Effect of process variables on formation of dynamic strain induced ultrafine ferrite during hot torsion testing

Ultrafine grain sizes were produced using hot torsion testing of a 0.11C-1.68Mn-0.20Si (wt-%) steel, with ultrafine ferrite (&lt;1 &micro;m) nucleating intragranularly during testing by dynamic strain induced transformation. A systematic study was made of the effect of isothermal deformation temperature, strain level, strain rate, and accelerated cooling during deformation on the formation of ultrafine ferrite by this process. Decreasing the isothermal testing temperature below the Ae3 temperature led to a greater driving force for ferrite nucleation and thus more extensive nucleation during testing; the formation of Widmanst&auml;tten ferrite prior to, or early during, deformation imposed a lower temperature limit. Increasing the strain above that where ferrite first began 0.8 at 675C and a strain rate of 3 s&macr;1 increased the intragranular nucleation of ferrite. Strain rate appeared to have little effect on the amount of ferrite formed. However, slower strain rates led to extensive polygonisation of the ferrite formed because more time was available for ferrite recovery. Accelerated cooling during deformation followed by air cooling to room temperature led to a uniform microstructure consisting of very fine ferrite grains and fine spherical carbides located in the grain boundaries regions. Air cooling after isothermal testing led to carbide bands and a larger ferrite grain size.<br /

Untangling the physical components of galaxies using infrared spectra

The two main physical processes that underpin galaxy evolution are star formation and accretion of mass in active galactic nuclei (AGN). Understanding how contributions from these processes vary across cosmic time requires untangling their relative contributions. The infrared part of the electromagnetic spectrum contains a number of AGN and star formation diagnostics e.g. emission lines from ionised gas or polyaromatic hydrocarbons (PAHs), and the shape of the continuum. Despite the higher resolution of data from Spitzer’s IRS spectrograph, separating out emission from star formation and AGN is carried out using limited spectral features or simplistic templates. In the first part of this thesis, I show how sophisticated data analysis techniques can make full use of the wealth of spectral data. I demonstrate how the popular multivariate technique, Principal Component Analysis (PCA), can classify different types of ultra luminous infrared galaxies (ULIRGs), whilst providing a simple set of spectral components that provide better fits than state-of-the art radiative transfer models. I show how an alternative multivariate technique, Non-Negative Matrix Factorisation (NMF) is more appropriate by applying it to over 700 extragalactic spectra from the CASSIS database and demonstrating its capability in producing spectral components that are physically intuitive, allowing the processes of star formation and AGN activity to be clearly untangled. Finally, I show how rotational transition lines from carbon monoxide and water, observed by the Herschel Space Observatory, provides constraints on the physical conditions within galaxies. By coupling the radiative transfer code, RADEX, with the nested sampling routine, Multinest, I carry out Bayesian inference on the CO spectral line energy distribution ladder of the nearby starburst galaxy, IC342. I also show that water emission lines provide important constraints the conditions of the ISM of on one of the most distant starburst galaxies ever detected, HFLS3

Book Vouchers: An Exploratory Analysis of Their Use and Effectiveness

Book vouchers serve as one component of need-based financial aid packages at the College of Southern Nevada, one of the nation’s largest community colleges. This study compared the academic performance of FAFSA applicants in attendance during the 2008-09 and 2009-10 academic years. A basic exploratory analysis was conducted that examined the academic outcomes of seven students groups with different financial aid packaging outcomes. Student groups were ranked by their academic performance, which comprised of grade point average, percentages of full-time attendance, and percentage of successful, full-time attendance completion. Within these measures, book voucher recipients were found to have better overall academic performance than students who received Federal Pell Grants – even when Pell was combined with institutional grant or work-study funds

AN ANALYSIS OF OCCUPATIONAL HEALTH IN PORK PRODUCTION

The rapid expansion of large-scale pork production has been accompanied by increasing concerns regarding potential detrimental consequences of environmental hazards on the health of producers. This study makes use of health indicators obtained from attendees at the World Pork Expo between 1991 and 1995 to evaluate the impact of pork production generally and of confinement production, specifically, on producer health. The analysis expands existing studies because the larger number of participants allows for detailed analysis, both nonfarmers and non-pork farmers are used as controls, both objective as well as self-reported health measures are considered, and personal characteristics such as height, weight, age, gender, smoking habits, and years of exposure to confinement operations and swine operations are controlled. The analysis shows that pork producers are more likely to report nagging respiratory symptoms (cough, sinus problems, sore throat) than are other farmers. Confinement operators have increased incidence of some symptoms relative to other pork producers. However, there was no evidence of permanent loss of pulmonary function associated with pork production or confinement operation. Farmers suffered from a greater incidence of hearing loss and loss of dominant hand strength relative to nonfarmers. Pork producers had even greater incidence of lost hand strength than other farmers but had no added incidence of hearing loss. On the plus side, farmers had lower blood pressure than did nonfarmers.

CHANGES IN THE STRUCTURE OF WAGES IN THE U.S. PORK INDUSTRY

Consolidation in the U.S. pork industry continues to reduce the number of operations, while increasing the demand for hired labor. This paper explores how wages have evolved over time by decomposing the increase in wages into a change in the level of wages, human capital, and returns to human capital.Labor and Human Capital, Livestock Production/Industries,

Principal Component Analysis and Radiative Transfer modelling of Spitzer IRS Spectra of Ultra Luminous Infrared Galaxies

The mid-infrared spectra of ultraluminous infrared galaxies (ULIRGs) contain a variety of spectral features that can be used as diagnostics to characterise the spectra. However, such diagnostics are biased by our prior prejudices on the origin of the features. Moreover, by using only part of the spectrum they do not utilise the full information content of the spectra. Blind statistical techniques such as principal component analysis (PCA) consider the whole spectrum, find correlated features and separate them out into distinct components. We further investigate the principal components (PCs) of ULIRGs derived in Wang et al.(2011). We quantitatively show that five PCs is optimal for describing the IRS spectra. These five components (PC1-PC5) and the mean spectrum provide a template basis set that reproduces spectra of all z<0.35 ULIRGs within the noise. For comparison, the spectra are also modelled with a combination of radiative transfer models of both starbursts and the dusty torus surrounding active galactic nuclei. The five PCs typically provide better fits than the models. We argue that the radiative transfer models require a colder dust component and have difficulty in modelling strong PAH features. Aided by the models we also interpret the physical processes that the principal components represent. The third principal component is shown to indicate the nature of the dominant power source, while PC1 is related to the inclination of the AGN torus. Finally, we use the 5 PCs to define a new classification scheme using 5D Gaussian mixtures modelling and trained on widely used optical classifications. The five PCs, average spectra for the four classifications and the code to classify objects are made available at: http://www.phys.susx.ac.uk/~pdh21/PCA/Comment: 11 pages, 12 figures, accepted for publication in MNRA

A test for complementarities among multiple technologies that avoids the curse of dimensionality

We propose a strategy to identify the complementarity or substitutability among technology bundles. Under the assumption that alternative technologies are independent, we develop a hypothetical distribution of multiple technology adoptions. Differences between the observed distribution of technology choices and the hypothetical distribution can be subjected to statistical tests. Combinations of technologies that occur with greater frequency than would occur under independence are complementary technologies. Combinations that occur with less frequency are substitute technologies. This method is easily applied to simultaneous decisions regarding many technologies. We use the strategy to evaluate multiple technology adoptions on U.S. hog farms. We find that some technologies used in pork production are substitutable for one another while others are complementary. However, as the number of bundled technologies increases, they are increasingly likely to be complementary with one another, even if subsets are substitutes when viewed in isolation. This finding suggests that farmers have an incentive to adopt many technologies at once. Larger farms and farms run by more educated operators are the most likely to adopt multiple technologies. The complementarity among technologies in large bundles is contributing to a form of returns to scale that contributes to growth in average farm size.human capital; technology; adoption; complementarity; substitutability; independence; hogs; pork; farm size

Firm Size, Technical Change And Wages In The Pork Sector, 1990 -2005

Economists have long puzzled over the fact that large firms pay higher wages than small firms, even after controlling for worker’s observed productive characteristics. One possible explanation has been that firm size is correlated with unobserved productive attributes which confound firm size with other productive characteristics. This study investigates the size-wage premium in the context of firms competing within a single market for a relatively homogeneous product: hogs. We pay particular attention to the matching process by which workers are linked to farms of different size and technology use, and whether the matching process may explain differences in wages across farms. The study relies on four surveys of employees on hog farms collected in 1990, 1995, 2000, and 2005. We find that there are large wage premia paid to workers on larger farms that persist over time. Although more educated and experienced workers are more likely to work on larger and more technologically advanced hog farms, the positive relationships between wages and both farm size and technology adoption remain large and statistically significant even after controlling for differences in observable worker attributes and in the observed sorting process of workers across farms.pork; technology; Hog Farms; Wages; Propensity Score; Size; Wage Premium

Using accelerometer, high sample rate GPS and magnetometer data to develop a cattle movement and behaviour model

The study described in this paper developed a model of animal movement, which explicitly recognised each individual as the central unit of measure. The model was developed by learning from a real dataset that measured and calculated, for individual cows in a herd, their linear and angular positions and directional and angular speeds. Two learning algorithms were implemented: a Hidden Markov model (HMM) and a long-term prediction algorithm. It is shown that a HMM can be used to describe the animal's movement and state transition behaviour within several “stay” areas where cows remained for long periods. Model parameters were estimated for hidden behaviour states such as relocating, foraging and bedding. For cows’ movement between the “stay” areas a long-term prediction algorithm was implemented. By combining these two algorithms it was possible to develop a successful model, which achieved similar results to the animal behaviour data collected. This modelling methodology could easily be applied to interactions of other animal specie

Firm Size, Technical Change and Wages: Evidence from the Pork Sector from 1990-2005

A long-standing puzzle in labor economics has been the positive relationship between wages and firm size. Even after controlling for worker's observed characteristics such as education, work experience, gender, and geographic location, a significant firm size wage effect averaging 15 percent remains. This paper investigates whether the size-wage premium on hog farms persists over time and whether the magnitude is growing or shrinking. The paper pays particular attention to the matching process by which workers are allocated to farms of different size and technology use, and whether the matching process may explain differences in wages across farms. The study relies on four surveys of employees on hog farms collected in 1990, 1995, 2000, and 2005. The survey was conducted across the United States. The data allow us to evaluate how farm size and technology adoption have changed over time and how employee pay has changed in response to these changes. Detailed investigations of these pay differences between small and large hog farms and between farms using few and many technologies show that the differences cannot be explained away by differences in the education, work experience, or geographic location of the farm. Although more educated and experienced workers are more likely to work on larger and more technologically advanced hog farms, the positive relationships between wages and both farm size and technology remain large and statistically significant when differences in observable worker attributes are controlled. Furthermore, these effects are reinforcing in that large hog farms also adopt more technologies, and so the firm size effect persists even after differences in the number of technologies are held constant. The size-wage and technology-wage prema have persisted over time, and we cannot reject the null hypothesis that the premia are constant over the sample period.Agribusiness, Livestock Production/Industries,