Increasing Sustainability of Logistic Networks by Reducing Product Losses: A Network DEA Approach

This paper considers a multiproduct supply network, in which losses (e.g., spoilage of perishable products) can occur at either the nodes or the arcs. Using observed data, a Network Data Envelopment Analysis (NDEA) approach is proposed to assess the efficiency of the product flows in varying periods. Losses occur in each process as the observed output flows are lower than the observed input flows. The proposed NDEA model computes, within the NDEA technology, input and output targets for each process. The target operating points correspond to the minimum losses attainable using the best observed practice. The efficiency scores are computed comparing the observed losses with the minimum feasible losses. In addition to computing relative efficiency scores, an overall loss factor for each product and each node and link can be determined, both for the observed data and for the computed targets. A detailed illustration and an experimental design are used to study and validate the proposed approach. The results indicate that the proposed approach can identify and remove the inefficiencies in the observed data and that the potential spoilage reduction increases with the variability in the losses observed in the different periods.Ministerio de Ciencia DPI2017-85343-PFondo Europeo de Desarrollo Regional DPI2017-85343-

Estimation of productivity change of NBA teams from 2006-07 to 2012-13 seasons

"... acknowledgements at FiT Publishing"The aim of this work is to evaluate the productivity change of the NBA teams during the last seven seasons (from 2006-07 to 2012-13). Within that period of time, a new collective bargaining agreement (CBA) of the National Basketball Association (NBA) was ratified before season 2011-12, ending a 161-day lockout. The Malmquist Productivity Index (MPI) has been used to measure the total factor productivity, while an input-oriented Network DEA approach is used to compute the distance of each observation to the corresponding frontier. The results reveal that there has been technological progress for the last few seasons, excluding that of the 2011 lockout, and an increasing efficiency change. This means that best practices are improving and that most teams have been reducing their payrolls to catch up with these practices, thus backing up the owners’ proposal to reduce players’ income. Also regression results show that changes in the number of wins are more dependent upon scale efficiency change than upon budget or efficiency changes

Ranking efficient DMUs using cooperative game theory

The problem of ranking Decision Making Units (DMUs) in Data Envelopment Analysis (DEA) has been widely studied in the literature. Some of the proposed approaches use cooperative game theory as a tool to perform the ranking. In this paper, we use the Shapley value of two different cooperative games in which the players are the efficient DMUs and the characteristic function represents the increase in the discriminant power of DEA contributed by each efficient DMU. The idea is that if the efficient DMUs are not included in the modified reference sample then the efficiency score of some inefficient DMUs would be higher. The characteristic function represents, therefore, the change in the efficiency scores of the inefficient DMUs that occurs when a given coalition of efficient units is dropped from the sample. Alternatively, the characteristic function of the cooperative game can be defined as the change in the efficiency scores of the inefficient DMUs that occurs when a given coalition of efficient DMUs are the only efficient DMUs that are included in the sample. Since the two cooperative games proposed are dual games, their corresponding Shapley value coincide and thus lead to the same ranking. The more an ef- ficient DMU impacts the shape of the efficient frontier, the higher the increase in the efficiency scores of the inefficient DMUs its removal brings about and, hence, the higher its contribution to the overall discriminant power of the method. The proposed approach is illustrated on a number of datasets from the literature and compared with existing methods

Multiobjective centralized DEA approach to Tokyo 2020 Olympic Games

"Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License...."There exist two types of Data Envelopment Analysis (DEA) approaches to the Olympic Games: conventional and fixed-sum outputs (FSO). The approach proposed in this paper belongs to the latter category as it takes into account the total number de medals of each type awarded. Imposing these constraints requires a centralized DEA perspective that projects all the countries simultaneously. In this paper, a multiobjective FSO approach is proposed, and the Weighted Tchebychef solution method is employed. This approach aims to set all output targets as close as possible to their ideal values. In order to choose between the alternative optima, a secondary goal has been considered that minimizes the sum of absolute changes in the number of medals, which also renders the computed targets to be as close to the observed values as possible. These targets represent the output levels that could be expected if all countries performed at their best level. For certain countries, the targets are higher than the actual number of medals won while, for other countries, these targets may be lower. The proposed approach has been applied to the results of the Tokyo 2020 Olympic Games and compared with both FSO and non-FSO DEA method

Oportunidad de la política de rectificación en producción continua

El presente trabajo analiza las políticas posibles para tratar los defectos no críticos presentes en lotes de producción continua como modelo lineal de costes en función de la tasa de rectificación de errores. Se adjunta el resultado de una aplicación en el supuesto de que la calidad del lote se distribuya según la ley gamma-Poisson

Complementary heuristic to dual approaches to the capacitated lot-sizing problem

Este trabajo presenta una heurística de varios pasos para la obtención de soluciones admisibles al problema de la planificación de la producción con limitaciones de capacidad, a partir de las soluciones aproximadas que presentan los métodos duales basados en la relajación del problema. La heurística es complementaria a la aplicación de dichos métodos, buscando soluciones admisibles derivadas de las proporcionadas por la solución a la relajación

A methodological approach for designing and sequencing product families in Reconfigurable Disassembly Systems

Purpose: A Reconfigurable Disassembly System (RDS) represents a new paradigm of automated disassembly system that uses reconfigurable manufacturing technology for fast adaptation to changes in the quantity and mix of products to disassemble. This paper deals with a methodology for designing and sequencing product families in RDS. Design/methodology/approach: The methodology is developed in a two-phase approach, where products are first grouped into families and then families are sequenced through the RDS, computing the required machines and modules configuration for each family. Products are grouped into families based on their common features using a Hierarchical Clustering Algorithm. The optimal sequence of the product families is calculated using a Mixed-Integer Linear Programming model minimizing reconfigurability and operational costs. Findings: This paper is focused to enable reconfigurable manufacturing technologies to attain some degree of adaptability during disassembly automation design using modular machine tools. Research limitations/implications: The MILP model proposed for the second phase is similar to the well-known Travelling Salesman Problem (TSP) and therefore its complexity grows exponentially with the number of products to disassemble. In real-world problems, which a higher number of products, it may be advisable to solve the model approximately with heuristics. Practical implications: The importance of industrial recycling and remanufacturing is growing due to increasing environmental and economic pressures. Disassembly is an important part of remanufacturing systems for reuse and recycling purposes. Automatic disassembly techniques have a growing number of applications in the area of electronics, aerospace, construction and industrial equipment. In this paper, a design and scheduling approach is proposed to apply in this area. Originality/value: This paper presents a new concept called Reconfigurable Disassembly System, which represents disassembly systems with reusability, scalability, agility and reconfigurability features. These features and some specific costs are considered as part of the proposed methodology

Aplicación de los principios de la Gestión del Conocimiento y la Calidad a las tareas docentes universitarias en el contexto del Espacio Europeo de Educación Superior

El presente trabajo se centra en la adaptación de la práctica docente universitaria bajo los principios de las teorías de la Gestión del Conocimiento y la Calidad en el contexto de cambio y adaptación de los planes de estudio al marco del nuevo Espacio Europeo de Educación Superior. El trabajo se estructura en los apartados que siguen. En la introducción se presentan los conceptos básicos aplicados. En el segundo apartado se analiza el papel de los fundamentos de la gestión del conocimiento en el contexto del EEES. En el tercer apartado se presenta el diseño del modelo docente propuesto, técnicas empleadas, estructura, etc. En el cuarto apartado se presentan los resultados de la aplicación del modelo en el entorno y la realidad docente obtenidos en la implementación real del modelo en los varios años. En el quinto apartado se analiza el efecto y las posibilidades de las nuevas tecnologías en el contexto del modelo propuesto. Por último, en las conclusiones, se presentan una serie de reflexiones sobre el modelo, su operatividad y resultados.This paper proposes some advices for improving university-teaching processes using a Knowledge Management (KM) and Total Quality Management (TQM) approach. This effort is motivated by the profound pedagogical changes due to the new European Higher Education Space (EHES). The paper presents a conceptual model that includes a cause-effect diagram and diverse techniques and aids. Actual experiences of several years implementing the model in several courses are reported

Analysing the Structure of the Global Wheat Trade Network: An ERGM Approach

Nº Artículo: 1967This paper studies the relationship between wheat trading countries using both descriptive and statistical inference methods for complex networks. The global Wheat Trade Network (WTN) and its evolving topological characteristics is analysed for the periods 2009–2013 and 2014–2018, using the Food and Agriculture Organization (FAO) data. The network characterisation measures in both periods are rather stable. There are some differences, however, in the magnitude of some measures (e.g., connectivity or disassortativity), and a higher degree of inequality in the distribution of the number of partners and the distribution of trade volume in the period 2014–2018. An Exponential Random Graph Model (ERGM) has been applied to identify significant determinants associated with the presence/absence of trade links between countries. The results indicate that wheat trade links are driven mainly by country openness, reciprocity (mutual importer-exporter relationship), whether the exporting country is US or Canada and the geographical location of importer and exporter. Other factors, such as the economic size of the importing country, if the importing country is US or Canada and the land surface of the exporting country also contribute less to capture interlinkages of WTN.Ministerio de Economía, Industria y Competitividad DPI2017-85343-

Primal-dual approach to the capacitated production planning problem whith concave costs

Este trabajo estudia el problema de planificaci6n de la producci6n representado por un modelo de costes c6ncavos sujeto a limitaciones de capacidad. La relajaci6n lineal del modelo es analizada usando un enfoque primal-dual. Las soluciones del dual se obtienen resolviendo para cada producto modelos sin restricciones de capacidad asignando un precio a las mismas. El primal reducido supone un test de admisibilidad de dichas soluciones. El dual reducido permite calcular los nuevos precios recomendados asociados a las restricciones de capacidad. El trabajo concluye con un algoritmo propuesto para seleccionar los sucesivos precios de forma que se garantice una mejora hacia la solución óptima