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2,044 results on '"Melnik, Roderick"'

352. Thermo-Mechanical Wave Propagation In Shape Memory Alloy Rod With Phase Transformations

Author

Wang, Linxiang and Melnik, Roderick V. N.

Subjects
Condensed Matter - Materials Science, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

Many new applications of ferroelastic materials require a better understanding of their dynamics that often involve phase transformations. In such cases, an important prerequisite is the understanding of wave propagation caused by pulse-like loadings. In the present study, a mathematical model is developed to analyze the wave propagation process in shape memory alloy rods. The first order martensite transformations and associated thermo-mechanical coupling effects are accounted for by employing the modified Ginzburg-Landau-Devonshire theory. The Landau-type free energy function is employed to characterize different phases, while a Ginzburg term is introduced to account for energy contributions from phase boundaries. The effect of internal friction is represented by a Rayleigh dissipation term. The resulted nonlinear system of PDEs is reduced to a differential-algebraic system, and Chebyshev's collocation method is employed together with the backward differentiation method. A series of numerical experiments are performed. Wave propagations caused by impact loadings are analyzed for different initial temperatures. It is demonstrated that coupled waves will be induced in the material. Such waves will be dissipated and dispersed during the propagation process, and phase transformations in the material will complicate their propagation patterns. Finally, the influence of internal friction and capillary effects on the process of wave propagation is analyzed numerically., Comment: Keywords: nonlinear waves, thermo-mechanical coupling, martensite transformations, Ginzburg-Landau theory, Chebyshev collocation method

Published
2007
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365. Discovery and Assessment of New Target Sites for Anti-HIV Therapies

Author

Breward, Chris, Heffernan, Jane, Robert M., Miura, Madras, Neal, Ockendon, John, Sørensen, Mads Peter, Anderssen, Robert, Melnik, Roderick, McGuinness, Mark, Qazi, Sanjive, Breward, Chris, Heffernan, Jane, Robert M., Miura, Madras, Neal, Ockendon, John, Sørensen, Mads Peter, Anderssen, Robert, Melnik, Roderick, McGuinness, Mark, and Qazi, Sanjive

Published
2008

374. Preface

Author

Tesdall, Allen M., primary, Jung, Jae-Hun, additional, Kotsireas, Ilias, additional, and Melnik, Roderick, additional

Published
2013
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375. Numerical Model For Vibration Damping Resulting From the First Order Phase Transformations

Author

Wang, Linxiang X., Melnik, Roderick V. N., Wang, Linxiang X., and Melnik, Roderick V. N.

Abstract

A numerical model is constructed for modelling macroscale damping effects induced by the first order martensite phase transformations in a shape memory alloy rod. The model is constructed on the basis of the modified Landau-Ginzburg theory that couples nonlinear mechanical and thermal fields. The free energy function for the model is constructed as a double well function at low temperature, such that the external energy can be absorbed during the phase transformation and converted into thermal form. The Chebyshev spectral methods are employed together with backward differentiation for the numerical analysis of the problem. Computational experiments performed for different vibration energies demonstrate the importance of taking into account damping effects induced by phase transformations., Comment: Keywords: martensite transformation, thermo-mechanical coupling, vibration damping, Ginzburg-Landau theory

Published
2007

377. Tuning -factor of electrons through spin-orbit coupling in GaAs/AlGaAs conical quantum dots.

Author

Prabhakar, Sanjay and Melnik, Roderick

Subjects
*GALLIUM arsenide, *QUANTUM dots, *SPIN-orbit interactions, *QUANTUM logic, *LOGIC circuits, *ELECTRONS, *ELECTRONIC band structure
Abstract

We investigate band structures of three-dimensional conical quantum dots (QDs). In particular, we explore the influence of the Rashba and Dresselhaus spin-orbit couplings in the variation of effective -factor of electrons in such QDs. We demonstrate that the interplay between the Rashba and Dresselhaus spin-orbit couplings can provide further insight into underlying physical phenomena and assist in the design of quantum logic gates for the application in spintronic devices. [ABSTRACT FROM AUTHOR]

Published
2016
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378. Three Dimensional Metallic Carbon from Distorting sp³-Bond.

Author

Yong Cheng, Melnik, Roderick, Yoshiyuki Kawazoe, and Bin Wen

Subjects
*CARBON, *CHEMICAL bonds, *CHEMICAL potential, *CHEMICAL synthesis, *ORBITAL hybridization
Abstract

Owing to the outstanding properties of metallic carbon as well as their great potential applications, design and synthesis of metallic carbon have long attracted considerable attention. In this work, a new three-dimensional metallic carbon (dubbed as Tri-C9) has been built by distorting the sp³ hybridization bond. Our first-principles calculations results indicate that Tri-C9 is a metastable metallic carbon, and that the metallic behavior of Tri-C9 originates from the π bonds near Fermi level. This study offers a new way to design all-sp³ hybridized metallic carbon via distorting the sp³-bond. In addition, a feasible synthesis route for Tri-C9 has been proposed by compressing graphite. [ABSTRACT FROM AUTHOR]

Published
2016
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380. Gate-controlled electron spins in quantum dots.

Author

Prabhakar, Sanjay, Melnik, Roderick, and Bonilla, Luis L.

Subjects
*ELECTRON spin, *QUANTUM dots, *MAGNETIC fields, *FINITE element method, *SPIN-orbit interactions, *THERMAL conductivity, *SEMICONDUCTORS
Abstract

In this paper we study the properties of anisotropic semiconductor quantum dots (QDs) formed in the conduction band in the presence of the magnetic field. The Kane-type model is formulated and is analyzed by using both analytical and finite element techniques. Among other things, we demonstrate that in such quantum dots, the electron spin states in the phonon-induced spin-flip rate can be manipulated with the application of externally applied anisotropic gate potentials. More precisely, such potentials enhance the spin flip rates and reduce the level crossing points to lower quantum dot radii. This happens due to the suppression of the g-factor towards bulk crystal. We conclude that the phonon induced spin-flip rate can be controlled through the application of spin-orbit coupling. Numerical examples are shown to demonstrate these findings. [ABSTRACT FROM AUTHOR]

Published
2013
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