动力学破缺和真空自发破缺的手征SU(2)L×SU(2)R×U(1)σ模型

将SU(2)_L×SU(2)_R手征对称的σ模型推广到带电磁场情况下的手征σ模型,采用研究自恰性方程的方法研究了同时具有动力学破缺和真空自发破缺的手征SU(2)_L×SU(2)_R×U(1)σ模型,得到了考虑动力学自发破缺、真空自发破缺和电磁相互作用后,σ、π介子和核子都出现了不同的质量修正,并得到此模型中σ,π和核子以不同方式依赖于动力学破缺的具体表示.     

同位素对Ca+HCl，Ca+DCl，Ca+TCl反应立体动力学性质的影响

基于准经典轨线方法和Verbockhaven等人通过多参考组态相互作用计算建立的势能面研究了Ca+HCl/Ca+DCl/Ca+TCl反应中的矢量相关效应. 计算和分析了 P(θr)和 P(Φr)以及(2π/σ)(dσ₀₀/dω_t), (2π/σ)(dσ₂₀/dω_t), (2π/σ)(dσ₂₂₊/dω_t), (2π/σ)(dσ_21-/dω_{t相似文献}   

顶色辅助的人工色理论中荷电的Top介子在LC实验中对顶夸克产生的修正

讨论了顶色辅助的人工色理论预言的赝标量Goldstones粒子(TC介子和Top介子)在LC实验中对顶夸克产生的贡献,发现Top介子对顶夸克产生截面σ_tt的贡献是主要的,在大部分参数空间中荷电Top介子的贡献非常大.当取合理的参数时,荷电Top介子对的σ_tt贡献可以达到8%左右,能够被LC的实验探测到.     

中子相对论唯象光学势与相对论微观光学势

用计算机自动调参数方法,通过最佳符合¹²C到²³⁸U十个核素在入射中子能量E_n=20—1000MeV的全截面σ_t,去弹截面σ_non和弹性散射角分布σ_el(θ),得到了一套普适相对论唯象光学势(RPOP).同时,用基于Walecka模型的相对论微观光学势(RMOP)分析了同样的数据.通过对两种相对论光学势的比较,给出了对它们进行改进的方向.     

核反应总截面参数化计算

给出了一个计算核反应总截面的参数化公式.用此公式计算了包括低能、中高能区大量系统的核反应总截面,且和实验数据进行了比较.讨论了反应总截面σ_R与中子过剩自由度(N-Z)的关系,以及相互作用半径R与轰击能量E_cm的关系.     

轻子原子核深部非弹散射中核结合效应的不同处理之比较

本文采用在壳动力学和总能量守恒条件对肪冲近似进行了运动学修正,由此计算了核结合效应在轻子原子核深部非弹散射中的影响,并将这种模型与采用离壳动力学计算核结合效应的模型进行了对比,发现两种模型对束缚核子的结构函数F₁(x)及Callan-Gross比率R_A=σ_L/σ_T给出不同的结果和预言.与实验的对比表明:在壳处理比离壳处理解释更多的实验现象,而且与实验的符合也更好一些.     

双金属纳米团簇Au2@Cu6电子结构的稳定性：闭壳层作用和多中心键

采用密度泛函理论方法,研究了近年来实验报道的双金属纳米团簇Au₂@Cu₆的电子结构和成键特征. 一般认为,纳米团簇Au₂@Cu₆中(CuSH)₆环和(Au₂PH₃)₂两部分之间的相互作用可以看作是d¹⁰-σ闭壳相互作用. 然而,化学成键分析表明,两个部分之间存在一个十中心两电子(10c-2e)的多中心键. 将该结构与其他双金属纳米团簇M₂@Cu₆(M=Ag、Cu、Zn、Cd、Hg)做对比分析,结果表明除了d¹⁰-σ闭壳层相互作用外,多中心键也是配合物的电子结构稳定性的原因. 这一结果将为理解闭壳层相互作用提供有利的帮助.     

BES主漂移室的宇宙线测试结果

简要描述了北京谱仪(BES)主漂移室的结构和宇宙线实验安排,给出利用宇宙线测试主漂移室性能的主要结果.单元内具有线性的漂移距离S-漂移时间T关系.室的单丝空间分辨率σ_x=210～240μm.相当室内40次dE/dx取样的能量分辨率为8.7%.主漂移室运行稳定.     

量子群Uqp(u2)模型对A～190区超形变带研究

用双参数量子群U_qp(u₂)理论模型公式对A～190区47条超形变(SD)转动带进行了系统分析.计算得到的Eγ跃迁谱与实验较好地吻合;按转动带自旋指定的3种方案确定¹⁹⁴Hg(1),¹⁹⁴Pb(1)的带首自旋,结果与实验一致.此外,进一步讨论了核软度参数σ1的物理意义,发现一对旋称对偶带的σ1几乎全等.     

具有无穷维Virasoro型对称代数的(3+1)维可积模型

利用无中心的Virasoro型对称李代数[σ(f₁(t)),σ(f₂(t))] =σ(f₁f₂-f₂f₁)的每一个实现，能得到各种高维模型．通过一些特殊实现，给出了具有Virasoro型对称代数意义下的许多（3+1）维可积模型     

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.