90,134 research outputs found
Indium adhesion provides quantitative measure of surface cleanliness
Indium tipped probe measures hydrophobic and hydrophilic contaminants on rough and smooth surfaces. The force needed to pull the indium tip, which adheres to a clean surface, away from the surface provides a quantitative measure of cleanliness
Effects of H2O, CO2, and N2 Air Contaminants on Critical Airside Strain Rates for Extinction of Hydrogen-Air Counterflow Diffusion Flames
Coaxial tubular opposed jet burners (OJB) were used to form dish shaped counterflow diffusion flames (CFDF), centered by opposing laminar jets of H2, N2 and both clean and contaminated air (O2/N2 mixtures) in an argon bath at 1 atm. Jet velocities for flame extinction and restoration limits are shown versus wide ranges of contaminant and O2 concentrations in the air jet, and also input H2 concentration. Blowoff, a sudden breaking of CFDF to a stable ring shape, occurs in highly stretched stagnation flows and is generally believed to measure kinetically limited flame reactivity. Restore, a sudden restoration of central flame, is a relatively new phenomenon which exhibits a H2 dependent hysteresis from Blowoff. For 25 percent O2 air mixtures, mole for mole replacement of 25 percent N2 contaminant by steam increased U(air) or flame strength at Blowoff by about 5 percent. This result is consistent with laminar burning velocity results from analogous substitution of steam for N2 in a premixed stoichiometric H2-O2-N2 (or steam) flame, shown by Koroll and Mulpuru to promote a 10 percent increase in experimental and calculated laminar burning velocity, due to enhanced third body efficiency of water in: H + O2 + M yields HO2 + M. When the OJB results were compared with Liu and MacFarlane's experimental laminar burning velocity of premixed stoichiometric H2 + air + steam, a crossover occurred, i.e., steam enhanced OJB flame strength at extinction relative to laminar burning velocity
Temperature automation for a propellant mixer
The analysis and installation of an automatic temperature controller on a propellant mixer is presented. Ultimately, the entire mixing process will come under automation, but since precise adherence to the temperature profile is very difficult to sustain manually, this was the first component to be automated. Automation is not only important for producing a uniform product, but it is necessary for envisioned space-based propellant production
Postflight trajectory reassembly AC-6
Postflight trajectory reassembly analysis of Atlas Centaur flight AC-
Elite male Flat jockeys display lower bone density and lower resting metabolic rate than their female counterparts: implications for athlete welfare
To test the hypothesis that daily weight-making is more problematic to health in male compared with female jockeys, we compared the bone-density and resting metabolic rate (RMR) in weight-matched male and female Flat-jockeys. RMR (kcal.kg-1 lean mass) was lower in males compared with females as well as lower bone-density Z-scores at the hip and lumbar spine. Data suggest the lifestyle of male jockeys’ compromise health more severely than females, possibly due to making-weight more frequently
Quantum Phase Transitions beyond the Landau's Paradigm in Sp(4) Spin System
We propose quantum phase transitions beyond the Landau's paradigm of Sp(4)
spin Heisenberg models on the triangular and square lattices, motivated by the
exact Sp(4) SO(5) symmetry of spin-3/2 fermionic cold atomic system
with only wave scattering. On the triangular lattice, we study a phase
transition between the spin ordered phase and a
spin liquid phase, this phase transition is described by an O(8) sigma model in
terms of fractionalized spinon fields, with significant anomalous scaling
dimensions of spin order parameters. On the square lattice, we propose a
deconfined critical point between the Neel order and the VBS order, which is
described by the CP(3) model, and the monopole effect of the compact U(1) gauge
field is expected to be suppressed at the critical point.Comment: 6 pages, 3 figure
Exact renormalization group equations and the field theoretical approach to critical phenomena
After a brief presentation of the exact renormalization group equation, we
illustrate how the field theoretical (perturbative) approach to critical
phenomena takes place in the more general Wilson (nonperturbative) approach.
Notions such as the continuum limit and the renormalizability and the presence
of singularities in the perturbative series are discussed.Comment: 15 pages, 7 figures, to appear in the Proceedings of the 2nd
Conference on the Exact Renormalization Group, Rome 200
The Arecibo Dual-Beam Survey: The HI Mass Function of Galaxies
We use the HI-selected galaxy sample from the Arecibo Dual-Beam Survey
(Rosenberg & Schneider 2000) to determine the shape of the HI mass function of
galaxies in the local universe using both the step-wise maximum likelihood and
the 1/V_tot methods. Our survey region spanned all 24 hours of right ascension
at selected declinations between 8 and 29 degrees covering ~430 deg^2 of sky in
the main beam. The survey is not as deep as some previous Arecibo surveys, but
it has a larger total search volume and samples a much larger area of the sky.
We conducted extensive tests on all aspects of the galaxy detection process,
allowing us to empirically correct for our sensitivity limits, unlike the
previous surveys. The mass function for the entire sample is quite steep, with
a power-law slope of \alpha ~ -1.5. We find indications that the slope of the
HI mass function is flatter near the Virgo cluster, suggesting that
evolutionary effects in high density environments may alter the shape of the HI
mass function. These evolutionary effects may help to explain differences in
the HI mass function derived by different groups. We are sensitive to the most
massive sources (log M > 5x10^10 M\solar) over most of the declination range,
\~1 sr, and do not detect any massive low surface brightness galaxies. These
statistics restrict the population of Malin 1-like galaxies to <5.5x10^-6
Mpc^-3.Comment: ApJ accepted, 12 page
Renormalization Group Study of the soliton mass on the (lambda Phi^4)_{1+1} lattice model
We compute, on the model on the lattice, the soliton
mass by means of two very different numerical methods. First, we make use of a
``creation operator'' formalism, measuring the decay of a certain correlation
function. On the other hand we measure the shift of the vacuum energy between
the symmetric and the antiperiodic systems. The obtained results are fully
compatible.
We compute the continuum limit of the mass from the perturbative
Renormalization Group equations. Special attention is paid to ensure that we
are working on the scaling region, where physical quantities remain unchanged
along any Renormalization Group Trajectory. We compare the continuum value of
the soliton mass with its perturbative value up to one loop calculation. Both
quantities show a quite satisfactory agreement. The first is slightly bigger
than the perturbative one; this may be due to the contributions of higher order
corrections.Comment: 19 pages, preprint DFTUZ/93/0
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