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531.
A technique for choosing a rational load-carrying scheme and weight analysis at the early stages of designing lifting surfaces with the use of a special model of the finite element method is proposed. The distribution of structure loads is determined with regard for its deformation. The numerical example is presented. 相似文献
532.
We analyze the well-known statements of optimal design problems for load-bearing maximum rigidity structures in which a principle of the minimum of total potential energy of structure deformation is used. A version of the generalized statement of optimization problems for processes described by linear equations with a symmetric operator is proposed. On the basis of the version outlined, we present a mathematical algorithm for obtaining beam structures of maximum rigidity, in which the finite element method is used to solve an analytical problem. We give the numerical results of solving two problems of optimal design of maximum rigidity structures that are simulated by cantilever and statically indeterminate beams. 相似文献
533.
As examples of application of the technique suggested in the first part of this work, the problems of optimizing the trajectories of spacecraft transfers between circular coplanar orbits are considered in this second part. During the transfer the spacecraft is controlled by the vector of thrust of a limited-thrust jet engine. The mass consumption is minimized for a limited time of transfer. Extreme trajectories with two and three powered sections (Homan-type and bi-elliptic transfer trajectories) are numerically determined. The solution of these well-studied problems allows one to compare the results of applying the suggested technique with the results of application of other previously used techniques. 相似文献
534.
G. V. Kasatkin 《Cosmic Research》2005,43(4):245-253
The potential of gravity forces is found inside a thin homogeneous ring when the ring’s mean radius is much larger than the diameter of its cross section. Rings with elliptic and almost circular cross sections are considered.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 4, 2005, pp. 260–268.Original Russian Text Copyright © 2005 by Kasatkin. 相似文献
535.
A. Zanini M. Storini O. Saavedra 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The worldwide distribution of High Mountain Observatories provides a unique opportunity for performing contemporary measurements under different geomagnetic/altitude conditions and for collecting long-term data series. In this context, the history and some activities performed at two historical Research Stations are summarized: Chacaltaya Laboratory (Bolivia) and the Testa Grigia Research Station (Italy). 相似文献
536.
Based on the topological representation and transformation of the elementary chevron structure module, we propose the dependences that relate the geometrical parameters of rollers with the chevron structure element sizes for the transverse scheme of rotary creasing and bending. The calculation scheme is realized in the form of the parametrized geometrical model using CAD SolidWorks aids. 相似文献
537.
An algorithm for solving a boundary-value problem of deforming structures made of composite materials is considered. The polynomial solutions of the equation system for the linear theory of elasticity for the anisotropic medium in displacements are used in this algorithm. 相似文献
538.
V. A. Parkhomov G. N. Zastenker M. O. Riazantseva B. Tsegmed T. A. Popova 《Cosmic Research》2010,48(1):86-100
We present the results of studying the magnetospheres’s response to sharp changes of the solar wind flow (pressure) based
on observations of variations of the ions flux of the solar wind onboard the Inreball-1 satellite and of geomagnetic pulsations (the data of two mid-latitude observatories and one auroral observatory are used).
It is demonstrated that, when changes of flow runs into the magnetosphere, in some cases short (duration ~ < 5 min) bursts
of geomagnetic pulsations are excited in the frequency range Δf~ 0.2–5 Hz. The bursts of two types are observed: noise bursts without frequency changes and wide-band ones with changing
frequency during the burst. A comparison is made of various properties of these bursts generated by pressure changes at constant
velocity of the solar wind and by pressure changes on the fronts of interplanetary shock waves at different directions of
the vertical component of the interplanetary magnetic field. 相似文献
539.
We investigate the relative occurrence rate for various types of the solar wind and their geoeffectiveness for magnetic storms
with Dst < —50 nT. Both integrated effect for the entire time 1976–2000 and variations during this period of 2.5 cycles of solar activity
are studied As raw data for the analysis we have used the catalog of large-scale types of the solar wind for the period 1976-2000
(see ftp://ftp.iki.rssi.ru/omni/) created by us with the use of the OMNI database (http://omni.web.gsgc.nasa.gov) [1] and
described in detail in [2]. The average annual numbers of different type of events are as follows: 124 ±81 for the heliospheric
current sheet (HCS), 8 ±6 for magnetic clouds (MC), 99 ±38 for Ejecta, 46 ±19 for Sheath before Ejecta, 6 ±5 for Sheath before
MC, and 63 ±15 for CIR. The measurements that allowed one to determine a source in the solar wind were available only for
58% of moderate and strong magnetic storms (with index Dst < —50 nT) during the period 1976–2000. Magnetic clouds (MC) are shown to be the most geoeffective (~61%). The CIR events and
Ejecta with Sheath region are three times less geoeffective (~20–21 %). Variations of occurrence rate and geoeffectiveness
of various types of the solar wind in the solar cycle are discussed. 相似文献
540.
O.S. Yakovchouk I.S. Veselovsky K. Mursula 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We present and discuss here the first version of a data base of extreme solar and heliospheric events. The data base contains now 87 extreme events mostly since 1940. An event is classified as extreme if one of the three critical parameters passed a lower limit. The critical parameters were the X-ray flux (parameter R), solar proton flux (parameter S) and geomagnetic disturbance level (parameter G). We find that the five strongest extreme events based on four variables (X-rays SEP, Dst, Ap) are completely separate except for the October 2003 event which is one the five most extreme events according to SEP, Dst and Ap. This underlines the special character of the October 2003 event, making it unique within 35 years. We also find that the events based on R and G are rather separate, indicating that the location of even extreme flares on the solar disk is important for geomagnetic effects. We also find that S = 3 events are not extreme in the same sense as R > 3 and G > 3 events, while S = 5 events are missing so far. This suggests that it might be useful to rescale the classification of SEP fluxes. 相似文献