The purpose of this dissertation is to develop a methodology for designing active control laws in a computational aeroelasticity environment. The methodology involves employing a systems identification technique to develop an explicit state-space model for control law design from the output of a computational aeroelasticity code. The particular computational aeroelasticity code employed in this dissertation solves the transonic small disturbance equation using a time-accurate, finite-difference scheme. Linear structural dynamics equations are integrated simultaneously with the computational fluid dynamics equations to determine the time responses of the structural outputs. These structural outputs are employed as the input to a modern systems identification technique that determines the Markov parameters of an "equivalent linear system". The eigensystem realization algorithm is then employed to develop an explicit state-space model of the equivalent linear system. Although there are many control law design techniques available, the standard Linear Quadratic Guassian technique is employed in this dissertation. The computational aeroelasticity code is modified to accept control laws and perform closed-loop simulations. Flutter control of a rectangular wing model is chosen to demonstrate the methodology. Various cases are used to illustrate the usefulness of the methodology as the nonlinearity of the computational fluid dynamics system is increased through increased angle-of-attack changes. / Ph. D.

Active control of sound radiation from vibrating structures has been an area of much research in the past decade. In Active Structural Acoustic Control (ASAC), the minimization of sound radiation is achieved by modifying the response of the structure through structural inputs rather than by exciting the acoustic medium (Active Noise Control, ANC). The ASAC technique often produces global far-field sound attenuation with relatively few actuators as compared to ANC. The structural control inputs of ASAC systems are usually constructed adaptively in the time domain based on a number of error signals to be minimized. One of the primary concerns in active control of sound is then to provide the controller with appropriate ``error'' information. Early investigations have implemented far-field microphones, thereby providing the controller with actual radiated pressure information. Most structure-borne sound control approaches now tend to eliminate the use of microphones by developing sensors that are integrated in the structure. This study presents a new sensing technique implementing such an approach. A structural acoustic sensor is developed for estimating radiation information from vibrating structures. This technique referred to as Discrete Structural Acoustic Sensing (DSAS) provides time domain estimates of the radiated sound pressure at prescribed locations in the far field over a broad frequency range. The structural acoustic sensor consists of a set of accelerometers mounted on the radiating structure and arrays of digital filters that process the measured acceleration signals in real time. The impulse response of each filter is constructed from the appropriate radiation Green's function for the source area associated with each accelerometer. Validation of the sensing technique is performed on two different systems: a baffled rectangular plate and a baffled finite cylinder. For both systems, the sensor is first analyzed in terms of prediction accuracy by comparing estimated and actual sound pressure radiated in the far field. The analysis is carried out on a numerical model of the plate and cylinder as well as on the real structures through experimental testing. The sensor is then implemented in a broadband radiation control system. The plate and cylinder are excited by broadband disturbance inputs over a frequency range encompassing several of the first flexural resonances of the structure. Single-sided piezo-electric actuators provide the structural control inputs while the sensor estimates are used as error signals. The controller is based on the filtered-x version of the adaptive LMS algorithm. Results from both analytical and experimental investigations are again presented for the two systems. Additional control results based on error microphones allow a comparison of the two sensing approaches in terms of control performance. The major outcome of this study is the ability of the structural acoustic sensor to effectively replace error microphones in broadband radiation control systems. In particular, both analytical and experimental results show the level of sound attenuation achieved when implementing Discrete Structural Acoustic Sensing rivaled that achieved with far-field error microphones. Finally, the approach presents a significant alternative over other existing structural sensing techniques as it requires very little system modeling. / Ph. D.

The mitochondrial membrane bound flavoenzymes monoamine oxidase A and B (MAO-A and MAO-B) catalyze the a-carbon oxidation of a variety of amines including neurotransmitters such as dopamine and serotonin. Although the primary structures of these enzymes have been established from the corresponding gene sequences, relatively little is known regarding the structural features of the active sites which lead to the selectivities observed with various substrates and inhibitors. In spite of many efforts, these enzymes have not been crystallized. In the absence of X-ray structures, the design, synthesis, and evaluation of biological activity remain the only way to assess a view of the active sites, through SAR and QSAR studies. The excellent MAO-A and/or B substrate and inhibitor properties of various 1,4-disubstituted-1,2,3,6-tetrahydropyridine derivatives offer an interesting opportunity to probe the active sites of MAO-A and MAO-B. In an effort to explore the spatial features of the active sites, we have synthesized series of substituted tetrahydropyridines, evaluated their biological activity with purified MAO-A and MAO-B, and carried out a topological analysis of the MAO active sites using molecular modeling. In addition, the results described in this thesis provide evidence that the MAO-A and MAO-B active sites differ in shape, regions of activity, and areas that tolerate polar interactions. The role of MAO in neurodegenerative processes such as Parkinson's Disease has been recognized for some time. The structurally unique parkinsonian inducing substrate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is bioactivated to neurotoxic metabolites. The mechanism of neurotoxicity has been studied extensively and it is known that MAO-B catalyzes the conversion of MPTP to the 2,3-dihydro-1-methyl-4-phenylpyridinium species (MPDP+) which undergoes further oxidation to the neurotoxic metabolite 1-methyl-4-phenyl pyridnium (MPP+). However, the role of MAO-A in mediating a neurotoxic response, has not been fully defined due to the lack of selective MAO-A substrates. In this thesis, we have investigated the neurotoxic potential of several tetrahydropyridines in C57Bl/6 mice and the ability of selective inhibitors to protect against the expression of MAO mediated neurotoxicity. / Ph. D.

An advanced model of active control of fan noise for ultra high bypass turbofan engines has been developed. This model is based on a boundary integral equation method and simulates the propagation, radiation and control of the noise generated by an engine fan surrounded by a duct of finite length and cylindrical shape, placed in a uniform flow. Control sources, modeled by point monopoles placed along the wall of the engine inlet or outlet duct, inject anti-noise into the duct to destructively interfere with the sound field generated by the fan. The duct inner wall can be lined or rigid. Unlike current methods, reflection from the duct openings is taken into account, as well as the presence of the evanescent modes. Forward, as well as backward (i.e., from the rear of the engine), external radiation is computed. The development of analytical expressions for the sound field resulting from both the fan loading noise and the control sources is presented. Two fan models are described. The first model uses spinning line sources with radially distributed strength to model the loading force that the fan blades exert on the medium. The second model uses radial arrays of spinning point dipoles to simulate the generation of fan modes of specific modal amplitudes. It is shown that these fan models can provide a reasonable approximation of actual engine fan noise in the instance when the modal amplitude of the propagating modes or the loading force distribution on the fan blades, is known. Sample cases of active noise control are performed to demonstrate the feasibility of the model. The results from these tests indicate that this model 1) is conducive to more realistic studies of active control of fan noise on ultra high bypass turbofan engines because it accounts for the presence of evanescent modes and for interference between inlet and outlet radiation, which were shown to have some impact on the performance of the active control system; 2) is very useful because it allows monitoring of any region of the acoustic field; 3) is computationally fast, and therefore suitable to conduct parametric studies. Finally, the potential that active noise control techniques have for reducing fan noise on an ultra high bypass turbofan engine is investigated. Feedforward control algorithms are simulated. Pure active control techniques, as well as hybrid (active/passive) control techniques, are studied. It is demonstrated that active noise control has the potential to reduce substantially, and over a relatively large far field sector, the fan noise radiated by an ultra high bypass turbofan engine. It is also shown that a hybrid control system can achieve significantly better levels of noise reduction than a pure passive or pure active control system, and that its optimum solution is more robust than the one achieved with a pure active control system. The model has shown to realistically predict engine acoustic behavior and is thus likely to be a very useful tool for designing active noise control systems for ultra high bypass turbofan engines. / Ph. D.

DAVAs are distributed active and passive devices that can be numerically modelled to provide optimum control of low frequency (< 1000 Hz) mean square velocity and sound power radiation. A numerical model of a multi-DAVA system was developed using the Rayleigh-Ritz method coupled to a hierarchical finite element set (p-method). The numerical model was validated and used to optimize DAVA configurations using lightweight treatments (< 10 % the weight of the base plate weight). The optimizations were performed using genetic algorithms implemented in parallel. They were used to minimize, either passively or actively, the mean square velocity and sound power radiation of different plates having arbitrary boundary conditions (free, simply supported or clamped). Some optimization were also used to determine the optimum number of DAVAs needed, as well as to compare DAVA attenuations with attenuations obtained from optimum Active Constraining Layer Damping (ACLD) treatments. Preliminary results on the passive minimization of the mean square velocity of a simply supported plate with three devices showed that DAVA treatments produce better attenuations than ACLD treatments in the frequency range of interest [2-1000 Hz], and these increased attenuations were due in part to the better capabilities of DAVA treatments to tackle the plate first bending modes. Apart from the free plate, which showed anyway a very low baseline sound transmission, excellent attenuations were obtained both passively and actively for minimizing the mean square velocity and sound power radiation of the simply supported and clamped plates. Following, numerical studies of a DAVA treatment around the optimum solution showed that changing the DAVA top plate stiffness resulted in decreased attenuation, while increasing the DAVA foam layer loss factor increased the attenuation, and decreasing the foam loss factor resulted in decreased attenuation. Finally, by varying the area of the single optimum DAVA that passively minimizes the sound power of the plate, it has been shown that both smaller/lighter and larger/heavier DAVA treatments lead to decreased passive attenuation upon the optimum single DAVA passive solution. Finally, experimental results have further validated the DAVA numerical model, and DAVA treatments have shown excellent passive and active experimental attenuations over various flexible plate structures. / Ph. D.

The single-degree-of-freedom (SDOF) system is the most widely used model for vibration isolation systems. The SDOF system is a simple but worthy model because it quantifies many results of an isolation system. For instance, a SDOF model predicts that the high frequency transmissibility increases when the isolator has passive damping although this does not occur for an isolator implementing active damping. A severe limitation of this system is that it cannot be used when the base and/or equipment are flexible. System flexibility has been considered in previous literature but the flexibility has always been approximated which leads to truncation errors. The analysis used in this work is more sophisticated in that it can model the system flexibility without the use of any approximations. Therefore, the true effects of system flexibility can be analyzed analytically. Current literature has not fully explored the choice of mount frequency or actuator placement for flexible systems either. It is commonly suggested that isolators should be designed with a low-frequency mount. That is, the isolator frequency should be much lower than any of the system frequencies. It is shown that these isolators tend to perform best in an overall sense; however, mount frequencies designed between system modes tend to have a coupling effect. That is, the lower frequencies have such a strong interaction between each other that when isolator damping is present, multiple system modes are attenuated. Also, when the base and equipment are flexible, isolator placement becomes a critical issue. For low-frequency mount designs, the first natural frequency can shift as much as 15.6% for various isolator placements. For a mid-frequency mount design, the shift of the first three modes can be as high as 34.9%, 26.6% and 11.3%, respectively, for varying isolator placements. NOTE: (03/2011) An updated copy of this ETD was added after there were patron reports of problems with the file. / Ph. D.

This dissertation develops a modeling and simulation methodology for design, verification, and testing (DVT) power supply system using a virtual prototype. The virtual prototype is implemented before the hardware prototyping to detect most of the design errors and circuit deficiencies that occur in the later stage of a standard hardware design verification and testing procedure. The design iterations and product cost are reduced significantly by using this approach. The proposed modeling and simulation methodology consists of four major parts: system partitioning, multi-level modeling of device/function block, hierarchical test sequence, and multi-level simulation. By applying the proposed methodology, the designer can use the virtual prototype effectively by keeping a short simulation CPU time as well as catching most of the design problems. The proposed virtual prototype DVT procedure is demonstrated by simulating a 5 V power supply system with a main power supply, a bias power supply, and other protection, monitoring circuitry. The total CPU time is about 8 hours for 780 tests that include the basic function test, steady stage analysis, small-signal stability analysis, large-signal transient analysis, subsystem interaction test, and system interaction test. By comparing the simulation results with the measurements, it shows that the virtual prototype can represent the important behavior of the power supply system accurately. Since the proposed virtual prototype DVT procedure verifies the circuit design with different types of the tests over different line and load conditions, many circuit problems that are not obvious in the original circuit design can be detected by the simulation. The developed virtual prototype DVT procedure is not only capable of detecting most of the design errors, but also plays an important role in design modifications. This dissertation also demonstrates how to analyze the anomalies of the forward converter with active-clamp reset circuit extensively and facilitate the design and improve the circuit performances by utilizing the virtual prototype. With the help of the virtual prototype, it is the first time that the designer is able to analyze the dynamic behavior of the active-clamp forward converter during large-signal transient and optimize the design correspondingly. / Ph. D.

It is now well established that a substantial fraction of all galaxy assembly occurs in intense bursts of star formation and black hole accretion, but the role of these two modes and how much they affect one another remains unclear. We thus investigate this in three complementary studies. In the first, we assemble a sample of 513 quasars identified by the Sloan Digital Sky Survey with detections by Herschel. These objects span a redshift range of 0 < z < 4, and their SEDs give a mean SFR of ~1000M☉/year. When comparing these SFRs to the intrinsic properties of the quasars, we find no clear connections between the quasars and the ongoing star formation events in their hosts. We then look for evidence of AGN feedback in broad absorption line (BAL) quasars, as such features are indicative of outflowing material. We find that high-ionization BAL quasars have indistinguishable properties to those of classical quasars. In our second study, which describes an iron low-ionization BAL quasar, SDSS J121441.42-000137.8, our results are again consistent with no feedback. Thus, it seems unlikely that feedback plays a dominant role in quenching star formation at the extreme SFRs seen in our BAL objects. We lastly study the host of an optically-bright quasar, SDSS J160705.16+355358.6, with evidence of an ongoing merger. We create the Point Spread Function (PSF) using a star that is in the same part of the field as our object, a method which is relatively unexplored. By subtracting the PSF, we are able to extract some of the host properties. We compare two PSF creation methods and find the empirical approach to be superior. Fits to the SEDs of the two galaxies are consistent with both falling on or above the main sequence of star formation. It is additionally plausible that these two galaxies could coalesce into a single massive quiescent galaxy by z ~ 2, and thus serve as progenitors to this class of galaxy that has proven challenging to our understanding of galaxy assembly. / Doctor of Philosophy / Quasars are among some of the brightest objects in the Universe and are powered by supermassive black holes that are rapidly accreting new material. The light from these distant objects can be detected across the electromagnetic spectrum, with each wavelength regime offering new insight into their properties. Further, if we look at their spectra, the features appear redshifted, i.e. they are at longer wavelengths compared to the expected values on Earth. More distant objects have higher redshifts. This, coupled with the constant speed of light, tells us that light from a quasar that has reached us on Earth must have been emitted many years ago; in other words, quasars offer glimpses into the past and can be used study how our Universe has assembled over time. Star formation and quasar activity in galaxies have been shown to coexist across all redshifts. This suggests a deep connection between a galaxy's stellar and black hole mass assemblies. Both peak at z ~ 2, implying that a substantial amount of all galaxy assembly took place in high-redshift, dusty bursts of star formation and quasar activity. This dust absorbs light originally emitted at optical/UV wavelengths and reradiates it in the infrared, making infrared wavelengths the perfect regime in which to investigate the connection between the two processes. In this dissertation, I have focused specifically on quasars with detections at both optical and far-infrared (FIR) wavelengths to determine what effect, if any, quasars have on the galaxies in which they reside. The optical emission of these systems describes the properties of the quasars, while the FIR estimates star formation rates (SFRs) in their hosts. Many astronomers invoke something called feedback, in which the quasar regulates the host star formation, to align theory with observations. We search for evidence of this process in the very bright quasars located within extremely star-forming systems. We, however, find no such evidence. This could imply that, at the high luminosities of our systems, feedback is not the dominant effect in regulating star formation, but perhaps some host self-regulation is instead. It could also imply that the feedback timescale is much shorter than that of either quasar or extreme star formation activity, making direct observations of feedback difficult.

Traditional vehicle suspension system is equipped with isolated shock absorbers that can only dissipate energy by themselves. Hydraulic interconnected suspension uses hydraulic circuits to connect each shock absorber, so that the energized hydraulic fluid can be utilized to counter unwanted body motion to improve the overall dynamic performance. The hydraulic interconnected suspension is a proven concept that has shown good potential in controlling body rolling and decoupling the warp mode from other dynamic modes. Hydraulic interconnected suspension is still passive and lack of adaptivity, while some active or semi-active suspension technologies allow the shock absorbers to counter the road disturbances using external power input. Active suspensions such as electro-magnetic shock absorbers use the variable viscosity of magnetofluid to alter the damping characteristics of the suspension to adapt to quickly changing road conditions. The energy demand from an active suspension can reach the level of kilowatts in certain cases, which results in lowered fuel efficiency of the vehicle. To find a balanced solution to dynamic performance and energy efficiency, this paper introduces a new form of energy-harvesting suspension that is integrated in a hydraulically interconnected suspension (HIS) system. The combined energy-harvesting and hydraulic interconnection features provide improved energy efficiency and vehicle dynamics performance. A single cylinder model is built in AMESim for preliminary study and validated in a bench test. The bench test results proved the authenticity of the theoretical model, and the model is then used to predict the system performance and guide the hardware construction. Based on the proven single cylinder model, and a full car model are developed to validate the effectiveness of the overall system design. Different dynamic input scenarios are used for model simulation, which includes single-wheel sinusoidal input, braking test and double lane change test. In the double lane change test, the EHHIS sees averagely 70% improved in roll angle relative to a conventional suspension, and averagely 22% improvement relative to simple hydraulically interconnected suspension. The power generated is found to reach maximum at 4 Ω external resistance and the highest average power generated is more than 70 watts at 2 hz 20 mm sinusoidal input. A road test of a half vehicle EHHIS system is done. From the road test results, the EHHIS meets the expectations of reducing roll angles. The riding comfort is evaluated with the RMS value of the vertical acceleration and is found to have minimum compromise from the greater damping coefficient. / Master of Science / Better road handling dynamics and riding comfort has always been after by the automotive industry. The vehicle body may experience all kinds of movement such as roll, pitch and bounce, every type of these motion can cause safety risks and passenger fatigue. Traditional vehicle suspension system is equipped with isolated oil shock absorbers that can only dissipate energy by pushing the oil through damping valves. A concept called hydraulic interconnected suspension can use hydraulic circuits to connect each shock absorber, so that the energized hydraulic fluid can be utilized to counter unwanted body motion to improve the overall riding experience. The hydraulic interconnected suspension (HIS) is a proven concept that has shown good potential in stabilizing the vehicle body in rough road conditions. Hydraulic interconnected suspension is still passive and lack of adaptivity, while active suspensions such as electro-magnetic shock absorbers can use external power supply to force the to adapt to quickly changing road conditions. The energy demand from an active suspension can reach the level of kilowatts in certain cases, which results in lowered fuel efficiency of the vehicle. Additionally, actively supplying power to the system always have the risk of functional failure due to power loss. To find a balanced solution to dynamic performance and energy efficiency, this paper introduces a new form of energy-harvesting suspension that is integrated in a hydraulically interconnected suspension (EHHIS) system. The combined energy-harvesting and HIS system provide improved energy efficiency as well as vehicle dynamics performance. Each system is composed of four connected hydraulic cylinders on each wheel and other auxiliaries. To investigate the effectiveness of the entire system, a single cylinder model is first built in AMESim for preliminary study and validated in the experiments. The bench test results proved the authenticity of the theoretical model, and the model is then used to predict the system performance and guide the hardware construction. Based on the proven single cylinder model, and a full car model are developed to validate the effectiveness of the overall system design. Different road condition scenarios are used for model simulation, which includes single-wheel sinusoidal input, braking test and double lane change test. In the double lane change test, the EHHIS system sees averagely 70% improved in roll angle relative to a conventional suspension, and averagely 22% improvement relative to simple hydraulically interconnected suspension. In the breaking test, the EHHIS-equipped vehicle experiences smoother pitching behavior and less oscillations. The power generated is found to reach maximum at 4 Ω external resistance and the highest average power generated is more than 70 watts at 2 hz 20 mm sinusoidal input.

The feasibility of applying active control theory to control both the transient and steady state response of a two cable-stayed bridge has been investigated. The bridge has been modeled as a two degree freedom system in bending and torsion, excited by both buffeting and self-excited loads. The existing suspension cables have been used as active tendons by which the control forces are applied to the bridge deck at the points of the anchorage. The control force from each suspension cable is actuated through a hydraulic-servomechanism which is regulated by the sensed motion of the bridge deck at the anchorage of the cable. Stability and steady state response analyses have been presented for both controlled and uncontrolled motion. The power requirement for the control devices has been derived. Finally, numerical examples have been worked out to demonstrate the feasibility of the derived theory for two cable-stayed bridges. / Ph. D.