• Communications for Statistical Applications and Methods
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• 제22권6호
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• pp.675-683
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• 2015

In the 21st century, we now face the serious problems of the enormous consumption of the energy resources. Depending on the power consumption increases, both China and South Korea face a reduction in available resources. This paper considers the regression models and time-series models to compare the performance of the forecasting accuracy based on Mean Absolute Percentage Error (MAPE) in order to forecast the electricity demand accurately on the short-term period (68 months) data in Northeast China and find the relationship with Korea. Among the models the support vector regression (SVR) model shows superior performance than time-series models for the short-term period data and the time-series models show similar results with the SVR model when we use long-term period data.

• 설비공학논문집
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• 제15권4호
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• pp.287-293
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• 2003

This study examined the temperature-dependent regression model of energy consumption based on various measuring period. The methodology employed was to construct temperature-dependent linear regression model of daily energy consumption from one day to three months data-sets and to compare the annual heating energy consumption predicted by these models with actual annual heating energy consumption. Heating energy consumption from a building in Daejon was examined experimentally. From the results, predicted value based on one day experimental data can have error over 100%. But predicted value based on one week experimental data showed error over 30%. And predicted value based on over three months experimental data provides accurate prediction within 6% but it will be required very expensive.

• 한국항해학회지
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• 제3권1호
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• pp.19-28
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• 1979

There are two different assertions on the rolling error in the solid-controlled gyro compass which contains two rotors in its inner gyro sphere. One assertion is that there is a rolling error and the other is that there is no rolling error. This paper examines the rolling error caused by the centrifugal force by the experiment to reveal that the first assertionis reasonable, and it also attempts to explain qualitatively how the rolling error occurs. The Hokushin-Plath gyro compass is chosen as a model. The rolling error is examined by the swing test in various periods. From the tests, the following results are obtained. As long as the swing is continued under the fixed condition of the ship's heading, the swinging period and the amplitude, no error appears. In case the gyro compass is affected by the swingings except those of the cardinal planes, the error starts to appear only after the swing is finished and it is increasing slowly. It takes about 20 minutes for the error to reach its maximum value. The type of this error is a quadrantal one which makes the ship's heading high in the first and third quarters and low in the second and fourth quarters. But in each case the experimental maximum error is greater than the theorectical one.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.86.1-86
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• 2001

Combined with a counter, wheel or strip encoders which have equally divided markers are one of frequent measuring choices towards various applications in terms of cost, simplicity, and diversity of measurements, e.g., measuring displacement, velocity, acceleration, and so on. Often, velocity is measured by counting the series of reference clocks for a period of time which sensor-carrying device took for traveling two adjacent encoding markers. Quantizaion error of such that the disturbance caused by quantization error is under control. This paper identifies design issues, developes theory, and proposes a paradigm to design a velocity measurement system such ...

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.208-210
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• 1998

A high speed digital distance relaying algorithm based on a modified least square error method is proposed. To obtain stable phasor values very Quickly, first, a lowpass filter which has very short transient period and no overshoot is used. Secondly, the conventional least square error method is modified to the one having the data window of 3 samples by applying a FIR filter which removes the DC-offset component in current relaying signals.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1707-1713
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• 2016

This paper proposes a dc error compensation algorithm using dq-synchronous coordinate transform digital phase-locked-loop in single-phase grid-connected converters. The dc errors are caused by analog to digital conversion and grid voltage during measurement. If the dc offset error is included in the phase-locked-loop system, it can cause distortion in the grid angle estimation with phase-locked-loop. Accordingly, recent study has dealt with the integral technique using the synchronous reference frame phase-locked-loop method. However, dynamic response is slow because it requires to monitor one period of grid voltage. In this paper, the dc offset error compensation algorithm of the improved response characteristic is proposed by using the synchronous reference frame phase-locked-loop. The simulation and the experimental results are presented to demonstrate the effectiveness of the proposed dc offset error compensation algorithm.

• 한국자동차공학회논문집
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• 제4권4호
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• pp.190-200
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• 1996

Step-by-step time integration methods are widely used for solving structural dynamics problem. One difficult yet critical choice an analyst must make is to decide an appropriate time step size. The choice of time step size has a significant effect on solution accuracy and computational expense. The objective of this research is to derive error estimate for newly developed time integration method and develop automatic time step size control algorithm for structural dynamics. A formula for computing error tolerance is derived based on desired period resolution. An automatic time step size control strategy is proposed based on a normalized local error estimate for the generalized-α method. Numerical examples demonstrate the developed strategy satisfies general design criteria for time step size control algorithm for dynamic problem.

• 한국구조물진단유지관리공학회 논문집
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• 제15권2호
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• pp.153-160
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• 2011

최근들어 사장교나 현수교와 같은 케이블 형식의 장대교량이 많이 건설되거나 계획중에 있다. 하지만 도로교 설계기준에 제시된 풍하중 산정시 중요한 요인인 기본풍속 산정함에 있어서 1995년까지 측정된 풍속자료를 근거로 한 일반교량에 적합한 풍속을 명시하고 있어 장대교량에 적합한 풍속에 대한 재검토가 필요한 상황이다. 본 연구에서는 태풍의 빈도가 높고 대부분의 장대교량이 건설되고 있는 서남해안지역으로 구체화하였다. 풍하중기준과 같이 극치I형분포(Gumbel분포)에 의해 일반교량에 적용할 100년, 장대교량에 적용할 200년 재현기대풍속을 적률법과 최소자승법의 두 가지 방법으로 추정하고, 극한 상황인 해상에서 불어오는 풍속으로 보정하여 지상풍속보다 약 17%정도 큰 값을 추정하였다. RMS error 방법에 의해 재현기대풍속의 적합성을 평가한 결과 최소자승법이 서남해안지역의 경우 적합성이 우수하였다.

• Journal of the Korean Data and Information Science Society
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• 제22권3호
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• pp.401-412
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• 2011

본 연구는 벡터오차수정모형을 이용하여 유럽 탄소배출권 현물가격의 일간 시계열자료를 분석한다. 내생변수로는 탄소배출권가격 이외에 오일가격, 천연가스가격, 전력가격, 석탄가격 등 모두 5개 변수를 고려하며, 분석기간은 유럽 배출권가격의 왜곡이 발생한 제1단계 기간 (2005~2007년)을 피해 제2단계 기간 (2008년 4월 21일~2010년 3월 31일)을 대상으로 하였다. 시계열변수의 안정성 및 공적분 검정 결과, 모든 변수들이 단위근을 갖으며 또한 공적분 벡터가 존재하는 것으로 나타나서 분석모형으로서 벡터자기회귀모형 대신에 벡터오차수정모형을 채택하였다. 분석결과, (1) 오일, 천연가스, 전력 등의 가격이 배출권가격에 대해 원인으로 작용하는 그랜저인과관계가 존재하였다. (2) 충격 반응분석에서 배출권가격은 오일가격의 외생적 충격에 대해 가장 크게 반응하였고, 석탄가격의 충격에 대해서는 초기 상승 후 하락, 전력가격과 천연가스가격의 충격에 대해서는 초기 상승 후 음 (-)으로 감소하는 반응을 보였다. (3) 예측오차 분산분해 분석에서 배출권가격에 대해 가장 큰 영향을 주는 요인은 초기 (3기)에는 오일가격>석탄가격>천연가스가격>전력가격의 순이었으나 이후 (20기)에는 전력가격>오일가격>석탄가격>천연가스가격의 순으로 나타났다.

• Earthquakes and Structures
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• 제14권4호
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• pp.305-312
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• 2018

Significant research efforts were undertaken to evaluate seismic performance of vertically irregular buildings on flat ground. However, there is scarcity of study on seismic performance of buildings on hill slopes. The present study attempts to investigate seismic behaviour of reinforced concrete irregular stepback building frames with different configurations on sloping ground. Based on extensive regression study of free vibration results of four hundred seventeen frames with varying ground slope, number of story and span number, a modification is proposed to the code based empirical fundamental time period estimation formula. The modification to the fundamental time period estimation formula is a simplified function of ground slope and a newly introduced equivalent height parameter to reflect the effect of stiffness and mass irregularity. The derived empirical formula is successfully validated with various combinations of slope and framing configurations of buildings. The correlation between the predicted and the actual time period obtained from the free vibration analysis results are in good agreement. The various statistical parameters e.g., the root mean square error, coefficient of determination, standard average error generally used for validation of such regression equations also ensure the prediction capability of the proposed empirical relation with reasonable accuracy.