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Photopolarimeter Based On Planar Grating Diffraction, R. M.A. Azzam, K. A. Giardina

Electrical Engineering Faculty Publications

A division-of-amplitude photopolarimeter (DOAP) is described that employs a diffraction grating in the conventional spectrometer orientation with the grating grooves normal to the plane of incidence. Four coplanar diffracted orders are used for polarimetric analysis to determine all four Stokes parameters of incident light simultaneously and virtually instantaneously (with the speed being determined solely by the photodetectors and their associated electronics); a fifth order is used for alignment by autocollimation or by use of a position-sensing quadrant detector. To sensitize the instrument for the +45° and -45° azimuths of incident linearly polarized light and for the handedness of incident circular …

Coherence Peak And Superconducting Energy Gap In Rb_{3}C_{60} Observed By Muon Spin Relaxation, R. F. Kiefl, W. A. Macfarlane, K. H. Chow, S. Dunsiger, T. L. Duty, T. M. S. Johnston, J. W. Schneider, J. Sonier, Laurent Brard, Robert M. Strongin, J. E. Fischer, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

Muon spin relaxation resulting from spin exchange scattering of endohedral muonium (μ+e-) with thermal electronic excitations has been observed in the fullerene superconductor Rb₃C₆₀. The temperature dependence of T₁^-1 shows a coherence peak just below T_c and can be fit to the conventional Hebel-Slichter theory for spin relaxation in a superconductor with a broadened BCS density of states. The average energy gap for electronic excitations, Δ/k_B=53(4) K or 2Δ/ k_BT_c=3.6(3), is consistent with the BCS weak coupling limit.

High-Voltage Variable Resistor For Ion Energy Spectroscopy, Timothy J. Gay, V. D. Irby, S. P. Yallaly

Timothy J. Gay Publications

A high-voltage variable resistor was designed, built, and implemented to modify an ion-energy spectrometer for the study of ion-atom collisions in which the projectiles change charge. The resistor is remotely switchable from 0 to 2050 MΩ and has a voltage rating of 200 kV. The design criteria and the electrical and mechanical details of the apparatus are discussed. The design and construction of an ancillary device, comprising two precision resistive-divider voltmeters, are also discussed.

Non-Contact Measurement For Thermal Conductivity Of Diamond-Like And Hard Carbon Thin Films, Ganming Qin

Theses

In this research work, non-contact temperature measurement was applied to determine the thermal conductivity of diamond-like and hard carbon thin films. Dielectric materials widely used as thin films in device manufacturing are SiO₂, Si₃N₄, polymer, and etc. However, their heat dissipating capacity is not good for power devices. It is necessary to develop a new material for this purpose. Diamond crystal is a high quality dielectric material. It has the highest room-temperature thermal conductivity [k=20W (cm · K) at 20°C] among all materials. In addition, it has high electrical resistivity ( >10¹⁶ Ω …

Behavior Of Disordered Co-Pd, Co-Ag, And Co-Mo Alloys In Multilayer Interfaces, Z.S. Shan, Ping He, C. Moore, John A. Woollam, David J. Sellmyer

David Sellmyer Publications

Local environment effects are important for understanding interfacial magnetism in artificially structured multilayers. For this reason, stable and/or metastable disordered alloys Co_xM_1-x (M=Pd, Ag, Mo) were fabricated in a dc cosputtering system. The magnetization as a function of composition and temperature were measured and analyzed in terms of a mean-field model. The local environment effect on the Co moment from its Ag (or Mo) neighbors and the Pd moment from its Co neighbors are studied. It is found that the polarized Pd moment increases linearly with an increasing number of nearest Co neighbors and the Co moment …

Interface Magnetism And Superparamagnetism Of Co/Cu Multilayers, Z.S. Shan, S. Nafis, John A. Woollam, Sy_Hwang Liou, David J. Sellmyer

Sy-Hwang Liou Publications

The magnetic properties of Co/Cu multilayers were investigated from 5 to 380 K and analyzed in terms of the interface magnetism and mean-field model. The interface, which is about 1.2 Å thick, is nonmagnetic at room temperature and becomes magnetic at 5 K with the average magnetization of 40% of the pure Co magnetization. The samples of X Å Co/10 Å Cu behaved superparamagnetically as X ranged from 4 to 6.5 Å and did not show superparamagnetic behavior for thinner or thicker Co layer thickness.

Magnetization Reversal In Co/Cr Multilayer Films, D. Wang, Roger D. Kirby, B. W. Robertson, David J. Sellmyer

Roger Kirby Publications

Magnetization reversal of Co/Cr multilayer films is studied by utilizing initial magnetization curves, minor loops, isothermal and dc demagnetization remanence curves, and temperature dependence of the loops. Electron microscope observations reveal that the films consist of columnar grains of size from 400 to 800 Å. It is suggested that the magnetization reversal is dominated by rotation of single-domain grains. Numerical calculations are performed based on the Stoner–Wohlfarth coherent rotation model for noninteracting, single-domain particles of uniaxial anisotropy. The calculated results agree qualitatively with the experimental results. To investigate the quantitative differences, magnetic interactions among the grains are measured in terms …

Unusual Thermal Stability Of A Site-Ordered Mc60 Rocksalt Structure (M=K, Rb, Or Cs), Q. Zhu, O. Zhou, J. E. Fischer, Andrew R. Mcghie, W. R. Romanow, Robert M. Strongin, M. A. Cichy, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

X-ray diffraction and differential scanning calorimetry of M_xC₆₀, with x∼1 and M=K, Rb, or Cs, reveal an unusual T-dependent phase sequence. A low-symmetry ground state is found, while the high-T limit is an ordered rocksalt structure in which only the octahedral sites are occupied. The unusual high-T stability of this ordered phase is attributed to the entropy of molecular orientational disorder and/or thermal disorder of the alkali-metal ions within the octahedral sites. Unique to K_xC₆₀ with x≥1.4, we find at intermediate temperatures an fcc site-disordered lattice gas …

Properties Of Rigid Foams For Application As Materials For Light Weight Structures In Space, Huichen Chi

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The mechanical and mesoscopic structural properties of rigid cellular foam made of polystyrene have been investigated. Basic properties (e.g., density, total and available porosity, permeability, surface area, isotropicity, and cell size and cell wall thickness distributions) were measured. In most cases, alternative methods were used to determine which methods were most appropriate for the type of samples we studied. Standard compression and deflection mechanical tests were performed. The stress-strain curves and related mechanical properties were found to agree with standard cellular structural models of open-cell foams.

We investigated the effects of small (~ < 5 atm) hydrostatic stress applied to foam samples for long periods of time (~one day). We observed large changes (up to a factor of three) in the stress-strain diagrams, Young's modulus, elastic collapse stress, ultimate strength, resilience, Poisson's ratio, permeability, penetration depth, and available porosity. Effects were most pronounced above 2 atm applied pressure differential, but were observed even for 1 atm loads. Short-term exposure to loads up to ten times as large did not cause comparable changes. These changes were interpreted as resulting from observed changes in the mesoscopic structure occurring near the surface using standard cellular structural models.

This work was originally motivated by applications …

A Novel Technique For Studying The Shear Elastic Properties Of Weak Solids, Jason A. Payne '93

Honors Projects

We have developed a simple, inexpensive, and precise technique to measure the shear elastic modulus of weak solids using electromagnetic and optical tools. This technique can be easily adapted to measure the viscosity of a liquid also. A Helmholtz pair was used to produce a torque on a permanent magnet mounted on the smaller of two concentric cylinders, coupled by the material to be studied. The torque was controlled precisely and measured accurately in terms of the current flowing through the coils of the Helmholtz pair. An optical lever was employed to measure the angular displacement of the inner cylinder …

A Lattice Gas Approach To The Structure And Dynamics Of Electrorheological Fluids, Jie Chen '93

Honors Projects

Electrorheological fluids consist of a colloidal suspension of dielectric particles in a continuous fluid of smaller dielectric constant. Molecular dynamics simulations of these fluids in an applied electric field have recently been shown to produce percolated, columnar structures. No systematic attempt has been made so far to simultaneously include the effects of temperature and the viscous drag due to the continuous fluid. We propose a dipolar lattice gas model for electrorheological fluids and study the resulting structures and dynamics. We attempt to incorporate the effect of the viscosity of the continuous medium by a dynamic ansatz that determines the range …

Electrostatic Positioning Of Droplets In Turbulent Flows (Lstm 375/Te/93), Nihad E. Daidzic, Adrian Melling

Aviation Department Publications

Report LSTM 375/TE/93, Lehrstuhl fuer Stroemungsmechanik Universitaet Erlangen-Nuernberg Cauerstr. 4, 8520 Erlangen Germany.

Temperature Dependence Of Optical Properties For Amorphous Silicon At Wavelengths Of 632.8 And 752 Nm, P.T. Leung, Nhan Do, Oguz Yavas, Andrew C. Tam, Wing P. Leung, Hee K. Park, Costas P. Grigoropoulos, Johannes Boneberg, Paul Leiderer

Physics Faculty Publications and Presentations

The temperature dependence of the optical properties for amorphous silicon is studied at wavelengths of 632.8 and 752 nm. Both the refractive index and extinction coefficient increase linearly with temperature for 752 nm, while the refractive index decreases and the extinction coefficient increases for 632.8 nm. The rate of increase of the extinction coefficient at 632.8 nm is twice as much as that for 752 nm.

The Effects Of Electron Radiation On The Glass Transition Temperature Of A Polyetherimide, Kristen Tulloch Kern

Physics Theses & Dissertations

The effects of electron radiation on a polyetherimide (PEI), Ultem*, were investigated. In particular, the changes in the glass transition temperature (T_g) with absorbed radiation dose were studied. The polymer was exposed to mono-energetic beams of 100-keV electrons and 1.0-MeV electrons for doses up to 100 megagray (MGy). Dosimetry for the exposures was based on Monte-Carlo simulations of the transfer of energy from an energetic electron to the polymer and on comparison to Nylon standards. Dynamic mechanical analysis was used to determine the (T_g) for non-exposed PEI and the changes in (T_g) resulting from …

Electron Microscopy Study Of Magnetosomes In A Cultured Coccoid Magnetotactic Bacterium, Fiona C. Meldrum, Stephen Mann, Brigid R. Heywood, Richard B. Frankel, D. A. Bazyllinski

Physics

Intracellular magnetite (Fe₃O₄) crystals produced by the magnetotactic bacterium MC-1 were analyzed by transmission electron microscopy (TEM). Strain MC-1 represents the first-reported isolation of a coccoid magnetotactic bacterium in axenic culture. The magnetosomes of this bacterium displayed a pseudo-hexagonal prismatic habit, were elongated along the crystallographic direction, and were truncated by {111}, {100} and {110} faces. The presence of {111} truncations represents a modification of the magnetosome morphology previously determined for those in other coccoid bacteria. Study of immature crystals produced by strain MC-1 showed that the crystal morphology was controlled even at early stages of …

Electron Microscopy Study Of Magnetosomes In Two Cultured Vibrioid Magnetotactic Bacteria, Fiona C. Meldrum, Stephen Mann, Brigid R. Heywood, Richard B. Frankel, Dennis A. Bazylinski

Physics

Magnetite (Fe₃0₄) crystals produced by two strains of cultured vibrioid magnetotactic bacteria were studied by high-resolution transmission electron microscopy (HRTEM). Both magnetotactic strains were characterized by single chains of magnetite crystals aligned along the long axes of the cells. The strains, designated as MV-2 and MV-4, produced crystals that differed markedly in size and morphology. Crystals present in MV-4 cells were generally larger than those in MV-2 cells and displayed significantly smaller aspect ratios. Crystallographic analysis of the magnetosomes of MV-2 revealed an elongated hexagonal habit based on a prism of {110} faces capped by {111} …

Design And Performance Evaluation Of A Gas Chromatograph Micromachined In A Single Crystal Silicon Substrate, Rocky R. Reston

Theses and Dissertations

This investigation designed and developed a miniature gas chromatograph (GC) using silicon micromachining techniques. The GC is composed of a miniature sample injector (10 µl sample loop); a 0.9 m long, rectangular-shaped (300 µm width and 10 micrometers height) capillary column coated with a 0.2 µm thick copper phthalocyanine (CuPc) stationary phase; and a dual-detector scheme incorporating a CuPc-coated chemiresistor and a 125 µm diameter thermal conductivity detector bead. Micromachining was employed to fabricate the sample injector interface, the GC column, and the dual-detector cavity. A novel processing technique was developed to sublime the CuPc stationary phase coating on the …

Self-Referenced Speckle Holography (Srsh) Image Reconstruction Performance, John R. Devey

Theses and Dissertations

The Speckle Holography technique uses a series of short exposure images and associated wave front sensor measurements to reconstruct astronomical images. The reconstruction technique effectively boosts the amplitude of high spatial frequencies to allow for finer resolution of astronomical objects. A simulation package that calculates the optical transfer function (OTF) of a telescopic system was previously developed for the Phillips Laboratory. This software was modified slightly to provide the Speckle Holography system transfer function (STF) for a telescopic system under varying seeing conditions.

Characterization Of Laboratory Generated Turbulence By Optical Phase Measurements, Eric P. Magee

Theses and Dissertations

The resolution achieved by an optical imaging system in the presence of the random effects of the atmosphere is severely degraded from the theoretical diffraction limit. Techniques exist for recovering near diffraction limited performance of an imaging system in the presence of atmospheric turbulence. As opposed to laboratory testing, testing image enhancement techniques in the Earth's atmosphere imposes many limitations. Unfavorable weather conditions could result in the loss of time and money invested in conducting the experiments. With a properly characterized turbulence generator, with statistics that match those of the atmosphere, experimental testing of image enhancement techniques can be conducted …

Construction And Testing Of A Neutron And Gamma Spectrometry System Using Pulse Shape Discrimination With An Organic Scintillator, Robert S. Pope

Theses and Dissertations

The goal of this thesis was to construct and test a neutron detector to measure the energy spectrum of 1 to 14-MeV neutrons in the presence of gammas. A spectrometer based on the process of pulse shape discrimination (PSD) was constructed, in which the scintillator NE-213 was used. The primary neutron/ gamma sources used were 78-mCi and 4.7-Ci ²³⁹PuBe sources, while 4.7-µCi and 97.6-µCi ²²Na gamma sources were used for energy calibration and additional testing of the detector. Proton recoil spectra and Compton electron spectra were unfolded with the neutron and gamma unfolding code FORIST to generate the …

Multiple Evolutionary Origins Of Magnetotaxis In Bacteria, Edward F. Delong, Richard B. Frankel, Dennis A. Bazylinski

Physics

Magnetosomes are intracellular, iron-rich, membrane-enclosed magnetic particles that allow magnetotactic bacteria to orient in the earth's geomagnetic field as they swim. The magnetosomes of most magnetotactic bacteria contain iron oxide particles, but some magnetotactic species contain iron sulfide particles instead. Phylogenetic analyses of small subunit ribosomal RNA sequences showed that all known magnetotactic bacteria of the iron oxide type are associated with the a subgroup of the Proteobacteria in the domain Bacteria. In contrast, uncultured magnetotactic bacteria of the iron sulfide type are specifically related to the dissimilatory sulfate-reducing bacteria within the δ subdivision of the Proteobacteria. These findings indicate …

Tissue Characterization And Imaging Using Photon Density Waves, Lars O. Svaasand, Bruce J. Tromberg, Richard C. Haskell, Tsong-Tseh Tsay, Michael W. Berns

All HMC Faculty Publications and Research

The optical properties of brain tissues have been evaluated by measuring the phase velocity and attenuation of harmonically modulated light. The phase velocity for photon density waves at 650-nm wavelength has been found to be in the range of 5 to 12% of the corresponding velocity in a nonscattering medium, and the optical penetration depth was in the range 2.9 to 5.2 mm. These results are used to predict the resolution of optical imaging of deep tissue structures by diffusely propagating incoherent photons. The results indicate that structures of a few millimeters in linear dimension can be identified at 10 …

Motorized Throttle Plate, John D. Crawford

Opportunities for Undergraduate Research Experience Program (OURE)

The objective of this project was to develop a throttle plate mechanism that can be used to simulate transient engine operation. This throttle plate was designed so as to regulate the quantity of air flow entering a Port Fuel Injected (PFI) spark ignition engine prior to the combustion of the fuel-air mixture. The throttle plate is linked to a data acquisition system in order to study the port fuel injection characteristics of the fuel-air mixture. This data acquisition system links the throttle plate angular position information to data obtained using a nonintrusive laser based diagnostic technique, therefore enabling the study …

Catalysis Of Charcoal Emissions, James M. Horak

Opportunities for Undergraduate Research Experience Program (OURE)

This paper is about the development of a system to reduce the emissions of charcoal kilns with the catalyst from automotive catalytic converters. This device, called the charcoal kiln emissions oxidizer (CKEO), was designed and fabricated to meet the goal of a cost effective means to reduce the carbon monoxide and hydrocarbon emissions from charcoal kilns. Testing of the CKEO was never carried out as a test site could not be secured by this writing. The need for the CKEO, the theory behind it, and a procedure to test it are presented.

Application Of Sunlight Mapping In Solar Car Design, Jeffrey Shapiro, Rob Ziegler, Matt Spaethe, Rick Jenkins

Opportunities for Undergraduate Research Experience Program (OURE)

The design of a solar car is a combination of trade-offs between the mechanical, aerodynamic, and photovoltaic systems. The mechanical and aerodynamic systems can be computationally modeled very well using commercial software. Clouds prevent the photovoltaic system from being modeled as well. This research explores a new way to accurately simulate almost every array configuration imaginable. Using this method, quantitative simulations are produced.

Damage Assessment Of Composite Structures With Embedded Optical Fibers, Peter E. Hackett

Opportunities for Undergraduate Research Experience Program (OURE)

One of the important features of smart composite structures is their capability to observe their own performance for proper functioning and self-diagnostic purposes. The low velocity impact damage of composite structures (matrix cracking, fiber breakage, delamination, etc.) is often difficult to detect visually and can significantly reduce the strength of the structure. The objective of this research is to develop a technique for fabricating composite laminates that will facilitate the embedment of optical fibers. Composite test specimens will be fabricated in the composite material laboratory. The fabrication of composite laminates with a health monitoring and damage assessment system capable of …

Performance Analysis For The Ccn Collection Apparatus, Deborah K. Bircher

Opportunities for Undergraduate Research Experience Program (OURE)

This paper concerns the performance testing of a system to collect and chemically analyze cloud condensation nuclei (CCN). These are the atmospheric particles which nucleate cloud drops.

The air is humidified by passage through the "haze chamber", consisting of parallel vertical plates that are covered with cotton cloth and are kept wet by water supplied at the top edge. The plates are adiabatic , and should equilibrate in temperature at the wet bulb temperature of the incoming air. Measurements of the plate temperature with eighty thermocouples indicate behavior consistent with theory.

Another part of the system is called the CFD …

Active Buckling Control Of Composite Plates, Bradley Wayne Gentelin

Opportunities for Undergraduate Research Experience Program (OURE)

The objective of the research project is to investigate the feasibility of using the rapidly growing technology of smart materials in actively controlling the buckling of laminated composite plates. Advanced composite structures are susceptible to structural instabilities under compression loadings, and the proper control of such instabilities is essential to the effective performance of the structures. The focus of the research activity is to perform an experimental study of using embedded piezoelectric materials for enhancing the critical buckling loads of laminated composite plates. The forces induced by the piezoelectric actuators under the applied voltage fields will be used to counterbalance …

Two Methods For Attenuation Of Vibration In Structures, Kevin Mark Mcclendon

Opportunities for Undergraduate Research Experience Program (OURE)

The purpose of this report is to discuss methods of suppressing vibration in space trusses. The discussion is centered on the approach, structural attributes, and effectiveness of each method. One approach uses structural active members which are actuated to produce “anti-vibration” to cancel vibrations in the truss. The other method is to implement passive and active damping devices at the base of the space truss, where it will absorb vibrations by fluctuating the stiffness of the structures foundation.

Quantam Wave Turbulence, Alejandro Garcia, M. Haeri, S. Putterman, P. Roberts

Faculty Publications

The nonlinear quantum kinetic equation for the interaction of sound waves is solved via analytic and numerical techniques. In the classical regime energy cascades to higher frequency (ω) according to the steady-state power law ω-3/2. In the quantum limit, the system prefers a reverse cascade of energy which follows the power law ω-6. Above a critical flux, a new type of spectrum appears which is neither self-similar nor close to equilibrium. This state of nonlinear quantum wave turbulence represents a flow of energy directly from the classical source to the quantum degrees of freedom.