연속 섬유강화 복합재료 리바 개발에 관한 연구

한길영,이동기,김성용 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.2

This paper describes the need for a ductile Fiber Reinforced Plastic(FRP) reinforcement for concrete structures. Using the material hybrid and geometric hybrid, it is demonstrated that the pseudo-ductility characteristic can be generated in FRP rebar. Ductile hybrid FRP bars were successfully fabricated at 4mm and 10mm nominal diameters using an hand lay up method. Tensile specimens from these bars were tested and compared with behavior of FRP rebar and steel bar. The summarized results are as follows : The tensile strength of CFRP, KFRP and GFRP rebar with nominal diameter ψ4mm, respectively, showed 91.7kg/mm^2, 66.5kg/mm^2, 53.6kg/mm^2. The tensile strength of CFRP, KFRP, GFRP rebar with nominal diameter ψ10mm by the hand lay up method, respectively, showed 125.4kg/mm^2, 54.1kg/mm^2, 46kg/mm^2.

우리나라 한중콘크리트 적용기간의 변화에 관한 고찰

한민철,김경민,신동안,윤기원,한천구 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1(구조계)

In this paper. variations of the period of cold weather concrete in Korea are discussed based on the climate data of Korean Meteorological Adminstration(KMA). Determination of the period of cold weather concrete with the region is done by following Korean Concrete Institute(KCD, American Concrete Institute(ACD and AIJ(Architectural Institute of Japan(AIJ) specification. Present study is compared with previous study done by the authors. Period of cold weather concrete is found to increase with high altitude and in-land and mountain area. Period of cold weather concrete by present study is shorted compared with that of previous study by about 3~6 days regardless of applied specification. Especially. the period of cold weather concrete at southern region near sea is reduced remarkably compared with that of previous study. This is due the rise of mean air temperature by global warming. In the scope of present study, period of cold weather concrete is provided with table and map diagram.

정신지체 특수학교 초등교사의 체육목표 인식 분석

한동기 서울대학교 체육연구소 2001 서울大學校 體育硏究所論集 Vol.22 No.1

The purpose of this study was to analyze the special teachers' recognition about the goals of physical education in the primary school for the students with mental retardation. The subjects of this study were 237 teachers who were randomly selected from the primary schools for the students with mental retardation which were located in Seoul, Kyong-Ki, and In-Chon areas. The t-test and one-way ANOVA were used to analyze the data in statistics. The results of this study were as follow: 1.Compared to the female teachers' group, the male teachers' group showed The higher recognition level on the goals except on the goal of psychic equilibrium and spatial orientation. 2.There were differences in the goals of physiological efficiency, spatial orientation, and cultural involvement between the groups by age in the primary school for the students with mental retardation. 3.There were differences in the goals of the physiological efficiency, object manipulation, communication, group interaction, and cultural involvement among the groups by career. 4.Teachers of lower grade(1 ∼3) showed the higher level of recognition on the goals of 6 areas except the goal of spatial orientation compared to the teachers' recognition level of upper grade(4 ∼ 6). 5.There were no differences in recognition level of the goals of the physical education between the teachers with PE class responsible and the teachers without PE class respollsible.

관동맥 질환 환자에서 전산화단층촬영상의 복부지방 분포 및 형광안저 촬영

한혜자,홍종면,차상훈,김동운,남기병,최미영,강세웅,박남규,이석재 충북대학교 의과대학 충북대학교 의학연구소 1996 忠北醫大學術誌 Vol.6 No.2

배경 및 목적 : 죽상경화증의 원인 인자중 하나인 복부지방의 축적도를 복부 전산화 단층 촬영술로 정량화 하여 관동맥 질환과의 상관 관계를 살펴보고자 하려고, 또한 형광 안저 촬영 검사상의 죽상 경화증 정도와 관동맥 질환과의 상관 관계를 알아보고자 하였다 대상 및 방법 : 관동맥 조영술을 시행한 환자중 관동맥조영술 소견상 50% 이상의 협착이 있는 경우를 관동맥 질환군(n=15)으로 정의하였고, 관동맥 조영술 소견상 관동맥 질환이 없고 허혈성 뇌혈관질환, 당뇨병 및 고혈압이 없는 환자들을 대조군(n=11)으로 하였다. 배꼽 위치에서 복부 전산화 단층 촬영을 시행하여 총 복부 지방면적(total abdomen fat area, TAFA). 복강내 지방면적(abdomen visceral fat area, AVFA) 및 복부 피하지방면적(abdomen subcutaneous fat area, ASFA)을 측정하였고, 그 비를 구하여 비교 분석하였다 또한 형광 안저 촬영 검사를 시행하여 동-정맥비와 동-정맥교차수 및 팔망막 순환기 시간을 측정하여 비교 분석하였다. 결과 : 1) 복부 전산화 단층 촬영 : 대조군과 관동맥 질환군은 복강내 지방면적/(AVFA/TAFA)은 각각 53.9±8.3, 56.1±8.5으로 통계적으로 유의한 차이가 없었고, 또 복강내 지방면적/복부 피하지방면적(AVFA/ASFA)도 각각 0.90±0.30, 0.82±0.26으로 통계적으로 유의한 차이가 없었다 (p>0.05). 2) 형광안저 촬영 검사 ; 대조군과 관동맥 질환군에서 동-전맥비(%)는 각각 72.1±4.9, 62.5±6.1, 동-정맥 교차수는 0.3±0.5, 1.1±1.1, 팔망막 순환기 시간(msec)은 15.3±1.8, 17.8±4.0으로 세 지표 모두에서 통계적으로 유의한 차이가 있었다 (p<0.05). 결론 : 관동맥 질환 환자에서 전산화 단층촬영을 이용하여 구한 복부지방의 분포양상(복강내 지방의 구성 비율 등)은 정상 대조군과 차이가 없었다. 관동맥 질환 환자와 정상 대조군에서 형광 안저 촬영 검사로 측정한 동정맥 직경비, 동정맥교차현상수 및 팔망막순환시간은 각각 통계적으로 의미 있는 차이가 있었다 Background : We quantitatively evaluated the abdominal fat distribution by computed tomography(CT) in coronary artery disease patients and the findings of fluorescence angiography in coronary artery disease patients. Methods: Among the patients who were done coronary angiography(CAG), the control group(n=11) has no angiographically significant stenosis(<50%) and the coronary artery disease(CAD) group(n=15) has more than one significant stenosis(>52%). We examined abdominal CT at umbilicus level and fluorescence angiography in all patients. In abdominal CT, we calculated total abdominal fat area(TAFA), abdominal visceral fat asea(AVFA) and abdominal subcutaneous fat area(ASFA) and their ratios. In fluorescence angiography, we calculated that artery-vein ratio(AV ratio), artery-vein cross number(AV cross No) and antecubital-retinal circulation time. Results: 1) Abdominal CT A. AVFA/TAFA(㎡) ; Control group : CAD group = 53.9±8.3 : 56.1±8.5 (p〉0.05) B. AVFA/ASFA(㎡) ; Control group : CAD group = 0.90±0.30 : 0.82±0.26 (p〉0.05) 2) Fluorescence angiography A. AV ratio(%) ; Control group : CAD group = 72.1±4.9 : 62.5±6.1 (p〈0.05) B. AV cross No ; Control group : CAD group = 0.3±0.5 : 1.1±1.1 (p〈0.05) C. Antecubital - retinal circulation time(ms) Control group : CAD group = 15.3±1.8 : 17.8±4.0 (p<0.05) Conclusion : There was significant association between the FAG findings and CAG findings but there was no significant association between the abdominal fat distribution by abdominal CT and CAG findings.

콘크리트 구조물용 GFRP리바의 기계적 특성에 관한 연구

한길영,이동기,김성용,전상기,최종대,박준식 조선대학교 에너지.자원신기술연구소 2000 에너지·자원신기술연구소 논문지 Vol.22 No.2

In this paper was studied on the mechanical characteristics of Glass Fiber Reinforced Plastics(GFRP) of the steel bar it is to replace The advantage of FRP such as high strength low weight and chemical inertness or noncorrosiveness can be fully exploited. GFRP bar were successfully fabricated at 10mm nominal diameters and hollow types using a pultrusion method Tensile and bending specimens from this bar were tested and compared with behavior of GFRP rebar and steel bar.

치과병원에서 사용되는 진단영상에 대한 JPEG 2000 압축률에 대한 평가

정기훈,한원정,유동수,최순철,김은경 대한구강악안면방사선학회 2005 Imaging Science in Dentistry Vol.35 No.3

Purpose : To find out the proper compression ratios without degrading image quality and affecting lesion detectability on diagnostic images used in dentistry compressed with JPEG 2000 algorithm. Materials and Methods : Sixty Digora periapical images, sixty panoramic computed radiographic (CR) images, sixty computed tomographic (CT) images, and sixty magnetic resonance (MR) images were compressed into JPEG 2000 with ratios of 10 levels from 5 : 1 to 50 : 1. To evaluate the lesion detectability, the images were graded with 5 levels (1: definitely absent; 2: probably absent; 3: equivocal; 4: probably present; 5: definitely present), and then receiver operating characteristic analysis was performed using the original image as a gold standard. Also to evaluate subjectively the image quality, the images were graded with 5 levels (1: definitely unacceptable; 2: probably unacceptable; 3: equivocal; 4: probably acceptable; 5: definitely acceptable), and then paired t-test was performed. Results : In Digora, CR panoramic and CT images, compressed images up to ratios of 15 : 1 showed nearly the same lesion detectability as original images, and in MR images, compressed images did up to ratios of 25 : 1. In Digora and CR panoramic images, compressed images up to ratios of 5 : 1 showed little difference between the original and reconstructed images in subjective assessment of image quality. In CT images, compressed images did up to ratios of 10 : 1 and in MR images up to ratios of 15 : 1. Conclusion : We considered compression ratios up to 5 : 1 in Digora and CR panoramic images, up to 10 : 1 in CT images, up to 15 : 1 in MR images as clinically applicable compression ratios.

서울지역 대기오염이 호흡기계질환 수진건수에 미치는 단기영향에 관한 연구

임종한,이종태,김동기,신동천,노재훈 大韓産業醫學會 1998 대한직업환경의학회지 Vol.10 No.3

Several studies have reported the associations between airborne particles and/or ozone and respiratory diseases. This study examined whether such an association could be seen in Seoul, one of the greatest city in Korea. We compiled daily records of hospital visits in Seoul from November 1, 1995 to October 31, 1996. The daily averages of ozone and particle matter whose diameter is 10 ㎛ or less(PM10) from all monitoring stations were computed. Daily respiratory hospital visits were regressed on temperature, humidity, day of weak indicators, seasonal variation indicators, and air pollution. Each pollutant was first examined individually and then two pollutant models were fitted. Results : Both PM10 and Ozone were associated with increased risk of respiratory hospital visits. The relative risk of respiratory hospital visits for 50 ㎍/㎥ increase in PM10(lagged 2 days) was 1.11(95% confidence interval: 1.05-1.18). The PM10 associations was insensitive to alternative methods control for weather, including exclusion of extreme temperature days and control for temperature on another day. The ozone results were more sensitive to the approach for weather control. The relative risk of respiratory hospital visits for 0.01 ppm increase in O₃was 1.08(95% confidence interval 1.00-1.17). The magnitude of the PM10 effect in Seoul, where SO₂was essential present, was similar to that reported in the Europe and United states. In conclusion, The consistency of investigations of the health effects of air pollution suggest that attention should be paid to the control of air pollution.

섬유강화 복합재료의 사출성형에 있어서 섬유배향에 미치는 성형조건의 영향

이동기,한길영,김성용 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.2

Injection molding is a very important industrial process for the manufacturing of plastics objects. During an injection molding process of composites, the fiber-matrix separation and fiber orientation are caused by the flow of molten polymer/fiber mixture. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation orientation and injection molding conditions. So far, there is no research on the measurement of fiber orientation using image processing. In this study, the effects of fiber content ratio and molding condition on the fiber orientation-angle distributions are studied experimentally. Using the image processing method, the fiber orientation distribution of weld-line parts in injection-molded products is assessed. And the effects of fiber content and injection molding conditions on the fiber orientation functions are also discussed.

수분흡수가 섬유강화 고분자 복합판의 기계적 성질에 미치는 영향

김혁,한길영,이동기 조선대학교 생산기술연구소 1995 生産技術硏究 Vol.17 No.1

Nowadays, it is common and becoming more popular to use fiber-reinforced polymeric composites(FRP) in order to reduce the lightweight of the structures such as marine vehicles, automobiles and airplane. It investigates the residual strength characteristics of composite under the environment of high temperature and humidity. The residual strength of FRP is known to be greatly influenced by temperature, humidity etc. In this context, the hygrothermal effect of changing the fiber contents and orientation are investigated in order to provide better residual strength characteristics. When exposed long terms in high temperature and humidity, the randomly oriented composites is to be more stable than the unidirection one.

Metal Oxide Sensor Array를 이용한 사과와 귤의 신선도 분석

임향주,한도수,조성동,김기윤 조선대학교 기초과학연구소 2000 自然科學硏究 Vol.23 No.1

The Electronic Nose has been designed to provide objective and reproducible aroma discrimination on a wide variety to human nose. The sensor array in combination with sophisticated chemometrics and artificial neural network software provides the output displaying the closeness of difference in aroma patterns of different samples. As an application the system has been used to discriminate of the fresh and decomposing apples and oranges. The discrimination has been successfully demonstrated.