The Experts below are selected from a list of 176169 Experts worldwide ranked by ideXlab platform
Natalio Mingo - One of the best experts on this subject based on the ideXlab platform.
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the atomistic green s Function method an efficient simulation approach for nanoscale phonon transport
Numerical Heat Transfer Part B-fundamentals, 2007Co-Authors: W Zhang, Timothy S Fisher, Natalio MingoAbstract:This article presents a general formulation of an atomistic Green's Function (AGF) method. The atomistic Green's Function approach combines atomic-scale fidelity with asymptotic treatment of large-scale (bulk) features, such that the method is particularly well suited to address an emerging class of multiscale transport problems. A detailed mathematical derivation of the phonon Transmission Function is provided in terms of Green's Functions and, using the Transmission Function, the heat flux integral is written in Landauer form. Within this theoretical framework, the required inputs to calculate heat flux are equilibrium atomic locations and an appropriate interatomic potential. Relevant algorithmic and implementation details are discussed. Several examples including a homogeneous atomic chain and two heterogeneous atomic chains are included to illustrate the applications of this methodology.
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thermal conductivities of individual tin dioxide nanobelts
Applied Physics Letters, 2004Co-Authors: Li Shi, Xiangyang Kong, Qing Hao, Natalio Mingo, Zheng WangAbstract:We have measured the thermal conductivities of a 53-nm-thick and a 64-nm-thick tin dioxide (SnO2) nanobelt using a microfabricated device in the temperature range of 80–350 K. The thermal conductivities of the nanobelts were found to be significantly lower than the bulk values, and agree with our calculation results using a full dispersion Transmission Function approach. Comparison between measurements and calculation suggests that phonon–boundary scattering is the primary effect determining the thermal conductivities.
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thermoelectric figure of merit and maximum power factor in iii v semiconductor nanowires
Applied Physics Letters, 2004Co-Authors: Natalio MingoAbstract:The relative contributions of electronic and lattice effects to figure of merit enhancement are studied, for nanowires made of InSb, InAs, GaAs, and InP, as a Function of nanowire thickness. The main thermoelectric magnitudes are computed in the bulk and nanowire cases by the exact solution of the Boltzmann transport equation. The lattice thermal conductivity is obtained by a full dispersions Transmission Function approach, using interatomic potentials for the system. An upper limit to the maximum power factor is obtained for narrow thickness. InSb nanowires stand out as the best choice for thermoelectric applications among the four compounds considered, while GaAs and InP are not expected to be suitable for practical applications.
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thermal conductivities of individual tin dioxide nanobelts
Volume!, 2004Co-Authors: Li Shi, Xiangyang Kong, Qing Hao, Natalio Mingo, Zheng WangAbstract:We have measured the thermal conductivities of a 53-nm-thick and a 64-nm-thick tin dioxide (SnO2 ) nanobelt using a microfabricated device in the temperature range of 80–350 K. The uncertainty of the measurement result was estimated to be 10 percent. The thermal conductivities of the nanobelts were found to be significantly lower than the bulk values, and agree with our calculation results using a full dispersion Transmission Function approach. Comparison between measurements and calculation suggests that phonon-boundary scattering is the primary effect determining the thermal conductivities.© 2004 ASME
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calculation of si nanowire thermal conductivity using complete phonon dispersion relations
Physical Review B, 2003Co-Authors: Natalio MingoAbstract:The lattice thermal conductivity of crystalline Si nanowires is calculated. The calculation uses complete phonon dispersions, and does not require any externally imposed frequency cutoffs. No adjustment to nanowire thermal conductivity measurements is required. Good agreement with experimental results for nanowires wider than 35 nm is obtained. A formulation in terms of the Transmission Function is given. Also, the use of a simpler, nondispersive ``Callaway formula,'' is discussed from the complete dispersions perspective.
Liliana Arrachea - One of the best experts on this subject based on the ideXlab platform.
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optimal thermoelectricity with quantum spin hall edge states
Physical Review Letters, 2019Co-Authors: Daniel Gresta, Mariano Real, Liliana ArracheaAbstract:We study the thermoelectric properties of a Kramers pair of helical edge states of the quantum spin Hall effect coupled to a nanomagnet with a component of the magnetization perpendicular to the direction of the spin-orbit interaction of the host. We show that the Transmission Function of this structure has the desired qualities for optimal thermoelectric performance in the quantum coherent regime. For a single magnetic domain, there is a power generation close to the optimal bound. In a configuration with two magnetic domains with different orientations, pronounced peaks in the Transmission Functions and resonances lead to a high figure of merit. We provide estimates for the fabrication of this device with HgTe quantum-well topological insulators.
Zheng Wang - One of the best experts on this subject based on the ideXlab platform.
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thermal conductivities of individual tin dioxide nanobelts
Applied Physics Letters, 2004Co-Authors: Li Shi, Xiangyang Kong, Qing Hao, Natalio Mingo, Zheng WangAbstract:We have measured the thermal conductivities of a 53-nm-thick and a 64-nm-thick tin dioxide (SnO2) nanobelt using a microfabricated device in the temperature range of 80–350 K. The thermal conductivities of the nanobelts were found to be significantly lower than the bulk values, and agree with our calculation results using a full dispersion Transmission Function approach. Comparison between measurements and calculation suggests that phonon–boundary scattering is the primary effect determining the thermal conductivities.
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thermal conductivities of individual tin dioxide nanobelts
Volume!, 2004Co-Authors: Li Shi, Xiangyang Kong, Qing Hao, Natalio Mingo, Zheng WangAbstract:We have measured the thermal conductivities of a 53-nm-thick and a 64-nm-thick tin dioxide (SnO2 ) nanobelt using a microfabricated device in the temperature range of 80–350 K. The uncertainty of the measurement result was estimated to be 10 percent. The thermal conductivities of the nanobelts were found to be significantly lower than the bulk values, and agree with our calculation results using a full dispersion Transmission Function approach. Comparison between measurements and calculation suggests that phonon-boundary scattering is the primary effect determining the thermal conductivities.© 2004 ASME
Peter J Hudson - One of the best experts on this subject based on the ideXlab platform.
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breaking beta deconstructing the parasite Transmission Function
Philosophical Transactions of the Royal Society B, 2017Co-Authors: Hamish Mccallum, Rachel Norman, Beth Levick, Peter J Hudson, Mark Viney, Sarah E. Perkins, Anthony J. Wilson, Andy Fenton, Joanne LelloAbstract:Transmission is a fundamental step in the life cycle of every parasite but it is also one of the most challenging processes to model and quantify. In most host–parasite models, the Transmission pro...
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parasite Transmission reconciling theory and reality
Journal of Animal Ecology, 2002Co-Authors: Andy Fenton, Jonathan P Fairbairn, Rachel Norman, Peter J HudsonAbstract:Summary 1 Arguably the most important and elusive component of host–parasite models is the Transmission Function. Considerable empirical and theoretical work has focused on determining the correct formulation of this Function although, to date, there has been little attempt to combine these studies to develop general insights into how observed Transmission rates affect host–parasite dynamics. 2 Here, estimates of Transmission rates from a range of host–parasite systems in the literature are described using a phenomenological Function which takes into account how Transmission varies with host and parasite densities. This Function is placed in the appropriate model framework to determine the consequences of the observed Transmission rates for each system. 3 All of the parasites had decreasing per capita Transmission rates with increasing parasite densities suggesting that parasites tend to saturate at high densities, either as hosts become limiting or due to heterogeneities amongst the host population. In terms of the responses to host density, the parasites fell into two groups: those with increasing or decreasing Transmission rates. This dichotomy was due to the biology of the organisms; the former group infect through cannibalism, which increased at high densities as the individuals became stressed, whereas the latter group infected through free-living stages, resulting in a form of spatial structuring reducing the number of hosts available for infection. 4 A metapopulation model was developed where hosts and parasites interacted in discrete patches according to the appropriate Transmission Function, with neighbouring patches linked by dispersal. The model suggested that small-scale, localized Transmission events can drive large-scale epizootics at the metapopulation level. This emphasizes the importance of correctly describing and quantifying the Transmission Function at the individual level. 5 Traditionally, the formulation of the Transmission Function has depended on the scale of observation. This work shows that Transmission should be considered from the viewpoint of the organisms concerned. Observed Transmission rates are a consequence of the biology of the individuals meaning it should be possible to develop a priori hypotheses concerning the nature of the Transmission Function from a basic understanding of the life history of the organisms concerned.
H O Tekin - One of the best experts on this subject based on the ideXlab platform.
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photon and neutron shielding characteristics of samarium doped lead alumino borate glasses containing barium lithium and zinc oxides determined at medical diagnostic energies
Results in physics, 2019Co-Authors: M Almatari, O Agar, E E Altunsoy, Onder Kilicoglu, M I Sayyed, H O TekinAbstract:Abstract In the present work, we studied the radiation shielding parameters such as mass attenuation coefficients, effective atomic number, half value layer, mean free path, macroscopic effective removal cross-sections and neutron Transmission Function for samarium doped lead alumino borate glasses containing barium, lithium and zinc oxides at medical diagnostic energies (between 20 and 150 keV) using MCNPX code. The results showed that the photon attenuation depends on the type of modifier used (i.e. ZnO, BaO or Li2O) and also, upon the energy of the photon. The higher mass attenuation coefficients were found for the glass containing BaO. The results also revealed that the glass containing Li2O has the maximum effective atomic number between 20 and 40 keV. In addition, some important neutron shielding parameters such as macroscopic effective removal cross-sections (ΣR) and neutron Transmission Function (N/N0) have been calculated for investigated glass samples.
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Photon and neutron shielding characteristics of samarium doped lead alumino borate glasses containing barium, lithium and zinc oxides determined at medical diagnostic energies
Elsevier, 2019Co-Authors: M Almatari, O Agar, E E Altunsoy, Onder Kilicoglu, M I Sayyed, H O TekinAbstract:In the present work, we studied the radiation shielding parameters such as mass attenuation coefficients, effective atomic number, half value layer, mean free path, macroscopic effective removal cross-sections and neutron Transmission Function for samarium doped lead alumino borate glasses containing barium, lithium and zinc oxides at medical diagnostic energies (between 20 and 150 keV) using MCNPX code. The results showed that the photon attenuation depends on the type of modifier used (i.e. ZnO, BaO or Li2O) and also, upon the energy of the photon. The higher mass attenuation coefficients were found for the glass containing BaO. The results also revealed that the glass containing Li2O has the maximum effective atomic number between 20 and 40 keV. In addition, some important neutron shielding parameters such as macroscopic effective removal cross-sections (ΣR) and neutron Transmission Function (N/N0) have been calculated for investigated glass samples. Keywords: XCOM, Glasses, MCNPX, Attenuation, Gamma photon, Neutro
