Physical Sciences and Mathematics Commons^™

Assessment Of Passive Fire Protection On Steel-Girder Bridges, Michael Davidson

Masters Theses & Specialist Projects

Bridges in the US are severely damaged or suffer collapse from fires at significant rates, even when compared to other hazards such as earthquakes. Fire-induced bridge collapses are perpetuated by the general lack of installed fire protection systems. Therefore, new materials and applications are needed to mitigate structural damage that can be caused to civil infrastructure by severe fires. Accordingly, the objective of this study is to further the development of new fire protection applications in transportation structures. Specifically, the investigation centers on the development of new applications in passive fire protection materials, within the context of shielding steel-girder bridges …

Hybrid Nanostructures For Artificial Machine Olfaction, Landon Joseph Oakes

Masters Theses & Specialist Projects

The detection of low level concentrations of particles in a gaseous environment is of importance to many fields, especially Homeland Security. The ability to identify ppb concentrations of explosives and their degradation products can aid in the detection of improvised explosive devices (IEDs), ammunition dumps, or hidden explosives. One method of accomplishing this task is through the use of an array of chemiresistors in an electronic nose device. For this study, chemiresistors were constructed using 3-D silica nanospring mats with a contiguous film of ZnO nanocrystals and ZnO nanocrystals decorated by metallic nanoparticles. Samples with an average grain size of …

Doppler-Broadening Of Light Nuclei Gamma-Ray Spectra, Melinda D. Whitfield

Masters Theses & Specialist Projects

Non-destructive methods of material interrogation are used to locate hidden explosives and thwart terrorism attempts. In one such method materials are bombarded with neutrons which react with the nuclei of the atoms within causing a de-excitation process emitting a gamma-ray. The spectrum displayed by the collection of these gamma-rays gives valuable information regarding the material’s elemental make-up. It has been hypothesized that gamma-rays from neutron-induced gamma-ray reactions on light elements with atomic numbers less than 20, including most of the gamma-rays of interest in explosives detection, are Doppler-broadened. This thesis focuses on the gamma ray spectra from the 4438 keV …

A Numerical Investigation Of A Certain One-Dimensional Ising Model, Jimmy Green

Masters Theses & Specialist Projects

The model is a linear chain in which each spin interacts with its 2r nearest neighbors, the interaction energy being proportional to 1/r. Using a method similar to that of Montroll, the partition function of the model in the thermodynamic limit is shown to be related to the largest eigenvalue of a certain matrix. The largest eigenvalue of the matrix is determined numerically for 3 < r < 12.

Also, a correct method is demonstrated for evaluating an improper limit of the model, in which the interaction range is set to the chain length before the limit of an infinite number of spins is …

Analysis Of Differential Corrosion On High-Silicon Steel Laminations, Sompob Tingthanathikul

Masters Theses & Specialist Projects

The Cutler-Hammer plant in Bowling Green, Kentucky,manufactures laminated steel armatures for electrical starters (large relays) on which corrosion occurs only in some regions. The manufacturing process includes a heat treatment step from which the laminations emerge with a non-uniform surface appearance.

Laminations from corroded regions of an armature have red oxide (Fe₂0^₃) on the edges, while the sides have a black coating of partly-burned cutting-machine oil residue. The purpose of the project was to investigate the mechanisms of this corrosion and why it does not occur uniformly and to suggest practical solutions for the plant.

Emission …

Determination Of Energy Levels & Oscillator Strengths Of 2% Nd:Y2o3, Kung-Chuan Shao

Masters Theses & Specialist Projects

The absorption spectrum of 2% Nd:Y₂O₃ has been obtained at room termperature. It has been used to determine the crystalline energy levels.

Through counting the number of Stark components, degeneracies have been determined for oscillator strength calculations.

Overlapping absorption lines were analyzed into their components.

Oscillator strengths have been measured for those well-identified and analyzed transitions in the variable and near ultraviolet regions of the 2% Nd:Y₂O₃ absorption spectrum.

The Wavelength Dependence Of Herpes Simplex Viral Inactivation & Ultraviolet Enhanced Reactivation, Richard Detsch

Masters Theses & Specialist Projects

The degrees of Ultraviolet Enhanced Reactivation (UVR) by mammalian cells of Heroes simplex virus inactivated by different wavelengths of far ultraviolet radiation were measure'. The wavelength dependence of UVR is presented for the wavelength region 238 nm to 297 nm. The shape of the UVR curve suggests that virus directed repair is less dependent on the wavelength of UV radiation than are cellular repair mechanisms. The wavelength dependence of Herpes simplex inactivation by far UV radiation is also presented. The shape of the virus inactivation curve suggests the involvement of both DNA and protein.

Simulative Investigation Of The Detection Of Modes Of Luminosity Variation In Astrophysical Sources, James Collins

Masters Theses & Specialist Projects

Five astronomical data analysis methods were evaluated, using computer simulation techniques, for minimum detection levels, periodicity detection, and parameter estimation sensitivities. The evaluation of these methods was accomplished using three basic waveforms with the addition of ten “random” noise samples from a Gaussian distribution of known parameters. The chi-square and t-test methods were evaluated in detecting low-amplitude variability and brightness level shifts. Results indicate both methods have a strong dependence on the estimation of the standard deviation (σ) where a 0.1 change in σ will affect detection rates by ten to twenty-five percent at the ninety-five percent confidence level. The …

Ionization Studies Of Nitrogen & Nitrogen-Sulfur Hexaflouride Mixtures, Amir Fallahi

Masters Theses & Specialist Projects

Ionization measurements as a function of concentration and pressure have been made in nitrogen and nitrogen-sulfur hexafluoride gas mixtures containing either cyclopropane, ethylene, propylene, acetylene, ethane, or impurity. These studies have been made to understanding of the gas kinetics involved propane as contribute in nitrogen an to the and nitrogen-sulfur hexafluoride laser systems. Impurity gases were chosen on the basis of their ionization potentials relative to the C³π_u state in nitrogen that is responsible for the lasing action. Analysis of the data indicated that a Jesse effect exists for those impurity gases whose ionization potentials lie below …

A Study Of He+ + Ar Collisions At Energies Between 600 Ev & 1500 Ev, Alton Dull Jr.

Masters Theses & Specialist Projects

This investigation was undertaken in order to confirm and to extend earlier studies of processes whereby energy and angular momentum are transferred from external to internal degrees of freedom in low velocity collisions between ions and atoms. Specifically, this investigation sought to verify the proper functioning of a device designed to study low velocity atomic and molecular collisions, to confirm results obtained in an earlier study of spectra produced by collisions of He⁺ions with argon atoms, and to extend the energy and wavelength ranges of this study to 1500 eV and 6200 Å, respectively.

The data was in …

Ultraviolet Stimulated Thermoluminescent Response Characteristics Of Aluminum Oxide, Edward Ryan Iii

Masters Theses & Specialist Projects

This investigation has demonstrated that some aluminum oxide crystals have high sensitivity and are well suited for detecting and measuring ultraviolet radiation rates significantly less than .01 µW/cm².

The thermoluminescent glow curve, linearity of response, and fading of the crystals were determined. An action spectrum was performed to determine the relative sensitivities of several crystals in a range of wavelengths from 230 nm to 546 nm.

The sensitivity of the crystals was found to decrease as a function of exposure. \n explanation for the decrease in sensitivity due to the presence of high temperature traps is presented.

This …

Ultraviolet Stimulated Thermoluminescent Response Characteristics Of Aluminum Oxide, Edward Ryan

Masters Theses & Specialist Projects

This investigation has demonstrated that some aluminum oxide crystals have high sensitivity and are well suited for detecting and measuring ultraviolet radiation rates significantly less than 0.1 pW/cm2. The thermoluminescent glow curve, linearity of response, and fading of the crystals were determined. An action spectrum was performed to determine the relative sensitivities of several crystals in a range of wavelengths from 230 nm to 546 nm. The sensitivity of the crystals was found to decrease as a function of exposure. An explanation for the decrease in sensitivity due to the presence of high temperature traps is presented. This investigation has …

Calculated Temperature Of Grid Lateral Wires In Microwave Power Triodes, Jewell Tucker

Masters Theses & Specialist Projects

In microwave power triodes the grid drive power causes grid lateral wire heating. This development calculates the temperature of the wire as a function of the drive power, physical dimensions and characteristics of the wire material, for the following boundary conditions:

I. Constant grid drive, grid lateral wire of infinite length not connected to a heat sink.

II. Same as I except the wire is of finite length brazed to a grid frame.

III. The grid excitation in the form of pulses, and the grid lateral wire of finite length brazed to a grid frame.

the equations were verified experimentally …

Ultraviolet Excitation Thermoluminescence Of Lead-Manganese Calcium Carbonate, Dennis Schrope

Masters Theses & Specialist Projects

Calcium carbonate with impurities of lead and manganese have produced measurable thermoluminescence (TL) when excited by ultraviolet (uv) radiation. In this investigation the lead impurities comprise the majority of trapping centers stimulated by uv irradiation. In addition, centers associated with the CO₃groups have been found to be capable of absorbing uv and ultimately producing TL. The 2537 Å mercury line is primarily responsible for stimulating these centers, and the response was found to be linear to 0.6734 joules/cm².

The thernoluminescence response was discovered to be dependent on the concentrations of lead and manganese. However, for a …

An Alternate Solution To The Two-Dimensional Ising Model, B. Craig Meyers

Masters Theses & Specialist Projects

An alternate solution for the two-dimensional Ising model in a zero external magnetic field is presented. Following Kaufman, the partition function is written as the trace of a certain matrix product. The trace can be evaluated by computing the determinant of a related matrix. The determinant is evaluated by finding the product of its eigenvalues; in the thermodynamic limit the result is equivalent to that found by Onsager.

Ultraviolet Photosimulated Thermoluminescence Of Lithium Flouride, Martin Payne

Masters Theses & Specialist Projects

TLD-100 (lithium fluoride) thermoluminescence dosimeters are widely employed for the detection of ionizing radiations. This paper shows that these dosimeters may also serve as practical germicidal ultraviolet radiation dosimeters. To measure ultraviolet radiation, the TLD-100 dosimeters are first exposed to 500,000 roentgens of gamma radiation and then annealed at 300°C. Subsequent dosage of ultraviolet radiation may be determined by observation of photostimulated thermoluminescence of the crystal. The presented data indicate that the thermoluminescence response is linear for exposures up to 6,000 µjoule/cm² and independent of exposure rate from 0.1 µ watt/cm² to above 50 µwatt/cm². Optical …

Determination Of (N, 2n) Reaction Isomeric Cross Section For 87rb, 112cd, 138bz, And 186w Using 14 Mev Neutrons, Hsiao-Chueh Kao

Masters Theses & Specialist Projects

The purpose of this investigation was to measure the cross section for each of the reactions 87_{Rb(n, 2n)} 86m_Rb, 112_{Cd(n, 2n)}111m_Cd, 138_{Ba(n, 2n)} 137m_Ba and 186_{W(n, 2n)} 185m_W at 14.7 ± 0.03 MeV incident neutron energy. The incident neutron flux was determined during each irradiation from the activity produced in copper or aluminum disks between which the isotopically enriched sample was sandwiched. The 63_{Cu(n, 2n)}62_Cu and 27_{Al(n, p)}27_Mg reaction cross sections were assumed to be 593 ± 45 mb and 73 ± 5 …

Electron-Beam Retardation Contact Potential Of Cuprous Oxide, James Lindle

Masters Theses & Specialist Projects

The purpose of this research is to determine the contact potential of cuprous oxide, Cu₂O, with respect to gold. A band model for cuprous oxide is presented.

Single-crystal cuprous oxide is prepared from Oxygen Free High Conductivity copper equilibrated at 120°C and at atmospheric pressure. The contact potential difference of cuprous oxide (using gold as a reference) is measured in a bakeable ultrahigh vacuum system using a modified version of Nelson's electron beam retardation method. Measurements made at 10^-6 torr and at room temperature give a value of 0.1 +/-0.05 eV for the contact potential difference of …

Thermionic Space Charge Oscillations, William Carl

Masters Theses & Specialist Projects

Thermionic electrons emitted into a potential well will produce radiation, the frequency of which is determined by the transit time of the electrons. This paper investigates the case where radiation is produced by a vacuum tube in which two Pierce guns face each other, one acting as the emitter, the other acting as a reflector. Symmetry and the focusing of the electron beam by the Pierce guns make it possible to make an accurate determination of the electron transit time. Measurements showed that the period of the oscillation was 1.5 times the period required for an electron to traverse the …

X-Ray Induced Luminescence Of Sapphire And Ruby, Ivan Collier Jr.

Masters Theses & Specialist Projects

Over the past decade the luminescence properties of sapphire (∝-AL₂O₃) and ruby (Al₂O₃:Cr₂O₃) have been the subject of many investigations because of their importance in materials technology. Sapphire and ruby are at present used as lasing materials, radiation dosimeters, and as optical windows. In order that these operations may be made more efficient, and that other useful luminescent properties may be systematically explored and developed, much attention has been given to understanding the luminescent mechanisms from the standpoint of the physics of the solid state. However, mechanisms have …

Determination Of The Time Delay In The Arrival Of Jovian Signals At Opposite Ends Of A Long Baseline Fringe Synthesis Interferometer, Roger Scott

Masters Theses & Specialist Projects

In order to determine the size of the decametric sources, the technique of long baseline radio interferometry is being employed. The University of Florida at Gainesville is a pioneer in this field. In 1964, T. D. Carr introduced the procedure of recording the signals received at each end of an interferometer on magnetic tape and comparing the re-corded signals at a later time. This eliminated the necessity for transmission lines over the length of the baseline, allowing greater separation to attain higher resolution.

Determination Of (N, 2n) Reaction Cross-Sections For 71ga, 106cd & 138ba Using 14 Mev Neutrons, Thomas Helm

Masters Theses & Specialist Projects

The increasing trend towards the use of activation analysis as an analytic means of identifying elements and determining their relative abundance demands more accurate values of reaction cross-sections. Accurate values of cross-sections are also important in the investigation of possible shell effects in reaction mechanisms. Many activation cross-sections for reactions produced by 14 MeV neutrons have been measured because of the relative ease with which this energy of neutrons can be produced. Low voltage accelerators are capable of producing 14. MeV neutrons by the ³H( d,n)⁴He reaction. Although many people^(1-5) have measured the (n,2n) reaction cross-sections …

-Ray Induced Luminescence Of Ruby, Wayne Cooke

Masters Theses & Specialist Projects

Since the advent of the laser there has appeared a multitude of scientific papers describing the various parameters that would affect the lasing action of the ruby laser. Many investigations have been carried out to determine the efficiency of the R-line fluorescence in ruby: however very little work has been done concerning the X-ray-induced luminescence of ruby.

Certainly the applications to laser technology would be of sufficient importance to merit a study of ruby under continuous irradiation, although this was not the main stimulus that motivated this investigation. The original program of study was undertaken to determine if there existed …

A Nonsecond Time-Of-Flight Spectometer, David Moorman

Masters Theses & Specialist Projects

The purpose of this thesis was to construct a time-of-flight spectrometer using plastic scintillators coupled to photomultiplier tubes as the primary detectors. A time-of-flight spectrometer with at least 2.0 nanoseconds of time resolution was desired.

Electrical Conductivity & Seebeck Effect In Activated Molybdenum Oxide Hydrogen Detectors, John Hooker

Masters Theses & Specialist Projects

This thesis describes the results and analysis of Seebeck coefficient and electrical conductivity measurements on "activated", molybdenum-oxide, thin film hydrogensensing elements. The work was undertaken in an effort to produce data that would be useful in obtaining an understanding of the electronic processes which cause large electrical conductivity changes in molybdenum-oxide upon exposure to small concentrations of hydrogen in air. The results are analyzed using a simple band model of a semiconductor. This model is shown to give reasonable results at high temperatures; however, a departure from the usual .! model is required in order to explain the results at …

Crossed Field Trochoidal Trajectory Devices For Investigating The Reflection Of Slow Electrons From Metallic Surfaces, Stan Lemaster

Masters Theses & Specialist Projects

The objective of this study was to build preliminary devices . which could be used to measure electron reflection coefficient values using crossed electric and magnetic fields. The technique for using crossed fields to measure reflection coefficients was developed at Air Force Cambridge Research Laboratories. The reflection coefficient is the ratio of the number of electrons in a reflected beam to the number of electrons in an incident beam striking a surface.

The work described herein was a part of a project authored by AFCRL under contract AF19 (628)-5940; Project 8605 (with Western Kentucky University being the contractor) which was …

Solid State Electrolysis Of Yttria Stablized Zirconia, John Newman

Masters Theses & Specialist Projects

Zirconium dioxide, or zirconia, is seemingly an ideal refractory oxide, having a high melting point (2680°C), low thermal expansion and also a considerable resistance to most forms of chemical attack. Early researchers soon found that zirconia, in the pure form, was actually of very limited use as a refractory because of sudden and disruptive volume changes accompanying a change in crystal structure which occurs at a temperature of about 1100 o C. It was discovered that this crystal structure change could be suppressed by the addition of one of a number of alkaline earth or rare earth oxides. These additive …

Noise In Cadmium Sulfide & Cadmium Selenide Photoconductive Cells, Edward Foster

Masters Theses & Specialist Projects

The primary object of this investigation is to design a system, including equipment and procedures, that can be used to evaluate the noise characteristics of photoconductive cells. The data once collected must be in a comprehensive and useful form. The secondary object is to use this system to evaluate a large number of cells of various types and to compare their noise profiles in a manner such that definite conclusions can be drawn concerning the absolute noise levels and profiles generated by the various cell types and the relations that may exist between the cells' noise output and the way …

Environmental Effects On The Resistivity Of Palladium-Silver Alloy Films In High Vacuum, Frank Snyder

Masters Theses & Specialist Projects

The reported usage of the palladium-silver alloy films as resistors in the electronics industry has been in encapsulated form. By mounting the resistor inside vacuum electron devices, there is the possibility of eliminating the encapsulation. A literature search has revealed no reported efforts of experiments with unencapsulated resistors and certainly no reports of the palladium-silver alloy resistor in vacuum tubes or other high vacuum environments. Therefore, the research reported in this thesis will concentrate on the environmental effects on resistivity of palladium-silver alloy films in high vacuum.

The Value Of High School Physics To The College Student, Emery White

Masters Theses & Specialist Projects

Secondary school science consists of biology, chemistry, physics, or a combination course known as general science. General science deals only with the practical side of the laws of physics. It fails to go into detail and very often omits the law entirely. Physics in high school requires a special room in the building which is not easily adapted to other use. A large amount of expensive equipment is need to teach it efficiently. Can all of this expense be justified? Is the student who ends his school career with high school graduation sent out into life with a large amount …