• 전자공학회논문지A
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• 제33A권5호
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• pp.24-30
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• 1996

In this paper, we propose a fast code acquisition method that can reduce drastically the mean acquisition time of the direct sequence spread spectrum (DS-SS) system by using and integrated search and verification (ISV) scheme. The proposed method performs simultaneously the search and verification processes at every search cell, through storing sufficiently long signal samples enough to perform the verification process form the previously received samples. We analyze and acquisition performance in the case of Gaussian channel to evaluate theacquisition perfomrance of the proposed method. From the simple numericl analysis result, we have shown that the acquisition performance of the proposed method is better than that of the conventional serial search method, and the performance improvement becomes more prominent as the channel environment becomes degraded.

• 전자공학회논문지A
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• 제28A권11호
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• pp.855-865
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• 1991

A simple method for analysis of serial search burst-format direct-sequence spread-spectrum (DS-SS) code acquisition system had been recently proposed, and therein, the effect of the code autocorrelation sidelobes on the performance of DS-SS code acquisition system has been assessed [4],[5]. In this paper, a new hybrid scheme which combines the serial search with maximum likelihood search is proposed to eliminate the deleterious effect of code autocorrelation sidelobes, and the performance is analyzed for the additive withe Gaussian noise (AWGN) channels. To analyze the performance of this system, we have generalized the method used in [4],[5] to arbitrary burst-format DS-SS acquisition schemes. The results show that a new hybrid scheme has good immunity against the effect of code autocorrelation sidelobes. Thevalidity of the presented approach has been confirmed form the results of simulation.

• 한국기계가공학회지
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• 제12권4호
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• pp.114-122
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• 2013

This study introduces an optimization methodology for the determination of gate location that ensures the melt flow balance within a part cavity of injection mold. A new sequential direct-search scheme based on the recursive reduction of the designer-specified gate design area is developed, and it is integrated with a commercial flow simulation tool for optimization. To quantify the level of melt flow balance, we employ the maximum difference among the fill times for the melt fronts to reach the boundary elements of part cavity as objective function. The proposed methodology is successfully applied in the case study of melt flow balancing in molding of a bar code scanner model. The result shows that the melt flow balance at the optimized gate positions is significantly improved from that for the initial gate position.

• 한국정보통신학회논문지
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• 제11권10호
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• pp.1968-1976
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• 2007

본 논문에서는 다양한 페이딩 채널을 모델화 할 수 있는 나카가미-m 확률밀도함수를 이용하여 이동통신 채널 환경에서 필연적으로 존재하는 페이딩 환경을 고려한 MC DS-CDMA시스템의 직 병렬 혼합 동기 획득 성능을 분석 하였다. 동기 획득 시스템은 검색모드(Search Mode)와 확인모드(Verification Mode)를 갖도록 설계하여 나카가미-m 확률밀도 함수를 이용하여 동기 획득에 필요한 신호검출확률(Probability of Detection), 탐지 실패 확률 (Probability of Miss), 및 오경보율(False Alarm Rate)을 이론적으로 유도하여 직 병렬 혼합 동기 획득 알고리즘의 평균 동기 획득 시간(MAT)를 유도하고 시뮬레이션을 통하여 검증하였다.

• 한국통신학회논문지
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• 제21권7호
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• pp.1803-1813
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• 1996

This paper describes an automatic threshold decision using a maximum mismatched correlation value in the direct sequence spread spectrum (DS-SS) system. For received PN codes with different single-to-noise ratio (SNR), this scheme is able to detect a desired threshold value in the search mode, i.e. a maximum mismstched correlation value, so that value is utilized as a threshold for the verification mode. Performance of the proposed scheme in both the additive white gaussian noise (AWGN) and frequency-selective Rayleigh fading channels is analyzed through the Monte Carlo simulation. And hardware implementation of this scheme using a DSP processor is demonstrated. The proposed acquisition shceme is compared to the conventional constant threshold (CT) scheme, and significant improvement of performance is shown. Analysis of system performance in the verification mode is presented, and key quantities such as the false alarm probability and the detection probability are derived in a AWGN channel.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 전기설비전문위원
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• pp.74-76
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• 2009

In this paper, search method and sliding mode observer are developed for efficiency optimization of induction motor. The proposed control scheme consists of efficiency controller and adaptive backstepping controller. A search controller for which information of input of fuzzy controller is included in efficiency controller that uses a direct vector controlled induction motor. The search controller is based on the "Rosenbrock" method and finds the flux level at the minimum input power of induction motor. Once this optimal flux level has been determined, this information is utilized to update the rule base of a fuzzy controller A sliding mode observer is designed to estimate rotor flux and an adaptive backstepping controller is also used to compensate for mechanical uncertainties in the speed control of induction motor. Simulation results are presented to validate the proposed controller.

• 한국통신학회논문지
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• 제23권7호
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• pp.1699-1706
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• 1998

This paper presents a threshold decision technique for direct sequence code acquistion employing Pseudo-Noise(PN) matched filter. The probabilities of detection and false alarm are derived as a measure of the system performance in both nonfading and nonselective Rician fading channels. For received PN codes with different SNR, the proposed acquisition scheme is able to detect a desired threshold in the search mode so that this value is utilized as a threshold for the verification mode. Thus, there is no need to determine a threshold by applying the Neyman-Person ciriteron. It is shown that this scheme achieves lower probability of false alarm than the acquisition scheme based on the Neyman-Person criterion, giving comparable performance in terms of the probability of detection.

• 한국통신학회논문지
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• 제31권7A호
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• pp.682-688
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• 2006

본 논문에서는 파일롯 채널(pilot channel)이 존재하는 직접확산 코드분할 다중접속 방식(DS-CDMA)에서 PN 코드의 초기 동기획득 성능을 개선하기 위해 연판정 기법을 사용하는 방법을 제안한다. 본 논문에서 제안하는 연판정 기법을 하이브리드 동기획득 알고리듬에 적용하고, 평균 동기획득 시간 측면에서 분석한다. 분석을 위해, 제안된 방식의 수학적 모델을 제시하고, IMT-2000 채널모델에서 시뮬레이션을 수행한다. 수식적인 분석 결과, 제안된 방식이 한 쌍의 임계치를 사용하는 기존 방식에 비해 평균 동기획득 시간에서 약 0.2초 내지 0.4초 정도의 성능향상을 가져오는 것을 보여준다. 이것은 연판정 기법이 기존의 경판정 기법의 사용으로 인한 성능열화를 보상함으로써 생기는 이득이라고 볼 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1646_1647
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• 2009

In this paper, Takagi-Sugeno(T-S) fuzzy controller and search method are developed for efficiency optimization of induction motors(IMs). The proposed control scheme consists of efficiency controller and adaptive backstepping controller. A search controller for which information of input of T-S fuzzy controller is included in efficiency controller that uses a direct vector controlled induction motor. A sliding mode observer is designed to estimate rotor flux and an adaptive backstepping controller is used to control of speed of IMs. Simulation results are presented to validate the proposed controller.

• 한국기계가공학회지
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• 제9권6호
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• pp.21-28
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• 2010

This study shows an optimization procedure for an automatic determination on the gate position to ensure the fill-uniformity within a part cavity by using the injection molding simulation. For an optimization, the maximum pressure-difference within a part cavity induced at the stage of filling is used to evaluate degree of fill-uniformity. In addition, a direct search scheme based on the reduction of design space is developed and applied in the optimization problem. This corresponding proposed methodology was applied in the optimization on the gate location for a CD-tray molding, as a result, showed the improvement of the fill-uniformity within the cavity.