• Journal of Powder Materials
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• v.17 no.4
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• pp.312-318
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• 2010

High speed steels (HSS) were used as cutting tools and wear parts, because of high strength, wear resistance, and hardness together with an appreciable toughness and fatigue resistance. Conventional manufacturing process for production of components with HSS was used by casting. The powder metallurgy techniques were currently developed due to second phase segregation of conventional process. The powder injection molding method (PIM) was received attention owing to shape without additional processes. The experimental specimens were manufactured with T42 HSS powders (59 vol%) and polymer (41 vol%). The metal powders were prealloyed water-atomised T42 HSS. The green parts were solvent debinded in normal n-Hexane at $60^{\circ}C$ for 24 hours and thermal debinded at $N_2-H_2$ mixed gas atmosphere for 14 hours. Specimens were sintered in $N_2$, $H_2$ gas atmosphere and vacuum condition between 1200 and $1320^{\circ}C$. In result, polymer degradation temperatures about optimum conditions were found at $250^{\circ}C$ and $480^{\circ}C$. After sintering at $N_2$ gas atmosphere, maximum hardness of 310Hv was observed at $1280^{\circ}C$. Fine and well dispersed carbide were observed at this condition. But relative density was under 90%. When sintering at $H_2$ gas atmosphere, relative density was observed to 94.5% at $1200^{\circ}C$. However, the low hardness was obtained due to decarbonization by hydrogen. In case of sintering at the vacuum of $10^{-5}$ torr at temperature of $1240^{\circ}C$, full density and 550Hv hardness were obtained without precipitation of MC and $M_6C$ in grain boundary.

• Journal of Conservation Science
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• v.33 no.3
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• pp.155-165
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• 2017

As interest in the public display of art and outdoor sculptures is increasing, the conservation and treatment of these sculptures is becoming increasingly crucial. Long-term exposure to the natural elements and atmospheric pollution can cause corrosion and deterioration in outdoor sculptures. In the case of Kim Chan Shik's "Feeling", which was exhibited in the outdoor sculpture park at the National Museum of Modern and Contemporary Art (MMCA), the patina of the sculpture was damaged during a long outdoor exhibition. Therefore, the treatment process was as follows: recording of condition, sanding, repatination, and wax coating. Consequently, the sculpture was restored similar to the original. Chemical analysis revealed that the sculpture was crafted from bronze and was cast from a quaternary alloy of Cu-Pb-Sn-Zn. The welding is lower in Zn, Sn, and Pb content than the metal used in the sculpture itself. Bright strains contain about 13.0 wt% Sn and 10.5 wt% Pb. The strains are higher in Sn and Pb content than the rest of the metal in the sculpture (7.0 wt% Sn and 4.4 wt% Pb). As a result of component analysis and microstructure observation, the material is estimated to have been made by casting without artificial treatment.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.6
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• pp.339-347
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• 2017

The objectives of this study were to analyze ecological characteristics of fish compositions and estimate the optimal ecological flow using the physical habitat simulation system (PHABSIM) in Wonju stream and Boseong river. We sampled fishes using two gears such as casting net and kicknet to determine fish distribution and also measured flow velocity, water depth, bed material at the point where fish collected. Total number of species and individuals sampled were 20 and 2,104, respectively and dominant species was Zacco platypus (39.7%) and subdominant species was Z. koreanus (RA: 15.8%) in Wonju stream. In Boseong river, collected fishes were 1,638 individuals, 28 species. Dominant and sub-dominant species was Z. platypus (RA: 22.0%) and Microphysogobio yaluensis (RA: 17.2%), respectively. For calculating habitat suitability index (HSI), we selected Z. platypus as representative fish species and analyzed water depth and flow velocity. Water depth and flow velocity were 0.2-0.6 m, 0.1-0.3 m/s, respectively in Wonju stream and 0.3-0.6 m, 0-0.3 m/s, respectively in Boseong river. According to the analysis of ecological flow simulation, optimal flow was 1.1 cms and 0.3 cms in Wonju stream and 0.4cms, 2.2cms in Boseong river at up and down stream respectively. WUA (Weighted Usable Area) was 9.5%, 26.6% in Wonju stream and 34.8%, 53.3% in Boseong river at up and down stream respectively.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.5 no.2
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• pp.9-16
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• 1999

Edible films were prepared from proteins extracted from soybean curd residue by alkaline extraction and isoelectric precipitation. Effects of film forming solution pH and plasticizers on mechanical and barrier properties of edible films were studied. films were formed within pH $7{\sim}11$ with tensile strength (TS) of $2.9{\sim}3.3$ MPa. Films produced under pH 10 had the highest TS and Elongation (E) (3.3 MPa and 60.1%) but no significant difference was observed among water vapor permeabilities (WVP) of film. Glycerol, sorbitol and its mixture (1:1, w/w) were added as plasticizers. The concentration and mixing ratio of plasticizers also affected the TS, E and WVP of films. TS of films decreased from 15.0 MPa to 2.9 MPa as plasticizer concentration increased from 0.4 to 0.8 g plasticizer/g protein. At a plasticizer concentration, the highest TS was observed when sorbitol was used whereas the highest E was measured when mixture of glycerol and sorbitol was used as plasticizer WVP of films increased as the plasticizer concentration increased. Films plasticized with glycerol showed the highest WVP among the films with the same plasticizer concentrations. Edible films prepared from soybean curd residue protein showed very low oxygen permeabilities ($29.5{\sim}61.1aL{\cdot}m/m^2{\cdot}s{\cdot}Pa$) and oil resistance at all plasticizer concentration level tested.

• Korean Journal of Veterinary Research
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• v.47 no.1
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• pp.7-17
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• 2007

The left main descending artery (LMDA) of left coronary artery (LCA) in rats runs around the left side of conus arteriosus after arising from the aortic sinus and descends to the apex of heart with branching several branches into the wall of left ventricle (LV). The ligation site of LMDA for myocardial infarction (MI) is the 2~4 mm from LCA origin, between the pulmonary trunk and left auricle. The characteristics that rat heart has no interventricular groove on the surface and its coronary arteries run intramyocardially with branching several branches give the difficulty in surgery for MI which resulted in expected size. This study was aimed to elucidate the branching patterns of the left coronary artery for analysis of MI size and for giving the basic data to producing small MI intentionally in 2 male species that are widely used, Sprague-Dowley (SD) and Wistar-Kyoto (WKY), in the world. Red latex casting was followed by the microdissection in 27 and 28 hearts of SD and WKY male rats, respectively. The branching patterns of LMDA were classified into 3 major types and others based on the left ventricular branches (L). The Type I, Type II, Type III and others are shown in 55.6%, 22.2%, 14.8%, and 7.4% in SD, 60.7%, 10.7%, 7.1%, and 21.5% in WKY, respectively. The branching number of the first left ventricular branch (L1) that are distribute the upper one third of LV was 1.2~1.5, and its branching sites were ranging 0.9~2.1 ᒠfrom LCA origin. L2, the second left ventricular branch distributing middle one third of LV, was the number of 1.2~1.4 and branching out ranging 5.1~5.7 mm. L3, the third left ventricular branch of LMDA distributing lower one third of LV, was the number of 1~1.5 and branching out ranging 7.0~9.3 mm from LCA origin. The common branch of L1 and L2 was branched from LMDA with the number of 1.1, and its site was located in the distance of mean of 1.5 mm and 2.8 mm in SD and WKY, respectively. The common branch of L2 and L3 was branched from LMDA with the number of 1, and its site was located in the distance of mean of 7.2 mm and 2.9 mm in SD and WKY, respectively. The right ventricular branches (R) of LMDA were short and branched in irregularly compared with L. The number of 1~4 of R were branched from LMDA. With regarding to the distribution area of L and the ligation site for MI, moderate MI (25~35% of LV) might be resulted in 70.4% and 60.7% in SD and WKY rats. Small MI might be produced intentionally if the ligation would be located at the 4~6 mm from LCA origin in the left side of LMDA. These data wold be helpful to expect the size of MI and to reproduce of small MI, intentionally, in rat hearts.

• Journal of the Korean Wood Science and Technology
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• v.39 no.3
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• pp.197-205
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• 2011

Cellulose nanofibrils (CNF) with 50~100 nm diameter were manufactured from micro-size cellulose by an application of a high-pressure homogenizer at 1,400 bar. High strength nanopapers were prepared over a filter paper by a vacuum filtration from CNF suspension. After reinforcing and dispersing CNF suspension, hydroxypropyl cellulose (HPC) and polyvinyl alcohol (PVA)-based composites were tailored by solvent- and film-casting methods, respectively. After 2, 4, 6 and 8 passes through high-pressure homogenizer, the tensile strength of the nanopapers were extremely high and increased linearly depending upon the pass number. Chemical modification of 1H, 1H, 2H, 2H-perfluorodecyl-triethoxysilane (PFDTES) on the nanopapers significantly increased the mechanical strength and water repellency. The reinforcement of 1, 3, and 5 wt% CNF to HPC and PVA resins also improved the mechanical properties of the both composites.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1683-1688
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• 2012

Topology optimization is applied for the lightweight design of three main parts of a vertical articulated robot: a base frame, a lower and a upper frame. Design domains for optimization are set as large solid regions that completely embrace the original parts, which are discretized by using three-dimensional solid elements. Design variables are parameterized one-to-one to the material properties of each element by using the SIMP method. The objective of optimization is set as the multi-objective form combining the natural frequencies and mean compliances of a structure for which load steps of interest are selected from the multibody dynamics analysis of a robot. The obtained results of topology optimization are post-processed to designs favorable to manufacturability for casting process. The final optimized results are 11.0% (base frame), 12.0% (lower frame) and 10.0% (upper frame) lighter with similar or even higher static and dynamic stiffnesses than the original models.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.362-366
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• 1999

Membranes for biosensor were prepared from poly(vinyl chloride) (PVC)l derivatives using the solution casting method, and their gas permeabilities were studied. The polymer membranes dried slowly in air showed higher permeability coefficients than those dried in vacuum. The permeabilily coefficients of carboxylated poly(vinyl chloride) (CPVC) membranes for $O_2$ and $CO_2$ decreased as the pressure of the feed gas increased. The addition of dioctylphthalate (DOP) enhanced the permeation rates for $O_2$ and $CO_2$. For example, the permeability coefficients of CPVC membranes containing 30 wt. % DOP for $O_2$ and $CO_2$ at 100 psig were 2.03 and 0.96 Barrer, respectively, which were about 4~5 times higher than those of the membranes without DOP. Poly(vinyl chloride-co-vinyl acetate-co-vinyl alcohol) (Syn-PVCAcAl) obtained by hydrolysis of poly(vinyl chloride-co-vinyl acetate (PVCA) showed a higher permeability coefficient for $CO_2$ in the presence of DOP than that for commercial PVCAcAl, but did not show any significant difference in permeability for $O_2$.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.495-499
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• 2010

To develop chemical and biosensors, this paper studies sensing characteristics of bulk carbon nanotube (CNT) electrodes by means of their electrical impedance properties due to their large surface area and excellence chemical absorptivity. The sensors were fabricated in the form of film and nano web style by using composite process for mass production. The bulk composite electrodes were fabricated with singlewall and multi-wall carbon nanotubes based on host polymers such as Nafion and PAN, using a solution-casting and an electrospinning technique. The resistance and the capacitance of electrodes were measured with LCR meter under the various amounts of buffer solution to study the electrical impedance change properties of them. On the experimental of sensor electrode, impedance characteristics of the composite electrode are affected by its host polymer and nanofiller and its sensing response showed saturated result after applying some amounts of buffer solution for test chemical. Especially, the capacitance values showed drastic changes while the resistance values only changed within few percent range. It is deduced that the ions in the solution penetrated and diffused into the electrodes surface changed the electrical properties of the electrodes much like a doping effect.

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.466-472
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• 2008

Purple Gold is the alloy consisting of 78wt%Au-22wt%Al, and is expressed as a chemical formula, $AuAl_2$. Lately it is being used for the material of accessories or the decorative ornaments, being one of the colored golds having the peculiar purple color, like White Gold and Pink Gold. Purple Gold has the weak point in shaping through casting process due to the bad malleability and castability, being the intermetalic compound of Au and Al. Therefore, it is possible to produce the final product only by the cutting and the grinding process or to use it as a decorative coat with the thin film evaporation. This study implemented two kinds of thin film experiments. One is the case that heat treatment was made after Au and Al deposition evaporated separately with a weight ratio 78:22 on the 200nm$SiO_2$/Si substrate. The other is the case that the surface deposition was made through the vacuum evaporation, keeping the glass substrate temperature remain room temperature, using the bulk $AuAl_2$ as a source. The final film property was measured, focusing on the Purple Gold's color and thickness through the bare eye inspection, the microstructure analysis, the surface resistance analysis, the color difference analysis, and XRD analysis. Purple Gold was not formed, as the excessive surface agglomeration occurred, in case of being produced and treated thermally with 12.5nmAu/40nmAl/200nm$SiO_2$/Si structure. Our results suggest that of Purple Gold films, showing the same purple color as the bulk's, were successfully deposited with the direct thermal evaporation from the $AuAl_2$ bulk source.