Reflection of magneto-thermo-elastic waves from a rotating elastic half-space

Models of generalized magneto-thermo-elasticity based on the Lord-Shulman theory (LS) with one relaxation time, the Green-Lindsay theory (GL) with two relaxation times, as well as the classical dynamic coupled theory (CD), are used to study the electro-magneto-thermo-elastic interactions in a semi-infinite perfectly conducting solid. The elastic medium rotates with uniform angular velocity. The initial magnetic field is parallel to the boundary of the half-space. Reflection of magneto-thermo-elastic waves under generalized thermo-elasticity theory is studied. The reflection coefficients are obtained.     

The Effect of Magnetic Field on 2-D Problem for a Mode-I Crack of a Fiber-Reinforced in Generalized Thermoelasticity

In the present paper, the coupled theory, Lord–?hulman theory, and Green–Lindsay theory are introduced to study the influence of a magnetic field on the 2-D problem of a fiber-reinforced thermoelastic. These theories are also applied to study the influence of reinforcement on the total deformation of an infinite space weakened by a finite linear opening Mode-I crack. The material is homogeneous and an isotropic elastic half-space. The crack is subjected to a prescribed temperature and stress distribution. Normal mode analysis is used to solve the problem of a Mode-I crack. Numerical results for the temperature, the displacement, and thermal stress components are given and illustrated graphically in the absence and the presence of the magnetic field. A comparison between the three theories is also made for different depths.     

The Effect of Rotation on a Fiber-Reinforced Medium under Generalized Magneto-Thermoelasticity with Internal Heat Source

In the present article, we discussed the transient waves caused by a line heat source with a uniform velocity inside a rotating half-space fiber-reinforced thermoelastic media permeated into a uniform magnetic field. The formulation of the problem is applied under the coupled theory (CD), Green-Lindsay (G-L) theory, and Lord-Shulman (L-S) theory. The normal mode analysis is used to obtain expressions for the temperature, displacement components, and thermal stresses. Numerical results are given and illustrated graphically. A comparison is made with the results predicted by three theories in the presence and absence of magnetic field and rotation as well as fiber-reinforced.     

Magneto-rotation-fibre-reinforced thermoelastic with gravity and energy dissipation

In this article, two theories of the generalized thermoelasticity Green-Naghdi theory (of type II and III) are applied, as well as the coupled theory to study the effect of magnetic field and rotation under influence of gravity on 2D problem of a fibre-reinforced thermoelastic. The normal mode analysis is used to obtain the expressions for the temperature, displacement components and the thermal stresses distributions. The resulting formulation is applied for two different concrete problems. The first concerns the case of a punch moving across the surface of semi-infinite thermoelastic half-space subjected to appropriate boundary conditions. The second deals with a thick plate subjected to a time-dependent heat source on each face. Numerical results are illustrated graphically for each problem considered. A comparison is made with the results predicted obtained by the two theories in the presence and absence of magnetic field, rotation and gravity field.     

Geometric T–Ω approach to solve eddy currents coupled to electric circuits

This paper describes a systematic geometric approach to solve magneto‐quasi‐static coupled field–circuit problems. The field problem analysis is based on formulating the boundary value problem with an electric vector potential and a scalar magnetic potential. The field–circuit coupling and the definition of potentials are formally examined within the framework of homology theory. Copyright © 2007 John Wiley & Sons, Ltd.     

Energy coupled to matter for magnetic alignment of rare earth–doped alumina

Energy coupled to matter (ECM) concepts such as magnetic field–assisted processing were used to align rare earth–doped alumina ceramics in the presence of applied fields. The addition of gadolinium and ytterbium dopants to alumina increased the magnetic susceptibility anisotropies, and induced magnetic torques that led to significant alignment of ceramic particles under the application of magnetic fields as low as 1.8?T. In comparison, undoped alumina materials showed minimal alignment under applied field strengths as high as 9?T. Density function theory modeling indicated that the specific dopant type dictated changes in the magnetic properties of different rare earth–doped alumina systems by directly affecting the magnetic moment localization and magnetocrystalline anisotropy.     

The Effect of Mechanical Force on Generalized Thermoelasticity in a Fiber-Reinforcement Under Three Theories

The present paper is concerned with effect of mechanical force on generalized thermoelasticity in a fiber-reinforcement. The formulation is applied to generalized thermoelasticity based on the coupled theory, Lord–Shulman theory, and Green–Lindsay theory. The analytical expression of the displacement components, stresses, and temperature are obtained in the physical domain and illustrated graphically using normal mode analysis. Comparisons are made among the three theories for the field quantities in the absence and in the presence of a fiber-reinforcement as well as for different values of mechanical force.     

A study into statistical regularities of extinction of a DC electric arc in an axisymmetric magnetic field

A statistical investigation is performed of the extinction of a 30–350 A electric arc in a vacuum gap, in which permanent magnets are used to generate an axisymmetric magnetic field with different ratios between the radial and axial components of magnetic field induction. Dependences are given of the duration of stable arcing and limiting interruption currents on the magnetic field induction and on the size of contact gap.     

旋转半无限大体广义电磁热弹性耦合的二维问题

基于广义热弹性理论,研究了热和电可导的旋转半无限大体在其表面受随时间变化的热作用的广义电磁热弹性耦合的二维问题。半无限大体置于恒定的磁场中,受热作用产生膨胀变形,由于外加磁场的作用,介质中产生了感应的电场和感应的磁场。该文建立了电磁热弹性耦合的控制方程,利用正则模态法求解,得到了问题的解析解,并给出了各物理量的分布规律。可以看出,介质中呈现出电磁热弹耦合效应,由于旋转,位移和应力的幅值有很明显的降低,而旋转对温度和感应的磁场的影响不大。     

Bose-Einstein condensation and superfluidity of trapped polaritons in graphene and quantum wells embedded in a microcavity

The theory for spontaneous coherence of short-lived quasiparticles in two-dimensional excitonic systems is reviewed, in particular, quantum wells (QWs) and graphene layers (GLs) embedded in microcavities. Experiments with polaritons in an optical microcavity have already shown evidence of Bose-Einstein condensation (BEC) in the lowest quantum state in a harmonic trap. The theory of BEC and superfluidity of the microcavity excitonic polaritons in a harmonic potential trap is presented. Along the way, we determine a general method for defining the superfluid fraction in a two-dimensional trap, within the angular momentum representation. We discuss BEC of magnetoexcitonic polaritons (magnetopolaritons) in a QW and GL embedded in an optical microcavity in high magnetic field. It is shown that Rabi splitting in graphene is tunable by the external magnetic field B, while in a QW the Rabi splitting does not depend on the magnetic field in the strong B limit.     

Structural,Electrical and Magnetic Behaviour of FeTe0.5Se0.5 Superconductor

We report the synthesis as well as structural and physical properties of the bulk polycrystalline FeTe and FeTe_0.5Se_0.5 compounds. These samples are synthesised by the solid state-reaction method via vacuum encapsulation. Both studied compounds are crystallized in a tetragonal phase with space group P4/nmm. The parent FeTe compound shows an anomaly in resistivity measurement at around 78 K, which is due to the structural change along with a magnetic phase transition. The superconductivity in the FeTe_0.5Se_0.5 sample at 13 K is confirmed by the resistivity measurements. DC magnetisation along with an isothermal (M–H) loop shows that FeTe_0.5Se_0.5 possesses bulk superconductivity. The upper critical field is estimated through resistivity ρ (T,H) measurements using Gingzburg–Landau (GL) theory and is above 50 T with 50 % resistivity drop criterion. The origin of the resistive transition broadening under magnetic field is investigated by thermally activated flux flow. The magnetic field dependence of the activation energy of the flux motion is discussed.     

Specific heat jump of two-band superconductor KFe2As2 using Ginzburg-Landau theory

In this study specific heat jump using two-gap Ginzburg-Landau (GL) theory has been calculated. In contrast to the previous approaches, we have taken into account intergradient order parameters interaction in the GL free energy functional. The thermodynamic magnetic field revealed nonlinear temperature dependence due to interband interaction between order parameters and their gradients. The calculations showed that the specific heat jump in two-order parameter superconductors was smaller than that of single-order parameter superconductors. It has been shown that such a model is in good agreement with experimental data for KFe₂As₂ superconductors.     

Reflection and Refraction of Micropolar Magneto-thermoviscoelastic Waves at the Interface between Two Micropolar Viscoelastic Media

Using micropolar generalized thermoviscoelastic theories, problems of reflection and refraction of magneto-thermoeviscoelastic waves at the interface between two viscoelastic media are studied when a uniform magnetic field permeates the media. Coefficient ratios of reflection and refraction are obtained using continuous boundary conditions. Some special cases are considered, i.e., the absence of micropolar and viscous effects. By numerical calculations, variations of the amplitude ratios of reflection and refraction coefficients with the angle of incidence are shown graphically for incident rotational and dilatational waves at the interface between two media (one medium is aluminium-epoxy micropolar iscoelastic material, and the other is magnesium crystal micropolar viscoelastic material). Comparing the generalized thermoelastic theories developed by Lord and Shulman (LS) and by Green and Lindsay (GL) in this paper to conventional dynamics (CD) theory the effects of a magnetic field and viscosity are shown numerically in this paper.     

大挠度简支矩形薄板在热、力、磁耦合作用下的分岔与混沌

本文针对大挠度四边不可移简支薄板,研究其在机械载荷、电磁场与温度场耦合作用下的混沌运动。在板壳与磁弹性力学理论的基础上,考虑温度场的影响,推导出在横向稳恒磁场和机械载荷共同作用下薄板的非线性磁弹性耦合振动方程。利用Melnikov函数法,求出该动力系统Smale马蹄变换意义下出现混沌运动的条件,并对该系统振动方程进行数值模拟。通过具体算例,得到了系统的分岔图、位移波形图、相平面轨迹及庞加莱截面图,讨论了机械载荷、磁场以及温度场的参数对系统混沌运动的影响。由仿真结果可知,通过变化机械载荷、磁场和温度场参数,可以控制系统的振动特性。     

Using the third-order shear deformation theory to examine magnetic-mechanical buckling of a two-dimensional functionally graded cylindrical panel with longitudinal and circumferential stiffeners

In this study, the magnetic-mechanical buckling of a cylindrical panel made of two-dimensional functionally graded materials (2D-FGMs) has been investigated. The panel contains longitudinal and circumferential stiffeners and has been subjected to a uniform magnetic field as well as axial load. Material properties of the cylindrical panel are assumed to vary continuously in radial and thickness directions as a function of the volume fraction of the components. The magnetic field has been exerted radially. Equilibrium and stability equations have been derived using both Hamilton's principle and principle of minimum potential energy based on the third-order shear deformation theory (TSDT). The generalized differential quadrature method (GDQ) has been employed to solve the coupled differential equations. Moreover, the effect of geometry, load, magnitude of the magnetic field, number of stiffeners, and volume fraction coefficient on the critical buckling load has been determined. The results are in good agreement with the previous related works.     

Generalized electromagneto-thermoviscoelastic in case of 2-D thermal shock problem in a finite conducting medium with one relaxation time

Summary. This paper studies the problem of two-dimensional electromagneto-thermovisco-elasticity based on Lord-Shulman theory for a thermally and electrically conducting half-space solid whose surface is subjected to a thermal shock. There acts an initial magnetic field parallel to the plane boundary of the half-space. The medium deforms because of thermal shock and due to the application of the magnetic field, it results in induced magnetic and electric fields in the medium. The normal mode analysis is used to obtain the exact expressions for the considered variables. The distributions of the temperature, displacement, stress, induced magnetic and electric fields are represented graphically. Comparisons are made with the results predicted by both the coupled theory and with the theory of generalized thermo-viscoelasticity with one relaxation time.     

The frozen-field approximation and the Ginzburg-Landau equations of superconductivity

The Ginzburg-Landau (GL) equations of superconductivity provide a computational model for the study of magnetic flux vortices in type-II superconductors. In this article it is shown through numerical examples and rigorous mathematical analysis that the GL model reduces to the frozen-field model when the charge of the Cooper pairs (the superconducting charge carriers) goes to zero while the applied field stays near the upper critical field.     

An analytical solution for the effect of initial stress,rotation, magnetic field and a periodic loading in a thermo-viscoelastic medium with a spherical cavity

In this article, an analytical solution for the effect of initial stress, the rotation, and the relaxation times in a magneto-thermo-viscoelastic homogeneous medium with a spherical cavity subjected to periodic loading is presented. The distribution of displacements, temperature, and stresses in a homogeneous medium, in the context of generalized thermo-elasticity using the Green-Lindsay (GL) theory is discussed and obtained in analytical form. The results are displayed graphically to illustrate the effect of initial stress, the rotation, relaxation times, magnetic field, and viscoelasticity. Comparisons are made with the previous work in the absence of rotation and initial stress.     

Magnetoresistance of Carbon Nanotube with the Kane Dispersion Law

Abstract

Considering the nanotube as effective conducting media the magnetoresistance is calculated. For an electron motion along nanotube axis the spin–orbital interaction is considered as perturbation and the Dirac equation is solved for longitudinal wave functions. It is shown that in this case a magnetic field can be considered as perturbation for energy spectrum and density matrix diagonal components for each spin orientation are needed to calculate the nanotube conductivity. For narrow gap nanotube the magnetoresistance depends linearly on a weak magnetic field. Our results show that in nanotubes the negative magnetoresistance (NMR) can be described without theory of weak localization.