• 전기전자학회논문지
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• 제19권3호
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• pp.335-341
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• 2015

최근 들어 철강의 두께 제어를 위해 고정밀도의 절대 위치 검출 센서에 대한 필요성은 증가하고 있다. 열악한 공장 환경 하에서 직선 운동하는 실린더의 절대 위치를 측정하기 위해서는 LVDT가 널리 사용된다. 본 논문에서는 1 미크론의 고해상도를 가지는 3상 LVDT 및 L/D (LVDT to digital) 변환기를 구현하였다. 이를 위하여 첫째 U, V, W 3상 정현파에 대한 시그널링을 FPGA로 설계하였다. 둘째 위치 정보에 대한 A상, B상 펄스 파형 출력 알고리즘을 구현하였다. 마지막으로 성능 평가를 위하여 기존의 센서들과 비교하였다. 실험 결과 직선성 편이 오차는 0.009788 [mm] 로써 2.2% 향상된 결과를 얻었고 정현파의 왜곡률은 평균 0.0751%로 기존보다 33%의 향상된 결과를 얻어 우수한 센서임을 입증하였다.

• 한국통신학회논문지
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• 제36권9C호
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• pp.589-595
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• 2011

본 논문에서는 다중경로 페이딩 (multipath fading) 채널 환경에서 직교 주파수 분할 다중 (orthogonal frequency division multiplexing: OFDM) 시스템을 위한 개선된 다중단계 (mu1ti-stage) 타이밍 옵셋 (timing offset) 추정기법을 제안한다. 제안한 기법은 기존의 다중단계 타이밍 옵셋 추정기법이 랜덤한 다중경로 채널 성분에 민감하다는 점을 개선하기 위해 상호 상관함수 샘플 표준편차를 이용한다. 모의실험 결과를 통해 제안한 기법이 기존 기법에 비해 우수한 정추정확률과 (correct estimation probability) 평균제곱오차 (mean square error: MSE) 성능을 가짐을 보인다.

• 대한전기학회논문지:전력기술부문A
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• 제54권10호
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• pp.480-486
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• 2005

This paper proposes a method to consider an aging failure probability and survival probability of power system components, though only aging failure probability has been considered in existing mean life calculation. The estimates of the mean and its standard deviation is calculated by using Weibull distribution, and each estimated parameters is obtained from Data Analytic Method (Type H Censoring). The parameter estimation using Data Analytic Method is simpler and faster than the traditional calculation method using gradient descent algorithm. This paper shows calculation procedure of the mean life and its standard deviation by the proposed method and illustrates that the estimated results are close enough to real historical data of combustion turbine generating units in Korean systems. Also, this paper shows the calculation procedures of a probabilistic failure prediction through a stochastic data analysis. Consequently, the proposed methods would be likely to permit that the new deregulated environment forces utilities to reduce overall costs while maintaining an are-related reliability index.

• Ocean and Polar Research
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• 제30권2호
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• pp.149-158
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• 2008

The characteristic analysis of the estimated population parameters, i.e., standard deviation and error bound of coastal pollutant concentrations (hereafter PC, i.e., COD, TN, and TP concentrations), was carried out by using environmental data with different sampling frequency in Lake Shihwa and Incheon coastal zone. The results clearly show that standard deviation of the PC increases as its mean value increases. The error bounds of the annual mean values based on seasonally measured DO concentrations and PC data in Incheon coastal zone were estimated as ranges 2.26 mg/l, $0.68{\sim}0.86\;mg/l$, $0.62{\sim}0.80\;mg/l$, and $0.074{\sim}0.082\;mg/l$, respectively. In terms of annual mean of the DO concentration and PC in Lake Shihwa, the error bounds based on monthly measured data from 1997 to 2003 were also estimated as ranges 4.0 mg/l, 3.0 mg/l, $0.5{\sim}1.0\;mg/l$, and 0.05 mg/l, respectively. The error bound on the basis of real-time monitoring data is $7{\sim}13%$ only as compared to that of monthly measured data.

• 제어로봇시스템학회논문지
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• 제22권4호
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• pp.253-265
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• 2016

We propose an obstacle classification method using multi-decision factors and decision sections based on Single 2D LiDAR. The existing obstacle classification method based on single 2D LiDAR has two specific advantages: accuracy and decreased calculation time. However, it was difficult to classify obstacle type, and therefore accurate path planning was not possible. To overcome this problem, a method of classifying obstacle type based on width data was proposed. However, width data was not sufficient to enable accurate obstacle classification. The proposed algorithm of this paper involves the comparison between decision factor and decision section to classify obstacle type. Decision factor and decision section was determined using width, standard deviation of distance, average normalized intensity, and standard deviation of normalized intensity data. Experiments using a real autonomous vehicle in a real environment showed that calculation time decreased in comparison with 2D LiDAR-based method, thus demonstrating the possibility of obstacle type classification using single 2D LiDAR.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.67-69
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• 2004

ZnO varistor ceramics which were fabricated with variation of added of 0.01, 0.02, 0.03, 0.05, 0.1mol% $Nb_2O_5$ sintered at $1150^{\circ}C$. In the specimen added 0.05mol% $Nb_2O_5$, sintered density was $5.87g/cm^3$ and electrical properties were superior to any other components. The nonlinear coefficient was 75, and clamping voltage ratio was 1.40. And, endurance surge current in the specimen added 0.05mol% $Nb_2O_5$ was $6500A/cm^2$, and deviation of varistor voltage was -1.7%. As P.C.T and T.C.T environment test were succeed in all specimens, and deviation of varistor voltage in the specimen added 0.3mol% $Nb_2O_5$ was -0.81%. All specimens showed a good leakage current property in the High Temperature Continuous Load Test for 1000hr, at $85^{\circ}C$, and variation rate of the varistor voltage was -1.71%.

• 한국작물학회지
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• 제45권6호
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• pp.374-381
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• 2000

This study was conducted to select sesame varieties with high cultural stabilities by comparing several parameters of agronomic traits under the different cultural environments. Of the six areas, Iksan and Jinju areas which showed positively larger environment index values were relatively adequate cultural conditions for sesame. At the comparison of cultural stability of agronomic traits by Eberhart and Russell regression model among sesame breeding lines, Suwon 169 showed more stable regression coefficient values to the number of capsules per plant, number of seeds per capsule and seed weight per plant, and Iksan 12 showed more stable regression coefficient values to culm length and weight per plant. At the comparison of cultural stability of yield per 10a, Suwon 169 and Iksan 12 among sesame breeding lines showed more stable respectively, deviation values of 0.99, 0.98 respectively, and more less regression deviation values of 0.074, 0.167 respectively. Therefore those breeding lines are comparatively higher stabilities to yield determining agronomic traits under the different cultural environments, and it was concluded that those two breeding lines had the possibility to recommend promising breeding lines in the future.

• 한국공간정보시스템학회 논문지
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• 제11권2호
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• pp.89-98
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• 2009

데이터 스트림은 다양한 입력속도로 끊임없이 입력되고 데이터 스트림을 저장하는 메모리상의 저장공간은 유한하기 때문에 때때로 저장공간을 초과하는 데이터가 입력되는 경우가 발생한다. 이 문제를 해결하기 위해 초과되는 데이터의 일부를 버려 메모리 초과를 방지하는 부하제한 기법이 연구되었다. 기존의 부하제한 기법은 데이터의 편차에 따른 최적의 샘플링 비율을 갖는 랜덤 샘플링을 사용한다. 그러나 이 기법은 공간적 특성을 고려하지 않기 때문에 공간 질의에 사용되는 데이터와 사용되지 않는 데이터를 구분하지 않고 샘플링 한다. 그래서 공간 질의가 포함되는 u-GIS 환경에서는 질의 정확도가 감소하는 문제가 발생하였다. 본 논문에서는 공간 질의와 비공간 질의가 동시에 발생하는 u-GIS 환경에서 질의 정확도를 보다 향상 시키는 부하제한 기법을 연구하였다. 이 기법은 동시에 실행되는 공간 질의의 공간적 이용도에 따라 차등적으로 샘플링을 하여, 질의에 이용될 확률이 낮은 데이터를 샘플링을 한다. 제안된 부하제한 기법은 공간질의가 존재하는 경우 질의 정확도를 크게 향상 시켰고, 샘플링 중 공간 필터링 연산을 적용하여 질의처리 속도도 일부 향상 시켰다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.69-74
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• 2006

Recently, spillways are need to control stable water level for supporting main dams because of floods by unusual change of weather such as Typhoon Rusa. This study has been focused on the amount of leakage through the rock mass distributed fractures and joints under the opened emergency spillway. It is very important to evaluate the amount of leakage as these affect stability of spillway by interaction between effective stress and pore pressure. The commercial program MAFIC has been used for analyzing groundwater flow in fractured rock mass. The results showed that the values of range, average and deviation of leakage were $2.85\sim\;3.79\times10^{-1}$, $3.32\times10^{-1}$ and $1.70\times10^{-2}\;m^3/day/m^2$ respectively. Secondary, we have estimated the effect of grouting after the transmissivity$(T_f)$ of joint 1 as main pathway of leakage known from above results was changed from $1.78\times10^{-7}$ to $1.59\times10^{-9}\;m^2/s$. The results showed that the values of range, average and deviation of leakage were $7.80\times10^{-4}\sim1.53\times10^{-3}$, $1.18\times10^{-3}$ and $1.32\times10^{-4}\;m^3/day/m^2$ respectively. As the result, the amount of leakage after grouting has been decreased by a ratio of 1 to 277.

• Journal of Welding and Joining
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• 제26권2호
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• pp.85-91
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• 2008

In general, the quality of a welding process tends to vary with depending on the work environment or external disturbances. Hence, in order to achieve the desirable quality of welding, we should have the optimal welding condition that is not significantly affected by these changes in the environment or external disturbances. In this study, we used a dual response surface method in consideration of both the mean output variables and the standard deviation in order to optimize the V-groove arc welding process. The input variables for GMA welding process with the dual response surface are welding voltage, welding current and welding speed. The output variables are the welding quality function using the shape factor of bead geometry. First, we performed welding experiment on the interested area according to the central composite design. From the results obtained, we derived the regression model on the mean and standard deviation between the input and output variables of the welding process and then obtained the dual response surface. Finally, using the grid search method, we obtained the input variables that minimize the object function which led to the optimal V-groove arc welding process.