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Multiscale Design of Responsive and Shape-Morphing Materials
Get PDFResponsive materials have attracted significant attention as platforms for soft robotic systems, biomedical devices, and reconfigurable structures, among other applications. To tailor their functionality, these materials are often engineered to exhibit non-trivial shape-morphing to enable behaviors such as actuation and locomotion, where the material itself acts as the sensor and controller. However, implementation of these materials has so far been hindered by 1) limited response mechanisms that are stable, reversible, and reprogrammable and 2) shape-morphing that is restricted to a relatively small number of target geometries with relatively low complexity. This thesis aims to expand the response mechanisms available in the design of materials and to translate molecular scale responses into macroscopic shape change that gives rise to targeted mechanical behavior.
This work begins by introducing a design for hydrogels that swell and shrink in response to visible light irradiation by taking advantage of photoreversible host-guest chemistry. We then demonstrate designs for microfabrication of light-triggered bending actuators and for light-patternable wrinkling instabilities. However, these hydrogels rely on the presence of β-cyclodextrin to achieve significant light response. To address this, we next investigate another design for visible light responsive hydrogels based on ortho-substituted azobenzenes, which exhibit volume change without relying on host-guest complexation. We further demonstrate a scheme for the synthesis of these ortho-substituted azobenzenes containing di-functional polymerizable groups, with potential applicability in visible light responsive, main-chain polymeric materials.
Next, a design concept for mechanical metamaterials with switchable rigidity is introduced. We fabricate single 2D unit cells on the macroscale and show that their behavior is consistent with numerical models. The concept is further illustrated with a microfabricated 3D lattice superstructure, and by incorporating a temperature-responsive hydrogel to achieve in-situ tuning of rigidity. Finally, we explorethe fabrication of minimal, non-Euclidean surfaces using silicone elastomers. The surfaces possess a broken symmetry, which gives rise to a zero elastic energy deformation mode. The free and forced dynamics of this zero-energy mode are investigated.
Overall, the findings presented in this work demonstrate progress towards improving response mechanisms in soft materials, and designing new shape-morphing motifs from which exotic mechanical properties can emerge.</p
New Paradigms in Quantum Education for the Second Quantum Revolution
Get PDFQuantum information science (QIS) is an emerging field of research and education at the intersection of physics, electrical engineering, computer science, and beyond (e.g. math, chemistry, materials science) that leverages the fundamental laws of quantum mechanics to surpass classical limitations on information processing. The rising stature of this field in the 2020s, recognized by the 2025 UN International Year of Quantum Science and Technology (IYQ), provides an impetus to rethink the way we teach quantum physics in the classroom and in society. At the same time, the rapid growth of QIS education programs and the infusion of government and private-sector funding for QIS workforce development provides a rare opportunity for the physics education research (PER) community to be involved in curriculum development from the beginning.
In Ch. 0, I outline a vision of “quantum education for H.E.R.”: an acronym for what I have come to believe are three core values that QIS education should strive to embody. First, quantum education ought to be holistic, striving to help students gain content fluency (Ch. 4), hands-on research skills (not the subject of this dissertation), and critical thinking for relating quantumtechnologies development to societal impacts (Appendix A) simultaneously. Second, in recognition of the need to diversify the quantum workforce as both an ethical and practical imperative, QIS education ought to be equity-oriented (Ch. 3 and 5). Finally, central to the focus of all chapters of this thesis, QIS education and particularly curriculum and assessment development should be research-based.
In the remaining chapters of this thesis, I discuss the contributions of my research toward the realization of this vision, with a central emphasis on development of the Quantum Computing Conceptual Survey (QCCS) validated assessment. Ch. 1 provides a brief overview of the historical, physical, and technological context of the Second Quantum Revolution, followed by a detailed review of existing QIS education literature to date. The remainder of the thesis is divided roughly into two main sections. Ch. 2 and 3 discuss methodologies and findings of initial scoping studies designed to help our team better understand the field of QIS education in the US. Ch. 4 and 5, meanwhile, center on the development, refinement, and validation of the Quantum Computing Conceptual Survey (QCCS), the first research-based assessment instrument developed to specifically measure student understanding of QIS fundamentals. The conclusion (Ch. 6) returns to the key themes of holistic, equity-oriented, and research-based quantum education and explores how the work done so far in this thesis contributes to this vision, the outlook for future scholarship in QIS education, and key takeaways for educators and policymakers.</p
On the Real Roots and Real Eigenvalues of the Generalized Large Box Model for Random Polynomials and Random Matrices
Get PDFLet n and N be in N, and for 0 ≤ i ≤ n−1, let αi < βi ∈ R. Consider the monic polynomial in a single complex variable of the form fn(z) = zn + an−1zn−1 +··· +a1z +a0 whose coefficients ai are uniformly distributed on [αiN,βiN]∩Z for each 0 ≤ i ≤ n−1 and jointly independent. This random polynomial model is referred to as the generalized large box model. When instead αij < βij for 1 ≤ i,j ≤ n and one considers the n-by-n random matrix whose entries are uniformly distributed on [αijN,βijN] ∩ Z for each 1 ≤ i,j ≤ n and jointly independent, we say that the matrix is drawn from the generalized large box model ensemble.
This thesis is organized into five chapters. Chapter 1 develops and presents the history of the relevant random polynomial and random matrix models, related results, and notation.
Chapters 2 and 3 are concerned with finding the probability that random polynomials whose coefficients obey the generalized large box model have all real roots, as N → ∞. Specifically, in Chapter 2, discriminant and root analysis methods are applied to low degree polynomials, obtaining explicit answers. These methods further find an extremely dominant root, denoted by ξn, for all degrees; this is a root whose modulus is not tight as N → ∞, while the moduli of the remaining roots are tight as N → ∞. This expands upon on a discovery made by Dubickas and Sha [Exp. Math., 24(3):312–325, 2015]. As N → ∞, we show that ξn is real with probability tending to 1 and that |ξn + an−1| converges in distribution to |X/Y |, where X is uniformly distributed on [αn−2,βn−2], Y is uniformly distributed on [αn−1,βn−1], and X and Y are independent.
In Chapter 3, we consider non-monic degree n−1 polynomials whose coefficients are uniformly distributed on [αi,βi] for 0 ≤ i ≤ n − 1 and jointly independent, referred to as generalized bounded height model polynomials. As N → ∞, the probability that the degree n generalized large box model polynomial with coefficients uniformly distributed on [αiN,βiN] ∩ Z for 0 ≤ i ≤ n−1 and jointly independent has all real roots converges to the probability that the degree n − 1 generalized bounded height model polynomial with coefficients uniformly distributed on [αi,βi] for 0 ≤i≤n−1andjointly independent has all real roots. The methods of Bert´ok, Hajdu, and Peth¨o [J. Number Theory, 179:172–184, 2017] are used to express this probability in terms of an integral formula. For the special case when αi = 0 and βi = 1 for 0 ≤ i ≤ n−1, a relation to the Selberg integral is explored and we show that the probability of such a polynomial having all real roots is positive and monotonically decreasing in n.
In Chapters 4 and 5, the analogous question of the probability that the random matrix whose entries are drawn from the generalized large box model ensemble has all real eigenvalues is considered. In Chapter 4 we begin by letting αij < βij for 1 ≤ i,j ≤ n and consider the n-by n random matrix whose entries are uniformly distributed on [αij,βij] for each 1 ≤ i,j ≤ n and jointly independent. This matrix ensemble is referred to as the generalized bounded height ensemble. Using Edelman’s method [J. Multivariate Anal., 60(2):203–232, 1997], we factor these matrices into their real Schur decomposition and present an integral formula for the probability that generalized bounded height ensemble matrices have all real roots. In Chapter 5, we show that if A is an n-by-n random matrix with entries that are uniformly distributed on [αijN,βijN] ∩ Z for 1 ≤ i,j ≤ n and jointly independent and B is an n-by-n random matrix with entries that are uniformly distributed on [αij,βij] for 1 ≤ i,j ≤ n and jointly independent, then for each 0 ≤ k ≤ n, as N →∞,theprobability that A has exactly k real eigenvalues converges to the probability that B has exactly k real eigenvalues. Moreover, the empirical spectral measure of A/N converges weakly in distribution to the empirical spectral measure of B and the joint distribution of the eigenvalues of A/N converges in distribution to the joint distribution of the eigenvalues of B.
Finally, still in Chapter 5, we consider rank one perturbations of the random matrix A whose entries are all independently and identically (iid) uniformly distributed on [−N,N]∩Z. We say that Ais drawn from the large box model ensemble. Letting P be the matrix whose entries are all µN, we consider the limiting spectral behavior of A+P in the three cases where µN/N → ∞,µN/N → 0, and µN/N → c, for c ∈ R. If limN→∞ µN N =∞, the eigenvalues of A+P µN converge almost surely to the eigenvalues of P/µN, and the largest eigenvalue (in magnitude) is real with probability tending to 1. Additionally, the centered and correctly normalized largest eigenvalue of A + P converges in distribution to a Bates distribution with n2 parameters. If limN→∞ µN N =0, the empirical spectral measures of A+P N and A N both converge weakly in distribution to the empirical spectral measure of the matrix whose entries are iid and uniformly distributed on [−1,1]; the joint distribution of the eigenvalues of A N and A+P N both converge in distribution to the joint distribution of eigenvalues of the same random matrix. If limN→∞ µN N =c>0,the empirical spectral measure of A+P N converges weakly in distribution to the empirical spectral measure of the matrix whose entries are iid and uniformly distributed on [−1 + c,1 + c]. In addition, if c > 12, we show that as N → ∞, A+P N has exactly one real outlier eigenvalue and provide a range for its location.</p
An Analysis of the Phonological Loanword Process of English Technological Words Into French
Get PDFTechnology has been a tool that has shaped humanity and communication. The invention of the Internet drastically changed the speed and ease of communication across large spans of distances. This opened up a new method of communication. Internet-based communication allowed language to spread across the globe. This language contact created a new method that fell within its domain of communication and vocabulary. Social media, streaming, virtual communication, and Internet-based operations were spread through language contact. This study aims to describe how Internet communication, specifically the impact of YouTube, has affected loanword acquisition of these English technological words into French. Furthermore, this study demonstrates the importance of phonological inventory in resolutions of inventory constraints between English and French. In observations of 933 tokens of 18 loanwords, it was found that loanwords that were used more in both English and French had a smaller edit distance between English and the French loanword, that phonological inventory and inventory constraints were the main causes of changes in the adaptation process, and that loans borrowed after the popularization of YouTube had smaller edit distances, and thus were more similar to English pronunciations.</p
Computational Methods of Optimization and Geometry Processing for Physics Applications
Get PDFThis thesis presents novel computational methods in two distinct, yet not disjoint subfields of applied mathematics, and is consequently divided into two parts.
In Part I, we consider methods of numerical optimization as applied to problems in scientific experimentation, in which a limited quantity of available resources must be carefully allocated to maximize the performance of the experiment. In the first chapter of Part I, this takes the form of discovering optimized ultrasound transmission sequences which, when imaged in the REFoCUS framework, produce high quality images. In the second chapter of Part I, this takes the form of discovering optimized measurement protocols for the verification of quantum states through fidelity estimation.
In Part II, we consider methods of computational geometry as applied to problems in multiphysics simulation, in which geometrically complex objects must be computationally handled in a way that is reliable and robust to numerical imperfection. In the first and second chapter of Part II, we develop methods of evaluating the generalized winding number for general curves and surfaces, from which we derive methods of determining containment for geometric objects which otherwise do not define an interior volume. In the third chapter of Part II, we develop a method of 3D material interface reconstruction by means of optimally defining a collection of half-spaces whose convex intersection has geometric moments as close as possible to provided reference data.</p
Embodied Carbon Emissions Benchmarks of Residential and Commercial Reference Buildings in the United States
Get PDFBuildings are responsible for 40% of global emissions. Embodied carbon (EC) emissions, or the emissions associated with the extraction, manufacture, use, and disposal of materials, represent 13% of global emissions, signifying an important priority for decarbonizing buildings. Despite its high global emissions, EC remains underrepresented in research, policy, and design relative to operational energy and carbon. EC benchmarks, which provide reference points for emissions in building construction, are a critical tool for quantifying and comparing the EC emissions of ‘typical’ building construction. This dissertation explores the central research question of ‘What are the EC emissions of representative archetypal buildings in the US?’ by establishing theoretical, science-based benchmarks for key US building typologies.
This dissertation proposes and implements a methodology for defining theoretical, science-based benchmarks through the use of material quantity takeoffs, deterministic life cycle assessment (LCA), and probabilistic LCA. The benchmarks proposed in this dissertation represent the three most commonly constructed building typologies in the US: single-family residential, commercial office, and multifamily residential apartment buildings. The scope of the LCAs conducted herein primarily account for a building’s foundation, core, and shell, and consider both cradle-to-gate and cradle-to-grave emissions. The key metrics associated with these benchmarks are deterministic material use intensity (MUI, kg/m2) results and both deterministic and probabilistic embodied carbon intensities (ECI, kgCO2e/m2) representing different building designs, LCA tools, and building typologies. This dissertation also considers biogenic carbon storage and whole-life energy and carbon emissions. Chapter II is an investigation of the literature pertaining to EC benchmarking efforts globally and it summarizes the limitations of existing benchmarks. Chapter III establishes MUI and cradle-to-gate ECI benchmarks for single-family residential buildings. Chapter IV extends this analysis to a cradle-to-grave scope, as well as whole-life carbon and whole-life energy impacts. Chapter V applies a cradle-to-grave analysis to commercial office buildings, while also addressing design variability by modeling structural material choices and lateral loading scenarios. Chapter VI develops benchmarks for multifamily residential apartment buildings, and features parametric design that accounts for material quantity variability. Chapters III, V, and VI each consider uncertainty and variability in embodied carbon coefficients.
Findings reveal that EC results are highly dependent on building typology and design parameters, such as primary structural material, substructure type, and bay size. Deterministic cradle-to-gate ECIs range from 39 to 121 kgCO2e/m2 for single-family residential buildings, 114 to 337 kgCO2e/m2 for commercial office buildings, and 89 to 715 kgCO2e/m2 for multifamily residential buildings. Each chapter details critical differences in ECI per material, building design, and LCA tool. The probabilistic LCA results underscore the variability in LCA data and enable comparative statistical analyses.
This dissertation establishes a replicable framework for establishing theoretical EC benchmarks for buildings in the US. These benchmarks provide a foundation for building emissions comparisons, policy development, and stock-level analyses. The underlying methodologies enable future updates and expansions to the scope of this study to test alternative design strategies and new LCA data.</p
Robust Inference Methods with Applications to Synthetic Controls
Get PDFThis dissertation contains three chapters that develop novel estimation and inference methods for Synthetic Control Estimators, as well as techniques for robust inference that are more generally applicable. The first chapter ‘A Method of Moments Approach to Asymptotically Unbiased Synthetic Controls' introduces a new Synthetic Control Estimator, which is constructed using a General Method of Moments approach where units not being included in the Synthetic Control are used as instruments. I show that my Synthetic Control Estimator will be asymptotically unbiased as the number of pre-treatment time periods goes to infinity, and if both the number of post-treatment time periods goes to infinity as well, then the average of treatment effect can be consistently estimated. I provide a model selection procedure for deciding whether a unit should be used as an instrument or as a control. The second chapter ‘Robust Inference when Nuisance Parameters may be Partially Identified with Applications to Synthetic Controls' studies conducting inference for the average treatment effect on the treated with a Synthetic Control Estimator, where the vector of control weights is a nuisance parameter which is often constrained, high dimensional, and may be only partially identified even when the average treatment effect on the treated is point-identified. I provide a new method yielding asymptotic normality for an estimate of the parameter of interest, even when all three of these complications are present. This is accomplished by first estimating the nuisance parameter using a regularization penalty to achieve a form of identification, and then estimating the parameter of interest using moment conditions that have been orthogonalized with respect to the nuisance parameter. The third chapter ‘A General Approach to Conducting Inference when the Parameter is Near or at the Boundary' I develop and extend Wald, Conditional Likelihood Ratio, and Conditional Lagrange Multiplier tests using a quasi-unconstrained estimator, which is asymptotically normal even when the true parameter vector is near or at the boundary. I show that these tests control asymptotic size in a uniform sense. Furthermore, I extend existing work analyzing the power properties of these test when the parameter is at the boundary.</p
Transport and Phase-State of Organic Chemical Compounds in Indoor and Outdoor Environments
Get PDFAir quality (AQ) plays an important role in health and climate outcomes. The World Health Organization (WHO) estimates that 99% of humans live in areas where AQ exceeds healthy limits. The effects of poor indoor and outdoor AQ are associated with seven million annual premature deaths. This thesis presents three studies which aim to increase our understanding of AQ through studies of the chemistry, chemical transport, and phase-state in indoor and outdoor environments.
In the first project, a laboratory study of VOC oxidation was used to assess the functionality of four common vapor pressure estimation methods. These methods, EVAPORATION, SIMPOL, SPARC, and Nannoolal, were assessed for their impact on secondary organic aerosol yields modeled in two chemical systems: C8–C14 1-alkenes and C9– C15 2-methyl-1-alkenes reactions with OH radicals in the presence of NOx. The modeled results indicated poor to moderate model-measurement agreement for all methods and indicated decreasing model efficacy with increasing chemical functionality.
The second project studied the development of indoor surface films in a lecture hall at the University of Colorado, Boulder. The goal of the study was to assess how several sources contribute to these films. Diurnal samples were collected over one week and results indicated that films developed more quickly during the day than at night but that contributions to the horizontal films from four sources were roughly the same: ~60% insoluble particles (IP), ~2% organic particles from the supply air (OPSup), ~8% condensed SVOC (COC), and ~30% organic particles with indoor sources (OPRoom).
In the third project, the surface film and aerosol samples collected from the second project were analyzed with High Performance Liquid Chromatography coupled to an Iodide Chemical Ionization Mass Spectrometer with a Vaporization Inlet for Aerosols (HPLC-VIA-CIMS). The data were used for mass balancing of the organic categories only, the results of which were in good agreement with the results determined in the second project: ~8% OPSup, ~15% COC, and ~77% OPRoom. Eight potential chemical formulas were also identified from the high-resolution MS data and tracked across all samples to illustrate their transport and contribution to the films. The results exemplify the complex chemical make-up of these rapidly developing films and the importance of continued research to fully understand their contribution to indoor environments. </p
Temporal Dynamics in Surface Water – Groundwater Interactions Inferred From High-Resolution Observations in Streambank Wells
Get PDFGains in streamflow from groundwater and, conversely, losses of streamflow to groundwater, have wide-ranging implications for water quantity and quality. Studies have revealed the potential for stream water levels and adjacent nearby groundwater elevations to be used in conjunction for studying this phenomenon across vast spatial scales based on inferred lateral hydraulic gradients. However, previous studies have used only snapshots in time of these elevations, which may not capture the temporal variability of these processes. This study uses high-resolution observations of stream and nearby groundwater elevations from multiple years across 5 snowmelt-dominated watersheds in the intermountain west to study the seasonal changes in gradients between surface water and groundwater. We found that at every site there were substantial changes in the magnitude and direction of these gradients at seasonal to weekly timescales, usually corresponding to times when stream elevations are changing greatly, such as during snowmelt runoff. This shows that while individual measurements can be useful in revealing these dynamics, high temporal resolution observations are required to capture them accurately. This method further shows the utility of collecting paired surface and groundwater elevations. We also developed a simple metric using the change in surface water and groundwater elevations to evaluate stream-aquifer response to watershed scale processes.</p
The Effect of LED Pulse-Width Modulation of Light on Visual Performance
Get PDFTemporal light modulation (TLM), commonly referred to as "flicker" can create visual discomfort, worsened reading time and accuracy, erratic eye movements, and headaches, among others. In most new construction projects, LED luminaires are being specified in conjunction with a pulse-width modulation (PWM) dimming system. While PWM systems have controllability and energy efficiency advantages over constant current dimming systems, they intentionally introduce TLM into the space due to the varying duty cycle of the LED waveform. To evaluate the impact of TLM likely present in workspaces with LED dimming, we measured reading time and the number of reading mistakes made during a reading task when participants were exposed to LED luminaires with different levels of duty cycle that mimic those in a traditional office setting. Interestingly, there was not sufficient statistical evidence to infer a relationship exists between the duty cycle of an LED light source and the reading time and accuracy of the participants. These findings contribute to the inconsistent results on the effects of TLM in the architectural lighting literature, likely due to the many combinations of environmental variables possible for evaluating human performance under TLM. This suggests that the development of metrics, predictive equations, and TLM standards is necessary for refining experimental research in the area and ultimately understanding the effects of pulse-width modulation on human visual performance.</p
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