• Journal of Power Electronics
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• v.16 no.4
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• pp.1565-1577
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• 2016

For grid-connected LCL-filtered inverters, dual-loop current control with an inner-loop active damping (AD) based on capacitor current feedback is generally used for the sake of current quality. However, existing studies on capacitor current feedback AD with a control delay do not reveal the mathematical relation among the dual-loop stability, capacitor current feedback factor, delay time and LCL parameters. The robustness was not investigated through mathematical derivations. Thus, this paper aims to provide a systematic study of dual-loop current control in a digitally-controlled inverter. At first, the stable region of the inner-loop AD is derived. Then, the dual-loop stability and robustness are analyzed by mathematical derivations when the inner-loop AD is stable and unstable. Robust design principles for the inner-loop AD feedback factor and the outer-loop current controller are derived. Most importantly, ensuring the stability of the inner-loop AD is critical for achieving high robustness against a large grid impedance. Then, several improved approaches are proposed and synthesized. The limitations and benefits of all of the approaches are identified to help engineers apply capacitor current feedback AD in practice.

• Journal of Auto-vehicle Safety Association
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• v.12 no.4
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• pp.13-22
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• 2020

This paper presents an adaptive feedback based actuator fault detection and tolerant control algorithms for longitudinal functional safety of autonomous driving. In order to ensure the functional safety of autonomous vehicles, fault detection and tolerant control algorithms are needed for sensors and actuators used for autonomous driving. In this study, adaptive feedback control algorithm to compute the longitudinal acceleration for autonomous driving has been developed based on relationship function using states. The relationship function has been designed using feedback gains and error states for adaptation rule design. The coefficients in the relationship function have been estimated using recursive least square with multiple forgetting factors. The MIT rule has been adopted to design the adaptation rule for feedback gains online. The stability analysis has been conducted based on Lyapunov direct method. The longitudinal acceleration computed by adaptive control algorithm has been compared to the actual acceleration for fault detection of actuators used for longitudinal autonomous driving.

• Physical Therapy Rehabilitation Science
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• v.12 no.3
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• pp.327-333
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• 2023

Objective: The purpose of this study was to investigate the effects of wearing an immediate vibration feedback device at the lumbar region on the spine angle in a sitting position. Design: Cross-sectional study. Methods: The subjects were 28 healthy university students who were randomized to three interventions. Each condition (A: in a normal chair with an immediate feedback device, B: on the gym ball, C: in a normal chair) spent 10 minutes watching the video, and the order of the experiments was randomized, and the measurements were taken consecutively. Results: The results showed significant differences in cervical and thoracic angles between conditions and time. Post hoc tests showed no difference at 1 minute, but significant differences at 5 and 10 minutes. Conclusions: In conclusion, all angles increased over time in all conditions, but the condition of wearing an immediate vibration feedback device with a lower increase was more useful in maintaining spinal angles than the other two conditions. This study suggests that immediate vibration feedback devices may be an alternative to prevent the loss of spinal angle in occupations and environments with prolonged sedentary postures, and further research is needed to investigate the effectiveness of prolonged application.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.8
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• pp.1161-1168
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• 2002

In this paper, the throughput performance of an ARQ scheme is analyzed with noisy feedback channel, in order to exactly analysis for performance of an ARQ scheme. An ARQ mechanism is presented by state diagram, and the throughput of an ARQ scheme is mathematically derived using generation function for a signal flow graph. The channel is modeled by the Nakagami-m fading channel which is distributed over far and wide, and the throughput performance of an ARQ scheme, which is applied in BPSK and BFSK systems, according to feedback gain and fading index m is analyzed through computer simulation. In the results, It is shown conformed that the throughput of an ARQ scheme decreased according to the increase of the noise for feedback channel, but it increased according to the increase of the feedback gain and fading index m. Also, it is shown that the throughput of an ARQ scheme using BPSK system is superior to BFSK system because of the difference of bit error probability between BPSK and BFSK systems.

• The Journal of Pediatrics of Korean Medicine
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• v.22 no.1
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• pp.25-34
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• 2008

Objectives The purpose of this study is to investigate whether Korean oriental pediatrics hospitals are using their feedback surveys to improve their medical conditions. Methods We selected 24 oriental medicine university hospitals and sent surveys to investigate. 15 of those surveys were analyzed. Results The results were classified as follows; Only 9 of university hospital said that they are currently using their feedback surveys to improve their services. Question for asking the purpose of doing their feedback surveys, 58.3% of hospital responded to get some information for diagnosis, 25% of them said to see the progress of treatment of specific disease, and 16.7% answered for using their data to the further studies. The question about the reason why hospital were need to make these feedback surveys, 46.2% of them answered to apply better service, 38.4% of them said to post medical journal. The question for asking what do oriental medical hospitals check from feedback surveys, 40% of them said they check Ryodoraku, 33.3% was pulse diagnostic apparatus, EAV(Electro-puncture According to Voll) was 26.7%. The classification according to purpose of test resulted as follows; information for diagnosis was 48.1%, the progress of a disease was 37.3%. In addition oriental medical test there were blood test, radiological test, brain waves test, Hair Tissue Mineral Analysis(HTMA), ultrasonic test, body composition analysis. Conclusions Further clinical research is necessary for improvement of using the feedback survey effectively.

• Journal of the Korean Society of Physical Medicine
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• v.18 no.3
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• pp.47-53
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• 2023

PURPOSE: A visual feedback method was proposed to induce brain stimulation in a stroke patient, and among them, there was a treatment using a mirror. On the other hand, mirror therapy focuses only on the functional changes in body movements, and analysis of neurophysiological mechanisms of brain activity is lacking. In addition, studies on evaluating the activity and response generated in specific brain regions during visual feedback training using mirrors are insufficient. METHODS: Fifteen healthy adults (male: 10, female: 5, Years: 23.33 ± 1.23), who were right-handed were recruited. By attaching the C3, Cz, and C4 channels in the sensorimotor cortex using an electroencephalogram, training was performed under the conditions without mirror-based visual feedback (No-condition) and with visual feedback (Tasks-condition). At this time, the immediate activity of the mu-rhythm in response to training was separated and evaluated. RESULTS: The tasks-condition of C3, Cz, and C4 channels activated the relative mu-rhythm rather than the no-condition, and all showed significant differences (p < .05). In addition, in all channels at the start time, the tasks-condition was more active than the no-condition (p < .05). The activity of the cortical response was higher in the tasks-condition than in the no-condition (p < .05). CONCLUSION: The mu-rhythm activity can be evaluated objectively when visual feedback using a mirror is applied to healthy subjects, and a basic analysis protocol is proposed.

• Journal of the Korean Mathematical Society
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• v.32 no.4
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• pp.869-876
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• 1995

Piezo devices such as piezoceramic patches knwon as collocated rate sensor and actuators are commonly used in control of flexible structure (see, e.g., [1]) and noise reduction. Recently, Ito and Kang ([4]) developed a nonlinear feedback control synthesis for regulating fluid flow using these devices.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.64.4-64
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• 2002

$\textbullet$ Contents 1 Introduction $\textbullet$ Contents 2 Problem Statement $\textbullet$ Contents 3 Adaptive Output Feedback Control Design $\textbullet$ Contents 4 Stability analysis $\textbullet$ Contents 5 Simulation Result $\textbullet$ Contents 6 Conclusions

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.3
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• pp.129-137
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• 2018

VOCs have been used as the most definitive resource to reflect customer feedback when developing products and services. However, due to the development of the Internet and the emergence of SNS, VOC is no longer the only channel that represents customer opinions. There are also a number of studies showing that many customers express complaints through channels other than VOCs. In this paper, we analyze the difference between the official VOC data and the data collected through the external channel, and suggest ways to reflect the various opinions of customers. To do this, this study uses keyword analysis that can identify differences according to frequency through social network, modular analysis to distinguish topics according to centrality and similarity, and emotional analysis to confirm word polarity (positive and negative). The results of this study show that the opinions of the customers were different depending on channels such as VOCs and external channels. Therefore, the collected data through VOC as well as external channels should be used in order to reflect the opinions of customers. In particular, this paper confirms that the results of one channel may vary depending on the channel characteristics even for the same channel. This confirms that collecting voc only on certain channels may differ from what real customers require. Therefore, data collected through VOCs as well as external channels must be used to reflect various customer feedback.

• Journal of the Korean Society of Systems Engineering
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• v.19 no.2
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• pp.46-58
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• 2023

Deterministic safety analysis is a crucial part of safety assessment, particularly when it comes to demonstrating the safety of nuclear power plant designs. The traditional approach to deterministic safety analysis models is to model the nuclear core using point kinetics. However, this simplified approach does not fully reflect the real core behavior with proper moderator and fuel reactivity feedbacks during the transient. The use of Multi-Physics approach allows more precise simulation reflecting the inherent three-dimensionality (3D) of the problem by representing the detailed 3D core, with instantaneous updates of feedback mechanisms due to changes of important reactivity parameters like fuel temperature coefficient (FTC) and moderator temperature coefficient (MTC). This paper addresses a CEA ejection accident at hot full power (HFP), in which the underlying strong and un-symmetric feedback between thermal-hydraulics and reactor kinetics exist. For this purpose, a multi-physics analysis tool has been selected with the nodal kinetics code, 3DKIN, implicitly coupled to the thermal-hydraulic code, RELAP5, for real-time communication and data exchange. This coupled approach enables high fidelity three-dimensional simulation and is therefore especially relevant to reactivity initiated accident (RIA) scenarios and power distribution anomalies with strong feedback mechanisms and/or un-symmetrical characteristics as in the CEA ejection accident. The Systems Engineering approach is employed to provide guidance in developing the work in a systematic and efficient fashion.