• Journal of Korea Foundry Society
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• v.23 no.3
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• pp.137-146
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• 2003

The main purpose of this study is to investigate the effects of process parameter on alpha-case formation of Ti and TiAl castings. The previous studies showed that the molten titanium is excessively reactive to the refractory oxide mold, resulting in alpha-caes of the titanium castings regardless of composition of titanium alloys. However, the behavior of the alpha-case formation of TiAl alloy is not consistent with conventional titanium alloy. In order to investigate the alpha-case formation of Ti and TiAl castings with process parameter, especially the associated factors of investment mold such as mold material, binder and mold preheating temperature. An attempt has been made to characterize the alpha-case of titanium casting by using optical microscope, EDS, XRD, EMPA and hardness profiles. The formation of the alpha-case on the surface of pure titanium during investment casting was rather by that of solid solution with metallic element from mold material. The required mold strength was obtained with $CaZrO_3$ because of the possibility of using water soluble binder. However, the separation phenomenon between facing and back-up mold materials should be considered. The interfacial reaction of TiAl alloy showed different behavior from that of pure titanium and $Al_2O_3$ was best mold materials. The effect of binder as well as mold material on the formation of alpha-case was significant.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4491-4498
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• 2022

The thermal stress between W plasma-facing material (PFM) and Cu heat sink in fusion reactors can be significantly reduced by using a W-Cu functionally graded material (W-Cu FGM) interlayer. However, there is still considerable stress at the joining interface between W and W-Cu FGM in the W/W-Cu FGM/Cu portions. In this work, we fabricate W skeletons with continuous gradients in porosity by a modified sedimentation method. Sintering densification behavior and pore characteristics of the sedimented W skeletons at different sintering temperatures were investigated. After Cu infiltration, the final W-Cu FGM was obtained. The results indicate that the pore size and porosity in the W skeleton decrease gradually with the increase of sintering temperature, but the increase of skeleton sintering temperature does not reduce the gradient range of composition distribution of the final prepared W-Cu FGM. And W-Cu FGM with composition distribution from pure W to W-20.5wt.% Cu layer across the section was successfully obtained. The thickness of the pure W layer is about one-fifth of the whole sample thickness. In addition, the prepared W-Cu FGM has a relative density of 94.5 % and thermal conductivity of 185 W/(m·K). The W-Cu FGM prepared in this work may provide a good solution to alleviate the thermal stress between W PFM and Cu heat sink in the fusion reactors.

• Journal of Navigation and Port Research
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• v.30 no.9
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• pp.763-766
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• 2006

In this paper, the EM wave absorbers were designed and fabricated for X -band sensors using Carbon of dielectric material with CPE. The complex relative permittivity of samples is calculated by using measurement results of S-parameter. We simulated the double-layered type EM wave absorber with broad bandwidth using the measured complex relative permittivity by changing the thickness and layer, which was fabricated based on the simulated design The fabricated EM wave absorber consists of 1 mm first layer sheet facing metal with Carbon composition ratio 70 vol. % and 1.5 mm second layer sheet with Carbon composition ratio 60 vol. %. The measured results showed a good agreement to the simulated ones. It is found toot the optimized absorption ability of double-layered type EM wave absorber with thickness of 2.5 mm is higher than 10 dB from 7.8 GHz to 13.3 GHz.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.200.1-200.1
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• 2016

Tungsten coatings on the graphite (CX-2320) were successfully deposited using the vacuum plasma spraying (VPS) method. An optimum coating procedure was developed and coating thicknesses of $409{\mu}m$ (without an interlayer) and $378{\mu}m$ (with an interlayer) were obtained with no cracks and no signs of delamination. The mechanical characteristics and microstructure of the tungsten coating layers were investigated using a Vickers hardness tester, FE-SEM, EDS, and XRD. The effect of a titanium interlayer on the properties of the tungsten coating was investigated. It was shown that the titanium interlayer prevented the diffusion of carbon to the tungsten layer, thereby suppressing the formation of tungsten carbide. Vickers hardness data yielded values that were 62.5 ~ 80.46% of those for bulk tungsten, indicating that tungsten coatings on graphite can be utilized as a plasma-facing material. High heat flux tests were performed by using thermal plasma with a maximum flux of $10MW/^2$. Vickers hardness after the heat flux test is performed to see a change in the mechanical properties. The formationof a tungsten carbide and the effect of the titanium interlayer for the diffusion barrier are investigated by using energy dispersion spectroscopy (EDS).

• Journal of the Korean Institute of Rural Architecture
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• v.17 no.4
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• pp.67-74
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• 2015

Due to an inability to accommodate for the rapidly increasing number of printed materials, Korean academic libraries are facing serious space shortage problems. Very few academic institutions have the funds to expand existing libraries or construct new facilities in order to accommodate the influx of printed materials. Despite not having the luxury to create new space, many establishments continue to implement the open access system. Seeing that such a system is only user friendly when used in a spacious facility, the maintenance of the open access system is unreasonable. Only few libraries consider the space efficient closed access system which helps to resolve storage space shortage. In the current state of the problem, improving the efficiency to which books are stored in existing storage areas within a library facility is the only appropriate solution. Enacting methods to improve physical space utilization within a fixed volume library facility will undoubtedly diminish the space shortage issue at hand. In this article, several space efficiency improvement approaches are discussed. Methods of book storage plan re-layout (floor, plan, ceiling, height, bookshelf design), book arrangement possibilities, and the reduction of the physical volume of reserved materials are each examined.

• Journal of Agricultural Extension & Community Development
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• v.14 no.1
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• pp.171-195
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• 2007

Gyeonggi rice has been placed relatively favorable market position in the domestic rice market. With the superiority of its quality, gyeonggi rice has been well recognized to consumers. The price of gyeonggi rice has placed higher position than that of others. But, gyeonggi rice are facing crisis on the competition by regional brands. Therefore, this study was carried out to find the differentiated marketing strategies on problem related with the product differentiation and brand marketing of gyeonggi rice. In order to find out how much the effort on the product differentiation of gyeonggi rice affects the price and brand recognition, fifty RPCs in gyeonggi province were surveyed. As the results, $22{\sim}23%$ of harvested rice which was gathered into RPC was come out 'obscurity of production origin' when we consider material hull rice in the original production territory by collecting time and channel. With comparing sales weight of gyeonggi rice by the place of shipment, agricultural cooperative channel was the highest by 44.7%. And, wholesaler comes to 17.7%, discount outlet store was 13.9%, large quantity delivery in business was 11.1%, and department store was only 5.2%. Finally, we could consider to adopt the traceability system on gyeonggi rice distribution system from production to consumers' table to get consumers' credibility and compete imported high quality rice.

• Transactions on Electrical and Electronic Materials
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• v.11 no.3
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• pp.93-105
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• 2010

Complementary metal-oxide-semiconductor (CMOS) technology scaling has been a main key for continuous progress in silicon-based semiconductor industry over the past three decades. However, as the technology scaling enters nanometer regime, CMOS devices are facing many serious problems such as increased leakage currents, difficulty on increase of on-current, large parameter variations, low reliability and yield, increase in manufacturing cost, and etc. To sustain the historical improvements, various innovations in CMOS materials and device structures have been researched and introduced. In parallel with those researches, various new nanoelectronic devices, so called "Beyond CMOS Devices," are actively being investigated and researched to supplement or possibly replace ultimately scaled conventional CMOS devices. While those nanoelectronic devices offer ultra-high density system integration, they are still in a premature stage having many critical issues such as high variations and deteriorated reliability. The practical realization of those promising technologies requires extensive researches from device to system architecture level. In this paper, the current researches and challenges on nanoelectronics are reviewed and critical tasks are summarized from device level to circuit design/CAD domain to better prepare for the forthcoming technologies.

• Environmental Engineering Research
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• v.18 no.2
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• pp.91-94
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• 2013

Recently Ibadan in southwestern Nigeria has been facing severe water shortage due to the increase of population, social and economic activities. In order to meet the shortfall, attempts to utilize rainwater harvesting (RWH) have been made to provide an alternative source of water supply. A desk study was conducted to review various RWH technologies locally, regionally and globally. A hydrological analysis was also carried out using rainfall data for 30 years from two meteorological stations, with the aim of providing a more sustainable RWH system for water supply to private individuals, organizations, and government agencies. RWH is found to be technically feasible based on the prevailing rainfall pattern with over 90% of households having a rooftop constructed from technically appropriate materials. Results of the study indicate that an average roof of $80m^2$ will collect 82,835 L/yr (45 L/person/day) for a family of five people which is about the required water demand for drinking and cooking purposes. Hence, the capacity of storage tanks and the catchment area required for an all-purpose water supply system based on RWH are quite large. These can be reduced to affordable sizes, by collecting and storing water for cooking and drinking only while non-potable uses are supplemented by water from other sources. However, it must be highlighted that due to the type of roofing material, rainwater should go through proper treatment in order to be used for potable purposes. This study clearly shows that Ibadan city has a good rainwater harvesting potential.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.244-244
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• 2011

핵융합장치 내부의 플라즈마 대면재료는 고온의 플라즈마와 직접 대면하므로 수 십 MW/$m^2$에 이르는 큰 열부하에 따른 재료의 물성변화, 즉 고온환경에 따른 재료의 팽윤, 크리프(creep) 변형 그리고 금속이 가역성이나 연성을 잃는 취화현상 등이 중요한 연구주제이다. 고열부하의 인가를 통한 핵융합대면재료의 물성실험은 현재 국내에서는 탄소히터, 열플라즈마 등을 이용하여 이루어지고 있으며 국외에서는 짧은 시간에 큰 열부하를 인가할 수 있는 고출력 전자빔장치가 주요한 열부하실험장치로 활용되고 있다. 본 연구에서는 기초적인 실험이 가능한 고열부하용 전자빔조사장치를 제작하여 대표적인 플라즈마 대면재료인 텅스텐에 60 keV, 30 mA의 전자빔을 조사한 후 고열부하에 따른 텅스텐의 물성변화를 측정하였다.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.5
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• pp.533-543
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• 2016

Supplying clean and safe water to people is facing both quantitative and qualitative challenges. Due to climate change, access to freshwater becomes increasingly difficult, while pollution from various sources decreases the public trust in water quality. Managed aquifer recharge (MAR) which stores and uses surface water in aquifer is receiving attention as a new technology to secure freshwater. Recently, there is a global expansion in the attempt to combine general purification plants and hazard analysis and critical control point (HACCP) which manages all the process from raw material to consumer for food safety. This research is about an attempt to apply HACCP to the drinking water supply process using MAR to secure both quantity and quality of drinking water. The study site is a MAR plant being constructed in the downstream area of the Nakdong River Basin, South Korea. The incorporation of HACCP with MAR-based water supply system is expected to enhance the safety and reliability of drinking water.