SEARCH · Search NASA
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Cd(OsO4)2(N2)2 is Iron carbide-derived structured and crystallizes in the cubic F-43m space group. The structure is zero-dimensional and consists of sixteen ammonia molecules, four cadmium molecules, and eight OsO4 clusters. In each OsO4 cluster, Os5+ is bonded in a tetrahedral geometry to four equivalent O2- atoms. All Os–O bond lengths are 1.73 Å. O2- is bonded in a single-bond geometry to one Os5+ atom.
Zn(OsO4)2(N2)2 is Iron carbide-derived structured and crystallizes in the cubic F-43m space group. The structure is zero-dimensional and consists of sixteen ammonia molecules, eight OsO4 clusters, and four zinc molecules. In each OsO4 cluster, Os5+ is bonded in a tetrahedral geometry to four equivalent O2- atoms. All Os–O bond lengths are 1.73 Å. O2- is bonded in a single-bond geometry to one Os5+ atom.
OsTe2Cl12 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one OsTe2Cl12 sheet oriented in the (0, 0, 1) direction. Os4+ is bonded to six Cl1- atoms to form OsCl6 octahedra that share corners with six equivalent TeCl6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are two shorter (2.34 Å) and four longer (2.35 Å) Os–Cl bond lengths. Te4+ is bonded to six Cl1- atoms to form TeCl6 octahedra that share corners with three equivalent OsCl6 octahedra. The corner-sharing octahedra tilt angles range from 48–56°. There are a spread of Te–Cl bond distances ranging from 2.35–3.01 Å. There are six inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a single-bond geometry to one Te4+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Te4+ atom. In the third Cl1- site, Cl1- is bonded in a 2-coordinate geometry to one Os4+ and one Te4+ atom. In the fourth Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to one Os4+ and one Te4+ atom. In the fifth Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to one Os4+ and one Te4+ atom. In the sixth Cl1- site, Cl1- is bonded in a single-bond geometry to one Te4+ atom.
An experimental investigation (Test OA-309) was conducted using 0.0405-scale Space Shuttle Orbiter Model 16-0 in the North American Aerodynamics Laboratory 7.75 x 11.00-foot Lowspeed Wind Tunnel. The primary purpose was to locate and study any flow conditions or vortices that might have caused damage to the Advanced Flexible Reusable Surface Insulation (AFRSI) during the Space Transportation System STS-6 mission. A secondary objective was to evaluate vortex generators to be used for Wind Tunnel Test OS-314. Flowfield visualization was obtained by means of smoke, tufts, and oil flow. The test was conducted at Mach numbers between 0.07 and 0.23 and at dynamic pressures between 7 and 35 pounds per square foot. The angle-of-attack range of the model was -5 degrees through 35 degrees at 0 or 2 degrees of sideslip, while roll angle was held constant at zero degrees. The vortex generators were studied at angles of 0, 5, 10, and 15 degrees.
The purpose of program VIEW is to compute view factors between specified surfaces and to be compatible with level 15.5 of the NASTRAN structural analysis program. Program VIEW is a modification of a (finite element) view factor computation program called RAVFAC. VIEW is designed to run on an IBM System/360 operating under OS (operating system), with a minimum region size of 110 K bytes. The actual computation of view factors is still performed exactly as it was in the original version of RAVFAC. In developing VIEW, RAVFAC was modified to satisfy the following compatibility requirements: (1) accept finite element input which can also be used as input to NASTRAN, (2) produce output (view factors) in a format which can be used as input to NASTRAN, and (3) follow NASTRAN program design so that in the future VIEW can be incorporated into NASTRAN as a subroutine. The VIEW program permits computation of the view factors between surfaces, taking into account the presence of any intermediate surfaces. VIEW also computes these view factors either by contour integration or by finite difference (double summation) methods.
OsO2F3 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of two OsO2F3 clusters. there are two inequivalent Os7+ sites. In the first Os7+ site, Os7+ is bonded in an octahedral geometry to one O2- and five F1- atoms. The Os–O bond length is 1.68 Å. There are a spread of Os–F bond distances ranging from 1.89–2.05 Å. In the second Os7+ site, Os7+ is bonded in a 6-coordinate geometry to three O2- and three F1- atoms. All Os–O bond lengths are 1.71 Å. There are a spread of Os–F bond distances ranging from 1.90–2.24 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Os7+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one Os7+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Os7+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Os7+ atom. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to two Os7+ atoms. In the second F1- site, F1- is bonded in a 2-coordinate geometry to two Os7+ atoms. In the third F1- site, F1- is bonded in a single-bond geometry to one Os7+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Os7+ atom. In the fifth F1- site, F1- is bonded in a single-bond geometry to one Os7+ atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one Os7+ atom.
Gd3OsO7 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are six inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 pentagonal bipyramids that share corners with two OsO6 octahedra, corners with two equivalent GdO7 pentagonal bipyramids, and edges with two OsO6 octahedra. The corner-sharing octahedra tilt angles range from 42–49°. There are a spread of Gd–O bond distances ranging from 2.24–2.60 Å. In the second Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.36–2.52 Å. In the third Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.33–2.54 Å. In the fourth Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.28–2.75 Å. In the fifth Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 pentagonal bipyramids that share corners with two OsO6 octahedra, corners with two equivalent GdO7 pentagonal bipyramids, and edges with two OsO6 octahedra. The corner-sharing octahedra tilt angles range from 41–50°. There are a spread of Gd–O bond distances ranging from 2.25–2.61 Å. In the sixth Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.28–2.73 Å. There are two inequivalent Os5+ sites. In the first Os5+ site, Os5+ is bonded to six O2- atoms to form OsO6 octahedra that share corners with two equivalent OsO6 octahedra, corners with two GdO7 pentagonal bipyramids, and edges with two GdO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 31–32°. There are a spread of Os–O bond distances ranging from 1.93–2.03 Å. In the second Os5+ site, Os5+ is bonded to six O2- atoms to form OsO6 octahedra that share corners with two equivalent OsO6 octahedra, corners with two GdO7 pentagonal bipyramids, and edges with two GdO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 31–32°. There are a spread of Os–O bond distances ranging from 1.94–2.02 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded to three Gd3+ and one Os5+ atom to form distorted OGd3Os tetrahedra that share corners with six OGd3Os tetrahedra, corners with three OGd3Os trigonal pyramids, edges with two OGd4 tetrahedra, and edges with two equivalent OGd3Os trigonal pyramids. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Gd3+ and two Os5+ atoms. In the third O2- site, O2- is bonded to three Gd3+ and one Os5+ atom to form distorted OGd3Os trigonal pyramids that share corners with eight OGd3Os tetrahedra, corners with three OGd3Os trigonal pyramids, and edges with two OGd4 tetrahedra. In the fourth O2- site, O2- is bonded to four Gd3+ atoms to form a mixture of edge and corner-sharing OGd4 tetrahedra. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two Gd3+ and two Os5+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Gd3+ and one Os5+ atom. In the seventh O2- site, O2- is bonded to three Gd3+ and one Os5+ atom to form a mixture of distorted edge and corner-sharing OGd3Os tetrahedra. In the eighth O2- site, O2- is bonded to three Gd3+ and one Os5+ atom to form distorted OGd3Os tetrahedra that share corners with seven OGd3Os tetrahedra, corners with four OGd3Os trigonal pyramids, and edges with three OGd4 tetrahedra. In the ninth O2- site, O2- is bonded to three Gd3+ and one Os5+ atom to form distorted OGd3Os trigonal pyramids that share corners with seven OGd3Os tetrahedra, corners with two OGd3Os trigonal pyramids, and edges with three OGd4 tetrahedra. In the tenth O2- site, O2- is bonded to four Gd3+ atoms to form OGd4 tetrahedra that share corners with ten OGd3Os tetrahedra, corners with two equivalent OGd3Os trigonal pyramids, edges with two OGd4 tetrahedra, and edges with two OGd3Os trigonal pyramids. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to two Gd3+ and one Os5+ atom. In the twelfth O2- site, O2- is bonded to four Gd3+ atoms to form OGd4 tetrahedra that share corners with ten OGd3Os tetrahedra, corners with two equivalent OGd3Os trigonal pyramids, edges with two OGd4 tetrahedra, and edges with two OGd3Os trigonal pyramids. In the thirteenth O2- site, O2- is bonded to three Gd3+ and one Os5+ atom to form distorted OGd3Os trigonal pyramids that share corners with six OGd4 tetrahedra, corners with three OGd3Os trigonal pyramids, and edges with four OGd3Os tetrahedra. In the fourteenth O2- site, O2- is bonded to four Gd3+ atoms to form OGd4 tetrahedra that share corners with eight OGd4 tetrahedra, corners with four OGd3Os trigonal pyramids, edges with three OGd3Os tetrahedra, and an edgeedge with one OGd3Os trigonal pyramid.
OsO2F3 crystallizes in the monoclinic Pc space group. The structure is one-dimensional and consists of two OsO2F3 ribbons oriented in the (0, 1, 0) direction. there are two inequivalent Os7+ sites. In the first Os7+ site, Os7+ is bonded in an octahedral geometry to one O2- and five F1- atoms. The Os–O bond length is 1.68 Å. There is three shorter (1.89 Å) and two longer (2.04 Å) Os–F bond length. In the second Os7+ site, Os7+ is bonded in a 6-coordinate geometry to three O2- and three F1- atoms. All Os–O bond lengths are 1.71 Å. There are a spread of Os–F bond distances ranging from 1.90–2.25 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Os7+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one Os7+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Os7+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Os7+ atom. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Os7+ atom. In the second F1- site, F1- is bonded in a 2-coordinate geometry to two Os7+ atoms. In the third F1- site, F1- is bonded in a single-bond geometry to one Os7+ atom. In the fourth F1- site, F1- is bonded in a distorted bent 150 degrees geometry to two Os7+ atoms. In the fifth F1- site, F1- is bonded in a single-bond geometry to one Os7+ atom. In the sixth F1- site, F1- is bonded in a single-bond geometry to one Os7+ atom.
Pt2Os(Pt)2 crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of six platinum black molecules and three Pt2Os sheets oriented in the (0, 0, 1) direction. In each Pt2Os sheet, Os2- is bonded to six equivalent Os2- and six equivalent Pt+0.50+ atoms to form a mixture of face, edge, and corner-sharing OsOs6Pt6 cuboctahedra. All Os–Os bond lengths are 2.80 Å. All Os–Pt bond lengths are 2.71 Å. Pt+0.50+ is bonded in a 3-coordinate geometry to three equivalent Os2- atoms.
Detailed analyses are reported on the concentrations of the noble metals Pd, Os, Ir, Pt, and Au in an early Archean spherule bed (S4) of probably impact origin from the lower Fig Tree Group, Barberton Greenstone Belt, South Africa. Compared to other sedimentary deposits of known or suspected impact origin, some noble metals are present in exceptionally high concentrations. Noble metal abundances are fractionated relative to abundances in chondrites with ratios of Os/Ir, Pt/Ir, Pd/Ir, and Au/Ir at only 80, 80, 41, and 2 percent of these values on CI chondrites. Although an extraterrestrial source is favored for the noble metal enrichment, the most plausible cause of the fractionation is by regional hydrothermal/metasomatic alteration.
In areas where biogenic emissions are oxidized in the presence of anthropogenic pollutants, it has become increasingly apparent that secondary organic aerosol (SOA) formation from biogenic volatile organic compounds (BVOCs) is substantially enhanced. The Amazon forest is the dominant source of BVOCs globally, and the forest is rapidly being converted to urban and agricultural uses. We participated in a collaborative field study located in the Amazon region around Manaus, Brazil, in 2014 (Green Ocean Amazon; GoAmazon). This study was designed to comprehensively examine how BVOC emissions (specifically, the most highly emitted non-methane hydrocarbon, isoprene, and lesser studied sesquiterpenes) and their interaction with anthropogenic pollution (i.e., nitrogen oxides, sulfur dioxide, and black carbon) alter the atmosphere’s oxidative capacity, influence secondary aerosol formation, atmospheric composition and, ultimately, affect the earth’s radiation balance and climate. We provide the first hourly, in-situ measurement of 30 sesquiterpenes and 4 diterpenes, roughly estimating that sesquiterpene oxidation contributes to 10-14% of ozone reactive loss by terpenes and at least 0.4–5% (median 1 %) of total submicron OA mass. However, this is likely a low-end estimate, as evidence for additional unaccounted sesquiterpenes and their oxidation products clearly exists. We also provide new perspectives on sulfate, NO x , and particle acidity influencing isoprene-derived SOA, comparing the central Amazon environment with Southeastern U.S.A. summer, representing clean to polluted conditions, respectively. We find that summed concentrations of isoprene-derived SOA tracers correlated with particulate sulfate spanning three orders of magnitude, suggesting that 1 μg m -3 reduction in sulfate corresponds with at least ~0.5 μg m -3 reduction in isoprene-derived SOA. We also find that SOA mass derived from isoprene oxidation in the presence of NO x is primarily comprised of aerosol sulfate bound with isoprene oxidation products (i.e. organosulfates), ~97% in the Amazon and ~55% in the Southeastern U.S. We infer under natural conditions in high isoprene emission regions, preindustrial aerosol sulfate was almost exclusively isoprene-derived organosulfates, which are traditionally thought as representative of anthropogenic influence. We further report the first field observations showing that particle acidity impacts the distribution of isoprene oxidation tracers in the gas and particle phases, providing physicochemical insight into isoprene SOA formation chemistry. Coupled with other co-located measurements by the DOE Atmospheric Radiation Measurement (ARM) team and collaborating PIs at our measurement site (called T3), on the G1 aircraft, and at additional field sites (T0, T1, T2) this data set has been used to understand emission, oxidation, and particle formation pathways at the molecular level, to elucidate how these pathways change when influenced by anthropogenic sources, and to evaluate their importance for the atmospheric budget of aerosols and the earth’s radiation balance on regional scales. Recommendations: Further constraint of the role of sesquiterpenes on ozone (O 3 ) reactivity and SOA formation is limited by the availability of authentic standards and synthesized compounds of sesquiterpenes and their oxidation products. Future research efforts should focus on making such standards available via custom synthesis to allow for accurate quantification and focused oxidation experiments that will fully elucidate the chemistry of these compounds in the atmosphere. Further, reductions in aerosol sulfate (via SO 2 emissions control) continues to be one of the most effective methods to reduce SOA formation from isoprene, but the concerted role of ammonia (NH 3 ) gas emissions from (agricultural) industry and other sources requires more investigation to better understand the role of aerosol acidity in SOA formation and potential controls. As GoAmazon particles can be more acidic compared to areas with greater anthropogenic NH 3 emissions, this promotes relatively greater organosulfate (OS) formation from isoprene even in the presence of NO x . Because OS and inorganic sulfate differ in water uptake properties, this implies preindustrial aerosol sulfate (albeit less abundant) may have been less reflective than current earth system models assume. Further research should investigate the radiative impacts of organic vs inorganic sulfate in aerosols to improve model representation. Finally, future work (currently underway) should include constraint of the contributions of monoterpene (C 10 H 16 ) BVOCs and biomass burning VOCs as precursors to SOA formation in the region as well as their impacts on radiative forcing in the climate system.
A gas sensor includes a substrate and a pair of interdigitated metal electrodes selected from the group consisting of Pt, Pd, Au, Ir, Ag, Ru, Rh, In, and Os. The electrodes each include an upper surface. A first solid electrolyte resides between the interdigitated electrodes and partially engages the upper surfaces of the electrodes. The first solid electrolyte is selected from the group consisting of NASICON, LISICON, KSICON, and .beta.''-Alumina (beta prime-prime alumina in which when prepared as an electrolyte is complexed with a mobile ion selected from the group consisting of Na.sup.+, K.sup.+, Li.sup.+, Ag.sup.+, H.sup.+, Pb.sup.2+, Sr.sup.2+ or Ba.sup.2+). A second electrolyte partially engages the upper surfaces of the electrodes and engages the first solid electrolyte in at least one point. The second electrolyte is selected from the group of compounds consisting of Na.sup.+, K.sup.+, Li.sup.+, Ag.sup.+, H.sup.+, Pb.sup.2+, Sr.sup.2+ or Ba.sup.2+ ions or combinations thereof.
A gas sensor comprises a substrate layer; a pair of interdigitated metal electrodes, said electrodes include upper surfaces, the electrodes selected from the group consisting of Pt, Pd, Au, Ir, Ag, Ru, Rh, In, Os, and their alloys. A first layer of solid electrolyte staying in between electrode fingers and partially on said upper surfaces of said electrodes, said first layer selected from NASICON, LISICON, KSICON and.beta.''-Alumina. A second layer of metal carbonate(s) as an auxiliary electrolyte engaging said upper surfaces of the electrodes and the first solid electrolyte. The metal carbonates selected from the group consisting of the following ions Na.sup.+, K.sup.+, Li.sup.+, Ag.sup.+, H.sup.+, Pb.sup.2+, Sr.sup.2+, Ba.sup.2+, and any combination thereof. An extra layer of metal oxide selected from the group consisting of SnO.sub.2, In.sub.2O.sub.3, TiO.sub.2, WO.sub.3, ZnO, Fe.sub.2O.sub.3, ITO, CdO, U.sub.3O.sub.8, Ta.sub.2O.sub.5, BaO, MoO.sub.2, MoO.sub.3, V.sub.2O.sub.5, Nb.sub.2O.sub.5, CuO, Cr.sub.2O.sub.3, La.sub.2O.sub.3, RuO.sub.3, RuO.sub.2, ReO.sub.2, ReO.sub.3, Ag.sub.2O, CoO, Cu.sub.2O, SnO, NiO, Pr.sub.2O.sub.3, BaO, PdO.sub.2, HfO.sub.3, HfO.sub.3 or other metal oxide and their mixtures residing above and in engagement with the second electrolyte to improve sensor performance and/or to reduce sensor heating power consumption.
The distributions of trace elements between the lunar interior and pristine crustal rocks were controlled by the composition of starting materials, lunar core formation, and crystallization of the lunar magma ocean (LMO) [1]. This study focuses on the partitioning of highly siderophile elements (HSE) including Re, Os, Ir, Ru, Pt, Rh, Pd and Au as well as the moderately siderophile elements Mo and W, and the lithophile elements of Hf and Sr. Our experiments also include Ga, which can be slightly siderophile, but is mostly considered to be chalcophile. Partitioning of these elements is not well known at the conditions of a crystallizing LMO. Previous studies of HSE partitioning in silicate systems have yielded highly variable results for differing oxygen fugacity (fO2) and pressure [2-4]. For example, under certain conditions Pt is compatible in clinopy-roxene [2] and Rh and Ru are compatible in olivine [3]. The silicate compositions used for these experiments were nominally basaltic. Ruthenium, Rh, and Pd are incompatible in plagioclase under these conditions[4]. However, this latter study was done at extremely oxidizing conditions and at atmospheric pressure, possibly limiting the applicability for consideration of conditions of a crystallizing LMO. In this study we address the effects of pressure and oxygen fugacity on the crystal/liquid partition coefficients of these trace elements. We are especially interested in the plagioclase/melt partition coefficients so that it may be possible to use reverse modeling to constrain the concentrations of these elements in the lunar mantle through their abundances in pristine crustal rocks.
In this paper, we apply two theoretical turbulence models, DIA and the recent GISS model, to study properties of a turbulent channel flow. Both models provide a turbulent kinetic energy spectral function E(k) as the solution of a non-linear equation; the two models employ the same source function but different closures. The source function is characterized by a rate n sub s (k) which is derived from the complex eigenvalues of the Orr--Sommerfeld (OS) equation in which the basic flow is taken to be of a Poiseuille type. The O--S equation is solved for a variety of Reynolds numbers corresponding to available experimental data. A physical argument is presented whereby the central line velocity characterizing the basic flow, U0 sup L, is not to be identified with the U0 appearing in the experimental Reynolds number. The theoretical results are compared with two types of experimental data: (1) turbulence bulk properties, and (2) properties that depend stongly on the structure of the turbulence spectrun at low wave numbers. The only existing analytical expression for Pi (k) cannot be used in the present case because it applies to the case of a flat plate, not a finite channel.
Fifteen siderophile and volatile trace elements (Os, Re, Ir, Pd, Ni, Au, Sb, Ge, Se, Ag, In, Zn, Cd, Bi, Tl) and U were determined by radiochemical neutron activation analysis in a spheroidal aphanitic clast and a clast of coarse-grained anorthositic gabbro from breccia 73215 and in three types of aphanite and two clasts of fine-grained anorthositic gabbro from breccia 73255. In common with most Apollo 17 fragment-laden melt rocks, the aphanites from 73215 and 73255 predominantly contain a Group 2 meteoritic component, which is apparently derived from the Serenitatis impact. All aphanitic lithologies contain the same meteoritic component, and are probably cogenetic. The clasts of fine-grained anorthositic gabbro contain substantial amounts (2% to 6% Cl equivalent based on Au) of a pre-Serenitatis Group 3 component. The clast of coarse-grained anorthositic gabbro is low in siderophile elements (0.4% Cl equivalent), and the meteoritic component (Group 5) is not well-defined. A strong correlation exists between Ir and Au in both the aphanites and the anorthositic gabbro clasts, which argues against the breccias 73215 and 73255 being open systems for Au
In this paper, we apply two theoretical turbulence models, DIA and the recent GISS model, to study properties of a turbulent channel flow. Both models provide a turbulent kinetic energy spectral function E(k) as the solution of a non-linear equation; the two models employ the same source function but different closures. The source function is characterized by a rate n sub s (k) which is derived from the complex eigenvalues of the Orr-Sommerfeld (OS) equation in which the basic flow is taken to be of a Poiseuille type. The O-S equation is solved for a variety of Reynolds numbers corresponding to available experimental data. A physical argument is presented whereby the central line velocity characterizing the basic flow, U0 sup L, is not to be identified with the U0 appearing in the experimental Reynolds number. The theoretical results are compared with two types of experimental data: (1) turbulence bulk properties, and (2) properties that depend strongly on the structure of the turbulence spectrum at low wave numbers. The only existing analytical expression for Pi (k) cannot be used in the present case because it applies to the case of a flat plate, not a finite channel.
Visual inspection makes easier to ensure the integrity and safety of spent nuclear fuel (SNF) than any classical techniques. Various classical techniques have been applied but there are no reliable methods to qualitatively and quantitatively verify spent fuel in dry storage. Thus, the present authors have developed the prototype safeguards apparatus for dry storage employing the array of He-4 gas scintillation detectors (S670E, Arktis Radiation Detectors Ltd., Switzerland), newly designed to simultaneously measure thermal and fast neutrons without any moderators. The S670E detector has a cylindrical shape with a diameter of 52 mm and active length of 600 mm (total length: 875 mm). The detector is filled by He-4 gas with an approximate pressure of 180 bar for fast neutron detection, and its inner wall is coated by Li-6 for thermal neutron detection. The scintillation lights generated via Li-6 nuclear reaction and elastic scattering are collected by 24 SiPMs linearly paired at the center of the detector. The detector delivers a TTL (Transistor-Transistor Logic) output for pulse readout and UART (Universal Asynchronous Receiver Transmitter) for device control. In order to assess feasibility of the apparatus, an experimental system has been designed, built, and optimized via computational studies. Cf-252 neutron sources and linearly arrayed detectors, working as a single detector, were occupied for this study due to the difficulties in working with SNF. The laboratory scale cask (diameter: 0.67 m, height: 1.5 m), minimized by a factor of 10 compared to the actual thickness of a commercial TN-32 cask, was also manufactured. The detector array was designed to rotate the lab-scale cask and obtain 36 image profiles at every 10 degrees. All profiles were aligned in single frame image called a sinogram, and the cross-sectional image was then fabricated by the inverse radon transform algorithm. These experiments have been repeated with different configurations and numbers of sources. Some gamma-ray sources were also measured with neutron sources in order to distinguish between neutron and gamma-ray pulses. Basically, a He-4 detector is designed to run on Linux OS so it is difficult to directly apply to Windows-based equipment widely used in S. Korea. Therefore, a new data acquisition board working on Windows OS was designed and built. The board mainly consists of FPGA (Field Programmable Gate Array) and SoC (System on Chip) for TTL pulse readout, sorting measured data, and transferring data to a user interface. In conclusion, the tomographic system at lab-scale has shown considerable potential to detect a partial or gross defect of encapsulated assemblies in dry storage. Next steps of this study will be to 1) repeatedly carry out experiments to demonstrate scientific reliability and validity, and 2) numerically integrate signals with weight factors to enhance the image quality since the suggested system based on passive interrogation method requires longer measurement time. Finally, the system will apply to a commercial dry storage phased out soon in S. Korea. (authors)