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Zhang T.,Du W.Y.,Zhan C.Y.,Wang M.M.,Deng H.W.,Xie Z.M.,Li H. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8
The synergistic effect of ZrC nanoparticle pining and Re solution in W matrix on the thermal stability of tungsten was studied by investigating the evolution of the microstructure, hardness and tensile properties after annealing in a temperature range of 1000e1700 C. The results of metallography, electron backscatter diffraction pattern and Vickers micro-hardness indicate that the rolled W-1wt%Re-0.5 wt% ZrC alloy has a higher recrystallization temperature (1600 Ce1700 C) than that of the rolled pure W (1200 C), W-0.5 wt%ZrC (1300 C), W-0.5 wt%HfC (1400e1500 C) and WeK-3wt%Re alloy fabricated by the same technology. The molecular dynamics simulation results indicated that solution Re atoms in W matrix can slow down the self-diffusion of W atoms and form dragging effect to delay the growth of W grain, moreover, the diffusion coefficient decrease with increasing Re content. In addition, the ZrC nanoparticles can pin the grain boundaries and dislocations effectively, preventing the recrystallization. Therefore, synergistic effect of solid solution Re element and dispersed ZrC nanoparticles significantly increase recrystallization temperature
ZhEng, D. W.,Huang, Y. P.,Tang, T. A.,Cui, Q.,Li, A. Z.,Zhou, S. X.,He, Z. J.,Chen, Z.,Zhang, X. J.,Kwor, R. 대한전자공학회 1993 ICVC : International Conference on VLSI and CAD Vol.3 No.1
A novel process for silicon on insulator(SOI) technology has been presented. Single crystal Si is grown by molecular beam epitaxy(MBF) on a porous silicon(PS) system consisting of two layers of PS with different microstructures. Subsequent lateral oxidation converts the structure to SOI wish excellent insulation property. Si islands with a width of 135㎛ and low doping concentration have been achieved.
가변속 압축기를 갖는 냉동시스템의 Decoupling제어를 위한 과열도 특성 해석
이동우(D. W. Lee),Li Hua,정석권(S. K. Jeong) 한국동력기계공학회 2005 한국동력기계공학회 학술대회 논문집 Vol.- No.-
In a variable speed refrigeration system, the control of capacity and superheat are conducted by inverters and electronic expansion valves respectively for saving energy' and improving cost of performance. There are many drawbacks in efficient control for the superheat and the capacity independently because of the system's inherent non-linearity and long time constant with delay time. Therefore, empirical models than precise mathematical models obtained from the energy conservative law are mainly used for application until now. Decoupling method for controlling the capacity and the superheat independently is suggested in this paper. The relations between the superheat and cost of performance are examined in detail. Also, the empirical dynamic model in decoupling control is investigated through some experiments.
NONLINEAR ANALYSIS OF SELF-EXCITED VIBRATION IN WHEELED TRACTOR VEHICLE’S DRIVELINE
X.-H. LI,J.-W. ZHANG,C.-C. ZENG 한국자동차공학회 2006 International journal of automotive technology Vol.7 No.5
A nonlinear analysis of torsional self-excited vibration in the driveline system for wheeled towing tractors was presented, with a 2-DOF mathematical model. The vibration system was described as a second-order ordinary differential equation. An analytical approach was proposed to the solution of the second-order ODE. The mathematical neighborhood concept was used to construct the interior boundary and the exterior boundary. The ODE was proved to have a limit cycle by using Poincare-Bendixson Annulus Theorem when two inequalities were satisfied. Because the two inequalities are easily satisfied, the self-excited vibration is inevitable and even the initial slip rate is little. However, the amplitude will be almost zero when the third inequality is satisfied. Only in a few working modes of the towing tractor the third inequality is not satisfied. It is shown by experiments that the torsional self-excited vibration in the driveline of the vehicle is obvious.
Li Hua,이동우(D. W. Lee),정석권(S. K. Jeong) 한국동력기계공학회 2006 한국동력기계공학회 학술대회 논문집 Vol.- No.-
This paper describes PI controller design to control the variable speed refrigeration system effectively. The conventional control schemes of the system are mainly focused on representative two control methods, superheat control and capacity control. In the variable speed refrigeration system, the capacity and the superheat are controlled by inverters and electronic expansion valves respectively for saving energy and improving cost performance. The capacity and superheat can not be controlled independently because of interfering loop when the compressor speed and opening angle electronic expansion valve is varied. Therefore, we suggest decoupling model to eliminate the interfering loop at first. Next, we designed PI controller and investigated the control performance through some numerical simulations.
Fan M. Yang,Li J. Li,Guo W. He 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.6
In the present work, zirconium-doped metal oxide of TiO₂(ZrN) was synthesized and functionalized with different amount of tetraethylenepentamine (TEPA). The physical properties of the materials were tested using temperature-programmed desorption of NH₃, X-ray diffractometer, X-ray photoelectron spectrometer, scanning electron microscope, transmission electron microscope, energy dispersion spectrum, Inductively coupled plasma atomic emission spectroscopy, Infrared spectrometer, N₂ adsorption-desorption analyzer, energy dispersion spectrum and thermogravimetric analyzer. Zr species has a positive effect on the enhancement of the thermal stability and amine utilization. After the introduction of Zr, the decomposition temperature of TEPA is improved to 180℃. Over TEPA decorated adsorbents, physical adsorption and chemical adsorption occurs simultaneously. When the adsorption time is 75℃, CO₂ flow rate is 20 mL/min, the adsorbent of TEPA(40)/TiO₂(Zr0.1) exhibit a remarkable amine utilization of 83.5%.
( Stacey C. Y. Li ),( Catherine W. C. Chan ),( Janet K. Y. Chan ) 한국폐기물자원순환학회 2022 ISSE 초록집 Vol.2022 No.-
Mobile phones have become one of the most indispensable items of our daily life. People normally have the practice of reselling their old phones or other electronic devices because of their high value. However, the USB cables normally come with these gadgets are always forgotten. As the USB cables are made of plastics and metals, it would be a waste of resources if they were sent to the landfill directly. There is a lack of data and studies regarding the amount of USB cable waste, and people’s handling and disposing habits of them in Hong Kong. This action-cum-research project, namely “Off-lines”, therefore aims to raise people’s awareness on e-waste beginning with a type of waste that everyone has, that is USB cable, and to fill in the research gap on people’s awareness and knowledge on this kind of e-waste. One hundred and fifty collection points were set up all over Hong Kong by this project and successfully collected over 7,700 unwanted cables from the public. This project also conducted a questionnaire survey from February 2022 to May 2022 and received 457 valid responses from the public. The results of the questionnaires show that nearly 70% of respondents do not know USB cables can be recycled. The three major reasons for not recycling USB cable are: 1) Not knowing any collection points (71%); 2) Lack of knowledge on USB cable recycling (67%); and 3) Inconvenient and insufficient collection points (67%). Upcycling workshops were also organised not only to provide a chance for the participants to have hands-on experience on making knots with USB cables, but also to inspire them to think out of the box and give any unwanted item a second life. Feedback from the public and also the business sector found the project very meaningful and successfully heightened the public awareness on e-waste issues. Collaboration with green groups and other partnering organisations should be extended to provide wider and immersive networks for collecting unwanted USB cables or other cables.