678 research outputs found
Thermal analysis of antenna backup structure. Part 1. Methodology development
An analytic method was devised to predict the temperature distribution in typical antenna structural back-up members. The results are in agreement with those obtained by a numerical shooting method. The analytic method shows potential in simplifying the thermal analysis process for complex back-up antenna structures
The physiological cost of wearing the propellant handler's ensemble at the Kennedy Space Center
The potential for exposure to toxins used in the propulsion systems of spacecraft dictates the use of a whole body protective suit, the Propellant Handler's Ensemble (PHE) during preflight preparation and launching. The weight, structure, and operating parameters of the PHE may be expected to have a significant impact upon the metabolic, cardiovascular, and thermal responses of the user, especially during ambient temperature extremes and high workload situations. Four male subjects participated in tests in -7, 23, and 43 C (20, 74, and 110 F) environments in two versions of the PHE, the autonomous backpack (BP) and the hoseline (HL) supplied configuration. Measurements included heart rate (HR) rectal temperature, four skin temperatures, oxygen (O2), and carbon dioxide (CO2) in the helmet area, interior suit temperature, and suit pressure. Exercise metabolism was estimated from HR, PHE weight, and treadmill speed and grade. The HR responses between each PHE configuration were not statistically different. As a percentage of HR maximum, the mean values were 79 percent (COLD), 84 percent (LAB), and 90 percent (HOT). Helmet O2 and CO2 levels were correlated with percent HR max (P less than 0.001). Rectal temperatures were similar for each PHE configuration, except in the HOT exposure where the BP version exceeded the HL configuration (P less than 0.05). In nearly every instance the HR was driven to moderately high levels, the supplied respiratory gases were not optimum, and thermal adversity was a primary stressor. Our findings suggest that medical and physical fitness standards, along with operational restrictions, should be imposed upon PHE users to avoid situations that could adversely affect the worker
An Occupational Performance Test Validation Program for Fire Fighters at the Kennedy Space Center
We evaluated performance of a modified Combat Task Test (CTT) and of standard fitness tests in 20 male subjects to assess the prediction of occupational performance standards for Kennedy Space Center fire fighters. The CTT consisted of stair-climbing, a chopping simulation, and a victim rescue simulation. Average CTT performance time was 3.61 +/- 0.25 min (SEM) and all CTT tasks required 93% to 97% maximal heart rate. By using scores from the standard fitness tests, a multiple linear regression model was fitted to each parameter: the stairclimb (r(exp 2) = .905, P less than .05), the chopping performance time (r(exp 2) = .582, P less than .05), the victim rescue time (r(exp 2) = .218, P = not significant), and the total performance time (r(exp 2) = .769, P less than .05). Treadmill time was the predominant variable, being the major predictor in two of four models. These results indicated that standardized fitness tests can predict performance on some CTT tasks and that test predictors were amenable to exercise training
Almost-zero-energy Eigenvalues of Some Broken Supersymmetric Systems
For a quantum mechanical system with broken supersymmetry, we present a
simple method of determining the ground state when the corresponding energy
eigenvalue is sufficiently small. A concise formula is derived for the
approximate ground state energy in an associated, well-separated, asymmetric
double-well-type potential. Our discussion is also relevant for the analysis of
the fermion bound state in the kink-antikink scalar background.Comment: revised version, to be pubilshed in PR
Schr\"{o}dinger Fields on the Plane with non-Abelian Chern-Simons Interactions
Physical content of the nonrelativistic quantum field theory with non-Abelian
Chern-Simons interactions is clarified with the help of the equivalent first-
quantized description which we derive in any physical gauge.Comment: 12 pages, LaTex, SNUTP 94-1
Chern-Simons States and Topologically Massive Gauge Theories
In an abelian topologically massive gauge theory, any eigenstate of the
Hamiltonian can be decomposed into a factor describing massive propagating
gauge bosons and a Chern-Simons wave function describing a set of
nonpropagating ``topological'' excitations. The energy depends only on the
propagating modes, and energy eigenstates thus occur with a degeneracy that can
be parametrized by the Hilbert space of the pure Chern-Simons theory. We show
that for a {\em nonabelian} topologically massive gauge theory, this degeneracy
is lifted: although the Gauss law constraint can be solved with a similar
factorization, the Hamiltonian couples the propagating and nonpropagating
(topological) modes.Comment: 11 page
Stochastic collective dynamics of charged--particle beams in the stability regime
We introduce a description of the collective transverse dynamics of charged
(proton) beams in the stability regime by suitable classical stochastic
fluctuations. In this scheme, the collective beam dynamics is described by
time--reversal invariant diffusion processes deduced by stochastic variational
principles (Nelson processes). By general arguments, we show that the diffusion
coefficient, expressed in units of length, is given by ,
where is the number of particles in the beam and the Compton
wavelength of a single constituent. This diffusion coefficient represents an
effective unit of beam emittance. The hydrodynamic equations of the stochastic
dynamics can be easily recast in the form of a Schr\"odinger equation, with the
unit of emittance replacing the Planck action constant. This fact provides a
natural connection to the so--called ``quantum--like approaches'' to beam
dynamics. The transition probabilities associated to Nelson processes can be
exploited to model evolutions suitable to control the transverse beam dynamics.
In particular we show how to control, in the quadrupole approximation to the
beam--field interaction, both the focusing and the transverse oscillations of
the beam, either together or independently.Comment: 15 pages, 9 figure
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