共查询到20条相似文献,搜索用时 62 毫秒
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在组分夸克模型中重子共振态的光子激发下,通过数值计算核子上光子总吸收截面σ1/2和σ3/2,检验了Gerasimov–Drell–Heam(GDH)求和规则.这种计算包括了总计17个低激发的、非奇异重子共振态.发现纵横相干截面在随Q2变化的求和规则研究中扮演了重要角色.结果显示在94%可信度上这些共振态使GDH求和规则饱和.特别是在Q2=0和小Q2的区域,主要是共振态P33(1232)激发使求和规则饱和.在Q2=1.0GeV2以下,GDH积分有一个很强的Q2依赖性质,且在Q2=0.3GeV2附近变号.由于共振态贡献的迅速下降,当Q2>1.0GeV2时,GDH积分对Q2依赖变弱. 相似文献
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在J/ψ强子衰变过程中,伴随f0(975)产生的玻色共振态X,若衰变为一对正反赝标介子,它的自旋-宇称只能是产JPC=(奇)--.这里给出了过程的角分布螺旋度形式,并就如何确认X为1--或3--介子作了讨论.认为北京谱仪在K+K-π+π-四叉道中见到的反冲f0(975)的共振态X1(1573)是一个可能的新共振态. 相似文献
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利用螺旋度角分布分析和推广的矩分析方法,讨论了J?ψ衰变过程J/ψ→p+X,X→Δ+π,其中p和Δ分别是反质子和自旋–宇称为(3/2)+的Δ重子,给出了相应于自旋–宇称为(1/2)±,(3/2)±和(5/2)±的重子共振态(包括混杂重子态)X的角分布和矩表达式.它们可以用来确定重子共振态X的自旋. 相似文献
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采用相对论平均场理论研究K凝聚对中子星物质的影响. 研究发现即使在含重子八重态和Δ共振态(n,p,Λ,Σ+,Σ0,Σ-,Ξ0,Ξ-,Δ0,Δ-)的中子星物质中,K-, K0凝聚也可以发生, 并详细研究了超子与K凝聚相互影响的行为. K0凝聚压低K-凝聚, 促进Δ共振态的出现, 在中子星的核心区域, 最终形成多种重子共存的、各重子数密度趋于均衡、且K0凝聚占最大比重的中子星物质. K凝聚使物态方程变软, 进而减小中子星的最大质量, 使之更接近于中子星正则质量. 相似文献
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用推广的矩分析方法讨论了过程J/ψ→X+f0(980),X→K+K-,f0(980)→π+π-.利用得到的矩表达式,可以确定玻色共振态X的自旋-宇称. 相似文献
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Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide 总被引:1,自引:0,他引:1
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. 相似文献
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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. 相似文献
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S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
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. 相似文献
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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. 相似文献
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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. 相似文献
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A transient suppression method for piezoelectric ceramic transducer is presented. By adding some special pedestal pulses to the original transmitted signal, the transient effects in the output of the transducer can be just precisely transmission by use of a narrowband transducer. canceled, thereby achieving the broadband The experimental results show that the transient responses of the sinusoid pulses and coded signals are suppressed successfully and the acoustic waveforms radiated into the surrounding water are improved significantly. 相似文献
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We experimentally demonstrate amplitude squeezed soliton utilizing intensity-dependent self-phase modulation in an asymmetric Sagnac interferometer.The system.whose components are connected via ferrule connector/physical connection(FC/PC)fiber connectors,constitutes all-fiber configuration to generate squeezed soliton.Soliton amplitude reduction measured by homodyne detection is near 4.0 dB below the shot-noise level.Optimal squeezing fields in both simple and compact all-fiber configuration are obtained. 相似文献
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The(2 1)-dimensional nonlinear Schr(o)dinger(NLS)equation with spatially inhomogeneous nonlinearities is investigated,which describes propagation of light in(2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities.New types of optical modes and nonlinear effects in optical media are presented numerically.The results reveal that the regular split of beam can be obtained in (2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities,by adjusting the guiding parameter.Furthermore,the stability of beam regular split is discussed numerically,and the results reveal that the beam regular split is stable to the finite initial perturbations. 相似文献
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In the real-world application of face recognition system, owing to the difficulties of collecting samples or storage space of systems, only one sample image per person is stored in the system, which is so-called one sample per person problem. Moreover, pose and illumination have impact on recognition performance. We propose a novel pose and illumination robust algorithm for face recognition with a single training image per person to solve the above limitations. Experimental results show that the proposed algorithm is an efficient and practical approach for face recognition. 相似文献