• 한국산학기술학회논문지
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• 제13권5호
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• pp.1996-2001
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• 2012

본 시각 검사시스템은 전자 부품과 같이 잘 형성된 표면 재료에 널리 사용되고 있다. 반사 능력이 나쁜 재료의 경우, 시각 검사시스템이 도입될 때 많은 문제점이 발생한다. 혼합 생산 라인에서 진위의 모델을 알 수 없을 때 저 반사비와 많은 노이즈에도 잘 작동할, 강인한 시각 검사시스템을 개발하였다. 유형을 인식하기 위하여 k-means를 이용한 작업물 인식 기법이 제안되었다. 인식 유형에 기반하여 active contour라는 노이즈에 강인한 분할 기법이 영상에서 특징을 분할하는데 응용되었다. 오차 변화를 조정하는데 Kalman 필터가 사용되었다. 자동시각 검사시스템의 실험은 프로젝터를 이용한 수작업 측정의 정확도 수준을 보여준다.

• 천문학회보
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• 제41권1호
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• pp.42.1-42.1
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• 2016

We examined thousands of light curves of stars brighter than 18.0 mag in I band and less than mean magnitude error of 0.1 mag in V band from the OGLE-III eclipsing binary catalogue, and found 90 new binary systems exhibiting apsidal motion. In this study, the samples of apsidal motion stars in the SMC were increased by 250 percent than previously known. In order to determine the period of the apsidal motion for the binaries, we analysed in detail both light curves and eclipse timings using the MACHO and OGLE photometric database obtained for about 20 yrs. For the eclipse timing diagrams of the systems, new times of minimum light were derived from the full light curve combined at intervals of one yr from the survey data. The binaries presented in this paper have apsidal motion periods in the range of 12-918 yrs. An additional short-term oscillation was detected in five systems (OGLE-SMC-ECL-1634, 1947, 3035, 4946, and 5382), which most likely arise from the existence of a third body orbiting each eclipsing binary. All of the selected systems can be used for the statistical study of the interior structure of the stars in the SMC through their apsidal motions due to the homogeneous data and consistent analysis methods.

• ETRI Journal
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• 제29권5호
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• pp.633-640
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• 2007

We report an experimental demonstration of 40 Gbps all-optical 3R regeneration with all-optical clock recovery based on InP semiconductor devices. We also obtain alloptical non-return-to-zero to return-to-zero (NRZ-to-RZ) format conversion using the recovered clock signal at 10 Gbps and 40 Gbps. It leads to a good performance using a Mach-Zehnder interferometric wavelength converter and a self-pulsating laser diode (LD). The self-pulsating LD serves a recovered clock, which has an rms timing jitter as low as sub-picosecond. In the case of 3R regeneration of RZ data, we achieve a 1.0 dB power penalty at $10^{-9}$ BER after demultiplexing 40 Gbps to 10 Gbps with an eletroabsorption modulator. The regenerated 3R data shows stable error-free operation with no BER floor for all channels. The combination of these functional devices provides all-optical 3R regeneration with NRZ-to-RZ conversion.

• Journal of Communications and Networks
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• 제8권3호
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• pp.290-296
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• 2006

In this paper, a generalized blind adaptive algorithm is introduced for multi-user detection of direct sequence code division multiple access (OS-COMA) wireless communication systems. The main property of the proposed algorithm is its ability to resolve the multipath fading channel resulting in inter symbol interference (ISI) as well as multiple access interference (MAI). Other remarkable properties are its low complexity and mitigation to the near-far problem as well as its insensitivity to asynchronous transmission. The proposed system is based on the minimization of the output energy and convergence to the minimum mean square error (MMSE) detector. It is blind in the sense that it needs no knowledge of the other users' signatures, only the intended user signature and timing are required. Furthermore, the convergence of the minimum output energy (MOE) detector to the MMSE detector is analytically proven in case of M-ary PSK. Depicted results show that the performance of the generalized system dominates those previously considered. Further improvements are obtained when multiple input multiple output (MIMO) technique is employed.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.336-340
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• 2003

The frame synchronization should be acquired before performing other data-aided receiving algorithms, such as data-aided channel equalizing, beam-forming and phase, symbol timing, and frequency synchronizing, since all of them are using preamble or training sequence to estimate the amount of error from the received signal. In this paper, we present a new frame synchronization scheme for underwater ultrasonic image burst transmission system, which computes the correlation between received symbol sequence and one CAZAC sequence, composed of the latter half of the first CAZAC sequence of preamble and the first half of the second CAZAC sequence of preamble and then compares a threshold value. If the correlation value is bigger than the threshold value, the frame detector determines that the frame synchronization is achieved at that sample.

• 한국통신학회논문지
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• 제32권1C호
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• pp.59-66
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• 2007

본 논문에서는 ISO/IEC 18000-6 Type-B RFID 시스템에서 태그 응답신호, 즉 리더 수신신호에서 허용오차 (Tolerance)와 잡음이 미치는 영향에 대해서 알아보고, 이에 대한 영향을 최소화하는 방법을 제안한다. 제안된 방법은 오버 샘플링된 수신 신호를 가지고 가변천이검출윈도우를 이용하여 허용오차에 의한 영향을 제거하고 비트가 천이되는 위치를 검출하며, 이전의 비트 천이에서 현재 비트 천이까지의 윈도우 내 수신 신호를 평균하여 잡음의 효과를 줄인다. 제안된 방법을 적용하여 자체 제작한 리더에서 성능 테스트한 결과를 상용리더와의 비교 실험결과로 제시한다.

• 한국자동차공학회논문집
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• 제22권7호
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• pp.84-89
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• 2014

Not only the emission regulation of on-road vehicle engine, but also emission regulation of off-road engine have been reinforced. It is the reason of wide application of emission reduction technology for off-road engines. In this study, optimization of engine parameters (Injector hole number, Injection timing and EGR rate) for reduction of NOx and smoke emissions were conducted by using the analysis of sensitivity and S/N ratio of Taguchi method(DOE). As results, this paper shows optimum value of the parameters for NOx and smoke emission reduction. From the result of reproducibility verification, it is final that the prediction value of NOx and smoke has the error of below 10%. Consequently, the method and results of this study will be used for quantitative reference to EGR control mapping in next study.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.565-573
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• 2017

This paper presents a multistage in-flight alignment (MIFA) method for a strapdown inertial navigation system (SDINS) suitable for moving vehicles with no initial attitude references. A SDINS mounted on a moving vehicle frequently loses attitude information for many reasons, and it makes solving navigation equations impossible because the true motion is coupled with an undefined vehicle attitude. To determine the attitude in such a situation, MIFA consists of three stages: a coarse horizontal attitude, coarse heading, and fine attitude with adaptive Kalman navigation filter (AKNF) in order. In the coarse horizontal alignment, the pitch and roll are coarsely estimated from the second order damping loop with an input of acceleration differences between the SDINS and GPS. To enhance estimation accuracy, the acceleration is smoothed by a scalar filter to reflect the true dynamics of a vehicle, and the effects of the scalar filter gains are analyzed. Then the coarse heading is determined from the GPS tracking angle and yaw increment of the SDINS. The attitude from these two stages is fed back to the initial values of the AKNF. To reduce the estimated bias errors of inertial sensors, special emphasis is given to the timing synchronization effects for the measurement of AKNF. With various real flight tests using an UH60 helicopter, it is proved that MIFA provides a dramatic position error improvement compared to the conventional gyro compass alignment.

• 한국산학기술학회논문지
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• 제12권4호
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• pp.1502-1508
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• 2011

본 연구에서는 전자제어 분사방식 소형엔진의 모델을 개발하기 위하여 기존 소형엔진의 제원을 바탕으로 1차원 모델을 구성하였다. 새롭게 구성된 모델의 성능해석을 수행하고 이를 실험결과와 분석하여 모델의 타당성을 확인하였다. 1차원 성능 모델의 토크 및 출력 해석결과는 실험결과와 3%이내의 오차를 보였으며, 소형엔진의 토크 및 출력 특성을 우수하게 예측하고 있다. 소형 엔진의 성능향상을 위해 엔진의 흡입성능에 미치는 성능인자의 영향력을 분석하였다.

• 한국정보과학회논문지:시스템및이론
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• 제26권7호
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• pp.788-812
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• 1999

본 논문에서는 범용 워크스테이션 환경하에서 수행되는 멀티미디어 응용프로그램(application)을 지원하기 위한 비례지분 방식의 CPU 스케줄러를 제시한다. 이러한 목적을 위하여 일반적 태스크의 지원을 위해 설계된 스트라이드 스케줄러를 확장한다. 멀티미디어 응용프로그램의 시간 요구사항을 명시하기 위하여 새로운 스케줄링 파라미터들을 도입한다. 비율조정기를 도입한 결과 스케줄링의 정확도의 오차는 O(1)로 감소하였다. 별도의 태스크 그룹을 설정하여 상대적 지분과 절대적 지분을 부여했다. 모의실험을 사용하여 스케줄러의 성능을 평가하였다. 그 결과, 제안된 스케줄러는 증가된 정확도와 적응성 및 유연성을 가짐을 알 수 있었다. Abstract This paper presents a proportional-share CPU scheduler which can support multimedia applications in a general-purpose workstation environment. For this purpose, we have extended the stride scheduler which is designed originally for conventional tasks. New scheduling parameters are introduced to specify timing requirements of multimedia applications. Through the use of the rate regulator, the accuracy error of the scheduling is reduced to O(1). Separate task groups are proposed to represent both relative shares and absolute shares. The proposed scheduler is evaluated using a simulation study. The results show that the proposed scheduler achieves improved accuracy and adaptability as well as flexibility.