1,105 research outputs found
Analysis Of Surface Orange Peel Of Automotive Aluminum Alloy Pipe Using Electron Backscatter Diffraction (EBSD)
The occurrence of orange peel in 6xxx alloy tube for automotive application was studied by super depth metallographic microscope and EBSD. The results revealed obvious ups and downs morphology at the surface after tube hydroforming. Compared with the undeformed case, more grains existed in the concave areas rather than individual out-of-plane displacement. The influence of surface orange peel on grain boundary morphology, crystal orientation, and texture are discussed. It is concluded, that surface orange peel is controlled by the spatial distribution of grain orientations and grain size through the thickness of the sample
Concern for Information Privacy and Online Consumer Purchasing
Although electronic commerce experts often cite privacy concerns as barriers to consumer electronic commerce, there is a lack of understanding about how these privacy concerns impact consumers\u27 willingness to conduct transactions online. Therefore, the goal of this study is to extend previous models of e-commerce adoption by specifically assessing the impact that consumers\u27 concerns for information privacy (CFIP) have on their willingness to engage in online transactions. To investigate this, we conducted surveys focusing on consumers\u27 willingness to transact with a well-known and less well-known Web merchant. Results of the study indicate that concern for information privacy affects risk perceptions, trust, and willingness to transact for a well-known merchant, but not for a less well-known merchant. In addition, the results indicate that merchant familiarity does not moderate the relationship between CFIP and risk perceptions or CFIP and trust. Implications for researchers and practitioners are discussed
Granular Solid Hydrodynamics
Granular elasticity, an elasticity theory useful for calculating static
stress distribution in granular media, is generalized to the dynamic case by
including the plastic contribution of the strain. A complete hydrodynamic
theory is derived based on the hypothesis that granular medium turns
transiently elastic when deformed. This theory includes both the true and the
granular temperatures, and employs a free energy expression that encapsulates a
full jamming phase diagram, in the space spanned by pressure, shear stress,
density and granular temperature. For the special case of stationary granular
temperatures, the derived hydrodynamic theory reduces to {\em hypoplasticity},
a state-of-the-art engineering model.Comment: 42 pages 3 fi
First Principle Local Density Approximation Description of the Electronic Properties of Ferroelectric Sodium Nitrite
The electronic structure of the ferroelectric crystal, NaNO, is studied
by means of first-principles, local density calculations. Our ab-initio,
non-relativistic calculations employed a local density functional approximation
(LDA) potential and the linear combination of atomic orbitals (LCAO). Following
the Bagayoko, Zhao, Williams, method, as enhanced by Ekuma, and Franklin
(BZW-EF), we solved self-consistently both the Kohn-Sham equation and the
equation giving the ground state charge density in terms of the wave functions
of the occupied states. We found an indirect band gap of 2.83 eV, from W to R.
Our calculated direct gaps are 2.90, 2.98, 3.02, 3.22, and 3.51 eV at R, W, X,
{\Gamma}, and T, respectively. The band structure and density of states show
high localization, typical of a molecular solid. The partial density of states
shows that the valence bands are formed only by complex anionic states. These
results are in excellent agreement with experiment. So are the calculated
densities of states. Our calculated electron effective masses of 1.18, 0.63,
and 0.73 mo in the {\Gamma}-X, {\Gamma}-R, and {\Gamma}-W directions,
respectively, show the highly anisotropic nature of this material.Comment: 13 Pages, 4 Figures, and 2 Table
Pharmacogenetic aspects of the use of tacrolimus in renal transplantation: Recent developments and ethnic considerations
Introduction: Tacrolimus (Tac) is effective in preventing acute rejection but has considerable toxicity and inter-individual variability in pharmacokinetics and pharmacodynamics. Part of this is explained by polymorphisms in genes encoding Tac-metabolizing enzymes and transporters. A better understanding of Tac pharmacokinetics and pharmacodynamics may help to minimize different outcomes amongst transplant recipients by personalizing immunosuppression.Areas covered: The pharmacogenetic contribution of Tac metabolism will be examined, with a focus on recent discoveries, new developments and ethnic considerations.Expert opinion: The strongest and most consistent association in pharmacogenetics is between the CYP3A5 genotype and Tac dose requirement, with CYP3A5 expressers having a ∼ 40-50% higher dose requirement compared to non-expressers. Two recent randomized-controlled clinical trials using CYP3A5 genotype, however, did not show a decrease in acute rejections nor reduced toxicity. CYP3A4∗22, CYP3A4∗26, and POR∗28 are also associated with Tac dose requirements and may be included to provide the expected improvement of Tac therapy. Studies focusing on the intracellular drug concentrations and on calcineurin inhibitor-induced nephrotoxicity also seem promising. For all studies, however, the ethnic prevalence of genotypes should be taken into account, as this may significantly impact the effect of pre-emptive genotyping
Hidden degree of freedom and critical states in a two-dimensional electron gas in the presence of a random magnetic field
We establish the existence of a hidden degree of freedom and the critical
states of a spinless electron system in a spatially-correlated random magnetic
field with vanishing mean. Whereas the critical states are carried by the
zero-field contours of the field landscape, the hidden degree of freedom is
recognized as being associated with the formation of vortices in these special
contours. It is argued that, as opposed to the coherent backscattering
mechanism of weak localization, a new type of scattering processes in the
contours controls the underlying physics of localization in the random magnetic
field system. In addition, we investigate the role of vortices in governing the
metal-insulator transition and propose a renormalization-group diagram for the
system under study.Comment: 17 pages, 16 figures; Figs. 1, 7, 9, and 10 have been reduced in
quality for e-submissio
Nonadiabatic approach to dimerization gap and optical absorption coefficient of the Su-Schrieffer-Heeger model
An analytical nonadiabatic approach has been developed to study the
dimerization gap and the optical absorption coefficient of the
Su-Schrieffer-Heeger model where the electrons interact with dispersive quantum
phonons. By investigating quantitatively the effects of quantum phonon
fluctuations on the gap order and the optical responses in this system, we show
that the dimerization gap is much more reduced by the quantum lattice
fluctuations than the optical absorption coefficient is. The calculated optical
absorption coefficient and the density of states do not have the
inverse-square-root singularity, but have a peak above the gap edge and there
exist a significant tail below the peak. The peak of optical absorption
spectrum is not directly corresponding to the dimerized gap. Our results of the
optical absorption coefficient agree well with those of the experiments in both
the shape and the peak position of the optical absorption spectrum.Comment: 14 pages, 7 figures. to be published in PR
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