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전자기력에 의한 연주 Slab 내의 교반유동에 관한 수치적 연구
이재헌,이성우,신영길,김희창 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.1
A Numerical study was performed for the two-dimensional turbulent stirring flow created by linear motor in a continuous casting system. A k-εturbulent model was applied to solve time-averaged turbulent momentum equations within the computation domain. Four different situations in a stirring system being consisted of two-dimensional slab of 1 m(width) × 0.2 m(height) have been investigated, that is : Model (A) : W =0.1 m and B_0=0.01 tesla, Model (B) : W =0.3 m and B_0=0.01 tesla, Model (C) : W =0.1 m and B_0=0.02 tesla, Model (D) : W =0.3 m and B_0=0.02 tesla, where W is the length of linear motor and B_0 is the magnetic flux applied on the motor-side-surface of the slab. The results shows that the flow characteristics depends mainly on the magnetude of B_0 not on W. The order of the magnitudes of turbulent intensity at four flow situations were almost same. However, the magnitude of turbulent viscosity became much less in case of greater B_0 than in smaller B_0. Therefore it is recommended that the stirrer with greater B_0 should be used to make finer stirring action.
( Jae Rim Lee ),( Mary Jo Katras ),( Jean W. Bauer ) 대한가정학회 2010 International Journal of Human Ecology Vol.11 No.2
This study explicitly identifies the main values that rural welfare recipients reveal when they talk about their experiences with welfare and welfare reform. An inductive analysis of values is conducted using interview data from 49 current and former recipients of Temporary Assistance for Needy Families (TANF) residing in the states of Massachusetts, Maryland, Minnesota, and New York. Seven main values that emerge from the data are self-esteem, autonomy, uniqueness, advancement, security, independence, and fairness. A conceptual diagram of these values is developed to illustrate how these values are related.
정밀주조된 A356 Al 합금의 미세조직과 기계적 성질과 미치는 HIPping의 영향
김낙준,이민하,김재중,김경훈,이성학,이의휘 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.2
The effects of HIPping on high-cycle fatigue properties of investment cast A356 Al alloys were investigated in this study. Tensile and high-cycle fatigue tests were conducted for cast alloys, two of which were HIPped, and then the test data were analyzed in relation with microstructures, tensile and fracture properties, and fatigue fracture mode. Eutectic Si particles were homogeneously dispersed in the matrix of the cast A356 Al alloys, but there were many large pores formed as cast defects. The high-cycle fatigue results indicated that fatigue strength of the HIPped alloys was higher than that of the non-HIPped alloys because of the significant reduction in volume fraction of pores by HiPping. In the non-HIPped specimens, fatigue cracks initiated at large pores adjacent to the specimen surface and then propagated down to several hundreds micrometers depth while coalescing with other large pores. On the other hand, the HIPped specimens, where pores did not affect the fatigue substantially, fatigue cracks propagated along eutectic Si particles formed at solidification cell boundaries, thereby showing improved fatigue strength by 40∼50% over the non-HIPped specimens.