22,849 research outputs found
Thermally conducting electron transfer polymers
New polymeric material exhibits excellent physical shock protection, high electrical resistance, and thermal conductivity. It is especially useful for electronic circuitry, such as subminiaturization of components and modular construction of circuits
Improved thermally conducting electron transfer polymers
Development of polymers with improved heat transfer coefficients for use in encapsulating electronic modules is discussed. Chemical reactions for synthesizing the polymers are described and thermodynamic and physical properties are analyzed
A theoretical and experimental investigation of cylindrical electrostatic probes at arbitrary incidence in flowing plasma
The theory for calculating the current collected by a negatively biased cylindrical electrostatic probe at an arbitrary angle of attack in a weakley ionized flowing plasma is presented. The theory was constructed by considering both random and directed motion simultaneous with dynamic coupling of the flow properties and of the electric field of the probe. This direct approach yielded a theory that is more general than static plasma theories modified to account for flow. Theoretical calculations are compared with experimental electrostatic probe data obtained in the free stream of an arc-heated hypersonic wind tunnel. The theoretical calculations are based on flow conditions and plasma electron densities measured by an independent microwave interferometer technique. In addition, the theory is compared with laboratory and satellite data previously published by other investigators. In each case the comparison gives good agreement
Service Development Programme: Maximising Life Opportunities for Teenagers. Teenagers' Views and Experiences of Sex and Relationships Education, Sexual Health Services and Family Support Services in Kent - Survey findings for Year 2
This brief report provides findings from data collected in year 2 of a survey of teenagers' views and experiences of sex and relationships education and sexual health services in Kent. The data in year 2 was collected in Autumn 2005, a year after the data collected in year 1. The purpose of this report is to highlight the results in year 2 which differ from the year 1 survey data. It is to be used in conjunction with the report in year 1 entitled "Service Development Programme: Maximising Life Opportunies for Teenagers: Teenagers' Views and Experiences of Sex and Relationships Educatioon, Sexual Health Services and Family Suupport Services in Kent: Survey Findings July 2005". The final report on the survey will consist of findings from further analysis of the data from year 1 and year 2 merged together, available at the end of 2006
Spin-Flavor Structure of Large N Baryons
The spin-flavor structure of large N baryons is described in the 1/N
expansion of QCD using quark operators. The complete set of quark operator
identities is obtained, and used to derive an operator reduction rule which
simplifies the 1/N expansion. The operator reduction rule is applied to the
axial currents, masses, magnetic moments and hyperon non-leptonic decay
amplitudes in the limit, to first order in breaking, and
without assuming symmetry. The connection between the Skyrme and quark
representations is discussed. An explicit formula is given for the quark model
operators in terms of the Skyrme model operators to all orders in for
the two flavor case.Comment: 36 pages, 2 eps figures, uses revte
Cold Flow Determination of the Internal Flow Environment Around the Submerged TVC Nozzle for the Space Shuttle SRM
A series of subscale cold flow tests was performed to quantify the gas flow characteristics at the aft end of the Space Shuttle Solid Rocket Motor. This information was used to support the analyses of the redesigned nozzle/case joint. A portion of the thermal loads at the joint are due to the circumferential velocities and pressure gradients caused primarily by the gimbaling of the submerged nose TVC nozzle. When the nozzle centerline is vectored with respect to the motor centerline, asymmetries are set up in the flow field under the submerged nozzle and immediately adjacent to the nozzle/case joint. Specific program objectives included: determination of the effects of nozzle gimbal angle and propellant geometry on the circumferential flow field; measurement of the static pressure and gas velocities in the vicinity of the nozzle/case joint; use of scaling laws to apply the subscale cold flow data to the full scale SRM; and generation of data for use in validation of 3-D computational fluid dynamic, CFD, models of the SRM flow field. These tests were conducted in the NASA Marshall Space Flight Center Airflow Facility with a 7.5 percent scale model of the aft segment of the SRM. Static and dynamic pressures were measured in the model to quantify the flow field. Oil flow data was also acquired to obtain qualitative visual descriptions of the flow field. Nozzle gimbal angles of 0, 3.5, and 7 deg were used with propellant grain configurations corresponding to motor burn times of 0, 9, 19, and 114 seconds. This experimental program was successful in generating velocity and pressure gradient data for the flow field around the submerged nose nozzle of the Space Shuttle SRM at various burn times and gimbal angles. The nature of the flow field adjacent to the nozzle/case joint was determined with oil droplet streaks, and the velocity and pressure gradients were quantified with pitot probes and wall static pressure measurements. The data was applied to the full scale SRM thru a scaling analysis and the results compared well with the 3-D computational fluid dynamics computer model
Pion-Nucleon Phase Shifts in Heavy Baryon Chiral Perturbation Theory
We calculate the phase shifts in the pion-nucleon scattering using the heavy
baryon formalism. We consider phase shifts for the pion energy range of 140 to
MeV. We employ two different methods for calculating the phase shifts -
the first using the full third order calculation of the pion-nucleon scattering
amplitude and the second by including the resonances and as
explicit degrees of freedom in the Lagrangian. We compare the results of the
two methods with phase shifts extracted from fits to the pion-nucleon
scattering data. We find good to fair agreement between the calculations and
the phase shifts from scattering data.Comment: 14 pages, Latex, 6figures. Revised version to appear in Phys.Rev.
Development of phosphorylated adhesives
The synthesis of epoxy prepolymers containing phosphorus was carried out in such a manner as to provide adhesives containing at least 5 percent of this element. The purpose of this was to impart fire retardant properties to the adhesive. The two epoxy derivatives, bis(4-glycidyl-oxyphenyl)phenylphosphine oxide and bis(4-glycidyl-2-methoxyphenyl)phenylphosphonate, and a curing agent, bis(3-aminophenyl)methylphosphine oxide, were used in conjunction with one another and along with conventional epoxy resins and curing agents to bond Tedlar and Polyphenylethersulfone films to Kerimid-glass syntactic foam-filled honeycomb structures. Elevated temperatures are required to cure the epoxy resins with the phosphorus-contaning diamine; however, when Tedlar is being bonded, lower curing temperatures must be used to avoid shrinkage and the concomitant formation of surface defects. Thus, the phosphorus-containing aromatic amine curing agent cannot be used alone, although it is possible to use it in conjunction with an aliphatic amine which would allow lower cure temperatures to be used. The experimental epoxy resins have not provided adhesive bonds quite as strong as those provided by Epon 828 when compared in peel tests, but the differences are not very significant. It should be noted, if optimum properties are to be realized. In any case the fire retardant characteristics of the neat resin systems obtained are quite pronounced, since in most cases the self-extinguishing properties are evident almost instantly when specimens are removed from a flame
On the structure of large N cancellations in baryon chiral perturbation theory
We show how to compute loop graphs in heavy baryon chiral perturbation theory
including the full functional dependence on the ratio of the Delta--nucleon
mass difference to the pion mass, while at the same time automatically
incorporating the 1/N cancellations that follow from the large-N spin-flavor
symmetry of baryons in QCD. The one-loop renormalization of the baryon axial
vector current is studied to demonstrate the procedure. A new cancellation is
identified in the one-loop contribution to the baryon axial vector current. We
show that loop corrections to the axial vector currents are exceptionally
sensitive to deviations of the ratios of baryon-pion axial couplings from SU(6)
values
BARYON-BARYON INTERACTIONS IN LARGE N_C CHIRAL PERTURBATION THEORY
Interactions of two baryons are considered in large chiral perturbation
theory and compared to the interactions derived from the Skyrme model. Special
attention is given to a torus-like configuration known to be present in the
Skyrme model.Comment: 18 pages, REVTEX, 8 uuencoded PS figures appende
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