• 한국안전학회지
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• 제33권4호
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• pp.72-77
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• 2018

There are various approaches to prevent industrial accidents, of which the focus on human factors is behavior based safety(BBS). The BBS provides positive feedback on safety behavior and corrective feedback on unsafe behavior. Determining the feedback ratio of positive and correct feedback is an important issue in BBS. The purpose of this study was to examine the effects of positive and corrective feedback ratio on safety performance and feedback acceptance. The participants of this study were sixty undergraduate and graduate students at C University in Seoul, Korea. Participants were asked to work on a simulated welding task. The independent variable of was different positive vs. corrective feedback ratio (1:1 and 1:4). The dependent variables were the amount and the number of correctly completed work tasks, compliance rate of safety behavior, and feedback acceptance. The experimental design of this study was 2 x 2 mixed design. The results showed that feedback, regardless of the ratio, increased both correctly completed work tasks and the compliance rate of safety behavior, while 1:1 positive vs. corrective feedback ratio was more effective than 1:4 ratio. In addition, 1:1 ratio produced higher level of feedback acceptance compared to 1:4 ratio.

• 전자공학회논문지A
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• 제33A권7호
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• pp.1-14
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• 1996

Effects of the external optical feedback on the optical transmission characteristics were evaluated for 3 kinds of commercialized DFB-LD modules for 2.5Gbps optical communication systems. As a result, intensity noise induced by external optical feedback via generating the external cavity modes deteriorated the transmission performances of sthe DFB-LD modules as much as 1.5dB, 1.2dB, and 1.0dB for the maximum feedback ratio of -8.8dB which corresponds to the worst reflection along the fiber transmission line. Additional penalty of 0.5dB was occurrred when state of polarization of feedback light was adjusted. From the experiments evaluating the isolation ratio of the single polarization optical isolator, decrease of the polarization dependent isolation ratio as much as 10dB from that of specification and the effective isolation ratio as much as 20dB from that of specification was mjor cause of high sensitivity of DFB-LD modules to external feedback. It was suggested that polarization independent optical isolator or single polarization optical isolator with isolation ratio specification of more than 40dB is required for 2.5Gbps DFB-LD modules with complete suppression of external feedback effects.

• 한국자동차공학회논문집
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• 제4권3호
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• pp.102-111
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• 1996

For the air-fuel ratio control in a fuel injection SI engine, the Jump-Ramp control algorithm has been widely adopted by using the on/off type oxygen sensor. But the Jump-Ramp control method has limitation on treating the frequency and amplitude of the air-fuel ratio oscillation. This study suggests another feedback control logic named modulated fuel feedback control, which has a concept of pre-tuned air-fuel ratio oscillation. In the modulation method, the oxygen sensor output is not treated as on/off signal but as analog signal for feedback. By using the modulation method, the frequency and the amplitude of air-fuel ratio oscillation can be adjustable to some extent for improving the conversion efficiency of the Three-Way Catalyst. The result shows that the performance of the modulation method is better than that Jump-Ramp control method in reducing the amplitude of the air-fuel ratio oscillation as well as in increasing the frequency of the air-fuel ratio oscillation.

• 한국자동차공학회논문집
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• 제10권3호
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• pp.201-208
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• 2002

In this paper, the control strategy of ratio changing system for a metal belt CVT adopting primary pressure regulation is developed, and the shirting performance of pressure regulating type CVT with the suggested control strategy is investigated. The control strategy suggested in this study is composed of 2 feedback loop, one is speed ratio feedback and the other is primary pressure feedback. The pressure feedback is adopted to ensure prohibiting a belt slip during transient period in a fast downshift mode. Simulation results show that the system with suggested control strategy gives appropriate response time and tracking Performance for upshift and also gives a proper primary pressure which can prohibit the belt slip. In addition, it is fecund that the given system has an acceptable servo property in tracking the target speed ratio and robustness for the disturbance of line pressure.

• 한국멀티미디어학회논문지
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• 제16권9호
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• pp.1067-1076
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• 2013

Known as an important criterion that evaluates performance of future high-speed backbone networks, burst data loss ratio is well-studied in Optical Burst Switching networks. Current literatures mostly focus on reduce burst loss ratio without considering the system stability and link utilization after reducing. In this paper, we propose a novel framework which comes from feedback theoretic to dynamically control burst loss ratio in OBS. The proposed scheme tries to track the pre-set values of burst loss ratio and increases the stability and link utilization degree. The simulation results show that measured burst loss ratio always tracks setup reference with small errors, wavelength channel utilization is increased up to 2% and the system stability is also improved.

• 한국통신학회논문지
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• 제36권7C호
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• pp.413-420
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• 2011

본 논문에서는 양이 보청기의 음향궤환 및 잡음을 제거하기 위한 새로운 알고리즘을 제안한다. 이 알고리즘은 이중 마이크를 사용하여 잔차신호에서 음성신호를 제거한 후 궤환제거 필터의 계수를 갱신시킴으로써 수렴성능을 향상시킨다. 먼저 궤환제거기가 마이크 선호에서 궤환신호를 제거하고, 이어서 빔포밍 기법을 이용하여 잡음을 제거한다. 양이 보청기의 안정적 수렴을 보장하기 위해 좌측 및 우측 보청기를 분리하여 먼저 좌측 보청기를 수렴시키고 나서 그 다음 우측 보청기를 수렴시키는 과정으로 진행한다. 본 연구에서 제안한 궤환 및 잡음제거기의 성능을 검증하기 위하여 시뮬레이션 프로그램을 작성하고 모의실험을 수행하였다. 실험 결과, 제안한 적응 알고리즘을 사용하면 기존의 알고리즘을 사용하는 경우보다 궤환제거기에서 평균 14.43 dB의 SFR(Signal to Feedback Ratio), 잡음제거기에서 평균 10.19 dB의 SNR(Signal to Noise Ratio) 개선효과를 향상시킬 수 있는 것으로 확인하였다.

• Journal of Mechanical Science and Technology
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• 제15권6호
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• pp.699-708
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• 2001

This paper presents a new approach to the AFR (Air-to-Fuel Ratio) control problem, which is based on the wide-band oxygen sensor output. The dedicated nonlinear controller is based on the feedback lineaization technique. It is well known that the feedback linearizing control technique requires an exact model of the plant for the cancellation of plant nonlinearities. A sliding mode control scheme is applied which can effectively compensate the modeling uncertainties. The measurement time delay of an oxygen sensor limits the gain of the feedback controller. Hence, time delay compensation procedure is necessary for the improvement of control performance. The Smith predictor is adopted to compensate the effects of time delay. The simulation and experimental results show that the proposed controllers can effectively reduce the transient peaks of AFR in spite of fast tip-in and tip-out maneuvers of the throttle.

• Journal of applied mathematics & informatics
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• 제31권3_4호
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• pp.385-398
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• 2013

In this paper, a turbidostat model with ratio-dependent growth rate and impulsive state feedback control is considered. We obtain sufficient conditions of the globally asymptotically stable of the system without impulsive state feedback control. We also obtain that the system with impulsive state feedback control has periodic solution of order one. Sufficient conditions for existence and stability of periodic solution of order one are given. In some cases, it is possible that the system exists periodic solution of order two. Our results show that the control measure is effective and reliable.

• 한국전자통신학회논문지
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• 제14권6호
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• pp.1249-1256
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• 2019

본 논문에서는 보청기의 음향궤환 및 잡음을 제거하기 위한 새로운 알고리즘을 제안한다. 이 알고리즘은 기존의 FIR 구조를 이용하는 대신 신경망 적응예측필터를 이용한 심층학습 알고리즘으로 궤환 및 잡음제거 성능을 향상시킨다. 먼저 궤환제거기가 마이크 신호에서 궤환신호를 제거하고, 이어서 Wiener 필터기법을 이용하여 잡음을 제거한다. 잡음 제거는 음성신호가 가진 주기적 성질에 따라 선형예측모델을 이용하여 잡음이 포함된 음성신호로부터 음성을 추정해내는 것이다. 한 루프 안에 포함된 두 적응 시스템의 안정적 수렴을 보장하기 위해 궤환제거기 및 잡음제거기의 계수 업데이트를 분리하여 실시하며 제거 후 생성된 잔차신호를 이용하여 수렴시키는 과정을 진행한다. 본 연구에서 제안한 궤환 및 잡음제거기의 성능을 검증하기 위하여 시뮬레이션 프로그램을 작성하고 모의실험을 수행하였다. 실험 결과, 제안한 심층학습 알고리즘을 사용하면 기존의 FIR 구조를 사용하는 경우보다 궤환제거기에서 약 10 dB의 SFR(: Signal to Feedback Ratio), 잡음제거기에서 약 3 dB의 SNRE(: Signal to Noise Ratio Enhancement) 개선효과를 얻을 수 있는 것으로 확인되었다.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.277-282
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• 2006

With the aim of achieving half the regulated value of EURO-3 Emission Regulations, an ultra low emission motorcycle has been developed based on a motorcycle with an 1800 $cm^3$, horizontal opposed 6-cylinder engine. For the fuel supply system, an electronically controlled fuel injection system was applied. For the emission purification system, three-way catalysts, a feedback control system with a LAF(Linear Air-Fuel ratio) sensor, and a secondary air induction system were applied. To reduce CO and HC emissions during cold starting, an early catalyst activation method combining RACV(Rotary Air Control Valve) and retarded ignition timing was applied. After the catalyst activation, air-fuel ratio was controlled to maximize the purification ratio of the catalyst according to vehicle speed. For the air-fuel ratio control system, the LAF sensor was used. Furthermore, fine adjustment by the LAF feedback control reduced torque fluctuation due to the air-fuel ratio change. As a result, smooth ride feeling was maintained. Owing to these technologies, half the regulated value of EURO-3 has been achieved without any negative impact to the large-scaled motorcycles' drivability. This paper presents the developed ultra low emission technologies including the control method using an LAF sensor.