• 한국자기학회:학술대회 개요집
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• 한국자기학회 1998년도 추계연구발표회 논문개요집
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• pp.26-27
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• 1998

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.127.4-127
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• 2001

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. A number of visual or optical technologies have been successfully applied to measure three dimensional surfaces. Especially, the shape measurement using an interferometric principle becomes a successful methodology. However, those conventional interferometric methods to measure surface profile have an inherent shortcoming, namely 2∏ ambiguity problem. The problem inevitably happens when the object to be measured has discontinuous shape due to the repetition of interferometric signal with phase period of 2∏. Therefore, in this paper, we choose as a shape measuring method, ...

• Smart Structures and Systems
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• 제14권5호
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• pp.831-845
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• 2014

This paper proposed a discrete wavelet transform based method for time-varying physical parameter identification of shear type structures. The time-varying physical parameters are dispersed and expanded at multi-scale as profile and detail signal using discrete wavelet basis. To reduce the number of unknown quantity, the wavelet coefficients that reflect the detail signal are ignored by setting as zero value. Consequently, the time-varying parameter can be approximately estimated only using the scale coefficients that reflect the profile signal, and the identification task is transformed to an equivalent time-invariant scale coefficient estimation. The time-invariant scale coefficients can be simply estimated using regular least-squares methods, and then the original time-varying physical parameters can be reconstructed by using the identified time-invariant scale coefficients. To reduce the influence of the ill-posed problem of equation resolving caused by noise, the Tikhonov regularization method instead of regular least-squares method is used in the paper to estimate the scale coefficients. A two-story shear type frame structure with time-varying stiffness and damping are simulated to validate the effectiveness and accuracy of the proposed method. It is demonstrated that the identified time-varying stiffness is with a good accuracy, while the identified damping is sensitive to noise.

• 한국전자파학회논문지
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• 제25권5호
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• pp.607-617
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• 2014

본 논문은 OTM(On-The-Move: 이동형) 위성단말을 위해 통신 지역에서 지형/지물에 의해 발생될 수 있는 위성신호의 음영 지역을 분석하는 방법을 제시하였다. 지형/지물 정보를 포함하는 3D map을 HTZ warfare M&S(Modeling & Simulation) 도구를 이용하여 수신 신호의 프로파일을 얻고, 이를 Markov 모델을 이용하여 통계적으로 분석하였다. M&S 데이터의 분석 결과는 대전 도심을 실 주행시험을 통해 확보한 수신 프로파일과 비교하였다. 비교 분석 결과, 수신 프로파일은 약 74.8%의 일치를 보였으며, 가로수 영향 배제시 수신 프로파일의 통계적 분석 결과 또한 유사함을 보였다.

• 한국전자파학회논문지
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• 제24권12호
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• pp.1173-1180
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• 2013

2005년에 처음 소개된 HRRP-JEM(High Resolution Range Profile-Jet Engine Modulation) 영상은 항공기 표적에 탑재된 제트 엔진의 장착 위치를 추정함으로써 레이더 표적 인식을 수행한다. 본 논문에서는 복소 신호의 이심률을 기반으로 HRRP-JEM 영상에서 제트 엔진 위치를 추정하기 위한 새로운 접근법을 제시한다. 복소 신호의 이심률은 HRRP-JEM 영상을 구성하는 어떤 거리 성분(range bin)에서의 레이더 수신 신호에 미치는 JEM 성분의 기여도를 효과적으로 산출할 수 있다. 따라서 JEM 성분의 기여도가 가장 큰 거리 성분이 제트 엔진의 위치에 해당하며, 이를 짚어냄으로써 보다 정량적이고 신뢰성 있는 제트 엔진 위치 추정이 가능할 것으로 기대된다. 사실적인 항공기 모델의 시뮬레이션 결과를 통해 본 논문에서 제안한 개념의 유효성을 입증하였다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.367-369
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• 2002

We have designed ramp profile excitation pulse based on the Shinnar-Le Roux (SLR) algorithm. The algorithm provides many advantages to pulse designers. The first advantage is the freedom of deciding the amplitudes, frequencies, and ripple sizes of stopband, passband, and transition band of pulse profile. The second advantage is the freedom of deciding the pulse phase, more specifically, minimum phase, linear phase, maximum phase, and any phase between them. The minimum phase pulse is the best choice in the case of 3D TOF, because it minimizes the echo time, which implies the best image quality in the same MR examination condition. In addition, the half echo technique is slightly modified in our case. In general, using the half echo technique means that the acquired data size is half and the rest part can be filled with complex conjugate of acquired data. But in our case, the echo center is just shifted to left, which implies the reduction of echo time, and the acquired data size is the same as the one without using the half echo technique. In this case, the increase of right part of data leads to improvement of the resolution and the decrease of left part of data leads to decrease of signal to noise ratio. Since in the case of 3D TOF, the signal to noise ratio is sufficiently high and the resolution is more important than signal to noise ratio, the proposed method appears to be significantly affective and gives rise to the improved high resolution angiograms.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.179-182
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• 1988

Since the bits in any encoded PCM word are of different importance to the bit positions, in order to improve the signal to noise ratio the technique that the encoded signal bits are weighted for the QPSK transmission system, is presented. Also the erasure zone is established at the detector, such that if the output falls into the erasure zone, the regenerated sample is replaced by interpolation. Two weighting methods are shown here. One is the method that the same weighting profile is used to Q and I dimension in QPSK signal constellations. The other is diferent weighting to Q and I dimension. The gains of this new technique in overall signal s/n compared to conventional QPSK transmission system were 5 db and 2db, respectively.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.54-65
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• 1997

To quantify the LII signals from soot particle of flames in diesel engine cylinder, a new method has been proposed for correcting LII signal attenuated by soot particles between the measuring point and the detector. It has been verified by an experiment on a laminar jet ethylene-air diffusion flame. Being proportional to the attenuation, the ratio of LII signal at two different detection wavelengths can be used to correct the measured LIIsignal and obtain the unattenuated LII signal, from which the soot volume fraction in the flame can be estimated. Both the 1064-nm and frequency-doubled 532-nm beams from the Nd : YAG laser are used. Single-shot, one-dimensional(1-D) line images are recorded on the intensified CCD camera, with the rectangular-profile laser beam using 1-mm-diameter pinhole. Two broadband optical interference filters having the center wavelengths of 647 nm and 400 nm respectively and a bandwidth of 10 nm are used. This two-wavelength correction has been applied to the ethylene-air coannular laminar diffusion flame, previously studied on soot formation by the laser extinction method in this laboratory. The results by the LII measurement technique and the conventional laser extinction method at the height of 40 nm above the jet exit agreed well with each other except around outside of the peaks of soot concentration, where the soot concentration was relatively high and resulting attenuation of the LII signal was large. The radial profile shape of soot concentration was not changed a lot, but the absolute value of the soot volume fraction around outside edge changed from 4ppm to 6.5 ppm at r=2.8mm after correction. This means that the attenuation of LII signal was approximately 40% at this point, which is higher than the average attenuation rate of this flame, 10~15%.

• 방송공학회논문지
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• 제18권3호
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• pp.435-444
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• 2013

ATSC (Advanced Television System Committee) 지상파 DTV(Digital Television) 방송시스템은 6 MHz 대역폭을 이용하여 최대 19.2 Mbps의 데이터 전송률을 지원하지만, 멀티패스 페이딩이 발생하는 도심 환경에서는 수신 성능이 급격히 나빠지는 단점을 가지고 있다. 도심 환경에서 DTV 수신기의 성능 열화를 개선하기 위해서는 무엇보다 멀티패스 페이딩 채널을 측정하고 분석하는 것이 중요하다. 하지만 ATSC 지상파 DTV 방송시스템의 8-VSB(Vestigial Sideband Modulation) 변조 방식은 동위상 채널에만 DTV 심볼 데이터를 전송하기 때문에, 직교위상 채널을 예측하지 않으면 정확한 멀티패스 페이딩 채널 측정이 어려워진다. 본 논문에서는 지상파 DTV 방송시스템의 VSB 펄스성형 필터를 이용하여 직교위상 채널을 예측하고, 이를 통해 멀티패스 페이딩 채널을 보다 정확하게 측정하는 DTV 채널 프로파일 측정기술을 제안하고 모의실험을 통해서 성능을 분석하였다.

• 한국광학회지
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• 제23권4호
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• pp.159-166
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• 2012

본 연구에서는 질소와 산소의 회전 라만 신호를 측정하여 낮 시간 온도 측정이 가능한 라이다 시스템을 자체 개발하였다. 태양광에 의한 배경신호를 줄이기 위하여 파장의 폭이 좁고(0.5 nm) 제거율이 높은($10^{-6}$) 회절판과 간섭필터를 이용하였다. 개발된 장치의 성능을 검증하기 위하여 라이다를 수평방향으로 조사하여 온도 특성을 얻고 기상청에서 주어지는 값과 비교하여 상관관계가 일치함을 알 수 있었다. 그리고 수직온도분포로 얻기 위하여 수평으로 얻은 검정 값을 사용하였다. 또한 수직방향으로 조사하여 미국 표준 데이터와 비교하였으며, 존데 데이터와 검정을 통한 본 연구의 결과를 비교하였다.