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University of Massachusetts Amherst

2024

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Articles 1 - 16 of 16

Full-Text Articles in Physical Sciences and Mathematics

Use Of Unoccupied Aerial Vehicle (Drones) Based Remote Sensing To Model Platform Topography And Identify Human-Made Earthen Barriers In Salt Marshes, Joshua J. Ward Mar 2024

Use Of Unoccupied Aerial Vehicle (Drones) Based Remote Sensing To Model Platform Topography And Identify Human-Made Earthen Barriers In Salt Marshes, Joshua J. Ward

Masters Theses

Elevation is a foundational driver of salt marsh morphology. Elevation governs inundation and hydrological patterns, vegetation distribution, and soil health. Anthropogenic impacts at grand scales (e.g., rising sea levels) and local scales (e.g., infrastructure) have altered the elevation of the salt marsh surface, changing the topography and morphology of these ecosystems. This study establishes and assesses means to document and analyze these impacts using Unoccupied Aerial Vehicle (UAV) based remote sensing to model platform topography. This thesis’s first and primary study presents and compares methods of producing high-resolution digital terrain models (DTMs) with UAV-based Digital Aerial Photogrammetry (DAP) and Light …


Extracting Dnn Architectures Via Runtime Profiling On Mobile Gpus, Dong Hyub Kim Mar 2024

Extracting Dnn Architectures Via Runtime Profiling On Mobile Gpus, Dong Hyub Kim

Masters Theses

Due to significant investment, research, and development efforts over the past decade, deep neural networks (DNNs) have achieved notable advancements in classification and regression domains. As a result, DNNs are considered valuable intellectual property for artificial intelligence providers. Prior work has demonstrated highly effective model extraction attacks which steal a DNN, dismantling the provider’s business model and paving the way for unethical or malicious activities, such as misuse of personal data, safety risks in critical systems, or spreading misinformation. This thesis explores the feasibility of model extraction attacks on mobile devices using aggregated runtime profiles as a side-channel to leak …


Multi-Scale Simulations Of Dynamic Protein Structures And Interactions, Yumeng Zhang Mar 2024

Multi-Scale Simulations Of Dynamic Protein Structures And Interactions, Yumeng Zhang

Doctoral Dissertations

Intrinsically disordered proteins (IDPs) are functional proteins that lack stable tertiary structures in the unbound state. They frequently remain dynamic even within specific complexes and assemblies. IDPs are major components of cellular regulatory networks and have been associated with cancers, diabetes, neurodegenerative diseases, and other human diseases. Computer simulations are essential for deriving a molecular description of the disordered protein ensembles and dynamic interactions for mechanistic understanding of IDPs in biology, diseases, and therapeutics. However, accurate simulation of the heterogeneous ensembles and dynamic interactions of IDPs is extremely challenging because of both the prohibitive computational cost and demanding force field …


An Efficient Privacy-Preserving Framework For Video Analytics, Tian Zhou Mar 2024

An Efficient Privacy-Preserving Framework For Video Analytics, Tian Zhou

Doctoral Dissertations

With the proliferation of video content from surveillance cameras, social media, and live streaming services, the need for efficient video analytics has grown immensely. In recent years, machine learning based computer vision algorithms have shown great success in various video analytic tasks. Specifically, neural network models have dominated in visual tasks such as image and video classification, object recognition, object detection, and object tracking. However, compared with classic computer vision algorithms, machine learning based methods are usually much more compute-intensive. Powerful servers are required by many state-of-the-art machine learning models. With the development of cloud computing infrastructures, people are able …


Automated Identification And Mapping Of Interesting Mineral Spectra In Crism Images, Arun M. Saranathan Mar 2024

Automated Identification And Mapping Of Interesting Mineral Spectra In Crism Images, Arun M. Saranathan

Doctoral Dissertations

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) has proven to be an invaluable tool for the mineralogical analysis of the Martian surface. It has been crucial in identifying and mapping the spatial extents of various minerals. Primarily, the identification and mapping of these mineral spectral-shapes have been performed manually. Given the size of the CRISM image dataset, manual analysis of the full dataset would be arduous/infeasible. This dissertation attempts to address this issue by describing an (machine learning based) automated processing pipeline for CRISM data that can be used to identify and map the unique mineral signatures present in …


Data To Science With Ai And Human-In-The-Loop, Gustavo Perez Sarabia Mar 2024

Data To Science With Ai And Human-In-The-Loop, Gustavo Perez Sarabia

Doctoral Dissertations

AI has the potential to accelerate scientific discovery by enabling scientists to analyze vast datasets more efficiently than traditional methods. For example, this thesis considers the detection of star clusters in high-resolution images of galaxies taken from space telescopes, as well as studying bird migration from RADAR images. In these applications, the goal is to make measurements to answer scientific questions, such as how the star formation rate is affected by mass, or how the phenology of bird migration is influenced by climate change. However, current computer vision systems are far from perfect for conducting these measurements directly. They may …


Policy Gradient Methods: Analysis, Misconceptions, And Improvements, Christopher P. Nota Mar 2024

Policy Gradient Methods: Analysis, Misconceptions, And Improvements, Christopher P. Nota

Doctoral Dissertations

Policy gradient methods are a class of reinforcement learning algorithms that optimize a parametric policy by maximizing an objective function that directly measures the performance of the policy. Despite being used in many high-profile applications of reinforcement learning, the conventional use of policy gradient methods in practice deviates from existing theory. This thesis presents a comprehensive mathematical analysis of policy gradient methods, uncovering misconceptions and suggesting novel solutions to improve their performance. We first demonstrate that the update rule used by most policy gradient methods does not correspond to the gradient of any objective function due to the way the …


Multi-Slam Systems For Fault-Tolerant Simultaneous Localization And Mapping, Samer Nashed Mar 2024

Multi-Slam Systems For Fault-Tolerant Simultaneous Localization And Mapping, Samer Nashed

Doctoral Dissertations

Mobile robots need accurate, high fidelity models of their operating environments in order to complete their tasks safely and efficiently. Generating these models is most often done via Simultaneous Localization and Mapping (SLAM), a paradigm where the robot alternatively estimates the most up-to-date model of the environment and its position relative to this model as it acquires new information from its sensors over time. Because robots operate in many different environments with different compute, memory, sensing, and form constraints, the nature and quality of information available to individual instances of different SLAM systems varies substantially. `One-size-fits-all' solutions are thus exceedingly …


Quantum Chaos, Integrability, And Hydrodynamics In Nonequilibrium Quantum Matter, Javier Lopez Piqueres Mar 2024

Quantum Chaos, Integrability, And Hydrodynamics In Nonequilibrium Quantum Matter, Javier Lopez Piqueres

Doctoral Dissertations

It is well-known that the Hilbert space of a quantum many-body system grows exponentially with the number of particles in the system. Drive the system out of equilibrium so that the degrees of freedom are now dynamic and the result is an extremely complicated problem. With that comes a vast landscape of new physics, which we are just recently starting to explore. In this proposal, we study the dynam- ics of two paradigmatic classes of quantum many-body systems: quantum chaotic and integrable systems. We leverage certain tools commonly employed in equilibrium many-body physics, as well as others tailored to the …


High Resolution Mass Spectrometry As A Platform For The Analysis Of Polyoxometalates, Their Solution Phase Dynamics, And Their Biological Interactions., Daniel T. Favre Mar 2024

High Resolution Mass Spectrometry As A Platform For The Analysis Of Polyoxometalates, Their Solution Phase Dynamics, And Their Biological Interactions., Daniel T. Favre

Doctoral Dissertations

Polyoxometalates (POMs) are a class of inorganic molecule of increasing interest to the inorganic, bioinorganic and catalytic communities among many others. While their prevalence in research has increased, tools and methodologies for the analysis of their fundamental characteristics still need further development. Decavanadate (V10) specifically has been postulated to have several unique properties that have not been confirmed independently. Mass spectrometry (MS) and its ability to determine the composition of solution phase species by both mass and charge is uniquely well suited to the analysis of POMs. In this work we utilized high-resolution mass spectrometry to characterize V10 in aqueous …


Toltec: A New Multichroic Imaging Polarimeter For The Large Millimeter Telescope, Nat S. Denigris Mar 2024

Toltec: A New Multichroic Imaging Polarimeter For The Large Millimeter Telescope, Nat S. Denigris

Doctoral Dissertations

The TolTEC camera is a new millimeter-wave imaging polarimeter designed to fill the focal plane of the 50-m diameter Large Millimeter Telescope (LMT). Combined with the LMT, TolTEC offers high angular resolution (5", 6.3", 9.5") for simultaneous, polarization-sensitive observations in its three wavelength bands: 1.1, 1.4, and 2.0 mm. Additionally, TolTEC is designed to reach groundbreaking mapping speeds in excess of 1 deg2/mJy2/hr, which will enable the completion of deep surveys of large-scale structure, galaxy evolution, and star formation that are currently limited when considering practical observation times for other ground-based observatories. This thesis covers the …


Development Of A Decision Support System Webtool For Historic And Future Low Flow Estimation In The Northeast United States With Applications Of Machine Learning For Advancing Physical And Statistical Methodologies, Andrew F. Delsanto Mar 2024

Development Of A Decision Support System Webtool For Historic And Future Low Flow Estimation In The Northeast United States With Applications Of Machine Learning For Advancing Physical And Statistical Methodologies, Andrew F. Delsanto

Doctoral Dissertations

Droughts are a global challenge and anthropogenic climate change is expected to increase the frequency and severity of extreme low flow events. A major challenge for resource managers is how best to incorporate future climate change projections into low flow event estimations, especially in ungaged basins. Using both physically based hydrology models and statistical models, this dissertation contributes novel methodologies to three key challenges associated with 7-day, 10-year low flow (7Q10) estimation in the northeast United States. Chapter 2 builds upon statistically based 7Q10 estimation in ungaged basins by comparing multiple machine learning algorithms to classical statistical methodologies. This chapter’s …


Uncover: Jwst Spectroscopy Of Three Cold Brown Dwarfs At Kiloparsec-Scale Distances, Sam E. Cutler, Et. Al. Jan 2024

Uncover: Jwst Spectroscopy Of Three Cold Brown Dwarfs At Kiloparsec-Scale Distances, Sam E. Cutler, Et. Al.

Astronomy Department Faculty Publication Series

We report JWST/NIRSpec spectra of three distant T-type brown dwarfs identified in the Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization (UNCOVER) survey of the Abell 2744 lensing field. One source was previously reported as a candidate T dwarf on the basis of NIRCam photometry, while two sources were initially identified as candidate active galactic nuclei. Low-resolution 1–5 μm spectra confirm the presence of molecular features consistent with T dwarf atmospheres, and comparison to spectral standards infers classifications of sdT1, T6, and T8–T9. The warmest source, UNCOVER-BD-1, shows evidence of subsolar metallicity, and atmosphere model fits indicate …


X-Ray Detection Of The Most Extreme Star-Forming Galaxies At The Cosmic Noon Via Strong Lensing, Q Daniel Wang, Carlos Garcia Diaz, Min S. Yun, Et. Al. Jan 2024

X-Ray Detection Of The Most Extreme Star-Forming Galaxies At The Cosmic Noon Via Strong Lensing, Q Daniel Wang, Carlos Garcia Diaz, Min S. Yun, Et. Al.

Astronomy Department Faculty Publication Series

Hyperluminous infrared galaxies (HyLIRGs) are the most extreme star-forming systems observed in the early Universe, and their properties still elude comprehensive understanding. We have undertaken a large XMMNewton observing programme to probe the total accreting black hole population in three HyLIRGs at z = 2.12, 3.25, and 3.55, gravitationally lensed by foreground galaxies. Selected from the Planck All-Sky Survey to Analyse Gravitationally lensed Extreme Starbursts (PASSAGES), these HyLIRGs have apparent infrared luminosities >1014 L. Our observations revealed X-ray emission in each of them. PJ1336+49 appears to be dominated by high-mass X-ray binaries (HMXBs). Remarkably, the luminosity …


Alma-Legus. Ii. The Influence Of Subgalactic Environments On Molecular Cloud Properties, Daniela Calzetti, Et. Al. Jan 2024

Alma-Legus. Ii. The Influence Of Subgalactic Environments On Molecular Cloud Properties, Daniela Calzetti, Et. Al.

Astronomy Department Faculty Publication Series

We compare the molecular cloud properties in subgalactic regions of two galaxies, barred spiral NGC 1313, which is forming many massive clusters, and flocculent spiral NGC 7793, which is forming significantly fewer massive clusters despite having a similar star formation rate to NGC 1313. We find that there are larger variations in cloud properties between different regions within each galaxy than there are between the galaxies on a global scale, especially for NGC 1313. There are higher masses, line widths, pressures, and virial parameters in the arms of NGC 1313 and the center of NGC 7793 than in the interarm …


Uncover Spectroscopy Confirms The Surprising Ubiquity Of Active Galactic Nuclei In Red Sources At Z > 5, Sam E. Cutler, John R. Weaver, Katherine E. Whitaker, Et. Al. Jan 2024

Uncover Spectroscopy Confirms The Surprising Ubiquity Of Active Galactic Nuclei In Red Sources At Z > 5, Sam E. Cutler, John R. Weaver, Katherine E. Whitaker, Et. Al.

Astronomy Department Faculty Publication Series

The James Webb Space Telescope is revealing a new population of dust-reddened broad-line active galactic nuclei (AGN) at redshifts z ≳ 5. Here we present deep NIRSpec/Prism spectroscopy from the Cycle 1 Treasury program Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization (UNCOVER) of 15 AGN candidates selected to be compact, with red continua in the rest-frame optical but with blue slopes in the UV. From NIRCam photometry alone, they could have been dominated by dusty star formation or an AGN. Here we show that the majority of the compact red sources in UNCOVER are dust-reddened AGN: 60% …