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Physics Colloquium - Graduate Student Presentations

This is a past event.

Thursday, January 27, 2022, 4 pm– 5 pm

This is a past event.

Thursday, January 27 @ 4pm – Fisher Hall 139 & Zoom

Hybrid-Mode: The students will give their talks in Fisher Hall 139. Please join in-person or by zoom.

Nithin Allwayin [Advisor: Dr. Raymond Shaw]
An Automated Algorithm to Identify Characteristic Droplet Size
Distributions in Clouds

Clouds cover a significant portion of the earth's surface and play a crucial role in
modifying its climate. Droplet-level interactions of these clouds are not resolved in
numerical models, and hence parameterizations, derived from averaged
quantities are used to represent them. But do ``local'' droplet size distributions of
relevance to cloud processes look like average distributions? If not, can they be
represented by a small number of characteristic size distributions?
We introduce an algorithm to search for and classify such characteristic
distributions. To do this, we combine hypothesis testing, specifically the Kolmogorov
Smirnov test, and a widely-used machine-learning algorithm for identifying clusters
of samples with similar properties: Density- based spatial clustering of applications
(DBSCAN). The method is explored using data obtained from Holographic Detector
for Clouds (HOLODEC) deployed during the Aerosol and Cloud Experiments in the
Eastern North Atlantic (ACE-ENA) field campaign. The algorithm identifies evidence
of the existence of clusters of nearly-identical local size distributions.

Sushree Dash [Advisor: Dr. Miguel Levy]
Boosting Optical Nonreciprocity - A Surface Reconstruction
Phenomenon in Iron Garnets

The miniaturization of non-reciprocal devices for on-chip optical isolator integration
calls for further technological development to increase efficiency over presently
available products. In a previous study on Bi-substituted lutetium iron garnets, we
showed that surface reconstruction resulted in significant changes in the density of
states leading to a large enhancement in Faraday rotation. For this study, we did
S-TEM and XAS-XMCD analysis. We tried to compare and analyze the bulk structure
with the surface structure in the above two methods.
Subsequent studies conducted by us via UV and visible optical, XPS, and magnetic
circular dichroism have provided a deeper understanding of the role of the surface
in electronic transitions responsible for the Faraday effect. This study provides a
valuable tool for improved materials technology towards the on-chip integration
of non-reciprocal devices in optical circuits.

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