• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.829-833
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• 2001

In a conventional speed sensorless stator flux­oriented (SFO) induction machine drive system, the estimated speed is delayed in transients by the use of a low pass filter. This paper investigates the problem of a conventional speed sensorless SFO system due to the delay of the estimated speed in the field weakening region. In addition, this paper proposes a method to estimate exactly speed by using Kalman filter. The proposed method is verified by simulation and experiment with a 5-hp induction motor drive.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2003년도 하계학술대회
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• pp.3-6
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• 2003

Effect to altered geometry of a suggested defected ground structure(DGS) unit cell was investigated . And equivalent circuit model was extracted from the DGS unit cell A microstrip band Pass filter with DGS has been designed in this Paper. The BPF with DGS was fabricated and obtained experimental results with network analyzer HP8510C. Experimental results show the center frequency of 2.45GHz, the insertion loss of 0.85dB, and the 3-dB bandwidth of 470MHz (19.5%). The center frequency of BPF is 2.4GHz which is available for wireless LAN.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.206-210
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• 2000

본 논문에서는 PLL 주파수 합성기를 이용한 900 MHz 대역의 무선 마이크용 송신기를 설계 및 제작하였다. 위상잡음을 고려한 주파수 합성기는 VCO, Loop Filter 및 RF 중폭부로 구성한 후 HP EEsof ADS ver. 1.3을 이용하여 설계하였다. VCO는 구조가 간단하며 변조가 용이한 직접변조방식을 사용하였으며 Loop Filter는 주파수 합성기의 기준 고조파 성분을 낮추기 위해 수동 3차 필터를 사용하였다. 주파수 대역 928.125 MHz～929.875 MHz 내에서 채널간격 125 kHz를 갖으며 15개의 채널이 되도록 분주비를 설정한 주파수 합성기는 제작 결과, 송신기 출력 9.3 dBm과 위상잡음이 100 kHz에서 -113 dBc/Hz 이하의 위상잡음 특성을 나타내었고 불요주파수 특성은 -80 dBc 이하의 특성을 나타내었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.200-202
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• 2005

In this paper, improved rotor position estimation for position sensorless control system of the SRM (Switched Reluctance Motor) is presented. For more accurate rotor position estimation, the PLL (Phase Locked Loop) based position interpolation is adapted. In the current-flux-rotor position lookup table based rotor position estimation, the inherent current and flux-linkage ripple can cause the position estimation error. Instead of the conventional low-pass filter, the PLL based position interpolation technique is used for the better dynamic performance. The developed rotor position estimation scheme is realized using TMS320F2812 digital signal processor and prototype 1-hp SRM.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.423-426
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• 2002

Undoped-GaN thin film is deposited on Sapphire substrate by MOCVD. SAW velocity is measured with tile center frequency by HP8753C. Center frequency is 266.52 MHz and SAW velocity is 5330㎧ when wavelength was 20 Um. insertion loss, Q factor and side love attenuation is 41.265 dB, 257.41 and over 23 dB. k'i is calculated from tile measured data. k2'is from 1 % to 4 %. TCF is -61.817pp/m/$^{\circ}C$.

• 한국전자파학회논문지
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• 제11권8호
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• pp.1305-1312
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• 2000

본 논문에서는 Finitely Backed Conductor(FBC) CPW(Coplanar Waveguides) 구조를 이용한 대역 통과 필터를 제안한다. 특히, 마이크로 스트립 전송 선로와 비교하여 CPW구조의 단점인 적은 결합량 문제를 해결하기 위한 방법으로 구조적 변화를 통한 특성 향상을 소개한다. 본 논문에서는 FBC 구조를 이용하여 협대역 대역 통과 필터를 제안하였으며, 측정 결과를 통해 삽입 손실의 향상 효과를 확인할 수 있다. Finitely backed conductor(FBC)를 이용한 CPW 대역 통과 필터를 설계하기 위해 FEM 방식을 이용한 HP사의 HFSS 소프트웨어를 사용하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 추계학술대회 논문집
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• pp.3-6
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• 2002

In a conventional speed sensorless stator flux-oriented(SFO) induction motor drive system, when the estimated speed is transformed into the sample-data model using the first-forward difference approximation, the sampled data model has a modeling error which, in turn, produces an error in the rotor speed estimation. The error included in the estimated speed is removed by the use of a low pass filter (LPF). As the result, the delay of the estimated speed occurs in transients by the use of the LPF This paper investigates the problem of a conventional speed sensorless SFO system due to the delay of estimated speed in the filed weakening region. In addition, this paper proposes a method to estimate exactly speed by using Luenberger observer, The proposed method is verified by experiment with a 5-hp induction motor drive.

• 전력전자학회논문지
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• 제8권4호
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• pp.351-358
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• 2003

본 논문에서는 IGBT PWM 인버터 구동 유도전동기 고정자 권선에서의 스위칭 써지전압 분포특성을 분석하였다. 고정자 권선의 턴 및 코일간의 전압분포를 해석하기 위하여 케이블을 포함한 유도전동기의 등가모델을 제안하고, 유한요소법을 이용하여 고주파 파라메타를 산출하였다 또한, 유도전동기, IGBT PWM 인버터 및 케이블등에 대한 전체 시스템의 EMTP 시뮬레이션을 통하여 인버터 상승시간, 케이블 길이 및 스위칭 주파수 등의 영향에 따른 전압분포를 분석하였다. 380[V], 50[HP] 유도전동기 고정자 권선을 대상으로 한 전압분포 특성실험을 통하여 인버터용 전동기 설치 및 과전압 억제용 필터 설계시의 유용한 자료를 제시하였다.

• 한국정보시스템학회지:정보시스템연구
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• 제30권2호
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• pp.147-163
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• 2021

Purpose The study aims to predict real estate prices by utilizing regional characteristics. Since real estate has the characteristic of immobility, the characteristics of a region have a great influence on the price of real estate. In addition, real estate prices are closely related to economic development and are a major concern for policy makers and investors. Accurate house price forecasting is necessary to prepare for the impact of house price fluctuations. To improve the performance of our predictive models, we applied LSTM, a widely used deep learning technique for predicting time series data. Design/methodology/approach This study used time series data on real estate prices provided by the Ministry of Land, Infrastructure and Transport. For time series data preprocessing, HP filters were applied to decompose trends and SOM was used to cluster regions with similar price directions. To build a real estate price prediction model, SVR and LSTM were applied, and the prices of regions classified into similar clusters by SOM were used as input variables. Findings The clustering results showed that the region of the same cluster was geographically close, and it was possible to confirm the characteristics of being classified as the same cluster even if there was a price level and a similar industry group. As a result of predicting real estate prices in 1, 2, and 3 months, LSTM showed better predictive performance than SVR, and LSTM showed better predictive performance in long-term forecasting 3 months later than in 1-month short-term forecasting.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.201-204
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• 2002

This paper describes the hydrodynamic characteristics of a test-bed AUV SNUUV-I constructed at Seoul National University. The main purpose of the AUV is to carry out fundamental control and hydrodynamic experiments. Its configuration is basically a long cylinder of 1.35m in length and 0.25m in diameter with delta-type wings near its rear end. On the edge of each wing, a thruster of 1/4HP is mounted, which is used for both drive and turn the vehicle for horizontal movement as the output control power is varied. A pair of control surfaces installed near its font part generates pitch moments for vertical movement. The 6 DOF mathematical model of SNUUV-I contains hydrodynamic forces and moments expressed in terms of a set of hydrodynamic coefficients. These coefficients can be classified into linear damping coefficients, linear inertial coefficients and nonlinear damping coefficients. It is important to estimate the exact value of these coefficients to control the vehicle precisely. Among these, the linear coefficients are known to affect the motion of the vehicle dominantly. The linear damping coefficients are estimated by using Extended Kalman Filter. The responses of the vehicle to input signals are used to estimate the hydrodynamic coefficients, which can be inferred from output signals measured from an IMU (inertial motion unit) sensor, while the linear inertial coefficients are calculated by a potential code. By using these coefficients estimated as described above, a simulation program is constructed using Matlab.