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<p> Powder Metallurgy (P/M) offers a very efficient method to produce high volume, high throughput steel parts. The two most important property issues affecting P/M steels are: (I) possessing high mechanical properties despite having inherent internal porosity; (2) maintaining very tight dimensional tolerances during processing (sintering). Researchers are continually looking at ways to improve these two properties while keeping costs down. As in wrought and cast steels, in most applications P/M steels are alloyed; in P/M processing, alloys are typically added to Fe + C powder mixes as elemental powders. The entire mix of Fe+ C +elemental alloying additives are then consolidated under high pressure and sintered at high temperatures to strengthen the compact. The current work deals mainly with the the most commonly used alloying additives in P/M steels, Ni and Cu. </p> <p> While it is well-known that Ni and Cu do indeed improve the mechanical performance of steels and do affect the dimensional change of P/M parts in specific ways, for over 50 years the same standard Ni and Cu powders have been used in the industry. With new breakthroughs in the production of extra-fine metal powders (- 1-2 urn) P/M researchers now must examine the effect of particle size of alloying additions on the performance of sintered steels. Prior to the current work, significant documented work investigating the effect of particle size of Ni and Cu on the performance of P/M steels was very limited. </p> <p> The current work examined: (I) Ni powder particle size effects in P/M Ni steels; (2) Ni powder particle size effects in P/M Ni-Cu steels; (3) Ni and Cu powder particle size effects in P/M Ni-Cu-Mo steels. </p> <p> Specific focus was on determining the effects of particle sizes on the dimensional control and mechanical peformance of P/M steels. With both Ni and Cu, the finer the powder addition the better the dimensional control and mechanical performance of the steels. In steels containing both Ni and Cu, finer Ni also improved the distribution and diffusion of Cu. This suggested that there was a significant interaction between Ni and Cu during sintering which could be tailored to improve properties. The effect of changing Ni particle size on overall steel properties was significantly greater than the effect of changing Cu particle size. </p> <p> Mechanistic analyses via optical microscopy, SEM-EDX and E-SEM investigation, dilatometry, and differential thermal analysis were carried out to explain the results. Mathematical models were also developed to show the effect of Ni and Cu particle size on diffusion into the Fe matrix during sintering. </p> / Thesis / Master of Applied Science (MASc)

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The fossil record is the primary source of information on the history of life. As such, it is important to understand the limitations of this record. One critical area in which there is still much work to be done is in understanding how the fossil record, and our interpretation of it, may be biased. Herein, the fidelity between the life and death assemblage of an extant brachiopod with respect to morphological variability is studied using geometric morphometrics. The results from several analyses confirm a high degree of morphological variability with little change in mean shape between the living and sub-fossil assemblage. Additionally, there is no evidence of distinct morphogroups in either assemblage. These trends persist at all depths and size classes indicating that this species could be recognized as a single, rather than multiple, species if only fossil data were available. The second chapter involves the recognition and quantification of a worker bias in monographs of brachiopods and bivalves. Most specimens studied came from the 65th to 69th percentile of their species' bulk-collected size-frequency distribution. This indicates a significant bias toward monograph specimens that are larger than the mean size of the bulk sample. When compared at the species level, this bias was found to be highly consistent among the 86 species included in the study. Thus, size measurements of monographed specimens reliably and consistently record a similar size class for any given species, and this bias is easily corrected during meta-analyses. Chapter three focuses on bivalves and brachiopods from a modern tropical shelf and quantifies the magnitude of time averaging (temporal mixing) for these two different organisms. This is accomplished by dating a suite of shells from each site using amino acid racemization calibrated with several radiocarbon dates. By studying the age distributions for each species it is determined that, despite some site to site differences, both bivalve and brachiopod species exhibit a similar time averaging magnitude when collected from the same region or depositional system. This indicates that fossil assemblages of these species may have very similar resolution. / Ph. D.

This study investigated the impact of Virginia's K-3 Primary Class Size Reduction Program on student achievement in reading. The theoretical framework hypothesized that a reduction in class size and sustained professional development would impact instructional strategies implemented by teachers which would result in increased reading achievement by students. Information regarding the history of class size research was presented to provide readers with a chronological overview of the topic. In addition, statewide class size reduction initiatives from Indiana, Tennessee, Wisconsin, and California were reviewed. Data were collected using administrator and teacher surveys as well as an analysis of the Virginia Standards of Learning Assessments for Grade 3 English and the Phonological Awareness Literacy Screening (PALS) results for schools participating in the research study. The findings revealed that the Virginia K-3 Primary Class Size Reduction Program benefited grade 3 students according to gender, ethnicity, and socioeconomic status. <i>Vita removed at the author's request. GMc Feb. 4, 2013</i> / Ph. D.

The objectives of this dissertation were to evaluate genetic and environmental relationships between lamb and ewe traits including body weight, fleece weight and quality, prolificacy, body condition, ewe stayability and lamb survival. Average heritability estimates for lamb birth weight (BWT), weaning weight (WW), maternal weaning weight, yearling body weight, fleece weight, spinning count and staple length were 0.19, 0.09, 0.08, 0.35, 0.38, 0.25, and 0.31 respectively. Heritability estimates for adult traits averaged 0.43 for body weight (AW), 0.13 for body condition (AC), and 0.12 for number of lambs born per ewe lambing (NLB). Correlations between direct additive AW and direct additive and maternal lamb weights ranged from 0.21 to 0.96 (P < 0.05) and 0.29 to 0.53 (P < 0.05), respectively, with residual correlations ranging from 0.05 to 0.95. Correlations of lamb traits with adult body condition and NLB were generally not different from zero; genetic and residual correlations ranged from -0.52 to 0.69 and -.39 to 0.31, respectively. Ewe stayability was analyzed as overall stayability (STAYn|2) which indicated the presence or absence of a ewe at n yrs of age, given that she was present at 2 yrs of age, and marginal stayability (STAYn|1-n) recording the presences of a ewe at n yrs of age, given that she was in the flock the previous year. Additive variance in ewe stayability was only found in stayability at 5 and 6 yr of age (P < 0.05). Heritability estimates for STAY5|4 and STAY6|2 from multiple trait analyses with other traits averaged 0.08 and 0.10, respectively. Phenotypic correlations between STAY and all other traits were near zero, ranging from -0.04 to 0.03. The estimated correlations between additive effects on STAY5|4 and STAY6|2 and additive maternal effects on WW were positive (both 0.46; P < 0.05). Genetic correlations between STAY5|4 and WW, adult weight, and NLB were 0.06, 0.13 and -0.06 (P > 0.10), respectively. However, genetic correlations between STAY6|2 and WW, adult weight, and NLB were negative (-0.17, -0.32 (P < 0.05) and -0.03, respectively). Significant genetic variation was thus present in stayability, with nonzero genetic correlations present between STAY, maternal milk, WW, and adult weight. Survival analysis was performed using a proportional hazards model to measure the probability of lamb death before weaning. Lamb survival was recorded as the day of age at death. Records were censored if a live lamb was artificially removed from their litter before death. Fixed effects on survival included ewe age, litter size, sex, and linear and quadratic BWT. Average age of death was 13.7 d. Censoring of records before weaning occurred in 12.9% of the total lambs born. Risk ratios indicated lambs from yearlings and ewes older than 5 yr had the greater risk of death, as did triplet and quadruplet lambs. Linear and quadratic BWT effects on lamb survival were found (P < 0.05) and accounted for most of the litter size effects in large litters. The influence of informative censoring was considered by assuming that lambs censored by 3 d of age had died at the time of censoring. Heritability of lamb survival at 3 d of age (estimated using an animal model in MTDFREML) was near zero, ranging from 0.00 to 0.01. The lack of additive variance suggests that improvement in lamb survival should be made through changes in management practices. / Ph. D.

Dinosaurs are the largest animals to ever walk on the continents and some reached body sizes of up to 70 tons. Observation of their closest living relatives, birds and crocodylians, could never allow for prediction of gigantic dinosaurian forms. Therefore, the fossil record is crucial to understanding the evolutionary changes of these animals through time, including body size trends. The reptile group Archosauria encompasses living and extinct birds and crocodylians as well as non-avian dinosaurs and crocodile relatives called pseudosuchians. My research focuses on studying fossils of extinct archosaurs to determine how the morphology of their skeletons allowed for growth to large body sizes. I am specifically interested in how the vertebral column fits together and how the structures that articulate vertebrae change throughout the phylogeny (i.e. family tree) of Archosauria. Although major body size trends are well known for archosaurs, less research has focused on skeletal features that are associated with the evolution of large body size in that group. I hypothesize that the vertebral column will have these features. To answer the question of how vertebrae morphology is related to body size, I first described eight vertebrae from a large pseudosuchian archosaur Poposaurus langstoni. This animal possesses an accessory articulation between the vertebrae in its trunk region (i.e. between the neck and hips) called the hyposphene-hypantrum articulation. I then surveyed vertebrae from across Archosauria and found a close fit of presence of the articulation with large sizes and that it evolves independently in several archosaur groups. / Master of Science

Broiler nutrition can be affected by many different factors, and diets can be made up of a wide variety of components. Feed enzymes, different Ca sources, and various ingredient particle sizes all contribute to broiler nutritional status and need to be investigated to determine their full effects on the bird. The objective of the first study was to evaluate various Ca sources and microbial phytases using an in vitro assay to simulate broiler digestion. The trial measured total Ca and P, soluble Ca and P, and pH. It involved limestone, dicalcium phosphate, highly soluble Ca (HSC), whey, and a control with no added Ca. Each diet was supplemented with 0 or 500 FTU/kg of phytase 1 or phytase 2. Diets were analyzed for total Ca and P and then were subjected to a gastric phase digestion, including the addition of HCl and pepsin, with incubation times of 5, 10, or 20 min. They were also subjected to a gastric phase and a SI phase digestion, including the addition of HCl, pepsin, NaHCO3, and pancreatin with incubation times of 5, 10, 20, or 60 min. The objective of the second study was to evaluate various particle sizes, Ca sources, and source locations using the same in vitro assay. Large, medium, and fine particle sizes, as well as limestone from 4 different locations and HSC were subjected to the same assays and conditions as in the first trial. These studies suggest that HSC is a highly soluble Ca source, phytase improves P solubility in vitro, fine particle size is more soluble than large particle size in vitro, and location from which the Ca source is obtained can affect Ca and P solubility. The in vitro assay utilized in this study is a fast and cost efficient technique for evaluating and comparing parameters of broiler diets to make recommendations for commercial poultry nutrition. / Master of Science

The accuracy of sediment transport models depends on identifying an appropriate sediment settling velocity. Determining this value for mud suspensions can be difficult because cohesive mud particles can aggregate, forming flocs whose sizes are a function of hydrodynamic and physiochemical conditions of the suspension. Here we present a new model refining the predicted floc size based on hydrodynamic conditions and inherited floc sizes, as well as on the salinity of the fluid environment. The improvements come from modifications made to the Winterwerp (1998) (W98) model. These improvements include: limiting floc size to the Kolmogorov microscale and including an initial salinity dependence. Limiting floc size in this way brings the model predictions more in line with flocculation theory and experimental observations. The salinity dependence was introduced based on a preliminary set of experiments that were conducted to examine floc growth rate and equilibrium size under different salinity conditions. In these experiments, increasing salinity from 2.5 to 10 PSU did not affect equilibrium floc size. However, the increases in salinity did result in longer times to equilibrium and an apparent increase in floc density or fractal dimension. The modified W98 model allows calibrated aggregation and breakup coefficients obtained under one set of concentration values (for both sediment and salinity) to be used to predict floc size under other concentration conditions. Comparing the modified W98 model with laboratory data shows more accurate predictive values, indicating that the modified W98 equation is a promising tool for incorporation into larger sediment transport models. / Master of Science

Within the last few years, retail sales have averaged an annual growth of about 4% with electronic commerce retail sales averaging an increase of over 20% per year (U.S Census Bureau, 2008). The e-commerce retail sector of apparel, accessories, and footwear reached $18.3 billion in sales and ranked as a top selling category (Shop.org, 2007). A growing apparel market with strong buying power is the plus-size clothing industry with approximately $32 billion in sales in 2005, and an average of about a 10% growth rate each year (Yadegaran, 2006). Despite the growth in the industry, little empirical research has been conducted regarding plus-size Internet apparel shoppers. Additionally the field lacks research that focuses on garment fit for the plus-size market. The purpose of this study was to examine the effects of product presentation factors, visual fit information (size of model photographed) and written fit information (fit related product description), on plus-size women's perceived fit risk, purchase intention, and loyalty intentions in Internet apparel shopping. This study employed a 2 x 2 between subjects' factorial design: visual fit information (plus-size model vs. non plus-size model) by written fit information (more elaborate vs. less elaborate). Four mock web pages were created to closely mimic the design of a true plus-size Internet apparel retailer. Each web page presented a model wearing the same dress for plus-size women and a written product description. The stimuli consisted of an identical dress in color and style, presented on both a plus-size model and a non plus-size model, and similar written fit information with more detailed information about garment style, garment dimensions, and fit editorial presentation for more elaborate stimuli. One hundred fourteen women between the ages of 19 and 64 participated in this study for incentives such as a free plus-size apparel gift-card, using snowball sampling method. Using descriptive statistics, multivariate analyses of variance and univariate analyses of variance, the present research showed (1) no main effects of visual fit information on perceived fit risk, purchase intention, and loyalty intention, and (2) no main effects of written fit information on perceived fit risk, purchase intention and loyalty intention. The study added valuable empirical findings to the literature on the relationship between fit related information and perceived fit risk, purchase intention and loyalty intention among plus-size Internet apparel shoppers. / Master of Science