published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Wong Kwok Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 88-93). / Abstracts in English and Chinese. / LIST OF FIGURES --- p.VI / LIST OF TABLES --- p.IX / ACKNOWLEDGEMENTS --- p.X / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Literature review on self-sensing purely active system --- p.3 / Chapter 1.3 --- Literature review on active constrained layer treatment --- p.5 / Chapter 1.4 --- Introduction to enhanced active constrained layer treatment --- p.8 / Chapter 1.5 --- Objectives of this research --- p.10 / Chapter 1.6 --- Thesis outline --- p.11 / Chapter CHAPTER 2 --- CONTROL LAW IMPLEMENTATION --- p.12 / Chapter 2.1 --- Electrical equivalent model of piezoelectric material --- p.12 / Chapter 2.2 --- Bridge circuit --- p.14 / Chapter 2.2.1 --- Strain rate sensing bridge circuit --- p.14 / Chapter 2.2.2 --- Strain sensing bridge circuit --- p.17 / Chapter 2.3 --- Control laws implementation --- p.19 / Chapter 2.3.1 --- Strain rate feedback control --- p.19 / Chapter 2.3.2 --- Positive position feedback (PPF) control --- p.21 / Chapter 2.3.3 --- Modified strain rate feedback control --- p.25 / Chapter CHAPTER 3 --- EXPERIMENTAL STUDIES --- p.28 / Chapter 3.1 --- Experimental setup --- p.28 / Chapter 3.2 --- Test of actuating ability --- p.30 / Chapter 3.3 --- Test of sensing ability --- p.32 / Chapter 3.4 --- Open loop response --- p.34 / Chapter 3.5 --- Closed loop response --- p.36 / Chapter 3.6 --- Chapter summary --- p.52 / Chapter CHAPTER 4 --- SYSTEM MODELING AND SIMULATION --- p.53 / Chapter 4.1 --- Literature review on finite element method --- p.53 / Chapter 4.1.1 --- Element stiffness matrix through potential energy --- p.57 / Chapter 4.1.2 --- Element mass matrix through kinetic energy --- p.58 / Chapter 4.2 --- System modeling --- p.59 / Chapter 4.2.1 --- Stiffness and mass matrices of beam layer --- p.63 / Chapter 4.2.2 --- Stiffness and mass matrices of piezoelectric layer --- p.64 / Chapter 4.2.3 --- Stiffness and mass matrices of VEM layer --- p.67 / Chapter 4.2.4 --- Stiffness and mass matrices of beam edge elements --- p.71 / Chapter 4.3 --- Simulation --- p.76 / Chapter 4.4 --- Chapter summary --- p.83 / Chapter CHAPTER 5 --- SUMMARY AND FUTURE WORK --- p.84 / Chapter 5.1 --- Summary --- p.84 / Chapter 5.2 --- Future Work --- p.87 / BIBLIOGRAPHY --- p.88

Law Wai Wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 64-66). / Abstracts in English and Chinese. / 摘要 --- p.i / ABSTRACT --- p.ii / ACKNOWLEDGEMENTS --- p.iii / CONTENTS --- p.iv / LIST OF FIGURES --- p.vi / LIST OF TABLES --- p.ix / Chapter 1 --- INTRODUCTION / Chapter 1.1 --- Background --- p.1 / Chapter 1.1.1 --- Piezoelectric Materials --- p.1 / Chapter 1.1.2 --- Self-sensing Actuation --- p.2 / Chapter 1.2 --- Literature Review --- p.3 / Chapter 1.3 --- Motivation --- p.5 / Chapter 1.4 --- Thesis Organization --- p.6 / Chapter 2 --- STRUCTURE MODELING AND FORMULATION / Chapter 2.1 --- Overview of Piezoelectricity --- p.7 / Chapter 2.2 --- Modeling of the Smart Structure --- p.8 / Chapter 2.2.1 --- Electromechanical Conversion --- p.8 / Chapter 2.2.2 --- Model Derivation Using Hamilton's Principle --- p.10 / Chapter 2.3 --- Discretization of Equation of Motion --- p.15 / Chapter 2.4 --- Sensing Model of the Piezoelectric Sensor --- p.20 / Chapter 2.4.1 --- Strain Sensing Model --- p.21 / Chapter 2.4.2 --- Strain Rate Sensing Model --- p.23 / Chapter 2.5 --- Model Validation --- p.25 / Chapter 3 --- CONTROL OF SMART STRUCTURE / Chapter 3.1 --- Strain Rate Feedback Control --- p.27 / Chapter 3.2 --- Positive Position Feedback Control --- p.31 / Chapter 3.3 --- Unbalanced Bridge Effect on Closed Loop Stability --- p.36 / Chapter 3.4 --- Self-Compensation of Capacitance Variation --- p.39 / Chapter 4 --- EXPERIMENTAL STUDIES / Chapter 4.1 --- Experiment Setup --- p.47 / Chapter 4.2 --- Experiment Results --- p.48 / Chapter 4.2.1 --- Open Loop Response --- p.48 / Chapter 4.2.2 --- Closed Loop Response with Balanced Bridge --- p.49 / Chapter 4.2.3 --- Closed Loop Response with Unbalanced Bridge --- p.51 / Chapter 4.2.4 --- Closed Loop Response upon Sudden Change in Bridge Parameter --- p.53 / Chapter 4.2.5 --- Closed Loop Response upon Temperature Variation --- p.57 / Chapter 4.2.6 --- Frequency Response --- p.58 / Chapter 5 --- SUMMARY / Chapter 5.1 --- Conclusion --- p.51 / Chapter 5.2 --- Future Work --- p.62 / BIBLIOGRAPHY --- p.63

Ng Tsz Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 67-70). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.ii / ACKNOWLEDGEMENTS --- p.iii / LIST OF FIGURES --- p.iv / LIST OF TABLES --- p.ix / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Literature Review --- p.3 / Chapter 1.3 --- Research Objectives --- p.5 / Chapter 1.4 --- Thesis Organization --- p.5 / Chapter CHAPTER 2 --- MODELING OF PIEZOELECTRIC SENSOR/GENERATOR --- p.6 / Chapter 2.1 --- Constitutive Equations --- p.6 / Chapter 2.2 --- Voltage Output of Piezoelectric Materials --- p.9 / Chapter 2.2.1 --- Short Circuit --- p.9 / Chapter 2.2.2 --- Open Circuit --- p.11 / Chapter 2.3 --- Sensitivity and Power Generation --- p.13 / Chapter 2.4 --- Modeling and Analysis of Sensor Structure --- p.23 / Chapter 2.4.1 --- Damping Ratio Estimation --- p.25 / Chapter (a) --- Half-power bandwidth method --- p.25 / Chapter (b) --- Linear interpolation method --- p.25 / Chapter 2.4.2 --- Trade-off between Resonant Frequency and Output Sensitivity of a Sensor --- p.29 / Chapter (a) --- Maximize Sme with constant wn --- p.31 / Chapter (b) --- Maximize wn with constant Sme --- p.33 / Chapter 2.5 --- Model Accuracy --- p.39 / Chapter CHAPTER 3 --- POWER HARVESTING --- p.41 / Chapter 3.1 --- Circuit Model --- p.41 / Chapter 3.2 --- Energy Storage --- p.47 / Chapter 3.3 --- Size Effect on Power Output --- p.49 / Chapter 3.4 --- Power Harvesting Circuit --- p.50 / Chapter 3.4.1 --- Performance of the Power Harvesting Circuit --- p.51 / Chapter (a) --- Power Harvesting Circuit Efficiency --- p.52 / Chapter (b) --- Useful Power Output --- p.53 / Chapter (c) --- System Efficiency --- p.56 / Chapter (d) --- Relationship between Input Excitation and Charge Time --- p.57 / Chapter 3.5 --- Harvested Energy for Wireless Transmission --- p.60 / Chapter CHAPTER 4 --- CONCLUDING REMARKS --- p.64 / Chapter 4.1 --- Sensor/Generator Design --- p.64 / Chapter 4.2 --- Potential Applications --- p.64 / Chapter 4.3 --- Conclusion --- p.65 / Chapter 4.4 --- Future Work --- p.66 / REFERENCES --- p.67 / APPENDIX --- p.71

Besides system level analyses, some implementation issues on switching interface circuits are also investigated. These interfaces show a great potential on harvesting efficiency improvement. Based on the experimental observation, it is found that there is a voltage reversion after every inversion in SSHI, which weakens the harvesting performance. This influence is caused by the dielectric loss in piezoelectric material. A revised model as well as detailed analysis are proposed to evaluate the influence of dielectric loss over the harvesting power degradation. / Considering the practical implementation, a modified self-powered switching interface circuit is proposed. It can achieve better isolation among components and involve less dissipative components. Improved analysis on this self-powered switching interface circuit is also provided. It is shown that the higher the excitation level, the more beneficial for replacing the SEH interface with the self-powered switching interface; meanwhile, the closer between the performances of self-powered and ideal (external powered) switching interfaces. / Owing to the great reduction on power consumption of integrated circuits (ICs) and miniaturization during the past decades, the energy harvesting technique has gained much interest recently with the inspiration that more devices in wireless sensor networks as well as mobile electronics could power themselves by scavenging the ambient energy in different forms. Piezoelectric energy harvesting (PEH) is one of the most widely studied techniques to scavenge energy from ambient vibration sources. With the electromechanical nature, a PEH device can be divided into mechanical and electrical parts. The two parts are linked by the piezoelectric transducer. Literatures on PEH are reviewed and discussed. In the research of PEH, generally there are four different research foci on: mechanical part, electrical part, piezoelectric transduction, and system. / This thesis provides new insight into the research of piezoelectric energy harvesting from some systematic viewpoints. The modeling process of a single degree-of-freedom (SDOF) PEH system is firstly discussed. It shows how the model of a PEH device is built from the material level to element level, and then to device level. In the systematic analysis to PEH devices, the energy flow and impedance based analysis are highlighted. A detailed analysis on the energy flow within the PEH system provides good understanding on the system. However, up to now, most of the researches on PEH have been mainly concerned with the absolute amount of energy that can be harvested from vibrating structures; the detailed energy flow within the system as well as its effect on the vibrating structure, were seldom discussed. By studying the energy flow within three applications of standard energy harvesting (SEH), resistive shunt damping (RSD), and synchronized switching harvesting on inductor (SSHI), it can be concluded that, in a PEH system, the two functions of energy harvesting and dissipation are coexistent. Both of them bring out structural damping. New factors are defined to give a more comprehensive evaluation on the energy flow in PEH systems. / To enhance the harvesting power by using the impedance matching is not new; yet, previous literatures on impedance matching for PEH oversimplified the problem. Without clarification on the energy flow in the PEH system, their objectives on power optimization were ambiguous. Some literatures even assumed that the harvesting interfaces, which are nonlinear in nature, can be equalized to linear loads, and the load impedance can be arbitrarily set. With the understanding on energy flow within piezoelectric devices, we clarify the objective of impedance matching, and further demonstrate that the range of equivalent impedance of existing harvesting interfaces is in fact constrained, rather than unlimited. The analyses on system level provide guideline to improve the harvesting performances. Improvements can be made with innovative designs in either mechanical configuration, piezoelectric transducer, or interface circuit. / Liang, Junrui. / Adviser: Wei-Hsin Liao. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves [145]-155). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Based on constitutive equations of piezoelectricity and two-port modeling method, the models of piezoelectric materials are investigated. The equivalent circuit models of the piezoelectric element in the energy harvesting system are explored. It is found that there exists an optimal external impedance that gives the maximum output power. Experiments are conducted to verify the optimal impedance theory. / The energy storage devices in the piezoelectric energy harvesting system are analyzed. The charge/discharge efficiencies of the energy storage devices are mainly considered. Based on the analysis of the electric characteristics of the energy storage devices, we find the leakage resistances of the energy storage devices are the dominant factor that influences the charge/discharge efficiency in the piezoelectric energy harvesting system. A quick test method is proposed to experimentally study the charge/discharge efficiencies of the energy storage devices. The experimental results verify our findings. Adaptability, lifetime, and protection circuit of the energy storage devices are also discussed. It can be concluded that the supercapacitors are suitable and more attractive than the rechargeable batteries to store the energy in the piezoelectric energy harvesting system. / Two schemes of piezoelectric energy harvesting circuits are analyzed: one-stage and two-stage energy harvesting schemes. The efficiency of the two-stage harvesting scheme is found to be related to several factors including the energy storage device voltage. Analysis and experiments using one-stage energy harvesting circuit to harvest a varying excitation source are explored. The results show that one-stage energy harvesting scheme can achieve higher efficiency than the two-stage scheme towards a range of energy storage voltages. / Using piezoelectric elements to harvest energy from ambient vibration has been of great interest recently. Because the power harvested from the piezoelectric elements is relatively low, energy storage devices are needed to accumulate the energy for intermittent use and energy harvesting circuits are applied to transfer the electrical energy from the sources to the storage devices. Therefore, a piezoelectric energy harvesting system can be basically divided into three parts: the energy source, the energy harvesting circuit, and the energy storage device. These three parts are explored in this thesis. / Guan Mingjie. / "September 2006." / Adviser: Wei-Hsin Liao. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1822. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 123-128). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 47-50).

Thesis (M.S.)--Worcester Polytechnic Institute. / Keyword: turbulence. Includes bibliographical references (p. 75-78).

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