• International Journal of Korean Welding Society
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• 제3권1호
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• pp.29-33
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• 2003

The ferritic stainless steels are generally considered to have poor weldability compared with that of the austenitic stainless steels. However the primary advantages of ferritic stainless steels include lower material cost than the more commonly used austenitic stainless steels and a greater resistance to stress corrosion cracking. Thus, the weldability of ferritic stainless steels was investigated in this study. In concerning the weldability, Grain size measurement test, Erichsen test and Varestraint test were involved. full penetration welds were produced by autogeneous direct current straight polarity (DCSP) and pulsed currents gas tungsten arc welding (GIAW) and the effect of pulsed currents welding on the welds was compared to that of DCSP welding. The results showed that pulsed current was effective to refine grain size in the weld metal and the finest grain size was obtained at the frequency of 150Hz. In addition, the ductility of welds was lower than that of base metal. Finally, autogeneous type 444 welds were less susceptible to macro solidification cracks, but more sensitive to micro cracks; SEM/EDS analysis indicated that all the inclusions in the crack showed enrichment of Mn, Si, O and S.

• Nuclear Engineering and Technology
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• 제12권2호
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• pp.88-98
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• 1980

원통형 관속을 흐르는 뜨거운 단상 유체의 응고 과정을 해석적인 방법과 실험적인 방법으로 연구 하였다. 파라핀초와 Wood's Metal을 뜨거운 유체로 사용하여 일련의 실험을 하였다. 이 실험 데이터로 부룩해븐 연구소에서 개발한 응고과정에 대한 기존 준정적 수리해석 모델을 증명하였다. 또한 이 실험결과, 수직관속을 순간적으로 흐르며 응고하는 과정에 미치는 여러가지 매개변수의 영향에 관한 자료를 얻게 되었다. 이 실험에 사용한 기구와 실험 방법 도 아울러 기술하였다. 녹은 유체의 순간적으로 흘러내리는 양에 대한 수학적 모델의 예측 결과를 실험데이터와 비교하기 위해 도표로 제시하였다. 또한, 수학적 모델을 고속증식로(LMFBR)에 사고가 일어 났을 경우에 응용하여 보았다.

• 한국주조공학회지
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• 제27권2호
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• pp.88-94
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• 2007

General criteria for the risering design of steel castings and commercial codes for the flow and solidification analysis were used to design the optimized risering in V-process. Three type of specimens were chosen including thin plates and a thick disc. Sided riser installed in the front of a plate casting was effective to prevent the shrinkage defects and to increase the casting yield ratio. Exothennic sleeve and chill were also effective. It was possible to apply the general criteria for the risering design of steel castings to V-process. Temperature of a mold surface was expected to rise over $1,000^{\circ}C$ in the temperature calculation considering radiation effect of molten metal in the mold. Since weakening temperature of the vinyl used in V-process is about $70^{\circ}C$, it should be emphasized that a proper coating of the vinyl film is necessary to prevent the possibility of burning out of the vinyl by the molten metal.

• Journal of Welding and Joining
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• 제16권5호
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• pp.56-66
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• 1998

During solidification or welding of alloys, the solute redistribution brings out microsegregation. The microsegregation causes the formation of non-equilibrium second phases, shrinkage and porosity degrading mechanical/chemical properties Therefore, it has been required to predict microsegregation quantitatively. To predict the degree of microsegregation, more exact and appropriate computer simulation technique has been actively used during last two decades. To predict the degree of microsegregation in weld metal, an advanced two dimensional model was suggested. In the new model, both primary and secondary arm regions were defined for the analysis region. The growth in the primary arm regina was assumed to be a planar for effective calculation. Especially, for the growth of a secondary arm, a simple and effective mathematical function was established to show the growing pattern, the solute diffusion in the solid phase was calculated by finite difference method (FDM). The solid-liquid interface movement was considered to be in local equilibrium state. The experiments for welding of 310S stainless steel were carried out in order to examined the reasonability and feasibility of this model. The concentration profiles of the solute predicted by this model were compared with those obtained from experimental works.

• 한국환경과학회지
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• 제19권2호
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• pp.255-260
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• 2010

A stabilization/solidification (S/S) process for lead (Pb) contaminated soils was evaluated using waste cow bone containing apatite like compounds. Soil samples obtained form firing range were treated with waste cow bone. The effectiveness of stabilization was evaluated based on the Korean Standard Leaching Test (KSLT) and soil pH. The leached concentration reduced with increased in dose of waste cow bone. Overall, the KSLT results showed that Pb concentration in soils are significantly affected by amount of waste cow bone. When soil amended with 20 % of waste cow bone, less than 0.1 mg/kg was leached, and soil pH was increased from 6.5 to 8.4. Same results were obtained when finer waste cow bone was applied. The reachable concentration of Pb in soil showed in inversely proportional to solid/liquid ratio. Aging periods indicate improving mix design was applied. Relatively high lead concentrations was observed at the first 1 days, however leaching profile are reduced significantly over time for all mix designs.

• 대한기계학회논문집B
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• 제26권5호
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• pp.648-657
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• 2002

This paper presents a numerical analysis on the solidification characteristics in twin-roll strip casting. Unstructured fixed-grid system was employed to deal with phase change. Melting of pure gallium was analyzed to confirm the validity of present program in both structured and unstructured grid systems. An algorithm for simultaneous calculation of the temperature in the roll and the molten metal pool was developed. The flow field in the pool and heat transfer features between pool and roll were shown. The effect of process parameters was also studied. Since the geometry of the molten metal Pool significantly deforms along the casting direction, unstructured grid system is more efficient. The unstructured grid system gives almost the same accuracy, even though the number of grids is only 60% of the structure done.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2003년도 가을 학술논문집
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• pp.220-225
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• 2003

원자력발전소에서 발생하는 방사성 폐액은 일반적으로 액체폐기물처리계통 폐액증발기 및 농축 폐액건조설비에서 증발 및 건조 공정을 통해 수분을 함유하지 않은 분말형태로 변한다. 이 분말형태의 폐기물은, 취급 시와 처분 후 안전성을 확보할 수 있도록, 파라핀과 균일하게 혼합되어 고화된 후 철제드럼에 포장된다. 농축폐액건조설비를 이용하여 농축폐액을 건조시킨 후 분말 형태의 폐기물을 파라핀과 혼합하는 공정을 수행할 때, 방사성 폐액 중 붕소와 나트륨의 몰비가 0.2를 초과하는 경우, 분말형태의 폐기물이 파라핀과 균일하게 혼합되지 않고 층을 이루어 분리되어 드럼에 안정고화가 잘 안되는 경우가 발생하였고 또한 일부는 드럼화 전에 설비 내에 고착되는 현상이 발생하는 것을 경험하였다.

• Journal of Welding and Joining
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• 제20권5호
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• pp.93-98
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• 2002

The effect of bonding misfit on single crystallization of transient liquid phase (TLP) bonded joints of single crystal superalloy CMSX-2 was investigated using MBF-80 insert metal. The bonding misfit was defined by (100) twist angle (rotating angle) at bonded interface. TLP bonding of specimens was carried out at 1523K for 1.8ks in vacuum. The post-bond heat treatment consisted of the solution and sequential two step aging treatment was conducted in the Ar atmosphere. The crystallographic orientation analysis across the TLP bonded joints was conducted three dimensionally using the electron back scattering pattern (EBSP) method. EBSP analyses f3r the bonded and post bonded heat treated specimens were conducted. All bonded joints had misorientation centering around the bonded interface for as-bonded and post-bond heat treated specimens with rotating angle. The average misorientation angle between both solid phases in bonded interlayer was almost identical to the rotating angle at bonded interface. HRTEM observation revealed that the atom arrangement of both solid phases in bonded interlayer was quite different across the bonded interface. It followed that grain boundary was formed in bonded interface. It was confirmed that epitaxial growth of the solid phase occurred from the base metal substrates during TLP bonding and single crystallization could not be achieved in joints with rotating angle.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.174-179
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• 2005

In the super slow speed die casting process, the casting defects due to melt flow should be controlled in order to obtain sound casting products. The casting defects that are caused by molten metal were cold shut formation, entrapment of air, gas, and inclusion. But the control of casting defects has been based on the experience of the foundry engineers. The calculation of simulation can produce very useful and important results. The calculation data of die casting process condition from the computer simulation by the Z-CAST is made to insure that the liquid metal is injected at the right velocity range and that the filling time is small enough to prevent premature solidification. The parameters of runner shape that affected on the optimized conditions that was calculated with simple equation were investigated. These die casting process control techniques of automobile valve body mid-plate have achieved good agreement with the experimental data of tensile strength, hardness test, and material structure photographies satisfactory results.

• 자원환경지질
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• 제37권1호
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• pp.99-106
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• 2004

환경오염저감 및 제어기술은 환경/방재 기술분야로 포스트 반도체 주력산업의 고도화분야에 해당되며, 그 중 오염토양 및 지하수 복원기술은 앞으로 많은 수요가 예상되는 핵심기술이라 할 것이다. 국내의 경우 폐금속광산이 다수 존재하며 이로 인한 중금속 및 비소오염문제가 심각해지고 있는 시점에서 이를 복원하기 위한 최신기술의 동향을 알아보는 것이 필요할 것이다. 현재 이 분야의 선진국인 미국 및 유럽각국에서의 기술개발은 2차적인 오염을 유발하지 않을 청정기술의 개발과 개발기술의 현장적용에 초점이 맞추어 지고 있는 추세이다. 여기에 최근에 개발되어진 신기술중에 이러한 장점으로 인해 주목받고 있는 기술인 전기동력학 기술, 투수성 반응벽체기술, 고형화/안정화기술, 박테리아를 이용한 생체흡착기술, 박테리아를 이용한 용출기술, 식물정화기술을 소개하고자 한다.