Electrical conduction of a thin cylindrical wire in a longitudinal magnetic field

The electric conductivity of a metallic cylindrical wire in a longitudinal magnetic field is calculated. The case when the radius of the wire is much smaller than its length is considered. As the boundary condition of the problem, the condition of diffuse reflection of electrons from the inner surface of the wire is adopted. Limiting cases are considered and the results are discussed.     

Detection of positive and negative ions in a wire ionization counter filled with atmospheric air

The physical processes occurring during the detection of individual ions in a wire counter filled with atmospheric air are studied, and the amplitude distribution of electric pulses is measured. It is shown that a positive ion is detected due to electron emission from the surface of a negatively charged wire, whereas a negative ion is detected due to electron detachment near a positively charged wire. The secondary processes accompanying the neutralization of positive ions at a negatively charged external electrode and negatively charged wire are considered. It is established that, in contrast to standard proportional counters, these secondary processes result in an increase in the number of electric pulses rather than in an increase in the electric pulse amplitude. The wire counter allows the detection of both ions produced inside the detector and ions injected into the detector from the ambient air. Possible applications of air-filled wire detectors are described.     

Wire coating by withdrawal from a bath of fourth order fluid

This Letter looks an analysis for withdrawal of cylinder. The flow depends upon the wire velocity. The fluid considered is a fourth order fluid. The problem is modeled using cylindrical coordinates for velocity and pressure distributions. The solution of the governing equation is obtained using homotopy analysis method (HAM). The variations of the velocity, volume flow rate, radius of coated wire, shear stress and force on the total wire are presented graphically and discussed for emerging non-Newtonian parameter.     

A peculiarity of diffraction measurements using a Gaussian laser beam

Numerical modelling of the Gaussian beam diffraction by a wire near the Fraunhofer limit is presented. Two cases are considered: the case of the wire being on the axis of the beam and the case of the wire being off-axis. For the case where the wire is on the axis, the displacements of the diffracted minima are calculated. For the off-axis case, the changes in the positions of the maxima and minima and the power density are calculated. The conditions are determined at which the measurements made using a Gaussian beam can be calculated using the formula for plane waves. This work arises in connection with research being performed into the Doppler spectrum of big particles.     

Current Collection by a Long Wire in Near-Earth Orbit

Investigation of the current collected by a long wire in space has application to long antennas and the proposed space shuttle tethered subsatellite. Langmuir's result for current collection by a moving probe in a plasma is used to obtain expressions for the voltage and current as functions of position along a wire. Two cases are considered: firstly, one end of the wire is grounded to the plasma and secondly, the wire is allowed to assume a natural grounding point. Results are obtained as a function of the wire resistivity, length and diameter for various particle densities. Calculations for a 2mm diameter copper wire show that a current of 0.066 amperes of oxygen ions will be collected by a tether of 10 km in length.     

Polarons in a cylindrical quantum well wire with finite confining potential

The polaron self-energy and the correction to the electron effective mass in a cylindrical quantum well wire (QWW) are studied by the perturbation approach. The interactions of electrons with different phonon modes in the QWW system, including the confined longitudinal optical phonon modes, in the wire (LO1), in the barrier materials (LO2) and in the interface optical (IO) phonon modes, are considered. The result shows that the LO1 phonon’s contribution to the polaron self-energy increases gradually as the radius of the wire increases, and finally reaches that of the three-dimensional limit, while the LO2 phonon contributes only when the radius of the wire is very small. Also, the contribution of the IO phonon modes first increases quickly as the wire radius increases and soon reaches a maximum, then reduces to zero monotonically.     

基于连续弹性理论分析量子线线宽对应变分布和带隙的影响

基于连续弹性理论分别采用数值方法和格林函数法讨论了量子线的应变分布.格林函数法可以得到应变分布的解析表示式,对规则形状的量子线的应变分布计算比较方便;连续弹性理论采取的是数值解法,结果精度不如格林函数法,但是能方便计算任意形状量子线的应变分布情况, 并可以考虑不同材料的弹性常数的影响.文章还具体讨论了量子线线宽对应变分布和带隙的影响,结果表明：沿线宽方向,应变的绝对值逐渐减小,并随线宽的增加而变大;带隙则随线宽的减小而增大. 关键词： 连续弹性理论 格林函数法 应变 带隙     

Influence of water conductivity on shock waves generated by underwater electrical wire explosion

The new application of electrical explosion of wire (EEW) used in petroleum industry is to enhance oil recovery (EOR). Because of the complex environment underground, the effect of underground water conductivity on EEW should be considered. This work describes the effect of water conductivities on discharge current, voltage and shock waves. It was found that the effect of water conductivity contains two parts. One is the shunt effect of saline water, which can be considered as a parallel load with the copper wire between the electrodes connected to the discharge circuit. The peak pressure of shock waves are gradually decrease with the increase of water conductivity. The other is the current loss through saline water directly to the ground ends without flowing through the electrodes. The shunt effect is the main factor affecting the wire discharge process. As the charging voltage increased, the energy loss caused by these two parts are all reduced. These indicate that increasing the charging voltage to a certain value will increase the energy efficiency to generate a more powerful shock waves in conductive water.     

Electron Raman scattering in cylindrical quantum wires

Electron Raman scattering (ERS) is investigated in a free-standing semiconductor quantum wire of cylindrical geometry for two classes of materials CdS and GaAs. The differential cross section (DCS) involved in this process is calculated as a function of a scattering frequency and the radius of the cylinder. Electron states are considered to be confined within a free-standing quantum wire (FSW). Single parabolic conduction and valence bands are assumed. The selection rules are studied. Singularities in the spectra are found and interpreted for various radii of the cylinder.     

On reflection from interfaces with some spatially dispersive metamaterials

Plane-wave reflection from interfaces with single and double wire media is considered. Such media exhibit strong spatial dispersion even at very low frequencies which causes appearance of additional waves. The problem of additional boundary conditions (ABC) in application to wire media is discussed and an ABC-free approach, known in solid state physics, is used. Expressions for the fields and Poynting vectors of refracted waves are derived. The directions and values of the power density flow of refracted waves are found and conservation of the power flow through the interface is checked.     

The phonon effects on the impurity states in cylindrical quantum wire with a finite confining potential

The variational method and the effective mass approximation are applied to calculate the binding energies of the hydrogenic impurity states in a cylindrical quantum wire with finite deep potential well. The phonon effects on the impurity states are considered by taking both the couplings of the electron-phonon and the impurity ion-phonon into account. The numerical results for the GaAs cylindrical quantum wire are given and discussed. It is found that the ion-phonon interaction reduces the impurity binding energy and supplies key contribution to the energy shift, but the electron-phonon coupling enhances the binding energy less. Longitudinal optical (LO) phonons play more important role than interface optical (IO) phonons in the impurity potential screening. The polaron effect caused by LO phonons is more important when the wire is thinner, otherwise the LO phonons are dominant for the thicker wires.     

Electrons in a curvilinear quantum wire

The adiabatic motion of electrons in curvilinear quantum wires was studied. It was assumed that the cross section of a wire was constant along its length. The potential that limited electron motion across a wire and the shape of the cross section of the wire were considered arbitrary, while the curvature and the torsion (defined as the derivative of the cross section rotation angle with respect to the length) were assumed to be small. An effective nonrelativistic Hamiltonian for the motion of electrons along a wire with the conservation of transverse quantum numbers was obtained. The spin-orbit coupling Hamiltonian related to the curvature and torsion of a wire was found. Particular cases of a rectilinear twisted quantum wire with a noncircular cross section and a curvilinear quantum wire on a plane were studied. Various transverse potential models limiting the motion of electrons were considered. In particular, the coefficients of the effective Hamiltonian for quantum wires with rectangular and circular cross sections and hard walls and for wires with a parabolic potential were found.     

Hot wire anemometer response in a flow with acoustic disturbances

The response of a hot wire to acoustic disturbances in a low velocity flow is considered, taking account of disturbances in flow temperature, density, velocity and pressure. It is shown that operation at a fixed wire temperature requires that contributions other than that due to velocity disturbances alone have a net effect which increases with mean flow speed. Elimination of the effects of pressure, density and temperature disturbances so that the wire indicates only the velocity disturbance of the acoustic wave may be achieved by operating the wire at a selected temperature. This optimal wire temperature decreases as the mean flow velocity increases.     

Optical and photoelectric properties of helical quantum wires

The appearance of a steady current in a helical quantum wire under circularly polarized light is predicted. The effect is associated with the appearance of a travelling electromagnetic wave in the coordinate system related to the wire, the wavelength being determined by the period of the helix. The gyrotropy of a medium consisting of parallel quantum wires is considered.     

The mobility of charge carriers in a size-quantized coated semiconductor wire

Within the framework of a staircase infinitely deep potential well model, the mobility of charge carriers is calculated for scattering on impurity centers located on the axis of a size-quantized semiconducting coated wire. Calculations are done for the dielectric constant mismatch of the wire, coating and surrounding environment, taking into account the difference of the effective masses in the wire and coating. The effect of a longitudinal magnetic field on mobility is also considered. Numerical results are presented for the GaAs–Ga_1−xAl_xAs system at different values of the wire and coating radii, the alloy concentration x, and magnetic field.     

Spin Polarization and Andreev Conductance through a Diluted Magnetic Semiconductor Quantum Wire with Spin--Orbit Interaction

Spin-dependent Andreev reflection and spin polarization through a diluted magnetic semiconductor quantum wire coupled to normal metallic and superconductor electrodes are investigated using scattering theory. When the spin-orbit coupling is considered, more Andreev conductance steps appear at the same Fermi energy. Magnetic semiconductor quantum wire separates the spin-up and spin-down electrons. The Fermi energy, at which different- spin-state electrons begin to separate, becomes lower due to the effect of the spin-orbit interaction. The spin filter effect can be measured more easily by investigating the Andreev conductance than by investigating the normal conductance.     

Informational contenet of the high order diffraction pattern

The information content of the diffraction pattern in the region of very high orders is considered. It is shown that high order diffraction pattern represents a superresolution width indicator of the particle track in nuclear emulsion. A principally new experimental setup designed for width measurements of the wires and particle tracks is described. The first experiments performed for tungsten wire as an object are presented. It is shown that the relative error of the measurement made by this new technique is as small as 0.03% for tungsten wire of the diameter ≅26 μm. The article is published in the original.     

Effect of surface scattering of charge carriers on the high-frequency conductivity of a thin cylindrical semiconductor wire

The problem of high-frequency conductivity of a thin cylindrical semiconductor wire has been solved by the kinetic method. The diffuse-specular mechanism of reflection of charge carriers from the inner surface of the wire has been considered. Calculations have been performed for an n-type (p-type) nondegenerate semiconductor with a standard spherically symmetric energy band. The ratio between the cross-section radius of the wire and the mean free path of charge carriers is assumed to be arbitrary.     

Phonon-assisted absorption of hypersound in a rectangular quantum wire

The mechanisms of the Landau-Rumer process and of the process of two-phonon decay of microwave phonons are considered for a rectangular quantum wire. For GaAs wires with a free surface and various transverse dimensions, the coefficients of absorption of confined microwave phonons of the lowest hybrid width mode are calculated. The phononic and electronic mechanisms of hypersound absorption in rectangular wires and unbounded solids are compared. At low temperatures, the inclusion of cubic anharmonicity in a wire leads to an exponential temperature dependence of the hypersound absorption for the Landau-Rumer process and to the dominant absorption due to decay processes; in the latter case, the exponent of the frequency dependence decreases. At sufficiently high temperatures, the phonon-assisted absorption dominates over the electron-assisted absorption in a quantum wire of a nondegenerate material.     

Structural stability and electronic properties of GaSb nanowires

The structural stability and electronic properties of four different shapes of GaSb nanowire have been studied by ab-initio method using the generalized gradient approximations. The different structures were two atom linear wire, two atom zigzag wire, four atom square wire and six atom hexagonal wire. The geometry optimization and the stability of all nanowires were investigated. We explore the minimum energy atomic configuration for all the considered shapes. We find that four atom square wire configuration has greater stability in comparison to other shapes. The analysis of density of states and band structures of optimized nanowires predicts that semiconducting nanowires may be metallic or semiconducting. The behavior entirely depends upon the geometrical structure.