Numerical resolution of an exact heat conduction model with a delay term

In this paper we analyze, from the numerical point of view, a dynamic thermoelastic problem. Here, the so-called exact heat conduction model with a delay term is used to obtain the heat evolution. Thus, the thermomechanical problem is written as a coupled system of partial differential equations, and its variational formulation leads to a system written in terms of the velocity and the temperature fields. An existence and uniqueness result is recalled. Then, fully discrete approximations are introduced by using the classical finite element method to approximate the spatial variable and the implicit Euler scheme to discretize the time derivatives. A priori error estimates are proved, from which the linear convergence of the algorithm could be derived under suitable additional regularity conditions. Finally, a two-dimensional numerical example is solved to show the accuracy of the approximation and the decay of the discrete energy.Peer ReviewedPostprint (published version

Government employment and pay : a global and regional perspective

The authors try to replace myths about government pay and employment with reliable facts from a survey for about 100 countries in the early 1900s. The study also outlines the general nature of civil service problems in the different regions. Nevertheless, while the facts are useful to"flag"possible problems and initiate a dialogue, recommendations for reform must be based on country-specific analysis. Globally, government employment is negatively associated with wages, and positively with the fiscal deficit (although the availability of financing is more important) and with per capita income (confirming"Wagner's Law"). But the global results stem almost entirely from strong results for Africa and Latin America. Civil service reform has suffered in the past from an overemphasis on retrenchment for fiscal reasons. Its true objective, for each country, is to achieve a civil service of the size and skill-mix, incentives, professional ethos, and accountability needed to provide public goods, help formulate and enforce the rules, and intervene to remedy market failures -as these government roles happen to be defined in the country in question. Civil service reform can begin with various diagnostic and fact-finding activities. The key measures concern rightsizing, incentives, and accountability. These are all relative notions: the right size of the workforce depends on the roles assigned to government; wage adequacy depends on private compensation levels; and strengthening of accountability must define accountability for what and to whom. When retrenchment is warranted, it must be carried out with great care to avoid skill reduction, demoralization, and lower-quality service. Adequate compensation is a must, and wage compression isto be avoided. But performance bonuses, popular in some advanced countries, have been only marginally effective in improving performance in developing countries, even in the private sector. And they can be dangerous in countries with ethnic, clan, or religious conflicts. Finally, improvements in accountability will most often require greater external openness and systematic feedback from service users.Banks&Banking Reform,Enterprise Development&Reform,Municipal Financial Management,Decentralization,Environmental Economics&Policies,National Governance,Banks&Banking Reform,Municipal Financial Management,Environmental Economics&Policies,Economic Policy, Institutions and Governance

An international statistical survey of government employment and wages

This paper complements a separate study in this Series ("Government Employment and Pay: A Global and Regional Perspective,"Policy Research Working Paper 1771, May, 1997) by providing the detailed statistical and econometric evidence on which that separate study is based. The authors briefly summarize the key findings of the earlier paper for the reader's convenience and to permit this paper to stand alone. However, the purpose of the paper is to provide the couintry-by-country statistics. The reader is referred to the companion paper for a description and analysis of the main findings.Municipal Financial Management,Environmental Economics&Policies,Labor Policies,Banks&Banking Reform,National Governance,Municipal Financial Management,Health Monitoring&Evaluation,National Governance,Environmental Economics&Policies,Banks&Banking Reform

Analysis and modeling of PEM fuel cell systems

Analisi e modellazione di sistemi a celle a combustibile di tipo PEMThe purpose of this thesis is to create a transient model of a PEM fuel cell system, based on Matlab Simulink, as general, flexible and adaptable as possible, in order to be easily set on different type of systems. The object of the study is the development of the simulation tool, and its validation against literature and experimental data. An important aim of the developed dynamic semi-empirical model is to try to adopt a theoretical physics-based approach whenever possible, in order to have an accurate scientific correlation between experimental output and theoretical laws, without neglecting the accuracy that could be provided by empirical equations. The major work is focused on the fuel cell stack modeling and involves also a large review of literature analysis concerning the simulation of PEM-FCs. In order to guarantee the adaptability of the model, taking inspiration from the latest studies in this field, a differential evolution algorithm is developed to realize the fitting process of the modeled polarization curve, by means of the stack voltage model, on experimental data. This algorithm has a strategic importance for the choice and the setting of the stack voltage equations on the real static performance of the PEM fuel cell system analyzed, with a proved error of about 2-3%. The transient behaviors captured in the model includes flow characteristics, inertia dynamics, lumped-volume manifold filling dynamics, time evolving-homogeneous reactant pressure or mole fraction, membrane humidity and thermal response of fuel cell and cooling system. From one side, the validation against literature data of Section 4 is realized after the development of a general dynamic PEM-FC system model described in Section 2 and 3, comprising all the components normally present in these systems. The comprehensive dynamic model proposed, usually not presented in literature, perform very well respect to the experimental data, comprising the thermic data and the hydration of the membrane, the most important operative parameters but also the most complex ones to simulate. On the other side, the HI-SEA Joint Laboratory, between Fincantieri S.p.A. and the University of Genoa, allows to study a PEM fuel cell system of 8 stacks sized 33 kW each for a total maximum power of 260 kW. The adaptation and the simplification of the dynamic model to this plant layout helps to study a bigger and more complex PEM-FC system and to validate the model to the experimental data. The simplification of the dynamic model starts form the necessity to set the equations only by the commercially available data, usually limited to the datasheet information. This limitation makes the HI-SEA model less detailed but, at the same time, simpler and able to provide different important results, as the stack and cooling system thermal balances, starting from few easily obtainable data

Las cofradías rurales en Tierra de Campos. La religiosidad popular en el Antiguo Régimen

Las cofradías religiosas constituyeron una de las principales formas de sociabilidad del Antiguo Régimen, cuya principal tarea, además de la espiritual, fue la caritativa y asistencial. El objetivo de este trabajo, intenta establecer la importancia de estas hermandades en los ámbitos rurales de la Castilla Moderna. Para ello es preciso acudir a la revisión historiográfica de las últimas décadas, y también a las fuentes documentales de archivo, libros de cuentas, reglas y estatutos de aquellas hermandades. Así, se pueden establecer algunas claves de la sociedad sacralizada del Antiguo Régimen, centradas en la decisiva actuación de estas entidades en el mundo rural.Departamento de Historia Moderna, Contemporánea y de América, Periodismo y Comunicación Audiovisual y PublicidadGrado en Histori

Spontaneous nucleation of structural defects in inhomogeneous ion chains

Structural defects in ion crystals can be formed during a linear quench of the transverse trapping frequency across the mechanical instability from a linear chain to the zigzag structure. The density of defects after the sweep can be conveniently described by the Kibble-Zurek mechanism. In particular, the number of kinks in the zigzag ordering can be derived from a time-dependent Ginzburg-Landau equation for the order parameter, here the zigzag transverse size, under the assumption that the ions are continuously laser cooled. In a linear Paul trap the transition becomes inhomogeneous, being the charge density larger in the center and more rarefied at the edges. During the linear quench the mechanical instability is first crossed in the center of the chain, and a front, at which the mechanical instability is crossed during the quench, is identified which propagates along the chain from the center to the edges. If the velocity of this front is smaller than the sound velocity, the dynamics becomes adiabatic even in the thermodynamic limit and no defect is produced. Otherwise, the nucleation of kinks is reduced with respect to the case in which the charges are homogeneously distributed, leading to a new scaling of the density of kinks with the quenching rate. The analytical predictions are verified numerically by integrating the Langevin equations of motion of the ions, in presence of a time-dependent transverse confinement. We argue that the non-equilibrium dynamics of an ion chain in a Paul trap constitutes an ideal scenario to test the inhomogeneous extension of the Kibble-Zurek mechanism, which lacks experimental evidence to date.Comment: 19 pages, 5 figure

Structural defects in ion crystals by quenching the external potential: the inhomogeneous Kibble-Zurek mechanism

The non-equilibrium dynamics of an ion chain in a highly anisotropic trap is studied when the transverse trap frequency is quenched across the value at which the chain undergoes a continuous phase transition from a linear to a zigzag structure. Within Landau theory, an equation for the order parameter, corresponding to the transverse size of the zigzag structure, is determined when the vibrational motion is damped via laser cooling. The number of structural defects produced during a linear quench of the transverse trapping frequency is predicted and verified numerically. It is shown to obey the scaling predicted by the Kibble-Zurek mechanism, when extended to take into account the spatial inhomogeneities of the ion chain in a linear Paul trap.Comment: 5 pages, 3 figure

Helmes-Hayes/Santoro (eds.): Everett Hughes

Book review of: Helmes-Hayes, Richard C., and Marco Santoro (eds.) (2016) The Anthem companion to Everett Hughes, London, New York: Anthem Press. 243 pp. ISBN: 978-0-85728-178-4. Price: $ 115 / £ 70 (Hardcover

Inclusive education proposals for ADHD adolescent girls in EFL in the high school

Attention to diversity is a current issue which must be considered as a crucial and relevant aspect to deal with in education. The present work consists in providing inclusive education proposals addressed to a classroom of English as foreign language in the whole stage of Compulsory Secondary Education with adolescent girls with Attention Deficit Hyperactivity Disorder (ADHD). After doing a research on the legal framework covering the issue of attention to diversity, especially in Castilla y León (Spain), dealing with the aspects to be taken into account concerning ADHD, particularly girls with the disorder, and studying in detail the educational approaches which seem to be more beneficial and useful to meet the demands of diversity, this dissertation gives inclusive proposals as teaching projects to be implemented in the classroom. These projects consist of three parts: the explanation of some activities following the approaches selected, their benefits for ADHD adolescent girls, and some drawbacks of the approaches.Departamento de Filología InglesaMáster en Profesor de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanzas de Idioma