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).

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.

염해 및 한발에 대한 보리의 생화학적 반응 - 항산화효소 활성 및 아미노산 함량의 변화

김대욱,허화영,서세정,이영호,김시주,Kim, Dea-Wook,Heo, Hwa-Young,Suh, Sae-Jung,Lee, Yeong-Ho,Kim, Si-Ju 한국작물학회 2006 Korean journal of crop science Vol.51 No.suppl1

To differentiate barley responses to drought and salt stress, barley seedlings at the second leaf stage were treated with 218 mM NaCl and 29.5% PEG6000 iso-osmotic to 218 mM NaCl for 6 days. Shoot fresh weight and leaf relative water content of barley seedlings were more reduced by drought compared to salt stress. Hydrogen peroxide content increased under both stress conditions, but its accumulation was more severe at 6 days after salt stress. The activity of ascorbate peroxidase, glutathione reductase (GR) and catalase (CAT) was enhanced until 4 days after salt stress. On the other hand, the activity of GR and CAT increased gradually until 6 days after drought. Among the amino acids measured in this study, the accumulation of glycine, arginine and GABA (${\gamma}-aminobutyric$ acid) was lower under salt stress than drought. However, considerably larger amount of proline was accumulated by salt stress. It is concluded that the antioxidant enzymes activity and amino acid content of barley seed-lings were differently regulated in response to the isoosmotic condition of salt and drought stress. 본 연구는 삼투포텐셜이 동일한 NaCl과 PEG6000 용액을 사용하여 염해와 한발에 대한 보리의 생화학적 반응을 검토하였으며 시험결과를 요약하면 다음과 같다. 1. 보리의 지상부 생육 및 보리 잎의 상대수분함량은 염해보다 한발에 의해서 더욱 감소하였다. 2. 과산화수소의 발생은 염해처리 후 6일에 한발보다 27.5% 많았으며, 영해처리 후 4일에 나타난 APX, CAT 및 GR의 활성은 한발처 리보다 각각 12.6%, 27.9%, 23.3% 높았다. 한편, 보리의 경우 CAT의 활성은 한발보다 염해조건에서 더욱 신속하게 유도되는 것으로 나타났다. 3. 아미노산 함량의 변화는 염해 및 한발처리에 의해서 서로 다른 양상을 보였다. 특히 glycine, arginine 및 GABA의 함량은 한발처리에서 더욱 증가하였으나, proline의 함량은 염해처리에서 크게 증가하였다. 4. 본 연구를 통해서 보리의 항산화효소 활성 및 아미노산 함량이 염해와 한발에 의해서 상이하게 조절되는 것이 확인되었다. 이러한 결과들은 염해에 대한 보리의 특이적인 반응지표가 될 수 있을 것으로 생각되었다.

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.

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.

공동주택단지 근린시설 배치유형별 커뮤니티의식분석에 관한 연구

김대욱,정응호,류지원,Kim Dae-Wuk,Jung Eung-Ho,Ryu Ji-Won 한국주거학회 2005 한국주거학회 논문집 Vol.16 No.6

This Study is to analyse the community-consciousness depending on the location type of the neighborhood facility in apartment complex, in order to set up the fundamental criteria for the location type which can increase the community-consciousness. For the purpose of this study, Shopping center, Playground and Resting Area are selected among the neighborhood facilities and they were analysed on the basis of the Belonging-Sense, Affection-sense and the personnel Interchange. The results of this study are as follows: Shopping center should be located in the Main-Enterance of Apartment Complex and be constructed as low building along the street. In case of the Playground that was compared with the Central type and Decentral type, the Central type is proper for the increasing of community-consciousness. In case of the Resting Area that was compared with the Mixture type involving a playground and Independent type except for a playground, the independent type is acceptable for the location-type to increase the community-consciousness owing to all analyses.

다중 주파수를 이용한 캐비테이션 기포의 분포량 추정

김대욱,나형술,최지웅,나정열,강돈혁,Kim, Dae-Uk,La, Hyoung-Sul,Choi, Jee-Woong,Na, Jung-Yul,Kang, Don-Hyug 한국음향학회 2009 韓國音響學會誌 Vol.28 No.3

캐비테이션 기포 (cavitation bubble)가 존재하는 유체 내에서 다중 주파수 (multi-frequency)를 송수신할 때 음파의 감쇠(attenuation)와 음속 (sound speed) 변화가 발생되었고, 이 특징을 이용하여 기포의 크기와 분포량을 추정하였다. 음향실험은 $20{\sim}300\;kHz$ 대역의 다중 주파수를 이용하여 실시하였고, 기포가 존재하는 경우와 존재하지 않는 경우의 주파수별 음속 비와 음파의 감쇠 값을 측정하였다. 캐비테이션 기포는 모터 끝에 장착된 둥근 막대형 블레이드 (blade)를 물 속에서 고속회전시켜 발생되었다. 캐비테이션 기포의 크기 및 분포량은 모터의 회전 속도, 블레이드 끝단 (tip)의 겉넓이를 변화시키며 관측하였고, 기포 생성 후 시간별 기포량 감소율을 측정하였다. 실험 결과 발생된 기포의 크기는 반경 $10{\sim}60{\mu}m$였고, $10{\sim}20{\mu}m$와 $20{\sim}30{\mu}m$ 반경의 기포가 전체의 약 45%와 25%를 차지하였다. 세부실험 결과로 모터의 회전 속도가 증가할수록 더 많은 양의 기포가 발생되지만 블레이드 끝단 면적의 증가와 기포 발생량의 변화는 상관성이 없음을 확인하였다. 또한 기포량의 감소율은 지속시간별로 일정하였고, 2분 이내에 전체량의 80%가 소멸됨을 관측하였다. 음향실험의 결과를 검증하기 위해 동일한 조건에서 광학카메라로 촬영한 기포 분포량과 비교하였다. Distribution of cavitation bubbles relative to change of the sound speed and attenuation in the water was estimated using acoustic signal from 20 to 300 kHz in two cases that cavitation bubbles exist and do not exist. To study generation and extinction property of cavitation bubble, bubble distribution was estimated in three cases: change of rotation speed (3000-4000 rpm), surface area of blade ($32-98\;mm^2$) and elapsed time (30-120 sec). As a result, the radii of the generated bubbles ranged from 10 to $60{\mu}m$, and bubble radius of $10-20{\mu}m$ and $20-30{\mu}m$ was accounted for 45 and 25% of the total number of cavitation bubbles, respectively. And generation bubble population correlated closely with the rotating speed of the blades but did not correlate with the surface area of blade. It was observed that 80% of total bubble population disappeared within 2 minutes. Finally, acoustic data of bubble distribution was compared with optical data.

주거지역 종세분화에 따른 주거환경 개선에 관한 연구 - 바람길을 중심으로 -

김대욱,정응호,류지원,차재규,이준영,Kim, Dae-Wuk,Jung, Eung-Ho,Ryu, Ji-Won,Cha, Jae-Gyu,Lee, Jun-Young 한국주거학회 2010 한국주거학회 논문집 Vol.21 No.2

Various environmental problems due to rapid industrialization and urbanization have worsened to such an extent that they threaten the environmental restitution of the globe and become a critical international issue. Korean government has presented the concept of green growth as a new state vision for the next 60 years and is making efforts to solve these environmental problems. Daegu Metropolitan City has faced various environmental problems including overpopulation of the city, traffic pollution, household waste accumulation and the green zone problem because of the increase of urbanization over the last few decades. As such urbanization continues, the quality of residential environments is rapidly deteriorating and the intensive use of the land leads to an increase of building area, raising the temperatures of cities. There have therefore been demands for healthy, pleasant and satisfying residential environments and for the improvement of existing residential environments, and this demand has been fully recognized by society. Nevertheless, current residential complex developments concentrate only on raising the efficiency of land use. In related laws of the past (Daegu Metropolitan City, Urban Planning Municipal Ordinance as of October 10, 2003) an attempt was made to impose a standard to segmentalize the building-to-land ratio, floor area ratio and regulations of number of floors vertically. However, these laws have now been abolished and the regulations are being eased. The purpose of this study was to analyze the characteristics of the floating wind before and after the vertical segmentation of residential areas (Daegu Metropolitan City, Urban Planning Municipal Ordinance as of October 10, 2003) by using KLAM_21, a model that enables analysis and prediction of the flow and generation of cold wind. The purpose is also to present a plan to improve the quality of residential areas when developing a building lot and redeveloping housing areas.