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Caballero-Morales S.-O.,Technological University of Mixteca
Mathematical Problems in Engineering

Shewhart or control charts are important Statistical Process Control (SPC) techniques used for prompt detection of failures in a manufacturing process and minimization of production costs which are modelled with nonlinear functions (cost functions). Heuristic methods have been used to find the chart's parameters integrated within the cost function that best comply with economic and statistical restrictions. However heuristic estimation is highly dependent on the size of the search space, the set of initial solutions, and the exploration operators. In this paper the 3D analysis of the cost function is presented to more accurately identify the search space associated with each parameter of X ¯ control charts and to improve estimation. The parameters estimated with this approach were more accurate than those estimated with Hooke and Jeeves (HJ) and Genetic Algorithms (GAs) under different failure distributions. The results presented in this work can be used as a benchmark to evaluate and improve the performance of other heuristic methods. © 2014 Santiago-Omar Caballero-Morales. Source

Caballero-Morales S.-O.,Technological University of Mixteca
The Scientific World Journal

An approach for the recognition of emotions in speech is presented. The target language is Mexican Spanish, and for this purpose a speech database was created. The approach consists in the phoneme acoustic modelling of emotion-specific vowels. For this, a standard phoneme-based Automatic Speech Recognition (ASR) system was built with Hidden Markov Models (HMMs), where different phoneme HMMs were built for the consonants and emotion-specific vowels associated with four emotional states (anger, happiness, neutral, sadness). Then, estimation of the emotional state from a spoken sentence is performed by counting the number of emotion-specific vowels found in the ASR's output for the sentence. With this approach, accuracy of 87-100% was achieved for the recognition of emotional state of Mexican Spanish speech. © 2013 Santiago-Omar Caballero-Morales. Source

The application of Preventive Maintenance (PM) and Statistical Process Control (SPC) are important practices to achieve high product quality, small frequency of failures, and cost reduction in a production process. However there are some points that have not been explored in depth about its joint application. First, most SPC is performed with the X-bar control chart which does not fully consider the variability of the production process. Second, many studies of design of control charts consider just the economic aspect while statistical restrictions must be considered to achieve charts with low probabilities of false detection of failures. Third, the effect of PM on processes with different failure probability distributions has not been studied. Hence, this paper covers these points, presenting the Economic Statistical Design (ESD) of joint X-bar-S control charts with a cost model that integrates PM with general failure distribution. Experiments showed statistically significant reductions in costs when PM is performed on processes with high failure rates and reductions in the sampling frequency of units for testing under SPC. © 2013 Caballero Morales. Source

Caballero-Morales S.-O.,Technological University of Mixteca
The Scientific World Journal

The Mixtec language is one of the main native languages in Mexico. In general, due to urbanization, discrimination, and limited attempts to promote the culture, the native languages are disappearing. Most of the information available about the Mixtec language is in written form as in dictionaries which, although including examples about how to pronounce the Mixtec words, are not as reliable as listening to the correct pronunciation from a native speaker. Formal acoustic resources, as speech corpora, are almost non-existent for the Mixtec, and no speech technologies are known to have been developed for it. This paper presents the development of the following resources for the Mixtec language: (1) a speech database of traditional narratives of the Mixtec culture spoken by a native speaker (labelled at the phonetic and orthographic levels by means of spectral analysis) and (2) a native speaker-adaptive automatic speech recognition (ASR) system (trained with the speech database) integrated with a Mixtec-to-Spanish/Spanish-to-Mixtec text translator. The speech database, although small and limited to a single variant, was reliable enough to build the multiuser speech application which presented a mean recognition/translation performance up to 94.36% in experiments with non-native speakers (the target users). © 2013 Santiago-Omar Caballero-Morales. Source

Castillo-Torres J.,Technological University of Mixteca
Optics Communications

Direct and indirect transition energies near the optical absorption band edge for lithium niobate crystals doped with zinc at several concentrations have been obtained. These energy values are larger than those corresponding to undoped lithium niobate even when zinc concentration is above the optical damage threshold value. For any zinc concentration, 4.0 eV was measured for direct transition energy and a range of 3.8-3.9 eV was determined for indirect transition energy; whereas 3.8 and 3.6 eV were obtained, respectively, for the corresponding values of pure lithium niobate. In addition, phonon and Urbach energies were also calculated where these values are lesser than those of pure lithium niobate. Both behaviors remain unchanged regardless of whether the zinc concentration is above or below the optical damage critical value. Substitution of only lithium vacancies and antisite defects by zinc atoms for any concentration of doping may explain the results. © 2012 Elsevier B.V. All rights reserved. Source

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