151,488 research outputs found

    An extension of Chebfun to two dimensions

    Get PDF
    An object-oriented MATLAB system is described that extends the capabilities of Chebfun to smooth functions of two variables defined on rectangles. Functions are approximated to essentially machine precision by using iterative Gaussian elimination with complete pivoting to form “chebfun2” objects representing low rank approximations. Operations such as integration, differentiation, function evaluation, and transforms are particularly efficient. Global optimization, the singular value decomposition, and rootfinding are also extended to chebfun2 objects. Numerical applications are presented

    Introduction to ABACUS - A branch-and-cut System

    Get PDF
    The software system ABACUS is an object-oriented framework for the implementation of branch-and-cut and branch-and-price algorithms. This paper shows the basics of its application to combinatorial and mixed integer optimization problems

    Object-Oriented Multi-Disciplinary Design, Analysis, and Optimization Tool

    Get PDF
    An Object-Oriented Optimization (O3) tool was developed that leverages existing tools and practices, and allows the easy integration and adoption of new state-of-the-art software. At the heart of the O3 tool is the Central Executive Module (CEM), which can integrate disparate software packages in a cross platform network environment so as to quickly perform optimization and design tasks in a cohesive, streamlined manner. This object-oriented framework can integrate the analysis codes for multiple disciplines instead of relying on one code to perform the analysis for all disciplines. The CEM was written in FORTRAN and the script commands for each performance index were submitted through the use of the FORTRAN Call System command. In this CEM, the user chooses an optimization methodology, defines objective and constraint functions from performance indices, and provides starting and side constraints for continuous as well as discrete design variables. The structural analysis modules such as computations of the structural weight, stress, deflection, buckling, and flutter and divergence speeds have been developed and incorporated into the O3 tool to build an object-oriented Multidisciplinary Design, Analysis, and Optimization (MDAO) tool

    Object Oriented Finite Element Analysis for Structural Optimization using p-Elements

    Get PDF
    The optimization of continuous structures requires careful attention to discretization errors. Compared to ordinary low order formulation (h-elements) in conjunction with an adaptive mesh refinement in each optimization step, the use of high order finite elements (so called p-elements) has several advantages. However, compared to the h-method a higher order finite element analysis program poses higher demands from a software engineering point of view. In this article the basics of an object oriented higher order finite element system especially tailored to the use in structural optimization is presented. Besides the design of the system, aspects related to the employed implementation language Java are discussed

    Static and dynamic structure in design patterns

    Get PDF
    technical reportDesign patterns are a valuable mechanism for emphasizing structure, capturing design expertise, and facilitating restructuring of software systems. Patterns are typically applied in the context of an object-oriented language and are implemented so that the pattern participants correspond to object instances that are created and connected at run-time. This paper describes a complementary realization of design patterns, in which the pattern participants are statically instantiated and connected components. Our approach separates the static parts of the software design from the dynamic parts of the system behavior. This separation makes the software design more amenable to analysis, enabling more effective and domain specific detection of system design errors, prediction of run-time behavior, and more effective optimization. This technique is applicable to imperative, functional, and object-oriented languages: we have extended C, Scheme, and Java with our component model. In this paper, we illustrate this approach in the context of the OSKit, a collection of operating system components written in C

    Search-based system architecture development using a holistic modeling approach

    Get PDF
    This dissertation presents an innovative approach to system architecting where search algorithms are used to explore design trade space for good architecture alternatives. Such an approach is achieved by integrating certain model construction, alternative generation, simulation, and assessment processes into a coherent and automated framework. This framework is facilitated by a holistic modeling approach that combines the capabilities of Object Process Methodology (OPM), Colored Petri Net (CPN), and feature model. The resultant holistic model can not only capture the structural, behavioral, and dynamic aspects of a system, allowing simulation and strong analysis methods to be applied, it can also specify the architectural design space. Both object-oriented analysis and design (OOA/D) and domain engineering were exploited to capture design variables and their domains and define architecture generation operations. A fully realized framework (with genetic algorithms as the search algorithm) was developed. Both the proposed framework and its suggested implementation, including the proposed holistic modeling approach and architecture alternative generation operations, are generic. They are targeted at systems that can be specified using object-oriented or process-oriented paradigm. The broad applicability of the proposed approach is demonstrated on two examples. One is the configuration of reconfigurable manufacturing systems (RMSs) under multi-objective optimization and the other is the architecture design of a manned lunar landing system for the Apollo program. The test results show that the proposed approach can cover a huge number of architecture alternatives and support the assessment of several performance measures. A set of quality results was obtained after running the optimization algorithm following the proposed framework --Abstract, page iii

    Expert System for Structural Optimization Exploiting Past Experience and A-priori Knowledge.

    Get PDF
    The availability of comprehensive Structural Optimization Systems in the market is allowing designers direct access to software tools previously the domain of the specialist. The use of Structural Optimization is particularly troublesome requiring knowledge of finite element analysis, numerical optimization algorithms, and the overall design environment. The subject of the research is the application of Expert System methodologies to support nonspecialists when using a Structural Optimization System. The specific target is to produce an Expert System as an adviser for a working structural optimization system. Three types of knowledge are required to use optimization systems effectively; that relating to setting up the structural optimization problem which is based on logical deduction; past, experience; together with run-time and results interpretation knowledge. A knowledge base which is based on the above is set, up and reasoning mechanisms incorporating case based and rule based reasoning, theory of certainty, and an object oriented approach are developed. The Expert SVstem described here concentrates on the optimization formulation aspects. It is able to set up an optimization run for the user and monitor the run-time performance. In this second mode the system is able to decide if an optimization run is likely to converge to a, solution and advice the user accordingly. The ideas and Expert System techniques presented in this thesis have been implemented in the development; of a prototype system written in C++. The prototype has been extended through the development of a user interface which is based on XView

    Optimal Reactive Power Dispatch Formulated as Quadratic OPF and Solved via CS-SLP

    Get PDF
    Increased penetration of inverter interfaced renewable energy resources creates challenges and opportunities for reactive power management in the modern electricity grid. Because of the multiplicity of new resources, new computational tools and optimization models are needed in formulating and solving the Optimal Reactive Power Dispatch Problem (ORPD). In this paper, we propose (1) an object-oriented ORPD formulation based on high-fidelity modeling of each device in the network, especially those with VAR/V control capability and (2) a two-step Convex Solution-Sequential Linear Programming algorithm. The proposed method introduces two innovations: (a) high fidelity quadratized models of each component of the power system with emphasis on those components that have VAR/V control capability; and (b) an object oriented convexification of the resulting quadratic OPF problem; the solution is obtained by first solving the convex problem using public solvers for convex problems and them removing the relaxation and solving the original OPF using SLP, starting from the solution of the relaxed (convex) problem

    An extensible genetic algorithm framework for problem solving in a common environment

    Get PDF
    An object-oriented framework is described for solving mathematical programs using genetic algorithms (GA). The advantages of this framework are its extensibility, modular design, and accessibility to existing programming code. The framework also incorporates a graphical user's interface that may be used to build new GA's as well as run GA simulations. Two power system problems are solved by implementing genetic algorithms using the framework. The first is a continuous optimization problem and the second an integer programming problem. We illustrate the flexibility of the framework as well as its other features on our test problems.published_or_final_versio
    corecore