• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.6
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• pp.1828-1847
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• 2014

Coordinated multi-point (CoMP) transmission has been regarded as a potential technology for LTE-Advanced. In frequency division duplexing systems, channel quantization is applied for reporting channel state information (CSI). Considering the dynamic number of cooperation base stations (BSs), asymmetry feature of CoMP channels and high searching complexity, simply increasing the size of the codebook used in traditional multiple antenna systems to quantize the global CSI of CoMP systems directly is infeasible. Per-cell codebook based channel quantization to quantize local CSI for each BS separately is an effective method. In this paper, the theoretical upper bounds of system throughput are derived for two codeword selection schemes, independent codeword selection (ICS) and joint codeword selection (JCS), respectively. The feedback overhead and selection complexity of these two schemes are analyzed. In the simulation, the system throughput of ICS and JCS is compared. Both analysis and simulation results show that JCS has a better tradeoff between system throughput and feedback overhead. The ICS has obvious advantage in complexity, but it needs additional phase information (PI) feedback for obtaining the approximate system throughput with JCS. Under the same number of feedback bits constraint, allocating the number of bits for channel direction information (CDI) and PI quantization can increase the system throughput, but ICS is still inferior to JCS. Based on theoretical analysis and simulation results, some recommendations are given with regard to the application of each scheme respectively.

• Journal of Advanced Navigation Technology
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• v.22 no.4
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• pp.325-335
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• 2018

Limited access to state information in the design of a feedback controller has brought out a significant amount of research on the design of an output feedback controller. Despite its long endeavor to find an optimal one, it is still an open problem. Thus, we focus on the comparison of existing states of arts in the design of a static output feedback controller in terms of stability and complexity so as to find further research direction in this field. To this end, we present eight design methods in a unified presentation. We also provide the complete description of algorithms which can be applicable to any system configuration. Stability performance and complexity in terms of processing time are evaluated through numerical simulations. Simulation results show that the algebraic controller (AC) algorithm [20] has the smallest complexity while the scaling linear matrix inequality (SLMI) algorithm [18] seems to achieve the best stability in most cases with much higher complexity.

• Journal of Internet Computing and Services
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• v.24 no.6
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• pp.23-29
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• 2023

As an effort to maximize the immersiveness of user experience in virtual reality, there have been constant efforts to provide a user with tactile sensation by providing haptic feedback. Most of the haptic feedback methods, however, can create only limited or unrealistic haptic sensations since they utilize affordable actuators such as a vibrotactile actuator. When it comes to martial arts training or a game, the limitation of such haptic feedback is apparent due to the significant difference between the physical impact of hitting an object and the sensation departed from a vibrotactile actuator. Noting this, we proposed a haptic impact system that can create a haptic impact when the user hits a virtual object with the fist. The haptic interface uses a quick-return mechanism that can deliver haptic impact feedback to a user's fist. The realism of the haptic impact was evaluated by conducting a human-subject experiment. The results indicate a significant effect of haptic feedback on the realism of the virtual impact.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.3
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• pp.208-213
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• 2004

This paper is concerned with the theoretical estimation of the single-input single-output(SISO) positive position feedback(PPF) controller and the derivation of the stability conditions for the multi-input multi-output (MIMO) PPF controller. Although the stability condition for the SISO PPF controller was derived in the earlier works, the question regarding the performance estimation of the SISO PPF controller has never been studied theoretically. Hence, the SISO PPF controller for the single degree-of-freedom system was first investigated and then control parameters including gain, the filter frequency, and the damping factor of the PPF controller were analyzed in detail thus providing the design methodology for the SISO PPF controller. In the case of real structure. there are infinite number of natural modes so that some modes are to be controlled by a limited number of actuator and sensor. Based on the theoretical results on the SISO PPF controller, the stability condition for the multi-input multi-output PPF controller was derived when only the few number of modes are to be controlled. The control spillover problem is also discussed in detail.

• The Journal of Information Systems
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• v.18 no.3
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• pp.135-154
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• 2009

As the knowledge is recognized as a core factor of organization's competitiveness and creation of value added, the importance of knowledge management is also increased. To achieve the successful knowledge management, it is important to establish strategy that consider essential purpose of knowledge management such as creating and sharing of knowledge resource, improving performance, and continuing organizational innovation within the organization and influence factor inside and outside of organization. Until now, however, the research for knowledge management strategy was mostly limited to the statistical analysis based on the unilinear causality model, and systematic access and analysis that consider interaction and feedback structure between factors. In this paper, we developed the novel decision-making framework for successful strategy establishment by applying the analytic network process(ANP). Specifically. we derive clusters and components to decide the interaction and feedback structure between the elements of knowledge management by literature studies. And we produced relative importance and preference of clusters, components and alternatives dealing with feedback structure through the survey of experts in the field or related one of knowledge management. In result of this study, we expect that it will help the knowledge officer to decide establishing knowledge management strategy.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.10
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• pp.1-6
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• 2011

In this paper, the sum-rate and BER performances of MU-MIMO system employing quantized differential feedback technique are analyzed over temporrally correlated channels. Several differential codebooks are assumed in the analysis such as quasi-diagonal codebook, spherical cap codebook, and differential equal gain codebook. The simulation results indicates that the system employing quantized differential feedback technique provides significant performance improvement. The performance improved 0.6bps/Hz at least in terms of sum-rate, and 4dB power gain is provided in terms of average BER.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.1007-1014
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• 2004

This paper presents a study of low frequencies volume velocity vibration control of a smart panel in order to reduce sound transmission. A distributed piezoelectric quadratically shaped polyvinylidene fluoride (PVDF) polymer film is used as a uniform force actuator and an array of $4\;{\times}\;4$ accelerometer is used as a volume velocity sensor for the implementation of a single-input single-output control system. The theoretical and experimental study of sensor-.actuator frequency response function shows that this sensor-actuator arrangement provides a required strictly positive real frequency response function below about 900 Hz. Direct velocity feedback could therefore be implemented with a limited gain which gives reductions of about 15 dB in vibration level and about 8 dB in acoustic power level at the (1,1) mode of the smart panel. It has been also shown that the shaping error of PVDF actuator could limit the stability and performance of the control system.

• Journal of Korean language education
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• v.25 no.1
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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.

• Journal of The Geomorphological Association of Korea
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• v.24 no.3
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• pp.61-81
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• 2017

Traditional approaches to surface moisture problems in the context of aeolian research have focused on the initiation of sand movement, developing various models for predicting threshold velocity on a wet surface. They have been unsatisfactory, however, in explaining field observations because they have not incorporated spatiotemporal variability of surface moisture, the interactions between transported sand grains and surface, and the role of aeolian transport in controlling surface moisture. As Nield (2011) showed, a simplified numerical model can be used to investigate this issue. This research aims to explore the feedback structures between aeolian transport and surface moisture using a modified sand slab model. Key modifications are the introduction of simultaneous updating scheme for all the slabs and moisture-assigning procedures with and without aeolian transport. The major findings are as follows. Moist surface conditions suppress sand slab movement, leading to the development of smaller-scale topography. Available sands for aeolian transport are determined by the vertical patterns of moisture content with its variations from groundwater to the surface. Sand patches on a wet surface act as a localized source area. Sand movement drives immediate changes in surface moisture rather than time-lag reponses, mostly when moist conditions are dominant.

• Science of Emotion and Sensibility
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• v.24 no.3
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• pp.115-124
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• 2021

Non-verbal communication is important in human interaction. It provides a layer of information that complements the message being transmitted. This type of information is not limited to human speakers. In human-robot communication, increasing the animacy of the robotic agent-by using non-verbal cues-can aid the expression of abstract concepts such as emotions. Considering the physical limitations of artificial agents, robots can use light and movement to express equivalent emotional feedback. This study analyzes the effects of LED and motion animation of a spherical robot on the emotion being expressed by the robot. A within-subjects experiment was conducted at the University of Tsukuba where participants were asked to rate 28 video samples of a robot interacting with a person. The robot displayed different motions with and without light animations. The results indicated that adding LED animations changes the emotional impression of the robot for valence, arousal, and dominance dimensions. Furthermore, people associated various situations according to the robot's behavior. These stimuli can be used to modulate the intensity of the emotion being expressed and enhance the interaction experience. This paper facilitates the possibility of designing more affective robots in the future, using simple feedback.