11,284 research outputs found
Millimeter radiometer system technology
JPL has had a large amount of experience with spaceborne microwave/millimeter wave radiometers for remote sensing. All of the instruments use filled aperture antenna systems from 5 cm diameter for the microwave Sounder Units (MSU), 16 m for the microwave limb sounder (MLS) to 20 m for the large deployable reflector (LDR). The advantages of filled aperture antenna systems are presented. The requirements of the 10 m Geoplat antenna system, 10 m multified antenna, and the MLS are briefly discussed
Hadron Loops: General Theorems and Application to Charmonium
In this paper we develop a formalism for incorporating hadron loops in the
quark model. We derive expressions for mass shifts, continuum components and
mixing amplitudes of "quenched" quark model states due to hadron loops, as
perturbation series in the valence-continuum coupling Hamiltonian. We prove
three general theorems regarding the effects of hadron loops, which show that
given certain constraints on the external "bare" quark model states, the
valence-continuum coupling, and the hadrons summed in the loops, the following
results hold: (1) The loop mass shifts are identical for all states within a
given N,L multiplet. (2) These states have the same total open-flavor decay
widths. (3) Loop-induced valence configuration mixing vanishes provided that
{\L}_i \neq \L_f or . The charmonium system is used as a
numerical case study, with the decay model providing the
valence-continuum coupling. We evaluate the mass shifts and continuum mixing
numerically for all 1S, 1P and 2S charmonium valence states due to loops of D,
D, D and D meson pairs. We find that the mass shifts are quite
large, but are numerically similar for all the low-lying charmonium states, as
suggested by the first theorem. Thus, loop mass shifts may have been "hidden"
in the valence quark model by a change of parameters. The two-meson continuum
components of the physical charmonium states are also found to be large,
creating challenges for the interpretation of the constituent quark model.Comment: 10 pages, 1 ps figure. Typos corrected; discussion of psi-eta_c mass
splitting added, published versio
Computer programs for prediction of structural vibrations due to fluctuating pressure environments. Volume 1 - Theoretical analyses Final report
Theoretical analyses for computer program to calculate random vibrations of reinforced rectangular cylindrical panels in fluctuating pressure environmen
Simple pressure gauge for uranium hexafluoride
A sensitive detector and pressure gauge for uranium hexafluoride in high‐vacuum systems is described. Negative surface ionization of UF_6 occurs on ribbon filaments operated at temperatures too low for electron emission to be significant. The ion current measured on a cylindrical collector surrounding the filament assembly varies regularly with UF_6 pressure below 10^(−3) Torr. Different filament materials are considered, including rhenium, thoriated tungsten, and platinum. Rhenium is found to be the most satisfactory material for operation of diode emitters as a pressure gauge. Gauge constants (in A Torr^(−1)) are derived from comparing negative surface ionization currents with the response of a capacitance manometer and are shown to be independent of temperature within a reasonable operating range. The effects of exposing the rhenium filament to various gases is considered, and it is shown that brief exposure to acetylene substantially improves the operating characteristics of the gauge
Associated Charmonium Production in p-pbar Annihilation
In this paper we summarize our recent results for low energy associated
charmonium production cross sections, using 1) crossing symmetry, and 2) an
explicit hadronic model. These predictions are of relevance to the planned
charmonium and charmonium hybrid production experiment PANDA at GSI.Comment: 5 pages, 5 figures. Contribution to the Second Meeting of the APS
Topical Group on Hadron Physics GHP2006. (Nashville, TN, 22-24 Oct. 2006
Margery Kempe, viatrix
Margery Kempe journeyed on pilgrimage from England to Compostela in 1417, a visit briefly noted in her quasi-autobiographical Book. This article examines and contextualises that journey as a facet of a life and a text marked by many similar pilgrimages. In addition, it fits pilgrimage into her life as viatrix, engaged on a spiritual journey not to terrestrial shrines, but to heavenly salvation.Margery Kempe peregrinó desde Inglaterra a Compostela en 1417, una visita de la que dejó constancia en su cuasi-autobiográfico Libro. Este artículo analiza y contextualiza esa travesía como una parte de una vida y un texto marcados por peregrinajes similares. Además, integra la peregrinación en su vida como viatrix, comprometida con un viaje espiritual no hacia santuarios terrenales, sino a la salvación celestial.
[gl] Margery Kempe peregrinou desde Inglaterra a Compostela en 1417, unha visita da que quedou constancia no seu case-autobiográfico Libro. Este artigo analiza e contextualiza esa travesía coma unha parte dunha vida e un texto marcados por peregrinacións semellantes. Ademais, integra a peregrinación na súa vida coma viatrix, comprometida cunha viaxe espiritual non cara a santuarios terreais, senón á salvación celestial
Charmonium-Nucleon Dissociation Cross Sections in the Quark Model
Charmonium dissociation cross sections due to flavor-exchange
charmonium-baryon scattering are computed in the constituent quark model. We
present results for inelastic and scattering amplitudes
and cross sections into 46 final channels, including final states composed of
various combinations of , , , and . These results
are relevant to experimental searches for the deconfined phase of quark matter,
and may be useful in identifying the contribution of initial
production to the open-charm final states observed at RHIC through the
characteristic flavor ratios of certain channels. These results are also of
interest to possible charmonium-nucleon bound states.Comment: 10 pages, 5 eps figures, revte
Multigrid for hypersonic viscous two- and three-dimensional flows
The use of a multigrid method with central differencing to solve the Navier-Stokes equations for hypersonic flows is considered. The time dependent form of the equations is integrated with an explicit Runge-Kutta scheme accelerated by local time stepping and implicit residual smoothing. Variable coefficients are developed for the implicit process that removes the diffusion limit on the time step, producing significant improvement in convergence. A numerical dissipation formulation that provides good shock capturing capability for hypersonic flows is presented. This formulation is shown to be a crucial aspect of the multigrid method. Solutions are given for two-dimensional viscous flow over a NACA 0012 airfoil and three-dimensional flow over a blunt biconic
A 36GHz traveling wave maser for use in radio astronomy
Development of 36 GHz low noise traveling wave maser radiometer for radio astronomy usag
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