• Nuclear Engineering and Technology
• /
• 제42권3호
• /
• pp.249-258
• /
• 2010

Recently, many utilities have considered interim dry storage of spent nuclear fuel as an option for increasing spent fuel storage capacity. Foreign nuclear regulatory committees have provided some regulatory and licensing requirements for relatively low- and medium-burned spent fuel with respect to the prevention of spent fuel degradation during transportation and interim dry storage. In the present study, the effect of cladding creep and hydride distribution on spent fuel degradation is reviewed and performance tests with high-burned Zircaloy-4 and advanced Zr alloy spent fuel are proposed to investigate the effect of burnup and cladding materials on the current regulatory and licensing requirements. Creep tests were also performed to investigate the effect of temperature and tensile hoop stress on hydride reorientation and subsequently to examine the temperature and stress limits against cladding material failure. It is found that the spent fuel failure is mainly caused by cladding creep rupture combined with mechanical strength degradation and hydride reorientation. Hydride reorientation from the circumferential to radial direction may reduce the critical stress intensity that accelerates radial crack propagation. The results of cladding creep tests at $400^{\circ}C$ and 130MPa hoop stress performed in this study indicate that hydride reorientation may occur between 2.6% to 7.0% strain in tube diameter with a hydrogen content range of 40-120ppm. Therefore, it is concluded that hydride re-orientation behaviour is strongly correlated with the cladding creep-induced strain, which varies as functions of temperature and stress acting on the cladding.

• 치위생과학회지
• /
• 제12권6호
• /
• pp.634-643
• /
• 2012

직무스트레스는 점차 복잡하고 다양화되어 가는 현대사회에서 건강 및 구강건강에 중요한 문제로 대두되고 있다. 본 연구는 2012년 6월 1일부터 6월 20일까지 366명의 근로자를 대상으로 직무스트레스와 구강건조정도를 파악하고 자가 구강증상을 측정하여 직무스트레스 및 구강건조정도와의 관련성을 알아보고자 하였다. 연구결과 다음과 같다. 1. 성별에 따른 직무스트레스 수준 차이 결과 남성은 직무요구, 관계갈등, 직장문화에서 상위 50%에 속해 있었으며. 여성은 관계갈등, 직무불안정, 직장문화에서 상위 50%에 속해있었다. 2. 직무스트레스 수준에 따른 구강건조감과 자가 구강증상의 차이 결과, 구강건조감은 직장문화에서 유의한 차이를 나타냈다. 구강증상은 직무요구, 관계갈등, 조직체계, 보상 부적절, 직무스트레스에서 유의한 차이를 나타냈다. 3. 구강건조감은 직장문화와 양의 상관관계를 나타냈으며, 구강증상은 직무요구, 관계갈등, 직무불안정, 조직체계, 직무스트레스, 구강건조감과 양의 상관관계를 나타냈다. 4. 직장문화, 보상부적절은 구강건조감에 유의한 영향을 주는 것으로 나타났으며, 구강건조감, 직무불안정, 조직체계는 구강증상에 유의한 영향을 주는 것으로 나타났다. 따라서 근로자 개인의 구강건강증진과 기업의 생산성 향상을 위해 직무스트레스의 원인을 정확히 파악하여야 하며, 스트레스로 인한 구강 내 증상을 인지하고 관리함으로써 삶의 질 향상에 큰 영향을 미칠 것이다.

• 한국융합학회논문지
• /
• 제9권12호
• /
• pp.331-336
• /
• 2018

본 연구는 평소 자신의 업무에 대하여 지각하는 스트레스 지수가 높은 30~40대 직장 여성 50명을 대상으로 미용대체 요법이 스트레스 완화에 미치는 복합적인 영향을 분석하여 급변하는 현대사회에서 여성 직장인들이 받는 스트레스를 완화시켜 건강하고 아름다운 삶을 유지하는데 도움을 주고자 하였다. 미용요법은 향기요법과 건식 이완 마사지를 15분간 시행하였으며, 시행 전 설문을 통하여 스트레스 지수를 확인하였다. 실험은 주1회 4주간 시행되었고 결과 측정은 타액 내 코티졸의 농도로 분석하였다. 그 결과 실험 전 스트레스 지수 평균은 3.97로 높게 나타났으며, 실험 후 대상자들의 코티졸 농도는 유의하게(p<0.05) 낮아졌고 특히, 기혼과 부양책임을 가진 대상자들에게서 더 많은 변화를 보였다. 이상의 결과로 향을 이용한 건식이완 마사지는 스트레스가 심한 30~40대 여성들의 심신 안정에 매우 효과적인 것으로 판단되며 이러한 미용적 방안을 잘 적용한다면 스트레스 관리에 도움이 될 것으로 판단된다.

• Nutrition Research and Practice
• /
• 제11권6호
• /
• pp.461-469
• /
• 2017

BACKGROUND/OBSECTIVE: Airway inflammation by eosinophils, neutrophils and alveolar macrophages is a characteristic feature of asthma that leads to pathological subepithelial thickening and remodeling. Our previous study showed that oxidative stress in airways resulted in eosinophilia and epithelial apoptosis. The current study investigated whether glutathione-containing dry yeast extract (dry-YE) ameliorated eosinophilia, goblet cell hyperplasia and mucus overproduction. MATERIALS/METHOD: This study employed $2{\mu}g$/mL lipopolysaccharide (LPS)- or 20 ng/mL eotaxin-1-exposed human bronchial epithelial cells and ovalbumin (OVA)-challenged mice. Dry-YE employed in this study contained a significant amount of glutathione (140 mg in 100 g dry yeast). RESULTS: Human bronchial epithelial cell eotaxin-1 and mucin 5AC (MUC5AC) were markedly induced by the endotoxin LPS, which was dose-dependently attenuated by nontoxic dry-YE at 10-50 ${\mu}g$/mL. Moreover, dry-YE inhibited the MUC5AC induction enhanced by eotaxin-1, indicating that eotaxin-1-mediated eosinophilia may prompt the MUC5AC induction. Oral supplementation with 10-100 mg/kg dry-YE inhibited inflammatory cell accumulation in airway subepithelial regions with a reduction of lung tissue level of intracellular adhesion molecule-1. In addition, ${\geq}50$ mg/kg dry-YE diminished the lung tissue levels of eotaxin-1, eosinophil major basic protein and MUC5AC in OVA-exposed mice. Alcian blue/periodic acid schiff staining revealed that the dry-YE supplementation inhibited goblet cell hyperplasia and mucus overproduction in the trachea and bronchiolar airways of OVA-challenged mice. CONCLUSIONS: Oxidative stress may be involved in the induction of eotaxin-1 and MUC5AC by endotoxin episode and OVA challenge. Dry-YE effectively ameliorated oxidative stress-responsive epithelial eosinophilia and mucus-secreting goblet cell hyperplasia in cellular and murine models of asthma.

• 한국작물학회지
• /
• 제49권4호
• /
• pp.271-278
• /
• 2004

This study was conducted to obtain basic information of growth, chlorophyll, and $Na^+\;and\;K^+$ content of rice (Oryza sativa L.) seedlings after transplanting in different NaCl conditions. Plants grown in pots for 8 days after germination were grown for 10 days after transplanting in 50 and 100 mM NaCl concentrations. At higher NaCl concentration, plant height, root length, dry weight and chlorophyll content were reduced with NaCl stress. Among rice cultivars, the shoot dry weight of Gancheokbyeo, Janganbyeo and Hwasungbyeo, and the root dry weight of Janganbyeo, Gancheokbyeo and Juanbyeo showed relatively low reduction compared to the other rice cultivars at 100 mM NaCl stress. The $Na^+$ content in seedling rapidly increased with the increase of NaCl concentration but $K^+$ contents decreased. There was a significant relationship between $Na^+$ content and shoot and root dry weight after transplanting rice seedlings to saline conditions. The shoot and root dry weight showed highly negative relationship with the $Na^+/K^+$ ratio in saline conditions.

• Molecules and Cells
• /
• 제43권7호
• /
• pp.632-644
• /
• 2020

The molecular mechanism underlying autophagy impairment in the retinal pigment epithelium (RPE) in dry age-related macular degeneration (AMD) is not yet clear. Based on the causative role of poly(ADP-ribose) polymerase 1 (PARP1) in RPE necrosis, this study examined whether PARP1 is involved in the autophagy impairment observed during dry AMD pathogenesis. We found that autophagy was downregulated following H₂O₂-induced PARP1 activation in ARPE-19 cells and olaparib, PARP1 inhibitor, preserved the autophagy process upon H₂O₂ exposure in ARPE-19 cells. These findings imply that PARP1 participates in the autophagy impairment upon oxidative stress in ARPE-19 cells. Furthermore, PARP1 inhibited autolysosome formation but did not affect autophagosome formation in H₂O₂-exposed ARPE-19 cells, demonstrating that PARP1 is responsible for impairment of late-stage autophagy in particular. Because PARP1 consumes NAD⁺ while exerting its catalytic activity, we investigated whether PARP1 impedes autophagy mediated by sirtuin1 (SIRT1), which uses NAD⁺ as its cofactor. A NAD⁺ precursor restored autophagy and protected mitochondria in ARPE-19 cells by preserving SIRT1 activity upon H₂O₂. Moreover, olaparib failed to restore autophagy in SIRT1-depleted ARPE-19 cells, indicating that PARP1 inhibits autophagy through SIRT1 inhibition. Next, we further examined whether PARP1-induced autophagy impairment occurs in the retinas of dry AMD model mice. Histological analyses revealed that olaparib treatment protected mouse retinas against sodium iodate (SI) insult, but not in retinas cotreated with SI and wortmannin, an autophagy inhibitor. Collectively, our data demonstrate that PARP1-dependent inhibition of SIRT1 activity impedes autophagic survival of RPE cells, leading to retinal degeneration during dry AMD pathogenesis.

• 터널과지하공간
• /
• 제30권3호
• /
• pp.256-269
• /
• 2020

본 연구의 목적은 KURT 화강암 시료의 포화유무에 따른 균열손상 기준과 파괴인성의 변화를 측정하는 것이다. 이를 위하여 일축압축시험을 이용한 소성체적변형률을 통해 KURT 화강암의 균열손상 기준을 도출하였다. 또한 암석의 파괴인성을 보다 신뢰성 있게 측정하기 위해 암석의 비선형적 변형에 대한 보정(Level II Method; ISRM, 1988) 을 통해 포화유무에 따른 KURT 화강암의 수정 파괴인성(corrected fracture toughness)을 측정하였다. 시험결과 건조시료의 평균 균열개시 응력(σ_ci)과 균열손상 응력(σ_cd)은 91.1 MPa과 128.7 MPa이었으며, 포화시료의 평균 균열개시 응력(σ_ci)과 균열손상 응력(σ_cd)은 58.2 MPa과 68.2 MPa이었다. 건조시료에 비해 포화시료의 균열개시 응력은 36% 감소하였으며 균열손상 응력은 건조시료 대비 47%나 감소되는 결과를 나타내었다. 균열손상 응력(σ_cd)이 상대적으로 더욱 감소하였음을 감안할 때 시료의 포화로 인해 더 낮은 응력조건에서 구조물에 대한 손상이 쉽게 발생할 수 있음을 알 수 있다. KURT 화강암의 비선형성을 고려한 수정 파괴인성은 0.811 MPa·m^0.5이었으며 포화시료의 수정 파괴인성은 0.620 MPa·m^0.5이었다. 즉 암석의 비선형성을 고려함으로써 파괴인성의 증가를 확인할 수 있었으며, 암석의 포화시 수정 파괴인성은 24% 감소하였다. 따라서 지하수 포화로 인해 암석 내 균열의 생성과 진전에 대한 저항성이 감소함을 알 수 있다.

• 전자공학회논문지D
• /
• 제35D권2호
• /
• pp.60-69
• /
• 1998

Polysilicon surface mdoification tecnique is developed to reduce the sticking of microstructures fabricated by micromachining. Modified anti-sticking grain holes are simply formed by two-step dry eth without additional photolithography nor deposition of thin films. Both process-induced sticking and in-use sticking are successfully reduced more than two times by adopting grain holed polysilicon substrate. A sticking model for cantilever beam is derived. This model includes bending moment stems from stress gradient along the thickness directionof structural polysilicon. Because the surface tension of rinse liquid and the surface energy of the solids to be stuk tend to decrease in recently developed anti-sticking techniques, the effect of stress gradient will play an important role to analyze the sticking phenomena. Effect of the temperature during post-release rinse and dry is modelled and verified experimentally. Based on developed anti-sticking polysilicon structure and the sticking model, sticking of microstructure, fabricated by simple wet process including sacrificial layer etch and rinse with deionized water without special equimpment for post-release rinse and dry was alleviated more than 3.5 times.

• 한국주조공학회지
• /
• 제3권2호
• /
• pp.92-99
• /
• 1983

This study has been carried out to investigate into the difference of rolling life and rolling wear characteristics for various gray cast iron under unlubricated dry rolling condition by amsler type wear test with 9.09% sliding.The results obtained from this study are summerized as follows: 1) It has been found that the amount of rolling wear id decreased when tensile strength and hardness are low, and then the rolling life up to generation of abnormal wear is conspicuously increased. 2) At the given condition the amount of rolling wear has been found to decrease as carbon equivalent of gray cast iron increases and resistance of crack propagation is an important factor on improvement of wear characteristics. 3) The amount of rolling wear is increased with increasing rolling revolution and wear of gray cast iron under dry rolling condition is characterized by three modes; initial wear, stationary wear and abnormal wear. 4) It has been found that the amount of rolling wear is increased with increasing maximum compressive stress and extremely increased when maximum compressive stress is over 59.1kg.f/mm.

• Nuclear Engineering and Technology
• /
• 제50권2호
• /
• pp.306-312
• /
• 2018

There is an increasing need in the United States and around the world to move used nuclear fuel from wet storage in fuel pools to dry storage in casks stored at independent spent fuel storage installations or interim storage sites. Under normal conditions, the Nuclear Regulatory Commission limits cladding temperature to $400^{\circ}C$ for high-burnup (>45 GWd/mtU) fuel, with higher temperatures allowed for low-burnup fuel. An analysis was conducted with FRAPCON-4.0 on three modern fuel designs with three representative used nuclear fuel storage temperature profiles that peaked at $400^{\circ}C$. Results were representative of the majority of US light water reactor fuel. They conservatively showed that hoop stress remains below 90 MPa at the licensing temperature limit. Results also show that the limiting case for hoop stress may not be at the highest rod internal pressure in all cases but will be related to the axial temperature and oxidation profiles of the rods at the end of life and in storage.