• Food Science and Preservation
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• v.16 no.2
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• pp.266-275
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• 2009

To develop new high-quality Yakchobugak, features of Lactococcus lactis-fermented waxy rice paste after addition of some colored powdered agro-food products were investigated. Total and reducing sugars of waxy rice paste fermented by lactic acid bacteria were higher than those of control raw waxy rice paste. Total acidity gradually increased as powder concentration rose, being 1.02-1.56% and 0.96-1.87% in samples fermented with Cucurbita maxima and Capsicum annuum powders, respectively; these values were 3-4 times those in rice fermented with other powders. Fermented waxy rice paste viscosities were lower than those of non-fermented samples. The viscosities of samples fermented with Curcuma longa and Opuntia ficus powders were in the range $100-160{\times}10^4$ centipoise($mPa{\cdot}s$), and those of pastes fermented with Robus coreanus and Camellia sinensis extracts were under $40{\times}10^4mPa{\cdot}s$. Hunter color lightness(L) values decreased and yellowness(b) values rose after fermentation. Waxy rice paste fermented with Robus coreanus showed uniform particle size distribution, and many pores, by scanning electron micrography.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.4
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• pp.546-554
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• 2007

Statement of problem: Die materials require abrasion resistance, dimensional stability with time, and high surface wettability for adequate material properties. Wear of gypsum materials is a significant problem in the fabrication of accurately fitting cast prosthetic devices. So It has been recommended that the use of die hardener before carving or burnishing of the wax pattern. Purpose: The purpose of this study was to compare the abrasion resistance and surface microhardness(Knoop) with 3 commonly used gypsum die materials(MG Crystal Rock, Super plumstone, GC $FUJIROCK^{(R)}$ EP) with and without the application of 2 die hardeners. Material and methods: Three die materials were evaluated for abrasion resistance and surface microhardness after application of 2 die hardeners(Die hardener and Stone die & plaster hardener). Thirty specimens of each gypsum material were fabricated using an impression of resin die(Pattern resin; GC Corporation, Japan) with 1-mm high ridges, sloped 90 degrees. Gypsum materials were mixed according to manufacturer's recommendations and allowed to set 24 hours before coating. Specimens were arbitrary assigned to 1 of 3 treatment subgroups (n=10/subgroup): no treatment(control), coated with Die hardener, and coated with Stone die & plaster hardener. Abrasion resistance(measured by weight loss) was evaluated using device in 50g mass perpendicular to the ridges. Knoop hardness was determined by loading each specimen face 5 times for 15 seconds with a force of 50g. A scanning electron microscope was used to evaluate the surface of specimens in each treatment subgroup. Conclusions: The obtained results were as follows: 1. 3 types of die stone evaluated in this study did not show significant differences in surface hardness and abrasive resistance(P<.05). 2. In the abrasive resistance test, there were no significant differences between GC $FUJIROCK^{(R)}$ EP and MG Crystal Rock with or without 2 die hardener(P<.05). 3. Super plumstone treated with Stone die & plaster hardener showed increased wear loss(P<.05) 4. Die hardener coatings used in this study decreased the surface hardness of the gypsum material(P<.05).

• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.2
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• pp.149-159
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• 2006

Statement of problem. Porcelain repair mainly involves replacement with composite resin, but the bond strength between composite resin and all-ceramic coping materials has not been studies extensively. Purpose. The objective of this study was to investigate the influence of composite resin and ceramic etching pattern on shear bond strength of Empress2 ceramic and observe the change of microstructure of ceramic according to etching methods. Material and methods. Eighty-five cylinder shape ceramic specimens (diameter 5mm, IPS Empress 2 core materials) embeded by acrylic resin were used for this study. The ceramic were specimens divided into sixteen experimental groups with 5 specimens in each group and were etched with phosphoric acid(37%, 65%) & hydrofluoric acid (4%, 9%) according to different etching times(30s, 60s, 120s 180s). All etched ceramic surfaces were examined morphologically using SEM(scanning electron microscopy). Etched surfaces of ceramic specimens were coated with silane (Monobond-S) & adhesive(Heliobond) and built up composite resin using Teflon mold. Accomplished specimens were tested under shear loading until fracture on universal testing machine at a crosshead speed 1mm/min; the maximum load at fracture(kg) was recorded. Shear bond strength data were analyzed with one way ANOVA and Duncan tests.(P<.05) Results. Maximum shear bond strength was $30.07{\pm}2.41(kg)$ when the ceramic was etched with 4% hydrofluoric acid at 120s. No significant difference was found between phosphoric etchant group and control group with respect to shear bond strength. Conclusion. Empress 2 ceramic surface was not etched by phosphoric acid, but etched by hydrofluoric acid.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.5
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• pp.620-639
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• 1999

Indirect composite resins are used as an popular effective esthetic material in prosthetic dentistry, often with metallic substructure that provides support for restorations. Recently, new indirect composite resins as a substitute of ceramic have been developed. These resins provide good esthetics, with a wide range of hue and chroma. And the flexural strength of those is in the range of 120-150MPa, Which is higher than that of feldspathic Ceramic, and similar th that of Dicor. Although it has many merits, one of the major clinical problems of composite resins is the bond failure between metal and resin due to insufficient interfacial bond strength. The purpose of this study was to evaluate shear bond strength of the reinforced indirect composite resin to dental alloys. Three different composite resin systems($Artglass^{(R)},\;Sculpture^{(R)},\;Targis^{(R)}$) as test groups and ceramic($VMK\;68^{(R)}$) as control group were bonded to Ni-Cr-Be alloy($Rexillium\;III^{(R)}$) and gold alloy(Deva 4). All specimens were stored at $^37{\circ}C$ distilled water for 24 hours and the half of specimens were thermocycled 2000 times at temperature from $5^{\circ}C\;to\;60^{\circ}C$. The shear bond strengths of reinforced indirect composite resins to dental alloys were measured by using the universal testing machine, and modes of debonding were observed by stereoscope and scanning electron microscope. The results were as follows: 1 The shear bond strengths of reinforced indirect composite resins to dental alloys were approximately half those of ceramic to dental alloys(P<0.01). 2. There was no significant difference between the shear bond strength of several reinforced indirect composite resins to metal. 3. Alloy type did not affect on the shear bond strengths of resin to metal, but the shear bond strengths of ceramic to gold alloys were higher than those of ceramic to Ni-Cr alloys(P<0.05). 4. The shear bond strengths of Artglass and Targil to gold alloys were significantly decreased after thermocycling treatment(P<0.01). 5. Sculpture showed cohesive, adhesive, and mixed failure modes, but Artglass and Targis showed adhesive or mixed failures. And ceramic showed cohesive and mixed failures.

• Journal of the Korean Geographical Society
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• v.42 no.4
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• pp.506-525
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• 2007

Incision into bedrock channel is the primary control of landform evolution, but research into bedrock incision process stagnated for long time. Due to the scaling problem of the application of results from flume studies to bedrock channel, there is a strong need to simulate the bedrock incision process with more realistic models. As a part of investigation into controls of bedrock channel incision, three-dimensional changes of rock surface with abrasion was investigated with physical modelling. 18 rock plates were abraded with various sediment particle size and sediment load and abraded surfaces of the plates were scanned with high resolution 3-D scanner. To identify the spatial pattern of erosion of the rock plates, various methods were used. There was no synthetic or holistic method that showed all features of bedrock plate produced by abrasion, so each plate was analyzed using some available methods. Contour maps, shaded relief maps and profiles show that abrasion concentrated on the centre of plate (cross profile) and upstream and downstream edges (longitudinal profile) and eroded area extended inwards. It also found that the cracks and boundaries of forming materials easily eroded than other parts. Changing patterns of surface roughness were investigated with profiles, regression analysis and spectral analysis. Majority of plates showed decrease in small-scale roughness, but it depends on microstructures of the plates rather than general hardness or other factors. SEM inspection results supported this idea.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.145-145
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• 2008

High-k materials have been paid much more attention for their characteristics with high permittivity to reduce the leakage current through the scaled gate oxide. Among the high-k materials, $ZrO_2$ is one of the most attractive ones combing such favorable properties as a high dielectric constant (k= 20 ~ 25), wide band gap (5 ~ 7 eV) as well as a close thermal expansion coefficient with Si that results in good thermal stability of the $ZrO_2$/Si structure. During the etching process, plasma etching has been widely used to define fine-line patterns, selectively remove materials over topography, planarize surfaces, and trip photoresist. About the high-k materials etching, the relation between the etch characteristics of high-k dielectric materials and plasma properties is required to be studied more to match standard processing procedure with low damaged removal process. Among several etching techniques, we chose the inductively coupled plasma (ICP) for high-density plasma, easy control of ion energy and flux, low ownership and simple structure. And the $BCl_3$ was included in the gas due to the effective extraction of oxygen in the form of $BCl_xO_y$ compounds. During the etching process, the wafer surface temperature is an important parameter, until now, there is less study on temperature parameter. In this study, the etch mechanism of $ZrO_2$ thin film was investigated in function of $Cl_2$ addition to $BCl_3$/Ar gas mixture ratio, RF power and DC-bias power based on substrate temperature increased from $10^{\circ}C$ to $80^{\circ}C$. The variations of relative volume densities for the particles were measured with optical emission spectroscopy (OES). The surface imagination was measured by scanning emission spectroscope (SEM). The chemical state of film was investigated using energy dispersive X-ray (EDX).

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.269-279
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• 2003

This study investigated the mechanical properties of precious metal-ceramic alloy joined by the laser-welding and the soldering compared with the parent metal. Twenty-four tensile specimens were cast in precious metal-ceramic alloy and divided into three groups of eight. All specimens in the control group(group 1) were left in the as-cast condition. Group 2 and 3 were the test specimens, which were sectioned at the center. Eight of sectioned specimens were joined by soldering with a propane-oxygen torch, and the remaining specimens were joined by laser-welding. After joining, each joint diameter was measured, and then tested to tensile failure on an Instron machine. Failure loads were recorded, and then fracture stress(ultimate tensile strength), 0.2% yield strength and % elongation calculated. These data for three groups were subjected to a one-way analysis of variance(ANOVA). Neuman-Keuls post hoc test was then used to determine any significant differences between groups. The fracture locations, fracture surfaces were examined by SEM(scanning electron microscope). The results were as follows: 1) The tensile strength and 0.2% yield strength of the soldered group($280.28{\pm}49.35MPa$, $160.24{\pm}26.67MPa$) were significantly less than both the as-cast group($410.99{\pm}13.07MPa$, $217.82{\pm}17.99MPa$) and the laser-welded group($383.56{\pm}59.08MPa$, $217.18{\pm}12.96MPa$). 2) The tensile strength and 0.2% yield strength of the laser-welded group were about each 98%, 99.7% of the as-cast group. There were no statistically significant differences in these two groups(p<0.05). 3) The percentage elongations of the soldered group($3.94{\pm}2.32%$) and the laser-welded group($5.06{\pm}1.08%$) were significantly less than the as-cast group($14.25{\pm}4.05%$) (p<0.05). 4) The fracture of the soldered specimens occurred in the solder material and many porosities were showed at the fracture site. 5) The fracture of the laser-welded specimens occurred also in the welding area, and lack of fusion and a large void was observed at the center of the fracture surface. However, the laser-welded specimens showed a ductile failure mode like the as- cast specimens. The results of this study indicated that the tensile strengths of the laser-welded joints were comparable to those of the as-cast joints and superior to those of the soldered joints.

• Journal of Oral Medicine and Pain
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• v.32 no.1
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• pp.35-43
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• 2007

This study was conducted to investigate the preventing effects of OPB (water extracts of Rehmannia glutinosa Libosch and Eleutherococcus senticosus Max) on bone loss in ovariectomized rats. Twenty Sprague Dawley rats of 13 week-old were divided into two groups: control group (ovariectomized, OVX)) and experimental group (OVX + OPB). The preventing effects of OPB on bone loss, OPB were fed with 100 mg OPB/kg body weight from 3 days after ovariectomization. The duration of the treatment period was 8 weeks. All bone mineral density, bone mineral content indices and bone strength indices measured by peripheral quantitative computerized tomography (pQCT) and serum bone marker assessment were carried out at end of experiment. pQCT scanning showed that OVX induced a significant decrease in cancellous bone mineral density in the proximal tibia ($-29.8{\pm}3.0%$). These decreases were significantly prevented by the administration of OPB 100 mg/kg ($-21.4{\pm}2.3%$. p<0.05). Bone strength indices showed significant difference between OVX and OPB treated rats (anti-fracture, anti-twisting, p<0.05). These data suggested that administration of OPB inhibited the loss of bone in OVX rats. CTx level were lower than in the OPB-treated animals compared with OVX. However there was no significant difference between OVX and OPB treated OVX rat. Our results suggest that OPB is effective in preventing the development of bone loss induced by ovariectomy in rats.

• Journal of Marine Bioscience and Biotechnology
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• v.9 no.1
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• pp.14-21
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• 2017

The purpose of this study was to inhibit biofouling on a selectively permeable membrane (SPM) and increase biomass productivity in marine photobioreactors (PBRs) for microalgal cultivation by chemical treatment. Surfaces of a SPM, composed of polyethylene terephthalate (PET), was sulfonated to decrease hydrophobicity through attaching negatively charged sulfonic groups. Reaction time of sulfonation was varied from 0 min to 60 min. As the reaction time increased, the water contact angle value of SPM surface was decreased from $75.5^{\circ}$ to $44.5^{\circ}$, indicating decrease of surface hydrophobicity. Furthermore, the water permeability of sulfonated SPM was increased from $5.42mL/m^2/s$ to $10.58mL/m^2/s$, which reflects higher nutrients transfer rates through the membranes, due to decreased hydrophobicity. When cultivating Tetraselmis sp. using 100-mL floating PBRs with sulfonated SPMs, biomass productivity was improved by 34% compared with the control group (non-reacted SPMs). In addition, scanning electron microscopic observation of SPMs used for cultivation clearly revealed lower degree of cell attachment on the sulfonated SPMs. These results suggest that sulfornation of a PET SPM could improve microalgal biomass productivity by increasing nutrients transfer rates and inhibiting biofouling by algal cells.

• Korean journal of food and cookery science
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• v.16 no.6
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• pp.670-676
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• 2000

Dohaengbyoung was prepared with the addition of glutinous rice at 0%, 10%, 20%, 30%, 40% or 50%, and their sensory quality and physical characteristics were compared. In sensory quality, the more glutinous rice was added, the higher the color intensity, moistness hardness, chewiness, springiness and cohesiveness were. Meanwhile, the more glutinous rice was added, the lower the color quality was. Dohaengbyoung with 20% glutinous rice showed the highest score in taste, texture, moistness and overall quality. The control sample with 0% glutinous rice showed the highest values in lightness(L) and redness(a) in color, and the more glutinous rice was added, the lower the values were. In textural characteristics, as the amount of glutinous rice increased, the hardness, cohesiveness, gumminess and brittleness of Dohaengbyoung were increased. The lightness and redness were negatively correlated with the moistness, hardness, cohesiveness and springness； however, they were positively correlated with the color quality. Scanning electron microscopy revealed that the addition of glutinous rice to Dohaengbyoung exhibited small pores and coarse surface.