16,805 research outputs found
Improved fire-resistant coatings
Water-base coatings containing potassium silicate show improvement in areas of quick air-drying, crack, craze, and abrasion resistance, adherence, and leach resistance. Coatings are useful as thermal-barrier layers in furnaces, and as general purpose fire resistant surfaces where vapor impermeability is not a requirement
Fire resistant coating composition Patent
Fireproof potassium silicate coating composition, insoluble in water after applicatio
Atmospheric contaminant sensor. Book 2: Appendices
Appendices containing equipment specifications and performance test data of the atmospheric contaminant sensor for submarines are presented
Detection of Gravitational Waves from the Coalescence of Population-III Remnants with Advanced LIGO
The comoving mass density of massive black hole (MBH) remnants from
pre-galactic star formation could have been similar in magnitude to the
mass-density of supermassive black holes (SMBHs) in the present-day universe.
We show that the fraction of MBHs that coalesce during the assembly of SMBHs
can be extracted from the rate of ring-down gravitational waves that are
detectable by Advanced LIGO. Based on the SMBH formation history inferred from
the evolution of the quasar luminosity function, we show that an observed event
rate of 1 per year will constrain the SMBH mass fraction that was contributed
by MBHs coalescence down to a level of ~10^-6 for 20 solar mass MBH remnants
(or ~10^-4 for 260 solar mass remnants).Comment: 4 pages, 2 figures. Submitted to ApJ Letter
Redshifted 21cm Signatures Around the Highest Redshift Quasars
The Ly-alpha absorption spectrum of the highest redshift quasars indicates
that they are surrounded by giant HII regions, a few Mpc in size. The neutral
gas around these HII regions should emit 21cm radiation in excess of the Cosmic
Microwave Background, and enable future radio telescopes to measure the
transverse extent of these HII regions. At early times, the HII regions expand
with a relativistic speed. Consequently, their measured sizes along the
line-of-sight (via Ly-alpha absorption) and transverse to it (via 21 cm
emission) should have different observed values due to relativistic time-delay.
We show that the combined measurement of these sizes would directly constrain
the neutral fraction of the surrounding intergalactic medium (IGM) as well as
the quasar lifetime. Based on current number counts of luminous quasars at z>6,
an instrument like LOFAR should detect >2 redshifted 21cm shells per field
(with a radius of 11 degrees) around active quasars as bright as those already
discovered by SDSS, and >200 relic shells of inactive quasars per field. We
show that Ly-alpha photons from the quasar are unable to heat the IGM or to
couple the spin and kinetic temperatures of atomic hydrogen beyond the edge of
the HII region. The detection of the IGM in 21cm emission around high redshift
quasars would therefore gauge the presence of a cosmic Ly-alpha background
during the reionization epoch.Comment: 11 pages, 6 figures. Submitted to Ap
Harvesting Systems Evaluation in Caspian Forests
A project, "Logging System Evaluation", was initiated by the Iranian Forest Service and Teheran University in 1988. The objective is to develop a quantitative basis for job layout and planning, operations management, and forest management. Initial work is focusing on transportation functions, the largest single cost component. A brief discussion of harvesting conditions in the Caspian forest is followed by the results of initial investigations of rubber-tired skidding
Filling the holes: Evolving excised binary black hole initial data with puncture techniques
We follow the inspiral and merger of equal-mass black holes (BHs) by the
moving puncture technique and demonstrate that both the exterior solution and
the asymptotic gravitational waveforms are unchanged when the initial interior
solution is replaced by constraint-violating ``junk'' initial data. We apply
this result to evolve conformal thin-sandwich (CTS) binary BH initial data by
filling their excised interiors with arbitrary, but smooth, initial data and
evolving with standard puncture gauge choices. The waveforms generated for both
puncture and filled-CTS initial data are remarkably similar, and there are only
minor differences between irrotational and corotational CTS BH binaries. Even
the interior solutions appear to evolve to the same constraint-satisfying
solution at late times, independent of the initial data.Comment: 5 pages, 5 figures, accepted by PRD Rapid Communications, RevTe
Technical Efficiency Evaluation of Logging Contractors Using a Nonparametric Model
Data Envelopment Analysis (DEA) models were used to measure the technical efficiency of a sample of logging contractors. DEA is a nonparametric efficiency measurement technique based on linear programming methods. This paper demonstrates how DEA models can be applied in a forest operations context to gain insights on the factors which affect technical efficiency and performance.
Twenty-three fully mechanized loggers were compared in regards to the efficiency with which they converted inputs – dollars of capital, consumables, and labor – into output – tons of wood. Overall, for the period of 1988 to 1994, the logging contractors studied were efficient, but some were considerably less efficient than others. Low capacity utilization had a negative impact on technical efficiency. The scale of an operation also influenced technical efficiency. For the sample, the most productive scale size was estimated to be around 75,000 tons per year
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