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Commercial aviation transportation has experienced an overwhelming growth over the years. However, this expansion has encountered an important barrier: noise. Several studies have shown that residents in these areas experience problems such as stress and sleep disturbance. These problems have translated into demands for a better quality of life from airport residents which in turn have translated into more stringent aircraft noise regulations. As a result, large amounts of resources have been diverted towards the improvement of existing noise attenuation technologies and the development of more effective ones. In terms of turbofan generated noise, the most widely used technology is that of absorbent materials or liners. In recent investigations Alonso et al. have combined Herschel/Quincke (HQ) tubes with liners. This combination has the potential of effectively controlling pure tones and broadband noise in inlet sections of modern turbofan engines. Since a comprehensive approach for engine noise reduction will involve both inlet and aft HQ-Liner systems, additional research efforts were needed to evaluate their performance at reducing aft fan radiation In the present work, a combination of traditional liners and Herschel/Quincke waveguide resonators for aft fan radiation control is proposed. A theoretical model is developed in order to predict noise reduction due to such systems. The newly developed tool was then utilized to design an HQ-liner that was installed and tested in the aft section of the NASA Active Noise Control Fan (ANCF) rig. This experimental data was utilized to prove the potential of these systems and to validate the mathematical model. Analytical predictions correlate well with experiments. The NASA ANCF rig is not representative of a real turbofan engine. In order to assess the behavior of HQ-Liners in a more realistic environment a new system was specifically designed for a generic turbofan engine and its performance analyzed. The sound field inside HQ tubes has been described assuming plane waves only. This assumption limits the model to frequencies below the tube first resonance. In order to overcome this limitation a new model accounting for higher order modes inside the tubes has been developed. / Ph. D.

Leaves and fruit of nine apple (Malus x domestica Borkh.) genotypes were evaluated for insect injury in 1998 and 1999. Foliar and fruit injury from 12 insect species was inconsistently affected by genotype. Spraying trees with oil affected neither fruit insect injury nor fruit phytotoxicity. In choice feeding assays, incidence of Japanese beetle (JB) feeding and leaf area consumed was greater for 'Liberty' than for 'York.' Genotypes did not differ in no-choice feeding assays. Choice and no-choice feeding assays between apple and oak indicated that JB could distinguish host plants in an artificial environment. Trichome density appeared different among three genotypes. 'York', the non-preferred genotype, had highest specific leaf weight and concentration of phloridzin, a feeding repellent. 'Liberty' the preferred genotype, had the lowest specific leaf weight, and had the highest concentration of quercitrin, a feeding stimulant. Olfactory stimuli of JB was evaluated with a Y-tube olfactometer. Beetles preferred the side of the Y-tube containing leaf tissue of apple or Virginia creeper over the side with no leaf. Beetles did not choose one plant species over the other. Bias test of beetle orientation in the Y-tube olfactometer indicated that in the morning, but not the afternoon, beetles preferentially moved into the left side of the Y-tube. Humidity did not affect beetle orientation. In darkness JB preferred a leaf disc over a paper disc and beetles tended to remain on the leaf. / Ph. D.

The combination of traditional passive acoustic liners with Herschel-Quincke (HQ) waveguides is proposed in this work as a device for Turbofan Engine Noise Control. The approach consists of installing circumferential arrays of HQ tubes on the lined sector of the inlet of a turbofan engine. A theoretical model is developed to predict the performance of this system assuming that the engine inlet is a circular lined duct with uniform mean flow. The tube-duct interfaces are modeled as finite piston sources that couple the sound field inside the duct with the dynamics of the HQ tubes. The finite piston source radiation is modeled in terms of a new closed form Green's function, which is found as the solution of the non-homogeneous convected acoustic wave equation with soft wall boundary conditions. The Green's function is extended from a point source to a finite piston by using the Divergence Theorem in the appropriate form. The dynamics of the HQ tube are both modeled as plane waves inside a straight tube and experimentally determined. The experimental determination of the HQ-dynamics is undertaken using impedance tubes with a 4-microphone technique. The newly developed theoretical model was used to predict the performance of a combined HQ-Liner system, which was tested on a scale simulated turbofan rig. The model is validated for broadband noise with the experimental data obtained from this test rig. The analytical predictions are shown to correlate well with experimental data. The results of the application of a HQ-Liner on a turbofan engine show a great potential in order to improve the performance of traditional passive acoustic liners. / Ph. D.

Dysregulation of apoptosis during development is a possible mechanism for teratogen-induced birth defects. Neural tube defects (NTDs) are the second most common fetal malformations. Non-specific stimulation of maternal immune system prevents birth defects. This study investigated the role of dysregulated apoptosis in formation of NTDs from two teratogens: valproic acid (VA) and an unknown teratogen found in tap water. Interferon- γ (IFN γ) was used to stimulate maternal immunity to evaluate the role of altered apoptosis in this protective mechanism. Apoptosis was evaluated using flow cytometry, Terminal Transferase dUTP Nick End Labeling (TUNEL) assay and gene expression changes by RT2 Profiler PCR arrays. Additionally, changes in the expression of key signal transduction pathway genes that play a role in development were determined. Increased apoptosis, suggesting involvement in VA teratogenicity, was observed along the neural tube in both normal and abnormal embryos from VA-exposed dams. Increased apoptosis in normal VA-exposed embryos suggests that VA may alter other cellular processes such as cell proliferation and differentiation in addition to apoptosis. Apoptotic percentages in embryos with NTDs from IFNγ+VA dams were similar to controls, which indicated resistance to teratogen-induced apoptosis. In IFNγ+VA-exposed embryos with NTDs, immune stimulation failed to prevent apoptosis. VA initiated both death and survival signaling in the embryos; however, upregulation of the apoptotic genes and down regulation of anti-apoptotic genes of p53 and Bcl2 family tended to shift the balance towards death signaling. This change in gene expression patterns could result in increased apoptosis and NTDs in VA-exposed embryos. Immune stimulation normalized changes in the expression of pro-apoptotic signaling molecules. These results suggest immune stimulation protects embryos from teratogenicity of VA by preventing VA-induced apoptosis. VA altered the hedgehog, Wnt, retinoic acid and fibronectin signaling pathways in embryos with NTDs. These results suggest that VA also disrupted signaling pathways required for various morphogenic events during organogenesis. Immune stimulation normalized the expression of Fn1 and Hspb1 and thus may mediate protection through these signaling pathways. In tap water exposed embryos, no change in apoptotic pattern was observed by flow cytometry, TUNEL assay and RT-PCR. Also, none of the signal transduction pathway genes tested were significantly altered in tap water-exposed embryos. This suggests that apoptosis is not a mechanism for teratogenicity resulting from exposure to the contaminant in tap water. / Ph. D.

The insect respiratory system serves as a model for both robust microfluidic transport and mate- rial design. In the system, the convective flow of gas is driven through local deformations of the tracheal network, a phenomenon that is dependent on the unique structure and material properties of the tracheal tissue. To understand the underlying mechanics of this method of gas transport, we studied the microstructure and material properties of the primary thoracic tracheal tubes of the American cockroach (Periplaneta americana). We performed quasi-static uniaxial tests on the tissue which revealed a nonlinear stress-strain response even under small deformations. A detailed analysis of the tissue's microstructural arrangement using both light and electron mi- croscopy revealed the primary sources of reinforcement for the tissue as well as heterogeneity on the meso-scale that may contribute to the physiological function of the tracheae during respi- ration. Finally, a custom mechanical testing system was developed with which inflation-extension tests on the tracheae were used to gather data on the biaxial elastic response of the tissue over a wide range of physiologically relevant loading conditions. From information gathered about the material microstructure, a robust constitutive model was chosen to quantify the biaxial response of the tracheae. This model will provide a basis from which to simulate the behavior of tracheal net- works in future computational studies. This study gives the first description of the elastic response of the tracheae which is essential for understanding the mechanics of respiration in insects. Thus it brings us closer to the realization of novel bio-inspired microfluidic systems and materials that utilize mechanical principles from the insect respiratory system. / Ph. D.

An experimental program has been undertaken to gain a more fundamental understanding of dense-phase pneumatic transport of cohesionless solids. A 50.8 mm internal diameter circulating unit with both horizontal and vertical sections has been constructed . The pipe material is transparent lexan which allows for visual observation of the flow pattern. The particles used were a mixture of 95% white and 5% black polyethylene granules (particle diameter approximately 3 mm). The black particles were used to aid the visual observation of the flow pattern. The flow patterns ranged from dilute-phase flow to dense-phase plug flow. High-speed photographic techniques have been used to document the flow patterns in both the horizontal and vertical sections. Pressure drop measurements across a 70 cm test section have been coordinated with the film work. At the higher superficial air velocities (approximately 15 m/sec), the particles flow in a dilute suspension within the air stream. The pressure drop across the 70 cm section fluctuates very rapidly. For the horizontal dilute-phase flow, the mean pressure drop is approximately 0.12 kPa with fluctuations ranging from 0 to 0.3 kPa. For the vertical dilute-phase flow, the mean pressure drop is approximately 0.25 kPa with fluctuations ranging from 0 to 0.5 kPa. Upon reducing the superficial air velocity to 6.8 m/sec, the flow pattern in the horizontal section changes to a type of strand flow. The particles are conveyed in a dilute phase above a stationary layer. Large peaks in the pressure drop data (approximately 1 to 2 kPa) correspond to increases in the dilute-phase solids concentration. At the lower superficial air velocities (below 5 m/sec) , the solids flow pattern changes to dense-phase flow. The particles move in the form of plugs that occupy the entire pipe cross-section. For the horizontal flow, the plug length ranged from 0.17 to 0.60 m and the pressure drop across the plugs ranged from 1 to 5.2 kPa. The pressure gradient range can be predicted from the equations of Konrad et al. (1980). The analysis of the vertical dense-phase flow films is not as straightforward as the horizontal films. However, the flow pattern resembles that described by Konrad (1987) and there is qualitative agreement with the concepts outlined by Konrad (1987). / Master of Science

Composite concrete filled steel tube columns are increasingly used for high-rise building structures, owing to their excellent structural performance such as superior load-bearing capacity, high ductility, good energy dissipation and fire behaviour which arises from the combination of the two different materials in the structure. Composite structures exploit the characteristics of steel and concrete; steel with its high tensile strength and ductility and concrete with its high compressive strength and stiffness. In general, concrete filled composite columns with circular hollow sections (CHS) have the advantage over columns with other section shapes due to the circular cross sections providing a uniform confinement to the concrete core.

Abdominal pumping is a widespread behavior in insects. However, there remains ambiguity surrounding the abdominal pumping behavior, both in terms of describing what exactly abdominal pumping is (i.e., if various modes of operation exist) and also what function(s) abdominal pumping serves (and if function is conserved across groups of insects). In some insects respiratory patterns have been correlated with abdominal movements, although the specific mechanical effects of these movements on the animal\'s respiratory system are generally unknown. Conversely, some insects (such as beetles, ants, and crickets) create convection in the respiratory system by compressing their tracheal tubes, yet the underlying physiological mechanisms of tracheal collapse are also unknown. This study aimed to investigate the relationship between abdominal pumping and the compression of tracheal tubes in the darkling beetle, Zophobas morio. I observed the movements of the abdomen and tracheal tubes using synchrotron x-ray imaging and video cameras, while concurrently monitoring CO2 expiration. I identified and characterized two distinct abdominal movements differentiated by the synchrony (the pinch movement) or lack of synchrony (the wave movement) of abdominal tergite movement. Tracheal tube compressions (and corresponding CO2 pulses) occurred concurrently with every pinch movement. This study provides evidence of a mechanistic linkage between abdominal movements and tracheal tube compressions in the ground beetle, Zophobas morio. / Master of Science