A356합금의 품질지수에 미치는 미소기공율의 영향

이충도 한국주조공학회 2018 한국주조공학회지 Vol.38 No.5

The dependence of the tensile properties on variations in the porosity of A356 aluminium alloys was investigated in terms of the quality index of the tensile properties based upon the ultimate tensile strength and elongation as well as the variation of the strength coefficient and strain-hardening exponent with regard to a T6 treatment. The test specimens were prepared by low-pressure die-casting and a subsequent T6 treatment, and the experimental results of a tensile test carried out at room temperature were compared to the theoretical description using a modified constitutive model. The nominal value of the quality index of A356 alloys increases gradually with a lapse of the ageing time upon a T6 treatment, despite the fact that this value is temporarily decreased during the initial stage of ageing from a solutionised condition. Additionally, the quality index depends practically upon the porosity variation with a power law relationship without regard to whether in solutionised or artificial aged conditions. The theoretical description indicates that the strength coefficient directly determines the nominal level of the quality index. Moreover, the overall dependence of the quality index on the porosity variation is remarkably weakened with an increase in the tensile strain, whereas the quality index depends sensitively upon the porosity variation with a low value of the strain-hardening exponent.

Defect Susceptibility of Sensile Strength to Microporosity Variation in As-Cast Magnesium Alloys with Different Grain Sizes

이충도 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.4

The variability in the tensile strength of as-cast AM60 and AZ91 alloys was investigated in terms of the defect susceptibility to the variation in grain size and microporosity. The microporosity was measured from the quantitative fractography analysis through scanning electron microscopy (SEM) observation on fractured surface after tensile test. The ultimate tensile strength (UTS) of both alloys can be characterized as a power law relationship to microporosity variation in terms of the defect susceptibility and maximum strength achievable in the defect-free condition. The defect susceptibility of tensile strength to microporosity variation is decreased remarkably with grain refinement. The defect susceptibility of AZ91 alloy to microporosity variation exhibits more sensitive dependence on the variation in grain size than AM60 alloy. Also, the dependence of UTS on the variation in grain size is described as a power law relationship for various levels of microporosity. The variation on effective void area fraction by the damage evolution of Mg17Al12 phase may introduce a practically significant decrease of load bearing capacity, less than by microporosity variation. The Hall-Petch relation of both alloys in the defect-free condition could be suggested as maximum values of friction stress and locking parameter.

7. 極地에서의 海洋建設

李忠東(이충동) 대한토목학회 1986 대한토목학회지 Vol.34 No.6

Dependence of Fatigue Life of Low-Pressure Die-Cast A356 Aluminum Alloy on Microporosity Variation

이충도,Suk Jong Yoo 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.4

The aim of the present study was to investigate the dependence of the high cycle fatigue property on themicroporosity variation of a low-pressure die-cast A356 alloy. Also, it aimed to describe quantitatively therelationship between the fatigue property and monotonic tensile strength using modified Basquin’s equationwhich takes into account the microporosity variation. The fatigue life of the A356 alloy can be described by anexponential dependence on the variation of the fractographic porosity, in terms of the modified Basquin’s equationwhich is composed of the defect susceptibility of fatigue life to microporosity variation and the maximum tensilestrength achievable in the defect-free condition. Using a modified form of Basquin’s equation, the maximumvalues of the fatigue strength coefficient and exponent in the defect-free condition are 341.5 MPa and-0.076, respectively, even though the nominal values of fatigue strength coefficient and exponent withoutconsideration of microporosity variation are 237.6MPa and -0.048, respectively. Also, the difference betweenthe maximum tensile strength and the fatigue strength coefficient on modified Basquin’s equation is about120MPa, and it arises from variation in the deformation behavior due to the difference of loading conditionbetween the monotonic and cyclic test modes such as the strain rate, Bauschinger effect, cyclic work hardeningand damage accumulation on loading condition.

원심주조법에 의한 주철-Babbitt Metal 복합관 제조에 관한 연구

이충도,강춘식 ( Chung Do Lee,Choon Sik Kang ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.1

N/A Conventional manufacturing process for cast iron-babbitt metal composite is complicate and bimetallic bonding by centrifugal casting is also difficult because their melting point is largely different and nonmetallic inclusion exists on outer shell. This study is aiming to simplify multistage process by adding Cu-powder as insert metals during cast iron solidification. The variables on fabrication of composite pipe are mold rotating speed and inner surface temperature of outer metal. The optimum temperature range for fusion bonding between cast iron and Cu-layer was 1100℃-1140℃ in case of mold rotating speed was 700rpm. When the inner surface of Cu-layer was at 900℃, the value of interfacial hardness between Cu-layer and babbitt metal were higher than Cu-matrix by forming diffusion layer, interfacial products between Cu-layer and babbitt metal are proved to be Cu_6Sn_5(η)by XRD.

Effect of Strain Rate on Elastic-Plastic Deformation in High Cycle Fatigue Properties

이충도 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.6

The aim of the present study was to investigate the contribution of the strain rate to the transition of elastic-plastic deformation behavior and the difference between the fatigue strength coefficient and monotonictensile strength in terms of the modified Basquin’s relation, which considers microporosity variation. Thetransition phenomena of elastic-plastic deformation were evaluated through comparison of the overall contour ofthe hysteresis loops measured in high cycle fatigue tests of a low-pressure die-cast A356 alloy. The increase ofthe alternating stress amplitude at a given excitation frequency causes a variation in the strain rate per unit timeinterval that depends fundamentally on the excitation frequency. In addition, the transition of elastic-plastic deformationbehavior is induced by variation of strain rate in high cycle fatigue test, i.e., typically, a variation ofthe elastic modulus and extension of the elastic deformation region, compared with monotonic deformationunder a very slow strain rate. The dependence of the elastic modulus on the strain rate due to the variation of thestress amplitude can be described in an exponential form of strain rate. The modified Basquin’s equation whichincludes the contribution of the strain rate and microporosity to the fatigue strength coefficient and fatigue lifewas re-established, including the dependence of the elastic modulus and transition of elastic-plastic deformationon the variation of the strain rate.

The Impact of Androgen Receptor and Histone Deacetylase 1 Expression on the Prognosis of Ductal Carcinoma In Situ

이충만,정일용,박양순,윤경원,조휘경,박혜진,이희진,이새별,김희정,고범석,이종원,손병호,안세현,김지선 한국유방암학회 2020 Journal of breast cancer Vol.23 No.6

Purpose: Factors associated with invasive recurrence (REC) of ductal carcinoma in situ (DCIS) are less known. This study was aimed at identifying better biomarkers to predict the prognosis of DCIS. Methods: RNA extracted from formalin-fixed paraffin-embedded blocks of twenty-four pure DCIS cases was subjected to differential gene expression analysis. The DCIS cases were selected by matching age and estrogen receptor status. Sixteen REC-free and 8 invasive-REC cases with disease-free interval of > 5 years were analyzed. Immunohistochemistry (IHC) staining was used to validate sixty-one independent pure DCIS cases, including invasive-REC (n = 16) and REC-free (n = 45) cases. Results: Eight differentially expressed genes (DEGs) were statistically significant (log 2-fold change [FC] < –1 or > 1 and p < 0.001). Less than ½ fold expression of CUL1, androgen receptor (AR), RPS27A, CTNNB1, MAP3K1, PRKACA, GNG12, MGMT genes was observed in the REC group compared to the no evidence of disease group. AR and histone deacetylase 1 (HDAC1) genes were selected for external validation (AR: log 2-FC − 1.35, p < 0.001, and HDAC1: log 2-FC − 0.774, p < 0.001). External validation showed that the absence of AR and high HDAC1 expression were independent risk factors for invasive REC (hazard ratio [HR], 5.04; 95% confidence interval [CI], 1.24–20.4; p = 0.023 and HR, 3.07; 95% CI, 1.04–9.04; p = 0.042). High nuclear grade 3 was also associated with long-term invasive REC. Conclusion: Comparative gene expression analysis of pure DCIS revealed 8 DEGs among recurring cases. External validation with IHC suggested that the absence of AR and overexpression of HDAC1 are associated with a greater risk of long-term invasive REC of pure DCIS.

Field terminator를 이용한 CMA 제작에 관한 연구

이충만(C. M. Lee),성면창(M. C. Sung),권순남(S. N. Kwon),정광호(K. Jeong) 한국진공학회(ASCT) 1996 Applied Science and Convergence Technology Vol.5 No.4

Field terminator를 이용하여 single path cylindrical mirror analyser를 제작하였다. 먼저 컴퓨터 모의실험을 바탕으로 CMA의 원통형 전극양단에서 fringing field effect를 최소로 하여 log-scale의 등전위면을 그대로 유지하는 terminator의 전압비와 위치 등을 구하였다. 계산된 전압을 직렬로 연결된 금속산화물저항으로 만든 voltage divider로 field terminator에서 직접 인가하여 CMA의 fringing field effect를 줄이는 방법을 개발하였다. 이 방법으로 제작된 CMA의 분해능이 △E/E = 0.4% 이상임을 확인하였다. We constructed a single path cylindrical mirror analyser(CMA) using field terminator method. With computer simulation, the best fit voltage ratio and position of the field terminator was determined which maintain log-scale equipotential line near both end of the CMA. Then we construct field terminator with voltage divider of metal-oxide resisters which reduces the fringe field effect. The resolving power of the CMA was better than △E/E = 0.4%.

순수주의의 아동문학과 `꿈`의 해석

이충일(Lee Chungil) 한국아동청소년문학학회 2016 아동청소년문학연구 Vol.- No.18

This paper sought to review the interpretation of dreams in Kang Socheon’s literature and the limitation. This is a exploration of when the diagram of ‘Kang Socheon Literature = Dream’ began and what that dream signifies. As a result, the ‘dream’ of Kang Socheon has close relationships with the romantic world view, and the internal characteristics has the tendency of corresponding with the purism of the 1960s. One must note that in such views, the principles of innocence of considering the dreams and fantasies of children as important, but viewing them as immature beings were reflected. However, after the 1990s, Kang Socheon’s ‘dream’ starts to expand the aesthetic fields as literary methods. In the process, In this process, it is thankful that 「Photo Studio Taking Photos of Dreams」 was shed light upon as fantasy story, but by idealizing dream, the problems of misinterpreting the piece. Expanding the meaning to ‘fundamentals of human’ and ‘pure and ideal search for dreams’ without considering the limitations of the literature then was a case in which the internal analysis of the text was led to the jump to the sense of subject. The more serious problem is the distorted interpretation as if the consciousness of the cold war present in Kang Socheon’s literature is a healthy idea of unification. With dreams and fantasies in its core, there are not as many people who have constructed the best area as Kang Socheon in our history of children’s literature. The detailed fantasy area and the smooth style is a characteristic of Kang Socheon’s literature and a precious asset of our history of children’s literature. However, excessive attribution of meaning toward ‘dream’ seems to become a repulsive factor in identifying Kang Socheon’s literature. Especially, the works of distinctive anti-communism needs to be reconsidered.

한국 서해에서 수온 및 염분에 미치는 기상 인자의 영향

이충일,이종희,김동선,Lee, Chung-Il,Lee, Jong-Hee,Kim, Dons-Sun 해양환경안전학회 2007 해양환경안전학회지 Vol.13 No.1

1971년부터 2001년까지 해양 및 기상관측 자료를 활용하여 한국 서해에서 기상인자(기온, 바람, 강수량)가 수온과 염분 변화에 미치는 영향을 분석 하였다. 그 결과 수온-기온, 수온-강수량, 염분-풍속은 정상관(+)을, 수온-풍속, 염분-기온, 염분-강수량은 역상관(-)의 관계를 보였다. 기상인자와 해양인자간의 시간지연(time lag)은 표층에서 $0{\sim}4$개월, 저층까지 기상의 영향이 도달하는 데에는 표층보다 $0{\sim}4$개월의 시간지연이 더 있었다. 수온은 같은 해의 기온 변화의 영향을 크게 받는 반면, 염분은 그 직전해의 강수량의 영향을 크게 받았다. 풍속의 강약에 따라 수온, 염분의 변동 폭 또한 함께 변하였다. The effect of meteorological factors such as air temperature (AT), wind speed (WS), precipitation (Pre) on the variation of water temperature (WT) and salinity (Sal) in the West Sea of Korea for the period 1971 to 2001 was illustrated. As a result of this study, WT-AT, WT-Pre, and Sal-WS had positive correlation, reversely WT-WS, Sal-AT and Sal- Pre had negative correlation. In the surface layer, time lag between atmospheric factors and oceanographic factors was 0 to 4 months, on the other hand in the bottom layer, it was delayed 0 to 4 months compared to the surface. WT was affected by AT in the same year, but Sal was affected by precipitation in the previous year. The variation of WT and Sal was in harmony with change of wind speed.