也谈虚位移原理中广义坐标的选择

讨论了在应用虚位移原理时选择广义坐标应注意的问题，指出正确理解广义坐标的定义是正确选择广义坐标的前提。     

分析力学中单摆模型广义坐标选取的任意性分析

分析力学中单摆模型的广义坐标若选取为竖直方向高度,则存在＂矛盾＂,貌似破坏了广义坐标选取的任意性,本文针对此问题进行了分析,并提出了两种修正后的广义坐标选取方案来解决此＂矛盾＂,从而说明在单摆模型中广义坐标选取的任意性没有被破坏.     

分析力学中坐标选择的教学探讨

广义坐标是分析力学中描述力学体系位形的物理量。在实际教学过程中,发现学生存在对系统自由度判断存在困惑,从而担心所选择坐标数目大于广义坐标数目而带来错误。本文不仅探讨了广义坐标选择在实际教学过程中的教学技巧与要点,还通过理论分析和实际例子,表明只要所选坐标能确定研究对象的位形,则坐标的数目只影响问题解决的复杂程度,而不影响最终结果。     

单自由度振系固有频率不含弹簧静变形的充要条件

教材示例几乎都使用固有频率表达式不显含弹簧静变形的例子,但确实存在相反的情形.本文针对单自由度振动系统,研究了弹簧静变形从固有频率表达式中消失的充要条件.由于采用了能使广义质量为常数的广义坐标,从而只用研究系统的势能.研究发现静变形消失的充要条件是:在静平衡位置弹簧轴线与其运动端点的轨迹相切,且以弹簧运动端点位移为广义坐标所得到广义质量对广义坐标的导数应为0.     

也谈约束,变换方程和Hamilton函数

约束的稳定与否和广义坐标的选择都对坐标变换方程有影响，因而对 Ｈａｍｉｌｔｏｎ函数是否是总机械能有影响．认为Ｈａｍｉｌｔｏｎ函数的性质仅仅决定于如何选取广义坐标而与约束性质无关的观点是片面的．     

也谈正则动量的量子化

《大学物理》 １９８９年第８期刊载了吴汉舟同志《广义坐标正则动量的量子化》一文．本文提出了与该文不同的论点和结果．本文认为，广义坐标中正则动量的量子化形式应该是协变微分算符乘以普适常数－ｉｈ．     

谈动力学中的两个问题

讨论了在一类动力学问题中静摩擦力方向的变化与广义坐标的独立性问题     

正则动量的量子化

回顾了历年来《大学物理》有关广义坐标下正则动量如何量子化问题的讨论,并对此问题发表了作的看法。     

广义坐标中的量子化

本文对广义坐标中的量子化问题，给出了一个比较系统和扼要的讨论．先给出了广义坐标Ｓｃｈｒｏｄｉｎｇｅｒ表象中的量子化规则，然后给出了在这个表象中的动能算符．并且用来讨论了一个无自旋粒子的球坐标表象的例子．最后讨论了根据对应原理从经典力学表达式写出量子力学表达式的一般性原则问题。     

约束,变换方程和Hamilton函数

受理想、完整约束并且主动力全为保守力的力学 系统，如果所选的广义坐标使变换方程中不显含时间， 则相应的Ｈａｍｉｌｔｏｎ函数是系统的总机械能；如果所选 的广义坐标使变换方程中显合时间，则相应的 Ｈａｍｉｌｔｏｎ 函数是系统的广义能量．系统所受到的约束是否稳定，不能作为Ｈａｍｉｌｔｏｎ函数是否总机械能的判据．     

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.     

Synergistic effects on iodine release in potassium iodide solution by combination of ultrasound and visible light irradiations

Iodine release in potassium iodide solution has been investigated under the irradiations of ultrasound and visible light respectively and simultaneously. We have observed that the amount of iodine liberated under the combined irradiation of ultrasound and visible light is larger than the sum of that under the respective irradiations of ultrasound and visible light, indicating a synergistic effect of ultrasound and visible light irradiations. Based on the investigation of the reaction kinetics of iodine liberated, we have ascribed the synergistic effect to the perfect stirring of the photochemical reactor induced by the applying simultaneous ultrasound. The ideal stirring can result in the homogenization of the primary light effect in the whole reaction medium, which induces the acceleration of the photochemical reaction. On behavior of our knowledge, there are few reports on the investigations of utilizing the combination of ultrasonic energy and light energy to accelerate the reaction yield and rate as well as the kinetics of the reaction.     

Experimental study on SC RF cavities by using China large grain niobium for ILC

Large grain niobium has the potential of simplifying the production sequence and consequently reducing the cost of the superconducting RF cavities for ILC.To investigate the feasibility of fabrication and the possibility to achieve high gradient by large grain cavities,two 1.3 GHz cavities were made of China large grain niobium and a series of vertical tests were carried out following several different surfaces treatment procedures.Two cavities have both reached the high gradient of more than 43 MV/m repeatedly and the maximum accelerating field of 47.9 MV/m has been achieved by China large grain niobium.This paper introduces the features of the fabrication and surface treatments on the large grain cavities and presents the preliminary results of the research.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

A modified voice conversion algorithm using compressed sensing

A voice conversion algorithm,which makes use of the information between continuous frames of speech by compressed sensing,is proposed in this paper.According to the sparsity property of the concatenated vector of several continuous Linear Spectrum Pairs（LSP）in the discrete cosine transformation domain,this paper utilizes compressed sensing to extract the compressed vector from the concatenated LSPs and uses it as the feature vector to train the conversion function.The results of evaluations demonstrate that the performance of this approach can averagely improve 3.21%with the conventional algorithm based on weighted frequency warping when choosing the appropriate numbers of speech frame.The experimental results also illustrate that the performance of voice conversion system can be improved by taking full advantage of the inter-frame information,because those information can make the converted speech remain the more stable acoustic properties which is inherent in inter-frames.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

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.     

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.     

Use of Isotope Analysis in Solving Environmental Problems in Power Engineering

Abstract

During hydraulic dumping of ashes at a sludge bed of the power plant at Mělnik (north of Prague), new springs originated which wetted houses and properties at the small village of Podvlci. The sludge bed as well as the village lie at the southwestern margin of the alluvial plain of the Labe (Elbe) River at the foot of a slope built of Cretaceous sedimentary rocks. By analyzing the concentrations of radiocarbon and tritium, it was possible to determine the origin of the water and the ratio of the modern and original groundwater in the new springs in the surroundings of the sludge bed. To substitute the present dump the operation of which should be stopped, establishing of a new one has been proposed within the alluvial plain. By means of stable isotopes and radionuclides, the relations between the groundwater in the Quaternary sediments and in the underlying Middle Turonian confined aquifer were studied, because changes in the hydrogeological regime have to be expected due to the operation of the proposed new sludge bed.