一个新的相对论的无奇异点的重子顶点形状因子

提出了一个新的、相对论的、无奇异点的重子顶点形状因子.这个形状因子满足强相互作用过程中,散射振幅从t道到s道变化的交叉对称性.     

交叉相位引致艾里-厄米-高斯光束在单轴晶体传输时光斑连续转动

按照单轴晶体光束传输理论,求得了具有交叉相位艾里-厄米-高斯光束(AiHGB)在单轴晶体中传输时的解析表达式.数值模拟计算结果表明,具有初始交叉相位的AiHGB在晶体中传输时仍是线偏振的,但不一定是传输不变的.具体地讲,有赖于交叉相位系数、光束参数及晶体材料参数,初始交叉相位会引起AiHGB光斑连续转动,在从近场到远场的整个传输过程中总的转动角是90°.并且交叉相位系数足够大时,AiHGB光斑只有纯转动;而交叉相位系数适当小时,AiHGB光斑除了取向转动还有光斑形状变化.这些结果表明通过恰当选择晶体材料(即折射率)和附加交叉相位因子的系数,可以精准调控光束花样形状的取向与结构,也可用于确定晶体材料折射率或测定交叉相位因子的系数.     

f0(400—1200)物理本质的探讨

对f₀(400—1200)的物理本质进行了探讨,将其分解为三部分:t道ρ介子和f₂(1270)介子交换部分以及一个很宽的s道共振态f₀(X).在ππ不变质量1.2GeV以下,用t道ρ介子交换就可以很好地解释同位旋为2的ππS波散射实验数据.但是,在能量高于1.2GeV时,t道f₂(1270)介子交换的贡献必须计入.利用同位旋为2的ππS波散射过程对t道ρ介子和f₂(1270)介子交换中的形状因子进行约束,通过重新拟合CERN-Munich(CM)实验数据来获得f₀(X)的参数.结果表明,确实需要引入一个在1.6—1.7GeV附近具有极点的较宽的0⁺⁺的共振态,其极点是(1.69–0.26i)GeV.     

带区近似中的π-π高能散射行为和复l平面的奇异性

本文是在带区近似下研究非弹性中间态对复l平面奇异性和交叉道高能行为的贡献。处理的方法是应用迭代来求解Chew,Frautschi和Mandelstam所提出的高能联立方程组。文中给出了表示s道高能振幅f(s,t)和t道分波振幅f_l(t)的n次迭代结果的一般公式。在上述f(s,t)的迭代公式中,Chew,Frautschi和Mandelstam提出的愈来愈发散的困难实际上并不出现。一次迭代的结果给出:i)总截面在能量不是非常高时将缓慢下降,但最后仍趋于常数;ii)衍射角分布将有一较长的尾部,随着能量增加,长尾部分将向小角度范围扩张;iii)在t道复l平面中出现割线,割线位于实轴上,右端当t=0时在l=1处,随着t减少,右端向左移动,在s道小角度范围,移动速度约为真空极点的一半。高次迭代结果定性上与一次迭代相似。     

电离层钡云释放早期动力学行为的数值模拟

在中性钡云扩散动力学模型的基础上,考虑钡原子的氧化和电离损耗, 探讨了钡云释放早期(t≤ 100 s)的演化基本特征、钡云形态、亮度以及电子密度分布等问题. 得到了不同释放量(1, 10 kg)、不同释放高度(250, 300 km)和不同初始形状因子(1, 10) 条件下钡云释放早期动力学行为的数值模拟结果.     

光子-核子散射的双谱函数和γ+p→p+π++π-非弹性截面

本文将带区近似法推广到光子-核子散射过程。由t道弹性么正条件导出了光子-核子散射的带区谱函数和s道散射振幅的吸收部分,由此计算了光生π介子的非弹性截面,并与实验作了比较。     

在巴黎势的波函数中氘核的形状因子A(Q~2)(英文)

在非相对论的框架内和应用描述了高动量过程的巴黎势所产生的氘核的波函数,计算了氘核的电磁形状因子A(Q~2)。A(Q~2)因子化为氘核的结构函数Z(t)和偶极形状G_D(t)之积。结构函数Z(t)是用巴黎势的波函数做数值计算而得到的。对A(Q~2)的预言跟实验数据的分析非常一致,这一对实验结果的成功描述说明:氘核形状因子A(Q~2)这一简单的理论描述是非常成功的,并且可以用到氘核的其他静态性质的研究。     

关于某些偶偶核的回弯现象的机理

本文利用一种带交叉的双带图象,计算了某些偶偶核高自旋态的能谱、B(E2)值和迴磁比因子g.据此对它们的回弯现象的机理进行了分析,并讨论了区分形状相变、转动排列和对崩溃效应的可能的判据.     

在微扰论中的Regge割线

本文用微扰论研究了一个s道的梯形图在动量输送t变大及几个外质量也变大时(～t^1/2)的渐近性质。又用了微扰论直接研究了当一个s道的梯形图与一个寻常极点平行地结合时整个振幅在t道的虚部的渐近性质应如何变化,证明了如果上述组合图所产生的s道分波振幅具有Regge割线,则割线开端必须较现有理论所给出的位置为左。     

格点QCD中有限体积下形状因子的内插计算

在格点QCD的框架下,讨论了计算强子的形状因子的过程中,有限体积效应对所得结果的影响,并且给出了计算连续动量空间上形状因子数值的内插算法.本文以π介子的形状因子为例,介绍了从格点QCD中得到的三点关联函数出发计算π介子的形状因子的方法,并说明有限体积效应使得计算结果只能在分立动量上给出.本文探讨了一种保持旋转对称性的内...     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.