48,973 research outputs found
Heat and work fluctuations for a harmonic oscillator
The formalism of Kundu et al. [J. Stat. Mech. (2011) P03007], for computing
the large deviations of heat flow in harmonic systems, is applied to the case
of single Brownian particle in a harmonic trap and coupled to two heat baths at
different temperatures. The large-t form of the moment generating function
~ g(s) exp[t m(s)], of the total heat flow Q from one of the baths
to the particle in a given time interval t, is studied and exact explicit
expressions are obtained for both m(s) and g(s). For a special case of the
single particle problem that corresponds to the work done by an external
stochastic force on a harmonic oscillator coupled to a thermal bath, the
large-t form of the moment generating function is analyzed to obtain the exact
large deviation function as well as the complete asymptotic forms of the
probability density function of the work.Comment: 11 pages, 6 figure
Generalized inequalities on warped product submanifolds in nearly trans-Sasakian manifolds
In this paper, we study warped product submanifolds of nearly trans-Sasakian
manifolds. The non-existence of the warped product semi-slant submanifolds of
the type is shown, whereas some characterization and
new geometric obstructions are obtained for the warped products of the type
. We establish two general inequalities for the
squared norm of the second fundamental form. The first inequality generalizes
derived inequalities for some contact metric manifolds [16, 18, 19, 24], while
by a new technique, the second inequality is constructed to express the
relation between extrinsic invariant (second fundamental form) and intrinsic
invariant (scalar curvatures). The equality cases are also discussed.Comment: 16 page
Quantification of food intake in Drosophila
Measurement of food intake in the fruit fly Drosophila melanogaster is often necessary for studies of behaviour, nutrition and drug administration. There is no reliable and agreed method for measuring food intake of flies in undisturbed, steady state, and normal culture conditions. We report such a method, based on measurement of feeding frequency by proboscis-extension, validated by short-term measurements of food dye intake. We used the method to demonstrate that (a) female flies feed more frequently than males, (b) flies feed more often when housed in larger groups and (c) fly feeding varies at different times of the day. We also show that alterations in food intake are not induced by dietary restriction or by a null mutation of the fly insulin receptor substrate chico. In contrast, mutation of takeout increases food intake by increasing feeding frequency while mutation of ovoD increases food intake by increasing the volume of food consumed per proboscis-extension. This approach provides a practical and reliable method for quantification of food intake in Drosophila under normal, undisturbed culture conditions
Ignition characterization of LOX/hydrocarbon propellants
The results of an evaluation of the ignition characteristics of the gaseous oxygen (Gox)/Ethanol propellant combination are presented. Ignition characterization was accomplished through the analysis, design, fabrication and testing of a spark initiated torch igniter and prototype 620 lbF thruster/igniter assembly. The igniter was tested over a chamber pressure range of 74 to 197 psia and mixture ratio range of 0.778 to 3.29. Cold (-92 to -165 F) and ambient (44 to 80 F) propellant temperatures were used. Spark igniter ignition limits and thruster steady state and pulse mode, performance, cooling and stability data are presented. Spark igniter ignition limits are presented in terms of cold flow pressure, ignition chamber diameter and mixture ratio. Thruster performance is presented in terms of vacuum specific impulse versus engine mixture ratio. Gox/Ethanol propellants were shown to be ignitable over a wide range of mixture ratios. Cold propellants were shown to have a minor effect on igniter ignition limits. Thruster pulse mode capability was demonstrated with multiple pulses of 0.08 sec duration and less
Anomalous Strength Characteristics of Tilt Grain Boundaries in Graphene
Using molecular dynamics simulations and first principles calculations, we
have studied the structure and mechanical strength of tilt grain boundaries in
graphene sheets that arise during CVD growth of graphene on metal substrates.
Surprisingly, we find that for tilt boundaries in the vicinity of both the
zig-zag and arm-chair orientations, large angle boundaries with a higher
density of 5-7 defect pairs are stronger than the low-angle boundaries which
are comprised of fewer defects per unit length. Interestingly, the trends in
our results cannot be explained by a continuum Griffith-type fracture mechanics
criterion, which predicts the opposite trend due to that fact that it does not
account for the critical bonds that are responsible for the failure mechanism.
We have identified the highly-strained bonds in the 7-member rings that lead to
the failure of the sheets, and we have found that large angle boundaries are
able to better accommodate the strained 7-rings. Our results provide guidelines
for designing growth methods to obtain grain boundary structures that can have
strengths close to that of pristine graphene
Synthesis Imaging of Dense Molecular Gas in the N113 HII Region of the Large Magellanic Cloud
We present aperture synthesis imaging of dense molecular gas in the Large
Magellanic Cloud, taken with the prototype millimeter receivers of the
Australia Telescope Compact Array (ATCA). Our observations of the N113 HII
region reveal a condensation with a size of ~6" (1.5 pc) FWHM, detected
strongly in the 1-0 lines of HCO+, HCN and HNC, and weakly in C_2H. Comparison
of the ATCA observations with single-dish maps from the Mopra Telescope and
sensitive spectra from the Swedish-ESO Submillimetre Telescope indicates that
the condensation is a massive clump of ~10^4 solar masses within a larger ~10^5
solar mass molecular cloud. The clump is centered adjacent to a compact,
obscured HII region which is part of a linear structure of radio continuum
sources extending across the molecular cloud. We suggest that the clump
represents a possible site for triggered star formation. Examining the
integrated line intensities as a function of interferometer baseline length, we
find evidence for decreasing HCO+/HCN and HCN/HNC ratios on longer baselines.
These trends are consistent with a significant component of the HCO+ emission
arising in an extended clump envelope and a lower HCN/HNC abundance ratio in
dense cores.Comment: 10 pages, 6 figures, to appear in Ap
Electroproduction of the d* dibaryon
The unpolarized cross section for the electroproduction of the isoscalar
di-delta dibaryon is calculated for deuteron target using a
simple picture of elastic electron-baryon scattering from the and the components of the deuteron. The calculated
differential cross section at the electron lab energy of 1 GeV has the value of
about 0.24 (0.05) nb/sr at the lab angle of 10 (30) for the
Bonn B potential when the dibaryon mass is taken to be 2.1 GeV. The cross
section decreases rapidly with increasing dibaryon mass. A large calculated
width of 40 MeV for combined with a small
experimental upper bound of 0.08 MeV for the decay width appears to have
excluded any low-mass model containing a significant admixture of the
configuration.Comment: 11 journal-style pages, 8 figure
Data Mining to Support Engineering Design Decision
The design and maintenance of an aero-engine generates a significant amount of documentation. When designing new engines, engineers must obtain knowledge gained from maintenance of existing engines to identify possible areas of concern. Firstly, this paper investigate the use of advanced business intelligence tenchniques to solve the problem of knowledge transfer from maintenance to design of aeroengines. Based on data availability and quality, various models were deployed. An association model was used to uncover hidden trends among parts involved in maintenance events. Classification techniques comprising of various algorithms was employed to determine severity of events. Causes of high severity events that lead to major financial loss was traced with the help of summarization techniques. Secondly this paper compares and evaluates the business intelligence approach to solve the problem of knowledge transfer with solutions available from the Semantic Web. The results obtained provide a compelling need to have data mining support on RDF/OWL-based warehoused data
Generalized Advanced Propeller Analysis System (GAPAS). Volume 2: Computer program user manual
The Generalized Advanced Propeller Analysis System (GAPAS) computer code is described. GAPAS was developed to analyze advanced technology multi-bladed propellers which operate on aircraft with speeds up to Mach 0.8 and altitudes up to 40,000 feet. GAPAS includes technology for analyzing aerodynamic, structural, and acoustic performance of propellers. The computer code was developed for the CDC 7600 computer and is currently available for industrial use on the NASA Langley computer. A description of all the analytical models incorporated in GAPAS is included. Sample calculations are also described as well as users requirements for modifying the analysis system. Computer system core requirements and running times are also discussed
Magnetic domain walls in constrained geometries
Magnetic domain walls have been studied in micrometer-sized Fe20Ni80 elements
containing geometrical constrictions by spin-polarized scanning electron
microscopy and numerical simulations. By controlling the constriction
dimensions, the wall width can be tailored and the wall type modified. In
particular, the width of a 180 degree Neel wall can be strongly reduced or
increased by the constriction geometry compared with the wall in unconstrained
systems.Comment: 4 pages, 6 figure
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