1,052 research outputs found
Computer program to assess impact of fatigue and fracture criteria on weight and cost of transport aircraft
A preliminary design analysis tool for rapidly performing trade-off studies involving fatigue, fracture, static strength, weight, and cost is presented. Analysis subprograms were developed for fatigue life, crack growth life, and residual strength; and linked to a structural synthesis module which in turn was integrated into a computer program. The part definition module of a cost and weight analysis program was expanded to be compatible with the upgraded structural synthesis capability. The resultant vehicle design and evaluation program is named VDEP-2. It is an accurate and useful tool for estimating purposes at the preliminary design stage of airframe development. A sample case along with an explanation of program applications and input preparation is presented
Hobby Lobby, Corporate Law, and the Theory of the Firm: Why For-Profit Corporations are RFRA Persons
The origin of galaxy scaling laws in LCDM
It has long been recognized that tight relations link the mass, size, and
characteristic velocity of galaxies. These scaling laws reflect the way in
which baryons populate, cool, and settle at the center of their host dark
matter halos; the angular momentum they retain in the assembly process; as well
as the radial distribution and mass scalings of the dark matter halos. There
has been steady progress in our understanding of these processes in recent
years, mainly as sophisticated N-body and hydrodynamical simulation techniques
have enabled the numerical realization of galaxy models of ever increasing
complexity, realism, and appeal. These simulations have now clarified the
origin of these galaxy scaling laws in a universe dominated by cold dark
matter: these relations arise from the tight (but highly non-linear) relations
between (i) galaxy mass and halo mass, (ii) galaxy size and halo characteristic
radius; and (iii) from the self-similar mass nature of cold dark matter halo
mass profiles. The excellent agreement between simulated and observed galaxy
scaling laws is a resounding success for the LCDM cosmogony on the highly
non-linear scales of individual galaxies.Comment: Contribution to the Proceedings of the Simons Conference
"Illuminating Dark Matter", held in Kruen, Germany, in May 2018, eds. R.
Essig, K. Zurek, J. Fen
Investigation into the mechanism of degradation of solar cells with silver- titanium contacts Final report
Electrochemical tests and physical measurements to determine degradation mechanism in solar cells with silver-titanium contacts exposed to humid atmosphere
SPARC CCMVal (2010), SPARC Report on the Evaluation of Chemistry-Climate Models: Chapter 5: Transport
Multi-Model Assessment of the Factors Driving the Ozone Evolution Over the 21st Century
The evolution of ozone from 1960 to 2100 is examined in simulations from fourteen chemistry-climate models. There is general agreement among the models at the broadest levels, with all showing column ozone decreasing at all latitudes from 1960 to around 2000, then increasing at all latitudes over the first half of the 21 st century (21 C), and latitudinal variations in the rate of increase and date of return to historical values. In the second half of the century, ozone is projected to carry on increasing, level off or even decrease depending on the latitude, resulting in variable dates of return to historical values at latitudes where column ozone has declined below those levels. Separation into partial column above and below 20 hPa reveals that these latitudinal differences are almost completely due to differences in the lower stratosphere. At all latitudes, upper stratospheric ozone increases throughout the 21 C and returns to 1960 levels before the end of the century, although there is a spread among the models in dates that ozone returns to historical values. Using multiple linear regression the upper stratospheric ozone increase comes from almost equal contributions due to decrease in halogens and cooling from increased greenhouse gas concentrations. The evolution of lower stratospheric ozone differs with latitude. In the tropical lower stratosphere an increase in tropical upwelling causes a steady decrease in ozone through the 21C, and total column ozone does not return to 1960 levels in all models. In contrast, lower stratospheric and total column ozone in middle and high latitudes increases during the 21 C and returns to 1960 levels. For all models there is an earlier return for ozone to historical levels in the northern hemisphere. This is thought to be due to interhemispheric differences in transport
Constraining quenching timescales in galaxy clusters by forward-modelling stellar ages and quiescent fractions in projected phase space
We forward-model mass-weighted stellar ages (MWAs) and quiescent fractions in
projected phase space (PPS), using data from the Sloan Digital Sky Survey, to
jointly constrain an infall quenching model for galaxies in
galaxy clusters at . We
find the average deviation in MWA from the MWA- relation depends on
position in PPS, with a maximum difference between the inner cluster and
infalling interloper galaxies of Gyr. Our model employs infall
information from N-body simulations and stochastic star-formation histories
from the UniverseMachine model. We find total quenching times of
Gyr and Gyr after first
pericentre, for and
galaxies, respectively. By using
MWAs, we break the degeneracy in time of quenching onset and timescale of star
formation rate (SFR) decline. We find that time of quenching onset relative to
pericentre is Gyr and
Gyr for our lower and higher stellar
mass bins, respectively, and exponential SFR suppression timescales are
Gyr and Gyr for our
lower and higher stellar mass bins, respectively. Stochastic star formation
histories remove the need for rapid infall quenching to maintain the bimodality
in the SFR of cluster galaxies; the depth of the green valley prefers quenching
onsets close to first pericentre and a longer quenching envelope, in slight
tension with the MWA-driven results. Taken together these results suggest that
quenching begins close to, or just after pericentre, but the timescale for
quenching to be fully complete is much longer and therefore ram-pressure
stripping is not complete on first pericentric passage.Comment: 21 pages, 13 figures, submitted to MNRA
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