• 한국정보통신학회논문지
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• 제15권1호
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• pp.33-40
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• 2011

본 논문에서는 단일 반송파 기반의 디지털 변조 기법들의 성능을 수중 통신 실험을 통하여 분석하였다. 통신 실험은 실제 해상에서 수행되었으며 적용된 변조기법은 위상 비동기 방식인 ASK, FSK와 위상 동기 방식의 QPSK이다. 통신 성능을 평가하기 위해 이미지 파일을 600bps~3Kbps의 전송률을 가지는 신호로 변조하여 전송하였다. 수신된 신호를 복조하여 BER을 추정한 결과 ASK와 FSK의 경우 보상 알고리즘 없이 $10^{-3}{\sim}10^{-4}$의 오차율을 나타내었고, QPSK의 경우 선형 등화기를 이용하여 $10^{-4}$의 오차율을 가지는 통신이 가능함을 확인하였다.

• 센서학회지
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• 제6권6호
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• pp.458-465
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• 1997

본 논문에서 자기 이상 검출시스템의 신호 대 잡음비 개선을 위하여 자기환경 필터의 이론을 제안하였다. 자기환경 필터는 검출센서와 기준센서로부터 자기장을 측정하여 주파수 공간에서 상관관계를 측정하여 구성된다. 이를 이용하면 간섭성 잡음을 제거시켜 신호대 잡음비론 개선시킬 수 있다. 최근 DSP 하드웨어 기술을 이용하면 자기환경 필터의 하드웨어 구현이 용이하다. 컴퓨터 시뮬레이션을 통하여 여러 자기 환경 조건에서 제안된 자기환경 필터의 성능을 보였다. 시뮬레이션 결과 자기환경 필터는 간섭성 잡음을 소거시킬 뿐만 아니라 센서의 오배치에 의한 오차를 제거하고 지역적으로 국한된 규칙적인 잡음도 제거할 수 있음을 알 수 있었다.

• Advances in aircraft and spacecraft science
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• 제6권6호
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• pp.497-513
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• 2019

A wind tunnel test was conducted that measured surface fluctuating pressures aft of a ramp at transonic speeds. Dynamic pressure test data was used to perform a study to determine best locations for streamwise sensor pairs for shocked and unshocked runs based on minimizing the error in root-mean-square acceleration response of the panel. For unshocked conditions, the upstream sensor is best placed at least 6.5 ramp heights downstream of the ramp, and the downstream sensor should be within 2 ramp heights from the upstream sensor. For shocked conditions, the upstream sensor should be between 1 and 7 ramp heights downstream of the shock, with the downstream sensor 2 to 3 ramp heights of the upstream sensor. The shock was found to prevent the passage coherent flow structures; therefore, it may be desired to use the shock to define the boundary of subzones for the purpose of loads definition. These recommendations should be generally applicable to a range of expansion corner geometries in transonic flow provided similar flow structures exist. The recommendations for shocked runs is more limited, relying on data from a single dataset with the shock located near the forward end of the region of interest.

• Journal of information and communication convergence engineering
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• 제12권3호
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• pp.140-144
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• 2014

A general linearly constrained adaptive array is examined in the weight vector space to illustrate the array performance with respect to the gain factor. A narrowband linear adaptive array is implemented in a coherent signal environment. It is shown that the gain factor in the general linearly constrained adaptive array has an effect on the linear constraint gain of the conventional linearly constrained adaptive array. It is observed that a variation of the gain factor of the general linearly constrained adaptive array results in a variation of the distance between the constraint plane and the origin in the translated weight vector space. Simulation results are shown to demonstrate the effect of the gain factor on the nulling performance.

• Journal of information and communication convergence engineering
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• 제15권3호
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• pp.137-142
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• 2017

A general linearly constrained narrowband adaptive array is examined in the eigenvector space. The optimum weight vector in the eigenvector space is shown to have the same performance as in the standard coordinate system, except that the input signal correlation matrix and look direction steering vector are replaced with the eigenvalue matrix and transformed steering vector. It is observed that the variation in gain factor results in the variation in the distance between the constraint plane and the origin in the translated weight vector space such that the increase in gain factor decreased the distance from the constraint plane to the origin, thus affecting the nulling performance. Simulation results showed that the general linearly constrained adaptive array performed better at an optimal gain factor compared with the conventional linearly constrained adaptive array in a coherent signal environment and the former showed similar performance as the latter in a noncoherent signal environment.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.951-954
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• 2003

Generally, for the burrs formed in machining are irregular and very sharp in shape, it is usually very difficult to measure burr accurately. But, it is proved that precision measurement for micro burr using the conoprobe sensor by conoscopic holography method is possible. We developed 3D burr measurement system using this sensor. The system is composed of Conoscopic laser Sensor, X-Y table, controller and 3D measurement program. Some measurements using the developed system are applied to burrs formed in micro drilling and piercing.

• 조명전기설비학회논문지
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• 제29권8호
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• pp.76-82
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• 2015

A hybrid fiber-optic sensor system which combines fiber Bragg grating sensors and a Michelson interferometer has been constructed and evaluated for condition monitoring of large scale wind turbines. In order to measure multiple stresses applied to wind turbines such as strain, temperature and vibration, the system uses single broadband light source. It addresses both types of sensors, which simplifies the optical setup and enhances the cost-effectiveness of condition monitoring system. An athermal-packaged FBG is used to supply quasi-coherent light, of which coherence length is about 3.28mm, for the Michelson interferometer demodulation. Experimental results demonstrated that the proposed fiber-optic sensor system was capable of measuring strain and temperature with measurement accuracy of 1pm. Also 500~2000Hz vibration signals were successfully analyzed by applying FFT signal processing to interference signals.

• 대한기계학회논문집
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• 제15권6호
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• pp.2062-2072
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• 1991

본 연구에서는 역류의 측정과 원주의 근접 후류의 난류 구조에 미치는 자유흐 름 난류의 영향을 정성적 및 정량적으로 조사하기 위하여, 역류가 존재할 경우나 순간 유입각이 매우 큰 경우에도 난류의 측정이 가능한 split film probe(이하 SFP로 줄여 표기함)를 사용하여 평균 유동장과 난류의 2차 및 3차 모멘트의 변화, 속도 변동 상관 의 변화 및 대규모 와류의 유출 주파수 특성 등을 측정 분석하여, 격자에 의해 형성된 서로 다른 자유흐름 난류특성에 따른 실험 결과들을 비교 검토 해보고자 한다.

• 한국공작기계학회논문집
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• 제16권5호
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• pp.145-150
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• 2007

Optical communication according to request of technology of communications and optical fiber to be full filed faster communication and pass over transmission capacity limit per unit area, per unit hour appeared, and this optical fiber acts the biggest role to influence performance of optical communication network. Optical fiber(PMF Polarization Maintaining Fiber) is used, and is used by electric field measurement, self-discipline measurement, sensor(Sensor) Department by high definition measure such as thermometry and storehouse component that use because make broad sense status and polarized light information in passageway and union with storehouse integrated circuit etc. that use broad sense interference developing could transmit in state that keep transmitting broad sense plane of polarization is polarized light existence. Also, research is developed by optical fiber for Coherent communication recently.

• 한국군사과학기술학회지
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• 제11권3호
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• pp.19-29
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• 2008

Underwater acoustic(UWA) communication is one of the most difficult field in terms of severe channel environments such as multipath propagation, high temporal and spatial variability of channel conditions. Therefore, it is important to model and analyze the characteristics of underwater acoustic channel such as multipath propagation, transmission loss, reverberation, and ambient noise. In this paper, UWA communication channel is modeled with a ray tracing method and applied to image transmission. Quadrature phase shift keying(QPSK) and multichannel decision feedback equalizer(DFE) are utilized as phase-coherent modulation method and equalization technique, respectively. The objective is to improve the performance of the image transmission using vertical sensor array instead of single sensor in the viewpoint of bit error rate(BER), constellation diagram, and received image quality.