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8th ASME/JSME Thermal Engineering Joint Conference

作者： Dirker, J. Meyer, J. P. Univ Pretoria ZA-0002 Pretoria South Africa

ISBN: (纸本)9780791854549

Conductive heat transfer has an important role to play in the cooling of for instance, electronic equipment. Due to its passive nature in relaying heat, internal conductive cooling may have advantages above internal convective heat transfer at small length scales. It does, however, require optimization of the distribution of high heat-conducting material. In this two-dimensional numerical study, the optimum distribution of high conductive material within rectangular heat-generating domains with different aspect ratios is investigated by using a topology optimization algorithm. The volume fraction of the high-conductive material is set at 10% of the total volume. Of interest are the influences of boundary conditions, thermal conductivity and optimization penalization levels on the resulting cooling material distribution. The obtained conducting trees are compared and discussed.

关键词： Heat Electronic equipment Topology optimization Convection Boundary-value problems Cooling Heat transfer optimization algorithms Thermal conductivity

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GEOMETRIC optimization OF MULTIPLE-ARRAYS OF MICROPIN-FINS

GEOMETRIC OPTIMIZATION OF MULTIPLE-ARRAYS OF MICROPIN-FINS

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8th ASME/JSME Thermal Engineering Joint Conference

作者： Ighalo, Fervent Urebho Bello-Ochende, Tunde Meyer, Josua Petrus Univ Pretoria Dept Mech & Aeronaut Engn ZA-0002 Pretoria South Africa

ISBN: (纸本)9780791854549

This study concerns the geometric design of a cylindrical micropin-fin heat sink with multiple row configurations. The objective is to maximize the rate of heat transfer from the solid to the fluid subject to total fin volume and manufacturing constraints. A heat sink with dimensions of I mm x 0.6 mm x I mm is used for the computational analysis. An automated gradient-based optimization algorithm, which effectively handles an objective function obtained from a computational fluid dynamics simulation is implemented. The optimal design is obtained as results of balance of conductive heat transfer along the pin-fins with laminar forced convection. In the first case, the fins are arranged in two rows of pin-fins with different geometric sizes (diameter, height, and spacing between the fins). The optimal configurations obtained as a function of thermal conductivity ratio and Reynolds number are found to be in good agreement with those obtained from theory and numerical optimization. In the second case, the fins are arranged in rows of three, the effect of thermal conductivity and Reynolds number on the optimal configuration and the maximized heat transfer rate from the arrays of cylinders is reported.

关键词： Heat sinks Cylinders Reynolds number Simulation Manufacturing Dimensions Forced convection optimization Fluids Heat transfer Design optimization algorithms Thermal conductivity Fins Computational fluid dynamics

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Numerical optimization of IM Based Test Bench for Wind Generators

Numerical Optimization of IM Based Test Bench for Wind Gener...

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7th International Symposium on Advanced Topics in Electrical Engineering (ATEE)

作者： Tudorache, Tiberiu Bostan, Valeriu Univ Politehn Bucuresti Fac Elect Engn MMAE Dept Bucharest Romania

ISBN: (纸本)9781457705076

This paper deals with the optimization of an electric drive system used to emulate the wind turbine in a wind generators test bench. The prime mover used to rotate the wind generators in the studied test bench is a three-phase Induction Motor IM whose motion is controlled using a vector control scheme. The numerical optimization methodology proposed in the paper refers to the smart identification of the most suitable PI regulators coefficients that provide the best system response in terms of stability, accuracy or speed. These coefficients are usually determined based on simplified hypotheses and then tuned manually so as the system response comply with the imposed criteria. The proposed methodology allows the automatic identification of these coefficients using intelligent optimization algorithms. This search procedure is used to better control a three-phase IM motor drive system destined to the emulation of the wind prime mover integrated in a wind generators test bench.

关键词： Wind Generators system response Automatic identification simulating optimization algorithms

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Performance enhancement of a time hopping - pulse position modulation ultra-wide-band system using guided local search

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IET COMMUNICATIONS 2011年第15期5卷 2212-2220页

作者： Naanaa, A. Belghith, S. Sys'com Laboratory Ecole Nationale d'Ingenieurs de Tunis (ENIT) Tunisia

In this study, the authors propose a method to minimise the multi-user interference (MUI) caused by multiple access (MA) in a time hopping ultra-wide-band (TH-UWB) system with line-of-sight (LOS) multi-path channel in a residential environment IEEE 802.15.4a channel model. The authors considered both synchronous and asynchronous cases. The problem is formulated as a combinatorial optimisation problem (COP) and solved by means of an efficient optimisation algorithm called guided local search (GLS). The optimisation criterion is the average collision number (ACN). The code optimisation method is validated by simulating the system and computing the binary error rate.

关键词： Pulse position modulation time hopping Ultra wideband technologies enhancing performance optimization algorithms optimal criterion

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Three-dimensional modular discriminant analysis (3DMDA): A new feature extraction approach for face recognition

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COMPUTERS & ELECTRICAL ENGINEERING 2011年第5期37卷 811-823页

作者： Safayani, Mehran Shalmani, Mohammad Taghi Manzuri Sharif Univ Technol Dept Comp Engn Tehran Iran

In this paper, we present a novel multilinear algebra based feature extraction approach for face recognition which preserves some implicit structural or locally-spatial information among elements of the original images. We call this method three-dimensional modular discriminant analysis (3DMDA). Our approach uses a new data model called third-order tensor model (3TM) for representing the face images. In this model, each image is partitioned into the several equal size local blocks, and the local blocks are combined to represent the image as a third-order tensor. Then, a new optimization algorithm called direct mode (d-mode) is introduced for learning three optimal projection axes. Extensive experimental results conducted on four benchmark face image databases, demonstrate that 3DMDA is much more effective and robust than state-of-the-art facial feature extraction methods on both classification accuracies and computational complexities. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Tensor Modularity images complexity classes Facial Recognition discriminant analysis Multilinear algebra optimization algorithms Feature extraction data models original image

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IN SITU EFFICIENCY DETERMINATION OF INDUCTION MOTOR: A COMPARATIVE STUDY OF EVOLUTIONARY TECHNIQUES

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APPLIED ARTIFICIAL INTELLIGENCE 2011年第2期25卷 116-140页

作者： Thangaraj, Radha Pant, Millie Raj, C. Thanga Nagar, Atulya K. Liverpool Hope Univ Dept Comp Sci Liverpool L16 9JD Merseyside England Indian Inst Technol Roorkee Uttar Pradesh India

Induction motor is the most frequently used electric machine in industrial and commercial applications because of its well-known advantages, including robustness, low price, maintenance free, and line start. The exact knowledge of some of the induction motor parameters is very important to implement efficient control schemes and its in situ efficiency determination. These parameters can be obtained by no-load test that is not easily possible for the motors working in process industries where continuous operation is required. In this present study, particle swarm optimization, differential evolution, and some of their recent variants are used for in situ efficiency determination of induction motor (5 hp) without performing no-load test. Detailed information about the methods for efficiency measurement is given. Results are compared with genetic algorithm and a physical efficiency measurement method, called torque-gauge method. The performances in terms of objective function (error in the efficiency) and convergence time prove the effectiveness of optimization algorithms used in this article.

关键词： no-load test induction motors electric machines continuous operation parametric motor Motor optimization algorithms

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Optimal estimation of harmonics in a dynamic environment using an adaptive bacterial swarming algorithm

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IET GENERATION TRANSMISSION & DISTRIBUTION 2011年第6期5卷 609-620页

作者： Ji, T. Y. Li, M. S. Wu, Q. H. Jiang, L. Univ Liverpool Dept Elect Engn & Elect Liverpool L69 3GJ Merseyside England

This study is concerned with optimal estimation of power system harmonics in dynamic environment, in which the fundamental frequency deviates with time. The estimation process utilises an adaptive bacterial swarming algorithm (ABSA), which is adaptive to dynamic environment, to estimate the frequencies and phases of the fundamental frequency, integral harmonics and inter-harmonics, along with a least-square method to estimate the amplitudes. ABSA is a generic optimisation algorithm designed from an adaptive searching framework that combines the underlying mechanisms of bacterial chemotaxis, quorum sensing and environment adaptation. Simulation studies have been carried out in three different conditions in comparison with generic algorithm (GA), and the results have shown that ABSA can effectively solve this type of problem and outperforms GA remarkably.

关键词： Environments Power system harmonics Swarming fundamental frequencies optimization algorithms optimal estimation Self tuning

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A study on scale factor in distributed differential evolution

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INFORMATION SCIENCES 2011年第12期181卷 2488-2511页

作者： Weber, Matthieu Neri, Ferrante Tirronen, Ville Univ Jyvaskyla Dept Math Informat Technol Jyvaskyla 40014 Finland

This paper proposes the employment of multiple scale factor values within distributed differential evolution structures. Four different scale factor schemes are proposed, tested, compared and analyzed. Two schemes simply employ multiple scale factor values and two also include an update logic during the evolution. The four schemes have been integrated for comparison within three recently proposed distributed differential evolution structures and tested on several various test problems. Numerical results show that, on average, the employment of multiple scale factors is beneficial since in most cases it leads to significant improvements in performance with respect to standard distributed algorithms. Although proper choice of a scale factor scheme appears to be dependent on the distributed structure, any of the proposed simple schemes has proven to significantly improve upon the single scale factor distributed differential evolution algorithms. (C) 2011 Elsevier Inc. All rights reserved.

关键词： Differential evolution Evolutionary algorithms Distributed algorithms Scale factor Structured populations optimization algorithms Computational intelligence optimization

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algorithms for optimizing the bandwidth cost of content delivery

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COMPUTER NETWORKS 2011年第18期55卷 4007-4020页

作者： Adler, Micah Sitaraman, Ramesh K. Venkataramani, Harish Univ Massachusetts Dept Comp Sci Amherst MA 01003 USA Google Inc Mountain View CA 94043 USA Fiksu Inc Boston MA 02110 USA

Content Delivery Networks (CDNs) deliver web content to end-users from a large distributed platform of web servers hosted in data centers belonging to thousands of Internet Service Providers (ISPs) around the world. The bandwidth cost incurred by a CDN is the sum of the amounts it pays each ISP for routing traffic from its servers located in that ISP out to end-users. A large enterprise may also contract with multiple ISPs to provide redundant Internet access for its origin infrastructure using technologies such as multihoming and mirroring, thereby incurring a significant bandwidth cost across multiple ISPs. This paper initiates the formal algorithmic study of bandwidth cost minimization in the context of a large enterprise or a CDN, a problem area that is both algorithmically rich and practically very important. First, we model different types of contracts that are used in practice by ISPs to charge for bandwidth usage, including average, maximum, and 95th-percentile contracts. Then, we devise an optimal offline algorithm that routes traffic to achieve the minimum bandwidth cost, when the network contracts charge either on a maximum or on an average basis. Next, we devise a deterministic (resp., randomized) online algorithm that achieves cost that is within a factor of 2 (resp., e/e-1) of the optimal offline cost for maximum and average contracts. In addition, we prove that our online algorithms achieve the best possible competitive ratios in both the deterministic and the randomized cases. An interesting theoretical contribution of this work is that we show intriguing connections between the online bandwidth optimization problem and the seemingly-unrelated but well-studied ski rental problem where similar optimal competitive ratios are known to hold. Finally, we consider extensions for contracts with a committed amount of spend (known as committed information rate or CIR) and contracts that charge on a 95th-percentile basis. (C) 2011 Elsevier B.V. All rights rese

关键词： Internet content delivery Content Delivery Networks optimization algorithms Bandwidth cost minimization Network algorithms Traffic management algorithms

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Simply structured controllers for parameter varying distributed systems

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SMART MATERIALS AND STRUCTURES 2011年第1期20卷 015006-1-015006-11页

作者： Chughtai, Saulat S. Werner, Herbert Hamburg Univ Technol Inst Control Syst D-21073 Hamburg Germany

This paper presents a systematic approach to the synthesis of simply structured controllers for large scale parameter varying distributed systems. The design and optimization procedure consists of two loops. In an inner loop, an efficient LMI-based optimization algorithm is used to evaluate the closed-loop performance. The outer loop uses evolutionary operators to iteratively search for the parameters of a controller network that achieves the best performance. For the purpose of performance evaluation, new sufficient LMI conditions are presented to find the induced L-2 norm of such systems. The conservatism of the analysis is reduced by the use of parameter dependent Lyapunov functions and by taking bounds on the parameter variation rates into account. Since the control algorithms are implemented on digital computers, the results are presented for discrete time and discrete space systems. The problem posed in this form is infinite dimensional, a gridding algorithm is also proposed to convert it into a finite dimensional problem. The approach is illustrated with two applications: active vibration control of a cantilever, and position control of a seismic cable. These examples illustrate that the performance analysis condition presented here is less conservative than previously presented LMI conditions. It is also demonstrated that the approach can be used to systematically design simply structured low-order controllers, while satisfying all performance requirements.

关键词： optimization Procedure optimum performance scale parameter Liapunov function vibration control Interim Local Management Interface discrete-time Position control Performance Evaluation Distributed Systems Computer algorithms low-order Controllers optimization algorithms

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