Quality time [QoS in 802.11e]

Wireless local area networks (WLANs) based on the IEEE 802.11 standard are now widespread. Most are used to provide access for mobile devices to a conventional wired infrastructure, and some are used where wires are not possible, forming an ad hoc network of their own. There are several varieties at the physical or radio layer (802.11, 802.11a, 802.11b, 802.11g), with each featuring different data rates, modulation schemes and transmission frequencies. However, all of them share a common medium access control (MAC) layer. As this is largely based on a contention approach, it does not allow prioritising of traffic or stations, so it cannot easily provide the quality of service (QoS) required by time-sensitive applications, such as voice or video transmission. In order to address this shortfall of the technology, the IEEE set up a task group that is aiming to enhance the MAC layer protocol so that it can provide QoS. The latest draft at the time of writing is Draft 11, dated October 2004. The article describes the yet-to-be-ratified 802.11e standard and is based on that draft.

Determination of the density of the multiple access interference of a CDMA system from its moments

A standard CDMA system is considered and an extension of Pearson's results is used to determine the density function of the interference. The method is shown to work well in some cases, but not so in others. However this approach can be useful in further determining the probability of error of the system with minimal computational requirements.

Dual-hop amplify-and-forward cooperative relaying in the presence of Tx and Rx in-phase and quadrature-phase imbalance

In this study, dual-hop channel state information-assisted amplify-and-forward (AF) cooperative systems in the presence of in-phase and quadrature-phase (I/Q) imbalance, which refers to the mismatch between components in the I and Q branches, are investigated. First, the authors analyse the performance of the considered AF cooperative protocol without compensation for the I/Q imbalance as the benchmark. Then, a compensation algorithm for the I/Q imbalance is proposed, which makes use of the received signals at the destination, from the source and the relay nodes, together with their conjugations to detect the transmitted signal. Moreover, the authors study the considered AF cooperative system implemented with the opportunistic relay selection and the proposed compensation mechanism for the I/Q imbalance. The performance of the AF cooperative system under study is evaluated in terms of average symbol error probability, which is derived by considering transmission in a Rayleigh fading environment. Numerical results are provided and show that the proposed compensation algorithm can efficiently mitigate the effect of the I/Q imbalance. On the other hand, it is observed that the AF cooperative system with opportunistic relay selection acquires a performance gain beyond that without relay selection.

Improving transmission reliability of low-power medium access control protocols using average diversity combining

Embedded computer systems equipped with wireless communication transceivers are nowadays used in a vast number of application scenarios. Energy consumption is important in many of these scenarios, as systems are battery operated and long maintenance-free operation is required. To achieve this goal, embedded systems employ low-power communication transceivers and protocols. However, currently used protocols cannot operate efficiently when communication channels are highly erroneous. In this study, we show how average diversity combining (ADC) can be used in state-of-the-art low-power communication protocols. This novel approach improves transmission reliability and in consequence energy consumption and transmission latency in the presence of erroneous channels. Using a testbed, we show that highly erroneous channels are indeed a common occurrence in situations, where low-power systems are used and we demonstrate that ADC improves low-power communication dramatically.

A história do "turismo social" no Serviço Social do Comércio - SP

Este trabalho é fruto de uma investigação realizada no doutorado em História, Política e Bens Culturais do Centro de Pesquisa e Documentação de História Contemporânea do Brasil da Fundação Getulio Vargas - orientada pela profa. Dra. Bianca Freire-Medeiros - acerca da constituição e implementação do turismo social no Serviço Social do Comércio do estado de São Paulo (Sesc-SP), examinando as circunstâncias em que o lazer e as experiências turísticas tornam-se relevantes nas políticas e ações da entidade. Procurou-se entender as transformações e readequações que nortearam as iniciativas da instituição e como as modificações no conceito de turismo social no Brasil e no mundo vêm dialogando com suas diretrizes, posturas e intenções. A metodologia privilegiada na pesquisa foi a história oral temática, no intuito de fazer o registro da história do envolvimento de profissionais com o turismo social do Sesc-SP. Foram realizadas vinte e duas entrevistas com (ex)profissionais e feitas algumas visitas à Biblioteca do departamento nacional do Sesc (Sesc-DN) e ao setor de memória e documentação (Sesc-Memórias) do departamento regional paulista do Sesc, lugares que congregam documentos importantes relacionados à história do turismo na instituição. Espacialmente a pesquisa situa-se no Sesc-SP, repartição atuante e “atenta” às ideias e mudanças envolvendo o turismo social, e representativa na história do fenômeno, no Brasil e no mundo. A circunscrição temporal da pesquisa abarca desde 1979 - ano em que o Sesc de São Paulo passa a desenvolver excursões, passeios e viagens com maior frequência e tenta se aprofundar conceitualmente do turismo social ao se aproximar de órgãos internacionais de relevância política e científica na área - até as ações realizadas em 2013, ano no qual termino a pesquisa de campo e as entrevistas. Durante a trajetória da pesquisa, dialoguei com o período que antecede este recorte, acerca dos empreendimentos do Sesc relacionados as práticas de lazer e turismo, gerando o capítulo 2. Antes, no capítulo 1, tentei reconhecer o lugar do turismo social na história das atividades turísticas no mundo, entendendo-o enquanto oportunidade de efetivação do direito ao lazer. Para alcance dos intentos da tese, como fontes foram utilizados documentos produzidos em âmbito institucional, articulados com a fala dos indivíduos entrevistados, trabalho conjugado especialmente no capítulo 3, em que trago reflexões a respeito do turismo social desenvolvido pelo Sesc-SP. Dentre as análises alvitradas, descrevo a dificuldade encontrada pela entidade ao expandir suas atividades turísticas, vindo a sofrer represálias do setor privado. Deve-se destacar que foi possível perceber a metamorfose conceitual/prática por qual passara o turismo social no Sesc-SP, agregando diferentes conteúdos ao fenômeno e modificando seus processos de trabalho e práticas profissionais. Ressalto ainda o papel ideológico da administração regional do Sesc-SP dentro do Serviço Social do Comércio no Brasil, notadamente na área do turismo. Por fim, envolvo no debate da tese as políticas sociais de turismo, compreendido enquanto possibilidade de lazer.

Recorte dos produtos educacionais em história no ensino da matemática e em didática da matemática a partir das dissertações e teses defendidas no brasil entre 1990-2010

This work has the main purpose of conducting a survey of educational products present in dissertations and doctoral theses focused on the use of history in mathematics teaching and Didactics of mathematics with a French foundation produced in graduate programs in the strict sense of the Brazil between 1990 and 2010, the areas of Education, Mathematics Education, school of Natural Sciences and Mathematics and related areas, according to the research proposal of Mendes (2010). Our interest was to select the products that present concrete proposals for educational activities that can be used in the classroom of Basic Education and Training of Teachers of Mathematics. The research was implemented through a bibliographic study documents the Bank of dissertations and theses from CAPES, libraries and archives of some Postgraduate programs in the country who focus their studies on the subject object of this research, besides the Brazilian Digital Library Theses and Dissertations (BDBTD). From this survey we selected works that present educational products materialized in blocks of activities based on the use of teaching history of mathematics to the classroom as well as the sequence of activities based on the Teaching of Mathematics. In possession of material, produce a CD-ROM containing the selected activities, in order to help support the work of teachers regarding the use of these activities, as a supplementary material to textbooks in their math classes

Uso das tecnologias na representação descritiva: o padrão de descrição bibliográfica semântica MarcOnt Initiative nos ambientes informacionais digitais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

O Turismo como um tema de pesquisa: um diálogo epistemológico a partir das produções dos programas de pós-graduação stricto sensu da Universidade Federal do Rio Grande do Norte, no período de 2007 a 2011

The study consists in an analysis of researches with tourism issues, in Master s and Doctoral level, investigating their epistemological trends, regarding the type of study that is being produced and the methods used. It is characterized as exploratory, documental and bibliographical, having undertaken a cross-sectional study which covers the period from 2007 to 2011. It analyzes the context of academically production in tourism, the nature of these researches, the methodological aspects adopted in these theses and dissertations, the philosophical inclinations and the coherence and contribution of the same. This research uses, the Digital Library of Theses and Dissertations (BDTD) and the secretariats of the Academic Centers of the Federal University of Rio Grande do Norte (UFRN) as means to collect data. It employs the technique of sampling by judgment and undertakes the research in various Academic Centers in UFRN, using the method of content analysis. It shows that, from the 643 studies analyzed, 43 of them have themes related to tourism, which characterized this study sample. This study realizes that PPGA is the largest producer of researches on tourism issues, ahead of PPGTur, which ranks the third position, in this aspect. Also realizes that all surveys analyzed are crosssectional and the theme further investigated, with 21% of the sample, is related to the marketing aspects of tourism, with the theme Directors of Hotels and Restaurants (DHR) . This research demonstrates that all sample surveys make use of interviews, and these are, mostly, structured. Also realizes that most of these studies, with 21% of the sample, employ the method of content analysis. The references in Portuguese are surveyed about five times more than the ones in other languages. It estimates that more than half of the sample is characterized as positivist, associated with aspects of functionalism. A minority of 21% of these researches seeks to identify and recommend solutions to the tourism issues, or even represent part of them. This research concludes that the studies in tourism are mostly unifocal, being driven by issues related to the touristic trade. PPGTur produces a number still unrepresentative of studies. The theses and dissertations of the sample are limited and/or unable to analyze the changes of the phenomenon caused by the time. The studies from the sample present criteria and make use of other methods and techniques to associate with the interviews and content analysis to obtain more solid and reliable data and results. They use a low number of references in languages other than Portuguese. Most of these studies, characterized as positivist-functionalist, investigate the functioning, planning, coordination and expectations in organizations, leaving aside other issues, also relevant for tourism. The number of studies aimed at identifying solutions to the problems of tourism, or that even represents part of them, is not expressive

Estudo das partículas inorgânicas de resinas compostas: revisão sistemática e caracterização química e morfológica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

O Programa Nacional Biblioteca da Escola e o seu impacto na sala de aula: a circulação e o acesso do livro de literatura no interior de uma escola municipal de ensino fundamental

Pós-graduação em Educação - FFC