7,735 research outputs found
Rayleigh number dependence of the Archimedes number dependent large-scale flow structure formation in mixed convection
No full textWe report on experimental investigations of large-scale flow structure formation in mixed convection. We characterize the flow field by measuring the velocity fields within a rectangular model room using 2D2C PIV. The control parameters are the Reynolds number Re, the Rayleigh number Ra and the Prandtl number Pr. All parameters are linked through the Archimedes number Ar. In 6.4x10-2 ≤ Ar ≤ 1.39x101, 4.2x103 ≤ Re ≤ 6.35x104 and Ra = 3.1x107, Ra = 1.8x108 and Pr = 0.713 we found flow 3 different flow structures. While keeping Ra and Pr constant and varying Ar through Re variations, we found an Ar dependence of the largescale flow structure formation within 6.4x10-2 ≤ Ar ≤ 1.39x101. Furthermore, we found a Ra dependence of the structure formation, which shifts the transition points between the structures to higher Archimedes numbers and reduces the mean velocities within the investigated domain
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In-field determination of ²²⁶Ra and ²²⁸Ra in the oil exploration sector
No full texttextThe presence of radioactivity in the production of oil is now a well-known phenomenon. Specifically ²²⁶Ra, ²²²Rn, ²²⁸Ra and ²¹⁰Pb and their various decay products are of environmental concern especially to the workers in the field. The Nuclear Engineering Teaching Lab at the University of Texas has been in collaboration with Enviroklean Product Development Inc. (EPDI) in Houston, an environmental restoration and chemical product company, in the clean-up of technologically enhanced naturally occurring radioactive material in the oil exploration sector. In particular radioactive scale build-up in the equipment has been an on-going concern. Unlike typical naturally occurring radioactive material (NORM) samples, ²²⁶Ra and ²³²Th, and their daughters dominate the radioactivity. As such, they are not in secular equilibrium with any of the radionuclides above the decay chain that emanate from ²³⁸U or ²³²Th. Respectively, this thesis sought to test a Cesium Iodide (CsI) detector for in-field analysis of NORM samples. Additionally, quality control procedures and an in-house reference material were created to facilitate this testing. This in-house reference material was used to thoroughly test the CsI detector against the radiation detection stalwarts of High Purity Germanium (HPGe) and Sodium Iodide (NaI). Neither the NaI nor CsI were able to detect the low energy ²¹⁰Pb photons, but ²²⁶̕²²⁸Ra were no issue for either detector. The CsI was found to be 33% more efficient than an HPGe and have twice the full-width half maximum resolution of the NaI (16 keV vs 31 keV at the 186.5 keV peak). The CsI was also able to reach detection limits of 361 +/- 20 pCi/g for ²²⁶Ra and 25 +/- 2 for pCi/g ²²⁸Ra in scale from west Texas. Additionally, the self-attenuation of the sample was evaluated and, as expected, the lower energy photons, e.g. ²¹⁰Pb, are significantly more attenuated than photons at higher energies. We found approximately a 79 % reduction in counts at 47 keV, 7% at 186 keV, and 5% at 911 keV. Self-attenuation must be factored in or there will be an underestimation of the radioactivity, especially for ²¹⁰Pb. The last issue faced while testing the CsI detector was its inability to discriminate the ²²⁸Ra peaks around 911 keV from other peaks in the vicinity. This problem was solved using an HPGe detector to find the ratio of wanted peaks to unwanted peaks around 911 keV photon. This ratio can be applied to the convoluted CsI peak around 911 keV to find the actual net counts coming from ²²⁸Ra. The detection limits, self-attenuation, and deconvolution ratio can all be used to develop software capable of accurately determining radioactivity concentrations in NORM in a field environment.Mechanical Engineerin
Reynolds numbers near the ultimate state of turbulent Rayleigh-Bénard convection
No full textWe report on measurements of the mean-flow Reynolds number ReU and the rms fluctuation Reynolds number ReV in turbulent Rayleigh-Bénard convection as a function of the Rayleigh number Ra for 4 x 1011 < Ra < 2 1014 and Pr ' 0:8. Both can be described by the same power law with an effective exponent = 0:44, in agreement with predictions for ReU but in disagreement with predictions for ReV
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
A map of the World on a new projection with a delineation of the various parts and phaenomena of the solar system ... [cartographic material] /
No full textDouble hemispherical map of the world with relief shown pictorially.; From: A new atlas of the mundane system.... ,Samuel Dunn , 2nd ed., Printed for Robert Sayer, 1788.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.map-rm2967; Library has another copy in RA 62.A new atlas of the mundane syste
Northern hemisphere [cartographic material] /
No full textMap of the Northern hemisphere with relief shown pictorially.; Rex Nan Kivell Collection Map NK 2456/17.; Library has copy also held at RA 54
Western hemisphere [cartographic material] /
No full textMap of Westerm hemisphere with relief shown pictorially.; Rex Nan Kivell Collection Map NK 2456/7.; Library also has copy held at RA 54 map 2
Lagrangian Raylaigh-Bénard convection
No full textUsing passive tracers as sensors, we obtain Lagrangian measurements of tracers position, velocity and temperature in Rayleigh-Bénard convection at Ra=10^7-10^9. We report on statistics of temperature, velocity, and heat transport (Nusselt number). We observe that the Nusselt number is characterized by a largely intermittent behavior, likely due to the interaction of temperature with turbulent velocity fluctuations
Photochemical behavior of some p-styryistilbenes and related compounds: Spectral properties and photoisomerization in solution and in solid state
No full textAuthor Posting. © The Authors (2006) This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in PHOTOCHEMISTRY AND PHOTOBIOLOGY, 82(6): 1645-1650. https://doi.org/10.1562/2006-01-17-RA-780ArticlePhotochemistry and Photobiology. 82(6): 1645-1650 (2006)journal articl
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