56,873 research outputs found
The focal plane reception pattern calculation for a paraboloidal antenna with a nearby fence
A computer simulation program is described which is used to estimate the effects of a proximate diffraction fence on the performance of paraboloid antennas. The computer program is written in FORTRAN. The physical problem, mathematical formulation and coordinate references are described. The main control structure of the program and the function of the individual subroutines are discussed. The Job Control Language set-up and program instruction are provided in the user's instruction to help users execute the present program. A sample problem with an appropriate output listing is made available as an illustration of the usage of the program
Semiclassical Time Evolution of the Holes from Luttinger Hamiltonian
We study the semi-classical motion of holes by exact numerical solution of
the Luttinger model. The trajectories obtained for the heavy and light holes
agree well with the higher order corrections to the abelian and the non-abelian
adiabatic theories in Ref. [1] [S. Murakami et al., Science 301, 1378(2003)],
respectively. It is found that the hole trajectories contain rapid oscillations
reminiscent of the "Zitterbewegung" of relativistic electrons. We also comment
on the non-conservation of helicity of the light holes.Comment: 4 pages, 5 fugure
The Luminosity - E_p Relation within Gamma--Ray Bursts and Implications for Fireball Models
Using a sample of 2408 time-resolved spectra for 91 BATSE gamma-ray bursts
(GRBs) presented by Preece et al., we show that the relation between the
isotropic-equivalent luminosity (L_iso) and the spectral peak energy (E_p) in
the cosmological rest frame, L_iso \propto E_p^2, not only holds within these
bursts, but also holds among these GRBs, assuming that the burst rate as a
function of redshift is proportional to the star formation rate. The possible
implications of this relation for the emission models of GRBs are discussed. We
suggest that both the kinetic-energy-dominated internal shock model and the
magnetic-dissipation-dominated external shock model can well interpret this
relation. We constrain the parameters for these two models, and find that they
are in a good agreement with the parameters from the fittings to the afterglow
data (abridged).Comment: 3 pages plus 5 figures, emulateapj style, accepted for publication in
ApJ Letter
Local density of states of a d-wave superconductor with inhomogeneous antiferromagnetic correlations
The tunneling spectrum of an inhomogeneously doped extended Hubbard model is
calculated at the mean field level. Self-consistent solutions admit both
superconducting and antiferromagnetic order, which coexist inhomogeneously
because of spatial randomness in the doping. The calculations find that, as a
function of doping, there is a continuous cross over from a disordered ``pinned
smectic'' state to a relatively homogeneous d-wave state with pockets of
antiferromagnetic order. The density of states has a robust d-wave gap, and
increasing antiferromagnetic correlations lead to a suppression of the
coherence peaks. The spectra of isolated nanoscale antiferromagnetic domains
are studied in detail, and are found to be very different from those of
macroscopic antiferromagnets. Although no single set of model parameters
reproduces all details of the experimental spectrum in BSCCO, many features,
notably the collapse of the coherence peaks and the occurence of a low-energy
shoulder in the local spectrum, occur naturally in these calculations.Comment: 9 pages, 5 figure
Temperature-dependent gap equations and their solutions in the SU(4) model of high-temperature superconductivity
Temperature-dependent gap equations in the SU(4) model of high-Tc
superconductivity are derived and analytical solutions are obtained. Based on
these solutions, a generic gap diagram describing the features of energy gaps
as functions of doping P is presented and a phase diagram illustrating the
phase structure as a function of temperature T and doping P is sketched. A
special doping point P_q occurs naturally in the solutions that separates two
phases at temperature T = 0: a pure superconducting phase on one side (P > P_q)
and a phase with superconductivity strongly suppressed by antiferromagnetism on
the other (P < P_q). We interpret P_q as a quantum phase transition point.
Moreover, the pairing gap is found to have two solutions for P < P_q: a small
gap that is associated with competition between superconductivity and
antiferromagnetism and is responsible for the ground state superconductivity,
and a large gap without antiferromagnetic suppression that corresponds to a
collective excited state. A pseudogap appears in the solutions that terminates
at P_q and originates from the competition between d-wave superconductivity and
antiferromagnetism. Nevertheless, this conclusion does not contradict the
preformed pair picture conceptually if the preformed pairs are generally
defined as any pairs formed before pairing condensation.Comment: 23 pages, 5 color figure
Resilience governance and acceptance of climate change policy in Taiwan Special Municipalities
Resilience is a city's continual ability to resist, adapt, change, and prepare for shocks and pressures, whether of environmental, social, institutional, or economic origin, in order to preserve city operations and improve responsiveness to future shocks. The goal of this research was to see how well each aspect of resilience governance (economic, social, environmental, and institutional) predicted acceptance of climate change policy (ACCP) in a Taiwan sample. A total of 1089 employees from the Environmental Protection Agency (EPA) from six special municipalities were included in the study (Taipei, New Taipei, Taoyuan, Taichung, Tainan, Kaohsiung). The analysis discovered that for all six cities, the economic dimension of resilience governance was significantly negatively correlated with the ACCP, while the social and institutional dimensions of resilience governance were significantly positively correlated with the ACCP. Furthermore, the institutional dimension of resilience governance was the only characteristic of resilience governance that consistently predicted EPA staffers' ACCP across six Taiwanese special municipalities
Unification of bulk and interface electroresistive switching in oxide systems
We demonstrate that the physical mechanism behind electroresistive switching
in oxide Schottky systems is electroformation, as in insulating oxides.
Negative resistance shown by the hysteretic current-voltage curves proves that
impact ionization is at the origin of the switching. Analyses of the
capacitance-voltage and conductance-voltage curves through a simple model show
that an atomic rearrangement is involved in the process. Switching in these
systems is a bulk effect, not strictly confined at the interface but at the
charge space region.Comment: 4 pages, 3 figures, accepted in PR
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