714 resultados para reliance
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Includes bibliography
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Incluye Bibliografía
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Incluye Bibliografía
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Includes bibliography
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Incluye Bibliografía
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The upcoming solar maximum, which is expected to reach its peak around May 2013, occurs at a time when our reliance on high-precision GNSS has reached unprecedented proportions. The perturbations of the ionosphere caused by increased solar activity pose a major threat to these applications. This is particularly true in equatorial regions where high exposure to solar-induced disturbances is coupled with explosive growth of precise GNSS applications. Along with the various types of solar-induced ionospheric disturbances, strong scintillations are amongst the most challenging, causing phase measurement errors up to full losses of lock for several satellites. Brazil, which heavily relies on high-precision GNSS, is one of the most affected regions due notably to the proximity to the southern crest of the ionospheric equatorial anomaly and to the South Atlantic Magnetic Anomaly. In the framework of the CIGALA project, we developed the PolaRxS™, a GNSS receiver dedicated to the monitoring of ionospheric scintillation indices not only in the GPS L1 band but for all operational and upcoming constellations and frequency bands. A network of these receivers was deployed across the whole Brazilian territory in order to first investigate and secondly to mitigate the impact of scintillation on the different signals, ensuring high precision GNSS availability and integrity in the area. This paper reports on the validation of the PolaRxS™ receiver as an ionospheric scintillation monitor and the first results of the analysis of the data collected with the CIGALA network.
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Includes bibliography
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Includes bibliography.
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Pós-graduação em Psicologia - FCLAS
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Statistical organizations of the Caribbean countries continue to face serious challenges posed by the increased demand for more relevant, accurate and timely statistical data. Tangible progress has been made in delivering key products in the area of economic statistics. The central banks of the subregion have assisted greatly in this respect. However, even in this branch of statistics there are still several glaring gaps. The situation is even worse in other areas of statistics including social and environmental statistics. Even though all countries of the subregion have committed to the Millennium Development Goals (MDGs) as well as to other internationally agreed development goals serious challenges remain with respect to the compilation of the agreed indicators to assist in assessing progress towards the goals. It is acknowledged that appreciable assistance has been provided by the various donor agencies to develop statistical competence. This assistance has translated into the many gains that have been made. However, the national statistical organizations require much more help if they are to reach the plateau of self reliance in the production of the necessary statistical services. The governments of the subregion have also committed to invest more in statistical development and in promoting a statistics culture in the Caribbean. The training institutions of the subregion have also started to address this urgent need by broadening and deepening their teaching curricula. Funding support is urgently required to develop the appropriate cadre of statistical professionals to deliver the required outputs. However, this training must be continuous and must be sustained over an appropriate period since the current turnover of trained staff is high. This programme of training will need to be intensive for a period of at least five years after which it may be reduced. The modalities of training will also have to be more focused and in addition to formal training at educational institutions there is much room for on-the-job training, group training at the national level and much more south-south capacity building. There is also an urgent need to strengthen cooperation and collaboration among the donor community in the delivery of assistance for statistical development. Several development agencies with very good intentions are currently operating in the Caribbean. There is a danger however, that efforts can be duplicated if agencies do not collaborate adequately. Development agencies therefore need to consult with each other much more and share there development agenda more freely if duplication is to be averted. Moreover, the pooling of resources can surely maximize the benefits to the countries of the subregion.
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Pós-graduação em Agronomia - FEIS
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Pós-graduação em Agronomia (Energia na Agricultura) - FCA
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Pós-graduação em Agronomia (Energia na Agricultura) - FCA
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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As comunicações marítimas são ainda fortemente efetivadas por meio de circuitos rádio convencionais empregando ondas terrestres, em bandas de MF a VHF, especialmente após a introdução de sistemática de chamadas seletivas digitais. Entretanto, um número significativo de procedimentos operacionais nas radiocomunicações ainda depende de intervenções de operador, reduzindo sua eficiência e dando margem ao cometimento de erros como emissão de falsos alarmes de socorro. Esses erros têm sido frequentes e têm ocasionado muito desvio de atenção das ocorrências reais e perdas de tempo nas instâncias que cuidam das ações de busca e salvamento no mar, afetando, seriamente, a confiabilidade no processo de comunicações terrestres. Em vista disto, propõem-se, nesta pesquisa, sistemáticas para controle das emissões de falsos alertas de socorro, nas transmissões por ondas terrestres, e para melhorar o processo vigente de transmissão de chamadas. As chamadas de socorro recebidas pelas estações costeiras são identificadas por estas, de acordo com as estações que as emitiu, objetivando subsidiar ações corretivas por instâncias competenrtes, para inibição de novas ocorrências. Paralelamente, maior nível de automação é proposto para os processos de chamadas, reduzindo-se a dependência de procedimentos manuais e, assim, as possibilidades de emissões equivocadas, além de melhor aproveitar o conceito de chamada seletiva do sistema vigente. Tais proposições dão maior eficiência e confiabilidade às comunições terrestres, úteis especialmente nas situações de emergências, sem adicionar significativas demandas operacionais nas estações, incentivando e melhorando as condições de comunicações no SMM por ondas terrestres.