• International Journal of Reliability and Applications
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• v.1 no.1
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• pp.89-104
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• 2000

Accelerated testing consists of a variety of test methods for shortening the life of products or hastening the degradation of their performance. This paper presents practical, modern statistical methods for evaluating the reliability of Nickel-Cadmium batteries at their design temperature of 2$0^{\circ}C$ by accelerated life test. Batteries have been life tested at three high temperature conditions, 50, 60, 7$0^{\circ}C$, respectively to yield failures quickly. The failures have been observed and judged by means of charge and discharge current integration. Analyses of life data from those conditions resulted in the Weibull distribution, which has been verified on the ground of the Kolmogorov-smirnov test and the pairwise t-test. Life data are modeled according to the Arrhenius life-temperature relationship. The mean life of tested batteries is assessed at about 590 cycles, and the activation energy of this chemical reaction is concluded to be 0.39eV as results. This study provides procedures for estimating the reliability of batteries in a short period, which has little been possible in domestic industries. The results can be applied in many fields such as proof testing, acceptance testing, and estimating assurance periods.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.151-154
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• 2002

The durability of two kinds of CFRP plates, carbon/UP and carbon/V, was studied under severe environmental conditions. Immersion into the chemical solutions and accelerated weathering were executed on the CFRP plates and the weight change under each condition was measured. After those treatments, the plates were tested by tensile testing machine to measure the mechanical properties and observed by SEM to find the damage behaviour of the surface. Comparing the virgin plates and the chemically exposed plates, both plates show severe deterioration of the mechanical properties. But, the plates subjected to alkali solution show much larger reduction than those of acidic solution and carbon/V has better chemical resistance than carbon/UP. The material properties of CFRP plate exposed to the weathering were deteriorated linearly proportional to the exposure time.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.354-354
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• 2006

Alginic acid-silica hydrogel films was prepared for testing as protective coating materials for PTFE OD membranes. Unprotected hydrophobic membranes are subject to wet-out when contacted by surface-active agents. Films were characterised using SEM, XRD, DSC, mechanical strength measurements, and water-swelling measurements. In OD trials using coated membranes, no wet-out occurred over the 15 h duration of three consecutive 5 h OD trials using orange oil-water mixtures. In the case of detergent solutions, the coating afforded protection to the membrane for 4-5 h. In a separate trial, no wet-out occurred when the coated side of the membrane was placed in contact with 1.2 wt % orange oil for 72 hours.

• Bulletin of the Korean Chemical Society
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• v.9 no.1
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• pp.44-48
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• 1988

The feasibility of the reduction of nortricyclanone (1) as a chemical probe for testing the proposed radical mechanism for NAD-dependent horse liver alcohol dehydrogenase (HLADH) reactions has been examined using computer graphics modeling. The resutls of this study suggest that the radical ring-opening of this probe molecule may involve too substantial a geometry reorganization for the molecule to serve as a chemical probe in detecting the possible presence of the radical intermediates in the HLADH reactions. This result suggests that one should exercise caution in extrapolating results obtained from chemically based radical probes in the solution phase to the topologically constrained systems such as enzyme-substrate reactions.

• Korean Chemical Engineering Research
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• v.62 no.4
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• pp.364-370
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• 2024

In response to the threats of global warming and climate change, the development of highly energy-efficient lean methane oxidation processes has become crucial. One promising technology is ozone-induced lean methane oxidation (O₃-LMO), which utilizes ozone as an oxidant and a transition metal-loaded zeolite as a catalyst. Our previous study demonstrated that the O₃-LMO system, employing a cobalt-exchanged BEA (Co-BEA) catalyst, effectively abates lean methane (500 ppm) at low temperatures below 200℃ under dry conditions. In this study, we investigated the effect of water vapors on the performance of Co-BEA-based O₃-LMO system. The results indicated that CH₄ conversion, CO₂ selectivity, and O₃ utilization efficiency of the system were not significantly affected by water vapors. Additionally, any temporary suppression of activity could be easily reversed through simple vacuum drying of the catalyst. The system maintained robust activity for over 18 hours during prolonged testing under wet conditions.

• 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.

• Membrane Journal
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• v.17 no.3
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• pp.233-243
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• 2007

In this study, a separate. which is a microporous membrane based on poly(vinylidene fluoride)(PVdF) was prepared by phase inversion method. Being prepared by dissolving the PVdF in the N,N'-dimethylformamide(DMF) with mechanical stirring, the homogenous casting solution was cast onto a clean glass plate. Pore size and porosity of the membranes were controlled by changing preparation condition. The highest porosity of the membrane was 78.6%. The mechanical property of the membrane was determined by using an universal testing machine(UTM). The morphology of the membrane was investigated by scanning electron microscopy(SEM). The cross-section of the membrane shows sponge-like small micro-pores.

• Membrane Journal
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• v.17 no.4
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• pp.359-368
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• 2007

The copolymer membranes, poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) were prepared by phase inversion method using as an additive with N,N-dimethylformamid as a solvent. The pores are generated during the solvent and non-solvent exchange process in the coagulation bath filled with non-solvent (distilled water). The highest porosity of the membrane was 60%. The surface and cross-section of the membranes was observed with a scanning electron microscopy (SEM). The mechanical property of the membrane was determined by using an universal testing machine (UTM). Tensile strength of measured membranes is presented the maximum 6.57 MPa at 30 wt% of PVdF-HFP.

• Journal of the Korean Geosynthetics Society
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• v.2 no.3
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• pp.19-24
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• 2003

Long-term performance of smooth and textured type HDPE geomembranes which were used to the liner and slope systems of waste landfills was examined. Artificial surface defects were added to the surface of geomembranes by scratch addition apparatus specially designed. The mechanical and frictional properties, chemical and ultra violet light resistances and oxidative induction time(OIT) of geomembranes were examined for the cases of defective/non-defective surfaces. Frictional properties of textured type geomembranes showed more excellent than those of smooth type geomembranes. Finally, it was known that the long-term performance of non-defective and textured geomembranes was better than that of defective geomembranes through chemical and UV resistance and OIT tests etc.

• Restorative Dentistry and Endodontics
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• v.17 no.1
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• pp.36-54
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• 1992

The purpose of this study was to compare the shear bond strengths to ground dentin surfaces of four dentinal bonding agents in 193 teeth. Various dentin surfaces treated with four dentin bonding agents were attached with two restorative composite resins. The effectiveness of the bonding were tested by the monitoring the shear bond strength. The shear bond strengths were measured after 2 hours and 24 hours after surface conditioning with four dentin bonding agents. Effects of EDTA, the additive illumination, and sealer treatments without primer on bond strength to dentin surfaces were assessed. In addition the effects of the thickness of specimens ranging from 0.65 mm to 1.95 mm and the ratio of catalyst and base paste on the bond strength of chemical cure composite resin were estimated. The shear bond strength was determined by testing specimens in the Instron universal testing machine (Model No. 1122) at a crosshead speed of 1.0 mm/min. Following condusions were drawn: 1. The highest mean shear bond strengths of chemical cure composite resin to dentin conditioning with dentin bonding agents aged 2 hours were obtained, and then that was decreased with time followed by EDTA treatment. 2. In light cure composite resin, the shear bond strength was increased following dentin conditioning with bonding agents with time, irradiation time and EDTA treatment except in SB group. 3. The thicker the composite resin specimen was, the less the shear bond strength in chemical cure composite resin was. 4. In light cure composite resin, there was a little change in shear bond strength following dentin conditioning with bonding agents. 5. In chemical cure composite resin, the shear bond strength was the highest in the ratio of 1/1 of catalyst and base part. 6. Without a dentin primer, shear bond strength to dentin conditioned only with UB sealer was the highest among four sealers in light cure composite resin.