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석광설,방선애,홍지형,이석조,김대곤,이대균,허정숙,이은정 한국대기환경학회 2004 한국대기환경학회지 Vol.20 No.4
The purpose of this study is 10 estimate of emission factors of the air pollutants for the melting furnaces for the iron and steel industry. The result of this study is able to obtain the emission factor of particulate matters (PM), sulfur dioxide, nitrogen oxides for melting furnace. The emission factors of each pollutants were as follows: - the emission factor varied between 6.13E-03 ∼ 6.12E-01kg/ton for PM - 1.59E-01 ∼ 2.45E+00kg/ton for S0₂ - 6.82E-02 ∼ 6.88E-01kg/ton for NOx, respectively. Analysis of the differences in the emission factors of ours and U.S. EPA's yielded the following results for the Wilcoxon method: p>0.05. The statistical analysis showed no differences in the our emission factors and U.S. EPA's
김대진(D. J. Kim),석창성(C. S. Seok),구재민(J. M. Koo),박재실(J. S. Park),서정원(J. W. Seo),구병춘(B. C. Goo) 한국철도학회 2004 한국철도학회 학술발표대회논문집 Vol.- No.-
Under cyclic loading, the fatigue failures of welded joints occur at weld toes which induce stress concentration by weld shape. So we need to obtain the peak stress and the S-N curve to assess the fatigue strength of welded joints. However the measurement of peak stress is of high uncertainty and low reproducibility, so we use nominal stress instead in fatigue tests of welded joints. In this study, fatigue tests to obtain S-N curves am FE analyses to obtain stress concentration factors were conducted for the two types of cruciform fillet welded joints, that is, load-carrying and non load-carrying types. Then we changed the obtained S-N curves to that based on peak stress using the bot-spot stress concept. From the analyses of the S-N curves obtained, we have concluded that there is a need to develop a new method to evaluate the fatigue life.
Shen, T.,Park, K.t.,Choi, J.g.,Moon, B.W.,Koo, J.M.,Seok, C.S. Pergamon Press 2017 Engineering fracture mechanics Vol.169 No.-
<P>The leak-before-break (LBB) concept was usually applied to design and estimate the piping system in nuclear power plant, which is based on the fracture resistance (J-R) curves of nuclear real pipe. However, the real pipe test is costly and difficult. Instead of the real pipe test, the J-R curves of standard specimens suggested in the ASTM El 820 were used. Nonetheless, the J-R curves obtained from the standard specimens are too conservative, owing to the differences in specimen geometries and loading configurations (constraint effect). Thus, in this study the equivalent stress gradient (curved ESG) specimens were developed to evaluate the J-R curves of nuclear real pipes (SA-312 TP304L) precisely. The curved ESG specimens were designed to show the same crack-opening stress gradients as those of the real pipes at the driving force J = J(Ic). The J(Ic) for stainless steel SA-312 TP304L was obtained by the J-R tests on standard compact tension (CT) specimens. Comparison of the J-R curves obtained from the curved ESG specimens and those obtained from the real pipes show that the curved ESG specimen can be used in the LBB concept to design and estimate the piping systems. (C) 2016 Elsevier Ltd. All rights reserved.</P>
역사이클하중하에서의 균열길이 측정법에 따른 파괴저항곡선의 평가
원종일,우흥식,석창성 한국산업안전학회 1998 한국안전학회지 Vol.13 No.4
J-R curve tests were performed on 1T compact specimens of SA516 Gr. 70 carbon steels under reverse cyclic loading. A Direct-Current Potential Drop (DCPD) method, one of the nondestructive techniques to detect flaw of structure, is being increasingly used for monitoring crack initiation and stable crack growth in typical fracture mechanics specimens for J-R testing. In many aspects this method is simpler than the unloading compliance method. The objective of this paper is to evaluate the J-R Curve according to the crack length measurement techniques under reverse cyclic loading. In order to prove the reliability and repeatability of the DCPD method, the crack length measured by using DCPD method was compared to one determined from unloading compliance. Consequently, this DCPD method correlated well with J-R curves and crack extension measurements determined from unloading compliance method.
Koo, J.M.,Park, S.,Seok, C.S. North-Holland Pub. Co 2013 Nuclear engineering and design Vol.259 No.-
The leak-before-break (LBB) concept is generally used to design the primary heat transport piping for a nuclear power plant. The LBB concept is based on the fracture resistance curve, which is obtained by J-R tests on various types of specimens. Fracture toughness data differ according to the various types of specimens. It has also been known that there is a difference in the constraint effect between real pipes and standard specimens, and LBB design using standard specimens is conservative. We propose a new type of specimen for J-R tests, a tensile compact pipe (CP) specimen, and perform fracture toughness tests on various types of specimens. We also perform constraint effect analysis on such specimens. The Q-stresses of the tensile CP specimens are lower than those of real pipes under 4-point bending, and are higher than those of elbow pipes. If the lever length of a tensile CP specimen is controlled, the specimen can simulate various stress conditions, and it is thought that the LBB design of piping in service can be performed using this specimen.
여지환(J.H.Yae),김태기(T.K.Kim),서명원(M.W.Suh),석창성(C.S.Seok),이재천(J.C.Lee),김성봉(S.B.Kim),이선일(S.I.Lee),김장성(J.S.Kim) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
Vehicle dynamic analysis have been widely investigated in the last ten years. This paper presents a mathematical vehicle model. braking force control parameters, wheel control logic, and vehicle control strategy to analyze the dynamic characteristics of a vehicle equipped with ABS(Anti-lock Brake System). Analyses on the braking characteristics were performed for straight and J-turn brakng on the various road surfaces including split-μ. Analysis results showed the combination of slip ratio and wheel acceleration were desirable for the control logic. The adoption of the wheel acceleration was necessary to decide the type of road surface. For the vehicle control strategy for split-μ. select high-low method was confirmed as the most effective one.<br/>
Evaluation of fracture toughness characteristics for nuclear piping using various types of specimens
Park, S.,Yoo, S.S.,Min, J.K.,Koo, J.M.,Seok, C.S. Applied Science Publishers ; Elsevier Science Ltd 2012 The International journal of pressure vessels and Vol.90 No.-
The leak-before-break (LBB) concept is based on the fracture resistance curve obtained by J-R tests for various types of specimens. But fracture toughness data of various types of specimens are different. For example, the estimates for fracture toughness of standard specimens are conservative when compared to the fracture toughness of real pipes because of the difference of the constraint effect between real pipes and standard specimens. Therefore, to estimate the integrity of real pipes based on elastic-plastic fracture mechanics, we have to first establish the relations among real pipes, standard CT specimens and curved CT specimens. In this study, we perform fracture toughness tests of nuclear piping materials using various types of specimens. And each J-R curve considered in the constraint effect is compared. The experimental results showed that a curved CT specimen is similar to the cases of pipes with small crack angles (60<SUP>o</SUP> and 120<SUP>o</SUP>) and a CT specimen is similar to the case of pipes with the crack length of 180<SUP>o</SUP>. Also, the Q-stress for curved CT specimens is higher than that of pure bending pipe specimens and lower than that of CT specimens.
Lee, S.K.,Seok, K.H.,Chae, H.J.,Lee, Y.H.,Han, J.S.,Jo, H.A.,Joo, S.K. Pergamon Press ; Elsevier Science Ltd 2017 Solid-state electronics Vol.129 No.-
We report a novel method to reduce source and drain (S/D) resistances, and to form a lightly doped layer (LDL) of bottom-gate polycrystalline silicon (poly-Si) thin-film transistors (TFTs). For application in driving TFTs, which operate under high drain voltage condition, poly-Si TFTs are needed in order to attain reliability against hot-carriers as well as high field-effect mobility (μ<SUB>FE</SUB>). With an additional doping on the p<SUP>+</SUP> Si layer, sheet resistance on S/D was reduced by 37.5% and an LDL was introduced between the channel and drain. These results contributed to not only a lower leakage current and gate-induced drain leakage, but also high immunity of kink-effect and hot-carrier stress. Furthermore, the measured electrical characteristics exhibited a steep subthreshold slope of 190mV/dec and high μ<SUB>FE</SUB> of 263cm<SUP>2</SUP>/Vs.