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101.
The acoustic wave equation is here discretized by conforming spectral elements in space and by the second order leap-frog
method in time. For simplicity, homogeneous boundary conditions are considered. A stability analysis of the resulting method
is presented, providing an upper bound for the allowed time step that is proportional to the size of the elements and inversely
proportional to the square of their polynomial degree. A convergence analysis is also presented, showing that the convergence
error decreases when the time step or the size of the elements decrease or when the polynomial degree increases. Several numerical
results illustrating these results are presented.
Mathematics subject classifications (2000) 65M06, 65M70, 65M12
This work was supported by MIUR (PRIN 2001 “Metodi numerici avanzati per equazioni alle derivate parziali di interesse applicativo”). 相似文献
102.
The performance of three-colour HgCdTe photovoltaic heterostructure detector is examined theoretically. In comparison with
two-colour detectors with two back-to-back junctions, three-colour structure contains an absorber of intermediate wavelength
placed between two junctions and electronic barriers are used to isolate this intermediate region. This structure was first
proposed by British workers.
Three-detector structures with different localizations of separating barriers are analyzed. The calculation results are presented
in the form of spatial distributions of bandgap energy and quantum efficiency.
Enhanced original computer programs are applied to solve the system of non-linear continuity equations for carriers and Poisson
equations. In addition, the numerical analysis includes the dependence of absorption coefficient on Burstein effect as well
as interference effects in heterostructure with metallic electrical contacts.
It is shown that the performance of the detector is critically dependent on the barrier’s doping level and position in relation
to the junction. This behaviour is serious disadvantage of the considered three-colour detector. A small shift of the barrier
location and doping level causes serious changes in spectral responsivity. 相似文献
103.
利用应变SiGe/Si异质pn结电容-电压(C-V)特性确定SiGe禁带宽度的技术.该技术根据SiGe/Si异质pn结C-V实验曲线,计算出 pn结接触电势差,并得到SiGe/Si的价带偏移量和导带偏移量,进而求得SiGe禁带宽度.该技术测试方法简便,其过程物理意义清晰,既适用于分立的SiGe/Si异质pn结,也可直接分析SiGe/Si异质结器件中的SiGe 禁带宽度.实验结果与理论计算及其他相关文献报道的结果符合较好.
关键词:
SiGe/Si
异质pn结
C-V
禁带宽度 相似文献
104.
Amplitude and phase of high frequency surface acoustic wave (SAW) fields are investigated by a novel scanning tunneling microscopy technique. The gap voltage is modulated at a slightly detuned high frequency. Due to the nonlinearity of the tunneling process a frequency mixing appears. For scanned areas with dimensions much smaller than the wavelength of the SAW a remarkable local variation of amplitude and phase of the tunneling current at the difference frequency is observed. Depending on the local morphology different components of the particle displacement vector are detected. Model calculations of amplitude and phase images are presented for a real topography. 相似文献
105.
It is proved that a sound-soft scatterer in R^N (N = 2, 3) is uniquely determined by a finite number of acoustic far-field measurements. The admissible scatterer possibly consists of finitely many solid obstacles and subsets of (N - 1)- dimensional hyperplanes. 相似文献
106.
D. V. Zakharov 《Theoretical and Mathematical Physics》2007,153(1):1388-1397
We consider the problem of describing the possible spectra of an acoustic operator with a periodic finite-gap density. On
the moduli space of algebraic Riemann surfaces, we construct flows that preserve the periods of the corresponding operator.
By a suitable extension of the phase space, these equations can be written with quadratic irrationalities.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 153, No. 1, pp. 46–57, October, 2007. 相似文献
107.
Zhi-Chi Zhu 《Acta Mechanica Solida Sinica》1990,3(4):457-468
Researches on sound propagation problems in ducts done by the author and other investigators in recent years are briefly discussed in this paper. The finite difference method used in fluid mechanics is used for solving these problems thus presenting an aspect of the development of research work in this field at home and abroad.The project supported by National Natural Science Foundation of China. 相似文献
108.
V. G. Aleksandrov A. A. Osipov 《Computational Mathematics and Mathematical Physics》2006,46(6):1061-1072
A method for the calculation of unsteady aerodynamic interaction of two plane airfoil cascades that are in relative motion in a subsonic flow of ideal gas is developed. This interaction provides a two-dimensional approximation of the flow in a stage of an axial turbomachine. The method is based on the reduction of the problem to the calculation of the unsteady flow in a single interblade passage of each of the cascades. The calculation uses generalized space-time periodicity relations corresponding to the unsteady process of interest. The calculation is based on the direct numerical integration of the non-stationary gas dynamics equations with the use of the finite difference Godunov-Kolgan-Rodionov scheme of the second approximation order with respect to time and space. The calculation procedure includes the determination of the acoustic fields that are generated by the stage in the incident flow and in the flow behind it. The results of the calculations that illustrate the accuracy of the numerical solution and the capabilities of the method are presented. 相似文献
109.
声波测井时孔隙地层中的声波首波平行于井轴沿井壁传播,它既有轴向位移分量,又有垂直于井壁的位移分量.这种以快纵波速度传播的波, 不仅含有由快、慢纵波势给出的梯度场,而且还含有由横波势给出的旋度场.慢纵波势的梯度是渗流位移首波的主要构成成分, 也是声电效应测井响应中存在伴随声波首波电场的主要原因.首波包含有旋度位移场,是存在伴随声波首波磁场的原因.
关键词:
孔隙介质
声波首波
诱导电磁场
测井 相似文献
110.