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121.
G. S. Anufriev 《Cosmic Research》2010,48(1):101-107
The isotopic composition and concentrations of helium are investigated in 9 samples taken from different depths of a soil
column delivered by the Luna-24 mission. It is demonstrated that, with allowance made for random errors, the isotopic composition of helium remains invariable.
The concentrations of helium are subject to considerable variations, the increases and decreases relative to the average value
reaching a factor of 1.5–2. Assuming that the full length of the soil column was formed due to long-term accumulation of lunar
clastic rocks (regolith), based on measurements of cosmogenic isotopes, a method of determining the rate of regolith accumulation
has been developed, as well as a method of determining the age of the column soil samples. It is found that the rate of regolith
accumulation is variable, and it changes over the column length within the limits (0.2–0.8 cm)/106 years. The range of the time for formation of the investigated part of the column is 100–600 million years. The observed
decreases of concentration (at 250 and 600 million years) can be associated with both solar and lunar processes. In particular,
a possibility of diffusion losses of helium due to the mechanism of jump-like diffusion is discussed, and diffusion parameters
are found. A comparison of time periods of the observed variations in the solar wind with paleontological epochs and periods
is made. 相似文献
122.
Dynamics of planets around other stars that demonstrate a variety of possible characteristics is of interest from the point
of view of realization of new scenarios of evolution which have not been realized in the Solar System. We consider the rotational
evolution of exoplanets under the action of gravitational perturbations and magnetic disturbances using the methods of quality
analysis and theory of bifurcation of multiparametric differential equations that describe evolution of non-resonant rotation
of a dynamically symmetric planet magnetized along its symmetry axis. We analyze 64 phase portraits describing the evolution
of angular momentum vector L for all possible values of planet parameters. The values of parameters are determined for the case when the direct rotation
of a planet is changed for its retrograde rotation. 相似文献
123.
A. S. Meshchanov 《Russian Aeronautics (Iz VUZ)》2010,53(4):382-393
The results obtained for the systems with a linear stationary object and scalar control of sliding and switching modes [1]
are further developed. The methods of forming five modes of system operation with discontinuous and linear vector control
at nominal and uncertain limited disturbances are suggested. The necessary quality of transient processes with regard to the
speed of response and zero stationary error at all five modes and also controlled oscillation frequency and amplitude of control
signals at the sliding modes are provided. The effective sequence of switching the modes mentioned during the finite and unlimited
time intervals is proposed. The results are useful for qualitative tracking of programmed motion for flight vehicles, robot
manipulators, and other technical and production systems. 相似文献
124.
The volume finite element in the form of hexahedron with nodal unknowns as components of the displacement vector and stress
tensor has been developed to analyze the shells of revolution. The displacement vector components for the inner point of the
finite element and the components of its stress tensor are expressed through the nodal unknowns using the method of vector
and tensor fields interpolation by the trilinear shape functions; that provides taking into account the finite element displacement
as a whole solid. The variational principle in a mixed formulation is applied to form the matrix of hexahedron deformation.
The efficiency of the proposed method for approximating the values being sought as vector and tensor fields in comparison
with the traditional method for approximating the values being sought as scalar fields is confirmed by a numerical example. 相似文献
125.
The paper presents a technique of calculating the life for gas turbine engine parts in a low cycle area based on the influence coefficients taking into account analytical and operational factors. A statistical method is used to determine the influence coefficients. 相似文献
126.
A comparison of temporal profiles of low-energy ion intensity and magnetic field magnitude in different periods of solar activity
in the outer heliosphere is carried out using the data of the Voyager 1 and Voyager 2 spacecraft. It is shown that temporal, spectral, and statistical characteristics of particle fluxes and magnetic field in
the heliospheric regions before and after the terminal shock in 2002–2008 had similar dynamics in different hemispheres. This
similarity allowed one to assume that, in the region of the inner heliospheric boundary, a quasistable spatial structure existed
moving together with the terminal shock in accordance with the solar wind pressure, as well as, probably, under the action
of the interstellar medium. It was revealed that the spatial dimensions of most details of this structure are less on Voyager 2, which, probably, is due to variation of the solar activity level, difference in latitude of spacecraft disposition, and
also the influence of the interstellar magnetic field. 相似文献
127.
I. A. Krivosheev A. G. Godovanyuk V. S. Fatikov G. I. Pogorelov 《Russian Aeronautics (Iz VUZ)》2010,53(1):57-62
A technique for linear interpolation of the multidimensional characteristics of a coaxial propeller fan with opposite rotation
propellers is proposed; the technique makes it possible to simulate the turbofan engine operation in the entire range of flight
conditions and reduce expenses for fullscale tests. The mathematical models obtained meet the requirements imposed in the
semi-full-scale simulation. 相似文献
128.
We present the results of investigation of the dynamics of (99942) Apophis asteroid, which will undergo a very close encounter
with the Earth on April 13, 2029. The region of possible motions of the asteroid is considered on the time interval (2004,
2040). In addition, it is shown that an increase of the observational interval (2004, 2006) until 2008 allowed us to reduce
significantly the area of possible motions. All investigations were performed by numerical methods with the help of algorithms
and software developed by us in the environment of parallel programming using the SKIF Cyberia multiprocessor computer of
the Tomsk State University. 相似文献
129.
The Lunar Gravity Ranging System for the Gravity Recovery and Interior Laboratory (GRAIL) Mission 总被引:1,自引:0,他引:1
William M. Klipstein Bradford W. Arnold Daphna G. Enzer Alberto A. Ruiz Jeffrey Y. Tien Rabi T. Wang Charles E. Dunn 《Space Science Reviews》2013,178(1):57-76
The Lunar Gravity Ranging System (LGRS) flying on NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission measures fluctuations in the separation between the two GRAIL orbiters with sensitivity below 0.6 microns/Hz1/2. GRAIL adapts the mission design and instrumentation from the Gravity Recovery and Climate Experiment (GRACE) to a make a precise gravitational map of Earth’s Moon. Phase measurements of Ka-band carrier signals transmitted between spacecraft with line-of-sight separations between 50 km to 225 km provide the primary observable. Measurements of time offsets between the orbiters, frequency calibrations, and precise orbit determination provided by the Global Positioning System on GRACE are replaced by an S-band time-transfer cross link and Deep Space Network Doppler tracking of an X-band radioscience beacon and the spacecraft telecommunications link. Lack of an atmosphere at the Moon allows use of a single-frequency link and elimination of the accelerometer compared to the GRACE instrumentation. This paper describes the implementation, testing and performance of the instrument complement flown on the two GRAIL orbiters. 相似文献
130.
S. Yu. Mikheev I. I. Shkarban Y. A. Ryzhov S. A. Khartov M. M. Gorshkov R. P. Markov 《Russian Aeronautics (Iz VUZ)》2012,55(1):108-112
A process of manufacture of porous membranes made of aluminum foil (Al 99.99%) by the method of electrochemical anodic oxidation followed by a continuous barrier layer removal with ion-plasma irradiation is described. The membranes having a 8 mm diameter made from AL2O3 with a thickness from 2 to 5 microns thick with a regular channel arrangement are obtained. A possibility to change the channel diameter in the range of 20?C100 nm by adjusting voltage and temperature during the oxidation is shown. We present the experimental dependencies of aluminum and aluminum oxide sputtering coefficients on the energy and incidence angle of xenon ions within the energy range of 100??400 eV. 相似文献