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Articles 1 - 30 of 40
Full-Text Articles in Engineering
Water-Soluble Polythiophene∕Nanocrystalline Tio2 Solar Cells, Qiquan Qiao, James T. Mcleskey Jr.
Water-Soluble Polythiophene∕Nanocrystalline Tio2 Solar Cells, Qiquan Qiao, James T. Mcleskey Jr.
Mechanical and Nuclear Engineering Publications
We report the characteristics of polymer∕nanocrystalline solar cells fabricated using an environmentally friendly water-soluble polythiophene and TiO2 in a bilayer configuration. The cells were made by dropping the polymer onto a TiO2nanocrystallinefilm and then repeatedly sweeping a clean glass rod across the polymer as it dried. The devices showed an open circuit voltage of 0.81 V, a short circuit current density of 0.35mA/cm2, a fill factor of 0.4, and an energy conversion efficiency of 0.13%. The water-soluble polythiophene showed significant photovoltaic behavior and the potential for use in solar cells.
Characteristics Of Water-Soluble Polythiophene: Tio2 Composite And Its Application In Photovoltaics, Qiquan Qiao, Lianyong Su, James Beck, James T. Mcleskey Jr.
Characteristics Of Water-Soluble Polythiophene: Tio2 Composite And Its Application In Photovoltaics, Qiquan Qiao, Lianyong Su, James Beck, James T. Mcleskey Jr.
Mechanical and Nuclear Engineering Publications
We have studied the characteristics of composites of an environmentally friendly water-soluble polythiophene sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] (PTEBS) and TiO2. We observed that the ultraviolet-visible absorption spectrum of low molecular weight PTEBS is redshifted possibly due to the formation of aggregates. Cyclic voltammetry reveals the values of highest occupied molecular orbitals and lowest unoccupied molecular orbitals for PTEBS. A factor of 7 in photoluminescence quenching indicates that the exciton dissociation and charge separation occur successfully at the PTEBS: TiO2 (1:1 by weight) interface. This enhances the possibility that the separated charges will reach the electrodes before recombining. Scanning electron micrograph images show …
A Multiple-Objective Decision Analysis Of Stakeholder Values To Identify Watershed Improvement Needs, Jason R. W. Merrick, Gregory S. Parnell, Jamison Barnett, Margot Garcia
A Multiple-Objective Decision Analysis Of Stakeholder Values To Identify Watershed Improvement Needs, Jason R. W. Merrick, Gregory S. Parnell, Jamison Barnett, Margot Garcia
Statistical Sciences and Operations Research Publications
The paper describes the use of multiple objective decision analysis to qualitatively and quantitatively assess the quality of an endangered watershed and guide future efforts to improve the quality of the watershed. The Upham Brook watershed is an urban watershed that lies at the interface of declining inner city Richmond, Virginia and growth-oriented Henrico County. A section of stream within the watershed has been identified as so dangerously polluted that it threatens the health of the residents who live within the watershed boundaries. With funding provided by the National Science Foundation, the Upham Brook watershed project committee was formed to …
Gan Resistive Hydrogen Gas Sensors, Feng Yun, Serguei A. Chevtchenko, Yong-Tae Moon, Hadis Morkoç, Timothy J. Fawcett, John T. Wolan
Gan Resistive Hydrogen Gas Sensors, Feng Yun, Serguei A. Chevtchenko, Yong-Tae Moon, Hadis Morkoç, Timothy J. Fawcett, John T. Wolan
Electrical and Computer Engineering Publications
GaN epilayers grown by organometallic vapor phase epitaxy have been used to fabricate resistivegas sensors with a pair of planar ohmic contacts. Detectible sensitivity to H2 gas for a wide range of gas mixtures in an Ar ambient has been realized; the lowest concentration tested is ∼0.1% H2 (in Ar), well below the lower combustion limit in air. No saturation of the signal is observed up to 100% H2 flow. Real-time response to H2 shows a clear and sharp response with no memory effects during the ramping cycles of H2 concentration. The change in current at a fixed voltage to …
Enhancement Of Phase Separation In The Ingan Layer For Self-Assembled In-Rich Quantum Dots, Il-Kyu Park, Min-Ki Kwon, Sung-Ho Baek, Young-Woo Ok, Tae-Yeon Seong, Seong-Ju Park, Yoon-Seok Kim, Yong-Tae Moon, Dong-Joon Kim
Enhancement Of Phase Separation In The Ingan Layer For Self-Assembled In-Rich Quantum Dots, Il-Kyu Park, Min-Ki Kwon, Sung-Ho Baek, Young-Woo Ok, Tae-Yeon Seong, Seong-Ju Park, Yoon-Seok Kim, Yong-Tae Moon, Dong-Joon Kim
Electrical and Computer Engineering Publications
The enhancement of phase separation in the InGaN layer grown on a GaN layer with a rough surface was investigated for the formation of self-assembled In-rich quantum dots(QDs) in the InGaN layer. Transmission electron microscopy images showed that In-rich QDs with a size of 2–5 nm were formed even in an InGaN layer with a low indium content, and a layer thickness less than the critical thickness. The room-temperature photoluminescence(PL) spectrum of this layer showed emission peaks corresponding to In-rich QDs. The temperature-dependent PL spectra showed dominant peak shifts to the lower energy side, indicating that the self-assembled In-rich QDs …
Effect Of N+-Gan Subcontact Layer On 4h–Sic High-Power Photoconductive Switch, K. Zhu, S. Doğan, Y.-T. Moon, J. Leach, F. Yun, D. Johnstone, Hadis Morkoç, G. Li, B. Ganguly
Effect Of N+-Gan Subcontact Layer On 4h–Sic High-Power Photoconductive Switch, K. Zhu, S. Doğan, Y.-T. Moon, J. Leach, F. Yun, D. Johnstone, Hadis Morkoç, G. Li, B. Ganguly
Electrical and Computer Engineering Publications
High-power photoconductive semiconductor switching devices were fabricated on 4H–SiC. In order to prevent current crowding, reduce the contact resistance, and avoid contact degradation, a highly n-doped GaN subcontact layer was inserted between the contact metal and the high resistivity SiC bulk. This method led to a two orders of magnitude reduction in the on-state resistance and, similarly, the photocurrent efficiency was increased by two orders of magnitude with the GaN subcontact layer following the initial high current operation. Both dry etching and wet etching were used to remove the GaN subcontact layer in the channel area. Wet etching was found …
Visible-Ultraviolet Spectroscopic Ellipsometry Of Lead Zirconate Titanate Thin Films, Hosun Lee, Youn Seon Kang, Sang-Jun Cho, Bo Xiao, Hadis Morkoç, Tae Dong Kang
Visible-Ultraviolet Spectroscopic Ellipsometry Of Lead Zirconate Titanate Thin Films, Hosun Lee, Youn Seon Kang, Sang-Jun Cho, Bo Xiao, Hadis Morkoç, Tae Dong Kang
Electrical and Computer Engineering Publications
We measured pseudodielectric functions in the visible-ultraviolet spectral range of Pb(ZrxTi1−x)O3 (x=0.2, 0.56, 0.82) (PZT)grown on platinized silicon substrate using the sol-gel method and also on (0001) sapphire using radio frequency sputtering method. Using a parametric optical constant model, we estimated the dielectric functions of the PZTthin films. Taking the second derivative of the fitted layer dielectric functions and using the standard critical point model, we determined the parameters of the critical points. In the second derivative spectra, the lowest bandgap energy peak near 4eV is fitted as a double peak for annealedPZTs associated with the perovskite phase. As-grown PZTs …
Surface Charging And Current Collapse In An Algan∕Gan Heterostructure Field Effect Transistor, S. Sabuktagin, S. Doğan, A. A. Baski, Hadis Morkoç
Surface Charging And Current Collapse In An Algan∕Gan Heterostructure Field Effect Transistor, S. Sabuktagin, S. Doğan, A. A. Baski, Hadis Morkoç
Electrical and Computer Engineering Publications
This work investigates the correlation between surfacecharging and current collapse in an AlGaN∕GaNheterostructurefield effect transistor.Surfacecharging due to applied biases was sensed by mapping the surface potential between the gate and drain using scanning Kelvin probe microscopy. Due to the bias, the surface band bending near the gate edge was observed to increase by as much as 1 eV. This increase of band bending is caused by an accumulation of excess charge near the surface during the applied bias. By varying the duration of the applied bias, we find that this accumulation of excess charge near the gate takes about 20 …
Are Spin Junction Transistors Suitable For Signal Processing?, S. Bandyopadhyay, M. Cahay
Are Spin Junction Transistors Suitable For Signal Processing?, S. Bandyopadhyay, M. Cahay
Electrical and Computer Engineering Publications
A number of spintronic analogs of bipolar junction transistors have been proposed for signal processing applications. Here, we show that some of these transistors unfortunately may not have sufficient voltage and current gains for signal processing. They may also have poor isolation between input and output terminals which hinders unidirectional propagation of logic signal from the driver stage to the output. Therefore, these devices may not improve state-of-the-art signal processing capability, although they may provide some additional functionality by offering nonvolatile storage. They may also have niche applications in nonlinear circuits.
Photoresponse Of N-Zno∕P-Sic Heterojunction Diodes Grown By Plasma-Assisted Molecular-Beam Epitaxy, Ya. I. Alivov, Ü. Özgür, S. Doğan, D. Johnstone, Vitaliy Avrutin, N. Onojima, C. Liu, J. Xie, Q. Fan, Hadis Morkoç
Photoresponse Of N-Zno∕P-Sic Heterojunction Diodes Grown By Plasma-Assisted Molecular-Beam Epitaxy, Ya. I. Alivov, Ü. Özgür, S. Doğan, D. Johnstone, Vitaliy Avrutin, N. Onojima, C. Liu, J. Xie, Q. Fan, Hadis Morkoç
Electrical and Computer Engineering Publications
High quality n-ZnOfilms on commercial p-type 6H–SiC substrates have been grown by plasma-assisted molecular-beam epitaxy, and n-ZnO∕p-SiCheterojunction mesa structures have been fabricated. Current-voltage characteristics of the structures had a very good rectifying diode-like behavior with a leakage current less than 2×10−4A/cm2 at −10V, a breakdown voltage greater than 20V, a forward turn on voltage of ∼5V, and a forward current of ∼2A/cm2 at 8V. Photosensitivity of the diodes was studied at room temperature and a photoresponsivity of as high as 0.045A∕W at −7.5V reverse bias was observed for photonenergies higher than 3.0eV.
Effectiveness Of Tin Porous Templates On The Reduction Of Threading Dislocations In Gan Overgrowth By Organometallic Vapor-Phase Epitaxy, Y. Fu, Y.-T. Moon, F. Yun, Ü. Özgür, J. Xie, S. Doğan, Hadis Morkoç, C. K. Inoki, T. S. Kuan, Lin Zhou, David J. Smith
Effectiveness Of Tin Porous Templates On The Reduction Of Threading Dislocations In Gan Overgrowth By Organometallic Vapor-Phase Epitaxy, Y. Fu, Y.-T. Moon, F. Yun, Ü. Özgür, J. Xie, S. Doğan, Hadis Morkoç, C. K. Inoki, T. S. Kuan, Lin Zhou, David J. Smith
Electrical and Computer Engineering Publications
We report on the reduction of threading dislocations in GaN overlayers grown by organometallic vapor phase epitaxy on micro-porous TiN networks. These networks were obtained by in situannealing of thin Ti layers deposited in a metalization chamber, on the (0001) face of GaN templates. Observations by transmission electron microscopy indicate dislocation reduction by factors of up to 10 in GaN layers grown on TiN networks compared with the control GaN.X-ray diffraction shows that GaNgrown on the TiN network has a smaller (102) plane peak width (4.6 arcmin) than the control GaN (7.8 arcmin). In low temperature photoluminescence spectra, a …
Near-Field Optical Spectroscopy And Microscopy Of Self-Assembled Gan∕Aln Nanostructures, A. Neogi, B. P. Gorman, Hadis Morkoç, T. Kawazoe, M. Ohtsu
Near-Field Optical Spectroscopy And Microscopy Of Self-Assembled Gan∕Aln Nanostructures, A. Neogi, B. P. Gorman, Hadis Morkoç, T. Kawazoe, M. Ohtsu
Electrical and Computer Engineering Publications
The spatial distribution and emission properties of small clusters of GaNquantum dots in an AlN matrix are studied using high-resolution electron and optical microscopy. High-resolution transmission electron microscopy reveals near vertical correlation among the GaNdots due to a sufficiently thin AlN spacer layer thickness, which allows strain induced stacking. Scanning electron and atomic force microscopy show lateral coupling due to a surface roughness of ∼50–60nm. Near-field photoluminescence in the illumination mode (both spatially and spectrally resolved) at 10K revealed emission from individual dots, which exhibits size distribution of GaNdots from localized sites in the stacked nanostructure. Strong spatial localization of …
Long Carrier Lifetimes In Gan Epitaxial Layers Grown Using Tin Porous Network Templates, Ü. Özgür, Y. Fu, Y.-T. Moon, F. Yun, Hadis Morkoç, H. O. Everitt, S. S. Park, K. Y. Lee
Long Carrier Lifetimes In Gan Epitaxial Layers Grown Using Tin Porous Network Templates, Ü. Özgür, Y. Fu, Y.-T. Moon, F. Yun, Hadis Morkoç, H. O. Everitt, S. S. Park, K. Y. Lee
Electrical and Computer Engineering Publications
Improved structural quality and radiative efficiency were observed in GaNthin filmsgrown by metalorganic chemical vapor deposition on TiN porous network templates formed by in situthermal annealing of Ti in ammonia. The room-temperature decay times obtained from biexponential fits to time-resolved photoluminescence data are longer than ever reported for GaN. The carrier lifetime of 1.86 ns measured for a TiN network sample is slightly longer than that for a 200 μm thick high-quality freestanding GaN. The linewidth of the asymmetric x-ray diffraction(XRD)(101¯2) peak decreases considerably with the use of TiN layer and with increasing in situannealing time, indicating the …
Dielectric Functions And Electronic Band Structure Of Lead Zirconate Titanate Thin Films, Hosun Lee, Youn Seon Kang, Sang-Jun Cho, Bo Xiao, Hadis Morkoç, Tae Dong Kang, Ghil Soo Lee, Jingbo Li, Su-Huai Wei, P. G. Snyder, J. T. Evans
Dielectric Functions And Electronic Band Structure Of Lead Zirconate Titanate Thin Films, Hosun Lee, Youn Seon Kang, Sang-Jun Cho, Bo Xiao, Hadis Morkoç, Tae Dong Kang, Ghil Soo Lee, Jingbo Li, Su-Huai Wei, P. G. Snyder, J. T. Evans
Electrical and Computer Engineering Publications
We measure pseudodielectric functions in the visible-deep ultraviolet spectral range of Pb(ZrxTi1−x)O3 (x=0.2,0.56,0.82) (PZT), Pb0.98Nb0.04 (Zr0.2Ti0.8)0.96O3, Pb0.91La0.09 (Zr0.65Ti0.35)0.98O3, and Pb0.85La0.15Ti0.96O3 films grown on platinized silicon substrates using a sol-gel method and on (0001) sapphire using a radio-frequency sputtering method. Using a parametric optical constant model, we estimate the dielectric functions(ϵ) of the perovskite oxide thin films. Taking the second derivative of the fitted layer dielectric functions and using the standard critical-point model, we determine the parameters of the critical points. In the second derivative spectra, the lowest band-gapenergy peak near 4 eVis fitted as a double peak for annealed PZTs …
Proposed Model For Bistability In Nanowire Nonvolatile Memory, V. Pokalyakin, S. Tereshin, A. Varfolomeev, D. Zaretsky, A. Baranov, A. Banerjee, Y. Wang, S. Ramanathan, S. Bandyopadhyay
Proposed Model For Bistability In Nanowire Nonvolatile Memory, V. Pokalyakin, S. Tereshin, A. Varfolomeev, D. Zaretsky, A. Baranov, A. Banerjee, Y. Wang, S. Ramanathan, S. Bandyopadhyay
Electrical and Computer Engineering Publications
Cadmium sulfide nanowires of 10‐nm diameter, electrodeposited in porous anodic alumina films, exhibit an electronic bistability that can be harnessed for nonvolatile memory. The current–voltage characteristics of the wires show two stable conductance states that are well separated (conductances differ by more than four orders of magnitude) and long lived (longevity>1 yr at room temperature). These two states can encode binary bits 0 and 1. It is possible to switch between them by varying the voltage across the wires, thus “writing” data. Transport behavior of this system has been investigated at different temperatures in an effort to understand the …
Growth And Characterization Of Sic Epitaxial Layers On Si- And C-Face 4h Sic Substrates By Chemical-Vapor Deposition, Kodigala Subba Ramaiah, I. Bhat, T. P. Chow, J. K. Kim, E. F. Schubert, D. Johnstone, S. Akarca-Biyikli
Growth And Characterization Of Sic Epitaxial Layers On Si- And C-Face 4h Sic Substrates By Chemical-Vapor Deposition, Kodigala Subba Ramaiah, I. Bhat, T. P. Chow, J. K. Kim, E. F. Schubert, D. Johnstone, S. Akarca-Biyikli
Electrical and Computer Engineering Publications
High-quality Schottky junctions have been fabricated on n-type 4H SiC epitaxial layers grown by chemical-vapor deposition on C- and Si-face substrates in order to understand the effect of growth direction on the growth mechanism and formation of defects. Atomic force microscopy analysis showed dramatic differences between the surfaces of SiC epilayers grown on C and Si faces. There was a significant step bunching in the SiC grown on Si-face substrates. Current-voltage, capacitance-voltage, and deep-level transient spectroscopy (DLTS) measurements were carried out on the Schottky junctions to analyze the junction characteristics. The Schottky junctions on C-face SiC showed larger barrier heights …
Efficacy Of Single And Double Sinx Interlayers On Defect Reduction In Gan Overlayers Grown By Organometallic Vapor-Phase Epitaxy, F. Yun, Y.-T. Moon, Y. Fu, K. Zhu, U. Ozgur, H. Morkoç, C. K. Inoki, T.S. Kuan, Ashutosh Sagar, R. M. Feenstra
Efficacy Of Single And Double Sinx Interlayers On Defect Reduction In Gan Overlayers Grown By Organometallic Vapor-Phase Epitaxy, F. Yun, Y.-T. Moon, Y. Fu, K. Zhu, U. Ozgur, H. Morkoç, C. K. Inoki, T.S. Kuan, Ashutosh Sagar, R. M. Feenstra
Electrical and Computer Engineering Publications
We report on the growth of and evolution of defects in GaN epilayers having single- and double-layer SiNx nanoporous insertion layers. The SiNx was formed in situ in the growth chamber of an organometallic vapor-phase epitaxy system by simultaneous flow of diluted silane and ammonia. The GaN epilayers and SiNx interlayers were grown on 6H-SiC substrates using three different nucleation layers, namely, low-temperature GaN, high-temperature GaN, and high-temperature AlN nucleation layers. X-ray-diffraction rocking curves and cross-sectional and plan-view transmission electron microscope analyses indicated that a nanoporous SiNx layer can reduce the dislocations density in the GaN overgrown layer to ∼3×108cm−2 …
Structural Analysis Of Ferromagnetic Mn-Doped Zno Thin Films Deposited By Radio Frequency Magnetron Sputtering, C. Liu, F. Yun, B. Xiao, S.-J. Cho, Y. T. Moon, H. Morkoç, Morad Abouzaid, R. Ruterana, K. M. Yu, W. Walukiewicz
Structural Analysis Of Ferromagnetic Mn-Doped Zno Thin Films Deposited By Radio Frequency Magnetron Sputtering, C. Liu, F. Yun, B. Xiao, S.-J. Cho, Y. T. Moon, H. Morkoç, Morad Abouzaid, R. Ruterana, K. M. Yu, W. Walukiewicz
Electrical and Computer Engineering Publications
We report on the structural analysis of ferromagnetic Mn-doped ZnO thin films deposited by radio frequency magnetron sputtering, using transmission electron microscopy (TEM), high-resolution x-ray diffraction, and Rutherford backscattering spectroscopy (RBS) measurements. The ferromagnetic Mn-doped ZnO film showed magnetization hysteresis at 5 and 300 K. A TEM analysis revealed that the Mn-doped ZnO included a high density of round-shaped cubic and elongated hexagonal MnZn oxide precipitates. The incorporation of Mn caused a large amount of structural disorder in the crystalline columnar ZnO lattice, although the wurtzite crystal structure was maintained. The observed ferromagnetism is discussed based on the structural characteristics …
Luminescence Properties Of Defects In Gan, Michael A. Reshchikov, Hadis Morkoç
Luminescence Properties Of Defects In Gan, Michael A. Reshchikov, Hadis Morkoç
Electrical and Computer Engineering Publications
Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet (UV) emitters and detectors (in photon ranges inaccessible by other semiconductors) and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these …
A Comprehensive Review Of Zno Materials And Devices, Ü. Özgür, Ya. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, Vitaliy Avrutin, S.-J. Cho, H. Morkoç
A Comprehensive Review Of Zno Materials And Devices, Ü. Özgür, Ya. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, Vitaliy Avrutin, S.-J. Cho, H. Morkoç
Electrical and Computer Engineering Publications
The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60 meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with …
Increased Carrier Lifetimes In Gan Epitaxial Films Grown Using Sin And Tin Porous Network Layers, Ü. Özgür, Y. Fu, Y. T. Moon, F. Yun, H. Morkoç, H. O. Everitt
Increased Carrier Lifetimes In Gan Epitaxial Films Grown Using Sin And Tin Porous Network Layers, Ü. Özgür, Y. Fu, Y. T. Moon, F. Yun, H. Morkoç, H. O. Everitt
Electrical and Computer Engineering Publications
Improved structural quality and radiative efficiency were observed in GaN thin films grown by metalorganic chemical vapor deposition on SiN and TiN porous network templates. The room-temperature decay times obtained from biexponential fits to time-resolved photoluminescence data are increased with the inclusion of SiN and TiN layers. The carrier lifetime of 1.86 ns measured for a TiN network sample is slightly longer than that for a 200μm-thick high-quality freestanding GaN. The linewidth of the asymmetric x-ray diffraction (XRD) (101¯2) peak decreases considerably with the use of SiN and TiN layers, indicating the reduction in threading dislocation density. However, no direct …
Characterization Of Electrosprayed Poly(Vinylidene Fluoride)/Cnt Nanocomposite, Ihab Maher Abdelsayed
Characterization Of Electrosprayed Poly(Vinylidene Fluoride)/Cnt Nanocomposite, Ihab Maher Abdelsayed
Theses and Dissertations
PVDF, Poly(vinylidene fluoride), is a polymer that has been studied for over four decades due to its good electromechanical properties, stability, and durability in various environments. Currently, PVDF is the only commercially available piezoelectric polymer. PVDF is a polymorph, which indicates the presence of several crystalline phases such as α, β, γ, and δ-phase. Oriented β-phase PVDF exhibits ferroelectric properties and displays the largest piezoelectricity amongst the four phases, which makes it the most desirable phase. Preparing oriented β-phase PVDF is a multi-step process, which is cost intensive, due to the time, labor and energy utilized. The main goal of …
Ab Initio : A New Concept In Engineering Education, A History Of The Design, Creation And Implementation Of A New School Of Engineering In Richmond, Virginia (1990-2000), Henry A. Mcgee Jr.
Ab Initio : A New Concept In Engineering Education, A History Of The Design, Creation And Implementation Of A New School Of Engineering In Richmond, Virginia (1990-2000), Henry A. Mcgee Jr.
VCU University History Books
Dr. Henry A. McGee, Jr., Founding Dean Emeritus of the School of Engineering at Virginia Commonwealth University, chronicles the history of the School of Engineering through his term as Founding Dean, 1994–1999. McGee details the process of creating a program aimed to balance innovation and entrepreneurship.
Electromechanical Characterization Of Poly(Dimethyl Siloxane) Based Electroactive Polymers, Wrutu Deepak Parulkar
Electromechanical Characterization Of Poly(Dimethyl Siloxane) Based Electroactive Polymers, Wrutu Deepak Parulkar
Theses and Dissertations
The main objectives of this thesis are 1) to evaluate the effect of cross-linking polar cyano phenyl (CN) groups on poly (dimethyl siloxane) (PDMS) and 2) to characterize the electromechanical properties of the resulting CN-PDMS blend as an electroactive actuator. Materials responding to an external stimulus are referred to as electroactive materials. There are several phenomena, which govern the mechanism in these materials, such as piezoelectricity, Maxwell's effect, ferroelectricity, electrostriction to name a few. These electroactive materials can be employed in several applications such as biomedical devices, robots, MEMs, aerospace vehicles, where the application is governed by the specific mechanism. …
Synthesis And Characterization Of Methylene Bis (P-Cyclohexyl Isocyanate)-Poly (Tetramethyl Oxide) Based Polyurethane Elastomers, Kennard Marcellus Brunson
Synthesis And Characterization Of Methylene Bis (P-Cyclohexyl Isocyanate)-Poly (Tetramethyl Oxide) Based Polyurethane Elastomers, Kennard Marcellus Brunson
Theses and Dissertations
This research concerns the development and characterization of methylene bis (p-cyclohexyl isocyanate/butanediol) (HMDI/BD) based polyurethanes used in connection with surface-active anti-microbial polyurethanes. Previously studied polyurethanes having an isophorone diisocyanate/butanediol (IPDI/BD) hard block contaminated water during dynamic contact angle (DCA) analyses. This contamination by unknown species confounds results from biocidal studies and jeopardizes the use of the polyurethane as a matrix polyurethane. By contrast, polyurethanes with methylene bis (p-cyclohexyl isocyanate)/butanediol hard block showed no contamination during DCA analysis. For this reason, further study of HMDI/BD/PTMO polyurethanes was conducted. HMDI/BD polyurethanes were synthesized with 15-50wt% hard block and a soft block of …
Iterative Methods For The Reconstruction Of Tomographic Images With Unconventional Source-Detector Configurations, Abey Mukkananchery
Iterative Methods For The Reconstruction Of Tomographic Images With Unconventional Source-Detector Configurations, Abey Mukkananchery
Theses and Dissertations
X-ray computed tomography (CT) holds a critical role in current medical practice for the evaluation of patients, particularly in the emergency department and intensive care units. Expensive high resolution stationary scanners are available in radiology departments of most hospitals. In many situations however, a small, inexpensive, portable CT unit would be of significant value. Several mobile or miniature CT scanners are available, but none of these systems have the range, flexibility or overall physical characteristics of a truly portable device. The main challenge is the design of a geometry that optimally trades image quality for system size. The goal of …
Experimental Design And Analysis Of Piezoelectric Synthetic Jets In Quiescent Air, Poorna Mane
Experimental Design And Analysis Of Piezoelectric Synthetic Jets In Quiescent Air, Poorna Mane
Theses and Dissertations
Flow control can lead to saving millions of dollars in fuel costs each year by making an aircraft more efficient. Synthetic jets, a device for active flow control, operate by introducing small amounts of energy locally to achieve non-local changes in the flow field with large performance gains. These devices consist of a cavity with an oscillating diaphragm that divides it, into active and passive sides. The active side has a small opening where a jet is formed, whereas and the passive side does not directly participate in the fluidic jet.Research has shown that the synthetic jet behavior is dependent …
Investigation Of Surface States And Device Surface Charging In Nitride Materials Using Scanning Kelvin Probe Microscopy, Mohammed Shahriar Sabuktagin
Investigation Of Surface States And Device Surface Charging In Nitride Materials Using Scanning Kelvin Probe Microscopy, Mohammed Shahriar Sabuktagin
Theses and Dissertations
In this work Scanning Kelvin Probe Microscopy (SKPM) was used to characterize surface states and device surface charging in nitride materials. Samples grown by Molecular Beam Epitaxy (MBE), Metal Organic Chemical Vapor Deposition (MOCVD) and Hydride Vapor Phase Epitaxy (HVPE) typically show a high surface band bending of about 1 eV. In an n-type sample with 3X1017 cm-3 carrier concentration, 1 eV upward band bending corresponds to 1.7X1012 cm-2 trapped charge density in the surface states. Under continuous ultraviolet (UV) illumination up to 0.6 eV surface photo voltage effect could be observed in some samples, which further indicates that surface …
Design, Fabrication And Performance Evaluation Of An Impedimetric Urea Biosensor System, Vandana Gupta
Design, Fabrication And Performance Evaluation Of An Impedimetric Urea Biosensor System, Vandana Gupta
Theses and Dissertations
An impedance bioanalyzer system comprising an in-vitro biotransducer, instrumentation and control software for the measurement of urea, potentially in blood dialysate, has been developed. The biotransducer comprises of a microlithographically fabricated interdigitated microsensor electrode (IME) onto which was cast a biorecognition layer conferred with the specificity of the enzyme urease. Urease hydrolysis of urea produces NH4+, HC03- and OH- ions that decrease the device's impedance. The temporal rate of change (kinetic) and the extent of change (equilibrium) of ion concentration were measured as the sensor's response. Five formats: [i) unPEGylated urease-containing poly(hydroxyethylmethacrylate) [p(HEMA)] hydrogel, ii) PEGylated urease-containing p(HEMA) hydrogel, iii) …
Reentrainment Of Submicron Solid Particles, Ramin Mortazavi
Reentrainment Of Submicron Solid Particles, Ramin Mortazavi
Theses and Dissertations
In this work, an experimental method is developed to study the effects of particle size, flow rate, pulsation, particle/substrate material, and temperature on the short-term reentrainment of submicron particles. The particles tested are in the size range of 10-900 nm and are deposited by wetting the inside of capillary tubes with a liquid suspension. The tubes are then dried in a desiccator. The particles are reentrained under turbulent dry air flow conditions and a condensation particle counter is used to measure the number of entrained particles.There has been very limited work done with nanoscale particles in general and no previous …