Based on the dynamic framework of Lorenz 96 model,the ensemble prediction system(EPS)containing stochastic forcing has been developed.In this system,effects of stochastic forcing on the model climate state and ensembl...Based on the dynamic framework of Lorenz 96 model,the ensemble prediction system(EPS)containing stochastic forcing has been developed.In this system,effects of stochastic forcing on the model climate state and ensemble mean prediction have been studied.The results show that the climate mean and standard deviation provided by a new computing paradigm by means of introduction of the proper stochastic forcing into numerical model integration process are closer to that of the true value than that made by the non-stochastic forcing.In other words,numerical model integration process with stochastic forcing has positive effect on the model climate state,and the effect is found to be positive mainly in the long lead time.Meanwhile,with respect to ensemble forecast effect yielded by white noise stochastic forcing,most results are better than those provided by no-stochastic forcing,and improvements pertaining to white noise stochastic forcing vary non-monotonically with the increase of the size of white noise.Moreover,the effects made by the identical white noise stochastic forcing also are different in various non-linear systems.With respect to EPS effect yielded by red noise stochastic forcing,most results are better than those provided by no-stochastic forcing,but only a part of ensemble forecast effect influenced by red noise is superior to that influenced by white noise.Finally,improvements pertaining to red noise stochastic forcing vary non-symmetrically and non-monotonically with the distribution of coefficientΦ.Besides,the selection of correlation coefficientΦis also dependent on non-linear models.展开更多
In this article,a grinding force model,which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism o...In this article,a grinding force model,which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism of grinding force,was established.Three key factors have been taken into accounts in this model,such as the contact friction force between abrasive grains and materials,the plastic deformation of material in the process of abrasive plowing,and the shear strain effect of material during the process of cutting chips formation.The model was finally validated by the orthogonal grinding experiment of powder metallurgy nickel-based superalloy FGH96 by using the electroplated CBN abrasive wheel.Grinding force values of prediction and experiment were in good consistency.The errors of tangential grinding force and normal grinding force were 9.8%and 13.6%,respectively.The contributions of sliding force,plowing force and chip formation force were also analyzed.In addition,the tangential forces of sliding,plowing and chip formation are 14%,19%and 11%of the normal forces on average,respectively.The pro-posed grinding forcemodel is not only in favor of optimizing the grinding parameters and improving grinding efficiency,but also contributes to study some other grinding subjects(e.g.abrasive wheel wear,grinding heat,residual stress).展开更多
基金Supported by National Natural Science Foundation of China(41205073,41275099)General Program of Nanjing Joint Center of Atmospheric Research(NJCAR2016MS02)
文摘Based on the dynamic framework of Lorenz 96 model,the ensemble prediction system(EPS)containing stochastic forcing has been developed.In this system,effects of stochastic forcing on the model climate state and ensemble mean prediction have been studied.The results show that the climate mean and standard deviation provided by a new computing paradigm by means of introduction of the proper stochastic forcing into numerical model integration process are closer to that of the true value than that made by the non-stochastic forcing.In other words,numerical model integration process with stochastic forcing has positive effect on the model climate state,and the effect is found to be positive mainly in the long lead time.Meanwhile,with respect to ensemble forecast effect yielded by white noise stochastic forcing,most results are better than those provided by no-stochastic forcing,and improvements pertaining to white noise stochastic forcing vary non-monotonically with the increase of the size of white noise.Moreover,the effects made by the identical white noise stochastic forcing also are different in various non-linear systems.With respect to EPS effect yielded by red noise stochastic forcing,most results are better than those provided by no-stochastic forcing,but only a part of ensemble forecast effect influenced by red noise is superior to that influenced by white noise.Finally,improvements pertaining to red noise stochastic forcing vary non-symmetrically and non-monotonically with the distribution of coefficientΦ.Besides,the selection of correlation coefficientΦis also dependent on non-linear models.
基金financial support for this work by the National Natural Science Foundation of China(Nos.51775275,51921003 and 51905363)the Funding for Outstanding Doctoral Dissertation in NUAA of China(No.BCXJ19-06)+1 种基金the Natural Science Foundation of Jiangsu Province of China(No.BK20190940)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.19KJB460008)。
文摘In this article,a grinding force model,which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism of grinding force,was established.Three key factors have been taken into accounts in this model,such as the contact friction force between abrasive grains and materials,the plastic deformation of material in the process of abrasive plowing,and the shear strain effect of material during the process of cutting chips formation.The model was finally validated by the orthogonal grinding experiment of powder metallurgy nickel-based superalloy FGH96 by using the electroplated CBN abrasive wheel.Grinding force values of prediction and experiment were in good consistency.The errors of tangential grinding force and normal grinding force were 9.8%and 13.6%,respectively.The contributions of sliding force,plowing force and chip formation force were also analyzed.In addition,the tangential forces of sliding,plowing and chip formation are 14%,19%and 11%of the normal forces on average,respectively.The pro-posed grinding forcemodel is not only in favor of optimizing the grinding parameters and improving grinding efficiency,but also contributes to study some other grinding subjects(e.g.abrasive wheel wear,grinding heat,residual stress).
