6,987 research outputs found
Computation of nucleation of a non-equilibrium first-order phase transition using a rare-event algorithm
We introduce a new Forward-Flux Sampling in Time (FFST) algorithm to
efficiently measure transition times in rare-event processes in non-equilibrium
systems, and apply it to study the first-order (discontinuous) kinetic
transition in the Ziff-Gulari-Barshad model of catalytic surface reaction. The
average time for the transition to take place, as well as both the spinodal and
transition points, are clearly found by this method.Comment: 12 pages, 10 figure
Application of satellite cloud-motion vectors in hurricane track prediction
Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Meteorology.Microfiche copy available in Archives and Science.Bibliography: leaf 38.by Alan L. Adams.M.S
Methods and systems for identifying a particle using dielectrophoresis
A system for identifying a particle. The system includes a microfluidic device; a microelectrode array including a plurality of electrodes, the microelectrode array disposed within the microfluidic device; a plurality of particles suspended in a solution and delivered to the microelectrode array using the microfluidic device; a signal generator operatively coupled to the microelectrode array; a particle detector adjacent to the microelectrode array; and a controller in operative communication with the signal generator and the particle detector. The controller is configured to apply an oscillating voltage signal to the microelectrode array between a low frequency and a high frequency at a sweep rate, wherein the sweep rate is no more than a maximum sweep rate, and determine a distribution of the plurality of particles relative to the microelectrode array at a plurality of frequency levels between the low frequency and the high frequency.https://digitalcommons.mtu.edu/patents/1139/thumbnail.jp
Towards absolute scales of radii and masses of open clusters
Aims: In this paper we derive tidal radii and masses of open clusters in the
nearest kiloparsecs around the Sun. Methods: For each cluster, the mass is
estimated from tidal radii determined from a fitting of three-parametric King's
profiles to the observed integrated density distribution. Different samples of
members are investigated. Results: For 236 open clusters, all contained in the
catalogue ASCC-2.5, we obtain core and tidal radii, as well as tidal masses.
The distributions of the core and tidal radii peak at about 1.5 pc and 7 - 10
pc, respectively. A typical relative error of the core radius lies between 15%
and 50%, whereas, for the majority of clusters, the tidal radius was determined
with a relative accuracy better than 20%. Most of the clusters have tidal
masses between 50 and 1000 , and for about half of the clusters, the
masses were obtained with a relative error better than 50%.Comment: 11 pages, 7 figures, accepted for publication in Astronomy &
Astrophysic
On the use of Lineal Energy Measurements to Estimate Linear Energy Transfer Spectra
This paper examines the error resulting from using a lineal energy spectrum to represent a linear energy transfer spectrum for applications in the space radiation environment. Lineal energy and linear energy transfer spectra are compared in three diverse but typical space radiation environments. Different detector geometries are also studied to determine how they affect the error. LET spectra are typically used to compute dose equivalent for radiation hazard estimation and single event effect rates to estimate radiation effects on electronics. The errors in the estimations of dose equivalent and single event rates that result from substituting lineal energy spectra for linear energy spectra are examined. It is found that this substitution has little effect on dose equivalent estimates in interplanetary quiet-time environment regardless of detector shape. The substitution has more of an effect when the environment is dominated by solar energetic particles or trapped radiation, but even then the errors are minor especially if a spherical detector is used. For single event estimation, the effect of the substitution can be large if the threshold for the single event effect is near where the linear energy spectrum drops suddenly. It is judged that single event rate estimates made from lineal energy spectra are unreliable and the use of lineal energy spectra for single event rate estimation should be avoided
Synthesis and Characterization of [Fe(Htrz)\u3csub\u3e2\u3c/sub\u3e(trz)](BF\u3csub\u3e4\u3c/sub\u3e)] Nanocubes
Compounds that exhibit spin-crossover (SCO) type behavior have been extensively investigated due to their ability to act as molecular switches. Depending on the coordinating ligand, in this case 1H-1,2,4-triazole, and the crystallite size of the SCO compound produced, the energy requirement for the spin state transition can vary. Here, SCO [Fe(Htrz)2(trz)](BF4)] nanoparticles were synthesized using modified reverse micelle methods. Reaction conditions and reagent ratios are strictly controlled to produce nanocubes of 40–50 nm in size. Decreases in energy requirements are seen in both thermal and magnetic transitions for the smaller sized crystallites, where, compared to bulk materials, a decrease of as much as 20 °C can be seen in low to high spin state transitions
Harmonic Measure for Percolation and Ising Clusters Including Rare Events
We obtain the harmonic measure of the hulls of critical percolation clusters
and Ising-model Fortuin-Kastelyn clusters using a biased random-walk sampling
technique which allows us to measure probabilities as small as 10^{-300}. We
find the multifractal D(q) spectrum including regions of small and negative q.
Our results for external hulls agree with Duplantier's theoretical predictions
for D(q) and his exponent -23/24 for the harmonic measure probability
distribution. For the complete hull, we find the probability decays with an
exponent of -1 for both systems.Comment: 4 pages, 5 figure
Effects of Youth Tobacco Access and Possession Policy Interventions on Heavy Adolescent Smokers
This study evaluated the effects of tobacco PUP (Purchase, Use and Possession) laws on tobacco use patterns among students in twenty-four towns, which were randomly assigned into an experimental and a control group. The experimental group involved both PUP law enforcement and reducing minors’ access to commercial sources of tobacco, and the condition for the control group involved only efforts to reduce minors’ access to commercial sources of tobacco. The present study found that adolescents in the control group had a significantly greater increase in the percentage of youth who smoked 20 or more cigarettes per day when compared to the experimental group
Fractal dimensions of the Q-state Potts model for the complete and external hulls
Fortuin-Kastelyn clusters in the critical -state Potts model are
conformally invariant fractals. We obtain simulation results for the fractal
dimension of the complete and external (accessible) hulls for Q=1, 2, 3, and 4,
on clusters that wrap around a cylindrical system. We find excellent agreement
between these results and theoretical predictions. We also obtain the
probability distributions of the hull lengths and maximal heights of the
clusters in this geometry and provide a conjecture for their form.Comment: 9 pages 4 figure
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