Strategic appraisal of energy models for Mozambique

The needs that an energy supply system must meet are constantly changing, due to technological, social and political reasons. Effective energy planning is a dynamic process that is repeated periodically and adjusts to changing conditions. Energy decision makers and planners are no longer able to rely on inductive decision making since they have to investigate the effect of various decision parameters and possible future changes. To help in this process, models have been developed where estimates of future load growth, candidate power plants, fuels and other key factors can be introduced, from which the planners can evaluate decision parameters and the available alternatives. The paper presents the different methodologies and practices that are used by 11 energy models for energy demand forecasting, supply side management and generation expansion planning, demand side management and integrated resource planning. The paper concludes to the presentation of a strategic appraisal of the examined energy models appropriate for energy planning in Mozambique. Three models are proposed for conducting demand forecasting, generation expansion planning and demand side management. Copyright © 2002 John Wiley & Sons, Ltd.     

Economic Model to Optimize Underground Utility Protection

The need for better protecting our vital infrastructure from being damaged or destroyed has received increased attention since the terrorist attacks on September 11, 2001. The tragedy of having thousands of innocent people die before the eyes of an entire nation awakened people to the reality of “managed” attacks of unthinkable magnitudes. However, tragedies of a smaller scale are a daily occurrence but accepted as “collateral damage” of work in an unsafe environment. This paper presents a cost-benefit analysis to address the question of how much money should be spent in protecting underground utilities from damage. During the study of an actual incident it was found that the total costs of such accidents are vastly underreported because only costs for emergency responses and repair are tallied up. This paper makes the case that a comprehensive approach for assessing the total economic impact of such incidents on the public, business, and government is the critical stepping stone to a mathematical optimization of expenditure for damage prevention. In addition, the reader will quickly realize that the use of the presented optimization model provides theoretical underpinning for the engineering profession in its effort to better protect our critical infrastructure from terrorist attacks.     

Efficient and accurate approach for powder compaction problems

 In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour; the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian (ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present spurious oscillations. Received: 20 March 2002 / Accepted: 15 October 2002 The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged.     

生产装置在线模拟与优化技术的应用

概述了以通用软件为基础开发化工生产装置严格在线模拟与优化系统的过程，介绍了在线模型的５个层次及其特点，以合成氨为例说明了在线模型的运行和应用情况。     

Wiener models of direction-dependent dynamic systems

Analysis of systems with direction-dependent dynamics is currently limited to cases in which the dynamics in the two directions of the output are first order; results for such systems have been published for both pseudo-random maximum-length binary (MLB) and inverse-repeat maximum-length binary (IR-MLB) inputs. These relatively limited analytical results make it useful to examine alternative ways of modelling such systems and in this paper, Wiener models are considered for this purpose. Methods for optimising the Wiener model parameters by matching the system and model cross-correlation functions, outputs, and discrete Fourier transforms of the outputs are considered, and the results are compared. These methods are also applied to a first-order direction-dependent system with a maximum-length ternary (MLT) input, for which no analytical results are currently available, and to a second-order system with an IR-MLB input.     

Significance of fluid regime in biological filtration

A dispersed flow model previously developed to study substrate utilization in unsaturated media was experimentally verified and its practical application was considered. For this purpose, measurements were made using tap water and a synthetic feed solution. The importance of the change in fluid regime as regards to the simultaneous transport and reaction within biological filters were demonstrated. The effect of drop formation and the breakage of liquid jets inside the filters on substrate utilization was also shown.     

Probabilistic linear models for multiresolution estimation in gray-level images

A multiresolution analysis of digital gray-level images is presented. A gray-level multi-scale framework is determined from two main assumptions: the gray scale is binary at the finest spatial resolution, and the gray levels of composed regions are obtained additively. In order to interrelate the gray-level histograms of the same image at different resolutions, probabilistic linear models are developed, which are then applied for estimation. Linear-optimization theory is used as a way of constructing such models. A general procedure for image processing is sketched, based on gray-level estimation. A versatile algorithm for nonlinear filtering is derived. Some examples of prospective applications are given.This work was partially supported by grant TIC91-646 from the DGYCIT of the Spanish Government.     

New and used temporal models: An issue of time

TheSpecial Issue on Applications of Temporal Models raises many issues of time: What are the important properties of time? How can time be best represented? How can one reason about time-dependent properties? What are the important directions of temporal research? This introductory piece very briefly surveys the current wide variety of temporal models, temporal reasoning methods, and applications to time-varying phenomena. Promising areas of investigation such as the verification of concurrent systems, knowledge-base representation methods, and dealing with theFrame Problem pass in fleeting review. Brief introductions to each of the works in the volume close the section.     

Local Structure of Alkaline-Earth Boroaluminate Crystals and Glasses: II, 11B and 27Al MAS NMR Spectroscopy of Alkaline-Earth Boroaluminate Glasses

¹¹B and ²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra of alkaline-earth boroaluminate glasses show that the structure of these glasses are far more complicated than previously thought. The relative concentrations of 3- and 4-coordinated boron vary as found by previous investigators using continuous-wave NMR methods, but the ²⁷Al NMR spectra indicate the presence of Al in 4-, 5-, and 6-fold coordination, in contrast to previous assignments. Analysis of the data based on local charge balance considerations provides a qualitative model that correctly predicts compositional variations of the NMR peak intensities and ²⁷Al chemical shifts for a wide range of boroaluminate glass compositions.