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A number of different structural concepts are currently under development as a means of placing large structures in orbit. Three commonly considered concepts are described. The radial rib structure and the hoop-column structure have undergone considerable early development because of their seeming potential for providing a reliably deployable reflector surface. In the present paper, attention is focused on truss structures which historically have been widely used in ground based structures because of their inherent simplicity, versatility, and high stiffness.
equilibrium, natural concepts
Preliminary conceptual approaches for both low earth orbit and geostationary Space Platforms have been developed in response to user requirements. These requirements include payload needs for: operational autonomy, power, size, environmental control (including dynamic, electromagnetic, gaseous, and particulates), on-orbit accessibility, communication and pointing. The concepts developed include both multipurpose and discipline dedicated platforms. In this paper these concepts, their evolution, and their relationship to the needs of the user are presented and discussed.
One of the papers published in volume 8 issue 1 of IREE concerns the role of threshold concepts. Our referees suggested that it would be helpful to provide readers with an introduction to the literature on threshold concepts to make the analysis presented in this paper more accessible to colleagues who have not come across the idea before. This we do in the second part of this editorial.
Cette thèse a comme sujet une exploration en largeur de concepts logiques en cryptographie et leur abstraction et combinaison linguistique en un système logique syncrétique, appelé CPL (pour Cryptographic Protocol Logic). Nous nous intéressons à deux aspects fondamentaux de la cryptographie. D'une part, à la sécurité de la communication (par opposition à la sécurité du stockage) de données, et d'autre part, aux protocoles cryptographiques (par opposition aux opérateurs cryptographiques). Les concepts logiques primaires explorés sont les suivants : les concepts modaux de la croyance, de la connaissance, des normes, de la prouvabilité, de l'espace, et du temps. Le trait distinctif de CPL est d'unifier et de raffiner une variété d'approches existantes. Ce trait est le résultat de notre conception holistique des formalismes basés sur les p...
Demographic Methods and Concepts presents the methods most commonly needed to work with statistical materials on population at national, regional and local levels. Unlike other textbooks in the field, clear non-technical language is used throughout to make demographic techniques accessible to a broad readership irrespective of background in mathematics. All the demographic techniques most relevant to the work of demographers, geographers, sociologists and planners are covered. Demographic concepts and practical strategies important in the interpretation of population statistics are also discussed. The book takes a unique and innovative computer-based approach to the visualisation of demographic concepts and data. The fully integrated accompanying CD-ROM contains spreadsheet modules, with on-screen controls and menus, run in Microsoft E...
This paper presents an alternative to the standard view that the evaluations that the so-called "thick" terms and concepts in ethics may be used to convey belong to their sense or semantic meaning. I describe a large variety of linguistic data that are well explained by the alternative view that the evaluations that (at least a very wide range of) thick terms and concepts may be used to convey are a certain kind of defeasible implications of their utterances which can be given a conversational explanation. I then provide some reasons to think that this explanation of the data is superior to the standard view, but a fuller assessment must await further work. In closing I briefly survey the largely deflationary consequences of this account regarding the significance of thick terms and concepts for evaluative thought and judgment.
Post-Galileo mission concepts considered possible for satellite-intensive investigations are presented, with consideration given to single and multiple target scenarios using orbiter and lander deployments. Candidate missions that satisfy the selected science objectives are identified, and specific scenario/target combinations which fall within performance constraints are chosen. The concepts are then developed into descriptive mission profiles. Also discussed are target encounter and deployment requirements, payload delivery, and operational considerations. Particular attention is given to Jupiter radiation effects and shielding requirements. A wide range of satellite-intensive missions is thought to be within the performance capabilities of earth-gravity-assisted ballistic trajectories and nuclear electric propulsion technology.
The Potential for V/STOL Aircraft Concepts for Air Transportation in the CALIFORNIA CORRIDOR in the 2010 time period is projected. The project description is to study the potential for V/STOL aircraft concepts in air transportation within the California Corridor, and emphasize V/STOL configurations that are innovative and unconventional in design for use in the 2010 time period. The project is consistent with the mission of the NASA/Ames Research Center and succeeding classes at Cal Poly can iterate and refine for meaningful results for NASA.
Several concepts of chemical-propulsion Space Vehicles (SVs) for manned Mars landing missions are presented. For vehicle sizing purposes, several specific missions were chosen from opportunities in the late 1990's and early 2000's, and a vehicle system concept is then described which is applicable to the full range of missions and opportunities available. In general, missions utilizing planetary opposition alignments can be done with smaller vehicles than those utilizing planetary opposition alignments. The conjunction missions have a total mission time of about 3 years, including a required stay-time of about 60 days. Both types of missions might be desirable during a Mars program, the opposition type for early low-risk missions and/or for later unmanned cargo missions, and the conjunction type for more extensive science/exploration m...
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