The present work investigates the nature of dry-friction whip and whirl through experimental and numerical methods. Efforts of the author, Dyck, Pavalek, and coworkers enabled the design and construction of a test rig that demonstrated and recorded accurately the character of multi-mode dry-friction whip and whirl. These tests examined steady state whip and whirl characteristics for a variety of rub materials and clearances. Results provided by the test rig are unparalleled in quality and nature to those seen in literature and possess several unique characteristics that are presented and discussed. A simulation model is constructed using the Texas A and M University (TAMU) Turbomachinery Laboratory rotordynamic software suite XLTRC2 comprised of tapered Timoshenko beam finite elements to form multiple degree of freedom rotor and stator models. These models are reduced by component mode synthesis to discard highfrequency modes while retaining physical coordinates at locations for nonlinear interactions. The interaction at the rub surface is modeled using a nonlinear Hunt and Crossley contact model with coulomb friction. Dry-friction simulations are performed for specific test cases and compared against experimental data to determine the validity of the model. These comparisons are favorable, capturing accurately the nature of dryfriction whirl. Experimental and numerical analysis reveals the existence of multiple whirl and whip regions spanning the entire range of frequencies excited during whirl, despite claims of previous investigations that these regions are predicted by Black's whirl solution, but are not excited in simulations or experiments. In addition, spectral analysis illustrates the presence of harmonic sidebands that accompany the fundamental whirl solution. These sidebands are more evident in whip, and can excite higher-frequency whirl solutions. Experimental evidence also shows a strong nonlinearity present in the whirl frequency ratio, which is greater than that predicted by the measured radius-toclearance ratio at the rub location. Results include whirl frequencies 250% of that predicted by the measured radius-to-clearance ratio.

In this study, the dependence of metal/Alq3 Schottky contact barrier on the current¡Vvoltage characteristics of organic light emitting diodes was investigated to know the charge injection mechanism of OLED with the single-layer metal/Alq3/ metal structures, and the current density increases obviously with the reduction of contact potential barrier. As the thin LiF layer is inserted between the Al electrode and the Alq3 layer, it shows that the electron injection was promoted, and higher electroluminescence efficiency was also obtained. Both the energetic barrier and the tunneling integral parameter are reduced when the LiF layer thickness increases. For very thin films of LiF, the beneficial effect of the barrier reduction is dominant. When the film grows thicker, the negative insulating effect becomes dominant. Besides of simulating the current¡Vvoltage characteristics of organic light emitting diodes (OLED) based on Alq3 in combination with different cathodes, it was simulated that the current¡Vvoltage characteristics of OLED with an inserted LiF layer between metal and organic material, and then the OLED with various thicknesses of LiF films were also simulated. Finally, the result of simulations was compared to achieve a better description for the characteristics of current¡Vvoltage for the single carrier and layer based OLED.

This study presents the GaSb epitaxial grown by molecular beam epitaxy (MBE) on the semi-insulating GaAs substrate and n+-GaAs substrate. Investigations are made to the effect of Sb4/Ga beam equivalent pressure (BEP) ratios on the current-voltage characteristics of the p-n hetero-junction and the metal-GaSb semiconductor Schottky contact for various metals deposited on n-type GaSb layers. Several growth conditions were taken to improve the quality of GaSb epitaxial films. The structure of GaSb epitaxial layers are characterized by the X-ray diffraction, and the optimum growth conditions 500¢J of substrate temperature and the Sb4/Ga flux ratio about 2~3 have been obtained. From the I-V curve of GaSb Schottky diodes, we know that the higher Sb4/Ga ratio will induce the lower breakdown voltage. Hence, the interface properties of hetero-junction between the GaSb/GaAs and metal/GaSb can be investigated by the current-voltage characteristics, in which the current leakages and the surface state density are strongly dependent on the ratio of Sb4/Ga BEP. Based on the thermionic emission theory, the barrier height obtained was decrease with the Sb4/Ga ratio increases. After metal deposited on the GaSb epitaxial film to form the Schottky diode, the density of surface states can be calculated from the relationship of metal work-function and barrier height, which were obtained from the current-voltage characteristics of Schottky diode measurement, and then it also found that the density of surface states show decrease as the Sb4/Ga ratio increase.

No description available.

No description available.

<p>This thesis deals with glued laminated beams with holes. Different hole geometries, circular and quadratic,  and reinforcement methods were investigated. A total of 24 tests were performed using two types of reinforcements (glass fiber and plywood) and testing unreinforced beam. During testing of the beams without reinforcement a contact free deformation measurement system was used to capture the deformation pattern. A commercial finite element software package was used to perform numerical calculations of the response of the beams. The FE-analyses were also compared with the experimental results. The test results showed that the reinforcement with plywood was more efficient than the reinforcement with glass fiber. In addition, the two hole geometries showed different failure behaviors. The beams with quadratic holes showed a less brittle behavior, although at a lower load level than the beams with circular holes.</p> / <p> </p><p>Denna rapport behandlar limträbalkar med hål. Olika hålgeometrier, cirkulära och kvadratiska hål, och olika metoder att förstärka balkarna vid hålet undersöktes. Totalt 24 enskilda provningar genomfördes med två olika förstärkningsmetoder (glasfiber och plywood) samt med balkar utan förstärkning. Vid provning av de oförstärkta balkarna användes ett system för beröringsfri deformationsmätning för att få en bild av deformationsmönstret. Ett kommersiellt finita elementprogram användes också för att analysera balkarnas respons och för att jämföra med provningsresultaten. Provningarna visade att förstärkningen med plywood var effektivare än förstärkningen med glasfiber. Vidare uppvisade de olika hålgeometrierna olika brottbeteenden, där de kvadratiska hålen gav mindre spröda brott, dock vid en i genomsnitt lägre brottlast än de cirkulära hålen.</p>

Proefschrift--Letteren--Vrije Universiteit te Amsterdam, 1996. / Résumé en néerlandais. Bibliogr. p. 269-279.

Habilitationsschrift--Neuere fremdsprachliche Philologie--Berlin--Freie Universität. / Bibliogr. p. 429-475.

Proefschrift--Tilburg--Katholieke universiteit Brabant, 1994. / Bibliogr. p. 253-265. Résumés en anglais, frison et néerlandais.

Akademisk avhandling--Uppsala, 1998. / Résumé en anglais. Bibliogr. p. [255]-262. Index.