In the parameter tracking of time-varying systems, the ordinary method is weighted least squares with the rectangular window or the exponential window. In this paper we propose a new kind of sliding window called the ...In the parameter tracking of time-varying systems, the ordinary method is weighted least squares with the rectangular window or the exponential window. In this paper we propose a new kind of sliding window called the multiple exponential window, and then use it to fit time-varying Gaussian vector autoregressive models. The asymptotic bias and covariance of the estimator of the parameter for time-invariant models are also derived. Simulation results show that the multiple exponential windows have better parameter tracking effect than rectangular windows and exponential ones.展开更多
利用有限元软件ABAQUS生死单元技术对12Mn Ni VR钢矩形窗口斜Y型坡口的焊接试验进行多道焊焊接模拟,计算分析了输入不同的焊接线能量对矩形窗口斜Y型坡口焊接试验的焊缝及热影响区残余应力峰值及其分布的影响。结果表明,线能量的改变对...利用有限元软件ABAQUS生死单元技术对12Mn Ni VR钢矩形窗口斜Y型坡口的焊接试验进行多道焊焊接模拟,计算分析了输入不同的焊接线能量对矩形窗口斜Y型坡口焊接试验的焊缝及热影响区残余应力峰值及其分布的影响。结果表明,线能量的改变对横向残余应力影响较大,对纵向残余应力的影响较小;且在一定范围内,Mises残余应力随线能量增大而增大的速率较为缓慢。此试验结果为进一步研究焊接线能量对焊接接头冷裂纹敏感性的影响提供了一定依据。展开更多
文摘In the parameter tracking of time-varying systems, the ordinary method is weighted least squares with the rectangular window or the exponential window. In this paper we propose a new kind of sliding window called the multiple exponential window, and then use it to fit time-varying Gaussian vector autoregressive models. The asymptotic bias and covariance of the estimator of the parameter for time-invariant models are also derived. Simulation results show that the multiple exponential windows have better parameter tracking effect than rectangular windows and exponential ones.
文摘利用有限元软件ABAQUS生死单元技术对12Mn Ni VR钢矩形窗口斜Y型坡口的焊接试验进行多道焊焊接模拟,计算分析了输入不同的焊接线能量对矩形窗口斜Y型坡口焊接试验的焊缝及热影响区残余应力峰值及其分布的影响。结果表明,线能量的改变对横向残余应力影响较大,对纵向残余应力的影响较小;且在一定范围内,Mises残余应力随线能量增大而增大的速率较为缓慢。此试验结果为进一步研究焊接线能量对焊接接头冷裂纹敏感性的影响提供了一定依据。
