플라즈마 침탄 공정을 이용한 SCM415강의 표면 경화 특성

김대욱,김동원,임병수,김석범,Kim, Dae-Wook,Kim, Dong-Won,Lim, Byeong-Soo,Kim, Seuk-Buom 한국재료학회 1998 한국재료학회지 Vol.8 No.8

현재 자동차용 소재 및 기계부품에 폭넓게 이용되는 SCM415강의 플라즈마 침탄 특성을 연구하기 위해 가스조성, 압력, 전류밀도, 온도 및 시간을 변수로 사용하였다. 가스조성의 경우 저합금강에서는 수소 가스 효과보다 메탄가스에 의해 주로 침탄특성이 좌우되며 메탄가스 100%일 때 시편 내의 모든 방향에서 경화층 분포가 일정하고, 최대의 유효경화깊이를 얻을 수 있었다. 가스압력이나 플라즈마 전압이 상승할 때 전류밀도가 상승하게 되는데, 이에 따라 최표면의 탄소농도가 증가되어 강의 유효경화깊이는 증대되었다. 침탄 온도일 경우 적어도 85$0^{\circ}C$이상되어야 유효경화깊이를 얻을 수 있었고, 온도가 상승할수록 유효경화깊이의 증가를 나타내어 침탄 효과가 우수하였다. 탄소의 확산 깊이는 침탄 시간의 제곱근에 비례하는 것으로 나타났다. 플라즈마 치탄한 강의 피로강도를 평가한 결과 열처리하지 않은 시편이나 재가열처리한 시편에 비해 높은 피로강도를 나타내었다. The influence of plasma carburizing process on the surface hardness of SCM415 low-alloy steel (0.15% C) was investigated under the various process conditions of gas composition. gas pressure, plasma current density. temperature and time. The effective case depth was found to depend on the amount of methan gas containing carbon. thus the deepest case depth and the uniform hardeness were obtained with the 100% methan gas. The case depth increased with the plasma current density. The effective plasma carburizing temperature of SCM415 steel was found to be higher than 85$0^{\circ}C$, and the case depth was proportional to the square root of carburizing time under the same current density. The bending fatigue strength of the plasma carburized specimen is' higher than those of as- received specimen or reheat-quenched specimen.

의학전문대학원 학생들의 수면과 심리적 요인

김대욱,김성곤,김지훈,양영희,정우영,이진성,Kim, Dae-Wook,Kim, Sung-Gon,Kim, Ji-Hoon,Yang, Young-Hui,Jung, Woo-Young,Lee, Jin-Seong 대한수면의학회 2013 수면·정신생리 Vol.20 No.2

목 적 : 의학전문대학원 학생들은 과도한 학업으로 인해 수면 시간이 부족하고 수면의 질이 낮다고 알려져 있다. 본 연구는 의학전문대학원 학생의 수면 양상 및 이와 연관이 있을 것으로 생각되는 심리적 문제를 조사하였다. 방 법 : 부산대학교 의학전문대학원 1~4학년 학생 352명을 대상으로 수면 양상, Pittsburgh sleep quality index(PSQI), Epworth sleepiness scale(ESS), global assessment of recent stress scale(GASS), the center for epidemiologic studies-depression scale(CES-D), and Moudsley obsessive-compulsive inventory(MOCI)를 조사하였다. 두 군간 연속변수 비교에는 독립 t-검정, 비연속비교는 ${\chi}^2$-검정, 두 변수간의 상관관계는 Pearson 상관분석, 그리고 세 군 이상 비교에는 ANOVA를 이용하였다(p<0.05, 양측검정). 결 과 : 평일 수면시간 5시간 36분, 주말 수면시간 7시간 39분으로, 주말 수면시간이 더 길었다(t=15.94, p<0.001). 취침 시각은 평일 0 : 49, 주말 1 : 34으로 주말에 더 늦게 취침하였고(t=-5.23, p<0.001), 기상 시각은 평일 6 : 58,. 주말 9 : 30으로 주말에 더 늦게 기상하였다(t=-24.48, p<0.001). PSQI는 ESS(r=0.383, p<0.001), GASS(r=0.326, p<0.001), CES-D(r=0.393, p<0.001), 그리고 MOCI 점수(r=0.247, p< 0.001)와 양의 상관관계를 보였지만, 성적과는 상관관계를 보이지 않았다(r=0.072, p=0.228). 학년이 높을수록 PSQI, GASS, CES-D, MOCI 점수가 낮았다(p<0.05). 결 론 : 의학전문대학원생들의 수면의 질은 낮았고 수면 시간은 부족하였다. 수면의 질은 주간졸림, 우울감, 스트레스, 강박 성향과 연관성이 있었다. Introduction: Although it is well known that medical students are not getting an adequate amount of sleep, there have been only a few studies on the sleep patterns of medical students and the related factors. Therefore, the present study aimed to investigate the medical students' sleep patterns and the related factors. Methods: A questionnaire package was administered to the $1^{st}$ to $4^{th}$ year medical students at one medical school. It consisted of questions asking about their lifestyles as well as Pittsburgh sleep quality index (PSQI), Epworth sleepiness scale (ESS), global assessment of recent stress scale (GASS), the center for epidemiologic studies-depression scale (CES-D), and Moudsley obsessive-compulsive inventory (MOCI). A total of 352 students (206 males and 146 females) responded to the survey and the result was analyzed using the independent t-test, the chi-square test, the paired t-test, Pearson's correlation and ANOVA. p-values of less than 0.05 were considered statistically significant in analyses. Results: The weekend bedtime was significantly delayed (0 : 49 on weekday ; 1 : 34 on weekend ; t=-5.23, p<0.001), the weekend rise time was delayed (6 : 58 on weekday ; 9 : 30 on weekend ; t=-24.48, p<0.001) and the total sleep time was increased on weekends (5 : 36 on weekday ; 7 : 39 on weekend ; t=15.94, p<0.001). The PSQI score of all subjects was 6.43{\pm}2.64. PSQI was positively correlated with ESS (r=0.383, p<0.001), GASS (r=0.326, p<0.001), CES-D (r=0.393, p< 0.001), and MOCI (r=0.247, p<0.001), but not with GPA (r=0.072, p=0.228. The more senior students had lower PSQI, GASS, CES-D, and MOCI score (p<0.05). Conclusion: Medical students were experiencing a lack of sleep during weekdays as they have a later bedtime and earlier rise time, and consequently had more hours of sleep on weekends. Overall, the medical students were experiencing poor sleep quality and sleep deprivation. Poor sleep quality is associated with psychological problems (daytime sleepiness, stress, depression, and obsessive tendency).

만성 외측 발목 불안정

김대욱,성기선,Kim, Dae-Wook,Sung, Ki-Sun 대한족부족관절학회 2018 대한족부족관절학회지 Vol.22 No.2

Chronic lateral ankle instability is a major complication of acute ankle sprains, which can cause discomfort in both daily and sports activity. In addition, it may result in degenerative changes to the ankle joint in the long term. An accurate diagnostic approach and successful treatment plan can be established based on a comprehensive understanding of the concept of functional and mechanical instability. The patients' history and correct physical examination would be the first and most important step. The hindfoot alignment, competence of the lateral ligaments, and proprioceptive function should be evaluated. Additional information can be gathered using standard and stress radiographs. In addition, concomitant pathologic conditions can be investigated by magnetic resonance imaging. Conservative rehabilitation composed of the range of motion, muscle strengthening, and proprioceptive exercise is the main treatment for functional instability and mechanical instability. Regarding the mechanical instability, surgical treatment can be considered for irresponsible patients after a sufficient period of rehabilitation. Anatomic repair (modified $Brostr{\ddot{o}}m$ operation) is regarded as the gold standard procedure. In cases with poor prognostic factors, an anatomical reconstruction or additional procedures can be chosen. For combined intra-articular pathologies, arthroscopic procedures should be conducted, and arthroscopic lateral ligament repair has recently been introduced. Regarding the postoperative management, early functional rehabilitation with short term immobilization is recommended.

KC-100 소형항공기 추진계통 비행시험 사례연구

김대욱,강성수,김찬조,우봉길,Kim, Dae-wook,Kang, Sung-soo,Kim, Chan-jo,Wu, Bong-gil 항공우주시스템공학회 2013 항공우주시스템공학회지 Vol.7 No.2

The conformity of propulsion system need to be evaluated thorough the flight test because it is an important part of the airplane to ensure the flight safety. In the small airplane development, the flight test according to KAS(Korean Airworthiness Standards) Part 23 is one of the ways to verify compliance in terms of satisfactory aircraft/engine/propeller integration. This thesis introduces means of verifying the compliance and test requirement of KAS Part 23 for the conformity of the propulsion system in small airplane. It also describes procedures and methods of propulsion system flight test through KC-100 airplane project.

The Effects of Ownership, Regulation and Marked Structure on the Pricing: Evidence from the U.S. Electricity and Natural Gas Industries

김대욱,Kim, Dae-Wook 한국환경경제학회 2008 자원·환경경제연구 Vol.17 No.4

본 논문은 미국의 전력산업과 천연가스산업이 본격적인 구조변화를 시작한 1999년부터 2001년까지의 자료를 사용하여 제도적인 변화가 시장가격에 미친 영향을 분석한다. 이를 위해 가격에 영향을 미치는 비용과 수요를 제어한 축약형태(reduced forms) 모형의 회귀분석을 사용하여, 본 논문은 제도적인 요소 중에서 구체적으로 어떠한 요소가 가격결정과 긴밀히 연결되어 있는지를 추정한다. 분석결과에 의하면 투자자 소유의 기업의 전력가격이 공기업에 비해서 보다 높은 것으로 추정되었다. 더불어 전기와 천연가스 2개의 상품을 공급하는 기업은 1개의 재화를 제공하는 기업에 비해서 두 재화를 보다 저렴한 가격으로 공급하는 규모의 경제를 가지고 있는 것으로 나타났다. 마지막으로 천연가스 기업간의 합병은 합병이 일어나지 않은 지역에 비해서 가스요금의 수준이 보다 높은 것으로 나타났다. In this paper, we examine the institutional prices differences in the electricity and natural gas industries using unbalanced panel data from 1999 to 2001. The changing market structures following deregulation in both markets allow us to examine the institutional prices differences by ownership type, market structure and merger activities. Estimating the reduced form, after controlling both intrinsic characteristic (marginal costs) and external factors (demand), allows us to identify the extent to which specific factors are correlated with the price. Furthermore it allows us to identify systematic institutional price differences in both electricity and natural gas markets. Our estimation results suggest that the private firms in electricity markets are associated with higher prices than public firms after controlling for demand and cost. We further find that dual-product firms in the natural gas industry and the electricity industry are associated with lower rates than single product firms. These results provide a weak evidence of economies of scope in the dual-product firms. Our results finally suggest that merger activities in natural gas markets are associated with higher rates.

교육부 중심 0-5세 유아학교 모델(안)의 단계별 정책 방향과 과제: 설립주체와 교사고용의 관점을 중심으로

김대욱,박창현,Kim, Dae-Wook,Park, Chang-Hyun 국제문화기술진흥원 2022 The Journal of the Convergence on Culture Technolo Vol.8 No.6

The Minister of Education has officially announced that the Ministry of Education will promote the integration of early childhood education and care. The core of integration is the integration of kindergartens and child care centers, and it is necessary to develop the specific model, so this study was conducted. After the discussion of integration, the discussion has focused on the "Young Children School", and there were differences of opinion on specific issues. Therefore, this study was conducted to propose the specific model for the "Young Children School" after kindergartens and child care centers were integrated with the Ministry of Education. The research question is to find out what the model of the 0-5-year-old young children school model centered on the Ministry of Education. In this study, assuming that integration of early childhood education and care was realized, a plan for integrating early childhood education institutions by type of establishment was proposed. As a conclusion of this study, first, a model of a 0-5-year-old young children school centered the Ministry of Education under the government responsibility is required. Second, a detailed school model that reflects the characteristics of each type of establishment should be developed. Finally, specific measures such as the reform of the teacher training system, the after-school course operation model, and the integration plan with the office of education and local governments should be presented during the young children school system.

기초지방자치단체 민주시민교육조례 도입의 영향요인 분석

김대욱 ( Kim Dae-wook ) 한국지방행정연구원 2022 地方行政硏究 Vol.36 No.2

최근들어 우리나라 지방자치단체의 민주시민교육에 대한 관심이 늘어나고 있다. 그러나 기존 연구는 광역지방자치단체에 초점을 두고 제도적 활성화 방안을 모색하고 있으나 기초지방자치단체에 대한 관심 및 도입의 영향요인에 대한 연구는 미흡하다. 이에 본 연구에서는 연구의 공백상태에 있는 기초지방자치단체 민주시민교육조례 도입의 영향요인을 실증적으로 분석하였다. 이를 위해 이론적 검토를 통해 상위정부요인, 정치적요인, 경제적요인, 사회적요인, 지방자치단체유형요인을 영향요인으로 도출하였다. 분석은 7기 기초지방자치단체를 대상으로 로지스틱 분석방법을 활용하였다. 분석결과 경제적요인인 재정자립도, 사회적요인인 시민단체수, 지방자치단체유형요인인 도시유형이 유의미한 영향요인인 것으로 나타났다. 이러한 결과는 민주시민교육조례가 가진 정치적 성격에 의한 것으로 추론되며 해석과 토론을 통해 보다 풍부한 논의를 진행하였다. Recently, interest in democratic citizenship education of local governments in Korea has been increasing. However, existing studies mostly focus on metropolitan local governments and seek institutional revitalization plans, but studies on the factors influencing the introduction and interest in municipal governments are insufficient. Therefore, this study empirically analyzed the factors influencing the introduction of the municipal governments’ democratic citizenship education ordinance. To this end, through theoretical review, higher government factors, political factors, economic factors, social factors, and local government type factors were derived as influencing factors. For the analysis, the logistic analysis method was used for the 7th local government. As a result of the analysis, it was found that financial independence as an economic factor, the number of civic groups as a social factor, and the city type as a type factor of local government were significant influencing factors. These results are inferred to be due to the political nature of the democratic citizenship education ordinance, and richer discussions were conducted through interpretation and discussion.

KT-1P 항공기 NVIS 시험평가 사례연구

김대욱(Dae-wook Kim),신택종(Taek-jong Shin),김찬조(Chan-jo Kim),우봉길(Bong-gil Wu) 항공우주시스템공학회 2015 항공우주시스템공학회 학술대회 발표집 Vol.2015 No.11

광용적맥파(PPG)를 이용한 사용자 감성 지수 예측 시스템 개발

김대욱(Dae-wook Kim),이종하(Jong-ha Lee) 대한전자공학회 2015 대한전자공학회 학술대회 Vol.2015 No.6

Quantitative evaluation of sensibility index is important to prevent stress-related disorders. Photo plethysmography (PPG) is a simple noninvasive method to monitor peripheral circulation, and provides heart rate variability index. The participants rested by sitting on a chair for 3 min 30 seconds. They then performed a computerized version of the Stroop color-word conflict test (CWT) for 3 min 30 seconds. Finally, they rested for 3 min 30 seconds. PPG was recorded throughout the experiment. The participants completed a brief form of the Profile of Mood States (POMS) questionnaire before and after the test. During CWT test, HRV and negative sensibility index were reduced. It means they are positive correlation. The physiological indices derived from PPG were changed by sensibility index. Our results indicate that PPG is one of the easiest methods to evaluate sensibility index quantitatively.

가격상한 제도 하에서 전략적 기업의 행위 분석

김대욱 ( Dae Wook Kim ),김종호 ( Jong Ho Kim ) 韓國産業組織學會 2007 産業組織硏究 Vol.15 No.1