超高速数控精密磨床磁浮轴承主轴单元设计

本文介绍了磁浮轴承的优点，并提出了磁浮轴承作为磨床主轴轴承的设计方法。同时，首次提出了超高速数控精密外圆磨床磁浮轴承主轴单元设计方法和设计过程。并针对一台300m／s超高速数控精密外圆磨床磁浮轴承主轴单元进行了设计。经过实验证明，提出的设计方法是正确的。同时，应用了该技术的超高速数控精密磨床，虽然初期投资成本高，但其优越的使用性能使其综合效益高。     

A new procedure to estimate the rainfall erosivity factor based on Tropical Rainfall Measuring Mission(TRMM) data

Soil erosion by water is the most important land degradation problem worldwide.In this paper a new procedure was developed to estimate the rainfall-runoff erosivity factor(R)based on Tropical Rainfall Measuring Mission(TRMM)satellite-estimated precipitation data,which consists of 3-h rainfall intensity data.In this method,R was calculated as the product of the maximum 180-min rainfall intensity and the rainfall energy.This procedure was applied to the Daling River basin in Liaoning Province,China,R in terms...     

Neumann展开Monte Carlo随机无网格点插值法

用Neumann展开Monte Carlo随机无网格点插值法(NMC-SMPIM)进行随机结构分析。在随机无网格点插值法(stochastic meshless point interpolation method,SMPIM)中,所求解问题的域由分布的节点表示;并且利用具有Delta函数性质的多项式进行节点插值,为此,很容易类似有限元法一样处理本质边界条件。同时利用Neumann展开法,建立随机结构分析的Neumann展开Monte Carlo随机无网格点插值法。数值实例表明,Neumann展开Monte Carlo随机无网格点插值法适用于材料变异系数大和要求精度高的随机结构分析。     

Mathematic principles of interrupted-sampling repeater jamming (ISRJ)

Coherent jamming is one of the important trends in modern radar electronic war- fare. High-speed sampling of wideband radio frequency (RF) signals and high iso- lation of two receive-transmit antennas are key technologies for the realization of coherent jamming. However, these technologies present significant challenges to engineering application. In this paper, a novel repeater jamming based on inter- rupted sampling technique is presented. For a jammer with a receive-transmit time-sharing antenna, a radar signal is sampled with a low rate by the jammer. Then, a train of false targets will be achieved after the jamming signal feed the matched filter of a pulse compression radar. For the case of the linear frequency modulated (LFM) pulse compression radars, mathematic principles of the interrupted-sam- pling repeater jamming is developed, and then the efficiency of the jamming is de- scribed and stated as expressions of key parameters which are also beneficial to the jamming design for other coherent radars.     

Performance of MODIS aerosol products at various timescales and in different pollution conditions over eastern Asia

High-quality aerosol optical depth(AOD) data derived from MODIS is widely used in studying spatiotemporal trends of fine particulate matter(PM_(2.5)) concentrations in eastern Asia. However, the differences of MODIS-AOD(3/10 km DT; 10 km DB)under four pollution situations(No-Po; Sl-Po; Mo-Po; Se-Po) are rarely considered. In this study, the MODIS-AOD and AODDifference spatial distributions from 2008 to 2017 are analyzed through annual/seasonal mean AOD maps generated at 0.1°×0.1° resolution. The MODIS-AOD performances are validated using AERONET AOD data for various pollution situations and aerosol types. Annual validations indicate that the 10-km DB algorithm provides the best performance, followed by 3-km DTand 10 km DT. The DB algorithm can provide spatially continuous AOD data for all seasons, whereas the DT algorithm often fails to yield valid data during winter. The validations under different pollution conditions illustrate that severe pollution significantly affects the validity of data obtained by the DB algorithm. However, the accuracy of DT-derived AOD data is robust against interference. Under the same pollution conditions, the correlation coefficient of the DB algorithm is smaller than that of the DT algorithm. The quantity of valid data in the DB product is higher than those in DT products for all pollution conditions, especially under Se-Po.