在较弱耦合下用Monte Carlo方法计算胶球质量的另一种途径

本文提出了通过改换格点作用量来实现在较弱耦合下计算胶球质量的一种途径.采用EXP作用量在β=4.4处用Monte Carlo方法计算了SU(2)格点规范理论的胶球质量.初步的结果是m(0⁺)≈(1.38±0.28)GeV,m(2⁺≤(1.39±0.41)GeV,且m(2⁺)/m(0⁺)～1.0甚至更小些.为便于比较,计算是在4³×8格点上完成的.     

相对论重离子碰撞中的横能和零度能的分布

基于参加者-旁观者图象,本文应用多源模型,计算了相对论重离子碰撞中的零度能分布和入射碎裂区的横能分布,以及零度能与横能的联合几率分布.对于60A GeV和200A GeV入射核¹⁶O与不同靶核的碰撞,计算结果与西欧中心WA80组的新实验数据符合很好.     

在α(p,p')ηα反应中的N(1535)激发及η介子产生

在相对论介子与核相互作用理论框架下, 对α(p,p')ηα反应进行了理论分析, 讨论了在入射质子和靶核上的N^*(1535)激发机制的特点. 以⁴He靶核为例, 在入射质子动能T_p=2.8GeV的情况下, 计算了反应截面, 末态ηN不变质量谱和出射η介子的角分布, 讨论了在兰州重离子冷却储存环(CSR)上开展实验研究的意义和可能性.     

200GeV/u的238U+238U核碰撞产生的双轻子谱(M≤4GeV/c2)的计算

在夸克味动力学的计算中,除包含u、d、s夸克及其反夸克外,还涉及粲夸克及其反夸克(cc),采用包含夸克味动力学效应的相对论性流体力学模型,计算了碰撞能量为200GeV/u的²³⁸U+²³⁸U核碰撞时形成的膨胀QGP及其在相变过程中发射的双轻子谱,轻子对的质量范围M≤4GeV/c².计算结果与CERNSPS的实验测量数据进行了定性的比较和分析,得到初步的结论:由于夸克碎块和味动力学效应,J/ψ→μ⁺+μ^－峰值被降低,导致低质量区(阈至1.35GeV/c²)谱的提高.     

利用QMD分析中高能质子入射208Pb的(p,xn)反应双微分截面

中高能质子入射重金属靶产生散裂中子是加速器驱动洁净核能系统的一个关键部分.利用量子分子动力学(QMD)模型研究入射质子能量在300MeV—1.5GeV,散裂靶为²⁰⁸Pb的(p,xn)核反应的双微分截面,QMD计算结果很好再现了实验数据,且QMD的计算结果明显优于HETC和LAHET.QMD在较宽的能区和核区满足加速器驱动洁净核能系统散裂靶物理计算的要求.     

具有双Y-型结构的Θ+的研究

采用由单胶子交换产生的库仑势加上流管模型给出的双Y-型禁闭势之和的相互作用势,分别计算了正、负宇称态的Θ⁺的质量, 给出负宇称态Θ⁺的质量为1.935GeV, 正宇称态Θ⁺的质量为2.082GeV. 其中较低的负宇称态仍比实验给出的Θ⁺(1540)的共振峰高出近400MeV.     

规范作用与引力的统一

在标准模型手征扩充理论的基础上,假定规范作用与引力统一,计算表明,夸克和轻子只可能有三代;所定出的统一点的能量标度为4.4×10¹⁸GeV轻子性夸克的质量标度为10¹⁰GeV.     

高能重离子碰撞中的末态分布与夸克物质信号

本文结合液体动力学模型与状态方程,分析讨论了高能重离子碰撞过程中是否发生相变以及相变的级次对末态分布的影响.由于集体效应随入射能量和核质量的增加而加强,预计对于RHIC(每对核子能量S=100+100GeV)上进行的¹⁹⁷Au-¹⁹⁷Au碰撞,快度分布有可能作为夸克物质形成的信号.     

用同位旋分离的RVUU模拟重离子碰撞

推广了原来的RVUU模型,进一步分离了粒子的同位旋自由度. 并用它模拟了每核子1GeV入射能量的Au+Au碰撞,得到了与实验符合很好的p.π⁺和K⁺动量谱,K⁺与π⁺多重数及其比值K⁺/π⁺随参加粒子数目的变化规律,同时从理论上分析了K⁺/π⁺产额比曲线的物理意义.     

中能重离子碰撞中的能量储存和核内部性质

在研究中能重离子碰撞中能量储存和入射道动力学关系的基础上,考虑不同有效质量(m^*/m)和不可压缩系数(K)对能量储存的影响,发现m^*/m会强烈影响中能重离子碰撞过程中的能量储存和热化过程,而K的影响并没有m^*/m那样强烈.     

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.     

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.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.