3,190 research outputs found
High-Q bismuth silicate nonlinear glass microsphere resonators
The fabrication and characterization of a bismuth-silicate glass microsphere resonator has been demonstrated. At wavelengths near 1550 nm, high-modes can be efficiently excited in a 179 ”m diameter bismuth-silicate glass microsphere via evanescent coupling using a tapered silica fiber with a waist diameter of circa 2 ”m. Resonances with Q-factors as high as were observed. The dependence of the spectral response on variations in the input power level was studied in detail to gain an insight into power-dependent thermal resonance shifts. Because of their high nonlinearity and high- factors, bismuth-silicate glass microspheres offer the potential for robustly assembled fully integrated all-optical switching devices
Coulomb gap in one-dimensional disordered electron systems
The density of states of one-dimensional disordered electron systems with
long range Coulomb interaction is studied in the weak pinning limit. The
density of states is found to follow a power law with an exponent determined by
localization length, and this power law behavior is consistent with the
existing numerical results.Comment: RevTeX4 file, 5 pages, no figures To appear in Physical Reviews
Critical behavior of the frustrated antiferromagnetic six-state clock model on a triangular lattice
We study the anti-ferromagnetic six-state clock model with nearest neighbor
interactions on a triangular lattice with extensive Monte-Carlo simulations. We
find clear indications of two phase transitions at two different temperatures:
Below a chirality order sets in and by a thorough finite size scaling
analysis of the specific heat and the chirality correlation length we show that
this transition is in the Ising universality class (with a non-vanishing
chirality order parameter below ). At the spin-spin
correlation length as well as the spin susceptibility diverges according to a
Kosterlitz-Thouless (KT) form and spin correlations decay algebraically below
. We compare our results to recent x-ray diffraction experiments on the
orientational ordering of CFBr monolayers physisorbed on graphite. We argue
that the six-state clock model describes the universal feature of the phase
transition in the experimental system and that the orientational ordering
belongs to the KT universality class.Comment: 8 pages, 9 figure
Flow field characteristics in the housing of noncircular gear flowmeter
Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.In order to find the factors which affect the accuracy of the
flow rate measurement, the inner flow characteristics of an
oval-gear flowmeter were investigated. Inner flow field was
analyzed by using the fluid-structure coupling technique with
ADINA-FSI (Fluid-Structure Interactions) module. The results
were compared with experimental results such as flow
visualization and measurements of flow rate, rpm, and pressure
drop.
As a result, the pressure on the rotor surface was
periodically changed with respect to the rotational angle, from
the maximum value of the inlet pressure to the minimum value
of the outlet pressure. The rotor tip velocity showed the
periodical changes with respect to the rotational angle. The
creation, movement, and discharge of vortices were observed
by turns around the upper and the lower rotor, which are
produced by the rotation of the rotor and the changes in the
flow passage area and contour in the housing. Larger pressure
difference between the inlet and the exit of the housing showed
higher flow rate. The flowmeter used in the present experiment
had the precision of 1%, in view of the ppl (pulse per liter)
variation as a function of flow rate. The power loss, the
difference between the theoretical driving power of the rotor
due to the pressure difference and the actual power of the rotor,
was increased as the flow rate was increased.vk201
The flavour singlet mesons in QCD
We study the flavour singlet mesons from first principles using lattice QCD.
We explore the splitting between flavour singlet and non-singlet for vector and
axial mesons as well as the more commonly studied cases of the scalar and
pseudoscalar mesons.Comment: 12 pages, LATEX, 4 ps figure
Toroidal mode number estimation of the edge-localized modes using the KSTAR 3-D electron cyclotron emission imaging system
A new and more accurate technique is presented for determining the toroidal mode number n of edge-localized modes (ELMs) using two independent electron cyclotron emission imaging (ECEI) systems in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The technique involves the measurement of the poloidal spacing between adjacent ELM filaments, and of the pitch angle ?? O of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that ?? O is nearly constant and thus well-defined at the midplane edge. Estimates of n obtained using two ECEI systems agree well with n measured by the conventional technique employing an array of Mirnov coils.open3
Quantum interference in the fluorescence of a molecular system
It has been observed experimentally [H.R. Xia, C.Y. Ye, and S.Y. Zhu, Phys.
Rev. Lett. {\bf 77}, 1032 (1996)] that quantum interference between two
molecular transitions can lead to a suppression or enhancement of spontaneous
emission. This is manifested in the fluorescent intensity as a function of the
detuning of the driving field from the two-photon resonance condition. Here we
present a theory which explains the observed variation of the number of peaks
with the mutual polarization of the molecular transition dipole moments. Using
master equation techniques we calculate analytically as well as numerically the
steady-state fluorescence, and find that the number of peaks depends on the
excitation process. If the molecule is driven to the upper levels by a
two-photon process, the fluorescent intensity consists of two peaks regardless
of the mutual polarization of the transition dipole moments. If the excitation
process is composed of both a two-step one-photon process and a one-step,
two-photon process, then there are two peaks on transitions with parallel
dipole moments and three peaks on transitions with antiparallel dipole moments.
This latter case is in excellent agreement with the experiment.Comment: 11 pages, including 8 figure
Phenomenology of the 1/N Expansion for Field Theories in Extra Dimensions
In this paper we review the properties of the 1/ expansion in
multidimensional theories. Contrary to the usual perturbative expansion it is
renormalizable and contains only logarithmic divergencies. The price for it is
the presence of ghost states which, however, in certain cases do not contribute
to physical amplitudes. In this case the theory is unitary and one can
calculate the cross-sections. As an example we consider the differential cross
section of elastic scattering in -dimensional world. We
look also for the unification of the gauge couplings in multidimensional
Standard Model and its SUSY extension which takes place at energies lower than
in 4 dimensions.Comment: Submitted for the SUSY07 proceedings, 4 pages, LaTeX, 4 eps figures +
3 axodraw figure
Interference-induced gain in Autler-Townes doublet of a V-type atom in a cavity
We study the Autler-Townes spectrum of a V-type atom coupled to a
single-mode, frequency-tunable cavity field at finite termperature, with a
pre-selected polarization in the bad cavity limit, and show that, when the mean
number of thermal photons and the excited sublevel splitting is very
large (the same order as the cavity linewidth), the probe gain may occur at
either sideband of the doublet, depending on the cavity frequency, due to the
cavity-induced interference.Comment: Minor changes are mad
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