• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.579-586
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• 2010

With the development of micrototal analysis systems (${\mu}TAS$), which is a result of enhancement of MEMS technology, rapid progress has been achieved in medical and biological research. The study of lab-on-a-chip (LOC) devices, which are types of ${\mu}TAS$ and which integrate the functions of mixing and analyzing tiny amounts of samples and reagents on one chip, has actively progressed. An LOC comprises microfluidic components such as micromixers and micropumps. Because the flow in a microfluidic system is generally laminar, it is very difficult to efficiently mix and feed fluid reagents. This paper presents the design and the method of fabrication of an MHD micropump for mixing fluids. By using this micropump, fluids are simultaneously mixed and pumped; this is achieved by coupling the Lorentz force and force exerted by an electric charge moving in an electric field.

• Particle and aerosol research
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• v.9 no.4
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• pp.261-269
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• 2013

The chemical mechanical polishing (CMP) process is widely used in semiconductor manufacturing process for planarization of various materials and structures. Point-of-use (POU) filters are used in most of the CMP processes in order to reduce the unwanted micro-scratches which may result in defects. The performance of the POU filter is depends on type and size of the abrasives used during cleaning process. For this reason, there is a need to evaluate POU filters for their filtration efficiency (FE) with different types of abrasives. In this study, we developed filter test system to evaluate the FE of POU using ceria and silica abrasives (slurry). The POU filter is roll type capsule filter with retention size of 0.2 ${\mu}m$. Two POU filters of different make are evaluated for FE. We observed that both POU filters show similar filtration efficiency for silica and ceria slurry. Results reveal that the ceria slurry and the colloidal silica particle are removed not only by mechanical way but also hydrodynamic and electrostatic interaction way.

• Korean System Dynamics Review
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• v.13 no.3
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• pp.47-66
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• 2012

This paper aims at investigating and identifying the factor that has led the back and forth relationship between China and the United States since 1989. Previous studies on this subject addressed the issue by taking either of two approaches: one with the micro view that interprets the back and forth relationship in the context of the end of the Cold war, on other hand, with the macro view that interprets the fragile relationship in the context of the rise of China. However, neither of the approaches explains with sufficiency the question at hand. Hence for the inquiry, this article suggests a fresh view by exploring alternative method of using a cognitive map of each nation's leader, Jiangzemin and Bill Clinton. This article provides an empirical analysis through the Selected works of Jiangzemin and the speeches of Bill Clinton in 1998 for the first time in the field of Sino-US relationship studies in Korea. With the results of the cognitive map analysis, we can reach the following four points. Firstly, indicators of the forth relationship between China and the US are: i) the recognition by Bill Clinton on the importance of China's economic growth and; ii) the US's cooperation of science technology with China. Second, the conflict between China and the US results from the discordance of opinions on the matter of human rights and military power. Second, the conflict will inevitably arise on environmental issues around the globe including a global warming. Third, while China has yet to find a legitimate reason to agree upon these issues with the US, the US urges China of its cooperation. Lastly, Both China and the US attach great importance to the alliance with Japan. This implicates that relatively, issues involving Japan take more control in the China-US relationship, than those of Korea Peninsula.

• Journal of Advanced Navigation Technology
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• v.21 no.2
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• pp.200-205
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• 2017

Modern sports are developing into sports science that incorporates science and various analytical simulation systems for improving records are being developed, and they are helping to improve actual game records. Therefore golf which is one of various sports events, has been popularized among the hobbyists and the general public and there is an increasing demand for correcting the movement attitude of the person. In response to these demands, many systems have been developed to analyze and correct golf swing postures. The golf swing accuracy analysis system analyzes the moments that can not be seen with the naked eye and guides them to understand easily. It can improve the golf swing motion through immediate feedback due to the visual effect. Using the knowledge of golf swing motion collected from golf swing video, we improved reliability. In addition, it provides the ability to visually check and analyze your golf swing video, allowing you to analyze each segment based on various golf swing classification methods.

• Journal of Power System Engineering
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• v.13 no.5
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• pp.95-102
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• 2009

A steam generator (boiler) in thermal power plants, consisting of more than 30,000 parts and components, can lead to the plant shutdown with damage to even the small part of the components; esp., like weld failures on boiler tubes. Consequently it is greatly demanded to improve the quality of the weld on the boiler tube for the stable operation of the power plants. Because of the feature of the welding, which is done past by melting the work pieces and adding a filler material that cools to become a strong coalescence, there is a great possibility that weld failures take place. As a result, it is regulated to make a non-destructive testing, like radiography test, to detect defects and flaws in the weld. The current film radiography test provides a lower image quality exceeding 2.0% of a basic quality level for a penetrameter, it is very likely to fail to detect micro defect. As a result, the prevention for the boiler tube failure has not been made effectively. In this study, computed radiography technology has been applied as a digital radiography test to the boiler tube weld, and Se-75 radiation source was used to improve the image quality, instead of Ir-192 source. As a result of this study, it is proven to save the time and cost for test and to enhance the quality level of penetrameter penetrating image, which enables to upgrade the quality of radiography test to the boiler tube weld.

• Journal of Powder Materials
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• v.22 no.6
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• pp.426-431
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• 2015

Microstructural examination of the Nb-Si-B alloys at Nb-rich compositions is performed. The Nb-rich corner of the Nb-Si-B system is favorable in that the constituent phases are Nb (ductile and tough phase with high melting temperature) and $T_2$ phase (very hard intermetallic compound with favorable oxidation resistance) which are good combination for high temperature structural materials. The samples containing compositions near Nb-rich corner of the Nb-Si-B ternary system are prepared by spark plasma sintering (SPS) process using $T_2$ and Nb powders. $T_2$ bulk phase is made in arc furnace by melting the Nb slug and the Si-B powder compact. The $T_2$ bulk phase was subsequently ball-milled to powders. SPS is performed at $1300^{\circ}C$ and $1400^{\circ}C$, depending on the composition, under 30 MPa for 600s, to produce disc-shaped specimen with 15 mm in diameter and 3 mm high. Hardness tests (Rockwell A-scale and micro Vickers) are carried out to estimate the mechanical property.

• Archives of design research
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• v.17 no.3
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• pp.123-132
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• 2004

This paper shows a study on the "Korean High Speed Train Design" method, its design process and the result in the form of aerodynamic optimal exterior design development of a prototype test train(HSR 350${\times}$). It was developed from 1996 until 2002, six years long in R '||'&'||' D project titled "Development of High Speed Railway Technology" The end result of the project is a prototype test train, which has two power cars, two motorized trailers and three trailers, had been tested successfully in the year 2003 to the highest speed limit 380km/h on high speed line. The improved conceptual design work of a new commercial train and next generation's train is also performed for future needs.uture needs.

• Journal of the Korean Society of Safety
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• v.26 no.4
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• pp.41-46
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• 2011

The purpose of this paper is to analyze the causes of accidents related to the 3 phase 170 kV gas insulated switchgear of a power system collected from accident sites to secure data for the prevention of similar accidents and provide important points of view regarding diagnosis for the prevention of accidents involving gas insulated switchgears. The analysis results of the causes of accidents involving gas insulated switchgears showed deformation of the manipulation lever installed at the S-phase, disconnection of the insulation rod connection, melting of the upper conductor, a damaged tulip, damage to the lower spacer and the spacer at the breaker, etc. It is believed from this result that the potential for accidents has expanded due to accumulated energy as a result of repeated deterioration. The carbonization depth of a GIS was formed near the screw (T2, T3) used to secure the lower pole of the S-phase tulip. It is not known what has caused the screws to be extruded and melted. However, it is thought that an unbalanced electromagnetic force, micro-discharge, surface discharge, etc., have occurred at that point. In addition, even though 16 years have passed since its installation, there was no installation defect, act of arson, accidental fire, etc. General periodical inspection and diagnosis failed to find the factors causing the accidents. As a system contained in a closed metal container, it has a high risk factor. Therefore, it is necessary to design, install and operate a GIS in accordance with the standard operational procedure (SOP). In addition, it is necessary to apply conversion technology for periodical SF6 gas analysis and precision safety diagnosis. It is expected that tracking and managing these changes in characteristics by recording the results on the history card will provide a significant accident prevention effect.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.3
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• pp.331-340
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• 2021

As the communication industry develops, the development of SoC (System on Chip) is increasing. Accordingly, the paradigm of technology design of industries and companies is changing. In the existing process, companies purchased micro-architecture, but now they purchase ISA (Instruction Set Architecture), and companies design the architecture themselves. RISC-V is an open instruction set based on a reduced instruction set computer. RISC-V is equipped with ISA, which can be expanded through modularization, and an expanded version of ISA is currently being developed through the support of global companies. In this paper, we present benchmarking frameworks ARIA, LEA, and PIPO of Korean block ciphers in RISC-V. We propose implementation methods and discuss performance by utilizing the basic instruction set and features of RISC-V.

• Journal of Space Technology and Applications
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• v.1 no.3
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• pp.364-374
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• 2021

This research discusses the change in radio frequency (RF) characteristics according to the number of Gores on the deployable mesh antennas for potential micro-satellite applications. The deployable type of lightweight mesh antenna can be used for various space missions such as communication/SAR/ SIGINT. In order to implement an ideal curvature of antenna surface, sufficient number of antenna rib structures are required. However, the increase in antenna ribs affects various design factors of the antenna system, especially total system mass, complexity of deployable mechanism and reliability. In this paper, the proper number of ribs for the mesh antenna were derived by comparison of electro-magnetic (EM) simulation results of example of antenna model in accordance with the various number of ribs.