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Piezoelectric energy harvester has become a new powering choice for small electronic device. Due to its piezoelectric effect, electric energy can be obtained from ambient vibrations. This thesis is intending to build a frequency-adjustable piezoelectric energy harvester system. The system is structured with two piezoelectric bimorph beams, which are connected to each other by a spring. The feasibility of the frequency-adjustable piezoelectric energy harvester has been proved by investigating effects of the spring, loading mass and impedance on the operation frequencies.

Purpose: In oncological orthopedics, navigation systems are limited to use in specialized centers, because specific, expensive, software is necessary. To resolve this problem, we present a technique using general spine navigation software to resect tumors located in different segments. Materials and Methods: This technique requires a primary surgery during which screws are inserted in the segment where the bone tumor is; next, a CT scan of the entire segment is used as a guide in a second surgery where a resection is performed under navigation control. We applied this technique in four selected cases. To evaluate the procedure, we considered resolution obtained, quality of the margin and its control. Results: In all cases, 1 mm resolution was obtained; navigation allowed perfect control of the osteotomies, reaching the minimum wide margin when desired. No complications were reported and all patients were free of disease at follow-up (average 25.5 months). Conclusions: This technique allows any bone segment to be recognized by the navigation system thanks to the introduction of screws as landmarks. The minimum number of screws required is four, but the higher the number of screws, the greater the accuracy and resolution. In our experience, five landmarks, placed distant from one another, is a good compromise. Possible disadvantages include the necessity to perform two surgeries and the need of a major surgical exposure; nevertheless, in our opinion, the advantages of better margin control justify the application of this technique in centers where an intraoperative CT scanner, synchronized with a navigation system or a dedicated software for bone tumor removal were not available.

The advent of Wide-Area measurement Systems has spurred interest in the use of non-local feedback signals for power swing damping control. Although damping can be improved through generator excitation systems, dc links and other grid connected power electronic converters, the full potential of wide-area measurements can be realized by coordinating the strategies used for multiple controllable devices in a grid. These strategies also need to be robust to partial or complete loss of communication, changes in operating points, topology and equipment outages, improve damping of all the controllable swing modes, and have adequate stability margins to avoid destabilization of untargeted modes. This thesis investigates a control strategy for multi-infeed and multi-terminal (also referred to as multiple embedded dc links in this thesis) dc links using local frequency difference signals as well as the frequency difference signals obtained from other dc links. This strategy combines the advantages of the local frequency difference signal with the additional degrees of freedom provided by the use of non-local frequency difference signals, to achieve targeted and enhanced swing mode damping for the poorly damped modes. Since the strategy uses only a limited set of non-local signals, the signals may be directly communicated to the dc links without having to be centrally collated with other system-wide measurements. The key aspect of the proposed strategy is the use of a symmetric positive definite (spd) gain matrix. This results in enhanced damping for all controllable swing modes. Furthermore, loss of communication between the dc links does not destroy the symmetric positive definiteness and the gain elements can be tuned to selectively enhance damping of poorly damped modes. Eigenvalue sensitivity analysis and case studies on a 3 machine 9 bus and 16 machine 68 bus system with multiple HVDC links are presented to demonstrate the key attributes and the effectiveness of this strategy. / October 2016

Ha Kwong-leung = 不同的生長處理對II-VI/III-V外延層的表面、結構和光學特性的影響 / 夏廣良. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 76-79). / Text in English; abstracts in English and Chinese. / Ha Kwong-leung = Bu tong de sheng chang chu li dui II-VI/III-V wai yan ceng de biao mian, jie gou he guang xue te xing de ying xiang / Xia Guangliang. / Acknowledgments --- p.i / Abstract --- p.ii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Brief introduction --- p.1 / Chapter 1.2 --- Background of the epitaxial growth --- p.4 / Chapter 1.3 --- Our work --- p.6 / Chapter Chapter 2 --- Experimental procedures / Chapter 2.1 --- Substrate preparation --- p.7 / Chapter 2.2 --- Metal-organic sources --- p.9 / Chapter 2.3 --- Growth conditions --- p.10 / Chapter Chapter 3 --- Characterization methods / Chapter 3.1 --- Surface morphology --- p.13 / Chapter 3.2 --- X-ray diffraction --- p.14 / Chapter 3.3 --- Optical properties / Chapter 3.3.1 --- Photoluminescence --- p.17 / Chapter 3.3.2 --- General properties of PL spectrum of ZnSe/GaAs --- p.18 / Chapter 3.4 --- Other techniques --- p.21 / Chapter Chapter 4 --- Influence on the properties of epilayers by the thickness of the low-temperature buffer layer --- p.22 / Chapter 4.1 --- Effects on the surface morphology --- p.23 / Chapter 4.2 --- Effects on the structural properties --- p.31 / Chapter 4.3 --- Effects on the optical properties --- p.35 / Chapter Chapter 5 --- Influence of thickness of epilayers on their properties --- p.39 / Chapter 5.1 --- Effects on the surface morphology --- p.40 / Chapter 5.2 --- Effects on the structural properties --- p.45 / Chapter 5.3 --- Effects on the optical properties --- p.50 / Chapter Chapter 6 --- Influence on the epilayers by passivating with different MO sources and different durations of interruption --- p.53 / Part I: Passivation by different MO sources / Chapter 6.1 --- Effects on the surface morphology --- p.55 / Chapter 6.2 --- Effects on the structural properties --- p.58 / Chapter 6.3 --- Effects on the optical properties --- p.61 / Part II: Different durations of interruption / Chapter 6.4 --- Effects on the surface morphology --- p.63 / Chapter 6.5 --- Effects on the structural properties --- p.66 / Chapter 6.6 --- Effects on the optical properties --- p.70 / Summary --- p.73 / Conclusions --- p.74 / References --- p.76

Connectedness has been identified as a powerful protective factor for adolescents. This study focused on the extent to which secondary students at the American International School of Utah (AISU) report perceptions of connectedness. Specifically, this work focused on school-level factors. It examined the extent to which participation in the school-wide interventions of Crew and Intensives influence perceptions of connectedness among AISU secondary students. Data collected provided insights about perceptions of connectedness within the AISU environment that may be used to inform current practices, identify additional student support needs, and improve future implementations. An Explanatory Sequential research design was used. This method included the use of quantitative measure administered and analyzed first, followed by a qualitative measure used to learn more about the quantitative results. The Hemingway Measure of Adolescent Connectedness Short Form by Michael Karcher served as the quantitative measure for this study. A semistructured interview protocol, created by the researcher, was used as the qualitative instrument. Results indicated that overall, study participants reported high-levels of connectedness on the Hemingway. Analysis of the Hemingway Subscales revealed that the Friends subscale had the highest levels of connectedness, followed by connectedness to Teacher. Connectedness to School was slightly lower than connectedness to Teachers. Connectedness to Peers showed moderate levels of connectedness. To learn more about the results of the quantitative stage of this study, semistructured interviews were conducted and analyzed using traditional deductive coding techniques. Results showed high-levels of connectedness associated with AISU as a school and with participation in Crew. Findings on the questions asking about Intensives showed that students appear to value the unique learning opportunities and ability to choose what they learn, more than they associated Intensives with connectedness.