共查询到20条相似文献,搜索用时 203 毫秒
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主要研究了气动噪声对光传输和成像的影响。流场求解采用法福尔平均N-S方程,并分别利用基于MUSCL格式的AUSMPW+分裂和二阶中心格式对流通量和粘性通量进行离散处理;用四步四阶Runge-Kutta格式对方程进行时间推进求解,采用J-B两方程模型并经Sarkar方法进行可压缩修正后用于湍流的数值模拟。采用基于光学传递函数的物理光学方法分析平均流动和湍流对光质的影响。研究表明:涡脉冲在运动过程中会引起光束沿涡脉冲运动方向产生较大的整体偏折,偏折幅度随时间而变,最大偏折幅度可以达到1.7 μrad;在与涡脉冲运动的垂直方向,整体偏折基本可以忽略不记。在涡脉冲横穿光束的过程中,平均流动会导致焦平面光强峰值有两次下降,平均流动对光强重新分布的影响比湍流脉动影响更强。涡脉冲在运动过程中,先导致光束能量在与涡脉冲运动垂直的方向上扩散,随后使之在涡脉冲运动方向上向外转移。因能量向外扩散,导致Strehl比在0.9 s时刻降低到0.60左右。 相似文献
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《光谱学与光谱分析》2016,(Z1)
利用时间依赖衰减全反射红外光谱同时探究了N,N-二甲基酰胺(DMF)和乙二醇等当量混合溶剂中两种有机溶剂在氧化石墨烯膜中扩散过程。结果表明,混合溶液中的DMF和乙二醇都可以扩散进入氧化石墨烯膜内部,但是乙二醇比DMF先扩散,而在扩散过程中,DMF比乙二醇扩散系数要大,且先达到平衡。 相似文献
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梅军 《工程物理研究院科技年报》2003,(1):455-459
利用俄歇电子能谱(AES)研究了高真空下温度和氧对铀铌合金表面成分的影响。结果表明在673K时,氧在合金表面表现出很强的解吸能力,温度加速氧离子、原子或分子向合金体内扩散,加速体内的C和U离子或原子向表面偏折。铀铌合金的高温氧化和室温氧化截然不同。 相似文献
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人教版高中《物理》第三册结合图1指出,光线经过棱镜左右侧面两次折射后都向底面偏折,因此得出结论:光线经过棱镜折射后向底面偏折.对此有不少学生甚至老师表示怀疑:当棱镜顶角较小,且光线在棱镜左侧面入射角较大时,光线在右侧面折射后会向上偏折一次,如图2所示.此时出射光线相对入射光线仍向底面偏折吗?仅利用作图似乎得不出这一结论,因此有必要作一较严密的推证. 相似文献
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模拟流场,校验自研发的偏折层析系统。根据光线偏折的光学原理,以及层析的数学、物理意义,研究开发了偏折层析程序。结合自研发的简单自相关代数迭代重建技术(simple self-correlative algebraic reconstruction technique:SSART),开发了一种新的层析系统,文章称“基于偏折光谱的非线性迭代层析系统”。用Gauss函数模拟复杂流场的一个切片,根据偏折层析算法计算该切片的偏折光谱,从偏折光谱中提取投影。采用SSART迭代重建算法重建截面。比较模拟重建结果与原场的差别,采用均方差 (mean-square error:MSE)和峰差(peak error:PE)指数标定重建效果,以检验算法的有效性。结果发现,应用开发的偏折层析程序,采用SSART迭代算法,能够精确重建模拟场,MSE稳定在0.000 09~0.000 11范围,PE稳定在0.007~0.013之间。因此,基于偏折光谱的非线性迭代层析系统能够根据偏折信息精确重建复杂流场。 相似文献
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Fourier transform infrared spectroscopy (FTIR) was employed to study the human epidermis larynx carcinoma cell lines (Hep-2) which were irradiated by different doses of X-ray.The results show that (1) the irradiation of X-ray damages the structure of the CH3 groups of the thymine in DNA,which restrains the reproduction of Hep-2 cells effectively,(2) the 8 Gy dose of X-ray irradiation changes the framework and the relative contents of some proteins,lipids and the nucleic acid molecules intercellular in the greatest degree,and (3) the 8 Gy dose of X-ray irradiation is the best irradiation dose for lowering the degree of the cancerization of Hep-2 cells according to the criteria for the degree of the cancerization reported recently.Meanwhile,the apoptosis of these cells were detected by using flow cytometry (FCM) primarily.It shows that the apoptotic ratio of the Hep-2 cells depends on the irradiation dose to some extent,but is not linearly.And the apoptotic ratio of the 12 Gy dose group is the maximum (20.36%),but the apoptotic ratios of the 2 to 8 Gy dose groups change little. 相似文献
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WANG Yan WU Wenfeng FAN Zhan LIANG Guolong 《声学学报:英文版》2014,(3):267-278
In order to ease the pass-band response distortion of the matrix pre-filter,a simple approach for designing matrix spatial filter is proposed,which minimizes the sum of the k maximal distortion norm(k is the number of the constraint points)within the pass-band,while constraining the filter response within the stop-band.Considering the costly amount of calculation of the high-resolution methods,an algorithm with small amount of calculation based on matrix pre-filtering and subspace fitting using acoustic vector array(MF-VSSF)is proposed.Through joint processing of signal subspace of both pressure and particle velocity,the pre-filtering matrix and the signal subspace is decreased to M-dimensional(M is the number of array-element),hence reduces the time-consumption of the matrix pre-filter design and DOA searching.Simulation results show that,the method offers the same performance as MUSIC with pre-filtering,but has much lesser amount of calculation.Moreover,the designed prefilter can efficiently suppress the interference in the stop-band and improve the estimation and resolution performance of successive DOA estimators. 相似文献
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The beam dynamic code PARMELA was used to simulate the transportation process of accelerating electrons in S-band SW linacs with different energies of 2.5, 6 and 20 MeV. The results indicated that in the ideal condition, the percentage of electron beam loss was 50% in accelerator tubes. Also we calculated the spectrum, the location and angular distribution of the lost electrons. Calculation performed by Monte Carlo code MCNP demonstrated that the radiation distribution of lost electrons was nearly uniform along the tube axis, the angular distributions of the radiation dose rates of the three tubes were similar, and the highest leaking dose was at the angle of 160° with respect to the axis. The lower the energy of the accelerator, the higher the radiation relative leakage. For the 2.5 MeV accelerator, the maximum dose rate reached 5% of the main dose and the one on the head of the electron gun was 1%, both of which did not meet the eligible protection requirement for accelerators. We adopted different shielding designs for different accelerators. The simulated result showed that the shielded radiation leaking dose rates fulfilled the requirement. 相似文献
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In order to understand the viscoelasticity of material, this research has been conducted to study the propagation characteristics of viscoelastic Rayleigh wave theoretically. A model is presented for the pulsed laser generation of ultrasound on viscoelastic medium surface. Referred to the Kelvin model, the frequency equation and the normal displacement of viscoelastic Rayleigh wave were derived, the influence of the viscoelastic modulus on dispersion and attenuation was discussed. From the theoretical calculation, it is shown that the effect of viscoelasticity on the attenuation of Rayleigh wave is more than that on its dispersion. In the case of a weak viscosity, the attenuation of viscoelastic Rayleigh wave is directly proportional to viscosity modulus; the effect of shear viscosity on the attenuation is much more than that of bulk viscosity. The transient response of viscoelastic Rayleigh wave was also simulated using Laplace and Hankel inversion transform, which are showed in good agreement with the theoretic predictions. The model provides a useful tool for the determination of viscoelastic parameters of medium. 相似文献
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The formulas of the quantum electrodynamics have been applied to calculate the spontaneous emission rate of excited atom in dielectric microcavity.The results exhibit damping oscillating Patterns which depend sensitively on the scaling parameter and geometrical structure.Compared with the case that the emitting atom is immersed in dielectric,the spontaneous emission rate is depressed obviously and the center or the mean value of the oscillations is intimately related to the real refractive index of the local position where the atom is.In order to explain this phenomenon,we utilize the closed-orbit theory to deal with the classical trajectories of the emitted photon.and extract the corresponding frequencies of the oscillations by Fourier transform.It is found that the oscillations can be represented in terms of the closed-orbits of the photon motion constrained in dielectric microcavity,thus providing another perspective on the spontaneous emission of atom sandwiched by dielectric slabs. 相似文献
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The spectrum of an electromagnetic light wave on scattering from a semisoft boundary medium is discussed within the accuracy of the first-order Born approximation. It is shown that spectral shifts and spectral switches are affected both by the polarization of the incident light wave and by the characters of the scat-tering medium. Moreover, numerical results show that the direction at which the spectral switch occurs is governed by the characters of the scattering medium, whereas the magnitude of the spectral switch is affected by the polarization of the incident light wave. 相似文献
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It is demonstrated experimentally that the anharmonic property of the quadrupole trap can be exploited to cool trapped atoms by modulating the trap potential anisotropically.This cooling effect arises from the energy-selective removal of the most energetic trapped atoms and the thermal equilibrium of the remaining atoms.The frequency dependences of the temperature and the fraction of the atoms left in the trap after the modulation are explored.It is also demonstrated that the cooling induced by parametric resonance can also increase the phase space density of the trapped atoms. 相似文献
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According to the equation of motion in the elastic medium and integral equation of target scattering, the sound scattering from the partially water-filled elastic spherical shells with and without an inner plate is studied using the finite element and boundary element method, and the scattering normalized form functions of the shell filled with different volume of water are computed and the mechanism of resonance scattering is analyzed. The results show that the resonance of the shell with partially water-filled and without the plate is mainly related to the volume of water, and the resonance is produced by inner water and the spherical shell. The resonance characteristics of partially water-filled elastic shell with the plate are similar to that of empty structured elastic spherical shell, and the sound field in inner water is weaker which indicates the main resonance characteristics are decided by spherical shell and the plate. In addition, the scattering characteristics of spherical shell with plate and one side full water-filled are greatly different from the partially water-filled ones. 相似文献
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During the evolution of the binary system,many physical processes occur,which can influence the orbital angular velocity and the spin angular velocities of the two components,and influence the non-synchronous or synchronous rotation of the system.These processes include the transfer of masses and angular momentums between the component stars,the loss of mass and angular momentum via stellar winds,and the deformation of the structure of component stars.A study of these processes indicates that they are closely related to the combined effects of tide and rotation.This means,to study the synchronous or non-synchronous rotation of binary systems,one has to consider the contributions of different physical processes simultaneously,instead of the tidal effect alone.A way to know whether the rotation of a binary system is synchronous or non-synchronous is to calculate the orbital angular velocity and the spin angular velocities of the component stars.If all of these angular velocities are equal,the rotation of the system is synchronous.If not,the rotation of the system is non-synchronous.For this aim,a series of equations are developed to calculate the orbital and spin angular velocities.The evolutionary calculation of a binary system with masses of 10M⊙+6M⊙shows that the transfer of masses and angular momentums between the two components,and the deformation of the components structure in the semidetached or in the contact phase can change the rotation of the system from synchronous into non-synchronous rotation. 相似文献