29,362 research outputs found
A new calibration method for time delay standard and its application
A method which is used to measure time delay accurately by using a Type 900-LB slotted line is described. The accuracy for calibrating time delay of a precision coaxial air line Type 900-L is about + or - (0.4 to 0.6)ps, and for coaxial cables with VSWR less than 1.5 and time delay t less than 50ns is about + or - (3 to 5)ps. Theoretical analysis and mathematical derivation of microwave networks in cascade are given. Methods to eliminate the errors which are caused by the discontinuities and the error analysis of the measuring system are presented. Skin effect analysis of the transient characteristic of coaxial transmission line are discussed in detail. Methods to eliminate the errors which result from using the calibrated time delay standard to calibrate time interval measurement instruments are presented. The estimation of errors and formulae for correction of those errors are described
A data collection scheme for identification of parameters in a driver model
A high gain steering controller to compensate for limitations in a handicapped driver's range of motion is employed when adapting vehicle to his use. A driver/vehicle system can become unstable as vehicle speed is increased, therefore it is desirable to use a computer simulation of the driver/vehicle combination as a design tool to investigate the system response prior to construction of a controller and road testing. Unknown driver parameters must be identified prior to use of the model for system analysis. A means to collect the data necessary for identification of these driver model parameters without extensive instrumentation of a vehicle to measure and record vehicle states is addressed. Initial tests of the procedure identified all of the driver parameters with errors of 6% or less
Classification of finite dimensional modules of singly atypical type over the Lie superalgebras sl(m/n)
We classify the finite dimensional indecomposable sl(m/n)-modules with at
least a typical or singly atypical primitive weight. We do this classification
not only for weight modules, but also for generalized weight modules. We obtain
that such a generalized weight module is simply a module obtained by
``linking'' sub-quotient modules of generalized Kac-modules. By applying our
results to sl(m/1), we have in fact completely classified all finite
dimensional sl(m/1)-modules.Comment: 17 pages, Late
Geometry and topology of two kinds of extreme Reissner-Nordstrm-anti-de Sitter black holes
Different geometrical and topological properties have been shown for two
kinds of extreme Reissner-Nordstrm-anti-de Sitter black holes. The
relationship between the geometrical properties and the intrinsic
thermodynamical properties has been made explicit.Comment: Latex, 12 pages, 4 figure
Electric-field-induced phase transition of <001> oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals
oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals were poled under
different electric fields, i.e. Epoling=4 kV/cm and Epoling=13 kV/cm. In
addition to the temperature-dependent dielectric constant measurement, X-ray
diffraction was also used to identify the poling-induced phase transitions.
Results showed that the phase transition significantly depends on the poling
intensity. A weaker field (Epoling=4 kV/cm) can overcome the effect of random
internal field to perform the phase transition from rhombohedral ferroelectric
state with short range ordering (microdomain) FESRO to rhombohedral
ferroelectric state with long range ordering (macrodomain) FElRO. But the
rhombohedral ferroelectric to tetragonal ferroelectric phase transition
originating from to polarization rotation can only be induced by a
stronger field (Epoling=13 kV/cm). The sample poled at Epoling=4 kV/cm showed
higher piezoelectric constant, d33>1500 pC/N, than the sample poled at
Epoling=13 kV/cm.Comment: 7 pages, 2 figure
A search on Dirac equation
The solutions, in terms of orthogonal polynomials, of Dirac equation with
analytically solvable potentials are investigated within a novel formalism by
transforming the relativistic equation into a Schrodinger like one. Earlier
results are discussed in a unified framework and certain solutions of a large
class of potentials are given.Comment: 9 page
Neutron spectroscopic factors of Ni isotopes from transfer reactions
177 neutron spectroscopic factors for nickel isotopes have been extracted by
performing a systematic analysis of the angular distributions measured from
(d,p) transfer reactions. A subset of the extracted spectroscopic factors are
compared to predictions of large-basis shell models in the full pf model space
using the GXPF1A effective interaction, and the (f5/2, p3/2, p1/2, g9/2) model
space using the JJ4PNA interaction. For ground states, the predicted
spectroscopic factors using the GXPF1A effective interaction in the full pf
model space agree very well with the experimental values, while predictions
based on several other effective interactions and model spaces are about 30%
higher than the experimental values. For low-energy excited states (<3.5 MeV),
the agreement between the extracted spectroscopic factors and shell model
calculations is not better than a factor of two.Comment: 18 pages, 4 figures, 2 tables. accepted for publication in PR
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