Scipedia: Documents published in 2008

Network and environmental impacts of passenger and airline response to cost and delay

Scipedia content — Wed, 03 Feb 2021 15:56:26 +0100

* † ‡† * *† § The Aviation Integrated Model is a policy assessment tool designed to simulate the operation and economic/environmental effects of local and world airline networks over the next 30-50 years within a modular framework. Feedback between demand, capacity, air traffic delays and policy measures is a key part of this model. For example, unconstrained model projections of US air transportation system growth with no passenger, airline or policy response included show average arrival delays of over two hours at major US airports in 2030, a condition that is unlikely to materialize. A more likely situation is that a combination of responses act to bring the air transport system to a new equilibrium at which higher fares, extra capacity or increased operational efficiency reduces the delays to a more acceptable level. Similarly, the application of policies designed to mitigate some of the environmental impacts of air transportation will also alter the system equilibrium state. In this paper we use the Aviation Integrated Model to systematically examine these feedback effects, concentrating specifically on the passenger response to increases in travel time, airfare, and policy responses to environmental concerns. We contrast the reference case in which the main feedback effect is passenger and airline response to air traffic delay with sample policy scenarios.

Modelling Airline Network Routing and Scheduling under Airport Capacity Constraints

Scipedia content — Wed, 03 Feb 2021 15:52:08 +0100

flight routing and scheduling model is under development that predicts airline routing and scheduling under airport capacity constraints. It consists of several components describing different aspects of the air transport system, including passenger demand, airline competition, flight delay, and airline cost. These models are integrated into a flight routing and scheduling model in which an objective function is defined to maximize airline system profit within a routing network, subject to constraints. This framework allows the relationships between fares, passenger demand, infrastructure capacity constraints, flight delays, flight frequencies, and routing network to be simulated. In this paper the integrated flight routing and scheduling model is first applied to a series of simple theoretical routing networks to illustrate its capabilities. With increasing airport capacity constraints the results show an increase in average fares, a decrease in O-D passenger demand, and a shift in flight routing away from the most constrained airports. The model is then applied to a network of airports in the United States with 2005 population, income and airport capacity inputs. With further development the model is to be applied to forecasting air traffic system growth, including network and schedule changes resulting from increasing delays, in the Aviation Integrated Modelling (AIM) project under development at the University of Cambridge. Copyright © 2008 by Antony D. Evans, Andreas Schafer, and Lynnette Dray.

The Federal Aviation Administration 2008 portfolio for research and development

Scipedia content — Wed, 03 Feb 2021 15:50:37 +0100

The Federal Aviation Administration (FAA) 2008 National Aviation Research Plan (NARP) is a performance-based plan that integrates and describes the FAA research and development (R&D) portfolio. The 2008 NARP supports both the current day-to-day operations of the National Airspace System (NAS) and the future vision for the Next Generation Air Transportation System (NextGen). The portfolio is comprised of 44 R&D programs that address air traffic management (ATM), aircraft safety, airports, the environment, human factors, operational concepts, aviation weather, unmanned aircraft, and wake turbulence requirements. In the 2008 NARP, ten R&D goals bridge the near-term goals of the FAApsilas strategic Flight Plan, the mid- and longer-term NextGen goals of the Operational Evolution Partnership (OEP), now called the NextGen Implementation Plan, and the work of the Joint Planning and Development Office. This integrated approach enables the FAA to address the current challenges of operating the safest, most efficient air transportation system in the world while building the research foundation for NextGen.

Modelling earthing systems and cables with Moment Methods

Scipedia content — Wed, 03 Feb 2021 15:44:19 +0100

The purpose of this paper is to present a method to model earthing systems subjected to lightning strikes with a one-dimensional moment method. This paper was conducted because an accurate method to model earthing systems subjected to lightning strikes, was deemed necessary. To name a few examples of relevant situations: supply stations of railway systems, from which also critical signalling infrastructure is fed, earthing systems of cellular phone basestations, located in the vicinity of high-antenna towers, prone to lightning strikes, and gas and oil pipelines. There exist already methods to solve this problem, based on circuit theory, but the electromagnetic method of this work is based directly on Maxwell’s equations and therefore more accurate. The earthing electrodes and meshes are represented as wire scatterers. First, the method is outlined for scatterers in a single medium. Next, the method is extended to model to presence of the soil-air interface layer. An approximate technique, known as the modified image theory, is used to account for the vicinity of the soil. Finally, a second extension is given so that cables without metal sheets which are in the vicinity of the earthing systems, can be included in the model. Thereafter, it is described how the method can be used to calculate the effects of lightning strikes on earthing structures, and finally a validation of the method is presented. The method is validated by applying it to simple situations which can also analytically be calculated, and by applying it to earthing structures for which the transient voltage was measured or calculated with circuit methods. A good agreement is seen. However, the method is computationally very expensive. ispartof: COMPEL vol:28 issue:4 pages:989-1004 ispartof: location:Graz, AUSTRIA status: published

Analysis of Environmental Impact of Eliminating Arrival Hold Short Operations for Runway Crossings at Dallas/Ft. Worth Airport

Scipedia content — Wed, 03 Feb 2021 15:42:29 +0100

This paper analyzes the environmental impact of eliminating arrival aircraft stops at active runway crossings. As the air traffic demand increases, innovative operating procedures to either reduce or maintain environmental impact will be required. To improve surface operation efficiency, as well as potentially reduce environmental harm, eliminating arrival aircraft stops at active runway crossings is being explored. This paper describes an analysis of active runway crossing operations for arrival aircraft, as well as a comparison of the fuel and emissions environmental impact of maintaining current active runway crossing operations versus eliminating aircraft hold short operations at active runway crossings. Three previously developed software tools were used in the data analysis. The results indicate a decrease in both emissions exposure levels and fuel consumption prior to a runway crossing on the order of 30% with the implementation of the operating procedure that eliminates hold short operations and allows continual taxi for runway crossings.

Efficient Simulation for Testing Loss of Separation Algorithms

Scipedia content — Wed, 03 Feb 2021 15:30:31 +0100

Given increased air traffic and the possible use of autonomous vehicles, there is interest in the verification of separation algorithms. Because of the complexity of the environment and the presence of perturbations, a candidate approach is simulation and Monte Carlo. There are several desirable properties of the simulation: realism, portability, transparency, and efficiency. This paper is an initial effort using MATLAB to study a separation algorithm. An original separation algorithm was developed to make this project independent of any other effort. The algorithms and program were effective enough and efficient enough that the project will proceed.

Modeling and Simulation of Space Vehicle Operations in the National Airspace System

Scipedia content — Tue, 02 Feb 2021 08:34:24 +0100

*† ‡ NASA’s Future ATM Concepts Evaluation Tool (FACET) provides an extensive set of modeling, simulation and analysis capabilities for studying air transportations in the National Airspace System. The Configurable Airspace Research and Analysis Tool (CARAT) has been developed to build on the FACET capabilities to develop an environment useful for studying the interaction between space vehicle operations in the airspace and the air traffic. CARAT introduces a flexible vehicle-model database that allows the user to easily add and configure space transportation vehicle models or air transportation vehicle models for integration with the FACET simulation. CARAT also provides capabilities for safety analyses, including trajectory analysis, debris modeling, and specific functions dealing with flight hazard areas in the airspace and on the surface: the Aircraft Hazard Area and Individual-Casualty Contour Analysis, respectively. The CARAT system was originally developed on the Windows platform, but has recently been updated to work with newer versions of FACET on the latter’s preferred platforms: Linux and other Unix variants, including the Apple Mac OS X. The update also provides a cleaner integration with FACET and additional enhancements in the area of vehicle modeling, including a redesigned software architecture for implementing aerospace models. Models of several aerospace vehicle that have recently garnered increasing interest have been added to the CARAT model database, including models for studying Ares launch vehicle concepts motivated by NASA’s Constellation Program, and several models of unmanned aerial vehicles.

Inter-Korean maritime dynamics in the Northeast Asian context

Scipedia content — Tue, 02 Feb 2021 08:20:28 +0100

http://crc.ehess.fr/document.php?id=467; Although nowadays inter-Korean trade is primarily shipped by sea, very limited attention has been paid to the specific role of maritime transport in inter-Korean relationships. Based upon a 20-year database of daily vessel movements, this paper relates the changing geography of inter-Korean connections with the evolution of the North Korean economy and territory. Main results show the convergence between inter-Korean economic cooperation and shipping growth. South Korean ports also provide a logistics platform facilitating North Korea's transit trade with the rest of the world. The convergence or divergence between economic integration and hub dependence are discussed and provide a base for further research

An Application Layer Gateway for Air Traffic Management Communication by Satellite

Scipedia content — Tue, 02 Feb 2021 08:17:34 +0100

onautical safety communication via satellite presents some interesting challenges, one of which is the problem of passing inelastic traffic (generated by real time events) over a limited bandwidth communication channel. Today’s aviation standards prescribe the use of a reliable transport protocol, a proposition that is inherently incompatible with inelastic traffic. Though network capacity should be sized for the normal peak load, one must assume that unusually high peak loads will occasionally occur, leading to congestion. This paper describes the concept of an application layer gateway, capable of mitigating congestion by re-ordering and, if necessary, selectively discarding messages in accordance with set rules. A demonstration test bed is described. Test results, confirming the capability of the gateway to relieve congestion, are also given.

Planning deliveries from end to beginning: an assessment methodology proposal for big cities in developing countries, with real case application

Scipedia content — Tue, 02 Feb 2021 07:40:37 +0100

This paper on delivery planning in large cities in developing countries is from the proceedings of 14th International Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. The authors stress that delivering cargo in big cities in developing countries is more difficult than in developed countries, primarily because the infrastructure and traffic conditions are worse. They present a case study using the DHL Exel Supply Chain in Sao Paolo, Brazil, then outline a methodology for choosing the best mode of cargo delivery in the urban area of populous cities in developing countries. The authors hypothesize that the best technical option may be to use smaller and lighter vehicles in order to reduce the traffic impact, have more agility, use more environmentally-friendly cleaner fuel, and to achieve easier access to central areas inside commercial centers. However, delivering cargo with a lot of small trucks can be much more expensive than full truck loads using bigger vehicles. The methodology can be used to create a process to choose between the conventional method that favors the agility, short storage and small trucks and the use of cargo consolidation, fewer stops, and larger trucks.

Prioritising Individual Water Mains for Renewal

Scipedia content — Tue, 02 Feb 2021 07:32:03 +0100

The statistical analysis of historical breakage patterns of water mains is a cost effective approach to discern their deterioration, where physical mechanisms that lead to their deterioration are often very complex and not well understood. Furthermore, data required to model these physical mechanisms are rarely available and prohibitively costly to acquire. Several models exist in the literature, which use various statistical methods to analyse patterns of pipe breakage histories. Some of these models were designed to address relatively large groups of pipes, which are presumed to be homogeneous with respect to their deterioration patterns, while others address individual water mains. However, predicting a breakage pattern in an individual pipe has proven to be quite a challenge and the validation of these models is generally done on the basis of aggregate breakage rate although the model purports to predict individual pipe behaviour. The structural deterioration of water mains and their subsequent failure are affected by many factors, both static (e.g., pipe material, pipe size, age (vintage), soil type) and dynamic (e.g., climate, cathodic protection, pressure zone changes). Dynamic factors can currently be considered only in a model that was designed to deal with pipe groups. While group deterioration analysis is important for high-level renewal planning, operational considerations require the prioritisation of individual pipe for renewal within such groups. Consequently, the National Research Council of Canada (NRC), with support from the American Water Works Association Research Foundation (AwwaRF) is investigating how to prioritise individual pipes within a so-called ‘homogeneous’ group of water mains. Several approaches have been explored in this research initiative with various degrees of success. In this paper we describe the development of a nonhomogeneous Poisson model, which considers dynamic factors that can affect water main failure and some preliminary results are reported.

Homopolar Pulse Welding for Offshore Deep Water Pipelines

Scipedia content — Tue, 02 Feb 2021 07:13:06 +0100

Homopolar Pulse Welding (HPW) is a one-shot resistance welding process being investigated as a method to join API 5L carbon steel line pipe. HPW utilizes the high current, low voltage electrical pulse produced by a homopolar generator to rapidly resistance heat the interface between abutting pipe ends, producing a full circumference resistance forge weld requiring no filler metal in under three seconds. A five year joint industry program is sponsoring HPW research with the goal of developing the process for deep water offshore pipeline construction utilizing the J-lay method. The first two years of the program have concentrated on weld parameter optimization by producing, testing, and evaluating welds in various grades, wall thicknesses, types and compositions of 3 inch nominal (3.5 inch OD) diameter API 5L carbon steel pipe. Mechanical properties of the welds and parent metal were evaluated by tensile testing, impact testing, and hardness traverse testing according to guidelines and criteria established by the industrial sponsors. HPW has demonstrated the capability to produce industrially acceptable full circumference welds in carbon steel pipe via a rapid, one-shot process.

Advanced Satellite Technologies for Air Traffic Management

Scipedia content — Tue, 02 Feb 2021 07:11:05 +0100

This paper presents the current limitations and possible future upgrades of satellite communication systems to satisfy the requirements of air traffic management using compact and low cost aeronautical terminals.

Joint Traffic Blocking and Routing Under Network Failures and Maintenances

Scipedia content — Tue, 02 Feb 2021 06:46:16 +0100

Under device failures and maintenance activities, network resources reduce and congestion may arise inside networks. In this paper, we study a dual approach that combines traffic blocking (rate-limiting) at the edge of a network and traffic rerouting inside the network. We formulate a joint ingress blocking and routing optimization problem and develop mechanisms to introduce blocking differentiations among users with different service priorities and with different level of impact to network congestions. Our evaluation result shows that by blocking only a small fraction of traffic, one can greatly reduce network congestion under severe failures and maintenance activities. Our solution efficiently identifies the optimal blocking among heterogeneous users and achieves much better performance in comparison with proportional traffic blocking. The proposed algorithms can be easily adopted by network service providers in their traffic engineering practices.

Demonstrator: V2V Communications in Automotive Multi-Sensor Multi-Target Tracking

Scipedia content — Tue, 02 Feb 2021 06:39:39 +0100

Today's automotive sensor systems for in-vehicle based target tracking, i.e. radar, lidar, camera, are limited to a field of view which is restricted by distance, angle and line-of-sight. Future driver assistance systems such as predictive collision avoidance or situation-aware adaptive cruise control require a more complete and accurate situation awareness in order to detect hazardous and inefficient situations in time. Therefore, we introduce multi-target tracking including vehicle-2-vehicle communications as a complementing sensor for future driver assistance systems. The demonstration presents set-up, functionality and results of multi-sensor multi-target tracking based on particle filtering.

Optimal Asynchronous Linear-Pipelines

Scipedia content — Tue, 02 Feb 2021 06:30:43 +0100

International audience; This paper introduces a new methodology for determining the minimum number of registers needed to pipeline a linear asynchronous pipeline so that the final cycle time meets some constraints. Moreover, the methodology defines the optimum placing for the registers; ends with an optimally pipelined circuit.

Study Of Sweet Corrosion In Horizontal Multiphase, Carbon Steel Pipelines

Scipedia content — Tue, 02 Feb 2021 06:27:57 +0100

Sweet corrosion in carbon steel pipelines carrying oil-water mixtures has long been a problem in the oil industry. A study to determine the corrosion rates and the type of deposits formed on the pipe surface under such multiphase flow conditions is described. Full pipe flow and slug flow conditions and the effect of a few inhibitors is studied. Temperatures up to 60C and several pressures, flow rates, oil-water fractions are also studied.

Departure Taxi Time Predictions Using ASDE-X Surveillance Data

Scipedia content — Tue, 02 Feb 2021 06:10:04 +0100

urate prediction of departure taxi times will help airlines to proactively manage push-times, to optimally assign scarce ramp resources, and to propagate delay information to destination airports in a more timely fashion. Air Traffic Control (ATC) will benefit via improved demand forecasts for the terminal area and enroute air sectors. An ancillary benefit to such predictions is the ability to discern factors contributing to longer taxi times. To facilitate accurate predictions, we will analyze the utility of the Airport Surface Detection Equipment, Model X (ASDE-X) surface surveillance data. Months of archived data support both historical analysis (i.e., under similar conditions, what happened in the past?) and a more dynamic real-time surface analysis (e.g., aircraft positions, queues, and runway utilization).

A collocation model for water-hammer dynamics with application to leak detection

Scipedia content — Tue, 02 Feb 2021 06:01:12 +0100

International audience; This paper presents a new model for so-called water hammer equations based on a collocation method. This model is shown to fairly represent possible leak effects in a pipeline and thus to be useful in the purpose of leak detection. This is illustrated in simulation by an example of observer based leak detector relying on this model.

Study on fast model predictive controllers for large urban traffic networks

Scipedia content — Tue, 02 Feb 2021 05:55:30 +0100

Traffic control is both an efficient and effective way to alleviate the traffic congestion in urban areas. Model Predictive Control (MPC) has advantages in controlling and coordinating urban traffic networks. But, the real-time computational complexity of MPC increases exponentially, when the network scale and the predictive time horizon grow. To improve the real-time feasibility of MPC, a simplified macroscopic urban traffic model is developed. Two MPC controllers are built based on the simplified model and a more detailed model. Simulation results of the two controllers show that the online optimization time is reduced dramatically by applying the simplified model, only losing a limited amount of control effectiveness. Additional techniques, like applying a control time horizon and an aggregation scheme, are implemented to reduce the computational complexity further. Simulation results show positive effects of these techniques.

Investigating a Near-Bed Submarine Pipeline in a Current

Scipedia content — Tue, 02 Feb 2021 05:48:56 +0100

This paper considers the lift forces acting on a pipeline with a small gap between the pipeline and the plane bottom or scoring bottom. A more reasonable fluid force on the pipeline has been obtained by applying the knowledge of modified potential theory (MPT), which includes the influences of the downstream wake. By finite element method, an iteration procedure is used to solve problems of the nonlinear fluid-structure interaction. Comparing the deflection and the stress distributions with the difference sea bottoms, the failure patterns of a spanning pipeline have been discussed. The results are essential for engineers to assess pipeline stability.

Technology Assessment Results of the Eurocontrol/FAA Future Communications Study

Scipedia content — Tue, 02 Feb 2021 05:43:27 +0100

The US Federal Aviation Administration (FAA) and Eurocontrol jointly initiated the future communications study (FCS) to develop a common approach for a globally harmonized air traffic management (ATM) communications system. The FCS includes operational concepts and communications requirements development, analysis of business and institutional elements, and identification and assessment of technology alternatives. The FCS technology assessment determined the best set of available technologies for aviation safety communications for ATM given key constraints such as cost, transition feasibility, technical requirements, and spectrum availability. From 2004 to 2007, the assessment progressed in three phases, yielding technical results and recommendations for development and phased implementation of a future aviation communications infrastructure.

A high-speed reconfigurable architecture for heterogeneous multimodal packet traffic generation

Scipedia content — Tue, 02 Feb 2021 05:32:16 +0100

Traffic modeling plays a key role in the study of packet switching systems, such as Internet routers. As line rates increase towards tens of gigabits per second, the duration of individual packets decreases, rendering real-time traffic generation a fundamental engineering challenge. In evaluation of these systems, it is critical to reproduce traffic conditions that approximate the target environment. Additionally, the ability to generate traffic flows that establish the limitations of a given algorithm or architecture is highly desirable. To address these issues, we propose a reconfigurable high-speed hardware architecture for heterogeneous multimodal packet generation. FPGA results demonstrate the scalability and flexibility of the proposed framework

Analysis of Current Sectors Based on Traffic and Geometry

Scipedia content — Tue, 02 Feb 2021 04:57:24 +0100

This paper desc ribes an evaluation of current sectors in the continental United States using a variety of traffic and geometric metrics. Most of the metrics have been computed using real track -data. In instances where this was not possible, s imulated traffic data are use d. Statistics of these metrics are summarized for higher altitude sectors in the twenty air route tr affic control centers and in eight geographical regions . The analysis shows that most sectors have fewer than twenty aircraft and three conflicts at any giv en time. Air traff ic in higher altitude sectors consists of mostly jets that fly in a narrow range of airspeeds and altitudes. A wide variation was found in the volume, area, height, length and transit times of the sectors. Most sectors were found to be el ongated and aligned in the direction of the traffic flows. The properties of today's sectors reflect the technologies and procedures used for air traffic control. With the introduction of automation, the design of airspace partitions will not be contrained by how controllers manage traffic. However, if controllers are involved to some degree in the future system, it might be useful to account for some of the characteristics of the current sectors in the design of future airspace partitions. I. Introductio n n the current national airspace system, design of sectors have evolved over a long period of time based on incremental addition of new technologies and procedures for air traffic control. Each sector has a fixed capacity. When these capacities are exce eded by traffic demand, traffic flows are restriced to bring the demand below capacity. The concept in Ref. 1 suggests that instead of restricting tr affic , which causes delays, airspace capacity can be increased by partitioning the airspace differently. Mo tivated by this concept, s everal methods for airspace partitioning that are described in Refs. 2 through 6 have been developed. These methods use some measure of controller workload to guide the design . In the future, with increased level of automation, ai rspace design might not be guided by controller workload considerations. Depending on how different the future design is from the current design, the controller's ability to actively separate aircraft might be limited. It might be useful to carry some of t he design features of the current system into the future one, if some role for human controller is envisioned in the future air traffic control system. The motivation for computing metrics for the existing sectors is to capture some of the design features of the current sectors. Since the design of current sectors is based on the routes of flight and controller workload considerations , metrics related to controller workload can be expected to capure the design features. There are numerous traffic and geom etry metrics described in the literature that have been found to be useful for modeling controller's perception of workload and in operational error studies. 7-11 These studies are limited to sectors in few centers. A comprehensive study of sectors in all t he twenty centers is unavailable. In this paper, thirty -three traffic and geometric metrics from Ref s. 7 to 11 are computed for 364 higher al titude sectors in each of the twenty centers, and in eight geographical regions. Higher altitude sectors were chos en because the benefits of airspace partitioning are expected to be realized in these sectors first. Data presented in this paper describes the design of the current sectors and will be found to be useful for comparing the designs of future airspace partit ions .

Traffic Engineering in case of interconnected and integrated layers

Scipedia content — Tue, 02 Feb 2021 04:51:35 +0100

In this paper, we compare two routing scenarios for grooming-capable optical-beared two-layer networks that are capable of meeting the Traffic Engineering (TE) objectives. The first one applies completely dynamic WDM layer that adapts instantly to all traffic changes. The second one is based on fixed WDM topology (“lower layer”). To achieve the best performance, the fixed lightpath system is optimized in advance according to the characteristics of the expected traffic. In both cases, the upper layer is assumed to be dynamic. We perform extensive simulations to compare these two multi-layer Routing and Traffic Engineering approaches that are currently both of particular practical interest with their inherent advantages and drawbacks.

3D airspace design by evolutionary computation

Scipedia content — Tue, 02 Feb 2021 04:28:08 +0100

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

A generalization of the Erlang formula of traffic engineering

Scipedia content — Tue, 02 Feb 2021 03:50:37 +0100

Consider a node in a communication network with n outgoing links grouped into k trunks of n1 ...., nk links respectively. n1+...+nk = n. Calls arrive in a Poisson stream of rate ? The state of the node is specified by the number of idle links in each trunk. A policy is a rule by which a call, finding the node in some state, is assigned to one of the available links in one of the available outgoing trunks. The links are assumed to have exponential holding times with mean 1/µ which are independent, and are independent of the arrival process. Further, a call assigned to trunk ?, 1 ?? ?k is immediately lost with probability (1--??)--this feature models the nature of the links and the congestion downstream of the node along that route. A call is said to be blocked if all the outgoing links are busy when it arrives. It is known that the blocking probability is independent of the assignment policy. We give an explicit closed form formula for the blocking probability Pb = 1/?n1j1 = 0 .. ?nkjk = 0 [n1, j1] ... [nk, jk](j1 + ... + jk)! (µ/?1)j1 ... (µ/?k)jk where ?1 = ?1 . ? ..., ?k = ?k . ?. This generalizes the well-known Erlang formula of traffic engineering.

About Some Specificities of Embedded Multiagent Systems Design

Scipedia content — Tue, 02 Feb 2021 02:52:31 +0100

This paper addresses the problem of distributed cooperative collision avoidance that supports efficient utilization of air space shared by several autonomous unmanned aerial vehicles. The novel multi-party collision avoidance (MPCA) algorithm is described. It is compared to the iterative peer-to-peer collision avoidance (IPPCA) algorithm that iteratively optimizes social welfare. The paper provides a set of experiments and a comparison of different collision avoidance mechanisms in a multi-agent model of air traffic.

Sequential Traffic Flow Optimization with Tactical Flight Control Heuristics

Scipedia content — Tue, 02 Feb 2021 02:28:49 +0100

‡A sequential optimization method is applied to manage air traffic flow under uncertainty in airspace capacity and demand. To support its testing, a decision support system is developed by integrating a deterministic integer programming model for assigning delays to aircraft under en route capacity constraints to reactively account for system uncertainties. To reduce computational complexity, the model assigns only departure controls, while a tactical control loop consisting of a shortest path routing algorithm and an airborne holding algorithm refines the strategic plan to keep flights from deviating into capacity constrained airspace. This integrated approach is used to conduct thirty-two, 6-hour fast-time simulation experiments to explore variations in the number and severity of departure controls, tactical reroutes, and airborne holding controls. Three feasible types of traffic flow controls emerged. The first type relied primarily on departure controls and strategic reroutes on the 300 to 400 nmi look-ahead horizon and worked best when rerouting occurred at a frequency of 10 to 15 minutes. The second type generated more tactical reroutes on the 200 ‐ 300 nmi look-ahead horizon and required little airborne holding or pre-departure control when rerouting occurred at a frequency of 5 minutes. The last type relied heavily on airborne holding controls and infrequent updates to the weather avoidance reroutes. This last type was the least desirable solution due to the impact of its airborne holding on airspace complexity and airspace users.

Optimally and equitably distributing delays with the aggregate flow model

Scipedia content — Tue, 02 Feb 2021 02:26:16 +0100

The aggregate flow model is used to determine how to distribute predeparture delays among air traffic control centers and across time to optimally satisfy constraints on airspace capacity and departure rates. To do so, a quadratic cost on cumulative departure delays is introduced, resulting in an optimization problem that can be quickly solved using convex optimization tools. Simulations using the model demonstrate the behavior of the national airspace system (NAS) when implementing optimal departure delays for a particular constraint scenario. These results show that capacity-constrained air traffic control Centers suffer the highest delays. Three approaches for increasing the equity of the distribution of delays across the NAS are investigated. The first involves setting an upper bound on the Gini coefficient, a quasi-convex measure of inequality. Another is to make delays in some centers more costly than in others. The last approach is to put an upper bound on the delay per departure for each center. Simulation results demonstrate that bounding delay per departure effectively reduces the delays for the constrained center. Enforcing an upper bound on the Gini coefficient and increasing the weight on delays in some centers may impose large delays on other centers when reducing the delays in the constrained center.

Rapid Prediction of Air Traffic for Trajectory Based Operations (ALTERNATE PAPER)

Scipedia content — Tue, 02 Feb 2021 02:15:31 +0100

Visualization of Spatial Sensor Data in the Context of Automotive Environment Perception Systems

Scipedia content — Tue, 02 Feb 2021 02:13:54 +0100

Spatial sensor systems in cars are gaining more and more importance. Such sensor systems are the foundation of future safety systems, such as automatic emergency brakes, as well as for interactive driver assistance systems. We have developed a system that can visualize such spatial sensor data. Two environments are supported: a laboratory setup for off-line experience and a car setup that enables live experience of spatially aligned laser scanner and video data in real traffic. We have used two visualization devices, a video see-through LCD flat panel (TFT) and an optical see-through head-mounted display (HMD) in both setups. For the laboratory setup, a back-projection table has been integrated as well. To present data in correct spatial alignment, we have installed tracking systems in both environments. Visualization schemes for spatial sensor data and for geometric models that outline recognized objects have been developed. We report on our system and discuss experiences from the development and realization phases. The system is not intended to be used as a component of real driver assistance systems. Rather, it can bridge the gap between human machine interface (HMI) designers and sensing engineers during the development phase. Furthermore, it can be both a debugging tool for the realization of environmental perception systems and an experimental platform for the design of presentation schemes for upcoming driver assistance systems.

Proactive identification of work and situational factors that can affect safety in air traffic control.

Scipedia content — Tue, 02 Feb 2021 01:56:40 +0100

In an organization where the safety level is high and incidents and serious accidents are very rare, a steady erosion of safety awareness and protective measures can occur, especially when productive demands rise. Thus, it is important to continuously identify and monitor aspects in the organization that can affect work performance and safety. In an ongoing joint research project between the LFV Group (Swedish state agency that operates airports and is responsible for air navigation services) and Lund University, the aim is to develop a questionnaire-based methodology for identifying and monitoring work and situational factors in Swedish air traffic control centers and towers in order to identify in advance aspects that can affect safety in the organization. This paper presents preliminary findings from interviews conducted to determine the variables for assessing work and situational factors as well as initial findings from a pilot study testing the questionnaire. Results from the interview sessions showed that when evaluating work and situational factors the following aspects should be included: safety culture, commitment, organizational climate, psychosocial work environment, leadership, communication, areas of conflict, and participation/involvement. Results from the pilot study showed that the majority of respondents found the questionnaire items to be of high relevance for finding deficiencies in the organization. Follow-up interviews or group discussions were recommended that would give additional and more detailed information. Preliminary results also revealed issues that could be further developed in the respondents’ work situations. Respondents with administrative tasks indicated communication skills and teamwork as areas for further improvement. Some air traffic controllers wanted more knowledge about aircraft specifications and a few thought it was too complicated to write reports on small deficiencies and incidents and believed this could negatively affect the safety reporting culture.

Impact behaviour of pressurised pipelines

Scipedia content — Tue, 02 Feb 2021 01:53:26 +0100

Experimental tests are reported on steel pipelines that have been struck by a relatively large rigid wedge-shaped mass travelling up to 10.4 m/s. A pipeline is supported across a span, is fully clamped at both ends and is struck at the mid-span and at the one quarter span positions. Most of the pipelines are pressurised with a nitrogen gas. The initial impact energy produces large inelastic ductile deformations of the pipeline and, in some cases, failure. The experimental results are compared with previous data obtained on larger diameter pipelines and observations are offered on the accuracy of the geometrically similar scaling of the final deformations. The results are also compared with several empirical equations and comments are made on their accuracy.

Modelling Intermittent Water Supply Systems with EPANET

Scipedia content — Tue, 02 Feb 2021 01:52:14 +0100

Modeling rural networks and intermittent water supply systems is a challenging task because these systems are not fully pressurized pipeline networks but networks with very low pressures, with restricted water supply hours per day, and with thousands of ferrule points and roof tank connections. The alternate emptying and refilling of water pipelines makes it problematic to apply standard EPANET based hydraulic models because of low pressures and pipes without water. EPANET source code was adjusted to allow for modeling pressure dependent demands, for dealing with low pressure and “dry pipe” situations. A configurable tool was developed for incorporating roof tanks into the water supply analysis and for better formulation and schematization of the system hydraulics. Two cases studies, water distribution model of Shillong in India and detailed water distribution model of Dhaka in Bangladesh are used to illustrate the practical use of this approach. The experience from using and adjusting the EPANET engine for the modeling of intermittent water supply systems is discussed in this paper.

Traffic engineering using new VS routing scheme

Scipedia content — Tue, 02 Feb 2021 01:45:01 +0100

Goal of traffic engineering in packet networks is to improve the network performance by providing support for congestion management, higher bandwidth utilization (or throughput), and QoS or priority-based services. Open shortest path first with traffic engineering extensions (OSPF-TE) (J. Moy, April 1998) and multiprotocol label switching (MPLS) protocols are commonly viewed as possible solutions. Both, the OSPF-TE with optimized link weights or MPLS with explicit optimal path set-ups, work ideally under static network conditions with a known demand-matrix. However, these methods do not provide scalability and flexibility to adapt to arbitrary, dynamic demand patterns in large networks. A novel traffic engineering scheme based on the virtual space (VS) routing (G. P. Saraph and P. Singh) is proposed here, which has the scalability, flexibility, and robustness to rapidly adapt to arbitrary, dynamic load conditions in large networks. Simulations are carried out on randomly constructed 40, 80, and 200-node networks with arbitrary demand matrices, which demonstrate excellent capability of the VS routing in terms of load balancing, packet throughput, and congestion avoidance. The proposed VS scheme is used for path selection in MPLS and integrated with the signaling protocols for path establishment, such as the constraint based routing (CR-LDP) (J. Ash et al., Jan. 2002) or resource reservation (RSVP-TE) (D. Awduche et. al., Jan 2002) protocols.

NGfast: a simulation model for rapid assessment of impacts of natural gas pipeline breaks and flow reductions at u.s. state borders and import points

Scipedia content — Tue, 02 Feb 2021 01:26:16 +0100

This paper describes NGfast, the new simulation and impact-analysis tool developed by Argonne National Laboratory for rapid, first-stage assessments of impacts of major pipeline breaks. The methodology, calculation logic, and main assumptions are discussed. The concepts presented are most useful to state and national energy agencies tasked as first responders to such emergencies. Within minutes of the occurrence of a break, NGfast can generate an HTML-formatted report to support briefing materials for state and federal emergency responders. Sample partial results of a simulation of a real system in the United States are presented.

Challenges of urban transport problems and city logistics: Sao Paulo city center case

Scipedia content — Tue, 02 Feb 2021 01:03:42 +0100

This paper on urban transport problems and city logistics is from the proceedings of 14th International Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. The authors use Sao Paulo, Brazil, as a case example to illustrate the concepts under discussion. They focus on the emerging concept of city logistics to improve the mobility of cities. At a simple level, global and continental scale logistics systems are organized around airports, seaports, road and rail systems and storage facilities, which all tend to be space extensive. Challenges include the need for growth in logistics systems to support the globalization of production and consumption, and the related spatial and functional restructuring of large scale urban regions. Topics include strategies to limit automobile circulation, prohibition of automobile travel in downtown areas during certain hours, traffic congestion, private automobile ownership, freight needs, infrastructure, decentralization, the benefits of city logistics, and new forms of goods organization.

Analysis and improvement of “The Last Mile” to and from the national airport as part of the mobility policy in the Brussels urban area

Scipedia content — Tue, 02 Feb 2021 00:51:10 +0100

This paper on urban mobility policy regarding airports is from the proceedings of 14th international Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. The authors note that as aviation is the fastest growing transport mode worldwide, there is an increasing number of passengers that need to be transported to and from the airport before and after their flights. They define the "last mile” as the distance between the starting point of the trip and the airport of departure or between the airport of arrival and the destination of the trip. The authors analyze the current situation of the passenger transport to and from Brussels Airport, which is located next to the ring road of Brussels; consequently passengers traveling by road to the airport influence traffic on the ring road and inversely congestion on this same ring road interferes with smooth passenger traffic to the airport. They propose that the capacity of public transport should therefore be increased and its catchment area should be extended to reduce the share of personal vehicles in the total passenger transport. They conclude with a discussion of planned mobility projects and their environmental impacts and sustainability, in light of expected development of the airport.

A checklist for planning and implementing Field Operational Tests of Intelligent Transport Systems

Scipedia content — Tue, 02 Feb 2021 00:26:18 +0100

Improved knowledge is needed to understand how drivers use intelligent transport systems, the short- and long-term effects of these systems, and how system performance can be optimized. The Field Operational Test, or FOT, is a powerful evaluation method that can be used to answer these and other questions. Although large-scale FOTs conducted in the past have yielded important knowledge, there is scope for improving the design and implementation of them. In this paper a checklist is presented that outlines the critical steps and considerations involved in successfully planning and implementing a FOT. It derives from work previously undertaken in the European Commission (EC)-funded FESTA (Field opErational teSt support Action) project.

Analysis of Climb Trajectory Modeling for Separation Assurance Automation

Scipedia content — Tue, 02 Feb 2021 00:14:06 +0100

Climb prediction uncertainty is a major source of error in trajectory-based automation for air traffic management. In this study, the performance of a trajectory-based automated separation assurance system is analyzed under different levels of uncertainty in laboratory simulations to investigate its robustness to climb uncertainty. Results indicate that this fully automated system can successfully detect and resolve 99% of conflicts in the high-altitude sectors of Fort Worth Center during 3-20 minutes prior to first loss of separation under near-zero uncertainty. Trajectory uncertainty was then incorporated into the simulation in the form of weight uncertainty. System performance remained unchanged for these scenarios when weight uncertainties ranged ± 10%. However, performance declined to 87% when this range was expanded to ± 20%.

4-D Perturbation Analysis of Conflict Scenarios

Scipedia content — Tue, 02 Feb 2021 00:13:44 +0100

*A method is presented for perturbing air traffic scenarios and analyzing the resulting conflicts. The perturbations consist of a specified range of spatial and temporal modifications of the trajectories, and the analysis identifies all possible conflicts within the perturbation range. This method enables new scenarios to be generated for simulation testing of air traffic management tools and concepts. Some potential applications are presented, such as the analysis of the sensitivity of a scenario to temporal perturbations, the prediction of areas of high-density traffic, and the estimation of conflict probabilities for long-range (one-to-six hour) trajectory predictions. A study of discrete and interpolated conflict detection accuracy as a function of the surveillance-sampling period is also presented, showing that interpolated detection halves the number missed conflicts when compare to discrete detection and that accuracy degrades significantly when the sampling period exceeds twelve seconds. I. Introduction To effectively cope with projected increased traffic demands on the National Airspace System (NAS), new operational concepts and tools are being researched and developed. The development must ensure that aircraft are separated at or above safe separation minima. When aircraft are predicted to violate the prescribed separation minima, they are said to be in conflict. Concepts that resolve conflicts and maintain safe separation are called separation assurance (SA) concepts. The effectiveness of SA concepts is evaluated through simulation using traffic scenarios that have conflicting flights. SA concepts need to be robust, so simulations need to be performed over a wide variety of scenarios containing diverse collections of conflicts. One can generate traffic scenarios containing conflicts from scratch, 1 but a more common practice is to generate scenarios by perturbing recorded scenarios derived from field observations or high-fidelity flight simulations. 2-4 This process shifts the original scenario trajectories in space and/or time to generate new scenarios with alternate sets of conflicts. These scenarios then drive simulations or exercise SA algorithms. Unfortunately, NAS simulations, especially ones involving live participants, can be extremely costly and time consuming. Therefore, efficiently identifying scenarios that have interesting or challenging sets of conflicts is desirable. Manual perturbations can be used to achieve this, but they risk not adequately representing the full range of potential scenarios. A more conservative approach is to generate a large number of randomly perturbed scenarios and then to evaluate them to detect conflicts. As the number of random perturbations increases, more potential conflicts are identified, but it is an extremely

Simulation Driven Experiment Control in Driver Assistance Assessment

Scipedia content — Mon, 01 Feb 2021 23:57:00 +0100

Embedded systems technologies and advances in micro electronics have accelerated the evolution of driver assistance systems towards more driving safety, comfort, entertainment and wayfinding. With the technological and quality progress, however, also goes the growing of interaction complexity, information overload, and intricate interface designs. Assessing interaction designs for in-car assistance services is an emerging and vibrant field of research. To avoid situations of possibly fatal danger when assessing driver assistance services in real driving situations, we propose trace-driven simulation to steer the experiments with users in a automotive driving simulator. Based on our own developments of driver assistance systems involving the sense of touch, i.e. exploiting haptics as a communication channel in vehicle-to-driver interactions, we demonstrate how pre-recorded traces of driving situations can control user studies. Our experiments show, that simulated driving journeys is a viable alternative to the more hazardous "on-the-road" user studies. With respect to haptics as an additional channel of communication we find that vibro-tactile stimuli are a promising means to raise driver attention when the visual and auditive channels fail due to overload.

Passenger intermodal terminal stations: role and infrastructure

Scipedia content — Mon, 01 Feb 2021 23:51:36 +0100

This paper on passenger intermodal terminal stations is from the proceedings of 14th International Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. The authors focus on the role of public transportation, utilizing various modes of transit, as a solution to the growing need for relieving traffic congestion, the associated environmental problems and the continuously increasing cost for transferring passengers. They suggest the concept of a transportation "station" as the key link in a chain of the different modes; the transitional stations should offer the essential conditions of comfort and security for the connection of the different means of transport.

New HMI concept for motorcycles: The Saferider approach

Scipedia content — Mon, 01 Feb 2021 23:42:12 +0100

For more than one decade the European Commission has been focusing on the enhancement of road safety by funding research on Advanced Driver Assistance Systems (ADAS) and Intelligent Vehicle Information Systems (IVIS) in the field of automotive. However, the application of such technologies in Powered-Two-Wheelers (PTW) is currently lacking behind. While in the automotive sector extended knowledge has been generated also on the Human-Machine Interface (HMI) for ADAS and IVIS this does by far not apply for the PTW sector. This paper presents the SAFERIDER (Advanced telematics for enhancing the safety and comfort of motorcycle riders) project outline and focuses on the new HMI concept and haptic interface devices that are developed within the project.

Case report of overcrowded buses and a possible solution

Scipedia content — Mon, 01 Feb 2021 23:36:19 +0100

This paper on overcrowded buses is from the proceedings of 14th International Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. The author presents a case report of overcrowded buses and offers a possible solution using project management methodology. The first part of the paper presents the case report scenario of Braga, the third-largest city in Portugal and one that has experienced a 25% population growth in the past three decades. The author then describes how project management is often used in huge projects, with lots of interlocutors, high quality and environmental standards and higher budgets, but in smaller projects, may be considered a waste of resources. The author contends that, with adjustments, project management methodology could be useful in small projects. A task plan is used to organize the tasks of the small project, including working team dimensions, deadlines and budget.

Market analysis for shifting of goods from road to rail by means of combined transport in Germany: Presentation held at Young reseachers seminar 2009 of European Conference of Transport Research Institutes-ECTRI, 3.-5.6.2009, Torino, Italy

Scipedia content — Mon, 01 Feb 2021 23:21:24 +0100

The current discussion about the necessity of worldwide CO2 reduction awakens interest of a growing number of companies to check the train as alternative to the truck transport. Additionally a broad public interest and programmes of the governments support the shift from road to rail. There are a lot of general discussions about the need and the advantages of the train transport. But it isn´t said, how much shiftable potential there exist. One point is, that most of the companies do not have an own railway access and have to use special terminals. This transport of containerised goods to the special terminals by truck and then by train to another terminal is called combined transport (CT). Another point is that some goods and production concepts have economical and technical requirements, the combined transport cannot fulfil. Thus, this paper first analyses and identifies which kinds of goods can be shifted from a tech-nical point of view and which kinds of transports are realistic and attractive to shift from an economical point of view. The goods are categorised in primary, secondary and tertiary potential to shift. Secondly, this paper elaborates on this basis, how much maximum potential that means for the market, and illustrates it in the case of Germany. The analysis concludes, that in the case of Germany the maximum shifting potential results in 10% of the current truck transports.

Studying NextGen Concepts with the Multi-Aircraft Control System

Scipedia content — Mon, 01 Feb 2021 22:50:36 +0100

This paper describes new functionality recently added to the Multi Aircraft Control System (MACS) software. MACS is a comprehensive research platfo rm used in the Airspace Operations Laboratory (AOL) at NASA Ames Research Center 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 exam ining distributed air traffic operations in complex air/ground environments. MACS was originally developed to rapidly prototype new interfaces, displays, tools and operational concepts for managing air traffic and evaluating them from different perspectiv es. New capabilities have been added to MACS to better investigate NextGen concepts, including the capability to simulate airspaces that span multiple Air Route Traffic Control Centers (ARTCCs) , and powerful tools for creating and editing custom traffic a nd weather scenarios.

Interdomain traffic engineering in a locator/identifier separation context

Scipedia content — Mon, 01 Feb 2021 22:45:01 +0100

The Routing Research Group (RRG) of the Internet Research Task Force (IRTF) is currently discussing several architectural solutions to build an interdomain routing architecture that scales better than the existing one. The solutions family currently being discussed concerns the addresses separation into locators and identifiers, LISP being one of them. Such a separation provides opportunities in terms of traffic engineering. In this paper, we propose an open and flexible solution that allows an ISP using identifier/locator separation to engineer its interdomain traffic. Our solution relies on the utilization of a service that transparently ranks paths using cost functions. We implement a prototype server and demonstrate its benefits in a LISP testbed. Peer reviewed

Semi-autonomous reference data generation for perception performance evaluation

Scipedia content — Mon, 01 Feb 2021 22:34:29 +0100

In the development phase of perception systems (e.g. for advanced driver assistance systems) general interest is pointing towards the performance of the respective detection and tracking algorithms. One common way to evaluate such systems relies on simulated data which is used as a reference. We present a semi-autonomous method, which allows the extraction of reference data from sensor recordings (including data at least from a camera and a distance measuring sensor device). Furthermore, we show how to combine these reference data with the output from the object detection system and how to derive performance statistics (detection and miss rates) of the system. As the generated reference information can be stored along with the sensor recordings, this method also facilitates the comparison of different software versions or algorithm parameters.

Detection of Traffic Congestion in Optical Remote Sensing Imagery

Scipedia content — Mon, 01 Feb 2021 22:32:28 +0100

new approach for the traffic congestion detection in time series of optical digital camera images is proposed. It is well suited to derive various traffic parameters such as vehicle density, average vehicle velocity, beginning and end of congestion, length of congestion or for other traffic monitoring applications. The method is based on the vehicle detection on the road segment by change detection between two images with a short time lag, the usage of a priori information such as road data base, vehicle sizes and road parameters and a simple linear traffic model based on the spacing between vehicles. The estimated velocity profiles for experimental data acquired by airborne optical remote sensing sensor - 3 K camera system - coincide quite well with the reference measurements.

Estimation of Air Traffic Delay Using Three Dimensional Weather Information

Scipedia content — Mon, 01 Feb 2021 22:23:37 +0100

This paper describes a weather-impacted traffic index based on three-dimensional weather information and applies it to air traffic delay estimation. The weather-impacted traffic indices were generated using the high-resolution Corridor Integrated Weather System, which provides accurate, automated and high update rate information on both convective weather location and echo tops. In contrast to other methods, the new index discounts an aircraft if it can fly over the weather-impacted area safely, thus incurring no delay. The index was used as an hourly input for various National Airspace System delay estimation models. The models used traffic and weather data from June 2007 and were validated with data from July 2007. Using the index with echo tops improves the delay estimates by two percent.

Integration of an Aggregate Flow Model with a Traffic Flow Simulator

Scipedia content — Mon, 01 Feb 2021 21:44:36 +0100

This paper describes a research and integration effort to develop computational tools to assess the performance of the National Airspace System (NAS). The problem of interest is focused on the en route airspace and how restrictions to aircraft movement are applied by air traffic controllers and traffic managers in response to demand overages or capacity shortfalls in sectors of airspace. To estimate and assess the efficiency of air traffic control responses, we apply the Large-capacity Cell Transmission Model (CTM(L)), which models the airspace system and its capacity constraints as a linear time invariant dynamical system, in which the state is a vector of aggregate aircraft counts. A mixed integer program is solved to minimize the control and delay of aircraft. We describe the integration of CTM(L) with NASA’s Future ATM Concepts Evaluation Tool (FACET). Using delay predictions, system metrics, and a visualization of the aggregated network, we apply the integrated environment to analyze and propose Traffic Flow Management (TFM) solutions for weather disturbances.

Evaluation of Rail Test Frequencies Using Risk Analysis

Scipedia content — Mon, 01 Feb 2021 21:35:58 +0100

Several industries now use risk analysis to develop inspection programs to ensure acceptable mechanical integrity and reliability. These industries include nuclear and electric power generation, oil refining, gas processing, onshore and offshore exploration and production, chemical processing, and pipelines. Risk analysis may also be used as a decision-making tool in the railroad industry to develop systematic improvements in track maintenance and inspection strategies. In the course of conducting research in support of the Federal Railroad Administration, a Monte Carlo risk assessment model has been developed to simulate certain aspects of rail inspection (also referred to as rail testing) to find and remove defects that may grow to sufficient size to cause rail failures. In this paper, the model is used to examine the relationship between the occurrence of rail failures and various operational factors. These operational factors include rail size, average axle loading, and inspection frequency. In addition, the risk assessment model is used to evaluate an alternative rail testing concept in which detector cars would conduct inspections at speeds higher than those used in current practice.

Comparison of quasi-regular composite-star and multi-hop structures for core networks

Scipedia content — Mon, 01 Feb 2021 21:23:12 +0100

novel composite-star architecture, nicknamed the Petaweb, has been recently proposed for high capacity optical core networks. Its topologic structure is such that electronic edge nodes are always connected to each other through a single core switch, and that the core switches are disconnected. The aim is to simplify the traffic engineering and the upgradeability of core networks. In its regular form, this architecture suffers from high fiber cost and low utilization. A recent work tackles the problem of directly designing a quasi-regular composite-star structure, showing that the network cost can get more than halved and that the resources utilization can be significantly improved. In this paper, we compare the quasi-regular composite-star structure to classical irregular multi-hop structures. We show that increasing the weight of a propagation delay virtual cost in the design dimensioning objective function, multi-hop core networks tend to assume a quasi-regular composite-star like topologic structure, with a few core fibers. This suggests that such an architecture is the natural solution whether length-dependent additive costs are considered as part of the design dimensioning objective.

Current Airspace Configuration Practices and Their Implications for Future Airspace Concepts

Scipedia content — Mon, 01 Feb 2021 21:10:42 +0100

The Next Generation Air Transportation System (NextGen) envisions a flexible, dynamic airspace structure that is better able to adapt to changing traffic conditions than today’s rigid system of airways and airspace sectors. However, to develop effective NextGen airspace concepts, a thorough understanding is needed of current airspace configuration practices, and of the constraints that influence airspace design. This paper describes current-day airspace configuration practices and the factors that affect the partitioning of today’s airspace. These observations are based on site visits to air traffic control facilities and subject matter expert critiques of potential future airspace designs. The implications that today’s airspace configuration practices have for NextGen airspace concepts are then discussed.

Using context and behavioral patterns for intelligent traffic management

Scipedia content — Mon, 01 Feb 2021 20:58:45 +0100

eer-reviewed The integration of information and communications technologies across existing transportation infrastructure, systems and vehicles is fundamental to reducing traffic congestion, to improving driver safety, and to improving traveler experiences. Central to such intelligent traffic management are techniques and algorithms that are capable of analyzing the wealth of available contextual sensor data in ???real time???. Initial existing approaches tend to apply probability models and inference techniques to optimize traffic flow but fail to take into account certain aspects of human behavior that can affect the flow of traffic, such as patterns in human travel behavior. In this paper we explore how vehicle context information can be combined with the behavioral patterns of travelers to facilitate and improve intelligent traffic management. We present services for deriving reports on vehicle journeys that assist in the analysis of route performance, for enabling passengers to have remote access to real-time route performance information, and for the observation, learning, and utilization of human travel behavior patterns. These services provide essential traffic analysis information that is ultimately expected to lead to further improvements in intelligent traffic management, which aims at easing the flow of traffic in urban and suburban environments.

Rapid Prototyping of IESTA: A Platform to Evaluate Innovative Air Transport Concepts

Scipedia content — Mon, 01 Feb 2021 20:43:31 +0100

HE European Airspace is becoming more and more congested as traffic is forecast to grow steadily over the next 20 years and beyond. To meet the challenge of sustainable growth of Air Transport Management in Europe, an Advisory Council for Aeronautics Research in Europe (ACARE) was launched in June 2001. ACARE's main focus is to establish and carry forward a Strategic Research Agenda (SRA 1/2) that will influence all European stakeholders in the planning of research programs, particularly national and EU programs, in line with the Vision 2020 and the goals it identifies. Among these programs, SESAR (Single European Sky ATM Research) and its various phases (from Definition to Development and ultimately Deployment) has the ambition to face the lack of commitment from a part of the Stakeholders or from deciders in previous initiatives. The Definition Phase, jointly funded by EUROCONTROL and the European Commission, will deliver a European ATM Master Plan based on future aviation requirements, and will identify the actions needed to achieve the objectives of SESAR. At the European level, other programs are strongly linked with SESAR, including the Joint Technology Initiatives (JTI) a new instrument provided by the European Seventh Framework Programme, to support research of long duration. One of those initiatives, called CLEAN SKY, will create various technology demonstrators, including flight test vehicles that will be essential for successful market introduction. Research into the future of the air transportation system critically depends upon the ability to evaluate the effects of the revolutionary candidate concepts across the entire air transportation system. The testing of these concepts through modeling and simulation can provide useful information on improvements on system capacity/safety and related environmental impact. In this evolutionary European context, the French Aerospace Laboratory (ONERA) is carrying out an ambitious program (IESTA) to design a modeling and simulation infrastructure able of evaluating innovative air transport concepts. This platform has to be considered as a mean to help harmonization of panEuropean assessment tools for innovative research on future Air Transport Systems (ATS). This paper firstly introduces organizational issues of the IESTA Program focusing on expected benefits of the underlying approach from the customer's point of view. We then discuss system architectural issues of the platform as well as technological features. Finally, we give a detailed presentation of a rapid prototype of the first version

Precise exception handling in discontinuous control flow scenarios for area-constrained systems

Scipedia content — Mon, 01 Feb 2021 20:43:01 +0100

Exception handling is one of the most complicated issues in pipelined processors. Several incomplete instructions are in process in the pipeline at any instant in time, and an exception may cause a state change of the processor (Hennessy and Patterson, 2002) at any such instant. Prior research efforts have proposed mechanisms for precise exception handling, but it is difficult to achieve precise exception handling in minimal area as required by embedded and processing-in-memory systems. This paper presents a correct and efficient exception handling scheme with a modest hardware resource. The presented idea maintains precise exception handling in the case of discrete control flow and has been implemented in 90 nm technology.

Performance comparison of multi-domain routing schemes in GMPLS networks with BGP

Scipedia content — Mon, 01 Feb 2021 20:36:16 +0100

We compare an enhancement of the BGP protocol for TE support in GMPLS networks with a simple TE extension of BGP in terms of signaling overhead and connection blocking ratio. Our results show increased performance of the enhanced BGP.

Initial Study of Controller/Automation Integration for NextGen Separation Assurance

Scipedia content — Mon, 01 Feb 2021 20:27:42 +0100

This paper describes an initial human-in-the-loop part-task study on service providerbased automated separation assurance for the Next Generation Air Transportation System (NextGen). The study varied levels of trajectory-based separation assurance automation from manual trial planning to fully automated conflict resolution over 1x, 2x and 3x traffic densities. The experiment was conducted in the Airspace Operations Laboratory at NASA Ames Research Center in August 2007. In this study envisioned trajectory based operations for the NextGen were simulated. The ground-side automation was responsible for conflict detection. Four recently retired air traffic controllers and five aviation knowledgeable students participated and were responsible for resolving potential conflicts between aircraft with varying levels of automation. Two combined sectors engaged participants in solving conflicts between an average of 30 (1x), 60 (2x), and 90 (3x) aircraft during the 30 minute long simulation runs, resulting in approximately 6 (1x), 42 (2x) and 90 (3x) conflicts per run. The within subjects design gave operators access to a fast manual trial planning function in half the human-in-the-loop runs. During the other half of the runs participants could also interact with the advanced airspace concepts’ conflict resolution algorithm developed at NASA Ames Research Center. The controllers could use the algorithm to request a conflict resolution trajectory and uplink it unchanged, modify the resolution trajectory using the trial planner and then uplink it, or cancel the modification. The analysis shows that in the simulated part-task setting the 2x density was very manageable and adequate for the interactive mode and was somewhat manageable with a manual trial planner. 3x density was somewhat manageable interactively, but would not pass the “spill your coffee” test. 3x density was unmanageable using the trial planning function alone and resulted in many separation violations. Objective and subjective data indicate that the conflict resolution automation was highly acceptable across traffic levels and provided efficient trajectory changes at high traffic densities. The conflict resolution automation reduced the average and the peak workload significantly. In this paper the problem, method, and key findings will be presented. This research is an initial step towards addressing the challenges associated with human/system integration for ground-based NextGen separation assurance and was funded by the Separation Assurance element of NASA’s Next Generation Air Transportation – Airspace Project.

The Need of Intelligent Driver Training Systems for Road Safety

Scipedia content — Mon, 01 Feb 2021 20:25:18 +0100

utomobiles have deeply impacted the way in which people travel but they have also caused a number of deaths and injury due to crashes. Driver inattention, inexperience, poor judgment and/or fatigue etc., are the major contributing factors in crashes. In order to address these complex issues, scientists have developed a number of technological systems ranging from anti-lock braking system (ABS), early warning systems to complete autonomous driving solutions. Driverpsilas driving competencies also play a vital role in judging the road environment and reacting in-time to avoid any possible collision. Therefore driverpsilas perceptual and motor skills remain a key factor impacting on-road safety. Currently, there is a need for researchers to develop and evaluate intelligent transport systems (ITS) that assess driving competencies. These tools should be designed to help driver instructors and drivers to accurately evaluate the driving behaviour. This paper outlines a vision for future research in the area of intelligent driver training systems for enhancing road safety and also presents preliminary implementation.

ARMA(1,1) modeling of Quake4 Server to client game traffic

Scipedia content — Mon, 01 Feb 2021 20:19:06 +0100

Modeling traffic generated by Internet based multiplayer computer games has attracted a great deal of attention in the past few years. In part this has been driven by a need to simulate correctly the network impact of highly interactive online game genres such as the first person shooter (FPS). Packet size distributions and autocorrelation models are important elements in the creation of realistic traffic generators for network simulators such as ns-2 and OMNET++. In this paper we show that ARMA(1,1) models capture the time series behaviour of Quake4 game traffic well. We also show that the random component of the ARMA models (the innovations) have distributions that appear to change little as the number of players increases.

An agent oriented analysis and modeling of airborne capabilities for trajectory based operations

Scipedia content — Mon, 01 Feb 2021 19:28:26 +0100

Current and future air traffic is requiring new procedures and systems to achieve a greater automation of air-traffic operations. Particular difficulty presents the automation of arrival air-traffic operations in terminal areas due to aircraft speeds and environment variability into a delimited airspace where multiple aircraft converge. Several projects have proposed guidelines to implement new operational concepts as well as airborne and ground systems to carry out corresponding procedures. Developing procedures and systems are closely related. Therefore, usually it requires to analyze and to design them in a combined manner. In this paper we present an agent-oriented analysis and modeling of airborne systems capabilities to perform automated arrival and approach procedures based on user preference trajectories. A detailed architecture model of airborne capabilities is achieved through a methodological analysis of an arrival traffic scenario within the trajectory based operations paradigm.

Document type: Conference object

Customization of application specific heterogeneous multi-pipeline processors

Scipedia content — Mon, 01 Feb 2021 16:29:37 +0100

In this paper we propose application specific instruction set processors with heterogeneous multiple pipelines to efficiently exploit the available parallelism at instruction level. We have developed a design system based on the Thumb processor architecture. Given an application specified in C language, the design system can generate a processor with a number of pipelines specifically suitable to the application, and the parallel code associated with the processor. Each pipeline in such a processor is customized, and implements its own special instruction set so that the instructions can be executed in parallel with low hardware overhead. Our simulations and experiments with a group of benchmarks, largely from Mibench suite, show that on average, 77% performance improvement can be achieved compared to a single pipeline ASIP, with the overheads of 49% on area, 51% on leakage power, 17% on switching activity, and 69% on code size.

A Tool for Creating and Parallelizing Bioinformatics Pipelines

Scipedia content — Mon, 01 Feb 2021 15:51:27 +0100

Bioinformatics pipelines enable life scientists to effectively analyze biological data through automated multi-step processes constructed by individual programs and databases. The huge amount of data and time consuming computations require effectively parallelized pipelines to provide results within a reasonable time. To reduce researchers' programming burden for pipeline creation and parallelization, we developed the bioinformatics pipeline generation and parallelization toolkit (BioGent). A user needs only to create a pipeline definition file that describes the data processing sequence and input/output files. A program termed schedpipe in the BioGent toolkit takes the definition file and executes the designed procedure. Schedpipe automatically parallelizes the pipeline execution by performing independent data processing steps on multiple CPUs, and by decomposing big datasets into small chunks and processing them in parallel. Schedpipe controls program execution on multiple CPUs through a simple application programming interface (API) of the Parallel Job Manager (PJM) library. As a part of the BioGent toolkit, PJM was developed to effectively launch and monitor programs on multiple CPUs using a message passing interface (MPI) protocol. The PJM API can also be used to parallelize other serial programs. A demonstration using PJM for parallelization shows 10% to 50% savings in time compared to an indigenous parallelization through a batch queuing system.

Banverket capacity consumption, congested infrastructure and traffic simulation with Railsys

Scipedia content — Fri, 29 Jan 2021 00:58:43 +0100

The capacity consumption in the Swedish network is high. Banverket (Swedish Rail Administration) declared Stockholm congested in April 2007. In October 2007 the lines Olskroken–Savedalen and Iggesund–Sundsvall were declared congested due to conflicts between different traffic operators during the capacity allocation process. Each year since 2001 Banverket has been calculating the capacity consumption for the Swedish network. It has been done manually. For studying capacity measures timetable analysis with Trainplan or traffic simulations with Railsys are made. Capacity measures are normally infrastructure investments, timetable alternatives or punctuality. For traffic simulations with Railsys, Banverket and KTH (Royal Institute of Technology, Stockholm) have established a Swedish Railsys user-group. This user-group is working with standardization for using Railsys in Sweden. There is a small consultant market for traffic simulations in Sweden. In Trainplan the running times are produced by the software tools Tigris – PcGTP.

Modified Bezier curve for 4D reference trajectory definition under flight profile constraint

Scipedia content — Fri, 29 Jan 2021 00:49:00 +0100

International audience; The task of establishing properly spaced landing sequences is quite demanding for air traffic controllers in heavy traffic conditions. Indeed, air traffic controllers combine two or more streams into a single stream before landing by means of radar vectoring and speed instructions. This high level task of sequencing aircraft is not currently communicated to the pilot. Instead, controller translate it into clearances to the pilot, typically radar vectoring and speed instructions. In this paper, the task of merging an aircraft over a specified meter fix is addressed through a novel ?Set Reference Path? procedure in which the air traffic controller may clear an aircraft to merge at a specified meter fix at a given time. This paper focuses on the definition of a reference path for time-based operations at meter fix. It includes path stretching operations, which occur when the aircraft is predicted to overfly too early a meter fix with respect to other traffic flow constraints. This paper presents a new approach to generate a reference path with length and endpoint constraints based on modified Bezier curves. Compared to reference trajectories based on straight lines and circle arcs, which are usual in the aviation community, the proposed approach allows for smooth control cues and avoids the scheduling between straight lines and circle arcs segments. The proposed design is followed by illustrative examples which show the effectiveness of the proposed approach.

Combining Airspace Sectors for the Efficient Use of Air Traffic Control Resources

Scipedia content — Fri, 29 Jan 2021 00:43:15 +0100

greedy heuristic algorithm for combining under-utilized airspace sectors to conserve air trac control resources is suggested and analyzed. Simulations using historical air trac data suggest that systematically combining under-utilized airspace sectors within centers can lead to signicantly fewer sectors and therefore a more ecient utilization of air trac control resources. The eciency gains are more modest when sectors are only allowed to combine with sectors in the same controller area of specialization. Parameters can be adjusted to ensure that this approach to combining sectors works well with operational procedures as well as to trade o eciency and the likelihood of sectors exceeding their capacity. Quantitative analyses show that the likelihood of sectors exceeding their capacities can be decreased eectively without signicant sacrices of eciency gains by changing the minimum capacity gap parameter.

Convergence of day-to-day traffic flow dynamics under tradable bottleneck permits

Scipedia content — Fri, 29 Jan 2021 00:42:44 +0100

This paper on traffic flow and bottle neck permits is from the proceedings of 14th international Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. The authors describe “tradable bottleneck permits” as a new transportation demand management scheme and discuss how they could be used to improve the efficiency for a general traffic network. The goal is to achieve a socially optimal state in which the total transportation cost is minimized by the decentralized behavior of agents. The authors discuss the microbehavior of the agents, the tatonnement process used for trading markets for the permits, the day-to-day dynamics of aggregated traffic flows and permit prices, and the macrodynamics by which the mean dynamics of the aggregated variables (flows and permit prices) converge to a socially optimal state. For the agents' behavior, the study used the best response model that is popular in evolutionary game theory.

Catchment areas for public transport

Scipedia content — Fri, 29 Jan 2021 00:26:59 +0100

This paper on catchment areas used for public transport is from the proceedings of 14th International Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. The authors explain that, in the planning of public transport, the catchment areas of stops are often included to estimate the potential number of travelers. They describe different approaches to GIS-based catchment area analyses, including the Circular Buffer approach which is the fundamental, but also the simplest approach; the Service Area approach, which is based on searches in road networks, represents the actual feeder routes, and is a more detailed approach; and the Service Area approach, which can be refined by adding additional resistance to certain points in the road network, e.g. stairways. The authors illustrate differences between the Circular Buffer approach and the Service Area approach and compare the sizes of the resulting catchment areas. One case example illustrates the strength of the Service Area approach and the impact on the catchment area when adding additional time resistance for the crossing of stairways. Another case example illustrates how the additional time resistance in stairways affects the catchment area of an underground station compared to a ground-level station. The benefits of catchment area analyses include improved planning of stops on a new line by calculating travel potential along the line; the prevention of inaccessible areas from being included in the catchment area; and the allowance of detours in feeder routes to/from stations. The authors conclude that GIS-based catchment area analyses are a beneficial multiple decision support tool for the planning of public transport where the level of detail can be suited to the purpose.

Prototype flight management capabilities to explore temporal RNP concepts

Scipedia content — Fri, 29 Jan 2021 00:19:16 +0100

Next generation air transportation system (NextGen) concepts of operation may require aircraft to fly planned trajectories in four dimensions - three spatial dimensions and time. A prototype 4D flight management capability is being developed by NASA to facilitate the development of these concepts. New trajectory generation functions extend todaypsilas flight management system (FMS) capabilities that meet a single required time of arrival (RTA) to trajectory solutions that comply with multiple RTA constraints. When a solution is not possible, a constraint management capability relaxes constraints to achieve a trajectory solution that meets the most important constraints as specified by candidate NextGen concepts. New flight guidance functions provide continuous guidance to the aircraftpsilas flight control system to enable it to fly specified 4D trajectories. Guidance options developed for research investigations include a moving time window with varying tolerances that are a function of proximity to imposed constraints, and guidance that recalculates the aircraftpsilas planned trajectory as a function of the estimation of current compliance. Compliance tolerances are related to required navigation performance (RNP) through the extension of existing RNP concepts for lateral containment. A conceptual temporal RNP implementation and prototype display symbology are proposed.

A multiple criteria, measurement-based admission control mechanism for Self-Aware Networks

Scipedia content — Fri, 29 Jan 2021 00:16:01 +0100

High demand and network congestion, can prevent multimedia applications and users from obtaining the network service they require for a successful operation. A way to control traffic congestion and satisfy all users' QoS requirements, without overprovisioning, is admission control (AC). This work presents a measurement-based AC mechanism, which improves the performance of a self-aware network (SAN) (E. Gelenbe et al., 2004) and provides QoS throughout the lifetime of all connections. Our algorithm is a multiple criteria AC algorithm, where each user can specify the QoS metrics that interest him/her. Our scheme which decides whether a new call should be allowed to enter the network based on measurements of the QoS metrics on each link of the network before and after the transmission of probe packets. The decision is based on a novel algebra of QoS metrics, inspired by Warshal's algorithm, that searches whether there is a feasible path to accommodate the new flow with out affecting the existing users. Our algorithm and the underlying mathematical principles was briefly described and we present experimental results, conducted in a large laboratory test-bed, under highly congested circumstances.

A New Meta-method for Graph Partitioning

Scipedia content — Fri, 29 Jan 2021 00:15:13 +0100

In this paper, a new meta-method based on the physical nuclear process is presented. This meta-method called Fusion-Fission is applied to the two different class of graph partitioning problems. This paper presents results found by this method in comparison with results of classical methods for an air traffic management problem, an image segmentation problem and applied to classical benchmarks. All of these applications of the Fusion-Fission method are successful and the results found by this method outperform state-of-the-art graph partitioning packages both on classical benchmarks and on the air traffic management problem.

Usefulness and effectiveness of HW and SW protection mechanisms in a processor-based system

Scipedia content — Thu, 28 Jan 2021 23:52:34 +0100

ISBN : 978-1-4244-2182-4; International audience; Fault-injection based dependability analysis has proved to be an efficient mean to predict the behavior of a circuit in presence of faults. Emulation-based approaches enable fast and flexible analyses of significant designs such as processors running significant application software. This paper presents the results obtained with an encryption application and questions the usefulness and the effectiveness of detection mechanisms in both hardware and software.

Interior design and accessibility aspects of the Superbus

Scipedia content — Thu, 28 Jan 2021 23:39:59 +0100

The Superbus (Fig.1) is a new public transport vehicle designed for comfortable, flexible and sustainable transportation. The Superbus, which drives at 250 km/h cruising speed on its dedicated infrastructures (the supertrack) and at conventional speed on existing roads, is safe, sustainable, and able to transport passengers and goods from point to point. In this paper the philosophy of the vehicle will be highlighted in terms of the vehicle fundamental concepts. Then, the analysis of the required personal space design will be discussed alongside the design criteria for accessibility. Finally, the layout of the vehicle will be described in its details.

QoS multi-spanning tree for optical burst switching

Scipedia content — Thu, 28 Jan 2021 23:32:57 +0100

Optical Burst Switching (OBS) has been proposed as a future high-speed switching technology for Internet Protocol (IP) networks that may be able to efficiently utilize extremely high capacity links without the need for optical-electronic (O/E) conversions at intermediate nodes. Among its benefits of supporting statistical multiplexing at a rational granularity, OBS still gives poor performance in terms of burst drop probability. In an Optical Burst Switched network, the existence of highly congested links could lead to unacceptable performance for the entire network, causing Quality of Service (QoS) degradation to flows inserted into the network. In this paper we propose a Multi-Spanning Tree architecture that improves QoS management by increasing the efficiency in the wavelength assignment process. The new protocol uses wavelength spanning trees on demand depending on the QoS constraints demanded by inserted traffics. Moreover, the protocol avoids burst overlapping on each edge of the spanning trees, while at the same time, permitting the reutilization of lambda assignments between nodes contained in the same branch. Therefore, the protocol allows traffic aggregation from many nodes into a single branch, improving efficiency and link utilization. We take a traffic engineering approach to branch selection with the objective of balancing the traffic across the network links to reduce congestion and to improve overall performance. In this paper, the architecture, the design of the protocol and some simulation results are presented.

Peer Reviewed

A multi-mode sensing system for corrosion detection using piezoelectric wafer active sensors

Scipedia content — Thu, 28 Jan 2021 23:18:20 +0100

BSTRACT As an emerging technology for in-situ damage detection and nondestructive evaluation, structural health monitoring with active sensors (active SHM) plays as a promising candidate for the pipeline inspection and diagnosis. Piezoelectric wafer active sensor (PWAS), as an active sensing device, can be permanently attached to the structure to interrogate it at will and can operate in propagating wave mode or electromechanical impedance mode. Its small size and low cost (about ~ $10 each) make itself a potentia l and unique technology for in-situ SHM application. The objective of the research in this paper is to develop a permanently installed in-situ multi-mode sensing system for the corrosion monitoring and prediction of critical pipeline systems. Such a system is used during in-service period, recording and monitoring the changes of the pipelines over time, such as corrosion, wall thickness, etc. Having the real-time data available, maintenance strategies based on these data can then be developed to ensure a safe and le ss expensive operation of the pipeline systems. After a detailed review of PWAS SHM methods, including ultrasonic, impedance, and thickness measurement, we introduce the concept of PWAS-based multi-mode sensing approach for corrosion detection in pipelines. Particularly, we investigate the potential for using PWAS waves for in thickness mode experimentally. Finally, experiments are conducted to verify the corrosion detection ability of the PWAS network in both metallic plate and pipe in a laboratory setting. Results show successful corrosion localization in both tests. Keywords : corrosion detection, thickness, in-situ monitoring, piezoelectric wafer active sensor, PWAS, Lamb wave

A review of automotive infrared pedestrian detection techniques

Scipedia content — Thu, 28 Jan 2021 23:18:05 +0100

In automotive design, the issue of safety remains a growing priority. Recently the focus has extended beyond the occupants of the vehicle and has turned towards other vulnerable road users (VRU). Simple night vision systems have already become an important safety feature in modern high end automobiles. The next generation of advanced driver assistance systems will automate the detection of VRUs, to improve safety further by not distracting the driver's attention from the road ahead, and even identifying dangerous situations where the driver may not. This paper presents a review of the state of the art image processing techniques for automatic detection and classification of VRUs in automotive far infrared imagery.

On hybrid-fuzzy classifier design: An empirical modeling scenario for corrosion detection in gas pipelines

Scipedia content — Thu, 28 Jan 2021 22:48:18 +0100

In this paper, a customized Fuzzy Inference System is presented to classify the corrosion and distinguish it from the geometric defects or normal state of the steel pipes used in gas/petroleum industry. The presented strategy is hybrid in the sense that it utilizes both the soft computing as well as conventional parametric modeling through Hinfin optimization methods. An experimental strategy is first outlined through which the necessary data is collected as A-scan which are the ultrasonic echoes pulses in ID. Then, using empirical modeling approach a parametric transfer function is obtained for each pulse. In this respect, each A-scan is treated as an output from a defining function when a pure metal's A-scan is used as its input. Three defining states are considered in the paper; healthy, corroded, and defective, corresponding to the healthy or very much less corroded metal, corroded metal, and metal with any artificial or other defects, respectively. Impulse responses for each of these parametric models are plotted and human heuristics is then utilized in coming up with a set of quantitative features that can be used in distinguishing these classes. This feature set is then supplied to the Fuzzy Inference system as input to be used in distinguishing various classes under study. The main contribution of this work is to elaborate the fact that corrosion modeling provides easier approach in classifying the A-scans better rather than the raw A-scan data which is more prone to noise errors and more dependent on the measuring device's parameters.

S-OSPF: A Traffic Engineering Solution for OSPF Based Best Effort Networks

Scipedia content — Thu, 28 Jan 2021 22:42:16 +0100

Open Shortest Path First (OSPF) is one of the most widely used intra-domain routing protocol. It is well known that OSPF protocol does not provide flexibility in terms of packet forwarding to achieve any network optimization objective. Because of the high cost of network assets and commercial and competitive nature of Internet service provisioning, service providers are interested in performance optimization of their networks. This helps in reducing congestion hotspots and improving resource utilization across the network, which, in turn, results in an increased revenue collection. One way of achieving this is through Traffic Engineering. Currently traffic engineering is mostly done by using MPLS. But legacy networks running OSPF would need to be upgraded to MPLS. To achieve better resource utilization without upgrading OSPF network to MPLS is a challenge. In this paper we present a simple but effective algorithm, called Smart OSPF (S-OSPF) to provide traffic engineering solution in an OSPF based best effort network. We formulate an optimization problem based on the traffic demand to minimize the maximum link utilization in the network. Routing of the traffic demand is achieved using OSPF. We have simulated S-OSPF on real networks of two service providers. Simulation results show that S- OSPF based traffic engineering solution performance very closely follows the optimal solution.

An assessment for UAS depart and approach operations

Scipedia content — Thu, 28 Jan 2021 22:16:46 +0100

Unmanned Aerial Systems (UAS) have great potential to be used in a wide variety of civil applications such as environmental applications, emergency situations, surveillance tasks and more. The development of Flight Control Systems (FCS) coupled with the availability of other Commercial Off-The Shelf (COTS) components is enabling the introduction of UAS into the civil market. The sophistication of existing FCS is also making these systems accessible to end users with little aeronautics expertise. However, much work remains to be done to deliver systems that can be properly integrated in standard aeronautical procedures used by manned aviation. In previous research advances have been proposed in the flight plan capabilities by offering semantically much richer constructs than those present in most current UAS autopilots. The introduced flight plan is organized as a set of stages, each one corresponding to a different flight phase. Each stage contains a structured collection of legs inspired by current practices in Area Navigation (RNAV). However, the most critical parts of any flight, the depart and approach operations in an integrated airspace remain mostly unexplored. This paper introduces an assessment of both operations for UAS operating in VFR and IFR modes. Problems and potential solutions are proposed, as well as an automating strategy that should greatly reduce pilot workload. Although the

Document type: Conference object

Image based estimation of pedestrian orientation for improving path prediction

Scipedia content — Thu, 28 Jan 2021 22:07:06 +0100

Pedestrian protection is an essential component of driver assistance systems. A pedestrian protection system should be able to predict the possibility of collision after detecting the pedestrian, and it is important to consider all the cues available in order to make that prediction. The direction in which the pedestrian is facing is one such cue that could be used in predicting where the pedestrian may move in future. This paper describes a novel approach to determine the pedestrianpsilas orientation using Support Vector Machine (SVM) based scheme. Instead of providing a hard decision, this scheme estimates the discrete probability distribution of the orientation. A Hidden Markov Model (HMM) is used to model the transitions between orientations over time and the orientation probabilities are integrated over time to get a more reliable estimate of orientation. Experiments showing the performance of estimating orientations are described to show the promise of the approach.

A Multi Objective Fuzzy-Based Controller for Front Differential Vehicles by Electrical Traction System on Non-Driven Wheels

Scipedia content — Thu, 28 Jan 2021 22:00:52 +0100

Using electrical machine in conventional vehicles, also called hybrid vehicles, has become a promising control scheme that enables some manners for fuel economy and driver assist for better stability. In this paper, vehicle stability control, fuel economy and driving/regeneration braking for a 4 WD hybrid vehicle is investigated by using an electrical machine on each non-driven wheels. Fourteen degree of freedom vehicle body modeling and ADVISOR power-train/electrical components model will be used for modeling. Driving/regeneration and stability enhancement are important in low and high speed respectively. The unequaled independent torques applied to the non-driven wheels provides the ability of vehicle dynamic control to assist the driver with path correction, thus enhancing cornering and straight-line stability and providing enhanced safety. So power managing between engine and electrical machines will be provided the fuel economy and regeneration in braking condition. For these goals, power management and yaw moment control will be down in low and high speed respectively by proper fuzzy controller. Finally, a series of MATLAB/SIMULINK simulation will carried out to evaluate the performance of the proposed structure.

Sustainable mobility in the city of Larissa

Scipedia content — Thu, 28 Jan 2021 21:48:01 +0100

This paper on sustainable mobility in the city of Larissa, Greece, is from the proceedings of 14th international Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. Larissa is a dynamic industrial, agricultural and cultural centre in the mainland of Greece with around 200,000 inhabitants. The author first briefly reviews the history of urban planning in Larissa, which began in the 1970s and since then has included a series of plans and studies that have been elaborated and implemented, all aiming at sustainable development, urban renaissance and sustainable mobility in the city center. Larissa uses a wide pedestrian network, as well as a less extended bike network, as an integral part of an infrastructure that connects the administrative center to the traditional, older part of the city and to the river shores zone. The author stresses that this infrastructure and framework has improved the quality of life and have had a direct positive impact on the physiognomy of the city. The author concludes with proposals of further sustainable mobility and urban transport policy for Larissa, discussing how these could be applied in towns of similar scale in the wider European area.

On performance sensitivity of urban transportation networks

Scipedia content — Thu, 28 Jan 2021 21:47:11 +0100

This paper on the performance sensitivity of urban transportation networks is from the proceedings of 14th International Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. The authors blame the continuous increase in traffic on increasing numbers of vehicles using a common infrastructure, leading to traffic congestion whenever mobility demand exceeds the infrastructure capacity. They outline a set of selection criteria to help in resource planning and in decision making, based on a sensitivity matrix computed for an a-priori chosen transportation performance index. The paper concludes with a simple case study that utilizes the proposed methodology for selecting interventions in urban transportation networks.

A comparison of the role of degraded modes of operation in the causes of accidents in rail and air traffic management

Scipedia content — Thu, 28 Jan 2021 21:33:39 +0100

Degraded modes of operation occur when technological systems fail to meet the levels of service that are expected by staff and managers. Over time, operators develop ‘work arounds’ that help them to cope with these degraded modes. This has led to a culture of ‘making do’ where co-workers try their best to maintain service provision in spite of system failures. The extent to which operators will adapt to degraded modes illustrates the flexibility and resilience of socio-technical systems. However, these adaptations and ‘work arounds’ undermine safety. A central aim of this paper is to begin to identify why teams of co-workers continue to operate safety critical systems when key elements of their infrastructure have been compromised, for example during routine maintenance. The following pages build on four case study accidents from the rail and air traffic management domains.

V2V Communications in Automotive Multi-sensor Multi-target Tracking

Scipedia content — Thu, 28 Jan 2021 21:14:06 +0100

Today's automotive sensor systems for in-vehicle based target tracking, i.e. radar, lidar, camera, are limited to a field of view which is restricted by distance, angle and line-of-sight. Future driver assistance systems such as predictive collision avoidance or situation-aware adaptive cruise control require a more complete and accurate situation awareness in order to detect hazardous and inefficient situations in time. Therefore, we introduce multi-target tracking including vehicle-2-vehicle communications as a complementing sensor for future driver assistance systems. The paper presents first simulation results of our algorithm which show promising outcomes.

The Scalability and Performance of Common Vector Solution to Generalized Label Continuity Constraint in Hybrid Optical/Packet Networks

Scipedia content — Thu, 28 Jan 2021 21:11:45 +0100

In hybrid optical/packet networks, wavelength and VLAN tag continuity along a label switched path are two common constraints. These two types of constraints, referred to as generalized label continuity constraints, have global significance in a network; namely, the label should appear only in other link- or node-disjoint paths. In considering these constraints, a solution is the common vector approach, which seeks a common available label along the path determined by CSPF without label constraints. In this paper, we provide an estimation method to compute the upper bound of the blocking probability for the above approach. We also address the scalability problem of the existing traffic engineering algorithms. We then present the simulation results corroborating with our analytical model.

Visual Longitudinal and Lateral Driving Assistance in the Head-Up Display of Cars

Scipedia content — Thu, 28 Jan 2021 21:10:00 +0100

Most car accidents occur due to longitudinal collisions or lane departure. We assume that the number of such accidents can be reduced, if the driver knows more precisely, where the car is heading and at which distance it can stop. To provide drivers with this kind of anticipation, we have developed two augmented reality based visualization schemes for longitudinal and lateral driver assistance in the head-up display (HUD) of cars. One presentation scheme indicates the braking distance by a virtual bar on the road. The second scheme adds the visualization of a drive-path between the car and the bar, zoning the entire region that the car will pass before coming to a complete halt. We have tested both schemes in a driving simulator in comparison to a baseline without visual assistance. Our results show, among other findings, that the bar is preferred, that it supports driving performance and that it does not increase mental workload.

PaCo: Probability-based path confidence prediction

Scipedia content — Thu, 28 Jan 2021 21:03:00 +0100

path confidence estimate indicates the likelihood that the processor is currently fetching correct path instructions. Accurate path confidence prediction is critical for applications like pipeline gating and confidence-based SMT fetch prioritization. Previous work in this domain uses a threshold-and-count predictor, where the number of unresolved, low-confidence branches serves as an estimate of path confidence. This approach is inaccurate since it implicitly assumes that all low-confidence branches have the same mispredict rate, and that high-confidence branches never mispredict. We propose an alternative path confidence predictor designed from first principles, called PaCo, that directly estimates the probability that the processor is on the goodpath, and considers contributions from all branches, both high and low confidence. Even though it uses only modest hardware, PaCo can estimate the processorpsilas goodpath likelihood with very high accuracy, with an RMS error of 3.8%. We show that PaCo significantly outperforms threshold-and-count predictors in pipeline gating and SMT fetch prioritization. In pipeline gating, while the best conventional predictor can reduce badpath instructions executed by 7% with a small loss in performance, PaCo can reduce bad-path instructions by 32% without any performance loss. In SMT fetch prioritization, using PaCo instead of conventional path confidence predictors improves performance by up to 23%, and 5.5% on average.

The parallelization of a highway traffic flow simulation

Scipedia content — Thu, 28 Jan 2021 20:35:59 +0100

This work implements and analyses a highway traffic flow simulation based on continuum modeling of traffic dynamics. A traffic-flow simulation was developed and mapped onto a parallel computer architecture. Two algorithms (the I-step and 2-step algorithms) to solve the simulation equations were developed and implemented. They were then tested on a Cray T3E, a 3-D toroidal mesh with very fast inter-processor communication (IPC) times. Tests with real traffic data collected from the freeway network in the metropolitan area of Minneapolis, MN were used to validate the accuracy and computation rate of the parallel simulation system. The execution time for a 24-hour traffic-flow simulation over a 15.5-mile freeway, which takes 65.7 minutes on a typical single processor computer, took only 2.39 seconds on the Cray T3E. The 2-step algorithm, whose goal is to trade off extra computation for fewer IPC's, was shown to save move than 5% on computation time. This parallel implementation has proven potential for real-time traffic engineering applications.

Advanced noise abatement departure procedures: Custom optimized departure profiles

Scipedia content — Thu, 28 Jan 2021 20:33:42 +0100

This paper presents the concept of custom optimized departure profiles, as an advanced form of noise abatement departure procedures. This concept relies on fixed routes in combination with individually optimized vertical de parture profiles. Although some environmental performance is lost by fixing the gro und track, an increase in complexity associated with free routing is eliminated as well, leading to a concept that does not seem to be incompatible with today’s Air Traffic Control pr inciples. By using a primitive form of trajectory negotiation between airline and ATC, sel ected flights can be allowed to perform an optimized departure without interfering with non-participating traffic. Apart from the concept itself, this paper also describes the depar ture profile optimization tool, which is based on a previously developed trajectory optimiza tion tool called NOISHHH. Finally -in a numerical example- a current standard ICAO-A procedure is compared with two optimized profiles for a Boeing 737 departure from Amsterdam Airport. Fuel burn, noise impact and the required time to a specified point are compared for the three departure profiles.

Elements for prioritizing between conflict resolutions in air traffic control

Scipedia content — Thu, 28 Jan 2021 20:15:19 +0100

International audience; The new Air Traffic Management concepts rely on high-precision 4-D trajectories, the predictability of which will greatly improve and result in an increase of the efficiency of decision aid tools. This will result in a reduction of air traffic controllerspsila workload through fewer interventions. However, a residual number of conflicts will remain to be managed by controllers. It would be interesting to select, each time it is possible, the conflicts to be handled by the controller rather than by the automated system. On the basis of previous studies, different traffic configurations and resolution types were identified. These were validated using a traffic sample. This validation should be considered preliminary one, due to the traffic data used (27 hours), insufficient compared to the possible sources of variation in relation to the resolution process and workload. However, the results already show some interesting information on how to allocate conflict solving in a future context, when both human and machine will share the task of solving conflicts. This may already contribute to better prioritize in conflict solving, but is mainly a plea for a comprehensive work on this question.

An evolutionary algorithm for unicast/multicast traffic engineering

Scipedia content — Thu, 28 Jan 2021 20:01:31 +0100

number of Traffic Engineering (TE) approaches have been recently proposed to improve the performance of network routing protocols, both developed over MPLS and intra-domain protocols such as OSPF. In this work, a TE approach is proposed for routing optimization in scenarios where unicast and multicast demands are simultaneously present. Evolutionary Algorithms are used as the optimization engine with overall network congestion as the objective function. The optimization aim is to reach a set of (near-)optimal weights to configure the OSPF protocol, both in its standard version and also considering the possibility of using multitopology variants. The results show that the proposed optimization approach is able to obtain networks with low congestion, even under scenarios with heavy unicast/multicast demands. This work was supported by the Portuguese Foundation for Science and Technology under project POSC/EIA/59899/2004, partially funded by FEDER.

Comparison of see-and-avoid performance in manned and remotely piloted aircraft

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

See-and-avoid is the current FAA approved method for pilots to avoid objects and other aircraft while flying in visual meteorological conditions (VMC). Although fully autonomous dasiasense-and-avoidpsila or dasiadetect-and-avoidpsila systems are in development, none are currently certified. Thus existing unmanned aerial vehicle (UAV) operations are limited to case-by-case restricted airspace or require escort by manned aircraft. Many UAVs are equipped with at least a forward-looking camera. In the transition between current technology and future fully autonomous, certified sense-and-avoid systems, it seems reasonable to require a ground-based operator to perform the see-and-avoid function. This paper discusses the flight-testing performed to establish air traffic detection ranges for low-time pilots, and for a low-cost UAV camera system. The system was evaluated to determine if it could provide the equivalent see-and-avoid performance as the tested pilots.

Tactical Conflict Resolution using Vertical Maneuvers in Enroute Airspace(ALTERNATE PAPER)

Scipedia content — Thu, 28 Jan 2021 19:59:34 +0100

This paper discusses an algorithm for computing vertical resolution maneuvers to resolve imminent air traffic conflicts in which loss of separation could occur in less than two minutes. Several procedures are used, including rejection of altitude amendments that could cause a conflict, temporary altitudes, step altitudes, and critical leveloff confirmation. These methods were tested on archived data from 100 actual operational errors, which tend to be more difficult to detect and resolve than routine conflicts. Successful resolution was achieved in simulation for 84 of them using vertical maneuvers only. Augmented altitude amendments were then added to the input files to simulate altitude amendments that should have been entered by the controller but were not, or to correct amendments to make them consistent with the pilot’s understanding. The number of successful resolutions increased to 94 of the 100 cases.

Application of self-selected pricing to the Japanese highway fee system based on the ETC

Scipedia content — Thu, 28 Jan 2021 19:49:32 +0100

This paper on self-selected pricing for highway fees is from the proceedings of 14th international Conference on Urban Transport and the Environment in the 21st Century, which was held in Malta in 2008. The author describes the electronic toll collection (ETC) commuting discount which is applied in Japan to travels of less than 100km, except in metropolitan areas. The theoretical base of this policy is that is will be a self-selecting road pricing which discriminates users on the basis of payment means, travel distance, time period, and space. The author notes that for this policy to be fully implemented, users must be presented with long-term incentives for installing ETC devices in their automobiles. The author reports on a study that applied the traditional bottleneck congestion model to the ETC commuting discount of highway fees. The results demonstrated that the self-select pricing mechanism eliminates the negative effects of granting discounts in the peak period. The conditions are based on the number of ETC users, the capacity of the bottleneck, and the length of the discounted period. The author cautions that these study results may not hold when ETC use becomes widespread and traffic congestion returns.

TIME: An Open Platform for Capturing, Processing and Delivering Transport-Related Data

Scipedia content — Thu, 28 Jan 2021 19:34:41 +0100

Road congestion and traffic-related pollution have a large, negative social and economic impact, and we believe many of these problems can be reduced through investment in monitoring, distribution and processing of traffic information. This paper outlines how our on-going work on the TIME project (transport information monitoring environment) provides a solution, using traffic sensor systems and the design and development of an open and decentralised software framework. We also discuss how we address the privacy and security implications of the increased use of sensors and data processing.

Traffic Complexity Measurement Under Higher Levels of Automation and Higher Traffic Densities

Scipedia content — Thu, 28 Jan 2021 19:22:14 +0100

n understanding of the complexity factors that affect controller workload under higher levels of automation for conflict detection and resolution and under higher traffic densities is critical for future operations. This paper examines traffic complexity variables under higher levels of automation where the human controller is still in the loop, but is being supported by advanced conflict detection and resolution automation. The study involved two conflict resolution automation modes (i.e., trial-planning automation and advisory automation) and three traffic densities (i.e., 1X, 2X and 3X). The results indicate that under the 1X traffic condition, controller workload was the lowest with advanced levels of automation. The complexity and workload increased progressively for the 2X and 3X traffic conditions. Results also showed that several variables such as horizontal proximity, aircraft density, separation criticality index, and two degrees of freedom indices appear to be relevant complexity measures for ...