5,731 research outputs found
Compression of ultrashort UV pulses in a self-defocusing gas
Compression of UV femtosecond laser pulses focused into a gas cell filled
with xenon is reported numerically. With a large negative Kerr index and normal
dispersion, xenon promotes temporal modulational instability (MI) which can be
monitored to shorten ~ 100 fs pulses to robust, singly-peaked waveforms
exhibiting a fourfold compression factor. Combining standard MI theory with a
variational approach allows us to predict the beam parameters suitable for
efficient compression. At powers < 30 MW, nonlinear dispersion is shown to
shift the pulse temporal profile to the rear zone.Comment: 4 pages, 4 figure
True airspeed measured by airborne laser Doppler velocimeter
Velocimeter utilizing carbon dioxide laser measures true airspeed of aircraft. Results of flight tests indicate that clear-weather airspeeds can be measured with accuracy better than 0.1% at altitudes up to 3000 meters; measurements can be made at much greater altitudes in cloudy or turbid air
SWINE PRODUCTION NETWORKS IN MINNESOTA: RESOURCES FOR DECISION MAKING
Swine production networks are becoming a significant part of the Minnesota swine industry, with at least 30 production networks in operation as of late 1995. There are probably at least 450 producers involved, representing at least nine percent of the state s sow inventory. Not counted in these numbers are a few other networks involved only in data-sharing or marketing as well as a large number of farmer-to-farmer custom/contract arrangements. We interviewed 20 producers involved in networks. None of the networks we surveyed had been in operation very long, with most in business no more than a year or two. It is too early to predict what their long-term success will be. Most of the respondents seemed pleased with the arrangements so far. An example financial analysis of a 1,400 sow network is presented in the paper. Pig pricing formulas and custom rates are discussed for sharing risks among the farrower, nursery and finisher members of the network. The staff paper is 34 pages plus a 26 page annotated reading list of other publications on networking and segregated early weaning.Livestock Production/Industries,
Welding, brazing, and soldering handbook
Handbook gives information on the selection and application of welding, brazing, and soldering techniques for joining various metals. Summary descriptions of processes, criteria for process selection, and advantages of different methods are given
Mantle formation, coagulation and the origin of cloud/core-shine: II. Comparison with observations
Many dense interstellar clouds are observable in emission in the near-IR,
commonly referred to as "Cloudshine", and in the mid-IR, the so-called
"Coreshine". These C-shine observations have usually been explained with grain
growth but no model has yet been able to self-consistently explain the dust
spectral energy distribution from the near-IR to the submm. We want to
demonstrate the ability of our new core/mantle evolutionary dust model THEMIS
(The Heterogeneous dust Evolution Model at the IaS), which has been shown to be
valid in the far-IR and submm, to reproduce the C-shine observations. Our
starting point is a physically motivated core/mantle dust model. It consists of
3 dust populations: small aromatic-rich carbon grains; bigger core/mantle
grains with mantles of aromatic-rich carbon and cores either made of amorphous
aliphatic-rich carbon or amorphous silicate. We assume an evolutionary path
where these grains, when entering denser regions, may first form a second
aliphatic-rich carbon mantle (coagulation of small grains, accretion of carbon
from the gas phase), second coagulate together to form large aggregates, and
third accrete gas phase molecules coating them with an ice mantle. To compute
the corresponding dust emission and scattering, we use a 3D Monte-Carlo
radiative transfer code. We show that our global evolutionary dust modelling
approach THEMIS allows us to reproduce C-shine observations towards dense
starless clouds. Dust scattering and emission is most sensitive to the cloud
central density and to the steepness of the cloud density profile. Varying
these two parameters leads to changes, which are stronger in the near-IR, in
both the C-shine intensity and profile. With a combination of aliphatic-rich
mantle formation and low-level coagulation into aggregates, we can
self-consistently explain the observed C-shine and far-IR/submm emission
towards dense starless clouds.Comment: Paper accepted for publication in A&A with companion paper "Mantle
formation, coagulation and the origin of cloud/core-shine: I. Dust scattering
and absorption in the IR", A.P Jones, M. Koehler, N. Ysard, E. Dartois, M.
Godard, L. Gavila
Investigation of the chemical kinetics of an advanced high energy propellant system Quarterly progress report, 1 Jun. - 1 Sep. 1968
Reaction kinetics of high energy oxygen difluoride diborane propellant syste
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