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381.
382.
Akinari Kaneko 《国际流体数值方法杂志》2001,36(3):329-349
False diapycnal mixing often occurs due to horizontal diffusion in the simulation of heat, salinity, or water quality in estuaries by using a σ co‐ordinated ocean model. The Princeton ocean model (POM) is used as a basic σ co‐ordinated model and is applied to Tokyo Bay. Only river discharges are introduced into the model as external forces. Two remedies recommended in the POM, Stelling's horizontal diffusion approximation, Huang's new diffusion formula, Song and Haidvogel's s co‐ordinates, and Smolarkiewicz advection scheme have all been examined for suppressing the false diapycnal mixing. The conclusions are that the simultaneous use of POM's remedy and Stelling's approximation and the simultaneous use of POM's remedy and s co‐ordinates are the most effective. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
383.
Nicole Turbé 《Comptes Rendus Mecanique》2002,330(6):391-396
We study the propagation of electromagnetic waves in a guide the section of which is a thin annulus. Owing to the presence of a small parameter, explicite approximations of the eigenmodes can be computed. To cite this article: N. Turbé, C. R. Mecanique 330 (2002) 391–396. 相似文献
384.
Tomasz Błachowicz 《Central European Journal of Physics》2003,1(1):153-178
Brillouin spectroscopy of acoustic phonons in transparent crystals and nontransparent metallic Co/Cu superlattices is reviewed.
The method presents a directional sensitivity of the experiment. This feature is useful in elastic constants measurements
in crystals and analysis of in-plane anisotropies of hyper-sound and spin waves in superlattices. Results for the LiTaO3, LiNbO3, LiNbO3:Cu, SLGO, SLAO crystals are provided. Spin wave results for the Co/Cu superlattices are presented. 相似文献
385.
Optimized Schwarz methods are working like classical Schwarz methods, but they are exchanging physically more valuable information between subdomains and hence have better convergence behaviour. The new transmission conditions include also derivative information, not just function values, and optimized Schwarz methods can be used without overlap. In this paper, we present a new optimized Schwarz method without overlap in the 2d case, which uses a different Robin condition for neighbouring subdomains at their common interface, and which we call two‐sided Robin condition. We optimize the parameters in the Robin conditions and show that for a fixed frequency an asymptotic convergence factor of 1 – O(h1/4) in the mesh parameter h can be achieved. If the frequency is related to the mesh parameter h, h = O(1/ωγ) for γ?1, then the optimized asymptotic convergence factor is 1 – O(ω(1–2γ)/8). We illustrate our analysis with 2d numerical experiments. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
386.
387.
In this paper, we provide results concerning the optimal feedback control of a system of partial differential equations which arises within the context of modeling a particular fluid/structure interaction seen in structural acoustics, this application being the primary motivation for our work. This system consists of two coupled PDEs exhibiting hyperbolic and parabolic characteristics, respectively, with the control action being modeled by a highly unbounded operator. We rigorously justify an optimal control theory for this class of problems and further characterize the optimal control through a suitable Riccati equation. This is achieved in part by exploiting recent techniques in the area of optimization of analytic systems with unbounded inputs, along with a local microanalysis of the hyperbolic part of the dynamics, an analysis which considers the propagation of singularities and optimal trace behavior of the solutions.Research partially supported by National Science Foundation Grant DMS #9504822 and Army Research Office Grant #35170-MA. 相似文献
388.
M. Ikehata G. N. Makrakis G. Nakamura 《Mathematical Methods in the Applied Sciences》2004,27(12):1367-1384
We prove the uniqueness for the identification of the refraction index for an inhomogeneity of compact support in an oceanic acoustic waveguide, assuming as observation data the Green's function on the surface of a vertical cylinder surrounding the inhomogeneity. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
389.
We consider an inverse scattering problem in a 3D homogeneous shallow ocean. Specifically, we describe a simple and efficient inverse method which can compute an approximation of the vertical projection of an immersed obstacle. This reconstruction is obtained from the far-field patterns generated by illuminating the obstacle with a single incident wave at a given fixed frequency. The technique is based on an implementation of the theory of the convex scattering support [S. Kusiak, J. Sylvester, The scattering support, Commun. Pure Appl. Math. (2003) 1525–1548]. A few examples are presented to show the feasibility of the method. 相似文献
390.
为在复杂的海洋环境噪声场中检测出目标海豚的某类声信号,设计了一种基于海豚声学特征的端点检测方法。根据海洋环境中噪声能量大且分布频率范围广,而海豚声音的时频特征具有持续时间短,、频率高且集中,、发声行为持续时间长的特点,将采集到的海洋声音进行分帧,计算单帧信号短时能量、谱质心和谱质心二阶偏移率,当海豚发出声信号时,谱质心和能量相应发生突变,截取发生突变的信号实现端点检测。通过与门限法等其他常见端点检测方法进行对比,结果表明,此方法在低信噪比的海洋环境下对单一海豚的某一类声信号检测准确度更高,同时具有较强的抗干扰能力。 相似文献