• Elastomers and Composites
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• v.32 no.5
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• pp.302-308
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• 1997

Over 1953/54 Karl Ziegler and Giulio Natta independently discovered new types of catalyst. Thus it was able to produce synthetic cis-polyisoprene rubber which has same properties like natural rubber, since then the amount of consumption was increased rapidly. The problem of disposing of used rubbers has become acute in recent years. cis-Polyisoprene was degraded in supercritical tetrahydrofuran and degree of degradation and product were observed by GPC, FT-IR, GC-MS analyses. As a result, degradation of cis-polyisoprene had small dependency upon the operating pressure, and was inhibited in concentration increase. And cis-polyisoprene was degraded into narrow molecular weight distribution oligomer in 3 hours, and more than 10 organic compounds were produced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.297-300
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• 1998

In this paper, we obtained the data, which is required in training the neural network and diagnosing the degradation degree, by introducing the AE detection that is effective method in ordinary degradation diagnosis on activation. Automatic detection system to detect acoustic. As the results of generalization tests by appling neural network to the unknown AE patterns obtained from specimens, firstly as to evaluate an objective performance of neural network, the recognition ratio for no-void specimen is appeared. Also, in the evaluation for the adaptability of neural network with a untrained type of no-void specimen, it is confirmed that the result appears.

• Journal of Applied Reliability
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• v.2 no.1
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• pp.15-22
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• 2002

This paper is concerned about an Accelerated Life Test for Micro Display Device which is being used in a Projection TV, in order to find a failure mode occurred in field in a short time, to identify a major factor to affect a life, and to estimate a mean life. For this purpose, we selected a temperature as a accelerated factor to perform a test and measured degradation of display device using visual inspection and chromaticity table. In the result of Accelerated Life Test, it is confirmed that failure mode is equal to the degradation of display device by vendor and the Temperature is a major factor to affect a failure. Besides, according as the display device is turned to green as degraded, it is identified that the change of the chromaticity value is one method to measure the degree of the degradation . So, we applied the optimal condition, which consider a cost and life to lower the Temperature which is a major factor acquired by the result of ALT, to PTV design

• Steel and Composite Structures
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• v.23 no.2
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• pp.239-250
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• 2017

In the concept of two-parameter fatigue failure criterion, the material fatigue failure is determined by the damage degree and the current stress level. Based on this viewpoint, a residual strength degradation model for stud shear connectors under fatigue loads is proposed in this study. First, existing residual strength degradation models and test data are summarized. Next, three series of 11 push-out specimen tests according to the standard push-out test method in Eurocode-4 are performed: the static strength test, the fatigue endurance test and the residual strength test. By introducing the "two-parameter fatigue failure criterion," a residual strength calculation model after cyclic loading is derived, considering the nonlinear fatigue damage and the current stress condition. The parameters are achieved by fitting the data from this study and some literature data. Finally, through verification using several literature reports, the results show that the model can better describe the strength degradation law of stud connectors.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.642-648
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• 2008

In order to analyze the causes of fossil power plant facilities due to a degradation and corrosion, artificial degraded materials composed of the facilities were manufactured. Various experiment were performed based on mechanical test, microstructure observation, hardness test, electrochemical potentiokinetic reactivation test(EPR) and corrosion scale thickness measurement test. The master curves were write out using Larson-Miller parameter to evaluate the degree of degradation with the above diagnosis methods. These data were applied to materials database of fossil power plant diagnosis. Finally expert system on the fossil power plant diagnosis was developed using the master curves and diagnosis algorithms.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.403-411
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• 2001

The aim of this study was to evaluate the resistance to degradation of four commercial composite resins in an alkaline solution. The brands studied were Unifil(GC, Japan), Palfique(Tokuyama Japan). Definite$Degussa-H\ddot{u}ls$ AG, Germany). Revolution(Kerr, U.S.A.). Preweighed discs of each brand were exposed 0.1N NaOH solution at $60^{\circ}C$. After 14 days they were removed, neutralized with HCl, washed with water and dried. Resistance to degradation was evaluated on the basis of following parameters: (a) mass loss(%) - determined from pre-and post-exposed specimen weights; (b) Si loss(ppm) - obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation depth$({\mu}m)$ - measured microscopically (SEM) from polished circular sections of exposed specimens. The results were follows: 1. The mass loss of Unifil was 3.21%, it was the highest of materials. But, there was no significant difference among the materials. 2. The degree of degradation layer depth was $107.69\sim47.40{\mu}m$, the sequence of the degree pf degradation layer depth was in descending order by Unifil, Palfique, Revolution, Definite. There was significant difference among the materials except Palfique and Definite. 3. The Si loss of Paltique was 8940.0ppm, it was the highest. There was significant difference among the materials, except Revolution and Definite(p<0.05). 4. The correlation coefficient between mass loss and degradation depth was relatively high(r = 0.06, p<0.05). 5. There was no significant coefficient correlation between Si loss and mass loss, and/or the degree of degradation layer depth and Si loss. 6. When observed with SEM, destruction of bonding is observed between resin matrix and filler. Above results suggested that the hydrolytic degradation is considered as evaluation factor of composite resins.

• Current Research on Agriculture and Life Sciences
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• v.6
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• pp.1-6
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• 1988

The experiment was conducted to study on the physiology of developing embryo and endosperm degradation during germination of Zea mays seeds treated with GA 20 and B-Nine 5000 ppm. Data obtained can be summerized as follows : 1. Swelling of seminal root increased the section of GA treatment more or less, on the other hand, the section of B-9 treatment inhibited slightly. 2. According to elapsing of seeding date, epithelial cell of Scutellum expansed in size, and the space of cell increased, that degree was enlarged as follows ; the section of GA, the section of Control, and the section of B-9. 3. According to the elapsing of seeding date, the formation of vascular organization embryo became clearer little by little, the lignification of vascular B-9 treatment section rather higher than the other section. 4. The degradation of Starch Grain is composed of near part of epithelial cell of Scutellum, the shape of degradation radiate from element of a disk shape, and the speed of degradation is the section of GA, the section of Control, the section of B-9 in turn.

• Journal of Microbiology and Biotechnology
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• v.15 no.2
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• pp.337-345
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• 2005

The degradation of phenanthrene, a model PAH compound, by microorganisms either in the mixed culture or individual strain, isolated from oil-contaminated soil in oil refmery vicinity sites, was examined. The effects of pH, temperature, initial concentration of phenanthrene, and the addition of carbon sources on biodegradation potential were also investigated. Results showed that soil samples collected from four oil refinery sites in Korea had different degrees of PAH contamination and different indigenous phenanthrene-degrading microorganisms. The optimal conditions for phenanthrene biodegradation were determined to be 30$^{circ}C$ and pH 7.0. A significantly positive relationship was observed between the microbial growth and the rate of phenanthrene degradation. However, the phenanthrene biodegradation capability of the mixed culture was not related to the degree of PAH contamination in soil. In low phenanthrene concentration, the growth and biodegradation rates of the mixed cultures did not increase over those of the individual strain, especially IC10. High concentration of phenanthrene inhibited the growth of microbial strains and biodegradation of phenanthrene, but was less inhibitory on the mixed culture. Finally, when non-ionic surfactants such as Brij 30 and Brij 35 were present at the level above critical micelle concentrations (CMCs), phenanthrene degradation was completely inhibited and delayed by the addition of Triton X100 and Triton N101.

• Journal of Environmental Science International
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• v.23 no.3
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• pp.473-481
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• 2014

Poly(lactide)s(PLA) is an attractive material to solve the problem of waste plastic accumulation in nature because of its biodegradability. The lactide exists in three stereoisomeric configurations: L-lactide, D-lactide, and meso-lactide. PLA stereocomplexes, formed by the mixing of two enantiomers, poly(L-lactide)(PLLA) and poly(D-lactide)(PDLA), have many favorable characteristics because the stereocomplex showed $50^{\circ}C$ higher melting point than each enantiomeric polymer and the resistance toward degradation increased. In this study, we investigated the influence of the composition and the optical purity of each component on the formation of stereocomplexes. Also, the nanofibers of stereochemical PLA and their blends were prepared by electrospinning method. The properties of the obtained fibers were analyzed by differential scanning calorimetry and scanning electron microscopy. The results showed that a degree of stereocomplex was controlled by change of optical purity of each component. The enzymatic degradation of the fibers were strongly dependent on the stereocomplex.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1142-1145
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• 2004

ZnO surge arresters continuously endure the operating voltages during the operation course, and in the mean time, which need to withstand occasionally transient voltages of lightning and switching overvoltages. Under these voltages, the ZnO varistors inside arresters would have aging phenomena, one important result of aging phenomena is the increasing of resistive currents of varistors, which leads to the increasing of power losses of varistors. And the operating voltage is continuously applied on the ZnO varistors, there is a degradation phenomenon existing in ZnO varistors. When the degradation reaches a certain degree, then the arrester must stop operation. The degradation is related to the applied voltage ratio, the applied voltage ratio is high, the degradation is quickly. When the power loss is higher than the thermal dispersion ability of house of arrester, then the arrester will thermally breakdown. In this study the thermal stability characteristics of surge arresters for high power wil be discussed on the view point of watt losses and thermal breakdown.