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1 – 10 of over 3000Mohamed I.A. Othman, W.M. Hasona and Elsayed M. Abd-Elaziz
The purpose of this paper is to introduce the coupled theory, Lord-Shulman theory with one relaxation time and Green-Lindsay theory with two relaxation times to study the…
Abstract
Purpose
The purpose of this paper is to introduce the coupled theory, Lord-Shulman theory with one relaxation time and Green-Lindsay theory with two relaxation times to study the influence of rotation on generalized micropolar thermoelasticity subject to thermal loading due to laser pulse. The bounding plane surface is heated by a non-Gaussian laser beam with pulse duration of 8 ps.
Design/methodology/approach
The problem has been solved numerically by using the normal mode analysis.
Findings
The thermal shock problem is studied to obtain the exact expressions for the displacement components, force stresses, temperature, couple stresses and micro-rotation. The distributions of the considered variables are illustrated graphically. Comparisons are made with the results predicted by three theories in the presence and absence of laser pulse and for different values of time.
Originality/value
Generalized micropolar thermoelastic solid.
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The purpose of this paper is to study the transient waves caused by a line heat source with a stable internal heat source inside isotropic homogenous thermoelastic perfectly…
Abstract
Purpose
The purpose of this paper is to study the transient waves caused by a line heat source with a stable internal heat source inside isotropic homogenous thermoelastic perfectly conducting half‐space permeate into a uniform magnetic field. The formulation is applied under three theories of generalized thermoelasticity Lord‐Shulman (L‐S) theory with one relaxation time, Green‐Lindsay (G‐L) theory with two relaxation times, as well as the classical dynamical coupled theory. The problem is reduced to the solution of three differential equations by introducing the elastic and thermoelastic potentials.
Design/methodology/approach
The normal mode analysis is used to obtain the expressions. Numerical results are given and illustrated graphically. Comparisons are made with the results predicted by the three theories in the presence and absence of magnetic field and the internal heat source.
Findings
The results are graphically described for the medium of copper. We can conclude that the magnetic field has a great effect on the displacement components and this effect produces the same trend under the three theories. The results show that the relaxation times have salient effect to the distribution of displacement at small values of time.
Originality/value
The present theoretical results may provide interesting information for experimental scientists /researchers/seismologist working on this subject.
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Rajneesh Kumar and Geeta Partap
The propagation of free vibrations in microstretch thermoelastic homogeneous isotropic, thermally conducting plate bordered with layers of inviscid liquid on both sides subjected…
Abstract
The propagation of free vibrations in microstretch thermoelastic homogeneous isotropic, thermally conducting plate bordered with layers of inviscid liquid on both sides subjected to stress free thermally insulated and isothermal conditions is investigated in the context of Lord and Shulman (L‐S) and Green and Lindsay (G‐L) theories of thermoelasticity. The secular equations for symmetric and skewsymmetric wave mode propagation are derived. The regions of secular equations are obtained and short wavelength waves of the secular equations are also discussed. At short wavelength limits, the secular equations reduce to Rayleigh surface wave frequency equations. Finally, the numerical solution is carried out for magnesium crystal composite material plate bordered with water. The dispersion curves for symmetric and skew‐symmetric wave modes are computed numerically and presented graphically.
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Mohamed I.A. Othman and Elsayed M. Abd-Elaziz
The purpose of this study is to obtain a general solution to the field equations of thermoelastic solid with voids and micro-temperatures under the gravitational field in the…
Abstract
Purpose
The purpose of this study is to obtain a general solution to the field equations of thermoelastic solid with voids and micro-temperatures under the gravitational field in the context of the three theories, namely, coupled theory (CT), Lord and Shulman theory and Green and Lindsay theory.
Design/methodology/approach
The normal mode analysis is used to obtain the exact expressions for the considered variables. Comparisons are made with the results obtained in the three theories with and without gravity. Some particular cases are also deduced from the present investigation.
Findings
The effect of the gravity on the displacement, the micro-temperature vector, the temperature distribution, the normal stress, the changes in the volume fraction field and the heat flux moments have been depicted graphically.
Research limitations/implications
Some particular cases are also deduced from the present investigation.
Originality/value
The results of the physical quantities have been illustrated graphically by a comparison between three different theories in the presence and absence of gravity.
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Badi H. Baltagi, Chihwa Kao and Long Liu
This paper studies test of hypotheses for the slope parameter in a linear time trend panel data model with serially correlated error component disturbances. We propose a test…
Abstract
This paper studies test of hypotheses for the slope parameter in a linear time trend panel data model with serially correlated error component disturbances. We propose a test statistic that uses a bias corrected estimator of the serial correlation parameter. The proposed test statistic which is based on the corresponding fixed effects feasible generalized least squares (FE-FGLS) estimator of the slope parameter has the standard normal limiting distribution which is valid whether the remainder error is I(0) or I(1). This performs well in Monte Carlo experiments and is recommended.
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Mohamed I.A. Othman and Kh. Lotfy
The purpose of this paper is to formulate a model of the equations of a two‐dimensional problem with the deformation of micropolar generalized thermoelastic medium with voids…
Abstract
Purpose
The purpose of this paper is to formulate a model of the equations of a two‐dimensional problem with the deformation of micropolar generalized thermoelastic medium with voids under the influence of various sources in the context of the Lord‐Shulman, Green‐Lindsay theories, as well as the classical dynamical coupled theory.
Design/methodology/approach
The normal mode analysis was used to obtain the exact expressions of the displacement components, force stress, coupled stress, change in volume fraction field and temperature distribution. Numerical results were given and illustrated graphically when the volume source was applied.
Findings
The presence of voids plays a significant role on all the physical quantities. The value of normal displacement and normal force stress increases while the temperature, tangential force stress and the couple stress increase and then decrease due to the presence of voids. The value of all the physical quantities converges to zero with increase in distance z.
Originality/value
Comparisons are made with the results predicted by the three theories in the presence and the absence of material constants due to voids.
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Himanshu Singla and Baljeet Singh
The purpose of this paper is to analyze the propagation characteristics of the Rayleigh-type surface wave in a thermally conducting mixture of an elastic solid and a Newtonian…
Abstract
Purpose
The purpose of this paper is to analyze the propagation characteristics of the Rayleigh-type surface wave in a thermally conducting mixture of an elastic solid and a Newtonian fluid by applying the mixture theory.
Design/methodology/approach
The governing equations are formulated in context of both Green–Lindsay (G-L) and Lord–Shulman (L-S) theories of generalized thermoelasticity. The specialized governing equations in a plane are solved by using the traditional approach, and a dispersion equation of the Rayleigh surface wave is obtained.
Findings
A program in MATLAB software is developed to solve the dispersion equation. The numerical results demonstrate a significant dependence of the wave speed and the attenuation coefficient of the Rayleigh wave on the frequency and porosity.
Originality/value
The problem considered on Rayleigh wave on the surface of a half-space containing a thermally conducting mixture is not studied in the literature yet. The theoretical and numerical findings of the study will guide the experimental scientists while finding applications in various engineering fields.
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The present investigation is concerned with a two‐dimensional problem in electromagnetic micropolar elasticity for a half‐space whose surface is subjected to mechanical or thermal…
Abstract
The present investigation is concerned with a two‐dimensional problem in electromagnetic micropolar elasticity for a half‐space whose surface is subjected to mechanical or thermal source in the presence of a transverse magnetic field. Laplace and Fourier transform technique is used to solve the problem. As an application of the approach concentrated/continuous mechanical or thermal source has been taken. The integral transforms have been inverted by using a numerical technique to obtain the components of normal strain, temperature distribution, normal force stress and tangential couple stress in the physical domain. The expressions of these quantities have been given and illustrated graphically to depict the magnetic effect for two different theories of generalized thermoelasticity, Lord and Shulman (L‐S theory) and Green and Lindsay (G‐L theory). Some special cases of interest are also deduced from the present investigation.
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George Lennox Sharman Shackle is now in his 82nd year having been born on 14 July 1903. Yet during the 25 years that I have known him (beginning when I was an undergraduate at the…
Abstract
George Lennox Sharman Shackle is now in his 82nd year having been born on 14 July 1903. Yet during the 25 years that I have known him (beginning when I was an undergraduate at the University of Liverpool in 1957) he has hardly seemed to change at all, in physical appearance, in temperament, and in his attitude to his work: retirement is a word that does not enter his vocabulary. In appearance, Professor Shackle lives up to the popular image: out of any crowd, “the man in the street” would have no hesitation in identifying him as a professor. He looks the true scholar (rounded glasses and all), benign, self‐contained, appearing absent‐minded, preoccupied with higher thoughts. Since, indeed, he has altered so little over the years it is difficult to think of him as having had to pass through the “ages of man”. As he has done so, however, his temperament has also hardly changed. He is a most modest and kind person, ever willing to assist those, young and old, who seek his help with the unravelling of economic theory. As with all true scholars and researchers of distinction, Professor Shackle's byword is humility.
Mohamed I.A. Othman and Montaser Fekry
The purpose of this paper is to study the effect of rotation and gravity on a homogeneous, isotropic, and generalized thermo-viscoelastic material with voids. The problem is…
Abstract
Purpose
The purpose of this paper is to study the effect of rotation and gravity on a homogeneous, isotropic, and generalized thermo-viscoelastic material with voids. The problem is studied in the context of the coupled theory, Lord-Shulman theory with one relaxation time, and Green-Lindsay theory with two relaxation times.
Design/methodology/approach
The analytical method used was the normal mode analysis technique.
Findings
Numerical results for the physical quantities were analyzed and presented graphically. The graphical results indicated that the effects of rotation and gravity were observable physical effects on the thermo-viscoelastic material with voids. Comparisons were made between the results obtained in the absence and presence of rotation and gravity.
Originality/value
In the present work, the authors investigated the effect of rotation and gravity on thermo-viscoelastic medium with voids. Comparisons were also made between the three theories in the absence and the presence of rotation and gravity. Such problems are very important in many dynamical systems.
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