200 N급 GCH₄/LOx 소형로켓엔진의 형상설계와 성능시험평가 (Part II: 정상상태 지상연소시험)

김민철,김영진,김정수,Kim, Min Cheol,Kim, Young Jin,Kim, Jeong Soo 한국추진공학회 2020 한국추진공학회지 Vol.24 No.1

200 N급 기체메탄/액체산소 소형로켓엔진의 성능시험평가 수행되었다. 산화제 공급압이 증가함에 따라 연소압과 추력이 증가하였으며, 이에 따라 비추력과 특성속도 및 그 효율이 증가하였다. 특성속도는 약 90%의 성능효율로 측정되었다. 시험조건의 연소실 종횡비 변화는 추력성능에 영향을 미치지 않았다. 또한, 시험결과의 신뢰도 확보를 위하여 불확도평가를 수행하였다. A performance evaluation of the 200 N-class GCH₄/LOx small rocket engine was performed through ground hot-firing test. As a result, the combustion pressure and thrust raised with the increase of the oxidizer supply pressure, and thus the specific impulse, characteristic velocity, and their efficiency increased. The characteristic velocity was measured at about 90% performance efficiency. The change of chamber aspect ratio did not affect the performance of the rocket engine in the test condition specified. In addition, uncertainty evaluation was conducted to ensure the reliability of the test results.

악하선에 발생한 거대 타석증의 치험례

김민철,민성윤,김지용,안제영,김형곤,박광호,Kim, Min-Chul,Min, Sung-Yoon,Kim, Ji-Yong,Ahn, Je-Young,Kim, Hyung-Gon,Park, Kwang-Ho 대한악안면성형재건외과학회 2005 Maxillofacial Plastic Reconstructive Surgery Vol.27 No.1

Sialolithiasis is the most common disease caused by calculi in a salivary gland and its duct. The pain and swelling of salivary gland is a chief complaint of patients presenting. Most salivary gland calculi occur in the submandibular gland, but can also occur in the parotid gland and the sublingual gland. One giant sialolith is rarely reported, while the several cases of one or multiple sialolith in the submandibular gland have reported in the literatures. In this case, we have removed the sialolith in which perforated mouth floor along Wharton's duct and report it.

ISP 수립과 ERP 구성요소에 대한 차이 검증

김민철,김종훈,김근형,Kim, Min-Cheol,Kim, Jong-Hoon,Kim, Keun-Hyung 한국정보통신학회 2007 한국정보통신학회논문지 Vol.11 No.10

본 연구는 경영 전략, 조직, 프로세스 분석 재설계 그리고, 정보시스템 구축방안 등과 연계하여 ISP(정보전략계획) 방법론에서 ISP의 이행가능성과 효율성 측면과 관련된 실증분석을 실시하였다. 이를 통해 ISP와 ERP를 중심으로 그 범위 및 추진방안을 상호비교하고 이를 통해 효율적인 프로세스 구축 및 재설계 방안으로서 정보시스템 담당자와 의사결정자로 하여금 IP전략 수립과 프로세스 재설계 리엔지니어링 추진에 따른 체계적인 접근방법에 대한 바람직한 방향을 도출한다. 즉 ISP와 ERP의 공통점과 차이점을 바탕으로 이를 계획(Plan)과 실행(Do)의 과정으로 연계함으로써 기업의 업무프로세스를 개선하고, 정보시스템의 중장기 전략의 수립과 BPR을 함께 추진하는 것이 바람직 한 방안임을 고려하여 그 대안으로 연계모델을 제시할 필요가 있음을 알 수 있었다. This study provides the most simplified ISP method while involving management strategy, organization process analysis, redesign and information system implementation strategy to enhance the feasibility and the efficiency of ISP. So this study compared the scope and the development projects of ISP and ERP. Through this, it provided a ISP connection model as a solution to effective process implementation and redesign and conducted study to provide systematic access method according to IT strategy implementation, process redesign and reengineering.

토양정화 공법 및 단위공정에 따른 토양건강성 평가

김민철,천미희,김정선,박민정,Kim, Mintchul,Chun, Mihee,Kim, Jungsun,Park, Minjeong 한국지하수토양환경학회 2021 지하수토양환경 Vol.26 No.6

The Soil Health Index (SHI) developed by Park et al. (2021) is used to evaluate soil health on remediated soils collected from several remediation project sites and monitored the changes of SHI during the remediation process of land farming, soil washing, and thermal desorption. In the case of land farming, the soils remediated below a legal standard didn't show any significant changes in indices of SHI except the downgrade of available phosphate from medium to a low level. The SHI scores were ranged from 52 to 56 in the contaminated soil and 54 to 57 in the remediated soil. With soil washing, bulk density changed from high to a low level, and available phosphate was lowered from medium to low level. As the SHI scores were evaluated as 58 to 63 for contaminated soil and 38 to 42 for remediated soils. For thermal desorption, soil respiration rate was reduced from high to low level and SHI was scored as 50 to 51 for contaminated soils and 43 to 47 for remediated soils. Even though any abrupt changes of the SHI in remediated soils were not identified in the soils used in this study, it is expected that soil in different conditions such as types and concentrations of contaminant and soil characteristics would result in distinguished changes of the SHI. There is a room for more studies collect diverse information on SHI across the country.

차세대 원전 대형 압력용기용 고강도 SA508 Gr.4N Ni-Cr-Mo계 저합금강 개발

김민철,박상규,이기형,이봉상,Kim, Min-Chul,Park, Sang-Gyu,Lee, Ki-Hyoung,Lee, Bong-Sang 한국압력기기공학회 2014 한국압력기기공학회 논문집 Vol.10 No.1

There is a growing need to introduce advanced pressure vessel steels with higher strength and toughness for the optimizatiooCn of the design and construction of longer life and larger capacity nuclear power plants. SA508 Gr.4N Ni-Cr-Mo low alloy steels have superior strength and fracture toughness, compared to SA508 Gr.3 Mn-Mo-Ni low alloy steel. Therefore, the application of SA508 Gr.4N low alloy steel could be considered to satisfy the strength and toughness required in advanced nuclear power plants. The purpose of this study is to characterize the microstructure and mechanical properties of SA508 Gr.4N low alloy steels. 1 ton ingot of SA508 Gr.4N model alloy was fabricated by vacuum induction melting followed by forging, quenching, and tempering. The predominant microstructure of the SA508 Gr.4N model alloy is tempered martensite having small packet and fine Cr-rich carbides. The yield strength at room temperature was 540MPa, and it was decreased with an increase of test temperature while DSA phenomenon occurred at around $288^{\circ}C$. Overall transition property of SA508 Gr.4N model alloy was much better than SA508 Gr.3 low alloy steel. The index temperature, $T_{41J}$, of SA508 Gr.4N model alloy was $-132^{\circ}C$ in Charpy impact tests, and reference nil-ductility transition temperature, $RT_{NDT}$ of $-105^{\circ}C$ was obtained from drop weight tests. From the fracture toughness tests performed in accordance with the ASTM standard E1921 Master curve method, the reference temperature, $T_0$ was $-147^{\circ}C$, which was improved more than $60^{\circ}C$ compared to SA508 Gr.3 low alloy steels.

통신사업자 관점에서의 유비쿼터스 헬스 시장 규모 추정

김민철,김동수,Kim, Min-Cheol,Kim, Dong-Soo 한국정보통신학회 2008 한국정보통신학회논문지 Vol.12 No.12

현재 유비쿼터스 헬스 시스템의 기술을 뒷받침할 수 있는 비즈니스 수익 모델의 개발 및 사업 유형화의 개발은 현실적으로 필요하며, 현재는 이러한 모델 개발을 시작하는 단계라 할 수 있다. 이러한 모델 개발과 관련하여 본 연구는 통신사업자 관점에서의 u-헬스 시장 규모 추정을 실시하였다. 이를 위해 가상시장 평가법(CVM)을 이용하여 유비쿼터스 헬스 시스템의 전체 시장에서 통신사업자 추정 비율을 적용하였다. 결론적으로 유비쿼터스 비즈니스 모델이 모바일에 근거한다는 가정 하에 유비쿼터스 시장에서는 통신사업자가 초기에 다른 시장의 참여자와의 전략적 제휴를 통해 계속적으로 시장점유율을 높일 수 있을 것으로 예측할 수 있다. This paper is to estimate the market potentiality of ubiquitous health(u-health) from a viewpoint of communication companies. For this estimation, we used the CVM and adopted the ratio of ovum(2000) in overall market of u-health. That is, firstly, we assumed the u-business model was based on mobile business approach. Through this estimation, we conclude that communication companies at the initial stage of the u-health market can continuously promote the market share ratio via strategic alliance with the players participating.

AHP를 활용한 문화.관광웹 사이트 평가

김민철,Kim, Min-Cheol 한국정보통신학회 2009 한국정보통신학회논문지 Vol.13 No.9

본 연구에서는 3C_D_T 웹사이트 평가모델의 항목 구성을 접목시켜, 현재 운영되고 있는 J지역 내 문화 관광 웹 사이트 평가 요소들에 대하여 중요하게 생각하는 상대적인 중요도를 계층적 분석과정(AHP: analytic hierarchy process)을 적용하여 네티즌들이 우선적으로 고려하는 평가요소들의 상대적인 비중과 우선순위를 산출하였다. 분석 결과, 콘텐츠(Contents) 요인이 가장 중요한 요소로 나타났으며, 민감도 분석 등을 추가로 실시하여 개선 방안에 대해 제시하였다. This study calculated the relative importance between evaluation factors of websites focused on culture and tourism in J region by 3C_D_T evaluation model of website. That is, this paper was analyzed by AHP (analytic hierarchy process) and calculated the relative weights and preference. In conclusion, this study showed that content was the most important factor and proposed the improvement planning through sensitivity analysis.

기술기사 3 - 가덕해저터널 내화시험 및 현장 시공 사례

김민철,Kim, Min-Cheol (사)한국토질및기초기술사회 2011 지반과 기술 Vol.8 No.1

유헬스에서의 확장된 기술수용모형 적용 - 자기효능의 영향 중심

김민철,Kim, Mincheol 한국정보통신학회 2014 한국정보통신학회논문지 Vol.18 No.12

본 논문은 스마트 폰 기반의 유비쿼터스 헬스 시스템의 수용 여부에 영향을 미치는 건강 자기효능감 (health self-efficacy) 및 기술 자기효능감 (technology self-efficacy) 요인들의 영향 정도를 확장된 기술수용모형(TAM)을 통하여 분석하는데 목표를 두고 있다. 본 논문에서는 표본의 크기를 고려하여 제시된 연구 모형을 검증하기 위하여 PLS-SEM 방법론을 적용하였다. 분석 결과, 제시된 연구모형의 적합성을 확인하였고, 각 경로 계수의 통계적 유의성 또한 분석이 되었다. 결국, 기술 자기효능감인 스마트 폰 기기의 사용에 대한 쉬운 접근성만 높일 수만 있다면, 사용 의도의 가능성이 높아짐을 확인할 수 있었다. The aim of this study was to search for the effects of health self-efficacy and technology self-efficacy on user's behavioural intention by the extended TAM focused on smartphone base ubiquitous health system. In this research, in view of small sample size, PLS - SEM methodology was applied to this study in order to the proposed research model. As a result of analysis, the statistical fitness of proposed research model was confirmed through GoF value and the path coefficient was calculated for the hypotheses test. Finally, the implications of analysis result showed that when the use of smartphone device could be easily accessed in the side of technology self-efficacy, the possibility of user's behavioural intention also might be higher.

Photoluminescence Characterization of Dependence of Si-Nanocrystals Formation in Si-Rich SiOx on Thickness, Oxygen Content, and the Existence of a SiO2 Cap Layer

김민철,Suk-Ho Choi,Kyung Joong Kim,Yong Min Park 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.6

Silicon-rich SiO$_x$ layers were fabricated in an ion beam sputtering deposition system by varying the thickness and the oxygen content ($x$) from 6 to 20 nm and from 1.0 to 1.8, respectively. The samples were subsequently annealed at 1100 $^\circ$C for 20 min to form Si nanocrystals (Si NCs) and were hydrogenated at 650 $^\circ$C for 1 h under a hydrogen gas flow to passivate the Si dangling bonds. High-resolution transmission electron microscopy (HRTEM) images demonstrated the existence of Si NCs. For $x \leq 1.2$, the photoluminescence (PL) peaks showed small blueshifts with increasing layer thickness for thinner samples, but the peak shifts became almost saturated with further increases in the layer thickness. For $x \geq 1.4$, the PL showed monotonic redshifts as the layer thickness was increased, resulting from the dominance of PL from the larger NCs in the bulk region of SiO$_x$. The SiO$_2$-capped samples were blue-shifted compared to the uncapped ones, which is consistent with the effect of the increase in x due to the mixing of the SiO$_x$ and the SiO$_2$ layers. Possible growth and luminescence mechanisms for the Si NCs are proposed to explain the experimental results.