类磷离子精细结构能级和辐射寿命

用全相对论多组态自洽场方法,计算了9个类磷离子的1s、2s、2p-、2p、3s、3p-、3p、3d-、3d、4s、4p-、4p、4d-、4d、4f-、4f、5s、5p-、5p、5d-、5d、5f-、5f、5g-、5g、6s、6p-、6p轨道的2309个精细结构能级和辐射寿命以及各种跃迁参数。能级的计算值和实验值符合得很好。同时,我们还发现了一些亚稳态能级。     

基于多阵列数据融合的宽带多声源定位研究

研究多个传声器阵列数据融合和宽带多声源近场定位算法。该算法首先融合多个传声器阵列数据,然后对多声源进行定位。由于充分利用多个阵列的数据,降低了分辨门限,提高了定位的精度和稳健性。通过仿真计算,证明了算法的有效性。     

人工神经网络在车辆声学分类中的应用

传统反向传播(BP,Back-Propagation)算法虽然解决了多层感知器的收敛问题,但是训练时间长、收敛速度慢。本文针对训练样本分布状态未知的问题,提出了一种有效的加速收敛方法,即对不同的训练样本选择不同的学习率。将这种改进的BP算法应用到履带车与轮式车的声学分类中,明显提高了算法的收敛速度、泛化能力及稳定性,并可根据需要调整两种车辆的识别率。     

室温下(Ga,Mn)As中载流子的自旋弛豫特性

运用飞秒时间分辨抽运-探测克尔光谱技术,研究了室温下退火及未退火(Ga,Mn)As的载流子自旋弛豫的激发能量密度依赖性,发现电子自旋弛豫时间随激发能量密度增加而增大,而在同一激发能量密度下,退火样品比未退火样品具有更短的载流子复合时间、电子自旋弛豫时间和更大的克尔转角,显示DP机理是室温下(Ga,Mn)As的电子自旋弛豫的主导机理.退火(Ga,Mn)As的超快克尔增强效应显示其在超高速全光自旋开关方面的潜在应用价值,也为(Ga,Mn)As铁磁性起源的p-d交换机理提供了证据. 关键词： (Ga Mn)As稀磁半导体 时间分辨克尔光谱 电子自旋弛豫 DP机理     

数值模拟探针诱导表面等离子体共振耦合纳米光刻

采用有损耗介质和色散介质的二维时域有限差分方法,数值模拟了以光波长514.5nm的p偏振基模高斯光束为入射光源,激发Kretschmann型表面等离子体共振,并通过探针的局域场增强效应实现纳米光刻的新方法——探针诱导表面等离子体共振耦合纳米光刻.分别就探针与记录层的间距以及探针针尖大小,模拟分析了不同情况下探针的局域场增强效应和记录层表面的相对电场强度振幅分布.结果表明,探针工作在接触模式时,探针的局域场增强效应最明显,记录层表面的相对电场强度振幅的对比度最大;当探针针尖距记录层5nm时,针尖下方记录层表面的相对电场强度振幅大于光刻临界值的分布宽度与针尖尺寸相近. 关键词： 纳米光刻 表面等离子体共振 时域有限差分方法     

Experimental and theoretical studies on high-temperature thermal properties of fibrous insulation

In the present paper, an experimental apparatus has been developed to measure heat transfer through high-alumina fibrous insulation for thermal protection system. Effective thermal conductivities of the fibrous insulation were measured over a wide range of temperature (300-973 K) and pressure (10⁻²-10⁵ Pa) using the developed apparatus. The specific heat and the transmittance spectra in the wavelength range of 2.5-25 μm were also measured. The spectral extinction coefficients and Rosseland mean extinction coefficients were obtained from transmittance data at various temperatures to investigate the radiative heat transfer in fibrous insulation. A one-dimensional finite volume numerical model combined radiation and conduction heat transfer was developed to predict the behavior of the effective thermal conductivity of the fibrous insulation at various temperatures and pressures. The two-flux approximation was used to model the radiation heat transfer through the insulation. The experimentally measured specific heat and Rosseland mean extinction coefficients were used in the numerical heat transfer model to calculate the effective thermal conductivity. The average deviation between the numerical results for different values of albedo of scattering and the experimental results was investigated. The numerical results for ω=1 and experimental data were compared. It was found that the calculated values corresponded with the experimental values within an average of 13.5 percent. Numerical results were consistent with experimental results through the environmental conditions under examination.     

Thermal Diffusivity of Film/Substrate Structures Characterized by Transient Thermal Grating Method

Transient thermal grating method is used to measure the thermal diffusivity of absorbing films deposited on transparent substrates. According to periodically modulated dielectric constant variations and thermoelastic deformations of the thin films caused by the transient thermal gratings, an improved optical diffraction theory is presented. In the experiment, the probing laser beam reflectively diffracted by the thermal grating is measured by a photomultiplier at different grating fringe spaces. The thermal diffusivity of the film can be evaluated by fitting the theoretical calculations of diffraction signals to the experimental measured data. The validity of the method is tested by measuring the thermal diffusivities of absorbing ZnO films deposited on glass substrates.     

Effects of Vacuum on Fused Silica UV Damage

Damage points induced by 355 nm laser irradiation increase more quickly on the surface of fused silica in vacuum of about 10^-3 Pa than in atmospheric air at the same fluence. The larger concentration of point defects in vacuum is confirmed by photoluminescence intensity. X-ray photoelectron spectroscopy and infrared absorption indicate the formation of sub-stoichiometric silica on the surface. The degradation mechanism of fused silica in vacuum is discussed.     

Pattern Formation in a Vibrated Granular Layer on an Inclined Base

We carry out the simulations of pattern formation in a two-dimensional vibrated granular layer on an inclined base by molecular dynamics. It is found that the maximum amplitude of the pattern is greater at the lower part than at the higher part of the base, and is proportional to the thickness of the layer. Meanwhile, the wavelength varies non-monotoniclly as the inclined angle of the base is increased.     

60Coγ射线辐照对肖特基二极管1/f噪声的影响

在肖特基二极管(schottky barrier diode,SBD)辐照损伤机理和总剂量效应分析的基础上,利用1/f噪声的迁移率涨落和载流子数涨落模型,深入研究辐照损伤对器件1/f噪声的影响.研究结果表明,辐照诱生新的界面态,改变界面态密度分布,进而调制了肖特基势垒高度,增大表面复合速度是引起器件性能退化主要原因,也是1/f噪声剧烈增加的主要原因.正因为如此,噪声与器件退化存在相关性,即噪声拟合参数B越大,偏离标准值越多,器件可靠性越差,抗辐照能力越低,在辐照环境下工作越容易失效.由此可知,1/f噪声特性可以用作SBD辐照损伤机理的研究工具,并有可能用于SBD抗辐射加固的无损评估.