• 한국수소및신에너지학회논문집
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• 제32권4호
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• pp.245-255
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• 2021

Various studies about metallic bipolar plates have been conducted to improve fuel cell performance through flow field design optimization. These research works have been mainly focused on fuel cells for vehicle, but not fuel cells for building. In order to reduce the price and volume of fuel cell stacks for building, it is necessary to apply a metallic flow field, In this study, for a metallic flow field applied to a fuel cell for building, the effect of a change in the flow field shape on the performance of a polymer electrolyte membrane fuel cell was confirmed using a model and experiments with a down-sizing single cell. As a result, the flow field using a metal foam outperforms the channel type flow field because it has higher internal differential pressure and higher reactants velocity in gas diffusion layer, resulting in higher water removal and higher oxygen concentration in the catalyst layer than the channel type flow field. This study is expected to contribute to providing basic data for selecting the optimal flow field for the full stack of polymer electrolyte membrane fuel cells for buildings.

• 대한토목학회논문집
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• 제39권3호
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• pp.369-380
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• 2019

PSC 구조물에 폭발과 같은 극한하중이 짧은 시간 동안 발생하게 되면 급작스러운 파괴와 그로 인한 수많은 인명 및 재산피해를 발생시킨다. 하지만 원전격납구조물, 가스탱크와 같은 PSC 구조물의 경우 방호 및 방재개념이 포함된 구조설계가 적용되지 않은 실정이며, 특히, 구조물 내부에서 발생하는 폭발압력하중은 피해규모가 외부폭발에 비해 훨씬 크기 때문에 내부폭발하중에 대한 검증은 반드시 필요하다. 따라서, 본 연구에서는 원전격납구조물의 내부폭발에 대한 저항성능을 검토하기 위해 이방향 프리스트레스트 콘크리트 축소모형을 제작하였다. 내부폭발 실험은 22.68, 27.22, 31.75 kg (50, 60, 70 lbs)의 ANFO 폭약을 이용하여 시편으로부터 1,000 mm의 거리에서 폭발시켰으며, 압력하중, 처짐, 변형률, 균열형상, 긴장력 변화 등의 데이터를 분석하였다. 본 연구결과를 이용하여 원전격납구조물의 내부폭발하중 발생 시 손상도 범위 예측이 가능할 것으로 판단된다.

• 한국수소및신에너지학회논문집
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• 제32권3호
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• pp.156-162
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• 2021

Mg hydride has a relatively high hydrogen storage amount of 7.6wt%, and inexpensive due to abundant resources, but has high reaction temperature and long reaction time because of treble oxidation reactivity and upper activation energy. Their range of applications could be further extended if their hydrogenation kinetics and degradation behavior could be improved. Therefore, the effect of CaO has improved the hydrogenation kinetics and slowed down the degradation. This study focused on investigating whether to improve the hydrogenation kinetics by synthesizing Mg₂NiH_x-5wt% CaO composites. The Mg₂NiH_x-5wt% CaO composites have been synthesized by hydrogen induced mechanical alloying. The synthesized composites were characterized by performing X-ray diffraction, Scanning Electron Microscopy, Brunauer-Emmett-Teller, Thermogravimetric, and Sivert's type automatic pressure-composition-temperature analysis. Hydriding kinetics were performed using an automatic PCT measurement system and evaluated over the temperature range of 423 K, 523 K, and 623 K. As a result of calculating the hydrogen adsorption amount through the hydrogenation kinetics curve, it was calculated as about 0.42wt%, 0.91wt%, and 1.15wt%, the highest at 623 K and the lowest at 423 K.

• 한국지반공학회논문집
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• 제36권12호
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• pp.117-124
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• 2020

본 연구는 온도에 따른 점성토의 전단 변형의 특성의 모사에 초점을 맞춘다. 일반적으로 온도가 상승할수록 정규압밀선은 간극비와 평균유효응력의 평면에서 하향 이동한다. 하지만 한계상태선은 온도변화에 따라 정규압밀선만큼 이동하지는 않는다. 따라서, 온도가 증가할수록, 한계상태 평균유효응력과 선행압밀 평균유효응력의 차이는 감소한다. 이를 반영하기 위해, 본 연구에서는 한계상태 평균유효응력을 기준으로 두 부분으로 나뉘어진 경계면을 적용하였다. 또한 Bangkok 점성토에 대해서 경계면을 구축하고, 비배수 삼축압축시험에 대해서 요소해석을 실시하였다. 요소해석 결과, 제안된 모델은 복잡한 강성 혹은 발달 법칙 없이 실험 데이터와 유사한 점성토의 온도에 따른 역학적 거동을 잘 모사하였다.

• Geomechanics and Engineering
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• 제24권4호
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• pp.389-397
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• 2021

Pile foundation is a typical form of bridge foundation and viaduct, and large-diameter rock-socketed piles are typically adopted in bridges with long span or high piers. To investigate the effect of a mountain slope with a deep overburden layer on the bearing characteristics of large-diameter rock-socketed piles, four centrifuge model tests of single piles on different slopes (0°, 15°, 30° and 45°) were carried out to investigate the effect of slope on the bearing characteristics of piles. In addition, three pile group tests with different slope (0°, 30° and 45°) were also performed to explore the effect of slope on the bearing characteristics of the pile group. The results of the single pile tests indicate that the slope with a deep overburden layer not only accelerates the drag force of the pile with the increasing slope, but also causes the bending moment to move down owing to the increase in the unsymmetrical pressure around the pile. As the slope increases from 0° to 45°, the drag force of the pile is significantly enlarged and the axial force of the pile reduces to beyond 12%. The position of the maximum bending moment of the pile shifts downward, while the magnitude becomes larger. Meanwhile, the slope results in the reduction in the shaft resistance of the pile, and the maximum value at the front side of the pile is 3.98% less than at its rear side at a 45° slope. The load-sharing ratio of the tip resistance of the pile is increased from 5.49% to 12.02%. The results of the pile group tests show that the increase in the slope enhances the uneven distribution of the pile top reaction and yields a larger bending moment and different settlements on the pile cap, which might cause safety issues to bridge structures.

• 한국콘텐츠학회논문지
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• 제22권6호
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• pp.184-193
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• 2022

최근 빈번히 사용되고 있는 '번아웃'은 치열한 경쟁 속에 사는 현대인들의 심리를 대변하는 대표적인 표현 중 하나다. 본 고에서는 직장인들의 힐링 영화로 손꼽히는 '꾸뻬씨의 행복여행'과 '잠깐만 회사 좀 관두고 올게' 두 편을 번아웃 관점에서 접근, 분석했다. 작품에서 나타난 번아웃의 증상은 무기력증, 짜증, 분노, 불면, 우울, 자살 충동 등이었으며, <꾸뻬씨..>의 경우 반복적인 상담업무에서 오는 가치 충돌이, <잠깐만..>의 경우 업무 과부하와 실적 압박, 동료 커뮤니티의 부재 등이 원인으로 작용하고 있었다. 이러한 번아웃 상태는 등장인물의 대사나 표정은 물론 다양한 사이즈의 부감쇼트와 낮은 조명, 주인공 앞쪽에 물건 배치 등을 통해 시각적으로 표현, 진단이 어려운 번아웃의 심리상태를 직관적으로 표현하고 있었다. 특히 번아웃의 진단 척도인 취미 생활이나 신체활동, 동료 커뮤니티의 유무 등이 번아웃에서 벗어나는데 도움이 된다는 것을 영화를 통해서도 확인할 수 있었다.

• Journal of Korea Trade
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• 제23권5호
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• pp.87-101
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• 2019

Purpose - This paper examines the effectiveness of the foreign exchange risk insurance system in the promotion of SME exports in Korea. The purpose of this study is to analyze the short-term and long-term responses of SME exports to foreign exchange risk insurance support policies. Based on these empirical studies, we would like to present some operational improvements to the operation of the foreign exchange risk insurance system. Design/methodology - In order to analyze the effect of exchange risk insurance on the exports of SMEs, a VAR model consisting of foreign exchange risk insurance underwriting values, export relative price, and domestic demand pressure, including export volume, was established. The study began with tests of the stationarity of time series data. The unit root tests showed that all concerned variables were non-stationary. Accordingly, the results of the cointegration test showed that the tested variables are not cointegrated. Finally, an impulse response function and variance decomposition analysis were conducted to analyze the impulse of foreign exchange risk insurance on exports of SMEs. Findings - As a result of estimating the VAR (1) model, foreign exchange risk insurance was found to be significant at a 1% significance level for SME' export promotion. In the impulse response analysis, SMEs' export response to the impulse of foreign exchange risk insurance showed that exports gradually increased until the third quarter, and then slowed down. However, the impulse did not disappear, and appeared continuously. Originality/value - This study analyzed the effect of foreign exchange insurance on exports of SMEs by applying the VAR model. In particular, this study is the first to analyze the short-term and long-term effects of foreign exchange risk insurance on exports of SMEs. The empirical evidence in the current study have a policy implication for the policy authority to support and promote the foreign exchange risk insurance in the effect of exchange rate volatility on Korea' export SMEs.

• 대한본초학회지
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• 제28권6호
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• pp.1-7
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• 2013

Objectives : The root of Peucedanum japonicum Thunberg (Peucedani Japonici Radix; PJR) has been traditionally used as an herbal medicine for the treatment of anti-headache, anti-paralysis, anti-cancer, vascular protection, and blood pressure regulation. In this study, we investigated the anti-allergic effect of PJR water extract on ovalbumin (OVA)-induced allergic asthma in mice. Methods : Mice were sensitized at days 1, 8 and 15 with OVA and airway challenged at days 22, 24, 26, 28, and 30 to induced allergic asthma. PJR-W extract at doses of 100 and 300 mg/kg/body weight (bw) was orally administered during OVA challenge once per a day. The levels of allergic mediators such as immunoglobulin (Ig) E, and Th1/Th2 cytokines (IFN-${\gamma}$ and IL-4) were measured in the sera of mice by ELISA. The histological change of lung tissue was observed with hematoxylin and eosin (H&E) staining. Results : The administration of PJR-W extract significantly decreased the serum levels of IgE, IL-4, and IFN-${\gamma}$ compared with those of OVA control group. In H&E staining, PJR-E extract inhibited OVA-induced airway inflammation and the inflammatory cells infiltration in the peribronchial regions of the lung. Conclusions : These results indicate that PJR-W extract has an anti-inflammatory and anti-allergic effect on allergic response through the down-regulation of allergic mediators, suggesting that this herb may be used as a useful source for the treatment of allergic inflammatory diseases such as asthma.

• Tribology and Lubricants
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• 제38권5호
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• pp.205-212
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• 2022

This paper presents experimental measurements of the structural characteristics of a two-pad beam-type gas foil journal bearing and its rotordynamic performance for a high-speed motor-driven turbocompressor. The test bearing had two top foils and two beam foils, each with an arc length of ~180°. Each beam foil was etched to obtain 40 beams with six geometries of different lengths and widths. The insertion of beam foils into the bearing housing produces equivalent beam heights. The structural tests of the bearing with a non-rotating journal revealed a smaller bearing clearance and larger structural stiffness for the load-on-pad configuration than for the load-between-pads configuration. Rotordynamic performance measurements during driving tests up to 100 krpm demonstrated synchronous vibrations and subsynchronous vibrations with large amplitudes. The test was repeated after inserting the shim between the top foil and beam foil to reduce the bearing radial clearance. The reduced bearing clearance resulted in a reduction in the peak amplitude of the synchronous vibrations and an increase in the speed at which the peak amplitude occurred. In addition, the onset speed and amplitude of the subsynchronous vibrations were dramatically increased and diminished, respectively. The rotor coast-down tests at 100 krpm show that the reduction in the bearing clearance extends the time to rotor stop, thus implying an improvement in hydrodynamic pressure generation and a reduction in bearing frictional torque.

• Journal of Veterinary Science
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• 제24권3호
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• pp.23.1-23.16
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• 2023

Background: Irritable bowel syndrome (IBS) is a functional bowel disorder (FBD). Objectives: To assess the therapeutic effects of paeoniflorin (PF) on IBS in rats. Method: Sixty male Sprague-Dawley rats were randomly divided into normal, model, positive drug, low-dose PF, medium-dose PF and high-dose PF groups (n = 10). After gavage for 2 consecutive weeks, the effect of PF on abdominal pain symptoms was assessed based on the abdominal withdrawal reflex (AWR) score, fecal water content and pathological changes in colon tissues. D-lactate, interleukin-1β (IL-1β), transforming growth factor-β (TGF-β) and tumor necrosis factor-α (TNF-α) were detected by enzyme-linked immunosorbent assay, and phosphorylated nuclear factor kappa B (p-NF-κB) p65 was detected by Western blotting. The abundance and diversity changes of intestinal flora were explored using 16S ribosomal RNA sequencing. Result: In PF groups, the mucosal morphology of colon tissues was intact, and the glands were arranged neatly and structured clearly, without obvious inflammatory cell infiltration. Compared with the model group, PF groups had significantly elevated pain threshold, and mRNA and protein levels of zonula occludens-1 (ZO-1) and occludin, decreased AWR score at 20 mmHg pressure, fecal water content, mRNA levels of IL-1β, TGF-β, and TNF-α, protein level of p-NF-κB p65 and level of serum D-lactate, and reduced levels of serum IL-1β, TGF-β, and TNF-α (p < 0.05, p < 0.01). PF groups had higher abundance of Lactobacillus, Akkermansia, Alistipes, and Bacteroides, but lower abundance of Desulfovibrio, Parasutterella, and Enterococcus than those of the model group. Conclusions: PF exerts therapeutic effects on IBS in rats probably by regulating the intestinal flora, and then up-regulating the expressions of ZO-1 and occludin in colon tissue while down-regulating the levels of IL-1β, TGF-β, TNF-α, D-lactate and p-NF-κB p65.