Engineering Commons^™

Understanding The Role Of Atom Trapping In The Evolution Of Hydrocarbon Transformation Catalyst Morphology, Griffin Canning

Chemistry and Chemical Biology ETDs

Converting alkanes to other, more chemically and economically valuable molecules requires catalysts that can survive elevated temperatures and highly reducing environments. These environments can cause many metal-nanoparticle based catalysts to sinter rapidly, causing a loss of activity. They must also tolerate the coke formation, as well, since coke can restrict access to active sites by gas phase molecules, thus lowering catalytic activity. While there are routes to improve both the sinter and coke resistance of catalysts, an alternative strategy is to develop a protocol for regenerating the activity of the catalyst in question when coke formation or sintering becomes problematic. …

Atom Trapping And Its Role On The Nucleation & Growth Of Platinum Nanoparticles, Deepak Kunwar

Chemistry and Chemical Biology ETDs

Diesel oxidation catalysts deactivate due to Pt sintering, a major problem in automotive industries. To make sure they operate effectively throughout the lifetime of the vehicle, automotive industries are putting an excessive amount of Pt. There is a need to develop a catalyst that serves long term performance with minimal use of Pt. Jones et al^.1 demonstrated that ceria traps Pt atoms. His work generated some logical and valid questions such as what is the mechanism for the formation of anomalously large Pt particles? What is the upper limit of Pt metal loading in the form of single atoms …

Radial Basis Densities And The Density Functional-Based Atom-In-Molecule: Designing Charge-Transfer Potentials, Godwin Amo-Kwao

Nanoscience and Microsystems ETDs

Classical potentials that are capable of describing charge transfer and charge polarization in complex systems are of central importance for classical atomistic simulation of biomolecules and materials. Current potentials—regardless of the system—do not generalize well, and, with the exception of highly-specialized empirical potentials tuned for specific systems, cannot describe chemical bond formation and breaking. The charge-transfer embedded atom method (CT-EAM), a formal, DFT-based extension to the original EAM for metals, has been developed to address these issues by modeling charge distortion and charge transfer in interacting systems using pseudoatom building blocks instead of the electron densities of isolated atoms. CT-EAM …

Integrating Deep Learning And Augmented Reality To Enhance Situational Awareness In Firefighting Environments, Manish Bhattarai

Electrical and Computer Engineering ETDs

We present a new four-pronged approach to build firefighter's situational awareness for the first time in the literature. We construct a series of deep learning frameworks built on top of one another to enhance the safety, efficiency, and successful completion of rescue missions conducted by firefighters in emergency first response settings. First, we used a deep Convolutional Neural Network (CNN) system to classify and identify objects of interest from thermal imagery in real-time. Next, we extended this CNN framework for object detection, tracking, segmentation with a Mask RCNN framework, and scene description with a multimodal natural language processing(NLP) framework. Third, …

"A Comparison Of Variable Selection Methods Using Bootstrap Samples From Environmental Metal Mixture Data", Paul-Yvann Djamen

Mathematics & Statistics ETDs

In this thesis, I studied a newly developed variable selection method SODA, and three customarily used variable selection methods: LASSO, Elastic net, and Random forest for environmental mixture data. The motivating datasets have neuro-developmental status as responses and metal measurements and demographic variables as covariates. The challenges for variable selections include (1) many measured metal concentrations are highly correlated, (2) there are many possible ways of modeling interactions among the metals, (3) the relationships between the outcomes and explanatory variables are possibly nonlinear, (4) the signal to noise ratio in the real data may be low. To compare these methods …

Advanced Parallel Algorithms In Computational Electromagnetics, Shu Wang

Electrical and Computer Engineering ETDs

The rapid development of high performance computing has pushed the computational electromagnetic(CEM) towards high accuracy, high fidelity and extreme computational scales. There is a great need for existing CEM solvers to have enhanced parallelism and scaling capability. The purpose of this dissertation is to investigate advanced parallel algorithms for both frequency and time domain solvers.

In frequency domain, this work first develop the underpinnings of parallel preconditioning technique and high-order transmission condition in the context of multi-solver scheme. The result is a computing resource-aware and implementation wise compact solver. Then this work targeted at developing efficient algorithms for cases where …

Methods Of Uncertainty Quantification For Physical Parameters, Kellin Rumsey

Mathematics & Statistics ETDs

Uncertainty Quantification (UQ) is an umbrella term referring to a broad class of methods which typically involve the combination of computational modeling, experimental data and expert knowledge to study a physical system. A parameter, in the usual statistical sense, is said to be physical if it has a meaningful interpretation with respect to the physical system. Physical parameters can be viewed as inherent properties of a physical process and have a corresponding true value. Statistical inference for physical parameters is a challenging problem in UQ due to the inadequacy of the computer model. In this thesis, we provide a comprehensive …

Generation Of Correlated Dual Frequency Combs With Pm Fiber Lasers For High-Precision Metrology, Hanieh Afkhamiardakani

Optical Science and Engineering ETDs

Intracavity Phase Interferometry (IPI) using two correlated, counter-propagating frequency combs (pulse trains) in mode-locked lasers has evolved into a powerful technique for high-precision metrology. In this method a physical parameter to be measured imparts a phase shift onto a pulse circulating in the laser cavity. Inside a laser cavity, that phase shift becomes a frequency shift (phase shift/round-trip time) applied to the whole frequency comb created by this pulse as it exits the cavity at each round-trip. This frequency shift is measured by interfering this comb with a reference comb created by a reference pulse circulating in the same mode-locked …

Radiation-Balanced Fiber Lasers And Amplifiers, Esmaeil Mobini Souchelmaei Mr

Optical Science and Engineering ETDs

Over the past decades, high-power fiber lasers and amplifiers have been extensively under research to achieve higher output powers. However, temperature rise in the core of fiber lasers and amplifiers has been a big issue in power-scaling. Radiation-balancing is a viable technique introduced for effective heat mitigation in lasers and amplifiers by S. Bowman in 1995. Radiation-balancing relies on solid-state laser cooling as a self-cooling mechanism to mitigate the generated heat in lasers and amplifiers. To implement the mentioned idea in fiber lasers and amplifiers, a set of issues should be scrutinized; (i) the amenability of silica glass (as the …

A Statistical Analysis Of The Unm Facets Design Identity & Beliefs Survey Data, Clarissa A. Sorensen-Unruh

Mathematics & Statistics ETDs

The NSF-funded FACETS (Formation of Accomplished Chemical Engineers for Transforming Society, NSF Award 1623105) grant aims to transform the undergraduate engineering experience in the Department of Chemical and Biological Engineering at the University of New Mexico to address attrition within engineering majors, especially among underserved populations (Brainard & Carlin, 1998). The UNM FACETS Design Identity & Beliefs survey, an assessment tool used as part of the research of the grant, generated the dataset used in this study. I performed several different statistical analyses on the dataset, including confirmatory factor analysis (CFA), principal component analysis (PCA), and cluster analysis. The …

Target Control Of Networked Systems, Isaac S. Klickstein

Mechanical Engineering ETDs

The control of complex networks is an emerging field yet it has already garnered interest from across the scientific disciplines, from robotics to sociology. It has quickly been noticed that many of the classical techniques from controls engineering, while applicable, are not as illuminating as they were for single systems of relatively small dimension. Instead, properties borrowed from graph theory provide equivalent but more practical conditions to guarantee controllability, reachability, observability, and other typical properties of interest to the controls engineer when dealing with large networked systems. This manuscript covers three topics investigated in detail by the author: (i) the …

Applications Of The Negatively-Charged Silicon Vacancy Color Center In Diamond, Forrest A. Hubert

Optical Science and Engineering ETDs

The spatial resolution and fluorescence signal amplitude in stimulated emission depletion (STED) microscopy is limited by the photostability of available fluorophores. Here, we show that negatively-charged silicon vacancy (SiV) centers in diamond are promising fluorophores for STED microscopy, owing to their photostable, near-infrared emission and favorable photophysical properties. A home-built pulsed STED microscope was used to image shallow implanted SiV centers in bulk diamond at room temperature. We performed STED microscopy on isolated SiV centers and observed a lateral full-width-at-half-maximum spot size of 89 ± 2 nm, limited by the low available STED laser pulse energy (0.4 nJ). For a …

Nonlinear Least Squares 3-D Geolocation Solutions Using Time Differences Of Arrival, Michael V. Bredemann

Mathematics & Statistics ETDs

This thesis uses a geometric approach to derive and solve nonlinear least squares minimization problems to geolocate a signal source in three dimensions using time differences of arrival at multiple sensor locations. There is no restriction on the maximum number of sensors used. Residual errors reach the numerical limits of machine precision. Symmetric sensor orientations are found that prevent closed form solutions of source locations lying within the null space. Maximum uncertainties in relative sensor positions and time difference of arrivals, required to locate a source within a maximum specified error, are found from these results. Examples illustrate potential requirements …

Mid-Ir Optical Refrigeration And Radiation Balanced Lasers, Saeid Rostami

Optical Science and Engineering ETDs

This dissertation reports recent advances in mid-infrared (mid-IR) optical refrigeration and Radiation Balanced Lasers (RBLs). The first demonstration of optical refrigeration in Ho:YLF and Tm:YLF crystals as promising mid-IR laser cooling candidates is reported. Room temperature laser cooling efficiency of Tm- and Ho-doped crystals at different excitation polarization is measured and their external quantum efficiency and background absorption are extracted. Complete characterization of laser cooling samples is obtained via performing detailed low-temperature spectroscopic analysis, and their minimum achievable temperature as well as conditions to achieve laser cooling efficiency enhancement in mid-IR are investigated. By developing a Thulium-doped fiber amplifier, seeded …