• ALGAE
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• v.24 no.4
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• pp.195-203
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• 2009

Most Skeletonema species have been identified under the name of S. costatum. To assess the morphological species diversity in the genus Skeletonema, we surveyed the nine localities in the coastal waters of South Korea. The light microscopy (LM) and scanning electron microscopy (SEM) observations in this study showed that ultrastructural features of genus Skeletonema discriminated among four species: S. dohrnii Sarno & Kooistra, S. marinoi Sarno & Zingone, S. subsalsum (Cleve) Bethge, and S. tropicum Cleve. In S. dohrnii, cell diameters were 3-6 ${\mu}m$ and the pervalvar axes were 13-19 ${\mu}m$. One or two partial chloroplasts were visible in a cell. Cells of S. marinoi were 4-10 ${\mu}m$ and the pervalvar axes were 8-18 ${\mu}m$. Each cell contained one chloroplast. Cells of S. subsalsum which contained 1-2 chloroplasts were 8-13 ${\mu}m$ and the pervalvar axes were 11-20 ${\mu}m$. Cells of S. tropicum were 10-18 ${\mu}m$ and the pervalvar axes were 4-9 ${\mu}m$. 2-4 chloroplasts were seen in each cell. Tip width of fultoportula in S. dohrnii and S. marioni was flared and flat, but that in S. subsalsum and S. tropicum was narrow. Morphological groups among them, S. dohrnii and S. marinoi were the most widely distributed in all seasons, while S. tropicum was only occurred in a summer season.

• Journal of Korea Foundry Society
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• v.26 no.5
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• pp.222-226
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• 2006

Steel making slag has gained a considerable attraction as one candidate of eco-materials in research fields for recycling resources. Thus, many researches have been performed but were limited to development of substitute for cement being used in the construction field. A little research work also has been done on development of higher value-added materials, including heat resistant and sound absorbing materials. For this reason, the present study were focused on macrostructure characterization of fabricated slag fibers which are applicable to heat resistant materials. The slag fibers were fabricated through a modified melt extraction method. The processing variables employed were the wheel speed and molten slag temperature. The synthesized fibers were characterized by optical microscope and scanning electron microscopy. It was found that the wheel speed of 1400 rpm generated better quality of mineral fibers in terms of the relative amount of shot, diameter and length. This was attributed to the relative extent of contact width between the flowing melt and the rotating wheel. The thickness of the slag fibers also were decreased with increasing the slag melt temperature due mainly to significant decrease in the viscosity of the slag melt. In addition, the lower melt temperature caused an increase in number of shots plus the mineral fibers.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.1
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• pp.71-81
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• 2009

Die steel for plastic molding were used as mold material of automobile parts and electronic component industry. The material of this paper has superior to mechanical properties, such as repair weldability, corrosion resistance and high temperature strength, required mold parts for semitransparent. Laser-induced surface hardening technology is widely adopted to improver fatigue life and wear resistance via localized hardening at the surface of mold parts. The objective of this research work is to investigate on the characteristics of surface hardening of the laser process parameters, such as beam travel speed, laser power and defocsued spot position, for the case of die steel for plastic molding. Lens for surface hardening of large area is plano-convex type with elliptical profile to maintain uniform laser irradiation. According to the experimental results, large size of hardened layer at the surface of die steel for plastic molding was achieved, and microstructure of this layer was lath martensite. Optimal surface status and mechanical property of hardened layer could be obtained at 1095Watt, $0.25{\sim}0.3m/min$, 0mm (focal length: 232mm) for laser power, beam travel speed, and focal position. Where, heat input was $0.793{\times}10^{3}J/cm^2$, and width of hardened layer was 27.58mm.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.5
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• pp.86-92
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• 2016

In this study, we used a polymer deposition system, based on fused deposition modeling, to fabricate the 3D scaffold and then fabricated micro-pores on a 3D scaffold using a salt leaching method. Materials included polycaprolactone (PCL) and sodium chloride (NaCl). The 3D porous scaffolds were fabricated according to blending ratio such as PCL (70 wt%)/NaCl (30 wt%) and PCL (50 wt%)/NaCl (50 wt%). The 3D porous scaffolds were observed by scanning electron microscopy. The results showed that 3D porous scaffolds had a deposition width of $500{\mu}m$, contained a pore size of $500{\mu}m$ and below $100{\mu}m$. To evaluate the 3D porous scaffolds for bone tissue engineering, we carried out the cell proliferation experiment using a CCK-8 and a mechanical strength test using a universal testing machine. In summary, the 3D porous scaffold was found to be suitable for cancellous bone of human in accordance with the result of in-vitro cell proliferation and mechanical strength. Thus, a 3D porous scaffold could be a promising approach for effective bone regeneration.

• Korean Journal of Plant Taxonomy
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• v.32 no.4
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• pp.363-382
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• 2002

Morphological characters of three taxa belonging to three genera (Fuirena, Kobresia, and Scleria) in Korean Cyperaceae were reexamined. The anatomical patterns of stems and leaves, and epidermal patterns of achenes and leaves were investigated by a scanning electron microscope (SEM) and a light microscope (LM). Based upon the results, the scientific and Korean names, which have not been clearly established, were reviewed. Morphological characters such as length and width of stem, leaf, bract, scale, achene, and shape of achene, spikelet, style base, scale, perianth, and anatomical characters such as shape of stem and leaf, shape of achene epidermal cell and silica body of leaf, size and frequency of stomatal complex, presence of bulliform cell were useful for an identification of the three taxa.

• Archives of Plastic Surgery
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• v.44 no.5
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• pp.413-419
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• 2017

Background In breast reconstruction using implants after unilateral mastectomy, it is challenging to create a natural, ptotic contour, and asymmetry is a potential drawback. To achieve breast symmetry and an ideal shape for both breasts, we performed contralateral augmentation in patients undergoing breast reconstruction with implants. Methods Patients underwent unilateral mastectomy and 2-stage reconstruction. During the second stage of the procedure, contralateral augmentation mammoplasty was performed. Preoperatively, we obtained the patients' demographic information, and we then assessed breast volume, the volume and dimensions of the inserted implants, and complications. Breast symmetry was observed by the surgeon and was assessed by measuring the disparity between the final volume of each breast. Results Contralateral augmentation was performed in 52 cases. When compared to patients who did not undergo a contralateral balancing procedure, patients who received contralateral augmentation were younger, thinner, and had smaller breasts. During implant selection for contralateral augmentation, we chose implants that were approximately 1 cm shorter in width, 1 level lower in height, and 1 or 2 levels lower in projection than the implants used for reconstruction. The postoperative breast contours were symmetric and the final volume discrepancy between each breast, which was measured by 3-dimensional scanning, was acceptable. Conclusions We demonstrate that contralateral augmentation can be recommended for patients who perceive their breasts to be small and not beautiful in order to achieve an ideal and beautiful shape for both breasts. Furthermore, this study offers guidelines for selecting the implant that will lead to the optimal aesthetic outcome.

• Journal of the Korean Vacuum Society
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• v.6 no.3
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• pp.287-292
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• 1997

This study was tried to form the silica waveguide using high density plasma. Plasma characteristics have been investigated as a function of etch parameters using a single Langmuir probe and optical emission spectroscopy(OES). As etch parameters, $CF_4/CHF_3$ ratio, bias power, and source power were chosen as main variables. The oxide etch characteristics of inductively coupled plasma(ICP) dry etcher such as the etch rate, etch profile, and surface roughness were investigated s a function of etch parameters. On the basis of these results, the core pattern of the wave guide composed of $SiO_2-P_2O_5$ was formed. It was confirmed that the etch rate of $SiO_2-P_2O_5$ core layer was 380 nm/min and the aluminum selectivity to oxide, that is, mask layer was approximately 30:1. The SEM images showed vertical etched profiles and minimal loss of pattern width.

• Journal of Powder Materials
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• v.13 no.6 s.59
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• pp.421-426
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• 2006

The microstructural and mechanical properties of Al-Si alloyed powder, prepared by gas atomization fallowed by hot extrusion, were studied by optical and scanning electron microscopies, hardness and wear testing. The gas atomized Al-Si alloy powder exhibited uniformly dispersed Si particles with particle size ranging from 5 to $8{\mu}m$. The hot extruded Al-Si alloy shows the average Si particle size of less than $1{\mu}m$. After heat-treatment, the average particle size was increased from 2 to $5{\mu}m$. Also, mechanical properties of extruded Al-Si alloy powder were analyzed before and after heat-treatment. As expected from the microstructural analysis, the heat-treated samples resulted in a decrease in the hardness and wear resistance due to Si particle growth. The friction coefficient of heat-treated Al-Si alloyed powder showed higher value tough all sliding speed. This behavior would be due to abrasive wear mechanism. As sliding speed increases, friction coefficient and depth and width of wear track increase. No significant changes occurred in the wear track shape with increased sliding speed.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.6
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• pp.718-726
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• 2007

There are many varieties of asbestos: chrysotile, crocidolite, amosite, tremolite, actinolite, and anthophylite. These are widely used in construction materials, brake lining, textile, and so on. Even though non-asbestos fibers such as glassfiber and rockwool have manufactured because asbestos causes asbestosis, lung cancer, mesothelioma, etc., some bad effects of non-asbestos have been also reported. PCM (phase contrast microscopy) and PLM (polarized light microscopy) have been used to qualitatively analyze asbestoses. These techniques have serious drawbacks when identifying and separating various asbestoses. Recently scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX) has been known as an useful tool to analyze airborne particle since it provides physical and chemical information simultaneously. The purpose of the study was to classify both asbestos and non-asbestos fibers and finally to develop their source profiles by using the SEM/EDX. The source profiles characterized by 6 different types of asbestos fibers and 2 types of non-asbestos fibers had been developed by analyzing a total of 380 fibers. Analytical parameters used in this study were length, width, aspect ratio, and shape as physical information, and Na, Mg, Al, Si, K, Ca, Cr, Mn, Fe, and Cu as chemical information. All the parameters were intensively reviewed.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.5
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• pp.80-84
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• 2015

Softness is considered one of the most important attributes of hygiene paper such as tissue and towel. Being subjective in nature, however, softness attribute has been generally believed to be impossible to evaluate using objective methods. Hallmark in his pioneering work proposed that tissue subjective softness should be mainly consisted of the bulk softness component and surface softness component. The bulk softness component can be determined by tensile stiffness; the surface softness component by surface tester. The surface friction turns out far more important than the surface roughness in determining the surface softness component. It cannot be too much emphasized that both results of the tensile stiffness and the surface friction should depend on measuring conditions such as an instrument used, sample sizes (e.g., basis weight, length, and width) and operating conditions of the instrument (e.g., gauge length, cross-head speed, size of stylus, and its scanning speed). This indicates that a direct comparison of the test results would be impossible or misleading unless they have been tested under the identical conditions. This may explain why the standard objective test method for tissue softness has not been available at present.