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891.
The 21st Century Aviation System can reduce the cost of flying, while substantially increasing the safety and security of cargo and carrier aircraft with an onboard pilot/s and a remote copilot residing in a secure ground-based simulator. 相似文献
892.
B. A. Antuf’ev 《Russian Aeronautics (Iz VUZ)》2008,51(3):227-231
A problem on low vibrations of a thin spherical shell is considered. A solid of finite dimensions is discretely attached to the shell by means of an elastic rod system. The calculation examples are presented. 相似文献
893.
The derivation of parametric equations for a limiting surface in the space of internal forces and moments that act in the rod cross-sections, using the basic concepts of plasticity theory and conventional hypotheses of the rod theory, is presented. The plastic properties of rod material are described by the Mises criterion. A case of small displacements and strains under static simple loading is considered. The results of solving a number of problems of constructing limiting curves in the planes of internal forces and moments are given. 相似文献
894.
A capillary-driven root module for plant growth in microgravity. 总被引:2,自引:0,他引:2
S B Jones D Or 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1998,22(10):1407-1412
A new capillary-driven root module design for growing plants in microgravity was developed which requires minimal external control. Unlike existing systems, the water supply to the capillary-driven system is passive and relies on root uptake and media properties to develop driving gradients which operate a suction-induced flow control valve. A collapsible reservoir supplies water to the porous membrane which functions to maintain hydraulic continuity. Sheet and tubular membranes consisting of nylon, polyester and sintered porous stainless steel were tested. While finer pore sized membranes allow greater range of operation, they also reduce liquid flux thereby constraining system efficiency. Membrane selection should consider both the maximum anticipated liquid uptake rate and maximum operating matric head (suction) of the system. Matching growth media water retention characteristics to the porous membrane characteristics is essential for supplying adequate liquid flux and gas exchange. A minimum of 10% air-filled porosity (AFP) was necessary for adequate aeration. The capillary-driven module maintained hydraulic continuity and proper gas exchange rates for more than 80 days in a plant growth experiment. 相似文献
895.
Loehr J. Siskaninetz W. Wiemeri J. Feld S. 《Aerospace and Electronic Systems Magazine, IEEE》1998,13(4):9-12
Avionic information processing and transmission requirements are increasing geometrically, with no end in sight, The only feasible way to meet them is to incorporate fiber-optic communication systems into avionic platforms, Such systems can be employed to replace standard electronic components, to augment existing systems, or to enable new technologies. In this paper, we survey the field of low-power communication systems from the avionics engineering perspective. We review the fundamental merits of optical fiber for information transmission and discuss various information modulation schemes. These modulation techniques determine the performance requirements for laser transmitters, We describe the horizontal- and vertical-cavity semiconductor lasers currently available for these systems, and measure their performance against the additional environmental constraints of avionics platforms. Finally, we outline expected near- and far-term trends in system and device development 相似文献
896.
M Durante T Kawata T Nakano S Yamada H Tsujii 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1998,22(12):1653-1662
We report measurements of chromosomal aberrations in peripheral blood lymphocytes from cancer patients undergoingradiotherapy treatment. Patients with cervix or esophageal cancer were treated with 10 MV X-rays produced at a LINAC accelerator, or high-energy carbon ions produced at the HIMAC accelerator at the National Institute for Radiological Sciences (NIRS) in Chiba. Blood samples were obtained before, during, and after the radiation treatment. Chromosomes were prematurely condensed by incubation in calyculin A. Aberrations in chromosomes 2 and 4 were scored after fluorescence in situ hybridization with whole-chromosome probes. Pre-treatment samples were exposed in vitro to X-rays, individual dose-response curves for the induction of chromosomal aberrations were determined, and used as calibration curves to calculate the effective whole-body dose absorbed during the treatment. This calculated dose, based on the calibration curve relative to the induction of reciprocal exchanges, has a sharp increase after the first few fractions of the treatment, then saturates at high doses. Although carbon ions are 2–3 times more effective than X-rays in tumor sterilization, the effective dose was similar to that of X-ray treatment. However, the frequency of complex-type chromosomal exchanges was much higher for patients treated with carbon ions than X-ray. 相似文献
897.
S.G. Anokhin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
We present here new XMM-Newton observations of 3 relatively cool clusters at z ≈ 0.4, complemented by archival observations of 3 other clusters at similar redshift. We derived the M–T and R–T relations from the hydrostatic equation using an isothermal temperature distribution. 相似文献
898.
The receipt of the Pioneer Award has given me a chance to look back over my professional life and the opportunity to take stock of how I helped shape a small part of the world. While I hope this process entertains my contemporaries, more importantly, I hope it stimulates those that are engaged in actively shaping the present. To describe the need for automatic picture transmission (APT), I must retrace the historical development of meteorological satellites. The idea for weather observations from a satellite originated with a small group of meteorologists at the U.S. Army Signal Corps Research and Development Lab. at Ft. Monmouth, N.J., and resulted in the design of Vanguard II. The Tiros and TOS series of satellites, and the design of Nimbus, followed soon thereafter. However, a faster picture dissemination than was available at that time was needed, and it was this necessity that sparked the development of APT. Nimbus was originally intended to be an operational system, but the advent of simpler, less costly stabilization systems made the Tiros evolution the clear winner. The geosynchronous weather satellites started nearly a decade later and evolved from the NASA Application Technology Satellite (ATS) series. All three systems, existing polar orbiting weather satellites, APT, and geosynchronous weather satellites, have changed meteorology and the reliability of weather forecasting profoundly. 相似文献
899.
N Desai H Wu K George S R Gonda F A Cucinotta 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(6):1362-1367
Space flight results in the exposure of astronauts to a mixed field of radiation composed of energetic particles of varying energies, and biological indicators of space radiation exposure provides a better understanding of the associated long-term health risks. Current methods of biodosimetry have employed the use of cytogenetic analysis for biodosimetry, and more recently the advent of technological progression has led to advanced research in the use of genomic and proteomic expression profiling to simultaneously assess biomarkers of radiation exposure. We describe here the technical advantages of the Luminex(TM) 100 system relative to traditional methods and its potential as a tool to simultaneously profile multiple proteins induced by ionizing radiation. The development of such a bioassay would provide more relevant post-translational dynamics of stress response and will impart important implications in the advancement of space and other radiation contact monitoring. 相似文献
900.
Track segment association, fine-step IMM and initialization with Doppler for improved track performance 总被引:2,自引:0,他引:2
Yeom S.-W. Kirubarajan T. Bar-Shalom Y. 《IEEE transactions on aerospace and electronic systems》2004,40(1):293-309
In this work we present a new track segment association technique to improve track continuity in large-scale target tracking problems where track breakages are common. A representative airborne early warning (AEW) system scenario, which is a challenging environment due to highly maneuvering targets, close target formations, large measurement errors, long sampling intervals, and low detection probabilities, provides the motivation for the new technique. Previously, a tracker using the interacting multiple model (IMM) estimator combined with an assignment algorithm was shown to be more reliable than a conventional Kalman filter based approach in tracking similar targets but it still yielded track breakages due to the difficult environment. In order to combine the broken track segments and improve track continuity, a new track segment association algorithm using a discrete optimization approach is presented. Simulation results show that track segment association yields significant improvements in mean track life as well as in position, speed, and course rms errors. Also presented is a modified one-point initialization technique with range rate measurements, which are typically ignored by other initialization techniques, and a fine-step IMM estimator, which improves performance in the presence of long revisit intervals. Another aspect that is investigated is the benefit of "deep" (multiframe or N-dimensional, with N > 2) association, which is shown to yield significant benefit in reducing the number of false tracks. 相似文献