The current study has evaluated shoreline dynamics and environmental change at St. Catherines Island, Georgia, with attention to the two major controls of barrier island formation and modification processes. These major controls include the increase in accommodation space, or the rate of sea level rise for the Georgia Bight which has remained constant in 20th and 21st century tide gauge data and dynamically changing rates of sediment supply based on anthropogenic modifications to land cover (Trimble, 1974) that are reflected in sediment transport (McCarney-Castle et al., 2010). Vibracoring and radiocarbon data provided valuable insights into the stratigraphy and development of St. Catherines Island. A stratigraphic model has been developed for the sediments associated with the Late Holocene accretional terrains where multiple small scale fluctuations in sea level have resulted in the formation of a sedimentary veneer punctuated with transgressive surfaces and regressive sequences. A working model for an interpolated Late Holocene sea level curve has been constructed using direct evidence from vibracore data as constraining points and indirect evidence from other regional sea level studies to provide additional structure. The relationship between the timing of the regressions versus periods of beach ridge formation and implications from the current shoreline dynamics study regarding the role of sediment supply complement each other. The ages of beach ridge formation strongly correlate to periods that are associated with regressions in sea level based on the sedimentary record and an evaluation of Late Holocene sea level conditions. The evaluation of anthropogenic modifications to the rate of sediment supply performed under the current study indicates that in spite of significant changes in sediment flux rates of +300% (pre-dam era) and -20% (post-dam era), shoreline retreat was continuous during the study period with an acceleration noted in the rates of shoreline retreat associated with spit and berm landforms during the post-dam or modern era. The two associations indicate strongly that the rate of sediment supply plays a secondary role to the major control of the rate of sea level rise in the formation and modification processes at St. Catherines Island.

No description available.

In this study, the thin titanium oxide (TiO2) film deposited on InP substrate was prepared by atomic layer deposition (ALD), which was used as gate oxide of InP Schottky barrier MOSFET. First, aluminum oxide (Al2O3) by ALD can be used as improvement in oxide of TiO2. Al2O3 of ALD has self-cleaning which can improve interface between oxide and substrate, the leakage current densities can reach 3.1 ¡Ñ 10-9 and 3.3 ¡Ñ 10-7 A/cm2. The Schottky barrier height(£XBp) of Al/InP with (NH4)2S treatment is 0.968 eV, which is higher than that of Al/InP without (NH4)2S treatment (0.806eV). The (NH4)2S solution is a moderate etchant to reduce surface oxides on InP. Therefore, Schottky barrier will not be influenced by Fermi level pinning. The electrical characteristics of Schottky barrier MOSFET with TiO2 as gate oxide were measured in this report. The drain current is 1.73£gA. The drain current increases rapidly when drain voltage is over 1V, it indicates that breakdown field of TiO2 thin film is not high enough. Due to advantages of ALD-Al2O3, such as self-cleaning ability and high breakdown field, the TiO2/Al2O3 prepared by ALD structure was used to improve the problem mentioned above. The electrical characteristics are much improved compared with a single TiO2 film, and drain current can reach 1.37 £gA. The rapid increase of drain current with the increased drain voltage is not observed. The transconductance and mobility are 4.45 ¡Ñ 10-7 S/£gm and 202.3 mm2/V-s, respectively, and a good sub-threshold behavior is obtained. Compared with other researches, we can find that Schottky barrier in on-state is higher than that of silicide sample. It indicates the InP Schottky barrier MOSFET characteristics are limited by high Schottky barrier.

Thermal barrier coatings (TBCs) have become an important part of turbine technology by providing thermal protection to the underlying metallic components. These coatings are typically made from a zirconia-based ceramics which have a low thermal conductivity and thermal expansion coefficients similar to those of the superalloys. Early failure in these coatings is most often due to foreign object damage and erosion resulting in delamination and spallation. To protect against these types of failure, new materials with increased toughness are needed. There are two main toughening mechanisms in ceramics: transformation toughening, which is limited to low temperature applications and ferroelastic toughening which is accessible at all temperatures. Ferroelastic toughening occurs when the c-axis of the tetragonal grain undergoes reorientation under the application of an external stress. In this study, ferroelastic toughening is examined by Raman spectroscopy. It is shown that by using polarized confocal Raman spectroscopy one can not only observed the ferroelastic process, but also measure the parameters that control the increase in toughness observed. Ferroelastic toughening was observed in two ways in the 18mol% ceria stabilized zirconia (18CSZ) samples studied here. Samples were either exposed to indentation damage or uniaxial loading. In both of these cases maps of the ceramic surface were taken using Raman spectroscopy following loading and the relative intensities of the tetragonal peaks were analyzed. The resulting intensity profiles were used to monitor the reorientation of domains corresponding to ferroelastic toughening. Changes in domain orientation were observed that corresponded to the reorientation of domains along cracks as well as on a larger scale along those cracks. Domain reorientation was also observed under uniaxial loading and the stresses required for domain formation and movement were measured.

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.

The government has pooled its resources to promote lifelong learning, considering the fact that lifelong learning is not only a deciding factor in the era of knowledge economy but also the most efficient way in its cultivation of democracy among the general public. In the study, I defined the scope of lifelong learning as three categories: Master, Master-work-experience, and other correspondence courses like those offered by National Open University. The population of this study is all the official in Penghu County. 347 subjects were surveyed and analyzed using the software SPSS 10.0. The purpose of this study, besides exploring the motivation and various barriers for the official in Penghu under the current government lifelong learning policy, is to understand whether the existing learning channels meet the needs and live up to the expectations of official in their pursuit of lifelong learning. The results of the study are for the reference of our government in its making of lifelong learning policy and the creation of a better learning environment. The findings are as follows: 1.The learning motivations of official for in-service training, broadly speaking, are (in descending order): further pursuit of education or personal interest, advancement in the career, participation in social service, and development of interpersonal relationship. 2.As a whole, the barriers facing official in their pursuit of further study are classified, in descending order, into institutional factors, circumstantial factors, intentional factors, and informative factors. 3.The official who fail to complete their study are due to (in descending order) circumstantial factors, institutional factors, personal concerns, and teaching factors. 4.Basically, official from different backgrounds show significant differences in terms of their respective motivations, barriers they encounter, and reasons for the termination of study. And among the many factors affecting the willingness to study, the education level seems not to be significantly correlated. As for the termination of study, the three factors¢w¢wage, marital status, and family monthly income are not significantly correlated. Suggestions are provided for in-service official, government policymaking mechanism, extension education environment and resources providers, and further studies based the findings of the study.

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.

This thesis uses aluminum porous board (AP board) to study the noise reduction for cooling tower. It sets the barrier to isolate the sound propagation. But it will happen diffracted phenomenon when sound wave impinging at the edge of barrier. So the mathematical model of acoustic diffraction on the barriers, which is set up by Hayek, is applied in this thesis. Base on this theorem, the AP board and the paths of sound propagation are analyzed. In experiment, it uses the sound intensity method to measure the cooling tower for determining the major source first. The major source is determined by ranking the sound power. And the suitable insulation material is selected by analysis the frequency band of major source. After analyzing, the major source of cooling tower is the region of fans by motor driven that is located upper the cooling tower. And its frequency range is between 25 Hz to 2500 Hz. So the AP board is a candidate since it has broadband characteristic on noise insulation. After aim of the major source, the noise barrier is studied for noise reduction. In this thesis, the U profile of barrier (looking down from above), which considers the situation in the field, is designed to surround the cooling tower. This barrier is made of aluminum board, and the aluminum porous board is applied to add on the upper barrier for noise reduction. To study the acoustic diffraction on the boundary of barrier, the thick of porous board is added on the upper barrier. The insulation effect is compared in the different condition after measuring the transmission loss. The T shape barrier is also designed for noise reduction evaluating in this thesis. Finally, the best-insulated effect is obtained when the complex board is added on the upper barrier. And the noise level is down to 59 dB around the environment. This result is matched the EPA noise standards.

In the generation of deep submicron semiconductor fabrication¡Atransmission delay is primarily caused by the parasitic resistance and capacitance (RC) in the multilevel interconnects. Besides¡Aelectromigration is also a serious issue for the reliability of devices . There are two principle methods of reducing the RC delay. The first method is to replace the Al wires with Cu interconnects which supply lower resistivity and high resistance to electromigration. The second method is to use a lower dielectric constant material as the inter-metal dielectric. But in Copper metallization¡Athe key issue of this technology is the formation of a thin barrier layer for Cu on the surface of the SiC film to prevent the absorption of water and diffusion of Cu. In this study¡Awe employed films SiC base compounds to investigate their chemical bonds, I-V characteristics comparisons with Al and Cu gate. On the other hand, because of serious C-V hysteretic phenomena, we try to analyze and build up models. There five models is reasonable for our experiment: (1) mobile ions, (2) dielectric polarization, (3) carrier injection, (4) gate-electrons injection, and (5) bound charges. They happens in different materials and structures.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Deposition rate; zirconia; TBC; texture; microstructure; EB-PVD. Includes bibliographical references (p. 78-79).