 2021 21:01:05 +0100

Questions connected to urban analysis study aspects that are not unilaterally translated into objective facts with particular regard to three issues: (1) the scientificity, and so the objectivity of the results; (2) the repeatability of the method in different contexts; and (3) the updating capability, and so the possibility of adding new data in order to modify the existing data and to obtain other results; the times, and so the sustainable possibility of using the results with respect to the evolution of a sustainable programming and town planning process. To answer these questions the method of analysis called PlaceMaker and the associated software, which is actually under development, have the following main characteristics: flexibility, facility and rapidity of use, strong graphical impact, and indexing of the results. PlaceMaker is a method for analyzing the contemporary urban landscape that is designed to identify the elements that do not feature in traditional mapping and which constitute the contemporary identity of the places, representing them in a complex map that renders those places intelligible. Starting from these premises, the objective of this work is to investigate the construction of complex indices starting from data and symbols related to the place-identity. In order to support the study and the project of the sustainable urban landscapes, the symbols created for the elaboration of the complex map, the final result of the analysis, are translated by the PlaceMaker software into numerical indices. Owing to these characteristics, the prime users of PlaceMaker are urban planners, administrators, citizens and all people involved in construction of a sustainable city. To complete the work suitable case studies are presented.

Principles of Timing Anomalies in Superscalar Processors

Scipedia content — Thu, 28 Jan 2021 20:52:35 +0100

The counter-intuitive timing behavior of certain features in superscalar processors that cause severe problems for existing worst-case execution time analysis (WCET) methods is called timing anomalies. In this paper, we identify structural sources potentially causing timing anomalies in superscalar pipelines. We provide examples for cases where timing anomalies can arise in much simpler hardware architectures than commonly supposed (i.e., even in hardware containing only in-orderfunctional units). We elaborate the general principle behind timing anomalies and propose a general criterion (resource allocation criterion) that provides a necessary (but not sufficient) condition for the occurrence of timing anomalies in a processor. This principle allows to state the absence of timing anomalies for a specific combination of hardware and software and thus forms a solid theoretic foundation for the time-predictable execution of real-time software on complex processor hardware.

Cooperation of cars and formation of cooperative groups

Scipedia content — Thu, 28 Jan 2021 19:39:39 +0100

Cooperation of cars capable to communicate bears a high potential with respect to safety in critical situations. Following a top-down design, cars form cooperative groups, exchange information available to them and establish a common relevant picture upon which critical situations are detected, optimal decisions for the groups are derived and are distributed in form of individual action sequences. This paper focuses on the formation of cooperative groups. To this end, a graph-based spatiotemporal distance measure is developed, using the concept of virtual meeting points within the road infrastructure. The distance measure is analyzed and it serves to define cooperative groups of cognitive automobiles.

Urban congestion charging: road pricing as a traffic reduction measure

Scipedia content — Thu, 28 Jan 2021 19:33:49 +0100

Thesis (M.Art. et Scien. (Town and Regional Planning))--North-West University, Potchefstroom Campus, 2005.

Condition Assessment of Water Mains using Fuzzy Evidential Reasoning

Scipedia content — Thu, 28 Jan 2021 19:25:08 +0100

This paper describes a method of combining fuzzy inference and evidential reasoning to quantify the corrosion rate of buried metallic pipes, i.e., cast-iron and ductile-iron. The method relies on two bodies of evidence: the corrosivity of surrounding soil and the corrosion rate estimated from measured maximum pit depth. Fuzzy inference is used to deduce a corrosivity criterion, viz., corrosivity potential (CoP), for each body of evidence. The two CoPs are then fused using evidential reasoning to obtain a CoP that is expected to be more reliable than that obtained from any one individual body of evidence. This type of criterion can help utility managers make informed decisions on how to protect their pipes exposed to different soil conditions. The proposed reasoning framework is demonstrated through a case study based on soil properties and corrosion rate data.

Sustainable Development and Strategic Transport Management in the Øresund Region

Scipedia content — Thu, 28 Jan 2021 19:18:42 +0100

This paper describes how concept of traffic planning has developed over the years and it has produced both long-term and short-termed solutions of different kinds. In general, however, in many urban and regional areas, traffic planning has until now not been able to treat and resolve the increasing problems relating to uncurbed traffic growth. Therefore new planning strategies and approaches are needed. In addition, the quality of transport networks and other types of traffic infrastructure are becoming more and more important features for metropols and regions when competing in attracting investment, development and knowledge. This is especially relevant for a cross-boarder region as the Oresund region treated in this paper. To ensure a sustainable development while at the same time upgrading the quality of urban and regional transport is thus a major challenge. To deal with this situation the paper outlines a wider approach to sustainable regional transport planning. This is done by setting up a so-called holistic approach to planning and afterwards, based on holistic planning, by presenting the ideas of Strategic Transport Management (STM) as an important new planning and management concept. Finally some conclusions are given together with a perspective.

Multi-Dimensional D-Transform Approach to Modeling and Control of the Air Traffic Environment

Scipedia content — Thu, 28 Jan 2021 19:16:34 +0100

n elegant model of air traffic flow based on the extension of one-dimensional D- transforms is described. Multi-dimensional D-transforms of aircraft trajectories are derived and linearly combined to form the model of the air traffic environment. Unlike other aggregate models of air traffic flow, the D-transform model can preserve the trajectory details of individual aircraft. Moreover, it allows the algebraic treatment of aircraft delay and re-routing. The application of the D-transform models to air traffic flow control and other related air traffic management problems are discussed.

Establishing 100-Year Service Life for Corrugated HDPE Drainage Pipe

Scipedia content — Thu, 28 Jan 2021 19:06:35 +0100

The design service life of corrugated high density polyethylene (HDPE) drainage pipe has been a subject of considerable debate and research over the past several years. While significant long-term performance data is available for smooth-walled polyethylene pipe, the data for corrugated drainage pipes is somewhat limited. This paper presents a method for determination of long-term service life of corrugated HDPE pipe by utilizing some of the current widely-accepted methods employed by the plastic pipe industry, while modifying them somewhat to take into account the unique geometry and installation conditions of buried corrugated pipe. The process for long-term service life prediction is two-fold: First, the anticipated service conditions of the drainage pipe must be assessed, including such factors as environmental conditions, soil and traffic loads, and the resulting long-term stresses and strains evident in the pipe. Second, the capacity of the material and the manufactured pipe product must be assessed. The service conditions of the pipe will vary by geographic location, based on temperature and soil and traffic loads. While deep installations may result in large compressive stresses on the pipe, shallow installation are more subject to bending and tensile stresses. Although these stress levels are typically lower in magnitude than the compressive stresses associated with deep burial conditions, they are considered a limiting condition as the material is more prone to failure in tension rather than compression. Recent research performed by Dr. Timothy McGrath for the Florida Department of Transportation on the limiting stress conditions of buried corrugated pipe is presented in this paper (McGrath and Hsuan, 2005). The capacity of the material to resist failure is the second factor that must be addressed. Based on its wide use as a piping material (i.e. gas, water, industrial, oil field, etc…) polyethylene is a highly scrutinized material and its mechanisms of failure are well known. For corrugated drainage pipe, the primary mechanisms of material failure are slow crack growth and oxidation or chemical failure. Some recently proposed methods by Dr. Grace Hsuan for the Florida Department of Transportation to ensure long-term material resistance to these failure modes are presented in this paper (McGrath and Hsuan, 2005).

BGP-like TE Capabilities for SHIM6

Scipedia content — Thu, 28 Jan 2021 19:04:44 +0100

In this paper we present a comprehensive set of mechanisms that restore to the site administrator the capacity of enforcing traffic engineering (TE) policies in a multiaddressed IPv6 scenario. The mechanisms rely on the ability of SHIM6 to securely perform locator changes in a transparent fashion to transport and application layers. Once an outgoing path has been selected for a communication by proper routing configuration in the site, the source prefix of SHIM6 data packets is rewritten by the site routers to avoid packet discarding due to ingress filtering. The SHIM6 locator preferences exchanged in the context establishment phase are modified by the site routers to influence in the path used for receiving traffic. Scalable deployment is ensured by the stateless nature of these mechanisms. Publicado

The electrical demand by transport on the grid after oil depletion

Scipedia content — Thu, 28 Jan 2021 18:56:33 +0100

the hand of a case study alternative energy sources, methods of transportation and their effect on the electricity grid once fossil fuels have been depleted is discussed. Three methods of sustainable transport are presented. The energy requirement for each is calculated as well as the requirements from the electricity grid for traveling a 200 km route. All three proposed methods are compared to current methods of transport. Specifically, the Superbus, an all electric vehicle, has also been considered as an alternative to future transport. The results obtained indicates that the Superbus is the better option regarding energy requirement from the electricity grid, while at the same time traveling at high speeds to make point to point transportation fast.

SATS HVO Procedures for Priority Landings and Mixed VFR/IFR Operations

Scipedia content — Thu, 28 Jan 2021 18:45:24 +0100

This paper describes a pilot in the loop simulation experiment of the small aircraft transportation system (SATS) higher volume operations (HVO) concept for off-nominal conditions conducted at the Air Traffic Operations Lab (ATOL), NASA Langley Research Center. The experiment was designed to validate procedures for priority landing requests and pilot cancellations of approach requests with subsequent transitions to visual flight rules (VFR). Priority landing requests during approach operations allow pilots to land ahead of others in the sequence. Cancellations of approach requests allow participating aircraft to cancel an approach sequence and transition to VFR if desired. Preliminary results show that pilots find the procedures acceptable with no increase in perceived workload as compared to nominal SATS HVO operations while pilot performance and situation awareness metrics are consistently high. Overall, subject pilots welcome the increased potential efficiency the concept offers and the increased ability to self-control while flying SATS HVO procedures.

The Airspace Operations Laboratory (AOL) at NASA Ames Research Center

Scipedia content — Thu, 28 Jan 2021 18:28:49 +0100

The Airspace Operations Laboratory (AOL) at NASA Ames Research Center hosts a powerful simulation environment for human-in-the-loop studies of air traffic operations. The capabilities have been developed at NASA Ames and cover a wide range of operational environments from current day operations to future operational concepts like those envisioned for the Next Generation Air Transportation System (NGATS). The research focus in the AOL is on examining air traffic control and management operations across multiple air traffic control sectors in rich air/ground environments that can include oceanic, enroute and terminal airspace. Past research involving the AOL includes distributed air/ground traffic management studies on trajectory negotiation, airborne self-separation and airborne spacing. Ongoing research with various government and industry partners include trajectory-oriented operations with limited delegation; multi sector planning; the US tailored arrivals initiative; airline-based sequencing and spacing, and airborne merging and spacing. In the future we expect using the AOL extensively for early exploration of operational questions crucial to the NGATS, like human-automation interaction, roles and responsibilities in distributed environments and required automation capabilities. This paper first gives an overview over philosophy, physical layout, software and connectivity of the AOL. Next, the available real-time capabilities are described in detail followed by a description of some important offline capabilities. The paper concludes with a summary of past and present research in the AOL and concluding remarks.

Routing path optimization in optical burst switched networks

Scipedia content — Thu, 28 Jan 2021 18:16:05 +0100

It is usually assumed that optical burst switched (OBS) networks employ shortest path routing along with next- hop burst forwarding. Shortest path routing minimizes delay and optimizes the utilization of resources, however, it often causes certain links to become congested while others remain underutilized. In a buffer-less OBS network in which burst drop probability is the primary metric of interest, the existence of a few highly congested links may lead to unacceptable performance for the entire network. In this paper, we take a traffic engineering approach to path selection in OBS networks with the objective of balancing the traffic across the network links in order to reduce congestion and improve overall performance. We present an approximate integer linear optimization problem, as well as a simple integer relaxation heuristic to solve the problem efficiently for large networks. Numerical results demonstrate that our approach is effective in reducing the network-wide burst drop probability, in many cases significantly, over shortest path routing.

The impact of energy prices on the sustainability of urban transport

Scipedia content — Thu, 28 Jan 2021 18:04:40 +0100

This paper is motivated by the recent strong energy price increases and the paper investigates the impact of these recent price increases on the demand and the composition of urban transport, both public and private. In the first section, the relative price change of private transportation due to fuel prices is estimated for Vienna, whereby the substitutability between public and private transport is investigated. In the second section, changes in consumer behavior related to the fuel efficiency of cars are discussed. In particular, the paper tries to quantify the impact of these price changes on the relative prices in the used-car market.

Advancements in Steel Making and the Effect on Pipeline Specifications

Scipedia content — Thu, 28 Jan 2021 17:51:02 +0100

This paper will go through the history of the steel making process and how these changes have affected the quality of steel. The process has changed dramatically from early processes to methods used today. Development of these methods resulted in more cost effective manufacturing. One of the methods developed was to use chemistry to enhance the steel. The chemistry of micro alloyed steels will be explained in detail and the benefits and drawbacks of specifying these types of steel for pipeline projects will be discussed. The elements that make up the steel composition, such as Carbon, Manganese, Sulfur, Columbium, and Vanadium, will be discussed and the effect on the steel will be explained. Actual steel making data will be presented and discussed. Pressure vessel quality steel and what the term means will be evaluated. Controlled rolling practices will be explained and how they can be used to affect the steel properties. The paper will take the information about steel and discuss how these changes should or could be used in the design and specifications for pipelines. Finally the cost benefit of these steels will be discussed.

Circumferential Guided Waves for Defect Detection in Coated Pipe

Scipedia content — Thu, 28 Jan 2021 17:49:57 +0100

Circumferential guided wave propagation behavior in a viscoelastic multi‐layered hollow cylinder is studied to provide a baseline for defect detection in tar coated pipelines. Theoretical work was carried out by developing the appropriate dispersion curves and wave structures for circumferential guided waves in a pipe coated with a viscoelastic material. Parameters that affect wave attenuation were investigated with some initial guidelines being established for improved penetration power. Low frequencies are suggested from both attenuation and detection depth points of view. Under this guidance, experiments utilizing a linear transducer array were conducted at a low frequency for successfully detecting delamination and volumetric defects in tar coated pipe. A study was carried out to find the appropriate features for defect detection in coated pipe and a test protocol based on this study is recommended and summarized.

How many traffic classes do we need in Wimax?

Scipedia content — Thu, 28 Jan 2021 17:44:39 +0100

This paper addresses the issue of multiservice support in IEEE 802.16 or WiMAX networks. The capacity for supporting multiple service classes is indeed important for any access technology where bandwidth is limited, which is the case for IEEE 802.16. The standard currently proposes four traffic classes, and specifies that for uplink traffic, the first one (UGS) receives periodic grants whereas the other three are served via polling. Supporting two different scheduling mechanisms may have a significant impact on the complexity of network interface cards, and therefore on the CAPEX for WiMAX networks. Based on this analysis, the present work investigates whether a 802.16 network that only supports the 3 polling based classes is still capable of providing the QoS levels expected for all types of applications. Both the transfer plane QoS, in terms of latency and jitter, and the command plane QoS, in terms of blocking probability are assessed. In particular, a simple, multiservice call admission control (CAC) mechanism is proposed that significantly improves on a previously proposed CAC mechanism by favouring real time traffic over non real time traffic. The outcome of this study shows that it is indeed possible to support stringent QoS with only polling based traffic classes, and fairly simple traffic engineering mechanisms fully described in the paper.

Tram layout and economic location in Coruna, 1914-1960

Scipedia content — Thu, 28 Jan 2021 17:39:48 +0100

The International Conference on the History of Transport, Traffic and Mobility (T2M) This paper aims to examine the relationship between the tram network and the location of economic activities in A Coruña, as a first step in the measure of the possible explanatory factors that determined the intra-urban economic location system. In order to do this I have selected three significant dates: the World War I (1914), which corresponds to the beginning of the tram’s electrification in the town, the pre-Spanish Civil war period (1935), and the start of the accelerated development of the Spanish economy, which coincided with the liberalization policy (1960). This last stage meant the definitive dismantling of the trams in the town (1962). The purpose of this methodology is to allow us to determine the medium-term influence of tram branch-line building on the spatial structure of the urban economy.

Distributed agent-based air traffic flow management

Scipedia content — Thu, 28 Jan 2021 17:24:45 +0100

traffic flow management is one of the fundamental challenges facing the Federal Aviation Administration (FAA) today. The FAA estimates that in 2005 alone, there were over 322,000 hours of delays at a cost to the industry in excess of three billion dollars. Finding reliable and adaptive solutions to the flow management problem is of paramount importance if the Next Generation Air Transportation Systems are to achieve the stated goal of accommodating three times the current traffic volume. This problem is particularly complex as it requires the integration and/or coordination of many factors including: new data (e.g., changing weather info), potentially conflicting priorities (e.g., different airlines), limited resources (e.g., air traffic controllers) and very heavy traffic volume (e.g., over 40,000 flights over the US airspace). In this paper we use FACET -- an air traffic flow simulator developed at NASA and used extensively by the FAA and industry -- to test a multi-agent algorithm for traffic flow management. An agent is associated with a fix (a specific location in 2D space) and its action consists of setting the separation required among the airplanes going though that fix. Agents use reinforcement learning to set this separation and their actions speed up or slow down traffic to manage congestion. Our FACET based results show that agents receiving personalized rewards reduce congestion by up to 45% over agents receiving a global reward and by up to 67% over a current industry approach (Monte Carlo estimation).

Gestion de la mobilité et de la QoS des réseaux de la nouvelle génération

Scipedia content — Tue, 26 Jan 2021 18:21:24 +0100

Les réseaux de la nouvelle génération (Next Generation Networks) sont basés sur l'intégration des différentes technologies d'accès. Pour garantir la QoS et la mobilité transparente d'un terminal se déplaçant d'une technologie d'accès à une autre, une gestion spéciale de mobilité et de QoS est nécessaire. Dans ce contexte, nous présentons les différentes architectures d'intégration existantes intégrant les réseaux UMTS et WLAN considérés comme des technologies complémentaires à s'intégrer naturellement, et les raisons principales à forcement intégrer ces deux technologies. Les travaux de recherche présentés dans cette thèse consistent à proposer une nouvelle architecture d'intégration entre UMTS et WLAN assurant un handover vertical transparent avec minimum de délai, minimum de dégradation de la QoS, et une probabilité de rejection des appels de handover minimale. On propose l'architecture "Anticipated Vertical Handover" basée sur le protocole de mobilité Fast MIPv6 dans le contexte du handover de UMTS à WLAN et vice versa, et le protocole de transfert du contexte (Context Transfer Protocol) CTP. Pour améliorer la QoS, "Mobility and QoS Management Architecture" MQMA est proposée. Un nouveau module appelé Inter-Domain Management (IDM) est introduit pour réaliser la gestion de QoS et pour guider la demande du handover au réseau d'accès capable de satisfaire les paramètres du handover. Dans le modèle MQMA, le protocole de gestion de mobilité et de la QoS (Mobility and QoS Management Protocol) est proposé pour contrôler les échanges de messages entre les différentes entités du modèle MQMA. Le handover peut être réalisé verticalement par VIDM ou guidé horizontalement au même réseau d'accès par HIDM. Dans ce cas, le handover horizontal est proposé pour servir le handover vertical (si ce dernier est bloqué). Le handover peut aussi être guidé au réseau WiMax par le SIDM, du fait que WiMax est considéré comme le réseau de destination en réserve, "stand-by" destination network, au cas où le handover vertical ou horizontal n'est pas possible.

İstanbul Deniz Otobüsleri Seferlerinin Simülasyon Yardımıyla Planlanması

Scipedia content — Tue, 26 Jan 2021 18:16:34 +0100

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007

Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2007

Dünyanın sayılı kentleri arasında olan ve giderek artan bir hızla büyüyen İstanbul’da, artık ciddi bir ulaşım planlamasına gereksinim vardır. Ulaşım planlamasında en önemli alanı toplu taşıma sisteminin geliştirilmesi ve verimli kullanılması kapsamaktadır. Toplu taşıma sisteminde giderek payı artması gereken denizyolu taşımacılığı ve onun parçası deniz otobüslerinin, etkin bir şekilde yönetilmesi gerekmektedir. Etkin ve verimli yönetim için birçok bilimsel metoddan bahsedilebilir. Bu tez kapsamında bu metodlardan simülasyon ele alınmıştır. Bu tez çalışmasının ana amacı, İstanbul’da kent içinde faaliyet gösteren deniz otobüsü filosu ve iskeleleri ile ilgili planlama yapılırken simülasyonun etkin bir araç olarak kullanılabilirliğinin araştırılmasıdır. Bu amaç doğrultusunda tez kapsamında kent içi tüm şebekeyi kapsayan bir model Promodel yazılımından faydalanılarak oluşturulmuştur. Oluşturulan bu model, farklı senaryolarla daha önce yapılmış çalışmaların analizinde kullanılmıştır. Tez ile birlikte verilen ekte modellerin kodları bulunmaktadır. Senaryoların sonuçları birbirleriyle karşılaştırılmış, deniz otobüsü planlamasında ileride neler yapılabileceği tartışılmıştır.

There is an urgent transport plan need for Istanbul, one of the few world cities with its increasing rate of population growth. The development and efficient use of public transportation constitute the most important fields of the transportation planning. The proportion of sea transportation and the sea buses as a part of it should be increased and administered effectively. There is a number of scientific methods for accomplishing an efficient and effective management. In this thesis, simulation of these methods is discussed. The main aim of this thesis is to investigate whether the simulation is an efective tool in the process of planning about the sea bus fleet and sea ports that are in service in Istanbul. A model including all the city network was built up by using Promodel which is a simulation software. This model was used in the analysis of recent studies set up on a variety of scenarios. The appendix contains the codes of the models. The results were compared and the possible projects in sea bus planning were discussed.

Yüksek Lisans

M.Sc.

Contribution to analysis of process capacity of cargo trains on single track railroad line in Brazil

Scipedia content — Tue, 26 Jan 2021 18:00:45 +0100

O expressivo crescimento do setor ferroviário com o processo de privatizações das operações a partir de 1996, fez com que a modalidade aumentasse sua participação na matriz de transportes brasileira. Porém, essa expansão, obtida essencialmente com a substituição e aumento de locomotivas e vagões, juntamente com a modernização do sistema de controle de tráfego, deverá em breve encontrar limites impostos pela geometria e superestrutura da malha ferroviária. O objetivo da dissertação é analisar como esses fatores afetam a capacidade de processamento de trens através de uma linha ferroviária singela. Para alcançar este objetivo desenvolveu-se um modelo capaz de identificar as características da via que restringem as velocidades e o headway das composições ferroviárias. O modelo proposto permite, através da análise de desempenho em cada um dos arcos de um trecho de linha ferroviária, obter uma medida de desempenho global no trecho e identificar os gargalos. O método adotado para determinar a capacidade do trecho para cenários operacionais alternativos é o da utilização de diagramas espaço-tempo. Os diagramas espaço-tempo são elaborados através de um algoritmo em MatLab que soluciona os conflitos nos cruzamentos para um determinado tempo de cruzamento nas estações e efetua a contagem de pares de trens. O desempenho dos trens em cada um dos arcos, dado de entrada do algoritmo, é adquirido através de um modelo de simulação de desempenho de trens elaborado pela Association of Amerian Railroads (AAR). Como aplicação prática apresenta-se uma análise de capacidade para um dos principais corredores de exportação, um trecho da Brasil Ferrovias S.A. entre as cidades de Santa Fé do Sul e Araraquara no estado de São Paulo. A análise dos resultados mostra que o principal fator limitante da velocidade média no espaço dos trens é a atual condição da superestrutura ferroviária e que, uma vez eliminada esta restrição, a supressão de passagens de nível e a relocação de estações de cruzamento, produzem ganhos expressivos. The expessive growth of the railway sector due to the privatization of the operations since 1996, is increasing the participation of this mode in the brazilian transport matrix. However, this growth is obtained mainly from the replacement and increase of the rolling stock and the modernization of the traffic control system, and will soon reach some important limits imposed by the railway geometry and superstructure. The thesis objective is to analyze how these factors affect the capacity to process trains through a single track railroad line. To reach this objective, a model that identifies the restrictions that impose limits to the speed and headways of the trains was developed. Through the performance analysis on each arc of a railway segment, the model obtains a global performance measure for the whole segment and identifies the bottlenecks. Time-space graphs are developed to determine the capacity of the segment for different operating scenarios. To build the space-time graphs, solve the conflicts at the crossings for a given time to cross and count the trains per day, an algorithm using the MathLab software was developed. The train performance on each arc is obtained through a simulation model developed by the Association of American Railroads (AAR). As a practical application, a capacity analysis of one of the most important export corridors is presented, a segment of the Brasil Ferrovias S.A. network between the cities of Santa Fé do Sul and Araraquara in the state of São Paulo. The analysis of the results shows that the present railway superstructure condition is the main train average space speed limiting factor and, once this restriction is eliminated, the supression of at grade crossings and the relocation of the crossing stations produce expressive gains.

Avaliação e comparação de desempenho entre a arquitetura IP e a arquitetura IP sobre MPLS"

Scipedia content — Tue, 26 Jan 2021 17:39:00 +0100

Este trabalho apresenta uma comparação e avaliação das arquiteturas de roteamento IP e IP sobre MPLS. Inicialmente, são apresentados alguns conceitos básicos dos protocolos IP e MPLS, e suas relações com a camada 2 do modelo OSI. Duas características foram analisadas: o processo de encaminhamento e as granularidades para engenharia de tráfego. A medição de desempenho foi feita com computadores Linux realizando a tarefa de roteamento/encaminhamento de datagramas IP em diferentes tipos de redes Ethernet. Com base nos resultados dos testes, é feita uma discussão sobre o desempenho e topologias adequadas para cada arquitetura. This work presents a comparison and evaluation of IP and the IP over MPLS routing architectures. Initially, some basic concepts of IP and MPLS protocols and their relationship with layer 2 of OSI model are introduced. Two characteristics were analyzed: the forwarding process and traffic engineering granularity. The performance analysis was realized on Linux computers routing/forwarding IP datagramas at different types of Ethernet networks. Considering the results of the tests, a discussion about performance and suitable topologies is made for each architecture.

Sustainable transport as an essential factor in quality of life: the case of São Paulo

Scipedia content — Tue, 26 Jan 2021 17:28:58 +0100

Os impactos ambientais do transporte assumem diversas formas e têm efeitos locais, regionais e globais. A crescente dimensão do tema desperta interesse mundial, expresso em inúmeras propostas voltadas à moderação dos impactos em áreas urbanas e em rodovias, bem como à integração entre transporte e sustentabilidade. O referencial teórico mostra que a recomendação de ações para redução de impactos ambientais depende de conhecimento do cenário de intervenção e também da compatibilidade entre propostas, características da área e necessidades da população local, ao passo que a análise do estado-da-arte em cidades globais baliza possíveis metas a atingir. O presente trabalho teve como objetivos criar uma metodologia de avaliação de impactos ambientais e investigar a relação entre transporte, qualidade ambiental e qualidade de vida em alguns locais de São Paulo. Tendo como norte os conceitos de transporte sustentável e desenho ambiental, foi elaborado um modelo de diagnóstico de qualidade ambiental e qualidade de vida. Para tanto, duas pesquisas foram aplicadas: uma subjetiva, caracterizando a demanda por infra-estrutura urbana e a qualidade de vida da população; e a outra objetiva, cujos resultados permitiram avaliar os impactos ambientais. As pesquisas ocorreram em 3 Subprefeituras do Município de São Paulo, sendo que a avaliação dos resultados teve como base o uso de alguns indicadores de qualidade ambiental e uma calculadora de externalidades, especialmente desenvolvidos para o estudo. A metodologia mostrou ser viável para diagnosticar a qualidade de vida da população local, as características físicas pontuais e os impactos ambientais resultantes do tráfego local. O levantamento facilitou a sugestão de uma série de intervenções pontuais, constituindo um instrumento de avaliação flexível e replicável em outras localidades. The environmental impacts of transport take a myriad of forms and spread locally, regionally and globally. The growing dimension of the issue raises worldwide interest, translated into a series of proposals focused on the mitigation of such impacts in urban areas and motorways, as well as the integration between transport and sustainability. The theoretical framework has shown that the suggestion of mitigation measures requires knowledge about the target scenario, and also balance among proposals, features of the area and the local population?s needs, whereas the analysis of transport in global cities provide some state-of-the-art examples likely to be pursued. The main objectives were to create a methodology for the environmental impact assessment and to investigate the relationship among transport, environmental quality and quality of life at specific spots in the City of São Paulo. Taking into account the concepts of sustainable transport and environmental design, a model for the diagnosis of environmetal quality and quality of life was prepared. For this purpose, two different surveys were carried out: one concerning subjective aspects, featuring the demand for urban infrastructure and the population?s quality of life; and another concerning objective aspects, whose analysis enabled the assessment of environmental impacts. These surveys took place at three administrative regions in the City of São Paulo. The analysis relied on some environmental quality indicators and a simple calculator, especially devised for this project. The methodology has proved to be feasible for the appraisal of the local population?s quality of life, the physical characteristics of the sampled spots and the environmental impacts resulting from local traffic. The survey has facilitated the recommendation of a series of local interventions, making up a flexible and easily adaptable assessment tool.

Traffic flow assessment and alternative scenarios for Victoria Square to South Terrace using Paramics V5.2 /

Scipedia content — Tue, 26 Jan 2021 17:25:33 +0100

Thesis (MTransportSysEngineering)--University of South Australia, 2007. Includes bibliographical references (leaves 68-69)

Global QoS model in the ISP networks: DiffServ aware MPLS Traffic Engineering

Scipedia content — Tue, 26 Jan 2021 16:50:21 +0100

Traffic Engineering is the one of the methods for improving the Quality of Service in the network like Internet. Multipath routing is a mechanism for load balancing in which the total load is spatially distributed over several paths. It can reduce congestion probability given by routing into best one path in the current Internet. We focus on MPLS network, which is usable in the ISP network. LSPs of MPLS provide path controllability by explicit route in the connectionless IP network."br /"Multipath routing scheme is established with two steps, selection of multiple candidate paths and traffic splitting among these selected paths. We compare some recent multipath routing algorithms based on MPLS in the point of scalability and stability. Of them, we pick up WDP and LDM for our hybrid approach which combines cross-steps of different algorithms. PER algorithm is proposed in the improvement of LDM's traffic splitting step. Using LDM, WDP and PER, three hybrid QoS algorithms by each step combination are made. Their performances are proved by simulation that they, especially LBWDP (Load Balancing over Widest Disjoint Paths), are more effective than LDM or MATE. "br /"For better QoS guarantee, we integrate DiffServ with our traffic engineering technique (DiffServ-aware MPLS Traffic Engineering: DS-TE). PEMS (PEriodic Multi-Step algorithm in DS-TE network) is proposed as one DS-TE model to differentiate the quality of service according to the class. For PEMS algorithm, we propose new algorithm to select candidate paths by proper metric of each traffic class. PER algorithm distributes the traffic among its own candidate paths by dynamic metric of requested class. Simulation results using ns-2 showed that PEMS can balance the load less than LBWDP but EF and AF classes can be ensured the better quality of service than LBWDP.; Le routage multi-chemins est une technique qui permet l'équilibrage de la charge en multiplexant les flux vers une destination sur plusieurs chemins. Nous proposons une approche de routage multi-chemins qui, peut être schématisée en deux étapes : l'étape de choix des chemins candidats et l'étape de distribution du trafic sur un sous-ensemble de ces chemins. "br /"Dans ce travail, nous avons commencé par effectuer une étude comparative d'un point scalabilité et stabilité, de plusieurs algorithmes de routage multi-chemins, basés sur MPLS. Cela nous a permis de retenir WDP pour la sélection des chemins candidats et LDM pour la distribution des demandes de trafic reçues par un routeur entrant du réseau d'un FAI. Nous proposons dans ce travail PER, un algorithme qui est une amélioration de l'algorithme de distribution de LDM. Ces différents algorithmes nous ont permis de réaliser plusieurs algorithmes « hybrides » dont LBWDP (Load Balancing over Widest Disjoint Paths) qui par simulation a été prouvé comme étant un algorithme plus performant que des modèles comme LDM ou MATE. "br /"Pour une meilleure garantie de QdS nous avons cherché à intégrer la différentiation de service (DiffServ) avec notre technique d'ingénierie de trafic (DiffServ-aware MPLS Traffic Engineering : DS-TE). Nous proposons PEMS (PEriodic Multi-Step algorithm for DS-TE network) comme un modèle de DS-TE pour différencier la qualité du service selon la classe du trafic. Dans ce cadre, nous proposons un nouvel algorithme de sélection de chemins candidats en fonctions des critères préférentiels de chaque classe de trafic. L'utilisation de PER permet ensuite de distribuer en fonction de critères dynamiques les demandes reçues sur les meilleurs chemins de chaque classe. Par simulation à l'aide de ns-2, nous avons montré que PEMS répartie moins bien la charge que LBWDP mais que les classes EF et AF ont une qualité de service meilleure que dans le cas de LBWDP.

User Preferred Trajectories in Commercial Aircraft Operation: Design and Implementation

Scipedia content — Tue, 26 Jan 2021 16:30:47 +0100

This report describes how an aircraft creates and flies its User Preferred Trajectory from take-off to landing, based on the objectives and constraints the aircraft is subjected to from a technological and operational viewpoint. A basic description of commercial aircraft operation is given, with an emphasis on identifying the different stakeholders (Air Navigation Service Providers, Airline Operation Center, Pilot/Aircraft, Airport and Civil Aviation Authority). A general description of Instrument Flight Rules operations is also given, together with an explanation of the capabilities of modern flight management systems. The objectives and constraints of the trajectory building process from an aircraft and air traffic management viewpoint are described in Chapter 4. Those are instrumental in understanding how the user preferred trajectory is built. The initial and detail route planning process is then described. The initial route planning is performed long before the flight and usually by the airline operating center, while detail flight planning, including take-off, runway and departure procedure is performed later by the crew. This process is re-performed minutes before take-off, and usually iterated during the flight when the details of approach and landing are communicated to the aircraft crew. The implementation of this user preferred trajectory is explained in terms of the options that the pilots have in the aircraft avionics to perform the mission. The implementation explained in this report is based on the avionics suite of a Boeing 737NG aircraft equipped with the most advanced flight management systems. An implementation of a user preferred trajectory, where the aircraft crew is able to best fulfill their objectives is composed of an idle or near idle descent from the cruise altitude. This type of descent, called an advanced continuous descent approach has been implemented by some air navigation service providers, airlines and airports, based on advanced technology that will be further described in this paper. Those procedures are called Green Approaches. In the last part of this report, the benefits of flying Green Approach procedures are analyzed by means of aircraft simulations. The analysis describes in detail the lateral and vertical trajectories of the Green Approaches at Stockholm’s Arlanda Airport and Brisbane Airport (Australia), together with the calculated advantages in term of fuel consumption, noise and gas emissions. QC 20101119

GMPLS multi-layer networking Routing and constraint-based path computation in optical network segments

Scipedia content — Tue, 26 Jan 2021 16:30:31 +0100

In recent years, IP based end-to-end services have grown in popularity. Efficiently meeting the user demand for such services, different techniques for traffic engineering transport networks have been developed. One such technique, currently being developed for multilayered networks, is Generalized Multi-Protocol Label Switching (GMPLS). GMPLS is a necessary networking technique because provisioning end-to-end services will today, and in the foreseeable future, very likely require the co-operation of multiple network layers. Here, the readiness of GMPLS for optical networks is investigated by reviewing the current support for optical networking components in the GMPLS standard documents. Based on this investigation, a candidate solution for routing and constraint-based path computation in optical network segments has been derived. This candidate solution is shown to efficiently handle the additional attributes and constraints inherent in optical networking components. De senaste åren har IP-baserade tjänster ökat i popularitet. För att effektivt möta de användarkrav som ställs på sådana tjänster har olika tekniker för att styra transportnätverk utvecklats. En sådan teknik, nu under utveckling för multi-lagrade nätverk, är GMPLS. GMPLS är en nödvändig nätverksteknik eftersom tillhandahållandet av sluttjänster mellan olika användare idag, och inom en överskådlig framtid, mycket sannolikt kommer att kräva samarbete mellan flera nätverkslager. Här undersöks GMPLS färdighet i optiska nätverk genom att se över det nuvarande stödet för optiska nätverkskomponenter i GMPLS standarddokument. Baserat på denna undersökning har en kandidatlösning för routing och begränsad vägberäkning i optiska nätverkssegment tagits fram. Denna kandidatlösning visas effektivt hantera de ytterligare attribut och restriktioner som existerar i optiska nätverkskomponenter.

Design of a competence-based assessment system for air traffic control training

Scipedia content — Tue, 26 Jan 2021 16:20:36 +0100

traffic control (ATC) simulator and on-the-job training requires a valid and reliable assessment system. Competence-based assessment results in more effective learning processes and better founded pass–fail decisions, which may contribute to an increased output of competent controllers from training. At Air Traffic Control The Netherlands (LVNL) we designed an assessment system based on a newly defined set of competences. The ATC Performance Model, derived from this competence analysis, has served as a framework for the design. This article describes the background, the design process, the properties, and the evaluation results of the competence-based assessment system in use by LVNL.

A Risk Analysis Framework for Maritime Transport of Packaged Dangerous Goods - A Validating Demonstration (Volumes I and II) - click here to view both volumes in PDF

Scipedia content — Tue, 26 Jan 2021 16:08:21 +0100

- Vol. I"br /" "br /" In this Volume of the thesis, which consists of two volumes, a risk analysis framework for application in the maritime transport system of packaged dangerous goods (PDG) is presented. In many countries, dangerous goods risks have been ranked high among public concerns. Such concerns are mainly due to the increasing volume of dangerous goods, human safety and health and environmental risks and threats they pose, and the general belief that these risks should be managed more efficiently and effectively. The literature study shows that, in recent years, the risk management system has become a "hot" topic for many countries and organisations. Many risk assessment frameworks have been developed in the shipping and other industries, sectors or areas. In the maritime industry, they are primarily developed for analysis of the risks for the industry in general and in particular for maritime transport of bulk dangerous cargoes such as oil, oil products, liquefied gases and other bulk liquid chemicals. The FSA (Formal Safety Assessment) framework of the International Maritime Organisation, which is one of the most widely used ("authoritative") frameworks in the shipping industry, is a generic framework. However, the framework is not intended for application in all circumstances, including the risks of the maritime transport of PDG. Consequently, the FSA is adapted or simply applied or tested in several maritime-related systems, activities and issues, but not in the maritime transport of PDG. Furthermore, a specific risk analysis framework for application in maritime transport of PDG has not been found. Therefore, on the basis of understanding gained from the extensive literature study of some of the world's best frameworks and techniques, guidelines and practices in shipping and other industries and sectors, and analysis of large amounts of empirical data, a risk analysis framework has been developed for readily application in the maritime transport system of PDG. Efforts have been made to strengthen validity and reliability of the framework. This study contributes to the communities of academics and practitioners. In Volume II of this thesis, the framework is demonstrated step-by-step in practice based on large amounts of empirical data. Recommendations for improving risk methodology and human safety and health and protection of the marine environment and property are provided."br /" "br /" Abstract - Vol. II"br /" "br /" Volume II of the thesis presents the results of the validating demonstration of the risk analysis framework presented in Chapter 5, Volume I. For a number of interrelated reasons, including enhancing external validity, ensuring data and methodology triangulations, and filling gaps and extending the data, the risk analysis framework is step-by-step demonstrated in practice based on combination of the qualitative and quantitative empirical data and data analysis methods. The main datasets included: a) a representative marine accident case history; and b) the statistical incident data collected from the two largest U.S.'s hazmat (hazardous materials) incident databases. In this study, considerable efforts have been made to enhance understanding of dangerous goods risks. Given the size and uniqueness of the empirical data, this study might be one of the largest of its kind, and some of the results might not be found elsewhere. Based on understanding and the results of the risk analysis, detailed recommendations for improving human safety and health, and the protection of the marine environment and property are provided. The validating demonstration showed that the risk analysis framework satisfies both validity and reliability conditions. The results of the risk analysis replicated the framework. This study contributes to both communities - academics and practitioners alike. Given the representativeness, the large size and the diversity of the data, and the universal properties of the systems and risks studied, many results and recommendations are also valid for other systems and risks in other locations, countries or regions, including the countries of the Baltic Sea Region. Some results will assist relevant organisations or institutions to predict and explain phenomena. They may serve as the basis for further study and development of risk evaluation criteria in the field. The risk analysis framework contains many specific and detailed guidelines and firsthand experiences that will assist, but not guarantee, risk analysts to prepare and perform risk analyses and projects, including identification, selection and collection of relevant risk-related data and data analysis methods and techniques, and generation and presentation of detailed, valid, reliable as well as transparent results in a more efficient and effective manner.

Innovation and Regulatory Reform in Public Transport : Innovative Capabilities and Learning of the Public Transport Organisations

Scipedia content — Tue, 26 Jan 2021 15:58:09 +0100

xtabstractThis thesis is a result from a project funded by the co-operative research programme T3 of the Netherlands Organisation of Applied Scientific Research TNO and the Netherlands Research School for Transport, Infrastructure, and Logistics TRAIL TRAIL Thesis Series no. 2006/5, The Netherlands TRAIL Research School, Delft, The Netherland

İstanbul’da Kent İçi Raylı Sistemler Ve Üstyapı Hesapları

Scipedia content — Tue, 26 Jan 2021 15:33:40 +0100

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007

Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2007

Bu çalışmada ilk bölümde demiryolu üstyapısı ve üstyapıyı oluşturan elemanlar incelenmiştir. Ray, travers, balast ve bağlantı malzemeleri ve demiryolu üstyapısı içindeki işlevleri anlatılmıştır. Geçmişten günümüze üstyapı elemanlarının kısaca gelişimine değinilmiş, günümüzde kullanılan yeni tipleri tanıtılmıştır. İkinci bölümde İstanbul’da kent içi raylı sistemler incelenmiş ve mevcut, yapım aşamasında ve proje safhasında olan hatlar tanıtılmıştır. Üstyapıları bilinen mevcut hatlar, Aksaray-Havalimanı Hafif Metro Hattı, Kabataş-Zeytinburnu Cadde Tramvayı, Taksim-4.Levent İstanbul Metrosu tanıtılmış, üstyapıları incelenmiştir. Üstyapı tipleri kesinleşmemiş yapım ve proje aşamasında hatların üstyapılarına değinilmemiş, genel olarak tanıtımları yapılmıştır. Üçüncü bölümde demiryolu üstyapı hesapları anlatılmış ve mevcut raylı sistemlerin üstyapı hesabı yapılmıştır. Bu hesaplarda Winkler’in elastik ortama oturan kiriş hipotezi baz alınmıştır. Bu hipotezi demiryolu üstyapısı hesabında kullanırken Zimmerman yöntemi takip edilmiştir. Üstyapı hesabında statik yükler için bulunan sonuçlara dinamik etkilerin katılmasında Eisenmann’ın geliştirdiği Münih Teknik Üniversitesi Karayolları ve Demiryolları İnşaatı Enstitüsü’nün verdiği üstyapı biçimine ve hıza bağlı formulasyonlar kullanılmıştır., Bulunan dinamik değerler neticesinde mevcut üstyapıların yeterli oldukları tahkikler sonucunda bulunmuştur.

In this study, railway superstructure and the superstructure components constituting the superstructure are examined. Rail, sleeper, ballast and fastenings and their functions in railway superstructure are explained. The development of these superstructure components through the history is mentioned and the new types which are used today are introduced. In the second section, railway systems of Istanbul are examined and the current tracks, the tracks under construction and the ones in the phase of planning are introduced. The current tracks with known superstructure, Aksaray – Airport Line, Kabataş – Zeytinburnu Tram, Taksim - 4. Levent İstanbul Subway are introduced and their superstructures are examined. The superstructure features of the tracks with indefinite superstructure types which are under construction or in the phase of planning are not mentioned, only general presentations of them are annexed. In the third section, superstructure calculations of railway systems are explained and the superstructure calculations of current railway systems are computed. In these calculations, Winkler s hypothesis about the joist fitting upon an elastic ground is taken as the main basis. When applying this hypothesis to the calculation of railway systems superstructure, Zimmermann method is followed. For consolidating the dynamic factors with the results about the static loads in the calculation, the formulations which depend on the type of the superstructure and speed and which are developed by Eisenmann and given by Munich Technical University Highways and Railways Construction Institute are used. The current superstructures are investigated in the light of the calculated dynamic values and are proven to qualified.

Yüksek Lisans

M.Sc.

Adaptive multi-path routing for internet traffic engineering

Scipedia content — Tue, 26 Jan 2021 14:30:51 +0100

Ivan Gojmerac Zsfassung in dt. Sprache Wien, Techn. Univ., Diss., 2007 OeBB

Model-Based Visual Localisation Of Contours And Vehicles

Scipedia content — Tue, 26 Jan 2021 14:16:01 +0100

El treball d'aquesta tesi es centra en l'anàlisi de seqüències de vídeo, aplicant tècniques basades en models per extreure'n informació quantitativa. En concret, es realitzen diferents propostes en dues àrees d'aplicació: el seguiment de formes basat en models de contorns, i la detecció i seguiment de vehicles en imatges proveïdes per una camera instal·lada en una plataforma mòbil. El treball dedicat al seguiment de formes s'enquadra en el paradigma de contorns actius, del qual presentem una revisió de les diferents propostes existents. En primer lloc, mesurem el rendiment obtingut pels algorismes de seguiment més comuns (filtres basats en Kalman i filtres de partícules), i en segon lloc avaluem diferents aspectes de la seva implementació en un extens treball experimental on es consideren múltiples seqüències sintètiques, distorsionades amb diferents graus de soroll. Així, mitjançant aquest estudi determinem la millor manera d'implementar a la pràctica els algorismes de seguiment clàssics, i identifiquem els seus pros i contres. Seguidament, el treball s'orienta cap a la millora dels algoritmes de seguiment de contorns basats en filtres de partícules. Aquest algorismes aconsegueixen bons resultats sempre que el número de partícules utilitzades sigui suficient, però malauradament la quantitat de partícules requerides creix exponencialment amb el número de paràmetres a estimar. Per tant, i en el context del seguiment de contorns, presentem tres variants del filtre de partícules clàssic, corresponents a tres noves estratègies per tractar aquest problema. En primer lloc, proposem millorar el seguiment de contorns mirant de propagar més acuradament les partícules emprades per l'algorisme d'una imatge a la següent. Això ho duem a terme utilitzant una aproximació lineal de la funció de propagació òptima. La segona estratègia proposada es basa en estimar part dels paràmetres de manera analítica. Així, es pretén fer un ús més productiu de les partícules emprades, reduint la part dels paràmetres del model que s'han d'estimar amb elles. El tercer mètode proposat té com a objectiu treure profit del fet de que, en aplicacions de seguiment de contorns, sovint els paràmetres relatius a la transformació rígida es poden estimar prou acuradament independentment de la deformació local que el contorn presenti. Això s'utilitza per realitzar una millor propagació de les partícules, concentrant-les més densament en la zona on el contorn seguit es troba. Aquestes tres propostes es validen de manera extensiva en seqüències amb diferents nivells de soroll, amb les que es mesura la millora aconseguida. A continuació proposem tractar directament l'origen del problema anterior mitjançant la reducció del nombre de paràmetres a estimar per tal de seguir una determinada forma d'interès. Per aconseguir això, proposem modelar aquesta forma usant múltiples models, on cadascun requereix una quantitat de paràmetres inferior a la requerida per un únic model. Es proposa un nou mètode per aprendre aquests models a partir d'un conjunt d'entrenament, així com un nou algorisme per emprar-los en el seguiment dels contorns. Els resultats experimentals certifiquen la validesa d'aquesta proposta. Finalment, la tesi es centra en el desenvolupament d'un sistema de detecció i seguiment de vehicles. Les propostes realitzades comprenen: un mòdul de detecció de vehicles, un mòdul dedicat a determinar la posició i velocitat 3D dels vehicles detectats, i un mòdul de seguiment per actualitzar la localització dels vehicles a la carretera de manera precisa i eficient. Es realitzen diverses aportacions originals en aquests tres temes, i se n'avalua el rendiment. This thesis focuses the analysis of video sequences, applying model-based techniques for extracting quantitative information. In particular, we make several proposals in two application areas: shape tracking based on contour models, and detection and tracking of vehicles in images acquired by a camera installed on a mobile platform.The work devoted to shape tracking follows the paradigm of active contours, from which we present a review of the existent approaches. First, we measure the performance of the most common algorithms (Kalman based filters and particle filters), and then we evaluate its implementation aspects trough an extensive experimental study, where several synthetic sequences are considered, distorted with different degrees of noise. Thus, we determine the best way to implement in practice these classical tracking algorithms, and we identify its benefits and drawbacks.Next, the work is oriented towards the improvement of contour tracking algorithms based on particle filters. These algorithms reach good results provided that the number of particles is high enough, but unfortunately the required number of particles grows exponentially with the number of parameters to be estimated. Therefore, and in the context of contour tracking, we present three variants of the classical particle filter, corresponding to three new strategies to deal with this problem. First, we propose to improve the contour tracking by propagating more accurately the particles from one image to the next one. This is done by using a linear approximation of the optimal propagation function. The second proposed strategy is based in estimating part of the parameters analytically. Thus, we aim to do a more productive use of the particles, reducing the amount of model parameters that must be estimated through them. The third proposed method aims to exploit the fact that, in contour tracking applications, the parameters related to the rigid transform can be estimated accurately enough independently from the local deformation presented by the contour. This is used to perform a better propagation of the particles, concentrating them more densely in the zone where the tracked contour is located. These three proposals are validated extensively in sequences with different noise levels, on which the reached improvement is evaluated.After this study, we propose to deal directly with the origin of the previous problem by reducing the number of parameters to be estimated in order to follow a given shape of interest. To reach that, we propose to model the shape using multiple models, where each one requires a lower quantity of parameters than when using a unique model. We propose a new method to learn these models from a training set, and a new algorithm to use the obtained models for tracking the contours. The experimental results certify the validity of this proposal.Finally, the thesis focuses on the development of a system for the detection and tracking of vehicles. The proposals include: a vehicle detection module, a module devoted to the determination of the three-dimensional position and velocity of the detected vehicles, and a tracking module for updating the location of vehicles on the road in a precise and efficient manner. Several original contributions are done in these three subjects, and their performance is evaluated empirically.

Variational problems in"br /"transportation theory with mass concentration

Scipedia content — Tue, 26 Jan 2021 13:58:06 +0100

The thesis includes the study of several variational problems involving both transport costs and concentration criteria. Some problems are given by the minimization of functional defined on the marginal measures of a transport problem, requiring one to be concentrated, the other diffuse and the two of them close to each other in a transportation sense. This is what is mainly developed in Chapters 1-3. Other chapters are devoted to different models of transportation which involve, in the definition of the cost, sort of concentration criteria about the path particles follow along the transport, giving raise to congestion or branching effects. Several problems are defined on one-dimensional structures (networks, rectifiable supports of vector measures, length constrained sets...) and their regularity, at a blow-up level, is discussed in the last two chapters. The models come in most cases from applications to urban planning, biology (tree, leaves and blood system), geophysics (river basins) and fluid mechanics. the thesis has been written under the supervision of Prof. G. Buttazzo and defended in December at SNS, Pisa; Plusieurs problèmes d'optimisation liés à la théorie du transport optimal, concernant aussi des critères de concentration, sont étudiés. Il s'agit, pour ce qui est des primiers chapitres, de la minimization de fonctionnelles definies sur les mesures marginales du porblème de transport, en demandant que l'une soit concentrée et l'autre diffusée, alors que les deux doivent être proche au sense du transport de masse. D'autres chapitres portent sur des modèles différentes qui considèrent la concentration des parcours suivis par les particules lors du mouvement, en donnant des effets de congestion ou branchement. Plusieurs problèmes font apparaître des structures de dimension 1 (reseaux, supports rectifiables de mesures vectorielles, ensemble sous contraintes de longueur...) et leur régularité (blow-up) est étudiée dans les deux derniers chapitres. Les modèles viennent dans la majorité des cas de possibles applications à la planification urbaine, la biologie (arbres, feuilles et système sanguin), la géophysique (bassins fluviaux) et la mécanique des fluides. La thèse a été écrite sous la direction du Prof. Buttazzo et soutenue à l'Ecole Normale Supérieure de Pise.

Slot-Exchange Mechanisms and Weather-Based Rerouting within an Airspace Planning and Collaborative Decision-Making Model

Scipedia content — Tue, 26 Jan 2021 13:49:21 +0100

We develop and evaluate two significant modeling concepts within the context of a large-scale Airspace Planning and Collaborative Decision-Making Model (APCDM) and, thereby, enhance its current functionality in support of both strategic and tactical level flight assessments. The first major concept is a new severe weather-modeling paradigm that can be used to assess existing tactical en route flight plan strategies such as the Flight Management System (FMS) as well as to provide rerouting strategies. The second major concept concerns modeling the mediated bartering of slot exchanges involving airline trade offers for arrival/departure slots at an arrival airport that is affected by the Ground Delay Program (GDP), while simultaneously considering issues related to sector workloads, airspace conflicts, as well as overall equity concerns among the airlines. This research effort is part of an $11.5B, 10-year, Federal Aviation Administration (FAA)-sponsored program to increase the U.S. National Airspace (NAS) capacity by 30 percent by the year 2010. Our innovative contributions of this research with respect to the severe weather rerouting include (a) the concept of â Probability-Netsâ and the development of discretized representations of various weather phenomena that affect aviation operations; (b) the integration of readily accessible severe weather probabilities from existing weather forecast data provided by the National Weather Service (NWS); (c) the generation of flight plans that circumvent severe weather phenomena with specified probability levels, and (d) a probabilistic delay assessment methodology for evaluating planned flight routes that might encounter potentially disruptive weather along its trajectory. Given a fixed set of reporting stations from the CONUS Model Output Statistics (MOS), we begin by constructing weather-specific probability-nets that are dynamic with respect to time and space. Essential to the construction of the probability-nets are the point-by-point forecast probabilities associated with MOS reporting sites throughout the United States. Connections between the MOS reporting sites form the strands within the probability-nets, and are constructed based upon a user-defined adjacency threshold, which is defined as the maximum allowable great circle distance between any such pair of sites. When a flight plan traverses through a probability-net, we extract probability data corresponding to the points where the flight plan and the probability-net strand(s) intersect. The ability to quickly extract this trajectory-related probability data is critical to our weather-based rerouting concepts and the derived expected delay and related cost computations in support of the decision-making process. Next, we consider the superimposition of a flight-trajectory-grid network upon the probability-nets. Using the U.S. Navigational Aids (Navaids) as the network nodes, we develop an approach to generate flight plans that can circumvent severe weather phenomena with specified probability levels based on determining restricted, time-dependent shortest paths between the origin and destination airports. By generating alternative flight plans pertaining to specified threshold strand probabilities, we prescribe a methodology for computing appropriate expected weather delays and related disruption factors for inclusion within the APCDM model. We conclude our severe weather-modeling research by conducting an economic benefit analysis using a k-means clustering mechanism in concert with our delay assessment methodology in order to evaluate delay costs and system disruptions associated with variations in probability-net refinement-based information. As a flight passes through the probability-net(s), we can generate a probability-footprint that acts as a record of the strand intersections and the associated probabilities from origin to destination. A flight planâ s probability-footprint will differ for each level of data refinement, from whence we construct route-dependent scenarios and, subsequently, compute expected weather delay costs for each scenario for comparative purposes. Our second major contribution is the development of a novel slot-exchange modeling concept within the APCDM model that incorporates various practical issues pertaining to the Ground Delay Program (GDP), a principal feature in the FAAâ s adoption of the Collaborative Decision-Making (CDM) paradigm. The key ideas introduced here include innovative model formulations and several new equity concepts that examine the impact of â at-least, at-mostâ trade offers on the entire mix of resulting flight plans from respective origins to destinations, while focusing on achieving defined measures of â fairnessâ with respect to the selected slot exchanges. The idea is to permit airlines to barter assigned slots at airports affected by the Ground Delay Program to their mutual advantage, with the FAA acting as a mediator, while being cognizant of the overall effect of the resulting mix of flight plans on air traffic control sector workloads, collision risk and safety, and equity considerations. We start by developing two separate slot-exchange approaches. The first consists of an external approach in which we formulate a model for generating a set of package-deals, where each package-deal represents a potential slot-exchange solution. These package-deals are then embedded within the APCDM model. We further tighten the model representation using maximal clique cover-based cuts that relate to the joint compatibility among the individual package-deals. The second approach significantly improves the overall model efficiency by automatically generating package-deals as required within the APCDM model itself. The model output prescribes a set of equitable flight plans based on admissible trades and exchanges of assigned slots, which are in addition conformant with sector workload capabilities and conflict risk restrictions. The net reduction in passenger-minutes of delay for each airline is the primary metric used to assess and compare model solutions. Appropriate constraints are included in the model to ensure that the generated slot exchanges induce nonnegative values of this realized net reduction for each airline. In keeping with the spirit of the FAAâ s CDM initiative, we next propose four alternative equity methods that are predicated on different specified performance ratios and related efficiency functions. These four methods respectively address equity with respect to slot-exchange-related measures such as total average delay, net delay savings, proportion of acceptable moves, and suitable value function realizations. For our computational experiments, we constructed several scenarios using real data obtained from the FAA based on the Enhanced Traffic Management System (ETMS) flight information pertaining to the Miami and Jacksonville Air Route Traffic Control Centers (ARTCC). Through our experimentation, we provide insights into the effect of the different proposed modeling concepts and study the sensitivity with respect to certain key parameters. In particular, we compare the alternative proposed equity formulations by evaluating their corresponding slot-exchange solutions with respect to the net reduction in passenger-minutes of delay for each airline. Additionally, we evaluate and compare the computational-effort performance, under both time limits and optimality thresholds, for each equity method in order to assess the efficiency of the model. The four slot-exchange-based equity formulations, in conjunction with the internal slot-exchange mechanisms, demonstrate significant net savings in computational effort ranging from 25% to 86% over the original APCDM model equity formulation. The model has been implemented using Microsoft Visual C++ and evaluated using a C++ interface with CPLEX 9.0. The overall results indicate that the proposed modeling concepts offer viable tools that can be used by the FAA in a timely fashion for both tactical purposes, as well as for exploring various strategic issues such as air traffic control policy evaluations; dynamic airspace resectorization strategies as a function of severe weather probabilities; and flight plan generation in response to various disruption scenarios. Ph. D.

A risk-sensitive approach for airline network revenue management problems

Scipedia content — Tue, 26 Jan 2021 13:45:31 +0100

In this thesis, airline network revenue management problem is considered for the case with no cancellations and overbooking. In literature, there exist several approximate probabilistic and deterministic mathematical models developed in order to maximize expected revenue at the end of the reservation period. The aim of this study is to develop models considering also the risks involved in the proposed booking control policies. Two linear programming models are proposed which incorporate the variance of the revenue. The objective of the models is to effectively balance the tradeoff between the expectation and variance of the revenue. The performances of the proposed models are compared to the previous models through a numerical study. The seat allocations resulting from the mathematical models are used in a simulation model working with several booking control policies. The probability distributions of the revenues are investigated and the revenues are compared in terms of expectation, standard deviation, coefficient of variation and probability of poor performance. It is observed that the use of the proposed models decreases the variability of the revenue and thereby the risk of probability of poor performance. Also, the expected revenues obtained by implementing the solutions of the proposed models with nested booking control policies turn out to be higher than other probabilistic models as long as the degree of variance incorporation is within some interval. When compared with the deterministic models, the proposed models provides for the decision makers with alternative, preferable policies in terms of the expectation and the variability measures. M.S. - Master of Science

Development of Next Generation Multiphase Pipe Flow Prediction Tools

Scipedia content — Mon, 25 Jan 2021 19:55:02 +0100

The developments of oil and gas fields in deep waters (5000 ft and more) will become more common in the future. It is inevitable that production systems will operate under multiphase flow conditions (simultaneous flow of gas, oil and water possibly along with sand, hydrates, and waxes). Multiphase flow prediction tools are essential for every phase of hydrocarbon recovery from design to operation. Recovery from deep-waters poses special challenges and requires accurate multiphase flow predictive tools for several applications, including the design and diagnostics of the production systems, separation of phases in horizontal wells, and multiphase separation (topside, seabed or bottom-hole). It is crucial for any multiphase separation technique, either at topside, seabed or bottom-hole, to know inlet conditions such as flow rates, flow patterns, and volume fractions of gas, oil and water coming into the separation devices. Therefore, the development of a new generation of multiphase flow predictive tools is needed. The overall objective of the proposed study is to develop a unified model for gas-oil-water three-phase flow in wells, flow lines, and pipelines to predict flow characteristics such as flow patterns, phase distributions, and pressure gradient encountered during petroleum production at different flow conditions (pipe diameter and inclination, more » fluid properties and flow rates). In the current multiphase modeling approach, flow pattern and flow behavior (pressure gradient and phase fractions) prediction modeling are separated. Thus, different models based on different physics are employed, causing inaccuracies and discontinuities. Moreover, oil and water are treated as a pseudo single phase, ignoring the distinct characteristics of both oil and water, and often resulting in inaccurate design that leads to operational problems. In this study, a new model is being developed through a theoretical and experimental study employing a revolutionary approach. The basic continuity and momentum equations is established for each phase, and used for both flow pattern and flow behavior predictions. The required closure relationships are being developed, and will be verified with experimental results. Gas-oil-water experimental studies are currently underway for the horizontal pipes. Industry-driven consortia provide a cost-efficient vehicle for developing, transferring, and deploying new technologies into the private sector. The Tulsa University Fluid Flow Projects (TUFFP) is one of the earliest cooperative industry-university research consortia. TUFFP's mission is to conduct basic and applied multiphase flow research addressing the current and future needs of hydrocarbon production and transportation. TUFFP participants and The University of Tulsa are supporting this study through 55% cost sharing. « le

Effective and Robust Coordination of Traffic Signals on Arterial Streets, Volume 1, Research Report

Scipedia content — Mon, 25 Jan 2021 19:48:51 +0100

Many transportation agencies use Synchro and SimTraffic software package to optimize signal coordination. In general, this software package effectively reduces the efforts of traffic systems engineers and improves the quality of the designed coordination. Nevertheless, the initial solutions given by the software packages usually require adjustment, at both the design and implementation stages. The major objective of this research, therefore, is to reduce the time and effort needed in solution tuning and thus to improve the effectiveness and the efficiency of using Synchro/SimTraffic in arterial signal coordination design. The research outcome is expected to help traffic systems engineers reach reasonable signal settings in a shorter time. The first task of this research was to survey INDOT traffic system engineers and document INDOT’s criteria for a good coordination plan. The outcome of this task served as the yardstick for other proposed design improvement procedures. The second part of the research focused on the Synchro/SimTraffic-based procedures of optimizing signal settings for urban streets and the practices and methods of using Synchro were scrutinized thoroughly. The outcome of this part of the research is a collection of supplemental guidelines for software-based selection of signal settings on urban streets. Finally, the robustness of the arterial signal coordination procedure was investigated. In current practice, signals are optimized to traffic volumes that represent a single time interval. In spite of the randomness of traffic, these plans, however, are executed for a long period of time until obvious insufficiencies of the signal timings are noticed and re-timing is necessary. The robustness of several alternative approaches was considered in the same traffic condition settings. The outcomes of these investigations are assembled into the second volume of this report, Guidelines of Design. The guidelines are in accordance with the defined criteria of good signal control along urban streets. The guidelines are not a manual of arterial signal design since every arterial system has its individual problems and requires specific treatment that cannot be reached by a uniform set of procedures. Instead, experiences collected from current traffic systems engineers and lessons learned through research are compiled into the guidelines to help reduce field tuning of the signal settings. The resulting guidelines are practical and they require no extra data beyond the current data collection practice. The guideline can serve as a reference for experienced traffic engineers and as an educational tool for new traffic engineers. The robustness of the signal design procedures was also investigated. Models for extracting the traffic variation pattern from 12 hours of traffic counts were developed based on real data collected at Purdue University. These models were used to generate reasonable traffic inputs to the micro-simulation tool. The robustness of the current signal design procedures was evaluated using these simulated traffic inputs. Several practical alternatives to the current arterial signal optimization were also evaluated using the same inputs. The performances of these methods were compared, and it was concluded that no obvious way to consistently improve the robustness of current signal design procedure is available.

Innovative Sensors for Pipeline Crawlers: Rotating Permanent Magnet Inspection

Scipedia content — Mon, 25 Jan 2021 19:11:29 +0100

Internal inspection of pipelines is an important tool for ensuring safe and reliable delivery of fossil energy products. Current inspection systems that are propelled through the pipeline by the product flow cannot be used to inspect all pipelines because of the various physical barriers they may encounter. To facilitate inspection of these ''unpiggable'' pipelines, recent inspection development efforts have focused on a new generation of powered inspection platforms that are able to crawl slowly inside a pipeline and can maneuver past the physical barriers that limit internal inspection applicability, such as bore restrictions, low product flow rate, and low pressure. The first step in this research was to review existing inspection technologies for applicability and compatibility with crawler systems. Most existing inspection technologies, including magnetic flux leakage and ultrasonic methods, had significant implementation limitations including mass, physical size, inspection energy coupling requirements and technology maturity. The remote field technique was the most promising but power consumption was high and anomaly signals were low requiring sensitive detectors and electronics. After reviewing each inspection technology, it was decided to investigate the potential for a new inspection method. The new inspection method takes advantage of advances in permanent magnet strength, along with theirmore » wide availability and low cost. Called rotating permanent magnet inspection (RPMI), this patent pending technology employs pairs of permanent magnets rotating around the central axis of a cylinder to induce high current densities in the material under inspection. Anomalies and wall thickness variations are detected with an array of sensors that measure local changes in the magnetic field produced by the induced current flowing in the material. This inspection method is an alternative to the common concentric coil remote field technique that induces low-frequency eddy currents in ferromagnetic pipes and tubes. Since this is a new inspection method, both theory and experiment were used to determine fundamental capabilities and limitations. Fundamental finite element modeling analysis and experimental investigations performed during this development have led to the derivation of a first order analytical equation for designing rotating magnetizers to induce current and positioning sensors to record signals from anomalies. Experimental results confirm the analytical equation and the finite element calculations provide a firm basis for the design of RPMI systems. Experimental results have shown that metal loss anomalies and wall thickness variations can be detected with an array of sensors that measure local changes in the magnetic field produced by the induced current flowing in the material. The design exploits the phenomenon that circumferential currents are easily detectable at distances well away from the magnets. Current changes at anomalies were detectable with commercial low cost Hall Effect sensors. Commercial analog to digital converters can be used to measure the sensor output and data analysis can be performed in real time using PC computer systems. The technology was successfully demonstrated during two blind benchmark tests where numerous metal loss defects were detected. For this inspection technology, the detection threshold is a function of wall thickness and corrosion depth. For thinner materials, the detection threshold was experimentally shown to be comparable to magnetic flux leakage. For wall thicknesses greater than three tenths of an inch, the detection threshold increases with wall thickness. The potential for metal loss anomaly sizing was demonstrated in the second benchmarking study, again with accuracy comparable to existing magnetic flux leakage technologies. The rotating permanent magnet system has the potential for inspecting unpiggable pipelines since the magnetizer configurations can be sufficiently small with respect to the bore of the pipe to pass obstructions that limit the application of many inspection technologies. Also, since the largest dimension of the Hall Effect sensor is two tenths of an inch, the sensor packages can be small, flexible and light. The power consumption, on the order of ten watts, is low compared to some inspection systems; this would enable autonomous systems to inspect longer distances between charges. This project showed there are no technical barriers to building a field ready unit that can pass through narrow obstructions, such as plug valves. The next step in project implementation is to build a field ready unit that can begin to establish optimal performance capabilities including detection thresholds, sizing capability, and wall thickness limitations.« le

DOUBLE SHELL TANK (DST) WASTE TRANSFER LINE ENCASEMENT INTEGRITY ASSESSMENT TECHNOLOGY STUDY

Scipedia content — Mon, 25 Jan 2021 19:04:57 +0100

MECHANICAL TESTING OF CARBON STEEL IN HIGH PRESSURE HYDROGEN

Scipedia content — Mon, 25 Jan 2021 18:58:04 +0100

The methods and interim results from a testing program to quantify hydrogen effects on mechanical properties of carbon steel pipeline and pipeline weld materials are provided. The scope is carbon steels commonly used for natural gas pipelines in the United States that are candidates for hydrogen service in the hydrogen economy. The mechanical test results will be applied in future analyses to evaluate service life of the pipelines. The results are also envisioned to be part of the bases for construction codes and structural integrity demonstrations for hydrogen service pipeline and vessels. Tensile properties of one type of steel (A106 Grade B) in base metal, welded and heat affected zone conditions were tested at room temperature in air and high pressure (1500 psig) hydrogen. A general reduction in the materials ability to plastically deform was noted in this material when specimens were tested in 1500 psig hydrogen. Furthermore, the primary mode of fracture was changed from ductile rupture in air to cleavage with secondary tearing in hydrogen. The mechanical test program will continue with tests to quantify the fracture behavior in terms of J-R curves for these materials at air and hydrogen pressure conditions.

Connecting to Compete 2007 : Trade Logistics in the Global Economy--The Logistics Performance Index and Its Indicators

Scipedia content — Mon, 25 Jan 2021 18:15:05 +0100

This is the first report presenting the Logistics Performance Index (LPI) and indicators. It aims to shed light on how different countries are doing in the area of trade logistics, and what they can do to improve their performance. It is based on a worldwide survey of the global freight forwarders and express carriers who are the most active in international trade. LPI and its underlying indicators constitute a unique dataset to measure country performance across several dimensions of logistics and to benchmark that logistics performance against 150 countries. It provides the empirical basis to understand and compare differences in trade logistics as well as to inform policy with respect to difficult bottlenecks and tradeoffs. As a tool for policymakers, professionals, development agencies, and other stakeholders, it will directly support the fast-growing agenda for reforms and investments in trade and transport facilitation. The report provides some insights on the cost of poor logistics to country competitiveness and the sources of those higher costs. Beyond cost and time taken to deliver goods, the predictability and reliability of supply chains is increasingly important in a world of just-in-time production sharing. Costs related to hedging against uncertainty are significant. Equally, cost and quality of logistics are determined not just by infrastructure and the performance of public agencies, but also by the availability of quality and competitive private services. Moreover, in many developing countries, problems of adverse geography are compounded by a weak modern services sector due to poor institutions or over-regulation. The report closes with some practical insights, advocating a comprehensive, integrated approach to ensure that actions in one area are not rendered ineffective by bottlenecks in another.

Operational Challenges in Gas-To-Liquid (GTL) Transportation Through Trans Alaska Pipeline System (TAPS)

Scipedia content — Mon, 25 Jan 2021 17:35:10 +0100

Oil production from Alaskan North Slope oil fields has steadily declined. In the near future, ANS crude oil production will decline to such a level (200,000 to 400,000 bbl/day) that maintaining economic operation of the Trans-Alaska Pipeline System (TAPS) will require pumping alternative products through the system. Heavy oil deposits in the West Sak and Ugnu formations are a potential resource, although transporting these products involves addressing important sedimentation issues. One possibility is the use of Gas-to-Liquid (GTL) technology. Estimated recoverable gas reserves of 38 trillion cubic feet (TCF) on the North Slope of Alaska can be converted to liquid with GTL technology and combined with the heavy oils for a product suitable for pipeline transport. Issues that could affect transport of this such products through TAPS include pumpability of GTL and crude oil blends, cold restart of the pipeline following a prolonged winter shutdown, and solids deposition inside the pipeline. This study examined several key fluid properties of GTL, crude oil and four selected blends under TAPS operating conditions. Key measurements included Reid Vapor Pressure, density and viscosity, PVT properties, and solids deposition. Results showed that gel strength is not a significant factor for the ratios of GTL-crude oil blend mixtures (1:1; 1:2; 1:3; 1:4) tested under TAPS cold re-start conditions at temperatures above - 20 F, although Bingham fluid flow characteristics exhibited by the blends at low temperatures indicate high pumping power requirements following prolonged shutdown. Solids deposition is a major concern for all studied blends. For the commingled flow profile studied, decreased throughput can result in increased and more rapid solid deposition along the pipe wall, resulting in more frequent pigging of the pipeline or, if left unchecked, pipeline corrosion.

Globalna mreža logističnih kurirskih služb za 21. stoletje

Scipedia content — Mon, 25 Jan 2021 17:09:45 +0100

The development of logistics has contributed a lot to all the branches of economy. A successful economic subject cannot exist without a well-developed logistic branch. The organization of logistics has become a strategic element of the policy making of enterprises. Modern logistics enables us to bring into line different interests in material flow management. Global organizers of logistic services are developing and specialising in some essential services, such as combining of cargo into assembly consignements and also their distribution. The biggest global tenderers of logictic services are considered (DHL, TNT, FEDEX, UPS, etc). Razvoj logistike je v veliki meri pripomogel k razcvetu vseh panog gospodarstva. Ni uspešnega gospodarskega subjekta, ki ne bi imel zelo razvito vejo logistike. V gospodarstvu postaja organiziranost logistike strateški element vodenja podjetij. Logistika torej sodi med tista področja, ki bodo pomembno vplivala na naše življenje, zato je razvoj logističnega sistema izjemnega pomena, tako za gospodarstvo kakor tudi za negospodarske dejavnosti. Torej nam sodobna logistika omogoča uskladitev različnih interesov v upravljanju materialnega toka. Razvijajo se globalni organizatorji logističnih storitev, ki se razvijejo in specializirajo na nekaj ključnih storitev, med katere spada združevanja tovora v zbirne pošiljke ter tudi sama distribucija teh pošiljk. Med največje globalne ponudnike logističnih storitev prištevamo podjetja kot so: DHL, TNT, FED EX, UPS ...

Remaining Sites Verification Package for the 100-B-22:1 Pipelines and Associated Soils, Waste Site Reclassification Form 2005-042

Scipedia content — Mon, 25 Jan 2021 14:56:38 +0100

The 100-B-22:1 pipelines and associated soils were part of the 100-B Area water treatment facilities. The 100-B-22:1 waste site is limited to those pipelines that interconnected the 185-B Filter House, the 126-B-2 Clearwells, the 185-B Deaeration Plant, and the 190-B Process Pumphouse. None of the 100-B-22:1 pipelines carried environmentally significant contamination. In accordance with the historical information and field observations of this evaluation, the results support a reclassification of this site to No Action required to meet future rural-residential uses and be protective of groundwater and the Columbia River.

Development of a Decision Support System for Selection of Trenchless Technologies to Minimize Impact of Utility Construction on Roadways

Scipedia content — Mon, 25 Jan 2021 14:43:50 +0100

The need to replace deteriorating underground utility infrastructure and to expand utility services increases the need for utility conduits to intersect roadways. Open-trench method is currently the most widely used method for installation of underground pipelines and conduits of all sizes. However, open-cut construction has several shortcomings, chief amongst which are: health and safety concerns of workers, surface disturbance, disruption to vehicular/pedestrian traffic and reduction of pavement life. Today, other cost-effective alternatives exist to traditional open-trench construction. These methods are categorized as "trenchless technologies" as they require minimum trenching (excavation). While the benefits of trenchless technology are quite apparent when compared to the conventional open-cut process, it is necessary to carefully evaluate the suitability and appropriateness of trenchless technologies on a project-by-project basis through due consideration of site conditions such as access, right-of-way, geotechnical conditions, etc. Unfortunately, this is not always done due to the lack of a proper evaluation tool that takes into account all the project-specific criteria in a systematic fashion. Consequently, in some instances, the improper use of trenchless technologies has resulted in failures such as heaving or subsidence of the pavement, damage to nearby utilities and facilities, and even fatalities. The primary objectives of this study included the following: a) Development of a Decision Support System for the selection and performance of trenchless technologies for the installation of conduits under roadways; b) Development of specifications for selected trenchless construction methods; and c) Development of a multimedia educational tool to train Indiana Department of Transportation (INDOT) engineers. All these objectives were accomplished. The deployment of the specifications and tools developed as part of this study will be undertaken by the INDOT.

An Autonomic MPLS DiffServ-TE Domain

Scipedia content — Mon, 25 Jan 2021 12:30:01 +0100

MPLS DiffServ-TE combines the advantages of DiffServ and MPLSTE by allowing a differentiation of services and a traffic engineering based on a fast packet switching technology. However, such MPLS DiffServ-TE network needs an efficient method for Quality of Service (QoS) guaranteeing. In addition, the management of such a network is not a simple function and could not be done manually. In fact, it would be much more economic and effective to let equipments handle a part of the tasks attributed currently to the human administrator. In this paper, a novel architecture based on a Multi-Agent System is proposed to automatically manage MPLS DiffServ-TE domains. To meet the QoS requirements, an LSP creation strategy, based on a traffic-driven approach and depending on the traffic load, is proposed. It determines when to set up a new LSP and when to forward a new traffic in an already existing one. This strategy reduces the number of LSPs and the number of signalling operations in the network. Simulation results are provided to illustrate the efficiency of our proposition.

Informing the specification of a large-scale socio-technical system with models of human activity

Scipedia content — Mon, 25 Jan 2021 12:22:30 +0100

In this paper, we present our experience of using rich and detailed models of human activity in an existing socio-technical system in the domain of air traffic control to inform a use case-based specification of an enhanced future system, called DMAN. This work was carried out as part of a real project for Eurocontrol, the European Organisation for the Safety of Air Navigation. We describe, in outline, the kinds of models we used, and present some examples of the ways in which these models influenced the specification of use cases and requirements for the future system. We end with a discussion of lessons learnt.

Flight Performance of Fixed and Rotary Wing Aircraft

Scipedia content — Mon, 25 Jan 2021 12:10:46 +0100

Calculation and optimisation of flight performance is required to design or select new aircraft, efficiently operate existing aircraft, and upgrade aircraft. It provides critical data for aircraft certification, accident investigation, fleet management, flight regulations and safety. This book presents an unrivalled range of advanced flight performance models for both transport and military aircraft, including the unconventional ends of the envelopes. Topics covered include the numerical solution of supersonic acceleration, transient roll, optimal climb of propeller aircraft, propeller performance, long-range flight with en-route stop, fuel planning, zero-gravity flight in the atmosphere, VSTOL operations, ski jump from aircraft carrier, optimal flight paths at subsonic and supersonic speed, range-payload analysis of fixed- and rotary wing aircraft, performance of tandem helicopters, lower-bound noise estimation, sonic boom, and more. This book will be a valuable text for undergraduate and post-graduate level students of aerospace engineering. It will also be an essential reference and resource for practicing aircraft engineers, aircraft operations managers and organizations handling air traffic control, flight and flying regulations, standards, safety, environment, and the complex financial aspects of flying aircraft. Â· Unique coverage of fixed and rotary wing aircraft in a unified manner, including optimisation, emissions control and regulation. Â· Ideal for students, aeronautical engineering capstone projects, and for widespread professional reference in the aerospace industry. Â· Comprehensive coverage of computer-based solution of aerospace engineering problems; the critical analysis of performance data; and case studies from real world engineering experience. Â· Supported by end of chapter exercises, an extensive Instructor's Manual and downloadable flight performance modelling code.

The Boundaries of Welfare Economics: Transport Appraisal in the UK

Scipedia content — Mon, 25 Jan 2021 11:58:13 +0100

This book revisits traditional evaluation methods, such as costâbenefit analysis, to try and find a balance between the ever-increasing demand for transport, the search for sustainable mobility and green transport solutions, and the limited financial resources that governments are able to invest in transport infrastructure projects.

Sustainable Transportation

Scipedia content — Mon, 25 Jan 2021 11:50:33 +0100

This paper discusses possible contributions of psychologists to sustainable transportation. It is argued that in order to reach sustainable transportation, among others, behaviour changes of individual car users are needed. As transport policies will be more effective if they target important antecedents of travel behaviour, first, factors influencing such behaviour are discussed. It is argued that car use is very attractive and sometimes even necessary for many different reasons. This implies that a combination of policies is called for, each targeting different factors that support car use and hinder the use of more sustainable modes of transport. Next, the paper elaborates on policy strategies that may be employed to achieve sustainable transportation by changing car use. Increasing the attractiveness of sustainable transport modes by means of pull measures seems not sufficient to reduce the level of car use. Besides, car use should be made less attractive by means of push measures to force drivers to reconsider their travel behaviour. The acceptability of such policies may be increased by clearly communicating the aim of these policies, and the expected positive consequences (e.g., less congestion, improved environmental quality). Moreover, possible negative effects for individual freedom may be compensated by implementing additional policies aimed at facilitating the use of sustainable transport modes.

Document type: Part of book or chapter of book