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이정희,Jae-Hee Park,Jae-Hoon Lee,Jae-Seung Lee,Jong-Wook Kim,Kye-Seok Lee,Sung-Bum Bae,Sung-Ho Hahm 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
Based on investigating the effects of isoelectronic Al-doping on GaN film, a new layer structure is proposed for a heterostructure field effect transistor (HFET) including an isoelectronic Al-doped channel. The electron mobility measured at 77 (300) K significantly increased from 145 (130) cm$^2$/V$\cdot$s in the undoped sample to 823 (440) cm$^2$/V$\cdot$s in the Al-doped sample grown with a trimethylaluminum flow rate of 3 $\mu$mol /min, while maintaining the background doping concentration below $\sim$ 6 $\times$ 10$^{16}$ cm$^{-3}$. Two-dimensional electron gas mobilities of 1690 and 9280 cm$^2$/Vs were measured for a 25-nm Al$_{0.3}$Ga$_{0.7}$N/1-nm AlN/70-nm Al-doped channel/GaN heterostucture at 300 and 77 K, respectively. The improved results are explained based on a decrease in the compensating acceptors or other defects associated with the formation of screw dislocation due to the incorporation of Al in the channel layer, plus a decrease in the alloy disorder scattering in the heterostructure based on introducing a binary thin AlN layer between the Al$_{0.3}$Ga$_{0.7}$N and Al-doped channel layers.
이정희,Se-Yeong Lee,곽재섭 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.12
A rotational electro-magnetic finishing (REMF) was an effective way to minimize burr and improve edge quality on the surface. This study conducted two stages of explicit dynamic simulations: signle collision analysis and multiple collision analysis to verify the effect of abrasives’ behavior on the deburring processes. From observed results, successful deburring depended on the total amount of abrasives and the collision angle. Based on the simulated results and response surface methodology, it was found that the accuracy was reached approximately 95.4 %. Additionally, the maximum deburring area from the predictive model and simulation were similar to 2.27 mm 2 and 2.37 mm 2 , respectively, at rotational speed of 1800 rpm, abrasive diameter of 0.7 mm, and abrasive weight of 2.0 kg. In the experimental verification, the results were in good agreement with the experimental data, although specific values did not correspond exactly. Thus, the suggested approach adopting explicit dynamic simulations could effectively evaluate deburring performance in the REMF process.
초산납이 생쥐 간뇌의 미세구조 및 Catecholamine 대사에 미치는 영향
이정희,유창규,최임순,Lee, Jung-Hee,Yoo, Chang-Kyu,Choe, Rim-Soon 한국현미경학회 1988 Applied microscopy Vol.18 No.2
The present experiment was performed to investigate the acute and subacute effect of lead acetate on ultrastructural and biochemical changes in mouse diencephalon. In acute case, mouse were peritoneally injected with lead acetate at a dose of 0.26 mmole/kg body weight, and after treatment, mouse were sacrificed at time intervals of 12, 24, 48, and 96 hours. In subacute case, mouse were injected at doses of 0.07 mmoie/kg B. W. and 0.13 mmole/kg B.W. once at two days, and after treatment, mouse wee sacrificed at 1 week, 2 weeks, and 3 weeks. It was observed that after acute treatment, changes composed of increased monoamine oxidase activity, $Na^{+}-K^{+}$ ATPase activity, decreased $Mg^{2+}$-APTase activity, wrinkled myelin, swollen Golgi apparatus and more dense synaptic vesicle in nerve terminal. After subacute treatment, decreased monoamine oxidase activity, increased $Mg^{2+}$-ATPase, $Na^{+}-K^{+}$ ATPase, lose of myelin, uneven mitochondrial distribution, synaptic vesicular density and edema, but at a higher dose the effect was more severe. Therefore, lead acetate caused abnormal change of diencephalon, and at a subacute, it appears metal accumulative toxicity.
수지가공포의 유리 Formaldehyde 발생억제( I ) -요소에 의한 후처리효과-
이정희,이순원,김성련,Lee Jung Heui,Lee Soon Won,Kim Sung Reon 한국의류학회 1979 한국의류학회지 Vol.3 No.2
In order to control free formaldehyde release from fabric finished with urea-formaldehyde precondensate, the resin finished fabric was padded in urea or acylamide solution, dried and cured at $140^{\circ}C$. The effect of aftertreatment with urea or acrylamide on free formaldehyde release and on characteristics of resin finished fabric were examined. It was shown that aftertreatment with urea was effective to control free formaldehyde release, the free formaldelyde content in aftertreated fabric could be reduced from 900 ppm to 200 ppm and formaldehyde release under accelerated storage condition was also reduced from 8000 ppm to 1000 ppm. Polyacrylamide formed in the fiber during aftertreatment appeared to be a formaldehyde capture. Especially by washing the aftertreated fabric, the ability to control formaldehyde release under accelerated condition was not dimimished in contrast with aftertreated with unea. It suggests that polyacrylamide can be used as a formaldehyde capture which withstand diminution from washing.