Numerical solution of the two-dimensional time-dependent multigroup equations

Also issued as a Ph. D. thesis in the Dept. of Nuclear Engineering, MIT, 1969"MIT-3903-1."Includes bibliographical references (leaves 60-61)Contract AT(30-1)-390

Aircraft cabin water spray disbenefits study

The concept of utilizing a cabin water spray system (CWSS) as a means of increasing passenger evacuation and survival time following an accident has received considerable publicity and has been the subject of testing by the regulatory agencies in both the United States and Europe. A test program, initiated by the CAA in 1987, involved the regulatory bodies in both Europe and North America in a collaborative research effort to determine the benefits and 'disbenefits' (disadvantages) of a CWSS. In order to obtain a balanced opinion of an onboard CWSS, NASA, and FAA requested the Boeing Commercial Airplane Group to investigate the potential 'disbenefits' of the proposed system from the perspective of the manufacturer and an operator. This report is the result of a year-long, cost-sharing contract study between the Boeing Commercial Airplane Group, NASA, and FAA. Delta Air Lines participated as a subcontract study team member and investigated the 'return to service' costs for an aircraft that would experience an uncommanded operation of a CWSS without the presence of fire. Disbenefits identified include potential delays in evacuation, introduction of 'common cause failure' in redundant safety of flight systems, physiological problems for passengers, high cost of refurbishment for inadvertent discharge, and potential to negatively affect other safety systems

The diet of woodland caribou populations in west-central Alberta

The diet of woodland caribou (Rangifer tarandus caribou) populations in the foothills and Rocky Mountains of west-central Alberta was estimated by microhistological analyses of feces collected in winter and summer. In winter, terrestrial lichens averaged 60-83% of fecal fragment densities in both areas. In the mountains, decreasing proportions of terrestrial lichens and increasing proportions of conifer needles and moss indicated decreasing accessibility of forage because of deeper/harder snow. Apparent diets in summer were dominated by Salix spp., sedges, and lichens. However, forb inflorescences and stems were largely undetected by the microhistological technique and results for summer samples must be interpreted accordingly. We conclude that the conservation and management of forest ecotypes of caribou must include options of lichen-rich habitats as a major component of management plans

In-line characterisation of continuous phase conductivity in slurry flows using artificial intelligence tomography

Electrical Impedance Tomography (EIT) can be applied to monitor a variety of mineral and chemical processes including: velocity measurements in drilling cuttings and hydrocyclone operations. Hydraulic conveying systems rely upon the knowledge of slurry density to ensure efficient transportation of the solids. Typically, density measurements exploit the attenuation of gamma ray photons which poses complex safety, operational and regulatory concerns with Electrical Impedance Tomography affording a non-nuclear alternative to traditional approaches. To optimise the accuracy of this non-nuclear density measurement, the electrical conductivity of the aqueous phase in a multi-component slurry, is required. Whilst conductivity probes are sufficiently accurate, there are often drawbacks and limitations due to installation restrictions, as it is difficult to separate aqueous and solid phases in real-time. Electrical Impedance Fingerprinting (EIF), is a novel measurement technique which characterises formulation properties, in-situ, based upon electrical impedance sensing and artificial intelligence algorithms. This paper outlines the development of EIF and its application to monitor aqueous phase conductivity in multi-component slurries, containing sands and clays. EIF accurately predicts this conductivity with high accuracy and a root-mean squared error of 0.055 mS cm−1. This development ensures accurate non-nuclear density measurements (<5%) are obtained across an extended aqueous electrical conductivity range of 1.5–70 mS cm−1. This encompasses the majority of target hydraulic conveying systems in mining operations. EIF also enhances the functionality of ‘traditional’ electrical tomography as not only are mineral processes able to be visualised, but the process materials are simultaneously characterised, to improve process understanding, optimisation and control

Crossover between Thermally Assisted and Pure Quantum Tunneling in Molecular Magnet Mn12-Acetate

The crossover between thermally assisted and pure quantum tunneling has been studied in single crystals of high spin (S=10) uniaxial molecular magnet Mn12 using micro-Hall-effect magnetometry. Magnetic hysteresis and relaxation experiments have been used to investigate the energy levels that determine the magnetization reversal as a function of magnetic field and temperature. These experiments demonstrate that the crossover occurs in a narrow (0.1 K) or broad (1 K) temperature interval depending on the magnitude of the field transverse to the anisotropy axis.Comment: 5 pages, 4 figure

Photogrammetric system and method used in the characterization of a structure

A photogrammetric system uses an array of spaced-apart targets coupled to a structure. Each target exhibits fluorescence when exposed to a broad beam of illumination. A photogrammetric imaging system located remotely with respect to the structure detects and processes the fluorescence (but not the illumination wavelength) to measure the shape of a structure

Laser Ablation Surface Preparation of Ti-6A1-4V for Adhesive Bonding

Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable bonds. Laser ablation imparts both topographical and chemical changes to a surface which can lead to increased bond durability. A laser based process provides an alternative to chemical-dip, manual abrasion and grit blast treatments which are expensive, hazardous, polluting, and less precise. This report documents preliminary testing of a surface preparation technique using laser ablation as a replacement for the chemical etch and abrasive processes currently applied to Ti-6Al-4V alloy adherends. Failure mode, surface roughness, and chemical makeup were analyzed using fluorescence enhanced visualization, microscopy, and X-ray photoelectron spectroscopy, respectively. Single lap shear tests were conducted on bonded and aged specimens to observe bond strength retention and failure mode. Some promising results showed increasing strength and durability of lap shear specimens as laser ablation coverage area and beam intensity increased. Chemical analyses showed trends for surface chemical species which correlated with improved bond strength and durability. Combined, these results suggest that laser ablation is a viable process for inclusion with or/and replacement of one or more currently used titanium surface treatments. On-going work will focus on additional mechanical tests to further demonstrate improved bond durability

X chromosome effects and their interactions with mitochondrial effects

We report a simple and rapid method for detecting additive genetic variance due to X-linked loci in the absence of marker data for this chromosome. We examined the interaction of this method with an established method for detecting mitochondrial linkage (another source of sex-asymmetric genetic covariance). When applied to data from the Collaborative Study on the Genetics of Alcoholism, this method found evidence of X-chromosomal linkage for one continuous trait (ntth1) and one discrete trait (SPENT). Evidence of mitochondrial contribution was found for one discrete trait (CRAVING) and three continuous traits (ln(CIGPKYR), ecb21, and tth1). Results for ntth1 suggest that methods that do not also allow for male-female heterogeneity in environmental variance may be overly conservative in detection of X-chromosomal effects