共轴均匀带电薄圆盘间的相互作用力

本文利用静电场的高斯定律和环路定律巧妙地求出了均匀带电圆盘在空间任一点所产生的电场 ,进而计算出了共轴均匀带电薄圆盘之间的相互作用力     

均匀带电薄圆盘的电势及等势面

根据电势的叠加原理，导出了均匀带电薄圆盘电势的级数表达式，并进而给出了等势面方程。     

叠加法求均匀带电球体电场问题

现有教材中计算均匀带电圆盘轴线电场强度公式,只得到场强大小,没有明确给出场点和圆盘的相对位置与场强方向之间的关系。若根据场强叠加的方法利用此公式计算均匀带电球体的场强分布,容易得到错误的结果。将符号函数引入均匀带电圆盘轴线上电场强度计算式,可以得到场强大小及相对于圆盘的方向,清楚而准确地给出均匀带电圆盘轴线电场强度。利用该公式再次求解均匀带电球体电场,结果与利用高斯定理得到的结果完全相符。     

变速旋转均匀带电薄圆盘空间电磁场 的迭代计算

利用场的轴对称性,巧妙联合运用麦克斯韦方程组,以轴线上的场为初值,通过反复迭代的方法,获得了变速旋转的均匀带电薄圆盘空间电磁场的无穷级数表达式。     

匀角速转动带电薄圆盘产生的磁场分布计算与讨论

在球坐标系中,通过求解多个区域的拉普拉斯方程,得到匀角速转动带电薄圆盘产生的标量磁位和磁场分布,进而给出转动薄圆盘的中心、中心轴线上、近区和远区的磁场.     

万有引力场与库仑场形式上相似性的研究

就均匀薄球壳和均匀带电薄球壳、均匀球体和均匀带电球体的内部以及外部,从场力、场和势三个方面,对它们的相似性作出分析与比较.     

均匀带电圆盘的静电势问题

讨论了均匀带电圆盘静电势问题的两种解法，即延拓法和方程法，澄清了延拓法求解中的一些错误。     

均匀带电椭球的静电自能——“‘带电厚椭球壳空腔内的电场’一文的补充”续

计算一般形状的均匀带电椭球的静电自能,该椭球是由非导体构成的.方法是把该椭球分割成无限多个与其共轴的、等偏心率的薄椭球壳,通过考虑各个薄椭球壳的自能和它们之间的相互作用能,导出均匀带电椭球的静电自能公式.     

有限长均匀带电薄圆柱面的电场

由场的叠加原理,导出了有限长均匀带电薄圆柱面电势和电场的级数表达式.     

薄圆盘直径端点之间电阻的研究

针对薄圆盘直径端点之间电阻难以利用传统直接积分法或数值解法测量的问题,本文利用有限元分析法研究了薄圆盘直径端点之间电阻的测量方法。利用Comsol multiphysics设计薄圆盘电阻测量平台,通过在薄圆盘直径端点设计电极,研究了薄圆盘直径端点之间电阻随薄圆盘半径、电极位置、薄圆盘上小孔位置和大小的变化规律;利用最小二乘法拟合薄圆盘直径端点之间电阻表达式,实现薄圆盘直径端点之间电阻间接测量;在典型条件下,利用直接积分测量法对上述测量方法进行验证,结果表明本文提出的方法误差较小。本文研究工作对薄圆盘电阻的设计具有指导意义,且该研究方法还可以推广用于其他形状电阻的设计。     

A study on the best irradiation dose of X-ray for Hep-2 cells by Fourier transform infrared spectroscopy

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.     

Modification to first-order Born approximation for improved prediction of scattered sound from weakly scattering objects

When deriving the Fourier diffraction theorem based on the first-order Born approximation,the difference between wave number of the scattering object and that of the surrounding medium is ignored,causing substantial errors in sound scattering prediction.This paper modifies the Born approximation by taking into account the amplitude and phase changes between the scattering object and the water due to the wave number difference.By changing the radius and center position of the sampling circle in the Fourier domain,accuracy of the predicted sound scattering is improved.With the modified Born approximation,the computed far-field directional pattern of the scattered sound from a circular cylinder is in good agreement with the rigorous solution.Numerical calculations for several objects with different shapes are used to show applicability and effectiveness of the proposed method.     

Study on the radiation problem caused by electron beam loss in accelerator tubes

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.     

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.     

Factors affecting the spectrum of an electromagnetic light wave on scattering from a semisoft boundary medium

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.     

Temperature Sensitivity Control and Mechanical Stress Effect of Boron-Doped Long-Period Fiber Gratings

We will present in this work the quantitative analysis of the relationship between the doping concentrations of GeO 2 and B 2 O 3 in the core and cladding regions and the temperature sensitivity of the resonance wavelength shift in long-period fiber gratings (LPFGs). Based on this analysis, the temperature sensitivity was suppressed and enhanced to 0.002 nm/°C and 0.28 nm/°C, respectively. We will also discuss the effect of the residual mechanical stress on the optical and mechanical properties of LPFGs. In particular, we will present the measurement results of the dependence of the refractive index change and mechanical strength on the residual mechanical stress in the boron-doped fibers with depressed clad and matched clad.     

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.     

Time domain finite volume method for the transient response and natural characteristics of structural-acoustic coupling in an enclosed cavity

A time domain finite volume method（TDFVM）based on wave theory is developed to analyze the transient response and natural characteristics of structural-acoustic coupling problems in an enclosed cavity.In the present method,the elastic dynamic equations and acoustic equation in heterogeneous medium are solved in solid domains and fluid domains respectively.The structural-acoustic coupling is implemented according to the continuity condition of the particle velocity along the normal direction and the normal traction equilibrium condition on the interface.Several numerical examples are presented to validate the effectiveness and accuracy of the present TDFVM.Then the effects of water depth on the acoustic and vibration characteristics and the natural characteristics of a structural-acoustic coupling system are analyzed.The numerical results show that the increase of water depth leads to a stronger coupling between the water and structure and the decrease of natural frequencies of coupling system,The computational cost and memory of this method are small and it can be applicable to structural-acoustic coupling problems in the heterogeneous fluid.     

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.     

Analysis of Laser-generated Rayleigh wave on viscoelastic materials

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.