Scipedia: Documents published in 2009

PRINCIPLES FOR MODELLING TECHNOLOGICAL PROCESSES IN TRANSPORT TERMINAL

Scipedia content — Tue, 23 Mar 2021 07:05:34 +0100

technological process is evaluated as a random process and assessed in respective models. The methodology of formalizing technological processes in the terminal and criteria for optimal control and the quality of the technological process are suggested. In addition, models and algorithms for the optimal control of freight clearing technological process are proposed. First published online: 27 Oct 2010

Document type: Article

Towards a European ITS for freight transport and logistics: results of current EU funded research and prospects for the future

Scipedia content — Tue, 23 Mar 2021 04:37:12 +0100

Objective The purpose of this paper is to review the developments of the last 15 years in the field of Freight Transport research and innovation, primarily (but not exclusively) in Europe focusing on the “Intelligent Transport Systems” aspects.

Document type: Article

The REM Observing Software

Scipedia content — Mon, 22 Mar 2021 21:42:38 +0100

The Rapid Eye Mount (REM) is a 60 cm robotic telescope located at La Silla, Chile. Its Observing Software (REMOS) is constituted by a set of distributed intercommunicating processes organized around a central manager. Together they grant the system safety, automatically schedule and perform observations with two simultaneous cameras of user-defined targets, and drive fast reaction to satellite alerts. Subsequent data reduction is left to pipelines managed by each camera.

Document type: Article

An agent-based analysis of the German electricity market with transmission capacity constraints

Scipedia content — Tue, 16 Feb 2021 13:20:50 +0100

While some agent-based models have been developed for analyzing the German electricity market, there has been little research done on the emerging issue of intra-German congestion and its effects on the bidding behavior of generator agents. Yet, studies of other markets have shown that transmission grid constraints considerably affect strategic behavior in electricity markets. In this paper, the implications of transmission constraints on power markets are analyzed for the case of Germany. Market splitting is applied in the case of congestion in the grid. For this purpose, the agent-based modeling of electricity systems (AMES) market package developed by Sun and Tesfatsion is modified to fit the German context, including a detailed representation of the German high-voltage grid and its interconnections. Implications of transmission constraints on prices and social welfare are analyzed for scenarios that include strategic behavior of market participants and high wind power generation. It can be shown that strategic behavior and transmission constraints are inter-related and may pose severe problems in the future German electricity market.

Let the business cycle! A spatial multilevel analysis of cycling to work

Scipedia content — Tue, 16 Feb 2021 13:15:48 +0100

The daily commute is still the main source of traffic congestion. Despite transport research emphasis on commuters, the work end of home to work travel receives less attention. However, employers influence the commute behaviour of employees in different ways. The Belgian database Home-to-Work-Traffic (HTWT) contains information on accessibility, work regimes and mobility management initiatives of 7460 worksites of large employers in Belgium. In a spatial multilevel regression model both contextual and worksite factors are incorporated to investigate the share of cycling employees. While controlling for different economic, physical and other factors, the provision of bicycles by the employer seems to be successful, while the effect of bicycle facilities is less clear, partly due to the fact that bicycle facilities are more popular in less cycle-friendly areas. Het dagelijkse pendelverkeer is nog steeds de voornaamste bron van verkeerscongestie. Ondanks de nadruk die transportonderzoek legt op dit pendelverkeer, blijft de werkkant van het woon-werkverkeer onderbelicht. Nochtans beïnvloeden werkgevers het pendelgedrag van hun werknemers op verschillende manieren. De Belgische databank woon-werkverkeer bevat informatie over de bereikbaarheid, de arbeidstijden en mobility management maatregelen van 7460 werklocaties van grote werkgevers gevestigd in België. In een ruimtelijk multilevel regressiemodel zijn zowel omgevings- als werklocatiefactoren opgenomen om het aandeel fietsende werknemers te verklaren. Rekening houdend met economische, fysische en andere factoren, lijkt het actief aanbieden van fietsen door de werkgever een succesvolle maatregel, terwijl het effect van de klassieke fietsvoorzieningen minder duidelijk is, onder meer omdat deze vooral terug te vinden zijn in minder fietsvriendelijke gebieden.

The Mediterranean case

Scipedia content — Tue, 16 Feb 2021 13:14:29 +0100

The Short Sea Shipping (SSS) market is strongly diversified, due to the variety of cargoes, vessel types and capacity, and segmented due to the existence of many national and peripheral submarkets. It is observed that prices differ considerably among transport services of similar distance routes and/or similar demand characteristics. The aim of this study is to identify factors influencing SSS operators pricing policies for both the sea and the inland part of intermodal chains, in an integrated framework. The analysis is based on the comparison of parameters influencing the cost structure and the pricing policy. The analysis of data collected through telephone and face-to-face interviews reveals that fuel, port cost, and market drivers with fuel cost being the most important elements influencing the variation in both the cost function and the pricing policy. Cost variations are also influenced by the cost of hinterland transport and the size of shipments, while pricing policy varies according to destination and type of goods transported. These findings contribute in understanding the SSS market and its operation. However, due to the complexity of self-organised systems, validating the presented cost and pricing structures remains a challenge.

Electric bicycles in The Netherlands: Current developments and future possibilities

Scipedia content — Tue, 16 Feb 2021 13:02:41 +0100

Developments with electric bicycles in the Netherlands are progressing rapidly. The number of electric bicycles sold is rises every year. Cycling is a very popular mode of transport in The Netherlands. In 2008 more than one million bicycles were sold. At the moment one out of ten bicycles sold is already an electric one. Electric bicycles are popular among the elderly and people with physical constraints. The government also wants to stimulate commuters to use the e-bicycle instead of the car. There are a few reasons for this: Less congestion, more environmental and health benefits. Research performed by TNO showed that commuters who use an electric bicycle might drive 1.5 times further than with a traditional bicycle, allowing a large group of potential new users to use cycling as mode for their commuting transport. The number of trips by bicycle has to potential to grow by 3 to 5% and the number of bicycle kilometres to grow by 4 to 12% even. The number of car trips might decrease with 1.6% and the number of car kilometres with a lower value due to the replacement of mainly shorter car trips. Pilot projects are set up now to introduce e-bicycles to commuters. A majority of the participants of the first two pilots held are positive about the e-bicycles as an alternative for the car in commuting traffic. An extensive large two year pilot will start in Eindhoven to stimulate commuters to use the e-bicycle instead of the car. TNO will investigate the mobility effects of the use of the e-bicycle from this pilot.

Optimisation model for integration of cooling and heating systems in large industrial plants

Scipedia content — Tue, 16 Feb 2021 12:48:16 +0100

Large industrial plants have often hundreds of heating and cooling heat exchangers. A common situation is that cooling demands of the processes are satisfied without any deeper analysis of the overall impact of the cooling systems on the plant’s economy or the environment. If cooling water is available it is used as much as needed and then pumped back to the river, some degrees warmer. An optimisation model was developed for integration of cooling and heating systems to tackle the problem. An industrial cooling system is a complex energy system comprising different options of producing cooling, distribution pipelines for cold media and cooling storages. Integration of power generation and heating systems to the cooling systems was included in the model. An illustrative example is presented in the paper. 10 process streams with cooling demand and 10 streams with heating demand were chosen, situated at different locations at the plant site. The optimal matches between the streams were found together with the sizes of the heat exchangers and the demands of hot and cold utilities. The costs of pipelines and the pumping costs of the streams are included in the model. The model can be used in the design of greenfield and retrofit investments and in versatile what-if analyses of the plant design or operation.

Incentive-based control of ad hoc networks: A performance study

Scipedia content — Tue, 16 Feb 2021 12:41:00 +0100

htmlabstractAd hoc networks are self-configuring networks of mobile nodes, connected by wireless links. If a destination node is beyond the transmission range of an origin node, then the nodes must cooperate to provide a multi-hop route. Any node can act as a sender, receiver or transit node. It is clear that it is in a node‚The interest to be a sender or receiver, but it is less clear what the value is of forwarding traffic on behalf of other nodes. The nodes should therefore be given incentives to act as transit nodes, otherwise the network would fail to function. A way to do so is by introducing for each node a credit balance, where nodes use credits to pay for the costs of sending their own traffic, and earn credits by forwarding traffic from other nodes. However, nodes that are located near the edge of the network will attract little transit traffic and earn few credits. In contrast, nodes located near the centroid of the network will attract transit traffic and earn credits. We investigate various ways of providing nodes near the edge of the network with preferential treatment in order to improve their credit balance and their throughputs. We next focus on the situation where each node can move to improve its utility expressed in terms of either credit balance or throughput. Here radio interference plays an important role, as it defines an interesting trade-off: nodes may prefer to be close together in order to reduce the power needed to transmit data, but on the other hand proximity increases radio interference, and has therefore a negative effect on connectivity. Simulation experiments reveal that the positions of the nodes converge to non-trivial optimal positions on 2D and 3D surfaces.

Application-Based Congestion Control Policy for the Communication Channel in VANETs

Scipedia content — Tue, 16 Feb 2021 12:29:01 +0100

This letter proposes a novel proactive congestion control policy for vehicular ad-hoc networks, in which each vehicle's communication parameters are adapted based on their individual application requirements. Contrary to other approaches, where transmission resources tend to be assigned based on system-level performance metrics, the technique proposed in this paper aims to individually satisfy the target application performance of each vehicle, while globally minimising the channel load to prevent channel congestion.

Geocapacity: economic feasibility of CCS in networked systems

Scipedia content — Tue, 16 Feb 2021 12:27:56 +0100

Decision Support System (DSS) has been developed to evaluate the technical and economical feasibility of CO2 storage in the subsurface. The DSS performs a detailed, stochastic analysis of the technical and economical aspects of a CCS project, which consists of any number of CO2 sources and sinks plus the connecting pipeline network. The DSS uses the database of CO2 emission points and storage locations in Europe that has been compiled in the EU Geocapacity project. The system is a combination of an internet application, which visualises the database and allows the user to select sources and sinks and create a pipeline network, and an application to be run on a local computer, which performs a stochastic analysis of the costs of a CO2 capture, transport and storage system. The DSS provides not only an estimate of the total CCS cost, but also an analysis of the elements in the CCS chain (capture, compression, transport and storage), enabling a feasibility analysis on several levels. © 2009 Elsevier Ltd. All rights reserved.

Initial infrastructure development strategies for the transition to sustainable mobility

Scipedia content — Tue, 16 Feb 2021 12:16:51 +0100

Within the Dutch transition policy framework, the transition to hydrogen-based transport is seen as a promising option towards a sustainable transport system. This transition requires the build-up of a hydrogen infrastructure as a certain level of refuelling infrastructure is necessary before (even the most innovative or environmentally friendly) consumers will substitute their conventional car for a hydrogen vehicle (Dunn 2002). This is often referred to as the chicken-and-egg problem of infrastructure development. However, the build-up of infrastructure is costly and irreversible and it is therefore important for policymakers to gain insight in the minimally required levels of initial infrastructure that will still set off the transition. In this paper we therefore present a diffusion model for the analysis of the effects of different strategies for hydrogen infrastructure development on hydrogen vehicle fleet penetration. Within the simulation model, diffusion patterns for hydrogen vehicles were created through the interactions of consumers, refuelling stations and technological learning. We compare our results to the benchmark patterns derived from the hydrogen roadmap. The strategies for initial infrastructure development differ with respect to the placement (urban or nationwide) and the number of initial refuelling stations. Simulation results indicate that when taking social learning between consumers into account, diffusion is generally lower than in the benchmark patterns. Furthermore, simulation results indicate that a nationwide deployment strategy generally leads to faster diffusion of hydrogen vehicles than a strategy focused on urban areas. These demand side aspects of the transition to sustainable mobility are considered especially important in the Netherlands since besides the high cost associated with infrastructure investment the Netherlands do not have a domestic car industry so that policy measures will most likely focus on infrastructure and consumers. Increased insights in the relation between infrastructure development strategies and hydrogen vehicle diffusion are thus necessary to further manage the transition to sustainable mobility.

Historical analysis of blockages in wastewater pipelines in Oslo and diagnosis of causative pipeline characteristics

Scipedia content — Tue, 16 Feb 2021 12:14:43 +0100

The city of Oslo is evaluating strategies for the selection of appropriate materials for the pipelines and manholes of its wastewater network. The overarching motive is to minimise construction-related failures over the system lifetime and also ensure that it is able to avert flooding events. This paper analyses the blockage records of the last 16 years (1991–2006) in the wastewater pipeline network of Oslo. For the purpose of the analysis, the pipeline stock is categorised on the basis of pipe diameter, material of fabrication, slope and age. Proneness to blockages is studied and attempts are made to correlate the same to the size, material, slope and age. The analyses performed confirm that older and small diameter sewage pipelines made of concrete, laid almost horizontal to the ground surface are the high-priority candidates, and more importantly enables one to compare among the different categories and classes of pipelines.

An adaptive mesh refinement solver for large-scale simulation of biological flows

Scipedia content — Tue, 16 Feb 2021 12:11:12 +0100

The observation that hemodynamic forces play an important role in the pathophysiology of the cardiovascular system has led to the need for characterizing in vivo hemodynamics on a patient-specific basis. However, the introduction of computational hemodynamics in clinical research contexts is bound to the availability of integrated workflows for analyses on large populations. Since such workflows must rely on automated geometry-driven mesh generation methods, the availability of robust solvers featuring adaptive mesh refinement strategies is essential to ensure that the approach can be adopted on a large scale. In this paper, we present an open-source solver for the incompressible Navier–Stokes equations based on the libMesh finite elements library, featuring adaptive mesh refinement and parallelization. The solution scheme is a second-order velocity correction in rotational form. By presenting numerical tests on benchmark cases, we demonstrate that the coupling of this solution strategy with adaptive mesh refinement leads to a solver with good accuracy characteristics despite the relative simplicity of the scheme adopted. The availability of this solver within the Vascular Modeling Toolkit project leads to a widely available, seamless pipeline from images to simulation ready to be applied in clinical research environments. Copyright © 2009 John Wiley & Sons, Ltd.

The flow around a pipeline with a spoiler

Scipedia content — Tue, 16 Feb 2021 11:58:42 +0100

WOS: 000275650200011

Offshore pipelines are buried in the seabed to be protected from the damage Caused by hydrodynamic forces or by human activities. However, because of soil erosion and interaction of currents with the pipeline on the moveable seabed, the processes of local Scouring and, sometimes, self-burial of pipelines take place.To increase the rate and extent of scouring, the technique of attaching a spoiler to the pipeline hits been developed. In this Study, two-dimensional, steady, turbulent flow around a horizontal pipeline with a spoiler near a smooth wall investigated experimentally by using the particle image velocimetry technique. The effect of the spoiler was examined for the Reynolds numbers of Re(D) = 840, 1500, 4150, and 9500 based on the pipe diameter. The effect of the spoiler on the process Of Scouring is investigated through the parameters of the measured instantaneous and time-averaged patterns of the velocity vector field and the streamline topology. The results indicated that the attachment of the spoiler to the pipeline increases the length of the upstream and downstream separation regions and it is also observed that the spoiler does not significantly increase the rate of the flow that passes through the gap and the shear stress acting on the seabed.

Scientific and Technological Research Council of Turkey (TUBITAK) [107M641]

The author would like to acknowledge the support of Scientific and Technological Research Council of Turkey (TUBITAK contract no. 107M641).

Investigations of safety risks in converted electric vehicles

Scipedia content — Tue, 16 Feb 2021 11:48:19 +0100

Within the departments Environmentally Sustainable Transport and Automotive of TNO (Netherlands organisation for applied scientific research) several projects investigating safety aspects of electric vehicles have been conducted, including one in cooperation with KEMA and RDW of the Netherlands. Most attention in these projects was given to cars that were converted to electric, starting from conventional vehicles. This choice was made because most of the electric vehicles present in the Netherlands are of the converted kind. Only recently larger numbers of OEM Electric Vehicles have become available. In the study practical safety guidelines for the companies involved in the conversion business have been established. In general it can be concluded that converted vehicles carry greater safety risks due to the way they are made (retrofit) and different, less stringent approval tests for individually modified vehicles. This study presents a strategy to -focusing on safety- optimally convert to electric. Electric, functional as well as crash safety were covered and recommendations were given for each.

A dynamic programming heuristic for vehicle routing with time-dependent travel times and required breaks

Scipedia content — Tue, 16 Feb 2021 11:41:40 +0100

For the intensively studied vehicle routing problem (VRP), two real-life restrictions have received only minor attention in the VRP-literature: traffic congestion and driving hours regulations. Traffic congestion causes late arrivals at customers and long travel times resulting in large transport costs. To account for traffic congestion, time-dependent travel times should be considered when constructing vehicle routes. Next, driving hours regulations, which restrict the available driving and working times for truck drivers, must be respected. Since violations are severely fined, also driving hours regulations should be considered when constructing vehicle routes, even more in combination with congestion problems. The objective of this paper is to develop a solution method for the VRP with time windows (VRPTW), time-dependent travel times, and driving hours regulations. The major difficulty of this VRPTW extension is to optimize each vehicle’s departure times to minimize the duty time of each driver. Having compact duty times leads to cost savings. However, obtaining compact duty times is much harder when time-dependent travel times and driving hours regulations are considered. We propose a restricted dynamic programming (DP) heuristic for constructing the vehicle routes, and an efficient heuristic for optimizing the vehicle’s departure times for each (partial) vehicle route, such that the complete solution algorithm runs in polynomial time. Computational experiments demonstrate the trade-off between travel distance minimization and duty time minimization, and illustrate the cost savings of extending the depot opening hours such that traveling before the morning peak and after the evening peak becomes possible.

Optical Core Networks Research in the e-Photon-ONe+ project

Scipedia content — Tue, 16 Feb 2021 11:39:43 +0100

This paper reports a summary of the joint research activities on Optical Core Networks within the e-Photon-ONe+ project. It provides a reasonable overview of the topics considered of interest by the European research community and supports the idea of building joint research activities that can leverage on the expertise of different research groups. Thisworkwas supported by the e-Photon/ONe+ and BONE (“Building the Future Optical Network in Europe”) projects funded by the European Commission through the 6th and 7th ICT-Framework Programme

Children’s annoyance reactions to aircraft and road traffic noise

Scipedia content — Tue, 16 Feb 2021 11:34:25 +0100

10 pages.-- PACS: 43.50.Qp; 43.50.Lj; 43.66.Lj

Since annoyance reactions of children to environmental noise have rarely been investigated, no source specific exposure-response relations are available. The aim of this paper is to investigate children's reactions to aircraft and road traffic noise and to derive exposure-response relations. To this end, children's annoyance reactions to aircraft and road traffic noise in both the home and the school setting were investigated using the data gathered in a cross-sectional multicenter study, carried out among 2844 children (age 9–11 years) attending 89 primary schools around three European airports. An exposure-response relation was demonstrated between exposure to aircraft noise at school (LAeq,7–23 h) and severe annoyance in children: after adjustment for confounders, the percentage severely annoyed children was predicted to increase from about 5.1% at 50 dB to about 12.1% at 60 dB. The findings were consistent across the three samples. Aircraft noise at home (LAeq,7–23 h) demonstrated a similar relation with severe annoyance. Children attending schools with higher road traffic noise (LAeq,7–23 h) were more annoyed. Although children were less annoyed at levels above 55 dB, the shapes of the exposure-response relations found among children were comparable to those found in their parents.

Peer reviewed

Heart on the road

Scipedia content — Tue, 16 Feb 2021 11:32:50 +0100

Driving a vehicle is a task affected by an increasing number and a rising complexity of Driver Assistance Systems (DAS) resulting in a raised cognitive load of the driver, and in consequence to the distraction from the main activity of driving. A number of potential solutions have been proposed so far, however, although these techniques broaden the perception horizon (e. g. the introduction of the sense of touch as additional information modality or the utilization of multimodal instead of unimodal interfaces), they demand the attention of the driver too. In order to cope with the issues of workload and/or distraction, it would be essential to find a non-distracting and noninvasive solution for the emergence of information. In this work we have investigated the application of heart rate variability (HRV) analysis to electrocardiography (ECG) data for identifying driving situations of possible threat by monitoring and recording the autonomic arousal states of the driver. For verification we have collected ECG and global positioning system (GPS) data in more than 20 test journeys on two regularly driven routes during a period of two weeks. The first results have shown that an indicated difference of the arousal state of the driver for a dedicated point on a route, compared to its usual state, can be interpreted as a warning sign and used to notify the driver about this, perhaps safety critical, change. To provide evidence for this hypothesis it would be essential in the next step to conduct a large number of journeys on different times of the day, using different drivers and various roadways.

Achieving Accurate and Efficient Prediction of HVAC Diaphragm Noise at Realistic Reynolds and Mach Numbers

Scipedia content — Tue, 16 Feb 2021 11:19:26 +0100

Despite the aeroacoustic expertise reached nowadays in air and ground transportation, energy sector or domestic appliances, reaching a decibel accuracy of an acoustic prediction for industrial cases is still challenging. Strong investments are made nowadays by oil and gas companies to determine and reduce the sound produced by °ow inside industrial ducts, such as pipelines or gazoduct. Heating, Ventilating and Air Conditioning noise reduction in a car has become a strong condition of comfort for passengers and then a concern for car manufacturers.

Air versus terrestrial transport modalities: An energy and environmental comparison

Scipedia content — Tue, 16 Feb 2021 11:08:48 +0100

In the last 15 years, worldwide air transportation has grown at an average yearly rate of 4.5%. Forecasts confirm that this could be the average increase rate for the next 20 years, although recent oscillation of oil price translated into a slowing down of such a trend, with several air companies forced out of business. Within this framework, low cost airlines keep increasing their market share, in so making airplane to compete with terrestrial transport modalities, not only for medium and long distance, but also for short trips. This is because air transport is obviously faster than transport by trains and cars, and most often it also is a cheaper option in money terms.

Algorithm to create a CCS low-cost pipeline network

Scipedia content — Tue, 16 Feb 2021 11:05:11 +0100

Within the EU-funded GeoCapacity project an economic analysis computer tool is developed for the evaluation of carbon capture and storage (CCS) systems comprising of a set of multiple sources of CO2 and storage locations. As a part of that tool, an algorithm has been developed to create low-cost pipeline networks to connect sources of CO2 and storage reservoirs. The main features of the algorithm are: •Input parameters are the size and location of CO2 sources and storage reservoirs•The algorithm determines the trajectory, capacity and costs of the connecting pipes•If necessary junctions are created, i.e. connections are created between sources and pipelines and/or storage locations and pipelines•The algorithm has a step wise approach. The pipeline network is built-up by successively adding a pipe in each step, until all sources are connected to storage reservoirs•In each step all possible combinations are examined and the one with the lowest costs is added to the system•The pipe costs have a non linear relation with the flow rate•Cost ranges for pipeline network are presented reflecting uncertainties in data of supply of CO2 from sources as well in storage capacity of sinks. © 2009 Elsevier Ltd. All rights reserved.

Transitions and strategic niche management : towards a competence kit for practitioners

Scipedia content — Tue, 16 Feb 2021 10:58:56 +0100

Structural problems in modern societies, such as climate change and congestion problems, require 'transitions' towards a more susTWNnable fulfilment of social needs. Recent research shows that experimenting in niches is crucial for learning about social challenges and stimulating transitions. Through a series of 'transition experiments' in different niches, social innovations can be improved and eventually replace dominant practice. This article reviews the literature on transitions and strategic niche management and argues that it has a strong analytical core, but less effort has been made to develop a managerial perspective. The authors aim to contribute to such perspective by developing a 'competence kit': a learning module that provides practitioners (e.g., policy makers, companies, intermediary organisations and NGO's) that are involved in transition experiments with an analytical framework, guidelines and tools and recognisable examples. The results from the first workshop with practitioners to explore potential applications of the competence kit are promising. Copyright © 2010 Inderscience Enterprises Ltd.

The environmental implications of airlines' choice of aircraft size

Scipedia content — Tue, 16 Feb 2021 10:58:42 +0100

One of the main outcomes of open skies policies is the importance of service frequency in the competition between airlines. To keep load factors high while offering high frequency service, airlines tend to reduce the size of the aircraft used. On short-haul routes this phenomenon is even more apparent, especially on routes between hub airports, even though these routes and airports are often congested. This choice of service frequency and aircraft size must have important environmental consequences that this paper aims to evaluate and quantify. The analysis considers local air pollution, climate change and noise impacts and aims to evaluate whether the competitive environment that drives airlines to offer high frequency service carries an environmental penalty. The analysis showed that increasing aircraft size and adjusting the service frequency to offer similar seating capacity will increase local pollution but decrease climate change impact and noise pollution. When local pollution and climate change impacts are monetized and aggregated the analysis showed that environmental benefits will result from increasing aircraft size. But these benefits, in monetary terms, were found to be relatively small and sensitive to the assumptions made. © 2009 Elsevier Ltd. All rights reserved.

Capacity evaluation of multi-lane traffic roundabout

Scipedia content — Tue, 16 Feb 2021 10:57:07 +0100

The entry capacity at a traffic roundabout is typically evaluated for each entry approach, considering the circulating flow and geometric characteristics, e.g., the US highway capacity manual model and the UK Linear Regression model. These models are not appropriate for analyzing multi-lane roundabouts because they do not take into account the possible unequal traffic distribution between the circulating lanes. This paper introduces a lane-based methodology that evaluates the entry capacity for each individual lane while considering the traffic distribution on the circulating lanes. The arrival and circulating flows are formulated based on drivers' lane choice patterns. We then modify and extend the formulae from existing models for the analysis of capacity of multi-lane roundabout. Based on the analysis, we show that higher capacity can be achieved when the utilization on the circulating lanes is more balanced. This result can lead to improved design and management techniques to increase the capacity of multi-lane roundabout.

Evolution of Internet Address Space Deaggregation: Myths and Reality

Scipedia content — Tue, 16 Feb 2021 10:45:50 +0100

Internet routing table size growth and BGP update churn are two prominent Internet scaling issues. There is widespread belief in a high and fast growing number of ASs that deaggregate prefixes, e.g., due to multi-homing and for the purpose of traffic engineering. Moreover, researchers often blame specific classes of ASs for generating a disproportionate amount of BGP updates. Our primary objective is to challenge such widespread assumptions (“myths”) and not solely to confirm previous findings. Surprisingly, we find severe discrepancies between existing myths and reality. According to our results, there is no trend towards more aggressive prefix deaggregation or traffic engineering over time. With respect to update dynamics, we observe that deaggregated prefixes generally do not generate a disproportionate number of BGP updates, with respect to their share of the BGP routing table. On the other side, we observe much more widespread traffic engineering in the form of AS path prepending and scoped advertisements compared to previous studies. Overall, our work gives a far more positive picture compared to the alarming discourses typically heard: The impact of “bad guys” on routing table size growth and BGP churn has not changed for the worse in recent years. Rather, it increases at the same pace as the Internet itself.

Driving with a congestion assistant; mental workload and acceptance

Scipedia content — Tue, 16 Feb 2021 10:41:09 +0100

New driver support systems are developed and introduced to the market at increasing speed. In conditions of traffic congestion drivers may be supported by a "Congestion Assistant", a system that combines the features of a Congestion Warning System (acoustic warning and gas pedal counterforce) and a Stop & Go system (automatic gas and brake pedal during congestion). To gain understanding of the effects of driving with a Congestion Assistant on drivers, mental workload of drivers was registered under different conditions as well as acceptance of the system. Mental workload was measured by means of physiological registrations, i.e. heart rate, a secondary task and with the aid of subjective scaling techniques. Acceptance was measured with an acceptance scale. The study was carried out in an advanced driving simulator. Driving with the Congestion Assistant while in congestion potentially leads to decreased driver mental workload, whereas just before congestion starts, i.e. developing just noticeable, the system may add to the workload of the driver. Acceptance is generally high after experiencing the system, though not in all respects. (c) 2008 Elsevier Ltd. All rights reserved.

Policy discourse, people’s internal frames, and declared aircraft noise annoyance: An application of Q-methodology

Scipedia content — Tue, 16 Feb 2021 10:40:35 +0100

ft noise annoyance is studied extensively, but often without an explicit theoretical framework. In this article, a social approach for noise annoyance is proposed. The idea that aircraft noise is meaningful to people within a socially produced discourse is assumed and tested. More particularly, it is expected that the noise policy discourse influences people’s assessment of aircraft noise. To this end, Q-methodology is used, which, to the best of the authors’ knowledge, has not been used for aircraft noise annoyance so far. Through factor analysis five distinct frames are revealed: “Long live aviation!,” “aviation: an ecological threat,” “aviation and the environment: a solvable problem,” “aircraft noise: not a problem,” and “aviation: a local problem.” It is shown that the former three frames are clearly related to the policy discourse. Based on this observation it is argued that policy making is a possible mechanism through which the sound of aircraft is turned into annoyance. In addition, it is concluded that the experience of aircraft noise and, in particular, noise annoyance is part of coherent frames of mind, which consist of mutually reinforcing positions and include non-acoustical factors.

Asset management for urban wastewater pipeline networks

Scipedia content — Tue, 16 Feb 2021 10:32:49 +0100

Pipelines account for the lion's share of the lifetime costs of any typical urban wastewater collection. While the deterioration of pipeline is the obvious "frontline‟ reason to adopt Asset Management practices, a more overarching driver is the need to gravitate towards sustainable development and set short and long term objectives encompassing economic, social and environmental goals. Optimising the expenses and providing the required levels of service to customers are the twin targets of wastewater utilities. Oslo Vann og Avløpsetaten – the water/wastewater utility in the Norwegian capital, considered as case study in this paper, is sprucing up its data-bank, rightly realising that a very effective information management system is the spine of Asset Management.

Reti per la mobilità e sicurezza

Scipedia content — Tue, 16 Feb 2021 10:15:43 +0100

Una riflessione centrale nell’ambito del rapporto mobilità e sicurezza è quella relativa al ruolo che le reti per la mobilità rivestono, o possono rivestire, nel garantire la sicurezza del territorio rispetto a fattori di rischio, naturali o antropici. Già da alcuni anni, accrescere la sicurezza delle comunità insediate ai rischi costituisce uno degli obiettivi prioritari delle strategie volte ad orientare in chiave di sostenibilità lo sviluppo urbano e territoriale. Le reti per la mobilità rivestono, in tale contesto, un ruolo centrale: essenziali supporti alla vita quotidiana delle comunità - da cui dipende in molti casi la salute, il comfort e, più in generale, il benessere socioeconomico - esse rappresentano, da un lato ,elementi esposti e spesso ad elevata vulnerabilità rispetto ai diversi fenomeni calamitosi; dall’altro, attrezzature di importanza strategica per la gestione dell’emergenza, indispensabili per garantire l’accesso e l’esodo dalle aree colpite nella fase dell’immediato post evento. Il danneggiamento o la ridotta funzionalità di tali reti può incrementare, anche significativamente, le perdite di vite umane conseguenti ad un evento calamitoso, oltreché indurre danni economici rilevanti anche su orizzonti temporali di medio-lungo periodo. Inoltre, ampliando il campo di attenzione dalle reti come supporti fisici ai flussi di persone e beni che esse supportano, gli impatti di un evento calamitoso su singoli elementi di tali reti possono indurre eventi secondari anche di grande rilevanza quali, ad esempio, rilasci tossici o esplosioni, dovute a danni sulla rete che coinvolgono mezzi per il trasporto di sostanze pericolose o serbatoi localizzati lungo la rete o all’interno dei nodi della rete di trasporto. Tuttavia, nonostante la riconosciuta centralità delle reti per la mobilità, nel garantire la sicurezza del territorio, le analisi di rischio sono state a lungo incentrate prevalentemente sui manufatti edilizi, focalizzando al più l’attenzione sui danni fisici che un dato evento poteva indurre su singoli elementi della rete stessa. È ancora abbastanza recente la consapevolezza che le reti per la mobilità costituiscono un sistema, caratterizzato da rilevanti connessioni e interdipendenze: sia in quanto ciascun elemento della rete è connesso a tutti gli altri, sia in quanto numerose sono le interdipendenze non solo tra le diverse tipologie di infrastrutture a rete ma anche tra infrastrutture a rete e sistemi urbani. Strade e ferrovie, ad esempio, potrebbero non subire danni diretti in conseguenza di un evento calamitoso ma danni o guasti, anche rilevanti, conseguenti al danneggiamento di altre infrastrutture a rete: da quelle elettriche a quelle fognarie. Analogamente, all’interno di un tessuto urbano, le reti viarie e ferroviarie potrebbero subire perdite di funzionalità a causa di ostruzioni provocate dal crollo, parziale o totale, di manufatti edilizi. In ragione di tali considerazioni, il contributo proposto evidenzia i molteplici aspetti della vulnerabilità delle reti per la mobilità e la loro rilevanza nel concorrere a determinare la vulnerabilità di un sistema urbano o territoriale ad eventi calamitosi. Si propone, quindi, un approfondimento del concetto di vulnerabilità delle reti per la mobilità, evidenziandone gli aspetti finora maggiormente esplorati in ambito scientifico. Infine, viene proposta una riflessione su un comune della Regione Campania caratterizzato da rilevanti problemi idrogeologici e dalla presenza di un impianto industriale a rischio di incidente rilevante. Tale riflessione – frutto di un più ampio studio sviluppato dagli autori nell’ambito del PRIN 2006-2008 dal titolo “Sistemi di allarme precoce: aspetti tecnici, urbanistici e di comunicazione” – evidenzia come le tradizionali analisi di rischio, generalmente incentrate su singoli eventi calamitosi, possono talvolta condurre ad investimenti di potenziamento o adeguamento delle reti per la mobilità che, nati per accrescere la sicurezza del territorio, si traducono, di contro, in un complessivo incremento delle condizioni di vulnerabilità.

Design and evaluation of a four-dimensional interface for air traffic control

Scipedia content — Tue, 16 Feb 2021 10:13:36 +0100

The increasing complexity of the Air Traffic System is pushing toward the development of innovative and more automated tools conceived to manage it. In this scenario an important role is played by HCI (Human Computer Interfaces) used by air traffic controllers and operators to visualize and interact with air traffic data. Currently, information about 3D scenery is displayed with a two-dimensional representation. This paper presents the design, development and evaluation of an innovative interface for ATC (Air Traffic Control) based on a 4D (3D space + time) visualization display. The proposed interface allows the operator to perceive all the information, including meteorological conditions, that is useful for TWR/APP (ToWeR/APProach) control in a unique 4D synthetic reconstruction of the airport area. Particular attention is dedicated to the fourth variable, time, which is a fundamental parameter in ATC. A simple and fast trajectory prediction algorithm has been implemented in order to provide the operator with an effective “user assistance” tool in conflict detection activities. The interface has been evaluated by performing test simulations and surveys were used to collect results and useful advice for its future development.

A bio-inspired approach for streaming applications in wireless sensor networks based on the Lotka-Volterra competition model

Scipedia content — Tue, 16 Feb 2021 10:13:19 +0100

In the new era of Ambient Intelligence, wireless sensor networks (WSNs) are seen to bridge the gap between physical world and the Internet, making a large amount of information accessible anywhere, anytime. Over the last few years, WSNs are being developed towards a large number of multimedia streaming applications, e.g. video surveillance, traffic control systems, health monitoring, and industrial process control. WSNs consist of small sensor devices (nodes) that are capable of working unattended, without centralized control, under dynamically changing conditions. However, these devices face important limitations in terms of energy, memory and computational power. The uncontrolled use of limited resources in conjunction with the unpredictable nature of WSNs in terms of traffic load injection, wireless link capacity fluctuations and topology modifications may lead to congestion. Congestion can cause increased packet loss and delay. This paper proposes a bio-inspired congestion control approach for WSNs streaming applications that necessitate controlled performance with graceful degradation. In the proposed approach, congestion in WSNs is prevented (or at least minimized) by regulating the rate of each traffic flow based on the Lotka-Volterra competition model. Performance evaluations reveal that the proposed approach achieves adaptability to changing traffic loads, scalability and fairness among flows, while providing graceful performance degradation as the offered load increases. © 2010 Elsevier B.V. All rights reserved. 33 17 2039 2047 "p"Cited By :20

Analysis of barriers in the transition toward sustainable mobility in the Netherlands

Scipedia content — Tue, 16 Feb 2021 10:11:36 +0100

The transition toward a sustainable transportation system in the Netherlands takes place in the context of the Dutch “Transition management policy framework”. We study four tech¬nological routes that the “Platform Sustainable Mobility” has selected for this goal: (1) hybridization of vehicles, (2) liquid biofuels, (3) natural gas as a transportation fuel and (4) hydrogen as a transportation fuel. These technological routes all envision large-scale changes in vehicle propulsion technology and fuel infrastructure. Furthermore, they compete for the scarce resources available to invest in new (fuel) infrastructures, which implicates that these ‘transition paths’ are also interdependent at the level of the mobility system. The main outcome of the analysis is the identification of barriers that are currently blocking the transition toward sustainable mobility. Barriers are classified as being related to (1) technology and vehicle development, (2) the availability of (fuel) infrastructures, and (3) elements of the institutional infrastructure. The transition management framework currently misses guidelines for coping with (competing) technologies that each requires large infrastructural investments. We further argue that avoiding undesired lock-ins and creating a beneficial institutional context for sustainable mobility cannot be pursued at the transition path level. Therefore, we recommend that a more systemic approach should be taken to the tran¬si¬tion to sustainable mobility, in which the inter¬dependencies between the transition paths are critically assessed and in which the possibilities to legitimize sustainable mobility as a whole should be used.

Constrained minimum lightpath affinity routing in multi-layer optical transport networks

Scipedia content — Tue, 16 Feb 2021 10:05:49 +0100

In this paper, a new traffic engineering-capable routing and wavelength assignment scheme is proposed to efficiently handle LSP and lightpath setup requests with different QoS requirements on modern multi-layer (fully optical core and time-division multiplexed edge) transport networks. The objectives of the proposed algorithm are to minimize the rejection probability by maximizing the network load balancing and efficiently handling the grooming of several LSPs on the same lightpath while respecting the constraints of the optical node architecture and considering both traffic engineering and QoS requirements. The proposed solution consists of a two-stage RWA algorithm: each time a new request arrives, an on-line dynamic grooming scheme finds a set of feasible lightpaths which fulfill the QoS and traffic engineering requirements; then, the best feasible lightpath is selected, aiming to keep the network unbalancing and blocking probability as low as possible in the medium and long term, according to a novel global path affinity minimization concept. Extensive simulation experiments have been performed in which our on-line dynamic RWA algorithm demonstrated significant performances. Thanks to its optimal network resource usage and to its reasonable computational space and time complexity, the algorithm can be very attractive for the next-generation optical wavelength-switched networks. Â© 2008-2010 - IOS Press and the authors. All rights reserved.

What location policy can bring to sustainable commuting: an empirical study in Brussels and Flanders, Belgium

Scipedia content — Tue, 16 Feb 2021 10:03:38 +0100

Policies on spatial planning and on mobility often take it for granted that a location policy that favours situating human activities near junctions of public transport results in a frequent use of sustainable modes of transport. But in the daily practice of mobility planning we come across more and more critical statements. As the Flemish Ministry of Mobility and Public Works considers investing resources in an improved location policy, they asked for evidence on the possible results of location policy on sustainable commuting in a Flemish context, including Brussels. Quite exceptionally, we utilise the individual census data from nearly all 1, 2 million Flemish commuters. These detailed data allow a precise description of the commuter characteristics of different locations and allow the construction of a robust geographical pattern. We focus the analysis on four kinds of locations: railway stations, public transport junctions, urban areas and areas with a high economic density. An exploratory data analysis suggests that people working and/or living in these areas travel less distance, especially by car, and make more use of public transport and slow modes. A cluster analysis shows that there are spatial differences, resulting in clear geographical patterns, which suggest that policies should be spatially differentiated. As a result, we support the idea of using location policy to produce more sustainable commuting. From a methodological point of view, we conclude that census data are irreplaceable to meet the requirements of spatial representativity needed to construct detailed geographical patterns of commuting.

AN ARTIFICIAL INTELLIGENT APPROACH TO TRAFFIC ACCIDENT ESTIMATION: MODEL DEVELOPMENT AND APPLICATION

Scipedia content — Tue, 16 Feb 2021 09:58:50 +0100

KGUNGOR, ALI PAYIDAR/0000-0003-0669-5715; DOGAN, Erdem/0000-0001-7802-641X WOS: 000267724800007 This study proposes an Artificial Neural Network (ANN) model and a Genetic Algorithm (GA) model to estimate the number of accidents (A), fatalities (F) and injuries (I) in Ankara, Turkey, utilizing the data obtained between 1986 and 2005. For model development, the number of vehicles (N), fatalities, injuries, accidents and population (P) were selected as model parameters. In the ANN model, the sigmoid and linear functions were used as activation functions with the feed forward-back propagation algorithm. In the GA approach, two forms of genetic algorithm models including a linear and an exponential form of mathematical expressions were developed. The results of the GA model showed that the exponential model form was suitable to estimate the number of accidents and fatalities while the linear form was the most appropriate for predicting the number of injuries. The best fit model with the lowest mean absolute errors (MAE) between the observed and estimated values is selected for future estimations. The comparison of the model results indicated that the performance of the ANN model was better than that of the GA model. To investigate the performance of the ANN model for future estimations, a fifteen year period from 2006 to 2020 with two possible scenarios was employed. In the first scenario, the annual average growth rates of population and the number of vehicles are assumed to be 2.0 % and 7.5%, respectively. In the second scenario, the average number of vehicles per capita is assumed to reach 0.60, which represents approximately two and a half-fold increase in fifteen years. The results obtained from both scenarios reveal the suitability of the current methods for road safety applications.

Parking Policies and Quality of Urban Environment

Scipedia content — Tue, 16 Feb 2021 09:53:27 +0100

Dai numerosi Documenti dell’Unione Europea emerge con chiarezza che se la mobilità rappresenta indiscutibilmente un elemento propulsore dello sviluppo urbano, le politiche per la mobilità, e in particolare per la mobilità urbana, necessitano di un deciso ri-orientamento al fine di mitigarne i rilevanti costi ambientali. Ad oggi, il dibattito scientifico e le numerose iniziative promosse in sede europea per la definizione di forme di trasporto urbano sostenibile sembrano convergere su un punto: per accrescere la sostenibilità della mobilità urbana è indispensabile ridurre il numero complessivo di auto e incoraggiare l’utilizzo del trasporto pubblico. In tale contesto, qual è il ruolo della sosta, che rappresenta indiscutibilmente una delle componenti chiave di una mobilità urbana prevalentemente affidata all’auto privata? Le scelte in materia di sosta costituiscono, di fatto, un elemento chiave per ridurre la dipendenza dall’auto privata all’interno delle città, oltreché rappresentare un rilevante punto di congiunzione tra politiche di trasporto e politiche di uso del suolo. “Regolando la fornitura di parcheggi disponibili, l’uso dell’auto privata può essere scoraggiato, rafforzando allo stesso tempo l’uso di modalità di trasporto alternative”. In altre parole, la drastica limitazione dell’offerta di sosta costituisce uno dei principali strumenti per liberare le città dal traffico veicolare: “sapendo che a destinazione il parcheggio non è disponibile, si sceglieranno modi alternativi per raggiungerle”. La sosta viene dunque oggi riconosciuta da un lato quale problema cruciale, soprattutto nelle aree centrali delle grandi città in grado, in molti casi, di ridurne significativamente l’attrattività, dall’altro quale fattore strategico per un complessivo ripensamento della mobilità in ambito urbano, quale il metodo più diffusamente e agevolmente accettato per limitare l’uso dell’auto. A fronte di tali considerazioni, questo contributo esplora il complesso rapporto tra politiche della sosta, politiche della mobilità e politiche mirate all’innalzamento della qualità urbana evidenziando, da un lato, la crescente centralità che le politiche per la mobilità hanno assunto ai fini del miglioramento della qualità urbana, dall’altro, la perdurante incoerenza tra politiche della sosta e politiche della mobilità. Infine, sulla base di alcune esperienze innovative in ambito internazionale e dei principali orientamenti che provengono dalla letteratura scientifica, il contributo delinea alcuni indirizzi per ri-orientare le politiche della sosta in ambito urbano, ponendo l’accento su tre esigenze chiave: una più stretta coerenza tra politiche della sosta e politiche per la mobilità; una più efficace gestione della domanda di sosta -specie in alcune aree urbane e per alcune tipologie di sosta- in alternativa a politiche di incremento dell’offerta; una maggiore attenzione all’integrazione tra politiche della mobilità e scelte di assetto del territorio, che condizionano in molti casi in misura rilevante la domanda di sosta.

Optimal Scheduling of Replacement and Rehabilitation in Wastewater Pipeline Networks

Scipedia content — Tue, 16 Feb 2021 09:53:05 +0100

To fulfil the objective of providing acceptable level of service to customers, the water managers have to plan how to operate, maintain and rehabilitate the system under budget constraints. The model presented in this paper uses risk cost as an appropriate framework to define the optimal replacement time prediction based on the balance between investment for replacing and expenditures for maintaining the asset. An economic analysis compares the costs associated with maintaining an existing pipe in service, being completely depreciated or not, to the cost of replacing or rehabilitating the pipe. On this basis, the right time in the future to rehabilitate the pipeline can be determined. The costs associated with an existing pipe include direct operational and maintenance costs and indirect costs, such as those associated with risk of failure. The optimal replacement time is identified as the year in which the cost to maintain the existing stock of pipes exceed the investment to replace it. A dynamic programming tool was developed to search the vast combinatorial solution space of the problem. The model was applied, with the aim of supporting management decisions, to the wastewater network of Oslo in Norway, managed by Oslo Vann og Avløpsetaten (Oslo VAV), using available real-world information to estimate expected costs of maintenance and rehabilitation. The results show that a constant value for lifetime should not be applied to all the pipelines in the stock, as currently done by the utility for long-term investment; rather it is wiser to define different values for different cohorts of pipelines, to reduce the uncertainties associated with generalisations for simplification. The model has been applied to wastewater pipes, but is in principle valid for any aging infrastructure.

Water and Wastewater Pipe Nondestructive Evaluation and Health Monitoring: A Review

Scipedia content — Mon, 15 Feb 2021 12:32:33 +0100

Civil infrastructures such as bridges, buildings, and pipelines ensure society's economic and industrial prosperity. Specifically, pipe networks assure the transportation of primary commodities such as water, oil, and natural gas. The quantitative and early detection of defects in pipes is critical in order to avoid severe consequences. As a result of high-profile accidents and economic downturn, research and development in the area of pipeline inspection has focused mainly on gas and oil pipelines. Due to the low cost of water, the development of nondestructive inspection (NDI) and structural health monitoring (SHM) technologies for fresh water mains and sewers has received the least attention. Moreover, the technical challenges associated with the practical deployment of monitoring system demand synergistic interaction across several disciplines, which may limit the transition from laboratory to real structures. This paper presents an overview of the most used NDI/SHM technologies for freshwater pipes and sewers. The challenges that said infrastructures pose with respect to oil and natural gas pipeline networks will be discussed. Finally, the methodologies that can be translated into SHM approaches are highlighted.

Document type: Article

Control y simulación de tráfico urbano en Colombia: Estado del arte

Scipedia content — Mon, 15 Feb 2021 10:21:59 +0100

Las condiciones actuales de la movilidad en Colombia generan interrogantes acerca de qué tan apropiadas son las estrategias de control de tráfico aplicadas en las redes urbanas del país. Con esto en mente, se plantea una revisión de las estrategias de control y plataformas de simulación de sistemas de tráfico más utilizadas en Colombia y en otras partes del mundo; con el propósito de caracterizar el nivel de desarrollo del país en el estudio e implementación de estrategias de control de tráfico urbano y, posteriormente, formular propuestas orientadas hacia la mejora de la movilidad urbana en el país./ The current mobility conditions in Colombia give place to questions about the suitability of the traffic control strategies applied on the Colombian urban networks. Therefore, a review of the control strategies and simulation platforms used in Colombia and around the world is shown. This is done to characterize the level of development of the country, in terms of research and implementation of such control strategies and, furthermore, to formulate proposals oriented towards the improvement of the Colombian urban mobility.

Document type: Article

Um modelo de otimização da operação de terminais petrolíferos usando a teoria das restrições como pré-processamento

Scipedia content — Mon, 15 Feb 2021 10:09:59 +0100

Na programação de operações de movimentação de petróleo em complexos portuários contendo navios, píeres, tanques e oleodutos, um modelo de otimização das operações é frequentemente utilizado. Entretanto, devido à complexidade do problema, o tempo computacional é um fator limitante. Neste artigo, estuda-se a aplicação de um modelo de programação linear inteira mista (PLIM) existente na literatura e propõe-se uma etapa de pré-processamento, baseada na teoria das restrições (TOC), com o objetivo de reduzir o tempo computacional. A partir da identificação do gargalo do problema, determinadas restrições são retiradas do modelo numa etapa de pré-processamento. Para verificar a escolha das restrições críticas no pré-processamento, uma análise baseada na noção de preço dual do LP é apresentada. Embora a otimalidade da solução não seja garantida, os resultados mostram uma pequena deterioração da solução em relação à ótima. Porém, com o tempo computacional significativamente reduzido."br"In the scheduling of oil transfer operations for harbor plants containing ships, piers, tanks and pipelines, an optimization model is frequently used. However, due to the complexity involved, computational time is a real concern. In this paper, a mixed integer linear programming model (MILP) found in the literature is studied and a preprocessing procedure is proposed. This procedure is based on the Theory of Constraints (TOC), which is used to reduce the model compilation time. Since the problem bottleneck is identified, the corresponding constraints are not considered in the preprocessing step. An analysis based on LP dual price is also carried out to verify actions taken in the preprocessing step. Although optimality cannot be assured, the results obtained show a minor deviation from the optimal solution but with a significant computational time gain.

Document type: Article

Rotterdam, city of electric transport

Scipedia content — Fri, 12 Feb 2021 16:21:39 +0100

Traffic and transport is an important cause of air-quality and noise pollution in Rotterdam. Solving these problems needs various measurements in our region

cycling, walking and improving public transport are part in that. But large scale use of clean, silent and energy efficient vehicle technologies is also a crucial part for a future sustainable transport system.For the long term, Rotterdam regards the electric vehicle technology as the most promising solution for a real sustainable transport system. In the mean time, Rotterdam already started impulse-projects to create a market basis for large scale introduction of electric and hybrid-electric vehicles on the principle that seeing and trying is believing.The energy company Eneco has originated from the Rotterdam municipal energy company GEB and is a very logical partner for the city of Rotterdam (still being a main shareholder in Eneco) when it comes to implementing projects where sustainable electricity is the most sound option.

Document type: Article

Allotment booking in intermodal transport

Scipedia content — Fri, 12 Feb 2021 16:02:36 +0100

The article presents a valuable concept seeking to solve the problem of demand uncertainty in intermodal transport. Regular traffic is quite important for moving containers, trailers and swap bodies. To keep regularity with uncertain demand means to have backlogs or empty space. Both of them are inefficient from an economical point of view. In practice, a day‐by‐day demand forecast is meaningful only for the next two or three days. This poses serious allotment management problems to freight forwarders and shippers since long‐term contract allotments need to be planned many months ahead. The article presents a stochastic dynamic programming model for a short‐term allotment planning a model that would be very valuable for implementing intermodal solutions. The presented model evaluates optimal cost policy based on the economic trade‐off between the cost of backlogged shipment and the cost of acquiring additional allotment. First published online: 27 Oct 2010

Document type: Article

Navigation Aids Performance Evaluation for Precision Approaches

Scipedia content — Fri, 12 Feb 2021 14:36:53 +0100

The paper deals with the evaluation of the expected performance of aircraft approaches and landings operated with different navigation systems, both traditional and satellite-based. Flight dynamics characteristics and control authority of the approaching aircraft are considered in order to obtain an overall manoeuvre evaluation. The technique from the presented analysis applies to different operative conditions, taking into account aircraft requirements, navigation systems features, and environmental constraints. The aim is to offer a tool to be used in the very preliminary design phase for system performance analysis in different scenarios, such as airport ground systems adoption and air traffic control requirements compliance; later, the same tool can be tuned to complement and direct the required real flight trials to validate an already fielded solution. A numerical code referring to the presented analytical model has been implemented and some applications concerning the system's performance evaluation and planning are proposed to illustrate the algorithm capabilities. The tool and the proposed analysis technique indeed are successful in providing a quantitative assessment of the differences among several possible approaches.

Document type: Article

Developing the composed probability model to predict household trip production (a case study of Isfahan city)

Scipedia content — Fri, 12 Feb 2021 13:35:43 +0100

Household trip production is not a constant parameter and vary based on socio‐economic characteristics. Even households produce several numbers of trips in each category (households with constant socio‐economic characteristics). The purpose of the present study is to model a variation of household trip production rate in statistical societies. To achieve the purpose, a concept of Bayesian Inference has been used. The city of Isfahan was selected as a case study. First, the likelihood distribution function was determined for average household trip production. Then, likelihood distribution was determined for the numbers of household trips separating odd and even trips. In order to increase the precision of the function, the concept of Bayesian inference was utilized. To insert household socio‐economic variables in the function, the disaggregate model was calibrated for average household trip production. Statistical indices and χ2 test show that the likelihood distribution function of average household trip production follows the gamma distribution and the numbers of household trip production follows the poisson distribution. The final composed probability distribution was determined on the basis of Bayesian inference. The related function was created with a compilation of the mean parameter distribution function (gamma distribution) and the numbers of household trip production (poisson distribution). Finally, the disaggregate model was inserted to the final composed probability function instead of the mean parameter. The obtained results show that the use of Bayesian inference method would open up the possibility of modeling the variation of household trip production rate in statistical societies. Also it would be possible to insert socio‐economic characteristics in the model to predict the likelihood of real produced trips for each category of household. First published online: 27 Oct 2010

Document type: Article

MODELLING MODAL SHIFT DUE TO THE ENHANCED LEVEL OF BUS SERVICE

Scipedia content — Fri, 12 Feb 2021 13:33:22 +0100

This study is concerned with the estimation of the probable shift of auto‐rickshaw (three wheeled motorized para‐transit vehicle) users to the bus due to an increase in its level of service after providing exclusive bus lanes on Indian city roads carrying heterogeneous traffic. The quantum of an increase in the level of bus service due to the introduction of an exclusive bus lane was determined using a recently developed simulation model of heterogeneous traffic flow. The data on other factors (variables) that might cause modal shift from the auto‐rickshaw to the bus was collected conducting a home‐interview survey based on the stated preference approach. A binary logit model of mode‐choice was then calibrated using the collected data and the model was also validated using a holdout sample. A mode‐choice probability curve to depict the possible shift of auto‐rickshaw users to the bus is developed taking difference in the travel times of two‐modes as the basis to serve as a user friendly tool to analyze the possible modal shift for a wide range of the values of the involved variables. First published online: 27 Oct 2010

Document type: Article

Ethyleenvisie GreenRail : ethyleen bij treintransport van potplanten

Scipedia content — Thu, 11 Feb 2021 17:56:13 +0100

Sierteeltgewassen zijn bederfelijke producten, gevoelig voor temperatuur, vocht en lange(re) donkerperiodes. Niet adequate conditionering zal mogelijk tot meer uitval leiden en zou de introductie van deze nieuwe, duurzame transportoptie in de weg kunnen staan. Wageningen UR Food & Biobased Research heeft in dit kader onderzoek gedaan naar de 20 belangrijkste bloeiende en groene planten. Daarnaast zijn meerdere transportzendingen begeleidt en testen in de praktijk uitgevoerd. Dit heeft geresulteerd in een transportprotocol met aanbevelingen t.a.v. kwaliteitsborging in treintransport. Daarnaast is een literatuurstudie gedaan naar mogelijke problemen door ethyleen in deze specifieke keten van sierteeltgewassen

Traffic Congestion and Infant Health: Evidence from E-ZPass

Scipedia content — Thu, 11 Feb 2021 14:21:05 +0100

We exploit the introduction of electronic toll collection, (E-ZPass), which greatly reduced both traffic congestion and vehicle emissions near highway toll plazas. We show that the introduction of E-ZPass reduced prematurity and low birth weight among mothers within 2 kilometers (km) of a toll plaza by 10.8 percent and 11.8 percent, respectively, relative to mothers 2–10 km from a toll plaza. There were no immediate changes in the characteristics of mothers or in housing prices near toll plazas that could explain these changes. The results are robust to many changes in specification and suggest that traffic congestion contributes significantly to poor health among infants. (JEL I12, J13, Q51, Q53, R41)

Network Measures in Civil Air Transport: A Case Study of Lufthansa

Scipedia content — Mon, 08 Feb 2021 12:34:15 +0100

Network analysis has already a long history in operations research and quantitative social science research. In the past, much attention has been paid to shortest-route algorithms (for example, the travelling salesman problem), where the spatial configuration of networks was put in the centre of empirical investigation. Integer programming, linear and nonlinear programming turned out to offer a proper analytical toolbox. In recent years, we have seen several new trends, in particular, the rise of hub-and-spoke systems in liberalized networks, the emergence of dynamic adjustments to new competitive conditions and the increase in complexity in international networks. Furthermore, it appears that in the past decades many social, spatial and economic systems show an organized pattern characterized by network features, such as transportation, telecommunication, information or energy systems. As a consequence, much attention has recently been paid to the study of network properties emerging in many social, spatial and economic fields, as witnessed by the vast amount of literature published in the past years. Air transport is a prominent example of modern network constellations and will be addressed in this paper from a connectivity perspective. Air transport shows indeed clear network features, which impact on the way single airline carriers operate. The abundant scientific literature on airline networks has addressed this topic in terms of theoretical modelling and empirical measurements on different typologies of airline network configurations. This strand of recent research aimed to measure the network structure in relation to the effects of: (a) the market deregulation in United States in 1978 and in the European Union in the 1990s, (b) new trends in recent airline business strategies denoted as ‘low cost’ principles. Low cost carriers developed rather fast after the deregulation policy, by acquiring a competitive network advantage on traditional airlines, which consequently seemed to reorganise rapidly their airline network to respond to the new market dynamics. In this context, interesting research has emerged that mainly addressed the issue of describing and classifying networks by means of geographical concentration indices of traffic or flight frequency. These measures, such as the Gini concentration index or the Theil index, provide a proper measure of frequency or traffic concentration of the main airports in a simple, well-organized network. However, if a real-world network structure is complex, including multi-hub or mixed point-to-point and hub-spokes connections, the concentration indices may record high values for all types of structure, but fail to clearly discriminate between different network shapes. There is a need for a more appropriate measurement of connectivity structures in complex networks. Starting from the above considerations and research challenges, the present paper aims to investigate the scientific potential and applicability of a series of network connectivity/concentration indices, in order to properly typify and map out complex airline network configurations. Specifically, these various network indicators will be adopted and tested to describe the main properties – in terms of the network connectivity and configuration – of Lufthansa’s airline system.

Utilizing near-infrared and colour information in an automotive wide-dynamic-range night vision system for driver assistance

Scipedia content — Mon, 08 Feb 2021 12:31:24 +0100

Vision-based driver assistance systems utilizing both colour and nearinfrared (NIR) can significantly reduce the risk of traffic accidents by improving night visibility of the roadway and obstacles. The night vision system described here combines within a single imager wide dynamic range (WDR) technology with sensitivity extended into the NIR, and colour capability. The multiple-slope CMOS pixel covers a dynamic range of more than 120 dB. Adaptive control algorithms ensure detection reliability by maintaining the incremental signal-tonoise ratio (iSNR). Colour sensing is based on a modified colour filter array (CFA) with a 4th channel to capture monochrome information from the imager’s entire sensitivity range including the NIR component of the headlight spectrum that is invisible to the driver. Virtual NIR filter algorithms extract relevant colour information that is then fused to the luminance information, resulting in up to 70% higher sensitivity than conventional colour cameras.

ADOSE – Bio-Inspired In-Vehicle Sensor Technology for Active Safety

Scipedia content — Mon, 08 Feb 2021 12:28:50 +0100

Reliable Advanced Driver Assistance Systems (ADAS) are intended to assist the driver under various traffic, weather and other environment conditions. The growing traffic requires sensors and systems which handle difficult urban and non-urban scenarios. For such systems new cost-efficient sensor technologies are developed and evaluated in the EU-FP7 project ADOSE (reliable Application-specific Detection of road users with vehicle On-board Sensors, providing the vehicle with a virtual safety belt by addressing complementary safety functions.

Traffic Light Control by Multiagent Reinforcement Learning Systems

Scipedia content — Mon, 08 Feb 2021 12:14:04 +0100

Traffic light control is one of the main means of controlling road traffic. Improving traffic control is important because it can lead to higher traffic throughput and reduced traffic congestion. This chapter describes multiagent reinforcement learning techniques for automatic optimization of traffic light controllers. Such techniques are attractive because they can automatically discover efficient control strategies for complex tasks, such as traffic control, for which it is hard or impossible to compute optimal solutions directly and hard to develop hand-coded solutions. First, the general multi-agent reinforcement learning framework is described, which is used to control traffic lights in this work. In this framework, multiple local controllers (agents) are each responsible for the optimization of traffic lights around a single traffic junction, making use of locally perceived traffic state information (sensed cars on the road), a learned probabilistic model of car behavior, and a learned value function which indicates how traffic light decisions affect longterm utility, in terms of the average waiting time of cars. Next, three extensions are described which improve upon the basic framework in various ways: agents (traffic junction controllers) taking into account congestion information from neighboring agents; handling partial observability of traffic states; and coordinating the behavior of multiple agents by coordination graphs and the max-plus algorithm. © 2010 Springer-Verlag Berlin Heidelberg.

Using Hidden Markov Chains for Modeling P2P-TV Traffic

Scipedia content — Mon, 08 Feb 2021 10:25:58 +0100

The increasing success of P2P-TV applications, that may overwhelm the network with their large volume of traffic in the near future, calls for the need of new traffic models that can effectively represent the traffic generated by these applications. In this paper, we study the traffic generated by PPLive and SopCast, that are among the most popular P2P-TV applications of today, and propose Hidden-Markov chains for modeling the traffic they generate. Our results show that the models are quite accurate and can be effectively used in many networking tasks such as network performance analysis, network planning and dimensioning, traffic engineering.

Recognition of Situation Classes at Road Intersections

Scipedia content — Mon, 08 Feb 2021 10:22:41 +0100

The recognition and prediction of situations is an indispensable skill of future driver assistance systems. This study focuses on the recognition of situations involving two vehicles at intersections. For each vehicle, a set of possible future motion trajectories is estimated and rated based on a motion database for a time interval of 2–4 seconds ahead. Realistic situations are generated by a pairwise combination of these individual motion trajectories and classified according to nine categories with a polynomial classifier. In the proposed framework, situations are penalised for which the time to collision significantly exceeds the typical human reaction time. The correspondingly favoured situations are combined by a probabilistic framework, resulting in a more reliable situation recognition and collision detection than obtained based on independent motion hypotheses. The proposed method is evaluated on a real-world differential GPS data set acquired during a test drive of 10 km, including three road intersections. Our method is typically able to recognise the situation correctly about 1–2 seconds before the distance to the intersection centre becomes minimal.

Approximation algorithms for free-label maximization

Scipedia content — Mon, 08 Feb 2021 10:17:57 +0100

Inspired by air-traffic control and other applications where moving objects have to be labeled, we consider the following (static) point-labeling problem: given a set P of n points in the plane and labels that are unit squares, place a label with each point in P in such a way that the number of free labels (labels not intersecting any other label) is maximized. We develop efficient constant-factor approximation algorithms for this problem, as well as PTASs, for various label-placement models.

Auditory messages for speed advice in advanced driver assistance systems

Scipedia content — Mon, 08 Feb 2021 10:15:22 +0100

Simple tones in in-car systems are mostly used for status indication or warning and alerting purposes. We argue that simple tones can also be used for the purpose of advising drivers through an Advanced Driver Assistance System (ADAS). Our ADAS application is called Cooperative Speed Assistance (CSA), where drivers receive advice to slow down or speed up to coordinate their speed with the speed of other vehicles in the traffic. Two concepts of auditory messages are presented: Looping messages are played as long as the advice applies, while Toggle messages mark the beginning and the end of an advice. For each concept, two prototypes of simple-tone signals were designed based on existing guidelines about sound characteristics affecting urgency and evaluation by users. The temporal characteristics of the signals indicated how much or how fast drivers should adapt their speed. The concepts were evaluated by having users drive in a driving simulator. Objective measurements indicated that there was no difference in effectiveness between the two concepts. Subjective evaluation indicated that users preferred the Toggle concept.

Energy management in hybrid electric vehicles : benefit of prediction

Scipedia content — Mon, 08 Feb 2021 10:10:33 +0100

Hybrid vehicles require a supervisory algorithm, often referred to as energy management strategy, which governs the drivetrain components. In general the energy management strategy objective is to minimize the fuel consumption subject to constraints on the components, vehicle performance and driver comfort. Typically, we have to deal with two difficulties in the design of an energy management strategy. Firstly, the nonlinear behavior of the components results in a nonconvex cost function, complicating the use of optimization methods. Different approaches to deal with the nonconvexity are discussed. Secondly, the future power and velocity trajectories are unknown. Prediction of the future trajectories, based upon either past or predicted vehicle velocity and road grade trajectories, could help in obtaining a solution close to optimal. The benefit of prediction, compared to a heuristic and an optimal control strategy that uses only actual vehicle data, is shown with an example of a hybrid truck at a highway trajectory in a hilly environment. Results indicate that prediction has benefits only when the slopes have sufficient grade and length, such that the battery state-of-charge boundaries are reached. © 2010 IFAC.

Modeling and Experimenting with Vehicular Traffic Congestion for Distributed Advanced Traveler Information Systems

Scipedia content — Mon, 08 Feb 2021 10:08:37 +0100

dvanced Traveler Information Systems, which have for long been regarded as one of the most promising future applications of wireless vehicular networks for use in the ﬁeld of Intelligent Transportation Systems (ITS), are eﬀectively becoming part of today’s reality. Many drivers already access the information provided by such systems, for example checking for the state of the streets along a given route or reading traﬃc jam alerts on the displays of smart-phones or Personal Navigation Devices (PNDs). Based on such information, drivers, or their PNDs, select the best paths to reach their destinations. Clearly, in order to be eﬀective, such systems are required to reliably estimate and forecast vehicular congestion states. Moreover, they should also be capable of eﬃciently utilizing the wireless channel resources, as the amount of information that may be exchanged by such systems in dense urban areas grows with the number of services supported by the onboard devices and the amount of vehicles that install them. To answer these challenges, we here discuss how a distributed ATIS can: a) implement an eﬀective vehicular congestion detection and forecasting model, and, b) eﬃciently disseminate traﬃc information. The advantage of distributing an ATIS is that each vehicle can compute and redistribute accurate vehicular congestion information very rapidly, with little overhead and without resorting to a central entity. In order to validate our approach, we present the outcomes of a real world experimentation, as well as of multiple simulations.

Integration and concentration: the evolution af air transport in the EU

Scipedia content — Mon, 08 Feb 2021 10:08:26 +0100

The last years have witnessed a deep modification of air transport stakeholder’s behaviours. Airlines competition has been exacerbated by the downturns in the economic conditions while airport competition has been emerging as a result of the less governmental intervention in financing airport investments. The first aspect has resulted in a mix-model adopted by EU airlines in the intra EU market, which implies that network airlines have adopted few of the strategies that have guaranteed the establishment of the low fares carriers while low cost carriers have adopted simple hubbing models and have been continuously increasing the number of major airport served. The volatility of the air transport liberalized and deregulated market has been analysed in the scientific literature and these aspects can be perceived as further evidences of the increased volatility. In order to limit the negative effects of volatility in the EU air transport market, air transport players have been sought manners to enhance stability. Airlines mergers or acquisitions, buyout of airport operator’s shares by airlines, airport-airline partnership for ad-hoc infrastructure development or buyout of airport’s shares by other airport operators are examples of this will for a greater stability of the system. This paper involves all these aspects, This paper analyses all these aspects highlighting the pursuing of greater stability by the fragile EU air transport system.

Recognition and Prediction of Situations in Urban Traffic Scenarios

Scipedia content — Mon, 08 Feb 2021 10:08:01 +0100

The recognition and prediction of intersection situations and an accompanying threat assessment are an indispensable skill of future driver assistance systems. This study focuses on the recognition of situations involving two vehicles at intersections. For each vehicle, a set of possible future motion trajectories is estimated and rated based on a motion database for a time interval of 2-4 s ahead. Possible situations involving two vehicles are generated by a pairwise combination of these individual motion trajectories. An interaction model based on the mutual visibility of the vehicles and the assumption that a driver will attempt to avoid a collision is used to rate possible situations. The correspondingly favoured situations are classified with a probabilistic framework. The proposed method is evaluated on a real-world differential GPS data set acquired during a test drive of about 10 km, including three road intersections. Our method is typically able to recognise the situation correctly about 1.5-3 s before the last vehicle has passed its minimum distance to the centre of the intersection.

An efficient model-based method for coordinated control of urban traffic networks

Scipedia content — Mon, 08 Feb 2021 10:04:29 +0100

Traffic control is an effective and also efficient approach to reduce traffic jams. To alleviate the traffic congestion in an urban traffic network, a traffic control strategy that can coordinate the whole traffic network from a global point of view, is required. In this paper, an advanced control strategy, i.e. Model Predictive Control (MPC), is applied to control and coordinate urban traffic networks. However, the on-line computational complexity becomes a big challenge when the scale of the traffic network gets larger. To overcome this problem, the MPC control strategy is reformulated and solved efficiently on-line by a Mixed-Integer Linear Programming (MILP) solver. An MPC controller based on MILP is established and studied for the urban traffic network in different traffic scenarios. The simulation results show that the MILP-based MPC controller is a promising approach to reduce the on-line computational complexity of MPC controllers for urban traffic networks.

Context sensitive design and safety review of bike lanes

Scipedia content — Mon, 08 Feb 2021 09:57:57 +0100

In these days of increasing congestion on our roads, bicycles provide a valuable contribution to mobility in Europe. Their relatively small size and low cost enable them to blend efficiently into in the traffic flow while needing less space compared to other vehicles. However, cyclists form one of the most vulnerable groups of road users. So the design of safe infrastructures for all travelers categories, included the cyclists, becomes a primary requirement. To obtain these results, Road Safety Audits and Road Safety Reviews are very useful tool. In this paper the authors, starting from results collected on a bike lane placed in Rimini, a city of Emilia-Romagna characterized by high bicycle traffic flows especially in summer when many people head for this place for their holidays, provide useful results for designers, construction and maintenance contractors, in order to obtain safe bike lane.

3-D Trajectory Optimization for UAS Insertion in Civil Non-Segregated Airspace

Scipedia content — Mon, 08 Feb 2021 09:54:39 +0100

The use of UAS (Uninhabited Aerial System) in civil missions addresses quite a number of questions related to safety, security and economics, but the most critical challenge the civil UAS will face is the insertion into civil airspace. Avoiding collisions between aircrafts, expediting and maintaining an orderly flow of air traffic are very important goals for Air Traffic Management (ATM). The methodology we propose matches aeronautical science and operation research with ATM constraints and it is based on a two phases procedure: strategic and tactical. The strategic phase is based on Mixed Integer Linear Programming (MILP) and the Travelling Salesman Problem (TSP) method; it is performed off-line and gives as output a basic 3D route in order to allow the UAV to fly over N target points selected by the operator, avoiding fixed obstacles and minimizing an assigned cost function (fuel consumption, time and environmental impact). Once computed the route, the tactical phase starts, which is entirely performed on-line during flight. Civil air traffic constraints (minimum separation) are taken into account using TAR (Traffic Avoidance Resolution) module that combines a simple geometric computation with a TSP time extension model. The results coming from simulation are analyzed using Computer Graphic tools in order to easily and rapidly evaluate the performances of the proposed model. Separation between the UAV and physical obstacles, no fly-zones or other aircrafts populating the scenario, can be evaluated. Moreover, results coming from optimization such as trajectory and the associated fuel consumption, time or environmental impact of the mission are displayed.

Robust Control Schemes for Induction Motor Drives for Electric Vehicle Applications

Scipedia content — Mon, 08 Feb 2021 09:51:03 +0100

Three control schemes for the operation of induction motors in the field-weakening region are compared and assessed in terms of performance and complexity. These three control schemes fully utilize the maximum available voltage and current at any speed, and thus provide the maximum possible torque in the entire field weakening region. For the comparison, the three control schemes were implemented on the same experimental platform, i.e. the same Digital Signal Processor (DSP) board, power inverter and motor drive. In this way, it is possible to judge not only the performance of each solution, but also its requirements in terms of computational time, tuning complexity, parameter knowledge and stability of operation.

Long-term vehicle motion prediction

Scipedia content — Mon, 08 Feb 2021 09:47:31 +0100

Future driver assistance systems will have to cope with complex traffic situations, especially in the road crossing scenario. To detect potentially hazardous situations as early as possible, it is therefore desirable to know the position and motion of the ego-vehicle and vehicles around it for several seconds in advance. For this purpose, we propose in this study a long-term prediction approach based on a combined trajectory classification and particle filter framework. As a measure for the similarity between trajectories, we introduce the quaternion-based rotationally invariant longest common subsequence (QRLCS) metric. The trajectories are classified by a radial basis function (RBF) classifier with an architecture that is able to process trajectories of arbitrary non-uniform length. The particle filter framework simultaneously tracks and assesses a large number of motion hypotheses (102 ), where the class-specific probabilities estimated by the RBF classifier are used as a-priori probabilities for the hypotheses of the particle filter. The hypotheses are clustered with a mean-shift technique and are assigned a likelihood value. Motion prediction is performed based on the cluster centre with the highest likelihood. While traditional motion prediction based on curve radius and acceleration is inaccurate especially during turning manoeuvres, we show that our approach achieves a reasonable motion prediction even for long prediction intervals of 3 s for these complex motion patterns.

Use of traffic engineering techniques to increase resilience of SCADA networks

Scipedia content — Mon, 08 Feb 2021 09:41:23 +0100

In this paper we present the approach we have taken in the INSPIRE (INcreasing Security and Protection through Infrastructure REsilience) project to increase the protection of Critical Infrastructures (CIs). The core idea of the INSPIRE project is to protect Critical Infrastructures by making the underlying communication network more secure and resilient. In order to do so, we devised a routing mechanism that allows the communication infrastructure interconnecting SCADA (Supervisory Control And Data Acquisition) systems, the key building blocks of CIs, to be resilient to both node failures and attacks. The approach is to split the packets of a SCADA traffic flow on two node-disjoint paths by exploiting the capabilities of the Multi-Protocol Label Switching communication paradigm. The security of the SCADA traffic is improved since the proposed approach allows for a fast re-route of the flows traversing a node under attack, thus preserving the confidentiality of the transmitted information.

Admission Control and Drop strategies in a UPnP-QoS controlled home network

Scipedia content — Mon, 08 Feb 2021 09:41:07 +0100

The spread of novel multimedia services such as audio and video streaming, HDTV and online gaming have become a ordinary in the home networks. Therefore, the possibility to manage the Quality of Service (QoS) within an home environment becomes a crucial factor for the satisfaction of the user. In this paper we propose an enhanced Admission Control and Drop strategies for a UPnP-QoS controlled home network to guarantee QoS for multiple concurrent services. The UPnP-QoS architecture works well in the case of moderate traffic loads, but may fail whenever the network becomes overloaded. The paper demonstrates how the combined use of the proposed admission control and drop solutions with the UPnP-QoS framework avoids network congestion and guarantees QoS to all the admitted traffic streams. A proof of concept Java implementation has been developed to demonstrate the expected results in a real home environment.

Parallel Subdivision Surface Rendering and Animation on the Cell BE Processor

Scipedia content — Mon, 08 Feb 2021 09:40:54 +0100

—Subdivision Surfaces provide a compact way to describe a smooth surface using a mesh model. They are widely used in 3D animation and nearly all modern modeling programs support them. In this work we describe a complete parallel pipeline for real-time interactive editing, processing and rendering of smooth surface primitives on the Cell BE. Our approach makes it possible to edit and render these high-order graphics primitives passing them directly to a parallel pipeline which tessellates them just before rendering. We describe a combination of algorithmic, architectural and back-end optimizations that enable us to render smooth subdivision surfaces in real time and to dynamically deform 3D models represented by subdivision surfaces.

Economic Importance of Air Transport and Airport Activities in Belgium

Scipedia content — Sun, 07 Feb 2021 13:37:53 +0100

This study is a publication issued by the Microeconomic Analysis service of the National Bank of Belgium, in partnership with the Department of Transport and Regional Economics of the University of Antwerp (UA). It is the outcome of a first research project on the Belgian airport and air transport sector. The former relates to the economic activities within the airports of Antwerp, Brussels, Charleroi, Kortrijk, Liège and Ostend, while the latter concentrates on the air transport business as a whole. In the past few years, the logistics business has come to play a significant part in income creation in our country, whose economy is to a large extent driven by services1. Air transport and airports in particular are driving forces in this context, not only in terms of business generated within the air transport cluster, but also in terms of airports' attractiveness. On world scale an overall growth of cargo and passengers could be observed in the last ten years. However, the air transport sector has undergone a major crisis during the 2001-2003 period, when passenger traffic numbers first fell sharply and then stagnated. Only after 2003 this activity has picked up again and this until the third quarter of 2008. Cargo traffic on its part recovered already in 2002. In Belgium, a similar evolution can be observed. It should be stressed however that between 1997 and 2007 cargo volumes grew much faster than passenger traffic did. The rankings of European airports underline the importance of cargo traffic for Belgium: In 2006 Brussels, Liège and Ostend-Bruges respectively occupy ranks 6, 8, and 20 in the European cargo airport top 20, while for passenger airports, Brussels can only be found at the end of the top 20. In this study, a sectoral approach has been followed by focusing, for every airport, on two major economic activity components: the air transport cluster on the one hand and other airport-related sectors on the other hand. In that respect, annual accounts data from the Central Balance Sheet Office were used for the calculation of direct effects, the social balance sheet analysis and the study of financial ratios. Due to an inevitable time lag in the data provision, the analysis was limited to 2006. Like in other sectoral studies published by the Bank, indirect effects have also been estimated on the basis of data from the National Accounts Institute. In 2006, the total activities under review –direct and indirect, inside and outside airports- accounted for roughly 6.2 billion euro, i.e. 2 p.c. of Belgium's GDP and domestic employment. Considering the direct effects only, these percentages both amounted to 0.8 p.c. The three major airports, i.e. Brussels, Charleroi and Liège, alone account for 95.2 p.c. of the direct value added generated by the six airports under review. They represent 0.5 p.c. of Belgian GDP and, taking account of the indirect effects, 1.1 p.c. of the national income. Furthermore, it has to be pointed out that most Belgian airports are specialised. While the airports of Liège and Ostend focus on air cargo, Charleroi Airport deals mostly with low-cost passenger transport. Moreover, the smaller regional airports like Antwerp and Kortrijk focus on business travel. The analysis was completed in December 2008

Girth Weld Failure in a Large Diameter Gas Transmission Pipeline

Scipedia content — Wed, 03 Feb 2021 22:00:55 +0100

There have been several recent weld failures either during the initial post construction hydrostatic tests, or immediately following construction. Girth welds typically do not fail as a result of internal hoop loads without the contribution of loads due to out side forces. External loading should be considered during design, welding procedure development, construction, and pipeline operations. This paper presents one example where a girth weld failed as a result of preexisting 1940’s weld imperfections and recent, 1980’s, external loading. This analysis of the girth weld failure in the 30-inch pipeline included an initial failure analysis, a fracture mechanics analysis, and a finite element analysis that integrated the pipe-soil interaction, as well as localized stresses associated with weld imperfections. A critical part of this study was to evaluate how changes in soil conditions associated with a drought followed by soil saturation associated with rainfall, contributed to lack of local support and increased overburden loads associated with the saturated soil. The failure analysis of the ruptured girth weld and surrounding pipe concluded that the failure of the girth weld was caused by increased bending loads imposed on the pipeline after recent construction activities, and that the fracture initiated at a lack-of-penetration/fusion imperfection that was 20 1/4-inches long and 0.110 inches deep. A coupled investigation using finite element and fracture mechanics analyses verified numerically that with reduced-strength soil, stresses were generated in the girth weld of sufficient magnitude to cause a fracture. Temperature, terrain, and fatigue were considered, but were not deemed to significant enough to affect the stresses or other conditions that resulted in the failure. The overriding observation of this study is that no single factor contributed to the failure that occurred. Rather, the girth weld failure was the result of weld imperfections that generated elevated stresses due to excessive loads imparted to the pipe due to settlement associated with non-compact backfill associated with excavation work. Had the pipe not displaced vertically due to localized soil conditions, it is unlikely that the pipeline would have failed. The recent excavation activities were adequate for normal soil conditions; however, dry soil at the time of construction resulted in lack of compaction and excessive moisture just prior to the failure that generated in differential settlement and heavy overburden, combined with lack of penetration imperfection in the girth weld in question, resulted in generating excessive bending stresses that contributed to the eventual failure of the pipeline.Copyright © 2010 by ASME

Using Industry Standards for Designing Composite Repair Systems for Corroded Process Piping

Scipedia content — Wed, 03 Feb 2021 21:54:05 +0100

significant amount of work has transpired over the past several years in generating consensus-based standards that include ASME PCC-2 and ISO 24817 for developing composite repair systems. The intent in developing these standards has been to provide industry with guidelines for designing composite repair systems to ensure that damaged piping and pipelines are safely and properly reinforced. With the numerous composite repair systems currently available to operators, the importance of evaluating the capabilities of each system cannot be overstated. The fundamental design variables available to manufacturers are stiffness, strength, and thickness of the composite. A properly-designed repair system ensures that strains in the reinforced steel and reinforcing composite material do not reach unacceptable levels. This paper provides a basic overview of the design philosophy embedded into the current design codes, as well as presenting results associated with several specific studies that were conducted to evaluate composite repair performance.Copyright © 2010 by ASME

TraffCon: an intelligent traffic control system for wireless vehicular networks

Scipedia content — Wed, 03 Feb 2021 21:48:25 +0100

Traffic congestion is a very serious problem which is becoming ever worse as the growth in the number of cars on the road significantly outpaces the provision of road capacity. This paper presents TraffCon, a novel traffic management system (TMS) for wireless vehicular networks that combats this problem by seeking to optimize the usage of the existing road capacity. It also outlines an architecture which includes a novel server-side decision making module, that enables the dissemination of instructions to vehicles; if followed these result in optimal road usage.

Impact of plug-in electric vehicles on the supply grid

Scipedia content — Wed, 03 Feb 2021 21:44:23 +0100

This paper presents a case study describing the impact of charging process of plug in hybrid vehicles (PHEV) and all electrical vehicles (EV) on the supply grid. The paper shows the distortion produced in the grid by the simultaneous charge of a large fleet of vehicles and the corrective actions taken to guarantee the Electromagnetic Compatibility with other loads in the same grid. The goal of the investigation was to establish a design guide for parking facilities.

Peer Reviewed

Tensor Field guidance for time-based waypoint arrival of UAVs by 4D trajectory generation

Scipedia content — Wed, 03 Feb 2021 21:41:28 +0100

This paper looks at incorporating time information into a waypoint trajectory-generation technique known as Vector Field Guidance to give a 4D trajectory generator henceforth known as Tensor Field Guidance. The time-based information is local in that it is relative from waypoint to waypoint. We envisage that a higher-level controller or an Air Traffic Management system automates the waypoint generation, while our approach optimizes the travel time between waypoints. We present results from simulations, showing an increase in accuracy of “Distance to go” estimates over traditional “as-the-crowflies” yielding less error in time-based arrivals.

Design Analysis of Corridors-in-the-Sky

Scipedia content — Wed, 03 Feb 2021 21:26:35 +0100

Corridors-in-the-sky is a new airspace structure designed to accommodate high density trac by grouping flights with similar trajectories. Less air trac controller workload is expected than with classic airspace structures. Thus, corridors-in-the-sky may increase national airspace capacity and reduce flight delays. To evaluate/design corridors-in-thesky, besides identifying locations, their utilization, altitudes, and impacts on non-corridor trac need to be analyzed. Although not providing complete analysis, this paper chooses a single corridor and presents analyses of its spatial and temporal utilization, impact on the remaining trac, and the potential benefit caused by o-loading the trac from underlying sectors. Methods developed to assist the analysis are described. Analysis results visualize the utilizations of the corridor, suggest the number of lanes, and show the possibility of deploying corridors dynamically. It is shown that combined lane options would be a better choice to lower the impact on non-corridor users compared with other options. Finally, analysis shows significant reduction of peak aircraft count in underlying sectors with only one corridor enabled.

User Equilibrium in a Bottleneck under Multipeak Distribution of Preferred Arrival Time

Scipedia content — Wed, 03 Feb 2021 21:19:38 +0100

20 pages; International audience; This paper studies the pattern of departure times at a single bottleneck, under general heterogeneous preferred arrival times. It delivers three main outputs. Firstly, the existence of equilibrium is proven without the classical "S-shape" assumption on the distribution of preferred arrival time i.e. that demand, represented by the flow rate of preferred arrival times, may only exceed bottleneck capacity on one peak interval. Secondly, a generic algorithm is given to solve the departure time choice equilibrium problem. Lastly, the graphical approach that pervades the algorithm provides insight in the structure of the queued periods, especially so by characterizing the critical instants at which the entry flow switches from a loading rate (over capacity) to an unloading one (under capacity) and vice versa. Numerical illustration is given.

Tamper Evident Microprocessors

Scipedia content — Wed, 03 Feb 2021 21:19:01 +0100

Most security mechanisms proposed to date unquestioningly place trust in microprocessor hardware. This trust, however, is misplaced and dangerous because microprocessors are vulnerable to insider attacks that can catastrophically compromise security, integrity and privacy of computer systems. In this paper, we describe several methods to strengthen the fundamental assumption about trust in microprocessors. By employing practical, lightweight attack detectors within a microprocessor, we show that it is possible to protect against malicious logic embedded in microprocessor hardware. We propose and evaluate two area-efficient hardware methods - TrustNet and DataWatch - that detect attacks on microprocessor hardware by knowledgeable, malicious insiders. Our mechanisms leverage the fact that multiple components within a microprocessor (e.g., fetch, decode pipeline stage etc.) must necessarily coordinate and communicate to execute even simple instructions, and that any attack on a microprocessor must cause erroneous communications between micro architectural subcomponents used to build a processor. A key aspect of our solution is that TrustNet and DataWatch are themselves highly resilient to corruption. We demonstrate that under realistic assumptions, our solutions can protect pipelines and on-chip cache hierarchies at negligible area cost and with no performance impact. Combining TrustNet and DataWatch with prior work on fault detection has the potential to provide complete coverage against a large class of microprocessor attacks.

Describing air traffic flows using stochastic programming

Scipedia content — Wed, 03 Feb 2021 21:18:24 +0100

International audience; The objectives of Air Traffic Management (ATM) system is to ensure safe and efficient operation of an individual flight as well as to maximize the overall capacity and minimize the adverse environmental impacts of the air transportation system. To achieve these objectives, airspace capacity, which drives capacity and traffic flow management policies, should be more properly estimated according to the detailed traffic configuration. There have been some efforts to describe the complexity of a traffic situation based on the idea of modeling airspace onto a dynamical system. This paper extends the previous research efforts by accounting for uncertainties on aircraft's positions and velocities. The proposed method is illustrated with examples.

Computation of Multi-Constrained Paths in Multi-Domain MPLS-TE Networks

Scipedia content — Wed, 03 Feb 2021 21:16:15 +0100

International audience; The present paper proposes a novel method for computing inter-domain paths subject to multiple independent additive constraints in MPLS-TE networks. An efficient solution to this problem is a key element for providing services with guaranteed performance across domain boundaries. However, the inherent hardness of the multi-constrained path computation as well as inter-domain scalability and security constraints complicate the computation problem. We propose a novel algorithm named kID-MCP that tackles the computational complexity of the problem by reducing the number of paths included in the computation process. kID-MCP is compatible with existing techniques and fulfills the security requirements. We undergo a complexity analysis that shows that kID-MCP scales well. Moreover, a simulation study reveals that kID-MCP finds a solution in most situations. These results indicate that the computation of inter-domain multi-constrained paths is tractable in practice, which opens interesting perspectives for QoS routing and traffic engineering among multiple operators.

Towards an ecological four-dimensional self-separation assistance display

Scipedia content — Wed, 03 Feb 2021 21:03:50 +0100

In today’s airspace, rapidly increasing amounts of traffic are pushing the limits of capacity and safety. In an effort to optimize available airspace, various initiatives have been undertaken to investigate future air traffic management concepts. In these efforts, a shift towards trajectory-based environments can be identified, where user needs and performance capabilities are leading to user-preferred routing, using Airborne Separation Assurance Systems. This paper describes the initial research towards an ecological design of a fourdimensional Separation Assistance interface. Based on a work-domain analysis, several perspective projections of travel constraints are proposed, as well as an initial layout for the display concept. Key issues in the current design are discussed, with recommendations for future work.

A Method for Scheduling Air Traffic with Uncertain En Route Capacity Constraints

Scipedia content — Wed, 03 Feb 2021 21:00:24 +0100

method for scheduling ground delay and airborne holding for flights scheduled to fly through airspace with uncertain capacity constraints is presented. The method iteratively solves linear programs for departure rates and airborne holding as new probabilistic information about future airspace constraints becomes available. The objective function is the expected value of the weighted sum of ground and airborne delay. In order to limit operationally costly changes to departure rates, they are updated only when such an update would lead to a significant cost reduction. Simulation results show a 13% cost reduction over a rough approximation of current practices. Comparison between the proposed as needed replanning method and a similar method that uses fixed frequency replanning shows a typical cost reduction of 1% to 2%, and even up to a 20% cost reduction in some cases.

MyTIS: a MAS-based TIS for public transport users

Scipedia content — Wed, 03 Feb 2021 21:00:05 +0100

This paper will report on the development of myTIS, which is a multi-agent based architecture to support public transport users in planning and executing their trips on a daily basis. Commuters that use public transport in their daily lives are frequently faced with problems, such as finding out what time the next bus service to a certain destination arrives or how to improve their travel experience to minimize the time spend in transit. On the other hand, non-commuters must address even more complicated issues, as they are not familiar with the network and would need continuous assistance throughout the trip realization. These scenarios bring about interesting and challenging problems that suggest the adequacy of the multi-agent systems (MAS) metaphor. In a first abstraction exercise, it is very intuitive to identify such characteristics in the public transport domain. myTIS (where the TIS excerpt stands for traveler information system) is intended to be a cross-platform for public transport travelers, divided in terms of agents that cooperate to fulfill users’ trip planning goals Such a design decision is a requirement as the system must cover the whole decision-making process of a commuting plan. The methodological approach followed in this project includes a modeling phase, in which the requirements of the system and its main functionalities are defined. This phase is supported by an in-depth state-of-the-art review and the study of similar applications and results in the design of a new generation MAS-based traveler information system.

Risk Assessment for Water Mains Using Fuzzy Approach

Scipedia content — Wed, 03 Feb 2021 20:47:27 +0100

The concept of responding to the risk of water pipelines failure has been undergoing through a great change from being active to being proactive to failure events by planning for rehabilitation plans that maintain the water main in good working conditions. This paper designs a framework to evaluate the risk of water main failure using hierarchal fuzzy expert system. There are sixteen risk-of-failure factors that represent both the probability of failure and the negative consequences of failure event and are categorized into four main risk-of-failure factors. A risk of failure model is built that evaluates the risk of pipelines failure using Fuzzy Expert System technique that accounts for the uncertainty usually encountered when evaluating the risk of failure. Some of the findings are that the pipe age gives a strong indication of the condition of the water mains, then, the pipe material and breakage rate come into play, and that the damage to surroundings/business disruption has the most negative impact of a failure event.

An Aggregate Sector Flow Model for Air Traffic Demand Forecasting

Scipedia content — Wed, 03 Feb 2021 20:39:06 +0100

Sector capacity, number of aircraft permitted in a region of the airspace referred to as a sector, is used to limit air traffic to an amount that can be safely handled by a human controller. The traditional approach for predicting traffic demand in a sector involves the simulation of trajectories of individual aircraft. The demand provided by this approach is inaccurate for hourly time horizons. This paper explores the use of linear time varying aggregate models constructed using historical data for predicting sector demand. Since air traffic varies with the seasons, day of the week and weather, multiple aggregate models can be built to represent different situations. The paper evaluates the accuracy of using a single aggregate model and compares it with the improvements that can be achieved by using several aggregate models and selecting the best model based on hypothesis testing. The paper also presents the results of using a combination of probability-weighted predictions from several aggregate models. Evaluation of the prediction errors for all the high-altitude sectors in Indianapolis Center for a month shows that the multiple aggregation models result in smaller errors; errors vary with the sector and do not vary significantly with the prediction interval.

Effects of aircraft trajectories geometrical features upon air traffic controllers' conflict judgments

Scipedia content — Wed, 03 Feb 2021 20:36:36 +0100

International audience; This work is a twofold contribution to the analysis of conflict detection process in air traffic controllers (ATCos). The first one addresses methodological aspects and proposes a way to get responses as close as possible to controllers' actual expertise without using artifacts such as rating scales or inferring judgments from verbal material. The second objective is to compare the influence of three geometrical features of aircraft encounters and their capacity to alter an accurate perception of conflicts. The proposed methodology appeared to be useful for collecting expertise as controllers quickly appropriated it, and led to get coherent data. Its use can be envisaged when a reliable representation of mental picture of ATCos is essential. Concerning the geometrical features of aircraft trajectories, aircraft attitudes i.e., the fact they are stable, climbing of descending, entailed significant differences on detection accuracy. To a lesser extent, catch-ups and segmented trajectories showed a capacity to make an accurate perception of conflicts more difficult. These results must be interpreted as tendencies more than precise or quantified results. As the objective of this experiment was to be a pre-experiment in preparation for future collecting in the framework of the European project SESAR, a few different choices concerning the trajectories to be used in the traffic scenarios will help to precise these results.

An aeronautical data link security architecture overview

Scipedia content — Wed, 03 Feb 2021 20:25:03 +0100

International audience; This paper reviews existing security mechanisms for aeronautical data link communication: current support and availability of such features are described. With an Open Systems Interconnection (OSI) reference model-driven analysis, each solution is classified and analyzed according to the layer where security is deployed and a relevant taxonomy is proposed. Moreover, advantages, drawbacks, and possible threats of every security mechanisms previously introduced are discussed. According to this security infrastructure overview, a proposal for an efficient security architecture adapted to the aeronautical context is made for future studies. Satellite communication-based system specific problematic is taken into account with a constraint bandwidth and the need of reduced overhead for any additional mechanisms.

Integration of a multifunctional and multispectral optical sensor for automotive applications using surface mountable planar optical interconnect

Scipedia content — Wed, 03 Feb 2021 20:23:19 +0100

In this paper we present the design and fabrication of a low cost surface mountable planar optical interconnect and the integration in a low-cost multifunctional and multispectral CMOS vision sensor (MFOS) to detect critical environmental parameters (fog, rain, twilight) providing, at the same time, information on the driving scenario (oncoming vehicles, VRUs in night conditions). The project ADOSE addresses research challenges in the area of accident prevention; the focus is on functional, performance and cost limits of current sensors and Advanced Driver Assistance Systems for their extensive market penetration. The 3D structure of the interconnect makes it possible to guide collimated light to dedicated detection regions on a CMOS imager, thus making a virtual partition of the sensitive imager area in sub-areas, usually not needed by the applications requiring the frontal view monitoring, possible. Therefore one imager chip can be used for several sensing and imaging functions. The optical system can be passively assembled and is surface mountable resulting in low cost fabrication.

Impact of traffic symbol directional cues on pilot performance during TCAS events

Scipedia content — Wed, 03 Feb 2021 20:19:13 +0100

Implementation of Automatic Dependent Surveillance — Broadcast (ADS-B) technology enables aircraft to broadcast, receive and display a number of aircraft parameters that were not previously available to pilots. While significant research has been conducted regarding Cockpit Display of Traffic Information (CDTI) display format, there is little research to assess the impact this additional information would have on pilot response to Traffic Alert and Collision Avoidance System II (TCAS II) Traffic Advisory (TA)/Resolution Advisory (RA) events. The purpose of this study is to determine the impact of providing directionality information for traffic symbols on a TCAS traffic display during a TA/RA event. This issue is particularly relevant for shared TCAS/CDTI displays. The study supported the development of CDTI performance standards through RTCA, Inc. Twenty-three current and qualified Boeing 737 (B737) pilots flew two 35-minute flight segments in a full motion B737 Next Generation (NG) flight simulator, one flight segment with modified symbology that included traffic directionality information and one with standard TCAS symbology that does not directly provide directionality information. During each flight segment, pilots experienced six separate TA/RA encounters that were counter-balanced to vary encounter geometry, phase of flight and visual conditions. Of the 276 planned RA encounters, 251 RAs actually occurred. In some cases, no RA was received due to either pilot maneuvering (22 cases) or simulator issues (three cases). Dependent measures included pilot responses to TCAS TA/RA encounters and pilot use of TCAS displays as measured by eye tracking data. The results indicate that inclusion of traffic directional information on a traffic display during TCAS TA/RA encounters does not negatively affect pilot response to RAs as measured by timing and magnitude of the RA response. Directional information also yielded no observed effect on pilot scans (allocation of gaze). Although effect of symbology was not observed, horizontal and/or vertical maneuvering beyond that commanded by the RA was observed in 90 of 273 possible TCAS TA/RA encounters, independent of symbology. Such maneuvering may be appropriate, depending on the information and context. However, eye tracking and subjective data suggest the maneuvering decisions may be based on the traffic display and not based on visual acquisition or other information. While the overall RA compliance rate was high, the degree of vertical and horizontal maneuvering during the TA/RA event should be better understood since TCAS traffic displays are not intended to support maneuvering. Further research is required to better understand the circumstances in which maneuvering occurs and the resulting impact on the air traffic system.

Repair of High Pressure Pipe Fittings Using Composite Materials

Scipedia content — Wed, 03 Feb 2021 20:13:45 +0100

Pipelines and piping frequently suffer from metal loss that threatens their integrity and serviceability. Multiple repair options exist for straight sections of pipe; however, repair options for pipe fittings such as elbows and tees are typically limited to composite repair systems, or section replacement. The latter method can be costly as it often requires at least a partial shut down of the pipeline while the section is replaced. A composite repair system however, can be performed in place during operations at a greatly reduced cost. The main challenge with the composite repair system is the required demonstrated ability to restore integrity and serviceability to the same level as the original metal system. Over the past 10 years, Stress Engineering Services, Inc. has been greatly involved in evaluating the ability of many composite repair systems to restore the original pipeline structural integrity by testing methods and analysis methods. The current paper investigated the ability of the Armor Plate Pipe Wrap (APPW) system to restore the burst pressure of tee and elbow pipe fittings with 60% metal loss to that of a nominal thickness system. In this program four full scale burst tests were conducted: on 12-inch nominal pipe size (NPS) Y52 tee and elbow pipe fittings. All four fittings had 60% metal loss; two were repaired with APPW, and the other two were not repaired. Prior to burst testing, elastic plastic finite element analyses (FEA) were performed to adequately size the repair thickness. The results of the FEA calculations predicted the restoration of the burst pressures of the repaired fittings up to a 1.6% agreement with the actual burst pressure results. Furthermore, the burst pressure of the 60% metal loss tee was increased from 3,059 psi (unrepaired) to 4,617 psi, or a 51% improvement. The burst pressure of the 60% metal loss elbow was increased from 2,610 psi to 4,625 psi, or a 77% improvement. Both the analysis and testing results demonstrated that composite materials can restore the pressure integrity of corroded tee and elbow pipe fittings.Copyright © 2010 by ASME

Why equity is a pipedream: Analysis of the dynamics of overscheduled NAS resources

Scipedia content — Wed, 03 Feb 2021 20:13:09 +0100

One of the major issues in the proposed concepts-of-operations for NEXTGEN is the equitable allocation of overscheduled National Airspace System (NAS) resources. Although federal regulations, Congressional policies, and modernization plans call for equitable allocation of publicly held resources, the mechanisms for equitable allocation, and the trade-offs that must be made between stakeholders, exhibit a high degree of social, political, and economic complexity. Further, the allocations that are routinely made in Traffic Flow Management (TFM) and Air Traffic Control (ATC) are subject to widespread perceptions of systemic inequity and economic inefficiency. This paper describes the properties associated with the dynamic allocation of an overscheduled resource. The mathematical model demonstrates that (i) a natural asymmetry exists in the allocation, (ii) this asymmetry results in a low probability (≪ 10%) of an equitable allocation of resources amongst groups of flights (e.g. airlines), and (iii) increased competition reduces the likelihood of equitable allocations. These theoretical results establish the “feasible space” in which claims of equity can be made, suggests refinements of the existing allocation schemes, and establishes the framework for a regulatory role in proposed market-based mechanisms.

Numerical simulation of heavy oil flows in pipes using the core-annular flow technique

Scipedia content — Wed, 03 Feb 2021 20:12:44 +0100

The importance of heavy oils in the world market for petroleum has increased very quickly in the last years. The reserves of heavy oils in the world are estimated at 3 trillion barrels, while reserves of light oils have reduced progressively in the last decade. The high oil viscosity creates major problems in the production and transportation of the oil. This situation leads to the high pressure and power required for its flow, overloading and damaging the equipment, increasing the cost of production. Due to the need to develop new alternatives that will make the production and transport of heavy oil economically viable, this work has the objective to study, numerically, the behavior of isothermal multiphase flow (heavy oil and water), type “core flow”, in pipelines, using the software CFX 3D. The pressure drop was determinated to a core-flow in a pipe with 7 in. diameter, 2.7 Pa.s oil viscosity and water at environment temperature. Results of the pressure, velocity and volume fraction distributions of the phases are presented and analyzed. It was verified that the pressure drop was reduced 58 times when compared to that obtained with oil flow alone in the pipe.

Limit State Design Based on Experimental Methods for High Pressure Subsea Pipeline Design

Scipedia content — Wed, 03 Feb 2021 20:08:30 +0100

The design of offshore subsea pipelines is facing new challenges as the pipeline industry is moving into environments requiring high pressure design. Conventional pipeline design codes such as ASME B31.4 and B31.8 establish pressure limits based on percentage of the pipe material’s minimum specified yield strength. While this has traditionally worked for relatively thin-walled pipe at moderate pressures, there are concerns that full utilization of the material’s capacity is not being realized when designing for high pressure conditions. Additionally, there are concerns regarding the ability to achieve high quality manufacturing and consistently fabricate welds in thick-wall pipes. This paper presents details on a testing program that incorporated full-scale burst testing to qualify the design pressure for an 18-inch × 0.75-inch, Grade X65 subsea gas pipeline using the methodology of API RP 1111. A lower bound burst pressure was established based on the recorded burst pressures to which a design margin of 0.72 was applied to determine a design pressure. Had the pipeline been conventionally-designed using ASME B31.8, the design pressure would have been 3,900 psi. However, using the experimentally-based design option in API RP 1111 the resulting design pressure was 4,448 psi. This results in a net increase in the design pressure of 14 percent. When one considers either the potential cost savings in material requirements at construction or the additional throughput associated with higher design pressures for a given pipeline system, it is not difficult to demonstrate the economic benefits derived in performing a more rigorous material qualification and limit state design process based on experimental methods as presented in API RP 1111.Copyright © 2010 by ASME

Deferability: A Concept for Incremental Air Traffic Management Decision Making

Scipedia content — Wed, 03 Feb 2021 20:01:26 +0100

Dealing with uncertainty poses a challenge for traffic flow management (TFM) decision making, for example, when rerouting flights to avoid forecast convective weather. These decisions impose costs and delays on flights, and weather does not always materialize where it was forecast or with the forecasted severity. Deciding on a good strategy to take now when faced with uncertain and probabilistic forecasts is difficult for human decision makers. We have developed the deferability concept as an approach for building TFM decision support systems that make decisions incrementally. Simulation studies show this concept can be an effective way to manage airspace congestion using uncertain traffic and weather forecasts.

Sustainable urban transport—the contested role of car manufacturers

Scipedia content — Wed, 03 Feb 2021 19:51:04 +0100

This paper describes how unsustainable urban transport is often linked to an unhealthy overdose of cars and road traffic. Due to the imperative of corporate social responsibility the car industry can no longer ignore this scapegoat role. This paper identifies two strategic options car manufacturers can espouse to tackle this challenge: (a) anticipating external developments and trends (corporate foresight) and (b) participating in policy making and agenda setting. While the first option aims at increasing economic objectives, i.e. preparing for changing market conditions, the latter can help achieve corporate responsibility objectives if based on principles of sustainable development. Drawing on selected examples of anticipating and participating activities of the automotive industry and their respective opportunities and limits, this paper will explore how these activities, if based on sustainable development principles, can help companies adopt a more favorable role and strengthen the cooperation of the public and private sectors in the quest for sustainable development.

Potential industry applications using gas hydrate technology

Scipedia content — Wed, 03 Feb 2021 19:49:39 +0100

Over the past decade, gas hydrates have stimulated significant interest and triggered fundamental research. Primarily, the focus has been on hydrate blockage in pipelines, and on naturally occurring gas hydrates. However, gas hydrates can be useful in many different ways that can be pertinent to our industry, thanks to their unique structural packing where only certain molecules can enter the gas hydrate cavities. Among the several potential uses of gas hydrate technology are gas separation, transportation and storage of natural gas, desalination, and carbon dioxide disposal. In particular, it is possible to (i) separate the heavier components (pentane and higher) from natural gas, and (ii) capture, store and transport natural gas. This paper proposes a workflow for capturing, storing and transporting gas in the hydrate form, particularly for situations where there are infrastructural constraints such as lack of pipelines. These applications of gas hydrate technology can have potential benefits to the oil and gas industry.

Enhancing Collaboration in Air Traffic Flow Management

Scipedia content — Wed, 03 Feb 2021 19:44:47 +0100

This paper extends the concept of credit points to enhance collaboration between participants in air traffic flow management. In earlier research, a preferred route selection method was presented, where users expend credit points to prioritize the flight paths for each of their pre-departure flights. This method of prioritizing flights provides a mechanism to incorporate users’ preferences in air traffic management subject to airspace congestion and weather impact constraints. In the current research, the airport arrival and departure rates at the top 70 airports are incorporated. In order to analyze the equity of arrival and departure schedules, the flight distributions at those airports were constructed for the 40 largest flight operators in the United States. The credit-points concept gives airborne flights the highest priority, enabling them to better maintain their schedule. A negotiation mechanism for participants to reassess their decisions for improved operations is described. Results for violations of arrival/departure rates and airspace constraints (due to volume and weather) before and after implementing the concept, along with credit use and incurred delays are presented. Results indicate that the credit-points concept is feasible for users to incorporate their preferences of important flights. The overall delay compared to a schedule based system reduces while maintaining airspace and airport capacities. Also, the equity increases for participating users as more constraints are added due to better utilization of available airspace.

Alerting the Drivers about Road Signs with Poor Visual Saliency

Scipedia content — Wed, 03 Feb 2021 19:42:40 +0100

This paper proposes an improvement of Advanced Driver Assistance System based on saliency estimation of road signs. After a road sign detection stage, its saliency is estimated using a SVM learning. A model of visual saliency linking the size of an object and a size-independent saliency is proposed. An eye tracking experiment in context close to driving proves that this computational evaluation of the saliency fits well with human perception, and demonstrates the applicability of the proposed estimator for improved ADAS.

BGP-aware IGP Link Weight Optimization in Presence of Route Reflectors

Scipedia content — Wed, 03 Feb 2021 19:41:02 +0100

The first generation of IGP Link Weight Optimizers (LWOs) was based on presumably invariant intra-domain traffic matrices only, ignoring the fact that updating link weights had a side effect on these traffic matrices due to hot-potato routing, thus result- ing in suboptimal link weight settings, and sometimes to very bad performance. The second generation of IGP LWOs, referred to as BGP-aware LWOs, has been able to optimize link weights while taking hot-potato effects into account. However, these tools relied on the complete visibility assumption fulfilled by e.g. a full-mesh iBGP configu- ration. This paper proposes a third generation LWO, still BGP-aware, but also able to work with iBGP con- figurations based on route reflectors, which usually hide some reachability information from routers. This partial visibility may cause various problems, including path deflections (i.e., the actual egress router is not the expected one), which may in turn create forwarding loops. Our LWO embeds a BGP routing solver which can always predict the actual egress router, even when route reflectors are used. It can also forbid solutions leading to path deflection. Its efficiency is evaluated on a real dataset, and compared to other LWOs. Index Terms—Traffic Engineering, Hot-potato Rout- ing, BGP, IGP, OSPF, Path Deflection

Bayesian Tracking of Linear Structures in Aerial Images

Scipedia content — Wed, 03 Feb 2021 19:38:57 +0100

The interpretation of aerial images is difficult, especially for low-resolution images. Although solutions have been worked on for many years, performance of these systems is still not sufficient to be useful in practical applications. One potential solution is to create systems composed of many specialized modules. We introduce one such module, a Bayesian tracker for linear structures, such as pipelines and access roads. We show that the tracker can be used successfully to detect these structures in low-resolution images.