• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.586-591
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• 2001

This research investigated the feasibility of the accelerated carbonation of cement waste forms with carbon dioxide in a supercritical state. Hydraulic cement has been used as a main solidification matrix for the immobilization of radioactive and/or hazardous wastes. As a result of the hydration reaction for major compounds of portland cement, portlandite (Ca(OH)$_2$) is present in the hydrated cement waste form. The chemical durability of a cement form is expected to increase by converting portlandite to the less soluble calcite (CaCO$_3$). For a faster reaction of portlandite with carbon dioxide, SCCD (supercritical carbon dioxide) rather than gaseous $CO_2$, in ambient pressure is used. The cement forms fabricated with an addition of slated lime or Na-bentonite were cured under ambient conditions for 28days and then treated with SCCD in an autoclave maintained at 34$^{\circ}C$ and 80atm. After SCCD treatment, the physicochemical properties of cement matrices were analyzed to evaluate the effectiveness of accelerated carbonation reaction. Conversion of parts of portlandite to calcite by the carbonation reaction with SCCD was verified by XRD (X-ray diffraction) analysis and the composition of portlandite and calcite was estimated using thermogravimetric (TG) data. After SCCD treatment, tile cement density slightly increased by about 1.5% regardless of the SCCD treatment time. The leaching behavior of cement, tested in accordance with an ISO leach test method at 7$0^{\circ}C$ for over 300 days, showed a proportional relationship to the square root of the leaching time, so the major leaching mechanism of cement matrix was diffusion controlled. The cumulative fraction leached (CFL) of calcium decreased by more than 50% after SCCD treatment. It might be concluded that the enhancement of the characteristics of a cement matrix by an accelerated carbonation reaction with SCCD is possible to some extent.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.211-216
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• 2012

Proton Exchange Membrane Fuel Cells (PEMFC) are the most appropriate for energy source of small robot applications. PEMFC has superior in power density and thermodynamic efficiency as compared with the Direct Methaol Fuel Cell (DMFC). Furthermore, PEMFC has lighter weight and smaller size than DMFC which are very important factors as small robot power system. The most significant factor of mobile robots is weight which relates closely with energy consumption and robot operation. This research tried to find optimum specifications in terms of type, number of cell, active area, cooling method, weight, and size. In order to find optimum 500W PEMFC, six options are designed in this paper and studied to reduce total stack weight by applying new materials and design innovations. However, still remaining problems are thermal management, robot space for energy sources, and so on. For a thermal management, design options need to analysis of Computational Fluid Dynamics (CFD) for determining which option has the improved performance and durability.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.9 no.4
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• pp.309-317
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• 2015

In this paper, we proposed the standard test specification for safety and function of hiking stick for the elderly. We have concluded nine factors representing specification of hiking stick through analysis of hiking patents and research papers, products survey of business market, case studies for damaged hiking stick and expert surveys. To test the factors, we designed three different kinds of apparatus to examine twist resistance, stick and tip durability and stick straightness. The sample of hiking sticks purchased from market based on Naver sales ranking top to fifteenth. As a result, we concluded six-standard test specification based on eccentric load, adjustable parts load, hand strap load, basket load, tip load and pull load of hiking stick.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1267-1272
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• 2007

In the case of the railway bridge, there are following the progress of works after the drainage method of a bridge surface - vibration proof rubber establishment, track gravel construction and rail construction etc. But these works are not enforced consecutively by the execution and economical reason. This is the reason of the long period of exposure after drainage execution. In many case, from the deterioration phenomenon by long term exposure of surface, there are a lot of occasions that do not keep primitive penetration depth waterproof primitive time. It is the most important that select the drainage method that have durability - it is not fallen in long-term exposure of surface. The major objective of this study is to deduce objective analysis result through examination about the Deterioration Restraining Agent method and to master KNOW-HOW of DRA drainage method. Through the study, minimize economical damage by frequent repair and reinforcement and present the reasonable standard of judgement fot drainage method of construction.

• Journal of the Korean Society of Clothing and Textiles
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• v.40 no.3
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• pp.456-464
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• 2016

A new combat uniform is improved for added combat safety with various functions such as survivability, battle conformity and a camouflage performance system. Camouflage performance is an important factor in terms of combat survivability since it makes identification difficult and provide security. The combat uniform is worn under extreme conditions (exposure to ultraviolet light, sweat and friction) and an excellent color fastness to repeated washing is required. In this study, we investigated the color management, durability and discoloration of new combat uniform fabric with a digital pattern for camouflage performance to provide preliminary color management data. We examined color differences between standard fabric and mass-produced combat uniform fabrics, color differences between each military supply contract firm and color changes in combat uniforms after 60 washing cycles. The slight color differences between standard fabric and mass-produced combat uniform fabrics were tolerable under quality criteria of Republic of Korea Ministry of National Defense. However, the differences between the military supply contract firms were recognizable to the naked eye and increased with repeated washing. Continuous research on color fastness under repeated washing and color management is required to standardize reliability from each military supply contract firm for the daytime performance of a combat uniform's camouflage.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.509-516
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• 1994

Liquid phase hydrogenation come into use for the removal process of unsaturated hydrocarbon such as croton aldehyde. The croton aldehyde is generated in a very small amount as by-product in the ethanol production, and it is converted into n-butanol through hydrogenation. Liquid phase hydrogenation is low energy consumption process as compared with gas phase hydrogenation. The nickel catalyst is selected with respect to the economic aspect such as durability and cost. The analysis of the conversion were performed by method of the PMT(permangante time) test. The PMT was sharply decreased as the initial concentrations of croton aldehyde in the ethanol solution were increased. The hydrogenation of croton aldehyde to n-butanol was carried out in sequence after the saturation of the carbon-carbon double bond. The formation of both butyraldehyde and n-butanol followed zero order kinetics. Within expermental conditions the PMT gets longer as reaction temperature goes higer and as LHSV becomes slower, while the reaction pressure has almost no relation with PMT.

• Geotechnical Engineering
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• v.12 no.2
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• pp.33-42
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• 1996

The weathering of mudrock in the Pohang area is mainly caused by slaking and swelling when the mudrock is absorbed with water. In this regard, this paper chows the results of chemical analysis and the identification of rock-forming minerals from XRD. It also compares the slaking and swelling characteristics of mudrocks sampled from 3 different sites. The chief rock -forming minerals are the quartz, and the several types of clay minerals. The slake durability indices are ranged from 71% to 96%, and these values are closely related to the liquid limit of the powdered nock specimen. In a similar manner to the slaking characteristics the greatest values of the swelling pressure and the swelling strain were measured from the mudrock specimen with the highest value of liquid limit. The greatest measured values of the swelling pressure and the swelling strain are 9.4 kg 1 cm2 and 33.5% respectively. The residual sheer strength of mudrock decreases as the number of wet -diy cycles increases, and the residual strength at 5 cycles are measured to c,=0.24kg/cm2 and p,=28$^{\circ}$. The lowest residual strength is measured at the fresh rock -rock contact surface in the moist condition of which values are cr: 0 and n,: 21.5$^{\circ}$.

• Journal of Hydrogen and New Energy
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• v.24 no.2
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• pp.186-192
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• 2013

In order to reduce the costs and to improve the durability of solid oxide fuel cell (SOFC), the operating temperature should be decreased while the power density is maintained as much as possible. However, lowering the operating temperature increases the cathode interfacial polarization resistances dramatically, limiting the performance of low-temperature SOFC at especially purely electronic conducting cathode. To improve cathode performance at low temperature, the number of reaction sites for the oxygen reduction should be increased by using a mixed ionic and electronic conducting (MIEC) material. In this study, anode-supported fuel cells with two different thicknesses of the MIEC cathode were fabricated and tested at various operating temperatures. The anode supported cell with $32.5{\mu}m$-thick BSCFZn-LSCF cathode layer showed much lower polarization resistance than that with $3.2{\mu}m$ thick cahtode and higher power density especially at low temperature. The effects of cathode layer thickness on the electrochemical performance are discussed with analysis of impedance spectra.

• The Journal of Advanced Prosthodontics
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• v.6 no.4
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• pp.272-277
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• 2014

PURPOSE. The purpose of this study was to investigate the impact of different surface treatment methods and thermal ageing on the bond strength of autopolymerizing acrylic resin to Co-Cr. MATERIALS AND METHODS. Co-Cr alloy specimens were divided into five groups according to the surface conditioning methods. C: No treatment; SP: flamed with the Silano-Pen device; K: airborne particle abrasion with $Al_2O_3$; Co: airborne particle abrasion with silica-coated $Al_2O_3$; KSP: flamed with the Silano-Pen device after the group K experimental protocol. Then, autopolymerized acrylic resin was applied to the treated specimen surfaces. All the groups were divided into two subgroups with the thermal cycle and water storage to determine the durability of the bond. The bond strength test was applied in an universal test machine and treated Co-Cr alloys were analyzed by scanning electron microscope (SEM). Two-way analysis of variance (ANOVA) was used to determine the significant differences among surface treatments and thermocycling. Their interactons were followed by a multiple comparison' test performed uing a post hoc Tukey HSD test (${\alpha}=.05$). RESULTS. Surface treatments significantly increased repair strengths of repair resin to Co-Cr alloy. The repair strengths of Group K, and Co significantly decreased after 6,000 cycles (P<.001). CONCLUSION. Thermocycling lead to a significant decrease in shear bond strength for air abrasion with silica-coated aluminum oxide particles. On the contrary, flaming with Silano-Pen did not cause a significant reduction in adhesion after thermocycling.

• Earthquakes and Structures
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• v.11 no.6
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• pp.925-942
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• 2016

With ongoing development of earthquake engineering research and the lessons learnt from a series of strong earthquakes, the seismic design concept of "resilience" has received much attention. Resilience describes the capability of a structure or a city to recover rapidly after earthquakes or other disasters. As one of the main features of urban constructions, tall buildings have greater impact on the sustainability and resilience of major cities. Therefore, it is important and timely to quantify their seismic resilience. In this work, a quantitative comparison of the seismic resilience of two tall buildings designed according to the Chinese and US seismic design codes was conducted. The prototype building, originally designed according to the US code as part of the Tall Building Initiative (TBI) Project, was redesigned in this work according to the Chinese codes under the same design conditions. Two refined nonlinear finite element (FE) models were established for both cases and their seismic responses were evaluated at different earthquake intensities, including the service level earthquake (SLE), the design-based earthquake (DBE) and the maximum considered earthquake (MCE). In addition, the collapse fragility functions of these two building models were established through incremental dynamic analysis (IDA). Based on the numerical results, the seismic resilience of both models was quantified and compared using the new-generation seismic performance assessment method proposed by FEMA P-58. The outcomes of this study indicate that the seismic resilience of the building according to the Chinese design is slightly better than that according to the US design. The conclusions drawn from this research are expected to guide further in-depth studies on improving the seismic resilience of tall buildings.