• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.942-948
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• 2011

The performance of a supercharger for vehicle using solar cell attached on the exterior of a car, an auxiliary battery, and an air compressor was evaluated in this study. This supercharger is composed of a solar cell of 40W, a battery of 60 Ah, an air compressor of 17 A, 8 $kgf/cm^2$ and an air tank of 8L. It takes about 6 days to charge the battery with the solar cell and the high pressure air of 8L can be supplied about 70 times to engine intake with this battery. The intake pressure increased by about 20~40% with this supercharger. The vehicle power and accelerating performance are enhanced by 87% and 50% each in the low speed range. But the performance improved little in the high speed range because of the rather constant flow rate of air supplied by this type of supercharger.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.131-134
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• 1998

This work was carried out to develop a pattern on the nanometer scale using plasma polymerization and plasma etching. This study is also aimed at developing a resist for the nano process and a vacuum lithography process. The thin films of plasma polymerization were fabricated by the plasma po1ymerization of inter-electrode capacitively coupled gas flow system. After delineating the pattern at accelerating voltage of 30[kV]. ranging the dose of 1∼500[${\mu}$C/$\textrm{cm}^2$], the pattern was developed with dry tree and formed by plasma etching. By analysing of the molecule structure using FT-lR, it was confirmed that the thin films of PPMST contains the functional radicals of the MST monomer. The thin films of PPMST had a highly crosslinked structure resulting in a higher molecule weight than the conventional resist.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.108-111
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• 2014

본 논문에서는 스마트폰에 탑재되는 모바일 GPU 를 활용하여 만화 형식의 영상을 생성하는 과정을 가속하는 방법을 제시하였다. 또한 모바일 GPU 에 적합한 벡터 데이터 타입과 벡터 명령어의 사용 및 워크 그룹 크기에 의한 영향을 고려한 최적화를 적용하였다. 제안하는 모바일 GPU 가속 기법의 검증을 위해 OpenCL API 를 이용하여 구현하였다 실험 결과를 통해 제안하는 기법이 모바일 CPU 기반의 처리 방법 보다 800% 이상의 성능 향상을 있음을 확인하였다.

• The Journal of Engineering Geology
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• v.20 no.3
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• pp.231-242
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• 2010

In order to assess applicability of debris flow simulation on natural terrain in Korea, this study introduced the DEBRIS-2D program which had been developed by Liu and Huang (2006). For simulation of large debris flows composed of fine and coarse materials, DEBRIS-2D was developed using the constitutive relation proposed by Julien and Lan (1991). Based on the theory of DEBRIS-2D, this study selected a valley where a large debris flow was occurred on July 16th, 2006 at Deoksanri, Inje county, Korea. The simulation results show that all mass were already flowed into the stream at 10 minutes after starting. In 10minutes, the debris flow reached the first geological turn and an open area, resulting in slow velocity and changing its flow direction. After that, debris flow started accelerating again and it reached the village after 40 minutes. The maximum velocity is rather low between 1 m/sec and 2 m/sec. This is the reason why debris flow took 50 minutes to reach the village. The depth change of debris flow shows enormous effect of the valley shape. The simulated result is very similar to what happened in the field. It means that DEBRIS-2D program can be applied to the geologic and topographic conditions in Korea without large modification of analysis algorithm. However, it is necessary to determine optimal reference values of Korean geologic and topographic properties for more reliable simulation of debris flows.

• Corrosion Science and Technology
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• v.12 no.6
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• pp.274-279
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• 2013

Flow accelerated corrosion (FAC) of the carbon steel piping in nuclear power plants (NPPs) has been major issue in nuclear industry. During the FAC, a protective oxide layer on carbon steel dissolves into flowing water leading to a thinning of the oxide layer and accelerating corrosion of base material. As a result, severe failures may occur in the piping and equipment of NPPs. Effect of alloying elements on FAC of pipe materials was studied with rotating cylinder FAC test facility at $150^{\circ}C$ and at flow velocity of 4m/s. The facility is equipped with on line monitoring of pH, conductivity, dissolved oxygen(DO) and temperature. Test solution was the demineralized water, and DO concentration was less than 1 ppb. Surface appearance of A 106 Gr. B which is used widely in secondary pipe in NPPs showed orange peel appearance, typical appearance of FAC. The materials with Cr content higher than 0.17wt.% showed pit. The pit is thought to early degradation mode of FAC. The corrosion product within the pit was enriched with Cr, Mo, Cu, Ni and S. But S was not detected in SA336 F22V with 2.25wt.% Cr. The enrichment of Cr and Mo seemed to be related with low, solubility of Cr and Mo compared to Fe. Measured FAC rate was compared with Ducreaux's relationship and showed slightly lower FAC rate than Ducreaux's relationship.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.813-819
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• 1999

Inner crack-like pores with controlled amount of Ca impurity level in the high purity alumina single crystal sapphire had been created by micro-fabrication technique which includes ion implantation photo-lithography Ar ion milling and hot press technique. The morphological change and the healing of crack-like pore in the Ca doped high purity single crystal alumina during high temperature heat treatment in vacuum were observed using optical microscopy. The hexagonal bridging ligaments were developed and the size of hexagonal bridging ligaments had been increased with temperature and Ca amount and had grown to their corner rounded. It appeared that the hexagonal bridging ligaments would have an equilbrium size with temperature and the amount of Ca addition. Three kinds of crack-like pore healing type were observed. Edge regression and ligament growth were observed from relatively low temperature in the crack-like pore. Edge regression were found in almost all of the crack-like pore but the ligament growth were found only in the several crack-like pores accelerating heating very fast. Flow type healing was observed above $1800^{\circ}C$ and It healed the crack-like pore very slowly.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.E1
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• pp.1-14
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• 2004

Meteorological mechanisms in association with long-range transport of Asian dust in April 2001 have been investigated using weather maps, satellite images, TOMS and surface $PM_{10}$ data, backward trajectories, plus modeling output results (geopotential heights, horizontal wind vectors, potential temperatures, and streamlines). The results indicated that long -range transport of Asian dust to the west coast of North America was associated with strong westerlies between the Aleutian low and the Pacific high acting as a conveyor belt. Accelerating westerly flows due to cyclogenesis at the source regions over East Asia transported pollution from the continent to the central Pacific. When the system reached the Aleutian Islands, the intensity of troughs and the westerlies were amplified in the North Pacific. Thereafter the winds between the Aleutian Islands and the Pacific Ocean were more intensified from the air flow transport of the conveyor belt. Consequently, the strong wind in the conveyor belt enhanced the dust transport from the Pacific Ocean to the west coast of North America. This was evidenced by $PM_{10}$ concentration (maximum of about $100{\mu}g\;m^{-3}$) observed In California. Further evidence of the dust transport was found through the observation of satellite images, the distribution of TOMS aerosol index, and the analyses of streamlines and backward trajectories.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.1
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• pp.22-27
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• 2016

This experimental study deals with the mechanism of spoilers that cause scouring around pipelines. The design methodology was applied to spoilers for accelerating pipelines that undergo self-burial into the sand-bed and evaluated using approaching experimental analysis. The experimental study was conducted to investigate the self-burial ability of submarine pipelines with two types of sand-bed models: silt and sand. Spoilers of different heights were attached to the top of the pipeline for each experiment case. The relationship between the relative scour depth and spoiler height was evaluated by applying different flow velocities and sand diameters and comparative analysis was performed with values obtained from similarity experiments and theory. The experimental study will be useful in establishing a database for the design of spoilers.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.3
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• pp.115-125
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• 2020

This paper investigates the impact of working capital management on the firm's profitability. The research sample includes 119 non-financial listed companies on Vietnam stock market over a period of 9 years from 2010 to 2018. Two statistical approaches include Ordinary least squares (OLS) and fixed effects model (FEM) are employed to address econometric issues and to improve the accuracy of the regression coefficients. The empirical results show the negative and significant impacts of the working capital management, which measured by cash conversion cycle (CCC) and three components of the CCC including accounts receivable turnover in days (ARD), inventory turnover in days (INVD), and accounts payable turnover in days (APD) on the firm's profitability measured by return on assets (ROA) and Tobin's Q. It implies that firms can increase profitability by keeping the optimization of the working capital management measured by the CCC, which includes shortening the time to collect money from clients, accelerating inventory flow and hold the low payment time to creditors. Besides, the profitability of firms was impacted by the sale growth rate, firm size, leverage, and age. Therefore, this paper provides a new insight to managers on how to improve the firm's profitability with working capital management.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.9
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• pp.1095-1104
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• 1997

When a high-speed railway train enters a tunnel, a compression wave is generated ahead of the train and propagates along the tunnel, compressing and accelerating the rest air in front of the wave. At the exit of the tunnel, an impulsive wave is emitted outward toward the surrounding, which causes a positive impulsive noise like a kind of sonic boom produced by a supersonic aircraft. With the advent of high-speed train, such an impulsive noise can be large enough to cause the noise problem, unless some attempts are made to alleviate its pressure levels. For the purpose of the impulsive noise reduction, the present study investigated the effect of a vertical bleed duct on the compression wave propagating into a model tunnel. Numerical results were obtained using a Piecewise Linear Method and testified by experiment of shock tube with an open end. The results showed that the vertical bleed duct reduces the maximum pressure gradient of compression wave front by about 30 percent, compared with the straight tunnel without the bleed duct. As the width of the vertical bleed duct becomes larger, reduction of the impulsive noise is expected to be greater. However the impulsive noise is independent of the height of the vertical bleed duct.