Multi-sample analysis of moment-structures: Asymptotic validity of inferences based on second-order moments

In moment structure analysis with nonnormal data, asymptotic valid inferences require the computation of a consistent (under general distributional assumptions) estimate of the matrix $\Gamma$ of asymptotic variances of sample second--order moments. Such a consistent estimate involves the fourth--order sample moments of the data. In practice, the use of fourth--order moments leads to computational burden and lack of robustness against small samples. In this paper we show that, under certain assumptions, correct asymptotic inferences can be attained when $\Gamma$ is replaced by a matrix $\Omega$ that involves only the second--order moments of the data. The present paper extends to the context of multi--sample analysis of second--order moment structures, results derived in the context of (simple--sample) covariance structure analysis (Satorra and Bentler, 1990). The results apply to a variety of estimation methods and general type of statistics. An example involving a test of equality of means under covariance restrictions illustrates theoretical aspects of the paper.

On the throughput-WIP trade-off in queueing systems, diminishing returns and the threshold property: A linear programming approach

We present a new unifying framework for investigating throughput-WIP(Work-in-Process) optimal control problems in queueing systems,based on reformulating them as linear programming (LP) problems withspecial structure: We show that if a throughput-WIP performance pairin a stochastic system satisfies the Threshold Property we introducein this paper, then we can reformulate the problem of optimizing alinear objective of throughput-WIP performance as a (semi-infinite)LP problem over a polygon with special structure (a thresholdpolygon). The strong structural properties of such polygones explainthe optimality of threshold policies for optimizing linearperformance objectives: their vertices correspond to the performancepairs of threshold policies. We analyze in this framework theversatile input-output queueing intensity control model introduced byChen and Yao (1990), obtaining a variety of new results, including (a)an exact reformulation of the control problem as an LP problem over athreshold polygon; (b) an analytical characterization of the Min WIPfunction (giving the minimum WIP level required to attain a targetthroughput level); (c) an LP Value Decomposition Theorem that relatesthe objective value under an arbitrary policy with that of a giventhreshold policy (thus revealing the LP interpretation of Chen andYao's optimality conditions); (d) diminishing returns and invarianceproperties of throughput-WIP performance, which underlie thresholdoptimality; (e) a unified treatment of the time-discounted andtime-average cases.

Optimal second-degree price discrimination and arbitrage: On the role of asymetric information among buyers

The traditional theory of monopolistic screening tackles individualself-selection but does not address the possibility that buyers couldform a coalition to coordinate their purchases and to reallocate thegoods. In this paper, we design the optimal sale mechanism which takesinto account both individual and coalition incentive compatibilityfocusing on the role of asymmetric information among buyers. We showthat when a coalition of buyers is formed under asymmetric information,the monopolist can do as well as when there is no coalition. Although inthe optimal sale mechanism marginal rates of substitution are notequalized across buyers (hence there exists room for arbitrage), theyfail to realize the gains from arbitrage because of the transaction costsin coalition formation generated by asymmetric information.

World population growth and fertility patterns, 1960-2000. A simple model explaining the evolution of world's fertility during the second half of the 20th Century

In this paper we attempt to describe the general reasons behind the world populationexplosion in the 20th century. The size of the population at the end of the century inquestion, deemed excessive by some, was a consequence of a dramatic improvementin life expectancies, attributable, in turn, to scientific innovation, the circulation ofinformation and economic growth. Nevertheless, fertility is a variable that plays acrucial role in differences in demographic growth. We identify infant mortality, femaleeducation levels and racial identity as important exogenous variables affecting fertility.It is estimated that in poor countries one additional year of primary schooling forwomen leads to 0.614 child less per couple on average (worldwide). While it may bepossible to identify a global tendency towards convergence in demographic trends,particular attention should be paid to the case of Africa, not only due to its differentdemographic patterns, but also because much of the continent's population has yet toexperience improvement in quality of life generally enjoyed across the rest of theplanet.

Implementing TURF analysis through binary linear programming

This paper introduces the approach of using Total Unduplicated Reach and Frequency analysis (TURF) to design a product line through a binary linear programming model. This improves the efficiency of the search for the solution to the problem compared to the algorithms that have been used to date. The results obtained through our exact algorithm are presented, and this method shows to be extremely efficient both in obtaining optimal solutions and in computing time for very large instances of the problem at hand. Furthermore, the proposed technique enables the model to be improved in order to overcome the main drawbacks presented by TURF analysis in practice.

Optimization of multiclass queueing networks with changeover times via the achievable region method: Part II, the multi-station case

We address the problem of scheduling a multi-station multiclassqueueing network (MQNET) with server changeover times to minimizesteady-state mean job holding costs. We present new lower boundson the best achievable cost that emerge as the values ofmathematical programming problems (linear, semidefinite, andconvex) over relaxed formulations of the system's achievableperformance region. The constraints on achievable performancedefining these formulations are obtained by formulatingsystem's equilibrium relations. Our contributions include: (1) aflow conservation interpretation and closed formulae for theconstraints previously derived by the potential function method;(2) new work decomposition laws for MQNETs; (3) new constraints(linear, convex, and semidefinite) on the performance region offirst and second moments of queue lengths for MQNETs; (4) a fastbound for a MQNET with N customer classes computed in N steps; (5)two heuristic scheduling policies: a priority-index policy, anda policy extracted from the solution of a linear programmingrelaxation.

Motivation and content Language Integrated Learning : an impulse for Second Language Teaching

“Estudiantes motivados producen profesores motivados y viceversa” (Lesley Denham)La cita refleja el efecto recíproco que tiene el comportamiento del profesor en el compromiso de los estudiantes a lo largo del año y viceversa. Es sorprendente como, destacando las fortalezas de cada estudiante en lugar de sus debilidades, nunca comparándolos entre ellos sino con su propio rendimiento, puede despertar una motivación intrínseca en el estudiante, y una merecida satisfacción personal para el profesor.Sin embargo, no existen botones motivacionales mágicos que podamos pulsar y hacer que el alumno quiera aprender. Como profesores, tomar la iniciativa será crucial: dar a nuestros estudiantes el espacio suficiente para experimentar, realzar su autonomía, e intuir las respuestas a través de un proceso inductivo. En definitiva, hacerles protagonistas de su proceso de aprendizaje.Incluir AICLE en la clase de inglés es una metodología que nos ayudará a conseguirlo. Los estudiantes asocian AICLE con algo interesante y divertido, diferente a las sesiones teóricas. Como resultado, al utilizar la lengua, lo hacen movidos por sus sentimientos, aprendiendo de forma implícita.“Estudiants motivats produeixen professors motivats i viceversa” (Lesley Denham)La cita reflecteix l'efecte recíproc que té el comportament del professor en el compromís dels estudiants al llarg de l'any i viceversa. És sorprenent com, destacant les fortaleses de cada estudiant en lloc de les seves debilitats, mai comparant-los entre ells sinó amb el seu propi rendiment, pot despertar una motivació intrínseca a l'estudiant, i una merescuda satisfacció personal per al professor.No obstant això, no existeixen botons motivacionals màgics que puguem prémer i fer que l'alumne vulgui aprendre. Com a professors, prendre la iniciativa serà crucial: donar als nostres estudiants l'espai suficient per experimentar, realçar la seva autonomia, i intuir les respostes a través d'un procés inductiu. En definitiva, fer-los protagonistes del seu procés d'aprenentatge.Incloure AICLE en la classe d'anglès és una metodologia que ens ajudarà a aconseguir-ho. Els estudiants consideren AICLE interessant i divertit, diferent a les sessions teòriques. Com a resultat, en utilitzar la llengua, ho fan moguts pels seus sentiments, aprenent de forma implícita.

Transferencia en la adquisición de segundas lenguas. Un estudio con alumnado rumano en un contexto bilingüe = Transfer in second language acquisition. A study with Romanian schoolchildren in a bilingual context

Situados en el contexto catalán, el artículo estudia la influencia de la L1 (rumano) en algunos aspectos morfosintácticos de la adquisición de las L2s. Para ello se analizan las competencias lingüísticas en catalán y castellano de un grupo de escolares cuya L1 es el rumano y que cursan 2.º y 4.º de ESO. Los datos muestran que los alumnos cuya L1 es el rumano, a pesar de dominar una lengua románica cercana a las lenguas de aprendizaje (L2/L3), presentan dificultades comparables a otros colectivos con otras lenguasde origen. Por otra parte, nuestra investigación confirma que la L1 de este alumnado juega un importante papel en la adquisición de ambas lenguas, concluyendo que parte de los errores hallados son aquellos que se basan en estructuras de la lengua propia

The second law of thermodynamics and the global climate system : A review of the maximum entropy production principle

The long-term mean properties of the global climate system and those of turbulent fluid systems are reviewed from a thermodynamic viewpoint. Two general expressions are derived for a rate of entropy production due to thermal and viscous dissipation (turbulent dissipation) in a fluid system. It is shown with these expressions that maximum entropy production in the Earth s climate system suggested by Paltridge, as well as maximum transport properties of heat or momentum in a turbulent system suggested by Malkus and Busse, correspond to a state in which the rate of entropy production due to the turbulent dissipation is at a maximum. Entropy production due to absorption of solar radiation in the climate system is found to be irrelevant to the maximized properties associated with turbulence. The hypothesis of maximum entropy production also seems to be applicable to the planetary atmospheres of Mars and Titan and perhaps to mantle convection. Lorenz s conjecture on maximum generation of available potential energy is shown to be akin to this hypothesis with a few minor approximations. A possible mechanism by which turbulent fluid systems adjust themselves to the states of maximum entropy production is presented as a selffeedback mechanism for the generation of available potential energy. These results tend to support the hypothesis of maximum entropy production that underlies a wide variety of nonlinear fluid systems, including our planet as well as other planets and stars

Second differential of the entropy as a criterion for the stability in low-dimensional climate models

The second differential of the entropy is used for analysing the stability of a thermodynamic climatic model. A delay time for the heat flux is introduced whereby it becomes an independent variable. Two different expressions for the second differential of the entropy are used: one follows classical irreversible thermodynamics theory; the second is related to the introduction of response time and is due to the extended irreversible thermodynamics theory. the second differential of the classical entropy leads to unstable solutions for high values of delay times. the extended expression always implies stable states for an ice-free earth. When the ice-albedo feedback is included, a discontinuous distribution of stable states is found for high response times. Following the thermodynamic analysis of the model, the maximum rates of entropy production at the steady state are obtained. A latitudinally isothermal earth produces the extremum in global entropy production. the material contribution to entropy production (by which we mean the production of entropy by material transport of heat) is a maximum when the latitudinal distribution of temperatures becomes less homogeneous than present values

Student experiences in a course blended learning

Fascination is a project for design students, developed jointly by the Technical University of Catalonia (UPC) and the University of Technology Thonburi (KMUTT), which works with two groups of students, one group of participants in Spain and another group in Thailand where, hands-on activities, a range of technologies are used to prepare students for the lessons, through learning activities and content. This research paper presents the test of both a general model and a tool for measuring the participants’ experiences in a course that uses a blended learning methodology, with the aim of collecting empirical evidence to justify the effort of applying this methodology, based on the participants’ satisfaction. The procedure used in the conceptualization of the survey, the generation of topics, the collection of data, and the validation of the scale of various items are described here. The information, provided by the 26 people surveyed about the course and the virtual environment that was used, was analyzed to measure their perceptions and explore possible relations. Finally the conclusions of the research and the future work are presented.

Development of a microprocessor controlled energy harvester using a Peltier element

Nowadays it is necessary to research other types of energy alternatives and find the way to supply and save the energy we waste. The aim of the project consist of programming a microprocessor to measure if an oven radiates heat to the exterior, for the measure It is used a Peltier element that generates a voltage depending of the temperature difference between the oven and the air of the place where the oven is situated; The energy generated by the oven will be recollected in a condensor. A sensor will be used to know the exact measure. The second part of the project the main propose, is the development of a harvester. The microprocessor will use the voltage produced by the Peltier element to supply the electricity that it needs to work. A low power circuit and the appropriate software are needed to save the voltage generated.

Plan estratégico 2012-2105 para la empresa Automatizaciones Eléctricas, SL

La empresa moderna, se encuentra en una situación actual de incertidumbre en la que además está más expuesta a factores externos con el aumento de la competencia y el impacto de la globalización. Se enfrenta a un panorama que debe ser gestionado adecuadamente para asegurar su supervivencia y el éxito de su existencia. En este TFC, se presenta una de las herramientas ‘buque insignia’ del Management moderno, aquella que está destinada a ser la base de la Gestión de la empresa y que cada vez más se hace imprescindible para la construcción de un futuro cada vez más incierto, la Planificación Estratégica. El Plan Estratégico 2012-2015 de AESL se desarrolla en varios apartados que intentarán dar con las claves de la dirección que la empresa debe seguir y propone los objetivos que encontrará a través de la puesta en marcha de las acciones y estrategias determinadas. La primera etapa, y la más extensa, realiza un Análisis de la situación externa e interna de la empresa además de un Diagnóstico de la misma. Se analizan diversos factores que pueden contribuir o hacer peligrar el futuro de la empresa, y constituye el punto de partida de la planificación. En la segunda etapa, y con la información de la anterior fase, comienza la fijación de los Objetivos Corporativos y la definición de las Decisiones Estratégicas que han de transformar nuestro rumbo actual en el logro de esos objetivos. Las estrategias no sólo comportarán un ámbito corporativo, también se centrarán en estrategias funcionales con un carácter más definitorio en el interior de la empresa. Por último, la tercera y última etapa, aglutinará todas estas Decisiones estratégicas para transformarlas en las Decisiones Operativas, aquellas que se encargarán de gestionar el día a día de la empresa a través de los Planes de Acción, que suponen la etapa de mayor concreción del Plan. Este Plan a 3 años deberá erigirse como la herramienta de planificación más importante de la empresa, debiendo guiar las principales decisiones tomadas y convirtiéndose en un instrumento de consulta no sólo para decidir hoy lo que se hará en el futuro sino también para mantener unos niveles altos de competitividad en el tremendo esfuerzo que supone la gestión de una PYME.