24,051 research outputs found
Doppler radar having phase modulation of both transmitted and reflected return signals
A microwave radar signal is generated for transmission through an antenna. Before transmission, the signal is phase modulated by 0 deg or 90 deg amounts during each alternate half-cycles of an intermediate frequency (IF) clock signal. After transmission and return, the signal is again phase modulated the same amounts during each alternate half-cycles. The return phase modulated signal is mixed with a leakage signal component of the microwave signal, leaving an IF Doppler. The IF Doppler signal may then be amplified, removing any requirement that direct current level signals be amplified and also removing the effect of detector noise from the Doppler signal
Phonon density of states and compression behavior in iron sulfide under pressure
We report the partial phonon densities of states (DOS) of iron sulfide, a possible component of the rocky planet's core, measured by the Fe-57 nuclear resonant inelastic x-ray scattering and calculate the total phonon DOS under pressure. From the phonon DOS, we drive thermodynamic parameters. A comparison of the observed and estimated compressibilities makes it clear that there is a large pure electronic contribution in the observed compressibility in the metallic state. Our results present the observation of thermodynamic parameters of iron sulfide with the low-spin state of an Fe2+ ion at the high density, which is similar to the condition of the Martian core
Large thermal Hall coefficient in bismuth
We present a systematical study of thermal Hall effect on a bismuth single
crystal by measuring resistivity, Hall coefficient, and thermal conductivity
under magnetic field, which shows a large thermal Hall coefficient comparable
to the largest one in a semiconductor HgSe. We discuss that this is mainly due
to a large mobility and a low thermal conductivity comparing theoretical
calculations, which will give a route for controlling heat current in
electronic devices.Comment: 4pages, 3 figure
Density matrix renormalization group algorithm for Bethe lattices of spin 1/2 or 1 sites with Heisenberg antiferromagnetic exchange
An efficient density matrix renormalization group (DMRG) algorithm is
presented for the Bethe lattice with connectivity and antiferromagnetic
exchange between nearest neighbor spins or 1 sites in successive
generations . The algorithm is accurate for sites. The ground states
are magnetic with spin , staggered magnetization that persists
for large and short-range spin correlation functions that decrease
exponentially. A finite energy gap to leads to a magnetization
plateau in the extended lattice. Closely similar DMRG results for = 1/2 and
1 are interpreted in terms of an analytical three-site model.Comment: 7 Pages and 8 figure
Mathematical Support to Braneworld Theory
The braneworld theory appear with the purpose of solving the problem of the
hierarchy of the fundamental interactions. The perspectives of the theory
emerge as a new physics, for example, deviation of the law of Newton's gravity.
One of the principles of the theory is to suppose that the braneworld is local
submanifold in a space of high dimension, the bulk, solution of Einstein's
equations in high dimension. In this paper we approach the mathematical
consistency of this theory with a new proof of the fundamental theorem of
submanifolds for case of semi-Riemannian manifolds. This theorem consist an
essential mathematical support for this new theory. We find the integrability
conditions for the existence of space-time submanifolds in a pseudo-Euclidean
space.
Keywords: Submanifolds, Braneworld, Pseudo-Riemannian geometryComment: 10 page
New electronic orderings observed in cobaltates under the influence of misfit periodicities
We study with ARPES the electronic structure of CoO2 slabs, stacked with
rock-salt (RS) layers exhibiting a different (misfit) periodicity. Fermi
Surfaces (FS) in phases with different doping and/or periodicities reveal the
influence of the RS potential on the electronic structure. We show that these
RS potentials are well ordered, even in incommensurate phases, where STM images
reveal broad stripes with width as large as 80\AA. The anomalous evolution of
the FS area at low dopings is consistent with the localization of a fraction of
the electrons. We propose that this is a new form of electronic ordering,
induced by the potential of the stacked layers (RS or Na in NaxCoO2) when the
FS becomes smaller than the Brillouin Zone of the stacked structure
Phase Change Observed in Ultrathin Ba0.5Sr0.5TiO3 Films by in-situ Resonant Photoemission Spectroscopy
Epitaxial Ba0.5Sr0.5TiO3 thin films were prepared on Nb-doped SrTiO3
(100)substrates by the pulsed laser deposition technique, and were studied by
measuring the Ti 2p - 3d resonant photoemission spectra in the valence-band
region as a function of film thickness, both at room temperature and low
temperature. Our results demonstrated an abrupt variation in the spectral
structures between 2.8 nm (~7 monolayers) and 2.0 nm (~5 monolayers)
Ba0.5Sr0.5TiO3 films, suggesting that there exists a critical thickness for
phase change in the range of 2.0 nm to 2.8 nm. This may be ascribed mainly to
the intrinsic size effects.Comment: 13 pages, 4 figure
Axiomatic Holonomy Maps and Generalized Yang-Mills Moduli Space
This article is a follow-up of ``Holonomy and Path Structures in General
Relativity and Yang-Mills Theory" by Barrett, J. W. (Int.J.Theor.Phys., vol.30,
No.9, 1991). Its main goal is to provide an alternative proof of this part of
the reconstruction theorem which concerns the existence of a connection. A
construction of connection 1-form is presented. The formula expressing the
local coefficients of connection in terms of the holonomy map is obtained as an
immediate consequence of that construction. Thus the derived formula coincides
with that used in "On Loop Space Formulation of Gauge Theories" by Chan, H.-M.,
Scharbach, P. and Tsou S.T. (Ann.Phys., vol.167, 454-472, 1986). The
reconstruction and representation theorems form a generalization of the fact
that the pointed configuration space of the classical Yang-Mills theory is
equivalent to the set of all holonomy maps. The point of this generalization is
that there is a one-to-one correspondence not only between the holonomy maps
and the orbits in the space of connections, but also between all maps from the
loop space on to group fulfilling some axioms and all possible
equivalence classes of bundles with connection, where the equivalence
relation is defined by bundle isomorphism in a natural way.Comment: amslatex, 7 pages, no figure
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