11,426 research outputs found
Improved compression molding technology for continuous fiber reinforced composite laminates. Part 2: AS-4/Polyimidesulfone prepreg system
AS-4/polyimidesulfone (PISO2) composite prepreg was utilized for the improved compression molding technology investigation. This improved technique employed molding stops which advantageously facilitate the escape of volatile by-products during the B-stage curing step, and effectively minimize the neutralization of the consolidating pressure by intimate interply fiber-fiber contact within the laminate in the subsequent molding cycle. Without the modifying the resin matrix properties, composite panels with both unidirectional and angled plies with outstanding C-scans and mechanical properties were successfully molded using moderate molding conditions, i.e., 660 F and 500 psi, using this technique. The size of the panels molded were up to 6.00 x 6.00 x 0.07 in. A consolidation theory was proposed for the understanding and advancement of the processing science. Processing parameters such as vacuum, pressure cycle design, prepreg quality, etc. were explored
Response of East Texas Mid-Rotation Loblolly Pine Plantations to Poultry Litter and Chemical Fertilizer Amendments
Rank 3 permutation characters and maximal subgroups
In this paper we classify all maximal subgroups M of a nearly simple
primitive rank 3 group G of type L=Omega_{2m+1}(3), m > 3; acting on an L-orbit
E of non-singular points of the natural module for L such that 1_P^G <=1_M^G
where P is a stabilizer of a point in E. This result has an application to the
study of minimal genera of algebraic curves which admit group actions.Comment: 41 pages, to appear in Forum Mathematicu
Rare kaon decays in SUSY with non-universal A terms
We study the rare kaon decays in the framework of general SUSY models. Unlike
the results in the literature, we find the contributions from the gluino
exchange to the branching ratio of can reach the
central value () of the new E787 data while the
predicted value of standard model is less than . We also find that
the same effects also enhance the decays of ,
and .Comment: 9 pages, references added, revised version to appear in J. Phys.
Split Two-Higgs-Doublet Model and Neutrino Condensation
We split the two-Higgs-doublet model by assuming very different vevs for the
two doublets: the vev is at weak scale (174 GeV) for the doublet \Phi_1 and at
neutrino-mass scale (10^{-2} \sim 10^{-3} eV) for the doublet \Phi_2. \Phi_1 is
responsible for giving masses to all fermions except neutrinos; while \Phi_2 is
responsible for giving neutrino masses through its tiny vev without introducing
see-saw mechanism. Among the predicted five physical scalars H, h, A^0 and
H^{\pm}, the CP-even scalar h is as light as 10^{-2} \sim 10^{-3}eV while
others are at weak scale. We identify h as the cosmic dark energy field and the
other CP-even scalar H as the Standard Model Higgs boson; while the CP-odd A^0
and the charged H^{\pm} are the exotic scalars to be discovered at future
colliders. Also we demonstrate a possible dynamical origin for the doublet
\Phi_2 from neutrino condensation caused by some unknown dynamics.Comment: version in Europhys. Lett. (discussions added
Numerical Solutions of Supersonic and Hypersonic Laminar Compression Corner Flows
An efficient time-splitting, second-order accurate, numerical scheme is used to solve the complete Navier-Stokes equations for supersonic and hypersonic laminar flow over a two-dimensional compression corner. A fine, exponentially stretched mesh spacing is used in the region near the wall for resolving the viscous layer. Good agreement is obtained between the present computed results and experimental measurement for a Mach number of 14.1 and a Reynolds number of 1.04 x 10(exp 5) with wedge angles of 15 deg, 18 deg, and 24 deg. The details of the pressure variation across the boundary layer are given, and a correlation between the leading edge shock and the peaks in surface pressure and heat transfer is observed
Experimental verification of a self-consistent theory of the first-, second-, and third-order (non)linear optical response
We show that a combination of linear absorption spectroscopy, hyper-Rayleigh
scattering, and a theoretical analysis using sum rules to reduce the size of
the parameter space leads to a prediction of the two-photon absorption
cross-section of the dye AF455 that agrees with two-photon absorption
spectroscopy. Our procedure, which demands self-consistency between several
measurement techniques and does not use adjustable parameters, provides a means
for determining transition moments between the dominant excited states based
strictly on experimental characterization. This is made possible by our new
approach that uses sum rules and molecular symmetry to rigorously reduce the
number of required physical quantities.Comment: 10 pages, 9 figure
A momentum-space representation of Feynman propagator in Riemann-Cartan spacetime
We first construct generalized Riemann-normal coordinates by using
autoparallels, instead of geodesics, in an arbitrary Riemann-Cartan spacetime.
With the aid of generalized Riemann-normal coordinates and their associated
orthonormal frames, we obtain a momentum-space representation of the Feynman
propagator for scalar fields, which is a direct generalization of Bunch and
Parker's works to curved spacetime with torsion. We further derive the
proper-time representation in dimensional Riemann-Cartan spacetime from the
momentum-space representation. It leads us to obtain the renormalization of
one-loop effective Lagrangians of free scalar fields by using dimensional
regularization. When torsion tensor vanishes, our resulting momentum-space
representation returns to the standard Riemannian results.Comment: 12 page
Litter management strategies to reduce odour emissions from poultry litter
Litter conditions in meat chicken sheds are important for providing a healthy and comfortable environment for the birds and to regulate the emission of odours, which can impact on the surrounding community. Litter is considered the primary source of odour in meat chicken sheds. Mismanagement of litter odour control can result in public annoyances and possible breach of regulations.
Odour emissions from poultry litter are complex due to:
- The existence of multiple odorant sources within litter (i.e. fresh excreta, friable litter and cake);
- Formation and emission of numerous odorants; and
- Significant spatial and temporal variability of moisture content, porosity, pH, ventilation air-flow, temperature, humidity, and bird activity.
To date, there still exists a big knowledge gap in the relationship between specific litter conditions and odour emissions.
To address this knowledge gap as well as to help tailor effective litter odour management strategies, this project pursued the following objectives:
- Investigate how odour emissions from litter, in terms of chemical composition and emission rates, were affected by different litter conditions. Special attention was paid to water as it affects many of the chemical, physical, and microbial properties of litter.
- Review, quantify, and evaluate application of common litter management practices on the formation and emission of odours and odorants from poultry litter
Direct Emission of multiple strange baryons in ultrarelativistic heavy-ion collisions from the phase boundary
We discuss a model for the space-time evolution of ultrarelativistic
heavy-ion collisions which employs relativistic hydrodynamics within one region
of the forward light-cone, and microscopic transport theory (i.e. UrQMD) in the
complement. Our initial condition consists of a quark-gluon plasma which
expands hydrodynamically and hadronizes. After hadronization the solution
eventually changes from expansion in local equilibrium to free streaming, as
determined selfconsistently by the interaction rates between the hadrons and
the local expansion rate. We show that in such a scenario the inverse slopes of
the -spectra of multiple strange baryons (, ) are practically
unaffected by the purely hadronic stage of the reaction, while the flow of
's and 's increases. Moreover, we find that the rather ``soft''
transverse expansion at RHIC energies (due to a first-order phase transition)
is not washed out by strong rescattering in the hadronic stage. The earlier
kinetic freeze-out as compared to SPS-energies results in similar inverse
slopes (of the -spectra of the hadrons in the final state) at RHIC and SPS
energies.Comment: 4 pages, 3 figures, statistics for Omegas improved, slight revision
of the manuscript (expansion of hadronization volume more emphasized,
pi-Omega scattering is discussed very briefly
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