Effects on the damping of ultrasonic transducers due to a lack of parallelism in the piezoelectric element

Using a theoretical model, we simulate the responses of piezoelectric transducers having lack of parallelism between their two faces. Verification of the model's validity is carried out by recording theoretical and experimental responses of piezoelectric transmitters and receivers with different degrees of parallelism defects. We conclude that, by using a simple theoretical model, we may forecast experimental responses of a transducer whose faces are not rigorously parallel.     

光电效应伏安特性实验改进研究

光电效应实验及理论解释,为量子理论的建立奠定了基础,在光电效应伏安特性实验中,如何有效减少实验影响因素,提高测量结果的精确度,成为光电效应伏安特性实验改进的一个关键点。本从光电效应实验测量的伏安曲线出发,分析理论与实验结果上的差异,提出了影响实验结果的因素以及相应的实验操作办法,为光电效应伏安特性实验的改进,获得更加精确的实验数据以及光电效应实验的应用奠定了基础。     

Sizing Large Hollow Micro-Balloons with the phase doppler interferometer

A combined theoretical and experimental study has been conducted to evaluate the effectiveness of using large, hollow micro-balloons as LDV seed particles. The study has focused on the ability of phase Doppler systems to size hollow microballoons, the ability of large micro-balloons to respond to high frequency spatial and temporal flow field variations, and the overall advantages and disadvantages of using large microballoons instead of conventional LDV seed particles, such as very small water droplets or polystyrene latex (PSL) particles. This paper discusses the development of a theoretical phase Doppler response model for stratified spheres, the experimental facility, and the theoretical and experimental results.     

The transition energy for the polymorphic transformation of CsCl

The transition energy of CsCl for the transformation I ? II has been determined by means of theoretical and experimental methods. The theoretical method was based on a generalized expression of the repulsion energy introduced byWasastjerna and used in his theory of ionic solid solutions [18]. In the present work, the theoretical value of the transition energy, 880±220 cal/mole, is considerably smaller than previous theoretical results and agrees well with our experimental value, 690±28 cal/mole.     

Controlling the propagation of broadband light pulses by Electromagnetically Induced Transparency

We present an experimental and theoretical investigation, performed on hot sodium atoms in a ladder scheme, showing the control of the absorption and of the propagation velocity of a probe light pulse with a spectral bandwidth as large as 1.8 GHz. The predictions of the theoretical model compare favorably with the experimental results.     

云爆弹外壳体厚度对威力的影响规律研究

通过对不同厚度壳体的速度和动能进行理论分析,给出了壳体对燃料抛撒的影响规律;同时开展了不同厚度壳体的云爆装置试验,得到了装置威力与壳体厚度的关系.研究结果表明:采用薄壳体,并加强壳体与端盖的连接强度,可以提高中心抛撒药能量的利用率,进而提高一次起爆型燃料空气弹(SEFAE)的威力,试验结果与理论分析结果一致.     

Influence of a magnetic field parallel to the cathode surface on the near-cathode drop in the potential in a normal glow discharge

Data are presented of experimental and theoretical studies concerning the influence of a magnetic field parallel to the cathode surface on the near-cathode drop in the potential U_k. U_k is shown to grow with increasing magnetic field. The theoretical and experimental results are in good agreement.     

Are the Laws of Physics Inevitable?

Social constructionists believe that experimental evidence plays a minimal role in the production of scientific knowledge, while rationalists such as myself believe that experimental evidence is crucial in it. As one historical example in support of the rationalist position, I trace in some detail the theoretical and experimental research that led to our understanding of beta decay, from Enrico Fermi’s pioneering theory of 1934 to George Sudarshan and Robert Marshak’s and Richard Feynman and Murray Gell-Mann’s suggestion in 1957 and 1958, respectively, of the V–A theory of weak interactions. This is not a history of an unbroken string of successes, but one that includes incorrect experimental results, incorrect experiment-theory comparisons, and faulty theoretical analyses. Nevertheless, we shall see that the constraints that Nature imposed made the V–A theory an almost inevitable outcome of this theoretical and experimental research.     

On the mechanism of the effect of ultrasound on a nematic liquid crystal at oblique incidence

Based on an experimental study of the optical response of a homeotropically aligned nematic liquid crystal layer to the action of obliquely incident longitudinal ultrasonic waves, the applicability of the new theoretical model postulating the streaming mechanism of molecule reorientation is justified. It is shown that, in the frequency range 0.9–3.6 MHz, theoretical calculations with the use of this model are in both qualitative and quantitative agreement with experimental data.     

量化计算在二芳基二硫代膦酸结构和光谱分析中的应用

在拉曼和红外光谱分析中，谱峰的归属直接关系到对分子结构的判定。本工作以量子化学理论计算为基础，探索对二芳基二硫代磷酸实验拉曼谱图进行谱峰归属的可行性。结果表明：二芳基二硫代膦酸理论计算谱图与实验谱图具有相关性，理论计算谱图可以指导实验谱图谱峰的归属分析。     

塑料光纤纤端光场测试结果及分析

对纤端光场进行了理论分析,分别利用塑料光纤和多模光纤作为接收光纤对塑料光纤的出射纤端光场进行了测量,并与理论分析结果进行了比较,给出了合理的调和参数.传输距离较长的塑料光纤由于高阶模的泄漏,纤端光场分布非常接近高斯分布.实验结果表明了理论分析结果和调和参数选择的合理性.     

Anomalous Internal Conversion as a Clue to Solving the <Superscript>209</Superscript>Bi Puzzle

A numerical analysis of the specific-difference (SD) method for eliminating the Bohr–Weisskopf effect in the theory of hyperfine splitting is performed within a more general theory of anomalous nuclear moments. The limiting accuracy of the SD method is demonstrated. In analyzing experimental data on the hyperfine splitting in H- and Li-like ions of ²⁰⁹Bi, it is found that the disagreement between theoretical and experimental results that was reported recently was due to going beyond this theoretical accuracy. Prospects of further experimental and theoretical studies in these realms are discussed.     

Temperature dependence of the refractive index of optical fibers

Many experimental investigations on the temperature dependence of the refractive index of optical fibers have been reported previously, however a satisfying theoretical explanation for it is still absent. In this paper, a theoretical model about the temperature dependence of the refractive index of optical fibers is presented and it is in agreement with the previous experimental results. This work is a significant reference for the research and development of temperature sensors based on optical fiber delay lines.     

Simulation and experimental study of the influence of a front face layer on the response of ultrasonic transmitters

Using a theoretical model, we simulate the ultrasonic pressure generated by a piezoelectric transmitter whose active element has its front face perfectly connected to a layer with parallel faces. This simulation takes into consideration the characteristic parameters of the piezoelectric ceramic, the layer and the propagation medium.Verification of the validity of the model is carried out by assessing, qualitatively and quantitatively, theoretical and experimental responses obtained with different values of layer thickness. Having correctly verified the model solely by simulation, we examine the influence of the nature of the layer on the transmitter response and give an energetics interpretation of the results. We conclude that by using a simple theoretical model, we may forecast the experimental response of a transducer which has a front face layer.     

Fine structure of the 1s3p 3PJ level in atomic 4He: theory and experiment

The fine structure intervals in helium have been the focus of many theoretical and experimental studies in recent years with most of them concentrating on the 1s2p (3)P(J) levels. Here, we report on a theoretical calculation and an experimental determination of the 1s2p (3)P(J) fine structure intervals. The values from the theoretical calculation are 8113.730(6) and 658.801(6) MHz for the nu(01) and nu(12) intervals, respectively. The laser spectroscopic measurement reported here yields 8113.714(28) and 658.810(18) MHz for these intervals and is in excellent agreement with the theoretical calculation. Both, however, disagree significantly with the previous most precise experimental results.     

Velocity of propagation of the ionised front of a plasma cluster in the linear rail type accelerator. Theory

The experimental results obtained in the previous paper (Kalivoda L'., Rosenkranz J., Czech. J. Phys.B28 (1978), 1342) are discussed here. A model with an increasing plasma cluster inductance is used for theoretical analysis. The analysis of the obtained solution in the form of an alternating series yields a good agreement between theoretical and experimental conclusions.     

Electron correlations at the fractional quantum Hall edge

This paper reviews tunnel spectroscopy of fractional quantum Hall edges using cleaved-edge overgrown devices. Beginning with an intuitive introduction to various experimental and theoretical aspects, the device structure is reviewed, and the experimental result of a continuum of power-law tunneling exponents is revisited. The unanticipated behavior of the exponent with fractional filling factor is described, and all subsequent theoretical explanations for these results are laid out for comparison. Finally, we propose new directions for experimentally resolving the remaining questions.     

On the simulation of the pivot bearing inside HDD

The pivot bearing is an important mechanical component in HDD. Several quasi-rigid (QR) body motion modes of the HDD are related to the stiffness of the pivot bearing such as the axial translation mode, the lateral translation mode and the rocking mode. In the shock simulation of the HDD, the pivot bearing is often simplified to identical theoretical models wherein the bearing is simulated with springs or beams. The overall axial stiffness and the radial stiffness of these models are often carefully checked and match well with the experimental values. However, how well these theoretical models represent the rotational stiffness of the bearing is still not fully understood. This is partly due to the difficulties in obtaining the experimental rotational stiffness of the pivot bearing. In this paper, three different theoretical models are examined for the simulation of the bearing. The rotational stiffness of these three theoretical models is derived analytically. The theoretical formulations are verified with the finite element analysis results.     

An experimental study of acoustoelectric transducers with nonuniform distribution of the piezoelectric coefficient

In this paper, an experimental test of a theoretical model published previously is presented that describes the behavior of an acoustoelectric transducer with a nonuniform distribution of the piezoelectric coefficient within its bulk. Results of this theoretical model are first reviewed. Uniform and nonuniform piezoelectric transducers were fabricated, following a procedure described herein. The receive transfer functions of the transducers were recorded experimentally, and a comparison is made with the theoretical transfer functions predicted by the model, which shows good agreement. The transmit transfer functions of the uniform and nonuniform transducers were also measured and are reported. Numerical calculations of the different transfer functions given by the theoretical model for a uniform transducer associated with different backing materials are also presented, and the results are shown to be equivalent to the results following from the Mason equivalent circuit. Comparisons with experimental results and with Mason's equivalent circuit verified the new theoretical model.     

Theoretical Description of the Third Order Parametric Wave Mixing in a Gas-Filled Capillary of Femto-Second Laser Pulse

The theoretical signal-pressure curves are calculated from approximate analytical solutions of the coupledequations describing the third order parametric wave mixing in a gas-filled capillary of femto-second laser pulses. Thecomparison with the corresponding experimental curves suggests that the following three factors exert important influ-ences on the degree of fitting between the theoretical and experimental results: the walk-off, the phase modulation, andthe third order harmonic of idler pulse.