• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12A
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• pp.1146-1152
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• 2005

In this paper, we propose a compressed quantized channel state information (CQCSI) feedback scheme for multi-carrier mobile communication systems. The proposed CQCSI figures out the contiguous subsequences of equal QCSI's as separate types of runs across the subcarriers, and then encodes the types of runs using a truncated Huffman coding algorithm. Computer simulation shows that the proposed algorithm can reduce the QCSI feedback up to one tenth of the uncompressed, while providing a comparable performance with the conventional QCSI feedback schemes. To cope with special cases when the frequency selective fading is very high, we also propose a restricted CQCSI feedback scheme. The restricted CQCSI feedback has been proved under vehicular B channel model.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.67-76
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• 1997

In this paper we developed a tactile feedback device using repulsive force of magnets. The force of the tactile feedback device was derived from the Maxwell's stress method by using the concept of magnetic charge. Magnetic repulsive force is linear function with respect to current and nonlinear to displacement. Experimental data shows these characteristics. To compensate the fact that the presented tactile feedback device can not be controlled by close loop control, we developed a simulation model which predicts output displacement and force by using Runge-Kutta method. And, this paper evaluated the presented tactile feedback device and compared it with commercial tactile feedback devices.

• Journal of the Korean Society of Physical Medicine
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• v.7 no.4
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• pp.533-539
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• 2012

PURPOSE: The purpose of this study was to investigate the effect of pelvic floor muscle contraction with image feedback on Abdominal muscle thickness. METHODS: Twenty three adults participated in this study. Abdominal muscle thickness was measured by ultrasound in three condition(rest, pelvic floor muscle contraction, pelvic floor muscle contraction with image feedback). Subjects was contraction pelvic floor muscle by general method. And ultrasound(convex probe, 3.5MHz) was used to image feedback for selective pelvic floor muscle contraction. One-way ANOVA was used to compare abdominal muscle thickness in three condition. RESULTS: There was no significant difference in external oblique(p=.514) and internal oblique muscle(p=.250) thickness by three condition. There was significant difference in transverse abdominis thickness by three condition (Transverse abdominis thickness was highest while Pelvic floor muscle contraction than pelvic floor muscle contraction with image feedback and rest.)(p=.000). CONCLUSION: This study shows that pelvic floor muscle contraction with image feedback increase the thickness of transverse abdominis lesser than general pelvic floor muscle contraction.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.473-479
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• 2005

A key issue toward mobile multimedia communications is to create technologies for broadband signal transmission that ran support high quality services. Such a broadband mobile communications system should be able to overcome severe distortion caused by time-varying multi-path fading channel, while providing high spectral efficiency and low power consumption. For these reasons, an adaptive suboptimum decision feedback equalize. (DFE) for the single-carrier short-burst transmissions system is considered as one of the feasible solutions. For the performance improvement of the system with the short-burst format including the short training sequence, in this paper, the multiple-training least mean square (MTLMS) based DFE scheme with soft decision feedback is proposed and its performance is investigated in mobile wireless channels throughout computer simulation.

• Smart Structures and Systems
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• v.6 no.8
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• pp.921-938
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• 2010

Most of studies on control of beams containing piezoelectric sensors and actuators have been based on linear quadratic regulator (LQR) with state feedback or output feedback law. The aim of this study is to develop velocity-acceleration feedback law in the optimal control of smart piezoelectric beams. A new controller which is an optimal control system with velocity-acceleration feedback is presented. In finite element modeling of the beam, the variation of mechanical displacement through the thickness is modeled by a sinus model that ensures inter-laminar continuity of shear stress at the layer interfaces as well as the boundary conditions on the upper and lower surfaces of the beam. In addition to mechanical degrees of freedom, one electric potential degree of freedom is considered for each piezoelectric element layer. The efficiency of this control strategy is evaluated by applying to an aluminum cantilever beam under different loading conditions. Numerical simulations show that this new control scheme is almost as efficient as an optimal control system with state feedback. However, inclusion of the acceleration in the control algorithm increases practical value of a system due to easier and more accurate measurement of accelerations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.259-266
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• 2002

In the CDMA system, the Multiple access interference(MAI) causes system performance and capacity degradation. One of the MAI cancel method is a feedback detector that orthogonal decision-feedback detector(ODFD) and Deocrrelating decision-feedback detector(DDFD) have been studied by now. In this paper, we propose a blind adaptive ODFD(BA-ODFD) with blind equalizer combined ODFD, Also we simulate the operation of BA-ODFD in AWGN channel and Rayleigh (tiding channel. and compare blind adaptive ODFD with blind adaptive DDFD.

• Speech Sciences
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• v.13 no.3
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• pp.133-149
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• 2006

This study attempted to compare acoustic parameters, physiological observation and perceptual evaluation values obtained from the treatment and control groups in order to find out which of the self voice feedback therapies was better and which methods to train them were more effective. The experimental group carried out various self voice feedback therapies while the control group did only vocal hygiene. The acoustic measurement and voice manipulation for providing the patients visual, auditory feedback were done by a speech analysis software, Praat. The authors designed vocal hygiene, abdominal respiration and Praat self voice feedback therapies and applied them to 15 patients while applying only one vocal hygiene to 15 of the control group. For the purpose of examining the degree of their voice improvement after the treatment, pre- mid- and final evaluations were made for the two groups at the beginning, the 6th week and immediately after the 8th treatment session. Results of this study were as follows: The treatment group showed much improvement after receiving the voice treatment. In particular, acoustical and physiological indices from the optical endoscopy, pitch variation(Jitter), amplitude variation (Shimmer), maximum phonation time(MPT), and psychoacoustic evaluation showed statistically significant improvements over the control groups.

• The Mathematical Education
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• v.49 no.3
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• pp.299-311
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• 2010

The purpose of this study was to examine the effects of abstraction offer of basic concept principle and feedback of self-efficacy attributional and mathematical study ability of math underachievers in high school based on the attribution theory and self-efficacy theory. The hypothesis were posed as below : Hypothesis 1: The experimental group that takes the abstraction offer of concept principle and attributional feedback training would be better at most self-efficacy than the control group that doesn't. Hypothesis 2: The experimental group that takes the abstraction offer of concept principle and attributional feedback training would have better math achievement than the control group that doesn't. They were divided into an experimental group and a control group, and the attribution disposition, self-efficacy and academic achievement of the children were measured by pretest and posttest. For data analysis, SPSS/PC+ program was employed and t-test was conducted. The main findings of this study were as below : First, the abstraction offer of concept principle and attributional feedback training was effective for enhancing the math self-efficacy in high school underachievers. Second, the abstraction offer of concept principle and attributional feedback training was effective for increasing the math achievement in high school underachievers.

• Proceedings of the KAIS Fall Conference
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• 2003.11a
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• pp.236-242
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• 2003

ATM ABR service controls network traffic using feedback information on the network congestion situation in order to guarantee the demanded service qualities and the available cell rates. In this paper we apply the control method using queue length prediction to the formation of feedback information for more efficient ABR traffic control. If backward node receive the longer delayed feedback information on the impending congestion, the switch can be already congested from the uncontrolled arriving traffic and the fluctuation of queue length can be inefficiently high in the continuing time intervals. The feedback control method proposed in this paper predicts the queue length in the switch using the slope of queue length prediction function and queue length changes in time-series. The predicted congestion information is backward to the node. NLMS and neural network are used as the predictive control functions, and they are compared from performance on the queue length prediction. Simulation results show the efficiency of the proposed method compared to the feedback control method without the prediction. Therefore, we conclude that the efficient congestion and stability of the queue length controls are possible using the prediction scheme that can resolve the problems caused from the longer delays of the feedback information.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.3
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• pp.107-113
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• 2021

PURPOSE: Selective strengthening of the transverse abdominis muscle (TrA) during abdominal hollowing makes an important contribution to the stability and control of the spine. This study examined the effects of abdominal hollowing exercise (AHE) according to the visual feedback method on the external oblique, internal oblique, and transverse abdominis muscles. METHODS: Twenty healthy subjects were assigned randomly to an AHE with visual feedback from real-time ultrasound image (group A, n = 10), AHE with visual feedback with pressure biofeedback unit (group B, n = 10). Both groups underwent 20 min of AHE with visual feedback once daily, five days/week for two weeks. The changes in the muscle thickness of the TrA, internal oblique abdominal muscle (IO), and external oblique abdominal muscle (EO) were measured by ultrasonography. RESULTS: The thickness of TrA was changed significantly in both groups (p < .05). However, the lowest minimal detectable changes were achieved in Group A. The thickness of the IO and EO muscles in group A was changed significantly, but there were no significant changes in group B. CONCLUSION: Both visual feedback methods were effective for strengthening the TrA muscles selectively. Nevertheless, AHE with visual feedback using real-time ultrasound images may be more useful in trA muscle contraction.