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991.
线性矩阵方程的埃尔米特广义反汉密尔顿半正定解 总被引:1,自引:0,他引:1
利用埃尔米特广义反汉密尔顿半正定矩阵的表示定理,作者建立了线性矩阵方程在埃尔米特广义反汉密尔顿半正定矩阵集合中可解的充分必要条件,得到了解的一般表达式.对于逆特征值问题,也得到了可解的充分必要条件.对于任意一个 n 阶复矩阵,得到了相关最佳逼近问题解的表达式. 相似文献
992.
The Method of Fundamental Solution for a Radially Symmetric Heat Conduction Problem with Variable Coefficient
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We consider an inverse heat conduction problem with variable coefficient
on an annulus domain. In many practice applications, we cannot know the initial
temperature during heat process, therefore we consider a non-characteristic Cauchy
problem for the heat equation. The method of fundamental solutions is applied to
solve this problem. Due to ill-posedness of this problem, we first discretize the problem
and then regularize it in the form of discrete equation. Numerical tests are conducted
for showing the effectiveness of the proposed method. 相似文献
993.
Techniques developed for structural identification are typically devoted to obtaining a model, parametrical or not, on the basis of information on the structural response and on the forcing action, both assumed as known from experimental tests. In many situations, however, it may be necessary, or simply useful, to refer only to the measured response. In this paper we describe the theoretical aspects of a technique we have recently developed to identify the modal model in the frequency domain when the input is unknown. To simplify, we refer to unknown nonstationary base motion, but many of our conclusions can be extended to different situations. We show that, from a theoretical point of view, the identification problem has a unique solution, for this kind of input, when at least three time histories are known, and this circumstance had never been pointed out before. Because the theoretical analysis furnishes only necessary conditions for the existence of a unique solution, an extensive numerical analysis is reported in the second part of the paper, which also shows the sensitivity of the identification procedure. 相似文献
994.
E. Kriesten M.A. Voda A. Bardow V. Göke F. Casanova B. Blümich H.-J. Koss W. Marquardt 《Fluid Phase Equilibria》2009
Diffusion in liquids can still be predicted only with high uncertainty due to a lack of sufficient experimental data. Diffusion experiments are complex and time-consuming. Furthermore, the determination of the concentration dependence of the diffusion coefficients requires usually several experiments even for binary mixtures. A powerful model identification framework based on two fast experimental techniques is presented here. Raman inter-diffusion experiments in combination with a novel incremental identification technique establish the concentration dependence directly from the data without requiring a priori specification of the model structure. In regions where this technique is sensitive to error noise, it is complemented with NMR intra-diffusion measurements. Models describing the concentration dependence are identified in two steps. Based on the combined data suitable model candidates are proposed and initialized through basic curve fitting in the first identification step. A statistically sound dynamic optimization step yields the final model parameters. The methodology is exemplarily used to determine the diffusion coefficient in the mixture ethyl acetate–cyclohexane in the full concentration space. 相似文献
995.
Notes on Groundwater Age in Forward and Inverse Modeling 总被引:2,自引:0,他引:2
Timothy R. Ginn Hanieh Haeri Arash Massoudieh Laura Foglia 《Transport in Porous Media》2009,79(1):117-134
Several example applications of the groundwater age equation are used to derive some basic results about age in aquifers and
to draw linkages among published results involving temporal moments and aquifer–aquitard diffusive mass transfer. We then
describe a brief numerical study of an inverse problem in which hydraulic conductivities are identified using both piezometric
head and groundwater age data where inclusion of age data helps to reduce evidential nonuniqueness. This reflects the global
representation of flow process contained in age data, and that the value of age data in inverse identification of flow properties
depends on the paths taken by the sampled groundwater.
Paper presented at PORO2007, the 7th North American Workshop on Applications of the Physics of Porous Media, Puerto Vallarta,
Mexico, 2–6 November, 2007. 相似文献
996.
Supersonic biplanes can possibly achieve low-boom and low-drag supersonic flights. In the present study, aerodynamic analysis
and design of two-dimensional (2-D) biplanes were investigated with the help of computational fluid dynamics (CFD) tools.
By utilizing an inverse-design method, a 2-D biplane configuration with lower wave drag than the single flat-plate airfoil
at sufficient lift conditions (C
l > 0.14) was designed at its design Mach number (M
∞ = 1.7). In general, although, supersonic biplanes show superior aerodynamic characteristics at their design Mach numbers,
unfortunately, they are characterized by poor performances under their off-design conditions. Flow choking occurs at high
subsonic speeds, and continues to Mach numbers greater than the design Mach number in the acceleration stage due to flow hysteresis.
Hinged slats and flaps were applied as high-lift devices to avoid the flow choking and concomitant hysteresis problems, and
were also used as actual high-lift devices under take-off and landing conditions. As further improvement, morphing and Fowler
motion were considered. Finally, a series of 2-D biplane configurations from take-off (and landing) to cruise conditions were
studied by applying the slats and flaps, as well as morphing mechanisms, to our inversely designed biplane.
相似文献
997.
This paper describes an hybrid procedure for mechanical characterization of biological membranes. The in-plane displacement
field of a glutaraldehyde treated bovine pericardium patch obtained with an equi-biaxial tension test is measured with intrinsic
moiré and then compared with finite element predictions. Preliminary analysis of moiré patterns observed in the experiments
justifies the assumption of the constitutive model based on transversely isotropic hyperelasticity. In order to determine
the 16 hyperelastic constants included in the constitutive model and the fiber orientation, the difference Ω between displacement values measured with moiré and their counterpart determined numerically is minimized by means of multi-level
and multi-point simulated annealing. Results clearly demonstrate the efficiency of the identification procedure presented
in this research: in fact, residual difference between experimental data and numerical values of in-plane displacements is
less than 2%. In order to validate the entire identification process, another experimental test is conducted by inflating
the same specimen. Out-of-plane displacements, now measured with projection moiré, are compared with predictions of a new
finite element model reproducing the experimental test. The 16 hyper-elastic constants previously determined are given in
input to the inflation test FE model. Remarkably, experimental and numerical results are again in excellent agreement: maximum
percent error on w-displacement is less than 3%. 相似文献
998.
This paper deals with the identification of elasto-plastic constitutive parameters from deformation fields measured over the
surface of thin flat specimens with the grid method. The approach for recovering the constitutive parameters is the virtual
fields method. A dedicated algorithm is used for deriving the distribution of the 2D stress components from the measured deformation
fields. A state of plane stress is assumed. Guesses of the constitutive parameters are input in the algorithm and updated
until the stresses satisfy the principle of virtual work in the least squares sense. The advantage of this approach is that
it can handle very heterogeneous plastic flows and it is much faster than classical finite element model updating approaches.
An experimental application is provided to demonstrate it. Six mild steel double-notched specimens have been tested in a configuration
combining tension and in-plane bending. The identified parameters are in good agreement with their reference counterparts.
Stress fields are eventually reconstructed across the specimen all along the test for analyzing the evolution of the plastic
flow. 相似文献
999.
建议了一个新的HMQC实验的脉冲序列,其准备期和混合期分别为90°x(1H)-τ/2-180°x(1H,13C)-τ/2-90°x(1H,13C)和90°x(13C)-τ/2-180°x(1H,13C)-τ/2-,以及τ=(2JCH)-1(JCH为C-H偶合常数).在这个新的HMQC实验中,与碳-12相连质子的信号被有效地抑制,其抑制的机理与脉冲的相位循环无关.从而,它可以用于有效地抑制HMQC谱的噪音.特别是,在没有脉冲梯度场装置时,该方法显得非常实用 相似文献
1000.
The averaged systems of hydrodynamic equations for a structured medium in the Lagrangian and the Eulerian coordinates are discussed. In the general case, the equations cannot be reduced to the average hydrodynamic terms. Under propagation of long waves in media with structure, the non-linear effects appear and they are analyzed in the framework of the asymptotic averaged model. The heterogeneity in a medium structure always increases the non-linear effects for the long-wave perturbations. A new method for diagnostics of the properties of medium components by long non-linear waves is suggested (inverse problem). The mass contents of components in the media can be determined by this diagnostic method. 相似文献