• Microbiology and Biotechnology Letters
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• v.28 no.4
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• pp.219-222
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• 2000

To produce and utilize microbial cyclomaltodextrinase being industrially useful, we isolated an alkalophilic Bacillus strain from soil which was capable of degrading cyclodextrins. The newly isolated strain was aerobic, gram-positive, spore-forming, motile, rod shape(0.2~0.4$\times$1.4~4.4 $\mu\textrm{m}$), and 35.8 mol% of DNA base composition. Based on its morphological, phisiological, and biochemical properties, it was identified as alkalophilic Bacillus sp. KJ-133 and cultivated well in the ranges of $30~40^{\circ}C$ and pH 8.0~9.0 . The cyclomaltodextrinase of the strain showed maximal production after 48h of cultivation at $37^{\circ}C$, and the activity was inhibited by Ag2+, Hg2+, Cu2+, and p-chloromercuribenzoate.

• Transactions of Materials Processing
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• v.3 no.3
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• pp.271-281
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• 1994

Titanium-6242 $({\alpha}+{\beta})$ alloy has been used for aircraft engine components such as disks and blades, because it has an excellent strength/weight ratio at high temperatures. When this material is forged to manufacture disks, process parameters should be carefully designed to control strain and temperature distributions within the process windows by which desirable mechanical properties can be produced. In the present investigation, it was intended to design the process parameters for a conventional hot forging of this material by using a rigid-thermoviscoplastic finite element analysis technique. It was assumed that the process was performed by a screw press which is capable of maintaining a constant ram speed during loading. From the analysis results, it was found out that the initial temperature of the workpiece and the die shape were important parameters to control the forging process. In result, these parameters were properly designed for hot forging of a disk with specific dimensions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.5
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• pp.700-708
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• 1999

The optimum dimple shape and arrangement in the channel of a plate heat exchanger with staggered dimples are proposed in this study. Four important geometric parameters are selected as design variables, the pressure drop and heat transfer characteristics are examined in the channel of plate heat exchangers. The optimization is accomplished by minimizing the global criterion function which consists of the correlations of Nusselt number and pressure drop. The optimum geometric parameters were found at the dimensionless dimple distance (L) of 0.272, the dimensionless dimple angle ($\beta$) of 0.44, the dimensionless dimple volume (V) of 0.106 and the dimensionless dimple pitch (G) of 0.195. It is found that the heat transfer and pressure drop of the optimum model are increased by approximately 227.9% and 32.9%, respectively, compared to those of the base model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1897-1905
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• 2013

Rheological properties such as yield stress and viscosity is the main parameters to determine the fluidity of the debris flow. In this study, several series of rheometer tests were performed to investigate rheological properties of fine-grained soil samples with various sand contents and various liquidity indices. Test results indicated that the general shape of the flow curves for fine-grained soils had characteristics of a shear thinning fluid, with a decrease in viscosity as shear rate increases. The yield stress and viscosity of fine-grained soil samples with same sand content gradually decreased as the liquidity index increased. At the same liquidity index, yield stress and viscosity of fine-grained soil increased with an increase in sand content. The yield stress and viscosity of fine-grained soil greatly decreased with a slight increase in water content. Also, the yield stress and viscosity tend to increase with increasing concentration by volume($C_v$) of the fluid matrix. The values of the four coefficients ${\alpha}_1$, ${\alpha}_2$, ${\beta}_1$, and ${\beta}_2$ were obtained by regression analysis for each fine-grained soil.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.2
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• pp.238-246
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• 1996

High-density SiC-AIN solid solutions were fabricated from powder mixtures of $\beta$-SiC and AIN by hot-pressing in the 1870 to $2030^{\circ}C$ temperature range. The reaction of AIN and $\beta$-SiC (3C) powder transformed to the 2 H (wurzite) structure appeared to depend on the temperature and SiC/A1N ratio and seeds present. The crystalline phases consisted of a SiC-rich solid-solution phase and an A1N-rich solid-solution phase. At $2030^{\circ}C$ for 1 h, for a composition of 50 % AIN/50 % SiC with a seeding of $\alpha$-SiC, the complete solid solution could be obtained and the microstructures are equiaxed with a relatively homogeneous grain size of 2 H phases. The variation of the seeding of $\alpha$-SiC in SIC-A1N solid solutions could be attributed to the transformation behaviour and differences in size and shape of the grains, as well as to other factors, such as grain size distributions, compositional inhomogeneity, and structural defects.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.531-535
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• 2013

The effect of heat-treatment temperature on the activity of catalysts was studied by investigating $N_2O$ decomposition reaction in Fe ion-supported BEA Zeolite. As a result of $N_2O$ decomposition reaction experiment, $N_2O$ decomposition activity significantly decreased as heat-treatment temperature of Fe/BEA catalyst increased. the shape and size of the particles of Fe/BEA catalyst following the rise of heat-treatment temperature did not display a significant change. But following the rise of the heat-treatment temperature, its surface area was significantly reduced. Also it was confirmed that as the heat-treatment temperature rose, the crystallization of ${\beta}$ structure was greatly reduced. And as heat-treatment temperature rose, while SiO structure either increased or did not exhibit much change, the structure of Fe bonded with lattice structure was speculated to decrease. From the stated results, it was concluded that the increase of heat-treatment temperature became the cause of the declined activity of catalysts by destruction of its ${\beta}$ structure of bonding aluminium and Fe atoms.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.1
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• pp.1-17
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• 1997

The purpose of this study was to investigate the aspects of proliferation and bone nodule formation of osteogenic precursor cells. To determine the effects of ascorbic acid and dexamethasone upon capacity of osteoblast proliferation and bone nodule formation, cells were maintained in the presence of one or some of these additives for up to 30 days. Group I culture was maintained in standard medium(DMEM plus 10% plus antibiotics), group II was maintained in supplemented medium containing dexamethasone, group III was maintained in supplemented medium containing ascorbic acid and sodium-${\beta}$-glycerophosphate, and group IV was maintained in supplemented containing ascorbic acid, sodium-${\beta}$-glycerophosphate and dexamethasone. Morphology of bone nodules was observed with light microscope and electron microscope. The results were as follows: ${\bullet}$ Proliferation capacity of osteoblasts was not affected by single use of dexamethasone, but it was chiefly affected by ascorbic acid. ${\bullet}$ Cellular morphology was fibroblastic appearance initially, but, it was gradually changed to polygonal shape accompanied by confluency stage. ${\bullet}$ Pluripotent mesenchymal cells existed during primary culture, they were differentiated to adipocyte, chondrocyte, osteocyte according to culture condition. ${\bullet}$ Dexamethasone increased bone nodule formation under the condition that the culture was maintained with supplemented medium ascorbic acid and sodium-${\beta}$-glycerophosphate. ${\bullet}$ when the cultures were stained with alizarin red, the group supplemented with dexamethasone, ascorbic acid and sodium-${\beta}$-glycerophosphate showed the marked increase of bone nodule formation, but the group supplemented with ascorbic acid and sodium-${\beta}$-glycerophosphate revealed only small amounts of bone nodules. And the groups cultured without ascorbic acid showed no observed any of bone-like mass independent of dexamethasone addition.

• Journal of Embryo Transfer
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• v.30 no.3
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• pp.249-255
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• 2015

Diabetes mellitus, the most common metabolic disorder, is divided into two types: type 1 and type 2. The essential treatment of type 1 diabetes, caused by immune-mediated destruction of ${\beta}-cells$, is transplantation of the pancreas; however, this treatment is limited by issues such as the lack of donors for islet transplantation and immune rejection. As an alternative approach, stem cell therapy has been used as a new tool. The present study revealed that bone marrowderived mesenchymal stromal cells (BM-MSCs) could be transdifferentiated into pancreatic cells by the insertion of a key gene for embryonic development of the pancreas, the pancreatic and duodenal homeobox factor 1 (PDX1). To avoid immune rejection associated with xenotransplantation and to develop a new cell-based treatment, BM-MSCs from ${\alpha}$-1,3-galactosyltransferase knockout (GalT KO) pigs were used as the source of the cells. Transfection of the EGFP-hPDX1 gene into GalT KO pig-derived BM-MSCs was performed by electroporation. Cells were evaluated for hPDX1 expression by immunofluorescence and RT-PCR. Transdifferentiation into pancreatic cells was confirmed by morphological transformation, immunofluorescence, and endogenous pPDX1 gene expression. At 3~4 weeks after transduction, cell morphology changed from spindle-like shape to round shape, similar to that observed in cuboidal epithelium expressing EGFP. Results of RT-PCR confirmed the expression of both exogenous hPDX1 and endogenous pPDX1. Therefore, GalT KO pig-derived BM-MSCs transdifferentiated into pancreatic cells by transfection of hPDX1. The present results are indicative of the therapeutic potential of PDX1-expressing GalT KO pig-derived BM-MSCs in ${\beta}-cell$ replacement. This potential needs to be explored further by using in vivo studies to confirm these findings.

• Journal of the Korean Society of Food Culture
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• v.7 no.2
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• pp.105-112
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• 1992

The general properties(size, shape, fruit constituents) of ten different varieties of dried red pepper and the proximate chemical composition, carotenoids content and Hunter color values of their powders were examined in order to establish an objective instrumental method to evaluate the consumer acceptability of red pepper powder. The results of instrumentally measured color values were compared with the sensory acceptability data obtained from 100 housewives in Korea. Red carotenoid consisted of 68-85% of total carotenoids, while ${\beta}-carotene$ content showed close relationship with the sensory color preference. The values of Hunter color system, L,a,b and axL, showed significant relationships with the sensory color preference. Especially, axL value had close relationship with both color preference and pungency intensity of red pepper. Therefore, we suggest the consumer acceptability of red pepper powder can be determined instrumentally by axL value of colorimeter. Sensory acceptability=0.02001(axL)-12.5774

• Animal cells and systems
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• v.3 no.2
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• pp.207-213
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• 1999

During the differentiation of Naegleria gruberi amoebas into flagellates, the amoebas undergo sequential changes in cell shape and form new cellular organelles. To understand the nature of the signal which initiates this differentiation and the signal transduction pathway, we treated cells with four agents, PMA, retinoic acid (RA), okadaic acid, and cAMP. Retinoic acid and cAMP had specific effects on the differentiation of N. gruberi depending on the time of the drug treatment. Addition of (100$\mu$M) retinoic acid at the initiation of differentiation inhibited differentiation by blockinq the transcription of differentiation specific genes (e.g., $\beta$-tubulin). This inhibition of differentiation by retinoic acid was overcome by co-treatment with cAMP (or dbcAMP, 20 $\mu$M). Addition of retinoic acid at later stages (30 and 70 min) had no effect on the transcriptional regulation of the $\beta$-tubulin gene, however the differentiation was inhibited by different degrees. Co-treatment of cAMP at these stages did not overcome the inhibitory effect of retinoic acid. These results suggest that the role of retinoic acid as a transcriptional regulator might be conserved throughout the evolution of eukaryotes.