1,827 research outputs found
Analytical and experimental study of two concentric cylinders coupled by a fluid gap
From a structural point of view a liquid coolant type nuclear reactor consists of a heavy steel vessel containing the core and related mechanical components and filled with a hot fluid. This vessel is protected from the severe environment of the core by a shielding structure, the thermal liner, which is usually a relatively thin steel cylinder concentric with the reactor vessel and separated from it by a gap filled with the coolant fluid. This arrangement leads to a potential vibration problem if the fundamental frequency, or one of the higher natural vibration frequencies, of this liner system is close to the frequency of some vibration source present in the reactor vessel. The shell rigidly clamped at its base and free at the top was investigated since it is a better description of the conditions encountered in typical reactor designs
Resolved magnetic structures in the disk-halo interface of NGC 628
Magnetic fields are essential to fully understand the interstellar medium
(ISM) and its role in the disk-halo interface of galaxies is still poorly
understood. Star formation is known to expel hot gas vertically into the halo
and these outflows have important consequences for mean-field dynamo theory in
that they can be efficient in removing magnetic helicity. We perform new
observations of the nearby face-on spiral galaxy NGC 628 with the Karl G.
Jansky Very Large Array (JVLA) at S-band and the Effelsberg 100-m telescope at
frequencies of 2.6 GHz and 8.35 GHz. We obtain some of the most sensitive radio
continuum images in both total and linearly polarised intensity of any external
galaxy observed so far in addition to high-quality images of Faraday depth and
polarisation angle from which we obtained evidence for drivers of magnetic
turbulence in the disk-halo connection. Such drivers include a superbubble
detected via a significant Faraday depth gradient coinciding with a HI hole. We
observe an azimuthal periodic pattern in Faraday depth with a pattern
wavelength of 3.7 0.1 kpc, indicating Parker instabilities. The lack of a
significant anti-correlation between Faraday depth and magnetic pitch angle
indicates that these loops are vertical in nature with little helical twisting,
unlike in IC 342. We find that the magnetic pitch angle is systematically
larger than the morphological pitch angle of the polarisation arms which gives
evidence for the action of a large-scale dynamo where the regular magnetic
field is not coupled to the gas flow and obtains a significant radial
component. We additionally discover a lone region of ordered magnetic field to
the north of the galaxy with a high degree of polarisation and a small pitch
angle, a feature that has not been observed in any other galaxy so far and is
possibly caused by an asymmetric HI hole.Comment: 25 pages, Accepted for publication in Astronomy and Astrophysic
The Effect of Valve Cooling upon Maximum Permissible Engine Output as Limited by Knock
A Wright GR-1820-G200 cylinder was tested over a wide range of fuel-air ratios at maximum permissible power output as limited by knock with three different degrees of valve cooling. The valves used were stock valves (solid inlet valve and hollow sodium-cooled exhaust valve), hollow valves with no coolant, and hollow valves with flowing water as a coolant. Curves showing the variation in maximum permissible values of inlet-air pressure, indicated mean effective pressure, cylinder charge, and indicated specific fuel consumption with change in fuel-air ratio and valve cooling are shown. The use of valves cooled by a stream of water passing through their hollow interiors permitted indicated mean effective pressures 10 percent higher than the mean effective pressures permissible with stock valves when the engine was operated with fuel-air ratios from 0.055 to 0.065. Operation of the engine with lean mixtures with uncooled hollow valves resulted in power output below the output obtained with the stock valves. The data show an increase in maximum permissible indicated mean effective pressure due to cooling the valves, which averages only 2.1 percent with fuel-air ratios from 0.075 to 0.105
Operating Temperatures of a Sodium-Cooled Exhaust Valve as Measured by a Thermocouple
A thermocouple was installed in the crown of a sodium-cooled exhaust valve. The valve was then tested in an air-cooled engine cylinder and valve temperatures under various engine operating conditions were determined. A temperature of 1337 F was observed at a fuel-air ratio of 0.064, a brake mean effective pressure of 179 pounds per square inch, and an engine speed of 2000 rpm. Fuel-air ratio was found to have a large influence on valve temperature, but cooling-air pressure and variation in spark advance had little effect. An increase in engine power by change of speed or mean effective pressure increased the valve temperature. It was found that the temperature of the rear spark-plug bushing was not a satisfactory indication of the temperature of the exhaust valve
Caesarean Scar Ectopic: sonographic findings and management dilemmas
The 47th Annual Scientific Meeting of the British Medical Ultrasound Society: Ultrasound 2015, City Hall, Cardiff, Wales, UK, 9 - 11 December 2015The last decade has seen an increase in caesarean section (CS) rates in Ireland and internationally with a concommitant rise in the incidence of caesarean scar ectopic. Greater awareness of the common sonographic presentations of caesarean scar ectopic at different gestational ages may improve detection rates and reduce morbidity (Timor-Tritsch et al, 2012). The prevalence of caesarean scar ectopics is thought to be 1 in 2000 pregnancies causing significant morbidity and mortality (Sieczko et al, 2014). Defined as implantation of the pregnancy within the scar, it is thought to occur due to a fistula devoloped between the scar and the endometrium.The potential for uterine rupture causing massive haemorrhage is caused by trophoblastic invasion from the implantation site without the supportive myometrium (Jungkman and Anderson, 2015). Four cases identifed in an Irish tertiary referal centre over 4 years demonstrate the differing presentations of caesarean scar ectopic and the management dilemmas discussed in the setting of Irish legislation in relation to termination of pregnancy.
Discovery of a low-luminosity spiral DRAGN
Standard galaxy formation models predict that large-scale double-lobed radio
sources, known as DRAGNs, will always be hosted by elliptical galaxies. In
spite of this, in recent years a small number of spiral galaxies have also been
found to host such sources. These so-called spiral DRAGNs are still extremely
rare, with only cases being widely accepted. Here we report on the
serendipitous discovery of a new spiral DRAGN in data from the Giant Metrewave
Radio Telescope (GMRT) at 322 MHz. The host galaxy, MCG+07-47-10, is a face-on
late-type Sbc galaxy with distinctive spiral arms and prominent bulge
suggesting a high black hole mass. Using WISE infra-red and GALEX UV data we
show that this galaxy has a star formation rate of 0.16-0.75
Myr, and that the radio luminosity is dominated by
star-formation. We demonstrate that this spiral DRAGN has similar environmental
properties to others of this class, but has a comparatively low radio
luminosity of = 1.1210 W Hz, two orders
of magnitude smaller than other known spiral DRAGNs. We suggest that this may
indicate the existence of a previously unknown low-luminosity population of
spiral DRAGNS.Comment: 4 pages, Accepted for publication in Astronomy and Astrophysic
- …