1,302 research outputs found
Deuteron Momentum Distribution in KD2HPO4
The momentum distribution in KD2PO4(DKDP) has been measured using neutron
Compton scattering above and below the weakly first order
paraelectric-ferroelectric phase transition(T=229K). There is very litte
difference between the two distributions, and no sign of the coherence over two
locations for the proton observed in the paraelectric phase, as in KH2PO4(KDP).
We conclude that the tunnel splitting must be much less than 20mev. The width
of the distribution indicates that the effective potential for DKDP is
significantly softer than that for KDP. As electronic structure calculations
indicate that the stiffness of the potential increases with the size of the
coherent region locally undergoing soft mode fluctuations, we conclude that
there is a mass dependent quantum coherence length in both systems.Comment: 6 pages 5 figure
Angular distribution studies on the two-photon ionization of hydrogen-like ions: Relativistic description
The angular distribution of the emitted electrons, following the two-photon
ionization of the hydrogen-like ions, is studied within the framework of second
order perturbation theory and the Dirac equation. Using a density matrix
approach, we have investigated the effects which arise from the polarization of
the incoming light as well as from the higher multipoles in the expansion of
the electron--photon interaction. For medium- and high-Z ions, in particular,
the non-dipole contributions give rise to a significant change in the angular
distribution of the emitted electrons, if compared with the electric-dipole
approximation. This includes a strong forward emission while, in dipole
approxmation, the electron emission always occurs symmetric with respect to the
plane which is perpendicular to the photon beam. Detailed computations for the
dependence of the photoelectron angular distributions on the polarization of
the incident light are carried out for the ionization of H, Xe, and
U (hydrogen-like) ions.Comment: 16 pages, 4 figures, published in J Phys
Lithium-induced phase transitions in lead-free Bi0. 5Na0. 5TiO3 based ceramics
Lithium-substituted 0.95[0.94(Bi0.5Na(0.5–x)Lix)TiO3–0.06BaTiO3]–0.05CaTiO3 materials include the polar rhombohedral R3c and the weakly polar tetragonal P4bm phases. On increasing lithium content, the (R3c/P4bm) phase ratio decreased, while the rhombohedral and tetragonal lattice distortions remained the same. The temperature corresponding to the shoulder in the dielectric permittivity shows no clear shift with respect to lithium substitution because of the rhombohedral distortion remaining constant. Electrical poling produced an increase of the rhombohedral phase fraction together with a rise of the rhombohedral and tetragonal distortion. This confirmed the occurrence of a phase transition from the weakly polar to the polar phase during electrical poling. Four peaks found in the current–electric field (I–E) loops are related to reversible electric field induced transitions. By studying the temperature dependence of the current peaks in the I–E loops, it was found that the minimum temperature where these electric field induced transitions take place decreases with increasing lithium substitution
THE ROLE OF SODIUM IONS IN THE ACTIVATION OF ELECTROPHORUS ELECTRIC ORGAN ADENOSINE TRIPHOSPHATASE
Adsorption refinement of waste transformer oil using industrial montmorillonite-containing sorbents
The possibilities of adsorption contact refining of waste transformer oil with active montmorillonite-containing sorbents of «Filtrol» series of BASF Catalysts LLC corporation and Zikeevsk М-80 deposit sorbent have been investigated. Usage of F-160 sorbents of «Filtrol» series in the refinement process allows achieving high quality degree of lean transformer oil, permitting its further use in the equipment with operating voltage to 750 kV
Hybrid control trajectory optimization under uncertainty
Trajectory optimization is a fundamental problem in robotics. While optimization of continuous control trajectories is well developed, many applications require both discrete and continuous, i.e. hybrid controls. Finding an optimal sequence of hybrid controls is challenging due to the exponential explosion of discrete control combinations. Our method, based on Differential Dynamic Programming (DDP), circumvents this problem by incorporating discrete actions inside DDP: we first optimize continuous mixtures of discrete actions, and, subsequently force the mixtures into fully discrete actions. Moreover, we show how our approach can be extended to partially observable Markov decision processes (POMDPs) for trajectory planning under uncertainty. We validate the approach in a car driving problem where the robot has to switch discrete gears and in a box pushing application where the robot can switch the side of the box to push. The pose and the friction parameters of the pushed box are initially unknown and only indirectly observable
LAPW frozen-phonon calculation, shell model lattice dynamics and specific-heat measurement of SnO
An ab-initio Linear Augmented Plane-Wave (LAPW) calculation of the
zone-centered phonon frequencies of SnO has been performed. E symmetry has
been ascribed to the mode observed at 113 cm in Raman measurements,
discarding a previous B assignement. The other phonon modes measured by
Raman spectroscopy are also well reproduced. A new shell-model has also been
developed, that gives good agreement of the zone-centered frequencies compared
to the measured data and the LAPW results. Specific heat measurements have been
performed between 5 K and 110 K. Computation of the specific heat and the
M\"{o}ssbauer recoilless fraction with the improved shell-model shows a good
agreement with the experimental data as a function of temperature.Comment: 11 pages, 1 figure. to appear in Phys. Rev. B (November 1999
Evolution of the Velocity Ellipsoids in the Thin Disk of the Galaxy and the Radial Migration of Stars
Data from the revised Geneva--Copenhagen catalog are used to study the
influence of radial migration of stars on the age dependences of parameters of
the velocity ellipsoids for nearby stars in the thin disk of the Galaxy,
assuming that the mean radii of the stellar orbits remain constant. It is
demonstrated that precisely the radial migration of stars, together with the
negative metallicity gradient in the thin disk,are responsible for the observed
negative correlation between the metallicities and angular momenta of nearby
stars, while the angular momenta of stars that were born at the same
Galactocentric distances do not depend on either age or metallicity. (abridged)Comment: Astronomy Reports, Vol. 86 No. 9, P.1117-1126 (2009
Кафедре оптических и оптико-электронных приборов – 40 лет
Розглянуто історію заснування кафедри оптичних приладів в Київському політехнічному інституті. Представлена інформація про усіх завідувачів кафедри, підготовку інженерних і наукових кадрів, науково-методичні школи кафедри. Зроблено висновок про перспективи оптичного приладобудування в Україні.The history of the department of optical and optic-electronic devices in Kiev polytechnic institute is considered. The information about all the chiefs of the department, engineering education, scientific and methodological schools is given. The future of the optical instrument engineering
in Ukraine is concluded.Рассмотрена история основания кафедры оптических приборов в Киевском политехническом институте. Представлена информация о всех заведующих кафедрой, подготовке инженерных и научных кадров, научно-методических школах кафедры. Сделан вывод о перспективах оптического приборостроения в Украине
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