• Journal of Powder Materials
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• v.19 no.6
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• pp.435-441
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• 2012

A new manufacturing process of Fe-Cr-Al powder porous metal was attempted. First, ultra-fine fecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid (0.05~0.5% powders) was dispersed on PU (Polyurethane) foam through the electrospray process. And then degreasing and sintering processes were conduced. In order to examine the effect of sintering temperature in process, pre-samples were sintered for two hours at temperatures of $1350^{\circ}C$, $1400^{\circ}C$, $1450^{\circ}C$, and $1500^{\circ}C$, respectively, in $H_2$ atmospheres. A 24-hour TGA (thermo gravimetric analysis) test was conducted at $1000^{\circ}C$ in a 79% $N_2$+21% $O_2$ to investigate the high temperature oxidation behavior of powder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased with increasing sintering temperature (2.57% oxidation weight gain at $1500^{\circ}C$ sintered specimen). The high temperature oxidation mechanism of newly manufactured Fe-Cr-Al powder porous metal was also discussed.

• Journal of Powder Materials
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• v.21 no.1
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• pp.55-61
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• 2014

Fe-Cr-Al powder porous metal was manufactured by using new electro-spray process. First, ultra-fine fecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid (0.05~0.5% powders) was dispersed on Polyurethane foam through the electro-spray process. And then degreasing and sintering processes were conduced. In order to examine the effect of cell size ($200{\mu}m$, $450{\mu}m$, $500{\mu}m$) in process, pre-samples were sintered for two hours at temperature of $1450^{\circ}C$, in $H_2$ atmospheres. A 24-hour thermo gravimetric analysis test was conducted at $1000^{\circ}C$ in a 79% $N_2$ + 21% $O_2$ to investigate the high temperature oxidation behavior of powder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased with increasing cell size. In the $200{\mu}m$ porous metal with a thinner strut and larger specific surface area, the depletion of the stabilizing elements such as Al and Cr occurred more quickly during the high-temperature oxidation compared with the 450, $500{\mu}m$ porous metals.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.211-214
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• 2004

In the present study, the effect of SIDT (Strain Induced Dynamic Transformation) on the microstructure of medium carbon steels was investigated to develop spheroidized annealing-free steel wire rods. When $0.45\%C$ steels were hot-deformed under the conditions of heavy reduction at low temperatures, a microstructure quite different from conventional ferrite-pearlite structure was obtained. It was considered that this ferrite-cementite microstructure was obtained because very small retained austenite grains existing between fine SIDT ferrites prefer to transform to cementite and ferrite instead of pearlite during cooling. Through the present study, $0.45\%C$ steels containing ferrite-cementite (FC) structure instead of ferrite-pearlite structure was obtained in as-rolled state by introducing SIDT. The specimen containing the FC structure was much softer than that containing conventional ferrite-pearlite structure. Therefore, it is concluded that deforming medium carbon steels under the conditions of SIDT is a very powerful method to obtain soft steel wire rods which could be cold-forged without softening heat-treatment

• Journal of the Korean Wood Science and Technology
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• v.25 no.3
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• pp.50-57
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• 1997

The presence of slime in paper mills is practically universal. Many researches have been performed for many years to resolve the problem caused by the slime in pulp and paper mill. Many papers have been published to show the bacteria is a major cause of paper mill slime. Now that the recycling of the water has been increased and the regulations of a toxic chemical dosage have become more strengthen, the importance of the control of slime in pulp and paper mill recently has been more recognized. Therefore, to produce quality products at the lowest economic and environmental costs, a through study of the microbial ecology and the indentification of troublesome slime-forming bacteria is a quite necessary. The purpose of this paper is to indentify slime~forming bacteria isolated from the papermaking process. The samples were taken from four parts of making fine paper : machine chest, head box, wire part, white water tank. Machine chest showed the most numbers of bacteria, numbering $2.55{\times}10^7$. The different colony types were taken from the 105 dilution plate. Nine bacteria were identified u sing the Biolog system and the vitek system: 6 gram-negative bacteria, 3 gram-positive bacteria. They are Pseudomonas paucimobilis B., Staphylococcus sp., Acinetobacter calcoaceticus., Pseudomonas cepacia, Actinobaci1lus capsulatus, Acidovorax sp., Flavobacterium sp., and Staphylococcus auricularis in addition to one unidentified sp., Among them. Pseudomonas paucimobillis was found in all places where the samples were taken. And, each parts had the different predominant bacteria in it : Pseudomonas paucimobilis B. in machine chest, Acinetobactor calcoaceticus. in Wire Part and Staphylococcus sp. in head box.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.897-907
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• 2020

The flow characteristics of reactor fuel assembly always intrigue the designers and the experimentalists among the myriad phenomena that occur simultaneously in a nuclear core. In this work, the visual experimental method has been developed on the basis of refraction index matching (RIM) and particle image velocimetry (PIV) techniques to investigate the detailed flow characteristics in China fast reactor fuel subassembly. A 7-rod bundle of simulated fuel subassembly was fabricated for fine examination of flow characteristics in different subchannels. The experiments were performed at condition of Re=6500 (axial bulk velocity 1.6 m/s) and the fluid medium was maintained at 30℃ and 1.0 bar during operation. As for results, axial and lateral flow features were observed. It is shown that the spiral wire has an inhibitory effect on axial flow and significant intensity of lateral flow mixing effect is induced by the wire. The root mean square (RMS) of lateral velocity fluctuation was acquired after data processing, which indicates the strong turbulence characteristics in different flow subchannels.

• Archives of Plastic Surgery
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• v.50 no.3
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• pp.248-253
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• 2023

Metal fixation systems for cranial bone flaps cut by a drill are convenient devices for cranioplasty, but cause several complications. We use modified craniotomy using a fine diamond-coated threadwire saw (diamond T-saw) to reduce the bone defect, and osteoplasty calcium phosphate cement without metal fixation. We report our outcomes and tips of this method. A total of 78 consecutive patients underwent elective frontotemporal craniotomy for clipping of unruptured intracranial aneurysms between 2015 and 2019. The follow-up periods ranged from 13 to 66 months. The bone fixation state was evaluated by bone computed tomography (CT) and three-dimensional CT (3D-CT). The diamond T-saw could minimize the bone defect. Only one wound infection occurred within 1 week postoperatively, and no late infection. No pain, palpable/cosmetically noticeable displacement of the bone flap, fluid accumulations, or other complications were observed. The condition of bone fixation and the cosmetic efficacy were thoroughly satisfactory for all patients, and bone CT and 3D-CT demonstrated that good bone fusion. No complication typical of metal fixation occurred. Our method is technically easy and safety, and achieved good mid-term bone flap fixation in the mid-term course, so has potential for bone fixation without the use of metal plates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.183-184
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• 2007

A 40 Gb/s transimpedance amplifier IC was designed and fabricated with a InP/InGaAs HBTs technology. In this study, we interconnect 40Gbps trans impedance amplifier IC to a duroid substrate by a flip chip bonding instead of conventional wire bonding for interconnection. For flip chip bonding, we developed fine pitch bump with the $70{\mu}m$ diameter and $150{\mu}m$ pitch using WLP process. To study the effect of WLP, electrical performance was measured and analyzed in wafer and package module using WLP. The Small signal gains in wafer and package module were 7.24 dB and 6.93dB respectively. The difference of small signal gain in wafer and package module was 0.3dB. This small difference of gain is due to the short interconnection length by bump. The characteristics of return loss was under -10dB in both wafer and module. So, WLP process can be used for millimeter wave GaAs MMIC with the fine pitch pad and duroid substrate can be used in flip chip bonding process.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.80-88
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• 2011

The dental high-speed air turbine handpiece is one of the most popular devices that have been widely used as the main means of cutting tooth structure and restorative material in dentistry. In consideration of usage and marketability of the dental handpiece, it is obviously worthy of investigating it. The goal of this paper is to establish the relationship between the air turbine speed and the supply route inside the handpiece. To do this, the Computational Fluid Dynamics(CFD) tool, Fine$^{TM}$/Turbo is used and the optimal supply route position is suggested from the simulation results. In addition, as an attempt for domestic product, the reverse engineering process of a high speed dental handpiece by 3D X-Ray CT equipment and wire cutting is presented for the Mark II model in NSK. In doing so, the 3D modeling of the handpiece parts is carried out with CATIA V5, and the interference between parts is examined. Finally, the result of performance test for the prototype produced in this research is presented.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.2
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• pp.8-15
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• 2008

Wastewoods (logging residues) generated in Korea were used to make lignocellulosic fillers for papermaking. Lignocellulosic fillers could play great roles to increase retention efficiency and thus decrease turbidity of white water in papermaking process. In addition, lignocellulosic fillers could be used to improve physical properties of paper through their high affinity to cellulosic fibers, leading to the less use of chemical additives like retention aids. Wastewoods including Pinus densiflora and Quercus variabilis were chemically and mechanically treated for making fine particles passing through 100 mesh wire. The newly generated fillers showed larger particle size distribution than ground calcium carbonates but similar distribution to talc. In particular, pretreatment by hot water was more effective to generate smaller particle size than by alkali treatment. Lignocellulosic particles mixed with ground calcium carbonates under intense hybridizing condition greatly contributed to surface coverage of organic fillers in addition to filling to lumen and pits.

• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.72-77
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• 2005

The materials used in a ship screw propeller are commonly made with brass. The seawater corrosion and seawater cavitation of the screw propeller reduces the propulsive performance of the ship. In screw manufacturing, the corrosion rust of the screw propeller is removed through a hand grinding method. The grinding process produces dust of the heavy metals from the brass. The dust creates a poor working environment that is harmful to the health of the workers. An automatic corrosionrust removing apparatus, using a blasting method, was developed for the improvement of screw polishing conditions and its working environment. The performance of this apparatus was investigated by surface roughness, weight loss rate, hardness, electrochemical corrosion resistance, and cavitation erosion, after removing of the corrosion rust under various blasting conditions. Two medias of alumina and emery were used in this experiment. The surface roughness and hardness of the screw were improved by this apparatus. The electrochemical corrosion potential (Ecorr) and current density (Icorr) were measured by the dynamic polarization method, using a potentiostat,under the conditions of surface polishing with grinding, blasting, wire brushing, and fine sand papering. The test results prove that the new corrosion rust-removing apparatus improves the surface performance of a screw propeller.