• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.367-372
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• 1999

We have investigated the effects of electrical stress on poly-Si TFTs with different hydrogen passivation conditions. The amounts of threshod voltage shift of hydrogen passivated poly-Si TFTs are much larger than those of as-fabricated devices both under the gate only and the gate and drain bias stressing. Also, we have quantitatively analyzed the degradation phenomena by analytical method. We have suggested that the electron trapping in the gate dielectric is the dominant degradation mechanism in only gate bias stressed poly-Si TFT while the creation of defects in the channel region and $poly-Si/SiO_2$ interface is prevalent in gate and drain bias stressed device.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.759-767
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• 1995

This paper examines the electrical properties according to a curing time and a corona degradation in epoxy composites which are used for transformers. To consider these phenomena, the electrets were formed by appling high voltages to five kinds of specimens designed according to a constant mixing rate and then TSC(Thermally Stimulated Current) values at the temperature range of -160-200[>$^{\circ}C$] were measured from a series of experiments. The behaviour of carrier and its possible origins in epoxy composites were studied. Various effects of curing time and electric field on epoxy composites were also investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.12
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• pp.996-1001
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• 2010

Recently, the demand of ceramic metal halide lamp has been expanded. Therefore, the lamp with high efficiency and long lifetime are increasing and the evaluation of reliability is needed. In this paper, the degradation phenomena of ceramic metal halide lamp was studied. The lamp was tested for 3000 on/off cycles with each cycle having a duration of 20 minutes on and 20 minutes off based on the accelerated aging experiment based on "Reliability Standards RS C 0085". As result, the corrosion of arc tube and leak was appeared from reaction between inner wall of PCA and chemical elements, and distortion of electrode was resulted from difference of thermal expansion between arc tube of PCA and electrode. Also, the efficiency of lamp was decreased by the change of inner pressure, operation temperature, and driving voltage from wall blackening.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1735-1740
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• 2010

The propellant KM10, a single propellant manufactured nitrocellulose, is known to cause natural degradation phenomena at long term storage. The self-life was estimated using generally used high temperature acceleration aging tests to analyze the content of stabilizer and using the Arrhenius equation & Berthelot equation to calculate reaction rate constants. According to the result of this study, self-life of propellant KM10 using the Arrhenius equation & Berthelot equation appear significantly different as 43.73, 16.53years and when compared with the paper of E. R. Bixon, self-life of propellant KM10 predicted using the Arrhenius equation was reasonably determined.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.12
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• pp.1758-1763
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• 2004

This study was carried out to investigate gel forming and degradation properties (suwari and modori phenomena) of chicken surimi from mechanically deboned chicken meat (MDCM) at various setting temperatures and time. Chicken surimi was manufactured by a continuous process including chopping of MDCM, washing with 5% NaCl solution or pure water, standing, straining and centrifuging etc. Total process of washing for the MDCM from chopping to centrifuging was repeated over 3 cycles. Gel from prepared surimi were formed at $90^{\circ}C$ for 30 min after various setting treatments. The textural properties of gels were measured at the temperature ranges of low (10$^{\circ}C$), medium (25$^{\circ}C$ and $30^{\circ}C$) and high (45 to 70$^{\circ}C$). The compressive force (CF), hardness and fracturability of surimi gel at 10$^{\circ}C$ increased as setting time increased, and showed the highest value at 30 h of setting time. The CF and hardness of chicken surimi gel at 25$^{\circ}C$ and 30$^{\circ}C$ showed the highest values at 10 h of setting time. Most of gel strengths including CF, and texture profile analysis (TPA) values showed the highest levels in the range 47.5 to 52.5$^{\circ}C$ (p<0.05). The gel strength at 60$^{\circ}C$ increased slightly at 30 min, but then continued to decrease with longer setting times. There was no increase of gel strength at $70^{\circ}C$, but only a continuous decrease over setting time. In conclusion, suwari (gel setting) and modori (gel degradation) phenomena occur during the gel formation of surimi from MDCM. The temperature range in chicken surimi was 47.5 to 52.5$^{\circ}C$ for suwari and 60 to 70$^{\circ}C$ for modori.

• Korean Journal of Food Science and Technology
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• v.33 no.1
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• pp.66-71
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• 2001

Kinetic parameters for the texture degradation of three varieties of sweet potato during heating were determined using two alternative methods, the biphasic model and the fractional conversion method. The texture degradation of sweet potatoes during heating could be expressed by two simultaneous first order reactions using the biphasic method, whose activation energies were ranged $71.0{\sim}75.1\;kJ/mol\;and\;48.4{\sim}59.6\;kJ/mol$ for the initial fast texture degradation reaction and the slow texture degradation reaction at a prolonged heating period, respectively. However, the whole texture degradation phenomena of sweet potatoes during heating could also be explained by a single first order reaction using the fractional conversion method. The activation energies were $67.5{\sim}75.3\;kJ/mol$, which were comparable with those of the first phase reaction for the texture degradation determined by the biphasic model. A kinetic compensation effect shown between the kinetic parameters determined by both methods indicates that both methods can be conveniently used to determine kinetic parameters for the texture degradation of sweet potatoes by heating.

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.109-115
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• 2012

In order to evaluate the effect of structural degradation of a GFRP composite bogie frame due to ballast-flying phenomena, the impact test and residual compression test after impact was conducted for glass fiber/epoxy 4-harness satin woven laminate composites applied to skin part of a bogie frame. The impact test was performed using a instrumented impact testing system with energy levels of 5J, 10J, and 20J, and the impactor was designed to have various ballast shapes such as sphere, cube, and cone to consider the ballasted track environments. The residual compression strength was tested to evaluate the degradation of mechanical properties of impact-damaged laminate composites. The results showed that the damage area and the degradation of residual compressive strength after impact for laminate composites was increased with increase of impact energy for all ballast shapes, and was particularly most influenced by ballast shape of cone.

• Tribology and Lubricants
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• v.27 no.3
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• pp.134-139
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• 2011

The mechanical equipments which are exposed to impure environment undergo significant reductions in their own lifetimes. Several environmental test procedures have been developed to analyze these phenomena. Moreover in the industry to require shorter development duration, accelerated life testers artificially add test containments into machines. In this research JIS Z 8901 test powder was added into internal gear pumps which are used as oil pumps in vehicles and thus the effects of the addition on the degradation of the pumps were examined. Three kinds of contaminants were selected. Two of the contaminants are identical in particle size but different in the composition of the ingredients. The other pair have identical ingredients and composition but different particle size. The quantity of contaminants was also an interesting factor in this study. The results show that each JIS contaminant caused notable degradation in the discharge flow characteristic of pumps while friction torque degradation did not have any tendency. Finally leakage rates were deduced and equivalent wear volume ratios were calculated.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.3
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• pp.256-263
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• 2012

We studied the degradation phenomenon of Pt catalyst in PEMFC. We used the electron microscope analysis technique including the ultra-microtome pretreatment method, FEG-SEM and TEM analysis methods for analysis of Pt nanoparticles. The Pt catalyst degradation is observed not only in electrode site but also in membrane site. We investigated these various degradation phenomena. The cathode electrode layer thickness is reduced. The size of the catalyst is increased much larger than initial size in membrane site. The catalyst moved from electrode layer to the electrolyte membrane. The rounded shape of catalyst was changed to the polygon. As a result, we found that the catalyst degradation processes of migration and coarsening occurred by the followings mechanisms; (1) dissolution of Pt ; (2) diffusion of Pt ion ; (3) Pt ion chemical reduction in membrane; (4) Coarsening of Pt particles (Ostwald ripening) ; (5) polygon shape change of Pt by {111} plane growth.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.96-99
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• 2005

As the demand of internet networks using backbone communication systems recently increased, the researches on the high-speed wideband optical communication systems are required. For high-speed optical communication systems, asymmetric sampled grating distributed feedback laser diodes (DFB-LDs) are developed and the reliability of DFB-LDs is examined. The reliability of DFB-LDs is performed by monitoring I-V and L-I characteristics and two degradation phenomena related to the electrical characteristics of LDs are observed during the life tests. The first degradation phenomenon by increasing the reverse current is considered as a formation of leakage current path enough to prevent lasing operation in lateral blocking layer near active region of lasers. The second degradation phenomenon by decreasing the forward current is considered as activation of non-radiative Auger recombination process by thermal energy and the second degradation phenomenon is recovered after the off-test period at room temperature Eventually, evaluating the reliability of DFB LDs can allow us to improved the manufacturability in high-volume manufacturing.