• Korean Journal of Optics and Photonics
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• v.6 no.2
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• pp.101-107
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• 1995

To investigate the diffraction property of the Bessel beam for defocus which acts CFAP (Combined Filter of Amplitude and Phase), we calculated numerically the intensity, the radius of central spot, and the optical transfer function for the number of node of the Bessel beam when an optical system has an aberration-free or a spherical aberration. The Bessel beam has larger the maximum intensity and the OTF value for an optical system with a spherical aberration than that with an aberrationfree. Particularly, the OTF value at the point of maximum intensity for $W_{40}=3\lambda$is higher for the Bessel beam than for the Clear aperture. From these results, we know that the Bessel beam has the compensating effect. The Bessel beam also has the radius of central spot having a superresolution. We will useful for the fabrication of semiconductor device and the optical recording system using these effects.ffects.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.427-431
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• 2007

The safety and the durability of the arm as an automotive chassis part under the fatigue can be predicted in this study. The fatigue life is sharply decreased from 0.5 to 0.75 at the change of load which is the amplitude load divided by average load. But its life is slightly decreased at the change of load from 0.75 to 1.5. The influence of fatigue life according to the change of load can be predicted by these results. As the value of maximum damage is 2.2 and the value of maximum compressive strain or stress is $-6.93{\times}10^{-3}$ or 349 Mpa at the connected part of rod end applied by concentrated load respectively, there is the greatest possibility of destruction due to the compression at this part.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2C
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• pp.203-209
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• 2010

In this paper, we propose a new selected mapping (SLM) scheme for reducing peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals modulated with quadrature amplitude modulation (QAM), called amplitude and phase variant SLM (APSLM). Contrary to the conventional SLM which rotates the phases of QAM symbols in the frequency domain, the proposed scheme changes the magnitudes as well as the phases of QAM symbols by applying binary sequences to the binary data sequence before mapped to QAM symbols. Simulation results show that the proposed scheme has better PAPR reduction performance than the conventional SLM scheme for the QAM modulated OFDM signals, especially for the small number of subcarriers.

• Science of Emotion and Sensibility
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• v.6 no.1
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• pp.11-16
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• 2003

In this study, we examined the evaluation of virtual Reality (VR) according to the use of motion platform. We recorded electrogastrogram, skin conductance, blood volume, skin temperature, heart rate, and the frequency of eyeblink before, during, after virtual navigation in 33 subjects. We used simulator sickness questionnaire, presence questionnaire , and self-report to evaluate cybersickness and presence in VR system. All subjects experienced VR two times in Motion platform condition and non-Motion platform condition at two-week intervals. Presence score of motion platform condition was greater than non-motion platform condition. The frequency and severity of cybersickness were significantly reduced in motion platform condition than non-motion platform condition. These results suggest that the use of motion platform that synchronizes visual presentation provides higher presence and reduces cybersickness.

• Journal of the Korean Institute of Gas
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• v.11 no.4
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• pp.64-72
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• 2007

Under the AE methods, the valid condition analysis and evaluation the leak etc, resulted by the AE signal pattern on the bottom plate of ground tank at full. In next more, the gradient of accumulation amplitude distribution analysis and comparison the energy, count, and duration time that noise of EMI signal were removed. EMI signal showed height-energy, count, and duration time, it also appeared great gradient of accumulation distribution. Then, with the pure remaining AE signals cluster analysis and location. It would possibly assume of damage with corrosion. Total cluster 20 and energy showed between the maximum 11,990 and 8,565 which is much lower than above figure and event number showed from 8 to 5. Even when it difficult to certify damage by open, as it is raised higher height-sensitivity and threshold by 60 dB. It would possibly presume of location source more accurately.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.6
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• pp.104-110
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• 1997

In thes paper, the soung signals due to the collisions against the inside wall by conductint particles with in coaxial cylindrical electrodes, and the corresponding frequency spectrum are analyzed and discribed.Thesesound signals were detected and measured using ultrasonic and vibration sensors attached to the exterior of the GIS enclosure. In the case where a particls is bouncing about between these coaxoal electrodes, the sound signal was found to be more than 10[dB] greater than the background noise due to no particlel. Also, in the case where a particle collides and insulation breakdown caesed by the particle made it possible to determine the condition of the insulation inside the sealed GIS. Lastly, the relationship between the peak amplitude and RMS voltage of the measured signal, the diameter and length of the particle was analyzed. Using thes analysis, it is possible to confirm the size of particle.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.3
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• pp.254-262
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• 2003

In this study, acoustic emission (AE) signals due to surface cracking and moisture movement in the flat-sawn boards of oak (Quercus Variablilis) during drying under the ambient conditions were analyzed and classified using the principal component analysis. The AE signals corresponding to surface cracking showed higher in peak amplitude and peak frequency, and shorter in rise time than those corresponding to moisture movement. To reduce the multicollinearity among AE features and to extract the significant AE parameters, correlation analysis was performed. Over 99% of the variance of AE parameters could be accounted for by the first to the fourth principal components. The classification feasibility and success rate were investigated in terms of two statistical classifiers having six independent variables (AE parameters) and six principal components. As a result, the statistical classifier having AE parameters showed the success rate of 70.0%. The statistical classifier having principal components showed the success rate of 87.5% which was considerably than that of the statistical classifier having AE parameters.

• Journal of the Korean Society for Precision Engineering
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• v.2 no.1
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• pp.21-27
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• 1985

차량, 항공, 교량 및 기계구조물 등 랜덤한 실동하중을 받는 구조물의 응력 및 변위, 진동등의 피로 Data 또는 TRAFFIC 등에 의한 건축물의 변위 및 응력발생빈도를 집록하기 위한 Histogram Recorder System에 대한 내용과 측정예를 소개하고자 한다. 본 System은 8(4)챈 널의 스트레인 게이지 또는 스트레인 게이지식 각종변환기와 각종 Sensor로부터의 출력전압 등 Analog 입력을 수록하여, Digital 처리하여 micro computer를 사용, 미리 프로그램된 방식에 따라 측정과 동시에 실동시간으로 해석처리하여 빈도수로서 내부에 기억저장 시키는 것이다. 따라서 본 Histogtram Recorder 본체는 소형으로 견고하며 조금도 제어부분을 갖지 않고 소요의 해석방법의 프로그램백만을 셋트한 개별의 제어기만을 통해가지고 프로그램을 기입만 하며는 그다음은 손하나 안대고도, 그리고도 또 측정중에 제3자에 의한 제어조작 잘못이 발생할 위험도 없고 1 년이상에 걸친 장기간의 .+-. 32 Slices의 각 레벨당 각각 40 억을 넘는 대량의 빈도수를 자동적으로 집록 할 수가 있다. 집록된 Data는 제어장치에 의해 정리된 Datam는 제어장치에 의해 정리된 Histogram의 형태로 읽어나갈 수가 있어 관찰이 가능할 뿐만 아니라 프린터기록 또는 기록장치에 이송시켜서 Data 만 따로 가져올 수가 있어 필요에 따라서는 one line으로 Host computer에 접속시킬 수가 있어 더욱 고도의 처리를 할 수가 있다. 빈도해석프로그램으로서는 극대, 극소, 최대, 최소, 진폭, 시간 등을 pack으로서 준비되어 있어 이에 대한 시스템의 고성 동작 및 성능등을 소개하고자 한다.

• Geophysics and Geophysical Exploration
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• v.11 no.4
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• pp.310-317
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• 2008

Lg amplitude decrease $Q^{-1}$ is very important because the Lg phase is the largest seismic phase in Korea if hazardous earthquakes occurred at neighbor nations such as Japan and China. Since reliable $Q^{-1}$ from two station method can be obtained by long pair distance of stations or events, we used seismic stations both Korea and Japans recording Korean events. The obtained $Q^{-1}$ values, however, were anomalously high; these misguided values, inconsistent with tectonic activity of Korean Peninsula, seems to be related with high $Q^{-1}$ values of Japan region.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.2
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• pp.34-39
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• 2016

This paper presents a method to quantify R-ratio effect on J-integral under large-amplitude cyclic loading condition. Generally, monotonic tearing resistance curves are used to assess stability of cracked nuclear piping under seismic loading. However, it is well known that fracture toughness decrease at cyclic loading condition, according to R-ratio. For this reason, it is important to quantify the J-R curves under cyclic loading condition. To quantify the R-ratio effect, correction method which was proposed by Tranchand is considered. This method considers crack opening area in order to calculate modified J-integral. This method leads to an increase of fracture toughness. At R=-0.5 case, this method is good agreement with monotonic J-R curves. However, results show that this method has a limit to apply a large R-ratio case.