9,153 research outputs found
Multiple-compartment venting program
Computer program solves time-dependent energy and state equations for gas reservoirs, using the solutions of conductor conservation equations as mass and energy rate changes to reservoirs
Thermocouple, multiple junction reference oven
An improved oven for maintaining the junctions of a plurality of reference thermocouples at a common and constant temperature is described. The oven is characterized by a cylindrical body defining a heat sink with axially extended-cylindrical cavity a singularized heating element which comprises a unitary cylindrical heating element consisting of a resistance heating coil wound about the surface of metallic spool with an axial bore defined and seated in the cavity. Other features of the oven include an annular array of radially extended bores defined in the cylindrical body and a plurality of reference thermocouple junctions seated in the bores in uniformly spaced relation with the heating element, and a temperature sensing device seated in the axial bore for detecting temperature changes as they occur in the spool and circuit to apply a voltage across the coil in response to detected drops in temperatures of the spool
Dielectric screening of surface states in a topological insulator
Hexagonal warping provides an anisotropy to the dispersion curves of the
helical Dirac fermions that exist at the surface of a topological insulator. A
sub-dominant quadratic in momentum term leads to an asymmetry between
conduction and valence band. A gap can also be opened through magnetic doping.
We show how these various modifications to the Dirac spectrum change the
polarization function of the surface states and employ our results to discuss
their effect on the plasmons. In the long wavelength limit, the plasmon
dispersion retains its square root dependence on its momentum,
, but its slope is modified and it can acquire a weak
dependence on the direction of . Further, we find the existence
of several plasmon branches, one which is damped for all values of
, and extract the plasmon scattering rate for a representative
case.Comment: 11 pages, 8 figure
Equation of State of the Fermionic 2D Hubbard Model
We present results for the equation of state of the two-dimensional Hubbard
model on an isotropic square lattice as obtained from a controlled and
numerically exact large-cluster dynamical mean field simulation. Our results
are obtained for large but finite systems and are extrapolated to infinite
system size using a known finite size scaling relation. We present the energy,
entropy, double occupancy and nearest-neighbour spin correlations extrapolated
to the thermodynamic limit and discuss the implications of these calculations
on pseudogap physics of the 2D-Hubbard model away from half filling. We find a
strong behavioural shift in energy below a temperature which becomes more
pronounced for larger clusters. Finally, we provide reference calculations and
tables for the equation of state for values of doping away from half filling
which are of interest to cold atom experiments.Comment: 8 pages 6 figures - See Source for Supplementary Material File
Structured codebook design in CELP
Codebook Excited Linear Protection (CELP) is a popular analysis by synthesis technique for quantizing speech at bit rates from 4 to 6 kbps. Codebook design techniques to date have been largely based on either random (often Gaussian) codebooks, or on known binary or ternary codes which efficiently map the space of (assumed white) excitation codevectors. It has been shown that by introducing symmetries into the codebook, good complexity reduction can be realized with only marginal decrease in performance. Codebook design algorithms are considered for a wide range of structured codebooks
Real-time speech encoding based on Code-Excited Linear Prediction (CELP)
This paper reports on the work proceeding with regard to the development of a real-time voice codec for the terrestrial and satellite mobile radio environments. The codec is based on a complexity reduced version of code-excited linear prediction (CELP). The codebook search complexity was reduced to only 0.5 million floating point operations per second (MFLOPS) while maintaining excellent speech quality. Novel methods to quantize the residual and the long and short term model filters are presented
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