http://hdl.handle.net/2117/3320 2013-05-20T13:19:34Z http://hdl.handle.net/2117/19118 Title: Random test examples with known minimum for convex semi-infinite programming problems Authors: Ferrer Biosca, Alberto; Miranda Galcerán, Eva Abstract: A signi cant research activity has occurred in the area of convex semi- in nite optimization in the recent years. Many new theoretical, algorithm and computational contribution has been obtained . Despite these numerous con- tributions, there still exits a lack of representative convex semi-in nite test problems. Test problems are of major importance for researchers interested in the algorithmic development. This article is motivated by the scarcity of con- vex semi-in nite test problems and describes a procedure for generating convex semi-in nite families of test problems with optimal solution and optimal value known. 2013-05-07T11:19:15Z http://hdl.handle.net/2117/18691 Title: Optimal electricity market bidding strategies considering emission allowances Authors: Corchero García, Cristina; Heredia, F.-Javier (Francisco Javier); Cifuentes, Julián Abstract: There are many factors that influence the day-ahead market bidding strategies of a GenCo in the current energy market framework. In this work we study the influence of both the allowances and emission reduction plan and the in- corporation of the derivatives medium-term commitments in the optimal generation bidding strategy to the day-ahead electricity market. Two different technologies have been considered: the coal thermal units, high-emission technology, and the combined cycle gas turbine units, low-emission technology. The operational characteristics of both kinds of units are modeled in detail. We deal with this problem in the framework of the Iberian Electricity Market and the Spanish National Emissions and Allocation Plans. The economic implications for a GenCo of including the environmental restrictions of these National Plans are analyzed 2013-04-08T10:54:18Z http://hdl.handle.net/2117/18369 Title: Optimal sizing of microgrids: a fast charging station case Authors: Corchero García, Cristina; Cruz Zambrano, Miguel; Heredia, F.-Javier (Francisco Javier); Cairo Molins, Josep Ignasi; Igualada Gonzalez, Lucia; Romero Ortega, Aitor Abstract: In this work we focus on the optimal design of electric vehicle charging stations. We consider investment, operational costs, physical constraints and different electricity pricing strategies. The size of the various components in the microgrid architecture and the suitability of the storage system are analysed. The electric vehicle charging demand is modelled through a queuing system. 2013-03-18T13:03:39Z http://hdl.handle.net/2117/18368 Title: A new optimal electricity market bid model solved through perspective cuts Authors: Corchero García, Cristina; Mijangos Fernández, Eugenio; Heredia, F.-Javier (Francisco Javier) Abstract: On current electricity markets the electrical utilities are faced with very sophisticated decision making problems under uncertainty. Moreover, when focusing in the short-term management, generation companies must include some medium-term products that directly influence their short-term strategies. In this work, the bilateral and physical futures contracts are included into the day-ahead market bid following MIBEL rules and a stochastic quadratic mixed-integer programming model is presented. The complexity of this stochastic programming problem makes unpractical the resolution of large-scale instances with general-purpose optimization codes. Therefore, in order to gain efficiency, a polyhedral outer approximation of the quadratic objective function obtained by means of perspective cuts (PC) is proposed. A set of instances of the problem has been defined with real data and solved with the PC methodology. The numerical results obtained show the efficiency of this methodology compared with standard mixed quadratic optimization solvers. 2013-03-18T12:33:44Z http://hdl.handle.net/2117/17954 Title: On assessing the disclosure risk of controlled adjustment methods for statistical tabular data Authors: Castro Pérez, Jordi Abstract: Minimum distance controlled tabular adjustment is a recent perturbative approach for statistical disclosure control in tabular data. Given a table to be protected, it looks for the closest safe table, using some particular distance. Con trolled adjustment is known to provide high data utility. However, the disclosure risk has only been partially analyzed using theoretical results from optimization. This work ext ends these previous results, providing both a more detailed theoretical analysis, and an extensive empirical assess- ment of the disclosure risk of the method. A set of 25 instance s from the literature and four different attacker scenarios are considered, with sever al random replications for each scenario, both for L 1 and L 2 distances. This amounts to the solution of more than 2000 optimization problems. The analysis of the results shows th at the approach has low dis- closure risk when the attacker has no good information on the bounds of the optimization problem. On the other hand, when the attacker has good estima tes of the bounds, and the only uncertainty is in the objective function (which is a very strong assumption), the disclosure risk of controlled adjustment is high and it s hould be avoided. 2013-02-22T18:06:38Z http://hdl.handle.net/2117/17953 Title: Improving an interior-point approach for large block-angular problems by hybrid preconditioners Authors: Bocanegra, Silvana; Castro Pérez, Jordi; Oliveira, Aurelio R.L. Abstract: The computational time required by interior-point methods is often domi- nated by the solution of linear systems of equations. An efficient spec ialized interior-point algorithm for primal block-angular proble ms has been used to solve these systems by combining Cholesky factorizations for the block con- straints and a conjugate gradient based on a power series precon ditioner for the linking constraints. In some problems this power series prec onditioner re- sulted to be inefficient on the last interior-point iterations, wh en the systems became ill-conditioned. In this work this approach is combi ned with a split- ting preconditioner based on LU factorization, which is main ly appropriate for the last interior-point iterations. Computational result s are provided for three classes of problems: multicommodity flows (oriented and no noriented), minimum-distance controlled tabular adjustment for statistic al data protec- tion, and the minimum congestion problem. The results show that , in most cases, the hybrid preconditioner improves the performance an d robustness of the interior-point solver. In particular, for some block-ang ular problems the solution time is reduced by a factor of 10. 2013-02-22T17:36:16Z http://hdl.handle.net/2117/17774 Title: Nonlinear network flows with side constraints applied to short term hydrothermal coordination of electricity generation Authors: Heredia, F.-Javier (Francisco Javier); Nabona Francisco, Narcís 2013-02-14T18:09:53Z http://hdl.handle.net/2117/17410 Title: Present and future research on controlled tabular adjustment Authors: Castro Pérez, Jordi; González Alastrué, José Antonio Abstract: Controlled tabular adjustment (CTA) can be classi ed within the group of approaches that perturb output data (i.e., tabular data), unlike other methods that focus on the original microdata. Being a post-tabular data perturbation technique it becomes easier to guarantee consistency and quality of the released information (e.g., table additivity, preservation of subtotal or total cells of the original table, etc.). On the other hand, it may be computationally more costly than pre-tabular strategies. The purpose of this work is twofold. First, we will review a recently used heuristic to suboptimally solve CTA (which is a mixed integer linear optimization problem). For some tables this heuristic provided decent solutions much faster than other state-of-the-art optimization methods. This approach can be useful when CTA is applied to a pre-de ned "static" set of tables. The second goal of the paper is to provide and discuss variants of CTA when applied in an on-line table generation system. In this case, tables can be dynamically generated over time, and CTA has to face two new challenges: (i) it has to deliver an on-line fast solution; (ii) protection senses of sensitive cells have to be consistent (i.e, the same) when the same sensitive cell appears in two (or more) tables which are generated and protected at di erent moments. Some of these ideas will be implemented in the recently started Data without Boundaries FP7 EU project. 2013-01-17T17:57:13Z http://hdl.handle.net/2117/15925 Title: Rounding methods for protecting EU-aggregates Authors: Giessing, Sarah; Hundepool, Anco; Castro Pérez, Jordi Abstract: In the European Statistical System the statistical information is collected by the National Statistical Institutes (NSIs). The NSIs produce aggregate tables at the national level. They are also responsible for proper protection of these tables and hence they have to keep certain cells confidential, suppressing them from publications. Eurostat produces statistical information at the EU-level. However, the national suppressions hamper very much the publication of EU-aggregates although it is often only a few smaller countries having to keep their contribution to the EU-total confidential. This paper reports on a research-project that aims for making more EU aggregates available whilst at the same time guaranteeing the national suppressed figures to remain confidential. 2012-05-24T18:30:50Z http://hdl.handle.net/2117/15738 Title: Optimum short-term hydrothermal scheduling with spinning reserve through network flows Authors: Heredia, F.-Javier (Francisco Javier); Nabona Francisco, Narcís Abstract: Optimizing the thermal production of electricity in the short term in an integrated power system when a thermal unit commitment has been decided means coordinating hydro and thermal generation in order to obtain the minimum thermal generation costs over the time period under study. Fundamental constraints to be satisfied are the covering of each hourly load and satisfaction of spinning reserve requirements and transmission capacity limits. A nonlinear network flow model with linear side constraints with no decomposition into hydro and thermal subproblems was usedto solve and thermal scheduling. Hydrogeneration is linearized with respect to network variables and novel thermal generation and transmission network is introduced. Computational results are reported. 2012-04-17T17:31:33Z http://hdl.handle.net/2117/15166 Title: El apoyo público a la ciencia Authors: Revuelta, Gemma; Corchero García, Cristina Abstract: ¿Qué esperan los españoles de la ciencia y la tecnología? ¿son temas que despierten su interés? ¿qué opinión tienen sobre los recursos públicos destinados a este sector? Estas preguntas, relativas a las expectativas y actitudes del público respecto a la ciencia y tecnología, nunca faltan en los estudios de percepción social, ya que son cuestiones que exploran un aspecto clave: las tensiones –o la falta de las mismas– entre la ciencia y la sociedad. 2012-02-15T13:09:49Z http://hdl.handle.net/2117/15164 Title: Búsqueda activa y recepción pasiva de información sobre ciencia y tecnología Authors: Revuelta, Gemma; Corchero García, Cristina Abstract: Nos encontramos en una sociedad que tiene como motor un cambio tecnológico que permite comunicarse mucho más rápido y mucho más lejos que nunca antes en la historia, pero los cambios tecnológicos son a su vez consecuencia de cambios sociales y culturales. A la sociedad que estamos construyendo se le ha denominado de distintas maneras: sociedad de la información, sociedad del conocimiento, sociedad-red, etc. Así, en la sociedad red de Castells (Castells, 2006), el elemento tecnológico constituye un paradigma en el sentido definido por Khun. Es decir, un modelo conceptual que establece los principios de actuación y ayuda a explicar las transformaciones del conocimiento que se producen en las revoluciones científicas. El planteamiento de Castells es muy útil para analizar los cambios que se van produciendo en la sociedad, puesto que a la vez que marca la importancia de la expansión y difusión de las tecnologías de la información y la comunicación permite introducir en el análisis elementos sociales y culturales que también serán decisivos en el camino que tome esta “revolución”. Conviene también recordar que no todo el mundo participa en esta revolución social por igual. El dominio de algunas regiones y ciudades se afianza, mientras que emergen nuevas ciudades y regiones de poder, de la mano de los nuevos valores sociales. Se trata, como define Saskia Sassen (Sassen, 2007), de una “globalización desigual”. El ciudadano ideal de la sociedad del conocimiento no es probablemente aquel que más conocimientos tiene sino el que es capaz de buscar activamente la información que precisa o la que se corresponde con aquellos asuntos de su interés. También es, todo sea dicho, el que quiere que esta información esté disponible de forma rápida, inmediata a poder ser.Desde la aparición de la prensa de masas a finales del siglo XIX y hasta hace unos pocos años, los medios a los que ahora llamamos “convencionales” (prensa, radio y finalmente la televisión) han tenido prácticamente el monopolio de la información pública. Sin embargo, a medida que Internet se va expandiendo y el ciudadano va integrándose en la sociedad del conocimiento –o de la información, si se prefiere– las posiciones respectivas de los diferentes medios en el reparto del pastel de la comunicación han ido cambiando. Por otra parte, la difusión de las redes sociales electrónicas, propia del último lustro, introduce un nuevo elemento en la fórmula de la adquisición de la información que debe ser considerado (Campos Freire, 2008). 2012-02-15T13:03:50Z http://hdl.handle.net/2117/15074 Title: Recent advances in optimization techniques for statistical tabular data protection Authors: Castro Pérez, Jordi Abstract: One of the main services of National Statistical Agencies (NSAs) for the current Information Society is the dissemination of large amounts of tabular data, which is obtained from microdata by crossing one or more categorical variables. NSAs must guarantee that no confidential individual information can be obtained from the released tabular data. Several statistical disclosure control methods are available for this purpose. These methods result in large linear, mixed integer linear, or quadratic mixed integer linear optimization problems. This paper reviews some of the existing approaches, with an emphasis on two of them: cell suppression problem (CSP) and controlled tabular adjustment (CTA). CSP and CTA have concentrated most of the recent research in the tabular data protection field. The particular focus of this work is on methods and results of practical interest for end-users (mostly, NSAs). Therefore, in addition to the resulting optimization models and solution approaches, computational results comparing the main optimization techniques—both optimal and heuristic—using real-world instances are also presented. 2012-02-10T18:46:40Z http://hdl.handle.net/2117/14936 Title: Network model of short-term optimal hydrothermal power flow with security constraints Authors: Chiva, A; Heredia, F.-Javier (Francisco Javier); Nabona Francisco, Narcís Abstract: Optimizing the thermal production of electricity in the short term in an integrated system when a thermal unit commitment has been decided means coordinationg hydro and thermal generation costs over the time period under study. Fundamental constraints to be satisfied are the covering of each hourly load and satisfaction os spinning reserve requeriments and transmission capacity limits. A nonlinear network flow model with side constraints whit no decomposition into hysro and thermal subproblems was used to solve the hydrothermal scheduling. A novel thermal generation and transmission network is replicated with line outaged in order to obtain a secure multi-interval shot-term power flow. Computational results are reported. 2012-02-03T18:53:46Z http://hdl.handle.net/2117/14922 Title: Using a Mathematical Programming Modeling Language for Optimal CTA Authors: Castro Pérez, Jordi; Baena, Daniel Abstract: Minimum-distance controlled tabular adjustment methods (CTA) have been formulated as an alternative to the cell suppression problem (CSP) for tabular data. CTA formulates an optimization problem with fewer variables and constraints than CSP. However, the inclusion of binary decisions about protection sense of sensitive cells (optimal CTA) in the formulation, still results in a mixed integer-linear problem. This work shows how mathematical programming modeling languages can be used to develop a prototype for optimal CTA based on Benders method. Preliminary results are reported for some medium size two-dimensional tables. For this type of tables, the approach is competitive with other general-purpose algorithms implemented in commercial solvers. 2012-02-01T19:19:48Z