This research is to study the fundamental theory of Synthetic Aperture Sonar (SAS) through numerical simulation and experimental analysis. The basic principle of SAS is to enhance the capability of spatial resolution by moving the transducer element to increase aperture so that it achieves a better resolution. The factors affecting the capability of resolution include the actual size of the transducers, frequency and its bandwidth, pulse length, and moving speeds. The effects of various factors on the resolution were examined through numerical simulation. The results have shown that the smaller the true size of the transducer, the better the resolution. Moreover, when the bandwidth is increased, the resolution also increases. The SAS is sensitive to the speed of movement due to the fact that data acquisition may be limited, therefore the speed can not be too high, e.g., less than 1.5 m/s. The experiment was carried out in a water tank of size 4 m x 3.5 m x 2 m. The transducers of AST MK VI 192 kHz were employed to transmit and receive signals. Copper spheres of various sizes (3 cm, 6 cm, 8 cm diameter) were used as targets. The data were obtained and analyzed, and the results have shown that the resolution may be achieved by SAS analysis, establishing the fundamental principle and offering opportunity for future study.

The pyrrole imidazole alkaloids (PIA) is an ever-growing family of structurally related natural products isolated from several species of sponges which now features more than one hundred memebrs. Their complex molecular architectures, and in some cases, significant biological activities, have made these alkaloids the synthetic targets of a number of research groups across the world. In our approach, following early biosynthetic proposal by Kinnel and Scheuer and Al-Mourabit and Potier, it was envisioned that several of these alkaloids, namely palau’amine, axinellamine, konbu’acidin, styloguanidine and massadine, could be derived from a common chlorocyclopentane precursor through different modes of intramolecular cyclization. Building on the work done previously in our research group by Dr. Anja Dilley, Dr. Paul Dransfield, and Dr. Shaohui Wang, my investigations led to the synthesis of the angular aza-triquinane core of axinellamine and the peculiar transazabicyclo[ 3.3.0]octane core of palau’amine. In my further studies mono- and bis-pyrrole advanced intermediates were synthesized that contain the complete carbon framework of the target natural products. However, attempts to induce the pivotal, potentially biomimetic cyclizations expected to deliver the cores of the target alkaloids proved to be rather challenging, resulting in inconsistent and irreproducible results and leading to the exploration of an alternative, “abiotic” approach. My efforts in this direction resulted in the synthesis of a pentacyclic enamine precursor to styloguanidine and a pentacyclic carbinolamine suitable for the synthesis of palau’amine. Final attempts to complete the target natural products were however unsuccessful.

An experimental investigation was undertaken to determine the ability of Synthetic Jet Actuators to control the aerodynamic properties of a wing. The Synthetic Jet Actuator (SJA) was placed at two separate positions on a wing comprised of a NACA0015 airfoil. The first of the jet positions is located at 12% of the chord, hereby referred to as the leading edge Synthetic Jet Actuator. The second exit position is located at 99% chord of an airfoil and hereby is referred to as the trailing edge Synthetic Jet Actuator. The two locations produced different benefits as the angle of attack of the wing was increased. The leading edge Synthetic Jet Actuator delayed the onset of stall of an airfoil, suppressing stall up to 25 degrees angle of attack. The control of the aerodynamic characteristics was achieved by influencing the amount of the separated flowfield region. The effects of the dynamic stall vortex were investigated with wind tunnel testing during the pitching motion of an airfoil to determine how the flow reacts dynamically. The trailing edge synthetic jet actuator was investigated as a form of low angle “hingeless” control. The study investigated the effect of the jet momentum coefficient on the ability of the synthetic jet to modify the lifting and pitching moment produced from the wind tunnel model. The data indicates that, with the present implementation, the SJA-jet flap generates moderate lift and moment coefficient increments that should be suitable for hinge- less control. It was also shown that, for the current experimental setup and a given jet momentum coefficient, continuous blowing is more effective than oscillatory blowing/sucking. The data shows that combining the SJA with a Gurney flap does not result in performance enhancement.

Thesis (M.S.)--Boise State University, 2009. / Includes abstract. Includes bibliographical references (p. 46-49).

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xv, 155 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 120-123).

Thesis (Ph. D.)--Lehigh University, 2004. / Includes bibliographical reference and vita.

Thesis (M. Sc.)--York University, 1998. Graduate Programme in Earth and Space Science. / Typescript. Includes bibliographical references (leaves 111-114). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ42575.

Thesis (M.S.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 1998. / Includes bibliographical references (p. 89-90).

Motion coding in the brain undoubtedly reflects the statistics of retinal image motion occurring in the natural environment. Measuring the statistics of motion in natural scenes is an important tool for building our understanding of how the brain works. Unfortunately, there are statistics that are either impossible or prohibitively difficult to measure. For this reason, it is useful to measure scene statistics in artificial movies derived from simulated environments. This is a novel and important methodological approach that allows us to ask questions about optimal coding that are impossible otherwise. This dissertation describes a course of research that develops this research methodology, the simulated scene statistical approach. This dissertation applied the artificial scene statistical approach to understanding the visual statistics of motion during navigation through forest environments. An environmental model of forest scenes was developed based on previously measured range and surface texture statistics. Spatiotemporal power spectra were measured in both simulated and natural scenes for the task of first person motion through a forest environment. These image statistics measurements helped validate the environmental model. Next, the environmental model was used to simulate across-domain statistics to study the ideal aperture size of motion sensors. It was found that across a variety of different scene conditions, the optimal aperture size of motion sensors increases with the speed to which the sensor is tuned. This is an important constraint for understanding both how the brain encodes motion as well as for designing computer motion detectors. This theoretical research inspired a psychophysical experiment estimating the receptive-field size of human foveal motion discrimination. It was found that for narrow-band stimuli the ideal aperture size increases with spatial frequency, but is unchanging with respect to velocity or temporal frequency. This dissertation shows an approach to the study of vision that has applications in psychophysics, neuroscience and computer vision. The emphasis on accurate and validated environmental models for simulating scene statistics can help improve our understanding of the structure and function of the human visual system and also help us build more accurate and robust computer vision systems. / text

In this study, the sensitivity of the C-band (5.3 GHz) with a 23° incidence angle and the Ku-band (14.85 GHz) with 35°, 55°, and 75° incidence angles to surface soil moisture content from a semiarid region were evaluated. To obtain an improved soil moisture estimation, a practical technique to reduce the influence of soil roughness and vegetation in the SAR data was developed in a study area located in the Walnut Gulch Experimental Watershed, a representative site of shrub- and grass-dominated rangelands of the southwestern part of the United States. To correct for soil roughness effects, the C-band radar backscattering coefficients σ° from a wet season image were subtracted from a° derived from a dry season image. The assumption was that, in semiarid regions, the SAR data from the dry season was dependent only on the soil roughness effects. To correct for vegetation effects, an empirical relation between σ° and leaf area index was used, the latter derived from Landsat Thematic Mapper data. The results showed that when both soil roughness and vegetation effects were corrected for, the sensitivity of a° to soil moisture improved substantially. The sensitivity of σ° to soil moisture was also evaluated in agricultural fields with bare soil and periodic roughness components (planting row and furrow structures). Four types of SAR system configurations were analyzed: C-band with a 23° incidence angle and Ku-band with 35°, 55°, and 75° incidence angles. The test sites were located at the University of Arizona's Maricopa Agricultural Center, south of Phoenix, Arizona. The results showed that the sensitivity of σ° to soil moisture was strongly dependent upon the field conditions. The SAR signals were nearly insensitive to soil moisture for furrowed fields (furrow spacing ∼ 95 cm; amplitude ∼ 22 cm), but for fields with planting row structures (row spacing ∼ 24 cm; amplitude ∼ 2 cm), the SAR data were sensitive to soil moisture, particularly with the C-band at a 23° incidence angle and the Ku-band with a 35° incidence angle, regardless of the row direction.