41,425 research outputs found
Symplectic structure for elastic and chiral conducting cosmic string models
This article is based on the covariant canonical formalism and corresponding
symplectic structure on phase space developed by Witten, Zuckerman and others
in the context of field theory. After recalling the basic principles of this
procedure, we construct the conserved bilinear symplectic current for generic
elastic string models. These models describe current carrying cosmic strings
evolving in an arbitrary curved background spacetime. Particular attention is
paid to the special case of the chiral string for which the worldsheet current
is null. Different formulations of the chiral string action are discussed in
detail, and as a result the integrability property of the chiral string is
clarified.Comment: 18 page
Effects of low energy protons and high energy electrons on silicon
Low energy proton and high energy electron radiation effects on silicon solar cell
Study of radiation effects in Li-doped silicon solar cells
Radiation effects in lithium-doped silicon solar cell
ERTS-1 investigation of wetlands ecology
The author has identified the following significant results. Data from aircraft can be used for large scale mapping where detailed information is necessary, whereas Landsat-1 data are useful for rapid mapping of gross wetland boundaries and vegetative composition and assessment of seasonal change plant community composition such as high and low growth forms of Spartina alterniflora, Juncus roemarianus, and Spartina cynosuroides. Spoil disposal and wetland ditching activities may also be defined. Wetland interpretation is affected by tidal stage; drainage patterns are more easily detected at periods of low water. Species discrimination is easier at periods of high water during the growing season; upper wetland boundaries in fresh water tidal marshes are more easily delineated during the winter months when marsh vegetation is largely dead or dormant. Fresh water discharges from coastal streams may be inferred from the species composition of contiguous wetlands
Study and determination of an optimum design for space utilized lithium-doped solar cells, part 2
Lithium doped solar cell hardness to 1 MeV electron irradiatio
KIC 2856960: the impossible triple star
KIC 2856960 is a star in the Kepler field which was observed by Kepler for 4
years. It shows the primary and secondary eclipses of a close binary of 0.258d
as well as complex dipping events that last for about 1.5d at a time and recur
on a 204d period. The dips are thought to result when the close binary passes
across the face of a third star. In this paper we present an attempt to model
the dips. Despite the apparent simplicity of the system and strenuous efforts
to find a solution, we find that we cannot match the dips with a triple star
while satisfying Kepler's laws. The problem is that to match the dips the
separation of the close binary has to be larger than possible relative to the
outer orbit given the orbital periods. Quadruple star models can get round this
problem but require the addition of a so-far undetected intermediate period of
order 5 -- 20d that has be a near-perfect integer divisor of the outer 204d
period. Although we have no good explanation for KIC 2856960, using the full
set of Kepler data we are able to update several of its parameters. We also
present a spectrum showing that KIC 2856960 is dominated by light from a K3- or
K4-type star.Comment: 11 pages, 13 figures, accepted for publication in MNRAS August 21,
201
Analysis of airfoil transitional separation bubbles
A previously developed local inviscid-viscous interaction technique for the analysis of airfoil transitional separation bubbles, ALESEP (Airfoil Leading Edge Separation) has been modified to utilize a more accurate windward finite difference procedure in the reversed flow region, and a natural transition/turbulence model has been incorporated for the prediction of transition within the separation bubble. Numerous calculations and experimental comparisons are presented to demonstrate the effects of the windward differencing scheme and the natural transition/turbulence model. Grid sensitivity and convergence capabilities of this inviscid-viscous interaction technique are briefly addressed. A major contribution of this report is that with the use of windward differencing, a second, counter-rotating eddy has been found to exist in the wall layer of the primary separation bubble
Analysis of transitional separation bubbles on infinite swept wings
A previously developed two-dimensional local inviscid-viscous interaction technique for the analysis of airfoil transitional separation bubbles, ALESEP (Airfoil Leading Edge Separation), has been extended for the calculation of transitional separation bubbles over infinite swept wings. As part of this effort, Roberts' empirical correlation, which is interpreted as a separated flow empirical extension of Mack's stability theory for attached flows, has been incorporated into the ALESEP procedure for the prediction of the transition location within the separation bubble. In addition, the viscous procedure used in the ALESEP techniques has been modified to allow for wall suction. A series of two-dimensional calculations is presented as a verification of the prediction capability of the interaction techniques with the Roberts' transition model. Numerical tests have shown that this two-dimensional natural transition correlation may also be applied to transitional separation bubbles over infinite swept wings. Results of the interaction procedure are compared with Horton's detailed experimental data for separated flow over a swept plate which demonstrates the accuracy of the present technique. Wall suction has been applied to a similar interaction calculation to demonstrate its effect on the separation bubble. The principal conclusion of this paper is that the prediction of transitional separation bubbles over two-dimensional or infinite swept geometries is now possible using the present interacting boundary layer approach
Space shuttle three main engine return to launch site abort
A Return-to-Launch-Site (RTLS) abort with three Space Shuttle Main Engines (SSME) operational was examined. The results are trajectories and main engine cutoff conditions that are approximately the same as for a two SSME case. Requiring the three SSME solution to match the two SSME abort eliminates additional crew training and is accomplished with negligible software impact
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