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Developing a Magneto-Optical Kerr Effect Apparatus to Study Magnetic Semiconductors
No full textSpectroscopic ellipsometry and the magneto-optical Kerr effect (MOKE) were combined to measure the magneto-optical properties of Y3Fe5O15 (YIG) thin films. By studying the reflected and transmitted electromagnetic waves off of a material, one can completely represent the material with a dielectric tensor. The ellipsometry results showed that the YIG films are semiconductors with a band gap of approximately 2.25 eV. They also showed some defects present especially in the thinner films, demonstrated by a long tail in the lower-energy range of the imaginary part of the dielectric function. The MOKE measurements were performed at two different wavelengths (550 and 632 nm) with both the longitudinal and polar geometries. We were able to measure the Kerr rotation and ellipticity for all samples, and found that the signal was larger in the polar measurements compared to the longitudinal measurements. We found that the Kerr rotation reduces as the thickness of the YIG samples reduces, therefore indicating a decrease in the ferrimagnetic properties of the thinner YIG films. This result is contradictory to published results, and may be a consequence of the sample defects in the films. The ellipsometry results suggested higher defect concentrations in the thinner films, and therefore these samples may have a lower oxygen concentration, which is crucial in producing the magnetic properties of YIG. For the YIG films, from combining both spectroscopic ellipsometry and MOKE, we were able to obtain seven out of the nine elements in the dielectric tensor at 550 nm for all three YIG samples
Implementing Density Functional Theory and Ellipsometry to Analyze Films
No full textIn this thesis, I have shown that Density Functional Theory (DFT) is a superior technique to determine the electronic structure. We use lead chalcogenides (i.e. PbS, PbSe, and PbTe) and determined their dielectric functions by pursuing ellipsometry measurements and modeling the data. For these three systems, we performed GW-BSE and DFT calculations and obtained the band structure, the Density of States (DOS), the dielectric function, and the Joint Density of States (JDOS). Our calculations using GW-BSE seem to track the experimental dielectric functions well, particularly in the cases of PbTe and PbSe. The calculation results for JDOS is also predictive of our experimental spectra. While GW-BSE is able to compute the dielectric functions accurately, the computational cost is heavy and hence not practical with the computational infrastructure in our lab
Following the Crowd? A Topic Modeling Analysis of Twitter Discourse and Supreme Court Decisions
Get PDFThis project uses topic modeling to compare the top topics from Twitter posts with the text of the Supreme Court’s Dobbs v. Jackson ruling, which overturned Roe v. Wade in 2022. I analyzed whether the Court’s reasoning reflected public concerns or was disconnected. While some analysis of the Twitter data exists on the Kaggle dataset I used, I conducted this research independently of those results. By putting the Court’s language and public sentiment side by side, this project explores whether institutions are responding to what people care about
NLP Analysis of the Septuagint: Topic Modeling and Sentiment Analysis of Biblical Domestic Terms
Get PDFThis study conducts an exploratory data analysis (EDA) of topic modeling and sentiment analysis applied to the Septuagint (LXX – the Greek translations of the Old Testament and the New Testament in the original Koine Greek) as well as four English translations of the Bible (LSV, Darby, DR, and KJV). Utilizing Latent Dirichlet Allocation (LDA) for topic modeling, I compare the Vulgate-based translations to Septuagint-based translations, discovering marked differences between the two categories of translations. The Vulgate is the Latin translation of the Bible done by Jerome in 900 A. D. which is already one step away from the original Greek; another layer of separation into the English translation does prove to display a meaningful difference in delivery of content. Taking stand out words surrounding domesticity from the topics (such as bread, tent, servant, harvest), I put the original Greek words through Voyant Tools as well as a sentiment analysis notebook. In observing the data, I discovered that in the Gospels, Jesus uses domestic words in two senses: the physical and earthly, and the metaphysical and spiritual. When using the word, for example, servant in a physical sense, the sentiment is more negative; when using it in the sense of the servant of the Lord, these domestic words result in a more positive sentiment
My Life is Red, Yellow And Blue Respectively (Yellow Series) 我的生活分别是发红，发黄，发蓝的 （黄系列）
No full textIn the artist\u27s statement, Zhao Shaoruo explained that My life is Red, Yellow and Blue Respectively photographic series documented the artist\u27s personal life (spiritually and materially). It is composed of three different series, red, yellow and blue. There are ten photos in each series. Photos in the yellow series originated from old documentation of Mao\u27s personal and political life. In the original photos, Mao is depicted by standing among pupils, workers and farmers; in others, he is depicted giving a speech or clapping amid a meeting. The message is to show Mao\u27s leadership and how he is beloved by people. However, the artist replaced Mao\u27s face with his own. Another thing the artist did throughout the series is to hang his foot in the air upon a photo. Zhao was one of the protesting students at Tiananmen square democracy movement while attending the Central Academy of Fine Art. He was arrested shortly after the event and released the next year and arrested again for 50 days in 1994. His defiance toward authorities may be reflected in this series by mocking at the deification of Mao. By replacing Mao’s face with his own, he deconstructed the sublimity and seriousness of the propaganda and furthermore, lashed out at the incumbent government. (Zhuocheng Jiang \u2726)https://digital.kenyon.edu/zhou/1616/thumbnail.jp
