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Martinez J.B.,Polytechnic University Jose Antonio Echeverria
Journal of Hydroinformatics | Year: 2011

Optimization of water supply looped networks has attracted a great deal of attention from researchers for more than 30 years. As the classical water supply looped network optimization problem is mathematically non-convex and multimodal, the resulting solution of most approaches is uncertain in the sense of how close it is to the "best" solution. In many cases, this "best"' or "global" solution is invoked and pursued only intuitively without a clear understanding of its meaning. This paper discusses what is involved in "global" solutions and the role that pipe flow distribution can play to deal with non-convexity and multimodality in a new context. The author has introduced this new context recently after formulating a new objective function capable of finding a looped network that can be economically more attractive than its related branched one. Therefore, the convenience of an approach dealing with flows and heads, as relevant decision variables, is encouraged in this paper and its advantages enumerated under the new concepts. The entropy approach is studied critically and an example is provided for comparison with the proposed approach. © WA Publishing 2011.

Optoelectronic switches based on VO2 thin films are analyzed as input-output devices (I/O) of multiple responses to stimuli of electric tension, temperature and energy of the incident electromagnetic radiation. The representations used are based on their transfer function (TF), in the space state (SS) and in the representation of poles, zeros and gain (ZPK). Starting from there, the stability, observability, controllability and frequency response of these systems are investigated, which contributes to a better understanding of the operation of these devices and their potential applications.

Martinez J.B.,Polytechnic University Jose Antonio Echeverria
Journal of Hydroinformatics | Year: 2010

A new design methodology recently introduced for looped networks is now applied to branched networks. The methodology is based on cost analysis minimisation, network mathematical simulation under normal and failure states and reliability estimates. It is capable of obtaining not only an adequate value for the global reliability of a network but also the appropiate total design demand. This paper then presents a deeper insight into the comparison between looped and branched networks by applying the methodology to both types of networks and comparing the results in terms of cost and reliability. Considerations regarding available reliability definitions are also included which seem to favor volume-type definitions in practice. Results provide a rational foundation to reveal the superiority of looped networks over comparable branched networks by applying quantitative cost evaluations. © IWA Publishing 2010 Journal of Hydroinformatics.

Nieves D.C.,University of Boras | Nieves D.C.,Polytechnic University Jose Antonio Echeverria | Karimi K.,University of Boras | Karimi K.,Isfahan University of Technology | Horvath I.S.,University of Boras
Industrial Crops and Products | Year: 2011

Oil palm empty fruit bunches (OPEFB), a waste lignocellulosic material, which is the main byproduct of vegetable oil production industries in Indonesia and Malaysia, was utilized as a source for biogas production. Pretreatments using NaOH as well as phosphoric acid were investigated to improve the biogas production. Clear positive effects of the pretreatments on the yield of methane were observed. The best improvement was achieved when 8% NaOH for 60. min was used for the pretreatment, which resulted in 100% improvement in the yield of methane production. In addition, treatment with phosphoric acid resulted in 40% improvement in the methane yield compared with that of the untreated material. The results showed that the carbohydrate content of OPEFB could be efficiently converted to methane under the anaerobic digestion process. 97% of the theoretical value of methane production was achieved after the pretreatment with NaOH for 60. min. Moreover, the initial rate of methane production was also increased by more than 85% after the treatment with NaOH compared with that of the untreated OPEFB. © 2011 Elsevier B.V.

Garcia-Borroto M.,Polytechnic University Jose Antonio Echeverria | Martinez-Trinidad J.F.,National Institute of Astrophysics, Optics and Electronics | Carrasco-Ochoa J.A.,National Institute of Astrophysics, Optics and Electronics
Expert Systems with Applications | Year: 2015

Most understandable classifiers are based on contrast patterns, which can be accurately mined from decision trees. Nevertheless, tree diversity must be ensured to mine a representative pattern collection. In this paper, we performed an experimental comparison among different diversity generation procedures. We compare diversity generated by each procedure based on the amount of total, unique, and minimal patterns extracted from the induced tree for different minimal support thresholds. This comparison, together with an accuracy and abstention experiment, shows that Random Forest and Bagging generate the most diverse and accurate pattern collection. Additionally, we study the influence of data type in the results, finding that Random Forest is best for categorical data and Bagging for numerical data. Comparison includes most known diversity generation procedures and three new deterministic procedures introduced here. These deterministic procedures outperform existing deterministic method, but are still outperformed by random procedures. © 2015 Elsevier Ltd. All rights reserved.

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