938 resultados para Digital Mathematical Library


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A Administração Financeira surge no início do século XIX juntamente com o movimento de consolidação das grandes empresas e a formação dos mercados nacionais americano enquanto que no Brasil os primeiros estudos ocorrem a partir da segunda metade do século XX. Desde entãoo país conseguiu consolidar alguns centros de excelência em pesquisa, formar grupo significativo de pesquisadores seniores e expandir as áreas de pesquisa no campo, contudo, ainda são poucos os trabalhos que buscam retratar as características da produtividade científica em Finanças. Buscando contribuir para a melhor compreensão do comportamento produtivo dessa área a presente pesquisa estuda sua produção científica, materializada na forma de artigos digitais, publicados em 24 conceituados periódicos nacionais classificados nos estratos Qualis/CAPES A2, B1 e B2 da Área de Administração, Ciências Contábeis e Turismo. Para tanto são aplicadas a Lei de Bradford, Lei do Elitismo de Price e Lei de Lotka. Pela Lei de Bradford são identificadas três zonas de produtividade sendo o núcleo formado por três revistas, estando uma delas classificada no estrato Qualis/CAPES B2, o que evidencia a limitação de um recorte tendo como único critério a classificação Qualis/CAPES. Para a Lei do Elitismo de Price, seja pela contagem direta ou completa, não identificamos comportamento de uma elite semelhante ao apontado pela teoria e que conta com grande número de autores com apenas uma publicação.Aplicando-se o modelo do Poder Inverso Generalizado, calculado por Mínimos Quadrados Ordinários (MQO), verificamos que produtividade dos pesquisadores, quando feita pela contagem direta, se adequa àquela definida pela Lei de Lotka ao nível de α = 0,01 de significância, contudo, pela contagem completa não podemos confirmar a hipótese de homogeneidade das distribuições, além do fato de que nas duas contagens a produtividade analisada pelo parâmetro n é maior que 2 e, portanto, a produtividade do pesquisadores de finanças é menor que a defendida pela teoria.

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DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY WITH PRIOR ARRANGEMENT

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This work reports the developnent of a mathenatical model and distributed, multi variable computer-control for a pilot plant double-effect climbing-film evaporator. A distributed-parameter model of the plant has been developed and the time-domain model transformed into the Laplace domain. The model has been further transformed into an integral domain conforming to an algebraic ring of polynomials, to eliminate the transcendental terms which arise in the Laplace domain due to the distributed nature of the plant model. This has made possible the application of linear control theories to a set of linear-partial differential equations. The models obtained have well tracked the experimental results of the plant. A distributed-computer network has been interfaced with the plant to implement digital controllers in a hierarchical structure. A modern rnultivariable Wiener-Hopf controller has been applled to the plant model. The application has revealed a limitation condition that the plant matrix should be positive-definite along the infinite frequency axis. A new multi variable control theory has emerged fram this study, which avoids the above limitation. The controller has the structure of the modern Wiener-Hopf controller, but with a unique feature enabling a designer to specify the closed-loop poles in advance and to shape the sensitivity matrix as required. In this way, the method treats directly the interaction problems found in the chemical processes with good tracking and regulation performances. Though the ability of the analytical design methods to determine once and for all whether a given set of specifications can be met is one of its chief advantages over the conventional trial-and-error design procedures. However, one disadvantage that offsets to some degree the enormous advantages is the relatively complicated algebra that must be employed in working out all but the simplest problem. Mathematical algorithms and computer software have been developed to treat some of the mathematical operations defined over the integral domain, such as matrix fraction description, spectral factorization, the Bezout identity, and the general manipulation of polynomial matrices. Hence, the design problems of Wiener-Hopf type of controllers and other similar algebraic design methods can be easily solved.

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The use of digital communication systems is increasing very rapidly. This is due to lower system implementation cost compared to analogue transmission and at the same time, the ease with which several types of data sources (data, digitised speech and video, etc.) can be mixed. The emergence of packet broadcast techniques as an efficient type of multiplexing, especially with the use of contention random multiple access protocols, has led to a wide-spread application of these distributed access protocols in local area networks (LANs) and a further extension of them to radio and mobile radio communication applications. In this research, a proposal for a modified version of the distributed access contention protocol which uses the packet broadcast switching technique has been achieved. The carrier sense multiple access with collision avoidance (CSMA/CA) is found to be the most appropriate protocol which has the ability to satisfy equally the operational requirements for local area networks as well as for radio and mobile radio applications. The suggested version of the protocol is designed in a way in which all desirable features of its precedents is maintained. However, all the shortcomings are eliminated and additional features have been added to strengthen its ability to work with radio and mobile radio channels. Operational performance evaluation of the protocol has been carried out for the two types of non-persistent and slotted non-persistent, through mathematical and simulation modelling of the protocol. The results obtained from the two modelling procedures validate the accuracy of both methods, which compares favourably with its precedent protocol CSMA/CD (with collision detection). A further extension of the protocol operation has been suggested to operate with multichannel systems. Two multichannel systems based on the CSMA/CA protocol for medium access are therefore proposed. These are; the dynamic multichannel system, which is based on two types of channel selection, the random choice (RC) and the idle choice (IC), and the sequential multichannel system. The latter has been proposed in order to supress the effect of the hidden terminal, which always represents a major problem with the usage of the contention random multiple access protocols with radio and mobile radio channels. Verification of their operation performance evaluation has been carried out using mathematical modelling for the dynamic system. However, simulation modelling has been chosen for the sequential system. Both systems are found to improve system operation and fault tolerance when compared to single channel operation.

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In this thesis various mathematical methods of studying the transient and dynamic stabiIity of practical power systems are presented. Certain long established methods are reviewed and refinements of some proposed. New methods are presented which remove some of the difficulties encountered in applying the powerful stability theories based on the concepts of Liapunov. Chapter 1 is concerned with numerical solution of the transient stability problem. Following a review and comparison of synchronous machine models the superiority of a particular model from the point of view of combined computing time and accuracy is demonstrated. A digital computer program incorporating all the synchronous machine models discussed, and an induction machine model, is described and results of a practical multi-machine transient stability study are presented. Chapter 2 reviews certain concepts and theorems due to Liapunov. In Chapter 3 transient stability regions of single, two and multi~machine systems are investigated through the use of energy type Liapunov functions. The treatment removes several mathematical difficulties encountered in earlier applications of the method. In Chapter 4 a simple criterion for the steady state stability of a multi-machine system is developed and compared with established criteria and a state space approach. In Chapters 5, 6 and 7 dynamic stability and small signal dynamic response are studied through a state space representation of the system. In Chapter 5 the state space equations are derived for single machine systems. An example is provided in which the dynamic stability limit curves are plotted for various synchronous machine representations. In Chapter 6 the state space approach is extended to multi~machine systems. To draw conclusions concerning dynamic stability or dynamic response the system eigenvalues must be properly interpreted, and a discussion concerning correct interpretation is included. Chapter 7 presents a discussion of the optimisation of power system small sjgnal performance through the use of Liapunov functions.

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New media technologies, the digitisation of information, learning archives and heritage resources are changing the nature of the public library and museums services across the globe, and, in so doing, changing the way present and future users of these services interact with these institutions in real and virtual spaces. New digital technologies are rewriting the nature of participation, learning and engagement with the public library, and fashioning a new paradigm where virtual and physical spaces and educative and temporal environments operate symbiotically. It is with such a creatively disruptive paradigm that the £193 million Library of Birmingham project in the United Kingdom is being developed. New and old media forms and platforms are helping to fashion new public places and spaces that reaffirm the importance of public libraries as conceived in the nineteenth century. As people’s universities, the public library service offers a web of connective learning opportunities and affordances. This article considers the importance of community libraries as sites of intercultural understanding and practical social democracy. Their significance is reaffirmed through the initial findings in the first of a series of community interventions forming part of a long-term project, ‘Connecting Spaces and Places’, funded by the Royal Society of Arts.

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With the rapidly growing activities in electronic publishing ideas came up to install global repositories which deal with three mainstreams in this enterprise: storing the electronic material currently available, pursuing projects to solve the archiving problem for this material with the ambition to preserve the content in readable form for future generations, and to capture the printed literature in digital versions providing good access and search facilities for the readers. Long-term availability of published research articles in mathematics and easy access to them is a strong need for researchers working with mathematics. Hence in this domain some pioneering projects have been established addressing the above mentioned problems.

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The paper informs about the history of manuscript digitization in the National Library of the Czech Republic as well as about other issues concerning processing of manuscripts. The main consequence of the massive digitization and record and/or full text processing is a paradigm shift leading to the digital history.

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Digital information services are gradually becoming integrated with other systems and services such as library automation systems, student information services, and electronic learning systems. Users demand seamless access to a multitude of digital information services without leaving their desktop computers. They prefer using systems that recognize them when they log on, acknowledge their rights and privileges, and thus provide personalized information services. This paper summarizes the recent developments concerning integrated and personalized digital information services. It first emphasizes the role of the Internet in providing information services and then goes on to discuss the integration and personalization issues by emphasizing their importance for digital information services.

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In this paper some current digitization projects carried out by the Mathematical Institute of Serbian Academy of Science and Arts Belgrade and the Faculty of Mathematics Belgrade are described. The projects concern developing of a virtual library of retro-digitized books and an Internet data base and presentation of electronic editions of some leading Serbian journals in science and arts, and the work on the South-Eastern European Digitization Initiative (SEEDI).

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The first part presented at the meeting by A. Dipchikova is a brief report of the role of the National library as an institution in collecting, preserving and making accessible the national written heritage. Problems of digitization are examined from the point of view of the existing experience in cataloguing. Special attention is paid to the history and the significance of international standards, the experience in the field of development and maintenance of authority files on national and international level as well as in markup languages. Possibilities of using MARC and XML in the library are discussed. The second part presented here by E. Moussakova is giving an overview of the latest activities of the Library in the sphere of digitisation of the old Slavic manuscripts which are component of the national cultural heritage. It is pointed out that the current work is rather limited within the scope of preparation of metadata than being focused on digital products.

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Basic concepts for an interval arithmetic standard are discussed in the paper. Interval arithmetic deals with closed and connected sets of real numbers. Unlike floating-point arithmetic it is free of exceptions. A complete set of formulas to approximate real interval arithmetic on the computer is displayed in section 3 of the paper. The essential comparison relations and lattice operations are discussed in section 6. Evaluation of functions for interval arguments is studied in section 7. The desirability of variable length interval arithmetic is also discussed in the paper. The requirement to adapt the digital computer to the needs of interval arithmetic is as old as interval arithmetic. An obvious, simple possible solution is shown in section 8.