5,122 research outputs found

    Deep Space Network information system architecture study

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    The purpose of this article is to describe an architecture for the Deep Space Network (DSN) information system in the years 2000-2010 and to provide guidelines for its evolution during the 1990s. The study scope is defined to be from the front-end areas at the antennas to the end users (spacecraft teams, principal investigators, archival storage systems, and non-NASA partners). The architectural vision provides guidance for major DSN implementation efforts during the next decade. A strong motivation for the study is an expected dramatic improvement in information-systems technologies, such as the following: computer processing, automation technology (including knowledge-based systems), networking and data transport, software and hardware engineering, and human-interface technology. The proposed Ground Information System has the following major features: unified architecture from the front-end area to the end user; open-systems standards to achieve interoperability; DSN production of level 0 data; delivery of level 0 data from the Deep Space Communications Complex, if desired; dedicated telemetry processors for each receiver; security against unauthorized access and errors; and highly automated monitor and control

    Latest Developments in Industrial Hybrid Machine Tools that Combine Additive and Subtractive Operations

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    Hybrid machine tools combining additive and subtractive processes have arisen as a solution to increasing manufacture requirements, boosting the potentials of both technologies, while compensating and minimizing their limitations. Nevertheless, the idea of hybrid machines is relatively new and there is a notable lack of knowledge about the implications arisen from their in-practice use. Therefore, the main goal of the present paper is to fill the existing gap, giving an insight into the current advancements and pending tasks of hybrid machines both from an academic and industrial perspective. To that end, the technical-economical potentials and challenges emerging from their use are identified and critically discussed. In addition, the current situation and future perspectives of hybrid machines from the point of view of process planning, monitoring, and inspection are analyzed. On the one hand, it is found that hybrid machines enable a more efficient use of the resources available, as well as the production of previously unattainable complex parts. On the other hand, it is concluded that there are still some technological challenges derived from the interaction of additive and subtractive processes to be overcome (e.g., process planning, decision planning, use of cutting fluids, and need for a post-processing) before a full implantation of hybrid machines is fulfilledSpecial thanks are addressed to the Industry and Competitiveness Spanish Ministry for the support on the DPI2016-79889-R INTEGRADDI project and to the PARADDISE project H2020-IND-CE-2016-17/H2020-FOF-2016 of the European Union's Horizon 2020 research and innovation program

    Numerical modelling of a road restraint system

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    Dissertação de mestrado integrado em Engenharia Mecânica (área de especialização em Sistemas Mecatrónicos)The most important aspect when developing roads is safety. This factor represents a notable cost in development activities involving the construction of highways, and is, therefore, a factor widely studied in the academic community as well. As it is known, the finite element method is used to predict and simulate different phenomena in engineering applications, being increasingly used because it represents a significant cost savings, as it replaces the execution of experimental tests at full scale. Furthermore, it allows for geometric, behavioural (material) and boundary conditions definition changes. Finite element modelling also allows for calculations that involve the rigorous evaluation of fundamental engineering quantities, which in a mechanical test can be difficult to obtain or measure, because they are difficult to access or because they require equipment with limited access. For the modelling of the different components that make up the safety barrier model studied in this work, the Solidworks software was used, with the Sheet Metal tool, which allows to model the geometry in a similar way to the forming process. In the numerical simulation two approaches are presented. The first employs three-dimensional elements and solid screws in bolted connections. The second uses shell elements and connectors (connection functionalities) available in the finite element software libraries used. As the first approach did not achieve the desired success, the second approach constitutes a more detailed analysis for modelling an impact test. In addition to developing a model for future analysis of the barrier under study, an analysis of two modelling techniques that uses scripting and an interface is also carried out. The main limitation of this study is that it was not possible to validate the numerical model with experimental information, given the logistics involved. However, by comparing the information available in the literature, and analysing the current standards for the production of the studied containment solution, it was possible to conclude that the work carried out led to the production of a set of very consistent results.O aspeto mais importante aquando do desenvolvimento de estradas é a segurança. Este fator representa um custo destacável nas atividades de desenvolvimento que envolvem a construção de rodovias, sendo por isso um fator amplamente estudado também na comunidade académica. Como é sabido, o método dos elementos finitos é utilizado para prever e simular fenómenos diversos em aplicações de engenharia, sendo cada vez mais utilizado por representar uma poupança de custos significativa, pois substitui a execução de ensaios experimentais à escala real. Além disto, permite a realização de alterações geométricas, comportamentais (materiais) e de definição de condições de fronteira. A modelação por elementos finitos permite também a realização de cálculos que envolvem a avaliação rigorosa de grandezas fundamentais em engenharia, que num ensaio mecânico podem ser difíceis de obter ou medir, por serem de difícil acessibilidade ou por requerem equipamentos de acesso limitado. Na modelação dos diferentes componentes que constituem o modelo de barreira de segurança estudado neste trabalho, empregou-se o software Solidworks, com a ferramenta Sheet Metal, que permite modelar a geometria de uma maneira semelhante ao processo de conformação. Na simulação numérica são apresentadas duas abordagens. A primeira emprega elementos tridimensionais e parafusos sólidos nas ligações aparafusadas. A segunda recorre a elementos de casca e conectores (funcionalidades de ligação) disponíveis nas livrarias do software de elementos finitos utilizado. Sendo que na primeira abordagem não se alcançou o sucesso desejado, a segunda abordagem constitui uma análise mais detalhada para a modelação de um ensaio de impacto. Além de desenvolver um modelo para futuras análises à barreira em estudo, é também feita uma análise a duas técnicas de modelação que recorre a scripting e a uma interface. A principal limitação deste estudo reside em não ter sido possível validar o modelo numérico com informação experimental, atendendo à logística envolvida. No entanto, por comparação com a informação disponível na literatura, e analisadas as normas vigentes para a produção da solução de contenção estudada, foi possível concluir que o trabalho desenvolvido conduziu à produção de um conjunto de resultados muito coerentes.This work was supported by “ANI – Agência Nacional de Inovação”, through the project with the reference “COMPETE-2020/03/SI/2017 Nº033497”, entitled “Barreiras de segurança rodoviária”, with the acronym “BarRod”, through the “Programa Operacional Competitividade e Internacionalização” and the “Programa Operacional Competitividade e Internacionalização e o Programa Operacional Regional de Lisboa”, supported by “FEDER”

    TVL<sub>1</sub> Planarity Regularization for 3D Shape Approximation

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    The modern emergence of automation in many industries has given impetus to extensive research into mobile robotics. Novel perception technologies now enable cars to drive autonomously, tractors to till a field automatically and underwater robots to construct pipelines. An essential requirement to facilitate both perception and autonomous navigation is the analysis of the 3D environment using sensors like laser scanners or stereo cameras. 3D sensors generate a very large number of 3D data points when sampling object shapes within an environment, but crucially do not provide any intrinsic information about the environment which the robots operate within. This work focuses on the fundamental task of 3D shape reconstruction and modelling from 3D point clouds. The novelty lies in the representation of surfaces by algebraic functions having limited support, which enables the extraction of smooth consistent implicit shapes from noisy samples with a heterogeneous density. The minimization of total variation of second differential degree makes it possible to enforce planar surfaces which often occur in man-made environments. Applying the new technique means that less accurate, low-cost 3D sensors can be employed without sacrificing the 3D shape reconstruction accuracy

    COBE's search for structure in the Big Bang

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    The launch of Cosmic Background Explorer (COBE) and the definition of Earth Observing System (EOS) are two of the major events at NASA-Goddard. The three experiments contained in COBE (Differential Microwave Radiometer (DMR), Far Infrared Absolute Spectrophotometer (FIRAS), and Diffuse Infrared Background Experiment (DIRBE)) are very important in measuring the big bang. DMR measures the isotropy of the cosmic background (direction of the radiation). FIRAS looks at the spectrum over the whole sky, searching for deviations, and DIRBE operates in the infrared part of the spectrum gathering evidence of the earliest galaxy formation. By special techniques, the radiation coming from the solar system will be distinguished from that of extragalactic origin. Unique graphics will be used to represent the temperature of the emitting material. A cosmic event will be modeled of such importance that it will affect cosmological theory for generations to come. EOS will monitor changes in the Earth's geophysics during a whole solar color cycle

    The use of Eye Tracking Technology in Maritime High-Speed Craft Navigation

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