Straw return is an effective way to improve crop grain yield and potassium(K)use efficiency by increasing soil K content.However,the effects of straw return on soil K supplying capacity,replacement of K fertilizer,and...Straw return is an effective way to improve crop grain yield and potassium(K)use efficiency by increasing soil K content.However,the effects of straw return on soil K supplying capacity,replacement of K fertilizer,and K-use efficiency under maize(Zea mays L.)–rice(Oryza sativa L.)cropping systems are little studied.A two-year field experiment was conducted to determine the physiological determinants of K-use efficiency under straw return with four K fertilization rates.Sr33(straw returned plus 33%of K fertilizer applied)and Sr67(straw returned plus 67%of K fertilizer applied)increased annual crop yields by 1.5%and 3.2%and increased agronomic K-use efficiency by respectively 2.9 and 1.3-fold on average in the two years,compared with the conventional practice S0K100(no straw returned plus normal amounts of K fertilizer applied).The Sr33 and Sr67 treatments resulted in significantly greater equilibrium K concentration ratios(CR0 K)and specifically exchangeable K(KX)values according to quantity/intensity(Q/I)relationship analyses,indicating improvement of the potential soil K supply capacity.However,the Sr67 better maintained the soil exchangeable K level and K balance.The results suggested that K released from maize and rice straw can replace about half of chemical K fertilizer,depending on the available K content in maize–rice cropping system production.展开更多
Calcium hydroxide（CH） is applied to improve disinfection of root canals in most root canal retreatment. This study aimed to analyze the CH removal efficacy using 7 different root preparing files（K file, pre-curved ...Calcium hydroxide（CH） is applied to improve disinfection of root canals in most root canal retreatment. This study aimed to analyze the CH removal efficacy using 7 different root preparing files（K file, pre-curved K file, EndoActivator, Ultrasonic file, pre-curved ultrasonic file, F file and needle irrigation alone） with apical transportation. Standardized models of curved canal with such apical transportation or not were set up before applying CH to root canal for 7 days. Seven techniques described above were used for its removal. Then the roots were disassembled and digital photos were taken. The ratio of residual CH in the overall canal surface was calculated using the image analyzer image pro plus 6.0. The data were analyzed using one-way ANOVA with post hoc Tukey test. Results revealed that CH was effectively removed（P〈0.05） by using all 6 mechanical methods except irrigation alone. In curved root canals with apical transportation, EndoActivator, pre-curved ultrasonic file and F file were found to be more effective in removing CH than the other four file（P〈0.001）, while there was no significant difference among EndoActivator, pre-curved ultrasonic file and F file groups（P〉0.05）. The percentage of residual CH in the canal with apical transportation was higher than that in the canal without apical transportation（P〈0.05）. In conclusion, CH can be hardly removed completely. Canal with apical transportation will result in insufficient CH removal. EndoActivator, pre-curved ultrasonic file and F file are more effective in the curved root canal with apical transportation.展开更多
高效准确的短期负荷预测是电力系统安全稳定与经济运行的重要保障。针对峰荷与谷荷预测误差较大的问题,提出一种基于栅格法提取负荷曲线特征的卷积神经网络和长短期记忆网络(convolutional neural network and long short term memory n...高效准确的短期负荷预测是电力系统安全稳定与经济运行的重要保障。针对峰荷与谷荷预测误差较大的问题,提出一种基于栅格法提取负荷曲线特征的卷积神经网络和长短期记忆网络(convolutional neural network and long short term memory network,CNN-LSTM)混合预测模型。首先,采用K-Medoids算法对日负荷曲线聚类,将各聚类中心作为典型代表日负荷曲线。采用栅格法将典型代表日负荷曲线划分为若干个区间并依次编号,提取负荷曲线的特征。然后,将各典型代表日负荷曲线特征与对应负荷类型历史数据重构成新的特征集输入到CNN-LSTM混合神经网络中。利用CNN挖掘数据间的特征形成新的特征向量,再将该特征向量输入到LSTM中进行预测。最后,以美国新英格兰地区2012至2013年电力负荷数据集为例进行仿真验证。结果表明,所提方法在不同日期下的负荷预测精度均有所提升,并且在提升日负荷平均预测精度的同时,有效提升了峰荷、谷荷的预测精度。展开更多
要提高脱机手写字符识别的识别率,关键是特征的提取。主曲线是主成分分析的非线性推广,是通过数据分布“中间”并满足“自相合”的光滑曲线。通过对现有主曲线算法分析可知:软 K 段主曲线算法对提取出分布在弯曲度很大或相交曲线周围的...要提高脱机手写字符识别的识别率,关键是特征的提取。主曲线是主成分分析的非线性推广,是通过数据分布“中间”并满足“自相合”的光滑曲线。通过对现有主曲线算法分析可知:软 K 段主曲线算法对提取出分布在弯曲度很大或相交曲线周围的数据的主曲线效果较好。因此本文尝试用该主曲线算法来提取脱机手写字符的结构特征。实验结果表明,利用该主曲线算法来提取脱机手写字符的结构特征不但是可行的,而且取得较好的实验效果。它为脱机手写字符特征提取的研究提供了一条新途径。展开更多
对承受疲劳载荷的海洋平台K型管节点首先进行了静力测试,确定了沿着焊缝的热应力区的应力分布及热应力区最大应力点的位置,从而判断裂纹产生的位置;然后通过专用测试设备提供循环疲劳载荷,用ACPD(Alternating Current Potential Drop,...对承受疲劳载荷的海洋平台K型管节点首先进行了静力测试,确定了沿着焊缝的热应力区的应力分布及热应力区最大应力点的位置,从而判断裂纹产生的位置;然后通过专用测试设备提供循环疲劳载荷,用ACPD(Alternating Current Potential Drop,即交流电流势能落差法)技术检测裂纹的产生和增长过程,得到裂纹最深点,用S-N曲线估算其疲劳寿命。对已有裂纹的K型管节点,用应力强度因子估计其剩余寿命。同时用测试的结果验证了S-N的准确性和可靠性。展开更多
基金supported by the Special Fund for Agroscientific Research in the Public Interest of China(201503122)the National Natural Science Foundation of China(31571622)。
文摘Straw return is an effective way to improve crop grain yield and potassium(K)use efficiency by increasing soil K content.However,the effects of straw return on soil K supplying capacity,replacement of K fertilizer,and K-use efficiency under maize(Zea mays L.)–rice(Oryza sativa L.)cropping systems are little studied.A two-year field experiment was conducted to determine the physiological determinants of K-use efficiency under straw return with four K fertilization rates.Sr33(straw returned plus 33%of K fertilizer applied)and Sr67(straw returned plus 67%of K fertilizer applied)increased annual crop yields by 1.5%and 3.2%and increased agronomic K-use efficiency by respectively 2.9 and 1.3-fold on average in the two years,compared with the conventional practice S0K100(no straw returned plus normal amounts of K fertilizer applied).The Sr33 and Sr67 treatments resulted in significantly greater equilibrium K concentration ratios(CR0 K)and specifically exchangeable K(KX)values according to quantity/intensity(Q/I)relationship analyses,indicating improvement of the potential soil K supply capacity.However,the Sr67 better maintained the soil exchangeable K level and K balance.The results suggested that K released from maize and rice straw can replace about half of chemical K fertilizer,depending on the available K content in maize–rice cropping system production.
基金supported by the National Natural Science Foundation of China(No.81200781)
文摘Calcium hydroxide（CH） is applied to improve disinfection of root canals in most root canal retreatment. This study aimed to analyze the CH removal efficacy using 7 different root preparing files（K file, pre-curved K file, EndoActivator, Ultrasonic file, pre-curved ultrasonic file, F file and needle irrigation alone） with apical transportation. Standardized models of curved canal with such apical transportation or not were set up before applying CH to root canal for 7 days. Seven techniques described above were used for its removal. Then the roots were disassembled and digital photos were taken. The ratio of residual CH in the overall canal surface was calculated using the image analyzer image pro plus 6.0. The data were analyzed using one-way ANOVA with post hoc Tukey test. Results revealed that CH was effectively removed（P〈0.05） by using all 6 mechanical methods except irrigation alone. In curved root canals with apical transportation, EndoActivator, pre-curved ultrasonic file and F file were found to be more effective in removing CH than the other four file（P〈0.001）, while there was no significant difference among EndoActivator, pre-curved ultrasonic file and F file groups（P〉0.05）. The percentage of residual CH in the canal with apical transportation was higher than that in the canal without apical transportation（P〈0.05）. In conclusion, CH can be hardly removed completely. Canal with apical transportation will result in insufficient CH removal. EndoActivator, pre-curved ultrasonic file and F file are more effective in the curved root canal with apical transportation.
文摘高效准确的短期负荷预测是电力系统安全稳定与经济运行的重要保障。针对峰荷与谷荷预测误差较大的问题,提出一种基于栅格法提取负荷曲线特征的卷积神经网络和长短期记忆网络(convolutional neural network and long short term memory network,CNN-LSTM)混合预测模型。首先,采用K-Medoids算法对日负荷曲线聚类,将各聚类中心作为典型代表日负荷曲线。采用栅格法将典型代表日负荷曲线划分为若干个区间并依次编号,提取负荷曲线的特征。然后,将各典型代表日负荷曲线特征与对应负荷类型历史数据重构成新的特征集输入到CNN-LSTM混合神经网络中。利用CNN挖掘数据间的特征形成新的特征向量,再将该特征向量输入到LSTM中进行预测。最后,以美国新英格兰地区2012至2013年电力负荷数据集为例进行仿真验证。结果表明,所提方法在不同日期下的负荷预测精度均有所提升,并且在提升日负荷平均预测精度的同时,有效提升了峰荷、谷荷的预测精度。
文摘要提高脱机手写字符识别的识别率,关键是特征的提取。主曲线是主成分分析的非线性推广,是通过数据分布“中间”并满足“自相合”的光滑曲线。通过对现有主曲线算法分析可知:软 K 段主曲线算法对提取出分布在弯曲度很大或相交曲线周围的数据的主曲线效果较好。因此本文尝试用该主曲线算法来提取脱机手写字符的结构特征。实验结果表明,利用该主曲线算法来提取脱机手写字符的结构特征不但是可行的,而且取得较好的实验效果。它为脱机手写字符特征提取的研究提供了一条新途径。
文摘对承受疲劳载荷的海洋平台K型管节点首先进行了静力测试,确定了沿着焊缝的热应力区的应力分布及热应力区最大应力点的位置,从而判断裂纹产生的位置;然后通过专用测试设备提供循环疲劳载荷,用ACPD(Alternating Current Potential Drop,即交流电流势能落差法)技术检测裂纹的产生和增长过程,得到裂纹最深点,用S-N曲线估算其疲劳寿命。对已有裂纹的K型管节点,用应力强度因子估计其剩余寿命。同时用测试的结果验证了S-N的准确性和可靠性。
