• Journal of the Korean Solar Energy Society
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• v.35 no.4
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• pp.9-15
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• 2015

Black cobalt solar selective coatings were prepared by using an electroplating method. The changes in the optical properties of the black cobalt selective coating due to thermal degradation were analyzed by using the Auger electron spectroscopy (AES) and spectrophotometer. The black cobalt selective coating was prepared on a copper substrate by using a synthesized electrolyte with $CoCl_2$ and KSCN at a current density of ${\sim}0.5A/dm^2$ for 45s ~ 60s. Its optical properties were a solar absorptance (${\alpha}$) of the order of 0.80 ~ 0.84 and a thermal emittance (${\epsilon}$) of 0.01. From the AES depth profile analysis of heated sample, thermal degradation of the black cobalt selective coating heated for 33 hours at temperature of $350^{\circ}C$ occurred primarily due to interdiffusion at interface of cobalt and copper substrate. This results were predictable that the ${\alpha}$ decreases due to the thermal oxidation and diffusion.

• 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.

• Journal of the Korean Society of Safety
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• v.18 no.4
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• pp.64-70
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• 2003

The thermal properties of chloroprene rubber (CR) with $^{60}Co\;{\gamma}$-ray irradiation has been investigated. The prepared CR was irradiated up to 1000kGy radiation dose by $^{60}Co\;{\gamma}$-ray and the radiation degradation of CR was investigated by thermogravimetric analysis and differential acanning calorimetry. Dynamic mechanical properties measurement and FT-IR observation are carried out as well. From these analyses results, the glass transition temperature($T_g$), decomposition onset temperature(DOT), oxidative induction time(OIT), the peak temperature of loss modulus and mechanical tan ${\delta}$ values were compared for the radiation degradation level of CR. The tendency between $T_g$ and peak temperature of loss modulus and mechanical tan ${\delta}$ agreed well with radiation doses. Decomposition temperature, OIT and DOT showed the same tendencies as increasing radiation doses. It was verified that these analyses are available to estimate the degradation level of CR.

• Current Photovoltaic Research
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• v.12 no.1
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• pp.6-16
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• 2024

The efficiency of silicon solar cells is approaching a theoretical limit referred to as 'the state of the art'. Consequently, maintaining efficiency is more productive than pursuing improvements the last room for limiting efficiency. One of the primary considerations in silicon module conservation is the occurrence of failures and degradation. Degradation can be mitigated during the cell manufacturing stage, unlike physical and spontaneous failure. It is mostly because the chemical reaction is triggered by the carrier generation of thermal and light injection, an inherent aspect of the solar cell environment. Therefore, numerous researchers and cell manufacturers are engaged in implementing mitigation strategies based on the physical degradation mechanism.

• Journal of Energy Engineering
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• v.14 no.2 s.42
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• pp.105-111
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• 2005

In this study, the photocatalytic degradtion of D-glucose with the micro channel reactor was performed on the various experimental conditions. To apply the $TiO_2$ coating on the micro channel reactor, $TiO_2$ solution was synthesized by hydrolysis of titanium oxysulfate. The feeding rate was proportional to degradation rate of D-glucose solution over the micro channel reactor. Also, the reaction rate constant and Langmuir adsorption coefficient were calculated under various experimental conditions. And the results of these system photonic efficiencies were calculated. This study aims to understand the photocatalytic degradation characteristics on $TiO_2$ coating in the micro channel reactor experimented by the feed batch reaction system.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.3
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• pp.286-292
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• 2006

Chlamydomonas reinhardtii is a green algae that can use light energy and water to produce hydrogen under anaerobic condition. This work reports the effect of limiting factors on hydrogen production in sulfur deprived anaerobic C. reinhardtii culture. In order to confirm the relationship between hydrogen production and limiting factors such as residual PSII activity and endogenic substrate degradation, the increase in chlorophyll concentration and the decrease in starch concentration was investigated during sulfur deprivation. The overall hydrogen production increased depending on cell density in range of $0.4{\sim}0.96\;g$ DCW/l. At this time, the increase in chlorophyll concentration during 24 h after sulfur deprivation increased in proportion to hydrogen production, however, the decrease in starch concentration was not proportional to that. Therefore, hydrogen production under sulfur deprivation using green alga was closely associated with the residual PSII activity than the endogenic substrate degradation.

• IEMEK Journal of Embedded Systems and Applications
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• v.3 no.3
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• pp.158-166
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• 2008

These days, mobile embedded systems adopt flash memory capable of XIP feature since they can reduce memory usage, power consumption, and software load time. XIP provides direct access to ROM and flash memory for processors. However, using XIP incurs unnecessary degradation of applications' performance because direct access to ROM and flash memory shows more delay than that to main memory. In this paper, we propose a memory management framework, dynamic XIP, which can resolve the performance degradation of using XIP. Using a constrained RAM cache, dynamic XIP can dynamically change XIP region according to page access pattern to reduce performance degradation in execution time or energy consumption resulting from native XIP problem. The proposed framework consists of a page profiler gathering applications' memory access pattern using PMU and an XIP manager deciding that a page is accessed whether in main memory or in flash memory. The proposed framework is implemented and evaluated in Linux kernel. Our evaluation shows that our framework can reduce execution time at most 25% and energy consumption at most 22% compared with using XIP-only case adopted in general mobile embedded systems. Moreover, the evaluation shows that in execution time and energy consumption, our modified LRU algorithm with code page filters can reduce more than at most 90% and 80% respectively compared with applying just existing LRU algorithm to dynamic XIP.

• Steel and Composite Structures
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• v.25 no.5
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• pp.603-615
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• 2017

This experimental research presents the seismic performance of steel reinforced high-strength concrete (SRHC) short columns. Eleven SRHC column specimens were tested under simulated earthquake loading conditions, including six short column specimens and five normal column specimens. The parameters studied included the axial load level, stirrup details and shear span ratio. The failure modes, critical region length, energy dissipation capacity and deformation capacity, stiffness and strength degradation and shear displacement of SRHC short columns were analyzed in detail. The effects of the parameters on seismic performance were discussed. The test results showed that SRHC short columns exhibited shear-flexure failure characteristics. The critical region length of SRHC short columns could be taken as the whole column height, regardless of axial load level. In comparison to SRHC normal columns, SRHC short columns had weaker energy dissipation capacity and deformation capacity, and experienced faster stiffness degradation and strength degradation. The decrease in energy dissipation and deformation capacity due to the decreasing shear span ratio was more serious when the axial load level was higher. However, SRHC short columns confined by multiple stirrups might possess good seismic behavior with enough deformation capacity (ultimate drift ratio ${\geq}2.5%$), even though a relative large axial load ratio (= 0.38) and relative small structural steel ratio (= 3.58%) were used, and were suitable to be used in tall buildings in earthquake regions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.10
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• pp.1068-1078
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• 2004

In this paper we investigated the characteristics of surface degradation in silicone rubber due to corona exposure and recovery mechanism. It was shown that surface free energy was 22.42 mJ/$m^2$ on initial sample but surface free energy was approximately increased to 71.14 mJ/$m^2$ after 45 minutes. However, surface free energy on silicone rubber after corona discharge treatment was completely recovered within a short time due to diffusion of low molecular weight(LMW) silicone fluid. It was shown that corona discharge insured the increase of diffusible LMW chains, which could lead to recover the surface hydrophobicity. 200～370 g/mol distribution of LMW silicone fluid which was extracted by solvent-extraction with gel permeation chromatography (GPC) was contributed to recovery. The surface degradation characteristics on silicone rubbers and the recovery mechanism based on our results were discussed.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.164-174
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• 2018

The purpose of this work designed hybrid-structured and plasma effect photocatalyst of $Ag/In_2O_3/TiO_2/HNTs$ via sol-gel and photo-reduction methods. The structures, morphologies, optical and photoelectric performances of as-prepared photocatalysts were characterized via XRD, TEM, XPS, BET, UV-vis DRS, PL and photocurrents. The photocatalytic activity was evaluated by degradation of TC. The results showed that the hybrid-structure and plasma effect can effectively cause the multi-transfer of electrons and increase the separation rate of electron and hole pairs which obtained high photocatalytic activity. The photocatalytic degradation processes reveal that $^{\bullet}O_2{^-}$ and $h^+$ are major active species.