• Journal of Korean Society for Quality Management
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• v.34 no.1
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• pp.1-12
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• 2006

This paper presents a six sigma project for improving gate painting quality in a medium-sized automotive part company. The project follows a disciplined process of five macro phases: Define, Measure, Analyze, Improve, and Control. A CTQ(critical to quality) is determined based on COPQ(cost of poor quality) analysis, and a process map is utilized for identifying process input variables. Three KPIV s(key process input variable) are selected; Painting Temperature, Painting Quantity, and Painting Viscosity, and DOE(design of experiments) is utilized for finding the optimal process conditions for three KPIVs. MINITAB software is used for data analyses and DOE. The sigma level of defects rate has improved from 2.93 to 3.66.

• IE interfaces
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• v.16 no.spc
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• pp.7-13
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• 2003

This paper is concerned with a six sigma green belt training program. Comparative studies of existing training programs for three major companies (Samsung Electronics Company, Hyundai Motor Company, and LG Chemical Ltd.) and two consulting firms (Korean Standards Association and Korea Management Association) are made. Based on the comparative studies, a new green belt training program is proposed. The main focus of this program is on manufacturing, specially on cost and waste reductions, yield improvement, and operations with opportunity to improve capacity without major capital expenditure. The green belts take up to 4 or 5 days of intensive, highly quantitative training, roughly corresponding to the five macro phases of the six sigma methodology: define, measure, analyze, improve, and control. The six sigma tool sets for each phase are also specified.

• Journal of Korean Society for Quality Management
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• v.33 no.3
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• pp.135-148
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• 2005

This paper considers a six sigma project for reducing the project costs through project risk management. The project follows a disciplined process of five phases: define, measure, analyze, improve, and control. A risk management process map is used to identify process input and output variables. Seven key process input variables are selected by using C&E diagram and X-Y matrix and finally four vital few input variables are selected by the related statistical analysis. The optimum alternatives of the vital few input variables are obtained by the method of PUGH matrix. The process is running on control plan and we obtained substantial project cost reductions in early stage of the control phase.

• Journal of the Korea Safety Management & Science
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• v.11 no.1
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• pp.121-130
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• 2009

This paper considers a six sigma project for reducing the cost copper of the cable materials in a electric wire company. The project follows a disciplined process of five macro phases: define, measure, analyze, improve, and control (DMAIC). A process map is used to identify process input variables. Three key process input variables are selected by using an input variables are selected by using an input variable evaluation table: large cable, plating, and a twisted pair. DOE is utilized for finding the optimal process conditions of the three key process input variables. The implementing result of this six sigma project is enable for reducing of the 2.8% copper materials.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.75-79
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• 2013

This study was carried out to investigate the precipitation behavior of the ${\chi}$ phase and the impact toughness of 25%Cr-7%Ni-2%Mo-4%W super duplex stainless steel. The ${\chi}$ phase was precipitated in the early stage of aging, and with the increasing aging time. However, after reaching a maximum value, the number decreased as a result of the gradual transformation of the ${\chi}$ phase into the ${\sigma}$-phase. It was proved that the ${\chi}$ phase was an intermetallic compound, which represented a lower nickel concentration, higher chromium and molybdenum concentrations, and very higher tungsten concentration compared to the matrix phases. It also showed higher molybdenum and tungsten concentrations than the ${\sigma}$ phase. The decomposition of the ferrite phase into the ${\gamma}_2$ and ${\sigma}$ phases was retarded by W substitution for Mo. Thus, the number of ${\chi}$ phases increased. The impact value was decreased by the substitution of W for Mo. The impact toughness rapidly decreased with time when the ${\chi}$ phase began to precipitate in the initial stage of aging. The impact toughness was, therefore, greatly influenced for the precipitation of the ${\chi}$ phase.

• Korean Journal of Materials Research
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• v.24 no.11
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• pp.610-616
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• 2014

In this study, we investigated the precipitation behavior of the R-phase precipitated at the initial stage of aging and its effect on the pitting corrosion of 25%Cr-7%Ni-4%Mo super duplex stainless steel. The R-phase in super duplex stainless steel was mainly precipitated at the interface of ferrite/austenite phases and inside of the ferrite phase during the initial stage of aging, and it was transformed into the ${\sigma}$-phase with an increase in aging time. The ferrite phase was decomposed into a new austenite phase and ${\sigma}$-phase. The R phase was an intermetallic compound, which represented a lower Ni and higher Mo than the matrix, and also had a higher Mo and Cr concentration than the ${\sigma}$ phase. With an increasing aging time, the pitting potential $E_p$ was increased slowly by the precipitation of the R-phase, and it was then steeply decreased by the precipitation of the ${\sigma}$-phase. The R-phase was decreased the pitting potential, but its effect was smaller than effect of ${\sigma}$-phase.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.37-37
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• 2009

Due to their high corrosion resistance and improved mechanical properties super-duplex stainless steel (SDSS) are extensively used in petrochemical plants such as facilities in modern oil platform and off-shore process equipment. It is well known that the best mechanical and corrosion resistance properties of super-duplex stainless steel are obtained with a microstructure having approximately equal amounts of austenite and ferrite. And it is also known that sigma($\sigma$), chi($\chi$), secondary austenite(${\gamma}2$), chromium carbides and nitride affected adversely their properties. Therefore these phases must be avoided. However, effects of succeeding weld thermal cycle on the change of microstructure of weldment at multi-pass weld were not seldom experimentally researched. Therefore in the present work, the change of weldmetal microstructure and the effect of microstructure on pitting corrosion property at $40^{\circ}C$ by succeeding each weld thermal cycle were researched. The thermal history of root side was measured experimentally and the change of microstructure of root weld according to thermal cycle of each weld layer was evaluated. And the relationship between microstructure of root weld and pitting corrosion property at $40^{\circ}C$ was also investigated. Results of the present work are show as below. 1. The ferrite contents of root weld are gradually reduced by succeeding weld thermal cycle. 2. The 2nd phases such as sigma($\sigma$), chi($\chi$), secondary austenite(${\gamma}2$), chromium carbides and nitride are increased gradually by succeeding weld thermal cycle. 3. The pitting corrosion was detected in root weld part and weight loss by pitting corrosion is increased in proportional to the time exposed over $600^{\circ}C$ of the root weld. 4. The succeeding weld thermal cycles affect the microstructure of the former weldments and promote the formation of 2nd phases. That is, the more succeeding welds are added, the more 2nd phases are gradually increased. Consequently, it is thougth that this adversely affects pitting corrosion property.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.3
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• pp.241-247
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• 2014

This study presents the ultrasonic nonlinearity of AISI316 austenitic stainless steels subjected to longterm isothermal aging. These steels are attractive materials for use in industrial mechanical structures because of their strength at high-temperatures and their chemical stability. The test materials were subjected to accelerated heat-treatment in an electrical furnace for a predetermined aging duration. The variations in the ultrasonic nonlinearity and microstructural damage were carefully evaluated through observation of the microstructure. The ultrasonic nonlinearity stiffly dropped after aging for up to 1000 h and, then, monotonously decreased. The polygonal shape of the initial grain structures changed to circular, especially as the annealing twins in the grains dissolved and disappeared. The delta ferrite on the grain boundaries could not be observed at 1000 h of aging, and these continuously transformed into their sigma phases. Consequently, in the intial aging period, the rapid decrease in the ultrasonic nonlinearity was caused by voids, dislocations, and twin annihilation. The continuous monotonic decrease in the ultrasonic nonlinearity after the first drop resulted from the generation of $Cr_{23}C_6$ precipitates and ${\sigma}$ phases.

• Journal of Microbiology
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• v.45 no.6
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• pp.534-540
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• 2007

The Streptomyces coelicolor A3(2) genome contains six operons (rrnA to F) for ribosomal RNA synthesis. Transcription from rrnD occurs from four promoters (p1 to p4). We found that transcripts from the p1 and p3 promoters were most abundant in vivo in the early exponential phase. However, at later phases of exponential and stationary growth, transcripts from the p1 promoter decreased drastically, with the p3 and p4 transcripts constituting the major forms. Partially purified RNA polymerase supported transcription from the p3 and p4 promoters, whereas pure reconstituted RNA polymerase with core enzyme (E) and the major vegetative sigma factor ${\sigma}^{HrdB}$ ($E{\cdot}{\sigma}^{HrdB}$) did not. In order to assess any potential requirement for additional factor(s) that allow transcription from the p3 and p4 promoters, we fractionated a partially purified RNA polymerase preparation by denaturing gel filtration chromatography. We found that transcription from the p3 and p4 promoters required factor(s) of about 30-35 kDa in addition to RNAP holoenzyme ($E{\cdot}{\sigma}^{HrdB}$). Therefore, transcription from the p3 and p4 promoters, which contain a consensus -10 region but no -35 for ${\sigma}^{HrdB}$ recognition, are likely to be regulated by transcription factor(s) that modulate RNA polymerase holoenzyme activity in S. coelicolor.

• Applied Microscopy
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• v.33 no.3
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• pp.195-204
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• 2003

The Experimental calibration method has been investigated to correct d-spacing estimation and to identify phases in the electron diffraction data acquired by imaging plates. When the diffraction data from the imaging plate was corrected by the d-spacing calibration method with the radial intensity distribution plotting in this experiment, The accuracy of d-spacing estimation was significantly increased in errors of about 0.5%. The experimental calibration equation followed up the first order exponential decay function was derived from the trace of d-spacing deviation between the measured and the calculated values. It was applied to the analysis of d-spacing and the phase identification of the transitional phases formed from [001] gibbsite specimen by electron beam irradiation effect. In this case more accurate phase identification and d-spacing evaluation is possible for the transitional phases whose diffraction patterns are complicatedly superimposed. It is concluded that ${\chi}$-alumina, ${\gamma}$-alumina and ${\sigma}$-alumina are clearly identified as the major transitional phases formed from gibbsite by electron beam irradiation for 120 min.