37,341 research outputs found
A comprehensive analysis of cavitation and liquid impingement erosion data
Cavitation-erosion experimental data previously covering several materials tested in a rotating disk device and a magnetostriction apparatus were analyzed using new normalization and curve-fitting techniques. From this process a universal approach is derived which can include data from cavitation and liquid impingement studies for specific materials from different test devices
Universal approach to analysis of cavitation and liquid-impingement erosion data
Cavitation erosion experimental data was analyzed by using normalization and curve-fitting techniques. Data were taken from experiments on several materials tested in both a rotating disk device and a magnetostriction apparatus. Cumulative average volume loss rate and time data were normalized relative to the peak erosion rate and the time to peak erosion rate, respectively. From this process a universal approach was derived that can include data on specific materials from different test devices for liquid impingement and cavitation erosion studies
Theory of magnetism and metal-insulator transition in layered perovskite iridates
We investigate the metal-insulator transition in the layered Ruddelsden
Popper series of strontium iridates Srn+1IrnO3n+1. Tight-binding models of t2g
orbitals for n = 1, 2, and infinity are constructed, and changes in band
dispersion due to dimensionality and spin-orbit coupling are presented.
Identifying the states near the Fermi level to be predominantly Jeff = 1/2, we
use an effective Hubbard model to study the effect of correlations. Transitions
from a metallic state to various magnetically ordered states at different
critical interactions are obtained. A canted antiferromagnetic insulator is
found for Sr2IrO4, a c-axis collinear antiferromagnetic insulator for Sr3Ir2O7,
and non-coplanar canted antiferromagnetic insulator via magnetic metal for
SrIrO3. We derive the strong-coupling spin-model and compare the magnetic
ordering patterns obtained in the weak and strong coupling limits. We find that
they are identical, indicating that magnetic ordering is not sufficient to
justify Mott physics in this series of iridates.Comment: 11 pages, 18 figure
Solid spherical glass particle impingement studies of plastic materials
Erosion experiments on polymethyl methacrylate (PMMA), polycarbonate, and polytetrafluoroethylene (PTFE) were conducted with spherical glass beads impacting at normal incidence. Optical and scanning electron microscopic studies and surface profile measurements were made on specimens at predetermined test intervals. During the initial stage of damage to PMMA and polycarbonate, material expands or builds up above the original surface. However, this buildup disappears as testing progresses. Little or no buildup was observed on PTFE. PTFE is observed to be the most resistant material to erosion and PMMA the least. At low impact pressures, material removal mechanisms are believed to be similar to those for metallic materials. However, at higher pressures, surface melting is indicated at the center of impact. Deformation and fatigue appear to play major roles in the material removal process with possible melting or softening
Morphology of an aluminum alloy eroded by a jet of angular particles impinging at normal incidence
The erosion of an aluminum alloy impinged by crushed glass particles at normal incidence was studied. The erosion patterns were analyzed by scanning electron microscopy, energy dispersive X-ray spectroscopy, and surface profilometer measurements. From the analysis of specimens tested at various driving gas pressures and time intervals, four distinct erosion regions were identified. A study of pit morphology and its relationship to cumulative erosion was made. Cutting wear is believed to be the predominant material removal mechanism; some evidence of deformation wear was found during the incubation period
A study of the nature of solid particle impact and shape on the erosion morphology of ductile metals
Impulsive versus steady jet impingement of spherical glass bead particles on metal surfaces was studied using a gas gun facility and a commercial sand blasting apparatus. Crushed glass particles were also used in the sand blasting apparatus as well as glass beads. Comparisons of the different types of erosion patterns were made. Scanning electron microscopy, surface profilometry and energy dispersive X-ray spectroscopy analysis were used to characterize erosion patterns. The nature of the wear can be divided into cutting and deformation, each with its own characteristic features. Surface chemistry analysis indicates the possibility of complex chemical and/or mechanical interactions between erodants and target materials
First order phase transition in the Quantum Adiabatic Algorithm
We simulate the quantum adiabatic algorithm (QAA) for the exact cover problem
for sizes up to N=256 using quantum Monte Carlo simulations incorporating
parallel tempering. At large N we find that some instances have a discontinuous
(first order) quantum phase transition during the evolution of the QAA. This
fraction increases with increasing N and may tend to 1 for N -> infinity.Comment: 5 pages, 3 figures. Replaced with published version; two figures
slightly changed and some small changes to the tex
Numerical Approaches to Non-Destructive Depth Profiling by Variable Angle X-Ray Photoelectron Spectroscopy
Variable angle x-ray photoelectron spectroscopy (VAXPS), also known as angle-resolved x-ray photoelectron spectroscopy (ARXPS), is a method which can be used to depth profile the near surface region non-destructively. The intensity variation with angle of a given energy level in a sample contains the complete information about the concentration profile of the photoionized component in the depth probed. It has been shown that the intensity is the Laplace transform of the concentration profile. Theoretically it should be possible to uniquely determine the concentration profile as the inverse Laplace transform of the intensity data. After a brief background sketch, the numerical approaches which have been used to solve the inverse Laplace transform problem in VAXPS are discussed
Inversion improves the recognition of facial expression in thatcherized images
The Thatcher illusion provides a compelling example of the face inversion effect. However, the marked effect of inversion in the Thatcher illusion contrasts to other studies that report only a small effect of inversion on the recognition of facial expressions. To address this discrepancy, we compared the effects of inversion and thatcherization on the recognition of facial expressions. We found that inversion of normal faces caused only a small reduction in the recognition of facial expressions. In contrast, local inversion of facial features in upright thatcherized faces resulted in a much larger reduction in the recognition of facial expressions. Paradoxically, inversion of thatcherized faces caused a relative increase in the recognition of facial expressions. Together, these results suggest that different processes explain the effects of inversion on the recognition of facial expressions and on the perception of the Thatcher illusion. The grotesque perception of thatcherized images is based on a more orientation-sensitive representation of the face. In contrast, the recognition of facial expression is dependent on a more orientation-insensitive representation. A similar pattern of results was evident when only the mouth or eye region was visible. These findings demonstrate that a key component of the Thatcher illusion is to be found in orientation-specific encoding of the features of the face
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