Scipedia: Documents published in 2009

Energy management on board of a reduced scale hybrid automobile

Scipedia content — Mon, 01 Feb 2021 22:16:51 +0100

International audience; This paper presents a study which follows the present trend in the field of electric (or hybrid) vehicles E(H)V, having in mind that the major drawback of these last ones is the autonomy problem. Thus, by using a hybrid energy source (formed by ultracapacitors and battery) and with a proper current control (of polynomial type) one can get a good energy management which will increase the lifetime of the battery. Through numerical simulations and tests at reduced scale, the authors present a successfully energy management on board of a hybrid vehicle.

Asynchronous pipeline controller based on early acknowledgement protocol

Scipedia content — Mon, 01 Feb 2021 22:14:45 +0100

new asynchronous pipeline controller based on early acknowledgement protocol is proposed. The early acknowledgement protocol indicates acknowledgment by the falling edge of the acknowledgment signal, and thus, it can hide the overhead caused by a resetting phase of the handshake cycle. Advantage of employing the early acknowledgement protocol in a pipeline controller is demonstrated by comparing its performance with a very high-speed 2-phase pipeline controller and an ordinary 4-phase controller. The simulation results obtained in our experiment show that in a linear pipeline case with processing elements in-between the stages, our controller has performance comparable to the 2-phase controller, and outperforms the ordinarily 4-phase controller. Moreover, we have obtained interesting results in the case of a nonlinear pipeline with a Conditional Branch operation. In this case, a 2-phase controller needs to have a little complicated mechanism to handle the 2-phase operation for selecting a path, while our controller is trivial in construction similar to the ordinary 4-phase protocol controller. Due to such simplicity of the implementation, our controller has a slightly better performance compared to the 2-phase controller when each stage has a processing element.

A European Ecobono. Addressing the need of a joint solution for the European Transport System.

Scipedia content — Mon, 01 Feb 2021 22:10:30 +0100

This paper identifies weaknesses and opportunities in current Ecobono formulas (ecological bonus given to Short Sea Shipping users due to maritime transport lower externalities) using a SWOT analysis and presents an alternative European Ecobono. Among major findings we reached are the facts that weaknesses produced or inherent to current formulas as unfair competition between road carriers and budget limitation for the enforcement would be eliminated in case of applying a European alternative. The conclusion derived from the study brings out the idea that it is not possible to achieve collective European objectives by means of measures applied by individual member states.

Distributed feedback control for an Eulerian model of the National Airspace System

Scipedia content — Mon, 01 Feb 2021 22:06:45 +0100

This paper proposes an Eulerian model of traffic flows in the National Airspace System (NAS) and presents a distributed feedback control approach for managing the flows. The main contribution is the development of a model that reflects the way that air traffic controllers regulate traffic flows into their facilities, and of a feedback control approach that provides them with decision support, in a distributed manner that is consistent with the existing communication structure. The focus is on developing techniques that guarantee that the aircraft queues in each airspace sector, which are an indicator of air traffic controller workload, are kept small. It is shown that the problems of scheduling and routing aircraft flows in the NAS can be posed as the fluid approximation of a network of queues, and that under appropriate conditions, a MaxWeight policy can be used to determine a distributed feedback control law that stabilizes the system. Extensions to the problem of airport arrival/departure management, and to traffic flows that are driven by demand are also described.

Human-In-The-Loop (HITL) Simulation and Analysis of Optimized Profile Descent (OPD) Operations at Atlanta

Scipedia content — Mon, 01 Feb 2021 21:57:48 +0100

The MITRE Corporation’s Center for Advanced Aviation System Development (CAASD), under the sponsorship of the Federal Aviation Administration’s Air Traffic Organization (ATO), conducted a Human-in-the-Loop (HITL) simulation of Optimized Profile Descent (OPD) operations on the proposed DIRTY Area Navigation (RNAV) Standard Terminal Arrival (STAR) procedure into Atlanta’s Hartsfield-Jackson International Airport (ATL). The simulation, conducted at the Atlanta Terminal Radar Approach Control (TRACON) facility, assessed the workability of several alternatives for utilizing OPD operations on the DIRTY STAR. As a result of the evaluation, CAASD identified issues which would limit the use of the DIRTY STAR specifically, as well as OPDs more generally. In addition, CAASD was able to identify mitigating strategies and resolutions for many of the issues identified.

Commercial Low-Altitude UAS Operations in Population Centers

Scipedia content — Mon, 01 Feb 2021 21:56:12 +0100

Unmanned air systems (UAS) have numerous military, law enforcement, and commercial applications. Commercial potential in particular will not be realized until a comprehensive strategy is developed for safely and fully integrating UAS into the national airs pace system over both rural and urban regions. This paper overviews a broad spectrum of UAS commercial applications to motivate airspace integration. Focus is then placed on use of small to micro-scale UAS in potentially lucrative bu t ultimately challenging benchmark applications: on-demand surveillance over a densely-populated urban region. Following the introduction of urban use cases, we present alternative criteria for small UAS safety that focus not on vehicle preservation but instead on avoiding collateral damage to people and property on the ground as well as to higher-cost airborne assets. We conclude the paper with a discussion of safety preservation when a micro air vehicle over an urban area encounters turbulence or wind shear, a likely day-to-day scenario that can introduce significant risk of a forced landing given realistic constraints on disturbance rejection. This study, led by Raytheon, is part of a NASA Research Announcement activity for Integrating Advanced Concepts and Vehicles into NextGen. I. Introduction he pressing need to maximize commercial transport safety and capacity while minimizing environmental impact has resulted in a next-generation airspace system plan that focuses on two of three parts of the national airspace system: enroute airspace greater than FL100 and the airportal environment near runways. Large unmanned aerial systems (UAS) such as Global Hawk can fit within this structure as on-demand but infrequent operations. However, small UAS (SUAS) operations, where "small" is defined as a UAS under 35 pounds, will occupy airspace well under FL100 and would initially occupy uncontrolled airspace with no to extremely rare entry into congested airportal corridors. As part of the NASA Research Announcement (NRA) activities for Integrating Advanced Concepts and Vehicles in to NextGen, Raytheon and its collaborators, including the University of Michigan, studied the impact of four future vehicle classes on NextGen in 2025 through 2040, including SUAS. This paper investigates the use cases and safety issues arising from SUAS operating in densely- populated urban regions. Currently small UAS operations are conducted with an FAA Certificate of Authorization (CoA) typically granted to entities seeking operations below altitudes GA craft wo uld occupy. While appropriate for initial low-altitude UAS platform flight tests, the CoA does not provide the flexibility to operate commercially over evolving sites of public or individual interest. A limited number of operators, primarily in remote regions, have been granted permission to conduct UAS operations in designated test ra nges. These remote ranges will provide valuable means to test operational protocols, but they will not support a class of on-demand UAS operationseven approaching the freedom current GA and small commercial aircraft operators enjoy today. The primary cited impediment to UAS pervasively operating in the national airspace system (NAS) is increased risk, both real and perceived. Although early UAS maturation has occurred primarily in the DoD sector, if UAS-specific risk could be appropriately computed and controlled, regulatory, air traffic, and operational protocols can be introduced to flexibly accommodate rather than segregate UAS operations. As occupants of primarily uncontrolled airspace, SUAS would share the skies with general aviation (GA) operations. So long as commercial and private UAS and GA activities remain sparse, it may be sufficient to define special-use areas for UAS, or to adopt a simple deconfliction approach such as defining a specific flight altitude for UAS that only must be verified clear when GA traffic tran sits during climb or descent. Emerging "sense-and-avoid" technologies will enable UAS to evade a nearby aircraft, and will ideally be sufficiently small and low-cost to be affixed in most UAS platforms. Given sufficient risk mitigation for UAS operations, we can begin to consider an alternative model, where business use cases predict rapid UAS proliferation in the private and commercial sectors to an equal or even greater extent than ha s been observed in military operations. In this scenario, either the FAA will

Shifting towards environment-friendly modes: profiling travelers using Q-methodology

Scipedia content — Mon, 01 Feb 2021 21:52:32 +0100

Due to a variety of reasons, the previous century is characterized by an extraordinary growth in car use that has continued into the current century. This has resulted in serious environmental repercussions. Despite technological advancements, the externalities remain an ecological threat that can not be discarded by policy makers. Therefore, it is essential that policy makers focus on reducing car use and on stimulating the shift towards more environment-friendly transport modes. In this study, Q-methodology is adopted as the technique to segment people, and to ascertain which approaches and determinants matter to medium distance travel. Segmentation is important, as policy measures will be more efficient and effective if they are fine-tuned on specific target groups. The analysis revealed that four discourses preponderate the paradigm of environmentally sustainable transport: travelers who use public transport as a dominant alternative, car-dependent travelers, travelers with a positive perception of using public transport, and travelers with a preference for car use. Concerning rational, economic motives, individuals evaluate travel time reliability as most important. To increase the reliability policy makers should consider the use of separate bus lanes and traffic light manipulation. In addition, public transport can be made even more attractive, when costs of cars are made more variable by road or congestion charging. When the subjective motives are discussed, the differences between the different groups of travelers were more pronounced. Next to increasing the benefits of using public transport, policy makers should also pay attention to removing psycho-social barriers. Peer reviewed

Nonlinear parity space applied to an electric autonomous vehicle

Scipedia content — Mon, 01 Feb 2021 21:51:46 +0100

International audience; The autonomous navigation of an electric vehicle requires the implementation of a number of sensors and actuators intended to inform it about his environment or his position and velocity and deliver necessary inputs. That's why it is important to detect and locate sensor and actuator faults as soon as possible to enable the operator to run the vehicle in degraded mode or use the fault tolerant control system if it exists. The main purpose of this paper deals with sensors or actuators faults diagnosis of autonomous vehicle. A diagnosis method using a nonlinear model of the vehicle is developed. Nonlinear state space model of the autonomous electric vehicle is used with the method of nonlinear analytical redundancy to detect and to isolate faults occurred on sensors or actuators. Computer simulations are carried out to verify the effectiveness of the method.

Effects of aircraft trajectories geometrical features upon air traffic controllers' conflict judgments

Scipedia content — Mon, 01 Feb 2021 21:31:36 +0100

This work is a twofold contribution to the analysis of conflict detection process in Air Traffic Controllers (ATCos). The first one addresses methodological aspects and proposes a way to get responses as close as possible to controllers' actual expertise without using artifacts such as rating scales or inferring judgments from verbal material. The second objective is to compare the influence of three geometrical features of aircraft encounters and their capacity to alter an accurate perception of conflicts. The proposed methodology appeared to be useful for collecting expertise as controllers quickly appropriated it, and led to get coherent data. Its use can be envisaged when a reliable representation of mental picture of ATCos is essential. Concerning the geometrical features of aircraft trajectories, aircraft attitudes i.e., the fact they are stable, climbing of descending, entailed significant differences on detection accuracy. To a lesser extent, catch-ups and segmented trajectories showed a capacity to make an accurate perception of conflicts more difficult. These results must be interpreted as tendencies more than precise or quantified results. As the objective of this experiment was to be a pre-experiment in preparation for future collecting in the framework of the European project SESAR, a few different choices concerning the trajectories to be used in the traffic scenarios will help to precise these results.

Convective weather avoidance with uncertain weather forecasts

Scipedia content — Mon, 01 Feb 2021 21:26:25 +0100

This paper describes simulations of an automated planning system that routes flights around airspace impacted by forecasted convective weather. If the system predicts that a flight will enter a weather-impacted airspace within a predefined time horizon, it generates a new route. Because the forecasts are uncertain, the system periodically generates, using updates of the weather forecasts and radar tracks, new reroutes. The simulations included convective weather in the northeastern quadrant of the United States over a 24-hr period. Multiple simulations investigated the system performance as the planning horizon and planning frequency varied. As the planning horizon and frequency increased, the system successfully routed more traffic around weather but with more route changes. For a planning horizon of 20 to 120 minutes and a planning frequency of four cycles per hour, the reroutes increased flight time by 3.3% and avoided 79% of the weather-impacted airspaces that were detected. Most flights required one to three reroutes to pass by a weather-impacted airspace, while the worst case flights required six reroutes.

Analysis of potential gain from using hybrid vehicles in public transportation

Scipedia content — Mon, 01 Feb 2021 21:14:12 +0100

In the last two decades, the pollution in major cities was a growing concern. A significantly large contribution was made by road transportation sources to this problem. EU regulations on emissions and improvements in fu el quality sustained an improvement in air quality through reduction in pollutants. Latest trend taking the environmental issues into consideration in consumer car industry is hybrid vehicles, which use a conventional inner combustion engine using petroleum or diesel fuel, alongside with an electric engine, selectively using the necessary one depending on the current speed and power needs. As the vehicles equipped with this technology create less emission and consume less fuel, investigation o f the potential gain when used public transportation is inevitable. In this study, a comparison-based study will be done between traditional busses using fossil fu el and new technology busses that the Istanbul Municipality selected as candidate fleet, utilizing energy, finance, environment and social responsibility aspects. Doğuş Üniversitesi; TÜBİTAK

The Secure Pipes and Filters Pattern

Scipedia content — Mon, 01 Feb 2021 21:00:08 +0100

Many applications process or transform a stream of data. Such applications are organized as a sequence of different stages, which may be independent enough to be simultaneously carried out. The original Pipes and Filters pattern and the Parallel Pipes and Filters pattern describe those actions. We present here the Secure Pipes and Filters pattern as a secure version of the original patterns, which contains a minimal set of security mechanisms to provide a set of basic security functions. The Secure Pipes and Filters pattern includes ways to add security controls at each stage of processing, controlling that only predefined operations are applied to data streams, as well as securing data movement.

Numerical Investigation on Bearing Capacity of a Pipeline on Clayey Soils

Scipedia content — Mon, 01 Feb 2021 20:52:58 +0100

The bearing capacity of a pipeline foundation is crucial for the pipeline stability design. It is usually inappropriate to analyze the bearing capacity for the pipeline with special circular section directly by employing the theory for conventional rectangular strip footings. In this study, the ultimate loads of the pipeline on clayey soils are investigated numerically. A plane-strain finite element model is proposed to simulate the quasi-static process of the pipeline penetrating into the soil, in which the adaptive-grid technique and the ‘contact-pair’ algorithm are employed, and the Drucker-Prager constitutive model is used for modeling the soil plasticity. Based on the proposed numerical model, the development of soil plastic zone and the incremental-displacement vector field beneath the pipeline are examined numerically. It is indicated that, according to the obtained pipeline vertical load-displacement curves, concurrently referring to the plastic strain field and/or the soil incremental-displacement vector field, the shear failure type (e.g., general shear failure, punching shear failure) and the collapse loads can be thereby determined. The present numerical results match well with the analytical solutions of slip-line theory in plasticity mechanics.

Multi-Objective Clean Take-Off Flight Paths for Civil Aircraft

Scipedia content — Mon, 01 Feb 2021 20:44:35 +0100

The environmental impact of civil aviation at low altitudes concerns local air quality, the contribution to global warming and noise nuisances in residential areas located in the vicinity of airports. Aviation is responsible for only a small percentage of man-made CO2 and has a marginal impact on global warming compared to other sources, but the continuous growth of air traffic requires sustainable development to increase, creating economic value with less environmental impact. This research, integrated in the European JTI project Clean Sky, addresses the study of flight departure procedures that minimize the environmental impact of a single aircraft. Departure procedures minimizing perceived noise, the emission of nitrogen oxides and the contribution to the global production of carbon oxides are calculated. From an operational viewpoint, airlines will assign a different priority to each objective and the onboard calculator will provide the most environmental-friendly take-off flight path. These operational constraints entail that the designed algorithm must provide smooth and robust optimal flight paths.

Aircraft Punctuality at Arrival Terminal-Area: Impact on Sequence Conformance, Saturation and Cost

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

ft arrival punctuality is a key performance measure of the Single European Sky Air Traffic Management Research (SESAR) target concept. A large source of uncertainty in landing times today is due to the merging of poorly synchronised traffic streams in the terminal area (TMA). The objective of this collaborative study was to evaluate benefits of aircraft accurately controlling their own entry time in to the arrival terminal area. Probabilistic modelling is used to investigate the air traffic control performance benefits of aircraft respecting a Controlled Time of Arrival (CTA) at an initial approach fix (IAF~10,000 feet) agreed up to about one hour before with an accuracy of ±10s, 95% of the time. Results indicate the probability of a sequence of CTAs all being met within a tolerance of ±30s, greatly increases with proportion of aircraft RTA equipped. RTA equipage enables CTA sequences to be met for arrival control horizon times much longer than today with an air traffic controller using an arrival manager. The risk of a busy TMA saturating or having to re-sequence due to bunching at the IAF is reduced by orders of magnitude when all aircraft are equipped with RTA. Extended arrival control horizon times enabled by RTA allow delay absorption by speed control instead of path-stretching resulting in fuel savings increasing (relative to a controller without an arrival manager) from 110±10kg at 15 minutes to 150±25kg at 70 minutes.

Overview and flight-by-flight analysis of trajectory prediction systems using a 2D Galaxy Visualization

Scipedia content — Mon, 01 Feb 2021 20:23:44 +0100

new graphic visualization tool, Trajectory Galaxy Visualization (TrajGalaxyViz) has been developed that significantly enhances analysts' ability to determine the accuracy of flight trajectory predictions, i.e. the anticipated route of an aircraft. The partnership between the Federal Aviation Administration's Conflict Probe Assessment Team (CPAT) and the Software Engineering, Graphics, and Visualization (SEGV) research group at Rowan University has enabled the development of TrajGalaxyViz. TrajGalaxyViz is a system developed in Java that enables CPAT to measure the accuracy of flight trajectory prediction methods as well as perform comparisons of different flight trajectory methodologies. This paper explores the development and implementation of TrajGalaxyViz as well as its integration with a previously developed system, Trajectory Graphical User Interface (TrajGUI). TrajGalaxyViz greatly improves the ability to analyze the voluminous amount of data generated by the evaluation of a new air traffic control system.

Modeling and Analysis of a Free Spanning Pipeline With Randomly Distributed Corrosion

Scipedia content — Mon, 01 Feb 2021 20:19:32 +0100

Some corrosion defects will appear outside the aged submarine pipelines due to the corrosive sea environment. These defects can depress the strength and integration of the pipeline systems. This paper establishes a novel model using finite element method to describe the corroded pipelines with randomly distributed corrosion defects according to the probability function. Several free spanning pipelines models with random corrosion of different distributed parameters (averaged value and variance) are presented. Then the displacement and stress distribution of the pipelines are calculated subject to external fluid forces. The wet modes are calculated subsequently. At last the effects of the characteristic parameters of corrosion defects are discussed by analyzing the present results. Some conclusion may be useful for perceiving the randomly distributed corrosion how to affect the pipelines operation status.

The modern information systems for controlling the railway traffic as an indispensable tool of an infrastructure manager

Scipedia content — Mon, 01 Feb 2021 20:06:58 +0100

The information systems of an infrastructure manager (IM) are today an indispensable part of its basic technological processes. Their significance has been growing even more in the setting of the liberalized transport market, where many private railway undertakings (RU) or operators enter the railway network and content for its spare capacity. The contribution discusses covers the high-level structure of the key information systems of the infrastructure manager, their coverage of the aforementioned technological processes, from designing the timetables and ordering ad hoc paths, to the operational control in all of its spatial and time levels, to assessing the traffic and resolving the exceptional situations. As the most important feature, the authors emphasize a profound integration of all these systems, which involves unifying all the databases and facilitates reusing the captured data, which boosts the overall efficiency of the system. The authors draw from their huge experiences of developing, solving, implementing, and operating these systems, above all in the environment of Czech and Slovak railway networks.

Modeling, simulation, analysis and control of freeway traffic corridors

Scipedia content — Mon, 01 Feb 2021 20:02:49 +0100

Vehicular traffic congestion remains one of the major world-wide sources of productivity and efficiency loss, wasteful energy consumption, and avoidable air pollution. For example it is estimated that in 2007, congestion caused urban Americans to travel an additional 4.2 billion hours and to purchase an extra 2.9 billion gallons of fuel. In this talk I will describe a set of modeling and simulation Tools for Operational Planning (TOPL) developed to provide quick and quantitative assessments of the benefits that Transportation Management Center (TMC) control policies can provide on freeway corridors, in order to decrease congestion. A freeway corridor typically comprises a 40 kilometer freeway segment on a highly populated urban area, together with its adjoining major urban streets or arterials. The movement of vehicles in a corridor is regulated by programmable field control elements including arterial intersection signals, ramp-metering signals, and message signs that announce emergency conditions, set speed limits and tolls, and provide driver information. Traffic data is primarily collected through inductive loop detectors buried roughly every kilometer along the freeways' payment, as well as detectors located in some of the major corridor arterials. TOPL contains a self-calibrated Cell Transmission Model (CTM) traffic macroscopic simulator. This simulator relies on a well-accepted theoretical model of traffic flow; it is parsimonious and does not require parameters that cannot be estimated from traffic data; and has been tested for reliability on several freeways. Moreover, it is fast, running several hundred times faster than real time, which can be used with real-time measurements and statistically predicted short term future traffic demands to keep track of the current freeway traffic state, as well as make short-term predictions. I will also discuss the qualitative behavior of a single freeway based on the CTM, and will focus on several results regarding the structure and stability of the set of equilibrium states in single freeway, including the fact that the freeway decomposes into disjoint contiguous segments demarcated by bottleneck links, with each segment having qualitatively the same behavior. These properties will be further explored in the formulation of traffic responsive and coordinated ramp-metering policies, including a coordinated policy that minimizes travel time, model calibration and missing on-ramp imputation techniques, and congestion and state estimation techniques.

Packet Classification Algorithms: From Theory to Practice

Scipedia content — Mon, 01 Feb 2021 19:55:29 +0100

During the past decade, the packet classification problem has been widely studied to accelerate network applications such as access control, traffic engineering and intrusion detection. In our research, we found that although a great number of packet classification algorithms have been proposed in recent years, unfortunately most of them stagnate in mathematical analysis or software simulation stages and few of them have been implemented in commercial products as a generic solution. To fill the gap between theory and practice, in this paper, we propose a novel packet classification algorithm named HyperSplit. Compared to the well-known HiCuts and HSM algorithms, HyperSplit achieves superior performance in terms of classification speed, memory usage and preprocessing time. The practicability of the proposed algorithm is manifested by two facts in our test: HyperSplit is the only algorithm that can successfully handle all the rule sets; HyperSplit is also the only algorithm that reaches more than 6Gbps throughput on the Octeon3860 multi-core platform when tested with 64-byte Ethernet packets against 10K ACL rules.

Integration of optical telecommunications and radio access networks to assure quality of service

Scipedia content — Mon, 01 Feb 2021 19:43:29 +0100

In this work, we show how to control a Quality of Service in optical networks integrated with WiMAX access radio by means of the MPLS and WiMAX Class of Services, even in condition of traffic congestions.

In Field Application of an Innovative Sensor for Monitoring Road and Runway Surfaces

Scipedia content — Mon, 01 Feb 2021 19:35:13 +0100

Water and ice detection over road and runway surfaces is important to improve traffic safety and to reduce maintenance costs. An innovative low cost capacitive sensor was endowed with an algorithm based on the time derivative of the measured capacitance to indicate the transitions between dry, wet, or icy state of road and runway surfaces. The sensor was investigated theoretically and validated with experiments on field.

Design and Evaluation of a Dynamic Programming Flight Routing Algorithm Using the Convective Weather Avoidance Model

Scipedia content — Mon, 01 Feb 2021 19:31:13 +0100

The optimization of tra! c flows in congested airspace with varying convective weather is a challenging problem. One approach is to generate shortest routes between origins and destinations while meeting airspace capacity constraint in the presence of uncertainties, such as weather and airspace demand. This study focuses on development of an optimal flight path search algorithm that optimizes national airspace system throughput and e! ciency in the presence of uncertainties. The algorithm is based on dynamic programming and utilizes the predicted probability that an aircraft will deviate around convective weather. It is shown that the running time of the algorithm increases linearly with the total number of links between all stages. The optimal routes minimize a combination of fuel cost and expected cost of route deviation due to convective weather. They are considered as alternatives to the set of coded departure routes which are predefined by FAA to reroute pre-departure flights around weather or air tra! c constraints. A formula, which calculates predicted probability of deviation from a given flight path, is also derived. The predicted probability of deviation is calculated for all path candidates. Routes with the best probability are selected as optimal. The predicted probability of deviation serves as a computable measure of reliability in pre-departure rerouting. The algorithm can also be extended to automatically adjust its design parameters to satisfy the desired level of reliability.

PIPA: A High-Throughput Pipeline for Protein Function Annotation

Scipedia content — Mon, 01 Feb 2021 16:31:19 +0100

We developed Pipeline for Protein Annotation (PIPA), a genome-wide protein function annotation pipeline that runs in a high performance computing environment. PIPA integrates different tools and employs the Gene Ontology (GO) to provide consistent annotation and resolve prediction conflicts. PIPA has three modules that allow for easy development of specialized databases and integration of various bioinformatics tools. The first module, the pipeline execution module, consists of programs that enable the user access to and control of the pipelinepsilas parallel execution of multiple jobs, each searching a particular database for a chunk of the input data. The execution module wraps the second module, the core pipeline module. The integrated resources, the program for terminology conversion to GO, and the consensus annotation program constitute the main components of the core module. The third module is the preprocessing module. This last module contains the program for customized generation of protein function databases and the GO-mapping generation program, which creates GO mappings for the terminology conversion program. The current implementation of PIPA annotates protein functions by combining the results of an inhouse-developed database for enzyme catalytic function prediction (CatFam) and the results of multiple integrated resources, such as the 11 member databases of InterPro and the Conserved Domains Database, into common GO terms. A Web-page-based graphical user interface is developed based on the User Interface Toolkit. The pipeline is deployed on two LINUX clusters, JVN at the Army Research Laboratory Major Shared Resource Center and JAWS at the Maui High Performance Computing Center. Currently, scientists at the Naval Medical Research Center are using PIPA to predict protein functions for newly sequenced bacterial pathogens and their near-neighbor strains. Validation tests show that, on average, the CatFam database yields predictions of enzyme catalytic functions with accuracy greater than 95%. Test results of the consensus GO annotation show an improvement in performance of up to 8% when compared with annotations in which consensus is not used.

Evaluation method for behaviour of pipelines during earthquakes

Scipedia content — Mon, 01 Feb 2021 16:30:28 +0100

This paper presents a synthetic evaluating method for the seismic behaviour of pipelines during earthquakes. The proposed method consists mainly of three analytical methods, which are the reliability analysis method for lifeline networks, seismic response analysis of surface ground layers and the pseudo static response analysis of buried pipelines. The reliability analysis method for lifeline networks is based on the Monte Carlo method. The seismic response analysis method is two-dimensional effective stress analysis based on Biot’s two-phase mixture theory and Iai’s constitutive equation. The pipeline analysis is based on the beam theory on an elastic foundation and modified transfer matrix method. Numerical computations are performed for models with various conditions of ground and pipes. As a result, axial and lateral response characteristics of pipelines are shown and evaluated by relating with earthquakes, grounds and pipelines conditions.

Hierarchical Border Gateway Protocol (HBGP) for PCE-based multi-domain traffic engineering

Scipedia content — Mon, 01 Feb 2021 16:15:43 +0100

In multi-domain multi-carrier networks the effective use of network resources shall be achieved while guaranteeing an adequate level of confidentiality and scalability. A candidate solution to perform effective multi- domain Traffic Engineering (TE) is based on a combination of (i) hierarchical routing and (ii) path computation procedures. Hierarchical routing identifies the domain sequence to cross while path computation computes the strict end to end path. In this multi-domain study we first propose a hierarchical instance of BGP (HBGP) dedicated to TE information only. Then we propose and evaluate the integration of HBGP with path computation procedures based on IETF PCE architecture. Simulation results show that the hierarchical HBGP-PCE architecture, compared to current routing solutions based on BGP only, significantly improves the overall network resource utilization. In addition, this study identifies the network scenarios in which the aforementioned HBGP-PCE features provide significant advantages. Finally, the experimental implementation of the proposed HBGP-PCE architecture in a network testbed composed of commercially available routers shows the viability of the solution in real networks.

Proposed methodology for a data-driven simulation for estimating performance measures along signalized arterials in real-time

Scipedia content — Mon, 01 Feb 2021 16:12:20 +0100

Congestion is one of the major issues facing today?s transportation sector. Recent efforts have been geared toward providing traffic information to travelers, to facilitate better travel decisions, and transportation facility managers, to allow them to better manage traffic operations. Currently, real-time traffic information is primarily limited to freeways and a small subset of major arterials. This research effort explores the feasibility of an online data-driven simulation based methodology to address the lack of real-time arterial performance measures. The core of this methodology is the development of an online simulation tool that relies on commonly available arterial point sensor data, such as that from loop detectors or video cameras. Preliminary analysis indicates that the approach being considered is feasible as a model of the "real-world" was capable of reflecting performance measures with relatively high levels of accuracy. Limitations of the current research design and more immediate future directions are also presented.

Quantifying Desirable Air Route Attributes for a Reroute Generation Capability

Scipedia content — Mon, 01 Feb 2021 16:11:51 +0100

When airspace is partially or completely blocked by severe weather, a major challenge for airspace managers and users is the creation and selection of viable alternate routing for air traffic. Research is underway for an automate d capability to help to meet this challenge. An important component of such a capability is the quantification of the attributes of operationally-acceptable routes. In this paper we describe two such quantifications, for route lateral deviation, and for flow preference.

Stochastic airspace simulation tool development

Scipedia content — Mon, 01 Feb 2021 15:51:59 +0100

Modeling and simulation is often used to study the physical world when observation may not be practical. The overall goal of a recent and ongoing simulation tool project has been to provide a documented, lifecycle-managed, multi-processor capable, stochastic simulation capability enabling analysis of procedures and equipment for aircraft flight in the national airspace system (NAS). The tool is a Monte Carlo-based computer simulation program that contains the stochastic models of most components of the NAS, including navigation aids, surveillance systems, pilots, aircraft, air traffic controllers, and weather. It is also combined with discrete artifacts such as FAA database-supplied runway sizes and configurations, and obstacles. In addition, the tool possesses a fast-time airframe-type-specific kinematic aircraft model, a high-performance random number generator, a precise WGS-84-compliant elliptical earth model, and a graphical user interface integrating world-wide photo-realistic airport depictions and real-time three-dimensional animation. This paper presents an overview of the software tool and its formulation, including programming languages, environments, and other development tools; selection, design, and implementation of the mathematical models; and reviews the verification and validation processes.

Capacity improvement analytical tools and benchmark development for terminal operations

Scipedia content — Fri, 29 Jan 2021 00:55:56 +0100

With U.S. air traffic predicted to triple over the next fifteen years, new technologies and procedures are being considered to cope with this growth. As such, it may be of use to quickly and easily evaluate any new technologies or procedures against a set of benchmarks, including best case and worst case. In this paper, theoretical upper and lower capacity bounds are formulated along with a performance index equation to allow for the quantitative comparison and evaluation of different terminal area capacity-increasing enhancements. These benchmarks are then used with a conventional stochastic queueing model (M/D/1) and a selected capacity improvement in order to demonstrate how an example change impacts the terminal airspace capacity as compared to the theoretical worst case and best case. These mathematical tools may hold value in quantifying proposed technologies and procedures intended to improve efficiency and to absorb the predicted increase in air transportation, prior to any actual implementation.

Probabilistic Prediction of Aggregate Traffic Demand Using Uncertainty in Individual Flight Predictions

Scipedia content — Fri, 29 Jan 2021 00:51:40 +0100

(Abstract) Federal Aviation Administration (FAA) air traffic flow management (TFM) decision-making is based primarily on a comparison of deterministic predictions of demand and capacity at National Airspace System (NAS) elements such as airports, fixes and en- route sectors. The current Traffic Flow Management System (TFMS) and its decision- support tools ignore the stochastic nature of the predictions. Taking into account uncertainty in predictions and moving from deterministic to probabilistic TFM is an important part of the NextGen program that will help TFM specialists make better and more realistic decisions. This paper uses current TFMS data to analyze how uncertainty in prediction of arrival times for individual flights translates into uncertainty in prediction of aggregate traffic demand counts at arrival airports. A methodology was developed for probabilistic prediction of aggregate 15-minute demand counts by using the probability distributions of arrival time predictions for individual flights. A key element of the methodology is that the aggregate demand counts are predicted from extended sets of flights with the estimated times of arrival (ETAs) in both the interval of interest and several adjacent intervals. Numerical examples are presented that illustrate the difference between deterministic and probabilistic traffic demand predictions.

Numerical Reservoir-Wellbore-Pipeline Simulation Model of The Geysers Geothermal Field, California

Scipedia content — Fri, 29 Jan 2021 00:43:48 +0100

The Geysers geothermal field, located in Lake, Sonoma, and Mendocino Counties, California is the largest developed geothermal system in the world. Electric power generation started at The Geysers in 1960 with a 12 MW (gross) plant. The total installed capacity in the field peaked in 1989 at 2,043 MW. As more and more power plants were built during the 1980s and net mass withdrawals increased, reservoir pressures at The Geysers declined, eventually resulting in steam shortfalls and declining generation levels. This net withdraw is due to the fact that geothermal power plants at The Geysers typically lose about 70 to 80% of produced mass to evaporation in cooling towers, with the balance of mass being returned to the reservoir through injection of steam condensate. In response to this decline, field operators made modifications to the pipelines and turbines to be able to operate more efficiently at lower system pressures. Based on studies funded by the California Energy Commission that showed that injection of water from outside sources was the most effective method of managing the long-term decline in the resource, a program of augmented injection, using large volumes of treated sewage effluent, was started in the late 1990s. This program of augmented injection has brought mass injected, more or less, into parity with mass produced, and the rate of reservoir pressure decline has been significantly reduced. Still, optimizing the distribution of augmented injection throughout the field and making corresponding adjustments to plant and pipeline facilities is a complicated process, with many interdependencies. To aid in ongoing optimization of the field, an integrated model has been developed for the Northern California Power Agency (NCPA) that combines reservoir simulation with mathematical modeling of the wellbores, pipelines, and power plants. This integrated model, funded in part by the California Energy Commission, has proven very useful for evaluating the most cost-effective improvements to the combination of wells and surface facilities, and to study the benefit of increasing the volume of augmented injection.

An 11b pipeline ADC with dual sampling technique for converting multi-carrier signals

Scipedia content — Fri, 29 Jan 2021 00:42:09 +0100

This paper presents a dual sampling technique for analog-to-digital converters (ADCs) to convert multi-carrier signals more efficiently and proposes an 11b switched-capacitor pipeline ADC based on this technique. With the dual sampling technique, the input signal power of the ADC can be boosted without getting excessive clipping noise and the ADC can have a higher resolution over the critical low amplitude region. Hence the overall signal to thermal, quantization and clipping noise ratio is improved. The 11b pipeline ADC with the proposed technique achieves a wide input signal range of 2Vppd using a single 1.2V supply. Simulations show an improvement of about 5dB in SNDR and better than 10dB in MTPR compared to a conventional 11b ADC for converting multi-carrier signals.

Architecture of an IP-based aeronautical network

Scipedia content — Fri, 29 Jan 2021 00:36:25 +0100

The International Civil Aviation Organization (ICAO) has defined a mobile IPv6-based Aeronautical Telecommunications Network (ATN/IPS) as a next generation communication network for future Air Traffic Management (ATM). The ATN/IPS will be used with different terrestrial and satellite link technologies for supporting future ATM. In parallel, non-operational services will use different link technologies as well. In such an environment, the main challenge is to design a network architecture that integrates all link technologies in a way that mobile users (be it a cockpit user or a passenger) can make use of them in a seamless way. This paper presents the core functionalities developed within the NEWSKY project of such an integrated IP network architecture.

Simplified dynamic density based capacity estimation

Scipedia content — Fri, 29 Jan 2021 00:28:38 +0100

Methods for estimating constant and variable sector capacity based on an airspace complexity metric, simplified dynamic density, are proposed. Simplified dynamic density is a weighted sum of seven traffic components that contribute to airspace complexity. Constant and variable estimates of maximum sector capacity, based on projected flight tracks, are used to constrain the traffic demand in fast-time simulations. Delays and aircraft counts resulting from these methods are compared with those obtained using the capacities in the current system and based on the “5/3 of average sector flight time” rule. Results show that the simplified dynamic density based capacities produce lower system-wide delays and more throughputs, and indicate more predictable air traffic demands during the peak traffic period.

Path computation algorithms in NS2

Scipedia content — Fri, 29 Jan 2021 00:27:32 +0100

Originally designed to improve the efficiency of packets forwarding, MPLS provides support for Traffic Engineering and network resilience. Constrained-based path computation is a key building block for Traffic Engineering in MPLS networks, since it allows to set-up LSPs along paths that satisfy QoS constraints. This paper deals with two distinct categories of path computation algorithms: on-line path computation algorithms adn on-line multi path algorithms. All these algorithms have been implemented in NS2 as an extension of OSPF-TE\ s and integrated with RSVP-TE\ s.

Why Equity Is so Elusive: Dynamical Properties of Overscheduled National Airspace System Resources

Scipedia content — Fri, 29 Jan 2021 00:26:19 +0100

One of the major issues in the design of the concepts-of-operations for NEXTGEN is the equitable allocation of overscheduled National Airspace System (NAS) resources. Although federal regulations, Congressional policies, and modernization plans call for equitable allocation of publicly held resources, the mechanisms for equitable allocation, and the tradeoffs that must be made between stakeholders, exhibit a high degree of social, political, and economic complexity. Further, the allocations that are routinely made in Traffic Flow Management (TFM) and Air Traffic Control (ATC) are subject to widespread perceptions of systemic inequity and economic inefficiency. This paper describes the properties associated with the dynamic allocation of an overscheduled resource. The mathematical model demonstrates that (i) a natural equity asymmetry exists in the first-scheduled/firstallocated mechanism, (ii) this asymmetry results in a low probability (" 10%) of an equitable allocation of resources amongst groups of flights (e.g. airlines), and (iii) increased competition reduces the likelihood of equitable allocations. These theoretical results establish the "feasible space" in which claims of equity can be made, suggests refinements of the existing allocation schemes, and establishes the framework for a regulatory role in proposed market-based mechanisms.

Environmental impact assessment of the penetration of hydrogen technologies in Portugal's road transport

Scipedia content — Thu, 28 Jan 2021 23:48:17 +0100

Road traffic is one of the transportation sectors with faster growth and also one of the most important emitters of greenhouse gases (GHGs). In this work, an analysis of the environmental benefits resulting from the introduction of hydrogen on road transport in Portugal is made. Impact is analyzed mainly looking at the pollutant emissions provided by road transport at the point of use. Emissions associated to road transport have been estimated using the software COPERT (version 4), since it provides a detailed methodology for each specific pollutant related to the vehicle fleet of a region or country, as well as the driving conditions and fuel consumption. Passenger cars, light duty vehicles and public transport buses are the vehicles categories in which the hydrogen technology is foreseen. The hydrogen penetration rates (moderate and high) are extracted from the European Project HYWAYS. Two trends are then considered, which give penetration rates of 40.0 % and 74.5 % in 2050 for the moderate and high scenarios respectively.

Automatic Planning of Ground Traffic

Scipedia content — Thu, 28 Jan 2021 23:46:53 +0100

Ground traffic optimization is a major issue of air traffic management: optimal ground circulation could decrease flight delays and consequently decrease costs and increase passenger wellness. This paper proposes a planning algorithm for ground traffic based on contract reservation. It deals with time and speed uncertainty to ensure the feasability of the planned trajectories while avoiding conflicts between aircrafts. The algorithm efficiency is improved using pre-computed heuristics. The different algorithm versions are evaluated through simulations of a large european airport, namely the Frankfurt airport.

A complexity metric for automated separation

Scipedia content — Thu, 28 Jan 2021 23:40:58 +0100

metric is proposed to characterize airspace complexity with respect to an automated separation assurance function. The Maneuver Option metric is a function of the number of conflict-free trajectory change options the automated separation assurance function is able to identify for each aircraft in the airspace at a given time. By aggregating the metric for all aircraft in a region of airspace, a measure of the instantaneous complexity of the airspace is produced. A six-hour simulation of Fort Worth Center air traffic was conducted to assess the metric. Results showed aircraft were twice as likely to be constrained in the vertical dimension than the horizontal one. By application of this metric, situations found to be most complex were those where level overflights and descending arrivals passed through or merged into an arrival stream. The metric identified high complexity regions that correlate well with current air traffic control operations. The Maneuver Option metric did not correlate with traffic count alone, a result consistent with complexity metrics for human-controlled airspace.

Simulation of gas pipeline leakage using the characteristics method

Scipedia content — Thu, 28 Jan 2021 23:36:59 +0100

The modeling of gas leakage for understanding the process of pressure reduction and gas leakage rate of a hole is accomplished by zero-dimensional models of the tank and pipe. These models of the tank and pipe are suitable for simulation when the hole is very small or where there is a complete fracture. However, use of these two methods or a combination of them is suitable rather when the pipelines are very long. In zero-dimensional models the effects of complex boundaries are also ignored. In this study, the pipeline leakage is simulated by use of the one dimensional characteristics method. This model is perfect compared with both pipe or tank models, or a combination of them, and we can expand the simulation of gas pipeline leakage to the short pipelines and variable boundary conditions. This is important in order to calculate the volume of gas discharged from the pipelines when an accident occurs.

Two Methods for Computing Directional Capacity Given Convective Weather Constraints

Scipedia content — Thu, 28 Jan 2021 23:35:10 +0100

†‡ § We study two methods of computing directional capacity for en route airspaces with convective weather constraints. We consider future operations where jetway routing is removed and aircraft paths may conform over time with the geometry of hazardous weather constraints. Within a constant flight level, we an alyze the dominant demand direction ‐ a direction for which the majority of the flow would like to pass through a given portion of airspace. Then, we study two methods of measuring the directional capacity of the airspace. The first method, a grid-based method, considers ei ght fundamental directions for directional capacity, according to the standard dir ections of travel: North, East, South, and West and diagonal directions. The second method considers an arbitrary direction of flow and determines the directional capacity in that par ticular flow direction. We compare the directional demand to the available capacity in tha t direction to determine if demand exceeds capacity in that particular direction. Fin ally, we describe how these directional capacity metrics can be used in air traffic management applications.

Providing an User Centric Always Best Connection

Scipedia content — Thu, 28 Jan 2021 23:14:17 +0100

hough Quality of Experience (QoE) is perceived as a subjective measure of a user’s experience, it is the only measure that actually counts to a user of a service. It is essential to identify, quantify and ultimately improve the perception of QoE for a user. The PERIMETER project improves the user’s experience by identifying a more user-centric network selection, based on QoE calculations and user preferences. PERIMETER defines a generic QoE model which forms the basis for QoE signalling and QoE based content adaptation support. This paper provides an insight into how user centric seamless mobility is being achieved by PERIMETER, beginning with an explanation of QoE and the need for preferences. Next, more details of the complete system, including QoE management, user feedback and the final delivery, are provided. Finally, an outlook is given on PERIMETER’s future plans and its contributions to research in the Future Internet.

Assessing the Extent of Transport Social Exclusion among the Elderly

Scipedia content — Thu, 28 Jan 2021 23:09:04 +0100

“Social exclusion” is a concept that has become increasingly prominent in the UK and elsewhere in the last ten years. Social exclusion occurs as a result of a series of problems that prevent people from being able to participate in activities that are considered normal in their society. Some of these problems are related to issues of accessibility. This paper outlines work carried out in the context of the AUNT-SUE (Accessibility and User Needs in Transport in Sustainable Urban Environments) project to develop and model an appropriate set of accessibility benchmarks for older people. Results confirmed that the travel patterns of older people are very different from those of the average person in the UK and that it was necessary to tailor accessibility benchmarks to the characteristics of this group. A set of benchmarks was developed based on ability to undertake different types of activity. These benchmarks are currently being incorporated into AMELIA, a GIS-based tool for assessing the effect of different policy actions on accessibility. Issues that have arisen include how to model the myriad micro-level circumstances that affect the mobility of older people. Some initial analysis has shown that these details can make a substantial difference to the assessment of the accessibility of a destination. Examples are drawn from St Albans in Hertfordshire, UK.

Traffic Flow Management Using Aggregate Flow Models and the Development of Disaggregation Methods

Scipedia content — Thu, 28 Jan 2021 22:54:32 +0100

linear time-varying aggregate traffic flow model can be used t o develop Traffic Flow Management strategies based on optimization algorithms. However, there are no methods available in the literature to translate these aggregate solutions into actions involving individual aircraft. This paper describes and implements a computationally efficient disaggregation algorithm, which converts an aggregate (flow-based) solution to a flight-specific control action. Numerical results generated by the optimization method and the disaggregation algorithm are presented and illustrated by applying them to generate TFM schedules for a typical day in the U.S. National Airspace System. The results show that the disaggregation algorithm generates control actions for individual flights while keeping the air traffic behavior very close to the optimal solution.

Physical Modeling of Untrenched Pipeline Breakout From Sand-Bed in Ocean Currents

Scipedia content — Thu, 28 Jan 2021 22:42:35 +0100

The ultimate lateral soil resistance for pipe losing lateral stability on a sandy seabed under the action of ocean currents is investigated with a newly developed test facility by employing mechanical actuators to simulate hydrodynamic loads on the pipe. Two kinds of constraint conditions, i.e. anti-rolling pipe and freely-laid pipe, are taken into account, respectively. The experimental observations indicate that, the horizontal lateral soil resistance increases gradually to its maximum (ultimate) value when the additional settlement is fully developed. The buildup of the ultimate lateral soil resistance to the anti-rolling pipe benefits from not only the additional settlements but also the sand-particle collections in front of the moving pipe, especially for the anti-rolling pipes. The lateral-soil-resistance coefficient for the anti-rolling pipe is much larger than that for the freely-laid pipe. The pipe surface roughness also affects the lateral stability of anti-rolling pipes. A comparison is made between present mechanical-actuator tests and the previous water-flume tests, indicating the results of two types of tests are comparable and the local scour may reduce the pipe lateral stability in ocean currents.

Evaluation of Magnetic Meters for Irrigation Pipeline Measurement

Scipedia content — Thu, 28 Jan 2021 22:41:03 +0100

Magnetic flow meters are used to measure the flow rate of a liquid in a closed pipeline. This type of meter is becoming increasingly popular for measurement with agriculture applications. Electromagnetic meters were tested by the Irrigation Training and Research Center in pipelines located less than the 10 diameters upstream of disturbances with good results. Results show that location guidelines for placing a magnetic meter can be decreased even for turbulent conditions. This paper will discuss how a magnetic flow meter works, advantages and disadvantages of this type of meter, test results, and new guidelines for field applications. INTRODUCTION The accuracy and long-term success of any flow measurement program depends on many factors. Magnetic flow measurement is rapidly becoming the technique of choice in pipelines because of its simplicity and accuracy. However, the application of this technology has been limited in the past because of standard practice guidelines for magnetic flow meters, which have required installing the meters in a straight section of pipe at least 8-10 pipe diameters from any source of turbulence. In addition, standard practice recommends having at least two pipe diameters of straight unobstructed pipe downstream from the meter. However, in the case of many irrigation pumping plants, turnouts, and deliveries, these conditions can rarely be met without extensive and expensive modifications. Therefore, the Irrigation Training and Research Center (ITRC) at Cal Poly State University San Luis Obispo is currently investigating electromagnetic flow meters for potential applications under non-standard conditions. Several current manufacturers claim that their magnetic meters can perform well even in locations where only two diameter lengths of straight pipe are available. Testing was done by the ITRC on several magnetic meters at the Cal Poly Water Resources Facility to evaluate comments by the manufacturers and to make recommendations to irrigation districts and growers interested in this new technology. This research was conducted to determine: The accuracy of the magnetic meters in locations that are less than optimal The sensitivity of meters to increasing amounts of turbulence Since this research was conducted, there have been numerous field installations of magnetic meters in various irrigation applications in California. The general consensus is that they are working well. Presented at the May 17-21, 2009, World Environmental and Water Resources Congress in Kansas City, Missouri. http://www.itrc.org/papers/magmeter09.htm ITRC Paper No. P 09-002 Magnetic Meters According to Faraday’s Law, a voltage will be induced proportional to the velocity of a conductor as it moves at right angles through a magnetic field. The water in the pipe is the conductor. By simply measuring the voltage, a magnetic meter is able to calculate the volume of the liquid passing through a controlled section. Faraday's Formula: E is proportional to V x B x D E = The voltage generated in a conductor V = The velocity of the conductor B = The magnetic field strength D = The length of the conductor This principle works for irrigation water passing through the magnetic field generated by the magnetic meter since the water acts as the conductor. The basic operating principle for magnetic meters is illustrated in Figure 1. Note that this discussion is limited to full-bore or in-line magnetic meters. There are several other types of meters on the market but this type is the one that was evaluated. Figure 1. Operating principle for full-bore magnetic meter (Omega 2009) As seen in Figure 2, there are two electrodes located inside the magnetic meter to measure the induced voltage. The flow rate/totalizer indicator is located on the top of the unit. These units can be placed at any angle. It is recommended that they be rotated so that one of the electrodes does not sit on the bottom of the pipe. This helps prevent problems from sediment covering the electrode. Note that on the unit in Figure 2, the magnetic field is generated by an insert unit into the pipeline. Some manufacturers install the coils to generate the magnetic field outside of the spool piece. Presented at the May 17-21, 2009, World Environmental and Water Resources Congress in Kansas City, Missouri. http://www.itrc.org/papers/magmeter09.htm ITRC Paper No. P 09-002 Figure 2. View of typical magnetic meter (SeaMetrics 2009) Advantages of Magnetic Meters Highly accurate even with some flow disturbance. No headloss caused by meter. Is not impacted by trash, sediment, or sand. Can measure a wide range of velocity. This is a key criterion in areas that have seasonal high flows combined with very low flows. Has instantaneous and volumetric totalizing capability. Measurement accuracy is NOT affected by varying canal water levels. Minimal maintenance required. Temperature of the liquid has no effect on accuracy. Disadvantages of Magnetic Meters Cost is a major constraint. Recently the cost has dropped dramatically, but this is still the most expensive option in some cases. Pipe must be full (as is the case in most agricultural applications). Installation into existing sites is often difficult and expensive. Sensitivity to turbulence. Turbulence and Magnetic Meters Magnetic meters have been considered particularly tricky for pumping plants and turnouts, because of the meter’s sensitivity to turbulence. For example, one of the main problems associated with turnouts is the turbulence that occurs just downstream of the gate. Figure 3 shows a typical turnout application with a magnetic meter. Presented at the May 17-21, 2009, World Environmental and Water Resources Congress in Kansas City, Missouri. http://www.itrc.org/papers/magmeter09.htm ITRC Paper No. P 09-002 Figure 3. Conceptual sketch of magnetic meter installation for turnouts (not to scale) In 1998, Hanson and Schwankl published results from non-optimal flow meter testing in their paper Error Analysis of Flowmeter Measurements. Pipeline measurements were taken with different types of flow meters to determine the effects on error resulting from different degrees of turbulence caused by elbows, check valves, and a partially opened check valve. Measurements were made at 2, 5, 10, and 15 pipe diameters downstream from the source of turbulence. The results from Hanson and Schwankl (1998) indicated that for generally acceptable accuracy with propeller meters, pitot meters, and Doppler meters, measurements should be taken upstream of valves. The tests found that in some circumstances even with as little as 2 or 5 pipe diameters upstream of a flow meter, there were still large errors with all meters under conditions of severe turbulence. Since most applications require the flow measurement downstream of a valve or turnout gate, manufacturers have recently claimed that their magnetic flow meter technology is now able to work effectively in situations where there is as little as two diameters of pipe length available. ITRC tested several magnetic meters at the Cal Poly Water Resources Facility to investigate these claims.

Open vehicular data interfaces for in-car context inference

Scipedia content — Thu, 28 Jan 2021 22:38:56 +0100

In this paper, we present a concept for an open vehicular data interface and describe it's components and architecture. We discuss the enabled applications in the context of advanced driver assistance systems with a focus on human-machine interfaces, vehicle-to-x (V2X) communication and context inference systems. We conclude by a presentation of the initial implementation and deployed system.

Optimal trace compaction with property preservation

Scipedia content — Thu, 28 Jan 2021 21:59:14 +0100

Debugging design errors is a challenging manual task which requires the analysis of long simulation traces. Trace compaction techniques help engineers analyze the cause of the problem by reducing the length of the trace. This work presents an optimal error trace compaction technique based on incremental SAT. The approach builds a SAT instance from the Iterative Logic Array representation of the circuit and performs a binary search to find the minimum trace length. Since failing properties in the original trace must be maintained in the compacted trace, we enrich our formulation with constraints to guarantee property preservation. Extensive experiments show the effectiveness out SAT based approach as it preserves failing properties with little overhead to the SAT problem while demonstrating on average an order of magnitude in performance improvement.

NextGen technologies for mid-term and far-term air traffic control operations

Scipedia content — Thu, 28 Jan 2021 21:49:02 +0100

This paper describes technologies for mid-term and far-term air traffic control operations in the Next Generation Air Transportation System (NextGen). The technologies were developed and evaluated with human-in-the-loop simulations in the Airspace Operations Laboratory (AOL) at the NASA Ames Research Center. The simulations were funded by several research focus areas within NASA's Airspace Systems program and some were co-funded by the FAA's Air Traffic Organization for Planning, Research and Technology. Results indicate that advanced trajectory-based air traffic control automation at the controller workstation integrated with data com and moderate flight deck upgrades shows great promise to increase airspace capacity significantly in the mid-term and far-term.

Assisting air traffic control in planning and monitoring Continuous Descent Approach procedures

Scipedia content — Thu, 28 Jan 2021 21:41:45 +0100

Interference analysis for the future aeronautical communication system

Scipedia content — Thu, 28 Jan 2021 21:36:09 +0100

General and commercial aviation authorities have been using amplitude modulation communication systems for more than 70 years. Due to the great increase of air traffic during the last years, the VHF band tends towards saturation, whereas the aeronautical community faces new requirements: data rate, spectral efficiency and network capacity (maximum number of aircrafts simultaneously connected). Recently, the development of a new digital aeronautical communication system, named L-DACS, was proposed. This system will operate in the L band part allocated to aeronautics. There were many proposals but only two candidates have been pre-selected by the ITU and ICAO for this future communication system: L-DACS1 and L-DACS2. The deployment of this new system is expected to start after 2020. Among other issues, one important aspect is the impact of L-DACS on legacy systems. Actually, there are many onboard systems operating in L band, and any disfunction can put in danger the flight safety. This paper studies the maximum interference level generated by the two L-DACS candidates on a generic onboard receiver. Taking into account the antenna radiation pattern and the specific transmission mask of both candidates, the study determines the worst interference level and the corresponding spatial positions of the aircrafts around the receiver. The results show that the interference level can be determined by considering the several nearest aircrafts to the victim.

A New ILI Tool for Metal Loss Inspection of Gas Pipelines Using a Combination of Ultrasound, Eddy Current and MFL

Scipedia content — Thu, 28 Jan 2021 21:19:43 +0100

The two prevailing technologies in in-line inspection (ILI) of pipelines used for metal loss detection are magnetic flux leakage (MFL) and ultrasonic testing (UT). The ultrasonic method provides a more precise depth sizing as a direct measurement of the remaining thickness of the pipe wall is obtained. The advantage of providing more precise defect data leads, in turn, to a more accurate and reliable defect assessment thus reducing follow-up costs for the pipeline operator. As conventional ultrasonic tools, which are based on piezoelectric transducers, require a liquid coupling medium to couple the ultrasonic energy into the pipe wall, this technology is readily applicable to the majority of liquids pipelines, but not to gas pipelines (unless a batch of liquid is used). In order to apply ultrasonic ILI technology for metal loss inspection to gas pipelines directly, a new tool was developed based on the EMAT (electro-magnetic acoustic transducer) principle by which ultrasound is generated in the surface of the pipe wall through electromagnetic interaction. EMAT sensors utilize coils for sending and receiving ultrasound. Since coils can also be used to pick up MFL signals and eddy current signals, the sensors were designed such that, apart from the ultrasonic signals, these additional signals are recorded simultaneously. The availability of three simultaneous, independent measurements allows for considerable improvement with regard to both defect sizing and feature discrimination. In the paper, the new sensor concept and the setup of the ILI tool are described. First results are presented and discussed.Copyright © 2010 by ASME

Cutting the electric bill for internet-scale systems

Scipedia content — Thu, 28 Jan 2021 21:17:49 +0100

Energy expenses are becoming an increasingly important fraction of data center operating costs. At the same time, the energy expense per unit of computation can vary significantly between two different locations. In this paper, we characterize the variation due to fluctuating electricity prices and argue that existing distributed systems should be able to exploit this variation for significant economic gains. Electricity prices exhibit both temporal and geographic variation, due to regional demand differences, transmission inefficiencies, and generation diversity. Starting with historical electricity prices, for twenty nine locations in the US, and network traffic data collected on Akamai's CDN, we use simulation to quantify the possible economic gains for a realistic workload. Our results imply that existing systems may be able to save millions of dollars a year in electricity costs, by being cognizant of locational computation cost differences.

Nokia Corporation

National Science Foundation (U.S.) (Grant CNF–0435382)

Document type: Conference object

Temperature Field Prediction of a Multilayered Composite Pipeline Based on the Particle Filter Method

Scipedia content — Thu, 28 Jan 2021 20:55:15 +0100

Thermal management of subsea oil production systems in deep water environments is one of the main issues for petroleum exploitation operations. Thermal monitoring is crucial to avoid and control the formation of solid deposits, which in adverse operating conditions can result in blockages inside the production systems and consequently incur large financial losses. This paper aims to demonstrate the robustness of a Bayesian approach for accurate estimation of the produced fluid temperature field in a typical multilayered composite pipeline. The physical problem consists of a pipeline represented by a circular domain filled by a stagnant fluid (petroleum) with temperature dependent thermal properties, which is bounded by a multilayered composite pipe wall. The mathematical model governing the heat conduction problem in the multilayered wall and in the stagnant fluid was solved with the finite volume method. The Particle Filter method was used for the solution of the inverse transient problem involving the prediction of the temperature field in the medium, from limited temperature data available at one single location in the pipeline composite wall. The aim of this method is to represent the required posterior density function by a set of random samples with associated weights, and to compute the estimates based on these samples and weights. Results are presented in this paper by taking into account uncertainties in the state evolution and measurement models. Simulated temperature data is used in the inverse analysis for typical conditions observed during production shutdown periods.Copyright © 2010 by ASME

Design and analysis of ISP-friendly file distribution protocols

Scipedia content — Thu, 28 Jan 2021 20:54:06 +0100

In recent years, BitTorrent-like file-swarming applications are becoming so popular that they contribute to a large percentage of the current Internet traffic. Internet service providers (ISPs) not only need to cope with this traffic engineering problem, e.g., when and how to increase their network capacity, but more importantly, these P2P applications also increase their operating cost since large amount of the traffic has to go through the cross-ISP links. In this paper, we consider the design and analysis of an ISP-friendly file swarming protocol so as to reduce the cross-ISP traffic. We analytically show that the conventional P2P file-swarming protocols consume significant bandwidth on the cross-ISP links. We also derive an upper and lower bound for the cross-ISP traffic for ISP-friendly protocols which exploit the data locality property. We propose and implement an ISP-friendly protocol and carried out large scale experiments on the PlanetLab. Experimental results indicate that our protocol can significantly reduce the cross ISP-traffic and provide a reasonable file downloading time.

Energy-based modelling and simulation of a series hybrid electric vehicle propulsion system

Scipedia content — Thu, 28 Jan 2021 20:47:06 +0100

This paper presents an energy-based model of a series hybrid electric vehicle. The proposed propulsion system has a new configuration using a wound-rotor synchronous generator (WRSM) and a doublyfed induction machine (DFIM). From the classic dq dynamical equations of the WRSM and DFIM the port-controlled Hamiltonian models of each machine is described. One of the abilities of the port-based models is that the complete model is easy to obtain by means of interconnection rules. Following this, the Hamiltonian model of the whole system is obtained. Similarly, the bond graph approach allows to build a complex model by interconnecting several subsystems. This paper also contains bond graph models of the machines and the propulsion system. Numerical simulations are also presented in order to validate the proposed models.

Peer Reviewed

Constraint-based Context-Rule Representation and Risk Classification for Driver Assistance Systems

Scipedia content — Thu, 28 Jan 2021 20:43:39 +0100

Weight and dimensional parameters of a power drive for electrical vehicle

Scipedia content — Thu, 28 Jan 2021 20:40:13 +0100

The electric drive with the synchronous electrical machine of independent excitation differs by high specific parameters, adaptability to manufacture, simplicity of a design, and reliability. These properties of the electric drive allow using it in heavy conditions of operation. In particular, it can be recommended to use in electrical vehicles. The electric motor for this electric drive can be executed with two separate stator windings. Therefore, there are additional benefits connected to an opportunity of change of geometry of an iron stator stamp of the given type motor. In this report, the principle of operation of the electric drive with control system is considered. The different variants of a stator design of the electrical machine are discussed. The stator design allows improve of the mass and weight parameters of the electric machine. For the offered stator designs, the comparison of specific parameters (relationship of the nominal torque to load current) is carried out. The received results of analysis are discussed. Copyright © 2009 SAE International.

Fracture and Fatigue of Commercial Grade API Pipeline Steels in Gaseous Hydrogen

Scipedia content — Thu, 28 Jan 2021 20:35:42 +0100

Gaseous hydrogen is an alternative to petroleum-based fuels, but it is known to significantly reduce the fatigue and fracture resistance of steels. Steels are commonly used for containment and distribution of gaseous hydrogen, albeit under conservative operating conditions (i.e., large safety factors) to mitigate so-called gaseous hydrogen embrittlement. Economical methods of distributing gaseous hydrogen (such as using existing pipeline infrastructure) are necessary to make hydrogen fuel competitive with alternatives. The effects of gaseous hydrogen on fracture resistance and fatigue resistance of pipeline steels, however, has not been comprehensively evaluated and this data is necessary for structural integrity assessment in gaseous hydrogen environments. In addition, existing standardized test methods for environment assisted cracking under sustained load appear to be inadequate to characterize low-strength steels (such as pipeline steels) exposed to relevant gaseous hydrogen environments. In this study, the principles of fracture mechanics are used to compare the fracture and fatigue performance of two pipeline steels in high-purity gaseous hydrogen at two pressures: 5.5 MPa and 21 MPa. In particular, elastic-plastic fracture toughness and fatigue crack growth rates were measured using the compact tension geometry and a pressure vessel designed for testing materials while exposed to gaseous hydrogen.Copyright © 2010 by ASME

About the high capacity public transport networks territory functions

Scipedia content — Thu, 28 Jan 2021 20:09:23 +0100

transit system’s infrastructure (tramways, underground or light rails) plays a major role in satisfying people’s need for mobility – by size and the stability of their operation, and also by the independence of their quality performance compared to cars facing traffic congestion, because of their dedicated operation. The authors analyzed the potential transport capacity of the transit network infrastructures in order to define their territory functions, through urban people and poles to determine daily urban mobility preferences (for work, study, business purposes) and occasional mobility (for sports, tourism, culture, health caring purposes). In a structured space (Bucharest city), using a GIS map and TranCAD software, the authors defined the cover/serve index for the 72 study areas. (quasi-homogenous areas regarding their social-economic activities). The authors determined a hierarchy of those areas which help to establish directions to adapt transit infrastructure topology to the fast growing rate of the urban development. The territory functions characterization of the transit networks is used also to determine the hierarchy of the most highly attractive centroids (using an index that takes also into account both people density of the different areas and the distance to the popular centroids). The results of the study emphasize the disparities in urban territory served by the transit transport infrastructure; they can represent a useful tool in transit networks development strategies.

The Demand Bound Function Interface of Distributed Sporadic Pipelines of Tasks Scheduled by EDF

Scipedia content — Thu, 28 Jan 2021 20:02:20 +0100

In distributed real-time embedded systems (DRE), it is common to model an application as a set of task chains. Each chain is activated cyclically and must complete before an end-to-end deadline. Each task of the chain is bound to execute on a particular processing element. The complexity of designing and analyzing a DRE can be reduced by applying a component-based methodology: each pipeline can be seen as a component with its temporal characteristic summarized in its interface. Analysis can be carried out in two different steps: 1) derivation of the temporal interface of a component pipeline, 2) analysis of the whole system by integrating the temporal interfaces of the components. In this paper, we propose to describe the temporal interface of a task pipeline by a set of demand bound functions, one per each node on which the pipeline executes, and we describe an algorithm for computing the dbfs. First, we show that the scenario of strictly periodic activations is not the worst when the pipelines are sporadically activated. Then, we propose an exact algorithm for computing the dbfs. We show by experimental analysis that the computation time of the algorithm on pipelines with reasonable size is below one second on common PCs. Finally, we estimate the pessimism introduced by our analysis with respect to holistic analysis by an extensive set of simulations.

The technological model of operating area by the combined transport

Scipedia content — Thu, 28 Jan 2021 20:01:16 +0100

The contribution deals with design technology service model using the combined transport. It assesses the performance indicators in relation to price and quality of services provided and on this basis decides on the type of the transport. This is the decision-making processes, which should answer the question, whether used directly in road freight transport, direct rail freight transport or combined transport. In this contribution is the combined transport meant as a system between the conventional modes, which are transhipped goods from road vehicles to the rail cars or river boats.

Airline and Service Provider Collaborative Algorithms for Flight Route and Delay Decisions

Scipedia content — Thu, 28 Jan 2021 19:52:35 +0100

In this paper, algorithms are presented that model increased collaboration between the air traffic service provider and airspace users on flight route and delay decisions. These decisions are part of the traffic flow management function that constrains demand below capacity. Currently, users cannot make changes to the route or delay of a flight close to or after departure time and instead must send requests to the service provider who attempts to accommodate the users based on congestion and workload limitations. To mitigate this limitation, the algorithms model a new collaboration scheme. First, users directly implement their flight route and delay decisions, when the flight is further from the congested airspace, without sending a request to the service provider. The service provider can override their action when the flight becomes closer to the congested airspace. Second, users send flight ranking, route ranking and location-to-absorb-delay preferences to the service provider. The service provider may reject these preferences if needed. The algorithms are used to study whether increasing users’ responsibility and increasing their preferences would prevent maintaining demand below capacity. To prevent demand from exceeding capacity the algorithms impose limits, such as available routes and imposed flow rates, on user decisions. A simulation case demonstrates the impact of the collaboration schemes on reducing demand below capacity within an en-route center. Preliminary results indicate that aircraft delay and, to a larger extent, passenger delay are reduced. However, congestion is reduced by a smaller amount when user preferences are considered by the service provider. Giving users responsibility according to service provider limits and delay feedback did not increase congestion.

Models of Air Traffic Merging Techniques: Evaluating Performance of Point Merge

Scipedia content — Thu, 28 Jan 2021 19:52:05 +0100

new technique, Point Merge, for merging aircraft without vectoring in terminal areas (TMA), is modelled, and used in fast-time simulatio ns. Four arrival traffic streams are merged for landing on a single runway. A method for designing fast-time models of vectoring and Point Merge is proposed and validated using real-time simulation trajectories. Relative performances of fast-time simulations of t he corresponding models are compared. Interactions with departure traffic are also assess ed. Results show the Point Merge model reduces: mean controller task load (20±1%), the number of instructions to pilots (~30%), and fuel consumption (170±14 kg), compared with vectoring.

Geometric programming and mechanism design for air traffic conflict resolution

Scipedia content — Thu, 28 Jan 2021 19:44:26 +0100

We develop certain extensions of optimization-based conflict resolution methods in air traffic control. The problem considered concerns the scheduling of the crossing times of a set of aircraft through a metering fix, while maintaining aircraft separation. First, we show how to solve this combined path planning and scheduling problem using mixed-integer geometric programming. Second, the objective function used to determine the aircraft ordering at the fix is not given a priori but needs to be obtained from the airlines, which are strategic profit maximizing agents and could lie about their true cost. In order to realign individual and global objectives, we study the use of the Clarke-Groves mechanism in this context, which aims at extracting the true utility functions from the airlines using side-payments to the FAA.

Eye-Tracking Analysis of Near-Term Terminal Automation for Arrival Coordination

Scipedia content — Thu, 28 Jan 2021 19:42:16 +0100

Sponsored by the Federal Aviation Administration (FAA), The MITRE Corporation’s Center for Advanced Aviation System Development (CAASD) developed the Relative Position Indicator (RPI) concept. RPI is an automation concept to aid air traffic controllers in coordinating arrival traffic, reducing the need to vector for spacing during merging operations and, thus, retaining the benefits of Area Navigation (RNAV) and Required Navigation Performance (RNP) procedures. Validation activities involving an RPI research prototype have shown benefits in achieving more efficient merging and spacing of aircraft. Since the RPI concept makes additional information available on the situation display that can be referenced by the controller, an understanding of this information presence upon controller scan behavior was desired. As part of a Human-In-The-Loop (HITL) simulation of Denver operations conducted by CAASD, a comparison of two scenarios was made to evaluate the change in controller attentional allocation , as measured by an eye-tracking capability, when RPI is introduced. The simulated traffic consisted of predominantly RNAV operations and was managed with and without RPI automation. Participants were air traffic control specialists at Denver Terminal Radar Approach Control (TRACON) facility. Given the design of the RPI tool, two behavior changes were anticipated; 1) an increase of time spent scanning the primary flow of a merging flow geometry and 2) an increase of time spent scanning farther ahead or in advance of the merge point location. The eye-tracking analysis provides a preliminary indication that RPI does affect air traffic controller visual scanning patterns. Although the magnitude of change does not seem concerning , additional evaluation should be pursued to understand the impact of this change.

A New Design and Implementation of the Butterfly Unit on FPGA

Scipedia content — Thu, 28 Jan 2021 19:37:29 +0100

Multi-agent simulation of NAS infrastructure utilization in the presence of airline policies

Scipedia content — Thu, 28 Jan 2021 19:35:34 +0100

The saturation of capacity in the U.S. National Airspace System (NAS) has prompted a massive investment in the development of a modernized Air Traffic Control (ATC) system known as NextGen. The return on this investment is predicated on the availability of increased capacity where and when it is needed by the continuously evolving airline route system. The objective of this research is to develop policies for the design and development of NextGen that avoids under-utilization of ATC infrastructure in the presence of adaptive airline strategies. This paper describes a multi-agent simulation of airline route selection strategies for alternate trans-continental routes. The analysis shows the existence of a natural equilibrium that identifies a trade-off between ATC infrastructure utilization with airline operating costs over a range of alternate route distance, airline cost structures, and airline strategies. The implications of these results for NextGen planning and policy are discussed.

Load balancing inbound traffic in multihomed stub autonomous systems

Scipedia content — Thu, 28 Jan 2021 19:34:01 +0100

In the Internet, with many competing networks each trying to optimise its own bandwidth, a stub network has limited knowledge about user demands, available network resources and routing policies of other networks. This uncertainty makes the task of interdomain traffic engineering for a stub network very challenging. The basic aim of a stub network connected to multiple ISPs (multihomed) is to load balance its traffic among its various edge links. Our goal in this work is to distribute the incoming traffic of a multihomed stub network among its various edge links. The focus is on networks that primarily download traffic from the Internet. Regulating the incoming traffic is difficult since it will require to influence the behaviour of the remote destinations. We performed a systematic analysis of our problem and showed that even a restricted instance of the problem is NP-complete. We proposed simple, low-cost route control techniques to load balance traffic by reallocating the routes of outgoing traffic. The techniques were validated using synthetic as well as actual data collected under numerous traffic load conditions. Results show that we can achieve significant improvement in load balancing with minimum traffic re-assignments. Moreover, the proposed techniques neither require any third party assistance nor changes to existing protocols and network setup. This makes our schemes easily deployable in real networks.

An innovative dynamic bus lane system and its simulation-based performance investigation

Scipedia content — Thu, 28 Jan 2021 18:52:30 +0100

The strategy of exempting bus from other traffic through exclusive bus lanes (XBL) is prevalent. Rather than just deploying the XBL system, in this study, a new innovative dynamic bus lane (DBL) operation system which is expected to be more productive is initially introduced. Unlike conventional studies which are mainly focused on operational performance of buses, this study attempts to examine the influences on buses and adjacent traffic following the provision of both XBL and the new system. Impact measurements in terms of travel time and traffic conflicts changes are used as assessment indicators. Comparisons with the exclusive bus lane system as well as the mixed traffic flow are analyzed and highlighted through the application of micro-simulation approach. Simulation results showed that both XBL and DBL have positive impact on buses and negative impact on adjacent traffic. Traffic conflicts frequency will increase if either bus lane system is applied. Also it is found that DBL performs better than XBL in terms of achieving the goal of bus operation improvement while limited the performance deterioration to other vehicles and conflicts risks in a relative lower magnitude. Results also suggest the necessity of selecting the optimal strategies according to the tradeoff between the operational performance and safety performance under different traffic conditions.

Sensor fault detection by sliding mode observer applied to an autonomous vehicle

Scipedia content — Thu, 28 Jan 2021 18:50:00 +0100

International audience; This paper deals with sensors faults detection and isolation using method by observers. The principle is to reconstruct the state vector and measurements of the system by sliding mode observers and compare the estimated outputs with those measured. In this work, a multi observer's technique is used. It consists on construction of many observers, at least one observer for each output (sensor measurement). Each observer must be robust to noises and to other uncertainties but sensitive to sensor faults. The residual is the estimation error witch is the difference between sensor measurement and its estimated. Without failure in the sensor, this residual remains around zero and if a fault is occurred, it deviates significantly from zero. This method is applied to an autonomous electric vehicle called RobuCar. Simulation results are given at the end to show the effectiveness of the approach.

Air-to-Air Surveillance for Future ATM Systems

Scipedia content — Thu, 28 Jan 2021 18:36:42 +0100

This paper describes a prototype implementation of ADS-B in an air-to-air surveillance system. This air surveillance system was defined for an experimental project on future civilian air traffic management, which imposes new requirements over both air and ground surveillance systems. In this paper the relation between the different airborne and ground systems related to air surveillance is detailed, and the air surveillance and its algorithms are described. It is related with current ADS-B and TIS-B proposals, and defined as an extension of those systems. Finally, performance of the air surveillance is detailed, based on simulated scenarios, and some conclusions for future enhancements of ADS-B function are derived.

Document type: Conference object

Earthquake damage detection in Tehran’s water distribution system

Scipedia content — Thu, 28 Jan 2021 18:27:44 +0100

Iran is located in the one of world's large seismicity zones called ALPA (AlpHimalaya) and the mega city Tehran has is in a particularly dangerous situation. In a destructive earthquake, considerable damage occurs in buried structures such as the urban water supply system. In this study, the following objects are investigated: review of the damage analysis and seismic design of the water networks, review of the seismic information for water distribution systems, earthquake damage detection in water distribution systems, using an artificial neural network (ANN) and a general back error propagating perception to detect pipelines damaged due to earthquakes. The failure points are obtained by using the amount of water discharged from the tanks. The states probable failures have to be computed, the mathematical model for different states of pipe failure by which the damaged pipes could be detected through a back analysis. Since there are various types of failure, therefore, the ANN has been applied. Through a parametric study, different geometry, shape diameters and pressure of the water network are surveyed and the best network architecture for each case is obtained. The peak responses and phase delays are assumed to be network outputs. The network is trained in a supervised manner. The study shows the efficiency and capability of the ANN for modelling the observed nonlinear behaviour.

Environmental Information for the Next Generation Air Transpotration System

Scipedia content — Thu, 28 Jan 2021 18:07:50 +0100

It is estimated that weather is responsible for approximately 70% of all air traffic delays and cancellations. Annually, this produces an overall economic loss of nearly $40B. These and other negative impacts on the U.S. National Airspace System will increase to the point of unsustainability unless the system is radically transformed. A Next Generation Air Transportation System (NextGen) was proposed to accommodate the increasing demand for capacity and the super-density operations that this transformation will entail. The heart of the environmental information component that is being developed for the new system will be a 4-dimensional data cube which will include a single authoritative source for NextGen Air Traffic Management (ATM) systems. Aviation weather constraints and safety hazards typically comprise meso-scale, stormscale as well as microscale observables. These include convective weather, in-flight icing, turbulence, volcanic ash, space weather and the environmental impacts of aviation. Functional and performance requirements for the NextGen weather system are being established that will require significant improvements in current observations and forecasting capabilities. This will include satellite observations from geostationary and/or polar-orbiting sounders, imagers, lightning mappers, space weather monitors and other environmental observing systems. In 2003, a Joint Planning and Development Office (JPDO) was established by public law to design and implement NextGen. This paper provides the satellite meteorology community with useful insight on salient NextGen environmental information requirements that have been developed by the JPDO Weather Working Group. These efforts will help to shape current and future environmental satellite system capabilities, operations and applications. ____________________ Corresponding author address: John Murray, NASA Langley Research Center, MS 401-B, 21 Langley Blvd., Hampton, VA 23681. E-mail: john.j.murray@nasa.gov

On the interactions between non-cooperative P2P overlay and traffic engineering behaviors

Scipedia content — Thu, 28 Jan 2021 18:06:29 +0100

Emerging Peer-to-Peer (P2P) technologies have enabled various types of content to be efficiently distributed over the Internet. Most P2P systems adopt selfish peer selection schemes in the application layer that in some sense optimize the user quality of experience. On the network side, traffic engineering (TE) is deployed by ISPs in order to achieve overall efficient network resource utilization. These TE operations are typically performed without distinguishing between P2P flows and other types of traffic. Due to inconsistent or even conflicting objectives from the perspectives of P2P overlay and network-level TE, the interactions between the two and their impact on the performance for each is likely to be non-optimal, and also has not yet been investigated in detail. In this paper we study such non-cooperative interactions by modeling best-reply dynamics, in which the P2P overlay and network-level TE optimize their own strategies based on the decision of the other player in the previous round. According to our simulations results based on data from the ABILENE network, P2P overlays exhibit strong resilience to adverse TE operations in maintaining end-to-end performance at the application layer. In addition, we show that network-level TE may suffer from performance deterioration caused by greedy peer (re-)selection behavior in reacting to previous TE adjustments.

The transportation planning process in Slovakia

Scipedia content — Thu, 28 Jan 2021 18:03:24 +0100

The quality traffic-planning process is an important tool for achieving sustainable traffic. The modern platform for modeling and simulating traffic relations has also begun to be utilized in Slovakia. The Department of Civil Engineering at the University of Zilina uses German software PTV VISION. The complex multi-modal traffic model for Zilina town was created with PTV VISION modules (Visem, Visum, Vissim). The article presents the process of formation, calibration and practical utilization of a traffic model for city traffic problem solution. The micro simulation of critical zones amends the traffic model. The classic four-stage disaggregate process was applied for Zilina transport modeling. The town was split into 108 traffic zones. The traffic zones were classified by social and demographic characteristics. Six groups of population were classified within the study area. The matrices of interzonal transport relations were used as output data of the VISEM module and the matrices were used for assignments of the traffic network. Parameters in the infrastructure network and traffic zones were defined in the VISUM module. The result of many years experience in the field of traffic engineering was inserted in the traffic model. The authors have used our large database of traffic surveys and the results of transport-sociological analyses. The data were useful for the setting and calibration of the traffic model. The authors have set up new local parameters for a distribution function. The impact of new developing areas and induced traffic relations on the central part of Zilina was also observed. Next, the new transport relations and traffic problems were analyzed. This chosen part of the transport network was imported into a microsimulation model in the VISSIM. New alternative transport solutions and the impact on the infrastructure loading were explored in microscopic models. The quality of traffic load depends on the input data in the microsimulation. The best way is by using the complex macroscopic point of view.

Technical Challenges of Heavy Wall HFW Pipe Production for Bord Ga´is E´ireann Pipeline Project

Scipedia content — Thu, 28 Jan 2021 17:55:59 +0100

The recently constructed Bord Ga´is E´ireann, Curraleigh West to Midleton pipeline runs due north from the Midleton compressor station near the city of Cork in Southern Ireland. The 47.5 km, 610mm outside diameter pipeline, comprises over 30 km of 9.5 mm and 17 km of 19.1 mm wall thickness L450MB (X65) grade pipe. The pipe for the project was produced by Corinth Pipeworks (CPW), at its state of the art HFW pipe mill at Thisvi, Greece and represents a first in terms of the quantity of 19.1 mm L450MB (X65) HFW pipe produced by the mill for a specific project. The paper outlines the engineering approach adopted for the pipeline before describing in detail the production challenges faced by the pipe mill in successfully completing this demanding pipe order. Production of the 9.5 mm wall thickness pipe was not anticipated to present any particular difficulties. However, the principal concern associated with the manufacture of the 19.1 mm pipe was that the combination of wall thickness and strength level was toward the upper end of the commercially supplied wall thickness-strength combinations for HFW produced linepipe, particularly as the actual strength of the starting coil was well above the minimum specified level for L450MB (X65). In addition, to accommodate the demanding drop weight tear test (DWTT) toughness requirement the chemical composition of the 19.1 mm coil strip was above the permitted limits of the parent pipe standard EN 10208-2 [1] for the elements Cu & Ni, and the yield to tensile ratio was also above the 0.87 maximum level required by EN 10208-2 for L450MB (X65) grade pipe. Potential risks were therefore identified prior to production and mitigated by several methods detailed in the paper, including for example; increased initial production test frequency, close monitoring during pipe production, duplicate testing to verify mill results, identification of potential construction issues and weldability testing. A summary of production experience including statistical data for the production of both 9.5 mm and 19.1 mm pipe is presented. Also covered are the results of a supplementary investigation which makes a further assessment of the influence of the welding and heat treatment cycles on the final pipe properties. The paper concludes by referring to the overall successful construction phase of the project.

Analysis of traffic engineering information dissemination strategies in PCE-based multi-domain optical networks

Scipedia content — Thu, 28 Jan 2021 17:53:25 +0100

This paper presents and compares different TE information dissemination strategies between Path Computation Elements (PCEs) in multi-domain optical networks. In such network context, recent studies have found that path computation only with local domain visibility yields poor network performance. Accordingly, certain visibility between domains seems necessary. Aiming to fit the confidentiality requirements of the composing domains while improving the final network blocking probability, novel link aggregation techniques have been proposed, which summarize the state of network domains resources efficiently. This aggregated link information is afterwards disseminated to all the remainder domains in the network. To this end, we introduce different update triggering policies to make a good trade-off between routing information scalability and inaccuracy. The performance of all contributions has been supported by illustrative simulation results.

Analysis of a Multi-Trajectory Conflict Detection Algorithm for Climbing Flights

Scipedia content — Thu, 28 Jan 2021 17:50:49 +0100

Climb prediction uncertainty is a major source of error in trajectory-based automation for air traffic management. An algorithm to detect conflicts in the volume of airspace between fast-climb-rate and slow-climb-rate trajectories for climbing flights in the strategic detection time frame of 3-8 minutes was developed and evaluated using 12 hours of actual Fort Worth Center Host traffic data. Results indicate that conflict detections involving at least one climbing flight were made 2 minutes earlier on average using this multi-trajectory conflict detection algorithm than using a single-trajectory algorithm. Furthermore, although there were 55% more conflict detections using the multi-trajectory algorithm, only 15% of these additional detections were false alerts.

A Management System for Improving Traffic Efficiency in Transportation Infrastructures

Scipedia content — Thu, 28 Jan 2021 17:50:39 +0100

Result from evaluation of 4D trajectory management with contract-of-objectives

Scipedia content — Thu, 28 Jan 2021 17:43:06 +0100

Contract-of-Objectives (CoO) is designed in the context of trajectory-based Air Traffic Management (ATM), using mutually agreed objectives between Air Traffic Control (ATC), airlines and airports. This paper provides an overview of the foreseen validation of CoO and discusses the results of the first Human-in-the-Loop (HIL) evaluation of the concept of operations using CoO between Air Traffic Controllers (ATCos). This HIL real time evaluation is carried out in October 2008 in SkyGuide premises in Geneva, Switzerland. Measurements on system performance (i.e., Safety, Efficiency, and Capacity) as well as Human performances (i.e., workload, Situation Awareness, and acceptability) were collected and analyzed. Results show that ATCos are positive with the concept of operations, and they do agree on the principle of flying what were “planned, agreed and negotiated” on the planning phase as opposed to “first come, first served”. Results of the evaluations also show that CoO can be applied to 2008 and 2020 traffic level in Europe without any impact on System Safety.

Pedestrian tracking in infrared from moving vehicles

Scipedia content — Thu, 28 Jan 2021 17:42:01 +0100

The automatic detection and tracking of pedestrians in imagery constitute important and challenging problems both in computer vision and driver assistance systems. We address these problems for the case of a forward looking monocular infrared camera under strong vehicle induced camera motion. An integrated detection & tracking strategy is introduced based on a state-of-the-art feature based object detector originally developed for images in the visual spectrum. The proposed pedestrian detection algorithm can be applied to both infrared and visual imagery. We show the difficulties arising from the specifics of infrared data under strong camera motion and how to tackle these problems by replacing common motion models like the Kalman filter by a feature matching approach.

Climate Impact Evaluation as Part of Aircraft Pre-Design

Scipedia content — Thu, 28 Jan 2021 17:25:46 +0100

Here we present a methodology, which allows for an optimization of aircraft design aspects with regard to climate change. During the optimization, each iteration requires an estimate of a 3d emission distribution and from that an estimate of the climate impact. Hence it is necessary to distinguish the climate impact of two emission sets. This is difficult because considerable uncertainties of the overall climate impact from air traffic still exist. These uncertainties arise to a large extend from uncertainties in atmospheric processes. We address this problem by determining the difference in climate impact of two aircraft configurations for a large subset of parameter settings representing those atmospheric processes. Therefore a Monte-Carlo-Simulation for uncertainties of climate impacts is performed with AirClim, an efficient tool for climate evaluation of aircrafttechnology. The methodology is introduced and the principle mechanism is presented exemplarily with an application to aircraft emission inventories. The results show that although large uncertainties exist in the overall climate impact estimate of current air traffic, small differences in the emission pattern lead to stochastic significant changes in the climate impact. In the future this approach can be applied to evaluate and possibly minimize the climate impact of new aircraft technology.

A Simple Altitude Capture Avoiding TCAS Resolution Advisories During Level-Off Situations

Scipedia content — Thu, 28 Jan 2021 17:24:04 +0100

International audience; TCAS resolution advisories generation process during level-off situation is overviewed and illustrated on a real situation captured through mode S radar with RA downlink service. It underlines that one common type of resolution advisories is that which is issued when aircraft are expected to level-off 1000 feet apart, and are converging at the same time. These resolution advisories, often subsequently classed as ?operationally unnecessary? from an air traffic control standpoint, can be perceived as disturbing by controllers and by pilots. This issue has been tackled in this paper by proposing a method to prevent RA triggering during level off situation. This method is based on the setting of the altitude at which the autopilot switches towards the altitude capture mode and on an intrinsic parameter of the autopilot altitude capture mode, namely its natural frequency. It is shown that applying the proposed method to the illustrative example prevents the issuance of resolution advisories when aircraft are expected to level-off 1000 feet apart. The method which is presented is one of the simplest options, and allows altitude capture without triggering resolution advisories for vertical speeds up to 3000 feet/min. Nevertheless, the time needed by the aircraft to capture the cleared flight level is increased. Consequently, future work will focus on improving the time needed to capture the cleared flight level under the constraint to keep positive the distance between the autopilot altitude capture dynamic and the boundary of the RA zone.

The relationship between traffic congestion and road accidents: an econometric approach using GIS

Scipedia content — Wed, 27 Jan 2021 08:42:55 +0100

Both traffic congestion and road accidents impose a burden on society, and it is therefore important for transport policy makers to reduce their impact. An ideal scenario would be that traffic congestion and accidents are reduced simultaneously, however, this may not be possible since it has been speculated that increased traffic congestion may be beneficial in terms of road safety. This is based on the premise that there would be fewer fatal accidents and the accidents that occurred would tend to be less severe due to the low average speed when congestion is present. If this is confirmed then it poses a potential dilemma for transport policy makers: the benefit of reducing congestion might be off-set by more severe accidents. It is therefore important to fully understand the relationship between traffic congestion and road accidents while controlling for other factors affecting road traffic accidents. The relationship between traffic congestion and road accidents appears to be an under researched area. Previous studies often lack a suitable congestion measurement and an appropriate econometric model using real-world data. This thesis aims to explore the relationship between traffic congestion and road accidents by using an econometric and GIS approach. The analysis is based on the data from the M25 motorway and its surrounding major roads for the period 2003-2007. A series of econometric models have been employed to investigate the effect of traffic congestion on both accident frequency (such as classical Negative Binomial and Bayesian spatial models) and accident severity (such as ordered logit and mixed logit models). The Bayesian spatial model and the mixed logit model are the best models estimated for accident frequency and accident severity analyses respectively. The model estimation results suggest that traffic congestion is positively associated with the frequency of fatal and serious injury accidents and negatively (i.e. inversely) associated with the severity of accidents that have occurred. Traffic congestion is found to have little impact on the frequency of slight injury accidents. Other contributing factors have also been controlled for and produced results consistent with previous studies. It is concluded that traffic congestion overall has a negative impact on road safety. This may be partially due to higher speed variance among vehicles within and between lanes and erratic driving behaviour in the presence of congestion. The results indicate that mobility and safety can be improved simultaneously, and therefore there is significant additional benefit of reducing traffic congestion in terms of road safety. Several policy implications have been identified in order to optimise the traffic flow and improve driving behaviour, which would be beneficial to both congestion and accident reduction. This includes: reinforcing electronic warning signs and the Active Traffic Management, enforcing average speed on a stretch of a roadway and introducing minimum speed limits in the UK. This thesis contributes to knowledge in terms of the relationship between traffic congestion and road accidents, showing that mobility and safety can be improved simultaneously. A new hypothesis is proposed that traffic congestion on major roads may increase the occurrence of serious injury accidents. This thesis also proposes a new map-matching technique so as to assign accidents to the correct road segments, and shows how a two-stage modelling process which combines both accident frequency and severity models can be used in site ranking with the objective of identifying hazardous accident hotspots for further safety examination and treatment.

Pan European Corridors of Transport Infrastructure-Driving Sustainable Developments and Partnerships towards a well-being society

Scipedia content — Tue, 26 Jan 2021 18:28:30 +0100

2007/2008 Scenarios of the future European Union suggest that Europe will be part of a more globalised world economy, and will build even stronger relationships among neighbouring countries. It will have dense urban areas and a mutated climate. People’s lives will be transformed by breakthroughs in energy, transport and communication technologies. The transport sector in these forecasts will have to satisfy a greater demand for mobility. At the same time it will have to find solutions in order address its negative externalities, which affect the environment, the economy and the society. The Trans European Network of Transport (TEN-T) and the Pan-European Transport Corridors are defined as key instruments in order to achieve the economic growth and social integration within the EU political map. They are of a crucial importance when implementing EU enlargement policies towards neighbouring countries. The networks of transport and communication will further develop relations with EU neighbouring countries and will assist them in achieving most advanced standards. Corridor Eight is one of the ten “Pan European Corridors of Transport”, based on the trace of an antic roman corridor, “La Via Egnatia” (Fasolo. M. 2003). When taking in consideration the to date reports of the civil works, services, and the main operating indicators of the Corridor Eight as a part of Pan European Transport Corridors, the following may be observed: Corridor Eight it is not yet operational in all modes of transport and services along all its length and area. There are no railway links in different parts of it, while there is not high operational performance of the existing roads and highways. Consequently it does not fulfil its mission to enhance the movement of people, goods, information and experiences in all forms of transport from Adriatic and Ion Seas in the Mediterranean Sea to the Black Sea. It does not therefore link societies, natural resources and economies between two peninsulas and Euro-Asian region. Corridor Eight does not offer the necessary capacity and contemporary standards to afford flows of traffic for people, horizontal and vertical signallers, emergency situations and electricity black out situations, while there are not alternative electricity resources along its segments of roads, railways, seaports, etc. There are not clear demonstrations to satisfy a safe, secure, and healthy transport services along the area. Taking in consideration, • the conclusion that corridors of transport as spatial planed parts of the territory are confirmed to be effective tools for development and social integration between countries ; • the fact that international transport infrastructure realities are demonstrating to be competitive and complementary and of high standard service ; • that up to now regional and geopolitical realities has not been in favour of the Balkans; • that the future transport will be based on achieving goals of being clean, safe, secure, healthy and cost effective ; • that the society of countries along Corridor are clearly defined towards EU integration, and that being part of EU means obligation and standards must be achieved; • that in a near future Albania, FYROM (Macedonia) will be part of EU political map: The following research questions are addressed in the study: – Could countries like Albania, Macedonia and Bulgaria, develop sustainable transport along corridors of transport and their networks in order to be more competitive and complementary one among TEN –T and Pan-European Transport Corridors and areas? – What policies should be pursued and what strategies should be drawn while building corridors of transport infrastructure as a functional part of TEN-T and Pan-European transport corridors networks. How can those countries offer a comfortable, safe, healthy, secure transport to EU citizens as well as a multitude of choices in means of transport along Corridor Eight countries? – What partnerships must be raised to face the challenge of sustainable corridors of transport? – What policy should be pursued to turn corridors of transport into corridors of social integration and economic growth? – Could we, and which are the instruments to build a state of wellbeing along the corridors of infrastructure, beyond the political, natural, ethnic, religious and cultural borders, aiming towards walking local, achieving global ! The theory and conceptual approach to the transportation corridors will be presented by this study, to highlight social and economical benefits of transport activity as well as the consequences coming of it and regarding human activity, environment, bio natural diversities and global warming along corridors area. The presentation of the status of both: the Transnational European Network of Transport (TEN-T), as well as that of the Pan European Corridors of Transport in regard to the future sustainable policies and guidelines of the European Commission is one of prior objectives of this study. Consequently the research objective is to present the realities along Corridor Eight areas in relation to sustainable indicators. Finally, this study will endeavour to feature the best performing experiences and attempt to suggest the most beneficial solutions towards sustainable development in the societies along the countries of Corridor Eight. XXI Ciclo 1961

Short sea shipping : barriers, incentives and feasibility of truck ferry

Scipedia content — Tue, 26 Jan 2021 18:21:53 +0100

CIVINS (Civilian Institutions) Thesis document Many problems plague the United States' transportation infrastructure: congestion, poor roadway conditions, obsolescence, and maintenance cost not the least among these. In recent years, the Department of Transportation, through its Maritime Administration (MARAD), has begun a program for partial solution to this complex transportation issue. MARAD, acting on tasks assigned to it in the Energy Independence and Security Act of 2007, has established the Marine Highways Initiative to spur development of alternative and supplemental transportation modes that utilize inland waterways and coastlines of the United States. At the same time, the U.S. Department of Defense is investigating ways to fulfill its sealift requirements, while at the same time reducing its inventory of government owned vessels that do not trade. This paper explores the issues surrounding the current state of transportation and transportation infrastructure. It also seeks to determine the feasibility of a truck ferry that would accomplish both MARAD's Marine Highway as well as the Department of Defense's sealift goals. The feasibility study examines the hypothetical business' profitability through different funding and operating scenarios. The analysis also sets a framework for other studies by using open-source data to determine freight flows, potential costs and market share. http://archive.org/details/shortseshippingb109454310 Contract number: N62271-97-G-0026. CIVINS Approved for public release; distribution is unlimited.

Optimal Intercity Transportation Services with Heterogeneous Demand and Variable Fuel Price

Scipedia content — Tue, 26 Jan 2021 18:19:05 +0100

In this thesis we examine how fuel price variation affects the optimal mix of services in intercity transportation. Towards this end, we make two main contributions. The first is the development of an analytic total logistics cost model of intercity transportation, which is sensitive to fuel price and incorporates multiple classes of vehicles serving passengers with differentiated values of time. The second is an empirical investigation of the cost relationship between fuel price and operating cost for intercity transportation vehicles. The analytic total logistics cost models are combined with the empirical models to gain insights into the impact of fuel price on optimal service mixes in representative corridors. We consider a scheduled intercity transportation corridor on which different classes of intercity transportation vehicles serve passengers with differentiated values of time. In determining optimal service mix, we consider a central planner choosing the vehicles and service frequencies that provide the minimum total logistics cost for an intercity transportation corridor. The total logistics cost is the sum of the two main intercity transportation cost components: vehicle operator cost and passenger cost. In considering operating and passenger costs together, we balance cost efficiency and level of service of alternative vehicles with different cost structures and service attributes. In developing the total logistics cost model, we seek both analytic insights and numerical examples. To keep the model analytically tractable while at the same time incorporating multiple objectives, including fuel cost, operating cost, schedule delay, and line-haul time, we incorporate the continuum approximation method from logistics. In employing the continuum approximation, discrete variables are considered continuous, leading to analytic functions from which we can evaluate qualitatively the relationships among fuel price, service level, and comparative vehicle cost. An investigation of the analytic model suggests that, while a fuel price increase would increase costs for any corridor, the rate of cost increase for a corridor served by a mix of vehicle technologies diminishes more rapidly with fuel price. We also find that an increase in fuel price causes vehicles to become more differentiated with respect to the value of time of the passengers they serve. In other words, under high fuel prices the total logistics cost can be minimized by effectively segregating passengers on different types of vehicles according to their values of time. We complement the analytic findings with an empirical investigation of the cost relationship between fuel price and operating cost for different classes of intercity transportation vehicles. We perform this analysis for a subset of intercity transportation vehicles for which data is readily available: jet and turboprop aircraft. In developing a translog operating cost model for jet aircraft, we estimate a flexible functional form that provides a detailed representation of the empirical relationship between fuel cost and operating cost, allowing for substitution, scale, aircraft age, and other effects – including interactions – to be captured. The function reveals that as fuel price increases, airlines will take steps to use fuel more efficiently by leveraging other inputs; however, the potential for this supplier input substitution for fuel is rather modest. This finding reinforces the formulation of the analytic total logistics cost model, in which the only actions available to a central planner to reduce costs are changing technologies and service frequencies. It also proves that empirical models with simpler functional forms are able to accurately predict operating costs, despite the lack of variable interactions. Using linear empirical operating cost models, we estimate operating cost and total logistics costs for intercity transportation corridors served by single vehicle fleets of three different aircraft classes. We find that a specific turboprop aircraft model, with a relatively low fuel consumption rate, provides intercity transportation service with the minimum operating cost compared with a jet with smaller seating capacity over all fuel prices considered and medium-capacity jets for some fuel prices. However, this is no longer the case when total logistics cost is considered, due to the lower quality of passenger service turboprops provide. At a given intercity transportation corridor distance, the fuel price for which the total logistics cost per passenger is equal across turboprops and low-capacity jets is in the fuel price range experienced from 2004 and expected through 2020. For this fuel price range, the total logistics cost per passenger for the medium-capacity jet is generally lower than the turboprop and always lower the lowcapacity jet. This suggests that a mix of services between intercity transportation vehicles could minimize cost for this range of fuel price. To investigate the possibility of mixing services to reduce costs further, we combine the analytic total logistics cost model with the empirical models. In addition to a jet and turboprop aircraft model, we build a high speed rail cost model and consider high speed rail as an additional intercity transportation technology. We find the minimum cost vehicle combination to be sensitive to fuel price in a small transition zone within which the cost ordering of vehicle combinations changes significantly, whereas outside this zone the orderings are stable. As the transition area is in the range of fuel prices forecasted between the years 2010-2035, the results indicate fuel price changes between 2010 and 2035 may dramatically alter the most cost-effective ways to provide intercity passenger transport. We find that high speed rail is a part of a mixed vehicle service that can reduce total logistics cost, suggesting that an integrated air and rail strategy could be an effective tool to manage costs and fuel consumption for an intercity transportation system.

Park Et Bin Sistemi Ve İstanbul’daki Uygulaması

Scipedia content — Tue, 26 Jan 2021 18:18:34 +0100

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010

Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2010

Bu çalışmada, toplu taşıma kullanımını arttıran en etkili yöntemlerden biri olan Park Et Bin Sistemi (PEBS) incelenmiştir. Otomobil kullanımının azaltılması, ulaşımda sürdürülebilirliğin başarılması ve şehirlerin daha yaşanılır hale gelmesi için en etkili yol, toplu taşımanın kullanılmasıdır. PEBS’de amaç; otomobil sürücülerinin araçlarını, şehir merkezi dışındaki toplu taşıma istasyonlarının yakınında bulunan PEBS tesislerine park ettikten sonra, toplu taşıma araçlarını kullanarak gidecekleri yere daha rahat gitmelerini sağlamaktır. PEBS’in planlaması çok önemlidir. Sistemin yeri ve özelliği, toplu taşıma araçlarını kullanan otomobil sürücülerinin sayısını arttıracak şekilde düzenlenmelidir. PEBS kullanıcıların yolculuk davranışlarının analizi için, İstanbul’daki 6 PEBS tesisinde bir anket çalışması yapılmıştır. Anketten çıkan sonuç, sistemin toplu taşıma kullanımı arttırdığını ve trafik tıkanıklığını azaltabileceğini göstermiştir.

Park and Ride is one of the most effective methods which increase using public transport has been examined in this study. Using public transport is an effective way to decrease car using, to achieve sustainable and more livable cities. The aim behind Park and Ride System is to get people out of their cars near the public transport stations, before entering city center and provide drivers to go their destinations with public transportation. Park and Ride’s planning is extremely important. Location of facility and features of the system must be well planned to attract significant number of drivers. A survey study was applied to analyze Park and Ride’s users’ behaviors at 6 Park and Ride facilities in Istanbul. The findings showed that Park and Ride increased public transport users and could decrease traffic congestion.

Yüksek Lisans

M.Sc.

Shaping the Next Generation Air Transportation System with an Airspace Planning and Collaborative Decision Making Model

Scipedia content — Tue, 26 Jan 2021 18:06:09 +0100

This dissertation contributes to the ongoing national project concerning the \\emph{Next Generation Air Transportation System} (NextGen) that endeavors, in particular, to reshape the management of air traffic in the continental United States. Our work is part of this effort and mainly concerns modeling and algorithmic enhancements to the Airspace Planning and Collaborative Decision-Making Model (APCDM). First, we augment the APCDM to study an \\emph{Airspace Flow Program} (AFP) in the context of weather-related disruptions. The proposed model selects among alternative flight plans for the affected flights while simultaneously (a) integrating slot-exchange mechanisms induced by multiple Ground Delay Programs (GDPs) to permit airlines to improve flight efficiencies through a mediated bartering of assigned slots, and (b) considering issues related to sector workloads, airspace conflicts, as well as overall equity concerns among the involved airlines in regard to accepted slot trades and flight plans. More specifically, the APCDM is enhanced to include the following: \\begin{enumerate}[a.] \\item The revised model accommodates continuing flights, where some flight cannot depart until a prerequisite flight has arrived. Such a situation arises, for example, when the same aircraft will be used for the departing flight. \\item We model a slot-exchange mechanism to accommodate flights being involved in multiple trade offers, and to permit slot trades at multiple GDP airports (whence the flight connection constraints become especially relevant). We also model flight cancelations whereby, if a flight assigned to a particular slot is canceled, the corresponding vacated slot would be made available for use in the slot-exchange process. \\item Alternative equity concepts are presented, which more accurately reflect the measures used by the airlines. \\item A reduced variant of the APCDM, referred to as \\textbf{APCDM-Light}, is also developed. This model serves as a fast-running version of APCDM to be used for quick-turn analyses, where the level of modeling detail, as well as data requirements, are reduced to focus only on certain key elements of the problem. \\item As an alternative for handling large-scale instances of APCDM more effectively, we present a \\emph{sequential variable fixing heuristic} (SFH). The list of flights is first partitioned into suitable subsets. For the first subset, the corresponding decision variables are constrained to be binary-valued (which is the default for these decision variables), while the other variables are allowed to vary continuously between 0 and 1. If the resulting solution to this relaxed model is integral, the algorithm terminates. Otherwise, the binary variables are fixed to their currently prescribed values and another subset of variables is designated to be binary constrained. The process repeats until an integer solution is found or the heuristic encounters infeasibility. \\item We experiment with using the APCDM model in a \\emph{dynamic, rolling-horizon framework}, where we apply the model on some periodic basis (e.g., hourly), and where each sequential run of the model has certain flight plan selections that are fixed (such as flights that are already airborne), while we consider the selection among alternative flight plans for other imminent flights in a look-ahead horizon (e.g., two hours). \\end{enumerate} These enhancements allow us to significantly expand the functionality of the original APCDM model. We test the revised model and its variants using realistic data derived from the \\emph{Enhanced Traffic Management System} (ETMS) provided by the \\emph{Federal Aviation Administration} (FAA). One of the new equity methods, which is based on average delay per passenger (or weighted average delay per flight), turns out to be a particularly robust way to model equity considerations in conjunction with sector workloads, conflict resolution, and slot-exchanges. With this equity method, we were able to solve large problem instances (1,000 flights) within 30 seconds on average using a 1\\% optimality tolerance. The model also produced comparable solutions within about 20 seconds on average using the Sequential Fixing Heuristic (SFH). The actual solutions obtained for these largest problem instances were well within 1\\% of the best known solution. Furthermore, our computations revealed that APCDM-Light can be readily optimized to a 0.01\\% tolerance within about 5 seconds on average for the 1,000 flight problems. Thus, the augmented APCDM model offers a viable tool that can be used for tactical air traffic management purposes as an airspace flow program (particularly, APCDM-Light), as well as for strategic applications to study the impact of different types of trade restrictions, collaboration policies, equity concepts, and airspace sectorizations. The modeling of slot ownership in the APCDM motivates another problem: that of generating detoured flight plans that must arrive at a particular slot time under severe convective weather conditions. This leads to a particular class of network flow problems that seeks a shortest path, if it exists, between a source node and a destination node in a connected digraph $G(N,A)$, such that we arrive at the destination at a specified time while leaving the source no earlier than a lower bounding time, and where the availability of each network link is time-dependent in the sense that it can be traversed only during specified intervals of time. We refer to this problem as the \\emph{reverse time-restricted shortest path problem} (RTSP). We show that RTSP is NP-hard in general and propose a dynamic programming algorithm for finding an optimal solution in pseudo-polynomial time. Moreover, under a special regularity condition, we prove that the problem is polynomially solvable with a complexity of order $O(|N||A|)$. Computational results using real flight generation test cases as well as random simulated problems are presented to demonstrate the efficiency of the proposed solution procedures. The current airspace configuration consists of sectors that have evolved over time based on historical traffic flow patterns. \\citet{kopardekar_dyn_resect_2007} note that, given the current airspace configuration, some air traffic controller resources are likely under-utilized, and they also point out that the current configuration limits flexibility. Moreover, under the free-flight concept, which advocates a relaxation of waypoint traversals in favor of wind-optimized trajectories, the current airspace configuration will not likely be compatible with future air traffic flow patterns. Accordingly, one of the goals for the \\emph{NextGen Air Transportation System} includes redesigning the airspace to increase its capacity and flexibility. With this motivation, we present several methods for defining sectors within the \\emph{National Airspace System} (NAS) based on a measure of sector workload. Specifically, given a convex polygon in two-dimensions and a set of weighted grid points within the region encompassed by the polygon, we present several mixed-integer-programming-based algorithms to generate a plane (or line) bisecting the region such that the total weight distribution on either side of the plane is relatively balanced. This process generates two new polygons, which are in turn bisected until some target number of regions is reached. The motivation for these algorithms is to dynamically reconfigure airspace sectors to balance predicted air-traffic controller workload. We frame the problem in the context of airspace design, and then present and compare four algorithmic variants for solving these problems. We also discuss how to accommodate monitoring, conflict resolution, and inter-sector coordination workloads to appropriately define grid point weights and to conduct the partitioning process in this context. The proposed methodology is illustrated using a basic example to assess the overall effect of each algorithm and to provide insights into their relative computational efficiency and the quality of solutions produced. A particular competitive algorithmic variant is then used to configure a region of airspace over the U.S. using realistic flight data. The development of the APCDM is part of an ongoing \\emph{NextGen} research project, which envisages the sequential use of a variety of models pertaining to three tiers. The \\emph{Tier 1} models are conceived to be more strategic in scope and attempt to identify potential problematic areas, e.g., areas of congestion resulting from a severe convective weather system over a given time-frame, and provide aggregate measures of sector workloads and delays. The affected flow constrained areas (FCAs) highlighted by the results from these \\emph{Tier 1} models would then be analyzed by more detailed \\emph{Tier 2} models, such as APCDM, which consider more specific alternative flight plan trajectories through the different sectors along with related sector workload, aircraft conflict, and airline equity issues. Finally, \\emph{Tier 3} models are being developed to dynamically examine smaller-scaled, localized fast-response readjustments in air traffic flows within the time-frame of about an hour prior to departure (e.g., to take advantage of a break in the convective weather system). The APCDM is flexible, and perhaps unique, in that it can be used effectively in all three tiers. Moreover, as a strategic tool, analysts could use the APCDM to evaluate the suitability of potential airspace sectorization strategies, for example, as well as identify potential capacity shortfalls under any given sector configuration. Ph. D.

Electric vehicle charging coordinated by electricity suppliers : an economic impact analysis

Scipedia content — Tue, 26 Jan 2021 18:00:01 +0100

von Marion Glatz Zsfassung in dt. Sprache Wien, Techn. Univ., Dipl.-Arb., 2010

Simulation-Based Analysis of Wake Turbulence Encounters in Current Flight Operations

Scipedia content — Tue, 26 Jan 2021 17:23:53 +0100

One way to address the need for increased airspace system capacity is to reduce the separation requirements between aircraft in-flight. A key limiting factor to any reduction in separation is wake turbulence. The potential for aircraft to encounter wake turbulence poses a threat to both safety as well as increased efficiency. This research effort seeks to develop a model that can be used to evaluate the potential for wake encounters in todayâ s flight operations, as well as serve as a tool for evaluating future reduced separation scenarios. The wake encounter model (WEM) achieves this goal by integrating results from NASAâ s TDAWP wake turbulence prediction model with a flight operations model based on radar flight track data. Unique in this modelâ s design, is the ability to evaluate the potential for wake encounters throughout the terminal area versus previous research which has largely been restricted to areas near the runway. Expanding the modelâ s reach provides not only for a more thorough analysis of potential wake encounters, but also creates an effective tool for evaluating future reduced separation scenarios. "p" The WEM model was used to evaluate operations at three metropolitan airspaces in the United States: Atlanta, Los Angeles and New York. The results from these model runs indicated that potential wake encounters in todayâ s operations were few. More importantly, the results from the WEM create a baseline for wake turbulence exposure in todayâ s system, by which future scenarios can be compared against as part of any comprehensive reduced separation safety analysis. Master of Science

A Probabilistic Approach to the Air Traffic Management in The Next Generation Air Transportation System: Optimal Routing Decision With Geometric Recourse Model

Scipedia content — Tue, 26 Jan 2021 17:15:53 +0100

There has been growing interest in air transportation community to develop a routing decision model based on probabilistic characterization of severe weather. In the probabilistic air traffic management (PATM), decisions are made based on the stochastic weather information in the expected total cost sense. Probabilistic approach aims to enhance routing flexibility and reduce the risks associated with uncertainty of the future weather. In this research, a geometric model is adopted to generate optimal route choice when the future weather is stochastic. The geometric recourse model (GRM) is a strategic PATM model that incorporates route hedging and en-route recourse options to respond to weather change. Hedged routes are routes other than the nominal or detour route, and aircraft is re-routed to fly direct to the destination, which is called recourse, when the weather restricted airspace become flyable. Aircraft takes either the first recourse or the second recourse: The first recourse occurs when weather clears before aircraft reaches it flying on the initial route. The second recourse occurs when the aircraft is at the weather region. There are two variations of GRM: Single Recourse Model (SRM) with first recourse only and Dual Recourse Model (DRM) with both the first and second recourse options. When the weather clearance time follows a uniform distribution, SRM becomes convex with optimal route being either the detour or a hedged route. The DRM has a special property when the maximum storm duration time is less than the flight time to the tip of the storm on the detour route: it is always optimal to take the nominal route. The performance study is conducted by measuring the cost saving from either SRM or DRM. The result shows that there are cases with substantial cost saving, reaching nearly 30% with DRM.The ground-airborne hybrid model is an extension of the GRM, where both ground holding as well as route hedging are considered. The optimal combination of ground delay and route choice is determined by weather characteristics as well as the ground-airborne cost ratio. The numerical analysis reveals that whenever ground delay is required, the optimal route choice is the nominal one, while a non-nominal route is optimal when the ground delay is zero. There exists a unique critical cost ratio associated with given weather condition, which determines whether ground holding is optimal or not.

Mitigating distributed denial of service attacks with Multiprotocol Label Switching--Traffic Engineering (MPLS-TE)

Scipedia content — Tue, 26 Jan 2021 17:11:12 +0100

Denial of Service (DoS) occurs when legitimate users are prevented from using a service over a computer network. A Distributed Denial of Service (DDoS) attack is a more serious form of DoS in which an attacker uses the combined power of many hosts to flood and exhaust the networking or computing resources of a target server. In recent years, DDoS attacks have become a major threat to both civilian and military networks. Multi-Protocol Label Switching with Traffic Engineering (MPLS-TE) is an emerging technology that allows explicit, bandwidth-guaranteed packet forwarding paths to be established for different traffic flows. It provides a means for diverting packets of a suspected DDoS attack for analysis and cleaning before forwarding them to the actual destination. The objective of this research was to implement and evaluate the performance of an MPLS-TE based solution against DDoS attacks on a realistic test-bed network consisting of Cisco routers. The test-bed has been integrated with SnortÂ®, an open source Intrusion Detection System (IDS), to achieve automatic detection and to mitigate DDoS attacks. The test-bed network was subject to a series of malicious traffic flows with varying degrees of intensity. The results demonstrated that MPLS-TE is very effective in mitigating such attacks. The overall system response time and the router CPU loads are comparable to those reported by two former NPS theses that examined alternative solutions based on BGP blackhole routing. http://archive.org/details/mitigatingdistri109454817 Outstanding Thesis Hellenic Navy author. Approved for public release; distribution is unlimited.

Stochastic Methods for Dilemma Zone Protection at Signalized Intersections

Scipedia content — Tue, 26 Jan 2021 17:06:38 +0100

Dilemma zone (DZ), also called decision zone in other literature, is an area where drivers face an indecisiveness of stopping or crossing at the yellow onset. The DZ issue is a major reason for the crashes at high-speed signalized intersections. As a result, how to prevent approaching vehicles from being caught in the DZ is a widely concerning issue. In this dissertation, the author addressed several DZ-associated issues, including the new stochastic safety measure, namely dilemma hazard, that indicates the vehiclesâ changing unsafe levels when they are approaching intersections, the optimal advance detector configurations for the multi-detector green extension systems, the new dilemma zone protection algorithm based on the Markov process, and the simulation-based optimization of traffic signal systems with the retrospective approximation concept. The findings include: the dilemma hazard reaches the maximum when a vehicle moves in the dilemma zone and it can be calculated according the caught vehiclesâ time to the intersection; the new (optimized) GES design can significantly improve the safety, but slightly improve the efficiency; the Markov process can be used in the dilemma zone protection, and the Markov-process-based dilemma zone protection system can outperform the prevailing dilemma zone protection system, the detection-control system (D-CS). When the data collection has higher fidelity, the new system will have an even better performance. The retrospective approximation technique can identify the sufficient, but not excessive, simulation efforts to model the true system and the new optimization algorithm can converge fast, as well as accommodate the requirements by the RA technique. Ph. D.

Capturing socio-technical systems with agent-based modelling

Scipedia content — Tue, 26 Jan 2021 17:05:21 +0100

What is a suitable modelling approach for socio-technical systems? The answer to this question is of great importance to decision makers in large scale interconnected network systems. The behaviour of these systems is determined by many actors, situated in a dynamic, multi-actor, multi-objective and multi-level jungle. Models to support such an actor should be able to capture both the physical and social reality of the system, their interactions with one another and the external dynamic environment. Moreover, they must allow users to experiment with changes in both the physical and the social network configuration. To deal with these challenges a generic agent-based modelling framework for socio-technical systems is developed in this thesis. The cornerstone of the framework is a shared language formalised in an ontology, which forms the interface needed to bring different elements of the system (both social and physical) together, to interconnect different models and ensure interoperability. The re-usability of building blocks helps modellers build new models more efficiently. The models developed with the new framework are shown to offer valuable decision support in case studies of an oil refinery supply chain and an intermodal freight hub.

Sistema de adquisición de parámetros de tráfico vehicular

Scipedia content — Tue, 26 Jan 2021 16:52:02 +0100

En este documento se describe una sistema de adquisición de variables de tráfico vehicular usando técnicas de visión por computador mediante una cámara ubicada en una vía de máximo tres carriles, se describen los procedimientos a seguir en la ubicación de la cámara y las configuraciones propias del algoritmo para que se presente una efectividad en la estimación superior al 95%. This document describes an acquisition system for vehicular traffic variables using computer vision techniques using a camera on a maximum three-lane road, describes the procedures to be followed in the location of the camera and settings specific to the algorithm that estimate effectiveness in the estimation of traffic variables greater than 95%.

Simple and stable dynamic traffic engineering for provider scale ethernet

Scipedia content — Tue, 26 Jan 2021 16:43:37 +0100

Trabalho apresentado no âmbito do Mestrado em Engenharia Informática, como requisito parcial para obtenção do grau de Mestre em Engenharia Informática The high speeds and decreasing costs of Ethernet solutions has motivated providers’ interest in using Ethernet as the link layer technology in their backbone and aggregation networks. Provider scale Ethernet offers further advantages, providing not only an easy to manage solution for multicast traffic, but also transparent interconnection between clients’ LANs. These Ethernet deployments face altogether different design issues, requiring support for a significantly higher number of hosts. This support relies on hierarquization, separating address and virtual network spaces of customers and providers. In addition, large scale Ethernet solutions need to grant forwarding optimality. This can be achieved using traffic engineering approaches. Traffic engineering defines the set of engineering methods and techniques used to optimize the flow of network traffic. Static traffic engineering approaches enjoy widespread use in provider networks, but their performance is greatly penalized by sudden load variations. On the other hand, dynamic traffic engineering is tailored to adapt to load changes. However, providers are skeptical to adopt dynamic approaches as these induce problems such as routing instability, and as a result, network performance decreases. This dissertation presents a Simple and Stable Dynamic Traffic Engineering framework (SSD-TE), which addresses these concerns in a provider scale Ethernet scenario. The validation results show that SSD-TE achieves better or equal performance to static traffic engineering approaches, whilst remaining both stable and responsive to load variations.

Intermodal Barge Transport

Scipedia content — Tue, 26 Jan 2021 16:28:38 +0100

The thesis addresses the opportunities and conditions to increase the market share of intermodal barge transport in Northwest Europe. In particular, it focuses on strategies to improve the performances of the different links of the intermodal transport chain: the barge transport services, the transhipment at terminals and pre- and post-truck haulage operations. The thesis shows that the development of more complex barge transport services, implemented for instance in collection/distribution-, trunk-feeder- and hub-and-spoke service networks, can improve the market position of barge transport in the hinterland transport of containers and enables to open up new markets for intermodal barge transport. However, to support the well-functioning of these service networks appropriate terminal and transhipment concepts are needed. Basically there are three ‘locations’ in the network where tailor-made barge handling innovations are needed: (1) in the seaport, (2) in the capillaries of the waterway network and (3) in strategically located inland nodes, e.g. to support hub-and-spoke networks. In pre- and post-truck haulage, which has a relatively large share in the total chain costs, the challenge is to improve the organisation of these hauls through combining loaded trips. In developing business areas close to waterways favourable conditions are created for efficient pre- and post-haulage and this contributes to improving the competitiveness of intermodal barge transport.