Spatial Characteristics of Head-Related Transfer Function

The spatial characteristics of head-related transfer functions (HRTFs) are studied by a spatial Fourier analysis.A law of the HRTF spatial sampling in different elevation planes is obtained, and the corresponding spatial interpolating method used to recover the continuous HRTF is proposed. The method is valid, for the average error between the measured and interpolated HRTFs in the horizontal plane is about 0.5%. These results provide guidance for the discrete spatial measurement of HRTFs.     

Theoretical analysis of the acoustical characteristics of suspended micro-perforated panel absorbers

Sound absorption characteristics of suspended micro-perforated panel absorbers were investigated theoretically. The method of half thickness model of such panel absorber with quadripole analysis was used for predicting its acoustic performance. The analysis results show that the predictions agree well with the measurements of absorption in the reverberation chamber. The factors affecting the absorption characteristics for such absorbers were discussed, and some rules as design guidelines were given.     

Fractal Character for Tortuous Streamtubes in Porous Media

An analytical model for fractal dimension of tortuous streamtubes in porous media is derived. The proposed fractal dimension for tortuous streamtubes in porous media is expressed as a function of porosity and scale, and there is no empirical constant in the proposed expression. The model predictions for the fractal dimension of tortuous streamtubes in porous media are in good agreement with those by the box-counting method and with the observations of other researchers.     

温度对PSⅡCP4 7/D1/D2/Cytb559复合物荧光光谱特性的影响

采用激励光源为514.5 nm的分幅扫描单光子计数荧光光谱装置对经20℃、42℃和48℃不同温度处理后的反应中心复合物CP47/D₁/D₂/Cyt b559的荧光光谱特性进行了研究.经解析,获得不同温度处理后,CP47/D₁/D₂/Cyt b559复合物最大峰值未发生变化,均在682 nm,说明Chla670的能量都由Chla682接收,但损耗愈来愈小,在48℃时,损耗程度最小,而其荧光百分比未发生多大变化.振动副带～700 nm和～740 nm的中心波长都发生蓝移,在不同温度下分别为:20℃ 703 nm,749 nm;42℃ 697 nm,744 nm;48℃ 694 nm,740 nm.因此可以推测温度的升高,影响了CP47/D₁/D₂/Cyt b559色素蛋白的二级结构以及色素分子的空间位置,使最大峰值处的荧光强度逐渐降低,振动副带逐渐蓝移.42℃的温度已造成影响,48℃影响较大.     

大口径光束波前采样器(孔栅)的研制

应用平面波角谱理论，分析了采样器对光波场采样和分光的基本原理以及对空间采样频率的选择规则，描述了实际研制的大口径采样器的结构设计，并通过数值方法和高能激光大气传输实验研究了高能激光经采样器前／后的远场光斑分布关系。结果表明：利用光束波前采样器能高保真地实现对高能激光束的分光。     

高阶特征线性及其与semi-Lagrangian方法的比较

特征线性与semi-Lagrangian方法都是处理流体方程时间离散的两种有效的方法．它们比经典的半隐格式，如Backward-Euler／Adams-Bashforth方法有更好的稳定性．本提出一种基于高阶空间离散的特征线法，通过稳定性，精度和计算复杂性与semi-Lagrangian方法进行比较，分析了高阶特征线法的有效性和适用性，并从数值试验上对分析结果进行验证．     

Theoretical Analysis of Characteristics of GaxInl—x NyAsl—y／GaAs Quantum Well Lasers with Different Intermediate Layers

Based on the band anticrossing model, the effects of the strain-compensated layer and the strain-mediated layero n the band structure, gain and differential gain of GalnNAs/GaAs quantum well lasers have been investigated. The results show that the GaNAs barrier has a disadvantage in increasing the density of states in the conduction band. Meanwhile, the multilayer quantum wells need higher transparency carrier density than the GalnNAs/GaAs single quantum well with the same wavelength. However, they help to suppress the degradation of the differential gain. The calculation also shows that from the viewpoint of band structure, the strain-compensated structure and the strain-mediated structure have similar features.     

穆斯堡尔谱法及其应用

文章简介了穆斯堡尔效应、穆斯堡尔谱的产生以及穆斯堡尔效应的应用 ,说明它不仅在理论上具有深刻的意义 ,又有着广泛的应用价值 .     

二氟甲烷分子3a1和2b2轨道的电子动量谱

借助电子动量谱学结合量子化学理论和其他方法可以给出轨道电子在整个空间的分布信息,由此给出电子运动的完备描述[1,2 ] .清华大学电子动量谱学实验室近几年已成功地对甲烷[3] 、异丁烷[4 ] 、环戊烷[5] 、二乙酰等[6 ] 分子的轨道电子动量分布进行了测量.我们利用第二代电子动量谱仪首次对CH2 F2 分子3a1和2b2 轨道的电子动量谱进行测量,并与理论计算结果作了比较.同时还计算了坐标空间和动量空间中电子在x - y平面的密度分布.电子动量谱学最基本的过程是(e ,2e)反应,即电子与靶粒子碰撞而发生的电离过程.而对于(e ,2e)反应,含有大量信…     

级联三能级原子与单模场相互作用下的腔场谱

研究了高Q腔内级联三能级原子与单模光场相互作用模型的腔场谱.结果表明,原子初态处于上能级时，随R=g2/g1的增大,真空场的拉比峰个数按2→6→4→2→4的规律变化，在R1时，所有的拉比峰都消失.在初始场较弱时,腔场谱可出现3峰、5峰或7峰.在初始场很强时,腔场谱中只有单一的经典共振峰.如果原子初态处在中能级且R=1,腔场谱为简单的对称双峰结构，与标准J-C模型的谱相似. 关键词： 级联三能级原子 单模光场 腔场谱