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101.
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103.
Hee-Ryoung Cha Ji-Hun Yu Youn-Kyoung Baek Hae-Woong Kwon Tae-Hoon Kim Cheol-Woong Yang Tea-Soo Lim Yang-Do Kim Jung-Goo Lee 《Metals and Materials International》2014,20(5):909-914
The effect of Nd content and dehydrogenation speed on the microstructure and magnetic properties of hydrogenation-disproportionation-desorption-recombination (HDDR) processed Nd-Fe-B magnetic powders was studied. The NdxB6.4Ga0.3Nb0.2Febal (x=12.5–13.5, at.%) mold casting alloys were subjected to HDDR process after homogenization heat treatment. During desorption-recombination stage, dehydrogenation speed and time were systematically changed to control the speed of the desorption-recombination reaction. The higher Nd content resulted in better magnetic properties of the HDDR powder, and this was attributed to the thicker and more uniform Nd-rich phase at grain boundaries. It was also confirmed that the slow dehydrogenation speed could maximize the effect of high Nd content on the magnetic properties of HDDR powder. At the optimized dehydrogenation speed, the coercivity and remanence was 15.3 kOe and 13.0 kG, respectively, at 12.9 at.% Nd content, which resulted in a (BH)max of 36.8 MGOe. 相似文献
104.
Dong-Hyun Lee Jung-A Lee Moo-Young Seok Un Bong Baek Seung Hoon Nahm Jae-il Jang 《International Journal of Hydrogen Energy》2014
We explored the influences of hydrogen on small-scale strength of a linepipe steel through nanoindentation experiments with four pyramidal indenters. Interestingly, a transition from hydrogen-induced hardening to softening was observed as indenter sharpness increases. The transition was analyzed based on the enhancement in hydrogen's elastic shielding effects for a sharper indenter, which could be indirectly evidenced by the stress effects on indentation pile-up, dislocation density, and rate dependency of hardness. 相似文献
105.
Jin H. Choi Taehee Lee Mihwa Choi Young-Sung Yoo Seung-Wook Baek Joongmyeon Bae 《International Journal of Hydrogen Energy》2010
Using relatively simple and cheap joining process, anode-supported solid oxide fuel cell integrated with metal interconnect is fabricated and its impedance spectra are analyzed and compared with anode-supported cell at the operating temperature of 800 °C. The stable long-term performance is shown for about 800 h at 800 °C under the constant current density of 300 mA cm−2. The thermal cycle experiments from the operating temperature to the room temperature are also carried out in this study, while the maximum power density of 0.7 W cm−2 is indicated. The microstructures are analyzed using scanning electron microscope and energy dispersive X-ray spectra are analyzed for observing a diffusion of metal ions at the anode, adhesion layer and metal support. 相似文献
106.
Hee-Joon Chun Dong Baek KimDong-Ha Lim Weon-Doo LeeHo-In Lee 《International Journal of Hydrogen Energy》2010
A Pt-Nb2O5/C electrocatalyst was synthesized by a two-step process as an anode material in direct methanol fuel cell (DMFC). The Pt-Nb2O5/C catalysts heat-treated at different temperatures (400 and 500 °C) in flowing N2 were characterized by various methods such as inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, transmission electron microscopy, and X-ray photoemission spectroscopy (XPS). The heat-treated Pt-Nb2O5/C catalyst at 400 °C showed the best electrochemical activity for CO and methanol oxidations among the prepared catalysts. The XPS results showed the electronic structure change of Pt, indicating a formation of interaction between Pt and Nb2O5. It is suggested that a synergistic effect between Pt and Nb2O5 enhances the electrocatalytic activity for CO and methanol oxidations. We believe that Nb2O5-promoted Pt/C catalyst may be regarded as one of the attractive candidates as an anode material in DMFC. 相似文献
107.
Dong Baek Kim Hee-Joon Chun Yoon Kyung Lee Heock-Hoi Kwon Ho-In Lee 《International Journal of Hydrogen Energy》2010
Pt catalyst supported on Vulcan XC-72R containing 5 wt% NiO (Pt/NiO–C) showed larger electrochemical active surface area and higher electrochemical activity for methanol oxidation than Pt catalyst supported on Vulcan XC-72R using polyol method without NiO addition. Prepared Pt/NiO–C electrocatalyst was heat-treated at four temperatures (200, 400, 600, and 800 °C) in flowing N2. X-ray diffraction and temperature-programmed desorption results indicated that NiO was reduced to Ni in inert N2 during heat-treatments at temperatures above or equal to 400 °C, while oxygen from NiO reacted with carbon support due to the catalytic effect of Pt. The reduced Ni formed an alloy with Pt, which, according to the X-ray photoelectron spectroscopy data, resulted in a shift to a lower binding energy of Pt 4f electrons. The Pt/NiO–C electrocatalyst heat-treated at 400 °C showed the best activity in methanol oxidation due to the change in Pt electronic structure by Ni and the minimal aggregation of Pt particles. 相似文献
108.
Jai -Hyuk Hwang Jung -Soo Kim Seung -Ho Baek 《Journal of Mechanical Science and Technology》1999,13(1):42-49
In this paper, a modified Independent Modal Space Control (IMSC) that relaxes the fundamental hardware requirement of IMSC
is proposed for handling the vibration and attitude control problem of large, flexible structures. The method incorporates
a new switching algorithm for dynamically selecting controlled modes and a novel design technique for determining the modal
control force. The main advantage of the proposed method is that it minimizes the discontinuity of the modal control forces
and assures the asymptotic stability of the closed-loop system. The simplicity and efficiency of the method is demonstrated
through an example involving vibration control of a cantilevered beam. The system performance and stability of the proposed
method is compared with previously published methods that also seek to reduce the number of actuators in IMSC. 相似文献
109.
Dae Kyun Baek Tae Jo Ko Seung Han Yang 《Journal of Materials Processing Technology》2013,213(4):553-559
We present a new fabrication method that enables precision hole machining to be achieved by sacrificing the coating on the substrate in ultrasonic machining (USM). A hard wax coating is deposited on the glass substrate, and holes are precisely fabricated in the coated glass using USM. Finally, a wax coating is removed using a cleaning process. The wax coating protects the surface of the glass so that cracks are generated in the wax rather than on the surface. The surface accuracy of the glass substrate is evaluated at the hole entrance using the new tools in USM as a function of the thickness of the coating. The entrance diameters of the machined holes and the machining forces at the beginning of cutting are measured as a function of the thickness of the coating. The entrance cracks and out-of-roundness of the machined holes are generated in the sacrificed coating on the glass substrate; hence, the surface quality of the glass holes is enhanced in USM. 相似文献
110.
Won-Ju Cho Chang-Geun Ahn Kiju Im Jong-Heon Yang Jihun Oh In-Bok Baek Seongjae Lee 《Electron Device Letters, IEEE》2004,25(6):366-368
A plasma-doping technique for fabricating nanoscale silicon-on-insulator (SOI) MOSFETs has been investigated. The source/drain (S/D) extensions of the tri-gate structure SOI n-MOSFETs were formed by using an elevated temperature plasma-doping method. Even though the activation annealing after plasma doping was excluded to minimize the diffusion of dopants, which resulted in a laterally abrupt S/D junction, we obtained a low sheet resistance of 920 /spl Omega///spl square/ by the elevated temperature plasma doping of 527 /spl deg/C. A tri-gate structure silicon-on-insulator n-MOSFET with a gate length of 50 nm was successfully fabricated and revealed suppressed short-channel effects. 相似文献