Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Chemistry (36)
- Engineering (36)
- Computer Sciences (32)
- Physics (26)
- Artificial Intelligence and Robotics (21)
-
- Materials Science and Engineering (16)
- Polymer Chemistry (14)
- Materials Chemistry (13)
- Earth Sciences (12)
- Physical Chemistry (11)
- Mathematics (10)
- Statistics and Probability (10)
- Chemical Engineering (9)
- Nanoscience and Nanotechnology (9)
- Geology (8)
- Life Sciences (8)
- Organic Chemistry (8)
- Condensed Matter Physics (7)
- Astrophysics and Astronomy (6)
- Electrical and Computer Engineering (6)
- Inorganic Chemistry (6)
- Analytical Chemistry (5)
- Applied Mathematics (5)
- Biochemistry, Biophysics, and Structural Biology (5)
- Environmental Sciences (5)
- Mechanical Engineering (5)
- Polymer and Organic Materials (5)
- Biophysics (4)
- Computer Engineering (4)
- Institution
- Keyword
-
- Machine learning (7)
- Deep learning (4)
- Aerogels (3)
- Biomarkers (3)
- Data mining (3)
-
- Deep Learning (3)
- Temperature (3)
- Amphiphilic polymers (2)
- Arctic (2)
- Brush block copolymers (2)
- Classification (2)
- Cobalt (2)
- Diffusion (2)
- Doping (2)
- Information retrieval (2)
- Mass spectrometry (2)
- Nanofabrication (2)
- Natural language processing (2)
- Numerical modeling (2)
- Paleoclimate (2)
- Phonon (2)
- Robotics (2)
- Star formation (2)
- Stratified turbulence (2)
- 21P/Giacobini-Zinner (1)
- 2D (1)
- 2D Materials (1)
- 2P/Encke (1)
- 3D Print (1)
- AI (1)
Articles 31 - 60 of 126
Full-Text Articles in Physical Sciences and Mathematics
The Bivariate Luminosity-Hi Distribution Function Of Galaxies, Zhon Butcher
The Bivariate Luminosity-Hi Distribution Function Of Galaxies, Zhon Butcher
Doctoral Dissertations
To investigate the correlation between optical luminosity and Hi mass, we obtained 21cm Hi line observations from the 100m class Nanç ay Radio Telescope of 2600 galaxies in the local universe (900 ≤ cz ≤ 12000 km s−1 ). We first present the observations and basic results of the Nanc¸ay Interstellar Baryons Legacy Extragalactic Survey (NIBLES), followed by Arecibo follow-up Hi line observations of 305 Nanç ay Hi undetected galaxies. Analysis of the low-luminosity follow-up sources indicates that they may have, on average, a more concentrated stellar mass distribution than the Nanc¸ay detected galaxies of corresponding luminosity. Using the data …
Bruhat-Tits Buildings And A Characteristic P Unimodular Symbol Algorithm, Matthew Bates
Bruhat-Tits Buildings And A Characteristic P Unimodular Symbol Algorithm, Matthew Bates
Doctoral Dissertations
Let k be the finite field with q elements, let F be the field of Laurent series in the variable 1/t with coefficients in k, and let A be the polynomial ring in the variable t with coefficients in k. Let SLn(F) be the ring of nxn-matrices with entries in F, and determinant 1. Given a polynomial g in A, let Gamma(g) subset SLn(F) be the full congruence subgroup of level g. In this thesis we examine the action of Gamma(g) on the Bruhat-Tits building Xn associated to SLn(F) for n equals 2 and n equals 3. Our first main …
Game-Assisted Rehabilitation For Post-Stroke Survivors, Hee-Tae Jung
Game-Assisted Rehabilitation For Post-Stroke Survivors, Hee-Tae Jung
Doctoral Dissertations
Stroke is a leading cause of permanent impairments among its survivors. Although patients need to go through intensive, longitudinal rehabilitation to regain function before the stroke, patients show poor engagement and adherence to rehabilitation therapies which hampers their recovery. As a means to enhance stroke survivors' motivation, engagement, and adherence to intensive and longitudinal rehabilitation, the use of games in stroke rehabilitation has received attention from research and clinical communities. In order to realize this, it is important to take a holistic, end-to-end research approach that encompasses 1) the development of game technologies that are not only entertaining but also …
Numerical Climate Model Simulations Investigating The Role Of Arctic Sea Ice Export Events In Modulating Deglacial Climate, Anthony J. Joyce
Numerical Climate Model Simulations Investigating The Role Of Arctic Sea Ice Export Events In Modulating Deglacial Climate, Anthony J. Joyce
Doctoral Dissertations
Periods of abrupt climate cooling during the last deglaciation (20,000-8,000 yrs ago) are often attributed to glacial outburst floods slowing the Atlantic meridional overturning circulation (AMOC). Yet, despite over 40 years of research, conclusive evidence that such events significantly impact climate remains elusive. This study uses a climate model to investigate an alternative freshwater forcing mechanism in which the episodic break-up and mobilization of thick perennial Arctic sea ice might have disrupted large-scale climate. The results presented here show the first evidence that (1) the Arctic Ocean stored enormous volumes of freshwater during colder periods as thick masses of sea …
Neural Generative Models And Representation Learning For Information Retrieval, Qingyao Ai
Neural Generative Models And Representation Learning For Information Retrieval, Qingyao Ai
Doctoral Dissertations
Information Retrieval (IR) concerns about the structure, analysis, organization, storage, and retrieval of information. Among different retrieval models proposed in the past decades, generative retrieval models, especially those under the statistical probabilistic framework, are one of the most popular techniques that have been widely applied to Information Retrieval problems. While they are famous for their well-grounded theory and good empirical performance in text retrieval, their applications in IR are often limited by their complexity and low extendability in the modeling of high-dimensional information. Recently, advances in deep learning techniques provide new opportunities for representation learning and generative models for information …
Numerical Modeling Of Deformation Within Restraining Bends And The Implications For The Seismic Hazard Of The San Gorgonio Pass Region, Southern California, Jennifer Hatch
Doctoral Dissertations
Assessment of seismic hazards in southern California may be improved with more accurate characterization of active geometry, stress state, and slip rates along the active San Andreas fault strands within the San Gorgonio Pass region. For example, on-going debate centers on the activity and geometry of the Mill Creek and Mission Creek strands. Calculated misfits of model slip rates to geologic slip rates for six alternative active fault configuration models through the San Gorgonio Pass reveal two best-fitting models, both of which fit many but not all available geologic slip rates. Disagreement between the model and geologic slip rates indicate …
Socio-Political And Natural-Ecological Factors Influencing Urban Forest Management In Massachusetts, Rick W. Harper
Socio-Political And Natural-Ecological Factors Influencing Urban Forest Management In Massachusetts, Rick W. Harper
Doctoral Dissertations
The management of urban forest systems is a complex interaction of social-ecological elements where biophysical factors interact with social aspects including policy decision-makers, managers, and municipal and private-sector employees. In the New England states, tree wardens are the local officials responsible for the preservation, maintenance, and stewardship of the public trees of a municipality. In-person qualitative research interviews were conducted with 50 tree wardens throughout Massachusetts to understand position duties, responsibilities, and professional challenges at the community-level. Qualitative research interviews were also conducted with chairs from 13 volunteer urban tree committees across Massachusetts. The value of employing qualitative methodologies in …
Middle To Late Pleistocene Paleoenvironmental Reconstructions From Lake El'gygytgyn, Arctic Russia, Mary Helen Habicht
Middle To Late Pleistocene Paleoenvironmental Reconstructions From Lake El'gygytgyn, Arctic Russia, Mary Helen Habicht
Doctoral Dissertations
Climate change is a major issue challenging the world today. Our global society faces rising temperatures, variable weather patterns, and rising sea level among other associated issues. Our action (or inaction) to address current changes will have serious ramifications for life on our planet in the coming centuries and millennia. In order to provide context for these present and future changes, we can utilize the paleo record to understand the natural variability of Earth’s climate system. One region of the world is changing more rapidly than the global average. Over recent decades, the Arctic has experienced warmer temperatures, reduced sea …
Adaptive Feature Engineering Modeling For Ultrasound Image Classification For Decision Support, Hatwib Mugasa
Adaptive Feature Engineering Modeling For Ultrasound Image Classification For Decision Support, Hatwib Mugasa
Doctoral Dissertations
Ultrasonography is considered a relatively safe option for the diagnosis of benign and malignant cancer lesions due to the low-energy sound waves used. However, the visual interpretation of the ultrasound images is time-consuming and usually has high false alerts due to speckle noise. Improved methods of collection image-based data have been proposed to reduce noise in the images; however, this has proved not to solve the problem due to the complex nature of images and the exponential growth of biomedical datasets. Secondly, the target class in real-world biomedical datasets, that is the focus of interest of a biopsy, is usually …
Feature Space Modeling For Accurate And Efficient Learning From Non-Stationary Data, Ayesha Akter
Feature Space Modeling For Accurate And Efficient Learning From Non-Stationary Data, Ayesha Akter
Doctoral Dissertations
A non-stationary dataset is one whose statistical properties such as the mean, variance, correlation, probability distribution, etc. change over a specific interval of time. On the contrary, a stationary dataset is one whose statistical properties remain constant over time. Apart from the volatile statistical properties, non-stationary data poses other challenges such as time and memory management due to the limitation of computational resources mostly caused by the recent advancements in data collection technologies which generate a variety of data at an alarming pace and volume. Additionally, when the collected data is complex, managing data complexity, emerging from its dimensionality and …
A Multicarrier Technique For Monte Carlo Simulation Of Electrothermal Transport In Nanoelectronics, Tyler J. Spence
A Multicarrier Technique For Monte Carlo Simulation Of Electrothermal Transport In Nanoelectronics, Tyler J. Spence
Doctoral Dissertations
The field of microelectronics plays an important role in many areas of engineering and science, being ubiquitous in aerospace, industrial manufacturing, biotechnology, and many other fields. Today, many micro- and nanoscale electronic devices are integrated into one package. e capacity to simulate new devices accurately is critical to the engineering design process, as device engineers use simulations to predict performance characteristics and identify potential issues before fabrication. A problem of particular interest is the simulation of devices which exhibit exotic behaviors due to non-equilibrium thermodynamics and thermal effects such as self-heating. Frequently, it is desirable to predict the level of …
Increasing The Functionality Of Additive Manufacturing Through Atmospheric Microplasma And Nanotechnology, Alexander Jon Ulrich
Increasing The Functionality Of Additive Manufacturing Through Atmospheric Microplasma And Nanotechnology, Alexander Jon Ulrich
Doctoral Dissertations
Additive Manufacturing (AM) has been changing the manufacturing landscape for the last 20 years. As the interest and demand for both polymer and metal-based 3D printing has grown, the materials and machines used have increased in capabilities. Despite the growth and advancement, there are still a large number of improvements that can be made to add functionality to 3D printers. Metal AM, a subcategory of 3D printing, has garnered much attention among industrial applications with large companies such as General Electric trying to implement the technology to increase innovative designs for motors. Some of the limitations on AM have to …
Organically Modified Inorganic Nanoparticles For Halochromic Ionophores And Nucleic Acids, William Johnston
Organically Modified Inorganic Nanoparticles For Halochromic Ionophores And Nucleic Acids, William Johnston
Doctoral Dissertations
In this dissertation, four nanoparticle reaction schemes were developed as substrates for halochromic dyes or nucleic acids. The reaction schemes include the use of two substrates: silica nanoparticles and halloysite nanotubes. The protocols can incorporate silica (SiO2) nanoparticles and halloysite aluminosilicate (AlO2SiO2) nanotubes due to the presence of silane groups on the surface of either substrate. The reaction schemes are presented along with detailed protocols which were written to facilitate both reproducibility and to serve as an aid to further study and for easy modification of the protocol to suit a researcher's needs. The data is discussed in the materials …
Aztec Survey Of The Central Molecular Zone: Modeling Dust Seds With Hierarchical Bayesian Analysis, Yuping Tang
Aztec Survey Of The Central Molecular Zone: Modeling Dust Seds With Hierarchical Bayesian Analysis, Yuping Tang
Doctoral Dissertations
In this dissertation, we present a study based on the AzTEC/Large Millimeter Telescope (LMT) survey of dust continuum at 1.1mm on the central 200 parsecs (The Central Molecular Zone (CMZ)) of our Galaxy. Owing to its unusually high gas density and turbulence, strong magnetic field, and high cosmic ray flux, the CMZ represents an initial condition for star-formation typical of starburst galaxies in the distant universe. In order to understand dust properties in such an extreme environment. We perform a joint SED analysis of existing dust continuum surveys on the CMZ, from a wavelength of 160 μm to 1.1 mm. …
Allocative Poisson Factorization For Computational Social Science, Aaron Schein
Allocative Poisson Factorization For Computational Social Science, Aaron Schein
Doctoral Dissertations
Social science data often comes in the form of high-dimensional discrete data such as categorical survey responses, social interaction records, or text. These data sets exhibit high degrees of sparsity, missingness, overdispersion, and burstiness, all of which present challenges to traditional statistical modeling techniques. The framework of Poisson factorization (PF) has emerged in recent years as a natural way to model high-dimensional discrete data sets. This framework assumes that each observed count in a data set is a Poisson random variable $y ~ Pois(\mu)$ whose rate parameter $\mu$ is a function of shared model parameters. This thesis examines a specific …
A Study On Homogeneous Sheared Stably Stratified Turbulence, Gavin Portwood
A Study On Homogeneous Sheared Stably Stratified Turbulence, Gavin Portwood
Doctoral Dissertations
Homogeneous sheared and stably stratified turbulence is considered as a fundamental flow relevant to the study of geophysical turbulence and, generally, anisotropic turbulence. Numerical experiments are performed via high resolution direct numerical simulation (DNS) in a geophysically-relevant parameter space previously inaccessible to simulation. Turbulent dynamics relevant to the modeling of geophysical hydrodynamics are investigated as a function of mean flow and fluid parameters. An active tuning scheme is implemented to induce temporally stationary turbulent kinetic energy in order to evaluate turbulence that is statistically independent of initial conditions and spatio-temporally homogeneous. Subject to this constraint, the parametric dependence of the …
Double-Network Materials Via Frontal Polymerization & Supercritical Co2 Processing, Matthew Joseph Lampe
Double-Network Materials Via Frontal Polymerization & Supercritical Co2 Processing, Matthew Joseph Lampe
Doctoral Dissertations
This dissertation presents work focused on producing materials in non-equilibrium states by taking advantage of novel processing techniques. First, epoxy-based resins which can undergo radically promoted, cationic, thermal, frontal polymerization are investigated for their potential use as adhesives. These resins are found to be capable of sustaining propagating polymerization fronts between several different substrate materials, resulting in high levels of adhesion in some cases. In addition, a similar frontal resin was developed that can undergo sequential gelation and frontal polymerization. The gels are formed by radically crosslinking acrylate monomers within the epoxy resin. These gels can then be manipulated, and …
Probabilistic Models For Identifying And Explaining Controversy, Myungha Jang
Probabilistic Models For Identifying And Explaining Controversy, Myungha Jang
Doctoral Dissertations
Navigating controversial topics on the Web encourages social awareness, supports civil discourse, and promotes critical literacy. While search of controversial topics particularly requires users to use their critical literacy skills on the content, educating people to be more critical readers is known to be a complex and long-term process. Therefore, we are in need of search engines that are equipped with techniques to help users to understand controversial topics by identifying them and explaining why they are controversial. A few approaches for identifying controversy have worked reasonably well in practice, but they are narrow in scope and exhibit limited performance. …
Reactive And Stimuli-Responsive Sulfonium-Based Polymer Zwitterions, Cristiam Santa Chalarca
Reactive And Stimuli-Responsive Sulfonium-Based Polymer Zwitterions, Cristiam Santa Chalarca
Doctoral Dissertations
This dissertation describes the synthesis and characterization of novel monomers and (co)polymer zwitterions that incorporate trialkylsulfonium cations. The novel materials presented herein constitute a unique type of polymer zwitterions that exhibit salt- and temperature-dependent water solubility as well as inherent reactivity. The behavior of these polymers in aqueous solutions, as nanostructures, and at liquid-liquid interfaces was studied; in all cases, the inherent reactivity of the polymers was harnessed towards the fabrication of novel polymers and soft materials. Following an introductory chapter, Chapter 2 describes the synthesis of sulfonium sulfonate monomers and polymer zwitterions. Both styrenic and methacrylic monomers were synthesized …
Abstractions In Reasoning For Long-Term Autonomy, Kyle Hollins Wray
Abstractions In Reasoning For Long-Term Autonomy, Kyle Hollins Wray
Doctoral Dissertations
The path to building adaptive, robust, intelligent agents has led researchers to develop a suite of powerful models and algorithms for agents with a single objective. However, in recent years, attempts to use this monolithic approach to solve an ever-expanding set of complex real-world problems, which increasingly include long-term autonomous deployments, have illuminated challenges in its ability to scale. Consequently, a fragmented collection of hierarchical and multi-objective models were developed. This trend continues into the algorithms as well, as each approximates an optimal solution in a different manner for scalability. These models and algorithms represent an attempt to solve pieces …
Asymptotic And Numerical Analysis Of Coherent Structures In Nonlinear Schrodinger-Type Equations, Cory Ward
Asymptotic And Numerical Analysis Of Coherent Structures In Nonlinear Schrodinger-Type Equations, Cory Ward
Doctoral Dissertations
This dissertation concerns itself with coherent structures found in nonlinear Schrödinger-type equations and can be roughly split into three parts. In the first part we study a deformation of the defocusing nonlinear Schrödinger (NLS) equation, the defocusing Camassa-Holm NLS (CH-NLS) equation in both one and two space dimensions. We use asymptotic multiscale expansion methods to reduce this model to a Boussinesq-like equation, which is then subsequently used to obtain approximate solitary wave solutions for both the 1D and 2D CH-NLS equations. We then use direct numerical simulations to investigate the validity of these approximate solutions, their evolution, and their head-on …
Synthesis Of Magnetic Ion Doped Ii-Vi Benzenechalcogenolate Molecular Clusters, Fumitoshi Kato
Synthesis Of Magnetic Ion Doped Ii-Vi Benzenechalcogenolate Molecular Clusters, Fumitoshi Kato
Doctoral Dissertations
Diluted magnetic semiconductor quantum dots (DMS-QDs) is a class of material prepared by introducing a small percentage of magnetic impurities to impart new magneto-optical properties to the host nanocrystal (NC). Such materials are regarded as promising candidates for their potential application in spintronic devices. The overall functionality of the DMS‑QD is highly dependent on the dopant position within the host structure. A thorough understanding of the doping mechanism is, therefore, critical to gain better control over the dopant speciation in nanocrystal lattice and material properties. In this work, we utilized II‑VI molecular clusters that are analogous to bulk semiconductors as …
Flow-Induced Oscillations In Floating Offshore Wind Turbines, Daniel Carlson
Flow-Induced Oscillations In Floating Offshore Wind Turbines, Daniel Carlson
Doctoral Dissertations
The goal of this thesis is to experimentally study the structural dynamics, wake interaction, and fluid forces on the multiple-degree of freedom systems typical of floating wind turbines. Vortex--surface alignment about flexibly-mounted prisms is studied to investigate the response of barges and semi-submersible hulls, and new results pertaining to the galloping response kink for a prism with dual inline--crossflow resonance is presented. Flow--induced oscillations of a spar model free to rotate in 3D space is replicated and observed as 2D figure--eight orbits about the center of the spar. Methods to suppress the flow from exciting the spar are proposed. The …
Data-Driven Approach To Image Classification, Venkatesh Narasimhamurthy
Data-Driven Approach To Image Classification, Venkatesh Narasimhamurthy
Doctoral Dissertations
Image classification has been a core topic in the computer vision community. Its recent success with convolutional neural network (CNN) algorithm has led to various real world applications such as large scale management of photos/videos on cloud/social-media, image based search for online retailers, self-driving cars, building robots and healthcare. Image classification can be broadly categorized into binary, multi-class and multi-label classification problems. Binary classification involves assigning one of the two class labels to an instance. In multi-class classification problem, an instance should be categorized into one of more than two classes. Multi-label classification is a generalized version of the multi-class …
Modulating Dopant-Defect Interactions In Transition Metal Doped Colloidal Strontium Titanate Nanocrystals, William Harrigan
Modulating Dopant-Defect Interactions In Transition Metal Doped Colloidal Strontium Titanate Nanocrystals, William Harrigan
Doctoral Dissertations
Perovskites such as strontium titanate, a wide band gap semiconductor have been widely studied due to the multitude of potential applications in photocatalysis, multiferroics, sensing, and microelectronics. Various novel optical, electrical and magnetic properties can be imparted through the introduction of different transition metal dopant ions. The introduction of these impurities has been shown to impart functionality for various applications. The use of Cr3+has been shown to introduce defect levels into the band structure of SrTiO3and increase visible light utilization for photocatalysis. Transition metal doped highly crystalline colloidal SrTiO3nanocrystals (NC) were synthesized using two …
Northeastern Species In Hybrid Cross Laminated Timber, Hamid Kaboli
Northeastern Species In Hybrid Cross Laminated Timber, Hamid Kaboli
Doctoral Dissertations
Known in the building industry throughout the world, Cross Laminated Timber (CLT) is a massive timber building material with outstanding structural, fire, and seismic properties. CLT is a cost-competitive, sustainable construction material is a good candidate as a substitute material for concrete, masonry, and steel, in mid-rise and high-rise buildings. CLT is perpendicular layers of dimensional lumbers usually laminated together and forming a massive structural panel. This dissertation explores the viability of utilizing Massachusetts grown Eastern Hemlock and Eastern White Pine in CLT panels as pure or in conjunction with other high-value wood products. 59% of Massachusetts’ lands are covered …
Massive Graph Analysis In The Data Stream Model, Sofya Vorotnikova
Massive Graph Analysis In The Data Stream Model, Sofya Vorotnikova
Doctoral Dissertations
Graphs have become an abstraction of choice in modeling highly-structured data. The need to compute graph-theoretic properties of datasets arises in many applications that involve entities and pairwise relations between them. However, in practice the datasets in question can be too large to be stored in main memory, distributed across many machines, or changing over time. Moreover, in an increasing number of applications the algorithm has to make real time decisions as the data arrives, which puts further limitations on the time and space that can realistically be used. These characteristics render classical algorithmic approaches obsolete and necessitate the development …
Sorption Temperature And And The Stability Of Iron-Bound Soil Organic Matter, Michael L. Nguyen
Sorption Temperature And And The Stability Of Iron-Bound Soil Organic Matter, Michael L. Nguyen
Doctoral Dissertations
The preservation of soil organic matter (SOM) is an important control on the global cycling of carbon. Long-term preservation of SOM has important implications on soil fertility and climate regulation. Minerals, such as iron oxides, can react with SOM and serve as a preservation mechanism for SOM. Globally, iron oxide-SOM interactions form a “rusty carbon sink” which protects up to 22% of organic carbon in marine sediments. Climate changes, such as warming, may alter the size or efficacy of the “rusty carbon sink.” The effects of temperature, SOM composition, and mineral particle size on the formation and stability of iron …
Simulating Hydrogen Bonded Clusters And Zeolite Clusters For Renewable Energy Applications, Qinfang Sun
Simulating Hydrogen Bonded Clusters And Zeolite Clusters For Renewable Energy Applications, Qinfang Sun
Doctoral Dissertations
Our research attention is focused on the development of new fuel cell membrane materials and new zeolites which improve biomass conversion rate to meet the increasing demand of renewable and sustainable energy. We have simulated the dynamics of amphiprotic groups (pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, and tetrazole, acetic acid, formic acid, sulfuric acid, and phosphoric acid) as neat liquids and tethered via linkers to aliphatic backbones, to determine how tethering and varying functional groups affect hydrogen bond networks and reorientation dynamics, both factors thought to influence proton conduction. We used the DL_Poly_2 molecular dynamics code with the GAFF force field to …
Poetry: Identification, Entity Recognition, And Retrieval, John J. Foley Iv
Poetry: Identification, Entity Recognition, And Retrieval, John J. Foley Iv
Doctoral Dissertations
Modern advances in natural language processing (NLP) and information retrieval (IR) provide for the ability to automatically analyze, categorize, process and search textual resources. However, generalizing these approaches remains an open problem: models that appear to understand certain types of data must be re-trained on other domains. Often, models make assumptions about the length, structure, discourse model and vocabulary used by a particular corpus. Trained models can often become biased toward an original dataset, learning that – for example – all capitalized words are names of people or that short documents are more relevant than longer documents. As a result, …