Spatial Temporal Analysis of Electrically-Addressable Phase-Only Spatial Light Modulator

An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator (PAL-SLM) has been studied as a dynamic phase-only modulation device. A computer control feature of the spatial light modulator is strongly desired for practical applications. For those demands, an electrically-addressable phase-only spatial light modulator has been developed to combine a liquid crystal display (LCD) with a PAL-SLM (LCD-coupled PAL-SLM) and its performance has been reported. However, a temporal characteristic especially two-dimensional (2D) response has not been discussed before. In this paper, 2D response analysis system has been constructed by using a high-speed complementary Metal-Oxide-Semiconductor (CMOS) camera (1000 frames/sec) and the 2D-modulation characteristic of the LCD-coupled PAL-SLM has been observed. As a result, the LCD has a spatially non-uniform modulation characteristic due to a scanning addressing. It has the potential to cause problems in high speed switching for a computer generated hologram. On the other hand, the spatial non-uniformity has not been observed with the LCD-coupled PAL-SLM.     

Calculation of the energy losses of charged particles upon motion near a nanotube within dielectric formalism

A carbon nanotube has been simulated in the form of a cylindrical layer with a given dielectric function, taking into account the temporal dispersion of the medium. Quantization of the intrinsic electrical oscillations of a carbon nanotube electron subsystem has been performed. The polarization potential, which arises when a charged particle moves near a carbon nanotube, has been calculated and the energy loss caused by the excitation of surface plasmons has been obtained.     

Family of graphene-based superconducting devices

A family of highly sensitive devices based on a graphene nanobridge and superconducting electrodes has been developed, manufactured, and examined. These devices can be used to create a graphene-based integral receiver. A cold-electron bolometer prototype with superconductor-insulator-normal metal tunnel junctions has been studied. Its response to a change in the temperature and external microwave radiation has been measured. A superconducting quantum interferometer with a graphene strip as a weak coupling between superconducting electrodes has been examined. The corresponding modulation of the voltage by a magnetic field at a given current has been measured. The effect of the gate voltage on the resistance of graphene has been analyzed for these samples. To confirm that graphene is single-layer, measurements with the reference samples were performed in high magnetic fields, displaying the half-integer quantum Hall effect.     

Electron Spectrum of Nonlinear Cold Emission from a Metal under the Action of a Laser Shot

The nonlinear emission of electrons from a metal under the action of a femtosecond moderate-intensity laser pulse (laser shot) has been studied. A theoretical model of the process has been constructed based on the 1D nonstationary Schrödinger equation in the vacuum half-space with given boundary conditions for the electron wavefunction. This equation has been solved using the Laplace transformation. It has been assumed that the states of free electrons in a metal, which are described by the Sommerfeld theory of metals, are insignificantly influenced by the laser field. The energy spectrum of emitted electrons has been obtained, and its dependence on the parameters of the lased shot has been found. The calculated spectrum of nonlinear electron emission from a tungsten nanotip under the action of a 6.5-fs-long laser shot generating a field of 9.26 V/nm agrees with the experimental data.     

Magnetization and transport characteristics of layered high-temperature superconductors with different anisotropy parameters

The magnetization of a layered high-temperature superconductor with different anisotropy parameters has been calculated using the Monte Carlo method in the framework of a modified three-dimensional Lawrence–Doniach model with actual boundary conditions. The penetration of a magnetic flux into a bulk sample from the boundary has been simulated, and the curves of magnetization reversal of a high-temperature superconductor by an external magnetic field have been calculated for different anisotropy parameters γ and types of defects in the sample. It has been found that there are significant differences in the magnetization curves and transport properties of superconductors with different anisotropy parameters γ. The influence of tilted columnar defects on the critical current has been analyzed. A decreasing dependence of the critical current on the tilt angle of defects with respect to the c axis has been obtained. It has been shown that, as the anisotropy parameter increases, this dependence weakens and, for a specific value of γ, disappears. An explanation of the mechanism responsible for the disappearance of the dependence has been proposed.     

Non-contact sound velocities and attenuation measurements of several ceramics at elevated temperatures

Laser ultrasonic technique has been employed to carry out the sound velocities and attenuation measurements as a function of temperature in alumina, two kinds of silicon nitride and partially stabilized zirconia (PSZ) samples. Accuracy of the laser technique used has been checked in terms of the diffraction effect and reproducibility of the results. Results of attenuation at room temperature have been compared with quartz transducer technique. In PSZ, velocity behavior has become non-linear and also, a peak in attenuation has been observed around 500 degrees C. In one of the silicon nitride sample, which uses glassy sintering agent, attenuation has shown a sharp peak around 950 degrees C. Interestingly, when the experiment was repeated from 800 to 1000 degrees C, this anomalous attenuation peak has disappeared, leaving a background increasing towards higher temperatures.     

Evaporation waves in a metastable single-component liquid

In this paper, evaporation waves appearing at rapid depressurization of a vessel filled with liquid Freon R11 have been investigated experimentally. Regimes with a high-speed evaporation front have been revealed. It has been shown that the disintegration of a metastable liquid takes place in the form of a surface evaporation wave with a cellular structure of the front and anomalously high values of the coefficient of heat transfer from the liquid. The dependence of the evaporation front velocity on the initial temperature of the liquid has been obtained. A critical temperature value below which evaporation waves are not observed has been determined. Visualization of the evaporation front structure and dynamics with the use of a high-speed video camera has been performed. It has been found that the evaporation front motion has a pulsatory character. A method to calculate the surface evaporation wave with a quasi-plane interphase boundary has been developed. It is based on a model of nonequilibrium evaporation of the liquid and experimentally measured coefficients of the heat transfer from the liquid.     

Analysis and design of ring-resonator integrated hemi-elliptical lens antenna at terahertz frequency

In this paper, a novel lens integrated ring-resonator microstrip antenna is analyzed and simulated at 600 GHz. A mathematical model to compute the directivity of this kind of the antenna has been developed and the directivity of the antenna has been computed which is 18 dBi. The proposed model has been simulated by using CST Microwave Studio a commercially available simulator based on finite integral technique and similar result has been obtained. Further, the directivity of the antenna has also been computed by using the techniques reported in the literature and in this case also we have obtained the similar result. Later, a probe-fed patch integrated lens antenna has also been investigated to validate the correctness of the numerical method. To find the potential advantages of this kind of the structure, the ? 10 dB impedance bandwidth of the antenna has been compared to a lens-integrated probe-fed microstrip patch antenna and a significant enhancement in the bandwidth has been observed.     

Narrow-bandwidth operation of a XeCl laser with SFUR

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Study of the modification of spherical melamine-formaldehyde particles levitating in complex plasma

The surface modification of spherical melamine-formaldehyde particles during their levitation in a dusty plasma as a part of plasma–dust structures in a trap formed in strata in a neon glow discharge has been investigated using scanning electron microscopy. The dependence of the particle size on the time of plasma exposure has been found and measured, and the modification of the surface structure has been studied. The source of the observed modification has been interpreted.     

Maximally Entangled States of a Two-Qubit System

Entanglement has been explored as one of the key resources required for quantum computation, the functional dependence of the entanglement measures on spin correlation functions has been established, correspondence between evolution of maximally entangled states (MES) of two-qubit system and representation of SU(2) group has been worked out and the evolution of MES under a rotating magnetic field has been investigated. Necessary and sufficient conditions for the general two-qubit state to be maximally entangled state (MES) have been obtained and a new set of MES constituting a very powerful and reliable eigen basis (different from magic bases) of two-qubit systems has been constructed. In terms of the MES constituting this basis, Bell’s States have been generated and all the qubits of two-qubit system have been obtained. It has shown that a MES corresponds to a point in the SO(3) sphere and an evolution of MES corresponds to a trajectory connecting two points on this sphere. Analysing the evolution of MES under a rotating magnetic field, it has been demonstrated that a rotating magnetic field is equivalent to a three dimensional rotation in real space leading to the evolution of a MES.     

Vector Preisach hysteresis modeling: Measurement, identification and application

The paper presents a Preisach model to simulate the vector hysteresis properties of ferromagnetic materials. The vector behavior has been studied using a single sheet tester with a disk-shaped specimen at low frequency. The locus of the magnetic flux density vector has been controlled by a digital measurement system. An inverse vector Preisach hysteresis model has been developed and identified by applying the measured data. Finally, the inverse model has been inserted into a finite element procedure through the fixed point technique and the reduced magnetic scalar potential formulation to simulate the measurement system. The applicability of the measurement system as well as the developed model has been proven by comparing measured and simulated results.     

Mesoscopic Simulation of Polymers in Fluid Dynamics Problems

Dissipative Particle Dynamics has been used effectively as a modelling technique to perform Computational Fluid Dynamics. DPD preserves some molecular detail whereas in classical CFD this is lost. The technique has been tested in two cases of macromolecules in flow simulations. First, the behaviour of a polymer within a square capillary has been studied, which is the basis of hydrodynamic chromatography. Secondly, the effect of polymers on the melting in shear flow has been simulated.     

A semi-log-periodic array of spheroidal nanoelements: broadbanding nanoantennas

Nanoantenna arrays can offer unique possibilities for large local-field enhancement, high directivity, and also wavelength tunability over a wide spectral range. In this paper, a semi-log-periodic array of nanospheroidal elements has been studied, which exhibits a narrower beam and also a higher electric field enhancement in comparison with an equal size, equally distanced array of the same element. Through the numerical simulations, it has been presented that the suggested array is of a great potential for improvement of the directivity as well as the electric field enhancement over similar designs. Moreover, a considerable change has been observed in the electric field through gradual transformation of elements from sphere to very thin rod. Next, the effect of geometrical parameters on local-field enhancement has been investigated as a complementary job. Finally, it has been demonstrated that adjusting the number of elements can provide a narrower beam.     

单、双转子轴流风扇的内流特性与性能实验研究

本文针对某大型空调室外风扇系统采用双转子风扇时存在的体积大、风量不足和噪声大的缺陷,提出了采用单 转子风扇改进的措施,利用相似理论和CFD内流模拟方法,进行了内部流动的细节分析,并进行了性能、噪声实验,为 产品的更新和性能的改善提供了依据,投入使用取得了良好的经济效益。     

Influence of the external mechanical load on the formation of nanopores in an optical fiber under pulsed UV light

The joint action of an external tensile mechanical stress applied to a fiber and high-power UV light pulses on a photosensitive optical fiber has been investigated. The mechanism of formation of fiber Bragg gratings of the type IIA in photosensitive optical fibers has been revealed, and a theoretical model of their formation has been constructed. This mechanism has been confirmed by a series of experiments on the formation of fiber gratings. It has been established that the actions of UV light pulses on stressed and unstressed fibers differ fundamentally. The critical value of the tensile stress of the fiber at which structural defects intensively nucleate in the fiber under the joint action of the irradiation and external load has been determined. This stress coincides with the breaking stress in our experiments.     

Quantum model of the prolate spheroidal Thomson hydrogen atom

In a uniformly charged prolate spheroidal Thomson hydrogen atom the electron states have been investigated. It has been shown from the mathematical point of view that the problem is equivalent to a spheroidal hydrogen atom in a parabolic potential with the cylindrical symmetry. In the framework of adiabatic approximation, the energy of ground state has been calculated. Comparison with the case of uncharged spheroidal quantum dot has been made, and the analytical form of wave function of electron has been also obtained.     

Surname distribution in population genetics and in statistical physics

Surnames tend to behave like neutral genes, and their distribution has attracted a growing attention from genetists and physicists. We review the century-long history of surname studies and discuss the most recent developments. Isonymy has been regarded as a tool for the measurement of consanguinity of individuals and populations and has been applied to the analysis of migrations. The analogy between patrilineal surname transmission and the propagation of Y chromosomes has been exploited for the genetic characterization of families, communities and control groups. Surname distribution is the result of a stochastic dynamics, which has been studied either as a Yule process or as a branching phenomenon: both approaches predict the asymptotic power-law behavior which has been observed in many empirical researches. Models of neutral evolution based on the theory of disordered systems have suggested the application of field-theoretical techniques, and in particular the Renormalization Group, to describe the dynamics leading to scale-invariant distributions and to compute the related (critical) exponents.     

Performances of a thermal-storage module in a solar-energy power production perspective: A numerical assessment

Summary A theoretical model has been developed to describe the cyclic behaviour of a latent-heat thermal-storage module. Attention has been focused on power production applications, where stability of the heat supply as well as of the operating temperatures is a main concern. The model has been solved numerically; the heat transfer inside the storage module has been analysed to determine the conditions for a stable operation of the conversion system with minimum storage mass.     

随机分布的多圆孔的夫琅禾费衍射场分布研究

采用蒙特卡罗方法先对随机分布的多圆孔构成的衍射屏进行了分析计算,并与单个圆孔的衍射场进行了比较,结果表明,多圆孔的衍射场与单个小圆孔的衍射场有相同的条纹形状和条纹半径,但多圆孔衍射场的能量比单个圆孔的衍射场能量明显增加,同时场强变化不均匀,有叠加噪声的效果,在衍射艾里斑的中心处有一个强亮点.然后对大圆孔内随机分布着的小圆屏构成的衍射屏进行分析,得到了与多圆孔衍射类似的结论,这些结论与实验结果一致.