检索结果-内蒙古大学图书馆

Minimizing the object dimensions in circle and sphere packing problems

COMPUTERS & OPERATIONS RESEARCH 2008年第7期35卷 2357-2375页

作者： Birgin, E. G. Sobral, F. N. C. Univ Sao Paulo IME Dept Comp Sci BR-05508090 Sao Paulo SP Brazil

Given a fixed set of identical or different-sized circular items, the problem we deal with consists on finding the smallest object within which the items can be packed. Circular, triangular, squared, rectangular and also strip objects are considered. Moreover, 2D and 3D problems are treated. Twice-differentiable models for all these problems are presented. A strategy to reduce the complexity of evaluating the models is employed and, as a consequence, instances with a large number of items can be considered. Numerical experiments show the flexibility and reliability of the new unified approach. (C) 2007 Elsevier Ltd. All rights reserved.

关键词： packing of circles and spheres models algorithms non-linear programming

来源：评论

学校读者我要写书评

暂无评论

Coupled hydrological-economic modelling for optimised irrigated cultivation in a semi-arid catchment of West Africa

引用

ENVIRONMENTAL MODELLING & SOFTWARE 2008年第4期23卷 385-395页

作者： Ahrends, H. Mast, M. Rodgers, Ch. Kunstmann, H. Inst Meteorol & Climate Res IMK IFU Forschungszentrum Karlsruhe D-82467 Garmisch Partenkirchen Germany Univ Bonn Ctr Res & Dev D-5300 Bonn Germany

A coupled model system, consisting of a distributed hydrological model and an economic optimisation model, communicating via model interfaces, is developed and applied to investigate regional interdependencies between irrigated agriculture and regional water balance and to identify optimised cultivation strategies. The coupled model is employed in the context of a case study in the Atankwidi catchment in the northern Guinea Sudan zone of West Africa. The physically based hydrologic model WaSiM [Schulla, J., Jasper, K., 2001] is used to simulate the water balance of this catchment including a small reservoir-irrigation system complex. The economics of irrigated crop cultivation are optimized under hydrological constraints using the non-linear optimisation model GAMS-ECIM, encoded in GAMS (General Algebraic Modelling System). The coupled model system is utilized for empirical model testing under fictitious scenarios involving variable water availability for irrigation. Interdependencies between irrigation water application quantities and the water balance were identified and maximum agricultural profit was calculated using the coupled model system. The coupled model system is designed as decision-support tool for local authorities and agricultural stakeholders in the Ghanaian Upper East Region (UER). (C) 2007 Elsevier Ltd. All rights reserved.

关键词： model coupling distributed hydrological modelling economic modelling non-linear programming irrigated agriculture decision support West Africa

来源：评论

学校读者我要写书评

暂无评论

Optimization and guidance of very low-thrust transfers to geostationary orbit

Optimization and guidance of very low-thrust transfers to ge...

引用

57th International Astronautical Congress

作者： Gil-Fernandez, Jesus Tarabini, Lorenzo Graziano, Mariella Gomez-Tierno, M. A. GMV SA Madrid 28760 Spain

A new hybrid direct-indirect optimization algorithm is presented to compute the minimum-time transfer between two orbits, including the phasing with a desired spacecraft. Very-low thrust means several hundred revolutions to perform the large change in orbital elements. The optimal control solution of the fast-evolution problem combined with a direct method for the secular trajectory avoids the numerical instability arising in very long propagations, decreases the computational time, reduces the sensitivity to the initial guess and provides a feasible transfer at every optimization step. Optimization of transfers from GTO to GEO is presented and two types of trajectories are analysed, sub-synchronous (apogee constrained below GEO altitude) and super-synchronous (free apogee altitude). The optimization of a transfer from LEO to a very high orbit (11 ' 23 R E) is presented, showing the applicability of the method to different problems. A guidance algorithm is presented to compensate the deviations of the real trajectory from the optimal one due to off-nominal conditions. The results in closed-loop simulation of the guidance scheme to compensate detenninistic perturbations not considered in the optimization show good performances in both analysed missions.

关键词： trajectory optimization low-thrust optimal control non-linear programming guidance

来源：评论

学校读者我要写书评

暂无评论

Security Constrained Economic Dispatch with Secure Bilateral Transactions in Hybrid Electricity Markets

Security Constrained Economic Dispatch with Secure Bilateral...

引用

Joint International Conference on Power Systems Technology (POWERCON)/IEEE Power India Conference

作者： Kumar, Ashwani Chanana, Saurabh Natl Inst Technol Kurukshetra Dept Elect Engn Kurukshetra Haryana India

ISBN: (纸本)9781424417636

This paper proposes security constrained economic power dispatch (SCED) of the generators in the presence of secure bilateral transactions for hybrid electricity markets. The proposed non-linear optimization problem considers simultaneous minimization of deviations from scheduled transactions and minimization of fuel cost of the generators. The impact of bilateral transactions on fuel costs of generators and generation pattern has also been studied. The proposed technique has been applied on IEEE 24-bus reliability test system (IRTS).

关键词： non-linear programming secure transaction matrix security constrained economic dispatch transaction matrix pattern

来源：评论

学校读者我要写书评

暂无评论

Optimization based cost comparison between reinforced concrete and steel beams

Optimization based cost comparison between reinforced concre...

引用

4th International Conference on High Performance Structures and Materials

作者： Merta, I. Kravanja, S. Klansek, U. Vienna Univ Technol Inst Bldg Consturct & Technol A-1060 Vienna Austria Univ Maribor Fac Civil Engn Maribor Slovenia

ISBN: (纸本)9781845641061

This paper presents the optimization based cost comparison between reinforced concrete and doubly-symmetrical welded steel I beams. The task of the research was to define the spans at which each of two different considered structures would show its advantages. The optimization/comparison was performed for simply supported beams for spans between 5 and 30 meters and for a uniformly distributed variable imposed load of 5 kN/m. The structural optimization was performed by the nonlinear programming (NLP) approach. The cost objective function was defined for the optimization and subjected to structural analysis constraints. The structures were designed in accordance with Eurocodes for both the ultimate and serviceability limit states. Beside the optimal self-manufacturing costs, the results also include the optimal masses for the different considered structures.

关键词： structural optimization non-linear programming reinforced concrete beams steel beams

来源：评论

学校读者我要写书评

暂无评论

MINLP Optimization of a Single-Storey Industrial Steel Building

引用

STROJNISKI VESTNIK-JOURNAL OF MECHANICAL ENGINEERING 2008年第10期54卷 707-724页

作者： Zula, Tomaz Kravanja, Zdravko Kravanja, Stojan Univ Maribor Fac Civil Engn SLO-2000 Maribor Slovenia Univ Maribor Fac Chem & Chem Engn SLO-2000 Maribor Slovenia

The paper presents the topology and standard sizes optimization of a single-storey industrial steel building, made from standard hot rolled I sections. The structure consists of main portal frames, connected with purlins. The structural optimization is performed by the Mixed-Integer non-linear programming approach (MINLP). The MINLP performs a discrete topology and standard dimension optimization simultaneously with continuous parameters. Since the discrete/continuous optimization problem of the industrial building is non-convex and highly non-linear, the Modified Outer-Approximation/Equality-Relaxation (OA/ER) algorithm has been used for the optimization. Alongside the optimum structure mass, the optimum topology with the optimum number of portal frames and purlins as well as all standard cross-section sizes have been obtained. The paper includes the theoretical basis and a practical example with the results of the optimization. (C) 2008 Journal of Mechanical Engineering. All rights reserved.

关键词： industrial buildings topology optimization sizing optimization non-linear programming MINLP

来源：评论

学校读者我要写书评

暂无评论

On the Algorithm of Determination of Immobile Indices for Convex SIP Problems

引用

INTERNATIONAL JOURNAL OF APPLIED MATHEMATICS & STATISTICS 2008年第J08期13卷 13-33页

作者： Kostyukova, Olga I. Tchemisova, Tatiana V. Yermalinskaya, Svetlana A. Natl Acad Sci Belarus Inst Math Dept Math Syst Theory Surganov Str 11 Minsk 220072 BELARUS Univ Aveiro Dept Math P-3810193 Aveiro Portugal Belarussian State Univ Informat & Radioelect Dept Informat Minsk 220013 BELARUS

We consider convex Semi-Infinite programming (SIP) problems with a continuum of constraints. For these problems we introduce new concepts of immobility orders and immobile indices. These concepts are objective and important characteristics of the feasible sets of the convex SIP problems since they make it possible to formulate optimality conditions for these problems in terms of optimality conditions for some NLP problems (with a finite number of constraints). In the paper we describe a finite algorithm (DIO algorithm) of determination of immobile indices together with their immobility orders, study some important properties of this algorithm, and formulate the Implicit Optimality Criterion for convex SIP without any constraint qualification conditions (CQC). An example illustrating the application of the DIO algorithm is provided.

关键词： Convex Semi-Infinite programming non-linear programming optimality criterion constraint qualification condition immobile index immobility order

来源：评论

学校读者我要写书评

暂无评论

On retrial queueing model with fuzzy parameters

引用

PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS 2007年第1期374卷 272-280页

作者： Ke, Jau-Chuan Huang, Hsin-I Lin, Chuen-Horng Natl Taichung Inst Technol Dept Informat Management Taichung 404 Taiwan Natl Taichung Inst Technol Dept Stat Taichung 404 Taiwan

This work constructs the membership functions of the system characteristics of a retrial queueing model with fuzzy customer arrival, retrial and service rates. The a-cut approach is used to transform a fuzzy retrial-queue into a family of conventional crisp retrial queues in this context. By means of the membership functions of the system characteristics, a set of parametric non-linear programs is developed to describe the family of crisp retrial queues. A numerical example is solved successfully to illustrate the validity of the proposed approach. Because the system characteristics are expressed and governed by the membership functions, more information is provided for use by management. By extending this model to the fuzzy environment, fuzzy retrial-queue is represented more accurately and analytic results are more useful for system designers and practitioners. (c) 2006 Elsevier B.V. All rights reserved.

关键词： fuzzy parameters membership functions non-linear programming retrial queue

来源：评论

学校读者我要写书评

暂无评论

non-linear global optimization via parameterization and inverse function approximation: An artificial neural networks approach

引用

INTERNATIONAL JOURNAL OF NEURAL SYSTEMS 2007年第5期17卷 353-368页

作者： Mayorga, Rene V. Arriaga, Mariano Univ Regina Fac Engn Regina SK S4S 0A2 Canada

In this article, a novel technique for non-linear global optimization is presented. The main goal is to find the optimal global solution of non-linear problems avoiding sub-optimal local solutions or inflection points. The proposed technique is based on a two steps concept: properly keep decreasing the value of the objective function, and calculating the corresponding independent variables by approximating its inverse function. The decreasing process can continue even after reaching local minima and, in general, the algorithm stops when converging to solutions near the global minimum. The implementation of the proposed technique by conventional numerical methods may require a considerable computational effort on the approximation of the inverse function. Thus, here a novel Artificial Neural Network (ANN) approach is implemented to reduce the computational requirements of the proposed optimization technique. This approach is successfully tested on some highly non-linear functions possessing several local minima. The results obtained demonstrate that the proposed approach compares favorably over some current conventional numerical (Matlab functions) methods, and other non-conventional (Evolutionary Algorithms, Simulated Annealing) optimization methods.

关键词： artificial neural networks global optimization inverse functions non-linear programming

来源：评论

学校读者我要写书评

暂无评论

Using dynamic optimization technique to study the operation of batch reactors

引用

CANADIAN JOURNAL OF CHEMICAL ENGINEERING 2007年第4期85卷 465-478页

作者： Sun, Daim-Yuang Lin, Pi-Min Lin, Shu-Ping Natl Chinyi Inst Technol Dept Chem & Mat Engn Taichung 11 Taiwan

How to apply the global optimization technique, simulated annealing, and to explore the operation of batch reactors is addressed in this study. Based on the operating purposes and the imposed constraints, the batch reactor operations are first formulated as two optimal control problems: the maximal yield (or conversion) problem and the minimal operating time problem. The problems are then converted into nonlinear programming problems by the concept of control vector parameterization. The converted problems are solved by the algorithm derived from simulated annealing to determine the optimal operating policy and the performance index. These results are useful in assessing design and operation of batch reactors. In this article, the CSTR model is used to demonstrate the convenience and robustness of the proposed algorithm. Two typical reaction models are used to discuss the operations based on the optimal solutions.

关键词： dynamic optimization batch reactor operations non-linear programming simulated annealing control vector parameterization

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：