The IAEA ICSP on Numerical Benchmarks for Multiphysics Simulation of Pressurized Heavy Water Reactor Transients was initiated in 2016 to facilitate the development of a set of open access, standardized, numerical test problems for postulated accident scenarios in a CANDU styled Reactor. The test problems include a loss of coolant accident resulting from an inlet header break, a loss of flow accident caused by a single pump trip, and a loss of regulation accident due to inadvertently withdrawn adjusters. The Benchmark was split into phases, which included stand-alone physics and thermal-hydraulics transients, coupled steady state simulations, and coupled transients. This thesis documents the results that were generated through an original TRACE/PARCS coupling methodology that was developed specifically for this work. There is a strong emphasis on development methods and step by step verification throughout the thesis, to provide a framework for future research in this area. In addition to the Benchmark results, additional studies on propagation of fundamental nuclear data uncertainty, and sensitivity analysis of coupled transients are reported in this thesis. Two Phenomena and Key Parameter Identification and Ranking Tables were generated for the loss of coolant accident scenario, to provide feedback to the Benchmark Team, and to add to the body of work on uncertainty/sensitivity analysis of CANDU style reactors. Some important results from the uncertainty analysis work relate to changes in the uncertainty of figures of merit such as integrated core power, and peak core power magnitude and time, between small and large break loss of coolant accidents. The analysis shows that the mean and standard deviation of the integrated core power and maximum integrated channel power, are very close between a 30% header break and a 60% header break, despite the peak core power being much larger in the 60% break case. Furthermore, it shows that there is a trade off between the uncertainty in the time of the peak core power, and the magnitude of the peak core power, with smaller breaks showing a smaller standard deviation in the magnitude of the peak core power, but a larger standard deviation in when this power is reached during the transient, and vice versa for larger breaks. From the results of the sensitivity analysis study, this thesis concludes that parameters related to coolant void reactivity and shutoff rod timing and effectiveness have the largest impact on loss of coolant accident progressions, while parameters that can have a large impact in other transients or reactor designs, such as fuel temperature reactivity feedback and control device incremental cross sections, are less important. / Thesis / Master of Science (MSc) / This thesis documents McMaster’s contribution to an International Atomic Energy Agency Benchmark on Pressurized Heavy Water Reactors that closely resemble the CANDU design. The Benchmark focus is on coupling of thermal-hydraulics and neutron physics codes, and simulation of postulated accident scenarios. This thesis contains some select results from the Benchmark, comparing the results generated by McMaster to other participants. This thesis also documents additional work that was performed to propagate fundamental nuclear data uncertainty through the coupled transient calculations and obtain an estimate of the uncertainty in key figures of merit. This work was beyond the scope of the Benchmark and is a unique contribution to the open literature. Finally, sensitivity studies were performed on one of the accident scenarios defined in the Benchmark, the loss of coolant accident, to determine which input parameters have the largest contribution to the variability of key figures of merit.

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One of the many attempts to solve problems that plague America's schools is the implementation of uniform dress code policies. Those who favor uniforms contend that uniforms will increase attendance, enhance academic achievement, and improve classroom environment. Prior research studies ( Behling, 1991; Hughes, 1996; and Hoffler-Riddick, 1998) on the effects of mandatory school uniforms have been inconclusive in their findings. The purpose of this study was to examine the impact of mandatory uniform dress codes on student attendance, student achievement, and teachers' perceptions of classroom environment in two middle schools. The dependent variables were student attendance, student achievement, and teachers' perceptions of classroom environment. The independent variables were gender, race/ethnicity and time/years of teaching experience. Descriptive statistics and Analyses of Variance were used to analyze the data. Repeated Measures Analyses of Variance was used to analyze the attendance data in School A for three consecutive years. Analyses of Variance was used to measure the attendance and achievement data in School B for two consecutive years. A self-report questionnaire was designed to measure teachers' perceptions of the impact of uniforms on four domains of classroom environment: student attendance, student behavior, student achievement, and students' self-image. Three-way Analysis of Variance was used to analyze the data collected from the questionnaire. The results of this study determined that there were no statistically significant differences in overall student attendance or achievement in School A. There were improvements in student achievement in School B after the change in dress to school uniforms. There were inconsistent differences between race/ethnicity and gender with respect to attendance after uniform implementation in schools A and B. Absences increased in School A after the second year with uniforms. Student achievement improved for students in School B, but showed no change in School A. Based on the results of the Uniform Survey administered to teachers in both schools, the perception of classroom environment after uniforms was generally positive. Teachers overwhelmingly supported the uniform policy, but they were inconsistent in their opinions of the overall impact on classroom environment. Teachers in School A felt that student achievement and student self-image improved after the implementation of school uniforms, but they saw no improvements in student attendance or behavior. Teachers in School B felt that student attendance declined after the first year of uniform implementation; however, they felt that there were improvements in student behavior, student achievement, and student self-image. Future research should examine the impact of mandatory uniform dress codes on school climate, students' self-esteem, and the perceptions of parents, students and members of the community. / Ed. D.

There has been a great deal of interest in investigating numerous unique types of electrostatic and electromagnetic waves and instabilities in dusty plasmas. Dusty plasmas are characterized by the presence of micrometer or submicrometer size dust grains immersed in a partially or fully ionized plasma. In this study, a two-dimensional numerical model is presented to study waves and instabilities in dusty plasmas. Fundamental differences exist between dusty plasmas and electron-ion plasmas because of dust charging processes. Therefore, a primary goal of this study is to consider the unique effects of dust charging on collective effects in dusty plasmas. The background plasma electrons and ions here are treated as two interpenerating fluids whose densities vary by dust charging. The dust is treated with a Particle-In-Cell PIC model in which the dust charge varies with time according to the standard dust charging model. Fourier spectral methods with a predictor-corrector time advance are used to temporally evolve the background plasma electron and ion equations. The dust charge fluctuation mode and the damping of lower hybrid oscillations due to dust charging, as well as plasma instabilities associated with dust expansion into a magnetized background plasma are investigated using our numerical model. Also, an ion acoustic streaming instability in unmagnetized dusty plasmas due to dust charging is investigated. The numerical simulation results show good agreement with theoretical predictions and provide further insight into dust charging effects on wave modes and instabilities in dusty plasmas. / Ph. D.

An essential software development tool, code search engines are expected to provide superior accuracy, usability, and performance. However, prior research has neither (1) summarized, categorized, and compared representative code search engines, nor (2) analyzed the actual expectations that developers have for code search engines. This missing knowledge can empower developers to fully benefit from search engines, academic researchers to uncover promising research directions, and industry practitioners to properly marshal their efforts. This thesis fills the aforementioned gaps by drawing a comprehensive picture of code search engines, including their definition, standard processes, existing solutions, common alternatives, and developers' perspectives. We first study the state of the art in code search engines by analyzing academic papers, industry releases, and open-source projects. We then survey more than a 100 software developers to ascertain their usage of and preferences for code search engines. Finally, we juxtapose the results of our study and survey to synthesize a call-for-action for researchers and industry practitioners to better meet the demands software developers make on code search engines. We present the first comprehensive overview of state-of-the-art code search engines by categorizing and comparing them based on their respective search strategies, applicability, and performance. Our user survey revealed a surprising lack of awareness among many developers w.r.t. code search engines, with a high preference for using general-purpose search engines (e.g., Google) or code repositories (e.g., GitHub) to search for code. Our results also clearly identify typical usage scenarios and sought-after properties of code search engines. Our findings can guide software developers in selecting code search engines most suitable for their programming pursuits, suggest new research directions for researchers, and help programming tool builders in creating effective code search engine solutions. / Master of Science / When developing software, programmers rely on source code search engines to find code snippets related to the programming task at hand. Given their importance for software development, source code engines have become the focus of numerous research and industry projects. However, researchers and developers remain largely unaware of each other's efforts and expectations. As a consequence, developers find themselves struggling to determine which engine would best fit their needs, while researchers remain unaware what developers expect from search engines. This thesis address this problem via a three-pronged approach: (1) it provides a systematic review of the research literature and major engines; (2) it analyzes the results of surveying software developers about their experiences with and expectations for code search engines; (3) it presents actionable insights that can guide future research and industry efforts in code search engines to better meet the needs of software developers.

Peer code reviews play a critical role in maintaining code quality, and GitHub has introduced several new features to assist with the review process. One of these features is suggested changes, which allows for precise code modifications in pull requests to be suggested in review comments. Despite the availability of such helpful features, many pull requests remain unattended due to lower priority. To address this issue, we developed a bot called ``Suggestion Bot" to automatically review the codebase using GitHub's suggested changes functionality. An empirical study was also conducted to compare the effectiveness of this bot with manual reviews. The findings suggest that implementing this bot can expedite response times and improve the quality of pull request comments for pull-based software development projects. In addition to providing automated suggestions, this feature also offers valuable, concise, and targeted feedback. / Master of Science / Code review, often known as peer review, is a process used to ensure the quality of software. Code review is a process in software development that involves one or more individuals examining the source code of a program, either after it has been implemented or during a pause in the development process. The creator of the code cannot be one of the individuals. "Reviewers" refers to the individuals conducting the checking, excluding the author. However, the majority of reviewers won't have the time to examine and validate the peer's code base, so they'll assign it the lowest priority possible. This could cause pull requests to stall out without being reviewed. Therefore, as part of our research, we are creating a bot called SUGGESTION BOT that provides code changes in pull requests. The author can then accept, reject, or alter these ideas as a necessary component of the pull request. Additionally, we compared the effectiveness of our bot with the manual pull request review procedure, which clearly demonstrated that the incorporation of this bot significantly shortened the turnaround time. Besides giving automated recommendations, this functionality also provides useful, brief, and focused feedback.

The primary issue with developing new networking protocols is testing how the protocol will behave when deployed on a large scale; of particular interest is how it will interact with existing protocols. Testing a protocol using a network simulator has drawbacks. First, the protocol must be written for the simulator and then rewritten for actual deployment. Aside from the additional work, this allows for software bugs to be introduced between testing and implementation. More importantly, there are correctness issues. Since both the new and existing protocols must be specially written for the simulator, and not actual real-world implementations, the question remains if the behavior observed and, specifically, the interactions between the protocols are valid. Direct code execution environments solve the correctness problem, but there is the loss of control that a simulator provides. Our solution is to create an environment that allows direct code execution to occur on top of a network simulator. This thesis presents the primary component of that solution: Lunar (Linux User-level Network Architecture), a user-level library that is created from the network stack portion of the Linux operating system. This allows real-world applications to link against a simulator, with Lunar serving as the bridge. For this work, an implementation of Lunar was constructed using the 2.4.3 version of the Linux kernel. Verification testing was performed to demonstrate correct functioning of the library using both TCP (including TCP with loss) and UDP. Performance testing was done to measure the overhead that Lunar adds to a running application. Overhead was measured as the percent increase in the runtime of an application with Lunar as compared to the application running without it, and ranged from approximately 2% (running over 100 Mbps switched Ethernet) to approximately 39% (1 Gbps Myrinet). / Master of Science

This thesis takes a fresh look at software, treating it as a document, manuscript, corpus, or text to be consumed among communities of programmers and uncovering the social roles of these texts within two specific sub-communities and comparing them. In the paper, the social roles of the texts are placed within the context of the technical and cultural constraints and environments in which programs are written. Within that context, the comments emphasize the metaphoric status of programming languages and the social role of the comments themselves. These social roles are combined with the normative intentions for each comment, creating a dynamic relationship of form and function for both normative and identity-oriented purposes. The relationship of form and function is used as a unifying concept for a more detailed investigation of the construction of comments, including a look at a literary device that relies on the plural pronoun "we" as the subject. The comments used in this analysis are derived from within the source code of the Linux kernel and from a Corporate environment in the US. / Master of Science

As Cyber Physical Systems (CPS) are getting more complex and safety critical, Model Based Design (MBD), which consists of building formal models of a system in order to be used in verification and correct-by-construction code generation, is becoming a promising methodology for the development of the embedded software of such systems. This design paradigm significantly reduces the development cost and time while guaranteeing better robustness, capability and correctness with respect to the original specifications, when compared with the traditional ad-hoc design methods. SIMULINK has been the most popular tool for embedded control design in research as well as in industry, for the last decades. As SIMULINK does not have formal semantics, the application of the model based design methodology and tools to its models is very limited. In this thesis, we present a semantic translator that transform discrete time SIMULINK models into SIGNAL programs. The choice of SIGNAL is motivated by its polychronous formalism that enhances synchronous programming with asynchronous concurrency, as well as, by the ability of its compiler of generating deterministic multi thread code. Our translation involves three major steps: clock inference, type inference and hierarchical top-down translation. We validate the semantic preservation of our prototype tool by testing it on different SIMULINK models. / Master of Science

The United States is in the process of changing demographically. As a result, there is an increasing demand for culturally appropriate counseling services for minority groups. However, little research about counselors' ability to deal with issues stemming from bilingualism is available. As language is used to establish the relationship in counseling, the importance of counselors' understanding regarding how a second language may influence the counseling process is vital. Although numerous studies have thus far emphasized the significance of cultural knowledge and the need for bilingual counseling services, culturally diverse populations continue to be underserved due to language barriers (Gushue, Constantine, and Sciarra, 2008). The American Counseling Association's (ACA) Code of Ethics (2005; 2014) provides best-practice guidelines for appropriate bilingual support during the counseling session. However, few studies have explored the role played by a second or additional language during the counseling session (Marcos and Urcuyo, 1979; Oquendo, 1996; Ramos-Sanchez, 2009; Santiago-Rivera, Altarriba, Poll, Gonzalez-Miller, and Cragun, 2009; Tehrani and Vaughan, 2009). This study adds to the existing body of knowledge about bilingual counselors' experiences providing counseling services in a language in which they have not had professional training. Chapter One provides an overview of the problem, Chapter Two delivers an in-depth literature review, Chapter Three describes the methodology, Chapter Four provides findings of the study, and Chapter Five discusses the results and offers implications for bilingual counselors and counselor educators and supervisors as well as makes suggestions for further research. / Ph. D.