<p>Controlling the properties of single walled carbon nanotubes (SWNTs) is the major challenge toward their future applications. This dissertation describes several contributions to this chanllenge. </p><p>This dissertation begins with the brief review on carbon nanotubes (CNTs), including discovery, structure, properties, challenges, synthesis and applications. The remaining parts can be divided into three sections. They demonstrate the control of SWNT properties as well as their devices by direct synthesis and metal decoration. </p><p>Two studies are described on the control of SWNT properties by direct synthesis. The first demonstrates the controlled synthesis of SWNTs in terms of their diameter, uniformity, and density by the chemical vapor deposition (CVD) method. The approaches employed include using uniform nanoparticles with specific sizes as catalysts to grow different diameter SWNTs, specially small diameter tubes less than 1 nm; using laser irradiation to grow uniform and high quality SWNTs; and changing the gas flow pattern to obtain different density. The second study demonstrates the growth of aligned SWNTs by flow and substrate guidance. Horizontally aligned ultralong nanotubes are synthesized on Si substrate by both high flow and low flow. The guided growth by the quartz substrate is shown by a large variety of metal catalysts to further the understanding of the growth mechanism. Moreover, top gated FETs have been explored for the selective growth of purely semiconducting, horizontally aligned SWNTs grown on quartz by a ethanol/methanol mixture. </p><p>The control of SWNT device performance is also described, in particular, the correlation between the SWNT field effect transistor (FET) configuration and its gate dependence response. The effects of FET channel length, nanotube density and diameter on the device performance are demonstrated. A model has been constructed in order to simulate the electronic behavior. An interesting metallic behavior has been observed. </p><p>Finally, control of SWNT properties by Palladium decoration after growth is used to manipulate their properties. Moreover, two novel applications including improvement of carbon nanotube film conductivity and catalysis of nanostructure growth are developed.</p> / Dissertation

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In the study, the thickness of wave moved-sediment layers was measured under regular wave conditions as well as the initial slope of sea bed with grain size of medium diameter 0.237mm and 0.128mm. The initial bottom slope ( tan£\) is 1/45, and nineteen wave conditions were studied. For each case, we analyzed the results after about 28800 waves were made. Sands are similar density and grain size but different colors. After wave action, the clear boundary between the two layers (two different colors) of sands will be mixed into gray color by wave-induced vortex.According to unmoved-layer(white) and gray-layer to get the total wave-moved sediment quantity. Finally, we get the relationship between the wave-moved sediment quantity per wave( q) and two parameters( £`b and £Kb ) which were established by Liao (2005, doctorate draft). The grain size does not affect £`b , and we get the q= 6.486*10^-5*£`b . The relationships between and ¡G 0.110mm gets q=5.103*10^-6£Kb , 0.128mm gets q=1.139*10^-5*£Kb, and 0.237mm gets q=1.933*10^-5*£Kb .

The effects of a carbon nanotube (CNT) coating on bubble departure diameter and frequency in pool boiling experiments was investigated and compared to those on a bare silicon wafer. The pool boiling experiments were performed at liquid subcooling of 10 degrees Celsius and 20 degrees Celsius using PF-5060 as the test fluid and at atmospheric pressure. High-speed digital image acquisition techniques were used to perform hydrodynamic measurements. Boiling curves obtained from the experiments showed that the CNT coating enhanced critical heat flux (CHF) by 63% at 10 degrees Celsius subcooling. The CHF condition was not measured for the CNT sample at 20 degrees Celsius subcooling. Boiling incipience superheat for the CNT-coated surface is shown to be much lower than predicted by Hsu's hypothesis. It is proposed that bubble nucleation occurs within irregularities at the surface of the CNT coating. The irregularities could provide larger cavities than are available between individual nanotubes of the CNT coating. Measurements from high-speed imaging showed that the average bubble departing from the CNT coating in the nucleate boiling regime (excluding the much larger bubbles observed near CHF) was about 75% smaller (0.26 mm versus 1.01 mm)and had a departure frequency that was about 70% higher (50.46 Hz versus 30.10 Hz). The reduction in departure diameter is explained as a change in the configuration of the contact line, although further study is required. The increase in frequency is a consequence of the smaller bubbles, which require less time to grow. It is suggested that nucleation site density for the CNT coating must drastically increase to compensate for the smaller departure diameters if the rate of vapor creation is similar to or greater than that of a bare silicon surface.

Abstract: Background: At present, device closure of interatrial communication has become a well established technique in order to adequately treat severe left-to-right shunt associated with ASDs. During the traditional procedure, fluoroscopy with the waist of a compliant balloon is used to determine the appropriate size of the closure device and defect sizing. Choice of adequate closure device using transthoracic echocardiography (TTE) has been hitherto unreported. Methods & Materials: Between December 2002 and October 2004, 40 patients (15 males, 25 females, mean age; 11.7 ¡Ó 7.8 years ) with secundum ASDs underwent transcatheter closure at our institution. In group 1, 30 patients had the procedure by balloon sizing and TTE sizing. In 10 patients (group 2), TTE sizing was used as the sole too l for selecting device size and the device size was chosen to be based on the Amplatzer septal occluder ( ASO ) size and TTE size ratio in group 1. The procedure was performed under continuous transoesophageal echocardiographic monitor with general anesthesia. Results: The correlation was found between TTE and stretched balloon sizing diameter SBD ( y= 1.2645x-1.4465; R&#x00B2;=0.9861 ), and between TTE size and ASO size ( y = 1.3412x-1.2864; R&#x00B2;=0.9929 ) in group 1. In group 2, statistical correlation between TTE and ASO ( y=1.3419x-0.1172; R&#x00B2;=0.9934 ) was also found. Good linear regression between TTE size and ASO chosen size was noted in group 1 and group 2 (R&#x00B2;=0.99).In group 2, successful device implantation was accomplished in all patients whose device size was chosen to be based on the ASO and TTE ratio in group 1. Conclusions: TTE sizing is a safe and ideal method to measure interatrial defect and choose the occluding device respectively. With our experience, the sizing based on the TTE is generally easier than measurement from the balloon sizing.

The Interstate Highway System plays a vital role in our economic development by providing a continuous corridor for transporting goods and services. Currently, there is a need for repair and expansion of the existing highways, which include all bridges along its path. Because of the high demand for the highway system, repair and expansion must occur rapidly and efficiently. In recent years, precast bridge deck systems have become an efficient way to reduce construction time during repair. This thesis presents the experimental research of the behavior of the U-Bar joint detail used in precast bridge deck systems. This detail consists of staggered reinforcement extending beyond the precast deck portion into the joint. Six specimens utilizing the U-Bar detail were constructed and tested. Three specimens were tested in flexure to simulate the forces applied in a longitudinal deck joint, while three specimens were tested in pure tension to simulate the forces experienced in a transverse deck joint located over an interior pier. A tight 180° bend at 3db was desired in order to minimize the thickness of the deck. To achieve this tight bend, deformed wire reinforcement was chosen for the U-Bar detail due to the favorable material properties of deformed wire reinforcement. The purpose of the testing was to determine if the joint details could generate a precast deck system that could emulate the monolithic cast-in-place deck systems already in use. For monolithic behavior in a precast deck system, the joints must be able transfer shear, tension and moments. In this research, the joint overlap length was the most dominant variable, and should not be less than 152.4 mm (6”). The precast bridge deck joint should consist of high strength concrete with f’c of at least 68.9 MPa (10 ksi). The longitudinal reinforcement spacing should be no greater than 152.4 mm (6”).

As part of a state-funded Gopher Tortoise (Gopherus polyphemus Daudin) translocation project, I monitored actively grazed improved pastures to determine if they could serve as suitable recipient sites for the threatened Gopher Tortoise displaced by human development. For cattle ranches to be considered suitable recipient sites females must be able to acquire sufficient energy to produce a clutch of viable eggs, and sufficiently high quality vegetation must be available to support juvenile recruitment into the population. Vegetation surveys were conducted to determine the composition and percent cover of plant species, especially those containing high amounts of nutrients, specifically nitrogen. Resident and relocated females were radiographed during the 2010 and 2011 nesting seasons for the presence of shelled eggs. I was able to determine clutch size and egg diameter for both relocated and resident gravid females. Mean clutch sizes were not significantly different between years. Resident females had larger mean clutch sizes than relocated females in both years, significantly so in 2011, suggesting a period of stress and adjustment for relocated females. Egg diameters were significantly larger by 2.5 to 4.5 mm in 2010 for relocated and resident females, respectively, compared to 2011. Three females were recaptured in both years and exhibited the same trend of similar clutch sizes between years but significantly smaller eggs in 2011. A total of 68 unique taxa from 31 families were found, grasses (Poaceae) were the most dominant and covered a mean of 57% of the total sampled area. Four forb species occurred at much greater percent covers than all others. However, only two species (Richardia and Desmodium) were found to have adequate nutritional content and occur at percent covers greater than five percent, indicating that forage availability may be high, but forage quality may be inadequate to support growing juveniles. Burrow surveys indicate that at least some hatchlings are able to successfully leave the nest by the presence of hatchling size burrows scattered throughout the fields, but the ratio of juveniles to eggs laid is especially low. Survivorship of eggs, hatchlings and juveniles may be too low to support a sustainable Gopher Tortoise population in improved pasture possibly because of lack of adequate forage, burrow compaction by cows, lack of available natural shelter material for protection from desiccation, and the reduced ability of movement in thick pasture grasses, especially by hatchling and yearling tortoises.

We discuss two ways of measuring angular diameter distances in the Universe: (i) Baryon Acoustic Oscillation (BAO) , and (ii) strong gravitational lensing. For (i), we study the effects of survey geometry and selection functions on the 2-point correlation function of Lyman- alpha emitters in 1.9 < z < 3.5 for Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We develop a method to extract the BAO scale (hence a volume-averaged angular diameter distance D_V, which is a combination of the angular diameter distance and the Hubble expansion rate, i.e., [cz〖(1+z)〗^2 〖D_A〗^2 H^(-1) ]^(1/3)) from a spherically averaged 1-d correlation function. We quantify the statistical errors on such measurements. By using log-normal realizations of the HETDEX dataset, we show that we can determine DV from HETDEX at 2% accuracy using the 2-point correlation function. This study is complementary to the on-going effort to characterize the power spectrum using HETDEX. For (ii), a previous study (Para ficz and Hjorth 2009) looked at the case of a spherical lens following a singular isothermal distribution of matter and an isotropic velocity distribution, and found that combining measurements of the Einstein ring radius with the time delay of a strong lens system directly leads to a measurement of the angular diameter distance, D_A. Since this is a very new method, it requires more careful investigations of various real-world eff ects such as a realistic matter density pro file, an anisotropic velocity distribution, and external convergence. In more realistic lens confi gurations we find that the velocity dispersion is the dominant source of the uncertainty ; in order for this method to achieve competitive precision on measurements of DA, we need to constrain the velocity dispersion, down to the percent level. On the other hand, external convergence and velocity dispersion anisotropy have negligible e ect on our result. However, we also claim that the dominant source of the uncertainty depends largely on the image con figuration of the system, which leads us to the conclusion that studying the angular dependence of the lens mass distribution is a necessary component. / text

The semicircular canals detect head rotations and trigger compensatory movements that stabilize gaze and help maintain visual fixation. Mammals with large eyes and high visual acuity presumably require more precise gaze stabilization mechanisms because they experience degradation of spatial resolution at a lower threshold of uncompensated motion. Because semicircular canal radius of curvature is a primary determinant of canal sensitivity, species with large canal radii are expected to be capable of more precise gaze stabilization than species with small canal radii. Here the relationship between semicircular canal radius of curvature, eye size, and visual acuity is examined in a large sample of therian mammals. These results demonstrate that eye size and visual acuity both explain a significant proportion of the variance in mean canal radius of curvature after statistically controlling for the effects of body mass and phylogeny. These findings suggest that interspecific variation in semicircular canal radius of curvature is partly the result of selection for improved gaze stabilization in species with large eyes and acute vision. / text

The superior growth of Grand fir (Abies grandis) compared to Douglas-fir (Pseudostuga menziesii) on suitable coastal sites has previously been recognized on the basis of qualitative observations with little empirical evidence. For example, D.E. McMullan (1977, pers. comm.) reported 18% higher volume for a grand fir tree of the same height and age as a 108-year old Douglas-fir plus tree (No. 622) This study was undertaken by Bernardy (1988) to examine possible differences in the growth of grand fir and Douglas-fir growing in a mixed 40-year-old plantation of unknown origin. Trends in height, diameter and annual volume increment between the two species over time were examined. Expected growth performance (i.e. volume and form) of each species was inferred from trends identified at time of sampling.