Experiences with a simplified microsimulation for the Dallas/Fort Worth area

We describe a simple framework for micro simulation of city traffic. A medium sized excerpt of Dallas was used to examine different levels of simulation fidelity of a cellular automaton method for the traffic flow simulation and a simple intersection model. We point out problems arising with the granular structure of the underlying rules of motion.Comment: accepted by Int.J.Mod.Phys.C, 20 pages, 14 figure

A Cellular Automaton Model for Bi-Directionnal Traffic

We investigate a cellular automaton (CA) model of traffic on a bi-directional two-lane road. Our model is an extension of the one-lane CA model of {Nagel and Schreckenberg 1992}, modified to account for interactions mediated by passing, and for a distribution of vehicle speeds. We chose values for the various parameters to approximate the behavior of real traffic. The density-flow diagram for the bi-directional model is compared to that of a one-lane model, showing the interaction of the two lanes. Results were also compared to experimental data, showing close agreement. This model helps bridge the gap between simplified cellular automata models and the complexity of real-world traffic.Comment: 4 pages 6 figures. Accepted Phys Rev

Two Lane Traffic Simulations using Cellular Automata

We examine a simple two lane cellular automaton based upon the single lane CA introduced by Nagel and Schreckenberg. We point out important parameters defining the shape of the fundamental diagram. Moreover we investigate the importance of stochastic elements with respect to real life traffic.Comment: to be published in Physica A, 19 pages, 9 out of 13 postscript figures, 24kB in format .tar.gz., 33kB in format .tar.gz.uu, for a full version including all figures see http://studguppy.tsasa.lanl.gov/research_team/papers

Fuzzy cellular model for on-line traffic simulation

This paper introduces a fuzzy cellular model of road traffic that was intended for on-line applications in traffic control. The presented model uses fuzzy sets theory to deal with uncertainty of both input data and simulation results. Vehicles are modelled individually, thus various classes of them can be taken into consideration. In the proposed approach, all parameters of vehicles are described by means of fuzzy numbers. The model was implemented in a simulation of vehicles queue discharge process. Changes of the queue length were analysed in this experiment and compared to the results of NaSch cellular automata model.Comment: The original publication is available at http://www.springerlink.co

Adolescent Relationship Violence: Help-Seeking and Help-Giving Behaviors among Peers

Young people tend to disclose relationship violence experiences to their peers, if they disclose at all, yet little is known about the nature and frequency of adolescent help-seeking and help-giving behaviors. Conducted within a sample of 1,312 young people from four New York City high schools, this is the first paper to ask adolescent help-givers about the various forms of help they provide and among the first to examine how ethnicity and nativity impact help-seeking behaviors. Relationship violence victims who had ever disclosed (61 %) were more likely to choose their friends for informal support. Ethnicity was predictive of adolescent disclosure outlets, whereas gender and nativity were not. Latinos were significantly less likely than non-Latinos to ever disclose to only friends, as compared to disclosing to at least one adult. The likelihood of a young person giving help to their friend in a violent relationship is associated with gender, ethnicity, and nativity, with males being significantly less likely than females to give all forms of help to their friends (talking to their friends about the violence, suggesting options, and taking action). Foreign-born adolescents are less likely to talk or suggest options to friends in violent relationships. This study also found that Latinos were significantly more likely than non-Latinos to report taking action with or on behalf of a friend in a violent relationship. This research shows that adolescents often rely on each other to address relationship violence, underlining the importance of adolescents’ receipt of training and education on how to support their friends, including when to seek help from more formal services. To further understand the valuable role played by adolescent peers of victims, future research should explore both which forms of help are perceived by the victim to be most helpful and which are associated with more positive outcomes

A realistic two-lane traffic model for highway traffic

A two-lane extension of a recently proposed cellular automaton model for traffic flow is discussed. The analysis focuses on the reproduction of the lane usage inversion and the density dependence of the number of lane changes. It is shown that the single-lane dynamics can be extended to the two-lane case without changing the basic properties of the model which are known to be in good agreement with empirical single-vehicle data. Therefore it is possible to reproduce various empirically observed two-lane phenomena, like the synchronization of the lanes, without fine-tuning of the model parameters

X-ray photoemission spectroscopic investigation of surface treatments, metal deposition, and electron accumulation on InN

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A Systems Approach to Developing a Model that Predicts Crop Ontogeny and Maturity in Broccoli in South-East Queensland

Farmers need a well planned crop scheduling program to maintain a regular supply of broccoli (Brassica oleracea L. var. italica Plenck) to domestic and export markets which extend from May to September for crops in south-east Queensland. However, irregular production, due to variable temperatures, is a constraint in the production and distribution systems for broccoli. Variable temperatures influence the rate of crop development, time of harvest and crop quality, thereby impacting on marketing commitments which specify the amount, quality and date of supply. Thus, prediction of crop ontogeny is important for crop scheduling and maintaining continuity of supply of broccoli. Two methods are being used to develop a model of phenological development in broccoli. The first method uses a time of sowing experiment which records crop ontogeny for wide range of cultivars and climatic conditions. This method provides a high level of precision in determination of phenological events but has potential problem such as the difficulty of extrapolation from a small scale experiment to commercial crops. The second method uses historical records from a broccoli farm which reflect crop phenological development under commercial practice over a period of three years. This method has the advantage of using a number of crop performance records obtained from a range of prevailing climates but lacks the precision of the first method. Once both models exist, they can be separately validated against the data used to develop the other model. Furthermore, the ongoing year-by-year expansion in farm records represents new validation data for either model. Our three-step approach should lead to a more robust and credible model for predicting crop ontogeny in broccoli and it could also be applicable to other crops

Stability constants of europium complexes with a nitrogen heterocycle substituted methane-1,1-diphosphonic acid

Even in moderately acidic solutions ([H{sup +}] > 0.01 M), N-piperidinomethane-1,1-diphosphonic acid (H{sub 4}PMDPA) is a strong complexant of trivalent lanthanide ions that shows enhanced complex solubility over previously studied 1,1-diphosphonic acids. The protonation constants of PMDPA in 2.0 M H/NaClO{sub 4} were determined by potentiometric and NMR titrations, and the stability constants for formation of complexes with Eu{sup 3+} were determined by solvent extraction. Difference in protonation equilibria induced by addition of the nitrogen heterocycle results in an increase in the complexation strength of PMDPA. In solutions containing 0.1 M H{sup +} and ligand concentrations greater than 0.02 M, PMDPA is the most effective 1,1-diphosphonic acid for europium complexation studied thus far

Coherent Moving States in Highway Traffic (Originally: Moving Like a Solid Block)

Recent advances in multiagent simulations have made possible the study of realistic traffic patterns and allow to test theories based on driver behaviour. Such simulations also display various empirical features of traffic flows, and are used to design traffic controls that maximise the throughput of vehicles in heavily transited highways. In addition to its intrinsic economic value, vehicular traffic is of interest because it may throw light on some social phenomena where diverse individuals competitively try to maximise their own utilities under certain constraints. In this paper, we present simulation results that point to the existence of cooperative, coherent states arising from competitive interactions that lead to a new phenomenon in heterogeneous highway traffic. As the density of vehicles increases, their interactions cause a transition into a highly correlated state in which all vehicles practically move with the same speed, analogous to the motion of a solid block. This state is associated with a reduced lane changing rate and a safe, high and stable flow. It disappears as the vehicle density exceeds a critical value. The effect is observed in recent evaluations of Dutch traffic data.Comment: Submitted on April 21, 1998. For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.html and http://www.parc.xerox.com/dynamics