3,319 research outputs found
Investigation of Critical Burning of Fuel Droplets
An earlier analysis for the combustion response of a liquid monopropellant strand (hydrazine) was extended to consider individual droplets and sprays. While small drops gave low or negative response, large droplets provided response near unity at low frequencies, with the response declining at frequencies greater than the characteristic liquid phase frequency. Temperature gradients in the liquid phase resulted in response peaks greater than unity. A second response peak was found for large drops which corresponded to gas phase transient effects. Spray response was generally reduced from the response of the largest injected droplet, however, even a small percentage of large droplets can yield appreciable response. An apparatus was designed and fabricated to allow observation of bipropellant fuel spray combustion at elevated pressures. A locally homogeneous model was developed to describe this combustion process which allows for high pressure phenomena associated with the thermodynamic critical point
Optical Observations of PSR J0205+6449 - the next optical pulsar?
PSR J0205+6449 is a young ({\approx} 5400 years), Crab-like pulsar detected
in radio and at X and {\gamma}-ray energies and has the third largest spin-down
flux among known rotation powered pulsars. It also powers a bright synchrotron
nebula detected in the optical and X-rays. At a distance of {\approx} 3.2 kpc
and with an extinction comparable to the Crab, PSR J0205+6449 is an obvious
target for optical observations. We observed PSR J0205+6449 with several
optical facilities, including 8m class ground-based telescopes, such as the
Gemini and the Gran Telescopio Canarias. We detected a point source, at a
significance of 5.5{\sigma}, of magnitude i {\approx} 25.5, at the centre of
the optical synchrotron nebula, coincident with the very accurate Chandra and
radio positions of the pulsar. Thus, we discovered a candidate optical
counterpart to PSR J0205+6449. The pulsar candidate counterpart is also
detected in the g ({\approx}27.4) band and weakly in the r ({\approx}26.2)
band. Its optical spectrum is fit by a power law with photon index {\Gamma}0 =
1.9{\pm}0.5, proving that the optical emission if of non-thermal origin, is as
expected for a young pulsar. The optical photon index is similar to the X-ray
one ({\Gamma}X = 1.77{\pm}0.03), although the optical fluxes are below the
extrapolation of the X-ray power spectrum. This would indicate the presence of
a double spectral break between the X-ray and optical energy range, at variance
with what is observed for the Crab and Vela pulsars, but similar to the Large
Magellanic Cloud pulsar PSR B0540-69.Comment: 13 Pages, 4 Tables, 7 Figures, Accepted for publication in MNRA
Deep optical observations of the gamma-ray pulsar PSR J0007+7303 in the CTA 1 supernova remnant
The Fermi Large Area Telescope (LAT) discovered the time signature of a
radio-silent pulsar coincident with RX J0007.0+7302, a plerion-like X-ray
source at the centre of the CTA 1 supernova remnant. The inferred timing
parameters of the gamma-ray pulsar PSR J0007+7303 (P=315.8 ms; dot{P}\sim3.6
10^{-13} s s^{-1}) point to a Vela-like neutron star, with an age comparable to
that of CTA 1. The PSR J0007+7303 low distance (\sim 1.4 kpc), interstellar
absorption (A_V\sim 1.6), and relatively high energy loss rate (dot{E} \sim4.5
10^{35} erg s^{-1}), make it a suitable candidate for an optical follow-up.
Here, we present deep optical observations of PSR J0007+7303. The pulsar is not
detected in the Gran Telescopio Canarias (GTC) images down to a limit of r'\sim
27.6 (3 sigma), the deepest ever obtained for this pulsar, while William
Herschel Telescope (WHT) images yield a limit of V \sim 26.9. Our r'-band limit
corresponds to an optical emission efficiency \eta_{opt}= L_{opt}/dot{E} < 9.4
10^{-8}. This limit is more constraining than those derived for other Vela-like
pulsars, but is still above the measured optical efficiency of the Vela pulsar.
We compared the optical upper limits with the extrapolation of the XMM-Newton
X-ray spectrum and found that the optical emission is compatible with the
extrapolation of the X-ray power-law component, at variance with what is
observed, e.g. in the Vela pulsar.Comment: 5 pages, 3 figures, accepted for publication on MNRA
A MERLIN Observation of PSR B1951+32 and its associated Plerion
In an investigative 16 hour L band observation using the MERLIN radio
interferometric array, we have resolved both the pulsar PSR B1951+32 and
structure within the flat spectral radio continuum region, believed to be the
synchrotron nebula associated with the interaction of the pulsar and its `host'
supernova remnant CTB 80. The extended structure we see, significant at
4.5 , is of dimensions 2.5" 0.75", and suggests a sharp bow
shaped arc of shocked emission, which is correlated with similar structure
observed in lower resolution radio maps and X-ray images. Using this MERLIN
data as a new astrometric reference for other multiwavelength data we can place
the pulsar at one edge of the HST reported optical synchrotron knot, ruling out
previous suggested optical counterparts, and allowing an elementary analysis of
the optical synchrotron emission which appears to trail the pulsar. The latter
is possibly a consequence of pulsar wind replenishment, and we suggest that the
knot is a result of magnetohydrodynamic (MHD) instabilities. These being so, it
suggests a dynamical nature to the optical knot, which will require high
resolution optical observations to confirm.Comment: 12 pages, 2 figures. Accepted for publication in ApJ
Pesticide Application and Handling Technology: Proper Disposal of Empty Pesticide Containers
Recycling has become more and more popular as our awareness of environmental concerns grow. These environmental concerns have led to increased participation in recycling efforts among today\u27s farmers. Many farmers throughout Kentucky are now able to recycle their empty plastic pesticide containers (Five gallon or less) due to a statewide Rinse and Return program. Recycling of empty containers provides a safe means of disposal for applicators, reduces landfill space, and protects our valuable water resources
Pesticide Application and Handling Technology: Installing a Sprayer Tank Rinse Circuit
Proper tank rinsing techniques for agricultural sprayers are very important in order to protect against cross-contamination in subsequent loads and to ensure safe disposal of any excess chemicals and rinsate (rinse water). Spray tanks and other sprayer components should be cleaned after each use. In most situations, sprayer rinsate will have to be sprayed out in the field - either onto a reserved strip, or by over-spraying in the treated area (subject to the terms of the product label)
Segregation by thermal diffusion in granular shear flows
Segregation by thermal diffusion of an intruder immersed in a sheared
granular gas is analyzed from the (inelastic) Boltzmann equation. Segregation
is induced by the presence of a temperature gradient orthogonal to the shear
flow plane and parallel to gravity. We show that, like in analogous systems
without shear, the segregation criterion yields a transition between upwards
segregation and downwards segregation. The form of the phase diagrams is
illustrated in detail showing that they depend sensitively on the value of
gravity relative to the thermal gradient. Two specific situations are
considered: i) absence of gravity, and ii) homogeneous temperature. We find
that both mechanisms (upwards and downwards segregation) are stronger and more
clearly separated when compared with segregation criteria in systems without
shear.Comment: 8 figures. To appear in J. Stat. Mec
Integration Of An Extended Octagonal Ring Transducer And Soil Coulterometer For Identifying Soil Compaction
The soil coulterometer is an “on‐the‐go” electro‐mechanical system which collects impedance force data at multiple depths using an oscillating coulter. During the initial testing (summer 2006), only vertical soil impedance force data was collected using a pressure sensor. To improve the performance of the coulterometer, an extended octagonal ring transducer was integrated into the system to collect both the horizontal and vertical impedance forces given by the soil. In the summer of 2007, data was collected using the revised sensor from a typical central Kentucky field setting in a 0.8‐ha (2‐acre) plot. Four passes were made with the coulterometer. Seventy five coulter oscillations between depths of 100 mm (4 in.) and 305 mm (12 in.) were obtained for each pass. Ten standard cone penetrometer measurements were taken for each pass between depths of 100 mm (4 in.) and 305 mm (12 in.) using a multi‐probe soil cone penetrometer. Three soil bulk density and water content measurements between depths of 100 mm (4 in.) and 305 mm (12 in.) in steps of 50 mm (2 in.) were taken for each pass using a nuclear soil moisture/density gauge. Simple linear regression analysis was used to find the relationship between coulter indices (kN/m), cone index (MPa), dry soil bulk density (Mg/m3) and water content (%).Coefficients of determination (R2) as high as 0.996 were obtained between coulter indices and dry soil bulk density measurements and 0.998 for coulter indices and water content measurements
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