• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.125-126
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• 2023

This work explores the effectiveness of graphene nanoribbons (GNRs) in modifying the fire resistance of cement paste. The GNRs are added to the ordinary Portland cement at 0.10 wt% of the cement, and the sample is heated to target temperatures after curing for 28 days. Subsequently, the variations of compressive strength and pore structure are inquired by compared to the control sample without nano reinforcing and the sample with the same amount of carbon nanotubes (CNTs).

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.174-186
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• 1996

The purpose of this study was to evaluate the adaptability to tooth structure of composite resin and glass ionomer cement according to filling methods. In this study. two class V cavities were prepared on the buccal and lingual surface of each tooth of forty extracted human premolars. and they were randomly assigned into 4 groups with 10 teeth. The cavities of each group were filled with the CLEARFIL FII self curing resin(Control Group), Z-100 light curing resin (Group 1). $Vitremer^{TM}$ light curing glass ionomer cement(Group 2) and Z-100 light curing resin over the $Vitremer^{TM}$ liner(Group 3). The specimens underwent temperature changed from $5^{\circ}C$ to $55^{\circ}C$ five hundred times. After thermocycling. specimens were immersed in 2% methylene blue solution and stored in 100% relative humidity at $37^{\circ}C$ for 24 hours. And then. the specimens sectioned buccolingually. Degree of dye penetration at tooth-restoration interfaces were examined by Tool maker's microscope(x 200) and Image analyzer. The results were as follows : 1. On the occlusal margin. among the experimental groups. the group 2 showed the highest dye penetration($2.40{\pm}0.68$) and the group 3 showed the lowest dye penetration($1.15{\pm}0.37$). There was significant difference among the experimental groups(p<0.001). 2. On the gingival margin, among the experimental groups, the group 1 showed the highest dye penetration($3.30{\pm}0.57$) and the group 2 showed the lowest dye penetration($1.65{\pm}0.49$). There was significant difference among the experimental groups(p>0.001). 3. About total degree of dye penetration, the group 1 showed the highest dye penetration($2.25{\pm}1.17$) and the group 3 showed the lowest dye penetration ($1.43{\pm}0.55$). There was significant difference among the experimental groups(p<0.001). 4. The sum of dye penetration at occlusal margin was less than gingival margin. There was significant difference between occlusal margin and gingival margin (p<0.001). The results showed that differences were more pronounced at the gingival margin. Composite restorations inserted over the glass-ionomer liner demonstrated significantly less leakage than single restoration that used composite resin or glass-ionomer cement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1775-1781
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• 2008

The effects of the type of curing agent on the swelling of the natural rubber(NR) sponge applicable to the self-sealing layer of a helicopter fuel tank were investigated. The curing systems employed were peroxide and mixed ones of sulfur and peroxide. The NR compounds were prepared in a kneader and a roll-mill. The compounds were partially cured in a press at high pressure and subsequently cured fully with expansion in another press at atmospheric pressure. The apparent density of the NR sponge was measured and the cell structure was observed with scanning electron microscopy. The swelling experiments were performed at room temperature using toluene, iso-octane, and an aircraft fuel as a solvent. More rapid volume swelling of the NR sponge cured by peroxide was achieved than cured by sulfur and peroxide with similar amount of curing agent added in rubber compounds. The apparent density and cell structure of the sponge were extremely sensitive to the amount of peroxide, which influences again the swelling behavior of the NR sponge. It is important to control properly two reactions of decomposition of foaming agent and crosslinking of NR in the mold to obtain rapid swelling of the NR sponge on contact of the fuel.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1857-1862
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• 2008

Resonant frequency tuning of micro devices is essential to achieve performance uniformity and high sensitivity. Previously reported frequency tuning methods using electrostatic force or mass deposition are not directly applicable to non-conducting polymer devices and have limitations such as dielectric breakdown or low tunable bandwidth. In this paper, thermally frequency-tunable microactuators with poly-dimethylsiloxane membranes are proposed. Permanent and/or nonpermanent frequency tunings are possible using a simple temperature control of the device. Resonant frequency and Q-factor variations of devices according to temperature change were studied using a micro heater and laser Doppler vibrometer. The initial resonant frequencies determined by polymer curing and hardening temperatures are reversibly tuned by thermal cycles. The measured resonant frequency of 9.7 kHz was tuned up by ${\sim}25%$ and Q-factor was increased from 14.5 to 27 as the micro heater voltage increased from 0 to 70 V.

• Journal of Adhesion and Interface
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• v.16 no.1
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• pp.15-21
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• 2015

In this study, rheological properties and flow dynamics in roll coating process of basecoat paints have been investigated for automotive precoated metal (PCM) sheet applications. Various rheological properties for basecoats with three colors (black, blue, and silver), such as shear viscosity data at room temperature and elastic/viscous moduli under thermal curing condition, have been measured using a rotational rheometer. It is found that the relative portion of function groups inside basecoats and their viscosity level have greatly affected the formation of crosslinked networks by thermal curing. Also, operability coating windows for basecoats have been established in three-roll coating process system by observing their flow instabilities such as ribbing and cascade. It is confirmed that rheological approaches applied in this study have been usefully applied to develop environmentally-friendly PCM coating technology and optimally control the coating operations for non-Newtonian PCM paints.

• Textile Coloration and Finishing
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• v.34 no.3
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• pp.157-164
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• 2022

This study tried to analyze the heat resistance properties by blending epoxy and phenolic resin in a certain ratio, and to analyze the adhesive properties at the time of metal-polymer hetero-adhesion by applying Epoxy-phenolic resin between a silicon steel sheet and m-aramid sheet, the viscosity, adhesive peel strength, and adhesive cross section were measured using a rotational rheometer, a tensile tester(UTM), and a field emission scanning electron microscopy(FE-SEM). The thermal stability and heat resistance were confirmed by measuring the mass loss according to the temperature increase using Thermogravimetric analysis(TGA). After blending with epoxy and Phenolic resin(1:0.25 ratio) curing at 110℃ for 10 min, high adhesive strength was improved more than 40% compared to the adhesive strength using epoxy alone. When the space between the silicon steel sheet and m-aramid sheet, which is created during curing of the E-P blend, is cured with a slight weight, it is possible to control the empty space and improve adhesion.

• Journal of the Korea Institute of Building Construction
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• v.21 no.1
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• pp.21-29
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• 2021

The objective of this study is to evaluate the effect of the application of double layered bubble sheet on the curing of slab and wall concrete placed at the job site in cold weather and to offer a feasibility of Concrete IoT Management System(CIMS), which is wireless sensor network developed by the authors, to manage early age quality of the concrete in terms of temperature, maturity and strength development. Test results indicated that the application of bubble sheet enhances the insulation performance, which results in an increase of the temperature by around 1~20. 6℃. It is found that CIMS can gather the temperature, maturity and strength development data from the sensors embedded from 30 m far from CIMS successfully. Predicted compressive strengths by CIMS had good agreement with measured ones within 2 MPa error level until 7 days. It is thought that the combination of the bubble sheet application for cold weather protection and CIMS for quality management tool in cold weather concreting contributes to shorten the time for the form removal by one day.

• Food Science of Animal Resources
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• v.30 no.2
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• pp.277-285
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• 2010

The objective of this study was to manufacture spent layer chicken meat products by natural freeze-drying. The spent layers of chickens that were slaughtered at 80 wk were obtained from a local slaughter house and separated into two halves of carcasses. The samples were divided into the following groups: 1) control (non-curing), 2) curing, and 3) curing with 2% trehalose before drying. The cured meats were placed at $2^{\circ}C$ for 7 d and then transferred to a natural drying spot located in Injae City, Gangwondo, Korea. The experiment was conducted from January to March in 2008. The average temperature, RH, and wind speed were $-1.5^{\circ}C$, 63%, and 1.8 m/sec, respectively. The cured treatments showed higher pH, lower Aw and lower shear force value compared with the control. Based on the results of TBARS (2-thiobarbituric acid reactive substances) level and volatile basic nitrogen value, lipid oxidation and protein deterioration were inhibited in curing treatments during drying. Trehalose acted as a humectant because it maintained a lower water activity despite the relatively higher moisture content during drying. The polyunsaturated fatty acids content and sensory attributes were higher in cured treatments than in the control during drying. Most of the bacterial counts in the treated groups were lower by 2 Log CFU/g after 1 mon of drying, and Salmonella spp. and Listeria spp. were not found in any treatment. There was also no microbial safety problem associated with dried meat products. Based on the results of this experiment, dried meat products could be manufactured from precured spent layer chickens by natural freeze-drying during winter.

• Journal of the Korean Applied Science and Technology
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• v.33 no.1
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• pp.83-91
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• 2016

We studied the effect of battery deep cycle according to the way of active materials formation and the creation condition of electrode material, 3BS ($3PbO{\cdot}PbSO_4{\cdot}H_2O$) and 4BS ($4PbO{\cdot}PbSO_4$), in order to develop the batteries for Idle Stop & Go system. During the curing with active materials of anode and cathode, we found that the final creased active material was deformed by temperature control and it effects the durability of batteries. AGM battery and Flooded battery with 3BS active materials have excellent initial performance. And AGM battery with 4BS active materials shows the lower performance relatively. To compare and analyze of the formation efficiency of active materials, we tested the formation chagging steps with 3 steps and 9 steps differently. The results are that AGM battery with 4BS active materials is better on initial performance than AGM battery with 3BS. After the comparison of durability by DOD 17.5% life test, AGM battery is more suitable than flooded battery for the ISG system which needs the frequent deep cycle. In conclusion, AGM battery is the most suitable for ISG system and the life performance shows 80% difference according to the way of formation and curing of AGM batteries.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.6
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• pp.709-734
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• 2001

The aims of this experiment were to investigate the strain and temperature changes simultaneously within autopolymerzing acrylic resin specimens. A computerized data acquisition system with an electrical resistance strain gauge and a thermocouple was used over time periods up to 180 minutes. The overall strain kinetics, the effects of stress relaxation and additional heat supply during the polymerization were evaluated. Stone mold replicas with an inner butt-joint rectangular cavity ($40.0{\times}25.0mm$, 5.0mm in depth) were duplicated from a brass master mold. A strain gauge (AE-11-S50N-120-EC, CAS Inc., Korea) and a thermocouple were installed within the cavity, which had been connected to a personal computer and a precision signal conditioning amplifier (DA1600 Dynamic Strain Amplifier, CAS Inc., Korea) so that real-time recordings of both polymerization-induced strain and temperature changes were performed. After each of fresh resin mixture was poured into the mold replica, data recording was done up to 180 minutes with three-second interval. Each of two poly(methyl methacrylate) products (Duralay, Vertex) and a vinyl ethyl methacrylate product (Snap) was examined repeatedly ten times. Additionally, removal procedures were done after 15, 30 and 60 minutes from the start of mixing to evaluate the effect of stress relaxation after deflasking. Six specimens for each of nine conditions were examined. After removal from the mold, the specimen continued bench-curing up to 180 minutes. Using a waterbath (Hanau Junior Curing Unit, Model No.76-0, Teledyne Hanau, New York, U.S.A.) with its temperature control maintained at $50^{\circ}C$, heat-soaking procedures with two different durations (15 and 45 minutes) were done to evaluate the effect of additional heat supply on the strain and temperature changes within the specimen during the polymerization. Five specimens for each of six conditions were examined. Within the parameters of this study the following results were drawn: 1. The mean shrinkage strains reached $-3095{\mu}{\epsilon},\;-1796{\mu}{\epsilon}$ and $-2959{\mu}{\epsilon}$ for Duralay, Snap and Vertex, respectively. The mean maximum temperature rise reached $56.7^{\circ}C,\;41.3^{\circ}C$ and $56.1^{\circ}C$ for Duralay, Snap, and Vertex, respectively. A vinyl ethyl methacrylate product (Snap) showed significantly less polymerization shrinkage strain (p<0.01) and significantly lower maximum temperature rise (p<0.01) than the other two poly(methyl methacrylate) products (Duralay, Vertex). 2. Mean maximum shrinkage rate for each resin was calculated to $-31.8{\mu}{\epsilon}/sec,\;-15.9{\mu}{\epsilon}/sec$ and $-31.8{\mu}{\epsilon}/sec$ for Duralay, Snap and Vertex, respectively. Snap showed significantly lower maximum shrinkage rate than Duralay and Vertex (p<0.01). 3. From the second experiment, some expansion was observed immediately after removal of specimen from the mold, and the amount of expansion increased as the removal time was delayed. For each removal time, Snap showed significantly less strain changes than the other two poly(methyl methacrylate) products (p<0.05). 4. During the external heat supply for the resins, higher maximum temperature rises were found. Meanwhile, the maximum shrinkage rates were not different from those of room temperature polymerizations. 5. From the third experiment, the external heat supply for the resins during polymerization could temporarily decrease or even reverse shrinkage strains of each material. But, shrinkage re-occurred in the linear nature after completion of heat supply. 6. Linear thermal expansion coefficients obtained from the end of heat supply continuing for an additional 5 minutes, showed that Snap exhibited significantly lower values than the other two poly(methyl methacrylate) products (p<0.01). Moreover, little difference was found between the mean linear thermal expansion coefficients obtained from two different heating durations (p>0.05).