Scipedia: Documents published in 2012

Employing Traffic Lights as Road Side Units for Road Safety Information Broadcast

Scipedia content — Thu, 21 Jan 2021 15:42:39 +0100

There is great concern over growing road accidents and associated fatalities. In order to reduce accidents, improve congestion and offer smooth flow of traffic, several measures, such as providing intelligence to transport, providing communication infrastructure along the road, and vehicular communication, are being undertaken. Traffic safety information broadcast from traffic lights using Visible Light Communication (VLC) is a new cost effective technology which assists drivers in taking necessary safety measures. This chapter presents the VLC broadcast system considering LED-based traffic lights. It discusses the integration of traffic light Roadside Units (RSUs) with upcoming Intelligent Transportation Systems (ITS) architecture. Some of the offered services using this technology in vehicular environment together with future directions and challenges are discussed. A prototype demonstrator of the designed VLC systems is also presented.

Low Frequency Eddy Currents with Magnetic Saturation for In-Line Detection and Sizing of Stress Corrosion Cracks

Scipedia content — Thu, 21 Jan 2021 15:40:19 +0100

Under previous programs for the Pipeline Research Committee, Battelle has developed and field tested a low frequency eddy current instrument for characterizing stress corrosion cracks in pipelines. While a significant improvement over conventional magnetic particle inspections, the eddy current method as it was developed in these programs is limited to use for inspections of pipelines from the outside surface. This paper examines the possibility of using this low frequency eddy current equipment to detect and size stress corrosion cracks from the interior of the pipeline by magnetically saturating the pipeline to reduce its permeability and thereby increase penetration of the eddy currents into the pipe.

Efficiency Assurance of Human-Centered and Technology Driven Air Traffic Management

Scipedia content — Thu, 21 Jan 2021 15:35:09 +0100

Europe enjoys a very high level of aviation safety. However, the constant increase in air traffic is putting pressure on safety, and this has consequences in terms of delays. The technical measures, taken to improve the management of airspace in recent years, have created additional capacity, but this has rapidly been outstripped by the growth of traffic. Passengers are now demanding a better quality of air transport service especially in terms of punctuality, given that it is no longer the exception that flights are over half an hour late.

Introducing Behavioral Change in Transportation into Energy/Economy/Environment Models

Scipedia content — Thu, 21 Jan 2021 15:26:36 +0100

Transportation is vital to economic and social development, but at the same time generates undesired consequences on local, regional, and global scales. One of the largest challenges is the mitigation of energy-related carbon dioxide emissions, to which this sector already contributes one-quarter globally and one-third in the United States. Technology measures are the prerequisite for drastically mitigating energy use and all emission species, but they are not sufficient. The resulting need for complementing technology measures with behavioral change policies contrasts sharply with the analyses carried out by virtually all energy / economy / environment (E3) models, given their focus on pure technology-based solutions. This paper addresses the challenges for E3 models to simulate behavioral changes in transportation. A survey of 13 major models concludes that especially hybrid energy models would already be capable of simulating some behavioral change policies, most notably the imposition of the full marginal societal costs of transportation. Another survey of major macroscopic transportation models finds that key specifications required for simulating behavioral change have already been implemented and tested, albeit not necessarily on a global scale. When integrating these key features into E3 models, a wide range of technology and behavioral change policies could be analyzed.

Parallel Embedded Computing Architectures

Scipedia content — Thu, 21 Jan 2021 15:22:28 +0100

It was around the years 2003 to 2005 that a dramatic change seized the semiconductor industry and the manufactures of processors. The increasing of computing performance in processors, based on simply screwing up the clock frequency, could not longer be holded. All the years before the clock frequency could be steadily increased by improvements achieved both on technology and on architectural side. Scaling of the technology processes, leading to smaller channel lengths and shorter switching times in the devices, and measures like instruction-level-parallelism and out-of-order processing, leading to high fill rates in the processor pipelines, were the guarantors to meet Mooreâs law.

Tourism Life Cycle Assessment (LCA): Proposal of a New Methodological Framework for Sustainable Consumption and Production

Scipedia content — Thu, 21 Jan 2021 15:17:58 +0100

1Camillo De Camillis1,2, Paul Peeters3, Luigia Petti4 and Andrea Raggi4 1Dipartimento di Scienze, Universita degli Studi âG. dâAnnunzioâ, Pescara European Commission, Joint Research Centre, IES, Ispra* 3Center for Sustainable Transport and Tourism, NHTV Breda University of Applied Sciences, Breda, 4Dipartimento di Economia, Universita degli Studi âG. dâAnnunzioâ, Pescara 1,2,4Italy 3The Netherland

Low-Carbon Pilot Tour and Municipal Government Investment: Taiwan’s Experience

Scipedia content — Thu, 21 Jan 2021 15:15:07 +0100

In the 1980s the carbon-mitigation strategy of Taiwan focused on the recycling of community waste (Chang and Chang, 1993). In the 1990s and 2000s the strategy shifted to reducing the Green House Effect and introducing low-carbon energy technologies such as wind power, solar power, gas, biomass energy, and other reusable energies. Many policies tried to encourage businesses to development reusable energies such as tax deductions or subsidies. Many researches attempted to evaluate the policy effectiveness of the reduction of the various types of pollution, and most of results found that the reduction effects were not as good as the policy claimed or expected (Lee, 1996, Lee, 2003,Wang, 1999). In recent years, the government has tried to embed green construction, green life and green transportation into people's lives.

Evaluation of Drinking Water Quality in Three Municipalities of Romania: The Influence of Municipal and Customer's Distribution Systems Concerning Trace Metals

Scipedia content — Thu, 21 Jan 2021 15:12:09 +0100

When drinking water is distributed through pipelines, biofilms will grow on the inner surface of the pipes and soft deposits (organic and inorganic matter) and several metals will accumulate to the pipelines (Lehtola & al, 2004a). Discoloration of drinking water is one of the main reasons customers complain to their water company. An elevated concentration of iron or increased turbidity, affect taste, odor and color in drinking water. Unlined iron pipes in drinking water distribution networks develop extensive internal corrosion scales as the time of use increases. These corrosion scale deposits reduce the hydraulic capacity of the pipes and more energy is required to deliver water at a desire flow rate (Sarin et al., 2004).

Regulatory Requirements

Scipedia content — Thu, 21 Jan 2021 15:07:35 +0100

This chapter describes the current legislation and guidelines governing the conduct of clinical trials within country-specific and global contexts. Although many of these guidelines have been harmonised globally [such as International Council for Harmonization-Good Clinical Practice (ICH-GCP)], they are often enforced in accordance with country-specific legislation resulting in varying regulatory requirements and processes. Medicine Regulatory Authorities (MRAs) and Institutional Review Boards (IRBs) across the world must ensure that all clinical trials of both nonregistered medicines, comply with the necessary requirements for safety, quality, and efficacy prior to participant enrollment. Only once approval is received from each country-specific MRA (and there may be more than one) as well as the IRB may the trial commence. This chapter provides general oversight of regulatory processes in several countries as well as guidance as to where and how to access the documentation required for a clinical trial application (CTA). The regulatory submission process is the rate-limiting step of any clinical trial and significantly impacts on trial timelines. It is thus in the applicants best interest to ensure that they are familiar with each regulatory bodies' submission requirements and have an understanding of to what degree the country's legislation enforce these regulatory requirements.

Characterization of Mechanical Damage in Gas Transmission Pipelines

Scipedia content — Thu, 21 Jan 2021 14:56:06 +0100

Natural gas is one of the cheapest forms of energy and is the source of more than 30% of the energy produced in the USA [1]. 280,000 miles of gas transmission lines, 90,000 miles of gathering lines and 835,000 miles of distribution lines form a vast network across the country. It is imperative to assure the integrity of this vast network, for safe and economical transport of gas.

Emerging Technologies for Urban Traffic Management

Scipedia content — Thu, 21 Jan 2021 14:54:49 +0100

Nowadays, the number of vehicles on the road and the need of transporting people grow fast. Road transportation has become the backbone of industrialized countries. Nevertheless, the road network system in cities is not sufficient to cope with the current demands due to the size of roads available. Building additional or extending existing roads do not solve the traffic congestion problem due to the high costs and the environmental and geographical limitations. As a consequence, the modern society is facing more traffic jams, higher fuel bills and high levels of CO2 emissions.

Characterization of a Laser Scanner Sensor for the Use as a Reference System in Vehicular Relative Positioning

Scipedia content — Thu, 21 Jan 2021 14:48:42 +0100

Advanced Driver Assistance Systems (ADAS) play an important role in increasing the safety on todayâs roads. Forward collision warning systems, lane change assistants or cooperative adaptive cruise control are examples of safety relevant applications that rely on accurate relative positioning between vehicles. Current solutions found in commercial automobiles estimate the position of surrounding vehicles by measuring the distance with RADAR, cameras or IR-sensors. It is envisioned that the advent of inter-car communication will provide on-board relative positioning systems with further information about other vehicles in the surrounding area. While performing research in this field, the need of a proper reference system for testing new approaches originates. In the ideal case, such a reference system would yield the exact and continuous 3D baseline between two vehicles at any time in any circumstance. In this paper we will characterize the use of a laser scanner as a reference system for relative vehicle positioning.

Road Feature Extraction from High Resolution Aerial Images Upon Rural Regions Based on Multi-Resolution Image Analysis and Gabor Filters

Scipedia content — Thu, 21 Jan 2021 14:46:34 +0100

Accurate, detailed and up-to-date road information is of special importance in geo-spatial databases as it is used in a variety of applications such as vehicle navigation, traffic management and advanced driver assistance systems (ADAS). The commercial road maps utilized for road navigation or the geographical information system (GIS) today are based on linear road centrelines represented in vector format with poly-lines (i.e., series of nodes and shape points, connected by segments), which present a serious lack of accuracy, contents, and completeness for their applicability at the sub-road level. For instance, the accuracy level of the present standard maps is around 5 to 20 meters. The roads/streets in the digital maps are represented as line segments rendered using different colours and widths. However, the widths of line segments do not necessarily represent the actual road widths accurately. Another problem with the existing road maps is that few precise sub-road details, such as lane markings and stop lines, are included, whereas such sub-road information is crucial for applications such as lane departure warning or lane-based vehicle navigation. Furthermore, the vast majority of roadmaps aremodelled in 2D space, whichmeans that some complex road scenes, such as overpasses and multi-level road systems, cannot be effectively represented. In addition, the lack of elevation information makes it infeasible to carry out applications such as driving simulation and 3D vehicle navigation.

Seismic Damage Estimation in Buried Pipelines Due to Future Earthquakes – The Case of the Mexico City Water System

Scipedia content — Thu, 21 Jan 2021 14:43:48 +0100

Since the mid-70s, there have been advances in the development of models to better understand how earthquakes affect buried pipelines. These natural events can cause damage due to two phenomena: seismic wave propagation and permanent ground deformation. The combined effect of both phenomena in pipeline damage estimation is a subject still complex to address, especially if the objective is to estimate damage due to future earthquakes. In this chapter, the damage assessment methods only consider the impact of seismic wave propagation. The effects of permanent ground deformation phenomena, like ground subsidence, landslides, and ground rupture, are omitted. The exceptional damage caused by the 1985 Michoacan earthquake in Mexico City has encouraged researchers to develop sophisticated tools to estimate ground motion in the Valley of Mexico from Pacific coastal earthquakes, including the important site effects largely observed in the city. These tools have helped to better understand how earthquakes affect buildings and other structures like pipeline systems. The most remarkably case of pipeline damage caused by the 1985 seismic event is the extensive damage suffered by the Mexico City Water System (MCWS) that left almost 3.5 million people without water, and caused water service disruptions over a period of two months. The 1985 MCWS damage scenario has been extensively analyzed for developing models to better understand how seismic wave propagation affects buried pipelines; some of those models are employed in the future damage prediction methods described in this manuscript. Fragility functions are typically the tools most used to assess seismic damage in buried pipelines. These functions relate pipeline damage with seismic intensity. Pipeline damage is generally expressed as a linear pipe repair density. Seismic intensity is usually quantified through a seismic parameter. There are many seismic parameters used as arguments of fragility functions; the most important of these are described in Section 2. Section 3 describes the most important fragility functions proposed until now, including the two employed in the seismic damage estimation for the MCWS presented in Section 4. Finally, Section 5 contains a summary of the most important conclusions of this work.

Energy-Efficient Traffic Engineering

Scipedia content — Thu, 21 Jan 2021 14:35:17 +0100

The energy consumption in telecommunication networks is expected to grow considerably, especially in core networks. In this chapter, optimization of energy consumption is approached from two directions. In a first study, multilayer traffic engineering (MLTE) is used to assign energy-efficient paths and logical topology to IP traffic. The relation with traditional capacity optimization is explained, and the MLTE strategy is applied for daily traffic variations. A second study considers the core network below the IP layer, giving a detailed power consumption model. Optical bypass is evaluated as a technique to achieve considerable power savings over per-hop opticalâelectronicâoptical regeneration.

EPOL 2012 Proceedings Of The International Congress On Energy And Politics

Scipedia content — Thu, 21 Jan 2021 14:29:13 +0100

Supply Chain Security – Threats and Solutions

Scipedia content — Thu, 21 Jan 2021 14:28:41 +0100

In recent years, the cargo transport process has improved mainly in the areas of logistics efficiency and documentation handling. The World Trade Centre terror attack in 2001 changed the world and with it the conditions for logistics world-wide. The logistics consequences were according to[1]: It is instructive to note that these disruptions were not caused by the attack itself, but rather by the governmentâs response to the attack: closing borders, shutting down air traffic and evacuating buildings throughout the country. The aftermath to the attack brought needed attention to the vulnerability of modern supply chains. Supply chain vulnerability reflects sensitivity of the supply chain to disruption [2]. This vulnerability can in many cases be described as âunwanted effectsâ in the supply chain caused either by internal or external forces that create disturbances larger than the supply chain is designed to handle. The objective of Supply chain security is to prevent antagonistic threats from affecting the supply chain performance. Antagonistic threats and other risks and uncertainties are demarcated by three key words: deliberate (caused), illegal (defined by law), and hostile (negative impact for transport network activities) [3]. This chapter presents first the major antagonistic threats to the supply chain and secondly how these threats should be prevented. This leads to the current development of different supply chain security programs.

Evaluating the Integrity of Pressure Pipelines by Fracture Mechanics

Scipedia content — Thu, 21 Jan 2021 14:22:47 +0100

Large engineering structures made with the use of sophisticated technology often include material defects and geometrical imperfections. These defects or imperfections do not exert their influence on the initial behaviour of structures designed in accordance with standard rules. Under the action of loading varying in time, however, they can reveal themselves in long-term operation by the initiation and growth of a fatigue crack from a defect root. Similarly, stress corrosion (SC) cracks can develop in a structure when there is an initial stress concentrator and the structure is exposed to both mechanical stress and a corrosion medium. A condition for the growth of a small fatigue crack is that the level of cyclic stress should be above the limit value given by barriers existing in a steel, and a condition for the growth of SC cracks is that the stress is greater than a certain limit value for a specific corrosion medium. It is important to pay due attention to the behaviour of cracks under various gas pipeline loading conditions in different environments, and to the influence of these conditions on the residual strength and life of the gas pipeline. The existence of a crack in the wall of a high-pressure gas pipeline mostly implies a shortened remaining period of reliable operation.

Transcatter X-Ray Technique for the Inspection of Insulated, Oil-Carrying Pipelines

Scipedia content — Thu, 21 Jan 2021 14:18:07 +0100

Pipelines are subjected to corrosion and require periodic inspection. These pipes are generally covered with an insulating material, that is contained within a metal jacket. The removal of the insulating material is costly, and can hazardous if asbestos is the material being removed. Because a large number of pipes need to be inspected, a cost effective technique for the characterization of corrosion under insulation is desirable.

Batteries charging systems for electric and plug-in hybrid electric vehicles

Scipedia content — Thu, 21 Jan 2021 13:52:23 +0100

Many countries have a large dependence on imported fossil fuels whose prices increase almost every day. Knowing that much of this consumption is for transportation systems, it becomes essential to seek for alternatives. The natural bet is the electric mobility, namely through Electric Vehicles (EVs) and Plug-in Hybrid Electric Vehicles (PHEVs). However, the wide spread utilization of these vehicles has consequences on the electrical power grid, mainly in terms of load management and electric power quality, which are associated to the batteries charging systems. In this scenario, this chapter assesses the electric mobility integration in Smart Grid context, focusing different approaches to the operation of EVs and PHEVs charging processes and the specifications of the chargers, as well as different topologies of charging systems and their features, modes of operation, typical waveforms, and impact in the electrical power grid in terms of power quality. It is also presented a laboratory prototype of a bidirectional EV charger and shown some experimental results. This prototype was developed to charge the batteries aiming to preserve their lifespan, and to contribute to mitigate the degradation of the power quality. The experimental results show the operation of this prototype during the batteries charging process (G2V â Grid-to-Vehicle operation), and during the delivering of stored energy back to the electrical power grid (V2G â Vehicle-to-Grid operation). FEDER Funds - Operational Program for Competitiveness Factors â COMPETE FundaÃ§Ã£o para a CiÃªncia e a Tecnologia (FCT) - FCOMP-01-0124-FEDER-022674, MITPT/ EDAM-SMS/0030/2008

Velocity Effects and their Minimization in MFL Inspection of Pipelines — A Numerical Study

Scipedia content — Thu, 21 Jan 2021 13:49:24 +0100

A wide variety of methods are used for the inspection of the 448,000 kilometers of gas pipelines currently in operation in the United States. Speed and accuracy are the prime concerns in inspections of this magnitude. Magnetic flux leakage (MFL) inspection of pipelines [1], using a magnetizer moving at velocities up to 30 kilometers per hour, is currently the most commonly used inline inspection method. At these velocities the leakage field signal is significantly distorted due to motionally generated currents in the pipeline. Experimental measurements of the velocity effects is expensive and possible for only very limited choices of parameters such as geometry and dimensions of the probe, defect, etc. Analytical, closed form solutions for electromagnetic (EM) non-destructive testing (NDT) problems including velocity effects can be found for only the simplest examples and are impractical for most NDT problems. Numerical analysis techniques for the modeling of velocity effects in a variety of EM areas are developing rapidly [2], [3]. In modeling the MFL inspection, the numerical model is required to be capable of modeling non-uniform geometries in order to simulate defects. Also, for accurate predictions, nonlinearity in various regions of the geometry must be incorporated. A numerical model with these capabilities is an invaluable asset both in terms of studying in detail the total physics of the situation, and also to aid in the magnetizer design.

Maritime Ports And Inland Interconnections: A Transactional Analysis Of Container Barge Transport In France

Scipedia content — Thu, 21 Jan 2021 13:47:23 +0100

International audience; Recent research on maritime ports hinterlands points out the relevance of mass ground transport modes such as barge transport for enormous flows of containers to and from harbours, especially when a maritime port is located at the mouth of a river. Though, the modal share of container barge transport in French maritime ports (9% of TEU in Le Havre and 5% in Marseille in 2007) is significantly lower than elsewhere (32% in Rotterdam and 33% in Antwerp). Some reports and studies explain the viscosity of container barge transport flows as a result of several factors, generally concentrated around the seaport community. In continuation of previous seminal works, this paper adopts a neo-institutional approach (Williamson, 1985; 1996) of container barge transport to understand how the factors generating this viscosity are managed. Section 2 describes the characteristics of the transaction of container barge transport. Section 3 is devoted to its attributes (asset specificity, frequency, uncertainty). According to Williamsonâs (1996) remediableness criterion, the observed governance structure of a given transaction is presumed efficient and aligned to its attributes. Thus, Section 4 deals with observed governance structures of container barge transport chains with a focus on Le Havre, main French container seaport and shows how agents try to limit opportunism in ex-post haggling over quasi-rents or under-investments. Implementation of a new institutional environment to modify governance structures is analysed, and a comparison with currently implemented governance structures observed in Rhine is made. Finally, Section 5 suggests ways of dealing with the remaining coordination problems impeding the development of container barge transport in France.

Solution Space-Based Method

Scipedia content — Thu, 21 Jan 2021 13:42:57 +0100

In Air Traffic Control (ATC), controller workload has been an important topic of research. Many studies have been conducted in the past to uncover the art of evaluating workload. Many of which have been centered on the sector complexity or task demand based studies [1,2,3,4]. Moreover, all have the aim to understand the workload that was imposed on the controller and the extent to which the workload can be measured.

The Autonomous Flight

Scipedia content — Thu, 21 Jan 2021 13:33:07 +0100

Since airborne separation assurance is a fundamental principle of the FFA and the Airborne Separation Assurance System (ASAS) its main enabler, the AFA introduces the autonomous airborne separation assurance with AutonomousâASAS (AASAS). The AFA is marked by the machineâbased decisionâmaking, and the AFA is restricted to the ASAS and AASAS equipped aircraft but both types with autonomous flight capabilities. In the future the only humansâinâtheâloop conducting flight operations through AFA are going to be groundâ based UAS operators, air traffic flow managers of the next generation ATM, and systems supervisors (pilots of presentâday terminology) onboard remnant âoldâschoolâ manned aircraft. Based on 4D trajectory planning the AASAS concept covers machineâbased (a) traffic situational awareness, and (b) airborne spacing and selfâseparation assurance through (c) autonomous inâflight conflict detection and resolution.

Attenuation of Guided Wave Propagation by the Insulation Pipe

Scipedia content — Thu, 21 Jan 2021 13:28:39 +0100

Pipeline systems are widely used in gas, refinery, chemical and petro-chemical industries, which usually carry high pressure, high temperature or even highly corrosive fluids. Cracks and corrosion are often found at the outer or inner surface of pipeline and can lead to a serious thinning of wall thickness. Leaks or sudden failures of pipes can cause injuries, fatalities and environmental damage. Ultrasonic nondestructive techniques are available for the detection of wall loss associated with defects in the pipe. Unfortunately, a high proportion in pipelines of these industrial are insulated, so that even external corrosion cannot readily be detected by the conventional ultrasonic testing (single position measurement) without the removal of the insulation, which in most case is time-consuming and cost expensive. Especially in typically industrial plants, there are hundreds of kilometers of pipelines can be in operation. Making inspection of full pipelines is virtually impossible in industrial plants. There is therefore a quick reliable method for the detection of corrosion under insulation (CUI). This technique, called guided wave, employs a pulseecho system applied at a single location of a pipe where only a small section of insulation need to be removed, using waves propagation along the pipe wall. The changes in the response signal indicate the presence of an impedance change in the pipe. The shape and axial location of defects and features in the pipe are also determined by reflected signals and their arrival times. Propagation distance of many tens of meters can readily be obtained in steel pipes [1-6]. Since these guided waves are cylindrical Lamb waves along the pipe, no lateral spreading can occur and the propagation is essentially one-dimensional. In a uniform pipe, their amplitude with propagation distance is therefore only reduced by the material attenuation of the steel [7].

Computational Intelligence in Air Traffic Management

Scipedia content — Thu, 21 Jan 2021 13:19:42 +0100

The demand for increasing airport capacity combined with many constraints as well as the complexity of the data itself leads to the use of heuristic methods from the computational intelligence domain. More specifically, the focus in this paper is on how (fuzzy) clustering methods and evolutionary algorithms are applied on various aspects of the Air Traffic Management domain. Fuzzy clustering techniques have been used for data evaluation and pre-processing. One task is the identification and correction of noise and outliers in radar tracks as a pre-processing step. In addition, clustering has been applied to identify general flight routes in retrospective analysis tasks as well as to generate fuzzy rules, thus verifying or complementing expert knowledge regarding transfer passenger movements. Evolutionary algorithms are used to assist air- and ground traffic controllers. Namely in Rogena (free ROuting with GENetic Algorithms) for route planning and TRACC (Taxi Routes for Aircraft: Creation and Controlling) for ground movement planning. Both systems create conflict free routes for aircraft which are suggested to the air- and ground traffic controllers, respectively.

Analytical Procedures for Determining the Impacts of Reliability Mitigation Strategies

Scipedia content — Thu, 21 Jan 2021 13:11:40 +0100

Basic reliability issues are addressed in this study, which is not concerned with average travel times, but rather ways of describing travel times that reflect the uncertainty in the amount of time required to travel between two points. Some of the uncertainty is systematic, such as the normal ebb and flow of traffic within the course of a work day or season of the year. Congestion associated with this systematic uncertainty is called recurrent. Congestion due to unpredictable or unexpected events is called nonrecurrent. If every travel time observed over a highway section for a year is plotted, a distribution of travel time is obtained. This plotted distribution is the picture of travel time variability. Such distributions are the focus of this research, especially the degree to which recurring and nonrecurring congestion influence the nature of the distribution. This research shows how to derive performance measures from such distributions and recommends a set for use by managers, planners, and systems operators. The research reexamines the composition of the congestion puzzle in terms of the fractions attributable to recurrent and various sources of nonrecurrent congestion. The project team used before-and-after studies to determine the effectiveness of different types of actions, both operational and capacity improvements, in improving reliability. This study also examined the effect of the downturn of the economy on travel time reliability. Finally, this research resulted in two types of models that can be used to estimate or predict travel time reliability. These models have broad applicability to planning, programming, and systems management and operations.

Urban logistics pooling viability analysis via a multicriteria multiactor method

Scipedia content — Thu, 21 Jan 2021 13:07:07 +0100

Collaborative transportation and logistics pooling are relatively new concepts in research, but are very popular in practice. In the last years, collaborative transportation seems a good city logistics alternative to classical urban consolidation centres, but it is still in a development stage. This paper proposes a framework for urban logistics pooling ex-ante evaluation. This framework is developed with two purposes. The first is to generate comparable contrasted or progressive scenarios representing realistic situations; the second to simulate and assess them to make a "before-after" comparative analysis. In this framework, a demand generation model is combined with a route optimization algorithm to simulate the resulting routes of the proposed individual or collaborative distribution schemes assumed by each scenario. Then, several indicators can be obtained, mainly travelled distances, working times, road occupancy rates and operational monetary costs. To illustrate that framework, several scenarios for the urban area of Lyon (France) are simulated and discussed to illustrate the proposed framework possible applications.

When is Short Sea Shipping Environmentally Competitive?

Scipedia content — Wed, 20 Jan 2021 16:44:53 +0100

There is really no debate about the superior comparative efficiency of ships with respect to fuel consumption when calculated per deadweight tonne along routes of similar length. However, the emission figures calculated per deadweight tonne is only relevant for bulk transports, and fuel consumption per cargo tonne is quite different for typical short sea shipping services based on container or RoRo technologies. Further, other emissions to air, like sulphur dioxide, nitrogen oxides and particles, are typically very high for shipping â especially when no abatement technologies are applied.

Codification of fiber reinforced composite piping

Scipedia content — Mon, 26 Oct 2020 15:43:40 +0100

The goal of the overall project is to successfully adapt spoolable FRP currently used in the oil industry for use in hydrogen pipelines. The use of FRP materials for hydrogen service will rely on the demonstrated compatibility of these materials for pipeline service environments and operating conditions. The ability of the polymer piping to withstand degradation while in service, and development of the tools and data required for life management are imperative for successful implementation of these materials for hydrogen pipeline. The information and data provided in this report provides the technical basis for the codification for fiber reinforced piping (FRP) for hydrogen service. The DOE has invested in the evaluation of FRP for the delivery for gaseous hydrogen to support the development of a hydrogen infrastructure. The codification plan calls for detailed investigation of the following areas: System design and applicable codes and standards; Service degradation of FRP; Flaw tolerance and flaw detection; Integrity management plan; Leak detection and operational controls evaluation; Repair evaluation. The FRP codification process started with commercially available products that had extensive use in the oil and gas industry. These products have been evaluated to assure that sufficient structural integrity is available for a gaseousmoreÂ Â» hydrogen environment.Â«Â le

Document type: Report

Final report phase i study to characterize the market potential for non motorized travel

Scipedia content — Mon, 26 Oct 2020 13:48:16 +0100

The idea of livable communities suggests that people should have the option to utilize non-motorized travel (NMT), specifically walking and bicycling, to conduct their daily tasks. Forecasting personal travel by walk and bike is necessary as part of regional transportation planning, and requires fine detail not only about individual travel, but also on transportation and neighborhood infrastructure. In an attempt to characterize the 'market' potential for NMT, the Office of Planning, Federal Highway Administration (FHWA) funded the Center for Transportation Analysis (CTA) of the Oak Ridge National Laboratory (ORNL) to conduct a study. The objectives of this effort were to identify factors that influence communities to walk and bike and to examine why, or why not, travelers walk and bike in their communities. This study relied on information collected under the 2009 National Household Travel Survey (NHTS) as the major source of data, and was supplemented with data from the American Community Survey (ACS), educational survey, health, employment, and others. Initial statistical screening methods were applied to sort through over 400 potential predictor variables, and examined with various measures (e.g., walk trip per person, walk mileage per person, bike trip per person, bike mileage per person) as the dependent variables. moreÂ Â» The best geographic level of detail used in the modeling for this study was determined to be the Census block group level for walking and Census tract level for biking. The need for additional supplemental private data (i.e., Walk Scores and Nielsen employment data), and geospatial information that reflects land use and physical environments, became evident after an examination of findings from the initial screening models. To be feasible, in terms of costs and time, the geographic scale of the study region was scaled down to nine selected NHTS add-on regions. These regions were chosen based on various criteria including transit availability, population size, and a mix of geographic locations across the nation. Given the similarities in modeling results from walk trips and walk mileages, additional modeling efforts conducted under the later part of this study were focused on walk trips per person. Bike models were limited only with the stepwise logistic models using Census tracts in the selected regions. Due to NHTS sampling limitations, only about 12% of these tracts have bike trips recorded from NHTS sampled households. The modeling with NHTS bike data proved to be more challenging and time consuming than what was anticipated. Along with the late arrival of Nielsen employment data, the project team had to limit the modeling effort to focus on walking. Therefore, the final modeling and discriminant analysis was conducted only for walking trips. Â«Â le

Document type: Report

Zero discharge water management for horizontal shale gas well development

Scipedia content — Mon, 26 Oct 2020 11:19:09 +0100

Hydraulic fracturing technology (fracking), coupled with horizontal drilling, has facilitated exploitation of huge natural gas (gas) reserves in the Devonian-age Marcellus Shale Formation (Marcellus) of the Appalachian Basin. The most-efficient technique for stimulating Marcellus gas production involves hydraulic fracturing (injection of a water-based fluid and sand mixture) along a horizontal well bore to create a series of hydraulic fractures in the Marcellus. The hydraulic fractures free the shale-trapped gas, allowing it to flow to the well bore where it is conveyed to pipelines for transport and distribution. The hydraulic fracturing process has two significant effects on the local environment. First, water withdrawals from local sources compete with the water requirements of ecosystems, domestic and recreational users, and/or agricultural and industrial uses. Second, when the injection phase is over, 10 to 30% of the injected water returns to the surface. This water consists of flowback, which occurs between the completion of fracturing and gas production, and produced water, which occurs during gas production. Collectively referred to as returned frac water (RFW), it is highly saline with varying amounts of organic contamination. It can be disposed of, either by injection into an approved underground injection well, or treated to remove contaminants so that the water meets the requirements of either surface release or recycle use. Depending on the characteristics of the RFW and the availability of satisfactory disposal alternatives, disposal can impose serious costs to the operator. In any case, large quantities of water must be transported to and from well locations, contributing to wear and tear on local roadways that were not designed to handle the heavy loads and increased traffic. The search for a way to mitigate the situation and improve the overall efficiency of shale gas production suggested a treatment method that would allow RFW to be used as make-up water for successive fracs. RFW, however, contains dissolved salts, suspended sediment and oils that may interfere with fracking fluids and/or clog fractures. This would lead to impaired well productivity. The major technical constraints to recycling RFW involves: identification of its composition, determination of industry standards for make-up water, and development of techniques to treat RFW to acceptable levels. If large scale RFW recycling becomes feasible, the industry will realize lower transportation and disposal costs, environmental conflicts, and risks of interruption in well development schedules.

Document type: Report

A comparison between different methods to determine moisture transport properties of cementitious materials

Scipedia content — Mon, 26 Oct 2020 11:16:18 +0100

A number of methods for measuring moisture transport properties of cementitious materials were compared in a series of experiments. Two OPC mortars with two water-binder-ratios were wet cured for six months and used to produce specimens as discs with different thicknesses and diameters."br /" The cup methods were easy to use, reliable and fairly rapid but need a stable, surrounding, CO2-free climate, however. Evaluating the fundamental potential PSI eliminates the derivation that adds to the uncertainty."br /" Steady-state moisture distribution measurements are very time-consuming and the RH-profiling is a delicate matter. Moisture contents are scattering. Sorption experiments are very easy to perform but difficult to evaluate, because of the peculiar moisture-dependency of the diffusivity Dw and the difficulties to estimate the equilibrium conditions. Initial uniform conditions are difficult to obtain for low w/c-materials, except to initial self-desiccation."br /" Sorption experiments in small steps are uncertain; the initial and final conditions are difficult to define properly.

Document type: Report

National biodiesel infrastructure development initiative final program report

Scipedia content — Mon, 26 Oct 2020 10:11:29 +0100

Document type: Report

Automatic Handover Decision in Content Centric Networking

Scipedia content — Wed, 14 Oct 2020 16:32:49 +0200

Part 6: Poster Papers; International audience; The current Internet architecture was designed more than 30 years ago for a very different set of services than those used today. Several new architectures have been proposed for a Future Internet to better meet todays and future requirements. Content Centric Networking (CCN) is one of those new architectures gaining worldwide attention by researchers and the focus of this article. CCN is based on naming content instead of hosts allowing routers to cache popular content. It has been shown that CCN can also support point-to-point real-time conversations, for example voice or video calls. However, it has not been defined how node mobility can be achieved in such a real-time scenario with strong time constraints. In this paper a close study to the handover algorithms has been carried out. A handover decision maker, which is based on neuro-fuzzy system (NFS) is proposed and evaluated. The results show that the proposed decision maker meets the design targets.

Document type: Part of book or chapter of book

Soe reform time for serious corporate governance

Scipedia content — Wed, 14 Oct 2020 16:30:05 +0200

This policy paper is motivated by the Governments Pakistan: Framework for Economic Growth (FEG) 2011 which places weak corporate governance at the top of the software constraints to growth. The efforts to reform the State-Owned Enterprises (SOEs) have stalled in Pakistan for almost five yearswith significant negative implications not only in terms of fiscal losses, but also deteriorated and cost-ineffective service delivery. The paper suggests a number of urgent policy measures designed to improve the efficiency and effectiveness of SOEs. These include basic governance reforms, revamped commercialization processes and enhanced market regulations. The paper also provides some perspectives on international experience on SOE reforms combined with some suggestions on how the Government can move forward. The Policy Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about development issues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry the names of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development / World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent. SOE Reform: Time for Serious Corporate Governance

Document type: Book

A mixed integer linear programming model for transportation planning in the full truck load strategy to supply products with unbalanced demand in the just in time context a case study

Scipedia content — Wed, 14 Oct 2020 16:25:14 +0200

[EN] Growing awareness in cutting transport costs and minimizing the environmental impact means that companies are increasingly interested in using the full truck load strategy in their supply tasks. This strategy consists of filling trucks completely with one product type or a mixture of products from the same supplier. This paper aims to propose a mixed-integer linear programming model and procedure to fill trucks which considers limitations of stocks, stock levels and unbalanced demand and minimization of the total number of trucks used in the full truck load strategy. The results obtained from a case study are presented and are exported in a conventional spreadsheet available for a company in the automotive industry. Maheut ., JP.; García Sabater, JP. (2013). A Mixed-Integer Linear Programming Model for Transportation Planning in the Full Truck Load Strategy to Supply Products with Unbalanced Demand in the Just in Time Context: A Case Study. IFIP Advances in Information and Communication Technology. 397:576-583. doi:10.1007/978-3-642-40361-3_73 S 576 583 397

Document type: Part of book or chapter of book

How to Provide Accurate and Robust Traffic Forecasts Practically?

Scipedia content — Wed, 14 Oct 2020 16:23:36 +0200

With the development of our modern cities, growing traffic problems adversely affect peoples traveling convenience more and more, which has become one of the most crucial factors considered in urban planning and design in recent years. Urban traffic congestion is a severe problem that significantly reduces the quality of life in particularly metropolitan areas. However, frequently constructing new roads is not realistic and untenable in social and economic aspects. In the effort to deal with this intractable problem, so-called intelligent transportation systems (ITS) technologies are successfully implemented widely throughout the world nowadays. ITS with two important components advanced traffic management systems (ATMS) and advanced traveler information systems (ATIS) aim to relieve the increasing congestion and decrease travel time through providing information to the drivers by means of radio broadcasts or dynamic route guidance systems.

Document type: Part of book or chapter of book

Traffic Engineering

Scipedia content — Wed, 14 Oct 2020 16:23:09 +0200

The data demands and economics surrounding IP internetworking are such that IP routers are now connecting directly to SDH or DWDM systems. As such, many of the traditional mechanisms used to engineer the traffic over the physical infrastructure are no longer available. Consequently a new approach is required. This paper outlines a set of mechanisms and procedures, including enhancements to the layer 3 routeing and signalling protocols ad MPLS forwarding that, when combined, provide the capabilities to provide traffic engineering capabilities in an optical IP environment.

Document type: Book

The Contribution and Prospects of the Technical Development on Implementation of Electric and Hybrid Vehicles

Scipedia content — Wed, 14 Oct 2020 16:19:22 +0200

Population growth in the world had a constant value since the beginning of a new era to the 19th century when the population was 1 billion. The technological revolution is largely in? fluenced by that in this century, the population increase by 68 %. The population in the world increased by about 270 %, or over 6 billion people just in the 20 century. Although the UN in [1], estimates three possible scenarios of population growth in this century, the pic? ture 1, is the most possible one that predicts that the world population will increase by 2050. to about 8,9 billion, and afterwards it will be a slowdown so that by the end of the 21st cen? tury, and in the next few, does not expect the growth of population in the country. In any case, in the near future over the next four decades strong growth of the population is expect? ed. With the growth of population in the world there is a need to increase transportation of people, goods and raw materials as a prerequisite for the growth of production and con? sumption and the standards of living.

Document type: Part of book or chapter of book

Introduction. Mobility and Migration in Later Life

Scipedia content — Wed, 14 Oct 2020 16:12:27 +0200

Document type: Part of book or chapter of book

Chapter 3 an international dimension aviation

Scipedia content — Wed, 14 Oct 2020 16:05:21 +0200

Purpose To examine the relationship between aviation and climate change, and the international dimensions of air transport.\r \r Methodology/approach A review of aviation's impacts on the global climate, mitigation strategies to reduce this impact, and the possible consequences of climate change for commercial aviation.\r \r Findings Although a range of mitigation measures have been developed and implemented to reduce aircraft emissions in the short term, with some environmental benefit, there is a real need for the aviation sector to identify the possible impacts of climate change on air travel operations, both to aircraft in flight and to operations at airports. A further challenge will be to devise adaptation plans that will address the vulnerabilities and thus ensure safe aviation-related operations.\r \r Social implications The climate change impacts of aviation will adversely affect society. In addition, some individuals may have to reduce or stop flying as a result of increased taxes and legislation implemented in response to climate change.\r \r Originality/value of paper There is a novel focus on the adaptation challenges for the aviation industry in response to climate change.

Document type: Part of book or chapter of book

Recall Performance in Air Traffic Controllers Across the 24-hr Day: Influence of Alertness and Task Demands on Recall Strategies

Scipedia content — Wed, 14 Oct 2020 16:04:52 +0200

International audience; The aim of the present contribution is to test whether and to what extent cognitive load theory may account for working memory performance in the field of ergonomics. We will briefly present the theoretical and methodological principles of cognitive load theory, developed initially by Sweller (1988) in the field of educational psychology, and some of the more critical issues addressed recently. Thereafter, we report three experiments exploring the relations between the three load categories defined by cognitive load theory, by using working memory tasks. The influence of intrinsic and extrinsic cognitive load categories was explored by manipulating respectively task difficulty and time pressure. The consequences of the less documented germane load were proposed to depend on participants alertness that varies spontaneously across the day (Galy, Cariou, and Mélan, 2012). In order to test for additive effects between load categories, effects of intrinsic and extrinsic load were explored both separately and simultaneously, and when participants alertness level was either high or low. This procedure was tested in a mental arithmetic task and in a recall task performed by participants in controlled laboratory conditions and when the same arithmetic task was performed by air traffic controllers in a real-job situation. Results led to the conclusion of an additive interaction between intrinsic and extraneous cognitive load factors, in addition to modulatory effects by germane load.

Document type: Part of book or chapter of book

Achieving reliable and timely event dissemination over wan

Scipedia content — Wed, 14 Oct 2020 16:03:47 +0200

The design of large-scale critical infrastructures demands for innovative data dissemination services, able to jointly provide reliability and timeliness guarantees. Current middleware solutions do not address both these aspects. Indeed, fault tolerance is typically achieved at the cost of severe performance fluctuations, or timeliness is always obtained by softening the fault-tolerance requirements. In this paper we propose to fulfill this lack by combining two different approaches, namely coding and gossiping. We provide a theoretical model to evaluate the potential benefit of coding on the information delivery performance. These results are also confirmed by an experimental analysis conducted on a real air traffic control workload, which evidences how coding mitigates latency and overhead penalties to ensure reliable event notification.

Document type: Part of book or chapter of book

Demand side instruments to reduce road transportation externalities in the greater cairo metropolitan area

Scipedia content — Wed, 14 Oct 2020 15:55:42 +0200

Economically efficient prices for the passenger transportation system in the Greater Cairo Metropolitan Area would account for broader societal costs of traffic congestion and accidents, and local and global pollution. A $2.20 per gallon gasoline tax (2006 US$) would be economically efficient, compared with the current subsidy of $1.20 per gallon. Removal of the existing subsidy alone would achieve about three-quarters of the net benefits from subsidy elimination and the tax. Per-mile tolls could target congestion and accident externalities more efficiently than fuel taxes, although they are not practical at present. A combination of $0.80 per gallon gasoline tax to address pollution (versus $2.20 without tolls), and $0.12 and $0.19 tolls per vehicle mile on automobiles and microbuses, respectively, to address traffic congestion and accident externalities (versus $0.22 without fuel taxes) would be most efficient. Current public bus and rail subsidies are relatively close to efficient levels in the absence of such policies; however, if automobile and microbus externalities were fully addressed through more efficient pricing, optimal subsides to public transit would be smaller than current levels.

Document type: Book

Traffic sign classifier adaption by semi supervised co training

Scipedia content — Wed, 14 Oct 2020 15:52:38 +0200

The recognition of traffic signs in many state-of-the-art driver assistance systems is performed by statistical pattern classification methods. Traffic signs in European countries share many similarities but also vary in colour, size, and depicted symbols, making it hard to obtain one general classifier with good performance in all countries. Training separate classifiers for each country requires huge amounts of labelled training data. A well-trained classifier for one country can be adapted to other countries by semi-supervised learning methods to perform reasonably well with relatively low requirements regarding labelled training data. Self-training classifiers adapting themselves to unknown domains always risk that the adaption will become ineffective or even fail completely due to the occurrence of incorrectly labelled samples. To assure that self-training classifiers adapt themself correctly, advanced multi-classifier training methods like co-training are applied.

Document type: Part of book or chapter of book

Traffic Engineering Approaches in P2P Environments

Scipedia content — Wed, 14 Oct 2020 15:39:27 +0200

Nowadays, P2P applications proliferate in the Internet with distinct utilization contexts, being also an attractive model for the deployment of advanced Internet services. However, there are several undesirable effects that are caused by such applications, raising coexistence problems with Internet Service Providers (ISPs). In this context, using as case study BitTorrent like applications, this work explores a collaborative framework allowing that advanced efforts could be carried on between P2P applications and network level entities. In order to illustrate such framework, several Traffic Engineering (TE) mechanisms are devised in order to align some P2P dynamics with particular objectives pursued by network administrators. The simulation results show that both the proposed framework and corresponding illustrative mechanisms are viable and can effectively foster future research efforts within this field. (undefined)

Document type: Part of book or chapter of book

Taking Stock, December 2012

Scipedia content — Wed, 14 Oct 2020 15:38:02 +0200

This paper includes three parts: external economic environment, part one includes: global environment, regional environment, and risks. Vietnam's recent economic development, part two includes: a relatively stable macroeconomic situation, growth at record low, booming exports despite a slowing economy, sharp turnaround in external accounts, inflation dynamics, monetary policy, fiscal policy, and near-term outlook. Structural reforms and medium-term outlook, part three includes: context, restructuring of state-owned enterprises, banking Sector development, and poverty reduction.

Document type: Book

Brief announcement karyon towards safety kernels for cooperative vehicular systems

Scipedia content — Wed, 14 Oct 2020 15:37:30 +0200

KARYON, a kernel-based architecture for safety-critical control, is a European project that proposes a new perspective to improve performance of smart vehicle coordination focusing on Advanced Driver Assistance Systems (ADASs) and Unmanned Aerial Systems (UAS). The key objective is to provide system solutions for predictable and safe coordination of smart vehicles that autonomously cooperate and interact in an open and inherently uncertain environment. Currently, these systems are not allowed to operate on the public roads or in the air space, as the risk of causing severe damage cannot be excluded with sufficient certainty. The impact of the project is two-fold; it will provide improved vehicle density without driver involvement and increased traffic throughput to maintain mobility without a need to build new traffic infrastructures. The results will improve interaction in cooperation scenarios while preserving safety and assessing it according to standards. The prospective project results include self-stabilizing algorithms for vehicle coordination, communication and synchronization. In addition, we aim at showing that the safety kernel can be designed to be a self-stabilizing one.

Document type: Part of book or chapter of book

Tool supported risk modeling and analysis of evolving critical infrastructures

Scipedia content — Wed, 14 Oct 2020 15:37:03 +0200

Part 2: Workshop; International audience; Risk management is coordinated activities to direct and control an organization with regard to risk, and includes the identification, analysis and mitigation of unacceptable risks. For critical infrastructures consisting of interdependent systems, risk analysis and mitigation is challenging because the overall risk picture can be strongly affected by changes in only a few of the systems. In order to continuously manage risks and maintain an adequate level of protection, there is a need to continuously maintain the validity of risk models while systems change and evolve. This paper presents a risk analysis tool that supports the modeling and analysis of changing and evolving risks. The tool supports the traceability of system changes to risk models, as well as the explicit modeling of the impact on the risk picture. The tool, as well as the underlying risk analysis method, is exemplified and validated in the domain of air traffic management.

Document type: Part of book or chapter of book

Gridifying neuroscientific pipelines a soa recipe and experience from the neugrid project

Scipedia content — Wed, 14 Oct 2020 15:35:52 +0200

In recent times, innovative new e-Infrastructures have materialized all around the globe to address the compelling and unavoidably increasing demand on computing power and storage capacity. All fields of science have entered an era of digital explosion and thus need to face it with appropriate and scalable instruments. Amongst centurys cutting-edge technologies, the grid has become a tangible candidate which several initiatives have harnessed and demonstrated the added value of. Turning the concept into a concrete solution for Neurosciences, the neuGRID project aims to establish a grid-based e-Infrastructure providing neuroscientists with a powerful tool to address the challenge of developing and testing new markers of neurodegenerative diseases. In order to optimize the resulting grid and to deliver a user-friendly environment, neuGRID has engaged the process of migrating existing imaging and data mining toolkits to the grid, the so-called gridification, while developing a surrounding service oriented architecture of agnostic biomedical utilities. This chapter reports on a preliminary analysis of the issues faced in the gridification of neuroimaging pipelines and attempts to sketch an integration model able to cope with the several and heterogeneous applications used by neuroscientists.

Document type: Part of book or chapter of book

An Organizational Study into the Concept of Automation in a Safety Critical Socio-technical System

Scipedia content — Wed, 14 Oct 2020 15:35:39 +0200

Part 3: Evaluations, Interactions and Applications International audience Although automation has been introduced in all areas of public life, what seems to be missing is a reflection at the organizational or societal level about a policy of automation. By this we intend appropriate declarations made at the level of rationale, future plans and strategies to achieve intended goals and most importantly how those achievements will impact on various aspects of societal life, from legal responsibilities to moral and socio economic issues. In some public spheres these issues are becoming quite controversial because automation opens up possibilities of profound structural re-organization; however, we lack a discussion across and within different work domains to help us review methods or even methodological principles needed to gather and organize knowledge towards the construction of automation policies. This paper uses the UK service organization for Air Traffic Management Domain called NATS National Air traffic Service, as a case study to illustrate an example of an organization currently undertaking critical self-reflection about automation policy or lack of such, along with the illustration of some unresolved deep concerns raised by the development, introduction, and continued use of automation.

Document type: Part of book or chapter of book

I vde a novel approach to estimate vehicular density by using vehicular networks

Scipedia content — Wed, 14 Oct 2020 15:23:46 +0200

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-39247-4_6 Road traffic is experiencing a drastic increase in recent years, thereby increasing the every day traffic congestion problems, especially in cities. Vehicle density is one of the main metrics used for assessing the road traffic conditions. Currently, most of the existing vehicle density estimation approaches, such as inductive loop detectors or traffic surveillance cameras, require infrastructure-based traffic information systems to be installed at various locations. In this paper, we present I-VDE, a solution to estimate the density of vehicles that has been specially designed for Vehicular Networks. Our proposal allows Intelligent Transportation Systems to continuously estimate the vehicular density by accounting for the number of beacons received per Road Side Unit, as well as the roadmap topology. Simulation results indicate that our approach accurately estimates the vehicular density, and therefore automatic traffic controlling systems may use it to predict traffic jams and introduce countermeasures. Barrachina Villalba, J.; Garrido Picazo, MP.; Fogue, M.; Martínez, FJ.; Cano Escribá, JC.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2013). I-VDE: A Novel Approach to Estimate Vehicular Density by Using Vehicular Networks. En Ad-hoc, Mobile, and Wireless Network. Springer. 63-74. doi:10.1007/978-3-642-39247-4_6 Senia 63 74

Document type: Part of book or chapter of book

Trends in algorithms for nonuniform applications on hierarchical distributed architectures

Scipedia content — Wed, 14 Oct 2020 15:19:58 +0200

Scientific programmers are accustomed to expressing in their programs the who (variable declarations) and the what (operations), in some sequentialized order, and leaving to the systems software and hardware the questions of when and where. This act of delegation is appropriate at the small scales, since programmer management of pipelines, multiple functional units, and multilevel caches is presently beyond reward, and the depth and complexity of such performance-motivated architectural developments are sure to increase. However, disregard for the differential costs of accessing different locations in memory (the flat memory model) can put unnecessary amounts of synchronization and data motion on the critical path of program execution. Different organization of algorithms leading to mathematically equivalent results can have very different levels of exposed synchronization and data motion, and algorithmicists of the future will have to be conscious of and adapt to the distributed and hierarchical aspects of memory architecture.

Document type: Part of book or chapter of book

Implementing Sustainable Urban Travel Policies in China

Scipedia content — Wed, 14 Oct 2020 15:06:18 +0200

Urban transport will have a great impact on sustainable development. China is now the leading producer of motorized vehicles, and people have gradually realized that we cannot sustain endless motorization. China has adopted a sustainable development policy for many years, promoting public transport in successive five-year plans.

Document type: Part of book or chapter of book

Kongestia transportowa weryfikacja na przykladzie ?odzi

Scipedia content — Wed, 14 Oct 2020 15:04:51 +0200

W opracowaniu omówiono istot? oraz problematyk? kongestii transportowej rozumianej jako nadmierne zat?oczenie systemu transportu drogowego. Zagadnienie to rozpatrywane jest zarówno w aspekcie teoretycznym, jak i empirycznym. W pracy pos?u?ono si? przyk?adem miasta ?odzi, które boryka si? z problemami zat?oczenia komunikacyjnego. W celu przeanalizowania powy?szej problematyki, zbudowano kwestionariusz ankietowy, który pos?u?y? do weryfikacji postrzegania stanu transportowego w mie?cie. The article discussed the essence and problems of transport congestion understood as a congestion road transport system. This issue is examined in terms of both theoretical and empirical. The paper was used as an example the city of Lodz, which suffers from traffic congestion problems. In order to examine the above issues, built on a questionnaire that was used to verify the perception of the state of transportation in the city. Udost?pnienie publikacji Wydawnictwa Uniwersytetu ?ódzkiego finansowane w ramach projektu Doskona?o?? naukowa kluczem do doskona?o?ci kszta?cenia. Projekt realizowany jest ze ?rodków Europejskiego Funduszu Spo?ecznego w ramach Programu Operacyjnego Wiedza Edukacja Rozwój; nr umowy: POWER.03.05.00-00-Z092/17-00.

Document type: Part of book or chapter of book

Resolution numerique des equations de Navier-Stokes pour les fluides compressibles

Scipedia content — Wed, 14 Oct 2020 15:03:51 +0200

Document type: Part of book or chapter of book

Analysis of Historical River Floods - A Contribution Towards Modern Flood Risk Management

Scipedia content — Wed, 14 Oct 2020 14:56:24 +0200

The occurrence of several extreme flood events in Central Europe in the last two decades, in particular the flood along the Elbe River in 2002, and the resulting damage have shown shortcomings in the field of flood protection and have raised discussions on how to deal with flood risk in the future. As a consequence, the German Federal Ministry of Education and Research funded the "Risk Management of Extreme Flood Events" (RIMAX) research programme, which aimed at the development and implementation of improved instruments for flood risk management (www.rimax-hochwasser.de).

Document type: Part of book or chapter of book

Touch screens for the older user

Scipedia content — Wed, 14 Oct 2020 14:55:58 +0200

It has been 20 years since Ben Schneiderman predicted that there would be an increase in the use of touch screen applications yet it has been only in recent years that this prediction has come to pass. The concept of a touch screen computer was first introduced in 1965 by E.A. Johnson who described the possibilities of touch screen technology to support air traffic controllers. In this article Johnson describes how the touch display coupled to a computer can be considered as a keyboard, a novel approach at the time. Touch screens were brought into the public domain in 1971 by Elographics, Inc. which instigated the development of public touch screen technology such as automated teller machines (ATMs) and information kiosks (Brown et al., 2011). Another milestone in the history of touch technology was the introduction of the personal touch screen computer, HP-150, developed by Hewlett-Packard in 1983 (Sukumar, 1984). The purpose of this early design was to offer individuals an intuitive technology option. Although touch screen systems have maintained this intuitiveness and ease of use over the years, problems that existed with early systems still provide challenges for designers and developers to this day.

Document type: Part of book or chapter of book

Nordic Seniors on the Move : Mobility and Migration in Later Life

Scipedia content — Wed, 14 Oct 2020 14:52:39 +0200

"I believe that all people need to move about. Actually, some have difficulties in doing so. They stay in their home neighbourhoods, where theyve grown up and feel safe. I can understand that, but my wife and I, we didnt want that. We are more open to new ideas"."br /" "br /" This anthology is about seniors on the move. In seven chapters, Nordic researchers from various disciplines, by means of ethnographic methods, attempt to comprehend the phenomenon of Nordic seniors who move to leisure areas in their own or in other countries. "br /" \tThe number of seniors involved in this kind of migratory movement has grown considerably within the last 20 years. An increase in mass tourism is one explanation, but this may also be the result of generally stronger finances among the age group. Costa del Sol, along the Mediterranean coastline and Österlen in Southern Sweden are two examples of locations that have become attractive to lifestyle migrants. The warmer climate and the expectations of a certain quality of life are recurrent pull factors. The quote above gives voice to one of these seniors, stressing the necessity of moving. In his view, this signifies an open attitude to new ideas contrary to conventional images of old people as sedentary and disinclined to changes.\t"br /" \tIt is argued in this book that the fact that more people live longer, with better health, leads to a multiplicity of ways of growing old. As a result of this, paradoxes and polarities might arise; seniors cope with their lives all along the scale between fit and frail, weak and wealthy, poor and powerful, conservative, dynamic and unpredictable. This is valid for the Nordic seniors on the move as well. Moving may entail great economic dilemmas and challenges for individuals, social networks, and nation states. As shown here, mobility and migration have implications for identities, traditions, feelings of belonging, family relationships and friendships, health, images of old age, societal planning and policies, and even for religious attachment."br /" \tThe phenomenon of seniors on the move is accompanied by a growing academic interest and incorporates a variety of different perspectives and concepts, such as international retirement migration, rural retirement migration and health migration. This book contributes to the international body of literature about later life migration, specifically representing experiences made by Nordic seniors on the move. The incentive to place the Nordic countries in the limelight derives from the significant point that these countries largely share cultural and societal structures and - not least, the weather. The seven chapters representing experiences from a Nordic perspective are finalised by a chapter including an international perspective of retirement migration by the architect Deane Simpson who has studied and worked with gerotopias around the world."br /" \tThis anthology presents a joint statement, intended for international scholars in the field, but also for Nordic policymakers and practitioners involved in the daily life and needs of the many people who move in later life. If movers and migrants in later life wish for a good read you are most welcome."br /" "br /" "br /" The editors Anne Leonora Blaakilde and Gabriella Nilsson are both ethnologists affiliated with the Center for Healthy Ageing, University of Copenhagen, Denmark and the Department of Arts and Cultural Sciences, Lund University, Sweden, respectively.

Document type: Book

Development of a vehicle simulator based on a real car for research and education purposes

Scipedia content — Wed, 14 Oct 2020 14:52:00 +0200

The chapter presents a hardware-in-the-loop simulation environment, which is built in such a way that the simulator tends to the real vehicle functions as much as possible. The simulation system contains several components such as an Human Machine Interface (HMI), a high-accuracy validated simulation software operated on a PC and a visual system with real-time graphics. The simulator is equally suitable for educational and research purposes. All the vehicle engineer students use the simulator system during their curriculum, enabling the thorough understanding of modern vehicle functions, thus improving the competence of future generations of engineers. Moreover, the simulator system projects ahead the opportunity of new vehicle research that induces considerable additional scientific results.

Document type: Part of book or chapter of book

Broadcast abstraction in a stochastic calculus for mobile networks

Scipedia content — Wed, 14 Oct 2020 14:50:25 +0200

International audience We introduce a continuous time stochastic broadcast calculus for mobile and wireless networks. The mobility between nodes in a network is modeled by a stochastic mobility function which allows to change part of a network topology depending on an exponentially distributed delay and a network topology constraint. We allow continuous time stochastic behavior of processes running at network nodes, e.g. in order to be able to model randomized protocols. The introduction of group broadcast and an operator to help avoid flooding allows us to define a novel notion of broadcast abstraction. Finally, we define a weak bisimulation congruence and apply our theory on a leader election protocol.

Document type: Part of book or chapter of book

Low carbon pilot tour and municipal government investment taiwan s experience

Scipedia content — Wed, 14 Oct 2020 14:50:02 +0200

Document type: Part of book or chapter of book

Design of a Taxation System to Promote Electric Vehicles in Singapore

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

Part 2: Design, Manufacturing and Production Management; International audience; Electric vehicles offer a potential low-carbon alternative to todays gasoline-powered vehicles. In line with global trends, Singapore has expressed interest in promoting electric vehicles on its shores. This paper investigates the effects of taxation, namely tax rebates and carbon taxes, on the penetration of electric vehicles in Singapore. A consumer vehicular preference model was constructed using the logit model, and the effects on the economy determined through an inputoutput analysis. Multi-objective optimization is then used to find the optimal tax rate. Results indicate that a tax rebate minimizes the negative impact on the economy at a low penetration rate of electric vehicles, whereas a carbon tax minimizes the negative impact on GDP at a high penetration rate of above 60%.

Document type: Part of book or chapter of book

Inequality of opportunity, income inequality and economic mobility : some international comparisons

Scipedia content — Wed, 14 Oct 2020 14:39:26 +0200

Despite a recent surge in the number of studies attempting to measure inequality of opportunity in various countries, methodological differences have so far prevented meaningful international comparisons. This paper presents a comparison of ex-ante measures of inequality of economic opportunity (IEO) across 41 countries, and of the Human Opportunity Index (HOI) for 39 countries. It also examines international correlations between these indices and output per capita, income inequality, and intergenerational mobility. The analysis finds evidence of a "Kuznets curve" for inequality of opportunity, and finds that the IEO index is positively correlated with overall income inequality, and negatively with measures of intergenerational mobility, both in incomes and in years of schooling. The HOI is highly correlated with the Human Development Index, and its internal measure of inequality of opportunity yields very different country rankings from the IEO measure.

Document type: Book

Demographic Change and Transport

Scipedia content — Wed, 14 Oct 2020 14:34:51 +0200

This report is the literature review on demographic changes and transport of Work Package 1 of the EU project CONSOL, "CONcerns and SOLutions - Road Safety in the Ageing Societies" (contract period: 2011-2013).

The report is a state-of-the art report that combines current knowledge with new findings from relevant fields of basic research, focusing on the increasingly heterogeneous nature of the ageing population.

All CONSOL partners contributed to the report by writing parts of the report (authors), participating in the literature research and/or commenting to earlier versions of this report.

We would like to give special thanks to Heather Ward for constructive suggestions and inspiring comments to an earlier version of this report. Document type: Part of book or chapter of book

Temporally adaptive a algorithm on time dependent transportation network

Scipedia content — Wed, 14 Oct 2020 14:31:00 +0200

Traditional solutions to shortest path problems on time-varying transportation networks use traffic information only at precise moments regardless of considering the fact that the travel time through any link is dependent on the time entering that link. In this study, travel speed rather than travel time on each link is used as the time period dependent parameter to model time-dependent transportation networks, and a First-In-First-Out (FIFO) condition satisfied computational function of link travel time is then deduced based on kinematics. Finally, a temporally adaptive A* shortest path algorithm on this FIFO network is presented, where the time factor is introduced into the evaluation function, and the Euclidean distance divided by the maximum possible travel speed is used as a heuristic evaluator. An experiment on a real road network shows that the proposed algorithm is capable of foreseeing and bypassing forthcoming traffic congestion, at a cost only about 10% more in computational time than the traditional algorithm. In addition, frequent path reoptimization required with use of the traditional algorithm is effectively avoided.

Document type: Part of book or chapter of book

Improving the rural investment climate for businesses key to rural income generation

Scipedia content — Wed, 14 Oct 2020 14:29:21 +0200

An appropriate rural investment climate (RIC) is essential for rural businesses to be successful and generate employment and income in their communities. Improving the investment climate could facilitate income-generation activities in both farm and nonfarm sectors, thus reducing rural poverty. Nonfarm sector focused growth, combined with agricultural growth, and has been shown by Delgado et al. (1998) to have a significant impact on the local economy through the generation of employment and income. This study is the first to focus on both farm and nonfarm enterprises in its 2010 surveys of RIC in Yemen, Burkina Faso, Nigeria, and Mozambique unlike six previous RIC assessment (RICA) pilot projects that focused only on nonfarm enterprises. This report assesses the weaknesses and strengths of all RIC components in farm and nonfarm enterprises of the four countries surveyed, and recommends measures to address the weaknesses. The report identifies similar business obstacles for farm and nonfarm enterprises and four critical areas of the RIC to be improved. The results of the RICA are based on analyses of obstacles perceived by rural entrepreneurs and on assessments by RIC indicators, enterprise entry and exit, and enterprise performance. To have maximum synergy effects, farm and nonfarm enterprises should be promoted together.

Document type: Book

Microwave Beamforming Networks for Intelligent Transportation Systems

Scipedia content — Wed, 14 Oct 2020 14:21:36 +0200

An Intelligent Transportation System (ITS) is a system based on wireless communications which has been investigated for many years in order to provide new technologies able to improve safety and efficiency of road transportation with integrated vehicle and road systems. It combines all aspects of technology and systems design concepts in order to develop and improve transportation system of all kinds. ITS, which utilise information and communications technology in vehicle as well as within the roadside infrastructure, can also be used to improve mobility while increasing transport safety, reducing traffic congestion, maximising comfort, and reducing environmental impact (Andrisano et al., 2000). Intelligent transportation systems and applications can improve the quality of travel by selecting routes with up-to-the-minute information data, giving priority to response vehicle teams, notifying drivers about road incidents, and delivering ITS services to drivers. They can reduce fuel consumption by routing the vehicles to their destinations so that fuel waste is significantly reduced, and also fully utilise the capacity of the existing road vehicular networks by controlling the flow of vehicles based on traffic monitoring and detecting congestions.

Document type: Part of book or chapter of book

Evaluation of the Community Officer Project in Solomon Islands

Scipedia content — Wed, 14 Oct 2020 14:19:55 +0200

This evaluation assesses the performance of the Community Officer (CO) project, a trial community policing mechanism initiated by the Royal Solomon Islands Police Force (RSIPF) in late 2009, with assistance from the Participating Police Force (PPF) of the Regional Assistance to Solomon Islands (RAMSI). Current interest in community policing in Solomon Islands is occurring in the larger context of the rebuilding and reform of the RSIPF that has been taking place with the assistance of RAMSI. The Solomon Islands Government (SIG) and RSIPF are committed to introducing a viable form of community policing across the country.

Document type: Book

Breaking Free and Settling Down : Contradictory Cultural Meanings of Rural Retirement Migration among Swedish Seniors

Scipedia content — Wed, 14 Oct 2020 14:17:59 +0200

In this chapter, I argue that moving as a way to counter the negative aspects of ageing (actual as well as symbolic), is both dependent on mobility and contradictory to it. The overall purpose is to investigate the relation between moving and mobility in the accounts told by people who have chosen to migrate as seniors in order to enable a certain lifestyle. In what way does the discursive ideal of freedom and mobility, apparent in media and in popular science today, influence the way these seniors imagine, experience and talk about their move? To what extent do their accounts of retirement migration include traces of continuity and change, freedom and security, as well as mobility and rootedness? Could the move function as a way of breaking free and settling down simultaneously?

Document type: Part of book or chapter of book

Pervasive Gaming as a Potential Solution to Traffic Congestion: New Challenges Regarding Ethics, Privacy and Trust

Scipedia content — Wed, 14 Oct 2020 14:09:42 +0200

The following paper presents a review of the ethical, privacy and trust aspects relating to pervasive gaming in particular within the domain of traffic congestion. The paper deals explicitly with the challenges involved that fall between the gaps standard ethical practice and scientific research when studies comprise of those in the lab (where collection and use is heavily controlled) and those which take place in the wild where there is the requirement to share data possibly with external parties. Also where the nature of such work is at the borders of the concept of traditional study and a commercial running prototype.

Document type: Part of book or chapter of book

Protocol testing and performance evaluation for manets with non uniform node density distribution

Scipedia content — Wed, 14 Oct 2020 14:09:00 +0200

Part 6: New Testing Methods; International audience; In this paper, we focus on Mobile Ad-hoc Networks (MANETs) with non-uniform node density distribution such as Vehicular Ad-hoc Networks (VANETs) and Delay Tolerant Networks (DTNs), and propose a technique for protocol testing and performance evaluation. In such MANETs, node density varies depending on locations and time, and it dynamically changes every moment. In the proposed method, we designate node density distributions and their dynamic variations in a target area. Then, we construct a graph called TestEnvGraph where all node density distributions are treated as its nodes and they are connected by edges whose weights denote differences of two node density distributions. We specify a set of edges to be tested in the graph, formulate a problem for efficiently reproducing all the given node density distributions and their dynamic variations as a rural postman problem, find its solution and use it as the order of reproduction of designated node density distributions and their variations. Protocol testing is carried out by reproducing node density distributions in the derived order. We have designed and developed a method and its tool for mobility generation on MANETs, which can reproduce any designated node density distribution and its dynamic variations in a target area. From our experiments for a VANET protocol, we have shown that our method can give a similar trend in network throughput and packet loss rates compared with realistic trace based protocol testing.

Document type: Part of book or chapter of book

Two-phase MOBILE interconnection schemes for ultra-grain pipeline applications

Scipedia content — Wed, 14 Oct 2020 14:05:13 +0200

Trabajo presentado al 22nd PATMOS celebrado en Newcastle del 4 al 6 de septirmbre de 2012.

Document type: Part of book or chapter of book

Behavioural equivalences over migrating processes with timers

Scipedia content — Wed, 14 Oct 2020 13:05:04 +0200

International audience; The temporal evolution of mobile processes is governed by independently operating local clocks and their migration timeouts. We define a formalism modelling such distributed systems allowing (maximal) parallel execution at each location. Taking into account explicit timing constraints based on migration and interprocess communication, we introduce and study a number of timed behavioural equivalences, aiming to provide theoretical underpinnings of verification methods. We also investigate relationships between such behavioural equivalences.

Document type: Part of book or chapter of book

Virtual spring based 3d multi agent group coordination

Scipedia content — Wed, 14 Oct 2020 13:03:13 +0200

As future personal vehicles start enjoying the ability to fly, tackling safe transportation coordination can be a tremendous task, far beyond the current challenge on radar screen monitoring of the already saturated air traffic control. Our focus is on the distributed safe-distance coordination among a group of autonomous flying vehicle agents, where each follows its own current straight-line direction in a 3D space with variable speeds. A virtual spring-based model is proposed for the group coordination. Within a specified neighborhood radius, each vehicle forms a virtual connection with each neighbor vehicle by a virtual spring. As the vehicle changes its position, speed and altitude, the total resultant forces on each virtual spring try to maintain zero by moving to the mechanical equilibrium point. The agents then add the simple total virtual spring constraints to their movements to determine their next positions individually. Together, the multi-agent vehicles reach a group behavior, where each of them keeps a minimal safe-distance with others. A new safe behavior thus arises in the group level. With the proposed virtual spring coordination model, the vehicles need no direct communication with each other, require only minimum local processing resources, and the control is completely distributed. New behaviors can now be formulated and studied based on the proposed model, e.g., how a fast driving vehicle can find its way though the crowd by avoiding the other vehicles effortlessly1.

Document type: Part of book or chapter of book

Formal Software Verification at Model and at Source Code Levels

Scipedia content — Wed, 14 Oct 2020 12:50:09 +0200

International audience; In a software development lifecycle, it is often more than half of the development time that is dedicated to verification activities. Formal methods offer new possibilities for verification. In the specification phase, simulation or model-checking allow users to detect errors in models. In the implementation phase, analysis techniques, like static analysis, make the verification tasks more exhaustive and more automatic. In this context, we propose to take advantage of these methods to improve embedded software development processes based on the V-model.

Document type: Part of book or chapter of book

Tourism life cycle assessment (LCA) : proposal of a new methodological framework for sustainable consumption and production

Scipedia content — Tue, 29 Sep 2020 10:05:51 +0200

1Camillo De Camillis1,2, Paul Peeters3, Luigia Petti4 and Andrea Raggi4 1Dipartimento di Scienze, Universita degli Studi “G. d’Annunzio”, Pescara European Commission, Joint Research Centre, IES, Ispra* 3Center for Sustainable Transport and Tourism, NHTV Breda University of Applied Sciences, Breda, 4Dipartimento di Economia, Universita degli Studi “G. d’Annunzio”, Pescara 1,2,4Italy 3The Netherland

Document type: Part of book or chapter of book

Using energy criteria to admit flows in a wired network

Scipedia content — Tue, 29 Sep 2020 10:00:02 +0200

Admission control in wired networks has been traditionally used as a way to control traffic congestion and guarantee quality of service. Here, we propose an admission control mechanism which aims to keep the power consumption at the lowest possible level by restricting the more energy-demanding users. This work relies on the fact that power consumption of networking devices, and of the network as a whole, is not proportional to the carried traffic, as would be the ideal case [1]. As a result some operating regions may be more efficient than others and “jumps” may arise in power consumption when new traffic is added in the network. The proposed mechanism aims to keep power consumption in the lowest possible power consumption level, hopping to the next level only when necessary.

Document type: Part of book or chapter of book

Urban logistics pooling viability analysis via a multicriteria multiactor method

Scipedia content — Tue, 29 Sep 2020 09:57:58 +0200

Document type: Part of book or chapter of book

Reasoning about pipelines with structural hazards

Scipedia content — Tue, 29 Sep 2020 09:48:20 +0200

We have developed a formal definition of correctness for pipelines that ensures that transactions terminate and satisfy a functional specification. This definition separates the correctness criteria associated with the pipelining aspects of a design from the functional relationship between input and output transactions. Using this definition, we developed and formally verified a technique that divides the verification of a pipeline into two separate tasks: proving that the pipelining circuitry meets the pipelining correctness criteria and that the datapath and control circuitry meet the functional specification. The first proof is data independent (except for pipelines that use data-dependent control). The second proof is purely combinational: there is no notion of time and each possible input transaction can be dealt with independently. In addition, we have created a framework that structures and simplifies the proof of the pipelining circuitry.

Document type: Part of book or chapter of book

Ionospheric Propagation Effects on GNSS Signals and New Correction Approaches

Scipedia content — Tue, 29 Sep 2020 09:45:01 +0200

The ionosphere is the ionized part of the earth’s atmosphere lying between about 50 km and several earth radii (Davies, 1990) whereas the upper part above about 1000 km height up to the plasmapause is usually called the plasmasphere. Solar extreme ultraviolet (EUV) radiation at wave lengths " 130 nm significantly ionizes the earth’s neutral gas. In addition to photoionisation by electromagnetic radiation also energetic particles from the solar wind and cosmic rays contribute to the ionization. The ionized plasma can affect radio wave propagation in various ways modifying characteristic wave parameters such as amplitude, phase or polarization (Budden, 1985; Davies, 1990). The interaction of the radio wave with the ionospheric plasma is one of the main reasons for the limited accuracy and vulnerability in satellite based positioning or time estimation.\r \r A trans-ionospheric radio wave propagating through the plasma experiences a propagation delay / phase advance of the signal causing a travel distance or time larger / smaller than the real one. The reason of the propagation delay can be realized considering the nature of the refractive index which depends on the density of the ionospheric plasma. The refractive index (n ≠ 1) of the ionosphere is not equal to that of free space (n = 1). This causes the propagation speed of radio signals to differ from that in free space. Additionally, spatial gradients in the refractive index cause a curvature of the propagation path. Both effects lead in sum to a delay / phase advance of satellite navigation signals in comparison to a free space propagation.\r \r The variability of the ionospheric impact is much larger compared to that of the troposphere. The ionospheric range error varies from a few meters to many tens of meters at the zenith, whereas the tropospheric range error varies between two to three meters at the zenith (Klobuchar, 1996). The daily variation of the ionospheric range error can be up to one order of magnitude (Klobuchar, 1996). \r \r After removal of the Selective Availability (SA, i.e., dithering of the satellite clock to deny full system accuracy) in 2000, ionosphere becomes the single largest error source for Global Navigation Satellite Systems (GNSS) users, especially for high-accuracy (centimeter - millimeter) applications like the Precise Point Positioning (PPP) and Real Time Kinematic (RTK) positioning. Fortunately, the ionosphere is a dispersive medium with respect to the radio wave; therefore, the magnitude of the ionospheric delay depends on the signal frequency. The advantage is that an elimination of the major part of the ionospheric refraction through a linear combination of dual-frequency observables is possible. However, inhomogeneous plasma distribution and anisotropy cause higher order nonlinear effects which are not removed in this linear approach. Mainly the second and third order ionospheric terms (in the expansion of the refractive index) and errors due to bending of the signal remain uncorrected. They can be several tens of centimeters of range error at low elevation angles and during high solar activity conditions.\r \r Brunner & Gu (1991) were pioneers to compute higher order ionospheric effects and developing correction for them. Since then higher order ionospheric effects have been studied by different authors during last decades, e.g., Bassiri & Hajj (1993), Jakowski et al. (1994), Strangeways & Ioannides (2002), Kedar et al. (2003), Fritsche et al. (2005), Hawarey et al. (2005), Hoque & Jakowski (2006, 2007, 2008, 2010b), Hernandez-Pajares et al. (2007), Kim & Tinin (2007, 2011), Datta-Barua et al. (2008), Morton et al. (2009), Moore & Morton (2011). The above literature review shows that higher order ionospheric terms are less than 1% of the first order term at GNSS frequencies. Hernandez-Pajares et al. (2007) found sub-millimeter level shifting in receiver positions along southward direction for low latitude receivers and northward direction for high latitude receivers due to the second order term correction. Fritsche et al. (2005) found centimeter level correction in GPS satellite positions considering higher order ionospheric terms. Elizabeth et al. (2010) investigated the impacts of the bending terms described by Hoque & Jakowski (2008) on a Global Positioning System (GPS) network of ground receivers. They found the bending correction for the dual-frequency linear GPS L1-L2 combination to exceed the 3 mm level in the equatorial region. Kim & Tinin (2011) found that the systematic residual ionospheric errors can be significantly reduced (under certain ionospheric conditions) through triple frequency combinations. All these studies were conducted to compute higher order ionospheric effects on GNSS signals for ground-based reception. Recently Hoque & Jakowski (2010b, 2011) investigated the ionospheric impact on GPS occultation signals received onboard Low Earth Orbiting (LEO) CHAMP (CHAllenging Minisatellite Payload) satellite.\r \r In this chapter, the first and higher order ionospheric propagation effects on GNSS signals are described and their estimates are given at different level of ionospheric ionization. Multi-frequency ionosphere-free and geometry-free solutions are studied and residual terms in the ionosphere-free solutions are computed. Different correction approaches are discussed for the second and third order terms, and ray path bending correction. Additionally, we have proposed new approaches for correcting straight line of sight (LoS) propagation assumption error, i.e., ray path bending error for ground based GNSS positioning. We have modelled the excess path length of the signal in addition to the LoS path length and the total electron content (TEC) difference between a curved and LoS paths as functions of signal frequency, ionospheric parameters such as TEC and TEC derivative with respect to the elevation angle. We have found that using the TEC derivative in addition to the TEC information we can improve the existing correction results.

Document type: Part of book or chapter of book

The Application of Electric Drive Technologies in City Buses

Scipedia content — Tue, 22 Sep 2020 12:36:08 +0200

The development of innovative technologies is increasingly oriented towards electrification of vehicle propulsion systems expected to lead to: a reduction of harmful emissions, an increased efficiency of vehicles, improved performances, a reduction of fuel consumption, a reduction of noise, and potentially lower maintenance costs. An electric drive technology implies a technol‐ ogy employing at least one drive device called electric motor. Three key electric drive technol‐ ogies are: hybrid electric, battery electric, and fuel cell electric technologies. Document type: Part of book or chapter of book

Traducción automatizada de programas entre lenguajes de operaciones

Scipedia content — Mon, 27 Apr 2020 09:28:28 +0200

Los lenguajes de operaciones se usan para programar, en procedimientos organizados, las instrucciones a ser ejecutadas por una máquina, para realizar distintos tipos de operaciones. Para poder importar procedimientos existentes realizados en un lenguaje de operaciones dado, en frameworks de programación específicos para el diseño de operaciones, es necesario contar con traductores entre el lenguaje en que ha sido programado el procedimiento, y el lenguaje interno utilizado por el framework de diseño. La construcción de estos traductores puede ser automatizada si se establece un mapeo entre producciones equivalentes de las gramáticas de los lenguajes fuente y destino. Las producciones se pueden considerar equivalentes cuando a pesar de tener una sintaxis diferente, tienen la misma intención semántica y pueden ser equiparadas con un árbol de sintaxis abstracta en común. Debido a ciertas diferencias sintácticas, en ocasiones este árbol sintáctico común no puede ser hallado directamente. Esto se vuelve posible, sin embargo, al realizar en primer lugar ciertas transformaciones a los programas. Este artículo presenta un acercamiento específico a la construcción de reglas de transformación para resolver estas diferencias.Abstract:Operations languages are used to program the procedures that instruct machinery to perform specific operations. To import procedures in a given operations language, into a dedicated tool for designing operations, language translators are needed to translate those procedures to the design tool's internal operations language. The construction of these translators can be automated by mapping equivalent productions in the grammar of source and target language. Productions are considered equivalent when, in spite of a differing syntax, they have the same intended semantics and can be matched to a same abstract syntax tree. For some corresponding productions, due to syntactic differences, such a common abstract syntax tree cannot be found directly. However, they can be made to match by performing some specific program transformations first. This paper presents a specific approach to write transformation rules to resolve such mismatches.

Teoría de restricciones para procesos de manufactura

Scipedia content — Mon, 27 Apr 2020 09:26:31 +0200

La empresa “Productos Alexander” fabricante de snacks de la ciudad de Quito, tiene un sistema de producción que no permite el abastecimiento de los pedidos de sus clientes reflejando un índice de servicio al cliente de 89,58% ya que sus procesos están trabajando con capacidades que no se encuentran correctamente programadas, en vista de tal razón el objetivo de esta investigación es proponer un sistema de mejora continua con el fin de aumentar y efectivizar específicamente la producción de snacks de papas fritas utilizando la Teoría de Restricciones (TOC) como metodología científica. Se realizó la medición de capacidad de cada una de las operaciones que componen el proceso de elaboración de snacks y se identificó la restricción en el proceso de fritura, que no estaba trabajando el 100% del tiempo en la jornada diaria limitando así la capacidad de la fábrica, por lo que se optó por explotar la restricción para eliminarla. La propuesta planteada para explotar la restricción consiste en una mejor programación de la producción, reducción de lote de transferencia de proceso a proceso, programación de la cantidad de trabajo para cada uno de los operarios en la jornada, la preparación del proceso y la fijación de turnos en la hora de almuerzo de los operarios lo que contribuye a agilizar el proceso de fritura y permitir que trabaje a su máxima capacidad el 100% del tiempo.Dicha propuesta se puede considerar como una solución al problema y así mejorar los niveles de producción de la empresa, tomando en cuenta que en base a los indicadores de TOC el Beneficio Neto de la empresa aumentaría de $15 333.09 a $ 17 392.14 al cumplir en cantidad y a tiempo todos los pedidos de los clientes.Abstract:The company "Products Alexander" snack manufacturer in the city of Quito, has a production system that cannot supply customer orders, with a customer service index of 89,58%, also their processes are working with capabilities that are not properly programmed in given this reason the objective of this research is to propose a system of continuous improvement to increase production and make effective the snacks of chips using the Theory of Constraints (TOC) as a scientific methodology is to focus on solutions to critical problems of enterprises so that they approach their goal through a process of continuous improvement (Arias, 2006). The measurement was carried capacity of each of the operations which compose the preparation of snacks and identified restriction in the frying process, which was not working 100% of the daily time thereby limiting the ability of the factory, so we chose to exploit the constraint to eliminate it.The proposal made to exploit the constraint is a better production scheduling, reducingtransfer batch process to process, scheduling the amount of work for each of the operators inthe day, the preparation process and setting shifts at lunchtime for workers helping tostreamline the process of frying and allow work to full capacity 100% of the time. This proposalcan be considered as a solution to problems and improve production levels of the company,considering that based on indicators of TOC net income the company would increase from $ 15333.09 $ 17 392.14 in meeting quantity time and all customer orders.

Estimación de la estabilidad de un sazonador a base de amaranto reventado y maní tostado, a partir del índice de peróxidos

Scipedia content — Mon, 27 Apr 2020 09:24:34 +0200

El objetivo del presente trabajo fue evaluar la estabilidad, durante el almacenamiento, de un sazonador nutritivo elaborado con amaranto reventado y maní tostado, empleando el índice de peróxidos como un indicador del deterioro del producto. Para lo cual se almacenó el sazonador, empacado en fundas de polipropileno y aluminizadas, a condiciones ambientales (17°C, 50%HR) y aceleradas (35°C, 90%HR) durante 30 días; se analizó el índice de peróxidos cada 5 días. Se consideró que el índice de peróxidos, sigue una cinética de orden cero durante el tiempo de almacenamiento. Considerando que las grasas y aceites comestibles, pueden alcanzar un valor máximo de índice de peróxidos de 20 mEq/kg, se determinó que el sazonador nutritivo empacado en funda de polipropileno, y almacenado a condiciones ambientales (17°C y 50%HR) se mantuvo estable durante 81 días; mientras que el almacenado a condiciones aceleradas (35°C, 90%HR) alcanzó los 68 días. Asimismo el sazonador empaquetado en funda aluminizada, y almacenado aAbstract:The aim of this study was to evaluate the stability during storage of a nutritious seasoning made from popped amaranth and roasted peanuts, using peroxide index as an indicator of deterioration. The seasoning was stored in polypropylene and aluminized bags at room temperature (17 °C, 50% RH) or accelerated conditions (35 °C, 90% RH) during 30 days. The peroxide index was analyzed every five days. It was considered that the peroxide index followed a zero-order kinetic during the storage time. Assuming that oils and fats can reach a maximum level of the peroxide of 20 mEq/kg, it was observed that the nutritional seasonings packaged in the polypropylene bag stored at room temperature or accelerated conditions remained stable for 81 days 68 days, respectively. In the same way, the samples packaged in the aluminized bags and stored at room temperature remained stable for 101 days whereas the samples in the accelerated conditions reached 78 days.

Microfiltración tangencial

Scipedia content — Mon, 27 Apr 2020 09:22:38 +0200

El objetivo de este trabajo fue revisar los conceptos básicos y las aplicaciones de la tecnología de microfiltración tangencial (MFT) en la industria alimentaria, particularmente en jugos de fruta y derivados lácteos, entre otros. Se presenta, además, los tipos de membrana utilizadas en esta operación unitaria de separación. Finalmente, se resaltan brevemente los trabajos realizados en Ecuador con jugos de frutas locales y pretratamientos en leche de vaca.Abstract:The aim of this study was to review the basic concepts and applications of cross flow microfiltration technology (MFT) in the food industry, particularly in fruit juices and dairy products, among others. This review also presents the different types used in this unit operation. Finally, it briefly highlights the work done in Ecuador with native fruit juices and cow milk pretreatments.

Monitoreo de la reforestación en las quebradas en el Norte de Quito

Scipedia content — Mon, 27 Apr 2020 09:20:41 +0200

El Distrito Metropolitano de Quito (DMQ) comprende 61.563 has., las cuales albergan diversasespecies de flora y fauna. Los procesos de acelerada urbanización han dado lugar alestablecimiento de viviendas e invasiones que han presionado a los bosques que existíanespecialmente en las laderas del Pichincha y en las quebradas de la parte norte del distrito. ElMunicipio del Distrito Metropolitano de Quito (MDMQ) en sus Políticas de Patrimonio Natural,contempla la integración, conectividad, mantenimiento, recuperación, y rehabilitación deespacios naturales priorizados para seguridad ambiental del Distrito, cuya aplicación tienecomo objetivo específico el disminuir la afectación antrópica progresiva a ecosistemas yespacios naturales de conservación del Distrito. Con estos antecedentes se realiza unacontratación para la reforestación de once quebradas en la Administración Zonal La Delicia, lamisma que se realiza en los meses de abril – junio del presente año (2012) en un total de 43has. con el compromiso de siembra de 37.152 plantas. Para realizar el seguimiento a esteproceso se plantea un monitoreo inicial para conocer el estado de la reforestación y el impactocausado en las quebradas seleccionadas. Mediante recorridos y mapeo de sitio, se contabilizanlas plantas sembradas y supervivientes en cada una de las quebradas y se constata elcumplimiento de solo el 5,05% de la reforestación planteada.Abstract:The Metropolitan District of Quito covers 61.563 has., containing many species of flora andfauna. Accelerated urbanization processes have led to illegal housing and human invasions,putting pressure on existing forests, especially on the slopes of Pichincha and the ravines of thenorthern part of the District. The Metropolitan District of Quito, in its Natural Heritage Policy,prioritizes the integration, connectivity, maintenance, recovery and rehabilitation of naturalareas, to support the District environmental security. Focus is put on reducing the anthropiceffects on the affected ecosystems and natural areas. To reinforce this policy, the Municipalitysigned a contract for the reforestation of eleven ravines in La Delicia. The reforestation wasdone from April to June 2012, on a total of 43 has., with the commitment of planting 37.152plants. To track this process the Municipality planned an initial monitoring to determine thestatus of the reforestation and its impact on the selected ravines. Planted and surviving plantswere counted on each of the eleven ravines, and a compliance of only 5.05% of the plannedreforestation was verified.

Identificación de macro invertebrados bentónicos en los ríos: Pindo Mirador, Alpayacu y Pindo Grande; determinación de su calidad de agua

Scipedia content — Mon, 27 Apr 2020 09:18:43 +0200

En un estudio realizado en el mes de mayo del 2012, utilizando una red Surber de 30 x 30 cmde área de superficie y 0,5 mm de abertura de malla, en los ríos: Pindo Mirador, Pindo Grandey Alpayacu, ubicados en el sector de Mera, provincia de Pastaza de la Amazonía ecuatoriana,se analizó la diversidad y la abundancia de los macro invertebrados bentónicos utilizando losíndices BMWP/Col y EPT. Se logró determinar que la calidad del agua de los ríos PindoMirador y Pindo Grande es buena mientras la del río Alpayacu es mala. Este estudio da unaidea general de la situación ambiental de los ecosistemas lóticos cercanos a la EstaciónBiológica Pindo Mirador. Los resultados de ésta investigación permiten determinar laimportancia de las micro-cuencas de los ríos Pindo Mirador y Pindo Grande como fuente deagua para las poblaciones que se encuentran río abajo, así como el modo en el cual lapresencia o ausencia de organismos bioindicadores (macroinvertebrados) indica la calidad delagua y de los bosques de la micro-cuenca.Abstract:In May 2012, using a 30x30 cm surface and 0.5 mm aperture Surber net in the rivers: PindoMirador, Pindo Grande and Alpayacu, located in Mera, Pastaza, Ecuadorian Amazonia, thediversity and abundance of macro invertebrates was analyzed applying the BMWP/Col and theEPT indexes. It was determined the good Pindo Mirador, Pindo Grande and Alpayacu rivers’water quality, as well as the bad Alpayacu river’s water quality. This work provides an overviewof the environmental situation of aquatic ecosystems near Pindo Mirador Biological Station, ithighlights the importance of the rivers’ micro-watersheds near Pindo Mirador Biological Station,used as water source by the populations living downstream, and shows how macroinvertebrates can be used as bioindicators for the water and forests quality.

Understanding the current state of the NFC payment ecosystem: A graphbased analysis of market players and their relations

Scipedia content — Mon, 27 Apr 2020 09:16:46 +0200

El reciente desarrollo de la tecnología Near Field Communication (NFC) ha permitido la aparición de servicios de pago a través de teléfonos celulares. Además, esta innovación tecnológica ha iniciado una evolución continua relativa a las operaciones de pago. Las empresas y los investigadores proyectan que la función predominante de las tarjetas de crédito serán progresivamente sustituidos por dispositivos móviles. En este trabajo se describe en detalle NFC y se realiza un análisis de red basado en gráficos para determinar los participantesy las industrias involucradas en la red, así como las relaciones, incluyendo los conflictos, cooperaciones o alianzas entre los actores.Abstract:The recent development of Near Field Communication (NFC) technology has enabled the emergence of payment services using mobile phones. Furthermore, this technological innovation initiated an ongoing evolution concerning payment transactions. Companies and researchers project that the prevalent function of credit cards will be progressively substituted by mobile devices. In this paper NFC is described in detail and a graphed based network analysis is performed to determine players and industries involved in the network as well as the relations, including conflicts, cooperation, or alliances between these actors.

Megastore: structured storage for Big Data

Scipedia content — Mon, 27 Apr 2020 09:14:48 +0200

Megastore es uno de los componentes principales de la infraestructura de datos de Google, elcual ha permitido el procesamiento y almacenamiento de grandes volúmenes de datos (BigData) con alta escalabilidad, confiabilidad y seguridad. Las compañías e individuos que usanestá tecnología se están beneficiando al mismo tiempo de un servicio estable y de altadisponibilidad. En este artículo se realiza un análisis de la infraestructura de datos de Google,comenzando por una revisión de los componentes principales que se han implementado en losúltimos años hasta la creación de Megastore. Se presenta también un análisis de los aspectostécnicos más importantes que se han implementado en este sistema de almacenamiento y que le han permitido cumplir con los objetivos para los que fue creado.Abstract:Megastore is one of the building blocks of Google’s data infrastructure. It has allowed storingand processing operations of huge volumes of data (Big Data) with high scalability, reliabilityand security. Companies and individuals using this technology benefit from a highly availableand stable service. In this paper an analysis of Google’s data infrastructure is made, startingwith a review of the core components that have been developed in recent years until theimplementation of Megastore. An analysis is also made of the most important

The Particle Finite Element Method. An effective numerical technique for fluid-soil-structure interaction problems

María Jesús Samper — Mon, 25 Nov 2019 16:59:40 +0100

We present some developments in the Particle Finite Element Method (PFEM) for analysis of complex coupled problems in mechanics involving fluid-soil-structure interaction (FSSI). The PFEM uses an updated Lagrangian description to model the motion of nodes (particles) in both the fluid and the solid domains (the later including soil/rock and structures). A mesh connects the particles (nodes) defining the discretized domain where the governing equations for each of the constituent materials are solved as in the standard FEM. The stabilization for dealing with an incompressibility continuum is introduced via the finite calculus (FIC) method. An incremental iterative scheme for the solution of the non linear transient coupled FSSI problem is described. The procedure to model frictional contact conditions and material erosion at fluid-solid and solid-solid interfaces is described. We present several examples of application of the PFEM to solve FSSI problems such as the motion of rocks by water streams, the erosion of a river bed adjacent to a bridge foundation, the stability of breakwaters and constructions sea waves and the study of landslides.

Enforcing interface flux continuity in enhanced XFEM: stability analysis

María Jesús Samper — Wed, 30 Oct 2019 14:27:43 +0100

The finite element method is the established simulation tool for the numerical solution of partial differential equations in many engineering problems with many mathematical developments such as mixed finite element methods (FEMs) and other nonstandard FEMs like least-squares, nonconforming, and discontinuous Galerkin (dG) FEMs. Various aspects on this plus related topics ranging from order-reduction methods to isogeometric analysis has been discussed amongst the pariticpants form mathematics and engineering for a large range of applications.

Computable bounds of functional outputs in linear visco-elastodynamics

María Jesús Samper — Wed, 30 Oct 2019 14:18:59 +0100

This work presents a new technique yielding computable bounds of quantities of interest in the framework of linear visco-elastodynamics. A novel expression for the error representation is introduced, alternative to the previous ones using the Cauchy–Schwarz inequality. The proposed formulation utilizes symmetrized forms of the error equations to derive error bounds in terms of energy error measures. The practical implementation of the method is based on constructing admissible fields for both the original problem and the adjoint problem associated with the quantity of interest. Here, the flux-free technique is considered to compute the admissible stress fields. The proposed methodology yields estimates with better quality than the ones based on the Cauchy–Schwarz inequality. In the studied examples the bound gaps obtained are approximately halved, that is the estimated intervals of confidence are reduced

Adaptive reduced basis strategy based on goal oriented error assessment for stochastic problems

María Jesús Samper — Wed, 30 Oct 2019 14:11:12 +0100

In the framework of stochastic non-intrusive finite element modeling, a common practice is using Monte Carlo simulation. The main drawback of this approach is the computational cost, because it requires computing a large number of deterministic finite element solutions. The different Monte Carlo samplings correspond to realizations of the random variables characterizing the stochastic behavior of the model. Thus, this requires solving a set deterministic problems with the same structure, that is with variations concerning the material parameters and the loading data. Consequently, the different problems to be solved are in practice similar to each other. The reduced basis strategy is therefore a sensible option to reduce computational cost, provided that the quality of the numerical solution is guaranteed. The paper introduces a goal-oriented strategy allowing to successively enrich the reduced basis along the Monte Carlo process. The method is based on assessing the error of the reduced basis solution with a residual estimate for the prescribed quantity of interest. The efficiency of the proposed approach, which is particularly important if the number of independent random variables is large, is illustrated in 1D and 2D mechanical examples.

Modeling steel fiber reinforced concrete: numerical immersed boundary approach and a phenomenological mesomodel for concrete-fiber interaction

María Jesús Samper — Wed, 30 Oct 2019 13:59:18 +0100

Steel fiber reinforced concrete (SFRC) allows overcoming brittleness and weakness under tension, the main drawbacks of plain concrete. The influence of the fibers on the behavior of SFRC depends on their shape, length, slenderness, and also on their orientation and distribution into the plain concrete. The goal of this paper is to develop an ad hoc numerical strategy to account for the contribution of the fibers in the simulation of the mechanical response of SFRC. In the model presented, the individual fibers immersed in the concrete bulk are accounted for in their actual location and orientation. The selected approach is based on the ideas introduced in the immersed boundary (IB) methods. These methods were developed to account for 1D (or 2D) solids immersed in 2D (or 3D) fluids. Here, the concrete bulk is playing the role of the fluid and the cloud of steel fibers is acting as the immerse boundary (that is, a 1D structure in a 2D or 3D continuous). Thus, the philosophy of the IB methodology is used to couple the behavior of the two systems, the concrete bulk and fiber cloud, precluding the need of matching finite element meshes. Note that, considering the different size scales and the intricate geometry of the fiber cloud, the conformal matching of the meshes would be a restriction resulting in a practically unaffordable mesh.
In the proposed approach, the meshes of the concrete bulk and fiber cloud are independent, and the models are coupled imposing displacement compatibility and equilibrium of the two systems. In the applications presented here, the concrete bulk is modeled using a standard nonlinear damage model. The constitutive model for the fibers is designed to account for the complex interaction between fibers and concrete. The fiber models are based on the previous investigations describing the concrete-fiber interaction and its dependence on the factors identified to be relevant: shape of the fiber (straight or hooked) and angle between the fiber and crack plane.

A symmetric method for weakly imposing Dirichlet boundary conditions in embedded finite element meshes

María Jesús Samper — Thu, 05 Sep 2019 13:26:29 +0200

In this paper, we propose a way to weakly prescribe Dirichlet boundary conditions in embedded finite element meshes. The key feature of the method is that the algorithmic parameter of the formulation which allows to ensure stability is independent of the numerical approximation, relatively small, and can be fixed a priori. Moreover, the formulation is symmetric for symmetric problems. An additional element‐discontinuous stress field is used to enforce the boundary conditions in the Poisson problem. Additional terms are required in order to guarantee stability in the convection–diffusion equation and the Stokes problem. The proposed method is then easily extended to the transient Navier–Stokes equations.

A third‐order velocity correction scheme obtained at the discrete level

María Jesús Samper — Thu, 05 Sep 2019 13:18:21 +0200

In this work we explore a velocity correction method that introduces the splitting at the discrete level. In order to do so, the algebraic continuity equation is transformed into a discrete pressure Poisson equation and a velocity extrapolation is used. In Badia et al. (IJNMF, 2008, p. 351), where the method was introduced, the discrete Laplacian that appears in the pressure Poisson equation is approximated by a continuous one using an extrapolation for the pressure. In this work we explore the possibility of actually solving the discrete Laplacian. This introduces significant differences because the pressure extrapolation is avoided and only a velocity extrapolation is needed. Our numerical results indicate that it is the second‐order pressure extrapolation which makes third‐order methods unstable. Instead, second‐order velocity extrapolations do not lead to instabilities. Avoiding the pressure extrapolation allows to obtain stable solutions in problems that become unstable when the Laplacian is approximated. A comparison with a pressure correction scheme is also presented to verify the well‐known fact that the use of a second order pressure extrapolation leads to instabilities. Therefore we conclude that it is the combination of a velocity correction scheme with a discrete Laplacian that allows to obtain a stable third‐order scheme by avoiding the pressure extrapolation.

A nodal-based finite element approximation of the Maxwell problem suitable for singular solutions

María Jesús Samper — Thu, 05 Sep 2019 13:03:02 +0200

A new mixed finite element approximation of Maxwell's problem is proposed, its main features being that it is based on a novel augmented formulation of the continuous problem and the introduction of a mesh dependent stabilizing term, which yields a very weak control on the divergence of the unknown. The method is shown to be stable and convergent in the natural H(curl 0; Ω) norm for this unknown. In particular, convergence also applies to singular solutions, for which classical nodal-based interpolations are known to suffer from spurious convergence upon mesh refinement.

Stokes, Maxwell and Darcy: A single finite element approximation for three model problems

María Jesús Samper — Thu, 05 Sep 2019 12:57:00 +0200

In this work we propose stabilized finite element methods for Stokesʼ, Maxwellʼs and Darcyʼs problems that accommodate any interpolation of velocities and pressures. We briefly review the formulations we have proposed for these three problems independently in a unified manner, stressing the advantages of our approach. In particular, for Darcyʼs problem we are able to design stabilized methods that yield optimal convergence both for the primal and the dual problems. In the case of Maxwellʼs problem, the formulation we propose allows one to use continuous finite element interpolations that converge optimally to the continuous solution even if it is non-smooth. Once the formulation is presented for the three model problems independently, we also show how it can be used for a problem that combines all the operators of the independent problems. Stability and convergence is achieved regardless of the fact that any of these operators dominates the others, a feature not possible for the methods of which we are aware.