• International Journal of Ocean System Engineering
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• v.3 no.3
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• pp.111-115
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• 2013

Blasius equation describes the boundary layer formed over a flat plate inside a fluid and this equation is solved numerically by the method of moments which is a type of weighted residual methods. Compared to the traditionally used Runge - Kutta Method, Method of Moments propose a direct solution to Blasius Equation which makes it easier to solve. The obtained solutions show good agreement with the results found in literature and this study aims to demonstrate the power of the method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.79-80
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• 2019

This study was intended to examine the possibility of reducing hydration heat by FA substitution and combination of slag (CGS) from coal gasification power generation (IGCC) with mixed aggregate for concrete. The analysis results showed good results if liquidity increases as the ratio of CGS increases, air volume decreases, and compressive strength is mixed up to 25% in the residual aggregate. The results showed that the heat of hydration was reduced compared to plain due to the boron content of CGS as the CGS substitution rate increased, but it was larger due to the combination with FA substitution. It was found that the heat of hydration was reduced.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.43-48
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• 2019

We design a reconfigurable optical node for metropolitan WDM networks, and numerically study the capability of the node in the optical signal level. Unlike a long-haul WDM system, major limitations of metropolitan WDM systems are power loss, fiber dispersion and optical signal-to-noise ratio(OSNR) degradation due to EDFAs. Therefore, we include the behaviors of transmitter and receiver, and fiber, EDFAs, and optical filters(MUX/DeMux) in numerical simulations with varying parameters over wide range. From simulation results, we can identify the maximum span numbers for OC-48 and OC-192 to achieve $BER<10^{-12}$ using the node structure at various received powers and residual dispersions.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.1-5
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• 2021

Among elemental metals, niobium (Nb) has the highest superconducting transition temperature (T_c) at ambient pressure. Thus, Nb films have been used in superconducting electronics and radio frequency cavity applications. In this study, the depositional factors determining the crystallinity and T_c of Nb films were investigated. An Nb film grown at a sputtering temperature of 240℃ exhibited the maximum crystallinity of Nb and the minimum crystallinity of niobium oxide. X-ray photoelectron spectroscopy confirmed a maximum atomic percent of niobium and a minimum atomic percent of oxygen. A sputtering power of 210 W and a sputtering time of 50 min were the optimal conditions for Nb deposition, and the T_c of the optimized film (9.08 K) was close to that of bulk Nb (9.25 K). Transmission electron microscopy images of the thick film directly confirmed the removal of the typical in-plane compressive strain in the (110) plane caused by residual stress.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.784-791
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• 2019

In the present study, a series of tungsten austenitic stainless steel alloys have been developed by interchanging the molybdenum in standard SS316 by tungsten. This was done to minimize the long-life residual activation occurred in molybdenum and nickel after decommissioning of the power plant. The microstructure and mechanical properties of the prepared alloys are determined. For the sake of increasing multifunction property of such series of tungsten-based austenitic stainless steel alloys, gamma shielding properties were studied experimentally by means of NaI(Tl) detector and theoretically calculated by using the XCOM program. Moreover, fast neutrons macroscopic removal cross-section been calculated. The obtained combined mechanical, structural and shielding properties indicated that the modified austenitic stainless steel sample containing 1.79% tungsten and 0.64% molybdenum has preferable properties among all other investigated samples in comparison with the standard SS316. These properties nominate this new composition in several nuclear application domains such as, nuclear shielding domain.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.31-37
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• 2019

This study investigates the effects of long-term artificial-aging on hardness variation in the dissimilar metal weldments for nuclear power plant facilities. These dissimilar welds are inevitably required to join the components in nozzle parts of pressurized vessels, such as austenitic stainless steels and ferritic steels. A artificial thermal aging was conducted in an electrical furnace to simulate material degradation at high temperatures. The test materials were held at the temperature of $600^{\circ}C$ for 10000 hours and interrupted at various levels of degraded specimens. The degradation of hardness is a well-known phenomenon resulting from long-term aging or high-temperature degradation of structural materials. In this study, the variation of hardness at each position was different, and complicated in relation to microstructures such as twins, grains, precipitates, phase transformations, and residual stresses in dissimilar weldments. We discussed the variation of hardness in terms of microstructural changes during long-term aging.

• Journal of Environmental Science International
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• v.30 no.7
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• pp.597-604
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• 2021

The International Maritime Organization (IMO) ballast water management agreement (International Convention for the Control and Management of Ship's Ballast Water and Sediments) came into force on September 8, 2017. This study evaluated the disinfection performance of electrolysis, UV treatment, and electrolysis + UV combined, to improve the treatment of zooplankton (size ≥ 50 ㎛), which is expected to strengthen the standards for biodegradation efficiency. Among the methods used, the disinfection time leading to 100% death was in the order: electrolysis > electrolysis + UV > UV process. For the same level of disinfection performance, the amount of electricity required for the electrolysis, UV, and electrolysis + UV processes were 1,300 W.s, 8,400 W.S, and 4,500 W.s, respectively. The combination of electrolysis + UV process for inactivation of zooplankton in ballast water did not show a synergic effect owing to the slow disinfection time and high power consumption.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.7-9
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• 2020

국내 가정용 단상 태양광인버터의 주류는 3kW급으로 그린홈보급사업, 태양광 대여사업 및 여러지원사업, 자가설치 사업 등에 사용되고 있고, 100kW 태양광발전소에 설치되는 경우도 있다. 당사에서 전력변환 효율, 전력밀도 및 신뢰성 향상을 위해 개발하였으며, 추가적으로 요구되는 직류 지락 검출 및 Residual Current 검출 기능 구현을 목표로 개발한 3kW급 계통연계형 태양광 인버터의 특징 및 태양광인버터 개발에 있어 필요한 고려요소를 소개한다.

• Bulletin of the Korean Mathematical Society
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• v.61 no.3
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• pp.785-796
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• 2024

Let p be a prime. A group G is said to be residually p-finite if for each non-trivial element x of G, there exists a normal subgroup N of index a power of p in G such that x is not in N. In this note we shall prove that certain HNN extensions of free abelian groups of finite rank are residually p-finite. In addition some of these HNN extensions are subgroup separable. Characterisations for certain one-relator groups and similar groups including the Baumslag-Solitar groups to be residually p-finite are proved.

• Journal of the Korea Society of Computer and Information
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• v.25 no.1
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• pp.55-61
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• 2020

With the development of deep learning technology and advances in computing power, video-based research is now gaining more and more attention. Video data contains a large amount of temporal and spatial information, which is the biggest difference compared with image data. It has a larger amount of data. It has attracted intense attention in computer vision. Among them, motion recognition is one of the research focuses. However, the action recognition of human in the video is extremely complex and challenging subject. Based on many research in human beings, we have found that artificial intelligence-like attention mechanisms are an efficient model for cognition. This efficient model is ideal for processing image information and complex continuous video information. We introduce this attention mechanism into video action recognition, paying attention to human actions in video and effectively improving recognition efficiency. In this paper, we propose a new 3D residual attention network using convolutional neural network based on two attention models to identify human action behavior in the video. An evaluation result of our model showed up to 90.7% accuracy.