Scielo RSS <![CDATA[Journal of applied research and technology]]> http://www.scielo.org.mx/rss.php?pid=1665-642320140004&lang=es vol. 12 num. 4 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.mx/img/en/fbpelogp.gif http://www.scielo.org.mx <![CDATA[<b>A Study of Different Subsequence Elimination Strategies for the Soft Drink Production Planning</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400001&lng=es&nrm=iso&tlng=es The production of soft drinks involves two main stages: syrup preparation and bottling. To obtain the lots sequence in the bottling stage, three approaches are studied. They are based on the sub-tour elimination constraints used in mathematical models for the Asymmetric Traveling Salesman Problem. Two of the mathematical models are from the literature and use classical constraints. The third model includes multi-commodity flow constraints to eliminate disconnected subsequences. The computational behavior of the three models is studied using instances generated with data from the literature. The numerical results show that there are considerable differences among the three models and indicates that the multi-commodity formulation provides good results but it requires far more computational effort when the instances are solved by a commercial software. <![CDATA[<b>Assessing the Value of Delay to Short-Haul Carriers</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400002&lng=es&nrm=iso&tlng=es This paper aims at examining the commercial vehicle operators' value of delay (VOD) due to highway congestion in urban area. The VOD is a fundamental parameter that influences the private sector's response to public freight projects and policies. This paper adopts two methods to estimate the VOD; one being the stated preference (SP) survey and the other being simulation of a carrier's fleet operations. The former applies a Logit model and estimates a driver perceived VOD as $56.48 per vehicle per hour for the regular short-haul delivers. The latter gauges the economic impact of delay on carrier's fleet operations in the Houston highway network. The operations essentially reflect more of a just-in-time system due to the rather stringent time window constraints. The simulation is conducted on a rolling time horizon with a heuristic algorithm for dispatching trucks. The major findings include, but are not limited to as follows. The drivers paid by miles perceive a significantly higher VOD than the others; the drivers are more willing to pay for a faster trip when the toll charges do not come out of their own pockets; VOD increases with uncertainty and demand for capacity. The comparison between the survey and the simulation results also indicates that the interviewed drivers perceive a significantly lower VOD than they may actually experience as a fleet, an indicator of myopic vision. <![CDATA[<b>Efficient Frontier for Multi-Objective Stochastic Transportation Networks in International Market of Perishable Goods</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400003&lng=es&nrm=iso&tlng=es Effective planning of a transportation network influences tactical and operational activities and has a great impact on business. Planning typically considers multiple aspects such as variable transportation costs, various levels of customer service offered, security of goods, and traveling time. These aspects often vary with time. Although the minimum cost flow problem is a widely seen approach to configure a transportation network, there is no much work considering variations on arcs; even more, the problem with varying nodes has hardly been addressed. In this work is developed a mathematical model for the multi-objective minimum cost flow problem, applied in networks with varying attributes on arcs. The model finds the set of non-dominated solutions for a multi-objective stochastic network having variations in attributes of its arcs and nodes, such as cost or transportation time. A modified version of the two-stage method was used to address the stochastic nature of the problem combined with the epsilon-constraint method, which is used for building the set of non-dominated solutions. This paper presents the main features of the model, the theoretical bases and a computational implementation. Experiments were applied in a transport network for the exportation market of ornamental flowers as perishable goods from Mexico to the United States, which considered variations in border crossing times.<hr/>Una planeación eficaz de una red de transporte tiene un gran impacto en las empresas, al considerar múltiples aspectos como costos de transporte, seguridad de las mercancías, tiempo de viaje y demás niveles de servicio ofrecidos. Atributos que frecuentemente varían con el tiempo. Aunque el problema de flujo a costo mínimo (MCF) ha sido ampliamente visto para configurar redes de transporte, no hay muchos trabajos que consideren variaciones en los arcos. En este trabajo se desarrolla un modelo matemático para el problema MCF multi-objetivo, aplicado en redes con atributos variantes en los arcos. El modelo encuentra la Frontera Pareto para una red estocástica con variaciones en los atributos de costo o tiempo de transporte. Para enfrentar la naturaleza estocástica del problema se utiliza Descomposición de Benders para el problema estocástico de dos etapas, posteriormente se conjunta con el método £-restricción, que es utilizado para la construcción del conjunto de soluciones no dominadas. Este artículo presenta las principales características del modelo, las bases teóricas y una implementación computacional. Los experimentos fueron aplicados en una red de transporte para el mercado de exportación de flores ornamentales como productos perecederos desde México a Estados Unidos, considerando las variaciones en los tiempos de cruce de fronteras. <![CDATA[<b>Supply Chain Strategies for the International Interoceanic Mazatlan-Houston Logistic Corridor</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400004&lng=es&nrm=iso&tlng=es Describe the interoceanic Mazatlan-Houston Logistic Corridor (MHLC) as an alternative route to create sustainable competitive advantages for Mexican, USA, and international firms competing in an international marketplace. Taking into account the competitive advantages of utilizing this corridor for international trade, we analyze supply chain strategies for Mexican and international companies demanding economical logistic solutions in this region. It was found that the MHLC benefits efficient industry segments with demand well known in advance. It was also found that the potential of both inbound and outbound container traffic to the Asia-Pacific marketplace along this international commerce corridor fluctuates between 39,000 and 761,000 TEU'S.<hr/>El corredor logístico interoceánico Mazatlán-Houston (MHLC) se describe como una ruta alterna para crear ventajas competitivas sustentables para empresas mexicanas, estadounidenses, o internacionales que compitan en el mercado global. Considerando las ventajas competitivas al utilizar este corredor para comercio internacional, se analizan diversas estrategias de cadenas de distribución para empresas internacionales y mexicanas que demanden soluciones logísticas económicas en esta región. Se encontró que el MHLC beneficia segmentos industriales eficientes con demandas conocidas con anticipación. También, se encontró que el tráfico potencial de contenedores de importaciones y exportaciones para el mercado Asia-Pacífico en este corredor comercial internacional fluctúa ente 39,000 y 761,000 unidades equivalentes de veinte-pies. <![CDATA[<b>Determination of Network Configuration Considering Inventory Cost in a Supply Chain</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400005&lng=es&nrm=iso&tlng=es In this paper we show the importance of applying mathematical optimization when designing the distribution network in a supply chain, specifically in making decisions related location of facilities and inventory management, which are associated with different levels of planning but are closely related. The addressed problem is an extension of the classic capacitated facility location problem. The distinguishing features are: the inventory management, the presence of multiple plants, and the single source constraints in both echelons. A key issue is that demand at each distribution center is a function of the demands at the retailers assigned, which is a random variable whose value is not known at the time of designing the network. We focus on the mathematical modeling of the problem and the evaluation of the performance of the developed models, so, it can be observed the troubles that arise when modeling supply chains that consider different types of decisions.<hr/>En este artículo se muestra la importancia de la optimización matemática en el diseño de una cadena de suministros, específicamente en la toma de decisiones dentro de un problema de localización de instalaciones y un problema de inventarios. Dichas decisiones pertenecen a diferentes niveles de planeación aun así se encuentran estrechamente relacionadas. El problema es una extensión del clásico problema de localización de instalaciones capacitadas. Las características destacadas son: el manejo de inventarios, la presencia de múltiples plantas y las restricciones de única fuente en ambos niveles de la cadena. Un punto clave en la investigación consiste en definir la demanda de los centros de distribución como función de la demanda de los minoristas asignados, la cual es una variable aleatoria, cuyo valor es desconocido al momento de diseñar la red de distribución. Nos enfocamos en la modelación matemática del problema y en la evaluación del desempeño de los modelos desarrollados, de manera que es posible observar la dificultad que involucra modelar cadenas de suministros que consideran diferentes tipos de decisiones. <![CDATA[<b>Supply Chain Disruptions Propagation Caused by Criminal Acts</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400006&lng=es&nrm=iso&tlng=es To understand disruptions and their propagation along the supply chains is becoming critical for designing competitive global supply chains operating in emerging economies. It leads to economic damages to every organization involved in a supply chain, but it also decreases national logistics competitiveness. This research provides numerical elements in terms of significance of the security issue in Latin America, and at the same time, proposes a system dynamics assessment model based on real-life information, able to establish analysis scenarios in order to measure the impacts derived of supply chain disruptions propagation caused by criminal acts. Finally, useful conclusions for designing more resilient supply chains and future research are exposed.<hr/>Entender las disrupciones y su propagación a lo largo de las cadenas de suministro se ha vuelto crítico para el diseño de cadenas de suministro globales operando en economías emergentes. Esto no solo implican pérdidas económicas a cualquier organización involucrada en una cadena de suministro, sino que además disminuye la competitividad logística nacional. Este trabajo provee elementos numéricos de la importancia de la seguridad en América Latina y al mismo tiempo, propone un modelo de evaluación desde la metodología de dinámica de sistemas con base en información real, capaz de establecer escenarios para medir los impactos relacionados de la propagación de interrupciones en la cadena de suministro causados por actos criminales. Finalmente, se presentan conclusiones para el diseño de cadenas de suministro más resilientes, así como propuestas de investigación futura. <![CDATA[<b>Order Variability Decomposition: A New Variability Measure on Real Data</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400007&lng=es&nrm=iso&tlng=es It has been shown that, at least in simulated scenarios of variability decomposition in size and frequency, the way these components are measured largely determines the shape of their relationships. This study aims to build on this specific finding and tests how these measures of variability components behave on real data. Moreover, getting advantage of the type of available data, several models are setup to assess amplification on such variability components, and to evaluate the impact of the product type on both: amplification and component variability behaviors. We do this by performing model assessment with the traditional un-weighted C.V. measure, and then replicating the same evaluation with the recently proposed ADV measure.<hr/>Se ha demostrado que, al menos en escenarios simulados de descomposición de variabilidad, en tamaño y frecuencia, la manera en que se miden estos componentes determina en gran medida la forma de sus relaciones. Este estudio tiene como objetivo construir en este descubrimiento específico y evalúa cómo estas medidas de los componentes de variabilidad se comportan con datos reales. Además, aprovechando el tipo de información disponible, varios modelos son configurados para evaluar amplificación en dichos componentes de variabilidad, y analizar el impacto del tipo de producto en la amplificación y los comportamientos de variabilidad de los mencionados componentes. Hacemos esto mediante análisis de modelos utilizando la medida tradicional C.V. no-ponderado, y luego replicar la misma evaluación con la medida ADV propuesta recientemente. <![CDATA[<b>Two-Phase Decision Support Methodology for Design and Planning an Outcome-Driven Supply Chain</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400008&lng=es&nrm=iso&tlng=es Nowadays, Supply Chain success and competitiveness heavily depend on the integration of its components and adaptability to deal with a changing environment. This article suggests the integration of design and management of a Supply Chain from an outcome-driven perspective. We propose a two-phase decision-making support methodology: first suppliers are pre-screened by solving a multi criteria sorting problem, and then a design and management plan is generated by solving a Mixed Integer Linear Programming Model. Experimentally we showed that the proposed methodology can efficiently solve to optimality the most popular benchmark instances published in previous paper moreover our model also includes problem characteristics that have not been addressed together in previous published papers.<hr/>Actualmente, el éxito y competitividad de las cadenas de suministro depende en gran medida de la integración de sus componentes y la capacidad de adaptación a los cambios que se presenten. En este artículo se propone la integración del diseño y planeación de la cadena de suministro desde una perspectiva dirigida a resultados. Se propone una metodología de apoyo a la decisión de dos fases: en la primera fase de preselección los proveedores son pre-seleccionados resolviendo un problema de ordenamiento y en la segunda fase de diseño y planeación un modelo lineal entero mixto es resuelto. Experimentalmente se muestra que la metodología propuesta puede resolver de manera óptima instancias publicadas en artículos previos, por otra parte nuestro modelo incluye características que no han tratado en conjunto en los trabajos publicados anteriormente. <![CDATA[<b>Approximate Packing Circles in a Rectangular Container: Valid Inequalities and Nesting</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400009&lng=es&nrm=iso&tlng=es A problem of packing a limited number of unequal circles in a fixed size rectangular container is considered. The aim is to maximize the (weighted) number of circles placed into the container or minimize the waste. This problem has numerous applications in logistics, including production and packing for the textile, apparel, naval, automobile, aerospace and food industries. Frequently the problem is formulated as a nonconvex continuous optimization problem which is solved by heuristic techniques combined with the local search procedures. A new formulation is proposed based on using a regular grid approximated the container and considering the nodes of the grid as potential positions for assigning centers of the circles. The packing problem is then stated as a large scale linear 0-1 optimization problem. The binary variables represent the assignment of centers to the nodes of the grid. The resulting binary problem is then solved by the commercial software. Two families of valid inequalities are proposed to strengthening the formulation. Nesting circles inside one another is also considered. Numerical results are presented to demonstrate the efficiency of the proposed approach.<hr/>Se considera el problema de empaquetar un número limitado de círculos de radios diferentes en un contenedor rectangular de dimensiones fijas. El objetivo es maximizar el número (ponderado) de círculos dentro del contenedor o minimizar el desperdicio de espacio dentro del mismo. Este problema tiene numerosas aplicaciones dentro de la logística, incluyendo la producción y empaquetado para la industria textil, naval, automotriz, aeroespacial y la industria de alimentos. Frecuentemente, el problema es formulado como un problema de optimización continua no convexo que es resuelto con técnicas heurísticas combinadas con procedimientos de búsqueda local. Se propone una nueva formulación basada en el uso de una malla regular que cubre el contenedor y donde se considera a los nodos de la malla como posiciones potenciales para la asignación de centros de los círculos. El problema de empaquetamiento se escribe entonces, como un problema de optimización 0-1 a gran escala y es resuelto con software comercial. Resultados numéricos son presentados para demostrar la eficiencia del enfoque propuesto y realizar una comparación con los resultados conocidos. <![CDATA[<b>Dynamic Evaluation of Production Policies: Improving the Coordination of an Ethanol Supply Chain</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400010&lng=es&nrm=iso&tlng=es This paper uses System Dynamics modeling and process simulation to explore coordination in two logistic processes (procurement and production) of the supply chain of an ethanol plant. In that sense, three production scenarios are evaluated to identify: a) stock movement according to current inventory policies, and b) the critical variables affecting the coordination for these two processes. Since the main goal in the company is to meet customer demand, this research incorporates sales forecasting, and four performance indicators to evaluate the state of the processes: 1) average percentage of demand satisfaction, 2) maximum amount of ethanol in excess, 3) available ethanol at the end of the year, and 4) inventory costs. To model the case study, the change in production yield and specific constraints for the chain are considered. The simulation results show that System Dynamics modeling can be used to observe the effects of policies on inventory, and meeting the demand in a real system. It also can define the coordination for a supply chain and give information to improve it. The developed model uses STELLA® software to simulate the logistic processes and execute the evaluation employing the performance indicators.<hr/>Haciendo uso del modelado en Dinámica de Sistemas y simulación, se explora la coordinación de dos procesos logísticos (aprovisionamiento y producción) de la cadena de suministro de una alcoholera. En este sentido, la evaluación de tres escenarios de producción permite identificar: a) el movimiento del inventario de acuerdo a las políticas actuales de inventario, y b) las variables críticas que afectan la coordinación de estos dos procesos. Dado que el objetivo principal de la empresa es satisfacer la demanda del cliente, se incorpora un pronóstico de ventas, y cuatro indicadores de desempeño para evaluar el estado de los procesos: 1) el porcentaje promedio de la satisfacción de la demanda, 2) la cantidad máxima de etanol en exceso, 3) el etanol a disponer al finalizar el año, y 4) los costos de inventario. Para modelar el caso de estudio, se considera el cambio en el rendimiento de producción y las restricciones particulares de la cadena. Los resultados de la simulación muestran que la Dinámica de Sistemas puede utilizarse para observar los efectos de las políticas sobre el inventario, y la satisfacción de la demanda en un sistema real, igualmente, permite definir la coordinación para una cadena de suministro y proporcionar información para mejorarla. El modelo creado utiliza el software STELLA® para simular los procesos logísticos y para realizar la evaluación utilizando los indicadores de desempeño. <![CDATA[<b>A Parameter Free BBN Discriminant Function for Optimum Model Complexity versus Goodness of Data Fitting</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400011&lng=es&nrm=iso&tlng=es Bayesian Belief Network (BBN) is an appealing classification model for learning causal and noncausal dependencies among a set of query variables. It is a challenging task to learning BBN structure from observational data because of pool of large number of candidate network structures. In this study, we have addressed the issue of goodness of data fitting versus model complexity. While doing so, we have proposed discriminant function which is non-parametric, free of implicit assumptions but delivering better classification accuracy in structure learning. The contribution in this study is twofold, first contribution (discriminant function) is in BBN structure learning and second contribution is for Decision Stump classifier. While designing the novel discriminant function, we analyzed the underlying relationship between the characteristics of data and accuracy of decision stump classifier. We introduced a meta characteristic measure AMfDS (herein known as Affinity Metric for Decision Stump) which is quite useful in prediction of classification accuracy of Decision Stump. AMfDS requires a single scan of the dataset. <![CDATA[<b>Hybrid Non-Blind Watermarking Based on DWT and SVD</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400012&lng=es&nrm=iso&tlng=es Watermarking is identified as a major technology to achieve copyright protection and multimedia security. Therefore, recent studies in literature include some evident approaches for embedding data into a multimedia element. Because of its useful frequency component separation, the Discrete Wavelet Transform (DWT) is commonly used in watermarking schemes. In a DWT-based scheme, the DWT coefficients are modified with the data that represents the watermark. In this paper, we present a hybrid non-blind scheme based on DWT and Singular Value Decomposition (SVD). After decomposing the cover image into four sub bands (LL, HL, LH and HH), we apply the SVD to LL band and modify diagonal singular value coefficients with the watermark itself by using a scaling factor. Finally, LL band coefficients are reconstructed with modified singular values and inverse DWT is applied to obtain watermarked image. Experimental results show that the proposed algorithm is considerably robust and reliable. In comparison to the previous literature, peak signal-to-noise ratio (PSNR) values of watermarked images are increased by approximately 20%. In terms of PSNR values before and after attacks and of normalized similarity ratio (NSR); although watermark is embedded into LL sub band; our proposed method gives much more satisfactory results on filtering, scaling, Gaussian, JPEG compression, rotation and cropping than that of previous literature. <![CDATA[<b>Application of Different Algorithms to Optimal Design of Canal Sections</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400013&lng=es&nrm=iso&tlng=es Today the increased world population and therefore the growth demand has forced the researchers to investigate better water canal networks distributing much more water while at least keeping its quality. Canal design formulas are explicitly obtained for different cross-sections considering minimum area but optimal design of canal sections considering seepage and evaporation losses are still an open area to study. In this study, two different algorithms are applied to this problem and results are compared with the one in literature. Genetic algorithm and sequential quadratic programming technique are used in optimization. Triangular, rectangular and trapezoidal cross-sections are optimized. It is seen that both algorithms are giving more accurate results than in literature. <![CDATA[<b>Vehicle Handling Improvement with Steer-by-Wire System Using Hardware in the Loop Method</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400014&lng=es&nrm=iso&tlng=es In this paper, a control algorithm for improving vehicle handling has been proposed by applying correction angle to the steered wheel, based on the optimal and adaptive theory using Simulink MATLAB software. A 4DOF model with nonlinear tire and SBW subsystem is presented using hardware in the loop method. Since some space variables cannot be measured, an estimator is used to extract the measurable variables from the simulated model and convert them to the required variables of the controller. These variables are transmitted to the controller and then it adopts itself with new conditions and applies the best modification on the steering. The results reveal that the proposed controller can significantly improve vehicle handling during severe maneuvers. <![CDATA[<b>Synchronization of Irregular Complex Networks with Chaotic Oscillators: Hamiltonian Systems Approach</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400015&lng=es&nrm=iso&tlng=es Synchronization of multiple chaotic oscillators in Hamiltonian form is numerically studied and is achieved by appealing to complex systems theory [1-5]. The topology that we consider is the irregular coupled network. Two cases are considered: i) chaotic synchronization without master oscillator (where the final collective behaviour is a new chaotic state) and ii) chaotic synchronization with master oscillator (where the final collective behaviour is imposed by the dynamics of the master oscillator to multiple slave oscillators). The Hysteretic and Róssler chaotic oscillators in Hamiltonian form will be used as examples.<hr/>La sincronización de múltiples osciladores caóticos en forma Hamiltoniana es numéricamente estudiada y se logra apelando a la teoría de sistemas complejos [1-5]. La topología que consideramos es la red compleja irregular. Dos casos se consideran: i) sincronización caótica sin oscilador maestro (donde el comportamiento colectivo final de la red compleja es un estado caótico nuevo y ii) sincronización caótica con oscilador maestro (donde el comportamiento colectivo final de la red caótica es impuesto por la dinámica del oscilador maestro a los osciladores esclavos). Los osciladores caóticos de Róssler e Histéresis en forma Hamiltoniana se utilizan como ejemplos. <![CDATA[<b>Harmonic Distorted Load Control in a Microgrid</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400016&lng=es&nrm=iso&tlng=es In this paper the response of a microgrid to the interfaced harmonic distorted load is analyzed. A new control algorithm to mitigate harmonic distortion is considered for distributed generators (DGs) and the effect of this control scheme is shown in the currents of DGs and other loads. The proposed control algorithm is compared with the conventional control strategy for harmonic distorted loads that is sinusoidal source current strategy based on the instantaneous reactive power (IRP) theory. PSCAD simulation results for IRP theory control show high total harmonic distortion (THD) and 3rd harmonic percent. In comparison inner voltage and current controllers of the proposed control scheme with their disturbance rejection capability, mitigate THD and 3rd harmonic percent. For this control system MATLAB simulation results are shown. By demonstrating the traditional sinusoidal source current control strategy based on IRP theory, it is concluded that ignoring the distortion power (D) in compensating process and also sub-harmonics of Pap crossing from the controller interior high pass filter cause the presence of some harmonic components and high THD. <![CDATA[<b>A GPS-aided Inertial Navigation System in Direct Configuration</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400017&lng=es&nrm=iso&tlng=es This work presents a practical method for estimating the full kinematic state of a vehicle, along with sensor error parameters, through the integration of inertial and GPS measurements. This kind of system for determining attitude and position of vehicles and craft (either manned or unmanned) is essential for real time, guidance and navigation tasks, as well as for mobile robot applications. The architecture of the system is based in an Extended Kalman filtering approach in direct configuration. In this case, the filter is explicitly derived from the kinematic model, as well as from the models of sensors error. The architecture has been designed in a manner that it permits to be easily modified, in order to be applied to vehicles with diverse dynamical behaviors. The estimated variables and parameters are: i) Attitude and bias-compensated rotational speed of the vehicle, ii) Position, velocity and bias-compensated acceleration of the vehicle and iii) bias of gyroscopes and accelerometers. Experimental results with real data show that the proposed method is enough robust for its use along with low-cost sensors. <![CDATA[<b>An Energy Efficient Routing Protocol for Wireless Sensor Networks using A-star Algorithm</b>]]> http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1665-64232014000400018&lng=es&nrm=iso&tlng=es Sensors are regarded as significant components of electronic devices. In most applications of wireless sensor networks (WSNs), important and critical information must be delivered to the sink in a multi-hop and energy-efficient manner. Inasmuch as the energy of sensor nodes is limited, prolonging network lifetime in WSNs is considered to be a critical issue. In order to extend the network lifetime, researchers should consider energy consumption in routing protocols of WSNs. In this paper, a new energy-efficient routing protocol (EERP) has been proposed for WSNs using A-star algorithm. The proposed routing scheme improves the network lifetime by forwarding data packets via the optimal shortest path. The optimal path can be discovered with regard to the maximum residual energy of the next hop sensor node, high link quality, buffer occupancy and minimum hop counts. Simulation results indicate that the proposed scheme improves network lifetime in comparison with A-star and fuzzy logic(A & F) protocol.