Metal Oxidation Kinetics and the Transition from Thin to Thick Films

We report an investigation of growth kinetics and transition from thin to thick films during metal oxidation. In the thin film limit (< 20 nm), Cabrera and Mott's theory is usually adopted by explicitly considering ionic drift through the oxide in response to electric fields, where the growth kinetics follow an inverse logarithmic law. It is generally accepted that Wagner's theory, involving self-diffusion, is valid only in the limit of thick film regime and leads to parabolic growth kinetics. Theory presented here unifies the two models and provides a complete description of oxidation including the transition from thin to thick film. The range of validity of Cabrera and Mott's theory and Wagner's theory can be well defined in terms of the Debye-Huckel screening length. The transition from drift-dominated ionic transport for thin film to diffusion-dominated transport for thick film is found to strictly follow the direct logarithmic law that is frequently observed in many experiments

Syncopate: a senior design campaign

For my Senior Design Campaign, I created a theoretical nonprofit located in Marion County Indiana which provides the Indianapolis public school district with instruments and other materials they need to give their students a strong music education. The project focuses on designing a brand identity for the organization, Syncopate, and creating a compelling design campaign that emphasizes the goals of the company while also educating viewers about funding inequity in public schools. The five deliverables created for this project include a poster series, a billboard series, a sticker series, a website, and a motion graphic.Honors CollegeThesis (B.?

Citizenship in the Republic of Ireland: In the Context of the European Union and the Citizenship Referendum

In a world of increased globalization, the importance of citizenship may seem less and less important. However, I would assert that political belonging is becoming ever more important and is undergoing radical changes. The European Union (EU) is rapidly changing people’s understanding of citizenship. Rather than calling themselves Irish, people may soon be calling themselves European instead. Borders between countries are weakening and movement between them is increasing. Today a citizen of Latvia can live and work in Ireland as long as he or she so chooses. These changes in citizenship may actually have great implications for citizenship policy in the EU member-states. As an American, it was easy for me to take my citizenship for granted. However, U.S. or EU citizenship can put one at a distinct advantage over members of other countries. Being a citizen of the U.S., I have access to a vast amount of resources that are unavailable in other countries across the globe. And, until recently, I had been under the impression that someone fortunate enough to be born in such a nation-state would be a citizen of that state and have the same rights as everyone else. Those born in the United States are automatically citizens of the U.S. The same is true in Ireland, but that may be about to change. Ireland has proposed a citizenship referendum that would bring its citizenship laws in line with every other member of the European Union. Instead of citizenship by place of birth, the other EU member-states base citizenship on a combination of descent and length of residency of the parent. While the EU is expanding citizenship, it seems that Ireland has reacted by curtailing its application of citizenship. I hope to explore in this paper how the European Union is affecting citizenship entitlements in its member-states, as well as, why Ireland may be changing its application of citizenship. I have investigated these topics through the dialogue of the politicians and non-governmental organizations (NGOs) in Ireland. Their debate will continue through June 2004, but this paper describes and questions the current political discussion

Application-Oriented Design and Theoretical Investigation of a Screw-Type Steam Expander

Screw expanders offer a high potential for energy conversion in the lower and medium power range, for instance as expansion engines in closed loop power cycles. A common field of application is waste heat recovery where a certain heat flow is available to evaporate a working fluid in an organic Rankine cycle (ORC). In order to reach maximum cycle efficiency, the expander has to be designed with regards to the specific case of application. Design parameters, such as rotor geometry, size and inner volume ratio, have to be chosen in accordance to system parameters, for instance pressure levels and mass flow. Given that the available heat flow for the application is restricted, it is necessary to variably determine inlet and outlet pressure as well as the expansion mass flow in order to maximize the power output of the case specifically designed screw expander. The paper contains results of an exemplary design and dimensioning process of a screw expander for an organic Rankine cycle for exhaust heat recovery of internal combustion engines. Both geometric parameters and system parameters are varied in a wide range to maximize the overall power output. It is shown that especially for small scale applications a combination of an uncommonly large inner volume ratio with high inlet pressures can be advantageous despite the fact that only relatively small isentropic expander efficiency is reached. Further proceeding includes consideration of several part load Rankine cycle operation points where a method of averaging the final expander size is presented. During the dimensioning process chamber model simulation is used to predict the operation behavior of the screw expander where the chamber model of the machine is scaled under consideration of geometrical similarity (except of gap heights) during the simulation process at constant circumferential speed. Thus, it is assured that the actual expander mass flow matches the calculated ORC mass flow. Moreover, to estimate overall performance of the heat recovery system, a characteristic map of the selected screw expander is calculated to find pressure and expander speed depending operating points for part and full load. With the aim of validating the theoretical approach, experimental investigations of the designed machine are carried out on a water steam test rig at TU Dortmund University. To increase system simplicity, the oil-free prototype screw expander operates without timing gear which is enabled by a hard coated rotor surface. The experimental results are finally compared to corresponding chamber model simulations (will be presented but not be included in the paper)

Studies on the Reduction of Radon Plate-Out

The decay of common radioactive gases, such as radon, produces stable isotopes by a sequence of daughter particles with varied half-lives. These daughter particles are a significant source of gamma, neutron, and alpha particle backgrounds that can mimic desired signals in dark matter and neutrinoless double beta decay experiments. In the LUMINA Laboratory at Southern Methodist University (SMU), studies of radon plate-out onto copper samples are conducted using one of XIA's first five UltraLo 1800 alpha counters. We present results from investigations into various mitigation approaches. A custom-built copper holder (in either plastic or metal) has been designed and produced to maximize the copper's exposure to 220Rn. The 220Rn source is a collection of camping lantern mantles. We present the current status of control and experimental methods for addressing radon exposure levels.Comment: 4 pages, 1 figure, Conference Proceedings for Low Radioactivity Techniques 201

Voices Of Cooperating Teachers: Comparing Experiences Of Professional Development School And Traditional Student Teaching Models

This mixed-methods sequential study compared the experiences of cooperating teachers (CT) in a Professional Development School program and a traditional student teaching program. Cooperating teachers’ perspectives were gathered through an on-line survey and interviews. Information gathered was related to the preparation for acting as a CT, involvement with the student teaching process, professional benefits of acting as a CT, impact of the experience on their own teaching, and suggestions for improvements to the teacher preparation programs. Results indicate that no significant differences were found between the experiences of CTs in the different programs. Findings did reveal that CTs desire greater participation in the process and offer suggestions for improvement related to preparation program requirements such as length of student teaching, curricular knowledge, and edTPA

Fluid Flow through Front Clearances of Dry Running Screw Machines Using Dimensionless Numbers

Chamber model simulation is a common approach for the simulation of positive displacement machines. For this kind of simulation the clearance mass flow is usually predicted using an isentropic approach, which is corrected with a flow coefficient in order to picture the real flow conditions and the corresponding mass flow. The detailed knowledge of the flow coefficient and its dependencies is crucial for a meaningful simulation of positive displacement machines. This paper investigates the two-dimensional fluid flow through the front clearance of twin screw compressors using the finite volume method. Dimensionless numbers are determined using the PI-theorem and are varied systematically in order to show their influence on front clearance mass flow rate. The results are therefore useful for any dry running application with similar clearance geometry, independent of the type of gas (e.g. heat capacity, viscosity) and operating conditions (e.g. pressure, temperature, rotational speed). Results for a non-moving wall are compared with experimental results