28 resultados para Navies.


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La retirada de los aviones Harrier, en servicio en operaciones embarcadas con Armadas de diferentes países, está basada en la perspectiva de poder sustituirlos por el F-35B, versión de operación vertical del controvertido programa Joint Strike Fighter. Este proyecto en realidad engloba el diseño de tres aviones de combate muy distintos entre sí, que, a pesar de tener una considerable parte en común, y dados sus muy diferentes requisitos, es un proyecto tremendamente complejo. Como consecuencia de todo esto, y ante el sobrecoste y los continuos retrasos acumulados en el desarrollo de un proyecto tan ambicioso, se plantean numerosas incertidumbres temporales y económicas, que hacen atractivo el estudio de posibles alternativas de menor riesgo. Esta tesis es un trabajo de investigación tecnológica que plantea el estudio de la modificación de determinados diseños de aviones de combate de operación terrestre, con idea de que puedan satisfacer los exigentes requisitos de operación desde un buque. Tras estudiar las peculiaridades de dichas operaciones, y analizar los tipos de buque y sus necesidades de modificación asociadas más importantes, se propone qué acciones a realizar, y se identifican las áreas de mayor interés, permitiendo establecer un procedimiento objetivo de comparación, con el fin de poder seleccionar los potenciales candidatos para su adaptación. Se aplica esta metodología, en particular, a dos casos de diseño de especial interés; el Eurofighter Typhoon y el Saab Gripen. En ambos, y por lo que respecta a las modificaciones planteadas, no se aprecian especiales dificultades que permitan descartar las posibilidades técnicas de su adaptación. Por último, y dada la complejidad de la consecución del objetivo final, se sugieren posibles líneas de investigación, desde completar y extender la filosofía de trabajo a otros subsistemas, al análisis de los costes de las modificaciones. ABSTRACT The Harrier fleet has been in active service in several Navies from different countries as a carrier-based aircraft. However, this aircraft may be withdrawn and replaced by the F-35B, a vertical capability version of the controversial Joint Strike Fighter (JSF) programme, which great complexity and constant development delays raise numerous uncertainties from a temporal and economical point of view. In fact, this program encompasses the design of three different fighter aircraft which, at the same time, share many similarities. All these aspects led us to undertake the analysis of other lower-risk alternatives. This thesis is a technological research work aimed at studying those design changes required for several fighter aircraft, initially designed for ground operation, in order to make them fullfil the highly demanding requirements for operating from aircraft carriers. After analizing the peculiarities of such operations, and studying different types of ships as well as their most significant modifications, specific actions to undertake are proposed, and those areas of greatest interest are identified, for the purposes of establishing an objective comparison procedure, and selecting potential candidates for this adaptation. This methodology is applied to design two specific cases of particular concern: the Eurofighter Typhoon and the Saab Gripen. In both instances, no major problems have been encountered regarding the modifications suggested. Finally, given the complexity of the analysis performed, some future research lines are outlined such as completing and extending this methodology to other subsystems, and giving an initial estimate of the modification costs.

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"Portraits from memory of naval officers who were born between 1805 and 1827 and served their country for many years in all quarters of the globe."

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"An alphabetical arrangement of the ships of the Continental and United States Navies, with a historical sketch of each one."

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Publication suspended 1917-1918.

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A collection of "all the authentic and official Confederate memorial committee matter which has appeared heretofore in the newspapers, together with a list of the engagements that occurred between the Confederate and Federal armies and navies." cf. p. [3]

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Mode of access: Internet.

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A collection of miscellaneous pamphlets on World War I.

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Vol.1-26 called also anno 1-13

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Mode of access: Internet.

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The growth of criminal gangs and organized crime groups has created unprecedented challenges in Central America. Homicide rates are among the highest in the world, countries spend on average close to 10 percent of GDP to respond to the challenges of public insecurity, and the security forces are frequently overwhelmed and at times coopted by the criminal groups they are increasingly tasked to counter. With some 90 percent of the 700 metric tons of cocaine trafficked from South America to the United States passing through Central America, the lure of aiding illegal traffickers through provision of arms, intelligence, or simply withholding or delaying the use of force is enormous. These conditions raise the question: to what extent are militaries in Central America compromised by illicit ties to criminal groups? The study focuses on three cases: Nicaragua, El Salvador, and Honduras. It finds that: Although illicit ties between the military and criminal groups have grown in the last decade, militaries in these countries are not yet “lost’ to criminal groups. Supplying criminal groups with light arms from military stocks is typical and on the rise, but still not common. In general the less exposed services, the navies and air forces, are the most reliable and effective ones in their roles in interdiction. Of the three countries in the study, the Honduran military is the most worrying because it is embedded in a context where civilian corruption is extremely common, state institutions are notoriously weak, and the political system remains polarized and lacks the popular legitimacy and political will needed to make necessary reforms. Overall, the armed forces in the three countries remain less compromised than civilian peers, particularly the police. However, in the worsening crime and insecurity context, there is a limited window of opportunity in which to introduce measures targeted toward the military, and such efforts can only succeed if opportunities for corruption in other sectors of the state, in particular in law enforcement and the justice system, are also addressed. Measures targeted toward the military should include: Enhanced material benefits and professional education opportunities that open doors for soldiers in promising legitimate careers once they leave military service. A clear system of rewards and punishments specifically designed to deter collusion with criminal groups. More effective securing of military arsenals. Skills and external oversight leveraged through combined operations, to build cooperation among those sectors of the military that have successful and clean records in countering criminal groups, and to expose weaker forces to effective best practices.

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Com a presente evolução das railguns na Marinha dos Estados Unidos da América e possível instalação em seus navios num futuro muito próximo, outras marinhas se seguirão. Creio que será do interesse da Marinha Portuguesa acompanhar esta evolução tecnológica, considerando as vantagens que advém da adoção deste tipo de armamento. Neste documento são abordados os princípios básicos subjacentes ao funcionamento da railgun, com principal foco nas questões eletrodinâmicas. Pretende-se adquirir familiaridade com este novo tipo de armamento através do estudo crítico dos seus princípios de funcionamento. O princípio básico de funcionamento de uma railgun, à primeira vista, parece bastante simples, à luz da aplicação imediata da expressão da força de Lorentz sobre um condutor percorrido por corrente elétrica. No entanto, tudo se torna mais complicado no caso de uma variação rápida dos parâmetros envolvidos (regime transitório), que exige uma análise mais aprofundada do comportamento da corrente, campos elétrico e magnético, e todos os materiais envolvidos neste sistema. Este trabalho envolveu ainda a construção de duas railguns, uma primeira de dimensões mais pequenas para ganhar familiaridade com o sistema, e uma última de dimensões de laboratório na qual foram feitos vários disparos para testar diferentes tipos de material e dimensões de projétil. Em suma, é demonstrado neste documento uma análise, no domínio do tempo, da distribuição espacial do campo eletromagnético, corrente elétrica e consequente fluxo de energia, complementados por uma parte experimental.