• Nuclear Engineering and Technology
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• 제38권4호
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• pp.375-382
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• 2006

Characterization tests (load vs. displacement curve) are conducted for the springs of Zirconium alloy spacer grids for an advanced LWR fuel assembly. Twofold testing is employed: strap-based and assembly-based tests. The assembly-based test satisfies the in situ boundary conditions of the spring within the grid assembly. The aim of the characterization test via the aforementioned two methods is to establish an appropriate assembly-based test method that fulfills the actual boundary conditions. A characterization test under the spacer grid assembly boundary condition is also conducted to investigate the actual behavior of the spring in the core. The stiffness of the characteristic curve is smaller than that of the strap-wised boundary condition. This phenomenon may cause the strap slit condition. A spacer grid consists of horizontal and vertical straps. The strap slit positions are differentiated from each other. They affords examination of the variation of the external load distribution in the grid spring. Localized legions of high stress and their values are analyzed, as they may be affected by the spring shape. Through a comparison of the results of the test and FE analysis, it is concluded that the present assembly-based analysis model and procedure are reasonably well conducted and can be used for spring characterization in the core. Guidelines for improving the mechanical integrity of the spring are also discussed.

• 한국철도학회논문집
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• 제19권1호
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• pp.54-66
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• 2016

이 연구에서는 흡수경계조건을 적용하여 경계부분에서 발생한 갑작스런 하중조건의 변화에 의해 발생한 탄성파의 전달 및 반사현상을 감소시키고자 하였으며, 흡수경계조건이 사용 유무에 따른 효과를 검증하였다. 또한, 정점하중재하의 경우와 이동하중에 의한 동적해석결과를 비교함으로써 정점하중재하가 이동하중을 적절히 표현할 수 있는가의 여부를 분석하였다. 주행속력의 변화에 따른 KTX 열차조건에서의 이동하중에 의한 동적해석을 수행하여 아스팔트 콘크리트 궤도에서의 동적안정성을 검토하였으며, 준정적인 표준 열차하중에 의한 해석결과를 비교함으로써 아스팔트 콘크리트 궤도의 구조 안전성을 확인하였다.

• 설비공학논문집
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• 제22권10호
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• pp.679-686
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• 2010

A proprietary device is adopted to break out the membrane of cell in the rigid polyurethane foam. As it is known, the membrane of cell is hardly tearing-off thoroughly in a mechanical way due to both its elastic characteristic and micro sized pores. In this study, a novel experimental approach is introduced to burst out all gases inside the cells of the rigid polyurethane foam by abrasively grinding micro-cells completely into fine powder. The biggest advantage of this approach is to be capable of releasing all gases out from the cell even in the micro pores. As clearly reflected from the repeatability, the accuracy of the result is highly improved and high confidence in the data sets as well. For the measurements of not only gas composition but partial pressure for each gas simultaneously as well, a precision gas mass spectrometer is used in-line directly to the abrasive grinding device. To control the starting point of the polyurethane foam, all samples were prepared on site in the laboratory. Manufactured time is one of the most critical factors in characterization of cell gas composition because it is known that one of gas composition, especially, carbon dioxide, is diffused out dramatically in a short period of time as soon as it is foamed.

• 복식문화연구
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• 제16권3호
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• pp.518-532
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• 2008

The purposes of this study were to investigate the relationships between women's self-image and the preference and the wearing frequency of knit-wears, and to examine the characteristics of the design elements that influence the preferred knit-wear images. The subjects were 277 female college students and working women living in metropolitan area of Seoul. The data were analyzed by using descriptive analysis, factor analysis, Cronbach's $\alpha$-reliability coefficient, Pearson's correlation coefficient, and multiple regression analysis. Four dimensions of women's self-images were derived by factor analysis; elegance, conservativeness, individuality, and maturity. Women with conservative self-image preferred simple knit-wears and women with high rate for individuality preferred splendid and sporty knit-wears. Women with elegant self-image disliked sporty knit-wears. Women with conservative self-image preferred white, and those who rated their self-image to be individuality preferred various colors including yellow, blue, green, purple, pink, and sky-blue. Women with mature self-image preferred black and beige. Women with individuality as their self-image preferred jacquard pattern and abstract pattern. There was a higher wearing frequency for all four seasons for women with conservative self-image, and there was higher wearing frequency in the winter for those with elegant self-images. Women who preferred simple knit-wears showed preference for single color with no prints and low chroma color, and those who preferred sporty knit-wears showed preference for elastic materials. Women who preferred neat and elegant knit-wears showed preference for argyle check pattern.

• 한국전산구조공학회논문집
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• 제23권3호
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• pp.283-288
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• 2010

모바일 하버용 크레인은 항만 부두에 설치되어 있는 일반 지상식 크레인과는 달리 소형 경량 구조를 요구한다. RORI 크레인은 이러한 요구조건을 만족시키기 위해 고안된 신개념의 모바일 하버용 크레인 시스템으로서 해상에서 컨테이너 상하역 작업을 고속으로 처리할 수 있을 뿐만 아니라 운항 시에는 완전히 접을 수 있도록 되어 있다. 본 연구는 컨테이너 상하역 작업에 따른 RORI 크레인의 수평붐 끝단 처짐량 분석에 관한 내용으로, 카스틸리아노 정리를 이용한 이론적인 방법과 유한요소법에 의한 수치해석적인 방법을 적용하였다. 두 기법으로 구한 끝단 처짐량을 비교분석함으로써 유한요소해석의 타당성을 입증하고, 케이블의 초기장력에 따른 끝단 처짐량 변화특성을 파라메트릭하게 분석하였다.

• Corrosion Science and Technology
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• 제9권5호
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• pp.223-232
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• 2010

NiTi alloy has been used for orthodontic wire due to good mechanical properties, such as elastic strength, friction resistance, and high corrosion resistance. Recently, these wire were coated by polymer and ceramic materials for aesthetics. The purpose of this study was to investigate electrochemical characteristics of tooth colored NiTi wire using various instruments. Wires (round type and rectangular type) were used, respectively, for experiment. Polymer coating was carried out for wire. Specimen was investigated with optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and energy dispersive x-ray spectroscopy (EDS). The corrosion properties of the specimens were examined using potentiodynamic tests (potential range of -1500 ~ 2000 mV) and electrochemical impedance spectroscopy (frequency range of 100 kHz ~ 10 mHz) in a 0.9 % NaCl solution by potentiostat. From the results of polarization behavior, the passive region of non-coated NiTi wire showed largely, whereas, the passive region of curved NiTi wire showed shortly in anodic polarization curve. In the case of coated NiTi wire, pitting and crevice corrosion occurred severely at interface between non-coated and coated region. From the results of EIS, polarization resistance(Rp) value of non-coated round and rectangular NiTi wire at curved part showed $5.10{\times}10^5{\Omega}cm^2$ and $4.43{\times}10^5{\Omega}cm^2$. lower than that of coated NiTi wire. $R_p$ of coated round and rectangular NiTi wire at curved part showed $1.31{\times}10^6{\Omega}cm^2$ and $1.19{\times}10^6{\Omega}cm^2$.

• 한국농공학회지
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• 제39권3호
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• pp.72-82
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• 1997

In all inelastic deformations time rate effects are always present to some degree. Whether or not their exclusion has a significant influence on the prediction of the material behaviour depends upon several factors. In the study of structural components under static loading conditions at normal temperature it is accepted that time rate effects are generally not important. However metals, especially under high temperatures, exhibit simultaneously the phenomena of creep and viscoplasticity. In this study, elastoplastic and elasto-viscoplastic models include nonlinear geometrical effects were developed and several numerical examples are also included to verify the computer programming work developed here in this work. Comparisons of the calculated results, for the elasto-viscoplastic analysis of an internally pressurised thick cylinder under plane strain condition, have shown that the model yields excellent results. The results obtained from the numerical examples for an elasto-viscoplastic analysis of the Nuclear Reinforced Concrete Containment Structure(NRCCS) subjected to an incrementally applied internal pressure were summarized as follows : 1. The steady state hoop stress distribution along the shell layer of dome and dome wall junction part of NRCCS were linearly behave and the stress in interior surfaces was larger than that in exterior. 2.However in the upper part of the wall of NRCCS the steady state hoop stress in creased linearly from its inner to outer surfaces, being the exact reverse to the previous case of dome/dome-wall junction part. 3.At the lower part of wall of NRCCS, the linear change of steady state hoop stress along its wall layer began to disturb above a certain level of load increase.

• 한국산림과학회지
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• 제72권1호
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• pp.37-44
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• 1986

물참나무엽(葉)과 상수리나무엽(葉)의 수분특성인자(水分特性因子)의 계절변화(季節變化)를 p-v곡선법(曲線法)에 의해 측정(測定)하였다. 양수종(兩樹種)의 최대포수시(最大飽水時)의 침투압(浸透壓) ${\pi}_o$와 초기원형질(初期原形質) 분이점(分離點)의 침투압(浸透壓) ${\pi}_p$는 생육초기(生育初期)에 높고 성숙엽(成熟葉)이 되어 가면서 감소(減少)하였다. 전생육기간(全生育期間)을 통해 양수종(兩樹種)은 전수분량(全水分量)의 약(約) 10~20%의 수분(水分)을 상실(喪失)할 때 팽압(膨壓)이 0에 달(達)했다. 양수종(兩樹種)의 최대포수시(最大飽水時)의 유포(釉胞)의 탄성계수(彈性係數), Emax는 엽(葉)이 신장(伸長)함에 따라 증가(增加)하였으며, 경엽화(硬葉化)된 이후(以後)는 감소(減少)하였다. 오스몰수, Ns/DW의 위절변화(委節變化)는 물참나무엽(葉)이 상수리나무엽(葉)보다 컸으며, 상대함수율(相對含水率)(Vp/Vo, $RWC^*$, Vo/Vt)은 비교적 위절변화(委節變化)가 작았다.

• 한국지진공학회논문집
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• 제8권1호
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• pp.59-65
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• 2004

최근 강구조물의 고층화 및 장경간화로 인하여 SM570강재와 같은 고강도 강재의 적용을 필요로 하고 있다. 강구조물의 정확한 내진설계를 위한 내진구조해석시 비선형 반복하중을 받는 강재의 특성을 명확히 포현할 수 있는 구성식이 필요하다. SM570는 최근 그 사용이 증가하고 있으나 아직 반복소성거동의 구현 및 정식화에 관한 연구는 아직 미진하다. 본 연구에서는 인장 및 저싸이클 피로 실험을 통하여 SM570 강재의 반복소성모델을 제안하였다. 제안된 반복소성모델을 3차원 유한요소에 적용하여 SM570이 사용된 원형 강교각의 내진해석을 수행하였다. 실험결과와 내진해석을 통하여 본 연구에서 제안한 구성식은 SM570이 사용된 강구조물의 복잡한 소성거동을 정도 높게 구현함을 알 수 있었다.

• 한국지진공학회논문집
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• 제1권4호
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• pp.1-9
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• 1997

본 논문은 고층건물의 지진응답해석에서 탄성 및 탄소성 응답스펙트럼 해석법에 대하여 고찰한 것이다. 선형 구조물의 지진응답 해석에 널리 사용되고 있는 응답스펙트럼법은 여러 연구자들에 의해 서로 다른 모드 조합방법으로 제안되었으며, 이들 조합방법에 따른 차이점을 상세히 검토하였다. 탄소성 지진응답해석에 응답스펙트럼법은 아직 널리 사용되고 있지 못한 실정이다. 본 연구에서는 장주기를 갖는 고층 건물의 탄소성 지진응답해석에 응답스펙트럼을 확장하여 적용하는 방법을 제시한다. 본 논문에서 제안한 탄소성 응답스펙트럼법을 이용하면, 고층건물의 예비 설계에서 시간이력해석 대신으로 보다 간편히 탄소성 응답치를 예측하는 도구로서 활용할 수 있을 것으로 사료된다.