• 한국안전학회지
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• 제27권5호
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• pp.229-234
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• 2012

Operator's action time is evaluated from MAAP4 analysis used in conventional probabilistic safety assessment(PSA) of a nuclear power plant. MAAP4 code which was developed for severe accident analysis is too conservative to perform a realistic PSA. A best-estimate code such as RELAP5/MOD3, MARS has been used to reduce the conservatism of thermal hydraulic analysis. In this study, operator's action time of core cooling recovery operation is evaluated by using the MARS code, which its Fussell-Vessely(F-V) value was evaluated as highly important in a small break loss of coolant(SBLOCA) event and loss of component cooling water(LOCCW) event in previous PSA. The main conclusions were elicited : (1) MARS analysis provides larger time window for operator's action time than MAAP4 analysis and gives the more realistic time window in PSA (2) Sufficient operator's action time can reduce human error probability and core damage frequency in PSA.

• 한국유체기계학회 논문집
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• 제6권3호
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• pp.7-14
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• 2003

It is addressed that the turbulent broadband sound power from a sirocco fan can be modeled by the trailing edge noise. The trailing edge noise is usually influenced by inflow turbulence, separation, and boundary layer thickness on the blade. The design parameters such as solidity (c/s) and stagger angle are specified to predict performance and noise level because the separation and slip velocity are strongly affected by them along with the flow coefficient. This paper reports the effects of the stagger angle upon the trailing edge noise for various trailing edge shapes. It is believed that the serrated trailing edge provides break-up mechanism for organized convecting vortices, thereby reduce the overall noise level for every case of stagger angle.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.75-78
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• 2000

Since the most of malfunctions in the industrial equipment controlled by processors is occured by the Electrical Fast Transient(EFT), the International Electrotechnical Commission(IEC) prepared the dummy signal to test the immunity level of the equipments. In this paper. we designed a new EMC filter for power line in break-box, which is consist of the feed-through capacitor and ferrite materials with high permeability which was wound or inserted in the second layer of the power cable in order to increase common mode inductance. We have obtained a excellent insertion loss characteristics over wide frequency band from 100 KHz up to 6 GHz. It is expected that the new EMC filter could be effectively used for industrial, MIL, and medical equipments to reduce a malfunctions and be suitable for IEC 61000-4-4.

• Current Optics and Photonics
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• 제1권6호
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• pp.567-572
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• 2017

A novel slotted-core hexagonal photonic crystal fiber (PCF) for terahertz (THz) wave guiding is proposed in this paper. A trade-off managed between effective material loss (EML) and birefringence for efficient guidance of THz waves is illustrated in this article. The rectangular slot shaped air-holes break the symmetry of the porous-core which offers ultra-high birefringence of $8.8{\times}10^{-2}$. The proposed structure offers low bending loss of $1.07{\times}10^{-34}cm^{-1}$ and extremely low effective material loss (EML) of $0.035cm^{-1}$ at an operating frequency of 1.0 THz. In addition other guiding properties such as power fraction, dispersion and confinement loss are also discussed. The proposed THz waveguide can be effectively used for convenient transmission of THz waves.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.655-656
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• 2015

In this paper, diagnosis for 85 high voltage induction motors which have operated for more than 20 years in 18 wide area water supply offices were applied and the results of diagnosis were analysed. Furthermore, main factors that would be affecting rotor defects were selected and correlations between dependent variables which was magnitude for sideband frequency on current during operation and independent variables such as starting characteristic, operating time, number of operation, load factor, maker, rotation speed, capacity were analysed. It was clear that factors including starting characteristic, number of operation, maker, rotation speed caused break by correlation analysis. From this, regression equation was deduced through regression analysis. Based on suggested regression equation, it is applied usefully that we can estimate the condition of rotor without onsite diagnosis and plan the schedule of diagnosis.

• 한국작물학회지
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• 제24권1호
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• pp.1-10
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• 1979

In order to investigate the causes of epidemic out break of rice blast disease in 1978, investigations were undertaken in respect of climatic conditions, variety, cultural practice and plant pathology. During 1978, especially in August at heading time, it was higher temperature and humidity, higher frequency and amount of rainfall, lower amount of sunshine and solar radiation than less blast infested years. Nitrogen content in rice plant was higher than previous years. Acreage increase of semi-dwarf varieties brought about a result of proportional increase of new blast races which are able to infect the semi-dwarf varieties. It was concluded that those conditions mentioned above might have caused the result of severe neck blast disease in rice varieties in Korea, 1978.

• 한국컴퓨터정보학회논문지
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• 제5권2호
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• pp.105-114
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• 2000

본 논문에서는 1차원 움직임을 갖는 신호원의 위치를 실시간으로 탐지하기 위해 N개의 안테나를 반원형 구조로 배열하였고, 각각의 수신어레이로부터 수신 전력패턴과 3차 spline 보간법만을 사용하여 신호원의 입사각을 추정하고, 이로부터 신호원의 수평이동 좌표를 화면에 실시간으로 표시하는 시스템을 구현한 논문이다. 본 논문에서 사용한 신호원은 X 대역의 10.52GHz로 10-20dBm 사이의 송신출력으로 하였고, 신호원의 위치를 좌.우 ${\pm}15^{\circ}$ 이내의 임의의 좌표로 수평 이동하면서 제시한 방법의 타당성을 검증하고자 한다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.128-133
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• 2000

The objective of this research is to develop real-time failure detection techniques for damage assessment of composite materials using optical fiber sensors. Signals from matrix cracking or fiber fracture in composite laminates are treated by signal processing unit in real-time. This paper describes the implementation of time-frequency analysis such as the Short Time Fourier Transform(STFT) to determine the time of occurrence of failure. In order to verify the performance of the optical fiber sensor for stress wave detection, we performed pencil break test with EFPI sensor and compared it with that of PZT. The EFPI sensor was embedded in composite beam to sense the failure signals and a tensile test was performed. The signals of the fiber optic sensor when damage occurred were characterized using STFT and wavelet transform. Failure detection system detected the moment of failure accurately and showed good sensitivity with the infinitesimal failure signal.

• 한국기계가공학회지
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• 제5권3호
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• pp.58-64
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• 2006

The security of stability for fractures of all sorts of parts and structure has become a first subject these days. We have need to organize fatigue characteristics of weldment because fatigue break out suddenly without a change of shape. In this study, we execute the fatigue test according to different of the welding method at the same materials. It was investigated about a fatigue limit according to welding methods of SMAW, FCAW and SAW at normal temperature and a frequency of 10Hz. The important results of the experimental study on fatigue characteristics of weldment are as follows: The fatigue limit of welding methods became low in the order of SMAW, FCAW, SAW.

• 한국정보통신학회논문지
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• 제8권4호
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• pp.912-917
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• 2004

디지털 콘텐츠 산업이 핵심 신성장산업으로 등장하고 있으나 디지털 콘텐츠의 제작, 유통 및 관리상에서 디지털자료의 특성상 무한정 복제 및 해킹을 통한 손상 등의 문제가 심각하게 대두되고 있다. 이러한 문제들을 극복하기 위한 수단으로 제시되는 디지털 지적 재산권 보호를 위한 DRM(Digital Rights Management)기술의 하나인 디지털 워터마킹(Digital Watermarking)은 저작권 정보, 구입자 정보 등 저작권 보호에 필요한 정보를 디지털 콘텐츠에 몰래 숨겨놓는 기술이다. 지금까지 디지털 워터마킹 기술에 관한 연구는 주로 특정성 있는 워터마크 삽입과 검출 둥의 관점에서 연구되어 왔는데 본 연구에서는 지적재산권 보호를위한 광범위한 응용이 예상되는 워터마킹의 기법을 고찰하고 주파수영역에서 응용되는 웨이블릿 기반의 워터마킹 기법을 제안한다.