http://hdl.handle.net/2117/3406 2013-05-19T04:52:33Z http://hdl.handle.net/2117/18719 Title: Twenty-five analogies for explaining statistical concepts Authors: Behar, Roberto; Grima Cintas, Pedro; Marco Almagro, Lluís Abstract: The use of analogies is a resource that can be used for transmitting concepts and making classes more enjoyable. This article presents 25 analogies that we use in our introductory statistical courses for introducing concepts and clarifying possible doubts. We have found that these analogies draw students’ attention and reinforce the ideas that we want to transmit. 2013-04-09T09:54:11Z http://hdl.handle.net/2117/17873 Title: An approach to disaggregating total household water consumption into major end-uses Authors: Fontdecaba Rigat, Sara; Sánchez Espigares, Josep Anton; Marco Almagro, Lluís; Tort-Martorell Llabrés, Xavier; Cabrespina, Francesc; Zubelzu, Jordi Abstract: The aim of this project is to assign domestic water consumption to different devices based on the information provided by the water meter. We monitored a sample of Barcelona and Murcia with flow switches that recorded when a particular device was in use. In addition, the water meter readings were recorded every 5 and 1 s, respectively, in Barcelona and Murcia. The initial work used Barcelona data, and the method was later verified and adjusted with the Murcia data. The proposed method employs an algorithm that characterizes the water consumption of each device, using Barcelona to establish the initial parameters which, afterwards, provide information for adjusting the parameters of each household studied. Once the parameters have been adjusted, the algorithm assigns the consumption to each device. The efficacy of the assignation process is summarized in terms of: sensitivity and specificity. The algorithm provides a correct identification rate of between 70 % and 80 %; sometimes even higher, depending on how well the chosen parameters reflect household consumption patterns. Considering the high variability of the patterns and the fact that use is characterized by only the aggregate consumption that the water meter provides, the results are quite satisfactory. 2013-02-19T11:37:54Z http://hdl.handle.net/2117/16784 Title: Statistical methods in Kansei engineering: a case of statistical engineering Authors: Marco Almagro, Lluís; Tort-Martorell Llabrés, Xavier Abstract: Kansei engineering (KE) is a methodology used to incorporate emotions in products and services design. Its basic purpose is discovering in which way some properties of a product or a service convey certain emotions in its users. Data are typically collected using questionnaires. KE studies follow a model with three main steps: (i) defining the elicited emotions (semantic space); (ii) deciding on the factors that might affect the responses (space of properties); and (iii) modeling how each factor affects each response (synthesis phase). The procedure resembles that of an experimental design in an industrial context. However, practitioners of KE are hardly ever statisticians. Statistical techniques in KE are sometimes misused, and the discipline could benefit from a more extensive use of statistical methods. KE is thus a good area of application of statistical engineering: focusing not in advancement of statistics but on how current techniques can be best used in a new area. The aim of this paper is twofold: (i) to present the fundamentals of KE while giving an easy to understand example to illustrate the procedure; and (ii) to explain why KE is a good example of statistical engineering by proposing improvements that emanate from the adequate use of statistical techniques. 2012-10-23T11:35:05Z http://hdl.handle.net/2117/16683 Title: Time series outlier and intervention analysis: Irrigation management influences on soil water content in silty loam soil Authors: Basem, Aljoumani; Sánchez Espigares, Josep Anton; Cañameras Riba, Núria; Josa March, Ramon; Monserrat, Joaquim Abstract: Understanding the field soil water regime is fundamental in scheduling irrigation as well as for monitoring water flow and solute transport. This study was carried out on variable interval irrigation and used time series analysis techniques to predict the soil water content at the interested depth by measuring one single depth in order to precisely determine the next irrigation time and its effect on soil water content at the interested depth. Volumetric water content of silty loam soil in Barcelona was measured in situ with capacitance soil moisture sensors at five depths within the root zone for a horticultural crop during its life cycle in 2010. The time series consisted of hourly measurements of soil water content and was transformed to a stationary situation. Subsequently, the transformed data were used to conduct analyses in the time domain in order to obtain the parameters of a seasonal autoregressive integrated moving average (ARIMA) model. In the case of variable interval irrigation, predicting the soil water content time series cannot be properly explained by the ARIMA model and its underlying normality assumption. By completing the ARIMA model with intervention analysis and outlier detection, the prediction of soil water content in variable interval irrigation can be made. The transfer function models were then used to predict water contents at depths of interest (0.20, 0.35, 0.50 and 0.60 m depths) as well as the average water content WAVG in the top 0.60 m soil profile by measuring water content at 0.10 m depth. As a result, the predictions were logical. Also, the next irrigation time and its effect on soil water content at the depth of interest were correctly estimated. To confirm results of the models, the experiment was repeated in 2011, and the predicted and observed values agree reasonably well. Description: Soil volumetric water content; Autoregressive integrated moving average (ARIMA); Outlier detection; Transfer function model 2012-10-09T11:01:57Z http://hdl.handle.net/2117/14953 Title: Weeds, aphids, and specialist parasitoids and predators benefeit differently from organic and conventional cropping of winter cereals Authors: Caballero-López, Berta; Blanco-Moreno, José M.; Pérez-Hidalgo, Nicolás; Michelena-Saval, José M.; Pujade-Villar, Juli; Guerrieri, Emilio; Sánchez Espigares, Josep Anton; Sans, F. Xavier Abstract: The aphid–natural enemy interaction in winter wheat fields constitutes a complex system that has been frequently studied because of its implication for biological control. However, not all of the aphids living in cereal fields are crop pests, as there are also aphids living on weeds that may serve as alternative hosts or prey for aphid parasitoids or predators. In this context, a concomitant survey of the plant and insect communities was conducted to understand how different plant communities affect the abundance and richness of aphids and the interactions with their natural enemies. The plant community was split into functional groups (grasses, legumes and forbs), and the aphid community was divided into feeding groups according to their host preferences (specialists in grasses or forbs). The grass aphids, which dominated the total aphid catches, responded positively to grass cover, which was particularly enhanced in the conventional fields. Conversely, the forb aphids, which mainly conditioned the total species richness of the aphids, were closely correlated with the local abundance of legumes. The system of cereal aphid-parasitoids was enhanced in the conventional fields, where the abundance of grasses was higher, whereas the legumes of the organic fields indirectly played a key role in enhancing the richness of the parasitoids and the abundance of predators. Our findings indicate that a bottom-up effect exists throughout the plant community, aphids, and aphidophagous insects and that plant community characteristics should 2012-02-06T11:58:17Z http://hdl.handle.net/2117/14798 Title: Bayesian analysis of frequency count data Authors: Font Valverde, Martí; Puig Oriol, Xavier; Ginebra Molins, Josep Abstract: The zero truncated inverse Gaussian–Poisson model, obtained by first mixing the Poisson model assuming its expected value has an inverse Gaussian distribution and then truncating the model at zero, is very useful when modelling frequency count data. A Bayesian analysis based on this statistical model is implemented on the word frequency counts of various texts, and its validity is checked by exploring the posterior distribution of the Pearson errors and by implementing posterior predictive consistency checks. The analysis based on this model is useful because it allows one to use the posterior distribution of the model mixing density as an approximation of the posterior distribution of the density of the word frequencies of the vocabulary of the author, which is useful to characterize the style of that author. The posterior distribution of the expectation and of measures of the variability of that mixing distribution can be used to assess the size and diversity of his vocabulary. An alternative analysis is proposed based on the inverse Gaussian-zero truncated Poisson mixture model, which is obtained by switching the order of the mixing and the truncation stages. Even though this second model fits some of the word frequency data sets more accurately than the first model, in practice the analysis based on it is not as useful because it does not allow one to estimate the word frequency distribution of the vocabulary. 2012-01-25T12:11:32Z http://hdl.handle.net/2117/14642 Title: On the measure and the estimation of the evenness and diversity of vocabulary Authors: Ginebra Molins, Josep; Puig Oriol, Xavier Abstract: Modelling word or species frequency count data through zero truncated Poisson mixture models allows one to interpret the model mixing distribution as the distribution of the word or species frequencies of the vocabulary or population. As a consequence, estimates of their mixing density can be used as a fingerprint of the style of the author in his texts or of the ecosystem in its samples. Definitions of measure of the evenness and of measure of the diversity within a vocabulary or population are given, and the novelty of these definitions is explained. It is then proposed that the measures of the evenness and of the diversity of a vocabulary or population be approximated through the expectation of these measures under the word or species frequency distribution. That leads to the assessment of the lack of diversity through measures of the variability of the mixing frequency distribution estimates described above. 2012-01-18T11:20:31Z http://hdl.handle.net/2117/12915 Title: Management by facts: the common ground between total quality management and evidence-based management Authors: Tort-Martorell Llabrés, Xavier; Grima Cintas, Pedro; Marco Almagro, Lluís Abstract: It is widely agreed that, whenever possible, managers should base their decisions on scientific knowledge rather than gut feelings or intuitions. There are two main sources of scientific knowledge available to managers: external and internal. External knowledge comes from studies conducted outside the company and it is mainly generated by researchers at universities and business schools; a recent trend, under the name of evidence-based management, tries to potentiate it, despite the fact that as a source of scientific knowledge for management, it has two problems: it is difficult to generate and it is problematic to disseminate among managers. On the other hand, internal knowledge comes from studies conducted on the company’s process on which decisions have to be made and by the very same managers that have to make them. The paper argues that this kind of knowledge is easier to generate and use and thus that it has to be potentiated as the main source for scientific decisions; the idea is not new as it is one of the pillars of total quality management and there are methods and techniques of proved efficiency to put it into practice. 2011-07-11T10:51:47Z http://hdl.handle.net/2117/10149 Title: Thermal-Hydraulic Analysis Tasks for ANAV NPPs in Support of Plant Operation and Control Authors: Reventós Puigjaner, Francesc Josep; Batet Miracle, Lluís; Llopis, C.; Pretel Sánchez, Carme; Solé Vidal, Ignasi Abstract: Thermal-hydraulic analysis tasks aimed at supporting plant operation and control of nuclear power plants are an important issue for the Asociaci ´on Nuclear Asc ´o-Vandell ` os (ANAV). ANAV is the consortium that runs the Asc ´o power plants (2 units) and the Vandell ` os-II power plant. The reactors areWestinghouse-design, 3-loop PWRs with an approximate electrical power of 1000MW. The Technical University of Catalonia (UPC) thermal-hydraulic analysis team has jointly worked together with ANAV engineers at different levels in the analysis and improvement of these reactors. This article is an illustration of the usefulness of computational analysis for operational support. The contents presented were operational between 1985 and 2001 and subsequently changed slightly following various organizational adjustments. The paper has two different parts. In the first part, it describes the specific aspects of thermal-hydraulic analysis tasks related to operation and control and, in the second part, it briefly presents the results of three examples of analyses that were performed. All the presented examples are related to actual situations in which the scenarios were studied by analysts using thermal-hydraulic codes and prepared nodalizations. The paper also includes a qualitative evaluation of the benefits obtained by ANAV through thermal-hydraulic analyses aimed at supporting operation and plant control. 2010-11-05T14:40:13Z http://hdl.handle.net/2117/9269 Title: The Sichel Model and the mixing and truncation order Authors: Puig Oriol, Xavier; Ginebra Molins, Josep; Font Valverde, Martí Abstract: The analysis of word frequency count data can be very useful in authorship attribution problems. Zerotruncated generalized inverse Gaussian–Poisson mixture models are very helpful in the analysis of these kinds of data because their model-mixing density estimates can be used as estimates of the density of the word frequencies of the vocabulary. It is found that this model provides excellent fits for theword frequency counts of very long texts, where the truncated inverse Gaussian–Poisson special case fails because it does not allow for the large degree of over-dispersion in the data. The role played by the three parameters of this truncated GIG-Poisson model is also explored. Our second goal is to compare the fit of the truncated GIG-Poisson mixture model with the fit of the model that results from switching the order of the mixing and truncation stages. A heuristic interpretation of the mixing distribution estimates obtained under this alternative GIG-truncated Poisson mixture model is also provided. 2010-10-04T11:07:20Z http://hdl.handle.net/2117/7143 Title: Source of Confusion Authors: Tort-Martorell Llabrés, Xavier; Grima Cintas, Pedro; Marco Almagro, Lluís 2010-05-10T15:32:42Z http://hdl.handle.net/2117/6957 Title: MicroRNAs expression, chromosomal alterations and immunoglobulin variable Heavy chain hypermutations in Mantle Cell Lymphomas Authors: López-Guillermo, A; Navarro, A; Beà, Sílvia; Fernández, V; Prieto, M; Salaverria, I; Jares, P; Hartmann, E; Mozos, A; Hernández, L; Campo, E; Rossenwald, A; Serrano, Sergi; Solé Parellada, Francesc; Ott, G; Puig Oriol, Xavier; Colomer, D; Villamor, N. Abstract: The contribution of microRNAs (miR) to the pathogenesis of mantle cell lymphoma (MCL) is not well known.We investigated the expression of 86 mature miRs mapped to frequently altered genomic regions in MCL in CD5+/CD5 normal B cells, reactive lymph nodes, and purified tumor cells of 17 leukemic MCL, 12 nodal MCL, and 8MCL cell lines. Genomic alterations of the tumors were studied by single nucleotide polymorphism arrays and comparative genomic hybridization. Leukemic and nodal tumors showed a high number of differentially expressed miRs compared with purified normal B cells, but only some of them were commonly deregulated in both tumor types. An unsupervised analysis of miR expression profile in purified leukemic MCL cells revealed two clusters of tumors characterized by different mutational status of the immunoglobulin genes, proliferation signature, and number of genomic alterations. The expression of most miRs was not related to copy number changes in their respective chromosomal loci. Only the levels of miRs included in the miR-17-92 cluster were significantly related to genetic alterations at 13q31. Moreover, overexpression of miR-17-5p/miR-20a from this cluster was associated with high MYC mRNA levels in tumors with a more aggressive behavior. In conclusion, the miR expression pattern of MCL is deregulated in comparison with normal lymphoid cells and distinguishes two subgroups of tumors with different biological features. 2010-04-16T10:46:41Z http://hdl.handle.net/2117/6931 Title: On the measure and the estimation of evenness and diversity Authors: Ginebra Molins, Josep; Puig Oriol, Xavier Abstract: Modelling word or species frequency count data through zero truncated Poisson mixture models allows one to interpret the model mixing distribution as the distribution of the word or species frequencies of the vocabulary or population. As a consequence, estimates of their mixing density can be used as a fingerprint of the style of the author in his texts or of the ecosystem in its samples. Definitions of measure of the evenness and of measure of the diversity within a vocabulary or population are given, and the novelty of these definitions is explained. It is then proposed that the measures of the evenness and of the diversity of a vocabulary or population be approximated through the expectation of these measures under the word or species frequency distribution. That leads to the assessment of the lack of diversity through measures of the variability of the mixing frequency distribution estimates described above. 2010-04-14T10:56:09Z http://hdl.handle.net/2117/6755 Title: Comparing three-step heuristics for the permutation flow shop problem Authors: Ribas Vila, Immaculada; Companys Pascual, Ramón; Tort-Martorell Llabrés, Xavier Abstract: In this paper a three steps heuristic for the permutation flow shop problem is proposed. The objective is to minimize the maximum time for completing the jobs, or the makespan. The first two steps are inspired by the NEH heuristic, to which a new tie breaking strategy has been incorporated in the insertion phase. Furthermore, the reversibility property of the problem dealt with is taken as a tool for improving the obtained solution. The third step consists of an iterated local search procedure with an embedded local search which is a variant of the non exhaustive descent algorithm. The statistical analysis of the results shows the effectiveness of the proposed procedures. 2010-03-22T15:50:02Z