A novel photothermal excitation cracked medium in gravitational field with two-temperature and hydrostatic initial stress

A New Approach model for a theory of two temperature with finite linear opening Mode-I crack inside a semi-infinite semiconducting medium is presented. The mechanical force influence during the photothermal process with the influence of gravity and hydrostatic initial stress in two dimensions are used. The transient compressive stress wave travels along the crack from the loading region to the crack face. Using mathematical methods under the purview of different three theories (Lord–?hulman (LS) includes one relaxation time, Green–Lindsay (GL) includes two relaxation times, and the classical dynamical coupled theory (CD)). The exact expression of the physical quantities and the two temperature coefficient ratios are obtained analytically using the harmonic wave technique and illustrated graphically. Comparisons between the results of the three theories are also introduced.     

Temperature anisotropy relaxation of the one‐component plasma

The relaxation rate of a Maxwellian velocity distribution function that has an initially anisotropic temperature (T _‖≠T _⊥) is an important physical process in space and laboratory plasmas. It is also a canonical example of an energy transport process that can be used to test theory. Here, this rate is evaluated using molecular dynamics simulations of the one‐component plasma. Results are compared with the predictions of four kinetic theories; two treating the weakly coupled regime, namely (a) the Landau equation, and (b) the Lenard–Balescu equation, and two that attempt to extend the theory into the strongly coupled regime, namely (c) the effective potential theory and (d) the generalized Lenard–Balescu theory. The role of dynamic screening is studied, and is found to have a negligible influence on this transport rate. Oscillations and a delayed relaxation onset in the temperature profiles are observed at strong coupling, which are not described by the kinetic theories.     

Photothermal waves for two temperature with a semiconducting medium under using a dual-phase-lag model and hydrostatic initial stress

The dual-phase-lag (DPL) model with two different time translations and Lord–Shulman (LS) theory with one relaxation time are applied to study the effect of hydrostatic initial stress on medium under the influence of two temperature parameter(a new model will be introduced using two temperature theory) and photothermal theory. We solved the thermal loading at the free surface in the semi-infinite semiconducting medium-coupled plasma waves with the effect of mechanical force during a photothermal process. The exact expressions of the considered variables are obtained using normal mode analysis also the two temperature coefficient ratios were obtained analytically. Numerical results for the field quantities are given in the physical domain and illustrated graphically under the effects of several parameters. Comparisons are made between the results of the two different models with and without two temperature parameter, and for two different values of the hydrostatic initial stress. A comparison is carried out between the considered variables as calculated from the generalized thermoelasticity based on the DPL model and the LS theory in the absence and presence of the thermoelastic and thermoelectric coupling parameters.     

Nuclear magnetic resonance from a quasi two dimensional fluid

Pulsed Fourier transform nuclear magnetic resonance spectra of a quasi two-dimensional fluid, neopentane adsorbed upon graphite, have been measured. Large upfield chemical shifts arising from the diamagnetic anisotropy of the graphite substrate have been observed for the fluid phase and are consistent with the two-dimensional character of the layer. The shifts allow an estimate of the mean molecule-surface distance to be made. Diffusion constant measurements show an enhanced translational mobility compared with the bulk liquid at the same temperature. Spin-lattice and spin-spin relaxation time measurements cannot be explained by the theory of spin relaxation in bulk liquids but are in qualitative agreement with the behaviour predicted by theories of nuclear spin relaxation in two dimensions.     

The role of mosaic block structure on onset of deformation and fatigue of bulk crystallized polyethylene

The influence of the mosaic block structure of bulk-crystallized high-density polyethylene upon deformation within the elastic limit and upon fatigue phenomenon has been extensively studied in the temperature range of the α relaxation mechanism. The magnitude of elastic limit, estimated from two models involving a tilt sliding mechanism and a simple tension mechanism, was compared with experimental results obtained using a tensile tester and a dynamic viscoelastometer at various temperatures of measurement. The two models for onset of deformation are applied on the assumption that the intermosaic block region is selectively affected by strain without any structural change occurring in the mosaic block crystalline core. Also, dynamic mechanical properties were obtained on specimens subject to an increasing number of fatigue cycles. The variation of E'1, max, attributed to deformation processes of the intermosaic block region, is strongly affected by slight elongation and by fatigue cycling of the sample. A direct observation of the mosaic block structure is made with the electron microscope using a detachment replica of the surface of the bulk crystallized material, that has been elongated by 15% at 55°C in biaxial directions.     

The effect of rotation on plane waves in generalized thermo-microstretch elastic solid with one relaxation time for a mode-I crack problem

The present paper is aimed at studying the effect of rotation on the general model of the equations of the generalized thermo-microstretch for a homogeneous isotropic elastic half-space solid,whose surface is subjected to a Mode-I crack problem.The problem is studied in the context of the generalized thermoelasticity Lord-S hulman’s (L-S) theory with one relaxation time,as well as with the classical dynamical coupled theory (CD).The normal mode analysis is used to obtain the exact expressions for the displacement components,the force stresses,the temperature,the couple stresses and the microstress distribution.The variations of the considered variables through the horizontal distance are illustrated graphically.Comparisons of the results are made between the two theories with and without the rotation and the microstretch constants.     

Charge carrier sorting over energy in semiconductors by means of phonon diffusion

A study is made of anomalous temperature fields which occur in finite semiconductor specimens. These fields are created by charge carrier sorting over energy due to mutual electron-phonon entrainment at arbitrary rates of electron and phonon energy relaxation at the boundaries. Expressions are found for entrainment levels which depend on specimen dimensions, cooling length, and electron and phonon energy relaxation rates at the boundaries, which when exceeded cause the electron temperature differential between the boundaries to exceed the temperature differential between the heater T₁ and cooler T₂, producing an initiating phonon flux, while for scattering on deformation acoustical phonons these differentials have opposite algebraic sign. In the case where the electrons are thermally insulated, while the phonons have ideal thermal contact with heater and cooler, for total entrainment the electron temperature differential produced by charge carrier sorting over energy due to phonon entrainment is an order of magnitude higher than T₁-T₂, and produces the major contribution to thermo-emf in sufficiently short specimens.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 36–41, February, 1988.In conclusion the authors express their deep gratitude to Yu. G. Gurevich for his interest in the study and fruitful discussions.     

Influence of low temperature on the surface deformation of deformable mirrors

The two factors which influence the low temperature performance of deformable mirrors(DMs) are the piezoelectric stroke of the actuators and the thermally induced surface deformation of the DM. A new theory was proposed to explain the thermally induced surface deformation of the DM: because the thermal strain between the actuators and the base leads to an additional moment according to the theory of plates, the base will be bent and the bowing base will result in an obvious surface deformation of the facesheet. The finite element method(FEM) was used to prove the theory. The results showed that the thermally induced surface deformation is mainly caused by the base deformation which is induced by the coefficient of thermal expansion(CTE) mismatching; when the facesheet has similar CTE with the actuators, the surface deformation of the DM would be smoother. Then an optimized DM design was adopted to reduce the surface deformation of the DMs at low temperature. The low temperature tests of two 61-element discrete PZT actuator sample deformable mirrors and the corresponding optimized DMs were conducted to verify the simulated results. The results showed that the optimized DMs perform well.     

Outer-sphere nuclear spin relaxation in paramagnetic systems: a low-field theory

A low-field theory for paramagnetic relaxation enhancement (PRE), appropriate for the outer-sphere relaxation, is presented for the electron spin quantum number S = 1, 3/2, 2, 5/2, 3 and 7/2. The theory is used to calculate the PRE at low magnetic field, as a function of the translational diffusion coefficient, for various values of the electron spin quantum number, for small and fairly large values of the static zero-field splitting (ZFS), and for a given set of parameters determining the electron spin relaxation. We have found earlier that the static ZFS has a profound influence on the electron spin relaxation; such effects are also evident in the present study. Comparisons are made with other existing models for the outer-sphere PRE, and significant differences are found for slowly diffusing systems with large ZFS. The theory is also used to obtain a novel interpretation of experimental data for an acetone solution of a Mn(III) complex.     

Homotopy algebra morphism and geometry of classical string field theories

We discuss general properties of classical string field theories with symmetric vertices in the context of deformation theory. For a given conformal background, there are many string field theories corresponding to different decomposition of moduli space of Riemann surfaces. It is shown that any classical open string field theories on a fixed conformal background are A_∞-quasi-isomorphic to each other. This indicates that they have isomorphic moduli space of classical solutions. The minimal model theorem in A_∞-algebras plays a key role in these results. Its natural and geometric realization on formal supermanifolds is also given. The same results hold for classical closed string field theories, whose algebraic structures are governed by L_∞-algebras.     

Phase space geometry in scalar-tensor cosmology

We study the phase space of spatially homogeneous and isotropic cosmology in general scalar-tensor theories. A reduction to a two-dimensional phase space is performed when possible—in these situations the phase space is usually a two-dimensional curved surface embedded in a three-dimensional space and composed of two sheets attached to each other, possibly with complicated topology. The results obtained are independent of the choice of the coupling function of the theory and, in certain situations, also of the potential.     

Nonlinear instability of charged liquid jets: Effect of interfacial charge relaxation

A linear and nonlinear study has been made of cylindrical interface, carrying a uniform surface charge in the presence of a finite rate of charge relaxation, is investigated by using multiple scales method. The linear stability flow is analyzed by deriving a dispersion relation for the growth waves, and solving it analytically and numerically to find marginal stability curves. We investigate the electric charge relaxation effects on the stability of the flow by considering various limiting cases. We also examine the effects of finite charge relaxation times in axisymmetric and nonaxisymmetric modes. In the nonlinear approach, it is shown that the evolution of the amplitude is governed by a Ginzburg–Landau equation. There is also obtained a nonlinear modified Schrödinger equation describing the evolution of wave packets for small charge relaxation time. Further, the classic Schrödinger equation is obtained when the influence of relaxation time charge is neglected. On the other hand, the complex amplitude of quasi-monochromatic standing waves near the cutoff wavenumber is governed by a similarly type of nonlinear Schrödinger equation in which the roles of time and space are interchanged. This equation makes it possible to estimate the nonlinear effect on the cutoff wavenumber. The nonlinear theory, when used to investigate the stability of charged liquid jet, appears accurately to predict a new unstable regions. The effects of the surface charge and charge relaxation on the stability are identified. The various stability criteria are discussed both analytically and numerically and the stability diagrams are obtained.     

On crystal shear,lattice rotation and constraint stress in (1 1 0) channel die compression: rate-independent and viscoplastic analyses and predictions compared

Rate-independent crystal plasticity theory and a classic viscoplastic power-law are investigated, contrasted and compared for finite deformation analysis of fcc crystals in channel die compression, including full consideration of lattice straining. Both experiment-based anisotropic and isotropic (Taylor) hardenings are evaluated in rate-independent theory; and an unlimited range of power-law exponent n is considered in viscoplasticity. The focus is on predictions of lateral constraint stress, lattice rotation and crystal shear, and their comparison with experiment. General elastic-plastic equations (for both theories) are given for the range of unstable lattice orientations in (1?1?0) compression (‘range I’) and evaluated before and after a finite rotation of the lattice about the load axis. Equations also are given and evaluated for the ‘Brass’ orientation. It is shown that the theories can be in close agreement at the onset of finite deformation in range I, but that viscoplasticity gives results (for any n) after finite rotation that are in sharp contrast to rate-independent theory. The latter’s predictions for crystal shear and lattice rotation are in good to very good agreement with finite deformation experiments on aluminium and copper. The inclusion of lattice elasticity is found to have a negligible effect in range I. In contrast, for finite deformation in the stable Brass orientation, elastic-viscoplastic theory can be made to agree very closely with rate-independent theory and with experiment.     

A study of the disperse-particle hardening of EI702 steel

A study was made of aging EI702 austenitic steel. It was shown that the nature of the changes in the mechanical properties (deformation resistance, coefficient of hardening) with duration of aging is determined by the initial state of the material and the temperature of aging, two factors which determine the mechanism of decomposition.The effect of precipitation hardening of EI702 steel is analyzed on the basis of the existing theories of hardening by dispersed particles.     

Influence of thickness shear deformation on free vibrations of rectangular plates,cylindrical panels and cylinders of antisymmetric angle-ply construction

This paper is concerned with the influence of thickness shear deformation and rotatory inertia on the free vibrations of antisymmetric angle-ply laminated circular cylindrical panels. Two kinds of thickness shear deformable shell theories are considered. In the first one, uniformly distributed thickness shear strains through the shell thickness and, therefore, thickness shear correction factors are used. In the second theory a parabolic variation of thickness shear strains and stresses with zero values at the inner and outer shell surfaces is assumed. The analysis is mainly based on Love's approximations but, for purposes of comparison, Donnell's shallow shell approximations are also considered. For a simply supported panel, the equations of motion of the aforementioned theories, as well as of the corresponding classical theories, are solved by using Galerkin's method. For a family of graphite-epoxy angle-ply laminated plates and circular cylindrical panels, numerical results are obtained, compared and discussed and some interesting conclusions are made regarding the shell theories considered as well as the mathematical method employed.     

Dependence of hot carriers temperature on lattice temperature in CdS

Non-equilibrium carrier distributions were obtained in CdS at various temperatures from 77 to 400K. A study is made of the influence of the lattice temperature on the carrier temperature. It is found that the higher the lattice temperature the lower is the difference between carrier and lattice temperatures, though carriers are always thermalized among themselves. The results can be accounted for by carrier relaxation through optical polar phonon emission.     

Thermal Stress Analysis of a Continuous and Pulsed End-Pumped Nd:YAG Rod Crystal Using Non-Classic Conduction Heat Transfer Theory

In this paper, temperature distribution in the continuous and pulsed end-pumped Nd:YAG rod crystal is determined using nonclassical and classical heat conduction theories. In order to find the temperature distribution in crystal, heat transfer differential equations of crystal with consideration of boundary conditions are derived based on non-Fourier’s model and temperature distribution of the crystal is achieved by an analytical method. Then, by transferring non-Fourier differential equations to matrix equations, using finite element method, temperature and stress of every point of crystal are calculated in the time domain. According to the results, a comparison between classical and nonclassical theories is represented to investigate rupture power values. In continuous end pumping with equal input powers, non-Fourier theory predicts greater temperature and stress compared to Fourier theory. It also shows that with an increase in relaxation time, crystal rupture power decreases. Despite of these results, in single rectangular pulsed end-pumping condition, with an equal input power, Fourier theory indicates higher temperature and stress rather than non-Fourier theory. It is also observed that, when the relaxation time increases, maximum amounts of temperature and stress decrease.     

Temperature dependent statistical theory of two spin cross relaxations

A temperature dependent statistical theory of cross relaxation between two different spin systems is presented. An exact evaluation is made for the magnetic resonance line shape due to the diagonal part of the dipolar interaction at arbitrary temperatures. The cross relaxation transition probability is found to be inversely proportional to the Zeeman energy imbalance when it is large compared to dipolar energy. This seems to agree with the Mims experiment on Ruby in the negative frequency range.     

Nonlinear acoustic spectroscopy of carbonate rocks

The paper presents the results of experimental research into the nonlinear acoustic properties of carbonate rocks depending on saturation. The linear acoustic properties of the same sample depending on saturation were presented earlier in Physical Acoustics. The previously obtained data point to the isotropy of the material, which makes it possible to restrict analysis to only two vibration modes. Responses for finite deformations were measured for the longitudinal and shear modes of an isotropic sample, which made it possible to analyze the nonlinear properties of macroscopic deformations with a change in volume and pure displacement. A heretofore unknown feature of the response was revealed for finite deformation values; it is related to the occurrence of a jumplike transition from classical nonlinearity to a hysteresis type of nonlinearity. As well, the deformation amplitude corresponding to the transition depends on fluid saturation. We studied the slow relaxation that occurs after long-term excitation of a sample with a deformation amplitude on the order of 10^?6. Data are presented on relaxation for deformation from pure displacement and deformation with a change in volume, which made it possible to isolate features related to the type of deformation and to compare the obtained data with the earlier published theoretical model. These data are compared with the results of other research groups.