Demagnetization via Nucleation of the Nonequilibrium Metastable Phase in a Model of Disorder

We study both analytically and numerically metastability and nucleation in a two-dimensional nonequilibrium Ising ferromagnet. Canonical equilibrium is dynamically impeded by a weak random perturbation which models homogeneous disorder of undetermined source. We present a simple theoretical description, in perfect agreement with Monte Carlo simulations, assuming that the decay of the nonequilibrium metastable state is due, as in equilibrium, to the competition between the surface and the bulk. This suggests one to accept a nonequilibrium "free-energy" at a mesoscopic/cluster level, and it ensues a nonequilibrium "surface tension" with some peculiar low-T behavior. We illustrate the occurrence of intriguing nonequilibrium phenomena, including: (i) Noise-enhanced stabilization of nonequilibrium metastable states; (ii) reentrance of the limit of metastability under strong nonequilibrium conditions; and (iii) resonant propagation of domain walls. The cooperative behavior of our system may also be understood in terms of a Langevin equation with additive and multiplicative noises. We also studied metastability in the case of open boundaries as it may correspond to a magnetic nanoparticle. We then observe burst-like relaxation at low T, triggered by the additional surface randomness, with scale-free avalanches which closely resemble the type of relaxation reported for many complex systems. We show that this results from the superposition of many demagnetization events, each with a well- defined scale which is determined by the curvature of the domain wall at which it originates. This is an example of (apparent) scale invariance in a nonequilibrium setting which is not to be associated with any familiar kind of criticality.Comment: 26 pages, 22 figure

Understanding the dynamics of electricity supply, resources and pollution: Pakistan's case

10.1016/S0360-5442(01)00019-6Energy266595-606ENEY

The Application Of A Hydro Electric Production Simulation Model

This paper presents different applications for a system dynamics simulation model representing the technical aspects of hydro electric production. The base model, developed for a Norwegian utility company, original was designed to improve understanding of a complex, technical system in a group of non technical decision makers. Experience showed that the applicability of the model was more substantial than expected. Based on the original core model a number of applications where developed meeting as different demands as decision aid for daily production planning, learning aid for new operators, evaluation of capacity expansion plans, inspection of system parameters and measurements quality and to assess the value of future production potential. The paper describes the core model and how this core were expanded and used in a number of different applications. The development as well as the use of the applications are discussed. The model structure can be easily adapted to represent other hydro electric production sites and to support other applications. We are presently in the process of adapting the model for a Colombian utility company to assist them in determining the company’s value

The strategic micro-firm: A role play in management training for dynamic businesses

Purpose – The purpose of this paper is to present the main characteristics of the role-playing game “Strategic Micro-Firm” which aims to reproduce the fundamental features of a complex supply chain. Design/methodology/approach – A specific role-playing game is presented, in which a Balanced Scorecard is used as the reporting device and is the main tool for analysing players’ performance. The research design and the typical outcomes of several gaming sessions are discussed. Findings – The paper illustrates the strengths of using this specific role-playing game as a means for training managers to face complex and dynamic issues, such as the supply chain. Research limitations/implications – Depending on the features of the specific game and the interaction taking place, different kinds and various degrees of learning and performance improvements can occur. Therefore, it is not possible to provide a generalization. Practical implications – The paper shows that gaming can play a relevant role in management training, providing free and safe environments in which players can face decision-making issues and problem-solving challenges. Originality/value – The paper demonstrates how a specific role-playing game maybe used in management education/training to incentivize improvements in problem-solving skills as well as in communication and coordination. Role playing could be used for support in designing supply chain management policies, providing a safe, simulated environment where managerial strategies may be explored and discussed before their implementation. The paper’s originality relates to the adoption of the Balanced Scorecard as the main reporting and performance assessment tool for the gaming experience