The uncertainties of background contributions to J = 0 partial wave πK scattering phase shifts are carefully studied. We firstly point out that the circular cuts exhibit different characters in S1/1 and S3/2 waves. W...The uncertainties of background contributions to J = 0 partial wave πK scattering phase shifts are carefully studied. We firstly point out that the circular cuts exhibit different characters in S1/1 and S3/2 waves. While the former contributes negatively to the scattering length parameter, the latter contributes positively, i.e., has a wrong sign. This fact indicates that short range force contribu tions to the phase shift are non-negligible in the exotic channel. Nevertheless, it is verified that the κ pole will be affected only slightly with respect to the theoretical uncertainty in estimating the left hand cut contributions.展开更多
Mar-M247 is a nickel-based alloy which is well known as difficult-to-machine material due to its characteristics of high strength, poor thermal diffusion and work hardening. Calculation of shear stress by an analytica...Mar-M247 is a nickel-based alloy which is well known as difficult-to-machine material due to its characteristics of high strength, poor thermal diffusion and work hardening. Calculation of shear stress by an analytical force model to indicate the effect of coating material, cutting speed, feed rate on tool life and surface roughness was conducted experimentally. Cutting tests were performed using round inserts, with cutting speeds ranging from 50 to 300 rn/min, and feed rates from 0.1 to 0.4 mm/tooth, without using cooling liquids. The behavior of the TiN and TiCN layers using various cutting conditions was analyzed with orthogonal machining force model. Cutting results indicate that different coated tools, together with cutting variables, play a significant role in determining the machinability when milling Mar-M247.展开更多
Temperature data from SABER/TIMED and Empirical Orthogonal Function （EOF） analysis are taken to examine possible modulations of the temperature migrating diurnal tide （DW1） by latitudinal gradients of zonal mean z...Temperature data from SABER/TIMED and Empirical Orthogonal Function （EOF） analysis are taken to examine possible modulations of the temperature migrating diurnal tide （DW1） by latitudinal gradients of zonal mean zonal wind （ ζ ）. The result shows that ζ increases with altitudes and displays clearly seasonal and interannual variability. In the upper meso- sphere and lower thermosphere （MLT）, at the latitudes between 20°N and 20°S, when ζ strengthens （weakens） at equinoxes （solstices） the DW1 amplitude increases （decreases） simultaneously. Stronger maximum in March-April equinox occurs in both ζ and the DW1 amplitude. Besides, a quasi-biennial oscillation of DW1 is also found to be synchronous with ζ. The resembling spatial-temporal features suggest that ζ in the upper tropic MLT probably plays an important role in modulating semiannual, annual, and quasi-biennial oscillations in DW1 at the same latitude and altitude. In addition, ζ in the meso- sphere possibly affects the propagation of DW1 and produces SAO of DW1 in the lower thermosphere. Thus, SAO of DW1 in the upper MLT may be a combined effect of ζ both in the mesosphere and in the upper MLT, which models studies should determine in the future.展开更多
A novel approach is proposed for correcting command points and compressing discrete axis commands into a C2 continuous curve.The relationship between values of rotation angles and tool posture errors is firstly analyz...A novel approach is proposed for correcting command points and compressing discrete axis commands into a C2 continuous curve.The relationship between values of rotation angles and tool posture errors is firstly analyzed.A segmentation method based on values of rotation angles and lengths of adjacent points is then used to subdivide these command points into accuracy regions and smoothness regions.Since tool center points generated by CAD/CAM system are usually lying in the space that is apart from the desired curve within a tolerance distance,and the corresponding tool orientation vector may change a lot while the trajectory length of the tool center point is quite small,directly machining with such points will lead to problems of coarse working shape and long machining time.A correction method for command points is implemented so that good processing effectiveness can be achieved.Also,the quintic spline is used for compressing discrete command points into a C2 continuous smooth curve.The machining experiment is finally conducted to demonstrate the effectiveness of the proposed algorithm.展开更多
基金The project supported in part by National Natural Science Foundations of China under Grant Nos. 10575002, 10421503, and 10491306.Acknowledgments It is a pleasure to thank Prof. Han-Qing Zheng for valuable discussions and a careful reading of the manuscript.
文摘The uncertainties of background contributions to J = 0 partial wave πK scattering phase shifts are carefully studied. We firstly point out that the circular cuts exhibit different characters in S1/1 and S3/2 waves. While the former contributes negatively to the scattering length parameter, the latter contributes positively, i.e., has a wrong sign. This fact indicates that short range force contribu tions to the phase shift are non-negligible in the exotic channel. Nevertheless, it is verified that the κ pole will be affected only slightly with respect to the theoretical uncertainty in estimating the left hand cut contributions.
文摘Mar-M247 is a nickel-based alloy which is well known as difficult-to-machine material due to its characteristics of high strength, poor thermal diffusion and work hardening. Calculation of shear stress by an analytical force model to indicate the effect of coating material, cutting speed, feed rate on tool life and surface roughness was conducted experimentally. Cutting tests were performed using round inserts, with cutting speeds ranging from 50 to 300 rn/min, and feed rates from 0.1 to 0.4 mm/tooth, without using cooling liquids. The behavior of the TiN and TiCN layers using various cutting conditions was analyzed with orthogonal machining force model. Cutting results indicate that different coated tools, together with cutting variables, play a significant role in determining the machinability when milling Mar-M247.
基金supported by the National Natural Science Foundation of China(Grant Nos.41274153&41331069)the National Important Basic Research Project of China(Grant No.2011CB811405)+2 种基金the Chinese Academy of Sciences(Grant No.KZZD-EW-01-2)supported by the Specialized Research Fund for State Key Laboratoriesperformed by Numerical Forecast Modelling R&D and VR System of State Key Lab.of Space Weather and Special HPC work stand of Chinese Meridian Project
文摘Temperature data from SABER/TIMED and Empirical Orthogonal Function （EOF） analysis are taken to examine possible modulations of the temperature migrating diurnal tide （DW1） by latitudinal gradients of zonal mean zonal wind （ ζ ）. The result shows that ζ increases with altitudes and displays clearly seasonal and interannual variability. In the upper meso- sphere and lower thermosphere （MLT）, at the latitudes between 20°N and 20°S, when ζ strengthens （weakens） at equinoxes （solstices） the DW1 amplitude increases （decreases） simultaneously. Stronger maximum in March-April equinox occurs in both ζ and the DW1 amplitude. Besides, a quasi-biennial oscillation of DW1 is also found to be synchronous with ζ. The resembling spatial-temporal features suggest that ζ in the upper tropic MLT probably plays an important role in modulating semiannual, annual, and quasi-biennial oscillations in DW1 at the same latitude and altitude. In addition, ζ in the meso- sphere possibly affects the propagation of DW1 and produces SAO of DW1 in the lower thermosphere. Thus, SAO of DW1 in the upper MLT may be a combined effect of ζ both in the mesosphere and in the upper MLT, which models studies should determine in the future.
基金supported by the National Key Basic Research and Development Projects under Grant No.2011CB302400
文摘A novel approach is proposed for correcting command points and compressing discrete axis commands into a C2 continuous curve.The relationship between values of rotation angles and tool posture errors is firstly analyzed.A segmentation method based on values of rotation angles and lengths of adjacent points is then used to subdivide these command points into accuracy regions and smoothness regions.Since tool center points generated by CAD/CAM system are usually lying in the space that is apart from the desired curve within a tolerance distance,and the corresponding tool orientation vector may change a lot while the trajectory length of the tool center point is quite small,directly machining with such points will lead to problems of coarse working shape and long machining time.A correction method for command points is implemented so that good processing effectiveness can be achieved.Also,the quintic spline is used for compressing discrete command points into a C2 continuous smooth curve.The machining experiment is finally conducted to demonstrate the effectiveness of the proposed algorithm.
