• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.25-37
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• 2019

The conventional representative underground cavity restoration methods, which are mainly open-cut methods, require high cost and long period of time for the restoration. Therefore, various trenchless restoration methods have been proposed to improve these disadvantages. The underground cavity restoration method using the expansive material proposed in this paper is one of the trenchless methods. This method fills the underground cavity with high quality backfill soils through the small hole(s) at asphalt layer and compacts backfill soils by insertion of the expansive material within the cavity. In this study, the restoration method using expansive material was constructed in acrylic chamber. The restoration efficiency of the method was analyzed by the fill ratio and degree of relative compaction according to the location and number of bore holes. As a result of the experiment, the restoration efficiency and the optimum construction location were found to be irrelevant.

• Structural Engineering and Mechanics
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• v.63 no.3
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• pp.317-327
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• 2017

The addition of different types of polymers such as SBR, VAE, Acrylic, etc. in concrete and mortar leads to an increase in compressive, tensile and bond strength and decrease in permeability of polymer modified mortar (PMM) and concrete (PMC). The improvement in properties such as bond strength and impermeability makes PMM/PMC suitable for use as repair/retrofitting and water proofing material. In the present study effect of addition of fluoropolymer on the strength and permeability properties of mortar has been studied. In the cement mortar different percentages viz. 10, 20 and 30 percent of fluoropolymer by weight of cement was added. It has been observed that on addition of fluoropolymer in mortar the workability of mortar increases. In the present study all specimens were cast keeping the workability constant, i.e., flow value $105{\pm}5mm$, by changing the amount of water content in the mortar suitably. The specimens were cured for two different curing conditions. Firstly, these were cured wet for one day and then cured dry for 27 days. Secondly, specimens were cured wet for 7 days and then cured dry for 21 days. It has been observed that compressive strength and split tensile strength of specimens cured wet for 7 days and then cured dry for 21 days is 7-13 percent and 12-15 percent, respectively, higher than specimens cured one day dry and 27 days wet. The sorptivity of fluoropolymer modified mortar decreases by 88.56% and 91% for curing condtion one and two, respectively. However, It has been observed that on addition of 10 percent fluoropolymer both compressive and tensile strength decreases, but with the increase in percentage addition from 10 to 20 and 30 percent both the strengths starts increasing and becomes equal to that of the control specimen at 30 percent for both the curing conditions. It is further observed that percentage decrease in strength for second curing condition is relatively less as compared to the first curing condition. However, for both the curing conditions chloride ion permeability of polymer modified mortar becomes very low.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2008.04a
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• pp.101-108
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• 2008

Polymer electrolyte membrane (PEM) fuel cells are promising power generation devices which are ideal for residential and automobile applications, thanks to their fast transient characteristics. However, liquid water produced in PEM fuel cells should be properly managed to enhance the performances and durabilities of the cells. In this study, a visualization experiment was conducted to investigate the flow behavior of water droplets in cathode channels. The visualization experiment was done with four different model flow channels which were made by varying the material (Acrylic and Teflon) and the channel width (1 mm and 2 mm). Acrylic is hydrophilic (contact angle is about $80^{\circ}$) while Teflon is hydrophobic (contact angle is about $120^{\circ}$). A computational fluid dynamics (CFD) analysis was also performed to compare the observed and the simulated two-phase water/air flow characteristics in cathode channels. The computational models were made to be consistent with the geometries and surface properties of the model flow channels. Both the experimental and numerical results showed that the Teflon cathode channel with 1 mm width has the best water management performance among four model flow channels considered. A close correlation was found between the experimental visualization results and the numerical CFD simulation results.

• Conservation Science in Museum
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• v.21
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• pp.1-16
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• 2019

This study investigated the material properties of UV-curable Resin in order to identify stable materials for use in the restoration of glass cultural properties. Tested samples were based on acrylic UV-curable Resin (SECURE CP-7321®), to which urethane UV-curable Resin (FLGPCL04 Clear®) was added in 10% increments to produce eleven samples. The results showed that all eleven samples had similar properties in terms of refractive index, density, adhesive strength, and anti-yellowing. But the surface hardness and compressive strength were optimal and effective for maintaining the shape of artifacts after restoration treatment when the proportion of urethane resin was in the range of 10-20%. Based on these findings, the mixing sample [acrylic UV-curable Resin(9) : urethane UV-curable Resin(1)] was applied in the conservation treatment of a glass cultural propertie (Hwangbuk 519) excavated from the North Mound of Hwangnamdaechong, Tomb in Gyeongju.

• Journal of Environmental Science International
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• v.23 no.8
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• pp.1419-1428
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• 2014

Electron beam-induced grafting polymerization was employed to prepare Acrylic acid-grafted bacterial cellulose (BC-g-AAc). BC-g-AAc as an adsorbent was applied to remove heavy metals (e.g., As, Pb, and Cd). This study examined followings; morphological change of surface, adsorptive behavior of BC-g-AAc, and interpretation of adsorptive kinetics. Specific surface areas of BC and BC-g-AAc were $0.9527m^2g^{-1}$ for BC and $0.2272m^2g^{-1}$ for BC-g-AAc, respectively as measured by BET nitrogen adsorption, revealing the morphological change of the surface of BC-g-AAc. Batch adsorption test was performed to investigate adsorptive behavior of BC-g-AAc in aqueous solution. The amounts of Pb and Cd adsorbed on BC-g-AAc were $69mg\;g^{-1}$ and $56mg\;g^{-1}$, respectively. However, As was not adsorbed on BC-g-AAc due to its neutral nature. Both the Benaissa model and the Kurniawan model were applied in the study to interpret adsorptive kinetics. From the value of correction coefficient ($R^2$), adsorptive kinetics of Pb and Cd were subjected to Kurniawan model referred to pseudo-second-order. Taken together, the results of this study show that BC-g-AAc has potential as a heavy metal (eg., Pb, Cd)-adsorbent made of an environmentally friendly material.

• Polymer(Korea)
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• v.37 no.3
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• pp.302-307
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• 2013

We synthesized aliphatic epoxy acrylate monomer by the reaction of glycerol diglycidyl ether and acrylic acid. The reaction was monitored by FTIR, Raman spectroscopy and $^1H$ NMR. Electron-beam (E-beam) curing behaviors of the synthesized monomer were studied by spectroscopic analysis, glass transition temperature, and tensile properties. We found that curing reaction was complete in a low dosage of ca. 30 kGy. The viscosity of monomer was a low enough for coating without using diluents and the cured sample was highly transparent, indicating that the monomer can be used for an E-beam curable coating material on transparent optical films.

• The Journal of Advanced Prosthodontics
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• v.9 no.6
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• pp.453-462
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• 2017

PURPOSE. The purpose of this study was to investigate the in vitro cytotoxicity of thermoplastic denture base resins and to identify the possible adverse effects of these resins on oral keratinocytes in response to hot water/ food intake. MATERIALS AND METHODS. Six dental thermoplastic resin materials were evaluated: three polyamide materials (Smile tone, ST; Valplast, VP; and Luciton FRS, LF), two acrylic materials (Acrytone, AT; and Acryshot, AS), and one polypropylene resin material (Unigum, UG). One heat-polymerized acrylic resin (Vertex RS, RS) was chosen for comparison. After obtaining extracts from specimens of the denture resin materials (${\phi}=10$ mm and d=2 mm) under different extraction conditions ($37^{\circ}C$ for 24 hours, $70^{\circ}C$ for 24 hours, and $121^{\circ}C$ for 1 hour), the extracts (50%) or serial dilutions (25%, 12.5%, and 6.25%) in distilled water were co-cultured for 24 hours with immortalized human oral keratinocytes (IHOKs) or mouse fibroblasts (L929s) for the cytotoxicity assay described in ISO 10993. RESULTS. Greater than 70% viability was detected under all test conditions. Significantly lower IHOK and L929 viability was detected in the 50% extract from the VP ($70^{\circ}C$) and AT ($121^{\circ}C$) samples (P<.05), but only L929 showed reduced viability in the 50% and 25% extract from LF ($37^{\circ}C$) (P<.05). CONCLUSION. Extracts obtained from six materials under different extraction conditions ($37^{\circ}C$, $70^{\circ}C$, and $121^{\circ}C$) did not exhibit severe cytotoxicity (less than 70% viability), although their potential risk to oral mucosa at high temperatures should not be ignored.

• Polymer(Korea)
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• v.38 no.2
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• pp.138-143
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• 2014

${\alpha},{\omega}$-Hydroxypropyl polydimethylsiloxane (HO-PDMS) was prepared by hydrosilylation of hydrogen terminated polydimethylsiloxane with allyl alcohol. Polydimethylsiloxane modified urethane with isocyanate group (PSU) was prepared from cyclic trimer of hexamethylenediisocyanate with HO-PDMS. PDMS modified urethane base resin with acrylic group (PSUA) was prepared from the urethane reaction of PSU with isocyanate group and 2-hydroxyethylmethacrylate. Their structures were characterized using FTIR and NMR. Coating materials were prepared by mixing PSUA, acrylic hardner, photo-initiator, and solvent and coated on PET film to obtain flexible and hard coating film by UV irradiation. Transparency of coating film was 89.7%, contact angle, $88^{\circ}$, and pencil hardness, 3H.

• Journal of Conservation Science
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• v.27 no.4
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• pp.415-420
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• 2011

Urethane coating agent was made up in order to prevent corrosion on metal relics. This urethane coating agent was designed to solve problems linked to gloss and discoloration caused by existing acrylic coating agent which is mainly applied to metal relics. For the purpose, the urethane coating agent was made up which has lower gloss and slight color change. This coating agent formed thinner coating layer with excellent adhesion compared to the existing agent and has outstanding resistance to the surface oxidization of metal relics and water repellent on the surface. In addition, the agent is considered a stable coating agent replacing current acrylic coating agent with showing easy dissolution in organic solvents such as acetone, toluene and xylene with excellent result in reversible reaction.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.4
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• pp.793-800
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• 1997

Periotest(Siemens, Germany) has been used to test mobility of the implants clinically, however the effects of target materials and connection methods on the PTVs(Periotest Values) have not been evaluated. Periotest has been regarded as a reliable and objective tool to test implant and natural teeth mobility clinically, however this instrument showed different PTVs under various test conditions. This in vitro study was designed to compare PTVs of different veneering materials and prosthodontic designs (single and bridge restorations). To compare the effects of veneering materials on PTVs, 1 mm thickness of five different testing materials (porcelain, type III gold alloy, pure titanium, composite resin, acrylic resin) were placed on the resin block. Three full length of 13 mm Mark II implant fixtures were embedded into autopolymerizing resin block to fabricate single and bridge restorations. To evaluate effects of the connection method in single restorations, PTVs of screw retained(UCLA type) and cementation type(Cera-One system) were compared. Finally, to test reliability of PTVs of the final restorations, screw retained three unit short span PFM bridges were fabricated on the standard and Estheti-Cone abutments. All testing components were tightened with torque controller and PTVs of all specimens were measured 15 times for statistical analysis with SAS program. Following conclusions were made within the limit of this in vitro study. 1. PTVs of type III gold alloy, grade II titanium, composite resin veneering materials showed no significant differences, however acrylic resin and porcelain showed significant differences (P<0.05). 2. Single tooth restorations showed consistent PTVs as long as proper torque force was applied. 3. PTVs of bridge type prostheses was inconsistent regardless of abutment types. 4. PTVs of the prostheses showed higher scores and standard deviations than those of abutments regardless types of connection (P<0.05).