Growth of GaN Nanowires on Si Substrate Using Ni Catalyst in Vertical Chemical Vapor Deposition Reactor

남기석,서은경,박경수,Tae Yun Kim,Sang Hyun Lee,Young Hwan Mo,Hyun Wook Shim 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.1

GaN nanowires were successfully grown on Ni-coated Si substrate by direct reaction of gallium with ammonia gas in a home-made vertical tubular chemical vapor deposition reactor. The growth of GaN nanowires was uniformly observed across the Si substrate surface, but the density and average diameter of the nanowires varied along the position of the substrate surface. At the position of 5 cm above Ga source surface, the growth of GaN crystal grains was observed with few nanowires. The length of the nanowires reached several micrometers. The clear lattice fringes in HRTEM image revealed the growth of good quality hexagonal single-crystal GaN nanowires. Photoluminescence of the GaN nanowires showed a strong band edge emission at the energy position of ~3.4 eV with negligible deep level yellow emission. Field emission characteristics of the GaN nanowires showed that the turn-on field of GaN nanowires was ~7.4 V/um with a field enhancing factor b of ~555. The catalytic growth mechanism of the GaN nanowires was discussed on the basis of experimental results in this work.

가스터빈 엔진부품의 알루미나이징 기술 현황

남기석,변응선,Nam, Gi-Seok,Byeon, Eung-Seon 재료연구소 1999 機械와 材料 Vol.11 No.3

BCl₃-H₂-Ar 분위기를 이용한 2단계 플라즈마 보로나이징 특성

남기석,이구현,신평우,송요승,김배연,이득용,Nam, Kee-Seok,Lee, Gu-Hyun,Shin, Pyung-Woo,Song, Yo-Seung,Kim, Bae-Yeon,Lee, Deuk-Yong 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.6

A two-step plasma-assisted boronizing process was carried out on the AISI 1045 steel substrate to reduce the pore density introduced by a conventional single plasma boronizing process. The specimens were plasma boronized for 1 h at $650^{\circ}C$ and subsequently far 7 h at $800^{\circ}C$ in an atmosphere of $BCl_3-H_2-Ar$. The boride layer thickness was parabolic in boronizing time, a high HV reading of 1540 was found up to the boride layer thickness of $25{\mu}m$. It was found that the morphology of the boride layer prepared by the two-step boronizing process was changed from a columnar to a tooth-like structure and the pores in the borided steel were eliminated completely in comparison to those synthesized by the conventional single boronizing process, implying that it is highly applicable for enhancing the dense and compact coating properties of the low-alloy steel.

Caffeic Acid Diminishes the Production and Release of Thrombogenic Molecules in Human Platelets

남기석,남경수,박화진 한국생물공학회 2018 Biotechnology and Bioprocess Engineering Vol.23 No.6

Caffeic acid (CA) is a well-known to inhibit thrombogenic thromboxane A2 (TXA2) production, but there are no reports for the supply and usage of its precursor arachidonic acid (AA) and the release of serotonin, another thrombogenic molecule. In this study, we investigated the effect of CA on the phosphorylation of AA supply enzymes [cytosolic phospholipase A2α (cPLA2α), and phospholipase Cγ2 (PLCγ2)] and AA utilization enzymes [cyclooxygenase (COX)-1, TXA2 synthase (TXAS)] in collagen-activated human platelets. p38 MAPK phosphorylation associated with TXA2 production and c-Jun NH2-terminal kinase 1 (JNK1) phosphorylation associated with serotonin release were also determined. CA inhibited collagen-induced TXA2 production in a dose-dependent manner. It acted by counteracting the phosphorylation of AA release enzyme (PLCγ2) and AA utilization enzymes (COX-1 and TXAS) without affecting p38 MAPK and cPLA2α in collagenactivated human platelets. CA decreased collagen-released serotonin by inhibiting JNK1 phosphorylation. Therefore, our data demonstrate that CA might protect TXA2- and serotonin-mediated thrombogenesis.

일본의 기업지배구조에 대한 평가 및 전망

남기석,정호성 한국외국어대학교 국제지역연구센터 2009 국제지역연구 Vol.13 No.2

The japanese corporate governance has been recognized as one of the most efficient system from 1960's to 1980's in which business was booming. However long-term business recession forced japanese corporations to change their business practices and institutions into new ones. In this process, euro-american corporate governance system is considered as one of alternatives which will replace the traditional system. Some firms introduced euro-american corporate governance system but others still adhered to their traditional one. As a result of dichotomy in the form of corporate governance, do exist two groups which represent japanese and euro-american governance style respectively. Korea has experienced similar changes except that the reform of corporate governance was forced to be done very rapidly. The conflict between euro-american and korean traditional corporate governance practice still exists. It is apparent that it takes time for korea to have a stable governance system. So korea must keep herself searching best system strengthening business transparency and market discipline. 일본의 기업지배구조는 60년대말부터 시작하여 80년대까지 지속된 경제호황기에는 가장 효율적인 지배구조의 하나로서 인식되어 왔다. 그러나 90년대에 들어서면서부터 장기화된 경기후퇴로 기업지배구조의 근간을 이루어온 제도와 관행이 해체되기 시작하여 구미식 지배구조로의 개혁논의가 자연스럽게 대두되었다. 이후, 일본에서는 과거 제도와 충돌을 경험하는 가운데 다양한 지배구조모델을 실천적으로 도입해 왔다. 이에 따라 일본식 지배구조를 지키자는 그룹과 구미식 지배구조로의 변화를 지향하자는 그룹으로 이분화가 진행되었다. 그 후 일본기업의 통치구조는 외형적으로 일본형과 구미형이라고 하는 두 형태가 병행되며 구미식 주주자본주의로 서서히 그 무게중심이 옮겨가기 시작했다. 이러한 현상은 앞으로도 계속될 것으로 보이나 변화의 속도는 느려질 것으로 예상된다. 한편 한국도 97년 아시아금융위기이후 일본에서 추진된 지배구조개혁과 유사한 변화가 일어났지만 강제적인 규정에 의한 급격한 제도변화가 일어난 점에서 일본과 양상을 달리한다. 이 과정에서 구미식 지배구조가 절대우위라고 하는 인식이 확산되어 실제 경영관습과의 마찰이 빈번히 일어나고 있다. 일본의 예에서 보듯이 한국기업도 기업지배구조의 변화와 정착에 시간이 어느 정도 걸릴 것이라는 인식하에 경영투명성의 확보 및 시장규율의 강화를 전제로 한 한국식 지배구조를 모색해야만 할 것이다.

수소ㆍ연료전지 개발 현황과 전망

남기석 한국에너지학회 2009 한국에너지공학회 학술발표회 Vol.2009 No.-

M&A 이후의 기업지배구조 및 기업가치 변화

남기석 한일경상학회 2011 韓日經商論集 Vol.51 No.-

This paper studied the post M&A changes of corporate governance and firm value. Companies are able to enhance their corporate value by improving their corporate governance. For this purpose M&A can be measures of enhancing corporate value. This study investigates how corporate governance and value change after M&A. The result of this study is as follows. First, the overall impact of M&A on the corporate governance was not so great but post M&A public disclosure and Audit score has risen. This result means the improvement of board management and audit structure after M&A. Second, Long term effect of performance was estimated by Market-Model, CAPM, and Fama-French three factor model. In consequence abnormal return does not change uniformly and is not significant. But only positive CAAR change is significant under 5% significance level. Third, this study also investigated changes of financial variable before and after M&A. Assets and total assets turnover are shown to increase for the increasing group of CG score while does only assets for the falling group of CG score. Finally, this study shows that corporate governance and value are positively associated with firm value. This means that the improvement of board of directors and audit organization ultimately leads to post M&A increase of firm vlaue.

지 연성 근육통 (delayed onset muscle soreness) 에대한 경피선경자극 (transcutaneous electrical nerve stimulation) 의 효과

남기석,이윤주,김종만 한국전문물리치료학회 1997 한국전문물리치료학회지 Vol.4 No.3

The pW1JOse of this study was to determine the effects of transcutaneous electric머 nervestimulation (TENS) on delayed onset muscle soreness (DOMS). Twenty males performedeccentric exercise of the elbow flexor. Subjects were random1y assigned to oneof three groups: 1) a group (nl=7) that received low frequency TENS (7 Hz), 2) agroup (n"=7) that received high frequency TENS (500 Hz), 3) a control group (n3=6)that received no treatment. DOMS was induced in a standardised fashion in the nondominant elbow flexor of all subjects by repeated eccentric exercise. Treatments wereapplied immediately folllowing exercise and again at 24 hours and at 48 hours after. Subjects attended on three consecutive days for treatment and measurement of elbow flexion, extension and resting angle(universa! goniometer), and pain (Visual Analogue Scale;V AS) on a daily basis. Measurements were taken after treatment. Analysis of resultsusing repeated measures analysis of variance (ANOV A) and post hoc tests were as fol•lows: 1) there were betweengroups differences in pain va!ue at 48 hours after (p<0.05),2) one-way ANOV A with repeated measurement for pain, resting angle, flexion angleand extension angle revealed significant differences within low frequency TENS group,3) one-way ANOV A with repeated measurement for flexion angle revealed significantdífference wíthin high frequency TENS group.

Si (Ⅲ) 기판 위에 3C - SiC (Ⅲ) 박막의 성장기구

남기석,서영훈 ( Kee Suk Nahm,Young Hun Seo ) 한국화학공학회 1995 화학공학의이론과응용 Vol.1 No.2

레이저 빔을 이용한 공구강의 표면 강화

남기석,이구현 ( K . S . Nam,K . H . Lee ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.1

This work was to investigate suitable tool steels for hardening using laser beam, and was studied on carbon tool steels and alloyed tool steels such as STC3 steel, STS3 steel, STD11 steel and SKH51 steel. The surface hardness of HV700-1000 and the hardening depth of 2-2.5㎜ were obtained on STC3 steel and STS3 steel, and HV800-1000 was obtained on SKH51 steel. but STDll steel was not enough. Except STD11 steel, all steels used in this study can be hardened by laser quenching or laser rapid melting.