• 한국통신학회논문지
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• 제33권10B호
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• pp.855-864
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• 2008

대용량 장거리 WDM ($24{\times}40$ Gbps) 전송 시스템의 구현을 위해 단일 모드 광섬유에서 발생하여 WDM 채널 신호에 왜곡을 발생시키는 색 분산과 비선형 효과를 보상하는 광 링크 기술을 전산 시늉을 통해 살펴보고 그 설계 기준을 제안하였다. 링크 전송 기술은 전체 전송로에서 축적된 분산을 분산 보상 광섬유를 통해 보상하는 분산 제어 (DM; dispersion management)와 전체 전송로 중간에서 왜곡된 신호의 주파수를 반전시켜 보상하는 광위상 공액 기술로 구성된다. 본 연구에서 살펴본 DM은 집중형과 inline의 2 가지 구조이다. 전송 링크에 OPC (optical phase conjugator)만 적용된 WDM 전송 시스템에서의 경우에 비해 DM이 추가적으로 적용되면 모든 WDM 채널들의 눈 열림 패널티가 크게 개선되는 것을 확인하였다. 그리고 두 DM 구조 모두에서 유효 잉여 분산 범위를 이용하여 전송 링크의 설계 기준을 제시하였다. WDM 전체 채널들의 EOP 개선과 유효 잉여 분산 범위 모두 inline DM 구조가 집중형 DM 구조보다 더욱 양호한 결과를 나타냄을 확인하였다.

• 한국광학회지
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• 제8권2호
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• pp.134-141
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• 1997

기존의 .lambda.=1.31.mu.m에서 분산 최적화된 광통신시스템을 .lambda.=1.55.mu.m 광전송시스템으로 향상시키는데 필요한 분산보상 단일모드 광섬유(DCF)를 설계하였다. 총분산이 .lambda.=1.55.mu.m에서 큰 마이너스 분산치를 갖는 굴절율 분포를 얻기 위해 포물선 분포-이중클래드 광섬유의 분산특성을 해석하였다. 광섬유 스칼라 파동방정식으로부터 분산특성을 얻기 위해 1차원 유한요소법을 적용하였다. Reel에 감긴 DCF의 macro-bending에 의한 손실을 적절히 제한하기 위해, L $P_{01}$모드의 차단 파장이 .lambda.=1.80.mu.m이상이 되도록 설계하였다. 이 조건에 맞는 굴절율분포의 .lambda.=1.55.mu.m에서 분산의 하한치는 약 -120 ps/nm.km정도로 제한됨을 볼 수 있었다.다.

• 한국정밀공학회지
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• 제21권2호
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• pp.35-42
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• 2004

The control systems with friction cause the steady state error and slow response, because friction is a sensitive to the change of system condition and has highly nonlinear characteristics. To overcome these problems and do precise position control for a ball-screw system, we use Coulomb friction estimator and the sliding mode control(SMC) to compensate its negative effect. The applied SMC for tracking position has a characteristics of robust stability and reducing chattering, and is derived from the Lyapunov stability theorem and reaching condition. Compensating the estimated friction torque to the bounded disturbance term of the SMC's equivalent control input, it has a tracking performance better than the PID from the experimental results.

• 한국공작기계학회논문집
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• 제11권3호
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• pp.93-101
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• 2002

The effect of nonlinear friction in the low velocity is dominant in precise controlled mechanisms and it is difficult to identify the friction effect. The friction model which Canudas suggested so called, LuGre model is well expressed the friction effect as Streibeck in the law velocity. But it\`s model parameters were estimated continuously in operation for precise control. This paper suggests the sliding mode controller and observer for compensating the friction effect. Experimental results for a ball-screw system show that the proposed method has a good performance especially in the low velocity.

• 대한전기학회논문지
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• 제43권7호
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• pp.1158-1168
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• 1994

A variable structure control scheme(VSCS) with sliding mode that can be applied to the process with input/output(I/O) delay is proposed and its control performances is evaluated. The proposed VSCS with and output feedback scheme comprises a variable structure controller, a servo dynamic for tracking the set-poing, and a Smith predictor for compensating the effects of time delay. The robustness against the parameter variations and external disturbances can be achieved by the proposed VSCS even when the controlled process includes I/O delay. And the desired transient response is obtained by simple adjustment of the coefficients of the switching surface equation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.506-506
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• 2000

To improve control performance of a non-linear system, many other researches have used the sliding mode control algorithm. The sliding mode controller is known to be robust against nonlinear and unmodeled dynamic terms. However. this algorithm raises the inherent chattering caused by excessive switching inputs around the sliding surface. Therefore, in order to solve the chattering problem and improve control performance, this study has developed the sliding mode controller with a perturbation estimator using the observer-based fuzzy adaptive network generates the control input for compensating unmodeled dynamics terms and disturbance. And, the weighting parameters of the fuzzy adaptive network are updated on-line by adaptive law in order to force the estimation errors to converge to zero. Therefore, the combination of sliding mode control and fuzzy adaptive network gives rise to the robust and intelligent routine. For evaluating control performance of the proposed approach. tracking control simulation is carried out for the hydraulic motion simulator which is a 6-degree of freedom parallel manipulator.

• Journal of Information Processing Systems
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• 제20권1호
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• pp.105-115
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• 2024

The hybrid teaching approach of "MOOC + SPOC + Flipped Classroom" overcomes the constraints of time and space that are typically associated with traditional teaching methods, thus compensating for the shortcomings of traditional approaches. These changes in education are driven by the "Internet+" wave and the growing popularity of online teaching. The "MOOC + SPOC + Flipped Classroom" hybrid teaching mode can successfully compensate for the drawbacks of traditional teaching methods, thereby overcoming their restrictions. By defining relevant concepts, one can distill the key characteristics of the "MOOC + SPOC + Flipped Classroom" hybrid teaching mode. Formative assessment was employed to thoroughly evaluate the effectiveness of this teaching approach. By leveraging the advantages of massive open online course (MOOC), small private online course (SPOC), and flipped classroom, the "MOOC +SPOC + Flipped Classroom" teaching mode incorporates real-time student assessment through peer evaluation, computer-aided evaluation, and teacher evaluation. This mode promotes the simultaneous development of theoretical knowledge and practical skills, helping students to establish strong foundations while fostering their practical abilities. While the traditional teaching method remains fruitful, the convenience of today's network allows the teaching profession to continually evolve. The traditional teaching mode heavily relies on teachers, making it impossible to conduct lessons without them. However, the development of MOOC enables students to seek knowledge online from their preferred teachers, rather than solely relying on their assigned instructors.

• Journal of Advanced Marine Engineering and Technology
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• 제19권1호
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• pp.71-81
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• 1995

In this paper, a new speed control scheme for induction motor drives that regular sampled PWM and harmonic elimination switching pattern over the full range of output speed is presented. The proposed scheme(hybrid scheme) provides three mode and guarantees smooth voltage boost. A detailed description of the scheme, along with the relalization aspect, is described. Moreover, methods of compensating for dead time and optical transmission system of drive signal are proposed and investigated. Finally, experimental investigation of hybrid scheme is presented.

• 한국소음진동공학회논문집
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• 제18권10호
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• pp.997-1005
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• 2008

Linear motor stage is a useful device in precision engineering field because of its simple power transmission mechanism and accurate positioning. Even though linear motor stage shows fine positioning accuracy along travel axis, geometric dependent errors which relay on machining and assembling accuracy should be addressed to increase total positioning performances. In this paper, we suggests a cost effective yaw error compensation servo-system which is mounted on platform of the stage and nullify travel position dependent yaw error. This paper also provides a method of designing a sliding mode control which is robust to existing friction disturbance and model uncertainties. The reachability condition of slinding mode control for the yaw error compensating servo-system has been established. From some experimental results by using an experimental set-up, the sliding mode control showed its effective in disturbance rejection and its performance was superior to conventional linear controls.

• Journal of the Korean Wood Science and Technology
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• 제40권5호
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• pp.327-334
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• 2012

Wood and concrete show significantly different physical properties, and it need to be firstly understood for using wood-concrete composite. This study is performed for compensating this and effective hybridization of wood and concrete. This research in planned for wood-concrete composite after previous research which deals the shear performance with different anchorage length of steel rebar in wood. Yield mode and reference design value (Z) were derived using EYM (European Yield Model). And the yield mode changed before and after anchorage length of 10~15 mm - $I_s$ mode to IV mode. There was not increasing tendency of shear performance with increased anchorage length for over 20 mm of anchorage in concrete. And wood composite shows 65% and 93% on initial stiffness and yield load respectively compared with the wood-concrete composite. Wood-concrete composite showed brittle failure after yield point while wood-to-wood composite showed ductile failure.