• Journal of Sensor Science and Technology
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• v.16 no.6
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• pp.407-412
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• 2007

For $VO_{2}$ sensors applicable to temperature measurement by using the nature of semiconductor to metal transition, the crystallinity, microstructure, and temperature vs. resistance characteristics were investigated systematically as a function of the annealing condition. The starting materials, vanadium pentoxide ($V_{2}O_{5}$) powders, were mixed with vehicle to form paste. This paste was screen-printed on $Al_{2}O_{3}$ substrates and then $VO_{2}$ thick films were heat-treated at $450^{\circ}C$ to $600^{\circ}C$, respectively, for 1 hr in $N_{2}$ gas atmosphere for the reduction. As results of the temperature vs. resistance property measurements, the electrical resistance of the $V_{2}O_{5}$ sensor in phase transition range was decreased by $10^{3.9}$ order. The presented critical temperature sensor could be used in fire-protection and control systems.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.542-548
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• 2012

The viscosity of a ceramic slurry depends on the slurry concentration, particle shape and size, hydrodynamic interactions, temperature, shear rate, pre-treatment condition and the method of measurement with the selected equipment. Representative ceramic slurries with low to high viscosity levels are selected from colloidal silica, barium titanate slurry and glass frit paste. Rotational rheometers and vibrational viscometers are used to compare the measured viscosity for various ceramic slurries. The rotational rheometer measured the viscosity according to the change of the shear rate or the rotational speed. On the other hand, the vibrational viscometer measured one point of the viscosity in a fixed vibrational mode. The rotational rheometer allows the measurement of the viscosity of a ceramic paste with a viscosity higher than 100,000 cP, while the vibrational viscometer provides an easy and quick method to measure the viscosity without deformation of the ceramic slurry due to the measurement method. It is necessary to select suitable equipment with which to measure the viscosity depending on the purpose of the measurement.

• Restorative Dentistry and Endodontics
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• v.29 no.2
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• pp.191-199
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• 2004

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B；Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA；Ti-Core, Essential Dental Systems, USA；Support. SCI-Pharm. USA). Six assessments were made：working time. setting time. depth of polymerization. flexural strength. bonding strength. and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time：above 90 seconds. setting time：within 5 minutes). and showed significantly higher flexural strength than Core Paste. Dual A and B could. especially. reduce the setting time to 60 seconds when cured with $600mW/cm^2$ light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore. three domestic products and Ti-Core could reduce the microleakage effectively.

• Journal of the Korea Institute of Building Construction
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• v.19 no.2
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• pp.113-121
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• 2019

Single walled carbon nanotube (SWCNT) has been used as a material for reinforcing various advanced materials because it has superior mechanical properties. However, pure SWCNT that does not have any functional group has a hydrophobic character, and exists as bundles due to the strong Van der Waals attraction between each SWCNT. Due to these reasons, it is very difficult to disperse SWCNTs in the water. In this work, in order to use SWCNT for production of cementitious composites, SWCNT was first dispersed in water to make an aqueous solution. Sodium deoxycholate (DOC) and Sodium dodecyl sulfate (SDS) were chosen as surfactants, and the dosage of DOC and SDS were 2wt% and 1wt%, respectively. Sonication and ultracentrifugation were applied to separate each SWCNT and impurities. Using such processed SWCNT solutions, cement paste was prepared and its shear stress vs. strain rate relationship was studied. The yield stress and plastic viscosity of cement paste were obtained using Bingham model. According to the results in this work, cement pastes made with DOC and SDS showed similar rheological behavior to that of air entrained cement paste. While cement paste made with DOC 2 wt.% SWCNT solution showed similar rheological behavior to that of plain cement paste, cement paste made with SDS 1 wt.% SWCNT solution showed different rheological behavior showing much less yield stress than plain cement paste.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.467-474
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• 2020

Carbon nanotube has excellent mechanical strength and functionality, so it has been utilized in various applications. In recent years, utilization of carbon nanotube in construction material has started to get interests from researchers in the area of construction materials. However, there is limited amount of work with respect to the rheological properties of cement paste using carbon nanotube. In this work, solution made of multi-walled carbon nanotube with dispersing agent of polyvinyl pyrrolidone was used to prepare cement paste specimens, and rheological properties and 28 day compressive strengths of cement paste using multi-walled carbon nanotube were measured. According to the experimental results, as the amounnt of multi-walled carbon nanotube increased, plastic viscosity and yield stress of cement paste specimens also increased. It was also found that such effect was higher with lower w/c cement paste specimens. With respect to the compressive strength, it was maximized at carbon nanotube content of 0.1wt.% for w/c 0.30 cement paste, whereas the maximum strength of w/c 0.40 cement paste was observed with carbon nanotube content of 0.2wt%.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.128-137
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• 2019

PURPOSE. The aim of this study was to compare the effect of different finishing and polishing techniques on water absorption, water solubility, and microhardness of ceramic or glass-polymer based computer-aided design and computer-aided manufacturing (CAD/CAM) materials following thermocycling. MATERIALS AND METHODS. 150 disc-shaped specimens were prepared from three different hybrid materials and divided into five subgroups according to the applied surface polishing techniques. All specimens were subjected up to #4000 grit SiC paper grinding. No additional polishing has been done to the control group (Group I). Other polishing procedures were as follows: Group II: two-stage diamond impregnated polishing discs; Group III: yellow colored rubber based silicone discs; Group IV: diamond polishing paste; and Group V: Aluminum oxide polishing discs. Subsequently, 5000-cycles of thermocycling were applied. The analyses were conducted after 24 hours, 7 days, and 30 days of water immersion. Water absorption and water solubility results were analyzed by two-way ANOVA and Tukey post-hoc tests. Besides, microhardness data were compared by Kruskal-Wallis and MannWhitney U tests (P<.05). RESULTS. Surface polishing procedures had significant effects on water absorption and solubility and surface microhardness of resin ceramics (P<.05). Group IV exhibited the lowest water absorption and the highest microhardness values (P<.05). Immersion periods had no effect on the microhardness of hybrid ceramic materials (P>.05). CONCLUSION. Surface finishing and polishing procedures might negatively affect physical properties of hybrid ceramic materials. Nevertheless, immersion periods do not affect the microhardness of the materials. Final polishing by using diamond polishing paste can be recommended for all CAD/CAM materials.

• Journal of Food Hygiene and Safety
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• v.21 no.2
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• pp.92-99
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• 2006

For standardization of quality and reduction of salt concentration of pickles manufactured in Folk Villages of Sunchang Region, the physicochemical characteristics of 90 pickles of 10 items were compared. Persimmon, garlic, cucumber, radish, Codonopsis lanceolata L., and Japanese apricot pickles were mixed with kochujang, perilla leaf pickle was mixed with soybean paste, cucumber pickle in wine cake was mixed with wine cake, and red pepper was mixed with soybean paste or soy sauce. Moisture contents, pH, and titratable acidities of pickles were various depend upon characteristics of materials. Sugar contents of pickles test,34 were ranged from $22.10{\pm}3.04$ (red pepper pickled with soy sauce) to $55.53{\pm}7.67\;^oBrix$ (garlic pickle), and sugar contents of pickles mixed with kochujang were higher than those of soybean paste or soy sauce. Salt concentration of pickles were ranged from $3.56{\pm}1.11$ (Japanese apricot) to $9.15{\pm}6.35%$ (red pepper pickled with soy sauce), and salt concentration of pickle mixed with soy sauce was the highest among the pickles tested. Total aerobic counts of pickles tested were similarly ranged from $5.62{\pm}0.10$ (red pepper pickled with soy sauce) to $6.83{\pm}0.55$ log CFU/g (perilla leaf pickled with soybean paste). These results indicate salt concentration and quality of pickles manufactured in Folk Villages of Sunchang region must be lowered and standardized, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.55-61
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• 2010

The device with tantalum silicide heater were bonded by Ag paste and Au SBB(Stud Bump Bonding) onto the Au coated substrate. The shear test after Au ABB and the thermal performance under current stressing were measured. The optimum condition of Au SBB was determined by fractured surface after die shear test and $350^{\circ}C$ for substrate, $250^{\circ}C$ for die during flip chip bonding with bonding load of about 300 g/bump. With applying 5W through heater on the device, the maximum temperature with Ag paste bonding was about $50^{\circ}C$. That with Au SBB on Au coated Si substrate showed $64^{\circ}C$. The difference of maximum temperatures is only $14^{\circ}C$, even though the difference of contact area between Ag paste bonding and Au SBB is by about 300 times and the simulation showed that the contact resistance might be one of the reasons.

• Korean journal of food and cookery science
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• v.19 no.4
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• pp.454-462
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• 2003

Recently, the HACCP(Hazard Analysis Critical Control Point) system has been emphasized in food processing industries throughout the world. However, the system has, as yet, not been applied very well to domestic food industries. Due to the increase in the consumption of bakery products, more studies are required on the application of HACCP to establish the system in small-scale bakeries. This study was designed to provide basic data for setting management standards for HACCP, based on microbiological hazard evaluations of bakery products. Red bean paste filled breads, custard cream filled breads and cakes covered with fresh whipping cream were collected, and microbiological evaluations conducted on the raw materials, the manufacturing processes and potential hazards. The result showed the presence of coliforms in fresh cream of cakes and the soybean paste of soybean paste breads at levels as high as 105 CFU/g on the hazard analysis of the raw materials. Moreover, the general levels of bacteria and coliforms were over those of the standards during the intermediate fermentation and molding processes. Furthermore, high levels of coliforms were detected on the hands of the salesmen and bakers themselves. This suggests that the CCPs (Critical Control Points), such as fresh cream and red bean paste manufacturing process desperately require better management. There is also a requirement for education relating to personal hygiene for the production of hygienic bakery products and for the publics health.

• Food Science and Preservation
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• v.13 no.4
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• pp.472-476
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• 2006

In order to assess the possibility in utilizing the rice soybean paste(rice Doenjang) powder as food processing materials, the quality of pork cutlet sauce added with 0, 1, 3, 5, and 7%(w/w) of rice soybean paste powder was investigated. Viscosity of pork cutlet sauce ranged from 584 to 776 cP as soybean paste powder amounts increased. Lightness, redness and yellowness of pork cutlet sauce decreased with increasing rice soybean paste powder. Approximate composition of pork cutlet sauces containing rice soybean powder was $62.1\sim73.0%$ of moisture, $3.2\sim7.6%$ of crude protein $0.2\sim0.5%$ of crude fat $1.5\sim2.3%$ of crude fiber and $9.9\sim12.2%$ of crude ash. In sensory evaluation, the pork cutlet sauces added with 1% and 3% soybean paste powder showed more acceptable scores than market sauce.