Scipedia: Documents published in 2007

Direct observer design for leak detection and estimation in pipelines

Scipedia content — Tue, 02 Feb 2021 07:23:36 +0100

International audience; Some direct on-line observer-based approach for leak detection and isolation in pipelines is here presented and tested in simulation. Given indeed a number of possible leaks to be detected, an observer aiming at simultaneous estimation of magnitudes and positions of the leaks is given on the basis of some appropriate model on the one hand, and appropriate excitation on the other hand. The method is illustrated via simulation results.

Estimating Operational Benefits of Aircraft Navigation and Air Traffic Control Procedures using an Integrated Aviation Modeling and Evaluation Platform

Scipedia content — Tue, 02 Feb 2021 07:14:57 +0100

Complex constraints generally define the performance of air transportation systems. These constraints include aircraft operational characteristics, airline operating procedures, and Air Traffic Control (ATC) requirements. The operational variability that is present in complex air transportation systems and their components typically demands a Monte Carlo approach when modeling system performance metrics. However, the inherent variability is generally not known a priori. This calls for a separate model validation approach that yields estimates of system variability and validates baseline model performance. This paper reports on an integrated aviation modeling platform that was developed for comparing and evaluating proposed aircraft flight operations and ATC procedures. It integrates both an agent-based Monte Carlo modeling environment and a data-driven model validation capability. The capabilities are outlined, the validation approach is described, and examples are presented of performance metrics quantifying operational benefits of air navigation procedures that are currently being implemented at major U.S. airports.

Multi-metric QoS routing based on fuzzy theory in wireless mesh network

Scipedia content — Tue, 02 Feb 2021 06:58:35 +0100

A Service - Oriented Approach To Onshore Gas Transmission Pipeline Construction

Scipedia content — Tue, 02 Feb 2021 06:57:25 +0100

This research investigates whether a traditional manufacturing planning and control strategy would make Onshore Gas Transmission Pipeline Construction more competitive and if so, design the strategy. An in-depth case study of Gas Transmission Pipeline Construction was carried out, along with an extensive literature review. The current pipeline construction process was analyzed from a strategic management perspective. From this perspective, it was found that the traditional `make and sell' attitude of manufacturers has now almost entirely given way to a customer oriented `sense and respond' service philosophy. This is compounded by the needs for waste avoidance, cost efficiency and service to the customer. This research investigates the strategic opportunities for establishing advantages over competitors by designing unique service oriented supply chain strategies. Rather than relying on functional hierarchy and command and control governance where a chain of commitments are poorly connected and difficult to reconfigure, the pipeline construction participants is challenged to develop more flexible process designs around a state of the art service based architecture. Complexity reduction has traditionally been used to deal with intricate construction supply chains. However, the architecture developed and demonstrated in this research will allow participants in pipeline construction to develop strategic opportunities around ideas of complexity absorption. The architecture is built on the premise that complexity absorption creates an organization that is strategically superior because it becomes a complex adaptive system that is unique to that organization.

City logistics: A chaos between research and policy making? A review

Scipedia content — Tue, 02 Feb 2021 06:53:42 +0100

hough the interest in urban freight transport is growing, it is commonly seen as an area where there is, for several reasons, a lack of research, especially if it is compared with the amount of research that deals with passenger transport. The attention of governments especially for urban goods movement has increased over recent years and with that the number of studies in the urban goods movement field. However, the practice of city logistics policies is not very often the result of detailed analyses and evaluations. This is reflected in similar types of regulations repeated through the different cities regardless of their characteristics, the same schedules for time windows and load zones, and the failure to recognize different types of urban distribution which require different types of regulations. Apart from copying regulation frameworks, however, cities hardly share information, knowledge or cooperation. The lack of national or regional bodies dealing with city logistics, as there exist for urban passenger traffic, is significant. In this paper the authors address the main research contributions in city logistics and try to illustrate how the research contributions are (not) related to the daily practice of policymaking and town planning. Finally the paper ends with the conclusion that a real gap exists between research and practice and the paper provides some explanations, conditions and directions for setting up new research projects.

Head Pose Estimation for Driver Assistance Systems: A Robust Algorithm and Experimental Evaluation

Scipedia content — Tue, 02 Feb 2021 06:36:49 +0100

Recognizing driver awareness is an important prerequisite for the design of advanced automotive safety systems. Since visual attention is constrained to a driver's field of view, knowing where a driver is looking provides useful cues about his activity and awareness of the environment. This work presents an identity-and lighting-invariant system to estimate a driver's head pose. The system is fully autonomous and operates online in daytime and nighttime driving conditions, using a monocular video camera sensitive to visible and near-infrared light. We investigate the limitations of alternative systems when operated in a moving vehicle and compare our approach, which integrates Localized Gradient Orientation histograms with support vector machines for regression. We estimate the orientation of the driver's head in two degrees-of-freedom and evaluate the accuracy of our method in a vehicular testbed equipped with a cinematic motion capture system.

Development of a Low Application Temperature FBE Coating

Scipedia content — Tue, 02 Feb 2021 06:25:31 +0100

Fusion bonded epoxy (FBE) coatings have been used on pipelines as protection against corrosion for over 40 years. They have been used as a stand-alone product in single layer systems and as a primer in dual and three layer systems. To achieve optimal performance, current FBE products require application temperatures in excess of 230°C for single layer systems and 200°C for three layer systems. The introduction of high strength steels such as X80, X100 and X120 for use in pipeline construction has presented a challenge to the industry in terms of the availability of suitable coating systems. High strength steels (particularly grades X100 and greater) cannot withstand pre-heat temperatures in excess of 200°C. Exposure to the high heat required when coating with a typical FBE product results in the degradation of some of the key properties of these high strength steels. This paper will discuss the development and performance of a new generation FBE coating that can be applied at temperatures as low as 180°C for single layer systems and as low as 150°C for multi-layer systems. Performance of this new product will be compared to one of the best performing commercially available FBE products applied at 240°C.Copyright © 2008 by 3M

Taxinomie de représentations graphiques dynamiques

Scipedia content — Tue, 02 Feb 2021 06:23:23 +0100

National audience; The displays used by the air traffic controllers involve many animated visual entities. They are constrained by precise rules of representation. The richness of these representations highlights the lack of tools that may characterize them. The increments of such an instrument are numerous, in terms of validation, design and safety. The objective of the thesis is to study representations, to find out methods of characterization that would allow comparisons between representations, and eventually to check their interests.; Les images utilisées par les contrôleurs aériens comportent de nombreuses entités visuelles animées.Elles sont soumises à des règles de représentation précises.La richesse de ces représentations a mis en évidence l’absence d’outils permettant de les caractériser.Les incréments d’un tel instruments ont multiples, en termes de validation, de design et de sécurité.L’objectif de la thèse est d’étudier des représentations,de trouver des méthodes de caractérisation afin notamment de permettre des comparaisons entres vues et de vérifier leur intérêt.

Analysis of factors affecting fractures of rails welded by alumino-thermic welding

Scipedia content — Tue, 02 Feb 2021 06:07:03 +0100

On Latvian Railway, the use of the thermic welding is widespread using the ELECTRO-THERMIT Company technology. Today it is a basic method for rail joints. Experience of the operation of rails welded by the thermic welding showed that every year occur from 2 to 3 fractures of thermic joints on the main tracks between stations of Latvian Railway.Such emergence of cracks in the weld joint alongside the scores indicates of great residual stresses in the weld joints made by the thermic welding.

Green trajectories in high traffic TMAs

Scipedia content — Tue, 02 Feb 2021 05:47:19 +0100

New conflicting future demands in air travel like gain of capacity and coexistent reduction of environmental impact necessitate new airborne functions and a better integration of these capabilities in air traffic management (ATM). DLR's Advanced Flight Management System proved a highly accurate predictability of 4D trajectories in flight trials with the A330-300 Full Flight Simulator of ZFB Berlin and DLR's test aircraft ATTAS, a VFW 614 twin engine jet transport aircraft modified for research purposes. Due to an inefficient air-ground integration current terminal manoeuvring area (TMA) concepts do not support 4D-capable aircraft in flying fuel efficient and noise abating profiles. A trajectory based TMA handling is necessary to combine aircraft optimized flight profiles with high airport efficiency. This paper presents results of advanced continuous descent approaches (CDA) flight trials with the research aircraft ATTAS and simulation trials with the A330 full flight simulator. Furthermore, a trajectory based TMA concept is introduced as a possible solution for the current trade-off between green trajectories and high airport capacity even in high traffic situations.

A tool to design Functional Airspace Blocks

Scipedia content — Tue, 02 Feb 2021 05:38:08 +0100

This paper focuses on the selection of a technical tool for the establishment of functional airspace blocks in Europe. This paper shows that the creation of functional airspace blocks is a partitioning problem. Some state-of-the-art partitioning libraries and two metaheuristics are applied to this problem. Comparisons have been made between these libraries and metaheuristics. Results show that the Fusion Fission metaheuristic performs better. The purpose of this paper is not to give the best partition of Europe into functional airspace blocks. It only presents a study which compares and suggests different tools for the establishment of functional airspace blocks in Europe.

A Parallel and Distributed Analysis Pipeline for Performance Tree Evaluation

Scipedia content — Tue, 02 Feb 2021 05:01:23 +0100

Performance Trees are a unifying framework for the specification of performance queries involving measures and requirements. This paper describes an evaluation environment for Performance Trees comprising a client-side Performance Query Editor, incorporated as a module of the PIPE2 Petri net tool, and a cluster-based server-side evaluation engine. The latter combines the capabilities of a number of parallel and distributed analysis tools.

Estimation of Weather-Induced Arrival Delay Statistics Through Monte-Carlo Simulations

Scipedia content — Tue, 02 Feb 2021 04:56:23 +0100

ft have to be rerouted around severe weather to ensure safe operation. Consequent changes in the flight plan often leads to arrival delays. Due to the complexity of the weather patterns and the traffic flow structure, the uncertainties in aircraft arrival rates cannot be predicted analytically from the uncertainties in the weather forecasts. This paper demonstrates the use of Monte-Carlo simulation to transform the uncertainties in severe weather prediction into uncertainties in the arrival flow rate at given airports. The aircraft trajectories are propagated using a simulation model of the air traffic environment. A rerouting algorithm is defined to modify the aircraft flight plans for avoiding severe weather regions. Using the traffic data for a typical day as the baseline, 300 Monte-Carlo runs are carried out and the variations in the aircraft arrival patterns are quantified as a function of the weather prediction uncertainty for several airports in the continental United States.

Improved MPLS-TE LSP Path Computation using Preemption

Scipedia content — Tue, 02 Feb 2021 04:53:07 +0100

International audience; In Multi-Protocol Label Switching-Traffic Engineering (MPLS-TE) networks with distributed tunnel path computation on head-end routers, tunnel requests are handled one by one, in an uncoordinated manner without any knowledge of future and other requests. The order in which requests are handled has a significant impact on the network optimization and blocking probability. If it is not possible to control the arrival order, in return it is possible, in some cases, to reorder requests using the preemption function. This paper evaluates the impact of the arrival order, so as to determine efficient orders. It then proposes two preemption strategies so as to reorder arrivals and evaluate these strategies applied to the shortest constrained path computation algorithm.

Training value of a fixed-base flight simulator with a dynamic seat

Scipedia content — Tue, 02 Feb 2021 04:51:08 +0100

In this paper, we first explain that pilots experience airplane motion via multiple perceptual systems, which makes motion a candidate for simulation via stimulation of only a subset of these systems. Next, we discuss the relative merit of vestibular cues when piloting an airplane. This is followed by a comparison of the vestibular cues received in the airplane and those possible, or practicable, in an airline-pilot training simulator, considering also the history of flight-simulator motion and alternative technologies. We conclude that a vast body of research has shown that accurate cues are not achievable at present, and that those available have not been shown to improve transfer between airplane and simulator. We then examine the cost of motion, and posit that it may prohibit some airline pilots from reaping the benefits of simulator training, with a concomitant loss in passenger safety. This consideration is especially pertinent given the world-wide training needs. Moreover, the equipment, facility, and maintenance costs associated with hexapod-platform motion systems may serve to discourage operators from upgrading the simulator’s fidelity in other important areas, such as assuring that the simulator cockpit does in fact match the equipment in the target aircraft, and that the simulation includes realistic operational representation of the national air space, including the air-traffic-control environment. We describe current and planned research on the training effectiveness of an alternative approach, which provides trainees with visual motion and heave-onset cues in what otherwise corresponds to an FAA Level D Full Flight Simulator in terms of data fidelity. This includes the results of a “proof-of-concept” phase that culminated in the successful type-rating of six pilots on a twin-engine turboprop airplane.

Development of Image Processing Method for High Quality Pipeline Inspection

Scipedia content — Tue, 02 Feb 2021 04:44:18 +0100

Sewer pipelines are buried underground and often forgotten until serious failure happens. Effective and reliable sewer system management is very important for the safe and clean environment. In order to maintain the intended capacity of pipes, effective maintenance based on accurate condition assessment is required. This research suggests a new method that uses digital still images to overcome the limitations of common CCTV pipeline inspection systems. As a result high quality images are obtained for accurate and effective condition assessment of pipelines.

An estimation-based automatic vehicle location system for public transport vehicles

Scipedia content — Tue, 02 Feb 2021 04:06:41 +0100

PUBLISHED

Public transport vehicles often share a road network with other road users making their journeys susceptive to changing road conditions and especially to congestion. Travelers using such public transport increasingly depend on real-time information to plan their journeys. While such information can be provided by Automatic Vehicle Location (AVL) systems, AVLs depend heavily on large-scale deployment of designated sensory equipment, which may prevent their pervasive adoption. This paper presents a system for estimating vehicle location based on information generated by data sources typically integrated within existing ITS platforms. This enables location estimation for public transport vehicles without the need for deploying a designated sensor infrastructure in each vehicle, thereby reducing deployment and maintenance cost significantly. A prototypical vehicle location estimation system has been realized as part of and using data provided by the iTransIT ITS framework. Initial evaluation results show that such a system is feasible in a distributed manner and that estimated results are within 20% compared to empirical data.

The work described in this paper was partly supported by Lero - the Irish Software Engineering Research Centre. SFI)

Producing Coalbed Methane at High Rates at Low Pressures

Scipedia content — Tue, 02 Feb 2021 03:56:42 +0100

In the highly productive Coal Bed Methane (CBM) “Fairway” area of the San Juan Basin of Northern New Mexico and Southern Colorado, traditional reservoir-evaluation methods have failed to approximate production levels. The reservoir seems to have the potential to produce gas at nearly the same rates at reservoir pressures of under 100 psia as it had at 1,500-1,800 psia. This observation has a significant impact on the economics of late-life investments, on the design of wellbores, on well site equipment, and on pipelines. A nontraditional approach was taken to evaluate the long-term impacts of a mix of these interventions. This mix of interventions was taken and the analysis was generally a fair indicator of specific-well response to the proposed actions.

PM and NO2 at urban sites with different traffic exposure: curb site measurements in Flemish cities

Scipedia content — Tue, 02 Feb 2021 03:50:53 +0100

Road transport is known as one of the main sources of urban air pollution, especially PM and NOx. The knowledge that PM may induce adverse health effects is an incentive for progressive cities to evaluate local air quality and to consider what action should be taken. Existing air quality measurement networks measure air pollution at different sites and give an ‘average value’ for the surrounding area. However, most of these measurement stations are not located at hot spot locations, e.g. close to busy roads. The aim of this study is to assess the air quality at urban (curb site) locations. PM10 daily average values were measured during 3-4 weeks at six locations representing different ‘typical’ traffic locations: e.g. ring road, access road, parking route, local traffic. NO2 was measured at all locations. At the background location lowest concentrations were measured for all parameters. Differences in PM10 and NO2 were observed between the different locations. It seems that NO2 is more sensitive to traffic exposure than PM10. This is due to the higher background and background variation of PM10. The highest NO and NO2 values were measured at the bus location,. Highest concentrations of PM10 and black carbon are measured at the ring location. However some trends could not be explained.

Performance Modeling and Analysis of Asynchronous Linear-Pipeline with Time Variable Delays

Scipedia content — Tue, 02 Feb 2021 03:33:49 +0100

International audience; This paper introduces a new methodology for evaluating the performance of asynchronous linear-pipelines. The Token Vector Delay Model is introduced to capture delay variability, which can originate from data, process and/or environment. Then, closed form equations modeling handshaking protocols are defined. These equations enable us to construct an abstract analytical model of the pipeline. The analytical model is then solved to compute the circuit performance in the presence of time variable delays. The tool developed to implement the method enables the designer to analyze circuits with tens of pipeline stages in a few seconds.

MACS: A Simulation Platform for Today's and Tomorrow's Air Traffic Operations

Scipedia content — Tue, 02 Feb 2021 03:14:28 +0100

This paper describes the Multi Aircraft Control System (MACS) simulation platform developed in the Airspace Operations Laboratory (AOL) at NASA Ames Research Center. MACS is a comprehensive research tool that has been developed to increase the overall realism and flexibility of controller- and pilot-in-the loop air traffic simulations. The research focus in the AOL is on examining air traffic operations in rich air/ground environments that can include multiple oceanic, en route, and terminal airspace sectors. The AOL research and development team maintains and continuously expands the capabilities of MACS to rapidly prototype new interfaces, displays, tools and operational concepts for addressing the complex controller/pilot/automation integration crucial to the implementation of the Next Generation Air Transportation System (NextGen). Sample applications of the MACS software are presented to show the range of air traffic environments that can be investigated. Funding for this work was provided by NASA’s Aeronautics Research Mission Directorate (ARMD) and NGATS Airspace Systems research program.

Electrical-level synthesis of pipeline ADCs

Scipedia content — Tue, 02 Feb 2021 03:09:27 +0100

This paper presents a design tool for the synthesis of pipeline ADCs which is able to optimally map high-level converter specifications, such as the required effective resolution, onto electrical-level parameters, i.e., transistor sizes and biasing conditions. It is based on the combination of a behavioural simulator for performance evaluation, accurate models of the converter components, and an optimization algorithm to minimize the power and area consumption of the circuit solution. The design procedure is herein demonstrated with the complete design of a 0.13 mum CMOS 10 bits@60MS/s pipeline ADC, which only consumes 11.3 mW from a 1.2 V supply voltage. A close agreement between behavioural- and electrical-level simulations is obtained with only 0.2 bit deviation on the measured ENOB. Ministerio de Educación y Ciencia TEC2006-03022 Junta de Andalucía TIC-02818

Analysis of Air Traffic Controllers Decisions

Scipedia content — Tue, 02 Feb 2021 03:07:22 +0100

International audience; This paper presents an approach based on a multiple criteria decision making methodology (MCDM) to analyse the decisions of Air Traffic Controllers. This study will allow to model some tools able to assist the controllers in their tasks and particularly able to help them to assume the ceaseless increase of Air Traffic. Currently the platform AMANDA assists controllers on only one sector of control. This platform was very pleasant welcome, and we wish to extend these principles to adjacent sectors, and thus include tool to help the cooperation between adjacent controllers. This analysis is composed of three main points. First it is necessary to determine the decision making process of controllers. The second point consists of the application of the MCDM which guide all the study. And finally a repertory grid technique is applied in order to support the operational aspect of MCDM and to support the interviews. We begin this paper by a presentation of Air traffic Control and the problematic, we present then AMANDA and its principles, and the objectives for the new version. In a third part we describe the approach developed and a real example of its application, the results and analyses that we can deduce of this first grid are also presented. These results must be, of course, confirmed and validated by the controllers.

Agent-Based Assessment of Trajectory-Oriented Operations with Limited Delegation

Scipedia content — Tue, 02 Feb 2021 02:59:43 +0100

n evolutionary concept called "trajectory-oriented operations with limited delegation" is the subject of a preliminary assessment conducted using fast-time simulations with computational agents that represent air traffic controllers. The concept integrates technologies relevant to the Next Generation Air Transportation System (NGATS) and holds promise for efficiency gains by enabling aircraft to fly Continuous Descent Approaches (CDAs). The assessment focuses on how controller strategies and automation tools impact CDA operations. The results indicate the concept represents an advance toward higher-efficiency NGATS operations, and emphasize the importance of shared information and air traffic controller decision support tools.

The European project UpTun: results of four years of research to improve the level of fire safety in existing tunnels

Scipedia content — Tue, 02 Feb 2021 02:59:28 +0100

This paper describes how the European economy heavily relies on a sustainable transportation system. In this transportation system, tunnels are a key element. The safety systems of the existing tunnels were designed on the basis of traffic and its estimated growth of two or more decades ago. However, it appears that traffic has grown more significantly and also changed in composition (more combustible and flammable goods). Consequently the safety level in existing tunnels has decreased in cases where no intermediate measures were taken to cope with the changing supply of rolling stock. This holds throughout Europe, for road-, rail- and mass-transit tunnels. The UpTun project main objects have therefore been the development of innovative technologies where appropriate and where relevant comparing to and the assessment of existing technologies for tunnel application. The focus is on technologies in the areas of detection and monitoring, mitigating measures, influencing human response, and protection against structural damage and the main output is a set of innovative cost-effective technologies. This paper will give an overview of the project and the major achievements.

Elements of an Engineering-Based Integrity Management Program

Scipedia content — Tue, 02 Feb 2021 02:35:42 +0100

Establishing pipeline integrity requires an understanding of the specific threats, their relationship to the overall condition of the pipeline, and the mitigating measures required to assure safe operation. In the past, the pipeline industry relied on years of research and experience to develop a set of tools to analyze these threats and apply conservative solutions to ensure pipeline integrity. With the implementation of the Integrity Management Program (IMP) in 2004 by the Pipeline and Hazardous Material Safety Administration (PHMSA), pipeline integrity must be addressed by operators where the analysis methods and results must be documented and defendable. This paper presents a detailed discussion of how existing knowledge, advances in analytical techniques, experimental methods, and engineering rigor are combined to develop field-friendly tools to characterize and ensure pipeline integrity. Two case studies are included, the first, to demonstrate how the proposed method was used to assess the integrity of a corroded elbow, the second, provides the reader with an example of how to develop a tool for evaluating the severity of dents in pipelines using available public-domain research. It is the hope of the authors that the approach presented in this paper will foster further developments and advanced pipeline integrity management.Copyright © 2008 by ASME

Statistical Separation Standards for the Aircraft-Approach Process

Scipedia content — Tue, 02 Feb 2021 01:08:55 +0100

Demand for air transportation has been increasing. A response to this is enhancing the runway utilization and throughput before investing on new runways or instruments. Runway throughput can be increased by reducing in-trail landing separation between aircraft, but the consequence may be an increase in the chance of a severe wake vortex encounter or a simultaneous runway occupancy (or go-around). Current instrument flight rule (IFR) standards provide fixed separation minima for given pairs of wake vortex weight classes of aircraft. In practice, the observed separation is a random variable and fluctuates near or above the specified minimum. In this paper, we propose a framework for statistical separation standards that specifies not only a lower bound for the separation but also a standard for the target value and the variance of the process. We address the question of what a more efficient separation standard is in order to control the risk in the approach process. We also consider whether separation variability may be reduced by employing such standards, i.e. more detailed standards that take the "realized variability" into account. Analytical results of this study suggest that (under specific assumptions) throughput put can be increased to some extent without degrading safety for the given facilities, infrasructure, and weather condition. The arguments and concepts are illustrated with statistical observations from Detroit airport (DTW).

Eco-driving simulation: evaluation of eco-driving within a network using traffic simulation

Scipedia content — Tue, 02 Feb 2021 01:07:44 +0100

This paper describes how curbing global warming necessitates the reduction of greenhouse gases. Motor-vehicle companies are attempting to improve engine efficiencies but are constrained by technical limitations. Hence we try to change driving behavior to reduce fuel consumption. A change in driving style/habit to promote fuel efficiency and hence to reduce CO2 emissions is known as 'eco-driving'. One such eco-driving style is to reduce sudden acceleration and deceleration. A report based on eco-driving shows a 10–20% reduction in fuel consumption per vehicle; and hence, eco-driving is promoted by Japan's Ministry of Environment. However, a mass of eco-drivers might impede traffic flow which fosters traffic congestion. This study evaluates eco-driving with respect to a traffic network versus an individual vehicle. The authors performed field measurements of a vehicle's speed and acceleration versus normal and eco-driving styles and the authors input the data into a micro-traffic simulator (VISSIM, PTV AG). The paper built a simple road network with two signalized intersections. Ten simulations were done using different random-number seeds.

Safety of users in road evacuation: design of path choice models for emergency vehicles

Scipedia content — Tue, 02 Feb 2021 01:07:04 +0100

Within the framework of the SICURO research project, the main objective of this paper is to define the procedures that were planned and activated in emergencies in order to allow the evacuation of weak users (disabled, old persons, etc.) from the area affected by a disaster and design the optimal path for emergency vehicles to reduce evacuation times. Specification, calibration and validation of a path choice generation model in order to simulate the behavior of emergency vehicle drivers at an urban level during an evacuation is proposed. The authors specify the factors that affect path choice behavior and the two main approaches: one to one and many to one. The first regards the minimization of generalized cost of a path that connects an origin to a destination; the second instead considers the connection of one origin to many destinations. The authors report some experimental results, obtained in the context of the SICURO Project, by applying the proposed model to a real road transport network at urban scale during a simulation of an evacuation.

Retrenchment and the Atomicity Pattern

Scipedia content — Tue, 02 Feb 2021 01:02:57 +0100

The issues surrounding the question of atomicity, both in the past and nowadays, are briefly reviewed, and a picture of an ACID (atomic, consistent, isolated, durable) transaction as a refinement problem is presented. An example of a simple air traffic control system is introduced, and the discrepancies that can arise when read-only operations examine the state at atomic and finegrained levels are handled by retrenchment. Non-ACID timing aspects of the ATC example are also handled by retrenchment, and the treatment is generalised as the retrenchment Atomicity Pattern. The utility of the pattern is confirmed against a different case study, the Mondex Electronic Purse.

Urban transport planning for the North West University (Potchefstroom campus) and its environs: approach and core findings

Scipedia content — Tue, 02 Feb 2021 00:50:17 +0100

The North West University (NWU) is currently in a process of transformation because of the integration of higher education entities as a result of the democratization process that commenced in 1994. NWU is faced with various problems that are related to transport planning, parking provision, congestion and traffic flow. The actuality of this research is related to differences in trip making patterns of students, staff and visitors, as well as availability of public transport services and policies. This paper reports on research findings related to these inter relationships that resulted in ad hoc planning of facilities, and appropriate planning parameters which need to be developed and implemented in order to address the current reality and problems. The paper concludes with various transport planning solutions and alternatives selected through application of multi-criteria analysis. The transport plan includes optimal solutions for implementation that will enhance the planning and operation of road infrastructure supported by public transport services and measures as to address the local situation. Various universities in South Africa are also dealing with transport and spatial planning problems resulting from transformation based on integration of higher education institutions. This research is focused on transportation and traffic implications related to university campuses. Approaches on how it can be accommodated within the institutional transformation scenario are discussed, and will thus be of benefit to all universities located in urban areas in South Africa.

Model Estimates of Traffic Reduction in Storm Impacted En Route Airspace

Scipedia content — Tue, 02 Feb 2021 00:37:14 +0100

n understanding of convective weather impacts on en route airspace capacity is a first step toward development of predictive tools to support both tactical and strategic routing decisions in storm-impacted airspace. This study presents a model for traffic reductions in en route sectors that result from convective weather impacts. A model to predict the impact of convective weather on en route traffic, Traffic Normalized Fractional Route Availability (TNFRA), combines Weather Avoidance Fields (WAF) from the Convective Weather Avoidance Model (CWAM) with a model for route usage in air traffic control (ATC) sectors. The model estimates the number of flights that will be able to pass through convective weather in a given sector. Results show that TNFRA provides a relatively unbiased estimate of sector traffic when compared to actual operations during high impact – convective weather events.

Ground Operation Concept Testing Requirements and Challenges

Scipedia content — Tue, 02 Feb 2021 00:15:32 +0100

In view of the increasing air traffic demand as well as the increasing complexity of systems that operate in the Air Traffic Management (ATM) environment, many future concept research topics involving automation have been proposed to improve traffic efficiency and safety. The development of far-future concepts has a disruptive research path in which the concepts work with a future automation scenario that requires the consideration of transition from the current-day operation scenario. This research path allows for greater creativity in the re-thinking of air traffic control management systems without being tied into the pre-existent systems. However, such freedom comes at a cost of making assumptions pertaining to transition plausibility. This research strategy poses difficult challenges in creating the right environment to support development of the concept and other future concept research. This paper summarizes the requirements identified through experiments, including the use of suggestions from subject-matter experts, for implementing a proper research environment that can ultimately simulate the automated operations intended for air traffic controllers in the future. The purpose of this paper is to identify and address the factors limiting concept development and testing, and use lessons learned to improve the chances of viable concepts maturing to deployment readiness.

Novel Concepts for the Compression of Large Volumes of Carbon Dioxide

Scipedia content — Tue, 02 Feb 2021 00:07:16 +0100

In the effort to reduce the release of CO{sub 2} greenhouse gases to the atmosphere, sequestration of CO{sub 2} from Integrated Gasification Combined Cycle (IGCC) and Oxy-Fuel power plants is being pursued. This approach, however, requires significant compression power to boost the pressure to typical pipeline levels. The penalty can be as high as 8% to 12% on a typical IGCC plant. The goal of this research is to reduce this penalty through novel compression concepts and integration with existing IGCC processes. The primary objective of the study of novel CO{sub 2} compression concepts is to boost the pressure of CO{sub 2} to pipeline pressures with the minimal amount of energy required. Fundamental thermodynamics were studied to explore pressure rise in both liquid and gaseous states. For gaseous compression, the project investigated novel methods to compress CO{sub 2} while removing the heat of compression internal to the compressor. The high-pressure ratio due to the delivery pressure of the CO{sub 2} for enhanced oil recovery results in significant heat of compression. Since less energy is required to boost the pressure of a cooler gas stream, both upstream and interstage cooling is desirable. While isothermal compression has been utilized in some services, it has not been optimized for the IGCC environment. This project determined the optimum compressor configuration and developed technology concepts for internal heat removal. Other compression options using liquefied CO{sub 2} and cryogenic pumping were explored as well. Preliminary analysis indicates up to a 35% reduction in power is possible with the new concepts being considered.

Scheduling in Non-Blocking Buffered Three-Stage Switching Fabrics

Scipedia content — Mon, 01 Feb 2021 23:56:45 +0100

DeSiNe: a flow-level QoS Simulator of Networks

Scipedia content — Mon, 01 Feb 2021 23:55:30 +0100

In this paper we present DeSiNe, a modular flow-level network simulator. DeSiNe is aimed at performance analysis and benchmarking of Quality of Service routing algorithms and traffic engineering extensions. Several well-known QoS routing algorithms and traffic engineering extensions have been implemented in DeSiNe. The flow-level nature provides scalability, such that large networks and heavy-traffic conditions are possible. In this paper, the functional and structural design of DeSiNe are presented and the usability and various features are illustrated by means of several examples. The source code of DeSiNe is publicly available.

Composite hermite curves for time-based aircraft spacing at meter fix

Scipedia content — Mon, 01 Feb 2021 23:44:23 +0100

International audience; The delegation to the flight crew of some tasks currently performed by air traffic controllers provides new perspectives potentially to increase air traffic control efficiency. More specifically, the task of establishing properly spaced landing sequences is very demanding in heavy traffic conditions for the air traffic controllers in charge of the terminal maneuvering area. Automatic merging operations could relieve air traffic controllers of providing time-consuming radar-vectoring instructions. The outcomes of this paper are twofold: firstly composite Hermite curves to generate a path with length and endpoint constraints are presented. This reference trajectory is used to stretch the path of an airliner in order to delay its arrival on a meter fix chosen by air traffic control. Secondly, the design of a nonlinear control law based on feedback linearization to track the reference trajectory is presented. This communication treats level flight, but wind is considered. The design is followed by two illustrative examples which show the effectiveness of the proposed approach.

Evaluating the Effects of Wrinkle Bends on Pipeline Integrity

Scipedia content — Mon, 01 Feb 2021 23:36:48 +0100

Concerns exist among the pipeline industry about the effects of wrinkle bends on the long-term integrity of pipelines. For this reason, a study was sponsored to assess the relative severity of wrinkle bends present in the El Paso pipeline system. The study involved a combination of full-scale cyclic pressure fatigue tests, along with finite element analysis, to determine cycles to failure. Strain gages were installed on select samples to determine alternating stresses. Also included in the study was installation of E-glass composite repair materials (Armor Plate® Pipe Wrap) on selected wrinkles to determine the potential for life extension considering the presence of reinforcement. The study helped in developing “in-the-ditch” evaluation criterion and a tool to determine the severity of a specific wrinkle bend based on geometric parameters including wrinkle height and length. The effects of metal loss due to corrosion were also considered. Additionally, the experimental results demonstrated that composite materials can extend the fatigue life of wrinkle bends.Copyright © 2008 by ASME

Robust Routing with Unknown Traffic Matrices

Scipedia content — Mon, 01 Feb 2021 23:36:04 +0100

In this paper, we present an algorithm for intra-domain traffic engineering. We assume that the traffic matrix, which specifies traffic load between every source-destination pair in the network, is unknown and varies with time, but that always lies inside an explicitly defined region. Our goal is to compute a fixed robust routing with best worst case performance for all traffic matrices inside the bounding region. We formulate this problem as a semi-infinite programming problem. Then, we focus on a special case with practical merits, where (1) the traffic matrix region is assumed to be a polytope specified by a finite set of linear inequalities, and (2) our objective is to find the routing that minimizes the maximum link utilization. Under these assumptions, the problem can be formulated as a polynomial size linear programming (LP) problem with finite number of constraints. We further consider two specific set of constraints for the traffic matrix region. The first set is based on the hose model and limits the total traffic rate of network point of presence (PoP) nodes. The second set is based on the pipe model and limits the traffic between source-destination pairs. We study the effectiveness of each set of constraints using extensive simulations.

A Review of Lateral Driver Support Systems

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

Lateral driver support systems have the potential to reduce the number of accidents associated with -both intentional and unintentional -lane departures. Additionally, such systems may increase driving comfort and stimulate a more efficient traffic flow, thereby reducing traffic emissions and the costs associated with traffic delays. This paper provides a literature review to identify the current state of the art on lateral driver support systems. The emphasis is on sensor technology, detection algorithms and safety assessment algorithms.

Co-design by parallel prototyping: optical-flow detection case study

Scipedia content — Mon, 01 Feb 2021 23:07:42 +0100

Current OF routines have achieved greater accuracy over larger speeds by improvements in implementation. Unfortunately, the improvements require the processing of more image frames or larger spatial regions. General-purpose (gp) multicomputers can be deployed to reduce the timings recorded on workstations. The four methods parallelised herein are not unusual amongst OF methods in being amenable to data-farming. Parallelising a number of routines in a systematic manner is possible if a generalised framework is available such as is provided by the PPF methodology and knowledge of the common structure to OF methods. The advantage of parallel pipelines may be that independent stages of the pipeline can at a later time be transferred to more suitable hardware. (13 pages)

Modeling Channel Occupancy Times for Voice Traffic in Cellular Networks

Scipedia content — Mon, 01 Feb 2021 22:57:57 +0100

Call holding times in telephony networks are commonly approximated by exponential distributions to facilitate traffic engineering. However, for traffic engineering of cellular networks, channel occupancy times need to be modeled instead to facilitate analytical modeling or to feed network simulations. In this paper, we classify channel occupancy times and present an empirical study based on data obtained from a real cellular network to determine which probability distribution functions can approximate them better. The results are environment dependent, but no assumptions that can be influential are made, as opposed to previous analytical and simulation studies which results are highly dependent on the assumptions made by the authors. We show that all types of channel occupancy times can be approximated by lognormal distribution. For stationary users, channel occupancy times are commonly approximated by exponential distribution due to its tractability, assuming that cell residence times are also exponentially distributed. However, we show that lognormal distribution fits much better to both channel occupancy and call holding times regardless of whether users are stationary or mobile.

Effects of Automated Arrival Management, Airborne Spacing, Controller Tools, and Data Link

Scipedia content — Mon, 01 Feb 2021 22:33:43 +0100

The effects of automated arrival management, airborne spacing, controller tools, and data link on airspace operations were investigated in an air/ground simulation at NASA Ames Research Center in September 2006. Four radar-certified air traffic control (ATC) specialists in the Airspace Operations Laboratory (AOL), eight glass cockpit pilots in the Flight Deck Display Research Laboratory (FDDRL), and additional “ghost” pilots and controllers operated a heavy eastbound arrival push into Louisville’s Standiford airport (SDF) with high density crossing traffic. An arrival management system scheduled aircraft along Continuous Descent Approaches (CDAs) and data linked arrival information to participating aircraft automatically throughout the simulation. The 2x3 test matrix varied two flight deck conditions: (1) with and (2) without airborne spacing, over three ATC workstation conditions: (1) current day, (2) advanced ATC scheduling and spacing tools, and (3) the same tools integrated with controller pilot data link communication. The process of automatically data linking arrival messages to participating aircraft based on a runway schedule proved to be very effective in all conditions. Flight deck-initiated speed changes to meet the CDA speed schedule and lead aircraft assignments were acceptable to pilots and controllers. Airborne spacing reduced the mean and the variance of the inter-arrival spacing on final approach, consistent with prior research. Controller scheduling and spacing tools improved handling of non-participating aircraft which did not receive the arrival information. Energy management along the CDAs was a primary issue. The research is sponsored by the Super Density Operations element of NASA’s NGATS Airspace program and coordinated with the US merging and spacing team, with participation by the FAA, UPS, MITRE, and NASA.

Rationalization of urban road space by congestion: towards an alternative tool for travel demand management

Scipedia content — Mon, 01 Feb 2021 22:20:16 +0100

This paper discusses the subject matter of transport sustainability in urban environments from an equitable use of the urban road space on behalf of different transport modes. It provides the conceptual and methodological bases for the development of an alternative tool for transport demand management called Spatial Rationalization Charge by Congestion (SRC), which expresses the percentage of road space destined for private vehicles which has to be transferred to other transport modes of greater environmental efficiency (such as public transport and non motorized modes) according to the internalization of the externalities of the private vehicle.

MPLS-TE Routing: Adopting a Generic Architecture and Evaluating Various Implementation Approaches

Scipedia content — Mon, 01 Feb 2021 22:14:24 +0100

International audience; Various Multi-Protocol Label Switching-Traffic Engineering (MPLS-TE) Routing Systems have been proposed in the literature to achieve optimization of resources utilization, Quality-of-Service (QoS) and Fast Recovery. This paper proposes a generic architecture for MPLS-TE Routing Systems, which aims to ease the classification and the analysis of these systems. Then this paper defines a set of MPLS-TE classification criteria. The combination of these criteria leads to the identification of main families of MPLS-TE Routing Systems which are finally compared and qualitatively evaluated according to a set of metrics.

Sensor Web Design Studies for Realtime Dynamic Congestion Pricing

Scipedia content — Mon, 01 Feb 2021 22:09:37 +0100

Traffic congestion is a multi-billion dollar national problem and is worsening every year with population growth and increase in freight traffic. We present a model for realistic simulation studies to mitigate congestion in urban areas using dynamic congestion pricing on express toll lanes. Specifically, we identify and address the design issues needed to develop a real time event driven sensor Web observation system for traffic monitoring that provides dynamic congestion pricing. To assess the feasibility of this sensor Web system, we are in the process of conducting simulation studies based on real data for various system configurations to validate the mitigating impact of dynamic congestion pricing on intermodal freight flow to and from the ports in urban areas. In this paper, we focus on freight flow into the Baltimore corridor from its por

A data clustering approach to identify Logical Functional ATFCM Areas

Scipedia content — Mon, 01 Feb 2021 22:07:51 +0100

The paper presents the methodology designating to identify the network effect between a global set of capacity constraints made of sector and airport capacities. The goal is to solve this problem as locally as possible, this being possible by reducing the difficulty of global network impact assessment problem through the definition of Logical ATFCM Functional Areas (LFAAs). First, a new approach for the evaluation of the current network effect handled by the CFMU (EUROCONTROL Central Flow and Management Unit) slot allocation process is proposed. The assessment methodology including the definition of network effect indicators and statistical results are presented so as to provide a global insight of the network effect intensity and distribution. While this approach addresses network effect assessment in the post-operations phase, the second part of the paper introduces a methodology and key concepts aiming at anticipating the network effect through the definition of LFAAs. Thus, the present study aims to provide the initial methods, key concepts and tools to the definition of functional ATFCM areas.

Evaluating urban transportation quality: measuring transportation activity

Scipedia content — Mon, 01 Feb 2021 21:58:39 +0100

This paper describes how, when people think about transportation improvements, they often envision new modes of travel: canals, steamships, railroads, automobiles and air travel. What comes next? Rockets? Lighter-than-air ships? Teleporters? Perhaps these may become more common in the future. But they will not necessarily solve existing transportation problems such as urban traffic congestion, parking costs or traffic crashes. The next major breakthrough to improve transport system quality may simply consist of management strategies that result in more efficient use of existing transport resources. When all impacts are considered, such strategies are often the best solution to transportation problems. The paper first studies the definition and connotation of transportation efficiency and quality. From the viewpoint of different groups participating in urban transportation systems, different system functions and targets required by each group are analyzed. Then the corresponding system targets and evaluation rules required by the administrator are studied. Finally, the authors discuss different methods used to measure urban transportation, the different perspectives they represent, and how the selection of one or another method tends to affect transportation and land use planning decisions.

Pre- And End-Haulage Of Intermodal Container Terminals Modelled As A Full Truckload Pickup And Delivery Problem With Time Windows

Scipedia content — Mon, 01 Feb 2021 21:31:15 +0100

Road transport makes up a large share of total costs of intermodal transport. In this paper preand endhaulage in the service area of intermodal container terminals is modelled as a Full Truckload Pickup and Delivery Problem. A single container is delivered from the terminal to a customer or picked up at a customer location and returned to the terminal. Customers impose hard time windows. A two-phase insertion heuristic is developed. In a first phase delivery customers are paired with pickup customers. These pairs of customers are assigned to routes in a second phase. The initial solution is improved by a local search procedure based on a CROSS operator. The construction heuristic and improvement heuristic are demonstrated by means of a numerical example.

A Study of the Performance Evaluation for Airline Operation

Scipedia content — Mon, 01 Feb 2021 21:01:50 +0100

Comparison of two Detection Algorithms for Pipeline Leaks

Scipedia content — Mon, 01 Feb 2021 20:55:37 +0100

International audience; The aim of this paper is to compare two analytic detection algorithms for pipeline leaks in order to assess their effectivity. Parameters such as precision and velocity to detect and locate a leak, algorithm complexity, and application facilities are evaluated, with the purpose of finding the most useful algorithm for a future real-time implementation on a Mexican aqueduct.

Predictive Performance Analysis of a Parallel Pipelined Synchronous Wavefront Application for Commodity Processor Cluster Systems

Scipedia content — Mon, 01 Feb 2021 20:33:52 +0100

This paper details the development and application of a model for predictive performance analysis of a pipelined synchronous wavefront application running on commodity processor cluster systems. The performance model builds on existing work (Cao et al.) by including extensions for modern commodity processor architectures. These extensions, including coarser hardware benchmarking, prove to be essential in countering the effects of modern superscalar processors (e.g. multiple operation pipelines and on-the-fly optimisations), complex memory hierarchies, and the impact of applying modern optimising compilers. The process of application modelling is also extended, combining static source code analysis with run-time profiling results for increased accuracy. The model is validated on several high performance SMP systems and the results show a high predictive accuracy (les 10% error). Additionally, the use of the performance model to speculate on the performance and scalability of this application on a hypothetical cluster with two different problem sizes is demonstrated. It is shown that such speculative techniques can be used to support system procurement, run-time verification and system maintenance and upgrading

Failure of Prestressed Concrete Cylinder Pipe

Scipedia content — Mon, 01 Feb 2021 20:25:05 +0100

Prestressed concrete cylinder pipe (PCCP) tends to be of large diameter, making many failures of this type of pipe relatively catastrophic and costly. To date, most research has been focused on PCCP inspection technologies and performance prediction in order to minimize the risk to utilities from failures. The performance of Prestressed Concrete Cylinder Pipe has been an item of interest to water utilities for a long time. Fifteen years ago, AWWA Research Foundation (AwwaRF) and the Bureau of Reclamation initiated a study, Performance of Prestressed Concrete Pipe that was unfortunately never published. AwwaRF has also funded studies to develop software that uses fuzzy logic (Kleiner, et al. 2005) to predict future PCCP behavior useful if a utility has sufficient data from actual field experience with PCCP. Another AwwaRF report (Romer, et al. 2005), developed methodologies, techniques, protocols, and technology for identifying the specific conditions that lead to corrosion failures of PCCP. That study included testing the effects of cathodic protection on pre-existing notches in PCCP reinforcing wires, and compared the accuracy of similar internal investigative tools for the detection of broken PCCP reinforcing wires. This paper presents preliminary results of the most recent AwwaRF funded study, intended to collect, codify, expand upon, and disseminate the results of the previous studies on PCCP failures. The project began with a survey of a selected group of water utilities with a fair amount of PCCP in their systems, selected carefully to represent the range of conditions and variables that affect PCCP performance across North America. The survey results, combined with a pre-existing database of over 450 PCCP failures, were statistically projected over the installed PCCP base of North America, and provide a surprising indicator of failures and failure rate of PCCP.

Discussion of Issues Related to Surge in LNG Pipelines at Offloading Terminals

Scipedia content — Mon, 01 Feb 2021 20:04:16 +0100

Due to requirements of LNG unloading terminals, the pipelines used to transport the liquid operate near the vapor pressure of the LNG. If the operational pressure in the pipeline falls below the vapor pressure, pockets of gas will develop; when these pockets collapse, very high pressure pulses can be transmitted through the pipeline, an event known as surge or waterhammer. This paper discusses transients that occur during normal and upset plant operation and how these transients can induce surge in the pipeline. The paper concludes with an overview of the methods used to evaluate whether surge will occur and the peak pressure associated with surge events, with an overview of cases that are typical candidates for analysis.Copyright © 2008 by ASME

Innovative technologies for public transport

Scipedia content — Mon, 01 Feb 2021 19:56:56 +0100

This paper describes how, public transport systems are responsible for urban air pollution and their efficiency affects our daily lives and productivity. New advanced technologies have been developed in order to balance the negative effects of transport, in terms of air pollution, and also to improve mobility in city centers. This paper presents, after a short analysis of those effects, the state of the art of some of these technologies and how they can contribute to reduce such negative effects while improving transport efficiency. Among the innovative technologies presented, the so called ‘Tram-Train’ that offers a direct connection between the city center and the suburbs, eliminating the interchanges between train and public transport system has a specific relevance; the ‘advanced rubber-tired transport with guided running mode’ is also discussed: this system puts together the positive features of Tram systems, being powered electrically, and the flexibility of buses, having an onboard generator or batteries. Other technologies here included are: Battery Electric Vehicles (BEVs); Hybrid Electric Vehicles (HEVs); and Fuel Cell Electric Vehicles (FCEV). Also the Natural Gas Fuelled Vehicles (NGFV) can represent a solution for urban air pollution, in particular for lowering PM, CO and VOC emissions. The analysis of such technologies underlines how the problem of urban air pollution can be tackled through the adoption of new technologies for public transport systems.

An evaluation of the World Bank’s preparedness to meet future urban transport challenges

Scipedia content — Mon, 01 Feb 2021 19:55:14 +0100

This paper describes how, during 2006 an evaluation was undertaken by the World Bank Independent Evaluation Group (IEG) of the effectiveness of the Bank’s global support to the transport sector during the last ten years. This paper focuses on the results of the urban transport component of the study. Troubling issues include environmental damage, energy efficiency, and implications for climate change, traffic congestion, and transport safety, as well as questions relating to affordability and the logistical challenges of effective multimodal transportation. The World Bank has made significant progress in encouraging private sector contracting, especially of maintenance activities, but more modest success with institution building and ensuring infrastructure funding sustainability. However, the time has come to reassess priorities as a new more urban related agenda unfolds.

Travel time estimation using NiagaraST and latte

Scipedia content — Mon, 01 Feb 2021 19:46:46 +0100

To address increasing traffic congestion and its associated consequences, traffic managers are turning to intelligent transportation management. The latte project is extending data stream technology to handle queries that combine live streams with large data archives, motivated by needs in the Intelligent Transportation Systems (ITS) domain. In particular, we focus on queries that combine live data streams with large data archives. We demonstrate such stream-archive queries via the travel-time estimation problem. The demonstration uses the new latte system which has been developed using the NiagaraST stream processing system and the PORTAL transportation data archive.

Optimized Sampling Frequencies for Weld Reliability Assessments of Long Pipeline Segments

Scipedia content — Mon, 01 Feb 2021 19:37:45 +0100

In this paper, we describe new faster algorithms that design an optimal testing strategy for long pipeline segments.

Multi-Terabit/s IP Switching with Guaranteed Service for Streaming Traffic

Scipedia content — Mon, 01 Feb 2021 19:37:32 +0100

traffic on the Internet continues to grow exponentially, there is a real need to solve transmission and switching scalability. Moreover, future Internet traffic will be dominated by streaming media flows, such as video-telephony, video-conferencing, 3D video, virtual reality, and many more. Consequently, network solutions will need to offer quality of service and traffic engineering together with the above mentioned scalability - i.e., over-provisioning is not likely be a viable solution to accommodate streaming media traffic. This paper describes the architecture of a ultra-scalable IP switch and the first experiments with a prototypal implementation. The switch scalability is a consequence of it operating pipeline forwarding of packets, which also results in quality of service guarantees for UDP-based streaming applications, while preserving elastic TCP-based traffic as is, i.e., without affecting any existing applications based on "best- effort" services. Moreover, the prototype demonstrates the low complexity of pipeline forwarding implementation as the deployed network gear was realized from off-the-shelf components in only nine months through the design, implementation, and testing efforts of the authors.

An Adaptive Parallel Pipeline Pattern for Grids

Scipedia content — Mon, 01 Feb 2021 19:33:25 +0100

This paper introduces an adaptive parallel pipeline pattern which follows the GRASP (grid-adaptive structured parallelism) methodology. GRASP is a generic methodology to incorporate structural information at compile time into a parallel program that enables it to adapt automatically to dynamic variations in resource performance. GRASP instruments the pipeline with a series of pragmatic rules, which depend on particular performance thresholds based on the computation/communication patterns of the program and the availability of resources in the grid. Our parallel pipeline pattern is implemented as a parameterisable C/MPI API using a variable-size input data vector and a stage function array. We have evaluated its efficiency using a numerical benchmark stage function in a non-dedicated computational grid environment.

Cooperative content distribution and traffic engineering

Scipedia content — Mon, 01 Feb 2021 16:25:00 +0100

Traditionally, Internet Service Providers (ISPs) make profit by providing Internet connectivity, while content providers (CPs) play the more lucrative role of delivering content to users. As network connectivity is increasingly a commodity, ISPs have a strong incentive to offer content to their subscribers by deploying their own content distribution infrastructure. Providing content services in a provider network presents new opportunities for coordination between server selection (to match servers with subscribers) and traffic engineering (to select efficient routes for the traffic). In this work, we utilize a mathematical framework to show that separating server selection and traffic engineering leads to a sub-optimal equilibrium, even when the CP is given accurate and timely information about network conditions. Leveraging ideas from cooperative game theory, we propose that the system implements a Nash bargaining solution that significantly improves the fairness and efficiency of the joint system. This study is another step toward a systematic understanding of the interactions between those who generate and distribute content and those who provide and operate networks.

Branch prediction for network processors

Scipedia content — Mon, 01 Feb 2021 16:17:39 +0100

Meeting the future requirements of higher bandwidth while providing ever more complex functions, future network processors will require a number of methods of improving processing performance. One such method will involve deeper processor pipelines to obtain higher operating frequencies. Mitigation of the penalty costs associated with deeper pipelines have achieved by implementing prediction schemes, with previous execution history used to determine future decisions. In this paper we present an analysis of common branch prediction schemes when applied to network applications. Using widespread network applications, we find that unlike general purpose processing, hit rates in excess of 95% can be obtained in a network processor using a small 256-entry single level predictor. While our research demonstrates the low silicon cost of implementing a branch predictor, the long run times of network applications can leave the majority of the predictor logic idle, increasing static power and reducing device utilization.

The changing relations between foreland and hinterland at North Korean ports (1985-2006)

Scipedia content — Mon, 01 Feb 2021 16:08:07 +0100

Being one of the few remaining communist States in the world, North Korea offers a good example of a constrained economy facing dramatic internal and external pressures. Although land transport dominates in North Korea due to border trade with China and Russia, maritime transport better reflects its position in the global economy. Based on worldwide vessel movements at all ports connected to North Korea between 1985 and 2006, indicators of maritime connectivity closely match the country's evolution according to its political and economical changes. Alongside with a spatial contraction of forelands stemming from diplomatic isolation, industrial decline, trade embargo, and infrastructure dereliction after the collapse of the USSR (1991) and the nuclear crisis (1993-1994), results also show a process of regionalization and port concentration in Northeast Asia at a time of increased openness, cooperation projects, and foreign investments following the inter-Korean summit (2000) and the economic reforms (2002). Finally, comment are given about internal factors such as inter-regional disconnection, transport system dereliction, logistics costs, and accessibility that result in a growing divide between East and West co

Road Travel Time Information on VMS and Traffic Congestion

Scipedia content — Mon, 01 Feb 2021 15:49:56 +0100

Some years ago, progress in road telematics had made it possible to introduce time travel information in real time on VMS devices. Such information can lead road users to avoid congested areas as well as to waiting in a better condition for the end of the congestion. In a way, they increase congestion, in another way, they reduce it. Our research aimed at explaining the reasons why some people behave in a way and another one in. We assumed that travel time messages may be interpreted from several points of view, depending on driver knowledges in memory, experience and will, and as a result, the decision taken. An enquiry on a group of drivers aimed at analysing mental activity involved in decision taking process will be presented.

Gisting continuous speech

Scipedia content — Fri, 29 Jan 2021 00:44:03 +0100

The objective of this work is automatic, real-time "gisting" of voice traffic for updating of information in databases, for producing timely reports, and for prompt notification of events of interest. Specifically, the goal is to build a prototype, real-time system capable of processing radio communication between air traffic controllers and pilots; identifying dialogs and extracting their "gist" (e.g., identifying flights, determining whether they are landing or taking off), and producing a continuous output stream with that information. The approach is intended to be general and applicable to other domains.

Remote Medical Monitoring Through Vehicular Ad Hoc Network

Scipedia content — Fri, 29 Jan 2021 00:20:00 +0100

Several diseases and medical conditions require constant monitoring of physiological signals and vital signs on daily bases, such as diabetics, hypertension and etc. In order to make these patients capable of living their daily life it is necessary to provide a platform and infrastructure that allows the constant collection of physiological data even when the patient is not inside of the coverage area. The data must be rapidly "transported" to care givers or to the designated medical enterprise. The problem is particularly severe in case of emergencies (e.g. natural disasters or hostile attacks) when the communications infrastructure (e.g. cellular telephony, WiFi public access, etc) has failed or is totally congested. In this paper we present an evaluation of of the vehicular adhoc networks (VANET) as an alternate method of collecting patient pre-recorded physiological data and at the same time reconfiguring patient medical wearable body vests to select the data specifically requested by the physicians. Another important use of vehicular collection of medical data from body vests is prompted by the need to correlate pedestrian reaction to vehicular traffic hazards such as chemical and noise pollution and traffic congestion. The vehicles collect noise, chemical and traffic samples and can directly correlate with the "stress level" of volunteers. Â©2008 IEEE.

A 4D trajectory negotiation protocol for Arrival and Approach sequencing

Scipedia content — Fri, 29 Jan 2021 00:08:12 +0100

Future 4D TBO will require effective air- ground data link communication and negotiation protocols. This issue is especially critical in Arrival and Approach flight phase due to the variability of conditions into a short space-time environment where multiple aircraft simultaneously converge. Besides, several subtasks are closely related with effective air-ground negotiation protocols for 4D TBO in Terminal Areas: predicting accurate arrivals 4D trajectories, performing well established 4D trajectory formats for an effective interoperability between airborne and ground systems, designing efficient real-time aircraft arrival sequencer and scheduler algorithms, etc. In this paper we propose a 4D Trajectory Air- Ground Negotiation Protocol for Arrival and Approach Sequencing. The Negotiation Protocol has been implemented in an ad hoc multi-agent platform. Based on this proposal we summarize other relevant information that should be incorporated into the 4D trajectory information.

Document type: Conference object

GrooveNet: A Hybrid Simulator for Vehicle-to-Vehicle Networks

Scipedia content — Thu, 28 Jan 2021 23:58:29 +0100

Vehicular networks are being developed for efficient broadcast of safety alerts, real-time traffic congestion probing and for distribution of on-road multimedia content. In order to investigate vehicular networking protocols and evaluate the effects of incremental deployment it is essential to have a topology-aware simulation and test-bed infrastructure. While several traffic simulators have been developed under the Intelligent Transport System initiative, their primary motivation has been to model and forecast vehicle traffic flow and congestion from a queuing perspective. GrooveNet is a hybrid simulator which enables communication between simulated vehicles, real vehicles and between real and simulated vehicles. By modeling inter-vehicular communication within a real street map-based topography it facilitates protocol design and also in-vehicle deployment. GrooveNet?s modular architecture incorporates mobility, trip and message broadcast models over a variety of link and physical layer communication models. It is easy to run simulations of thousands of vehicles in any US city and to add new models for networking, security, applications and vehicle interaction. GrooveNet supports multiple network interfaces, GPS and events triggered from the vehicle?s on-board computer. Through simulation, we are able to study the message latency, and coverage under various traffic conditions. On-road tests over 400 miles lend insight to required market penetration.

Genetic Algorithm Based Ground Delay Program Computations for Sector Density Control

Scipedia content — Thu, 28 Jan 2021 23:54:48 +0100

Monitor Alert is triggered whenever the number of aircraft in an Air Traffic Control sector increases beyond its capacity limit. Departure rates at the airports feeding the airspace can be decreased to reduce the sector density. This paper presents a genetic algorithm for determining the optimal departure delays to be imposed on aircraft to maintain the sector counts below the Monitor Alert levels while minimizing the total delay in the system. The predicted state of the airspace is obtained using a fast-time airspace simulation system, which is then used to compute the quality of the resulting departure rates in the genetic algorithm. An interactive computing environment is used for implementing the optimization algorithm. Optimal aircraft departure results are presented for 2-airport and 10-airport example problems.

Study of Water Speed Sensitivity in a Multifunctional Thick-film Sensor by Analytical Thermal Simulations and Experiments

Scipedia content — Thu, 28 Jan 2021 23:39:35 +0100

The present paper deals with an application of the analytical thermal simulator DJOSER. It consist of the characterization of a water speed sensor realized in hybrid technology. The capability of the thermal solver to manage the convection heat exchange and the effects of the passivating layers make the simulation work easy and fast.

Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions)

A Dynamic I/O Model for TRACON Traffic Management

Scipedia content — Thu, 28 Jan 2021 23:22:25 +0100

This work investigates the TRACON flow management around a major airport. Aircraft flows are analyzed through a study of TRACON trajectories records. Rerouting and queuing processes are highlighted and airport characteristics are shown as function of the number of planes in the TRACON. Then, a simple input-output TRACON queuing and landing model is proposed. This model is calibrated and validated using available TRACON data. It reproduces the same phenomenon as the real system. This model is used to show the impact of limiting the number of aircrafts in the TRACON. A limited number of aircraft does not increase delays but reduces the controller's workload and increases safety.

Comment: 16 pages, 19 figures e

Virtual Measurement in Pipes: Part 1-Flowing Bottom Hole Pressure Under Multi-Phase Flow and Inclined Wellbore Conditions

Scipedia content — Thu, 28 Jan 2021 22:47:11 +0100

Pressure drop prediction in pipes is an old petroleum engineering problem. There is a long history of attempts to develop empirical correlations to predict the pressure drop in pipes. Some of these attempts have produced correlations that provide good prediction in some cases. However, their general applicability is questionable. Correlations that address only a specific class of problems exist. These types of correlation usually perform better than those which attempt to meet the need of a variety of problems. Usually, the higher the number of variables in the model the lesser the reliability and general applicability of the correlations. This is the result of using methodologies such as conventional regression analysis. In such methodologies, the chances of correctly and completely capturing the relationship between variables decreases as the number of variables increases. Many parameters could be involved in these types of problems, such as gas-oil ratios in two phase systems, water flow in three phase systems, and inclination angles of the pipe, to name a few. In this paper, the authors introduce a new methodology for developing prediction models for pipes. This method which has been named Virtual Measurement in Pipes (VMP), incorporates artificial neural networks (ANN) to address the development of tools to predict pressure drops in pipes and optimum design of pipelines under a variety of circumstances. The fundamental problem with conventional approaches resides in the inherent sequential and pointwise (as opposed to parallel and distributed) information processing methods used in development of such correlations. Because of this shortcoming, conventional methodologies are unable to address, define, or unravel the highly complex relationships between many variables involved in th e process. In this paper, artificial neural networks are used to develop a Virtual Measurement Tool to survey flowing bottom hole pressure (BHP) in multi-phase systems using information such as oil, gas and water flow rates, temperature, oil and gas gravity, pipe length, surface pressure, and inclination angles of the pipe. The developed Virtual Measurement Tool has been applied to th e published field data for flowing BHP predictions. VMP's predictions are compared to existing methods and the enhancement is clearly demonstrated. The developed VMP is applied to wellbore hydraulic problems. It addresses three-phase (oil, water, and gas) flow in wellbores. This tool applies to a variety of wells, including vertical wells and those with various degrees of inclination.

Effective Utilization of Air- and Ground-Based Technologies for Arrival Management

Scipedia content — Thu, 28 Jan 2021 22:39:15 +0100

Two recent simulations investigated air- and ground-based technologies for arrival management. In both studies professional air traffic controllers used prototype trajectorybased decision support tools to manage arrival flows that included airborne spacingequipped aircraft simulators flown by professional pilots. Taken together, the results illustrate how en route arrival flow conditioning, terminal-area spacing adjustments, and airborne merging and spacing capabilities may be used for effective arrival management in future high-traffic environments.

StreetSmart Traffic: Discovering and Disseminating Automobile Congestion Using VANET's

Scipedia content — Thu, 28 Jan 2021 22:30:28 +0100

utomobile traffic is a major problem in developed societies. We collectively waste huge amounts of time and resources traveling through traffic congestion. Drivers choose the route that they believe will be the fastest; however traffic congestion can significantly change the duration of a trip. Significant savings of fuel and time could be achieved if traffic congestion patterns could be effectively discovered and disseminated to drivers. We propose a system that uses a standard GPS driving aid, augmented with peer-to-peer wireless communication. The proposed system uses a combination of clustering and epidemic communication to find and disseminate dynamic traffic patterns.

Fault Detection in Flight Guidance Dynamics Based on Differential Flatness

Scipedia content — Thu, 28 Jan 2021 21:59:33 +0100

In this paper, flight guidance dynamics are shown to be implicit differentially flat with respect to the inertial position of an aircraft. This proves the existence of a set of relations between these flat outputs and the state variables representative of flight guidance dynamics and between these flat outputs and the basic inputs to flight guidance dynamics. A neural network is introduced to obtain, from the actual trajectory, nominal flight parameters which can be compared with actual values to detect abnormal behaviour.

Some remarks on vehicle following control systems with delays

Scipedia content — Thu, 28 Jan 2021 21:55:04 +0100

In this paper, we consider the problem of vehicle following control with delay. To solve the problem of traffic congestion, one of the solutions to be considered consists in organizing the traffic into platoons, that is groups of vehicles including a leader and a number of followers "tightly" spaced, all moving in a longitudinal direction. Excepting the stability of individual cars, the problem of avoidance of slinky type effects will be explicitly discussed. Sufficient conditions on the set of control parameters to avoid such a phenomenon will be explicitly derived in a frequency-domain setting. ©2007 IFAC.

Techniques for flow inversion on sampled data

Scipedia content — Thu, 28 Jan 2021 21:51:02 +0100

The distribution of flow sizes is a quantity of interest fundamental to traffic engineering and network modelling and only likely to become more important in the future. The recovery of the flow-length distribution from (sampled) packet data is referred to as flow-inversion. Traditional packet sampling methods cause distortions in a recovered distribution of flow-length. We propose an improved method for inverting data sampled using the technique known as sample-and-hold. We show that the technique improves upon existing inversion techniques illustrated using both real and artificial data sets. The technique described may have applications to other inversion problems.

Towards Systematic Air Traffic Management in a Regular Lattice

Scipedia content — Thu, 28 Jan 2021 21:46:56 +0100

[Abstract] A regular lattice combines two ideas: a repeating (or regular) airspace structure and layers of parallel tracks. A repeatin g or regular airspace structure has several advantages over an irregular structure. The skills or methods used to control traffic in one part of the structure are applicable throughout the structure. Regularity gives rise to multiple routes between two points wi th similar distances flown in each direction and at each flight level. Flow management can select routes which distribute traffic over a region. The same mechanism could be used to choose routes which avoid reserved areas. Properties which apply to an element of the airspace apply wherever that element is repeated, so that reasoning about a smal l region of the airspace can immediately be scaled up to apply to a much larger region. Layers of parallel tracks eliminate crossing conflicts between aircraft which are flying straight and level. Together with measures to preserve the stability of traffic flows (sufficient spacing, speed regulation, or ASAS sequencing procedures), traffic may be separated into two easily identifiable populations: a "stable" population of cruising aircraft, which require low controller monitoring per aircraft, since there are no crossing conflicts between cruising aircraft, and a population of aircraft in "transiti on" to or from the stable state, which require greater monitoring. A regular lattice allow s a fine-grained decomposition into sectors. This would allow air traffic control to be performed by a greater number of controllers, so increasing the capacity of the syst em. Results from fast-time simulations are reported.

The Price of Selfish Routing

Scipedia content — Thu, 28 Jan 2021 21:45:26 +0100

We study the problem of routing traffic through a congested network. We focus on the simplest case of a network consisting of m parallel links. We assume a collection of n network users each user employs a mixed strategy, which is a probability distribution over links, to control the shipping of its own assigned traffic. Given a capacity for each link specifying the rate at which the link processes traffic, the objective is to route traffic so that the maximum (over all links) latency is minimized. We consider both uniform and arbitrary link capacities. How much decrease in global performace is necessary due to the absence of some central authority to regulate network traffic and implement an optimal assignment of traffic to links? We investigate this fundamental question in the context of Nash equilibria for such a system, where each network user selfishly routes its traffic only on those links available to it that minimize its expected latency cost, given the network congestion caused by the other users. We use the Coordination Ratio, originally defined by Koutsoupias and Papadimitriou, as a measure of the cost of lack of coordination among the users roughly speaking, the Coordination Ratio is the ratio of the expectation of the maximum (over all links) latency in the worst possible Nash equilibrium, over the least possible maximum latency had global regulation been available. Our chief instrument is a set of combinatorial Minimum Expected Latency Cost Equations, one per user, that characterize the Nash equilibria of this system. These are linear equations in the minimum expected latency costs, involving the user traffics, the link capacities, and the routing pattern determined by the mixed strategies. In turn, we solve these equations in the case of fully mixed strategies, where each user assigns its traffic with a strictly positive probability to every link, to derive the first existence and uniqueness results for fully mixed Nash equilibria in this setting. Through a thorough analysis and characterization of fully mixed Nash equilibria, we obtain tight upper bounds of no worse than O(ln n/ln ln n) on the Coordination Ratio for (i) the case of uniform capacities and arbitrary traffics and (ii) the case of arbitrary capacities and identical traffics. © Springer 2007. 48 1 91 126 "p"Cited By :41

Advantages of a PCE-based control plane for LISP

Scipedia content — Thu, 28 Jan 2021 21:25:47 +0100

The Locator/Identifier Separation Protocol (LISP) is one of the candidate solutions to address the scalability issues in inter-domain routing. The current proposals for its control plane (e.g., ALT, CONS, NERD) have various shortcomings, including the potential dropping of packets at LISP routers during the resolution of the EID-to-RLOC mapping. In this paper, we introduce a new Control Plane (CP) for LISP supported by an architecture that borrows concepts from both the Path Computation Element (PCE) and Intelligent Route Control (IRC). Our CP is able to tackle three different problems simultaneously: (i) packets sourced from end-hosts are neither dropped nor queued during the mapping resolution; (ii) the EID-to-RLOC mapping can be obtained and configured approximately within the DNS resolution time needed to fetch the destination EID address; and (iii) our approach can blend IRC with the PCE capabilities, to perform upstream/ downstream Traffic Engineering (TE) through the dynamic management of the mappings. In particular, our CP supports the utilization of different LISP ingress and egress local routers for the same flow sourced from a domain.

Peer Reviewed

Characterization of Days Based on Analysis of National Airspace System Performance Metrics

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

Days of operations in the National Airspace System can be described in term of traffic demand, runway conditions, equipment outages, and surface and enroute weather conditions. These causes manifest themselves in terms of departure delays, arrival delays, enroute delays and traffic flow management delays, Traffic flow management initiatives such as, ground stops, ground delay programs, miles-in-trail restrictions, rerouting and airborne holding are imposed to balance the air traffic demand with respect to the available capacity, In order to maintain operational efficiency of the National Airspace System, the Federal Aviation Administration (FAA) maintains delay sad other statistics in the Air Traffic Operations Network (OPSNET) and the Aviation System Performance Metrics (ASPM) databases. OPSNET data includes reportable delays of fifteen minutes ox more experienced by Instrument Flight Rule (IFR) flights. Numbers of aircraft affected by departure delays, enroute delays, arrival delays and traffic flow delays are recorded in the OPSNET data. ASPM data consist of number of actual departures, number of canceled departures, percentage of on time departures, percentage of on time gate arrivals, taxi-out delays. taxi-in delays, gate delays, arrival delays and block delays. Surface conditions at the major U.S. airports are classified in terms of Instrument Meteorological Condition (IMC) and Visual Meteorological Condition (VMC) as a function of the time of the day in the ASPM data. The main objective of this paper is to use OPSNET and ASPM data to classify the days in the datasets into few distinct groups, where each group is separated from the other groups in terms of a distance metric. The motivations for classifying the days are two-fold, 1) to enable selection of days of traffic with particular operational characteristics for concept evaluation using system-wide simulation systems such as the National Aeronautics and Space Administration's Airspace Concepts Evaluation Tool (ACES) and 2) to enable evaluation of a given day with respect to the characteristics of the classified groups. The first part of the paper is devoted to the analysis of major trends seen in the OPSNET and ASPM data. The second part of the paper is devoted to describing features or measures derived from the OPSNET and ASPM data that are suitable for characterizing days, and the classification algorithm used for grouping the days. Finally, the method for evaluating the characteristics of a given day with respect to the properties of the groups is described.

Performance Metrics for Tactical Aircraft to Aircraft Conflicts

Scipedia content — Thu, 28 Jan 2021 21:20:26 +0100

n air traffic control system’s main function is to separate aircraft. The computer supporting the system assists the air traffic controllers by generating a conflict alert whenever it predicts that two aircraft are about to get too close to each other. The performance of the conflict alert function is a key element to the overall functioning of the air traffic control system. A set of metrics has been designed to measure the conflict alerting performance of an aircraft traffic control system. The key factors are the missed alert rate and the false alert rate. However there are several secondary factors that are essential to measuring the performance, especially in a simulation environment. This paper describes a set of metrics that have been developed to evaluate the performance of the FAA’s en route aircraft traffic control system. They have been applied to the existing system, the Host Computer System, and will be used to establish metrics for the new system now under development, the En Route Automation Modernization system. The metrics are calculated by post processing recorded data that has been produced by running a real time simulation of the air traffic system without controllers, using as input field recorded aircraft data that has been time shifted to induce aircraft-to-aircraft conflicts.

Aircraft conflict probe sensitivity to weather forecasts errors

Scipedia content — Thu, 28 Jan 2021 21:16:52 +0100

This study investigated the user request evaluation tool's (URET) prediction sensitivity to weather forecast error. A quantitative experiment was designed and performed by the Federal Aviation Administration's Conflict Probe Assessment Team (CPAT) to evaluate the impact of weather forecast errors on URET trajectory and conflict predictions. The experiment used approximately two hours of traffic data recorded at the Indianapolis en route center in May 1999. The flights were time shifted to generate a sufficient number of test conflicts using a genetic algorithm technique developed by CPAT. The resulting scenario was input into the URET prototype system. To induce weather forecast error, the weather input file (rapid update cycle, RUC) was altered by adding 20 or 60 knots to the wind magnitude, 45 or 90 degrees to the wind direction, and 5 or 15 degrees Kelvin to the air temperature. This produced seven URET runs for the experiment -the unaltered control run and six treatment runs. The analysis compared the control run against the treatment runs. A methodology was developed to compare the trajectory and conflict prediction accuracy of these runs. A statistical analysis provided evidence that the forecast errors in wind magnitude and direction had significant effect on the longitudinal trajectory error and a modest impact on retracted false alerts, which caused at most an increase in the false alert probability by six percent. It also showed that the air temperature runs did not have a significant effect. Based on this experiment, a controller suspecting errors in the input wind forecast should expect only a modest impact on URET predictions. The impact would mainly be a moderate increase in the number of retractions of its conflict predictions (defined in this study as a retracted false alert). If the controller notices an increase in retractions, it may be symptomatic of inaccurate wind forecasts, which should be investigated.

Hydraulic transient analysis and leak detection on transmission pipelines: Field tests, model calibration and inverse modelling

Scipedia content — Thu, 28 Jan 2021 20:19:55 +0100

The use of hydraulic transients for leak detection is theoretically possible assuming that water pipelines respond elastically and that current transient models are capable of replicating measured responses from real pipelines. This paper presents results for tests using hydraulic transients with and without a leak on a typical transmission main in South Australia. The size of the leak artificially introduced to the pipeline was set at the maximum limit of interest to South Australian Water Corporation operators. Based on the results of the field tests and modelling performed using a quasi-steady friction transient numerical model it was found that it was difficult to model the response of the pipeline, without and with the introduced leak, because of unsteady friction and mechanical dispersion and damping of the transient waveforms. Inverse analysis was performed using the quasi-steady friction transient model and it was found that leak could not be successfully detected. The transient model was improved by including unsteady friction and a viscous damping mechanism that was calibrated for inelastic mechanical effects using no-leak measured responses. Inverse transient analysis was performed using this improved model focussed on reflection information over 2L/a seconds of the measured leak responses and over an extended period. The small size of the direct reflections from the artificial leak made them difficult to discern amongst other reflections from elements not related to the leak. The inverse transient analysis performed over an extended period made use of leak damping information but was also affected by sources of damping not related to the leak. It was found that the improved forward transient model, in combination with prior information regarding the leak discharge (commonly available for flow monitored transmission pipelines), gave the best estimate of the location and size of the leak. However, the true leak was not identified as the optimal candidate following the inverse transient analysis because of persistent inadequacies in the replication of all the physical complexities affecting the measured transient responses.

ON THE RELEVANCE OF ON-LINE TRAFFIC ENGINEERING

Scipedia content — Thu, 28 Jan 2021 20:16:05 +0100

The evaluation of dynamic Traffic Engineering (TE) algorithms is usually carried out using some specific network(s), traffic pattern(s) and traffic engineering objective(s). As the behavior of a TE algorithm is a consequence of the interactions between the network, the traffic demand and the algorithm itself, the relevance of TE may depend on several network design aspects. In this paper, we evaluate well-known TE algorithms using real-world and generated network topologies and traffic demands. By re-scaling observed traffic demands, we are able to observe the behavior of TE algorithms under a variety of situations, which may not be observable in reality. We identify distinct network load regimes that correspond to different behaviors of the TE algorithms. We also study the impact of several network design aspects, like network provisioning and redundancy, on the relevance of TE algorithms. We find that there are specific situations under which TE algorithms are useful. These situations depend highly on shortcomings in the network provisioning as well as on the availability of alternative paths in the network.

Statistics of extremes, traffic jams and natural disasters

Scipedia content — Thu, 28 Jan 2021 20:15:01 +0100

nalyzing probability distributions from water level time series and calculating the first passage time distributions gives the probability of firstly exceeding a given threshold corresponding to a flood or general disaster event. The method will be applied to the water level recordings of the Danube river from which since 100 years very accurate notes exist. The method is transferred to time series of traffic volumes interpreting traffic breakdowns as extreme events. Three different traffic situations can be distinguished: (a) Stable traffic flow where any fluctuations decay over time (b) metastable traffic flow where fluctuations neither decay nor grow and (c) unstable traffic flow where a breakdown can be expected for sure if the observation time is long enough. The traffic dynamics is translated into a first passage time distribution. This describes the distribution of time periods observing for the first time the formation of a traffic jam of a certain length or number of vehicles. The distribution contains a time lag, a maximum corresponding to a time period of a Brownian motion drift reaching the critical jam length, and a tail describing exceptional long waiting times for jam formation. The cumulative first passage time distribution can be interpreted as breakdown probability distribution. It outlines when reaching a breakdown a given probability in an assumed observation time. It leads directly to the probabilistic definition of the capacity as a traffic volume leading to an unstable traffic pattern with a given probability within a given observation time. This definition can substitute the existing definitions and opens the possibility to quantitatively describing the influence of traffic control systems on the capacity.

Urban Traffic Intersection Incident Prediction Using AI Algorithm

Scipedia content — Thu, 28 Jan 2021 20:11:19 +0100

utomatic incident detection and characterization is urgently require in the development of advanced technologies used for reducing non-recurrent traffic congestion on urban traffic. This paper presents a new method using data mining to identify automatically freeway incidents. As a component of a real-time traffic adaptive control system for signal control, the algorithm feeds an incident report to the system’s optimization manager, which uses the information to determine the appropriate signal control strategy. Offline tests were conducted to substantiate the performance of the proposed incident detection algorithm based on simulated data. The test results indicate the feasibility of achieving real-time incident detection utilizing the proposed method.

A Collaborative Reinforcement Learning Approach to Urban Traffic Control Optimization

Scipedia content — Thu, 28 Jan 2021 20:06:24 +0100

eer-reviewed The high growth rate of vehicles per capita now poses a real challenge to efficient Urban Traffic Control (UTC). An efficient solution to UTC must be adaptive in order to deal with the highly-dynamic nature of urban traffic. In the near future, global positioning systems and vehicle-tovehicle/ infrastructure communication may provide a more detailed local view of the traffic situation that could be employed for better global UTC optimization. In this paper we describe the design of a next-generation UTC system that exploits such local knowledge about a junction???s traffic in order to optimize traffic control. Global UTC optimization is achieved using a local Adaptive Round Robin (ARR) phase switching model optimized using Collaborative Reinforcement Learning (CRL). The design employs an ARR-CRL-based agent controller for each signalized junction that collaborates with neighbouring agents in order to learn appropriate phase timing based on the traffic pattern. We compare our approach to non-adaptive fixed-time UTC system and to a saturation balancing algorithm in a largescale simulation of traffic in Dublin???s inner city centre. We show that the ARR-CRL approach can provide significant improvement resulting in up to ~57% lower average waiting time per vehicle compared to the saturation balancing algorithm.

Virtual Measurement in Pipes: Part 2-Liquid Holdup and Flow Pattern Correlations

Scipedia content — Thu, 28 Jan 2021 19:31:27 +0100

The prediction of liquid holdup and multiphase flow regimes present in a well or pipeline is very important to the petroleum industry. Liquid holdup, defined as the fraction of pipe occupied by liquid, and flow regimes must be predicted to design separation equipment and slug catchers in pipeline operations properly. It is also important when designing gas storage fields in depleted oil reservoirs.

Optimization of Sensor, Bus, and Fusion Schedules of a Time-Triggered Sensor Fusion System

Scipedia content — Thu, 28 Jan 2021 19:25:35 +0100

In this paper, we optimize a time-triggered, Kalman filter based, multi-sensor fusion system, used as an environmental perception platform for advanced driver assistance systems while satisfying constraints that are typical of a safety-related application. We argue that the overall system including effects from the sensor, bus, and fusion schedules as well as the treatment of measurements must be considered in order to optimize the fusion accuracy. Due to differences in measurement preprocessing data from sensors may not arrive in chronological order which requires special treatment for this out-of-sequence measurements (OOSM). As a result of this paper we identify regions in the scheduling parameter space that minimize the error covariance of the estimated states.

Control design for a mobile robot including tire behavior

Scipedia content — Thu, 28 Jan 2021 19:23:10 +0100

In order to support the development process of Advanced Driver Assistance systems for road vehicles, TNO is operating a hardware-in-the-loop test setup. In this facility, called VeHIL, vehicles in the direct neighborhood of the test vehicle are simulated using wheeled mobile robots. Due to the required type of maneuvers, these robots have independently driven and steered wheels. Consequently, the robot is overactuated. Furthermore, since the robot is capable of high dynamic maneuvers, slip effects caused by the tires can play an important role. A position controller based on feedback linearization is presented, using the so-called multicycle approach which regards the robot as a set of independent unicycles. As a result, the wheeled mobile robot is position controlled while each unicycle is controlled taking weight transfer as well as longitudinal and lateral tire slip into account. © 2008 IEEE.

Evolving distributed agents for managing air traffic

Scipedia content — Thu, 28 Jan 2021 19:14:01 +0100

traffic management offers an intriguing real world challenge to designing large scale distributed systems using evolutionary computation. The ability to evolve effective air traffic flow strategies depends not only on evolving good local strategies, but also on ensuring that those local strategies result in good global solutions. While traditional, direct evolutionary strategies can be highly effective in certain combinatorial domains, they are not well-suited to complex air traffic flow problems because of the large interdependencies among the local subsystems. In this paper, we propose an evolutionary agent-based solution to the air traffic flow problem. In this approach, we evolve agents both to learn the right local flow strategies to alleviate congestion in their immediate surroundings, and to prevent the creation of congestion "downstream" from their local areas. The agent-based approach leads to better and more fault-tolerant solutions. To validate this approach, we use FACET, an air traffic simulator developed at NASA and used extensively by the FAA and industry. On a scenario composed of three hundred aircraft and two points of congestion, our results show that an agent based evolutionary computation method, where each agent uses the system evaluation function, achieves 40% improvement over a direct evolutionary algorithm. In addition by creating agent-specific "difference evaluation functions" we achieve an additional 30% improvement over agents using the system evaluation.

A New Pre-emption Policy For MPLS-TE Networks

Scipedia content — Thu, 28 Jan 2021 19:12:10 +0100

International audience; The pre-emption mechanism may be used in Multi Protocol Label Switching Traffic Engineering (MPLS-TE) networks in order to reduce the number of rejected tunnels during failure. But pre-emption may have an impact on the convergence time, and it is required to minimize the number of pre-emptions per tunnel. For that purpose this paper proposes a new pre-emption policy allowing reducing or limiting the number of pre-emptions per tunnel, after a network failure. Two approaches are proposed: A pre-emption reduction approach where the least preempted tunnels are preempted in priority and a pre-emption limitation approach where a tunnel cannot be preempted more than N times during a given period. Simulation results show that we can limit the maximum number of pre-emptions for a given tunnel to only one, without significantly diminishing the rejection reduction capabilities.

A distributed scheme for bandwidth reallocation between working and recovery paths

Scipedia content — Thu, 28 Jan 2021 19:06:17 +0100

This paper presents a model of network failure recovery based on a scheme for reallocating bandwidth in path-oriented transport networks. We first describe the bandwidth reallocation scheme where, at specified time points, bandwidth can be switched to those routes that (possibly temporarily) value it most highly. This is done entirely according to local rules and without centralised control.We next describe our model of network failure recovery. We consider a protection switching recovery model which works with pre-established reserve-on-demand recovery routes. A reserve-on-demand recovery route allocates required resources after a failure on the working path has been detected. The bandwidth reallocation scheme is used to distribute bandwidth between the working routes before and after a failure, and between the working and recovery routes during the recovery cycle.To support the efficacy of such a system, we present a simulation model of failure recovery in a 30-node 46-link network. The simulation study reveals that bandwidth reallocation allows rapid recovery after the failure of a single link. Traffic is restarted on a recovery route within one round trip time and the recovery path attains the same Grade of Service (GoS) as its working counterpart within 0.1 call holding times.

CollaborationBus: An Editor for the Easy Configuration of Ubiquitous Computing Environments

Scipedia content — Thu, 28 Jan 2021 19:00:38 +0100

Early sensor-based infrastructures were often developed by experts with a thorough knowledge of base technology for sensing information, for processing the captured data, and for adapting the system's behaviour accordingly. In this paper we introduce the CollaborationBus application: a graphical editor that provides abstractions from base technology and thereby allows experts as well as non-experts to configure ubiquitous computing environments. By composing pipelines users can easily specify the information flows from selected sensors, via optional filters for processing the sensor data, to actuators changing the system behaviour according to their wishes. Users can compose pipelines for both home and work environments. An integrated sharing mechanism allows them to share their own compositions and to reuse and build upon others' compositions. Real-time visualisations help them understand the information flows through their pipelines. In this paper we present the concept and implementation of the CollaborationBus application

An Approach to Verify a Model for Translating Convective Weather Information to Air Traffic Management Impact

Scipedia content — Thu, 28 Jan 2021 19:00:20 +0100

‡This paper describes a method to determine the accuracy of the Convective Weather Avoidance Model which predicts the likelihood that pilots will deviate away from specific areas of convective activity. Visual inspection with a reduced data set helped refine the algorithms used in the verification and offered some preliminary results of the model’s accuracy in today’s airspace. This model has some explanatory power in predicting regions of airspace where pilots are willing to deviate or fly through. In some instances, pilots appeared not to make an early decision to deviate around convective weather and continued on course as the region appeared more passable when they reached it. In other instances, pilots skirted the edges of regions where the model expected pilots avoid. This behavior suggests edge areas of those model regions were more passable and the convection in that region was not uniform in intensity.

Dynamic Apparatus for CTOA Measurement in Pipeline Steels

Scipedia content — Thu, 28 Jan 2021 18:59:14 +0100

When a crack initiates and propagates in a pressurized pipe, the only thing that might stop this high-velocity event is the release of internal pressure (decompression), resulting in a deceleration in the crack-propagation rate. This deceleration can be achieved through the use of crack arrestors, or the ability of the pipeline material to resist ductile fracture. To evaluate the resistance to crack growth, the crack tip opening angle (CTOA) is used. Recent articles on the CTOA of pipeline steels at quasi-static rates with modified double cantilever beam specimens (MDCB), and at dynamic displacements rates by use of drop weight tear testing have provided data to support this need. These laboratory results from the literature, compared with results of full-scale tests, indicate that details of the fracture mode depend on the rate of fracture. To further study the dependence among the rate, fracture mode, and CTOA, a dynamic test apparatus was designed to perform CTOA testing of MDCB specimens, so that comparisons to quasi-static and full-scale results could be made. This new apparatus consists of a 500 kN uniaxial hydraulic test machine capable of stand-alone displacement rates of 300 mm/s, and a disc spring apparatus that is used to further accelerate the testing displacement rate. Initial results of the testing show that full slant fracture mode is observed at the highest rates tested for X65 and X100 steels. Maximum crack velocities approaching 10 m/s were recorded with highspeed photography. CTOA measurements were typically made at a position about 30 mm ahead of the pre-fatigue crack, over a distance of about 15 mm in the steady-state crack propagation regime. In this paper, we describe the high-speed apparatus, discuss the relationship among specimen configuration, crack speed, and CTOA, and present initial results on X65 and X100 pipeline steels.

Compact magnetic wheeled robot with high mobility for inspecting complex shaped pipe structures

Scipedia content — Thu, 28 Jan 2021 18:57:34 +0100

This paper describes a compact robot with two magnetic wheels in a bicycle arrangement, which is intended for inspecting the inner casing of pipes with complex shaped structures. The locomotion concept is based on an adapted magnetic wheel unit integrating two lateral lever arms. These arms allow for slightly lifting off the wheel in order to locally decrease the magnetic force, as well as laterally stabilizing the wheel unit. The robot has the main advantage to be compact and mechanically simple. It features 5 active degrees of freedom: 2 driven wheels each equipped with an active lifter-stabilizer and 1 steering unit. This paper also presents the design and implementation of a prototype robot and its high mobility is shown. It is able to pass 90deg convex and concave obstacles with any inclination regarding the gravity. Finally, it only requires limited space to maneuver, since turning on spot around the rear wheel is possible.

Using Testing Methods to Evaluate Pipeline Mechanical Integrity

Scipedia content — Thu, 28 Jan 2021 18:52:19 +0100

Evaluating the mechanical integrity of pipelines involves a variety of tools and skill sets. Over the past several years there has been an increased interest in assessing the performance of vintage pipeline systems and specifically evaluating the effects of existing defects on future performance. Examples of defects include girth and seam welds, corrosion, dents, and wrinkle bends. While lessons learned from prior experience and analysis are critical, the role of testing in the evaluation process is receiving focused attention. This paper includes detailed discussions on how testing has been used over the past decade to help pipeline companies assess the integrity of their pipeline systems. Specific emphasis is placed on helping the reader better understand what testing techniques are most appropriate and determining how to interpret and correlate the results into useful information for operating safe pipelines. Case studies are presented that include studies on seam welds subject to cyclic pressures, wrinkle bends, girth welds, and corrosion in dents. A well-designed test program can be used to validate numerical modeling efforts and provide engineers with insights regarding in situ behavior of pipeline systems.Copyright © 2008 by ASME

The Development of an Emergency Repair System, and a Case Study for a Remote Gas Pipeline

Scipedia content — Thu, 28 Jan 2021 18:51:37 +0100

Large diameter long distance gas pipelines are high value assets which have to be kept operating. When damage occurs, or the pipeline fails, a rapid repair is critical to allow full operation to re-start. Suitable equipment and skilled personnel are required to ensure a repair can be completed for the range of damage that can occur. Many locations around the world can be remote or hostile creating an absence of both available skills (such as welders) and equipment for emergency repairs. Consequently, some operators need comprehensive repair systems and skills that can be mobilised quickly and easily. This paper presents an overview of the options for the emergency repair of different types of pipeline damage, and provides a strategy, and a case study of the process used to define the equipment and support contracts needed by the operator of a gas pipeline in a remote area to ensure that they could complete a repair to any credible damage or failure within just 7 days.Copyright © 2008 by ASME