Geometría flexible para las estructuras de barras

This article brings a geometric proposal which can be applied to the bar structures. The starting point is the substitution of the usual knots in a structural web by a system of combining the bars tivo by two, which is achieved by twisting the bars in each knot. The tensile forces that appear and the introduction of joints in each of these knots allow the transition from a rigid or undeformablegeometiy to a neiv flexible" one leading to the possibility of one and the same structural web adopting different sizes while preserving its original geometric form

Disseny, implementació i avaluació d'un joc tangible basat en puzles per aprendre concepte de les enginyeries TIC

L'interès per les carreres relacionades amb les enginyeries del camp de les Tecnologies de la Informació i la Comunicació (TIC) va caient any rere any i això es tradueix en menys matriculacions per cada any que passa. Una de les causes principals és la falta de motivació i interès envers aquestes carreres. Aquest problema s’atribueix a que les metodologies d’aprenentatge tradicionals no s’adeqüen a les necessitats i requeriments dels estudiants d’avui dia, que han crescut envoltats de tecnologia, i se’ls coneix amb el nom en anglès de digitalnatives.L’aprenentatge basat en jocs sorgeix com a una possible solució per afrontar aquesta falta d’interès per les àrees del coneixement relacionades amb les enginyeries TIC. Aquest mètode d'aprenentatge consisteix en que els estudiants aprenguin conceptes de les TIC mentre estan jugant a un joc. Per tant, en el context d’aquest PFC, ens centrarem en el disseny i implementació d’un joc per aprendre conceptes bàsics de les enginyeries TIC. En concret, el disseny d’aquest joc segueix les característiques definides per un model conceptual que descriuquins són els elements necessaris per crear jocs basats en puzles: quins són els elements principals que componen aquests tipus de joc i quines pistes es poden afegir per guiar a l’estudiant en el procés d’aprenentatge amb el joc. Per altra banda, pel que fa a laimplementació del joc, s’utilitzarà tecnologia basada en interfícies tangibles.Per tal d’analitzar el joc basat en puzles que s’ha dissenyat i implementat per aprendre conceptes basics de les Enginyeries TIC, s’ha portat a terme una avaluació amb estudiants d’un centre educatiu. Aspectes com el disseny de pistes, l’experiència dels estudiants amb el joc il’aprenentatge amb el joc seran analitzats per extreure les conclusions oportunes.

Disseny, implementació i avaluació d'un joc tangible basat en puzles per a l'aprenentatge d'arquitectura d'ordinadors

Actualment existeix una falta d'interès per part dels estudiants a l'àrea de les enginyeries en Tecnologies de la Informació i la Comunicació (TIC) que es pot veure reflectida en el descens de les matriculacions universitàries en aquest àmbit. Aquest fet està relacionat amb que la nova generació d‟estudiants està constantment en contacte amb tota mena d'aparells tecnològics estimulants i a l‟hora de l‟estudi poden sofrir una falta d‟interès per l‟ús d‟una metodologia d'aprenentatge més tradicional. En aquest sentit s'ha investigat que l‟ús de jocs com a eina educativa pot ser una bona solució per afrontar aquesta falta d'interès. No obstant això, actualment no existeixen gaires jocs destinats a aprendre conceptes relacionats amb les enginyeries TIC i que proporcionin als estudiants els mecanismes d'ajuda necessaris per donar-los suport durant l'aprenentatge d‟aquests nous conceptes. En aquest projecte es desenvoluparà un joc educatiu per a estudiants amb l‟objectiu de proporcionar uns primers coneixements sobre les TIC. Per una banda, per al disseny del joc s‟utilitzarà un model conceptual que defineix els elements necessaris per a dissenyar jocs basats en resoldre puzles. A més, aquest model conceptual permet el disseny no només de jocs per a PCs, sinó també de jocs tangibles i exploratius (mitjançant tecnologia mòbil). En el nostre cas, ens centrarem en la implementació d‟un joc tangible. Per altra banda, pel que fa a la implementació, tindrem en compte l‟estàndard educatiu d‟IMS Learning Design, demostrant d‟aquesta manera que aquest tipus de jocs es poden beneficiar dels avantatges que aporten els estàndards educatius. Per tant, en aquest PFC es dissenyarà i implementarà un joc tangible basat en puzles dintre de l‟àrea d‟arquitectura d‟ordinadors. El joc constarà de tres mini-jocs que es presentaran com jocs de realitat augmentada amb el suport d‟un ordinador i unes peces físiques amb les que interactuaran els usuaris. El sistema proporcionarà un sistema d‟ajuda i un sistema de puntuació. Per últim, avaluarem el joc en un centre escolar amb estudiants de 4t d‟ESO amb la finalitat d'analitzar les valoracions dels estudiants respecte el joc i les pistes proporcionades.

Essays in general equilibrium asset pricing

ABSTRACT : Research in empirical asset pricing has pointed out several anomalies both in the cross section and time series of asset prices, as well as in investors' portfolio choice. This dissertation aims to discover the forces driving some of these "puzzling" asset pricing dynamics and portfolio decisions observed in the financial market. Through the dissertation I construct and study dynamic general equilibrium models of heterogeneous investors in the presence of frictions and evaluate quantitatively their implications for financial-market asset prices and portfolio choice. I also explore the potential roots of puzzles in international finance. Chapter 1 shows that, by introducing jointly endogenous no-default type of borrowing constraints and heterogeneous beliefs in a dynamic general-equilibrium economy, many empirical features of stock return volatility can be reproduced. While most of the research on stock return volatility is empirical, this paper provides a theoretical framework that is able to reproduce simultaneously the cross section and time series stylized facts concerning stock returns and their volatility. In contrast to the existing theoretical literature related to stock return volatility, I don't impose persistence or regimes in any of the exogenous state variables or in preferences. Volatility clustering, asymmetry in the stock return-volatility relationship, and pricing of multi-factor volatility components in the cross section all arise endogenously as a consequence of the feedback between the binding of no-default constraints and heterogeneous beliefs. Chapters 2 and 3 explore the implications of differences of opinion across investors in different countries for international asset pricing anomalies. Chapter 2 demonstrates that several international finance "puzzles" can be reproduced by a single risk factor which captures heterogeneous beliefs across international investors. These puzzles include: (i) home equity preference; (ii) the dependence of firm returns on local and foreign factors; (iii) the co-movement of returns and international capital flows; and (iv) abnormal returns around foreign firm cross-listing events in the local market. These are reproduced in a setup with symmetric information and in a perfectly integrated world with multiple countries and independent processes producing the same good. Chapter 3 shows that by extending this framework to multiple goods and correlated production processes; the "forward premium puzzle" arises naturally as a compensation for the heterogeneous expectations about the depreciation of the exchange rate held by international investors. Chapters 2 and 3 propose differences of opinion across international investors as the potential resolution of several international finance `puzzles'. In a globalized world where both capital and information flow freely across countries, this explanation seems more appealing than existing asymmetric information or segmented markets theories aiming to explain international finance puzzles.

Demócrito y Epicuro: el átomo como elemento y como límite onto-lógico

El presente artículo ofrece una interpretación parcialmente heterodoxa del atomismogriego que interpreta aquella revolucionaria teoría como: 1) Un salto adelante respecto de la ontología eleática que suministra una nueva base más sólida al principio básico de ésta,a saber, "El ser no puede generarse a partir del no-ser" (tesis más bien convencional y ya clásica). 2) Una respuesta, tímidamente formulada, a la pregunta pitagórica por una universalismensura de cada cosa, a saber, la hipótesis, claramente avanzada por Demócrito, de que las piezas constitutivas de la materia, las partículas atómicas, poseen infinitos tamañosdiferentes a fin de eludir las dificultades planteadas por el programa pitagórico y ejemplificadas en la inconmensurabilidad de la diagonal y el lado del cuadrado; dicha hipótesis (yaquí radica el aspecto innovador del artículo) podría considerarse como una anticipación implícita de la moderna noción de fluxión o infinitésimo; la refutación de dicha soluciónpor la teoría aristotélica del continuo forzará a la segunda generación de atomistas, encabezada por Epicuro, a intentar un nuevo enfoque del problema con la formulación de la teoríade las rninirnaepartes, que, según nuestra interpretación, habría que identificar con los límites geométricos de las figuras atómicas.

Bacterial sensors: synthetic design and application principles

Bacterial reporters are live, genetically engineered cells with promising application in bioanalytics. They contain genetic circuitry to produce a cellular sensing element, which detects the target compound and relays the detection to specific synthesis of so-called reporter proteins (the presence or activity of which is easy to quantify). Bioassays with bacterial reporters are a useful complement to chemical analytics because they measure biological responses rather than total chemical concentrations. Simple bacterial reporter assays may also replace more costly chemical methods as a first line sample analysis technique. Recent promising developments integrate bacterial reporter cells with microsystems to produce bacterial biosensors. This lecture presents an in-depth treatment of the synthetic biological design principles of bacterial reporters, the engineering of which started as simple recombinant DNA puzzles, but has now become a more rational approach of choosing and combining sensing, controlling and reporting DNA 'parts'. Several examples of existing bacterial reporter designs and their genetic circuitry will be illustrated. Besides the design principles, the lecture also focuses on the application principles of bacterial reporter assays. A variety of assay formats will be illustrated, and principles of quantification will be dealt with. In addition to this discussion, substantial reference material is supplied in various Annexes.

Sortir del Laberint : un joc per pensar

“Sortir del Laberint” és un joc tipus puzzle, l’objectiu principal del qual és aconseguir que el jugador pugui sortir d’un laberint amb el mínim nombre de passes i el més ràpid possible.

Unraveling the "pressure effect" in nucleation

The influence of the pressure of a chemically inert carrier gas on the nucleation rate is one of the biggest puzzles in the research of gas-liquid nucleation. Experiments can show a positive effect, a negative effect, or no effect at all. The same experiment may show both trends for the same substance depending on temperature, or for different substances at the same temperature. We show how this ambiguous effect naturally arises from the competition of two contributions: nonisothermal effects and pressure-volume work. Our model clarifies seemingly contradictory experimental results and quantifies the variation of the nucleation ability of a substance in the presence of an ambient gas. Our findings are corroborated by molecular dynamics simulations and might have important implications since nucleation in experiments, technical applications, and nature practically always occurs in the presence of an ambient gas.

Adaptació metrològica grega en l'arquitectura ibèrica de Catalunya: Puig de Sant Andreu d'Ullastret i Mas Castellar de Pontós

En el presente artículo se analiza la adopción en el contexto ibérico catalán de los patrones métricos característicos de las colonias griegas del Mediterráneo occidental. La determinación de la unidad de medida constructiva empleada, así como de su aplicación, ha sido posible mediante la identificación de los principios geométricos estructurales de las torres defensivas ibéricas.

Three essays in dynamic corporate finance

The three essays constituting this thesis focus on financing and cash management policy. The first essay aims to shed light on why firms issue debt so conservatively. In particular, it examines the effects of shareholder and creditor protection on capital structure choices. It starts by building a contingent claims model where financing policy results from a trade-off between tax benefits, contracting costs and agency costs. In this setup, controlling shareholders can divert part of the firms' cash ows as private benefits at the expense of minority share- holders. In addition, shareholders as a class can behave strategically at the time of default leading to deviations from the absolute priority rule. The analysis demonstrates that investor protection is a first order determinant of firms' financing choices and that conflicts of interests between firm claimholders may help explain the level and cross-sectional variation of observed leverage ratios. The second essay focuses on the practical relevance of agency conflicts. De- spite the theoretical development of the literature on agency conflicts and firm policy choices, the magnitude of manager-shareholder conflicts is still an open question. This essay proposes a methodology for quantifying these agency conflicts. To do so, it examines the impact of managerial entrenchment on corporate financing decisions. It builds a dynamic contingent claims model in which managers do not act in the best interest of shareholders, but rather pursue private benefits at the expense of shareholders. Managers have discretion over financing and dividend policies. However, shareholders can remove the manager at a cost. The analysis demonstrates that entrenched managers restructure less frequently and issue less debt than optimal for shareholders. I take the model to the data and use observed financing choices to provide firm-specific estimates of the degree of managerial entrenchment. Using structural econometrics, I find costs of control challenges of 2-7% on average (.8-5% at median). The estimates of the agency costs vary with variables that one expects to determine managerial incentives. In addition, these costs are sufficient to resolve the low- and zero-leverage puzzles and explain the time series of observed leverage ratios. Finally, the analysis shows that governance mechanisms significantly affect the value of control and firms' financing decisions. The third essay is concerned with the documented time trend in corporate cash holdings by Bates, Kahle and Stulz (BKS,2003). BKS find that firms' cash holdings double from 10% to 20% over the 1980 to 2005 period. This essay provides an explanation of this phenomenon by examining the effects of product market competition on firms' cash holdings in the presence of financial constraints. It develops a real options model in which cash holdings may be used to cover unexpected operating losses and avoid inefficient closure. The model generates new predictions relating cash holdings to firm and industry characteristics such as the intensity of competition, cash flow volatility, or financing constraints. The empirical examination of the model shows strong support of model's predictions. In addition, it shows that the time trend in cash holdings documented by BKS can be at least partly attributed to a competition effect.

Simulação computacional aplicada ao desenvolvimento de embalagens para bananas

Este trabalho propõe um método de projeto de embalagem para produtos hortícolas, buscando uma otimização integrada dos aspectos geométricos, estruturais e térmicos, ligados à facilitação do resfriamento e armazenamento refrigerado. Para o dimensionamento e otimização estrutural, foi utilizado o Método dos Elementos Finitos implementado pelo programa ANSYS, obtendo-se oito modelos virtuais de embalagens, com 10% e 14% de área efetiva de aberturas e geometria quadrada, retangular e circular. Para o desenvolvimento dos experimentos, que avaliaram a relação da área de aberturas com o tempo de sete-oitavos de resfriamento, foram construídos protótipos de tábuas de madeira (Pinnus elliotti) de reflorestamento. Nas embalagens, foram acondicionados aproximadamente 13 kg de banana variedade Nanica (Musa cavendishii, cultivar nanica), resfriada num túnel de ar forçado (vazão de ar de 0,32 m³ s-1, temperatura de 8,0±1,2ºC e umidade relativa de 84,5±2,6%). O tempo de resfriamento também foi comparado com aquele obtido quando a mesma quantidade de frutas foi resfriada em embalagens de papelão (2,5% de área efetiva de abertura) e madeira (18% de área efetiva de abertura). Os resultados demonstraram que, entre os protótipos propostos, não houve diferença significativa no tempo de resfriamento dos frutos acondicionados nas embalagens desenvolvidas, sendo o tempo médio de resfriamento de 40,71±2,81 min. Na comparação com as embalagens de papelão e madeira, houve diferenças significativas, sendo que as embalagens comerciais tiveram tempos de resfriamento de 1,25 e 2 vezes maiores. Concluiu-se que a simulação estrutural computacional, aliada a algoritmos de otimização, além de procedimentos experimentais ligados à cadeia do frio, são recursos promissores no auxílio de projetos para embalagens de transporte de produtos hortícolas.

How hard is a commercial puzzle: the eternity II challenge

Recently, edge matching puzzles, an NP-complete problem, have received, thanks to money-prized contests, considerable attention from wide audiences. We consider these competitions not only a challenge for SAT/CSP solving techniques but also as an opportunity to showcase the advances in the SAT/CSP community to a general audience. This paper studies the NP-complete problem of edge matching puzzles focusing on providing generation models of problem instances of variable hardness and on its resolution through the application of SAT and CSP techniques. From the generation side, we also identify the phase transition phenomena for each model. As solving methods, we employ both; SAT solvers through the translation to a SAT formula, and two ad-hoc CSP solvers we have developed, with different levels of consistency, employing several generic and specialized heuristics. Finally, we conducted an extensive experimental investigation to identify the hardest generation models and the best performing solving techniques.

PuzleFotoApp

Memòria del projecte final de carrera de l'aplicació PuzleFotoApp. Aquesta aplicació és un joc educatiu (pel sistema operatiu Android) que permet resoldre puzles lliscants.

Eternal recurrence in a Neo-Kantian context

In this essay, I argue that someone who adopted a falsificationism of the sort that I have attributed to Nietzsche would be attracted to the doctrine of eternal recurrence. For Nietzsche, to think the becoming revealed through the senses means falsifying it through being. But the eternal recurrence offers the possibility of thinking becoming without falsification. I then argue that someone who held Nietzsche's falsificationism would see in human agency a conflict between being and becoming similar to that in empirical judgment. In the light of this conflict only the eternal recurrence would offer the possibility of truly affirming life. I end by discussing how this reading of the eternal recurrence solves a number of puzzles that have bedeviled interpreters.

IS SELF-DECEPTION PRETENSE?

I assess Tamar Gendler's (2007) account of self-deception according to which its characteristic state is not belief, but imaginative pretense. After giving an overview of the literature and presenting the conceptual puzzles engendered by the notion of self-deception, I introduce Gendler's account, which emerges as a rival to practically all extant accounts of self-deception. I object to it by first arguing that her argument for abandoning belief as the characteristic state of self-deception conflates the state of belief and the process of belief-formation when interpreting David Velleman's (2000) thesis that belief is an essentially truth-directed attitude. I then call attention to the fact that Velleman's argument for the identity of motivational role between belief and imagining, on which Gendler's argument for self-deception as pretense depends, conflates two senses of 'motivational role'-a stronger but implausible sense and a weaker but explanatorily irrelevant sense. Finally, I introduce Neil Van Leeuwen's (2009) argument to the effect that belief is the practical ground of all non-belief cognitive attitudes in circum-stances wherein the latter prompt action. I apply this framework to Gendler's account to ultimately show that imaginative pretense fails to explain the existence of voluntary actions which result from self-deception.