• Journal of the Optical Society of Korea
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• 제19권3호
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• pp.237-240
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• 2015

We derived the average bit error rate (BER) of coherent free-space optical (FSO) systems with digital binary phase shift keying (BPSK) modulations over atmospheric turbulence channels with a gamma-gamma distribution. To obtain a generalized derivation in a closed-form expression, we used special integrals and transformations of the Meijer G function. Furthermore, we numerically analyzed and simulated the average BER behavior according to the average SNR for different turbulence strengths. Simulation results are demonstrated to confirm the analytical results.

• International Journal of Contents
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• 제14권1호
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• pp.18-27
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• 2018

The objective of this study was to derive approximate closed-form error rates for M-ary burst symbol transmission (MBST) of dual-hop adaptive decode-and-forward (ADF) cooperative relay systems over quasi-static Rayleigh fading channels. Within a burst, there are pilot symbols and data symbols. Pilot symbols are used for channel estimation schemes and each relay node's transmission mode selection schemes. At first, our focus was on ADF relay systems' error-events at relay nodes. Each event's occurrence probability and probability density function (PDF) were then derived. With error-event based approach, we derived a tractable form of PDF for combined signal-to-noise ratio (SNR). Averaged error rates were then derived as approximate expressions for arbitrary link SNR with different modulation orders and numbers of relays. Its accuracy was verified by comparison with simulation results.

• 반도체디스플레이기술학회지
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• 제10권2호
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• pp.97-102
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• 2011

Lots of 2D vision algorithms have been applied for inspection. However, these 2D vision algorithms have limitation in inspection applications which require 3D information data such as the height of semiconductor chips. Stereo vision is a well known method to measure the distance from the camera to the object to be measured. But it is difficult to apply for inspection directly because of its measurement error. In this paper, we propose two adjustment methods to reduce the error of the measured height data for stereo vision. The weight value based model is used to minimize the mean squared error. The average value based model is used with simple concept to reduce the measured error. The effect of these algorithms has been proved through the experiments which measure the height of semiconductor chips.

• 응용통계연구
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• 제6권2호
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• pp.303-309
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• 1993

오차에 대한 함수관계식이 불확실한 경우 두가지 실험계획법을 제시하였다. 하나는 모든 가능한 오차함수식을 대상으로 최저의 효율성을 높이는 방안이고 다른 하나는 확률을 이용한 최저의 평균효율성을 높이는 방안이다. 이러한 두 방법을 D-와 이분산 G-최적성에 적응시켜 그 차이점을 비교연구하였다.

• Current Optics and Photonics
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• 제3권3호
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• pp.204-209
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• 2019

In an optical interferometer that uses sinusoidal modulation and quadrature detection, the amplitude and offset of the interference signal vary with time, even without considering system noise. As a result, the circular Lissajous figure becomes elliptical, with wide lines. We propose and experimentally demonstrate a method for compensating quadrature detection error, based on digital signal processing to deal with scaling and fitting. In scaling, fluctuations in the amplitudes of in-phase and quadrature signals are compensated, and the scaled signals are fitted to a Lissajous unit circle. To do so, we scale the average fluctuation, remove the offset, and fit the ellipse to a unit circle. Our measurements of a target moving with uniform velocity show that we reduce quadrature detection error from 5 to 2 nanometers.

• 한국항공운항학회지
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• 제31권2호
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• pp.46-54
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• 2023

Helicopter pilots are required to perform many visual workloads in topographical avoidance, flight path modification and navigation, because helicopters operate at very low altitudes. The helicopter-specific instability also require the pilot to have precise perception and control. This has caused frequent human error in helicopter accidents. In Korea, two to three cases have occurred annually on average over the past 10 years, and this trend has not decreased. The purpose of this study was to identify human error risks in advance to prevent helicopter accidents and to help develop measures for missions and mission phases with high risk of human error. Through the study, the tasks and mission phases where accidents occur frequently were classified and the risk of human error was calculated for each mission phases. To this end, the task of frequent accidents during helicopter missions was first identified, detailed steps were classified, and the number of accidents was analyzed. Next, the AHP survey program was developed to measure the pilot's risk of human error and the survey was conducted on the pilots. Finally, the risk of human error by helicopter mission and by mission phases calculated and compared with the actual number of accidents.

• 한국환경과학회지
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• 제24권3호
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• pp.281-290
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• 2015

Recent climate change has led to fluctuations in agricultural production, and as a result national food supply has become an important strategic factor in economic policy. As such, in this study, panel data was collected to analyze the effects of seven meteorological elements on the production of five types of grain with error component panel data regression method following the test results of LM tests, Hausman test. The key factors affecting the production of rice were average temperature, average relative humidity and average ground surface temperature. The fluctuations in the other four grains types are not well explained by meterological elements. For other grains and beans, only average temperature and time (year) affect the production of other grains while average temperature, ground surface temperature, and time (year) influence the production of beans. For barley and millet, only average temperature positively affects the production of barley while ground surface temperature and time (year) negatively influence the production of millet. The implications of this study are as follow. First, it was confirmed that the meteorological elements have profound effects on the rice production. Second, when compared to existing studies, this study was not limited to rice but encompassed all five types of grains and went beyond other studies that were limited to temperature and rainfall to include various meteorological elements.

• 센서학회지
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• 제25권6호
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• pp.418-422
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• 2016

A filtering algorithm based on the decentralized moving average Kalman filter with uncertainties is proposed in this paper. The proposed filtering algorithm presented combines the Kalman filter with the moving average strategy. A decentralized fusion algorithm with the weighted sum structure is applied to the local moving average Kalman filters (LMAKFs) of different window lengths. The proposed algorithm has a parallel structure and allows parallel processing of observations. Hence, it is more reliable than the centralized algorithm when some sensors become faulty. Moreover, the choice of the moving average strategy makes the proposed algorithm robust against linear discrete-time dynamic model uncertainties. The derivation of the error cross-covariances between the LMAKFs is the key idea of studied. The application of the proposed decentralized fusion filter to dynamic systems within a multisensor environment demonstrates its high accuracy and computational efficiency.

• 한국인터넷방송통신학회논문지
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• 제12권4호
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• pp.167-172
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• 2012

통상의 인터넷 트래픽 측정은 특정시간 전후의 트래픽 변화량을 평균한 를 이용하지만, MRTG는 해당 인터페이스를 통하여 유통된 트래픽량을 측정하는 데에는 어느 정도 신뢰성이 있으나 트래픽이 인터페이스의 대역폭을 얼마만큼 점유하였는지는 추측할 수 밖에 없다. 본 논문은 이러한 MRTG의 트래픽 유통량에 근거한 평균 그래프가 실시간 대역폭 점유율 측면에서 어느 정도의 오차율을 보이는지 인터넷 서비스 유형별로 실시간 측정 분석하여 문제점을 파악해보려 했다. 실험결과 서비스 유형별로 적게는 1.4배에서 20배에 이르는 오차율을 보였다. 즉, MRTG 그래프에 의한 대역폭 산정은 원활한 서비스 및 ISP와의 계약 시 대역폭에 의하여 과금되는 구조에서는 상당한 문제점이 있을 수 있음은 증명하였다.

• 제어로봇시스템학회논문지
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• 제12권7호
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• pp.631-636
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• 2006

In this paper, an algorithm of time series function forecasting using GMDH(group method of data handling) algorithm that gives more weight to the recent data is proposed. Traditional methods of GMDH forecasting gives same weights to the old and recent data, but by the point of view that the recent data is more important than the old data to forecast the future, an algorithm that makes the recent data contribute more to training is proposed for more accurate forecasting. The average error rate of electric power demand forecasting by the traditional GMDH algorithm which does not use data weighting algorithm is 0.9862 %, but as the result of applying the data weighting GMDH algorithm proposed in this paper to electric power forecasting demand the average error rate by the algorithm which uses data weighting algorithm and chooses the best data weighting rate is 0.688 %. Accordingly in forecasting the electric power demand by GMDH the proposed method can acquire the reduced error rate of 30.2 % compared to the traditional method.