• 대한전기학회논문지:시스템및제어부문D
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• 제52권3호
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• pp.134-141
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• 2003

PID controllers with constant gains have been widely used in various control systems due to its powerful performance and easy implementation. But it is difficult to have uniformly good control performance in all operating conditions. In this paper, we propose a nonlinear variable PR controller with immune feedback mechanism. An immune feedback mechanism is based on the functioning of biological T-cells, they include both an active term, which controls response speed. and an inhibitive term, which controls stabilization effect. Therefore, the proposed nonlinear PID controller is based on immune responses of biological. immune feedback mechanism which is the cell mediated immunity and In order to choose the optimal nonlinear PID controller games, we also propose the tuning algorithm of nonlinear function parameter in immune feedback mechanism. To verify performance of the proposed algorithm, the speed control of nonlinear DC motor are performed. Front the simulation results, we have found that the proposed algorithm is more superior to the conventional constant fain PID controller.

• 한국압력기기공학회 논문집
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• 제13권2호
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• pp.51-59
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• 2017

Steam jets ejected from a rupture zone of high energy pipes may cause damage to adjacent structures. This event could lead to more serious accidents in nuclear power plants. Therefore, to prevent serious accidents, high energy pipes of nuclear power plants are designed according to the ANSI / ANS 58.2 technical standard. However, the US Nuclear Regulatory Commission (USNRC) has recently pointed out non-conservatism in existing high energy pipe fracture evaluation methods, and required the assessment of the unsteady load of the jet caused by a potential feedback mechanism as well as the impact range of steam jet, the jet impact loads and the blast wave effects at the initial breakage stage. The potential feedback mechanism refers to a phenomenon in which a vortex formed by impingement jets amplifies vortex itself and induces jet vibration in a shear layer. In this study, CFD methodology using the LES turbulence model is established and numerical analysis is carried out to evaluate the dynamic behavior of impingement jets and the potential feedback mechanism during jet impingement. Obtained results have been compared with an empirical correlation and experiment.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권5호
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• pp.259-267
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• 2003

In this paper, we propose a nonlinear variable PID controller using a cell-mediated immune response. An immune feedback response is based on the functioning of biological T-cells. An immune feedback response and P-controller of conventional PID controllers resemble each other in role and mechanism. Therefore, we extend immune feedback mechanism to nonlinear PE controller. And in order to choose the optimal nonlinear PID controller games, we also propose the on-line tuning algorithm of nonlinear functions parameters in immune feedback mechanism. The trained parameters of nonlinear functions are adapted to the variations of the system parameters and any command velocity. And the adapted parameters obtained outputs of nonlinear functions with an optimal control performance. To verify performances of the proposed control systems, the speed control of nonlinear BC motor is performed. The simulation results show that the proposed control systems are effective in tracking a command velocity under system variations.

• 센서학회지
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• 제31권4호
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• pp.260-265
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• 2022

In this study, we establish hyper-elastic haptic feedback in a virtual environment using finite element analysis techniques and develop a Force Torque (FT) sensor utilization method for application in tele-operation environments. In general, regarding haptic feedback data, in a tele-operation environment, the user is provided with feedback according to the measured force data when the model is inserted through an FT sensor. Conversely, in a virtual environment, the press-fitting model can be expressed through the spring-damper system rather than an FT sensor to provide feedback. However, unlike rigid and the elastic bodies, the hyper-elastic body represented by a spring-damper system in a virtual environment is a simple impedance model using stiffness and damping coefficients; it is limited in terms of providing actual feedback. Thus, in this study, haptic feedback was implemented using the data obtained from POD-RBF analysis results during hyper-elastic press-fitting experiments. The haptic feedback mechanism developed in this study was verified by comparing the FT sensor feedback data measured and calculated through hyper-elastic press-fitting experiments with spring-damper feedback data. Subsequently, the POD-RBF analysis feedback was compared and evaluated against the feedback mechanism of each environment through the test subject, and the similarities between the POD-RBF analysis feedback and FT sensor data feedback were verified.

• 한국경영과학회지
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• 제32권2호
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• pp.53-69
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• 2007

Internet shopping websites have offered comfort to consumers in shopping and built trust relationships with them by providing electronic agents for recommendation, escrow services, and customer centers etc. But as there is little big difference among the shopping websites in terms of technical competence, website design, operational policy, they recognize online feedback (reviews or recommendation of consumers or experts) and online feedback mechanism as important marketing tools. Based on online feedback related studies, this study explores antecedents (consensus, vividness of reviews, interactions in review boards) of the perceived effectiveness of review boards which are text-based feedback mechanisms and its consequences such as trust, satisfaction, and intention to use. The results show that the perceived effectiveness of review boards is significantly affected by vividness of reviews and interactions in review boards, and the impact of interaction in review boards on the perceived effectiveness of review boards is stronger than that of vividness of reviews. The results also show that the perceived effectiveness of review boards has a significant influence on trust and satisfaction with the shopping websites, and intention to use is influenced by both trust and satisfaction.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.728-732
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• 2008

본 연구는 운동 표상에 관한 뇌 메커니즘의 이해를 위해 fMRI를 이용한 측정 시스템을 개발하였다. 개발된 시스템의 검증을 위해 예비 실험을 시행하였다. fMRI task는 visual feedback을 제공하는 task와 차단하는 task 두 가지의 task로 구성되었다. 실험 결과 visual feedback이 제공되었을 때는 left superior orbital gyrus, bilateral precentral gyrus, left superior occipital gyrus, left supplementary motor area, right thalamus, right postcentral gyrus 그리고 right superior parietal lobule 같은 영역들이 활성화 되었다. Visual feedback이 차단되었을 때는 left precuneus, right middle temporal gyrus, bilateral supplementary motor area, right anterior cingulate cortex, left Inferior temporal gyrus, left insula lobe, right superior parietal lobule, bilateral postcentral gyrus 그리고 left precentral gyrus 같은 영역들이 활성화 되었다. 개발된 시스템을 통해서 visual feedback이 차단되었을 경우 운동 표상에 관한 뇌 메커니즘을 알아 볼 수 있었다.

• 한국정보시스템학회지:정보시스템연구
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• 제26권4호
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• pp.1-15
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• 2017

Purpose Through the provision of real time performance information about who is contributing and who is not in Electronic Brainstorming, prior studies evidenced a significant performance gain. However, it has been observed that the quantity-based performance feedback alone does not have enough restrictiveness to guide the performance behavior throughout the idea generation session. We included the notion of goal setting into the process performance feedback mechanism in an effort to regulate performance behavior and to better understand why individuals in Electronic Brainstorming are not obtaining enough stimulation benefits in the group interaction process. Design/methodology/approach We had developed real-time visual process performance feedback and modified to include goal setting. This mechanism visually displays individuals' performances two-dimensionally (quality for each idea vertically and quantity of ideas horizontally along with their goals). As individuals' contributions accumulate, the mechanism reveals performance histories by connecting the sequence of ideas in a time-series format, telling stories of individuals' performances. Then, we compared the performance outcome from this study with the outcomes from two prior studies (i.e., Jung et al., 2010 and Jung, 2014). Findings The results showed that the inclusion of goal setting into the process performance feedback solved the issue in the previous study. That was the lower than expected magnitude of performance enhancement of process performance feedback when compared to that of quantity-based feedback. It appears that goals as a motivational technique provide standards for systematic self-evaluation, serving as a cue to regulate performance behavior by strengthening the linkage between effort and performance. Thus, goals seem to set up a self-fulfilling prophecy, preconditioning better performance. However, the outcome still showed that its performance magnitude is unsatisfactory because the outcome of this study turned out to be close to the outcome of just quantity-based performance feedback in Jung et al.'s (2010) study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1785-1801
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• 2017

In recent years, image encryption algorithms have been developed rapidly in order to ensure the security of image transmission. With the assistance of our previous work, this paper proposes a novel chaotic image encryption algorithm based on self-adaptive model and feedback mechanism to enhance the security and improve the efficiency. Different from other existing methods where the permutation is performed by the self-adaptive model, the initial values of iteration are generated in a novel way to make the distribution of initial values more uniform. Unlike the other schemes which is on the strength of the feedback mechanism in the stage of diffusion, the piecewise linear chaotic map is first introduced to produce the intermediate values for the sake of resisting the differential attack. The security and efficiency analysis has been performed. We measure our scheme through comprehensive simulations, considering key sensitivity, key space, encryption speed, and resistance to common attacks, especially differential attack.

• 전기전자학회논문지
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• 제22권2호
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• pp.499-505
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• 2018

피드백 전계효과 트랜지스터는 채널 내부의 전자와 정공의 의해 발생하는 피드백 현상으로 이상적인 스위칭 특성을 갖기 때문에 최근 세계적으로 많은 연구가 진행되고 있다. 이 새로운 동작원리를 가지는 소자는 초저전력 스위칭 전자소자로 동작이 가능할 뿐만 아니라 채널 내부에 축적된 전자와 정공에 의한 히스테리시스 특성으로 메모리 소자로도 동작 가능하여 그 활용 범위가 넓다. 본 논문에서는 지금까지 제안된 다양한 구조의 피드백 전계효과 트랜지스터와 그 동작 메커니즘에 관해 확인하고 적용 가능 분야에 대해서 살펴본다.

• 한국컴퓨터정보학회논문지
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• 제3권1호
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• pp.35-46
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• 1998

비정형 데이터를 다루는 정보검색 시스템에서 검색의 정확도는 사용자의 인지에 의존하며 따라서 사용자의 검색 평가는 시스템의 효율을 측정하는 척도의 하나이다. 적합성피드백은 사용자의 검색 평가를 시스템에 입력하여 질의의 수정, 재 검색을 반복함으로써 재현율과 정확도를 높이고자 하는 질의 확장 방법의 일종이다. 본고에서는 적합성 피드백의이론적 배경과 구현 절차를 기술하였다.