• 한국건축시공학회지
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• 제19권2호
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• pp.123-130
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• 2019

환경부하저감 및 동절기 시공의 효율을 위해 환경부하저감형 한중콘크리트 시공기술로서 고로슬래그시멘트와 내한촉진제를 병용한 콘크리트에 있어 열화의 기점이 되는 수축균열에 관해 검토했다. 그 결과, 고로슬래그시멘트 및 내한촉진제를 첨가함으로서 자유수축변형량 및 동일재령에 있어서 균열포텐셜은 증가하는 경향으로 구속조건하에서의 균열의 발생도 빠른 것을 확인할 수 있었다. 이것은, 자유수축변형량의 증가와 함께 크리프에 의한 응력 이완량의 감소나 구속도의 증가 등이 원인으로서 생각할 수 있으며, 동절기 시공에 있어서 고로슬래그 및 내한촉진제를 적용할 때는 수축에 의한 균열발생에 대해 검토할 필요가 있다고 판단된다.

• Journal of Ginseng Research
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• 제35권3호
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• pp.331-338
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• 2011

Red ginseng (RG, the extract of Panax ginseng Meyer) has various biological and psychological activities and may also alleviate fatigue-related disorders. The present study was undertaken to evaluate what kind of fatigue red ginseng alleviate. Animals were orally administered with 50, 100, 200, 400 mg/kg of RG for 7 days. Before experiments were performed. Physiological stress (swimming, rotarod, and wire test) are behavioral parameters used to represent physical fatigue. Restraint stress and electric field test to a certain degree, induce psychological fatigue in animals. Plasma concentration of lactate and corticosterone (CORT) were also measured after these behavioral assays. RG supplementation (100 mg/kg) increased movement duration and rearing frequency of restrainted mice in comparison with control. 100 and 200 mg/kg of RG increased swimming time in cold water ($8{\pm}4^{\circ}C$) while at 100 mg/kg, RG increased electric field crossing over frequencies. 50, 100 and 200 mg/kg RG prolonged running time on the rotarod and at 100 mg/kg, it increased balancing time on the wire. RG at those doses also reduced falling frequencies. RG supplementation decreased plasma CORT levels, which was increased by stress. Lactate levels were not significantly altered. These results suggest that RG supplementation can alleviate more the damages induced by psychological than physical fatigue.

• Journal of Welding and Joining
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• 제28권4호
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• pp.26-32
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• 2010

The purpose of this study is to evaluate the residual stresses at the multi-pass FCA weldment using the finite element analysis (FEA). In order to do it, an H-type specimen was selected as a test specimen. The variable used was in-plane restraint intensity. The temperature distribution at the multi-pass FCA butt weldment was evaluated in accordance with the relevant guidance recommended by the KWJS. The effective conductivity for the weld metal corresponding to each welding pass was introduced to control the maximum temperature below the vaporization temperature of weld metal. The heat flux caused by welding arc was assumed to be applied to the weld metal corresponding to welding pass. With heat transfer analysis results, the distribution of transverse residual stresses was evaluated using the thermo-mechanical analysis and compared with the measured results by XRD and uniaxial strain gage. In thermo-mechanical analysis, the plastic strain resetting at the temperature above melting temperature of $1450^{\circ}C$ was considered and the weld metal and base metal was assumed to be bilinear kinematics hardening continuum. According to the comparison between FEA and experiment, transverse residual stresses at the multi-pass FCA butt weldment obtained by FEA had a good agreement with the measured results, regardless of in-plane rigidity. Based on the results, it was concluded that thermo-mechanical FE analysis based on temperature distribution calculated in accordance with the KWJS’s guidance could be used as a tool to predict the distribution of residual stress of the multi-pass FCA butt weldment.

• Journal of Ship and Ocean Technology
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• 제7권4호
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• pp.41-49
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• 2003

Welding deformation reduces the accuracy of ship hull blocks and decreases productivity due to the need for correction work. Preparing an error-minimizing guide at the design stage will lead to higher quality as well as higher productivity. Therefore, developing a precise method to predict the weld deformation is an essential part of it. This paper proposes an efficient method for predicting the weld deformation of complicated structures based on the inherent strain theory combined with the finite element method. A simulation of a stiffened panel confirmed the applicability of this method to simple ship hull blocks.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.469-470
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• 2010

The high-strength concrete(HSC) compared to normal concrete represents higher autogenous shrinkage due to lower water-to-binder ratio(W/B) and supplementaries, fly ash(FA) and granulated blast-furnace slag(BFS), etc. The potential of early age cracking which reduces durability of concrete structures is normally influenced by autogenous shrinkage and degree of restraint. Therefore, this paper studies on the evaluation of the characteristics of autogenous shrinkage for HSC, ultra-high-strength concrete(UHSC) containing admixtures by experimental test and the test results are compared with existed prediction models.

• 대한기계학회논문집A
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• 제30권11호
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• pp.1408-1416
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• 2006

A mathematical knee model was constructed using MADYMO. The purpose of this study is to present a more realistic model of the human knee to reproduce human knee motion. Knee ligaments were modeled as line elements and the surrounding muscles were considered as passive restraint elements. A calf-free-drop test was performed to validate the suggested model. A calf was dropped from the rest at about 65 degree flexed posture in the prone position. The motion data were recorded using four video cameras and then three dimensional data were acquired by Kwon3D motion analysis software. The results showed that general shapes of angular quantities were similar in both the experiment and computer simulation. Functional stability of the anterior cruciate ligament was explicitly revealed through this model.

• Journal of Welding and Joining
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• 제7권1호
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• pp.36-41
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• 1989

Among various calculation methods for residual stresses, inherent strain method can be useful one for its simplicity. In comparison with finite element method, it is more economical and efficient. First, inherent strain is assumed, and then incompatibility can be calculated from this inherent strain. Based on collocation method, incompatibility equation is solved assuming stress functions which satisfies boundary conditions. Assumed inherent strain can be determined through iterations on the condition that longitudinal residual stress in centerline is yield stress and transverse distortion is the same as predicted one from other method. Calculated results according to this analytic method yield good agreement with experimental ones.

• 콘크리트학회논문집
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• 제23권5호
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• pp.581-590
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• 2011

초고성능 시멘트 복합체(ultra-high-performance cementitious conposites, UHPCC)는 우수한 압축강도와 연성을 나타내기 때문에 구조 부재 적용 시 단면을 상당히 감소시키고, 낮은 물-결합재비와 고분말 혼화 재료의 사용으로 높은 수축 변형률이 발생하게 되어 거푸집 및 보강근 등의 구속에 의한 수축 균열의 발생 가능성이 크다. 그러므로 이 연구에서는 UHPCC의 수축을 저감시키기 위한 방법으로 팽창재와 수축 저감제를 조합하여 혼입하고 자유수축과 구속 수축 거동을 평가하여 적합성 여부를 산정하였다. 실험 결과 팽창재와 수축 저감제를 조합하여 혼입한 경우에 약 40~44%의 자유수축 저감 효과를 보였으며, 잔류 인장응력은 약 35%와 47% 감소하였다. 지속적인 구속 하중에 의한 인장 크리프의 발생으로 탄성 수축 응력의 약 61%, 64%가 이완되는 것으로 나타났으며, 따라서 구속 수축 거동을 평가할 때에는 반드시 크리프 효과를 고려해야 한다고 판단되었다. 구속도는 0.78~0.85로 나타났으며 팽창재와 수축 저감제의 혼입에 의한 영향은 미미하였고 콘크리트 링의 두께가 클수록 감소하는 경향을 보였다. 또한, UHPCC의 인장 크리프 변형률을 측정하고 재령에 따라 변하는 구속 하중을 적용한 4-매개 변수 크리프 예측 모델과 비교하였다.

• 콘크리트학회논문집
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• 제22권5호
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• pp.641-650
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• 2010

콘크리트의 수축으로부터 발생하는 구속응력은 균열을 유발하고, 그에 따라 황산염 및 염화이온의 침투로 인한 철근의 부식으로 인해 콘크리트 구조물의 내구성을 저하시킨다. 특히, W/B가 감소할수록 균열 발생 가능성이 크며, 따라서 고강도 콘크리트(HSC), 초고강도 콘크리트(UHSC)의 수축 및 균열 거동의 정확한 이해와 평가가 필요하다. 하지만, 기존의 비구속 수축 실험은 콘크리트의 강도발현, 응력의 이완, 균열강도 및 구속도 등을 고려할 수 없으며, 균열 발생에 영향을 미치는 수축량의 평가에 한계가 있었다. 따라서 이 연구에서는 비구속 수축실험과 구속 수축실험(ring-test)을 통하여 W/B(30, 25, 16%) 및 혼화재에 따른 HSC, UHSC의 수축, 균열 거동을 평가하였다. 실험 결과, 자기수축 및 총 건조수축은 W/B가 클수록, 플라이애쉬(FA) 및 고로슬래그미분말(BFS)의 치환율이 증가할수록 감소하는 것으로 나타났으며, W/B의 증가 및 콘크리트 두께의 증가, FA의 혼입은 균열 발생을 효과적으로 억제하는 것으로 나타났다.

• 임상간호연구
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• 제17권3호
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• pp.443-454
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• 2011

Purpose: The purpose of this study was to investigate the predictors of delirium in patients after orthopedic surgery. Methods: Participants were 121 orthopedic surgery patients from one university affiliated hospital located in Seoul. The instrument of Delirium Observation Screening Scale (DOS) developed by Schuurmans et al. (2003) was utilized. Data were collected from September 1st, 2010 to March 31st, 2011 and analyzed using SPSS 12.0 with descriptive statistics, t-test, chi-square test and logistic regression. Results: The delirium in patients after orthopedic surgery was occurred in 9 (7.4%) out of 121 patients. Several factors were associated with the delirium occurrence age, admission route, preadmission Activity of Daily Living (ADL), preadmission hearing aid use, preadmission walking degree, diagnosis, type of surgery, Intensive Care Unit (ICU) stay after surgery, restraint, drainage tube, time of admission to surgery, preoperative albumin and preoperative sodium. Preadmission ADL, preoperative sodium and time of admission to surgery were the significant predictors of the delirium occurrence. Conclusion: Study results may help nurses predicting and detecting delirium early and providing preventive measures to the patients with high risk of delirium after orthopedic surgery.