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841.
E. N. Parker 《Space Science Reviews》1973,14(3-4):576-581
A space mission to Jupiter and Saturn, and beyond, provides an opportunity to explore the low energy galactic cosmic rays, which are largely excluded from the inner solar system by the outward sweep of the magnetic fields in the solar wind. The low energy cosmic rays are believed to be responsible for much of the heating of the gaseous disk of the galaxy, so a measurement of their intensity will have far reaching effects on theories of the interstellar gas and the evolution of the galaxy. The nuclear abundances, and in particular the presence or absence of high Z nuclei, will give critical information on the proximity of cosmic ray sources.This is one of the publications by the Science Advisory Group. 相似文献
842.
Dynamics of the satellite angular momenta is modeled by ordinary differential equations with additive white noise. A feedback controller er is desired to maintain tolerable satellite momenta and to economize ze the fuel consumption. The stochastic optimal control problem is transformed into an equivalent deterministic optimization problem involving a parabolic partial differential equation. Necessary optimality y conditions are used to develop a computation algorithm. Results regarding optimal controls, expected costs, and confinement probabilities in different noisy environments are presented. 相似文献
843.
N.S. Meshalkina A.T. Altyntsev Yan Yihua 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(6):936-942
The goal is to study parameters of drifting type III bursts, and find out the emission mechanism of these bursts and understand what factors affect instantaneous spectral bandwidth of these bursts. 相似文献
844.
S. Takechi K. Nogami T. Miyachi M. Fujii N. Hasebe T. Iwai S. Sasaki H. Ohashi H. Shibata E. Grün R. Srama N. Okada 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
A cosmic dust monitor for use onboard a spacecraft is currently being developed using a piezoelectric lead zirconate titanate element (PZT). Its characteristics of the PZT sensor is studied by ground-based laboratory impact experiments using hypervelocity particles supplied by a Van de Graaff accelerator. The output signals obtained from the sensor just after the impact appeared to have a waveform that was explicitly related to the particle’s impact velocity. For velocities less than ∼6 km/s, the signal showed an oscillation pattern and the amplitude was proportional to the momentum of the impacting particle. For higher velocities, the signal gradually changed to a single waveform. The rise time of this single waveform was proportional to the particle’s velocity for velocities above ∼6 km/s. The present paper reports on results for the low velocity case and especially discusses the effect of an outer coating of the sensor with a paint, which is used to reduce heating by solar radiation. 相似文献
845.
N. V. Sonin 《Russian Aeronautics (Iz VUZ)》2008,51(1):97-100
The results of experimental studies of nonlinear aerosol oscillations in an open tube for a frequency equal to half the fundamental one are presented. The results can be used in designing aircraft engines. 相似文献
846.
During evolution, life on earth had adapted to the gravity of 1g. Due to space flight, in the last decades the question arose what happens to the brain under microgravity on the molecular level. Ion channels among others are the molecular basis of brain function. Therefore, the investigation of ion channel function under microgravity seems to be a promising approach to gather knowledge on brain function during space flight. In a first step, the ion channel forming peptide Alamethicin was used as a model channel in an artificial membrane. It is well suitable for this kind of investigation, since its properties are well described under standard gravity. For that reason, changes due to microgravity can be detected easily. All experiments were performed in the German drop tower at ZARM-FAB, Bremen. A special set-up was constructed based on the bilayer technique introduced by Mueller and Rudin. All functions of this set-up can be observed and controlled remotely. In the first set of experiments, a dramatic change of electrical properties of Alamethicin under microgravity could be observed. Mainly, the pore frequency is significantly reduced. 相似文献
847.
The application of numerical techniques for the solution of various external and internal inviscid gaseous flowfields is considered. The construction of numerical codes is discussed. This discussion includes the comparison of explicit and implicit finite-difference schemes, the examination of possibilities of the shock-capturing techniques and the consideration of nonregular nets. Also the order of the finite-difference approximation is analysed. The effectiveness of these principles is demonstrated for various flowfield simulations. 相似文献
848.
I. V. Mingalev N. M. Astaf’eva K. G. Orlov V. M. Chechetkin V. S. Mingalev O. V. Mingalev 《Cosmic Research》2012,50(3):233-248
Mechanisms of formation of cyclonic vortices in the tropical atmosphere of the Earth are investigated in the intratropical zone of convergence using numerical simulation made with the complete system of equations of gas dynamics taking into account transport of infrared radiation, phase transitions of water vapor into microdrops of water and ice particles, and sedimentation of these drops and ice particles in the field of gravity force. Observational data on the structure of dominant air streams, which are formed in the intratropical zone of convergence over the North Atlantic in the periods of its highest thermodynamic intensity and instability, are used in the initial and boundary conditions of the model. Formation of cyclonic vortex flows is obtained numerically at sufficiently strong bending of the intratropical zone of convergence. The results of numerical modeling are compared with the data of satellite microwave monitoring: global radio thermal fields of the Earth from the electronic collection GLOBAL-Field allowing one to study the structure of atmospheric motions in a wide range of space-time scales. 相似文献
849.
As the field of astrobiology matures and search strategies for life on other worlds are developed, the need to analyze in a systematic way the plausibility for life on other planetary systems becomes increasingly apparent. We propose the adoption of a simple plausibility of life (POL) rating system based on specific criteria. Category I applies to any body shown to have conditions essentially equivalent to those on Earth. Category II applies to bodies for which there is evidence of liquid water and sources of energy and where organic compounds have been detected or can reasonably be inferred (Mars, Europa). Category III applies to worlds where conditions are physically extreme but possibly capable of supporting exotic forms of life unknown on Earth (Titan, Triton). Category IV applies to bodies that could have seen the origin of life prior to the development of conditions so harsh as to make its perseverance at present unlikely but conceivable in isolated habitats (Venus, Io). Category V would be reserved for sites where conditions are so unfavorable for life by any reasonable definition that its origin or persistence there cannot be rated a realistic probability (the Sun, gas giant planets). The proposed system is intended to be generic. It assumes that life is based on polymeric chemistry occurring in a liquid medium with uptake and degradation of energy from the environment. Without any additional specific assumptions about the nature of life, the POL system is universally applicable. 相似文献
850.
Kaplan L.J. Ormsby J.F.A. Fowle E.N. Johnson K.R. Bates R.H.T. Bickel S.H. 《IEEE transactions on aerospace and electronic systems》1969,(4):654-660
A satellite has been designed for application to radar calibration. Electromagnetic and mechanical characteristics of the satellite and their influence on the selection of shape and other parameters are discussed. Theoretical and experimental scattering data are included. 相似文献