Aiming at mitigating end effects of empirical mode decomposition （EMD）, a new approach motivated by the non- equidistance grey model （NGM） termed as NGM（1,1） is proposed. Other than trapezoid formulas, the cubic...Aiming at mitigating end effects of empirical mode decomposition （EMD）, a new approach motivated by the non- equidistance grey model （NGM） termed as NGM（1,1） is proposed. Other than trapezoid formulas, the cubic Hermite spline is put forward to improve the accuracy of derivative to the accumulated generating operation （AGO） series. Hopefully, it is worth stressing that the proposed NGM（1,1） model is particularly useful for predicting uncertainty data. Qualitative and quantitative comparisons between the proposed approach and other well-known algorithms are carried out through computer simulations on synthetic as well as natural signals. Simulation results demonstrate the proposed method can reduce end effects and improve the decomposition results of EMD.展开更多
The reinforced concrete(RC) structural component might suffer a great damage under close-in explosion.Different from distant explosions, blast loads generated by the close-in explosion are non-uniformly distributed on...The reinforced concrete(RC) structural component might suffer a great damage under close-in explosion.Different from distant explosions, blast loads generated by the close-in explosion are non-uniformly distributed on the structural component and may cause both local and structural failure. In this study,an experimental study was conducted to investigate the dynamic responses of RC beams under doubleend-initiated close-in explosions. The experimental results show that the distribution of blast loads generated by the double-end-initiated explosion is much more non-uniform than those generated by single-point detonation, which is caused by the self-Mach-reflection effects. A 3 D finite element model was developed and validated in LS-DYNA by employing the modified K&C model. Intensive numerical calculations were conducted to study the influences of the initiation way, scaled distance and longitudinal reinforcement ratio on the dynamic responses and failure modes of RC beams. Numerical results show that the RC beam suffers greater damage as the cylindrical explosive is detonated at its double ends than the scenario in which the cylindrical explosive is detonated at its central point. RC beams mainly suffer flexural failure and flexure-shear failure under the double-end close-in explosion, and the failure modes of RC beams change from the flexural damage to flexure-shear damage as the scaled distance or the longitudinal reinforcement ratio decreases. The direct shear failure mode is not usually observed in the double-end-initiated explosion, since the intense blast loads is basically concentrated in the midspan of RC beam, which is due to self-Mach-reflection enhancement.展开更多
针对我国首个±1100 k V特高压直流工程(准东—皖南),研究了直流送受端接入系统方案。首先,对于直流送端系统,考虑直流再启动、闭锁等故障对电网的影响,采用直流安全稳定计算标准,从频率和电压稳定性角度研究送端换流站孤岛接入和...针对我国首个±1100 k V特高压直流工程(准东—皖南),研究了直流送受端接入系统方案。首先,对于直流送端系统,考虑直流再启动、闭锁等故障对电网的影响,采用直流安全稳定计算标准,从频率和电压稳定性角度研究送端换流站孤岛接入和联网接入2种方式的可行性。然后,对于直流受端系统,从提高多馈入短路比、抑制短路电流、平衡潮流分布3个层次,研究受端换流站单层接入500 k V、单层接入1000k V、分层接入1000 k V/500 k V这3种方式的可行性。最后,从受端换流站近区网架结构、接入通道选择等多角度研究并提出了换流站的系统接入网架方案。展开更多
基金supported by the National Natural Science Foundation of China (60975009 61171197+6 种基金 61174016)the Innovative Team Program of the NNSF of China (61021002)the National Basic Research Program of China (973 Program) (2012CB720000)the Shandong Provincial Natural Science Foundation (ZR2011FM005)the Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province (BS2010DX001)the Research Fund for the Doctoral Program of Higher Education of China (20092302110037 20102302110033)
文摘Aiming at mitigating end effects of empirical mode decomposition （EMD）, a new approach motivated by the non- equidistance grey model （NGM） termed as NGM（1,1） is proposed. Other than trapezoid formulas, the cubic Hermite spline is put forward to improve the accuracy of derivative to the accumulated generating operation （AGO） series. Hopefully, it is worth stressing that the proposed NGM（1,1） model is particularly useful for predicting uncertainty data. Qualitative and quantitative comparisons between the proposed approach and other well-known algorithms are carried out through computer simulations on synthetic as well as natural signals. Simulation results demonstrate the proposed method can reduce end effects and improve the decomposition results of EMD.
基金supported by the National Natural Science Foundations of China(Nos. 51622812, and 51427807)National Basic Research Program of China(No. 2015CB058003)China Postdoctoral Science Foundation(No. 2017M613379)
文摘The reinforced concrete(RC) structural component might suffer a great damage under close-in explosion.Different from distant explosions, blast loads generated by the close-in explosion are non-uniformly distributed on the structural component and may cause both local and structural failure. In this study,an experimental study was conducted to investigate the dynamic responses of RC beams under doubleend-initiated close-in explosions. The experimental results show that the distribution of blast loads generated by the double-end-initiated explosion is much more non-uniform than those generated by single-point detonation, which is caused by the self-Mach-reflection effects. A 3 D finite element model was developed and validated in LS-DYNA by employing the modified K&C model. Intensive numerical calculations were conducted to study the influences of the initiation way, scaled distance and longitudinal reinforcement ratio on the dynamic responses and failure modes of RC beams. Numerical results show that the RC beam suffers greater damage as the cylindrical explosive is detonated at its double ends than the scenario in which the cylindrical explosive is detonated at its central point. RC beams mainly suffer flexural failure and flexure-shear failure under the double-end close-in explosion, and the failure modes of RC beams change from the flexural damage to flexure-shear damage as the scaled distance or the longitudinal reinforcement ratio decreases. The direct shear failure mode is not usually observed in the double-end-initiated explosion, since the intense blast loads is basically concentrated in the midspan of RC beam, which is due to self-Mach-reflection enhancement.
文摘针对我国首个±1100 k V特高压直流工程(准东—皖南),研究了直流送受端接入系统方案。首先,对于直流送端系统,考虑直流再启动、闭锁等故障对电网的影响,采用直流安全稳定计算标准,从频率和电压稳定性角度研究送端换流站孤岛接入和联网接入2种方式的可行性。然后,对于直流受端系统,从提高多馈入短路比、抑制短路电流、平衡潮流分布3个层次,研究受端换流站单层接入500 k V、单层接入1000k V、分层接入1000 k V/500 k V这3种方式的可行性。最后,从受端换流站近区网架结构、接入通道选择等多角度研究并提出了换流站的系统接入网架方案。
