Scielo RSS <![CDATA[Computación y Sistemas]]> http://www.scielo.org.mx/rss.php?pid=1405-554620150001&lang=en vol. 19 num. 1 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.mx/img/en/fbpelogp.gif http://www.scielo.org.mx <![CDATA[<b>Editorial</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100001&lng=en&nrm=iso&tlng=en <![CDATA[<b>A Scatter Search Algorithm for Solving a Bilevel Optimization Model</b> <b>for Determining Highway Tolls</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100002&lng=en&nrm=iso&tlng=en The problem of determining optimal tolls established on a subset of arcs in a multicommodity capacitated transportation network is presented. The problem is formulated as a bilevel optimization problem where the upper level consists of an administrator who establishes tolls in some arcs of a network, while the lower level is represented by a group of users who travel along the shortest paths with respect to the travel cost. The objective is not only to increase the tolls, but also to maintain an optimal flow on the arcs of the network in order to maximize the leader's profit. If the leader sets very high toll values, the followers will be discouraged from using the tolled arcs, so the profit obtained from that decision is not going to be convenient for the leader. A methodology to solve this problem using optimization software at the lower level and the metaheuristic Scatter Search at the upper level is proposed. <![CDATA[<b>Finding Pure Nash Equilibrium for the Resource-Constrained Project Scheduling Problem</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100003&lng=en&nrm=iso&tlng=en The paper focuses on solving the Resource-Constrained Project Scheduling (RCPS) problem with a method based on intelligent agents. Parallelism for performing the tasks is allowed. Common and limited resources are available to all agents. The agents are non-cooperative and compete with each other for the use of common resources, thereby forming instances of RCPS problem. We analyze the global joint interaction of scheduling via a congestion network and seek to arrive at stable assignments of scheduling. For this class of network, stable assignments of scheduling correspond to a pure Nash equilibrium, and we show that in this case there is a guarantee of obtaining a pure Nash equilibrium in polynomial time complexity. The pure Nash equilibrium point for this congestion network will be a local optimum in the neighborhood structure of the projects, where no project can improve its completion time without negatively affecting the completion time of the total system. In our case, each state of the neighborhood represents an instance of the RCPS problem, and for solving such problem, we apply a novel greedy heuristic. It has a polynomial time complexity and works similar to the well-knowing heuristic NEH. <![CDATA[<b>Saving Time for Object Finding with a Mobile Manipulator Robot in</b> <b>3D Environment</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100004&lng=en&nrm=iso&tlng=en In this paper, we address the problem of reducing the time for finding an object. We consider both the time taken by our software to generate a search plan and the expected time to find the object when the plan is executed. The object is sought with a 7 degree of freedom mobile manipulator robot with an "eye-in-hand" sensor. The sensor is limited in both range and field of view. We propose two main strategies: 1) to coordinate the motion of robot's degrees of freedom optimizing only those most relevant for the task, and 2) to repair a previously computed plan whenever the environment changes locally. We have implemented all our algorithms and present simulation results in realistic environments. <![CDATA[<b>Randomized Algorithm based on Sliding Distributions for the Scheduling Problem in Grid Systems</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100005&lng=en&nrm=iso&tlng=en En este artículo se presenta un algoritmo aleatorizado para el problema de planificación de tareas compuestas por procesos con restricciones de precedencia en ambientes distribuidos tipo Grid. El algoritmo aleatorizado propuesto esta basado en una nueva técnica que hemos denominado como de distribuciones deslizantes, la cual busca combinar las ventajas de los algoritmos de aproximación deterministas y de los algoritmos aleatorizados tipo Montecarlo. El objetivo es proveer un algoritmo que con alta probabilidad entregue soluciones p-aproximadas, pero que al mismo tiempo tenga la capacidad de analizar el vecindario extendido de dichas soluciones para escapar de máximos o mínimos locales. En el artículo se demuestra que el algoritmo propuesto es correcto y se caracteriza de manera formal su complejidad temporal. Así mismo, se evalúa el desempeño del algoritmo por medio de una serie de experimentos basados en simulaciones. Los experimentos muestran que el algoritmo propuesto logra en general un desempeño superior al de los algoritmos que componen el estado del arte en planificación en sistemas Grid. Las métricas de desempeño utilizadas son retardo promedio, retardo máximo y utilización de la Grid.<hr/>In this paper we present a randomized algorithm for the online version of the Job Shop problem where jobs are composed of processes with precedence constraints and processors are organized in a Grid topology. The proposed randomized algorithm is based on a new technique that we have denominated as sliding distributions, which aims at combining the advantages of the deterministic approximation algorithms with those of the Montecarlo randomized algorithms. The objective is to provide an algorithm that delivers p-approximated solutions with high probability, but at the same time, is able to investigate an extended neighborhood of such solutions so that it can escape from local extrema. We formally characterize the temporal complexity of the proposed algorithm and show that it is correct. We also evaluate the performance of the proposed algorithm by means of a series of simulation-based experiments. The results show that the proposed algorithm outperforms the traditional state of the art algorithms for scheduling in Grid systems. The performance metrics are average delay, maximum delay, and Grid utilization. <![CDATA[<b>Classification of Encephalographic Signals using Artificial Neural Networks</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100006&lng=en&nrm=iso&tlng=en Para la clasificación de las señales del parpadeo y dolor muscular en el brazo derecho ocasionado por un agente externo, se proponen dos modelos de arquitecturas de redes neuronales artificiales, específicamente del tipo perceptron multicapa y sistema de inferencia neurodifuso adaptativo, ambos modelos utilizan aprendizaje supervisado. Se utilizan series de tiempo obtenidas del parpadeo y electroencefalografías de 15 personas en el rango de 23 a 25 años de edad, para generar una base de datos que se divide en dos conjuntos de datos: entrenamiento y prueba. Los resultados experimentales en el dominio del tiempo y de la frecuencia, de 50 pruebas aplicadas a cada modelo de red, muestran que ambas propuestas de arquitecturas de redes neuronales producen resultados exitosos.<hr/>For the signal classification of eye blinking and muscular pain in the right arm caused by an external agent, two models of artificial neural network architectures are proposed, specifically, the perceptron multilayer and an adaptive neurofuzzy inference system. Both models use supervised learning. The ocular and electroencephalographic time-series of 15 people in the range of 23 to 25 years of age are used to generate a data base which was divided into two sets: a training set and a test set. Experimental results in the time and frequency domain of 50 tests applied to each model show that both neural network architecture proposals for classification produce successful results. <![CDATA[<b>Pattern Recognition System Based on Data Mining for Analysis of Chemical Substances in Brain</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100007&lng=en&nrm=iso&tlng=en En este trabajo se presenta un Sistema de Minería de Datos para interpretar los cambios bioquímicos que ocurren en los cerebros de los roedores. El análisis manual de tales experimentos es impráctico debido a la naturaleza voluminosa de los datos que son generados y la naturaleza tediosa del análisis de su significado, por lo que información importante se pierde. Por esta razón, se ha diseñado un Sistema de Minería de Datos el cual contiene varios pasos (pre-procesamiento de los datos, clasificación de la información recolectada, etc.), y utiliza la Red Neuronal Artificial basada en la Teoría de Resonancia Adaptativa en la realización de algunos de ellos. En este artículo se describe el Sistema, y se prueba su funcionamiento estudiando los neurotransmisores glutámato y aspartato de muestras extraídas del cerebro de roedores.<hr/>This paper presents a data mining system for analyzing biochemical changes in the brain of rodents. Manual analysis of such experiments is impractical due to a huge volume of generated data and tedious analytical procedures; as a result, important information is lost. Addressing this issue, our paper proposes a data mining system consisting of several steps (preprocessing, data classification, etc.). In some of the steps we apply the artificial neural network based on the adaptive resonance theory. This paper describes the proposed system and experiments performed to validate it. In the experiments, glutamate and aspartate neurotransmitters in samples extracted from rodent brains were analyzed. <![CDATA[<b>An Approach for Prototype Generation based on Similarity Relations for Problems of Classification</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100008&lng=en&nrm=iso&tlng=en In this paper, a new method for solving classification problems based on prototypes is proposed. When using similarity relations for granulation of a universe, similarity classes are generated, and a prototype is constructed for each similarity class. Experimental results show that the proposed method has higher classification accuracy and a satisfactory reduction coefficient compared to other well-known methods, proving to be statistically superior in terms of classification's precision. <![CDATA[<b>Arabic Dialogue System for Hotel Reservation based on Natural Language Processing Techniques</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100009&lng=en&nrm=iso&tlng=en In this paper, we present an Arabic dialogue system (also referred to as a conversational agent) intended to interact with hotel customers and generate responses about reserving a hotel room and other services. The system uses text-based natural language dialogue to navigate customers to the desired answers. We describe the two main modules used in our system: the parser and the dialogue manager. The parser is based on the Government and Binding theory. Customers can inquire about room availability, hotel services and negotiate a desired reservation. We report an experiment with 500 volunteers unfamiliar with the system in a real environment. The users were asked to interact with the system and then to judge the dialogues as "very bad," "bad," "neutral," "good," or "very good." We found that 66.92% of the dialogues were judged to be "very good" and 92.3% were judged to be "good" or "very good". These results confirm the viability of using an Arabic dialogue system to tackle the problem of interactive Arabic dialogues. Finally, we discuss future directions for enhancing our dialogue system with more sophisticated and intuitive interaction. <![CDATA[<b>Evaluation of Ontological Relations in Corpora of Restricted Domain</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100010&lng=en&nrm=iso&tlng=en En este artículo proponemos una evaluación automática de relaciones en ontologías de dominio restringido. En particular, usamos varios patrones léxico sintácticos con la finalidad de evaluar las relaciones class-inclusion y relaciones ontológicas que contiene la ontología. Nuestro enfoque se centra en un corpus de referencia para encontrar evidencia de la validez de la relación. El enfoque es capaz de proporcionar una medida de exactitud para cada ontología evaluada, un valor asociado de alguna manera con la calidad de la relaciones de la ontología. Esta puntuación se da con cierto grado de confiabilidad, obtenida mediante la comparación de los resultados dados por el enfoque contra de la evaluación de expertos humanos y un baseline.<hr/>In this paper we propose a new approach for automatic evaluation of relations in ontologies of restricted domain. In particular, we use various lexico-syntactic patterns with the aim of evaluating the class-inclusion and ontological relations that the ontology holds. Our approach focuses on a reference corpus for finding evidence of the relation validity. The approach is capable to provide an accuracy measure for each ontology evaluated, a value associated in some way with the quality of the ontology relations. This score is given with a certain degree of reliability, and it is obtained by comparing the results given by our approach against the evaluation of human experts and a baseline. <![CDATA[<b>Clustering XML Documents Using Structure and Content based on a New Similarity Function OverallSimSUX</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100011&lng=en&nrm=iso&tlng=en Every day more digital data in semi-structured format are available on the World Wide Web, corporate intranets, and other media. Knowledge management using information search and processing is essential in the field of academic writing. This task becomes increasingly complex and defiant, mainly because collections of documents are usually heterogeneous, big, diverse, and dynamic. To resolve these challenges it is essential to improve management of time necessary to process scientific information. In this paper, we propose a new method of automatic clustering of XML documents based on their content and structure, as well as on a new similarity function OverallSimSUX which facilitates capturing the degree of similarity among documents. Evaluation of our proposal by means of experiments with data sets showed better results than those in previous work. <![CDATA[<b>AGIS</b>: <b>Towards an ISO9001 based Tool for Measuring Agility</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100012&lng=en&nrm=iso&tlng=en La norma ISO 9001:2008 es quizás el modelo de mejora de procesos más adoptado en el mundo. ISO 9001:2008 es un estándar de propósito general (para industrias manufactureras y empresas de servicios), que sienta las bases para la mejora de los procesos. También ha sido ampliamente adoptado en la industria de software. Por otro lado, las metodologías ágiles de desarrollo también están creciendo en adopción y popularidad. Aparentemente en oposición a los modelos formales de mejora, las metodologías ágiles sostienen la interacción entre las personas por sobre el seguimiento de los procesos. Sin embargo, ambos enfoques tienen el mismo problema, muchos sujetos claman éxitos en términos de certificación o agilidad, pero no pueden demostrarlo con datos reales. Por un lado, por ser de propósito general, una certificación ISO 9001:2008 es relativamente alcanzable. Y al mismo tiempo, malas interpretaciones del manifiesto ágil hacen que existan muchos equipos que se autodenominan ágiles sin seguir todos los valores del manifiesto. Este artículo presenta una herramienta que basada en los principios de mejora y auditoria de ISO 9001:2008. Esta herramienta es capaz de medir el grado de agilidad de un proceso de acuerdo a los valores del manifiesto ágil. El propósito de la misma es obtener una medida objetiva del proceso productivo que evite los falsos positivos de ambos lados.<hr/>ISO9001:2008 is probably the most widely adopted process improvement model in the world. ISO9001:2008 is a general purpose standard for service and production organizations, which established the groundwork for improving system processes in an enterprise. This standard has also been widely adopted in the software industry. On the other hand, agile development methodologies have been steadily gaining acceptance and popularity in the past decade. At a first glance, these two approaches are opposite. While agility preaches interaction above processes, ISO is a process-oriented approach to improvement. Nonetheless, both approaches share the same conundrum: both hold claims of compliance but there have been few data-backed-up success case studies. However, since ISO is a general purpose standard, its achievement is fairly attainable. In contrast, the agile development ecosystem is full of false positives that claim agility without achieving project success. This paper presents an assessment tool to measure agility based on ISO 9001:2008 process improvement principles. Our tool is capable of measuring a degree of agility aligned with the agile manifesto values. Its goal is to provide an objective measurement of agility that avoids false positives on both sides. <![CDATA[<b>Times of Execution of the Quantum NOT Gate Operating on One of Two Interacting Qubits</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100013&lng=en&nrm=iso&tlng=en It is generally believed that entanglement speeds up Quantum Information Processing (QIP). However, we prove that for a system of two interacting qubits through a XXZ Hamiltonian which are maximally entangled it is not possible to execute a quantum NOT gate operating on one of these two qubits. The interaction between the two qubits means presence of noise in one of them. If the two interacting qubits are not entangled, the times of execution of the quantum NOT gate operating on one of the two qubits are not small enough. Since the times of execution of the quantum NOT gate operating on one of the two interacting qubits is extremely large, we conclude that the execution of the quantum NOT gate operating on one of two interacting qubits is not possible. <![CDATA[<b>FPGA-Based Emulation of a Synchronous Phase-Coded Quantum Cryptography System</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100014&lng=en&nrm=iso&tlng=en We present FPGA-based emulation of a synchronous phase-coded quantum cryptography system. Several of the emulated subsystems are used for implementation in a free space demonstrative QPSK scheme for quantum key distribution with continuous variables (CV-QKD) using a base and optical phase synchronization. The CV-QKD systems are commonly implemented using QPSK modulation with switched or simultaneous detection. In this paper we only make use of one base of the QPSK system in order to get a simpler modulation (BPSK) scheme, used for demonstrative purposes. The reported results from the emulation and the experiment in terms of Quantum Bit Error Rate (QBER) and mutual information for different values of the number of photons per bit are in good agreement. <![CDATA[<b>Disturbance Rejection Using SPR0 Substitutions</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-55462015000100015&lng=en&nrm=iso&tlng=en The disturbance rejection, defined as the problem of designing control laws that ensure, where possible, exogenous disturbances that do not affect the output of the perturbed system, has been resolved by means of algebraic and geometric techniques. This is a steady linear case by means of the static feedback state. Modifications of the Smith form through the SPR0 substitutions are presented which guarantees infinite zeros of a linear single input, single output (SISO) system.