• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.787-793
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• 2015

In order to support reliable medium access control (MAC) layer multicast services in Broadband Wireless Access (BWA) networks, we here propose spreading codes (Cumulative ACK (CA) code and ARQ Feedback Request (AFR) code) based reliable multicast feedback scheme. The status indications based on the automatic repeat request (ARQ) mechanism are needed in some multicast services. In accordance with various wireless channel environments, we demonstrate the performance excellency of our proposed scheme with respect to required uplink resources compared with the original feedback scheme based on unicast ARQ feedback messages. In addition, we analyze packet error rate (PER) against the various wireless channel environments.

• Journal of the Korean Society for information Management
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• v.2 no.1
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• pp.108-135
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• 1985

When an information retrieval system is implemented on-line, users can interact with the system to improve the searches. There are studies which achieved dramatic improvements in system effectiveness by using automatic relevance feedback, a technique for reformulating a patron query based on initial retrieval result. In this thesis, an automatic query modification model was applied to a controlled keyword system.

• Current Optics and Photonics
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• v.4 no.6
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• pp.472-476
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• 2020

We have investigated the impact of optical filter bandwidth on the performance of all-optical automatic gain-controlled (AGC) erbium-doped fiber amplifiers (EDFAs). In principle, an optical bandpass filter (OBPF) should be placed within the feedback gain-clamping loop to set the lasing wavelength as well as the passband of the feedback amplified spontaneous emission (ASE) in all-optical AGC EDFA. From our measurement results, we found that the power level of feedback ASE with 0.1 nm passband of the optical filter was smaller than the ones with >0.2 nm passband cases. Therefore, the peak-to-peak power variation of the surviving channel with 0.1 nm passband was much larger than the ones with >0.2 nm passband. In addition, no significant difference in the power level of the feedback ASE was observed when the passband of the optical filter was ranging from 0.2 nm to 4.5 nm in our measurements. From these results, we have concluded that the passband of the optical filter should be slightly larger than 0.2 nm by taking into account the effect of feedback ASE power and the efficient use of the EDFA gain spectrum for the lasing ASE peak.

• Journal of Drive and Control
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• v.13 no.1
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• pp.1-9
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• 2016

Nowadays automatic transmission equipped vehicles prevail in construction and agricultural equipment due to their convenience in driving and operation. Though domestic vehicle manufacturers install imported electronic controlled transmissions at present, overseas products will be replaced by domestic ones in the near future owing to development efforts over the past 10 years. For passenger cars, there are many kinds of shift control algorithms that enhance the shift quality such as feedback and learning control. However, since shift control technologies for heavy duty vehicles are not highly developed, it is possible to improve the shift quality with an organized control method. A feedback control algorithm for neutral-into-gear shift, which is enabled during the inertia phase for the master clutch slip speed to track the slip speed reference, is proposed based on the power transmission structure of TH100. The performance of the feedback shift control is verified by a vehicle test which is implemented with firmware embedded TCU. As the master clutch engages along the predetermined speed trajectory, it can be concluded that the shift quality can be managed by a shift time control parameter. By extending the proposed feedback algorithm for neutral-into-gear shift to gear change and shuttle shift, it is expected that the quality of the shift can be improved.

• Journal of Korean Library and Information Science Society
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• v.31 no.2
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• pp.279-302
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• 2000

This study is to develop a new automatic system for the Korean thesaurus browser by which we can automatically control all the processes of searching queries such as, representation, generation, extension and construction of searching strategy and feedback searching. The system in this study is programmed by Delphi 4.0(PASCAL) and consists of database system, automatic indexing, clustering technique, establishing and expressing thesaurus, and automatic information retrieval technique. The results proved by this system are as follows: 1)By using the new automatic thesaurus browser developed by the new algorithm, we can perform information retrieval, automatic indexing, clustering technique, establishing and expressing thesaurus, information retrieval technique, and retrieval feedback. Thus it turns out that even the beginner user can easily access special terms about the field of a specific subject. 2) The thesaurus browser in this paper has such merits as the easiness of establishing, the convenience of using, and the good results of information retrieval in terms of the rate of speed, degree, and regeneration. Thus, it t m out very pragmatic.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.202-202
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• 2000

In this paper, the synchronous generator model which is derived from the swing equation and the Park's equation is transformed to an adequate form for feedback linearization. And the single controller is designed in order to play the role of both PSS and AVR. The result of the simulations shows that the stability of the system is guaranteed in the wide range of operating points.

• Proceedings of the Safety Management and Science Conference
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• 2000.11a
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• pp.203-216
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• 2000

In this paper, we Investigate rationales for feedback adjustment using some techniques associated with automatic process control based on some nonstatioary disturbance models. Feedback-control schemes are often operated so that the nature of the disturbance that is being compensated is concealed and unusual deviations from the target cannot be taken account of. In this connection feedback control schemes is useful to extend the idea of common causes and special causes to such systems. Minimum-cost feedback schemes are discussed for some simple ,but practically interesting ,models.

• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.482-484
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• 1997

This paper studies on a feedback active noise control method for the quasi stationary. The quasi one dimension space means a duct space which have a shorter 2th path than the one dimension space. To control noise signal, a feedback active noise control using FXLMS algorithm is used Computer simulation show that the algorithm can control noise signal in the quasi stationary.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.5
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• pp.15-22
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• 2002

A study is the selection of optimum forming condition for RP system. We develop the Automatic design program for machine element using visual LISP program in AutoCAD. Automatic design program reduces the required time for feedback between design and manufacturing of workpiece. Also we investigate the relationship between circularity of 3D solid model and circularity of rapid prototype using RP system and we will find optimum forming condition in RP system.

• Journal of Power Electronics
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• v.12 no.6
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• pp.886-894
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• 2012

This paper presents a secondary-side, dual-mode feedback LLC resonant controller IC with dynamic PWM dimming for LED backlight units. In order to reduce the cost, master and slave outputs can be generated simultaneously with a single LLC resonant core based on dual-mode feedback topologies. Pulse Frequency Modulation (PFM) and Pulse Width Modulation (PWM) schemes are used for the master stage and slave stage, respectively. In order to guarantee the correct dual feedback operation, Phased-Locked Loop (PLL)-based automatic duty control circuit is proposed in this paper. The chip is fabricated using $0.35{\mu}m$ Bipolar-CMOS-DMOS (BCD) technology, and the die size is $2.5mm{\times}2.5mm$. The frequency of the gate driver (GDA/GDB) in the clock generator ranges from 50 to 425 kHz. The current consumption of the LLC resonant controller IC is 40 mA for a 100 kHz operation frequency using a 15 V supply. The duty ratio of the slave stage can be controlled from 40% to 60% independent of the frequency of the master stage.