Global ETD Search
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Showing 1 to 16 of 16 for “"two temperature model"”.
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Modeling of high enthalpy flows for hypersonic re-entry and ground-based arc-jet testing
This work presents a simulation framework for modeling high enthalpy ionized gas flows during planetary entry flights and ground-based arc-jet testing. The system of Favre-averaged Navier-Stokes equations in thermo-chemical non-equilibrium with Spalart-Allmaras turbulence closure is outlined, along …
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Photoinduced dynamics studied by ultrafast single-shot pump-probe spectroscopy
… are discussed. In particular, we have invented a two-stage dual-beam noncollinear optical parametric amplifier to provide tunable sources for pump-probe spectroscopy. Next, the experimental setup of dual-echelon single-shot spectroscopy is illustrated with great detail and possible noise sources …
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Real-Time Dynamics of Electrons and Phonons from First Principles
… by equilibrium theories or phenomenological models such as the two-temperature model. This dissertation develops and applies a real-time, ab initio framework based on the time-dependent Boltzmann equation (TDBE) to investigate coupled electron–phonon dynamics in crystalline solids from …
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Molecular dynamic simulation of xenon bubble re-solution in uranium dioxide
This is a comprehensive study of two mechanisms of fission gas bubble re-solution in UO2 by molecular dynamics (MD) simulations: homogeneous re-solution and heterogeneous re-solution. For the homogeneous mechanism, a hybrid approach is employed whereby Monte Carlo (MC) simulations are used to …
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Energy relaxation in disordered insulators irradiated by ultrafast protons: a multiscale approach
… begin with a phenomenological extension of the two-temperature model, which characterises the relaxation using two time-scales; a rapid electron-phonon relaxation rate and a longer "chemical" relaxation rate linked to the decay of self-trapped excitons. This extended TTM correctly describes the …
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Effects of vacancies and electron temperature on the electron phonon coupling in cubic silicon carbide and their connection to the inelastic thermal spike
… Perturbation Theory - Classical Electron Gas model. The coupling factor was calculated as a function of electron temperature in pristine and defective 3C-SiC, and relaxed defective cells. The electron-phonon coupling is found to depend strongly on the electronic temperature and on the presence …
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The Effects of Temperature Slip on the Modeling of Systems With Heterogeneous and Homogeneous Reactions
In this research project, the effects of temperature slip are investigated in systems of low-pressure chemical vapor deposition (LPCVD), combustion synthesis, and catalytic combustion. The relations for the estimation of temperature slip are reviewed, and the influences of temperature slip on the …
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Photoinduced phase transitions and irreversible dynamics studied with single-shot spectroscopy
… range of systems are discussed. Experiments and modeling of photoinduced phase transitions in two classes of systems, semimetals and manganites, are presented. Both systems show collective structural change under photoexcitation that ultimately results in a low-symmetry to high-symmetry phase …
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Temporal dynamics of hot-electrons in metal films and alloys
… surface plasmon coupling with the conventional two-temperature model. Our results show that coupling to the propagating surface plasmon enhances the hot-carrier relaxation time due to the electric field confinement within a gold film. Finally, we explore the relaxation time of the excited …
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Vibrationally enhanced associative photodesorption of H2 (D2) from Ru(0001) : quantum and classical approaches
… of the desorption process is studied using a two-mode reduced dimensionality model with one vibrational coordinate and one translational coordinate of the adsorbate. The ground and excited electronic state potentials, and dipole function for the IR excitation are taken from first principles. …
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Ultrashort laser pulse-matter interaction: Fundamentals and early stage plasma dynamics
… energy coupling with different materials.^ A two-dimensional comprehensive hydrodynamic model for USLP ablation of metals and semiconductors is developed in this study. The model comprises a two-temperature model and a hydrodynamic model supplemented with a quotidian equation of state model, …
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Dynamics of Energy Carriers in Solids During Interaction with Ultrafast Laser Pulses
… and analyzing the measured signals with the two-temperature model (TTM), it is found that during the transient heating process, when electrons and phonons are in thermal nonequilibrium state, electrons in metal thin films can directly transfer energy to phonons in dielectric substrates. In …
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Photothermal properties and applications of gold nanorods
… bromide (CTAB) on the surface and exhibit two SPR peaks ranging from 500 to 900 nm depending on the aspect ratio of the GNRs. The surface of the GNRs can be modified by different ligands or polyelectrolyte layers in the aqueous environment. GNRs can also be immobilized on different …
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Reduced-order modeling of non-Boltzmann thermochemistry and radiation for hypersonic flows
… Traditional thermochemical and radiative models often introduce ad-hoc simplifications and rely on model parameters calibrated for a limited range of experimental conditions. Recent advances in computing power have allowed non-equilibrium internal state population distributions of gaseous …
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Using high pressure to study thermal transport and phonon scattering mechanisms
… from material interfaces. The heat flux per unit temperature drop across an interface is quantified by the interface thermal conductance. This conductance is difficult to study, as it is comprised of at least three components: bond stiffness at the interface, non-equilibrium resistance near the …
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Molecular Dynamics study of defect evolution mechanisms in material of interests for quantum technologies [Studio di Dinamica Molecolare dei meccanismi di evoluzione dei difetti nei materiali di interesse per le tecnologie quantistiche]
Abbiamo studiato la formazione e l'evoluzione dei difetti nel 3C–SiC utilizzando simulazioni di dinamica molecolare classica con potenziali interatomici dipendenti dall'ambiente. Il benchmarking preliminare ha incluso parametri reticolari, energie di formazione dei difetti e calcoli del punto di …