Scipedia: Documents published in 2006

Slėgio kampų nustatymas esant ribojimams ir optimizuojant svirtinius lankstinius mechanizmus

Scipedia content — Tue, 23 Mar 2021 01:59:24 +0100

In the present paper a method of analytical determination of reactions and angles of pressure is considered with the four-bar linkage as an example. The determined sequence for the expression of acceleration of the points and angle acceleration of the links is presented. Further the power analysis for Assur’s group is made. The equations of normal components of reactions are expressed as straight lines passing across given point in the given direction. The equations of the full reactions in the hinges are expressed as straight lines passing across two given points. After that the angles of pressure are expressed as the angles between directions of the speed and reactions. Pateikta reakcijų ir slėgio kampų analitinio nustatymo metodika, nagrinėjant paprasčiausią plokščią skriejiklio ir svirties lankstinį mechanizmą. Pateikta mechanizmo taškų pagreičių ir grandžių kampinių greičių nustatymo eilės tvarka. Atlikta sandaros grupės jėginė analizė. Normalinių reakcijų lankstuose lygtys išreiškiamos tiesių, nubrėžtų per tašką nurodyta kryptimi, lygtimis. Suminių reakcijų lankstuose lygtys išreiškiamos tiesių, nubrėžtų per du taškus, lygtimis. Slėgio kampai – kampai tarp greičių ir reakcijų krypčių. На примере шарнирного четырехзвенника рассмотрена методика аналитического определения сил реакций и углов давления. Представлена определенная последовательность для выражения ускорений точек механизма и угловых скоростей звеньев. Приведен силовой анализ для ассуровой группы. Уравнения нормальных составляющих реакций выражаются как прямые, проходящие через данную точку в заданном направлении. Уравнения полных реакций в шарнирах выражены как прямые, проходящие через две зад��нные точки. Затем выражены углы давления как углы между направлениями скоростей и реакций.

Document type: Article

SOME EMPIRICAL RELATIONS BETWEEN TRAVEL SPEED, TRAFFIC VOLUME AND TRAFFIC COMPOSITION IN URBAN ARTERIALS

Scipedia content — Tue, 23 Mar 2021 01:14:07 +0100

The effects of traffic mix (the percentage of cars, trucks, buses and so on) are of particular interest in the speed-volume relationship in urban signalized arterials under various geometric and control characteristics. The paper presents some empirical observations on the relation between travel speed, traffic volume and traffic composition in urban signalized arterials. A methodology based on emerging self-organizing structures of neural networks to identify regions in the speed-volume relationship with respect to traffic composition and Bayesian networks to evaluate the effect of different types of motorized vehicles on prevailing traffic conditions is proposed. Results based on data from a large urban network indicate that the variability in traffic conditions can be described by eight regions in speed-volume relationship with respect to traffic composition. Further evaluation of the effect of motorized vehicles in each region separately indicates that the effect of traffic composition decreases with the onset of congestion. Moreover, taxis and motorcycles are the primary affecting parameter of the form of the speed-volume relationship in urban arterials.

Document type: Article

End-site routing support for IPv6 multihoming1

Scipedia content — Tue, 23 Mar 2021 00:00:31 +0100

Multihoming is currently widely used to provide fault tolerance and traffic engineering capabilities. It is expected that, as telecommunication costs decrease, its adoption will become more and more prevalent. Current multihoming support is not designed to scale up to the expected number of multihomed sites, so alternative solutions are required, especially for IPv6. In order to preserve interdomain routing scalability, the new multihoming solution has to be compatible with Provider Aggregatable addressing. However, such addressing scheme imposes the configuration of multiple prefixes in multihomed sites, which in turn causes several operational difficulties within those sites that may even result in communication failures when all the ISPs are working properly. In this paper we propose the adoption of Source Address Dependent routing within the multihomed site to overcome the identified difficulties. Publicado

Document type: Article

On the Self-Similar Nature of ATM Network Traffic

Scipedia content — Mon, 22 Mar 2021 20:28:21 +0100

Modeling multimedia traffic is an important issue in performance analysis and design of communication networks. With introduction of new applications, the characteristics of data traffic changes. In this paper, a measurement study of ATM Network traffic has been carried out and it is shown that the recorded data exhibit self-similar features. The conclusions are supported by a comprehensive analysis using one of the most popular statistical methods called Indices of Dispersion. Our results validate one of the most striking findings of the present teletraffic research: a broad range of packet network traffic has fractal-like behavior. We also investigate three popular synthetic self-similar traffic models and find out the most accurate one for the measured traffic. Keywords: ATM, Modeling, Self-similar traffic, Indices of Dispersion, Hurst parameter, Performance Testing. Introduction The characterization of real traffic is a critical issue to the success of efficient traffic engineering in ATM networks. Research in this field has resulted in numerous models and techniques over the last decade (Bjorkman, Latour-Henner, Hasson, pers, and Miah, 1995; Stamoulis, Anagostu, and Georgantas, 1994). However, the developed traffic characterization methods have been, in general, rather complicated and demand intensive computation of several statistical parameters. There is a lack of simple and accurate methods that can be of practical use to network operators. Extensive data studies indicate that traffic in high-speed communications networks has long-memory and heavy tailed (impulsive) characteristics. With the rising popularity of multimedia applications over networks, these properties of the traffic are only likely to become more dominant, posing unique new challenges to designers of network systems and protocols. Traditional teletraffic theory cannot capture these traffic characteristics. During the last few years, significant research results have been proposed on models that capture self-similarity of traffic. These models, however, are inadequate for predicting queuing performance, delays, and buffer dimensions since the implications of the combination of self-similarity and impulsiveness queuing performance can be dramatically different from that of self-similarity alone. To the best of my knowledge there are no models that have been derived based on real traffic dynamics that also capture the data impulsiveness? The modeling of self-similar traffic appeared as an emerging and challenging field of the present teletraffic research. It seems that there are different promising approaches to capture this complex fractal-like behavior. Norros (1993, 1995) used a Gaussian self-similar process known as the Fractional Brownian Motion. Willinger, Taqqu, Sherman and Wilson (2004) applied the superposition of on/off sources with heavy-tailed on and off period. Erramilli (1994) and Singh and Erramilli (1999) studied different chaotic maps. The rest of this paper is organized as follows. In section 2 we give information about the self-similar traffic characteristics and the used techniques for measuring the self-similarity level (Hurst-parameter H). In section 3 we present the analysis based on the real measurements taken from the Eastern Mediterranean University (EMU) ATM network and find out the self-similarity level. In section 4 we investigate the three promising self-similar modeling approaches to capture the observed properties, and we find out the most appropriate model for EMU ATM network traffic. Finally, section 5 summarizes the results of the paper and identifies areas for future research. The Self-Similarity Phenomena and its Testing A self-similar phenomenon represents a process displaying structural similarities across a wide range of scales of a specific dimension. In other words, the reference structure is repeating itself over a wide range of scales of diverse dimensions (geometrical, or statistical, or temporal). …

Document type: Article

Attuning in-car user interfaces to the momentary cognitive load

Scipedia content — Tue, 16 Feb 2021 12:58:34 +0100

Cars, trucks and busses are more and more equipped with functions and services that drivers are supposed to operate and understand. The most important developments in this area are the Advanced Driver Assistance Systems (ADAS) and In Vehicle Information Systems (IVIS). In order to make sure that the driver understands and appreciates (comfort) these services and traffic safety is not at risk (distraction, workload), the HMI's (Human Machine Interfaces) of all these functions should be attuned to each other, to the driver, and to the context. For attuning the functions to each other, a HMI platform is needed on which these functions are integrated. For attuning the functions to the driver it is necessary to have knowledge about the momentary state of the driver and of the intentions of the driver at a certain moment. For attuning the functions to the context, it is required to sense the relevant environmental conditions or states. This paper shows that a recent cognitive task load model from process control domain can be applied for the design of adaptive in-car user interfaces. Furthermore, current developments of such interfaces are being discussed. © Springer-Verlag Berlin Heidelberg 2007.

A revised estimate of copper emissions from road transport in UNECE-Europe and its impact on predicted copper concentrations

Scipedia content — Tue, 16 Feb 2021 12:53:59 +0100

Comparisons of measured and model-predicted atmospheric copper concentrations show a severe underestimation of the observed concentrations by the models. This underestimation may be (partly) due to underestimated emissions of copper to air. Since the phase out of asbestos brake lining material, the composition of brake lining material has changed and may contain up to ∼15% copper. This makes brake wear from vehicles potentially an important source of atmospheric (particulate) copper concentrations. In this paper, we reassess the copper emissions due to exhaust emissions and brake wear from road transport. Overall, our reassessments result in an estimate of total copper emission to air in UNECE-Europe of 4.0-5.5 ktonnes yr-1, which is substantially higher than the previous estimate of 2.8 ktonnes yr-1. Copper concentrations over Europe are calculated with the LOTOS-EUROS model using the revised emission data as model input. The results show that the revised emission estimates are a major step towards gap closure of predicted versus observed copper concentrations in ambient air. Brake wear emissions may be responsible for 50-75% of the total copper emissions to air for most of Western Europe. The hypothesis that road transport is an important source of copper emissions is tested and confirmed by (1) reviewing available literature data of chemically speciated PM data from road tunnel studies and (2) the gradient observed in copper concentrations from ambient PM monitoring going from rural sites to street stations. The literature review and observational data suggest that the majority of the emitted PM10 brake wear particles is in the PM2.5-10 size range. The results of this study indicate that modification of brake lining composition is an important mitigation option to reduce copper exposure of the population in Western Europe. © 2007 Elsevier Ltd. All rights reserved.

Water hammer with column separation : a historical review

Scipedia content — Tue, 16 Feb 2021 12:11:40 +0100

Column separation refers to the breaking of liquid columns in fully filled pipelines. This may occur in a water-hammer event when the pressure in a pipeline drops to the vapor pressure at specific locations such as closed ends, high points or knees (changes in pipe slope). The liquid columns are separated by a vapor cavity that grows and diminishes according to the dynamics of the system. The collision of two liquid columns, or of one liquid column with a closed end, may cause a large and nearly instantaneous rise in pressure. This pressure rise travels through the entire pipeline and forms a severe load for hydraulic machinery, individual pipes and supporting structures. The situation is even worse: in one water-hammer event many repetitions of cavity formation and collapse may occur. This paper reviews water hammer with column separation from the discovery of the phenomenon in the late 19th century, the recognition of its danger in the 1930s, the development of numerical methods in the 1960s and 1970s, to the standard models used in commercial software packages in the late 20th century. A comprehensive survey of laboratory tests and field measurements is given. The review focuses on transient vaporous cavitation. Gaseous cavitation and steam condensation are beyond the scope of the paper.

Interactive road situation analysis for driver assistance and safety warning systems : framework and algorithms

Scipedia content — Tue, 16 Feb 2021 11:37:34 +0100

Road situation analysis in Interactive Intelligent Driver-Assistance and Safety Warning (I2DASW) systems involves estimation and prediction of the position and size of various on-road obstacles. Real-time processing, given incomplete and uncertain information, is a challenge for current object detection and tracking technologies. This paper proposed a development framework and novel algorithms for road situation analysis based on driving action behavior, where the safety situation is analyzed by simulating real driving action behaviors. First, we review recent development and trends in road situation analysis to provide perspective for the related research. Second, we introduce a road situation analysis framework, where onboard sensors provide information about drivers, traffic environment, and vehicles. Finally, on the basis of the previous frameworks, we proposed multiple-obstacle detection and tracking algorithms using multiple sensors including radar, lidar, and a camera, where a decentralized track-to-track fusion approach is introduced to fuse these sensors. In order to reduce the effect of obstacle shape and appearance, we cluster lidar data and then classify obstacles into two categories: static and moving objects. Future collisions are assessed by computation of local tracks of moving obstacles using extended Kalman filter, maximum likelihood estimation to fuse distributed local tracks into global tracks, and finally, computation of future collision distribution from the global tracks. Our experimental results show that our approach is efficient for road situation evaluation and prediction

Use of a vehicle-modelling tool for predicting CO2 emissions in the framework of European regulations for light goods vehicles

Scipedia content — Tue, 16 Feb 2021 11:36:30 +0100

The reduction of CO2 emissions and fuel consumption from road transportation constitutes an important pillar of the EU commitment for implementing the Kyoto Protocol. Efforts to monitor and limit CO2 emissions from vehicles can effectively be supported by the use of vehicle modelling tools. This paper presents the application of such a tool for predicting CO2 emissions of vehicles under different operating conditions and shows how the results from simulations can be used for supporting policy analysis and design aiming at further reductions of the CO2 emissions. For this purpose, the case of light duty goods (N1 category) vehicle CO2 emissions control measures adopted by the EU is analysed. In order to understand how certain design and operating aspects affect fuel consumption, a number of N1 vehicles were simulated with ADVISOR for various operating conditions and the numerical results were validated against chassis dynamometer tests. The model was then employed for analysing and evaluating the new EU legislative framework that addresses CO2 emissions from this vehicle class. The results of this analysis have shown the weaknesses of the current regulations and revealed new potential in CO2 emissions control. Finally the TREMOVE model was used for simulating a possible scenario for reducing CO2 emissions at fleet level. © 2006 Elsevier Ltd. All rights reserved. Chemicals / CAS: carbon dioxide, 124-38-9, 58561-67-4

Frequency Competition and Environmental Costs: An Application to European Air Transport Liberalization

Scipedia content — Tue, 16 Feb 2021 11:27:40 +0100

In this paper, we analyze symmetric frequency equilibria in airline markets; these equilibria are derived as multiproduct oligopoly solutions in a spatial competition model. Competitive equilibria are compared with a regulated equilibrium; in order to assess the welfare implications of European air transport liberalization, we compute numerical solutions using data for 21 regulated European interstate routes in 1990. We conclude that, following the introduction of competition in these markets, consumer welfare is significantly higher due to frequency increases and fare decreases. Profits decrease and, as a result of higher departure frequencies, environmental costs increase. However, the gains in consumer welfare more than compensate the decrease in profits and the rise in environmental costs. © 2006 Elsevier Ltd. All rights reserved.

Development of advanced driver assistance systems with vehicle hardware-in-the-loop simulations

Scipedia content — Tue, 16 Feb 2021 11:18:53 +0100

This paper presents a new method for the design and validation of advanced driver assistance systems (ADASs). With vehicle hardware-in-the-loop (VEHIL) simulations, the development process, and more specifically the validation phase, of intelligent vehicles is carried out safer, cheaper, and is more manageable. In the VEHIL laboratory, a full-scale ADAS-equipped vehicle is set up in a hardware-in-the-loop simulation environment, where a chassis dynamometer is used to emulate the road interaction and robot vehicles to represent other traffic. In this controlled environment, the performance and dependability of an ADAS is tested to great accuracy and reliability. The working principle and the added value of VEHIL are demonstrated with test results of an adaptive cruise control and a forward collision warning system. On the basis of the 'V' diagram, the position of VEHIL in the development process of ADASs is illustrated.

The IMAGINE source model for railway noise prediction

Scipedia content — Tue, 16 Feb 2021 11:13:28 +0100

The IMAGINE railway traffic noise source model is described, which is a further elaboration and completion of the Harmonoise model. Within the EU project Harmonoise, a model was proposed including most of the main railway noise sources. In the IMAGINE project, complete formulation was put forward taking all relevant physical sources but also main operating conditions into account, and default source data was proposed. At a given section of track with a given traffic flow, for each type of rolling stock, a combination of operating conditions and physical sources may occur. The operating conditions are constant speed, acceleration, braking, curving and stationary operation. The physical sources are rolling noise, impact noise, traction noise, curve squeal in points or curves, broadband or tonal braking noise and aerodynamic noise. The IMAGINE models for each physical source are presented and their relevance for each operating condition is discussed. Some examples of default input data are given and measurement methods to obtain source data are outlined.

Experience from a pilot trial

Scipedia content — Tue, 16 Feb 2021 11:05:48 +0100

This study was designed to present an online model which predicted travel times on an interurban two-lane two-way highway section on the basis of field measurements. "br/"The study included two parts: an evaluation of the performance of the model, and an examination of the possibility to improve the model in case of unsatisfactory performance. The model was based on MLP neural networks. The main results of the evaluation showed that the prediction model outperformed a non-predictive system. "br/"However, the model for one section had not performed as well during the trial period as was expected. This might be due to a slight change in the congestion phenomenon. After further development, the findings showed that the model could be improved considerably with new data. "br/"The main implication was that even a simple prediction model improves the quality of travel time information substantially, compared to estimates based directly on the latest measurements.

Method for Assessing Safety of Routes in a Road Network

Scipedia content — Tue, 16 Feb 2021 10:55:55 +0100

In the Netherlands, the concept of sustainably safe traffic is the leading vision in road safety policy and research. The main goal of a sustainably safe road transport system is to reduce the annual number of road accident casualties to a fraction of the current levels. Important requirements resulting from this vision are that trips follow safe roads as much as possible, trips be as short as possible, and the quickest and safest routes coincide. Modeling route choice will provide answers to the planning issues of sustainably safe traffic; however, the safety effects of these requirements constitute a totally different issue, which needs to be dealt with. The focus of this study is on the design of a method that enables the planner to determine the safety effects of existing route choice and the changes in route choice. A description of road safety can be made in various ways. When a microscopic model is used, conflicts between vehicles will be an integral part of the simulation. The outcome will be used to compare the types of conflicts in a given simulation with the types of conflicts that would be acceptable in a sustainably safe road environment, for example, conflicts with opposing vehicles should be minimized at high speed differentials. A so-called route diagram of each route can be checked according to a series of criteria, each representing requirements for a sustainably safe route choice. Each criterion of the route diagram contributes to the total safety level of a route by the number of demerit points scored by the criterion. The criteria are described and tested in a microsimulation of alternative routes in a synthetic road network.

Impacts of a congestion assistant on driving behaviour and acceptance using a driving simulator

Scipedia content — Tue, 16 Feb 2021 10:52:55 +0100

In-vehicle systems that assist the driver with his driving task are developed and introduced to the market at increasing rate. Drivers may be supported during congested traffic conditions by a so-called Congestion Assistant consisting of a mix of informing, assisting and controlling functions. This paper describes the impacts of the Congestion Assistant on the driver in terms of driving behaviour and acceptance. Thirty-seven participants took part in a driving simulator study. The observed driving behaviour showed promising improvements in traffic safety when approaching the traffic jam. Moreover, positive effects of the system on traffic efficiency can be expected in the jam. The participants stated to appreciate the Congestion Assistant, although not all functions were equally rated. To increase the performance and acceptance of the total system, some refinements were suggested. Keywords: Congestion Assistant; Driving simulator; Integrated system; Driving behaviour; Acceptance

An open source traffic engineering toolbox

Scipedia content — Tue, 16 Feb 2021 10:51:40 +0100

We present the TOTEM open source Traffic Engineering (TE) toolbox and a set of TE methods that we have designed and/or integrated. These methods cover intra-domain and inter-domain TE, IP-based and MPLS-based TE. They are suitable for network optimisation, better routing of traffic for providing QoS, load balancing, protection and restoration in case of failure, etc. The toolbox is designed to be deployed as an on-line tool in an operational network, or used off-line as an optimisation tool or as a traffic engineering simulator.

Peer Reviewed

Short-term effects of countermeasures for improved safety and mobility at marked pedestrian crosswalks in Borås, Sweden

Scipedia content — Tue, 16 Feb 2021 10:48:40 +0100

The Swedish code concerning car drivers’ responsibility to give way to pedestrians was strengthened in 2000. The primary aim of this study is to evaluate the short-term effects of the change in code. Another goal is to look at the effects of the reconstruction of four sites in Borås, Sweden. One site had changes made prior to the change of code, two test sites had countermeasures implemented during the study, and one comparison site was left unchanged. All the sites were chosen because schools were situated nearby. The focus of the evaluation was on children and elderly as pedestrians and cyclists."br/""br/"The goal of traffic calming of a 90 percentile driving speed below 30 km/h was not fulfilled at any of the test sites. A conclusion is that the height of a speed cushion is important. After the speed cushions were lowered from 70 mm to 55 mm, the 90 percentile speed increased from 34 km/h to 41 km/h. Sites with no speed cushions had much higher speeds."br/""br/"The design of an intersection influences road users’ behavior. At the site where one crosswalk was removed, pedestrians that were using the remaining marked crosswalk were given way to less frequently than at the other sites. At intersections where most pedestrians used marked crosswalks, the children benefited the most in mobility. At the intersection where pedestrians used marked crosswalks to a lower extent after reconstruction, children and the elderly had the smallest increase in frequency of being given way to. After reconstruction to a court-yard street, the pedestrians were given way to a lower extent compared with the other sites, though the vehicle speeds were the lowest observed at this study. At the sites were no physical changes were made, the change of code improved driver yield behavior, but no more towards children than other age groups.

Joint Route Planning under Varying Market Conditions

Scipedia content — Tue, 16 Feb 2021 10:23:57 +0100

Purpose - To provide empirical evidence on the level of savings that can be attained by joint route planning and how these savings depend on specific market characteristics. Design/methodology/approach - Joint route planning is a measure that companies can take to decrease the costs of their distribution activities. Essentially, this can either be achieved through horizontal cooperation or through outsourcing distribution to a logistics service provider. The synergy value is defined as the difference between distribution costs in the original situation where all entities perform their orders individually, and the costs of a system where all orders are collected and route schemes are set up simultaneously to exploit economies of scale. This paper provides estimates of synergy values, both in a constructed benchmark case and in a number of real-world cases. Findings - It turns out that synergy values of 30 per cent are achievable. Furthermore, intuition is developed on how the synergy values depend on characteristics of the distribution problem under consideration. Practical implications - The developed intuition on the nature of synergy values can help practitioners to find suitable combinations of distribution systems, since synergy values can quickly be assessed based on the characteristics of the distribution problem, without solving large and difficult vehicle routing problems. Originality/value - This paper addresses a major impediment to horizontal cooperation: estimating operational savings upfront.

Case study - Finland

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

The ultimate purpose of the transport system is to serve the needs and expectations of the end users, who in turn shape the system by their own behaviour, actions and investments. This paper examines, within the framework of the Large Technological Systems theory the possibility to categorise users of the transport system into homogeneous segments on the basis of their differences in daily mobility and transportation of goods. Furthermore, the potential to deepen this segmentation to describe the needs of, but later in the policy process also the social acceptance by, different user groups for new transport technology or policy, is examined.

Analysis of congestion periods of an m/m/∞-queue

Scipedia content — Tue, 16 Feb 2021 10:04:08 +0100

c-congestion period of an m/m/ ∞-queue is a period during which the number of customers in the system is continuously above level c. Interesting quantities related to a c-congestion period are, besides its duration Dc, the total area Ac above c, and the number of arrived customers Nc. In the literature Laplace transforms for these quantities have been derived, as well as explicit formulae for their means. Explicit expressions for higher moments and covariances (between Dc, Nc and Ac), however, have not been found so far. This paper presents recursive relations through which all moments and covariances can be obtained. Up to a starting condition, we explicitly solve these equations; for instance, we write E Dc2 explicitly in terms of E D02. We then find formulae for these starting conditions (which directly relate to the busy period in the m/m/ ∞ queue). Finally, a c-intercongestion period is defined as the period during which the number of customers is continuously below level c. Also for this situation a recursive scheme allows us to explicitly compute higher moments and covariances. Additionally we present the Laplace transform of a so-called intercongestion triple of the three performance quantities. It is also shown that expressions for the quantities of a c-intercongestion period can be used in an approximation for the c-congestion period. This is especially useful as the expressions for the c-intercongestion period are numerically more stable than those for the c-congestion period. © 2007 Elsevier Ltd. All rights reserved.

DRIVERS' EVALUATIONS OF THE ACTIVE ACCELERATOR PEDAL IN A REAL-LIFE TRIAL

Scipedia content — Mon, 15 Feb 2021 10:29:04 +0100

In a large-scale field trial, conducted between 2000 and 2001, the test drivers used the Active Accelerator Pedal for between 6 and 12 months in their regular cars. The drivers’ evaluations, elicited by questionnaires after one month of usage and at the end of the trial, were analysed with ANOVA (repeated-measure) and compared to the objectively measured effects in the same trial. The drivers found the system to be effective in decreasing their speed and believed their risk of being fined for speeding decreased drastically. On the other hand, their workload increased and their emotional state deteriorated. They reported an increased feeling of obstructing other drivers and reduced driving enjoyment. Between-subject effects showed a different way of using the system depending on age; younger drivers used the supporting function of the system more, while older drivers found the counter force more of a command to lower their speed. Time effects showed the importance of long-term evaluations and the interaction effects demonstrated how development of driver responses over time depend on driver type and initial attitude. Comparing driver subjective experiences and objectively measured effects, discrepancies were found in the magnitude of speed changes and car-following distances. The delegation of responsibility coincided well with the objectively measured effects. (Less)

Document type: Article

Fuel consumption and exhaust emissions of urban buses

Scipedia content — Thu, 11 Feb 2021 18:03:47 +0100

The research was carried out by the Finnish Public Transport Association. Altogether seven vehicles were measured, two two-axle Euro 3 -class vehicles as references, three new two-axle Euro 4 -class vehicles and two new three-axle vehicles. The measurements were carried out on a chassis dynamometer, using three cycles describing actual driving. In addition to fuel consumption, exhaust emissions were also recorded for these vehicles. The differences in fuel consumption and operating expenses were after all smaller than first anticipated. In the case of the Euro 3 -class reference vehicles, the difference between the two vehicles was as high as 7-10%. For new two-axle vehicles the difference in fuel consumption, when simulating urban driving, is only 3-4%. Due to different technical solutions, the results were anticipated to be greater. In suburban driving although, the difference is at its most 11%. In the class of two-axle vehicles, lowest fuel consumption was measured for a SCR vehicle, whereas in the case of the two three-axle vehicles, EGR technology resulted in lowest fuel consumption. The measurements do not give an unambiguous answer to whether the EGR- or SCR-technology is preferable regarding fuel consumption. The contemplation is hindered by two factors. On one hand, the order of superiority depends on the driving cycle, on the other, the actual exhaust emissions do not match with expectations. The two EGR vehicles (same make) produced higher NOx -emissions than the manufacturer's Euro 3 -engine. The most fuel efficient SCR -engine is not truly Euro 4 -class what comes to NOx -emissions. Only two of the new vehicles, both with SCR technology, produce NOx -emissions genuinely matching their classes. Both fuel consumption and exhaust emissions have been observed in the study. In case exhaust emissions were completely disregarded, fleet decisions might be directed towards fuel efficient vehicles which after all do not reach the level of emission performance that reasonably could be expected.

Cruise Tourism: challenges and opportunities for coastal regional development. The Carribean case of the West Indies.

Scipedia content — Thu, 11 Feb 2021 17:59:39 +0100

Cruise tourism is rapidly growing in the last ten years worldwide and not just in North America. From a niche market it is becoming an important way to diversify the tourist supply and a stimulus for the coastal regional develoment even if sustainability is challenging. Identifying an itinerary and route, is central both for tour operators and shipowners in order to define a cruise product, and for port authorities in major and marginal places. The Caribbean area has been a precurson of the fenomenom and in this working paper it is presented the case of the West Indies' area with a specific discussion about Barbados.

Integration and communication as central issues in Dutch negotiated agreements on industrial energy efficiency

Scipedia content — Thu, 11 Feb 2021 14:40:24 +0100

This paper analyses specific aspects of the implementation of the second multi-annual agreement for energy efficiency concluded in the Netherlands with various industrial sectors for the period 2002-2010. The agreement is a follow-up on a previous negotiated agreement that was generally seen as successful. This successor aims at stretching the limits of feasible and reasonably cost-effective improvements in energy efficiency. In order to achieve this, so-called expansion themes were included that typically urge communication and tuning between companies as they exceed the level of individual companies: sustainable products, sustainable industrial estates, sustainable transport and logistics and sustainable energy. While the potential benefits are very promising, the first years of implementation mostly taught lessons on the difficulties that have to be overcome in order to achieve these. This paper will discuss the emerging obstacles and positive experiences with the implementation of the expansion theme measures. Special attention will be given to the role of the consultation groups, which supervise the implementation of the sector agreements and consist of representatives of the relevant industry sector organization, government and an advisory agency. This follow-up consultation after the agreement is concluded to play an important role in stimulating integration issues such as the coherence of the energy efficiency measures in the sector, the tuning with other environmental and energy policies of government and the mutual trust between the partners. The paper is based on the official evaluation of this negotiated agreement by the authors, which was commissioned by the Dutch ministry for economic affairs. The results are not only informative on this particular negotiated agreement, but also provide lessons on the integration and communication aspects of this policy strategy in general.

Airline emissions of carbon dioxide in the European trading system

Scipedia content — Thu, 11 Feb 2021 14:32:47 +0100

simulation model of international tourist flows is used to estimate the impact of including carbon dioxide emissions from aviation fuels in the European Trading System. The effect on global carbon dioxide emissions from international aviation is minimal: -0.01% at current permit prices, and -0.13% for the aggressive climate policy advocated by the Stern Review. In the latter case, total CO2 emissions from fossil fuels would fall by 0.004%, and total greenhouse gas emissions by 0.002%. Tourist numbers in Europe would fall by up to 0.6%, and would increase in the rest of the world. If the permits are grandparented, the airlines would receive a subsidy of €3 bln at current prices, and €40 bln for the Stern policy. If permits are auctioned, the effect on the airline industry would be minimal. Including aviation in the market for emission permits has almost no effect on the environment and may have a negative effect on the economy.

Pricing and distributed QoS control for elastic network traffic

Scipedia content — Thu, 11 Feb 2021 14:26:49 +0100

Web measurements have shown that TCP flow sizes vary over several orders of magnitude. If network resources are shared fairly, the performance of short TCP flows is seriously degraded by long flows. This motivates prioritization of short over long flows, leading to significant performance improvement for short flows, with very little degradation for long ones. By imposing an appropriate pricing structure, users can be provided with incentives so as to enforce such a prioritization in a distributed manner. We study the situation where users randomly generate elastic flows (according to a Poisson process), whose sizes have a general probability distribution. Users may choose between two service classes that share the available resources with preemptive priority for one class. We assume fair sharing within each class and use a processor-sharing model with two priority classes to evaluate flow transmission times. For given price functions, users choose the service that best fits their profile, or refrain from service (`balk') if the prices exceed the willingness to pay for both services. We show that under mild modeling assumptions, the revenue maximizing Nash equilibrium is such that short flows opt for the premium service and long flows for the low-priority service. It is optimal for medium-sized flows to balk when the offered load is relatively high. Although this allocation is the result of distributed control, aside from the flows that balk, it accomplishes precisely the prioritization of short flows which improves overall performance as mentioned above.

The impact of competition on productive efficiency in European railways

Scipedia content — Thu, 11 Feb 2021 14:13:13 +0100

This paper empirically explores the relationship between competition design and productive efficiency in the railway industry. We use Data Envelopment Analysis (DEA) to construct efficiency scores, and explain these scores, using variables reflecting institutional factors and competition design. Our results suggest that competitive tendering improves productive efficiency, which is in line with economic intuition as well as with expectations on the design of competition. We also find that free entry lowers productive efficiency. A possible explanation for this result is that free entry may disable railway operators to reap economies of density. Our final result is that more autonomy of management lowers productive efficiency. Most of the incumbent railway companies are state owned and do not face any competitive pressure. As a consequence, increased independence without sufficient competition and adequate regulation may deteriorate incentives for productive efficiency.

Mosul Air Traffic Control Tower and Navigational Aids, Mosul, Iraq

Scipedia content — Thu, 11 Feb 2021 14:12:02 +0100

: The objective of this project assessment was to provide real-time relief and reconstruction project information to interested parties in order to enable appropriate action, when warranted. Specifically, we determined whether: 1. Project results were consistent with original objectives; 2. Project components were adequately designed prior to construction or installation; 3. Construction or rehabilitation met the standards of the design; 4. The Contractor's Quality Control (CQC) plan and the U.S. Government's Quality Assurance (QA) program were adequate; and 5. Sustainability was addressed.

Function and acceptance of overtaking assistant design tested in driving simulator experiment

Scipedia content — Mon, 08 Feb 2021 12:34:40 +0100

This paper describes a driving simulator experiment to test the functioning and acceptance of a standardized overtaking assistant design. On a simulated two-lane road, 24 participants drove 15 min with and without a prototype overtaking assistant The overtaking assistant calculated the available time to perform an overtaking maneuver, taking the preceding vehicle and opposing traffic into account When it was safe to overtake, the assistant showed a green sign to participants; when it was not safe, a red sign was shown. The number of overtaking maneuvers performed in the base scenario (without assistance) did not vary significantly from that in the assistant scenario. Male participants, however, did overtake significantly more than female participants. The reported activation level of all participants had grown significantly after the run with the overtaking assistant, compared with a similar run without assistance. Participants' ratings for the usefulness of the assistant and On how satisfying it was were both low; some participants thought the assistant was too careful (shows a red sign while it is safe to overtake), and others thought it was not careful enough (shows a green sign while it is not safe to overtake). The overtaking frequency of participants was not significantly related to sensation-seeking scores, which are highly related to risky driving. It was concluded that according to the performance of the overtaking maneuvers, it is possible to design a standardized overtaking assistant However, it should be possible to improve the system to suit the different drivers' perceptions better.

On Traffic Congestion Models à la Mohring and Harwitz

Scipedia content — Mon, 08 Feb 2021 12:30:33 +0100

far as we know, the problem of existence of a maximiser of the welfare function in traffic congestion models a la Mohring and Harwitz has never been posed. In this chapter we present a mathematically rigorous existence result and take the opportunity to provide a similar variant of their self-financing result.

A Particle System for Safety Verification of Free Flight in Air Traffic

Scipedia content — Mon, 08 Feb 2021 10:09:03 +0100

Under free flight, an aircrew has both the freedom to select their trajectory and the responsibility of resolving conflicts with other aircraft. The general belief is that free flight can be made safe under low traffic conditions. Increasing traffic, however, raises safety verification issues. This problem is formulated as one of estimating for a large scale stochastic hybrid system the probability of reaching a small collision set. The huge state space prohibits the use of existing numerical approaches to solve this safety verification problem. As an alternative we study randomization methods, the simplest of which would be to run many Monte Carlo simulations with a stochastic model of free flight operations, and count the number of runs during which a collision between two or more aircraft occurs. The huge state space prohibits such a straightforward MC simulation approach. By exploiting recent particle system theory by Del Moral and co-workers, this paper develops a sequential Monte Carlo simulation approach for the estimation of collision risk in a future air traffic scenario. The working of the resulting particle system is demonstrated for an eight aircraft scenario under free flight air traffic conditions.

Global stability analysis about a congestion control scheme for networks with time delay

Scipedia content — Mon, 08 Feb 2021 10:02:22 +0100

Dimirovski, Georgi M. (Dogus Author) -- Conference full title: 2007 American Control Conference: New York, NY, USA, July 9-13, 2007 In this paper, a congestion control scheme is developed, analyzed and implemented in a noncooperative game framework. By using a network model based on fluid approximations and through a realistic modeling of queues, the existence of a unique equilibrium is established as well as its global asymptotic stability for a general network topology, where boundary effects are also taken into account. The sufficient conditions are also provided for system stability when there is a bottleneck link shared by multiple users experiencing non-negligible communication delays. The theoretic results are meaningful for communication networks. This work is supported by the National Natural Science Foundation of China under Grant 60274009 and Specialized Research Fund for the Doctoral Program of Higher Education under Grant 20020145007.

Fracture Mechanics Approach for the Assessment of a Damaged Pipeline

Scipedia content — Mon, 08 Feb 2021 09:53:22 +0100

Nowadays, the damage assessment of pipelines using fracture mechanics techniques is a state-of-the-art methodology which allows a judgement whether the pipeline is fit-for-purpose over the residual lifetime (perhaps with a reduced pressure load) or has to be repaired or replaced. However, in some circumstances, uncertainty exists about its correct application, as this may be a matter of interpretation. This paper describes the analysis of a damaged pipeline based on a fracture mechanics approach for which the straightforward application of the flaw assessment standard BS 7910 without additional consideration of individual conservatism criteria could lead to misinterpretation. The investigation was carried out for pipelines under internal overpressure. The methodology applied considered large plastic deformation introduced during a repair measure. Since the repair or a subsequent overload resulted in the damage of a pipeline and could also have caused the damage of further components, evidence had to be provided that the structure was still damage-tolerant, i.e. that cracks, the existence of which could not be excluded, would not grow to a critical dimension over the projected lifetime. The investigation comprised the following steps: In a first step, the maximum crack size which could have survived the repair measure had to be specified. In this context, the choice of conservative input data and model parameters was essential in order to avoid any underestimation of the postulated crack size and geometry. Various criteria are discussed briefly here, placing special emphasis on global and local plastic collapse criteria. Secondly, the growth of this initial crack due to the operation stress had to be quantified; this was done by applying the so-called NASGRO approach. Finally, the critical crack dimensions had to be assessed. Fracture assessments were performed using various procedures, such as BS 7910, R6 and FITNET. A parameter study was carried out to demonstrate the potential conservatism of these assessment methods.Copyright © 2007 by ASME

Sustainable transport systems: trends and policies

Scipedia content — Wed, 03 Feb 2021 21:57:13 +0100

Sustainable transport systems meet all the main principles of sustainable development: protection of public health and environmental quality, respect of the ecosystems, limitation of emissions, sustainable use of renewable resources and minimum use of non-renewable resources. In the framework of this paper, the international trends and policies concerning sustainable transport systems are presented and discussed. The international organisations, which set these policies, are also presented. More specifically, the O.E.C.D. (Organisation for Economic Cooperation and Development) guidelines towards environmentally sustainable transport are considered to be very important. In addition, the European Community moves towards the implementation of a common transport policy facing two basic issues: breaking the link between economic growth and transport growth and achieving equal growth of all transport modes. Moreover, the E.C.M.T. (European Conference of Ministers of Transport) tries to create an integrated transport system through member countries and the rest of the continent by analysing environmental, social and traffic policy issues. Furthermore, the role of World Bank is considered to be very important in obtaining transport social sustainability, as it contributes to the creation of essential transport infrastructure in developing countries. Finally, the World Business Council for Sustainable Development (W.B.C.S.D.) started in 2002 the Sustainable Mobility Project, in order to set the goals of a sustainable transport system.

New Technologies for Sustainable Urban Transport in Europe

Scipedia content — Wed, 03 Feb 2021 21:44:50 +0100

http://trb.org/; International audience; In the past few years, the European Commission has financed several projects to examine how new technologies could improve the sustainability of European cities. These technologies concern new public transportation modes such as guided buses to form high capacity networks similar to light rail but at a lower cost and better flexibility, PRT (Personal Rapid Transit) and cybercars (small urban vehicles with fully automatic driving capabilities to be used in carsharing mode, mostly as a complement to mass transport). They also concern private vehicles with technologies which could improve the efficiency of the vehicles as well as their safety (Intelligent Speed Adaptation, Adaptive Cruise .Control, Stop&Go, Lane Keeping,...) and how these new vehicles can complement mass transport in the form of car-sharing services.

Empirical-based estimation of the effect on software dependability of a technique for architecture conformance verification

Scipedia content — Wed, 03 Feb 2021 21:34:06 +0100

The High Dependability Computing Program (HDCP) project is a NASA initiative for increasing dependability of software-based systems. It researches achieving high dependability by introducing new technologies. We focus on the evaluation of the effectiveness of technologies with respect to dependability. We employ empirical evaluation methods along with evaluation testbeds. In this paper, our technology evaluation approach is described. A testbed representative of air traffic control applications is used. An experiment to evaluate a technology to for identification of architectural violations is presented.

Wake Vortex Avoidance Versus Landing Capacity

Scipedia content — Wed, 03 Feb 2021 21:25:57 +0100

Wake vortex separations are limiting factor in landing capacity of airports. The increasing air traffic forms the need for more flexible separation procedures taking into account the actual weather situation and the parameters of a more individual aircraft pairing. The present separation standards have to be investigated carefully with the aim to discover possible margins by improving the limiting constrains without adverse effects on safety. Separation reductions can also be achieved by wake vortex avoidance using prediction systems for the wake related hazard zones their development and movement. Avoiding these zones allows safe and undisturbed flight operations. The definition of a reliable and validated safety criterion is the fundamental element for the determination of hazard areas. The presented definition is based on the normalized required roll control power of the encountering aircraft. For manually controlled aircraft the limit of the acceptable normalized roll control power can be established using full flight simulator studies and in-flight simulations. Parameterization of the relevant parameters leads to the universally applicable concept of the "Simplified Hazard Area Prediction" method (SHAPe). SHAPe provides the hazard area dimensions for specific approach situations. SHAPe is part of a Wake Vortex Prediction and Monitoring System developed within the DLR project Wirbelschleppe II for creating safe and reduced landing separations. Some general results for specific approach conditions on a single runway are presented.

Early application identification

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

International audience; The automatic detection of applications associated with net-work traffic is an essential step for network security and traffic engineering. Unfortunately, simple port-based clas-sification methods are not always efficient and systematic analysis of packet payloads is too slow. Most recent re-search proposals use flow statistics to classify traffic flows once they are finished, which limit their applicability for on-line classification. In this paper, we evaluate the feasibility of application identification at the beginning of a TCP con-nection. Based on an analysis of packet traces collected on eight different networks, we find that it is possible to distin-guish the behavior of an application from the observation of the size and the direction of the first few packets of the TCP connection. We apply three techniques to cluster TCP connections: K-Means, Gaussian Mixture Model and spec-tral clustering. Resulting clusters are used together with assignment and labeling heuristics to design classifiers. We evaluate these classifiers on different packet traces. Our re-sults show that the first four packets of a TCP connection are sufficient to classify known applications with an accu-racy over 90% and to identify new applications as unknown with a probability of 60%.

Emerging Definition of Next-Generation of Aeronautical Communications

Scipedia content — Wed, 03 Feb 2021 21:17:22 +0100

viation continues to experience rapid growth. In regions such as the United States and Europe air traffic congestion is constraining operations, leading to major new efforts to develop methodologies and infrastructures to enable continued aviation growth through transformational air traffic management systems. Such a transformation requires better communications linking airborne and ground-based elements. Technologies for next-generation communications, the required capacities, frequency spectrum of operation, network inter connectivity, and global interoperability are now receiving increased attention. A number of major planning and development efforts have taken place or are in process now to define the transformed airspace of the future. These activities include government and industry led efforts in the United States and Europe, and by international organizations. This paper will review the features, approaches, and activities of several representative planning and development efforts, and identify the emerging global consensus on requirements of next generation aeronautical communications systems for air traffic control.

A SENSOR AND DATA FUSION ALGORITHM FOR ROAD GRADE ESTIMATION

Scipedia content — Wed, 03 Feb 2021 21:14:16 +0100

Emerging driver assistance systems, such as look-ahead cruise controllers for heavy duty vehicles, require high precision digital maps. This contribution presents a road grade estimation algorithm for fusion of GPS and vehicle real-time sensor data, with measurements from previous runs over the same road segment. The resulting road grade estimate is thus enhanced using measurements from additional traversals of known roads. Distributed data fusion is utilized to ensure that the storage requirement of known roads does not increase when additional measurements are processed. The implemented algorithm, which is based on extended Kalman filtering and smoothing, is described in detail. Experiments on a Scania test vehicle show the advantages and some of the challenges with the proposed approach. QC 20120216

Fog detection using airport radar

Scipedia content — Wed, 03 Feb 2021 21:02:53 +0100

Fog is a significant factor affecting the Air Traffic Control (ATC). Significant limitations of the airport capacity are due to fog that causes the reduction of the visibility (Runway Visual Range, RVR). Today METAR (Meteorological Aviation Report) and forecasts TAF (Terminal Aerodrome Forecast) are only available to estimate the visibility variations, but not to estimate the RVR. Scope of this paper is to evaluate the performance of airport radar sensors to detect the fog.

Human-centered development of advanced driver assistance systems

Scipedia content — Wed, 03 Feb 2021 20:51:23 +0100

methodological approach is presented for the human-centered development of Advanced Driver Assistance Systems (ADAS). A procedure has been developed for the objective evaluation of potential impacts of ADAS usage on traffic safety. The procedure is based on the observation and analysis of the emergence resp. avoidance of driving errors (inadequate speed, insufficient safe distance, etc.) in conjunction with the usage of ADAS. Driving errors are assumed to occur by the coaction of functional ADAS features, the situational context and (psychological) behavioral backgrounds. The applicability of the approach is examplified with a simulated ADAS.

In-Situ Multi-Mode Sensing With Embedded Piezoelectric Wafer Active Sensors for Critical Pipeline Health Monitoring

Scipedia content — Wed, 03 Feb 2021 20:34:37 +0100

Pipelines are important infrastructures in petroleum and gas industries which are vital to the national economy. They are typically subjected to corrosion inside of the pipe and there is an urgent need for the development of a cost-effective, non-excavating, in-service, permanent critical pipeline damage detection and prediction system. In this paper, we proposed an in-situ multiple mode pipeline monitoring system by utilizing permanently installed piezoelectric wafer active sensors (PWAS). As an active sensing device, PWAS can be bonded to the structure or inserted into a composite structure, operated in propagating wave mode or electromechanical impedance mode. The small size and low cost (about ∼$10 each) make it a potential and unique technology for in-situ application. Additionally, PWAS transducers can operate at a temperature as high as 260°C which is sufficient for most critical pipeline systems used in gas/petroleum industry. This system can be used during in-service period, recording and monitoring the changes, such as cracks, impedance, wall thickness, etc., of the pipelines over time. Having the real-time data available, maintenance strategies based on these data can then be developed to ensure a safe and less expensive operation of the pipeline systems. The paper will first give an intensive literature review of current pipeline corrosion detection. Then, the basic principles of applying PWAS to in-situ SHM using in-plane propagation waves and impedance measurement for damage detection are studied and developed. Next, experiments were conducted to verify the corrosion detection and thickness measurement ability of PWAS sensor network in a laboratory setting and in water pipe with flowing fluid inside as well. In addition, the potential of PWAS application for high temperature pipeline thickness monitoring was also investigated.

Scan and Solve: Acquiring the Physics of Artifacts

Scipedia content — Wed, 03 Feb 2021 20:19:36 +0100

Existing physical artifacts including sculpture, mechanical parts, and anatomical structures are commonly acquired by modern surface and volumetric scanning technologies for archival, visualization, and diagnostic purposes. While the native representations for such data are largely sufficient for visualization purposes, more advanced field simulation currently requires extensive manual conversions into simplified surface and volume meshes compatible with the traditional finite element analysis pipeline. These conversions are tedious, error-prone, and require expertise in the mesh construction process. We demonstrate automated field simulation on acquired artifacts, bypassing the difficult geometric and topological meshing problems through a meshfree paradigm based on approximate distance fields computed from the native acquired data through sampling.Copyright © 2007 by ASME

Speed in the sustainable city

Scipedia content — Wed, 03 Feb 2021 20:07:33 +0100

This paper describes how speed is the basis of life style in the sustainable city development. The concept of speed in the development of the city is so important among optimal and multidisciplinary living styles. Recently, life styles are strongly affected by the concept of speed, therefore the designing process in the scale of city planning has started to be based on that factor. This is also the case in the newly developing cities. Speed will be analyzed by the ecological statement of the city, transportation, visual perception and recognition, aesthetical needs, multifunctional usages of common spaces and the formation and orientation of city centers in the sustainable cities. Speed is the basic principle in artificial intelligence. In this study, the speed factor with some examples on sustainable developed cities and criticizing this factor by making proposals will be discussed. Ankara, the capital city of Turkey, will also be analyzed. Showing examples of speed in city life style will bring together contemporary solutions as a result of this study. The most important thing is to mention the speed factor together with regular, comfortable and peaceful relaxing spaces. The ideal combination of speed and comfort is the basic aim of the study. The term speed does not only refer to transportation or time factor but also to the multidisciplinary and flexible usage of surroundings as well as aesthetic value and visual recognition.

Dynamic grooming in IP over WDM networks: a study with realistic traffic based on GANCLES simulation package

Scipedia content — Wed, 03 Feb 2021 20:06:43 +0100

Dynamic grooming capabilities lies at the hearth of many envisaged scenarios for IP over Optical networks, but studies on its performance are still in their infancy. This work addresses two fundamental aspects of the problem. First of all it presents a novel tool for the study of IP over Optical networks. The tool, freely available on-line, is a network level simulator named GANCLES that includes several innovative features allowing the study of realistic scenarios in IP over Optical networking, making it an ideal tool for Traffic Engineering purposes. GANCLES architecture enables the simulation of dynamic traffic grooming on top of a realistic network model that correctly describes the logical interaction between the optical and the IP layer, i.e., the mutual relationship between routing algorithms and lightpath assignment procedures at the optical layer and routing at the IP layer. Adding or removing lightpaths changes the logical IP topology, which affects IP routing and traffic patterns. The simulator allows for the description of Overlay, Augmented or Peer IP over Optical architectures, depending on the amount of information shared between the IP and optical domain. Second it analyzes and discusses several performance indices and aspects of different grooming policies in the IPO Overlay model, using different traffic models, some of them including elasticity of best effort traffic. Both regular and mesh topolo- gies are analyzed, and results clearly show that the correct evaluation of dynamic grooming policies in IPO networks requires a sophisticated level of modeling, since simplistic assumptions like Poisson traffic, or the incorrect representation of the interaction of IP and Optical control planes, may induce misleading results.

REGULATION OF THE BIMODAL TRAFFIC

Scipedia content — Wed, 03 Feb 2021 19:53:32 +0100

International audience; We consider an urban network with two traffic modes. We control the traffic lights in order to free the roads used by the public transport vehicles. To do this, we solve a flow assignement problem, from which we deduce an ideal distribution of private vehicles. Then using traffic lights, we design a regulator maintaining the car distributions in the roads around the ideal trajectory. This regulator is obtained by solving a linear quadratic problem. The result is a global feedback on the car numbers in the roads. We show the robustness of the obtained control. We compare the obtained results with those given by Bhouri and Lotito (2005).

Requirements for a standardized flow storage solution

Scipedia content — Wed, 03 Feb 2021 19:46:13 +0100

IP flow data provides input for accounting, traffic engineering and security applications. The storage of flow data is required to allow off-line processing, archiving, and sharing of traffic traces. Currently this is achieved with a variety of proprietary solutions, which results in a variety of formats as input for flow processing tools and hinders data sharing and tool reusability. In this paper we analyze the requirements for a standard file format for storing flow data, and propose using the upcoming standard IP flow information export protocol (IPFIX) as a basis for its design

Speech silicon AM: an FPGA-based acoustic modeling pipeline for hidden Markov model based speech recognition

Scipedia content — Wed, 03 Feb 2021 19:44:01 +0100

This paper presents the design of a FPGA-based hardware co-processor, based on the SPHINX 3 speech recognition engine from CMU; capable of performing acoustic modeling (AM) for medium sized vocabularies in real-time. By creating an input-driven pipeline for performing the calculations, we were able to maximize the throughput of the system while simultaneously minimizing the number of pipeline stalls. Use advanced placement techniques enabled post place-and-route speeds even greater than those necessary for real-time operation while operating at maximum workload. Further, by using input control vectors all FSMs were removed from the design, greatly increasing the flexibility of the design. These results combined with the ability to reprogram the system for different recognition tasks serve to create a system capable of in a vast array of environments. Synthesis to both Xilinx Virtex 4 and Spartan 3 FPGAs helps to further characterize the flexibility of the architecture.

Autostereoscopic displays for visualization of urban environments

Scipedia content — Wed, 03 Feb 2021 19:39:22 +0100

Two approaches in designing autostereoscopic displays capable of providing collaborative viewing of real time 3D scenery will be presented and discussed. Both techniques provide multiscopic "look around" capabilities and are applicable for situation rooms or mobile command centers. In particular, we discuss a prospective use of these displays for interactive visualization of detailed three-dimensional models of urban areas, and the specific demands associated with managing and rendering large volumes of highly detailed information. Latest advances in scanning, survey and registration in urban areas have provided a wealth of detailed three-dimensional data and imagery. Recent events have shown a severe need and demand for systems capable in a high-level 3D visualization upon homeland security posed by terrorist actions and natural disasters within urban areas, as well as for military operations in urban terrain (MOUT). The capacity to visualize sightlines, airflow, flooding, and traffic in real time 3D within dense urban environments is increasingly critical for military and civilian authorities, as well as urban planners and city managers. Development of a high-quality 3D imaging systems is critical also for such areas as medical data imaging, gaming industry, mechanical design and rapid prototyping.

Traffic modelling validation of advanced driver assistance systems

Scipedia content — Wed, 03 Feb 2021 19:36:46 +0100

This paper presents a microscopic traffic model for the validation of advanced driver assistance systems. This model describes single-lane traffic and is calibrated with data from a field operational test. To illustrate the use of the model, a Monte Carlo simulation of single-lane traffic scenarios is executed with application to cooperative adaptive cruise control system. The model is then validated by comparing the simulation results with data gathered from test drives. ©2007 IEEE.

Sustainable urban transport development : a modelling approach

Scipedia content — Wed, 03 Feb 2021 19:20:36 +0100

This paper describes how current transport systems and transport planning methods and models are not necessarily compatible with the requirements of sustainable transport development. Adequate transport systems can only be obtained by the use of a sustainable transport paradigm and an accompanying analytical framework. Therefore, this paper presents a theoretical framework, which is based on a paradigm for sustainable transport development. This paradigm advocates a comprehensive decision-making that anticipates and manages scarce resource use, including environment and finance, while developing the transport system in terms of quality of access and/or person throughput. Furthermore, a simplified version of a dynamic optimization model that can assist in the complex and political decision-making process with respect to sustainable transport development is introduced, based on the conceptualization and characterization of the sustainable urban transport development problem as a constrained optimization problem. Based on Pontryagin’s Maximum Principle, the dynamic model reveals control paths for achieving a sustainable and developed transport system. The model in its present form can be applied directly to strategic networks of limited numbers of (aggregated) zones and (aggregated) links.

Measuring indirect economic impacts arising from transportation investment by a SCGE model

Scipedia content — Wed, 03 Feb 2021 19:13:35 +0100

The objective of this paper is threefold. First, the paper presents a regionally disaggregated CGE model, in which “a region” is defined as a sub-area or a zone within a country or a particular area and the spatial dimension of the economy is explicitly included. In such a spatial CGE model, the estimation of interzonal trade flows has a critically important role: with the presence of shipping cost, suppliers would impose the cost on their sales prices for covering that cost, which changes the product shipping pattern for each type of commodity or service and thereby affects the efficiency of regional economies. Second, the paper proposes a new approach that links travel delay (attributable to congestion) and business productivity. Transportation investment changes the relative economic advantage that each region has through the changes in accessibility to material/service markets and labor markets. To estimate the rate return on transportation investment to reduce congestion, it is necessary to estimate how the specialized transportation policy to reduce congestion has economic impacts on regional economies. Finally, the paper explores the values of economic impacts measured by an application of the model to Tokai ring road project, which is an on-going project to build an expressway of about 160km in length connecting annularly many cities in Tokai region.

Historical centers: sustainable economic spaces, management for sustainable projects

Scipedia content — Wed, 03 Feb 2021 19:12:16 +0100

This paper describes how historical centers have the potential to unite, among other things, different cultures, architectonic and intangible patrimony, goods and services formally and informally produced, financial capitals, different levels of salaries and rents, real estate investment and patrimonial renovation projects. This paper studies, in the context of equity and sustainability objectives of city management, the degree of economic “factor” insertion in diverse areas and activities in historical centers. Methodologically, the paper presents the main factors and issues that constitute challenges for sustainable urban management and proposes a necessary strategy for public policy coordination and investment in city centers. The main objective is to delineate a sustainable city urban management in terms of its elements, parameters and instruments. This strategy responds to public sector demands regarding management options that could balance the growth and equity in the historical centers of cities. Some questions that arise in this context are: is there a relation between the economic dimension of historical centers and the social equity and inclusiveness in urban society in the framework of sustainability? Is the search for equity in Latin America and the Caribbean cities the economic management approach in historical centers? In management terms, how do institutions deal with the concepts of center and centrality? The discussion and analysis of the economic dimension of historical centers in Latin America and the Caribbean and their corresponding potential for urban development and equity will be synthesized based on tendencies, and will build a framework for sustainable urban projects for historical centers in this region.

Aligning Technology, Procedures, Operations, Programs, and People to Grow Capacity

Scipedia content — Wed, 03 Feb 2021 19:09:13 +0100

The Federal Aviation Administration forecasts that by 2015 more than 1 billion people each year will take to the skies in the United States, nearly a third more than today's number. Central to the FAA's efforts to prepare for the future is the operational evolution plan (OEP), which seeks to increase the capacity and efficiency of the National Airspace System by focusing on relieving congestion at 35 key airports. Through the OEP, the FAA commits to implementing a set of credible initiatives that focus the agency and the aviation community on solutions for the next 10 years. The goal has been to increase the effective capacity of the NAS by approximately 30 percent by 2011, and the OEP is close to declaring success today. The plan is also the vital link between the present state of aviation and the vision of a totally transformed air transportation that is being developed by the multi-agency joint planning and development office.

Scheduling Aircraft Landings Under Constrained Position Shifting

Scipedia content — Wed, 03 Feb 2021 18:31:20 +0100

Optimal scheduling of airport runway operations can play an important role in improving the safety and efficiency of the National Airspace System (NAS). Methods that compute the optimal landing sequence and landing times of aircraft must accommodate practical issues that affect the implementation of the schedule. One such practical consideration, known as Constrained Position Shifting (CPS), is the restriction that each aircraft must land within a pre-specified number of positions of its place in the First-Come-First-Served (FCFS) sequence. We consider the problem of scheduling landings of aircraft in a CPS environment in order to maximize runway throughput (minimize the completion time of the landing sequence), subject to operational constraints such as FAA-specified minimum inter-arrival spacing restrictions, precedence relationships among aircraft that arise either from airline preferences or air traffic control procedures that prevent overtaking, and time windows (representing possible control actions) during which each aircraft landing can occur. We present a Dynamic Programming-based approach that scales linearly in the number of aircraft, and describe our computational experience with a prototype implementation on realistic data for Denver International Airport.

Cooperative Cognitive Automobiles

Scipedia content — Wed, 03 Feb 2021 18:28:48 +0100

Safety requirements are among the most ambitious challenges for autonomous guidance and control of automobiles. A human-like understanding of the surrounding traffic scene is a key element to fulfill these requirements, but is a still missing capability of today's intelligent vehicles. Few recent proposals for driver assistance systems approach this issue with methods from the AI research to allow for a reasonable situation evaluation and behavior generation. While the methods proposed in this contribution are lend from cognition in order to mimic human capabilities, we argue that in the long term automated cooperation among traffic participants bears the potential to improve traffic efficiency and safety beyond the level attainable by human drivers. Both issues are major objectives of the Transregional Collaborative Research Centre 28 'cognitive automobiles,' TCRC28 that is outlined in the paper. Within this project the partners focus on systematic and interdisciplinary research on machine cognition of mobile systems as the basis for a scientific theory of automated machine behavior.

Improving ETMS Default Route Assignment

Scipedia content — Wed, 03 Feb 2021 18:26:17 +0100

nalysis was conducted to recommend improvements in selection of default routes, which FAA's enhanced traffic management system (ETMS) uses to project airspace sector demands before airlines file flight plans. The problem is that current ETMS default route predictions are poor for long-haul flights. This makes it difficult for air traffic managers to plan traffic flows. In this paper, various methods of selecting default routes for ETMS are presented and evaluated. The best of them are recommended for implementation. The recommendations are planned to be implemented in future ETMS releases and are predicted to noticeably improve default route selection.

Rapid development of high performance floating-point pipelines for scientific simulation

Scipedia content — Wed, 03 Feb 2021 18:13:30 +0100

In the last years, FPGAs became capable of performing complex floating-point based calculations. For many applications, highly parallel calculation units can be implemented which deliver a better performance than general-purpose processors. This paper focuses on applications where the calculations can be done in a pipeline, as it is often the case for simulations. A framework for rapid design of such calculation pipelines is described. The central part is a Perl based code generator, which automatically assembles floating-point operators into synthesizable hardware description code where the generator is directed by a pipeline description file. The framework is supplemented by various floating-point operators and support modules, which allow generating ready-to-use pipelines. The code generator dramatically reduces development time and produces high-quality results. The performance of the framework is demonstrated by the implementation of pipelines for gravitational forces and hydrodynamics.

Formalizing the incremental design and verification process of a pipelined protocol converter

Scipedia content — Wed, 03 Feb 2021 18:06:56 +0100

International audience; This work studies the relations between pipeline architectures and their specification expressed in CTL. We propose a method to build pipeline structures incrementally from a simple one (already verified) to a more complex one. Moreover, we show how each increment can be integrated in a CTL specification. We define increments to model treatment delay and treatment abortion of a pipeline flow, and we formalize the composition of the different increments. In order to represent the increments added to an architecture, we derive a set of CTL formulae transformations. Finally we model a control flow of a protocol converter by composition of these increments. We show how CTL properties of the complex architecture are built by applying automatic transformations on the set of CTL properties of the simplest architecture.

A path-following preview controller for autonomous air vehicles

Scipedia content — Wed, 03 Feb 2021 18:00:55 +0100

n operating concept and a laboratory analysis methodology were developed and tested to examine how four-dimensional trajectory analysis methods could support higher levels of automation for separation assurance in the National Airspace System. Real-time simulations were conducted in which a human controller generated conflict resolution trajectories using an automated trial planning resolution function, but only in response to conflicts detected and displayed by an automatic conflict detection function. Objective metrics were developed to compare aircraft separation characteristics and flying time efficiency under automated operations to that of today’s operations using common airspace and traffic scenarios. Simulations were based on recorded air traffic data from Fort Worth and Cleveland Centers and conducted using today’s and nearly two-times today’s traffic levels. Results suggest that a single controller using trajectory-based automation and data link communication of control clearances to aircraft could manage substantially more traffic than they do now with improved route efficiency while maintaining separation. The simulation and analysis capability provides a basis for further analysis of semi-automated, or fully automated, separation assurance concepts.

Simultaneous Statistical Delay and Slew Optimization for Interconnect Pipelines

Scipedia content — Wed, 03 Feb 2021 17:59:51 +0100

Process variation has become a major concern in the design of many nanometer circuits, including interconnect pipelines. This paper develops closed-form models to predict the delay distribution of an interconnect pipeline stage and the slew distributions of all the nets in the circuit. Also, a buffer sizing and re-placement algorithm is presented to minimize the area of interconnect pipelines while meeting the delay and slew constraints. Experiments show that ignoring location dependent variation can cause a timing yield loss of 8.8% in a delay limited circuit, and the area can be improved by over 10% when the location dependent variation and residual random variation are understood and separated. Furthermore, under equivalent area, an interconnect pipeline optimized with only sizing changes may violate the slew constraint on over 50% of the nets, so location change is needed to best optimize these circuits.

KiwiGrow™: a community and environmental health framework for sustainable development

Scipedia content — Wed, 03 Feb 2021 17:53:09 +0100

n easily understood community and environmental health framework was devised in this paper in order to provide the basis for a comprehensive assessment of the water and sanitary services for Waitakere City Council, Auckland, New Zealand. The framework, now known as KiwiGrow™ consists of a matrix that was obtained by considering seven key qualities of healthy ecosystems separately in social, economic, environmental and cultural contexts. A healthy ecosystem is supposed to be nurturing, supportive, stable, contributing, responsive, directed, and adaptive. Each of these terms takes on consistent but slightly different meanings within each of the four major contexts, providing an easily communicated and holistic framework for sustainable development. If adopted as a “mantra” within the community, it could have far reaching applications to the management of entities ranging from pocket wetlands and neighborhoods to entire regions. KiwiGrow™ can also underpin a new generation of easily understood, high impact “quadruple bottom line” sustainability reporting.

3D airspace sectoring by evolutionary computation

Scipedia content — Wed, 03 Feb 2021 17:52:44 +0100

International audience; This paper presents a new method for 3D cutting of geometrical space with application to airspace sectoring. This problem comes from the air traffic management but the proposed method may be applied to many other areas. This problem consists in finding a cutting of a 3D volume into sectors in order to balance the weights of sectors and which minimizes the flow cut on sector boundaries. A mathematical modeling of this problem has been proposed for which state space,objective functions and constraints are defined. The complexity of such problem being NP Hard,stochastic optimization have been used to address it. An Evolutionary Algorithm has been implemented for which chromosome coding and operators have been developed. Realistic problem instances have been tested on this algorithm for which the solutions produced fulfill our objective.

B-VHF - Selected Simulation Results and Assessment

Scipedia content — Wed, 03 Feb 2021 17:51:25 +0100

B-VHF is a proposal for a future aeronautical communication system in the VHF band based on an overlay concept, i.e. during the transition phase the B-VHF system shares the same frequency band with legacy VHF systems without interfering with them. In this paper, the overlay concept is evaluated by simulations of the physical and higher layers. Simulation results show that the B-VHF overlay system works in presence of interference from legacy VHF systems. The protocol is designed to allow using the available resources very efficiently and to provide voice and data services with the required quality of service.

Dynamic Modeling of Internet Traffic for Intrusion Detection

Scipedia content — Wed, 03 Feb 2021 17:49:01 +0100

/" "p"Computer network traffic is analyzed via mutual information techniques, implemented using linear and nonlinear canonical correlation analyses, with the specific objective of detecting UDP flooding attacks. NS simulation of HTTP, FTP, and CBR traffic shows that flooding attacks are accompanied by a change of mutual information, either at the link being flooded or at another upstream or downstream link. This observation appears to be topology independent, as the technique is demonstrated on the so-called parking-lot topology, random 50-node topology, and 100-node transit-stub topology. This technique is also employed to detect UDP flooding with low false alarm rate on a backbone link. These results indicate that a change in mutual information provides a useful detection criterion when no other signature of the attack is available.

A comparative study of single-layer and multi-layer traffic engineering approaches on transparent optical networks

Scipedia content — Wed, 03 Feb 2021 17:40:54 +0100

Date of Conference: 1-5 July 2007 Conference Name: 9th International Conference on Transparent Optical Networks, ICTON 2007 This paper comparatively studies single-layer and multi-layer traffic engineering strategies on an IP/MPLS/WDM network. These strategies are evaluated and compared in two different scenarios. In the first scenario, the strategies make use of statistical information on the traffic patterns. In the second scenario, the traffic engineering decisions are based on the instantaneous traffic information only. The performance and benefits of both approaches are discussed based on simulations considering both throughput and network resource usage. © 2007 IEEE.

Central East Pacific Flight Routing

Scipedia content — Wed, 03 Feb 2021 17:26:52 +0100

In this article the authors discuss possible advantages over user-preferred routing experienced by fixed Central East Pacific (CEP) routes for air traffic control (ATC) applications. Specifically, the authors assessed the time savings, fuel savings, and airspace complexity implications that might result in transitioning from structured CEP routes to user-preferred routes. A dynamic programming algorithm using wind-optimization and minimum travel-time was developed and tested using wind-optimal and nominal simulation routing for a period of five days. The complexity measures employed include two measures of time-varying airspace complexity, fuel savings, and time savings. Through the simulation testing, researchers found a high level of density variation. Correlations between wind-optimal routing and nominal routing were found with variations in flight density in time-varying complexity measures. Benefits from the proposed algorithm for this route include time savings of 4.8-9.9 minutes per flight and 192-347 kg fuel per flight.

Rail deregulation in Europe, and prospects of air rail integration

Scipedia content — Wed, 03 Feb 2021 17:25:56 +0100

International audience; We are looking into the evolution of cooperation and competition between airlines and railroads, in the context of rail deregulation, with the tools provided by network economics. After looking at the progress of rail deregulation in Europe, we describe the situation of air and rail in terms of cooperation (intermodality). We then examine the current strategies of airlines and railroads considered as networks industries. In this light, we then analyse their possible strategies in a context of rail deregulation, with a complete opening of rail markets. We conclude by assessing the possibility of emergence of multi-modal network operators.

External transport pricing and modal choice: evidence from a Paris case study

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

Many European studies have shown that prices paid by transport users do not cover the real cost of moving. Costs related to pollution, congestion, noise and accidents are only partially covered. External costs caused by travel using public transport are lower than using cars. This deduction has pushed many authorities to encourage the transfer of passenger traffic from private car to public transport. The purpose of this study is to estimate the impact of some external costs pricing on the commuters’ modal split between car and public transport. This paper will use two pricing schemes: exogenous toll and marginal social cost pricing. To put it into practice, the paper estimate Multinomial Logit (ML). On the other hand, ML has a critical assumption related to the Independence from Irrelevant Alternatives. In order to relax this property the paper will recast the model as a nested structure. Price scenarios through a Nested logit model are simulated. Therefore by estimating the choice probabilities, the paper will calculate the welfare gains. The aim results of this paper indicate that prices paid by transport users must reflect marginal external costs (mec). For the exogenous toll, the welfare gains are relatively small. This finding is not surprising because taxes are below the mec. For the marginal social cost pricing, all taxes are corrected so as to equal the mec; the welfare gain is estimated at 0.61%. It is also evident that a part of the reduction in car use is due to its substitution for public transport.

An Architecture for Situation-Aware Driver Assistance Systems

Scipedia content — Wed, 03 Feb 2021 17:00:28 +0100

Current Driver Assistance Systems merely use a minimum set of information. By using additional information of the environment hazardous situations can be detected earlier, more reliably and with a higher precision. This situational information has a significant impact not only on the hazard detection, but also on other modules such as the Human-Machine-Interface or knowledge distribution between vehicles over suitable networks. For a number of reasons situational information is inherently subject to uncertainty. This may be handled by the use of Dynamic Bayesian Networks, which we suggest can be used to represent these dynamic complex systems. The objective of this paper is to provide an architecture for Driver Assistance Systems that is aware of uncertain situational information in order to prevent accidents and reduce the number of traffic fatalities. It introduces the concepts of Utility-based Knowledge Exchange based on the consideration of other partners’ knowledge, the amount of inference that has taken place to identify a situation and current network conditions. Furthermore, we suggest a representation of Hazard Descriptions using Bayesian Network fragments.

Link Between the Joint Diagonalisation of Symmetrical Cubes and PARAFAC: An Application to Secondary Surveillance Radar

Scipedia content — Wed, 03 Feb 2021 16:51:49 +0100

The Manchester decoding algorithm (MDA) presented in N. Petrochilos and A.J. van der Veen (2004) succeeds in separating secondary surveillance radar (SSR) replies impinging on an array. The final step of the MDA consist of jointly diagonalizing a collection of several symmetric cubes by a sub-optimal technique. In this article, we demonstrate that it is in fact a PARAFAC problem with an almost symmetric solution. Furthermore, comparisons with other algorithms are carried out, with the help of computer simulation

SPR Method : Rehabilitation Technologies to Revive Decrepit Pipelines

Scipedia content — Wed, 03 Feb 2021 16:45:01 +0100

In the SPR (Sewage Pipe Renewal) method, a rigid PVC liner is formed inside an existing pipe by using a specially designed winding machine that is placed inside the existing pipe. A rigid PVC profile strip is fed through a manhole entrance above ground, and the winding machine is used to wind and interlock the profiles together to form a liner. Rehabilitation technologies are needed that can cope with various existing installation site conditions; i.e. long or curved pipelines, with round, square or horseshoe shaped crossections. Under such circumstances, we have developed a new technology to form the PVC liner in which self running winding machenes travel around a frame that is set inside the existing pipeline, and which is made to conform to the interior cross sectional shape of the pipe.

Path Stretching and Tracking for Time-Based Aircraft Spacing at Meter Fix

Scipedia content — Wed, 03 Feb 2021 16:42:31 +0100

International audience; The delegation to the flight crew of some tasks currently performed by air traffic controllers provides new perspectives potentially to increase air traffic control efficiency. More specifically, the task of establishing properly spaced landing sequences is very demanding in heavy traffic conditions for the air traffic controllers in charge of the terminal maneuvering area. Automatic merging operations could relieve air traffic controllers of providing time-consuming radar-vectoring instructions and could provide more optimal flight profiles to the aircraft. With these new tasks being transferred to the flight crew some automation in order to limit the workload is required. The outcomes of this paper are twofold: firstly it presents a technique to generate path stretching with length and endpoint constraints and secondly it provides a nonlinear control law to track the reference trajectory. The reference trajectory is used to stretch the path of a trailing aircraft in order to delay its arrival on a meter fix. The purpose of the nonlinear control law based on feedback linearization is to enable the trailing aircraft to follow the reference trajectory. This communication treats level flight, but wind is considered. The design is followed by two illustrative examples which show the effectiveness of the proposed approach.

Towards Performance Requirements for Airborne Spacing- A Sensitivity Analysis of Spacing Accuracy

Scipedia content — Wed, 03 Feb 2021 16:33:31 +0100

The objective of this air traffic management study was to analyse the trade-off between time spacing accuracy and corresponding control effort in a potential future application of airborne separation assistance systems (ASAS). The ASAS application airborne spacing sequencing and merging was simulated in fast-time. Lead aircraft speed profiles were generated using complete descent profiles from real-time experiments. For validation purposes, three metrics were derived from real-time experiments: time spacing error (accuracy), frequency of speed adjustments (control activity), and cumulative airspeed variations (control cost). Four experimental parameters were varied: automatic and manual speed control, spacing dead-zone, guidance law dynamics time constant and initial time spacing error. A trade-off between the metrics was found for a sequence of two aircraft by comparing their variation with the experimental parameters. Corresponding ‘minimum’ performance requirements for the metrics are proposed: (i) time spacing error - mean less than 1.5s with 0.5 to 85% of the values between -4 and +4s (automatic mode), and mean less than 2.5s with 0.5 to 85% of the values between -6 and +6s (manual mode), (ii) frequency of speed adjustments - mean less than 1 action per minute (manual mode) and (iii) cumulative airspeed variations - mean less than 10 knots (automatic and manual modes). These requirements form a basis for investigating sequences longer than two aircraft where chain propagation effects may lead to additional constraints.

AntSearch: An Ant Search Algorithm in Unstructured Peer-to-Peer Networks

Scipedia content — Wed, 03 Feb 2021 16:31:28 +0100

The most prevalent peer-to-peer (P2P) application till today is file sharing, and unstructured P2P networks can support inherent heterogeneity of peers, are highly resilient to peers' failures, and incur low overhead at peer arrivals and departures. Dynamic querying (DQ) is a new flooding technique which could estimate a proper time-to-live (TTL) value for a query flooding by estimating the popularity of the searched files, and retrieve sufficient results under controlled flooding range for reducing network traffic. Recent researches show that a large amount of peers in the P2P file sharing system are the free-riders, and queries are seldom hit by those peers. The free-riding problem causes a large amount of redundant messages in the DQ-like search algorithm. In this paper, we proposed a new search algorithm, called "AntSearch," to solve the problem. In AntSearch, each peer maintains its hit rate of previous queries, and records a list of pheromone values of its immediate neighbors. Based on the pheromone values, a query is only flooded to those peers which are not likely to be the free-riders. Our simulation results show that, compared with DQ and its enhanced algorithm DQ+, the AntSearch algorithm averagely reduces 50% network traffic at almost the same search latency as DQ+, while retrieving sufficient results for a query with a given required number of results.

Twin Cities truck traffic management strategies

Scipedia content — Wed, 03 Feb 2021 16:27:33 +0100

This paper describes how heavy commercial vehicles have significantly different vehicle performance characteristics than light vehicles, and generally have different trip patterns (both spatially and temporally). As a result, the special needs of heavy commercials are not always met by standard roadway and facility designs, traveler information, and roadway operating/management process. The purpose of the research described in this paper was to investigate the traffic management strategies that could be applied in the Twin Cities metropolitan area of Minneapolis/St, Paul, MN, in order to improve truck traffic transportation within the area, and to develop implementation plans for applying the strategies. All the strategies recommended are relatively low cost, represent marginal improvements, can be feasibly accomplished within a few years, and require no special financial appropriation. The investigators were surprised that the most promising strategies involved only low-cost or no-cost policy change as opposed to high capital costs infrastructure or design improvements.

Airbag for the closing of pipelines on explosions and leakages

Scipedia content — Tue, 02 Feb 2021 08:45:19 +0100

This paper is a result of international effort aimed at the construction of a device for quick closing of pipelines in the case of explosion propagation and/or chemical leakage. Such a problem exists in industries where flammable substances are transported by pipelines. The basic solution principle was the idea to use airbags similar to those utilized in cars. Two pipeline applications were taken into consideration: a low-pressure module able to suppress explosion propagation and a high-pressure module to stop leakages from, e.g. natural gas pipeline capable to be used for duct diameters up to 0.6 m, pressures up to 5 MPa and reaction times of 50 ms. It was necessary to construct a new airbag, capable of withstanding up to 10 bar pressure. The choice of material was critical to ensure sufficient strength and chemical resistance while retaining impermeability. CFD modeling of the bag deployment into a pipe flow and analysis of the bag shapes was also completed. Two gas generators were constructed and tested with novel propellant materials. Different airbag models were tested to evaluate their effectiveness. Risk analysis approach was applied to evaluate the safety and economic benefits of the new technology in different fields of application.

Integrating Aircraft Flows in the Terminal Area with no Radar Vectoring

Scipedia content — Tue, 02 Feb 2021 08:17:05 +0100

This paper reports on a series of small-scale experiments conducted with air traffic controllers. The objective was to assess benefits and limits of a method to integrate aircraft flows in the terminal area. The principle is to achieve the aircraft sequence on a point (with conventional direct-to instructions) using predefined legs at iso-distance to this point for path shortening or stretching. Open loop radar vectors (heading instructions) were no longer used and aircraft remained on lateral navigation mode. The method was found feasible, comfortable, safe and accurate although less flexible than today. Predictability was increased, workload and communications were reduced. The inter-aircraft spacing on final was as accurate as today, while descent profiles were improved. The flow of traffic was more orderly with a contained and predefined dispersion of trajectories. All these elements should contribute to improving safety.

A Fast and Efficient Route Finding Method for Car Navigation Systems with Neural Networks

Scipedia content — Tue, 02 Feb 2021 08:15:54 +0100

In this paper we have proposed a new route finding method for car navigation systems meanwhile, have utilized learning power and high speed of neural networks in our proposed method. Our suggested procedures miss most of limitations on standard algorithms planned for all these system

Sustainable urban transport in Lithuania: influence of land use and socio-economic development

Scipedia content — Tue, 02 Feb 2021 08:07:49 +0100

For sustainable urban transport planning, instead of the direct prediction of transport demand based on tendency prognosis, the connection between influential factors and demand is modeled in this paper. The prognosis of influential factors used takes into account the reasons behind public transport demand. Practical realization of such a task demands a detailed analysis of the influence of these factors on the transport demand presented. The influence of factors such as the development of economics, level of motorization, inhabitant density and land use on the transport demand is evaluated. Analysis is performed on the basis of the theoretical expressions of inhabitant mobility and the information of practical investigations.

Solving Probabilistic Airspace Congestion: Preliminary Benefits Analysis

Scipedia content — Tue, 02 Feb 2021 07:58:54 +0100

In the U.S. National Airspace System (NAS) a function called traffic flow management (TFM) seeks a balance between resource capacities and the demands placed upon them by air traffic. In general, capacity cannot be manipulated, and it is necessary for demand to be altered to meet a reduced capacity. Typically, demand can be altered in time (via delay, i.e., slowing flights so that the number per unit time is reduced) or space (via rerouting, when specific airspace sector capacity is reduced, e.g., during severe en route weather). This paper discusses the use of probability modeling for assessing airspace capacity, and discusses comparison of three techniques for generating solutions to the problem of demand allocation during reduced airspace capacity caused by severe en route weather.

Urban transport system benchmarking

Scipedia content — Tue, 02 Feb 2021 07:47:55 +0100

This paper elaborates on benchmarking as a means for facilitating policy makers during the decision making process aimed at improving urban transport system performances. The proposed benchmark contains five critical success factors: (1) accessibility; (2) cost of transport; (3) safety; (4) environmental pollution; and (5) congestion. The benchmark result provides policy-makers with figures that describe the position of each aspect of an urban transport system of a city or region compared with that of other cities or regions. In a case study the proposed benchmarking approach is tested by analyzing the performances of the urban transport systems of the two cities Berlin and Rotterdam. In making policies for urban transport systems, there are many aspects that should be taken into account, not only from government perspective (investment and operational cost), customer perspective (accessibility, safety, congestion and cost of transport), but also from sustainable development perspective (environment). These aspects should be added as additional criteria for the development of a sound transport policy. Aspects that have low performance should be enhanced in the future, while the “best in class” aspects, can be used by regions that perform less. The first results showed that benchmarking urban transport systems can give policy makers an improved insight in the performances in respect to that of other cities and indirect advice on future investments. In order to use the proposed approach more test benchmarks are necessary.

Modeling Time-Dependent Tolls under Transport, Land Use, and Environment Considerations

Scipedia content — Tue, 02 Feb 2021 07:42:28 +0100

Recently, there has been a resurgence of interest in road pricing. Along with the popularity of the concept of sustainability, transport planners no longer ignore the environmental considerations when analyzing and designing a transportation system for pricing. This paper develops an analytical model to determine the optimal tolls over time to control the traffic emissions while capturing the land-use transport interaction. To illustrate the effect of tolls on the transportation system with land use and environmental considerations, a numerical study is performed. The results show that the implementation of tolls can reduce the overall traffic emissions, generate more transit system revenue and alter the travelers’ choice of modes, routes, living and working locations.

Sustainable transport system using renewable energy and efficient electric vehicles

Scipedia content — Tue, 02 Feb 2021 07:40:11 +0100

This paper describes the most environmentally friendly model for a transportation system, based on the available technology, could involve the use of zero emission electric vehicles that are combined with a highly efficient electrical drive system and an electrical storage system that can be replenished using renewable energy sources. The paper presents the overall strategy of a transportation system. It presents a model for the dynamics and drive of an electric vehicle, describes a novel approach for optimizing the efficiency of induction motor drives, reports on practical evaluations of an electric vehicle drive under controlled laboratory conditions and relates the application of renewable sources of electrical energy to the transport sector. The results demonstrate the feasibility of the use of efficient electrical drive systems coupled with renewable energy sources as a strategy for a zero emission transportation system.

CAM04-1: Admission control in self aware networks

Scipedia content — Tue, 02 Feb 2021 07:38:10 +0100

The worldwide growth in broadband access and multimedia traffic has led to an increasing need for Quality- of-Service (QoS) in networks. Real time network applications require a stable, reliable, and predictable network that will guarantee packet delivery under QoS constraints. Network self- awareness through on-line measurement and adaptivity in response to user needs is one way to advance user QoS when overall network conditions can change, while admission control (AC) is an approach that has been commonly used to reduce traffic congestion and to satisfy users' QoS requests. The purpose of this paper is to describe a novel measurement-based admission control algorithm which bases its decision on different QoS metrics that users can specify. The self-observation and self- awareness capabilities of the network are exploited to collect data that allows an AC algorithm to decide whether to admit users based on their QoS needs, and the QoS impact they will have on other users. The approach we propose finds whether feasible paths exist for the projected incoming traffic, and estimates the impact that the newly accepted traffic will have on the QoS of pre-existing connections. The AC decision is then taken based on the outcome of this analysis.

Preferred service quality in domestic airlines: South Africa versus Italy

Scipedia content — Tue, 02 Feb 2021 07:20:25 +0100

This paper investigates the level of importance of pre selected service quality variables of local passengers with regard to the services rendered to them when making use of domestic airlines in South Africa and Italy. This information is relevant for management decision making with regard to maintaining a competitive position in a highly competitive air transport industry. The need for the study resulted from a worldwide tendency of economic downturn and the public caution on air travel, which is caused by the capacity of the airline industry to exceed demand substantially. The aim of this paper is therefore to identify the most important variables that travellers in South Africa and Italy value and expect from a domestic airline service provider. The outcome of the research may offer better understanding with regard to service quality management in the airline industry in developing countries and developed countries and could result in developing competitive strategies based upon quality concepts.

Generic architecture for MPLS-TE routing

Scipedia content — Tue, 02 Feb 2021 07:15:53 +0100

International audience; This paper deals with Multi-Protocol Label Switching-Traffic Engineering (MPLS-TE) routing systems which offer key traffic engineering features, including optimization of resources utilization, Quality-of-Service (QoS) and fast recovery. Numerous MPLS-TE routing systems have been defined in the past with their own advantages and drawbacks. This paper proposes a generic architecture for MPLS-TE routing system, with the main objective of helping in classification, analysis and improvement of these systems or the design of new systems. This architecture includes main functions that can be required in an MPLS-TE routing system. These functions and their interactions are described. Various approaches and options for the implementation and the distribution of these functions in network elements are qualitatively discussed.

A Routing Architecture for MPLS-TE Networks

Scipedia content — Tue, 02 Feb 2021 06:21:12 +0100

International audience; This paper deals with Multi-Protocol Label Switching-Traffic Engineering Routing (MPLS-TE Routing) Systems which offer key Traffic Engineering features, such as optimization of resources utilization, Quality-of-Service (QoS) and Fast Recovery. Numerous MPLS-TE Routing systems have been defined in the past with their own advantages and drawbacks. This paper proposes a generic architecture for MPLS-TE Routing Systems, with the main objective of helping in classification, analysis and improvement of these systems or the design of new systems. This architecture includes main functions that may be required in an MPLS-TE Routing System. These functions and their interactions are described. Various approaches and options for the implementation and the distribution of these functions in network elements are qualitatively analyzed. A classification of some well known MPLS-TE routing systems is finally proposed.

Human-Transient-into-the-Loop Simulation for NGATS

Scipedia content — Tue, 02 Feb 2021 05:59:02 +0100

Serious planning is underway for the United States Next Generation Air Transportation System. While design decisions are far from complete, there is consideration of having aircraft-trajectory control in space and time be determined by some combination of pilots, air-traffic personnel, and computers. Insofar as any control input is continuous in time, because of human perception and decision response times and/or computer multitasking or optimization-cycle times, there are likely to be time delays (e.g., human transients getting “into the control loop”) that could threaten control stability. Using the MATLAB Simulink dynamic simulation tool this paper examines some hypothetical situations and offers examples of how delays and signal sampling in aircraft control could cause unacceptable oscillations and instability.

Airborne Spacing in the Terminal Area: A study of Non-Nominal Situations

Scipedia content — Tue, 02 Feb 2021 05:57:28 +0100

This paper reports on small-scale experiments conducted with air traffic controllers. The objective was to investigate non-nominal situations when using airborne spacing in the terminal area. The following situations were considered: mixed equipage, holding patterns and typical unexpected events (go-around, emergency, radio failure, spacing instructions not correctly executed). In applying the airborne spacing procedure for non equipped aircraft, handling mixed equipage was found to be entirely feasible. Initial trends suggest that 50% equipped aircraft already brings some benefits compared to 0% although not as much as with 100%. Receiving aircraft from the holding patterns and then using airborne spacing for final integration was found feasible and comfortable. Recovering from the unexpected events was found less difficult than initially anticipated and was evaluated as similar to today’s operations.

Selection and evaluation of air traffic complexity metrics

Scipedia content — Tue, 02 Feb 2021 05:53:33 +0100

International audience; This paper presents an original method to evaluate air traffic complexity metrics. In previous works, we applied a principal component analysis (PCA) to find the correlations among a set of 27 complexity indicators found in the literature. Neural networks were then used to find a relationship between the components and the actual airspace sector configurations. Assuming that the decisions to group or split sectors are somewhat related to the controllers workload, this method allowed us to identify which components were significantly related to the actual workload. We now focus on the subset of complexity indicators issued from these components, and use neural networks to find a simple relationship between these indicators and the sector status.

A scalable heuristic for hybrid IGP/MPLS traffic engineering - Case study on an operational network

Scipedia content — Tue, 02 Feb 2021 05:42:59 +0100

In current IP networks, a classical way to achieve traffic engineering is to optimise the link metrics. This operation cannot be done too often and can affect the route of a lot of traffic. Multiprotocol Label Switching (MPLS) opens new possibilities to address the limitations of IP systems concerning traffic engineering thanks to explicit label-switched paths (LSPs). This paper proposes a new method based on simulated annealing meta-heuristic to compute a set of LSPs that optimise a given operational objective. The hybrid IGP/MPLS approach takes advantage of both IP and MPLS technologies and provides a flexible method to traffic engineer a network on a day to day basis. We illustrate the capabilities of our method with some simulations and a comparison with other techniques on an existing operational network. The results obtained by setting up a small number of LSPs are nearly optimal and better than by engineering the IGP weights. Moreover, although it could be combined with a static setting of the latter, SAMTE alone gives already the same results as this combination in much less CPU time, which thus allows an administrator to keep its initial and meaningful IGP metrics in his network. Peer reviewed

Bus priorities and their effects on local trade

Scipedia content — Tue, 02 Feb 2021 05:31:57 +0100

This paper describes how bus priorities are often favored by transport authorities in urban areas as a cost effective means of reducing traffic congestion and reliance on the car through promoting more sustainable travel. However, where their introduction involves the reduction in the availability of on-street parking in local shopping areas, opposition frequently arises from retailers concerned over the impact on car-borne trade. This paper reviews the links between transport policy, parking and the economy of local trade and considers the effects new bus priorities may have. There is strong evidence to suggest that car-borne and bus-borne shoppers are of fairly similar importance to trade, contrary to many retailers perceptions; furthermore the local nature of shopping in these areas and the consequent importance of the walking environment appears to be greatly underestimated.

High occupancy vehicle lanes — worldwide lessons for European practitioners

Scipedia content — Tue, 02 Feb 2021 05:10:31 +0100

This paper describes how Europe has long provided bus lanes and on-street bus priority measures. High Occupancy Vehicle (HOV) programs expand this practice to include private shared-ride vehicles (carpools) and other priority vehicles. There are a few HOV lanes in operation in Europe, and the interest is growing in their potential applicability to congested urban roadways. With over 200 HOV lane projects now in use on streets and highways around the world, there are useful lessons to be learned by those considering the HOV option in the European context. The reasons for project successes and failures are outlined, with particular attention paid to the constraints and operational issues prevalent in the European environment. Critical issues such as enforcement, conversion from general purpose use, design, and underutilization are explored. The documented effectiveness of HOV facilities in influencing mode choice is summarized. Finally, the future of HOV priority within the urban transport system is discussed, touching on high-tech enforcement solutions, HOV priority within tolled facilities, and the integration of HOV initiatives within broader Transportation Demand Management programs.

Suppressing Riser-Based Slugging in Multiphase Flow by State Feedback

Scipedia content — Tue, 02 Feb 2021 05:09:24 +0100

This paper proposes a state feedback design method for attenuating severe slugging in multiphase flow pipeline systems. The feedback is designed based on the input-output linearization method, and incorporates the saturation effect on the input. The designed feedback can suppress the slugging phenomena provided some sufficient conditions are satisfied. Finally, checking the conditions lead to the selection of the variable which is `more relevant' to be controlled.

The Marmaray Project in Istanbul: a shift from roads to railways

Scipedia content — Tue, 02 Feb 2021 04:45:34 +0100

This paper describes how Istanbul, with over ten million inhabitants, is one of the largest metropolitans in the world. The increasing population and the amount of disposable income have led to an increase in the demand for transportation in daily life. Unfortunately, the demand for transport is met mostly by the increasing use of cars. As a result of that, environmental problems associated with the use of cars raise concerns. In order to tackle both urban traffic congestion and air pollution, local authorities and the government are investing in alternative modes for urban transportation to road transport modes. Of these, the most notable one is the Marmaray Project. In fact, this project is also one of the most interesting transport projects of the world. The aim of the project is to shift the demand from road transportation on the bridges over the Istanbul Straight to public transportation with rail systems. The project consists of five parts: a rail system from Gebze to Sogutlucesme, a bored tube system under the surface between Sogutlucesme and Uskudar on the Asian side of Istanbul, an immersed tunnel under the Istanbul Straight from Uskudar to Sirkeci, a bored tunnel under the surface between Sirkeci and Kazlicesme and again a rail system from Kazlicesme to Halkali on the European side of Istanbul. The objectives of the Marmaray Projects are various. It has been estimated that when the project has been completed, the number of passengers travelling by the rail system will dramatically increase and Istanbul will have an efficient urban public transport system, which will significantly contribute to policies taken to cope with urban traffic congestion and air pollution caused by traffic.

Efficient OSPF weight allocation for intra-domain QoS optimization

Scipedia content — Tue, 02 Feb 2021 04:39:39 +0100

This paper presents a traffic engineering framework able to optimize OSPF weight setting administrative procedures. Using the proposed framework, enhanced OSPF configurations are now provided to network administrators in order to effectively improve the QoS performance of the corresponding network domain. The envisaged NP-hard optimization problem is faced resorting to Evolutionary Algorithms, which allocate OSPF weights guided by a bi-objective function. The results presented in this work show that the proposed optimization tool clearly outperforms common weight setting heuristics and, even under unfavorable scenarios, effective QoS improvement is achieved in the network domain. (undefined)

Auto-pipe and the X language: a pipeline design tool and description language

Scipedia content — Tue, 02 Feb 2021 04:39:00 +0100

uto-Pipe is a tool that aids in the design, evaluation and implementation of applications that can be executed on computational pipelines (and other topologies) using a set of heterogeneous devices including multiple processors and FPGAs. It has been developed to meet the needs arising in the domains of communications, computation on large datasets, and real time streaming data applications. This paper introduces the Auto-Pipe design flow and the X design language, and presents sample applications. The applications include the Triple-DES encryption standard, a subset of the signal-processing pipeline for VERITAS, a high-energy gamma-ray astrophysics experiment. These applications are discussed and their description in X is presented. From X, simulations of alternative system designs and stage-to-device assignments are obtained and analyzed. The complete system permits production of executable code and bit maps that may be downloaded onto real devices. Future work required to complete the Auto-Pipe design tool is discussed.

Computational Modeling of Air Traffic Control: Terminal Area Case Study

Scipedia content — Tue, 02 Feb 2021 04:11:43 +0100

This paper presents an air traffic control modeling case study in which agent performance on a simulated terminal-area air traffic control task was compared with human air traffic controller performance. The paper first provides background on the simulation with human air traffic controllers, and on prior air traffic control modeling research. It then presents an agent model that enables various air traffic control strategies to be evaluated. Results for four different control strategy models show that agent performance compares more favorably to human performance when clearance alternatives and resultant aircraft behaviors are more constrained. The paper discusses these results and describes proposed future enhancements. The research was conducted with support from the NASA Aviation Safety Program.