• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.290-293
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• 1988

This paper presents a lead compansator in the loop of PLL speed control system. The compansato improves dynamic response. Digital computer simulation shows its superiority to the conventional method.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.47-48
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• 2003

A polarization mode dispersion(PMD) compensator with a reponse time less than 200ms has been developed. In our PMD compensator, a reset-free $LiNbO_3$ polarization controller was used in order to reduce the response time, and the compensation algorithm was based on maximization of degree of polarizaiton(DOP).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.254-260
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• 1995

본 연구에서는 제어 알고리듬 적용면에서 가속도 계측이 보다 용이한 점을 고려하여 가속도가 포함된 가속도-속도-변위 되먹임 제어 알고리듬을 개발하고, 이를 유압식 능동 질량구동장치에 적용하여 능동제어시스템의 성능을 실증적으로 검토한다. 이 때 능동제어시스템의 구성요소들의 동특성을 시스템 모델링에 포함하여 제어력을 산정함으로써 시간 지연의 영향을 효과적으로 보상하는 방안을 제시한다.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.612-613
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• 2001

산소가 고갈된 환경속에서는 패각의 폐쇄가 일어나게 되며, 종에 따라 생리적 반응은 차이가 있을지라도, 대체로 저산소에 대한 생리적 보상 기작으로서 수류의 펌프작용과 환기 및 혈중내에서의 산소 수송능력이 증가된다. 저산소상태의 환경속에서는 혐기성 대사가 증가되는 대신, 호기성 대사가 억제되므로서 보유하고 있는 에너지의 사용을 최소화하여 제한된 시간동안 저산소 및 무산소 상태에서도 생존할 수 있다. (중략)

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.2
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• pp.52-58
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• 2000

This paper presents a novel power factor corrected(PFC) single-stage AC/DC half-bridge converter, which features discontinuous conduction mode(DCM) and soft-switching. The reduced conduction losses are achieved by the employment of a novel powder factor correction circuitry, instead of the conventional configuration composed of a front-end rectifier followed by a boost converter. To identify the validity of the proposed converter, simulated results of 500[W] converter with 100[V] input voltage and 50[V]output voltage are presented.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.12
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• pp.101-109
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• 2008

Induction motor needs reactive power to sustain the electromagnetic field required for rotating. If reactive power is provided by the load side instead of the source side, power factor will be increased. Power factor of induction motor is usually low and needs to be compensated with power capacitor. In domestic regulations, Capacitor capacity for the power factor correction of induction motor should be complied with the recommended value by the motor output. But, at the same output, characteristics of induction motor is different from each other by the rotation speed and is not suitable for application of regular capacitor value regardless of motor's characteristics. In this paper, we compared to each other with the existing value and new proposed value with rotation speed under the same output condition, confirmed that power capacitor capacity is needed to upgrade for the better power factor.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1699-1709
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• 2015

Moving terminals like high-speed-train undergo high Doppler frequency shift, and this leads to carrier frequency offsets that have to be compensated to avoid degradation of communication performance. In multiple access mechanism like OFDMA, base-stations need complex hardware to compensate the uplink frequency offset. In this paper, we propose a method, which can reduce burden of the base-station and makes frequency offset estimation and compensation simple. This method contains transmitting new synchronization signal, estimating frequency offsets in base-station, transmitting feedback information to terminal, and compensating the offset in uplink transmission. Simulation results show the proposed method operates well in high Doppler frequency shift conditions of 500 km/h which is the requirements of 5G mobile communication.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.898-906
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• 2002

In this paper, we investigated the improvement degree of transmission distance of the various initial frequency chirped optical pulse with 5 dBm initial power dependence on the various bit rate and fiber dispersion coefficient, when MSSI(Mid-Span Spectral Inversion) with the optimal pump power condition is adopted for the compensation method for optical pulse distortion. And we analyzed the influence of mutual relation of optical pulse frequency chirp and Kerr effect on the MSSI methods for the long-haul optical transmission through the computer simulation. We found that the compensation degree of distorted optical pulse varies as a consequence of the variation of combined phase modulation of self phase modulation(Kerr effect) and initial frequency chirp parameter dependence on the fiber dispersion coefficient. And we found that, if the transmission bit rate is increased k times, the dispersion coefficient value of dispersion shift fiber is decreased $2^k$ times so as to be almost the same performance of the transmission system with k times lower bit rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12A
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• pp.1009-1018
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• 2003

A new fading channel estimation technique is proposed for an OFDM based modem In the ITS system. The algorithm is based on the transfer function extraction of the channel using the pilot signals and compensated the channel preceding the equalization. The newly derived algorithm is division-free arithmetic operations allows the faster circuit operation and the smaller circuit size. Proposed techniques compensate firstly the distortion which is generated at fading channels and secondly eliminate inter-symbol interference. All algorithms are suitability estimated and improved for a system implementation using digital circuits. As the results, the circuit size is reduced by 20% of the conventional design and achieved about 10% performance improvement at low SNR under 10dB in case of ITS system adapted 16-QAM mode.

• 한국노년학
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• v.28 no.4
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• pp.1147-1164
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• 2008

There has been a sharp increase in the number of grandmothers raising grandchildren in contemporary Korean society. However, little is known about the complexity of the experiences of the custodial grandparenting. Most of the studies mainly examined burden/cost and have paid little attention to the positive aspects of custodial grandparenting. In order to overcome this limitation of previous research, this study aims 1) to examine not only the costs but also the rewards of custodial grandparenting and to explore related factors, 2) to develop the typology based on relative rewards-burden perception of grandmothers about custodial grandparenting and explore the group differences. The data were gathered from 449 grandmothers raising their grandchildren as a primary caregiver, using a structured questionnaire. The data were analyzed using descriptive statistics, correlation, hierarchical multiple regression and ANOVA, with SPSS WIN 12.0 program. Main findings are as follows: First, custodial grandmothers report not only care-giving burden such as physical burnout and economic burden but also various rewards such as joy of watching their grandchildren grow and feeling good about themselves to be a help with their adult children, i.e. grandchildren's father or mother. Second, factors related to the level of perceived cost of grandparenting are different from the factors affecting the positive aspects of grandparenting. Third, results of the two by two cross-tab analysis based on the level of rewards and burden show that about 32 percent of the grandparents belong to Type II group(high rewards-low cost). This result is quite contrary to the assumption of previous research focusing mostly on cost and burden of custodial grandparenting. Fourth, four groups were different in terms of grandmother & grandchildren's characteristics. Implications of these results are discussed.