47,096 research outputs found
A study of wing body blending for an advanced supersonic transport
Increases in supersonic cruise lift drag ratio were sought at Mach numbers 2.2 and 2.7 using wing body planform and thickness blending. Constrained twist and camber optimization was performed in the presence of nacelles. Wing and fuselage thickness distributions were optimized for either minimum volume wave drag or minimum total pressure wave drag. The zero leading edge suction lift drag ratios were determined for three wing planforms. The magnitude of the effect of leading edge suction on attainable lift drag ratio was defined on one planform and estimation of available leading edge suction was made
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An Evaluation of a Battery of Functional and Structural Tests as Predictors of Likely Risk of Progression of Age-Related Macular Degeneration.
Purpose: To evaluate the ability of visual function and structural tests to identify the likely risk of progression from early/intermediate to advanced AMD, using the Age-Related Eye Disease Study (AREDS) simplified scale as a surrogate for risk of progression. The secondary aim was to determine the relationship between disease severity grade and the observed functional and structural deficits. Methods: A total of 100 participants whose AMD status varied from early to advanced were recruited. Visual function was assessed using cone dark adaptation, 14 Hz flicker and chromatic threshold tests and retinal structure was assessed by measuring drusen volume and macular thickness. The predictive value of the tests was estimated using ordinal regression analysis. Group comparisons were assessed using analysis of covariance. Results: Change in cone dark adaptation (cone Ï„) and yellow-blue (YB) chromatic sensitivity were independent predictors for AMD progression risk (cone Ï„, pseudo R2 = 0.35, P < 0.001; YB chromatic threshold, pseudo R2 = 0.16, P < 0.001). The only structural predictor was foveal thickness (R2 = 0.05, P = 0.047). Chromatic sensitivity and cone dark adaptation were also the best functional tests at distinguishing between severity groups. Drusen characteristics clearly differentiated between participants with early and advanced disease, but were not able to differentiate between those with early AMD and controls. Mean differences in retinal thickness existed between severity groups at the foveal (P = 0.040) and inner (P = 0.001) subfields. Conclusions: This study indicates that cone Ï„, YB chromatic threshold and foveal thickness are independent predictors of likely risk of AMD progression
Toxicity studies of Coolanol 15 Final report, Jan. - Sep. 1965
Toxicity studies of synthetic fluid coolant for manned spacecraft heat transfer system
Heun equation, Teukolsky equation, and type-D metrics
Starting with the whole class of type-D vacuum backgrounds with cosmological
constant we show that the separated Teukolsky equation for zero rest-mass
fields with spin (gravitational waves), (electromagnetic
waves) and (neutrinos) is an Heun equation in disguise.Comment: 27 pages, corrected typo in eq. (1
Method and apparatus for supercooling and solidifying substances
An enclosure provides a containerless environment in which a sample specimen is positioned. The specimen is heated in the containerless environment, and the specimen melt is dropped through the tube in which it cools by radiation. The tube is alternatively backfilled with an inert gas whereby the specimen melt cools by both radiation and convection during its free fall. During the free fall, the sample is in a containerless, low-gravity environment which enhances supercooling in the sample and prevents sedimentation and thermal convection influences. The sample continues to supercool until nucleation occurs which is detected by silicon photovoltaic detectors. The sample solidifies after nucleation and becomes completely solid before entering the detachable catcher. The amount of supercooling of the specimen can be measured by knowing the cooling ratio and determining the time for nucleation to occur
Primordial Non-Gaussianity: Baryon Bias and Gravitational Collapse of Cosmic String Wakes
I compute the 3-D non-linear evolution of gas and dark matter fluids in the
neighbourhood of cosmic string wakes which are formed at high redshift
() for a ``realistic'' scenario of wake formation. These wakes
are the ones which stand out most prominently as cosmological sheets and are
expected to play a dominant r\^ole in the cosmic string model of structure
formation. Employing a high-resolution 3-D hydrodynamics code to evolve these
wakes until the present day yields results for the baryon bias generated in the
inner wake region. I find that today, wakes would be Mpc thick and
contain a 70% excess in the density of baryons over the dark matter density in
their centre. However, high density peaks in the wake region do not inherit a
baryon enhancement. I propose a mechanism for this erasure of the baryon excess
in spherically collapsed objects based on the geometry change around the
collapsing region. Further, I present heuristic arguments for the consequences
of this work for large scale structure in the cosmic string model and conclude
that the peculiarities of wake formation are unlikely to have significant
import on the discrepancy between power spectrum predictions and observations
in this model. If one invokes the nucleosynthesis bound on this
could be seen as strengthening the case against or for low Hubble
constants.Comment: 21 pages, 7 figures, 2 tables, prepared with the AASTeX package.
Minor modifications, results unchanged. ApJ in press, scheduled for Vol. 50
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