This thesis studies Lamb waves for long-range pipeline inspection. The property of Lamb waves propagation and the sensitivity of defect detection will be evaluated in this thesis. There are two groups of waves propagation in plate, first group of waves are called symmetrical Lamb waves, and the second group are called anti-symmetrical Lamb waves. Furthermore, there are three different mode types exist in hollow cylinder, such as the longitudinal, torsional, and flexural modes. By solving the characteristic equation of the Lamb wave problem, the dispersion character of the Lamb waves can be found. The phase and group velocity for different Lamb modes obtained from the dispersion curve are also studied in this thesis. In the experimental setup, the longitudinal wave is incident at certain incident angles and velocities to generate Lamb waves propagated on the stainless steel plate and carbon steel hollow cylinder. When the longitudinal waves are in the constructive interference in the medium, only one Lamb wave will propagate. As a result, compare with the measured data and theoretical predictions of the group velocities, it is observed that angle beam longitudinal waves offer an accurate and workable method for Lamb waves generation. To evaluate the sensitivity and resolution of the Lamb waves testing, additional experiments for detecting defects are carried out in this thesis. It is found that a single and pure Lamb wave is very useful for detection defects. Moreover, selected the non-dispersive Lamb modes for detection can keep the propagating wave shape without changing; also, only minimum energy is decayed as wave propagated.

Abstract Anisotropic wet etching is one of the key technologies for the microstructure fabrication in Micro Electro Mechanical Systems (MEMS). Agitation technique is one of the key parameters to affect significantly the quality of silicon anisotropic wet etching, which includes the etch rate and surface roughness. In general, magnetic stirring is used during silicon anisotropic wet etching operation. The ultrasonic agitation and add surfactant have been to replaced and to proceed a series of experiment for KOH solution and TMAH solution in this study. The results show that the ultrasonic agitation can reduce the surface roughness and achieve the high-quality etching surface, its roughness even is only about Ra 47.5Å. Besides, the etch rate is also increased slightly. But it is easily to cause the damage of the microstructure. The addition of anionic surfactant to the KOH solution without any agitation condition can achieve the same at the etching performance of the ultrasonic agitation. The addition of anionic surfactant and nonionic surfactant to the TMAH solution without any agitation condition can achieve the same at the etching performance of the ultrasonic agitation. TMAH solution adds nonionic surfactant not only improves the surface roughness, but also retards the phenomenon of the undercut. Keyword¡Ganisotropic wet etching, magnetic stirring, ultrasonic, surfactant

Thesis (M.Sc.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 77-78.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: welding; ultrasonic. Includes bibliographical references (p. 100-101).

Thesis--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.108-111, etc.).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 95-101).

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [273]-288).

The thesis project is aimed to automate ultrasonic Time-of-Flight (ToF) technique for saw log classification using signal processing. The ToF technique works in such a way that ultrasonic tone-burst pulses are sent into a saw log, and then the ToF that the pulses take for the propagation is measured and used to calculate the sound speed and further, the Modulus of Elasticity (MoE). Based on the MoE, the quality of the logs is predicted and presorted before sawing. Development of matched filters is the central task for automating the ToF technique.  The whole project was carried out in two different parts: 1) Fundamentals and MATLAB implementation, and 2) Real-time implementation based on digital signal processor.     In the first part, fundamentals on the ToF technique and matched filters have been studied, and then MATLAB simulations of matched filters for automating the technique have been made. After this, test measurements have been conducted. The test results are shown to be consistent with the simulation: matched filtering works well for automating the ToF technique. In the second part of the report, an embedded algorithm has been developed and implemented on a Digital Signal Processor. The algorithm is the first step in the automation of measurements. Eventually, two test measurements have been performed with the DSP. The results were obtained using both oscilloscope to visualize and MATLAB to plot the obtained debug log, and they have shown that the algorithm works, and can automatically measure the ToF, which is in turn used to calculate the sound speed and MoE. The further work on the project that needs to be done, is to applying the developed system to the real situations in sawmills, and improving it according to their requirements.

Sonoporation, being an ultrasound-induced membrane perforation phenomenon, has received considerable interest in view of its therapeutic potential and is rapidly emerging as a promising approach to facilitate drug delivery. This event generally occurs when acoustic cavitation develops in the vicinity of living cells, as the mechanical interactions between ultrasound and microbubble would exert a force that is substantial enough to create pores on the cell membrane. The resulting increase in cell membrane permeability is transient in nature, and short-term survival of sonoporated cells is generally assumed. However, it remains unclear as to whether sonoporation would affect the cell fate in the long run. In particular, the contemporary mechanistic understanding of sonoporation has lacked account of the cellular response at a subcellular level. This inherently raises concerns on the general therapeutic applicability of sonoporation in mediating drug delivery. This thesis first addressed the question of whether cell fate may be affected on time-lapse basis as a result of sonopopration. As observed our analysis of DNA contents and cytoplasmic signaling proteins, some cells were found to commit apoptosis (programmed cell death) after sonoporation while the remaining viable cells may enter into cell-cycle arrest that disrupted normal cell proliferation. These findings should carry two major implications from a drug-delivery standpoint. First, cellular protection strategies should be developed when using sonoporation for drug delivery in cases where cell viability should be maintained. Second, for cancer therapy where cell death is required, the cytotoxic impact of sonoporation may represent a complementary factor that can be leveraged upon in facilitating the delivery of anti-cancer drugs. Further investigations were conducted to gain insight into the intermediate transduction mechanism in which sonoporation has entailed to bring about various cytoplasmic signaling changes that promote cell-cycle arrest and apoptosis. Our results reveal a transient enhancement of intracellular Ca2+ concentration in sonoporated cells. This bioelectrical disruption event is often recognized as a central messenger to instigate a series of cell-fate regulation pathways. In addition, observations on cell membrane repair revealed an exocytotic patching mechanism, accumulation of internal vesicles and increased activities in the Golgi apparatus. Given that the elevated Ca2+ level were observed in sonoporate cells, a follow-up study was conducted to investigate the potential role of endoplasmic reticulum (ER) and mitochondria in sonoporation-induced bioeffects. These two organelles were found to be activated in succession and in ways connected to the initiation of pro-apoptotic signaling. In particular, stress response was found to be active in the ER, and this in turn induced the dysfunction of mitochondria. Also, our time-lapse observations on the mitochondrial membrane potential have confirmed that this organelle is involved in facilitating sonoporation-induced apoptosis. In summary, investigations of time-lapse dynamics of cellular and subcellular responses mediated by sonoporation are so important in elucidating the fate of the sonoporated cells and understanding the mechanism in which sonoporation has entailed to instigate the sequential signaling pathways that bring cells into such conditions, thereby refining the therapeutic role of this biophysical phenomenon and making it more efficient in facilitating drug delivery. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This work explored the design considerations on the real-time medical ultrasound adaptive beamformer implementations using different computing platforms: CPU, GPU and FPGA. Adaptive beamforming has been well considered as an advanced solution for improving the image quality of medical ultrasound imaging machines. Although it provides promising improvements in lateral resolution, image contrast and imaging penetration depth, the use of adaptive beamforming is substantially more computationally demanding than conventional delay-and-sum beamformers. In order not to compromise the real-time performance of medical ultrasound systems, an accelerated solution is desirable. In this work, CPU implementation was used as a baseline implementation, based on which the intrinsic characteristics of the algorithm were analyzed. After the analysis of a particular adaptive beamforming algorithm, minimum-variance adaptive beamforming, two design parameters M and L were found to affect the implementation performance in two aspects: computational demand and image quality. The trends of the two aspects were contradictory with respect to the increment of M and L values. In our experiments, when M and L increased, the computational demand increased in a cubic curve; meanwhile, the image quality did not have much improvement when the increased values of M and L entered certain ranges. Since we targeted at a real-time solution without sacrificing the good image quality that adaptive beamforming proposed, a tradeoff was made on the selection of M and L values to balance the two contradictory requirements. Built upon the theoretical algorithmic analysis of the real-time adaptive beamformer realization, the implementations were developed with FPGA and GPU. While a dedicated hardware solution might be able to address the computational demand of the particular design, the need for an efficient algorithm exploration framework demanded a reprogrammable platform solution that was high-performance and easily reconfigurable. Besides, although a simple processor could provide convenient algorithm exploration via software development environment, real-time performance was usually not achievable. As a result, a reprogrammable medical ultrasound research platform for investigating advanced imaging algorithms was constructed in our project. The use of FPGA and GPU for implementing the real-time adaptive beamformer on our platform was explored. In our test cases, both FPGA- and GPUbased solutions achieved real-time throughput exceeding 80 frames-per-second, and over 38x improvement when compared to our baseline CPU implementation. Moreover, the implementations were also evaluated in terms of portability, data accuracy, programmability, and system integration. Due to its high power consumption, high-performance GPU solution is best suited for bedside applications, while FPGAs are more suitable for portable and hand-held medical ultrasound machines. Besides, while the development time on GPU platform remains much lower than its FPGA counterpart, the FPGA solution is effective in providing the necessary I/O bandwidth to enable an end-to-end real-time reconfigurable medical ultrasound image formation system. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy