为了评估同化时间序列叶面积指数(leaf area index,LAI)和蒸散发(evapotranspiration,ET)产品对冬小麦产量估测的有效性和适用性,该文选择陕西省关中平原冬小麦为研究对象,以SWAP为作物生长动态模型,利用冬小麦关键生育期的遥感观测和S...为了评估同化时间序列叶面积指数(leaf area index,LAI)和蒸散发(evapotranspiration,ET)产品对冬小麦产量估测的有效性和适用性,该文选择陕西省关中平原冬小麦为研究对象,以SWAP为作物生长动态模型,利用冬小麦关键生育期的遥感观测和SWAP模拟LAI、ET趋势变化信息构建代价函数,以SCE-UA作为优化算法最小化代价函数,重新初始化SWAP模型中的出苗日期和灌溉量2个参数。重点比较了基于向量夹角和一阶差分2种代价函数的冬小麦单产估测精度。结果表明,同化MODIS LAI和ET后,冬小麦产量的估测精度比未同化精度(r=0.57,RMSE=1 192 kg/hm2)有显著提高,并且基于向量夹角代价函数法同化策略的单产估测精度(r=0.75,RMSE=494 kg/hm2)高于一阶差分代价函数法(r=0.73,RMSE=667 kg/hm2)的估测精度。该方法为其他区域的水分胁迫模式下遥感与作物模型双变量数据同化提供了参考。展开更多
By calculating the hourly standard deviation of the first-order differences of the horizontal geomagnetic com- ponent minute data, a new index Vr to represent the variation rate of the geomagnetic field was introduced...By calculating the hourly standard deviation of the first-order differences of the horizontal geomagnetic com- ponent minute data, a new index Vr to represent the variation rate of the geomagnetic field was introduced. Vr-indices show similar trends in the temporal change at different observatories and have simultaneous peak values at the observatories cov- ering a large span geographically, which reveals that the source of geomagnetic disturbances represented by Vr is in the mag- netosphere. Based on the comparison among Vr, Kp and ap, it is found that generally Vr changes linearly with Kp and ap, which means that the rapid changes of magnetic field usually exist together with magnetic disturbances. But there are excep- tions. As Vr can be easily produced by individual observatory in quasi real time and is more sensitive to the variation rate of geomagnetic field rather than the field itself, it can be expected to serve for monitoring or predicting the geomagnetic-induced event in a quick and intuitive way.展开更多
从提高满足少数民族普通话高自然度语音合成与高精度语音识别的实际应用需求出发,首次从实验语音学的角度对初级、中级和高级阶段的50名维吾尔族汉语学习者与10名母语为汉语普通话的说话人声调的一阶差分与时长以及相似度进行对比,并对...从提高满足少数民族普通话高自然度语音合成与高精度语音识别的实际应用需求出发,首次从实验语音学的角度对初级、中级和高级阶段的50名维吾尔族汉语学习者与10名母语为汉语普通话的说话人声调的一阶差分与时长以及相似度进行对比,并对其声调的一阶差分模式、声调时长等韵律参数进行了实验分析,得出维吾尔族学生对汉语声调的偏误情况以及与中国少数民族汉语水平等级考试(Master of Human Kinetics, MHK)成绩的关系。通过实验结果可以发现,三组维吾尔族人学习普通话的声调都有困难。两种语言的音系,语调和重音等特性影响了第二语言中的声调特性。归纳了维吾尔族学习者声调的基本声学特征,总结出了一些重要的规则和结论;为解决给汉语语音处理带来的困难,尤其是少数民族汉语的语音合成和语音识别方面的声调问题,提供了重要的参考依据。展开更多
文摘By calculating the hourly standard deviation of the first-order differences of the horizontal geomagnetic com- ponent minute data, a new index Vr to represent the variation rate of the geomagnetic field was introduced. Vr-indices show similar trends in the temporal change at different observatories and have simultaneous peak values at the observatories cov- ering a large span geographically, which reveals that the source of geomagnetic disturbances represented by Vr is in the mag- netosphere. Based on the comparison among Vr, Kp and ap, it is found that generally Vr changes linearly with Kp and ap, which means that the rapid changes of magnetic field usually exist together with magnetic disturbances. But there are excep- tions. As Vr can be easily produced by individual observatory in quasi real time and is more sensitive to the variation rate of geomagnetic field rather than the field itself, it can be expected to serve for monitoring or predicting the geomagnetic-induced event in a quick and intuitive way.
文摘从提高满足少数民族普通话高自然度语音合成与高精度语音识别的实际应用需求出发,首次从实验语音学的角度对初级、中级和高级阶段的50名维吾尔族汉语学习者与10名母语为汉语普通话的说话人声调的一阶差分与时长以及相似度进行对比,并对其声调的一阶差分模式、声调时长等韵律参数进行了实验分析,得出维吾尔族学生对汉语声调的偏误情况以及与中国少数民族汉语水平等级考试(Master of Human Kinetics, MHK)成绩的关系。通过实验结果可以发现,三组维吾尔族人学习普通话的声调都有困难。两种语言的音系,语调和重音等特性影响了第二语言中的声调特性。归纳了维吾尔族学习者声调的基本声学特征,总结出了一些重要的规则和结论;为解决给汉语语音处理带来的困难,尤其是少数民族汉语的语音合成和语音识别方面的声调问题,提供了重要的参考依据。
