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991.
Studies of temperature dependences of ac magnetization were carried out for a superconducting lead-porous glass nanocomposite. Double peaks were found on the imaginary part of ac magnetization which were accompanied with double steps on the real part. The lower-temperature anomalies in ac magnetization differed noticeably when they were obtained upon cooling and warming. The double peaks were treated as two phase transitions in the vortex system: the liquid-solid transition which occurs close to the onset of superconductivity and solid-solid one which is triggered by superconductivity in confined lead islands. 相似文献
992.
本文通过将使用时间在可能发生故障的时刻划分成时间区间,对修如旧模型下的多部件系统,在修理延迟条件下,对各类故障在同一时间区间里相容的条件下导出了任意给定时刻设备的可用度函数,并对文[3]中的算法做了改进,得到了更精确更合理的结果 相似文献
993.
Raman study of a natural hydrous phlogopite was carried out at temperatures up to 500 °C for the first time. Evolution of four well-resolved Raman modes at wavenumbers 196, 278, 322, and 682 cm−1 was followed in detail with temperature increase. The analysis of data reveals linear decrease of vibrational wavenumbers in the studied temperature range, with small but experimentally significant discontinuities occurring at a temperature of 365±15 °C. Although the overall appearance of Raman spectra remains intact on crossing this temperature, the presence of discontinuities, as well as a marked difference between Gruneisen parameters calculated for high- and low-temperature ranges, signifies the presence of a temperature-induced phase transformation. By combining and correlating the results of the present Raman study with the high-temperature X-ray work performed by Tutti et al. [High-temperature study and thermal expansion of phlogopite, Phys. Chem. Miner. 27 (2000) 599-603] we arrive at the interpretation of a temperature-induced structural phase transformation in phlogopite without a significant symmetry change, with an underlying microscopic mechanism involving deformation of Mg octahedra and rotation of tetrahedral grid from ditrigonal toward hexagonal at the transition temperature. 相似文献
994.
Phase diagrams of 1,2,4,5-tetrachlorobenzene–β-naphthol and 1,2,4,5-tetramethylbenzene–succinonitrile systems which are organic analogues of a nonmetal–nonmetal and a nonmetal–metal system, respectively, show the formation of a simple eutectic (melting point 103.7°C) with 0.71 mole fraction of β-naphthol in the former case and a monotectic (melting point 76.0°C) with 0.07 mole fraction of succinonitrile and a eutectic (melting point 52.5°C) with 0.97 mole fraction of succinonitrile in the latter case. The growth behaviour of the pure components, the eutectics and the monotectic studied by measuring the rate of movement of the solid–liquid interface in a capillary, suggests that the data obey the Hillig–Turnbull equation, v=u(ΔT)n, where v is the growth velocity, ΔT is the undercooling and u and n are constants depending on the nature of the materials involved. From the values of enthalpy of fusion determined by the DSC method using Mettler DSC-4000 system, entropy of fusion, interfacial energy, enthalpy of mixing and excess thermodynamic functions were calculated. The optical microphotographs of pure components and polyphase materials show their characteristic features. 相似文献
995.
996.
In this paper, several sufficient conditions are obtained to guarantee that the n-dimensional cellular neural network can have even (?2n) memory patterns. In addition, the estimations of attractive domain of such stable memory patterns are obtained. These conditions, which can be directly derived from the parameters of the neural networks, are easily verified. A new design procedure for cellular neural networks is developed based on stability theory (rather than the well-known perceptron training algorithm), and the convergence in the new design procedure is guaranteed by the obtained local stability theorems. Finally, the validity and performance of the obtained results are illustrated by two examples. 相似文献
997.
John A. Ford Yasushi Narushima Hiroshi Yabe 《Computational Optimization and Applications》2008,40(2):191-216
Conjugate gradient methods are appealing for large scale nonlinear optimization problems, because they avoid the storage of
matrices. Recently, seeking fast convergence of these methods, Dai and Liao (Appl. Math. Optim. 43:87–101, 2001) proposed a conjugate gradient method based on the secant condition of quasi-Newton methods, and later Yabe and Takano (Comput.
Optim. Appl. 28:203–225, 2004) proposed another conjugate gradient method based on the modified secant condition. In this paper, we make use of a multi-step
secant condition given by Ford and Moghrabi (Optim. Methods Softw. 2:357–370, 1993; J. Comput. Appl. Math. 50:305–323, 1994) and propose two new conjugate gradient methods based on this condition. The methods are shown to be globally convergent
under certain assumptions. Numerical results are reported. 相似文献
998.
Similar to the problem of linearization, the “small divisor problem” also arises in the discussion of invertible analytic solutions of a class of q-difference equations. In this paper we give the existence of such solutions under the Brjuno condition and prove that the equation may not have a nontrivial analytic solution when the Brjuno condition is violated. These results are applied to discussing a nonlinear iterative equation. 相似文献
999.
Giovanna Bonfanti Maria Grazia Naso 《Journal of Mathematical Analysis and Applications》2008,345(1):186-202
In this paper we analyze a dynamic unilateral contact problem between two thermoelastic beams. We establish the existence of a weak global-in-time solution, by a penalization method. Moreover, we study the asymptotic behavior of such a solution proving that the energy associated to the system decays exponentially to zero, as time goes to infinity. 相似文献
1000.
Eitan Altman Konstantin Avrachenkov Merouane Debbah Daniel Sadoc Menasche 《Operations Research Letters》2008,36(2):160-164
We study non-cooperative constrained stochastic games in which each player controls its own Markov chain based on its own state and actions. Interactions between players occur through their costs and constraints which depend on the state and actions of all players. We provide an example from wireless communications. 相似文献