2,836 research outputs found
Planetary/DOD entry technology flight experiments. Volume 3: Planetary entry flight experiments handbook
The environments produced by entry into Jupiter and Saturn atmospheres are summarized. Worst case design environments are identified and the effect of entry angle, type of atmosphere and ballistic coefficient variations are presented. The range of environments experienced during earth entry is parametrically described as a function of initial entry conditions. The sensitivity of these environments to vehicle ballistic coefficient and nose radius is also shown. An elliptical deorbit maneuver strategy is defined in terms of the velocity increment required versus initial entry conditions and apoapsis altitude. Mission time, ground track, and out of plane velocity penalties are also presented. Performance capabilities of typical shuttle launched boosters are described including the initial entry conditions attainable as a function of paylaod mass and apoapsis altitude
Planetary/DOD entry technology flight experiments. Volume 4: DOD entry flight experiments
For abstract, see vol. 1
Planetary/DOD entry technology flight experiments. Volume 1: Executive summary
The feasibility of using the space shuttle to launch planetary and DoD entry flight experiments was examined. The results of the program are presented in two parts: (1) simulating outer planet environments during an earth entry test, the prediction of Jovian and earth radiative heating dominated environments, mission strategy, booster performance and entry vehicle design, and (2) the DoD entry test needs for the 1980's, the use of the space shuttle to meet these DoD test needs, modifications of test procedures as pertaining to the space shuttle, modifications to the space shuttle to accommodate DoD test missions and the unique capabilities of the space shuttle. The major findings of this program are summarized
Frequency shift of hyperfine transitions due to blackbody radiation
We have performed calculations of the size of the frequency shift induced by
a static electric field on the clock transition frequencies of the hyperfine
splitting in Yb+, Rb, Cs, Ba+, and Hg+. The calculations are used to find the
frequency shifts due to blackbody radiation which are needed for accurate
frequency measurements and improvements of the limits on variation of the fine
structure constant, alpha. Our result for Cs (delta nu E^2=-2.26 times
10^{-10}Hz/(V/m)^2) is in good agreement with early measurements and ab initio
calculations. We present arguments against recent claims that the actual value
might be smaller. The difference (approx 10%) is due to the contribution of the
continuum spectrum in the sum over intermediate states.Comment: Added discussion of Cs results and reference
The role of alkane coordination in C–H bond cleavage at a Pt(II) center
The rates of CFormula H bond activation for various alkanes by [(N–N)Pt(Me)(TFEd3)]+ (N Formula N = ArFormula NFormula C(Me)Formula C(Me)Formula NFormula Ar; Ar = 3,5-di-tert-butylphenyl; TFE-d3 = CF3CD2OD) were studied. Both linear and cyclic alkanes give the corresponding alkene-hydride cation [(N–N)Pt(H)(alkene)]+ via (i) rate determining alkane coordination to form a CFormula H {sigma} complex, (ii) oxidative cleavage of the coordinated CFormula H bond to give a platinum(IV) alkyl-methyl-hydride intermediate, (iii) reductive coupling to generate a methane {sigma} complex, (iv) dissociation of methane, and (v) beta-H elimination to form the observed product. Second-order rate constants for cycloalkane activation (CnH2n), are proportional to the size of the ring (k ~ n). For cyclohexane, the deuterium kinetic isotope effect (kH/kD) of 1.28 (5) is consistent with the proposed rate determining alkane coordination to form a CFormula H {sigma} complex. Statistical scrambling of the five hydrogens of the Pt-methyl and the coordinated methylene unit, via rapid, reversible steps ii and iii, and interchange of geminal CFormula H bonds of the methane and cyclohexane CFormula H {sigma} adducts, is observed before loss of methane
Post-Traumatic Stress Disorder, Obesity, and Marijuana Use in Marine Corps Veterans
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Post-Traumatic Stress Disorder, Obesity, and Marijuana Use in Marine Corps Veterans
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Nonlinear Dynamics of Capacitive Charging and Desalination by Porous Electrodes
The rapid and efficient exchange of ions between porous electrodes and
aqueous solutions is important in many applications, such as electrical energy
storage by super-capacitors, water desalination and purification by capacitive
deionization (or desalination), and capacitive extraction of renewable energy
from a salinity difference. Here, we present a unified mean-field theory for
capacitive charging and desalination by ideally polarizable porous electrodes
(without Faradaic reactions or specific adsorption of ions) in the limit of
thin double layers (compared to typical pore dimensions). We illustrate the
theory in the case of a dilute, symmetric, binary electrolyte using the
Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae
are available for salt adsorption and capacitive charging of the diffuse part
of the double layer. We solve the full GCS mean-field theory numerically for
realistic parameters in capacitive deionization, and we derive reduced models
for two limiting regimes with different time scales: (i) In the
"super-capacitor regime" of small voltages and/or early times where the porous
electrode acts like a transmission line, governed by a linear diffusion
equation for the electrostatic potential, scaled to the RC time of a single
pore. (ii) In the "desalination regime" of large voltages and long times, the
porous electrode slowly adsorbs neutral salt, governed by coupled, nonlinear
diffusion equations for the pore-averaged potential and salt concentration
Negative phase time for Scattering at Quantum Wells: A Microwave Analogy Experiment
If a quantum mechanical particle is scattered by a potential well, the wave
function of the particle can propagate with negative phase time. Due to the
analogy of the Schr\"odinger and the Helmholtz equation this phenomenon is
expected to be observable for electromagnetic wave propagation. Experimental
data of electromagnetic wells realized by wave guides filled with different
dielectrics confirm this conjecture now.Comment: 10 pages, 6 figure
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