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1.
There are some curved interfaces in ocean acoustic waveguides. To compute wave propagation along the range with some marching methods, a flattening of the internal interfaces and a transforming equation are needed. In this paper a local or-thogonal coordinate transform and an equation transformation are constructed to flatten interfaces and change the Helmholtz equation as a solvable form. For a waveguide with a flat top, a flat bottom and n curved interfaces, the coefficients of the trans-formed Helmholtz equation are given in a closed formulation which can be thought of as an extension of the formal work related to the equation transformation with two curved internal interfaces. In the transformed horizontally stratified waveguide, the one-way reformulation based on the Dirichlet-to-Neumann (DtN) map is then used to reduce the boundary value problem to an initial value problem. Numerical implementation of the resulting operator Riccati equation uses a large range step method to discretize the range variable and a truncated local eigenfunction expansion to approximate the operators. This method is particularly useful for solving long range wave propagation problems in slowly varying waveguides. Furthermore, the method can also be applied to wave propagation problems in acoustic waveguides associated with varied density. 相似文献
2.
Youliang Cheng Ph. D. 《上海大学学报(英文版)》1997,1(2):130-134
By using perturbation methods, the evolution equation is derived for the second-order internal solitary waves in stratified
fluids of great depth, which is a kind of inhomogeneous linearized Benjamin-Ono equation.
Project supported by the National Natural Science Foundation of China.(19672035) 相似文献
3.
In order to achieve a modulator with broad bandwidth and perfect impedance match, a novel electro-optical modulator based
on GeO2-doped silica waveguides on silicon substrate is designed. The finite element model of the whole electro-optical modulator
is established by means of ANSYS. With the finite element method analysis, the performance of the novel modulator is predicted.
The simulation reveals that the designed modulator operates with a product of 3 dB optical bandwidth and modulating length
of 226.59 GHz·cm, and a characteristic impedance of 51.6 Ω at 1 550 nm wavelength. Moreover, the calculated electrical reflected
power of coplanar waveguide electrode is below −20 dB in the frequency ranging from 45 MHz to 65 GHz. Therefore, the designed
modulator has wide modulation bandwidth and perfect impedance match.
Supported by National Natural Science Foundation of China (No.60577023)and Key Laboratory of Opto-Electronics Information
and Technical Science of Ministry of Education, China.
LI Jiusheng, born in 1976, male, Dr. 相似文献
4.
This paper discusses the validity of (adaptive) Lagrange generalized plain finite element method (FEM) and plate element method
for accurate analysis of acoustic waves in multi-layered piezoelectric structures with tiny interfaces between metal electrodes
and surface mounted piezoelectric substrates. We have come to conclusion that the quantitative relationships between the acoustic
and electric fields in a piezoelectric structure can be accurately determined through the proposed finite element methods.
The higher-order Lagrange FEM proposed for dynamic piezoelectric computation is proved to be very accurate (prescribed relative
error 0.02%–0.04%) and a great improvement in convergence accuracy over the higher order Mindlin plate element method for
piezoelectric structural analysis due to the assumptions and corrections in the plate theories. The converged Lagrange finite
element methods are compared with the plate element methods and the computed results are in good agreement with available
exact and experimental data. The adaptive Lagrange finite element methods and a new FEA computer program developed for macro-
and micro-scale analyses are reviewed, and recently extended with great potential to high-precision nano-scale analysis in
this paper and the similarities between piezoelectric and seismic wave propagations in layered structures and plates are stressed.
Project supported by SRF for ROCS, SEM of China and partially by Zhejiang Provincial Natural Science Foundation (NSF) of China. 相似文献
5.
介质波导具有损耗小和辐射小的特点,广泛应用于光通讯领域。平板波导是一种重要的平面介质波导,其中的TE波和TM波的传输特性,更是为波导器件的设计提供理论支持。本征方程是分析传输特性的重要方程,而TE波较TM波具有相对简单的电磁场连续性边界条件,其本征方程已有详细介绍。从TM波的波动方程出发,推导出三层平板波导TM波的场分布,并根据电磁场的连续性边界条件,逐步推到出它的本征方程。 相似文献
6.
n-soliton-like solutions of three non-isospectral equations, the non-isospectral mKdV equation, the non-isospectral sine-Gordon equation and the non-isospeetral nonlinear Schroedinger equation were obtained by using the Hirota method. 相似文献
7.
Stress analysis of anisotropic thick laminates in cylindrical bending using a semi-analytical approach 总被引：1，自引：0，他引：1
LU Chao-feng LIM C.W. XU Feng 《浙江大学学报(A卷英文版)》2007,8(11):1740-1745
Semi-analytical elasticity solutions for bending of angle-ply laminates in cylindrical bending are presented using the state-space-based differential quadrature method (SSDQM). Partial differential state equation is derived from the basic equations of elasticity based on the state space concept. Then, the differential quadrature (DQ) technique is introduced to discretize the longitu- dinal domain of the plate so that a series of ordinary differential state equations are obtained at the discrete points. Meanwhile, the edge constrained conditions are handled directly using the stress and displacement components without the Saint-Venant principle. The thickness domain is solved analytically based on the state space formalism along with the continuity conditions at interfaces. The present method is validated by comparing the results to the exact solutions of Pagano’s problem. Numerical results for fully clamped thick laminates are presented, and the influences of ply angle on stress distributions are discussed. 相似文献
8.
Influence of input acoustic power on regenerator＇s performance 总被引：2，自引：0，他引：2
TANG Ke HUANG Zhong-jie JIN Tao BAO Rui CHEN Guo-bang 《浙江大学学报(A卷英文版)》2007,8(9):1452-1456
Performance of a pulse tube cooler significantly depends on the efficient operation ofits regenerator. Influence of input acoustic power on regenerator＇s performance is simulated and analyzed with simple harmonic analysis method. Given regenerator＇s dimensions and pressure ratio, there is an optimal input acoustic power for achieving a highest coefficient of performance, due to a compromise between relative time-averaged total energy flux in regenerator and relative acoustic power at regenerator＇s cold end. Additionally, optimal dimensions of regenerator are also estimated and presented for different input acoustic powers. The computed optimal diameter obviously increases with increase of input acoustic power, while the optimal length decreases slightly, and as a result, a larger input acoustic power requires a smaller aspect ratio （length over diameter）. 相似文献
9.
ZHANG Ri-dong WANG Shu-qing 《浙江大学学报(A卷英文版)》2006,7(12):1984-1988
INTRODUCTION Bilinear systems are a kind of important nonlinear systems with relatively simple structure, and many industrial processes can be described as a bilinear system. Thus research on the control of this kind of systems is very important. On the other hand, model predictive control (MPC) (Clarke et al., 1987) has been widely used in industrial applications and many predictive control methods focusing on bilinear systems are emerging (Bloemen et al., 2001; Fontes et al., 2004; He… 相似文献
10.
A new optimization algorithm based on chaos 总被引：8，自引：0，他引：8
LU Hui-juan ZHANG Huo-ming MA Long-hua 《浙江大学学报(A卷英文版)》2006,7(4):539-542
INTRODUCTION Chaos (Wang et al., 2002) is a common nonlin- ear phenomenon, whose action is complex and similar to that of randomness. The characteristics of chaos being highly sensitive to the initial value of chaos make a world of differences due to the ergodic prop- erty of the phase space—chaos can go through all states in certain ranges without repetition; the inher- ent randomness of the system—means that chaos behavior is similar to randomness which is disorderly; but at the same t… 相似文献
11.
In this paper, the authors present the results of their study on the scheme of reconstructing the atomic wave function by
using a standing wave laser beam. The scheme effectively avoids the initial random phase problem of the running light wave
of lasers. The paper presents the relation between measured data and the atomic wave function, whose reconstruction procedure
is also analyzed.
Project supported by NSFC, Zhejiang Province Natural Science Foundation, and Gao Guangbiao Key Foundation of Zhejiang University. 相似文献
12.
按准解析法，从理论上给出了Ｔｉ：ＬｉＮｂＯ３条形波导沿深度方向有效折射率的解析表达式，并按此式计算了典型波导的场分布及模折射率．这对于研究有金属覆盖层的条形波导的传播特性是特别有用的．本文还明确给出了确定导模场最大值位置的方法，因而对波导与波导、波导与光纤的耦合有一定的指导意义 相似文献
13.
Pithc-synchronous articulatory synthesis incorporated with the inverse solution of speech production
This paper presents a new proposal to synthesize natural sounds with less control parameters by combining the inverse speech
production and pitch-synchronous articulatory synthesis. The pitch-synchronous excited Reflection-Type Line Analog (RTLA)
model is employed as the synthesis filter. Multi-rate system sampling and dynamic scattering wave adjustment are used to handle
the variable VT length and the acoustic continuity. The synthesizer is controlled by vocal-tract (VT) area functions. Given
the targets of formant trajectories, the dynamic VT area function which is modeled by time variant VT length is derived using
an inverse solution of speech production. A distinguishing feature of this method is that artificially specified formant trace
can be precisely aimed in the synthetical sounds. Experimental results show that the formant target can be well matched by
the synthetic sounds. Potential application to text-to-speech conversion of this method is discussed.
Project supported by NSFC (69972046), and Zhenjiang Provincial Natural Science Foundation of China (698076). 相似文献
14.
This paper discusses the application of the boundary contour method for resolving plate bending problems. The exploitation
of the integrand divergence free property of the plate bending boundary integral equation based on the Kirchhoff hypothesis
and a very useful application of Stokes' Theorem are presented to convert surface integrals on boundary elements to the computation
of bending potential functions on the discretized boundary points, even for curved surface elements of arbitrary shape. Singularity
and treatment of the discontinued corner point are not needed at all. The evaluation of the physics variant at internal points
is also shown in this article. Numerical results are presented for some plate bending problems and compared against analytical
and previous solutions.
Project(No: ZE0208) supported by the National Science Foundation of Zhejiang Province, China 相似文献
15.
A new photonic bandgap (PBG) cover for a patch antenna with a photonic bandgap substrate is introduced. The plane wave expansion
method and the FDTD method were used to calculate such an antenna system. Numerical results for the input return loss, radiation
pattern, surface wave, and the directivity of the antennas are presented. A comparison between the conventional patch antenna
and the new PBG antenna is given. It is shown that the new PBG cover is very efficient for improving the radiation directivity.
The physical reasons for the improvement are also given.
Project supported by the National Natural Science Foundation of China (No. 90101024) and the Science and Technologies of Zhejiang
Provinc (No. ZD0002) 相似文献
16.
As Huston's form of Kane's equation cannot be easily applied to large deployable structures, what is needed is further development
of Kane's equation as described in this paper. Fully-Cartesian-coordinate (FCC) method uses Cartesian coordinates of points
and Cartesian components of unitary vectors as generalized coordinates to describe three-dimension mechanisms. This FCC method
avoids the need to consider angular coordinates and the resulting solution is just the space position of the structures. The
FCC form of Kane's equation derived in this study is suitable for solution by computer method and is a good base for further
simulation research. A numerical example showed that it is effective.
Project supported by Natural Science Foundation of China (69982009) and High Technology Plan ‘863’ Foundation (863-2-2-1-12) 相似文献
17.
One-dimensional traffic model was studied with the consideration of stochastic deceleration by using the lattice Boltzmannmethod.The evolution equation for vehicle density was derived,which has the form of the Burgers equation exhibiting the effect of viscosity corresponding to the deceleration.The simulation with the model shows that the variation of vehicle density in space tends to a periodic one,which implies the existence of kinematic waves in the 1D traffic flow and coincides with theoretical prediction. 相似文献
18.
A method was presented to implement the detecting and tracking of moving targets through omnidirectional vision. The method
combined optical flow with particle filter arithmetic, in which optical flow field was used to detect and locate moving targets
and particle filter was used to track the detected moving objects. According to the circular image character of omnidirectional
vision, the calculation equation of optical flow field and the tracking arithmetic of particle filter were improved based
on the polar coordinates at the omnidirectional center. The edge of a randomly moving object could be detected by optical
flow field and was surrounded by a reference region in the particle filter. A dynamic motion model was established to predict
particle state. Histograms were used as the features in the reference region and candidate regions. The mutual information
(MI) and Gaussian function were combined to calculate particle weights. Finally, the state of tracked object was computed
by the total particle states with weights. Experiment results show that the proposed method could detect and track moving
objects with better real-time performance and accuracy.
Supported by Tianjin Higher Education Technology Development Foundation (No.20071308), Tianjin Natural Science Foundation
(06YFJMJC03600) and National Natural Science Foundation of China (No.60773073).
YANG Shuying, born in 1964, female, Dr, Prof. 相似文献
19.
A repulsive vortex-vortex interaction model was used to numerically study the melting transition of the two-dimensional vortex
system with Monte Carlo method. Then a δ-function-like peak in the specific heat was observed and the internal energy showed
a sharp drop at the melting temperature, which indicated that there exists a first-order melting transition at finite temperatures.
The Lindemann criterion was also investigated and valid, but different from previous simulation results.
Project supported by the Science and Technology Ministry of China (No. NKBRST-G19990646) and Zhejiang Provincial Natural Science
Foundation (No. 199031) 相似文献
20.
Abstract A new function-valued partial Padé-type approximation was introduced in the polynomial space, and an explicit determinant formula was derived by means of some orthogonal polynomials. This method can be applied to estimating surplus eigenvalues of the Fredholm integral equation of the second kind when its partial eigenvalues have been known, and at the same time, it can be applied to solving the approximating solution of the given equation. 相似文献