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Effect of Hydride Reorientation on Delayed Hydride Cracking In Zr-2.5Nb Tubes
Yun Yeo Bum,Kim Young Suk,Im Kyung Soo,Cheong Yong Moo,Kim Sung Soo Korean Nuclear Society 2003 Nuclear Engineering and Technology Vol.35 No.6
The objective of this study is to investigate the reorientation of hydrides with applied stress intensity factor, the peak temperature and the time when to apply the stress intensity factor in a Zr-2.5Nb pressure tube during its thermal cycle treatment. Cantilever beam (CB) specimens with a notch of 0.5 mm in depth made from the Zr-2.5Nb tube were subjected to electrolytic hydrogen charging to contain 60 ppm H and then to a thermal cycle involving heating to the peak temperature of either 310 or $380^{\circ}C$, holding there for 50 h and then cooling to the test temperature of $250^{\circ}C$. The stress intensity factor of either 6.13 or $18.4\;MPa\sqrt{m}$ was applied at the beginning of the thermal cycle, at the end of the hold at the peak temperatures and after cooling to the test temperature, respectively. The reorientation of hydrides in the Zr-2.5Nb tube was enhanced with the increased peak temperature and applied stress intensity factor. Furthermore, when the CB specimens were subjected to $18.4\;MPa\sqrt{m}$ from the beginning of the thermal cycle, the reoriented hydrides occurred almost all over the Zr-2.5Nb tube, surprisingly suppressing the growth of a DHC crack. In contrast, when the CB specimens were subjected to the stress intensity factor at the test temperature, little reorientation of hydrides was observed except the notch region, leading the Zr-2.5Nb to grow a large DHC crack. Based on the correlation between the reorientation of hydrides and the DHC crack growth, a governing factor for DHC is discussed along with the feasibility of the Kim's DHC model.
CANDU Zr-2.5Nb 압력관에서 수소화물 재석출 거동
윤여범(Yeo-Bum Yun),김영석(Young-Suk Kim),정현철(Hyeon-Cheol Jeong),임경수(Kyung-Soo Im),김성수(Sung-Soo Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8
The objective of this study is to investigate the reorientation of zirconium-hydrides in the water-quenched and furnace-cooled Zr-2.5Nb tubes with different peak temperatures and applied stress. To this end, cantilever beam (CB) specimens containing 60 ppm hydrogen were subjected to a thermal cycle treatment where the peak temperature changed from 310 to 380 ℃ and stresses were applied at the test temperature of 250 ℃approached by cooling from the peak temperature. The water-quenched CB specimens with a fine distribution of smaller hydrides had an enhanced reorientation of hydrides from the circumferential direction to the radial direction compared to the furnace-cooled CB. Further, the number of reoriented hydride increased remarkably with increasing peak temperature from 310℃ to 380℃. The reoriented hydrides increased with increased applied stress during the thermal cycle. The reorientation behavior of the hydrides ahead of the crack tip is discussed in terms of plastic deformation caused by changing when to apply stress to the CB specimens subjected to a thermal cycle.
Evaluation of the Biochars pH on NH₃ Volatilization
Yun-Gu Kang(강윤구),Jin-Hyuk Chun(천진혁),Jae-Han Lee(이재한),Yeo-Uk Yun(윤여욱),Gi-Bum Yi(이기범),Taek-Keun Oh(오택근) 한국토양비료학회 2021 한국토양비료학회 학술발표회 초록집 Vol.2021 No.11
Nitrogen (N) is one of the most vital nutrient elements in plant growth. The plant quality and quantity varies depending on the amount of N. However, owing to the moderately low N use efficiencies by the growing crops, a considerably large percentage of it about 10 - 20% is volatilized to the atmosphere as form of NH₃ and N₂O. The volatilized NH₃ reacts with various oxides (NO<SUB>x</SUB>, SO<SUB>x</SUB>) to generate secondary particulate matter (PM2.5). Therefore, this study aimed to assess if biochars pH can impact its capacity of lessening NH3 emitted from the fertilized agricultural fields. Biochar was applied with 1% (w w<SUP>-1</SUP>) while N in form of urea was applied at three different rates of 160, 320, and 640 kg ha<SUP>-1</SUP>. NH₃ was collected using a dynamic chamber method and analyzed following the indophenol blue method after extraction with 2 M KCl solution. Based on the results indicate that the daily NH₃ emissions peaked within 4 - 7 days after fertilizations and decreased sharply afterwards. biochar amendments greatly reduced NH₃ emissions in all the treatments. The greatest reduction of 25% in relation to the control came from the neutral biochar (pH 6.7) applied to the soil fertilized with the 320 kg N ha<SUP>-1</SUP> and is thus, the most effective way of reducing NH3 volatilizations.
녹차카테킨과 에피갈로카테킨갈레이트의 산화적 스트레스에 대한 억제효과
윤여표(Yeo Pyo Yun),박종범(Jong Bum Park),허문영(Moon Young Heo) 대한약학회 2001 약학회지 Vol.45 No.1
Green tea catechins (GTC) and its major component, (-)-epigallocatechin gallate (EGCG) were studied for their protective effect against reactive oxygen species (ROS)-induced oxidative stress. GTC and EGCG showed the strong antioxidative effects on the lipid peroxidation of ethyl linolate with Fenton's reagent and free radical scavenging effect to DPPH radical generation. They also protected H2O2-or KO2-induced cytotoxicity in CHL cells or mouse splenocytes. These results indicate that GTC and EGCG are acpable of protecting the lipid peroxidation, free radical generation and cytotoxicity induced by ROS. The mechanism of inhibition in ROS-induced cytotoxicity may be due to their antioxidative and free radial scavenging properties. Therefore, GTC and EGCG may be useful chemopreventive agents by protecting the free radical generation which are involved in cancer and aging.
Kim, Bum-Joon,Hong, Seong-Karp,Lee, Keun-Hwa,Yun, Yeo-Jun,Kim, Eui-Chong,Park, Young-Gil,Bai, Gil-Han,Kook, Yoon-Hoh American Society for Microbiology 2004 Journal of clinical microbiology Vol.42 No.3
<P>A novel duplex PCR method that can amplify the 235- and 136-bp rpoB DNAs of Mycobacterium tuberculosis complex and nontuberculous mycobacteria (NTM), respectively, with two different sets of primers was used to differentially identify 44 reference strains and 379 clinical isolates of mycobacteria in a single-step assay. Showing 100% sensitivity and specificity, the duplex PCR method could clearly differentiate M. tuberculosis complex and NTM strains. In addition, restriction fragment length polymorphism analysis and direct sequencing of the amplicon of NTM could be used to supplement species identification.</P>
Anti-oxidative and Photo-protective Effects of Coumarins Isolated from Fraxinus chinensis
Lee, Bum-Chun,Lee, So-Yong,Lee, Hwa-Jeong,Sim, Gwan-Sub,Kim, Jin-Hui,Kim, Jin-Hwa,Cho, Young-Ho,Lee, Dong-Hwan,Pyo, Hyeong-Bae,Choe, Tae-Boo,Moon, Dong-Cheul,Yun, Yeo-Pyo,Hong, Jin-Tae 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.10
Free radicals and reactive oxygen species (ROS), which are generated by UV irradiation, may cause serious injury to skin cell membranes, DNA and functional proteins. In addition, these agents stimulate the expressions of matrix metalloproteinases (MMPs), which can degrade most components of the extracellular matrix (ECM), including collagen. In order to develop new anti-photoaging agents, five major components from the extract of Fraxinus chinensis extract (FCE) were identified. Two of the major components of FCE were found to be esculin (11.2%) and esculetin (1.9%). FCE ($IC_{50}:\;50.0{\mu}g/mL$ 1, 1-diphenyl-2-picrylhydrazyl (DPPH); $19.8{\mu}g/mL$, superoxide anion radical) and esculetin ($IC_{50}:\;2.1{\mu}g/mL$ DPPH; $0.6{\mu}g/mL$, superoxide anion radical) showed strong antioxidative activities. Of the compounds tested, esculetin showed the strongest scavenging activity against DPPH radicals, followed by superoxide anions from the xanthine/xanthine oxidase system. The intracellular ROS scavenging activity showed that oxidation of 5-(6-)-chloromethyl-2', 7'-dichlorodihydrofluorescein diacetate ($CM-H_2DCFDA$) was effectively inhibited by esculetin, with potent free radical scavenging activity was also shown in UVB-irradiated human dermal fibroblasts (HDFs). Moreover, treatment of UVA-irradiated HDFs with esculetin resulted in dose-dependent decreases in the expression levels of MMP-1 mRNA and protein. From these results, FCE and one of its components, esculetin, were predicted to be potentially useful as ingredients in cosmetics for protecting against photoaging.
Voluntary stand-up physical activity enhances endurance exercise capacity in rats
Seo, Dae Yun,Lee, Sung Ryul,Kwak, Hyo-Bum,Seo, Kyo Won,McGregor, Robin A,Yeo, Ji Young,Ko, Tae Hee,Bolorerdene, Saranhuu,Kim, Nari,Ko, Kyung Soo,Rhee, Byoung Doo,Han, Jin The Korean Society of Pharmacology 2016 The Korean Journal of Physiology & Pharmacology Vol.20 No.3
Involuntary physical activity induced by the avoidance of electrical shock leads to improved endurance exercise capacity in animals. However, it remains unknown whether voluntary stand-up physical activity (SPA) without forced simulating factors improves endurance exercise capacity in animals. We examined the effects of SPA on body weight, cardiac function, and endurance exercise capacity for 12 weeks. Twelve male Sprague-Dawley rats (aged 8 weeks, n=6 per group) were randomly assigned to a control group (CON) or a voluntary SPA group. The rats were induced to perform voluntary SPA (lifting a load equal to their body weight), while the food height (18.0 cm) in cages was increased progressively by 3.5 every 4 weeks until it reached 28.5 cm for 12 weeks. The SPA group showed a lower body weight compared to the CON group, but voluntary SPA did not affect the skeletal muscle and heart weights, food intake, and echocardiography results. Although the SPA group showed higher grip strength, running time, and distance compared to the CON group, the level of irisin, corticosterone, genetic expression of mitochondrial biogenesis, and nuclei numbers were not affected. These findings show that voluntary SPA without any forced stimuli in rats can effectively reduce body weight and enhance endurance exercise capacity, suggesting that it may be an important alternative strategy to enhance endurance exercise capacity.
김태석,여익현,이윤범 한국콩연구회 1995 韓國콩硏究會誌 Vol.12 No.2
포장두부의 안정성을 측정하고자 하는 미생물실험은 결과가 1∼2일 후에야 나오므로 생산 또는 판매현장에서 측정하는 것은 불가능하다. 바로 측정하여 결과를 예측할 수 있는 간접지표는 유통기한이 짧은 식품의 경우 더욱 필요한 상황이다. 따라서, 본 연구는 포장두부 충진수의 탁도 및 pH를 간접지표로 이용하여 미생물적 안정성을 측정할 수 있는지를 확인하였다. 또한, 저온살균(70℃)을 통하여 초기 미생물수준을 낮추므로 충진수의 탁도 및 pH와 미생물수준의 관계를 보다 정확하게 측정, 비교하였다. 저온살균시 포장두부의 일반성분에 영향을 미치는지를 분석하였는데 두부의 수분, 조단백, 조지방, 회분 등의 일반성분 조성에는 영향을 미치지 않는다. 저장성(10℃) 에 있어서는 부패의 초기수준을 10^7∼10^8CFU/g 으로 할때, 무처리 대조군의 경우 4일 경과후 부패가 진행된 것에 비하여 저온살균처리 5분의 경우 7일, 10분의 경우 10일 경과후 미생물 수준이 부패 초기수준에 도달하였으며, 20분 이상처리군의 경우 15일 경과 시점까지 10^7 CFU/g에 미치지 않았다. 포장두부에서 두부에 존재하는 미생물의 증가와 두부 충진수의 탁도 및 pH는 상관관계가 있어서 두부의 미생물의 10^5 CFU/g 수준에 이르면 충진수의 탁도는 0.1 이상의 값을 나타내었고 부패의 초기수준에 이르면 충진수의 탁도는 1.0 이상의 값을 나타내었다. pH의 경우 두부의 미생물의 10^5 CFU/g 수준에 이르면 충진수의 pH는 5.6 이하의 값을 나타내었고 부패의 초기수준에 이르면 5.0 이하의 값을 나타내었다. 포장두부에서 간접지표로 선택한 충진수의 pH의 탁도는 두부의 미생물수와 밀접한 관계를 나타내었다.