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Articles 1 - 13 of 13
Full-Text Articles in Engineering
Design Of A Meta-Material With Targeted Nonlinear Deformation Response, Zachary Satterfield
Design Of A Meta-Material With Targeted Nonlinear Deformation Response, Zachary Satterfield
All Theses
The M1 Abrams tank contains track pads consist of a high density rubber. This rubber fails prematurely due to heat buildup caused by the hysteretic nature of elastomers. It is therefore desired to replace this elastomer by a meta-material that has equivalent nonlinear deformation characteristics without this primary failure mode. A meta-material is an artificial material in the form of a periodic structure that exhibits behavior that differs from its constitutive material. After a thorough literature review, topology optimization was found as the only method used to design meta-materials. Further investigation determined topology optimization as an infeasible method to design …
Potential-Flow Inflow Model Including Wake Distortion And Contraction, Jianzhe Huang
Potential-Flow Inflow Model Including Wake Distortion And Contraction, Jianzhe Huang
McKelvey School of Engineering Theses & Dissertations
Dynamic wake models have been used in real-time flight simulations for over thirty years. The models have evolved from the earliest, three-degree-of-freedom models (derived from momentum theory) to full finite-state models derived from potential flow theory by a formal Galerkin method. These models are widely used in industry, but still have some drawbacks that need to be remedied. These drawbacks include: 1.) lack of good convergence both on the disk and off the disk (one can use one or the other but not both), 2.) poor results downstream in the limit of shallow skew angles, 3.) poor convergence inside of …
Nonlinear Optical Conductivity Of Two-Dimensional Semiconductors With Rashba Spin-Orbit Coupling In Terahertz Regime, Yee Sin Ang, J C. Cao, Chao Zhang
Nonlinear Optical Conductivity Of Two-Dimensional Semiconductors With Rashba Spin-Orbit Coupling In Terahertz Regime, Yee Sin Ang, J C. Cao, Chao Zhang
Yee Sin Ang
We reveal that two-dimensional semiconductors with Rashba spin-orbit interaction (R2DG) exhibit exceptionally strong nonlinear optical response (NOR) in the terahertz frequency regime. The spin-split of the parabolic energy band in R2DG allows strong multiple-photon process to occur via inter-subband mechanism. We show sharp multiple photon edges in the nonlinear conductivity. The edges correspond to the cut-off effect produced by the multiple-photon process. For Rashba coupling parameter of λ R ≈ 10−10 eV m, electric field strength in the order of only 102 V/cm is required for the NOR to dominate over the linear response. Furthermore, the roles of the parabolic …
Nonlinear Optical Properties Of Bilayer Graphene In Terahertz Regime, Yee Sin Ang, S Sultan, Rodney Vickers, Chao Zhang
Nonlinear Optical Properties Of Bilayer Graphene In Terahertz Regime, Yee Sin Ang, S Sultan, Rodney Vickers, Chao Zhang
Yee Sin Ang
We have carried out a theoretical and computation study of optical response of bilayer graphene in the terahertz regime. It is found that the optical response of bilayer graphene can be significantly enhanced by nonlinear process for fields greater than 1000v/cm. The optical nonlinearity of bilayer graphene persists even in room temperature. This suggests that bilayer graphene can potentially be utilized as a temperature-robust nonlinear material in the terahertz regime.
Intraband Nonlinear Terahertz Waves Absorption Of Gapped Graphene, Asya Tawfiq, Yee Sin Ang, Chao Zhang
Intraband Nonlinear Terahertz Waves Absorption Of Gapped Graphene, Asya Tawfiq, Yee Sin Ang, Chao Zhang
Yee Sin Ang
The effect of bandgap opening on the intraband nonlinear optical response of graphene in terahertz frequency regime is theoretically investigated. The nonlinear optical response of gapped graphene is found to be sensitively influenced by the bandgap level and temperature. © 2012 IEEE.
Strong Nonlinear Optical Response Of Bilayer Graphene In The Terahertz Regime, Yee Sin Ang, Chao Zhang
Strong Nonlinear Optical Response Of Bilayer Graphene In The Terahertz Regime, Yee Sin Ang, Chao Zhang
Yee Sin Ang
We demonstrate that bilayer graphene exhibits strong nonlinear optical response in the terahertz frequency regime.The electric field strength required to generate single-frequency and triple-frequency nonlinear optical responses comparable to the linear optical response is only moderate and can be easily achieved in laboratory.This strong nonlinear optical response persists even in room temperature.This suggests that bilayer graphene can potentially be utilized in nonlinear terahertz photonics
Nonlinear Optical Spectrum Of Two-Dimensional Electron Gas With Rashba Spin-Orbit Interaction In Thz Frequency Regime, Yee Sin Ang, C Zhang, Qinjun Chen
Nonlinear Optical Spectrum Of Two-Dimensional Electron Gas With Rashba Spin-Orbit Interaction In Thz Frequency Regime, Yee Sin Ang, C Zhang, Qinjun Chen
Yee Sin Ang
We theoretically calculate the nonlinear optical spectrum of two-dimensional electron gas in the presence of Rashba spin-orbit interaction in terahertz frequency regime. For Rashba coupling parameter in the order of 0.4 eVÅ, the nonlinear optical response exceeds the linear response with the application of an external electric field strength in the order of 103 V/cm.
Two-Color Nonlinear Optical Response Of Graphene With Broken Ab-Symmetry, Yee Sin Ang, Chao Zhang
Two-Color Nonlinear Optical Response Of Graphene With Broken Ab-Symmetry, Yee Sin Ang, Chao Zhang
Yee Sin Ang
We demonstrate that the bandgap opening in graphene induced by AB-sublattice symmetry breaking leads to a strong nonlinear optical response for frequencies well below the bandgap where linear response is strictly forbidden. Our result suggests that one type of graphene with such symmetry breaking, semihydrogenated graphene, can have a unique potential as a two-color nonlinear material in the terahertz photonics.
Nonlinear Optical Response Of Graphene Superlattice In Terahertz Frequency Regime, Yee Sin Ang, Chao Zhang
Nonlinear Optical Response Of Graphene Superlattice In Terahertz Frequency Regime, Yee Sin Ang, Chao Zhang
Yee Sin Ang
We investigate the nonlinear optical response of a Kronig-Penney type graphene superlattice in which the Fermi velocity of the massless Dirac quasiparticle anisotropically depends on the direction of propagation. Such velocity anisotropy results in enhanced nonlinear optical response in terahertz frequency regime.
Dynamic Model Of A Non-Linear Pneumatic Pressure Modulating Valve Using Bond Graphs, Christopher L. Brubaker
Dynamic Model Of A Non-Linear Pneumatic Pressure Modulating Valve Using Bond Graphs, Christopher L. Brubaker
ETD Archive
This research develops a mathematical model of the dynamic pressure response to a variable travel input of a pneumatic pressure modulating valve intended for use in a vehicle air brake system. Generically, the valve is a multi-domain system consisting of a mechanical portion and a pneumatic portion. Included in the mechanical portion of the model are compliance of the springs, inertia of the components, and resistance of the sliding components. The pneumatic portion of the model includes capacitance due to the compressibility of the gas, flow resistance through connected plumbing, and flow resistance through the valve control orifices. The development …
Nonlinear Terahertz Response Of Hgte/Cdte Quantum Wells, Qinjun Chen, Matthew Sanderson, C Zhang
Nonlinear Terahertz Response Of Hgte/Cdte Quantum Wells, Qinjun Chen, Matthew Sanderson, C Zhang
Faculty of Engineering and Information Sciences - Papers: Part A
2015 AIP Publishing LLC. Without breaking the topological order, HgTe/CdTe quantum wells can have two types of bulk band structure: direct gap type (type I) and indirect gap type (type II). We report that the strong nonlinear optical responses exist in both types of bulk states under a moderate electric field in the terahertz regime. Interestingly, for the type II band structure, the third order conductivity changes sign when chemical potentials lies below 10meV due to the significant response of the hole excitation close to the bottom of conduction band. Negative nonlinear conductivities suggest that HgTe/CdTe quantum wells can find …
Nano And Nanostructured Materials For Optical Applications, Panit Chantharasupawong
Nano And Nanostructured Materials For Optical Applications, Panit Chantharasupawong
Electronic Theses and Dissertations
Nano and nanostructured materials offer unique physical and chemical properties that differ considerably from their bulk counterparts. For decades, due to their fascinating properties, they have been extensively explored and found to be beneficial in numerous applications. These materials are key components in many cutting-edge optic and photonic technologies, including photovoltaics, waveguides and sensors. In this dissertation, the uses of nano and nanostructured materials for optical applications are investigated in the context of optical limiting, three dimensional displays, and optical sensing. Nanomaterials with nonlinear optical responses are promising candidates for self-activating optical limiters. In the first part of this study, …
Modern Digital Chirp Receiver: Theory, Design And System Integration, Stephen Ray Benson
Modern Digital Chirp Receiver: Theory, Design And System Integration, Stephen Ray Benson
Browse all Theses and Dissertations
Chirp signals can achieve a high range resolution without sacrificing SNR or maximum range, making them a strong candidate for use in radar and sonar applications. Chirp signals are also power efficient and resistant to interference, making them well suited for communication applications as well. The proposed digital high chirp rate receivers will showcase the use of digital instantaneous frequency measurement (IFM) devices for high chirp rate measurement. The receivers are paired with a high resolution time-of-arrival algorithm, capable of detecting the TOA and TOD of a pulse with an average error of less than 2ns. The high resolution pulse …