Tungsten carbide-based metal matrix composite coatings are deposited by PTAW (Plasma Transferred Arc Welding) on production critical components in oil sands mining. Homogeneous distribution of the reinforcement particles is desirable for optimal wear resistance in order to reduce unplanned maintenance shutdowns. The homogeneity of the coating can be improved by controlling the heat transfer, solidification rate of the process and the volume fraction of carbide. The degree of settling of the particles in the deposit was quantified using image analysis. The volume fraction of carbide was the most significant factor in obtaining a homogeneous coating. Lowering the current made a modest improvement in homogeneity. Changes made in other operational parameters did not effect significant changes in homogeneity. Infrared thermography was used to measure the temperature of the surface of the deposit during the welding process. The emissivity of the materials was required to acquire true temperature readings. The emissivity of the deposit was measured using laser reflectometry and was found to decrease from 0.8 to 0.2 as the temperature increased from 900C to 1200C. A correction algorithm was applied to calculate the actual temperature of the surface of the deposit. The corrected temperature did increase as the heat input of the weld increased. A one dimensional mathematical model of the settling profile and solidification of the coatings was developed. The model considers convective and radiative heat input from the plasma, the build-up of the deposit, solidification of the deposit and the settling of the WC particles within the deposit. The model had very good agreement with the experimental results of the homogeneity of the carbide as a function of depth. This fundamental model was able to accurately predict the particle homogeneity of an MMC deposited by an extremely complicated process. It was shown that the most important variable leading to a homogeneous coating is to operate at the packing saturation limit of the reinforcement. In the case of the MMC explored, a fully homogeneous coating was obtained with 50 vol% WC in a NiCrBSi matrix. / Materials Engineering

Ductile steel plate shear walls are an established lateral load resisting system. Past research indicates that cold-rolled infill panels less than 1 mm in thickness present one solution to an overstrength problem arising from selecting an infill panel thickness based on ease of welding and handling. This research program examines several possible welding procedures and joint geometry to connect the thin infill panel to the thick boundary elements. Primary welding parameters include short-circuiting gas metal arc welding process, electrode and shielding gas selection, heat input, and use of a chill strip. Four configurations of the infill panel-to-boundary element joint and two configurations of a lap splice joint between two sheets of thin steel in the infill panel were tested in monotonic tension and cyclic tension-compression. A quasi-static cyclic test of a single-storey moment resisting frame steel plate shear wall validated the use of one welding procedure and joint geometry. / Structural Engineering

Cross flow heat exchangers are a fairly common apparatus employed throughout many industrial processes. For these types of systems, correlations have been extensively developed. However, there have been no correlations done for very high enthalpy flows as produced by Arnold Engineering Development Center’s (AEDC) H2 facility. The H2 facility uses a direct current electric arc to heat air which is then expanded through a converging-diverging nozzle to impart a supersonic velocity to the air. This high enthalpy, high temperature air must be cooled downstream by the use of a cross flow heat exchanger. It is of interest to evaluate the actual performance of the air cooler to determine the effectiveness of possible facility upgrades. In order to characterize cooler effectiveness, a numerical model is built to calculate per-tube-row energy balances using real (temperature and pressure dependent) air and water properties and cross-flow Nusselt number calculations.

The main goal of this thesis is a contribution to the classification of all incidence geometries of rank two on which some group PSL(2,q), q a prime power, acts flag-transitively. Actually we require that the action be RWPRI (residually weakly primitive) and (2T)1 (doubly transitive on every residue of rank one). In fact our definition of RWPRI requires the geometry to be firm (each residue of rank one has at least two elements) and RC (residually connected). The main goal is achieved in this thesis. It is stated in our "Main Theorem". The proof of this theorem requires more than 60pages. Quite surprisingly, our proof in the direction of the main goal uses essentially the classification of all subgroups of PSL(2,q), a famous result provided in Dickson’s book "Linear groups: With an exposition of the Galois field theory", section 260, in which the group is called Linear Fractional Group LF(n, pn). Our proof requires to work with all ordered pairs of subgroups up to conjugacy. The restrictions such as RWPRI and (2T)1 allow for a complete analysis. The geometries obtained in our "Main Theorem" are bipartite graphs; and also locally 2-arc-transitive graphs in the sense of Giudici, Li and Cheryl Praeger. These graphs are interesting in their own right because of the numerous connections they have with other fields of mathematics.

Exposure to a strong T-helper 2 (Th2)-like environment during fetal development may promote allergy development. Increased cord blood (CB) levels of the Th2-associated chemokine CCL22 were associated with allergy development during the first 2 y of life. The aim of the present study was to determine whether CB Th1- and Th2-associated chemokine levels are associated with allergy development during the first 6 y of life, allowing assessment of respiratory allergic symptoms usually developing in this period. The CB levels of cytokines, chemokines, and total IgE were determined in 56 children of 20 women with allergic symptoms and 36 women without allergic symptoms. Total IgE and allergen-specific IgE antibody levels were quantified at 6, 12, 24 mo, and 6 y of age. Increased CB CCL22 levels were associated with development of allergic sensitization and asthma and increased CCL17 levels with development of allergic symptoms, including asthma. Sensitized children with allergic symptoms showed higher CB CCL17 and CCL22 levels and higher ratios between these Th2-associated chemokines and the Th1-associated chemokine CXCL10 than nonsensitized children without allergic symptoms. A pronounced Th2 deviation at birth, reflected by increased CB CCL17 and CCL22 levels, and increased CCL22/CXCL10 and CCL17/CXCL10 ratios might promote allergy development later in life.

Subduction zones are places where one hydrated oceanic plate goes underneath another plate, and releases its fluids into the overlying mantle wedge. Slab-derived fluids play a key role in subduction zone processes. They serpentinize the cold forearc mantle at shallow depths; and deeper, they trigger hydrous mantle melting beneath the arc volcanoes and sometimes at backarc basin (BAB) spreading center. Examining the composition of arc and BAB magmas helps understanding genesis of subduction-related magmas, nature and composition of their mantle sources and slab-derived fluids. However, investigating such processes at shallow subduction zones is challenging, because the cold forearc mantle generally does not melt. Here, I investigate an unusual region in the southernmost Mariana convergent margin in the Western Pacific, near the Challenger Deep. The SE Mariana forearc stretched to accommodate opening of the southernmost Mariana Trough ~5Ma ago, opening the SE Mariana forearc rift (SEMFR) and causing seafloor spreading ~2.7-3.7Ma ago. The subducted slab beneath SEMFR deepens from <50km to ~100km, thus studying SEMFR lavas provides a unique opportunity to understand shallow subduction processes. By examining the major and trace element composition, the Pb-Nd-Sr isotopic ratios and the volatile contents (H2O, CO2, Cl, S, F) of SEMFR basalts, associated glassy rinds and olivine-hosted melt inclusions (Ol-MI) collected during three cruises (YK08-08, YK10-12, TN273), I show that: (i) SEMFR lavas were produced by adiabatic decompression melting of depleted asthenospheric BAB-like mantle at ~30±6.6 km depth and 1224±40oC; (ii) Ol-MI represent hydrous melts trapped by forearc mantle olivines. Xenocrysts were entrained with SEMFR basalts during ascent; (iii) SEMFR mantle flowed from the forearc towards the arc volcanoes and was metasomatized by shallow aqueous fluids; (iv) SEMFR shallow fluids are more aqueous than the fluids released beneath the Mariana arc and Mariana BAB; (v) the aqueous slab-derived fluids and the volatile fluxes are greatest at ~50-100km slab depth, suggesting that the minerals from the subducting plate mostly broke down beneath the arc to release their fluids. Such results provide new insights into shallow subduction processes, as previous studies showed that volatile fluxes and aqueous slab-derived fluids should increase toward the trench.

Quaternary cubic (TixCr1 − xAl~ 0.60)1 N1 coatings with 0 &lt; x &lt; 0.33 have been grown using reactive cathodic arc evaporation. When adding Ti the hardness was retained after annealing up to 1100 °C which is a dramatic improvement compared to CrAlN coatings. The coatings showed an age hardening process caused by spinodal decomposition into coherent TiCr- and Al-rich cubic TiCrAlN domains and the formation of hexagonal AlN precipitates and cubic TiCrN domains in the vicinity of the grain boundaries. The improved hardness was attributed to the stabilization of the cubic structure suppressing the formation and growth of hexagonal AlN. Furthermore, the presence of Ti atoms generated incoherent nanometer-sized crystallites within the hexagonal AlN precipitates disrupting the hexagonal lattice during the coarsening process. The addition of Ti promoted the formation of a TiO2 layer over Al2O3 resulting in a lower oxidation resistance. However, by tuning the composition it is possible to design coatings to have both good oxidation resistance and good high temperature mechanical stability. / <p>Funding Agencies|SSF project Designed multicomponent coatings, MultiFilms||</p>

Submerged arc welding (SAW) is often the method of choice in pressure vessel fabrication. This process features high production rates, welding energy and/or welding speed and requires minimal operator skill. The selection of appropriate parameters in SAW is essential, not only to optimize the welding process in order to maintain the highest level of productivity, but also to obtain the most desirable mechanical properties of the weld.<p> The focus of this study was to investigate the effect of welding speed on the properties of SA516 Grade 70. Plates of SA516 Gr. 70 steel 17 mm x 915 mm x 122 mm were submerged arc welded with a welding current of 700 A and welding speeds of 15.3, 12.3 and 9.3 mm/s. Following the welding; strength, microstructure, hardness and impact toughness of the specimens were examined. Charpy impact testing was performed according to ASTM E 23 on specimens notched in the weld metal (WM) and in the heat-affected zone (HAZ), to measure the impact toughness. Fractography was performed on broken specimens using optical and scanning electron microscopy in order to correlate the mechanisms of fracture with the impact toughness values.<p> The highest hardness values were in the coarse-grained HAZ followed by the WM with the lowest hardness in the parent metal (PM). The HAZ had higher impact toughness than the WM and PM for all welding speeds. The slowest welding speed (9.3 mm/s) obtained complete penetration and therefore produced the most visually sound weld. The fastest welding speed (15.3 mm/s) had the narrowest HAZ and showed good ductile-to-brittle transition behaviour for both the WM and HAZ specimens, but produced incomplete penetration defects. Welding speed had little affect on the notch toughness of the HAZ with only a 9 J rise in upper shelf energy and an 8 °C drop in the impact transition temperature (ITT) with increased welding speed from 9.3 to 15.3 mm/s. However, for the WM, there was a 63 J drop in the upper shelf energy but also a 41 °C improvement of the ITT between the 9.3 and 15.3 mm/s welding speeds.

Metal foams and wire meshes are open cell structures with low weight and density, high permeability and high thermal conductivity which make them attractive for a wide range of industrial applications involving fluid flow and heat transfer. In this study, the effect of natural convection, radiation and heat transfer enhancement of metal foams and wire meshes of 10 and 40 PPI (pores per inch) heat exchangers were examined and compared for different heat exchanger orientation, coolant flow rate and atmosphere temperature. Thermal spray coating processes were also used in development of a new class of high temperature stainless steel heat exchangers. Stainless steel wire mesh heat exchangers were prototyped by connecting the tube to the wire mesh using wire arc thermal spray coating. Thermal spray coating provided efficient connections between the wire mesh and the tubes’ outer surface, and has potential to replace expensive brazing or other metal connection techniques.

This exhibition is a direct response to my own religious upbringing. I chose to explore the oppression upon women, gays and people of color by religious intolerance. The Church dictates social and political mores that affect our society and culture and the way we are treated and governed. The use of the bible and conservative belief structures to defend the ill manner in which we are treated should not be ordained in today’s social construct. In the Name of god addresses issues from the Inquisition to the current war for control over women’s bodies and our reproductive systems. By revisiting the past and illustrating earlier evidence of religious corruption, I intend to demonstrate this countries lack of understanding of anything other.