A theoretical and experimental study of the stable equilibrium positions of spheres levitated by two horizontal laser beams

We show that there are various stable equilibrium positions for transparent glass spheres levitated by two horizontal TEM₀₀ laser beams. We present both a theoretical study of the equilibrium positions and the experimental results confirming our theory. To carry out this work, we perform a technique for micromanipulation of microspheres by laser beams. Considering the precision and the stability obtained, this technique could be used to settle the spherical targets involved in laser experiments.     

Continuous-wave photothermal deflection spectroscopy with fundamental and harmonic responses

A diffraction theory of continuous-wave photothermal deflection (PD) spectroscopy with fundamental and harmonic responses is presented. The displacement of the probe beam centroid is found to be a rigorous measurement of PD effect, which leads to a set of analytical solutions to the fundamental and the second-order harmonics. Harmonics are caused by the diffraction of the probe beam in the mirage region, which could not be handled by geometric-optics theory. This theory can be used to study bulk materials, thin films, and layered-structure samples. Experimental results are in good agreement with the theory.     

基于损耗介质加载波导的回旋行波管放大器的互作用分析

损耗介质波导对提高回旋行波管放大器的稳定性等性能具有积极的作用.本文基于损耗介质波导中工作模式的场表达式,推导出电子回旋脉塞互作用线性理论.通过系统的数值计算发现损耗介质波导与光滑金属圆波导中的工作模式从场型分布和色散关系上都具有一一对应关系;通过Laplace变换,利用互作用线性理论计算工作模式的起振场型和阈值,并研究互作用系统磁场、电流和介质层对放大特性的影响.这些研究成果对促进损耗介质在回旋行波管放大器中的运用和高稳定性回旋行波管放大器的发展具有积极的作用.     

Experimental and theoretical study of the multiple scattering of acoustical waves in inhomogeneous media

To describe the propagation of acoustic waves in concrete, we used the results of Waterman for the complex propagation constant in a scattering medium. This makes it possible to calculate the attenuation and phase velocity in the medium concerned. The agreement between theoretical and experimental results being very poor for concrete, we searched for a synthetic medium with a closer correspondence to the theoretical pattern assumed, to determine whether the theory works better for such media. In fact, the synthetic medium gave experimental results in good agreement with the theoretical ones. The results allow us to suggest the use of a more precise treatment suggested by Fikioris and Waterman, which could lead to a better agreement for concrete. However, this extension will be reserved for a later publication.To put an end to the confusion created by misprints in the expressions of certain publications, which have been used as such without correction by some authors, we include here full details of the theory used by us, and give an explanation of our notation.     

Invariant‐Based Pulse Design for Three‐Level Systems Without the Rotating‐Wave Approximation

In this paper, a scheme is put forward to design pulses which drive a three‐level system based on the reverse engineering with Lewis‐Riesenfeld invariant theory. The scheme can be applied to a three‐level system even when the rotating‐wave approximation (RWA) can not be used. The amplitudes of pulses and the maximal values of detunings in the system could be easily controlled by adjusting control parameters. We analyze the dynamics of the system by an invariant operator, so additional couplings are unnecessary. Moreover, the approaches to avoid singularity of pulses are studied and several useful results are obtained. We hope the scheme could contribute to fast quantum information processing without RWA.     

Multi-scale toggle operator for constructing image sharpness measure

To construct effective image sharpness measure with good discrimination ability, a multi-scale toggle operator based algorithm is proposed in this paper. Firstly, toggle operator is used to extract image details. And, the multi-scale theory is used in toggle operator to extract multi-scale image details. Then, the final image details are obtained through applying the pixel-wise maximum operation on the extracted multi-scale image details. Finally, the mean value of the obtained final image details is used as the constructed image sharpness measure. Experimental results on different images show that, the proposed image sharpness measure could correctly quantify the clarity of image and is suitable for discriminating the image clarity change.     

风速测量实验的设计与探究

基于电磁理论和空气动力学的相关知识,利用磁铁、金属棒和DISLAB传感器等器件设计并制作了风速测量系统,可准确地测量2-11级范围内的风速值.该装置还可作为演示电磁感应现象的设计型实验内容,实验过程中可加深学生对电磁感应现象的理解,并提高学生对matlab软件的应用能力.     

扩展互作用振荡器非线性理论与模拟

为了对扩展互作用振荡器(EIO)进行更为高效研究与设计,提出了一种非线性理论与数值模拟相结合的方法对其进行分析,编制了基于一维电子圆盘模型的数值计算程序,并结合MAGIC模拟结果对其准确性进行了讨论。非线性模拟中,35GHz EIO输出功率为125W,频率为35.01GHz,对应的MAGIC模拟结果分别为100W,35.11GHz;110GHz EIO输出功率为220W,频率为107.9GHz,对应的MAGIC模拟结果分别为190W,107.93GHz。非线性方法使得模拟速度有了很大的提高,单次计算时间小于5min,并且所得数据与传统软件模拟得到的特性曲线相比变化趋势一致、数值上也较为接近。     

ВЛИЯНИЕ КОНЕЧНЫХ РАЗ МЕРОВ ЯДРА НА β-СПЕКТР УНИКАЛЬНЫХ ПЕРЕХОДО В ПЕРВОГО ЗАПРЕЩЕНИЯ

The influence of the dimensions of a nucleus on the form of the spectra of unique first forbidden transitions is investigated. The results of a theoretical analysis are compared with the experimental results. Experiments are proposed whereby the exactness of the different approximations used in the theory of beta decay could be verified. The questions have a direct relation to the proofs of the presence of weak magnetism during beta decay.     

Applications of micromagnetics

The main idea in the original development of the theory of micromagnetics was to avoid the crude approximations and the arbitrary assumptions and constraints used in the domain theory. It was hoped that a theory could be built which would describe rigorously all the magnetization processes, from the nucleation of a wall surrounding a reversed domain, through the motion of this wall in the crystal, to its final disappearance in the saturated sample, including high-frequency phenomena like ferromagnetic resonance. In principle this goal can be achieved, at least for ideal crystals, by solving a certain set of non-linear partial differential equations. The solution is definitely not easy, but it could be done for relatively simple cases with modern computers. Choosing, say, a spherical single crystal of an appropriate material, should lead to computations which are very lengthly, but not prohibitively so. The reason this has never been done is that it is known in advance that a solution for such an idealized case cannot have much physical significance in the application to any real sample. This is known from studies of the nucleation of magnetization reversal in a previously saturated crystal for several simple geometries, in which either an analytic solution or upper and lower bounds could be given, as discussed in a previous review.¹ In all these cases, the calculated nucleation field approached the experimental values only for experiments done under conditions approaching the idealized assumptions, but was very different from the results of the more usual experiments. The difference was also qualitatively understood¹ as being mostly due to surface roughness in soft magnetic materials, and due to lattice defects (probably dislocations) in hard magnetic materials.     

Sound propagation and scattering in media with random inhomogeneities of sound speed, density and medium velocity

This review presents both classical and new results of the theory of sound propagation in media with random inhomogeneities of sound speed, density and medium velocity (mainly in the atmosphere and ocean). An equation for a sound wave in a moving inhomogeneous medium is presented, which has a wider range of applicability than those used before. Starting from this equation, the statistical characteristics of the sound field in a moving random medium are calculated using Born-approximation, ray, Rytov and parabolic-equation methods, and the theory of multiple scattering. The results obtained show, in particular, that certain equations previously widely used in the theory of sound propagation in moving random media must now be revised. The theory presented can be used not only to calculate the statistical characteristics of sound waves in the turbulent atmosphere or ocean but also to solve inverse problems and develop new remote-sensing methods. A number of practical problems of sound propagation in moving random media are listed and the further development of this field of acoustics is considered.     

Quantum Interference in Time

I discuss the interpretation of a recent experiment showing quantum interference in time. It is pointed out that the standard nonrelativistic quantum theory does not have the property of coherence in time, and hence cannot account for the results found. Therefore, this experiment has fundamental importance beyond the technical advances it represents. Some theoretical structures which consider the time as an observable, and thus could, in principle, have the required coherence in time, are discussed briefly, and the application of Floquet theory and the manifestly covariant quantum theory of Stueckelberg are treated in some detail. In particular, the latter is shown to account for the results in a simple and consistent way.     

用太赫兹时域光谱技术探测天冬酰胺的低频集体吸收频谱

用太赫兹时域光谱技术研究了室温条件下的多晶天冬酰胺样品的光谱特征，得到了相应的吸收谱和折射率.这说明样品在这个波段存在光谱响应，可以用来探测分子的结构和振动情况.研究发现，天冬酰胺在实验测量有效光谱范围(0.5—2.4THz)内有两个吸收峰，一个是位于1.642—1.758THz的宽带峰，另一个是位于2.266THz的吸收峰.用密度泛函方法在B3LYP/6-31+G(d,p)基组下做了模拟计算，并对获得的频谱进行了解析，计算得到的峰位与实验结果符合较好. 关键词： 太赫兹 时域光谱技术 氨基酸 天冬酰胺     

孕周的超声无损估计

本文讨论了孕周的超声无损估计方法,传统上,对孕周的估计是通过Ｂ型超声测量胎儿器官的有关参数,辅以经验公式而得到。但是由于经验公式无统一形式,且参数皆单独使用,估计结果离散度大,难以实用化。本文对Ｂ型超声测量所得胎儿参数应用数量化理论,建立孕周自动估计的方法。由于在实际应用中,应用数量比理论所得的相应正规方程,难以满足通常求解方法的前提条件,本文引入广义逆矩阵理论求解正规方程。另外,本文进一步讨论了     

Temperature dependency of phase transitions in polymer-dispersed nematic liquid crystal mediums

In this work, electrical measurements were performed on a polymer-dispersed LC sample so that we could demonstrate the temperature dependent molecular behavior, determined according to the electrical response of the system. Experimental results are found to be in favorable accordance with the molecular theory in several aspects. Critical temperatures, order parameters and entropy of transition are acquired for the studied system.     

Heat-source transformation thermotics: from boundary-independent conduction to all-directional replication

All objects in nature are essentially heat sources due to their non-zero temperatures, but the control of them are seldom explored in the theory of transformation thermotics, which largely results from the complicated and uncontrollable parameters given by this theory. Here we put forward an equivalence operation to overcome this challenge, and then show analytical, simulation and experimental evidence for boundary-independent conduction and all-directional replication. The former represents the counterintuitive boundary-independent behavior of thermal conduction surrounded by arbitrary boundaries; the latter denotes a thermal copy of arbitrary shaped objects, which has the accurate shape of isotherms of the objects along all directions. The equivalence operation could be an applicable method for achieving uniform heating, boundary-independent cloaking, all-directional camouflaging, etc. Our results could also give hints for both freely controlling heat transfer and delicately designing similar conduction and replication in other disciplines like electrostatics and particle diffusion.     

Theory and analysis of frequency-domain photoacoustic tomography

A new frequency-domain approach to photoacoustic tomography has recently been proposed, promising to overcome some of the shortcomings associated with the pulsed photoacoustic approach. This approach offers many of the benefits of pulsed photoacoustics but requires a different set of equations for modeling of the forward and inverse problems due to the longer time scales involved in the optical input signal. The theory of photoacoustic tomography with an optical input that is not necessarily a short pulse is considered in this paper. The full optical, thermal, and acoustic governing equations are derived. A transfer function approach is taken for the solution and analysis of this problem. The results and implications are compared with those of pulsed photoacoustics and traditional ultrasonic diffraction tomography. A Fourier diffraction theorem is also presented, which could be used as a basis for the development of tomographic imaging algorithms.     

Sound propagation and scattering in media with random inhomogeneities of sound speed,density and medium velocity

Abstract

This review presents both classical and new results of the theory of sound propagation in media with random inhomogeneities of sound speed, density and medium velocity (mainly in the atmosphere and ocean). An equation for a sound wave in a moving inhomogeneous medium is presented, which has a wider range of applicability than those used before. Starting from this equation, the statistical characteristics of the sound field in a moving random medium are calculated using Born-approximation, ray, Rytov and parabolic-equation methods, and the theory of multiple scattering. The results obtained show, in particular, that certain equations previously widely used in the theory of sound propagation in moving random media must now be revised. The theory presented can be used not only to calculate the statistical characteristics of sound waves in the turbulent atmosphere or ocean but also to solve inverse problems and develop new remote-sensing methods. A number of practical problems of sound propagation in moving random media are listed and the further development of this field of acoustics is considered.     

Prediction of adsorption of xenon in zeolite NaA with molecular density functional theory

The Tarazona model of molecular density functional theory is used to determine the adsorption isotherm and the density distribution of xenon atoms in zeolite NaA. We consider the alpha cage of NaA to be fully three-dimensional and we introduce a basis set for the density distribution to make the solution computationally tractable. The results of this density functional theory model are compared to previous results of grand canonical Monte Carlo simulations for the same system.We dedicate this paper to Professor Herbert Wagner, whose excellent contributions to density functional theory typify his valuable role in the advancement of statistical physics     

The connection between the coercive force and the initial susceptibility of plastically deformed ferromagnetics

The paper describes the results of measurement on four ferromagnetic materials, plastically deformed in broad limits, which show that between the coer ive force and the inverse value of the initial susceptibility there exists a linear correlation. With two of the given materials this correlation could be explained on the basis of the Becker-Kersten theory of coercive force and initial permeability. The paper also describes the experimental equipment used and gives practical principles in the construction of the coercimeter and permeameter. It also gives a method of determining the influence of the skin-effect of the magnetic field on the results of measurement.