共查询到20条相似文献,搜索用时 15 毫秒
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C. K. Chen W. Eckstein B. M. U. Scherzer 《Applied Physics A: Materials Science & Processing》1983,31(1):37-44
The areal density and the depth distribution of3He trapped in Ni as a function of the bombarding fiuence was measured in the energy range of 1–25 keV and at angles of incidence between 0 and 85° using nuclear reaction analysis. At fluences below saturation a linear relation is found between the areal density and the fiuence. From its slope the trapping and reflection coefficients can be determined. The experimental data for trapping and reflection coefficients and for the depth profiles were compared with computer simulation results from the TRIM program. To reduce uncertainties in the absolute values of the experimental trapping coefficients, they were normalized to the TRIM values at normal incidence. The dependence of the measured reflection coefficient on the angle of incidence between 0 and 80° shows good agreement with the calculated data for incident energies from 3 to 25 keV, but for 1 keV the measured reflection coefficients are higher than the calculated ones. 相似文献
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The phased beam tracing method (PBTM) was suggested as a medium-frequency simulation technique for the calculation of impulse response, although main assumptions of geometric acoustics still hold. The phased method needs the reflection coefficient for characterizing the acoustic property of a surface and the complex wave number for describing the propagation characteristics. In this study, two types of approximate real reflection coefficients derived from the measured absorption coefficient were tested for a practical applicability. As a test example, pressure impulse responses and energy impulse responses computed from the PBTM were compared with those from the measurement and the ordinary beam tracing method. The PBTM employing the approximate reflection coefficients greatly increased the accuracy of the prediction compared to the ordinary beam tracing method, in particular at the medium-frequency range in octave bands above the Schroeder cutoff frequency. A comparison was made between angle-dependent and angle-independent reflection coefficients in the calculation of acoustic measures. Although the angle-dependent reflection coefficient yielded best matched results with measured data, but the simple angle-independent reflection coefficient can be also used with a reasonably good precision. 相似文献
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Shin Muroya 《中国物理 C》2007,31(12)
We investigate coefficients in the Israel-Stewart's causal hydrodynamics and discuss the way to calculate them microscopic theory.Based on the hadro-molecular simulation based on an event generator URASiMA,we evaluate the coefficients for a hot and dense hadronic fluid. 相似文献
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提出了一种基于有限宽超声束反射的固-固界面退化特性评价方法,从理论和数值仿真角度进行了分析和计算。将两固体界面间的薄层简化为界面弹簧模型,以界面法向和切向劲度系数表征界面的退化程度。通过数值计算求得有限宽超声纵波束在不同入射角和界面不同退化程度下的反射横波、反射纵波的镜面反射系数。进一步地,通过建立二维有限元模型,仿真研究了有限宽超声纵波束在给定入射角及界面不同退化程度下镜面反射系数的变化规律。结果表明,反射纵波和反射横波的镜面反射系数随有限宽超声纵波束的入射角及界面劲度系数的改变而变化,且存在镜面反射系数随界面劲度系数单调且敏感变化的入射角,据此可准确评价界面的退化程度。 相似文献
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采用传递矩阵法,同步联立改进的Biot理论,对含液固界面的双相多孔锂离子电池的超声反射与透射系数进行理论求解。考虑锂离子的摇摆特性对电极力学性能的影响,计算了对应状态下液/固界面的双相多孔锂离子电池声反射及透射系数的角度谱与频率谱。同时,构建了不同荷电状态时含单元锂离子电池的频域仿真模型,以萃取对应的超声反射及透射角度谱及频率谱,并与理论计算结果对比吻合良好。随后,以多单元锂离子电池为例,在不同的荷电状态下,分析了反射与透射系数随斜入射角度、入射波频率的变化关系,并分别指出了其角度谱及频率谱特征点随荷电状态的变化特征,为锂离子电池运行状态的超声无损测量提供了理论基础。 相似文献
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The effects of ion focusing and blocking on surface scattering at a grazing angle is investigated by computer simulation, where primary ions are bombarded along the semichannel direction. When varying the angle of incidence, the ion focusing effect is clearly observed in reflection coefficients at the specular reflection. 相似文献
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现场测量声信号需要消除因声反射而产生的干扰。本文根据传声通道的响应特性,提出一种用倒频谱技术消除声反射影响的方法。计算机模拟和在消声室进行的自由场与人为设立一、两个反射面情况的对比实验都表明,该方法有效。 相似文献
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固体间界面的物理模型和界面对声波的反射 总被引:4,自引:0,他引:4
简要描述了模拟两固体间界面特性的弹簧模型,该模型最早是根据静力学方法提出的,后来用固体间界面薄层的声波反射方法加以改进,从界面弹簧模型可以方便地得到界面外近似边界条件,其中包含界面“弹簧”振子的劲度常数和质量,文章还给出了两相间固体中界面声反射系数的表达式,介绍了测量界面劲度常数的超声反射谱方法。最后讨论了仍关声波与界面相互作用研究领域中最近的一些研究进展。 相似文献
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The backscattering of heavy ions from surfaces is investigated by computer simulation (TRIM.SP). The particle and energy reflection coefficients are shown to scale with the ratio of target mass to ion mass as well as with the reduced energy for >0.02 and for normal incidence. At lower energies not only the scaling breaks down but also the effect of a chemical binding influences the reflection coefficient. The calculated data include also the dependence of the reflection coefficients on the angle of incidence as well as angular and energy distributions. Simulated results are in reasonable agreement with those from analytical theory and experiment. 相似文献
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采用Legendre正交多项式法,对液/固界面声波反射和透射系数进行求解。利用Legendre正交多项式对正交各向异性板中的位移解进行展开,推导出板中的应力和波动控制方程。联立液/固界面的边界条件和波动控制方程,建立线性无关方程组,用以计算液/固界面的反射和透射系数及Legendre多项式的展开系数,计算所得铝板液/固界面的反射和透射系数与传递矩阵法的计算结果吻合良好。以单向纤维增强复合材料板为例,在不同的方位角下,分析了反射和透射系数随斜入射角度、入射波频率的变化关系,以及板中声场的位移分布。所取Legendre正交多项式截止阶数越大,可用来计算的频厚积范围越大。研究拓展了Legendre正交多项式法的适用范围,为材料力学性能的声学测量提供了理论基础。 相似文献
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量子力学势垒穿透问题的光学类比 总被引:4,自引:2,他引:2
用量子态的线性叠加原理和波函数及其一阶导数的连续性,求解一维方势垒散射问题,得出各区域的波函数,最后求出了反射系数、透射系数以及势垒内部的概率流密度和概率分布,并得到由散射态过渡到束缚态的条件,另外,还将其自然过渡到一维对称方势阱的问题上去。 相似文献
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Summary We have analysed the response of a random elastic layer to scalar waves incident from a homogeneous medium. Working up to
second order in the stochastic fluctuations, we have proposed a rational approximation for the computation of the reflection
and amplification coefficients. After successfully checking the method by a numerical simulation, we have considered a problem
of interest in earthquake engineering. 相似文献
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A. B. Rinkevich L. N. Romashev V. V. Ustinov E. A. Kuznetsov 《International Journal of Infrared and Millimeter Waves》2007,28(7):567-578
The changes in the propagation constant of the TE10 mode of a rectangular waveguide with a metallic nanostructure, occurring under an external magnetic field have been investigated.
Expressions for complex reflection and transmission coefficients have been derived. The dependence of the reflection coefficient
upon the intensity of the external magnetic field is analyzed. It is shown that the experimental values of the propagation
constant or the reflection and transmission coefficients can be used to estimate the value of the microwave magnetoresistance
of nanostructures. Experiments on the measurement of the reflection and transmission coefficients in a waveguide with an (Fe/Cr)n nanostructure have been performed in millimeter and centimeter wave bands. 相似文献
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The possibility of measuring the ultrasound attenuation coefficient and its frequency dependence in a one-side accessible
medium is considered under the assumption that the medium contains reflectors with unknown reflection coefficients and the
measurements are performed in the reflection geometry. The possibility of measuring the reflection coefficients themselves
is indicated. All the above parameters can be measured even when the reflector has the form of a layered structure. 相似文献