SiO2气凝胶中ZnS∶Mn纳米微晶的发光性质

利用溶胶 凝胶法在SiO2 气凝胶中制得了ZnS∶Mn纳米微晶 ,并对微晶的X射线衍射谱、激发 发射光谱、发光效率、时间分辨光谱进行了研究 ,讨论了发光性质变化的原因。实验表明 ,Mn2 + 在纳米微晶中的发光效率相对于体材料有明显的提高 ,弛豫时间也比在体材料中缩短了约一个数量级     

^143Pm高自旋态研究

通过熔合蒸发反应^129Te(^19F,4nγ）布居了^143Pm的高自旋态,利用在束γ谱学方法,对^143Pm的高自旋态核结构进行了研究,测量了γ射线单谱和γ－γ符合谱,并进行了γ射线各向异性以及DCO比率分析,建立了激发高能达10535．4keV的能级纲图,其中包括新发现的32条γ射线和17个新能级,用弱耦合模型对^143Pm的晕态能级结构进行了解释。     

Multiplicity of positive solutions to period boundary value problems for second order impulsive differential equations

This paper deals with the existence and multiplicity of positive solutions to second order period boundary value problems with impulse effects. The proof of our main results relies on a well-known fixed point theorem in cones. The paper extends some previous results and reports some new results about impulsive differential equations.     

Inclusive excitation-energy distributions of hot nuclei from 44 MeV/nucleon Ar- and 32 MeV/nucleon Kr-induced reactions

Inclusive neutron multiplicity distributions were measured by means of 4π liquid-scintillator detectors for Ar and Kr-induced reactions at 44 MeV/nucleon and 32 MeV/nucleon, respectively. For all the systems studied, the observed distributions exhibit a bump structure at large multiplicity, corresponding to highly dissipative collisions. For Ar-induced reactions, the excitation energies necessary to explain the most probable neutron multiplicity associated with these dissipative collisions are estimated, the correspondence between excitation energy and neutron multiplicity being calculated in the framework of the statistical model. The so-obtained values of excitation energies, which are systematically lower than those predicted using the massive-transfer picture, are discussed.     

基于二次引导滤波的红外图像增强算法及其FPGA实现

针对红外图像细节模糊、对比度低等问题,提出了一种基于二次引导滤波的红外图像增强算法。首先,将原始红外图像作为引导图像,使用引导滤波提取出红外图像的细节信息;其次,将得到的细节信息再进行一次引导滤波处理提取出噪声更低的细节信息;最后,将原始红外图像和两部分的细节信息进行加权求和,实现红外图像增强。该算法能够提高红外图像对比度,增强红外图像细节信息。实验结果表明：相比于其他增强算法,本文算法增强之后的红外图像平均对比度提高了123%～246%,平均梯度提升了56%～101%,视觉效果获得明显改善,更能突显细节特征。基于可编程逻辑门阵列(field programmable gate array, FPGA)实现该算法时,占用资源低,处理640×512像素分辨率的单帧红外图像所需时间可达10.12 ms,能满足红外探测系统的实时性要求,具有一定的实用价值。     

Applications of the modified Faddeev equations: t + dμ-

We present calculations of the cross-sections for elastic as well as for muon transfer in t + dμ^- collisions below the tμ^-(n = 2) threshold. The appropriate mass-scaled Jacobi coordinates are used in the direct and rearrangement channels. The K-matrix elements are obtained from the solution of multichannel Faddeev equations in the configuration space formulation. A bipolar expansion and spline representation are used in the numerical solution of the modified Faddeev equations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Measuring the power-law exponent of an atmospheric turbulence phase power spectrum with a Shack Hartmann wave-front sensor

For non-Kolmogorov turbulence we develop a differential angle-of-arrival fluctuation coefficient, which is the ratio between the transverse and longitudinal differential angle-of-arrival variances, and a slope structure-correlation coefficient, which is the ratio between the transverse and longitudinal differences of the slope correlation function and the slope structure function, to measure the power-law exponent of a phase power spectrum with a Shack-Hartmann wave-front sensor: The differential arrival-of-angle fluctuation coefficient and the slope structure-correlation coefficient are both related to power-law exponent beta and are independent of strength parameter rho(0) of the turbulence. We compare the methods developed and use them to evaluate beta in recently completed horizontal atmospheric experiments for 1000-m laser beam propagation.     

Effects on structure and superconductivity for La and Ca codoping in YBa2Cu3Oy cuprates

The nominal composition of Y_0.8Ca_0.2Ba_2−xLa_xCu₃O_y (YBLCO) cuprates with x≤0.50 has been synthesized by the standard solid state reaction technique. X-ray diffraction and the resistivity measurements are used to characterize the structure and the superconductivity of YBLCO cuprates. There is no structural phase transition in the whole doping range. The dependencies of the lattice constants and some other structural parameters on the content of La for the samples YBLCO with x≤0.20 are different than those for the samples with x≥0.25. The zero resistance temperature T_c0 increases with the increase of the content of La in YBLCO as x≤0.20, and decreases as x≥0.25. We compared these results with those of Nd-doped Y_0.8Ca_0.2Ba_2−zNd_zCu₃O_y cuprates. It seems that T_c0 is related to the structural parameters due to Ca and La codoping in YBLCO.     

不同切型BaTiO3晶体二波耦合特性研究

分析了光折变晶体的电光系数对二波耦合特性的影响,二波耦合能量转移方向不仅依赖于晶体中光生载流子的电荷符号以及入射光与晶体ｃ轴的相对取向,而且依赖于晶体光系数各分量的相对大小;这种特性别明显地表现在相向二波耦合作用中。