http://hdl.handle.net/2117/2261 2013-05-23T22:42:52Z http://hdl.handle.net/2117/19373 Title: A MILP model to design hybrid wind-photovoltaic isolated rural electrification projects in developing countries Authors: Ferrer Martí, Laia; Domenech Lega, Bruno; García Villoria, Alberto; Pastor Moreno, Rafael Abstract: Electrification systems based on the use of renewable energy sources are a suitable option for providing electricity to isolated communities autonomously. Wind and hybrid wind–photovoltaic (PV) systems are increasingly getting attention. To electrify scattered communities, designs that combine individual systems and microgrids have recently proven advantageous. In this paper we present a mathematical programming model to optimize the design of hybrid wind–PV systems that solves the location of the wind–PV generators and the design of the microgrids, taking into account the demand of the consumption points and the energy potential. The criterion is the minimization of the initial investment cost required to meet the demand. The proposed hybrid model is tested with realistic size instances and results show the instances are efficiently solved. Moreover, the model is applied to real case studies in Peru; obtained results verify that the hybrid model efficiently finds solutions that significantly reduce cost. http://hdl.handle.net/2117/17646 Title: A branch and bound algorithm for the response time variability problem Authors: García Villoria, Alberto; Corominas Subias, Albert; Delorme, Xavier; Alexandre, Dolgui; Wieslaw, Kubiak; Pastor Moreno, Rafael Abstract: The response time variability problem (RTVP) is an NP-hard scheduling problem that has been studied intensively recently and has a wide range of real-world applications in mixed-model assembly lines, multithreaded computer systems, network environments and others. The RTVP arises whenever products, clients or jobs need to be sequenced in order to minimise the variability in the time between two successive points at which they receive the necessary resources. To date, the best exact method for solving this problem is a mixed integer linear programming (MILP) model, which solves to optimality most of instances with up to 40 units to be scheduled in a reasonable amount of time. The goal of this paper is to increase the size of the instances that can be solved to optimality. We have designed an algorithm based on the branch and bound (B&B) technique to take advantage of the particular features of the problem. Our computational experiments show that the B&B algorithm is able to solve larger instances with up to 55 units to optimality in a reasonable time 2013-02-12T09:00:11Z http://hdl.handle.net/2117/17617 Title: Heuristic indicators for the design of community off-grid electrification systems based on multiple renewable energies Authors: Ranaboldo, Matteo; Ferrer Martí, Laia; García Villoria, Alberto; Pastor Moreno, Rafael Abstract: Off-grid rural electrification project configurations which consider hybrid generation systems based on multiple renewable sources and the implementation of micro-grids are the most promising design solutions. The efficient design of those systems is a complex task that is facing several technical issues such as limited time and resources available for the purpose, especially in developing countries. This study proposes indicators for supporting and improving the design of community off-grid electrification projects considering hybrid generation and micro-grids. A (Grid Generation Score) GGS is defined in order to identify most promising locations for being the generation point of a micro-grid. The (No- Generation Score) NGS and the (Independent Generation Score) IGS evaluate respectively if a point should be reliably connected to a micro-grid or should better be an independent generation point. All indicators could be easily and quickly calculated at a very first stage of the plan of a community project requiring as input data only demand and resource distributions in the studied area. It is shown that the utilization of proposed indictors can enhance the design of stand-alone community electrification projects based on renewable energies. 2013-02-11T09:41:02Z http://hdl.handle.net/2117/17119 Title: A Delphi study on Technology Enhanced Learning (TEL) applied on Computer Science (CS) skills Authors: Porta, Marcela; Mas Machuca, Marta; Martínez Costa, Carme; Maillet, Katherine Abstract: Technology Enhanced Learning (TEL) is a new pedagogical domain aiming to study the usage of information and communication technologies to support teaching and learning. The following study investigated how this domain is used to increase technical skills in Computer Science (CS). A Delphi method was applied, using three-rounds of online survey questions, given to 17 TEL experts from different European countries. The results showed that these experts consider TEL an effective and interesting support to acquire CS skills. Furthermore, the findings revealed the five best tools in TEL to acquire necessary CS knowledge. Future research can provide a guideline to implement effective TEL tools in CS studies. This manuscript investigates Technology Enhanced Learning (TEL) tools and its applications to learn specific skills in CS. As general content the results of a Delphi study that identifies the benefits of TEL while teaching are highlighted. 2012-12-12T12:15:08Z http://hdl.handle.net/2117/17111 Title: Planificación estratégica de la capacidad en una empresa del sector limentación Authors: Companys Pascual, Ramón; Ribas Vila, Immaculada; Bautista Valhondo, Joaquín Abstract: En esta comunicación se describe el procedimiento propuesto a una empresa del sector de la alimentación para planificar la capacidad productiva de las diferentes plantas aprovechando el cambio de ubicación forzoso de una de ellas. El caso de estudio puede servir de referencia a otros profesionales que se enfrenten a una situación semejante. 2012-12-12T10:17:30Z http://hdl.handle.net/2117/17083 Title: Strengths and weaknesses of computer science degrees: The perception from European students Authors: Porta, Marcela; Maillet, Katherine; Martínez Costa, Carme; Mas Machuca, Marta Abstract: Purpose: The following investigation aims to highlight strengths and weaknesses of the computer science degree from the part of students. Design/methodology/approach: This paper presents the results of a quantitative investigation that sheds light on student’s motivations to pursue or reject computer science. Findings: The study identified the reasons that cause this rejection and suggest them as opportunities to enhance the domain in the future. Practical implications: This study is a preliminary phase of a larger research goal which aims to identify the strategies presented to computer science education using technology to foster interest in the domain among students and professionals in Europe. Originality/value: The declining number of computer science students in Europe is producing negative consequences in the technology field that affect other sectors like the economic and educational ones. In order to analyze this situation and in view of providing solutions to stop the decline, it is primordial to understand the reasons that retain students to choose this domain of study or that attract and retain them in the field. 2012-12-10T11:39:00Z http://hdl.handle.net/2117/15893 Title: El paisaje portuario en viñetas Authors: Ojeda Rodríguez, Jordi Abstract: The term “comic” is used to refer to a strip or sequence of cartoons/vignettes with or without text that tell a story (however short it might be) in which at least one character appears in more than one vignette. The comic is recognised as the ninth art form, and there are a great variety of types and names, depending on the source and the format: historieta, tebeo, manga, bande dessinée, banda desenhado, fumetti or comic-book, amongst others. Virtually every country has its own characters and collections, and those that deal with universal subject matter or historical questions transcend frontiers and gradually become known the world over, the following being such examples: Tintin, Asterix, Mortadelo and Filemón, Corto Maltés, Superman, Spiderman or Flash Gordon, which have now become real classics. Comics undoubtedly have the ability to convey knowledge and feelings. Their educational value enables children and adults alike to gain insight into different areas of reality, in the past and present, dealing with almost every aspect of life: nature, mankind, technology, legends, cultures, history, adventures, etc., allowing the reader to explore the boundaries between fiction and reality, even heralding a future that can prove to be most unexpected and surprising. Comics make learning easier and stimulate the imagination, and they are an excellent resource for developing creative thinking and artistic sensitivity, while at the same time encouraging the reader to adopt a critical stance. They can be suitable instruments for creatively and intelligently explaining the world of ports and the sea, and to make this accessible to all types of potential reader. This is particularly the case where the port landscape is concerned, because of the nature of the artistic discipline that is deeply rooted in the way cartoons or vignettes are illustrated. 2012-05-18T10:43:23Z http://hdl.handle.net/2117/15601 Title: Propuesta de un algoritmo genético para la programación diaria de los pedidos de una empresa del sector de la construcción Authors: Pinto, Carola; Coves Moreno, Anna Maria Abstract: El objetivo del presente trabajo es proponer un algoritmo genético para determinar la programación integrada de la producción y de la distribución de un producto de carácter perecedero y no almacenable, el hormigón. La empresa en cuestión cuenta con diferentes plantas productivas desde las cuales distribuye los pedidos hasta cada obra, con la ayuda de una flota de vehículos. La programación de los pedidos se efectúa el día anterior a su distribución, siendo el objetivo cumplir con el nivel de servicio acordado con el cliente y minimizar su coste asociado. El problema es NP-hard. Los resultados obtenidos muestran que el algoritmo genético propuesto realiza la programación minimizando costes y respetando las condiciones de entrega pactadas con el cliente. 2012-03-16T09:49:01Z http://hdl.handle.net/2117/15524 Title: Optimal manufacturing policy in a reverse logistic system with dependent stochastic returns and limited capacities Authors: Benedito Benet, Ernest; Corominas Subias, Albert Abstract: The stochastic models of systems with reverse logistics usually assume that the quantity of products returned is independent of sales. This hypothesis is obviously not true and can lead to suboptimal production policies. In this paper a new sales-dependent returns model is described. In this model, the returns depend on the useful life of the products sold and on the probability of an end-of-life product being returned. A Markov decision problem is formulated in order to obtain the optimal manufacturing policy. A numerical example is provided to illustrate the use of the defined model. An approximated Markov decision model is defined where the optimal policy is easily obtained. The optimal policies of the original and the approximated models are compared. 2012-03-08T11:00:01Z http://hdl.handle.net/2117/15094 Title: Exploring critical success factors of knowledge management projects in the consulting sector Authors: Mas Machuca, Marta; Martínez Costa, Carme Abstract: Knowledge management (KM) and critical success factors (CSFs) are interesting issues in the current business world. Knowledge is an important driving force for business success and competiveness, especially in the consulting industry whose core business is to sell knowledge itself. Previous works suggested a positive relation between the CSF and the success of a KM project, but only few of them related it in a quantitative way. This paper aims to identify the CSF in a consulting firm (strategic, cultural and technological factors) and to build a success model for designing KM projects based on these CSF identified. This model was tested using structured equation model. With this study we contribute to recognising the importance of these success factors in a KM project in the consulting industry to achieve the maximum success. 2012-02-13T12:38:04Z http://hdl.handle.net/2117/14056 Title: Solving the Fm|block|Cmax problem using bounded dynamic programming Authors: Bautista Valhondo, Joaquín; Cano Pérez, Alberto; Companys Pascual, Ramón; Ribas Vila, Immaculada Abstract: We present some results attained with two variants of Bounded Dynamic Programming algorithm to solve the Fm|block|Cmax problem using as an experimental data the well-known Taillard instances. We have improved the best known solutions for 17 of Taillard's instances, including the 10 instances from set 12. 2011-11-24T11:23:49Z http://hdl.handle.net/2117/13619 Title: Codigestion of cow and guinea pig manure in low-cost tubular digesters at high altitude Authors: Garfi, Marianna; Ferrer Martí, Laia; Pérez Bort, Irene; Flotats Ripoll, Xavier; Ferrer Martí, Ivet 2011-10-21T12:59:03Z http://hdl.handle.net/2117/11762 Title: Optimizing microwind rural electrification projects. A case study in Peru Authors: Ferrer Martí, Laia; Pastor Moreno, Rafael; Capó Plaza, Gregori Miquel; Velo García, Enrique Abstract: Electrification systems based on the use of renewable energy sources are suitable for providing electricity to isolated communities autonomously. Specifically, electrification by wind power is one of the technological options that have been used recently in projects implemented in the Andean highlands of Peru. To date, these projects have tended to install individual microwind turbines at each demand point. Alternatively, we propose a solution that considers both individual generators and microgrids.We develop a mathematical model that gives the location and size or type of the wind turbines and the design of the microgrids, taking into account the demand of the consumption points and the wind potential. The criterion is the minimization of the initial investment cost required to meet the demand. The model is validated by application to a real case in the northern highlands of Peru. Results show that microgrids are used despite the village dispersion, and the solutions significantly reduce the initial investment costs. 2011-03-09T15:28:05Z http://hdl.handle.net/2117/11114 Title: Improving social capital: a social network monitoring system Authors: Monguet Fierro, José María; Ojeda Rodríguez, Jordi; Cadima, Rita; Ferreira, Carlos Abstract: To increase communication and collaboration opportunities, members of a community must be aware of the social networks that exist within that community. This paper describes a social network monitoring system that enables users to register their interactions and visualize their social networks. The system was implemented in two distributed learning communities and the results have shown that this system facilitates collecting information about social interactions. Furthermore, the visualization of the social networks, given as feedback, appeared to have a positive impact on users, augmenting their social network awareness. 2011-01-20T09:52:50Z http://hdl.handle.net/2117/9641 Title: Planning production using mathematical programming: The case of a woodturning company Authors: Pastor Moreno, Rafael; Altamiras, Jordi; Mateo Doll, Manuel 2010-10-12T16:26:05Z