Physical Sciences and Mathematics Commons^™

The Effect Of Polymer Stiffness On Magnetization Reversal Of Magnetorheological Elastomers, Andy T. Clark, David Marchfield, Zheng Cao, Tong Dang, Nan Tang, Dustin Gilbert, Elise A. Corbin, Kristen S. Buchanan, Xuemei Cheng

Physics Faculty Research and Scholarship

Ultrasoft magnetorheological elastomers (MREs) offer convenient real-time magnetic field control of mechanical properties that provides a means to mimic mechanical cues and regulators of cells in vitro. Here, we systematically investigate the effect of polymer stiffness on magnetization reversal of MREs using a combination of magnetometry measurements and computational modeling. Poly-dimethylsiloxane- based MREs with Young’s moduli that range over two orders of magnitude were synthesized using commercial polymers SylgardTM 527, Sylgard 184, and carbonyl iron powder. The magnetic hysteresis loops of the softer MREs exhibit a characteristic pinched loop shape with almost zero remanence and loop widening at intermediate fields …

Heterogenous Reduction Of Co2 Over Boron-Rich Alb2, Jose C. Berger

Honors Undergraduate Theses

Evidence suggests that the recent drastic changes in the global climate have been caused by greenhouse gases, especially CO­₂. As a result, scientists are aiming to develop processes that either minimize the production of these gases or convert them into products of higher value. To that end, the catalytic properties of a two-dimensional boron-rich material were investigated. Herein is reported that such a material can reduce CO₂ into benzene, C₃ species, and C₄ species at relatively low temperatures (225-450 ℃) and pressures (0.38 MPa). Current data suggest that a low-temperature induction period (e.g., 225 ℃) …

Measuring And Comparing Social Bias In Static And Contextual Word Embeddings, Alan Cueva Mora

Dissertations

Word embeddings have been considered one of the biggest breakthroughs of deep learning for natural language processing. They are learned numerical vector representations of words where similar words have similar representations. Contextual word embeddings are the promising second-generation of word embeddings assigning a representation to a word based on its context. This can result in different representations for the same word depending on the context (e.g. river bank and commercial bank). There is evidence of social bias (human-like implicit biases based on gender, race, and other social constructs) in word embeddings. While detecting bias in static (classical or non-contextual) word …

Numerical Testcases To Study Proudman Resonance Using Shallow Water Models, Nicole Beisiegel, Jorn Behrens

Conference papers

Proudman resonance is the dominant mechanism behind meteotsunamis. We develop a comprehensive set of testcases to validate numerical methods focusing on the performance with respect to represent mentioned resonance. With the test cases we assess the wave amplification in dependence of characteristics of the pressure perturbation, model parameters, model resolution, and bathymetry characteristics. We use the compilation of tests to validate an adaptive discontinuous Galerkin (DG) model for the two-dimensional non-linear shallow water equations. As the tests are highly sensitive to model resolution, we use the adaptive mesh capabilities of the model to locally refine the disturbance and thus gain …

Using Circle Packings To Approximate Harmonic Measure Distribution Functions, Ella Wilson

Undergraduate Mathematics Day: Past Content

Harmonic measure distribution functions, h-functions, encode information about the geometry of domains in the plane. Specifically, given a domain and a basepoint in the domain, for a fixed radius, r, the value h(r) is the probability that a Brownian particle first exits the domain within distance r of the basepoint. There are many domains for which we can compute h-functions, such as the disk and the inside and outside of a wedge. However, exact computation is often difficult or impossible for more complicated domains, so we need methods to approximate these h-functions. In this paper, we develop two methods for …

Comparative Investigation Of Structure And Operating Parameters On The Performance And Reaction Dynamic Of Co Conversion On Silica Aerogel And Fumed-Silica-Supported Pd Catalysts, Rola Mohammad Al Soubaihi, Khaled M. Saoud, Joydeep Dutta

VCUarts Qatar Faculty Research

The catalyst morphology, metal-support interaction, and reaction conditions greatly influence the catalytic performance and reaction dynamics. Similarly, the dispersion of the metal within the support plays a crucial role in the thermal stability and sintering of the catalyst. Furthermore, temperature-dependent conversion hysteresis is well-known to occur during ignition and extinction of exothermic CO oxidation over supported Pd catalysts due to the variation of CO adsorption on the surface or bulk oxidation of Pd and the ability of the catalyst to regenerate the active sites. Herein, the catalytic performance and the hysteresis behavior of mesoporous silica aerogel supported Pd (Pd/a-SiO2), and …

Nlp@Vcu: Crop Characteristic Extraction Framework, Cora Lewis, Bridget Mcinnes, Getiria Onsongo

Summer REU Program

We developed a crop characteristic extraction framework. Starting from a custom SpaCy named entity recognition model, we added pre-trained word embeddings and a part-of-speech based entity expansion post-processing step. Then, we implemented an evaluation framework that functioned as a 5-fold cross validation wrapper for SpaCy custom training. Preliminary results showed improvement in the extraction framework after these additions.

Measuring The Social And Ecological Performance Of Agricultural Innovations On Rangelands: Progress And Plans For An Indicator Framework In The Ltar Network, S. Spiegal, N. P. Webb, E. H. Boughton, R. K. Boughton, A. Bentley Brymer, P. E. Clark, C. D. Holifield Collins, D. L. Hoover Et. Al

School of Natural Resources: Faculty Publications

No abstract provided.

Search For The Decay Bs0 →Ηη, B. Bhuyan, K. J. Nath, J. Borah, I. Adachi, H. Aihara, S. Al Said, D. M. Asner, H. Atmacan, V. Aulchenko, T. Aushev, R. Ayad, V. Babu, I. Badhrees, A. M. Bakich, P. Behera, J. Bennett, V. Bhardwaj, T. Bilka, J. Biswal

Faculty and Student Publications

We report results from a search for the decay Bs0→ηη using 121.4 fb-1 of data collected at the (5S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We do not observe any signal and set an upper limit on the branching fraction of 14.3×10-5 at 90% confidence level. This result represents a significant improvement over the previous most stringent limit.

Why People Tend To Overestimate Joint Probabilities, Olga Kosheleva, Vladik Kreinovich

Departmental Technical Reports (CS)

It is known that, in general, people overestimate the probabilities of joint events. In this paper, we provide an explanation for this phenomenon -- as explanation based on Laplace Indeterminacy Principle and Maximum Entropy approach.

How To Deal With Conflict Of Interest Situations When Selecting The Best Submission, Olga Kosheleva, Vladik Kreinovich

Departmental Technical Reports (CS)

In many practical situations when we need to select the best submission -- the best paper, the best candidate, etc. -- there are so few experts that we cannot simply dismiss all the experts who have conflict of interest: we do not want them to judge their own submissions, but we would like to take into account their opinions of all other submissions. How can we take these opinions into account? In this paper, we show that a seemingly reasonable idea can actually lead to bias, and we explain how to take these opinions into account without biasing the final …

What Is A Natural Probability Distribution On The Class Of All Continuous Functions: Maximum Entropy Approach Leads To Wiener Measure, Vladik Kreinovich, Saeid Tizpaz-Niari

Departmental Technical Reports (CS)

While many data processing techniques assume that we know the probability distributions, in practice, we often only have a partial information about these probabilities -- so that several different distributions are consistent with our knowledge. Thus, to apply these data processing techniques, we need to select one of the possible probability distributions. There is a reasonable approach for such selection -- the Maximum Entropy approach. This approach selects a uniform distribution if all we know is that the random variable if located in an interval; it selects a normal distribution if all we know is the mean and the variance. …

Macrocausality Implies Lorenz Group: A Physics-Related Comment On Guts's Results, Olga Kosheleva, Vladik Kreinovich

Departmental Technical Reports (CS)

It is known that, in the space-time of Special Relativity, causality implies Lorenz group, i.e., if we know which events can causally influence each other, then, based on this information, we can uniquely reconstruct the affine structure of space-time. When the two events are very close, quantum effects, with their probabilistic nature, make it difficult to detect causality. So, the following question naturally arises: can we uniquely reconstruct the affine structure if we only know causality for events which are sufficiently far away from each other? Several positive answers to this question were provided in a recent paper by Alexander …

Smoothed Bounded-Confidence Opinion Dynamics On The Complete Graph, Solomon Valore-Caplan

HMC Senior Theses

We present and analyze a model for how opinions might spread throughout a network of people sharing information. Our model is called the smoothed bounded-confidence model and is inspired by the bounded-confidence model of opinion dynamics proposed by Hegselmann and Krause. In the Hegselmann–Krause model, agents move towards the average opinion of their neighbors. However, an agent only factors a neighbor into the average if their opinions are sufficiently similar. In our model, we replace this binary threshold with a logarithmic weighting function that rewards neighbors with similar opinions and minimizes the effect of dissimilar ones. This weighting function can …

Multi-Agent Pathfinding In Mixed Discrete-Continuous Time And Space, Thayne T. Walker

Electronic Theses and Dissertations

In the multi-agent pathfinding (MAPF) problem, agents must move from their current locations to their individual destinations while avoiding collisions. Ideally, agents move to their destinations as quickly and efficiently as possible. MAPF has many real-world applications such as navigation, warehouse automation, package delivery and games. Coordination of agents is necessary in order to avoid conflicts, however, it can be very computationally expensive to find mutually conflict-free paths for multiple agents – especially as the number of agents is increased. Existing state-ofthe- art algorithms have been focused on simplified problems on grids where agents have no shape or volume, and …

Inhibitors Of Alpha-Synuclein Aggregation, Jemil Ahmed

Electronic Theses and Dissertations

Alpha-Synuclein (αS) – a neuronal, disordered, presynaptic protein – aggregates into amyloid fibrils and accumulates in the substantia nigra pars compacta of Parkinson's Disease (PD) patients. The aggregation and accumulation of αS amyloid fibrils leads to death of dopaminergic neurons; a hallmark of PD. Although it’s not clear why αS aggregates, prior studies have found that intrastriatal injection of fibril alone is sufficient to cause PD pathology in mouse and non-human primates models. These observations implicate αS as a therapeutic target against PD.

Unfortunately, there are three caveats when attempting to target αS. First, αS is a neuronal protein expressed …

Model-Based Testing Of Smart Home Systems Using Efsm, Cefsm, And Fsmapp, Afnan Mohammed Albahli

Electronic Theses and Dissertations

Smart Home Systems (SHS) are some of the most popular Internet of Things (IoT) applications. In 2021, there were 52.22 million smart homes in the United States and they are expected to grow to 77.1 million in 2025 [71]. According to MediaPost [74], 69 percent of American households have at least one smart home device. The number of smart home systems poses a challenge for software testers to find the right approach to test these systems. This dissertation employs Extended Finite State Machines (EFSMs) [6, 24, 105], Communicating Extended Finite State Machines (EFSMs) [68] and FSMApp [10] to generate reusable …

On Loop Commutators, Quaternionic Automorphic Loops, And Related Topics, Mariah Kathleen Barnes

Electronic Theses and Dissertations

This dissertation deals with three topics inside loop and quasigroup theory. First, as a continuation of the project started by David Stanovský and Petr Vojtĕchovský, we study the commutator of congruences defined by Freese and McKenzie in order to create a more pleasing, equivalent definition of the commutator inside of loops. Moreover, we show that the commutator can be characterized by the generators of the inner mapping group of the loop. We then translate these results to characterize the commutator of two normal subloops of any loop.

Second, we study automorphic loops with the desire to find more examples of …

Expanding The Network Evaluation Toolkit: Combining Social Network Analysis & Qualitative Comparative Analysis, Debbie Gowensmith

Electronic Theses and Dissertations

Collective action networks are complex systems of interrelated individuals or groups that come together for a common social change purpose (Ernstson, 2011). Researchers have used social network analysis (SNA) to examine the relationship structures and characteristics of collective action networks. However, determining whether collective action networking produces outcomes has been challenging because networks are complex, affected by context, and produce interdependent data. I addressed these challenges by pairing SNA with qualitative comparative analysis (QCA), a configurational comparative method. Using QCA, researchers can tease out which conditions are necessary or sufficient to produce an outcome. I analyzed a collective action network …

Characterization Of Cyclopropyl Synthases Involved In The Maturation Of Ribosomally Synthesized And Posttranslationally Modified Peptides, Yi Lien

Electronic Theses and Dissertations

Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a large class of natural products with significant human health implications. RiPPs are synthesized from a genetically encoded precursor peptide that undergoes significant modifications by maturing enzymes, or maturases. Recently, radical-S-adenosylmethionine (rSAM) enzymes have emerged as an important family of RiPP maturases. rSAM enzymes have been shown to install ether, thioether, and carbon-carbon bonds on the precursor peptide. These modifications usually define the backbone structure of the mature RiPP. This thesis describes the characterization of a novel RiPP modification catalyzed by the radical S-adenosylmethionine enzyme TigE. TigE belongs to the TIG biosynthetic …

Using The Fraction Of Missing Information (Fmi) In Selecting Auxiliary Variables To Impute Missingness In Confirmatory Factor Analysis (Cfa), Dareen Taha Alzahrani

Electronic Theses and Dissertations

This study aimed to investigate the effectiveness of using the fraction of missing information (FMI) to select auxiliary variables in imputing missing data in confirmatory factor analysis (CFA). This was done by conducting two studies (a simulation study and an empirical study). A Monte Carlo simulation technique was used to compare the performance and the effect of the restrictive strategy based on FMI and the inclusive strategy on parameter estimate bias and parameter estimate efficiency. The missing data mechanisms, missing data proportion, correlation strength between the analysis variables and auxiliary variables, and the inclusive and restrictive strategies were assessed in …

Could Alexa Increase Your Social Worth?, Peter Tripp

Electronic Theses and Dissertations

People have historically used personal introductions to build social capital, which is the foundation of career networking and is perhaps the most effective way to advance a career (Lin, 2001). With societal changes, such as the pandemic (Venkatesh & Edirappuli, 2020), and the increasing capabilities of Artificial Intelligence (AI), new approaches may emerge that impact societal relationships. Social capital theory highlights the need for reciprocal agreements to establish the trust between parties (Gouldner, 1960). My theoretical prediction and focus of this research include two principles: The impact of reciprocity in evaluating trust of the source of the introduction and the …

Understanding The Impacts Of Urban Agriculture In Gentrifying Neighborhoods In Denver, Kate Johnson

Electronic Theses and Dissertations

Urban Agriculture is prominent in cities across the United States and has been studied in relation to food security, sustainability, and gentrification. Urban agriculture is context specific and can include individual gardens, community gardens, guerilla gardening, and urban farms. Urban agriculture is a product of the community it is based in, depending on politics, history, and social environments. For these reasons, the relationship between urban agriculture and the community is an area where more research is needed. This thesis explores the role visible gardens play in community building, sustainability, and food security in gentrifying neighborhoods in Denver. Through qualitative methods …

Digital Searching: A Grounded Theory Study On The Modern Search Experience, Nicolas Armando Parés

Electronic Theses and Dissertations

This Grounded theory study explores US adults' modern information search process as they pursue information through digital search user interfaces and tools. To study the current search process, a systematic grounded theory methodology and two data collection methods, a think-aloud protocol and semi-structured interviews, are used to develop the theory. The emerging theory addressed two tightly connected research questions that asked, “What is the process by which humans search and discover information?” and “What is the process by which search and discovery interfaces and tools support the modern search process?”

The study collects participant data from US adults who have …

Classification Of Electropherograms Using Machine Learning For Parkinson’S Disease, Soroush Dehghan

Electronic Theses and Dissertations

Parkinson’s disease (PD) is a neurodegenerative movement disorder that progresses gradually over time. The onset of symptoms in people who are suffering from PD can vary from case to case, and it depends on the progression of the disease in each patient. The PD symptoms gradually develop and exacerbate the patient’s movements throughout time. An early diagnosis of PD could improve the outcomes of treatments and could potentially delay the progression of this disorder and that makes discovering a new diagnostic method valuable. In this study, I investigate the feasibility of using a machine learning (ML) approach to classify PD …

Directly Polymerizable Co Releasing Molecules, Jackson Snow

Electronic Theses and Dissertations

Despite the commonly held consensus that carbon monoxide (CO) is toxic, it has been shown to be an essential signaling molecule in the human neuronal system and has been noted to have anti-inflammatory properties, act as a vasodilator, have anti-proliferative impacts on tumors, and many other beneficial effects. The current limitation to using CO as a therapeutic molecule is delivering the proper dosages using CO releasing molecules (CORMs) without exhibiting toxicity. The first chapter of this thesis will review the biological significance of CO in biological systems, the limitations of existing CORMs, and the properties of diphenylcyclopropenone (DPCP) that make …

Frequency Analysis Of Trabecular Bone Structure, Daniel Parada San Martin

Electronic Theses and Dissertations

Medical data is hard to obtain due to privacy laws making research difficult. Many databases of medical data have been compiled over the years and are available to the scientific community. These databases are not comprehensive and lack many clinical conditions. Certain type of medical conditions are rare, making them harder to obtain, or are not present at all in the aforementioned databases. Due to the sparsity or complete lack of data regarding certain conditions, research has stifled. Recent developments in machine learning and generative neural networks have made it possible to generate realistic data that can overcome the lack …

Humanizing Computational Literature Analysis Through Art-Based Visualizations, Alexandria Leto

Electronic Theses and Dissertations

Inequalities in gender representation and characterization in fictional works are issues that have long been discussed by social scientists. This work addresses these inequalities with two interrelated components. First, it contributes a sentiment and word frequency analysis task focused on gender-specific nouns and pronouns in 15,000 fictional works taken from the online library, Project Gutenberg. This analysis allows for both quantifying and offering further insight on the nature of this disparity in gender representation. Then, the outcomes of the analysis are harnessed to explore novel data visualization formats using computational and studio art techniques. Our results call attention to the …

Local-Global Results On Discrete Structures, Alexander Lewis Stevens

Electronic Theses and Dissertations

Local-global arguments, or those which glean global insights from local information, are central ideas in many areas of mathematics and computer science. For instance, in computer science a greedy algorithm makes locally optimal choices that are guaranteed to be consistent with a globally optimal solution. On the mathematical end, global information on Riemannian manifolds is often implied by (local) curvature lower bounds. Discrete notions of graph curvature have recently emerged, allowing ideas pioneered in Riemannian geometry to be extended to the discrete setting. Bakry- Émery curvature has been one such successful notion of curvature. In this thesis we use combinatorial …

Bicycles And Transit: Weather Or Not: A Study On The Effect Of Weather And Air Quality On Bicycle-Transit, Bicycle, Rail Transit Counts In Denver, Christiana M. Fairfield

Electronic Theses and Dissertations

The movement of people and goods within metropolitan areas is critically important to the operational efficiency and functionality of cities. This study explores the influence of local weather conditions and the air quality index on bicycle-transit user in Denver, Colorado. Based on bicycle-transit having two key components, bicycle and transit, the effect of local weather conditions and the air quality index is also explored with bicycle use and rail-transit usage. Key findings include: (1) the most significant variable across all three modes is temperature, (2) for bicycle-transit and bicycle use, there is a steady increase in ridership as temperatures increase …