Hong Kong higher education in transition: The academic community\u27s perception at the time of 1997 retrocession

The purpose of this study was to ascertain the perceptions of selected faculty and academic administrators of the 1997 retrocession of Hong Kong to China with respect to the dual challenge of Hong Kong higher education assisting with the modernization of socialist Mainland China while maintaining its function supporting the capitalist system in Hong Kong. Twenty-five selected faculty and academic administrators in two representative universities of Hong Kong were interviewed at the eve of the retrocession. Four related themes were investigated in the interviews: the implications of “one country, two systems,” the ability of the Hong Kong higher education system to reposition itself in its new context, the perceived impact of the retrocession on the work of faculty and academic administrators in higher education, and the respondents\u27 advice to the government of the Special Administrative Region. Interviewees responded that “one country, two systems” could result in the modernization of Mainland Chinese society while preserving Hong Kong\u27s historic autonomy. Hong Kong higher education experienced a rapid expansion within the fourteen year transitional period (1984–97). Two major tasks were identified for the time following the retrocession: first, redefine the mission of each institution to emphasize different functions, and second, with increased emphasis on research during the transition period, insure a continued balanced emphasis on quality teaching. In serving the goal of China\u27s modernization, Hong Kong academics thought themselves to be in a strong position to assist in the areas of business, social sciences, natural sciences, and technology. Hong Kong academics could foresee working together with their counterparts on the Mainland to strengthen a modern research enterprise and a civil culture with all the proven values from the East and West. They believe that the preservation of the academic freedom in Hong Kong\u27s universities was vital for the transformation of the two societies

FUNDAMENTAL INVESTIGATION ON ANION BINDING EMPLOYING THE HYDROGEN BOND ENHANCED HALOGEN BOND

Noncovalent interactions play a critical role in chemistry and biochemistry. Understanding how to modulate closely situated noncovalent interactions is of utmost importance in the design of functional materials, supramolecular assemblies, pharmaceuticals, and catalysts. Over the past two decades, there has been a significant surge in research and applications on halogen bonds, driven by their exceptional properties such as high directionality and unique tunability when compared to hydrogen bonds. Taking inspiration from nature and other synthetic anion-binding receptors that effectively employ multiple noncovalent interactions in a concerted manner, we have developed an innovative preorganization strategy termed the Hydrogen Bond Enhanced Halogen Bond. This unique combination of hydrogen and halogen bond interactions yields an anion-binding performance over an order of magnitude greater than that achieved with either hydrogen bonds or halogen bonds alone. In-depth investigations, including examinations of solvent effects and substituent impacts, have been undertaken to gain insights into this interaction. We have also pushed the boundaries of this interaction by incorporating non-traditional C-H hydrogen bond donors. This dissertation provides significant insights of this interaction fueling the development of new generations of halogen bond-based anion receptors with exciting applications in anion recognition, organocatalysis, anion transport, and anion sensing. The ensuing chapters provide a comprehensive overview of this study. Chapter 1 introduces halogen bonding, tracing its evolution from hydrogen bonds, elucidating unique traits, and exploring preorganization strategies within the Hydrogen Bond Enhanced Halogen Bond (HBeXB). It also uncovers the captivating realm of anion binding through halogen bonds, highlighting their significance in applications. In Chapter 2, the investigation delves into intriguing solvatochromism and fluorescence responses to anions in halogen bonding anion receptors. Chapter 3 delves into the intricate interplay between hydrogen and halogen bonds, with a focus on quantification of the substituent effects in the hydrogen bond enhanced halogen bond. In Chapter 4, we delve into unconventional approaches to enhance halogen bonds using non-traditional hydrogen bonds, shedding light on anion binding in solution and offering innovative insights into this facet of XB···anion interaction. Finally, Chapter 5 summarizes our findings and offers a glimpse into the future

4D Printing Dielectric Elastomer Actuator Based Soft Robots

4D printing is an emerging technology that prints 3D structural smart materials that can respond to external stimuli and change shape over time. 4D printing represents a major manufacturing paradigm shift from single-function static structures to dynamic structures with highly integrated functionalities. Direct printing of dynamic structures can provide great benefits (e.g., design freedom, low material cost) to a wide variety of applications, such as sensors and actuators, and robotics. Soft robotics is a new direction of robotics in which hard and rigid components are replaced by soft and flexible materials to mimic mechanisms that works in living creatures, which are crucial for dealing with uncertain and dynamic tasks. However, little research on direct printing of soft robotics has been reported. Due to the short history of 4D printing, only a few smart materials have been successfully 4D printed, such as shape memory and thermo-responsive polymers, which have relatively small actuation strains (up to ~8%). In order to produce the large motion, dielectric elastomer actuator (DEA), a sheet of elastomer sandwiched between two compliant electrodes and known as artificial muscle for its high elastic energy density and capability of producing large strains (~200%), is chosen as the actuator for soft robotics. Little research on 3D printing silicone DEA soft robotics has been done in the literature. Thus, this thesis is motivated by applying the advantages in 3D printing fabrication methods to develop DEA soft robotics. The ultimate research goal is to demonstrate fully printed DEA soft robots with large actuation. In Chapter 1, the research background of soft robotics and DEAs are introduced, as well as 3D printing technologies. Chapter 2 reports the rules of selecting potentially good silicone candidates and the printing process with printed material characterizations. Chapter 3 studies the effects of pre-strain condition on silicone material properties and the performance of DEA configurations, in order to obtain large actuation strain. In Chapter 4, two facial soft robots are designed to achieve facial expressions as judged by a smiling lip and expanding pupils based on DEA actuation. Conclusions and future developments are given in chapter 5 and 6, respectively

Development of Novel Battery Materials for Lithium-Ion Batteries and Beyond

As fossil fuels are depleting and causing environmental issues, it becomes imperative to widely implement renewable energies (e.g., solar and wind power). In this context, electrical energy storage (EES) systems are essential to accommodate the intermittent supply and uneven distribution of renewable energies. To this end, high-energy-density EES devices are highly demanded, such as rechargeable batteries. This dissertation presents my efforts in developing novel battery materials for lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and solidstate lithium batteries (SSLBs). These efforts include electrochemical evaluations of battery materials, surface modifications of electrodes via atomic layer deposition (ALD), and advanced characterizations of batteries materials. In this dissertation, my first effort invested on the growth of ZnO nanofilms via ALD. ALD technique possesses some unrivaled merits, including atomic-scale controllability, excellent uniformity and conformality, and the accessibility of a large variety of materials. In the past decade, it has been widely used for surface-modifying battery electrodes. This study investigated growth characteristics and underlying mechanisms of ALD ZnO nanofilms using diethylzinc and water precursors. The temperature-controllable growth and crystal-orientation of ALD ZnO films were disclosed. This study offered key understanding and preliminary preparation for the following study to surface-modify electrode materials. A subsequent effort was focused on developing a novel anode for SIBs. SIBs have attracted an ever-growing research interest, due to their cost-effectiveness as large-scale stationary EES devices. However, compared with LIBs, SIBs are significantly hindered by the lack of suitable anodes. In this study, Cu2S was chosen for high capacity and fast-charge capability. The nitrogendoped graphene (NG) wrapped Cu2S (Cu2S@NG) composite anode exhibited stable cyclabilityand excellent rate capability. The electrochemical mechanism was investigated using synchrotronbased X-ray techniques. Whereas the parasitic reactions at the electrode/electrolyte interface continuously deteriorated performance, which could be resolved by surface modifications via ALD. In the sequential effort to enhance interfacial stability of Cu2S@NG anode, the electrochemically inactive Al2O3 via ALD was selected as the coating material. A 6-nm ultrathin Al2O3 coating could improve the interfacial stability of the Cu2S@NG anode and thereby enhance its electrochemical performance with the highest capacity reported to date. Additionally, this dissertation includes an effort in investigating a promising solid-state electrolyte (SSE), Li7La3Zr2O12 (LLZO). Conventionally, flammable liquid-organic electrolytes have been used in LIBs but induced some safety issues (e.g., fires and explosions). In this regard, SSEs are highly regarded to replace liquid organic electrolytes. LLZO is among the most promising SSEs with high ionic conductivity (~10-3 S cm-2 at room temperature) and high stability with Li metal anode. Nevertheless, LLZO’s stability in the ambient storage is challenging, causing deteriorated ionic conductivity and interfacial instability. This study investigated the structural and stoichiometric reversibility of air-aged LLZO during heat treatment. In addition, the correlation between restoration degree and dopant chemistry was unveiled. In summary, the contributions in this dissertation provide critical understandings to electrochemical mechanisms and degradation causes of novel electrode and electrolyte materials and demonstrate the vital surface modification route via ALD for enhanced performance

集積化AlGaN/GaNイオン感応性電界効果トランジスタに関する研究

AlGaN/GaN heterostructure ion-sensitive field-effect transistors (ISFETs) can provide high sensitivity and fast response due to the high electron mobility and high electron density providing by the two-dimensional electron gas (2DEG) generated at the AlGaN/GaN heterostructure interface. My research mainly focuses on the investigation of the integrated AlGaN/GaN ISFETs for pH sensing. To achieve high performance on AlGaN/GaN ISFET pH sensor, we fabricated sensors with different Al composition (25%, and 35%). We compared the characteristics of the sensors with 25% and 35% Al composition. The pH sensor with Al composition (35%) in the barrier layer with a 16 nm transition layer of 25% Al composition shows better surface sensitivity (SV) of 56.01 mV/pH, which is higher than that of the sensor with 25% Al composition (53.94 mV /pH), but worse current sensitivity SA (-0.095 mA/pH Vs -0.102 mA/pH). In addition, threshold voltage increases from approximately -1.6 V to approximately -0.8 V when measured in alkaline solution for 5 times, along with a decreasing output current. High-resolution SEM photos show that there are high density hexagonal pits with the size of approximately 100 nm on the device surface, presenting the etching effect along the dislocations during alkaline sensing. The X-ray photoelectron spectroscopy (XPS) demonstrates that the intensity of the Ga3d and Al2p spectra decreases after pH sensing measurement, implying the variation of chemical component occurs in the upper AlGaN thin layer. Many voids with a size of approximately 100 nm were observed from the transmission electron microscope (TEM) pictures, which are comparable with that of the scanning electron microscope (SEM). Combining with the energy dispersive X-ray spectroscopy (EDX), the degradation in electrical performance can be attributed to the transformation of AlGaN into oxide as well as the followed alkaline solution dissolve. To avoid the reaction of surface Al with solution, a 3 nm GaN cap layer was added. To reduce the barrier layer thickness, a recessed gate with a length of 2 μm and a depth of about 14 nm was formed. The current sensitivity of the AlGaN/GaN ISFET pH sensors has been improved by 61%, from 52.25 to 84.39 μA/pH, by the recessed-gate structure and ammoniate water treatment. A pH meter system based on the GaN pH sensor was constructed and evaluated. GaN-based ISFET can measure the pH value of the solutions with similar circuit, whether in the linear region or the saturation region. The measurement is stable and repeatable. The small current in the linear region can make the measurement stable and fast, but the resolution is a bit low. High resolution can be obtained in the saturation region, but the measurement is unstable due to excessive current. The Schottky barrier diode (SBD) based on GaN can be used for temperature sensing, and the temperature sensitivity can be improved by different structure design. A recessed anode AlGaN/GaN SBD is suitable to integrate with GaN-based power device for temperature sensor application. The temperature dependent forward voltage at a fixed current shows good linearity, resulting in a sensitivity of approximately 1.0 mV/K. The p-NiO guard ring can suppress the electric field at the anode/GaN interface and field crowding at the anode edge effectively, which enhances the breakdown voltage to approximately -250 V. Using the same material, we can design an integrated device sensor based on GaN to measure temperature and pH simultaneously, which will solve the measurement deviation of pH sensor at different temperatures