• 전기의세계
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• v.27 no.2
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• pp.64-68
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• 1978

By applying the streamer breamer breakdown criterion and the surface roughness factor, the effet of field distortion due to conductor surface roughness on breakdown is investigated theoretically in a uniform-field of compressed SF$_{6}$. It has been shown that the streamer constant has a significant influence on the threshold of breakdown and different shapes of protrusions do not result in different thresholds of breakdowns. Moreover, uniform-field tests can give results which apply to e-ratio coaxial-electrode systems of practical dimensions, and may offer some advantages compared with coaxial-electrode tests.s.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.903-904
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• 2006

In recent years, the research in porous metal got rapid development in China, especial in Northwest Institute for Non-ferrous Metal Research (NIN). Many porous metals with different raw material and different shapes were developed, which successfully employed in many fields. We believe we will earn more rapid development in the future.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.455-456
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• 2008

A numerical study was conducted on the effect of flame holder which could be added to the inlet duct of Integral Rocket-Ramjet. Two different types of flame holder installations, flame holder without sudden expansion region and flame holder with small sudden expansion region, were compared and showed different flame shapes and pressure rise in the combustor.

• Fashion & Textile Research Journal
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• v.20 no.3
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• pp.331-342
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• 2018

This paper enables stakeholders involved in textile industry to gain an overview of standards used for care labelling and help establish a common standard that could be used as a universal standard. This study provides a comprehensive and detailed analytical study of care labelling standards adopted by common countries in the textile market. It was found that the development of a universal system for care labeling could enhance the trade of textile articles and assist consumers in caring for textile articles. Universal care label systems could be characterized by two main features of inclusiveness and comprehensiveness. The range of instructions and symbols presented were found different among standards. Insignificant differences in symbols' shapes were found between standards for bleaching, ironing and professional cleaning. The washing process had the widest variety of instructions; in addition, options were provided by stated standards. Different meanings were found for similar shapes in some tumble drying symbols. The study findings show the importance of enhancing text based standards or the development of an understandable format across as many cultures as possible. The unification of symbols and meanings may be needed to provide global consumers consistent guidance. The efficiency of a detailed standard that provides and covers a wide range of instructions is an important aspect. The visibility and practicality of offering variable options/symbols in one standard is an important aspect for developing a universal care label system.

• East Asian mathematical journal
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• v.28 no.2
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• pp.109-133
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• 2012

In this research, I selected a Singapore elementary mathematics textbook which substantially reflects Singapore curriculum, and compared it with Korean one to understand how they differ in the contents system of the curriculum focused on the contents of the geometry and measurement strand, and analyzed their common points and different points intensively with textbooks for sixth-grade students. Also, I translated a chapter of the textbook, 'Mathematics in Action'. That chapter was about circumference and the area of the circle which is related to the shapes part. Then, I taught it to the experimental group to compare their achievement and the change of reaction to studying the shape-related parts with those of the control group. The results are the followings. First, when we analyze the contents of shape-related part of the textbooks for sixth-grade students of both countries, Singaporean textbook contains more contents that are introduced for the first time, which implies that it is more desirable to teach new concepts of shapes when students are in their higher grades. Second, as for the way they develop the activity of each chapter, Korean textbook sticks to a uniform way, while the Singapore textbook uses various ways for different subjects and grades. In addition, when they organize the contents of the textbook, they emphasize the importance of student's activity and lead students with various methods by suggesting several questions and situations.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1737-1742
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• 2014

In this research, we further developed the one-step seed mediated method to synthesize gold nanoparticles (GNPs) and control their resulting shapes to obtain hexagonal, triangular, rod-shaped, and spherical gold nanostructures. Our method reveals that the reaction kinetics of formation of GNPs with different shapes can be controlled by the rate of addition of ascorbic acid, because this is the critical factor that dictates the energy barrier that needs to be overcome. This in turn affects the growth mechanism process, which involves the adsorption of growth species to gold nanoseeds. There were also observable trends in the dimensions of the GNPs according to different rates of addition of ascorbic acid. We performed further analyses to investigate and confirm the characteristics of the synthesized GNPs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2101-2107
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• 2012

A current velocity measurement radar for a river or a stream estimates Doppler frequencies of return echoes to extract the corresponding surface velocity information. It is very important to maintain the reliability and accuracy of these velocity estimates for water resource management such as flooding or drought conditions. However, received Doppler spectra of water surface return echoes have very widely varying shapes according to different measurement environments and weather conditions. Therefore, serious problems may arise in maintaining the reliability and accuracy of velocity estimating algorithm in a radar sensor because of Doppler spectra which can have many different kind of shapes. Therefore, in this paper, an appropriate Doppler spectrum model is suggested to simulate many various Doppler spectra. This model can be very useful in validating the reliability and accuracy of surface velocity estimates.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.2027-2033
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• 2003

The purpose of this study is to investigate the stratification of fuel vapor with different in-cylinder flow, piston cavity and injection timings in an optically accessible engine. Three different piston shapes that are F(Flat), B(Bowl) and R(Re-entrance) types were used. The images of liquid and vapor fuel were captured under the motoring condition using Laser Induced Exciplex Fluorescence technique. As a result, at early injection timing of 270 BTDC, liquid fuel was evaporated faster by tumble flow than swirl flow, where most of fuel vapor were transported by tumble flow to the lower region and both sides of cylinder for the F-type piston. At late injection timing of 90 BTDC, tumble flow appears to be moving the fuel vapor to the intake side of the cylinder, while swirl flow convects the fuel vapor to the exhaust side. The concentration of mixture in the center region was highest in the B-type piston, while fuel vapor was transported to the exhaust side by swirl flow in F and R-type pistons. At the injection timing of 60 BTDC, the R-type piston was better for stratification due to a relatively smaller bowl diameter than the others.

• Smart Structures and Systems
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• v.3 no.4
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• pp.475-494
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• 2007

This paper deals with the development of an innovative distributed construction system based on smart prefabricated concrete elements for the real-time condition assessment of civil infrastructure. So far, two reduced-scale prototypes have been produced, each consisting of a $0.2{\times}0.3{\times}5.6$ m RC beam specifically designed for permanent instrumentation with 8 long-gauge Fiber Optic Sensors (FOS) at the lower edge. The sensing system is Fiber Bragg Grating (FBG)-based and can measure finite displacements both static and dynamic with a sample frequency of 625 Hz per channel. The performance of the system underwent validation in the laboratory. The scope of the experiment was to correlate changes in the dynamic response of the beams with different damage scenarios, using a direct modal strain approach. Each specimen was dynamically characterized in the undamaged state and in various damage conditions, simulating different cracking levels and recurrent deterioration scenarios, including cover spalling and corrosion of the reinforcement. The location and the extent of damage are evaluated by calculating damage indices which take account of changes in frequency and in strain-mode-shapes. The outcomes of the experiment demonstrate how the damage distribution detected by the system is fully compatible with the damage extent appraised by inspection.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.4
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• pp.313-319
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• 2007

The effect of capillary cross-section geometry on evaporation is investigated in terms of the meniscus shape, evaporation rate and evaporation-induced flow for circular, square and rectangular cross-sectional capillaries. The shapes of water and ethanol menisci are not much different from each other in square and rectangular capillaries even though the surface tension of water is much larger than that of ethanol. On the other hand, the shapes of water and ethanol menisci are very different from each other in circular capillary. The averaged evaporation fluxes in circular and rectangular capillaries are measured by tracking the meniscus position. At a given position, the averaged evaporation flux in rectangular capillaries is much larger than that in circular capillary with comparable hydraulic diameter. The flow near the evaporating meniscus is also measured using micro-PIV, so that the rotating vortex motion is observed near the evaporating ethanol and methanol menisci except for the case of methanol meniscus in rectangular capillary. This difference is considered to be due to the existence of corner menisci at the four comers.