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Heterogeneous Oxidation Of Multi-Component Aqueous Organic Aerosols: The Effect Of Transport Phenomena And Reaction Compartment On Reaction Kinetics., Tadini Wenyika Masaya

Graduate Theses, Dissertations, and Problem Reports (ETD)

The surface-bulk partitioning of small organic molecules in aqueous droplets was investigated using molecular dynamics. The air-particle interface was modeled using a 80-Å cubic water box containing series of organic molecules and surrounded by gaseous OH radicals. The properties of the organic solutes within the interface and the water-bulk were examined at a molecular-level using density profiles and radial pair distribution functions. Molecules containing only polar functional groups such as urea and glucose are found predominantly in the water bulk, forming an exclusion layer near the water surface. Substitution of a single polar group by an alkyl group in sugars …

Experimental And Theoretical Investigation On The Initiation Mechanism Of Low-Rank Coal's Self-Heating Process, Yinan Zhang

Graduate Theses, Dissertations, and Problem Reports (ETD)

Coal spontaneous combustion remains a safety concern during coal mining, transportation, and storage and requires further investigation to develop effective prevention and control strategies. While various intrinsic and extrinsic conditions may influence coal self-heating, low-rank coals are more prone to spontaneous combustion, especially in humid climates. Therefore, quantifying the effect of extrinsic moisture on the self-heating of low-rank coals is critical for understanding the high propensity of low-rank coals for spontaneous combustion. Many studies have qualitatively evaluated the role of extrinsic moisture on the coal self-heating. Despite this, few studies have quantified the contribution of extrinsic moisture on wetting and …

Microwave Enhanced Electron Energy Distribution Functions, John Samuel Mckee

Graduate Theses, Dissertations, and Problem Reports (ETD)

The use of two (or more) radio frequency (RF) sources at different frequencies is a common technique in the plasma processing industry to control ion energy characteristics separately from plasma generation. A similar approach is presented here with the focus on modifying the electron population in argon and helium plasmas. The plasma is generated by a helicon source at a frequency f0 = 13.56 MHz. Microwaves of frequency f1 = 2.45 GHz are then injected into the helicon source chamber perpendicular to the background magnetic field. The microwaves damp on the electrons via R-mode (anti-parallel to the background magnetic field …

The Impact Of Formation And Fracture Properties Alternations On The Productivity Of The Multi-Stage Fractured Marcellus Shale Horizontal Wells., Dalal Aldbayan

Graduate Theses, Dissertations, and Problem Reports (ETD)

As the reservoir deplete, the pore pressure decreases and the effective stress increases. The increase in the effective stress results in the formation compaction which can alter the formation and hydraulic fracture properties. This is particularly significant for a Marcellus shale horizontal well with multi-stage hydraulic fracture due to low Young's modulus and moderate Poisson's ratio of the Marcellus shale. The degree of the effective stress increase depends on the initial productivity of the well, which is influenced by the hydraulic fracture properties, formation properties, as well as the operating conditions. Therefore, it is necessary to couple the geomechanical and …

The Burning Bush: Linking Lidar-Derived Shrub Architecture To Flammability, Michelle S. Bester

Graduate Theses, Dissertations, and Problem Reports (ETD)

Light detection and ranging (LiDAR) and terrestrial laser scanning (TLS) sensors are powerful tools for characterizing vegetation structure and for constructing three-dimensional (3D) models of trees, also known as quantitative structural models (QSM). 3D models and structural traits derived from them provide valuable information for biodiversity conservation, forest management, and fire behavior modeling. However, vegetation studies and 3D modeling methodologies often only focus on the forest canopy, with little attention given to understory vegetation. In particular, 3D structural information of shrubs is limited or not included in fire behavior models. Yet, understory vegetation is an important component of forested ecosystems, …

Improving Robotic Decision-Making In Unmodeled Situations, Nicholas Scott Ohi

Graduate Theses, Dissertations, and Problem Reports (ETD)

Existing methods of autonomous robotic decision-making are often fragile when faced with inaccurate or incompletely modeled distributions of uncertainty, also known as ambiguity. While decision-making under ambiguity is a field of study that has been gaining interest, many existing methods tend to be computationally challenging, require many assumptions about the nature of the problem, and often require much prior knowledge. Therefore, they do not scale well to complex real-world problems where fulfilling all of these requirements is often impractical if not impossible. The research described in this dissertation investigates novel approaches to robotic decision-making strategies which are resilient to …

Staff Education In Caring For Children With Type 1 Diabetes, Freda Ansah-Larbi

Walden Dissertations and Doctoral Studies

AbstractType1 diabetes affects over 1.6 million people living in the United States of which about 200,000 are children under the age of 20, with an increase of 1.9% per year between 2002–2015. The large number of children with type 1 diabetes was observed in the project’s practice setting. In addition to the physical health impact on children, this disease also has major personal, economic, and social impacts on children and their families. Therefore, effective management is essential in reducing the risk of complications and achieving an overall improvement in the quality of life of patients. The purpose of the project …

Experiences With Addiction Transfer Among Weight Loss Surgery Recipients, Latoya Smalls

Walden Dissertations and Doctoral Studies

Obesity remains a significant problem linked to psychological, behavioral, metabolic, and environmental factors. Some individuals who struggle with obesity turn to weight loss surgery. Studies exploring the long-term effects of weight loss surgery and its connection with transfer addiction have reached conflicting findings. This phenomenological study was conducted according to procedures developed by Husserl and Giorgi. Data were collected for this qualitative study through semistructured interviews with 10 bariatric weight loss surgery recipients. Data were analyzed using the five stages of Giorgi’s descriptive phenomenological method process of data analysis. Analysis of the data led to five themes and eight subthemes. …

Kindergarten Teachers' Perspectives On School Readiness In Children Who Attended Military Installation Childcare Centers, Juliana Wilson

Walden Dissertations and Doctoral Studies

Limited literature exists on the effectiveness of prekindergarten programs located on military installations in the United States. The children who attend these programs may not receive school readiness preparation equivalent to that received by their peers who attend community-based prekindergarten programs, which follow different guidelines. The purpose of this study was to gain insight into the kindergarten readiness of children who attended preschool on military installations as described by teachers in community-based kindergarten classrooms. Pianta's work on school readiness formed the conceptual framework of this basic qualitative study. The research question addressed how kindergarten teachers describe school readiness in children …

Structure-Dependent Characterizations Of Multistationarity In Mass-Action Reaction Networks, Galyna Voitiuk

Graduate Theses, Dissertations, and Problem Reports (ETD)

This project explores a topic in Chemical Reaction Network Theory. We analyze networks with one dimensional stoichiometric subspace using mass-action kinetics. For these types of networks, we study how the capacity for multiple positive equilibria and multiple positive nondegenerate equilibria can be determined using Euclidian embedded graphs. Our work adds to the catalog of the class of reaction networks with one-dimensional stoichiometric subspace answering in the affirmative a conjecture posed by Joshi and Shiu: Conjecture 0.1 (Question 6.1 [26]). A reaction network with one-dimensional stoichiometric subspace and more than one source complex has the capacity for multistationarity if and only …

Ear Biometrics: A Comprehensive Study Of Taxonomy, Detection, And Recognition Methods, Susan Awm El-Naggar

Graduate Theses, Dissertations, and Problem Reports (ETD)

Due to the recent challenges in access control, surveillance and security, there is an increased need for efficient human authentication solutions. Ear recognition is an appealing choice to identify individuals in controlled or challenging environments. The outer part of the ear demonstrates high discriminative information across individuals and has shown to be robust for recognition. In addition, the data acquisition procedure is contactless, non-intrusive, and covert. This work focuses on using ear images for human authentication in visible and thermal spectrums. We perform a systematic study of the ear features and propose a taxonomy for them. Also, we investigate the …

Development Of A Machine Learning Model To Characterize The Performance Of A Selective Catalytic Reduction On Filter After-Treatment System For A Heavy-Duty Diesel Engine, Samuel A. Okeleye

Graduate Theses, Dissertations, and Problem Reports (ETD)

Particulate matter (PM) and Oxides of Nitrogen (NOx) are the major pollutants in diesel engines, an attempt to control one leads to an increase in the other, a phenomenon known as PM-NOx trade-off in diesel engine emission control. Currently, these two pollutants are controlled by the Diesel Particulate Filter (DPF) and the Selective Catalytic Reduction (SCR) after-treatment system respectively, in addition to the Diesel Oxidation Catalyst (DOC) which helps to provide 1:1 split of NO/NO₂ and helps with raising exhaust gas temperatures. Today, heavy-duty diesel engines feature a DPF, a primary SCR and a secondary SCR. Despite this complex …

Scaling Theory Of 3d Magnetic Reconnection X-Line Spreading, Milton Arencibia

Graduate Theses, Dissertations, and Problem Reports (ETD)

Magnetic reconnection is fundamental process in plasmas that converts magnetic energy into kinetic and thermal energy via a change in magnetic topology. Magnetic reconnection is known to mediate eruptive solar flares, geomagnetic substorms that create the Northern lights, heating and particle acceleration in controlled fusion devices, and is thought to be an important process in numerous settings in high-energy astrophysics. Classical models of reconnection are two-dimensional (2D), but naturally occurring reconnection is three-dimensional (3D), and a manifestation of the 3D nature is that the x-line where the magnetic field topology changes has a finite extent in the direction normal to …

Size Effect And Anisotropy On The Strength Of Shale Under Compressive Stress Conditions, Yun Zhao

Graduate Theses, Dissertations, and Problem Reports (ETD)

The underground coal mines in the Appalachian region report the highest rate of roof falls in the United States. The immediate roof of these mines is mostly composed of shale. The in-situ strength of shale is necessary for designing roof support to prevent roof falls. Estimating the in-situ strength of shale requires the knowledge of both size effect and anisotropy. This research used literature review, theoretical analysis, numerical modeling, and laboratory experiment to systematically investigate the size effect and anisotropy of shale strength under compressive strength conditions.

Literature review involved a comprehensive summary of previous research on the size effect …

Modeling And Optimization Of A Novel Chilled Ammonia Absorption Process And Amine-Appended Metal-Organic Frameworks For Co2 Capture, Ryan Keith Hughes

Graduate Theses, Dissertations, and Problem Reports (ETD)

Post-combustion capture is one of the leading technologies for CO₂ abatement from anthropogenic sources which have contributed significantly to the rise of atmospheric greenhouse gases. Specifically, solvent-based capture post-combustion processes are the industry standard but can suffer drawbacks such as high energy penalties and corrosion. In this work, two possible improvements are investigated which have been recently proposed in the literature. The first is aqueous ammonia as a capture solvent which has been shown to have several advantages including, but not limited to, a lower regeneration energy. The second is a novel solid sorbent, an amine-appended metal-organic framework (MOF). …

Polarization Properties Of Millisecond Pulsars: Astrophysical Interpretations And Applications, Haley Megan Wahl

Graduate Theses, Dissertations, and Problem Reports (ETD)

Pulsars are some of the most extreme objects in the universe; their small yet incredibly predictable spin periods coupled with their strong magnetic fields make them ideal laboratories for study. Not only are they interesting objects themselves, but they can also help us probe different astrophysical environments, such as the interstellar magnetic field and the solar corona.

These stars are highly polarized, and that polarization comes into play in various fields of pulsar physics (such as constraining models of pulsar emission), but obtaining that polarization information can be difficult, as the polarization properties of the light can change as the …

A Multi-Method Examination Of The Effects Of Students’ Unconscious Biases On Student Evaluations Of Instructors, Brittany M. Kowalski

Graduate Theses, Dissertations, and Problem Reports (ETD)

In this dissertation, I complete three studies to evaluate potential reactions to target role congruity, especially gender role congruity, through an examination of Student Evaluations of Instructors (SEIs). Target role congruity refers to assessments an observer makes of whether or not the various roles a target person fills “fit” with one another. For example, a woman surgeon may be perceived as being in an incongruent role due to the masculine characteristics associated with the occupation and the continued dominance of men in the field. Researchers utilizing congruity theories has shown that both women and men in roles that are incongruent …

Planar Chiral Metasurfaces With Maximal And Tunable Chiroptical Response Driven By Bound States In The Continuum, Tan Shi, Zi-Lan Deng, Guangzhou Geng, Xianzhi Zeng, Yixuan Zeng, Guangwei Hu, Adam Overvig, Junjie Li, Cheng-Wei Qiu, Andrea Alù, Yuri S. Kivshar, Xiangping Li

Advanced Science Research Center

Optical metasurfaces with high quality factors (Q-factors) of chiral resonances can boost substantially light-matter interaction for various applications of chiral response in ultrathin, active, and nonlinear metadevices. However, current approaches lack the flexibility to enhance and tune the chirality and Q-factor simultaneously. Here, we suggest a design of chiral metasurface supporting bound state in the continuum (BIC) and demonstrate experimentally chiroptical responses with ultra-high Q-factors and near-perfect circular dichroism (CD = 0.93) at optical frequencies. We employ the symmetry-reduced metaatoms with high birefringence supporting winding elliptical eigenstate polarizations with opposite helicity. It provides a convenient way for achieving the maximal …

Reciprocity Of Thermal Diffusion In Time-Modulated Systems, Jiaxin Li, Ying Li, Pei-Chao Cao, Minghong Qi, Xu Zheng, Yu-Gui Peng, Baowen Li, Xue-Feng Zhu, Andrea Alù, Hongsheng Chen, Cheng-Wei Qiu

Advanced Science Research Center

The reciprocity principle governs the symmetry in transmission of electromagnetic and acoustic waves, as well as the diffusion of heat between two points in space, with important consequences for thermal management and energy harvesting. There has been significant recent interest in materials with time-modulated properties, which have been shown to efficiently break reciprocity for light, sound, and even charge diffusion. However, time modulation may not be a plausible approach to break thermal reciprocity, in contrast to the usual perception. We establish a theoretical framework to accurately describe the behavior of diffusive processes under time modulation, and prove that thermal reciprocity …

Coherent Full Polarization Control Based On Bound States In The Continuum, Ming Kang, Ziying Zhang, Tong Wu, Xueqian Zhang, Quan Xu, Alex Krasnok, Jiaguang Han, Andrea Alù

Advanced Science Research Center

Bound states in the continuum (BICs) are resonant modes of open structures that do not suffer damping, despite being compatible with radiation in terms of their momentum. They have been raising significant attention for their intriguing topological features, and their opportunities in photonics to enhance light-matter interactions. In parallel, the coherent excitation of optical devices through the tailored interference of multiple beams has been explored as a way to enhance the degree of real-time control over their response. Here, we leverage the combination of these phenomena, and exploit the topological features of BICs in the presence of multiple input beams …

Fast Encirclement Of An Exceptional Point For Highly Efficient And Compact Chiral Mode Converters, Xiaoqian Shu, Aodong Li, Guangwei Hu, Jian Wang, Andrea Alù, Lin Chen

Advanced Science Research Center

Exceptional points (EPs) are degeneracies at which two or more eigenvalues and eigenstates of a physical system coalesce. Dynamically encircling EPs by varying the parameters of a non- Hermitian system enables chiral mode switching, that is, the final state of the system upon a closed loop in parameter space depends on the encircling handedness. In conventional schemes, the parametric evolution during the encircling process has to be sufficiently slow to ensure adiabaticity. Here, we show that fast parametric evolution along the parameter space boundary of the system Hamiltonian can relax this constraint. The proposed scheme enables highly efficient transmission and …

Stability Bounds On Superluminal Propagation In Active Structures, Robert Duggan, Hady Moussa, Younes Ra'di, Dimitrios L. Sounas, Andrea Alù

Advanced Science Research Center

Active materials have been explored in recent years to demonstrate superluminal group velocities over relatively broad bandwidths, implying a potential path towards bold claims such as information transport beyond the speed of light, as well as antennas and metamaterial cloaks operating over very broad bandwidths. However, causality requires that no portion of an impinging pulse can pass its precursor, implying a fundamental trade-off between bandwidth, velocity and propagation distance. Here, we clarify the general nature of superluminal propagation in active structures and derive a bound on these quantities fundamentally rooted into stability considerations. By applying filter theory, we show that …

Radio-Transparent Dipole Antenna Based On A Metasurface Cloak, Jason Soric, Younes Ra'di, Diego Farfan, Andrea Alù

Advanced Science Research Center

Antenna technology is at the basis of ubiquitous wireless communication systems and sensors. Radiation is typically sustained by conduction currents flowing around resonant metallic objects that are optimized to enhance efficiency and bandwidth. However, resonant conductors are prone to large scattering of impinging waves, leading to challenges in crowded antenna environments due to blockage and distortion. Metasurface cloaks have been explored in the quest of addressing this challenge by reducing antenna scattering. However, metasurface-based designs have so far shown limited performance in terms of bandwidth, footprint and overall scattering reduction. Here we introduce a different route towards radiotransparent antennas, in …

What Is Green Infrastructure? A Study Of Definitions In Us City Planning, Zbigniew J. Grabowski, Timon Mcphearson, A Marissa Matsler, Peter M. Groffman, Steward Ta Pickett

Advanced Science Research Center

In response to interdependent challenges, city planners are increasingly adopting “green infrastructure” (GI). Reviewing 122 plans from 20 US cities, we identify what types of city plans address and define GI, including the concepts associated with GI, as well as the types, functions, and benefits of GI. The most common plans that feature GI, some of which focus exclusively on GI, comply with US Clean Water Act regulations for stormwater and sewer systems. Municipalities also address GI through diverse planning processes, including the creation of comprehensive citywide plans. Many of these plans (~40%) do not explicitly define GI. When they …

Assembly Mechanism Of Early Hsp90-Cdc37-Kinase Complexes, Dimitra Keramisanou, M.V. Vasantha Kumar, Nicole Boose, Rinat R. Abzalimov, Ioannis Gelis

Advanced Science Research Center

Molecular chaperones have an essential role for the maintenance of a balanced protein homeostasis. Here, we investigate how protein kinases are recruited and loaded to the Hsp90-Cdc37 complex, the first step during Hsp90-mediated chaperoning that leads to enhanced client kinase stability and activation. We show that conformational dynamics of all partners is a critical feature of the underlying loading mechanism. The kinome co-chaperone Cdc37 exists primarily in a dynamic extended conformation but samples a low-populated, well-defined compact structure. Exchange between these two states is maintained in an assembled Hsp90-Cdc37 complex and is necessary for substrate loading. Breathing motions at the …

Characterization Of Site-Specific Vegetation Activity In Alaskan Wet And Dry Tundra As Related To Climate And Soil State, Michael Gregory Brown, Kyle C. Mcdonald, Reiner Zimmermann, Nicholas Steiner, Stephanie Devries, Laura Bourgeau-Chavez

Advanced Science Research Center

We present discrete (2-h resolution) multi-year (2008–2017) in situ measurements of seasonal vegetation growth and soil biophysical properties from two sites on Alaska's North Slope, USA, representing dry and wet sedge tundra. We examine measurements of vertical active soil layer temperature and soil moisture profiles (freeze/thaw status), woody shrub vegetation physiological activity, and meteorological site data to assess interrelationships within (and between) these two study sites. Vegetation phenophases (cold de-hardening start, physiological function start, stem growth start, stem growth end, physiological function end, cold hardening completion) were found to have greater interannual day of year (DOY) occurrence variability at the …

Moiré-Driven Topological Transitions And Extremeanisotropy In Elastic Metasurfaces, Simon Yves, Matheus Inguaggiato Nora Nora Rosa, Mohit Gupta, Massimo Ruzzene, Andrea Alù

Advanced Science Research Center

The twist angle between a pair of stacked 2D materials has been recently shown to control remarkable phenomena, including the emergence of flat-band superconductivity in twisted graphene bilayers, of higher-order topological phases in twisted moiré superlattices, and of topological polaritons in twisted hyperbolic metasurfaces. These discoveries, at the foundations of the emergent field of twistronics, have so far been mostly limited to explorations in atomically thin condensed matter and photonic systems, with limitations on the degree of control over geometry and twist angle, and inherent challenges in the fabrication of carefully engineered stacked multilayers. Here, this work extends twistronics to …

Photonics Of Time-Varying Media, Emanuele Galiffi, Romain Tirole, Shixiong Yin, Huanan Li, Stefano Vezzoli, Paloma A. Huidobro, Mário G. Silveirinha, Riccardo Sapienza, Andrea Alù, J. B. Pendry

Advanced Science Research Center

Time-varying media have recently emerged as a new paradigm for wave manipulation, due to the synergy between the discovery of highly nonlinear materials, such as epsilon-near-zero materials, and the quest for wave applications, such as magnet-free nonreciprocity, multimode light shaping, and ultrafast switching. In this review, we provide a comprehensive discussion of the recent progress achieved with photonic metamaterials whose properties stem from their modulation in time. We review the basic concepts underpinning temporal switching and its relation with spatial scattering and deploy the resulting insight to review photonic time-crystals and their emergent research avenues, such as topological and non-Hermitian …

An Archimedes' Screw For Light, Emanuele Galiffi, Paloma A. Huidobro, J. B. Pendry

Advanced Science Research Center

An Archimedes’ Screw captures water, feeding energy into it by lifting it to a higher level. We introduce the first instance of an optical Archimedes’ Screw, and demonstrate how this system is capable of capturing light, dragging it and amplifying it. We unveil new exact analytic solutions to Maxwell’s Equations for a wide family of chiral space-time media, and show their potential to achieve chirally selective amplification within widely tunable parity-time-broken phases. Our work, which may be readily implemented via pump-probe experiments with circularly polarized beams, opens a new direction in the physics of time-varying media by merging the rising …

Adapting A Narrative Curriculum To A Remote Format In The Context Of Socially Distanced Middle School Education Resulting From Covid-19, Jeremiah Piña, Rebecca Mazur, Glenn Ellis, Al Rudnitsky, Beth Mcginnis-Cavanaugh, Sonia Ellis, Isabel Huff, Crystal M. Ford

Engineering: Faculty Publications

This paper describes the development of two versions of an NGSS-aligned principles of engineering design unit for use in middle schools. By employing a narrative framework that can help students to connect more deeply with the human contexts and consequences of the engineering design process, our goal was to enhance students’ cognitive and emotional engagement in the learning of engineering design concepts. We first detail the design of an initial version of the unit, titled The Survivorama, which used narrative to enrich a primarily traditional, in-person teaching approach. We then describe the adapted version of the unit, titled the Molasses …