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Full-Text Articles in Physical Sciences and Mathematics

Geometric Representation Learning, Luke Vilnis Apr 2021

Geometric Representation Learning, Luke Vilnis

Doctoral Dissertations

Vector embedding models are a cornerstone of modern machine learning methods for knowledge representation and reasoning. These methods aim to turn semantic questions into geometric questions by learning representations of concepts and other domain objects in a lower-dimensional vector space. In that spirit, this work advocates for density- and region-based representation learning. Embedding domain elements as geometric objects beyond a single point enables us to naturally represent breadth and polysemy, make asymmetric comparisons, answer complex queries, and provides a strong inductive bias when labeled data is scarce. We present a model for word representation using Gaussian densities, enabling asymmetric entailment ...


Video Adaptation For High-Quality Content Delivery, Kevin Spiteri Apr 2021

Video Adaptation For High-Quality Content Delivery, Kevin Spiteri

Doctoral Dissertations

Modern video players employ complex algorithms to adapt the bitrate of the video that is shown to the user. Bitrate adaptation requires a tradeoff between reducing the probability that the video freezes (rebuffers) and enhancing the quality of the video. A bitrate that is too high leads to frequent rebuffering, while a bitrate that is too low leads to poor video quality. In this dissertation we propose video-adaptation algorithms to deliver content and maximize the viewer's quality of experience (QoE).

Video providers partition videos into short segments and encode each segment at multiple bitrates. The video player adaptively chooses ...


Phenomenology Of Fermion Production During Axion Inflation, Michael Roberts Apr 2021

Phenomenology Of Fermion Production During Axion Inflation, Michael Roberts

Doctoral Dissertations

We study the production of fermions through a derivative coupling to an axion inflaton and the effects of the produced fermions on the scalar and tensor metric perturbations. We show how such a coupling can arise naturally from supergravity with an axion-like field driving large-field inflation and small instanton-like corrections. We present analytic results for the scalar and tensor power spectra, and estimate the amplitude of the non-Gaussianties in the equilateral regime. The scalar spectrum is found to have a red-tilted spectral index, small non-Gaussianities, and can be dominant over the vacuum contribution. In contrast, the tensor power spectrum from ...


Concentration Inequalities In The Wild: Case Studies In Blockchain & Reinforcement Learning, A. Pinar Ozisik Apr 2021

Concentration Inequalities In The Wild: Case Studies In Blockchain & Reinforcement Learning, A. Pinar Ozisik

Doctoral Dissertations

Concentration inequalities (CIs) are a powerful tool that provide probability bounds on how a random variable deviates from its expectation. In this dissertation, first I describe a blockchain protocol that I have developed, called Graphene, which uses CIs to provide probabilistic guarantees on performance. Second, I analyze the extent to which CIs are robust when the assumptions they require are violated, using Reinforcement Learning (RL) as the domain.

Graphene is a method for interactive set reconciliation among peers in blockchains and related distributed systems. Through the novel combination of a Bloom filter and an Invertible Bloom Lookup Table, Graphene uses ...


Electrospinning Fibers Via Complex Coacervation, Xiangxi Meng Apr 2021

Electrospinning Fibers Via Complex Coacervation, Xiangxi Meng

Doctoral Dissertations

Electrospun fibers are high-surface-area materials widely used in applications ranging from batteries to wound dressings. Typically, an electrospinning precursor solution is prepared by dissolving a high-molecular-weight polymer in an organic solvent to form a sufficiently entangled solution. Our approach bypasses the requirement for entanglements and completely avoids toxic chemicals by focusing on using an aqueous complex coacervates solution. Coacervates are a dense, polymer-rich liquid phase resulting from the associative electrostatic complexation of oppositely charged macroions.

We were the first to demonstrate that liquid complex coacervates could be successfully electrospun into polyelectrolyte complex (PEC) fibers. A canonical coacervate system was formed ...


A Search For New Resonances Decaying Into A Weak Vector Boson And A Higgs Boson In Hadronic Final States With The Atlas Detector At The Large Hadron Collider, Zachary Alden Meadows Apr 2021

A Search For New Resonances Decaying Into A Weak Vector Boson And A Higgs Boson In Hadronic Final States With The Atlas Detector At The Large Hadron Collider, Zachary Alden Meadows

Doctoral Dissertations

A search for heavy resonances decaying to a $W$ or $Z$ boson and a Higgs boson in the final state is described. The search uses $139\ \mathrm{fb}^{-1}$ of proton-proton collision data at $\sqrt{s} = 13$ TeV collected by the ATLAS detector at the CERN Large Hadron Collider from 2015 to 2018. The results are presented in terms of constraints on a simplified model with a heavy vector triplet. Upper limits are set on the production cross-section times branching fraction for resonances decaying into a W/Z boson and a Higgs boson in the mass range between 1.2 ...


Seismic Characteristics Of The Eastern North American Crust And Upper Mantle: The Formation And Evolution Of Continental Lithosphere, Cong Li Apr 2021

Seismic Characteristics Of The Eastern North American Crust And Upper Mantle: The Formation And Evolution Of Continental Lithosphere, Cong Li

Doctoral Dissertations

The impact of past tectonic events on formation and modification of continental lithosphere over the course of Earth’s history remains as an open question of fundamental importance. Physical properties of continental crust and mantle lithosphere, such as their age, thickness, composition, temperature, and velocity, contain crucial information for informing this question. Eastern North America provides at least two complete records of supercontinent assembly and breakup over the past 1.3 Ga, serving as a natural laboratory for our understanding of continental lithosphere evolution and for integrating geologic and geophysical observations. In this thesis, I have investigated the seismic properties ...


Compact Representations Of Uncertainty In Clustering, Craig Stuart Greenberg Apr 2021

Compact Representations Of Uncertainty In Clustering, Craig Stuart Greenberg

Doctoral Dissertations

Flat clustering and hierarchical clustering are two fundamental tasks, often used to discover meaningful structures in data, such as subtypes of cancer, phylogenetic relationships, taxonomies of concepts, and cascades of particle decays in particle physics. When multiple clusterings of the data are possible, it is useful to represent uncertainty in clustering through various probabilistic quantities, such as the distribution over partitions or tree structures, and the marginal probabilities of subpartitions or subtrees.

Many compact representations exist for structured prediction problems, enabling the efficient computation of probability distributions, e.g., a trellis structure and corresponding Forward-Backward algorithm for Markov models that ...


Utilizing Graph Structure For Machine Learning, Stefan Dernbach Apr 2021

Utilizing Graph Structure For Machine Learning, Stefan Dernbach

Doctoral Dissertations

The information age has led to an explosion in the size and availability of data. This data often exhibits graph-structure that is either explicitly defined, as in the web of a social network, or is implicitly defined and can be determined by measuring similarity between objects. Utilizing this graph-structure allows for the design of machine learning algorithms that reflect not only the attributes of individual objects but their relationships to every other object in the domain as well. This thesis investigates three machine learning problems and proposes novel methods that leverage the graph-structure inherent in the tasks. Quantum walk neural ...


Neural Methods For Answer Passage Retrieval Over Sparse Collections, Daniel Cohen Apr 2021

Neural Methods For Answer Passage Retrieval Over Sparse Collections, Daniel Cohen

Doctoral Dissertations

Recent advances in machine learning have allowed information retrieval (IR) techniques to advance beyond the stage of handcrafting domain specific features. Specifically, deep neural models incorporate varying levels of features to learn whether a document answers the information need of a query. However, these neural models rely on a large number of parameters to successfully learn a relation between a query and a relevant document.

This reliance on a large number of parameters, combined with the current methods of optimization relying on small updates necessitates numerous samples to allow the neural model to converge on an effective relevance function. This ...


Sociolinguistically Driven Approaches For Just Natural Language Processing, Su Lin Blodgett Apr 2021

Sociolinguistically Driven Approaches For Just Natural Language Processing, Su Lin Blodgett

Doctoral Dissertations

Natural language processing (NLP) systems are now ubiquitous. Yet the benefits of these language technologies do not accrue evenly to all users, and indeed they can be harmful; NLP systems reproduce stereotypes, prevent speakers of non-standard language varieties from participating fully in public discourse, and re-inscribe historical patterns of linguistic stigmatization and discrimination. How harms arise in NLP systems, and who is harmed by them, can only be understood at the intersection of work on NLP, fairness and justice in machine learning, and the relationships between language and social justice. In this thesis, we propose to address two questions at ...


Assessing The Impacts To Society Associated With The Use Of Alternative Ammunition For Hunting On National Wildlife Refuges, Christopher Cahill Apr 2021

Assessing The Impacts To Society Associated With The Use Of Alternative Ammunition For Hunting On National Wildlife Refuges, Christopher Cahill

Masters Theses

Attempts to eliminate lead ammunition use for hunting through regulatory approaches can be controversial and contentious, despite extensive scientific evidence of the detrimental effect of lead on wildlife species. In the United States, voluntary approaches to non-lead use that have used outreach and education in place of regulatory approaches have achieved sustained behavioral change in hunter ammunition choice. However, voluntary approaches to alternative ammunition use can be confronted with both practical and social barriers. In collaboration with U.S. Fish and Wildlife Service and U.S. Geological Survey Cooperative Research Units Program, this study assessed the practical and social barriers ...


Data For « Does Invasion Science Encompass The Invaded Range? A Comparison Of The Geographies Of Invasion Science Versus Management In The U.S. », Lara Munro, Bridget Griffin, Brittany Laginhas, Bethany Bradley Jan 2021

Data For « Does Invasion Science Encompass The Invaded Range? A Comparison Of The Geographies Of Invasion Science Versus Management In The U.S. », Lara Munro, Bridget Griffin, Brittany Laginhas, Bethany Bradley

Data and Datasets

Data collected from English-language articles published between 1999-2018 on the ten most studied invasive plants in the United States.


Drivers Of English Syntactic Change In The Canadian Parliament, Liwen Hou, David Smith Jan 2021

Drivers Of English Syntactic Change In The Canadian Parliament, Liwen Hou, David Smith

Proceedings of the Society for Computation in Linguistics

Corpus linguists have long noted the "colloquialization'' of many genres of English. While the average decline in many features of formal speech is obvious in aggregate, we are better able to disentangle drivers of change by examining Canadian parliamentary speeches coded for characteristics of individual speakers across more than 100 years---much longer than previous studies of individuals' language change in a common environment. While many language changes proceed by cohort replacement and often originate with female speakers, the Canadian Hansard shows that most speakers employed increasingly colloquial language over their careers and that gender effects are mostly explained by the ...


Global Divergence And Local Convergence Of Utterance Semantic Representations In Dialogue, Yang Xu Jan 2021

Global Divergence And Local Convergence Of Utterance Semantic Representations In Dialogue, Yang Xu

Proceedings of the Society for Computation in Linguistics

We use deep contextualized embedding models (BERT & ELMo) and shallow word embedding models (Fasttext & GloVe) to study the alignment between dialogue interlocutors at the semantic representation level, with the goal to examine the interactive alignment model (IAM) theory. We have observed both divergence and convergence patterns in dialogue: First, the semantic distance between two adjacent utterances increases with their relative positions within the dialogue, i.e., utterances at the later stage are more semantically apart than the earlier ones. Second, semantic distance also increases with the physical distance between utterances, i.e., utterances that are physically closer have more similar ...


Addressing Data Integration Challenges To Link Ecological Processes Across Scales, Elise F. Zipkin, Erin R. Zylstra, Alexander D. Wright, Sarah P. Saunders, Andrew O. Finley, Michael C. Dietze, Malcom S. Itter, Morgan W. Tingley Jan 2021

Addressing Data Integration Challenges To Link Ecological Processes Across Scales, Elise F. Zipkin, Erin R. Zylstra, Alexander D. Wright, Sarah P. Saunders, Andrew O. Finley, Michael C. Dietze, Malcom S. Itter, Morgan W. Tingley

Environmental Conservation Faculty Publication Series

Data integration is a statistical modeling approach that incorporates multiple data sources within a unified analytical framework. Macrosystems ecology – the study of ecological phenomena at broad scales, including interactions across scales – increasingly employs data integration techniques to expand the spatiotemporal scope of research and inferences, increase the precision of parameter estimates, and account for multiple sources of uncertainty in estimates of multiscale processes. We highlight four common analytical challenges to data integration in macrosystems ecology research: data scale mismatches, unbalanced data, sampling biases, and model development and assessment. We explain each problem, discuss current approaches to address the issue, and ...


The Earth, William Clement Jan 2021

The Earth, William Clement

Sustainability Education Resources

The Earth is a 4-credit introduction to the Geosciences. This course is required for several majors in the College of Natural Science at the University of Massachusetts Amherst. These majors include Earth Systems, Environmental Science, and Geology. The course also fulfills a 4-credit Physical Science (PS) General Education requirement and may be an elective science course in a number of other majors. Our goal in Geology 101 is to provide a basic knowledge of how the Earth works, the role of the geologist in contemporary society, and the application of geologic knowledge in solving real world problems. These are broad ...


Diversity, Globalization, And Sustainability: Introduction To Human Geography, Toby Applegate Jan 2021

Diversity, Globalization, And Sustainability: Introduction To Human Geography, Toby Applegate

Sustainability Education Resources

Diversity, Globalization, and Sustainability is a wide-ranging introduction to the ways people shape the world they live in. We will study the themes and concepts of human geography through the current issues and large questions that guide them. Lectures and reading will focus on the geographic aspects of cultural diversity, population issues, states vs. nations, the global economy, development, urbanization and the human transformation of the earth. We will cover major subdivisions of human geography including cultural geography, population geography, economic geography, social geography, political geography and environmental geography.


Information Flow, Artificial Phonology And Typology, Adamantios Gafos Jan 2021

Information Flow, Artificial Phonology And Typology, Adamantios Gafos

Proceedings of the Society for Computation in Linguistics

In the context Artificial Grammar Learning (AGL) experiments, it is possible to quantify how effectively a stimulus has conveyed information and specifically the information the experimenter thinks it was designed to convey. At the most basic level, this can be done if one has access to the response variability of independent responses to the same stimulus (or subparts of the stimulus). The variability of these responses serves as an index of the amount of information that flows from the source of the stimulus to the perceiver. Quantifying information flow in this way, it is shown that under conditions where participants ...


Vowel Harmony Viewed As Error-Correcting Code, Yvo Meeres, Tommi A. Pirinen Jan 2021

Vowel Harmony Viewed As Error-Correcting Code, Yvo Meeres, Tommi A. Pirinen

Proceedings of the Society for Computation in Linguistics

Robustness reduces the risk of information loss. At present the notion of error-correcting codes (ECCs) is used to achieve robustness in technical fields only. Viewing fault-tolerant natural systems as systems equipped with error-correcting codes permits a formal comparison of natural and technical robustness.

Instancing natural language (NL), we show differences in technical and natural error-correcting approaches. By picking a specific grammar phenomenon which some NLs exhibit – vowel harmony (VH) – we show that (1) VH can be formalized as an ECC as well as (2) VH adds to the robustness of its NL. We provide empirical as well as formal evidence ...


Beyond Green Cars And Goddesses: Gender, The Global Environment, And Sustainability, Kiran Asher Jan 2021

Beyond Green Cars And Goddesses: Gender, The Global Environment, And Sustainability, Kiran Asher

Sustainability Education Resources

Gender, the environment and sustainability are key terms in debates about economic globalization and social justice. While not new, they are reemerging as part of the post-2015 sustainable development agenda. This course will introduce students to the perceived and existing links between women, gender, and the global environment as they appear in 21st century discussions about sustainable development. Through readings, lectures and discussions will explore the following questions:  When did the environment and sustainability emerge as key biological and social issues on global agendas?  What are their connections to economic globalization? To colonialism and capitalism?  How did women and gender ...


Can Rnns Trained On Harder Subject-Verb Agreement Instances Still Perform Well On Easier Ones?, Hritik Bansal, Gantavya Bhatt, Sumeet Agarwal Jan 2021

Can Rnns Trained On Harder Subject-Verb Agreement Instances Still Perform Well On Easier Ones?, Hritik Bansal, Gantavya Bhatt, Sumeet Agarwal

Proceedings of the Society for Computation in Linguistics

The main subject and the associated verb in English must agree in grammatical number as per the Subject-Verb Agreement (SVA) phenomenon. It has been found that the presence of a noun between the verb and the main subject, whose grammatical number is opposite to that of the main subject, can cause speakers to produce a verb that agrees with the intervening noun rather than the main noun; the former thus acts as an agreement attractor. Such attractors have also been shown to pose a challenge for RNN models without explicit hierarchical bias to perform well on SVA tasks. Previous work ...


Environmental Decision-Making, Ezra Markowitz Jan 2021

Environmental Decision-Making, Ezra Markowitz

Sustainability Education Resources

Over the past 30 years, there has been a growing recognition amongst environmental advocates, resource managers, policymakers and researchers that the underlying cause of most environmental, conservation and sustainability issues is human behavior. As NRC and ENVIRSCI majors, you have received extensive technical training in how natural systems operate yet relatively little training when it comes to influencing or understanding how people make environmental decisions that affect those natural systems. Recognizing the fundamental role that human decision-making plays in shaping the environment reveals a new set of tools and approaches for both understanding the challenges we face and confronting those ...


The Zoltar Forecast Archive, A Tool To Standardize And Store Interdisciplinary Prediction Research, Nicholas G. Reich, Matthew Cornell, Evan L. Ray, Katie House, Khoa Le Jan 2021

The Zoltar Forecast Archive, A Tool To Standardize And Store Interdisciplinary Prediction Research, Nicholas G. Reich, Matthew Cornell, Evan L. Ray, Katie House, Khoa Le

Biostatistics and Epidemiology Faculty Publications Series

Forecasting has emerged as an important component of informed, data-driven decision-making in a wide array of felds. We introduce a new data model for probabilistic predictions that encompasses a wide range of forecasting settings. This framework clearly defnes the constituent parts of a probabilistic forecast and proposes one approach for representing these data elements. The data model is implemented in Zoltar, a new software application that stores forecasts using the data model and provides standardized API access to the data. In one real-time case study, an instance of the Zoltar web application was used to store, provide access to, and ...


Model Data For 'Co2 And Tectonic Controls On Antarctic Climate And Ice-Sheet Evolution In The Mid-Miocene', Anna Ruth Halberstadt Jan 2021

Model Data For 'Co2 And Tectonic Controls On Antarctic Climate And Ice-Sheet Evolution In The Mid-Miocene', Anna Ruth Halberstadt

Data and Datasets

This is the data repository associated with the manuscript "CO2 and Tectonic Controls on Antarctic Climate and Ice-Sheet Evolution in the Mid-Miocene" containing all model output files relevant to the project. We use an ensemble of asynchronously coupled climate - ice sheet - vegetation model simulations spanning a range of CO2 concentrations, Transantarctic Mountain uplift scenarios, and glacial/interglacial climatic conditions to identify climate and ice-sheet conditions consistent with Antarctic mid-Miocene terrestrial and marine geological records. Details about the content of the data repository can be found in the readme.txt file located in the repository.


Abiotic Stress And Biotic Factors Mediate Range Dynamics On Opposing Edges, Alexej P. K. Sirén, Christopher S. Sutherland, Christopher A. Bernier, Kimberly J. Royar, Jillian R. Kilborn, Catherine B. Callahan, Rachel M. Cliché, Leighlan S. Prout, Toni Lyn Morelli Jan 2021

Abiotic Stress And Biotic Factors Mediate Range Dynamics On Opposing Edges, Alexej P. K. Sirén, Christopher S. Sutherland, Christopher A. Bernier, Kimberly J. Royar, Jillian R. Kilborn, Catherine B. Callahan, Rachel M. Cliché, Leighlan S. Prout, Toni Lyn Morelli

Environmental Conservation Faculty Publication Series

Aim

In the face of global change, understanding causes of range limits are one of the most pressing needs in biogeography and ecology. A prevailing hypothesis is that abiotic stress forms cold (upper latitude/altitude) limits, whereas biotic interactions create warm (lower) limits. A new framework – Interactive Range‐Limit Theory (iRLT) – asserts that positive biotic factors such as food availability can ameliorate abiotic stress along cold edges, whereas abiotic stress can have a positive effect and mediate biotic interactions (e.g., competition) along warm limits.

Location

Northeastern United States

Taxon

Carnivora

Methods

We evaluated two hypotheses of iRLT using occupancy ...


How Can Employers Contribute To Reducing Commuter-Generated Carbon Emissions? Evaluating Employer-Provided Commuter Benefits In Cambridge, Ma, Mary Richards Dec 2020

How Can Employers Contribute To Reducing Commuter-Generated Carbon Emissions? Evaluating Employer-Provided Commuter Benefits In Cambridge, Ma, Mary Richards

Masters Theses

Encouraging a more sustainable commuter mode shift and improving urban transportation systems have the potential to reduce anthropogenic greenhouse gas emissions (GHGs), a major contributor to climate change. Replacing some single-occupancy vehicle (SOV) trips with alternative modes of transportation, such as public transit, walking, or bicycling, represents one approach to begin reducing transportation-related emissions. Collectively, these shifts in transportation patterns would help to reduce the negative social, economic, and environmental costs associated with high rates of personal vehicle use. Employer-provided benefits programs have the potential to influence commuter behavior by making sustainable, alternative commuting choices a more convenient and economically ...


Does Invasion Science Encompass The Invaded Range? A Comparison Of The Geographies Of Invasion Science Versus Management In The U.S., Lara Munro Dec 2020

Does Invasion Science Encompass The Invaded Range? A Comparison Of The Geographies Of Invasion Science Versus Management In The U.S., Lara Munro

Masters Theses

Biases in invasion science lead to a taxonomic focus on plants, particularly a subset of well-studied plants, and a geographic focus on invasions in Europe and North America. Geographic biases could also cause some branches of invasion science to focus on a subset of environmental conditions in the invaded range, potentially leading to an incomplete understanding of the ecology and management of plant invasions. While broader, country-level geographic biases are well known, it is unclear whether these biases extend to a finer scale and thus affect research within the invaded range. This study assessed whether research sites for ten well-studied ...


Metric Learning Via Linear Embeddings For Human Motion Recognition, Byoungdoo Kong Dec 2020

Metric Learning Via Linear Embeddings For Human Motion Recognition, Byoungdoo Kong

Masters Theses

We consider the application of Few-Shot Learning (FSL) and dimensionality reduction to the problem of human motion recognition (HMR). The structure of human motion has unique characteristics such as its dynamic and high-dimensional nature. Recent research on human motion recognition uses deep neural networks with multiple layers. Most importantly, large datasets will need to be collected to use such networks to analyze human motion. This process is both time-consuming and expensive since a large motion capture database must be collected and labeled. Despite significant progress having been made in human motion recognition, state-of-the-art algorithms still misclassify actions because of characteristics ...


Crustal Evolution Of The New England Appalachians: The Rise And Fall Of A Long-Lived Orogenic Plateau, Ian Hillenbrand Dec 2020

Crustal Evolution Of The New England Appalachians: The Rise And Fall Of A Long-Lived Orogenic Plateau, Ian Hillenbrand

Masters Theses

The rise and demise of mountain belts, caused by growth, modification, or removal of the continental lithosphere are fundamental processes that influence almost all Earth systems. Understanding the nature, timing, and significance of active processes in the creation and evolution of modern mountain belts is challenged by a lack of middle crustal and lower crustal exposures. Analogues can be found in ancient orogens, whose deeply eroded roots offer a window into deeper processes, yet this record is complicated by overprinting events and complex deformational histories. Research presented herein constrains the tectonic history of multistage Appalachian Orogen, type locality of the ...