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Jun‑hyun Jo,Min‑seok Park,Kyung‑woo Yi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.11
Hypo peritectic steels exhibit a high possibility of longitudinal crack during continuous casting. Therefore, many researchershave studied the mechanisms of crack generation in hypo peritectic steel. Stress in solidified shell, or volume contractionwith small liquid fractions were suggested as the mechanisms of crack generation. A new model was developed for predictingpossibility of crack generation by calculating strain rates in solid, volume contraction rate during solidification, and theprobability of liquid unfilling in continuous cooling processes. The results show that massive transformation from the δphase to the γ phase, and peritectic transformation during solidification can be the main crack generation mechanisms. Furthermore,a linear relationship exists between the amount of undercooling for peritectic transformation (dTp) and the carboncontent of the boundary for dividing the two crack generation mechanisms. Additionally, the longitudinal crack ratios ofthe field results are analyzed through strain rates in solid and liquid unfilling possibilities. Relative positions in the range ofhypo peritectic steel and effective carbon contents are suggested to analyze the crack ratio of steels with alloying elements. This analysis shows that the results obtained from the new models for crack generation possibility are usable, and dTpcangenerate the behavioral differences in crack generation according to the conditions.
Phase Transformation Modeling for Hypo Peritectic Steel in Continuous Cooling
Jun‑hyun Jo,Kyung‑woo Yi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
Phase change of steel during cooling affects the slab qualities in continuous casting. Especially, crack susceptibility of hypoperitectic steel is high because large volume shrinkage occurs by peritectic phase transformation during solidification andcooling. In continuous cooling, phase change is different from the behaviors under the equilibrium condition, such as undercoolingand extend of peritectic reaction, etc. Therefore, we develop a new phase change model considering thermodynamics,empirical equations, and carbon diffusion in each phase to predict phase change behavior during continuous cooling. Inthis model, phase change of hypo peritectic steel comprises 5 stages until all phases become the γ phase. The velocities ofthe δ/γ interface and phase fractions during cooling are calculated according to cooling rate, undercooling of the γ phase,and carbon contents. The results show that if solidification ends by the δ phase during dTp,the γ phase is formed by massivetransformation. On the contrary, if peritectic reaction starts with liquid, the γ phase is formed and grows by diffusionaltransformation. In latter case, massive transformation of remaining δ phase can occur with high undercooling or very fastcooling rates. This analysis shows that there are several different paths depending on carbon contents of hypo peritectic steels.
김치 유산균인 Lactobacillus sp. JJ-2001이 생산하는 Bacteriocin에 관한 연구
조영배,조우제,조영임,이은주,김성구,전홍기 부산대학교 유전공학연구소 1997 분자생물학 연구보 Vol.13 No.-
The microorganisms producing bacteriocin from kimch were screened, and among them,a strain showing the highest bacteriocin activity and stability was isolated. Based on the taxonomic characteristics of its morphological, cultural and physiological properties, the isolatef strain was characterized as Lactobacilius sp..To identify optimal conditions for the growth and the production of bacteriocin from the isolated strain,nutrient source, initial pH, and culture temperature were evaluated. Physiochemical properties of bacteriocin was also investigated. The potimal condition for the production of bacteriocin and the cell growth was obtained at 2% glucose, 1% beef extract as organic nitrogen source,1%(NH_4)_2SO_4 as inorganic nitrogen source,and 0.1% Tween 80. The isolated strain showed the maximum growth at 25℃. The inhibitory range of its antimicrobial substance aginst gram positive bacteria was marrow and its inhibitory activity was maintained between pH3.0 and pH8.0. The antimicrobial activity of bacteriocin from the isolated strain was stable at 50℃.
조영석,권기현,이준철,나소영,이효진,홍우정,이유선,김군순,송민호,김영건,노흥규 충남대학교 의학연구소 2003 충남의대잡지 Vol.30 No.2
Prediction of thrapeutic response to radioiodine in Graves' disease is poorly understood. Although thyrotropin binding inhibitor immunoglobulin(TBII) level is a strong index for relapse after antithyroid drug medication, conflicting results are reported regarding its prognostic significance in Graves' disease treated with RAI. This study is dengned to evaluate possible relationship between post-treatment hypothyroidism and TBII in Graves' disease treated with RAI. Fourty two patient with Graves' disease after radioiodine treatment were studied retrospectively. The subject were divided into hypothyroid group and euthyroid or hyperthyroid group. We evaluated the association of hypothyroidism and TBII with radioiodine treatment dose. The mean age of hypothyroid group was 48±11 years and euthyroid or hyperthyroid group was 47±12 years. There was no difference in two groups. And there was no significant difference in post- treatment TBII between two groups(49.9±28.5%, 29.9±14.3%, p-value >0.05). The treatment-dose had no influence on post-treatment thyroid state. Euthyroid or hyperthyroid group was done with 13.6±6.9mCi and hypothyroid group was 17.0±10.4mCi(p-value > 0.05). TBII had no prognostic significance on long-term hypothyrodism in Graves' disease treated with radioiodine. And, treatment-dose had no influence on post-treatment thyroid state.
SC법에 의한 9Al₂O₃·2B₂O₃/AC4CH 금속기 복합재료의 인장강도특성
박원조,이준우 慶尙大學校 1999 論文集 Vol.38 No.-
This study makes the preform by squeeze casting method with AC4CH alloy of Al-Mg-Si line, which is in sale for the matrix and aluminum before whisker(9Al₂O₃·2B₂O₃) for reinforcement. The Characteristic on the fatigue life, fracture mechanism and the X-ray diffraction analysis of AC4CH and MMC composite are investigated. The results of X-ray diffraction, we found that mechanical preparations are generally reduced because it can not just it is original aging time by MgO·Al₂O₃ of spinal type, which of the reactions between whisker and small amount of Mg in the Matrix. Tensile strength of whisker, surface of whisker before T6 treatment had no reaction formation and it is damage was very small but whisker after T6 treatment had a lot of reaction formation.
Jo, Jun Woo,Jee, Byung Chul,Suh, Chang Suk,Kim, Seok Hyun The Korean Society for Reproductive Medicine 2013 Clinical and Experimental Reproductive Medicine Vol.40 No.4
Objective: To compare the mouse oocyte vitrification outcomes of the CryoLogic vitrification method (CVM) and the conventional open method using a Cryotop. Two CVM methods (original CVM and modified CVM) were tested. Methods: Mature oocytes obtained from female BDF-1 mice were vitrified by two-step exposure to equilibrium and vitrification solutions. Three vitrification protocols were tested on three groups: the CVM-kit, modified CVM, and Cryotop groups. After exposure to the two solutions, the oocytes were vitrified. After warming, the oocytes were fertilized in vitro, and the embryo development was assessed. Blastomeres positive for caspase were counted using an in situ assay kit. The spindle morphology and chromosome configurations of warmed vitrified oocytes were also assessed. Results: The modified CVM and Cryotop groups showed similar developmental capacities, and similar proportions of cells with intact spindles and chromosome configurations. The modified CVM protocol was superior to the original CVM protocol for developmental competence and intact spindle preservation. However, the CVM group showed a relatively higher number of apoptotic cells in blastocysts. Conclusion: Closed vitrification using the modified CVM protocol may be used as an alternative to the conventional open method, but strategies to decrease apoptosis in the blastomere need to be investigated.
Won Jun Jo,Ha Seon Sim,Hye Jin Lee,Yu Hyun Moon,Ui Jeong Woo,Soo Bin Jung,Su Ran Ahn,Jung Su Jo,Sung Kyeom Kim 한국원예학회 2021 한국원예학회 학술발표요지 Vol.2021 No.10
The photosynthetic rates of leaves depend on the crop characteristics and vertical position of the leaf in terms of leaf age and development stages. The photosynthetic models of crops are an important factor for manipulating the optimum CO₂ concentration and light intensity for crop productivity in a greenhouse. However, few models have been proposed to estimate the net photosynthetic rate according to leaf positions. The purpose of this study was to predict and validate the leaf photosynthetic rate of cucumber (Cucumis sativus L., cv. Goodmorning) by the vertical positions using a photosynthetic model. The leaf photosynthetic rate at the vertical positions was measured under several CO₂ concentrations and light intensity conditions in the three plants. Leaf photosynthetic was analyzed using the FvCB (Farquhar, von Caemmerer, and Berry) model and validated as a multivariable photosynthetic model. As the CO₂ concentration and light intensity increased, the photosynthetic rate of the leaf showed a saturation curve. The CO₂ concentrations and light intensities saturation point were the highest in the upper leaf (at three internodes below the meristems) and lowest in the bottom leaf (at two or three internodes over the substrate area). The maximum carboxylation capacity (μmol·CO₂·m<SUP>-2</SUP>·s<SUP>-1</SUP>) and maximum electron transport rate (μmol·m<SUP>-2</SUP>·s<SUP>-1</SUP>) estimated in the FvCB model were high accuracies in regression analysis. As a result of comparing the actual measured photosynthetic rate and the estimated values through the FvCB model, the R² values at the bottom, middle, and upper leaf were 0.89, 0.89, and 0.87, respectively. The root means square errors values at the bottom, middle, and upper leaf were 2.521, 2.958, and 3.200, respectively. The leaf photosynthetic rate for each vertical position estimated from the FvCB model was similar to the actual measured value. Results, the FvCB model could be feasible to establish optimal CO₂ concentration and light intensity to maintain the productivity of cucumber in greenhouse cultivation.