Thermally activated interface motion in a disordered ferromagnet

We investigate interface motion in disordered ferromagnets by means of Monte Carlo simulations. For small temperatures and driving fields a so-called creep regime is found and the interface velocity obeys an Arrhenius law. We analyze the corresponding energy barrier as well as the field and temperature dependence of the prefactor.Comment: accepted for publication in Computer Physics Communication

Interface Motion in Disordered Ferromagnets

We consider numerically the depinning transition in the random-field Ising model. Our analysis reveals that the three and four dimensional model displays a simple scaling behavior whereas the five dimensional scaling behavior is affected by logarithmic corrections. This suggests that d=5 is the upper critical dimension of the depinning transition in the random-field Ising model. Furthermore, we investigate the so-called creep regime (small driving fields and temperatures) where the interface velocity is given by an Arrhenius law.Comment: some misprints correcte

Creep motion in a random-field Ising model

We analyze numerically a moving interface in the random-field Ising model which is driven by a magnetic field. Without thermal fluctuations the system displays a depinning phase transition, i.e., the interface is pinned below a certain critical value of the driving field. For finite temperatures the interface moves even for driving fields below the critical value. In this so-called creep regime the dependence of the interface velocity on the temperature is expected to obey an Arrhenius law. We investigate the details of this Arrhenius behavior in two and three dimensions and compare our results with predictions obtained from renormalization group approaches.Comment: 6 pages, 11 figures, accepted for publication in Phys. Rev.

Monte Carlo Dynamics of driven Flux Lines in Disordered Media

We show that the common local Monte Carlo rules used to simulate the motion of driven flux lines in disordered media cannot capture the interplay between elasticity and disorder which lies at the heart of these systems. We therefore discuss a class of generalized Monte Carlo algorithms where an arbitrary number of line elements may move at the same time. We prove that all these dynamical rules have the same value of the critical force and possess phase spaces made up of a single ergodic component. A variant Monte Carlo algorithm allows to compute the critical force of a sample in a single pass through the system. We establish dynamical scaling properties and obtain precise values for the critical force, which is finite even for an unbounded distribution of the disorder. Extensions to higher dimensions are outlined.Comment: 4 pages, 3 figure

The depinning transition of a driven interface in the random-field Ising model around the upper critical dimension

We investigate the depinning transition for driven interfaces in the random-field Ising model for various dimensions. We consider the order parameter as a function of the control parameter (driving field) and examine the effect of thermal fluctuations. Although thermal fluctuations drive the system away from criticality the order parameter obeys a certain scaling law for sufficiently low temperatures and the corresponding exponents are determined. Our results suggest that the so-called upper critical dimension of the depinning transition is five and that the systems belongs to the universality class of the quenched Edward-Wilkinson equation.Comment: accepted for publication in Phys. Rev.

Breakdown and recovery in traffic flow models

Most car-following models show a transition from laminar to ``congested'' flow and vice versa. Deterministic models often have a density range where a disturbance needs a sufficiently large critical amplitude to move the flow from the laminar into the congested phase. In stochastic models, it may be assumed that the size of this amplitude gets translated into a waiting time, i.e.\ until fluctuations sufficiently add up to trigger the transition. A recently introduced model of traffic flow however does not show this behavior: in the density regime where the jam solution co-exists with the high-flow state, the intrinsic stochasticity of the model is not sufficient to cause a transition into the jammed regime, at least not within relevant time scales. In addition, models can be differentiated by the stability of the outflow interface. We demonstrate that this additional criterion is not related to the stability of the flow. The combination of these criteria makes it possible to characterize commonalities and differences between many existing models for traffic in a new way

Depinning transition and thermal fluctuations in the random-field Ising model

We analyze the depinning transition of a driven interface in the 3d random-field Ising model (RFIM) with quenched disorder by means of Monte Carlo simulations. The interface initially built into the system is perpendicular to the [111]-direction of a simple cubic lattice. We introduce an algorithm which is capable of simulating such an interface independent of the considered dimension and time scale. This algorithm is applied to the 3d-RFIM to study both the depinning transition and the influence of thermal fluctuations on this transition. It turns out that in the RFIM characteristics of the depinning transition depend crucially on the existence of overhangs. Our analysis yields critical exponents of the interface velocity, the correlation length, and the thermal rounding of the transition. We find numerical evidence for a scaling relation for these exponents and the dimension d of the system.Comment: 6 pages, including 9 figures, submitted for publicatio

Аудит промышленной безопасности предприятия

В данное время, когда фактически нет города, где бы не работали предприятия, особый смысл имеет промышленная безопасность. С каждым годом увеличивается количество опасных объектов. Исходя из этого, проблема с безопасностью возведена в ранг основных ценностей на государственном уровне. Часто в промышленно развитых странах установлен жесткий контроль лицензирования ОПО, строительства, эксплуатации и т.д. Безопасность сооружений в этих странах контролируется государственными органами. Промышленная безопасность опасных объектов - это определенная защита общества и страны от различных техногенных катастроф и аварий. Для того, чтобы обеспечить безопасность, проводится комплекс мероприятий, которые ориентированы, прежде всего, на обеспечение безопасности технических объектов. Все организации, которые эксплуатируют опасный производственный объект, должны временами производить вышесказанные мероприятия. Это указано в Федеральном законе «О промышленной безопасности опасных производственных объектов» Цель работы: проверка соответствия установленным требованиям ПБ, подготовка рекомендаций по устранению выявленных нарушений в УНДиПР МЧС России по Томской области.At the moment, when there is virtually no city, where enterprises would not work, industrial safety has a special meaning. Every year the number of dangerous objects increases. Proceeding from this, the security problem is elevated to the rank of basic values at the state level. Often in industrialized countries, strict control of GCO licensing, construction, operation, etc. is established. The safety of facilities in these countries is controlled by government agencies.Industrial safety of hazardous facilities is a certain protection of society and the country from various man-made disasters and accidents. In order to ensure safety, a set of measures is carried out, which are focused, first of all, on ensuring the safety of technical facilities. All organizations that operate a hazardous production facility must at times produce the aforesaid activities. This is indicated in the Federal Law "On Industrial Safety of Hazardous Production Facilities" The purpose of the work: verification of compliance with the established requirements of the PB, the preparation of recommendations for the elimination of identified violations in the UNDiPR of EMERCOM of Russia for the Tomsk region