• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2003년도 춘계학술대회논문집
• /
• pp.195-198
• /
• 2003

High temperature deformation and softening behavior of SAF 2507 super duplex stainless steel (SDSS) has been investigated in connection with an FEM analysis of hot forging process. Flow curves at various strain rates and temperatures were determined first from compression tests, and the kinetics of dynamic recrystallization were also formulated through the analysis of load relaxation test results. Applying the dynamic materials and proposed by Prasad et al., it was possible to determine the characteristics of deformation behavior effectively at a given condition of deformation. Constitutive relations and recrystallization kinetics formulated from the test results were then implemented in a commercial FEM code. Flow stress compensation formulated upon the volume fraction of recrystallization and adiabatic heating was found to improve significantly the FEA solutions in predicting the forming load and the distribution of recrystallized volume fraction after forging.

• Journal of Welding and Joining
• /
• 제33권5호
• /
• pp.20-25
• /
• 2015

Clad steel has good corrosion resistance and mechanical properties arising from the hot rolling of dissimilar metals, such as carbon steel and stainless steel. However both good corrosion resistance from the cladding plate material(stainless steel) and mechanical properties from the base plate material (carbon steel) are difficult to obtain because the different steels display opposite behaviors during the cladding process. In order to make clad steel for application in the hulls of ships, proper materials selection and heat-treatment conditions are necessary. In this study, mechanical properties of base plate materials with different chemical composition were evaluated according to heat condition of cladding plate material.

• 한국미생물·생명공학회지
• /
• 제19권6호
• /
• pp.553-560
• /
• 1991

Bacillus circulans로부터 mitomycin C처리에 의해 유발되는 Bacteriophage Sigma FA1을 서당밀도균배 원심법 (sucrose gradient centrifugation)에 의해 분리, 정제하였다. Sigma FA1의 감수성숙주에 대한 치사작용은 single-hit 방식이었다. 한편, 세포에 감여된 후 phage DNA는 천천히 분해되기 시작했으며, 본 연구의 결과는 Sigma FA1의 세포에 대한 치사작용이 기존의 것과는 다른 것임을 입증시켰으며, 이는 단 백질분해기능에서 유래되는 듯 했다.

• 소성∙가공
• /
• 제10권6호
• /
• pp.465-470
• /
• 2001

Hole flanging experiments are performed on flat circular plates with a hole in the center and the flangeability and fracture behaviors of TRIP steels and ferrite-Bainite duplex steels were examined. In the hole flanging, deformation by lip and petalling occurs when plates are struck by punches of various shapes and high circumferential strains induced in the target material cause radial cracking and the subsequent rotation of the affected plate material in a number of symmetric petals. In all cases, failure of the plate was due to lip fracture that results from multiple localized neckings that take place around the hole periphery where straining is most severe and a somewhat regular pattern was observed in a fracture shape. The neck characteristics in flange formation and the transition from the lip to petal mode at which fracture occurs were compared with two materials.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2000년도 춘계학술대회논문집
• /
• pp.119-122
• /
• 2000

Dynamic deformation of metallic materials mostly accompanies substantial amounts of deformation heat. Since the flow stress of deformation is sensitive to temperature implication of heat due to plastic work is essential to the evaluation of constitutive relations. In this study a series of compression tests were conducted for SAF 2507 super duplex stainless steel and the accumulation of deformation heat was calculated through numerical integration method. Isothermal flow surfaces were deduced from subsequent logarithmic interpolation. Simple closed die forging process was analyzed and optimized with commercial FEM code applying both raw and calibrated material database.

• Molecules and Cells
• /
• 제26권3호
• /
• pp.308-313
• /
• 2008

In animals, microRNAs (miRNAs) and small interfering RNAs (siRNAs) repress expression of protein coding genes by assembling distinct RNA-induced silencing complexes (RISCs). It has previously been shown that passenger-strand cleavage is the predominant mechanism when siRNA duplexes are loaded into Argonaute2 (Ago2)-containing RISC, while an unwinding bypass mechanism is favored for miRNA duplexes with mismatches. Here I present experimental data indicating that some mammalian miRNAs are assembled into Ago2-containing RISC by cleaving their corresponding miRNA star strands. This phenomenon may depend on the secondary structure near the scissile phosphate of the miRNA duplex. In addition, I show that ATP is not required for star-strand cleavage in this process. Taken together, the data here provide insight into the miRNA-loading mechanisms in mammals.

• 한국측량학회:학술대회논문집
• /
• 한국측량학회 2004년도 추계학술발표회 논문집
• /
• pp.435-440
• /
• 2004

In this study, it is aimed to construct a remote home doctor system utilizing GIS technique. Remote home doctor system consists of three major compartments ; full-duplex communication system, visible communication system, and data backup system. On this system, a company request home doctor is connected with environment specialists and pollution control equipment company. The database in this system consists of spatial data and attribute data. Spatial data are made by topographic data and company location data. Attribute data consists in document data, status of company, products, amount of raw material used, odor discharge process, pollution discharge information and prevention equipments.

• 소성∙가공
• /
• 제12권4호
• /
• pp.308-313
• /
• 2003

High temperature deformation and softening behavior of SAF 2507 super duplex stainless steel (SDSS) has been investigated in connection with an FEM analysis of hot forging process. Flow curves at various strain rates and temperatures were determined first from compression tests, and the kinetics of dynamic recrystallization were also formulated through the analysis of load relaxation test results. Using the dynamic materials theory proposed by Prasad, the deformation behavior was effectively determined for various conditions. Constitutive relations and recrystallization kinetics formulated from the test results were then implemented in a commercial FEM code. The forming load as well as the distribution of recrystallized volume fraction after forging was successfully predicted by means of the flow stress compensation formulated upon the volume fraction of recrystallization and adiabatic heating.

• 한국표면공학회지
• /
• 제51권3호
• /
• pp.172-178
• /
• 2018

In this paper, effects of potassium permanganate, pottasium dichromate, sodium molybdate on lean duplex stainless steel were studied by GDOES, OCP, potentiodynamic curves. The stainless steels were chemically passivated in each nitric acid solutions containing 4wt.% oxidants for 1 hour. As a result, when potassium dichromate or sodium molybdate was added, content of Fe was decreased and content of Cr was increased. Consequently, corrosion resistance of passive film was increased. But in case of potassium permanganate was added, contrastively, content of Fe was increased and content of Cr was decreased. So corrosion resistance was decreased. Adding sodium molybdate in nitric acid for chemical surface treatment process was the most effective among oxidants and also it showed the most stable anti-corrosion in SST.

• Advances in materials Research
• /
• 제4권1호
• /
• pp.1-12
• /
• 2015

Low carbon steel of composition 0.05C - 0.18 Mn - 0.012 Si is intercritically annealed at temperatures $750^{\circ}C$, $775^{\circ}C$ and $800^{\circ}C$. The equilibrated alloys of different amounts of austenite with varying carbon contents are quenched in iced water. The same alloys are subcritically annealed at $675^{\circ}C$ and $700^{\circ}C$ for varying periods of times; the subcritically annealed alloy samples are quenched in iced water. Optical, scanning electron and transmission electron microscopy are carried out for all the samples. The dislocation structure, its distribution and density present in the above prepared duplex ferrite martensite steels are studied. The martensites are found to be highly dislocated due to lattice invariant deformation. At the same time ferrite adjoining the martensite areas also exhibits quite a high dislocation density. The high dislocation density is favorable for strain ageing and hence bakes hardenability. EDS analyses were carried out for both martensite and ferrite phases; it is found that the degree of supersaturation in ferrite together with carbon content in martensite varies with the process parameters. The microhardness test results show that the hardness values of different phases differ appreciably with process parameters. The microstructures and the corresponding microanalyses reveal that differently processed steels contain phases of varying compositions and different distribution.