This paper is organized as follows. Part A presents the context of reconfiguring transitic systems and the main idea in implementing the decision step. It comprises sections 1 to 3. Section 3 presents an example that ...
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This paper is organized as follows. Part A presents the context of reconfiguring transitic systems and the main idea in implementing the decision step. It comprises sections 1 to 3. Section 3 presents an example that illustrates the concepts presented in the next sections. Parts B and C express the models and principles used to simulate transitic systems, the result of which will be helpful for choosing the new configuration. Part B focuses mainly on models. It comprises sections 4 to 6. Part C focuses mainly on simulation principles. It comprises sections 7 to 10.
Development of user-friendly and flexible scientific programs is a key to their usage, extension and maintenance. This article presents an object-oriented programming approach for the development of FER/Mech-a softwar...
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Development of user-friendly and flexible scientific programs is a key to their usage, extension and maintenance. This article presents an object-oriented programming approach for the development of FER/Mech-a software with interactive graphics for use in the design and analysis of two and three dimensional multibody dynamic systems. The general organization of the developed software system is given which includes the solver and the pre/postprocessors with a friendly Graphical User interfaces. The concept of absolute natural coordinates is discussed to model rigid bodies in order to satisfy the constraints of modularity. Two case studies with graphical representations illustrate some functionalities of the program. (C) 2003 Elsevier Ltd. All rights reserved.
During the last 50 years, the development of better numerical methods and more powerful computers has been a major enterprise for the scientific community. In the same time, the finite element method has become a wide...
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During the last 50 years, the development of better numerical methods and more powerful computers has been a major enterprise for the scientific community. In the same time, the finite element method has become a widely used tool for researchers and engineers. Recent advances in computational software have made possible to solve more physical and complex problems such as coupled problems, nonlinearities, high strain and high-strain rate problems. In this field, an accurate analysis of large deformation inelastic problems occurring in metal-forming or impact simulations is extremely important as a consequence of high amount of plastic flow. In this presentation, the object-oriented implementation, using the C++ language, of an explicit finite element code called DynELA is presented. The object-oriented programming (OOP) leads to better-structured codes for the finite element method and facilitates the development, the maintainability and the expandability of such codes. The most significant advantage of COP is in the modeling of complex physical systems such as deformation processing where the overall complex problem is partitioned in individual sub-problems based on physical, mathematical or geometric reasoning. We first focus on the advantages of OOP for the development of scientific programs. Specific aspects of OOP, such as the inheritance mechanism, the operators overload procedure or the use of template classes are detailed. Then we present the approach used for the development of our finite element code through the presentation of the kinematics, conservative and constitutive laws and their respective implementation in C++. Finally, the efficiency and accuracy of our finite element program are investigated using a number of benchmark tests relative to metal forming and impact simulations. (C) 2003 Elsevier B.V. All rights reserved.
Interruptions to supply and sags of distribution system voltage are the main aspects causing customer complaints. There is a need for analysis of supply reliability and voltage sag to relate system performance with ne...
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Interruptions to supply and sags of distribution system voltage are the main aspects causing customer complaints. There is a need for analysis of supply reliability and voltage sag to relate system performance with network structure and equipment design parameters. This analysis can also give prediction of voltage dips, as well as relating traditional reliability and momentary outage measures to the properties of protection systems and to network impedances. Existing reliability analysis software, often requires substantial training, lacks automated facilities, and suffers from data availability. Thus it requires time-consuming manual intervention for the study of large networks. A user-friendly sag and reliability assessment tool (SRAT) has been developed based on existing impedance data, protection characteristics, and a model of failure probability. The new features included in SRAT are a) efficient reliability and sag assessments for a radial network with limited loops, b) reliability evaluation associated with realistic protection and restoration schemes, c) inclusion of momentary outages in the same model as permanent outage evaluation, d) evaluation of the sag transfer through meshed subtransmission network, and e) simplified probability distribution model determined from available faults records. Examples of the application of the tools to an Australian distribution network are used to illustrate the application of this model.
In this paper, we consider non-isothermal two-phase flow of two components (air and water) in gaseous and liquid phases in extremely low-permeable porous media through the use of the finite element method (FEM). Inter...
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In this paper, we consider non-isothermal two-phase flow of two components (air and water) in gaseous and liquid phases in extremely low-permeable porous media through the use of the finite element method (FEM). Interphase mass transfer of the components between any of the phases is evaluated by assuming local thermodynamic equilibrium between the phases. Heat transfer occurs by conduction and multiphase advection. General equations of state for phase changes (Clausius-Clapeyron and Henry law) as well as multiphase properties for the low-permeable bentonites are implemented in the code. Additionally we consider the impact of swelling/shrinking processes on porosity and permeability changes. The numerical model is implemented in the context of the simulator RockFlow/RockMech (RF/RM), which is based on object-oriented programming techniques. The finite element formulations are written in terms of dimensionless quantities. This has proved to be advantageous for preconditioning composite system matrices of coupled multi-field problems. Three application examples are presented. The first one examines differences between the Richards' approximation and the multicomponent/multiphase approach, and between two numerical coupling schemes. The second example serves as partial verification against experimental results and to demonstrate coherence between different element types. The last example shows simultaneous desaturation and resaturation in one system.
The use of object-oriented programming in software development allows software systems to be more robust and more maintainable. At the same time, the development time and expense are also reduced. To achieve these ben...
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The use of object-oriented programming in software development allows software systems to be more robust and more maintainable. At the same time, the development time and expense are also reduced. To achieve these benefits, object-oriented applications use dynamic memory management (DMM) to create generic objects that can be reused. Consequently, these applications are often highly dynamic memory intensive. For the last three decades, several DMM schemes have been proposed. Such schemes include first fit, best fit, segregated fit, and buddy systems. Because the performance (e.g., speed, memory utilization, etc.) of each scheme differs, it becomes a difficult choice in selecting the most suitable approach for an application and what parameters (e.g., block size, etc.) should be adopted. In this paper, a DMM simulation tool and its usage are presented. This tool receives DMM traces of C/C++ or Java programs and performs simulation according to the scheme (first fit, best fit, buddy system, and segregated fit) defined by the user. Techniques required to obtain memory traces are presented. At the end of each simulation run, a variety of performance metrics are reported to the users. By using this tool, software engineers can evaluate system performance and decide which algorithm is the most suitable. Moreover, hardware engineers can perform a system analysis before hardware (e.g., modified buddy system, first fit, etc.) is fabricated. (C) 2003 Elsevier Inc. All rights reserved.
A fundamental question in object-oriented design is how to design maintainable software. According to expert opinion, a delegated control style, typically a result of responsibility-driven design, represents object-or...
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A fundamental question in object-oriented design is how to design maintainable software. According to expert opinion, a delegated control style, typically a result of responsibility-driven design, represents object-oriented design at its best, whereas a centralized control style is reminiscent of a procedural solution, or a "bad" object-oriented design. This paper presents a controlled experiment that investigates these claims empirically. A total of 99 junior, intermediate, and senior professional consultants from several international consultancy companies were hired for one day to participate in the experiment. To compare differences between (categories of) professionals and students, 59 students also participated. The subjects used professional Java tools to perform several change tasks on two alternative Java designs that had a centralized and delegated control style, respectively. The results show that the most skilled developers, in particular, the senior consultants, require less time to maintain software with a delegated control style than with a centralized control style. However, more novice developers, in particular, the undergraduate students and junior consultants, have serious problems understanding a delegated control style, and perform far better with a centralized control style. Thus, the maintainability of object-oriented software depends, to a large extent, on the skill of the developers who are going to maintain it. These results may have serious implications for object-oriented development in an industrial context: Having senior consultants design object-oriented systems may eventually pose difficulties unless they make an effort to keep the designs simple, as the cognitive complexity of "expert" designs might be unmanageable for less skilled maintainers.
In real-time simulation, the simulated system should display the same (or very close) timing behavior as the target system. The simulation accuracy is increased as the simulation time unit is decreased. Although there...
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In real-time simulation, the simulated system should display the same (or very close) timing behavior as the target system. The simulation accuracy is increased as the simulation time unit is decreased. Although there are several models for such systems, the TMO model is particularly appropriate due to its natural support for real-time distributed object-oriented programming. This paper discusses the results of the implementation of a real-time airplane-landing simulator on a distributed computing environment using the TMO model. Copyright (C) 2004 John Wiley Sons, Ltd.
This paper shows that one can reason at a meta level about the structure of object-oriented source code in a language-independent way. To achieve this, we propose a language-independent meta-level interface to extract...
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This paper shows that one can reason at a meta level about the structure of object-oriented source code in a language-independent way. To achieve this, we propose a language-independent meta-level interface to extract complex information about the structure of the source code. This approach is validated by defining a set of logic queries to detect object-oriented best practice patterns and design patterns in two different languages: Smalltalk and Java. The queries were applied to two similar medium-sized applications available for each language, and the results were confirmed by manually investigating the source code and available documentation. (C) 2003 Elsevier Ltd. All rights reserved.
A new software system called PHENIX (Python-based Hierarchical ENvironment for Integrated Xtallography) is being developed for the automation of crystallographic structure solution. This will provide the necessary alg...
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A new software system called PHENIX (Python-based Hierarchical ENvironment for Integrated Xtallography) is being developed for the automation of crystallographic structure solution. This will provide the necessary algorithms to proceed from reduced intensity data to a refined molecular model, and facilitate structure solution for both the novice and expert crystallographer. Here we review the features of PHENIX and briefly describe the recent advances in infrastructure and algorithms.
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