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111.
N.I. Amel’kin 《Journal of Applied Mathematics and Mechanics》2011,75(2):140-153
A satellite in the form of a system of bodies that does not have the property of a gyrostat in the general case is considered. An algorithm for determining all the equilibrium configurations of the system that correspond to steady motions in a central gravitational field and an algorithm for analysing their stability are given. A method based on Routh's first theorem is used to investigate the asymptotic stability of the steady motions in the unconstrained problem. Three effects caused by internal dissipation are established in a model example: stabilization of the satellites in a neighbourhood of rotations about a normal to the orbital plane, which is codirectional with the axis of the largest moment of inertia, evolution of elliptic orbits into circular orbits, and capture of the satellites in resonant oscillatory modes of motion. 相似文献
112.
N.I. Amel’kin 《Journal of Applied Mathematics and Mechanics》2011,75(3):247-257
The steady motions of a rigid body carrying several two-degree-of-freedom powered gyroscopes in a uniform external field are investigated. It is shown that when the installation scheme of the gyroscopes in the carrying body is collinear, the problem of determining the steady motions of the system and analysing their secular stability reduces for the most part to the previously solved, similar problem for a system with one gyroscope. It is established that when there is dissipation in the axes of the gyroscope frames, the system tends asymptotically to a state of rest if the absolute value of the total angular momentum of the system lies in the segment of possible absolute values of the angular momentum of the gyroscope rotors. The results of an analysis of the steady motions of a system carrying two gyroscopes with a non-collinear installation scheme are presented. 相似文献
113.
Amel Benyoucef Didier Klein Olivier Rapaud Christian Coddet Boumediene Benyoucef 《Journal of Physics and Chemistry of Solids》2009,(12):1487-1495
This paper reports the results of the thermal stability study of M–YSZ (M=Ni, Cu, Co, Cu–Co, Ni–Cu–Co) SOFC anode cermets materials at different heat treatment temperatures. The cermets were elaborated by atmospheric plasma spraying (APS) with optimized conditions and then submitted to heat treatments at 800 and 1000 °C, respectively. Scanning electron microscopy and X-ray diffraction were used to characterize, respectively, the morphology and structure of obtained films, before and after thermal annealing. A correlation was made between the differential scanning calorimetry analysis results and those obtained by X-ray diffraction. Focusing, in this study, on YSZ matrix thermal stability, the obtained results were as follows: the monometallic cermets with the lowest amount of metal and the trimetallic one exhibited a good stability at 800 °C, whereas at 1000 °C, all considered cermets were unstable with a eutectoid decomposition of YSZ matrix. 相似文献
114.
115.
The sulfamide functional group is increasingly relevant in both medicinal and bioorganic chemistry. We report here practical access to a series of N2,N5-substituted five-membered cyclosulfamides. The five-membered heterocyclic motif was prepared starting from proteogenic amino acids and chlorosulfonyl isocyanate via the Mitsunobu reaction. Selected chemical and spectral proprieties and the antimicrobial evaluation of these compounds are detailed. 相似文献
116.
Summary The solvolysis of thetrans-[Co(4-Mepy)4Cl2]ClO4 complex was studied in 0 to 70% v/v H2O: MeOH mixtures at 40, 45, 50 and 55 °C. The high negative S* values found for the complex cation under investigation, relative to that oftrans- [Co(py)4Cl2]+ reported in the literature, were attributed to the substituent methyl groups. The free energies of transfer of both the ground and the transition states were calculated from which the dominant effect of the solvent on the transition state is apparent. 相似文献
117.
Amel Ben Othman Young Hoon Lee Keisuke Ohto Rym Abidi Yang Kim Jacques Vicens 《Journal of inclusion phenomena and macrocyclic chemistry》2008,62(1-2):187-191
Hyperbranched molecules, 4–8, based on calixarenes attached to newly synthesised cores 2 and 3 have been prepared. Preliminary complexation studies of the complexation of Zn(Pic)2 by 8 showed that the ligand prefers to bind the picrate anions. 相似文献
118.
Different solvents including cyclohexane, dichloromethane, chloroform, toluene, 1-octanol, and methyl isobutyl ketone (MIBK) have been evaluated in extracting copper(II) from nitrate medium by salicylideneaniline. Extracted species differs from solvent to solvent: CuL2 in cyclohexane, toluene, 1-octanol, and methyl isobutyl ketone. However, in dichloromethane or chloroform, there are two complexes of the type CuL2 and CuL2(HL). The extraction constants and percentage of extraction (%E) are calculated for different solvents. Solvent played an important role in recovering copper(II) from the aqueous solution, thus affecting the extraction equilibrium and extraction efficiency. The nonpolar solvent showed better performance than the polar solvent. The maximum extraction efficiency was 85.75% at pH?=?4.5, which was from cyclohexane. 相似文献
119.
N. I. Amel’kin 《Mechanics of Solids》2007,42(4):517-529
To study the stability of steady rotations of a control moment gyro system with internal dissipation, we use the Barbashin-Krasovskii theorem and the relation, established in [1], between the Lyapunov function and steady motions. Taking into account the special properties of the original problem, we reduce it to a lower-dimensional problem.We give a detailed presentation of an algorithm for analyzing the stability of steady motions of a gyrostat and use this algorithm to perform a complete study for two systems consisting, respectively, of one and two gyros whose gimbal axes are parallel to the principal axis of inertia of the system. Each steady motion is identified as either asymptotically stable or unstable. We find periodic motions that exist only in the presence of dynamic symmetry and which are regular precessions. For the system with two gyros, we prove the asymptotic stability of quiescent states and prove that in the angular momentum range where these states are defined the system does not have any other stable motions. 相似文献
120.
We say that a graph G is quasi claw-free if every pair (a
1, a
2) of vertices at distance 2 satisfies {u∈N (a
1)∩N (a
2) | N[u]⊆N[a
1]∪N [a
2]}≠∅. A cycle C is m-dominating if every vertex of G is of distance at most m from C. We prove that if G is a κ-connected (κ≥2) quasi claw-free graph then either G has an m-dominating cycle or G has a set of at least κ+1 vertices such that the distance between every pair of them is at least 2m+3.
Received: June 12, 1996 Revised: November 9, 1998 相似文献