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In this thesis, the author presents a numerical and experimental study of the application of active constrained layer damping to a clamped-clamped plate. Piezoelectric actuators with modal controllers are used to improve the performance of vibration suppression from the passive constrained layer damping treatment. Surface damping treatments are often effective at suppressing higher frequency vibrations in thin-walled structures such as beams, plates and shells. However, the effective suppression of lower frequency modes usually requires the additional of an active vibration control scheme to augment the passive treatment. Advances in the technologies associated with so-called smart materials are dramatically reducing the cost, weight and complexity of active structural control and make it feasible to consider active schemes in an increasing number of applications. Specifically, a passive constrained layer damping treatment is enhanced with an active scheme employing a piezoceramic (PZT) patch as the actuator. Starting with an established finite element formulation it is shown how model updating and model reduction are required to produce a low-order state-space model which can be used as the basis for active control. The effectiveness of the formulation is then demonstrated in a numerical study. Finally, in the description of the experimental study it is shown how modes in the frequency range from 0 to 600 Hz are effectively suppressed: the two lowest modes (bending and torsional) through active control, the higher modes (around ten in number) by the passive constrained damping layer. The study'S original contribution lies in the experimental demonstration that given a sufficiently accurate model of the plate and passive constrained damping layer, together with a suitable active feedback control algorithm, spillover effects are not significant even when using a single sensor and single actuator. The experimental traces show, in some instances, minor effects due to spillover. However, it can be concluded that the presence of the passive layer introduces sufficient damping into the residual modes to avoid any major problems when using only the minimum amount of active control hardware.

With the advent of new high data rate wireless applications, as well as growth of existing wireless services, demand for additional bandwidth is rapidly increasing. Existing spectrum allocation policies of the Federal Communications Commission (FCC) prohibits unlicensed access to licensed spectrum, constraining them instead to several heavily populated, interference-prone frequency bands, which causes spectrum scarcity. However, it has been shown by several spectrum measurement campaigns that the current licensed spectrum usage across time and frequency is inefficient. Therefore, a concept of unlicensed users temporarily ``borrowing" spectrum from incumbent license holders to improve the spectrum utilization, called ``spectrum pooling", which is based on dynamic spectrum access (DSA), is proposed. Cognitive radio is a communication paradigm that employs software-defined radio technology in order to perform DSA and offers versatile, powerful and portable wireless transceivers. Orthogonal frequency division multiplexing (OFDM) is a promising candidate for cognitive radio transmission. OFDM supports high data rates that are robust to channel impairments. In addition, some subcarriers can be deactivated which constitutes a non-contiguous OFDM (NC-OFDM) transmission. However, one of the biggest problems for OFDM transmission is high out-of-band (OOB) radiation, which is caused by sinc-type function representing the symbols during one time constant. Thus, high sidelobe may occur that will interfere with neighboring transmissions. This thesis presents two novel techniques for NC-OFDM sidelobe suppression. Another concern about cognitive radio systems is that the influence of frequency-selective fading channel. Consequently, this thesis also presents a combined approach employing power loading, bit allocation and sidelobe suppression for OFDM-based cognitive radio systems optimization.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 3, 2007) Includes bibliographical references (p. 65-66).

BALB/c nude mice 6 weeks old were inoculated with glioma C6 cell-line and the efficacy of the different amount of Etanidazole-discs and Taxol-microspheres was investigated. Poly (D,L-lactic-co-glycolic acid) (PLGA) was used as the main encapsulating polymer and polyethylene glycol was added to increase the porosity. The 1% drug loading microspheres of each drug were produced by spray drying and the discs were obtained by compressing the Etanidazole-microspheres. Intra-tumoral injection followed by irradiation resulted in high systemic dosage and thus systemic toxicity. Tumors grown for 6 days, 9 days and 16 days were implanted with 0.5 mg or 1.0 mg or 1.5 mg of the drug. A radiation dosage of 2 Gy each time for a number of times was given for animals implanted with Etanidazole and no irradiation was given for animals implanted with Taxol. Increasing the number of doses clearly decreased the rate of tumor growth. The increase in the amount of drug on smaller sized tumors controlled the tumor better and there was agglomeration of the microspheres resulting in deviation of release profile of the drug as compared to the in vitro studies. It was observed that 1.0 mg of Taxol given to a tumor grown for 6 days was able to suppress the tumor for a total period of approximately two months and no tumor resurrection was observed during the second month. / Singapore-MIT Alliance (SMA)

Priming refers to a change in the ability to identify, produce, or classify a stimulus as a result of a previous encounter with the same or a related stimulus. Recent neuroimaging studies often found behavioral priming to co-occur with a reduction in neural activations in various cortical regions, which is called repetition suppression. It is thought that repetition suppression is closely related to behavioral priming, and may even be the underlying neural mechanism that supports priming. However, current literature still has several unsolved questions about the relationship between repetition suppression and priming. The present dissertation set out to further elucidate their relationship. In Study 1, a mirror-word identification task was used to limit overlap between study and test to a primarily perceptual level with little or no conceptual overlap nor top-down modulation. Repetition suppression was found in visual perceptual and frontal phonological regions involved at both study and test, supporting a "component process" view that repetition suppression and priming can occur at a perceptual level with limited conceptual or top-down processes involved. In Study 2, three perceptual priming tasks and one conceptual priming task were used to directly examine component process view's prediction that perceptual priming would be correlated with posterior repetition suppression and conceptual priming would be correlated with frontal repetition suppression. The results showed that both perceptual and conceptual priming involved repetition suppression in both frontal and posterior perceptual regions, at least when measured with our paradigm and tasks, and both frontal and posterior repetition suppression effects were correlated with behavioral priming in all four perceptual and conceptual priming tasks. This finding suggests that both frontal and posterior perceptual regions are involved in perceptual and conceptual priming, and that they are most likely working in concert with one another during priming, as exemplified by an interactive view of priming. Taken together, our data suggest that priming may be supported by several different underlying mechanisms, such as bottom-up processes (component process view of priming), top-down modulation and frontal-posterior interaction/synchrony.

<p> A response conditioned to a specific stimulus will generalize to similar stimuli. Various reports have indicated that the slope of the gradient of generalization changes over a period of time. The experiments reported here investigated the generalization of an emotional response, originally conditioned to an 80 db. white noise to a 60 db. white noise. In different groups the tests for generalization were begun immediately after conditioning or after a 4 day waiting period. In further groups the animals' time during the delay period was variously taken up with bar pressing sessions; new conditioning trials with a light CS; unsignalled shock presentations, or they merely stayed in their home cages.</p> / Thesis / Master of Arts (MA)

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