Engineering Physics Commons^™

Laser-Induced Recoverable Surface Patterning On Ni50ti50 Shape Memory Alloys, Saidjafarzoda Ilhom

Masters Theses & Specialist Projects

Shape memory alloys (SMAs) are a unique class of smart materials exhibiting extraordinary properties with a wide range of applications in engineering, biomedical, and aerospace technologies. In this study, an advanced, efficient, low-cost, and highly scalable laser-assisted imprinting method with low environmental impact to create thermally controllable surface patterns is reported. Two different imprinting methods were carried out mainly on Ni50Ti50 (at. %) SMAs by using a nanosecond pulsed Nd:YAG laser operating at 1064 nm wavelength and 10 Hz frequency. First, laser pulses at selected fluences were directly focused on the NiTi surface, which generated pressure pulses of up to …

Investigation Of The Addition Of Basalt Fibres Into Cement, Jahi Palme

Masters Theses & Specialist Projects

Mechanical properties of concrete are most commonly determined using destructive tests including: compression, flexure, and fracture notch specimen tests. However, nondestructive tests exist for evaluating the properties of concrete such as ultrasonic pulse velocity and impact echo tests. One of major issues with concrete (which has cement as its prime ingredient) is that unlike steel it is quasi-brittle material. It tends to want to crack when tensile stresses develop. Fibres have been added to concrete for many years to reduce the amount of and size of cracks cause by temperature changes or shrinkage. In more recent years, significant research 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 …

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 …

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 …

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.