• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.225-226
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• 2002

In this work, the friction and wear behavior under' various lubrication regimes were investigated. The objective of this work is to develop an Accelerated Life Test (ALT) method for the durability evaluation of a machine element which is operated under lubrication. Electric contact resistance and frictional forces were measured with respect to a wide range of the loads and speeds under various lubrication regimes using a pin-on-disk type tribotester. From the experimental results, it could be found that an effective and reliable ALT method could be achieved by controlling the lubrication regime through the measurements of friction coefficient and contact resistance with respect to load and sliding speed.

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.558-563
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• 2014

To study the effects of fabrication methods on the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs), membrane-electrode assemblies (MEAs) were fabricated using a Dr blade method, a spray method, screen print method and screen print + spray method. The performance of single cells assembled with the prepared MEAs were initially measured and compared. Electrode accelerated stress testing (AST) involving a potentiostatic step-wave with 10 s at 0.6 V followed by 30 s at 0.9 V was applied to test durability of MEAs. Before and after 6,000cycles of the AST, I-V curves, impedance spectra, cyclic voltammograms, linear sweep voltammetry (LSV) and transmission electron microscope (TEM) were measured. Under the operating conditions, the Dr Blde MEA exhibited the highest initial performance. After electrode accelerated stress testing, screen print + spray MEA showed lowest degradation rate.

• Journal of the Korean Solar Energy Society
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• v.37 no.4
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• pp.35-47
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• 2017

Energy efficiency solutions are being pursued as a sustainable approach to reducing energy consumption and related gas emissions across various sectors of the economy. Vacuum Insulation Panel (VIP) is an energy efficient advanced insulation system that facilitates slim but high-performance insulation, based on a porous core material evacuated and encapsulated in a barrier envelope. Although VIP has been applied in buildings for over a decade, it wasn't until recently that efforts have been initiated to propose and adopt a global standard on characterization and testing of VIP. One of the issues regarding VIP is its durability and aging due to pressure and moisture dependent increase of the initial low thermal conductivity with time; more so in building applications. In this paper, the aging of commercially available VIP was investigated experimentally; thermal conductivity was tested in accordance with ISO 8302 standard (guarded hot box method) and long-term durability was estimated based on a non-linear pressure-humidity dependent equation based on study of IEA/ECBCS Annex 39, with the aim of assessing durability of VIP for use in buildings. The center-of-panel thermal conductivity after 25 years based on initial 90% fractile with a confidence level of 90 % for the thermal conductivity (${\lambda}90/90$) ranged from 0.00726-0.00814 (W/m K) for silica core VIP. Significant differences between manufacturer-provided data and measurements of thermal conductivity and internal pressure were observed.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.362-367
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• 2023

Recently, research and development of proton exchange membrane fuel cells (PEMFC) membranes are progressing in the direction of thinning to reduce prices and improve performance. Demand for hydrogen-powered vehicles for commercial vehicles is also increasing, and their durability should be five times greater than those for passenger vehicles. Despite the thinning of the membranes, the durability of the membranes must be increased five times, so the improvement of the durability of the membranes has become more important. Since the acceleration durability evaluation time also needs to be shortened, the protocol using oxygen instead of air in the existing protocol was applied to a 10 ㎛ thin membrane to evaluate durability. The accelerated durability test (Open circuit voltage holding) was terminated at 720 hours. If the air-based department of energy (DOE) protocol was used, a lifespan of 450,000 km of driving hours would be expected, with a durability of about 1,500 hours. During the chemical durability evaluation, the active area of the electrode decreased by 51%, suggesting that catalyst degradation had an effect on membrane durability. Reducing the catalyst degradation rate is expected to increase membrane durability.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.433-436
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• 1999

Long-term durability of the reinforced concrete structures exposed to marine environment deteriorates seriously by the attack of the chloride ion from see water results in corrosion of steel reinforcement in concrete. Their coating effect is aluminum oxide-isocyanate-based coating material, resistance of chloride penetration, carbonation and freezing and thawing resistance were compared to acryl-based coating material and sealer type o waterproofing material. Aluminum oxide-isocyante-based and acryl-based coating material show higher resistance to chloride penetration and carbonation than the sealer type do waterproofing material and aluminum oxide-isocyanate-based coating resist about 99% of chloride penetration. Resultants to the accelerated test for freezing and thawing, coating concrete show higher resistance than non-coating concrete, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.574-577
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• 2006

Recently, the deterioration due to salt damage and carbonation as the main factors of deteriaoration of the domestic reinforced concrete structures has been increased. Also the national and social concern about the durability recovery of the deteriorated reinforced concrete structures is geratly being raised. Therefore, it is the final purposes of this study to develop the performance evaluation technique for durability of reinforced concrete structures deteriorated due to salt damage and carbonation with the proposal of the service life prediction method for the investigation and diagnosis of reinforced concrete structures, and accelerated test in Lab.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.787-792
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• 2003

The purpose of this study is to suggest the fundamental data of durability which effects on the Carbonation of concrete by adding various admixture additives. Thus, We have experimented the accelerated test on the concrete blending which was admixed by blast furnace slag, fly-ash, silica fume , durability amelioration and it was cured 7weeks after twenty eight days water curing. The result of this experiment is that Carbonation speed increased extremely when water cement ratio went up, and by growing of replace cement ratio of admixture additives. The specimen which was added fly-ash, blast furnace slag, silica fume has the faster Carbonation speed than the specimen which was not added admixture additives. All of these specimen, fly-ash has the fastest progress speed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.30-31
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• 2019

Carbonation of the root concrete reduces the durability of the reinforced concrete, and it is important to check the carbonation resistance of the concrete to ensure the durability of the reinforced concrete structure. In this study, a basic study on the prediction of carbonation progress was conducted by considering the mixing conditions of concrete using deep learning algorithm during the theory of artificial neural network theory. The data used in the experiment used values that converted the carbonation velocity coefficient obtained from the mixing conditions of concrete and the accelerated carbonation experiment into the actual environment. The analysis shows that the error rate of the deep learning model according to the Hidden Layer is the best for the model using five layers, and based on the five Hidden layers, we want to verify the predicted performance of the carbonation speed coefficient of the carbonation test specimen in which the exposure experiment took place in the real environment.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.221-224
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• 2004

Several factors of concrete durability decline factor are acted as complex deterioration and is happened not that happen by simplicity deterioration. Specially, in case of sea construction, as complex salt damage, carbonation and freezing & thawing, concrete surface and pore structure is deteriorated. Therefore, analyzing concrete carbonation and pore structure after freezing and thawing test by fresh water and sea water in this research, we wish to study about acceleration of decline of durability and complex deterioration by concrete surface deterioration in sea environment.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.253-256
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• 2004

Recently, construction works of scale are getting larger with economic growth. Shotcreting is one of major processes in tunnels construction. Accelerator is used in tunnel and underground structures to ensure early strength of shotcrete. Silicate based accelerator and aluminate based accelerator is getting widely in the field. But these accelerators have many problems due to decesase of long-term strength and low quality of the hardened shotcrete. in order to solve these problems, recently developed powder types cement mineral accelerator. In this study, we tested chloride permeability, freezing and thawing and accelerated carbonation of shotcrete. As a result of the test, wet-mixed shotcrete with powder types cement mineral accelerator exhibited durability improvement compared to the conventional shotcrete accelerator.