• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.839-845
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• 2021

In this study, it shows the efficiency of each refrigerant through simulation method for ORC (Organic Rankine Cycle) power generation that converts waste heat discarded by ship exhaust into electricity for the purpose of reducing CO₂ emission and increasing ship waste heat recovery. by Simulation was performed with waste heat from the exhaust gas which is relatively high temperature and cooling sea water which is relatively low temperature from ships. As a result of the sea water cooling ORC power generating system, efficiency of the working fluid with R717 is highest as a 2.86 % and the next working fluid is R152a, R134a, R143a and R125a.

• Journal of the Korea Convergence Society
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• v.10 no.4
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• pp.131-138
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• 2019

Diesel engines have important advantages over its gasoline counterpart including high thermal efficiency, high fuel economy and low emissions of CO, HC and $CO_2$. However, NOx reducing is more difficult on diesel engines because of the high $O_2$ concentration in the exhaust, marking general three way catalytic converter ineffective. Two method available technologies for continuous NOx reduction onboard diesel engines are Urea-SCR and LNT. The implementation of the Urea-SCR systems in design engines have made it possible for 2.5l and over engines to meet the tightened NOx emission standard of Euro-6. In this study, we investigate the characteristics of NOx reduction with respect to engine speed, load, types of catalyst and the $NH_3$/NOx ratio and present the conditions which maximize NOx reduction. Also we provide detailed experimental data on Urea-SCR which can be used for the preparation for standards beyond Euro-6.

• Corrosion Science and Technology
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• v.3 no.2
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• pp.59-66
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• 2004

In construction of new ships and large steel bridges in Korea, pre-construction primers (PCP), also known as shop primer, are routinely used and retained as an integral part of the protective coating system. Retention of PCP's can significantly reduce building schedule and cost. Retaining PCP through the so-called "sweep blasting" procedure eliminates or minimizes the necessity of a second blast operation, thus shortening overall schedule as well as reducing labor cost and hazardous waste disposal cost. This study evaluates the feasibility of retaining PCP as the part of primer for high performance protective coating systems applied to ships' hull, bottom and ballast tanks. Upon proving that the retention of the PCP is a viable option, the process of coating application can he improved significantly in terms of cost and working schedule of new ships and large steel bridges. Results indicate that use of the PCP via sweeping blasting in conjunction with standard high performance protective coating systems does not degrade the overall performance of the coating systems. At the same time, it is also highly recommended that the secondary surface preparation should consist of grit blasting of weld burnt and other damaged areas to SSPC SP-IO grade (Sa 2.5 Gr.), Near White Blast Cleaning with proper application and attention to detail.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.440-448
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• 2004

In this paper, to make a solar cell of II-Ⅵ ZnTe compound semiconductor, we studied for the property of the transparent electrode(AZO) and Buffer layer(ZnO), and for reducing the energyband gap of optical absorber layer which are most effective on its efficiency. The ZnTe thin film was used the optical absorber layer of solar cell. Zn and Te were deposited using the co-sputtering method. The thin film was sputtered RF power of Zn/50W and Te/30W, respectively and a substrate temperature of foot under Ar atmosphere of 10mTorr. The energy band gap of the thin film was 1.73ev Then the thin film was annealed at $400^{\circ}C$ for 10sec under a vacuum atmosphere. The energy band gap of 1.67eV was achieved and the film composition ratio of Zn and Te was 32% and 68%. At the best condition, the Solar Cell was manufactured and the efficiency of 6.85% (Voc: 0.69V, Jsc: 21.408㎃/$cm^2$, Fill factor (FF): 0.46) was achieved.

• Membrane and Water Treatment
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• v.1 no.3
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• pp.193-206
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• 2010

Organic fouling and biofouling pose a significant challenge to the membrane filtration process. Photocatalysis-membrane hybrid system is a novel idea for reducing these membranes fouling however, when $TiO_2 photocatalyst nanoparticles are used in suspension, catalyst recovery is not only imposes an extra step on the process but also significantly contributes to increased membrane resistance and reduced permeate flux. In this study, $TiO_2$ photocatalyst has been immobilized by coating on the microfiltration (MF) membrane surface to minimize organic and microbial fouling. Nano-sized $TiO_2$ was first synthesized by a sol-gel method. The synthesized $TiO_2$ was coated on a Poly Vinyl Difluoride (PVDF) membrane (MF) surface using spray coating and dip coating techniques to obtain hybrid functional composite membrane. The characteristics of the synthesized photocatalyst and a functional composite membrane were studied using numerous instruments in terms of physical, chemical and electrical properties. In comparison to the clean PVDF membrane, the $TiO_2$ coated MF membrane was found more effective in removing methylene blue (20%) and E-coli (99%).

• Plant Journal
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• v.14 no.2
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• pp.33-38
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• 2018

The CFB boilers technology is facing a number of challenges. Among them, boiler tube erosion, sintering by bed inventory overheating and high self consumed service power are major ones. This study was conducted to obtain allowable bed inventory with the Yeosu Power Plant, a 300 MW class CFB boiler. For the test, bed pressure was reduced from design pressure of 4.5 KPa to 2.5 KPa by reducing bed inventory, at fixed turbine output, coal consumption rate and air flow. Consequently, reducing the lower bed inventory is effective to decrease bed temperature but excessive reducing might increase bed temperature due to lack of circulating fluidized materials. Also, in case of the Yeosu Plant boiler using subbituminous coal as its primary fuel, its bed temperature change is highly affected by not only the amount of bed inventory, but also the boiler capacity and coal contents.

• Environmental and Resource Economics Review
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• v.23 no.2
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• pp.157-185
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• 2014

The Kyoto Protocol has extended its life until 2020 by the decision at COP18 in Doha, Qatar in 2012. So has the Kyoto Mechanism of CDM, JI, and ETS. Nonetheless, the sustainability of CDM projects is jeopardized by the recent rule changes in the international emissions trade market such as EU ETS and the price decrease in emission credits. In particular, the domestic CDM projects reducing non-$CO_2$ GHG emissions are being directly affected. This study examines the trend of carbon credit price change in the international market. It also examines how the rule changes in the international emissions trade market have affected domestic non-$CO_2$ CDM projects through which mechanisms. The policy implications drawn from this study is two-fold: it suggests how the government can assist the project developers in utilizing GHG emission reduction technologies and the market in promoting investment environment before the domestic ETS enters into effect in 2015; apart from possible measures within ETS, an additional measures such as bilateral carbon offset system is suggested to help the private sector reduce uncertainty in investment and increase options to choose.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.268-276
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• 2015

In this study, $CO_2$ reduction type quaternary component high fluidity concrete was produced with more than 80% reduction in cement quantity to increase the use of industrial byproducts and enhance construction performance, thereby reducing $CO_2$ emissions. Furthermore, the quality properties, and $CO_2$ reduction performance of this concrete were evaluated. As a result of the quality evaluation of quaternary component blended high fluidity concrete with $CO_2$ reduction, the target performance could be achieved with a 80% or more reduction of cement quantity by mixing a large amount of industrial byproducts. The required performance level was obtained even though the flow, dynamic, and durability characteristics decreased a little compared to conventional mix. In addition, to analyze the $CO_2$ reduction performance of quaternary component blended high fluidity concrete with $CO_2$ reduction, the life cycle assessment (LCA) of the concrete was performed and the results showed that compared to the conventional mix, the carbon emissions decreased by 62.2% and the manufacturing cost by 24.5%.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.269-276
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• 2004

A marine diesel engine should realize optimal efficiency operation while reducing NOx. Fuel injection systems by electronic control can become effective means for that. Although it would be able to get more precise engine control compared to the mechanical injection system, it needs some accurate and instant information in order to bring its ability into full play while sailing on the sea. Very important information of them is shaft torque and continuous combustion pressure of all cylinders. The system presented in this report can deliver those data.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.2
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• pp.124-127
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• 2004

W/n-GaN Schottky diodes were irradiated with $^{60}Co\;{\gamma}-rays$ to doses up to 315Mrad. The barrier height obtained from current-voltage (I-V) measurements showed minimal change from its estimated initial value of ${\sim}0.4eV$ over this dose range, though both forward and reverse I-V characteristics show evidence of defect center introduction at doses as low as 150 Mrad. Post irradiation annealing at $500^{\circ}C$ increased the reverse leakage current, suggesting migration and complexing of defects. The W/GaN interface is stable to high dose of ${\gamma}-rays$, but Au/Ti overlayers employed for reducing contact sheet resistance suffer from adhesion problems at the highest doses.