269 research outputs found
Applicability valuation for evaluation of surface deflection in automotive outer panels
Upon unloading in a forming process there is elastic recovery, which is the release of the elastic strains and the redistribution of the residual stresses through the thickness direction, thus producing surface deflection. It causes changes in shape and dimensions that can create major problem in the external appearance of outer panels. Thus surface deflection prediction is an important issue in sheet metal forming industry. Many factors could affect surface deflection in the process, such as material variations in mechanical properties, sheet thickness, tool geometry, processing parameters and lubricant condition. The shape and dimension problem in press forming is defined as a trouble mainly caused by the elastic recovery of materials during the forming. The use of high strength steel sheets in the manufacturing of automobile outer panels has increased in the automotive industry over the years because of its lightweight and fuel-efficient improvement. But one of the major concerns of stamping is surface deflection in the formed outer panels. Hence, to be cost effective, accurate prediction must be made of its formability. The automotive industry places rigi
Spin-density functional approach to thermodynamic and structural consistence in the charge and spin response of an electron gas
We use spin-density functional theory to obtain novel expressions for the
charge and spin local-field factors of an electron gas in terms of its
electron-pair structure factors. These expressions (i) satisfy the
compressibility and spin susceptibility sum rules; (ii) keep account of kinetic
correlations by means of an integration over the coupling strength; and (iii)
provide a practical self-consistent scheme for evaluating linear response and
liquid structure. Numerical illustrations are given for the dielectric response
of the paramagnetic electron gas in both three and two dimensions.Comment: 9 pages, 3 figures, submitted to Solid State Commu
Giant magnetoelectric effect in pure manganite-manganite heterostructures
Obtaining strong magnetoelectric couplings in bulk materials and
heterostructures is an ongoing challenge. We demonstrate that manganite
heterostructures of the form show strong multiferroicity
in magnetic manganites where ferroelectric polarization is realized by charges
leaking from to due to repulsion. Here, an
effective nearest-neighbor electron-electron (electron-hole) repulsion
(attraction) is generated by cooperative electron-phonon interaction. Double
exchange, when a particle virtually hops to its unoccupied neighboring site and
back, produces magnetic polarons that polarize antiferromagnetic regions. Thus
a striking giant magnetoelectric effect ensues when an external electrical
field enhances the electron leakage across the interface.Comment: 13 page
Hardware Circuit Implementation of Automatic Control of Static Var Compensator (SVC) using Micro Controller
The design, Fabrication of 1Kvar 1-phase fixed capacitor-thyristor controlled reactor (FC-TCR) type SVC based on microcontroller have been developed in the laboratory for SMSL(Single Machine Single Load) Test System. The test system is setup in the laboratory with a 3-phase Synchronous Machine of 5kva capacity and a 1-phase Induction Motor of 1HP Rating. Brake test have been performed on the Induction Motor by taking the supply from one of the phases of Synchronous Generator. The bus voltage is fall down from 230 V to 195 V on Full Load. Automatic control circuit Hardware of this SVC have been designed and fabricated based on Microcontroller LPC 2148 chip, the most modern industrial controller. The same test system also has been tested with SVC automatic control circuit and experimental results have been presented in this paper. The P-V Curves of the SMSL Test system with and without SVC Control have been plotted which shows the effectiveness of Automatic control of SVC on Voltage Stability enhancement
Improved Privacy Preserving Profile Matching in Online Social Networks
Social networking  became popular because of its digital communication technologies tools for extending the social circle of people. Privacy preservation became a significant issue in social networking. This work discussed user profile matching with privacy preservation and introduced a group of   profile matching protocols. Online social network with a mixture of public and private user profiles to predict the private attributes of users. We map this problem to a relational classification problem and we propose practical models that use friendship and group membership information (which is often not hidden) to infer sensitive attributes. The key novel idea is that in addition to friendship links, groups can be carriers of significant information. To the best of our knowledge, this is the first work that uses operation-based and group-based classification to study privacy implications in social networks with mixed public and private user profiles
Effective mass enhancement in two-dimensional electron systems: the role of interaction and disorder effects
Recent experiments on two-dimensional (2D) electron systems have found a
sharp increase in the effective mass of electrons with decreasing electron
density. In an effort to understand this behavior we employ the many-body
theory to calculate the quasiparticle effective mass in 2D electron systems.
Because the low density regime is explored in the experiments we use the
approximation where the vertex correction describes the
correlation effects to calculate the self-energy from which the effective mass
is obtained. We find that the quasiparticle effective mass shows a sharp
increase with decreasing electron density. Disorder effects due to charged
impurity scattering plays a crucial role in density dependence of effective
mass.Comment: To appear in Solid State Communication
Orbital ordering in undoped manganites via a generalized Peierls instability
We study the ground state orbital ordering of , at weak
electron-phonon coupling, when the spin state is A-type antiferromagnet. We
determine the orbital ordering by extending to our Jahn-Teller system a
recently developed Peierls instability framework for the Holstein model [1]. By
using two-dimensional dynamic response functions corresponding to a mixed
Jahn-Teller mode, we establish that the mode determines the orbital
order.Comment: A few changes made. Accepted in Phys. Rev.
Analytical expressions for the charge-charge local-field factor and the exchange-correlation kernel of a two-dimensional electron gas
We present an analytical expression for the static many-body local field
factor of a homogeneous two-dimensional electron gas, which
reproduces Diffusion Monte Carlo data and embodies the exact asymptotic
behaviors at both small and large wave number . This allows us to also
provide a closed-form expression for the exchange and correlation kernel
, which represents a key input for density functional studies of
inhomogeneous systems.Comment: 5 pages, 3 figure
Spin polarization in a two-dimensional electron gas
We evaluate the charge and longitudinal spin response functions of a
two-dimensional electron gas with interactions in an arbitrary state of
spin polarization, using a structurally self-consistent approach to treat
exchange and correlations. From the results we assess the nature of the
magnetic order in the electronic ground state in zero magnetic field as a
function of electron density. We find that states of partial spin polarization
are thermodynamically unstable at all values of the coupling strength and that
a first-order phase transition occurs with increasing coupling strength from
the magnetically disorderd (paramagnetic) phase to the fully spin-polarized
(ferromagnetic) phase. This behavior is in qualitative agreement with diffusion
Monte Carlo data, although the location of the phase transition is
underestimated in our calculations.Comment: 12 pages, 10 figuer
Correlation energy of a two-dimensional electron gas from static and dynamic exchange-correlation kernels
We calculate the correlation energy of a two-dimensional homogeneous electron
gas using several available approximations for the exchange-correlation kernel
entering the linear dielectric response of the system.
As in the previous work of Lein {\it et al.} [Phys. Rev. B {\bf 67}, 13431
(2000)] on the three-dimensional electron gas, we give attention to the
relative roles of the wave number and frequency dependence of the kernel and
analyze the correlation energy in terms of contributions from the plane. We find that consistency of the kernel with the electron-pair
distribution function is important and in this case the nonlocality of the
kernel in time is of minor importance, as far as the correlation energy is
concerned. We also show that, and explain why, the popular Adiabatic Local
Density Approximation performs much better in the two-dimensional case than in
the three-dimensional one.Comment: 9 Pages, 4 Figure
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