共查询到20条相似文献,搜索用时 46 毫秒
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We develop a numerical model to investigate the localization of surface-exciton polaritons in the presence of random roughness and spatial dispersion.It is found that the localication occurs in a limited frequency range near the maximum frequency of surface-exciton polaritons.The decaying length in the extended region is much larger than that in the localized region.The localization of surface-exciton polaritons is due to the destructive interference between waves scattered from the rough surface. 相似文献
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HU Yin DONG Zheng-Chao 《理论物理通讯》2008,50(9):771-776
Taking into account the quantum size effect and the spin dependence of the electronic band structure, and including the spin dependence of the scattering from bulk impurities and two different sets of surface roughness, we present a theory on the electronic transport in magnetic film, in which the average autocorrelation function (ACF) for surface roughness is described by a Gaussion model. Our result shows that the conductivity is a sensitive function of surface roughness and exchange energy. It is also found that in the thin film limit and in the lower-order approximation of the surface scattering, the total conductivity is given by a sum of conductivities of all the subbands and the two spin channels, for each subband and each spin channel the scattering rates due to the impurities and two surfaces are additive. 相似文献
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《声学学报:英文版》2020,(3)
The Kirchhoff approximation with a modified reflection coefficient is used to calculate the three-dimensional acoustic scattering of a Gaussian rough under-ice surface.The concept of a local statistical average reflection coefficient of an under-ice surface is proposed in the calculation model.The scattered sound field of a two-dimensional Gaussian rough under-ice surface is divided into coherent scattering and incoherent scattering.A formula is derived for the scattering coefficient of each scattering component,and the three-dimensional scattering intensity is obtained.The relationships between the scattering intensity and(ⅰ) the root-meansquare height of the Gaussian rough under-ice surface,(ⅱ) the angle of incidence,and(ⅲ) the sound frequency are analyzed.The scattering intensity of a Gaussian rough under-ice surface is measured in a laboratory water tank,and the calculation results of the theoretical model are verified.The experimental results are compared with those of the theoretical model using(ⅰ) the present local statistical average reflection coefficient of an under-ice surface and(ⅱ) the mirror reflection coefficient of an under-ice surface from the literature.The calculation results of the model using the local statistical average reflection coefficient agree well with the experimental results. 相似文献
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Effect of inner-surface roughness of conical target on laser absorption and fast electron generation 下载免费PDF全文
The effect of inner-surface roughness of conical targets on the generation of fast electrons in the laser-cone interaction is investigated using particle-in-cell simulation. It is found that the surface roughness can reduce the fast-electron number (in the energy range E 〉 1 MeV) and energy, as compared to that from a cone with smooth inner wall. A scaling law for the laser reflectivity based on the vacuum-heating model is derived. Both theory and simulation indicate that laser reflection increases with the height-to-width ratio of the periodic inner surface structure and approaches that of a smooth cone as this ratio becomes zero. 相似文献
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This paper discusses the classification of seabed sediments using normally incident,high frequecysound pulse.A number of investigators used the reflectivity of sound on the sea bottom and some otherquantities as features for classifying the sediment types.We suggest a new feature which is independentof the reflectivity and roughness of the seabed.Our feature is extracted from relative form of echoenvelope,and is closely correlated to the attenuation of sound in sediments.The attenuation in differ-ent sediments varies in the range of about tenfold,and can be a good feature for classification.Weused a high frequency signal of 120 KHz to get greater difference in attenuation of different sediments.In order to avoid the influence of seabottom roughness,we use a directional transducer and put it nearto the bottom.In the laboratory,a Bayes classifier is implemented by computer,and a fairly highsuccess rate is achieved. 相似文献
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LU Laiyu WANG Chenghao ZHANG Bixing 《声学学报:英文版》2006,25(4):297-309
The dispersive characteristic of the Rayleigh wave propagating in a stratified media was analyzed by a time-frequency analysis method, the Reassignment of Smooth Pseudo-Wigner Ville Distribution (RSPWVD). Theoretical simulations and experiments were implemented for a homogeneous half-space and a two-layered half-space. It is indicated that the group velocity dispersion curves in different frequency ranges obtained by experimental result are all corresponding to the dominant modes in their surface displacement amplitudes. Such a mode identification of the multi-mode Rayleigh waves is required in inversing the medium parameters. 相似文献
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Theoretical and interpretative study on the subject of photodetachment of H^- near a partially reflecting surface is presented, and the absorption effect of the surface is investigated on the total and differential cross sections using a theoretical imaging method. To understand the absorption effect, a reflection parameter K is introduced as a multiplicative factor to the outgoing detached-electron wave of H^- propagating towards the wall. The reflection parameter measures, how much electron wave would reflect from the surface; K = 0 corresponds to no reflection and K = 1 corresponds to the total reflection. 相似文献
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PENG Zhaohui ZHOU Jixun & ZHANG Renhe .Institute of Acoustics Chinese Academy of Sciences Beijing China .School of Mechanical Engineering Georgia Institute of Technology Atlanta GA USA 《中国科学G辑(英文版)》2004,47(6):702-716
1 Introduction Backward scattering of sound due to sediment is the main source of shallow waterreverberation. In order to predict the reverberation or detect sediment properties frommeasured reverberation data, a reasonable in-plane bistatic backward scattering (BBS)model is essential. The scattering can be caused by the roughness of water-sediment in-terface or by inhomogeneities within the volume of sediment. A great deal of researchhas been done on sediment backscattering, most of which h… 相似文献
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张文 李宁蒋玲 缪巍林镇辉 姚骑均史生才陈健 吴培亨S.I.Svechnikov Yu. B. Vachtomin S. V. Antipov B. M. voronov G. N. Gol'tsman 《中国物理快报》2007,24(6):1778-1781
A quasi-optical superconducting NbN hot-electron bolometer (HEB) mixer is measured in the frequency range of 0.5-2.5 THz for understanding of the frequency dependence of noise temperature of THz coherent detectors. It has been found that noise temperature increasing with frequency is mainly due to the coupling loss between the quasioptical planar antenna and the superconducting HEB bridge when taking account of non-uniform distribution of high-frequency current. With the coupling loss corrected, the superconducting HEB mixer demonstrates a noise temperature nearly independent of frequency. 相似文献
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Extraction of Parameters of Random Self-Affine Fractal Surfaces from Light Scattered Intensity by Levenberg-Marquardt Algorithm 下载免费PDF全文
A method for simultaneously extracting the parameters of self-affine fractal surfaces from a single experimental profile of scattered intensity data is proposed. The Levenberg-Marquardt algorithm is introduced to fit the theoretical equation for the scattering intensity profile to the experimental data. A precision system is designed for acquisition of scattering intensity data using the Boxcar integration technique. The surface parameters extracted (root-mean-square roughness w, lateral correlation length ζ, and roughness exponent α) are compared to those obtained using atomic force microscopy. 相似文献
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从拉格朗日函数的不确定性出发,通过作为积分上发的坐标函娄之作用量S=∫tt1Ldt′=S(x^μ)及其不确定性,得到ψ与ψ′=e^-iqa(x^μ)ψ等效-定域规范不变性或日局域对称性。 相似文献
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本介绍了不确定的有关概念、名词术语,给出了不确定度A类分量、B类分量和展伸不确定度的表达式。说明了不确定度在高校实验教学中的应用,列举了不确定度在实验中应用实例。 相似文献
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