• Journal of Astronomy and Space Sciences
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• 제27권3호
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• pp.221-230
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• 2010

A 4+12+16 amplitude phase shift keying (APSK) modulation outperforms other 32-APSK modulations in a nonlinear additive white Gaussian noise (AWGN) channel because of its intrinsic robustness against AM/AM and AM/PM distortions caused by the nonlinear characteristics of a high-power amplifier. Thus, this modulation scheme has been adopted in the digital video broadcasting-satellite2 European standard. And it has been considered for high rate transmission of telemetry data on deep space communications in consultative committee for space data systems which provides a forum for discussion of common problems in the development and operation of space data systems. In this paper, we present an improved bits-to-symbol mapping scheme with a better bit error rate for a 4+12+16 APSK signal in a nonlinear AWGN channel and propose a simple signal detection algorithm for the 4+12+16 APSK from the presented bit mapping.

• 전자공학회논문지C
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• 제36C권3호
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• pp.35-46
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• 1999

디지털 통신 시스템에서 입력 신호의 주파수와 위상 오차를 보정하는 디지털 위상 오차 보상기(derotator)를 CORDIC (COordinate Rotation DIgital Computer) 알고리즘을 이용하는 VLSI로 구현하였다. CORDIC은 주어지는 위상값에 따라 입력 신호를 직접 회전시키므로, 디지털 주파수 합성기 (Direct Digital Frequency Synthesizer)와 복소수 승산기를 이용하는 기존의 구현 방법에 비해 하드웨어 면에서 간단하다. 디지털 위상 오차 보상기는 작은 위상 오차를 누적하므로 arctangent 함수의 선형 근사를 이용한 고속의 CORDIC 알고리즘을 이용하는 기존에 비해 약 24%의 속도 향상이 가능하였다. 본 설계된 IC는 0.6㎛ triple metal 공정을 이용하였으며, 전체 칩 면적은 6.8㎟ , 트랜지스터의 개수는 11,400 개다. 측정 결과 최대 동작 주파수는 25 MHz이다

• 전기학회논문지
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• 제58권1호
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• pp.173-180
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• 2009

It is difficult to predict non-stationary or chaotic time series which includes the drift and/or the non-linearity as well as uncertainty. To solve it, we propose an effective prediction method which adopts data preprocessing and multiple model TS fuzzy predictors combined with model selection mechanism. In data preprocessing procedure, the candidates of the optimal difference interval are determined based on the correlation analysis, and corresponding difference data sets are generated in order to use them as predictor input instead of the original ones because the difference data can stabilize the statistical characteristics of those time series and better reveals their implicit properties. Then, TS fuzzy predictors are constructed for multiple model bank, where k-means clustering algorithm is used for fuzzy partition of input space, and the least squares method is applied to parameter identification of fuzzy rules. Among the predictors in the model bank, the one which best minimizes the performance index is selected, and it is used for prediction thereafter. Finally, the error compensation procedure based on correlation analysis is added to improve the prediction accuracy. Some computer simulations are performed to verify the effectiveness of the proposed method.

• 조명전기설비학회논문지
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• 제20권5호
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• pp.64-71
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• 2006

전력설비의 비정상적인 온도변화를 감시할 목적으로 10개의 광섬유격자를 이용하여 $1[^{\circ}C]$ 이내의 온도분해능을 가지는 준분배형 광섬유 온도센서를 제작하였다. 파장가변 FP 필터를 스캔하여 얻어지는 PD 출력파형의 피크위치를 검색하여 광섬유격자 센서의 출력변화를 읽어내었고, 가우시안 line-fitting 알고리즘으로 광섬유격자의 반사스펙트럼 왜곡에 의한 영향을 보상하고 정밀도를 향상시켰다. 제작한 센서시스템과 기준 온도계로 사용한 thermocouple 간의 측정값 오차는 1[%] 이내이며, 선형화 오차는 약 0.37[%]으로 측정되었다.

• 전자공학회논문지A
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• 제28A권9호
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• pp.721-728
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• 1991

In this paper, a magneto-optic modulator has been designed by using single crystal BSO and polycrystal ZnSe as Faraday cells. And practical core-type optical current sensors using pure iron and permalloy have been prepared and experimented. In order to obtain efficient magnetic field detection, LED(NEC OD08358, 0.87 $\mu$m) was used as optical source, PIN-PD(OD-8454)as optical receiver and multi-mode optical fiber (100/140$\mu$m) as transmission line. The characteristics matrix of the optical element was calculated by Stokes parameter, and optic modulation characteristics equations were derived by Muller matrix. Electromagnetic analysis program (FLUX 2D, micro VAX 3600) by finite element method was used to find the magnetic flux density around the core. The measuring error of the output voltage to input current has been masured below 5% in the range of 50A to 1000A. As the temperature was changed from -20$^{\circ}C$ to 60$^{\circ}C$, the maximum measurement error of the optical output has been found to be 0.5% at 60$^{\circ}C$. These experimental results show good temperature and linearity characteristics. The SNR of the overall system was 47dB in case of 600A (250.2 Oe) conductor current and the system has good noise immunity.

• 한국전자파학회논문지
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• 제12권1호
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• pp.99-106
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• 2001

본 논문에서는 선형화 특성이 우수하고, 대역폭이 넓은 feedforward 선형화 기법을 이용하여 IMT-2000용 1-Watt 급 증폭기를 설계 제작하였다. Feedforward는 외부환경(온도, 입력 전력 레벨, 시간 등)의 변화에 민감하므로 마이크로컨트롤러를 이용하여 이를 제어하였다. 35dB 의 이득과 40dBm의 최고전력을 갖는 주증폭기를 설계하였고, 각 루프의 신호를 상쇄하기 위해서 반사형 가변감쇄기와 위상변화기를 사용하였다. 2.11 2.17GHz 대역에서 측정 결과 신호루프에서 주신호를 35dB이상 상쇄하였으며, 오차루프에서 30dB 이상 오차신호를 상쇄하여 60dBc 이상의 선형화 특성을 얻을 수 있었다.

• 로봇학회논문지
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• 제12권1호
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• pp.26-32
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• 2017

Previous shape sensors including bend sensors and optic fiber based sensors are widely used in various applications including goniometer and surgical robots. But theses sensors have large nonlinearity, limited in the range of sensing curvature, and sometimes are expensive. This study suggests a new concept of bend sensor using cable-conduit which consists of the outer sheath and the inner wire. The outer sheath is made of helical coil whose length of the central line changes as the sheath bends. This length change of the central line can be measured with the length change of the inner cable. The modeling and the experimental results show that the output signal of the proposed sensor is linearly related with the bend angle of the sheath with root mean square error of 5.3% of $450^{\circ}$ sensing range. Also the polynomial calibration of the sensor can decrease the root mean square error to 2.1% of the full sensing range.

• 산업경영시스템학회지
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• 제42권1호
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• pp.129-136
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• 2019

In this study, we proposed a model for forecasting power energy demand by investigating how outside temperature at a given time affected power consumption and. To this end, we analyzed the time series of power consumption in terms of the power spectrum and found the periodicities of one day and one week. With these periodicities, we investigated two time series of temperature and power consumption, and found, for a given hour, an approximate linear relation between temperature and power consumption. We adopted an exponential smoothing model to examine the effect of the linearity in forecasting the power demand. In particular, we adjusted the exponential smoothing model by using the variation of power consumption due to temperature change. In this way, the proposed model became a mixture of a time series model and a regression model. We demonstrated that the adjusted model outperformed the exponential smoothing model alone in terms of the mean relative percentage error and the root mean square error in the range of 3%~8% and 4kWh~27kWh, respectively. The results of this study can be used to the energy management system in terms of the effective control of the cross usage of the electric energy together with the outside temperature.

• 대한방사선기술학회지:방사선기술과학
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• 제41권6호
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• pp.603-610
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• 2018

This study examined the following: accuracy of the exposure conditions in the inverter device and three-phase device; output waveform over the exposure conditions; and average and standard deviation of the output waveform. After assessing whether the dose corresponding to the theoretical dose was presented, the following conclusions were obtained: 1. The accuracy of the tube voltage(kVp) and tube current(mA) exposure time(sec) was within the tolerable level prescribed in Korea's Safety Management Standards. In the error, Inverter device was large the tube voltage and exposure time, the three-phase device was large the tube current. 2. In terms of the output waveform of the exposure conditions and the average and standard deviation of the output waveform, the higher tube voltage and larger tube current resulted in greater standard deviation in pulsation. Moreover, the standard deviation of pulsation was shown to be greater in the inverter device than the three-phase device; there was also greater standard deviation in the inverter device considering the exposure time. 3. Regarding the exposure conditions over the output dose, all linearity showed the coefficient of variation which had an allowable limit of error within 0.05. Although the output dose ratio for the inverter device was 1.00~1.10 times no difference that of the three-phase device, there was almost no difference in dose ratio between the tube currents.

• 분석과학
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• 제37권2호
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• pp.114-122
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• 2024

A transmission Raman spectroscopy-based quantitative model, which can analyze the content of a drug product containing naproxen sodium as its active pharmaceutical ingredient (API), was developed. Compared with the existing analytical method, i.e., high-performance liquid chromatography (HPLC), Raman spectroscopy exhibits high test efficiency owing to its shorter sample pre-treatment and measurement time. Raman spectroscopy is environmentally friendly since samples can be tested rapidly via a nondestructive method without sample preparation using solvent. Through this analysis method, rapid on-site analysis was possible and it could prevent the production of defective tablets with potency problems. The developed method was applied to the assays of the naproxen sodium of coated tablets that were manufactured in commercial scale and the content of naproxen sodium was accurately predicted by Raman spectroscopy and compared with the reference analytical method such as HPLC. The method validation of the new approach was also performed. Further, the specificity, linearity, accuracy, precision, and robustness tests were conducted, and all the results were within the criteria. The standard error of cross-validation and standard error of prediction values were determined as 0.949 % and 0.724 %, respectively.