• Resources Recycling
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• v.19 no.5
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• pp.31-43
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• 2010

To fabricate porous SiC candle filter for filtration facility of the IGCC system, the candle type filter preforms were fabricated by ramming and vacuum extrusion process. A commercially available ${\alpha}$-SiC powders with various particle size were used as starting raw materials, and $44\;{\mu}m$ mullite, $CaCO_3$ powder were used as non-clay based inorganic sintering additive. The candle typed preforms by ramming process and vacuum extrusion were sintered at $1400^{\circ}C$ for 2h in air atmosphere. The effect of forming method and particle size of filter matrix on porosity, density, strength (flexural and compressive strength) and microstructure of the sintered porous SiC candle tilters were investigated. The sintered porous SiC filters which were fabricated by ramming process have more higher density and strength than extruded filter in same particle size of the matrix, and its maximum density and 3-point bending strength were $2.00\;g/cm^3$ and 45 MPa, respectively. Also, corrosion test of the sintered candle filter specimens by different forming method was performed at $600^{\circ}C$ for 2400h using IGCC syngas atmosphere for estimation of long-term reliability of the candle filter matrix.

• Korean Journal of Plant Taxonomy
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• v.42 no.1
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• pp.40-49
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• 2012

The NE Asiatic Solidago virgaurea complex in Korea has been reported on 5 taxa (S. virgaurea subsp. asiatica, S. virgaurea var. taquetii, S. virgaurea var. coreana, S. virgaurea subsp. leiocarpa, and S. virgaurea subsp. gigantea). However, the broad morphological variations and a lack of diagnostic characteristics have made it difficult to distinguish these taxa and have thus resulted in a complicated taxonomy in the complex. Therefore, to clarify the classification and delimitation of each taxon, the morphological characteristics of the S. virgaurea complex were investigated by examining the original descriptions and type specimens. Field work was also conducted to investigate the morphological and geographic features. In conclusion, S. japonica Kitam., as a legitimate name, was distributed all over the country except for the Is. Ulleung-do in Korea, as distinguished from S. virgaurea L. Both S. virgaurea var. taquetii and S. virgaurea var. coreana were considered as synonyms of S. japonica, as their morphological characteristics were within the variation range of those of S. japonica. Furthermore, S. virgaurea subsp. leiocarpa does not occur in Korea. Additional investigations are required to clarify the classification of S. virgaurea subsp. gigantea, whose populations were not found during the investigation in this study. S. dahurica, meanwhile, was distributed in the northern part of North Korea.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.41-48
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• 2000

In this study, microstructure and mechanical properties and electrical conductivities of in situ Cu-Fe-Xi(Xi=Ag, Cr or Co) alloy wires obtained by cold drawing combined with intermediate heat treatments have investigated. During cold working the primary and secondary dendrite arms are aligned along the drawing direction and elongated into filaments after deformation processing. The addition of Ag was found to be more effective in reducing the microstructural scale at the given draw ratio than that of Co or Cr throughout the drawing processing. The ultimate tensile strength and the conductivity of the Cu-Fe based composites containing Ag were higher than those of Cu-Fe composites containing Co or Cr. The good mechanical and electrical properties of Cu-Fe-Ag wires may be associated with the more uniform distribution of the finer filaments in the wires containing silver. The strength of Cu-Fe-Xi composites is dependent on the spacing of the Fe filaments in accord with a Hall-Petch relationship. The fracture surfaces of all the specimens showed ductile-type fracture and iron filaments occasionally observed on the fracture surfaces.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.47.1-47.10
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• 2019

Background: Hyaluronic acid (HA) has been applied as a primary biomaterial for temporary soft tissue augmentation and as a carrier for cells and the delivery of growth factors to promote tissue regeneration. Although HA derivatives are the most versatile soft tissue fillers on the market, they are resorbed early, within 3 to 12 months. To overcome their short duration, they can be combined with cells or growth factors. The purpose of this study was to investigate the stimulating effects of human fibroblasts and basic fibroblast growth factors (bFGF) on collagen synthesis during soft tissue augmentation by HA hydrogels and to compare these with the effects of a commercial HA derivative (Restylane^®). Methods: The hydrogel group included four conditions. The first condition consisted of hydrogel (H) alone as a negative control, and the other three conditions were bFGF-containing hydrogel (HB), human fibroblast-containing hydrogel (HF), and human fibroblast/bFGF-containing hydrogel (HBF). In the Restylane^® group (HGF), the hydrogel was replaced with Restylane^® (R, RB, RF, RBF). The gels were implanted subdermally into the back of each nude mouse at four separate sites. Twelve nude mice were used for the hydrogel (n = 6) and Restylane^® groups (n = 6). The specimens were harvested 8 weeks after implantation and assessed histomorphometrically, and collagen synthesis was evaluated by RT-PCR. Results: The hydrogel group showed good biocompatibility with the surrounding tissues and stimulated the formation of a fibrous matrix. HBF and HF showed significantly higher soft tissue synthesis compared to H (p < 0.05), and human collagen type I was well expressed in HB, HF, and HBF; HBF showed the strongest expression. The Restylane^® filler was surrounded by a fibrous capsule without any soft tissue infiltration from the neighboring tissue, and collagen synthesis within the Restylane^® filler could not be observed, even though no inflammatory reactions were observed. Conclusion: This study revealed that HA-based hydrogel alone or hydrogel combined with fibroblasts and/or bFGF can be effectively used for soft tissue augmentation.

• Imaging Science in Dentistry
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• v.30 no.4
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• pp.275-279
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• 2000

Purpose: Radiation damage is produced and viable cell number is reduced. We need to know the type of cell death by the ionizing radiation and the amount and duration of cell cycle arrest. In this study, we want to identified the main cause of the cellular damage in the oral cancer cells and normal keratinocytes with clinically useful radiation dosage. Materials and Methods: Human gingival tissue specimens obtained from healthy volunteers were used for primary culture of the normal human oral keratinocytes (NHOK). Primary NHOK were prepared from separated epithelial tissue and maintained in keratinocyte growth medium containing 0.15 mM calcium and a supplementary growth factor bullet kit. Fadu and Hep-2 cell lines were obtained from KCLB. Cells were irradiated in a /sup 137/Cs γ-irradiator at the dose of 10 Gy. The dose rate was 5.38 Gy/min. The necrotic cell death was examined with Lactate Dehydrogenase (LDH) activity in the culture medium. Every 4 day after irradiation, LDH activities were read and compared control group. Cell cycle phase distribution and preG1-incidence after radiation were analyzed by flow cytometry using Propidium Iodine staining. Cell cycle analysis were carried out with a FAC Star plus flowcytometry (FACS, Becton Dickinson, USA) and DNA histograms were processed with CELLFIT software (Becton Dickinson, USA). Results: LDH activity increased in all of the experimental cells by the times. This pattern could be seen in the non-irradiated cells, and there was no difference between the non-irradiated cells and irradiated cells. We detected an induction of apoptosis after irradiation with a single dose of 10 Gy. The maximal rate of apoptosis ranged from 4.0% to 8.0% 4 days after irradiation. In all experimental cells, we detected G2/M arrest after irradiation with a single dose of 10 Gy. Yet there were differences in the number of G2/M arrested cells. The maximal rate of the G2/M ranges from 60.0% to 80.0% 24h after irradiation. There is no significant changes on the rate of the G0/G1 phase. Conclusion: Radiation sensitivity was not related with necrosis but cell cycle arrest and apoptosis. These data suggested that more arrested cell is correlated with more apoptosis.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.11
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• pp.4549-4553
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• 2015

Background: Colorectal carcinoma (CRC) is one of the major causes of cancer death worldwide. Data from the literature indicate differences between the proliferation rate of endothelial cells relative to the morphology growth type, possibly due to origin of specimens (autopsy material, surgery fragments) or quantification methods. Vascular endothelial growth factor (VEGF) is a factor that stimulates the proliferation of endothelial cells. It is expressed in more than 90% of cases of metastatic CRC. Aim: The aim of this study was to evaluate the endothelial cell proliferation and VEGF expression in primary tumors and corresponding liver metastases. Materials and Methods: Our study included 24 recent biopsies of primary tumors and corresponding liver metastases of CRC cases. CD34/Ki67 double immunostaining and RNA scope assay for VEGF were performed. Results: In the primary tumors analysis of VEGFmRNA expression indicated no significant correlation with differentiation grade, proliferative and non-proliferative vessels in the intratumoral and peritumoral areas. In contrast, in the corresponding liver metastases, VEGFmRNA expression significantly correlated with the total number of non-proliferative vessels and total number of vessels. CD34/Ki67 double immunostaining in the cases with poorly differentiated carcinoma indicated a high number of proliferating endothelial cells in the peritumoral area and a low number in the intratumoral area for the primary tumor. Moderately differentiated carcinomas of colon showed no proliferating endothelial cells in the intratumoral area in half of the cases included in the study, for both, primary tumor and liver metastasis. In well differentiated CRCs, in primary tumors, a high proliferation rate of endothelial cells in the intratumoral area and a lower proliferation rate in the peritumoral area were found. A low value was found in corresponding liver metastasis. Conclusions: The absence of proliferative endothelial cells in half of the cases for the primary tumors and liver metastases in moderately differentiated carcinoma suggest a vascular mimicry phenomenon. The mismatch between the total number of vessels and endothelial proliferation in primary tumors indicate that a functional vascular network is already formed or the existence of some mechanisms influenced by other angiogenic factors.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.197-204
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• 2016

Concrete walls of neutron generating facilities such as fusion reactors and fission reactors become radioactive by neutron irradiation. Both low-activation and neutron shielding are a critical concern at the dismantling stage after the shutdown of facilities with a requirement of radioactive waste management. To tackle this, two types of additives were investigated in fabricating mortar specimens: synthetic high polymers and boron carbide. It is well known that a hydrogen atom is effective in neutron shielding by an elastic scattering because its mass is almost the same as that of the neutron. And boron is an effective neutron absorber with a big neutron absorption cross section. In this study, the effect of the type, shape, and size of polymers were investigated as well as that of boron carbide. Total 16 mix designs were prepared to reveal the effect of polymers on mechanical properties and neutron shielding performance. The neutron does equivalent of polymers-based mortar for fast neutrons decreased by 36 %, and the count rate of boron carbide-based mortar with regard to thermal neutrons decreased by 90 % compared to conventional mortar. These results showed that a combination of polymers and boron carbide compounds has potential to reduce the thickness of neutron shields as well as radioactive waste from reactors.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.465-468
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• 2008

SHCCs (Strain Hardening Cement Composites) show the high energy tolerance capacity due to the interfacial bonding of the fibers to the cement matrix. For effective material design and application of SHCCs, it is needed to investigate the compression, four-point bending, direct tensile response of SHCCs with different types of fibers and water-cement ratio. For these purposes, three kinds of fibers were used: PP(polypropylene, 2.0%), PVA(Polyvinyl alcohol, 2.0%), PE (Polyethylene, 1.0%). Also, effects of water-cement ratio(0.45, 0.60) on the SHCCs were evaluated in this paper. As the result of test, SHCCs with PVA and PE fiber were showed better overall behavior than specimens with PP fibers on bending and direct tensile test. Also, for the same type of fiber, SHCCs with water-cement ratio of 0.45 exhibited higher ultimate strength than specimen with water-cement ratio of 0.60 on compression strength, and showed the multiple cracking on bending and direct tensile test. Therefore, to improve of workability and dispersibility of SHCCs on water-cement ratio of 0.60, continual studies were needed.

• Journal of the Korea Institute of Building Construction
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• v.11 no.2
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• pp.127-135
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• 2011

In this study, the engineering characteristics of outer wall insulation panels according to type of insulation materials, their combination, and the contents of insulation materials were tested. Vermiculate, ceramic bead, perlite and expanded polystyrene were used as insulation materials. Flexural strength and thermal conductivity depending on the insulation materials used were measured. It was found that the flow of fresh mortar significantly decreased with an increase in the contents of insulation materials. In terms of the effect of insulation materials on thermal conductivity, an increase in insulation materials resulted in a decrease of thermal conductivity. In particular, PL and EPS, when used together, have lower thermal conductivity than other materials. Regarding the flexural strength of the hardened mortar, the strength showed a tendency to gradually decrease according to the increase in contents of insulation materials, compared to that of the plain mortar. In terms of the flexural strength depending on various types of insulation materials and its combination, it was found that the flexural strength of cement mortar containing 3% of vermiculate(V)+ceramic bead(CB)+perlite(PL) was the highest among the specimens tested.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.6
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• pp.278-282
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• 2010

The doping effect of thulium on electrical properties and degradation behavior in barium titanate ceramics ($BaTiO_3$) was investigated in terms of generations of core-shell structure and micro-chemical changes through highly accelerated degradation test. The dielectric specimens of pellet type and multi-layered sheets were prepared by using $BaTiO_3$ with undoped and doped with 1 mol% $Tm_2O_3$. The $BaTiO_3$ ceramics doped with 1 mol% $Tm_2O_3$ had 40% higher dielectric constant (${\varepsilon}$ = 2700) than that of the undoped $BaTiO_3$ specimen at curie temperature and met X7R specification. According to the result of highly accelerated degradation test conducted at $150^{\circ}C$, 70 V, and 24 hr, the oxygen diffusion was declined in dielectrics doped with 1 mol% $Tm_2O_3$. The $Tm^{3+}$ ion substituted selectively Ba site and Ti site and contributed to the generation of the core-shell structure. Oxygen vacancies occurred by substitution for Ti site could reduce excess oxygen that reacted to the Ni electrode.