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弹性声波与表面缺陷相互作用的数值模拟 总被引:1,自引:1,他引:0
为了分析材料表面缺陷对声表面波传播的影响,以弹性动力学理论为基础,采用有限元方法数值模拟了声表面波沿金属表面传播及其与表面缺陷的相互作用.通过数值模拟弹性声表面波与不同深度、不同宽度的表面缺陷相互作用过程,得到了声表面波经不同表面缺陷后的反射和透射表面波波形,并对波形进行快速傅里叶变换分析.结果表明,弹性声表面波与表面缺陷相互作用后,产生反射Rayleigh波和透射Rayleigh波:随着表面缺陷深度和宽度的增加,Rayleigh波反射率相应增加,而透射率相应减小. 相似文献
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In this paper,we have calculated the band structure of strained quantum well (QW) semiconductor optical amplifiers (SOAs) by using plane wave expansion method (PWEM) and finite difference method (FDM),respectively.The difference between these two numerical methods is presented.First,the solution of Schr(o)dinger's equation in a conduction band for parabolic potential well is used to check the validity and accuracy of these two numerical methods.For the PWEM,its stability and computational speed are investigated as a function of the number of plane waves and the period of QW.For FDM,effects of mesh size and QW width on its accuracy and calculation time are discussed.Finally,we find that the computational speed of FDM generally is faster than that of PWEM.However,the PWEM is more efficient than the FDM when wider SOAs are needed to be calculated.Therefore,to obtain high accuracy and efficient numerical solutions for band structures,numerical methods should be selected depending on required accuracy,device structure and further applications. 相似文献
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This paper presents a novel scheme to incorporate quantum effect in classical hydrodynamic model. The scheme can be applied to multi-dimensional and transient conditions and no additional equations are required to solve quantum potential, so complexity of equations is drastically reduced. Simulation results show consistent with that of Monte Carlo simulation. This technology provides an efficient method for investigating quantum effect in small size semiconductor devices. A new guess method for hydrodynamics model has also been proposed in this paper and a 2D hydrodynamic simulator based on quantum correction and new initial guess method has been developed. The solution obtained from DD model gives a good initial guess of HD model. Its advantage is it can achieve convergence after a few iterations because initial guess is closed to final solution. Two-dimensional simulations have been carried out on a few nanoscale devices. The results have been compared with that of other initial guess methods and the significant differences have been found, especially in numerical stability. 相似文献
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为了得到工艺参量对层裂的影响,运用有限元模拟的方法,采用最大拉应力瞬时断裂准则来判断板料是否发生层裂,并对各参量对层裂的影响进行了分析;进行了激光冲击成形试验,用电子扫描显微镜对冲击后的试样进行观察,并运用应力波传播分析了层裂的产生、发展、形成。结果表明,层裂易发生在激光冲击区域内,其次是在光斑边缘处,而在冲击区域外不可能发生层裂;脉冲宽度、峰值压力和板料厚度对层裂发生的位置影响较大,而光斑直径对层裂发生的位置几乎没有影响。这对激光冲击成形的发展具有指导意义。 相似文献
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为详细揭示纳秒单脉冲激光能量沉积激波减小波阻的机理,分别研究了单脉冲激光能量沉积与正激波相互作用、单脉冲激光能量沉积与弓形激波超声速流场相互作用。鉴于常用数值模拟方法不考虑空气的离解和电离,不能合理模拟激光能量沉积诱导等离子体热核的空间分布,采用泪滴形能量分布,且耦合有限速率化学反应模型,所得到的激波和热核演化过程的数值模拟结果与实验吻合程度高,验证了所提出模拟方法的合理性。分别选取马赫数为1.92条件下的正激波和弓形激波,入射激光能量大小为10.1 mJ和12 mJ,研究表明:单脉冲激光能量沉积诱导形成的等离子体热核通过正激波后,形成上下对称的涡环结构;在弓形激波条件下,在波后形成的低压涡环引起波阻减小,这是激波减阻的主要机理。 相似文献
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人对矩形隧道中电磁波传输特性的影响 总被引:1,自引:0,他引:1
用三维有限元方法研究了单个人对矩形隧道中无线信号的影响,得出如下结论:随着工作频率的提高,存在人体的不均匀波导段的反射系数增加,透射系数降低,从而损耗在人体中的入射功率的比例也增加。当工作频率大于一定值时,这种变化趋势变得不明显。人体的电特征参数的变化对反射系数、透射系数和损耗的影响不很明显。 相似文献
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为了研究金属板料在脉冲激光辐照下的响应、激光冲击下板料的变形特性、激光脉冲能量对金属板料变形量的影响以及脉冲激光光斑内冲击波压力的分布情况,采用高功率钕玻璃激光系统对LD31板进行了单次冲击变形实验,同时利用有限元软件ABAQUS对板料变形过程进行了模拟。结果表明,激光冲击条件下板料变形时呈现粘塑性性质;激光脉冲能量是影响板料变形量的主要因素,且板料变形大小随脉冲能量的增加呈非线性增大;激光冲击时激光光斑作用区域内冲击波压力并不是均匀分布,而是沿径向减小。 相似文献
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Non-uniform distribution of carrier lifetime over the area of power bipolar semiconductor devices results in a non-uniform distribution of on-state current density and switching loses. Consequently, it results in non-uniform temperature distribution which can negatively influence the device reliability. Several methods can be used for measuring carrier lifetime distribution both in starting single crystal material and in device structures after high-temperature processes. Advantages and disadvantages of individual methods and an optimum area of applications are discussed in this paper. This paper is mostly oriented on a possibility to use LBIC method for measuring carrier lifetime distribution in the bulk of high voltage large-area devices, especially N+NPP+ diode structures. 相似文献
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针对使用扫描电镜(SEM)进行半导体器件破坏性物理分析(DPA)和失效分析(FA)时,芯片表面不作喷镀处理的问题,提出了减小或消除电荷累积的试验方法。试验结果表明,正确应用SEM低电压技术,选择加速电压1.0 kV~2.0 kV、电子束斑2.0,结合积分技术,可在芯片表面不作喷镀处理,并满足国军标要求下,得到分辨率和性噪比均很好的图片。 相似文献
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The aim of this paper is to present an effective numerical model of fluctuation phenomena in semiconductor structures with
an arbitrarily defined doping profile and variable-band structure. The model enables the spectral intensity of the noise current
to be calculated. It is known that the 1/f noise may result in fluctuations of the carrier mobility. It is not clear, however,
why strong 1/f noise is observed in reverse-biased HgCdTe nonequilibrium photodiodes when saturation currents are usually
very low. In the present paper, we try to answer this question. Although the nonequilibrium mode of operation leads to the
reduction of the generation-recombination (g-r) noise, it increases the electric field as well as the band mobility of carriers
and its fluctuations. The observed low-frequency noise is due to the fluctuations of current density caused by mobility fluctuations
assisted by the electric field. 相似文献
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为了研究激光冲击波在铝合金薄板中的传播特性,采用数值仿真的方法,分析了不同节点路径下,冲击波在3003铝合金薄板中的传播特性。研究结果表明,激光加载初期,板料表面光斑边缘位置处应力最大,而板料表面中心区域仅为较小的波动,1000 ns后,表面波传播至板料上的凹模口对应位置,同时中心位置区域应力增大至200 MPa,塑性变形加大,板料变形不均匀,易出现减薄失效问题;沿激光冲击方向,经历60 ns压力波传播至板料自由面,并回传拉伸波,在102 ns左右,拉应力达到最大值1782 MPa,板料易出现层裂失效问题。因此针对激光冲击波在铝合金薄板中传播特性的研究对提高铝合金薄板激光冲击成形性能具有重要的意义。 相似文献
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激光冲击强化残余应力场的数值仿真分析 总被引:10,自引:1,他引:10
有限元分析(FEM)是预测激光冲击强化处理(LSP)后材料的残余应力场、合理优化冲击参数非常有效的方法。通过对材料冲击响应过程的分析,建立了激光冲击强化处理的有限元分析模型,实现了激光冲击强化处理残余应力场的数值仿真。根据显式分析得到的材料内部各种能量变化过程,结合应力波理论,验证显式分析过程的正确性,提出显式分析求解时间的选择方法;分析了单次和多次冲击下材料内部的残余应力场分布,分析结果与实验结果非常接近。数值分析结果表明,表面残余应力在冲击区域内分布比较均匀,表层的残余应力梯度较小;多次重复冲击后,材料的残余压应力明显增加,残余压应力影响深度也显著加深;随着冲击次数的增加,材料的残余应力场趋于饱和。 相似文献
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