• Korean Journal of Optics and Photonics
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• v.22 no.1
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• pp.40-45
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• 2011

Design and fabrication of a TCRR (Triple-coupler Ring Resonator) filter which can provide a doubled FSR (Free Spectral Range) compared with a conventional DCRR (Double-coupler Ring Resonator) filter, are discussed. Through the use of a polymer material with a good thermo-optic property and with high contrast between core and cladding polymer, a compact TCRR filter composed of straight and curved buried waveguides of small radius is designed and fabricated. The transmission characteristics from the through and drop ports are measured using a tunable laser and a fiber array block, and the FSR is observed to be 4.4 nm, about twice that of DCRR filter, and almost the same as that obtained from the analysis using a transfer matrix method.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.115-128
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• 2006

A technical analysis of current scramjet and combined-cycle engine is presented. Substantial research has been pursued to characterize the operation mechanism of scramjet propulsion, especially in the areas of flame stabilization and system integration, dramatically over the years in support of both military and space access application. Major technology that had significant impact on the maturation of scramjet propulsion technology are dual combustion ramjet, dual mode ramjet, and combined cycle engine to cover a typical wide rage of flight, up to flight Mach number 10. Notable are the fundamental and practical techniques, for instance, scram propulsion itself, thermal relaxation and protection using endothermic fuel and/or CSiC composit materials, and design/manufacture of movable intake and nozzle, to realize high speed propulsion system in near future.

• The Journal of Information Technology
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• v.7 no.3
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• pp.11-18
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• 2004

Learning procedure in the neural network is updating of weights between neurons. Unadequate initial learning coefficient causes excessive iterations of learning process or incorrect learning results and degrades learning efficiency. In this paper, adaptive learning algorithm is proposed to increase the efficient in the learning algorithms of Self-Organization Neural Networks. The algorithm updates the weights adaptively when learning procedure runs. To prove the efficiency the algorithm is experimented to classification of strokes which is the reference handwritten character. The result shows improved classification rate about 1.44~3.65% proposed method compare with Kohonan and Mao's algorithms, in this paper.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7A
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• pp.659-667
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• 2002

In this dissertation, in the Turbo Code used for error correction coding of the recent digital communication systems, we propose a new S-R interleaver that has the better performance than the existing block interleaver, and the Turbo Decoder that has the parallel concatenated New structure using the MAP algorithm. For real-time voice and video services over the third generation mobile communications, the performance of two proposed methods is analyzed by the reduced decoding delay using the variable decoding method by computer simulation over multipath channels of DS-CDMA system. Also, a Modified NCMA based on conventional NCMA is proposed to improve the channel efficiency in the mobile communication system, and is investigated over the multi-user environment of DS-CDMA system through computer simulation.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.3
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• pp.210-215
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• 2004

The dynamic model of ac servo motor is influenced very much due to rotor resistance change and nonlinear characteristic. By using the sliding mode control the dynamic behavior of system can be made insensitive to plant parameter change and external disturbance. This paper describes the application of the sliding mode control for position control of ac servo motor. The control scheme is derived and designed. A design method based on external load parameters has been developed for the robust control of ac induction servo drive. The proposed control scheme are given based on the variable structure controller and slip frequency vector control. Simulated results are given to verify the proposed design method by adoption of sliding mode and show robust control for a change of shaft initial J, viscous friction B and torque disturbance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.703-705
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• 2016

In this paper, we developed a wideband PIMD system to measure passive intermodulation distortion signals of mobile communication RF passive module. To represent wideband characteristic, we designed a receiver that meets low-noise and wideband characteristics in RF receiver. It allows high dynamic range in the RF receiver front end. In designed passive intermodulation distortion measurement system, we programed to display a PIMD signal with FPGA/DSP at PC. Implemented PIMD system was variable from 650 MHz to 2700 MHz and show up to -138 dB minimum detectable $3^{rd}$ passive inetrmodulation distortion signal.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.771-777
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• 2008

In this paper, a frequency doubler using modified time-delay technique is proposed. A voltage controlled delay line (VCDL) in the proposed frequency doubler compensates the group delay time mismatching between input and delayed signal. With the group delay time matching and waveform shaping using the adjustable Schmitt triggers, the unwanted fundamental component($f_0$) and the higher order harmonics such as third and fourth are diminished excellently. In result, only the doubled frequency component($2f_0$) appears dominantly at the output port. The frequency doubler is designed at 1.15 GHz of $f_0$ and fabricated with TSMC $0.18\;{\mu}m$ CMOS process. The measured output power at $2f_0$ is 2.67 dBm when the input power is 0 dBm. The obtained suppression ratio of $f_0,\;3f_0$, and $4f_0$ to $2f_0$ are 43.65, 38.65 and 35.59 dB, respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.59-59
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• 2000

원자력발전소 1차계통과 격납용기 내부에서 사용되는 주요 부품들은 운전중에 발생한 방사 성 물질들의 침투와 홉착에 의해 오염되어 간다. 이 오염된 부품 및 장비, 공구, 방호복, 방호모자, 작업화 등의 세정과 정비를 위해서는 제염이 선행되어야 한다. 현재의 제염법은 2차 방사성 폐기물을 발생하는 문제점이 있다. 따라서I 2차 폐기물의 발생을 근원적으로 줄일 수 있는 새로운 제염방안이 절실히 요구되고 있는 실정이다. 본 논문에서는 이러한 문제점을 해결할 수 있는 제염법을 개발하기 위해 2가지 방법을 적용하였다. 첫째로, 원자력 발전소에 서 나오는 방사능 오염 세탁물 제염을 위한 액체 및 초임계 이산화탄소를 이용한 방사능 오염물 제염기를 개발하였다. 제염기는 반응기(16 liteer), 회수시스템 그리고 저장용기로 구성되어있다. 세정에 사용된 모든 이산화탄소는 회수되어 재사용 되어지므로 2차 폐기물의 발생을 근원적으로 없앨 수 있다. 제염성능실험결과 제염지수가 목표치보다는 낮았다. 이는 제염 기에 계면활성제와 기계적인 힘을 가한다면 높은 제염지수를 얻을 수 있을 것으로 예상된다. 둘째로, 발전소에서 나오는 오염된 공구나 장비의 세척을 위한 가변형 노즐 드라이 아이스 세척 장치를 개발하였다. 표면세정시 얼음층 형성방지를 위하여 열공급장치를 부착하였다. 유라표면에 지문을 묻혀 실험한 결과 쉽게 제거되었다. 실제 발전소에 있는 P Pump-housing의 표면을 실험한 결과 방사능의 약 40-80%가 제거되었다. 이 장치는 검출기, 제어장치, 용액상에서 세척될 수 없는 장치에 적용할 수 있는 효율적인 세척법이다. 이는 프리프레그의 표면처리 가 충과 충간의 접착강도를 증가시키고 또한 탄소섬유와 에폭시 간의 계면력을 증가시킨데 기인하는 것으로 사려된다.되었으며, duty-on 시간의 증가에 따라 $Cr_2N$ 상의 형성이 점점 많아져 80% duty-on 시간 경우에는 거의 CrN과 $Cr_2N$ 상이 공존하는 것으로 나타났다. 또한 duty-on 시간이 증가할수록 회절피크의 세기가 증가하여 결정화가 더 많이 진행되어짐을 알 수 있었다. 마찬가지로 바이어스 펄스이 주파수에 다른 결정성의 변화도 펄스의 주파수가 증가할수록 박막이 결정성이 좋아지고 $Cr_2N$ 상이 쉽게 형성되었다. 증착 진공도에 따른 결정성은 상대적으로 질소의 농도가 높은 낮은 진공도에서는 CrN 상이 주로 형성되었으며, 반대로 높은 진공도에서는 $Cr_2N$ 상이 많이 만들어졌다. 즉 $1.3{\times}10^{-2}Torr$의 증착 진공도에서는 CrN 상만이 보이는 반면 $9.0{\tiems}1-^{-2}Torr$ 진공도에서부터 $Cr_2N$ 상이 형성되기 시작하여 $5.0{\tiems}10^{-2}Torr$ 진공도에서는 두개의 상이 혼재되어 있음을 알 수 있었다. 박막의 내마모성을 조사한 결과 CrN 박막의 마찰 계수는 초기에 급격하게 증가한 후 0.5에서 0.6 사이의 값으로 큰 변화를 보이지 않았으며, $Cr_2N$ 박막도 비슷한 거동을 보였다.차 이, 목적의 차이, 그리고

• Journal of Internet of Things and Convergence
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• v.10 no.1
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• pp.1-6
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• 2024

In order to increase the use of electric vehicles (EVs) and minimize grid strain, microgrid using renewable energy must take an important role. Microgrid may use fossil fuels such as small diesel power, but in many cases, they can be supplied with energy from renewable energy, which is an eco-friendly energy source. However, renewable energy such as solar and wind power have variable output characteristics. Therefore, in order to meet the charging and discharging energy demands of electric vehicles and at the same time supply load power stably, it is necessary to review the configuration of electric vehicle charging infrastructure that utilizes diesel power or electric vehicle-to-grid (V2G) as a parallel energy source in the microgrid. Against this background, this study modelized a microgrid that can stably supply power to loads using solar power, wind power, diesel power, and V2G. The proposed microgrid uses solar power and wind power generation as the primary supply energy source to respond to power demand, and determines the operation type of the load's electric vehicles and the rotation speed of the load synchronous machine to provide stable power from diesel power for insufficient generations. In order to verify the system performance of the proposed model, we studied the stable operation plan of the microgrid by simulating it with MATLAB /Simulink.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.779-789
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• 2016

The effective rainfall is calculated considering the soil moisture. It utilizes observed data directly in order to incorporate the soil moisture into the rainfall-runoff model, or it calculates indirectly within the model. The rainfall-runoff model, IHACRES, used in this study computes the catchment wetness index (CWI) first varying with temperature and utilize it for estimating precipitation loss. The nonlinear relationship between the CWI and the effective rainfall in the Hapcheondam watershed was derived and utilized for the long-term runoff calculation. The effects of variable and constant CWI during calibration and validation were suggested by flow regime. The results show the variable CWI is generally more effective than the constant CWI. The $R^2$ during high flow period shows relatively higher than the ones during normal or low flow period, but the difference between cases of the variable and constant CWI was insignificant. The results indicates that the high flow is relatively less sensitive to the evaporation and soil moisture associated with temperature. On the other hand, the variable CWI gives more desirable results during normal and low flow periods which means that it is crucial to incorporate evaporation and soil moisture depending on temperature into long-term continuous runoff simulation. The NSE tends to decrease during high flow period with high variability which could be natural because NSE index is largely influenced by outliers of underlying variable. Nevertheless overall NSE shows satisfactory range higher than 0.9. The utilization of variable CWI during normal and low flow period would improve the computation of long-term rainfall-runoff simulation.