1,634 research outputs found

    Study of pressure losses in tubing and fittings Final report, Jun. 1, 1964 - Jun. 1, 1966

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    Steady state and transient fluid flow equations for predicting friction and pressure in tubing and fitting systems - computer progra

    Study of pressure losses in tubing and fittings Quarterly progress report, Dec. 1965 - Feb. 1966

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    Pressure losses in tubing and fittings - flow systems analysis, entrance effects in flexible metal hoses, and methods for analyzing flow over rough surfac

    Vibration effects on heat transfer in cryogenic systems Quarterly progress report, Jul. 1 - Sep. 30, 1967

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    Water test apparatus used to determine vibration effects on heat transfer in cryogenic system

    Vibration effects on heat transfer in cryogenic systems Quarterly progress report no. 1, Jun. 1 - Aug. 31, 1966

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    Vibration effects on natural convection and fluid transport properties in cryogenic system

    LOFAR observations of radio burst source sizes and scattering in the solar corona

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    Low frequency radio wave scattering and refraction can have a dramatic effect on the observed size and position of radio sources in the solar corona. The scattering and refraction is thought to be due to fluctuations in electron density caused by turbulence. Hence, determining the true radio source size can provide information on the turbulence in coronal plasma. However, the lack of high spatial resolution radio interferometric observations at low frequencies, such as with the LOw Frequency ARray (LOFAR), has made it difficult to determine the true radio source size and level of radio wave scattering. Here we directly fit the visibilities of a LOFAR observation of a Type IIIb radio burst with an elliptical Gaussian to determine its source size and position. This circumvents the need to image the source and then de-convolve LOFAR's point spread function, which can introduce spurious effects to the source size and shape. For a burst at 34.76 MHz, we find full width at half maximum (FWHM) heights along the major and minor axes to be 18.818.8^\prime ± 0.1\pm~0.1^\prime and 10.210.2^\prime ± 0.1\pm~0.1^\prime, respectively, at a plane of sky heliocentric distance of 1.75 R_\odot. Our results suggest that the level of density fluctuations in the solar corona is the main cause of the scattering of radio waves, resulting in large source sizes. However, the magnitude of ε\varepsilon may be smaller than what has been previously derived in observations of radio wave scattering in tied-array images.Comment: 6 pages, 3 figures, accepted for publication in Astronomy & Astrophysic

    Observations of Low Frequency Solar Radio Bursts from the Rosse Solar-Terrestrial Observatory

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    The Rosse Solar-Terrestrial Observatory (RSTO; www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53 05'38.9", 7 55'12.7") in 2010 to study solar radio bursts and the response of the Earth's ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range 10-870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range 10-400 MHz are obtained with 4 sweeps per second over 600 channels. Here, we describe the RSTO solar radio spectrometer set-up, and present dynamic spectra of a sample of Type II, III and IV radio bursts. In particular, we describe fine-scale structure observed in Type II bursts, including band splitting and rapidly varying herringbone features

    Tracking a beam of electrons from the low solar corona into interplanetary space with the Low Frequency Array, Parker Solar Probe and 1 au spacecraft

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    Type III radio bursts are the result of plasma emission from mildly relativistic electron beams propagating from the low solar corona into the heliosphere where they can eventually be detected in situ if they align with the location of a heliospheric spacecraft. Here we observe a type III radio burst from 0.1-16 MHz using the Parker Solar Probe (PSP) FIELDS Radio Frequency Spectrometer (RFS), and from 10-80 MHz using the Low Frequency Array (LOFAR). This event was not associated with any detectable flare activity but was part of an ongoing noise storm that occurred during PSP encounter 2. A deprojection of the LOFAR radio sources into 3D space shows that the type III radio burst sources were located on open magnetic field from 1.6-3 RR_\odot and originated from a specific active region near the East limb. Combining PSP/RFS observations with WIND/WAVES and Solar Terrestrial Relations Observatory (STEREO)/WAVES, we reconstruct the type III radio source trajectory in the heliosphere interior to PSP's position, assuming ecliptic confinement. An energetic electron enhancement is subsequently detected in situ at the STEREO-A spacecraft at compatible times although the onset and duration suggests the individual burst contributes a subset of the enhancement. This work shows relatively small-scale flux emergence in the corona can cause the injection of electron beams from the low corona into the heliosphere, without needing a strong solar flare. The complementary nature of combined ground and space-based radio observations, especially in the era of PSP, is also clearly highlighted by this study.Comment: 17 pages, 10 figures, Submitted to ApJ, April 15 202

    The global precipitation response to volcanic eruptions in the CMIP5 models

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    We examine the precipitation response to volcanic eruptions in the Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations compared to three observational datasets, including one with ocean coverage. Global precipitation decreases significantly following eruptions in CMIP5 models, with the largest decrease in wet tropical regions. This also occurs in observational land data, and ocean data in the boreal cold season. Monsoon rainfall decreases following eruptions in both models and observations. In response to individual eruptions, the ITCZ shifts away from the hemisphere with the greater concentration of aerosols in CMIP5. Models undergo a longer-lasting ocean precipitation response than over land, but the response in the short satellite record is too noisy to confirm this. We detect the influence of volcanism on precipitation in all three datasets in the cold season, although the models underestimate the size of the response. In the warm season the volcanic influence is only marginally detectable

    Mind the gap? The persistence of pathological discourses in urban regeneration policy

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    Urban regeneration policy has historically framed policy problems using a discourse that pathologises areas and spatial communities. Since 2001 in England, and 2002 in Scotland a structural change in policy has occurred where citywide partnerships are now meant overcome structural spatial inequalities, countering pathological explanations. This paper uses historical and discourse analysis to evaluate one of the major community regeneration strategies developed by the Scottish Executive in 2002: Better Communities in Scotland: Closing the Gap. It seeks to ask whether structural change in policy was paralleled by discursive change; what discursive path dependence is evidenced? The text is placed in the historic context of UK urban renewal policies dating back to the launch of the Urban Programme in 1968 and particularly the policy discourse created by the influential Conservative government policy of 1988 New Life for Urban Scotland and the wider discourses of poverty and neighbourhood renewal policy created by Labour governments since 1997. The close textual analysis of the text shows that Better Communities in Scotland continues to pathologise spatial communities. Although this suggests a degree of historical path dependency, the historic breadth of the analysis also problematises simple historical determinism
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