• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.157-162
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• 1997

Silicon Nitride samples with different microstructure were prepared by hot pressing and subsequent heat treatment under N2 gas pressure. The fracture toughness (KIC)of Si3N4 increased with the increase of grain size, but the bending strength of plain specimen($\sigma$F) decreased. The relation between fracture stress($\sigma$c) and equivalent crack length(ae) agreed well with the calculated values by process zone size failure criterion. A probabilistic failure assessment curve is proposed based on both statistical character of $\sigma$F and KIC.

• Journal of the Korean Geophysical Society
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• v.4 no.4
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• pp.257-266
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• 2001

The properties of electrical resistance of Mn-Co-Ni-Fe oxide-based therrnistor with various Fe contents in sintering process at 1200 to 1400℃ for 4 hours in air atmosphere for fabricating therrnistor materials were investigated. The results were as follows: all samples showed single cubic spinel crystal structures in all region. The electrical conductivinity is the highlest thermistor sintered at 1300℃ for 4 hours. In general when the Fe content is increased except F-2, the resistivity increases and relatively the conductivity decreases. Particularly F-2 composition exhibited the highlest electrical conductivity(1.4x $10^-3$$Ω$cm) and relatively low B constant(2906K)

• Korean Journal of Ecology and Environment
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• v.41 no.1
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• pp.90-97
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• 2008

The aim of this research was to detect and observe delivering generation effects from $F_0$ generation exposed to 4-nonylphenol 4NP) to $F_1$ generation on Tigriopus japonicus. The nauplius survival rate of $F_1$ from $F_0$ exposed to low 4NP concentration was significantly lower than other concentrations. Among the developmental process, copepodite first emergence day (CE) and adult male first emergence day (ME) on $F_1$ were accelerated relatively high concentration conditions. The sex ratio of $F_1$ was different between control group and treatment groups for 1, 10 and $30{\mu}g\;L^{-1}$ 4NP. The fecundity of $F_1$ was not significantly affected (except, $0.1{\mu}g\;L^{-1}$ 4NP). When 4NP concentrations were increased, first brooding day (FB) of F 1 was generally delayed. The length, width, and biomass of $F_1$ adult female were smaller than control group. In addition, the width and biomass of adult male were narrower or smaller than control group.

• Communications of the Korean Mathematical Society
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• v.25 no.3
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• pp.385-389
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• 2010

In 1997, Exton, by mainly employing a widely-used process of resolving hypergeometric series into odd and even parts, obtained some new and interesting summation formulas with arguments 1 and -1. We aim at showing how easily many summation formulas can be obtained by simply combining some known summation formulas. Indeed, we present 22 results in the form of two generalized summation formulas for the generalized hypergeometric series $_4F_3$, including two Exton's summation formulas for $_4F_3$ as special cases.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.595-599
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• 1996

The behaviour of the internal bubbles present in $CaF_{2}$ crystals was characterized crystallographically using a variety of the mircroscopical technique. The bubble defects were found to be aligned on the characteristic planes and directions depending on the crystals structure of the $CaF_{2}$. The AFM analysis revealed that these behaviors are related to the S-surface formation by the negative grain growth mechanism.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.204-209
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• 2002

In this study, $UO_4{\cdot}2NH_4F$, the precipitates which has low solubility, was obtained by chemical precipitation method to recover and reuse the trace uranium from the liquid waste producing in AUC process and for this compound it was characterized by means of chemical analysis, TG-DTA, XRD and FT-IR analyses. This compound was analyzed as $UO_4{\cdot}2NH_4F$ and shape of this precipitate was hexagonal type, having the size of 2∼3 ${\mu}m$. Also, the intermediates were obtained as $UO_4F,\;UO_4,\;UO_3,\;and\;U_3O_8$ by the thermal decomposition over the temperature of 220, 310, 515 and 640$^{\circ}C$, respectively. It is concluded that under the condition of a constant heating rate of 5$^{\circ}C$/min in air atmosphere range of between room temperature and 800$^{\circ}C$, thermal decomposition reaction mechanism of $UO_4{\cdot}2NH_4F$ is as follow; $UO_4{\cdot}2NH_4F{\rightarrow}UO_4F{\rightarrow}UO_4{\rightarrow}UO_3{\rightarrow}U_3O_8$.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.4
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• pp.149-158
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• 2015

Up-to-date manufacturing companies have faced a market-driven environment of pull production order. There should be a difference in operating manufacturing resources according to the type, quantity, and delivery time of manufactured products, because the process situation in pull production is changed by customer orders. And it should be taken into account from the stage of preparing for production such as process design and the placement and utilization of manufacturing resources. However, the feasibility of production plans is limited because most of small manufacturing businesses make production/supply plan of the parts and products assuming that equipment abilities in scheduling is sufficient without managing process standard information systemically. In this study, a discrete event simulation system based on BOM (bill of material), that is F-OPIS (online productivity innovation system), is introduced and a case study on application of the system leading to improving productivities is presented. F-OPIS deals with a decision-problem on production management and it is specialized for small-and- medium sized manufacturing companies. The target company of this case study is a typical small-and-medium sized manufacturing company in Korea, that produces various machined parts. The target company adopts make-to-stock production management to prevent tardy delivery because of fluctuations in demand. Therefore, it is required to apply an efficient inventory control solution for improving productivities. In this paper, based on the constraints of working capacity of manufacturing resources, the bottleneck process is analyzed as production conditions are changed. Consequently, an improvement plan is proposed, that eventually enhances overall utilization rates of resources in the bottleneck process and reduces overall production lead-time and inventory level.

• Water for future
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• v.25 no.2
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• pp.61-66
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• 1992

This study was to determine the static acute toxicity on Daphnia magna for the Electric cable Factory Wastewater. Activated sludge process was used to treat the wastewater with three different F/M ratios, 0.36, 0.2, 0.1 mg COD/day.mg MLSS. The results of laboratory bioassay with Daphnia magna were as follows. 1)24hr, 48hr-LC$ of the influent were 17.33% and 11.73%. 2)24hr-LC $ of effluents treated with F/M ratio 0.36,0.26 and 0.1mg COD/day.mg MLSS were 26.69% 32.70% and 38.36% respectively, 48-LC$ of these effluents were 14.48% 27.88% and 31.58% respectively. 3)According to various F/M ratios, the ratios of dffluent 48hr-LC$ to filtrated 48hr-LC$ were 1.58, 1.83 and 1.47respectively 4)Activated sludge process effluents treated with activated carbon had little toxicity on Daphnia magna.

• Journal of Korean Foot and Ankle Society
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• v.16 no.3
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• pp.175-180
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• 2012

Purpose: To evaluate the radiological and clinical results after open reduction and internal fixation with calcaneal F plate and locking calcaneal plate using lateral extensile approach in the treatment of intra-articular calcaneal fracture Materials and Methods: This study included 34 cases of 33 patients followed up for at least 6 months postoperatively. F plate was applied in 18 cases (Group 1), locking plate was used in 16 cases (Group 2) and compared radiological and clinical results between two groups. Results: Radiollogically, the mean Bohler angle was improved from $5.5^{\circ}$ preoperatively to $20.1^{\circ}$ postoperatively and $18.8^{\circ}$ at the last follow up in group 1 and $8.6^{\circ}$ preoperatively, $21.4^{\circ}$ postoperatively and $20.3^{\circ}$ at last follow up in group 2. Bone union was observed in all cases and 4 cases of screw loosening were noted in Group 1 with extended fracture to anterior process. At the last follow up, both groups showed clinical results in American orthopedic foot and ankle society ankle hindfoot score, 76(77 in Sanders type II and 75 in type III) in group 1 and 72(73 in type II and 70 in type III) in group 2. Conclusion: F plate and locking plate showed firm fixation and satisfactory clinical results in the treatment of intra-articular calcaneal fracture. We suggest applying locking plate in cases with extended fracture to anterior process, considering screw loosenings in those who were treated with F plate fixation.

• Journal of the Korea Society for Simulation
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• v.18 no.4
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• pp.185-195
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• 2009

As most systems get more complicated, system analysis using simulation has been taken notice of. One of the core parts of simulation analysis is validation of a simulation model, and we can identify how well the simulation model represents the real system with this validation process. The difference between input data of two systems has an effect on the comparison between a simulation model and a real system at validation stage, and the result with such difference is not enough to ensure high credibility of the model. Accordingly, in this paper, we construct a model based on Trace-driven simulation which uses identical input data with the real system. On the other hand, to validate a model by each class, not by an unique statistic, we validate the model using a metric transformed from F-measure which estimates performance of a classifier in data mining field. Finally, this procedure enables precise validation process of a model, and it helps modification by offering feedback at the validation phase.