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31.
J.‐C. Wallet E.M. Gaydou H. Lachekar V. Pichon‐Pesme 《Crystal Research and Technology》2000,35(8):1001-1009
The structures of two solid inclusion compounds with the 2',6'‐dimethoxyflavone host molecule, 1, were investigated by single‐crystal X‐ray analysis. Both compounds, 1�3‐bromo‐2,6‐dimethoxybenzoic acid (1:1) and 1�3‐chloro‐2,6‐dimethoxybenzoic acid (1:1) crystallize in the centrosymmetric group P‐1. The complexation involves an intermolecular hydrogen bond between the carbonyl group of the flavone and the acidic hydrogen of the acid. 相似文献
32.
Precision densities and sound velocities for solutions of selected univalent electrolytes and nonelectrolytes in DMSO have been measured at 25°C, and apparent molar isentropic compressibilities and volumes evaluated. The data were extrapolated to infinite dilution to obtain standard state partial molar quantities, K
s,2
°
, and V
2
°
. Values of V
2
°
and K
s,2
°
for alkali metal halides in DMSO are very similar to those in water. The results confirm conclusions derived from data in water and other nonaqueous solvents that K
s,2
°
and V
2
°
for alkali metal halides are strongly dependent on solvent compressibility. K
s,2
°
becomes more negative and V
2
°
decreases as solvent compressibility increases. Attempts to determine ionic K
s,2
°
values suggest that a significant dissymmetry exists between 4P+ and 4B– in DMSO, whereas in water and MeOH, these large ions appear to behave similarly. Ionic V
2
°
values support this conclusion. Steric hindrance in the DMSO molecule is believed to be responsible for this dissymmetry. 相似文献
33.
Julian Henn 《Acta Crystallographica. Section A, Foundations and Advances》2012,68(6):703-704
It is shown that expectation values of Poisson‐distributed random numbers exist not only for the well known positive integer powers but also for negative integer powers. A recursion formula for the calculation of expectation values of powers differing by one is given. This recursion formula helps to find an analytical representation for both positive and negative integer powers in terms of the hypergeometric function. 相似文献
34.
35.
K.D. Mombaur H.G. Bock J.P. Schlder R.W. Longman 《ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik》2005,85(7):499-515
We present a numerical method that optimizes the open‐loop stability of solutions of periodic optimal control problems. We consider general periodic processes that may have several phases, each characterized by its own set of differential equations, and discontinuities of the state variables and the right hand side between phases. Stability is measured in terms of the spectral radius of the monodromy matrix which results in a nonsmooth optimization criterion. We have applied this method to design walking robots that can perform stable periodic gaits without any sensors or feedback; three such examples are presented in this paper. 相似文献
36.
M. Beldiman Ioana Boac&#x; G. Marinoschi 《ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik》2013,93(9):633-647
We address an optimization problem related to a diffusive flow in a nonhomogeneous porous medium. More exactly, the purpose is to control by a flow parameter an optimal average of the solution in a subset of the domain. The state model is degenerate and ill‐posed and this requires to develop a technique of optimization for a singular state system. 相似文献
37.
Using a multi‐objective evolutionary algorithm (MOEA) and enhanced surrogate approximations, the present study demonstrates the numerical analysis and optimization of staggered‐dimple channels. Two surrogates, the response surface approximation (RSA) model and the Kriging (KRG) model, are applied in light of the surrogate fidelity of the approximate analysis. An enhanced Pareto‐optimal front is obtained by performing local resampling of the Pareto‐optimal front, which provides relatively more accurate Pareto‐optimal solutions in the design space for each surrogate model. Three dimensionless design variables are selected, which are related to geometric parameters, namely, the channel height, dimple print diameter, dimple spacing, and dimple depth. Two objective functions are selected that are related to the heat transfer and pressure loss, respectively. The objective‐function values are numerically evaluated through Reynolds‐averaged Navier–Stokes analysis at the design points that are selected through the Latin hypercube sampling method. Using these numerical simulations two surrogates, viz, the RSA and Kriging models, are constructed for each objective function and a hybrid MOEA is applied to obtain the Pareto‐optimal front. For the particular implementation of surrogate models, it is observed that Pareto‐optimal predictions of the RSA model are better than those of the KRG model, whereas the KRG model predicts equally well at the off‐Pareto‐region (region away from the Pareto‐optimal solutions), which is not the case with the RSA model. The local resampling of the Pareto‐optimal front increases the fidelity of the approximate solutions near the Pareto‐optimal region. The ratios of the channel height to the dimple print diameter and of the dimple print diameter to the dimple pitch are found to be more sensitive along the Pareto‐optimal front than the ratio of the dimple depth to the print diameter. The decrease of the ratio of the channel height to the dimple diameter and the increase of the ratio of the dimple print diameter to the pitch lead to greater heat transfer at the expense of the pressure loss, whereas the ratio of the dimple depth to the print diameter is rather insensitive to Pareto‐optimal solutions. Pareto‐optimal solutions at higher values of the Nusselt number are associated with higher values of the pressure loss due to the increased recirculation, mixing of fluid and vorticity generation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
38.
Active control of a flexible cantilever plate with multiple time delays is investigated using the discrete optimal control method. A controller with multiple time delays is presented. In this controller, time delay effect is incorporated in the mathematical model of the dynamic system throughout the control design and no approximations and assumptions are made in the controller derivation, so the system stability is easily guaranteed. Furthermore, this controller is available for both small time delays and large time delays. The feasibility and efficiency of the proposed controller are verified through numerical simulations in the end of this paper. 相似文献
39.
多孔金属材料多功能化设计的若干进展 总被引：2，自引：1，他引：1
超轻多孔金属材料因其具有优良的结构效率和广泛的多功能应用前景,近年来已成为国内外众多研究所关注的热点. 本文就学术界关注的多孔金属材料的宏观等效模型建模与材料微结构的多功能优化设计进行了综述. 相似文献
40.
P. Lin P. Leid H. Gao 《ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik》2007,87(1):14-23
In this paper, we discuss a parabolic system governed by bilinear control, modeled according to Newton's Law. At first we prove that the system is exactly null controllable in long time T > 0 by locally distributed bilinear control and we further prove the exact null controllability in long time T > 0 of the semilinear parabolic equation yt‐Δ y + b |∇ y|2=ξou with traditionally additive locally distributed control and the existence of the control optimal time for the system. Then, we deduce an exact controllability result to particular stationary functions when we are acting over the whole domain and to particular stationary functions vanishing outside some ball included in the control domain when the control domain is as small as we want. 相似文献