• Proceedings of the KWS Conference
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• 2006.05a
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• pp.195-197
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• 2006

The present study examined the characteristics of high speed welding thin metal sheet using single mode fiber laser of averaged maximum output power 300 W. Due to the fiber laser that has a good quality of beam can make a very small focusing beam size, thin metal sheet welding and high speed key hole welding can be peformed by high power density.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.40-41
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• 2003

(self-focusing)을 이용한 커렌즈 모드록킹(Kerr-lens mode-locking； KLM) 방법을 이용하면 간단한 구조를 갖는 공진기로 100 펨토초(femto=10-13) 미만의 레이저 펄스를 생성할 수 있다. KLM 티타늄사파이어(Ti：sapphire) 레이저의 발달로 10 펨토초 영역의 레이저 펄스를 간단하게 생성할 수 있게 되었으며 특히, 넓은 스펙트럼 폭을 가지는 처프거울(chirped mirror)의 사용과 정확한 분산의 보정을 통한 5 펨토초(800 nm 파장의 두 주기에 해당) 영역의 레이저 펄스 생성도 보고되고 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.223-226
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• 2017

With the development of information technology, users are provided with information they want through mobile device in various situations. When users communicate with information, there is interaction through gesture activities such as tapping and experience in the process. Experience through interaction in mobile affect the user's psychology. This is important because it is related to the behavior of the user in the future. Various types of information presentation methods have been researched in mobile environment. However, there are more research focusing on functional interactivity. The purpose of this study is to investigate the effect of interaction and usage mode on satisfaction, usefulness, and intention to use for sound text presentation that is user-centered. As variables for my study, there are two factors which are interactivity and usage mode. The interactivity type is composed of two ways that are: High and Low depending on modality and message interactivity; and the usage mode is composed of Action mode and Goal mode depending on whether user has a task or not. The experimental design is $2{\times}2$. The same content is provided in (a) only Modality interactivity, and (b) Modality and Message interactivity are provided. Depending on usage mode, (a) Action mode is processed without a specific task, and (b) Goal mode is performed with a specific task to participants. The experimental study demonstrated that there is a difference in satisfaction, usefulness, and intention to use depending on the difference of interaction and usage mode when providing information in mobile environment. The results of this study are summarized as follows: interaction and usage mode have significant influence on mobile user's satisfaction, usefulness, intention to use.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.53.2-53.2
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• 2015

Fiber Bragg gratings (FBGs) are the most compact and reliable method of suppressing atmospheric emission lines in the infrared for ground-based telescopes. It has been proved that real FBGs based filters were able to eliminate 63 bright sky lines with minimal interline losses in 2011 (GNOSIS). Inscribing FBGs on multi-core fibers offers advantages. Compared to arrays of individual SMFs, the multi-core fiber Bragg grating (MCFBG) is greatly reduced in size, resistant to damage, simple to fabricate, and easy to taper into a photonics lantern (PRAXIS). Multi-mode fibers should be used and the number of modes has to be large enough to capture a sufficient amount of light from the telescope. However, the fiber Bragg gratings can only be inscribed in the single-mode fiber. A photonic lantern bi-directionally converts multi-mode to single-mode. The number of cores in MCFBGs corresponds to the mode. For a writing system consisting of a single ultra-violet (UV) laser and phase mask, the standard writing method is insufficient to produce uniform MCFBGs due to the spatial variations of the field at each core within the fiber. Most significant technical challenges are consequences of the side-on illumination of the fiber. Firstly, the fiber cladding acts as a cylindrical lens, narrowing the incident beam as it passes through the air-cladding interface. Consequently, cores receive reduced or zero illumination, while the focusing induces variations in the power at those that are exposed. The second effect is the shadowing of the furthest cores by the cores nearest to the light source. Due to a higher refractive index of cores than the cladding, diffraction occurs at each core-cladding interface as well as cores absorb the light. As a result, any core that is located directly behind another in the beam path is underexposed or exposed to a distorted interference pattern from what phase mask originally generates. Technologies are discussed to overcome the problems and recent experimental results are presented as well as simulation results.

• Journal of radiological science and technology
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• v.22 no.2
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• pp.33-39
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• 1999

This paper included a data analysis of the unit of medical devices using mainternance recording card that had medical devices of unit failure mode, hospital of failure mode and MTBF. The results of the analysis were as follows : 1. Medical devices of unit failure mode was the highest in QC/PM such A hospital as 33.9%, B hospital 30.9%, C hospital 30.3%, second degree was the Electrical and Electronic failure such A hospital as 23.5%, B hospital 25.3%, C hospital 28%, third degree was mechanical failure such A hospital as 19.5%, B hospital 22.5%, C hospital 25.4%. 2. Hospital of failure mode was the highest in Mobile X-ray device(A hospital 62.5%, B hospital 69.5%, C hospital 37.4%), and was the lowest in Sono devices(A hospital 16.76%, B hospital 8.4%, C hospital 7%). 3. Mean time between failures(MTBT) was the highest in SONO devices and was the lowest in Mobile X-ray devices which have 200 - 400 failure hours. 4. Anverage failure ratio was the highest in Mobile X-ray devices(A hospital 31.3%, B hospital 34.8%, C hospital 18.7%), and was the lowest in Sono(Ultrasound) devices (A hospital 8.4%, B hospital 4.2%, C hospital 3.5%). 5. Failure ratio results of medical devices according to QC/PM part of unit failure mode were as follows ; A hospital was the highest part of QC/PM (50%) in Mamo X-ray device and was the lowest part of QC/PM(26.4%) in Castro X-ray. B hospital was the highest part of QC/PM(56%) in Mobile X-ray device, and the lowest part of QC/PM(12%) in Gastro X-ray. C hospital was the highest part of QC/PM(60%) in R/F X-ray device, and the lowest a part of QC/PM(21%) in Universal X-ray. It was found that the units responsible for most failure decreased by systematic management. We made the preventive maintenance schedule focusing on adjustement of operating and dust removal.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.1
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• pp.8-18
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• 2024

The present study concerns reduced order modeling of a marine diesel engine, which can be used for outlier detection in status monitoring and carbon intensity index calculation. Principal Component Analysis (PCA) is introduced for the reduced order modeling, focusing on the feasibility of detecting and treating nonlinear variables. By cross-correlation, it is found that there are seven non-linear data channels among 23 data channels, i.e., fuel mode, exhaust gas temperature after the turbocharger, and cylinder coolant temperatures. The dataset is handled so that the mean is located at the nominal continuous rating. Polynomial presentation of the dataset is also applied to reflect the linearity between the engine speed and other channels. The first principal mode shows strong effects of linearity of the most data channels to show the linearity of the system. The non-linear variables are effectively explained by other modes. second mode concerns the temperature of the cylinder cooling water, which shows small correlation with other variables. The third and fourth modes correlates the fuel mode and turbocharger exhaust gas temperature, which have inferior linearity to other channels. PCA is proven to be applicable to data given in binary type of fuel mode selection, as well as numerical type data.

• The Mathematical Education
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• v.61 no.4
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• pp.597-612
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• 2022

Recently, large-scale mathematics assessments are shifting from traditional paper-based tests to computer-based tests, nationally and internationally. This study explored the mode effect (the difference in student achievement by the change of test mode) according to the types of test items, the technological function reflected in the items, the characteristics of students' computer use, and the computer-based test environment. To this end, we analyzed the results of the 2020 national assessment of educational achievement of high school mathematics conducted on a paper and computer basis. As a result, firstly, the mode effect induced by the mode transition was generally insignificant, but the mode effect was larger in the extended response type than other types. Secondly, there were differences in the mode effect according to the transition to test with computer mode where innovative items were added. Thirdly, the difference between mode effects was statistically significant according to the student's sense of efficacy in computer use. The results of this study suggest that innovative items should be introduced deliberately according to the targeted content and competency in evaluation, and that assessment design and environment preparation need to be carefully developed so that nonessential abilities other than students' mathematical ability or incidental situation do not distort the assessment results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.976-979
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• 2002

A focusing grating coupler (FGC) was not fabricated by the 'Continuous Path Control' writing strategy but by an electron-beam lithography system of more general exposure mode, which matches not only the address grid with the grating period but also an integer multiple of the address grid resolution (5 nm), To more simplify the fabrication, we are able to reduce a process step without large decrease of pattern quality by excluding a conducting material or layer such as metal (Al, Cr, Au), which are deposited on top or bottom of an e-beam resist to prevent charge build-up during e-beam exposure. A grating pitch period and an aperture feature size of the FGC designed and fabricated by e-beam lithography and reactive ion etching were ranged over 384.3 nm to 448.2 nm, and $0.5{\times}0.5mm^2$ area, respectively, This fabrication method presented will reduce processing time and improve the grating quality by means of a consideration of the address grid resolpution, grating direction, pitch size and shapes when exposing. Here our investigations concentrate on the design and efficient fabrication results of the FGC for coupling from slab waveguide to a spot in free space.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.1
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• pp.47-55
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• 2012

A structural health monitoring technique for locating impact position in a plate structure is presented in this paper. The method employs a single sensor and spatial focusing of time reversal (TR) acoustics. We first examine the TR focusing effect at the impact position and its surroundings through simulation and experiment. The imaging results of impact points show that the impact source location can be accurately estimated in any position of the plate. Compared to existing techniques for locating impact or acoustic emission source, the proposed method has the benefits of using a single sensor and not requiring material properties and geometry of structures. Furthermore, it does not depend on a particular mode of dispersive Lamb waves that is frequently used in other ultrasonic testings of plate-like structures.

• Journal of the Korean Society of Fashion and Beauty
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• v.1 no.1 s.1
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• pp.65-78
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• 2003

This research is to provide practical help in learning hair and makeup illustration skills by presenting techniques for hair and makeup drawing; to serve efficient illustration education; and to enhance the status of beauty and contribute to artistic development. Hair style and makeup techniques include graphical one, pattern-centered one, one using pattern paper, simplifying one and mood one expressing image. Of them, this research made the illustrations to use cosmetics, color pencils and pastel based on the graphical technique. for each design of the illustrations, ethnic, sexy, natural, romantic and gorgeous images, which were considered to be appropriate to the graphical technique, were chosen by the researcher out of hair and makeup styles that appeared in the fashion magazines including Vogue, Gap, Mode et Mode from 2000 through 2001. In particular, they were chosen with focusing on basic styles. The summaries below were found with the experience of making illustrations. Various techniques and skills are required to express the ideas of hair and makeup styles. Of them, the graphical technique is very useful as the primary step to learn various techniques and improve drawing skills. First, the graphical technique may enable not only expressing what is desired to draw as is, but also accurately representing hair and makeup designs so as to convey objective expression. In this regard, it is a proper way to achieve its inherent purpose as conveyance of messages. Second, more accurate styling of hair and makeup is available through graphical expression, which helps understand related practical techniques. In addition, makeup illustration, which is expressed through direct makeup products and instruments, may serve skill improvement since such direct use provides the feeling of real makeup. Third, the graphical technique as a basic drawing skill may unrestrictedly show the artist's expression ability. Fourth, although artistic merits implying individuality and creativity should be shared through illustrations that express the artist's ideas or emotions, the graphical technique is the easiest method to beginners who just started learning of illustration, in that it enables expression without highly advanced skills.