세라믹재 연삭시 연삭특성에 관한 연구

최병주(Byung-Joo Choi),박성구(Seong-Ku Park),김광복(Bok-Kwang Kim) 산업기술교육훈련학회 2009 산업기술연구논문지 (JITR) Vol.14 No.3

The number of parts made of ceramic materials has gradually been increased in field of mechanical engineering and, such a mechanical engineering ceramics have spread because of three very favourable characteristic features, namely, heat, wear, and corrosion resistance. Therefore, the elaboration of suitable grinding technologies is important. Grinding is problematic because crack-free ceramics are difficult to process owing to their particular micro structures. In this paper the mechanism of the material removal and crack formation, residual stress and the surface roughness of workpiecs in grinding are examined so experimental result is as follow The mechanism of material removal in the grinding of ceramics is considered the type of brittle fracture and the surface roughness shows almost constant trend with actual wheel depth of cut.

신생아 특발성 기흉 환아에 대한 위험인자 및 예후에 관한 연구

최병주 ( Byung Joo Choi ),정조원 ( Jo Won Jung ),배선찬 ( Seon Chan Bae ),박문성 ( Moon Sung Park ),양정인 ( Jeong In Yang ) 대한주산의학회 2000 大韓周産醫學會雜誌 Vol.11 No.4

금강하구 연안에서 고주파 레이더로 관측된 표층해류에 대한 객관적 유속산출 적용

황진아,이상호,최병주,김창수,Hwang, Jin-A,Lee, Sang-Ho,Choi, Byung-Joo,Kim, Chang-Soo 한국해양학회 2011 바다 Vol.16 No.1

금강하구 연안역에서 고주파 레이더를 사용하여 2008년 12월부터 2009년 2월까지 표층류를 관측하였는데, 관측된 표층류 자료는 전파의 간섭과 기상 상황에 따라 일시적으로 관측이 이루어지지 않는 구역들이 있었다. 관측된 구역의 자료를 보충하기 위하여 최적보간 과정을 개발하여 적용하였다. 금강하구 연안역에서 표층류의 공간적 상관성의 특성을 조사하고 최적보간법을 이용하여 공간적 결측 구역을 보충하였으며, 보간된 표층류의 시공간적 분포와 산출유속 오차 패턴을 조사하였다. 연구해역 표층 순환에서 조류가 우세하므로 연안역 관측 지점들 사이의 표층해류간 상관계수가 0.7 이상이었다. 원 자료를 보간하기 위해 관측 자료공분산(C), 지역화한 공간평균 공분산($C^G_{sm}$), 지수함수를 이용한 맞춤 평균공분산($C_{ft}$)을 사용하였다. 최적보간이 결측 구간을 채우고, 관측 자료의 시계열 중에서 뾰족하게 튀어나온 비정상적인 자료 부분을 억제하였으며, 그 결과 보간한 유속 자료의 분산은 원 자료의 분산보다 작았다. 공간적 자료획득률이 70% 이상(이하)일 때, $C^G_{sm}$ ($C_{ft}$)를 이용하면 C를 이용한 경우에 비해 보간 오차가 상대적으로 작았다. Surface currents were observed by high-frequency (HF) radars off the Keum River estuary from December 2008 to February 2009. The dataset of observed surface currents had data gaps due to the interference of electromagnetic waves and the deteriorating weather conditions. To fill the data gaps an optimal interpolation procedure was developed. The characteristics of spatial correlation in the surface currents off the Keum River estuary were investigated and the spatial data gaps were filled using the optimal interpolation. Then, the temporal and spatial distribution of the interpolated surface currents and the patterns of interpolation error were examined. The correlation coefficients between the surface currents in the coastal region were higher than 0.7 because tidal currents dominate the surface circulation. The sample data covariance matrix (C), spatially averaged covariance matrix with localization ($C^G_{sm}$) and covariance matrix fitted by an exponential function ($C_{ft}$) were used to interpolate the original dataset. The optimal interpolation filled the data gaps and suppressed the spurious data with spikes in the time series of surface current speed so that the variance of the interpolated time series was smaller than that of the original data. When the spatial data coverage was larger (smaller) than 70% of the region, the interpolation error produced by $C^G_{sm}$ ($C_{ft}$) was smaller compared with that by C.

3D 프린팅 CFRP 초음파 피로 시험편 설계를 위한 강화 섬유 벽에 따른 진동 특성 분석 해석

강영재(Young-Jae Kang),최병주(Byung-Joo Choi),이문구(Moon-Gu Lee),전용호(Yong-Ho Jeon) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12

Defect Classification of Cross-section of Additive Manufacturing Using Image-Labeling

Jeong-Seong Lee(이정성),Byung-Joo Choi(최병주),Moon-Gu Lee(이문구),Jung-Sub Kim(김정섭),Sang-Won Lee(이상원),Yong-Ho Jeon(전용호) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.7

Recently, the fourth industrial revolution has been presented as a new paradigm and additive manufacturing (AM) has become one of the most important topics. For this reason, process monitoring for each cross-sectional layer of additive metal manufacturing is important. Particularly, deep learning can train a machine to analyze, optimize, and repair defects. In this paper, image classification is proposed by learning images of defects in the metal cross sections using the convolution neural network (CNN) image labeling algorithm. Defects were classified into three categories: crack, porosity, and hole. To overcome a lack-of-data problem, the amount of learning data was augmented using a data augmentation algorithm. This augmentation algorithm can transform an image to 180 images, increasing the learning accuracy. The number of training and validation images was 25,920 (80 %) and 6,480 (20 %), respectively. An optimized case with a combination of fully connected layers, an optimizer, and a loss function, showed that the model accuracy was 99.7 % and had a success rate of 97.8 % for 180 test images. In conclusion, image labeling was successfully performed and it is expected to be applied to automated AM process inspection and repair systems in the future.

초음파를 이용한 마이크로 혼합기 제작

전용호(Yongho Jeon),최병주(Byung-Joo Choi),강승준(Seung-Joon Kang),김동권(Dong-Kwon Kim),김현정(Hyun-Jung Kim),이문구(Moon Gu Lee) 한국생산제조학회 2013 한국생산제조학회지 Vol.22 No.3

필라멘트트위스트피치가 Bi-2223테이프의 통전손실에 미치는 영향

정재훈(Jae-Hoon Jung),류경우(Kyung-Woo Ryu),최병주(Byung-Ju Choi),장석헌(Seok-Hern Jang),주진호(Jin-ho Joo) 대한전기학회 2002 대한전기학회 학술대회 논문집 Vol.2002 No.7

소아의 기도내 이물흡인에 대한 임상적 고찰 - 수원 및 남부경기 지역 환자를 중심으로 -

이수영(Soo Young Lee),전계리(Gye Ree Jeon),최병주(Byung Joo Choi),배기수(Ki Soo Pai),고중화(Jung Hwa Koh),전영명(Young Myung Jeon) 대한소아알레르기호흡기학회(구 대한소아알레르기 및 호흡기학회) 2000 소아알레르기 및 호흡기학회지 Vol.10 No.3

목 적 : 기도내 이물흡인은 1-4세의 소아에서 비교적 흔히 발생할 수 있는 우발적 사고로 치료되지 않으면 종국에는 기도 폐색에 의한 급성 호흡부전과 만성 폐 감염, 무기폐 등을 일으켜 사망에 이를 수 있는 질환으로 조속한 진단과 치료가 요구된다. 본 연구에서는 아주대학교병원을 내원하여 진단 치료받은 수원 및 남부경기 지역 환자를 중심으로 소아의 기도내 이물흡인에 따른 임상증상, 이물 종류 및 조기진단에 따른 재원기간과 합병증 둥을 분석하였다. 방 법 : 1994년 11월부터 2000년 10월까지 6년 동안 아주대학교병원 소아과에 기도내 이물흡인으로 입원 치료받았던 19명을 대상으로 하였다. 의무기록을 바탕으로 성별 및 연령분포, 이물흡인의 병력, 이물흡인 후 진단까지의 기간, 이물 흡인에 따른 증상 및 이학적 소견, 흉부 X-선 소견, 이물의 종류 및 기도내 위치, 재원기간 및 합병증 등을 분석하였다. 결 과 : 기도내 이물 흡인 환아의 평균 연령은 2년 5개월로 남아에서 더 호발하였으며 흡인의 병력을 알고 있었던 경우는 11례(57.9%)였고, 이중 4례는 24시간내 진단 및 내시경적 이물 제거가 이루어졌다. 흡인에 따른 가장 흔한 증상으로는 기침(73.6%)과 호흡음 감소(57.9%)였으며 흉부 X-선 이상소견으로는 폐기종(68.4%)이 가장 흔한 소견이었다. 19례 모두 기관지 내시경하에 이물을 제거하였으며 이 중 식물성 이물이 73.6%로 가장 흔하였으며 좌우 기관지에 유사한 비율로 분포하였다. 대상 환자 중 2례는 1차 기관지 내시경 시행시 이물이 발견되지 않았으며, 재원 기간 중 컴퓨터 단층 촬영을 시행하여 이물이 확인되어 재차 기관지 내시경을 시행 받았던 경우였다. 충 19례의 평균 입원기간은 7.47일이었으며 이 중 24시간내 진단되었던 4례의 평균 입원기간은 3.75일로 24시간 이후 진단되었던 15례의 평균 입원기간(8.61일)에 비해 짧았다(=0.012). 결 론 : 소아의 기도내 이물흡인은 3세 이하에서 가장 흔하며 특징적인 임상증상과 이학적 소견을 나타내므로 병력청취에 주의를 기울여 조속한 진단과 함께 적절한 치료시 입원기간이 단축됨을 알 수 있었다. Purpose : Foreign bodies in the airway of infant and children require prompt diagnosis and removal. To evaluate the pattern of clinical characteristics and disease course, we reviewed and analyzed a 6-year experience with pediatric airway foreign bodies in children. Methods : We retrospectively reviewed the medical records of pediatric foreign body aspiration managed by pediatric and otorhinolaryngologic departments of Ajou University Hospital from November 1994 to October 2000. Nineteen cases of aspiration were collected and we analyzed their age, sex, symptoms, duration between onset of symptoms and diagnosis, initial simple radiographic findings, matierials of aspirations, anatomic location of foreign body, length of hospital day, and complications. Results : The mean age was 2.7 years and male-to-female ratio of 1.8: 1. In 11 cases, choking episode was identified by parents or patients. The correct diagnosis was made within first 24 hours of aspiration in 4 patients; while in 15 cases, the proper diagnosis was done after 24 hours. The most common presenting symptoms were cough(73.6%) and decreased breath sounds(57.9%) and the most common initial finding of simple radiographs was emphysema, presented in 68.4% of patients. Vegetable substances, particularly peanuts were the most common material of identified foreign body. Nine foreign bodies were in the right bronchus, 8 in the left bronchus and 2 in the subglottic area. The mean duration of admissions were 3.75 days in pateints who were diagnosed within 24 hours, however, 8.61 days in those with a delayed diagnosis(P=0.012). Conclusion : Taken together, the majority of accidental foreign body aspiration in airway was found under 3-year of age. Pediatricians and parents should be conscious to check for history of foreign body aspiration who have suspicious clinical features of aspiration, for early diagnosis and proper management without complications and long term morbidity.

수평자장에 대한 Bi-2223테이프의 자화손실 특성

柳炅佑(Kyung-Woo Ryu),韓亨周(Hyung-Ju Han),崔炳柱(Byung-Ju Choi),羅浣洙(Wan-Soo Nah),朱鎭晧(Jin-Ho Joo) 대한전기학회 2001 전기학회논문지 B Vol.50 No.4

만성 간질환에서 당뇨병의 유병률

이현철(Hyun Chul Lee),허갑범(Kap Bum Huh),홍성관(Sung Kwan Hong),노현정(Hyun Jung Roh),최병주(Byung Joo Choi),안상훈(Sang Hoon An),서일(Il Suh),한광협(Kwang Hyup Han) 대한내과학회 1999 대한내과학회지 Vol.57 No.3

N/A The insulin resistance and the altered glucose metabolism in chronic liver disease increase the alteration of glucose intolerance and the prevalence of diabetes mellitus. The prevalence of DM is higher in advanced cirrhosis than in early cirrhosis and higher in C-viral hepatitis or alcoholic liver disease than in B-viral hepatitis. The purpose of this study is to assess the prevalence of DM in chronic liver disease in Korea. Methods : We reviewed the medical records of 417 patients with chronic liver disease who visit the Yonsei University Sevrance Hospital from January 1994 to March 1998. We examined fasting blood sugar, biochemical study and abdominal ultrasonography. DM was defined on the basis of fasting hyperglycemia (fasting blood sugar exceeding 140 mg/dl) at least two consecutive samples or active treatment with insulin or oral hypoglycemic agents. Results :1) The DM prevalence was 16.8%(70 cases) in total patients and 25.0% (56 cases) in cirrhotic patients. 2) According to sex, there was no statistically significant difference in DM prevalence(16.8% in men and 18.1% in women P=0.78). 3) The DM prevalence was increased with increasing of age(0% in below 30 years, 4.9% in 31-40, 19.6% in 41-50, 22.9% in 51-60, 21.3% in 61-70 and 44.4% in over 71 years, P<0.01). 3) According to severity of liver disease, the DM prevalence was higher in uncompensated cirrhosis than in compensated cirrhosis(2.3% in chronic viral carrier, 8.8% in chronic hepatitis, 17.9% in cirrhosis Child class A, 33.9% in class B, 29.5% in class C). 4) According to cause of liver disease, the DM prevalence was higher in C-viral hepatitis and alcoholics than in B-viral hepatitis(12.1% in B-viral hepatitis, 35.1% in C-viral hepatitis, 40.0% in alcoholics). Conclusion : The prevalence of diabetes in the patients with chronic liver disease is much higher than in general population. And the DM prevalence is increased in advanced cirrhosis and C-viral or alcoholic hepatitis. The early diagnosis and treatment of DM in chronic liver disease patients are important. (Korean J Med 57:281-287, 1999)