The relation between a black hole and a general blackbody system

Taking a black hole as a black body system, using general black body radiation theory, a Schwarzschild black hole and a Kerr--Newman black hole are investigated respectively. It is concluded that a black hole can be regarded as an ideal general black body system exactly for the changing process only. However, a stationary global black hole cannot be smoothly regarded as a general black body system. A black hole has some special characteristics which different from a general thermodynamics system. This conclusion means that a black hole should be inherently dynamical, at least when it is taken as a black body system.     

Interaction of a bounded ultrasonic beam with a thin inclusion inside a plate

A theoretical study of the reflection of a two-dimensional Gaussian ultrasonic beam, incident at a Lamb angle of a plate containing a thin rectangular inclusion at an arbitrary position, is presented on the basis radiation mode theory. The inclusion is parallel to the plate surface and its thickness is assumed to be much smaller than the ultrasonic wavelength. It is shown that the amplitude and phase of the reflected beam profile can be used for accurate inclusion characterization. However, this only holds for certain internal positions of the inclusion and for material combinations that do not strongly perturb the excitation of Lamb waves in the plate. When these conditions are satisfied, it is possible to define the Lamb waves and the associated experimental conditions for which good estimates can be obtained of the position of the beginning point of the inclusion as well as of the length and the thickness of the inclusion.     

Creating a Reference Plane Ultrasonic Wave in a Fluid Using a Plane Piezoelectric Transducer with a Large Wave Dimension

Acoustical Physics - The article discusses the possibility of using a plane piezoelectric transducer with a large wave dimension as the source of a reference plane ultrasonic wave, which can be...     

Experimental results on a hydrostatic bearing lubricated with a magnetorheological fluid

Magnetorheological fluids can be used as a smart lubricant as a result of the fact that its properties can be changed with the use of a magnetic field. Local flow resistance and local pressure can be generated by applying a local magnetic field. This work presents a hydrostatic bearing in which the pressure profile of a conventional hydrostatic bearing is recreated with solely the use of a magnetic field and a magnetorheological fluid. The magnetic field is applied only locally at the outer edges of the bearing with the use of an electromagnet. The principle is demonstrated with the use of an experimental setup and a model from literature.     

Landau dynamics of a grey soliton in a trapped condensate

It is shown that grey soliton dynamics in a one-dimensional trap can be treated within the framework of the local density approximation as Landau dynamics of a quasiparticle. A soliton of arbitrary amplitude moves in the trapping potential without deformation of its density profile as a particle of mass 2m. The dynamics in the local density approximation is shown to be consistent with the perturbation theory for dark solitons. Dynamics of a vortex ring in a trap is discussed qualitatively.     

Spin-polarized current in a Rashba ring pumped by a microwave field

We report a theoretical study on generation of a spin polarized charge current with arbitrary spin polarization, including the fully-spin-polarized current. In a two-terminal mesoscopic ring device, the Rashba spin-orbit coupling (RSOC) is considered as well as a microwave field applied on one of arms of the ring. It is shown that at zero external bias a spin current can be produced in addition to the usual charge current pumped by the microwave field, which is attributed to the the quantum interference effect of the RSOC induced spin precession phase. By varying the system parameters such as the microwave frequency and the RSOC strength, not only the magnitude but also the direction of the spin current can be efficiently controlled, moreover, the spin-polarization degree of the charge current can readily be tuned by these system parameters in the range [-1,1]. Since all the parameters can be controlled electrically in our study, the proposed device may shed light on the possibility of an all-electrical generation and tuning of a spin-polarized current in the field of the spintronics.     

Thermodynamics of a gas-coal massif and a nonuniform gas distribution in a coal bed

The thermodynamic potential of a coal bed is calculated, and the gas pressure in the crack-pore system of the bed is shown to be nonuniformly distributed. This pressure is high in “weak“ regions in the bed, i.e., at the sites of a high porosity, low elastic moduli, and low solubility, as well as at high bearing pressure sites. All these phenomena are caused by the elastic interaction of a gas with a solid-state coal frame and the possibility of the formation of a solid solution in the coal. The relative increase in the gas pressure at these sites is estimated. The results obtained can be used to predict the localization of explosive and outburst regions in coal beds.     

Pressure variation by a magnetohydrodynamic method at the surface of a body placed in a supersonic flow

This study is aimed at investigating the possibility of pressure variation near the surface of a body placed in a supersonic flow as a model of an aerofoil or the nose of an aircraft by organizing a surface gas discharge in a magnetic field transverse to the flow. The flow parameters and pressure are mainly affected by the ponderomotive Lorentz force acting on the gas in the direction orthogonal to the direction of the organized discharge current and leading to the removal or compression of the gas at the surface of the body and, hence, a variation of pressure. Experimental data on the visualization of the flow and on the pressure at the surface of the body are considered for various configurations of the current and intensities of the gas discharge and magnetic field; it is demonstrated that such configurations of the current and magnetic field near the surface of the body under investigation can be organized in such a way that the pressure at the front part as well as the upper and lower surfaces of the body under investigation can be increased or decreased, thus changing the aerodynamic drag and the aerofoil lift. Such a magnetohydrodynamic control over aerodynamic parameters of the aircraft can be used during takeoff and landing as well as during steady-state flight and also during the entrance into dense atmospheric layers. This will considerably reduce the thermal load on the surface of the body in the flow.     

Design of a memcapacitor emulator based on a memristor

Since Hewlett-Packard?s solid state implementation of a memristive system in 2008, a lot of research has begun to develop applications using this new component. As it is not available as a two terminal device yet, emulating circuits must be developed. Building on our previous work to develop an analog model of a memristor, a memcapacitor emulator is proposed in this Letter. This model can be realized by transforming a memristor emulator to a memcapacitor emulator. The characteristics of a memcapacitor are based on the theory proposed by L.O. Chua. The transformation process is described in detail in this Letter. Simulation and experimental results are given as well.     

Buckling of a compressed elastic membrane: a simple model

The buckling of a folded membrane submitted to a bi-axial compression is studied in the framework of the continuum non-linear elasticity theory. We show that the formation of the fold patterning can be quantitatively well described with a simple non-linear model. As a matter of fact, with this model, we recover the experimental phase diagram of a secondary buckling instability with a very good precision. In addition, depending on the anisotropy of the applied compressive stress, we find that the buckling coarsening dynamics can be described as a 1D spinodal decomposition (for a uni-axial stress) or as a 2D XY model (for an isotropic bi-axial stress) with an irrotational non-scalar order parameter. For an isotropic bi-axial stress, we indeed recover the famous coarsening exponent: n=1/4. This exponent has to be confirmed experimentally.     

Phonon-Assisted Resonant Tunnelling through a Triple-Quantum-Dot： a Phonon-Signal Detector

We study the effect of electron-phonon interaction on current and zero-frequency shot noise in resonant tunnelling through a series triple-quantum-dot coupling to a local phonon mode by means of a nonperturbative mapping technique along with the Green function formulation. By fixing the energy difference between the first two quantum dots to be equal to phonon frequency and sweeping the level of the third quantum dot, we find a largely enhanced current spectrum due to phonon effect, and in particular we predict current peaks corresponding to phonon-absorption and phonon-emission assisted resonant tunnelling processes, which show that this system can be acted as a sensitive phonon-signal detector or as a cascade phonon generator.     

Unruh effect in a waveguide

Here we demonstrate that photons launched into a specially designed metamaterial waveguide act as massive quasi-particles, which experience strong acceleration. Laser light propagating through such a waveguide may be used as a thermometer which would measure the Unruh temperature. Moreover, the metamaterial waveguide design may be approximated by a tapered optical waveguide.     

Development of a self-oscillating ultrasonic micro-motor and its application to a watch

We have developed an ultrasonic micro-motor for use as a micro-actuator in place of an electromagnetic motor. This ultrasonic micro-motor, which can be driven by a single signal and in which the change of the direction of the rotor movement can be made easily by selecting the electrode to apply the driving signal, can easily construct a self-oscillating circuit and simplify the driving circuit. We have also simplified the motor structure, which is easy to miniaturize and mass-produce. We applied a version of this motor with a diameter of 8 mm to a vibration alarm, and one with a diameter of 4.5 mm to a driving source of a calendar mechanism in a watch. This ultrasonic micro-motor is expected to be of use as a new driving source in a broad range of fields.     

The design of a polarizing beam splitter made from a dielectric rectangular-groove grating

It has been reported that a polarizing beam splitter based on a rectangular-groove grating (a grating polarizing beam splitter) can be easily designed for specific applications using the modal method. In this paper, the eigenvalue equation of the modal method is transformed to a new form. Using this new form of the eigenvalue equation, it is shown that the design of a grating polarizing beam splitter can be independent of the incident wavelength. The period and the groove depth can be designed using values normalized to the incident wavelength, which apply to a range of wavelengths as long as the effects of dispersion can be neglected. Numerical simulations of fused silica gratings are presented and analyzed. It is concluded that the preferable choice for the grating period is 0.8–0.9 times the incident wavelength.     

Normal modes in a solitary wave solution to a double sine-Gordon equation

In a double sine-Gordon system the internal oscillations of a solitary wave solution can be viewed as normal modes in a number of sine-Gordon 2π-kinks and the ratio between the frequencies can be predicted. For three 2π-kinks this ration is √3.     

Rigorous solution of a problem for a cylindrical cavity containing a ferrite

Conclusions Equation (6) relates the complex frequency for a TM_nmo mode in a cylindrical cavity to the geometrical parameters, ferrite parameters, and volume and position of the specimen.Formula (6) is a generalization of characteristic equations previously derived [3, 4], which are of great value.The dispersion equation of (6) is of interest in that it allows one to calculate the effects of the dielectric parameters on the cavity, which is of value if a large tuning range is needed.Numerical results are rather laborious to obtain, but some valuable conclusions can be drawn in a relatively simple fashion, as will be shown in a forthcoming paper.     

Accurate color predictability based on a spectral retardance model of a twisted-nematic liquid-crystal display

In this work we present the application of a simple physical model to accurately predict the broadband spectral transmittance and colorimetric properties of a twisted-nematic liquid crystal display (TNLCD). We spectroscopically calibrate the retardance parameters to evaluate the spectrum of the light transmitted by a TNLCD sandwiched between two linear polarizers. When the TNLCD is illuminated with a broadband light source, the full spectrum can be predicted as a function of the addressed gray level for any arbitrary orientation of the polarizers. Thus, the color of the transmitted light can be also be estimated with very good accuracy. As an example, a polarizers' configuration is shown that yields, without using color filters, a relatively large color gamut compared to the standard configuration. Experimental results confirming the validity of such predictions are presented, both on the measured spectral responses as well as on the trajectories at different chromatic diagrams.     

Charging of a dust particle in a plasma with a nonextensive ion distribution function

The dust charge neutralization in a plasma with nonextensive ions is considered. The condition that the total current to a grain be zero is expressed in terms of the Lambert function. The fall-off of the net negative dust charge is then considered and a parameter study conducted, assuming hydrogen as well as argon plasma. Owing to ion nonextensivity, the dust charge reduction becomes much faster. Moreover, stronger is the ions correlation, more important is the involved electron depletion for a complete dust “decharging”.     

Estimation of a displacement parameter of a quantum system

A displacement parameter such as the angle of rotation or the position of a quantum system, or the phase of a harmonic oscillation, is to be estimated by observing the system with an apparatus that applies to it an operator-valued measure (o.v.m.). The o.v.m. minimizing the average cost of errors in the estimate is determined by quantum estimation theory for a system in a pure state. The best estimate of the parameter is found to be the more accurate, the greater the uncertainty of the dynamical variable serving as the infinitesimal generator of the displacement group. The relation of this result to such uncertainty principles as those between angle and angular momentum, and between oscillator phase and photon number, is discussed. A lower bound to the variance of an unbiased estimate of the time of occurrence of an event in the evolution of a system is derived from the quantum-mechanical Cramér-Rao inequality. It is inversely proportional to the square of the uncertainty of the energy of the system.     

Conservation of spin current as a consequence of a 2D Fermi surface

The possible existence of a previously unseen conservation in the theory of Fermi liquids is proposed for a two-dimensional geometry. If the ground state can be described by a smooth curve in momentum space then one expects spin current to be conserved, as it is not the case in three dimensions. Some immediate consequences that can be checked experimentally are pointed out.