64 resultados para field of solenoid

em Consorci de Serveis Universitaris de Catalunya (CSUC), Spain


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Peer-reviewed

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In terms of the Fourier spectrum, a simple but general analytical expression is given for the evanescent field associated to a certain kind of non-paraxial exact solutions of the Maxwell equations. This expression enables one to compare the relative weight of the evanescent wave with regard to the propagating field. In addition, in those cases in which the evanescent term is significant, the magnitude of the field components across the transverse profile (including the evanescent features) can be determined. These results are applied to some illustrative examples.

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The aim of this paper is to give an explicit formula for the num- bers of abelian extensions of a p-adic number field and to study the generating function of these numbers. More precisely, we give the number of abelian ex- tensions with given degree and ramification index, and the number of abelian extensions with given degree of any local field of characteristic zero. Moreover, we give a concrete expression of a generating function for these last numbers

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The primary purpose of this exploratory empirical study is to examine the structural stability of a limited number of alternative explanatory factors of strategic change. On the basis of theoretical arguments and prior empirical evidence from two traditional perspectives, we propose an original empirical framework to analyse whether these potential explanatory factors have remained stable over time in a highly turbulent environment. This original question is explored in a particular setting: the population of Spanish private banks. The firms of this industry have experienced a high level of strategic mobility as a consequence of fundamental changes undergone in their environmental conditions over the last two decades (mainly changes related to the new banking and financial regulation process). Our results consistently support that the effect of most explanatory factors of strategic mobility considered did not remain stable over the whole period of analysis. From this point of view, the study sheds new light on major debates and dilemmas in the field of strategy regarding why firms change their competitive patterns over time and, hence, to what extent the "contextdependency" of alternative views of strategic change as their relative validation can vary over time for a given population. Methodologically, this research makes two major contributions to the study of potential determinants of strategic change. First, the definition and measurement of strategic change employing a new grouping method, the Model-based Cluster Method or MCLUST. Second, in order to asses the possible effect of determinants of strategic mobility we have controlled the non-observable heterogeneity using logistic regression models for panel data.

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In this paper, 27 studies from the last decade which deal more or less explicitly with the International New Venture, global start-up or born-global phenomenon are first identified, and then fully examined and critically assessed as a basis for obtaining an adequate view of the state-of-the-art of this increasingly important research avenue in the field of International Entrepreneurship (IE). The methodology used for this synthetic review allow us to analyze a number of recent, purposefully-chosen studies that are systematically compared along the following criteria: 1) main objective and type of research; 2) theoretical framework/s of reference, 3) methodological issues, and 4) main findings and/or conclusions. As a result of this literature review, a critical assessment follows in which the most relevant benefits and contributions as well as potential drawbacks, limitations or major discrepancies in the research activities conducted so far are discussed. Finally, some suggestions and implications are provided in the form of future research directions.

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Actualment, la resposta de la majoria d’instrumentació operacional i dels dosímetres personals utilitzats en radioprotecció per a la dosimetria neutrònica és altament dependent de l’energia dels espectres neutrònics a analitzar, especialment amb camps neutrònics amb una important component intermitja. En conseqüència, la interpretació de les lectures d’aquests aparells es complicada si no es té un coneixement previ de la distribució espectral de la fluència neutrònica en els punts d’interès. El Grup de Física de les Radiacions de la Universitat Autònoma de Barcelona (GFR-UAB) ha desenvolupat en els últims anys un espectròmetre de neutrons basat en un Sistema d’Esferes Bonner (BSS) amb un contador proporcional d’3He com a detector actiu. Els principals avantatges dels espectròmetres de neutrons per BSS són: la seva resposta isotròpica, la possibilitat de discriminar la component neutrònica de la gamma en camps mixtos, i la seva alta sensibilitat neutrònica als nivells de dosi analitzats. Amb aquestes característiques, els espectròmetres neutrònics per BSS compleixen amb els estándards de les últimes recomanacions de la ICRP i poden ser utilitzats també en el camp de la dosimetria neutrònica per a la mesura de dosis en el rang d’energia que va dels tèrmics fins als 20 MeV, en nou ordres de magnitud. En el marc de la col•laboració entre el GFR - UAB i el Laboratorio Nazionale di Frascati – Istituto Nazionale di Fisica Nucleare (LNF-INFN), ha tingut lloc una experiència comparativa d’espectrometria per BSS amb els feixos quasi monoenergètics de 2.5 MeV i 14 MeV del Fast Neutron Generator de l’ENEA. En l’exercici s’ha determinat l’espectre neutrònic a diferents distàncies del blanc de l’accelerador, aprofitant el codi FRUIT recentment desenvolupat pel grup LNF. Els resultats obtinguts mostren una bona coherència entre els dos espectròmetres i les dades mesurades i simulades.

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Thermal systems interchanging heat and mass by conduction, convection, radiation (solar and thermal ) occur in many engineering applications like energy storage by solar collectors, window glazing in buildings, refrigeration of plastic moulds, air handling units etc. Often these thermal systems are composed of various elements for example a building with wall, windows, rooms, etc. It would be of particular interest to have a modular thermal system which is formed by connecting different modules for the elements, flexibility to use and change models for individual elements, add or remove elements without changing the entire code. A numerical approach to handle the heat transfer and fluid flow in such systems helps in saving the full scale experiment time, cost and also aids optimisation of parameters of the system. In subsequent sections are presented a short summary of the work done until now on the orientation of the thesis in the field of numerical methods for heat transfer and fluid flow applications, the work in process and the future work.

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The field of laser application to the restoration and cleaning of cultural assets is amongst the most thriving developments of recent times. Ablative laser technological systems are able to clean and protect inestimable works of art subject to atmospheric agents and degradation over time. This new technology, which has been developing for the last forty year, is now available to restorers and has received a significant success all over Europe. An important contribution in the process of laser innovation has been carried out in Florence by local actors belonging to a creative cluster. The objects of the analysis are the genesis of this innovation in this local Florentine context, and the relationships among the main actors who have contributed in it. The study investigates how culture can play a part in the generation of ideas and innovations, and which are the creative environments that can favour it. In this context, the issue of laser technologies for the restoration of cultural heritage has been analysed as a case study in the various paths taken by the Creative Capacity of the Culture (CCC).

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Recent research in the field of study abroad shows that study abroad participation among all U.S. students increased 20% since 2001 and nearly 200,000 U.S. students currently go abroad each year. Additionally, about 8% of all undergraduate degree recipients receive part of their education abroad. Although quantitative studies have dominated research on study abroad, my research project calls for a qualitative approach since the goal is to understand what study abroad is as a cultural event, what authentic cultural immersion is, how program stakeholders understand and perceive cultural immersion, and how cultural immersion in programs can be improved. Following the tradition of ethnographic and case study approaches in study abroad research, my study also pivots on ethnography. As an ethnographer I collected data mainly through participant observation, semi-structured interviews, and document analysis. The study abroad participants were a group of undergraduate native speakers of English studying Spanish for seven weeks in Cádiz, a small costal city in southern Spain, as well as program coordinators, host community members, and professors. I also examined the specific program design features, particularly the in-class and out-of-class activities that students participated in. The goal was to understand if these features were conducive to authentic immersion in the language and culture. Eventually, I elaborated an ethnographic evaluation of the study abroad program and its design features suggesting improvements in order to enhance the significance and value of study abroad as a cultural event. Among other things, I discussed the difficulties that students had at the beginning of their sojourn to understand local people, get used to their host families’ small apartments, get adjusted to new schedules and eating habits, and venture out from the main group to individually explore the new social and cultural fabric and interact with the host community. The program evaluation revealed the need for carefully-designed pre-departure preparation sessions, pre-departure credit-bearing courses in intercultural communication, and additional language practice abroad and opportunities to come in contact with the local community through internships, volunteer or field work. My study gives an important contribution in study abroad research and education. It benefits students, teachers, and study abroad directors and coordinators in suggesting ideas on how to improve the program and optimize the students’ cultural experiences abroad. This study is also important because it investigated how US undergraduate learners studying the Spanish language and culture approach and perceive the study abroad experience in Spain.

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El Library and Learning Support Working Group (LLSWG) és una xarxa europea de professionals de biblioteca i de la informació i educadors dins de l'Associació Europea d'Universitats d'Ensenyament (EADTU). EADTU és l'organització que representa tant les universitats obertes i d'ensenyament a distància com els consorcis nacionals d'institucions d'ensenyament superior actius en els camps d'educació de distància i e-learning. El 2005 l'Associació Europea d'Universitats d'Ensenyament de Distància (EADTU) presentava a la Comissió Europea una proposta de projecte sobre Mobilitat Virtual anomenada E-MOVE. El projecte incloïa, entre d'altres, un paquet de treball referent a biblioteca i suport a l'aprenentatge al context de mobilitat virtual. Aquest fou desenvolupat pel LLSWG de l'EADTU.

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Aquest document de treball mira d'establir un nou camp d'investigació a la cruïlla entre els fluxos de migració i d'informació i comunicació. Hi ha diversos factors que fan que valgui la pena adoptar aquesta perspectiva. El punt central és que la migració internacional contemporània és incrustada en la dinàmica de la societat de la informació, seguint models comuns i dinàmiques interconnectades. Per consegüent, s'està començant a identificar els fluxos d'informació com a qüestions clau en les polítiques de migració. A més, hi ha una manca de coneixement empíric en el disseny de xarxes d'informació i l'ús de les tecnologies d'informació i comunicació en contextos migratoris. Aquest document de treball també mira de ser una font d'hipòtesis per a investigacions posteriors.

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We present a computer vision system that associates omnidirectional vision with structured light with the aim of obtaining depth information for a 360 degrees field of view. The approach proposed in this article combines an omnidirectional camera with a panoramic laser projector. The article shows how the sensor is modelled and its accuracy is proved by means of experimental results. The proposed sensor provides useful information for robot navigation applications, pipe inspection, 3D scene modelling etc

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Catadioptric sensors are combinations of mirrors and lenses made in order to obtain a wide field of view. In this paper we propose a new sensor that has omnidirectional viewing ability and it also provides depth information about the nearby surrounding. The sensor is based on a conventional camera coupled with a laser emitter and two hyperbolic mirrors. Mathematical formulation and precise specifications of the intrinsic and extrinsic parameters of the sensor are discussed. Our approach overcomes limitations of the existing omni-directional sensors and eventually leads to reduced costs of production

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Aquest article s'aplica un enfocament comparatiu de la gestió del sector petrolier en dos països rics en petroli a l'Orient Mitjà: Aràbia Saudita i els Emirats Àrabs Units (EAU). Més explícitament, s'examinen els factors que millor expliquen la variació en les estratègies que han vingut aplicant en el sector des de l'establiment de les seves empreses petrolieres nacionals (NOC). Recorrent a la literatura sobre expropiació / privatització en el camp d'Estudis de l'Energia, en aquest treball es proposa un marc teòric per analitzar la lògica que hi ha al darrera de les diferents formes d'exploració i les estratègies de producció en el sector petrolier. Teòricament, aquesta investigació té com a objectiu avançar en un conjunt d'eines d'anàlisi per abordar millor i entendre els determinants reals del procés de presa de decisions en el upstream. Empíricament, el model es prova en els casos divergents d'Aràbia Saudita i els Emirats Àrabs Units, i una sèrie de lliçons s'han extret. En última instància, aquest treball ha d'augmentar la conscienciació entre els erudits i els polític, tant sobre el poc coneixement que tenim sobre els mecanismes interns que impulsen les estratègies ascendents en el majors estats productor de petroli.