Engineering Physics Commons^™

Doping Dependence Of Electronic And Mechanical Properties Of Gase1−XTeX And Ga1−XInXSe From First Principles, Zs. Rak, S. D. Mahanti, K. C. Mandal, N. C. Fernelius

Faculty Publications

No abstract provided.

Nonlinear Observers For Human-In-The-Loop Control Systems, Samuel Kitchen Mckinley

Master's Theses - Daytona Beach

The development of models for a human-in-the-loop with hardware is an area of ongoing research. The ability to simulate a human-in-the-loop with hardware provides a platform for better understanding the dynamics of human and machine cognition. A human-in-the-loop model provides information that can be used to design more efficient human interfaces and smarter autonomous assistant controllers. This can make a complex task such as flying an aircraft safer and more accessible. This thesis explores different possibilities for human operator models to be modeled in the loop with a vehicle. A human is modeled as a linear state feedback controller in …

Simulation Of Temperature Distributions In Tissue Upon Laser Pulse Irradiation Including Water Mass Transfer, Deepthi Nagulapally

Electrical & Computer Engineering Theses & Dissertations

Lasers, due to their unique characteristics, have tremendous applications in the medical field. Generally all laser applications in hie-medicine involve the propagation of laser energy through tissue. Energy is deposited giving rise to many physical, hie-chemical, and mechanical effects. Among these are dynamical changes in the local temperature distributions within the tissue. Analysis of the temperature changes requires the creation of an appropriate optical transmission and heat flow model that incorporates user specified laser parameters. Here, a numerical simulation model was developed to study both steady state and time dependent temperature distributions due to pulsed laser radiation within user specified …

Boron Carbide Based Solid State Neutron Detectors: The Effects Of Bias And Time Constant On Detection Efficiency, Nina Hong, John Mullins, Keith Foreman, Shireen Adenwalla

Shireen Adenwalla Papers

Neutron detection in thick boron carbide(BC)/n-type Si heterojunction diodes shows a threefold increase in efficiency with applied bias and longer time constants. The improved efficiencies resulting from long time constants have been conclusively linked to the much longer charge collection times in the BC layer. Neutron detection signals from both the p-type BC layer and the n-type Si side of the heterojunction diode are observed, with comparable efficiencies. Collectively, these provide strong evidence that the semiconducting BC layer plays an active role in neutron detection, both in neutron capture and in charge generation and collection.

Rubidium Recycling In A High Intensity Short Duration Pulsed Alkali Laser, Wooddy S. Miller

Theses and Dissertations

Laser induced fluorescence was used to study how pump pulse duration and alkali recycle time effects maximum power output in a Diode Pumped Alkali Laser (DPAL) system. A high intensity short pulsed pump source was used to excited rubidium atoms inside a DPAL-type laser. The maximum output power of the laser showed a strong dependence upon the temporal width of the pump pulse in addition to the input pump intensity. A linear relationship was observed between the maximum output power and the pulse width due to the effective lifetime of the excited state, defined as the time it takes for …

Robust Isothermal Electric Control Of Exchange Bias At Room Temperature, Xi He, Ning Wu, Anthony N. Caruso, Elio Vescovo, Kirill D. Belashchenko, Peter A. Dowben, Christian Binek

Kirill Belashchenko Publications

Voltage-controlled spin electronics is crucial for continued progress in information technology. It aims at reduced power consumption, increased integration density and enhanced functionality where non-volatile memory is combined with highspeed logical processing. Promising spintronic device concepts use the electric control of interface and surface magnetization. From the combination of magnetometry, spin-polarized photoemission spectroscopy, symmetry arguments and first-principles calculations, we show that the (0001) surface of magnetoelectric Cr₂O₃ has a roughness-insensitive, electrically switchable magnetization. Using a ferromagnetic Pd/Co multilayer deposited on the (0001) surface of a Cr₂O₃ single crystal, we achieve reversible, room-temperature isothermal switching …

Far-Field Optical Nanoscopy Based On Continuous Wave Laser Stimulated Emission Depletion, C. Kuang, Wei Zhao, Guiren Wang

Faculty Publications

Stimulated emission depletion (STED) microscopy is one of the breakthrough technologies that belong to far-field optical microscopy and can achieve nanoscale spatial resolution. We demonstrate a far-field optical nanoscopy based on continuous wave lasers with different wavelengths, i.e., violet and green lasers for excitation and STED, respectively. Fluorescent dyes Coumarin 102 and Atto 390 are used for validating the depletion efficiency. Fluorescent nanoparticles are selected for characterizing the spatial resolution of the STED system. Linear scanning of the laser beams of the STED system along one line of a microscope slide, which is coated with the nanoparticles, indicates that a …

Finite Element Analysis Of Ring-Shaped Emission Profile In Plasma Bullet, Yukinori Sakiyama, David B. Graves, Julien Jarrige, Mounir Laroussi

Electrical & Computer Engineering Faculty Publications

Using a one-way coupled model of neutral gas flow and plasma dynamics we report a mechanism to explain the ring-shaped emission pattern that has been observed experimentally in plasma bullets at atmospheric pressure. We solve a fluid model with the local field approximation in one-dimensional cylindrical coordinates, corresponding to a cross-section of a plasma bullet. Pulselike uniform electric field is assumed to be applied perpendicular to the simulation domain. Time and spatially resolved spectroscopic measurements support the simulation results.

Strain Energy And Lateral Friction Force Distributions Of Carbon Nanotubes Manipulated Into Shapes By Atomic Force Microscopy, Mark C. Strus, Roya R. Lahiji, Pablo Ares, Vincente Lopez, Arvind Raman, Ron R. Reifenberger

Other Nanotechnology Publications

The interplay between local mechanical strain energy and lateral frictional forces determines the shape of carbon nanotubes on substrates. In turn, because of its nanometer-size diameter, the shape of a carbon nanotube strongly influences its local electronic, chemical, and mechanical properties. Few, if any, methods exist for resolving the strain energy and static frictional forces along the length of a deformed nanotube supported on a substrate. We present a method using nonlinear elastic rod theory in which we compute the flexural strain energy and static frictional forces along the length of single walled carbon nanotubes (SWCNTs) manipulated into various shapes …

Pressure-Driven Transport Of Particles Through A Converging-Diverging Microchannel, Ye Ai, Sang W. Joo, Yingtao Jiang, Xiangchun Xuan, Shizhi Qian

Mechanical Engineering Faculty Research

Pressure-driven transport of particles through a symmetric converging-diverging microchannel is studied by solving a coupled nonlinear system, which is composed of the Navier–Stokes and continuity equations using the arbitrary Lagrangian–Eulerian finite-element technique. The predicted particle translation is in good agreement with existing experimental observations. The effects of pressure gradient, particle size, channel geometry, and a particle’s initial location on the particle transport are investigated. The pressure gradient has no effect on the ratio of the translational velocity of particles through a converging-diverging channel to that in the upstream straight channel. Particles are generally accelerated in the converging region and then …

Electron Multipactor: Theory Review, Comparison And Modeling Of Mitigation Techniques In Icepic, Neil G. Rogers

Theses and Dissertations

Mitigation approaches for single surface multipactor at dielectric windows are investigated using Particle-In-Cell (PIC) simulations. Initially baseline susceptibility diagrams are constructed analytically and compared with self-consistent, dynamic system trajectories. The power deposited on the surface of a dielectric window in an HPM system is considered using three different methods and the results of PIC simulations. Geometric mitigation is then considered by varying the window orientation with respect to the HPM electric held. Small angular deviations, less than 20 degrees, from the nominal case of normal incidence show dramatic changes in the susceptibility diagram. A materials approach to mitigation is then …

The Effect Of Copt Crystallinity And Grain Texturing On Properties Of Exchange-Coupled Fe/Copt Systems, H. Oguchi, A. Zambano, M. Yu, Jason R. Hattrick-Simpers, D. Banerjee, Y. Liu, Z. L. Wang, J. P. Liu, S. E. Lofland, D. Josell, I. Takeuchi

Faculty Publications

The effect of the crystallinity and the grain texturing of CoPt hard layers on exchange coupled Fe/CoPt soft/hard magnetic systems was studied using gradient thickness multilayer thin films. We have studied the hard layer structures by transmission electron microscopy and x-ray diffraction, and characterized the exchange coupling interaction through magnetization loops obtained by the magneto-optical Kerr effect measurement. We found that exchange coupling strongly depends on the crystalline characteristics of the CoPt hard layer. There is correlation between the mixture of different grain orientations of the CoPt hard layer and coupling efficiency. In particular, interlayer coupling is enhanced when there …

Biomarker Identification For Prostate Cancer Using An Efficient Feature Selection Algorithm, Vamsi Krishnam Raju Mantena

Electrical & Computer Engineering Theses & Dissertations

In recent years, there has been an increased interest in using protein mass spectrometry to identify biomarkers that discriminate diseased from healthy individuals. A biomarker is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathological processes, or pharmacological responses to a therapeutic intervention. Identifying biomarkers will be an important step towards disease characterization and patient management. One challenge of biomarker identification is how to handle the high dimensional mass spectral data. In this thesis, we applied an efficient feature selection algorithm to mass spectrometry data obtained from prostate tissue samples to identify prostate …

Raman Studies Of 1,3,5,7 Cyclooctatetraene At High Pressure, Martin Galley, Ed Romano, Sergey Tkachev, Michael Pravica

Undergraduate Research Opportunities Program (UROP)

We performed Raman spectroscopic studies of 1,3,5,7-cyclooctatetraene at elevated pressures up to 10 GPa with the aim of examining possible planarization of the molecule and further studying two prior-discovered phases of the solid with pressure. The Raman excitation source was a Krypton-ion laser operating at 674.1 nm (give wavelength).

1,3,5,7 Cyclooctatetraene has an octagonal formation however it is not aromatic or anti-aromatic (not a subject to the 4n+2 Huckel’s rule) [1]. As a result, its adopts a somewhat reactive tub shape. Upon the addition or removal of one to two electrons under ambient conditions, the molecule planarizes and becomes aromatic …

Predicting The Hydrogen Pressure To Achieve Ultralow Friction And Diamondlike Carbon Surfaces From First Principles, Haibo Guo, Yue Qi, Xiaodong Li

Faculty Publications

Hydrogen atmosphere can significantly change the tribological behavior at diamond and diamondlike carbon (DLC) surfaces and the friction-reducing effect depends on the partial pressure of hydrogen. We combined density functional theory modeling and thermodynamic quantities to predict the equilibrium partial pressures of hydrogen at temperature T, P_H2 (T), for a fully atomic hydrogen passivated diamondsurface. Above the equilibrium P_H2 (T), ultralow friction can be achieved at diamond and DLC surfaces. The calculation agrees well with friction tests at various testing conditions. We also show that P_H2 (T) …

Performance Comparison Of Pb(Zr0.52Ti0.48)O3-Only And Pb(Zr0.52Ti0.48)O3-On-Silicon Resonators, Hengky Chandrahalim, Sunil A. Bhave, Ronald G. Polcawich, Jeff Pulskamp, Dan Judy, Roger Kaul, Madan Dubey

Faculty Publications

This paper provides a quantitative comparison and explores the design space of lead zirconium titanate (PZT)–only and PZT-on-silicon length-extensional mode resonators for incorporation into radio frequency microelectromechanical system filters and oscillators. We experimentally measured the correlation of motional impedance (R_X) and quality factor (Q) with the resonators’ silicon layer thickness (t_Si). For identical lateral dimensions and PZT-layer thicknesses (t_PZT), the PZT-on-silicon resonator has higher resonant frequency (f_C), higher Q (5100 versus 140), lower R_X (51 Ω versus 205 Ω), and better linearity [third-order input intercept …

Combinatorial Investigation Of Magnetostriction In Fe-Fa And Fe-Ga-Al, Jason R. Hattrick-Simpers, Dwight Hunter, Corneliu M. Craciunescu, Kyu Sung Jang, Makoto Murakami, James Cullen, Manfred Wuttig, Ichiro Takeuchi, Samuel E. Lofland, Leonid Bendersky, Noble Woo, Robert Bruce Vandover, Toshiya Takahashi, Yasubumi Furuya

Faculty Publications

A high-throughput high-sensitivity optical technique for measuringmagnetostriction of thin-film composition-spread samples has been developed. It determines the magnetostriction by measuring the induced deflection of micromachined cantilever unimorph samples. Magnetostrictionmeasurements have been performed on as-deposited Fe–Ga and Fe–Ga–Al thin-film composition spreads. The thin-film Fe–Ga spreads display a similar compositional variation of magnetostriction as bulk. A previously undiscovered peak in magnetostriction at low Ga content was also observed and attributed to a maximum in the magnetocrystalline anisotropy. Magnetostrictive mapping of the Fe–Ga–Al ternary system reveals the possibility of substituting up to 8at.%Al in Fe₇₀Ga₃₀ without significant degradation of magnetostriction.

). Size Dependency Of The Elastic Modulus Of Zno Nanowires: Surface Stress Effect, Guofeng Wang, Xiaodong Li

Faculty Publications

Relation between the elastic modulus and the diameter (D) of ZnOnanowires was elucidated using a model with the calculated ZnOsurface stresses as input. We predict for ZnOnanowires due to surface stress effect: (1) when D>20nm, the elastic modulus would be lower than the bulk modulus and decrease with the decreasing diameter, (2) when 20nm>D>2nm, the nanowires with a longer length and a wurtzite crystal structure could be mechanically unstable, and (3) when D<2nm, the elastic modulus would be higher than that of the bulk value and increase with a decrease in nanowire diameter.

Nanoindentation Of The A And C Domains In A Tetragonal Batio3 Single Crystal, Young-Bae Park, Matthew J. Dicken, Zhi-Hui Xu, Xiaodong Li

Faculty Publications

Nanoindentation in conjunction with piezoresponse force microscopy was used to study domain switching and to measure the mechanical properties of individual ferroelectric domains in a tetragonal BaTiO₃ single crystal. It was found that nanoindentation has induced local domain switching; the a and c domains of BaTiO₃ have different elastic moduli but similar hardness.Nanoindentationmodulus mapping on the a and c domains further confirmed such difference in elasticity. Finite element modeling was used to simulate the von Mises stress and plastic strain profiles of the indentations on both a and c domains, which introduces a much higher stress level than …

Parmela Based Simulations On Jefferson Lab Free Electron Laser Injector, Deepesh Kumar Koppunuru

Electrical & Computer Engineering Theses & Dissertations

Free Electron Lasers (FELs) have many applications and are under continuing development to meet various needs and in areas from materials processing to life sciences research. This is because of its unique capability of generating high-average power, coherent, and wavelength tunable light by employing relativistic beam of un-bounded electrons. The main challenge in FEL development is the generation of a high intensity, high-quality electron beam in an injector. Further acceleration to relativistic energies is accomplished in a linear accelerator (LINAC) for producing laser light in a device known as wiggler. The Jefferson Lab FEL team intents to increase the injector …

Parallel Fast Multipole Method For Molecular Dynamics, Reid G. Ormseth

Theses and Dissertations

We report on a parallel version of the Fast Multipole Method (FMM) implemented in the classical molecular dynamics code, NAMD (Not Another Molecular Dynamics program). This novel implementation of FMM aims to minimize interprocessor communication through the modification of the FMM grid to match the hybrid force and spatial decomposition scheme already present in NAMD. This new implementation has the benefit of replacing all-to-all communications broadcasts with direct communications between nearest neighbors. This results in a significant reduction in the amount of communication compared to earlier attempts to integrate FMM into common molecular dynamics programs. The early performance of FMM …

Investigation Of Magnetic Field Profile Effects In Hall Thrusters, Oren Kornberg

Master's Theses - Daytona Beach

The purpose of this study was to show the relationship of different magnetic field profiles to the acceleration region length of a Hall thruster. The general transport equations were simplified and solved using a one-dimensional analysis. Some of the model assumptions include quasineutrality, Maxwellian electrons, and negligible thruster wall effects. The solved equation kept magnetic field as an input to the model for the analysis. The magnetic field was altered by changing the shape through the thruster, while keeping the maximum point fixed, and by shifting the profile, while keeping the shape fixed. Results indicate a strong correlation between the …

Investigation Of Cdznte Crystal Defects Using Scanning Probe Microscopy, Goutam Koley, J. Liu, K. C. Mandal

Faculty Publications

No abstract provided.

Rapid Structural Mapping Of Ternary Metallic Alloy Systems Using The Combinatorial Approach And Cluster Analysis, C. J. Long, Jason R. Hattrick-Simpers, M. Murakami, R. C. Srivastava, I. Takeuchi, V. L. Karen, X. Li

Faculty Publications

We are developing a procedure for the quick identification of structural phases in thin film composition spread experiments which map large fractions of compositional phase diagrams of ternary metallic alloy systems. An in-house scanning x-ray microdiffractometer is used to obtain x-ray spectra from 273 different compositions on a single composition spread library. A cluster analysissoftware is then used to sort the spectra into groups in order to rapidly discover the distribution of phases on the ternary diagram. The most representative pattern of each group is then compared to a database of known structures to identify known phases. Using this method, …

Self-Assembled Composite Nano-/Micronecklaces With Sio2 Beads In Boron Strings, Hai Ni, Xiaodong Li

Faculty Publications

Nano-/micronecklaces with SiO₂ beads in boron strings were synthesized by simply sublimating the desired powders in a sealed quartz tube at high temperature. The boron strings have a rectangular cross section with width varying from 80to1000nm while the SiO₂ beads bear either spindle or spherical shape with a size ranging from 100nmto5μm. The spacing between the SiO₂ beads is uniform in each boron string. Both the boron strings and the SiO₂ beads are amorphous and free of defects. The supersaturated vapors of silicon and oxygen induced the SiO₂ bead formation.

Erratum: “Terahertz Studies Of The Dielectric Response And Second-Order Phonons In A Gase Crystal” [Appl. Phys. Lett.87, 182104 (2005)], B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal

Faculty Publications

No abstract provided.

Characterization And Quantum Efficiency Validation Of Ingaas Linear Focal Plane Array, Christopher Salenga Garcia

Electrical & Computer Engineering Theses & Dissertations

A 1x1024 InGaAs linear hybrid focal plane array (FPA) with CMOS readout was characterized at room temperature to analyze its electrical and optical properties and to measure its performance parameters.

The most important parameter of an FPA is the gain constant K, which allows conversion of the FPA output measurement unit from digital counts into the number of generated signal electrons. For FPAs with CMOS readout, the commonly used meanvariance method for determining K often underestimates its value. A more reliable method for finding K is the photon transfer technique, which is developed for FPAs with CCD readout. This …

Dynamics Of An Atmospheric Pressure Plasma Plume Generated By Submicrosecond Voltage Pulses, Xinpei Lu, Mounir Laroussi

Electrical & Computer Engineering Faculty Publications

Nonequilibrium plasmas driven by submicrosecond high voltage pulses have been proven to produce high-energy electrons, which in turn lead to enhanced ionization and excitations. Here, we describe a device capable of launching a cold plasma plume in the surrounding air. This device, "the plasma pencil," is driven by few hundred nanosecond wide pulses at repetition rates of a few kilohertz. Correlation between current-voltage characteristics and fast photography shows that the plasma plume is in fact a small bulletlike volume of plasma traveling at unusually high velocities. A model based on photoionization is used to explain the propagation kinetics of the …

Fourier Transform Analysis Of Terahertz Radiation, Chikaodira N. Okpo

Electrical & Computer Engineering Theses & Dissertations

Advances in terahertz radiation (T-rays) technology have great promise in various technological areas ranging from medical technology, imaging technology and accelerator technology. At Thomas Jefferson Laboratory, the Free Electron Laser division (FEL) produces very powerful beam of laser light by accelerating electrons in bunches along a beamline. This laser light absorbs and releases energy at various wavelengths. The new FEL upgrade led to the production of very bright terahertz (THz) radiation with an average power of 1 00watts which is about 100,000 times brighter than those produced elsewhere. These T-rays have very significant applications in the Laboratory. The most significant …

Ozone Concentration In An Atmospheric Pressure Air Plasma Jet, Srinivas Reddy Suddala

Electrical & Computer Engineering Theses & Dissertations

A stable micro-plasma jet in air was generated from a direct current discharge between two molybdenum electrodes (0.25 mm thick) that were separated by an alumina insulator of the same thickness. The after-glow plasma jet was generated by blowing air through the space between the electrodes. A change from laminar to turbulent flow was observed at a gas flow rate of 140 ml/min. The length of the plasma jet increased with flow rate in the laminar mode to approximately 15 mm and decreased in the turbulent mode.

Increasing the gas flow rate up to 200 ml/min at a constant discharge …