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소형펀치시험의 유한요소해석에 의한 Mn-Mo-Ni 저합금강의 파괴강도 평가
李載奉,金民喆,吳聳俊,朴宰鶴,李奉相 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.12
The critical fracture stresses(σ^*_f (sp)) in various low alloy steels for reactor pressure vessel(RPV) have been evaluated by finite element analysis(FEA) of small punch test in the cleavage temperature region(-150 ∼ -196℃). In order to improve the accuracy of the FEA results on small punch tests, the uniaxial stress-strain properties beyond the necking were optimized by comparing the results of uniaxial tensile test and its finite element analysis. The loaddisplacement curves and distances from center to fracture surface(D_f) of FEA results are in good consistence with the experimental results. The σ^*_f(sp) from small punch test in various reactor pressure vessel(RPV) steels were found to have a linear relationship to the values from the precracked specimens(σ^*_f(PCVN)). This result indicates that small punch tests could be a useful method to evaluate the cleavage fracture behavior of the low alloy steels.
초음파 측정법에 의한 아스팔트 세멘트의 점탄성 특성 평가
이재학 한국비파괴검사학회 2000 한국비파괴검사학회지 Vol.20 No.5
이 연구에서는 점탄성 재료중의 하나인 아스팔트 시멘트의 점탄성 특성을 초음파를 이용하여 측정하는 방법에 대하여 고찰하였다. 2.25MHz의 주파수에서 -20℃부터 60℃까지의 온도변화에 따른 파속도와 감쇠를 측정한 후, 선형 점탄성 이론에 근거하여 저장 및 손실 종탄성율, 손실 탄젠트, 저장 및 손실 종컴플라이언스와 같은 물성변화를 구하였다. Maxwell과 Voigt-Kelvin 점탄성 모델을 이용하여 응력완화 및 크리프 거동과 점도의 변화도 예측하였다. 또한 중첩원리와 이동인자의 타당성을 문헌에 보고된 결과와 비교함으로써 입증할 수 있었다. This study investigates the method to measure the viscoelastic properties of asphalt cement, one of the viscoelastic mateials, using the ultrasound. The wave speed and attenuation were measured from -20˚C to 60˚C at the frequency of 2.25MHz. Then, the storage and loss longitudinal moduli, loss tangent, storage and loss longitudinal compliances were found depending on the temperatures based on the linear viscoelastic theory. Stress relaxation, creep, and viscosity were predicted using Maxwell and Voigt-Kelvin viscoelastic models. The validity of superposition principle and shift factor were verified by comparing the present results to the data reported in the literatures.
Global climate teleconnection with rainfall erosivity in South Korea
Lee, Jai Hong,Lee, Joon-hak,Julien, Pierre Y. Elsevier 2018 Catena Vol.167 No.-
<P><B>Abstract</B></P> <P>Rainfall Erosivity Index (REI) defined as the product of rainfall kinetic energy and rainfall intensity is a well-known hydrologic indicator of the potential risk of soil erosion. Global and regional scale climatic teleconnections with REI variability over South Korea are examined. We calculate leading patterns of observed monthly REIs using the Empirical Orthogonal Teleconnection (EOT) and Function (EOF) decomposition techniques. Also we used monthly statistical analyses using cross-correlation and lag regression for the leading modes and global atmospheric circulation measurement in the Pacific and Indian Ocean. As a result, the northern inland mode is applicable during summer season and the southern coastal mode applies to fall-winter season. The temporal evolution of REI exhibits mostly increasing and depends on interdecadal oscillation patterns. The leading EOT modes explain more variance in REI than the EOF modes during warm and cold seasons. The findings from this study illustrate that the tropical ENSO forcing has the coherent association with fall and winter REI patterns, and the Indian Ocean dipole is identified as a driver for REI variability in November. The monsoon circulations over western North Pacific also exhibit significant negative correlation with the December modes. The September leading modes also show a positive correlation with the tropical cyclone activity. Leading patterns in September and November have predictability up to five month lead time from the tropical Pacific Sea Surface Temperatures (SSTs). In addition, predictability from the Pacific SSTs for above normal extreme value of REI is greater than that for below normal value in winter. In conclusion, South Korea experiences climatic teleconnection between the large scale climate indices and mid-latitude hydrologic variables.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Teleconnection between climate indices and midlatitude rainfall erosivity was detected. </LI> <LI> Significant modes were detected based on empirical orthogonal teleconnection. </LI> <LI> CI-REI relationships show significant positive and negative correlations. </LI> <LI> Predictability for REI patterns by SST was demonstrated through regression mapping. </LI> </UL> </P>
Mutation of K-ras Oncogene in Thyroid Tumor Tissue
Lee, Jai Hak,Lee, Jong Seo,Kim, Seung Nam,Chang, Suk Kyun,Yoo, Seung Jin,Song, Young Tack,Cho, Won Il,Choo, Sang Yong CATHOLIC MEDICAL CENTER 1993 Bulletin of the Clinical Research Institute Vol.21 No.1
Point mutation of oncogene, one of the genetic alteration in cancer development, has been found in many malignant tumor tissues, Among those malignant tumors, the incidence of point mutation of K-ras oncogene was reported over 90% in pancreatic cancers, 40-50% in colotectal cancer, 25-30% in lung cancers and less than 10% in urogenital, breast or cervical cancers. Several investigators have reported the incidence of point mutation of ras oncogene was 30-50% in benign thyroid tumors and 50-80% in malignant thyroid tumors with some difference by tumor cell differentiation. Also some reports suggested ras mutation may constitute early steps in thyroid tumorigenesis. But there if few report about relation between point mutation and characteristics of mutation. In order to find out the incidence of k-ras oncogene point mutation and relation with characteristics of mutation in thyroid tumors, authors isolated DNA from each 10 normal tissue and benign and malignant tumor tissues. And then, point mutations of K-ras oncogene (four characteristics of codon 12 and one characteristic of codon 13) were detected by paired PCR with mutation-specific primer and agarose gel electrophoresis methods. The resets are as follows; 1. Any mutation was not detected in normal thyroid tissues. While point mutations were detected 7/10 cases (70%) of benign thyroid tumor tissues and in 9/10 cases (90%) of malignant tumor tissues. 2. The incidence of GGT-AGT mutation was highest in benign thyroid tumors (60%) and lowest in malignant thyroid tumors (30%). The incidences of GGT-GAT, TGT-GTT and GGC-GAC mutations were high in malignant tumors (60%). 3. There were 8/9 cases (89%) in malignant tumors and 5/7 cases (71%) in benign tumors of positive mutations over two Hinds of mutation. And also 5/9 cases (56%) of malignant tumors and 4/7 case (51%) of benign tumors expressed positive mutations over 3 kinds. Moreover two cases of each benign and malignant turners expressed all of five mutations. With above result, authors proposed that high incidence of point mutation of k-ras oncogene was detected in benign (70%) and malignant (90%) thyroid turners, and especially high incidence of GGT-AGT mutation (60%,) in benign tumors while high incidence of GGT-GAT, TGT, GTT and GGC-GAC mutations(60%) in malignant turners were noted. Also authors suggested that the point mutation may constitute early steps of thyroid tumorigenesis.