The recipes of optical radiative properties manipulation are their materials chemistry, nano/microscale geometry, and transport properties of quasiparticle carriers such as photons, phonons, and electrons. The important technical element in optical properties is the dielectric function of materials, which is different for metals, dielectrics, 2D materials, and phase transition materials. Graphene has a unique electrical conductivity profile which have metallic nature depending on the frequency, but also has a negative thermal expansion coefficient that makes graphene unique. Hence, graphene creates wrinkles when deposited on the substrate as temperature decreases to room temperature from high substrate temperature. We also study phase transition material, particularly vanadium dioxide that transitions from insulating to metallic phase based on temperature change; we investigate its role in far-field thermal radiation. Other transition metal oxides are studied as a thermally and electrically tunable plasmonic gratings: Transition metal oxides include vanadium dioxide, tungsten trioxide, and molybdenum trioxide. The work demonstrates plasmonic phenomena and absorptance/emittance tunability. First, surface plasmon polariton along the graphene (SPPG) when wrinkles are formed above the plasmonic grating is studied. The resonance peak shift is modeled for both magnetic polariton (MP) with inductor-capacitor (LC) circuit and SPPG with Fabry-Perot phase change model. Second, the self-adaptive …

Recent advances in manufacturing and growing concerns on the sustainability of aviation environment have led to a remarkable interest in electrical unmanned aerial systems (UASs) in the past decade. Among various UAS types, the newly designed quadrotor biplane tailsitter class is capable of delivering a wide range of civilian and military tasks, relying on its Vertical Take-Off and Landing (VTOL) capability as well as great maneuverability. Nevertheless, as such UASs employ rotors to generate thrust, and wings to generate lift, and operate at less-understood low to mid-Reynolds flow regime, they experience complicated flight aerodynamics with a noise generation mechanism which is different from common aircrafts. The present work aims at addressing this knowledge gap by studying the aerodynamics and aeroacoustics of a UAS of this type designed by the Army Research Lab. High-fidelity computational fluid dynamics (CFD) simulations are carried out for a wide range of operating conditions to understand the physics involved in the UAS aerodynamics and characterize its performance. Relying on the CFD results, a physics-informed reduced order model (ROM) is developed based on machine learning algorithms, to predict the propellers effects on the wings and calculate the dominant loads. The results of this study indicate that the …

Additively manufactured (AM) 316L and 17-4PH stainless steel parts, concretely made by laser powder bed fusion (L-PBF), are characterized and micro-mechanical properties of those steels are analyzed. This study also explored and extended to proton irradiation and small-scale mechanical testing of those materials, to investigate how irradiation affects microstructural evolution and thus mechanical properties at the surface level, which could be detrimental in the long term in nuclear applications. In-depth anisotropy analysis of L-PBF 316L stainless steel parts with the variations of volumetric energy density, a combined study of nanoindentation with EBSD (electron backscatter diffraction) mapping is shown to be an alternative methodology for enriching qualification protocols. Each grain with a different crystallographic orientation was mapped successfully by proper indentation properties. <122> and <111> oriented grains displayed higher than average indentation modulus and hardness whereas, <001>, <101>, and <210> oriented grains were found to be weaker in terms of indentation properties. Based on an extensive nanoindentation study, L-PBF 17-4 PH stainless steels are found to be very sensitive to high load rates and irradiation further escalates that sensitivity, especially after a 0.25 s-1 strain rate. 3D porosity measurement via X-ray microscope ensures L-PBF stainless steel parts are of more than …

Immersed boundary (IB) methods are attractive due to their ability to simulate flow over complex geometries on a simple Cartesian mesh. Unlike conformal grid formulation, the mesh does not need to conform to the shape and orientation of the boundary. This eliminates the need for complex mesh and/or re-meshing in simulations with moving/morphing boundaries, which can be cumbersome and computationally expensive. However, the imposition of boundary conditions in IB methods is not straightforward and numerous modifications and refinements have been proposed and a number of variants of this approach now exist. In a nutshell, IB methods in the literature often suffer from numerical oscillations, implementation complexity, time-step restriction, burred interface, and lack of generality. This limits their ability to mimic conformal grid results and enforce Neumann boundary conditions. In addition, there is no generic IB capable of solving flow with multiple potentials, closely/loosely packed structures as well as IBs of infinitesimal thickness. This dissertation describes a novel 2$ ^{\text{nd}} $ order direct forcing immersed boundary method designed for simulation of two- and three-dimensional incompressible flow problems with complex immersed boundaries. In this formulation, each cell cut by the IB is reshaped to conform to the shape of the IB. IBs …

In order to better understand the changes occurring in the internal environment of the pyrolysis process a method of monitoring the internal environment in real time is the key objective of this study. To accomplish this objective four tasks were laid out in order to develop an effective way of monitoring the changes in gases present as pyrolysis is occurring as well as in material activation processing. For all processing the self-activation process was used which combines pyrolysis and thermal activation into a single step process. In the first task 10 hard wood species were activated and the resulting properties were compared to see the impact of wood species on the resulting carbon structures. In order to understand the impact of gas concentration on the resulting carbons the second task developed a gas sensor array which effectiveness was corroborated using GC-MS and then comparisons of the changes in the resulting were made. For the third task the gas sensor array was used to analyze the production of CO2 gas and a triple Gaussian model was developed to model the changes in gas production throughout processing. H2 gas production was modeled in the fourth task using the same Gaussian model as …

Lignocellulose is the most abundant biopolymer on earth and offers excellent potential for sustainable manufacturing. Because lignocellulose is structurally complex and resistant to decomposition, innovative degradation strategies are necessary to unlock its value. In this dissertation, a green manufacturing process through enzyme-triggered self-cultured bacteria retting for lignocellulosic fiber was developed and investigated. The mechanism of the lignocellulosic fiber retting at a controlled degradation strategy was studied. This enzymatic degradation strategy utilizes a small amount of enzyme to trigger a large aggregation of specific bacteria to obtain clean fibers. Industrial hemp (Cannabis sativa L.) fiber was successfully retted with this strategy. The degradation of pectin was proved through an environmental scanning electron microscope and reducing sugar analysis. The bacterial successions were identified by 16S rRNA gene metagenomic sequencing. The results showed that Bacillaceae dominated the hemp retting conditions containing 1% pectinase, suggesting that pectinase can manipulate bacterial community succession by changing the nutrients available to bacteria through the degradation of pectin. This degradation strategy has 20-25% less environmental impact than the thermochemical degradation strategy, resulting in better fiber consistency and much shorter processing time (3-5 days) than the traditional water degradation strategy. The study on the degradation of lignin-rich lignocellulose also …

Motivated by previous relevant research on phononics including both active and passive phononics, the interest of faster turnability and more functions of the active phononics of further study led to this proposing research topic: magnetic field tunable active functional phononics. The first design of magnetic field tunable reciprocal--non-reciprocal transmission acoustic device was established, material was characterized, and numerical simulation has been performed. The simulation results show clear T-symmetric breaking non-reciprocity due to energy level splitting effect with Doppler effect – an acoustic Zeeman effect. Inspired by this preliminary work, further experiments were planned to demonstrate this effective Zeeman effect in phononics and effectively charged phonons in water based ferro-fluid. The objectives of this work as the next series of tasks were to illustrate acoustic Zeeman effect and acoustic Landau levels in various strength of magnetic field to investigate a design non-reciprocal sound device with magnetic field switching, which could be controlled on the amount of non-reciprocity with the strength of magnetic field. Once this new field first discovered by the proposed study tasks, more active tunable magnetic field phononics devices could be designed and exemplified in terms of both simulations and experiments. Faster and more controllable active phononic devices could …