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11.
The motion of a spacecraft with small asymmetry relative to its center of mass is considered. The restoring aerodynamic moment of the spacecraft is described by the Fourier series in terms of the angle of attack with the two first sinusoidal and the first cosinusoidal terms. A solution for the angle of attack in the undisturbed rotational motion is found. The analytical expression is obtained for the integral of action taken along the separatrices that separate the rotational and oscillatory regions of the phase portrait of a system. The transition of the spacecraft's motion from planar rotational to oscillatory is investigated. This transition is caused by a slow variation of moment characteristic coefficients, as well as by the presence of small asymmetry and damping and slow variation of their coefficients. Analytical formulas are obtained for determining the times of transition from rotational to oscillatory motion, as well as for the critical angular velocity of beyond-the-atmosphere rotation. When this critical velocity is exceeded, body rotation proceeds for a long time interval (planar autorotation arises). 相似文献
12.
The problem of target motion analysis (TMA) has been the subject of an important literature. However, present methods use data estimated by a short time analysis (azimuths, Dopplers, etc.). For far sources, the nonstationarities of the array processing outputs, induced by the sources motion, may be simply modeled. This model leads one to consider directly a spatio-temporal TMA. Then new (spatio-temporal) data can be estimated. These estimates correspond to a long time analysis. Further, note that they are estimated independently of the (classical) bearings. In this general framework, the concept of source trajectory replaces the classical instantaneous bearings. Corresponding TMA algorithms are then studied. Then the study of statistical performance is carefully studied 相似文献
13.
T. K. Sirazetdinov 《Russian Aeronautics (Iz VUZ)》2007,50(1):30-36
A brief review of studies on simulation and control of a porous cooling process taking into account material transpiration is given. An approximated solution for an equation of the one-dimensional problem of fast ablation is also presented. 相似文献
14.
The results of the experimental studies of damping characteristics of a composite torsion bar in the helicopter main rotor
hingeless hub are presented. A variant of their improvement is considered. 相似文献
15.
We present an algorithm for calculating the shells of revolution with the branching meridian using the triangular finite elements, the rigidity matrices of which are formed based on the vector method of displacement interpolation [1]. The correct kinematic and static conditions of shell conjugation on the line of their coupling have been developed. The shell structure consisting of a cylinder and adjacent shells is calculated under various conditions of support. 相似文献
16.
I. S. Akhmed’yanov 《Russian Aeronautics (Iz VUZ)》2009,52(4):383-389
The application of the quadrature method [1] to analyzing the shells of revolution under symmetrical loading relative to the
zero meridian is considered. The method can be treated as a generalization of the method presented in [2] to solve the Volterra
integral equation of the second kind. 相似文献
17.
A problem of determining a shape of the airfoil being streamlined by a potential incompressible inviscid flow is solved by
the successive approximation method using a specified chord velocity diagram. It is shown that a closed airfoil that possesses
a specified chord velocity diagram can be constructed with a sufficient accuracy; if the chord diagram is unsuccessfully specified,
the closed airfoil may prove to be not univalent, that is, physically unrealizable. 相似文献
18.
Y Kitaya M Kiyota I Aiga K Yabuki K Nitta A Ikeda S Nakayama 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(5):37-40
In order to collect basic data about CO2 and O2 budgets of a plant cultural system in a CELSS, the variation of the CO2 absorption rates of lettuce and turnips were observed during the growing period, under different conditions. The O2 release rates were deduced from the CO2 absorption rates multiplied by 32/44. As a result, when the light intensity, the photoperiod and the atmospheric CO2 concentration increased, the rates also increased. The effects on the turnips were more significant than those on the lettuce. Turnips at 310 micromoles/m2/s of PPFD, 24 hours of photoperiod and 1100 ppm of CO2 concentration grew most actively in the present experimental conditions. One turnip absorbed 32.3 g CO2 and released 23.5 g O2 for 6 days between 24 days and 30 days after sowing. 相似文献
19.
L. V. Zasova V. I. Moroz V. M. Linkin I. V. Khatuntsev B. S. Maiorov 《Cosmic Research》2006,44(4):364-383
The goal of this paper is to summarize the experimental data on the atmosphere of Venus obtained after 1985, when the VIRA (Venus International Reference Atmosphere) or COSPAR model was published. Among the most important results that have appeared since then are the following: measurements of the vertical temperature profile by the VEGA spacecraft with high precision and high altitude resolution; measurements made with balloons of the VEGA spacecraft; radio occultation measurements of Magellan, Venera-15, and Venera-16; and temperature profiles derived from the data of infrared spectrometry obtained by Venera-15. The new result as compared to VIRA is the creation of a model of the atmosphere in the altitude range 55 to 100 km dependent on local time. This model is presented in our paper in tabulated form. 相似文献
20.
Microbial processes in frozen food 总被引:2,自引:0,他引:2
O Geiges 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,18(12):109-118
Deep freezing of food and storage at −19°C is a standard conservation procedure in food technology. The lower limit of growth of bacteria in food is from about −5°C to about −8°C, whereas the reproduction limit of yeasts is 2 to 3°C lower. Storage temperatures above −10°C should therefore not be used. At −18°C, a commonly used storage temperature, no growth of microorganisms will occur. The microorganisms mainly found at the lower growth limit are Pseudomonas sp. and basidiomycete yeasts. The reduction in the number of microorganisms due to freezing, storage, and thawing is not of practical importance. Microbial enzymes, in particular lipases and proteases, are still active at −18°C. Therefore, the quality of raw products and good hygiene at the production site are most important. 相似文献