晶粒棱长、尺寸与拓扑学特征之间关系的Monte Carlo仿真研究

采用Potts模型Monte Carlo方法研究了晶粒棱长、尺寸与拓扑学特征之间的统计关系.结果表明,晶粒棱长与晶粒面数之间呈线性统计关系,并且平均N面体晶粒模型和Poisson-Voronoi组织均支持该结论.不同时刻的晶粒长大仿真数据表明,在准稳态晶粒长大阶段晶粒棱长的分布具有自相似性.个体晶粒的平均棱长随晶粒面数（或晶粒尺寸）的增加而逐渐增大,这说明一些理论模型中采用的“不同面数的晶粒平均棱长均相等”的假设具有局限性.仿真数据和纯铁实验数据均表明,晶粒尺寸与晶粒面数之间的统计关系表现为一条单调递增的凸曲线. 关键词： 晶粒棱长 晶粒尺寸 拓扑学 Monte Carlo仿真     

Theoretical and Experimental Study of the Diffraction Intensity of Gradient Refractive-Index Lenses

We develop the wave-optics approach for calculating the diffraction distribution of gradient refractiveindex lenses and observing the diffraction pattern of gradient refractive-index lenses in the experiments. The results of our calculation are in good agreement with the experimental results obtained. We show that the diffraction can be regarded as a method to check the quality of the refractive-index distributions of gradient refractive-index lenses.     

线性调频信号激励过阻尼双稳系统的随机共振现象研究

线性调频信号是工程中常见的一种信号, 由于其为非周期信号, 无法以频域信噪比作为衡量其是否产生随机共振的测量手段, 故鲜有文献研究以线性调频信号为激励信号的随机共振现象. 本文利用线性调频信号在最优分数阶Fourier变换域上的能量聚集性, 首次提出以最优分数阶Fourier变换域上定义的信噪比作为测量手段, 研究了线性调频信号叠加高斯白噪声激励过阻尼双稳系统的随机共振现象, 且发现了以线性调频信号为激励信号时产生的新现象, 即随着信号频率的增大, 随机共振将逐渐减弱, 并给出了合理的解释.仿真的结果与理论分析一致, 验证了本文所提出方法的有效性. 关键词： 线性调频信号 分数阶Fourier变换 随机共振     

Correction of B0 susceptibility induced distortion in diffusion-weighted images using large-deformation diffeomorphic metric mapping

Geometric distortion caused by B0 inhomogeneity is one of the most important problems for diffusion-weighted images (DWI) using single-shot, echo planar imaging (SS-EPI). In this study, large-deformation, diffeomorphic metric mapping (LDDMM) algorithm has been tested for the correction of geometric distortion in diffusion tensor images (DTI). Based on data from nine normal subjects, the amount of distortion caused by B0 susceptibility in the 3-T magnet was characterized. The distortion quality was validated by manually placing landmarks in the target and DTI images before and after distortion correction. The distortion was found to be up to 15 mm in the population-averaged map and could be more than 20 mm in individual images. Both qualitative demonstration and quantitative statistical results suggest that the highly elastic geometric distortion caused by spatial inhomogeneity of the B0 field in DTI using SS-EPI can be effectively corrected by LDDMM. This postprocessing method is especially useful for correcting existent DTI data without phase maps.     

Thermoluminescence characteristics of rare-earth-doped LiCaBO3 phosphor

LiCaBO₃ was synthesized by high-temperature solid-state reaction. The influence of different rare earth dopants, i.e. Dy³⁺, Tb³⁺, Tm³⁺ and Ce³⁺, on thermoluminescence (TL) of LiCaBO₃ phosphor was discussed. We studied the TL properties and some dosimetric characteristics of Ce³⁺-activated LiCaBO₃ phosphor in detail. The effect of the concentration of Ce³⁺ on TL was investigated, the result of which showed that the optimum Ce³⁺ concentration was 1 mol%. The TL kinetic parameters of LiCaBO₃:0.01Ce³⁺ were studied by computer glow curve deconvolution (CGCD) method. The three-dimensional (3D) TL emission spectra were also studied, peaking at 431 and 474 nm due to the characteristic transition of Ce³⁺. We also studied the linearity, annealing condition, reproducibility, fading and different heating rate of the LiCaBO₃:0.01Ce³⁺ phosphor.     

Ultrafast photo-induced turning of magnetization and its relaxation dynamics in GaMnAs

We report that,by linearly polarized pumping of different wavelengths,Kerr transients appear at zero magnetic field only in the case when GaMnAs samples are initialized at 3 K by first applying a 0.8 Tesla field and then returning to zero field.We find that,instead of magnetization precession,the near-band gap excitation induces a coherent out-of-plane turning of magnetization,which shows very long relaxation dynamics with no precession.When photon energy increases,the peak value of the Kerr transient incre...     

A novel low-swing interconnect optimization model with delay and bandwidth constraints

Interconnect power and repeater area are important in the interconnect optimization of nanometer scale integrated circuits.Based on the RLC interconnect delay model,by wire sizing,wire spacing and adopting low-swing interconnect technology,this paper proposed a power-area optimization model considering delay and bandwidth constraints simultaneously.The optimized model is verified based on 65-nm and 90-nm complementary metal-oxide semiconductor(CMOS) interconnect parameters.The verified results show that averages of 36% of interconnect power and 26% of repeater area can be saved under 65-nm CMOS process.The proposed model is especially suitable for the computer-aided design of nanometer scale systems-on-chip.     

基于棱镜扫描法的太阳光谱仪光谱定标

为了标定扫描式棱镜太阳光谱仪的棱镜不同转动角度对应的中心波长和光谱带宽,利用了一种棱镜扫描方法对太阳光谱仪的光谱响应函数进行测量。该方法使用固定的单色光波长,控制棱镜转动实现单色光的像在探测器位置扫描,并通过坐标映射得到响应位置的光谱响应函数。文中根据光谱响应函数的定义,推导出棱镜扫描法与单色仪波长扫描方法波长定标原理上的等效性。之后分别以532 nm固体激光器和632.8 nm氦氖激光器为光源,使用棱镜扫描法测量太阳光谱仪对应波长位置的光谱响应函数,并以单色仪波长扫描法实验作为对比。实验结果表明,对于扫描式棱镜太阳光谱仪,棱镜扫描法测量的中心波长分别为531.86和632.67 nm,其准确度优于单色仪波长扫描法测得的531.39和631.97 nm。由于不受单色仪性能的限制,前者测量的光谱带宽值也优于后者。最后以汞灯为光源使用棱镜扫描法对太阳光谱仪进行了光谱定标实验,实现了特征光谱定标法结合棱镜扫描法对中心波长及光谱带宽的标定。该方法同样可以应用于扫描式光栅光谱仪以及单色仪的光谱定标。     

生地当归药队煎剂的表面增强拉曼散射光谱

为揭示单味煎剂与方剂间的关系,分别测试分析了生地当归药队、单味药生地和单味药当归煎剂的表面增强拉曼散射(surface-enhanced Raman scattering, SERS)光谱,并对其进行谱峰归属。本文主要针对存在于三种煎剂中的17个拉曼信号(538,622,732,761,835,876,959,1 145,1 245,1 276,1 326,1 402, 1 456,1 470,1 518,1 546和1 605 cm-1)进行讨论。生地当归药队煎剂SERS光谱在538,732,761,835,876,959,1 145,1 245,1 276,1 326,1 402,1 456,1 470,1 518和1 605 cm-1处,出现15个明显的拉曼信号;生地煎剂SERS光谱在538,761,835,876,959,1 145,1 245,1 276,1 326,1 402,1 470,1 518和1 546 cm-1处,出现13个明显的拉曼信号;当归煎剂SERS光谱在538,622,732,761,835,876,959,1 245,1 326和1 402 cm-1处,出现10个明显的拉曼信号。生地当归药队煎剂SERS光谱保留了和未观察到生地和当归单味煎剂的某些拉曼峰,且产生了生地和当归单味煎剂中所没有的拉曼信号(1 456和1 605 cm-1),即产生新药物成分。生地当归药队煎剂所包含的药物成分并非是生地和当归单味药物煎剂所含药物成分的简单相加。结果表明,SERS光谱可能为方剂研究提供一种高灵敏度、快速准确和操作简单的检测方法。     

基于ARM+DSP索力检测技术的研究与应用

针对斜拉索的基频检测系统进行了研究,提出基于ARM+DSP的拉索振动信号分析检测技术.首先分析了前端振动信号的采集方法和信号处理技术,然后在ARM+DSP平台中进行基频分析算法的实现与优化,最终选取SEED-DEC138工业参考设计平台,并利用双核芯片进行关键模态分析算法的移植优化以及预处理算法的开发,实现了一种新的斜拉索振动信号处理系统.试验结果表明:新系统既能保证较高的检测精度,同时也能保证很好的实时性.