복합고체절연물의 극저온 절연성능 평가를 위한 임펄스 내전압시험

김우석,유승덕,현옥배,김혜림,임성우,양성은,김희선,Kim, W.S.,Ryu, S.D.,Hyun, O.B.,Kim, H.R.,Yim, S.W.,Yang, S.E.,Kim, H.S. 한국초전도학회 2011 Progress in superconductivity Vol.13 No.1

High voltage insulation in cryogenic environment is one of big issues for development of superconducting power application, such as superconducting fault current limiter, transformer, transmission cable, and so on. We had proposed a composite solid insulator composed of plastics and polymer insulation sheets for a use of high voltage superconducting power applications. It is well known that the G10 FRP keeps its mechanical strength at very low temperature and the PPLP is very good insulator adopted as insulations for superconducting transmission cables. The composition of these two materials will show very good electrical and mechanical properties adequate for the insulation components of superconducting power applications, such as bushing, insulation barrier, and even for a cryostat. Dielectric strengths of prepared samples were measured at the temperature of boiling point of liquid nitrogen at atmospheric pressure, which will be presented in this paper to show a usefulness of this technique.

고자장 NMR용 마그네트 개발 동향

김우석,Kim, U-Seok 한국초전도저온공학회 2015 초전도와 저온공학 Vol.17 No.1

영아 담도폐쇄증 진단에서 Tc-99m DISIDA 간담도주사와 경피간침생검의 의의

김우석,박우현,최순옥,김상표,Kim, Woo-Suk,Park, Woo-Hyun,Choi, Soon-Ok,Kim, Sang-Pyo 대한소아외과학회 1997 소아외과 Vol.3 No.1

본 저자들은 1992년 3월부터 1996년 4월까지 신생아 울체성 황달의 감별진단, 특히 신생아담도폐쇄증과 신생아 간염의 감별진단에 있어 Tc-99m DISIDA 간담도주사와 경피간침생검을 시행하여 다음과 같은 결과를 얻었다. 질환별로 볼 때 전체 60예의 환아 중에서 담도패쇄증이 23예, 신생아 감염이 34예였으며 경정맥고영양법으로 인한 황달이 2예, Alagille 증후군이 1예였다. Tc-99m DISIDA 간담도주사는 60명의 환아를 대상으로 실시하였다. BA 진단에 대한 민감도와 특이도는 각각 96%와 32%로서 높은 민감도를 보인 반면 특이도는 낮게 나타났으며 전체적인 진단 정확도는 57%였다. 경피간침생검은 Tc-99m DISIDA 간담도주사를 실시한 60명의 환아중 장관내 방사능이 나타나지 않았던 38명의 환아에서 40회 실시하였는데, 경피간침생검에 BA 진단에 대한 민감도는 88%, 특이도는 96%로 모두 높았으며 전체적인 진단 정확도는 93%였다. 본 연구를 요약하면 Tc-99m DISIDA 간담도주사는 특이도 32%, 양성예측율 47%로서 Tc-99m DlSIDA 간담도주사에서 장관내 방사능이 배설이 되지 않을 때는 경피간침생검이 반드시 필요하리라 생각되며, 일단 장관내 방사능이 배출되면 BA는 배제할 수 있으리라 생각된다. 경피간침생검은 전체적인 진단율이 93%로 높으나, BA 환아에서 8주전에 경피간침생검시는 NH와 감별이 어려울 수 있으며, 또 일부 NH, 경정맥고영양법 관련 울체성 황달에서는 경피간침생검시 BA와 감별이 어려울 수 있으므로, 임상경과를 보아서 의심스러우면 재 경피간침생검을 시행하던지 타 진단법을 응용해서 참고하여야 할 것으로 생각된다. To differentiate biliary atresia from intraheaptic cholestasis, Tc-99m DlSIDA hepatobiliary scintigraphies and percutaneous needle biopsies of 60 consecutive infants were evaluated retrospectively. Twenty three patients had biliary atresia and 37 patients intraheaptic cholestasis(neonatal hepatitis 34, TPN induced jaundice 2 and Dubin-Johnson syndrome 1). All sixty patients underwent Tc-99m DlSIDA hepatobiliary scintigraphy with phenobarbital pretreatment. Of 23 patients with biliary atresia, 22 were correctly interpreted showing 96% sensitivity while of 37 patients with intraheaptic cholestasis, only 12 had intestinal excretion of radionuclide showing 32% specificity. Among the forty needle biopsies, 17 of biliary atresia and 23 of intrahepatic cholestasis, 37 were correctly interpreted as either having biliary atresia or intrahepatic cholestasis. The overall diagnostic accuracy was 93%. Of 3 misdiagnosed cases, the histologic findings of two patients with biliary atresia(aged 43 days and 54 days at the first needle biopsy) were essentially the same as those of neonatal hepatitis. Follow-up biopsies, however, showed findings consistent with biliary atresia. The third one(VLBW premie with history of 8 weeks of TPN) showed mild ductal proliferation and portal fibrosis. This was interpreted as suspicious for biliary atresia. Jaundice resolved gradually. In summary, patients who have intestinal excretion of radionuclide on Tc-99m DlSIDA hepatobiliary scintigraphy, biliary atresia can be ruled out. But the patients who do not have intestinal excretion of radionuclide should have further investigation by needle biopsy. Judicious use of Tc-99m DISIDA hepatobiliary scintigraphy and percutaneous needle biopsy can give a diagnostic accuracy of 95% or more in cases of infantile cholestasis.

차량과 콘크리트 교각의 직접충돌해석법과 충돌하중이력곡선을 이용한 간접충돌해석법 비교연구

김우석,김경진,이재하,Kim, WooSeok,Kim, Kyeongjin,Lee, Jaeha 한국전산구조공학회 2014 한국전산구조공학회논문집 Vol.27 No.6

본 연구에서는 차량과 교각의 직접충돌해석을 통하여 기존 설계기준(도로교설계기준, AASHOTO LRFD)에서 아직 고려하고 있지 않은 동적영향을 고려한 실제 교각의 충돌 파괴 거동을 다양한 경계조건별로 검토하였다. 선정된 차량은 10톤, 16톤, 38톤의 Cargo 트럭이며 교각은 경부고속도로 상 일반적인 제원으로 선정하였다. 해석결과 가장 많은 파괴는 상부구조의 고려없이 교각의 상부면을 구속하였을 시에 발생하였으며 상부구조는 2차적인 영향을 교각에 전달하기 보다는 충돌에너지를 일부 흡수하는 역할을 하며 파괴를 감소시키는 것으로 확인되었다. 또한 해석의 효율성을 위해 차량과 강체간 충돌시 발생하는 충돌하중이력곡선을 교각에 외력으로 부여한 간접충돌해석을 수행하고, 이를 직접충돌해석 결과와 비교하였다. 해석 결과 직접충돌해석 결과와 매우 유사하게 교각의 거동을 예측하는 것으로 확인되었으며 해석효율성 또한 높아져 해석시간은 약 92%정도 감소하였다. 이러한 간접충돌해석법은 다양한 기존 모델이나 다른 해석프로그램에도 쉽게 부여될 수 있어 그 활용범위가 증가할 것으로 판단된다. In design standards such as AASHTO LRFD and Korea Highway Bridge Design, the dynamic behaviors under the impact loading has not been considered and it recommends of using a static force for designing bridge column against vehicle collisions. Accordingly, in this study, models of vehicle collisions to concrete bridge column were developed with various boundary conditions in order to take into account dynamic behaviour of the column. Cargo trucks of 10tons, 16tons and 38tons were selected and a typical type of concrete bridge pier column along the Kyungbu highway in Korea was selected for this study. Results from this study indicate that the static load specified in the design standards are too small compared to results obtained in this study. It was also found that a consideration of the bridge superstructure allowed smaller damages of concrete bridge pier column under truck impact loadings. Furthermore, a comparison study of direct impact analysis of vehicle to bridge-column with in-direct impact analysis using load-time history functions was performed. The in-direct impact analysis shows that the use of load-time history graph improves the computational cost up to 92% and predict the behaviors of the bridge column under the impact loadings well. The obtained load-time history graph could be easily applied to several existing models.

반주기내 한류성능을 위한 진공차단기의 아크소호

김우석,박충렬,현옥배,김혜림,임성우,유승덕,양성은,Kim, W.S.,Park, C.R.,Hyun, O.B.,Kim, H.R.,Yim, S.W.,Yu, S.D.,Yang, S.E. 한국초전도학회 2010 Progress in superconductivity Vol.12 No.1

A double line commutation (DLC) type SFCL with first peak limiting function has been proposed for ideal fault current limiting operation. Very fast switching (commutation) without any arc or high voltage problems for any kind of switching device is needed for the first peak current limiting. We've tried to find suitable conditions for a successful switching of a Vacuum Interrupter (VI) with HTS elements as a Peak Current limiting Resistance (PCR).

비분산 적외선 분광법을 이용한 Co₂농도 고속 분석기의 Sampling Module 특성에 관한 실험적 연구

김우석,손덕영,박영무,유재석,이종화,Kim, Woo-Seok,Shon, Deok-Young,Park, Young-Moo,Yoo, Jae-Suk,Lee, Jong-Hwa 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.3

A fast response analyzer for measuring carbon dioxide concentration has been developed for transient characteristic and researches tested on internal combustion engine. The analyzer uses the well known NDIR(Non-Dispersive Infrared) method with miniaturized detection system, giving a time constant of approximately 30 microsecond, and sampling module consists of capillary tube. Since the transit time and the time constant of the sampling system depend on the sampling conditions, it is necessary to investigate the characteristics of sampling system before applied to exhaust gas measurement in engine. A unique method was designed to study the influence of the diameter of transfer sample line and operating conditions of the FRNDIR on transit time and time constant. A database of transit time and time constant was built up for different measured and simulated pressure conditions. The database can be used for correcting eventual $CO_2$ concentration measurement.

순환골재를 사용한 고강도 철근콘크리트보의 휨거동에 관한 연구

김우석,여진동,곽윤근,강현구,홍성걸,Kim, Woo-Suk,Yeo, Jin-Dong,Kwak, Yoon-Keun,Kang, Thomas H.K.,Hong, Sung-Gul 대한건축학회 2012 대한건축학회논문집 Vol.28 No.3

Currently, approximately 90% of waste concrete is being used solely for landfills. Of the total waste concrete only about 14% is made into aggregate and recycled. Such usage is a very low-efficiency method of recycling these materials, under-utilizing an important and valuable asset. Common engineering practice has thus far failed to promote the design of structural members using recycled aggregates. Moreover, appropriate structural design standards for such materials have not been established, despite the number of domestic research studies which have been, and are being, conducted. Such practices overlook the fact that the recycling of aggregate from demolished concrete structures is both structurally and economically beneficial. In making full use of recycled concrete aggregates (RCA) it is necessary to understand its mechanical properties such as compressive, tensile and flexural strengths, and bond strength, as well as its structural performance. The main objectives of this research study are the investigation of flexural performance and the evaluation of the potential applications of RCA on concrete structures. For this, flexural tests of 12 reinforced high-strength concrete beams with RCA were performed. The current test data were examined in terms of flexural strength, along with the data from previously tested reinforced concrete beams with RCA. It is anticipated that this research will play a role of establishing the structural design standards for concrete members with RCA.

일체식 교대 교량의 대횡변위를 위한 교대와 H형 말뚝 연결부의 개발

김우석,이재하,박대효,Kim, Woo Seok,Lee, Jaeha,Park, Taehyo 한국전산구조공학회 2013 한국전산구조공학회논문집 Vol.26 No.4

본 논문에서는 일체식 교대 교량의 장대화 및 내진성능 향상을 위해 가장 중요한 역할을 하는 교대-H형 강말뚝 연결부의 성능을 향상시키기 위하여 기존의 연결부의 균열형상을 파악하고, 이를 기반으로 새로운 형태의 연결부를 제안하기 위하여 철근을 활용하여 강성을 증가시키는 방법과 강말뚝의 형상을 개선하여 연성을 개선시키는 방법을 모색하였다. 먼저, 기존 연결부의 성능을 향상시키기 위하여 연결부 주변에 PennDOT에 규정된 철근상세와 나선철근의 배치와 HSS 튜브를 사용하였으나, PennDOT의 철근 상세와 HSS 튜브는 연결부의 성능을 향상시키지 못 했으나, 나선철근은 균열을 효과적으로 차단시키는 것을 확인할 수 있었다. 하지만, 철근의 구속효과로 인해 강말뚝의 저항력이 변위에 선형적으로 비례하여 증가하므로 교량의 상부구조에 축력을 발생시키는 효과를 가져왔다. 따라서, 강말뚝의 형상을 개선하기 위하여 콘크리트 교대에 매입된 부분의 플랜지를 제거하는 방법과 콘크리트 외부에서 플랜지의 폭을 축소시키는 형태를 검토하였다. 두 가지 방안 모두 균열을 억제하는데 효과적인 방법이었으나, 플랜지를 제거하는 쪽의 연결부가 더욱 효과적이었다. Abutment-to-pile connection in an integral abutment bridge is vulnerable to lateral displacement induced by thermal movement of the superstructure. However, previous researches have merely focused on the connection. In order to improve the performance of the connection, new abutment-to-pile connection designs were proposed based on quasi-static nonlinear finite element model. The reinforcement detail specified in PennDOT DM4 and HSS tube were barely effective in controlling crack growing but spiral rebar effectively performed to delay crack growth as well as absorbing energy capacity. However, it was found that delaying cracking and strengthening the connection also caused the high lateral load in superstructures. Consequently, shape of HP pile were modified to introduce plastic hinge of the HP pile for reducing the lateral load in superstructures. Connections with modified HP pile significantly prevented crack propagations under the lateral displacement.

복합섬유로 보강된 순환골재 콘크리트의 성능평가에 관한 연구 사례 고찰

김우석,곽윤근,Kim, Woo-Suk,Kwak, Yoon-Keun 한국복합신소재구조학회 2015 복합신소재학회논문집 Vol.6 No.2

현수교 풍진동에 관한 2D 간단해석 및 변수연구

김우석,이재하,Kim, Woo Seok,Lee, Jaeha 한국전산구조공학회 2013 한국전산구조공학회논문집 Vol.26 No.6

본 연구에서는 풍진동에 대한 현수교의 거동을 예측하기 위하여 바닥판의 비틀림강성을 고려하여 Mckenna and Tuama 모델(2001)을 개선한 2D 간단해석 방법을 제안하였다. 기존의 모델은 풍속이 증가할수록, 진동수가 낮아질수록 비정상적인 값을 나타내고, 비틀림모드의 공진현상을 묘사할 수 없었다. 이에 본 연구에서는 비틀림강성을 고려하여 풍속에 따른, 진동수에 따른 비틀림진동을 분석하였다. 해석결과 진동 초기의 수직모드는 점차 비틀림모드로 전이되며 수직모드는 안정적으로 진동하는 것을 확인하였다. 또한 비틀림강성 효과를 고려하여 해석을 수행한 결과 수직모드는 시간이 경과함에 따라 안정화되는 모습을 보이나 비틀림 진폭은 일정시간(약 200초) 이후 나타나기 시작하여 비틀림각을 지속적으로 유지하였으며 맥놀이 주기는 풍속이 증가하면서 점차 감소하였다. 비틀림 강성에 따라 서로 다른 풍하중의 풍속과 진동수에 비틀림모드의 공진현상을 나타내므로 실제 설계에는 반드시 이러한 영향이 고려되어야 할 것이다. In this paper, 2D simple analyses were performed in order to predict the large torsional oscillations in a suspension bridge based on Makenna and Tuama model(2001). The existing model(Makenna and Tuama, 2001) has shown unrealistic results as the wind speed increases and frequency decreases. Furthermore, resonance could not be simulated by the existing model. Therefore, in this study, new model was proposed with a consideration of the torsional resistance. The vertical and rotational behaviors of the deck in the suspension bridge were analyzed. Analysis results showed that at first vertical oscillations were observed and it was gradually transformed to the rotation oscillations. With the consideration of the torsional resistance, it was shown that vertical behavior were stabilized as time passed. However, the rotational behavior was not stabilized and was kept until the end of analysis. Beat periods decreased while the wind speed increased. The resonance of the rotational mode was dependent to the rotational resistance. Obtained results could be applied for the design of the suspension bridge under the wind load.