1,174 research outputs found
Comparative Analysis of Various Superconducting and Non-Superconducting Fault Current Limiting Devices Designed for Operation in a 110kV/100 MW Power Network
AbstractAs it is known one of the most promising fault current limiting (FCL) devices for high-power electric networks can be the so-called transformer type superconducting fault current limiter (SFCL) with the primary winding connected to the load in series and the secondary one shortened by a fast-acting circuit-breaker. These devices when made of conventional materials can be very large and expensive – e.g., for a 100 MW circuit under protection the total mass of copper winding conductors can exceed 15 tons and the heat losses in a normal operating mode can be more than 200kW. Therefore, using of high-temperature superconductors (HTSC) can be a solution which can sufficiently improve the mass, geometrical and operational characteristics of an FCL. Unlike other superconducting AC devices, the magnetic field in SFCL does not exceed 0.1 – 0.2 T what allows using HTSC windings even at a comparatively high level of AC losses existing nowadays. In this paper is performed a comparative analysis of various designs of SCFL with the non-superconducting FCL. It has been shown that the former have a mass by an order of magnitude lower than the latter and the rate of lowering of heat losses in a normal operating mode is the same. The equalization of costs of both designs is expected to be reached within the nearest 3 – 5 five years
AdS/CFT Equivalence Transformation
We show that any conformal field theory in d-dimensional Minkowski space, in
a phase with spontaneously broken conformal symmetry and with the dilaton among
its fields, can be rewritten in terms of the static gauge (d-1)-brane on
AdS_(d+1) by means of an invertible change of variables. This nonlinear
holographic transformation maps the Minkowski space coordinates onto the brane
worldvolume ones and the dilaton onto the transverse AdS brane coordinate. One
of the consequences of the existence of this map is that any (d-1)-brane
worldvolume action on AdS_(d+1)\times X^m (with X^m standing for the sphere S^m
or more complicated curved manifold) admits an equivalent description in
Minkowski space as a nonlinear and higher-derivative extension of some
conventional conformal field theory action, with the conformal group being
realized in a standard way. The holographic transformation explicitly relates
the standard realization of the conformal group to its field-dependent
nonlinear realization as the isometry group of the brane AdS_(d+1) background.
Some possible implications of this transformation, in particular, for the study
of the quantum effective action of N=4 super Yang-Mills theory in the context
of AdS/CFT correspondence, are briefly discussed.Comment: LaTeX, 19 pages, minor correction in Abstrac
The multifrequency Siberian Radioheliograph
The 10-antenna prototype of the multifrequency Siberian radioheliograph is
described. The prototype consists of four parts: antennas with broadband
front-ends, analog back-ends, digital receivers and a correlator. The prototype
antennas are mounted on the outermost stations of the Siberian Solar Radio
Telescope (SSRT) array. A signal from each antenna is transmitted to a workroom
by an analog fiber optical link, laid in an underground tunnel. After mixing,
all signals are digitized and processed by digital receivers before the data
are transmitted to the correlator. The digital receivers and the correlator are
accessible by the LAN. The frequency range of the prototype is from 4 to 8 GHz.
Currently the frequency switching observing mode is used. The prototype data
include both circular polarizations at a number of frequencies given by a list.
This prototype is the first stage of the multifrequency Siberian
radioheliograph development. It is assumed that the radioheliograph will
consist of 96 antennas and will occupy stations of the West-East-South subarray
of the SSRT. The radioheliograph will be fully constructed in autumn of 2012.
We plan to reach the brightness temperature sensitivity about 100 K for the
snapshot image, a spatial resolution up to 13 arcseconds at 8 GHz and
polarization measurement accuracy about a few percent.
First results with the 10-antenna prototype are presented of observations of
solar microwave bursts. The prototype abilities to estimate source size and
locations at different frequencies are discussed
Calculation of DC arc plasma torch voltage-current characteristics based on Steenbeck model
Modern technology of treatment of waste and equilibrium plasma chemistry is based on plasma technology of
gas heating using the direct current arc plasma torches. The work is devoted to the problem of the determination of
plasma torches parameters and power sources parameters (working voltage and current of plasma torch) at the predesigning
stage. The sequence of calculation of voltage-current characteristics of DC arc plasma torch is proposed.
It is shown that the simple Steenbeck model of arc discharge in cylindrical channel makes it possible to carry out
this calculation. The results of the calculation are confirmed by the experiments.Современная технология обработки отходов и равновесной плазмохимии основана на плазменной технологии нагрева газа, используя плазменные горелки дуги постоянного тока. Работа посвящена проблеме определения параметров плазменных горелок и параметров источников питания (рабочее напряжение и ток плазменной горелки) на стадии проектирования. Предложена последовательность расчета вольт-амперных характеристик плазменной горелки дуги постоянного тока. Показано, что простая модель Штейнбека дугового разряда в цилиндрическом канале делает возможным провести этот расчет. Результаты расчета подтверждены экспериментами.Сучасна технологія обробки відходів та рівноважної плазмохімії основана на плазмовій технології
нагріву газу, використовуючи плазмові горілки дуги сталого струму. Робота присвячена проблемі
визначення параметрів плазмових горілок та параметрів джерел живлення (робочої напруги та струму
плазмової горілки) на стадії проектування. Запропонована послідовність розрахунку вольт-амперних
характеристик плазмової горілки дуги сталого струму. Показано, що проста модель Штейнбека дугового
розряду в циліндричному каналі робить можливим провести цей розрахунок. Результати розрахунку
підтверджені експериментами
Two-proton overlap functions in the Jastrow correlation method and cross section of the OC reaction
Using the relationship between the two-particle overlap functions (TOF's) and
the two-body density matrix (TDM), the TOF's for the
OC reaction are calculated on the
basis of a TDM obtained within the Jastrow correlation method. The main
contributions of the removal of and pairs from O
are considered in the calculation of the cross section of the
OC reaction using the Jastrow TOF's
which include short-range correlations (SRC). The results are compared with the
cross sections calculated with different theoretical treatments of the TOF's.Comment: 10 pages, 8 figures, ReVTeX
QCD sum rules analysis of the rare B_c \rar X\nu\bar{\nu} decays
Taking into account the gluon correction contributions to the correlation
function, the form factors relevant to the rare B_c \rar X \nu\bar{\nu}
decays are calculated in the framework of the three point QCD sum rules, where
stands for axial vector particle, , and vector particles,
. The total decay width as well as the branching ratio of these
decays are evaluated using the dependent expressions of the form factors.
A comparison of our results with the predictions of the relativistic
constituent quark model is presented.Comment: 21 Pages, 2 Figures and 5 Table
Mass spectra of doubly heavy Omega_QQ' baryons
We evaluate the masses of baryons composed of two heavy quarks and a strange
quark with account for spin-dependent splittings in the framework of potential
model with the KKO potential motivated by QCD with a three-loop beta-function
for the effective charge consistent with both the perturbative limit at short
distances and linear confinement term at long distances between the quarks. The
factorization of dynamics is supposed and explored in the nonrelativistic
Schroedinger equation for the motion in the system of two heavy quarks
constituting the doubly heavy diquark and the strange quark interaction with
the diquark. The limits of approach, its justification and uncertainties are
discussed. Excited quasistable states are classified by the quantum numbers of
heavy diquark composed by the heavy quarks of the same flavor.Comment: 14 pages, revtex4-file, 3 eps-figures, 5 tables, typos correcte
Jastrow-type calculations of one-nucleon removal reactions on open - shell nuclei
Single-particle overlap functions and spectroscopic factors are calculated on
the basis of Jastrow-type one-body density matrices of open-shell nuclei
constructed by using a factor cluster expansion. The calculations use the
relationship between the overlap functions corresponding to bound states of the
-particle system and the one-body density matrix for the ground state of
the -particle system. In this work we extend our previous analyses of
reactions on closed-shell nuclei by using the resulting overlap functions for
the description of the cross sections of reactions on the open -
shell nuclei Mg, Si and S and of S
reaction. The relative role of both shell structure and short-range
correlations incorporated in the correlation approach on the spectroscopic
factors and the reaction cross sections is pointed out.Comment: 11 pages, 5 figures, to be published in Phys. Rev.
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