• Information and Communications Magazine
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• v.20 no.10
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• pp.43-49
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• 2003

우리나라는 아ㆍ태지역에서의 IT Hub 국가로 도약하고 첨단분야의 핵심기술기반을 확보하기위해 세계 선진 국가를 연결하는 TEIN, 아태지역 내 주요국가를 연결하는 APII Testbed 등의 초고속 연구망을 구축 운영하고 있다. APII Testbed는 1994년 APEC 정상회담에서 우리나라가 제안하고 1995년 제1차 APEC 정보통신장관회의에서 채택한 사업으로 아ㆍ태지역 정보통신 기반 구축을 위한 초고속 연구망이다. 또한 TEIN은 2000년 서울에서 개최된 제3차 ASEM 정상회의에서 채택된 ASEM의 국제기구사업으로 유럽과 아시아의 연구망을 연결하는 초고속 연구망으로서의 중요성을 갖는다. 현재, 국내 240개 기관이 TEIN/APII Testbed를 통해 IPv6, Grid 등 차세대 인터넷과 기상, 의료 등 다양한 기술응용분야에서의 국제공동연구가 수행되고 있으며, 아시아 및 유럽지역과의 급속한 연구수요 증가로 인해 TEIN/APII Testbed 증설이 적극 추진되고 있는 상황이다. 본고에서는 TEIN/APII Testbed의 추진배경 및 성과를 살펴보고 향후 발전방향을 전망하여 우리나라가 연구인프라 부문에서 한단계 진일보한 ‘IT 강국’으로서의 위상과 역할을 갖추기 위한 발전방안을 모색해 보고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.111-116
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• 2009

As an experimental technique to analyze the far-field characteristics of underwater cylindrical array sensors, cylindrical acoustic holography is studied. Inside an laboratory water tank, far-field directivity patterns as well as near-field source images are reconstructed from the measured hologram by hydrophone array. Approximate equation for far-field directivity estimation is derived based on stationary phase method. The simulation and experiment show well usefulness of the proposed method in application of underwater array sensors.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.29-36
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• 2009

The analysis of Radar signal, telecommunication, bioengineering, seismic, and acoustic signal is consist of the Non-stationary signal which has non-linear phase variation. Non-stationary signal means that the physical properties of signal depend on time variation and the instantaneous frequency represents physical property of these type of signal. Thus estimation of the instantaneous frequency of non-stationary signal is important subject in signal processing. In this work, the instantaneous frequency analysis method utilizing continuous wavelets transform is represented and compared with Hilbert Transform method.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.781-783
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• 2004

재산권을 보호하기 위한 주요한 수단의 하나로 한국에서는 인감이 주로 사용되고 있다 본 논문에서는 인감의 동정(identification)을 위한 경제적이면서도 성능이 우수한 방법을 제안한다. 이 방법은 위상한 정상관을 이용하고 있다 이 방법을 이용하면 인감 패턴의 2치화, 세선화, 특징점 추출과 같은 복잡한 전처리과정을 거치지 않고도 등록된 인감과 입력인감이 같은 종류인지를 비교적 용이하게 구분해 낼 수 있다. 실험에서는 7종류의 각각의 인감에 대한 5가지 입력인감인 35개 인감화상을 사용하여 본 방법이 효과적임을 보인다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.11
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• pp.18-25
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• 2006

Unsteady aerodynamic force measurements were carried out in order to investigate the effects of phase difference of a dragonfly-type model with two pairs of wing. A load-cell was employed to measure the aerodynamic force generated by a plunging motion of the dragonfly-type model. The dragonfly-type model has a dynamic similarity with real one, and incidence angles of fore- and hind-wing are 0° and 10°, respectively. Other experimental conditions are as follows: The freestream velocity was 1.6 m/sec and corresponding chord Reynolds number was 2.88×103, and phase differences of fore- and hind-wing were 0°, 90°, 180° and 270°. The variation of aerodynamic coefficients during one cycle of the wing motion is presented. Results show that the lift is generated during the downstroke motion and the drag generated during the hind-wing‘s downstroke motion with the lift generation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.5036-5041
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• 2010

This paper introduces the complex-version of an Euclidean distance minimization algorithm based on a set of delta functions. The algorithm is analyzed to be able to compensate inherently the channel phase distortion caused by inferior complex channels. Also this algorithm has a relatively small size of Gaussian kernel compared to the conventional method of using a randomly generated symbol set. This characteristic implies that the information potential between desired symbol and output is higher so that the algorithm forces output more strongly to gather close to the desired symbol. Based on 16 QAM system and phase distorted complex-channel models, mean squared error (MSE) performance and concentration performance of output symbol points are evaluated. Simulation results show that the algorithm compensates channel phase distortion effectively in constellation performance and about 5 dB enhancement in steady state MSE performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.408-414
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• 2005

The VCDRO(Voltage Controlled Dielectric Resonate. Oscillator) with low phase noise is designed using nonlinear analysis, and its phase noise characteristics are compared with that of Lesson's equation. The microstripline coupled with dielectric resonator is realized as a high impedance inverter to improve the phase noise performance, and the quality factor of resonator circuit can be transferred to active device with the enhanced the loaded quality factor. The worst case and part stress analyses are achieved to obtain the high reliability of VCDRO and the reliability analysis is accomplished to estimate the probability of operation at the end of life. The developed VCDRO has the oscillating tuning factor of 0.56MHZ1V for the control voltage range of 0-l2V. This VCDRO requires the DC power of 136mW. The phase noise characteristics exhibit good performances of -94.18dBc/Hz (a)10KHz and -116.3dBc/Hz (a)100KHz. And, the output power over 7.33dBm is measured.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.413-417
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• 2014

In coherent superhigh speed optical transmission link, compensating the system impairments are critical issues. Among these issues, phase noise and carrier frequency offset are the most important impairments which interrupt the signal recovery. This paper suggests a algorithm of digital signal processing that compensates the phase noise and carrier frequency offset and verified its validity. The suggested digital signal processing algorithm has a lower computational complexity compared with the previous algorithms, so it can ease the burden of signal processing at the receiver to provide high speed optical transmission system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.217-222
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• 2014

This paper discusses about the beam pattern distortion caused by the failures of some antenna modules in the active array antenna and analyses the possibility of improvement through applying the beam pattern compensation method previously studied. The beam pattern distortion which is mostly represented as an increase of the sidelobe level, can be suppressed through re-synthesizing each module's magnitude and phase. This method was applied to the prototype of active array antenna system, and the results of antenna pattern distortion and compensation were analyzed and measured in the Near Field Chamber. Array failures are generally divided into random TR module failures and TRU(TR Unit: combination of TR modules, Beam Computation module, Power supply module) failures. The results of beam pattern compensation were analyzed in each failure and compared to the results of the simulation. The beam pattern compensation results applied to the real active antenna array system showed the similar to the simulation results. Consequently, it was verified the beam pattern could be compensated with the magnitude and phase adjustment of other normal antenna modules.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.3
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• pp.228-234
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• 2009

In this paper, we present an analytical method that provides fast and efficient evaluation of the power losses and the conversion efficiency for phase-shift controlled full-bridge converter. In the proposed method, the conduction losses are evaluated by calculating the effective values of the ideal current waveform first and incorporating them into an exact equivalent circuit model of the phase-shift controlled full-bridge converter that includes all the parasitic resistances of the circuit components. While the conduction losses are accurately accounted for the synchronous rectification, the core losses are assumed to be negligible in order to simplify the analysis. The validity and accuracy of the proposed method are verified with experiments on a prototype phase-shift controlled full-bridge converter. An excellent correlation between the experiments and theories are obtained for the input voltages of 400V, output voltage 12V and maximum power 720W.