Nonlinear Absorption and Dispersion Response in Optically Dense Media Driven by a Single-Mode Laser

Taking the density-dependent near dipole-dipole （NDD） interaction into consideration, we theoretically investigate the response of nonlinear absorption and dispersion in optically dense media of three-level atoms driven by a single-mode probe laser. The influence of the NDD effects on the absorption and dispersion spectra of the probe field is predicted via numerical calculations. It is shown that the NDD effects reduce gradually to transient absorption and amplification with the increase of the strengths of the NDD interaction, but do not change the steady-state behavior. Due to the presence of the NDD effects, steady-state absorption spectra exhibit asymmetric double-peak structure and overall shifts when a continuous-wave （cw） probe field is applied. However, frequency dispersion spectra are insensitive to them near the zero detuning.     

β-Delayed Proton Decays of 133Sm and 149Yb

¹³³Sm was produced via fusion evaporation in the reaction ⁴⁰Ca+⁹⁶Ru. Its β-delayed proton decay was studied by means of “p-γ” coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, γ-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The possible spins and parities of ¹³³Sm were extracted by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces of ¹³³Sm were calculated by using the Woods-Saxon Strutinsky method. Comparing the experimental and calculated results, the spins and parities of ¹³³Sm were assigned to be 5/2⁺ and 1/2^－, which is reconciled with our published simple (EC+β⁺) decay scheme of ¹³³Sm in 2001. In addition, our experimental data on the beta-delayed proton decay of ¹⁴⁹Yb reported in Eur. Phys. J., 2001, A12: 1—4 was also analyzed by using the same method. The spin and parity of ¹⁴⁹Yb was assigned to be 1/2^－.     

Matlab在光学信息处理仿真实验中的应用

提出了一种利用计算机并通过Matlab软件仿真光学信息处理实验的方法 ,其特点是可以随意改变物理参量 ,克服了光学实验上难以实现的操作 .文中分别给出了光栅衍射、空间滤波、图像边缘增强、相关识别等实验的部分仿真结果 .     

提高生物大分子NMR分辨率和灵敏度的有效方法：TROSY和CRINEPT

随着NMR谱仪和实验技术的发展,以及²H、¹⁵N、¹³C标记技术的发展和完善,先后出现了多种异核多维和多共振脉冲实验方法,测定分子量不大于30 kDa的蛋白质的溶液三维结构不再是困难的事. 但是,对于分子量大于30 kDa的蛋白质,由于共振峰数目的增多和谱线增宽,其结构测定依然很困难. 虽然提高磁场强度能够提高分辨率和灵敏度,但是,800 MHz以上的NMR谱仪造价昂贵,难以普及,促使NMR工作者不断寻求能够提高分辨率和灵敏度的新的脉冲实验方法. 到目前为止,比较成功的方法是TROSY^[1]和CRINEPT^[2], 以及在此基础上发展的新方法. 文中对TROSY和CRINEPT的基本原理、最新发展,以及它们在蛋白质结构测定和分子间相互作用研究等方面的广泛应用做了综述.      

掺杂聚乙炔中的孤子振动定域模

在SSH模型基础上,本文研究了掺杂聚乙炔链中杂质势对孤子振动模的束缚影响。不同边界条件下的数值计算发现Goldstone模将受到杂质钉扎并出现两个新的定域模g₁′和g₂′。另外,还得到了其它已知的定域模g₂,g₃和g₅,这些定域模随杂质势的敏感程度各有不同,在所取参数下取得了与实验基本一致的结果。 关键词：     

超声跟踪反常氯化亚汞声光器件的设计及性能分析

氯化亚汞（Hg₂Cl₂）单晶具有独特的声光特性,这使得Hg₂Cl₂声光器件-Bragg盒适用于各种光信号处理。本文以超声跟踪反常器件的设计思想为基础,得出了Hg₂Cl₂器件的设计参数,并分析了这类新型器件的性能。结果表明,该器件有良好的性能,特别是其体积比同类TeO₂器件小得多。这些优点使之可望成为二维声光信号处理系统的关键器件。     

标量介子f0(980)光生过程γp→pf0(980)的研究

轻标量介子性质研究是当今中高能核物理研究中的热点问题之一,特别是质量低于1 GeV的标量介子f₀（980）的内部结构一直存在争议,至今未达成共识。基于前人的研究结果,运用有效拉氏量方法,对f₀（980）粒子的光生过程γp→pf₀（980）进行了更深入的理论研究。探讨了两种传播子形式下得矢量介子ρ和ω交换的贡献,第一种是选择雷吉传播子,第二种是选择普通费曼传播子。第二种形式的微分散射截面理论结果与现有实验数据符合比第一种形式的结果好。基于此,计算了两种形式的总截面,两种形式给出的理论结果相差很大。另外,给出了γp→pf₀（980）→pπ+π-过程的π+π-不变质量分布的理论预言,发现π+π-不变质量分布对于f₀（980）于K-K的耦合常数（g_f0KK）有很强的依赖关系,不同的g_f0KK给出明显不同的π+π-不变质量分布。将来相关实验数据可以验证这些理论预言,并对矢量介子传播子形式和耦合常数g_f0KK做出限制,加深人们对f₀（980）粒子的认识。We study the scalar meson f0(980) in the γp→pf0(980) reaction within an effective Lagrangian approach. Based on previous studies, we calculate the differential cross sections of this reaction. We take two types of the propagators of vector mesons ρ and ω, one is the Regge form, the other one is the normal Feynman propagator. It is found that our theoretical results for the differential cross sections with the Feynman propagator are in agreement with the current experimental data. For the total cross sections, the results with the two types of propagator are much different. On the other hand, we predict the π+π- invariant mass distribution of the γp→pf0(980)→pπ+π- reaction. We find that the π+π- invariant mass distribution depends sensitively on the value of the coupling constant gf0KK. We hope that the future experiments can test our model calculation and give further constraints on the value of gf0KK and also the nature of f0(980).     

Spatial interpolation of HRTFs and signal mixing for multichannel surround sound

From the point of spatial sampling, spatial interpolation of HRTFs (head-related transfer functions) and signal mixing for multichannel (surround) sound are analyzed. First, it is proved that they are mathematically equivalent. Different methods for HRTFs interpolation are equivalent to different signal mixing methods for multichannel sound. Then, a stricter derivation for the signal mixing of multichannel sound and the law of sine for stereophonic sound is given. It is pointed out that trying to reconstruct lateral HRTFs by adjacent linear interpolation is wrong. And for accurate sound image localization, the conventional equation of adjacent linear interpolation of HRTFs is revised. At last, it is also pointed out that some methods used in the analysis of HRTFs and multichannel sound can be used for reference mutually.     

快脉冲直线变压器驱动源模块的原理及实验

 介绍了直线型变压器驱动源（LTD）产生快脉冲的基本原理及技术优势,阐述了快脉冲LTD模块设计的要点,设计了输出脉冲上升时间小于100 ns的快脉冲LTD模块,并进行了初步的实验研究。实验得到该LTD模块充电±16 kV时,短路放电的电流峰值为23.7 kA,电流振荡1/4周期为69.6 ns;充电±50 kV驱动0.85 Ω负载时,电流峰值为41.4 kA,上升时间为36.8 ns（10%~90%）和60.8 ns（0~100%）。     

应用数据挖掘的束流状态描述建模

聚类分析是描述数据群体特征的有效方法.然而,随着挖掘数据库规模的增大,评分函数极值搜索是计算复杂度很高的问题.文中提出了一种新的算法,并将其运用到束流状态描述建模中.试验结果表明,该算法快速有效.同时,重复性是电子储存环的重要指标,聚类模型可作为机器研究和决策的依据,具有指导意义.