Engineering Commons^™

Development Of Mems-Based Corrosion Sensor, Feng Pan

Graduate Theses and Dissertations

This research is to develop a MEMS-based corrosion sensor, which is used for monitoring uniform, galvanic corrosion occurring in infrastructures such as buildings, bridges. The corrosion sensor is made up of the composite of micro/nano metal particles with elastomers. The mechanism of corrosion sensor is based on the mass transport of corrosive species through the sensor matrix. When the metal particles in the matrix corrode, the electrical resistivity of the material increases due to increasing particle resistances or reduction of conducting pathways. The corrosion rate can be monitored by detecting the resistivity change in sensing elements. The life span of …

Optimization Of Nonlinear Switch Cells For Switching Converters, Bradley Alan Reese

Graduate Theses and Dissertations

Switch cells consist of an array of power switches and passive components which can replace the main switches alone in many power topologies, allowing reduced switching loss without altering the power topology directly. This thesis discusses the development of a switch cell topology that utilizes a saturable resonant inductor to reduce the size and power loss of the cell. Additionally, the cell transfers energy stored in the inductor into a capacitor for efficient energy storage during the cell's conduction region. This energy is then transferred back to the system when the cell turns off, thus reducing the total switching energy.

Plasmonic And Photonic Designs For Light Trapping In Thin Film Solar Cells, Liming Ji

Graduate Theses and Dissertations

Thin film solar cells are promising to realize cheap solar energy. Compared to conventional wafer cells, they can reduce the use of semiconductor material by 90%. The efficiency of thin film solar cells, however, is limited due to insufficient light absorption. Sufficient light absorption at the bandgap of semiconductor requires a light path more than 10x the thickness of the semiconductor. Advanced designs for light trapping are necessary for solar cells to absorb sufficient light within a limited volume of semiconductor. The goal is to convert the incident light into a trapped mode in the semiconductor layer.

In this dissertation, …

Conductive Concrete For Electromagnetic Shielding – Methods For Development And Evaluation, Aaron P. Krause

Computer and Electronics Engineering: Dissertations, Theses, and Student Research

This research investigates the development and evaluation innovative methods for the use of conductive concrete as an electromagnetic shield. New testing methods are developed to determine the best conductive components to use in the design of a concrete mixture for shielding that shows the best promise. The conductive concrete mixture has the potential to provide electromagnetic shielding that is cost-effective in terms of construction, operation, and maintenance compared to conventional approaches. Two testing methods, Small Sample Testing and Large Slab Testing, are developed based on standardized testing methods that have been modified for the testing of conductive concrete mixtures. As …

Energy Harvesting Of Human Kinetic Movement, David Marusiak, Julia Carrillo

Electrical Engineering

Development of kinetic energy scavenging applications from the human body necessitates additional research to assist in designating a mounting position for a potential device. A data acquisition system adequately provides a parametric average power comparison among four locations on the body (waist, upper arm, hand, and calf) for both a male and female subject. Experimentally, the hand-held device provided the highest average power. Thus, subsequent investigation at set speeds provides further analysis of the output’s characteristically linear behavior. The physical energy-harvesting device features a plastic tube casing wrapped with the stationary coiled wire through which a neodymium magnet oscillates. While …

Multi-Hole Waveguide Directional Couplers, Mahmoud Moghavvemi, Hossein Ameri Mahabadi, Farhang Alijani

Hossein Ameri Mahabadi

1. Introduction The directional couplers are inherently assumed as four-port devices, which consisted of two transmission lines that are electromagnetically coupled to each other. The first port is named as input, and the second one as output or transmitted, the third one as sampling or coupled and the fourth one as isolated or terminated. By using a special design the input power is divided between output and coupled port in a certain ratio named coupling factor. The required value for coupling factor P1/P3 defines the range of applications for directional couplers. Based on the application, coupling factor could be any …

Fiber-Tip Fabry-Perot Interferometric Sensor Based On A Thin Silver Film, Fawen Guo

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Fiber-optic sensors have many advantages, including small size, light weight, immunity to electromagnetic interference, and the capability of remote sensing. Fiber- tip sensors are fabricated on a fiber tip and are the smallest type of fiber-optic sensor. The fiber-tip sensors have attracted a great deal of attention in past years for pressure, temperature, and acoustic sensing.

In this thesis, a fiber-tip sensor based on an ultra-thin silver film was proposed and demonstrated for highly sensitive and high frequency ultrasonic detection. The film is prepared by the vacuum thermal deposition method and then transferred to the fiber tip. The sensor has …

Large Coercivity In Nanostructured Rare-Earth-Free Mnₓga Films, Don Heiman, Tom Nummy, Steve Bennett, Tom Cardinal

Donald Heiman

The magnetic hysteresis of MnₓGa films exhibit remarkably large coercive fields as high as μₒHC=2.5 T when fabricated with nanoscale particles of a suitable size and orientation. This coercivity is an order of magnitude larger than in well-ordered epitaxial film counterparts and bulk materials. The enhanced coercivity is attributed to the combination of large magnetocrystalline anisotropy and ~50-100 nm size nanoparticles. The large coercivity is also replicated in the electrical properties through the anomalous Hall effect. The magnitude of the coercivity approaches that found in rare-earth magnets, making them attractive for rare-earth-free magnet applications.

Characterization Of Turn-On Time Delay In A Fiber Grating Fabry-Perot Lasers, Faisal Rafiq Mahamd Adikan

Faisal Rafiq Mahamd Adikan

In this paper, turn-on time delay characteristics of a fiber grating Fabry-Perot (FGFP) laser are numerically investigated by considering all the carrier recombination rate (CRR) R(N) coefficients (nonradiative, A(nr); radiative, B; and Auger coefficient, C). The results show that the turn-on time delay significantly reduces by increasing the injection current (I-inj) and/or the initial value of carrier density (N-i). Meanwhile, the turn-on time delay increases by increasing the CRR coefficients. However, its effect can be minimized by increasing I-inj and/or N-i. In addition, the turn-on time delay can be reduced by increasing the external optical feedback (OFB) level. Moreover, it …

Degenerate Parallel Conducting Layer And Conductivity Type Conversion Observed From P-Ge1 - YSnY (Y = 0.06%) Grown On N-Si Substrate, Mee-Yi Ryu, Yung Kee Yeo, M. Ahoujja, Thomas R. Harris, Richard T. Beeler, John Kouvetakis

Faculty Publications

Electrical properties of p-Ge_1−ySn_y (y = 0.06%) grown on n-Si substrate were investigated through temperature-dependent Hall-effect measurements. It was found that there exists a degenerate parallel conducting layer in Ge_1−ySn_y/Si and a second, deeper acceptor in addition to a shallow acceptor. This parallel conducting layer dominates the electrical properties of the Ge_1−ySn_y layer below 50 K and also significantly affects those properties at higher temperatures. Additionally, a conductivity type conversion from p to n was observed around 370 K for this sample. A two-layer conducting model was used …

Serpentine Low Loss Trapezoidal Silica Waveguides On Silicon, Xiaomin Zhang, Mark Harrison, Audrey Harker, Andrea M. Armani

Engineering Faculty Articles and Research

We report the fabrication and characterization of straight and serpentine low loss trapezoidal silica waveguides integrated on a silicon substrate. The waveguide channel was defined using a dual photo-lithography and buffered HF etching and isolated from the silicon substrate using an isotropic silicon etchant. The waveguide is air-clad and thus has a core-cladding effective index contrast of approximately 25%. Measured at 658, 980 and 1550nm, the propagation loss was found to be 0.69, 0.59, and 0.41dB/cm respectively, with a critical bending radius less than 375μm. The waveguide’s polarization behavior was investigated both theoretically and experimentally. Additionally, the output power shows …

Ground Vehicle Navigation Using Magnetic Field Variation, Jeremiah A. Shockley

Theses and Dissertations

The Earth's magnetic field has been the bedrock of navigation for centuries. The latest research highlights the uniqueness of magnetic field measurements based on position due to large scale variations as well as localized perturbations. These observable changes in the Earth's magnetic field as a function of position provide distinct information which can be used for navigation. This dissertation describes ground vehicle navigation exploiting variation in Earth's magnetic field using a self-contained navigation system consisting of only a magnetometer and magnetic field maps. In order to achieve navigation, effective calibration enables repeatable magnetic field measurements from different vehicles and facilitates …

Fabrication Of A Multimode Interference Device In A Low-Loss Flat-Fiber Platform Using Physical Micromachining Technique, Faisal Rafiq Mahamd Adikan

Faisal Rafiq Mahamd Adikan

A physical micromachining technique is demonstrated in a low-loss flat-fiber substrate to fabricate a multimode interference (MMI) device. The flat-fiber substrate is a low-index-contrast material; however, by making use of two physically micromachined trenches, lateral confinement is achieved providing high index contrast for the MMI region. A 1 x 3 MMI device exhibiting 1.89 dB of excess loss has been demonstrated.

Efficient, Wide Angle, Structure Tuned 1 X 3 Photonic Crystal Power Splitter At 1550 Nm For Triple Play Applications, Faisal Rafiq Mahamd Adikan

Faisal Rafiq Mahamd Adikan

We propose a wide angle, efficient and low loss 1 x 3 power splitter based on triangular lattice air holes silicon slab Photonic Crystal (PhC). Desired power splitting ratio was achieved by altering the structure at the junction area of the power splitter. Simulation results obtained using 2-D finite difference time domain method show that for TE polarization incident signal, the power is distributed almost equally with total normalized transmission of 99.74% and negligible reflection loss at the 1550 nm optical operating wavelength. In addition, the power splitter can operate at 1388 nm and 1470 nm optical wavelengths.

Direct Uv Written Optical Waveguides In Flexible Glass Flat Fiber Chips, Faisal Rafiq Mahamd Adikan

Faisal Rafiq Mahamd Adikan

A glass-based substrate technology that fills the gap between a truly flexible extended length distributed sensor medium and the multifunctionality of optical chips is demonstrated. Flat fiber chips will open further degrees of freedom to control the behavior of light via mechanical manipulation. A flexible flat format will also allow straightforward incorporation into smart structures. Coupled with low manufacturing costs, these flexichips can also be a key enabler to disposable high-end sensing devices or fully distributed point sensors. In this study, Bragg gratings were used to demonstrate the optical flatness of the flat fiber core layer. Furthermore, the effective index …

Commissioning Of The Asta Laser Lab With Uv Pulse Length Characterization, Daniel Kelley, Jeff Corbett

STAR Program Research Presentations

The Linac Coherent Light Source (LCLS) at SLAC depends on a photocathode electron gun to provide the linear accelerator with the raw material – electrons – used for making X-ray laser pulses. The photocathode used in the LCLS Injector is a clean copper plate in high vacuum. When the cathode is struck with high energy UV light, electrons are liberated from its surface and then accelerated down the linac with radio-frequency electric fields. These fast-moving bunches of electrons are directed through an undulator magnet to radiate X-ray light.

Although scientists have been using photocathode techniques at SLAC for 25 years, …

Optical Mode Study Of Galium Nitride Based Laser Diodes, Douglas Cattarusa

Electrical Engineering

This paper focuses on the optical mode analysis of laser diodes to improve light emission. Under the mode analysis, we compare the optical confinement factor (OCF) percentage of the emitting light from the LDs. There are two structures which we analyze: a basic GaN waveguide structure and an InGaN waveguide structure. The second structure has additional InGaN waveguides and is analyzed under two additional design variations: the concentration of Indium and the thickness of the top waveguide layer. The results of this study indicate introducing InGaN waveguide layers correlates with lower order modes (zero and first order) and increase the …

Spectral Analysis Of Encrypted Chaotic Signals Using Fast Fourier Transforms And Laboratory Spectral Analyzers, Monish Ranjan Chatterjee, Abhinay Kundur

Electrical and Computer Engineering Faculty Publications

The use of acousto-optic chaos, as manifested via first-order feedback in an acousto-optic Bragg cell, in encrypting a message wave and subsequently recovering the message in the receiver using a chaotic heterodyne strategy, has been reported recently [1-3]. In examining the dynamical system analytically using computer simulation, (expected) modulated chaos waveforms are obtained within specified observation windows.

Because of the relatively random nature inherent in chaos waveforms, it is essentially impossible to ascertain from the visual display of the chaotic wave whether a given message signal has in fact modulated the chaotic "carrier". In fact, it has been observed from …

3.5 To 30 Mhz Automatic Antenna Impedance Matching System, William Blodgett

Electrical Engineering

Two-way communications using 3 to 30 MHz, high-frequency (HF) radio, also known as shortwave radio, provides worldwide coverage with no infrastructure required between stations. Amateur or “Ham” radio operators apply this advantage to long distance communications and to provide disaster relief communications. Optimum frequencies for long distance propagation are time-of-day variant necessitating an operating frequency range of 3 to 30 MHz. HF half wave dipole antenna length varies from 15 to 150 ft over this range. Fixed-length antenna impedance varies with frequency due to physical dimension dependent capacitance and inductance. Maximum transmitter to antenna power transfer occurs when the transmission …

Highly Sensitive X-Ray Detectors In The Low-Energy Range On N-Type 4h-Sic Epitaxial Layers, K. C. Mandal, P. G. Muzykov, J. R. Terry

Faculty Publications

No abstract provided.

Switch Yard Operation In Thermal Power Plant(Katpp Jhalawar Rajasthan), Radhey Shyam Meena Er.

Radhey Shyam Meena

Switchyard Provides the facilities for switching ,protection & Control of electric power. To handle high Voltage power with proper Safety measures. To isolate the noises coming from the grid with true 50Hz power SWITCH YARD IS IMPORTANT PART IN THERMAL PLANT. IN KALISINDH THERMAL 400KV AND 220KV SWITCH YARD LOCATED.

Infrared Study Of Er3+/Yb3+ Co-Doped Geo2-Pbo-Bi2o3 Glass, Faisal Rafiq Mahamd Adikan

Faisal Rafiq Mahamd Adikan

Heavy metal oxide glasses, containing bismuth and/or lead in their glass structure are new alternatives for rare eart (RE) doped hosts. Hence, the study of the structure of these vitreous systems is of great interest for science and technology. In this research work, GeO2-PbO-Bi2O3 glass host doped with Er3+/Yb3+ ions was synthesized by a conventional melt quenching method. The Fourier transform infrared (FTIR) results showed that PbO and Bi2O3 participate with PbO4 tetragonal pyramids and strongly distort BiO6 octahedral units in the glass network, which subsequently act as modifiers in glass structure. These results also confirmed the existence of both …

Chalcogenide Microsphere Fabricated From Fiber Tapers Using Contact With A High-Temperature Ceramic Surface, Pengfei Wang, Ganapathy Murugan, Gilberto Bramilla, Ming Ding, Yuliya Semenova, Qiang Wu, Gerald Farrell

Articles

The fabrication 1 and characterization of a 2 chalcogenide glass microsphere resonator has been demonstrated. 3 At wavelengths near 1550 nm, whispering gallery mode 4 resonances can be efficiently excited in a 74-μm-diameter 5 chalcogenide glass microsphere via evanescent coupling using a 6 tapered silica glass fiber with a waist diameter of circa 2 μm. 7 Resonances with Q-factors greater than 105 were observed. 8 Due to the high nonlinearity properties of the chalcogenide 9 material and the ease of fabrication process, chalcogenide 10 microspheres offer the potential for robustly assembled fully 11 integrated photonic devices. 12 Index Terms—Chalcogenide

Modeling, Identification, Validation And Control Of A Hybrid Maglev Ball System, Ahmed Elhussein E. Mekky

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, the electrodynamics of a single axis hybrid electromagnetic suspension Maglev system was modeled and validated by applying it to a single axis hybrid maglev ball experiment. By exploring its linearized model, it was shown that the single axis hybrid Maglev ball has inherently unstable dynamics. Three control scenarios were explored based on the linearized model; (1) Proportional, Deferential (PD) control, (2) Proportional, Deferential, Integral (PID) and (3) PID controller with pre-filtering. This thesis has shown that a PID controller with a pre-filtering technique can stabilize such a system and provide a well-controlled response.

A parametric system identification …

Application Of Chebyshev Formalism To Identify Nonlinear Magnetic Field Components In Beam Transport System, Michael Spata

Physics Theses & Dissertations

An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a beam-based technique for characterizing the extent of the nonlinearity of the magnetic fields of a beam transport system. Horizontally and vertically oriented pairs of air-core kicker magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the beam orbit relative to the unperturbed reference orbit. Fourier decomposition of the position data at eight different points along the beamline was then used to measure the amplitude of these frequencies. For a purely linear transport system one expects to find solely the …

Reconfigurable Antenna And Rf Circuits Using Multi-Layer Stretchable Conductors, Riaz Ahmed -. Liyakath

USF Tampa Graduate Theses and Dissertations

The growth of flexible electronics industry has given rise to light-weight, flexible devices which have a wide range of applications such as wearable electronics, flexible sensors, conformal antennas, bio-medical applications, solar cells etc. Though several techniques exist to fabricate flexible devices, the limiting factors have been durability, cost and complexity of the approach. In this research, the focus has been on developing stretchable (flexible) conductors using a multi-layer structure of metal and conductive rubber. The stretchable conductors developed using this approach do not lose electrical connection when subjected to large strains up to 25%. Also, the conductivity of the conductive …

Millimeter Wave Carrier Generation Based On A Double-Brillouin-Frequency Spaced Fiber Laser, Faisal Rafiq Mahamd Adikan

Faisal Rafiq Mahamd Adikan

An all-optical generation of a millimeter wave carrier from a multiwavelength Brillouin-erbium fiber laser is presented. Four-channel output with spacing of about 21.5 GHz is generated from the fiber laser by controlling the gain in the cavity. A dual-wavelength signal with spacing correspondent to six orders of Brillouin frequency shift is obtained by suppressing the two channels at the middle. Heterodyning these signals at the high-speed photodetector produces a millimeter wave carrier at 64.17 GHz. Temperature dependence characteristic of Brillouin frequency shift realize the flexibility of generated millimeter wave frequency to be tuned at 6.6 MHz/ degrees C. (C) 2012 …

The Effect Of Polarization And Ingan Quantum Well Shape In Multiple Quantum Well Light Emitting Diode Heterostructures, Patrick M. Mcbride

Master's Theses

Previous research in InGaN/GaN light emitting diodes (LEDs) employing semi-classical drift-diffusion models has used reduced polarization constants without much physical explanantion. This paper investigates possible physical explanations for this effective polarization reduction in InGaN LEDs through the use of the simulation software SiLENSe. One major problem of current LED simulations is the assumption of perfectly discrete transitions between the quantum well (QW) and blocking layers when experiments have shown this to not be the case. The In concentration profile within InGaN multiple quantum well (MQW) devices shows much smoother and delayed transitions indicative of indium diffusion and drift during …

Rayleigh-Based Raman Fiber Laser With Passive Erbium-Doped Fiber For Secondary Pumping Effect In Remote L-Band Erbium-Doped Fiber Amplifier, Faisal Rafiq Mahamd Adikan

Faisal Rafiq Mahamd Adikan

This work focuses on a secondary pumping scheme for remote L-band erbium-doped fiber amplifier (R-EDFA) generated by integrating Rayleigh-based ultralong Raman fiber laser (ULRFL) with a section of passive erbium-doped fiber (EDF). A selective wavelength reflector combined with Rayleigh feedback in the transmission span forms the ULRFL cavity while the passive EDF deployed at the end of the span converts the ULRFL into a secondary C-band pump. Optimum ULRFL wavelength is determined by tuning the selective wavelength reflector across the C-band region. Combination of R-EDFA gain, Raman amplification, and passive EDF provides gain improvement as high as 15.5 dB over …

Day/Night Band Imager For A Cubesat, Eric Stanton

Electrical Engineering

Day/Night Band (DNB) earth sensing and meteorological systems like the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) provide visible wavelength imagery 24 hours a day that is used primarily for cloud imaging in support of weather forecasting. This paper describes a compact push-broom imager that meets low light imaging requirements for DMSP OLS and the NOAA/NASA Joint Polar Satellite System (JPSS) as documented in the Integrated Operational Requirements Document [1] (IORD) including the imager design, system level concepts of operation for data collection, radiometric and spatial calibration, and data transmission to Earth. This small, lightweight imager complies with …