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Mean free path
About: Mean free path is a research topic. Over the lifetime, 4412 publications have been published within this topic receiving 114418 citations.
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TL;DR: New heat-conduction equations, named ballistic-diffusive equations, which are derived from the Boltzmann equation are presented, showing that the new equations are a better approximation than the Fourier law and the Cattaneo equation for heat conduction at the scales when the device characteristic length is comparable to the heat-carrier mean free path.
Abstract: We present new heat-conduction equations, named ballistic-diffusive equations, which are derived from the Boltzmann equation. We show that the new equations are a better approximation than the Fourier law and the Cattaneo equation for heat conduction at the scales when the device characteristic length, such as film thickness, is comparable to the heat-carrier mean free path and/or the characteristic time, such as laser-pulse width, is comparable to the heat-carrier relaxation time.
499 citations
TL;DR: In this paper, the elastic energy propagation in a three dimensional infinite elastic medium, in which scatterers are distributed homogeneously and randomly, is investigated by a statistical method, and a space-time distribution of the mean energy density of the scattered waves is obtained as Es(r, t)=(W 0/4πlVtr)1n((Vt+r)/(Vt-r)) for Vt≥r, where r is the distance from the source and W 0 is the total energy radiated.
Abstract: The elastic energy propagation in a three dimensional infinite elastic medium, in which scatterers are distributed homogeneously and randomly, is investigated by a statistical method. A single isotropic scattering process is investigated. The elastic medium is characterized by the wave velocity V and the distribution of the scatterers is characterized by the mean free path l. It is assumed that the elastic energy is radiated spherically from the source at a time t=0 in a short time duration. A space-time distribution of the mean energy density of the scattered waves is obtained as Es(r, t)=(W0/4πlVtr)1n((Vt+r)/(Vt-r)) for Vt≥r, where r is the distance from the source and W0 is the total energy radiated. A uniform spatial distribution is constructed far behind the wave front and near the source. The mean energy density Es is proportional to t-2 for t_??_2r/V and independent of r and W0. Several important properties of coda waves observed near the hypocenter are explained qualitatively by this solution when heterogeneities in the earth are interpreted as the scatterers and Es corresponds to the power spectrum of coda waves.
458 citations
TL;DR: The phonon thermal conductivity of a multilayer is calculated for transport perpendicular to the layers and it is shown that the conductivity has a minimum value for a layer thickness somewhat smaller then the mean free path of the phonons.
Abstract: The phonon thermal conductivity of a multilayer is calculated for transport perpendicular to the layers. There is a crossover between particle transport for thick layers to wave transport for thin layers. The calculations show that the conductivity has a minimum value for a layer thickness somewhat smaller then the mean free path of the phonons.
456 citations
02 May 2000-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, a review of matter transformation induced in crystalline inorganic insulators by swift heavy ions is presented, with the emphasis on new results obtained for amorphizable materials such as Gd3Ga5O12, GeS, and LiNbO3 and for nonamorphizable crystals such as SnO2, LiF and CaF2.
Abstract: A review of matter transformation induced in crystalline inorganic insulators by swift heavy ions is presented. The emphasis is made on new results obtained for amorphizable materials such as Gd3Ga5O12, GeS, and LiNbO3 and for non-amorphizable crystals such as SnO2, LiF and CaF2. Assuming that latent tracks result from a transient thermal process, a quantitative development of a thermal spike is proposed. The only free parameter is the electron–lattice interaction mean free path λ. With this parameter it is possible to quantitatively describe track radii, whatever the bonding character of the crystal is, in a wide range of ion velocities assuming two specific criteria: tracks may result from a rapid quenching of a cylinder of matter in which the energy deposited on the lattice has overcome either the energy necessary to reach a quasi-molten phase in the case of amorphizable materials or the cohesion energy in the case of non-amorphizable materials. The evolution of the λ parameter versus the band gap energy of the considered insulator will be presented. On the basis of this discussion some predictions are developed.
425 citations
TL;DR: In this paper, the authors present experimental evidence that the room temperature thermal conductivity (kappa) of individual multiwalled carbon and boron-nitride nanotubes does not obey Fourier's empirical law of thermal conduction.
Abstract: We present experimental evidence that the room temperature thermal conductivity (kappa) of individual multiwalled carbon and boron-nitride nanotubes does not obey Fourier's empirical law of thermal conduction. Because of isotopic disorder, kappa's of carbon nanotubes and boron-nitride nanotubes show different length dependence behavior. Moreover, for these systems we find that Fourier's law is violated even when the phonon mean free path is much shorter than the sample length.
420 citations