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Sample records for alleviate traffic congestion

  1. Agent Reward Shaping for Alleviating Traffic Congestion

    NASA Technical Reports Server (NTRS)

    Tumer, Kagan; Agogino, Adrian

    2006-01-01

    Traffic congestion problems provide a unique environment to study how multi-agent systems promote desired system level behavior. What is particularly interesting in this class of problems is that no individual action is intrinsically "bad" for the system but that combinations of actions among agents lead to undesirable outcomes, As a consequence, agents need to learn how to coordinate their actions with those of other agents, rather than learn a particular set of "good" actions. This problem is ubiquitous in various traffic problems, including selecting departure times for commuters, routes for airlines, and paths for data routers. In this paper we present a multi-agent approach to two traffic problems, where far each driver, an agent selects the most suitable action using reinforcement learning. The agent rewards are based on concepts from collectives and aim to provide the agents with rewards that are both easy to learn and that if learned, lead to good system level behavior. In the first problem, we study how agents learn the best departure times of drivers in a daily commuting environment and how following those departure times alleviates congestion. In the second problem, we study how agents learn to select desirable routes to improve traffic flow and minimize delays for. all drivers.. In both sets of experiments,. agents using collective-based rewards produced near optimal performance (93-96% of optimal) whereas agents using system rewards (63-68%) barely outperformed random action selection (62-64%) and agents using local rewards (48-72%) performed worse than random in some instances.

  2. Proceedings of the ITE's 1987 national conference on strategies to alleviate traffic congestion

    SciTech Connect

    Not Available

    1988-01-01

    These proceedings discuss the papers presented at the conference on the subject of traffic congestion. The topics discussed were: Surveillance control and driver information system; fiber optics for traffic surveillance; solutions to traffic problems; traffic management in Texas; truck operations; traffic engineering; parking standards and requirements; and planning of improving traffic flow on local streets.

  3. Traffic congestion in interconnected complex networks

    NASA Astrophysics Data System (ADS)

    Tan, Fei; Wu, Jiajing; Xia, Yongxiang; Tse, Chi K.

    2014-06-01

    Traffic congestion in isolated complex networks has been investigated extensively over the last decade. Coupled network models have recently been developed to facilitate further understanding of real complex systems. Analysis of traffic congestion in coupled complex networks, however, is still relatively unexplored. In this paper, we try to explore the effect of interconnections on traffic congestion in interconnected Barabási-Albert scale-free networks. We find that assortative coupling can alleviate traffic congestion more readily than disassortative and random coupling when the node processing capacity is allocated based on node usage probability. Furthermore, the optimal coupling probability can be found for assortative coupling. However, three types of coupling preferences achieve similar traffic performance if all nodes share the same processing capacity. We analyze interconnected Internet autonomous-system-level graphs of South Korea and Japan and obtain similar results. Some practical suggestions are presented to optimize such real-world interconnected networks accordingly.

  4. Traffic congestion and dispersion in Hurricane evacuation

    NASA Astrophysics Data System (ADS)

    Tanaka, Katsunori; Nagatani, Takashi; Hanaura, Hirotoshi

    2007-03-01

    We study the traffic congestion and dispersion of vehicles occurring on a single lane highway in Hurricane evacuation. The traffic congestion depends on both sensitivity and speed of the leading vehicle. When the leading vehicle moves with low speed, the vehicular traffic exhibits the stop and go-wave (oscillating congested traffic) for low sensitivity, while the traffic results in the homogeneous congested traffic for high sensitivity. The traffic dispersion is measured by the time difference between the leading and rear vehicles. The time difference fluctuates highly for the oscillating congestion traffic, while it keeps a constant value for the homogeneous congested traffic. The traffic states in Hurricane evacuation is connected to the phase diagram of conventional traffic.

  5. Congestion in different topologies of traffic networks

    NASA Astrophysics Data System (ADS)

    Wu, J. J.; Gao, Z. Y.; Sun, H. J.; Huang, H. J.

    2006-05-01

    In the present paper, we consider three different types of networks (random, small-world, and scale-free) with dynamic weights and focus on how the characteristic parameters (degree distribution exponent, rewiring probability, and clustering coefficient) affect the degree of congestion and the efficiency. Experiment simulation shows that the scale-free and small-world networks are more prone to suffering from congestion than random ones at low traffic flows, but the scale-free network is more sensitive than the small-world one. Compared with other two topologies, the scale-free network, while its congestion factor rises slowly, can support much more volume of traffic as the traffic flow increases. Results also indicate that for the same value of congestion factor, there may be a different efficiency, which shows that only congestion or efficiency alone cannot evaluate the performance of networks effectively.

  6. Analyzing freeway traffic under congestion: Traffic dynamics approach

    SciTech Connect

    Nam, D.H.; Drew, D.R.

    1998-05-01

    This paper presents an analysis of freeway traffic flows under congestion based on the principle of traffic dynamics, using the example of recurring congestion. Queuing and discharging mechanisms are analyzed using the fundamental concept of conservation of vehicles. These analysis results are applied for reviewing the two conventional macroscopic analysis tools, deterministic queuing analysis and shock-wave analysis. Comparative study results have demonstrated that (1) the two methods are fundamentally different from the traffic modeling point of view; (2) deterministic queuing analysis always underestimates the overall magnitude of delays compared to shock-wave analysis; and (3) the area between the demand and the capacity curves in a queuing diagram is analytically equivalent to total vehicle-hours of travel in congestion as opposed to the widely accepted total vehicle-hours of delay. The study results imply that the guidelines of the 1994 Highway Capacity Manual may result in the underestimation of congestion-related statistics. For the purposes of illustration and verification, a numerical example problem is provided.

  7. Computational realizations of the entropy condition in modeling congested traffic flow. Final report

    SciTech Connect

    Bui, D.D.; Nelson, P.; Narasimhan, S.L.

    1992-04-01

    Existing continuum models of traffic flow tend to provide somewhat unrealistic predictions for conditions of congested flow. Previous approaches to modeling congested flow conditions are based on various types of special treatments at the congested freeway sections. Ansorge (Transpn. Res. B, 24B(1990), 133-143) has suggested that such difficulties might be substantially alleviated, even for the simple conservation model of Lighthill and Whitman, if the entropy condition were incorporated into the numerical schemes. In this report the numerical aspects and effects of incorporating the entropy condition in congested traffic flow problems are discussed. Results for simple scenarios involving dissipation of traffic jams suggest that Godnunov's method, which in a numerical technique that incorporates the entropy condition, is more accurate than two alternative methods. Similarly, numerical results for this method, applied to simple model problems involving formation of traffic jams, appear at least as realistic as those obtained from the well-known code of FREFLO.

  8. Congestion Transition in Air Traffic Networks

    PubMed Central

    Monechi, Bernardo; Servedio, Vito D. P.; Loreto, Vittorio

    2015-01-01

    Air Transportation represents a very interesting example of a complex techno-social system whose importance has considerably grown in time and whose management requires a careful understanding of the subtle interplay between technological infrastructure and human behavior. Despite the competition with other transportation systems, a growth of air traffic is still foreseen in Europe for the next years. The increase of traffic load could bring the current Air Traffic Network above its capacity limits so that safety standards and performances might not be guaranteed anymore. Lacking the possibility of a direct investigation of this scenario, we resort to computer simulations in order to quantify the disruptive potential of an increase in traffic load. To this end we model the Air Transportation system as a complex dynamical network of flights controlled by humans who have to solve potentially dangerous conflicts by redirecting aircraft trajectories. The model is driven and validated through historical data of flight schedules in a European national airspace. While correctly reproducing actual statistics of the Air Transportation system, e.g., the distribution of delays, the model allows for theoretical predictions. Upon an increase of the traffic load injected in the system, the model predicts a transition from a phase in which all conflicts can be successfully resolved, to a phase in which many conflicts cannot be resolved anymore. We highlight how the current flight density of the Air Transportation system is well below the transition, provided that controllers make use of a special re-routing procedure. While the congestion transition displays a universal scaling behavior, its threshold depends on the conflict solving strategy adopted. Finally, the generality of the modeling scheme introduced makes it a flexible general tool to simulate and control Air Transportation systems in realistic and synthetic scenarios. PMID:25993476

  9. Congestion transition in air traffic networks.

    PubMed

    Monechi, Bernardo; Servedio, Vito D P; Loreto, Vittorio

    2015-01-01

    Air Transportation represents a very interesting example of a complex techno-social system whose importance has considerably grown in time and whose management requires a careful understanding of the subtle interplay between technological infrastructure and human behavior. Despite the competition with other transportation systems, a growth of air traffic is still foreseen in Europe for the next years. The increase of traffic load could bring the current Air Traffic Network above its capacity limits so that safety standards and performances might not be guaranteed anymore. Lacking the possibility of a direct investigation of this scenario, we resort to computer simulations in order to quantify the disruptive potential of an increase in traffic load. To this end we model the Air Transportation system as a complex dynamical network of flights controlled by humans who have to solve potentially dangerous conflicts by redirecting aircraft trajectories. The model is driven and validated through historical data of flight schedules in a European national airspace. While correctly reproducing actual statistics of the Air Transportation system, e.g., the distribution of delays, the model allows for theoretical predictions. Upon an increase of the traffic load injected in the system, the model predicts a transition from a phase in which all conflicts can be successfully resolved, to a phase in which many conflicts cannot be resolved anymore. We highlight how the current flight density of the Air Transportation system is well below the transition, provided that controllers make use of a special re-routing procedure. While the congestion transition displays a universal scaling behavior, its threshold depends on the conflict solving strategy adopted. Finally, the generality of the modeling scheme introduced makes it a flexible general tool to simulate and control Air Transportation systems in realistic and synthetic scenarios. PMID:25993476

  10. Urban traffic congestion; A search for new solutions

    SciTech Connect

    Howie, D. )

    1989-10-01

    Urban traffic congestion will be the major challenge for traffic engineers into the 1990s. Urban communities will not be content to wait passively for traffic authorities to tinker at the edges of the problem; they are likely to demand more effective solutions than are now being delivered. Concerns about growth in urban traffic congestion are widespread in all monitorized countries. Even the United States, with its extensive freeway system, faces major problems in trying to deal with rapidly growing levels of urban traffic congestion. This paper explores the opportunity to apply new and innovative solutions available as a result of advances in technology over recent years. An underlying theme in the paper is that the available technology has outstripped the ability of traffic engineers to deliver creative solutions to traffic problems.

  11. Making the Traffic Operations Case for Congestion Pricing: Operational Impacts of Congestion Pricing

    SciTech Connect

    Chin, Shih-Miao; Hu, Patricia S; Davidson, Diane

    2011-02-01

    Congestion begins when an excess of vehicles on a segment of roadway at a given time, resulting in speeds that are significantly slower than normal or 'free flow' speeds. Congestion often means stop-and-go traffic. The transition occurs when vehicle density (the number of vehicles per mile in a lane) exceeds a critical level. Once traffic enters a state of congestion, recovery or time to return to a free-flow state is lengthy; and during the recovery process, delay continues to accumulate. The breakdown in speed and flow greatly impedes the efficient operation of the freeway system, resulting in economic, mobility, environmental and safety problems. Freeways are designed to function as access-controlled highways characterized by uninterrupted traffic flow so references to freeway performance relate primarily to the quality of traffic flow or traffic conditions as experienced by users of the freeway. The maximum flow or capacity of a freeway segment is reached while traffic is moving freely. As a result, freeways are most productive when they carry capacity flows at 60 mph, whereas lower speeds impose freeway delay, resulting in bottlenecks. Bottlenecks may be caused by physical disruptions, such as a reduced number of lanes, a change in grade, or an on-ramp with a short merge lane. This type of bottleneck occurs on a predictable or 'recurrent' basis at the same time of day and same day of week. Recurrent congestion totals 45% of congestion and is primarily from bottlenecks (40%) as well as inadequate signal timing (5%). Nonrecurring bottlenecks result from crashes, work zone disruptions, adverse weather conditions, and special events that create surges in demand and that account for over 55% of experienced congestion. Figure 1.1 shows that nonrecurring congestion is composed of traffic incidents (25%), severe weather (15%), work zones, (10%), and special events (5%). Between 1995 and 2005, the average percentage change in increased peak traveler delay, based on

  12. Fluctuation-induced traffic congestion in heterogeneous networks

    NASA Astrophysics Data System (ADS)

    Stepanenko, A. S.; Yurkevich, I. V.; Constantinou, C. C.; Lerner, I. V.

    2012-11-01

    In studies of complex heterogeneous networks, particularly of the Internet, significant attention was paid to analyzing network failures caused by hardware faults or overload, where the network reaction was modeled as rerouting of traffic away from failed or congested elements. Here we model another type of the network reaction to congestion —a sharp reduction of the input traffic rate through congested routes which occurs on much shorter time scales. We consider the onset of congestion in the Internet where local mismatch between demand and capacity results in traffic losses and show that it can be described as a phase transition characterized by strong non-Gaussian loss fluctuations at a mesoscopic time scale. The fluctuations, caused by noise in input traffic, are exacerbated by the heterogeneous nature of the network manifested in a scale-free load distribution. They result in the network strongly overreacting to the first signs of congestion by significantly reducing input traffic along the communication paths where congestion is utterly negligible.

  13. Traffic congestion classification using motion vector statistical features

    NASA Astrophysics Data System (ADS)

    Riaz, Amina; Khan, Shoab A.

    2013-12-01

    Due to the rapid increase in population, one of the major problems faced by the urban areas is traffic congestion. In this paper we propose a method for classifying highway traffic congestion using motion vector statistical properties. Motion vectors are estimated using pyramidal Kanada-Lucas-Tomasi (KLT) tracker algorithm. Then motion vector features are extracted and are used to classify the traffic patterns into three categories: light, medium and heavy. Classification using neural network, on publicly available dataset, shows an accuracy of 95.28%, with robustness to environmental conditions such as variable luminance. Our system provides a more accurate solution to the problem as compared to the systems previously proposed.

  14. Traffic Congestion Detection System through Connected Vehicles and Big Data.

    PubMed

    Cárdenas-Benítez, Néstor; Aquino-Santos, Raúl; Magaña-Espinoza, Pedro; Aguilar-Velazco, José; Edwards-Block, Arthur; Medina Cass, Aldo

    2016-01-01

    This article discusses the simulation and evaluation of a traffic congestion detection system which combines inter-vehicular communications, fixed roadside infrastructure and infrastructure-to-infrastructure connectivity and big data. The system discussed in this article permits drivers to identify traffic congestion and change their routes accordingly, thus reducing the total emissions of CO₂ and decreasing travel time. This system monitors, processes and stores large amounts of data, which can detect traffic congestion in a precise way by means of a series of algorithms that reduces localized vehicular emission by rerouting vehicles. To simulate and evaluate the proposed system, a big data cluster was developed based on Cassandra, which was used in tandem with the OMNeT++ discreet event network simulator, coupled with the SUMO (Simulation of Urban MObility) traffic simulator and the Veins vehicular network framework. The results validate the efficiency of the traffic detection system and its positive impact in detecting, reporting and rerouting traffic when traffic events occur. PMID:27136548

  15. Predictability of road traffic and congestion in urban areas.

    PubMed

    Wang, Jingyuan; Mao, Yu; Li, Jing; Xiong, Zhang; Wang, Wen-Xu

    2015-01-01

    Mitigating traffic congestion on urban roads, with paramount importance in urban development and reduction of energy consumption and air pollution, depends on our ability to foresee road usage and traffic conditions pertaining to the collective behavior of drivers, raising a significant question: to what degree is road traffic predictable in urban areas? Here we rely on the precise records of daily vehicle mobility based on GPS positioning device installed in taxis to uncover the potential daily predictability of urban traffic patterns. Using the mapping from the degree of congestion on roads into a time series of symbols and measuring its entropy, we find a relatively high daily predictability of traffic conditions despite the absence of any priori knowledge of drivers' origins and destinations and quite different travel patterns between weekdays and weekends. Moreover, we find a counterintuitive dependence of the predictability on travel speed: the road segment associated with intermediate average travel speed is most difficult to be predicted. We also explore the possibility of recovering the traffic condition of an inaccessible segment from its adjacent segments with respect to limited observability. The highly predictable traffic patterns in spite of the heterogeneity of drivers' behaviors and the variability of their origins and destinations enables development of accurate predictive models for eventually devising practical strategies to mitigate urban road congestion. PMID:25849534

  16. Predictability of Road Traffic and Congestion in Urban Areas

    PubMed Central

    Wang, Jingyuan; Mao, Yu; Li, Jing; Xiong, Zhang; Wang, Wen-Xu

    2015-01-01

    Mitigating traffic congestion on urban roads, with paramount importance in urban development and reduction of energy consumption and air pollution, depends on our ability to foresee road usage and traffic conditions pertaining to the collective behavior of drivers, raising a significant question: to what degree is road traffic predictable in urban areas? Here we rely on the precise records of daily vehicle mobility based on GPS positioning device installed in taxis to uncover the potential daily predictability of urban traffic patterns. Using the mapping from the degree of congestion on roads into a time series of symbols and measuring its entropy, we find a relatively high daily predictability of traffic conditions despite the absence of any priori knowledge of drivers' origins and destinations and quite different travel patterns between weekdays and weekends. Moreover, we find a counterintuitive dependence of the predictability on travel speed: the road segment associated with intermediate average travel speed is most difficult to be predicted. We also explore the possibility of recovering the traffic condition of an inaccessible segment from its adjacent segments with respect to limited observability. The highly predictable traffic patterns in spite of the heterogeneity of drivers' behaviors and the variability of their origins and destinations enables development of accurate predictive models for eventually devising practical strategies to mitigate urban road congestion. PMID:25849534

  17. Traffic Congestion Detection System through Connected Vehicles and Big Data

    PubMed Central

    Cárdenas-Benítez, Néstor; Aquino-Santos, Raúl; Magaña-Espinoza, Pedro; Aguilar-Velazco, José; Edwards-Block, Arthur; Medina Cass, Aldo

    2016-01-01

    This article discusses the simulation and evaluation of a traffic congestion detection system which combines inter-vehicular communications, fixed roadside infrastructure and infrastructure-to-infrastructure connectivity and big data. The system discussed in this article permits drivers to identify traffic congestion and change their routes accordingly, thus reducing the total emissions of CO2 and decreasing travel time. This system monitors, processes and stores large amounts of data, which can detect traffic congestion in a precise way by means of a series of algorithms that reduces localized vehicular emission by rerouting vehicles. To simulate and evaluate the proposed system, a big data cluster was developed based on Cassandra, which was used in tandem with the OMNeT++ discreet event network simulator, coupled with the SUMO (Simulation of Urban MObility) traffic simulator and the Veins vehicular network framework. The results validate the efficiency of the traffic detection system and its positive impact in detecting, reporting and rerouting traffic when traffic events occur. PMID:27136548

  18. Congestion and communication in confined ant traffic

    NASA Astrophysics Data System (ADS)

    Gravish, Nick; Gold, Gregory; Zangwill, Andrew; Goodisman, Michael A. D.; Goldman, Daniel I.

    2014-03-01

    Many social animals move and communicate within confined spaces. In subterranean fire ants Solenopsis invicta, mobility within crowded nest tunnels is important for resource and information transport. Within confined tunnels, communication and traffic flow are at odds: trafficking ants communicate through tactile interactions while stopped, yet ants that stop to communicate impose physical obstacles on the traffic. We monitor the bi-directional flow of fire ant workers in laboratory tunnels of varied diameter D. The persistence time of communicating ant aggregations, τ, increases approximately linearly with the number of participating ants, n. The sensitivity of traffic flow increases as D decreases and diverges at a minimum diameter, Dc. A cellular automata model incorporating minimal traffic features--excluded volume and communication duration--reproduces features of the experiment. From the model we identify a competition between information transfer and the need to maintain jam-free traffic flow. We show that by balancing information transfer and traffic flow demands, an optimum group strategy exists which maximizes information throughput. We acknowledge funding from NSF PoLS #0957659 and #PHY-1205878.

  19. Traffic Congestion on a University Campus: A Consideration of Unconventional Remedies to Nontraditional Transportation Patterns

    ERIC Educational Resources Information Center

    Kaplan, Dave; Clapper, Thomas

    2007-01-01

    U.S. transportation data suggest that the number of vehicle miles traveled has far surpassed new capacity, resulting in increased traffic congestion in many communities throughout the country. This article reports on traffic congestion around a university campus located within a small town. The mix of trip purposes varies considerably in this…

  20. Algorithm and data support of traffic congestion forecasting in the controlled transport

    NASA Astrophysics Data System (ADS)

    Dmitriev, S. V.

    2015-06-01

    The topicality of problem of the traffic congestion forecasting in the logistic systems of product movement highways is considered. The concepts: the controlled territory, the highway occupancy by vehicles, the parking and the controlled territory are introduced. Technical realizabilityof organizing the necessary flow of information on the state of the transport system for its regulation has been marked. Sequence of practical implementation of the solution is given. An algorithm for predicting traffic congestion in the controlled transport system is suggested.

  1. How Travel Demand Affects Detection of Non-Recurrent Traffic Congestion on Urban Road Networks

    NASA Astrophysics Data System (ADS)

    Anbaroglu, B.; Heydecker, B.; Cheng, T.

    2016-06-01

    Occurrence of non-recurrent traffic congestion hinders the economic activity of a city, as travellers could miss appointments or be late for work or important meetings. Similarly, for shippers, unexpected delays may disrupt just-in-time delivery and manufacturing processes, which could lose them payment. Consequently, research on non-recurrent congestion detection on urban road networks has recently gained attention. By analysing large amounts of traffic data collected on a daily basis, traffic operation centres can improve their methods to detect non-recurrent congestion rapidly and then revise their existing plans to mitigate its effects. Space-time clusters of high link journey time estimates correspond to non-recurrent congestion events. Existing research, however, has not considered the effect of travel demand on the effectiveness of non-recurrent congestion detection methods. Therefore, this paper investigates how travel demand affects detection of non-recurrent traffic congestion detection on urban road networks. Travel demand has been classified into three categories as low, normal and high. The experiments are carried out on London's urban road network, and the results demonstrate the necessity to adjust the relative importance of the component evaluation criteria depending on the travel demand level.

  2. Containing air pollution and traffic congestion: Transport policy and the environment in Singapore

    NASA Astrophysics Data System (ADS)

    Chin, Anthony T. H.

    Land transportation remains one of the main contributors of noise and air pollution in urban areas. This is in addition to traffic congestion and accidents which result in the loss of productive activity. While there is a close relationship between traffic volumes and levels of noise and air pollution, transport authorities often assume that solving traffic congestion would reduce noise and air pollutant levels. Tight control over automobile ownership and use in Singapore has contributed in improving traffic flows, travel speeds and air quality. The adoption of internationally accepted standards on automobile emissions and gasoline have been effective in reducing air pollution from motor vehicles. Demand management measures have largely focused on controlling the source of traffic congestion, i.e. private automobile ownership and its use especially within the Central Business District during the day. This paper reviews and analyzes the effectiveness of two measures which are instrumental in controlling congestion and automobile ownership, i.e. road pricing and the vehicle quota scheme (VQS). While these measures have been successful in achieving desired objectives, it has also led to the spreading of traffic externalities to other roads in the network, loss in consumer welfare and rent seeking by automobile traders.

  3. Traffic congestion forecasting model for the INFORM System. Final report

    SciTech Connect

    Azarm, A.; Mughabghab, S.; Stock, D.

    1995-05-01

    This report describes a computerized traffic forecasting model, developed by Brookhaven National Laboratory (BNL) for a portion of the Long Island INFORM Traffic Corridor. The model has gone through a testing phase, and currently is able to make accurate traffic predictions up to one hour forward in time. The model will eventually take on-line traffic data from the INFORM system roadway sensors and make projections as to future traffic patterns, thus allowing operators at the New York State Department of Transportation (D.O.T.) INFORM Traffic Management Center to more optimally manage traffic. It can also form the basis of a travel information system. The BNL computer model developed for this project is called ATOP for Advanced Traffic Occupancy Prediction. The various modules of the ATOP computer code are currently written in Fortran and run on PC computers (pentium machine) faster than real time for the section of the INFORM corridor under study. The following summarizes the various routines currently contained in the ATOP code: Statistical forecasting of traffic flow and occupancy using historical data for similar days and time (long term knowledge), and the recent information from the past hour (short term knowledge). Estimation of the empirical relationships between traffic flow and occupancy using long and short term information. Mechanistic interpolation using macroscopic traffic models and based on the traffic flow and occupancy forecasted (item-1), and the empirical relationships (item-2) for the specific highway configuration at the time of simulation (construction, lane closure, etc.). Statistical routine for detection and classification of anomalies and their impact on the highway capacity which are fed back to previous items.

  4. Microscopic theory of spatial-temporal congested traffic patterns at highway bottlenecks.

    PubMed

    Kerner, Boris S; Klenov, Sergey L

    2003-09-01

    A microscopic theory of spatial-temporal congested traffic patterns at highway bottlenecks due to on-ramps, merge bottlenecks (a reduction of highway lanes), and off-ramps is presented. The basic postulate of three-phase traffic theory is used, which claims that homogeneous (in space and time) model solutions (steady states) of synchronized flow cover a two dimensional region in the flow-density plane [B. S. Kerner, Phys. Rev. Lett. 81, 3797 (1998); Trans. Res. Rec. 1678, 160 (1999)]. Phase transitions leading to diverse congested patterns, pattern evolution, and pattern nonlinear features have been found. Diagrams of congested patterns, i.e., regions of the pattern emergence dependent on traffic demand, have been derived. Diverse effects of metastability with respect to the pattern formation have been found. The microscopic theory allows us to explain the main empirical pattern features at on-ramps and off-ramps which have recently been found [B. S. Kerner, Phys. Rev. E 65, 046138 (2002)]. (i) Rather than moving jams, synchronized flow first occurs at bottlenecks if the flow rate is slowly increasing. Wide moving jams can spontaneously occur only in synchronized flow. (ii) General patterns (GP) and synchronized flow patterns (SP) can spontaneously emerge at the bottlenecks. There can be the widening SP (WSP), the moving SP (MSP), and the localized SP. (iii) At on-ramps cases of "weak" and "strong" congestion should be distinguished. In contrast to weak congestion, under strong congestion the flow rate in synchronized flow in GP reaches a limit flow rate, the frequency of the moving jam emergence reaches a maximum, i.e., the GP characteristics under strong congestion do not depend on traffic demand. (iv) At the off-ramp GP with weak congestion occur. (v) A study of the pattern formation on a highway with two bottlenecks shows that diverse expanded patterns can occur, which cover both bottlenecks. SP first emerged at the downstream bottleneck can be caught at the

  5. Evaluation of the public health impacts of traffic congestion: a health risk assessment

    PubMed Central

    2010-01-01

    Background Traffic congestion is a significant issue in urban areas in the United States and around the world. Previous analyses have estimated the economic costs of congestion, related to fuel and time wasted, but few have quantified the public health impacts or determined how these impacts compare in magnitude to the economic costs. Moreover, the relative magnitudes of economic and public health impacts of congestion would be expected to vary significantly across urban areas, as a function of road infrastructure, population density, and atmospheric conditions influencing pollutant formation, but this variability has not been explored. Methods In this study, we evaluate the public health impacts of ambient exposures to fine particulate matter (PM2.5) concentrations associated with a business-as-usual scenario of predicted traffic congestion. We evaluate 83 individual urban areas using traffic demand models to estimate the degree of congestion in each area from 2000 to 2030. We link traffic volume and speed data with the MOBILE6 model to characterize emissions of PM2.5 and particle precursors attributable to congestion, and we use a source-receptor matrix to evaluate the impact of these emissions on ambient PM2.5 concentrations. Marginal concentration changes are related to a concentration-response function for mortality, with a value of statistical life approach used to monetize the impacts. Results We estimate that the monetized value of PM2.5-related mortality attributable to congestion in these 83 cities in 2000 was approximately $31 billion (2007 dollars), as compared with a value of time and fuel wasted of $60 billion. In future years, the economic impacts grow (to over $100 billion in 2030) while the public health impacts decrease to $13 billion in 2020 before increasing to $17 billion in 2030, given increasing population and congestion but lower emissions per vehicle. Across cities and years, the public health impacts range from more than an order of

  6. Packet Traffic Dynamics Near Onset of Congestion in Data Communication Network Model

    NASA Astrophysics Data System (ADS)

    Lawniczak, A. T.; Tang, X.

    2006-05-01

    The dominant technology of data communication networks is the Packet Switching Network (PSN). It is a complex technology organized as various hierarchical layers according to the International Standard Organization (ISO) Open Systems Interconnect (OSI) Reference Model. The Network Layer of the ISO OSI Reference Model is responsible for delivering packets from their sources to their destinations and for dealing with congestion if it arises in a network. Thus, we focus on this layer and present an abstraction of the Network Layer of the ISO OSI Reference Model. Using this abstraction we investigate how onset of traffic congestion is affected for various routing algorithms by changes in network connection topology. We study how aggregate measures of network performance depend on network connection topology and routing. We explore packets traffic spatio-temporal dynamics near the phase transition point from free flow to congestion for various network connection topologies and routing algorithms. We consider static and adaptive routings. We present selected simulation results.

  7. Analysis of traffic congestion induced by the work zone

    NASA Astrophysics Data System (ADS)

    Fei, L.; Zhu, H. B.; Han, X. L.

    2016-05-01

    Based on the cellular automata model, a meticulous two-lane cellular automata model is proposed, in which the driving behavior difference and the difference of vehicles' accelerations between the moving state and the starting state are taken into account. Furthermore the vehicles' motion is refined by using the small cell of one meter long. Then accompanied by coming up with a traffic management measure, a two-lane highway traffic model containing a work zone is presented, in which the road is divided into normal area, merging area and work zone. The vehicles in different areas move forward according to different lane changing rules and position updating rules. After simulation it is found that when the density is small the cluster length in front of the work zone increases with the decrease of the merging probability. Then the suitable merging length and the appropriate speed limit value are recommended. The simulation result in the form of the speed-flow diagram is in good agreement with the empirical data. It indicates that the presented model is efficient and can partially reflect the real traffic. The results may be meaningful for traffic optimization and road construction management.

  8. Reducing Traffic Congestions by Introducing CACC-Vehicles on a Multi-Lane Highway Using Agent-Based Approach

    NASA Technical Reports Server (NTRS)

    Arnaout, Georges M.; Bowling, Shannon R.

    2011-01-01

    Traffic congestion is an ongoing problem of great interest to researchers from different areas in academia. With the emerging technology for inter-vehicle communication, vehicles have the ability to exchange information with predecessors by wireless communication. In this paper, we present an agent-based model of traffic congestion and examine the impact of having CACC (Cooperative Adaptive Cruise Control) embedded vehicle(s) on a highway system consisting of 4 traffic lanes without overtaking. In our model, CACC vehicles adapt their acceleration/deceleration according to vehicle-to-vehicle inter-communication. We analyze the average speed of the cars, the shockwaves, and the evolution of traffic congestion throughout the lifecycle of the model. The study identifies how CACC vehicles affect the dynamics of traffic flow on a complex network and reduce the oscillatory behavior (stop and go) resulting from the acceleration/deceleration of the vehicles.

  9. Highly Dynamic and Adaptive Traffic Congestion Avoidance in Real-Time Inspired by Honey Bee Behavior

    NASA Astrophysics Data System (ADS)

    Wedde, Horst F.; Lehnhoff, Sebastian; van Bonn, Bernhard; Bay, Z.; Becker, S.; Böttcher, S.; Brunner, C.; Büscher, A.; Fürst, T.; Lazarescu, A. M.; Rotaru, E.; Senge, S.; Steinbach, B.; Yilmaz, F.; Zimmermann, T.

    Traffic congestions have become a major problem in metropolitan areas world-wide, within and between cities, to an extent where they make driving and transportation times largely unpredictable. Due to the highly dynamic character of congestion building and dissolving this phenomenon appears even to resist a formal treatment. Static approaches, and even more their global management, have proven counterproductive in practice. Given the latest progress in VANET technology and the remarkable commercially driven efforts like in the European C2C consortium, or the VSC Project in the US, allow meanwhile to tackle various aspects of traffic regulation through VANET communication. In this paper we introduce a novel, completely decentralized multi-agent routing algorithm (termed BeeJamA) which we have derived from the foraging behavior of honey bees. It is highly dynamic, adaptive, robust, and scalable, and it allows for both avoiding congestions, and minimizing traveling times to individual destinations. Vehicle guidance is provided well ahead of every intersection, depending on the individual speeds. Thus strict deadlines are imposed on, and respected by, the BeeJamA algorithm. We report on extensive simulation experiments which show the superior performance of BeeJamA over conventional approaches.

  10. Design and Implementation of Real-Time Vehicular Camera for Driver Assistance and Traffic Congestion Estimation

    PubMed Central

    Son, Sanghyun; Baek, Yunju

    2015-01-01

    As society has developed, the number of vehicles has increased and road conditions have become complicated, increasing the risk of crashes. Therefore, a service that provides safe vehicle control and various types of information to the driver is urgently needed. In this study, we designed and implemented a real-time traffic information system and a smart camera device for smart driver assistance systems. We selected a commercial device for the smart driver assistance systems, and applied a computer vision algorithm to perform image recognition. For application to the dynamic region of interest, dynamic frame skip methods were implemented to perform parallel processing in order to enable real-time operation. In addition, we designed and implemented a model to estimate congestion by analyzing traffic information. The performance of the proposed method was evaluated using images of a real road environment. We found that the processing time improved by 15.4 times when all the proposed methods were applied in the application. Further, we found experimentally that there was little or no change in the recognition accuracy when the proposed method was applied. Using the traffic congestion estimation model, we also found that the average error rate of the proposed model was 5.3%. PMID:26295230

  11. Design and Implementation of Real-Time Vehicular Camera for Driver Assistance and Traffic Congestion Estimation.

    PubMed

    Son, Sanghyun; Baek, Yunju

    2015-01-01

    As society has developed, the number of vehicles has increased and road conditions have become complicated, increasing the risk of crashes. Therefore, a service that provides safe vehicle control and various types of information to the driver is urgently needed. In this study, we designed and implemented a real-time traffic information system and a smart camera device for smart driver assistance systems. We selected a commercial device for the smart driver assistance systems, and applied a computer vision algorithm to perform image recognition. For application to the dynamic region of interest, dynamic frame skip methods were implemented to perform parallel processing in order to enable real-time operation. In addition, we designed and implemented a model to estimate congestion by analyzing traffic information. The performance of the proposed method was evaluated using images of a real road environment. We found that the processing time improved by 15.4 times when all the proposed methods were applied in the application. Further, we found experimentally that there was little or no change in the recognition accuracy when the proposed method was applied. Using the traffic congestion estimation model, we also found that the average error rate of the proposed model was 5.3%. PMID:26295230

  12. TCP with source traffic shaping (TCP-STS): an approach for network congestion reduction

    NASA Astrophysics Data System (ADS)

    Elaywe, Ali H.; Kamal, Ahmed E.

    2002-07-01

    The Transmission Control Protocol (TCP), provides flow control functions which are based on the window mechanism. Packet losses are detected by various mechanisms, such as timeouts and duplicate acknowledgements, and are then recovered from using different techniques. A problem that arises with the use of window based mechanisms is that the availability of a large number of credits at the source may cause a source to flood the network with back-to-back packets, which may drive the network into congestion, especially if multiple sources become active at the same time. In this paper we propose a new approach for congestion reduction. The approach works by shaping the traffic at the TCP source, such that the basic TCP flow control mechanism is still preserved, but the packet transmissions are spaced in time in order to prevent a sudden surge of traffic from overflowing the routers' buffers. Simulation results show that this technique can result in an improved network performance, in terms of reduced mean delay, delay variance, and packet dropping ratio.

  13. Transport growth in Bangkok: Energy, environment, and traffic congestion. Workshop proceedings

    SciTech Connect

    Philpott, J.

    1995-07-01

    Bangkok, the capital of Thailand, is a physically and economically complexcity with a complicated transport system. With daily traffic congestion averaging 16 hours, the air quality is such that to breathe street level pollution for 8 eight hours is roughly equivalent to smoking nine cigarettes per day. Estimates suggest idling traffic costs up to $1.6 billion annually. Energy use within the transport sector is on a steady rise with an estimated increase in 11 years of two and one half times. Severe health impacts have begun to effect many residents - young children and the elderly being particularly vulnerable. Bangkok`s air quality and congestion problems are far from hopeless. Great potential exists for Bangkok to remedy its transport-related problems. The city has many necessary characteristics that allow an efficient, economical system of transport. For example, its high density level makes the city a prime candidate for an efficient system of mass transit and the multitude and close proximity of shops, street vendors, restaurants, and residential areas is highly conducive to walking and cycling. Technical knowledge and capacity to devise and implement innovative policies and projects to address air quality and congestion problems is plentiful. There is also consensus among Bangkokians that something needs to be done immediately to clear the air and the roads. However, little has been done. This report proposes a new approach to transport planning for Bangkok that integrates consideration of ecological, social, and financial viability in the process of making decisions regarding managing existing infrastructure and investments in new infrastructure. Selected papers have been indexed separately for inclusion in the Energy Science and Technology Database.

  14. Increasing Intelligence in Inter-Vehicle Communications to Reduce Traffic Congestions: Experiments in Urban and Highway Environments

    PubMed Central

    Filho, Geraldo P. R.; Guidoni, Daniel L.; Pessin, Gustavo; Villas, Leandro A.; Ueyama, Jó

    2016-01-01

    Intelligent Transportation Systems (ITS) rely on Inter-Vehicle Communication (IVC) to streamline the operation of vehicles by managing vehicle traffic, assisting drivers with safety and sharing information, as well as providing appropriate services for passengers. Traffic congestion is an urban mobility problem, which causes stress to drivers and economic losses. In this context, this work proposes a solution for the detection, dissemination and control of congested roads based on inter-vehicle communication, called INCIDEnT. The main goal of the proposed solution is to reduce the average trip time, CO emissions and fuel consumption by allowing motorists to avoid congested roads. The simulation results show that our proposed solution leads to short delays and a low overhead. Moreover, it is efficient with regard to the coverage of the event and the distance to which the information can be propagated. The findings of the investigation show that the proposed solution leads to (i) high hit rate in the classification of the level of congestion, (ii) a reduction in average trip time, (iii) a reduction in fuel consumption, and (iv) reduced CO emissions PMID:27526048

  15. Increasing Intelligence in Inter-Vehicle Communications to Reduce Traffic Congestions: Experiments in Urban and Highway Environments.

    PubMed

    Meneguette, Rodolfo I; Filho, Geraldo P R; Guidoni, Daniel L; Pessin, Gustavo; Villas, Leandro A; Ueyama, Jó

    2016-01-01

    Intelligent Transportation Systems (ITS) rely on Inter-Vehicle Communication (IVC) to streamline the operation of vehicles by managing vehicle traffic, assisting drivers with safety and sharing information, as well as providing appropriate services for passengers. Traffic congestion is an urban mobility problem, which causes stress to drivers and economic losses. In this context, this work proposes a solution for the detection, dissemination and control of congested roads based on inter-vehicle communication, called INCIDEnT. The main goal of the proposed solution is to reduce the average trip time, CO emissions and fuel consumption by allowing motorists to avoid congested roads. The simulation results show that our proposed solution leads to short delays and a low overhead. Moreover, it is efficient with regard to the coverage of the event and the distance to which the information can be propagated. The findings of the investigation show that the proposed solution leads to (i) high hit rate in the classification of the level of congestion, (ii) a reduction in average trip time, (iii) a reduction in fuel consumption, and (iv) reduced CO emissions. PMID:27526048

  16. Long-Term Correlations and Multifractality of Traffic Flow Measured by GIS for Congested and Free-Flow Roads

    NASA Astrophysics Data System (ADS)

    di, Baofeng; Shi, Kai; Zhang, Kaishan; Svirchev, Laurence; Hu, Xiaoxi

    2016-02-01

    In this paper, a GIS-based method was developed to extract the real-time traffic information (RTTI) from the Google Maps system for city roads. The method can be used to quantify both congested and free-flow traffic conditions. The roadway length was defined as congested length (CL) and free-flow length (FFL). Chengdu, the capital of Sichuan Province in the southwest of China, was chosen as a case study site. The RTTI data were extracted from the Google real-time maps in May 12-17, 2013 and were used to derive the CL and FFL for the study areas. The Multifractal Detrended Fluctuation Analysis (MFDFA) was used to characterize the long-term correlations of CL and FFL time series and their corresponding multifractal properties. Analysis showed that CL and FFL had demonstrated time nonlinearity and long-term correlations and both characteristics differed significantly. A shuffling procedure and a phase randomization procedure were further integrated with multifractal detrending moving average (MFDMA) to identify the major sources of multifractality of these two time series. The results showed that a multifractal process analysis could be used to characterize complex traffic data. Traffic data collected and methods developed in this paper will help better understand the complex traffic systems.

  17. Reasoning the Causality of City Sprawl, Traffic Congestion, and Green Land Disappearance in Taiwan Using the CLD Model

    PubMed Central

    Chen, Mei-Chih; Chang, Kaowen

    2014-01-01

    Many city governments choose to supply more developable land and transportation infrastructure with the hope of attracting people and businesses to their cities. However, like those in Taiwan, major cities worldwide suffer from traffic congestion. This study applies the system thinking logic of the causal loops diagram (CLD) model in the System Dynamics (SD) approach to analyze the issue of traffic congestion and other issues related to roads and land development in Taiwan’s cities. Comparing the characteristics of development trends with yearbook data for 2002 to 2013 for all of Taiwan’s cities, this study explores the developing phenomenon of unlimited city sprawl and identifies the cause and effect relationships in the characteristics of development trends in traffic congestion, high-density population aggregation in cities, land development, and green land disappearance resulting from city sprawl. This study provides conclusions for Taiwan’s cities’ sustainability and development (S&D). When developing S&D policies, during decision making processes concerning city planning and land use management, governments should think with a holistic view of carrying capacity with the assistance of system thinking to clarify the prejudices in favor of the unlimited developing phenomena resulting from city sprawl. PMID:25383609

  18. Hopf bifurcation and uncontrolled stochastic traffic-induced chaos in an RED-AQM congestion control system

    NASA Astrophysics Data System (ADS)

    Wang, Jun-Song; Yuan, Rui-Xi; Gao, Zhi-Wei; Wang, De-Jin

    2011-09-01

    We study the Hopf bifurcation and the chaos phenomena in a random early detection-based active queue management (RED-AQM) congestion control system with a communication delay. We prove that there is a critical value of the communication delay for the stability of the RED-AQM control system. Furthermore, we show that the system will lose its stability and Hopf bifurcations will occur when the delay exceeds the critical value. When the delay is close to its critical value, we demonstrate that typical chaos patterns may be induced by the uncontrolled stochastic traffic in the RED-AQM control system even if the system is still stable, which reveals a new route to the chaos besides the bifurcation in the network congestion control system. Numerical simulations are given to illustrate the theoretical results.

  19. Input-Output Modeling and Control of the Departure Process of Congested Airports

    NASA Technical Reports Server (NTRS)

    Pujet, Nicolas; Delcaire, Bertrand; Feron, Eric

    2003-01-01

    A simple queueing model of busy airport departure operations is proposed. This model is calibrated and validated using available runway configuration and traffic data. The model is then used to evaluate preliminary control schemes aimed at alleviating departure traffic congestion on the airport surface. The potential impact of these control strategies on direct operating costs, environmental costs and overall delay is quantified and discussed.

  20. The Physics of Traffic Congestion and Road Pricing in Transportation Planning

    NASA Astrophysics Data System (ADS)

    Levinson, David

    2010-03-01

    This presentation develops congestion theory and congestion pricing theory from its micro- foundations, the interaction of two or more vehicles. Using game theory, with a two- player game it is shown that the emergence of congestion depends on the players' relative valuations of early arrival, late arrival, and journey delay. Congestion pricing can be used as a cooperation mechanism to minimize total costs (if returned to the players). The analysis is then extended to the case of the three- player game, which illustrates congestion as a negative externality imposed on players who do not themselves contribute to it. A multi-agent model of travelers competing to utilize a roadway in time and space is presented. To realize the spillover effect among travelers, N-player games are constructed in which the strategy set includes N+1 strategies. We solve the N-player game (for N = 7) and find Nash equilibria if they exist. This model is compared to the bottleneck model. The results of numerical simulation show that the two models yield identical results in terms of lowest total costs and marginal costs when a social optimum exists. Moving from temporal dynamics to spatial complexity, using consistent agent- based techniques, we model the decision-making processes of users and infrastructure owner/operators to explore the welfare consequence of price competition, capacity choice, and product differentiation on congested transportation networks. Component models include: (1) An agent-based travel demand model wherein each traveler has learning capabilities and unique characteristics (e.g. value of time); (2) Econometric facility provision cost models; and (3) Representations of road authorities making pricing and capacity decisions. Different from small-network equilibrium models in prior literature, this agent- based model is applicable to pricing and investment analyses on large complex networks. The subsequent economic analysis focuses on the source, evolution

  1. Understanding congested travel in urban areas.

    PubMed

    Çolak, Serdar; Lima, Antonio; González, Marta C

    2016-01-01

    Rapid urbanization and increasing demand for transportation burdens urban road infrastructures. The interplay of number of vehicles and available road capacity on their routes determines the level of congestion. Although approaches to modify demand and capacity exist, the possible limits of congestion alleviation by only modifying route choices have not been systematically studied. Here we couple the road networks of five diverse cities with the travel demand profiles in the morning peak hour obtained from billions of mobile phone traces to comprehensively analyse urban traffic. We present that a dimensionless ratio of the road supply to the travel demand explains the percentage of time lost in congestion. Finally, we examine congestion relief under a centralized routing scheme with varying levels of awareness of social good and quantify the benefits to show that moderate levels are enough to achieve significant collective travel time savings. PMID:26978719

  2. Understanding congested travel in urban areas

    PubMed Central

    Çolak, Serdar; Lima, Antonio; González, Marta C.

    2016-01-01

    Rapid urbanization and increasing demand for transportation burdens urban road infrastructures. The interplay of number of vehicles and available road capacity on their routes determines the level of congestion. Although approaches to modify demand and capacity exist, the possible limits of congestion alleviation by only modifying route choices have not been systematically studied. Here we couple the road networks of five diverse cities with the travel demand profiles in the morning peak hour obtained from billions of mobile phone traces to comprehensively analyse urban traffic. We present that a dimensionless ratio of the road supply to the travel demand explains the percentage of time lost in congestion. Finally, we examine congestion relief under a centralized routing scheme with varying levels of awareness of social good and quantify the benefits to show that moderate levels are enough to achieve significant collective travel time savings. PMID:26978719

  3. Understanding congested travel in urban areas

    NASA Astrophysics Data System (ADS)

    Çolak, Serdar; Lima, Antonio; González, Marta C.

    2016-03-01

    Rapid urbanization and increasing demand for transportation burdens urban road infrastructures. The interplay of number of vehicles and available road capacity on their routes determines the level of congestion. Although approaches to modify demand and capacity exist, the possible limits of congestion alleviation by only modifying route choices have not been systematically studied. Here we couple the road networks of five diverse cities with the travel demand profiles in the morning peak hour obtained from billions of mobile phone traces to comprehensively analyse urban traffic. We present that a dimensionless ratio of the road supply to the travel demand explains the percentage of time lost in congestion. Finally, we examine congestion relief under a centralized routing scheme with varying levels of awareness of social good and quantify the benefits to show that moderate levels are enough to achieve significant collective travel time savings.

  4. Urban traffic simulated from the dual representation: Flow, crisis and congestion

    NASA Astrophysics Data System (ADS)

    Hu, Mao-Bin; Jiang, Rui; Wang, Ruili; Wu, Qing-Song

    2009-05-01

    We propose a traffic simulation model for urban system based on the dual graph representation of a urban road network and with a random entering vehicle rate. To avoid the shortcoming of “Space Syntax” of ignoring the road's metric distance, we consider both the motion of the vehicles along roads and the navigation of the vehicles in the network. Simulations have shown some basic properties of urban traffic system, such as flux fluctuation, crisis and dissipation, phase transition from a free flow to jams, overall capacity, the distribution of traveling time, and the fundamental diagram. The system's behavior greatly depends on the topology of the transportation network. A well-planned lattice grid can keep more vehicles travelling. The critical entering vehicle rate is much greater in lattice grid than in a self-organized network. The vehicles have to travel longer time in a self-organized urban system due to the navigation cost.

  5. An Experimental Study of the Noise Due to Traffic in a Congested Urban Area

    NASA Astrophysics Data System (ADS)

    Sangeetha, M.; Sankar, P.

    2016-03-01

    Noise pollution in an urban environment is an issue of serious concern in the major cities of India. There are various factors that contribute to the increase of noise levels in urban areas. The intensity of traffic is one of the factors which contributes to a drastic increase in environmental noise. The management of noise pollution has to be considered in the decision making process. In this paper, an attempt is made to study the existing noise level due to the traffic in Velachery which is declared as a sensitive area by the Ministry of Environment and Forestry (MoEF). The noise level data is collected using the MS6710 digital sound meter. The Custic simulation software version 3.2 is used for finding the propagation of noise. The spatial patterns of measurement were also calculated, in the sub-urban area of Velachery, Chennai, Tamilnadu, India. A means of transmitting this data to vehicles moving in the area, through a wireless medium is simulated using NCTUns 6.0 (network simulator), to enable drivers to understand the environmental conditions. A hardware was also designed which can be used to transmit and receive the noise data using the Zigbee module. A noise transmitting station is placed at a junction, so that it can transmit this noise data to the receivers which are fitted inside the vehicles.

  6. Traffic Signal Synchronization in the Saturated High-Density Grid Road Network

    PubMed Central

    Hu, Xiaojian; Lu, Jian; Wang, Wei; Zhirui, Ye

    2015-01-01

    Most existing traffic signal synchronization strategies do not perform well in the saturated high-density grid road network (HGRN). Traffic congestion often occurs in the saturated HGRN, and the mobility of the network is difficult to restore. In order to alleviate traffic congestion and to improve traffic efficiency in the network, the study proposes a regional traffic signal synchronization strategy, named the long green and long red (LGLR) traffic signal synchronization strategy. The essence of the strategy is to control the formation and dissipation of queues and to maximize the efficiency of traffic flows at signalized intersections in the saturated HGRN. With this strategy, the same signal control timing plan is used at all signalized intersections in the HGRN, and the straight phase of the control timing plan has a long green time and a long red time. Therefore, continuous traffic flows can be maintained when vehicles travel, and traffic congestion can be alleviated when vehicles stop. Using the strategy, the LGLR traffic signal synchronization model is developed, with the objective of minimizing the number of stops. Finally, the simulation is executed to analyze the performance of the model by comparing it to other models, and the superiority of the LGLR model is evident in terms of delay, number of stops, queue length, and overall performance in the saturated HGRN. PMID:25663835

  7. Interacting RNA polymerase motors on a DNA track: effects of traffic congestion and intrinsic noise on RNA synthesis.

    PubMed

    Tripathi, Tripti; Chowdhury, Debashish

    2008-01-01

    RNA polymerase (RNAP) is an enzyme that synthesizes a messenger RNA (mRNA) strand which is complementary to a single-stranded DNA template. From the perspective of physicists, an RNAP is a molecular motor that utilizes chemical energy input to move along the track formed by DNA. In many circumstances, which are described in this paper, a large number of RNAPs move simultaneously along the same track; we refer to such collective movements of the RNAPs as RNAP traffic. Here we develop a theoretical model for RNAP traffic by incorporating the steric interactions between RNAPs as well as the mechanochemical cycle of individual RNAPs during the elongation of the mRNA. By a combination of analytical and numerical techniques, we calculate the rates of mRNA synthesis and the average density profile of the RNAPs on the DNA track. We also introduce, and compute, two different measures of fluctuations in the synthesis of RNA. Analyzing these fluctuations, we show how the level of intrinsic noise in mRNA synthesis depends on the concentrations of the RNAPs as well as on those of some of the reactants and the products of the enzymatic reactions catalyzed by RNAP. We suggest appropriate experimental systems and techniques for testing our theoretical predictions. PMID:18351890

  8. The Stability of Multi-modal Traffic Network

    NASA Astrophysics Data System (ADS)

    Han, Ling-Hui; Sun, Hui-Jun; Zhu, Cheng-Juan; Wu, Jian-Jun; Jia, Bin

    2013-07-01

    There is an explicit and implicit assumption in multimodal traffic equilibrium models, that is, if the equilibrium exists, then it will also occur. The assumption is very idealized; in fact, it may be shown that the quite contrary could happen, because in multimodal traffic network, especially in mixed traffic conditions the interaction among traffic modes is asymmetric and the asymmetric interaction may result in the instability of traffic system. In this paper, to study the stability of multimodal traffic system, we respectively present the travel cost function in mixed traffic conditions and in traffic network with dedicated bus lanes. Based on a day-to-day dynamical model, we study the evolution of daily route choice of travelers in multimodal traffic network using 10000 random initial values for different cases. From the results of simulation, it can be concluded that the asymmetric interaction between the cars and buses in mixed traffic conditions can lead the traffic system to instability when traffic demand is larger. We also study the effect of travelers' perception error on the stability of multimodal traffic network. Although the larger perception error can alleviate the effect of interaction between cars and buses and improve the stability of traffic system in mixed traffic conditions, the traffic system also become instable when the traffic demand is larger than a number. For all cases simulated in this study, with the same parameters, traffic system with dedicated bus lane has better stability for traffic demand than that in mixed traffic conditions. We also find that the network with dedicated bus lane has higher portion of travelers by bus than it of mixed traffic network. So it can be concluded that building dedicated bus lane can improve the stability of traffic system and attract more travelers to choose bus reducing the traffic congestion.

  9. Dynamic route guidance strategy in a two-route pedestrian-vehicle mixed traffic flow system

    NASA Astrophysics Data System (ADS)

    Liu, Mianfang; Xiong, Shengwu; Li, Bixiang

    2016-05-01

    With the rapid development of transportation, traffic questions have become the major issue for social, economic and environmental aspects. Especially, during serious emergencies, it is very important to alleviate road traffic congestion and improve the efficiency of evacuation to reduce casualties, and addressing these problems has been a major task for the agencies responsible in recent decades. Advanced road guidance strategies have been developed for homogeneous traffic flows, or to reduce traffic congestion and enhance the road capacity in a symmetric two-route scenario. However, feedback strategies have rarely been considered for pedestrian-vehicle mixed traffic flows with variable velocities and sizes in an asymmetric multi-route traffic system, which is a common phenomenon in many developing countries. In this study, we propose a weighted road occupancy feedback strategy (WROFS) for pedestrian-vehicle mixed traffic flows, which considers the system equilibrium to ease traffic congestion. In order to more realistic simulating the behavior of mixed traffic objects, the paper adopted a refined and dynamic cellular automaton model (RDPV_CA model) as the update mechanism for pedestrian-vehicle mixed traffic flow. Moreover, a bounded rational threshold control was introduced into the feedback strategy to avoid some negative effect of delayed information and reduce. Based on comparisons with the two previously proposed strategies, the simulation results obtained in a pedestrian-vehicle traffic flow scenario demonstrated that the proposed strategy with a bounded rational threshold was more effective and system equilibrium, system stability were reached.

  10. Network congestion analysis of gravity generated models

    NASA Astrophysics Data System (ADS)

    Maniadakis, Dimitris; Varoutas, Dimitris

    2014-07-01

    The network topology has lately proved to be critical to the appearance of traffic congestion, with scale-free networks being the less affected at high volumes of traffic. Here, the congestion dynamics are investigated for a class of networks that has experienced a resurgence of interest, the networks based on the gravity model. In addition, supplementary to the standard paradigm of uniform traffic volumes between randomly interacting node pairs, more realistic gravity traffic patterns are used to simulate the flows in the network. Results indicate that depending on the traffic pattern, the networks have different tolerance to congestion. Experiment simulation shows that the topologies created on the basis of the gravity model suffer less from congestion than the random, the scale-free or the Jackson-Rogers ones under both random and gravity traffic patterns. The congestion level is found to be approximately correlated with the network clustering coefficient in the case of random traffic, whereas in the case of gravity traffic such a correlation is not a trivial one. Other basic network properties such as the average shortest path and the diameter are seen to correlate fairly well with the congestion level. Further investigation on the adjustment of the gravity model parameters indicates particular sensitivity to network congestion. This work may have practical implications for designing traffic networks with both reasonable budget and good performance.

  11. Congestion and cascades in payment systems.

    SciTech Connect

    Glass, Robert John, Jr.; Beyeler, Walter Eugene; Soramaki, Kimmo; Bech, Morten Linnemann

    2006-06-01

    We develop a parsimonious model of the interbank payment system to study congestion and the role of liquidity markets in alleviating congestion. The model incorporates an endogenous instruction arrival process, scale-free topology of payments between banks, fixed total liquidity that limits banks' capacity to process arriving instructions, and a global market that distributes liquidity. We find that at low liquidity, the system becomes congested and payment settlement loses correlation with payment instruction arrival, becoming coupled across the network. The onset of congestion is evidently related to the relative values of three characteristic times: the time for banks' net position to return to zero, the time for banks to exhaust their liquidity endowments, and the liquidity market relaxation time. In the congested regime, settlement takes place in cascades having a characteristic size. A global liquidity market substantially diminishes congestion, requiring only a small fraction of the payment-induced liquidity flow to achieve strong beneficial effects.

  12. Integrated Traffic Flow Management Decision Making

    NASA Technical Reports Server (NTRS)

    Grabbe, Shon R.; Sridhar, Banavar; Mukherjee, Avijit

    2009-01-01

    A generalized approach is proposed to support integrated traffic flow management decision making studies at both the U.S. national and regional levels. It can consider tradeoffs between alternative optimization and heuristic based models, strategic versus tactical flight controls, and system versus fleet preferences. Preliminary testing was accomplished by implementing thirteen unique traffic flow management models, which included all of the key components of the system and conducting 85, six-hour fast-time simulation experiments. These experiments considered variations in the strategic planning look-ahead times, the replanning intervals, and the types of traffic flow management control strategies. Initial testing indicates that longer strategic planning look-ahead times and re-planning intervals result in steadily decreasing levels of sector congestion for a fixed delay level. This applies when accurate estimates of the air traffic demand, airport capacities and airspace capacities are available. In general, the distribution of the delays amongst the users was found to be most equitable when scheduling flights using a heuristic scheduling algorithm, such as ration-by-distance. On the other hand, equity was the worst when using scheduling algorithms that took into account the number of seats aboard each flight. Though the scheduling algorithms were effective at alleviating sector congestion, the tactical rerouting algorithm was the primary control for avoiding en route weather hazards. Finally, the modeled levels of sector congestion, the number of weather incursions, and the total system delays, were found to be in fair agreement with the values that were operationally observed on both good and bad weather days.

  13. Performance analysis of reactive congestion control for ATM networks

    NASA Astrophysics Data System (ADS)

    Kawahara, Kenji; Oie, Yuji; Murata, Masayuki; Miyahara, Hideo

    1995-05-01

    In ATM networks, preventive congestion control is widely recognized for efficiently avoiding congestion, and it is implemented by a conjunction of connection admission control and usage parameter control. However, congestion may still occur because of unpredictable statistical fluctuation of traffic sources even when preventive control is performed in the network. In this paper, we study another kind of congestion control, i.e., reactive congestion control, in which each source changes its cell emitting rate adaptively to the traffic load at the switching node (or at the multiplexer). Our intention is that, by incorporating such a congestion control method in ATM networks, more efficient congestion control is established. We develop an analytical model, and carry out an approximate analysis of reactive congestion control algorithm. Numerical results show that the reactive congestion control algorithms are very effective in avoiding congestion and in achieving the statistical gain. Furthermore, the binary congestion control algorithm with pushout mechanism is shown to provide the best performance among the reactive congestion control algorithms treated here.

  14. Traffic accidents on a single-lane road with multi-slowdown sections

    NASA Astrophysics Data System (ADS)

    Li, Xingli; Kuang, Hua; Fan, Yanhong; Zhang, Guoxin

    2014-02-01

    In this paper, an extended cellular automaton model is proposed to simulate the complex characteristics of traffic flow and the probability of the occurrence of traffic accidents by considering the modified conditions for determining whether traffic accidents happen and the effect of multi-slowdown sections on a highway. The simulation results show that the multi-slowdown sections can lead to multiphase coexistences (i.e. free flow phase, congestion phase and saturation phase) in traffic system. The fundamental diagram shows that the number of slowdown section does not influence the mean velocity and the mean flow under the periodic boundary condition, but the existence of slowdown sections can effectively reduce the occurrence of traffic accident. In particular, it is found that the probability of car accidents to occur is the largest at the joint of the normal-speed section and slowdown section, and the underlying mechanism is analyzed. In addition, to design the appropriate limited speed and reduce the differences between the normal speed and limited speed will alleviate traffic congestion and reduce the occurrence of traffic accidents obviously.

  15. Traffic flow theory and characteristics

    SciTech Connect

    Hauer, E.; Pagitsas, E.; Shin, B.T.; Maze, T.H.; Hurley, J.W. Jr.

    1981-01-01

    Estimation of turning flows from automatic counts; a probabilistic model of gap acceptance behavior; sensitivity of fuel-consumption and delay values from traffic simulation; traffic data acquisition from small-format photography; decentralized control of congested street networks; improved estimation of traffic flow for real-time control; Maxband, a program for setting signals on arteries and triangular networks are discussed.

  16. The Influence of Individual Driver Characteristics on Congestion Formation

    NASA Astrophysics Data System (ADS)

    Wang, Lanjun; Zhang, Hao; Meng, Huadong; Wang, Xiqin

    Previous works have pointed out that one of the reasons for the formation of traffic congestion is instability in traffic flow. In this study, we investigate theoretically how the characteristics of individual drivers influence the instability of traffic flow. The discussions are based on the optimal velocity model, which has three parameters related to individual driver characteristics. We specify the mappings between the model parameters and driver characteristics in this study. With linear stability analysis, we obtain a condition for when instability occurs and a constraint about how the model parameters influence the unstable traffic flow. Meanwhile, we also determine how the region of unstable flow densities depends on these parameters. Additionally, the Langevin approach theoretically validates that under the constraint, the macroscopic characteristics of the unstable traffic flow becomes a mixture of free flows and congestions. All of these results imply that both overly aggressive and overly conservative drivers are capable of triggering traffic congestion.

  17. Microscale traffic simulation and emission estimation in a heavily trafficked roundabout in Madrid (Spain).

    PubMed

    Quaassdorff, Christina; Borge, Rafael; Pérez, Javier; Lumbreras, Julio; de la Paz, David; de Andrés, Juan Manuel

    2016-10-01

    This paper presents the evaluation of emissions from vehicle operations in a domain of 300m×300m covering a complex urban roundabout with high traffic density in Madrid. Micro-level simulation was successfully applied to estimate the emissions on a scale of meters. Two programs were used: i) VISSIM to simulate the traffic on the square and to compute velocity-time profiles; and ii) VERSIT+micro through ENVIVER that uses VISSIM outputs to compute the related emissions at vehicle level. Data collection was achieved by a measurement campaign obtaining empirical data of vehicle flows and traffic intensities. Twelve simulations of different traffic situations (scenarios) were conducted, representing different hours from several days in a week and the corresponding NOX and PM10 emissions were estimated. The results show a general reduction on average speeds for higher intensities due to braking-acceleration patterns that contribute to increase the average emission factor and, therefore, the total emissions in the domain, especially on weekdays. The emissions are clearly related to traffic volume, although maximum emission scenario does not correspond to the highest traffic intensity due to congestion and variations in fleet composition throughout the day. These results evidence the potential that local measures aimed at alleviating congestion may have in urban areas to reduce emissions. In general, scenario-averaged emission factors estimated with the VISSIM-VERSIT+micro modelling system fitted well those from the average-speed model COPERT, used as a preliminary validation of the results. The largest deviations between these two models occur in those scenarios with more congestion. The design and resolution of the microscale modelling system allow to reflect the impact of actual traffic conditions on driving patterns and related emissions, making it useful for the design of mitigation measures for specific traffic hot-spots. PMID:27232968

  18. Basic model for traffic interweave

    NASA Astrophysics Data System (ADS)

    Huang, Ding-wei

    2015-09-01

    We propose a three-parameter traffic model. The system consists of a loop with two junctions. The three parameters control the inflow, the outflow (from the junctions,) and the interweave (in the loop.) The dynamics is deterministic. The boundary conditions are stochastic. We present preliminary results for a complete phase diagram and all possible phase transitions. We observe four distinct traffic phases: free flow, congestion, bottleneck, and gridlock. The proposed model is able to present economically a clear perspective to these four different phases. Free flow and congestion are caused by the traffic conditions in the junctions. Both bottleneck and gridlock are caused by the traffic interweave in the loop. Instead of directly related to conventional congestion, gridlock can be taken as an extreme limit of bottleneck. This model can be useful to clarify the characteristics of traffic phases. This model can also be extended for practical applications.

  19. Integrated traffic system

    SciTech Connect

    Creighton, H. ); Allen, R.; Stewart, S.; Hayto, S. )

    1990-11-01

    The traffic congestion on our roads today is becoming a critical problem. There is increased fuel consumption as cars wait along poorly timed arterials. Safety is threatened as poor traffic flow leads to collisions. This paper reports that Transport Canada and the Ministry of Transportation Ontario has developed an integrated traffic system (ITS). The system is designed to enable the optimization of traffic flow on existing roadways. The ITS system contains a data-base management system for traffic data (including accidents, roadway volumes, and signal timing details) and links this data base to the traffic analysis programs. This will ease the data management situation within the municipalities and standardize the traffic operations and reduce duplication of computerization development efforts.

  20. Percolation properties in a traffic model

    NASA Astrophysics Data System (ADS)

    Wang, Feilong; Li, Daqing; Xu, Xiaoyun; Wu, Ruoqian; Havlin, Shlomo

    2015-11-01

    As a dynamical complex system, traffic is characterized by a transition from free flow to congestions, which is mostly studied in highways. However, despite its importance in developing congestion mitigation strategies, the understanding of this common traffic phenomenon in a city scale is still missing. An open question is how the traffic in the network collapses from a global efficient traffic to isolated local flows in small clusters, i.e. the question of traffic percolation. Here we study the traffic percolation properties on a lattice by simulation of an agent-based model for traffic. A critical traffic volume in this model distinguishes the free state from the congested state of traffic. Our results show that the threshold of traffic percolation decreases with increasing traffic volume and reaches a minimum value at the critical traffic volume. We show that this minimal threshold is the result of longest spatial correlation between traffic flows at the critical traffic volume. These findings may help to develop congestion mitigation strategies in a network view.

  1. Route guidance strategies revisited: Comparison and evaluation in an asymmetric two-route traffic network

    NASA Astrophysics Data System (ADS)

    He, Zhengbing; Chen, Bokui; Jia, Ning; Guan, Wei; Lin, Benchuan; Wang, Binghong

    2014-12-01

    To alleviate traffic congestion, a variety of route guidance strategies have been proposed for intelligent transportation systems. A number of strategies are introduced and investigated on a symmetric two-route traffic network over the past decade. To evaluate the strategies in a more general scenario, this paper conducts eight prevalent strategies on an asymmetric two-route traffic network with different slowdown behaviors on alternative routes. The results show that only mean velocity feedback strategy (MVFS) is able to equalize travel time, i.e. approximate user optimality (UO); while the others fail due to incapability of establishing relations between the feedback parameters and travel time. The paper helps better understand these strategies, and suggests MVFS if the authority intends to achieve user optimality.

  2. A Novel Biobjective Risk-Based Model for Stochastic Air Traffic Network Flow Optimization Problem

    PubMed Central

    Cai, Kaiquan; Jia, Yaoguang; Zhu, Yanbo; Xiao, Mingming

    2015-01-01

    Network-wide air traffic flow management (ATFM) is an effective way to alleviate demand-capacity imbalances globally and thereafter reduce airspace congestion and flight delays. The conventional ATFM models assume the capacities of airports or airspace sectors are all predetermined. However, the capacity uncertainties due to the dynamics of convective weather may make the deterministic ATFM measures impractical. This paper investigates the stochastic air traffic network flow optimization (SATNFO) problem, which is formulated as a weighted biobjective 0-1 integer programming model. In order to evaluate the effect of capacity uncertainties on ATFM, the operational risk is modeled via probabilistic risk assessment and introduced as an extra objective in SATNFO problem. Computation experiments using real-world air traffic network data associated with simulated weather data show that presented model has far less constraints compared to stochastic model with nonanticipative constraints, which means our proposed model reduces the computation complexity. PMID:26180842

  3. A Novel Biobjective Risk-Based Model for Stochastic Air Traffic Network Flow Optimization Problem.

    PubMed

    Cai, Kaiquan; Jia, Yaoguang; Zhu, Yanbo; Xiao, Mingming

    2015-01-01

    Network-wide air traffic flow management (ATFM) is an effective way to alleviate demand-capacity imbalances globally and thereafter reduce airspace congestion and flight delays. The conventional ATFM models assume the capacities of airports or airspace sectors are all predetermined. However, the capacity uncertainties due to the dynamics of convective weather may make the deterministic ATFM measures impractical. This paper investigates the stochastic air traffic network flow optimization (SATNFO) problem, which is formulated as a weighted biobjective 0-1 integer programming model. In order to evaluate the effect of capacity uncertainties on ATFM, the operational risk is modeled via probabilistic risk assessment and introduced as an extra objective in SATNFO problem. Computation experiments using real-world air traffic network data associated with simulated weather data show that presented model has far less constraints compared to stochastic model with nonanticipative constraints, which means our proposed model reduces the computation complexity. PMID:26180842

  4. Dynamic congestion control mechanisms for MPLS networks

    NASA Astrophysics Data System (ADS)

    Holness, Felicia; Phillips, Chris I.

    2001-02-01

    Considerable interest has arisen in congestion control through traffic engineering from the knowledge that although sensible provisioning of the network infrastructure is needed, together with sufficient underlying capacity, these are not sufficient to deliver the Quality of Service required for new applications. This is due to dynamic variations in load. In operational Internet Protocol (IP) networks, it has been difficult to incorporate effective traffic engineering due to the limited capabilities of the IP technology. In principle, Multiprotocol Label Switching (MPLS), which is a connection-oriented label swapping technology, offers new possibilities in addressing the limitations by allowing the operator to use sophisticated traffic control mechanisms. This paper presents a novel scheme to dynamically manage traffic flows through the network by re-balancing streams during periods of congestion. It proposes management-based algorithms that will allow label switched routers within the network to utilize mechanisms within MPLS to indicate when flows are starting to experience frame/packet loss and then to react accordingly. Based upon knowledge of the customer's Service Level Agreement, together with instantaneous flow information, the label edge routers can then instigate changes to the LSP route and circumvent congestion that would hitherto violate the customer contacts.

  5. On-board congestion control for satellite packet switching networks

    NASA Technical Reports Server (NTRS)

    Chu, Pong P.

    1991-01-01

    It is desirable to incorporate packet switching capability on-board for future communication satellites. Because of the statistical nature of packet communication, incoming traffic fluctuates and may cause congestion. Thus, it is necessary to incorporate a congestion control mechanism as part of the on-board processing to smooth and regulate the bursty traffic. Although there are extensive studies on congestion control for both baseband and broadband terrestrial networks, these schemes are not feasible for space based switching networks because of the unique characteristics of satellite link. Here, we propose a new congestion control method for on-board satellite packet switching. This scheme takes into consideration the long propagation delay in satellite link and takes advantage of the the satellite's broadcasting capability. It divides the control between the ground terminals and satellite, but distributes the primary responsibility to ground terminals and only requires minimal hardware resource on-board satellite.

  6. Evaluation of TCP congestion control algorithms.

    SciTech Connect

    Long, Robert Michael

    2003-12-01

    Sandia, Los Alamos, and Lawrence Livermore National Laboratories currently deploy high speed, Wide Area Network links to permit remote access to their Supercomputer systems. The current TCP congestion algorithm does not take full advantage of high delay, large bandwidth environments. This report involves evaluating alternative TCP congestion algorithms and comparing them with the currently used congestion algorithm. The goal was to find if an alternative algorithm could provide higher throughput with minimal impact on existing network traffic. The alternative congestion algorithms used were Scalable TCP and High-Speed TCP. Network lab experiments were run to record the performance of each algorithm under different network configurations. The network configurations used were back-to-back with no delay, back-to-back with a 30ms delay, and two-to-one with a 30ms delay. The performance of each algorithm was then compared to the existing TCP congestion algorithm to determine if an acceptable alternative had been found. Comparisons were made based on throughput, stability, and fairness.

  7. Local debris congestion in the geosynchronous environment with population augmentation

    NASA Astrophysics Data System (ADS)

    Anderson, Paul V.; Schaub, Hanspeter

    2014-02-01

    Forecasting of localized debris congestion in the geostationary (GEO) regime is performed to investigate how frequently near-miss events occur for each of the longitude slots in the GEO ring. The present-day resident space object (RSO) population at GEO is propagated forward in time to determine current debris congestion conditions, and new probability density functions that describe where GEO satellites are inserted into operational orbits are harnessed to assess longitude-dependent congestion in "business-as-usual" launch traffic, with and without re-orbiting at end-of-life. Congestion forecasting for a 50-year period is presented to illustrate the need for appropriately executed mitigation measures in the GEO ring. Results indicate that localized debris congestion will double within 50 years under current 80% re-orbiting success rates.

  8. Local Debris Congestion in the Geosynchronous Environment with Population Augmentation

    NASA Astrophysics Data System (ADS)

    Anderson, P.; Schaub, H.

    2013-08-01

    Forecasting of localized debris congestion in the geostationary (GEO) ring is performed to investigate how frequently near-miss events occur for every longitude slot at GEO. A parallelized propagation routine is used to propagate the current resident space object (RSO) population at GEO forward in time, and representative augmentation of this population is implemented to simulate congestion in "business-as-usual" launch traffic, with and without mitigation at end-of-life. Congestion forecasting for a 50- year time frame is presented to illustrate the need for both appropriately-executed mitigation and active remediation measures at GEO.

  9. Physics of Traffic Flow

    NASA Astrophysics Data System (ADS)

    Davis, L. C.

    2015-03-01

    The Texas A&M Transportation Institute estimated that traffic congestion cost the United States 121 billion in 2011 (the latest data available). The cost is due to wasted time and fuel. In addition to accidents and road construction, factors contributing to congestion include large demand, instability of high-density free flow and selfish behavior of drivers, which produces self-organized traffic bottlenecks. Extensive data collected on instrumented highways in various countries have led to a better understanding of traffic dynamics. From these measurements, Boris Kerner and colleagues developed a new theory called three-phase theory. They identified three major phases of flow observed in the data: free flow, synchronous flow and wide moving jams. The intermediate phase is called synchronous because vehicles in different lanes tend to have similar velocities. This congested phase, characterized by lower velocities yet modestly high throughput, frequently occurs near on-ramps and lane reductions. At present there are only two widely used methods of congestion mitigation: ramp metering and the display of current travel-time information to drivers. To find more effective methods to reduce congestion, researchers perform large-scale simulations using models based on the new theories. An algorithm has been proposed to realize Wardrop equilibria with real-time route information. Such equilibria have equal travel time on alternative routes between a given origin and destination. An active area of current research is the dynamics of connected vehicles, which communicate wirelessly with other vehicles and the surrounding infrastructure. These systems show great promise for improving traffic flow and safety.

  10. Visual Analysis of Air Traffic Data

    NASA Technical Reports Server (NTRS)

    Albrecht, George Hans; Pang, Alex

    2012-01-01

    In this paper, we present visual analysis tools to help study the impact of policy changes on air traffic congestion. The tools support visualization of time-varying air traffic density over an area of interest using different time granularity. We use this visual analysis platform to investigate how changing the aircraft separation volume can reduce congestion while maintaining key safety requirements. The same platform can also be used as a decision aid for processing requests for unmanned aerial vehicle operations.

  11. Global forward-predicting dynamic routing for traffic concurrency space stereo multi-layer scale-free network

    NASA Astrophysics Data System (ADS)

    Xie, Wei-Hao; Zhou, Bin; Liu, En-Xiao; Lu, Wei-Dang; Zhou, Ting

    2015-09-01

    Many real communication networks, such as oceanic monitoring network and land environment observation network, can be described as space stereo multi-layer structure, and the traffic in these networks is concurrent. Understanding how traffic dynamics depend on these real communication networks and finding an effective routing strategy that can fit the circumstance of traffic concurrency and enhance the network performance are necessary. In this light, we propose a traffic model for space stereo multi-layer complex network and introduce two kinds of global forward-predicting dynamic routing strategies, global forward-predicting hybrid minimum queue (HMQ) routing strategy and global forward-predicting hybrid minimum degree and queue (HMDQ) routing strategy, for traffic concurrency space stereo multi-layer scale-free networks. By applying forward-predicting strategy, the proposed routing strategies achieve better performances in traffic concurrency space stereo multi-layer scale-free networks. Compared with the efficient routing strategy and global dynamic routing strategy, HMDQ and HMQ routing strategies can optimize the traffic distribution, alleviate the number of congested packets effectively and reach much higher network capacity. Project supported by the Youth Science Funds of Shandong Academy of Sciences, China (Grant No. 2014QN032).

  12. Local empathy provides global minimization of congestion in communication networks

    NASA Astrophysics Data System (ADS)

    Meloni, Sandro; Gómez-Gardeñes, Jesús

    2010-11-01

    We present a mechanism to avoid congestion in complex networks based on a local knowledge of traffic conditions and the ability of routers to self-coordinate their dynamical behavior. In particular, routers make use of local information about traffic conditions to either reject or accept information packets from their neighbors. We show that when nodes are only aware of their own congestion state they self-organize into a hierarchical configuration that delays remarkably the onset of congestion although leading to a sharp first-order-like congestion transition. We also consider the case when nodes are aware of the congestion state of their neighbors. In this case, we show that empathy between nodes is strongly beneficial to the overall performance of the system and it is possible to achieve larger values for the critical load together with a smooth, second-order-like, transition. Finally, we show how local empathy minimize the impact of congestion as much as global minimization. Therefore, here we present an outstanding example of how local dynamical rules can optimize the system’s functioning up to the levels reached using global knowledge.

  13. Continuum modeling of cooperative traffic flow dynamics

    NASA Astrophysics Data System (ADS)

    Ngoduy, D.; Hoogendoorn, S. P.; Liu, R.

    2009-07-01

    This paper presents a continuum approach to model the dynamics of cooperative traffic flow. The cooperation is defined in our model in a way that the equipped vehicle can issue and receive a warning massage when there is downstream congestion. Upon receiving the warning massage, the (up-stream) equipped vehicle will adapt the current desired speed to the speed at the congested area in order to avoid sharp deceleration when approaching the congestion. To model the dynamics of such cooperative systems, a multi-class gas-kinetic theory is extended to capture the adaptation of the desired speed of the equipped vehicle to the speed at the downstream congested traffic. Numerical simulations are carried out to show the influence of the penetration rate of the equipped vehicles on traffic flow stability and capacity in a freeway.

  14. The Physics of Traffic

    NASA Astrophysics Data System (ADS)

    Davis, L. Craig

    2006-03-01

    Congestion in freeway traffic is an example of self-organization in the language of complexity theory. Nonequilibrium, first-order phase transitions from free flow cause complex spatiotemporal patterns. Two distinct phases of congestion are observed in empirical traffic data--wide moving jams and synchronous flow. Wide moving jams are characterized by stopped or slowly moving vehicles within the jammed region, which widens and moves upstream at 15-20 km/h. Above a critical density of vehicles, a sudden decrease in the velocity of a lead vehicle can initiate a transition from metastable states to this phase. Human behaviors, especially delayed reactions, are implicated in the formation of jams. The synchronous flow phase results from a bottleneck such as an on-ramp. Thus, in contrast to a jam, the downstream front is pinned at a fixed location. The name of the phase comes from the equilibration (or synchronization) of speed and flow rate across all lanes caused by frequent vehicle lane changes. Synchronous flow occurs when the mainline flow and the rate of merging from an on-ramp are sufficiently large. Large-scale simulations using car-following models reproduce the physical phenomena occurring in traffic and suggest methods to improve flow and mediate congestion.

  15. A Bayesian ridge regression analysis of congestion's impact on urban expressway safety.

    PubMed

    Shi, Qi; Abdel-Aty, Mohamed; Lee, Jaeyoung

    2016-03-01

    With the rapid growth of traffic in urban areas, concerns about congestion and traffic safety have been heightened. This study leveraged both Automatic Vehicle Identification (AVI) system and Microwave Vehicle Detection System (MVDS) installed on an expressway in Central Florida to explore how congestion impacts the crash occurrence in urban areas. Multiple congestion measures from the two systems were developed. To ensure more precise estimates of the congestion's effects, the traffic data were aggregated into peak and non-peak hours. Multicollinearity among traffic parameters was examined. The results showed the presence of multicollinearity especially during peak hours. As a response, ridge regression was introduced to cope with this issue. Poisson models with uncorrelated random effects, correlated random effects, and both correlated random effects and random parameters were constructed within the Bayesian framework. It was proven that correlated random effects could significantly enhance model performance. The random parameters model has similar goodness-of-fit compared with the model with only correlated random effects. However, by accounting for the unobserved heterogeneity, more variables were found to be significantly related to crash frequency. The models indicated that congestion increased crash frequency during peak hours while during non-peak hours it was not a major crash contributing factor. Using the random parameter model, the three congestion measures were compared. It was found that all congestion indicators had similar effects while Congestion Index (CI) derived from MVDS data was a better congestion indicator for safety analysis. Also, analyses showed that the segments with higher congestion intensity could not only increase property damage only (PDO) crashes, but also more severe crashes. In addition, the issues regarding the necessity to incorporate specific congestion indicator for congestion's effects on safety and to take care of the

  16. Cloud-based large-scale air traffic flow optimization

    NASA Astrophysics Data System (ADS)

    Cao, Yi

    The ever-increasing traffic demand makes the efficient use of airspace an imperative mission, and this paper presents an effort in response to this call. Firstly, a new aggregate model, called Link Transmission Model (LTM), is proposed, which models the nationwide traffic as a network of flight routes identified by origin-destination pairs. The traversal time of a flight route is assumed to be the mode of distribution of historical flight records, and the mode is estimated by using Kernel Density Estimation. As this simplification abstracts away physical trajectory details, the complexity of modeling is drastically decreased, resulting in efficient traffic forecasting. The predicative capability of LTM is validated against recorded traffic data. Secondly, a nationwide traffic flow optimization problem with airport and en route capacity constraints is formulated based on LTM. The optimization problem aims at alleviating traffic congestions with minimal global delays. This problem is intractable due to millions of variables. A dual decomposition method is applied to decompose the large-scale problem such that the subproblems are solvable. However, the whole problem is still computational expensive to solve since each subproblem is an smaller integer programming problem that pursues integer solutions. Solving an integer programing problem is known to be far more time-consuming than solving its linear relaxation. In addition, sequential execution on a standalone computer leads to linear runtime increase when the problem size increases. To address the computational efficiency problem, a parallel computing framework is designed which accommodates concurrent executions via multithreading programming. The multithreaded version is compared with its monolithic version to show decreased runtime. Finally, an open-source cloud computing framework, Hadoop MapReduce, is employed for better scalability and reliability. This framework is an "off-the-shelf" parallel computing model

  17. Auctionable fixed transmission rights for congestion management

    NASA Astrophysics Data System (ADS)

    Alomoush, Muwaffaq Irsheid

    Electric power deregulation has proposed a major change to the regulated utility monopoly. The change manifests the main part of engineers' efforts to reshape three components of today's regulated monopoly: generation, distribution and transmission. In this open access deregulated power market, transmission network plays a major role, and transmission congestion is a major problem that requires further consideration especially when inter-zonal/intra-zonal scheme is implemented. Declaring that engineering studies and experience are the criteria to define zonal boundaries or defining a zone based on the fact that a zone is a densely interconnected area (lake) and paths connecting these densely interconnected areas are inter-zonal lines will render insufficient and fuzzy definitions. Moreover, a congestion problem formulation should take into consideration interactions between intra-zonal and inter-zonal flows and their effects on power systems. In this thesis, we introduce a procedure for minimizing the number of adjustments of preferred schedules to alleviate congestion and apply control schemes to minimize interactions between zones. In addition, we give the zone definition a certain criterion based on the Locational Marginal Price (LMP). This concept will be used to define congestion zonal boundaries and to decide whether any zone should be merged with another zone or split into new zones. The thesis presents a unified scheme that combines zonal and FTR schemes to manage congestion. This combined scheme is utilized with LMPs to define zonal boundaries more appropriately. The presented scheme gains the best features of the FTR scheme, which are providing financial certainty, maximizing the efficient use of the system and making users pay for the actual use of congested paths. LMPs may give an indication of the impact of wheeling transactions, and calculations of and comparisons of LMPs with and without wheeling transactions should be adequate criteria to approve

  18. How congestion shapes cities: from mobility patterns to scaling

    PubMed Central

    Louf, Rémi; Barthelemy, Marc

    2014-01-01

    The recent availability of data for cities has allowed scientists to exhibit scalings which present themselves in the form of a power-law dependence on population of various socio-economical and structural indicators. We propose here a stochastic theory of urban growth which accounts for some of the observed scalings and we confirm these predictions on US and OECD empirical data. In particular, we show that the dependence on population size of the total number of miles driven daily, the total length of the road network, the total traffic delay, the total consumption of gasoline, the quantity of CO2 emitted and the relation between area and population of cities, are all governed by a single parameter which characterizes the sensitivity to congestion. Our results suggest that diseconomies associated with congestion scale superlinearly with population size, implying that –despite polycentrism– cities whose transportation infrastructure rely heavily on traffic sensitive modes are unsustainable. PMID:24990624

  19. How congestion shapes cities: from mobility patterns to scaling

    NASA Astrophysics Data System (ADS)

    Louf, Rémi; Barthelemy, Marc

    2014-07-01

    The recent availability of data for cities has allowed scientists to exhibit scalings which present themselves in the form of a power-law dependence on population of various socio-economical and structural indicators. We propose here a stochastic theory of urban growth which accounts for some of the observed scalings and we confirm these predictions on US and OECD empirical data. In particular, we show that the dependence on population size of the total number of miles driven daily, the total length of the road network, the total traffic delay, the total consumption of gasoline, the quantity of CO2 emitted and the relation between area and population of cities, are all governed by a single parameter which characterizes the sensitivity to congestion. Our results suggest that diseconomies associated with congestion scale superlinearly with population size, implying that -despite polycentrism- cities whose transportation infrastructure rely heavily on traffic sensitive modes are unsustainable.

  20. Network traffic behaviour near phase transition point

    NASA Astrophysics Data System (ADS)

    Lawniczak, A. T.; Tang, X.

    2006-03-01

    We explore packet traffic dynamics in a data network model near phase transition point from free flow to congestion. The model of data network is an abstraction of the Network Layer of the OSI (Open Systems Interconnect) Reference Model of packet switching networks. The Network Layer is responsible for routing packets across the network from their sources to their destinations and for control of congestion in data networks. Using the model we investigate spatio-temporal packets traffic dynamics near the phase transition point for various network connection topologies, and static and adaptive routing algorithms. We present selected simulation results and analyze them.

  1. Congestion control and routing over satellite networks

    NASA Astrophysics Data System (ADS)

    Cao, Jinhua

    Satellite networks and transmissions find their application in fields of computer communications, telephone communications, television broadcasting, transportation, space situational awareness systems and so on. This thesis mainly focuses on two networking issues affecting satellite networking: network congestion control and network routing optimization. Congestion, which leads to long queueing delays, packet losses or both, is a networking problem that has drawn the attention of many researchers. The goal of congestion control mechanisms is to ensure high bandwidth utilization while avoiding network congestion by regulating the rate at which traffic sources inject packets into a network. In this thesis, we propose a stable congestion controller using data-driven, safe switching control theory to improve the dynamic performance of satellite Transmission Control Protocol/Active Queue Management (TCP/AQM) networks. First, the stable region of the Proportional-Integral (PI) parameters for a nominal model is explored. Then, a PI controller, whose parameters are adaptively tuned by switching among members of a given candidate set, using observed plant data, is presented and compared with some classical AQM policy examples, such as Random Early Detection (RED) and fixed PI control. A new cost detectable switching law with an interval cost function switching algorithm, which improves the performance and also saves the computational cost, is developed and compared with a law commonly used in the switching control literature. Finite-gain stability of the system is proved. A fuzzy logic PI controller is incorporated as a special candidate to achieve good performance at all nominal points with the available set of candidate controllers. Simulations are presented to validate the theory. An effocient routing algorithm plays a key role in optimizing network resources. In this thesis, we briefly analyze Low Earth Orbit (LEO) satellite networks, review the Cross Entropy (CE

  2. Analysis of the congestion effects of link failures in wide area networks

    NASA Astrophysics Data System (ADS)

    Tipper, David; Hammond, Joseph L.; Sharma, Sandeep; Khetan, Archana; Balakrishnan, Krishnan; Menon, Sunil

    1994-01-01

    In this paper, we present the results of a study to determine the effects of link failures on the performance of a network in terms of the occurrence of congestion due to traffic restoration after a failure. The network studied is a virtual circuit based packet switched wide area network. A generic queueing framework is developed to study the effect of failures and the subsequent traffic restoration on network performance. In general, the congestion resulting after a failure is a transient phenomenon. Hence, a numerical methods based nonstationary queueing analysis is conducted in order to quantify the effects of failures in terms of the transient behavior of queue lengths and packet loss probabilities. A bounding relationship is developed whereby a network node can determine whether or not congestion will occur as the result of traffic restoration after a failure.

  3. Large-Scale Transportation Network Congestion Evolution Prediction Using Deep Learning Theory

    PubMed Central

    Ma, Xiaolei; Yu, Haiyang; Wang, Yunpeng; Wang, Yinhai

    2015-01-01

    Understanding how congestion at one location can cause ripples throughout large-scale transportation network is vital for transportation researchers and practitioners to pinpoint traffic bottlenecks for congestion mitigation. Traditional studies rely on either mathematical equations or simulation techniques to model traffic congestion dynamics. However, most of the approaches have limitations, largely due to unrealistic assumptions and cumbersome parameter calibration process. With the development of Intelligent Transportation Systems (ITS) and Internet of Things (IoT), transportation data become more and more ubiquitous. This triggers a series of data-driven research to investigate transportation phenomena. Among them, deep learning theory is considered one of the most promising techniques to tackle tremendous high-dimensional data. This study attempts to extend deep learning theory into large-scale transportation network analysis. A deep Restricted Boltzmann Machine and Recurrent Neural Network architecture is utilized to model and predict traffic congestion evolution based on Global Positioning System (GPS) data from taxi. A numerical study in Ningbo, China is conducted to validate the effectiveness and efficiency of the proposed method. Results show that the prediction accuracy can achieve as high as 88% within less than 6 minutes when the model is implemented in a Graphic Processing Unit (GPU)-based parallel computing environment. The predicted congestion evolution patterns can be visualized temporally and spatially through a map-based platform to identify the vulnerable links for proactive congestion mitigation. PMID:25780910

  4. Large-scale transportation network congestion evolution prediction using deep learning theory.

    PubMed

    Ma, Xiaolei; Yu, Haiyang; Wang, Yunpeng; Wang, Yinhai

    2015-01-01

    Understanding how congestion at one location can cause ripples throughout large-scale transportation network is vital for transportation researchers and practitioners to pinpoint traffic bottlenecks for congestion mitigation. Traditional studies rely on either mathematical equations or simulation techniques to model traffic congestion dynamics. However, most of the approaches have limitations, largely due to unrealistic assumptions and cumbersome parameter calibration process. With the development of Intelligent Transportation Systems (ITS) and Internet of Things (IoT), transportation data become more and more ubiquitous. This triggers a series of data-driven research to investigate transportation phenomena. Among them, deep learning theory is considered one of the most promising techniques to tackle tremendous high-dimensional data. This study attempts to extend deep learning theory into large-scale transportation network analysis. A deep Restricted Boltzmann Machine and Recurrent Neural Network architecture is utilized to model and predict traffic congestion evolution based on Global Positioning System (GPS) data from taxi. A numerical study in Ningbo, China is conducted to validate the effectiveness and efficiency of the proposed method. Results show that the prediction accuracy can achieve as high as 88% within less than 6 minutes when the model is implemented in a Graphic Processing Unit (GPU)-based parallel computing environment. The predicted congestion evolution patterns can be visualized temporally and spatially through a map-based platform to identify the vulnerable links for proactive congestion mitigation. PMID:25780910

  5. A successful traffic relief program

    SciTech Connect

    Dimino, R.A.; Bezkorovainy, G.; Campbell, B.

    1987-08-01

    This article reports that in August 1986, under the direction of Mayor Raymond Flynn, the City of Boston initiated Phase I of a Traffic Relief Program (TRP). The program was an interagency effort of the Boston Transportation Department and the Boston Police Department, to provide increased enforcement of the city's traffic and parking regulations on congested roadways in downtown Boston. The TRP is a reaffirmation of the city's philosophy that major arterials' primary function is the movement of traffic during periods of heavy traffic flow. There were six objectives: to reduce vehicular travel time along travel corridors; to increase street/intersection capacity; to eliminate vehicular blockage at intersections; to eliminate double parking; to eliminate pedestrian/vehicular conflicts at intersections and thus reduce the potential number of accidents; and to provide clear regulatory and street name signage.

  6. Adapting End Host Congestion Control for Mobility

    NASA Technical Reports Server (NTRS)

    Eddy, Wesley M.; Swami, Yogesh P.

    2005-01-01

    Network layer mobility allows transport protocols to maintain connection state, despite changes in a node's physical location and point of network connectivity. However, some congestion-controlled transport protocols are not designed to deal with these rapid and potentially significant path changes. In this paper we demonstrate several distinct problems that mobility-induced path changes can create for TCP performance. Our premise is that mobility events indicate path changes that require re-initialization of congestion control state at both connection end points. We present the application of this idea to TCP in the form of a simple solution (the Lightweight Mobility Detection and Response algorithm, that has been proposed in the IETF), and examine its effectiveness. In general, we find that the deficiencies presented are both relatively easily and painlessly fixed using this solution. We also find that this solution has the counter-intuitive property of being both more friendly to competing traffic, and simultaneously more aggressive in utilizing newly available capacity than unmodified TCP.

  7. Dynamics of TCP traffic over ATM networks

    NASA Astrophysics Data System (ADS)

    Romanow, Allyn; Floyd, Sally

    1995-05-01

    We investigate the performance of TCP connections over ATM networks without ATM-level congestion control and compare it to the performance of TCP over packet-based networks. For simulations of congested networks, the effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. The low throughput is due to wasted bandwidth as the congested link transmits cells from 'corrupted' packets, i.e., packets in which at least one cell is dropped by the switch. We investigate two packet-discard strategies that alleviate the effects of fragmentation. Partial packet discard, in which remaining cells are discarded after one cell has been dropped from a packet, somewhat improves throughput. We introduce early packet discard, a strategy in which the switch drops whole packets prior to buffer overflow. This mechanism prevents fragmentation and restores throughput to maximal levels.

  8. Air pollution and health risks due to vehicle traffic.

    PubMed

    Zhang, Kai; Batterman, Stuart

    2013-04-15

    Traffic congestion increases vehicle emissions and degrades ambient air quality, and recent studies have shown excess morbidity and mortality for drivers, commuters and individuals living near major roadways. Presently, our understanding of the air pollution impacts from congestion on roads is very limited. This study demonstrates an approach to characterize risks of traffic for on- and near-road populations. Simulation modeling was used to estimate on- and near-road NO2 concentrations and health risks for freeway and arterial scenarios attributable to traffic for different traffic volumes during rush hour periods. The modeling used emission factors from two different models (Comprehensive Modal Emissions Model and Motor Vehicle Emissions Factor Model version 6.2), an empirical traffic speed-volume relationship, the California Line Source Dispersion Model, an empirical NO2-NOx relationship, estimated travel time changes during congestion, and concentration-response relationships from the literature, which give emergency doctor visits, hospital admissions and mortality attributed to NO2 exposure. An incremental analysis, which expresses the change in health risks for small increases in traffic volume, showed non-linear effects. For a freeway, "U" shaped trends of incremental risks were predicted for on-road populations, and incremental risks are flat at low traffic volumes for near-road populations. For an arterial road, incremental risks increased sharply for both on- and near-road populations as traffic increased. These patterns result from changes in emission factors, the NO2-NOx relationship, the travel delay for the on-road population, and the extended duration of rush hour for the near-road population. This study suggests that health risks from congestion are potentially significant, and that additional traffic can significantly increase risks, depending on the type of road and other factors. Further, evaluations of risk associated with congestion must

  9. Development of decision support systems for real-time freeway traffic routing: Volume 2. Final report

    SciTech Connect

    Sadek, A.W.; Smith, B.L.; McGhee, C.C.; Demetsky, M.J.

    1998-10-01

    Real-time traffic flow routing is a promising approach to alleviating congestion. Existing approaches to developing real-time routing strategies, however, have limitations. The study explored the potential for using case-based reasoning (CBR), an emerging artificial intelligence paradigm, to overcome such limitations. CBR solves new problems by reusing solutions of similar past problems. To illustrate the feasibility of the approach, the research team developed and evaluated a prototype CBR routing system for the interstate network in Hampton Roads, Virginia. They generated cases for building the system`s case-base using a heuristic dynamic traffic assignment (DTA) model designed for the region. Using a second set of cases, the research team evaluated the performance of the prototype system by comparing its solutions with those of the DTA model. The research team found that CBR has the potential to overcome many of the limitations to existing approaches to real-time routing and a CBR routing system is capable of producing high-quality solutions with reasonable a case-base size. In addition, the research team found that real-time traffic flow routing will likely lead to significant user cost savings.

  10. Congestion on Multilane Highways

    SciTech Connect

    Greenberg, J.M.; Klar, A.; Rascle, M.

    2002-07-01

    We present a new model for traffic on a multilane freeway (with n lanes). Our basic descriptors are the car density {rho} (in cars/mile) taken across all lanes in the freeway and the average car velocity u (in miles/hour). In this paper we present a model which incorporates both equilibrium curves and a simple switching mechanism which allows cars to transit from one equilibrium curve to the other. This switching mechanism, when combined with the continuity equation, produces relaxation or self-excited oscillations in the system and these oscillations are what interests us here.

  11. Pelvic Congestion Syndrome

    PubMed Central

    Durham, Janette D.; Machan, Lindsay

    2013-01-01

    Patients with pelvic congestion syndrome present with otherwise unexplained chronic pelvic pain that has been present for greater than 6 months, and anatomic findings that include pelvic venous insufficiency and pelvic varicosities. It remains an underdiagnosed explanation for pelvic pain in young, premenopausal, usually multiparous females. Symptoms include noncyclical, positional lower back, pelvic and upper thigh pain, dyspareunia, and prolonged postcoital discomfort. Symptoms worsen throughout the day and are exacerbated by activity or prolonged standing. Examination may reveal ovarian tenderness and unusual varicosities—vulvoperineal, posterior thigh, and gluteal. Diagnosis is suspected by clinical history and imaging that demonstrates pelvic varicosities. Venography is usually necessary to confirm ovarian vein reflux, although transvaginal ultrasound may be useful in documenting this finding. Endovascular therapy has been validated by several large patient series with long-term follow-up using standardized pain assessment surveys. Embolization has been shown to be significantly more effective than surgical therapy in improving symptoms in patients who fail hormonal therapy. Although there has been variation in approaches between investigators, the goal is elimination of ovarian vein reflux with or without direct sclerosis of enlarged pelvic varicosities. Symptom reduction is seen in 70 to 90% of the treated females despite technical variation. PMID:24436564

  12. Hysteresis phenomena of the intelligent driver model for traffic flow

    NASA Astrophysics Data System (ADS)

    Dahui, Wang; Ziqiang, Wei; Ying, Fan

    2007-07-01

    We present hysteresis phenomena of the intelligent driver model for traffic flow in a circular one-lane roadway. We show that the microscopic structure of traffic flow is dependent on its initial state by plotting the fraction of congested vehicles over the density, which shows a typical hysteresis loop, and by investigating the trajectories of vehicles on the velocity-over-headway plane. We find that the trajectories of vehicles on the velocity-over-headway plane, which usually show a hysteresis loop, include multiple loops. We also point out the relations between these hysteresis loops and the congested jams or high-density clusters in traffic flow.

  13. Privacy-Sensitive Congestion Charging

    NASA Astrophysics Data System (ADS)

    Beresford, Alastair R.; Davies, Jonathan J.; Harle, Robert K.

    National-scale congestion charging schemes are increasingly viewed as the most viable long-term strategy for controlling congestion and maintaining the viability of the road network. In this paper we challenge the widely held belief that enforceable and economically viable congestion charging schemes require drivers to give up their location privacy to the government. Instead we explore an alternative scheme where privately-owned cars enforce congestion charge payments by using an on-board vehicle unit containing a camera and wireless communications. Our solution prevents centralised tracking of vehicle movements but raises an important issue: should we trust our neighbours with a little personal information in preference to entrusting it all to the government?

  14. Analytical Solution of Traffic Cellular Automata Model

    NASA Astrophysics Data System (ADS)

    Lo, Shih-Ching; Hsu, Chia-Hung

    2009-08-01

    Complex traffic system seems to be simulated successfully by cellular automaton (CA) models. Various models are developed to understand single-lane traffic, multilane traffic, lane-changing behavior and network traffic situations. However, the result of CA simulation can only be obtained after massive microscopic computation. Although, the mean field theory (MFT) has been studied to be the approximation of CA model, the MFT can only applied to the simple CA rules or small value of parameters. In this study, we simulate traffic flow by the NaSch model under different combination of parameters, which are maximal speed, dawdling probability and density. After that, the position of critical density, the slope of free-flow and congested regime are observed and modeled due to the simulated data. Finally, the coefficients of the model will be calibrated by the simulated data and the analytical solution of traffic CA is obtained.

  15. Reinforcement learning for congestion-avoidance in packet flow

    NASA Astrophysics Data System (ADS)

    Horiguchi, Tsuyoshi; Hayashi, Keisuke; Tretiakov, Alexei

    2005-04-01

    Occurrence of congestion of packet flow in computer networks is one of the unfavorable problems in packet communication and hence its avoidance should be investigated. We use a neural network model for packet routing control in a computer network proposed in a previous paper by Horiguchi and Ishioka (Physica A 297 (2001) 521). If we assume that the packets are not sent to nodes whose buffers are already full of packets, then we find that traffic congestion occurs when the number of packets in the computer network is larger than some critical value. In order to avoid the congestion, we introduce reinforcement learning for a control parameter in the neural network model. We find that the congestion is avoided by the reinforcement learning and at the same time we have good performance for the throughput. We investigate the packet flow on computer networks of various types of topology such as a regular network, a network with fractal structure, a small-world network, a scale-free network and so on.

  16. Macroscopic traffic modeling with the finite difference method

    SciTech Connect

    Mughabghab, S.; Azarm, A.; Stock, D.

    1996-03-15

    A traffic congestion forecasting model (ATOP), developed in the present investigation, is described briefly. Several macroscopic models, based on the solution of the partial differential equation of conservation of vehicles by the finite difference method, were tested using actual traffic data. The functional form, as well as the parameters, of the equation of state which describes the relation between traffic speed and traffic density, were determined for a section of the Long Island Expressway. The Lax method and the forward difference technique were applied. The results of extensive tests showed that the Lax method, in addition to giving very good agreement with the traffic data, produces stable solutions.

  17. Analysis of Aircraft Clusters to Measure Sector-Independent Airspace Congestion

    NASA Technical Reports Server (NTRS)

    Bilimoria, Karl D.; Lee, Hilda Q.

    2005-01-01

    The Distributed Air/Ground Traffic Management (DAG-TM) concept of operations* permits appropriately equipped aircraft to conduct Free Maneuvering operations. These independent aircraft have the freedom to optimize their trajectories in real time according to user preferences; however, they also take on the responsibility to separate themselves from other aircraft while conforming to any local Traffic Flow Management (TFM) constraints imposed by the air traffic service provider (ATSP). Examples of local-TFM constraints include temporal constraints such as a required time of arrival (RTA), as well as spatial constraints such as regions of convective weather, special use airspace, and congested airspace. Under current operations, congested airspace typically refers to a sector(s) that cannot accept additional aircraft due to controller workload limitations; hence Dynamic Density (a metric that is indicative of controller workload) can be used to quantify airspace congestion. However, for Free Maneuvering operations under DAG-TM, an additional metric is needed to quantify the airspace congestion problem from the perspective of independent aircraft. Such a metric would enable the ATSP to prevent independent aircraft from entering any local areas of congestion in which the flight deck based systems and procedures may not be able to ensure separation. This new metric, called Gaggle Density, offers the ATSP a mode of control to regulate normal operations and to ensure safety and stability during rare-normal or off-normal situations (e.g., system failures). It may be difficult to certify Free Maneuvering systems for unrestricted operations, but it may be easier to certify systems and procedures for specified levels of Gaggle Density that could be monitored by the ATSP, and maintained through relatively minor flow-rate (RTA type) restrictions. Since flight deck based separation assurance is airspace independent, the challenge is to measure congestion independent of sector

  18. Hidden geometry of traffic jamming.

    PubMed

    Andjelković, Miroslav; Gupte, Neelima; Tadić, Bosiljka

    2015-05-01

    We introduce an approach based on algebraic topological methods that allow an accurate characterization of jamming in dynamical systems with queues. As a prototype system, we analyze the traffic of information packets with navigation and queuing at nodes on a network substrate in distinct dynamical regimes. A temporal sequence of traffic density fluctuations is mapped onto a mathematical graph in which each vertex denotes one dynamical state of the system. The coupling complexity between these states is revealed by classifying agglomerates of high-dimensional cliques that are intermingled at different topological levels and quantified by a set of geometrical and entropy measures. The free-flow, jamming, and congested traffic regimes result in graphs of different structure, while the largest geometrical complexity and minimum entropy mark the edge of the jamming region. PMID:26066222

  19. 23 CFR 973.214 - Indian lands congestion management system (CMS).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) Transportation demand management measures; (B) Traffic operational improvements; (C) Public transportation... 23 Highways 1 2010-04-01 2010-04-01 false Indian lands congestion management system (CMS). 973.214... HIGHWAYS MANAGEMENT SYSTEMS PERTAINING TO THE BUREAU OF INDIAN AFFAIRS AND THE INDIAN RESERVATION...

  20. Depression and congestive heart failure.

    PubMed

    Guck, Thomas P; Elsasser, Gary N; Kavan, Michael G; Barone, Eugene J

    2003-01-01

    The prevalence rates of depression in congestive heart failure patients range from 24%-42%. Depression is a graded, independent risk factor for readmission to the hospital, functional decline, and mortality in patients with congestive heart failure. Physicians can assess depression by using the SIG E CAPS + mood mnemonic, or any of a number of easily administered and scored self-report inventories. Cognitive-behavior therapy is the preferred psychological treatment. Cognitive-behavior therapy emphasizes the reciprocal interactions among physiology, environmental events, thoughts, and behaviors, and how these may be altered to produce changes in mood and behavior. Pharmacologically, the selective serotonin reuptake inhibitors are recommended, whereas the tricyclic antidepressants are not recommended for depression in congestive heart failure patients. The combination of a selective serotonin reuptake inhibitor with cognitive-behavior therapy is often the most effective treatment. PMID:12826775

  1. Querying and Extracting Timeline Information from Road Traffic Sensor Data.

    PubMed

    Imawan, Ardi; Indikawati, Fitri Indra; Kwon, Joonho; Rao, Praveen

    2016-01-01

    The escalation of traffic congestion in urban cities has urged many countries to use intelligent transportation system (ITS) centers to collect historical traffic sensor data from multiple heterogeneous sources. By analyzing historical traffic data, we can obtain valuable insights into traffic behavior. Many existing applications have been proposed with limited analysis results because of the inability to cope with several types of analytical queries. In this paper, we propose the QET (querying and extracting timeline information) system-a novel analytical query processing method based on a timeline model for road traffic sensor data. To address query performance, we build a TQ-index (timeline query-index) that exploits spatio-temporal features of timeline modeling. We also propose an intuitive timeline visualization method to display congestion events obtained from specified query parameters. In addition, we demonstrate the benefit of our system through a performance evaluation using a Busan ITS dataset and a Seattle freeway dataset. PMID:27563900

  2. A Survey on Urban Traffic Management System Using Wireless Sensor Networks.

    PubMed

    Nellore, Kapileswar; Hancke, Gerhard P

    2016-01-01

    Nowadays, the number of vehicles has increased exponentially, but the bedrock capacities of roads and transportation systems have not developed in an equivalent way to efficiently cope with the number of vehicles traveling on them. Due to this, road jamming and traffic correlated pollution have increased with the associated adverse societal and financial effect on different markets worldwide. A static control system may block emergency vehicles due to traffic jams. Wireless Sensor networks (WSNs) have gained increasing attention in traffic detection and avoiding road congestion. WSNs are very trendy due to their faster transfer of information, easy installation, less maintenance, compactness and for being less expensive compared to other network options. There has been significant research on Traffic Management Systems using WSNs to avoid congestion, ensure priority for emergency vehicles and cut the Average Waiting Time (AWT) of vehicles at intersections. In recent decades, researchers have started to monitor real-time traffic using WSNs, RFIDs, ZigBee, VANETs, Bluetooth devices, cameras and infrared signals. This paper presents a survey of current urban traffic management schemes for priority-based signalling, and reducing congestion and the AWT of vehicles. The main objective of this survey is to provide a taxonomy of different traffic management schemes used for avoiding congestion. Existing urban traffic management schemes for the avoidance of congestion and providing priority to emergency vehicles are considered and set the foundation for further research. PMID:26828489

  3. A Survey on Urban Traffic Management System Using Wireless Sensor Networks

    PubMed Central

    Nellore, Kapileswar; Hancke, Gerhard P.

    2016-01-01

    Nowadays, the number of vehicles has increased exponentially, but the bedrock capacities of roads and transportation systems have not developed in an equivalent way to efficiently cope with the number of vehicles traveling on them. Due to this, road jamming and traffic correlated pollution have increased with the associated adverse societal and financial effect on different markets worldwide. A static control system may block emergency vehicles due to traffic jams. Wireless Sensor networks (WSNs) have gained increasing attention in traffic detection and avoiding road congestion. WSNs are very trendy due to their faster transfer of information, easy installation, less maintenance, compactness and for being less expensive compared to other network options. There has been significant research on Traffic Management Systems using WSNs to avoid congestion, ensure priority for emergency vehicles and cut the Average Waiting Time (AWT) of vehicles at intersections. In recent decades, researchers have started to monitor real-time traffic using WSNs, RFIDs, ZigBee, VANETs, Bluetooth devices, cameras and infrared signals. This paper presents a survey of current urban traffic management schemes for priority-based signalling, and reducing congestion and the AWT of vehicles. The main objective of this survey is to provide a taxonomy of different traffic management schemes used for avoiding congestion. Existing urban traffic management schemes for the avoidance of congestion and providing priority to emergency vehicles are considered and set the foundation for further research. PMID:26828489

  4. Phase Transitions and the Korteweg-De Vries Equation in the Density Difference Lattice Hydrodynamic Model of Traffic Flow

    NASA Astrophysics Data System (ADS)

    Tian, Jun-Fang; Yuan, Zhen-Zhou; Jia, Bin; Fan, Hong-Qiang

    2013-03-01

    We investigate the phase transitions and the Korteweg-de Vries (KdV) equation in the density difference lattice hydrodynamic (DDLM) model, which shows a close connection with the gas-kinetic-based model and the microscopic car following model. The KdV equation near the neutral stability line is derived and the corresponding soliton solution describing the density waves is obtained. Numerical simulations are conducted in two aspects. On the one hand, under periodic conditions perturbations are applied to demonstrate the nonlinear analysis result. On the other hand, the open boundary condition with random fluctuations is designed to explore the empirical congested traffic patterns. The phase transitions among the free traffic (FT), widening synchronized flow pattern (WSP), moving localized cluster (MLC), oscillatory congested traffic (OCT) and homogeneous congested traffic (HCT) occur by varying the amplitude of the fluctuations. To our knowledge, it is the first research showing that the lattice hydrodynamic model could reproduce so many congested traffic patterns.

  5. "Playboy bunny" sign of congestive heart failure.

    PubMed

    Hokama, Akira; Arakaki, Shingo; Shibata, Daisuke; Maeshiro, Tatsuji; Kinjo, Fukunori; Fujita, Jiro

    2011-11-01

    In emergency, ultrasound has been widely used as a noninvasive and effective examination to evaluate congestive heart failure. We highlight "Playboy Bunny" sign as a reliable marker and an important clue to the diagnosis of passive hepatic congestion, caused by congestive heart failure. PMID:22224133

  6. Cycle-by-cycle analysis of congested flow at signalized intersections

    SciTech Connect

    Rouphail, N.M. )

    1991-03-01

    The increasing number of traffic signals and traffic signal systems in urban areas in the United States is influencing traffic-flow patterns on roadways. Because of the closer proximity of traffic signals (whether coordinated or not), there are fewer observed variations in traffic flow demand during peak hour, and fewer signals in urban areas now operate in truly isolated mode. This is especially true in the case of heavy demand volumes where upstream signals tend to filter traffic at the signal capacity (that is, at virtually a fixed rate). From the traffic engineer's standpoint, the issues associated with congested flow are quite different from those occurring under normal operation (some would even argue that congestion of gridlock is now considered normal operation). The following questions may be asked: How long will it take to clear the congestion developed during peak period; What maximum overflow queue can be expected; How much improvement can be achieved through better signal coordination The principal tool available to traffic engineers for the analysis of signalized intersections in the United States is the {ital Highway Capacity Manual} (HCM). Yet, none of the issues mentioned above is adequately addressed in the HCM. For example, the HCM method uses a fixed peak period of analysis of 15 minutes for calculating level of service. The HCM method has no mechanism for estimating queues, or for estimating when peak-period queues can be cleared on an approach. Furthermore, signal coordination effects are expressed by a set of progression factors that have a very loose correspondence to signal offsets. More important, all analyses in the 1985 HCM are performed assuming average conditions in 15-minute peak period without considering the cycle-by-cycle variation in flows, queues, and delays. Finally, the level-of-service analysis is limited to situations with no initial queue at the start of the peak period and to volume-to-capacity ratios under 1.20.

  7. Shanghai alleviates noise pollution

    SciTech Connect

    Ding Runling

    1983-07-14

    ''Environmental noise is now under control in Shanghai, the level of environmental noise is basically holding steady, and in some areas industrial and traffic noise has decreased.'' These were the conclusions of research by Hong Zonghui (3163 1350 6540) and Wang Shixian (3769 6164 6343) of Tongji University's Acoustics Laboratory, as put forward at a recent public academic lecture at Tongji University. In order to eliminate noise from the environment, Tongji University in the early 1970's began conducting investigations and research on noise pollution and its control together with concerned units in this city. After tests in a network of 2,117 points throughout the city, they determined that the most common form of noise pollution is traffic, which accounts for 50 percent of all noise. Since 1979, this city has adopted successive measures in the area of traffic control in order to eliminate the source of noise. Traffic noise has now dropped about 3 decibels in the city. This research report also pointed out that according to the results of regional environmental noise tests, this city does not meet the noise pollution standards set by the state. Tugboats on the Suzhou He blow their whistles late at night, and the noise at riverside homes can reach 82 decibels; the Fangua Lane residential district is close to a railroad where engine noise can reach 89 decibels and affect the residents' health. In addition, rather serious noise pollution is produced by more than 300 handicraft, light industry, textile, and electrical machinery plants.

  8. Priority Based Congestion Control Dynamic Clustering Protocol in Mobile Wireless Sensor Networks.

    PubMed

    Jayakumari, R Beulah; Senthilkumar, V Jawahar

    2015-01-01

    Wireless sensor network is widely used to monitor natural phenomena because natural disaster has globally increased which causes significant loss of life, economic setback, and social development. Saving energy in a wireless sensor network (WSN) is a critical factor to be considered. The sensor nodes are deployed to sense, compute, and communicate alerts in a WSN which are used to prevent natural hazards. Generally communication consumes more energy than sensing and computing; hence cluster based protocol is preferred. Even with clustering, multiclass traffic creates congested hotspots in the cluster, thereby causing packet loss and delay. In order to conserve energy and to avoid congestion during multiclass traffic a novel Priority Based Congestion Control Dynamic Clustering (PCCDC) protocol is developed. PCCDC is designed with mobile nodes which are organized dynamically into clusters to provide complete coverage and connectivity. PCCDC computes congestion at intra- and intercluster level using linear and binary feedback method. Each mobile node within the cluster has an appropriate queue model for scheduling prioritized packet during congestion without drop or delay. Simulation results have proven that packet drop, control overhead, and end-to-end delay are much lower in PCCDC which in turn significantly increases packet delivery ratio, network lifetime, and residual energy when compared with PASCC protocol. PMID:26504898

  9. Distributive routing and congestion control in wireless multihop ad hoc communication networks

    NASA Astrophysics Data System (ADS)

    Glauche, Ingmar; Krause, Wolfram; Sollacher, Rudolf; Greiner, Martin

    2004-10-01

    Due to their inherent complexity, engineered wireless multihop ad hoc communication networks represent a technological challenge. Having no mastering infrastructure the nodes have to selforganize themselves in such a way that for example network connectivity, good data traffic performance and robustness are guaranteed. In this contribution the focus is on routing and congestion control. First, random data traffic along shortest path routes is studied by simulations as well as theoretical modeling. Measures of congestion like end-to-end time delay and relaxation times are given. A scaling law of the average time delay with respect to network size is revealed and found to depend on the underlying network topology. In the second step, a distributive routing and congestion control is proposed. Each node locally propagates its routing cost estimates and information about its congestion state to its neighbors, which then update their respective cost estimates. This allows for a flexible adaptation of end-to-end routes to the overall congestion state of the network. Compared to shortest-path routing, the critical network load is significantly increased.

  10. Priority Based Congestion Control Dynamic Clustering Protocol in Mobile Wireless Sensor Networks

    PubMed Central

    Beulah Jayakumari, R.; Jawahar Senthilkumar, V.

    2015-01-01

    Wireless sensor network is widely used to monitor natural phenomena because natural disaster has globally increased which causes significant loss of life, economic setback, and social development. Saving energy in a wireless sensor network (WSN) is a critical factor to be considered. The sensor nodes are deployed to sense, compute, and communicate alerts in a WSN which are used to prevent natural hazards. Generally communication consumes more energy than sensing and computing; hence cluster based protocol is preferred. Even with clustering, multiclass traffic creates congested hotspots in the cluster, thereby causing packet loss and delay. In order to conserve energy and to avoid congestion during multiclass traffic a novel Priority Based Congestion Control Dynamic Clustering (PCCDC) protocol is developed. PCCDC is designed with mobile nodes which are organized dynamically into clusters to provide complete coverage and connectivity. PCCDC computes congestion at intra- and intercluster level using linear and binary feedback method. Each mobile node within the cluster has an appropriate queue model for scheduling prioritized packet during congestion without drop or delay. Simulation results have proven that packet drop, control overhead, and end-to-end delay are much lower in PCCDC which in turn significantly increases packet delivery ratio, network lifetime, and residual energy when compared with PASCC protocol. PMID:26504898

  11. The traffic crisis and a tale of two cities: Traffic and air quality in Bangkok and Mexico City

    SciTech Connect

    Pendakur, V.S.; Badami, M.G.

    1995-12-31

    This paper focuses on congestion management techniques, traffic congestion levels and air quality. By using data from Bangkok and Mexico City, it illustrates the need for drastic changes in transportation policy tools and techniques for congestion management and for improving environmental quality. New approaches to investment and regulatory policy analysis and implementation are suggested. This requires the inclusion of all costs and benefits (economic and ecological) in the policy matrix so that investment and regulatory policies act in unison. Megacities are dominant in social, political and economic terms. 30 to 60% of national GDP is typically produced in these cities. Their human and motor vehicle populations have been doubling every 15-20 and 6-10 years respectively. They also have the most severe traffic congestion and air quality problems. They have the nation`s highest incidence of poverty and absolute poverty. Large portions of their populations endure severely unhealthy housing and sanitation conditions. Following are important characteristics of urban transportation systems in the megacities: the city centres are heavily congested with motorized traffic; traffic crawl rates vary from 2 to 10 km/hr; car and motorcycle ownership are increasing at annual rates of 10-12% and 15-20% respectively; significant air pollution with no relief in sight; TDM strategies are primarily creating new supply of road capacity; fairly high transit trips with substantial transit investments; weak air pollution monitoring and enforcement; and fairly cheap fuel and high costs of vehicles.

  12. Signalling and obfuscation for congestion control

    NASA Astrophysics Data System (ADS)

    Mareček, Jakub; Shorten, Robert; Yu, Jia Yuan

    2015-10-01

    We aim to reduce the social cost of congestion in many smart city applications. In our model of congestion, agents interact over limited resources after receiving signals from a central agent that observes the state of congestion in real time. Under natural models of agent populations, we develop new signalling schemes and show that by introducing a non-trivial amount of uncertainty in the signals, we reduce the social cost of congestion, i.e., improve social welfare. The signalling schemes are efficient in terms of both communication and computation, and are consistent with past observations of the congestion. Moreover, the resulting population dynamics converge under reasonable assumptions.

  13. A knowledge-based system for controlling automobile traffic

    NASA Technical Reports Server (NTRS)

    Maravas, Alexander; Stengel, Robert F.

    1994-01-01

    Transportation network capacity variations arising from accidents, roadway maintenance activity, and special events as well as fluctuations in commuters' travel demands complicate traffic management. Artificial intelligence concepts and expert systems can be useful in framing policies for incident detection, congestion anticipation, and optimal traffic management. This paper examines the applicability of intelligent route guidance and control as decision aids for traffic management. Basic requirements for managing traffic are reviewed, concepts for studying traffic flow are introduced, and mathematical models for modeling traffic flow are examined. Measures for quantifying transportation network performance levels are chosen, and surveillance and control strategies are evaluated. It can be concluded that automated decision support holds great promise for aiding the efficient flow of automobile traffic over limited-access roadways, bridges, and tunnels.

  14. Bronchovascular role in pulmonary congestion.

    PubMed

    McIlveen, S A

    2000-12-01

    1. A postulated role for the bronchial circulation in the development of pulmonary congestion may be based on recent studies of bronchovascular control. 2. The bronchial circulation is the nutrient blood supply of the conducting airways and, therefore, plays an important role in the function of the bronchial mucosa. Mucosal swelling secondary to elevation of mucosal capillary hydrostatic pressure may decrease airway calibre, increase resistance to airflow and precipitate symptoms of pulmonary congestion. 3. Resting mucosal capillary hydrostatic pressure is relatively constant due to autoregulation of bronchial blood flow and is maintained low by nett bronchovascular constriction due to the dominance of autonomic vasoconstriction over nitric oxidedependent vasodilatation. 4. Bronchial blood flow is also regulated by cardiac afferent reflexes. Stimulation of cardiac vagal and spinal afferents produces vasodilatation and vasoconstriction, respectively. Tonic activity of cardiac spinal afferents probably contributes to the resting autonomic vasoconstriction. 5. Therefore, mild heart failure, which is associated with abnormal cardiovascular reflex function, may decrease cardiac spinal afferent-mediated bronchial vasoconstriction and produce active dilatation due to stimulation of cardiac vagal afferents by excessive myocardial stretch, leading to bronchial mucosal swelling and pulmonary congestion. PMID:11117228

  15. Development and Application of a Traffic Stream Model Under Heterogeneous Traffic Conditions

    NASA Astrophysics Data System (ADS)

    Thankappan, Ajitha; Vanajakshi, Lelitha

    2015-12-01

    Traffic stream models provide relationships among the three basic traffic variables namely speed, flow and density under steady-state conditions. Since reported stream models are mainly developed for homogeneous traffic conditions, they may not be directly suitable for Indian traffic condition which is heterogeneous and lacks lane discipline. Only very limited studies have been reported from India in this respect and the present study develops an optimal speed-density relation and from that derive theoretically the speed-flow and flow density relations that are suitable for the study stretch under consideration. The results indicate that the developed model is able to represent the steady-state macroscopic behavior of the traffic stream with reasonable accuracy. An application of such a stream model for a real time application is also demonstrated. The results obtained are promising showing the potential for the use of such stream models for real time application such as a congestion information system.

  16. From Traffic Flow to Economic System

    NASA Astrophysics Data System (ADS)

    Bando, M.

    The optimal velocity model which is applied to traffic flow phenomena explains a spontaneous formation of traffic congestion. We discuss why the model works well in describing both free-flow and congested flow states in a unified way. The essential ingredient is that our model takes account of a sort of time delay in reacting to a given stimulus. This causes instability of many-body system, and yields a kind of phase transition above a certain critical density. Especially there appears a limit cycle on the phase space along which individual vehicle moves, and they show cyclic behavior. Once that we recognize the mechanism the same idea can be applied to a variety of phenomena which show cyclic behavior observed in many-body systems. As an example of such applications, we investigate business cycles commonly observed in economic system. We further discuss a possible origin of a kind of cyclic behavior observed in climate change.

  17. Traffic Monitor

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Mestech's X-15 "Eye in the Sky," a traffic monitoring system, incorporates NASA imaging and robotic vision technology. A camera or "sensor box" is mounted in a housing. The sensor detects vehicles approaching an intersection and sends the information to a computer, which controls the traffic light according to the traffic rate. Jet Propulsion Laboratory technical support packages aided in the company's development of the system. The X-15's "smart highway" can also be used to count vehicles on a highway and compute the number in each lane and their speeds, important information for freeway control engineers. Additional applications are in airport and railroad operations. The system is intended to replace loop-type traffic detectors.

  18. The effects of congestions tax on air quality and health

    NASA Astrophysics Data System (ADS)

    Johansson, Christer; Burman, Lars; Forsberg, Bertil

    The "Stockholm Trial" involved a road pricing system to improve the air quality and reduce traffic congestion. The test period of the trial was January 3-July 31, 2006. Vehicles travelling into and out of the charge cordon were charged for every passage during weekdays. The amount due varied during the day and was highest during rush hours (20 SEK = 2.2 EUR, maximum 60 SEK per day). Based on measured and modelled changes in road traffic it was estimated that this system resulted in a 15% reduction in total road use within the charged cordon. Total traffic emissions in this area of NO x and PM10 fell by 8.5% and 13%, respectively. Air quality dispersion modelling was applied to assess the effect of the emission reductions on ambient concentrations and population exposure. For the situations with and without the trial, meteorological conditions and other emissions than from road traffic were kept the same. The calculations show that, with a permanent congestion tax system like the Stockholm Trial, the annual average NO x concentrations would be lower by up to 12% along the most densely trafficked streets. PM10 concentrations would be up to 7% lower. The limit values for both PM10 and NO 2 would still be exceeded along the most densely trafficked streets. The total population exposure of NO x in Greater Stockholm (35 × 35 km with 1.44 million people) is estimated to decrease with a rather modest 0.23 μg m -3. However, based on a long-term epidemiological study, that found an increased mortality risk of 8% per 10 μg m -3 NO x, it is estimated that 27 premature deaths would be avoided every year. According to life-table analysis this would correspond to 206 years of life gained over 10 years per 100 000 people following the trial if the effects on exposures would persist. The effect on mortality is attributed to road traffic emissions (likely vehicle exhaust particles); NO x is merely regarded as an indicator of traffic exposure. This is only the tip of the ice

  19. Study of Driving Fatigue Alleviation by Transcutaneous Acupoints Electrical Stimulations

    PubMed Central

    Wang, Fuwang; Wang, Hong

    2014-01-01

    Driving fatigue is more likely to bring serious safety trouble to traffic. Therefore, accurately and rapidly detecting driving fatigue state and alleviating fatigue are particularly important. In the present work, the electrical stimulation method stimulating the Láogóng point (劳宫PC8) of human body is proposed, which is used to alleviate the mental fatigue of drivers. The wavelet packet decomposition (WPD) is used to extract θ, α, and β subbands of drivers' electroencephalogram (EEG) signals. Performances of the two algorithms (θ + α)/(α + β) and θ/β are also assessed as possible indicators for fatigue detection. Finally, the differences between the drivers with electrical stimulation and normal driving are discussed. It is shown that stimulating the Láogóng point (劳宫PC8) using electrical stimulation method can alleviate driver fatigue effectively during longtime driving. PMID:25254242

  20. State Traffic Data: Traffic Safety Facts, 2001.

    ERIC Educational Resources Information Center

    National Center for Statistics and Analysis (NHTSA), Washington, DC.

    This brief provides statistical information on U.S. traffic accidents delineated by state. A map details the 2001 traffic fatalities by state and the percent change from 2000. Data tables include: (1) traffic fatalities and fatality rates, 2001; (2) traffic fatalities and percent change, 1975-2001; (3) alcohol involvement in fatal traffic crashes,…

  1. Imaging Findings of Congestive Hepatopathy.

    PubMed

    Wells, Michael L; Fenstad, Eric R; Poterucha, Joseph T; Hough, David M; Young, Phillip M; Araoz, Philip A; Ehman, Richard L; Venkatesh, Sudhakar K

    2016-01-01

    Congestive hepatopathy (CH) refers to hepatic abnormalities that result from passive hepatic venous congestion. Prolonged exposure to elevated hepatic venous pressure may lead to liver fibrosis and cirrhosis. Liver dysfunction and corresponding clinical signs and symptoms typically manifest late in the disease process. Recognition of CH at imaging is critical because advanced liver fibrosis may develop before the condition is suspected clinically. Characteristic findings of CH on conventional images include dilatation of the inferior vena cava and hepatic veins; retrograde hepatic venous opacification during the early bolus phase of intravenous contrast material injection; and a predominantly peripheral heterogeneous pattern of hepatic enhancement due to stagnant blood flow. Extensive fibrosis can be seen in chronic or severe cases. Hyperenhancing regenerative nodules that may retain hepatobiliary contrast agents are often present. Magnetic resonance (MR) elastography can show elevated liver stiffness and may be useful in evaluation of fibrosis in CH because it can be incorporated easily into routine cardiac MR imaging. Preliminary experience with MR elastography suggests its future use in initial evaluation of patients suspected of having CH, for monitoring of disease, and for assessment after therapy. To facilitate appropriate workup and treatment, radiologists should be familiar with findings suggestive of CH at radiography, ultrasonography, computed tomography, MR imaging, and MR elastography. In addition, knowledge of underlying pathophysiology, comparative histologic abnormalities, and extrahepatic manifestations is useful to avoid diagnostic pitfalls and suggest appropriate additional diagnostic testing. (©)RSNA, 2016. PMID:27284758

  2. Congestion control and charging for the ABR service category in ATM networks

    NASA Astrophysics Data System (ADS)

    Casals, O.; Blondia, Chris L.; Cerda, Llorenc; Van Houdt, Benny

    1998-10-01

    The available bit service (ABR) is a promising 'best effort' service designed to achieve in ATM networks high efficiency and low cell loss. Since the ATM forum approved a first standard, intensive research has been done about ABR. The aim of this paper is to analyze the main research topics involved in ABR, namely: the evaluation of traffic and congestion control schemes, conformance definition and policing and charging.

  3. Remotely Accessed Vehicle Traffic Management System

    NASA Astrophysics Data System (ADS)

    Al-Alawi, Raida

    2010-06-01

    The ever increasing number of vehicles in most metropolitan cities around the world and the limitation in altering the transportation infrastructure, led to serious traffic congestion and an increase in the travelling time. In this work we exploit the emergence of novel technologies such as the internet, to design an intelligent Traffic Management System (TMS) that can remotely monitor and control a network of traffic light controllers located at different sites. The system is based on utilizing Embedded Web Servers (EWS) technology to design a web-based TMS. The EWS located at each intersection uses IP technology for communicating remotely with a Central Traffic Management Unit (CTMU) located at the traffic department authority. Friendly GUI software installed at the CTMU will be able to monitor the sequence of operation of the traffic lights and the presence of traffic at each intersection as well as remotely controlling the operation of the signals. The system has been validated by constructing a prototype that resembles the real application.

  4. Modeling and simulating for congestion pedestrian evacuation with panic

    NASA Astrophysics Data System (ADS)

    Wang, Jinhuan; Zhang, Lei; Shi, Qiongyu; Yang, Peng; Hu, Xiaoming

    2015-06-01

    A new multi-agent based congestion evacuation model incorporating panic behavior is proposed in this paper for simulating pedestrian evacuation in public places such as a stadium. Different from the existing results, pedestrians in this model are divided into four classes and each pedestrian's status can be either normal, being overtaken, or casualty. The direction of action for each individual is affected by competitive ability, distance to the exits as well as number and density of occupants within the view field of the agent. Our simulations exhibit that during the evacuation process: (1) The agents gather in front of the exits spontaneously and present arched shapes close to the exits. (2) Under the panic state the agents cohere closely and almost do not change the target exit. So other alternative exits are ignored. (3) For the case without obstacle, the casualties under panic increase greatly. But if there are obstacles (chairs), the congestion can be alleviated. Thus the casualties are reduced. (4) If certain exit is partly clogged, the evacuation becomes more efficient when adding a virtual leader. The overall simulation results show that the proposed model can reproduce the real evacuation process in a stadium quite well.

  5. Congestion and flow control in signaling system No. 7: Impacts of intelligent networks and new services

    SciTech Connect

    Zepf, J.; Rufa, G. )

    1994-04-01

    This paper focuses on the transient performance analysis of the congestion and flow control mechanisms in CCITT Signaling System No. 7 (SS7). Special attention is directed to the impacts of the introduction of intelligent services and new applications, e.g., Freephone, credit card services, user-to-user signaling, etc. In particular, we show that signaling traffic characteristics like signaling scenarios or signaling message length as well as end-to-end signaling capabilities have a significant influence on the congestion and flow control and, therefore, on the real-time signaling performance. One important result of our performance studies is that if, e.g., intelligent services are introduced, the SS7 congestion and flow control does not work correctly. To solve this problem, some reinvestigations into these mechanisms would be necessary. Therefore, some approaches, e.g., modification of the Signaling Connection Control Part (SCCP) congestion control, usage of the SCCP relay function, or a redesign of the MTP flow control procedures are discussed in order to guarantee the efficacy of the congestion and flow control mechanisms also in the future. 16 refs.

  6. Buffet Load Alleviation

    NASA Technical Reports Server (NTRS)

    Ryall, T. G.; Moses, R. W.; Hopkins, M. A.; Henderson, D.; Zimcik, D. G.; Nitzsche, F.

    2004-01-01

    High performance aircraft are, by their very nature, often required to undergo maneuvers involving high angles of attack. Under these conditions unsteady vortices emanating from the wing and the fuselage will impinge on the twin fins (required for directional stability) causing excessive buffet loads, in some circumstances, to be applied to the aircraft. These loads result in oscillatory stresses, which may cause significant amounts of fatigue damage. Active control is a possible solution to this important problem. A full-scale test was carried out on an F/A-18 fuselage and fins using piezoceramic actuators to control the vibrations. Buffet loads were simulated using very powerful electromagnetic shakers. The first phase of this test was concerned with the open loop system identification whereas the second stage involved implementing linear time invariant control laws. This paper looks at some of the problems encountered as well as the corresponding solutions and some results. It is expected that flight trials of a similar control system to alleviate buffet will occur as early as 2001.

  7. Implementing and Simulating Dynamic Traffic Assignment with Intelligent Transportation Systems in Cube Avenue

    NASA Technical Reports Server (NTRS)

    Foytik, Peter; Robinson, Mike

    2010-01-01

    As urban populations and traffic congestion levels increase, effective use of information and communication tools and intelligent transportation systems as becoming increasingly important in order to maximize the efficiency of transportation networks. The appropriate placement and employment of these tools within a network is critical to their effectiveness. This presentation proposes and demonstrates the use of a commercial transportation simulation tool to simulate dynamic traffic assignment and rerouting to model route modifications as a result of traffic information.

  8. Revised lattice Boltzmann model for traffic flow with equilibrium traffic pressure

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Lu, Wei-Zhen; Xue, Yu; He, Hong-Di

    2016-02-01

    A revised lattice Boltzmann model concerning the equilibrium traffic pressure is proposed in this study to tackle the phase transition phenomena of traffic flow system. The traditional lattice Boltzmann model has limitation to investigate the complex traffic phase transitions due to its difficulty for modeling the equilibrium velocity distribution. Concerning this drawback, the equilibrium traffic pressure is taken into account to derive the equilibrium velocity distribution in the revised lattice Boltzmann model. In the proposed model, a three-dimensional velocity-space is assumed to determine the equilibrium velocity distribution functions and an alternative, new derivative approach is introduced to deduct the macroscopic equations with the first-order accuracy level from the lattice Boltzmann model. Based on the linear stability theory, the stability conditions of the corresponding macroscopic equations can be obtained. The outputs indicate that the stability curve is divided into three regions, i.e., the stable region, the neutral stability region, and the unstable region. In the stable region, small disturbance appears in the initial uniform flow and will vanish after long term evolution, while in the unstable region, the disturbance will be enlarged and finally leads to the traffic system entering the congested state. In the neutral stability region, small disturbance does not vanish with time and maintains its amplitude in the traffic system. Conclusively, the stability of traffic system is found to be enhanced as the equilibrium traffic pressure increases. Finally, the numerical outputs of the proposed model are found to be consistent with the recognized, theoretical results.

  9. Research on the net amount of air traffic network

    NASA Astrophysics Data System (ADS)

    Hu, Jun; Wu, Zhenya

    2013-03-01

    As accurate prediction of traffic flow states could reduce the congestion possibility, the theoretical study of air traffic was how to determinate the next time the state with fluid mechanics based on random condition. Then, a novel depicting method of air traffic flow is proposed, which calculated the change of net amount in flow conservation equation with discrete time loss queuing, further, it could determine the relationship between flow and density. Compared to the existing general algorithm, the threshold of net amount was presented in the method, and it had good adaptability.

  10. Congestion Based Mechanism for Route Discovery in a V2I-V2V System Applying Smart Devices and IoT

    PubMed Central

    Parrado, Natalia; Donoso, Yezid

    2015-01-01

    The Internet of Things is a new paradigm in which objects in a specific context can be integrated into traditional communication networks to actively participate in solving a determined problem. The Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) technologies are specific cases of IoT and key enablers for Intelligent Transportation Systems (ITS). V2V and V2I have been widely used to solve different problems associated with transportation in cities, in which the most important is traffic congestion. A high percentage of congestion is usually presented by the inappropriate use of resources in vehicular infrastructure. In addition, the integration of traffic congestion in decision making for vehicular traffic is a challenge due to its high dynamic behavior. In this paper, an optimization model over the load balancing in the congestion percentage of the streets is formulated. Later, we explore a fully congestion-oriented route discovery mechanism and we make a proposal on the communication infrastructure that should support it based on V2I and V2V communication. The mechanism is also compared with a modified Dijkstra’s approach that reacts at congestion states. Finally, we compare the results of the efficiency of the vehicle’s trip with the efficiency in the use of the capacity of the vehicular network. PMID:25835185

  11. Congestion based mechanism for route discovery in a V2I-V2V system applying smart devices and IoT.

    PubMed

    Parrado, Natalia; Donoso, Yezid

    2015-01-01

    The Internet of Things is a new paradigm in which objects in a specific context can be integrated into traditional communication networks to actively participate in solving a determined problem. The Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) technologies are specific cases of IoT and key enablers for Intelligent Transportation Systems (ITS). V2V and V2I have been widely used to solve different problems associated with transportation in cities, in which the most important is traffic congestion. A high percentage of congestion is usually presented by the inappropriate use of resources in vehicular infrastructure. In addition, the integration of traffic congestion in decision making for vehicular traffic is a challenge due to its high dynamic behavior. In this paper, an optimization model over the load balancing in the congestion percentage of the streets is formulated. Later, we explore a fully congestion-oriented route discovery mechanism and we make a proposal on the communication infrastructure that should support it based on V2I and V2V communication. The mechanism is also compared with a modified Dijkstra's approach that reacts at congestion states. Finally, we compare the results of the efficiency of the vehicle's trip with the efficiency in the use of the capacity of the vehicular network. PMID:25835185

  12. Comparison of congestion controls for data services on ATM networks

    NASA Astrophysics Data System (ADS)

    Choi, Yonshik; Campbell, Graham

    1999-11-01

    The Internet consists of a network of networks. Internet users and service provides want to provide and receive multiple services. The legacy networks till now have provided narrow bandwidth that has restricted the range of services. Asynchronous Transfer Mode (ATM) can simultaneously deliver multiple services over one network and today ATM has become a component of the Internet. An ATM switch can deliver current Internet data using UBR or ABR services. Unspecified Bit Rate (UBR) using AAL5 is the most common offering these days for data transport. Because UBR does not guarantee any QoS categories and it is a `best effort' service, cell-discarding protocols must coexist. Congestion control is always a host topic for data networks. In data networks many flow mechanisms to resolve network congestion have been proposed. Cell loss is one of the most important and critical categories for traffic management of data networking. We compare the well-known Early Packet Discard for UBR with Quantum Flow Control for ABR services with TCP over ATM. Simulation results are provided that allow a comparison of both techniques.

  13. Traffic Monitor

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Intelligent Vision Systems, Inc. (InVision) needed image acquisition technology that was reliable in bad weather for its TDS-200 Traffic Detection System. InVision researchers used information from NASA Tech Briefs and assistance from Johnson Space Center to finish the system. The NASA technology used was developed for Earth-observing imaging satellites: charge coupled devices, in which silicon chips convert light directly into electronic or digital images. The TDS-200 consists of sensors mounted above traffic on poles or span wires, enabling two sensors to view an intersection; a "swing and sway" feature to compensate for movement of the sensors; a combination of electronic shutter and gain control; and sensor output to an image digital signal processor, still frame video and optionally live video.

  14. Treatment of congestion in upper respiratory diseases

    PubMed Central

    Meltzer, Eli O; Caballero, Fernan; Fromer, Leonard M; Krouse, John H; Scadding, Glenis

    2010-01-01

    Congestion, as a symptom of upper respiratory tract diseases including seasonal and perennial allergic rhinitis, acute and chronic rhinosinusitis, and nasal polyposis, is principally caused by mucosal inflammation. Though effective pharmacotherapy options exist, no agent is universally efficacious; therapeutic decisions must account for individual patient preferences. Oral H1-antihistamines, though effective for the common symptoms of allergic rhinitis, have modest decongestant action, as do leukotriene receptor antagonists. Intranasal antihistamines appear to improve congestion better than oral forms. Topical decongestants reduce congestion associated with allergic rhinitis, but local adverse effects make them unsuitable for long-term use. Oral decongestants show some efficacy against congestion in allergic rhinitis and the common cold, and can be combined with oral antihistamines. Intranasal corticosteroids have broad anti-inflammatory activities, are the most potent long-term pharmacologic treatment of congestion associated with allergic rhinitis, and show some congestion relief in rhinosinusitis and nasal polyposis. Immunotherapy and surgery may be used in some cases refractory to pharmacotherapy. Steps in congestion management include (1) diagnosis of the cause(s), (2) patient education and monitoring, (3) avoidance of environmental triggers where possible, (4) pharmacotherapy, and (5) immunotherapy (for patients with allergic rhinitis) or surgery for patients whose condition is otherwise uncontrolled. PMID:20463825

  15. Congestion Control for a Fair Packet Delivery in WSN: From a Complex System Perspective

    PubMed Central

    2014-01-01

    In this work, we propose that packets travelling across a wireless sensor network (WSN) can be seen as the active agents that make up a complex system, just like a bird flock or a fish school, for instance. From this perspective, the tools and models that have been developed to study this kind of systems have been applied. This is in order to create a distributed congestion control based on a set of simple rules programmed at the nodes of the WSN. Our results show that it is possible to adapt the carried traffic to the network capacity, even under stressing conditions. Also, the network performance shows a smooth degradation when the traffic goes beyond a threshold which is settled by the proposed self-organized control. In contrast, without any control, the network collapses before this threshold. The use of the proposed solution provides an effective strategy to address some of the common problems found in WSN deployment by providing a fair packet delivery. In addition, the network congestion is mitigated using adaptive traffic mechanisms based on a satisfaction parameter assessed by each packet which has impact on the global satisfaction of the traffic carried by the WSN. PMID:25177722

  16. Unattended vehicle detection for automatic traffic light control

    NASA Astrophysics Data System (ADS)

    Abdel Hady, Aya Salama; Moustafa, Mohamed

    2013-12-01

    Machine vision based traffic light control depends mainly on measuring traffic statistics at cross roads. Most of the previous studies have not taken unattended vehicles into consideration when calculating either the traffic density or the traffic flow. In this paper, we propose incorporating unattended vehicles into a new metric for measuring the traffic congestion. In addition to the vehicle motion analysis, opening the driver's side door is an important indicator that this vehicle is going to be unattended. Therefore, we focus in this paper on presenting how to detect this event for stationary vehicles from a live camera or a video feed. Through a set of experiments, we have found out that a Scale Invariant Feature Transform (SIFT) feature-descriptor with a Support Vector Machines (SVM) classifier was able to successfully classify open-door vehicles from closed-door ones in 96.7% of our test dataset.

  17. A Novel P2P traffic Prediction Algorithm Based on Hybrid Model

    NASA Astrophysics Data System (ADS)

    Zhi-jie, Han; Ru-chuan, Wang; Xiao-yang, Duan

    The increasing P2P network traffic on the Internet has leaded to the problem of network congestion. In the consequence of the diversification of the P2P traffic and protocol, research on the management of P2P traffic has had many problems needed to resolve. P2P traffic Prediction is kernel problem in the P2P traffic management. Based on the P2P traffic characters, this thesis present a P2P traffic model, gived a traffic prediction algorithm bases on wavelet-analysis, and proved the accuracy of the algorithm. Simulation has experiment figures that the algorithm a high prediction precision and superior real-time performance.

  18. Stabilization of traffic flow in optimal velocity model via delayed-feedback control

    NASA Astrophysics Data System (ADS)

    Jin, Yanfei; Hu, Haiyan

    2013-04-01

    Traffic jams may occur due to various reasons, such as traffic accidents, lane reductions and on-ramps. In order to suppress the traffic congestion in an optimal velocity traffic model without any driver's delay taken into account, a delayed-feedback control of both displacement and velocity differences is proposed in this study. By using the delay-independent stability criteria and the H∞-norm, the delayed-feedback control can be determined to stabilize the unstable traffic flow and suppress the traffic jam. The numerical case studies are given to demonstrate and verify the new control method. Furthermore, a comparison is made between the new control method and the method proposed by Konishi et al. [K. Konishi, M. Hirai, H. Kokame, Decentralized delayed-feedback control of an optimal velocity traffic model, Eur. Phys. J. B 15 (2000) 715-722]. The results show that the new control method makes the traffic flow more stable and improves the control performance.

  19. Performance analysis of ATM ABR service under self-similar traffic in the presence of background VBR traffic

    SciTech Connect

    Benke, G. |; Brandt, J.; Chen, H.; Dastangoo, S.; Miller, G.J.

    1996-05-01

    Recent empirical studies of traffic measurements of packet switched networks have demonstrated that actual network traffic is self-similar, or long range dependent, in nature. That is, the measured traffic is bursty over a wide range of time intervals. Furthermore, the emergence of high-speed network backbones demands the study of accurate models of aggregated traffic to assess network performance. This paper provides a method for generation of self-similar traffic, which can be used to drive network simulation models. The authors present the results of a simulation study of a two-node ATM network configuration that supports the ATM Forum`s Available Bit Rate (ABR) service. In this study, the authors compare the state of the queue at the source router at the edge of the ATM network under both Poisson and self-similar traffic loading. These findings indicate an order of magnitude increase in queue length for self-similar traffic loading as compared to Poisson loading. Moreover, when background VBR traffic is present, self-similar ABR traffic causes more congestion at the ATM switches than does Poisson traffic.

  20. Encapsulating urban traffic rhythms into road networks.

    PubMed

    Wang, Junjie; Wei, Dong; He, Kun; Gong, Hang; Wang, Pu

    2014-01-01

    Using road GIS (geographical information systems) data and travel demand data for two U.S. urban areas, the dynamical driver sources of each road segment were located. A method to target road clusters closely related to urban traffic congestion was then developed to improve road network efficiency. The targeted road clusters show different spatial distributions at different times of a day, indicating that our method can encapsulate dynamical travel demand information into the road networks. As a proof of concept, when we lowered the speed limit or increased the capacity of road segments in the targeted road clusters, we found that both the number of congested roads and extra travel time were effectively reduced. In addition, the proposed modeling framework provided new insights on the optimization of transport efficiency in any infrastructure network with a specific supply and demand distribution. PMID:24553203

  1. Focus on renal congestion in heart failure

    PubMed Central

    Afsar, Baris; Ortiz, Alberto; Covic, Adrian; Solak, Yalcin; Goldsmith, David; Kanbay, Mehmet

    2016-01-01

    Hospitalizations due to heart failure are increasing steadily despite advances in medicine. Patients hospitalized for worsening heart failure have high mortality in hospital and within the months following discharge. Kidney dysfunction is associated with adverse outcomes in heart failure patients. Recent evidence suggests that both deterioration in kidney function and renal congestion are important prognostic factors in heart failure. Kidney congestion in heart failure results from low cardiac output (forward failure), tubuloglomerular feedback, increased intra-abdominal pressure or increased venous pressure. Regardless of the cause, renal congestion is associated with increased morbidity and mortality in heart failure. The impact on outcomes of renal decongestion strategies that do not compromise renal function should be explored in heart failure. These studies require novel diagnostic markers that identify early renal damage and renal congestion and allow monitoring of treatment responses in order to avoid severe worsening of renal function. In addition, there is an unmet need regarding evidence-based therapeutic management of renal congestion and worsening renal function. In the present review, we summarize the mechanisms, diagnosis, outcomes, prognostic markers and treatment options of renal congestion in heart failure. PMID:26798459

  2. Traffic and related self-driven many-particle systems

    NASA Astrophysics Data System (ADS)

    Helbing, Dirk

    2001-10-01

    Since the subject of traffic dynamics has captured the interest of physicists, many surprising effects have been revealed and explained. Some of the questions now understood are the following: Why are vehicles sometimes stopped by ``phantom traffic jams'' even though drivers all like to drive fast? What are the mechanisms behind stop-and-go traffic? Why are there several different kinds of congestion, and how are they related? Why do most traffic jams occur considerably before the road capacity is reached? Can a temporary reduction in the volume of traffic cause a lasting traffic jam? Under which conditions can speed limits speed up traffic? Why do pedestrians moving in opposite directions normally organize into lanes, while similar systems ``freeze by heating''? All of these questions have been answered by applying and extending methods from statistical physics and nonlinear dynamics to self-driven many-particle systems. This article considers the empirical data and then reviews the main approaches to modeling pedestrian and vehicle traffic. These include microscopic (particle-based), mesoscopic (gas-kinetic), and macroscopic (fluid-dynamic) models. Attention is also paid to the formulation of a micro-macro link, to aspects of universality, and to other unifying concepts, such as a general modeling framework for self-driven many-particle systems, including spin systems. While the primary focus is upon vehicle and pedestrian traffic, applications to biological or socio-economic systems such as bacterial colonies, flocks of birds, panics, and stock market dynamics are touched upon as well.

  3. Phases of scaling and cross-correlation behavior in traffic

    NASA Astrophysics Data System (ADS)

    Kantelhardt, Jan W.; Fullerton, Matthew; Kämpf, Mirko; Beltran-Ruiz, Cristina; Busch, Fritz

    2013-11-01

    While many microscopic models of traffic flow describe transitions between different traffic phases, such transitions are difficult to quantify in measured traffic data. Here we study long-term traffic recordings consisting of ≈2900 days of flow, density, and velocity time series with minute resolution from a Spanish motorway. We calculate fluctuations, cross-correlations, and long-term persistence properties of these quantities in the flow-density diagram. This leads to a data-driven definition of (local) traffic states based on the dynamical properties of the data, which differ from those given in standard guidelines. We find that detrending techniques must be used for persistence analysis because of non-stationary daily and weekly traffic flow patterns. We compare our results for the measured data with analysis results for a microscopic traffic model, finding good agreement in most quantities. However, the simulations cannot easily reproduce the congested traffic states observed in the data. We show how fluctuations and cross-correlations in traffic data may be used for prediction, i.e., as indications of increasing or decreasing velocities.

  4. Microscopic features of moving traffic jams

    NASA Astrophysics Data System (ADS)

    Kerner, Boris S.; Klenov, Sergey L.; Hiller, Andreas; Rehborn, Hubert

    2006-04-01

    Empirical and numerical microscopic features of moving traffic jams are presented. Based on a single vehicle data analysis, it is found that within wide moving jams, i.e., between the upstream and downstream jam fronts there is a complex microscopic spatiotemporal structure. This jam structure consists of alternations of regions in which traffic flow is interrupted and flow states of low speeds associated with “moving blanks” within the jam. Moving blanks within a wide moving jam resemble electron holes in the valence band of semiconductors: As the moving blanks that propagate upstream appear due to downstream vehicle motion within the jam, so appearance of electron holes moving with the electric field results from electron motion against the electric field in the valence band of semiconductors. Empirical features of moving blanks are found. Based on microscopic models in the context of the Kerner’s three-phase traffic theory, physical reasons for moving blanks emergence within wide moving jams are disclosed. Microscopic nonlinear effects of moving jam emergence, propagation, and dissolution as well as a diverse variety of hysteresis effects in freeway traffic associated with phase transitions and congested traffic propagation are numerically investigated. Microscopic structure of moving jam fronts is numerically studied and compared with empirical results.

  5. Alleviating Stress for Women Administrators.

    ERIC Educational Resources Information Center

    Ten Elshof, Annette; Tomlinson, Elaine

    1981-01-01

    Describes a workshop designed to help women administrators assess individual stress levels. Stress can be alleviated through exercise, support groups or networking, sleep and diet, relaxation, guided fantasy, and planned activity. The long-term implications include preventing illness and making women more effective within the administrative…

  6. Simulation of three lanes one-way freeway in low visibility weather by possible traffic accidents

    NASA Astrophysics Data System (ADS)

    Pang, Ming-bao; Zheng, Sha-sha; Cai, Zhang-hui

    2015-09-01

    The aim of this work is to investigate the traffic impact of low visibility weather on a freeway including the fraction of real vehicle rear-end accidents and road traffic capacity. Based on symmetric two-lane Nagel-Schreckenberg (STNS) model, a cellular automaton model of three-lane freeway mainline with the real occurrence of rear-end accidents in low visibility weather, which considers delayed reaction time and deceleration restriction, was established with access to real-time traffic information of intelligent transportation system (ITS). The characteristics of traffic flow in different visibility weather were discussed via the simulation experiments. The results indicate that incoming flow control (decreasing upstream traffic volume) and inputting variable speed limits (VSL) signal are effective in accident reducing and road actual traffic volume's enhancing. According to different visibility and traffic demand the appropriate control strategies should be adopted in order to not only decrease the probability of vehicle accidents but also avoid congestion.

  7. Automatic Data Traffic Control on DSM Architecture

    NASA Technical Reports Server (NTRS)

    Frumkin, Michael; Jin, Hao-Qiang; Yan, Jerry; Kwak, Dochan (Technical Monitor)

    2000-01-01

    We study data traffic on distributed shared memory machines and conclude that data placement and grouping improve performance of scientific codes. We present several methods which user can employ to improve data traffic in his code. We report on implementation of a tool which detects the code fragments causing data congestions and advises user on improvements of data routing in these fragments. The capabilities of the tool include deduction of data alignment and affinity from the source code; detection of the code constructs having abnormally high cache or TLB misses; generation of data placement constructs. We demonstrate the capabilities of the tool on experiments with NAS parallel benchmarks and with a simple computational fluid dynamics application ARC3D.

  8. Automation of Data Traffic Control on DSM Architecture

    NASA Technical Reports Server (NTRS)

    Frumkin, Michael; Jin, Hao-Qiang; Yan, Jerry

    2001-01-01

    The design of distributed shared memory (DSM) computers liberates users from the duty to distribute data across processors and allows for the incremental development of parallel programs using, for example, OpenMP or Java threads. DSM architecture greatly simplifies the development of parallel programs having good performance on a few processors. However, to achieve a good program scalability on DSM computers requires that the user understand data flow in the application and use various techniques to avoid data traffic congestions. In this paper we discuss a number of such techniques, including data blocking, data placement, data transposition and page size control and evaluate their efficiency on the NAS (NASA Advanced Supercomputing) Parallel Benchmarks. We also present a tool which automates the detection of constructs causing data congestions in Fortran array oriented codes and advises the user on code transformations for improving data traffic in the application.

  9. When does highway construction to mitigate congestion reduce carbon emissions? A Case Study: The Caldecott Tunnel

    NASA Astrophysics Data System (ADS)

    Thurlow, M. E.; Maness, H.; Wiersema, D. J.; Mcdonald, B. C.; Harley, R.; Fung, I. Y.

    2014-12-01

    The construction of the fourth bore of the Caldecott Tunnel, which connects Oakland and Moraga, CA on State Route 24, was the second largest roadway construction project in California last year with a total cost of $417 million. The objective of the fourth bore was to reduce traffic congestion before the tunnel entrance in the off-peak direction of travel, but the project was a source of conflict between policy makers and environmental and community groups concerned about the air quality and traffic impacts. We analyze the impact of the opening of the fourth bore on CO2 emissions associated with traffic. We made surface observations of CO2from a mobile platform along State Route 24 for several weeks in November 2013 incorporating the period prior to and after the opening of the fourth bore on November 16, 2013. We directly compare bottom-up and top-down approaches to estimate the change in traffic emissions associated with the fourth bore opening. A bottom-up emissions inventory was derived from the high-resolution Performance Measurement System (PeMs) dataset and the Multi-scale Motor Vehicle and Equipment Emissions System (MOVES). The emissions inventory was used to drive a box model as well as a high-resolution regional transport model (the Weather and Regional Forecasting Model). The box model was also used to derive emissions from observations in a basic inversion. We also present an analysis of long-term traffic patterns and consider the potential for compensating changes in behavior that offset the observed emissions reductions on longer timescales. Finally, we examine how the results from the Caldecott study demonstrate the general benefit of using mobile measurements for quantifying environmental impacts of congestion mitigation projects.

  10. Congestive heart failure in the elderly.

    PubMed

    Rengo, F; Acanfora, D; Trojano, L; Furgi, G; Picone, C; Iannuzzi, G L; Vitale, D F; Rengo, C; Ferrara, N

    1996-01-01

    Several aspects of congestive heart failure are discussed in the light of international literature and of recent findings of our group. The annual incidence of heart failure in elderly subjects, aged >or=75y, is 13 to 50/1000, while it is 1.6/1000 in people aged 45-54 y. The prevalence of heart failure is about 3% in subjects aged 45-64% in subjects aged more than 65 y and 10% in subjects aged more than 75 y. These data are confirmed by our population based study in elderly subjects. The etiology of congestive heart failure is similar in elderly and middle-aged patients. However, several anatomo-functional, hormonal and autonomic nervous system changes, typical of congestive heart failure, occur during physiologic ageing processes also. These findings may explain the dramatic evolution of congestive heart failure in elderly patients. Moreover, some features of the elderly - e.g. comorbidity, atypical clinical presentations, loss of autonomy, increased iatrogen risk should be considered. No specific drugs exist for the pharmacologic treatment of heart failure in the elderly, so that the geriatric specificity in the treatment of heart failure can be recognized in the art of drug choice and dosage, to obtain the best results with the least side effects. The multiple etiology of congestive heart failure, the comorbidity, the loss of autonomy and the deterioration of cognitive functions suggest the need for multidimensional approach and continuative intervention in elderly patients with heart disease, and in particular with congestive heart failure. Further studies on disease- and age-related changes are necessary to develop new and more potent strategies to secure 'successful ageing'. PMID:15374141

  11. Capacity-constrained traffic assignment in networks with residual queues

    SciTech Connect

    Lam, W.H.K.; Zhang, Y.

    2000-04-01

    This paper proposes a capacity-constrained traffic assignment model for strategic transport planning in which the steady-state user equilibrium principle is extended for road networks with residual queues. Therefore, the road-exit capacity and the queuing effects can be incorporated into the strategic transport model for traffic forecasting. The proposed model is applicable to the congested network particularly when the traffic demands exceeds the capacity of the network during the peak period. An efficient solution method is proposed for solving the steady-state traffic assignment problem with residual queues. Then a simple numerical example is employed to demonstrate the application of the proposed model and solution method, while an example of a medium-sized arterial highway network in Sioux Falls, South Dakota, is used to test the applicability of the proposed solution to real problems.

  12. Congestive Heart Failure and Central Sleep Apnea.

    PubMed

    Sands, Scott A; Owens, Robert L

    2016-03-01

    Congestive heart failure (CHF) is among the most common causes of admission to hospitals in the United States, especially in those over age 65. Few data exist regarding the prevalence CHF of Cheyne-Stokes respiration (CSR) owing to congestive heart failure in the intensive care unit (ICU). Nevertheless, CSR is expected to be highly prevalent among those with CHF. Treatment should focus on the underlying mechanisms by which CHF increases loop gain and promotes unstable breathing. Few data are available to determine prevalence of CSR in the ICU, or how CSR might affect clinical management and weaning from mechanical ventilation. PMID:26972039

  13. Traffic-driven SIR epidemic spreading in networks

    NASA Astrophysics Data System (ADS)

    Pu, Cunlai; Li, Siyuan; Yang, XianXia; Xu, Zhongqi; Ji, Zexuan; Yang, Jian

    2016-03-01

    We study SIR epidemic spreading in networks driven by traffic dynamics, which are further governed by static routing protocols. We obtain the maximum instantaneous population of infected nodes and the maximum population of ever infected nodes through simulation. We find that generally more balanced load distribution leads to more intense and wide spread of an epidemic in networks. Increasing either average node degree or homogeneity of degree distribution will facilitate epidemic spreading. When packet generation rate ρ is small, increasing ρ favors epidemic spreading. However, when ρ is large enough, traffic congestion appears which inhibits epidemic spreading.

  14. Effects of mental workload on physiological and subjective responses during traffic density monitoring: A field study.

    PubMed

    Fallahi, Majid; Motamedzade, Majid; Heidarimoghadam, Rashid; Soltanian, Ali Reza; Miyake, Shinji

    2016-01-01

    This study evaluated operators' mental workload while monitoring traffic density in a city traffic control center. To determine the mental workload, physiological signals (ECG, EMG) were recorded and the NASA-Task Load Index (TLX) was administered for 16 operators. The results showed that the operators experienced a larger mental workload during high traffic density than during low traffic density. The traffic control center stressors caused changes in heart rate variability features and EMG amplitude, although the average workload score was significantly higher in HTD conditions than in LTD conditions. The findings indicated that increasing traffic congestion had a significant effect on HR, RMSSD, SDNN, LF/HF ratio, and EMG amplitude. The results suggested that when operators' workload increases, their mental fatigue and stress level increase and their mental health deteriorate. Therefore, it maybe necessary to implement an ergonomic program to manage mental health. Furthermore, by evaluating mental workload, the traffic control center director can organize the center's traffic congestion operators to sustain the appropriate mental workload and improve traffic control management. PMID:26360199

  15. Jamitons: Phantom Traffic Jams

    ERIC Educational Resources Information Center

    Kowszun, Jorj

    2013-01-01

    Traffic on motorways can slow down for no apparent reason. Sudden changes in speed by one or two drivers can create a chain reaction that causes a traffic jam for the vehicles that are following. This kind of phantom traffic jam is called a "jamiton" and the article discusses some of the ways in which traffic engineers produce…

  16. Traffic operations, traffic signal systems, and freeway operations 1995. Transportation research record

    SciTech Connect

    1995-12-31

    ;Contents: Analysis of Temporal and Spatial Variability of Free Speed Along a Freeway Segment; A Case for Freeway Mainline Metering; Development of a Freeway Congestion Index Using an Instrumented Vehicle; New Method for Estimating Freeway Incident Congestion; Costs and Benefits of Vision-Based, Wide-Area Detection in Freeway Applications; Caltrans Interstate 15 Reversible High-Occupancy Lanes: 1994 Status; Evaluation of Minnesota I-394 High-Occupancy-Vehicle Transportation System; Design of Incident Detection Algorithms Using Vehicle-to-Roadside Communication Sensors; Examining the Potential of Using Ramp Metering as a Component of an ATMS; Incident Management via Courtesy Patrol: Evaluation of a Pilot Program in Colorado; Artificial Neural Networks for Freeway Incident Detection; Development of Advanced Traffic Signal Control Strategies for Intelligent Transportation Systems: Multilevel Design; REALBAND: An Approach for Real-Time Coordination of Traffic Flows on Networks; Model to Evaluate the Impacts of Bus Priority on Signalized Intersections; REALTRAN: An Off-Line Emulator for Estimating the Effects of SCOOT; Pioneer Application of Passer IV in the Houston Metro-RCTSS Project; Uniform and Variable Bandwidth Arterial Progression Schemes; Bus-Preemption Under Adaptive Signal Control Environments; Testing and Light Rail Signal Control Strategies by Combining Transit and Traffic Simulation Models; Validation of Simulation Software for Modeling Light Rail Transit; and Techniques To Assess Delay and Queue Length Consequences of Bus Preemption.

  17. Distributed Trajectory Flexibility Preservation for Traffic Complexity Mitigation

    NASA Technical Reports Server (NTRS)

    Idris, Husni; Wing, David; Delahaye, Daniel

    2009-01-01

    The growing demand for air travel is increasing the need for mitigation of air traffic congestion and complexity problems, which are already at high levels. At the same time new information and automation technologies are enabling the distribution of tasks and decisions from the service providers to the users of the air traffic system, with potential capacity and cost benefits. This distribution of tasks and decisions raises the concern that independent user actions will decrease the predictability and increase the complexity of the traffic system, hence inhibiting and possibly reversing any potential benefits. In answer to this concern, the authors propose the introduction of decision-making metrics for preserving user trajectory flexibility. The hypothesis is that such metrics will make user actions naturally mitigate traffic complexity. In this paper, the impact of using these metrics on traffic complexity is investigated. The scenarios analyzed include aircraft in en route airspace with each aircraft meeting a required time of arrival in a one-hour time horizon while mitigating the risk of loss of separation with the other aircraft, thus preserving its trajectory flexibility. The experiments showed promising results in that the individual trajectory flexibility preservation induced self-separation and self-organization effects in the overall traffic situation. The effects were quantified using traffic complexity metrics based on Lyapunov exponents and traffic proximity.

  18. Delivering Faster Congestion Feedback with the Mark-Front Strategy

    NASA Technical Reports Server (NTRS)

    Liu, Chunlei; Jain, Raj

    2001-01-01

    Computer networks use congestion feedback from the routers and destinations to control the transmission load. Delivering timely congestion feedback is essential to the performance of networks. Reaction to the congestion can be more effective if faster feedback is provided. Current TCP/IP networks use timeout, duplicate Acknowledgement Packets (ACKs) and explicit congestion notification (ECN) to deliver the congestion feedback, each provides a faster feedback than the previous method. In this paper, we propose a markfront strategy that delivers an even faster congestion feedback. With analytical and simulation results, we show that mark-front strategy reduces buffer size requirement, improves link efficiency and provides better fairness among users. Keywords: Explicit Congestion Notification, mark-front, congestion control, buffer size requirement, fairness.

  19. Managing congestive heart failure using home telehealth.

    PubMed

    Schneider, Nina M

    2004-10-01

    Congestive heart failure (CHF) is the leading cause of rehospitalization and loss of revenue for home care agencies and hospitals. This article outlines how an agency used telehealth to provide CHF patients quality care and improved outcomes while decreasing the number of skilled home nursing visits and reducing rehospitalization rates to 1.2%. PMID:15486513

  20. Understanding widely scattered traffic flows, the capacity drop, and platoons as effects of variance-driven time gaps

    NASA Astrophysics Data System (ADS)

    Treiber, Martin; Kesting, Arne; Helbing, Dirk

    2006-07-01

    We investigate the adaptation of the time headways in car-following models as a function of the local velocity variance, which is a measure of the inhomogeneity of traffic flow. We apply this mechanism to several car-following models and simulate traffic breakdowns in open systems with an on-ramp as bottleneck and in a closed ring road. Single-vehicle data and one-minute aggregated data generated by several virtual detectors show a semiquantitative agreement with microscopic and flow-density data from the Dutch freeway A9. This includes the observed distributions of the net time headways for free and congested traffic, the velocity variance as a function of density, and the fundamental diagram. The modal value of the time headway distribution is shifted by a factor of about 2 under congested conditions. Macroscopically, this corresponds to the capacity drop at the transition from free to congested traffic. The simulated fundamental diagram shows free, synchronized, and jammed traffic, and a wide scattering in the congested traffic regime. We explain this by a self-organized variance-driven process that leads to the spontaneous formation and decay of long-lived platoons even for a deterministic dynamics on a single lane.

  1. “Playboy Bunny” Sign of Congestive Heart Failure

    PubMed Central

    Hokama, Akira; Arakaki, Shingo; Shibata, Daisuke; Maeshiro, Tatsuji; Kinjo, Fukunori; Fujita, Jiro

    2011-01-01

    In emergency, ultrasound has been widely used as a noninvasive and effective examination to evaluate congestive heart failure. We highlight “Playboy Bunny” sign as a reliable marker and an important clue to the diagnosis of passive hepatic congestion, caused by congestive heart failure. PMID:22224133

  2. Efficient congestion control scheme for providing QoS to I-VPN

    NASA Astrophysics Data System (ADS)

    De Marco, Martino; Trabucchi, Sara

    1998-12-01

    In this paper we outline an overall network architecture for the Internet Service Providers who want offer an Internet- Virtual Private Network service with QoS guarantees and, at the same time, with a high-level of efficiency in the network resource usage. The proposed approach is based on the negotiation of a service level agreement, which includes the definition of profile of traffic the user is allowed to emit. The ingress nodes perform an adaptive shaping of the user traffic entering the network, driven by a fast congestion notification scheme. In this scenario, the adoption of a service architecture based on a class-of- service concept enables the Internet Service Provider to offer different level of network performance according to the customer needs.

  3. Criticism of generally accepted fundamentals and methodologies of traffic and transportation theory: A brief review

    NASA Astrophysics Data System (ADS)

    Kerner, Boris S.

    2013-11-01

    It is explained why the set of the fundamental empirical features of traffic breakdown (a transition from free flow to congested traffic) should be the empirical basis for any traffic and transportation theory that can be reliably used for control and optimization in traffic networks. It is shown that the generally accepted fundamentals and methodologies of the traffic and transportation theory are not consistent with the set of the fundamental empirical features of traffic breakdown at a highway bottleneck. To these fundamentals and methodologies of the traffic and transportation theory belong (i) Lighthill-Whitham-Richards (LWR) theory, (ii) the General Motors (GM) model class (for example, Herman, Gazis et al. GM model, Gipps’s model, Payne’s model, Newell’s optimal velocity (OV) model, Wiedemann’s model, Bando et al. OV model, Treiber’s IDM, Krauß’s model), (iii) the understanding of highway capacity as a particular (fixed or stochastic) value, and (iv) principles for traffic and transportation network optimization and control (for example, Wardrop’s user equilibrium (UE) and system optimum (SO) principles). Alternatively to these generally accepted fundamentals and methodologies of the traffic and transportation theory, we discuss the three-phase traffic theory as the basis for traffic flow modeling as well as briefly consider the network breakdown minimization (BM) principle for the optimization of traffic and transportation networks with road bottlenecks.

  4. Criticism of generally accepted fundamentals and methodologies of traffic and transportation theory

    SciTech Connect

    Kerner, Boris S.

    2015-03-10

    It is explained why the set of the fundamental empirical features of traffic breakdown (a transition from free flow to congested traffic) should be the empirical basis for any traffic and transportation theory that can be reliable used for control and optimization in traffic networks. It is shown that generally accepted fundamentals and methodologies of traffic and transportation theory are not consistent with the set of the fundamental empirical features of traffic breakdown at a highway bottleneck. To these fundamentals and methodologies of traffic and transportation theory belong (i) Lighthill-Whitham-Richards (LWR) theory, (ii) the General Motors (GM) model class (for example, Herman, Gazis et al. GM model, Gipps’s model, Payne’s model, Newell’s optimal velocity (OV) model, Wiedemann’s model, Bando et al. OV model, Treiber’s IDM, Krauß’s model), (iii) the understanding of highway capacity as a particular stochastic value, and (iv) principles for traffic and transportation network optimization and control (for example, Wardrop’s user equilibrium (UE) and system optimum (SO) principles). Alternatively to these generally accepted fundamentals and methodologies of traffic and transportation theory, we discuss three-phase traffic theory as the basis for traffic flow modeling as well as briefly consider the network breakdown minimization (BM) principle for the optimization of traffic and transportation networks with road bottlenecks.

  5. The Conception Approach to the Traffic Control in Czech Cities - Examples from Prague

    NASA Astrophysics Data System (ADS)

    Tichý, Tomáš; Krajčír, Dušan

    Modern and economic development of contemporary towns is without question highly dependent upon traffic infrastructure progress. Automobile transport intensity is dramatically rising in large towns and other Czech and European cities. At the same time number of traffic congestions and accidents is increasing, standing times are becoming longer and ecological stress is also escalated. To solve this situation seems to be the most effective solution to design intelligent traffic light intersection control system, variable message signs, preference of public transportation, road line traffic control and next telematics subsystems. This control system and subsystems should improve permeability of traffic road network with a respect for all demands on recent trends of traffic development in towns and regions.

  6. Improving Explicit Congestion Notification with the Mark-Front Strategy

    NASA Technical Reports Server (NTRS)

    Liu, Chunlei; Jain, Raj

    2001-01-01

    Delivering congestion signals is essential to the performance of networks. Current TCP/IP networks use packet losses to signal congestion. Packet losses not only reduces TCP performance, but also adds large delay. Explicit Congestion Notification (ECN) delivers a faster indication of congestion and has better performance. However, current ECN implementations mark the packet from the tail of the queue. In this paper, we propose the mark-front strategy to send an even faster congestion signal. We show that mark-front strategy reduces buffer size requirement, improves link efficiency and provides better fairness among users. Simulation results that verify our analysis are also presented.

  7. Traffic chaotic dynamics modeling and analysis of deterministic network

    NASA Astrophysics Data System (ADS)

    Wu, Weiqiang; Huang, Ning; Wu, Zhitao

    2016-07-01

    Network traffic is an important and direct acting factor of network reliability and performance. To understand the behaviors of network traffic, chaotic dynamics models were proposed and helped to analyze nondeterministic network a lot. The previous research thought that the chaotic dynamics behavior was caused by random factors, and the deterministic networks would not exhibit chaotic dynamics behavior because of lacking of random factors. In this paper, we first adopted chaos theory to analyze traffic data collected from a typical deterministic network testbed — avionics full duplex switched Ethernet (AFDX, a typical deterministic network) testbed, and found that the chaotic dynamics behavior also existed in deterministic network. Then in order to explore the chaos generating mechanism, we applied the mean field theory to construct the traffic dynamics equation (TDE) for deterministic network traffic modeling without any network random factors. Through studying the derived TDE, we proposed that chaotic dynamics was one of the nature properties of network traffic, and it also could be looked as the action effect of TDE control parameters. A network simulation was performed and the results verified that the network congestion resulted in the chaotic dynamics for a deterministic network, which was identical with expectation of TDE. Our research will be helpful to analyze the traffic complicated dynamics behavior for deterministic network and contribute to network reliability designing and analysis.

  8. Analysis of Trajectory Flexibility Preservation Impact on Traffic Complexity

    NASA Technical Reports Server (NTRS)

    Idris, Husni; El-Wakil, Tarek; Wing, David J.

    2009-01-01

    The growing demand for air travel is increasing the need for mitigation of air traffic congestion and complexity problems, which are already at high levels. At the same time new information and automation technologies are enabling the distribution of tasks and decisions from the service providers to the users of the air traffic system, with potential capacity and cost benefits. This distribution of tasks and decisions raises the concern that independent user actions will decrease the predictability and increase the complexity of the traffic system, hence inhibiting and possibly reversing any potential benefits. In answer to this concern, the authors proposed the introduction of decision-making metrics for preserving user trajectory flexibility. The hypothesis is that such metrics will make user actions naturally mitigate traffic complexity. In this paper, the impact of using these metrics on traffic complexity is investigated. The scenarios analyzed include aircraft in en route airspace with each aircraft meeting a required time of arrival in a one-hour time horizon while mitigating the risk of loss of separation with the other aircraft, thus preserving its trajectory flexibility. The experiments showed promising results in that the individual trajectory flexibility preservation induced self-separation and self-organization effects in the overall traffic situation. The effects were quantified using traffic complexity metrics, namely dynamic density indicators, which indicated that using the flexibility metrics reduced aircraft density and the potential of loss of separation.

  9. A Novel Congestion Avoidance Technique for Simultaneous Real-Time Medical Data Transmission.

    PubMed

    Yaakob, Naimah; Khalil, Ibrahim

    2016-03-01

    The use of wireless body sensor networks (WBSN) in medical services aims at providing continuous monitoring of patients' physiological data. However, the scarce resources in WBSN nodes limit their capabilities to cope with massive traffic during multiple, simultaneous data transmissions. This will create a high tendency for congestion, causing severe performance degradation. Congestion may lead to high number of packet loss and unbounded delay which are critical and may lead to wrong diagnosis. This paper, therefore, aims at improving this limitation using a novel congestion avoidance technique to avoid losing real-time and life-critical medical data (e.g., electrocardiogram and electroencephalography) which are vital for diagnosis. The main idea is to integrate the existing rate control scheme of relaxation theory (RT) with a method known as max-min fairness (MMF) to achieve better performance. The MMF can be accomplished using a progressive filling algorithm, which cuts-down excessive sending rates that may overwhelme the limited buffer in WBSN. This paper builds upon our prior study, which provides a preliminary analysis of RT technique in single node. Our current technique integrates the MMF phase to enhance RT performance when the transmission rates exceed certain threshold. Performance evaluation on RT-MMF technique shows remarkable performance improvements, while maintaining the desired quality of service. PMID:26960217

  10. Can complexity decrease in congestive heart failure?

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sayan; Palit, Sanjay Kumar; Banerjee, Santo; Ariffin, M. R. K.; Rondoni, Lamberto; Bhattacharya, D. K.

    2015-12-01

    The complexity of a signal can be measured by the Recurrence period density entropy (RPDE) from the reconstructed phase space. We have chosen a window based RPDE method for the classification of signals, as RPDE is an average entropic measure of the whole phase space. We have observed the changes in the complexity in cardiac signals of normal healthy person (NHP) and congestive heart failure patients (CHFP). The results show that the cardiac dynamics of a healthy subject is more complex and random compare to the same for a heart failure patient, whose dynamics is more deterministic. We have constructed a general threshold to distinguish the border line between a healthy and a congestive heart failure dynamics. The results may be useful for wide range for physiological and biomedical analysis.

  11. Current Management of Congestive Heart Failure

    PubMed Central

    Lopez, J.F.

    1989-01-01

    Congestive heart failure is still one of the most common causes of death in our society. Treatment should be approached systematically with a set of well-defined objectives, which include rest, a low-sodium diet, inotropic agents, diuretics, and peripheral vasodilators. Patients receiving treatment for congestive heart failure should be examined daily for symptomatic improvement, cardiac signs, and accurate recording of total fluid intake and output. Serum electrolyte levels and chest X-ray films should also be checked intermittently. When using powerful diuretics or vasodilators, the physician should be aware of the risk-benefit ratio because many of these drugs, alone or in combination, may produce undesirable or even fatal side-effects. PMID:20469506

  12. Oxygen free radicals and congestive heart failure.

    PubMed Central

    Belch, J J; Bridges, A B; Scott, N; Chopra, M

    1991-01-01

    Plasma lipid peroxides (malondialdehyde) and thiols were measured in 45 patients with congestive heart failure and 45 controls. Malondialdehyde concentrations were significantly higher in the patients with congestive heart failure (median 9.0 nmol/ml interquartile range (IQR) 7.9-10.2) than in the controls (median 7.7 nmol/ml (IQR 6.9-9.2)). Plasma thiols were significantly lower in congestive heart failure (median 420 mumol/l (IQR 379-480)) than in the controls (median 463 mumol/l (IQR 445-525)). There was a significant but weak negative correlation between malondialdehyde and left ventricular ejection fraction (r = -0.35) and a positive correlation between plasma thiols and left ventricular ejection fraction (r = 0.39). This study provides clinical support for experimental data indicating that free radicals may be important in heart failure. It also suggests that the degree of free radical production may be linked to the severity of the disease. PMID:2039668

  13. Traffic Flow Estimates.

    ERIC Educational Resources Information Center

    Hart, Vincent G.

    1981-01-01

    Two examples are given of ways traffic engineers estimate traffic flow. The first, Floating Car Method, involves some basic ideas and the notion of relative velocity. The second, Maximum Traffic Flow, is viewed to involve simple applications of calculus. The material provides insight into specialized applications of mathematics. (MP)

  14. The Investigation of the Traffic Flow Behavior in Tollbooths Using Cellular Automaton Model

    NASA Astrophysics Data System (ADS)

    Jetto, K.; Ez-Zahraouy, H.; Benyoussef, A.

    Tollbooths are used to collect tolls and to control traffic flow. However, the presence of these tollbooths will slow down traffic, especially in heavily traveled roads. As a consequence, drivers and goods will spend more time and fuel waiting in a long queue. Unfortunately, there are a few papers in the literature, which have been addressed the effect of tollbooths on the traffic flow; whereas in this paper is, the properties of traffic flow inside the tollbooths are investigated. The proposed cellular automaton traffic model, with open boundaries, is based on some changing lane rules, which are inspired on the situations inside the toll plaza. The vehicles enter the plaza with an injecting rate α, and they leave with an extracting rate β, which is inversely proportional to the time service Tw. The simulation results show the existence of three phases in the phase diagram (α, β), namely: the low density phase, the congested phase, and the jamming phase. Furthermore, it is found that the vehicles does not spend the same time Tm in the plaza, even if they have the same time service. This analysis states clearly that the existence of the congested phase and the fluctuation Tm are due to the non-zero values of the probability P of changing the lane. Such phenomena disappear when P = 0, i.e., the drivers move without changing their lane. In other words, the human behavior (spontaneous changing lanes) is responsible for the congestion observed in the tollbooth.

  15. Mobile Crowd Sensing for Traffic Prediction in Internet of Vehicles.

    PubMed

    Wan, Jiafu; Liu, Jianqi; Shao, Zehui; Vasilakos, Athanasios V; Imran, Muhammad; Zhou, Keliang

    2016-01-01

    The advances in wireless communication techniques, mobile cloud computing, automotive and intelligent terminal technology are driving the evolution of vehicle ad hoc networks into the Internet of Vehicles (IoV) paradigm. This leads to a change in the vehicle routing problem from a calculation based on static data towards real-time traffic prediction. In this paper, we first address the taxonomy of cloud-assisted IoV from the viewpoint of the service relationship between cloud computing and IoV. Then, we review the traditional traffic prediction approached used by both Vehicle to Infrastructure (V2I) and Vehicle to Vehicle (V2V) communications. On this basis, we propose a mobile crowd sensing technology to support the creation of dynamic route choices for drivers wishing to avoid congestion. Experiments were carried out to verify the proposed approaches. Finally, we discuss the outlook of reliable traffic prediction. PMID:26761013

  16. Statistical evaluation and modeling of Internet dial-up traffic

    NASA Astrophysics Data System (ADS)

    Faerber, Johannes; Bodamer, Stefan; Charzinski, Joachim

    1999-08-01

    In times of Internet access being a popular consumer applications even for `normal' residential users, some telephone exchanges are congested by customers using modem or ISDN dial-up connections to their Internet Service Providers. In order to estimate the number of additional lines and switching capacity required in an exchange or a trunk group, Internet access traffic must be characterized in terms of holding time and call interarrival time distributions. In this paper, we analyze log files tracing the usage of the central ISDN access line pool at University of Stuttgart for a period of six months. Mathematical distributions are fitted to the measured data and the fit quality is evaluated with respect to the blocking probability caused by the synthetic traffic in a multiple server loss system. We show how the synthetic traffic model scales with the number of subscribers and how the model could be applied to compute economy of scale results for Internet access trunks or access servers.

  17. Mobile Crowd Sensing for Traffic Prediction in Internet of Vehicles

    PubMed Central

    Wan, Jiafu; Liu, Jianqi; Shao, Zehui; Vasilakos, Athanasios V.; Imran, Muhammad; Zhou, Keliang

    2016-01-01

    The advances in wireless communication techniques, mobile cloud computing, automotive and intelligent terminal technology are driving the evolution of vehicle ad hoc networks into the Internet of Vehicles (IoV) paradigm. This leads to a change in the vehicle routing problem from a calculation based on static data towards real-time traffic prediction. In this paper, we first address the taxonomy of cloud-assisted IoV from the viewpoint of the service relationship between cloud computing and IoV. Then, we review the traditional traffic prediction approached used by both Vehicle to Infrastructure (V2I) and Vehicle to Vehicle (V2V) communications. On this basis, we propose a mobile crowd sensing technology to support the creation of dynamic route choices for drivers wishing to avoid congestion. Experiments were carried out to verify the proposed approaches. Finally, we discuss the outlook of reliable traffic prediction. PMID:26761013

  18. Information transfer and phase transitions in a model of internet traffic

    NASA Astrophysics Data System (ADS)

    Solé, Ricard V.; Valverde, Sergi

    2001-01-01

    In a recent study, Ohira and Sawatari presented a simple model of computer network traffic dynamics. These authors showed that a phase transition point is present separating the low-traffic phase with no congestion from the congestion phase as the packet creation rate increases. We further investigated this model by relaxing the network topology using a random location of routers. It is shown that the model exhibits nontrivial scaling properties close to the critical point, which reproduce some of the observed real Internet features. At criticality, the net shows maximum information transfer and efficiency. It is shown that some of the key properties of this model are shared by highway traffic models, as previously conjectured by some authors. The relevance to Internet dynamics and to the performance of parallel arrays of processors is discussed.

  19. Modeling Application Traffic

    NASA Astrophysics Data System (ADS)

    Aktas, Ismet; King, Thomas; Mengi, Cem

    Communication networks require a deep understanding of the source of generated traffic, i.e., the application. A multitude number of applications exist that generate different types of traffic, for example web, peer-to-peer, voice, and video traffic. Within the scope of performance analysis of protocols for communication networks, modeling and generating of such traffic is essential to achieve accurate and credible results. This requires that the most relevant aspects are captured by analyzing the traffic and subsequently properly represented in the application model.

  20. Bangkok: Anatomy of a traffic disaster

    SciTech Connect

    Poboon, C.; Kenworthy, J.; Barter, P.

    1995-12-31

    Traditional urban and transport policy which relies on road-base planning has been proven inadequate for tackling Bangkok`s traffic chaos. After employing such policy for more than three decades Bangkok traffic has become a disaster and the city has become notorious world-wide for its traffic congestion and air pollution. The simplistic application of theses largely American models took little consideration if any of the walking city and transit city structure of Bangkok. The policies recommended by the authors rely on the awareness of Bangkok`s unique characteristics and also encompass social and environmental aspects. The worldwide comparison has contributed substantially to more insight in selecting the appropriate measures for Bangkok. The introduction of a mass rapid transit system, water transport improvement, control of car use, provision of infrastructure for walking and cycling, improvement in paratransit together with transit-oriented land use development are believed to be able to work effectively in Bangkok. Nevertheless, institutional improvement including public participation is very necessary to achieve these urban planning and transport strategies. With the combination of these sustainable urban and transport policies, it is possible for Bangkok to be converted into a city for people again, though it will take probably 10 to 20 years or more for substantial improvements.

  1. [Reduction of automobile traffic: urgent health promotion policy].

    PubMed

    Tapia Granados, J A

    1998-03-01

    During the last few decades, traffic injuries have become one of the leading causes of death and disability in the world. In urban areas, traffic congestion, noise, and emissions from motor vehicles produce subjective disturbances and detectable pathological effects. More than one billion people are exposed to harmful levels of environmental pollution. Because its combustion engine generates carbon dioxide (CO2), the automobile is one of the chief sources of the gases that are causing the greenhouse effect. The latter has already caused a rise in the average ambient temperature, and over the next decades it will predictable cause significant climatic changes whose consequences, though uncertain, are likely to be harmful and possibly catastrophic. Aside from the greenhouse effect, the relentless growth of parking zones, traffic, and the roadway infrastructure in urban and rural areas is currently one of the leading causes of environmental degradation. Urban development, which is nearly always "planned" around traffic instead of people, leads to a significant deterioration in the quality of life, while it also destroys the social fabric. Unlike the private automobile, public transportation, bicycles, and walking help reduce pollution, congestion, and traffic volume, as well as the morbidity and mortality resulting from injuries and ailments related to pollution. Non-automobile transportation also encourages physical activity--with its positive effect on general health--and helps reduce the greenhouse effect. The drop in traffic volume and the increased use of alternate means of transportation are thus an integrated health promotion policy which should become an inherent part of the movement for the promotion of healthy cities and of transportation policies and economic policy in general. PMID:9567647

  2. Traffic dynamics on two-layer complex networks with limited delivering capacity

    NASA Astrophysics Data System (ADS)

    Ma, Jinlong; Han, Weizhan; Guo, Qing; Wang, Zhenyong

    2016-08-01

    The traffic dynamics of multi-layer networks has attracted a great deal of interest since many real networks are comprised of two or more layers of subnetworks. Due to its low traffic capacity, the average delivery capacity allocation strategy is susceptible to congestion with the wildly used shortest path routing protocol on two-layer complex networks. In this paper, we introduce a delivery capacity allocation strategy into the traffic dynamics on two-layer complex networks and focus on its effect on the traffic capacity measured by the critical point Rc of phase transition from free flow to congestion. When the total nodes delivering capacity is fixed, the delivering capacity of each node in physical layer is assigned to the degree distributions of both the physical and logical layers. Simulation results show that the proposed strategy can bring much better traffic capacity than that with the average delivery capacity allocation strategy. Because of the significantly improved traffic performance, this work may be useful for optimal design of networked traffic dynamics.

  3. Traffic dynamics: Its impact on the Macroscopic Fundamental Diagram

    NASA Astrophysics Data System (ADS)

    Knoop, Victor L.; van Lint, Hans; Hoogendoorn, Serge P.

    2015-11-01

    Literature shows that-under specific conditions-the Macroscopic Fundamental Diagram (MFD) describes a crisp relationship between the average flow (production) and the average density in an entire network. The limiting condition is that traffic conditions must be homogeneous over the whole network. Recent works describe hysteresis effects: systematic deviations from the MFD as a result of loading and unloading. This article proposes a two dimensional generalization of the MFD, the so-called Generalized Macroscopic Fundamental Diagram (GMFD), which relates the average flow to both the average density and the (spatial) inhomogeneity of density. The most important contribution is that we show this is a continuous function, of which the MFD is a projection. Using the GMFD, we can describe the mentioned hysteresis patterns in the MFD. The underlying traffic phenomenon explaining the two dimensional surface described by the GMFD is that congestion concentrates (and subsequently spreads out) around the bottlenecks that oversaturate first. We call this the nucleation effect. Due to this effect, the network flow is not constant for a fixed number of vehicles as predicted by the MFD, but decreases due to local queueing and spill back processes around the congestion "nuclei". During this build up of congestion, the production hence decreases, which gives the hysteresis effects.

  4. Nonuniform traffic spots (NUTS) in multistage interconnection networks

    SciTech Connect

    Lang, T.; Kurisaki, L. . Dept. of Computer Science)

    1990-09-01

    The performance of multistage interconnection networks for multiprocessors is degraded when the traffic pattern produces nonuniform congestion in the blocking switches, that is, when there exist nonuniform traffic spots. For some specific patterns the authors evaluate this degradation in performance and propose modifications to the network organization and operation to reduce the degradation. Successful modifications are the use of diverting switches and the extension of the network with additional links. The use of these modifications makes the network more effective for a larger variety of traffic patterns. The authors also consider the case in which the network carries the superposition of two types of traffic. One type is the high throughput data and instruction traffic, while the other consists of control and I/O packets which are of low throughput but have severe real-time constraints. The authors conclude that diverting switches and networks with additional links are also suitable for assuring low latency for the real-time traffic, especially when using the displacing mode.

  5. Demonstration of alternative traffic information collection and management technologies

    NASA Astrophysics Data System (ADS)

    Knee, Helmut E.; Smith, Cy; Black, George; Petrolino, Joe

    2004-03-01

    Many of the components associated with the deployment of Intelligent Transportation Systems (ITS) to support a traffic management center (TMC) such as remote control cameras, traffic speed detectors, and variable message signs, have been available for many years. Their deployment, however, has been expensive and applied primarily to freeways and interstates, and have been deployed principally in the major metropolitan areas in the US; not smaller cities. The Knoxville (Tennessee) Transportation Planning Organization is sponsoring a project that will test the integration of several technologies to estimate near-real time traffic information data and information that could eventually be used by travelers to make better and more informed decisions related to their travel needs. The uniqueness of this demonstration is that it will seek to predict traffic conditions based on cellular phone signals already being collected by cellular communications companies. Information about the average speed on various portions of local arterials and incident identification (incident location) will be collected and compared to similar data generated by "probe vehicles". Successful validation of the speed information generated from cell phone data will allow traffic data to be generated much more economically and utilize technologies that are minimally infrastructure invasive. Furthermore, when validated, traffic information could be provided to the traveling public allowing then to make better decisions about trips. More efficient trip planning and execution can reduce congestion and associated vehicle emissions. This paper will discuss the technologies, the demonstration project, the project details, and future directions.

  6. Autonomous Congestion Control in Delay-Tolerant Networks

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott; Jennings, Esther; Schoolcraft, Joshua

    2006-01-01

    Congestion control is an important feature that directly affects network performance. Network congestion may cause loss of data or long delays. Although this problem has been studied extensively in the Internet, the solutions for Internet congestion control do not apply readily to challenged network environments such as Delay Tolerant Networks (DTN) where end-to-end connectivity may not exist continuously and latency can be high. In DTN, end-to-end rate control is not feasible. This calls for congestion control mechanisms where the decisions can be made autonomously with local information only. We use an economic pricing model and propose a rule-based congestion control mechanism where each router can autonomously decide on whether to accept a bundle (data) based on local information such as available storage and the value and risk of accepting the bundle (derived from historical statistics). Preliminary experimental results show that this congestion control mechanism can protect routers from resource depletion without loss of data.

  7. Congestion Measures for Organized Markets in the U.S.

    SciTech Connect

    Fisher, Emily; Eto, Joseph H.

    2013-12-16

    Transmission lines deliver electricity that is generated at power plants to loads. When there is not sufficient transmission capacity to schedule or transport all desired electricity transfers, the transmission system is constrained, and the particular line, flowgate or interface is congested. While it is useful to measure congestion for several reasons—to identify where and how much congestion exists and how this changes over time, to determine whether or what to do about it, and to assess the effectiveness of actions taken—it is challenging to measure congestion in a meaningful and consistent way across markets or over time in the same market. This paper examines current public reporting of congestion measures for organized markets in the U.S., and what these measures can and cannot tell us about congestion across regions or over time in the same region.

  8. Mobile Phones in a Traffic Flow: A Geographical Perspective to Evening Rush Hour Traffic Analysis Using Call Detail Records

    PubMed Central

    Järv, Olle; Ahas, Rein; Saluveer, Erki; Derudder, Ben; Witlox, Frank

    2012-01-01

    Excessive land use and suburbanisation around densely populated urban areas has gone hand in hand with a growth in overall transportation and discussions about causality of traffic congestions. The objective of this paper is to gain new insight regarding the composition of traffic flows, and to reveal how and to what extent suburbanites’ travelling affects rush hour traffic. We put forward an alternative methodological approach using call detail records of mobile phones to assess the composition of traffic flows during the evening rush hour in Tallinn, Estonia. We found that daily commuting and suburbanites influence transportation demand by amplifying the evening rush hour traffic, although daily commuting trips comprises only 31% of all movement at that time. The geography of the Friday evening rush hour is distinctive from other working days, presumably in connection with domestic tourism and leisure time activities. This suggests that the rise of the overall mobility of individuals due to societal changes may play a greater role in evening rush hour traffic conditions than does the impact of suburbanisation. PMID:23155461

  9. Overcoming the Pigou-Downs Paradox Using Advanced Traffic Signal Control

    NASA Astrophysics Data System (ADS)

    Fowdur, S. C.; Rughooputh, S. D. D. V.

    2013-06-01

    Expansion of a road network has often been observed to cause more congestion and has led researchers to the formulation of traffic paradoxes such as the Pigou-Downs and the Braess paradoxes. In this paper, we present an application of advanced traffic signal control (ATSC) to overcome the Pigou-Downs paradox. Port Louis, the capital city of Mauritius is used to investigate the effect of using a harbor bridge to by-pass the city center. Using traffic cellular automata (TCA) simulations it has been shown how, if traffic is only gradually deviated along the by-pass, an overall longer travel time and decreased flux would result. By making use of ATSC, which involves traffic lights that sense the number of vehicles accumulated in the queue, better travel times and fluxes are achieved.

  10. An improved cellular automaton model considering the effect of traffic lights and driving behaviour

    NASA Astrophysics Data System (ADS)

    He, Hong-Di; Lu, Wei-Zhen; Dong, Li-Yun

    2011-04-01

    This paper proposes an improved cellular automaton model to describe the urban traffic flow with the consideration of traffic light and driving behaviour effects. Based on the model, the characteristics of the urban traffic flow on a single-lane road are investigated under three different control strategies, i.e., the synchronized, the green wave and the random strategies. The fundamental diagrams and time-space patterns of the traffic flows are provided for these strategies respectively. It finds that the dynamical transition to the congested flow appears when the vehicle density is higher than a critical level. The saturated flow is less dependent on the cycle time and the strategies of the traffic light control, while the critical vehicle density varies with the cycle time and the strategies. Simulated results indicate that the green wave strategy is proven to be the most effective one among the above three control strategies.

  11. Feedback control scheme of traffic jams based on the coupled map car-following model

    NASA Astrophysics Data System (ADS)

    Zhou, Tong; Sun, Di-Hua; Zhao, Min; Li, Hua-Min

    2013-09-01

    Based on the pioneering work of Konishi et al. [Phys. Rev. E (1999) 60 4000], a new feedback control scheme is presented to suppress traffic jams based on the coupled map car-following model under the open boundary condition. The effect of the safe headway on the traffic system is considered. According to the control theory, the condition under which traffic jams can be suppressed is analyzed. The results are compared with the previous results concerning congestion control. The simulations show that the suppression performance of our scheme on traffic jams is better than those of the previous schemes, although all the schemes can suppress traffic jams. The simulation results are consistent with theoretical analyses.

  12. Electricity transmission congestion costs: A review of recent reports

    SciTech Connect

    Lesieutre, Bernard C.; Eto, Joseph H.

    2003-10-01

    Recently, independent system operators (ISOs) and others have published reports on the costs of transmission congestion. The magnitude of congestion costs cited in these reports has contributed to the national discussion on the current state of U.S. electricity transmission system and whether it provides an adequate platform for competition in wholesale electricity markets. This report reviews reports of congestion costs and begins to assess their implications for the current national discussion on the importance of the U.S. electricity transmission system for enabling competitive wholesale electricity markets. As a guiding principle, we posit that a more robust electricity system could reduce congestion costs; and thereby, (1) facilitate more vibrant and fair competition in wholesale electricity markets, and (2) enable consumers to seek out the lowest prices for electricity. Yet, examining the details suggests that, sometimes, there will be trade-offs between these goals. Therefore, it is essential to understand who pays, how much, and how do they benefit in evaluating options (both transmission and non-transmission alternatives) to address transmission congestion. To describe the differences among published estimates of congestion costs, we develop and motivate three ways by which transmission congestion costs are calculated in restructured markets. The assessment demonstrates that published transmission congestion costs are not directly comparable because they have been developed to serve different purposes. More importantly, critical information needed to make them more comparable, for example in order to evaluate the impacts of options to relieve congestion, is sometimes not available.

  13. Analysis of the influence of occupation rate of public transit vehicles on mixing traffic flow in a two-lane system

    NASA Astrophysics Data System (ADS)

    Qian, Yong-Sheng; Shi, Pei-Ji; Zeng, Qiong; Ma, Chang-Xi; Lin, Fang; Sun, Peng; Yin, Xiao-Ting

    2009-09-01

    Based on the existing classical cellular automaton model of traffic flow, a cellular automaton traffic model with different-maximum-speed vehicles mixed on a single lane is proposed, in which public transit and harbour-shaped bus stops are taken into consideration. Parameters such as length of cellular automaton, operation speed and random slow mechanism are re-demarcated. A harbour-shaped bus stop is set up and the vehicle changing lane regulation is changed. Through computer simulation, the influence of occupation rate of public transit vehicles on mixed traffic flow and traffic capacity is analysed. The results show that a public transport system can ease urban traffic congestion but creates new jams at the same time, and that the influence of occupation rate of public transit vehicles on traffic capacity is considerable. To develop urban traffic, attention should be paid to the occupation rate of public transit vehicles and traffic development in a haphazard way should be strictly avoided.

  14. Beating the traffic with commuting alternatives

    SciTech Connect

    1995-05-01

    This pamphlet describes how, by encouraging commuting options, local governments can help reduce air pollution, fuel consumption, and traffic congestion. Minimizing these problems makes the community more appealing to businesses, residents, and visitors and boosts the local economy. Approaches to alternative transportation are as varied as the communities devising and using them. But the critical factor is initiative from local governments, often one of communities largest employers. They can use and promote commuting alternatives among their employees. Local governments can also promote alternative transportation among other employers and the general public. They can provide information on commuting options, improve the infrastructure, and use local authority to require and reward those changes necessary to make alternative transportation a widely accepted part of community life. Best of all, local governments can lead by example and establish a template for other employers to follow.

  15. Delay Banking for Managing Air Traffic

    NASA Technical Reports Server (NTRS)

    Green, Steve

    2008-01-01

    Delay banking has been invented to enhance air-traffic management in a way that would increase the degree of fairness in assigning arrival, departure, and en-route delays and trajectory deviations to aircraft impacted by congestion in the national airspace system. In delay banking, an aircraft operator (airline, military, general aviation, etc.) would be assigned a numerical credit when any of their flights are delayed because of an air-traffic flow restriction. The operator could subsequently bid against other operators competing for access to congested airspace to utilize part or all of its accumulated credit. Operators utilize credits to obtain higher priority for the same flight, or other flights operating at the same time, or later, in the same airspace, or elsewhere. Operators could also trade delay credits, according to market rules that would be determined by stakeholders in the national airspace system. Delay banking would be administered by an independent third party who would use delay banking automation to continually monitor flights, allocate delay credits, maintain accounts of delay credits for participating airlines, mediate bidding and the consumption of credits of winning bidders, analyze potential transfers of credits within and between operators, implement accepted transfers, and ensure fair treatment of all participating operators. A flow restriction can manifest itself in the form of a delay in assigned takeoff time, a reduction in assigned airspeed, a change in the position for the aircraft in a queue of all aircraft in a common stream of traffic (e.g., similar route), a change in the planned altitude profile for an aircraft, or change in the planned route for the aircraft. Flow restrictions are typically imposed to mitigate traffic congestion at an airport or in a region of airspace, particularly congestion due to inclement weather, or the unavailability of a runway or region of airspace. A delay credit would be allocated to an operator of a

  16. Performance of various input-buffered and output-buffered ATM switch design principles under bursty traffic: Simulation study

    NASA Astrophysics Data System (ADS)

    Liew, Soung C.

    1994-02-01

    This paper investigates the packet loss probabilities of several alternative input-buffered and output-buffered switch designs with finite amounts of buffer space. The effects of bursty traffic, modeled by geometrically distributed active and idle periods, are explored. Methods for improving switch performance are classified, and their effectiveness for dealing with bursty traffic discussed. This work indicates that bursty traffic can degrade switch performance significantly and that it is difficult to alleviate the performance degradation by merely restricting the offered traffic load. Unless buffers are shared, or very large buffers provided, strategies that improve throughput under uniform random traffic are not very effective under bursty traffic. For input-buffered switches, our investigation suggests that the specific contention resolution scheme we use is a more important performance factor under bursty traffic than it is under uniform random traffic.

  17. Nutrient dyshomeostasis in congestive heart failure.

    PubMed

    Kamalov, German; Holewinski, Joshua P; Bhattacharya, Syamal K; Ahokas, Robert A; Sun, Yao; Gerling, Ivan C; Weber, Karl T

    2009-07-01

    The clinical syndrome congestive heart failure (CHF) has its origins rooted in a salt-avid state mediated largely by effector hormones of the renin-angiotensin-aldosterone system. In recent years, this cardiorenal perspective of CHF has taken on a broader perspective. One which focuses on a progressive systemic illness, whose major features include the presence of oxidative stress in diverse tissues and elevated circulating levels of proinflammatory cytokines coupled with a wasting of soft tissues and bone. Experimental studies, which simulate chronic renin-angiotensin-aldosterone system activation, and translational studies in patients with salt avidity having decompensated biventricular failure with hepatic and splanchnic congestion have forged a broader understanding of this illness and the important contribution of a dyshomeostasis of Ca2+, Mg2+, Zn2+, Se2+, and vitamins D, B12, and B1. Herein, we review biomarkers indicative of the nutrient imbalance found in CHF and raise the question of a need for a polynutrient supplement in the overall management of CHF. PMID:19593100

  18. Medical management of congestive heart failure.

    PubMed Central

    Arai, A. E.; Greenberg, B. H.

    1990-01-01

    The syndrome of congestive heart failure can result from a variety of cardiac disorders of which left ventricular dysfunction is the most common. The clinical presentation is determined by the interaction between cardiac dysfunction and a series of compensatory mechanisms that are activated throughout the body. Therapy for this disorder is best approached through an understanding of this complex relationship and an appreciation for the influence of preload, afterload, and contractility on cardiac performance. Recent important advances in therapy include the use of combined diuretic therapy, a better understanding of the value of the digitalis glycosides, and evidence that angiotensin-converting enzyme (ACE) inhibitors can relieve symptoms and prolong life. More intensive therapy earlier in the course of congestive heart failure appears to have some clinical benefit. The use of ACE inhibitors during this phase may delay progression of the underlying left ventricular dysfunction. Future therapy will be influenced by the results of ongoing trials that are testing both new agents and expanded indications for drugs that are currently available. PMID:2244376

  19. Towards a physics of Internet traffic in a geographic network

    NASA Astrophysics Data System (ADS)

    Baker, R. G. V.

    2012-02-01

    A set of equations from a biased random walk are shown to describe the time-based Gaussian distributions of Internet traffic relative to the Earth's time zones. The Internet is an example of a more general physical problem dealing with motion near the speed of light relative to different time frames of reference. The second order differential equation (DE) takes the form of 'time diffusion' near the speed of light or alternatively considered as a complex variable with real time and imaginary longitudinal components. Congestion waves are generated by peak global traffic from different time zones following the Earth's revolution. The DE is divided into space and time operators for discussion and each component solution, including constants, is illustrated using data from a global network compiled by the Stanford Linear Accelerator Centre (SLAC). Indices of global and regional phase congestion for the monitoring sites are calculated from standardised regressions from the Earth's rotation. There is also a J-curve limit to transferring information by the Internet and this is expressed as an inequality underpinned by the speed of light with examples from US and European traffic. The research returns to an often little known theme of Isaac Newton's: mixing physics with geography. In our case, the equations define trajectories of information packets travelling near the speed of light, navigating within networks and between longitudes, relative to the Earth's rotation.

  20. Estimates of CO2 traffic emissions from mobile concentration measurements

    NASA Astrophysics Data System (ADS)

    Maness, H. L.; Thurlow, M. E.; McDonald, B. C.; Harley, R. A.

    2015-03-01

    We present data from a new mobile system intended to aid in the design of upcoming urban CO2-monitoring networks. Our collected data include GPS probe data, video-derived traffic density, and accurate CO2 concentration measurements. The method described here is economical, scalable, and self-contained, allowing for potential future deployment in locations without existing traffic infrastructure or vehicle fleet information. Using a test data set collected on California Highway 24 over a 2 week period, we observe that on-road CO2 concentrations are elevated by a factor of 2 in congestion compared to free-flow conditions. This result is found to be consistent with a model including vehicle-induced turbulence and standard engine physics. In contrast to surface concentrations, surface emissions are found to be relatively insensitive to congestion. We next use our model for CO2 concentration together with our data to independently derive vehicle emission rate parameters. Parameters scaling the leading four emission rate terms are found to be within 25% of those expected for a typical passenger car fleet, enabling us to derive instantaneous emission rates directly from our data that compare generally favorably to predictive models presented in the literature. The present results highlight the importance of high spatial and temporal resolution traffic data for interpreting on- and near-road concentration measurements. Future work will focus on transport and the integration of mobile platforms into existing stationary network designs.

  1. Infantile Hepatic Hemangioendothelioma Associated With Congestive Heart Failure: Two Case Reports With Different Outcomes.

    PubMed

    Wang, Tao; Wang, Yibin; Liang, Yun; Lu, Guoyan

    2015-12-01

    Infantile hepatic hemangioendothelioma (IHH) is rare which can regress spontaneously. Arteriovenous shunts within hemangiomas, however, may result in pulmonary artery hypertension (PAH) and congestive heart failure (CHF).The authors report 2 young infants suffering from multifocal IHH associated with CHF were both treated with glucocorticoid and transcatheter arterial embolization (TAE), but had different outcomes. The PAH decreased immediately and the symptoms of CHF were alleviated after TAE for both of them. For the Tibetan infant, the development was normal with tumor regression by follow-up. For the Han ethnic neonate, PAH increased again in the seventh day with progressive cardiovascular insufficiency. Ultrasound showed a persisting perfusion caused by collateralization around occluded main feeders. Furthermore, a pulmonary infection occurred and ventilation was performed. As a result, the infant died from multiorgan failure caused by CHF and infection.TAE is a treatment of reducing shunting for hemangiomas. Fistula recanalization in multifocal IHH, however, might be an important risk factor affecting the outcome of TAE. TAE should be further evaluated with special attention to anatomy of feeding and draining vessels, and cardiopulmonary conditions. In addition, the patients were susceptible to secondary pulmonary infection because of lung congestion. As well, the infant from the high altitude area showed better adaptability to hypoxia. PMID:26717373

  2. Integrated arterial and freeway operation control strategies for IVHS advanced traffic management systems. Summary report, September 1997--January 1998

    SciTech Connect

    Mahmassani, H.S.; Valdes, D.M.; Machemehl, R.B.; Tassoulas, J.; Williams, J.C.

    1998-10-01

    This study focuses on traffic congestion, primarily that occurring on freeway corridors in metropolitan areas. Lack of coordination in the operation of various components of the system is often a major source of inefficiency, resulting in greater delays to motorists than what might be achievable with the existing physical infrastructure.

  3. Empirical macroscopic features of spatial-temporal traffic patterns at highway bottlenecks.

    PubMed

    Kerner, Boris S

    2002-04-01

    Results of an empirical study of congested patterns measured during 1995-2001 at German highways are presented. Based on this study, various types of congested patterns at on and off ramps have been identified, their macroscopic spatial-temporal features have been derived, and an evolution of those patterns and transformations between different types of the patterns over time has been found out. It has been found that at an isolated bottleneck (a bottleneck that is far enough from other effective bottlenecks) either the general pattern (GP) or the synchronized flow pattern (SP) can be formed. In GP, synchronized flow occurs and wide moving jams spontaneously emerge in that synchronized flow. In SP, no wide moving jams emerge, i.e., SP consists of synchronized flow only. An evolution of GP into SP when the flow rate to the on ramp decreases has been found and investigated. Spatial-temporal features of complex patterns that occur if two or more effective bottlenecks exist on a highway have been found out. In particular, the expanded pattern where synchronized flow covers two or more effective bottlenecks can be formed. It has been found that the spatial-temporal structure of congested patterns possesses predictable, i.e., characteristic, unique, and reproducible features, for example, the most probable types of patterns that are formed at a given bottleneck. According to the empirical investigations the cases of the weak and the strong congestion should be distinguished. In contrast to the weak congestion, the strong congestion possesses the following characteristic features: (i) the flow rate in synchronized flow is self-maintaining near a limit flow rate; (ii) the mean width of the region of synchronized flow in GP does not depend on traffic demand; (iii) there is a correlation between the parameters of synchronized flow and wide moving jams: the higher the flow rate out from a wide moving jam is, the higher is the limit flow rate in the synchronized flow. The

  4. 14 CFR 137.51 - Operation over congested areas: General.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    .... 137.51 Section 137.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... AGRICULTURAL AIRCRAFT OPERATIONS Operating Rules § 137.51 Operation over congested areas: General. (a) Notwithstanding part 91 of this chapter, an aircraft may be operated over a congested area at altitudes...

  5. 14 CFR 137.51 - Operation over congested areas: General.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    .... 137.51 Section 137.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... AGRICULTURAL AIRCRAFT OPERATIONS Operating Rules § 137.51 Operation over congested areas: General. (a) Notwithstanding part 91 of this chapter, an aircraft may be operated over a congested area at altitudes...

  6. 14 CFR 137.51 - Operation over congested areas: General.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    .... 137.51 Section 137.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... AGRICULTURAL AIRCRAFT OPERATIONS Operating Rules § 137.51 Operation over congested areas: General. (a) Notwithstanding part 91 of this chapter, an aircraft may be operated over a congested area at altitudes...

  7. Computers in Traffic Education.

    ERIC Educational Resources Information Center

    Alexander, O. P.

    1983-01-01

    Traffic education covers basic road skills, legal/insurance aspects, highway code, accident causation/prevention, and vehicle maintenance. Microcomputer applications to traffic education are outlined, followed by a selected example of programs currently available (focusing on drill/practice, simulation, problem-solving, data manipulation, games,…

  8. Regulation of air traffic

    NASA Technical Reports Server (NTRS)

    DEVALUEZ

    1922-01-01

    The ways in which the international and internal French air traffic accords interact with each other is outlined in this report. The principal questions covered by the present legislation are as follows: 1) Conditions of safety which must be fulfilled by aircraft; 2) Licenses for members of the crew; 3) Traffic rules to be observed by French and foreign aircraft.

  9. Visualization of Traffic Accidents

    NASA Technical Reports Server (NTRS)

    Wang, Jie; Shen, Yuzhong; Khattak, Asad

    2010-01-01

    Traffic accidents have tremendous impact on society. Annually approximately 6.4 million vehicle accidents are reported by police in the US and nearly half of them result in catastrophic injuries. Visualizations of traffic accidents using geographic information systems (GIS) greatly facilitate handling and analysis of traffic accidents in many aspects. Environmental Systems Research Institute (ESRI), Inc. is the world leader in GIS research and development. ArcGIS, a software package developed by ESRI, has the capabilities to display events associated with a road network, such as accident locations, and pavement quality. But when event locations related to a road network are processed, the existing algorithm used by ArcGIS does not utilize all the information related to the routes of the road network and produces erroneous visualization results of event locations. This software bug causes serious problems for applications in which accurate location information is critical for emergency responses, such as traffic accidents. This paper aims to address this problem and proposes an improved method that utilizes all relevant information of traffic accidents, namely, route number, direction, and mile post, and extracts correct event locations for accurate traffic accident visualization and analysis. The proposed method generates a new shape file for traffic accidents and displays them on top of the existing road network in ArcGIS. Visualization of traffic accidents along Hampton Roads Bridge Tunnel is included to demonstrate the effectiveness of the proposed method.

  10. The Traffic Light Challenge

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2014-01-01

    Traffic lights are an important part of the transportation infrastructure, regulating traffic flow and maintaining safety when crossing busy streets. When they go awry or become nonfunctional, a great deal of havoc and danger can be present. During power outages, the street lights go out all over the affected area. It would be good to be able to…

  11. Autonomous Congestion Control in Delay-Tolerant Networks

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.; Jennings, Esther H.

    2005-01-01

    Congestion control is an important feature that directly affects network performance. Network congestion may cause loss of data or long delays. Although this problem has been studied extensively in the Internet, the solutions for Internet congestion control do not apply readily to challenged network environments such as Delay Tolerant Networks (DTN) where end-to-end connectivity may not exist continuously and latency can be high. In DTN, end-to-end rate control is not feasible. This calls for congestion control mechanisms where the decisions can be made autonomously with local information only. We use an economic pricing model and propose a rule-based congestion control mechanism where each router can autonomously decide on whether to accept a bundle (data) based on local information such as available storage and the value and risk of accepting the bundle (derived from historical statistics).

  12. Expanding the Use of Time-Based Metering: Multi-Center Traffic Management Advisor

    NASA Technical Reports Server (NTRS)

    Landry, Steven J.; Farley, Todd; Hoang, Ty

    2005-01-01

    Time-based metering is an efficient air traffic management alternative to the more common practice of distance-based metering (or "miles-in-trail spacing"). Despite having demonstrated significant operational benefit to airspace users and service providers, time-based metering is used in the United States for arrivals to just nine airports and is not used at all for non-arrival traffic flows. The Multi-Center Traffic Management Advisor promises to bring time-based metering into the mainstream of air traffic management techniques. Not constrained to operate solely on arrival traffic, Multi-Center Traffic Management Advisor is flexible enough to work in highly congested or heavily partitioned airspace for any and all traffic flows in a region. This broader and more general application of time-based metering is expected to bring the operational benefits of time-based metering to a much wider pool of beneficiaries than is possible with existing technology. It also promises to facilitate more collaborative traffic management on a regional basis. This paper focuses on the operational concept of the Multi-Center Traffic Management Advisor, touching also on its system architecture, field test results, and prospects for near-term deployment to the United States National Airspace System.

  13. Trafficability and workability of soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Trafficability and workability are soil capabilities supporting operations of agricultural machinery. Trafficability is a soil's capability to support agricultural traffic without degrading soils and ecosystems. Workability is a soil capability supporting tillage. Agriculture is associated with mech...

  14. Coal-truck impacts on highway safety and traffic characteristics

    SciTech Connect

    Eck, R.W.; Polus, A.; Halkias, J.A.

    1982-07-01

    A computer simulation model of accident rates and delay times is used to quantify highway hazards and congestion introduced by increases in large coal trucks. The effects of trucks on long grades, where the speed differences between trucks and other vehicles becomes greater, increases the potential for accident. Long lines of slow-moving trucks, however, reduce accidents because they reduce the opportunity for passing. At best, the trucks make traffic flow less stable. The results of this study can help in the design of passing lanes and improved grade alignment. 18 references. (DCK)

  15. Nasal congestion in infants and children: a literature review on efficacy and safety of non-pharmacological treatments.

    PubMed

    Chirico, G; Quartarone, G; Mallefet, P

    2014-12-01

    The most common causes of nasal obstruction and runny nose in infants and children are infections, mainly of viral origin, or allergies. In neonates and infants viral upper respiratory tract infections (URTI) are frequently observed during episodes of nasal obstruction. Saline irrigation of the nose is believed to alleviate URTI symptoms by helping to eliminate excess mucus, to reduce congestion and by contributing to improve breathing. Objective of the study was to review the efficacy and safety of non-pharmacological options for the treatment of nasal congestion and its sequelae, in infants and children, with a special focus on hypertonic and isotonic solutions and other medical devices, including nasal aspirators. Available data indicate that nasal symptoms in children with allergic rhinitis or acute sinusitis significantly improved following nasal saline irrigation. The use of medical devices is less documented. Nasal aspiration with a medical device, associated with an isotonic saline solution, during viral rhinitis, has been shown to lower the risk of developing acute otitis media and rhinosinusitis, in comparison with a group treated with physiological saline solution alone. Safety and tolerability have been evaluated and no serious adverse events have been reported. Literature data highlighted the good tolerability. The use of isotonic and hypertonic saline solutions to relief nasal congestion in infants and children is widespread; it is a safe and valuable therapeutic support, and can reduce the use of medications (antihistamines, decongestant, antibiotics, corticosteroids) during the treatment of URTIs. PMID:25336097

  16. Evaluation of TCP Congestion Control Algorithms on the Windows Vista Platform

    SciTech Connect

    Li, Yee-Ting; /SLAC

    2006-07-07

    CTCP, an innovative TCP congestion control algorithm developed by Microsoft, is evaluated and compared to HSTCP and StandardTCP. Tests were performed on the production Internet from Stanford Linear Accelerator Center (SLAC) to various geographically located hosts to give a broad overview of the performances. We find that certain issues were apparent during testing (not directly related to the congestion control algorithms) which may skew results. With this in mind, we find that CTCP performed similarly to HSTCP across a multitude of different network environments. However, to improve the fairness and to reduce the impact of CTCP upon existing StandardTCP traffic, two areas of further research were investigated. Algorithmic additions to CTCP for burst control to reduce the aggressiveness of its cwnd increments demonstrated beneficial improvements in both fairness and throughput over the original CTCP algorithm. Similarly, {gamma} auto-tuning algorithms were investigated to dynamically adapt CTCP flows to their network conditions for optimal performance. While the effects of these auto-tuning algorithms when used in addition to burst control showed little to no benefit to fairness nor throughput for the limited number of network paths tested, one of the auto-tuning algorithms performed such that there was negligible impact upon StandardTCP. With these improvements, CTCP was found to perform better than HSTCP in terms of fairness and similarly in terms of throughput under the production environments tested.

  17. Congestion Prediction Modeling for Quality of Service Improvement in Wireless Sensor Networks

    PubMed Central

    Lee, Ga-Won; Lee, Sung-Young; Huh, Eui-Nam

    2014-01-01

    Information technology (IT) is pushing ahead with drastic reforms of modern life for improvement of human welfare. Objects constitute “Information Networks” through smart, self-regulated information gathering that also recognizes and controls current information states in Wireless Sensor Networks (WSNs). Information observed from sensor networks in real-time is used to increase quality of life (QoL) in various industries and daily life. One of the key challenges of the WSNs is how to achieve lossless data transmission. Although nowadays sensor nodes have enhanced capacities, it is hard to assure lossless and reliable end-to-end data transmission in WSNs due to the unstable wireless links and low hard ware resources to satisfy high quality of service (QoS) requirements. We propose a node and path traffic prediction model to predict and minimize the congestion. This solution includes prediction of packet generation due to network congestion from both periodic and event data generation. Simulation using NS-2 and Matlab is used to demonstrate the effectiveness of the proposed solution. PMID:24784035

  18. Comprehensive Software Eases Air Traffic Management

    NASA Technical Reports Server (NTRS)

    2007-01-01

    To help air traffic control centers improve the safety and the efficiency of the National Airspace System, Ames Research Center developed the Future Air Traffic Management Concepts Evaluation Tool (FACET) software, which won NASA's 2006 "Software of the Year" competition. In 2005, Ames licensed FACET to Flight Explorer Inc., for integration into its Flight Explorer (version 6.0) software. The primary FACET features incorporated in the Flight Explorer software system alert airspace users to forecasted demand and capacity imbalances. Advance access to this information helps dispatchers anticipate congested sectors (airspace) and delays at airports, and decide if they need to reroute flights. FACET is now a fully integrated feature in the Flight Explorer Professional Edition (version 7.0). Flight Explorer Professional offers end-users other benefits, including ease of operation; automatic alerts to inform users of important events such as weather conditions and potential airport delays; and international, real-time flight coverage over Canada, the United Kingdom, New Zealand, and sections of the Atlantic and Pacific Oceans. Flight Explorer Inc. recently broadened coverage by partnering with Honeywell International Inc.'s Global Data Center, Blue Sky Network, Sky Connect LLC, SITA, ARINC Incorporated, Latitude Technologies Corporation, and Wingspeed Corporation, to track their aircraft anywhere in the world.

  19. Numerical simulation of freeway traffic flow

    SciTech Connect

    Liu, G.; Lyrintzis, A.S.; Michalopoulos, P.G.

    1997-11-01

    A new high-order continuum model is presented in this paper. This high-order model exhibits smooth solutions rather than discontinuities, is able to describe the amplification of small disturbances on heavy traffic, and allows fluctuations of speed around the equilibrium values. Furthermore, unlike some earlier high-order models, it does not result in negative speeds at the tail of congested regions and disturbance propagation speeds greater than the flow speed. The model takes into account the relaxation time as a function of density and, in the equilibrium limit, it is consistent with the simple continuum model. A Riemann-problem-based numerical method is proposed for the solution of the new high-order model. Modeling of interrupted flow behavior such as merging, diverging, and weaving is also investigated. Based on the new high order model, the proposed numerical method and the modeling of interrupted flow, a versatile code is developed for the numerical simulation of freeway traffic flow that includes several freeway geometries. The authors compare the high-order model with the simple continuum model and the proposed numerical method with the Lax method based on 30-s and 5-min field data. The model is tested in interrupted flow situations (e.g., pipeline, merging, diverging, and weaving areas). A comparison of numerical results with limited field data shows that the high-order model performs better than the simple continuum model and describes better than a previously proposed method.

  20. The impact of the congestion charging scheme on ambient air pollution concentrations in London

    NASA Astrophysics Data System (ADS)

    Atkinson, R. W.; Barratt, B.; Armstrong, B.; Anderson, H. R.; Beevers, S. D.; Mudway, I. S.; Green, D.; Derwent, R. G.; Wilkinson, P.; Tonne, C.; Kelly, F. J.

    On 17th February 2003, a congestion charging scheme (CCS), operating Monday-Friday, 07:00-18:00, was introduced in central London along with a programme of traffic management measures. We investigated the potential impact of the introduction of the CCS on measured pollutant concentrations (oxides of nitrogen (NO X, NO and NO 2), particles with a median diameter less than 10 microns (PM 10), carbon monoxide (CO) and ozone (O 3)) measured at roadside and background monitoring sites across Greater London. Temporal changes in pollution concentrations within the congestion charging zone were compared to changes, over the same time period, at monitors unlikely to be affected by the CCS (the control zone) and in the boundary zone between the two. Similar analyses were done for CCS hours during weekends (when the CCS was not operating). Based on the single roadside monitor with the CCS Zone, it was not possible to identify any relative changes in pollution concentrations associated with the introduction of the scheme. However, using background monitors, there was good evidence for a decrease in NO and increases in NO 2 and O 3 relative to the control zone. There was little change in background concentrations of NO X. There was also evidence of relative reductions in PM 10 and CO. Similar changes were observed during the same hours in weekends when the scheme was not operating. The causal attribution of these changes to the CCS per se is not appropriate since the scheme was introduced concurrently with other traffic and emissions interventions which might have had a more concentrated effect in central London. This study provides important pointers for study design and data requirements for the evaluation of similar schemes in terms of air quality. It also shows that results may be unexpected and that the overall effect on toxicity may not be entirely favourable.

  1. Complexity of spatiotemporal traffic phenomena in flow of identical drivers: Explanation based on fundamental hypothesis of three-phase theory

    NASA Astrophysics Data System (ADS)

    Kerner, Boris S.

    2012-03-01

    Based on numerical simulations of a stochastic three-phase traffic flow model, we reveal the physics of the fundamental hypothesis of three-phase theory that, in contrast with a fundamental diagram of classical traffic flow theories, postulates the existence of a two-dimensional (2D) region of steady states of synchronized flow where a driver makes an arbitrary choice of a space gap (time headway) to the preceding vehicle. We find that macroscopic and microscopic spatiotemporal effects of the entire complexity of traffic congestion observed up to now in real measured traffic data can be explained by simulations of traffic flow consisting of identical drivers and vehicles, if a microscopic model used in these simulations incorporates the fundamental hypothesis of three-phase theory. It is shown that the driver's choice of space gaps within the 2D region of synchronized flow associated with the fundamental hypothesis of three-phase theory can qualitatively change types of congested patterns that can emerge at a highway bottleneck. In particular, if drivers choose long enough spaces gaps associated with the fundamental hypothesis, then general patterns, which consist of synchronized flow and wide moving jams, do not emerge independent of the flow rates and bottleneck characteristics: Even at a heavy bottleneck leading to a very low speed within congested patterns, only synchronized flow patterns occur in which no wide moving jams emerge spontaneously.

  2. Effect of desired speed variability on highway traffic flow.

    PubMed

    Lipshtat, Azi

    2009-06-01

    Traffic flow is a function of many natural, environmental, and human factors. Not only that weather and road condition can vary, but drivers' decisions and policies also can affect the flow. Here we analyze the effect of distribution of desired speeds. We show that a broader distribution can reduce the flow efficiency and increase congestions. Since different drivers react differently to changes in weather or road conditions, such a change leads to a change in desired speed distribution as well. As a result, nonintuitive changes in traffic flow may occur. Besides providing insight and analyzing the underlying mechanism of a collective phenomenon, this example sheds light on a fundamental aspect of computational modeling. Although "mean-field" models that deal with average values only and ignore variability are simpler and easier to analyze, they can very easily turn into oversimplifications and miss relevant qualitative phenomena. PMID:19658567

  3. Cluster-size dependent randomization traffic flow model

    NASA Astrophysics Data System (ADS)

    Gao, Kun; Wang, Bing-Hong; Fu, Chuan-Ji; Lu, Yu-Feng

    2007-11-01

    In order to exhibit the meta-stable states, several slow-to-start rules have been investigated as modification to Nagel-Schreckenberg (NS) model. These models can reproduce some realistic phenomena which are absent in the original NS model. But in these models, the size of cluster is still not considered as a useful parameter. In real traffic, the slow-to-start motion of a standing vehicle often depends on the degree of congestion which can be measured by the clusters' size. According to this idea, we propose a cluster-size dependent slow-to-start model based on the speed-dependent slow-to-start rule (VDR) model. It gives expected results through simulations. Comparing with the VDR model, our new model has a better traffic efficiency and shows richer complex characters.

  4. Efficacy and safety of fixed-dose loratadine/montelukast in seasonal allergic rhinitis: effects on nasal congestion.

    PubMed

    Prenner, Bruce; Anolik, Robert; Danzig, Melvyn; Yao, Ruji

    2009-01-01

    A need exists for safe, effective therapy for the relief of the symptoms of allergic rhinitis (AR) that also consistently relieves nasal congestion, the most common and bothersome symptom. This study was performed to assess efficacy and safety of a once-daily tablet containing 10 mg of loratadine, an antihistamine, and 10 mg of montelukast, a leukotriene antagonist (SCH 445761) versus placebo and pseudoephedrine (PSE; 240 mg once-daily formulation; active comparator). In a multicenter, parallel-group, double-blind, double-dummy, randomized study, 1095 subjects with documented history of seasonal AR and positive skin-prick test to a prevailing aeroallergen were treated for 15 days with fixed-dose combination loratadine/montelukast (L/M), PSE, or placebo. After randomization, subjects rated severity of nasal congestion and measured peak nasal inspiratory flow (PNIF) rate in the morning and evening. The change in quality of life from baseline was also assessed. L/M and PSE were significantly more effective than placebo in alleviating nighttime and daytime nasal congestion and improving PNIF rate, an objective measure of nasal obstruction. There were no significant differences between L/M and PSE for any efficacy analysis including improvement in the quality of life. Subjects treated with L/M experienced a similar incidence of total adverse events versus placebo and a lower incidence of total adverse events (including dizziness, insomnia, jitteriness, nausea, and dry mouth) versus PSE. Nasal decongestant activity of L/M was significantly higher than that of placebo and similar to that of PSE in symptomatic AR subjects. L/M showed a safety profile similar to placebo and was better tolerated than PSE. Thus, L/M offers a safe and efficacious alternative to PSE for the treatment of nasal congestion associated with AR. PMID:19549427

  5. Feedback control for car following model based on two-lane traffic flow

    NASA Astrophysics Data System (ADS)

    Ge, Hong-xia; Meng, Xiang-pei; Zhu, Hui-bing; Li, Zhi-Peng

    2014-08-01

    In the paper, two-lane traffic flow considering lane changing behaviors has been discussed based on the control theory, and the friction interference which is from the neighbor lane has been taken into account. By using the control method, the stability condition is derived. The feedback signals, which include vehicular information from both lanes, acting on the two-lane traffic system have been introduced into the Full Velocity Difference car-following model. In the end, simulations are conducted to examine the validity and reasonability of the control method. It is proven that lane changing behaviors can aggravate the traffic perturbation. The traffic flow congestion could be suppressed by using the control method and the simulation results are in good agreement with the theoretical analysis.

  6. Traffic stability of a car-following model considering driver’s desired velocity

    NASA Astrophysics Data System (ADS)

    Zhang, Geng; Sun, Di-Hua; Liu, Wei-Ning; Liu, Hui

    2015-07-01

    In this paper, a new car-following model is proposed by considering driver’s desired velocity according to Transportation Cyber Physical Systems. The effect of driver’s desired velocity on traffic flow has been investigated through linear stability theory and nonlinear reductive perturbation method. The linear stability condition shows that driver’s desired velocity effect can enlarge the stable region of traffic flow. From nonlinear analysis, the Burgers equation and mKdV equation are derived to describe the evolution properties of traffic density waves in the stable and unstable regions respectively. Numerical simulation is carried out to verify the analytical results, which reveals that traffic congestion can be suppressed efficiently by taking driver’s desired velocity effect into account.

  7. Finding the biased-shortest path with minimal congestion in networks via linear-prediction of queue length

    NASA Astrophysics Data System (ADS)

    Shen, Yi; Ren, Gang; Liu, Yang

    2016-06-01

    In this paper, we propose a biased-shortest path method with minimal congestion. In the method, we use linear-prediction to estimate the queue length of nodes, and propose a dynamic accepting probability function for nodes to decide whether accept or reject the incoming packets. The dynamic accepting probability function is based on the idea of homogeneous network flow and is developed to enable nodes to coordinate their queue length to avoid congestion. A path strategy incorporated with the linear-prediction of the queue length and the dynamic accepting probability function of nodes is designed to allow packets to be automatically delivered on un-congested paths with short traveling time. Our method has the advantage of low computation cost because the optimal paths are dynamically self-organized by nodes in the delivering process of packets with local traffic information. We compare our method with the existing methods such as the efficient path method (EPS) and the optimal path method (OPS) on the BA scale-free networks and a real example. The numerical computations show that our method performs best for low network load and has minimum run time due to its low computational cost and local routing scheme.

  8. Simulation study of traffic car accidents in single-lane highway

    NASA Astrophysics Data System (ADS)

    Bentaleb, Khalid; Lakouari, Noureddine; Marzoug, Rachid; Ez-Zahraouy, Hamid; Benyoussef, Abdelilah

    2014-11-01

    In this paper we numerically study the probability Pac of the occurrence of car accidents in the extended Nagel-Schreckenberg (NS) model in the case of mixture of fast (Vmax1=5) and slow vehicles (Vmax2=1) by taking also to the risky overtaking of fast vehicles. In comparison with previous existing models, we find that accidents can occur in the free traffic phase and/or congested one depending on the overtaking rate of fast vehicles. The effect of evacuation of damaged vehicles from the road with probabilities Pevf and Pevs of fast and slow vehicles respectively on the traffic flow behavior is also computed.

  9. Estimation of the full marginal costs of port related truck traffic.

    PubMed

    Berechman, Joseph

    2009-11-01

    NY region is expected to grow by additional 1 million people by 2020, which translates into roughly 70 million more tons of goods to be delivered annually. Due to lack of rail capacity, mainly trucks will haul this volume of freight, challenging an already much constrained highway network. What are the total costs associated with this additional traffic, in particular, congestion, safety and emission? Since a major source of this expected flow is the Port of New York-New Jersey, this paper focuses on the estimation of the full marginal costs of truck traffic resulting from the further expansion of the port's activities. PMID:19796817

  10. The Traffic Management Advisor

    NASA Technical Reports Server (NTRS)

    Nedell, William; Erzberger, Heinz; Neuman, Frank

    1990-01-01

    The traffic management advisor (TMA) is comprised of algorithms, a graphical interface, and interactive tools for controlling the flow of air traffic into the terminal area. The primary algorithm incorporated in it is a real-time scheduler which generates efficient landing sequences and landing times for arrivals within about 200 n.m. from touchdown. A unique feature of the TMA is its graphical interface that allows the traffic manager to modify the computer-generated schedules for specific aircraft while allowing the automatic scheduler to continue generating schedules for all other aircraft. The graphical interface also provides convenient methods for monitoring the traffic flow and changing scheduling parameters during real-time operation.

  11. Air Traffic Network Project

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The high level requirement of the Air Traffic Network (ATN) project is to provide a mechanism for evaluating the impact of router scheduling modifications on a networks efficiency, without implementing the modifications in the live network.

  12. Study on traffic characteristics for a typical expressway on-ramp bottleneck considering various merging behaviors

    NASA Astrophysics Data System (ADS)

    Sun, Jie; Li, Zhipeng; Sun, Jian

    2015-12-01

    Recurring bottlenecks at freeway/expressway are considered as the main cause of traffic congestion in urban traffic system while on-ramp bottlenecks are the most significant sites that may result in congestion. In this paper, the traffic bottleneck characteristics for a simple and typical expressway on-ramp are investigated by the means of simulation modeling under the open boundary condition. In simulations, the running behaviors of each vehicle are described by a car-following model with a calibrated optimal velocity function, and lane changing actions at the merging section are modeled by a novel set of rules. We numerically derive the traffic volume of on-ramp bottleneck under different upstream arrival rates of mainline and ramp flows. It is found that the vehicles from the ramp strongly affect the pass of mainline vehicles and the merging ratio changes with the increasing of ramp vehicle, when the arrival rate of mainline flow is greater than a critical value. In addition, we clarify the dependence of the merging ratio of on-ramp bottleneck on the probability of lane changing and the length of the merging section, and some corresponding intelligent control strategies are proposed in actual traffic application.

  13. Transportation network policy modeling for congestion and pollution control: A variational inequality approach

    NASA Astrophysics Data System (ADS)

    Ramanujam, Padma

    1999-08-01

    Public concern over the state of the environment has grown over the past decade. All indications are that this concern will continue to influence policy making into the foreseeable future. Road transport is seen as the major contributor to environmental degradation. Transportation planners around the world face the question: cleaner air and/or faster commutes? While individual vehicles can be made more environmentally friendly, the sheer scale of growth in world-wide vehicle numbers is projected to cause significant environmental degradation in the longer run, and in the absence of newer and stricter polices. It is a challenge for governments to find policies that ensure congestion-free metropolitan areas while guaranteeing both critical environmental quality levels and a sufficient infrastructure access to all groups involved. The objective of the dissertation is to provide a mathematical framework to study transportation policy models for the purpose of controlling congestion and pollution. Towards this objective. a series of transportation policy models are developed to study travel behavior and to quantity the reductions in congestion and automobile emissions. The dissertation begins with a brief historical overview of some of the pioneering works in urban transportation economics and later presents the theoretical foundation for the transportation policy models developed. The dissertation introduces single modal and multimodal transportation network policy models that accomplish road pricing with the imposition of goal targets on link loads. as well as, integrated traffic equilibrium models with marketable mobile emission permits. Furthermore, equilibrium conditions are derived for each model, and both qualitative analysis and computational procedures are studied. Finally, the dissertation concludes with a comparative study of the relationship between regulatory pricing models and marketable emission permit transportation models and a discussion on key factors

  14. A Hidden Markov Model for Urban-Scale Traffic Estimation Using Floating Car Data.

    PubMed

    Wang, Xiaomeng; Peng, Ling; Chi, Tianhe; Li, Mengzhu; Yao, Xiaojing; Shao, Jing

    2015-01-01

    Urban-scale traffic monitoring plays a vital role in reducing traffic congestion. Owing to its low cost and wide coverage, floating car data (FCD) serves as a novel approach to collecting traffic data. However, sparse probe data represents the vast majority of the data available on arterial roads in most urban environments. In order to overcome the problem of data sparseness, this paper proposes a hidden Markov model (HMM)-based traffic estimation model, in which the traffic condition on a road segment is considered as a hidden state that can be estimated according to the conditions of road segments having similar traffic characteristics. An algorithm based on clustering and pattern mining rather than on adjacency relationships is proposed to find clusters with road segments having similar traffic characteristics. A multi-clustering strategy is adopted to achieve a trade-off between clustering accuracy and coverage. Finally, the proposed model is designed and implemented on the basis of a real-time algorithm. Results of experiments based on real FCD confirm the applicability, accuracy, and efficiency of the model. In addition, the results indicate that the model is practicable for traffic estimation on urban arterials and works well even when more than 70% of the probe data are missing. PMID:26710073

  15. A Hidden Markov Model for Urban-Scale Traffic Estimation Using Floating Car Data

    PubMed Central

    Wang, Xiaomeng; Peng, Ling; Chi, Tianhe; Li, Mengzhu; Yao, Xiaojing; Shao, Jing

    2015-01-01

    Urban-scale traffic monitoring plays a vital role in reducing traffic congestion. Owing to its low cost and wide coverage, floating car data (FCD) serves as a novel approach to collecting traffic data. However, sparse probe data represents the vast majority of the data available on arterial roads in most urban environments. In order to overcome the problem of data sparseness, this paper proposes a hidden Markov model (HMM)-based traffic estimation model, in which the traffic condition on a road segment is considered as a hidden state that can be estimated according to the conditions of road segments having similar traffic characteristics. An algorithm based on clustering and pattern mining rather than on adjacency relationships is proposed to find clusters with road segments having similar traffic characteristics. A multi-clustering strategy is adopted to achieve a trade-off between clustering accuracy and coverage. Finally, the proposed model is designed and implemented on the basis of a real-time algorithm. Results of experiments based on real FCD confirm the applicability, accuracy, and efficiency of the model. In addition, the results indicate that the model is practicable for traffic estimation on urban arterials and works well even when more than 70% of the probe data are missing. PMID:26710073

  16. Congestion control of high-speed networks

    NASA Astrophysics Data System (ADS)

    1993-06-01

    We report on four areas of activity in the past six months. These areas include the following: (1) work on the control of integrated video and image traffic, both at the access to a network and within a high-speed network; (2) more general/game theoretic models for flow control in networks; (3) work on fault management for high-speed heterogeneous networks to improve survivability; and (4) work on all-optical (lightwave) networks of the future, designed to take advantage of the enormous bandwidth capability available at optical frequencies.

  17. A Study of Control Plane Stability with Retry Traffic: Comparison of Hard- and Soft-State Protocols

    NASA Astrophysics Data System (ADS)

    Aida, Masaki; Takano, Chisa; Murata, Masayuki; Imase, Makoto

    Recently problems with commercial IP telephony systems have been reported one after another, in Japan. One of the important causes is congestion in the control plane. It has been recognized that with the current Internet it is important to control not only congestion caused by overload of the data plane but also congestion caused by overload of the control plane. In particular, “retry traffic,” such as repeated attempts to set up a connection, tends to cause congestion. In general, users make repeated attempt to set up connections not only when the data plane is congested but also when the control plane in the network is overloaded. The latter is caused by user behavior: an increase in the waiting time for the processing of connection establishment to be completed tends to increase his or her initiation of reattempts. Thus, it is important to manage both data plane and control-plane resources effectively. In this paper, we focus on RSVP-based communication services including IP telephony, and introduce a model that takes account of both data-plane and control-plane systems, and we examine the behavior of retry traffic. In addition, we compare the system stability achieved by two different resource management methods, the hard-state method and the soft-state method.

  18. Auction Mechanism to Allocate Air Traffic Control Slots

    NASA Technical Reports Server (NTRS)

    Raffarin, Marianne

    2003-01-01

    This article deals with an auction mechanism for airspace slots, as a means of solving the European airspace congestion problem. A disequilibrium, between Air Traffic Control (ATC) services supply and ATC services demand are at the origin of almost one fourth of delays in the air transport industry in Europe. In order to tackle this congestion problem, we suggest modifying both pricing and allocation of ATC services, by setting up an auction mechanism. Objects of the auction will be the right for airlines to cross a part of the airspace, and then to benefit from ATC services over a period corresponding to the necessary time for the crossing. Allocation and payment rules have to be defined according to the objectives of this auction. The auctioneer is the public authority in charge of ATC services, whose aim is to obtain an efficient allocation. Therefore, the social value will be maximized. Another objective is to internalize congestion costs. To that end, we apply the principle of Clarke-Groves mechanism auction: each winner has to pay the externalities imposed on other bidders. The complex context of ATC leads to a specific design for this auction.

  19. Characterization of Visual Scanning Patterns in Air Traffic Control

    PubMed Central

    McClung, Sarah N.; Kang, Ziho

    2016-01-01

    Characterization of air traffic controllers' (ATCs') visual scanning strategies is a challenging issue due to the dynamic movement of multiple aircraft and increasing complexity of scanpaths (order of eye fixations and saccades) over time. Additionally, terminologies and methods are lacking to accurately characterize the eye tracking data into simplified visual scanning strategies linguistically expressed by ATCs. As an intermediate step to automate the characterization classification process, we (1) defined and developed new concepts to systematically filter complex visual scanpaths into simpler and more manageable forms and (2) developed procedures to map visual scanpaths with linguistic inputs to reduce the human judgement bias during interrater agreement. The developed concepts and procedures were applied to investigating the visual scanpaths of expert ATCs using scenarios with different aircraft congestion levels. Furthermore, oculomotor trends were analyzed to identify the influence of aircraft congestion on scan time and number of comparisons among aircraft. The findings show that (1) the scanpaths filtered at the highest intensity led to more consistent mapping with the ATCs' linguistic inputs, (2) the pattern classification occurrences differed between scenarios, and (3) increasing aircraft congestion caused increased scan times and aircraft pairwise comparisons. The results provide a foundation for better characterizing complex scanpaths in a dynamic task and automating the analysis process. PMID:27239190

  20. Reducing transit bus emissions: Alternative fuels or traffic operations?

    NASA Astrophysics Data System (ADS)

    Alam, Ahsan; Hatzopoulou, Marianne

    2014-06-01

    In this study, we simulated the operations and greenhouse gas (GHG) emissions of transit buses along a busy corridor and quantified the effects of two different fuels (conventional diesel and compressed natural gas) as well as a set of driving conditions on emissions. Results indicate that compressed natural gas (CNG) reduces GHG emissions by 8-12% compared to conventional diesel, this reduction could increase to 16% with high levels of traffic congestion. However, the benefits of switching from conventional diesel to CNG are less apparent when the road network is uncongested. We also investigated the effects of bus operations on emissions by applying several strategies such as transit signal priority (TSP), queue jumper lanes, and relocation of bus stops. Results show that in congested conditions, TSP alone can reduce GHG emissions by 14% and when combined with improved technology; a reduction of 23% is achieved. The reduction benefits are even more apparent when other transit operational improvements are combined with TSP. Finally a sensitivity analysis was performed to investigate the effect of operational improvements on emissions under varying levels of network congestion. We observe that under “extreme congestion”, the benefits of TSP decrease.

  1. Characterization of Visual Scanning Patterns in Air Traffic Control.

    PubMed

    McClung, Sarah N; Kang, Ziho

    2016-01-01

    Characterization of air traffic controllers' (ATCs') visual scanning strategies is a challenging issue due to the dynamic movement of multiple aircraft and increasing complexity of scanpaths (order of eye fixations and saccades) over time. Additionally, terminologies and methods are lacking to accurately characterize the eye tracking data into simplified visual scanning strategies linguistically expressed by ATCs. As an intermediate step to automate the characterization classification process, we (1) defined and developed new concepts to systematically filter complex visual scanpaths into simpler and more manageable forms and (2) developed procedures to map visual scanpaths with linguistic inputs to reduce the human judgement bias during interrater agreement. The developed concepts and procedures were applied to investigating the visual scanpaths of expert ATCs using scenarios with different aircraft congestion levels. Furthermore, oculomotor trends were analyzed to identify the influence of aircraft congestion on scan time and number of comparisons among aircraft. The findings show that (1) the scanpaths filtered at the highest intensity led to more consistent mapping with the ATCs' linguistic inputs, (2) the pattern classification occurrences differed between scenarios, and (3) increasing aircraft congestion caused increased scan times and aircraft pairwise comparisons. The results provide a foundation for better characterizing complex scanpaths in a dynamic task and automating the analysis process. PMID:27239190

  2. Ant traffic rules.

    PubMed

    Fourcassié, Vincent; Dussutour, Audrey; Deneubourg, Jean-Louis

    2010-07-15

    Many animals take part in flow-like collective movements. In most species, however, the flow is unidirectional. Ants are one of the rare group of organisms in which flow-like movements are predominantly bidirectional. This adds to the difficulty of the task of maintaining a smooth, efficient movement. Yet, ants seem to fare well at this task. Do they really? And if so, how do such simple organisms succeed in maintaining a smooth traffic flow, when even humans experience trouble with this task? How does traffic in ants compare with that in human pedestrians or vehicles? The experimental study of ant traffic is only a few years old but it has already provided interesting insights into traffic organization and regulation in animals, showing in particular that an ant colony as a whole can be considered as a typical self-organized adaptive system. In this review we will show that the study of ant traffic can not only uncover basic principles of behavioral ecology and evolution in social insects but also provide new insights into the study of traffic systems in general. PMID:20581264

  3. A Hybrid Differential Invasive Weed Algorithm for Congestion Management

    NASA Astrophysics Data System (ADS)

    Basak, Aniruddha; Pal, Siddharth; Pandi, V. Ravikumar; Panigrahi, B. K.; Das, Swagatam

    This work is dedicated to solve the problem of congestion management in restructured power systems. Nowadays we have open access market which pushes the power system operation to their limits for maximum economic benefits but at the same time making the system more susceptible to congestion. In this regard congestion management is absolutely vital. In this paper we try to remove congestion by generation rescheduling where the cost involved in the rescheduling process is minimized. The proposed algorithm is a hybrid of Invasive Weed Optimization (IWO) and Differential Evolution (DE). The resultant hybrid algorithm was applied on standard IEEE 30 bus system and observed to beat existing algorithms like Simple Bacterial foraging (SBF), Genetic Algorithm (GA), Invasive Weed Optimization (IWO), Differential Evolution (DE) and hybrid algorithms like Hybrid Bacterial Foraging and Differential Evolution (HBFDE) and Adaptive Bacterial Foraging with Nelder Mead (ABFNM).

  4. Congestion Induced by the Structure of Multiplex Networks

    NASA Astrophysics Data System (ADS)

    Solé-Ribalta, Albert; Gómez, Sergio; Arenas, Alex

    2016-03-01

    Multiplex networks are representations of multilayer interconnected complex networks where the nodes are the same at every layer. They turn out to be good abstractions of the intricate connectivity of multimodal transportation networks, among other types of complex systems. One of the most important critical phenomena arising in such networks is the emergence of congestion in transportation flows. Here, we prove analytically that the structure of multiplex networks can induce congestion for flows that otherwise would be decongested if the individual layers were not interconnected. We provide explicit equations for the onset of congestion and approximations that allow us to compute this onset from individual descriptors of the individual layers. The observed cooperative phenomenon is reminiscent of Braess' paradox in which adding extra capacity to a network when the moving entities selfishly choose their route can in some cases reduce overall performance. Similarly, in the multiplex structure, the efficiency in transportation can unbalance the transportation loads resulting in unexpected congestion.

  5. 75 FR 22770 - National Electric Transmission Congestion Study

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-30

    ... is seeking comments on all aspects of the study. The full text of the 2009 Congestion Study is... in each area.\\2\\ \\1\\ See 71 FR 45047 (August 6, 2006). \\2\\ See 72 FR 56992 (October 5, 2007)....

  6. Autonomous Congestion Control in Delay-Tolerant Networks

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott; Jennings, Esther; Schoolcraft, Joshua

    2006-01-01

    This presentation highlights communication congestion control in delay-tolerant networks (DTNs). Large-scale future space exploration will offer complex communication challenges that may be best addressed by establishing a network infrastructure. However, current internet techniques for congestion control are not well suited for operation of a network over interplanetary distances. An alternative, delay-tolerant technique for congestion control in a delay-tolerant network is presented. A simple DTN was constructed and an experimental congestion control mechanism was applied. The mechanism appeared to be effective and each router was able to make its bundle acceptance decisions autonomously. Future research will examine more complex topologies and alternative bundle acceptance rules that might enhance performance.

  7. Congestion Induced by the Structure of Multiplex Networks.

    PubMed

    Solé-Ribalta, Albert; Gómez, Sergio; Arenas, Alex

    2016-03-11

    Multiplex networks are representations of multilayer interconnected complex networks where the nodes are the same at every layer. They turn out to be good abstractions of the intricate connectivity of multimodal transportation networks, among other types of complex systems. One of the most important critical phenomena arising in such networks is the emergence of congestion in transportation flows. Here, we prove analytically that the structure of multiplex networks can induce congestion for flows that otherwise would be decongested if the individual layers were not interconnected. We provide explicit equations for the onset of congestion and approximations that allow us to compute this onset from individual descriptors of the individual layers. The observed cooperative phenomenon is reminiscent of Braess' paradox in which adding extra capacity to a network when the moving entities selfishly choose their route can in some cases reduce overall performance. Similarly, in the multiplex structure, the efficiency in transportation can unbalance the transportation loads resulting in unexpected congestion. PMID:27015514

  8. Congestion Avoidance Testbed Experiments. Volume 2

    NASA Technical Reports Server (NTRS)

    Denny, Barbara A.; Lee, Diane S.; McKenney, Paul E., Sr.; Lee, Danny

    1994-01-01

    DARTnet provides an excellent environment for executing networking experiments. Since the network is private and spans the continental United States, it gives researchers a great opportunity to test network behavior under controlled conditions. However, this opportunity is not available very often, and therefore a support environment for such testing is lacking. To help remedy this situation, part of SRI's effort in this project was devoted to advancing the state of the art in the techniques used for benchmarking network performance. The second objective of SRI's effort in this project was to advance networking technology in the area of traffic control, and to test our ideas on DARTnet, using the tools we developed to improve benchmarking networks. Networks are becoming more common and are being used by more and more people. The applications, such as multimedia conferencing and distributed simulations, are also placing greater demand on the resources the networks provide. Hence, new mechanisms for traffic control must be created to enable their networks to serve the needs of their users. SRI's objective, therefore, was to investigate a new queueing and scheduling approach that will help to meet the needs of a large, diverse user population in a "fair" way.

  9. Temporal variation of traffic on highways and the development of accurate temporal allocation factors for air pollution analyses

    NASA Astrophysics Data System (ADS)

    Batterman, Stuart; Cook, Richard; Justin, Thomas

    2015-04-01

    Traffic activity encompasses the number, mix, speed and acceleration of vehicles on roadways. The temporal pattern and variation of traffic activity reflects vehicle use, congestion and safety issues, and it represents a major influence on emissions and concentrations of traffic-related air pollutants. Accurate characterization of vehicle flows is critical in analyzing and modeling urban and local-scale pollutants, especially in near-road environments and traffic corridors. This study describes methods to improve the characterization of temporal variation of traffic activity. Annual, monthly, daily and hourly temporal allocation factors (TAFs), which describe the expected temporal variation in traffic activity, were developed using four years of hourly traffic activity data recorded at 14 continuous counting stations across the Detroit, Michigan, U.S. region. Five sites also provided vehicle classification. TAF-based models provide a simple means to apportion annual average estimates of traffic volume to hourly estimates. The analysis shows the need to separate TAFs for total and commercial vehicles, and weekdays, Saturdays, Sundays and observed holidays. Using either site-specific or urban-wide TAFs, nearly all of the variation in historical traffic activity at the street scale could be explained; unexplained variation was attributed to adverse weather, traffic accidents and construction. The methods and results presented in this paper can improve air quality dispersion modeling of mobile sources, and can be used to evaluate and model temporal variation in ambient air quality monitoring data and exposure estimates.

  10. Temporal variation of traffic on highways and the development of accurate temporal allocation factors for air pollution analyses

    PubMed Central

    Batterman, Stuart; Cook, Richard; Justin, Thomas

    2015-01-01

    Traffic activity encompasses the number, mix, speed and acceleration of vehicles on roadways. The temporal pattern and variation of traffic activity reflects vehicle use, congestion and safety issues, and it represents a major influence on emissions and concentrations of traffic-related air pollutants. Accurate characterization of vehicle flows is critical in analyzing and modeling urban and local-scale pollutants, especially in near-road environments and traffic corridors. This study describes methods to improve the characterization of temporal variation of traffic activity. Annual, monthly, daily and hourly temporal allocation factors (TAFs), which describe the expected temporal variation in traffic activity, were developed using four years of hourly traffic activity data recorded at 14 continuous counting stations across the Detroit, Michigan, U.S. region. Five sites also provided vehicle classification. TAF-based models provide a simple means to apportion annual average estimates of traffic volume to hourly estimates. The analysis shows the need to separate TAFs for total and commercial vehicles, and weekdays, Saturdays, Sundays and observed holidays. Using either site-specific or urban-wide TAFs, nearly all of the variation in historical traffic activity at the street scale could be explained; unexplained variation was attributed to adverse weather, traffic accidents and construction. The methods and results presented in this paper can improve air quality dispersion modeling of mobile sources, and can be used to evaluate and model temporal variation in ambient air quality monitoring data and exposure estimates. PMID:25844042

  11. Exhaust Emissions Measured Under Real Traffic Conditions from Vehicles Fitted with Spark Ignition and Compression Ignition Engines

    NASA Astrophysics Data System (ADS)

    Merkisz, Jerzy; Lijewski, Piotr; Fuć, Paweł

    2011-06-01

    The tests performed under real traffic conditions provide invaluable information on the relations between the engine parameters, vehicle parameters and traffic conditions (traffic congestion) on one side and the exhaust emissions on the other. The paper presents the result of road tests obtained in an urban and extra-urban cycles for vehicles fitted with different engines, spark ignition engine and compression ignition engine. For the tests a portable emission analyzer SEMTECH DS. by SENSORS was used. This analyzer provides online measurement of the concentrations of exhaust emission components on a vehicle in motion under real traffic conditions. The tests were performed in city traffic. A comparative analysis has been presented of the obtained results for vehicles with individual powertrains.

  12. Phase transitions in traffic flow on multilane roads

    NASA Astrophysics Data System (ADS)

    Kerner, Boris S.; Klenov, Sergey L.

    2009-11-01

    Based on empirical and numerical analyses of vehicular traffic, the physics of spatiotemporal phase transitions in traffic flow on multilane roads is revealed. The complex dynamics of moving jams observed in single vehicle data measured by video cameras on American highways is explained by the nucleation-interruption effect in synchronized flow, i.e., the spontaneous nucleation of a narrow moving jam with the subsequent jam dissolution. We find that (i) lane changing, vehicle merging from on-ramps, and vehicle leaving to off-ramps result in different traffic phases—free flow, synchronized flow, and wide moving jams—occurring and coexisting in different road lanes as well as in diverse phase transitions between the traffic phases; (ii) in synchronized flow, the phase transitions are responsible for a non-regular moving jam dynamics that explains measured single vehicle data: moving jams emerge and dissolve randomly at various road locations in different lanes; (iii) the phase transitions result also in diverse expanded general congested patterns occurring at closely located bottlenecks.

  13. Controlling traffic jams by time modulating the safety distance

    NASA Astrophysics Data System (ADS)

    Gaididei, Yu. B.; Gorria, C.; Berkemer, R.; Kawamoto, A.; Shiga, T.; Christiansen, P. L.; Sørensen, M. P.; Starke, J.

    2013-10-01

    The possibility of controlling traffic dynamics by applying high-frequency time modulation of traffic flow parameters is studied. It is shown that the region of the car density where the uniform (free) flow is unstable changes in the presence of time modulation compared with the unmodulated case. This region shrinks when the speed-up of cars does not exceed some critical value and expands in the opposite case. The flux of the time-modulated flow is an increasing function of the amplitude of the modulation for traffic flows whose density is larger than 1/h where h is the safety distance in the nonmodulated case, while it is a decreasing function in the opposite case. In other words, the safety distance time modulation facilitates car propagation in the case when the mean distance between cars in the congestive traffic is less than h and hinders it when the neighboring cars in the flow are well separated. A link between a microscopic description and the macroscopic fundamental diagram is established.

  14. Stability analysis of traffic flow with extended CACC control models

    NASA Astrophysics Data System (ADS)

    Ya-Zhou, Zheng; Rong-Jun, Cheng; Siu-Ming, Lo; Hong-Xia, Ge

    2016-06-01

    To further investigate car-following behaviors in the cooperative adaptive cruise control (CACC) strategy, a comprehensive control system which can handle three traffic conditions to guarantee driving efficiency and safety is designed by using three CACC models. In this control system, some vital comprehensive information, such as multiple preceding cars’ speed differences and headway, variable safety distance (VSD) and time-delay effect on the traffic current and the jamming transition have been investigated via analytical or numerical methods. Local and string stability criterion for the velocity control (VC) model and gap control (GC) model are derived via linear stability theory. Numerical simulations are conducted to study the performance of the simulated traffic flow. The simulation results show that the VC model and GC model can improve driving efficiency and suppress traffic congestion. Project supported by the National Natural Science Foundation of China (Grant Nos. 71571107 and 11302110). The Scientific Research Fund of Zhejiang Province, China (Grant Nos. LY15A020007, LY15E080013, and LY16G010003). The Natural Science Foundation of Ningbo City (Grant Nos. 2014A610030 and 2015A610299), the Fund from the Government of the Hong Kong Administrative Region, China (Grant No. CityU11209614), and the K C Wong Magna Fund in Ningbo University, China.

  15. Improving traffic flow at a 2-to-1 lane reduction with wirelessly connected, adaptive cruise control vehicles

    NASA Astrophysics Data System (ADS)

    Davis, L. C.

    2016-06-01

    Wirelessly connected vehicles that exchange information about traffic conditions can reduce delays caused by congestion. At a 2-to-1 lane reduction, the improvement in flow past a bottleneck due to traffic with a random mixture of 40% connected vehicles is found to be 52%. Control is based on connected-vehicle-reported velocities near the bottleneck. In response to indications of congestion the connected vehicles, which are also adaptive cruise control vehicles, reduce their speed in slowdown regions. Early lane changes of manually driven vehicles from the terminated lane to the continuous lane are induced by the slowing connected vehicles. Self-organized congestion at the bottleneck is thus delayed or eliminated, depending upon the incoming flow magnitude. For the large majority of vehicles, travel times past the bottleneck are substantially reduced. Control is responsible for delaying the onset of congestion as the incoming flow increases. Adaptive cruise control increases the flow out of the congested state at the bottleneck. The nature of the congested state, when it occurs, appears to be similar under a variety of conditions. Typically 80-100 vehicles are approximately equally distributed between the lanes in the 500 m region prior to the end of the terminated lane. Without the adaptive cruise control capability, connected vehicles can delay the onset of congestion but do not increase the asymptotic flow past the bottleneck. Calculations are done using the Kerner-Klenov three-phase theory, stochastic discrete-time model for manual vehicles. The dynamics of the connected vehicles is given by a conventional adaptive cruise control algorithm plus commanded deceleration. Because time in the model for manual vehicles is discrete (one-second intervals), it is assumed that the acceleration of any vehicle immediately in front of a connected vehicle is constant during the time interval, thereby preserving the computational simplicity and speed of a discrete-time model.

  16. Atrial Fibrillation, Congestive Heart Failure, and the Middle Cerebral Artery.

    PubMed

    Ameriso, S F; Sager, P; Fisher, M

    1992-10-01

    Atrial fibrillation and congestive heart failure are risk factors for ischemic stroke usually attributed to cardiac embolism. To define potential alternative mechanisms, patients with atrial fibrillation and congestive heart failure were investigated by transcranial Doppler. Middle cerebral artery (MCA) blood flow velocities were analyzed in neurologically asymptomatic patients with nonvalvular (n = 10) and valvular (n = 13) atrial fibrillation, patients in normal sinus rhythm with congestive heart failure (n = 13), and control subjects (n = 11). Compared to patients in sinus rhythm with congestive heart failure and to control subjects, patients in both atrial fibrillation groups had significantly greater beat-to-beat variation in peak, mean, and diastolic velocities and in pulsatility index. Peak, mean, and diastolic MCA velocities in patients with atrial fibrillation and those with congestive heart failure were significantly less than those in control subjects. Patients with nonvalvular atrial fibrillation had a higher pulsatility index compared to each of the other three groups. These findings demonstrate substantial nonemboligenic alterations of the intracranial circulation associated with atrial fibrillation and congestive heart failure, and also provide an intracranial hemodynamic profile that may distinguish valvular from nonvalvular atrial fibrillation. PMID:27309151

  17. Environmentally reformed travel habits during the 2006 congestion charge trial in Stockholm--a qualitative study.

    PubMed

    Henriksson, Greger; Hagman, Olle; Andréasson, Håkan

    2011-08-01

    Policy measures that reduce or replace road traffic can improve environmental conditions in most large cities. In Stockholm a congestion charge was introduced during a test period in 2006. This was a full-scale trial that proved to meet its targets by reducing traffic crossing the inner city segment during rush hours by 20%. Emissions of carbon dioxide and particles were also substantially reduced. This study, based on in-depth interviews with 40 inhabitants, analyses how and why new travel habits emerged. The results show that particular, sometimes unexpected, features of everyday life (habits, resources, opportunities, values, etc.) were crucial for adjustment of travel behaviour in relation to the policy instrument. One example was that those accustomed to mixing different modes of transport on a daily basis more easily adapted their travel in the targeted way. On a more general level, the results revealed that the policy measure could actually tip the scales for the individual towards trying out a new behaviour. PMID:21909301

  18. Environmentally Reformed Travel Habits During the 2006 Congestion Charge Trial in Stockholm—A Qualitative Study

    PubMed Central

    Henriksson, Greger; Hagman, Olle; Andréasson, Håkan

    2011-01-01

    Policy measures that reduce or replace road traffic can improve environmental conditions in most large cities. In Stockholm a congestion charge was introduced during a test period in 2006. This was a full-scale trial that proved to meet its targets by reducing traffic crossing the inner city segment during rush hours by 20%. Emissions of carbon dioxide and particles were also substantially reduced. This study, based on in-depth interviews with 40 inhabitants, analyses how and why new travel habits emerged. The results show that particular, sometimes unexpected, features of everyday life (habits, resources, opportunities, values, etc.) were crucial for adjustment of travel behaviour in relation to the policy instrument. One example was that those accustomed to mixing different modes of transport on a daily basis more easily adapted their travel in the targeted way. On a more general level, the results revealed that the policy measure could actually tip the scales for the individual towards trying out a new behaviour. PMID:21909301

  19. Impact of Distracted Driving on Safety and Traffic Flow

    PubMed Central

    Stavrinos, Despina; Jones, Jennifer L.; Garner, Annie A.; Griffin, Russell; Franklin, Crystal A.; Ball, David; Welburn, Sharon C.; Ball, Karlene K.; Sisiopiku, Virginia P.; Fine, Philip R.

    2015-01-01

    Studies have documented a link between distracted driving and diminished safety; however, an association between distracted driving and traffic congestion has not been investigated in depth. The present study examined the behavior of teens and young adults operating a driving simulator while engaged in various distractions (i.e., cell phone, texting, and undistracted) and driving conditions (i.e., free flow, stable flow, and oversaturation). Seventy five participants 16 to 25 years of age (split into 2 groups: novice drivers and young adults) drove a STISIM simulator three times, each time with one of three randomly presented distractions. Each drive was designed to represent daytime scenery on a 4 lane divided roadway and included three equal roadway portions representing Levels of Service (LOS) A, C, and E as defined in the 2000 Highway Capacity Manual. Participants also completed questionnaires documenting demographics and driving history. Both safety and traffic flow related driving outcomes were considered. A Repeated Measures Multivariate Analysis of Variance was employed to analyze continuous outcome variables and a Generalized Estimate Equation (GEE) poisson model was used to analyze count variables. Results revealed that, in general more lane deviations and crashes occurred during texting. Distraction (in most cases, text messaging) had a significantly negative impact on traffic flow, such that participants exhibited greater fluctuation in speed, changed lanes significantly fewer times, and took longer to complete the scenario. In turn, more simulated vehicles passed the participant drivers while they were texting or talking on a cell phone than while undistracted. The results indicate that distracted driving, particularly texting, may lead to reduced safety and traffic flow, thus having a negative impact on traffic operations. No significant differences were detected between age groups, suggesting that all drivers, regardless of age, may drive in a manner

  20. Impact of distracted driving on safety and traffic flow.

    PubMed

    Stavrinos, Despina; Jones, Jennifer L; Garner, Annie A; Griffin, Russell; Franklin, Crystal A; Ball, David; Welburn, Sharon C; Ball, Karlene K; Sisiopiku, Virginia P; Fine, Philip R

    2013-12-01

    Studies have documented a link between distracted driving and diminished safety; however, an association between distracted driving and traffic congestion has not been investigated in depth. The present study examined the behavior of teens and young adults operating a driving simulator while engaged in various distractions (i.e., cell phone, texting, and undistracted) and driving conditions (i.e., free flow, stable flow, and oversaturation). Seventy five participants 16-25 years of age (split into 2 groups: novice drivers and young adults) drove a STISIM simulator three times, each time with one of three randomly presented distractions. Each drive was designed to represent daytime scenery on a 4 lane divided roadway and included three equal roadway portions representing Levels of Service (LOS) A, C, and E as defined in the 2000 Highway Capacity Manual. Participants also completed questionnaires documenting demographics and driving history. Both safety and traffic flow related driving outcomes were considered. A Repeated Measures Multivariate Analysis of Variance was employed to analyze continuous outcome variables and a Generalized Estimate Equation (GEE) Poisson model was used to analyze count variables. Results revealed that, in general more lane deviations and crashes occurred during texting. Distraction (in most cases, text messaging) had a significantly negative impact on traffic flow, such that participants exhibited greater fluctuation in speed, changed lanes significantly fewer times, and took longer to complete the scenario. In turn, more simulated vehicles passed the participant drivers while they were texting or talking on a cell phone than while undistracted. The results indicate that distracted driving, particularly texting, may lead to reduced safety and traffic flow, thus having a negative impact on traffic operations. No significant differences were detected between age groups, suggesting that all drivers, regardless of age, may drive in a manner

  1. Virginia's traffic management system

    SciTech Connect

    Morris, J.; Marber, S. )

    1992-07-01

    This paper reports that Northern Virginia, like most other urban areas, faces the challenge of moving more and more vehicles on roads that are already overloaded. Traffic in Northern Virginia is continually increasing, but the development surrounding Interstate 395, 495, and 66 makes little room available for roadway expansion. Even if land were unlimited, the strict requirement of the Clean Air Act make building roads difficult. This paper reports that ensuring the most efficient use of the interstate highways is the goal of the Virginia Department of Transportation's (VDOT's) traffic management system (TMS). TMS is a computerized highway surveillance and control system that monitors 30 interstate miles on I-395, I-495, and I-66. The system helps squeeze the most use from these interstates by detecting and helping clear accidents or disabled vehicles and by smoothing traffic flow. TMS spots and helps clear an average of two incidents a day and prevents accidents caused by erratic traffic flow from ramps onto the main line. For motorists, these TMS functions translate into decreased travel time, vehicle operating costs, and air pollution. VDOT's TMS is the foundation for the intelligent vehicle-highway systems of tomorrow. It employs several elements that work together to improve traffic flow.

  2. Traffic air quality index.

    PubMed

    Bagieński, Zbigniew

    2015-02-01

    Vehicle emissions are responsible for a considerable share of urban air pollution concentrations. The traffic air quality index (TAQI) is proposed as a useful tool for evaluating air quality near roadways. The TAQI associates air quality with the equivalent emission from traffic sources and with street structure (roadway structure) as anthropogenic factors. The paper presents a method of determining the TAQI and defines the degrees of harmfulness of emitted pollution. It proposes a classification specifying a potential threat to human health based on the TAQI value and shows an example of calculating the TAQI value for real urban streets. It also considers the role that car traffic plays in creating a local UHI. PMID:25461063

  3. Gust alleviation - Criteria and control laws

    NASA Technical Reports Server (NTRS)

    Rynaski, E. G.

    1979-01-01

    The relationships between criteria specified for aircraft gust alleviation and the form of the control laws that result from the criteria are considered. Open-loop gust alleviation based on the linearized, small perturbation equations of aircraft motion is discussed, and an approximate solution of the open-loop control law is presented for the case in which the number of degrees of freedom of the aircraft exceeds the rank of the control effectiveness matrix. Excessive actuator lag is compensated for by taking into account actuator dynamics in the equations of motion, resulting in the specification of a general load network. Criteria for gust alleviation when output motions are gust alleviated and the closed-loop control law derived from them are examined and linear optimal control law is derived. Comparisons of the control laws reveal that the effectiveness of an open-loop control law is greatest at low aircraft frequencies but deteriorates as the natural frequency of the actuators is approached, while closed-loop methods are found to be more effective at higher frequencies.

  4. Lightweight, Economical Device Alleviates Drop Foot

    NASA Technical Reports Server (NTRS)

    Deis, B. C.

    1983-01-01

    Corrective apparatus alleviates difficulties in walking for victims of drop foot. Elastic line attached to legband provides flexible support to toe of shoe. Device used with flat (heelless) shoes, sneakers, crepe-soled shoes, canvas shoes, and many other types of shoes not usable with short leg brace.

  5. Dynamic routing control in heterogeneous tactical networks with multiple traffic priorities

    NASA Astrophysics Data System (ADS)

    Fecko, Mariusz A.; Wong, Larry; Kang, Jaewong; Cichocki, Andrzej; Kaul, Vikram; Samtani, Sunil

    2012-05-01

    To efficiently use alternate paths during periods of congestion, we have devised prioritized Dynamic Routing Control Agent (pDRCA) that (1) selects best links to meet the bandwidth and delay requirements of traffic, (2) provides load-balancing and traffic prioritization when multiple topologies are available, and (3) handles changes in link quality and traffic demand, and link outages. pDRCA provides multiplatform load balancing to maximize SATCOM (both P2P and multi-point) and airborne links utilization. It influences link selection by configuring the cost metrics on a router's interface, which does not require any changes to the routing protocol itself. It supports service differentiation of multiple traffic priorities by providing more network resources to the highest priority flows. pDRCA does so by solving an optimization problem to find optimal links weights that increase throughput and decrease E2E delay; avoid congested, low quality, and long delay links; and exploit path diversity in the network. These optimal link weights are sent to the local agents to be configured on individual routers per traffic priority. The pDRCA optimization algorithm has been proven effective in improving application performance. We created a variety of different test scenarios by varying traffic profile and link behavior (stable links, varying capacity, and link outages). In the scenarios where high priority traffic experienced significant loss without pDRCA, the average loss was reduced from 49.5% to 13% and in some cases dropped to 0%. Currently, pDRCA is integrated with an open-source software router and priority queues on Linux as a component of Open Tactical Router (OTR), which is being developed by ONR DTCN program.

  6. Order and disorder in traffic and self-driven many-particle systems

    NASA Astrophysics Data System (ADS)

    Helbing, Dirk

    2002-07-01

    During the last decade, physicists have identified various spatio-temporal patterns of motion in vehicle and pedestrian traffic. Moreover, by applying and extending methods from statistical physics and non-linear dynamics, these have been successfully explained by means of self-driven many-particle models. Some of the questions now understood are the following: Why are vehicles sometimes stopped by so-called "phantom traffic jams," although they all like to drive fast? What are the mechanisms behind stop-and-go traffic? Why are there several different kinds of congestion, and how are they related? Why do most traffic jams occur considerably before the road capacity is reached? Can a temporary reduction of the traffic volume cause a lasting traffic jam? What is the origin of fluctuations in traffic systems and which consequences do they have? Why do pedestrians moving in opposite directions normally organize in lanes, while nervous crowds are "freezing by heating?" Why do panicking pedestrians produce dangerous deadlocks?

  7. Quality of congestive heart failure care

    PubMed Central

    Maddocks, Heather; Marshall, J. Neil; Stewart, Moira; Terry, Amanda L.; Cejic, Sonny; Hammond, Jo-Anne; Jordan, John; Chevendra, Vijaya; Denomme, Louisa Bestard; Thind, Amardeep

    2010-01-01

    ABSTRACT OBJECTIVE To study the feasibility of using electronic medical record (EMR) data from the Deliver Primary Healthcare Information (DELPHI) database to measure quality of care for patients with congestive heart failure (CHF) in primary care and to determine the percentage of patients with CHF receiving the recommended care. DESIGN Items listed on the Ontario Ministry of Health and Long-Term Care Heart Failure Patient Care Flow Sheet (CHF flow sheet) were assessed and measured using EMRs of patients diagnosed with CHF between October 1, 2005, and September 30, 2008. SETTING Ten primary health care practices in southwestern Ontario. PARTICIPANTS Four hundred eighty-eight patients who were considered to have CHF because at least 1 of the following was indicated in their EMRs: an International Classification of Diseases billing code for CHF (category 428), an International Classification of Primary Care diagnosis code for heart failure (ie, K77), or “CHF” reported on the problem list. MAIN OUTCOME MEASURES Number of CHF flow sheet items that were measurable using EMR data from the DELPHI database. Percentage of patients with CHF receiving required quality-of-care items since the date of diagnosis. RESULTS The DELPHI database contained information on 60 (65.9%) of the 91 items identified using the CHF flow sheet. The recommended tests and procedures were recorded infrequently: 55.5% of patients with CHF had chest radiographs; 32.6% had electrocardiograms; 32.2% had echocardiograms; 30.5% were prescribed angiotensin-converting enzyme inhibitors; 20.9% were prescribed β-blockers; and 15.8% were prescribed angiotensin II receptor blockers. CONCLUSION Low frequencies of recommended care items for patients with CHF were recorded in the EMR. Physicians explained that CHF care was documented in areas of the EMR that contained patient identifiers, such as the encounter notes, and was therefore not part of the DELPHI database. Extractable information from the EMR

  8. Water and Sodium in Heart Failure: A Spotlight on Congestion

    PubMed Central

    Greene, Stephen J.; Torres, Daniele; Alderman, Michael; Bonventre, Joseph Vincent; Di Pasquale, Pietro; Gargani, Luna; Nohria, Anju; Fonarow, Gregg C.; Vaduganathan, Muthiah; Butler, Javed; Paterna, Salvatore; Stevenson, Lynne Warner; Gheorghiade, Mihai

    2015-01-01

    Despite all available therapies, the rates of hospitalization and death from heart failure (HF) remain unacceptably high. The most common reasons for hospital admission are symptoms related to congestion. During hospitalization, most patients respond well to standard therapy and are discharged with significantly improved symptoms. Post-discharge, many patients receive diligent and frequent follow-up. However, rehospitalization rates remain high. One potential explanation is a persistent failure by clinicians to adequately manage congestion in the outpatient setting. The failure to successfully manage these patients post-discharge may represent an unmet need to improve the way congestion is both recognized and treated. A primary aim of future HF management may be to improve clinical surveillance to prevent and manage chronic fluid overload while simultaneously maximizing the use of evidence-based therapies with proven long-term benefit. Improvement in cardiac function is the ultimate goal and maintenance of a “dry” clinical profile is important to prevent hospital admission and improve prognosis. This paper focuses on methods for monitoring congestion, and strategies for water and sodium management in the context of the complex interplay between the cardiac and renal systems. A rationale for improving recognition and treatment of congestion is also proposed. PMID:24942806

  9. The Classroom Traffic Jam

    ERIC Educational Resources Information Center

    Edwards, Arthur W.

    1977-01-01

    The importance of energy conservation is developed in this simulation. Children draw an automobile and then are asked to drive it through the classroom roadways. When a traffic jam results, students offer ways to eliminate it. The importance of mass transportation and car pools is stressed by the teacher. (MA)

  10. Surface Traffic Management Research

    NASA Technical Reports Server (NTRS)

    Jung, Yoo Chul

    2012-01-01

    This presentation discusses an overview of the surface traffic management research conducted by NASA Ames. The concept and human-in-the-loop simulation of the Spot and Runway Departure Advisor (SARDA), an integrated decision support tool for the tower controllers and airline ramp operators, is also discussed.

  11. Pedestrians. Traffic Safety Facts, 2000.

    ERIC Educational Resources Information Center

    National Highway Traffic Safety Administration (DOT), Washington, DC.

    This document provides statistical information on U.S. traffic accidents involving pedestrians. Data tables include: (1) trends in pedestrian and total traffic fatalities, 1990-2000; (2) pedestrians killed and injured, by age group, 2000; (3) non-occupant traffic fatalities, 1990-2000; (4) pedestrian fatalities, by time of day and day of week,…

  12. Traffic Safety Facts, 2001: Pedestrians.

    ERIC Educational Resources Information Center

    National Highway Traffic Safety Administration (DOT), Washington, DC.

    This document provides statistical information on U.S. traffic accidents involving pedestrians. Data tables include: (1) trends in pedestrian and total traffic fatalities, 1991-2001; (2) pedestrians killed and injured, by age group, 2001; (3) non-occupant traffic fatalities, 1991-2001; (4) pedestrian fatalities, by time of day and day of week,…

  13. On-board closed-loop congestion control for satellite based packet switching networks

    NASA Technical Reports Server (NTRS)

    Chu, Pong P.; Ivancic, William D.; Kim, Heechul

    1993-01-01

    NASA LeRC is currently investigating a satellite architecture that incorporates on-board packet switching capability. Because of the statistical nature of packet switching, arrival traffic may fluctuate and thus it is necessary to integrate congestion control mechanism as part of the on-board processing unit. This study focuses on the closed-loop reactive control. We investigate the impact of the long propagation delay on the performance and propose a scheme to overcome the problem. The scheme uses a global feedback signal to regulate the packet arrival rate of ground stations. In this scheme, the satellite continuously broadcasts the status of its output buffer and the ground stations respond by selectively discarding packets or by tagging the excessive packets as low-priority. The two schemes are evaluated by theoretical queuing analysis and simulation. The former is used to analyze the simplified model and to determine the basic trends and bounds, and the later is used to assess the performance of a more realistic system and to evaluate the effectiveness of more sophisticated control schemes. The results show that the long propagation delay makes the closed-loop congestion control less responsive. The broadcasted information can only be used to extract statistical information. The discarding scheme needs carefully-chosen status information and reduction function, and normally requires a significant amount of ground discarding to reduce the on-board packet loss probability. The tagging scheme is more effective since it tolerates more uncertainties and allows a larger margin of error in status information. It can protect the high-priority packets from excessive loss and fully utilize the downlink bandwidth at the same time.

  14. On-board closed-loop congestion control for satellite based packet switching networks

    NASA Astrophysics Data System (ADS)

    Chu, Pong P.; Ivancic, William D.; Kim, Heechul

    1993-12-01

    NASA LeRC is currently investigating a satellite architecture that incorporates on-board packet switching capability. Because of the statistical nature of packet switching, arrival traffic may fluctuate and thus it is necessary to integrate congestion control mechanism as part of the on-board processing unit. This study focuses on the closed-loop reactive control. We investigate the impact of the long propagation delay on the performance and propose a scheme to overcome the problem. The scheme uses a global feedback signal to regulate the packet arrival rate of ground stations. In this scheme, the satellite continuously broadcasts the status of its output buffer and the ground stations respond by selectively discarding packets or by tagging the excessive packets as low-priority. The two schemes are evaluated by theoretical queuing analysis and simulation. The former is used to analyze the simplified model and to determine the basic trends and bounds, and the later is used to assess the performance of a more realistic system and to evaluate the effectiveness of more sophisticated control schemes. The results show that the long propagation delay makes the closed-loop congestion control less responsive. The broadcasted information can only be used to extract statistical information. The discarding scheme needs carefully-chosen status information and reduction function, and normally requires a significant amount of ground discarding to reduce the on-board packet loss probability. The tagging scheme is more effective since it tolerates more uncertainties and allows a larger margin of error in status information. It can protect the high-priority packets from excessive loss and fully utilize the downlink bandwidth at the same time.

  15. Characterizing Longitude-Dependent Orbital Debris Congestion in the Geosynchronous Orbit Regime

    NASA Astrophysics Data System (ADS)

    Anderson, Paul V.

    The geosynchronous orbit (GEO) is a unique commodity of the satellite industry that is becoming increasingly contaminated with orbital debris, but is heavily populated with high-value assets from the civil, commercial, and defense sectors. The GEO arena is home to hundreds of communications, data transmission, and intelligence satellites collectively insured for an estimated 18.3 billion USD. As the lack of natural cleansing mechanisms at the GEO altitude renders the lifetimes of GEO debris essentially infinite, conjunction and risk assessment must be performed to safeguard operational assets from debris collisions. In this thesis, longitude-dependent debris congestion is characterized by predicting the number of near-miss events per day for every longitude slot at GEO, using custom debris propagation tools and a torus intersection metric. Near-miss events with the present-day debris population are assigned risk levels based on GEO-relative position and speed, and this risk information is used to prioritize the population for debris removal target selection. Long-term projections of debris growth under nominal launch traffic, mitigation practices, and fragmentation events are also discussed, and latitudinal synchronization of the GEO debris population is explained via node variations arising from luni-solar gravity. In addition to characterizing localized debris congestion in the GEO ring, this thesis further investigates the conjunction risk to operational satellites or debris removal systems applying low-thrust propulsion to raise orbit altitude at end-of-life to a super-synchronous disposal orbit. Conjunction risks as a function of thrust level, miss distance, longitude, and semi-major axis are evaluated, and a guidance method for evading conjuncting debris with continuous thrust by means of a thrust heading change via single-shooting is developed.

  16. On the Inefficiency of Equilibria in Linear Bottleneck Congestion Games

    NASA Astrophysics Data System (ADS)

    de Keijzer, Bart; Schäfer, Guido; Telelis, Orestis A.

    We study the inefficiency of equilibrium outcomes in bottleneck congestion games. These games model situations in which strategic players compete for a limited number of facilities. Each player allocates his weight to a (feasible) subset of the facilities with the goal to minimize the maximum (weight-dependent) latency that he experiences on any of these facilities. We derive upper and (asymptotically) matching lower bounds on the (strong) price of anarchy of linear bottleneck congestion games for a natural load balancing social cost objective (i.e., minimize the maximum latency of a facility). We restrict our studies to linear latency functions. Linear bottleneck congestion games still constitute a rich class of games and generalize, for example, load balancing games with identical or uniformly related machines with or without restricted assignments.

  17. Stochastic Model of Traffic Jam and Traffic Signal Control

    NASA Astrophysics Data System (ADS)

    Shin, Ji-Sun; Cui, Cheng-You; Lee, Tae-Hong; Lee, Hee-Hyol

    Traffic signal control is an effective method to solve the traffic jam. and forecasting traffic density has been known as an important part of the Intelligent Transportation System (ITS). The several methods of the traffic signal control are known such as random walk method, Neuron Network method, Bayesian Network method, and so on. In this paper, we propose a new method of a traffic signal control using a predicted distribution of traffic jam based on a Dynamic Bayesian Network model. First, a forecasting model to predict a probabilistic distribution of the traffic jam during each period of traffic lights is built. As the forecasting model, the Dynamic Bayesian Network is used to predict the probabilistic distribution of a density of the traffic jam. According to measurement of two crossing points for each cycle, the inflow and outflow of each direction and the number of standing vehicles at former cycle are obtained. The number of standing vehicle at k-th cycle will be calculated synchronously. Next, the probabilistic distribution of the density of standing vehicle in each cycle will be predicted using the Dynamic Bayesian Network constructed for the traffic jam. And then a control rule to adjust the split and the cycle to increase the probability between a lower limit and ceiling of the standing vehicles is deduced. As the results of the simulation using the actual traffic data of Kitakyushu city, the effectiveness of the method is shown.

  18. Principled negotiation and distributed optimization for advanced air traffic management

    NASA Astrophysics Data System (ADS)

    Wangermann, John Paul

    Today's aircraft/airspace system faces complex challenges. Congestion and delays are widespread as air traffic continues to grow. Airlines want to better optimize their operations, and general aviation wants easier access to the system. Additionally, the accident rate must decline just to keep the number of accidents each year constant. New technology provides an opportunity to rethink the air traffic management process. Faster computers, new sensors, and high-bandwidth communications can be used to create new operating models. The choice is no longer between "inflexible" strategic separation assurance and "flexible" tactical conflict resolution. With suitable operating procedures, it is possible to have strategic, four-dimensional separation assurance that is flexible and allows system users maximum freedom to optimize operations. This thesis describes an operating model based on principled negotiation between agents. Many multi-agent systems have agents that have different, competing interests but have a shared interest in coordinating their actions. Principled negotiation is a method of finding agreement between agents with different interests. By focusing on fundamental interests and searching for options for mutual gain, agents with different interests reach agreements that provide benefits for both sides. Using principled negotiation, distributed optimization by each agent can be coordinated leading to iterative optimization of the system. Principled negotiation is well-suited to aircraft/airspace systems. It allows aircraft and operators to propose changes to air traffic control. Air traffic managers check the proposal maintains required aircraft separation. If it does, the proposal is either accepted or passed to agents whose trajectories change as part of the proposal for approval. Aircraft and operators can use all the data at hand to develop proposals that optimize their operations, while traffic managers can focus on their primary duty of ensuring

  19. Gust Alleviation Using Direct Gust Measurement

    NASA Technical Reports Server (NTRS)

    Hoppe, Sven Marco

    2000-01-01

    The increasing competition in the market of civil aircraft leads to operating efficiency and passenger comfort being very important sales arguments. Continuous developments in jet propulsion technology helped to reduce energy consumption, as well as noise and vibrations due to the engines. The main problem with respect to ride comfort is, however, the transmittance of accelerations and jerkiness imposed by atmospheric turbulence from the wings to the fuselage. This 'gust' is also a design constraint: Light airplane structures help to save, energy, but are more critical to resist the loads imposed by turbulence. For both reasons, efficient gust alleviation is necessary to improve the performance of modern aircraft. Gust can be seen as a change in the angle of attack or as an additional varying vertical component of the headwind. The effect of gust can be very strong, since the same aerodynamic forces that keep the airplane flying are involved. Event though the frequency range of those changes is quite low, it is impossible for the pilot to alleviate gust manually. Besides, most of the time during the flight, the, autopilot maintains course and the attitude of flight. Certainly, most autopilots should be capable of damping the roughest parts of turbulence, but they are unable to provide satisfactory results in that field. A promising extension should be the application of subsidiary, control, where the inner (faster) control loop alleviates turbulence and the outer (slower) loop controls the attitude of flight. Besides the mentioned ride comfort, another reason for gust alleviation with respect to the fuselage is the sensibility of electrical devices to vibration and high values of acceleration. Many modern airplane designs--especially inherently instable military aircraft--are highly dependent on avionics. The lifetime and the reliability of these systems is thus essential.

  20. Self-organized lane formation and optimized traffic flow in army ants.

    PubMed

    Couzin, I D; Franks, N R

    2003-01-22

    We show how the movement rules of individual ants on trails can lead to a collective choice of direction and the formation of distinct traffic lanes that minimize congestion. We develop and evaluate the results of a new model with a quantitative study of the behaviour of the army ant Eciton burchelli. Colonies of this species have up to 200 000 foragers and transport more than 3000 prey items per hour over raiding columns that exceed 100 m. It is an ideal species in which to test the predictions of our model because it forms pheromone trails that are densely populated with very swift ants. The model explores the influences of turning rates and local perception on traffic flow. The behaviour of real army ants is such that they occupy the specific region of parameter space in which lanes form and traffic flow is maximized. PMID:12590751

  1. Research on urban public traffic network with multi-weights based on single bus transfer junction

    NASA Astrophysics Data System (ADS)

    An, Xin-lei; Zhang, Li; Zhang, Jian-gang

    2015-10-01

    Regarding single bus transfer junction as a research object, this paper constructs the urban traffic network models with multi-weights taking different bus lines in bus transfer junction as the network nodes, that is, the urban traffic network with multi-weights is given different properties weights at every edge. According to the method of network split, the complex network with multi-weights is split into several different single weighted complex networks. Then, we study the global synchronization of the new network model by changing congestion degrees, transfers coefficient and passenger flow density between different bus lines. Finally, analytical and simulated results are given to show the impact of different properties weights to the public traffic network balance.

  2. Development of simulation techniques suitable for the analysis of air traffic control situations and instrumentation

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A terminal area simulation is described which permits analysis and synthesis of current and advanced air traffic management system configurations including ground and airborne instrumentation and new and modified aircraft characteristics. Ground elements in the simulation include navigation aids, surveillance radars, communication links, air-route structuring, ATC procedures, airport geometries and runway handling constraints. Airborne elements include traffic samples with individual aircraft performance and operating characteristics and aircraft navigation equipment. The simulation also contains algorithms for conflict detection, conflict resolution, sequencing and pilot-controller data links. The simulation model is used to determine the sensitivities of terminal area traffic flow, safety and congestion to aircraft performance characteristics, avionics systems, and other ATC elements.

  3. Traffic-driven epidemic outbreak on complex networks: How long does it take?

    NASA Astrophysics Data System (ADS)

    Yang, Han-Xin; Wang, Wen-Xu; Lai, Ying-Cheng

    2012-12-01

    Recent studies have suggested the necessity to incorporate traffic dynamics into the process of epidemic spreading on complex networks, as the former provides support for the latter in many real-world situations. While there are results on the asymptotic scope of the spreading dynamics, the issue of how fast an epidemic outbreak can occur remains outstanding. We observe numerically that the density of the infected nodes exhibits an exponential increase with time initially, rendering definable a characteristic time for the outbreak. We then derive a formula for scale-free networks, which relates this time to parameters characterizing the traffic dynamics and the network structure such as packet-generation rate and betweenness distribution. The validity of the formula is tested numerically. Our study indicates that increasing the average degree and/or inducing traffic congestion can slow down the spreading process significantly.

  4. Energy conservation in ad hoc multimedia networks using traffic-shaping mechanisms

    NASA Astrophysics Data System (ADS)

    Chandra, Surendar

    2003-12-01

    In this work, we explore network traffic shaping mechanisms that deliver packets at pre-determined intervals; allowing the network interface to transition to a lower power consuming sleep state. We focus our efforts on commodity devices, IEEE 802.11b ad hoc mode and popular streaming formats. We argue that factors such as the lack of scheduling clock phase synchronization among the participants and scheduling delays introduced by back ground tasks affect the potential energy savings. Increasing the periodic transmission delays to transmit data infrequently can offset some of these effects at the expense of flooding the wireless channel for longer periods of time; potentially increasing the time to acquire the channel for non-multimedia traffic. Buffering mechanisms built into media browsers can mitigate the effects of these added delays from being mis-interpreted as network congestion. We show that practical implementations of such traffic shaping mechanisms can offer significant energy savings.

  5. Simulation study of World Wide Web traffic over the ATM ABR service

    NASA Astrophysics Data System (ADS)

    Vandalore, Bobby; Kalyanaraman, Shivkumar; Jain, Raj; Goyal, Rohit; Fahmy, Sonia

    1998-10-01

    Asynchronous transfer-mode (ATM) is the technology chosen for implementing the broadband integrated services digital network. The performance of internet protocols over ATM is an extremely important research area. As web traffic forms a major portion of the Internet traffic, we model WWW servers and clients running over an ATM network using the available bit rate (ABR) service. The WWW servers are modeled using a variant of the SPECweb96 benchmark, while the WWW clients are based on a model proposed. The traffic generated is typically bursty, having active and idle transmission periods. A timeout occurs after a certain idle interval. During idle periods, the underlying TCP congestion windows remain large until the timer expires. This raises the possibility of large queues at the switches, if the source rates ar not controlled by ABR. We study this problem and show that ABR scales well to a large number of bursty TCP sources in the system.

  6. The Buchanan Report, environment and the problem of traffic in 1960s Britain.

    PubMed

    Gunn, Simon

    2011-01-01

    Traffic congestion in Britain's towns and cities grew with the exponential rise of car ownership in the 1950s and 1960s. The Buchanan Report, Traffic in Towns (1963), was a pioneering response to this problem, advancing a series of radical solutions for how cities could be adapted to mass car ownership. This article examines the contemporary debate about traffic among planners and politicians in the 1960s and considers both short-term responses to the Buchanan Report and its longer term effects in cities such as Leeds and Leicester. The legacy of Buchanan was ambivalent: while many of its prescriptions favoured a new, environmentally sensitive approach to the historic fabric and urban living, the report's arguments for radical reconstruction pointed to the building of urban motorways. Paradoxically, the growth of environmental awareness in 1960s Britain was linked to the endeavour to modernize the nation's towns and cities and to create the conditions for a car-owning society. PMID:22400427

  7. Particle-based model for skiing traffic

    NASA Astrophysics Data System (ADS)

    Holleczek, Thomas; Tröster, Gerhard

    2012-05-01

    We develop and investigate a particle-based model for ski slope traffic. Skiers are modeled as particles with a mass that are exposed to social and physical forces, which define the riding behavior of skiers during their descents on ski slopes. We also report position and speed data of 21 skiers recorded with GPS-equipped cell phones on two ski slopes. A comparison of these data with the trajectories resulting from computer simulations of our model shows a good correspondence. A study of the relationship among the density, speed, and flow of skiers reveals that congestion does not occur even with arrival rates of skiers exceeding the maximum ski lift capacity. In a sensitivity analysis, we identify the kinetic friction coefficient of skis on snow, the skier mass, the range of repelling social forces, and the arrival rate of skiers as the crucial parameters influencing the simulation results. Our model allows for the prediction of speed zones and skier densities on ski slopes, which is important in the prevention of skiing accidents.

  8. Congestion estimation technique in the optical network unit registration process.

    PubMed

    Kim, Geunyong; Yoo, Hark; Lee, Dongsoo; Kim, Youngsun; Lim, Hyuk

    2016-07-01

    We present a congestion estimation technique (CET) to estimate the optical network unit (ONU) registration success ratio for the ONU registration process in passive optical networks. An optical line terminal (OLT) estimates the number of collided ONUs via the proposed scheme during the serial number state. The OLT can obtain congestion level among ONUs to be registered such that this information may be exploited to change the size of a quiet window to decrease the collision probability. We verified the efficiency of the proposed method through simulation and experimental results. PMID:27367066

  9. [Erythropoiesis-stimulating agents in congestive heart failure patients].

    PubMed

    Robles Perez-Monteoliva, Nicolás Roberto; Macías Núñez, Juan Francisco; Herrera Pérez de Villar, Julio

    2014-03-01

    Congestive heart failure is a disease of high incidence and prevalence in the elderly. Anemia is associated with an increased mortality in these patients. This article reviews the cumulated evidence about the use of erythropoiesis-stimulating agents in congestive heart failure patients. Although some improvement in quality of life has been shown, it has not been found any decrement on mortality and, as a result, together with the high drug cost, it is not recommended the use of this kind of drugs in heart failure patients. PMID:24012446

  10. Reducing automobile traffic: an urgent policy for health promotion.

    PubMed

    Tapia Granados, J A

    1998-04-01

    In recent decades traffic injuries have become a leading cause of death and disability the world over. In congested urban areas, the noise and emissions from vehicle engines cause discomfort and disease. More than one billion people are exposed daily to harmful levels of atmospheric contamination. Because internal combustion generates carbon dioxide (CO2), the automobile is a principal contributor to the greenhouse effect, which has significantly raised the temperature of the atmosphere. Scientists anticipate that in coming decades the greenhouse effect will produce alterations in climate that are very likely to be harmful and possibly catastrophic. Meanwhile, burgeoning traffic and rural and urban highway infrastructures are already among the principal causes of environmental degradation. Urban development, because it is nearly always "planned" to accommodate automobiles rather than people, reduces the quality of life and tears the social fabric. In contrast to private automobiles, public transportation, bicycles, and walking produce little environmental contamination or injury-related morbidity and mortality. These modes of transport involve more physical activity, with its positive health effects, and avoid contributing to the greenhouse effect. The reduction of automobile traffic and substitution of alternative modes of transport are essential policies for health promotion. They should be incorporated in "healthy cities" programs and general economic policies. PMID:9608812

  11. Modeling traffic on crossroads

    NASA Astrophysics Data System (ADS)

    Wastavino, L. A.; Toledo, B. A.; Rogan, J.; Zarama, R.; Muñoz, V.; Valdivia, J. A.

    2007-07-01

    A simplified traffic model is studied, consisting of two vehicles traveling through a sequence of crossroads regulated by yield signs. A car approaching a yield sign stops if, in the other street, there is a car closer than a certain distance xtol from the intersection. It is shown that the function which maps the state of the vehicles displays a period doubling transition to chaos. An interesting feature of the dynamics is that for extremely cautious drivers ( xtol too large), the map turns chaotic, thus becoming a potential source of emergent jams. Complex behavior such as the one observed in this simple system seems to be an essential ingredient in traffic patterns, and could be of relevance in studying actual crossroads situations.

  12. Road Traffic Noise

    NASA Astrophysics Data System (ADS)

    Beckenbauer, Thomas

    Road traffic is the most interfering noise source in developed countries. According to a publication of the European Union (EU) at the end of the twentieth century [1], about 40% of the population in 15 EU member states is exposed to road traffic noise at mean levels exceeding 55 dB(A). Nearly 80 million people, 20% of the population, are exposed to levels exceeding 65 dB(A) during daytime and more than 30% of the population is exposed to levels exceeding 55 dB(A) during night time. Such high noise levels cause health risks and social disorders (aggressiveness, protest, and helplessness), interference of communication and disturbance of sleep; the long- and short-term consequences cause adverse cardiovascular effects, detrimental hormonal responses (stress hormones), and possible disturbance of the human metabolism (nutrition) and the immune system. Even performance at work and school could be impaired.

  13. Butyrate protects rat liver against total hepatic ischemia reperfusion injury with bowel congestion.

    PubMed

    Liu, Bin; Qian, Jianmin; Wang, Qingbao; Wang, Fangrui; Ma, Zhenyu; Qiao, Yingli

    2014-01-01

    Hepatic ischemia/reperfusion (I/R) injury is an unavoidable consequence of major liver surgery, especially in liver transplantation with bowel congestion, during which endotoxemia is often evident. The inflammatory response aggravated by endotoxin after I/R contributes to liver dysfunction and failure. The purpose of the present study was to investigate the protective effect of butyrate, a naturally occurring four-carbon fatty acid in the body and a dietary component of foods such as cheese and butter, on hepatic injury complicated by enterogenous endotoxin, as well as to examine the underlying mechanisms involved. SD rats were subjected to a total hepatic ischemia for 30 min after pretreatment with either vehicle or butyrate, followed by 6 h and 24 h of reperfusion. Butyrate preconditioning markedly improved hepatic function and histology, as indicated by reduced transaminase levels and ameliorated tissue pathological changes. The inflammatory factors levels, macrophages activation, TLR4 expression, and neutrophil infiltration in live were attenuated by butyrate. Butyrate also maintained the intestinal barrier structures, reversed the aberrant expression of ZO-1, and decreased the endotoxin translocation. We conclude that butyrate inhibition of endotoxin translocation, macrophages activation, inflammatory factors production, and neutrophil infiltration is involved in the alleviation of total hepatic I/R liver injury in rats. This suggests that butyrate should potentially be utilized in liver transplantation. PMID:25171217

  14. A new lattice model of traffic flow with the consideration of individual difference of anticipation driving behavior

    NASA Astrophysics Data System (ADS)

    Peng, Guanghan

    2013-10-01

    In this paper, we propose a new lattice model of traffic flow with the consideration of individual difference of anticipation driving behavior. The linear stability condition and the mKdV equation are derived from linear stability analysis and nonlinear analysis, respectively. Furthermore, numerical simulation shows that the anticipation driving behavior can increase the cell number of low density, which means that more cars can run freely and traffic congestion can be suppressed efficiently by taking the anticipation driving behavior into account in lattice model. Moreover, with the coefficient of the anticipation driving behavior increasing, the low density region turns wide corresponding to individual difference of anticipation driving behavior.

  15. Development of an empirical model to estimate real-world fine particulate matter emission factors: the traffic air quality model.

    PubMed

    Soliman, Ahmed S M; Jacko, Robert B; Palmer, George M

    2006-11-01

    The purpose of the study was to quantify the impact of traffic conditions, such as free flow and congestion, on local air quality. The Borman Expressway (I-80/94) in Northwest Indiana is considered a test bed for this research because of the high volume of class 9 truck traffic traveling on it, as well as the existing and continuing installation of the Intelligent Transportation System (ITS) to improve traffic management along the highway stretch. An empirical traffic air quality (TAQ) model was developed to estimate the fine particulate matter (PM2.5) emission factors (grams per kilometer) based solely on the measured traffic parameters, namely, average speed, average acceleration, and class 9 truck density. The TAQ model has shown better predictions that matched the measured emission factor values more than the U.S. Environmental Protection Agency (EPA)-PART5 model. During congestion (defined as flow-speeds < 50 km/hr [30 mi/hr]), the TAQ model, on average, overpredicted the measured values only by a factor of 1.2, in comparison to a fourfold underprediction using the EPA-PART5 model. On the other hand, during free flow (defined as flow-speeds > 80 km/hr [50 mi/hr]), the TAQ model was conservative in that it overpredicted the measured values by 1.5-fold. PMID:17117739

  16. A Space-Time Network-Based Modeling Framework for Dynamic Unmanned Aerial Vehicle Routing in Traffic Incident Monitoring Applications

    PubMed Central

    Zhang, Jisheng; Jia, Limin; Niu, Shuyun; Zhang, Fan; Tong, Lu; Zhou, Xuesong

    2015-01-01

    It is essential for transportation management centers to equip and manage a network of fixed and mobile sensors in order to quickly detect traffic incidents and further monitor the related impact areas, especially for high-impact accidents with dramatic traffic congestion propagation. As emerging small Unmanned Aerial Vehicles (UAVs) start to have a more flexible regulation environment, it is critically important to fully explore the potential for of using UAVs for monitoring recurring and non-recurring traffic conditions and special events on transportation networks. This paper presents a space-time network- based modeling framework for integrated fixed and mobile sensor networks, in order to provide a rapid and systematic road traffic monitoring mechanism. By constructing a discretized space-time network to characterize not only the speed for UAVs but also the time-sensitive impact areas of traffic congestion, we formulate the problem as a linear integer programming model to minimize the detection delay cost and operational cost, subject to feasible flying route constraints. A Lagrangian relaxation solution framework is developed to decompose the original complex problem into a series of computationally efficient time-dependent and least cost path finding sub-problems. Several examples are used to demonstrate the results of proposed models in UAVs’ route planning for small and medium-scale networks. PMID:26076404

  17. A Space-Time Network-Based Modeling Framework for Dynamic Unmanned Aerial Vehicle Routing in Traffic Incident Monitoring Applications.

    PubMed

    Zhang, Jisheng; Jia, Limin; Niu, Shuyun; Zhang, Fan; Tong, Lu; Zhou, Xuesong

    2015-01-01

    It is essential for transportation management centers to equip and manage a network of fixed and mobile sensors in order to quickly detect traffic incidents and further monitor the related impact areas, especially for high-impact accidents with dramatic traffic congestion propagation. As emerging small Unmanned Aerial Vehicles (UAVs) start to have a more flexible regulation environment, it is critically important to fully explore the potential for of using UAVs for monitoring recurring and non-recurring traffic conditions and special events on transportation networks. This paper presents a space-time network- based modeling framework for integrated fixed and mobile sensor networks, in order to provide a rapid and systematic road traffic monitoring mechanism. By constructing a discretized space-time network to characterize not only the speed for UAVs but also the time-sensitive impact areas of traffic congestion, we formulate the problem as a linear integer programming model to minimize the detection delay cost and operational cost, subject to feasible flying route constraints. A Lagrangian relaxation solution framework is developed to decompose the original complex problem into a series of computationally efficient time-dependent and least cost path finding sub-problems. Several examples are used to demonstrate the results of proposed models in UAVs' route planning for small and medium-scale networks. PMID:26076404

  18. Advanced traffic management systems and high-occupancy-vehicle systems. Transportation research record

    SciTech Connect

    1996-12-31

    ;Contents: Distributed Approach to Real-Time Control of Complex Signalized Networks; MULTIBAND-96: A Program for Variable-Bandwidth Progression Optimization of Multiarterial Traffic Networks; Determination of Timings in Signal Systems with Traffic-Actuated Controllers; Combined Model for Signal Control and Route Choice in Urbn Traffic Networks; Multivariate Optimization Strategies for Real-Time Traffic Control Signals; Implementation Vision for Distributed Control of Traffic Signal Subsystems; Current Developments in SCOOT: Version 3; Estimating Impact of Signal Hardware Improvements; Guidelines for Actuated Controllers in Coordinated Systems; Evaluation of Bus Priority Signal Strategies in Ann Arbor, Michigan; NETSIM-Based Approach to Evaluation of Bus Preemption Strategies; Simulation-Based Methodology for Evaluation of High-Occupancy-Vehicle Facilities; Predicting High-Occupancy-Vehicle Facility Demand; Evaluation of High-Occupancy-Vehicle Lanes on Long Island Expressway; Effect on Congestion and Motorcycle Safety of Motorcycle Travel on High-Occupancy-Vehicle Facilities in Virginia; Development of Arterial High-Occupancy-Vehicle Land Enforcement Techniques; Multiple-Interval Freeway Traffic Flow Forecasting; New Methodology for Smoothing Freeway Loop Detector Data: Introduction to Digital Filtering; Evaluation of Compliance Rates and Travel Time Calculation for Automatic Alternative Route Guidance Systems on Freeways; Algorithm for Controlling Spillback from Ramp Meters; Systemwide Analysis of Freeway Improvements; Transferability of Freeway Incident Detection Algorithms; Deriving Incident Management Measures Using Incident Probability Models and Simulation; and I-880 Field Experiment: Data-Base Development and Incident Delay Estimation Procedures.

  19. A two-lane cellular automaton traffic flow model with the influence of driver, vehicle and road

    NASA Astrophysics Data System (ADS)

    Zhao, Han-Tao; Nie, Cen; Li, Jing-Ru; Wei, Yu-Ao

    2016-07-01

    On the basis of one-lane comfortable driving model, this paper established a two-lane traffic cellular automata model, which improves the slow randomization effected by brake light. Considering the driver psychological characteristics and mixed traffic, we studied the lateral influence between vehicles on adjacent lanes. Through computer simulation, the space-time diagram and the fundamental figure under different conditions are obtained. The study found that aggressive driver makes a slight congestion in low-density traffic and improves the capacity of high-density traffic, when the density exceeds 20pcu/km the more aggressive drivers the greater the flow, when the density below 40pcu/km driver character makes an effect, the more cautious driver, the lower the flow. The ratio of big cars has the same effect as the ratio of aggressive drivers. Brake lights have the greatest impact on traffic flow and when the density exceeds 10pcu/km the traffic flow fluctuates. Under periodic boundary conditions, the disturbance of road length on traffic is minimal. The lateral influence only play a limited role in the medium-density conditions, and only affect the average speed of traffic at low density.

  20. 23 CFR 972.214 - Federal lands congestion management system (CMS).

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... LANDS HIGHWAYS FISH AND WILDLIFE SERVICE MANAGEMENT SYSTEMS Fish and Wildlife Service Management Systems... for congestion (e.g., level of service); (ii) Identify the causes of congestion; (iii)...

  1. 23 CFR 972.214 - Federal lands congestion management system (CMS).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... LANDS HIGHWAYS FISH AND WILDLIFE SERVICE MANAGEMENT SYSTEMS Fish and Wildlife Service Management Systems... for congestion (e.g., level of service); (ii) Identify the causes of congestion; (iii)...

  2. 23 CFR 971.214 - Federal lands congestion management system (CMS).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... LANDS HIGHWAYS FOREST SERVICE MANAGEMENT SYSTEMS Forest Highway Program Management Systems § 971.214... document measures for congestion (e.g., level of service); (ii) Identify the causes of congestion;...

  3. Living on the Edge of Stagnant Water: An Assessment of Environmental Impacts of Construction-Phase Drainage Congestion Along Dhaka City Flood Control Embankment, Bangladesh

    NASA Astrophysics Data System (ADS)

    Rasid, Harun; Mallsk, Azim U.

    1996-01-01

    Environmental impacts of the construction-phase drainage congestion along the Dhaka City Flood Control Embankment were assessed by a pilot questionnaire survey (in 1991) among the target population adjacent to the embankment. The results of the survey indicated that, despite significant alleviation of river flooding, the majority of the respondents experienced a new type of flood problem in the form of stagnant water inside the embankment, immediately following its construction. Not only had this stagnant water flooded and damaged their property, it had exposed them to a number of other environmental problems, such as accumulation of municipal sewage, foul odors, mosquitoes, and growth of water hyacinth. The study found that the respondents’ assessments of these environmental problems differed significantly according to the magnitude of the impact of stagnant water upon two subgroups within the target population. A postsurvey follow-up in 1994 indicated that this problem of drainage congestion had largely been alleviated by completing the construction of a number of drainage regulators. The study concludes by stressing the importance of synchronizing the construction of drainage structures with that of the embankment systems and by underlining policy implications for flood-vulnerable land use adjacent to embankments.

  4. Bottleneck Congestion Games with Logarithmic Price of Anarchy

    NASA Astrophysics Data System (ADS)

    Kannan, Rajgopal; Busch, Costas

    We study bottleneck congestion games where the social cost is determined by the worst congestion on any resource. In the literature, bottleneck games assume player utility costs determined by the worst congested resource in their strategy. However, the Nash equilibria of such games are inefficient since the price of anarchy can be very high and proportional to the number of resources. In order to obtain smaller price of anarchy we introduce exponential bottleneck games, where the utility costs of the players are exponential functions of their congestions. In particular, the delay function for any resource r is M^{C_r}, where C r denotes the number of players that use r, and M is an integer constant. We find that exponential bottleneck games are very efficient and give the following bound on the price of anarchy: O(log|R|), where R is the set of resources. This price of anarchy is tight, since we demonstrate a game with price of anarchy Ω(log|R|). We obtain our tight bounds by using two novel proof techniques: transformation, which we use to convert arbitrary games to simpler games, and expansion, which we use to bound the price of anarchy in a simpler game.

  5. 14 CFR 137.51 - Operation over congested areas: General.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... aircraft must be operated as follows: (i) No person may take off a multiengine airplane over a congested... engine aircraft must be operated as follows: (i) Except for helicopters, no person may take off a loaded... inoperative in the takeoff configuration or 115 percent of the power-off stall speed in the...

  6. Understanding congestion in China's medical market: an incentive structure perspective.

    PubMed

    Sun, Zesheng; Wang, Shuhong; Barnes, Stephen R

    2016-04-01

    Congestion has become one of the most important factors leading to patient dissatisfaction and doctor-patient conflicts in the medical market of China. In this study, we explore the causes and effects of structural congestion in the Chinese medical market from an incentive structure perspective. Our analysis reveals that prior medical system reforms with price regulation in China have induced hospitals to establish incentives for capital-intensive investments, while ignoring human capital, and have driven medical staff and patients to higher-level hospitals, reinforcing an incentive structure in which congestion in higher-level hospitals and idle resources in lower-level hospitals coexist. The existing incentive structure has led to cost increases and degradation of human capital and specific factor effects. Recent reforms to reduce congestion in the Chinese medical market were not effective. Most of them had no impact on and did not involve the existing distorted incentive structure. Future reforms should consider rebalancing expectations for medical quality, free flow of human capital and price regulation reforms to rebuild a new incentive structure. PMID:26185181

  7. Pelvic congestion syndrome: demonstration and diagnosis by helical CT.

    PubMed

    Desimpelaere, J H; Seynaeve, P C; Hagers, Y M; Appel, B J; Mortelmans, L L

    1999-01-01

    Pelvic pain is a common gynaecological complaint, sometimes without any obvious etiology. We report a case of pelvic congestion syndrome, an often overlooked cause of pelvic pain, diagnosed by helical computed tomography. This seems to be an effective and noninvasive imaging modality. PMID:9933685

  8. Teaching Congestive Heart Failure to Doctor of Pharmacy Students.

    ERIC Educational Resources Information Center

    Parker, Robert B.

    1992-01-01

    This paper summarizes a lecture given to pharmacy students that emphasizes the pathophysiologic mechanisms causing congestive heart failure and the effects of drugs on these mechanisms. The approach shows the importance of drug therapy in this disorder and how this knowledge can improve patient care. An appendix provides a case study. (GLR)

  9. Design of proportional-derivative-type state feedback controllers for congestion control of transmission control protocol networks

    NASA Astrophysics Data System (ADS)

    Azadegan, Masoumeh; Beheshti, Mohammad T. H.; Tavassoli, Babak

    2015-07-01

    A new proportional-derivative-type state feedback controller is proposed for congestion control of transmission control protocol (TCP) networks. An analytical TCP model is adopted. In the proposed control scheme, it is possible to efficiently control the TCP traffic using only the queue length at the router without the need to know the TCP window size which is not available locally. The results are presented in terms of delay-dependent linear matrix inequality. The proposed method is verified by simulation examples using NS software, and the effectiveness and superiority of our method over other control schemes, such as the proportional-integral, random early detection and generalised minimum variancemethods, are also shown.

  10. Increased walking variability in elderly persons with congestive heart failure

    NASA Technical Reports Server (NTRS)

    Hausdorff, J. M.; Forman, D. E.; Ladin, Z.; Goldberger, A. L.; Rigney, D. R.; Wei, J. Y.

    1994-01-01

    OBJECTIVES: To determine the effects of congestive heart failure on a person's ability to walk at a steady pace while ambulating at a self-determined rate. SETTING: Beth Israel Hospital, Boston, a primary and tertiary teaching hospital, and a social activity center for elderly adults living in the community. PARTICIPANTS: Eleven elderly subjects (aged 70-93 years) with well compensated congestive heart failure (NY Heart Association class I or II), seven elderly subjects (aged 70-79 years) without congestive heart failure, and 10 healthy young adult subjects (aged 20-30 years). MEASUREMENTS: Subjects walked for 8 minutes on level ground at their own selected walking rate. Footswitches were used to measure the time between steps. Step rate (steps/minute) and step rate variability were calculated for the entire walking period, for 30 seconds during the first minute of the walk, for 30 seconds during the last minute of the walk, and for the 30-second period when each subject's step rate variability was minimal. Group means and 5% and 95% confidence intervals were computed. MAIN RESULTS: All measures of walking variability were significantly increased in the elderly subjects with congestive heart failure, intermediate in the elderly controls, and lowest in the young subjects. There was no overlap between the three groups using the minimal 30-second variability (elderly CHF vs elderly controls: P < 0.001, elderly controls vs young: P < 0.001), and no overlap between elderly subjects with and without congestive heart failure when using the overall variability. For all four measures, there was no overlap in any of the confidence intervals, and all group means were significantly different (P < 0.05).

  11. 23 CFR 972.214 - Federal lands congestion management system (CMS).

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... LANDS HIGHWAYS FISH AND WILDLIFE SERVICE MANAGEMENT SYSTEMS Fish and Wildlife Service Management Systems § 972.214 Federal lands congestion management system (CMS). (a) For purposes of this section, congestion... 23 Highways 1 2011-04-01 2011-04-01 false Federal lands congestion management system (CMS)....

  12. Observations on traffic flow patterns and traffic engineering practice

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Gao, Lixin

    2002-07-01

    Border Gateway Protocol allows ASs to apply diverse routing policies for selecting routes and propagating reachability information to other ASs. This enables network operators to configure routing policies so as to control traffic flows between ASs. However, BGP is not designed for the inter-AS traffic engineering. This makes it difficult to implement effective routing policies to address network performance and utilization problems. Network operators usually tweak routing policies to influence the inter-domain traffic among the available links. This can lead to undesirable traffic flow patterns across the Internet and degrade the Internet traffic performance. In this paper, we show several observations on Internet traffic flow patterns and derive routing policies that give rise to the traffic flow patterns. Our results show that an AS can reach as much as 20% of the prefixes via a peer link even though there is a path via a customer link. In addition, an AS can reach as much as 80% of the prefixes via a provider link even though there is a path via a peer link. Second, we analyze the cause of the prevalence of these traffic patterns. Our analysis shows that an AS typically does not receive the potential route from its customers or peers. Third, we find that alternate routes have with lower propagation delay than the chosen routes for some prefixes. This shows that some traffic engineering practices might adversely affect Internet performance.

  13. Nuclear traffic and peloton formation in fungal networks

    NASA Astrophysics Data System (ADS)

    Roper, Marcus; Hickey, Patrick; Lewkiewicz, Stephanie; Dressaire, Emilie; Read, Nick

    2013-11-01

    Hyphae, the network of microfluidic pipes that make up a growing fungal cell, must balance their function as conduits for the transport of nuclei with other cellular functions including secretion and growth. Constant flow of nuclei may interfere with the protein traffic that enables other functions to be performed. Live-cell imaging reveals that nuclear flows are anti-congestive; that groups of nuclei flow faster than single nuclei, and that nuclei sweep through the colony in dense clumps. We call these clumps pelotons, after the term used to describe groups of cycle racers slip-streaming off each other. Because of the pelotons, individual hyphae transport nuclei only intermittently, producing long intervals in which hyphae can perform their other functions. Modeling reveals how pelotons are created by interactions between nuclei and the hyphal cytoskeleton, and reveal the control that the fungus enjoys over peloton assembly and timing.

  14. Urban traffic from the perspective of dual graph

    NASA Astrophysics Data System (ADS)

    Hu, M.-B.; Jiang, R.; Wu, Y.-H.; Wang, W.-X.; Wu, Q.-S.

    2008-05-01

    Urban traffic is modeled using a dual graph representation of the urban transport network, where roads are mapped to nodes and intersections are mapped to links. The proposed model considers both the navigation of the vehicles in the network and the motion of the vehicles along roads. The vehicle-holding ability of roads and the vehicle-turning ability at intersections are also incorporated. The overall handling ability of the system can be quantified by a phase transition from free flow to congestion. Simulations show that the system's handling ability greatly depends on the topology of the transportation network. In general, a well-planned grid can hold more vehicles, and its overall handling ability is much greater than that of a growing self-organized network.

  15. Successive linear optimization approach to the dynamic traffic assignment problem

    SciTech Connect

    Ho, J.K.

    1980-11-01

    A dynamic model for the optimal control of traffic flow over a network is considered. The model, which treats congestion explicitly in the flow equations, gives rise to nonlinear, nonconvex mathematical programming problems. It has been shown for a piecewise linear version of this model that a global optimum is contained in the set of optimal solutions of a certain linear program. A sufficient condition for optimality which implies that a global optimum can be obtained by successively optimizing at most N + 1 objective functions for the linear program, where N is the number of time periods in the planning horizon is presented. Computational results are reported to indicate the efficiency of this approach.

  16. Neural predictive control for active buffet alleviation

    NASA Astrophysics Data System (ADS)

    Pado, Lawrence E.; Lichtenwalner, Peter F.; Liguore, Salvatore L.; Drouin, Donald

    1998-06-01

    The adaptive neural control of aeroelastic response (ANCAR) and the affordable loads and dynamics independent research and development (IRAD) programs at the Boeing Company jointly examined using neural network based active control technology for alleviating undesirable vibration and aeroelastic response in a scale model aircraft vertical tail. The potential benefits of adaptive control includes reducing aeroelastic response associated with buffet and atmospheric turbulence, increasing flutter margins, and reducing response associated with nonlinear phenomenon like limit cycle oscillations. By reducing vibration levels and thus loads, aircraft structures can have lower acquisition cost, reduced maintenance, and extended lifetimes. Wind tunnel tests were undertaken on a rigid 15% scale aircraft in Boeing's mini-speed wind tunnel, which is used for testing at very low air speeds up to 80 mph. The model included a dynamically scaled flexible fail consisting of an aluminum spar with balsa wood cross sections with a hydraulically powered rudder. Neural predictive control was used to actuate the vertical tail rudder in response to strain gauge feedback to alleviate buffeting effects. First mode RMS strain reduction of 50% was achieved. The neural predictive control system was developed and implemented by the Boeing Company to provide an intelligent, adaptive control architecture for smart structures applications with automated synthesis, self-optimization, real-time adaptation, nonlinear control, and fault tolerance capabilities. It is designed to solve complex control problems though a process of automated synthesis, eliminating costly control design and surpassing it in many instances by accounting for real world non-linearities.

  17. Rolling maneuver load alleviation using active controls

    NASA Technical Reports Server (NTRS)

    Woods-Vedeler, Jessica A.; Pototzky, Anthony S.

    1992-01-01

    Rolling Maneuver Load Alleviation (RMLA) was demonstrated on the Active Flexible Wing (AFW) wind tunnel model in the LaRC Transonic Dynamics Tunnel. The design objective was to develop a systematic approach for developing active control laws to alleviate wing incremental loads during roll maneuvers. Using linear load models for the AFW wind-tunnel model which were based on experimental measurements, two RMLA control laws were developed based on a single-degree-of-freedom roll model. The RMLA control laws utilized actuation of outboard control surface pairs to counteract incremental loads generated during rolling maneuvers and roll performance. To evaluate the RMLA control laws, roll maneuvers were performed in the wind tunnel at dynamic pressures of 150, 200, and 250 psf and Mach numbers of .33, .38, and .44, respectively. Loads obtained during these maneuvers were compared to baseline maneuver loads. For both RMLA controllers, the incremental torsion moments were reduced by up to 60 percent at all dynamic pressures and performance times. Results for bending moment load reductions during roll maneuvers varied. In addition, in a multiple function test, RMLA and flutter suppression system control laws were operated simultaneously during roll maneuvers at dynamic pressures 11 percent above the open-loop flutter dynamic pressure.

  18. Rolling Maneuver Load Alleviation using active controls

    NASA Technical Reports Server (NTRS)

    Woods-Vedeler, Jessica A.; Pototzky, Anthony S.

    1992-01-01

    Rolling Maneuver Load Alleviation (RMLA) has been demonstrated on the Active Flexible Wing (AFW) wind tunnel model in the NASA Langley Transonic Dynamics Tunnel. The design objective was to develop a systematic approach for developing active control laws to alleviate wing incremental loads during roll maneuvers. Using linear load models for the AFW wind-tunnel model which were based on experimental measurements, two RMLA control laws were developed based on a single-degree-of-freedom roll model. The RMLA control laws utilized actuation of outboard control surface pairs to counteract incremental loads generated during rolling maneuvers and actuation of the trailing edge inboard control surface pairs to maintain roll performance. To evaluate the RMLA control laws, roll maneuvers were performed in the wind tunnel at dynamic pressures of 150, 200, and 250 psf and Mach numbers of 0.33, .38 and .44, respectively. Loads obtained during these maneuvers were compared to baseline maneuver loads. For both RMLA controllers, the incremental torsion moments were reduced by up to 60 percent at all dynamic pressures and performance times. Results for bending moment load reductions during roll maneuvers varied. In addition, in a multiple function test, RMLA and flutter suppression system control laws were operated simultaneously during roll maneuvers at dynamic pressures 11 percent above the open-loop flutter dynamic pressure.

  19. An intelligent traffic controller

    SciTech Connect

    Kagolanu, K.; Fink, R.; Smartt, H.; Powell, R.; Larsen, E.

    1995-12-01

    A controller with advanced control logic can significantly improve traffic flows at intersections. In this vein, this paper explores fuzzy rules and algorithms to improve the intersection operation by rationalizing phase changes and green times. The fuzzy logic for control is enhanced by the exploration of neural networks for families of membership functions and for ideal cost functions. The concepts of fuzzy logic control are carried forth into the controller architecture. Finally, the architecture and the modules are discussed. In essence, the control logic and architecture of an intelligent controller are explored.

  20. On the Existence of Optimal Taxes for Network Congestion Games with Heterogeneous Users

    NASA Astrophysics Data System (ADS)

    Fotakis, Dimitris; Karakostas, George; Kolliopoulos, Stavros G.

    We consider network congestion games in which a finite number of non-cooperative users select paths. The aim is to mitigate the inefficiency caused by the selfish users by introducing taxes on the network edges. A tax vector is strongly (weakly)-optimal if all (at least one of) the equilibria in the resulting game minimize(s) the total latency. The issue of designing optimal tax vectors for selfish routing games has been studied extensively in the literature. We study for the first time taxation for networks with atomic users which have unsplittable traffic demands and are heterogeneous, i.e., have different sensitivities to taxes. On the positive side, we show the existence of weakly-optimal taxes for single-source network games. On the negative side, we show that the cases of homogeneous and heterogeneous users differ sharply as far as the existence of strongly-optimal taxes is concerned: there are parallel-link games with linear latencies and heterogeneous users that do not admit strongly-optimal taxes.

  1. Economical Video Monitoring of Traffic

    NASA Technical Reports Server (NTRS)

    Houser, B. C.; Paine, G.; Rubenstein, L. D.; Parham, O. Bruce, Jr.; Graves, W.; Bradley, C.

    1986-01-01

    Data compression allows video signals to be transmitted economically on telephone circuits. Telephone lines transmit television signals to remote traffic-control center. Lines also carry command signals from center to TV camera and compressor at highway site. Video system with television cameras positioned at critical points on highways allows traffic controllers to determine visually, almost immediately, exact cause of traffic-flow disruption; e.g., accidents, breakdowns, or spills, almost immediately. Controllers can then dispatch appropriate emergency services and alert motorists to minimize traffic backups.

  2. An optimization model for the US Air-Traffic System

    NASA Technical Reports Server (NTRS)

    Mulvey, J. M.

    1986-01-01

    A systematic approach for monitoring U.S. air traffic was developed in the context of system-wide planning and control. Towards this end, a network optimization model with nonlinear objectives was chosen as the central element in the planning/control system. The network representation was selected because: (1) it provides a comprehensive structure for depicting essential aspects of the air traffic system, (2) it can be solved efficiently for large scale problems, and (3) the design can be easily communicated to non-technical users through computer graphics. Briefly, the network planning models consider the flow of traffic through a graph as the basic structure. Nodes depict locations and time periods for either individual planes or for aggregated groups of airplanes. Arcs define variables as actual airplanes flying through space or as delays across time periods. As such, a special case of the network can be used to model the so called flow control problem. Due to the large number of interacting variables and the difficulty in subdividing the problem into relatively independent subproblems, an integrated model was designed which will depict the entire high level (above 29000 feet) jet route system for the 48 contiguous states in the U.S. As a first step in demonstrating the concept's feasibility a nonlinear risk/cost model was developed for the Indianapolis Airspace. The nonlinear network program --NLPNETG-- was employed in solving the resulting test cases. This optimization program uses the Truncated-Newton method (quadratic approximation) for determining the search direction at each iteration in the nonlinear algorithm. It was shown that aircraft could be re-routed in an optimal fashion whenever traffic congestion increased beyond an acceptable level, as measured by the nonlinear risk function.

  3. Long-Range Emergency Preemption of Traffic Lights

    NASA Technical Reports Server (NTRS)

    Bachelder, Aaron

    2005-01-01

    A forwarding system could prove beneficial as an addition to an electronic communication-and-control system that automatically modifies the switching of traffic lights to give priority to emergency vehicles. A system to which the forwarding system could be added could be any of a variety of emergency traffic-signal-preemption systems: these include systems now used in some municipalities as well as advanced developmental systems described in several NASA Tech Briefs articles in recent years. Because of a variety of physical and design limitations, emergency traffic-signal- preemption systems now in use are often limited in range to only one intersection at a time: in a typical system, only the next, closest intersection is preempted for an emergency vehicle. Simulations of gridlock have shown that such systems offer minimal advantages and can even cause additional delays. In analogy to what happens in fluid dynamics, the forwarding system insures that flow at a given location is sustained by guaranteeing downstream flow along the predicted route (typically a main artery) and intersecting routes (typically, side streets). In simplest terms, the forwarding system starts by taking note of any preemption issued by the preemption system to which it has been added. The forwarding system predicts which other intersections could be encountered by the emergency vehicle downstream of the newly preempted intersection. The system then forwards preemption triggers to those intersections. Beyond affording a right of way for the emergency vehicle at every intersection that lies ahead along any likely route from the current position of the vehicle, the forwarding system also affords the benefit of clearing congested roads far ahead of the vehicle. In a metropolitan environment with heavy road traffic, forwarding of preemption triggers could greatly enhance the performance of a pre-existing preemption system.

  4. Traveling waves in an optimal velocity model of freeway traffic.

    PubMed

    Berg, P; Woods, A

    2001-03-01

    Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137]. PMID:11308709

  5. Traveling waves in an optimal velocity model of freeway traffic

    NASA Astrophysics Data System (ADS)

    Berg, Peter; Woods, Andrew

    2001-03-01

    Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137].

  6. Commercial machine vision system for traffic monitoring and control

    NASA Astrophysics Data System (ADS)

    D Agostino, Salvatore A.

    1992-03-01

    Traffic imaging covers a range of current and potential applications. These include traffic control and analysis, license plate finding, reading and storage, violation detection and archiving, vehicle sensors, and toll collection/enforcement. Experience from commercial installations and knowledge of the system requirements have been gained over the past 10 years. Recent improvements in system component cost and performance now allow products to be applied that provide cost effective solutions to the requirements for truly intelligent vehicle/highway systems (IVHS). The United States is a country that loves to drive. The infrastructure built in the 1950s and 1960s along with the low price of gasoline created an environment where the automobiles became an accessible and intricate part of American life. The United States has spent $DLR103 billion to build 40,000 highway miles since 1956, the start of the interstate program which is nearly complete. Unfortunately, a situation has arisen where the options for dramatically improving the ability of our roadways to absorb the increasing amount of traffic is limited. This is true in other countries as well as in the United States. The number of vehicles in the world increases by over 10,000,000 each year. In the United States there are about 180 million cars, trucks, and buses and this is estimated to double in the next 30 years. Urban development, and development in general, pushes from the edge of our roadways out. This leaves little room to increase the physical amount of roadway. Americans now spend more than 1.6 billion hours a year waiting in traffic jams. It is estimated that this congestion wasted 3 billion gallons of oil or 4% of the nation's annual gas consumption. The way out of the dilemma is to increase road use efficiency as well as improve mass transportation alternatives.

  7. Near real-time traffic routing

    NASA Technical Reports Server (NTRS)

    Yang, Chaowei (Inventor); Cao, Ying (Inventor); Xie, Jibo (Inventor); Zhou, Bin (Inventor)

    2012-01-01

    A near real-time physical transportation network routing system comprising: a traffic simulation computing grid and a dynamic traffic routing service computing grid. The traffic simulator produces traffic network travel time predictions for a physical transportation network using a traffic simulation model and common input data. The physical transportation network is divided into a multiple sections. Each section has a primary zone and a buffer zone. The traffic simulation computing grid includes multiple of traffic simulation computing nodes. The common input data includes static network characteristics, an origin-destination data table, dynamic traffic information data and historical traffic data. The dynamic traffic routing service computing grid includes multiple dynamic traffic routing computing nodes and generates traffic route(s) using the traffic network travel time predictions.

  8. Large scale traffic simulations

    SciTech Connect

    Nagel, K.; Barrett, C.L.; Rickert, M.

    1997-04-01

    Large scale microscopic (i.e. vehicle-based) traffic simulations pose high demands on computational speed in at least two application areas: (i) real-time traffic forecasting, and (ii) long-term planning applications (where repeated {open_quotes}looping{close_quotes} between the microsimulation and the simulated planning of individual person`s behavior is necessary). As a rough number, a real-time simulation of an area such as Los Angeles (ca. 1 million travellers) will need a computational speed of much higher than 1 million {open_quotes}particle{close_quotes} (= vehicle) updates per second. This paper reviews how this problem is approached in different projects and how these approaches are dependent both on the specific questions and on the prospective user community. The approaches reach from highly parallel and vectorizable, single-bit implementations on parallel supercomputers for Statistical Physics questions, via more realistic implementations on coupled workstations, to more complicated driving dynamics implemented again on parallel supercomputers. 45 refs., 9 figs., 1 tab.

  9. Residential traffic exposure and children's emergency department presentation for asthma: a spatial study

    PubMed Central

    2009-01-01

    Background There is increasing evidence that residential proximity to roadways is associated with an elevated risk of asthma exacerbation. However, there is no consensus on the distance at which these health effects diminishes to background levels. Therefore the optimal, clinically relevant measure of exposure remains uncertain. Using four spatially defined exposure metrics, we evaluated the association between residential proximity to roadways and emergency department (ED) presentation for asthma in Perth, Western Australia. Method The study population consisted of 1809 children aged between 0 and 19 years who had presented at an ED between 2002 and 2006 and were resident in a south-west metropolitan area of Perth traversed by major motorways. We used a 1:2 matched case-control study with gastroenteritis and upper limb injury as the control conditions. To estimate exposure to traffic emissions, we used 4 contrasting methods and 2 independently derived sources of traffic data (video-monitored traffic counts and those obtained from the state government road authority). The following estimates of traffic exposure were compared: (1) a point pattern method, (2) a distance-weighted traffic exposure method, (3) a simple distance method and (4) a road length method. Results Risk estimates were sensitive to socio-economic gradients and the type of exposure method that was applied. Unexpectedly, a range of apparent protective effects were observed for some exposure metrics. The kernel density measure demonstrated more than a 2-fold (OR 2.51, 95% CI 2.00 - 3.15) increased risk of asthma ED presentation for the high exposure group compared to the low exposure group. Conclusion We assessed exposure using traffic data from 2 independent sources and compared the results of 4 different exposure metric types. The results indicate that traffic congestion may be one of the most important aspects of traffic-related exposures, despite being overlooked in many studies on the

  10. Application of Epidemiology Model on Complex Networks in Propagation Dynamics of Airspace Congestion.

    PubMed

    Dai, Xiaoxu; Hu, Minghua; Tian, Wen; Xie, Daoyi; Hu, Bin

    2016-01-01

    This paper presents a propagation dynamics model for congestion propagation in complex networks of airspace. It investigates the application of an epidemiology model to complex networks by comparing the similarities and differences between congestion propagation and epidemic transmission. The model developed satisfies the constraints of actual motion in airspace, based on the epidemiology model. Exploiting the constraint that the evolution of congestion cluster in the airspace is always dynamic and heterogeneous, the SIR epidemiology model (one of the classical models in epidemic spreading) with logistic increase is applied to congestion propagation and shown to be more accurate in predicting the evolution of congestion peak than the model based on probability, which is common to predict the congestion propagation. Results from sample data show that the model not only predicts accurately the value and time of congestion peak, but also describes accurately the characteristics of congestion propagation. Then, a numerical study is performed in which it is demonstrated that the structure of the networks have different effects on congestion propagation in airspace. It is shown that in regions with severe congestion, the adjustment of dissipation rate is more significant than propagation rate in controlling the propagation of congestion. PMID:27336405

  11. Application of Epidemiology Model on Complex Networks in Propagation Dynamics of Airspace Congestion

    PubMed Central

    Dai, Xiaoxu; Hu, Minghua; Tian, Wen; Xie, Daoyi; Hu, Bin

    2016-01-01

    This paper presents a propagation dynamics model for congestion propagation in complex networks of airspace. It investigates the application of an epidemiology model to complex networks by comparing the similarities and differences between congestion propagation and epidemic transmission. The model developed satisfies the constraints of actual motion in airspace, based on the epidemiology model. Exploiting the constraint that the evolution of congestion cluster in the airspace is always dynamic and heterogeneous, the SIR epidemiology model (one of the classical models in epidemic spreading) with logistic increase is applied to congestion propagation and shown to be more accurate in predicting the evolution of congestion peak than the model based on probability, which is common to predict the congestion propagation. Results from sample data show that the model not only predicts accurately the value and time of congestion peak, but also describes accurately the characteristics of congestion propagation. Then, a numerical study is performed in which it is demonstrated that the structure of the networks have different effects on congestion propagation in airspace. It is shown that in regions with severe congestion, the adjustment of dissipation rate is more significant than propagation rate in controlling the propagation of congestion. PMID:27336405

  12. An economic way of reducing health, environmental, and other pressures of urban traffic: a decision analysis on trip aggregation

    PubMed Central

    Tuomisto, Jouni T; Tainio, Marko

    2005-01-01

    Background Traffic congestion is rapidly becoming the most important obstacle to urban development. In addition, traffic creates major health, environmental, and economical problems. Nonetheless, automobiles are crucial for the functions of the modern society. Most proposals for sustainable traffic solutions face major political opposition, economical consequences, or technical problems. Methods We performed a decision analysis in a poorly studied area, trip aggregation, and studied decisions from the perspective of two different stakeholders, the passenger and society. We modelled the impact and potential of composite traffic, a hypothetical large-scale demand-responsive public transport system for the Helsinki metropolitan area, where a centralised system would collect the information on all trip demands online, would merge the trips with the same origin and destination into public vehicles with eight or four seats, and then would transmit the trip instructions to the passengers' mobile phones. Results We show here that in an urban area with one million inhabitants, trip aggregation could reduce the health, environmental, and other detrimental impacts of car traffic typically by 50–70%, and if implemented could attract about half of the car passengers, and within a broad operational range would require no public subsidies. Conclusion Composite traffic provides new degrees of freedom in urban decision-making in identifying novel solutions to the problems of urban traffic. PMID:16309549

  13. Quantitative multiplex CARS spectroscopy in congested spectral regions

    NASA Astrophysics Data System (ADS)

    Müller, Michiel; Rinia, Hilde A.; Bonn, Mischa; Vartiainen, Erik M.; Lisker, Melanie; van Bel, Aart

    2007-02-01

    A novel procedure is developed to describe and reproduce experimental coherent anti-Stokes Raman scattering (CARS) data, with particular emphasis on highly congested spectral regions. The approach - exemplified here with high-quality multiplex CARS data - makes use the maximum entropy method for phase retrieval. The retrieved imaginary part of the nonlinear susceptibility is shown to be equal to the spontaneous Raman spectrum. The phase retrieval procedure does not influence the noise contained in the spectra. The conversion of CARS to Raman data permits a quantitative interpretation of CARS spectra. This novel approach is demonstrated for highly congested multiplex CARS spectra of sucrose, fructose and glucose. This novel procedures enables extraction of vibrational information from multiplex CARS data without the use of a priori information of the sample.

  14. Generic vehicle speed models based on traffic simulation: Development and application

    SciTech Connect

    Margiotta, R.; Cohen, H.; Elkins, G.; Rathi, A.; Venigalla, M.

    1994-12-15

    This paper summarizes the findings of a research project to develop new methods of estimating speeds for inclusion in the Highway Performance Monitoring System (HPMS) Analytical Process. The paper focuses on the effects of traffic conditions excluding incidents (recurring congestion) on daily average ed and excess fuel consumption. A review of the literature revealed that many techniques have been used to predict speeds as a function of congestion but most fail to address the effects of queuing. However, the method of Dowling and Skabardonis avoids this limitation and was adapted to the research. The methodology used the FRESIM and NETSIM microscopic traffic simulation models to develop uncongested speed functions and as a calibration base for the congested flow functions. The chief contributions of the new speed models are the simplicity of application and their explicit accounting for the effects of queuing. Specific enhancements include: (1) the inclusion of a queue discharge rate for freeways; (2) use of newly defined uncongested flow speed functions; (3) use of generic temporal distributions that account for peak spreading; and (4) a final model form that allows incorporation of other factors that influence speed, such as grades and curves. The main limitation of the new speed models is the fact that they are based on simulation results and not on field observations. They also do not account for the effect of incidents on speed. While appropriate for estimating average national conditions, the use of fixed temporal distributions may not be suitable for analyzing specific facilities, depending on observed traffic patterns. Finally, it is recommended that these and all future speed models be validated against field data where incidents can be adequately identified in the data.

  15. Behavioral interventions for alleviating psychotic symptoms.

    PubMed

    Corrigan, P W; Storzbach, D M

    1993-04-01

    Behavioral interventions can augment the effects of antipsychotic medication in alleviating hallucinations, delusions, and conceptual disorganization. Such interventions may be based on operant conditioning and reinforcement strategies and on training in coping skills. Reinforcement strategies have been used to decrease the rate of confused speech, delusional talk, and other psychotic behaviors, but they appear to have little effect on the subjective distress patients experience as a result of such symptoms. Strategies that teach patients skills for coping with psychotic symptoms include cognitive reframing methods, nonconfrontational methods that help patients find alternative explanations for delusions, and use of humming to interfere with subvocal movements of the larynx muscles, which may be related to auditory hallucinations. The authors review studies of the effectiveness of these interventions and suggest an approach integrating reinforcement and training in coping skills that may help reduce psychotic symptoms. PMID:8096490

  16. Autonomous Distributed Congestion Control Scheme in WCDMA Network

    NASA Astrophysics Data System (ADS)

    Ahmad, Hafiz Farooq; Suguri, Hiroki; Choudhary, Muhammad Qaisar; Hassan, Ammar; Liaqat, Ali; Khan, Muhammad Umer

    Wireless technology has become widely popular and an important means of communication. A key issue in delivering wireless services is the problem of congestion which has an adverse impact on the Quality of Service (QoS), especially timeliness. Although a lot of work has been done in the context of RRM (Radio Resource Management), the deliverance of quality service to the end user still remains a challenge. Therefore there is need for a system that provides real-time services to the users through high assurance. We propose an intelligent agent-based approach to guarantee a predefined Service Level Agreement (SLA) with heterogeneous user requirements for appropriate bandwidth allocation in QoS sensitive cellular networks. The proposed system architecture exploits Case Based Reasoning (CBR) technique to handle RRM process of congestion management. The system accomplishes predefined SLA through the use of Retrieval and Adaptation Algorithm based on CBR case library. The proposed intelligent agent architecture gives autonomy to Radio Network Controller (RNC) or Base Station (BS) in accepting, rejecting or buffering a connection request to manage system bandwidth. Instead of simply blocking the connection request as congestion hits the system, different buffering durations are allocated to diverse classes of users based on their SLA. This increases the opportunity of connection establishment and reduces the call blocking rate extensively in changing environment. We carry out simulation of the proposed system that verifies efficient performance for congestion handling. The results also show built-in dynamism of our system to cater for variety of SLA requirements.

  17. Traffic Safety for Special Children

    ERIC Educational Resources Information Center

    Wilson, Val; MacKenzie, R. A.

    1974-01-01

    In a 6 weeks' unit on traffic education using flannel graphs, filmstrips and models, 12 special class students (IQ 55-82) ages 7- to 11-years-old learned six basic skills including crossing a road, obeying traffic lights and walking on country roads. (CL)

  18. Steering Kids to Traffic Safety.

    ERIC Educational Resources Information Center

    PTA Today, 1991

    1991-01-01

    Guidelines to help parents explain traffic safety to children cover the following: school bus safety (e.g., remain seated, do not shout); walking (e.g., obey traffic signals, cross at crosswalks); driving (e.g., wear seatbelts, enter and exit from the curb side); and biking (e.g., wear helmets, do not ride at night). (SM)

  19. Traffic Calming: A Social Issue

    ERIC Educational Resources Information Center

    Crouse, David W.

    2004-01-01

    Substantial urban growth fueled by a strong economy often results in heavy traffic thus making streets less hospitable. Traffic calming is one response to the pervasiveness of the automobile. The issues concern built environments and involve multiple actors reflecting different interests. The issues are rarely technical and involve combinations of…

  20. 36 CFR 1004.13 - Obstructing traffic.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... flow of traffic. ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Obstructing traffic. 1004.13 Section 1004.13 Parks, Forests, and Public Property PRESIDIO TRUST VEHICLES AND TRAFFIC SAFETY §...

  1. The impact of traffic-flow patterns on air quality in urban street canyons.

    PubMed

    Thaker, Prashant; Gokhale, Sharad

    2016-01-01

    We investigated the effect of different urban traffic-flow patterns on pollutant dispersion in different winds in a real asymmetric street canyon. Free-flow traffic causes more turbulence in the canyon facilitating more dispersion and a reduction in pedestrian level concentration. The comparison of with and without a vehicle-induced-turbulence revealed that when winds were perpendicular, the free-flow traffic reduced the concentration by 73% on the windward side with a minor increase of 17% on the leeward side, whereas for parallel winds, it reduced the concentration by 51% and 29%. The congested-flow traffic increased the concentrations on the leeward side by 47% when winds were perpendicular posing a higher risk to health, whereas reduced it by 17-42% for parallel winds. The urban air quality and public health can, therefore, be improved by improving the traffic-flow patterns in street canyons as vehicle-induced turbulence has been shown to contribute significantly to dispersion. PMID:26412198

  2. Model-free approach to optimal signal light timing for system-wide traffic control

    SciTech Connect

    Spall, J.C.; Chin, D.C.

    1994-12-31

    A long-standing problem in traffic engineering is to optimize the flow of vehicles through a given road network. Improving the timing of the traffic signals at intersections in the network is generally the most powerful and cost-effective means of achieving this goal. However, because of the many complex aspects of a traffic system-human behavioral considerations, vehicle flow interactions within the network, weather effects, traffic accidents, long-term (e.g., seasonal) variation, etc.-it has been notoriously difficult to determine the optimal signal light timing. This is especially the case on a system- wide (multiple intersection) basis. Much of this difficulty has stemmed from the need to build extremely complex open-loop models of the traffic dynamics as a component of the control strategy. This paper presents a fundamentally different approach for optimal light timing that eliminates the need for such an open-loop model. The approach is based on a neural network (or other function approximator) serving as the basis for the control law, with the weight estimation occurring in closed-loop mode via the simultaneous perturbation stochastic approximation (SPSA) algorithm. Since the SPSA algorithm requires only loss function measurements (no gradients of the loss function), there is no open-loop model required for the weight estimation. The approach is illustrated by simulation on a six-intersection network with moderate congestion and stochastic, nonlinear effects.

  3. RATE-ADJUSTMENT ALGORITHM FOR AGGREGATE TCP CONGESTION CONTROL

    SciTech Connect

    P. TINNAKORNSRISUPHAP, ET AL

    2000-09-01

    The TCP congestion-control mechanism is an algorithm designed to probe the available bandwidth of the network path that TCP packets traverse. However, it is well-known that the TCP congestion-control mechanism does not perform well on networks with a large bandwidth-delay product due to the slow dynamics in adapting its congestion window, especially for short-lived flows. One promising solution to the problem is to aggregate and share the path information among TCP connections that traverse the same bottleneck path, i.e., Aggregate TCP. However, this paper shows via a queueing analysis of a generalized processor-sharing (GPS) queue with regularly-varying service time that a simple aggregation of local TCP connections together into a single aggregate TCP connection can result in a severe performance degradation. To prevent such a degradation, we introduce a rate-adjustment algorithm. Our simulation confirms that by utilizing our rate-adjustment algorithm on aggregate TCP, connections which would normally receive poor service achieve significant performance improvements without penalizing connections which already receive good service.

  4. Dynamically-induced structures formation in congested magma

    NASA Astrophysics Data System (ADS)

    Petford, N.

    2008-12-01

    Crystal fabrics preserved in igneous rocks offer a glimpse into the magma emplacement process. Detailed field mapping, in combination with AMS studies, seem to provide the best available data for unravelling intrusion architecture on the decimetre scale. However, a full and proper understanding of the fluid dynamics of congested fluid-particle mixtures during shear remains elusive. This is a shame as without recourse to such fundamental understanding, the interpretation of structural field data in the context of magma flow remains problematic. One way to gain insight into the process is to treat flowing magma as a dynamic material with a rheology similar to sheared, congested slurries. The fancy that dense magma equates to a high temperature slurry is an attractive one, and opens up a way to examine the emplacement process that does not rely exclusively on equilibrium thermodynamics as a final explanation of commonly observed igneous structures. Instead, using examples from mafic rocks where cooling has been rapid, the idea is put forward that in high Peclet number suspensions (where particle diffusion is negligible), shearing and non- Newtonian behaviour imparts a rich diversity of structures including layering, grading and flow segregation. Key to understanding the rheology, hence flow dynamics of congested magma, is the particle microstructure, a still poorly known essence of suspension flows. Where magma transport is continental in scale and long lived (e.g. Large Igneous Provinces), rotation of the earth may in theory endow a small but potentially measurable imprint on the preserved flow fabric.

  5. Using Variable Speed Limits to Eliminate Wide Moving Jams: a Study Based on Three-Phase Traffic Theory

    NASA Astrophysics Data System (ADS)

    Wang, Yizhi; Zhang, Yi; Hu, Jianming; Li, Li

    2012-09-01

    One frequently observed congested traffic flow pattern is wide moving jam (WMJ), in which the average vehicle speed is very low and the density is very high. In some recent studies, variable speed limits (VSL) were proposed as effective measures to eliminate or abate the influence of jam waves. However, in most of these studies, the stochastic features of driving behaviors and the resulting uncertainty of traffic flow dynamics were not fully considered. In this paper, we use cellular automaton (CA) model-based simulations to test the performances of different VSL control strategies and apply the three-phase traffic theory to further analyze the obtained results. Based on the simulation results, we got two novel findings. Firstly, we observed seven, instead of the previously assumed six, states of traffic flow in the evolution process of WMJ, when VSL were applied. Secondly and more importantly, we found that inappropriate speed limit may induce new WMJ and exaggerate congestions in two ways: one way corresponds to an F → J transition and the other corresponds to an F → S → J transition. Based on these findings, the appropriate lower bound of VSL was finally discussed in this paper.

  6. Traffic flow on realistic road networks with adaptive traffic lights

    NASA Astrophysics Data System (ADS)

    de Gier, Jan; Garoni, Timothy M.; Rojas, Omar

    2011-04-01

    We present a model of traffic flow on generic urban road networks based on cellular automata. We apply this model to an existing road network in the Australian city of Melbourne, using empirical data as input. For comparison, we also apply this model to a square-grid network using hypothetical input data. On both networks we compare the effects of non-adaptive versus adaptive traffic lights, in which instantaneous traffic state information feeds back into the traffic signal schedule. We observe that not only do adaptive traffic lights result in better averages of network observables, they also lead to significantly smaller fluctuations in these observables. We furthermore compare two different systems of adaptive traffic signals, one which is informed by the traffic state on both upstream and downstream links and one which is informed by upstream links only. We find that, in general, both the mean and the fluctuation of the travel time are smallest when using the joint upstream-downstream control strategy.

  7. Traffic information computing platform for big data

    SciTech Connect

    Duan, Zongtao Li, Ying Zheng, Xibin Liu, Yan Dai, Jiting Kang, Jun

    2014-10-06

    Big data environment create data conditions for improving the quality of traffic information service. The target of this article is to construct a traffic information computing platform for big data environment. Through in-depth analysis the connotation and technology characteristics of big data and traffic information service, a distributed traffic atomic information computing platform architecture is proposed. Under the big data environment, this type of traffic atomic information computing architecture helps to guarantee the traffic safety and efficient operation, more intelligent and personalized traffic information service can be used for the traffic information users.

  8. A Cooperative Human-Adaptive Traffic Simulation (CHATS)

    NASA Technical Reports Server (NTRS)

    Phillips, Charles T.; Ballin, Mark G.

    1999-01-01

    NASA is considering the development of a Cooperative Human-Adaptive Traffic Simulation (CHATS), to examine and evaluate performance of the National Airspace System (NAS) as the aviation community moves toward free flight. CHATS will be specifically oriented toward simulating strategic decision-making by airspace users and by the service provider s traffic management personnel, within the context of different airspace and rules assumptions. It will use human teams to represent these interests and make decisions, and will rely on computer modeling and simulation to calculate the impacts of these decisions. The simulation objectives will be to examine: 1. evolution of airspace users and the service provider s strategies, through adaptation to new operational environments; 2. air carriers competitive and cooperative behavior; 3. expected benefits to airspace users and the service provider as compared to the current NAS; 4. operational limitations of free flight concepts due to congestion and safety concerns. This paper describes an operational concept for CHATS, and presents a high-level functional design which would utilize a combination of existing and new models and simulation capabilities.

  9. Interaction between worsening renal function and persistent congestion in acute decompensated heart failure.

    PubMed

    Wattad, Malak; Darawsha, Wisam; Solomonica, Amir; Hijazi, Maher; Kaplan, Marielle; Makhoul, Badira F; Abassi, Zaid A; Azzam, Zaher S; Aronson, Doron

    2015-04-01

    Worsening renal function (WRF) and congestion are inextricably related pathophysiologically, suggesting that WRF occurring in conjunction with persistent congestion would be associated with worse clinical outcome. We studied the interdependence between WRF and persistent congestion in 762 patients with acute decompensated heart failure (HF). WRF was defined as ≥0.3 mg/dl increase in serum creatinine above baseline at any time during hospitalization and persistent congestion as ≥1 sign of congestion at discharge. The primary end point was all-cause mortality with mean follow-up of 15 ± 9 months. Readmission for HF was a secondary end point. Persistent congestion was more common in patients with WRF than in patients with stable renal function (51.0% vs 26.6%, p <0.0001). Both persistent congestion and persistent WRF were significantly associated with mortality (both p <0.0001). There was a strong interaction (p = 0.003) between persistent WRF and congestion, such that the increased risk for mortality occurred predominantly with both WRF and persistent congestion. The adjusted hazard ratio for mortality in patients with persistent congestion as compared with those without was 4.16 (95% confidence interval [CI] 2.20 to 7.86) in patients with WRF and 1.50 (95% CI 1.16 to 1.93) in patients without WRF. In conclusion, persisted congestion is frequently associated with WRF. We have identified a substantial interaction between persistent congestion and WRF such that congestion portends increased mortality particularly when associated with WRF. PMID:25700802

  10. Road traffic injuries in Mozambique.

    PubMed

    Romão, Francelina; Nizamo, Hanifa; Mapasse, Domingos; Rafico, Momede Mussá; José, João; Mataruca, Simão; Efron, M Lúcia; Omondi, Lucas O; Leifert, Thelma; Bicho, Joaquim M L Marungo

    2003-01-01

    Road traffic injuries affect the economy, health and quality of life of the people of Mozambique. Current road safety programmes are inadequate and inefficient given the magnitude of the problem. Data reported on road traffic crashes in the period 1990 to 2000 from the National Institute for Road Safety, the traffic police and the Central Hospital of Maputo were reviewed. The burden of road traffic injuries in Mozambique is rising, with at least three people killed daily. The age group most affected is 25-38 (39.35%), followed by 16-24 (20.79%). The main causes of crashes include reckless driving, drunken driving, roads with potholes, inadequate signs, lack of protection for pedestrians, and inadequate traffic law enforcement. However, the data are not adequate to reveal the true magnitude of the problem. Data collected by different sources are incomplete and not coordinated with other sources and databases. In urban areas, however, better response to crashes, treatment of the injured, reporting and data collection is attributable to a greater concentration of police and medical facilities. Road traffic safety programmes in Mozambique are inadequate and inefficient, starting with the data collection system. Improvement of injury surveillance systems is needed to help make road traffic safety a national development agenda priority and for developing and implementing road safety policies. For road safety programmes to be effective, government must facilitate stakeholders' involvement, and the clear definition of government activities, civil society activities and public-private partnerships need to be established. PMID:12772487

  11. Self-management in Future Internet Wireless Networks: Dynamic Resource Allocation and Traffic Routing for Multi-service Provisioning

    NASA Astrophysics Data System (ADS)

    Chochliouros, Ioannis P.; Alonistioti, Nancy; Spiliopoulou, Anastasia S.; Agapiou, George; Mihailovic, Andrej; Belesioti, Maria

    Evolution towards the Future (Internet) networks necessitates inclusion of self-management capabilities in modern network infrastructures, for a satisfactory provision of related services and for preserving network performance. We have considered a specific targeted methodology, in the form of the generic cognitive cycle model, which includes three distinct processes (i.e. Monitoring, Decision Making and Execution), known as the “MDE” model, able to support dynamic resource allocation and traffic routing schemes. For further understanding of the issue we have examined two essential use-cases of practical interest, both in the context of modern wireless infrastructures: The former was about dynamic spectrum re-allocation for efficient use of traffic, while the latter has examined intelligent dynamic traffic management for handling network overloads, to avoid congestion.

  12. Effect of self-similar traffic on the performance and buffer requirements of ATM ABR edge devices

    SciTech Connect

    Dastangoo, S.; Miller, G.J.; Chen, H.; Brandt, J.

    1996-02-05

    Previous studies demonstrated that Ethemet local area network traffic is statistically self-similar and that the commonly used Poisson models are not able to capture the fractal characteristics of Ethemet traffic. This contribution uses simulated self-similar traffic traces from the MITRE Corporation and Sandia`s simulation software to evaluate the ABR performance of an ATM backbone. The ATM backbone interconnects Ethemet LANs via edge devices such as routers and bridges. We evaluate the overall network performance in terms of throughput, response time, fairness, and buffer requirements. Because typical edge devices perform simple forwarding functions, their usual mechanism for signaling network congestion is packet dropping. Therefore, we believe that the proper provisioning of buffer resources in ATM edge devices is crucial to the overall network performance.

  13. Internet Usage at Elementary, Middle and High Schools: A First Look at K-12 Traffic from Two US Georgia Counties

    NASA Astrophysics Data System (ADS)

    Miller, Robert; Matthews, Warren; Dovrolis, Constantine

    Earlier Internet traffic analysis studies have focused on enterprises [1,6], backbone networks [2,3], universities [5,7], or residential traffic [4]. However, much less is known about Internet usage in the K-12 educational system (elementary, middle and high schools). In this paper, we present a first analysis of network traffic captured at two K-12 districts in the US state of Georgia, also comparing with similar traces collected at our university (Georgia Tech). An interesting point is that one of the two K-12 counties has limited Internet access capacity and it is congested during most of the workday. Further, both K-12 networks are heavily firewalled, using both port-based and content-based filters. The paper focuses on the host activity, utilization trends, user activity, application mix, flow characteristics and communication dispersion in these two K-12 networks.

  14. Spreading of Traffic Jam in a Traffic Flow Model

    NASA Astrophysics Data System (ADS)

    Nagatani, Takashi

    1993-04-01

    A cellular automaton (CA) model is presented to simulate the traffic jam induced by a traffic accident. The spreading of jamming cars induced by a car crash is investigated by computer simulation. An analogy is proposed between the crystal growth and the traffic-jam spreading. The scaling behavior of the traffic-jam spreading is studied. It is shown that the number N of jamming cars scales as N≈t2.34± 0.03 for p above the dynamical jamming transition pc{=}0.35 and N≈t1.07 below pc where t is the time and p is the density of cars. The time constant ts, which is the time required for all cars to stop, scales as ts≈p-1.07± 0.03 for p

  15. The effect of communications and traffic situation displays on pilots awareness of traffic in the terminal area

    NASA Technical Reports Server (NTRS)

    Melanson, D.; Curry, R. E.; Howell, J. D.; Connelly, M. E.

    1973-01-01

    The Air Traffic Control (ATC) system is evolving under a general plan specified by the Federal Aviation Administration. Among the developments being considered is the Discrete Address Beacon System (DABS). The use of this system, although relieving congestion on the communications frequencies, would eliminate information about other aircraft because the party line communications now in use would be lost. One alternative to restore this lost information is an Airborne Traffic Situation Display (TSD). Experienced airline and military pilots participated in a factorial design to evaluate two types of communication (discrete address, party line) and two types of displays (TSD, no TSD). A stop-action quiz was used to evaluate their knowledge of other aircrafts' position, altitude, speed, heading, rate of climb, identity, and landing sequence number. Significant differences between conditions were detected, primarily in the position variables. Workload, as measured by a spare capacity side-task, showed a main effect of displays and a significant interaction between displays and communications. The data are summarized by plotting each display/communication condition configuration in the plane defined by information and workload index. A limited number of blunders by other aircraft were included in the simulations with a significant, but not entirely satisfactory, improvement in blunder detection attributed to the TSD.

  16. Kinetic theory of vehicular traffic

    NASA Astrophysics Data System (ADS)

    Iannini, M. L. L.; Dickman, Ronald

    2016-02-01

    We review the kinetic theory of traffic proposed by Prigogine and Herman in which the Boltzmann equation is adapted to vehicular traffic. The kinetic equation and its solution are discussed, and a novel distribution of desired velocities that is more suitable for describing real traffic conditions is analyzed. We also study the stationary velocity distribution at the transition between individual and collective flow patterns. At this transition, the distribution splits into a smoothly varying regular part, in which vehicles have nonzero velocities, and a singular one, corresponding to stopped vehicles. Computational methods for obtaining the stationary velocity distribution and the full space-time evolution of the vehicular distribution are explained.

  17. Study on a novel traffic engineering model for IP over ASON network

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Li, Yanhe; Zheng, Xiaoping; Zhang, Hanyi

    2005-02-01

    The major goal of TE (traffic engineering) is to facilitate efficient and reliable network operations while simultaneously optimizing network utilization and traffic performance. Therefore it is necessary to introduce TE mechanism to ISPs" (Internet Service Providers") networks with the purpose of improving network performance and reducing costs. In this paper, a novel TE mechanism based on GMPLS (Generalized Multi-Protocol Label Switching) is proposed and analyzed in detail, and is demonstrated on a network with IP over ASON (automatically switched optical network) architecture. The ASON layer acts as the server of IP layer which uses traditional IP protocols, and realizes TE mechanism through the method of dynamically changing bandwidth seen by IP layer through UNI (User-Network Interface). Simulation results have shown that the model has a superior operational agility to the conventional method and lower congestion probability in certain conditions.

  18. Integrated risk/cost planning models for the US Air Traffic system

    NASA Technical Reports Server (NTRS)

    Mulvey, J. M.; Zenios, S. A.

    1985-01-01

    A prototype network planning model for the U.S. Air Traffic control system is described. The model encompasses the dual objectives of managing collision risks and transportation costs where traffic flows can be related to these objectives. The underlying structure is a network graph with nonseparable convex costs; the model is solved efficiently by capitalizing on its intrinsic characteristics. Two specialized algorithms for solving the resulting problems are described: (1) truncated Newton, and (2) simplicial decomposition. The feasibility of the approach is demonstrated using data collected from a control center in the Midwest. Computational results with different computer systems are presented, including a vector supercomputer (CRAY-XMP). The risk/cost model has two primary uses: (1) as a strategic planning tool using aggregate flight information, and (2) as an integrated operational system for forecasting congestion and monitoring (controlling) flow throughout the U.S. In the latter case, access to a supercomputer is required due to the model's enormous size.

  19. Benefit of HSP90α intervention on ischemia-reperfusion injury of venous blood-congested flaps

    PubMed Central

    HU, XIAO-YING; CHEN, ZHEN-YU; ZHANG, BIN; LENG, XIANG-FENG; FAN, XIAO-JIAN; LIU, TAO

    2016-01-01

    In order to decrease the incidence of flap necrosis after reconstructive surgeries, new approaches are required. In the present study, a model of venous congested flaps in rats was established to test the heat shock protein (HSP) 90α, ‘F-5’, protein as an intervention therapy to alleviate ischemia-reperfusion injury. A recombinant plasmid pET15b-F-5 carrying the HSP90α gene was constructed and the induced protein was purified from bacterial cell cultures. The rats in the study were divided into three different intervention groups: group A rats were treated with normal saline prior to flap establishment, group B rats were treated with HSP90α, ‘F-5’, protein prior to flap establishment, and group C rats were treated with the same ‘F-5’ protein after the surgical procedure. Additionally, the reperfusion time-points, ischemia for 6 or 8 h (5 rats each), were established in each group. After set periods of time, the flaps were observed for skin appearance, blood flow, survival rate and histological changes including neovascularization and re-epithelialization. The results showed that the flaps in the rats pre-treated with ‘F-5’ protein performed better than the flaps of rats in the other two groups: the blood flow was higher, flap survival rate was increased, inflammatory cell infiltration was decreased and angiogenesis increased, and new skin structure was better completed by the end of the experiment. The parameters examind were improved for all the groups when the ischemia time was 6 h instead of 8 h. In conclusion, HSP90α intervention prior to flap establishment was shown to be beneficial in the model of ischemia-reperfusion injury in venous-congested flaps. PMID:27347036

  20. Dynamics of traffic flow with real-time traffic information

    NASA Astrophysics Data System (ADS)

    Yokoya, Yasushi

    2004-01-01

    We studied dynamics of traffic flow with real-time information provided. Provision of the real-time traffic information based on advancements in telecommunication technology is expected to facilitate the efficient utilization of available road capacity. This system has a potentiality of not only engineering for road usage but also the science of complexity series. In the system, the information plays a role of feedback connecting microscopic and macroscopic phenomena beyond the hierarchical structure of statistical physics. In this paper, we tried to clarify how the information works in a network of traffic flow from the perspective of statistical physics. The dynamical feature of the traffic flow is abstracted by a contrastive study between the nonequilibrium statistical physics and a computer simulation based on cellular automaton. We found that the information disrupts the local equilibrium of traffic flow by a characteristic dissipation process due to interaction between the information and individual vehicles. The dissipative structure was observed in the time evolution of traffic flow driven far from equilibrium as a consequence of the breakdown of the local-equilibrium hypothesis.

  1. Lactobacillus plantarum CCFM639 alleviates aluminium toxicity.

    PubMed

    Yu, Leilei; Zhai, Qixiao; Liu, Xiaoming; Wang, Gang; Zhang, Qiuxiang; Zhao, Jianxin; Narbad, Arjan; Zhang, Hao; Tian, Fengwei; Chen, Wei

    2016-02-01

    Aluminium (Al) is the most abundant metal in the earth's crust. Al exposure can cause a variety of adverse physiological effects in humans and animals. Our aim was to demonstrate that specific probiotic bacteria can play a special physiologically functional role in protection against Al toxicity in mice. Thirty strains of lactic acid bacteria (LAB) were tested for their aluminium-binding ability, aluminium tolerance, their antioxidative capacity, and their ability to survive the exposure to artificial gastrointestinal (GI) juices. Lactobacillus plantarum CCFM639 was selected for animal experiments because of its excellent performance in vitro. Forty mice were divided into four groups: control, Al only, Al plus CCFM639, and Al plus deferiprone (DFP). CCFM639 was administered at 10(9) CFU once daily for 10 days, followed by a single oral dose of aluminium chloride hexahydrate at 5.14 mg aluminium (LD50) for each mouse. The results showed that CCFM639 treatment led to a significant reduction in the mortality rates with corresponding decrease in intestinal aluminium absorption and in accumulation of aluminium in the tissues and amelioration of hepatic histopathological damage. This probiotic treatment also resulted in alleviation of hepatic, renal, and cerebral oxidative stress. The treatment of L. plantarum CCFM639 has potential as a therapeutic dietary strategy against acute aluminium toxicity. PMID:26610803

  2. An Advanced Buffet Load Alleviation System

    NASA Technical Reports Server (NTRS)

    Burnham, Jay K.; Pitt, Dale M.; White, Edward V.; Henderson, Douglas A.; Moses, Robert W.

    2001-01-01

    This paper describes the development of an advanced buffet load alleviation (BLA) system that utilizes distributed piezoelectric actuators in conjunction with an active rudder to reduce the structural dynamic response of the F/A-18 aircraft vertical tails to buffet loads. The BLA system was defined analytically with a detailed finite-element-model of the tail structure and piezoelectric actuators. Oscillatory aerodynamics were included along with a buffet forcing function to complete the aeroservoelastic model of the tail with rudder control surface. Two single-input-single-output (SISO) controllers were designed, one for the active rudder and one for the active piezoelectric actuators. The results from the analytical open and closed loop simulations were used to predict the system performance. The objective of this BLA system is to extend the life of vertical tail structures and decrease their life-cycle costs. This system can be applied to other aircraft designs to address suppression of structural vibrations on military and commercial aircraft.

  3. Alleviating spatial conflict between people and biodiversity.

    PubMed

    Luck, Gary W; Ricketts, Taylor H; Daily, Gretchen C; Imhoff, Marc

    2004-01-01

    Human settlements are expanding in species-rich regions and pose a serious threat to biodiversity conservation. We quantify the degree to which this threat manifests itself in two contrasting continents, Australia and North America, and suggest how it can be substantially alleviated. Human population density has a strong positive correlation with species richness in Australia for birds, mammals, amphibians, and butterflies (but not reptiles) and in North America for all five taxa. Nevertheless, conservation investments could secure locations that harbor almost all species while greatly reducing overlap with densely populated regions. We compared two conservation-planning scenarios that each aimed to represent all species at least once in a minimum set of sampling sites. The first scenario assigned equal cost to each site (ignoring differences in human population density); the second assigned a cost proportional to the site's human population density. Under the equal-cost scenario, 13-40% of selected sites occurred where population density values were highest (in the top decile). However, this overlap was reduced to as low as 0%, and in almost all cases to <10%, under the population-cost scenario, when sites of high population density were avoided where possible. Moreover, this reduction of overlap was achieved with only small increases in the total amount of area requiring protection. As densely populated regions continue to expand rapidly and drive up land values, the strategic conservation investments of the kind highlighted in our analysis are best made now. PMID:14681554

  4. A cellular automaton model based on empirical observations of a driver’s oscillation behavior reproducing the findings from Kerner’s three-phase traffic theory

    NASA Astrophysics Data System (ADS)

    Yang, Haifei; Lu, Jian; Hu, Xiaojian; Jiang, Jun

    2013-09-01

    In this paper, we propose a new cellular automaton model based on the well known three-phase traffic theory. The model takes into account the mechanism of a driver’s oscillation behavior obtained from engineering experiments in real traffic conditions. This mechanism shows the inner competition between speed adaptation and distance adjustment effects. The speed adaptation effect leads to synchronized flow, whereas a pinch region emerges, associated with the spontaneous occurrence of wide moving jams, due to distance over-adjustment. Numerical simulations are carried out both with periodic and with open boundary conditions in order to investigate the spatiotemporal features of traffic flow. The results indicate that our model is able to reproduce the three distinct traffic phases and exhibit the four congested patterns upstream of an isolated on-ramp, which is in good consistency with the results predicted from the three-phase theory.

  5. Nitrendipine binding in congestive heart failure due to myocardial infarction

    SciTech Connect

    Dixon, I.M.; Lee, S.L.; Dhalla, N.S. )

    1990-03-01

    Depressed cardiac pump function is the hallmark of congestive heart failure, and it is suspected that decreased influx of Ca2+ into the cardiac cell is responsible for depressed contractile function. Since Ca2+ channels in the sarcolemmal membrane are considered to be an important route for the entry of Ca2+, we examined the status of Ca2+ receptors/channels in failing rat hearts after myocardial infarction of the left ventricular free wall. For this purpose, the left coronary artery was ligated and hearts were examined 4, 8, and 16 weeks later; sham-operated animals served as controls. Hemodynamic assessment revealed decreased total mechanical energy (left ventricular systolic pressure x heart rate), increased left ventricular diastolic pressure, and decreased positive and negative dP/dt in experimental animals at 4, 8, and 16 weeks. Although accumulation of ascites in the abdominal cavity was evident at 4 weeks, other clinical signs of congestive heart failure in experimental rats were evident from the presence of lung congestion and cardiac dilatation at 8 and 16 weeks after induction of myocardial infarction. The density of Ca2+ receptors/channels in crude membranes, as assessed by (3H)nitrendipine binding assay, was found to be decreased in the uninfarcted experimental left ventricle at 8 and 16 weeks; however, no change in the affinity of nitrendipine was evident. A similar depression in the specific binding of another dihydropyridine compound, (3H)PN200-110, was also evident in failing hearts. Brain and skeletal muscle crude membrane preparations, unlike those of the right ventricle and liver, revealed a decrease in Ca2+ receptors/channels density in experimental animals at 16 weeks.

  6. 36 CFR 4.13 - Obstructing traffic.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... interfere with the normal flow of traffic. ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Obstructing traffic. 4.13... VEHICLES AND TRAFFIC SAFETY § 4.13 Obstructing traffic. The following are prohibited: (a) Stopping...

  7. Turbulent Dispersion of Traffic Emissions

    NASA Astrophysics Data System (ADS)

    Staebler, R. M.; Gordon, M.; Liggio, J.; Makar, P.; Mihele, C.; Brook, J.; Wentzell, J. J.; Gong, S.; Lu, G.; Lee, P.

    2010-12-01

    Emissions from the transportation sector are a significant source of air pollution. Ongoing efforts to reduce the impacts require tools to provide guidance on policies regarding fuels, vehicle types and traffic control. The air quality models currently used to predict the effectiveness of policies typically treat traffic emissions as a source uniformly distributed across the surface of a model grid. In reality, emissions occur along lines above the surface, in an initially highly concentrated form, and are immediately mixed by traffic-enhanced turbulence. Differences between model and reality in terms of both chemistry and dispersion are to be expected. The ALMITEE (Advancing Local-scale Modeling through Inclusion of Transportation Emission Experiments) subproject FEVER (Fast Evolution of Vehicle Emissions from Roadways), conducted on multi-lane highways in the Toronto area in the summer of 2010, included measurements to quantify the evolution and dispersion of traffic emissions. Continuous micro-meteorological data (heat and momentum fluxes, temperature, humidity and incoming solar radiation) were collected 10m from the road, next to a traffic camera used to determine traffic density, composition and speed. Sonic anemometers and an aircraft turbulence probe mounted on a mobile lab provided measurements of turbulent dispersion both directly in traffic on the highway as well as on perpendicular side roads, as a function of distance from the highway. The mobile lab was equipped with instruments to characterize the aerosol size and mass distributions, aerosol composition including black carbon content, NO, NO2, CO2, CO, SO2 and VOCs at high time resolution. Preliminary results on the consequences of turbulent dispersion of traffic emissions levels under a variety of conditions will be disseminated.

  8. Fully automated urban traffic system

    NASA Technical Reports Server (NTRS)

    Dobrotin, B. M.; Hansen, G. R.; Peng, T. K. C.; Rennels, D. A.

    1977-01-01

    The replacement of the driver with an automatic system which could perform the functions of guiding and routing a vehicle with a human's capability of responding to changing traffic demands was discussed. The problem was divided into four technological areas; guidance, routing, computing, and communications. It was determined that the latter three areas being developed independent of any need for fully automated urban traffic. A guidance system that would meet system requirements was not being developed but was technically feasible.

  9. The modifying effect of socioeconomic status on the relationship between traffic, air pollution and respiratory health in elementary schoolchildren.

    PubMed

    Cakmak, Sabit; Hebbern, Christopher; Cakmak, Jasmine D; Vanos, Jennifer

    2016-07-15

    The volume and type of traffic and exposure to air pollution have been found to be associated with respiratory health, but few studies have considered the interaction with socioeconomic status at the household level. We investigated the relationships of respiratory health related to traffic type, traffic volume, and air pollution, stratifying by socioeconomic status, based on household income and education, in 3591 schoolchildren in Windsor, Canada. Interquartile range changes in traffic exposure and pollutant levels were linked to respiratory symptoms and objective measures of lung function using generalised linear models for three levels of income and education. In 95% of the relationships among all cases, the odds ratios for reported respiratory symptoms (a decrease in measured lung function), based on an interquartile range change in traffic exposure or pollutant, were greater in the lower income/education groups than the higher, although the odds ratios were in most cases not significant. However, in up to 62% of the cases, the differences between high and low socioeconomic groups were statistically significant, thus indicating socioeconomic status (SES) as a significant effect modifier. Our findings indicate that children from lower socioeconomic households have a higher risk of specific respiratory health problems (chest congestion, wheezing) due to traffic volume and air pollution exposure. PMID:27064731

  10. Congestive Heart Failure home monitoring pilot study in urban Denver.

    PubMed

    Bakhshi, Saba; Li, Xin; Semenov, Nikolay; Apodaca-Madrid, Jesús; Mahoor, Mohammad H; Newman, Kimberly E; Long, Carlin S; Neuman, Christine

    2011-01-01

    With a growing number of low-income patients developing Congestive Heart Failure in urban Denver, accessible and affordable solutions are needed to provide home management options. A multidisciplinary team evaluated currently available options for telemonitoring and developed a solution for an initial pilot study. This system is currently used in the Denver Metro area (Colorado) for 44 CHF patients. Preliminary results show this approach is effective and has reduced the patients' average length of stay at the hospital compared to historical data and control patients who do not use a remote monitoring system. PMID:22255008

  11. Pimobendan and its use in treating canine congestive heart failure.

    PubMed

    Bowles, Danielle; Fry, Darren

    2011-11-01

    Pimobendan, a calcium sensitizer and phosphodiesterase III inhibitor, has positive inotropic and vasodilatory properties. Its use in patients with naturally occurring congestive heart failure (CHF) has been studied in a number of blinded, randomized, multicenter clinical trials. It has been shown to improve quality of life, reduce heart insufficiency scores, and increase median survival times for patients with CHF due to dilated cardiomyopathy and myxomatous valvular disease. Although most studies have reported positive findings, some potential adverse effects have also been described. Studies are under way to further evaluate the effects of this novel positive inotrope and vasodilator in canine cardiac disease. PMID:22101450

  12. Improving Congestive Heart Failure Care with a Clinical Decision Unit.

    PubMed

    Carpenter, Jo Ellen; Short, Nancy; Williams, Tracy E; Yandell, Ben; Bowers, Margaret T

    2015-01-01

    Evidence supporting the development of Clinical Decision Units (CDUs) to impact congestive heart failure readmission rates comes from several categories of the literature. In this study, a pre-post design with comparison group was used to evaluate the impact of the CDU. Early changes in clinical and financial outcome indicators are encouraging. Nurse leaders seek ways to improve clinical outcomes while managing the current financially challenging environment. Implementation of a CDU provides many opportunities for nurse leaders to positively impact clinical care and financial performance within their institutions. PMID:26625578

  13. Understanding how roadside concentrations of NOx are influenced by the background levels, traffic density, and meteorological conditions using Boosted Regression Trees

    NASA Astrophysics Data System (ADS)

    Sayegh, Arwa; Tate, James E.; Ropkins, Karl

    2016-02-01

    Oxides of Nitrogen (NOx) is a major component of photochemical smog and its constituents are considered principal traffic-related pollutants affecting human health. This study investigates the influence of background concentrations of NOx, traffic density, and prevailing meteorological conditions on roadside concentrations of NOx at UK urban, open motorway, and motorway tunnel sites using the statistical approach Boosted Regression Trees (BRT). BRT models have been fitted using hourly concentration, traffic, and meteorological data for each site. The models predict, rank, and visualise the relationship between model variables and roadside NOx concentrations. A strong relationship between roadside NOx and monitored local background concentrations is demonstrated. Relationships between roadside NOx and other model variables have been shown to be strongly influenced by the quality and resolution of background concentrations of NOx, i.e. if it were based on monitored data or modelled prediction. The paper proposes a direct method of using site-specific fundamental diagrams for splitting traffic data into four traffic states: free-flow, busy-flow, congested, and severely congested. Using BRT models, the density of traffic (vehicles per kilometre) was observed to have a proportional influence on the concentrations of roadside NOx, with different fitted regression line slopes for the different traffic states. When other influences are conditioned out, the relationship between roadside concentrations and ambient air temperature suggests NOx concentrations reach a minimum at around 22 °C with high concentrations at low ambient air temperatures which could be associated to restricted atmospheric dispersion and/or to changes in road traffic exhaust emission characteristics at low ambient air temperatures. This paper uses BRT models to study how different critical factors, and their relative importance, influence the variation of roadside NOx concentrations. The paper

  14. Arctigenin alleviates ER stress via activating AMPK

    PubMed Central

    Gu, Yuan; Sun, Xiao-xiao; Ye, Ji-ming; He, Li; Yan, Shou-sheng; Zhang, Hao-hao; Hu, Li-hong; Yuan, Jun-ying; Yu, Qiang

    2012-01-01

    Aim: To investigate the protective effects of arctigenin (ATG), a phenylpropanoid dibenzylbutyrolactone lignan from Arctium lappa L (Compositae), against ER stress in vitro and the underlying mechanisms. Methods: A cell-based screening assay for ER stress regulators was established. Cell viability was measured using MTT assay. PCR and Western blotting were used to analyze gene and protein expression. Silencing of the CaMKKβ, LKB1, and AMPKα1 genes was achieved by RNA interference (RNAi). An ATP bioluminescent assay kit was employed to measure the intracellular ATP levels. Results: ATG (2.5, 5 and 10 μmol/L) inhibited cell death and unfolded protein response (UPR) in a concentration-dependent manner in cells treated with the ER stress inducer brefeldin A (100 nmol/L). ATG (1, 5 and 10 μmol/L) significantly attenuated protein synthesis in cells through inhibiting mTOR-p70S6K signaling and eEF2 activity, which were partially reversed by silencing AMPKα1 with RNAi. ATG (1-50 μmol/L) reduced intracellular ATP level and activated AMPK through inhibiting complex I-mediated respiration. Pretreatment of cells with the AMPK inhibitor compound C (25 μmol/L) rescued the inhibitory effects of ATG on ER stress. Furthermore, ATG (2.5 and 5 μmol/L) efficiently activated AMPK and reduced the ER stress and cell death induced by palmitate (2 mmol/L) in INS-1 β cells. Conclusion: ATG is an effective ER stress alleviator, which protects cells against ER stress through activating AMPK, thus attenuating protein translation and reducing ER load. PMID:22705729

  15. Why may allopregnanolone help alleviate loneliness?

    PubMed

    Cacioppo, S; Cacioppo, J T

    2015-12-01

    Impaired biosynthesis of Allopregnanolone (ALLO), a brain endogenous neurosteroid, has been associated with numerous behavioral dysfunctions, which range from anxiety- and depressive-like behaviors to aggressive behavior and changes in responses to contextual fear conditioning in rodent models of emotional dysfunction. Recent animal research also demonstrates a critical role of ALLO in social isolation. Although there are likely aspects of perceived social isolation that are uniquely human, there is also continuity across species. Both human and animal research show that perceived social isolation (which can be defined behaviorally in animals and humans) has detrimental effects on physical health, such as increased hypothalamic pituitary adrenal (HPA) activity, decreased brain-derived neurotrophic factor (BDNF) expression, and increased depressive behavior. The similarities between animal and human research suggest that perceived social isolation (loneliness) may also be associated with a reduction in the synthesis of ALLO, potentially by reducing BDNF regulation and increasing HPA activity through the hippocampus, amygdala, and bed nucleus of the stria terminalis (BNST), especially during social threat processing. Accordingly, exogenous administration of ALLO (or ALLO precursor, such as pregnenolone), in humans may help alleviate loneliness. Congruent with our hypothesis, exogenous administration of ALLO (or ALLO precursors) in humans has been shown to improve various stress-related disorders that show similarities between animals and humans i.e., post-traumatic stress disorders, traumatic brain injuries. Because a growing body of evidence demonstrates the benefits of ALLO in socially isolated animals, we believe our ALLO hypothesis can be applied to loneliness in humans, as well. PMID:26365247

  16. Semiautomated Management Of Arriving Air Traffic

    NASA Technical Reports Server (NTRS)

    Erzberger, Heinz; Nedell, William

    1992-01-01

    System of computers, graphical workstations, and computer programs developed for semiautomated management of approach and arrival of numerous aircraft at airport. System comprises three subsystems: traffic-management advisor, used for controlling traffic into terminal area; descent advisor generates information integrated into plan-view display of traffic on monitor; and final-approach-spacing tool used to merge traffic converging on final approach path while making sure aircraft are properly spaced. Not intended to restrict decisions of air-traffic controllers.

  17. Prediction of traffic-related nitrogen oxides concentrations using Structural Time-Series models

    NASA Astrophysics Data System (ADS)

    Lawson, Anneka Ruth; Ghosh, Bidisha; Broderick, Brian

    2011-09-01

    Ambient air quality monitoring, modeling and compliance to the standards set by European Union (EU) directives and World Health Organization (WHO) guidelines are required to ensure the protection of human and environmental health. Congested urban areas are most susceptible to traffic-related air pollution which is the most problematic source of air pollution in Ireland. Long-term continuous real-time monitoring of ambient air quality at such urban centers is essential but often not realistic due to financial and operational constraints. Hence, the development of a resource-conservative ambient air quality monitoring technique is essential to ensure compliance with the threshold values set by the standards. As an intelligent and advanced statistical methodology, a Structural Time Series (STS) based approach has been introduced in this paper to develop a parsimonious and computationally simple air quality model. In STS methodology, the different components of a time-series dataset such as the trend, seasonal, cyclical and calendar variations can be modeled separately. To test the effectiveness of the proposed modeling strategy, average hourly concentrations of nitrogen dioxide and nitrogen oxides from a congested urban arterial in Dublin city center were modeled using STS methodology. The prediction error estimates from the developed air quality model indicate that the STS model can be a useful tool in predicting nitrogen dioxide and nitrogen oxides concentrations in urban areas and will be particularly useful in situations where the information on external variables such as meteorology or traffic volume is not available.

  18. Aeronautical Communications Research and Development Needs for Future Air Traffic Management Applications

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.

    2002-01-01

    Continuing growth in regional and global air travel has resulted in increasing traffic congestion in the air and on the ground. In spite of occasional temporary downturns due to economic recessions and catastrophic events, average growth rates of air travel have remained high since the 1960s. The resulting congestion, which constrains expansion of the air transportation industry, inflicts schedule delays and decreases overall system efficiency, creating a pressing need to develop more efficient methods of air traffic management (ATM). New ATM techniques, procedures, air space automation methods, and decision support tools are being researched and developed for deployment in time frames stretching from the next few years to the year 2020 and beyond. As these methods become more advanced and increase in complexity, the requirements for information generation, sharing and transfer among the relevant entities in the ATM system increase dramatically. However, current aeronautical communications systems will be inadequate to meet the future information transfer demands created by these advanced ATM systems. Therefore, the NASA Glenn Research Center is undertaking research programs to develop communication, methods and key technologies that can meet these future requirements. As part of this process, studies, workshops, testing and experimentation, and research and analysis have established a number of research and technology development needs. The purpose of this paper is to outline the critical research and technology needs that have been identified in these activities, and explain how these needs have been determined.

  19. Passive load alleviation bi-stable morphing concept

    NASA Astrophysics Data System (ADS)

    Arrieta, A. F.; Bilgen, O.; Friswell, M. I.; Hagedorn, P.

    2012-09-01

    In wind turbines, large loads caused by fluid structure interaction leading to fatigue failure and added robustness to withstand high bending stresses on the root of blades constitute important design bottlenecks. Implementation of morphing offers a potential solution for such challenges in wind turbine blades. In this letter, a passive load alleviating bi-stable morphing concept is proposed. A bi-stable specimen designed to have different stiffness and dynamic response characteristics on each stable state is devised as a compliant structure. Passive alleviation mechanisms require no active components to achieve the load alleviation objective, resulting in lighter and simpler designs in comparison to actively morphed solutions.

  20. A passive gust alleviation system for a light aircraft

    NASA Technical Reports Server (NTRS)

    Roesch, P.; Harlan, R. B.

    1975-01-01

    A passive aeromechanical gust alleviation system was examined for application to a Cessna 172. The system employs small auxiliary wings to sense changes in angle of attack and to drive the wing flaps to compensate the resulting incremental lift. The flaps also can be spring loaded to neutralize the effects of variations in dynamic pressure. Conditions for gust alleviation are developed and shown to introduce marginal stability if both vertical and horizontal gusts are compensated. Satisfactory behavior is realized if only vertical gusts are absorbed; however, elevator control is effectively negated by the system. Techniques to couple the elevator and flaps are demonstrated to restore full controllability without sacrifice of gust alleviation.

  1. [Echo-color-Doppler in male pelvic congestion syndrome].

    PubMed

    Sarteschi, Lelio Mario; Simi, Stefano; Turchi, Paolo; DeMaria, Maurizio; Morelli, Girolamo

    2002-12-01

    The pelvic congestion syndrome has been widely studied in the female sex, while there are not many publications on the male equivalent. Prostatitis represent the most frequent affections of the genito-urinary male tract that require the urologic consult, but in the majority of the cases the etiology of such affections remains unknown. Some forms of microscopic hematuria or macroscopic hematuria are also cryptogenetic. Varicocelectomy is widely given in the infertile patients, but not always the intervention achieves a recovery of the semen quality. In this work we revisit the anatomy of the pelvic male venous drain and we depict its objective findings with the echo-color-Doppler sonography (ECD). The purpose of the study is to encourage a polycentric uro-andrologic search on large numbers, with the goal of resolve if the ECD pictures of congestion pelvic syndrome could have relation with some "prostatitis syndromes", with some cryptogenetic hematuria and/or with the prognosis of the infertile patients undergone to varicocelectomy. PMID:12508723

  2. Nonlinear dynamics of congestive heart failure (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Bernjak, Alan; Clarkson, Peter B. M.; McClintock, Peter V. E.; Stefanovska, Aneta

    2005-05-01

    Preliminary results are reported from a research project analysing congestive heart failure in terms a stochastic coupled-oscillator model of the cardiovascular system. Measurements of blood flow by laser Doppler flowmetry (LDF) have been processed by use of the wavelet transform to separate its oscillatory components, which number at least five. Particular attention was concentrated on the frequency content near 0.01 Hz, which is known to be associated with endothelial function. The LDF was carried out in conjunction with iontophoretically administered acetylcholine (ACh) and sodium nitroprusside (SNP) in order to evaluate endothelial reactivity. Measurements were made on 17 congestive heart failure (CHF) patients (a) on first diagnosis, and (b) again several weeks later after their treatment with a β-blocker had been stabilised. The results of these two sets of measurements are being compared with each other, and with data from an age and sex-matched group of healthy controls. It is confirmed that endothelial reactivity is reduced in CHF patients, as compared to healthy controls, and it is found that one effect of the Beta-blocker is to ameliorate the loss of endothelial function in CHF. The implications of these results are discussed.

  3. Congestive cardiac failure: central role of the arterial blood pressure.

    PubMed Central

    Harris, P

    1987-01-01

    A review of the history of our knowledge and understanding of the peripheral oedema of congestive cardiac failure points to the conclusion that an inability of the heart to maintain the arterial pressure is of central importance in this condition. Although the function of the circulation is to perfuse the tissues, the body monitors the adequacy of its perfusion, not not through metabolic messengers carried from the tissues in the blood stream, but by sensing the arterial pressure; and the mechanisms evoked act to maintain the arterial pressure. In the short term this is achieved by autonomic regulation of the heart and blood vessels; in the longer term the arterial pressure is maintained through an increase in the blood volume by a retention of salt and water by the kidney. To support the latter process, intrinsic renal mechanisms are successively magnified by the renin-angiotensin-aldosterone system and by the activities of the sympathetic system and vasopressin. The natriuretic influence mediated through volume receptors and the release of atrial peptide is overruled by the arterial baroreceptors, so that the body maintains the arterial pressure at the expense of an increase in blood volume. In these ways the syndrome of congestive cardiac failure may be regarded as one which arises when the heart becomes chronically unable to maintain an appropriate arterial pressure without support. PMID:3311096

  4. Quasi-static evolution and congested crowd transport

    NASA Astrophysics Data System (ADS)

    Alexander, Damon; Kim, Inwon; Yao, Yao

    2014-04-01

    We consider the relationship between Hele-Shaw evolution with drift, the porous medium equation with drift, and a congested crowd motion model originally proposed by Maury et al (2010 Math. Models Methods Appl. Sci. 20 1787-821). We first use viscosity solutions to show that the porous medium equation solutions converge to the Hele-Shaw solution as m → ∞ provided the drift potential is strictly subharmonic. Next, using the gradient-flow structure of both the porous medium equation and the crowd motion model, we prove that the porous medium equation solutions also converge to the congested crowd motion as m → ∞. Combining these results lets us deduce that in the case where the initial data to the crowd motion model is given by a patch, or characteristic function, the solution evolves as a patch that is the unique solution to the Hele-Shaw problem. While proving our main results we also obtain a comparison principle for solutions with the minimizing movement scheme based on the Wasserstein metric, of independent interest.

  5. Improving UDP/IP Transmission Without Increasing Congestion

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott

    2006-01-01

    Datagram Retransmission (DGR) is a computer program that, within certain limits, ensures the reception of each datagram transmitted under the User Datagram Protocol/Internet Protocol. [User Datagram Protocol (UDP) is considered unreliable because it does not involve a reliability-ensuring connection-initiation dialogue between sender and receiver. UDP is well suited to issuing of many small messages to many different receivers.] Unlike prior software for ensuring reception of UDP datagrams, DGR does not contribute to network congestion by retransmitting data more frequently as an ever-increasing number of messages and acknowledgements is lost. Instead, DGR does just the opposite: DGR includes an adaptive timeout-interval- computing component that provides maximum opportunity for reception of acknowledgements, minimizing retransmission. By monitoring changes in the rate at which message-transmission transactions are completed, DGR detects changes in the level of congestion and responds by imposing varying degrees of delay on the transmission of new messages. In addition, DGR maximizes throughput by not waiting for acknowledgement of a message before sending the next message. All DGR communication is asynchronous, to maximize efficient utilization of network connections. DGR manages multiple concurrent datagram transmission and acknowledgement conversations.

  6. Dynamic Congestion Control using MDB-Routing Algorithm

    NASA Astrophysics Data System (ADS)

    Anuradha, S.; Raghu Ram, G.

    2014-01-01

    This paper presents high through put routing algorithm. Modified depth Breadth routing algorithm takes a decision in moving forward packet in the next node which will visit to reach its final destination. Load balancing to improve the performance of distributed by processing power of the entire system to smooth out process of very high congestion at individual nodes, by transferring some of the load of heavily loaded nodes to the other nodes for processing. This achieves a 306.53 average time for packet, compared with the DB routing which achieves 316.13 average time for packet. Results shows that the proposed Modified depth Breadth achieves 348 average time when compared to DB routing which gives 548 for 3500 packets on 5 × 5 grid. Further results show that no of dead packets significantly reduced in the case of MDB. This focuses on Routing Network and Tables. These Network tables includes the information used by a routing algorithm to take a decision in moving forward the packet in the next node which will visit to reach its final destination. Load balancing try to improve the performance of a distributed system by processing power of the entire system to smooth out periods of very high congestion at individual nodes, which is done by transferring some of the load of heavily loaded nodes to other nodes for processing.

  7. Congestion phenomena caused by matching pennies in evolutionary games

    NASA Astrophysics Data System (ADS)

    Szabó, György; Szolnoki, Attila

    2015-03-01

    Evolutionary social dilemma games are extended by an additional matching-pennies game that modifies the collected payoffs. In a spatial version players are distributed on a square lattice and interact with their neighbors. First, we show that the matching-pennies game can be considered as the microscopic force of the Red Queen effect that breaks the detailed balance and induces eddies in the microscopic probability currents if the strategy update is analogous to the Glauber dynamics for the kinetic Ising models. The resulting loops in probability current breaks symmetry between the chessboardlike arrangements of strategies via a bottleneck effect occurring along the four-edge loops in the microscopic states. The impact of this congestion is analogous to the application of a staggered magnetic field in the Ising model; that is, the order-disorder critical transition is wiped out by noise. It is illustrated that the congestion induced symmetry breaking can be beneficial for the whole community within a certain region of parameters.

  8. Estimation of annual average daily traffic for off-system roads in Florida. Final report

    SciTech Connect

    Shen, L.D.; Zhao, F.; Ospina, D.I.

    1999-07-28

    Estimation of Annual Average Daily Traffic (AADT) is extremely important in traffic planning and operations for the state departments of transportation (DOTs), because AADT provides information for the planning of new road construction, determination of roadway geometry, congestion management, pavement design, safety considerations, etc. AADT is also used to estimate state wide vehicle miles traveled on all the roads and is used by local governments and the environmental protection agencies to determine compliance with the 1990 Clean Air Act Amendment. Additionally, AADT is reported annually by the Florida Department of transportation (FDOT) to the Federal Highway Administration. In the past, considerable efforts have been made in obtaining traffic counts to estimate AADT on state roads. However, traffic counts are often not available on off-system roads, and less attention has been paid to the estimation of AADT in the absence of counts. Current estimates rely on comparisons with roads that are subjectively considered to be similar. Such comparisons are inherently subject to large errors, and also may not be repeated often enough to remain current. Therefore, a better method is needed for estimating AADT for off-system roads in Florida. This study investigates the possibility of establishing one or more models for estimating AADT for off-system roads in Florida.

  9. Analysis of random drop for gateway congestion control. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Hashem, Emam Salaheddin

    1989-01-01

    Lately, the growing demand on the Internet has prompted the need for more effective congestion control policies. Currently No Gateway Policy is used to relieve and signal congestion, which leads to unfair service to the individual users and a degradation of overall network performance. Network simulation was used to illustrate the character of Internet congestion and its causes. A newly proposed gateway congestion control policy, called Random Drop, was considered as a promising solution to the pressing problem. Random Drop relieves resource congestion upon buffer overflow by choosing a random packet from the service queue to be dropped. The random choice should result in a drop distribution proportional to the bandwidth distribution among all contending TCP connections, thus applying the necessary fairness. Nonetheless, the simulation experiments demonstrate several shortcomings with this policy. Because Random Drop is a congestion control policy, which is not applied until congestion has already occurred, it usually results in a high drop rate that hurts too many connections including well-behaved ones. Even though the number of packets dropped is different from one connection to another depending on the buffer utilization upon overflow, the TCP recovery overhead is high enough to neutralize these differences, causing unfair congestion penalties. Besides, the drop distribution itself is an inaccurate representation of the average bandwidth distribution, missing much important information about the bandwidth utilization between buffer overflow events. A modification of Random Drop to do congestion avoidance by applying the policy early was also proposed. Early Random Drop has the advantage of avoiding the high drop rate of buffer overflow. The early application of the policy removes the pressure of congestion relief and allows more accurate signaling of congestion. To be used effectively, algorithms for the dynamic adjustment of the parameters of Early Random Drop

  10. Can Earth Sciences Help Alleviate Global Poverty?

    NASA Astrophysics Data System (ADS)

    Mutter, J. C.

    2004-12-01

    essential and could hold the key to making gains toward alleviating the burden of global poverty.

  11. The Traffic Adaptive Data Dissemination (TrAD) Protocol for both Urban and Highway Scenarios.

    PubMed

    Tian, Bin; Hou, Kun Mean; Zhou, Haiying

    2016-01-01

    The worldwide economic cost of road crashes and injuries is estimated to be US$518 billion per year and the annual congestion cost in France is estimated to be €5.9 billion. Vehicular Ad hoc Networks (VANETs) are one solution to improve transport features such as traffic safety, traffic jam and infotainment on wheels, where a great number of event-driven messages need to be disseminated in a timely way in a region of interest. In comparison with traditional wireless networks, VANETs have to consider the highly dynamic network topology and lossy links due to node mobility. Inter-Vehicle Communication (IVC) protocols are the keystone of VANETs. According to our survey, most of the proposed IVC protocols focus on either highway or urban scenarios, but not on both. Furthermore, too few protocols, considering both scenarios, can achieve high performance. In this paper, an infrastructure-less Traffic Adaptive data Dissemination (TrAD) protocol which takes into account road traffic and network traffic status for both highway and urban scenarios will be presented. TrAD has double broadcast suppression techniques and is designed to adapt efficiently to the irregular road topology. The performance of the TrAD protocol was evaluated quantitatively by means of realistic simulations taking into account different real road maps, traffic routes and vehicular densities. The obtained simulation results show that TrAD is more efficient in terms of packet delivery ratio, number of transmissions and delay in comparison with the performance of three well-known reference protocols. Moreover, TrAD can also tolerate a reasonable degree of GPS drift and still achieve efficient data dissemination. PMID:27338393

  12. The Traffic Adaptive Data Dissemination (TrAD) Protocol for both Urban and Highway Scenarios

    PubMed Central

    Tian, Bin; Hou, Kun Mean; Zhou, Haiying

    2016-01-01

    The worldwide economic cost of road crashes and injuries is estimated to be US$518 billion per year and the annual congestion cost in France is estimated to be €5.9 billion. Vehicular Ad hoc Networks (VANETs) are one solution to improve transport features such as traffic safety, traffic jam and infotainment on wheels, where a great number of event-driven messages need to be disseminated in a timely way in a region of interest. In comparison with traditional wireless networks, VANETs have to consider the highly dynamic network topology and lossy links due to node mobility. Inter-Vehicle Communication (IVC) protocols are the keystone of VANETs. According to our survey, most of the proposed IVC protocols focus on either highway or urban scenarios, but not on both. Furthermore, too few protocols, considering both scenarios, can achieve high performance. In this paper, an infrastructure-less Traffic Adaptive data Dissemination (TrAD) protocol which takes into account road traffic and network traffic status for both highway and urban scenarios will be presented. TrAD has double broadcast suppression techniques and is designed to adapt efficiently to the irregular road topology. The performance of the TrAD protocol was evaluated quantitatively by means of realistic simulations taking into account different real road maps, traffic routes and vehicular densities. The obtained simulation results show that TrAD is more efficient in terms of packet delivery ratio, number of transmissions and delay in comparison with the performance of three well-known reference protocols. Moreover, TrAD can also tolerate a reasonable degree of GPS drift and still achieve efficient data dissemination. PMID:27338393

  13. How to alleviate perineal pain following an episiotomy.

    PubMed

    Steen, Mary; Cummins, Bernie

    2016-03-30

    Rationale and key points An episiotomy increases maternal morbidity in the postnatal period. Alleviating perineal pain is an important aspect of maternal health care. ▶ A combination of pain relief methods, systemic and localised, may be required to alleviate perineal pain associated with an episiotomy. ▶ It is important that midwives and doctors advise women on how to alleviate perineal pain, prevent infection and promote healing following an episiotomy. Reflective activity Clinical skills articles can help update your practice and ensure it remains evidence based. Apply this article to your practice. Reflect on and write a short account of: 1. The advice you would give to a woman who has recently given birth to alleviate perineal pain. 2. The short and long-term problems associated with perineal pain. Subscribers can upload their reflective accounts at rcni.com/portfolio . PMID:27027195

  14. Traffic gridlock on complex networks

    NASA Astrophysics Data System (ADS)

    Mendes, G. A.; da Silva, L. R.; Herrmann, H. J.

    2012-01-01

    Here we study how a traffic jam spreads on complex networks when driven by an increasing flux between certain initial and final points. For that purpose, we developed two new traffic models based on vehicular traffic and applied them on the Apollonian network and the Swiss road network. The first model is an electrical analog, using ohmic and non-ohmic resistors which is a classical approach in Physics while the second one which we call the herding model, is based on human driving behavior. For both models, we study the sequence of clogged roads up to the traffic gridlock and display the fragilities of the network. In the electrical model, by increasing the external potential, resistors burn out, as the voltage drop between the ends increases above a certain threshold. Analyzing both models, we observed some power-law functions that occur only near a traffic gridlock as well as the dependence on topological features of the network and influence on flux and the robustness in Apollonian networks of different generations.

  15. Road traffic injuries in Colombia.

    PubMed

    Rodríguez, Deysi Yasmin; Fernández, Francisco José; Acero Velásquez, Hugo

    2003-01-01

    Road traffic injuries are a leading public health problem in Colombia. Pedestrians are the most vulnerable road users, especially in the main urban centers of Bogotá, Medellin and Cali. Data analyzed in this report include official statistics from the National Police and the National Institute of Legal Medicine and Forensic Sciences for 1996-2000, and results of a study conducted at the National University of Colombia in 2000. Methods from the Highway Capacity Manual were used for determining physical and technical variables, and a Geographical Information System tool was used for the location and spatial analysis of the road traffic crashes. Pedestrians accounted for close to 32% of injuries and 40% of the deaths from road traffic crashes. The problem of road traffic crashes existed predominately in urban areas. In the main urban centers, pedestrians constituted nearly 68% of road traffic crash victims. The high level of risky road use behaviors demonstrated by pedestrians and drivers, and inadequate infrastructure for safe mobility of pedestrians in some sections of the road network were the main contributing factors. Major improvements were achieved in Bogotá following enhancements to the municipal transport system and other policies introduced since 1995. In conclusion, policies and programs for improving road safety, in particular pedestrian safety, and strengthening urban planning are top priority. PMID:12772483

  16. A traffic situation analysis system

    NASA Astrophysics Data System (ADS)

    Sidla, Oliver; Rosner, Marcin

    2011-01-01

    The observation and monitoring of traffic with smart visions systems for the purpose of improving traffic safety has a big potential. For example embedded vision systems built into vehicles can be used as early warning systems, or stationary camera systems can modify the switching frequency of signals at intersections. Today the automated analysis of traffic situations is still in its infancy - the patterns of vehicle motion and pedestrian flow in an urban environment are too complex to be fully understood by a vision system. We present steps towards such a traffic monitoring system which is designed to detect potentially dangerous traffic situations, especially incidents in which the interaction of pedestrians and vehicles might develop into safety critical encounters. The proposed system is field-tested at a real pedestrian crossing in the City of Vienna for the duration of one year. It consists of a cluster of 3 smart cameras, each of which is built from a very compact PC hardware system in an outdoor capable housing. Two cameras run vehicle detection software including license plate detection and recognition, one camera runs a complex pedestrian detection and tracking module based on the HOG detection principle. As a supplement, all 3 cameras use additional optical flow computation in a low-resolution video stream in order to estimate the motion path and speed of objects. This work describes the foundation for all 3 different object detection modalities (pedestrians, vehi1cles, license plates), and explains the system setup and its design.

  17. Congestion at Card and Book Catalogs--A Queuing-Theory Approach

    ERIC Educational Resources Information Center

    Bookstein, Abraham

    1972-01-01

    This paper attempts to analyze the problem of congestion, using a mathematical model shown to be of value in other similar applications. Three criteria of congestion are considered, and it is found that the conclusion one can draw is sensitive to which of these criteria is paramount. (8 references) (Author/NH)

  18. 76 FR 75875 - Plan for Conduct of 2012 Electric Transmission Congestion Study

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-05

    ... regional workshops and request for written comments in connection with the preparation of a study of electric transmission congestion pursuant to section 216(a)(1) of the Federal Power Act (76 FR 70122). This... for Conduct of 2012 Electric Transmission Congestion Study AGENCY: Office of Electricity Delivery...

  19. 23 CFR 450.320 - Congestion management process in transportation management areas.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 23 Highways 1 2014-04-01 2014-04-01 false Congestion management process in transportation management areas. 450.320 Section 450.320 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF... Programming § 450.320 Congestion management process in transportation management areas. (a) The...

  20. 23 CFR 450.320 - Congestion management process in transportation management areas.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 23 Highways 1 2011-04-01 2011-04-01 false Congestion management process in transportation management areas. 450.320 Section 450.320 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF... Programming § 450.320 Congestion management process in transportation management areas. (a) The...

  1. 23 CFR 450.320 - Congestion management process in transportation management areas.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 23 Highways 1 2012-04-01 2012-04-01 false Congestion management process in transportation management areas. 450.320 Section 450.320 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF... Programming § 450.320 Congestion management process in transportation management areas. (a) The...

  2. 23 CFR 450.320 - Congestion management process in transportation management areas.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 23 Highways 1 2013-04-01 2013-04-01 false Congestion management process in transportation management areas. 450.320 Section 450.320 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF... Programming § 450.320 Congestion management process in transportation management areas. (a) The...

  3. 23 CFR 450.320 - Congestion management process in transportation management areas.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false Congestion management process in transportation management areas. 450.320 Section 450.320 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF... Programming § 450.320 Congestion management process in transportation management areas. (a) The...

  4. On the mechanism of augmentation of electrocardiogram QRS complexes in patients with congestive heart failure responding to diuresis.

    PubMed

    Madias, John E

    2005-01-01

    Patients with congestive heart failure (CHF) responding to diuresis reveal marked augmentation of the QRS complexes (AUG-QRS) in their electrocardiograms (ECGs). Recently, such change in the ECG has been observed in patients with anasarca (AN) of varying etiology commensurate with partial alleviation of the volume overload; similar ECG change has been noted in patients with end-stage renal failure after hemodialysis. The mechanism for the AUG-QRS in patients with CHF has been debated, and many have ascribed this ECG change to the "Brody effect," linking the AUG-QRS to reduction of intracardiac blood volumes resulting from diuresis. However, the Brody effect (a theoretical formulation not fully validated by experimentation and associated with controversy in its clinical implementation) has not provided a satisfactory explanation for the AUG-QRS in patients with CHF. In contrast, the described association between amelioration of AN in a diverse patient population and AUG-QRS suggests that this ECG change in patients with CHF is due to an increased electrical resistance of the passive body volume conductor, resulting from water loss effected by diuresis. This thesis is supported by theoretical work, animal experimentation, and clinical evidence. PMID:15660348

  5. Changes in hypertension treatment and in congestive heart failure mortality in the United States.

    PubMed

    Yusuf, S; Thom, T; Abbott, R D

    1989-05-01

    The use of antihypertensive agents has increased in recent years and has been more marked among individuals in older age groups (65-74 years) than in middle-aged groups (45-54 years). Because hypertension is a strong risk factor for the development of congestive heart failure, more common use of antihypertensive agents would be expected to reduce the incidence of congestive heart failure. Examination of the national death statistics reveals decreases in congestive heart failure mortality at younger ages with mortality increases at older ages. The reasons for these divergent trends in congestive heart failure mortality in different ages and the apparent inconsistency with respect to the changes in the use of antihypertensive drugs are explored. We speculate that antihypertensive treatment does not completely prevent congestive heart failure but merely postpones its development by several decades. PMID:2490832

  6. Estimation of Congestion in Free Disposal Hull Models Using Data Envelopment Analysis

    PubMed Central

    Abbasi, M.; Jahanshahloo, G. R.; Rostamy-Malkhlifeh, M.; Hosseinzadeh Lotfi, F.

    2014-01-01

    This paper deals with evaluating congestion in free disposal hull (FDH) models. There are several approaches in data envelopment analysis (DEA) literatures which discuss the theory and application of congestion. However, almost all of these approaches considered convex DEA technologies. So, in the case of nonconvex technologies, including FDH technology, this field is almost nil. This paper makes an attempt to fill in this void. To do so, this study provides a pairwise comparisons-based algorithm to evaluate congestion in FDH model. This algorithm identifies the sources of congestion and estimates its amounts. It is also capable of detecting the losses amounts of output due to congestion. The validity of the proposed model is demonstrated using some numerical and empirical examples. PMID:25379531

  7. Estimation of congestion in free disposal hull models using data envelopment analysis.

    PubMed

    Abbasi, M; Jahanshahloo, G R; Rostamy-Malkhlifeh, M; Hosseinzadeh Lotfi, F

    2014-01-01

    This paper deals with evaluating congestion in free disposal hull (FDH) models. There are several approaches in data envelopment analysis (DEA) literatures which discuss the theory and application of congestion. However, almost all of these approaches considered convex DEA technologies. So, in the case of nonconvex technologies, including FDH technology, this field is almost nil. This paper makes an attempt to fill in this void. To do so, this study provides a pairwise comparisons-based algorithm to evaluate congestion in FDH model. This algorithm identifies the sources of congestion and estimates its amounts. It is also capable of detecting the losses amounts of output due to congestion. The validity of the proposed model is demonstrated using some numerical and empirical examples. PMID:25379531

  8. Venous Congestion, Endothelial and Neurohormonal Activation in Acute Decompensated Heart Failure: Cause or Effect?

    PubMed Central

    Colombo, Paolo C.; Doran, Amanda C.; Onat, Duygu; Wong, Ka Yuk; Ahmad, Myra; Sabbah, Hani N.; Demmer, Ryan T.

    2015-01-01

    Venous congestion and endothelial and neurohormonal activation are known to occur in acute decompensated heart failure (ADHF), yet the temporal role of these processes in the pathophysiology of decompensation is not fully understood. Conventional wisdom presumes congestion to be a consequence of worsening cardiovascular function; however, the biomechanically driven effects of venous congestion are biologically plausible contributors to ADHF that remain largely unexplored in vivo. Recent experimental evidence from human models suggests that fluid accumulation and venous congestion are not simply consequences of poor cardiovascular function, but rather are fundamental pro-oxidant, pro-inflammatory, and hemodynamic stimuli that contribute to acute decompensation. The latest advances in the monitoring of volume status using implantable devices allow for the detection of venous congestion before symptoms arise. This may ultimately lead to improved treatment strategies including not only diuretics, but also specific, adjuvant interventions to counteract endothelial and neurohormonal activation during early preclinical decompensation. PMID:25740404

  9. Traffic Flow Management and Optimization

    NASA Technical Reports Server (NTRS)

    Rios, Joseph Lucio

    2014-01-01

    This talk will present an overview of Traffic Flow Management (TFM) research at NASA Ames Research Center. Dr. Rios will focus on his work developing a large-scale, parallel approach to solving traffic flow management problems in the national airspace. In support of this talk, Dr. Rios will provide some background on operational aspects of TFM as well a discussion of some of the tools needed to perform such work including a high-fidelity airspace simulator. Current, on-going research related to TFM data services in the national airspace system and general aviation will also be presented.

  10. Psychobiology of depression/distress in congestive heart failure

    PubMed Central

    Hassan, Mustafa; Sheps, David S.

    2011-01-01

    Heart failure affects millions of Americans and new diagnosis rates are expected to almost triple over the next 30 years as our population ages. Affective disorders including clinical depression and anxiety are common in patients with congestive heart failure. Furthermore, the presence of these disorders significantly impacts quality of life, medical outcomes, and healthcare service utilization. In recent years, the literature has attempted to describe potential pathophysiologic mechanisms relating affective disorders and psychosocial stress to heart failure. Several potential mechanisms have been proposed including autonomic nervous system dysfunction, inflammation, cardiac arrhythmias, and altered platelet function. These mechanisms are reviewed in this article. Additional novel mechanisms such as mental stress-induced myocardial ischemia are also discussed. PMID:18368481

  11. Complexity in congestive heart failure: A time-frequency approach

    NASA Astrophysics Data System (ADS)

    Banerjee, Santo; Palit, Sanjay K.; Mukherjee, Sayan; Ariffin, MRK; Rondoni, Lamberto

    2016-03-01

    Reconstruction of phase space is an effective method to quantify the dynamics of a signal or a time series. Various phase space reconstruction techniques have been investigated. However, there are some issues on the optimal reconstructions and the best possible choice of the reconstruction parameters. This research introduces the idea of gradient cross recurrence (GCR) and mean gradient cross recurrence density which shows that reconstructions in time frequency domain preserve more information about the dynamics than the optimal reconstructions in time domain. This analysis is further extended to ECG signals of normal and congestive heart failure patients. By using another newly introduced measure—gradient cross recurrence period density entropy, two classes of aforesaid ECG signals can be classified with a proper threshold. This analysis can be applied to quantifying and distinguishing biomedical and other nonlinear signals.

  12. Respiratory sleep disorders in patients with congestive heart failure

    PubMed Central

    2015-01-01

    Respiratory sleep disorders (RSD) occur in about 40-50% of patients with symptomatic congestive heart failure (CHF). Obstructive sleep apnea (OSA) is considered a cause of CHF, whereas central sleep apnea (CSA) is considered a response to heart failure, perhaps even compensatory. In the setting of heart failure, continuous positive airway pressure (CPAP) has a definite role in treating OSA with improvements in cardiac parameters expected. However in CSA, CPAP is an adjunctive therapy to other standard therapies directed towards the heart failure (pharmacological, device and surgical options). Whether adaptive servo controlled ventilatory support, a variant of CPAP, is beneficial is yet to be proven. Supplemental oxygen therapy should be used with caution in heart failure, in particular, by avoiding hyperoxia as indicated by SpO2 values >95%. PMID:26380758

  13. An Evaluation Methodology for Traffic Awareness Displays

    NASA Technical Reports Server (NTRS)

    DeMaio, Joe; Dearing, Munro

    2004-01-01

    An evaluation methodology for traffic awareness displays for helicopters and other vertical/short takeoff aircraft was developed. Pilots of vertical/short takeoff aircraft wil1 require more traffic information than would pilots of conventional aircraft to avoid both other vertical/short takeoff traffic and conventional traffic. The BF Goodrich Skywatch traffic advisory display was used as a candidate display to develop a procedure for evaluating the usefulness of such displays. Four high-time helicopter pilots participated in a 16-hour flight evaluation. They flew a closed circuit in the San Francisco Bay Area. In one-half of the flights the evaluation pilot had the traffic advisory display as an aid in detecting and locating traffic. In the other half of the flights the traffic advisory display was not available to the evaluation pilot. Data examined include measures of traffic advisory display performance and pilot performance in detecting traffic, as well as subjective workload and situation awareness data. The traffic advisory system did not help the pilots to detect more traffic. The importance of detection to traffic awareness is discussed.

  14. Dynamic Density: An Air Traffic Management Metric

    NASA Technical Reports Server (NTRS)

    Laudeman, I. V.; Shelden, S. G.; Branstrom, R.; Brasil, C. L.

    1998-01-01

    The definition of a metric of air traffic controller workload based on air traffic characteristics is essential to the development of both air traffic management automation and air traffic procedures. Dynamic density is a proposed concept for a metric that includes both traffic density (a count of aircraft in a volume of airspace) and traffic complexity (a measure of the complexity of the air traffic in a volume of airspace). It was hypothesized that a metric that includes terms that capture air traffic complexity will be a better measure of air traffic controller workload than current measures based only on traffic density. A weighted linear dynamic density function was developed and validated operationally. The proposed dynamic density function includes a traffic density term and eight traffic complexity terms. A unit-weighted dynamic density function was able to account for an average of 22% of the variance in observed controller activity not accounted for by traffic density alone. A comparative analysis of unit weights, subjective weights, and regression weights for the terms in the dynamic density equation was conducted. The best predictor of controller activity was the dynamic density equation with regression-weighted complexity terms.

  15. Spatial correlation analysis of cascading failures: Congestions and Blackouts

    NASA Astrophysics Data System (ADS)

    Daqing, Li; Yinan, Jiang; Rui, Kang; Havlin, Shlomo

    2014-06-01

    Cascading failures have become major threats to network robustness due to their potential catastrophic consequences, where local perturbations can induce global propagation of failures. Unlike failures spreading via direct contacts due to structural interdependencies, overload failures usually propagate through collective interactions among system components. Despite the critical need in developing protection or mitigation strategies in networks such as power grids and transportation, the propagation behavior of cascading failures is essentially unknown. Here we find by analyzing our collected data that jams in city traffic and faults in power grid are spatially long-range correlated with correlations decaying slowly with distance. Moreover, we find in the daily traffic, that the correlation length increases dramatically and reaches maximum, when morning or evening rush hour is approaching. Our study can impact all efforts towards improving actively system resilience ranging from evaluation of design schemes, development of protection strategies to implementation of mitigation programs.

  16. Disability-adjusted life years in the assessment of health effects of traffic-related air pollution.

    PubMed

    Adamkiewicz, Ł; Badyda, A J; Gayer, A; Mucha, D

    2015-01-01

    Traffic-related air pollutants have an impact on human health and have been recognized as one of the main stressors that cause mortality and morbidity in urban areas. Research confirms that citizens living in the vicinity of main roads are strongly exposed to high concentrations of numerous air pollutants. In the present study the measurements of traffic-related parameters such as density, velocity, and structure were performed for cross-sections of selected street canyons in Warsaw, the capital city of Poland. In addition, the results of the general traffic measurements were used to describe the number of cars crossing the border of the city. Vehicle emissions of PM10 were calculated for the whole city area and changes of the PM10 concentration were modeled to present the exposure to this pollutant that could be attributable to traffic. The principles of the environmental burden of disease (EBD) were used. The assessment of the impact of traffic-related air pollutants on human health was made. The results, presented in disability-adjusted life years (DALY), were based on the outcomes of the study conducted in 2008-2012 in Warsaw, one the most congested agglomerations in Europe, and included the health damage effect of the exposure to high concentrations of air pollutants. DALY calculations were performed in accordance to the methodologies used in renowned international scientific research on EBD. PMID:25310938

  17. The Physics of Traffic Accidents

    ERIC Educational Resources Information Center

    Knight, Peter

    1975-01-01

    Shows how physics can be used to analyze and prevent traffic accidents by determining critical speeds on curves, the behavior of motor cycles and stability of articulated vehicles, and the visibility that is needed to make a minor road junction safe. (MLH)

  18. Overview. Traffic Safety Facts, 2000.

    ERIC Educational Resources Information Center

    National Highway Traffic Safety Administration (DOT), Washington, DC.

    This document provides statistical information on U.S. motor vehicle and traffic safety. Data include: (1) motor vehicle occupants and non-occupants killed and injured, 1990-2000; (2) persons killed and injured, and fatality and injury rates, 1990-2000; (3) restraint use rates for passenger car occupants in fatal crashes, 1990 and 2000; (4)…

  19. Traffic Safety Facts, 2001. Overview.

    ERIC Educational Resources Information Center

    National Highway Traffic Safety Administration (DOT), Washington, DC.

    This document provides statistical information on U.S. motor vehicle and traffic safety. Data include: (1) motor vehicle occupants and non-occupants killed and injured, 1991-2001; (2) persons killed and injured, and fatality and injury rates, 1991-2001; (3) restraint use rates for passenger car occupants in fatal crashes, 1991 and 2001; (4)…

  20. Deterministic models for traffic jams

    NASA Astrophysics Data System (ADS)

    Nagel, Kai; Herrmann, Hans J.

    1993-10-01

    We study several deterministic one-dimensional traffic models. For integer positions and velocities we find the typical high and low density phases separated by a simple transition. If positions and velocities are continuous variables the model shows self-organized critically driven by the slowest car.

  1. Optical traffic-sensing concept

    NASA Technical Reports Server (NTRS)

    Johnston, A. R.; Shimada, K.

    1978-01-01

    Scaled-up optical proximity detector is versatile traffic sensor that replaces or augments existing systems such as inductive loops. Photosensor which does not depend on ambient light has several features that protect it against spurious or ambiguous inputs. It could be implemented in several forms to cope with different roadway conditions.

  2. Broadcast control of air traffic

    NASA Technical Reports Server (NTRS)

    Litchford, G. B.

    1972-01-01

    The development of a system of broadcast control for improved flight safety and air traffic control is discussed. The system provides a balance of equality between improved cockpit guidance and control capability and ground control in order to provide the pilot with a greater degree of participation. The manner in which the system is operated and the equipment required for safe operation are examined.

  3. Children. Traffic Safety Facts, 2000.

    ERIC Educational Resources Information Center

    National Highway Traffic Safety Administration (DOT), Washington, DC.

    This document provides statistical information on the incidence of U.S. motor vehicle-related accidents and fatalities involving children. Data include: (1) total traffic fatalities among children 0-14 years old, by age group, 1990-2000; (2) total pedestrian fatalities among children 0-14 years old, by age group, 1990-2000; (3) total pedalcyclist…

  4. Traffic Safety Facts, 2001: Children.

    ERIC Educational Resources Information Center

    National Highway Traffic Safety Administration (DOT), Washington, DC.

    This document provides statistical information on the incidence of U.S. motor vehicle-related accidents and fatalities involving children. Data include: (1) total traffic fatalities among children 0-14 years old, by age group, 1991-2001; (2) total pedestrian fatalities among children 0-14 years old, by age group, 1991-2001; (3) total pedalcyclist…

  5. Traffic fatalities and economic growth.

    PubMed

    Kopits, Elizabeth; Cropper, Maureen

    2005-01-01

    This paper examines the relationship between traffic fatality risk and per capita income and uses it to forecast traffic fatalities by geographic region. Equations for the road death rate (fatalities/population) and its components--the rate of motorization (vehicles/population) and fatalities per vehicle (F/V)--are estimated using panel data from 1963 to 1999 for 88 countries. The natural logarithm of F/P, V/P, and F/V are expressed as spline (piecewise linear) functions of the logarithm of real per capita GDP (measured in 1985 international prices). Region-specific time trends during the period 1963-1999 are modeled in linear and log-linear form. These models are used to project traffic fatalities and the stock of motor vehicles to 2020. The per capita income at which traffic fatality risk (fatalities/population) begins to decline is 8600 US dollars (1985 international dollars) when separate time trends are used for each geographic region. This turning point is driven by the rate of decline in fatalities/vehicles as income rises since vehicles/population, while increasing with income at a decreasing rate, never declines with economic growth. Projections of future traffic fatalities suggest that the global road death toll will grow by approximately 66% over the next twenty years. This number, however, reflects divergent rates of change in different parts of the world: a decline in fatalities in high-income countries of approximately 28% versus an increase in fatalities of almost 92% in China and 147% in India. The road death rate is projected to rise to approximately 2 per 10,000 persons in developing countries by 2020, while it will fall to less than 1 per 10,000 in high-income countries. PMID:15607288

  6. Predicting Information Flows in Network Traffic.

    ERIC Educational Resources Information Center

    Hinich, Melvin J.; Molyneux, Robert E.

    2003-01-01

    Discusses information flow in networks and predicting network traffic and describes a study that uses time series analysis on a day's worth of Internet log data. Examines nonlinearity and traffic invariants, and suggests that prediction of network traffic may not be possible with current techniques. (Author/LRW)

  7. 30 CFR 56.9100 - Traffic control.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Traffic control. 56.9100 Section 56.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9100 Traffic control. To provide for the safe movement of...

  8. 30 CFR 57.9100 - Traffic control.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Traffic control. 57.9100 Section 57.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 57.9100 Traffic control. To provide for the safe movement of...

  9. 30 CFR 56.9100 - Traffic control.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Traffic control. 56.9100 Section 56.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9100 Traffic control. To provide for the safe movement of...

  10. 49 CFR 236.381 - Traffic locking.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Traffic locking. 236.381 Section 236.381..., MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Interlocking Inspection and Tests § 236.381 Traffic locking. Traffic locking shall be tested when placed in service...

  11. 49 CFR 236.381 - Traffic locking.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Traffic locking. 236.381 Section 236.381..., MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Interlocking Inspection and Tests § 236.381 Traffic locking. Traffic locking shall be tested when placed in service...

  12. 30 CFR 57.9100 - Traffic control.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Traffic control. 57.9100 Section 57.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 57.9100 Traffic control. To provide for the safe movement of...

  13. 49 CFR 236.381 - Traffic locking.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Traffic locking. 236.381 Section 236.381..., MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Interlocking Inspection and Tests § 236.381 Traffic locking. Traffic locking shall be tested when placed in service...

  14. 30 CFR 56.9100 - Traffic control.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Traffic control. 56.9100 Section 56.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9100 Traffic control. To provide for the safe movement of...

  15. 49 CFR 236.381 - Traffic locking.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Traffic locking. 236.381 Section 236.381..., MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Interlocking Inspection and Tests § 236.381 Traffic locking. Traffic locking shall be tested when placed in service...

  16. 49 CFR 236.381 - Traffic locking.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Traffic locking. 236.381 Section 236.381..., MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Interlocking Inspection and Tests § 236.381 Traffic locking. Traffic locking shall be tested when placed in service...

  17. 30 CFR 57.9100 - Traffic control.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Traffic control. 57.9100 Section 57.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 57.9100 Traffic control. To provide for the safe movement of...

  18. 30 CFR 56.9100 - Traffic control.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Traffic control. 56.9100 Section 56.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9100 Traffic control. To provide for the safe movement of...

  19. 30 CFR 57.9100 - Traffic control.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Traffic control. 57.9100 Section 57.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 57.9100 Traffic control. To provide for the safe movement of...

  20. 30 CFR 57.9100 - Traffic control.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Dumping Traffic Safety § 57.9100 Traffic control. To provide for the safe movement of self-propelled... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Traffic control. 57.9100 Section 57.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL...

  1. 36 CFR 1004.13 - Obstructing traffic.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 3 2013-07-01 2012-07-01 true Obstructing traffic. 1004.13 Section 1004.13 Parks, Forests, and Public Property PRESIDIO TRUST VEHICLES AND TRAFFIC SAFETY § 1004.13 Obstructing traffic. The following are prohibited: (a) Stopping or parking a vehicle upon a Presidio...

  2. 36 CFR 1004.13 - Obstructing traffic.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 3 2014-07-01 2014-07-01 false Obstructing traffic. 1004.13 Section 1004.13 Parks, Forests, and Public Property PRESIDIO TRUST VEHICLES AND TRAFFIC SAFETY § 1004.13 Obstructing traffic. The following are prohibited: (a) Stopping or parking a vehicle upon a Presidio...

  3. 49 CFR 1139.2 - Traffic study.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 8 2013-10-01 2013-10-01 false Traffic study. 1139.2 Section 1139.2... of General Commodities § 1139.2 Traffic study. (a) The respondents shall submit a traffic study for... “base-calendar year—actual.” The study shall include a probability sampling of the actual...

  4. 49 CFR 1139.2 - Traffic study.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 8 2014-10-01 2014-10-01 false Traffic study. 1139.2 Section 1139.2... of General Commodities § 1139.2 Traffic study. (a) The respondents shall submit a traffic study for... “base-calendar year—actual.” The study shall include a probability sampling of the actual...

  5. 49 CFR 1139.2 - Traffic study.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 8 2012-10-01 2012-10-01 false Traffic study. 1139.2 Section 1139.2... of General Commodities § 1139.2 Traffic study. (a) The respondents shall submit a traffic study for... “base-calendar year—actual.” The study shall include a probability sampling of the actual...

  6. 36 CFR 1004.13 - Obstructing traffic.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false Obstructing traffic. 1004.13 Section 1004.13 Parks, Forests, and Public Property PRESIDIO TRUST VEHICLES AND TRAFFIC SAFETY § 1004.13 Obstructing traffic. The following are prohibited: (a) Stopping or parking a vehicle upon a Presidio...

  7. 36 CFR 1004.13 - Obstructing traffic.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 3 2012-07-01 2012-07-01 false Obstructing traffic. 1004.13 Section 1004.13 Parks, Forests, and Public Property PRESIDIO TRUST VEHICLES AND TRAFFIC SAFETY § 1004.13 Obstructing traffic. The following are prohibited: (a) Stopping or parking a vehicle upon a Presidio...

  8. 15 CFR 265.22 - Bicycle traffic.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 15 Commerce and Foreign Trade 1 2013-01-01 2013-01-01 false Bicycle traffic. 265.22 Section 265.22... Bicycle traffic. No person shall ride a bicycle other than in a manner exercising due caution for pedestrian and other traffic. No person shall ride a bicycle on sidewalks or inside any building, nor...

  9. 15 CFR 265.22 - Bicycle traffic.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Bicycle traffic. 265.22 Section 265.22... Bicycle traffic. No person shall ride a bicycle other than in a manner exercising due caution for pedestrian and other traffic. No person shall ride a bicycle on sidewalks or inside any building, nor...

  10. 15 CFR 265.22 - Bicycle traffic.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 15 Commerce and Foreign Trade 1 2012-01-01 2012-01-01 false Bicycle traffic. 265.22 Section 265.22... Bicycle traffic. No person shall ride a bicycle other than in a manner exercising due caution for pedestrian and other traffic. No person shall ride a bicycle on sidewalks or inside any building, nor...

  11. 15 CFR 265.22 - Bicycle traffic.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 15 Commerce and Foreign Trade 1 2014-01-01 2014-01-01 false Bicycle traffic. 265.22 Section 265.22... Bicycle traffic. No person shall ride a bicycle other than in a manner exercising due caution for pedestrian and other traffic. No person shall ride a bicycle on sidewalks or inside any building, nor...

  12. 15 CFR 265.22 - Bicycle traffic.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 15 Commerce and Foreign Trade 1 2011-01-01 2011-01-01 false Bicycle traffic. 265.22 Section 265.22... Bicycle traffic. No person shall ride a bicycle other than in a manner exercising due caution for pedestrian and other traffic. No person shall ride a bicycle on sidewalks or inside any building, nor...

  13. 30 CFR 56.9100 - Traffic control.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Traffic control. 56.9100 Section 56.9100 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... Dumping Traffic Safety § 56.9100 Traffic control. To provide for the safe movement of...

  14. 14 CFR 25 - Traffic and Capacity Elements

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...) Editorial Note: For Federal Register citations affecting part 241, section 25, see the List of CFR Sections... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Traffic and Capacity Elements Section 25... Traffic Reporting Requirements Section 25 Traffic and Capacity Elements General Instructions. (a)...

  15. A macro traffic flow model accounting for real-time traffic state

    NASA Astrophysics Data System (ADS)

    Tang, Tie-Qiao; Chen, Liang; Wu, Yong-Hong; Caccetta, Lou

    2015-11-01

    In this paper, we propose a traffic flow model to study the effects of the real-time traffic state on traffic flow. The numerical results show that the proposed model can describe oscillation in traffic and stop-and-go traffic, where the speed-density relationship is qualitatively accordant with the empirical data of the Weizikeng segment of the Badaling freeway in Beijing, which means that the proposed model can qualitatively reproduce some complex traffic phenomena associated with real-time traffic state.

  16. Particulate Air Pollution and the Rate of Hospitalization for Congestive Heart Failure among Medicare Beneficiaries in Pittsburgh, Pennsylvania.

    PubMed Central

    Wellenius, Gregory A.; Bateson, Thomas F.; Mittleman, Murray A.; Schwartz., Joel

    2006-01-01

    We used a case-crossover approach to evaluate the association between ambient air pollution and the rate of hospitalization for congestive heart failure (CHF) among Medicare recipients (age ≥ 65) residing in Allegheny County (Pittsburgh area), PA, during 1987–1999. We also explored effect modification by age, gender, and specific secondary diagnoses. During follow-up, there were 55,019 admissions with a primary diagnosis of CHF. We found that particulate matter with aerodynamic diameter ≤ 10 μm (PM10), carbon monoxide (CO), nitrogen dioxide (NO2), and sulfur dioxide – but not ozone – were positively and significantly associated with the rate of admission on the same day in single-pollutant models. The strongest associations were observed with CO, NO2 and PM10. The associations with CO and NO2 were the most robust in two-pollutant models, remaining statistically significant even after adjusting for other pollutants. Patients with a recent myocardial infarction were at greater risk of particulate-related admission, but there was otherwise no significant effect modification by age, gender, or other secondary diagnoses. These results suggest that short-term elevations in air pollution from traffic-related sources may trigger acute cardiac decompensation of heart failure patients and that those with certain comorbid conditions may be more susceptible to these effects. PMID:15901623

  17. Assessment of the responsibility between a road traffic accident and medical defects after the traffic accident injury of knee joint.

    PubMed

    Chen, Jiemin; Xia, Wentao

    2012-04-01

    A 48-year-old Chinese woman was hit by a car in a road traffic accident. Local county hospital considered that her right knee was injured, but didn't find any sign of fracture from X-ray imaging. Then the hospital gave diagnosis of soft tissue contusion and the patient started to exercise with burden 21 days after her right lower limb was fixed by plaster slab. Four months later, she had to go back to the county hospital for recheck due to persistent pain on her right knee. Then, the right tibia outer plateau fracture was found. The patient rejected the advice of open reduction and internal fixation of right tibia plateau fracture. Instead, she accepted the unicompartmental knee arthroplasty in a hospital affiliated to a medical college. The patient felt the knee pain alleviated after surgery However, the joint dysfunction was aggravated even more. The patient used the legal procedure for personal compensation. Both driver and the insurance company disputed that the final consequence of the injured knee was due to not only the traffic accident, but also poor medical practice involved. Therefore the court consigned us to make judicial judgment of expertise. After investigation, we found the earliest X-ray graph after the accident had shown the fracture of right tibia outer plateau and right knee valgum, with articular surface involvement, and the traffic accident was considered as the primary cause of sequelae. At the same time, the county hospital missed the diagnosis of fracture, and led to insufficient fixation of right lower limb, which was not good for rehabilitation from fracture and joint injury. This was the secondary cause of sequelae. Additionally, instead of the standard therapy, the affiliated hospital of medical college made the unicompartmental knee arthroplasty four months later, which also had a little defect. It was the minor reason for the result. PMID:22391004

  18. Evolution of Traffic Jam in Traffic Flow Model

    NASA Astrophysics Data System (ADS)

    Fukui, Minoru; Ishibashi, Yoshihiro

    1993-11-01

    Traffic flow is simulated in a three-state cellular automaton model. In a two-dimensional cell without a crashed car, the ensemble average of the velocity of the cars is enhanced by the self-organization in the low-density phase of cars. In the high-density phase above p{=}0.5 of car density, the velocity is decreased and the system then degenerates into a global jamming phase in which all cars are stopped. A crashed car provides the seed of a jamming cluster, which grows into a global traffic jam even in the low-density phase. The growth of the jamming cluster is studied, and the time dependence of the number of jamming cars and the scaling law for the cell sizes are discussed.

  19. Simulation Study of Traffic Accidents in Bidirectional Traffic Models

    NASA Astrophysics Data System (ADS)

    Moussa, Najem

    Conditions for the occurrence of bidirectional collisions are developed based on the Simon-Gutowitz bidirectional traffic model. Three types of dangerous situations can occur in this model. We analyze those corresponding to head-on collision; rear-end collision and lane-changing collision. Using Monte Carlo simulations, we compute the probability of the occurrence of these collisions for different values of the oncoming cars' density. It is found that the risk of collisions is important when the density of cars in one lane is small and that of the other lane is high enough. The influence of different proportions of heavy vehicles is also studied. We found that heavy vehicles cause an important reduction of traffic flow on the home lane and provoke an increase of the risk of car accidents.

  20. Traffic flow theory and traffic flow simulation models. Transportation research record

    SciTech Connect

    1996-12-31

    ;Contents: Comparison of Simulation Modules of TRANSYT and INTEGRATION Models; Evaluation of SCATSIM-RTA Adaptive Traffic Network Simulation Model; Comparison NETSIM, NETFLO I, and NETFLO II Traffic Simulation Models for Fixed-Time Signal Control; Traffic Flow Simulation Through Parallel Processing; Cluster Analysis as Tool in Traffic Engineering; Traffic Platoon Dispersion Modeling on Arterial Streets; Hybrid Model for Estimating Permitted Left-Turn Saturations Flow Rate; and Passing Sight Distance and Overtaking Dilemma on Two-Lane Roads.

  1. Quantum random walks on congested lattices and the effect of dephasing

    PubMed Central

    Motes, Keith R.; Gilchrist, Alexei; Rohde, Peter P.

    2016-01-01

    We consider quantum random walks on congested lattices and contrast them to classical random walks. Congestion is modelled on lattices that contain static defects which reverse the walker’s direction. We implement a dephasing process after each step which allows us to smoothly interpolate between classical and quantum random walks as well as study the effect of dephasing on the quantum walk. Our key results show that a quantum walker escapes a finite boundary dramatically faster than a classical walker and that this advantage remains in the presence of heavily congested lattices. PMID:26812924

  2. Recovery of chylous pulmonary congestion in tuberous sclerosis complex-associated lymphangioleiomyomatosis.

    PubMed

    Kinoshita, Yoshiaki; Sakamoto, Atsuhiko; Hidaka, Kouko

    2014-01-01

    Chyloptysis and chylous pulmonary congestion are extremely rare complications of lymphangioleiomyomatosis (LAM). We report a case of a 50-year-old woman with tuberous sclerosis complex-associated LAM, who presented with expectorating milky-white bronchial casts. She was diagnosed with chyloptysis and chylous pulmonary congestion by sputum analysis. Her symptoms and lung infiltration were improved by oral sirolimus therapy; moreover, serum Krebs von den Lungen-6 (KL-6) levels paralleled the symptoms and lung infiltration of these complications. We suggest that serum KL-6 may be a useful monitoring biomarker of chyloptysis and chylous pulmonary congestion in LAM. PMID:25326562

  3. Diagnosis and Treatment of Depression in Patients With Congestive Heart Failure: A Review of the Literature

    PubMed Central

    Stern, Theodore A.; Hebert, Kathy A.; Musselman, Dominique L.

    2013-01-01

    Context: Major depressive disorder (MDD) can be challenging to diagnose in patients with congestive heart failure, who often suffer from fatigue, insomnia, weight changes, and other neurovegetative symptoms that overlap with those of depression. Pathophysiologic mechanisms (eg, inflammation, autonomic nervous system dysfunction, cardiac arrhythmias, and altered platelet function) connect depression and congestive heart failure. Objective: We sought to review the prevalence, diagnosis, neurobiology, and treatment of depression associated with congestive heart failure. Data Sources: A search of all English-language articles between January 2003 and January 2013 was conducted using the search terms congestive heart failure and depression. Study Selection: We found 1,498 article abstracts and 19 articles (meta-analyses, systematic reviews, and original research articles) that were selected for inclusion, as they contained information about our focus on diagnosis, treatment, and pathophysiology of depression associated with congestive heart failure. The search was augmented with manual review of reference lists of articles from the initial search. Articles selected for review were determined by author consensus. Data Extraction: The prevalence, diagnosis, neurobiology, and treatment of depression associated with congestive heart failure were reviewed. Particular attention was paid to the safety, efficacy, and tolerability of antidepressant medications commonly used to treat depression and how their side-effect profiles impact the pathophysiology of congestive heart failure. Drug-drug interactions between antidepressant medications and medications used to treat congestive heart failure were examined. Results: MDD is highly prevalent in patients with congestive heart failure. Moreover, the prevalence and severity of depression correlate with the degree of cardiac dysfunction and development of congestive heart failure. Depression increases the risk of congestive heart

  4. Reliable on-demand multicast routing with congestion control in wireless ad hoc networks

    NASA Astrophysics Data System (ADS)

    Tang, Ken; Gerla, Mario

    2001-07-01

    In this paper, we address the congestion control multicast routing problem in wireless ad hoc networks through the medium access control (MAC) layer. We first introduce the Broadcast Medium Window (BMW) MAC protocol, which provides reliable delivery to broadcast packets at the MAC layer. We then extend the wireless On-Demand Multicast Routing Protocol (ODMRP) to facilitate congestion control in ad hoc networks using BMW. Through simulation, we show that ODMRP with congestion control adapts well to multicast sources that are aggressive in data transmissions.

  5. 32 CFR 634.24 - Traffic planning and codes.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 4 2010-07-01 2010-07-01 true Traffic planning and codes. 634.24 Section 634.24... CRIMINAL INVESTIGATIONS MOTOR VEHICLE TRAFFIC SUPERVISION Traffic Supervision § 634.24 Traffic planning and... traffic supervision program includes traffic circulation planning and control of motor vehicle...

  6. 32 CFR 634.24 - Traffic planning and codes.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 4 2012-07-01 2011-07-01 true Traffic planning and codes. 634.24 Section 634.24... CRIMINAL INVESTIGATIONS MOTOR VEHICLE TRAFFIC SUPERVISION Traffic Supervision § 634.24 Traffic planning and codes. (a) Safe and efficient movement of traffic on an installation requires traffic supervision....

  7. Molecular Mechanisms of Chromium in Alleviating Insulin Resistance

    PubMed Central

    Hua, Yinan; Clark, Suzanne; Ren, Jun; Sreejayan, Nair

    2011-01-01

    Type 2 diabetes is often associated with obesity, dyslipidemia, and cardiovascular anomalies and is a major health problem approaching global epidemic proportions. Insulin resistance, a prediabetic condition, precedes the onset of frank type 2 diabetes and offers potential avenues for early intervention to treat the disease. Although lifestyle modifications and exercise can reduce the incidence of diabetes, compliance has proved to be difficult, warranting pharmacological interventions. However, most of the currently available drugs that improve insulin sensitivity have adverse effects. Therefore, attractive strategies to alleviate insulin resistance include dietary supplements. One such supplement is chromium, which has been shown reduce insulin resistance in some, but not all, studies. Furthermore, the molecular mechanisms of chromium in alleviating insulin resistance remain elusive. This review examines emerging reports on the effect of chromium, as well as molecular and cellular mechanisms by which chromium may provide beneficial effects in alleviating insulin resistance. PMID:22423897

  8. Target-tracking and identity management algorithms for air traffic surveillance

    NASA Astrophysics Data System (ADS)

    Balakrishnan, Hamsa

    The air traffic control system of the United States is responsible for managing traffic in the National Airspace System; safety is a paramount concern. The air traffic surveillance network has the task of collecting and processing information on the positions, velocities and identities of the aircraft in the system, before presenting it to air traffic controllers to use in maintaining an orderly flow of traffic. This dissertation attempts to design techniques that provide controllers with high-fidelity information about the aircraft in their controlled airspace, using the observations of the air traffic surveillance network. We propose algorithms for the efficient tracking of aircraft, as well as for maintaining beliefs of their identities. Such methods would improve the processing of aircraft situation data, particularly in a congested airspace with general aviation. In this thesis, we propose an algorithmic framework for the simultaneous tracking and identity management of multiple maneuvering targets. We design an algorithm that efficiently tracks the positions, velocities, flight modes, and identities of multiple aircraft in cluttered environments. We tackle the challenges of data association, identity management and state estimation of aircraft trajectories by proposing a modification of the Joint Probabilistic Data Association algorithm, an algorithm based on identity-mass flow, and a state estimation algorithm for tracking hybrid systems, respectively. The identity of each aircraft, an essential feature of aircraft situation data, is often not available but needs to be inferred from radar observations, and maintained in terms of probabilities. We present an algorithm to update the probabilistic matrices that represent the belief of aircraft identities, in the presence of intermittent measurements. We demonstrate the performance of the framework using examples drawn from air traffic surveillance. We also consider the problem of identifying stochastic hybrid

  9. A Concept for Robust, High Density Terminal Air Traffic Operations

    NASA Technical Reports Server (NTRS)

    Isaacson, Douglas R.; Robinson, John E.; Swenson, Harry N.; Denery, Dallas G.

    2010-01-01

    This paper describes a concept for future high-density, terminal air traffic operations that has been developed by interpreting the Joint Planning and Development Office s vision for the Next Generation (NextGen) Air Transportation System and coupling it with emergent NASA and other technologies and procedures during the NextGen timeframe. The concept described in this paper includes five core capabilities: 1) Extended Terminal Area Routing, 2) Precision Scheduling Along Routes, 3) Merging and Spacing, 4) Tactical Separation, and 5) Off-Nominal Recovery. Gradual changes are introduced to the National Airspace System (NAS) by phased enhancements to the core capabilities in the form of increased levels of automation and decision support as well as targeted task delegation. NASA will be evaluating these conceptual technological enhancements in a series of human-in-the-loop simulations and will accelerate development of the most promising capabilities in cooperation with the FAA through the Efficient Flows Into Congested Airspace Research Transition Team.

  10. Distributed and Centralized Conflict Management Under Traffic Flow Management Constraints

    NASA Technical Reports Server (NTRS)

    Feron, Eric; Bilimoria, Karl (Technical Monitor)

    2001-01-01

    The past year's activity has concentrated on the following two activities: (1) Refining and completing our study on the stability of interacting flows of aircraft when they have to resolve conflicts in a decentralized and sequential manner. More specifically, it was felt that some of the modeling assumptions made during previous research (such offset maneuvering models) could be improved to include more realistic models such as heading changes when analyzing interacting flow stability problems. We extended our analysis to achieve this goal. The results of this study have been submitted for presentation at the 2002 American Control Conference; (2) Examining the issues associated with delay propagation across multiple enroute sectors. This study was initiated at NASA in cooperation with Dr. Karl Bilimoria. Considering a set of adjacent sectors, this ongoing study concentrates on the effect of various traffic flow management strategies on the propagation of delays and congestion across sectors. The problem description and findings so far are reported in the attached working paper "Enroute sector buffering capacity."

  11. Simulation of traffic control signal systems

    NASA Technical Reports Server (NTRS)

    Connolly, P. J.; Concannon, P. A.; Ricci, R. C.

    1974-01-01

    In recent years there has been considerable interest in the development and testing of control strategies for networks of urban traffic signal systems by simulation. Simulation is an inexpensive and timely method for evaluating the effect of these traffic control strategies since traffic phenomena are too complex to be defined by analytical models and since a controlled experiment may be hazardous, expensive, and slow in producing meaningful results. This paper describes the application of an urban traffic corridor program, to evaluate the effectiveness of different traffic control strategies for the Massachusetts Avenue TOPICS Project.

  12. Alleviating Contingency Violations through Visual Analytics and Suggested Actions

    SciTech Connect

    Rice, Mark J.; Huang, Zhenyu; Chen, Yousu; Allwardt, Craig H.; Mackey, Patrick S.

    2013-07-21

    Contingency analysis (CA) is essential in maintaining a stable and secure power grid. It is required by operating standards that contingency violations need to be alleviated within 30 minutes. In today’s practice, operators normally make decisions based on the information they have with limited support. This paper presents a new feature of user suggested actions integrated in the graphical contingency analysis (GCA) tool, developed by the authors to help the operator’s decision making process. This paper provides a few examples on showing how the decision support element of the GCA tool is further enhanced by this new feature to alleviate contingency violations for better grid reliability.

  13. Experimental investigations on wake vortices and their alleviation

    NASA Astrophysics Data System (ADS)

    Savaş, Ömer

    2005-05-01

    Recent wake vortex research in the laboratory has benefited considerably from concurrent analytical and numerical research on the instability of vortex systems. Tow tank, with dye flow visualization and particle image velocimetry is the most effective combination for laboratory research. Passive and active wake alleviation schemes have been successfully demonstrated in the laboratory. The passive alleviation systems exploit the natural evolution of vortex instabilities while the active systems rely on hastening selected instabilities by forcing the vortices individually or as a system. Their practical applicability, however, will have to meet further criteria beyond those dictated by fluid dynamics. To cite this article: Ö. Savaş, C. R. Physique 6 (2005).

  14. Consequences of Slot Transactions on Airport Congestion and Environmental Protection

    NASA Technical Reports Server (NTRS)

    Abeyratne, Ruwantissa I.R.

    2000-01-01

    Recent trends in the liberalization of market access by many commercial airlines have opened the skies to virtually unlimited flights between many countries. However, this liberalization is stultified by the lack of airport capacity to accommodate the many flights that are generated by demand for capacity. Accordingly, the allocation of slots for open skies airlines remain dependent on the expansion and effective management of airport capacity. This article examines the ramifications of slot allocation on traffic peaking at airports and environmental concerns, which may emerge with this activity.

  15. Interaction of Airspace Partitions and Traffic Flow Management Delay with Weather

    NASA Technical Reports Server (NTRS)

    Lee, Hak-Tae; Chatterji, Gano B.; Palopo, Kee

    2011-01-01

    The interaction of partitioning the airspace and delaying flights in the presence of convective weather is explored to study how re-partitioning the airspace can help reduce congestion and delay. Three approaches with varying complexities are employed to compute the ground delays.In the first approach, an airspace partition of 335 high-altitude sectors that is based on clear weather day traffic is used. Routes are then created to avoid regions of convective weather. With traffic flow management, this approach establishes the baseline with per-flight delay of 8.4 minutes. In the second approach, traffic flow management is used to select routes and assign departure delays such that only the airport capacity constraints are met. This results in 6.7 minutes of average departure delay. The airspace is then partitioned with a specific capacity. It is shown that airspace-capacity-induced delay can be reduced to zero ata cost of 20percent more sectors for the examined scenario.

  16. SENTINEL-1/2 Data for Ship Traffic Monitoring on the Danube River

    NASA Astrophysics Data System (ADS)

    Negula, I. Dana; Poenaru, V. D.; Olteanu, V. G.; Badea, A.

    2016-06-01

    After a long period of drought, the water level of the Danube River has significantly dropped especially on the Romanian sector, in July-August 2015. Danube reached the lowest water level recorded in the last 12 years, causing the blockage of the ships in the sector located close to Zimnicea Harbour. The rising sand banks in the navigable channel congested the commercial traffic for a few days with more than 100 ships involved. The monitoring of the decreasing water level and the traffic jam was performed based on Sentinel-1 and Sentinel-2 free data provided by the European Space Agency and the European Commission within the Copernicus Programme. Specific processing methods (calibration, speckle filtering, geocoding, change detection, image classification, principal component analysis, etc.) were applied in order to generate useful products that the responsible authorities could benefit from. The Sentinel data yielded good results for water mask extraction and ships detection. The analysis continued after the closure of the crisis situation when the water reached the nominal level again. The results indicate that Sentinel data can be successfully used for ship traffic monitoring, building the foundation of future endeavours for a durable monitoring of the Danube River.

  17. Modelling total duration of traffic incidents including incident detection and recovery time.

    PubMed

    Tavassoli Hojati, Ahmad; Ferreira, Luis; Washington, Simon; Charles, Phil; Shobeirinejad, Ameneh

    2014-10-01

    Traffic incidents are key contributors to non-recurrent congestion, potentially generating significant delay. Factors that influence the duration of incidents are important to understand so that effective mitigation strategies can be implemented. To identify and quantify the effects of influential factors, a methodology for studying total incident duration based on historical data from an 'integrated database' is proposed. Incident duration models are developed using a selected freeway segment in the Southeast Queensland, Australia network. The models include incident detection and recovery time as components of incident duration. A hazard-based duration modelling approach is applied to model incident duration as a function of a variety of factors that influence traffic incident duration. Parametric accelerated failure time survival models are developed to capture heterogeneity as a function of explanatory variables, with both fixed and random parameters specifications. The analysis reveals that factors affecting incident duration include incident characteristics (severity, type, injury, medical requirements, etc.), infrastructure characteristics (roadway shoulder availability), time of day, and traffic characteristics. The results indicate that event type durations are uniquely different, thus requiring different responses to effectively clear them. Furthermore, the results highlight the presence of unobserved incident duration heterogeneity as captured by the random parameter models, suggesting that additional factors need to be considered in future modelling efforts. PMID:24974360

  18. Analysis of Factors for Incorporating User Preferences in Air Traffic Management: A system Perspective

    NASA Technical Reports Server (NTRS)

    Sheth, Kapil S.; Gutierrez-Nolasco, Sebastian

    2010-01-01

    This paper presents an analysis of factors that impact user flight schedules during air traffic congestion. In pre-departure flight planning, users file one route per flight, which often leads to increased delays, inefficient airspace utilization, and exclusion of user flight preferences. In this paper, first the idea of filing alternate routes and providing priorities on each of those routes is introduced. Then, the impact of varying planning interval and system imposed departure delay increment is discussed. The metrics of total delay and equity are used for analyzing the impact of these factors on increased traffic and on different users. The results are shown for four cases, with and without the optional routes and priority assignments. Results demonstrate that adding priorities to optional routes further improves system performance compared to filing one route per flight and using first-come first-served scheme. It was also observed that a two-hour planning interval with a five-minute system imposed departure delay increment results in highest delay reduction. The trend holds for a scenario with increased traffic.

  19. Vertical and horizontal variability in airborne nanoparticles and their exposure around signalised traffic intersections.

    PubMed

    Goel, Anju; Kumar, Prashant

    2016-07-01

    We measured size-resolved PNCs in the 5-560 nm range at two different types (4- and 3-way) of TIs in Guildford (Surrey, UK) at fixed sites (∼1.5 m above the road level), sequentially at 4 different heights (1, 1.5, 2.5 and 4.7 m), and along the road at five different distances (10, 20, 30, 45 and 60 m). The aims were to: (i) assess the differences in PNCs measured at studied TIs, (ii) identify the best fit probability distribution curves for the PNCs, (iii) determine vertical and horizontal decay profiles of PNCs, (iv) estimate particle number emission factors (PNEFs) under congested and free-flow traffic conditions, and (v) quantify the pedestrian exposure in terms of respiratory deposition dose (RDD) rates at the TIs. Daily averaged particle number distributions at TIs reflected the effect of fresh emissions with peaks at 5.6, 10 and 56 nm. Despite the relatively high traffic volume at 3-way TI, average PNCs at 4-way TI were about twice as high as at 3-way TI, indicating less favourable dispersion conditions. Generalised extreme value distribution fitted well to PNC data at both TIs. Vertical PNC profiles followed an exponential decay, which was much sharper at 4-way TI than at 3-way TI, suggesting ∼40% less exposure for people at first floor (4.7 m) to those at ground floor around 4-way TI. Vertical profiles indicated much sharper (∼132-times larger) decay than in horizontal direction, due to close vicinity of road vehicles during the along-road measurements. Over an order of magnitude higher PNEFs were found during congested, compared with free-flow, conditions due to frequent changes in traffic speed. Average RDD rate at 4-way TI during congested conditions were up to 14-times higher than those at 3-way TI (0.4 × 10(11) h(-1)). Findings of this study are a step forward to understand exposure at and around the TIs. PMID:27061475

  20. Air traffic management evaluation tool

    NASA Technical Reports Server (NTRS)

    Sridhar, Banavar (Inventor); Sheth, Kapil S. (Inventor); Chatterji, Gano Broto (Inventor); Bilimoria, Karl D. (Inventor); Grabbe, Shon (Inventor); Schipper, John F. (Inventor)

    2010-01-01

    Method and system for evaluating and implementing air traffic management tools and approaches for managing and avoiding an air traffic incident before the incident occurs. The invention provides flight plan routing and direct routing or wind optimal routing, using great circle navigation and spherical Earth geometry. The invention provides for aircraft dynamics effects, such as wind effects at each altitude, altitude changes, airspeed changes and aircraft turns to provide predictions of aircraft trajectory (and, optionally, aircraft fuel use). A second system provides several aviation applications using the first system. These applications include conflict detection and resolution, miles-in trail or minutes-in-trail aircraft separation, flight arrival management, flight re-routing, weather prediction and analysis and interpolation of weather variables based upon sparse measurements.

  1. Real-Time Traffic Information for Emergency Evacuation Operations: Phase A Final Report

    SciTech Connect

    Franzese, Oscar; Zhang, Li; Mahmoud, Anas M.; Lascurain, Mary Beth; Wen, Yi

    2010-05-01

    There are many instances in which it is possible to plan ahead for an emergency evacuation (e.g., an explosion at a chemical processing facility). For those cases, if an accident (or an attack) were to happen, then the best evacuation plan for the prevailing network and weather conditions would be deployed. In other cases (e.g., the derailment of a train transporting hazardous materials), there may not be any previously developed plan to be implemented and decisions must be made ad-hoc on how to proceed with an emergency evacuation. In both situations, the availability of real-time traffic information plays a critical role in the management of the evacuation operations. To improve public safety during a vehicular emergency evacuation it is necessary to detect losses of road capacity (due to incidents, for example) as early as possible. Once these bottlenecks are identified, re-routing strategies must be determined in real-time and deployed in the field to help dissipate the congestion and increase the efficiency of the evacuation. Due to cost constraints, only large urban areas have traffic sensor deployments that permit access to some sort of real-time traffic information; any evacuation taking place in any other areas of the country would have to proceed without real-time traffic information. The latter was the focus of this SERRI/DHS (Southeast Region Research Initiative/Department of Homeland Security) sponsored project. That is, the main objective on the project was to improve the operations during a vehicular emergency evacuation anywhere by using newly developed real-time traffic-information-gathering technologies to assess traffic conditions and therefore to potentially detect incidents on the main evacuation routes. Phase A of the project consisted in the development and testing of a prototype system composed of sensors that are engineered in such a way that they can be rapidly deployed in the field where and when they are needed. Each one of these sensors

  2. Software for Simulating Air Traffic

    NASA Technical Reports Server (NTRS)

    Sridhar, Banavar; Bilimoria, Karl; Grabbe, Shon; Chatterji, Gano; Sheth, Kapil; Mulfinger, Daniel

    2006-01-01

    Future Air Traffic Management Concepts Evaluation Tool (FACET) is a system of software for performing computational simulations for evaluating advanced concepts of advanced air-traffic management. FACET includes a program that generates a graphical user interface plus programs and databases that implement computational models of weather, airspace, airports, navigation aids, aircraft performance, and aircraft trajectories. Examples of concepts studied by use of FACET include aircraft self-separation for free flight; prediction of air-traffic-controller workload; decision support for direct routing; integration of spacecraft-launch operations into the U.S. national airspace system; and traffic- flow-management using rerouting, metering, and ground delays. Aircraft can be modeled as flying along either flight-plan routes or great-circle routes as they climb, cruise, and descend according to their individual performance models. The FACET software is modular and is written in the Java and C programming languages. The architecture of FACET strikes a balance between flexibility and fidelity; as a consequence, FACET can be used to model systemwide airspace operations over the contiguous U.S., involving as many as 10,000 aircraft, all on a single desktop or laptop computer running any of a variety of operating systems. Two notable applications of FACET include: (1) reroute conformance monitoring algorithms that have been implemented in one of the Federal Aviation Administration s nationally deployed, real-time, operational systems; and (2) the licensing and integration of FACET with the commercially available Flight Explorer, which is an Internet- based, real-time flight-tracking system.

  3. Therapeutic potential of anticytokine therapy in congestive heart failure.

    PubMed

    Aukrust, Pal; Yndestad, Arne; Damås, Jan K; Gullestad, Lars

    2004-01-01

    Accumulating evidence indicates that inflammatory cytokines play a pathogenic role in congestive heart failure (CHF) by influencing heart contractility, inducing hypertrophy, and promoting apoptosis or fibrosis, contributing to the continuous myocardial remodeling process. While several stimuli may be operating such as heat-shock protein, microbial antigen, bacterial lipopolysaccharide, shear and oxidative stress, hypoxia and oxidized low-density lipoprotein (LDL), it seems that the inflammatory response to these stimuli may represent a common final pathogenic pathway in CHF regardless of the initial event. Traditional cardiovascular drugs seem to have little influence on the overall cytokine network, and immunomudulatory therapy has emerged as a possible new treatment modality in CHF. Several animal studies, and some clinical pilot studies, have suggested that down-regulation of inflammatory cytokines may improve cardiac performance. On the other hand, preliminary results from the placebo-controlled studies suggest no effect, or even adverse effect, of antitumor necrosis factor (TNF) therapy on mortality and hospitalization. Although somewhat disappointing, these negative results do not necessarily argue against the 'cytokine hypothesis'. These studies just underscore the difficulties and the challenges in developing treatment modalities that can modulate the cytokine network in CHF patients resulting in anti-inflammatory and beneficial net effects. Further research in this area will have to more precisely identify the most important actors in the immunopathogenesis of CHF in order to develop more specific immunomodulating agents for this disorder. However, at present the beneficial role of anticytokine therapy in patients with CHF remains unproven. PMID:15134469

  4. Atrial natriuretic factor binding sites in experimental congestive heart failure

    SciTech Connect

    Bianchi, C.; Thibault, G.; Wrobel-Konrad, E.; De Lean, A.; Genest, J.; Cantin, M. )

    1989-10-01

    A quantitative in vitro autoradiographic study was performed on the aorta, renal glomeruli, and adrenal cortex of cardiomyopathic hamsters in various stages of heart failure and correlated, in some instances, with in vivo autoradiography. The results indicate virtually no correlation between the degree of congestive heart failure and the density of 125I-labeled atrial natriuretic factor ((Ser99, Tyr126)ANF) binding sites (Bmax) in the tissues examined. Whereas the Bmax was increased in the thoracic aorta in moderate and severe heart failure, there were no significant changes in the zona glomerulosa. The renal glomeruli Bmax was lower in mild and moderate heart failure compared with control and severe heart failure. The proportion of ANF B- and C-receptors was also evaluated in sections of the aorta, adrenal, and kidney of control and cardiomyopathic hamsters with severe heart failure. (Arg102, Cys121)ANF (des-(Gln113, Ser114, Gly115, Leu116, Gly117) NH2) (C-ANF) at 10(-6) M displaced approximately 505 of (Ser99, Tyr126)125I-ANF bound in the aorta and renal glomeruli and approximately 20% in the adrenal zona glomerulosa in both series of animals. These results suggest that ANF may exert a buffering effect on the vasoconstriction of heart failure and to a certain extent may inhibit aldosterone secretion. The impairment of renal sodium excretion does not appear to be related to glomerular ANF binding sites at any stage of the disease.

  5. Cerebral Venous Congestion as Indication for Thrombolytic Treatment

    SciTech Connect

    Tsai, Fong Y. Kostanian, Varoujan; Rivera, Monica; Lee, Kwo-Whie; Chen, Clayton C.; Nguyen, Thong H.

    2007-07-15

    Purpose. To carry out a retrospective analysis of patients with acute dural sinus thrombosis, and the role of cerebral venous congestion in patient management. Methods. Twenty-five patients were identified with the clinical and imaging diagnosis of acute dural sinus thrombosis. The imaging diagnosis was by magnetic resonance (MR) and/or computed tomography (CT) venography. There was a female predominance with a female to male ratio of 1.5 to 1 (16 women, 9 men). The age range was from 19 to 64 years old with an average age of 37 years. The first 10 patients, who ranged in age from 21 to 64 years old (average 37 years), received only anticoagulation therapy with heparin and warfarin for periods ranging from 5 days to 2 months. The remaining 15 patients ranged in age from 19 to 57 years old (average 38 years). They either underwent subsequent thrombectomy after a trial of anticoagulation therapy, or went straight to thrombectomy. These latter 15 patients had initial evidence of cerebral venous congestion, either clinically by severe or worsening symptoms despite anticoagulation therapy, or on initial or subsequent CT or MR imaging. In our experience, the cerebral venous congestion imaging findings included intracranial hemorrhage, a hematoma, or edema. The thrombolytic treatment technique consisted of the advancement of a 6 Fr guiding catheter to the jugular bulb or sigmoid sinus from a transfemoral approach. A microcatheter was then advanced to the proximal portion of the thrombus and then either tissue plasminogen activator (tPA) or urokinase was injected to prevent clot propagation. A balloon catheter was used to perform thrombectomy since the thrombolytic agents can be injected via the inner lumen with an inflated balloon. The inflated balloon helped to keep the venous flow from washing out the thrombolytic agent, thus facilitating the agent's effect. Results. The first 10 patients received only anticoagulation therapy with heparin and warfarin for periods

  6. Preserved Left Ventricular, Systolic Function in Clinical Congestive Heart Failure

    PubMed Central

    Lee, Bang Hun; Kim, Jeong Hyun; Lim, Heon Kil; Lee, Chung Kyun

    1987-01-01

    Although clinical congestive heart failure (CHF) is associated with significant left ventricular (LV) systolic dysfunction, recently it has been recognized that LV diastolic dysfunction also may occur in the absence of abnormal systolic performance. A retrospective study evaluated 23 patients with myocardial infarction and CHF who had undergone multigated blood pool scintigraphy and were found to have normal LV ejection fraction (≥ 50%). Average rapid filling velocity (RFV) and slow filling velocity (SFV) were both significantly reduced in CHF patients (5.1 ± 1.3 unit/s, 2.2 ± 1.4 unit/s respectively) compared with normal control group (3.9 ± 1.2 unit/s, 1.3 ± 0.8 unit/s respectively). Rapid filling time and total diastolic time were also significantly prolonged in CHF patients (p<0.01, p<0.05 respectively). There were no significant changes in heart rate and blood pressure between two groups. Thus, normal systolic LV function is encountered in patients with CHF and it appears to be prudent to evaluate diastolic performance as well for optimal therapeutic strategies for CHF patients. PMID:3154818

  7. Decrease of cardiac chaos in congestive heart failure

    NASA Astrophysics Data System (ADS)

    Poon, Chi-Sang; Merrill, Christopher K.

    1997-10-01

    The electrical properties of the mammalian heart undergo many complex transitions in normal and diseased states. It has been proposed that the normal heartbeat may display complex nonlinear dynamics, including deterministic chaos,, and that such cardiac chaos may be a useful physiological marker for the diagnosis and management, of certain heart trouble. However, it is not clear whether the heartbeat series of healthy and diseased hearts are chaotic or stochastic, or whether cardiac chaos represents normal or abnormal behaviour. Here we have used a highly sensitive technique, which is robust to random noise, to detect chaos. We analysed the electrocardiograms from a group of healthy subjects and those with severe congestive heart failure (CHF), a clinical condition associated with a high risk of sudden death. The short-term variations of beat-to-beat interval exhibited strongly and consistently chaotic behaviour in all healthy subjects, but were frequently interrupted by periods of seemingly non-chaotic fluctuations in patients with CHF. Chaotic dynamics in the CHF data, even when discernible, exhibited a high degree of random variability over time, suggesting a weaker form of chaos. These findings suggest that cardiac chaos is prevalent in healthy heart, and a decrease in such chaos may be indicative of CHF.

  8. Pattern of arrhythmias among Nigerians with congestive heart failure

    PubMed Central

    Ajayi, Olufemi E; Abiodun, Olugbenga O; Akintomide, Anthony O; Adebayo, Rasaaq A; Ogunyemi, Suraj A; Balogun, Michael O; Bamikole, Olaniyi J; Ajibare, Adeola O; Ajayi, Adesuyi A

    2015-01-01

    Background In patients with heart failure, death is often sudden due to life-threatening arrhythmias. This work was carried out to evaluate the pattern of arrhythmias in Nigerians with heart failure. Materials and methods Thirty subjects with congestive heart failure (CHF), 30 subjects with hypertensive heart disease, and 15 normal subjects with no obvious features of heart disease were evaluated with resting and 24-hour electrocardiographic monitoring and transthoracic echocardiography. Data were analyzed with one-way analysis of variance with post hoc Duncan’s analysis, Fisher’s exact test, and linear regression analysis using SPSS version 16. Results CHF subjects had more instances of supraventricular tachycardia (P=0.005), ventricular extrasystoles (P<0.001), bigeminy (P<0.001), trigeminy (P<0.001), couplets (P<0.001), triplets (P<0.001), and nonsustained ventricular tachycardia (VT) (P=0.003) than the other two control groups. They also showed a significantly longer VT duration (4.6±5.6 seconds) compared with the other groups (P<0.001). Linear regression analysis showed a significant direct relationship between VT and the maximum number of ventricular extrasystoles per hour (P=0.001). Conclusion Cardiac arrhythmias are common in subjects with CHF and are more frequent when compared with patients with hypertensive heart disease and normal subjects. PMID:25870514

  9. [Congestive heart failure in patients with chronic kidney disease].

    PubMed

    Poskurica, Mileta; Petrović, Dejan

    2014-01-01

    Cardiovascular disorders are the most frequent cause of death (46-60%) among patients with advanced chronic renal failure (CRF), and on dialysis treatment. Uremic cardiomyopathy is the basic pathophysiologic substrate, whereas ischemic heart disease (IHD) and anemia are the most important contributing factors. Associated with well-know risk factors and specific disorders for terminal kidney failure and dialysis, the aforementioned factors instigate congestive heart failure (CHF). Suspected CHF is based on the anamnesis, clinical examination and ECG, while it is confirmed and defined more precisely on the basis of echocardiography and radiology examination. Biohumoral data (BNP, NT-proBNP) are not sufficiently reliable because of specific volemic fluctuation and reduced natural clearance. Therapy approach is similar to the one for the general population: ACEI, ARBs, β-blockers, inotropic drugs and diuretics. Hypervolemia and most of the related symptoms can be kept under control effectively by the isolated or ultrafiltation, in conjunction with dialysis, during the standard bicarbonate hemodialysis or hemodiafiltration. In the same respect peritoneal dialysis is efficient for the control of hypervolemia symptoms, mainly during the first years of its application and in case of the lower NYHA class (II°/III°). In general, heart support therapy, surgical interventions of the myocardium and valve replacement are rarely used in patients on dialysis, whereas revascularization procedures are beneficial for associated IHD. In selected cases the application of cardiac resynchronization and/or implantation of a cardioverter defibrillator are advisable. PMID:25731010

  10. Optimal information transmission in organizations: search and congestion

    SciTech Connect

    Arenas, A.; Cabrales, A.; Danon, L.; Diaz-Guilera, A.; Guimera, R.; Vega-Redondo, F.

    2008-01-01

    We propose a stylized model of a problem-solving organization whose internal communication structure is given by a fixed network. Problems arrive randomly anywhere in this network and must find their way to their respective specialized solvers by relying on local information alone. The organization handles multiple problems simultaneously. For this reason, the process may be subject to congestion. We provide a characterization of the threshold of collapse of the network and of the stock of floating problems (or average delay) that prevails below that threshold. We build upon this characterization to address a design problem: the determination of what kind of network architecture optimizes performance for any given problem arrival rate. We conclude that, for low arrival rates, the optimal network is very polarized (i.e. star-like or centralized), whereas it is largely homogeneous (or decentralized) for high arrival rates. These observations are in line with a common transformation experienced by information-intensive organizations as their work flow has risen in recent years.

  11. Chance Constrained Input Relaxation to Congestion in Stochastic DEA. An Application to Iranian Hospitals

    PubMed Central

    Kheirollahi, Hooshang; Matin, Behzad Karami; Mahboubi, Mohammad; Alavijeh, Mehdi Mirzaei

    2015-01-01

    This article developed an approached model of congestion, based on relaxed combination of inputs, in stochastic data envelopment analysis (SDEA) with chance constrained programming approaches. Classic data envelopment analysis models with deterministic data have been used by many authors to identify congestion and estimate its levels; however, data envelopment analysis with stochastic data were rarely used to identify congestion. This article used chance constrained programming approaches to replace stochastic models with ‘‘deterministic equivalents”. This substitution leads us to non-linear problems that should be solved. Finally, the proposed method based on relaxed combination of inputs was used to identify congestion input in six Iranian hospital with one input and two outputs in the period of 2009 to 2012. PMID:25946925

  12. Chance Constrained Input Relaxation to Congestion in Stochastic DEA. An Application to Iranian Hospitals.

    PubMed

    Kheirollahi, Hooshang; Matin, Behzad Karami; Mahboubi, Mohammad; Alavijeh, Mehdi Mirzaei

    2015-01-01

    This article developed an approached model of congestion, based on relaxed combination of inputs, in stochastic data envelopment analysis (SDEA) with chance constrained programming approaches. Classic data envelopment analysis models with deterministic data have been used by many authors to identify congestion and estimate its levels; however, data envelopment analysis with stochastic data were rarely used to identify congestion. This article used chance constrained programming approaches to replace stochastic models with "deterministic equivalents". This substitution leads us to non-linear problems that should be solved. Finally, the proposed method based on relaxed combination of inputs was used to identify congestion input in six Iranian hospital with one input and two outputs in the period of 2009 to 2012. PMID:25946925

  13. [Case of congestive heart failure associated with hypereosinophilia developed during antibiotics treatment].

    PubMed

    Sato, Takeo; Hagiwara, Kiyofumi; Matsuno, Hiroaki; Akiyama, Osamu

    2005-10-01

    A 92-year-old man with a history of bronchial asthma and allergic rhinitis received antibiotics for sepsis by methicillin-resistant Staphylococcus aureus and multidrug-resistant Enterococcus gallinarum. During the antibiotics treatment, skin eruptions, liver dysfunction, and hypereosinophilia developed, followed by dyspnea, congestive heart failure, electrocardiographic abnormalities, and diffuse mild myocardial hypokinesis. After the discontinuation of the antibiotics and the administration of steroid, skin eruptions, liver dysfunction, and hypereosinophilia improved parallel with the improvement of the congestive heart failure. Vancomycin hydrochloride and teicoplanin were suspected as the causative drugs on the basis of the treatment course. Although congestive heart failure is rare in the case of drug-induced hypereosinophilia, it is one of life-threatening complications. We describe herein a case of congestive heart failure associated with hypereosinophilia developed during antibiotics treatment, successfully treated with steroid after the discontinuation of the causative drug. PMID:16407668

  14. Sequestration and Microvascular Congestion Are Associated With Coma in Human Cerebral Malaria

    PubMed Central

    Ponsford, Mark J.; Medana, Isabelle M.; Prapansilp, Panote; Hien, Tran Tinh; Lee, Sue J.; Dondorp, Arjen M.; Esiri, Margaret M.; Day, Nicholas P. J.; White, Nicholas J.

    2012-01-01

    The pathogenesis of coma in severe Plasmodium falciparum malaria remains poorly understood. Obstruction of the brain microvasculature because of sequestration of parasitized red blood cells (pRBCs) represents one mechanism that could contribute to coma in cerebral malaria. Quantitative postmortem microscopy of brain sections from Vietnamese adults dying of malaria confirmed that sequestration in the cerebral microvasculature was significantly higher in patients with cerebral malaria (CM; n = 21) than in patients with non-CM (n = 23). Sequestration of pRBCs and CM was also significantly associated with increased microvascular congestion by infected and uninfected erythrocytes. Clinicopathological correlation showed that sequestration and congestion were significantly associated with deeper levels of premortem coma and shorter time to death. Microvascular congestion and sequestration were highly correlated as microscopic findings but were independent predictors of a clinical diagnosis of CM. Increased microvascular congestion accompanies coma in CM, associated with parasite sequestration in the cerebral microvasculature. PMID:22207648

  15. 23 CFR 970.214 - Federal lands congestion management system (CMS).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... LANDS HIGHWAYS NATIONAL PARK SERVICE MANAGEMENT SYSTEMS National Park Service Management Systems § 970...: (i) Identify and document measures for congestion (e.g., level of service); (ii) Identify the...

  16. 23 CFR 970.214 - Federal lands congestion management system (CMS).

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... LANDS HIGHWAYS NATIONAL PARK SERVICE MANAGEMENT SYSTEMS National Park Service Management Systems § 970...: (i) Identify and document measures for congestion (e.g., level of service); (ii) Identify the...

  17. Bifurcation and stability of an improved time-delayed fluid flow model in internet congestion control

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Liang; Zhu, Jie; Luo, Xiao-Shu

    2009-09-01

    Based on the fluid flow time-delayed model proposed by Misra et al in internet congestion control, one modified time-delayed model is presented, where the influence of the communication delay on the router queue length is investigated in detail. The main advantage of the new model is that its stability domain is larger even without an extra controller. By linear stability analysis and numerical simulation, the effectiveness and feasibility of the novel model in internet congestion control are verified.

  18. Gust alleviation system to improve ride comfort of light airplanes

    NASA Technical Reports Server (NTRS)

    Stewart, E. C.; Phillips, W. H.; Hewes, D. E.

    1975-01-01

    System consists of movable auxiliary aerodynamic sensors mounted on fuselage and connected to trailing-edge flaps by rigid mechanical linkages. System achieves alleviation by reducing lift-curve slope of airplane to such a small value that gust-induced angles of attack will result in small changes in lift.

  19. Ganokendra: An Innovative Model for Poverty Alleviation in Bangladesh

    ERIC Educational Resources Information Center

    Alam, Kazi Rafiqul

    2006-01-01

    Ganokendras (people's learning centers) employ a literacy-based approach to alleviating poverty in Bangladesh. They give special attention to empowering rural women, among whom poverty is widespread. The present study reviews the Ganokendra-approach to facilitating increased political and economic awareness and improving community conditions in…

  20. Training Teachers as Key Players in Poverty Alleviation

    ERIC Educational Resources Information Center

    Benavente, Ana; Ralambomanana, Stangeline; Mbanze, Jorge

    2008-01-01

    This article presents several questions, reflections and suggestions on pre-service and in-service teacher training that arose during the project "Curricular innovation and poverty alleviation in sub-Saharan Africa". While recognizing that the situation in the nine countries taking part in the project, and in many other countries in the southern…