Power subsystem automation study

The purpose of the phase 2 of the power subsystem automation study was to demonstrate the feasibility of using computer software to manage an aspect of the electrical power subsystem on a space station. The state of the art in expert systems software was investigated in this study. This effort resulted in the demonstration of prototype expert system software for managing one aspect of a simulated space station power subsystem

Measurements of hyperfine structure in Ta II

We report the first extensive measurements of hyperfine structure in Ta II. Spectra of Ta II were recorded by high-resolution Fourier transform spectrometry in the region 10 000-53 000 cm-1(1886-10 000 Å) and the majority of observed lines show significant hyperfine structure. Computer fits to several hundred of these line profiles have yielded values of the magnetic dipole hyperfine interaction constant A for 88 energy levels with an uncertainty of between 0.5 and 10 per cent for the majority of A factors. The A factors range from −0.078 to +0.065 cm−1 for the even levels and from −0.064 to +0.083 cm−1 for the odd levels. For the majority of these A factors no previous measurements are known. Approximate values of the electric quadrupole hyperfine interaction constant B were found for 73 levels. These measurements of A and B factors allow, for the first time, the effects of hyperfine structure in Ta II lines to be correctly accounted for both in abundance analysis and in the resolution of blended lines in astrophysical spectr

Fe I Oscillator Strengths for the Gaia-ESO Survey

The Gaia-ESO Public Spectroscopic Survey (GES) is conducting a large-scale study of multi-element chemical abundances of some 100 000 stars in the Milky Way with the ultimate aim of quantifying the formation history and evolution of young, mature and ancient Galactic populations. However, in preparing for the analysis of GES spectra, it has been noted that atomic oscillator strengths of important Fe I lines required to correctly model stellar line intensities are missing from the atomic database. Here, we present new experimental oscillator strengths derived from branching fractions and level lifetimes, for 142 transitions of Fe I between 3526 {\AA} and 10864 {\AA}, of which at least 38 are urgently needed by GES. We also assess the impact of these new data on solar spectral synthesis and demonstrate that for 36 lines that appear unblended in the Sun, Fe abundance measurements yield a small line-by-line scatter (0.08 dex) with a mean abundance of 7.44 dex in good agreement with recent publications.Comment: Accepted for publication in Mon. Not. R. Astron. So

Silicon on Ceramic Process: Silicon Sheet Growth and Device Development for the Large-area Silicon Sheet and Cell Development Tasks of the Low-cost Solar Array Project

The technical and economic feasibility of producing solar cell quality sheet silicon was investigated. It was hoped this could be done by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Work was directed towards the solution of unique cell processing/design problems encountered with the silicon-ceramic (SOC) material due to its intimate contact with the ceramic substrate. Significant progress was demonstrated in the following areas; (1) the continuous coater succeeded in producing small-area coatings exhibiting unidirectional solidification and substatial grain size; (2) dip coater succeeded in producing thick (more than 500 micron) dendritic layers at coating speeds of 0.2-0.3 cm/sec; and (3) a standard for producing total area SOC solar cells using slotted ceramic substrates was developed

Archaeological Investigations at the Ikirahak Site Raise Questions Concerning Taltheilei Land Use in Southern Nunavut

We report a new Taltheilei site-type found off the west coast of Hudson Bay in southern Nunavut. The Taltheilei is an archaeological culture that existed in the Barrenlands of the central Canadian Subarctic between 2600 and 300 years ago. Their land use strategies were tethered to the seasonal migrations of the Beverly and Qamanirjuaq caribou herds throughout tundra and forest landscapes. Tundra-based sites are typically interpreted as short-lived summer camps, but our discovery of three unique pit-house sites on the shores of Maguse Lake raises new questions concerning diversity in Taltheilei tundra land use. Architectural, faunal, lithic, and geoarchaeological data recovered from the Ikirahak site (JjKs-7) support the hypothesis that Taltheilei groups were extending their tundra stays into the fall. We report the evidence from four excavated pit-house features. Terraced platforms along the internal perimeters of these houses suggest they were designed for cold season use. The faunal assemblage is dominated by caribou remains. Higher relative frequencies of appendicular elements suggest a focus on secondary butchering. A large fraction of the faunal assemblage is highly fragmented and calcined, which is consistent with heavy processing and the use of bone as an alternative fuel source. Higher frequencies of lithic debris around dwelling floor perimeters are suggestive of maintenance activities. Multi-element concentrations in dwelling and site-wide sediments also show that hearth refuse was dumped outside. These findings seem to reflect longer tundra occupations during fall, a land use strategy that was likely guided by Qamanirjuaq herd behaviour specific to the Maguse Lake area, fall hunting and processing goals, and ecologically couched mobility logistics. As just four pit-houses from one Taltheilei camp have been investigated to date, our understanding of these places within Taltheilei worlds and northern socio-ecologies is currently limited. Further research at Ikirahak, the other Maguse Lake pit-house sites, and at other caribou water crossings on the tundra of the Qamanirjuaq caribou range is needed to support or refute our hypotheses.Nous signalons un nouveau site de type taltheilei trouvé sur la côte ouest de la baie d’Hudson, dans le sud du Nunavut. La culture taltheilei est une culture archéologique qui a existé dans les landes de la zone subarctique centrale canadienne il y a de cela 2600 à 300 ans. Les stratégies d’utilisation des terres de cette culture étaient rattachées aux migrations saisonnières des hardes de caribous de Beverly et de Qamanirjuaq dans la toundra et la forêt. De manière générale, les sites trouvés dans la toundra sont interprétés comme des campements d’été de courte durée. Cependant, notre découverte de trois sites uniques de maisons semi-souterraines sur les rives du lac Maguse soulève de nouvelles questions au sujet de la diversité de l’utilisation de la toundra par les Taltheilei. Les données architecturales, fauniques, lithiques et géoarchéologiques recueillies au site d’Ikirahak soutiennent l’hypothèse selon laquelle les groupements de Taltheilei occupaient la toundra jusqu’à l’automne. Nous signalons des preuves en provenance de quatre aménagements de maisons semi-souterraines. Le long du périmètre interne de ces maisons, les plateformes en terrasses suggèrent qu’elles étaient conçues pour servir pendant la saison froide. Des restes de caribous dominent l’assemblage faunique. Des fréquences relatives plus élevées d’éléments appendiculaires laissent entrevoir que le dépeçage secondaire y occupait une grande place. Une grande fraction de l’assemblage faunique est fortement fragmentée et calcinée, ce qui correspond à une transformation importante et à l’utilisation des os comme source de combustible. Les grandes fréquences de débris lithiques entourant le périmètre des planchers d’habitations suggèrent des activités de maintenance. Les concentrations d’éléments multiples dans les sédiments des habitations et de l’ensemble du site indiquent également que les déchets des âtres étaient jetés à l’extérieur. Ces constatations laissent entrevoir de plus longues occupations de la toundra à l’automne, une stratégie d’utilisation des terres vraisemblablement guidée par le comportement propre à la harde de Qamanirjuaq dans la région du lac Maguse, par la chasse automnale et par les objectifs de transformation, de même que par la logistique de la mobilité en termes écologiques. Puisque seulement quatre maisons semi-souterraines d’un seul campement taltheilei ont été étudiées jusqu’à maintenant, nous comprenons toujours peu de choses au sujet de ces endroits dans le monde des Taltheilei et des socioécologies nordiques. Il y a lieu de pousser les recherches plus loin à Ikirahak, là où se trouvent les autres sites de maisons semi-souterraines du lac Maguse, ainsi qu’à d’autres passages de franchissement de l’eau sur la toundra du parcours des caribous de Qamanirjuaq afin de confirmer ou de réfuter nos hypothèses

Novel Approach to the Energy Analysis of Mine Cooling Strategies

The extraction of minerals and coal at increasing depth, employing higher-powered, mechanized machinery to increase production levels imposes an increased burden on the ability to maintain an acceptable mine climate. Any deterioration in the mine climate within working zones may adversely affect the health and safety of the workforce. The combination of the optimal design of the mine system layout, together with the selective application of suitable ventilation and cooling systems, may be used to control the climate within working zones. The adoption of mechanical cooling within mines is an expensive process in terms of both capital and operating costs. Therefore, as mechanized mining takes place at increased depth, the need to maintain or improve the mine climate becomes more expensive. Consequently, to decrease overhead costs, reduce energy consumption and meet current and future environmental obligations, it is essential to provide the mine operator with a method with which to determine the most cost effective and efficient mine cooling system. To perform this analysis it is necessary to have a good understanding of the energy balances governing both the operation and utilization of a cooling system. This paper introduces the application of a novel approach to energy analysis of mine cooling systems, with a combination of the concepts of exergy and composite curves. These methods are used extensively throughout chemical and process industries to increase energy efficiency and reduce capital and operating costs. An outline of the methods employed in the application of these techniques to the energy analysis of a mining cooling system is presented

Spitzer Observations of Low Luminosity Isolated and Low Surface Brightness Galaxies

We examine the infrared properties of five low surface brightness galaxies (LSBGs) and compare them with related but higher surface brightness galaxies, using Spitzer Space Telescope images and spectra. All the LSBGs are detected in the 3.6 and 4.5um bands, representing the stellar population. All but one are detected at 5.8 and 8.0um, revealing emission from hot dust and aromatic molecules, though many are faint or point-like at these wavelengths. Detections of LSBGs at the far-infrared wavelengths, 24, 70, and 160um, are varied in morphology and brightness, with only two detections at 160um, resulting in highly varied spectral energy distributions. Consistent with previous expectations for these galaxies, we find that detectable dust components exist for only some LSBGs, with the strength of dust emission dependent on the existence of bright star forming regions. However, the far-infrared emission may be relatively weak compared with normal star-forming galaxies.Comment: 20 pages, 8 figures, accepted to Ap

Atomic and Molecular Data for Optical Stellar Spectroscopy

High-precision spectroscopy of large stellar samples plays a crucial role for several topical issues in astrophysics. Examples include studying the chemical structure and evolution of the Milky Way galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Data are accumulating from instruments that obtain high-quality spectra of stars in the ultraviolet, optical and infrared wavelength regions on a routine basis. These instruments are located at ground-based 2- to 10-m class telescopes around the world, in addition to the spectrographs with unique capabilities available at the Hubble Space Telescope. The interpretation of these spectra requires high-quality transition data for numerous species, in particular neutral and singly ionized atoms, and di- or triatomic molecules. We rely heavily on the continuous efforts of laboratory astrophysics groups that produce and improve the relevant experimental and theoretical atomic and molecular data. The compilation of the best available data is facilitated by databases and electronic infrastructures such as the NIST Atomic Spectra Database, the VALD database, or the Virtual Atomic and Molecular Data Centre (VAMDC). We illustrate the current status of atomic data for optical stellar spectra with the example of the Gaia-ESO Public Spectroscopic Survey. Data sources for 35 chemical elements were reviewed in an effort to construct a line list for a homogeneous abundance analysis of up to 100000 stars.Comment: Published 30 April 2015 in Physica Script