UNT Libraries - 5 Matching Results
Search Results
- The Physics of Gaseous Exposures on Active Field Emission Microcathode Arrays
- The interaction of active molybdenum field emission microcathode arrays with oxygen, water, carbon dioxide, methane, hydrogen and helium gases was studied. Experiments were setup to measure the emission characteristics as a function of gas exposures. The resulting changes in the surface work function of the tips were determined from the Fowler-Nordheim plots. The kinetics of the FEA-gas interaction were studied by observing the ion species originating from the array during and after gas exposures with a high resolution quadrupole mass spectrometer. With the work function data and the mass spectrometry information, the mechanisms responsible for emission degradation and subsequent device recovery after exposures have been determined. The data obtained was used in estimating the device lifetimes under various vacuum environments. Also it was found that the gas exposure effects are similar in dc and pulsed modes of operation of the arrays, thus permitting the use of dc mode testing as an effective acceleration method in establishing the device lifetimes under various vacuum conditions. The vacuum conditions required for the long term emission current stability and reliability of vacuum microelectronic devices employing FEAs are established. Exposure of Mo field emitter arrays to oxygen bearing species like oxygen, water and carbon dioxide resulted in serious emission current degradation. Whereas, exposure to methane and hydrogen caused a significant increase in emission current. The control of residual gases like 02, C02 and H20 in the vacuum envelope is essential for the emission current stability and long term reliability of vacuum microelectronic devices employing field emission microcathode technology.
- Hawthorne's Use of Symbolism in Four Romances
- This thesis is a study of the four long romances, The Scarlet Letter, The House of the Seven Gables, The Blithedale Romance, and The Marble Faun, with emphasis upon Hawthorne's use of symbolism as a means of presenting the basic moral and spiritual truths of human life. The first chapter explains the nature of symbolism and the reasons why Hawthorne used it so extensively. In each of the last four chapters, the symbolism in a single romance is considered for the purpose of discovering the manner and effectiveness of its use in exemplifying the central theme of that particular story. Although Hawthorne's short stories are extremely rich in symbolism, it was not possible to include them in the present study.
- A Stylistic Analysis of Serge Prokofieff's "Second Concerto for Violin"
- The purpose of the following study is to make an analysis of the structural elements and stylistic characteristics in the Second Concerto for Violin by the modern Russian composer, Serge Prokofieff. These include the composer's treatment of form, melody, rhythm, harmony, and medium of expression.
- A Comparison of the Canzoni of Frescobaldi and Froberger
- It is the purpose of this thesis to discuss and compare the canzoni of Frescobaldi and Froberger and to show something of their influences on their successors.
- The Musical Setting of Eight Choruses for Typical Music Classes of Grades Four to Six
- These eight were selected as typical lyrics to meet the diverse interests of students in the intermediate grades and to aid the teachers of those students in transmitting desired precepts and ideals. The poems are short and varied in verse form. The subject matter ranges from pirates and fairies to one's own conscience and Christmas; the moods, from whimsicality and nonsense to patriotism and reverence. The marked poetic devices influencing the choice of these particular lyrics are their rhythmical and alliterative quality; their rich, lively, yet correct language; their vivid imagery; their emotional appeal; and in a few cases their narrative quality.