• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.318-318
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• 2012

인도네시아의 Citarum 유역을 대상으로 구축된 RRFS를 이용하여 해당유역의 상류에 위치한 다목적 댐인 Saguling 댐에 대한 2005년 월 유입량예측을 수행하여 보았다. 실제 예측과정에는 ESP 기법을 적용하였고 여기에 기상전망을 고려할 수 있는 사전처리기법인 PDF ratio 방법을 이용하여 유출량 시나리오의 발생확률을 갱신하였다. 이를 위하여 대상유역의 월 강우량 관측 자료에 대한 초보예측을 통하여 2005년 관측 강우량에 따라 기상전망을 생성하였다. 또한 Saguling 댐의 월 유입량 과거 관측자료에 대한 초보예측을 통하여 High Flow, Normal Flow, Low Flow에 대한 예측구간을 구성하여 보았다. Fig. 1과 Fig. 2는 각각 ESP 기법과 PDF ratio 방법을 이용하여 산정한 Normal Flow와 Low Flow의 상한계 유입량의 발생확률의 변화를 도시한 것이다. 관측 유입량이 발생한 구간의 예측확률을 기반으로 예측점수를 산정해 본 결과 ESP 기법에 의한 예측점수가 0.333을 상회하고 있음을 볼 수 있었다. 이는 ESP 기법에 의한 예측결과가 초보예측보다 정확도가 높음을 의미하는 것으로 본 연구에서 구성한 ESP 시스템의 적용성을 확인할 수 있다. 또한 고무적인 결과로서 PDF ratio 방법에 의한 예측점수가 ESP 기법에 의한 예측점수를 상회하고 있음을 확인할 수 있다. 이는 ESP 기법에 의한 예측결과를 확률기상전망을 이용하여 갱신할 경우 예측 정확도를 개선시킬 수 있음을 의미하는 것이다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.795-804
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• 2014

In this study, Andong Reservoir monthly and ten days inflows from July 2011 to September 2011 are predicted using SWAT model and ensemble technique. The weight method using monthly and ten days rainfall forecasts from Korea Meteorological Administration is applied for accurate analysis. If the rainfall prediction announced by Korea Meteorological Administration is close to the actual rainfall, the PDF-Ratio Method shows the best result. If the past high rainfall occurrence is close to the actual rainfall, the modified PDF-Ratio method shows the best result. This method can improve the prediction accuracy even though the Korea Meteorological Administration forecast is not accurate. On the contrary, if Korea Meteorological Administration forecast is different from the actual rainfall and the past rainfall occurrence statistics of lower section, the uniform method shows the best result.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.303-303
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• 2011

효율적인 수자원 관리를 위해서는 미래 수문자료의 예측치에 대한 구간을 추정하여 미래에 관측될 자료에 대한 정보를 얻는 문제는 어렵지만 중요한 부분에 해당한다. 특히 중장기 유량예측은 입력변수의 불확실성이 크므로 확률론적 방법을 적용한 예측이 유리하다. 본 연구에서는 SSARR 모형을 이용하여 현재 유역의 상태에 과거에 재현되었던 강우를 결합한 앙상블 유출시나리오를 생성하였다. 그리고 대청댐 월 유입량에 대한 확률론적 예측방안을 제시하기위하여 과거 시나리오의 관측 ESP(Ensemble Streamflow Prediction)확률 및 Croley방법, PDF-Ratio방법을 한국의 기상예측정보 실정에 맞는 가중치 부여방안으로 적용하여 분석하였다. 2010년도 상반기를 기준으로 각 분석 기법별 정확성을 검증한 결과 Croley, PDF-Ratio 등 기상전망을 가중치로 부여한 확률론적 예측기법의 효용성을 확인하였다.

• Journal of Korea Water Resources Association
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• v.44 no.10
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• pp.843-851
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• 2011

In hydrology, it is appropriate to use probabilistic method for forecasting mid/long term streamflow due to the uncertainty of input data. Through this study, it is expanded mid/long term forecasting system more effectively adding priory process function based on PDF-ratio method to the RRFS-ESP system for Guem River Basin. For implementing this purpose, weight is estimated using probabilistic weather forecasting information from KMA. Based on these results, ESP probability is updated per scenario. Through the estimated result per method, the average forecast score using ESP method is higher than that of naive forecasting and it confirmed that ESP method results in appropriate score for RRFS-ESP system. It is also shown that the score of ESP method applying revised inflow scenario using probabilistic weather forecasting is higher than that of ESP method. As a results, it will be improved the accuracy of forecasting using probabilistic weather forecasting.

• The Journal of the Acoustical Society of Korea
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• v.22 no.1
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• pp.42-47
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• 2003

This paper proposes the method to generate new test data using the sample shift of the start frame for SPRT(sequential probability ratio test) in speaker verification. The SPRT method is a effective algorithm that can reduce the test computational complexity. However, in making the decision procedure, SPRT can be executed on the assumption that the input samples are usually to be i.i.d. (Independent and Identically Distributed) samples from a probability density function (pdf), also it's not suitable method to apply for the short utterance. The proposed method can achieve SPRT regardless of the utterance length of the test data because it is method to generate the new test data through the sample shift of start frame. Also, the correlation property of data to be considered in the SPRT method can be effectively removed by employing the principal component analysis. Experimental results show that the proposed method increased the computational complexity of data for sample shift a little, but it has a good performance result more than a conventional method above the average 0.7% in EER (equal error rate).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.6
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• pp.538-545
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• 2002

In the orthogonal frequency division multiplexing (OFDM) system, the nonlinear distortion in the high power amplifier(HPA) degrades the system performance because of the high peak-to-average power ratio (PAPR). In this paper, a semi-analytical method is newly proposed for the performance evaluation of the nonlinearly distorted OFDM communication system. In the proposed method, at first, the probability density function (pdf) of the PAPR is generated by computer simulation. Then, mean and variance of the non-linear distortion noise process are computed. Next, the overall BER is found by the analytical method. When the equivalent SSPA model is applied in case of the QPSK/16-QAM and AWGN channel, the BER is calculated for the variation of the IBO(input back-off) and PAPR parameter. It is shown that the results by proposed method are very similar to those of the conventional Monte-Carlo method. The computation time can be considerably reduced than the conventional method that depends on the magnitudes of BER and IBO.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.339-344
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• 2016

Since transmissions of large amounts of data are frequent, users require more bandwidth, and the need for communications networks having greater bandwidth is increasing. One communications network satisfying this need is an optical communications network. Therefore, studies to increase the transmission capacity of optical communications systems have been carried out. However, in a general optical communications system, a signal transmitted through optical fiber (a transmission medium) is detected through direct detection in the receiving system. This method has a disadvantage in that the entire bandwidth of the optical signal cannot be utilized. Also, when transmitting an optical signal, there is a problem where the signal-to-noise ratio is affected by neighboring channels. To overcome this situation, various studies are being conducted to minimize the influence of external interference and noise. This paper overcomes the situation by transmitting spectrum-sliced signals using the digital transmission system, FSK. Analyzing the characteristics of the signals detected in the receiver of the optical communications system, Gaussian distribution is used for the PDF of the spectrum-sliced signal, and the signal at the receiving end of the optical communications system is assumed to have a k-square distribution. The results of the analysis confirmed it is better to transmit the spectrally divided signal rather than transmit the laser source.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6C
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• pp.429-437
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• 2008

Multiple-input multiple-output (MIMO) techniques can be used for the spectral efficiency enhancement of the cellular systems, which can be categorized into spatial multiplexing (SM) and spatial diversity schemes. MIMO systems suffer a severe performance degradation due to the intercell interference from the adjacent cells as the mobile terminal moves toward the cell boundary. Therefore for the spectral efficiency enhancement, an appropriate transmission scheme for the given channel environment and reception scheme which can mitigate the intercell interference are required. In this paper, we propose an adaptive signal transmission/reception scheme for the spectral efficiency improvement of $M_R{\times}M_T$ MIMO systems, present the decision criteria for the adaptive operation of the proposed scheme, and demonstrate the performance gain. The proposed scheme performs adaptive transmission using spatial multiplexing and spatial diversity, and adaptive reception using maximal ratio combining (MRC) and intercell spatial demultiplexing (ISD) when the spatial diversity transmission is used at the transmitter. Spatial multiplexing/demultiplexing is performed at the high signal-to-interference ratio (SIR) range, and the transmit diversity in conjunction with the adaptive reception uses either conventional MRC or ISD which can mitigate the $M_R-1$ interference signals, based on the mobile location. For the performance evaluation of the proposed adaptive scheme, the probability density function (pdf) of the effective SIR for the transmission/reception methods in consideration are derived for $M_R{\times}M_T$ MIMO systems. Using the results, the average effective SIR and spectral efficiency are presented and compared with simulation results.