• ETRI Journal
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• 제26권5호
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• pp.443-451
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• 2004

Since the publication of Alamouti's famous space-time block code, various quasi-orthogonal space-time block codes (QSTBC) for multi-input multi-output (MIMO) fading channels for more than two transmit antennas have been proposed. It has been shown that these codes cannot achieve full diversity at full rate. In this paper, we present a simple feedback scheme for rich scattering (flat Rayleigh fading) MIMO channels that improves the coding gain and diversity of a QSTBC for 2$^n$ (n=3, 4, ${\cdots}$) transmit antennas. The relevant channel state information is sent back from the receiver to the transmitter quantized to one or two bits per code block. In this way, signal transmission with an improved coding gain and diversity near to the maximum diversity order is achieved. Such high diversity can be exploited with either a maximum-likelihood receiver or low-complexity zero-forcing receiver.

• 한국어교육
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• 제25권1호
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• pp.203-234
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• 2014

This paper demonstrates how to incorporate the teaching of communication strategies into a large class of English-speaking learners of the Korean language. The method proposed here was developed to overcome the difficulty of conducting language activities involving communicative interactions amongst students and also between teacher and students in a large classroom. As a way of compensating the minimal opportunities for interactions in the classroom, students are given the task of expressing in Korean the English translations of authentic Korean comics via Twitter, which was later replaced with the feedback feature on Moodle, and then their Korean expressions are collected and projected onto a big screen. These collected expressions by students naturally differ from one another, helping students to realize that it is possible for them to express the same message or meaning in many different ways. The results of two separately conducted questionnaires show that this method is an effective way of providing students with significantly increased chances of producing 'comprehensible output' that requires them to think of how to communicate with their limited knowledge of the Korean language. Many students also commented that the teachers' feedback on errors provides them with the opportunity to learn about common errors as well as their own errors.

• 영어영문학
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• 제58권6호
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• pp.1085-1101
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• 2012

This study, guided by Engeström's (1999, 2001) activity theory which owes its theoretical lineage to sociocultural theory, explores how roles (peer feedback givers and receivers) and tasks are distributed among EFL students who engage in peer response. More specifically, as an extension of previous research of focusing on "stances" ESL students adopt, I investigate whether different roles in peer response groups make a difference in the nature of peer response and identify what underlays the different roles in peer group interaction. In addition, I examine whether different roles to the peer response create tensions and contradictions in peer response and how these created conflicts lead to changes in peer response activity system. The data I wish to consider is first-person narratives elicited from two EFL college students. I use Won's and Choi's (both pseudonyms) stories as a heuristic, which is a method that allowing one to proceed fruitfully in finding information. Foregrounded in this study are the students' different roles in the same peer response activity. A division of labor exists between Won/Choi and their peers - the way tasks are divided up and the way roles are structured. Yet Won and Choi adopted rather divergent roles when participating in peer response activity and carried out qualitatively different peer response activities. It is obvious here that the distribution of their roles in carrying out this particular peer response is shaped by Won' and Choi's perception about the validity of their peers' responses.

• International Journal of Control, Automation, and Systems
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• 제6권1호
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• pp.24-34
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• 2008

A novel neural network model, termed the standard neural network model (SNNM), similar to the nominal model in linear robust control theory, is suggested to facilitate the synthesis of controllers for delayed (or non-delayed) nonlinear systems composed of neural networks. The model is composed of a linear dynamic system and a bounded static delayed (or non-delayed) nonlinear operator. Based on the global asymptotic stability analysis of SNNMs, Static state-feedback controller and dynamic output feedback controller are designed for the SNNMs to stabilize the closed-loop systems, respectively. The control design equations are shown to be a set of linear matrix inequalities (LMIs) which can be easily solved by various convex optimization algorithms to determine the control signals. Most neural-network-based nonlinear systems with time delays or without time delays can be transformed into the SNNMs for controller synthesis in a unified way. Two application examples are given where the SNNMs are employed to synthesize the feedback stabilizing controllers for an SISO nonlinear system modeled by the neural network, and for a chaotic neural network, respectively. Through these examples, it is demonstrated that the SNNM not only makes controller synthesis of neural-network-based systems much easier, but also provides a new approach to the synthesis of the controllers for the other type of nonlinear systems.

• 한국전문물리치료학회지
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• 제11권3호
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• pp.11-18
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• 2004

This study is aimed at investigating the influence of different quantitative knowledge of results on the measurement error during lumbar proprioceptive sensation training. Twenty-eight healthy adult men participated and subjects were randomly assigned into four different feedback groups(100% relative frequency with an angle feedback, 50% relative frequency with an angle feedback, 100% relative frequency with a length feedback, 50% relative frequency with a length feedback). An electrogoniometer was used to determine performance error in an angle, and the Schober test with measurement tape was used to determine performance error in a length. Each subject was asked to maintain an upright position with both eyes closed and both upper limbs stabilized on their pelvis. Lumbar vertebrae flexion was maintained at $30^{\circ}$ for three seconds. Different verbal knowledge of results was provided in four groups. After lumbar flexion was performed, knowledge of results was offered immediately. The resting period between the sessions per block was five seconds. Training consisted of 6 blocks, 10 sessions per one block, with a resting period of one minute. A resting period of five minutes was provided between 3 blocks and 4 blocks. A retention test was performed between 10 minutes and 24 hours later following the training block without providing knowledge of results. To determine the training effects, a two-way analysis of variance and a one-way analysis of variance were used with SPSS Ver. 10.0. A level of significance was set at .05. A significant block effect was shown for the acquisition phase (p<.05), and a significant feedback effect was shown in the immediate retention phase (p>.05). There was a significant feedback effect in the delayed retention phase (p<.05), and a significant block effect in the first acquisition phase and the last retention phase (p<.05). In conclusion, it is determined that a 50% relative frequency with a length feedback is the most efficient feedback among different feedback types.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1279-1300
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• 2017

In the interweave cognitive networks, the interference from the primary user degrades the performance of the cognitive user transmissions. In this paper, we propose an adaptive cooperation scheme in the interweave cognitive networks to improve the performance of the cognitive user transmissions. In the proposed scheme for the bidirectional communication of two end-source cognitive users, the bidirectional communication is completed through the non-relay direct transmission, the one-way relaying cooperation transmission, and the two-way relaying cooperation transmission depending on the limited feedback from the end-sources. For the performance analysis of the proposed scheme, we derive the outage probability and the finite-SNR diversity multiplexing tradeoff (f-DMT) in a closed form, considering the imperfect spectrum sensing, the interference from the primary user, and the power allocation between the relay and the end-sources. The results show that compared with the direct transmissions (DT), the pure one-way relaying transmissions (POWRT), and the pure two-way relaying transmissions (PTWRT), the proposed scheme has better outage performance. In terms of the f-DMT, the proposed scheme outperforms the full cooperation transmissions of the POWRT and PTWRT.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.53-56
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• 2001

In this paper we discuss a direct satellite broadcasting system for vehicle. The proposed satellite-steering algorithm and controller based on it are designed for a communication and broadcasting system which uses the Mugungwha satellite. The Mugungwha satellite that the proposed system should steer is a geostationary orbit device. The satellite-steering algorithm computes azimuth and elevation with reference to a stationary point on earth. This is extended to a real satellite steering algorithm that considers position and attitude. Real moving position and attitude are represented by latitude, longitude, roll, pitch and yaw. To apply these five pieces of information to the reference satellite steering algorithm, we introduce Euler's degree coordinates that express independently the rotation of each axis relative to an axis. There are two ways a basic algorithm of the antenna of a vehicle can track and orient to satellite. One way is a feedback loop method for broadcasting gain, while the other is a feedback loop method for position and attitude of a vehicle. In the present paper, we design a controller of satellite broadcasting system for a vehicle using an algorithm that combines the two methods. We performed a simulation and experiment to prove effectiveness.

• 한국정보통신학회논문지
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• 제24권6호
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• pp.751-758
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• 2020

사물인터넷을 비롯한 다양한 형태의 통신을 활용한 응용분야가 생겨남에 따라 통신의 형태가 다양해지고 있다. 어떠한 응용은 빠른 피드백을 요구하기도 하고, 다른 응용은 수신여부와는 상관없이 데이터를 계속 보내기도 한다. 한 방향으로 데이터를 전송하는 것은 반대 방향 응답에 의해 확인될 수 있다. 이러한 정보 교환은 양방향 통신을 형성한다. 송신자는 수신자의 응답에 따라 다음 동작을 결정하므로 빠른 응답을 제공하는 것이 중요하다. 본 논문에서는 셀룰러 네트워크에서 양방향 통신의 전송지연 성능을 향상시키기 위한 기지국 협력 전송 기법을 제안한다. 양방향 트래픽뿐만 아니라 동일한 방향의 트래픽을 가진 협력 기지국을 활용하는 양방향 통신 기법을 고안하였다. 제안한 방식을 통하여 지연 시간 성능이 향상됨을 확인하였다.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제31권4호
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• pp.409-432
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• 2017

본 연구는 최근 과정 중심 평가의 중요성과 함께 주목 받고 있는 형성평가의 정착 및 운영을 위한 방안을 모색하고자 하였다. 그 방안의 하나로 설정한 학생 상호피드백을 통한 형성평가가 초등학교 4학년 학생들의 수학 학업 성취도와 수학적 태도에 미치는 영향을 살펴보았다. 본 연구를 진행하기 위해 동질성이 검증된 실험집단과 비교집단을 선정하여 실험집단에는 학생 상호피드백을 통한 형성평가를, 비교집단에는 본인 확인피드백을 통한 형성평가를 실시하였다. 그 결과, 학생 상호피드백을 통한 형성평가는 학생들의 수학 학업 성취도를 향상시키고, 학생 상호피드백을 통한 형성평가는 수학적 태도도 긍정적으로 변화시켰다. 이는 학생 상호피드백을 통한 형성평가가 초등학생들의 수학 학습에 있어서 인지적, 정의적 측면에 유의미한 영향을 미쳤다고 볼 수 있다.

• 대한전기학회논문지
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• 제40권7호
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• pp.696-705
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• 1991

This paper describes the procedures for pre-tuning and re-tuning the gains of PI controller based on output patterns -output error integral- of the unknown process which may not have any information, for example, system order, deadtime, time constant, etc. The key ideas of the proposed adaptive scheme are as follows. The scheme determines the initial gains by using ZNM (Ziegler-Nichols Method) with relay feedback, and then the adaptive algorithms by pattern recognition are introduced for re-runing the PI gains with on-line scheme whenever control conditions are changed. Because, among the various auto-tuning procedures, ANM with relay feedback has the difficulty in re-tuning with on-line and Bristol method has no comment on initial settings and has variables to pre-determine, which makes the algorithm comples, the proposed methods have the combined scheme with above two procedures to recover those problems. And this paper proposes a simple way to determine adaptive constant in Bristol method. To show the validity of the proposed method, an example is illustrated by computer simulation and a laboratory process, heat exchanger, is experimented.