549 research outputs found
Creativity - the relationship of intelligence quotient and adjustment to creativity
Thesis (M.F.A.)--Boston Universit
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Topology Driven Improvement of FDC Build Parameters
The likeliest failure origin for advanced ceramics parts, prepared by fused
deposition, is a void from improper fill. Adequate filling of each cross-section is dependent upon the deposition toolpath. Cross-sectional spaces are conventionally
filled with pre-defined parameters. We propose that adaptive build parameters will
control variations in geometry and property of a part. Voids, overfilling,
incomplete bonding and excess traversing can be suppressed by adjusting the fill
parameters for cross-sectional areas. Improved build parameters and toolpath
allows for faster build time and components ofj full density. Some implementations
are discussed and presented.Mechanical Engineerin
Multispectral imaging of organ viability during uterine transplantation surgery in rabbits and sheep
Uterine transplantation surgery (UTx) has been proposed as a treatment for permanent absolute uterine factor infertility (AUFI) in the case of the congenital absence or surgical removal of the uterus. Successful surgical attachment of the organ and its associated vasculature is essential for the organ’s reperfusion and long-term viability. Spectral imaging techniques have demonstrated the potential for the measurement of hemodynamics in medical applications. These involve the measurement of reflectance spectra by acquiring images of the tissue in different wavebands. Measures of tissue constituents at each pixel can then be extracted from these spectra through modeling of the light–tissue interaction. A multispectral imaging (MSI) laparoscope was used in sheep and rabbit UTx models to study short- and long-term changes in oxygen saturation following surgery. The whole organ was imaged in the donor and recipient animals in parallel with point measurements from a pulse oximeter. Imaging results confirmed the re-establishment of adequate perfusion in the transplanted organ after surgery. Cornual oxygenation trends measured with MSI are consistent with pulse oximeter readings, showing decreased StO2 immediately after anastomosis of the blood vessels. Long-term results show recovery of StO2 to preoperative levels
Hubble Space Telescope observations of Mars
Hubble Space Telescope (HST) afforded the possibility of resolving features as small as 100 km on the Martian surface even when it is at the far point of its orbit. Therefore it is ideally suited for monitoring seasonal changes on the red planet. The objectives research include: the study of Martian dust storms; use of images obtained through different filters to study the spectral reflectance of regions on the Martian surface; use of ultraviolet images and spectra to measure the amount of ozone in the planet's atmosphere as a function of location of the planet; use of images to study changes in the albedo of the Mars surface; and use of Planetary Camera images to study Martian clouds and to measure the opacity of the atmosphere
The perceptions of the recently ordained priests of Boston of their post-secondary education and formation in seminary
Thesis advisor: Ana Martinez-AlemanRoman Catholic Seminaries are post-secondary schools where men study in preparation for ordination for priesthood. In recent visitations by bishops to American seminaries faculty and students at all the seminaries were interviewed regarding the effectiveness of the curriculum. Noticeably absent from the consultations were the priests who had recently graduated from the seminary. This study, influenced by Dr. Dean Hoge's study: The First Five Years of the Priesthood interviewed twenty men who were ordained to the priesthood for the Archdiocese of Boston in the years 2001-2006. Using Pope John Paul II's seminal work of Pastores Dabo Vobis the qualitative study focused on the four areas of formation: human, intellectual, pastoral, and spiritual. The interviews were recorded, transcribed, and coded using axial coding and open coding as well as cross case analysis and triangulation. Among the findings are loneliness of the recently ordained, the need for clearer boundaries in relationships with faculty members and women in the parish, more realistic training, the need for more support from the archdiocese, and better screening of pastoral sites prior to and after ordination. The findings suggest from the perceptions of the recently ordained men that there is significant room for improvement in all areas of formation.Thesis (PhD) — Boston College, 2008.Submitted to: Boston College. Lynch School of Education.Discipline: Higher Education and Educational Administration
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Mathematical Formulations with Uncertain Data in Optimization and Inverse Problems
This dissertation broadly focuses on incorporating uncertainty into mathematical models and can be broken into three distinct sections. In the first (Ch. 2 and 3), we consider design matrix uncertainty for linear regression. The motivation is that many regressors or covariates used to build linear models, such as survey responses and other data subjective in nature, are intrinsically uncertain. We approach the problem from two angles: 1) using robust optimization and 2) an approximation method to construct an otherwise cumbersome objective for maximum likelihood estimation. Expressions for (sub)gradients are provided allowing for the use of efficient solvers. We illustrate the merit of both methods on synthetic data.
In the second section (Ch. 4 and 5), we focus on novel trust region methods that accept uncertainty in objective and gradient evaluations to reduce the computational burden. We introduce an algorithm named TROPHY (Trust Region Optimization using a Precision HierarchY) which uses variable precision arithmetic to reduce communication, storage, and energy costs. The other project uses a Hermite interpolation based framework to build model objectives using function and derivative information. Since not all partial derivatives are available or are expensive to compute, we make use of uncertain gradients to improve performance beyond standard interpolation methods. We also propose the use of sketching to ameliorate issues with redundant data and reduce the burden of inverting very large matrices.
The final section (Ch. 6) investigates how operator uncertainty impacts the ability to solve inverse problems accurately. Our goal is to localize regions of brain activity using optically pumped magnetometers which are novel sensors that show promise for use in magnetoencephalography. Through a series of simulations, we establish guidelines for sensor count, noise level, and forward model fidelity needed to localize brain activity to a specified accuracy
Effects of human land use and temperature on community dynamics in European forests
Climate change and human land use are thought to play a dominant role in the dynamics of European central-latitude forests in the Holocene. A wide range of mathematical and statistical models have been used to study the effects of these variables on forest dynamics, including physiologically-based simulations and phenomenological community models. However, for statistical analysis of pollen count data, compositional data analysis is particularly well suited, because pollen counts give only relative information. We studied the effects of changes in human land use and temperature on European central-latitude forest dynamics at 7 sites over most of the last , using a stochastic model for compositional dynamics of pollen count data. Our approach has a natural ecological interpretation in terms of relative proportional population growth rates, and does not require information on pollen production, dispersal, or deposition. We showed that the relative proportional population growth rates of Fagus and Picea were positively affected by intensified human land use, and that those of Tilia and Ulmus were negatively affected. Also, the relative proportional population growth rate of Fagus was negatively affected by increases in temperature above about . Overall, the effects of temperature on the rate of change of forest composition were more important than those of human land use. Although there were aspects of dynamics, such as short-term oscillations, that our model did not capture, our approach is broadly applicable and founded on ecological principles, and gave results consistent with current thinking
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