Ternary III-nitride alloys have enabled the design of various devices ranging from optoelectronics to power electronics due to their tunable band gap. BxGa1-xN is a wide band gap semiconductor with applications in detecting devices, power electronics and light-emitting diodes. The band gap can be modulated by changing the Boron concentration. It can be grown by metal-organic chemical vapor deposition as a mixed thin film of wurtzite and zincblende structures. In this work, we investigate the structural and electronic properties of BxGa1-xN (x<0.2) by first-principles calculations for both the wurtzite and zincblende phases. The formation energies of Si and Mg impurities and of a Ga vacancy are also calculated. We find that the wurtzite structure is favored over the zincblende structure. Furthermore, the Si and Mg impurities have relatively low formation energies in their neutral state, which indicates compatibility with BxGa1-xN, while a Ga vacancy has very high formation energy, hence being less likely to form spontaneously. Moreover, in the charged states, the formation energy of Mg is reasonably low for most values of the Fermi level, while the formation energy of Si depends linearly on the Fermi level, indicating challenges in achieving n-type conductivity. For a Ga vacancy in a triple acceptor state, the formation energy is reasonably low close to the conduction band, therefore, Ga vacancies interfere with n-type conductivity.

Indiana University-Purdue University Indianapolis (IUPUI) / Since the COVID-19 pandemic unexpectedly hit the world, the tourism industry has been impacted in every conceivable area. Environmental issues are recognized and considered essential to solve especially in the tourism industry. It is unavoidable that tourists bring both positive and negative impacts to a destination. Meanwhile, the tourism industry is eager to return to its pre-pandemic tourist numbers and levels of spending that traveler previously engaged in. The young generations, specifically Gen Y and Z, play an important role in the tourism market, and they often embody a mindset that takes into consideration issues of sustainability. However, they are not as active as expected in practicing sustainable travel behaviors. Sustainable tourism development and "green" travel practices are becoming increasingly necessary. The main purpose of this study is to identify the gaps between Gen Y and Z's intentions and their behaviors regarding sustainable travel. This study developed and tested a conceptual framework to understand this dynamic. This study identified two gaps: (a) the behavior-intention gap, which exists between Gen Y & Z's intentions and their behaviors in sustainable travel, and (b) daily life and sustainable travel gap, which is the gap between individuals’ daily sustainable habits and sustainable travel behaviors. The results of quantitative study indicated the factors contributed to the gaps included: (1) individuals who have bachelor’s degrees are more likely to conduct sustainable travel behaviors; (2) individuals who have daily sustainable habits; (3) individuals who have higher perceived consumer effectiveness. The implications of the study provide suggestions for destinations to promote sustainable travel and ways to encourage more sustainable traveling choices by travelers.

The goal of this Dissertation in Practice was to design a School Improvement Plan focused on improving reading performance of African American students at Suburban Middle School (SMS). The problem of practice was that African American students at Suburban Middle School have performed significantly lower than their White peers over the course of the 2009-2013 school years in reading performance. The reading deficiencies of African American students needed to be directly addressed in a new School Improvement Plan (SIP). The literature review of this study found that there are many different components that influence the reading performance of African American students. For this Dissertation in Practice, a new School Improvement Plan focused primarily on 6 different areas will be the end result. The components that will be examined are: 1) school climate, 2) utilization of data, 3) parental involvement, 4) professional development, 5) instructional strategies, and 6) collaboration. While these are the 6 key elements of successful models, there were also additional sub groupings within each element that also had an influence on student achievement levels. In addition to examining previous School Improvement Plans at SMS, the end result and final deliverable was a School Improvement Plan designed to close the existing achievement gap in reading between African American students and their peers at SMS. Suggested use for the new model of the School Improvement Plan was to focus specifically on the 6 key elements to address the reading performance of African American students.

Thesis advisor: Philip E. Strahan / The essays on the gender gap in entrepreneurship examine the trade-offs between women's family formation choices and career aspirations in the setting of small businesses and entrepreneurship. The first essay titled ``Family Comes First: Reproductive Health and the Gender Gap in Entrepreneurship,'' uses Census data to show how better access to reproductive care increases women's propensity to become entrepreneurs, correlates positively with female entrepreneurial activity, and negatively with female entrepreneurial age. Examining firm size and personal income suggests it also improves the success of female-led businesses. Finally, it shows how policies securing better reproductive care enable more women to become entrepreneurs and, potentially, drive economic growth. The second essay titled ``Reproductive Rights and Women's Access to Capital,'' explores the impact of reproductive care restrictions on female entrepreneurs seeking to raise capital. It tests the hypothesis that better access to reproductive care enables women to plan their family formation better, avoid unexpected pregnancies, and gain access to cheaper capital as a result of this reduced risk. This hypothesis is analyzed using restricted data from the National Longitudinal Survey of Youth (NLSY79) in a difference-in-differences setting around the enactment of state-level legislation limiting access to reproductive care. It finds restrictions on reproductive care to be detrimental to women seeking to raise capital and open their own firms. Women who have limited reproductive care access are less likely to borrow, end up taking smaller loan amounts, and have lower leverage ratios. The main contribution of the first essay is that it establishes a direction and causal relationship between reproductive care and entrepreneurship, and of the second essay is that it shows how the increased risk of unplanned pregnancy translates into reduced credit availability for female entrepreneurs at childbearing age. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Carroll School of Management. / Discipline: Finance.

Cavitation is detrimental to the performance of ships and submarines, causing noise, erosion, and vibration. This study seeks to understand cavitation inception and delay on a typical ducted propulsor by utilizing the SimCenter's unstructured simulation and design system: U2NCLE. Specifically, three fundamental questions are addressed: 1. What are the macroscale flow physics causing cavitation inception? 2. How does cavitation inception scale with Reynolds number? 3. How can tip-leakage vortex cavitation inception be suppressed? To study the physics of cavitation inception, a ducted propulso simulation is developed and extensively validated with experimental results. The numerical method is shown to agree very well with experimental measurements made in the vortex core. It was discovered that the interaction of the leakage and trailing edge vortices cause the pressure to drop to a local minimum, providing ideal conditions for inception to occur. However, experimental observation shows that inception does not occur at the minimum pressure location, but rather at the point where the two vortices completely coalesce. At the point of coalescence, the simulation reveals that the streamwise core velocity decelerates, causing the air nuclei to stretch and burst. A Reynolds number scaling analysis is performed for the minimum pressure and maximum velocity in the vortex core. First, the numerical method is validated on a flate plate at various Reynolds numbers to assess the ability of typical turbulence models to predict Reynolds numbers ranging from one million to one billion. This scaling analysis methodology is then applied to the propulsor simulation, revealing that the minimum pressure in the vortex core is much less dependent on Reynolds number than was previously hypothesized. Lastly, to investigate means of delaying cavitation inception, the propulsor is parameterized and studied using design optimization theory. Concepts of vortex alleviation evident in nature are used to suggest suitable parameterizations. Also, dimension reduction is used to reduced the number of design variables. Finally, the concepts are implemented, evaluated, and shown to completely decouple the two vortices causing cavitation inception. Moreover, the minimum pressure in the vortex core is significantly increased.

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