3,040 research outputs found
Maximizing phonon thermal conductance for ballistic membranes
At low temperatures, phonon scattering can become so weak that phonon
transport becomes ballistic. We calculate the ballistic phonon conductance G
for membranes using elasticity theory, considering the transition from three to
two dimensions. We discuss the temperature and thickness dependence and
especially concentrate on the issue of material parameters. For all membrane
thicknesses, the best conductors have, counter-intuitively, the lowest speed of
sound.Comment: 4 pages, 4 figures, proceedings to phonons 2007 conferenc
Hadronic structure in tau- -> pi- pi- pi+ neutrino decays
A model-dependent analysis of the hadronic substructure in tau- -> pi- pi-
pi+ neutrino decay is reported. The decay is dominated by the process tau- ->
a1(1260)- + neutrino, in which a1(1260)- -> rho0 pi- in an S-wave decay.
Amplitudes involving a1(1260) decays into isoscalars, especially a_1(1260)- ->
f0(600)pi-, are large. tau- -> pi- pi- pi+ neutrino decays via the pseudoscalar
pi(1300)- are small. These results support the resonant substructure reported
in the previously reported analysis of tau- -> pi0 pi0 pi- neutrino decay mode
from the same CLEO II data sample.Comment: Invited talk at the Seventh International Workshop on Tau Lepton
Physics (TAU02), Santa Cruz, CA, USA, September 2002, 7 pages, LaTeX, 7 eps
figure
Phytase improves apparent total tract digestibility of phosphorus and calcium in piglets fed diets with adequate or reduced phosphorus content
v2012o
Variational study of U(1) and SU(2) lattice gauge theories with Gaussian states in 1+1 dimensions
We introduce a method to investigate the static and dynamic properties of
both Abelian and non-Abelian lattice gauge models in 1+1 dimensions.
Specifically, we identify a set of transformations that disentangle different
degrees of freedom, and apply a simple Gaussian variational ansatz to the
resulting Hamiltonian. To demonstrate the suitability of the method, we analyze
both static and dynamic aspects of string breaking for the U(1) and SU(2) gauge
models. We benchmark our results against tensor network simulations and observe
excellent agreement, although the number of variational parameters in the
Gaussian ansatz is much smaller.Comment: 19 pages, 6 figures. Added references and corrected typo
Influence of the radial spacing between cathodes on the surface composition of iron samples sintered by hollow cathode electric discharge
The present work reports an investigation of the influence of the radial spacing between cathodes on the iron sintering process by hollow cathode electrical discharge, with surface enrichment of the alloying elements Cr and Ni. Pressed cylindrical samples of 9.5 mm diameter and density of 7.0 ± 0.1 g/cm³ were prepared by compaction of Ancorsteel 1000C iron powder. These samples, constituting the central cathode, were positioned concentrically in the interior of an external cathode machined from a tube of stainless steel AISI 310 (containing: 25% Cr, 16% Ni, 1.5% Mn, 1.5% Si, 0.03% C and the remainder Fe). Sintering was done at 1150 °C, for 120 min, utilizing radial spacings between the central and hollow cathodes of 3, 6 and 9 mm and a gas mixture of 80% Ar and 20% H2, with a flow rate of 5 cm³/s at a pressure of 3 Torr. The electric discharge was generated using a pulsed voltage power source, with a period of 200 mus. The radial spacing had only a slight influence on the quantity of atoms of alloying elements deposited and diffused on the surface of the sample. Analysis with a microprobe showed the presence of chrome (up to 4.0%) and nickel (up to 3.0%, in at. %) at the surface of the samples. This surface enrichment can be attributed to the mechanism of sputtering of the metallic atoms present in the external cathode, with the deposition of these elements on the sample surface and consequent diffusion within the sample.Universidade Federal de São Paulo (UNIFESP) Department of Mechanical EngineeringUniversidade Federal de Santa Catarina Department of Mechanical EngineeringUNIFESP, Department of Mechanical EngineeringSciEL
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