Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme pr...Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during E1 Nino events than during La Nina events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Nino and La Nina on the frequency of extreme precipitation events are found.展开更多
In this paper, we propose a new spatial-multiplexing(SM) scheme employing an orthogonal precoder over Rayleigh-fading channels for an erasure event in single frequency networks(SFN). To optimize the precoder, the aver...In this paper, we propose a new spatial-multiplexing(SM) scheme employing an orthogonal precoder over Rayleigh-fading channels for an erasure event in single frequency networks(SFN). To optimize the precoder, the average bit error rate(BER) is evaluated and minimized through a mathematical analysis. Compared to an ordinary SM, the proposed scheme guarantees identical BER performance under non-erasure fading channels and achieves a greatly improved performance under erasure fading channels, especially for a higher erasure-ratio and SNR values. This improvement is mainly due to the increase in the diversity gain incurred by the optimized precoder over the erasure event. We also compare the performance of the proposed SM to that of the conventional constellation-rotation(CR) scheme applied to the single antenna SFN systems. The results of a computer simulation show that the performance of the new scheme is more effective than that of a conventional CR across all simulation cases.展开更多
To calculate the deviations between single station magnitudes and average ones by the magnitude residual statistical method,the paper selects 13086 seismic events recorded by the Gansu broadband digital seismic networ...To calculate the deviations between single station magnitudes and average ones by the magnitude residual statistical method,the paper selects 13086 seismic events recorded by the Gansu broadband digital seismic network from January 2009 to December 2012. The frequency distribution and quantitative statistics of the deviations of earthquake magnitude are analyzed. The MLcalibration function is modified and a uniform local magnitude system characteristic of the Gansu region,is obtained.展开更多
基金supported by the program under Grant No.2007BAC29B04
文摘Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during E1 Nino events than during La Nina events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Nino and La Nina on the frequency of extreme precipitation events are found.
文摘In this paper, we propose a new spatial-multiplexing(SM) scheme employing an orthogonal precoder over Rayleigh-fading channels for an erasure event in single frequency networks(SFN). To optimize the precoder, the average bit error rate(BER) is evaluated and minimized through a mathematical analysis. Compared to an ordinary SM, the proposed scheme guarantees identical BER performance under non-erasure fading channels and achieves a greatly improved performance under erasure fading channels, especially for a higher erasure-ratio and SNR values. This improvement is mainly due to the increase in the diversity gain incurred by the optimized precoder over the erasure event. We also compare the performance of the proposed SM to that of the conventional constellation-rotation(CR) scheme applied to the single antenna SFN systems. The results of a computer simulation show that the performance of the new scheme is more effective than that of a conventional CR across all simulation cases.
基金supported by the China National Special Fund for Earthquake Scientific Research in Public Interests(201308009)
文摘To calculate the deviations between single station magnitudes and average ones by the magnitude residual statistical method,the paper selects 13086 seismic events recorded by the Gansu broadband digital seismic network from January 2009 to December 2012. The frequency distribution and quantitative statistics of the deviations of earthquake magnitude are analyzed. The MLcalibration function is modified and a uniform local magnitude system characteristic of the Gansu region,is obtained.
