직교이방성 판의 좌굴 및 압축재의 국부좌굴에 대한 해석적 연구

최진우,이강연,박정환,윤순종,Choi, Jin-Woo,Lee, Kang-Yeon,Park, Jung-Hwan,Yoon, Soon-Jong 한국복합신소재구조학회 2012 복합신소재구조학회논문집 Vol.3 No.1

이 연구에서는 직교이방성 판의 좌굴 및 직교이방성 판요소로 구성된 구조용 압축재의 국부좌굴에 대한 해석적 연구를 수행하였다. 섬유보강 폴리머 플라스틱 재료는 높은 비강도 및 비강성, 높은 부식저항성, 경량성 등 강재나 콘크리트와 비교해서 많은 장점을 가지고 있다. 특히, 펄트루젼 생산 방식은 섬유보강 폴리머 플라스틱 재료의 여러가지 생산방법 중 구조용 플라스틱 부재를 대량으로 생산하기에 가장 적합한 방법이다. 펄트루젼 생산방식은 부재의 축을 따라 주요 보강섬유가 배치되기 때문에 이 재료는 직교이방성으로 간주된다. 그러나, 펄트루젼 섬유보강 플라스틱 부재는 낮은 탄성을 갖고 있고 얇은 판요소로 구성되어 있기 때문에 압축하중이 재하될 경우 좌굴이 발생할 수 있다. 따라서, 이 부재를 설계하는데 안정성은 매우 중요한 문제가 된다. 이 연구에서는 기존의 연구를 따라서 직교이방성 판 및 직교이방성 판요소로 구성된 압축재의 국부좌굴에 대하여 검토하였으며, 국내에서 생산된 직교이방성 판요소로 구성된 압축재의 국부좌굴강도를 계산하였다. In this paper, we present the analytical study results pertaining to the buckling of the orthotropic plates and local buckling of structural compression members composed of orthotropic plate components. Fiber reinforced polymeric plastic (FRP) materials, have many advantages over conventional structural materials such as steel and concrete. The advantages of the FRP materials are high specific strength and stiffness, high corrosion resistance, right weight, etc. Among the various manufacturing methods, pultrusion process is one of the best choices for the mass production of structural plastic members. Since the major reinforcing fibers are placed along the axial direction of the member, this material is usually considered as an orthotropic (tranversely isotropic, more specifically) material. However, pultruded fiber reinforced plastic structural members have low modulus of elasticity and are composed of orthotropic thin plate components the members are prone to buckle. Therefore, stability is an important issue in the design of the pultruded FRP structural members. In this paper, the buckling of orthotropic plates and the local buckling of pultruded FRP structural members are investigated by following the previous research results and the local buckling strength of the member produced in the domestic manufacturer is found.

국내 의료기관에서 측방두부규격방사선촬영시 임상에서의 촬영조건 및 환자 선량

최진우,Choi, Jin-Woo 대한영상치의학회 2010 Imaging Science in Dentistry Vol.40 No.4

Purpose : To survey the radiographic examination protocol for lateral cephalometric radiographic examinations and to measure their patient doses in Korea and to compare the dose according to the size of hospital, the type of image receptor system, and the installation duration. Materials and Methods : The radiographic examination protocols (kVp, mA, and exposure time) for lateral cephalometric radiography were surveyed with 61 cephalometric radiographic equipments and their patient dose-area product (DAP) measured with a DAP meter (DIAMENTOR M4-KDK, PTW, Freiburg, Germany) for 51 cephalometric radiographic equipments. The radiographic examination protocols and patient doses were compared according to the size of hospital (university dental hospital, dental hospital, and dental clinic), the type of image receptor system (film-based, DR and CR type) and the installation duration, respectively. SPSS 12.0.1 for Windows (SPSS Inc., Chicago, USA) was used for independent t-test and ANOVA test. Results : The average protocols were 77.0 kVp, 12.7 mA, 6.2 second for cephalometric radiography. The average patient dose (DAP) was $128.0mGy\;cm^2$ and 3rd quartile dose (DAP) $161.1mGy\;cm^2$ for cephalometric radiography for adult male. There was no statistically significant difference at average patient DAP according to the size of hospital, the type of image receptor system, and the installation duration, repectively. Conclusion : The average patient dose was $128.0mGy\;cm^2$ and the third quartile patient dose $161.1mGy\;cm^2$ for lateral cephalometric radiography for adult male in Korea.

수상 부유식 태양광발전 구조물의 구조적 성능 평가

최진우,서수홍,주형중,윤순종,Choi, Jin Woo,Seo, Su Hong,Joo, Hyung Joong,Yoon, Soon Jong 대한토목학회 2014 대한토목학회논문집 Vol.34 No.5

최근 화석연료의 과도한 소비로 인해 다양한 환경문제가 발생하고 있으며, 이에 대한 대안으로 신재생에너지의 중요성과 그에 대한 시설의 수요가 꾸준히 증가하고 있다. 이러한 수요를 만족하기 위하여, 다수의 태양광발전 구조물들이 건설, 계획되고 있다. 그러나 대부분의 태양광발전 시설들은 육지에 시공되고 있기 때문에 토지 이용에 따른 건설비의 증가와 토지 개간에 의한 추가적인 환경문제 등이 발생하고 있다. 이러한 문제점을 해결하기 위하여 최근 국내에서는 FRP를 활용한 수상 부유식 태양광발전 구조물에 대한 연구를 지속적으로 수행하고 있다. FRP는 높은 강도와 내부식성 및 작은 단위중량 등의 장점을 가지고 있기 때문에 최근 토목분야에서 각광받고 있으며, 이러한 재료적 특성은 자중에 따라 부력체의 크기가 결정되는 수상 구조물에 특히 유용하다. 이 연구에서는 수상 부유식 태양광발전 구조물과 구조물을 구성하는 SMC FRP 수직재의 구조적 성능을 평가하기 위한 해석적, 실험적 연구를 수행하였다. 수상 부유식 태양광발전 구조물은 유한요소해석을 통해 정적거동을 평가하고, 실험을 통해 동적거동을 평가하였다. 또한 SMC FRP 수직재는 유한요소해석을 통해 구조안전성 및 좌굴안정성을 평가하였으며, 실험을 통해 압축 및 인발 하중에 대한 구조적 거동 특성을 검토하였다. 검토 결과 펄트루젼 FRP (pultruded FRP)와 SMC (Sheet Modoling Compound) FRP로 구성된 구조시스템은 외부하중에 대한 안전성을 확보하고 있음을 확인하였다. In recent years, numerous environmental problems associated with the excessive use of fossil fuel are taking place. For an alternative energy resource, the importance of renewable energy and the demands of facilities to generate renewable energy are continuously rising. To satisfy such demands, a large number of photovoltaic energy generation structures are constructed and planned with large scale. However, because these facility zones are mostly constructed on land, some troubles are occurred such as rising of construction cost due to the cost of land use, environmental devastation, etc. To solve such problems, the floating type photovoltaic energy generation system using FRP members have been developed in Korea. FRP members are recently available in civil engineering applications due to many advantages such as high strength, corrosion resistance, light weight, etc. and they are suitable to fabricate the floating structures because of their material properties. In this study, the analytical and experimental investigations to evaluate the structural performance of floating PV generation structure and SMC FRP vertical member which is used to fabricate the structure were conducted. The static and dynamic performances of floating PV generation structure are evaluated through the FE analysis and the experiment, respectively. Moreover, the structural safety evaluation and buckling analysis of SMC FRP vertical compression member are also conducted by the FE analysis, and the structural behavior of SMC FRP member under compression and pullout is investigated by the experiments. From this study, it was found that the structural system composed of pultruded FRP and SMC FRP members are safe enough to resist externally applied loads.

방향 모호성을 고려한 수중 음향 기반의 2차원 위치 추정 기술 개발

최진우,이영준,정종대,박정홍,최현택,Choi, Jinwoo,Lee, Yeongjun,Jung, Jongdae,Park, Jeonghong,Choi, Hyun-Taek 한국로봇학회 2017 로봇학회 논문지 Vol.12 No.4

Acoustic based localization is essential to operate autonomous robotic systems in underwater environment where the use of sensorial data is limited. This paper proposes a localization method using artificial underwater acoustic sources. The proposed method acquires directional angles of acoustic sources using time difference of arrivals of two hydrophones. For this purpose, a probabilistic approach is used for accurate estimation of the time delay. Then, Gaussian sum filter based SLAM technique is used to localize both acoustic sources and underwater vehicle. It is performed by using bearing of acoustic sources as measurement and inertial sensors as prediction model. The proposed method can handle directional ambiguity of time difference based source localization by generating Gaussian models corresponding to possible locations of both front and back sides. Through these processes, the proposed method can provide reliable localization method for underwater vehicles without any prior information of source locations. The performance of the proposed method is verified by experimental results conducted in a real sea environment.

MRI findings of a huge cystadenocarcinoma of the palate

최진우,Choi, Jin-Woo Korean Academy of Oral and Maxillofacial Radiology 2010 Imaging Science in Dentistry Vol.40 No.4

Cystadenocarcinoma of the salivary glands is a very rare, slow growing, and low-grade malignant neoplasm. It is characterized by predominantly cystic growth with or without the intraluminal papillary component. However, it lacks of any additional specific histopathologic features that characterize other types of salivary carcinomas showing cystic growth. Therefore, definite diagnosis of the cystadenocarcinoma is difficult and it is often misdiagnosed. It is conceptually the malignant counterpart of the benign cystadenoma. We present a cystadenocarcinoma on the palate of a 49-year-old man with special emphasis on magnetic resonance imaging.

복합신소재를 이용한 도로교통시설

최진우,윤순종,Choi, Jin-Woo,Yoon, Soon-Jeong 한국복합신소재구조학회 2010 복합신소재학회논문집 Vol.1 No.3

The Polychaete Assemblages on the Continental Shelf off the Southeastern Coast of Korea

최진우,고철환,Choi, Jin Woo,Koh, Chul Hwan The Korean Society of Oceanography 1989 韓國海洋學會誌 Vol.23 No.4

Polychaete assemblages and their responses to habitat conditions were investigated in the southeastern continental shelf of Korea. The result of cluster analysis revealed that the study area could be divided into two regions, one including the shallow coastal region and the other the offshore region. The shallow coastal region sustained 4 polychaete assemblages: Nothria holobranchiata assemblage in the most northern part of fine sediments off Pohang, Magelona-Maldane assemblage off Gampo, Ophelina acuminata assemblage in the middle coastal area off Ulsan, Nothria conchylega assemblage in the south part off Pusan. These coastal polychaete assemblages contained less than 10 species per station and showed very low species diversity (H' = 1.22-1.52). The offshore also contained 4 assemblages: Terebellides-Aglaophamus assemblage in the northern and deep area of very fine sediments, Myriochele oculata and Spiophanes kroyeri assemblages in the central area of sandy bottoms, and Ninoe palmata assemblage in the southern offshore of sandy bottom. The offshore assemblages showed rather more species and higher diversity than coastal assemblages (H' = 1.90-2.26). The offshore region consisting of sandy sediment showed very low population densities. Some dominant species showed specific preference to sediment types and this phenomenon could be detected through their feeding modes. Depth or bottom temperature seems to be related to the distribution of most dominant worms. Thus the polychaete assemblages of the study area are found to be under the control of both a gradient of sedimentary properties and that of bottom temperature.

光陽灣의 多毛類群集에 관한 硏究

최진우,고철환,Choi, Jin Woo,Koh, Chul Hwan 한국해양학회 1984 韓國海洋學會誌 Vol.19 No.2

This study was conducted to interpret the relations between the polychaete community and its environments in Kwangyang Bay during July, 1982. The type of sediments in the study area varies from sand to clay and the organic content obtained by ignition was in the ranges of 0.3% to 15.4%. The polychaetes which occurred at 25 stations comprised 70 species representing 63 genera and had an average density of 490 animals/m$\^$2/. The most abundant species were Lagis bocki (20%), Lumbrineris longifolia (10%), Chohe teres (7%), and Sternaspis scutata (5%). The polychaete populations show the highest density in muddy sand sediments and have a tendency to decrease their abundance in finer sediments such as bud and clay. The individual numbers of each feeding type show the same tendency. Kwangyang Bay consists of three distinct characteristic communities, representing different physical and biological factors: delta community, muddy flat community and channel community. Delta community has very poor organisms and seems to be determined by physical factors such as tidal current, and by sediment conditions and seems to be determined by physical factors such as tidal current, and by sediment conditions and by the food availability. Muddy flat community shows more diverse and higher abundance than delta community but seems to be impoverished by the stress of oxygen deficiency in sediments. Channel community has the highest density in the study area and comprises more various feeding types. This is probably due to the supply of allochthonous materials from the Seomjin River and offshore as food, the heterogeneous sediments and some biological interactions within habitats.

Distribution Pattern of Polychaete Worms on the Continental Shelf and Slope of the East Sea (Southwestern Sea of Japan), Korea

최진우,고철환,CHOI, JIN-WOO,KOH, CHUL-HWAN The Korean Society of Oceanography 1990 韓國海洋學會誌 Vol.25 No.1

본 연구는 동해의 대륙붕 및 대륙사면에서의 다모류 군집의 종 조성과 분포을 알 기 위해 수행되었다. 다모류의 채집은 1985년 4월에 1987년 4월, 10월의 3회의 항해 동안 이루어졌다. 채집된 다모류는 총 36과 112 종이었으며, 우점다모류는 Chaetozone setosa, Aglaophanus malmgrent Ampharete arctica Lerchellules horikoshii, Tharyx sp., 와 Magelona pacifica 등이었다. 본 조사지역의 다모류 군집에 대한 주요 기여종 들은 복반부의 냉수종들이었다. 특히 우점종들은 대륙붕에서부터 대륙사면 상부 혹은 중부에서 주로 분포하며, 특정 서식 깊이를 보였다. 전반적인 평균서식밀도를 300개체 / m$^2$이며, 송풍부도는 15종/0.2 m$^2$ 정도이다. 평균서믹밀도와 종풍부도지수는 600 m 나 그 이상의 수심에서 뚜렷한 변화를 보였다. 우점종의 평균서식밀도와 밀접한 상관 관계를 보인 물리적 환경은 수심, 수온, 니질함량, 평균입도 등이었다.

복합신소재를 이용한 상하수도관

최진우,윤순종,Choi, Jin-Woo,Yoon, Soon-Jong 한국복합신소재구조학회 2011 복합신소재학회논문집 Vol.2 No.2