Radial motion of a solid spherical body in a magnetic field

The object of the present paper is to investigate the radial motion of a solid spherical body, assumed to be homogeneous, isotropic and elastic, in presence of a magnetic field in the azimuthal direction. The body is assumed to be in a state of initial stress which is hydrostatic in nature. This theory of radial motion of a solid spherical body in a magnetic field has been utilised to find the small radial motion of a solid Earth assumed to be homogeneous isotropic elastic sphere in presence of a magnetic field in the azimuthal direction. Considering the effect of gravity and the initial stress produced by slow process of creep due to extra masses over the surface of the Earth, the fundamental equations of motion are derived which are non-linear in character and are solved. The times of a desired radial displacement are calculated in presence of a magnetic field only and in presence of the same magnetic field, initial stress and gravitational field, which are compared and exhibited numerically.     

Dielectric alignment of a non-polar molecule substituting a polar molecule in a lattice of molecular dipoles

The dielectric alignment of a dilute non-polar component in a polar solvent may be determined by NMR spectroscopy. In this paper a series expansion of the alignment up to second order terms in the dipolar interaction is presented for a non-polar molecule replacing a single polar molecule in a rigid lattice of molecular dipoles. Assuming isotropic polarizabilities for all molecules Van Vleck earlier applied the lattice model in a theory of the dielectric constant of a dilute solution.In the present calculation the polarizabilities of the non-polar molecule and the dipoles are assumed to be anisotropic and isotropic, respectively. The anisotropy of the non-polar molecule is relevant, since the value of the alignment is zero for the isotropic case. Different results are obtained for cubic lattices and for a lattice points are uniformly distributed.In absence of a rigid dipole moment of the solvent molecules the latter formula may be compared with that implicity deduced by Buckingham for the Kerr effect. In the limit of strong dipoles the orientation imposed by the rigid dipole moments appears to be the major contribution to the alignment of the non-polar molecule.     

Design and analysis of a scaled model of a high-rise, high-speed elevator

A novel scaled model is developed to simulate the linear lateral dynamics of a hoist cable with variable length in a high-rise, high-speed elevator. The dimensionless groups used to formulate the scaling laws are derived through dimensional analysis. The model parameters are selected based on the scaling laws and are subject to the material, size, and hardware constraints. It is demonstrated that while it is impossible to obtain a fully scaled model unless the model is extremely tall, a reasonably sized model can be designed and the scaling laws that are not satisfied can be rendered to have a minimal effect on the scaling between the model and prototype. In conjunction with the model design, an analysis of model tension in a closed band loop is developed. A new movement profile that ensures a continuous jerk function during the entire period of motion is derived. The dynamic response of the prototype cable and that of the model band under consideration are compared numerically. Practical considerations that occur in the design of the model are addressed. The methodology can be used to investigate the vibration of a very long cable in other applications.     

Electrostatic End-Plugging of a Plasma in a Cusp-Shaped Magnetic Field Composed of a Magnet Array

An end-loss of a plasma through a cusp-shaped magnetic field is experimentally investigated to be plugged by an electrostatic potential barrier. The main plasma is contained in a surface magnetic field whose one end is of cusp geometry. The potential barrier is set up near the cusp region by a production of another independent plasma whose space potential is controllable. The effects of the potential barrier on the end-plugging are studied with a measurement of the decay time of an after-glow plasma. It is observed that the decay time is improved by 2 ~ 3 times longer than that without the potential barrier. The experimental results are found to be consistent with preliminary estimated values.     

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.     

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.     

Thickness Determination for a Two-Layered Composite of a Film and a Plate by Low-Frequency Ultrasound

We present an ultrasonic method for determining the thickness of a composite consisting of a soft thin film attached to a hard plate substrate, by resonance spectra in the low frequency region, The interrogating waves can be incident only to the two-layered composite from the substrate side. The reflection spectra are obtained by FFT analysis of the compressive pulsed echoes from the composite, and the thicknesses of the film and the substrate are simultaneously inversed by the simulated annealing method from the resonant frequencies knowing other acoustical parameters in prior. The sensitivity of the method to individual thickness, its convergence and stability against experimental noises are studied, Experiment with interrogating wavelength 4 times larger than the film thickness in a sample of a polymer film （0.054mm） on an aluminium plate （6.24mm） verifies the validity of the method. The average relative errors in the measurement of the thicknesses of the film and the substrate are found to be -4.1% and -0.62%, respectively.     

Study of a bulk-Micromegas with a resistive anode

The design and performance of a Micromegas with a resistive anode are presented in this paper. A thin resistive sheet with volume resistivity of 10¹² Ω·m cm is glued onto the readout electrode surface and its performance is investigated by using a ⁵⁵Fe X-ray radioactive source in the operation gas of argon and isobutene mixtures (Ar/Iso=95/5). The gas gain at different mesh high voltage, counting rate and working time are given. Energy spectra at different working voltages are measured and the results are discussed. We have oberved that a Micromegas with a resistive anode can be operated at higer gain than a standard Micromegas without sparks.     

Stability of a charged particle in a combined Penning-Ioffe trap

The axial symmetry of a familiar Penning trap is broken by adding the radial magnetic field of an Ioffe trap. Despite the resulting loss of a confinement theorem, stable orbits related to adiabatic invariants are identified, expressions are given for their frequencies, and resonances that must be avoided are characterized. It seems feasible to experimentally realize the new Penning-Ioffe trap to test these theoretical predictions. It also may be possible to simultaneously confine cold positrons and antiprotons in a Penning-Ioffe trap, along with any cold antihydrogen they may form.     

Theoretical analysis of the formation of a layered ice structure at the surface of a plate placed in a flow of a supercooled water aerosol

The motion of the front of crystallization and the growth of a film at the surface of a plate are analyzed in the case of a laminar and in the case of a turbulent flow mode. Conditions are determined under which there occurs a transition from a matt inhomogeneous structure to a transparent homogeneous structure of ice. It is shown that, for a film to be steadily preserved at the plate surface, the film thickness must be larger than a critical equilibrium-thickness value h _b.c, in which case a transparent homogeneous structure of ice is formed. Otherwise, the film at the plate surface is unstable and disappears in the course of time. The icing of aircrafts is the most important application of the results obtained in this study.     

Dynamics of a charged particle in a linearly polarized traveling wave

The basic physical processes in laser-matter interaction, up to (for a neodymium laser) are now well understood, on the other hand, new phenomena evidenced in PIC code simulations have to be investigated above . Thus, the relativistic motion of a charged particle in a linearly polarized homogeneous electromagnetic wave is studied, here, using the Hamiltonian formalism. First, the motion of a single particle in a linearly polarized traveling wave propagating in a non-magnetized space is explored. The problem is shown to be integrable. The results obtained are compared to those derived considering a cold electron plasma model. When the phase velocity is close to c, it is shown that the two approaches are in good agreement during a finite time. After this short time, when the plasma response is taken into account no chaos take place at least when considering low densities and/or high wave intensities. The case of a charged particle in a traveling wave propagating along a constant homogeneous magnetic field is then considered. The problem is shown to be integrable when the wave propagates in vacuum. The existence of a synchronous solution is shown very simply. In the case when the wave propagates in a low density plasma, using a simplifying Lorentz transformation, it is shown that the system can be reduced to a time-dependent system with two degrees of freedom. The system is shown to be nonintegrable, chaos appears when a secondary resonance and a primary resonance overlap. Finally, stochastic instabilities are studied by considering the motion of one particle in a very high intensity wave perturbed by one or two low intensity traveling waves. Resonances are identified and conditions for resonance overlap are studied.     

Equilibrium of a gravitating plasma in a dipolar magnetic field

The equilibria of plasma in a dipolar magnetic field under the gravitational influence of a massive body (a star or black hole) and a self gravitating plasma are considered. Analytical solutions are found that can be useful for understanding the physics of plasma flows in accretion disks and star formation.     

Scattering from a rough layer of a random medium

This paper deals with scattering from a random-medium layer with rough boundaries. The fluctuations of the surface heights and medium permittivity are assumed to be small and smooth. All random quantities are assumed to be stationary and independent of each other. After the introduction of approximate boundary conditions, the system of partial differential equations is transformed into an integral equation where the fluctuations of the problem are represented as a zero-mean random operator. Employing smoothing, integral equations for the coherent fields are obtained. Use of the Helmholtz operator leads to solution for the coherent propagation constant while the boundary operators lead to coherent Fresnel coefficients. The characteristics of the results are illustrated by considering several examples.     

Propagation of a few-cycle laser pulse in a V-type three-level system

Propagation of a few-cycle laser pulse in a V-type three-level system (fine structure levels of rubidium) is investigated numerically. The full three-level Maxwell-Bloch equations without the rotating wave approximation and the standing slowly varying envelope approximation are solved by using a finite-difference time-domain method. It is shown that, when the usual unequal oscillator strengths are considered, self-induced transparency cannot be recovered and higher spectral components can be produced even for small-area pulses.     

The character of cooperative low-frequency oscillations in a model of a biopolymer

The oscillations in a model of a biopolymer are calculated under various excitation conditions. Relatively slow cooperative motions, which can be used to simulate conformational transitions in a biological macromolecule from one stable state to another, are analyzed.     

Vibration analysis of a wheel composed of a ring and a wheel-plate modelled as a three-parameter elastic foundation

The free in-plane vibrations of circular rings with wheel-plates as generalised elastic foundations are studied using analytical methods and numerical simulations. The three-parameter Winkler elastic layer is proposed as a mathematical model of the foundation. The effects of rotary inertia and shear deformation are included in the analytical model of the system. The motion equations of systems are derived on the basis of the thin ring theory and Timoshenko?s theory. The separation of variables method is used to find general solutions to the free vibrations. Elaborated analytical models are used to determine the natural frequencies and the natural mode shapes of vibrations of an arbitrarily chosen set of simplified models of aviation gears and railway wheels. The eigenvalue problem is formulated and solved by using a finite element representation for each simplified model. The results for these models are discussed and compared. The proposed solutions are verified by experimental investigation. It is important to note that the solutions proposed here could be useful to engineers dealing with the dynamics of aviation gears, railway wheels and other circular ring systems.     

Infrared detection of a planet next to a bright star

Humans have always dreamt about the possibility of existence of planets in solar systems other than our own. After flying by, dropping probes, and even landing devices on most planets within our own solar system, the search for extra-solar planet is included in every proposal to either build a larger and better earth-, space-, or moon-based telescope, or observatory facility. The preliminary analysis seems to indicate that wavelength band from 25 μm to 30 μm is most promising in solving this problem. A number of IR technological challenges are to be overcome before the actual detection system can even be considered in a detailed design. The significant technical challenges of finding a planet will be described. Then details are given on the feasibility of detecting a planet with an instrument concept designed specifically for this purpose, a space-based, rotating rotationally shearing interferometer.     

遗传算法在激光器谐振腔优化设计中的应用

讨论了用遗传算法优化设计普通激光器谐振腔参量的方法.以典型的50 cm长的氦氖(He-Ne)激光器为例,进行了具体计算.结果表明:对于输出相同的激光功率,模拟优化的谐振腔参量与传统局域化设计(非优化)的结果基本一致.通过适当匹配谐振腔参量,仍可提高激光(单模)的输出功率.     

Evolution of a randomly modulated breather in a nonlinear medium

The evolution of a randomly modulated sine-Gordon breather in a nonlinear medium is studied theoretically. The initial wave field is affected by multiplicative noise. For breather amplitude and velocity, the probability distribution function is determined by means of the inverse scattering transform and the method of cumulants. The distributions are shown to be non-Gaussian. The mean and the most probable values of the breather amplitude and velocity are calculated.     

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.