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Sanyang M.L.,University of Birmingham | Sanyang M.L.,University of the Gambia | Kaban A.,University of Birmingham
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

We consider Black-Box continuous optimization by Estimation of Distribution Algorithms (EDA). In continuous EDA, the multivariate Gaussian distribution is widely used as a search operator, and it has the well-known advantage of modelling the correlation structure of the search variables, which univariate EDA lacks. However, the Gaussian distribution as a search operator is prone to premature convergence when the population is far from the optimum. Recent work suggests that replacing the univariate Gaussian with a univariate Cauchy distribution in EDA holds promise in alleviating this problem because it is able to make larger jumps in the search space due to the Cauchy distribution's heavy tails. In this paper, we propose the use of a multivariate Cauchy distribution to blend together the advantages of multivariate modelling with the ability of escaping early convergence to efficiently explore the search space. Experiments on 16 benchmark functions demonstrate the superiority of multivariate Cauchy EDA against univariate Cauchy EDA, and its advantages against multivariate Gaussian EDA when the population lies far from the optimum. © Springer International Publishing Switzerland 2014.

Lopez-Garcia J.,Tomas Bata University in Zlin | Bilek F.,Tomas Bata University in Zlin | Lehocky M.,Tomas Bata University in Zlin | Junkar I.,Jozef Stefan Institute | And 3 more authors.
Vacuum | Year: 2013

Low-density polyethylene (LDPE) foils were surface-modified by using non-thermal non-equilibrium oxidative air 40 kHz frequency, radiofrequency (RF) and microwave (MW) discharge plasma treatment. The pristine and treated specimens were morphologically and chemically characterised by Scanning Electron Microscopy (SEM) imaging, X-ray Photoelectron Spectroscopy (XPS) and contact angle measurement with surface energy evaluation. In addition, printability and ink adhesion tests were carried out on the samples, and quantitatively appraised by UV-VIS transmission spectroscopy. The overall outcome indicated chemical and physical changes after each treatment, and the improvement of printability. The present approach could serve as a viable and promising method to improve printability of polyethylene. © 2013 Elsevier Ltd. All rights reserved.

Sesay C.,University of the Gambia | Chien L.-Y.,National Yang Ming University
African Journal of AIDS Research | Year: 2012

Knowing one's HIV status is fundamental to the prevention and treatment of HIV and AIDS. However, HIV prevention is defeated if individuals who opt to be tested fail to return for their test result. Despite the burden of HIV and AIDS in sub-Saharan Africa, regional studies on failure to return (FTR) for an HIV-test result are lacking. We investigated the factors associated with FTR in The Gambia, West Africa. FTR was analysed for 1 755 persons who attended an outpatient clinic during 2000 to 2009. Overall, the proportion of FTR was 30%. Logistic regression showed that FTR was significantly higher among males, individuals whose nationality was not Gambian, individuals with a history of condom use, and individuals who resided in an urban area. Persons who were younger than age 18 years and persons who had received some formal education were more likely to not return for the HIV-test result than were persons aged 40 years or older and persons without formal schooling. The results provide evidence for the need for appropriate strategies to increase the receipt of HIV-test results among people in the general population and among certain group profiles. © NISC (Pty) Ltd.

Sanyang M.L.,University of Birmingham | Sanyang M.L.,University of the Gambia | Kaban A.,University of Birmingham
2015 IEEE Congress on Evolutionary Computation, CEC 2015 - Proceedings | Year: 2015

In this paper, we present a new variant of EDA for high dimensional continuous optimisation, which extends a recently proposed random projections (RP) ensemble based approach by employing heavy tailed random matrices. In particular, we use random matrices with i.i.d. t-distributed entries. The use of t-distributions may look surprising in the context of random projections, however we show that the resulting ensemble covariance is enlarged when the degree of freedom parameter is lowered. Based on this observation, we develop an adaptive scheme to adjust this parameter during evolution, and this results in a flexible means of balancing exploration and exploitation of the search process. A comprehensive set of experiments on high dimensional benchmark functions demonstrate the usefulness of our approach. © 2015 IEEE.

Fan S.-K.S.,National Taipei University of Technology | Chang Y.-J.,Yuan Ze University | Aidara N.,University of the Gambia
Quality and Reliability Engineering International | Year: 2013

In most statistical process control (SPC) applications, it is often assumed that the quality of a process or product can be adequately represented by the distribution of a univariate quality characteristic. However, in some particular situations, the quality-related response of interest is not a single variable but a function of some independent variables. Such a functional relationship is called a profile. Recently, profile monitoring has drawn considerable attention in the statistical process control literature. This article proposes a new approach for the reflow process data, which applies the sum of sine functions to model the nonlinear profiles and then the vector of parameter estimates is monitored using the Hotelling T2 and metric control charts. Through an actual data set of the reflow process, the proposed approach is compared with the polynomial regression approach in phase I and phase II analyses. The experimental results show that the proposed approach demonstrates good abilities to detect outlying profiles in phase I and provides better out-of-control average run length performances than the polynomial regression approach in phase II. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.

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