1,945 research outputs found
Performance, emissions, and physical characteristics of a rotating combustion aircraft engine
The RC2-75, a liquid cooled two chamber rotary combustion engine (Wankel type), designed for aircraft use, was tested and representative baseline (212 KW, 285 BHP) performance and emissions characteristics established. The testing included running fuel/air mixture control curves and varied ignition timing to permit selection of desirable and practical settings for running wide open throttle curves, propeller load curves, variable manifold pressure curves covering cruise conditions, and EPA cycle operating points. Performance and emissions data were recorded for all of the points run. In addition to the test data, information required to characterize the engine and evaluate its performance in aircraft use is provided over a range from one half to twice its present power. The exhaust emissions results are compared to the 1980 EPA requirements. Standard day take-off brake specific fuel consumption is 356 g/KW-HR (.585 lb/BHP-HR) for the configuration tested
Parallel fabrication and single-electron charging of devices based on ordered, two-dimensional phases of organically functionalized metal nanocrystals
A parallel technique for fabricating single-electron, solid-state capacitance devices from ordered, two-dimensional closest-packed phases of organically functionalized metal nanocrystals is presented. The nanocrystal phases were prepared as Langmuir monolayers and subsequently transferred onto Al-electrode patterned glass substrates for device construction. Alternating current impedance measurements were carried out to probe the single-electron charging characteristics of the devices under both ambient and 77 K conditions. Evidence of a Coulomb blockade and step structure reminiscent of a Coulomb staircase is presented
On Gauge-Invariant Decomposition of Nucleon Spin
We investigate the relation between the known decompositions of the nucleon
spin into its constituents, thereby clarifying in what respect they are common
and in what respect they are different essentially. The decomposition recently
proposed by Chen et al. can be thought of as a nontrivial generalization of the
gauge-variant Jaffe-Manohar decomposition so as to meet the gauge-invariance
requirement of each term of the decomposition. We however point out that there
is another gauge-invariant decomposition of the nucleon spin, which is closer
to the Ji decomposition, while allowing the decomposition of the gluon total
angular momentum into the spin and orbital parts. After clarifying the reason
why the gauge-invariant decomposition of the nucleon spin is not unique, we
discuss which decomposition is more preferable from the experimental viewpoint.Comment: The version to appear in Phys. Rev.
Controllability on infinite-dimensional manifolds
Following the unified approach of A. Kriegl and P.W. Michor (1997) for a
treatment of global analysis on a class of locally convex spaces known as
convenient, we give a generalization of Rashevsky-Chow's theorem for control
systems in regular connected manifolds modelled on convenient
(infinite-dimensional) locally convex spaces which are not necessarily
normable.Comment: 19 pages, 1 figur
Monitoramento ambiental do herbicida clomazone, formulação solúvel, em águas de lavouras de arroz irrigado.
bitstream/item/30273/1/boletim-30.pd
Crystallization in suspensions of hard spheres: A Monte Carlo and Molecular Dynamics simulation study
The crystallization of a metastable melt is one of the most important non
equilibrium phenomena in condensed matter physics, and hard sphere colloidal
model systems have been used for several decades to investigate this process by
experimental observation and computer simulation. Nevertheless, there is still
an unexplained discrepancy between simulation data and experimental nucleation
rate densities. In this paper we examine the nucleation process in hard spheres
using molecular dynamics and Monte Carlo simulation. We show that the
crystallization process is mediated by precursors of low orientational
bond-order and that our simulation data fairly match the experimental data
sets
When flux standards go wild: white dwarfs in the age of Kepler
White dwarf stars have been used as flux standards for decades, thanks to
their staid simplicity. We have empirically tested their photometric stability
by analyzing the light curves of 398 high-probability candidates and
spectroscopically confirmed white dwarfs observed during the original Kepler
mission and later with K2 Campaigns 0-8. We find that the vast majority (>97
per cent) of non-pulsating and apparently isolated white dwarfs are stable to
better than 1 per cent in the Kepler bandpass on 1-hr to 10-d timescales,
confirming that these stellar remnants are useful flux standards. From the
cases that do exhibit significant variability, we caution that binarity,
magnetism, and pulsations are three important attributes to rule out when
establishing white dwarfs as flux standards, especially those hotter than
30,000 K.Comment: Accepted for publication in MNRAS; 7 pages, 4 figures, 2 table
Discovery of an ultramassive pulsating white dwarf
We announce the discovery of the most massive pulsating hydrogen-atmosphere
(DA) white dwarf (WD) ever discovered, GD 518. Model atmosphere fits to the
optical spectrum of this star show it is a 12,030 +/- 210 K WD with a log(g) =
9.08 +/- 0.06, which corresponds to a mass of 1.20 +/- 0.03 Msun. Stellar
evolution models indicate that the progenitor of such a high-mass WD endured a
stable carbon-burning phase, producing an oxygen-neon-core WD. The discovery of
pulsations in GD 518 thus offers the first opportunity to probe the interior of
a WD with a possible oxygen-neon core. Such a massive WD should also be
significantly crystallized at this temperature. The star exhibits
multi-periodic luminosity variations at timescales ranging from roughly 425-595
s and amplitudes up to 0.7%, consistent in period and amplitude with the
observed variability of typical ZZ Ceti stars, which exhibit non-radial g-mode
pulsations driven by a hydrogen partial ionization zone. Successfully
unraveling both the total mass and core composition of GD 518 provides a unique
opportunity to investigate intermediate-mass stellar evolution, and can
possibly place an upper limit to the mass of a carbon-oxygen-core WD, which in
turn constrains SNe Ia progenitor systems.Comment: 5 pages, 3 figures, Astrophysical Journal Letters, 771, L2 (2013
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