Finite element dynamic analysis of practical bladed discs

The dynamic characteristics of one blade, two discs and one shrouded, bladed disc, having 87 blades, are predicted by the application of the finite element method of analysis. The discs are modelled by using both annular and sector elements. The blades are modelled by means of shell elements. The shrouds are represented by both lumped masses and straight beam elements. The predicted frequencies are compared with experimental results.     

Analysis of the spatio-temporal scales of laminar premixed flames near equilibrium

The interplay between chemistry and transport is addressed by exploring the coupling between the spatial and temporal scales of one-dimensional laminar premixed combustion in reactive mixtures described by detailed chemical kinetics and multicomponent transport. System dynamics are investigated in the neighbourhood of the equilibrium state; in so doing, the time scales associated with modes of varying wavelength for the complete unsteady, spatially inhomogeneous system are obtained. The results reveal that short wavelength modes are dominated by diffusion-based time scales, and long wavelength modes are dominated by reaction-based time scales. The analysis further identifies critical wavelengths where the effects of reaction and diffusion are balanced, and it is seen that the critical wavelengths are well estimated by classical diffusion theory.     

Influence of Concentration of Vanadium in Zinc Oxide on Structural and Optical Properties with Lower Concentration

ZnO films doped with different vanadium concentrations are deposited onto glass substrates by dc reactive magnetron sputtering using a zinc target doped with vanadium. The vanadium concentrations are examined by energy dispersive spectroscopy （EDS） and the charge state of vanadium in ZnO thin films is characterized by x-ray photoelectron spectroscopy. The results of x-ray diffraction （XRD） show that all the films have a wurtzite structure and grow mainly in the c-axis orientation. The grain size and residual stress in the deposited films are estimated by fitting the XRD results. The optical properties of the films are studied by measuring the transmittance. The optical constants （refractive index and extinction coefficient） and the film thickness are obtained by fitting the transmittance. All the results are discussed in relation with the doping of the vanadium.     

Accurate measurement of the main refractive indices and thermo-optical coefficients of the calcite crystal

The main refractive indices of calcite crystal are measured by the means of auto-collimation, and the thermo-optical coefficients are calculated. The coefficient expression of Sellmeier equation is obtained by solving Sellmeier equation strictly and the refractive indices of different wavelengths are calculated, which accord with experimental esultsery well. The measured main refractive indices of calcite at 488-nm wavelength are identical with the values obtained by Sellmeier equation.     

Dependence of Photovoltaic Property of ZnO/Si Heterojunction Solar Cell on Thickness of ZnO Films

N-ZnO/p-Si heterojunctions are prepared by sputtering deposition of intrinsic ZnO films on p-Si substrates. Thicknesses of ZnO films are altered by varying the deposition time from I h to 3h. The electrical properties of these structures are analysed from capacitance-voltage （C V） and current-voltage （I-V） characteristics performed in a dark room. The results demonstrated that all the samples show strong rectifying behaviour. Photovoltaie property for the samples with different thicknesses of ZnO films are investigated by measuring open circuit voltage and short circuit current. It is found that photovoltages are kept to be almost constant of 320 m V along with the thickness while photoeurrents changing a lot. The variation mechanism of the photovoltade effect as a function of thickness of ZnO films is investigated.     

Kinetics and equilibrium of adsorption of organic solutes on mesoporous carbons

Static and kinetic studies on adsorption of nitrobenzene, 4-nitrophenol and 4-chlorophenol on two mesoporous carbons are performed. The carbon properties are analyzed by means of nitrogen adsorption. The adsorption experiments are performed in acidic buffer solutions in a wide range of concentrations. The static experiments are analyzed by means of Langmuir-Freundlich and Freundlich isotherms. The Lagergren, pseudo-second-order, intraparticle-diffusion and multi-exponent equations are used in the analysis of kinetic equilibria.     

强流激光离子源中的等离子体参数诊断

强流激光离子源是最有希望为重离子聚变直线感应加速器提供离子的离子源之一。离子源内等离子体决定了离子源性能和引出品质,为了了解强流激光离子源内等离子体参数,采用发射光谱和ICCD成像的方法对该离子源中的等离子体进行了诊断。该离子源由一台四倍频的266 nm Nd:YAG激光器和Cu靶组成,激光束经过透镜聚焦后照射在Cu靶上产生等离子体,激光打靶能量密度约为108 W/cm2,持续时间15 ns。ICCD相机拍摄了激光照射后等离子体的膨胀过程,初始时刻等离子体垂直表面喷射,膨胀速度约为1 cm/s。光谱仪测量了离子发射光谱,谱线主要由Cu原子的Cu Ⅰ谱线和Cu+离子的Cu Ⅱ谱线组成。采用Boltzmann图法得到膨胀等离子体电子激发温度约为1 eV,采用Stark展宽法得到电子密度约为1016 cm-3。     

食管癌血浆吸收光谱的研究

目前通过血浆检测诊断癌症的研究多为使用医学肿瘤标记物来测定,而通过光谱技术对其进行研究的不多。文章运用分光光度计对正常人与食管癌患者的血浆进行光谱检测,通过紫外吸收谱的参数统计与分析,发现两者的差异,为诊断食管癌提供了新的途径。     

三原子分子的喇曼散射

利用U(5)群链描述三原子分子振转谱的对称性质,并用群论方法计算了CO_2分子喇曼散射的跃迁矩阵元,给出了它的振动与转动喇曼散射截面.结果与实验较好地符合.     

The use of the regularities of nuclear backscattering of protons for analysis of hydrogen in the surface layers of materials

The regularities of backscattering of 7.7-MeV protons from nuclei are used to quantitatively determine the hydrogen concentration in materials by the example of hydrated titanium and zirconium samples. The results obtained by the nondestructive method are in good agreement with the data of chemical analysis by a destructive method.     

单轴晶光轴干涉图成因的理论分析

借助于数学工具和一种简单的实验装置,用直观的方法,使理论分析和图形相结合,从理论上解释了单轴晶光轴干涉图的成因,并给出了在白光照射下的干涉花样。搭建了实验光路,结果表明:若用单色光照射,干涉图为明暗相间圆环;若用白光照射,则为一个套一个的环状等色曲线。愈向视域边缘,干涉色级数愈高,等色曲线的数目愈多,密度愈大,表示晶体的双折射率愈大。实验结果与理论分析相吻合。     

Application of mixed order rate equations to adsorption of methylene blue on mesoporous carbons

Static and kinetic studies on adsorption of methylene blue on four synthesized mesoporous carbons are presented. The carbon properties are analyzed by means of nitrogen adsorption. The static experiments are analyzed by means of Langmuir-Freundlich and Freundlich isotherms. The Lagergren, pseudo-second-order and mixed order as well as the multi-exponent equations are used in analysis of kinetic equilibria. The properties of rate equations are compared and analyzed.     

Topology of two-dimensional turbulence

Velocity differences in the direct enstrophy cascade of two-dimensional turbulence are correlated with the underlying flow topology. The statistics of the transverse and longitudinal velocity differences are found to be governed by different structures. The wings of the transverse distribution are dominated by strong vortex centers, whereas the tails of the longitudinal differences are dominated by saddles. Viewed in the framework of earlier theoretical work, this result suggests that the transfer of enstrophy to smaller scales is accomplished in regions of the flow dominated by saddles.     

Laser ultrasound characterization of chemically prepared nano-structured silver

The ultrasonic properties of nano-structured silver (hereafter nm-Ag) are investigated by the laser ultrasonic technique. The nm-Ag superfine particles with a size of 20 to 27 nanometer (nm) are prepared by using a chemical method. Wafers of nm-Ag are fabricated under different pressing pressures and used as samples. The experimental results show that the ultrasonic velocity and attenuation of nm-Ag prepared by the chemical method depends on the pressing pressures and thus on the relative density. The elastic moduli values of nm-Ag prepared by the chemical method are deduced. The values are lower than those of polycrystalline and single-crystalline Ag. The detailed results, discussions, and comparisons with nm-Ag samples prepared by a physical method are presented. Received: 23 November 1998 / Accepted: 13 September 1999 / Published online: 24 March 2000     

Features of motion of interacting magnetic liquid drops

The features of simultaneous motion of two identical drops of magnetic liquid, which are determined by their hydrodynamic and magnetic interaction, are considered. The changes in the trajectories of drops initially moving in the same direction, caused by a variation of direction and magnitude of the applied dc and ac magnetic field, are studied experimentally and substantiated theoretically. The possibility of effective control of the motion of magnetic liquid drops by applying magnetic fields is demonstrated.     

The Temperature Dependence of the Effective Mass of a Two-Dimensional Polaron

The properties of a two-dimensional polaron in the polar crystal are discussed by means of a model which takes account of the atomicity of the lattice. The lattice vibration and the interaction between the electron and the lattice displacement are treated by second quantization-method. The self-trapped energy and the effective mass of the two-dimensional polaron are derived.     

Optics of helical periodic media in the presence of a wave modulating parameters of the medium: I. New regions of diffraction reflection

Reflection and transmission of light through a layer of a helical periodic medium in the presence of a longitudinal hypersonic field are studied. The cases of periodic and aperiodic media are considered in the perturbation theory approximation. Regions of diffraction reflection (RDRs) of different character are shown to appear, including RDRs caused by the helicity of the medium, by its stratification, and simultaneously by the medium helicity and stratification. The results are compared with the exact numerical solution of the problem.     

The possibility of reconstruction of two-dimensional random inhomogeneities in a shallow sea by frequency shifts of the spatial interference structure of the sound field

Fluctuations of frequency shifts of the spatial interference structure of the sound field in the oceanic waveguide, caused by a two-dimensional field of a random perturbation, are described. Various schemes of observation point spacing are considered. The possibility is shown to reconstruct the spatial spectrum of waveguide perturbations by measuring the spatial spectrum of the frequency shift of the interference pattern. The results of the theoretical treatment are illustrated by the examples of background internal waves and bottom roughness. The sensitivity of monitoring based on measurements of frequency shifts of the interference structure of the sound field is estimated. For medium perturbations by background internal waves, the fluctuations of liquid layer vibrations, sound speed, and temperature, which are minimum detectable by frequency shifts of the interference pattern, were estimated.     

溶剂对光致变色材料-乙基红的光学特性影响

研究了溶剂性质对光致变色材料乙基红光学性质的影响.用吸收谱测定了乙基红染料在不同溶剂中的溶剂化位移.对相同浓度多种乙基红溶液进行了Z-scan测量,测量了不同乙基红溶液的光限幅效应,并讨论了其与溶剂之间的关系.随极性增加,吸收谱蓝移,可以通过选择不同溶剂,改变非线性材料的应用窗口.实验结果表明,在连续光照射下,乙基红溶液的非线性折射主要由热效应引起,非线性折射系数n2受溶剂的热学性质影响较大.此外,Z-scan结果中的非线性吸收为饱和吸收.至于光限幅效应,主要受热效应影响,但亦可由吸收谱预测出在某波长处的动态范围.得出的结论有助于偶氮染料作为非线性材料的应用.     

Time-frequency analysis and modeling of the backscatter of categorized dolphin echolocation clicks for target discrimination

A set of dolphin echolocation clicks collected from an Atlantic bottlenose dolphin in Kaneohe Bay, Hawai'i from a previous experiment is examined in terms of their time and frequency characteristics. The center frequency and rms bandwidth are calculated for the clicks and these are clustered into four classes by using a model based on the Bayesian information criterion. The echo signatures are attained from a solid, elastic homogeneous sphere for each class of clicks from an acoustic scattering model. The results from the scattering model are compared to experimental values. The joint time-frequency content of the resulting echo signals is obtained by the reduced interference distribution (RID). The RIDs are plotted and examined for each signal class for four spherical targets of different material compositions. RID correlation values are obtained for a standard target versus comparison targets by using a time-frequency correlator. The results suggest that dolphins may discriminate by auditory inspection of the time-frequency information returned by the targets. The modification of the outgoing clicks and examination of time-frequency target information may be fundamental to a dolphin's ability to identify and discriminate targets.