Car-oriented mean-field theory for traffic flow models

We present a new analytical description of the cellular automaton model for single-lane traffic. In contrast to previous approaches we do not use the occupation number of sites as dynamical variable but rather the distance between consecutive cars. Therefore certain longer-ranged correlations are taken into account and even a mean-field approach yields non-trivial results. In fact for the model with $v_{max}=1$ the exact solution is reproduced. For $v_{max}=2$ the fundamental diagram shows a good agreement with results from simulations.Comment: LaTex, 10 pages, 2 postscript figure

Hysteresis phenomenon in deterministic traffic flows

We study phase transitions of a system of particles on the one-dimensional integer lattice moving with constant acceleration, with a collision law respecting slower particles. This simple deterministic ``particle-hopping'' traffic flow model being a straightforward generalization to the well known Nagel-Schreckenberg model covers also a more recent slow-to-start model as a special case. The model has two distinct ergodic (unmixed) phases with two critical values. When traffic density is below the lowest critical value, the steady state of the model corresponds to the ``free-flowing'' (or ``gaseous'') phase. When the density exceeds the second critical value the model produces large, persistent, well-defined traffic jams, which correspond to the ``jammed'' (or ``liquid'') phase. Between the two critical values each of these phases may take place, which can be interpreted as an ``overcooled gas'' phase when a small perturbation can change drastically gas into liquid. Mathematical analysis is accomplished in part by the exact derivation of the life-time of individual traffic jams for a given configuration of particles.Comment: 22 pages, 6 figures, corrected and improved version, to appear in the Journal of Statistical Physic

Affective Experience, Desire, and Reasons for Action

What is the role of affective experience in explaining how our desires provide us with reasons for action? When we desire that p, we are thereby disposed to feel attracted to the prospect that p, or to feel averse to the prospect that not-p. In this paper, we argue that affective experiences – including feelings of attraction and aversion – provide us with reasons for action in virtue of their phenomenal character. Moreover, we argue that desires provide us with reasons for action only insofar as they are dispositions to have affective experiences. On this account, affective experience has a central role to play in explaining how desires provide reasons for action

A Model for the Propagation of Sound in Granular Materials

This paper presents a simple ball-and-spring model for the propagation of small amplitude vibrations in a granular material. In this model, the positional disorder in the sample is ignored and the particles are placed on the vertices of a square lattice. The inter-particle forces are modeled as linear springs, with the only disorder in the system coming from a random distribution of spring constants. Despite its apparent simplicity, this model is able to reproduce the complex frequency response seen in measurements of sound propagation in a granular system. In order to understand this behavior, the role of the resonance modes of the system is investigated. Finally, this simple model is generalized to include relaxation behavior in the force network -- a behavior which is also seen in real granular materials. This model gives quantitative agreement with experimental observations of relaxation.Comment: 21 pages, requires Harvard macros (9/91), 12 postscript figures not included, HLRZ preprint 6/93, (replacement has proper references included

Cellular Automata Simulating Experimental Properties of Traffic Flows

A model for 1D traffic flow is developed, which is discrete in space and time. Like the cellular automaton model by Nagel and Schreckenberg [J. Phys. I France 2, 2221 (1992)], it is simple, fast, and can describe stop-and-go traffic. Due to its relation to the optimal velocity model by Bando et al. [Phys. Rev. E 51, 1035 (1995)], its instability mechanism is of deterministic nature. The model can be easily calibrated to empirical data and displays the experimental features of traffic data recently reported by Kerner and Rehborn [Phys. Rev. E 53, R1297 (1996)].Comment: For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.html and http://traffic.comphys.uni-duisburg.de/member/home_schreck.htm

Создание износостойкого покрытия с использованием непрерывного и импульсного электронного луча

В настоящей работе представлены результаты исследования влияния импульсной электронной обработки и последующего отжига на структуру и твердость покрытий из хромо-ванадиевого чугуна. Покрытия были получены методом электронно-лучевой наплавки на подложке из малоуглеродистой стали. После шлифования поверхности покрытий были обработаны локальноимпульсным сфокусированным в точку электронным пучком. Результаты исследования показали, что модифицированные зоны состоят из двух фаз. Первая фаза - пересыщенный аустенит. Вторая локально распределенные в объеме модифицированной зоны зародыши эвтектики. Результаты измерений системой NanoTest показали, что модифицированные зоны имеют низкие значения твердости. Низкие значения твердости, вероятно, обусловлено наличием значительного объема пересыщенного аустенита в модифицированной зоне. Отжиг приводит к значительному увеличению твердости модифицированных зон. В результате отжига (500°С ) пересыщенный аустенит распадается. Повышение температуры отжига до 1100°С приводит к росту и коагуляции карбидной фазы модифицированных зон