A new method for generating and analysing digital speckle shearing correlation fringe patterns

A method for generating a high visibility digital speckle shearing fringe pattern is proposed. A three-step phase shifting technique which involves the introduction of arbitrary phases is utilized. The phase shifting technique is carried out using a rotating mirror and a theoretical model which involves a linear correlation algorithm is discussed. Experimental results showing correlation fringe patterns and a deformation phase map are presented.     

Landau phenomenological theory of the pressure-induced phase transition of phospholipid bilayers

Acta physica Academiae Scientiarum Hungaricae - A theoretical model is developed to describe the temperature and pressure-induced phase transitions of phospholipid bilayer membranes simultaneously....     

芯轴型光纤水听器声压相移灵敏度响应分析

提出了一种带空气腔芯轴型光纤水听器的结构模型,并对其声压相移灵敏度的响应特性进行了研究.通过对空气腔芯轴型光纤水听器的基本原理和结构进行分析,得出光纤与弹性筒作用的相互关系;建立了动力学等效模型,得出带空气腔芯轴型光纤水听器声压相移灵敏度表达式以及频率特性的理论模型;利用有限元方法,得到芯轴型光纤水听器的响应模型.根据提出的结构和确定的参量制作出相应的探头,经过试验测试,其3 dB带宽约为30 kHz,测试结果验证了提出的理论模型与有限元模型的正确性.     

Magnetic properties of the Ashkin–Teller model on a hexagonal nanotube

A new theoretical model for nanomagnets represented by the Ashkin–Teller model on a core-shell hexagonal nanotube is proposed. The Mean Field Theory from the Bogoliubov inequality is applied to study the magnetizations, phase boundaries and tricritical points. For a positive couplings system (ferromagnetic), first order and continuous phase transitions between the stable, metastable and unstable states are observed. For a negative core-shell coupling system, only continuous phase transitions between the stable and unstable states are observed. The phase diagram is presented to illustrate the different phases and transitions exhibited by the model.     

自我质疑机制下公共物品博弈模型的相变特性

公共物品博弈是研究群体相互作用的经典模型,广泛用于解释自私个体间合作的涌现和保持.本文从理论分析和蒙特卡罗模拟两个方面研究了二维正方格子上一个有偿惩罚机制下随自我质疑更新规则演化的公共物品博弈模型的相变特性.理论分析方面,将公共物品博弈模型转化为一个外场不为零的铁磁Ising模型.通过有效能量发现:不存在惩罚时,个体间的耦合强度为零,体系只有外场作用;存在惩罚时,个体间包含最近邻、次近邻和第三近邻相互作用且外场不为零.蒙特卡罗模拟方面,首先验证了理论分析的正确性,然后对公共物品博弈模型相关的一级相变和二级相变进行了有限尺度标度分析.研究发现:1)蒙特卡罗模拟所得结果与类Ising模型分析结果完全吻合;2)相比二维Ising模型,公共物品博弈的二级相变临界指数发生了变化;3)公共物品博弈的一级相变与二维Ising模型相同.     

Simple Landau model of the smectic- A-isotropic phase transition

A simple Landau-type free energy function is presented to describe the smectic-A-isotropic phase transition. Varying the coupling between orientational and positional order parameters, a smectic-A-isotropic or a nematic-isotropic phase transition occurs. Within this model the smectic-A-isotropic phase transition is found to be always more strongly first order than the nematic-isotropic phase transition. The theoretical results are found to be in good agreement with all published experimental results. Received 27 June 2000     

复杂自适应系统动力学演化及其相变的一般理论

将此前已建立的描述复杂自适应系统动力学及其相变的理论做了进一步的推广,建立了更具实际意义的复杂自适应系统模型,并给出了其动力学演化和相变的一般理论-作为应用,对抛硬币游戏活动进行了数值模拟,并与相应的理论结果进行了对比-结果表明,两者符合很好- 关键词： 复杂自适应系统 自组织分离 聚集 动力学相变     

Comparison of Computer Simulated and Phantom Measured Phase Variance in the Study of Trabecular Bone

A new method using magnetic resonance phase images for the assessment of trabecular bone structure has recently been proposed. To test this method, a mathematical model is developed which calculates the phase distribution in gradient echo acquired phase images of a structure of Pyrex glass rods immersed in a copper sulfate solution. Several experiments were performed using a phantom built in the same way as the structure used in the mathematical model. The results from the model are compared with those from the phantom tests, and the influence of resolution and bone area fraction on the phase dispersion is studied. The good correlation between theoretical and experimental results shows that phase variance increases with increasing resolution and bone density. However, the dependence of variance on bone density is less prominent for large pixel sizes.     

Interferometric microimaging based on geometrical spin-redirection phase

A novel scheme for an interferometric microscope with which to visualize a geometrical spin-redirection phase image that represents the local inclination of microsurface structures of an object is proposed. The observed phase depends on the state of polarization and the optical constants of the object material, which enable one to distinguish the spin-redirection phase from the conventional dynamical-phase. A preliminary experiment was performed, and the phase images obtained were found to be consistent with those predicted by computer simulation based on a theoretical model.     

核物质液-气相变和热核稳定性

简述了研究核物质液－气相变的理论计算及研究热核稳定性的二相平衡模型．讨论了相变的临界温度及其对核物质大小、不对称度及库仑相互作用的依赖性．比较了用各种核力或模型算得的热核极限温度及实验结果． A brief introduction of the theoretical studies of liquid gas phase transition in nuclear matter and a two phase equilibrium model for studying stability of hot nuclei is presented. The critical temperature of the phase transition and its dependence on size and asymmetry of nuclear matter and Coulomb interaction are discussed. The limiting temperatures of hot nuclei calculated with various nuclear forces or models and experimental results are compared.     

DNA Intercalation in Neutral Multilamellar Membranes: Experiments and Theory

We report both an experimental and a theoretical work on the effect of confinement on a biological polymer (DNA) incorporated to multilamellar phase. We can see that even when no electrostatic interaction are involved this semi-flexible polymer can be incorporated in between the membranes. X-ray provides experimental evidence for the existence of a mixed DNA/Phospholipid structure. The nature of the DNA ordering is briefly described. A theoretical model is developed to describe the phase diagram. We emphasize the role of the isotropic/nematic transition of the DNA molecules to explain the ability to confine DNA in membranes.     

Waves in multilayer ferrite-dielectric transversely magnetized waveguides with an electrically controlled slowing factor

Multilayer wave-guiding structures comprising transversely magnetized ferrites are studied. A numerical theoretical model is constructed with the Galerkin method. An experimental investigation technique is developed. Theoretical and experimental results are found to be in good agreement. Such structures offer a high phase activity and may provide a basis for small-size millimeter-wave phase shifters and a new class of antenna systems, namely, integrated phased arrays.     

A continuous-wave ultrasound system for displacement amplitude and phase measurement

A noninvasive, continuous-wave ultrasonic technique was developed to measure the displacement amplitude and phase of mechanical structures. The measurement system was based on a method developed by Rogers and Hastings ["Noninvasive vibration measurement system and method for measuring amplitude of vibration of tissue in an object being investigated," U.S. Patent No. 4,819,643 (1989)] and expanded to include phase measurement. A low-frequency sound source was used to generate harmonic vibrations in a target of interest. The target was simultaneously insonified by a low-power, continuous-wave ultrasonic source. Reflected ultrasound was phase modulated by the target motion and detected with a separate ultrasonic transducer. The target displacement amplitude was obtained directly from the received ultrasound frequency spectrum by comparing the carrier and sideband amplitudes. Phase information was obtained by demodulating the received signal using a double-balanced mixer and low-pass filter. A theoretical model for the ultrasonic receiver field is also presented. This model coupled existing models for focused piston radiators and for pulse-echo ultrasonic fields. Experimental measurements of the resulting receiver fields compared favorably with theoretical predictions.     

A New Approach for Modeling of Industrial Adsorption Column

A theoretical analysis of the effect of velocity radial nonuniformity on nonstationary gas-solid adsorption processes in the column apparatuses is presented. The average concentration model, where the radial velocity component in the gas phase is equal to zero (in cases of a constant velocity radial nonuniformity along the column height), is used in the cases of an axial modification of the radial nonuniformity of the axial velocity components in the gas phase. The use of experimental data, for average concentrations in the gas phase at the column end, for a concrete process (physical or chemical adsorption), permits obtaining the gas phase model parameters related with the radial nonuniformity of the velocity. These parameter values allow using the average concentration model for modeling different adsorption processes.     

Theoretical model of phase exclusion conditions for the sum-frequency wave produced by a nonlinear acoustic source

A theoretical model of the sum-frequency wave field produced by a nonlinear acoustic source with three-frequency pumping is reported. The model allows for the dissipation and diffraction of the Gaussian beam. The sum-frequency wave is represented within the second-order approximation as a superposition of two synchronous copropagating waves with equal frequencies. It is shown that the spatial and amplitude-phase characteristics of the sum-frequency wave are affected not only by the amplitude-phase relations in the pumping spectrum, but also by the diffraction-caused variations in amplitudes and phases of the primary waves. This dependence is most clearly seen under the phase exclusion conditions, when the generation of the sum-frequency wave is actually suppressed (excluded) owing to the appropriate choice of the amplitude and phase pumping spectra. The theoretical results are found to agree well with experimental data. The possible practical applications of the phase exclusion conditions are as follows: inspection of inhomogeneous media, detection of objects near interfaces, reduction of nonlinear attenuation, acoustic measurements, etc.     

Phase separation in mixtures of hard core bosons

A theoretical investigation of boson versions of the t-J and t-J(z) models on the square lattice is carried out. In the t-J(z) model, phase separation between a hole-rich and a hole-free phase occurs, at sufficiently low hole doping, for arbitrarily small values of J(z). The boson t-J model, instead, features a uniform ground state at any doping for J/t< or =1.5. No evidence of a striped ground state is found. Relevance of this study to the corresponding fermion models is discussed. Fermi statistics is found to enhance the tendency toward phase separation; in particular, phase separation is predicted, at low doping, in the fermion t-J(z) model, at all values of J(z).     

Impedance characteristics of three-phase electrodes on solid electrolytes

Previously obtained theoretical expressions for the impedance associated with the diffusion of neutral species through a permeable electrode and along the electrode/electrolyte interface are discussed as they apply to gas electrodes on solid electrolytes. A new result, describing diffusion under circular electrode contacts, is obtained. Representative impedance-plane, admittance-plane and Bode-type plots are given for each theoretical model. The effects of rate-controlling adsorption-desorption exchange with the gas phase are considered, as is the applicability of the idealized theoretical models to irregular electrodes.     

Modulation of millimeter-waves using diode laser illumination of a silicon waveguide

A quantitative study of the phase and/or amplitude modulation of millimeter-waves by a diode laser is reported. Using millimeter-waves as a probe, the transport properties of an optically induced electron-hole plasma in a bulk silicon waveguide may be measured. A theoretical model has been developed to predict the temporal behavior of the plasma in the case of low level optical injection. This model agrees well with the measured data.     

Martensitic phase transitions in strong magnetic fields

The model of linear chains is used to study the lattice softening of A 15-compounds in strong magnetic fields. It is shown that a strong field stabilizes the cubic phase due to the Zeeman energy of the conduction electrons. Experiments are suggested to test our theoretical findings.