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In-silico simulation of porous media Conception and development of a greedy algorithm

MICROPOROUS AND MESOPOROUS MATERIALS 2011年第1-3期137卷 18-31页

作者： Roman-Alonso, G. Rojas-Gonzalez, F. Aguilar-Cornejo, M. Cordero-Sanchez, S. Castro-Garcia, M. A. Univ Autonoma Metropolitana Iztapalapa Dept Quim Mexico City 09340 DF Mexico Univ Autonoma Metropolitana Iztapalapa Dept Ingn Elect Mexico City 09340 DF Mexico

Cubic porous networks consisting of several millions of voids of different sizes are efficiently simulated through a greedy algorithm The porous network is built on the basis of the Dual Site-Bond Model in which a cavity (site) is always larger than any of its delimiting throats (bonds) When the initial configuration of the cubic network is established by means of a random (Monte Carlo) seeding on a lattice of sites and bonds the proper allocation of more pore elements becomes troublesome and time-consuming and there even exists the chance of not achieving a valid pore network The complexity of this pioneering Monte Carlo algorithm in the best case increases according to the third power of the number of pore elements and in the worst case is asymptotic to infinity Here we have succeeded in the development of an smart non-mistake initial seeding situation of sites and bonds that behaves in the way of a greedy algorithm An initial ordering of sites according to their sizes allows a proper assemblage of these hollows throughout the cubic lattice From this configuration the pore network evolves toward the most probable one by a series of legitimate random swappings between sites and bonds The complexity of the greedy algorithm remained proportional to the cubic power of the total number of sites In general the execution time of the greedy algorithm results to be faster than that employed with the previous Monte Carlo algorithm (C) 2010 Elsevier Inc All rights reserved

关键词： Interconnected void network Dual Site Bond Model optimization algorithms Monte Carlo method Computational complexity

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Minimum Unique Substrings and Maximum Repeats

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FUNDAMENTA INFORMATICAE 2011年第1-4期110卷 183-195页

作者： Ilie, Lucian Smyth, William F. Univ Western Ontario Dept Comp Sci London ON N6A 5B7 Canada McMaster Univ Dept Comp & Software Hamilton ON L8S 4K1 Canada Curtin Univ Technol Digital Ecosyst & Business Intelligence Inst Perth WA 6845 Australia

Unique substrings appear scattered in the stringology literature and have important applications in bioinformatics. In this paper we initiate a study of minimum unique substrings in a given string;that is, substrings that occur exactly once while all their substrings are repeats. We discover a strong duality between minimum unique substrings and maximum repeats which, in particular, allows fast computation of one from the other. We give several optimal algorithms, some of which are very simple and efficient. Their combinatorial properties are investigated and a number of open problems are proposed.

关键词： Unique minimum optimization algorithms Bioinformatics substring Cosmic strings

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Modified shuffled-frog-leaping algorithm in company with neural networks for harmonic distortion minimisation in real-time control applications of programmed pulse-width modulation inverters

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IET POWER ELECTRONICS 2011年第8期4卷 943-950页

作者： Alimardani, A. Mazaheri, B. Abdi, B. Hosseinian, S. H. Amirkabir Univ Technol Tehran Polytech Dept Elect Engn Tehran 158754413 Iran Sharif Univ Technol Dept Elect Engn Tehran Iran Islamic Azad Univ Damavand Branch Damavand Iran

Harmonic pollution minimisation in voltage-source programmed pulse-width modulation (PPWM) inverters is defined as a time-limited optimisation problem in real-time applications with variable DC sources. In order to obtain minimum total harmonic distortion (THD) as the objective function, shuffled-frog-leaping algorithm (SFLA) is modified and employed to calculate the switching angles and compared with non-linear programming as a traditional optimisation method. In addition, particle swarm optimisation and three of its modified versions as popular evolutionary optimisation algorithms are employed to ensure the capability of the proposed optimisation method. Moreover, modified sinusoidal PWM (MSPWM) THD is compared with PPWM THD. Furthermore, as the DC bus voltage in some applications might have high variations (in amplitude or frequency of fluctuations) in a short time, to acquire adequate response speed to this variation of DC source of inverters in real-time control applications, a neural network (NN) is trained by the off-line calculated results of MSFLA for various desired modulation indexes (various DC voltages). Simulation results demonstrate the accurate and high-speed response of the designed NN. The main contribution of this study is to provide a fast accurate method which can track the variation of DC source of inverters with high-quality solutions in real-time control applications.

关键词： voltage source Total harmonic distortion DC power supply In company high-speed response PULSE WIDTH real-time application program Real time control Reaction Time Pulse width modulation inverters time monitoring Neural network optimization algorithms Inventors dc bus voltage

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Enhancement of voltage profile and loss minimization in Distribution Systems using optimal placement and sizing of power system modeled DGs

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JOURNAL OF ELECTRICAL SYSTEMS 2011年第4期7卷 448-457页

作者： Yammani, Chandrasekhar Maheswarapu, Sydulu Matam, Sailajakumari Natl Inst Technol Dept Elect Engn Warangal 506004 Andhra Pradesh India

Distributed Generations (DGs) integration in distribution system is one of the options which give benefits like loss minimization, peak shaving, over load relieving and improved reliability. This paper presents a method for optimal placement and size of the DGs considering system loss minimization and voltage profile improvement as objective functions. The solar and wind systems are modeled as constant power factor model and variable reactive power model respectively. This work is tested on 37-bus and 69-bus Distribution Systems. The simulation technique based on Genetic Algorithm is studied. For all cases current injection based distribution load flow method is used.

关键词： Distributed Generation optimization algorithms Genetic Algorithm DG Modeling

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Ground States of Two-Dimensional Ising Spin Glasses: Fast algorithms, Recent Developments and a Ferromagnet-Spin Glass Mixture

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JOURNAL OF STATISTICAL PHYSICS 2011年第3期144卷 519-540页

作者： Hartmann, Alexander K. Carl von Ossietzky Univ Oldenburg Inst Phys D-26111 Oldenburg Germany

Using advanced numerical approaches based on optimization algorithms, much progress has been achieved for the study of the ground-state and low-temperature behavior of two-dimensional Ising spin glasses. Recent results led to a rather good understanding of these systems in the framework of the droplet-scaling theory. In this work, a pedagogical description of such an optimization-based approach is given and a short review of corresponding recent results is presented. Furthermore, original results are presented for a special type of system which combines a ferromagnetic sub lattice with a spin-glass sub lattice. Results for exact ground-state calculations up to system size N=1448x1448 are given. Past results of similar systems gave evidence that such a system might exhibit a spin-glass phase at finite temperatures. Nevertheless, the present results do not support this notion. But, for a suitable balance between ferromagnetic and +/- J spin-glass couplings, extremely large finite-size effects occur. Thus, when considering intermediate system sizes, the system looks as if it orders. Furthermore, although the system exhibits only a discrete set of interactions, a power-law behavior for the stiffness energy can be observed clearly for a large range of system sizes. This is in contrast to past studies of systems with discrete sets of bond values.

关键词： Spin glasses Ground states optimization algorithms Matching algorithms Domain walls Droplets SLE processes

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A Coronagraph Using a Liquid Crystal Array and a Deformable Mirror for Active Apodizing and Phase Corrections

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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC 2011年第901期123卷 341-347页

作者： Ren, Deqing Zhu, Yongtian Chinese Acad Sci Natl Astron Observ Nanjing Inst Astron Opt & Technol Nanjing 210042 Peoples R China Chinese Acad Sci Key Lab Astron Opt & Technol Nanjing Inst Astron Opt & Technol Nanjing 210042 Peoples R China Calif State Univ Northridge Dept Phys & Astron Northridge CA 91330 USA

Almost all high-contrast imaging coronagraphs proposed until now are based on passive coronagraph optical components. That is, the coronagraph cannot be actively controlled to be optimized for best performance. Pupil apodizing, which modifies the light transmission on the pupil, is one of the promising techniques for high-contrast imaging. Here, we propose, for the first time, a high-contrast imaging coronagraph that integrates a liquid crystal array for active pupil apodizing and a deformable mirror for active phase correction. In such a way, source errors such as the initial transmission error and wavefront error can be actively and efficiently compensated based on an optimized algorithm, which is optimized for maximum contrast in the discovery area. In addition, the use of a liquid crystal array makes this system more flexible and able to create any apodizing pupil, including square or circle aperture with or without central obstruction. in this article, we discuss the working principle and estimated performance of the coronagraph. We also demonstrate that the chromatic aberration induced by a liquid crystal array is sufficiently small, which makes it suitable to be used for ground-based near-infrared coronagraphic Extreme-AO systems.

关键词： crystal array Liquid Crystals optimization algorithms high-contrast arrays coronagraph phase correction wavefront error deformable mirrors CHROMATIC ABERRATION Transmission errors Pupil

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Exploiting Day-Ahead Electricity Price for Maximized Profit of Photovoltaic Systems

Exploiting Day-Ahead Electricity Price for Maximized Profit ...

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International Conference on Smart Grid Technology, Economics and Policies

作者： Abdalkarim Awad Peter Bazan Reinhard German Computer Networks and Communication Systems University of Erlangen

ISBN: (纸本)9781467359313

This paper proposes a methodology for optimal power management in a house with photovoltaic cells and battery storage. The proposed method exploits the day-ahead electricity market to enhance the profit of a household. An hourly-discretized optimization algorithm is proposed to identify the optimum daily operational strategy to be followed by the photovoltaic system, provided that a forecast for solar-power and load is available. This model is suitable to be applied in the real time operation of a typical house. The proposed strategy maximizes the individual revenue without shifting power demand. We explored the proposed algorithm with and without feed-in tariff. The results show that a typical house can save about 300 /year when app lying optimized power management.

关键词： Photovoltaic systems REAL TIME OPERATION Secondary batteries Solar collectors Domestic architecture Photovoltaic cells optimization algorithms Electricity LOAD Prices Power demand

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Application of Imperialist Competitive Algorithm to Design an Optimal Controller for LFC Problem

Application of Imperialist Competitive Algorithm to Design a...

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Annual Conference on IEEE Industrial Electronics Society

作者： Elyas Rakhshani Alvaro Luna Kumars Rouzbehi Pedro Rodriguez Technical University of Catalonia Department of Electrical Engineering Research Center on Renewable Electrical Energy Systems (SEER Center)

ISBN: (纸本)9781467324199

A novel optimization algorithm is presented to improve the design of optimal controllers for load frequency control problem. This algorithm is applied for two area LFC system with using an output feedback controller. In the practical power system, access to some of the state variables in LFC system is limited and measuring is also impossible. So an optimal output feedback controller with a practical viewpoint is proposed. The optimal control law is determined by minimizing a performance index under the output feedback conditions leading to a coupled matrix equation. In order to solve these equations traditional methods may be used. But for more accuracy and better design for this controller, ICA algorithm is applied to find the global optimal gain matrix of the controller. Simulation results of ICA are compared with the conventional design. Comparison shows the success of ICA for design of optimal controller.

关键词： optimal controllers competitive algorithms Full mold process Independent component analysis islet cell antibody performance indicators load frequency control control law feedback controller Output feedback State variable information matrix Controllers optimization algorithms

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AN IMPROVED MULTI-OBJECTIVE PARTICLE SWARM OPTIMIZER FOR AIR TRAFFIC FLOW NETWORK REROUTING PROBLEM

AN IMPROVED MULTI-OBJECTIVE PARTICLE SWARM OPTIMIZER FOR AIR...

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IEEE/AIAA Digital Avionics Systems Conference

作者： Miao Zhang Kai-quan Cai Yan-bo Zhu School of Electronic and Information Engineering Beihang University Aviation Data Communication Corporation

ISBN: (纸本)9781467316996

With the increasing incidence of malfunctions of air transportation system due to severe weather, the Air Traffic Flow Network Rerouting (ATFNR) is playing an important role in improving the global efficiency of air traffic. This paper adopts a multi-objective optimization model to solve the ATFNR problem to make a tradeoff between the total delay costs and the airlines fairness. Meanwhile, a specially-designed algorithm based on multi-objective comprehensive learning particle swarm optimizer (MOCLPSO) under the cooperative co-evolution framework is presented to handle this large scale, multi-objective real-world optimization problem. The empirical studies show that the presented methodology is effective and outperforms an existing approach to ATFNR problem as well as two well-known Multi-Objective optimization algorithms.

关键词： air traffic optimization algorithms malfunctions Airlines tradeoffs Network

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Achievable Performance in Product-Form Networks

Achievable Performance in Product-Form Networks

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Annual Allerton Conference on Communication, Control, and Computing

作者： Jaron Sanders Sem C. Borst Johan S. H. van Leeuwaarden Eindhoven University of Technology Bell Laboratories Alcatel-Lucent

ISBN: (纸本)9781467345378

We characterize the achievable range of performance measures in product-form networks where one or more system parameters can be freely set by a network operator. Given a product-form network and a set of configurable parameters, we identify which performance measures can be controlled and which target values can be attained. We also discuss an online optimization algorithm, which allows a network operator to set the system parameters so as to achieve target performance metrics. In some cases, the algorithm can be implemented in a distributed fashion, of which we give several examples. Finally, we give conditions that guarantee convergence of the algorithm, under the assumption that the target performance metrics are within the achievable range.

关键词： Network operators system parameter optimization algorithms realizable Performance metrics Network

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