• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.3
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• pp.51-58
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• 2002

The conventional code division multiple access(CDMA) detector shows severe degradation in communication quality as the number of users increases due to multiple access interferences(MAI). This problem thus restricts the user capacity. Various multiuser detection algorithms have been proposed to overcome the MAI problem. The existing detectors can be generally classified into one of the two categories : linear multiuser detection and subtractive interference cancellation detectors. In the linear multiuser detection, a linear transform is applied to the soft outputs of the conventional detector. In the subtractive interference cancellation detection, estimates of the interference are generated and subtracted out from the received signal. There has been great interest in the family of the subtractive interference cancellation detection because the linear multiuser detection exhibits the disadvantage of taking matrix inversion operations. The successive interference cancellation (SIC) and the parallel interference cancellation (PIC) are the two most popular structures in the subtractive interference cancellation detector. The SIC structure is very simple in hardware complexity, but has the disadvantage of increased processing delay time, while the PIC structure is good in performance, but shows the disadvantage of increased hardware complexity. In this paper we propose a mixed structure form of SIC and PIC in order to achieve good performance as well as simple hardware complexity. A performance analysis of the proposed scheme has been made, and the superior characteristics of the mixed structure are demonstrated by extensive computer simulations. 

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.1
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• pp.18-22
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• 2014

Residual stresses that occur during the welding process, are the main cause of failure and defects in welded structures. This paper, presents the use of an electronic processing laser speckle interferometer to measure the residual stress of a welded pipe for a nuclear power plant. A tensile testing machine was used to evaluate a welded pipe that failed in compression. The inform plane deformation and modulus of elasticity of the base metal and welds were measured using an interferometer. Varying the load on the welded pipe had a larger effect on the deformation of the base metal the other properties of the base metal and welds. The elastic moduli of the base metal and weld of the welded pipe were 202.46 and 212.14 GPa, respectively, the residual stress was measured to be 6.29 MPa.

• Journal of Chest Surgery
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• v.31 no.4
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• pp.398-401
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• 1998

A 56-year-old female with a permanent unipolar pacing(VVI) system underwent elective coronary bypass surgery and mitral valve replacement. Because the unipolar sensing is subject to considerable nonmyocardial electrical noise, the pacing function may be disturbed by the use of electrocautery. Temporary atrial and ventricular bipolar epicardial leads and external generator were used for maintaining A-V sequential pacing during the use of electrocautery. Before aortic cross-clamp was released after cardiac operation, regular cardiac rhythm could spontaneously be resumed with an integrated cardioplegic strategy, avoiding the use of defibrillator

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1388-1398
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• 2012

SAR(Synthetic Aperture Radar) systems can provide images of wide coverage in day, night, and all-weather conditions. However wideband SAR systems are known to be vulnerable to interferences from other devices operating at in-band or adjacent spectrums and this may lead to image corruptions. In this paper, a SAR point target simulator is developed that provides performance analysis on image distortion caused by interferences from other devices. Interference signals are generated based on the experimental data observed from acquired SAR raw data. Simulation results include typical SAR performance measures such as spatial resolution, peak to sidelobe ratio and integrated sidelobe ratio. Finally, SAR target simulations are performed and shown to correspond to the image corruptions found in real SAR missions affected by RF interferences.

• Journal of the Korean earth science society
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• v.27 no.5
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• pp.521-527
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• 2006

The EPMA analysis for CHIME dating requires standard materials, which include nuclear fuel materials that are rare and sensitive to handle. Any laboratory that does not meet these standards has had difficulties adopting the CHIME dating method. We have developed a working standard technique for CHIME dating to prepare standard materials without use of nuclear fuel materials. Mineral samples, such as small pieces of monazite that are homogeneous in X-ray intensities, are calibrated using well-characterized primary standards in one laboratory. Once this procedure is done, they can be readily usable as working standards in the other laboratories, only with measurement of X-ray intensities. This method is applicable in preparing standard materials for both chemical compositions and determination of X-ray interference correction factors, and it is independent from chemical composition of mineral standard.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.5 no.3
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• pp.169-173
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• 2012

This paper investigates the performance of Turbo equalization in wireless multipath channels. Turbo equalization mainly consists of a SISO(soft-in soft-out) equalizer and a SISO decoder. Iterative channel estimators can improve the accuracy of channel estimates by soft information fed back from the SISO decoder. Comparing iterative channel estimators with LMS(least mean square) and RLS(recursive least squares) algorithms, which are the most common algorithms to estimate and track a time-varying channel impulse response, the iterative channel estimator with RLS converges more faster than the one with LMS. However, the difference of BER(bit error rate) performances gradually decreases as the number of iterations for Turbo equalization increases.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.947-950
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• 2000

디지털 데이터 처리 및 전송과 함께 방대한 양의 디지털 데이터에 대한 저장 시스템의 용량 증가를 위한 신호처리 기법에 대해 관심이 날로 증가하고 있는 가운데, 다양한 기록 시스템에 대하여 고안된 여러 가지 채널 코딩 및 신호 검출 알고리즘을 분석, 검증하기 위한 시뮬레이터를 하드웨어적으로 구현하였다. 본 시뮬레이터는 광 기록 저장 채널에 대한 신호처리 시뮬레이션프로그램을 토대로 디지털 신호처리 프로세서(DSP)를 이용하여 RLL 변조 코드에 대한 인코더/디코더 및 채널을 통과한 데이터에 대해 심볼간 간섭을 제거하기 위한 등화기와 등화된 채널 출력 신호로부터 전송된 데이터를 결정하기 위한 여러 가지 신호 검출기를 설계하여 채널을 통과하기 전의 원본 데이터와 통과후의 출력 값에 대한 에러율을 분석, 검증하였다.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.102-105
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• 1998

차세대 이동통신 시스템을 위해 활발히 연구되고 있는 MC-CDMA 방식은 OFDM과 DS-CDMA의 장점을 결합하여 심벌간 간섭과 페이딩에 강하고 IFFT/FFT를 이용하여 효과적으로 변조/복조부를 구현할 수 있다는 장점을 갖는다. 하지만, 송신 신호가 다중 레벨 진폭 특성을 갖기 때문에 손신기에서 사용되는 고출력 증폭기의 포화 특성으로 인해 심각한 비선형 왜곡이 발생한다. 본 논문에서는 OFDM에서 이러한 비선형 왜곡의 보상을 위해 우리가 제안한 고정점 반복 기반의 사전왜곡기를 MC-CDMA 시스템에 적용하고, 이의 우수한 성능을 부가성 백색 가우시안 잡음 채널에서 64-FFT/IFFT을 이용하여 변조 및 복조를 수행하는 MC-CDMA 시스템에 대한 모의실험을 통해 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.3
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• pp.20-20
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• 2001

광섬유고리에 편광제어를 통해 여러 광경로들에 대해서 손실을 조정함으로써 손실이 작은 광경로에서 발진하게 함으로써 발진 파장을 가변시킬 수 있는 편광제어 파장가변 고리형 광섬유레이저를 구현하였다. 내부 공진편광기를 사용하여 1㎚의 종모드간격으로 발진을 일으킬 수 있었고 편광제어기 및 내부공진편광기를 조절해서 1540㎚에서 1560㎚의 범위에서 파장가변을 시킬 수 있었다. 또한 실험적으로 나타난 발진특성을 광경로와 복굴절손실의 개념을 사용하여 발진출력 특성을 분석함으로써 발진파장을 가변시키는 메카니즘을 추정해 보았다. 여기서 복굴절손실이 같은 광경로들의 종모드들 사이에 보강간섭이 일어나 발진파장을 변화시킬 수 있음을 알 수 있었다.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.4
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• pp.62-72
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• 1997

The optical power splitter/couplers based on MMI(multimode interference) in GaAs/AlGaAs are studied. We presetn a design of optical power splitter/couplers, which have deeply etched multimode waveguide. The properties and fabrication tolerance on the etching depth, multimode waveguide width are simulatedusing a FD-BPM (finite difference beam propgation method). Proposed 1*N optical of designed device is 0.7dB smaller than the optical power splitter with a shallowly etched MMI section. For 0.5dB excess loss, the predicted fabrication tolerance is 0.6.mu.m on the multimode waveguide width of the 14 optical power splitter with a deeply etched MMI section. Also excess loss and uniformity of poposed 32*32 optical power coupler are below 0.3dB. The excess loss of proposed 32*32 optical power coupler is 2dB smaller than the optical power coupler with a shallowly etched MMI section. It is shown that the optical power splitters/couplers with a deeply etched mMI section have low loss, good uniformity, and improved fabriction tolerance.