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971.
Miguel A. Olivares-Mendez Luis Mejias Pascual Campoy Ignacio Mellado-Bataller 《Journal of Intelligent and Robotic Systems》2013,69(1-4):189-205
The Cross-Entropy (CE) is an efficient method for the estimation of rare-event probabilities and combinatorial optimization. This work presents a novel approach of the CE for optimization of a Soft-Computing controller. A Fuzzy controller was designed to command an unmanned aerial system (UAS) for avoiding collision task. The only sensor used to accomplish this task was a forward camera. The CE is used to reach a near-optimal controller by modifying the scaling factors of the controller inputs. The optimization was realized using the ROS-Gazebo simulation system. In order to evaluate the optimization a big amount of tests were carried out with a real quadcopter. 相似文献
972.
The effectiveness of a layout design cannot be completely measured if the operational characteristics of the manufacturing system are ignored. There is, therefore, a need to develop integrated manufacturing system design models. In this paper, the integration of unit load and material-handling considerations in a facility layout design is presented. This integration is based on a stochastic model that captures the operational characteristics of the manufacturing system and a nonlinear mixed-integer program that incorporates a department formation and facility layout. The non-linear mixed-integer program is solved using a simulated annealing-based algorithm. Analytical results for different manufacturing system scenarios are presented and compared with results obtained using alternative QAP-type formulations. Based on our experiments and the characteristics of the different formulations, key observations are presented and discussed. 相似文献
973.
Fernando Cruz-Roldán José David Osés del Campo Juan Ignacio Godino-Llorente Luciano Boquete-Vázquez C. J. Bleakley 《Circuits, Systems, and Signal Processing》2010,29(2):169-181
It is well known that the frequency sampling approach to the design of Finite Impulse Response digital filters allows recursive
implementations which are computationally efficient when most of the frequency samples are integers, powers of 2 or null.
The design and implementation of decimation (or interpolation) filters using this approach is studied herein. Firstly, a procedure
is described which optimizes the tradeoff between the stopband energy and the deviation of the passband from the ideal filter.
The search space is limited to a small number of samples (in the transition band), imposing the condition that the resulting
filter have a large number of zeros in the stopband. Secondly, three different structures to implement the decimation (or
interpolation) filter are proposed. The implementation complexity, i.e., the number of multiplications and additions per input
sample, are derived for each structure. The results show that, without taking into account finite word-length effects, the
most efficient implementation depends on the filter length to decimation (or interpolation) ratio. 相似文献
974.
随着现代主义运动由盛而衰,建筑学中源于手工艺及机器大工业的"建造"概念被重新审视,而逐渐被"制造"所取代,"制造"与"建造"相比,其含义更复杂、多元,即不仅指向物质现实的实体塑造,还包括了意识形态的概念策划、设计策略、文本阐述等等。在这一理论框架下简介鲁本·A·阿尔克莱、罗密·赫奇·马钱特、雨果·P·萨格雷多、罗德里戈·佩雷斯·德·阿尔塞几位学者与此观念相关的研究成果。《新建筑》杂志将其所撰写的研究论文辑录为本期专栏,以期引起读者关注,并进一步对当代建筑及建筑设计的本质与意义进行批判性思考。 相似文献
975.
Lindsay S. Hernández-Muñoz Ignacio González Fabiane Caxico de Abreu Rogério Tavares Ribeiro Marcelo Navarro Carlos Frontana 《Electrochimica acta》2010,55(27):8325-9151
The effects of the position of a second nitroaromatic group (orthovs.paravs.meta) during reduction of nitrobenzenes were analysed. Cyclic voltammetric experiments in acetonitrile solution revealed that ortho-, meta- and para-dinitrobenzenes show two reversible reduction processes. An Electrochemical-Electron Spin Resonance (E-ESR) study showed that the corresponding radical anions of the ortho and para derivatives, electrogenerated during the first electron transfer uptake, remain the same even after the second monoelectronic process, increasing their intensity due to the presence of a comproportionation process (A2− + A → 2A−). For the case of the meta derivative, the electrogenerated radical anion at the first reduction peak is consumed at the second reduction step, forming a secondary radical species. During the electrochemical study of methyl 3,5-dinitrobenzoate, two successive and reversible electron processes were also observed; however, in this case, a very rare biradical dianion structure was found. The use of ESR-spectroelectrochemistry shed some light on controversial aspects of nitroaromatic reduction, especially concerning the second and further waves. These results were corroborated and interpreted with quantum chemical calculations of the molecular and electronic structures, electron affinities and spin densities. As a result, electrochemical mechanisms are presented and discussed. 相似文献
976.
Kristen Severson Mariano Martín Ignacio E. Grossmann 《American Institute of Chemical Engineers》2013,59(3):834-844
The production of biodiesel from algae is optimized using bioethanol following four different transesterification paths: alkali, enzymatic, and heterogeneous catalysts and supercritical conditions. The reactors are modeled using response surface methodology based on experimental results from the literature. These reactor models are implemented together with short‐cut methods for the other equipment (distillation columns, gravity separators, etc.) in order to recover the ethanol, separate the polar and nonpolar phases, and purify the glycerol and biodiesel produced to formulate the problem as a superstructure of alternatives. The aim is to simultaneously optimize and heat integrate the production of biodiesel using ethanol in terms of the reaction technology and the operating conditions. The optimal conditions in the reactors differ from the ones traditionally used because these results take the separation stages into account. In terms of the optimal process, the alkali catalyzed process is the most profitable, while the enzymatic one is also promising due to the lower consumption of energy and water, although it requires significant enzyme cost. © 2012 American Institute of Chemical Engineers AIChE J, 59: 834–844, 2013 相似文献
977.
Ignacio E. Grossmann Francisco Trespalacios 《American Institute of Chemical Engineers》2013,59(9):3276-3295
Discrete‐continuous optimization problems are commonly modeled in algebraic form as mixed‐integer linear or nonlinear programming models. Since these models can be formulated in different ways, leading either to solvable or nonsolvable problems, there is a need for a systematic modeling framework that provides a fundamental understanding on the nature of these models. This work presents a modeling framework, generalized disjunctive programming (GDP), which represents problems in terms of Boolean and continuous variables, allowing the representation of constraints as algebraic equations, disjunctions and logic propositions. An overview is provided of major research results that have emerged in this area. Basic concepts are emphasized as well as the major classes of formulations that can be derived. These are illustrated with a number of examples in the area of process systems engineering. As will be shown, GDP provides a structured way for systematically deriving mixed‐integer optimization models that exhibit strong continuous relaxations, which often translates into shorter computational times. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3276–3295, 2013 相似文献
978.
Miguel Sánchez-Soto Maria Lluisa Maspoch Jose Ignacio Velasco 《Polymer-Plastics Technology and Engineering》2013,52(1):16-23
The rejected fraction of plastics from different sorting plants has been studied in terms of composition, processability and enhancement potential. This waste stream consists of a coarse range of plastics families, polyethylene constituting the most abundant one. Blends with two recycled polyethylenes in different proportions were analyzed. The results showed that the mixed fraction was easy to process although it showed a brittle behavior. The addition of recycled polyethylene caused limited ductility improvements, although acceptable levels were achieved in certain mixing ratios. This work demonstrates that mixed plastic wastes can be transformed into a useful material. 相似文献
979.
Paola Checconi Rossella Sgarbanti Ignacio Celestino Dolores Limongi Donatella Amatore Alessandra Iuvara Alessandro Alimonti Enrico Garaci Anna Teresa Palamara Lucia Nencioni 《International journal of molecular sciences》2013,14(2):4148-4162
Cadmium (Cd) is a toxic heavy metal that is considered an environmental contaminant. Several sources of human exposure to Cd, including employment in primary metal industries, production of certain batteries, foods, soil and cigarette smoke, are known. Its inhalation has been related to different respiratory diseases and toxic effects, among which alterations of the physiological redox state in individuals exposed to the metal have been described. Host-cell redox changes characteristic of oxidative stress facilitate the progression of viral infection through different mechanisms. In this paper, we have demonstrated that pre-treatment with CdCl2 of MDCK cells increased influenza virus replication in a dose-dependent manner. This phenomenon was related to increased viral protein expression (about 40% compared with untreated cells). The concentration of CdCl2, able to raise the virus titer, also induced oxidative stress. The addition of two antioxidants, a glutathione (GSH) derivative or the GSH precursor, N-acetyl-l-cysteine, to Cd pre-treated and infected cells restored the intracellular redox state and significantly inhibited viral replication. In conclusion, our data demonstrate that Cd-induced oxidative stress directly increases the ability of influenza virus to replicate in the host-cell, thus suggesting that exposure to heavy metals, such as this, could be a risk factor for individuals exposed to a greater extent to the contaminant, resulting in increased severity of virus-induced respiratory diseases. 相似文献
980.
José Ignacio Recio-Rodríguez Manuel A Gómez-Marcos María C Patino-Alonso Cristina Agudo-Conde Emiliano Rodríguez-Sánchez Luis García-Ortiz 《Nutrition journal》2012,11(1):1-5