387 research outputs found
Microstructure and Wear Resistance of an Arc-Sprayed Fe-Based Coating after Surface Kemelting Treatment
The aim of the study was to improve the
lamellar structure and wear resistance of
arc-sprayed coatings. FeNiCrAl arc-sprayed
coatings were remelted by the tungsten inert gas
welding method. The as-sprayed and remelted
specimens were subjected to comparative structural
phase composition examination using optical
microscopy, scanning electron microscopy
and X-ray diffraction. Additionally, the effect
of the remelting treatment on the wear mechanism
of the arc sprayed coatings was also studied.
It was found from the experiments that the
tungsten inert gas surface process has the potential
to form pore- and crack-free coatings. Further
investigations showed that the dominant
mechanism of wear for the as-sprayed coatings
was oxide delamination and for the tungsten
inert gas remelted coatings was cutting and
ploughingУсовершенствованы пластинчатая структура и износостойкость покрытий, полученных
электродуговой металлизацией. С помощью дуговой сварки вольфрамовым электродом в
среде инертного газа проведена переплавка покрытий на основе FeNiCrAl, полученных электро-дуговой металлизацией. С использованием методов оптической микроскопии, растровой
электронной микроскопии и дифракции рентгеновских лучей осуществлено сравнительное
исследование структуры и фазового состава напыленных и переплавленных покрытий. Изучено влияние обработки путем переплавки на механизм износа покрытий, полученных электро-дуговой металлизацией. Установлено, что реализация дуговой сварки вольфрамовым электродом в среде инертного газа позволяет разрабатывать покрытия без пор и трещин. Даль-
нейшие исследования показали, что основной признак износа покрытий, полученных электро-дуговой металлизацией, – расщепление оксида, в то время как покрытий, переплавленных с
помощью дуговой сварки вольфрамовым электродом в среде инертного газа, – резание и
пропахивание.Удосконалено пластинчасту структуру та зносостійкість покриттів, отриманих електро-дуговою металізацією. За допомогою дугового зварювання вольфрамовим електро-дом у середовищі інертного газу проведено переплавку покриттів на основі FeNiCrAl,
отриманих електродуговою металізацією. Із використанням методів оптичної мікроскопії, растрової електронної мікроскопії та дифракції рентгенівських променів проведено порівняльне дослідження структури і фазового складу напилених і переплавлених покриттів. Вивчено вплив обробки шляхом переплавки на механізм зношення
покриттів, отриманих електродуговою металізацією. Установлено, що реалізація дугового зварювання вольфрамовим електродом у середовищі інертного газу дозволяє розробляти покриття без пор і тріщин. Подальші дослідження показали, що основними
ознаками зношення покриттів, отриманих електродуговою металізацією, є розщеплення оксиду, в той час як покриттів, переплавлених за допомогою дугового зварювання
вольфрамовим електродом у середовищі інертного газу, – різання і проорюванн
A peroxisome proliferator-activated receptor-δ agonist provides neuroprotection in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease
Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.Peer reviewedPublisher PD
Phase separation and ferroelectric ordering in charge frustrated LuFe2O4-x
The transmission electron microscopy observations of the charge ordering (CO)
which governs the electronic polarization in LuFe2O4-x clearly show the
presence of a remarkable phase separation at low temperatures. Two CO ground
states are found to adopt the charge modulations of Q1 = (1/3, 1/3, 0) and Q2 =
(1/3 + y, 1/3 + y, 3/2), respectively. Our structural study demonstrates that
the incommensurately Q2-modulated state is chiefly stable in samples with
relatively lower oxygen contents. Data from theoretical simulations of the
diffraction suggest that both Q1- and Q2-modulated phases have ferroelectric
ordering. The effects of oxygen concentration on the phase separation and
electric polarization in this layered system are discussed.Comment: 11 pages, 5 figure
Localization by disorder in the infrared conductivity of (Y,Pr)Ba2Cu3O7 films
The ab-plane reflectivity of (Y{1-x}Prx)Ba2Cu3O7 thin films was measured in
the 30-30000 cm-1 range for samples with x = 0 (Tc = 90 K), x = 0.4 (Tc = 35 K)
and x = 0.5 (Tc = 19 K) as a function of temperature in the normal state. The
effective charge density obtained from the integrated spectral weight decreases
with increasing x. The variation is consistent with the higher dc resistivity
for x = 0.4, but is one order of magnitude smaller than what would be expected
for x = 0.5. In the latter sample, the conductivity is dominated at all
temperatures by a large localization peak. Its magnitude increases as the
temperature decreases. We relate this peak to the dc resistivity enhancement. A
simple localization-by-disorder model accounts for the optical conductivity of
the x = 0.5 sample.Comment: 7 pages with (4) figures include
Density functional method for nonequilibrium electron transport
We describe an ab initio method for calculating the electronic structure,
electronic transport, and forces acting on the atoms, for atomic scale systems
connected to semi-infinite electrodes and with an applied voltage bias. Our
method is based on the density functional theory (DFT) as implemented in the
well tested Siesta approach (which uses non-local norm-conserving
pseudopotentials to describe the effect of the core electrons, and linear
combination of finite-range numerical atomic orbitals to describe the valence
states). We fully deal with the atomistic structure of the whole system,
treating both the contact and the electrodes on the same footing. The effect of
the finite bias (including selfconsistency and the solution of the
electrostatic problem) is taken into account using nonequilibrium Green's
functions. We relate the nonequilibrium Green's function expressions to the
more transparent scheme involving the scattering states. As an illustration,
the method is applied to three systems where we are able to compare our results
to earlier ab initio DFT calculations or experiments, and we point out
differences between this method and existing schemes. The systems considered
are: (1) single atom carbon wires connected to aluminum electrodes with
extended or finite cross section, (2) single atom gold wires, and finally (3)
large carbon nanotube systems with point defects.Comment: 18 pages, 23 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
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