The paper presents an overview of various modeling paradigms applicable to the analysis of complex decisionmaking problems that can be represented by large non-linear models. Such paradigms are illustrated by their ap...
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The paper presents an overview of various modeling paradigms applicable to the analysis of complex decisionmaking problems that can be represented by large non-linear models. Such paradigms are illustrated by their application to the analysis of a model that helps to identify and analyze various cost-effective policy options aimed at improving European air quality. Also presented is the application of this model to support intergovernmental negotiations. (C) 2000 Elsevier Science B.V. All rights reserved.
The association of object-oriented programming and symbolic computation techniques introduces certain changes in finite element code organization. The purpose of this approach is to speed up the design of new formulat...
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The association of object-oriented programming and symbolic computation techniques introduces certain changes in finite element code organization. The purpose of this approach is to speed up the design of new formulations. Previous papers have described the basic concepts of the method. In this paper, the focus is placed on functional aspects of symbolic tools for the development of finite element formulations. Two practical examples are used to illustrate this point. The first is a space-time formulation for an incompressible flow driven by the Navier-Stokes equations, and the second is a finite element derivation of the total potential energy for linear elasticity. (C) 2000 Elsevier Science B.V. All rights reserved.
We all know that the web is a fantastic resource of information that can help us, but we also know that information is often hard to find. Website Wanderer is a column where we have invited an active researcher or dev...
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We all know that the web is a fantastic resource of information that can help us, but we also know that information is often hard to find. Website Wanderer is a column where we have invited an active researcher or developer in some area to share their knowledge of which websites are worth visiting. In this issue, we focus on patterns-encapsulations of knowledge that can be reused in some way when developing software.
Computer-aided management of surface-water quality has been a field of continuous progress in the last decades. object-orientation offers the potential for the development of efficient software tools, capable of deali...
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Computer-aided management of surface-water quality has been a field of continuous progress in the last decades. object-orientation offers the potential for the development of efficient software tools, capable of dealing with the complexity of water resources and their policy making. In the present work an object-oriented approach has been developed for the analysis of point-source pollution control in river basins. The physical entities of the river basin and the conceptual entities of its water-quality simulation and control have been represented through objects. With the appropriate distribution of responsibilities among these objects and the specification of their collaborations, the assessment and simulation of river water quality can be performed. Alternative strategies of point-source pollution control can be also evaluated, and an optimised control scheme can be suggested. The above analysis has been implemented in the design and development of an easily extended and flexible software tool, using the object-oriented language Smalltalk Express. The tool has been successfully validated through the studies of the South Nation River Catchment in Canada and the Upper Mersey River Catchment in the United Kingdom. In this work the architecture of the software tool is outlined and the employed mathematical analysis along with the results of the case studies are presented. (C) 1999 Elsevier Science Ltd. All rights reserved.
A computer program of a forward reaching algorithm of dynamic programming is presented for optimal log bucking. The application is implemented using an object-oriented programming approach. Sensitivity analyses were a...
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A computer program of a forward reaching algorithm of dynamic programming is presented for optimal log bucking. The application is implemented using an object-oriented programming approach. Sensitivity analyses were applied for evaluating the effects in terms of economic value and usable volume, and of altering the price system for saw wood. The data used consisted of 451 Norway spruce (Picea abies (L.) Karst.) stems collected from 13 forest sites located in three regions in Norway. Grade I and Grade II saw wood and pulpwood were used. The mean timber value increased approximately 1% when the new price system was introduced. The value obtained by introducing the new prices varied between the sites (0.1%-1.6%) as well as between regions (0.3%-1.6%). The analyses based on taper equations over-estimated the total value for all the alternatives. Finally. decreasing the width of stem sections and increasing the number of log length alternatives increased the total value of the sample trees but increased the computation time.
In this paper we examine the structure of Maxwell equations in order to find clear signposts how to implement finite element software systems. The aim is to recognize the abstractions involved in Maxwell equations and...
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In this paper we examine the structure of Maxwell equations in order to find clear signposts how to implement finite element software systems. The aim is to recognize the abstractions involved in Maxwell equations and to exploit concepts of modern programming techniques, such as object-oriented design, to imitate the abstractions in numerical computing. As mathematics is the machinery to model physical phenomena, it is worth to imitate the same machinery in a software system. If a software system is constructed this way, it is partitioned into distinct components whose function is evident. And that is a basis for a software system that is modifiable and understandable, which are the main goals in software design.
Statistical environments such as S, R, XLisp-Stat, and others have had a dramatic effect on the way we, statistics practitioners, think about data and statistical methodology. However, the possibilities and challenges...
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Statistical environments such as S, R, XLisp-Stat, and others have had a dramatic effect on the way we, statistics practitioners, think about data and statistical methodology. However, the possibilities and challenges introduced by recent technological developments and the general ways we use computing conflict with the computational model of these systems. This article explores some of these challenges and identifies the need to support easy integration of functionality from other domains, and to export statistical methodology to other audiences and applications, both statically and dynamically. Existing systems can be improved in these domains with some already implemented extensions (see Section 5). However, the development of a new environment and computational model that exploits modern tools designed to handle many general aspects of these challenges appears more promising as a long-term approach. We present the architecture for such a new model named Omegahat. It lends itself to entirely new statistical computing paradigms. It is highly extensible at both the user and programmer level, and also encourages the development of new environments for different user groups. The Omegahat interactive language offers a continuity between the different programming tasks and levels via optional type checking and seamless access between the interpreted user language and the implementation language, Java. Parallel and distributed computing, network and database access, interactive graphics, and many other aspects of statistical computing are directly accessible to the user as a consequence of this seamless access. We describe the benefits of using Java as the implementation language for the environment and several innovative features of the user-level language which promise to assist development of software that can be used in many contexts. We also outline how this architecture can be integrated with existing environments such as R and S. The ideas are drawn from work wit
For plasma simulations, we developed a one-dimensional (1d) object-oriented Particle-in-Cell code for X11-based Unix workstations (XOOPIC) by modifying the current two-dimensional version which was originally develope...
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For plasma simulations, we developed a one-dimensional (1d) object-oriented Particle-in-Cell code for X11-based Unix workstations (XOOPIC) by modifying the current two-dimensional version which was originally developed by PTSG (Plasma theory and simulation group) in the University of California at Berkeley. We implemented a simplified field solve and current deposition in the code. We retained three components of particle velocity, although the spatial variation for particle position and field components is limited to one dimension. To verify the function of the Id code, we perform simulations with typical models such as the Child-Langmuir current model and electromagnetic wave propagation in plasma. In both cases, the simulation results quantitatively agree with the theory.
This paper presents a new object-oriented design of software for finite element calculations. Special attention is given to coupled problems with nonlinear materials. Fundamental ideas of object-oriented design, espec...
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This paper presents a new object-oriented design of software for finite element calculations. Special attention is given to coupled problems with nonlinear materials. Fundamental ideas of object-oriented design, especially high cohesion, low coupling and encapsulation of classes, are strictly taken into account. The concept is guided by the idea to reuse as many parts as possible, The hierachy of classes for the elements, materials and held problems can be extended easily by specialization.
Statistical software provides essential support for statisticians and others who are analyzing data or doing research on new statistical techniques. Those supported typically regard themselves as "users" of ...
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Statistical software provides essential support for statisticians and others who are analyzing data or doing research on new statistical techniques. Those supported typically regard themselves as "users" of the software, but as soon as they need to express their own ideas computationally, they in fact become "programmers." Nothing is more important for the success of statistical software than enabling this transition from user to programmer, and on to gradually more ambitious software design. What does the user need? How can the design of statistical software help? This article presents a number of suggestions based on past experience and current research. The evolution of the S system reflects some of these opinions. Work on the Omegahat software provides a promising direction for future systems that reflect similar motivations.
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