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Full-Text Articles in Engineering
Distributed Detection In Energy Harvesting Wireless Sensor Networks, Ghazaleh Ardeshiri
Distributed Detection In Energy Harvesting Wireless Sensor Networks, Ghazaleh Ardeshiri
Electronic Theses and Dissertations, 2020-
A conventional wireless sensor networks (WSN), consisting of sensors powered by nonrechargeable batteries, has a strictly limited lifetime. Energy harvesting (EH) from the environment is a promising solution to address the energy constraint problem in conventional WSNs, and to render these networks to self-sustainable networks with perpetual lifetimes. In EH-powered WSNs, where sensors are capable of harvesting and storing energy, power control is necessary to balance the rates of energy harvesting and energy consumption for data transmission. In addition, wireless communication channels change randomly in time due to fading. These together prompt the need for developing new power control strategies …
Data-Driven Power System Stability Analysis And Control, Jian Xie
Data-Driven Power System Stability Analysis And Control, Jian Xie
Electronic Theses and Dissertations, 2020-
In recent years, with the expansion of power system size, the increase of interconnection and the use of large-scale renewable energy, power system stability and safe operations have become more prominent, causing challenges to the normal operation of power grid. Traditional analysis rely on detailed models of the system. But for real power systems, the operating state of the system is variable, and the model-based analysis methods may not accurately reflect the real operating state of the system. Therefore, this dissertation is focused on data-driven stability analysis and control. First, a method for locating the oscillation source of multi-machine systems …
Development Of A Dual-Mode Cmos Microelectrode Array For The Simultaneous Study Of Electrochemical And Electrophysiological Activities Of The Brain, Geoffrey Mulberry
Development Of A Dual-Mode Cmos Microelectrode Array For The Simultaneous Study Of Electrochemical And Electrophysiological Activities Of The Brain, Geoffrey Mulberry
Electronic Theses and Dissertations, 2020-
Medical diagnostic devices are in high demand due to increasing cases of neurodegenerative diseases in the aging population and pandemic outbreaks in our increasingly connected global community. Devices capable of detecting the presence of a disease in its early stages can have dramatic impacts on how it can be treated or eliminated. High cost and limited accessibility to diagnostic tools are the main barriers preventing potential patients from receiving a timely disease diagnosis. This dissertation presents several devices that are aimed at providing higher quality medical diagnostics at a low cost. Brain function is commonly studied with systems detecting the …
Grid-Interactive Buildings: Modeling, Operations, And Security, Guanyu Tian
Grid-Interactive Buildings: Modeling, Operations, And Security, Guanyu Tian
Electronic Theses and Dissertations, 2020-
Smart grids and smart buildings are two highly interdependent energy infrastructure systems. Buildings rely on the grid to provide reliable power while their flexibility can also be utilized to enhance the reliability and efficiency of power system operations. The quantification of heating, ventilation, and air condition (HVAC) system flexibility is critical to the operations of both the grid and buildings in demand response (DR) programs. However, the flexibility quantification is challenging due to the non-linearity and non-convexity of thermal dynamics associated with HVAC components. This dissertation proposes a novel HVAC flexibility quantification method based on a semidefinite programming (SDP) formulation. …
Light Trapping Transparent Electrodes, Mengdi Sun
Light Trapping Transparent Electrodes, Mengdi Sun
Electronic Theses and Dissertations, 2020-
Transparent electrodes represent a critical component in a wide range of optoelectronic devices such as high-speed photodetectors and solar cells. Fundamentally, the presence of any conductive structures in the optical path leads to dissipation and reflection, which adversely affects device performance. Many different approaches have been attempted to minimize such shadowing losses, including the use of transparent conductive oxides (TCOs), metallic nanowire mesh grids, graphene-based contacts, and high-aspect ratio metallic wire arrays. In this dissertation I discuss a conceptually different approach to achieve transparent electrodes, which involves recapturing photons initially reflected by highly conductive electrode lines. To achieve this, light-redirecting …
The Proof Of Concept Of The Hurricane Imaging Radiometer: Hurricane Wind Speed And Rain Rate Retrievals, Jonathan Coto
The Proof Of Concept Of The Hurricane Imaging Radiometer: Hurricane Wind Speed And Rain Rate Retrievals, Jonathan Coto
Electronic Theses and Dissertations, 2020-
This dissertation presents the proof of concept for the Hurricane Imaging Radiometer (HIRAD), where remote sensing retrievals of the 2-dimensional wind and rain fields for several hurricanes are validated with independent measurements. A significant contribution of this dissertation is the development of a novel statistical calibration technique, whereby the HIRAD instrument is radiometrically calibrated, using modeled brightness temperatures (Tb) generated using a priori hurricane wind and rain fields that are statistically representative of the actual hurricane conditions at the time of the HIRAD brightness temperature measurements. For this calibration technique, the probability distribution function of the measured HIRAD Tb's is …
Mos2 Based Memristive Synapses For Neuromorphic Computing, Adithi Pandrahal Krishnaprasad Sharada
Mos2 Based Memristive Synapses For Neuromorphic Computing, Adithi Pandrahal Krishnaprasad Sharada
Electronic Theses and Dissertations, 2020-
Brain inspired computing enabled by memristors have gained prominence over the years due to its nano-scale footprint, reduced complexity for implementing synapses and neurons. Several demonstrations show two-dimensional (2D) materials as a promising platform for realization of robust and energy-efficient memristive synapses. Ideally, a synapse should exhibit low cycle-to-cycle (C-C) and device-to-device (D-D) variability along with high maximum /minimum conductance (Gmax/Gmin) ratio, linearity and symmetry in weight update for obtaining high learning accuracy in neural networks (NNs). However, the demonstration of neuromorphic circuits using conventional materials systems has been limited by high C-C and D-D variability and non-linearity in the …
Search Space Reduction Techniques For Solution Of Combinatorial Optimization Problems In Power System., Ranadhir Sarkar
Search Space Reduction Techniques For Solution Of Combinatorial Optimization Problems In Power System., Ranadhir Sarkar
Electronic Theses and Dissertations, 2020-
Power system is vulnerable to disastrous climate events due to sequential or successive equipment failure. In this dissertation, the problem of identifying the critical k-transmission lines that fail one after another in quick succession, and the distribution system restoration problem using tie-lines/sectionalizing switches formulated as a mixed-integer non-linear programming problem (MINLP) that determines load shed under various k-line removal scenarios are solved. These problems are combinatorial that have huge search space, and solution through enumeration is intractable for large power systems. For reduction of search space, the following mathematical tools are derived, (i) two power flow methods due to k-transmission …
Space-Time Photonics, Abbas Shiri
Space-Time Photonics, Abbas Shiri
Electronic Theses and Dissertations, 2020-
Many of the features of photonic devices, including some of the most ubiquitous components such as resonators and waveguides, are usually thought to be intrinsically dependent on their geometry and constitutive materials. As such, the behaviour of an optical field interacting with such devices is dictated by the boundary conditions imposed upon the field. For instance, the resonant wavelengths and linewidths of a planar cavity are expected to be set by the mirrors' reflectivity, cavity length, and refractive index. Henceforth, satisfying a longitudinal phase-matching condition allows for incident light to resonate with the cavity. As another example, consider the planar …
Reconfigurable Load-Modulated Power Amplifier For Energy- And Spectrum-Efficient Wireless Communications, Haifeng Lyu
Reconfigurable Load-Modulated Power Amplifier For Energy- And Spectrum-Efficient Wireless Communications, Haifeng Lyu
Electronic Theses and Dissertations, 2020-
With the increasing demand for faster date rates and extensive user connectivities, the complex modulation schemes and large-scaled arrays have been widely researched and employed in the modern wireless links e.g., 5G and beyond-5G systems. These pose major challenges to design the power amplifiers (PAs) to accommodate the system level evolution. As the critical part, the power amplifiers (PAs) dominate the output power, efficiency, linearity and reliability of the radio frequency (RF) transmitter. Consequently, the PA's capability of maintaining an efficient, linear and reliable signal amplification operation is essential to the communication systems. On the other hand, due to the …
4.74 Ghz Harmonically Operated Saw Device For Sensing Applications And Interrogation System, Michael Morales Otero
4.74 Ghz Harmonically Operated Saw Device For Sensing Applications And Interrogation System, Michael Morales Otero
Electronic Theses and Dissertations, 2020-
Surface acoustic wave (SAW) devices have provided solutions to many sensor applications. With the increasing use of the electromagnetic spectrum, the adoption of higher frequencies for new developments is becoming a necessity. SAW devices represent a solution for advancing many emerging sensor's needs given their inherent advantages such as: wireless operation, low cost, and ease of fabrication. However, the SAW technology has been typically limited to frequencies under 3 GHz due to size limitations, increased SAW losses, and the need of an interrogation system suitable for reading SAW sensors at higher frequencies. This dissertation presents the work done to push …
A Measurement System For Detection Of Intestinal Motility In Neonates By Monitoring Slow Wave Activity, Garett Goodale
A Measurement System For Detection Of Intestinal Motility In Neonates By Monitoring Slow Wave Activity, Garett Goodale
Electronic Theses and Dissertations, 2020-
Similar to how electrocardiographic waves are the pace making signals of the heart, slow waves are the pace making signals of the intestines. Slow waves are electrical signals in the intestines that determine the speed at which food can move through the intestine ensuring proper digestion and uptake of nutrients. It has been shown that slow waves can be measured in adults using non-invasive, surface electrodes. However, no study has investigated the measurements of slow waves in neonates, specifically pre-term neonates. Around 7% of pre-term neonates suffer from necrotizing enterocolitis (NEC) which is a condition that causes damage to the …
Development Of Holographic Phase Masks For Wavefront Shaping, Nafiseh Mohammadian
Development Of Holographic Phase Masks For Wavefront Shaping, Nafiseh Mohammadian
Electronic Theses and Dissertations, 2020-
This dissertation explores a new method for creating holographic phase masks (HPMs), which are phase transforming optical elements holographically recorded in photosensitive glass. This novel hologram recording method allows for the fast production of HPMs of any complexity, as opposed to the traditional multistep process, which includes the design and fabrication of a master phase mask operating in the UV region before the holographic recording step. We holographically recorded transmissive HPMs that are physically robust (they are recorded in a silicate glass volume), can handle tens of kilowatts of continuous wave (CW) laser power, are un-erasable, user defined, require no …
Light Guiding And Concentrating Using Self-Collimating Spatially-Variant Photonic Crystals, Chun Xia
Light Guiding And Concentrating Using Self-Collimating Spatially-Variant Photonic Crystals, Chun Xia
Electronic Theses and Dissertations, 2020-
Advances in integrated photonic devices require low loss, easy-to-integrate solutions for chip-to-chip and chip-to-fiber interfacing. Among the most common solutions are traditional lenses. However, circular lenses require additional mounting mechanisms to ensure proper alignment. Additionally, the beam routing functionality cannot be added to the traditional lenses unless they are combined with mirrors and operate in the reflection mode. In this dissertation, we investigate lens-embedded photonic crystals (LEPCs) as a solution to flat and multifunctional lenses. The concept is demonstrated by creating self-collimating lattices containing a gradient refractive index lens (GRIN-LEPC), a binary-shaped lens (B-LEPC), and a Fresnel-type binary-shaped lens (F-B-LEPC). …
Direct Laser Writing Below The Diffraction Limit By Exploring Multi-Pulse-Induced Physics, Boyang Zhou
Direct Laser Writing Below The Diffraction Limit By Exploring Multi-Pulse-Induced Physics, Boyang Zhou
Electronic Theses and Dissertations, 2020-
Ultrafast laser ablation has enabled high-precision processing of a wide range of materials including metals, semiconductors, dielectrics, and polymers. Several laser nanostructuring methods exist, including those based on optical near-fields, special material properties, surface plasmons, and multiphoton absorption (MPA). Among these methods, the MPA method has the potential for nanoscale direct laser writing by using a simple experimental setup. However, the understanding of the fundamental mechanism involved in the laser ablation process is still incomplete, and it remains challenging to obtain a feature size much smaller than the diffraction-limited spot size. The goal of this research is to understand how …
Integrated Electro-Optic, Microwave, And Nonlinear Photonic Devices On Thin-Film Lithium Niobate, Milad Gholipour Vazimali
Integrated Electro-Optic, Microwave, And Nonlinear Photonic Devices On Thin-Film Lithium Niobate, Milad Gholipour Vazimali
Electronic Theses and Dissertations, 2020-
Lithium niobate has numerous extraordinary features that make it useful for a wide range of applications, particularly in optics. The material's strong electro-optic effect and second-order nonlinearities are two prime examples with applications in optical modulation and wavelength conversion, respectively. The thin-film lithium niobate platform has revitalized the conventional applications of lithium niobate during the last decade. The platform is now one of the most actively investigated subdisciplines in integrated photonics. The waveguides on this innovative platform are high index contrast, resulting in a size reduction of more than 20 times and a bending radius decrease of about two orders …
Biomimetic Design, Modeling, And Adaptive Control Of Robotic Gripper For Optimal Grasping, Mushtaq Al-Mohammed
Biomimetic Design, Modeling, And Adaptive Control Of Robotic Gripper For Optimal Grasping, Mushtaq Al-Mohammed
Electronic Theses and Dissertations, 2020-
Grasping is an essential skill for almost every assistive robot. Variations in shape and/or weight of different objects involved in Activities of Daily Living (ADL) lead to complications, especially, when the robot is trying to grip novel objects for which it has no prior information –too much force will deform or crush the object while too little force will lead to slipping and possibly dropped objects. Thus, successful grasping requires the gripper to immobilize an object with the minimal force. In Chapter 2, we present the design, analysis, and experimental implementation of an adaptive control to facilitate 1-click grasping of …
Multi-Element Mobile Optical Wireless Communication Networks, Pooya Nabavi
Multi-Element Mobile Optical Wireless Communication Networks, Pooya Nabavi
Electronic Theses and Dissertations, 2020-
The capacity of traditional wireless radio-frequency (RF) networks such as wireless fidelity (Wi-Fi) is insufficient to meet ever-increasing demand for bandwidth stemming from growth in smart, connected devices. The omni-directional nature of RF signals does not allow easy solutions that involve adding more access points to support more devices and capacity because they start to interfere with each other. Optical wireless communications (OWC) have already extended the superb bandwidth capacity of wired optical datalinks to sites that cannot be connected by traditional optical fibers, such as satellites and disaster recovery areas. Development of OWC technologies for dense, multi-user environments promises …
Synthesis And Characterization Of P-Type Transparent Conducting Copper Gallium Oxide Thin Films, Ashwin Kumar Saikumar
Synthesis And Characterization Of P-Type Transparent Conducting Copper Gallium Oxide Thin Films, Ashwin Kumar Saikumar
Electronic Theses and Dissertations, 2020-
Transparent conducting oxides (TCO) are a special class of materials that possess both the properties of optical transparency and electrical conductivity. They find use in various applications such as flat panel displays, light-emitting diodes, solar cells, touch screens, smart windows, etc. Some of the most well-known and widely used TCOs are ZnO doped with Al, In2O3 doped with Sn, and SnO2 doped with F. All these TCOs are n-type in nature and show n-type conductivity. On the contrary, p-type TCOs are not very common, and due to their inherent low mobility, it is very challenging to synthesize highly conductive p-type …
Hydrogen And Peer-To-Peer Energy Exchanges For Deep Decarbonization Of Power Systems, Hamed Haggi
Hydrogen And Peer-To-Peer Energy Exchanges For Deep Decarbonization Of Power Systems, Hamed Haggi
Electronic Theses and Dissertations, 2020-
Decreasing costs of renewable energy resources and net-zero emission energy production policy, set by U.S. government, are two preeminent factors that motivate power utilities to deploy more system- or consumer-centric distributed energy resources (DERs) to decarbonize electricity production. Since, deep energy decarbonization cannot be achieved without high penetration of renewable energy sources, utilities should develop and invest in new business models for power system operation and planning during the energy transition. Considering the pathways to deeply decarbonize power systems, first, this dissertation proposes a novel hierarchical peer-to-peer (P2P) energy market design in active distribution networks. The framework integrates the distributional …
Broadband Power Amplifier Design With High Power, High Efficiency And Large Back-Off Range, Yuchen Cao
Broadband Power Amplifier Design With High Power, High Efficiency And Large Back-Off Range, Yuchen Cao
Electronic Theses and Dissertations, 2020-
As modern communication system technology develops, the demand for devices with smaller size, higher efficiency, and larger bandwidth has increased dramatically. To achieve this purpose, a novel architecture of load modulated balanced amplifier (LMBA) with a unique load-modulation characteristic different from any existing LMBAs and Doherty power amplifiers (DPAs) was presented, which is named as Pseudo-Doherty LMBA (PD-LMBA). Based on a special combination of control amplifier (carrier) and balanced amplifier (peaking) together with proper phase and amplitude controls, an optimal load-modulation behavior can be achieved for PD-LMBA leading to maximized efficiency over extended power back-off range. More importantly, the efficiency …
Fabrication Of Piezoelectric Field Effect Transistors For Acoustic Signal Detection, Luke Minks
Fabrication Of Piezoelectric Field Effect Transistors For Acoustic Signal Detection, Luke Minks
Electronic Theses and Dissertations, 2020-
In this study, a standard bulk FET design is fabricated with a piezoelectric gate, allowing a microwave-frequency voltage signal to be transmitted from a transducer to the transistor via acoustic conduction through the substrate. Using a single polycrystalline aluminum nitride film as the piezoelectric material, microwave-frequency piezoelectric transducers were fabricated in parallel with piezoelectric FETs. These device pairs function by generating high frequency acoustic waves in the substrate via application of AC voltage to the transducers; the transistors then recover these signals by detecting these waves in their gates via the piezoelectric film, reproducing an attenuated version of the original …
Reduced Footprint Probabilistic Inference Networks Using Novel Hybrid She-Mtj/Cmos Based Majority Gate, Harshavardhan Reddy Thummala
Reduced Footprint Probabilistic Inference Networks Using Novel Hybrid She-Mtj/Cmos Based Majority Gate, Harshavardhan Reddy Thummala
Electronic Theses and Dissertations, 2020-
In recent years, innovations in machine learning using artificial neural networks (ANN) have significantly increased and led to various applications like image recognition, text classification, machine translation, sequence recognition, etc. Earlier, research was focused on software-based DBNs, which are implemented on conventional von-Neumann architectures that provided flexibility but had few limitations. Recent studies have implemented hardware-based designs like FPGA-based, CMOS based, RRAM-based, and MRAM-based designs to overcome these limitations. Hybrid CMOS-MTJ-based RBMs provided significant area and energy improvements compared to other techniques. We herein implemented Spatial and Temporal redundant probabilistic interpolation network to improve the accuracy and provide fault tolerance …
Studies On Copper Indium Based Oxide Transparent Semiconducting Thin Films., Giji Skaria
Studies On Copper Indium Based Oxide Transparent Semiconducting Thin Films., Giji Skaria
Electronic Theses and Dissertations, 2020-
Transparent Conducting Oxides (TCOs) have unique optoelectronic properties which allow visible light to pass through while having reasonably high electrical conductivity. TCOs find a variety of applications ranging from uses in solar cells, optical displays, reflective coatings, light emission devices, low-emissivity windows, electrochromic mirrors, UV sensors, and windows, defrosting windows, electromagnetic shielding, and transparent electronics. The conductivity of TCOs can be tuned from insulating via semiconducting to conducting as well as their transparency adjusted depending on the donor/acceptor levels as well as the bandgap of the material. This enables the realization of both n-type and p-type TCOs which make them …
Diffractive Liquid Crystal Optical Elements For Near-Eye Displays, Jianghao Xiong
Diffractive Liquid Crystal Optical Elements For Near-Eye Displays, Jianghao Xiong
Electronic Theses and Dissertations, 2020-
Liquid crystal planar optics (LCPO) with versatile functionalities is emerging as a promising candidate for overcoming various challenges in near-eye displays, like augmented reality (AR) and virtual reality (VR), while maintaining a small form factor. This type of novel optical element exhibits unique properties, such as high efficiency, large angular/spectral bandwidths, polarization selectivity, and dynamic modulation. The basic molecular configuration of these novel reflective LCPO is analyzed, based on the simulation of molecular dynamics. In contrast to previously assumed planar-twist structure, our analysis predicts a slanted helix structure, which agrees with the measured results. The optical simulation model is established …
Patterned Liquid Crystal Devices For Near-Eye Displays, Kun Yin
Patterned Liquid Crystal Devices For Near-Eye Displays, Kun Yin
Electronic Theses and Dissertations, 2020-
As a promising next-generation display, augmented reality (AR) and virtual reality (VR) have shown attractive features and attracted broad interests from both academia and industry. Currently, these near-eye displays (NEDs) have enabled numerous applications, ranging from education, medical, entertainment, to engineering, with the help of compact and functional patterned liquid crystal (LC) devices. The interplay between LC patterns and NEDs stimulates the development of novel LC devices with unique surface alignments and volume structures, which in turn feedback to achieve more compact and versatile NEDs. This dissertation will focus on the patterned LC with applications in NEDs. Firstly, we propose …
Volumetric Microfabrication With Structured Light, He Cheng
Volumetric Microfabrication With Structured Light, He Cheng
Electronic Theses and Dissertations, 2020-
Multiphoton polymerization (MPP) as one of the direct laser writing techniques is capable of manufacturing three-dimensional (3D) micro-structures with complex shapes and novel functionalities. However, current MPP methods rely on point-by-point or layer-by-layer scanning and therefore are time-consuming. The low fabrication throughput of conventional MPP is the key factor that limits its wider adoption for industrial manufacturing over large surface area. One way to increase the fabrication speed is to turn layer-by-layer process into a volumetric process. An ideal volumetric printing method can fabricate structures with complex 3D geometry by single exposure and should be easy to implement. As a …
Power Inductors: Design, Modeling And Analysis, Subash Pokharel
Power Inductors: Design, Modeling And Analysis, Subash Pokharel
Electronic Theses and Dissertations, 2020-
Power inductors, or reactors as they are called in the power industry, are one of the fundamental components of a power system. They serve various purposes in both conventional and emerging power systems including: power flow control, fault current limitation, reactive power compensation, harmonic filtering, and others. This dissertation explores the design and applications of conventional power inductors and ways to overcome their shortcomings and expand their functionalities. In addition, novel inductor designs are proposed and analyzed to address power system challenges. A series of inductors, including traditional constant reactance inductor, gapless ferromagnetic core reactor (GFCR) (both costant and variable …
Intrinsically Mode Reconfigurable Load Modulation Balanced Amplifier Leveraging Transistor's Analog-Digital Duality, Niteesh Bharadwaj Vangipurapu
Intrinsically Mode Reconfigurable Load Modulation Balanced Amplifier Leveraging Transistor's Analog-Digital Duality, Niteesh Bharadwaj Vangipurapu
Electronic Theses and Dissertations, 2020-
The communication schemes have rapidly changed the face of the human means of communication. The evolution from one generation to another has triggered many challenges on the design methodologies of RF designers. As the evolution ensued, the spectrally efficient modulation schemes have resulted in the substantial rise of PAPR, the peak-to-average power ratio. To enable the efficient amplification of the high PAPR signals, this thesis explores the areas of Load modulated Balanced amplifiers that can be inherently reconfigured to achieve a better efficiency than the conventional RF power amplifiers that see a significant drop in the efficiency as the signal …