• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.13-19
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• 2012

The purpose of this study is to extract the major factors related to the deterioration mechanism of white organic light-emitting diodes(WOLED) by performing accelerated testing of temperature, voltage, time, etc., and to develop an accelerated life test(ALT) model. The measurement results of the brightness of the WOLED exhibited that their average brightness tended to increase as the operating voltage increased and that the half-life period of the brightness appeared after approximately 400 hours when the operating voltage was 20V and the ambient temperature was $85^{\circ}C$. It could be seen that although the WOLED showed comparatively the same brightness when the initial acceleration began after the operating voltage was applied to it, its brightness changed excessively after the WOLED's thermal storage had been made. In addition, it was observed that the half-life period was reduced as the ambient temperature and applied voltage increased. The strength of the WOLED which had been maintained in the range of visible light at the maximum load was reduced by the deterioration of the organic light emitting material due to the influence of the operating voltage and temperature, and the reduction of emitted light was small at low voltage and temperature. It could be seen that the failure of the WOLED during the ALT was caused by wear due to load accumulation over time, and that Weibull distribution was appropriate for the life distribution and acceleration was established between test conditions. From the WOLED analysis, it is thought that factors influencing the brightness deterioration are voltage, temperature, etc., and that comprehensive analysis considering discharge control, dielectric tangent margin, etc., would further increase the reliability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.12
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• pp.953-963
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• 2015

There is an increasing need to understand the thermal-hydraulic phenomena, including the critical heat flux (CHF), in narrow rectangular channels and consider these in system design. The CHF mechanism under a saturated flow boiling condition involves the depletion of the liquid film of an annular flow. To predict this type of CHF, the previous representative liquid film dryout models (LFD models) were studied, and their shortcomings were reviewed, including the assumption that void fraction or quality is constant at the boundary condition for the onset of annular flow (OAF). A new LFD model was proposed based on the recent constitutive correlations for the droplet deposition rate and entrainment rate. In addition, this LFD model was applied to predict the CHF in vertical narrow rectangular channels that were uniformly heated. The predicted CHF showed good agreement with 284 pieces of experimental data, with a mean absolute error of 18. 1 % and root mean square error of 22.9 %.

• Horticultural Science & Technology
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• v.30 no.6
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• pp.617-625
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• 2012

Tree peony is a traditional famous flower of China, and plays an important role in Chinese traditional culture. But the floral scent of tree peony in vivo is little known. In this study, in order to explore the floral composition of tree peony, floral volatiles of six cultivars, including Paeonia suffruticosa 'Zhaofen' (ZF), P. suffruticosa 'Luoyanghong' (LYH), P. ostii 'Fengdanbai' (FDB), P. ${\times}$ lemonei 'High noon' (HN), P. ${\times}$ lemonei 'Renown' (R), and P. rockii 'Gaoyuanshenghuo' (GYSH) were collected by dynamic headspace and then identified by Automated Thermal Desorption-Gas Chromatography/Mass Spectometry. The results showed that floral fragrances of the six cultivars were qualitatively and quantitatively distinct. A total of 105 volatiles involving ten categories were detected. But not all volatile categories were emitted from these cultivars. The six peony cultivars emitted some shared compounds and peculiar compounds. The total released amounts of volatiles emitted from six cultivars were found significantly different, which was greatest for 'GYSH'. The most abundant volatile compounds detected from 'ZF', 'LYH', 'FDB', 'HN', 'R', and 'GYSH' were respectively ${\alpha}$-pinene, 2,3-dihydroxy propanal, 3-methyl-1-butanol, 2-ethyl-1-hexanol, acetic acid 1-methylethyl ester, and 5-ethyl-2,2,3-trimethyl heptane. This result may contribute to exploring the biosynthesis and emission mechanism of floral scent in tree peony.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.311-311
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• 2013

The resistance switching memory devices have several advantages to take breakthrough for the limitation of operation speed, retention, and device scale. Especially, the metal-oxide materials such as ZnO are able to fabricate on the flexible and visible transparent plastic substrate. Also, the quantum dots (QDs) embedded in dielectric layer could be improve the ratio between the low and the high resistance becauseof their Coulomb blockade, carrier trap and induced filament path formation. In this study, we irradiated 0.2-MeV-electron beam on the ZnO/QDs/ZnO structure to control the defect and oxygen vacancy of ZnO layer. The metal-oxide QDs embedded in ZnO layer on Pt/glass substrate were fabricated for a memory device and evaluated electrical properties after 0.2-MeV-electron beam irradiations. To formation bottom electrode, the Pt layer (200 nm) was deposited on the glass substrate by direct current sputter. The ZnO layer (100 nm) was deposited by ultra-high vacuum radio frequency sputter at base pressure $1{\times}10^{-10}$ Torr. And then, the metal-oxide QDs on the ZnO layer were created by thermal annealing. Finally, the ZnO layer (100 nm) also was deposited by ultra-high vacuum sputter. Before the formation top electrode, 0.2 MeV liner accelerated electron beams with flux of $1{\times}10^{13}$ and $10^{14}$ electrons/$cm^2$ were irradiated. We will discuss the electrical properties and the physical relationships among the irradiation condition, the dislocation density and mechanism of resistive switching in the hybrid memory device.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.470-470
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• 2013

Recently, active materials such as amorphous silicon (a-Si), poly crystalline silicon (poly-Si), transition metal oxide semiconductors (TMO), and organic semiconductors have been demonstrated for flexible electronics. In order to apply flexible devices on the polymer substrates, all layers should require the characteristic of flexibility as well as the low temperature process. Especially, pentacene thin film transistors (TFTs) have been investigated for probable use in low-cost, large-area, flexible electronic applications such as radio frequency identification (RFID) tags, smart cards, display backplane driver circuits, and sensors. Since pentacene TFTs were studied, their electrical characteristics with varying single variable such as strain, humidity, and temperature have been reported by various groups, which must preferentially be performed in the flexible electronics. For example, the channel mobility of pentacene organic TFTs mainly led to change in device performance under mechanical deformation. While some electrical characteristics like carrier mobility and concentration of organic TFTs were significantly changed at the different temperature. However, there is no study concerning multivariable. Devices actually worked in many different kinds of the environment such as thermal, light, mechanical bending, humidity and various gases. For commercialization, not fewer than two variables of mechanism analysis have to be investigated. Analyzing the phenomenon of shifted characteristics under the change of multivariable may be able to be the importance with developing improved dielectric and encapsulation layer materials. In this study, we have fabricated flexible pentacene TFTs on polymer substrates and observed electrical characteristics of pentacene TFTs exposed to tensile and compressive strains at the different values of temperature like room temperature (RT), 40, 50, $60^{\circ}C$. Effects of bending and heating on the device performance of pentacene TFT will be discussed in detail.

• Journal of Conservation Science
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• v.36 no.1
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• pp.1-14
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• 2020

This study investigates the crystallinity distribution of ancient silk. Owing to the inherent multi-hierarchical structure of silk protein and the complicated structural changes that occur due to various burial environments, it is challenging but worthwhile to study ancient silk ageing behavior, which is based on the fact that ageing begins with a single fiber and then spreads to a whole fabric. Crystallinity was one of the most effective indicators found to reveal the ageing status of silk. Therefore, a synchrotron radiation-based X-ray diffraction(SR-XRD) method was employed to study the crystallinity distribution of single fibers of ancient silk unearthed from seven archaeological sites in China from historical periods including the warring states, Han dynasty, Song dynasty, and Ming dynasty. In comparison, the conventional X-ray diffraction method, which uses large amounts of samples, was also performed to determine the integral crystallinity of ancient silk. Thermal stability experiments by thermogravimetry(TG) as well as morphology observations by scanning electron microscopy(SEM) and optical microscopy(OM) all confirmed the deterioration of ancient silk. Moreover, the ageing mechanism of ancient silk was proposed with the assistance of an artificial ageing study. The results confirmed the effectiveness of SR-XRD as an ageing indicator, revealing the crystallinity distribution. This research could provide motivation to determine the deterioration status of ancient silk, and would also aid in explaining the fragility of ancient silk due to ageing.

• Journal of the Korean Society of Safety
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• v.5 no.2
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• pp.32-39
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• 1990

The ${\gamma}$-Fe$_2$O$_3$ compounds were oxidized in the furance after gas detecting sensor made molding as the Fe$_3$O$_4$ the synthesized Fe$_3$O$_4$, by ferrous sulfate and sodium hydroxide. Their sensities on carbon monoxide, ethyl alcohol and L. P. G. were measured at various temperatures, respectively. And then their electrical resistivities, thermal properties (D.T.A. ＆ T.G.A.), were examined about their having an effet on the gas-sensing in company with the effect of pure ${\gamma}$-Fe$_2$O$_3$ and the detecting sensor ${\gamma}$-Fe$_2$O$_3$, which reacts with $K_2$CO$_3$ in the hydrothermal coundition, and the electrical conductive mechanism was reflected simultaneously. It was observed that the electrical conductivities and response ratios showed highest value at the endothermic temperature part, 300~35$0^{\circ}C$ of D.T.A.―curve. Consequently, the response ratios and response times of the hydrothermal detecting sensor were higher than that of pure detecting sensor, the specific surface areas were the highest at the endothermic range of D.T.A.-curve. These response ratios of detecting sensor for $K_2$CO$_3$, process at hydrothermal condition on carbon monoxide appeared higher than that on ethyl alcohol and in case of L.P.G. last.

• Analytical Science and Technology
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• v.5 no.4
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• pp.443-454
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• 1992

The analysis, hydrolysis mechanism, oxidation, reduction, thermal decomposition and metabolism of irritant materials such as chloroacetophenone isomers, bromophenylacetonitrile isomers, o-chlorobenzylidenemalononitrile(CS), and ethylisothiocyanate, etc. are interested in forensic science. We had studied hydrolysis of CS in 10% MeOH-$H_2O$ and 10% dioxane-$H_2O$ at pH 1.0~11.0 and various temperatures. As a result, we identified o-chlorobenzaldehyde and malononitrile that were formed by hydrolysis of CS by using gas chromatography/mass spectrometry, UV/Vis spectrometry, and polarographic method.

• Journal of Conservation Science
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• v.21
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• pp.33-40
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• 2007

The consolidation application of SILRES BS OH 100 was investigated, which has been used for consolidation of the weathered shale. The liquid SILRES BS OH 100 was polymerized by the sol-gel reaction with air moisture, and the XRD patterns showed that the gel was an amorphous solid. The drastic weight reduction of the sample was found by differential thermal analysis, which was followed to the formation of $Si(OH)_4$ particles. After consolidation, the polymerized gel was filled into the voids within the shale. The capillary water absorption of the consolidated shale was reduced to 48.7%, and the abrasive strength was improved.

• The Korean Journal of Physiology
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• v.22 no.2
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• pp.245-257
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• 1988

The present study was undertaken to investigate the effect of clonidine on the response of the dorsal horn cells to intra-arterially administered bradykinin $(BK:40{\mu}g)$ and $K^+(4mg)$ in spinal cats and cats with intact spinal cord. The change in the activities of low threshold (LT), high threshold (HT) and wide dynamic range (WDR) cells induced by BK and $K^+$ were determined before and after treatment of animals with clonidine. Also studied was mechanism of inhibitory action of clonidine on the responses of dorsal horn cells to the chemical algogenics. Number of WDR cell responded to intra-arterially administered BK and $K^+$ was greater in spinal animals than in cats with intact spinal cord. Following administration of BK or $K^+$ no change was observed in the activity of LT cell whereas activity of HT cell increased invariably. The increased response of HT cell to BK and $K^+$ was markedly suppressed by clonidine. On the other hand, such inhibitory actions of clonidine were almost completely blocked by yohimbine. The majority of WDR cells were activated by $K^+$ while response of WDR cells to BK was diverse (excitatory, inhibitory or mixed). These results indicate that clonidine inhibits responses of the dorsal horn cells not only to thermal or mechanical stimulations but also to chemical algogenics, and that the inhibitory action of clonidine is generally mediated through excitation of ${\alpha}_2-adrenoreceptors$.