• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.12
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• pp.1208-1218
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• 2012

Disseminating broadcast information stably and reliably in IEEE 802.11-like CSMA wireless networks requires that a source should seek collision-free transmission to multiple receivers and keep track of the reception state of the multiple receivers. We propose a simple yet efficient feedback scheme for stable reliable broadcast in wireless networks, called 2-polling feedback, where the state of two receivers are checked by a source before its broadcast transmission attempt We present a performance analysis of the class of reliable broadcast feedback schemes in terms of two performance metrics (packet transmission delay and packet stable time). The analysis results show that the proposed 2-polling feedback scheme outperforms the current existing classes of feedback schemes in the literature, i.e., all-polling feedback and 1-polling feedback. The 2-polling feedback scheme has lower asymptotic complexity than the all-polling feedback, and has the same asymptotic complexity as the 1-polling feedback but exhibits almost 50 % reduction in packet stable time.

• Progress in Medical Physics
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• v.25 no.2
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• pp.72-78
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• 2014

The aim of the study is to test a hypothesis that quasi-breath-hold (QBH) biofeedback improves the residual respiratory motion management in gated 3D thoracic MR imaging, reducing respiratory motion artifacts with insignificant acquisition time alteration. To test the hypothesis five healthy human subjects underwent two gated MR imaging studies based on a T2 weighted SPACE MR pulse sequence using a respiratory navigator of a 3T Siemens MRI: one under free breathing and the other under QBH biofeedback breathing. The QBH biofeedback system utilized the external marker position on the abdomen obtained with an RPM system (Real-time Position Management, Varian) to audio-visually guide a human subject for 2s breath-hold at 90% exhalation position in each respiratory cycle. The improvement in the upper liver breath-hold motion reproducibility within the gating window using the QBH biofeedback system has been assessed for a group of volunteers. We assessed the residual respiratory motion management within the gating window and respiratory motion artifacts in 3D thoracic MRI both with/without QBH biofeedback. In addition, the RMSE (root mean square error) of abdominal displacement has been investigated. The QBH biofeedback reduced the residual upper liver motion within the gating window during MR acquisitions (~6 minutes) compared to that for free breathing, resulting in the reduction of respiratory motion artifacts in lung and liver of gated 3D thoracic MR images. The abdominal motion reduction in the gated window was consistent with the residual motion reduction of the diaphragm with QBH biofeedback. Consequently, average RMSE (root mean square error) of abdominal displacement obtained from the RPM has been also reduced from 2.0 mm of free breathing to 0.7 mm of QBH biofeedback breathing over the entire cycle (67% reduction, p-value=0.02) and from 1.7 mm of free breathing to 0.7 mm of QBH biofeedback breathing in the gated window (58% reduction, p-value=0.14). The average baseline drift obtained using a linear fit was reduced from 5.5 mm/min with free breathing to 0.6 mm/min (89% reduction, p-value=0.017) with QBH biofeedback. The study demonstrated that the QBH biofeedback improved the upper liver breath-hold motion reproducibility during the gated 3D thoracic MR imaging. This system can provide clinically applicable motion management of the internal anatomy for gated medical imaging as well as gated radiotherapy.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.3
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• pp.76-86
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• 1998

The Two-Mass Spring(TMS or Two-Inertia Resonance) system is one of the simplest models which generate a torsional vibration. In this system, it is required to design a controller achieving the control performance while suppressing the torsional vibration. In this paper, we compared and considered with the state feedback effects for the TMS system. By connecting each controller design to the state feedback control, we could predict each controller performances and decide weighting functions and parameters of LQ and $H_\infty$ controller.

• KIPS Transactions on Software and Data Engineering
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• v.6 no.7
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• pp.361-370
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• 2017

This paper proposes the architecture of test case generator that can generate test cases, considering feedback signals from subsystems controlled by an embedded system. In general, a closed system decides the next test input to its subsystem under its control referencing feedback signals from its subsystem. In such systems, it is hard to use the typical test cases generated without referencing feedback. The architecture proposed in this paper re-produces test cases in real time using feedback signals. The architecture is implemented and its effectiveness is verified through experimenting a demo system.

• The Journal of Korean Association of Computer Education
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• v.10 no.4
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• pp.125-133
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• 2007

Many researches have tried to introduce affective computing for Human-Computer Interaction (HCI). In the affective aspect, emotional memories significantly affect on people's cognitive processing activities. In this paper, to observe the effect of affective feedback for emotional state of learners in an e-learning environment, selected emotional feedback messages and delivery method are integrated into an e-learning system. Self reporting button for recognizing learner's emotional state are used for detecting learner's emotional states and the test results show that providing affective feedback to learner has positive effects in e-learning environment in terms of learner's academic achievements.

• Proceedings of the ESK Conference
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• 1998.04a
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• pp.76-80
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• 1998

디자인 개발시 사용자 참여의 중요성이 날로 증가하고 있는 것은 자명한 사실이다. 그중 사용성 평가에 서의 사용자의 참여는 비교적 활발한 상태이다. 하지만, 현재 기본적으로 행해지고 있는 렙에서의 사용 성 평가는 여러 가지 면에서 극히 제한적이며 비용이 많이 들고, 시간 또한 많이 소비된다. 또한 이러 한 평가는 광범위한 데이터의 수집과 빠른 피드백을 얻는 데 여러 가지 문제점을 가지고 있다. 우리가 사용성 평가에서 필요로 하는 것은 빠르고 정확한 피드백을 광범위하게 수집하여 디자인에 제공할 수 있는 방법이다. 본 연구에서는 디자인 개발에 있어 앞에서 설명한 빠르고 광범위한 사용자의 피드백을 얻기위한 방법으로 인터넷을 사용하여 사용자의 직접적인 참여-사용성 평가 등-가 가능하게 되었다는 것에 초점을 맞추었다. 사용성 평가를 위한 프로토 타이핑과 사용자의 문화적 배경과 성향을 가늠할 수 있는 질문들을 인터넷의 홈페이지에 올려 각각의 서로 다른 문화권에 속해 있는 사용자들이 제품 디자인 개발 과정에서 되는 사용자의 테스트 데이터를 원격 수집하여 디자인 평가/개발에 즉각적인 피드백을 제시하여 디자인 프로 세스에서의 사용자의 참여를 극대화 시킨다. 이렇게함으로써 상당한 분량의 상용성 평가를 단시간에 시행 하는 것이 가능하며 서로 다른 문화권에 속해있는 사용자의 관념적 특성과 사용형태의 현상적 특성을 밝히 고 이들간의 관계를 연계 분석하여 데이터의 질적인 향상또한 기대할 수 있을 것이다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.11a
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• pp.379-382
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• 2009

본 논문에서는 폐회로 다중 안테나 송수신 (closed-loop multiple-input multiple-output) 기법을 사용하는 적응형 협동 다중 홉 중계 시스템을 제안한다. 중계기와 기지국 사이의 이동성이 낮기 때문에, 폐회로 다중 안테나 송수신 기법은 개회로 다중 안테나 송수신 기법보다 높은 다이버시티 이득을 얻을 수 있다. 이 때, 한 개 이상의 중계 터미널들은 기지국으로 전송을 공유하고 프리코딩 가중치벡터를 피드백하기 위해 하나의 협동 그룹에 포함되어야 한다. 피드백 비트의 증가로 인한 전송량 감소를 최소화 하기 위해 코드북 기반의 최대비 전송 기법을 사용하여 비트백 비트수를 제한한다. 기지국은 협동 중계 그룹 중에서 채널 상태가 가장 좋은 중계기를 선택하고, 프리코딩을 위한 인덱스 값을 중계기에 피드백한다. 이러한 중계 시스템을 위해 피드백 형태와 선택 프로토콜 시나리오를 제안하고, 모의실험을 통해 중계기 선택에 따른 성능을 확인한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9A
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• pp.673-678
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• 2009

This paper presents a feedback method for improving the system capacity of MU-MIMO system for downlink channel environments. In a typical conventional feedback method, CVQ, in order to enhance the channel capacity, not only the feedback load is increased but also the quantization of the channel vector is increased, because the channel parameter of each user has to be fed back after quantizing one of the pre-defined N-codebook vectors. In this paper, a novel feedback method is proposed which provides an improved system capacity by transferring the channel state information without increasing the feedback load. Performance of the proposed method is compared to the conventional CVQ method through computer simulations. The simulation results show that the proposed method with 3-bit feedback provides a system capacity comparable to the CVQ method of 6-bit feedback when the number of transmit antennas is 2.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.2
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• pp.310-317
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• 2010

In this paper, we propose a method for swing-up and stabilization of a SESIP(Self-Erecting Single Inverted Pendulum) system which is one of the typical nonlinear systems. We use PV(Proportional velocity) controller for swinging up the pendulum and employ a PI-type state-feedback controller for stabilizing the pendulum. Control is switched to a stabilizing controller, which is designed to balance the inverted position of pendulum and the cart position to the near vertical position. Computer simulations are performed to illustrate the control performance of the proposed scheme.

• The Journal of the Korea Contents Association
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• v.11 no.9
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• pp.469-484
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• 2011

The purpose of this study was to examine the effect of arousal control training conjugated heart rate biofeedback for national substitute three archery players. The arousal control training programs was developed on previous researches and 3 archery experts and 1 sport psychologist had meetings. The training programs contained as orientation, breathing regulation, progressive relaxation technique, heart rate biofeedback, cognitive restructuring, routine and consisted of 24 weeks. XCOACH was utilized as heart rate biofeedback instrument. The effects was examined on competitive state anxiety inventory-2, archery score and ranking, observation, interviews and self assessment. As the results, the score of subfactor was improved on somatic state anxiety, cognitive state anxiety and self-confidence. As the results of observation, interviews and self assessment, the ability of arousal control was enhanced by using effective psychological skills conjugated heart rate biofeedback.