165 research outputs found
Ming Qing yi lai Hangzhou Wan nan an de she hui bian qian: Social transition of the south Hangzhou Bay area during the Ming and Qing dynasties.
No full text蔣宏達.Parallel title from added title page.Thesis (Ph.D.) Chinese University of Hong Kong, 2015.Includes bibliographical references (leaves 353-366).Jiang Hongda
Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity
No full textPhotothermal materials, especially photothermal plastics, are crucial building blocks for functional devices. Covalently immobilizing the photothermal carbon dots in plastic matrix is a promising method for producing efficient photothermal plastics. However, the reactive moieties of photothermal carbon dots are often destroyed because of harsh preparation conditions, preventing their covalent interaction with plastic matrix. Here, we conceptualized carbon dots with photocaged reactivity (P-CDs) for producing ultra-stable photothermal plastics. During the formation of P-CDs, hydroxyl moieties were maintained in the preparation environment. Upon UV irradiation, hydroxyl moieties of P-CDs were in situ converted into aldehyde groups and reacted with amino groups in the polysaccharide matrix, producing P-CD plastics. As-obtained P-CD plastics showed strong stability against solution immersion and UV aging. In particular, the P-CD plastics showed a high photothermal conversion efficiency of 46.6%. Such efficient and robust photothermal P-CD plastics were further applied to prepare a solar-driven thermoelectric generator (TEG) for energy generation
A non-Newtonian liquid metal enabled enhanced electrography
No full textBiopotential signals, like electrocardiography (ECG), electromyography (EMG), and electroencephalography (EEG), can help diagnose cardiological, musculoskeletal and neurological disorders. Dry silver/silver chloride (Ag/AgCl) electrodes are commonly used to obtain these signals. While a conductive hydrogel can be added to Ag/AgCl electrodes to improve the contact and adhesion between the electrode and the skin, dry electrodes are prone to movement. Considering that the conductive hydrogel dries over time, the use of these electrodes often creates an imbalanced skin-electrode impedance and a number of sensing issues in the front-end analogue circuit. This issue can be extended to several other electrode types that are commonly in use, in particular, for applications with a need for long-term wearable monitoring such as ambulatory epilepsy monitoring. Liquid metal alloys, such as eutectic gallium indium (EGaIn), can address key critical requirements around consistency and reliability but present challenges on low viscosity and the risk of leakage. To solve these problems, here, we demonstrate the use of a non-eutectic Ga–In alloy as a shear-thinning non-Newtonian fluid to offer superior performance to commercial hydrogel electrodes, dry electrodes, and conventional liquid metals for electrography measurements. This material has high viscosity when still and can flow like a liquid metal when sheared, preventing leakage while allowing the effective fabrication of electrodes. Moreover, the Ga–In alloy not only has good biocompatibility but also offers an outstanding skin-electrode interface, allowing for the long-term acquisition of high-quality biosignals. The presented Ga–In alloy is a superior alternative to conventional electrode materials for real-world electrography or bioimpedance measurement.</p
Optimization of substrate conformal imprint lithography (SCIL) and etching for nanostructure
No full textThe UV-SCIL fabrication process was developed and optimized to improve the quality of the nanostructures on the hard substrate transferred with substrate conformal imprint lithography (SCIL) technology. In particular, the key steps such as coating imprint resist, exposure time and etching time were investigated thoroughly. The experiment’s results illustrate that imprint resist could well serve as an etching mask for the dry etching process without oxygen plasma. The optimized etching condition and SCIL technology could also be used to transfer nanostructures on different substrates for metal nanostructured biosensors or nanophotonics
Solidification Simulation of Binary Al-Si Alloys: Prediction of Primary Dendrite Arm Spacing with Macro-Scale Simulations (~1mm Length Scale)
No full textTitle: Solidification Simulation of Binary Al-Si Alloys: Prediction of Primary Dendrite Arm Spacing with Macro-Scale Simulations (~1mm Length Scale), Author: Hongda Wang, Location: ThodeA new and improved algorithm and numerical method has been developed and validated to simulate the solidification of binary alloys considering optimized thermophysical material properties, undercooling of the liquidus temperature prior to solidification event of the primary
phase, fluid flow induced by natural convection and shrinkage during solidification in the solidifying domain. The simulation was for a two dimensional unsteady state solidification process inside a cylindrical container. The validation was carried out with reliable experiment
results for both upward and downward solidification modes. An additional advantage of the present numerical algorithm is the estimation of the instantaneous primary dendrite arm spacing at any location in the solidified component. It has been shown that the Bouchard-Kirkaldy
model (unsteady state solidification) to evaluate the primary dendrite arm spacing in an unsteady solidification process coupled with the Lehmann model to evaluate the primary arm spacing with the effect of fluid velocity in the liquid phase is accurate within acceptable error. The results from simulations using these models have a good agreement with experiment results for instantaneous primary dendrite arm spacing in the solidified microstructure. The effect of fluid flow on the evaluation of primary arm spacing is pronounced during downward solidification. However, the effect of primary arm spacing on fluid flow is insignificant, so it is acceptable to
apply average primary arm spacing during macro-scale solidification simulations. To obtain a valid simulation, the thermophysical material properties of the solid phase should be considered as function of temperature and that of the liquid can be considered as an average constant value. The inclusion of solidification shrinkage in the simulation has negligible effect on the solidification parameters during the upward solidification mode. However, significantly changes the direction and magnitude of the fluid velocity in the liquid phase and the magnitude of
primary arm spacing in the downward solidification mode. A valid solidification simulation of binary alloys to estimate accurate primary dendrite arm spacing could be achieved only with the consideration of the undercooling of the liquidus temperature. Optimized thermophysical
properties, and fluid flow in the domain caused by both solidification shrinkage and natural convection effects.ThesisDoctor of Philosophy (PhD
High speed phosphorescent white LED visible light communications without utilizing a blue filter
No full text
Controllable liquid metal microparticles production and patterning by miniaturized filter-sieve generators
No full textLiquid metal microparticles (LMMPs) with excellent conductivity and reactivity hold significant promise for applications in flexible electronics and sensors. However, current LMMP production methods face critical challenges, including achieving smaller particle sizes with low energy consumption, streamlining processes, and enhancing productivity. Herein, leveraging the tunable surface tension of LM droplets, a compact platform called the miniaturized filter-sieve generator (MFSG) is presented, for scalable, energy-efficient, and controllable LMMP production. The MFSG demonstrates high energy efficiency (average power consumption of 0.21 W) and productivity (6.51 × 105 particles per minute) while enabling precise control of microparticle sizes (2–300 µm). Furthermore, the MFSG can uniformly produce LMMPs with varied compositions. Harnessing these capabilities, a reconfigurable platform integrating the MFSG is developed to enable complex droplet patterning and an LMMP-based humidity sensor with high sensitivity. This innovative platform for on-demand LMMP production with low energy consumption will drive significant advancements in electronic devices and sensing systems.</p
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