12 research outputs found
Office of Exploration: Exploration studies technical report. Volume 2: Studies approach and results
The NASA Office of Exploration has been tasked with defining and recommending alternatives for an early 1990's national decision on a focused program of human exploration of the solar system. The Mission Analysis and System Engineering (MASE) group, which is managed by the Exploration Studies Office at the Johnson Space Center, is responsible for coordinating the technical studies necessary for accomplishing such a task. This technical report describes the process that has been developed in a case study approach. The four case studies that were developed in FY88 include: (1) human expedition to Phobos; (2) human expeditions to Mars; (3) lunar observatory; and (4) lunar outpost to early Mars evolution. The final outcome of this effort is a set of programmatic and technical conclusions and recommendations for the following year's work. Volume 2 describes the case study process, the technical results of each of the case studies, and opportunities for additional study. Included in the discussion of each case study is a description of the mission key features and profile. Mission definition and manifesting are detailed, followed by a description of the mission architecture and infrastructure. Systems concepts for the required orbital nodes, transportation systems, and planetary surface systems are discussed. Prerequisite implementation plans resulting from the synthesized case studies are described and in-depth assessments are presented
Políticas de Copyright de Publicações Científicas em Repositórios Institucionais: O Caso do INESC TEC
A progressiva transformação das práticas científicas, impulsionada pelo desenvolvimento das novas Tecnologias de Informação e Comunicação (TIC), têm possibilitado aumentar o acesso à informação, caminhando gradualmente para uma abertura do ciclo de pesquisa. Isto permitirá resolver a longo prazo uma adversidade que se tem colocado aos investigadores, que passa pela existência de barreiras que limitam as condições de acesso, sejam estas geográficas ou financeiras. Apesar da produção científica ser dominada, maioritariamente, por grandes editoras comerciais, estando sujeita às regras por estas impostas, o Movimento do Acesso Aberto cuja primeira declaração pública, a Declaração de Budapeste (BOAI), é de 2002, vem propor alterações significativas que beneficiam os autores e os leitores. Este Movimento vem a ganhar importância em Portugal desde 2003, com a constituição do primeiro repositório institucional a nível nacional. Os repositórios institucionais surgiram como uma ferramenta de divulgação da produção científica de uma instituição, com o intuito de permitir abrir aos resultados da investigação, quer antes da publicação e do próprio processo de arbitragem (preprint), quer depois (postprint), e, consequentemente, aumentar a visibilidade do trabalho desenvolvido por um investigador e a respetiva instituição. O estudo apresentado, que passou por uma análise das políticas de copyright das publicações científicas mais relevantes do INESC TEC, permitiu não só perceber que as editoras adotam cada vez mais políticas que possibilitam o auto-arquivo das publicações em repositórios institucionais, como também que existe todo um trabalho de sensibilização a percorrer, não só para os investigadores, como para a instituição e toda a sociedade. A produção de um conjunto de recomendações, que passam pela implementação de uma política institucional que incentive o auto-arquivo das publicações desenvolvidas no âmbito institucional no repositório, serve como mote para uma maior valorização da produção científica do INESC TEC.The progressive transformation of scientific practices, driven by the development of new Information and Communication Technologies (ICT), which made it possible to increase access to information, gradually moving towards an opening of the research cycle. This opening makes it possible to resolve, in the long term, the adversity that has been placed on researchers, which involves the existence of barriers that limit access conditions, whether geographical or financial. Although large commercial publishers predominantly dominate scientific production and subject it to the rules imposed by them, the Open Access movement whose first public declaration, the Budapest Declaration (BOAI), was in 2002, proposes significant changes that benefit the authors and the readers. This Movement has gained importance in Portugal since 2003, with the constitution of the first institutional repository at the national level. Institutional repositories have emerged as a tool for disseminating the scientific production of an institution to open the results of the research, both before publication and the preprint process and postprint, increase the visibility of work done by an investigator and his or her institution. The present study, which underwent an analysis of the copyright policies of INESC TEC most relevant scientific publications, allowed not only to realize that publishers are increasingly adopting policies that make it possible to self-archive publications in institutional repositories, all the work of raising awareness, not only for researchers but also for the institution and the whole society. The production of a set of recommendations, which go through the implementation of an institutional policy that encourages the self-archiving of the publications developed in the institutional scope in the repository, serves as a motto for a greater appreciation of the scientific production of INESC TEC
The global tree carrying capacity (keynote)
editorial reviewe
Department of Defense Dictionary of Military and Associated Terms
The Joint Publication 1-02, Department of Defense Dictionary of Military and Associated Terms sets forth standard US military and associated terminology to encompass the joint activity of the Armed Forces of the United States. These military and associated terms, together with their definitions, constitute approved Department of Defense (DOD) terminology for general use by all DOD components
Processing techniques for improved radar detection in spiky clutter
The problem of improved radar detection of targets embedded in spiky clutter is
addressed. Two main areas where improvements may be possible are investigated,
namely improved clutter suppression by doppler filtering, and improved Constant False
Alarm Rate (CFAR) processing. The clutter suppression performance of several doppler
processors is quantified under a wide range of conditions. It is shown that in spatially
homogeneous clutter ideal optimal (Hsiao) filters offer 2 to 3 dB higher improvement
factor than conventional techniques. Adaptive Hsiao filters are evaluated under conditions
of spatially heterogeneous clutter, and it is shown that practical losses due to filter
adaptivity and spectral heterogeneity will outweigh the superior performance of ideal
Hsiao filters in homogeneous clutter. It is concluded that improved doppler filtering
offers little scope for improving detection performance in spiky clutter, and that more
significant benefits are to be gained through improved CFAR processing. The performance
of three current generation CFAR processors is evaluated in spatially uncorrelated
K-distributed clutter to quantify detection losses. It is shown that losses of in excess of
10 dB can be expected in spiky clutter. Reducing the loss by exploitation of any spatial
correlation of the underlying clutter power is investigated. To this end a mathematically
rigorous model for spatially correlated K-distributed clutter is derived. An improved
CFAR processor based on optimal weighting of reference cells is formulated and
evaluated. It is shown that in highly correlated clutter CFAR loss can be reduced by 2 to
5 dB compared to Cell Averaging CFAR processors. An alternative "RDT-CFAR"
processor is formulated to eliminate reliance on spatial correlation, and this is shown to
reduce CFAR loss by more than 10 dB in spectrally homogeneous spiky clutter.
However, an increase in false alarm rate in clutter without constant spectrum is
demonstrated. The RDT-CFAR processor has been modified to eliminate dependence on
surrounding range bins. The resulting "δ-CFAR" processor reduces CFAR loss by more
than 10 dB in even moderately spiky clutter. It is also immune to extraneous targets and
clutter edges, and its false alarm performance is insensitive to clutter spikiness
Proceedings of the First International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics
1st International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Kruger Park, 8-10 April 2002.This lecture is a principle-based review of a growing body
of fundamental work stimulated by multiple opportunities to
optimize geometric form (shape, structure, configuration,
rhythm, topology, architecture, geography) in systems for heat
and fluid flow. Currents flow against resistances, and by
generating entropy (irreversibility) they force the system global
performance to levels lower than the theoretical limit. The
system design is destined to remain imperfect because of
constraints (finite sizes, costs, times). Improvements can be
achieved by properly balancing the resistances, i.e., by spreading
the imperfections through the system. Optimal spreading means
to endow the system with geometric form. The system
construction springs out of the constrained maximization of
global performance. This 'constructal' design principle is
reviewed by highlighting applications from heat transfer
engineering. Several examples illustrate the optimized internal
structure of convection cooled packages of electronics. The
origin of optimal geometric features lies in the global effort to
use every volume element to the maximum, i.e., to pack the
element not only with the most heat generating components, but
also with the most flow, in such a way that every fluid packet is
effectively engaged in cooling. In flows that connect a point to
a volume or an area, the resulting structure is a tree with high conductivity
branches and low-conductivity interstices.tm201