• Journal of the Korea Institute of Information and Communication Engineering
• /
• 제5권4호
• /
• pp.668-675
• /
• 2001

Recently, the performance of the commercial PCS(Personal Communication Service) system has been improved to the uppermost limit and ultimately the next generation mobile communication is to be realized by IMT-2000 (International Mobile Communication-2000) to provide multimedia services. Therefore, the new type receiving system is researched actively and one of the most important part in a receiver is direct conversion method. The direct conversion method is suitable for low power consumption, small size, MMIC, and low price, which is to be adopted to the next generation mobile communication systems. In this case, however, several problems occur due to DC-offset. The DC-offset suppresses amplification of the required signal because of the leakage signal of frequency synthesizer in the system. In this thesis, the removing method of DC-offset was considered. There are four removing techniques of DC-offset, which are AC-coupling, large capacitor, DC-feedback loop, and DC-free coding. Among these, the AC-coupling method is the most simplest method and the DC-feedback loop method has the best performance. Then, the performance of the AC-coupling method and DC-feedback loop method are evaluated by HP's ADS simulation tool. As a result, the AC-coupling method cannot be used to the digital communication systems due to data loss. On the other hand, it was confirmed that the DC-feedback loop method is suitable for the direct conversion receiver.

• The Journal of the Acoustical Society of Korea
• /
• 제18권4호
• /
• pp.38-46
• /
• 1999

In this paper, two methods were proposed to improve the performance of adaptive feedback cancellation in hearing aids. One is “Orthogonality principle acoustic feedback cancellation method(Orthogonality principle method)” to track optimal solution with monitoring the instantaneous gradient, the other is a method using the CLMS algorithm(CLMS method). In many simulation conditions, adaptive feedback cancellation method proposed in this paper was much better than Greenberg method by Sum-method LMS algorithm which is known the most excellent method by now in case of system mismatch, SNR and segmental SMR. Also. Orthogonality principle method is as good as CLMS method in terms of adaptive feedback cancellation in many simulation conditions.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• 제7권3호
• /
• pp.379-384
• /
• 2006

The paper describes a method of user feedback in order to enhance the retrieval effectiveness. In this paper, to overcome a weak point of the existing feedback function adapting fuzzy technique, we proposed the interaction function using gaussian function that gives different learning rate according to choice of components with same function. And, we grade degree that the user opinion is reflected to a system by applying user profile to the feedback function. User retrieval feedback method is adaptive retrieval method that makes a slow change for a long time using feedback function adapting gaussian function and user profile.

• Korean Journal of Health Education and Promotion
• /
• 제23권2호
• /
• pp.47-61
• /
• 2006

Object: This research has been conducted in order to conduct obesity prevention education providing feedback which is currently taught to the second grade students of middle school, understanding how this method of education affects the knowledge and of behavior towards obesity prevention, and that could be actually applied to classrooms. Method: A questionnaire was supplemented questionnaire whose content validity and reliability was verified in the preliminary research was used. The reliability of the research tool was Cronbach' ${\alpha}=0.70$ for obesity knowledge tool, and Cronbach' ${\alpha}=0.84$ for obesity prevention behavior tool. Result: 1) It turned out that feedback was significantly effective in improving the knowledge. 2) It turned out that the education method providing feedback was effective in improving the behavior. Conclusion: From the results of this research, it can be said that the obesity prevention education providing feedback was the most effective method in improving the obesity knowledge and prevention behavior of middle school students. Therefore, it is advisable that the obesity prevention education methods providing feedback should be developed and applied continuously.

• Proceedings of the KAIS Fall Conference
• /
• 한국산학기술학회 2003년도 Proceeding
• /
• pp.236-242
• /
• 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.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2005년도 ICCAS
• /
• pp.1911-1916
• /
• 2005

In this study, the basic motor control system had been investigated. The Discrete-Time Feedback Error Learning (DTFEL) method is used to control this system. This method is anologous to the original continuous-time version Feedback Error Learning(FEL) control which is proposed as a control model of cerebellum in the field of computational neuroscience. The DTFEL controller consists of two main parts, a feedforward controller part and a feedback controller part. Each part will deals with different control problems. The feedback controller deals with robustness and stability, while the feedforward controller deals with response speed. The feedforward controller, used to solve the tracking control problem, is adaptable. To make such the tracking perfect, the adaptive law is designed so that the feedforward controller becomes an inverse system of the controlled plant. The novelty of FEL method lies in its use of feedback error as a teaching signal for learning the inverse model. The PD control theory is selected to be applied in the feedback part to guarantee the stability and solve the robust stabilization problems. The simulation of each individual part and the integrated one are taken to clarify the study.

• Journal of the Korean Society of Industry Convergence
• /
• 제18권2호
• /
• pp.90-98
• /
• 2015

This research propose with image-based visual a new approach to design a feedback control of mobile robot. because mobile robot must be recharged periodically, it is necessary to detect and move to docking station. Generally, laser scanner is used for detect of position of docking station. CCD Camera is also used for this purpose. In case of using camera, the position-based visual servoing method is widely used. But position-based visual servoing method requires the accurate calibration and it is hard and complex work. Another method using cameras is inmage-based visual feedback. Recently, image based visual feedback is widely used for robotic application. But it has a problem that cannot have linear trajectory in the 3-dimensional space. Because of this weak point, image-based visual servoing has a limit for real application. in case of 2-dimensional movement on the plane, it has also similar problem. In order to solve this problem, we point out the main reason of the problem of the resolved rate control method that has been generally used in the image-based visual servoing and we propose an image-based visual feedback method that can reduce the curved trajectory of mobile robot in th cartesian space.

• Physical Therapy Rehabilitation Science
• /
• 제11권1호
• /
• pp.58-65
• /
• 2022

Objective: The purpose of this study was to investigate the effect of visual feedback bicycle training on running performance, maximal oxygen uptake and quadriceps muscle strength. Design: A randomized controlled trial. Methods: Fifteen healthy adult men with no musculoskeletal or nervous system disease and capable of bicycle training were included. After the pretest, subjects were randomly assigned to visual feedback bicycle training group and general fixed bicycle training group. Both groups were trained two times a week for three weeks, each week for a fixed time and number of repetitions, followed by a six week washout period and then crossing the training method. visual feedback bicycle training provides visual feedback of heart rate in real time using a monitor and a heart rate meter during bicycle training, and general fixed bicycle training performed general bicycle training without visual feedback. After training, each item was measured using a wearable technology, gas analyzer, isokinetic equipment. Results: The results of this study was significant differences in running performance, maximal oxygen uptake and quadriceps muscle strength in visual feedback bicycle training group (p<0.05). The differential effect was found between visual feedback bicycle training group and general fixed bicycle training group in running performance, maximal oxygen uptake, and quadriceps muscle strength (p<0.05). Conclusions: This study suggested that that visual feedback bicycle training can be applied as a useful training method to improve running performance, maximal oxygen uptake and quadriceps muscle strength.

• Journal of Korean Institute of Industrial Engineers
• /
• 제27권1호
• /
• pp.11-17
• /
• 2001

We consider the M/G/1 with Bernoulli feedback, where the served customers wait in the feedback queue for rework with probability p. It is important to decide the moment of dispatching in feedback systems because of the dispatching cost for rework. Up to date, researches have analyzed for the instantaneous-dispatching model or the case that dispatching epoch is determined by the state of feedback queue. In this paper we deal with a dispatching model whose dispatching epoch depends on main queue. We adopt supplementary variable method for our model and a numerical example is given for clarity.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• 제13권1호
• /
• pp.42-47
• /
• 2020

In OFDM-based very high-speed communication systems, FFT/IFFT processor should have several properties of low-area and low-power consumption as well as high throughput and low processing latency. Thus, radix-2k MDF (multipath delay feedback) architectures by adopting pipeline and parallel processing are suitable. In MDF architecture, the feedback memory which increases in proportion to the input signal word-length has a large area and power consumption. This paper presents a feedback memory size reduction method of radix-22 MDF IFFT processor for OFDM applications. The proposed method focuses on reducing the feedback memory size in the first two stages of MDF architectures since the first two stages occupy about 75% of the total feedback memory. In OFDM transmissions, IFFT input signals are composed of modulated data and pilot, null signals. In order to reduce the IFFT input word-length, the integer mapping which generates mapped data composed of two signed integer corresponding to modulated data and pilot/null signals is proposed. By simulation, it is shown that the proposed method has achieved a feedback memory reduction up to 39% compared to conventional approach.