• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.21.4-22
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• 2011

IVS (International VLBI Service for Geodesy and Astrometry) 통합분석센터는 개별 IVS 분석센터의 산출물을 통합하고 그 결과물을 IERS (International Earth Rotation and Reference Systems Service)에 제공하여 국제 지구기준좌표계를 구축하고 지구회전파라미터를 결정하는데 핵심적인 역할을 한다. 한국천문연구원(KASI)은 2008년 10월 IVS 통합분석센터로 선정되어 현재 통합 분석 시스템을 구축하고 있다. 정규운영에 앞서 통합용 분석 소프트웨어를 정비하고, KASI 통합분석센터의 통합해를 타 IVS 통합분석센터 통합해와 비교 검증하는 것은 필수적이다. 이 연구에서는 통합분석처리를 위해서 GPS 자료처리 소프트웨어인 Bernese 5.0을 IVS 산출물 형식에 맞추어 수정 보완한 후 활용한다. 이 발표에서는 1984년부터 현재까지의 IVS 분석센터의 장기간 산출물을 수집하고 Bernese 5.0을 이용하여 지구회전파라미터(X-극, Y-극, UT1-UTC와 각각의 시간변화율)의 통합해를 산출한 결과를 소개한다. 또한, 타 IVS 통합분석센터의 통합해와 비교 검증결과를 논한다.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.779-784
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• 2002

Porous concrete with a great deal of continuous porosity enables to contain water and to pass air freely through firmly hardened material, and allow necessary nutrients to reach roots of vegetation. Therefore, this paper deals with the voluntary properties and efficiency for planting of plant porous concrete. The results of experiment showed that void volumes were 17% to 31%, and compressive strength ranged between 80kgf/cm$^2$ and 180kgf/cm$^2$ when the ratio of the paste to aggregate was 0.3-0.5 When the aggregate size are 20-30mm, the paste to aggregate ratio is 0.3, and the length of Paranial Ryegress came up as 32cm. Ut supra the efficiency of planting goes through Paranial Ryegrass in result the length of plant are in compliance with void volume and aggregate size.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.359-364
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• 2004

This paper deals with the comparison of signal processing techniques of ultrasonic data. The goal of signal processing is the ultrasonic speckle suppression and the visibility enhancement of flaw-reflected ultrasonic echo. The performance of conventional SSP(split spectrum processing) method and the wavelet denoising method are compared and discussed for tested ultrasonic data. Tested ultrasonic data obtained from the weld area of centrifugal-casted stainless steel material and safe-ending material with holes and notch of variable depths are presented. In experimental results, the outputs of wavelet-based denoising method show the clear and sharp peaks at the positions of flaw-reflected echos comparing with those of SSP method.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.129-132
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• 2001

Recently, a ZVT boost converter is embedded in a power factor correction system. The control circuit of the converter assures soft-switching for all the MOSFETs and load regulation. The PFC system contains additional control circuits which assure the input voltage in a sinusoidal form and feed-forward line voltage regulation. In this paper, a soft switching boost converter with zero-voltage transition(ZVT) main switch using zero-current switching(ZCS) auxiliary switch is proposed. Operating intervals of the converter are persented and analyzed. The proposed results show that the main switch maintains UT while auxiliary switch retains ZCS for the complete specified line and load conditions.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1702-1707
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• 2007

The reduction of pipe-thickness induced by flow accelerated corrosion (FAC) is one of the most serious problems on the maintenance of piping system in nuclear power plants (NNP). If the thickness of a pipe component is reduced below the critical level, it cannot sustain pressure and consequently results in leakage or rupture. For this reason, wall thinning by FAC has been inspected in secondary side piping systems in NPPs. In this research Round Robin Test (RRT) was conducted to verify confidence of wall thinning measurement system in NPP. 12 inspectors from 3 companies participated and 23 specimens were used according to standard practice in RRT. The gage R&R analysis was introduced in regard to repeatability and reproducibility that are affected to measurement system errors. Confidence intervals of thickness measurement system were obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.3-7
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• 1995

Force generated during grinding process causes elastic defomation. The effect of this deforms a workpiecs. So grinding system is explainable using the concept of macining elasticity phenomenon. Machining elasticity is defined as ratio between the true depth of c ut, and an importnat factor to affect material removal mchanism and productivity. Generally, to produce accurate surface and dimensionally precise components operators depend on their experiences. Because of these, productivity is reduced and time is wasted. The objective of this reserch is to study the effect of grinding conditions, such as table speed, depth of cut on the machining elasticity parameter.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.279-286
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• 2000

The stud bolts tend to degrade faster by high temperature(over 45$0^{\circ}C$). Therefore, replacement cycle inspection of stud bolts were carried out various method such as ultrasonic test(UT), magnetic test(MT), wobble test, visual test and hardness test. Especially, wobble test method has been applied to determine replacement evaluation criteria of stud bolt after long time operation. We applied three different methods on the three site and the obtained data are compared with the results from the evaluation methods. From the results, the replacement criteria for stud bolts under high temperature in power plants are proposed.

• Broadcasting and Media Magazine
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• v.7 no.3
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• pp.83-93
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• 2002

본 고에서는 최근 표준화가 진행 중인 H.26L 부호기의 화면내 예측기법에 대해서 살펴보고자 한다 기존의 H.261, MPEG-1, MPEG-2등에서는 블록별로 독립적으로 UT 기반의 변환부호화를 수행하였으나, H.261의 화면내 부호화 방식은 공간 예측 및 정수형 변환을 사용한다. 또한, H.261에서 시작해서, MPEG-4에 이르기까지 지속적으로 사용되어 온 8x8화소 블록과는 달리 4x4또는 16x16단위의 처리, 휘도 성분과 색도 성분의 독립적인 처리 등 많은 새로운 부호화 방식이 도입되었다. 효과적인 예측 모드 부호화를 위해 주변 블록의 모드들을 이용한 예측 부호화 방식이 도입되었다. 기존의 가장 대표적인 화면내 부호화기인 H.263에 비해서 H.26L방식이 같은 화질에서 약40%의 추가적인 압축 효과가 있음을 확인하였다.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.5 no.2
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• pp.7-12
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• 2009

The flaws detected by the non-destructive surface test methods shall be sized by means of the volumetric test such as an UT(ultrasonic test) or an ECT(eddy current test) for the purpose of analyzing and repairing them. It is generally known that the ECT is a comparatively effective technique for the small size cracks which are located shallowly from the surface. On this study, the ECT technique was tried to size the depth of the crack-like EDM notches, and it is identified that the ECT is an appropriate depth sizing technique for the shallow cracks less than 3mm in the Martensitic CA6NM material.

• Journal of the Korean Society of Systems Engineering
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• v.12 no.1
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• pp.25-40
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• 2016

The Systems Engineering (SE) approach is characterized by the application of a structured engineering methodology for the design of a complex system or component. In this study, the SE methodology is used to design a nondestructive inspection system for Bottom Mounted Instrumentation (BMI) nozzles. We developed a system that enables nondestructive inspection of BMI nozzles during regular refueling outage without removing the reactor internals. A special ultrasonic (UT) probe is introduced to scan and detect cracks within the weld region of the nozzle. A 3D model of the inspection structure system was developed along with the reactor pressure vessel (RPV) and internals which permits a virtual 3D simulation of the operation to check the design concept and effectiveness of the system and to provide a good visualization of the system. This approach allows for a virtual walk through to verify the proposed BMI nozzle inspection system.