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2차원 직사각형 덕트 내부에 돌기부를 갖는 흐름의 동결특성에 관한 연구
오철,Oh, Cheol 한국마린엔지니어링학회 2003 한국마린엔지니어링학회지 Vol.27 No.6
Freezing of turbulent water flow between two horizontal cooled parallel plates with the separated region has been investigated experimentally. The flow separation was induced by vertical plates (two-dimensional plates) situated at the inlet of the rectangular channel. The degree of flow separation was varied by employing vertical thin plates with various heights. Three kinds of the vertical plates with 8.0, 9.8 and 12.5 mm in height were utilized. The Reynolds number and cooling temperature ratio were ranged from $3.45\times10^3 to 1.73\times10^4$ and 7.0 to 20.0 respectively, The measurements show that the flow separation influenced remarkably on the local ice formation characteristics. The location of the first ice layer and the average heat transfer at the ice surface were found be correlated as a function of the Reynolds number, the cooling temperature ratio, and the orifice height ratio.
오철,허금정,이원행,양진아,김기태,Oh, Chul,Huh, Geum-jung,Lee, Won-haeng,Yang, Jin-ah,Kim, Ki-tae 대한한방내과학회 2016 大韓韓方內科學會誌 Vol.37 No.2
Objective: Acne scarring is the most common sequela after dermal inflammation caused by acne. Many methods are currently used to treat acne scarring; doctors using traditional Korean medicine have also attempted to treat acne scarring in a new way that was developed from traditional methods. This study examines the effectiveness of re-cell therapy.Method: Eleven patients with various types of acne scars were treated by re-cell therapy. We used the global acne scarring classification (GASC) and ECCA (from the French “echelle d’evaluation clinique des cicatrices d’acne”), both of which are generally used to measure and grade the degree of acne scarring.Results: As a result of the treatment, the conditions of all patients were conspicuously improved in both scales. The GASC scores of the patients changed from grade 19.6±10.4 to grade 4.9±3.3 (p=0.001), and the ECCA scores changed from grade 120.9±28.7 to grade 41.8±18.3.Conclusion: Re-cell therapy showed effectiveness in treating acne scarring and could be applied in clinical cases.
고속도로 시설물 구간의 교통혼잡도와 사고율의 관계 분석 (신갈-안산 고속도로를 중심으로)
오철,장재남,장명순,Oh, Cheol,Chang, Jae-Nam,Chang, Myeong-Sun 대한교통학회 1999 대한교통학회지 Vol.17 No.2
고속도로 시설물 구간의 교통혼잡도(V/C)와 사고율의 관계를 분석하는 것이 본 연구의 목적이다. 본 연구에서 분석된 사고율과 V/C의 관계는 교통사고의 예측과 예방을 위한 기초 자료로 유용하게 쓰일 수 있을 것으로 판단된다. 본 연구에서는 신갈-안산간 고속도로의 개통시(92년)부터 97년까지의 교통량과 사고 자료를 이용하였으며, 시간당 사고율과 V/C를 계산하여 기본구간, 터널구간, 영업소구간의 V/C와 사고율(AR)을 비교·분석하였다. V/C와 사고율의 관계는 모든 구간에서 "U"형의 곡선 형태를 나타냈다. 분석 결과를 보면 V/C가 낮을 때 사고율이 가장 높았으며 V/C가 증가함에 따라 사고율이 감소하다가 일정수준 이상에서는 다시 사고율이 증가하는 것으로 나타났다. 영업소구간의 사고율이 V/C의 전 범위에 걸쳐 기본구간이나 터널구간보다 높게 나타났다. 터널구간의 경우 기본구간과 비교 시 V/C=0.67을 기준으로 그 이하에서는 기본구간이, 그 이상에서는 터널구간이 기본구간보다 사고율이 높은 것으로 분석되었다. V/C가 0.5∼0.8 구간에서는 기본구간과 터널구간의 사고 율이 큰 차이가 없는 것으로 나타났다. 기본구간 터널구간 영업소구간의 V/C가 각각 0.78, 0.75, 0.57일 때 사고율이 가장 낮은 것으로 나타났다. The objective of this study is to clarify the relationship between accident rate and V/C for freeway facility. The relationship can be used as a basic reference to predict and prevent traffic accident. The traffic volume and the number of accidents from 1992 to 1997 on Shingal-Ansan Freeway were analyzed in this study to clarify the relationship. Hourly accident rate and V/C were calculated for each facility sections : basic freeway section, tunnel section and toll gate section. The accident rate models consisting of an independent variable of V/C were established by repression analysis and compared with each other. The relationship between accident rates and V/C ratios represented U-shaped pattern for all sections. The result of this study indicates that accident rates are highest in the low hourly V/C range, decrease with increasing V/C ratio, and then increase as the V/C ratio increases. The accident rate of toll gate section is in general higher than that of other sections. Although the accident rate of tunnel section is higher than that of basic freeway section when V/C is above 0.67, there is no significant difference of accident rate between basic freeway and tunnel section when V/C is between 0.5 and 0.8. Basic freeway tunnel and toll gate section have the minimum accident rate when V/C is 0.78, 0.75 and 0.57 respectively.
오철,장명순,Oh, Cheol,Chang, Myeong-Sun 대한교통학회 1997 대한교통학회지 Vol.15 No.3
현재 사용되고 있는 신호등 설치기준은 교차로의 형태를 반영하고 있지 않다. 본 논문은 신호 및 비신호 T형 교차로에 대한 현장의 지체도 조사를 바탕으로 첨두시간 교통량을 이용한 T형 교차로의 신호등 설치기준을 개발하였다. 기준설정을 위해 교차로의 평균정지지체 최소화를 평가척도로 사용하였으며 주요 연구결과를 요약하면 다음과 같다. 첫째, T형 교차로의 지체도 모형은 주도로 교통량과 부도로 교통량을 독립변수로 하는 지수함수 형태를 갖는다. 둘째, T형 교차로의 신호등 설치기준은 T형으로 인한 현시의 감소로 MUTCD에서 제시하고 있는 신호등 설치기준과 비교시 타당성 교통량이 높게 나타났다. 셋째, T형 교차로의 신호등 설치를 위한 첨두시 교통량기준 도표를 작성하였으며, 평일의 하루중 주도로(양방향)의 시간당 교통량과 이에 사용하는 부도로의 시간당 교통량의 최대값을 도표에 표시했을 때 접근로 차로수의 조합에 해당하는 기준선의 상위영역에 위치하면 신호등을 설치하는 것이 교차로의 지체도를 최소화시킬수 있다.
오철,김범일,강연수,신문균,Oh, Cheol,Kim, Beom-Il,Kang, Youn-Soo,Shin, Monn-Kyun 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.4
This study proposes a methodology to assess the traffic safety benefits of technical regulation for pedestrian leg. Traffic safety benefit is defined as the injury reduction in this study. Actual accident analysis and simulation experiments using LS-Dyna3d are conducted to establish statistical models for developing the methodology. The relationship between collision speed and parameters of the regulation is explored. An application example of the proposed methodology is also presented for more comprehensive understanding. It is believed that the proposed methodology would be greatly utilized in developing various technologies and policies to protect pedestrian.
인공 우식 유발성 biofilm 구성성분의 시간 흐름에 따른 변화
오철 ( Chul Oh ),판딧싼토스 ( Santosh Pandit ),전재규 ( Jae-gyu Jeon ) 대한예방치과·구강보건학회 2019 大韓口腔保健學會誌 Vol.43 No.3
Objectives: The purpose of this study was to investigate changes in the composition of artificial cariogenic biofilms using a Streptococcus mutans biofilm model over a period of time. Methods: We analyzed the dry weight, colony forming unit (CFU) number, extracellular polysaccharide (EPS) biovolume, and acid production rate of S. mutans biofilms formed on saliva-coated hydroxyapatite discs after 26 h, 50 h, 74 h, 98 h, 171 h, and 195 h. In addition, we performed a laser scanning confocal fluorescence microscopy to determine the bacterial volume, EPS biovolume, and biofilm thickness. We calculated the biofilm density using dry weight and EPS biovolume. Results: Over a period of time, there was no change in the CFU number and acid production rate of S. mutans biofilms, but there was an increase in the dry weight and EPS biovolume of S. mutans biofilms. The bacterial volume, EPS biovolume, and biofilm thickness only increased in the 50-h-old biofilm; however, no change was observed in 50-195-h-old biofilms. In addition, an increase in the biofilm density was observed over time. Conclusions: These results suggest that the acid production ability of cariogenic biofilms does not change, but the biofilm density increases over time. However, due to scientific information, further research needs to be conducted in the field of dentistry to get further insights on the progression of cariogenic biofilms over time.