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Differential Evolution (differential + evolution)

Distribution by Scientific Domains
Chemistry33%
Business, Economics, Finance and Accounting33%
Engineering22%

Terms modified by Differential Evolution

  • differential evolution algorithm
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    Selected Abstracts

    Estimation of apparent thermal conductivity of carrot purée during freezing using inverse problem

    INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2009
    Viviana Cocco Mariani
    Summary This article presents an inverse problem to determine the apparent thermal conductivity of carrot purée during the freezing process. The heat diffusion equation with the enthalpy model is solved to estimate the thermal conductivity. A modern meta-heuristic of evolutionary computation field called Differential Evolution (DE) is applied for the solution of inverse problem. Experiments were performed to estimate the thermal conductivity of the carrot purée as a function of temperature, using two piecewise functions. A best least square fitting between the experimental and predicted temperature curves during freezing conditions is obtained using DE. Statistical analysis are considered with Gaussian error of 0.05 and zero mean showing than the results for one piecewise function are more stable than with another piecewise function. Good agreement between the reported and estimated temperature curves was obtained. The apparent thermal conductivity was observed to decrease asymptotically with temperature in the range [,40 °C, 0 °C] and stay approximately a constant value for temperatures bigger than 0 °C. [source]

    Application of differential evolution algorithm for optimal location and parameters setting of UPFC considering power system security

    EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 7 2009
    Husam I. Shaheen
    Abstract Unified power flow controller (UPFC) is one of the most effective flexible AC transmission systems (FACTS) devices for enhancing power system security. However, to what extent the performance of UPFC can be brought out, it highly depends upon the location and parameters setting of this device in the system. This paper presents an approach based on evolutionary algorithms (EAs) techniques to find out the optimal placement and settings of UPFC for enhancing power system security under single line contingencies (N-1 contingency). Firstly, we perform a contingency analysis and ranking process to determine the most severe line outage contingencies considering line overloads and bus voltage limit violations as a performance index. Secondly, we apply an evolutionary optimization technique, namely: differential evolution (DE) to find out the optimal location and parameters setting of UPFC under the determined contingency scenarios. To verify our proposed approach and for comparison purposes, we perform simulations on an IEEE 14-bus and an IEEE 30-bus power systems. The results we have obtained indicate that DE is an easy to use, fast, and robust optimization technique compared with genetic algorithm (GA). Installing UPFC in the optimal location determined by DE can significantly enhance the security of power system by eliminating or minimizing the overloaded lines and the bus voltage limit violations. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    School Attendance and Skill Premiums in France and the US: A General Equilibrium Approach,

    FISCAL STUDIES, Issue 4 2007
    David De La Croix
    We evaluate the effect of education policies, welfare programmes, technology and demographics on the differential evolution of the skill premium and on the rise in education investment in France and the US. We use a computable general equilibrium model with overlapping generations of individuals and endogenous education decisions. Human capital has two substitutable components - experience and education - both of which evolve endogenously over time. We use an original method to calibrate our model properly on the post-war period and run counterfactual experiments to assess the relative contributions of the different exogenous variables. The expansionary French education policy boosted the supply of skills and kept the skill premium low. In contrast, increasing education costs in the US contributed to increased wage differentials by reducing the rise in educational attainment. Skill-biased technical change is key to understanding rising school attendance and skill premiums in the US. It has a less important role and appears to be delayed in France. [source]

    Index tracking with constrained portfolios

    INTELLIGENT SYSTEMS IN ACCOUNTING, FINANCE & MANAGEMENT, Issue 1-2 2007
    Dietmar Maringer
    Passive portfolio management strategies, such as index tracking, are popular in the industry, but so far little research has been done on the cardinality of such a portfolio, i.e. on how many different assets ought to be included in it. One reason for this is the computational complexity of the associated optimization problems. Traditional optimization techniques cannot deal appropriately with the discontinuities and the many local optima emerging from the introduction of explicit cardinality constraints. More recent approaches, such as heuristic methods, on the other hand, can overcome these hurdles. This paper demonstrates how one of these methods, differential evolution, can be used to solve the constrained index-tracking problem. We analyse the financial implication of cardinality constraints for a tracking portfolio using an empirical study of the Down Jones Industrial Average. We find that the index can be tracked satisfactorily with a subset of its components and, more important, that the deviation between computed actual tracking error and the theoretically achievable tracking error out of sample is negligibly affected by the portfolio's cardinality. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Optimizing object classification under ambiguity/ignorance: application to the credit rating problem

    INTELLIGENT SYSTEMS IN ACCOUNTING, FINANCE & MANAGEMENT, Issue 2 2005
    Malcolm J. Beynon
    A nascent technique for object classification is employed to exposit the classification of US banks to their financial strength ratings, presented by the Moody's Investors Services. The classification technique primarily utilized, called CaRBS (classification and ranking belief simplex), allows for the presence of ignorance to be inherent. The modern constrained optimization method, trigonometric differential evolution (TDE), is adopted to configure a CaRBS system. Two different objective functions are considered with TDE to measure the level of optimization achieved, which utilize differently the need to reduce ambiguity and/or ignorance inherently during the optimization process. The appropriateness of the CaRBS system to analyse incomplete data is also highlighted, with no requirement to impute any missing values or remove objects with missing values inherent. Comparative results are also presented using the well-known multivariate discriminant analysis and neural network models. The findings in this study identify a novel dimension to the issue of object classification optimization, with the discernment between the concomitant notions of ambiguity and ignorance. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    GenX: an extensible X-ray reflectivity refinement program utilizing differential evolution

    JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2007
    Matts Björck
    GenX is a versatile program using the differential evolution algorithm for fitting X-ray and neutron reflectivity data. It utilizes the Parratt recursion formula for simulating specular reflectivity. The program is easily extensible, allowing users to incorporate their own models into the program. This can be useful for fitting data from other scattering experiments, or for any other minimization problem which has a large number of input parameters and/or contains many local minima, where the differential evolution algorithm is suitable. In addition, GenX manages to fit an arbitrary number of data sets simultaneously. The program is released under the GNU General Public License. [source]

    New and accurate synthesis formulas for open supported coplanar waveguides

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2010
    S. Kaya
    Abstract In this article, new and accurate synthesis formulas to compute the physical dimensions of open supported coplanar waveguides (OS-CPWs) are presented. The synthesis formulas are obtained with the use of differential evolution (DE) and particle swarm optimization (PSO) algorithms. They are useful for the computer-aided design of OS-CPWs. The average percentage errors of the synthesis formulas obtained by using DE and PSO algorithms are computed to be 1.26% and 1.67%, respectively, for 4560 OS-CPW samples having different electrical parameters and physical dimensions, as compared with the results of quasi-static analysis. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 262,269, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24908 [source]

    The evolution of submillimetre galaxies: two populations and a redshift cut-off

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008
    J. V. Wall
    ABSTRACT We explore the epoch dependence of number density and star formation rate for submillimetre galaxies (SMGs) found at 850 ,m. The study uses a sample of 38 SMG in the Great Observatories Origins Deep Survey (GOODS)-N field, for which cross-waveband identifications have been obtained for 35/38 members together with redshift measurements or estimates. A maximum-likelihood analysis is employed, along with the ,single-source-survey' technique. We find a diminution in both space-density and star formation rate at z > 3, closely mimicking the redshift cut-offs found for quasi-stellar objects (QSOs) selected in different wavebands. The diminution in redshift is particularly marked at a significance level too small to measure. The data further suggest, at a significance level of about 0.001, that two separately evolving populations may be present, with distinct luminosity functions. These results parallel the different evolutionary behaviours of Luminous Infrared Galaxies and Ultra-Luminous Infrared Galaxies, and represent another manifestation of ,cosmic down-sizing', suggesting that differential evolution extends to the most extreme star-forming galaxies. [source]

    Deciphered Chemical Shifts in Aliased Spectra Recorded with two Slightly Different Narrow Windows or Differential Chemical Shift Evolution

    CHEMPHYSCHEM, Issue 12 2010
    Mohammadali Foroozandeh
    The overlap of two HSQC spectra recorded with 10 and 9.9 ppm carbon spectral windows gives rise to highly resolved signals with a pattern providing unambiguous precise and accurate chemical shifts (see picture). Alternatively, the new DENA-HSQC pulse sequence takes advantage of a differential evolution of carbon chemical shift to do the same in a single experiment. Combined with multiplicity edition, DENA-HSQC advantageously replaces commonly used 1D DEPT-135 experiments. [source]