1,090 research outputs found
3D FEA modelling of laminated composites in bending and their failure mechanisms
keywords: 3D keywords: 3D keywords: 3D keywords: 3D keywords: 3DAbstract This paper developed three-dimensional (3D) Finite Element Analysis (FEA) to investigate the effect of fibre lay-up on the initiation of failure of laminated composites in bending. Tsai-Hill failure criterion was applied to identify the critical areas of failure in composite laminates. In accordance with the 3D FEA, unidirectional ([0]16), cross-ply ([0/90]4s) and angle-ply ([±45]4s) laminates made up of pre-preg Carbon Fibre Reinforced Plastics (CFRP) composites were manufactured and tested under three-point bending. The basic principles of Classical Laminate Theory (CLT) were extended to three-dimension, and the analytical solution was critically compared with the FEA results. The 3D FEA results revealed significant transverse normal stresses in the cross-ply laminate and in-plane shear stress in the angle-ply laminate near free edge regions which are overlooked by conventional laminate model. The microscopic images showed that these free edge effects were the main reason for stiffness reduction observed in the bending tests. The study illustrated the significant effects of fibre lay-up on the flexural failure mechanisms in composite laminates which lead to some suggestions to improve the design of composite laminates
Fractionation of protein adducts in rats and mice dosed with C-14 pentachlorophenol
Pentachlorophenol (PCP) induces liver cancer in mice, possibly due to covalent binding of PCP metabolites to critical macromolecules. In this work, covalent binding was related to PCP biotransformation and specific (cysteinyl) adducts of chlorinated quinones in liver and blood of Sprague-Dawley rats and B6C3F1 mice dosed with [C-14]PCP. Using a sequential scheme of scintillation counting along with selective cleavage of cysteinyl adducts by Raney nickel, we quantified total radiobinding, total covalent binding, non-cysteinyl protein binding, and specific protein adducts in liver nuclei (Np), liver cytosol (Cp), hemoglobin (Hb), and serum albumin (Alb). Almost all of the radiobinding to Np (> 98%) was attributed to covalent binding in both rats and mice. Regarding Cp, more covalent binding was observed in mice than in rats (100% versus 67%, P = 0.015). Very little binding was attributed to serum Alb (rats 1.3%, mice 2.6%, P = 0.046) or Hb (not detected in either species). These results indicate that the liver was the main organ for PCP metabolism and that relatively little of the dose of reactive metabolites became systemically available. Cysteinyl binding accounted for 76-91% of total covalent binding to Np and 68-76% of total covalent binding to Cp. In addition, five times more PCP was bioactivated in the livers of mice than in those of rats (2.14% of the dose bound to Cp in mice and 0.416% in rats). These results reinforce previous studies, suggesting that the liver was a target organ of PCP carcinogenicity and that mice were more susceptible to liver damage than rats. However, the sum of all quantified adducts accounted for only 7-8% of total cysteinyl binding to Np and 2% to Cp, suggesting that other uncharacterized binding species may be important to the toxicity of PCP
Ab-initio study of BaTiO3 surfaces
We have carried out first-principles total-energy calculations of (001)
surfaces of the tetragonal and cubic phases of BaTiO3. Both BaO-terminated
(type I) and TiO2-terminated (type II) surfaces are considered, and the atomic
configurations have been fully relaxed. We found no deep-gap surface states for
any of the surfaces, in agreement with previous theoretical studies. However,
the gap is reduced for the type-II surface, especially in the cubic phase. The
surface relaxation energies are found to be substantial, i.e., many times
larger than the bulk ferroelectric well depth. Nevertheless, the influence of
the surface upon the ferroelectric order parameter is modest; we find only a
small enhancement of the ferroelectricity near the surface.Comment: 8 pages, two-column style with 4 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#pad_sur
Spontaneous CP Violating Phase as The CKM Matrix Phase
We propose that the CP violating phase in the CKM mixing matrix is identical
to the CP phases responsible for the spontaneous CP violation in the Higgs
potential. A specific multi-Higgs model with Peccei-Quinn (PQ) symmetry is
constructed to realize this idea. The CP violating phase does not vanish when
all Higgs masses become large. There are flavor changing neutral current (FCNC)
interactions mediated by neutral Higgs bosons at the tree level. However,
unlike general multi-Higgs models, the FCNC Yukawa couplings are fixed in terms
of the quark masses and CKM mixing angles. Implications for meson-anti-meson
mixing, including recent data on mixing, and neutron electric dipole
moment (EDM) are studied. We find that the neutral Higgs boson masses can be at
the order of one hundred GeV. The neutron EDM can be close to the present
experimental upper bound.Comment: 16 pages, RevTex. Several typos corrected, and one reference adde
Indirect search for dark matter: prospects for GLAST
Possible indirect detection of neutralino, through its gamma-ray annihilation
product, by the forthcoming GLAST satellite from our galactic halo, M31, M87
and the dwarf galaxies Draco and Sagittarius is studied. Gamma-ray fluxes are
evaluated for the two representative energy thresholds, 0.1 GeV and 1.0 GeV, at
which the spatial resolution of GLAST varies considerably. Apart from dwarfs
which are described either by a modified Plummer profile or by a
tidally-truncated King profiles, fluxes are compared for halos with central
cusps and cores. It is demonstrated that substructures, irrespective of their
profiles, enhance the gamma-ray emission only marginally. The expected
gamma-ray intensity above 1 GeV at high galactic latitudes is consistent with
the residual emission derived from EGRET data if the density profile has a
central core and the neutralino mass is less than 50 GeV, whereas for a central
cusp only a substantial enhancement would explain the observations. From M31,
the flux can be detected above 0.1 GeV and 1.0 GeV by GLAST only if the
neutralino mass is below 300 GeV and if the density profile has a central cusp,
case in which a significant boost in the gamma-ray emission is produced by the
central black hole. For Sagittarius, the flux above 0.1 GeV is detectable by
GLAST provided the neutralino mass is below 50 GeV. From M87 and Draco the
fluxes are always below the sensitivity limit of GLAST.Comment: 14 Pages, 7 Figures, 3 Tables, version to appear on Physical Review
CP Phases in Correlated Production and Decay of Neutralinos in the Minimal Supersymmetric Standard Model
We investigate the associated production of neutralinos
accompanied by the neutralino
leptonic decay , taking into
account initial beam polarization and production-decay spin correlations in the
minimal supersymmetric standard model with general CP phases but without
generational mixing in the slepton sector. The stringent constraints from the
electron EDM on the CP phases are also included in the discussion. Initial beam
polarizations lead to three CP--even distributions and one CP--odd
distribution, which can be studied independently of the details of the
neutralino decays. We find that the production cross section and the branching
fractions of the leptonic neutralino decays are very sensitive to the CP
phases. In addition, the production--decay spin correlations lead to several
CP--even observables such as lepton invariant mass distribution, and lepton
angular distribution, and one interesting T--odd (CP--odd) triple product of
the initial electron momentum and two final lepton momenta, the size of which
might be large enough to be measured at the high--luminosity future
electron--positron collider or can play a complementary role in constraining
the CP phases with the EDM constraints.Comment: Revtex, 37 pages, 12 eps figure
The Dependence of the Superconducting Transition Temperature of Organic Molecular Crystals on Intrinsically Non-Magnetic Disorder: a Signature of either Unconventional Superconductivity or Novel Local Magnetic Moment Formation
We give a theoretical analysis of published experimental studies of the
effects of impurities and disorder on the superconducting transition
temperature, T_c, of the organic molecular crystals kappa-ET_2X and beta-ET_2X
(where ET is bis(ethylenedithio)tetrathiafulvalene and X is an anion eg I_3).
The Abrikosov-Gorkov (AG) formula describes the suppression of T_c both by
magnetic impurities in singlet superconductors, including s-wave
superconductors and by non-magnetic impurities in a non-s-wave superconductor.
We show that various sources of disorder lead to the suppression of T_c as
described by the AG formula. This is confirmed by the excellent fit to the
data, the fact that these materials are in the clean limit and the excellent
agreement between the value of the interlayer hopping integral, t_perp,
calculated from this fit and the value of t_perp found from angular-dependant
magnetoresistance and quantum oscillation experiments. If the disorder is, as
seems most likely, non-magnetic then the pairing state cannot be s-wave. We
show that the cooling rate dependence of the magnetisation is inconsistent with
paramagnetic impurities. Triplet pairing is ruled out by several experiments.
If the disorder is non-magnetic then this implies that l>=2, in which case
Occam's razor suggests that d-wave pairing is realised. Given the proximity of
these materials to an antiferromagnetic Mott transition, it is possible that
the disorder leads to the formation of local magnetic moments via some novel
mechanism. Thus we conclude that either kappa-ET_2X and beta-ET_2X are d-wave
superconductors or else they display a novel mechanism for the formation of
localised moments. We suggest systematic experiments to differentiate between
these scenarios.Comment: 18 pages, 5 figure
Supermassive Black Hole Binaries: The Search Continues
Gravitationally bound supermassive black hole binaries (SBHBs) are thought to
be a natural product of galactic mergers and growth of the large scale
structure in the universe. They however remain observationally elusive, thus
raising a question about characteristic observational signatures associated
with these systems. In this conference proceeding I discuss current theoretical
understanding and latest advances and prospects in observational searches for
SBHBs.Comment: 17 pages, 4 figures. To appear in the Proceedings of 2014 Sant Cugat
Forum on Astrophysics. Astrophysics and Space Science Proceedings, ed.
C.Sopuerta (Berlin: Springer-Verlag
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at GeV
Identified mid-rapidity particle spectra of , , and
from 200 GeV p+p and d+Au collisions are reported. A
time-of-flight detector based on multi-gap resistive plate chamber technology
is used for particle identification. The particle-species dependence of the
Cronin effect is observed to be significantly smaller than that at lower
energies. The ratio of the nuclear modification factor () between
protons and charged hadrons () in the transverse momentum
range GeV/c is measured to be
(stat)(syst) in minimum-bias collisions and shows little
centrality dependence. The yield ratio of in minimum-bias d+Au
collisions is found to be a factor of 2 lower than that in Au+Au collisions,
indicating that the Cronin effect alone is not enough to account for the
relative baryon enhancement observed in heavy ion collisions at RHIC.Comment: 6 pages, 4 figures, 1 table. We extended the pion spectra from
transverse momentum 1.8 GeV/c to 3. GeV/
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