Scipedia: Documents published in 2010

Investigating Requirements for the Design of a 3D Weather Visualization Environment for Air Traffic Controllers

Scipedia content — Thu, 21 Jan 2021 13:06:18 +0100

The present work aimed to discover controllers weather information needs and assess if 3D weather visualization could provide added benefits to controllers. The results of the survey can be summarized as follows. There are several differences in the weather information needs between en route and approach controllers, which logically reflect the different focus of activities carried out by each group of controllers. For example, approach controllers need very specific knowledge such as Wind, RVR, Visibility, etc. that is not normally required to en route controllers (at least, in the light of the results that we obtained). This fact has to be considered for the design of ATC weather interfaces, for example, by conceiving dedicated and customized weather representations that are suitable for the tasks that controllers actually perform. By this, we do not mean that information should be hidden from controllers; more simply, we claim that interfaces should avoid displaying unnecessary data and, eventually, providing extra information only upon request. Moreover, according to the results of this study, both en route and approach controllers seem to value and use critical weather information such as CB, Thunderstorm, Turbulence and Icing. As we stated in the previous sections, hazardous weather information has direct impact on the safety and efficiency of air traffic. Devising visual techniques for allowing controllers to perform Ã¢â¬Åahead assessmentsÃ¢â¬Â about weather hazards, could support controllers in identifying in advance strategic solutions for responding to the restrictions imposed by weather on upper space sectors, terminal areas and aerodromes. Controllers declared having a quite low degree of satisfaction about the displays currently used for hazardous weather information. In particular, both en route and approach controllers gave low scores to very critical weather data such as Wind Shear, Turbulence, CB and Icing. Suitable representations as well as projections of adverse weather events seem missing. We suppose that the solely textual representation largely contributes to this result and, perhaps, graphical information could better suit controllersÃÂ´ needs, independently from the interface style (either 2D or 3D). But, controllersÃ¢â¬â¢ comments gave promising insights on the use of 3D as a more intuitive representation of hazardous weather. However, at this stage of the study, we can only accept controllersÃ¢â¬â¢ comments as they are, hence, these ideas remain hypotheses that need further investigation. Short-term plans for continuing this research entail the implementation of a small mock-up of CB formation embedded into a sector with a realistic traffic flow. The choice of CB is justified by the fact that controllers expressed a high interest for having 3D representations of cumulonimbus and further stressed this interest in an explicit manner, adding comments in the questionnaire and during informal talks. We intend to perform additional demonstration sessions showing this new implementation and carrying out in-depth interviews with controllers, in order to understand what the supposed benefits of 3D weather images would be. Perhaps there are some specific visual properties of 3D weather representations that could indeed enhance controllersÃ¢â¬â¢ tasks. Understanding what these visual properties are, would give us sufficient information for defining the functional requirements of a more refined 3D prototype.

On the Performance of Grooming Strategies for Offloading IP Flows onto Lightpaths in Hybrid Networks

Scipedia content — Thu, 21 Jan 2021 13:05:48 +0100

International audience; Hybrid networks take data forwarding decisions at multiple network levels. In order to make an efficient use of hybrid networks, traffic engineering solutions (e.g., routing and data grooming techniques) are commonly employed. Within the specific context of a self-managed hybrid optical and packet switching network, one important aspect to be considered is how to efficiently and autonomically move IP flows from the IP level over lightpaths at the optical level. The more IP traffic is moved (offloaded), leaving the least amount of traffic on the IP level, the better. Based on that, we investigate in this paper different strategies to move IP flows onto lightpaths while observing the percentage of offloaded IP traffic per strategy.

Document type: Part of book or chapter of book

Overlooked density re thinking transportation options in suburbia

Scipedia content — Mon, 26 Oct 2020 15:49:31 +0100

Document type: Report

T ty tank farm interim surface barrier demonstration vadose zone monitoring plan

Scipedia content — Mon, 26 Oct 2020 15:43:58 +0100

The Hanford Site has 149 underground single-shell tanks that store hazardous radioactive waste. Many of these tanks and their associated infrastructure (e.g., pipelines, diversion boxes) have leaked. Some of the leaked waste has entered the groundwater. The largest known leak occurred from the T-106 Tank of the 241-T Tank Farm in 1973. Five tanks are assumed to have leaked in the TY Farm. Many of the contaminants from those leaks still reside within the vadose zone within the T and TY Tank Farms. The Department of EnergyÂs Office of River Protection seeks to minimize the movement of these contaminant plumes by placing interim barriers on the ground surface. Such barriers are expected to prevent infiltrating water from reaching the plumes and moving them further. The soil water regime is monitored to determine the effectiveness of the interim surface barriers. Soil-water content and water pressure are monitored using off-the-shelf equipment that can be installed by the hydraulic hammer technique. Four instrument nests were installed in the T Farm in fiscal year (FY) 2006 and FY2007; two nests were installed in the TY Farm in FY2010. Each instrument nest contains a neutron probe access tube, a capacitance probe, and four heat-dissipation units.moreÂ Â» A meteorological station has been installed at the north side of the fence of the T Farm. This document summarizes the monitoring methods, the instrument calibration and installation, and the vadose zone monitoring plan for interim barriers in T farm and TY Farm.Â«Â le

Document type: Report

Streamlining transportation corridor planning processess freight and traffic information

Scipedia content — Mon, 26 Oct 2020 13:47:45 +0100

The traffic investigation is one of the most important parts of an Environmental Impact Statement of projects involving the construction of new roadway facilities and/or the improvement of existing ones. The focus of the traffic analysis is on the determination of anticipated traffic flow characteristics of the proposed project, by the application of analytical methods that can be grouped under the umbrella of capacity analysis methodologies. In general, the main traffic parameter used in EISs to describe the quality of traffic flow is the Level of Service (LOS). The current state of the practice in terms of the traffic investigations for EISs has two main shortcomings. The first one is related to the information that is necessary to conduct the traffic analysis, and specifically to the lack of integration among the different transportation models and the sources of information that, in general, reside in GIS databases. A discussion of the benefits of integrating CRS&SI technologies and the transportation models used in the EIS traffic investigation is included. The second shortcoming is in the presentation of the results, both in terms of the appearance and formatting, as well as content. The presentation of traffic results (current and proposed) is discussed. ThismoreÂ Â» chapter also addresses the need of additional data, in terms of content and coverage. Regarding the former, other traffic parameters (e.g., delays) that are more meaningful to non-transportation experts than LOS, as well as additional information (e.g., freight flows) that can impact traffic conditions and safety are discussed. Spatial information technologies can decrease the negative effects of, and even eliminate, these shortcomings by making the relevant information that is input to the models more complete and readily available, and by providing the means to communicate the results in a more clear and efficient manner. The benefits that the application and use of CRS&SI technologies can provide to improve and expedite the traffic investigation part of the EIS process are presented.Â«Â le

Document type: Report

H2a biomethane model documentation and a case study for biogas from dairy farms

Scipedia content — Mon, 26 Oct 2020 11:26:31 +0100

The new H2A Biomethane model was developed to estimate the levelized cost of biomethane by using the framework of the vetted original H2A models for hydrogen production and delivery. For biomethane production, biogas from sources such as dairy farms and landfills is upgraded by a cleanup process. The model also estimates the cost to compress and transport the product gas via the pipeline to export it to the natural gas grid or any other potential end-use site. Inputs include feed biogas composition and cost, required biomethane quality, cleanup equipment capital and operations and maintenance costs, process electricity usage and costs, and pipeline delivery specifications.

Document type: Report

Instrumented pipeline initiative

Scipedia content — Mon, 26 Oct 2020 10:32:09 +0100

This report summarizes technical progress achieved during the cooperative agreement between Concurrent Technologies Corporation (CTC) and U.S. Department of Energy to address the need for a for low-cost monitoring and inspection sensor system as identified in the Department of Energy (DOE) National Gas Infrastructure Research & Development (R&D) Delivery Reliability Program Roadmap.. The Instrumented Pipeline Initiative (IPI) achieved the objective by researching technologies for the monitoring of pipeline delivery integrity, through a ubiquitous network of sensors and controllers to detect and diagnose incipient defects, leaks, and failures. This report is organized by tasks as detailed in the Statement of Project Objectives (SOPO). The sections all state the objective and approach before detailing results of work.

Document type: Report

Measuring sustainability of transport in the city - development of an indicator-set

Scipedia content — Mon, 26 Oct 2020 10:19:23 +0100

The HASTA indicator framework, covering the three dimensions of sustainability, i.e. Economic, Environmental and Social, to monitor sustainability of transport in Swedish cities was elaborated."br /" Under the three sustainability dimensions, there are 6 sustainability aspects (indicator groups), 2-3 per dimension; these are Efficiency, Accessibility (Economic dimension), Accessibility, Safety,"br /" Liveability (Social dimension); Emissions, Resource use (Environmental dimension). The accessibility indicator group is related with both economic and social sustainability. The individual indicators are structured in three levels of a hierarchical structure. The highest level is represented by the Outcome indicators which reflect the sustainability target in the subject area of the indicator."br /" These Outcome indicators are of both objectively measurable variables and subjective variables, reflecting how the inhabitants experience sustainability of transport in their city. On the lowest level, the Input indicators provide information on possible measures to make improvements in transport sustainability. On the intermediate level, the Output indicators show the effect of the adopted measures (Input indicators). There are 19 Outcome indicators, 22 Output indicators and 42 Input indicators.

Document type: Report

Mobilities and long term location choices in Belgium

Scipedia content — Mon, 26 Oct 2020 10:08:25 +0100

Mobility and transport evolve with time and the passing generations. Interactions are numerous between daily mobility and household migration (here defined as house moving implying a municipality change). The evolution of the transport system has deeply modified the barrier of distance and has largely opened the choices in terms of residence place. The continuing urban sprawl phenomenon resulting from these modifications has itself resulted in a strengthening of the property and housing market in certain territories, pushing people (young couples in particular) towards a residential localization which is further and further away from the traditional, urban activity centres. The tensions between daily and residential mobility have therefore increased, notwithstanding the recent rise in energy costs. This in turn generates unsustainable effects on society and environment. But these new residential choices have in parallel induced new mobility behaviours, based on an extensive (and probably excessive) use of the private car in daily trips (home-work/school, shopping, leisure ...). Social life itself (visits to friend and family) has become more spatially dispersed. One already knows that the propensity to change residence is determined by a number of individual or household characteristics such as age, citizenship or income, but the effects of long-term trends as population ageing, the evolution of the household/family structure on both residential choices and mobility behaviours remain so far largely unanticipated. This research project aimed at analyzing interactions between demographics and the evolution of mobilities at different time-scales. In particular, localization choice for household, daily accessibility and internal migrations ap pear to have strong relations.

Document type: Report

An evolutionary approach to pickup and delivery problem with time windows

Scipedia content — Wed, 14 Oct 2020 16:39:08 +0200

Recently, the quality and the diversity of transport services are more and more required. Moreover, in case of a great deal of services and selling goods, a significant part of price is transport cost. Thus, the design of models and applications which make possible efficient transport planning and scheduling becomes important. A great deal of real transport problems may be modelled by using Pickup and Delivery Problem with Time Windows (PDPTW) and capacity constraints, which is based on the realization of a set of transport requests by a fleet of vehicles with given capacities. Each request is described by pickup and delivery locations, time periods when pickup and delivery operations should be performed and needed load. Application of evolutionary approach has brought good results in case of another, simpler transport problem the Vehicle Routing Problem with Time Windows (VRPTW). This paper is aimed at proposing a straightforward extension of VRPTW based heuristics for the PDPTW.

Document type: Part of book or chapter of book

Experimental analysis of the sabul congestion control algorithm

Scipedia content — Wed, 14 Oct 2020 16:35:54 +0200

Several new protocols such as RBUDP, User-Level UDP, Tsunami, and SABUL, have been proposed as alternatives to TCP for high-speed data transfer. The purpose of this paper is to analyze experimentally the effects of SABUL congeston control algorithm on SABUL and performance metrics such as bandwidth utilization, self-fairness, and aggressiveness. Our results confirm some expected behavior of SABUL and reveal some less expected one. Our experiments also indicate that SABUL implementation and design can result in an even more erratic behavior and degraded performance under high-congestion conditions.

Document type: Part of book or chapter of book

Vom Planungsleitbild "Durchmischte Stadt" zu den Auswirkungen auf Alltagsmobilität am Beispiel der Hamburger Elbinseln

Scipedia content — Wed, 14 Oct 2020 16:35:24 +0200

Die "durchmischte" Stadt als Leitbild aktueller Stadtentwicklung wird im Kontext aktueller planerischer Diskussionen dargestellt und der Aspekt der Förderung der Alltagsmobilität wird als beispielhafter Indikator nachhaltiger sozial gerechter Entwicklung untersucht. Die Bedeutung und die Möglichkeiten planerischer Einflussnahme auf Alltagsmobilität sind Gegenstand grundsätzlicher Überlegungen, die darauf folgend am Beispiel der Elbinsel Wilhelmsburg vertieft werden. Beispielhaft erfolgt die Untersuchung des Hamburger Vorhabens "Sprung über die Elbe", speziell dessen Umsetzung in Form der Internationalen Bauausstellung IBA Hamburg als Beispiel für einen aktuellen, dem Leitbild der durchmischten Stadt folgendem, Stadtentwicklungsprozess. Hier wird der Frage nachgegangen, inwieweit die bestehenden Strukturen und die Bedürfnisse der ansässigen Bevölkerung berücksichtigt werden und eine Verbesserung der Alltagsmobilität als Instrument ihrer Förderung eingesetzt wird. Die Untersuchung will einen Überblick über die eingesetzten Maßnahmen schaffen und aufzeigen, welche zu einer gerechten Planung beitragen und für eine ausgleichende Verteilung von Chancen in Form einer für alle zugänglichen Alltagsmobilität in der Metropole sorgen. Es erfolgt keine Untersuchung von Verkehrsstatistiken und -zahlen, sondern von Planungszielen, Projektvorhaben und erzielten Ergebnissen. Abschließend wird deutlich, dass Elemente zur Fortentwicklung der Alltagsmobilität in einzelnen Projektvorhaben gefunden werden, aber keine übergreifende Untersuchung oder kein Maßnahmenplan zur Verbesserung vorliegt und eine Diskussion entweder im Detail oder auf abstrakter Ebene geführt wird. This article describes the "city of mixed functions" as a general principle of contemporary urban development against the background of the present discourse on urban planning. Based on this it looks into the advancement of everyday mobility as an exemplary indicator for social sustainable and equitable development. The meaning of everyday mobility and the possibilities of influencing it through urban planning are subjects of fundamental considerations. In the following part they are proved by using the example Wilhelmsburg, a quarter of the city of Hamburg. The local analysis starts with the research of Hamburg's political development concept titled "Sprung über die Elbe" ("Leap over the Elbe-river"). In detail there will be a look on one part of its spatial realization found in the project of the international building exhibition IBA Hamburg. This is an instance of contemporary urban planning under the guiding principle of the aforementioned "city of mixed functions". Following up the question how far the existing structures and the needs of the residents are allowed for and whether an improvement of everyday mobility is introduced as an instrument for their advancement, the research aims to provide an overview of the implemented measures, which contribute to equitable urban planning and social equity in the form of universally accessible everyday mobility in the metropolitan area of Hamburg. This does not include specific statistics and numbers related to transportation, but instead an analysis of the goals of urban planning, the intended projects, and the obtained results. Finally it becomes apparent that elements for the development of everyday mobility can be found in the individual intended projects. However, there exists no overarching investigation or strategy plan for everyday mobility. The existing discussion is hold either on an abstract level or in practical project details.

Document type: Book

Paging load congestion control in cellular mobile networks

Scipedia content — Wed, 14 Oct 2020 16:34:55 +0200

This paper addresses the requirement for a congestion control mechanism, in order to efficiently handle paging traffic over cellular networks. The standard simultaneous paging approach can easily result in congestion, for relatively small values of the offered load. Instead of differentiating paging capacity based on the incoming load, this approach is more oriented towards a limited-resource system. Considering that a paging channel usually experiences high and low utilization periods, it is proposed to differentiate the paging mechanism according to the processed load. Given medium or even mild overload conditions, several forms of sequential paging substantially decrease blocking probabilities, while presenting good delay behavior. Based on a queueing analysis, we are able to quantitatively estimate potential improvements, and point out the basic points of such an adaptive scheme.

Document type: Part of book or chapter of book

The Use of Computers for Controlling Electricity Flows in Sweden, 19501980

Scipedia content — Wed, 14 Oct 2020 16:30:17 +0200

Part 2: Computerizing Public Sector Industries International audience An important application of computers from the 1950s and onwards has been for designing and operating complex infrastructural systems like air traffic, telephony, railways, and electricity. This paper tells the story about how computers from the 1950s and onwards became an important tool for designing and operating the Swedish power grid. It describes two phases of this development. In the 1950s and 1960s, computers were used for making complicated calculations for designing power grids in a reliable way and optimizing the use of the different power plants. In a second phase starting in the late 1960s, computer systems were developed for real time monitoring supporting human control of the power grid. The paper analyzes by whom and for what purposes computers became tools for controlling electricity flows. In the conclusion, it also discusses the wider implications of computers for the development of the Swedish power system.

Document type: Part of book or chapter of book

Reliable and Restricted Quickest Path Problems

Scipedia content — Wed, 14 Oct 2020 16:29:22 +0200

In a dynamic network, the quickest path problem asks for a path minimizing the time needed to send a given amount of flow from source to sink along this path. In practical settings, for example in evacuation or transportation planning, the reliability of network arcs depends on the specific scenario of interest. In this circumstance, the question of finding a quickest path among all those having at least a desired path reliability arises. In this article, this reliable quickest path problem is solved by transforming it to the restricted quickest path problem. In the latter, each arc is associated a nonnegative cost value and the goal is to find a quickest path among those not exceeding a predefined budget with respect to the overall (additive) cost value. For both, the restricted and reliable quickest path problem, pseudopolynomial exact algorithms and fully polynomial-time approximation schemes are proposed.

Document type: Part of book or chapter of book

Infrastrukturentwicklung im europäischen Korridor Rotterdam-Genua: das INTERREG-IV-B-Projekt "Code 24"

Scipedia content — Wed, 14 Oct 2020 16:26:47 +0200

Die in den letzten Jahren stetig wachsende Mobilität wirkt sich auf die Entwicklung von Wirtschaft, Umwelt und Raum aus. Dabei treten neue Spannungsfelder zwischen Verkehrs- und Siedlungsentwicklung, aber auch zwischen Wirtschaft und Umwelt auf. Besonders große Verkehrszuwächse werden für den multimodalen Korridor Nr. 24 im Transeuropäischen Verkehrsnetz der Europäischen Union (TEN-V) zwischen Rotterdam und Genua prognostiziert. Der vorliegende Beitrag behandelt das INTERREG-IVB-Projekt "CODE 24", welches mit dem Aufbau eines Policy-Netzwerks die Korridorentwicklung mittels einer integrierten Betrachtungsweise im Sinne der Nachhaltigkeit vorantreiben möchte. Neben den Arbeitspaketen des Projekts zur Raumplanung und Infrastrukturentwicklung, zu Güterverkehr und Logistik sowie zur Kommunikation und Akzeptanz wird vertieft die Maßnahme "Planungsleitfaden für innovative Lärmschutzsysteme" dargestellt. Darin sollen unterschiedliche Lärmschutzsysteme systematisch analysiert werden und ein "Auralisationstool" zum Einsatz kommen, mit dem bereits in der Planungsphase die akustischen Auswirkungen der diskutierten Alternativen hörbar gemacht werden können. The growing mobility of the last years influences the development of economy, environment and space. In this context there are new areas of conflict both between transport and settlement development and between economy and environment. Extra high increases are expected in the multi-modal corridor No. 24 of the Trans-European Transport Network (TEN-T) between Rotterdam and Genua. The present article reflects the INTERREG-IVB-project "CODE 24", which wants to promote the corridor development sustainably with an integrated view. Beside the work packages of the project about spatial and infrastructural development, about freight transport and logistics and about communication and acceptance the action "planners' toolbox for innovative noise protection" is presented in detail. In this action several systems for noise protection will be systematically analysed and an "auralisation tool" will be used, with which the acoustic effects of discussed alternatives can be made audible already in the planning process.

Document type: Book

The SYNCROMAX Solution for Air Traffic Flow Management in Brazil

Scipedia content — Wed, 14 Oct 2020 16:26:16 +0200

At recent years, air traffic demand increased at double-digit figures at several Brazilian airports and as a consequence increased controller workload was observed at many Sectors of the Air Traffic Control Facilities, with clear indications that demand consistently surpassed the available capacity of airports and air traffic control units. Although determination of air traffic control capacity values is still a very subjective and controversial issue, with no proven and universally accepted method in place, there is no doubt that there are limits and operating at values above a certain threshold will impact the systems efficiency, and, ultimately, also its safety. Demand is defined as the number of aircraft requesting to use the Air Traffic Management system ABSTRACT

Document type: Part of book or chapter of book

Efficient Algorithm for Embedding Hypergraphs in a Cycle

Scipedia content — Wed, 14 Oct 2020 16:21:58 +0200

The problem of Minimum Congestion Hypergraph Embedding in a Cycle (MCHEC) is to embed the hyperedges of a hypergraph as paths in a cycle such that the maximum congestion (the maximum number of paths that use any single link in the cycle) is minimized. This problem has many applications, including minimizing communication congestions in computer networks and parallel computations. The MCHEC problem is NP-hard. We give a 1.8-approximation algorithm for the problem. This improves the previous 2-approximation results. The algorithm has the optimal O(mn) time for the hypergraph with m hyperedges and n nodes.

Document type: Part of book or chapter of book

Assessing the environmental co benefits of climate change actions

Scipedia content — Wed, 14 Oct 2020 16:14:35 +0200

This internal background paper has been prepared to help inform the 2010 environment strategy with respect to a proposed way forward on use of country systems. The World Bank Group environment strategy is built on three pillars: leveraging natural resources for growth and poverty reduction; managing the environmental risks to growth and development; and transforming growth paths. As part of its exploration of these three pillars, the strategy considers the question of environmental co-benefits of climate change actions. In particular, it poses the question of potential trade-offs between actions to address climate change and other local and regional environmental priorities, and considers how to maximize co-benefits arising from climate action. The primary objective of this background paper is to assess the potential for climate change mitigation and adaptation actions to provide environmental co-benefits, particularly in the quality of environmental media, flow of ecosystem services, and maintenance of biodiversity. To accomplish this, the paper is organized in five sections: section one gives provision of an organizing framework to identify and classify potential co-benefits; section two gives summary of the external literature on co-benefits; section three gives review of examples from the World Bank portfolio; section four presents initial thoughts on creation of enabling conditions for co-benefit provision; and section five gives review of implications for the environment strategy.

Document type: Book

QoS Dynamic Routing in Content Delivery Networks

Scipedia content — Wed, 14 Oct 2020 16:13:09 +0200

Recently, much research in quality of service (QoS) routing has focused on the unicast communication technique. However, Content Delivery Network (CDN) approach becomes popular because CDN enables effective and inexpensive improvement of Internet service quality. Therefore, we analyze in this paper a network processing two kinds of demands: content demands to CDN servers and standard unicast demands. Since MPLS defines effective mechanism for traffic engineering, we assume that the CDN is located in MPLS network. To examine the QoS performance of CDN-enabled MPLS network we propose new constraint-based algorithms for CDN server selection and evaluate relative performance of these algorithms and the most effective existing QoS unicast routing algorithms in terms of the demand rejection ratio.

Document type: Part of book or chapter of book

Interdomain traffic engineering with minimal BGP configurations

Scipedia content — Wed, 14 Oct 2020 16:12:56 +0200

We propose a method based on multi-objective combinatorial optimization to perform interdomain traffic engineering with minimal BGP configurations. Our method relies on an evolutionary algorithin that tries to minimize an objective function by finding the successive BGP filters to be applied on the BGP routes. We study the impact of the number of providers, the traffic aggregation in the AS-level topology and the objective function on the behavior of our algorithm.

Document type: Part of book or chapter of book

Multi agent environment for dynamic transport planning and scheduling

Scipedia content — Wed, 14 Oct 2020 16:09:21 +0200

Nowadays, transport requests of the society are becoming more and more common and important. Computer systems may be a useful tool for transport companies. This paper is aimed at presenting a system which simulates the functioning of a transport company. The theoretical problem, which needs to be solved, is a dynamic Pickup and Delivery Problem with Time Windows and capacity constraints (PDPTW). The nature of the problem, its distribution and the possibility of using a lot of autonomous planning modules, predestines to apply a multi-agent approach. Multi-agent approach facilitates the introduction of elements which do not appear in classical PDPTW as company organisation, different strategies of requests acceptation by different vehicles or communication among vehicles.

Document type: Part of book or chapter of book

Optimization of Traffic Behavior via Fluid Dynamic Approach

Scipedia content — Wed, 14 Oct 2020 16:05:08 +0200

Traffic regulation techniques for the optimization of car traffic flows in congested urban networks was considered. The approach used for the description of traffic flows is of fluiddynamic type. The main advantages of this approach, with respect to existing ones, can be summarized as follows. The fluid-dynamic models are completely evolutive, thus they are able to describe the traffic situation of a network at every instant of time. This overcomes the difficulties encountered by many static models. An accurate description of queues formation and evolution on the network is possible. The theory permits the development of efficient numerical schemes also for very large networks. This is possible since traffic at junctions is modelled in a simple and computationally convenient way (resorting to a linear programming problem). The performance analysis of the networks was made through the use of different cost functionals, measuring car average velocity weighted or not weighted with the number of cars moving on each road, the average travelling time, velocity variation, kinetic energy, etc. Exact analytical results were given for simple junctions of 1 ×2 and 2 × 1 type, and then used in order to simulate more complex urban networks. Moreover the problem of emergency vehicles transit has been treated. The problem has been faced choosing a route for emergency vehicles (not dedicated, i.e. not limited only to emergency needs) and redistributing traffic flows at junctions on the basis of the current traffic load in such way that emergency vehicles could travel at the maximum allowed speed along the assigned roads (and without blocking the traffic on other roads). All the optimization results have been obtained using a decentralized approach, i.e. an approach which sets local optimal parameters for each junction of the network. In future we aim to extend the optimization results to more general junctions and to explore global optimization techniques. In addition, the definition and optimization of functionals which take into account the emission and propagation of pollutants produced by cars might provide powerful technological tools to rationalize the design and use of public and private transportation resources, and to reduce unpleasant effects of urban traffic on the environment.

Document type: Part of book or chapter of book

Passive long range detection of aircraft towards a field deployable sense and avoid system

Scipedia content — Wed, 14 Oct 2020 16:02:22 +0200

Unmanned Aerial Vehicles (UAVs) typically fly blind with operators in distant locations. Most UAVs are too small to carry a traffic collision avoidance system (TCAS) payload or transponder. Collision avoidance is currently done by flight planning, use of ground or air based human observers and segregated air spaces. US lawmakers propose commercial unmanned aerial systems access to national airspace (NAS) by 30th September 2013. UAVs must not degrade the existing safety of the NAS, but the metrics that determine this have to be fully determined yet. It is still possible to state functional requirements and determine some performance minimums. For both manned and unmanned aircraft to fly safely in the same airspace UAVs will need to detect other aircraft and follow the same rules as human pilots.

Document type: Part of book or chapter of book

Handling two way tcp traffic in asymmetric networks

Scipedia content — Wed, 14 Oct 2020 16:02:06 +0200

The TCP congestion control protocol is mainly designed for bandwidth symmetric paths. As two-way asymmetric connections will probably become common case in the future with the widespread use of ADSL, satellites and other high-speed technologies, it is important to make sure that congestion will be properly handled in these environments. To this end, we propose in this paper a new Adaptive Class-based Queuing mechanism called ACQ for handling two-way TCP traffic over links that exhibit bandwidth asymmetry. ACQ runs at the entry of the slow link and relies on two separate classes, one for ACK packets and one for Data packets. ACQ proposes to adapt the weights of both classes according to the crossing traffic in order to maximize some utility function defined by the user or the network operator. We show by simulations that our mechanism is able to reach a good utilization of the available resources, managing then to maximize the satisfaction of the user of such asymmetric connections.

Document type: Part of book or chapter of book

Reducing packet loss by taking long range dependences into account

Scipedia content — Wed, 14 Oct 2020 15:56:42 +0200

We show that the fractal behavior of Internet traffic can be efficiently and practically employed to significantly reduce packet-loss. Thanks to recent advances in the theory of self-similar processes, we define the probabilistic congestion of a link, based on an estimated computation of the packet-loss probability over that link. This congestion parameter allows valid predictions on the future behavior of the network, on which one can base efficient routing strategies. We show how to implement the computation of the probabilistic congestion, and we illustrate several applications for improving unicast and multicast protocols.

Document type: Part of book or chapter of book

Automatic Management of the QoS within an Architecture Integrating New Transport and IP Services in a DiffServ Internet

Scipedia content — Wed, 14 Oct 2020 15:54:46 +0200

Lots of research works have been performed for about ten years around the QoS problem in the Internet, both but separately at the Transport and at the IP levels. Taking into account the emerging traffic engineering-based QoS solutions (Diffserv-oriented), this paper targets the integration of new Transport services and protocols together with these solutions. Starting from performance measurements performed over a national DiffServ platform, contributions exposed here deal with the proposition and the implementation of a session level protocol allowing the application programmers to be masked with the complexity of choosing the underlying new Transport and IP services, still being provided with a per flow QoS.

Document type: Part of book or chapter of book

A framework of map comparison methods to evaluate geosimulation models from a geospatial perspective

Scipedia content — Wed, 14 Oct 2020 15:54:20 +0200

Geosimulation is a form of microsimulation that seeks to understand geographical patterns and dynamics as the outcome of micro level geographical processes. Geosimulation has been applied to understand such diverse systems as lake ecology, traffic congestion and urban growth. A crucial task common to these applications is to express the agreement between model and reality and hence the confidence one can have in the model results. Such evaluation requires a geospatial perspective; it is not sufficient if the micro-level interactions are realistic. Importantly the interactions should be such that the meso and macro level patterns that emerge from the model are realistic. In recent years, a host of map comparison methods have been developed that address different aspects of the agreement between model and reality. This paper places such methods in a framework to systematically assess the breadth and width of model performance. The framework expresses agreement at the continuum of spatial scales ranging from local to the whole landscape and separately addresses agreement in structure and presence. A common reference level makes different performance metrics mutually comparable and guides the interpretation of results. The framework is applied for the evaluation of a constrained cellular automata model of the Netherlands. The case demonstrates that a performance assessment lacking either a multi-criteria and multi-scale perspective or a reference level would result in an unbalanced account and ultimately false conclusions.

Document type: Part of book or chapter of book

High performance heuristics for optimization in stochastic traffic engineering problems

Scipedia content — Wed, 14 Oct 2020 15:50:03 +0200

We consider a stochastic routing model in which the goal is to find the optimal route that incorporates a measure of risk The problem arises in traffic engineering, transportation and even more abstract settings such as task planning (where the time to execute tasks is uncertain), etc The stochasticity is specified in terms of arbitrary edge length distributions with given mean and variance values in a graph The objective function is a positive linear combination of the mean and standard deviation of the route Both the nonconvex objective and exponentially sized feasible set of available routes present a challenging optimization problem for which no efficient algorithms are known In this paper we evaluate the practical performance of algorithms and heuristic approaches which show very promising results in terms of both running time and solution accuracy.

Document type: Part of book or chapter of book

Modelling aspects of longitudinal control in an integrated driver model

Scipedia content — Wed, 14 Oct 2020 15:49:09 +0200

Simulating and predicting behaviour of human drivers with Digital Human Driver Models (DHDMs) has the potential to support designers of new (partially autonomous) driver assistance systems (PADAS) in early stages with regard to understanding how assistance systems affect human driving behaviour. This paper presents the current research on an integrated driver model under development at OFFIS within the EU project ISi-PADAS. We will briefly show how we integrate improvements into CASCaS, a cognitive architecture used as framework for the different partial models which form the integrated driver model. Current research on the driver model concentrates on two aspects of longitudinal control (behaviour a signalized intersections and allocation of visual attention during car following). Each aspect is covered by a dedicated experimental scenario. We show how experimental results guide the modelling process.

Document type: Part of book or chapter of book

Comfortable Driver Behavior Modeling for Car Following of Pervasive Computing Environment

Scipedia content — Wed, 14 Oct 2020 15:43:35 +0200

This paper demonstrates a novel car-following model based on driver or passengers comfort. As we know, hasty deceleration during emergency brake will cause passengers feel uncomfortable. According to the relationship between brake acceleration and peoples comfortable feeling, the comfortable model is setup. The model calculates the following cars acceleration by measuring the distance between the following car and the preceding car, the velocity of the following car, and controls the cars acceleration to make driver and passengers feel comfort. The paper combine the model with the pervasive computing concept, provoke the pervasive computing driver behavior modeling idea and turn it into reality to increase the adaptability and reliability of cars parts, when car equipped with this device, the prospect is not only the assistant driver or comfortable driver are realized in the car-following circumstance, but also the whole cars performance will be improved.

Document type: Part of book or chapter of book

Computational concerns in the integration of unmanned airborne systems into controlled airspace

Scipedia content — Wed, 14 Oct 2020 15:38:54 +0200

Unmanned Airborne Systems (UAS) offer significant benefits for long duration missions. They can also be used in situations where it is inappropriate to expose aircrew to increased levels of risk. Partly in consequence, they continue to experience accident rates that are significantly higher than those for most conventional aircraft. It can also be argued that increased mishap rates are due to lower standards of design and maintenance. UAS are, therefore, largely confined to segregated areas that are well away from other airspace users. There are growing commercial and political pressures for them to be integrated into airspace that is directly under the control of air traffic management. Police agencies would like to deploy miniature UAS in populated areas, for example, to augment conventional helicopter operations. There are proposals to operate unmanned freight operations from existing airports. Longer-term proposals include the use of UAS technology to replace the co-pilot. Automated systems might intervene only if the single human pilot is incapacitated. The following pages focus on the computational issues that form one part of wider set of 'system safety' concerns that must be addressed before UAS operations can be integrated into controlled airspace.

Document type: Part of book or chapter of book

Public Transport Capacity Analysis Procedures for Developing Cities

Scipedia content — Wed, 14 Oct 2020 15:36:49 +0200

The introduction of urban rail transit and high performance/quality/capacity bus transit systems throughout the world has dramatically improved the mobility of residents of cities in which they operate. The objectives of this work are: to provide a technical resource for transit planners and designers in developing cities in their public transport capacity and performance analysis work irrespective of mode. This report recommends methods of achieving practical transit capacity during normally encountered operating conditions. Where capacity is influenced by a measure of dispersion of some characteristic such as stop dwell time or vehicle headway, this is also noted. The purpose of measuring capacity is not just to provide a measure of system capability to transport passengers but also to provide some insight into the effect of service and physical design on customer service quality. When the demand for a service exceeds its schedule design capacity, service quality deteriorates either due to overcrowding on vehicles or at station platforms or diminished ability of customers to board the next arriving transport vehicle since it is already fully loaded, increased dwell times and hence decrease revenue speeds. The importance of service quality in transit capacity analysis cannot be overstated. Transit operators should be mindful that the urban transportation marketplace is more competitive. While it might be technically possible to design a service using a loading standard of 7 or 8 passengers per square meter, a number of customers will find that level intolerable and will seek alternate means of travel including walking (in the case of short distance trips), riding with someone else, riding taxis or purchasing a motorcycle or car. Accordingly, such loading standards should be thought of as interim measures until higher capacity at lower crowding can be achieved.

Document type: Book

Schneller öfter weiter immer dümmer

Scipedia content — Wed, 14 Oct 2020 15:36:22 +0200

Jede Beschleunigung erhöht das Risiko und die Häufigkeit von Fehlern, wenn Rückkopplung und Kontrolle nicht folgen können. Die technische Beschleunigung sowohl in der physischen Mobilität wie auch im Informationssystem führt nicht, wie zu erwarten wäre, zu intelligenteren, sondern zu dümmeren Ergebnissen. Was im Individualbereich zunächst als großer Vorteil erscheint - die mit externer Energie angetriebenen Verkehrsmittel, insbesondere das Auto - führt im System zu immer größerer Abhängigkeit von außen und zu Siedlungsstrukturen, die nicht nachhaltig sind. Die Dummheit der Verkehrs- und Stadtplanung muss von den Bewohnern mit immer größerem Einsatz immer teurer werdender Energie bezahlt werden. Die Ursache liegt in der heutigen Parkraumorganisation, die die Gesellschaft zwingt, an jedem Ort ihrer Aktivitäten in unmittelbarer Nähe Parkplätze anzuordnen, eine Folge der Reichsgaragenordnung aus 1939. Diese zwanghaft physische Kopplung kann nur aufgelöst werden, wenn man sie physisch löst, indem die Wege zum geparkten Auto nicht kürzer sein dürfen als die zur Haltestelle des öffentlichen Verkehrs und auch im Autoverkehr die Marktwirtschaft eingeführt wird. Dies führt zu intelligenteren Lösungen nicht nur in den Siedlungsstrukturen, sondern auch im individuellen Verhalten. Acceleration enhances the risk of mistakes if it is not controlled by feedback loops. The effect of modern technical fast transport systems like cars of information systems are not more intelligent solutions but the contrary. Benefits for the individual car users create more stupid settlement structures with increasing demand on external fossil fuel to be kept alive. Monofunctional urban structures have replaced the former vital pedestrian based sustainable cities. The main cause is the prevailing parking organization, which is based on a regulation from 1939 the Reichsgaragenordnung, forcing everybody to provide enough parking facilities adjacent to each human activity. This establishes an enormous binding force between man and car. This trap can only be opened if the walking distance to and from the parked car is longer than to the public transport stop and if market economy is introduced into the car traffic system. Anyone parking at home has to pay the full cost he creates for the society and the environment.

Document type: Book

The Democratic Republic of Congo's infrastructure: A continental perspective

Scipedia content — Wed, 14 Oct 2020 15:27:16 +0200

The Africa Infrastructure Country Diagnostic (AICD) has gathered and analyzed extensive data on infrastructure in around 40 Sub-Saharan countries, including the Democratic Republic of Congo (DRC). The results have been presented in reports covering different areas of infrastructure ICT, irrigation, power, transport, water and sanitation and different policy areas, including investment needs, fiscal costs, and sector performance. This report presents the key AICD findings for the DRC, allowing the country's infrastructure situation to be benchmarked against that of its African peers. Given that the DRC is a fragile state trying to catch up with other low-income countries (LICs) in the region, both fragile-state and LIC African benchmarks will be used to evaluate the DRC's situation. Detailed comparisons will also be made with immediate regional neighbors in Central Africa. Several methodological issues should be borne in mind. First, because of the cross-country nature of data collection, a time lag is inevitable. The period covered by the AICD runs from 2001 to 2006. Most technical data presented are for 2006 (or the most recent year available), while financial data are typically averaged over the available period to smooth out the effect of short-term fluctuations. Second, in order to make comparisons across countries, indicators had to be standardized to place the analysis on a consistent basis. This means that some of the indicators presented here may be slightly different from those that are routinely reported and discussed at the country level. During the period from 2001 to 2005, per capita economic growth in DRC was on average 2.1 percent higher than during the period from 1991 to 1995. Despite this improvement, growth levels, which oscillated between 4 and 8 percent in the early 2000s, still fell short of the sustained 7 percent per year needed to meet the Millennium Development Goals (MDGs). Improved telecommunications infrastructure has been the main driver of this change, contributing 1.1 percentage points to the country's per capita growth rate. Deficiencies in power infrastructure, on the other hand, held back per capita growth by 0.25 percentage point over this period.

Document type: Book

Energieeffiziente Mobilität durch Aktivierung menschlicher Ressourcen am Beispiel der Stadt Schwäbisch Gmünd

Scipedia content — Wed, 14 Oct 2020 15:25:33 +0200

Dieser Artikel zeigt am Beispiel der Stadt Schwäbisch Gmünd, wie sich auch in mittelgroßen Städten und Gemeinden im ländlichen Raum Maßnahmen verwirklichen lassen, um eine energieeffiziente Mobilität zu forcieren. Ein besonderer Schwerpunkt liegt hierbei auf dem Menschen, nicht auf technologischem Fortschritt. Der Artikel stellt zunächst die Ausgangssituation in Schwäbisch Gmünd dar. Im Weiteren beleuchtet er die wesentlichen mobilitätsbezogenen Maßnahmen des Energieeffizienzkonzeptes und zeigt Möglichkeiten auf, wie Energie im Bereich der Mobilität unter Berücksichtigung lokaler Besonderheiten bilanziert werden kann. This paper uses the example of Schwäbisch Gmünd to suggest ideas how medium-sized towns and communes especially in the rural area can implement arrangements to force energy-efficient mobility. The solutions focus mainly on human beings and their mobility behavior, not only on technological advance. First the paper presents the initial situation in Schwäbisch Gmünd. Further it shows the essential mobility-related arrangements of the energy efficiency strategy. Finally it identifies options to account energy in regard to mobility considering the local specific characteristics.

Document type: Book

Using Fourier Descriptors and Spatial Models for Traffic Sign Recognition

Scipedia content — Wed, 14 Oct 2020 15:19:04 +0200

Traffic sign recognition is important for the development of driver assistance systems and fully autonomous vehicles. Even though GPS navigator systems works well for most of the time, there will always be situations when they fail. In these cases, robust vision based systems are required. Traffic signs are designed to have distinct colored fields separated by sharp boundaries. We propose to use locally segmented contours combined with an implicit star-shaped object model as prototypes for the different sign classes. The contours are described by Fourier descriptors. Matching of a query image to the sign prototype database is done by exhaustive search. This is done efficiently by using the correlation based matching scheme for Fourier descriptors and a fast cascaded matching scheme for enforcing the spatial requirements. We demonstrated on a publicly available database state of the art performance. "p"Original Publication: Fredrik Larsson and Michael Felsberg, Using Fourier Descriptors and Spatial Models for Traffic Sign Recognition, SCIA konferens, 23-27 May 2011, Ystad Sweden, 2011, Lecture Notes in Computer Science, Image Analysis, 238-249. http://dx.doi.org/10.1007/978-3-642-21227-7_23 Copyright: Springer

Document type: Part of book or chapter of book

Wirtschaft und Mobilität - im Wechselspiel mit Gesellschaft und Raum: Einführung

Scipedia content — Wed, 14 Oct 2020 15:05:51 +0200

Document type: Book

A proposal for inter domain qos routing based on distributed overlay entities and qbgp

Scipedia content — Wed, 14 Oct 2020 15:05:21 +0200

This paper proposes a novel and incremental approach to Inter-Domain QoS Routing. Our approach is to provide a completely distributed Overlay Architecture and a routing layer for dynamic QoS provisioning, and to use QoS extensions and Traffic Engineering capabilities of the underlying BGP layer for static QoS provisioning. Our focus is mainly on influencing how traffic is exchanged among non-directly connected multi-homed Autonomous Systems based on specific QoS parameters. We provide evidence supporting the feasibility of our approach by means of simulation.

Document type: Part of book or chapter of book

Real time visualization of wake vortex simulations using computational steering and beowulf clusters

Scipedia content — Wed, 14 Oct 2020 15:03:10 +0200

In this paper, we present the design and implementation of POSSE, a new, lightweight computational steering system based on a client/server programming model. We demonstrate the effectiveness of this software system by illustrating its use for a visualization client designed for a particularly demanding real-time application--wake-vortex simulations for multiple aircraft running on a parallel Beowulf cluster. We describe how POSSE is implemented as an object-oriented, class-based software library and illustrate its ease of use from the perspective of both the server and client codes. We discuss how POSSE handles the issue of data coherency of distributed data structures, data transfer between different hardware representations, and a number of other implementation issues. Finally, we consider how this approach could be used to augment AVOSS (an air traffic control system currently being developed by the FAA) to significantly increase airport utilization while reducing the risks of accidents.

Document type: Part of book or chapter of book

A Contribution to Urban Transport System Analyses and Planning in Developing Countries

Scipedia content — Wed, 14 Oct 2020 15:02:25 +0200

The purpose of this chapter is to provide a contemporary statement of existing approaches to transport-land use planning in urban and regional areas to advise practising transport planners and students. The chapter concentrates on the knowledge that are available for the synthesis, analysis, and evaluation of alternative land use-transport-systems plans and regulations. First, the transportation planner must develop an understanding of the planning process before attempting to address herself to the broader polices issues. The first objective of this chapter is to provide transportation planners with an understanding of the land-use models and their application to urban and regional planning problems. The final objective covers policy, regulations and plans. Absence of physical space between people and firms is the definition of Economists to cities. Cities appear to supply the necessity to eliminate transport costs. Density lowers the costs of interacting with other people and speeds the flow of goods, people and ideas. The location and structure of cities is driven by the desire to eliminate transport costs. In this context, transportation technologies have been the primary determinant of the location and structure of cities. There is increasing concern across the world about increasing traffic congestion and the costs it imposes, particularly on accessibility, the environment, other social factors, such as accidents, and the economy in general. Growing personal car-mileage is engendering the well-known effects on the environment and transport systems, especially roads, which are not able to cope with the increasing amounts of traffic. Further development of innovative, integrated and well-balanced policies is strongly needed. Strong and ongoing growth in mobility, especially in road traffic, means that transport trends are unsustainable if only current policies are pursued: with constraints on resources, space, safety and the environment there are only limited possibilities to extend transport supply to safeguard accessibility. It is quite clear that the need for travel cannot really be avoided; it is crucial for the performance of social and economic functions in any society. People are not travelling much more often than twenty years ago, but they are travelling further and with greater use of the private car. Increasing car ownership is a central component of this (Transland, 2000). There is a lack of knowledge about the interaction between land use and transport and the related planning consequences. Institutional demands for integrated policymaking is 13

Document type: Part of book or chapter of book

Public private networks

Scipedia content — Wed, 14 Oct 2020 14:57:59 +0200

The provision of services and the production of wares and services nowadays often require the cooperation of partners from different sectors. These cooperations can comprise public and private organizations, companies, universities, NGOs, and other groupings as well as individuals. The cooperative collaboration is esteemed as a core element of democratic social systems within a free market economy (Kirsch, 1996; Pongsiri, 2001). As one relevant method of organizing such collaborations, public private networks (PPN) extend the concept of public private partnerships (PPP) by adding the idea of networking and its core elements. From a scientific point of view as well as from the business perspective there is a shortcoming in the systematic processing of ideas, motivations, and forms as well as implications for internal and external participants of PPPs/PPNs. In the following, partnerships between partners from public and private business environments will be discussed. (Pongsiri, 2001) In particular, PPPs and PPNs in the field of academic education will be portrayed, since the cooperation in knowledge intensive areas is seen as an important issue. (Inkpen, 1996; Seufert, von Krogh, & Back, 1999) In the following the concepts of PPPs and PPNs will be explained. This will be done by an extensive literature review. The aim is to provide the required definitions and to discuss the incorporated views of others.

Document type: Part of book or chapter of book

Optimization of bandwidth allocation in communication networks with penalty cost

Scipedia content — Wed, 14 Oct 2020 14:49:49 +0200

In this paper, we present an analysis on optimization and risk management in Communication Networks (CNs). The model is proposed for offline traffic engineering optimization, which takes a centralized view of bandwidth allocation, performance control, and risk control of network profit shortfall. First, we introduce a linear penalty cost in the CN optimization model and derive the optimal bandwidth capacity with the penalty cost. Then, we use the mean-variance approach to analyze the profit shortfall risk in CNs. Finally, numerical results are shown to reveal the impact of the penalty cost on the CNs performance.

Document type: Part of book or chapter of book

Improving Perceived Web Performance by Size Based Congestion Control

Scipedia content — Wed, 14 Oct 2020 14:46:27 +0200

Flow size based congestion control has the potential to improve user perceived Web performance due to the heavy tailed characteristic of file size distributions in the Web. After discussing the benefits and drawbacks of transport protocol and router based solutions for size based congestion control, guidelines for algorithm design are developed. Using these guidelines we find that size based congestion control needs to incorporate TCP models to avoid undesirable user incentives. Based on this insight we specify enhancements to TCP featuring size based congestion control and provide arguments for parameter settings. It is shown by simulation that our modified version of TCP significantly outperforms NewReno from a user perspective in scenarios using realistic models for Web traffic and topologies with multiple congested links.

Document type: Part of book or chapter of book

A scenarios based methodology for it portfolio planning

Scipedia content — Wed, 14 Oct 2020 14:41:36 +0200

One of the main topics in IT Portfolio Management, according to IT Governance models, is to plan and control information systems that are aligned with the company mission and objectives. The goal of the IT Portfolio Planning is to define which information systems are necessary and with which priority. In general, planning methodologies trace directions from a present point to a future and desired target. However, in many cases, companies can not control situations; events may occur that can not be avoided. A scenarios-based planning methodology can help managers to identify future events, their probability and consequences. A scenario represents a future situation that can not be controlled nor can be avoided. However, the study of future scenarios can help managers to plan reactions, so that company can create mechanisms for avoiding problems or for minimizing bad consequences. The goal of this chapter is to present an adaptation of the scenario-based methodology for IT and Information Systems Planning. The chapter will describe in details each step of the proposed methodology and discuss a study case. Steps include the identification of different scenarios and their corresponding antecedent events, the determination of probabilities and consequences of the events, how to calculate risks and how to plan Information Systems and IT resources to manage each scenario.

Document type: Part of book or chapter of book

Auf dem Weg zu einem Grundangebot von Mobilität in ländlichen Räumen: Probleme, Ursachen und Handlungsoptionen

Scipedia content — Wed, 14 Oct 2020 14:41:08 +0200

Der Beitrag geht der Frage nach, wie in ländlichen Räumen ein Grundangebot von Mobilität gewährleistet bzw. hergestellt werden kann. Dazu werden zunächst die Besonderheiten der Mobilität in ländlichen Räumen im Vergleich zu urbanen Gebieten herausgearbeitet sowie aktuelle Trends, Probleme und Konsequenzen für das ÖPNV-Angebot beleuchtet. Schließlich werden verschiedene Handlungsoptionen vorgestellt, wie mit diesen Entwicklungen umgegangen werden kann, um ein Grundangebot sicherstellen zu können. Dabei werden häufig bedarfsgesteuerte Bedienformen als Lösung angepriesen. Die Analyse zeigt jedoch, dass insbesondere in dünn besiedelten ländlichen Räumen erhebliche Finanzierungsdefizite zu erwarten sind. Deshalb werden weitere Alternativen, wie die Effizienzsteigerung im traditionellen ÖPNV, Bürgerbusse, organisierte Mitnahme im privaten Pkw, mobile und dezentrale Versorgung mit Dienstleistungen, Mitnahme durch andere Fahrdienste, Carsharing und Subjektförderung im ÖPNV diskutiert. Im Ergebnis zeigt sich, dass alle Handlungsoptionen sowohl Vor- als auch Nachteile aufweisen. Diese Vielfalt an Bedienformen kann jedoch dazu genutzt werden, das Angebot auf die spezifischen Bedingungen vor Ort zuzuschneiden, was zu einem abgestuften System von den Zentren zur Peripherie führt. The paper addresses the question how a basic provision of mobility could be assured in rural areas. To answer the research question, it analyses the particularities of rural mobility in comparison to urban areas, current trends and resulting problems for the public transport. Afterwards, the review presents different options for action to guarantee a basic mobility against these issues. In transport policy debates, demand responsive transport is often seen as a solution. However, many studies demonstrate the low potential of this transport service, mainly due to the low revenue-to-cost ratio of such services. Therefore, the paper discusses further alternatives including raising efficiency in traditional public transport, voluntary public transport, ride sharing in private cars or in cars of other transport services, mobile and decentral supply of services, car sharing and disbursing mobility vouchers. As a result, all researched alternatives have their particular strengths and weaknesses. The variety of mobility options can, thus, contribute to a tailor- made transport policy considering the specific local conditions. The conclusion comprises a gradual mobility system from core to periphery.

Document type: Book

Charting a New Course

Scipedia content — Wed, 14 Oct 2020 14:40:00 +0200

Infrastructure plays a key role in promoting economic growth and opportunities.In particular, the efficient provision of basic infrastructure services, like water and sanitation, is a key ingredient in fostering a country's social and economic development. Previous studies have found that infrastructure has a positive impact on output, and can improve economic opportunity, including health and education for the poor, particularly in developing countries. In Argentina, a 2005 study, found that child mortality fell by 8 percent in areas that had experienced improved coverage and quality of basic water and sanitation through utility reform, with most of the reduction occurring in low-income areas where the water network expanded the most. More generally, Fay and Morrison found that allowing the poorest quintile in developing countries the same access to basic services as the richest quintile would reduce child mortality by 8 percent and child under development by 14 percent. Calderon and Serven also found a significant positive impact of infrastructure access and quality on overall inequality. Furthermore, the book sheds some light on how to address the main challenge for the future which may be to attract specialized operators to the smaller municipalities which do not currently have them. For that purpose in Colombia, for example, over the last two years, the policy framework has been focused on promoting the sector's development, by using the departments as the intermediate institutional level between the National Government and the municipalities, to formulate programs with regional impact and promote comprehensive investment plans.

Document type: Book

Regionale Mobilität - erneuerbar und klimafreundlich

Scipedia content — Wed, 14 Oct 2020 14:24:35 +0200

Weltweit streben immer mehr Regionen Energieautonomie an. Angesichts der Zukunftsrisiken Klimawandel und Erdölverknappung beabsichtigen sie, ihren Energiebedarf zu 100% aus eigenen erneuerbaren und daher CO2-neutralen Quellen zu decken. Während viele Regionen bei der Produktion von Elektrizität und Wärme große Erfolge erzielen, gibt es hinsichtlich der Deckung des Verkehrsenergiebedarfs noch großen Forschungsbedarf. Um regionale Energieautonomie zu erreichen, müssen sowohl die eigenen erneuerbaren Quellen optimal genutzt als auch der Energiebedarf durch Effizienzsteigerungen so weit wie möglich gesenkt werden. Im Artikel werden verschiedene technische und planerische Optionen für den Verkehrsbereich vorgestellt und diskutiert. Besonderes Augenmerk gilt dabei der Frage, inwieweit sich Verkehrsflächen für die Erzeugung erneuerbarer Energie eignen. Die Umstellung der Verkehrsenergieversorgung auf erneuerbare regionale Quellen ist Chance und Herausforderung zugleich. Viele der negativen Umweltfolgen fossiler Mobilität werden sich voraussichtlich deutlich verringern oder sogar verschwinden. Die Installation von Photovoltaik-Elementen und anderen Anlagen der Energieerzeugung im öffentlichen Raum könnte allerdings auch existierende räumliche Qualitäten gefährden. Benötigt werden daher innovative Planungskonzepte und -instrumente. Bedarf besteht auch für neue Organisationsformen von Mobilität. Städtebau, Stadt- und Regionalplanung werden daher beim Übergang zu regionaler Energieautonomie eine wichtige Rolle spielen. A growing number of regions throughout the world aim at energy autonomy. In order to avoid climate and energy risks, they try to cover their energy demand to 100% by regional, renewable and hence carbon-neutral sources. Many of these regions are very successful in providing electricity and caloric energy, but as far as the energy demand of transport is concerned, there is still a big need for basic research. In order to achieve regional energy autonomy, it is necessary to increase the production of renewable energy as well as to reduce the energy demand. The article presents and discusses a set of relevant technological and planning options for the field of transport. Particular attention is paid to the generation potential of transport infrastructures for renewable energy. The switch from fossil to renewable energy is a chance as well as a challenge. Many of the environmental impacts of fossil-fueled transport are likely to diminish or even disappear. But the insertion of pv panels and other energy generating equipment in open spaces could also endanger existing spatial qualities. Hence innovative design concepts and controls should be developed. There is also a need for new organizational models for mobility. Urban and regional planning and urban design will therefore play an important role in the transition to regional energy autonomy.

Document type: Book

Collaborative decision making and information sharing for air traffic management operations

Scipedia content — Wed, 14 Oct 2020 14:24:10 +0200

One of the most notable concepts related to the future cooperative Air Traffic Management (ATM) is the Collaborative Decision Making (CDM). This new management philosophy of using collaborative technologies and procedures to enable ATM partners drives efforts towards the common goals of sharing and exchanging information. To support the implementation of CDM, a likely solution was found in the context of System of Systems (SoS), system integration, and interoperability. Service-Oriented Architecture (SOA) principles and technologies were recognized as one of the best alternatives to allow this implementation. Within this architecture, the System Wide Information Management (SWIM) has been developed on the last decade, and SWIM applications will be accessible to all ATM partners on the next decade by providing full airspace information, updated in real-time by all involved partners. This chapter presents an overview of key elements in information sharing for ATM and explains how SOA, SWIM, Aeronautical Information Management (AIM) and CDM support each other development.

Document type: Part of book or chapter of book

Minimum interference routing the precomputation perspective

Scipedia content — Wed, 14 Oct 2020 14:22:42 +0200

This paper focuses on the selection of bandwidth-guaranteed channels for communication sessions that require it. The basic idea comes from Minimum Interference Routing: select a feasible path that puts the least possible restriction on the transmission capacity offered by the network for other communicating parties. This is achieved by circumventing some critical bottleneck links. The main contribution of the paper is a method to assess the degree of link criticality facilitating efficient route precomputation even in the case, when up to date resource availability information is not immediately available.

Document type: Part of book or chapter of book

Schneller, öfter, weiter: Herausforderungen für eine mobile Gesellschaft von morgen

Scipedia content — Wed, 14 Oct 2020 14:20:09 +0200

In dem Beitrag geht es um aktuelle Trends und Herausforderungen der deutschen und europäischen Mobilitätsentwicklung. Hierzu zählen neben der Klima- und Energierelevanz des Verkehrs Themen wie soziale Differenzierung, demographischer Wandel und kulturelle Aspekte in ihrer Bedeutung für Mobilität und Verkehr aus einer sozialökologischen Perspektive. Es gibt Vorzeichen für einen möglichen Paradigmenwandel, der v.a. auf eine Dekarbonisierung des Verkehrs abhebt. Ein neues Leitbild einer multioptionalen, intermodalen Personenmobilität wird skizziert, das die Bedürfnisse einer sich weiter differenzierenden und pluralisierenden Gesellschaft aufgreift. Es basiert auf dem Rahmenkonzept "nachhaltige Mobilitätskultur" und auf drei Ebenen von Angeboten, die ein multioptionales Verkehrsangebot bilden. This article examines current trends and challenges of German and European mobility development. This includes besides climate and energy relevance of transport topics such as social differentiation, demographic change and cultural aspects, and looks at their significance for mobility and traffic from a socio-ecological perspective. There are signs for a possible change of paradigms which mainly emphasize the decarbonsation of transport. A new vision of a multioptional, intermodal mobility is sketched. It embraces the needs of a society that is taking on an ever more differentiated and pluralistic form. It bases on the framing concept of "sustainable mobility culture" and three levels within a transport system which form multi-optional transport products.

Document type: Book

Pipeline morphing and virtual pipelines

Scipedia content — Wed, 14 Oct 2020 14:19:41 +0200

Pipeline morphing is a simple but effective technique for reconfiguring pipelined FPGA designs at run time. By overlapping computation and reconfiguration, the latency associated with emptying and refilling a pipeline can be avoided. We show how morphing can be applied to linear and mesh pipelines at both word-level and bit-level, and explain how this method can be implemented using Xilinx 6200 FPGAs. We also present an approach using morphing to map a large virtual pipeline onto a small physical pipeline, and the trade-offs involved are discussed.

Document type: Part of book or chapter of book

Furthering World Bank Group's Corporate Environmental Sustainability

Scipedia content — Wed, 14 Oct 2020 14:15:47 +0200

The World Bank Group (WBG) has focused on reducing the environmental impacts of its internal operations and improving corporate environmental practices since 2002, when the WBG President announced WBG's commitment to Corporate Social Responsibility (CSR). The objective of this document is to summarize the actions WBG has taken thus far to reduce environmental impacts from internal operations and present an action plan to further integrate sustainability into WBG's internal operations. Although this work focuses on the environmental impact associated with WBG daily operations, the links between WBG policies and actions related to environmental management and the financial/social considerations are significant. The International Finance Corporation (IFC) footprint and World Bank corporate responsibility teams facilitate the sustainability commitment of the WBG and monitor and track its progress. These teams provide technical information and research support to a dedicated group of champions throughout the WBG who implement emission reduction activities. Budget for these activities flows primarily through the environment department, the general services department, and IFC facilities management and administration. The environment department and IFC facilities management each resource one staff member to provide back-up research support and to monitor and report on environmental metrics, with building engineers and managers and project officers from across the WBG contributing.

Document type: Book

Making igp routing robust to link failures

Scipedia content — Wed, 14 Oct 2020 14:12:11 +0200

An important requirement of a robust traffic engineering solution is insensitivity to changes, be they in the form of traffic fluctuations or changes in the network topology because of link failures. In this paper we focus on developing a fast and effective technique to compute traffic engineering solutions for Interior Gateway Protocol (IGPs) environments that are robust to link failures in the logical topology. The routing and packet forwarding decisions for IGPs is primarily governed by link weights. Our focus is on computing a single set of link weights for a traffic engineering instance that performs well over all single logical link failures. Such types of failures, although usually not long lasting, of the order of tens of minutes, can occur with high enough frequency, of the order of several a day, to significantly affect network performance. The relatively short duration of such failures coupled with issues of computational complexity and convergence time due to the size of current day networks discourage adaptive reactions to such events. Consequently, it is desirable to a priori compute a routing solution that performs well in all such scenarios. Through computational evaluations we demonstrate that our technique yields link weights that perform well over all single link failures and also scales well, in terms of computational complexity, with the size of the network.

Document type: Part of book or chapter of book

Contesting sustainability in infrastructure planning the debate of the public interest in brisbane s boggo road busway development

Scipedia content — Wed, 14 Oct 2020 14:11:13 +0200

Sustainable infrastructure demands that declared principles of sustainability are enacted in the processes of its implementation. However, a problem arises if the concept of sustainability is not thoroughly scrutinized in the planning process. The public interest could be undermined when the rhetoric of sustainability is used to substantiate a proposed plan. This chapter analyses the manifestation of sustainable development in the Boggo Road Busway Plan in Brisbane, Australia against the sustainability agenda set in the South East Queensland Regional and Transport Plans. Although the construction of the Busway was intended to improve public transport access in the region, its implementation drew significant environmental concerns. Local community groups contested the sustainability concept deployed in Queenslands infrastructure planning. Their challenges resulted in important concessions in the delivery of the Busway plan. This case demonstrates that principles of sustainable infrastructure should be measurable and that local communities be better informed in order to fulfill the public interest in regional planning.

Document type: Part of book or chapter of book

Mobilitätsverhalten der Wohnbevölkerung in Abhängigkeit von der Zentralität des Ortes

Scipedia content — Wed, 14 Oct 2020 14:06:10 +0200

Der Beitrag analysiert die Wechselwirkungen der Zentralität eines Ortes mit der Alltagsmobilität im Bundesland Oberösterreich. Für die im Oberösterreichischen Landesraumordnungsprogramm festgelegten Zentralitätsstufen wird auf Basis der Oberösterreichischen Verkehrserhebung das Mobilitätsverhalten der Wohnbevölkerung ab sechs Jahren an einem typischen Werktag näher betrachtet. Die Untersuchung zeigt, dass sich räumliche Strukturen auf den Anteil der Binnenwege an der Gesamtwegezahl, auf die mittlere Wegehäufigkeit pro Person und Tag und auf die Verkehrsmittelwahl auswirken. Hingegen verhält sich die Verteilung der Wegzwecke in allen Zentralitätsstufen sehr ähnlich. The article in hand analyses the interrelation between the centrality of a place and the traffic behaviour of its residents in everyday life. The evaluation is conducted for the province of Upper Austria which is situated in the northwest of Austria. The Upper Austrian Planning Programme determines four levels of centrality. For each level the traffic behaviour of the residents being six years of age and over is analysed for an average workday. The evaluation is based on the Upper Austrian Mobility Survey and shows that existing spatial structures affect the number of trips per person per day, the number of internal trips as well as the modal split. The purposes of the trips are similar within all levels of centrality.

Document type: Book

Assessing urban transportation development sustainable transportation perspectives for istanbul turkey

Scipedia content — Wed, 14 Oct 2020 14:05:41 +0200

UN Population Revisions indicate that more than 50% of the worlds population has lived in urban areas since 2008 and much of the future urban population increase will be absorbed more by the few metropolitan areas of rapidly growing developing countries (UN, 2008). Due to the accelerated urban growth and uncontrolled urban dispersion through naturally significant peripheral areas, sustainable urban growth management becomes a critical urban development policy in Istanbul. In this respect, the interaction among urban growth, urban transportation, rational land use allocations and sustainable transportation policies has an important role to achieve more sustainable urban development in Istanbul. Istanbul set a unique example of urban spatial development/urban transportation interaction with Bosphorus bridges and the connecting highways. This chapter first addresses urban spatial dispersion and transportation development interaction with special emphasis on the existing and proposed Bosphorus Bridges, and then correlates the results with the recent Transportation Master Plan and Environmental Master Plan. Although the latest Environmental Master Plan prepared by Istanbul Metropolitan Municipality foresights the progression of public transit systems and no third bridge crossing on Bosphorus, there is a top-down impact for the third bridge crossing and a road tunnel on Bosphorus by the Central Government. Due to the interaction among spatial dispersion, transportation development and existing infrastructure, proposed bridges, their connected highways and flyovers as well as recent transportation investments of the Istanbul Metropolitan Municipality are assessed under the light of sustainable urban transportation policies.

Document type: Part of book or chapter of book

ATM Systems and Wind Farms

Scipedia content — Wed, 14 Oct 2020 14:02:19 +0200

All radars are different (even if only due to the physical impacts of their operating locations) and creating a ‘rule of thumb’ for wind farm developments near all systems would require such a level of generalisation as to make it probably worthless. Therefore, in considering the effect of wind turbines on radar, developers need to focus on individual radars in the vicinity of their planned development. It is important also that developers appreciate the nature and extent of any problem. (Novak, 2009) For example, studies into air defence radars that take no account of the associated Command and Control systems may be of very limited value. Because both civil and military aviation communities have legitimate interests that must be protected; this includes protection against the adverse effects of wind turbines. However, there is scope for flexibility throughout the process of considering wind farm applications.

Document type: Part of book or chapter of book

Energie, Klima, Raum. Wie lässt sich Mobilität sinnvoll steuern? Einführung

Scipedia content — Wed, 14 Oct 2020 13:53:24 +0200

Document type: Book

Industry regulation through open source software a strategic ownership proposal

Scipedia content — Wed, 14 Oct 2020 13:07:30 +0200

International audience; This paper is about a twofold proposal submitted to the scrutiny of the OSS scientific community. It is first argued that OSS should be considered a means to establish an industry regulation. The motivation of this first proposal is the need for harmonization of the supply chain in certain industrial sectors. The Air Traffic Management industry (ATM) is the only case considered in this paper. However, it is assumed that the regulatory advantage of OSS is not specific to that industry. The second proposal is about how to establish such a regulation through OSS. It is argued that the legal ownership of the OSS product should be assigned to a public organization, preferably to an organization that would be dedicated to monitor and promote the evolution of that product. The motivation for these proposals is based on the analysis of possible scenarios of OSS ownership in the case of ATM. Perspectives concerning the preliminary implementation of the proposals are introduced.

Document type: Part of book or chapter of book

Intelligent editor for writing worst case execution time oriented programs

Scipedia content — Wed, 14 Oct 2020 13:02:12 +0200

To guarantee timeliness in hard real-time systems the knowledge of the worst-case execution time (WCET) for its time-critical tasks is mandatory. Accurate and correct WCET analysis for modern processor is a quite complex problem. Path analysis is required to identify a minimal set of possible execution paths. Further, the modeling of a processors internal states for features like caches or pipelines requires to consider possible interferences of these features.

Document type: Part of book or chapter of book

Safety, Efficiency and Autonomy - Mastering Conflicting Trends in Embedded Systems Design

Scipedia content — Wed, 14 Oct 2020 13:02:00 +0200

International audience; Embedded systems have developed from single microcontrollers to networked sys-tems and are moving further on to large open systems. As an example, automotive electronics started as a single microcontroller for engine control to develop into a local network of 50 and more electronic control units connected via several network standards and gateways which are found in current cars. These networks will be ex-tended by open wireless car-to-car or car-to-infrastructure communication enabling completely new functionality, such as advanced driver assistance systems that report approaching cars that could cause an accident. Other examples are found in health-care, where patients are monitored at home connected to a hospital data base and monitoring system rather than staying in the hospital for that purpose, or in smart buildings where different control functions are integrated to minimize energy con-sumption and adapt consumption to the available energy, or in energy supply net-works that are optimized to include renewable energy production. In all these cases we observe a transition from local closed networks with a single systems integrator controlling all design aspects (such as an automotive manufacturer) to larger open networks with many independent functions and different integrators following differ-ent design objectives. The Internet plays an important role supporting that trend. Unlike closed networks with a defined topology, such systems change over the life-time of a system.

Document type: Part of book or chapter of book

A Fair Bulk Data Transmission Protocol in Grid Environments

Scipedia content — Wed, 14 Oct 2020 13:01:00 +0200

In this paper, we propose FHSTCP (Fair High-Speed TCP) as an improvement of HSTCP, which adds a fair factor to eliminate the difference of congestion window caused by different RTT and adopts block-pacing to reduce the burstiness. Simulation results show that FHSTCP can alleviate the RTT unfairness meanwhile keeping advantages of HSTCP.

Document type: Part of book or chapter of book

Using Smartphones to Detect Car Accidents and Provide Situational Awareness to Emergency Responders

Scipedia content — Wed, 14 Oct 2020 12:56:50 +0200

Accident detection systems help reduce fatalities stemming from car accidents by decreasing the response time of emergency responders. Smartphones and their onboard sensors (such as GPS receivers and accelerometers) are promising platforms for constructing such systems. This paper provides three contributions to the study of using smartphone-based accident detection systems. First, we describe solutions to key issues associated with detecting traffic accidents, such as preventing false positives by utilizing mobile context information and polling onboard sensors to detect large accelerations. Second, we present the architecture of our prototype smartphone-based accident detection system and empirically analyze its ability to resist false positives as well as its capabilities for accident reconstruction. Third, we discuss how smartphone-based accident detection can reduce overall traffic congestion and increase the preparedness of emergency responders.

Document type: Part of book or chapter of book

Pma supplier selection using the mahalanobis taguchi system

Scipedia content — Wed, 14 Oct 2020 12:56:33 +0200

Most hi-tech industries owe at least some of their success to being in the right place at the right time. This is especially true for the aircraft parts manufacturer approval (PMA) industry. A PMA is both a design approval and a production approval. It is issued for the production of modification or replacement parts for aircraft, which includes materials, parts, processes, and appliances. In the current economic climate, airlines throughout the world are looking for partners with financial stability. The reason is simple, they want partners that will continue to support them with extra savings opportunities in the short and long-term future. As more and more PMA companies are advertising through the Internet, a supplier performance measurement model applying to each of these networked organizations will facilitate the airline selection of long-term PMA partners. In this chapter, the Mahalanobis Taguchi System (MTS) approach, a multivariate data based selection system, will be used to identify the promising PMA suppliers. Suppliers who are known to be promising are called promising groups and their performance data sets are used to create a reference metric for the promising PMA supplier population. In view of the synergetic performance of neural network and data mining technologies, it is expected that this MTS-based PMA partner selection method, implementing through a neural data mining system (NDMS) will provide a practical solution in the identification of the promising PMA suppliers.

Document type: Part of book or chapter of book

Schneller, öfter, weiter? Perspektiven der Raumentwicklung in der Mobilitätsgesellschaft. Einführung

Scipedia content — Wed, 14 Oct 2020 12:53:24 +0200

Document type: Book

Analysis of recipient executed trust funds

Scipedia content — Wed, 14 Oct 2020 12:52:59 +0200

In recent years, bilateral aid channeled through multilateral organizations like the World Bank has become an important vehicle for concessional finance for development. At the end of FY09, the World Bank held US$23.9 billion in trust, an amount that has doubled since FY05. While much of the growth reflects the increase in large Financial Intermediary Funds (FIFs), there has also been a rapid increase in Recipient Executed Trust Funds (RETFs). This paper aims to inform internal Bank audiences and stimulate discussion on some selected issues - primarily the growing importance of RETFs as a source of finance and relevance to Bank's country level operations. The report also examines briefly the link between RETF allocations and country performance. The report finds that disbursements of RETFs grew by twenty percent over FY03-FY09. Over this period the trends in regional disbursement shares shifted away from East Asia and Pacific and South Asia Regions to Africa Region. Recipient country concentration is evident: fifty percent of the disbursements have been from six countries - Afghanistan, West Bank and Gaza, Ethiopia, Vietnam, Indonesia and China. RETF disbursements, as a share of the combined International Bank for Reconstruction and Development (IBRD), International Development Association (IDA), and RETF, grew from five percent in FY03 to twelve percent in FY08, while that of IBRD and IDA fluctuated. The bulk of the disbursements from RETF grants were from IDA eligible countries. RETFs appear to have substituted for IDA in fragile and conflict affected states. Disbursements from RETF grants and IDA credits were broadly aligned by sector. There may be some correlation between RETF grants allocation and country performance but the results are not conclusive. The report identifies some areas for further examination: whether RETFs should complement or substitute for Bank operations in specific cases; and whether RETF allocations should be made on the basis of some need or performance based country priorities, outcomes and results.

Document type: Book

Richard branson screw it let s do it

Scipedia content — Wed, 14 Oct 2020 12:50:39 +0200

Document type: Part of book or chapter of book

On the Performance of Grooming Strategies for Offloading IP Flows onto Lightpaths in Hybrid Networks

Scipedia content — Wed, 14 Oct 2020 12:46:36 +0200

Document type: Part of book or chapter of book

Interdomain ingress traffic engineering through optimized as path prepending

Scipedia content — Tue, 29 Sep 2020 10:04:10 +0200

In INterdomain Ingress Traffic Engineering (INITE), a “target” Autonomous System (AS) aims to control the ingress link at which the traffic of one or more upstream source networks enters that AS. In practice, ISPs often manipulate, mostly in a trial-and-error manner, the length of the AS-Path attribute of upstream routes through a simple technique known as prepending (or padding). In this paper, we focus on prepending and propose a polynomial-time algorithm (referred to as OPV) that determines the optimal padding for an advertised route at each ingress link of the target network. Specifically, given a set of “elephant” source networks and some maximum load constraints on the ingress links of the target AS, OPV determines the minimum padding at each ingress link so that the load constraints are met, when it is feasible to do so. OPV requires as input an AS-Path length estimate from each source network to each ingress link. We describe how to estimate this matrix, leveraging the BGP Looking Glass Servers. To deal with unavoidable inaccuracies in the AS-Path length estimates, and also to compensate for the generally unknown BGP tie-breaking process in upstream networks, we also develop a robust variation (RPV) of the OPV algorithm.

Document type: Part of book or chapter of book

Cooperative content distribution scalability through self organization

Scipedia content — Tue, 29 Sep 2020 10:02:52 +0200

Peer-to-peer networks have often been touted as the ultimate solution to scalability. Although cooperative techniques have been initially used almost exclusively for content lookup and sharing, one of the most promising application of the peer-to-peer paradigm is to capitalize the bandwidth of client peers to quickly distribute large content and withstand flash-crowds (i.e., a sudden increase in popularity of some online content). Cooperative content distribution is based on the premise that the capacity of a network is as high as the sum of the resources of its nodes: the more peers in the network, the higher its aggregate bandwidth, and the better it can scale and serve new peers. Such networks can thus spontaneously adapt to the demand by taking advantage of available resources. In this paper, we evaluate the use of peer-to-peer networks for content distribution under various system assumptions, such as peer arrival rates, bandwidth capacities, cooperation strategies, or peer lifetimes. We argue that the self-scaling and self-organizing properties of cooperative networks pave the way for cost-effective, yet highly efficient and robust content distribution.

Document type: Part of book or chapter of book

A transition towards sustainable strategy making: integrating land use and transport knowledge types

Scipedia content — Tue, 29 Sep 2020 10:00:46 +0200

As extensively discussed by other scholars, there is a growing awareness that the integration of land use and transport (LUT) planning is a crucial prerequisite for the transition towards more sustainable transport patterns and urban development that foster interaction between people, support a sustainable business climate and reduces negative effects on the environment and climate (see, for example, Banister 2002, 2005; Cervero 1998; Meyer and Miller 2001; TRB 2004). However, in the Netherlands (and in other countries), such integration is scarcely present in daily planning practice (see, for instance, Hull and Tricker 2006). If anything, one can speak of policy coordination rather than ‘integration’; i.e. it is dialogue or information exchange which is geared at avoiding conflicts between projects, but does not seek to establish similar policy goals (Stead et al. 2004). Achieving integration in earlier phases of planning (for example, strategy development, goal orientation or visioning) can potentially produce shared policy goals, which would promote mutually reinforcing (instead of obstructing) land use and transport measures. However, for this to happen, a transition on its own is needed.

Document type: Part of book or chapter of book

Internationalisation and mobility in european vocational education and training : international report

Scipedia content — Tue, 29 Sep 2020 09:57:24 +0200

The international report is an outcome of the European Leonardo da Vinci project Internationalisation and Mobility in the students Curricula (INtheMC) carried out with eight partners from seven European countries. It analyses the situation of internationalisation and transnational mobility in vocational education and training (VET) in Europe. After outlining the initial situation the situation of VET in the partner countries the report shows the current situation and trends of internationalisation and mobility within VET. Then European instruments (Europass Mobility, EQF, ECVET), which promotes internationalisation and mobility in VET are presented also concerning the actual state of implementation in the partner countries. Following this, several available researches on target groups are displayed. Examples from best practice and obstacles are shown. Then the question is asked and in part answered: how to improve internationalisation and educational mobility in order to obtain desired outcomes in VET? The report ends with conclusions and proposals for promoting internationalisation and mobility in VET. (Orig.)

Document type: Book

Valuation of Ecosystem Services in World Bank Group Work

Scipedia content — Tue, 29 Sep 2020 09:50:48 +0200

In 2005, the Millennium Ecosystem Assessment (MA, 2005) provided the first comprehensive report on global ecosystems, the dependence of human societies on the services provided, current state, and likely future trajectory. The MA identified the failure to value ecosystem services as a major contributing cause. The 2001 environment strategy did not explicitly address environmental valuation, although the focus on poverty and environment implies a need for valuing natural resources and environmental services. In consultations on the 2010 environment strategy, a wide range of stakeholders stressed the importance of mainstreaming environmental services. To better direct limited resources for environmental valuation and training, a closer look is needed to identify the conditions under which valuation has had an impact on: policy and project design, policy dialogue in client countries, environmental investments, and strengthening the capacity of national institutions. This report presents a review of environmental valuation in World Bank operational and analytical work, identifying what has been done, and the impacts environmental valuation has had. The report identifies the conditions under which valuation is most likely to influence decision-makers, and finally, the implications for the 2010 environment strategy. The report is organized as follows: section one gives context; section two gives introduction; section three gives approach to learning from past experience; section four focuses on coverage of ecosystem services; section five presents prioritizing environmental valuation; section six deals with why environmental valuation not done; and section seven gives recommendations.

Document type: Book

Modeling control system failures and attacks the waterloo campaign to oil pipelines

Scipedia content — Tue, 29 Sep 2020 09:45:31 +0200

This paper presents a model for expressing control system failures and attacks on control protocols that involve the exchange of messages. Control failures and attacks are modeled using the notion of an attacker who can block and/or fabricate messages. These two attack mechanisms can cover a variety of scenarios ranging from control failures in the Waterloo Campaign to cyber attacks on oil pipelines. The model helps provide a comprehensive understanding of control system failures and attacks, which supports the development of strategies for attack as well as defense.

Document type: Part of book or chapter of book

Responsabilidad social

Scipedia content — Mon, 27 Apr 2020 09:51:37 +0200

Español:En

Estructuración del precio de un menú

Scipedia content — Mon, 27 Apr 2020 09:49:41 +0200

Español:El

Sistema de navegación automática controlada por voz para una silla de ruedas

Scipedia content — Mon, 27 Apr 2020 09:47:46 +0200

Español:El

Modelo de contaminación del aire

Scipedia content — Mon, 27 Apr 2020 09:45:49 +0200

La basura electrónica y la contaminación ambiental

Scipedia content — Mon, 27 Apr 2020 09:43:54 +0200

Español:En

Embutidos fortificados con proteína vegetal a base de quinua (Chenopodium quinoa Wild.)

Scipedia content — Mon, 27 Apr 2020 09:41:59 +0200

Español:El

Optimización de la geometría de la bomba hidráulica tipo jet

Scipedia content — Mon, 27 Apr 2020 09:40:04 +0200

Español:Este

Influencia del tratamiento UV-C sobre carambola (Averrhoa carambola L.) mínimamente procesada

Scipedia content — Mon, 27 Apr 2020 09:38:08 +0200

Español:La

Possibilities of the Particle Finite Element Method in computational mechanics

María Jesús Samper — Mon, 25 Nov 2019 16:23:09 +0100

We present some developments in the formulation of the Particle Finite Element Method (PFEM) for analysis of complex coupled problems in fluid and solid mechanics accounting for fluid-structure interaction and coupled thermal effects. The PFEM uses an updated Lagrangian description to model the motion of nodes (particles) in both the fluid and the structure domains. Nodes are viewed as material points which can freely move and even separate from the main analysis domain representing, for instance, the effect of water drops. A mesh connects the nodes defining the discretized domain where the governing equations are solved as in the standard FEM. The necessary stabilization for dealing with the incompressibility of the fluid is introduced via the finite calculus (FIC) method. An incremental iterative scheme for the solution of the non linear transient coupled fluid-structure problem is described. Extensions of the PFEM to allow for frictional contact conditions at fluid-solid and solid-solid interfaces via mesh generation are described. A simple algorithm to treat erosion in the fluid bed is presented. Examples of application of the PFEM to solve a number of coupled problems such as the effect of large wave on structures, the large motions of floating and submerged bodies, bed erosion situations and melting and dripping of polymers under the effect of fire are given.

An error estimator for separated representations of highly multidimensional models

María Jesús Samper — Mon, 04 Nov 2019 13:53:46 +0100

Fine modeling of the structure and mechanics of materials from the nanometric to the micrometric scales uses descriptions ranging from quantum to statistical mechanics. Most of these models consist of a partial differential equation defined in a highly multidimensional domain (e.g. Schrodinger equation, Fokker-Planck equations among many others). The main challenge related to these models is their associated curse of dimensionality. We proposed in some of our former works a new strategy able to circumvent the curse of dimensionality based on the use of separated representations (also known as finite sums decomposition). This technique proceeds by computing at each iteration a new sum that consists of a product of functions each one defined in one of the model coordinates. The issue related to error estimation has never been addressed. This paper presents a first attempt on the accuracy evaluation of such a kind of discretization techniques.

Strict error bounds for linear and nonlinear solid mechanics problems using a patch-based flux-free method

María Jesús Samper — Wed, 30 Oct 2019 11:54:59 +0100

We discuss, in this paper, a common flux-free method for the computation of strict error bounds for linear and nonlinear Finite Element computations. In the linear case, the error bounds are on the energy norm of the error, while, in the nonlinear case, the concept of error in constitutive relation is used. In both cases, the error bounds are strict in the sense that they refer to the exact solution of the continuous equations, rather than to some FE computation over a refined esh. For both linear and nonlinear solid mechanics, this method is based on the computation of a statically admissible stress field, which is performed as a series of local problems on patches of elements

Error estimation and quality control

María Jesús Samper — Wed, 30 Oct 2019 11:43:01 +0100

This chapter provides a description of the error assessment tools available for general finite element analysis, in particular those for solid and structural mechanics. The text focuses on goal-oriented error estimation, in terms of general quantities of interest rather than on energy norm. However, the energy norm estimates are also discussed because they are seen as basic tools that must be used for assessing the error in arbitrary functional outputs of the solution. Attention is paid to the classification of the different methodologies and their main characteristics.

A flux-free a posteriori error estimator for the incompressible Stokes problem using a mixed FE formulation

María Jesús Samper — Wed, 30 Oct 2019 11:12:41 +0100

In this contribution, we present an a posteriori error estimator for the incom- pressible Stokes problem valid for a conventional mixed FE formulation. Due to the saddle-point property of the problem, conventional error estimators de- veloped for pure minimization problems cannot be utilized straight-forwardly. The new estimator is built up by two key ingredients. At first, a computed error approximation, exactly fulfilling the continuity equation for the error, is obtained via local Dirichlet problems. Secondly, we adopt the approach of solving local equilibrated flux-free problems in order to bound the remaining, incompressible, error. In this manner, guaranteed upper and lower bounds, of the velocity ”energy norm” of the error as well as goal-oriented (linear) output functionals, with respect to a reference (overkill) mesh are obtained. In particular, it should be noted that this approach requires no computa- tion of hybrid fluxes. Furthermore, the estimator is applicable to mixed FE formulations using continuous pressure approximations, such as the Mini and Taylor-Hood class of elements. In conclusion, a few simple numerical examples are presented, illustrating the accuracy of the error bounds.

Modeling, with a unified level-set representation, of the expansion of a hollow in the ground under different physical phenomena

María Jesús Samper — Wed, 30 Oct 2019 11:06:41 +0100

This paper builds on the flexibility of the level-set representation to model in a unified manner the expansion of a hollow in the ground under different physical phenomena. In particular, the dissolving action of a flow of water in a saturated soil, and that of a jet of particles of water in a non-saturated one, are represented in a common framework. In that manner, the complex geometrical evolutions of the hollow can be followed without the need for remeshing and this approach allows for a smooth transition between saturated and non-saturated models of the soil. Implementation and numerical difficulties are discussed and two applications of industrial interest are considered. The first one describes the modeling of the piping phenomenon, and the second one the evolution of an excavation created by a leaking duct.

Accurate recovery-based upper error bounds for the extended finite element framework

María Jesús Samper — Tue, 29 Oct 2019 17:03:24 +0100

This paper introduces a recovery-type error estimator yielding upper bounds of the error in energy norm for linear elastic fracture mechanics problems solved using the extended finite element method (XFEM). The paper can be considered as an extension and enhancement of a previous work in which the upper bounds of the error were developed in a FEM framework. The upper bound property requires the recovered solution to be equilibrated and continuous. The proposed technique consists of using a recovery technique, especially adapted to the XFEM framework that yields equilibrium at a local level (patch by patch). Then a postprocess based on the partition of unity concept is used to obtain continuity. The result is a very accurate but only nearly-statically admissible recovered stress field, with small equilibrium defaults introduced by the postprocess. Sharp upper bounds are obtained using a new methodology accounting for the equilibrium defaults, as demonstrated by the numerical tests.

SUPG-based stabilization using a separated representations approach

María Jesús Samper — Tue, 29 Oct 2019 15:25:03 +0100

We have developed a new method for the construction of Streamline Upwind Petrov Galerkin (SUPG) stabilization techniques for the resolution of convection-diffusion equations based on the use of separated representations inside the Proper Generalized Decompositions (PGD) framework. The use of SUPG schemes produces a consistent stabilization adding a parameter to all the terms of the equation (not only the convective one). SUPG obtains an exact solution for problems in 1D, nevertheless, a generalization does not exist for elements of high order or for any system of convection-diffusion equations. We introduce in this paper a method that achieves stabilization in the context of Proper Generalzied Decomposition (PGD). This class of approximations use a representation of the solution by means of the sum of a finite number of terms of separable functions. Thus it is possible to use the technique of separation of variables in the context of problems of convection-diffusion that will lead to a sequence of problems in 1D where the parameter of stabilization is well known.

Error assessment and mesh adaptivity for regularized continuous failure models

María Jesús Samper — Mon, 28 Oct 2019 16:35:30 +0100

This paper deals with the adaptive finite element analysis of structural failure. A gradient-enhanced damage model has been chosen to simulate material degradation. Since this model is regularized in the post-peak regime, the finite element solution does not suffer from pathological mesh dependence and thus converges to an objective solution upon mesh refinement. However, the error analyses have shown that the error in the nonlocal equivalent strain field becomes dominant during the postpeak loading stages. The accuracy of the nonlocal equivalent strain field (and the corresponding damage quantity) also greatly influences the accuracy of the quantity of interest. Two error measures have been proposed. The goal-oriented error estimates have provided similar error distributions, although some small differences have been found in the softening regime. Objective error estimates, together with adaptive criteria, have been used to perform automated h-adaptivity during computation.

Assembling sparse matrices in MATLAB

María Jesús Samper — Mon, 28 Oct 2019 16:25:06 +0100

The assembly of sparse matrices is a key operation in finite element methods. In this study we analyze several factors that may have an influence on the efficiency of the assembly procedure.

Different insertion strategies are compared using two metrics: a Cost function (the number of memory movements) and actual computing time. An improved algorithm implemented in MATLAB is proposed. It reduces both memory operations and computing time for all tested cases.

The efficiency of the assembly process is found to be highly dependent on node and element numbering. The effect of the classic reverse Cuthill–McKee algorithm is, in most cases, positive and reduces computation costs.

Finally, the case where a sparse matrix has to be re‐assembled at each time step is studied. The efficiency of the assembly is improved if the matrix pattern is entirely or partially inherited from previous steps.

Thermal coupling of fluid and structural response of a tunnel induced by fire

María Jesús Samper — Thu, 05 Sep 2019 11:10:52 +0200

In this work we present the progress in the development of an algorithm for the simulation of thermal fluid–structural coupling in a tunnel fire. The coupling strategy is based on a Dirichlet/Neumann non‐overlapping domain decomposition of the problem, which is carried out by developing a master code that controls solvers dedicated to the fluid mechanics and to the solid mechanics simulation. The computational fluid dynamics formulation consists of a stabilized finite element approximation of the low Mach number equations based on the subgrid scale concept, that allows us to deal with convection‐dominated problems and to use equal order interpolation of velocity and pressure. The thermo‐structural model of the tunnel vault, that considers a multiphase porous material where pores are partly filled with liquid and partly by gas, is specially devised for the simulation of concrete at high temperatures and consists of balance equations for mass conservation of dry air, mass conservation of water species (both in the liquid and gaseous state), enthalpy conservation and linear momentum conservation taking phase changes into account. The developed algorithm is applied to the problem of the response of a tunnel to a fire. We consider the combustion process as a heat release which can vary usually from 1thinspaceMW for small car fires to 100 MW for catastrophic fires. The released heat is transferred to the concrete walls of the tunnel which could cause extensive and heavy damage of the structure.

Long-term stability estimates and existence of a global attractor in a finite element approximation of the Navier-Stokes equations with numerical sub-grid scale modeling

María Jesús Samper — Thu, 05 Sep 2019 10:24:26 +0200

Variational multiscale methods lead to stable finite element approximations of the NavierStokes equations, both dealing with the indefinite nature of the system (pressure stability) and the velocity stability loss for high Reynolds numbers. These methods enrich the Galerkin formulation with a sub-grid component that is modelled. In fact, the effect of the sub-grid scale on the captured scales has been proved to dissipate the proper amount of energy needed to approximate the correct energy spectrum. Thus, they also act as effective large-eddy simulation turbulence models and allow to compute flows without the need to capture all the scales in the system. In this article, we consider a dynamic sub-grid model that enforces the sub-grid component to be orthogonal to the finite element space in L 2 sense. We analyze the long-term behavior of the algorithm, proving the existence of appropriate absorbing sets and a compact global attractor. The improvements with respect to a finite element Galerkin approximation are the long-term estimates for the sub-grid component, that are translated to effective pressure and velocity stability. Thus, the stabilization introduced by the sub-grid model into the finite element problem is not deteriorated for infinite time intervals of computation.

Finite element approximation of turbulent thermally coupled incompressible flows with numerical sub-grid scale modeling

María Jesús Samper — Thu, 05 Sep 2019 10:16:33 +0200

The objective of this work is to describe a variational multiscale finite element approximation for the incompressible Navier-Stokes equations using the Boussinesq approximation to model thermal coupling. The main feature of the formulation in contrast to other stabilized methods is that we consider the subscales as transient and orthogonal to the finite element space. These subscales are solution of a differential equation in time that needs to be integrated. Likewise, we keep the effect of the subscales both in the nonlinear convective terms of the momentum and temperature equations and, if required, in the thermal coupling term of the momentum equation. This strategy allows us to approach the problem of dealing with thermal turbulence from a strictly numerical point of view and discuss important issues, such as the relationship between the turbulent mechanical dissipation and the turbulent thermal dissipation

Stabilized continuous and discontinuous Galerkin techniques for Darcy flow

María Jesús Samper — Thu, 05 Sep 2019 10:01:20 +0200

We design stabilized methods based on the variational multiscale decomposition of Darcy's problem. A model for the subscales is designed by using a heuristic Fourier analysis. This model involves a characteristic length scale, that can go from the element size to the diameter of the domain, leading to stabilized methods with different stability and convergence properties. These stabilized methods mimic different possible functional settings of the continuous problem. The optimal method depends on the velocity and pressure approximation order. They also involve a subgrid projector that can be either the identity (when applied to finite element residuals) or can have an image orthogonal to the finite element space. In particular, we have designed a new stabilized method that allows the use of piecewise constant pressures. We consider a general setting in which velocity and pressure can be approximated by either continuous or discontinuous approximations. All these methods have been analyzed, proving stability and convergence results. In some cases, duality arguments have been used to obtain error bounds in the L2-norm.

On the stabilization parameter in the subgrid scale approximation of scalar convection–diffusion–reaction equations on distorted meshes

María Jesús Samper — Thu, 05 Sep 2019 09:52:00 +0200

In this paper we revisit the definition of the stabilization parameter in the finite element approximation of the convection–diffusion–reaction equation. The starting point is the decomposition of the unknown into its finite element component and a subgrid scale that needs to be approximated. In order to incorporate the distortion of the mesh into this approximation, we transform the equation for the subgrid scale within each element to the shape-regular reference domain. The expression for the subgrid scale arises from an approximate Fourier analysis and the identification of the wave number direction where instabilities are most likely to occur. The final outcome is an expression for the stabilization parameter that accounts for anisotropy and the dominance of either convection or reaction terms in the equation.

The dissipative structure of variational multiscale methods for incompressible flows

María Jesús Samper — Tue, 03 Sep 2019 15:44:46 +0200

In this paper, we present a precise definition of the numerical dissipation for the orthogonal projection version of the variational multiscale method for incompressible flows. We show that, only if the space of subscales is taken orthogonal to the finite element space, this definition is physically reasonable as the coarse and fine scales are properly separated. Then we compare the diffusion introduced by the numerical discretization of the problem with the diffusion introduced by a large eddy simulation model. Results for the flow around a surface-mounted obstacle problem show that numerical dissipation is of the same order as the subgrid dissipation introduced by the Smagorinsky model. Finally, when transient subscales are considered, the model is able to predict backscatter, something that is only possible when dynamic LES closures are used. Numerical evidence supporting this point is also presented.

A numerical strategy to compute optical parameters in turbulent flow. Application to telescopes

María Jesús Samper — Tue, 03 Sep 2019 15:35:43 +0200

We present a numerical formulation to compute optical parameters in a turbulent air flow. The basic numerical formulation is a large eddy simulation (LES) of the incompressible Navier-Stokes equations, which are approximated using a finite element method. From the time evolution of the flow parameters we describe how to compute statistics of the flow variables and, from them, the parameters that determine the quality of the visibility. The methodology is applied to estimate the optical quality around telescope enclosures.

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