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Na, Eui-Gyun,Koh, Seung-Ki,Oh, Seok-Hyung The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.2
The contents of this paper include the evaluation of corrosion characteristics and the behaviour of stress corrosion cracking (SCC) for the weldment and post weld heat treatment (PWHT) specimen and parent of HT -60 steel using a slow strain rate test (SSRT) in synthetic seawater. Corrosion characteristics were obtained from the polarization curves by potentiostat, and SCC phenomena were evaluated through the parameters such as reduction of area and time to failure by comparing the experimental results in corrosive environment with those obtained in air. Corrosion rate of the weldment was the fastest, followed by parent and PWHT specimen. SCC phenomena between the weldment of HT-60 steel and synthetic seawater were shown. Besides, SCC was dependent upon the pulling speed greatly. Maximum severity of SCC was obtained at a speed of $10^{-6}mm/min$, whereas SCC could not be seen almost at $10^{-4}mm/min$. The resistance to SCC for PWHT specimen was improved considerably compared that of the weldment at $10^{-6}mm/min$. In case of SCC failure, it was verified from SEM examination that brittle mode and lots of pits could be seen at the fractured region near the surface of the specimen.
HT-80鋼 熔接材의 熔接後熱處理時 作用應力이 疲勞龜裂進展擧動에 미치는 影響
羅義均,吳錫炯 군산대학교 1992 群山水産專門大學 硏究報告 Vol.26 No.1
This study was conducted to examine the effects of the applied stress during PWHT on fatigue crack growth behaviours for the weldment of HT -80 steel. Stress during PWHT was applied to the weld HAZ in order to simulate the residual stress at welds. Submerged arc welding was done. Fatigue test was done at the frequency of 30Hz. The obtained data were analyzed between stress intensity factor range and crack growth rate. The fractured surface was observed by SEM and optical microscope. Crack growth rate of as -weld was slower than that of parent because of the singularities at HAZ. Crack growth rate for the specimen subjected to stress of 98Mpa was the fastest among PWHT specimens due to the precipitation of carbides which was formed during PWHT.
Na, Kun,Kim, Sungwon,Sun, Bo Kyung,Woo, Dae Gyun,Yang, Han Na,Chung, Hyung-Min,Park, Keun-Hong Wiley Subscription Services, Inc., A Wiley Company 2008 Journal of biomedical materials research. Part A Vol.a87 No.2
<P>This study examined the efficacy of poly(NiPAAm-co-AAc) as an injectable drug delivery vehicle and a cell therapeutic agent in the form of a supporting matrix for the chondrogenic differentiation of rabbit chondrocytes. The hydrogel constructs, which consisted of embedded cells co-encapsulating dexamethasone (Dex) and TGF β-1 or unloaded Dex, were used as controls to determine the effects of Dex and TGF β-1 on chondrogenic differentiation. The level of Dex and TGF β-1 released was monitored using a bioimaging method. The amount of Dex released from hydrogel was faster than that of TGF β-1. TGF β-1 was present in hydrogel for more than 4 weeks after the injection. The level of the cartilage associated ECM proteins was examined by immunohistochemical staining for collagen type II as well as by Safranin-O and Alcian blue (GAG) staining. These results highlight the potential of a thermo-reversible hydrogel mixed with the chondrocytes and differentiation delivery material for applications in neocartilage formation. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2008</P>
吳錫炯,羅義均 군산대학교 1992 群山水産專門大學 硏究報告 Vol.26 No.1
In recent year, owing to the automization of cutting tools, in-process dectction is more and more important. It is necessary to find how to estimate the tool wear because of problem about precision. Most of studies on in-process detection of tool wear have been carried out by prediction of tool life and measurement of force, heat, vibration, AE(acoustic emission) and image processing in cutting. In this paper, we deal with the relations of tool wear by variations in dynamic cutting force and then derived to correlate the wear with the dynamic component cutting force in the machining SUS304 which is welknown as difficult -to-machine material. The results obtained are as follows 1. At the view point of machinability for tool wear, even in case of same uncutchip cross-sectional area, to makes the slenderness ratio higher is advantageous. 2. The characteristics of RMS in cutting forces is correlated the wear and characterized by the tool life. It is suggested that applying the RMS to in-line process is a effective methods for detecting the tool wear.
Jo, Sooyeon,Na, Hyung Gyun,Choi, Yoon Seok,Bae, Chang Hoon,Song, Si-Youn,Kim, Yong-Dae The Korean Society of Ginseng 2022 Journal of Ginseng Research Vol.46 No.6
Background: Diesel exhaust particle (DEP) is a harmful kind of particulate matter known to exacerbate pre-existing respiratory diseases. Although their adverse effects on airway pathologies have been widely studied, the mechanistic analysis of signaling pathways and potential targets in reducing DEP-induced mucin secretion and pro-inflammatory cytokine production remain elusive. We, for the first time, investigated the effects of Korean Red Ginseng (KRG) extracts on mucin overproduction and airway inflammation induced by DEP. Methods: The effects of KRG and saponin on DEP-induced expression of MUC5AC and interleukin (IL)-6/8 were examined by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) in human airway epithelial NCI-H292 cells. We conducted Western blotting analysis to analyze the associated signaling pathways. To evaluate the effects of saponin treatment on DEP-induced MUC5AC expression and inflammatory cell infiltrations in ovalbumin (OVA)-sensitized mice, immunohistochemical (IHC) staining and real-time PCR were implemented. Results: The KRG extracts markedly attenuated DEP-induced MUC5AC expression in vitro by inhibiting the TLR4/TRIF/NF-𝛋B pathway. Furthermore, KRG and saponin inhibited DEP-induced pro-inflammatory cytokine IL-6/8 production. The in vivo study revealed that saponin blocked DEP-induced inflammation, mucin production and MUC5AC expression. Conclusion: Our study revealed that KRG extracts have inhibitory effects on DEP-induced expression of MUC5AC and the production of pro-inflammatory cytokines. This finding provides novel insights into the mechanism by which saponin alleviates diesel-susceptible airway inflammation, elucidating its potential as a phytotherapeutic agent for inflammatory pathologies of airway.
연구논문 : 사회과학 ; 키르기즈스탄의 농업현황 및 금후 농업기술 협력방안
곽재균 ( Jae Gyun Gwag ),고호철 ( Ho Cheol Ko ),강만정 ( Man Jung Kang ),허은숙 ( On Sook Hur ),노나영 ( Na Young Ro ),이주희 ( Ju Hee Rhee ),조규택 ( Gyu Taek Cho ),오세종 ( Se Jong Oh ),백형진 ( Hyung Jin Baek ),김연규 ( Yeon Gy 한국국제농업개발학회 2012 韓國國際農業開發學會誌 Vol.24 No.2
1. 키르기즈스탄은 중앙아시아의 동쪽에 동서로 길게 위치한 국가로서 국토의 약 90%가 해발 1,500 m 이상의 산악지대, 약 41%는 해발고도 3,000미터 이상의 고산지대, 평균해발은 2,750 m이며, 국토면적의 약 4%가 만년설과 빙하로 덮여 있다. 2. 키르기즈스탄은 전통적인 농업국가로서 농업이 경제의 축이며 농촌인구가 65%, 농업부문 종사자가 전 산업에서 차지하는 비율이 36%이고, 농업생산이 국가전체 GDP 에서 차지하는 비중이 20% 이상으로서 비교적 높은 편이다. 3. 이 나라의 농업은 강우량이 적고 건조한 기후조건 때문에 주로 관개에 의존하고 있으며, 관개재배 면적은 약 100만 ha이고, 주요 농작물은 밀, 사료용 호박, 보리, 감자, 옥수수, 사과이다. 특히 큰 일교차와 긴 일조시수를 가진 해발 1,700m의 이 시쿨 지역에서 생산되는 사과는 품질이 좋기로 유명하다. 4. 축산업이 농업전체 생산액에서 차지하는 비율이 61%를 넘어설 정도로 중요한데 주로 유목에 의존하고 있으며 유우, 육우, 면양이 주된 가축이고 양봉도 중요한 위치를 차지하고 있다. 5. 키르기즈스탄은 맥류, 사과, 양파 등의 원산지일 뿐만 아니라 고산식물종의 다양성이 풍부하고, 특히 사과의 야생종이 풍부하게 자생하고 있으며, 비타민 나무 등 많은 약용식물 들도 산야에 자생하고 있다. 6. 키르기즈스탄과는 2005년부터 4년 동안 유전자원 공동수집이 추진되었으나, 정부차원에서 농업기술협력 사업은 거의 추진되고 있지 않다. 효율적인 협력 사업을 위해서는 상호간의 국익에 도움이 될 수 있는 과제를 발굴하여 우선순위를 정하고 이에 따라 선택과 집중을 하여야 할 것으로 판단된다. 특히 키르기즈스탄은 농업유전자원 저장시설이 없고 관련분야에 대한 관심도 없으므로 금후 키르기즈스탄과는 농업유전자원에 대한 교육과 저장시설의 건설을 통하여 협력관계를 구축하면서 상호 도움이 되는 방안이 적극 모색되어야 할 것으로 사료된다. The Kirgyz Republic is situated in the north-east of Central Asia and shares borders with China to the east, Tajikistan to the south, Uzbekistan to the west and Kazakhstan to the North. The area of the Republic makes up 199.9 thousands km2 and just over 90 percent of the territory is over 1,500 meters above sea level and 41 percent is over 3,000 meters above sea level. The long term average temperature in July varies from 26.1oC in Jalal-Abad(altitude 763 m) to 17.3oC in Naryn(altitude 2,039 m), and the average temperature in January falls to as low as -2.7oC in Jalal-Abad and to -16.7oC in Naryn. Precipitation primarily occurs during the autumn-spring period. For five years average precipitation amounts to 327mm in Talas and 517mm in Jalal-Abad. The climate in Kyrgyzstan is continental with hot summers and cold winters, during which frost occurs all over the country. The frost-free period is 185 days per year in the Chu valley, 120-140 days per year in the Naryn valley and 240 days per year in the Fergana valley. Double cropping is therefore limited to vegetables. Natural pastures occupy 46.3% of the total area of Kirgyzstan, arable land occupy 6.8% (1,352 thousands ha), and 73.8% (997.5 thousands ha) of arable land is irrigated lands. Irrigated land is mainly cultivated for wheat, fodder crops and rice, Wheat occupy 31.6% of the cultivated areas, pumpkins for fodder 21.1% and barley 10.3%, Given the abundance of solar radiation and heat, the major factor limiting the use of agroclimatic and land resources is a deficit of water, fertilizer and machinery. Agriculture in Kirgyzstan was and still is the largest sector in Kirgyzstan`s economy, Agriculture account for approximately 20.2% of GDP in 2011, and approximately 65% of the population resides in rural areas, and 36.3% of the work force is engaged in agricultural production. Though traditionally agricultural country, Kirgyzstan imports a lot of agricultural products include wheat, pork meat, chicken meat and apples. Cotton, tobacco, wool, and meat are the main agricultural products, although only tobacco and cotton are exported in any quantity, Drops in production had been severe after the breakup of the Soviet Union in december 1991, but by mid-1995, production began to recover and exports began to increase. But still agricultural productivity is very low because of deficit of agricultural infrastructure as well as water and fertilizer. Important thing for expanding agricultural cooperation with Kirgyzstan is establishing the investment strategy considering their demands as well as mutual profit.