10,685 research outputs found
Finite Element Solution of Axisymmetrical Dynamic Problems of Shells of Revolution
Finite element solution for natural frequencies and mode shapes of free axisymmetrical vibrations and dynamic response of arbitrary rotationally symmetric shell
Flavor Changing Neutral Currents, an Extended Scalar Sector, and the Higgs Production Rate at the LHC
We study extensions of the standard model with additional colored scalar
fields which can couple directly to quarks. Natural suppression of flavor
changing neutral currents implies minimal flavor violation, and fixes the
scalars to transform as (8,2)_1/2 under the SU(3) X SU(2) X U(1) gauge
symmetry. We explore the phenomenology of the standard model with one
additional (8,2)_1/2 scalar, and discuss how this extension can modify flavor
physics and the Higgs boson production rate at the LHC. Custodial SU(2)
symmetry can be implemented for the octet scalars since they transform as a
real color representation. Additional weak scale degrees of freedom needed for
gauge unification are discussed.Comment: Minor change
Towards Identifying and closing Gaps in Assurance of autonomous Road vehicleS - a collection of Technical Notes Part 1
This report provides an introduction and overview of the Technical Topic Notes (TTNs) produced in the Towards Identifying and closing Gaps in Assurance of autonomous Road vehicleS (Tigars) project. These notes aim to support the development and evaluation of autonomous vehicles. Part 1 addresses: Assurance-overview and issues, Resilience and Safety Requirements, Open Systems Perspective and Formal Verification and Static Analysis of ML Systems. Part 2: Simulation and Dynamic Testing, Defence in Depth and Diversity, Security-Informed Safety Analysis, Standards and Guidelines
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Towards Identifying and closing Gaps in Assurance of autonomous Road vehicleS - a collection of Technical Notes Part 2
This report provides an introduction and overview of the Technical Topic Notes (TTNs) produced in the Towards Identifying and closing Gaps in Assurance of autonomous Road vehicleS (Tigars) project. These notes aim to support the development and evaluation of autonomous vehicles. Part 1 addresses: Assurance-overview and issues, Resilience and Safety Requirements, Open Systems Perspective and Formal Verification and Static Analysis of ML Systems. This report is Part 2 and discusses: Simulation and Dynamic Testing, Defence in Depth and Diversity, Security-Informed Safety Analysis, Standards and Guidelines
An introduction to a porous shape memory alloy dynamic data driven application system
Shape Memory Alloys are capable of changing their crystallographic structure due to changes of temperature and/or stress. Our research focuses on three points: (1) Iterative Homogenization of Porous SMAs: Development of a Multiscale Model of porous SMAs utilizing iterative homogenization and based on existing knowledge of constitutive modeling of polycrystalline SMAs. (2) DDDAS: Develop tools to turn on and off the sensors and heating unit(s), to monitor on-line data streams, to change scales based on incoming data, and to control what type of data is generated. The application must have the capability to be run and steered remotely. (3) Modeling and applications of porous SMA: Vibration isolation devices with SMA and porous SMA components for aerospace applications will be analyzed and tested. Numerical tools for modeling porous SMAs with a second viscous phase will be developed. The outcome will be a robust, three-dimensional, multiscale model of porous SMA that can be used in complicated, real-life structural analysis of SMA components using a DDDAS framework. © 2012 Published by Elsevier Ltd
Comparative Raman Studies of Sr2RuO4, Sr3Ru2O7 and Sr4Ru3O10
The polarized Raman spectra of layered ruthenates of the Srn+1RunO3n+1
(n=1,2,3) Ruddlesden-Popper series were measured between 10 and 300 K. The
phonon spectra of Sr3Ru2O7 and Sr4Ru3O10 confirmed earlier reports for
correlated rotations of neighboring RuO6 octahedra within double or triple
perovskite blocks. The observed Raman lines of Ag or B1g symmetry were assigned
to particular atomic vibrations by considering the Raman modes in simplified
structures with only one double or triple RuO6 layer per unit cell and by
comparison to the predictions of lattice dynamical calculations for the real
Pban and Pbam structures. Along with discrete phonon lines, a continuum
scattering, presumably of electronic origin, is present in the zz, xx and xy,
but not in the x'y' and zx spectra. Its interference with phonons results in
Fano shape for some of the lines in the xx and xy spectra. The temperature
dependencies of phonon parameters of Sr3Ru2O7 exhibit no anomaly between 10 and
300 K where no magnetic transition occurs. In contrast, two B1g lines in the
spectra of Sr4Ru3O10, corresponding to oxygen vibrations modulating the Ru-O-Ru
bond angle, show noticeable hardening with ferromagnetic ordering at 105 K,
thus indicating strong spin-phonon interaction.Comment: 9 pages, 12 figure
Origin of magnetoelectric behavior in BiFeO
The magnetoelectric behavior of BiFeO has been explored on the basis of
accurate density functional calculations. The structural, electronic, magnetic,
and ferroelectric properties of BiFeO are predicted correctly without
including strong correlation effect in the calculation. Moreover, the
experimentally-observed elongation of cubic perovskite-like lattice along the
[111] direction is correctly reproduced. At high pressure we predicted a
pressure-induced structural transition and the total energy calculations at
expanded lattice show two lower energy ferroelectric phases, closer in energy
to the ground state phase. Band-structure calculations show that BiFeO will
be an insulator in A- and G-type antiferromagnetic phases and a metal in other
magnetic configurations. Chemical bonding in BiFeO has been analyzed using
various tools and electron localization function analysis shows that
stereochemically active lone-pair electrons at the Bi sites are responsible for
displacements of the Bi atoms from the centro-symmetric to the
noncentrosymmetric structure and hence the ferroelectricity. A large
ferroelectric polarization (88.7 C/cm) is predicted in accordance
with recent experimental findings. The net polarization is found to mainly (
98%) originate from Bi atoms. Moreover the large scatter in experimentally
reported polarization values is due to the large anisotropy in the spontaneous
polarization.Comment: 19 pages, 12 figures, 4 table
Hydrogen atom in crossed external fields reexemined by the moment method
Recurrence relations of perturbation theory for hydrogen ground state are
obtained. With their aid polarizabilities in constant perpendicular electric
and magnetic fields are computed up to 80th order. The high orders asymptotic
is compared with its quasiclassical estimate. For the case of arbitrary mutual
orientation of external fields a general sixth order formula is given.Comment: 11 pages, LaTeX, 2 figures (eps
Design of metallic nanoparticles gratings for filtering properties in the visible spectrum
Plasmonic resonances in metallic nanoparticles are exploited to create
efficient optical filtering functions. A Finite Element Method is used to model
metallic nanoparticles gratings. The accuracy of this method is shown by
comparing numerical results with measurements on a two-dimensional grating of
gold nanocylinders with elliptic cross section. Then a parametric analysis is
performed in order to design efficient filters with polarization dependent
properties together with high transparency over the visible range. The behavior
of nanoparticle gratings is also modelled using the Maxwell-Garnett
homogenization theory and analyzed by comparison with the diffraction by a
single nanoparticle. The proposed structures are intended to be included in
optical systems which could find innovative applications.Comment: submitted to Applied Optic
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