SHS 공정에 의해 제조된 Mo_xW_1-xSi₂ 발열체의 열화메커니즘

이동원,이상헌,김용남,이성철,구상모,오종민,Lee, Dong-Won,Lee, Sang-Hun,Kim, Yong-Nam,Lee, Sung-Chul,Koo, Sang-Mo,Oh, Jong-Min 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.10

The degradation mechanism of $Mo_xW_{1-x}Si_2$ ultrahigh-temperature heating elements fabricated by self-propagating high-temperature synthesiswas investigated. The $Mo_xW_{1-x}Si_2$ specimens (with and without post-annealing) were subjected to ADTs (accelerated degradation tests) at temperatures up to $1,700^{\circ}C$ at heating rates of 3, 4, 5, 7, and $14^{\circ}C/min$. The surface loads of all the specimen heaters were increased with the increase in the target temperature. For the $Mo_xW_{1-x}Si_2$ specimens without annealing, many pores and secondary-phase particles were observed in the microstructure; the surface load increased to $23.9W/cm^2$ at $1,700^{\circ}C$, while the bending strength drastically reduced to 242 MPa. In contrast, the $Mo_xW_{1-x}Si_2$ specimens after post-annealing retained $single-Mo_xW_{1-x}Si_2$ phases and showed superior durability after the ADT. Consequently, it is thought that the formation of microcracks and coarse secondary phases during the ADT are the main causes for the degraded performance of the $Mo_xW_{1-x}Si_2$ heating elements without post-annealing.

Effect of post annealing on the microstructure, mechanical properties, and failure of Mo_xW_1-xSi₂ heaters produced by self-propagating high-temperature synthesis

Cho, Myung-Yeon,Lee, Sung-Chul,Park, Chulhwan,Lee, Daeseok,Koo, Sang-Mo,Moon, Kyoung-Sook,Lee, Dong-Won,Oh, Jong-Min Elsevier 2019 INTERMETALLICS Vol.110 No.-

<P><B>Abstract</B></P> <P>High-performance tungsten molybdenum disilicide (Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB>) heating elements were prepared using a self-propagating high temperature synthesis process. The effect of post annealing on the degradation behavior of the alloy was experimentally investigated. Increasing the attrition milling time up to 20 min during powder preparation resulted in Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters with the highest density, which increased the fracture strength compared to samples with shorter attrition times. Such samples were annealed and evaluated as heating elements using accelerated degradation tests and failure analysis in order to compare their structural characteristics and flexural strength with as-fabricated samples. The annealed Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heater showed a relatively dense structure with few pores and no secondary phases, apart from a SiO<SUB>2</SUB> layer. This favorable structure prevented bubble formation, which can result in fracturing of the heater, as revealed by evaluation at high temperatures with various heating rates. The flexural strength of the annealed specimen was 2.5-times higher than that of the as-fabricated specimen, which was attributed to removal of secondary phases during annealing. Failure time and surface load analyses were used to investigate the fracture mechanism of the Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters in detail at 1790 °C by quantifying bubble formation and the presence of secondary phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Self-propagating high temperature synthesis of Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters demonstrated. </LI> <LI> Post-annealed Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters were highly dense, with good flexural strength. </LI> <LI> Bubble formation (the main cause of fracture) suppressed at ultra-high temperature (above 1700 °C). </LI> <LI> Surface load, failure time, and bubble formation used to study fracture mechanisms. </LI> </UL> </P>

SHS 공정으로 제조된 Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si₂ 발열체의 가속수명시험과 고장분석

이동원(Dong-Won Lee),이상헌(Sang-Hun Lee),김용남(Yong-Nam Kim),이희수(Heesoo Lee),이성철(Sung-Chul Lee),구상모(Sang-Mo Koo),오종민(Jong-Min Oh) 한국전기전자학회 2017 전기전자학회논문지 Vol.21 No.3

고온자전합성과 후열처리 공정으로 MoxW1-xSi₂ 발열체를 제조하였다. MoxW1-xSi₂ 발열체의 신뢰성을 검증하기 위해 가속수명시험을 수행하였으며, 수명시간을 Minitab 프로그램으로 추정하였다. 또한, 가속수명시험 후의 MoxW1-xSi₂ 발열체의 고장분석을 전기적과 구조적 특성으로부터 수행하였다. 그 결과, MoxW1-xSi₂ 발열체의 지배적인 고장 유형은 발열체 내부의 크랙 형성과 SiO₂ 보호층의 박리임을 확인하였다. MoxW1-xSi₂ heaters were fabricated by self-propagating high-temperature synthesis (SHS) process and post sintering process. To validate the reliability of the MoxW1-xSi₂ heaters, the accelerated life test (ALT) was conducted, and then lifetime to MoxW1-xSi₂ heaters was estimated by using Minitab programs. Also, the failure analysis of MoxW1-xSi₂ heaters after ALT was performed through electrical and structural properties. As the results, it was confirmed that the dominant failure mode of MoxW1-xSi₂ heaters is the crack formation in heaters and the delamination of protective SiO₂ layers.

Over-expression of a seed specific hevein-like antimicrobial peptide from Pharbitis nil enhances resistance to a fungal pathogen in transgenic tobacco plants

Koo, Ja-Choon,Chun, Hyun-Jin,Park, Hyeong-Cheol,Kim, Min-Chul,Koo, Yoon-Duck,Koo, Seong-Cheol,Ok, Hyun-Mi,Park, Soo-Jeong,Lee, Sung-Ho,Yun, Dae-Jin,Lim, Chae-Oh,Bahk, Jeong-Dong,Lee, Sang-Yeol,Cho, Mo Plant molecular biology and biotechnology research 2002 Plant molecular biology and biotechnology research Vol.2002 No.-

Two hevein-like peptides from the seed of Pharbitis nil, designated Pharbitis nil antimicrobial peptide 1 (Pn-AMP1) and Pn-AMP2, had been purified previously. Both exhibit potent in vitro antifungal activity against a broad spectrum of phytopathogenic fungi. We now report the isolation of two cDNA clones, designated pnAMP-h1 and pnAMP-h2, and the corresponding genomic clones encoding these protein suggests that the peptides are produced as a prepropeptide consisting of and N-terminal signal peptide, the mature protein and C-terminal domains. The transcripts of the two genes are accumulated seed-specifically, and the maximum transcripts are observed in the mid-to-late stage of seed development. Constitutive over-expression of the pnAMP-h2 cDNA in transgenic tobacco under the control of the cauliflower mosaic virus 35S promoter conferred enhanced resistance against the oomycete Phytophthora parasitica, the causal agent of black shank disease. Thus the Pn-AMPs may play a role in the protection of seeds and may

Locally Advanced, Unresectable Pancreatic Cancer Treated by Stereotactic Radiation Therapy

Chul-Won Choi(최철원),Mi-Sook Kim(김미숙),Chul-Koo Cho(조철구),Seong-Yul Yoo(류성열),Kwang-Mo Yang(양광모),Hyung-Jun Yoo(유형준),Dong-Han Lee(이동한),Young-Hoon Ji(지영훈),Chul-Ju Han(한철주),Jin Kim(김진),Young-Han Kim(김영한) 대한방사선종양학회 2006 Radiation Oncology Journal Vol.24 No.1

목 적: 국소적으로 진행된, 절제 불가능한 췌장암 치료에 있어 고식적 방사선 치료와 비교하여 CyberKnife (CK)를 이용한 정위 방사선 치료의 생존율 및 급성 독성에 대해 분석하고자 하였다. 대상 및 방법: 2003년 4월부터 2004년 4월까지의, Eastern Cooperative Oncology Group (ECOG) 활동도 3 이하이며 CT 및 PET/CT로 평가하여 원격 전이 없는 국소 진행된 췌장암 환자 19명을 대상으로 하였다. 대상 환자는 점차 방사선량을 증가시키는 방법으로 33 Gy, 36 Gy, 39 Gy를 3분할로 각각 6명, 4명, 9명에서 CK를 이용한 정위 방사선 치료를 시행하였으며, 생존율 및 Radiation Therapeutic Oncology Group (RTOG) acute radiation morbidity criteria에 의한 위장관 독성을 분석하였다. 또한 나이, 성별, ECOG 수행 점수, 항암 치료,우회로 조성술(bypass surgery) 여부, 방사선량, CA19-9, 계획용 표적 체적(planning target volume, PTV), CT상 주위 장기 및 혈관 침범 여부 등을 Log Rank test를 이용하여 예후 인자를 평가하였다.결 과: 본 연구에서 중앙 생존 기간은 11개월, 1년 생존율은 36.8%였다. 추적 조사 기간 중(범위 3∼20개월, 중앙값 10개월) 유의한 위장관 급성 독성은 관찰되지 않았다. 단일 인자 분석에서 계획용 표적 체적만이 유의한 예후 인자로 80 cc 이하인 경우가 80 cc 이상인 경우보다 생존율이 높았으며(p-value<0.05), 나이, 성별, ECOG 수행 점수, 항암 치료, 우회로 조성술, CA19-9 수치, 주위 장기 및 혈관 침범 여부 등에서는 통계적으로 유의한 차이를 보이지 않았다. 다인자 분석에서는 65세 이하인 경우와 PTV 80 cc 이하인 경우에서 생존율이 높았다. 결 론: 고식적 방사선 치료, 고선량 입체조형 방사선 치료(high dose conformal radiation therapy), 수술 중 방사선 치료(intraoperative radiation therapy) 또는 세기 조절 방사선 치료(intensity modulated radiation therapy, IMRT)를 이용한 최근의 결과와 비교하여 CK를 이용한 정위 방사선 치료는 생존율 측면에서 비슷하거나 나은 결과를 보였다. 또한 심각한 부작용은 관찰되지 않았으며 짧은 기간의 치료로 환자에게 편의를 제공할수 있어 결과적으로 삶의 질을 향상시킬 수 있을 것이다. 따라서, 이 새로운 치료 방법은 국소 진행된, 절제불가능한 췌장암 환자에서 심각한 부작용 없는 효과적인 치료가 될 것으로 생각된다. 또한 계획용 표적 체적은 CK 치료의 유용한 예후 인자로 사용될 것이다. Purpose: In order to find out whether stereotactic radiation therapy (RT) using CyberKnife (CK) could improve survival rate and lower acute toxicity compared to conventional RT. Materials and Methods: From April 2003 through April 2004, 19 patients with Eastern Cooperative Oncology Group (ECOG) performance status ≤3 and locally advanced pancreas cancer without distant metastasis, evaluated by CT or PET/CT, were included. We administered stereotactic RT consisting of either 33 Gy, 36 Gy or 39 Gy in 3 fractions to 6, 4 and 9 patients, respectively, in an effort to increase the radiation dose step by step, and analyzed the survival rate and gastrointestinal toxicities by the acute radiation morbidity criteria of Radiation Therapeutic Oncology Group (RTOG). Prognostic factors of age, sex, ECOG performance score, chemotherapy, bypass surgery, radiation dose, CA19-9, planning target volume (PTV), and adjacent organ and vessel invasion on CT scan were evaluated by Log Rank test. Results: The median survival time was 11 months with 1-year survival rate of 36.8%. During follow-up period (range 3∼20 months, median 10 months), no significant gastrointestinal acute toxicity (RTOG grade 3) was observed. In univariate analysis, age, sex, ECOG performance score, chemotherapy, bypass surgery, radiation dose, CA19-9 level, and adjacent organ and vessel invasion did not show any significant changes of survival rate, however, patients with PTV (80 cc showed more favorable survival rate than those with PTV>80 cc (p-value<0.05). In multivariate analysis, age younger than 65 years and PTV>80 cc showed better survival rate. Conclusion: In terms of survival, the efficacy of stereotactic radiation therapy using CK was found to be superior or similar to other recent studies achieved with conventional RT with intensive chemotherapy, high dose conformal RT, intraoperative RT (IORT), or intensity modulated RT (IMRT). Furthermore, severe toxicity was not observed. Short treatment time in relation to the short life expectancy gave patients more convenience and, finally, quality of life would be increased. Consequently, this could be regarded as an effective novel treatment modality for locally advanced, unresectable pancreas cancer. PTV would be a helpful prognostic factor for CK.

Dealing with a Dynamic Economic Environment through International Collaboration

Chul-Mo KOO(구철모) 조선대학교 지식경영연구원 2012 기업과 혁신연구 Vol.5 No.3

본 연구는 한국과 인도네시아 경제적 교류협력을 개괄적으로 분석한 논문으로 자원의 보국인 인도네시아와 기술적 능력을 갖추고 있는 한국과 글로벌 협력의 현재상황과 향후 발전방안은 소개한 연구이다. 한국은 아시아에서 경제적 발전모델로 인도네시아의 발전모델로서 모방 또는 배움의 대상이 되고 있다. 특히 전자제품, 의류 및 직물에 완제품에 뛰어난 경쟁력과 기술소유를 갖고 있는 반면 인도네시아는 천연자원인 오일과 고무 그리고 가스유전등이 풍부한 나라로써 우리에게 자원개발의 동기를 충분이 제공하고 있는 나라이다. 상호 보완적인 경제적 기반구조하에 상호협력적인 모델이 절실이 요구되고 있는 이유도 이때문이라고 볼 수 있다. 본 연구의 시사점은 경제적 요인을 찾아내어 두 나라에서 상호 필요로 하는 요인과 효과를 규명하여 두 나라의 상호협력 관계가 더욱 진전되고 가능성 있는 비즈니스 기회를 모색하는데 있다고 볼 수 있다. This study, we investigated the existing collaboration between South Korea and Indonesia. The purpose of this study is to underscore the significance of the global collaboration between South Korea and Indonesia and to indicate how their cooperation may increase competitiveness under this global turmoil. The study of South Korea, as one of NIE countries is a producer and exporter of electronic, garment, and textiles, and Indonesia, as one of developing countries in East Asia, is a main producer of oil & gas and natural gas & its derivatives(economywatch, 2009) may strengthen the partnership idea between these countries. Insights identifying the economic components that contribute to the development of the nations would be useful as these factors under the co-control of both countries. The aim of this paper is to contribute to the better understanding of the economic issue between two countries.

Productivity vs. Quality of Software Development : An Empirical Study of the ISBSG Release 8

Chul-Mo Koo,Dong-Jin Park 한국디지털정책학회 2010 디지털융복합연구 Vol.8 No.1

진화심리학 이론에 의한 정보기술 진화의 이론적 접근에 연구

구철모(Koo, Chul-Mo),이대용(Lee, Dae-Yong) 대한경영학회 2011 大韓經營學會誌 Vol.24 No.5

소셜네트워크 서비스의 이용동기와 성과에 대한 실증연구

구철모(Chul Mo Koo),전유희(You Hee Joun),정남호(Nam Ho Chung) 한국경영학회 2012 經營學硏究 Vol.41 No.5

In domestic, Social Network Service(SNS) have grown rapidly and increasingly attracting the attention of academic and industry researchers Millions of users are trying to integrated SNS sites into their daily lives and practices. Almost of all sites support to maintain pre-existing social networks and connect unknown strangers depending on shared interests, political views, or enjoyable activities, and other stuffs. There contains diverse racial, sexual, religious, or national people beyond the local and limited geographic regions compared with the previous Internet based social sites. Current SNS site incorporate the creation of contents, dissemination of information & knowledge, and commercial purpose such like Google advertisement using their users. As fast developing digital devices including smartphone, tablet PC, internet based blogging, and photo and video clips, scholars desperately have began to study regarding diverse issues, which are related to contents that people create via network technologies. The first social network site was SixDegrees.com in 1997, which create profiles and surf the friends lists. Second, Ryze.com help people leverage their business networks in 2001, but it failed to achieve mass popularity. Third, a professional site such as LinkedIn focus on business people whom can connect strangers based on shared interests. MySpace differentiated itself by regularly adding features based on user demand that can make personalized pages. Unlike other SNSs, Facebook was designed to support exclusive college networks at first; they use Harvard University`s email address for finding social network. Currently, there is a big trend that people use SNSs as a tool for maintain pre-existing network, creating new people socially, and at the same time, explicitly find some business opportunities using personal and unlimited public networks. Like this, individual consciously express themselves in an online space, so called, self-presentation. The self-presentation and self-disclosure are mainly studying on offline setting in early stages, which individual convey an impression to others that are expressed to own interest to others. Thus, individuals expect to meet other people and are trying to behave self-presentation engaging in opposite partners accordingly. As developing SNSs, individuals are motivated to disclose self-disclosures of open and honest using diverse cues such as verbal and nonverbal and pictorial and video files to their friends as well as passing strangers. Virtual context, self-presentation seems different compared with face-to-face context. In the time and realm of SNSs, social users look for self-impression by posting text messages, pictures, video files. Under the digital environments, people interact to work, shop, learn, entertain, and be played. SNS provides increasingly the kinds of intention and behavior in online. Typically, self-presentation is the intentional and tangible component of identity. At SNS, people try to engage in others via a desired impression, which can maintain through performing coherent and complementary communications including displaying signs, symbols, brands made of digital stuffs (information, interest, pictures, etc.). In marketing area, consumers traditionally show self-present daily as they selct clothes, hairstyles, automobiles, logos, and so on, to impress others in any given context in a shopping mall or opera. So the self-presentation is contextual based on a specific setting, whereas SNS initiates people to self-present including pre-existing and stranger network beyond regional locality. So far, on offline site`s self-presentation would be very different from online site and would produce significant insights into user motives and behaviors in which SNS space, with a variety of digital symbols. Closely related to the concept of self-presentation, self-disclosure is the propensity an individual wish to reveal its personal information to others. SNS enables

조직의 흡수역량이 기업성과에 미치는 영향에 대한 실증연구

구철모(Chul Mo Koo),최정일(Jeong Il Choi) 한국경영학회 2008 經營學硏究 Vol.37 No.3

Absorptive capacity has been identified as a factor to affect on firm performance; however, there are few studies to identify its antecedents extensively from the external factors to the internal factors. Organizational absorptive capacity has focused on information flow and knowledge acquisition among the departments or the external firms, which has centered on innovation theory. This paper examined the mediation effect of organizational absorptive capacity between its antecedents such as environment factors, managerial attitude, IT usage, and organizational resource and the firm`s performance. This study collected the 126 firm level data through survey and tested research model and hypotheses by LISREL analysis. We found that managerial attitude, IT usage, and organizational resource affect organizational absorptive capacity, in turn, lead firm`s performance. Interestingly, managerial attitude influences organizational absorptive capacity but does not affect firm`s performance. This paper shows that the organizational absorptive capacity has the mediation effect between its antecedents and the firm`s performance and that it has the direct effect on the firm performance.