Based on the deformation characteristic of regular polygonal box stamped parts and the superfluous triangle material wrinkle model,the criterion of regular polygonal box stamped parts without wrinkle was deduced and u...Based on the deformation characteristic of regular polygonal box stamped parts and the superfluous triangle material wrinkle model,the criterion of regular polygonal box stamped parts without wrinkle was deduced and used to predict and control the wrinkle limit.According to the fracture model,the criterion of regular polygonal box stamped parts without fracture was deduced and used to predict and control the fracture limit.Combining the criterion for stamping without wrinkle with that without fracture,the stamping criterion of regular polygonal box stamped parts was obtained to predict and control the stamping limit.Taken the stainless steel0Cr18Ni9(SUS304)sheet and the square box stamped part as examples,the limit diagram was given to predict and control the wrinkle,fracture and stamping limits.It is suitable for the deep drawing without flange,the deep drawing and stretching combined forming with flange and the rigid punch stretching of plane blank.The limit deep-drawing coefficient and the minimum deep-drawing coefficient can be determined,and the appropriate BHF(blank holder force)and the deep-drawing force can be chosen.These provide a reference for the technology planning,the die and mold design and the equipment determination,and a new criterion evaluating sheet stamping formability,which predicts and controls the stamping process,can be applied to the deep drawing under constant or variable BHF conditions.展开更多
In the conditions of low Signal-to-Noise Ratio(SNR) of seismic data and a small quality of log information,the consequences of seismic interpretation through the impedance inversion of seismic data could be more preci...In the conditions of low Signal-to-Noise Ratio(SNR) of seismic data and a small quality of log information,the consequences of seismic interpretation through the impedance inversion of seismic data could be more precise. Constrained sparse spike inversion(CSSI) has advantage in oil and gas reservoir predication because it does not rely on the original model. By analyzing the specific algorithm of CSSI,the accuracy of inversion is controlled. Oriente Basin in South America has the low amplitude in geological structure and complex lithologic trap. The well predication is obtained by the application of CSSI.展开更多
针对卫星编队重构问题,提出了一种具有随机不确定性、推力约束和避障能力的随机模型预测控制(Stochastic model predictive control,SMPC)方法。由于不确定性的概率是有限的,足以违反约束条件,给随机不确定性的考虑带来了巨大的挑战。S...针对卫星编队重构问题,提出了一种具有随机不确定性、推力约束和避障能力的随机模型预测控制(Stochastic model predictive control,SMPC)方法。由于不确定性的概率是有限的,足以违反约束条件,给随机不确定性的考虑带来了巨大的挑战。SMPC利用概率不确定性描述来定义机会约束,通过引入约束违反概率,为处理约束的随机效应提供了一种有效的方法,且上述方法仅需知道不确定性的均值和方差。将SMPC问题转化为确定性凸问题,提出了一种切比雪夫不等式,将机会约束转化为确定性约束。最后对卫星编队重构问题进行了数值模拟,验证了SMPC算法的可行性和优越性。展开更多
文摘Based on the deformation characteristic of regular polygonal box stamped parts and the superfluous triangle material wrinkle model,the criterion of regular polygonal box stamped parts without wrinkle was deduced and used to predict and control the wrinkle limit.According to the fracture model,the criterion of regular polygonal box stamped parts without fracture was deduced and used to predict and control the fracture limit.Combining the criterion for stamping without wrinkle with that without fracture,the stamping criterion of regular polygonal box stamped parts was obtained to predict and control the stamping limit.Taken the stainless steel0Cr18Ni9(SUS304)sheet and the square box stamped part as examples,the limit diagram was given to predict and control the wrinkle,fracture and stamping limits.It is suitable for the deep drawing without flange,the deep drawing and stretching combined forming with flange and the rigid punch stretching of plane blank.The limit deep-drawing coefficient and the minimum deep-drawing coefficient can be determined,and the appropriate BHF(blank holder force)and the deep-drawing force can be chosen.These provide a reference for the technology planning,the die and mold design and the equipment determination,and a new criterion evaluating sheet stamping formability,which predicts and controls the stamping process,can be applied to the deep drawing under constant or variable BHF conditions.
基金Supported by the Fundamental Research Funds for the Central Universities(No.2011PY0186)
文摘In the conditions of low Signal-to-Noise Ratio(SNR) of seismic data and a small quality of log information,the consequences of seismic interpretation through the impedance inversion of seismic data could be more precise. Constrained sparse spike inversion(CSSI) has advantage in oil and gas reservoir predication because it does not rely on the original model. By analyzing the specific algorithm of CSSI,the accuracy of inversion is controlled. Oriente Basin in South America has the low amplitude in geological structure and complex lithologic trap. The well predication is obtained by the application of CSSI.
文摘针对卫星编队重构问题,提出了一种具有随机不确定性、推力约束和避障能力的随机模型预测控制(Stochastic model predictive control,SMPC)方法。由于不确定性的概率是有限的,足以违反约束条件,给随机不确定性的考虑带来了巨大的挑战。SMPC利用概率不确定性描述来定义机会约束,通过引入约束违反概率,为处理约束的随机效应提供了一种有效的方法,且上述方法仅需知道不确定性的均值和方差。将SMPC问题转化为确定性凸问题,提出了一种切比雪夫不等式,将机会约束转化为确定性约束。最后对卫星编队重构问题进行了数值模拟,验证了SMPC算法的可行性和优越性。
