Analysis of precipitable water vapor from GPS measurements in Chengdu region: Distribution and evolution characteristics in autumn

The rainfall process of Chengdu region in autumn has obvious regional features. Especially, the night-time rain rate of this region in this season is very high in China. Studying the spatial distribution and temporal variation of regional atmospheric precipitable water vapor (PWV) is important for our understanding of water vapor related processes, such as rainfall, evaporation, convective activity, among others in this area. Since GPS detection technology has the unique characteristics, such as all-weather, high accuracy, high spatial and temporal resolution as well as low cost, tracking and monitoring techniques on water vapor has achieved rapid developments in recent years. With GPS–PWV data at 30-min interval gathered from six GPS observational stations in Chengdu region in two autumns (September 2007–December 2007 and September 2008–December 2008), it is revealed that negative correlations exist between seasonally averaged value of GPS–PWV as well as its variation amplitude and local terrain altitude. The variation of PWV in the upper atmosphere of this region results from the water vapor variation from surface to 850 hPa. With the help of Fast Fourier Transform (FFT), it is found that the autumn PWV in Chengdu region has a multi-scale feature, which includes a seasonal cycle, 22.5 days period (quasi-tri-weekly oscillation). The variation of the GPS–PWV is related to periodical change in the transmitting of the water vapor caused by zonal and meridional wind strengths’ change and to the East Asian monsoon system. According to seasonal variation characteristics, we concluded that the middle October is the critical turning point in PWV content. On a shorter time scale, the relationship between autumn PWV and ground meteorological elements was obtained using the composite analysis approach.     

动态系统时延参数估计的重构输入法

首先指出了过去在进行时延系统参数估计时所用的近似处理方法的弊端，然后就动态系统未知时延参数的估计问题提出了重构系统输入的估计方法，并以极大似然估计迭代算法为基础给出了一套估计动态系统时延参数的算法，最后，应用所提出的方法进行了仿真计算，仿真结果表明，参数估计的精度极高，这说明该方法是可靠且可行的。     

机箱盖板金属型铸造工艺

采用计算机仿真技术对机箱盖板金属型铸造过程进行了充型和凝固模拟，并对铸造工艺进行了优化。     

拉伸件成形时的起皱原因及预防措施

分析了工件拉伸过程中起皱现象产生的原因,通过合理确定压力大小、拉伸系数、拉伸工序及选定适宜润滑剂、拉模等,成功解决了拉伸加工过程中的起皱问题,保证了拉伸件的精度和质量.     

Generalized approach to resolution analysis in BSAR

Bistatic synthetic aperture radars (BSARs) have been the focus of increasing research activity over the last decade. The generalized ambiguity function (GAF) of bistatic SAR is introduced here. First, the GAF for BSAR is represented in the delay-Doppler domain, and is then expanded to the spatial (coordinates) domain. From the GAF, comprehensive knowledge regarding the resolution of BSAR can be extracted, including the range and azimuth resolutions, as well as the area of a resolution cell of BSAR. These general results are also applied to the performance analysis of several particular BSAR geometries, including the space-surface-BSAR (SS-BSAR) system, to demonstrate the potential ability of this newly introduced system.     

某型飞机导航误差对CCD稳瞄系统目标搜索域的影响

分析了DG-1型多普勒／GPS组合导航系统，在不同工作方式下导航误差所引起的搜索方位角的误差；讨论了由于搜索方位角的变化引起的搜索域的变化。通过对机理的研究提出了解决办法。     

在HP VEE环境下仪器程控功能的检查方法

本文介绍了在Agilent HP VEE开发环境下，依据仪器驱动程序实现的仪器程控功能检测方法。这种方法可广泛地应用于军内外仪器仪表检测部门。     

Wire electrochemical machining with axial electrolyte flushing for titanium alloy

Titanium and its alloys have found very wide application in aerospace due to their excellent characteristics although their processing is still a challenge. Electrochemical machining is an important issue in the fabrication of titanium and titanium alloys. Wire electrochemical machining (WECM) is mainly used for workpiece cutting under the condition of different thickness plates. It has a great advantage over wire electro-discharge machining, which is the absence of heat-affected zone around the cutting area. Moreover, the wire electrode in WECM could be used repetitively because it is not worn out. Thus, much attention has been paid to WECM. The effective way of removing electrolysis products is of importance to WECM. In this paper, the axial electrolyte flushing is presented to WECM for removing electrolysis products and renewing electrolyte. The Taguchi experiment is conducted to optimize the machining parameters, such as wire feedrate, machining voltage, electrolyte concentration, etc. Experimental results show that WECM with axial electrolyte flushing is a promising issue in the fabrication of titanium alloy (TC1). The feasibility of multi-wire electrochemical machining is also demonstrated to improve the machining productivity of WECM.     

Blade-Loss-Caused Rubbing Dynamic Characteristics of Rotor-Bladed Disk-Casing System

Considering the elastic supports,the finite element model of rotor-bladed disk-casing system is established using commercial software ANSYS/LS-DYNA.Assuming that broken blade is released from the disk,the complicate rubbing responses of unbalanced rotor-bladed disk-casing system are studied under different operational speeds.In addition,influences of both plastic deformation of blade and casing failure are analyzed.The results show that there exist some multiple even fractional frequencies in the transient and steady vibration responses of unbalanced rotor.Besides,one nodal diameter vibration of bladed disk coupling with the lateral vibration of the shaft as well as the first order bending vibration of blade can be excited under low operational speed,while the first order bending vibration of blade coupling with the lateral vibration of disk-shaft is easily excited under high operational speed.During rubbing process,three distinct contact states can be observed:broken blade-casing contact,broken blade-blade component-casing contact and broken blade-casing contact/blade component-casing contact/blade selfcontact.It is worth noting that the third contact state is related to the operational speed.With the increase of operational speed,self-contact in the blade may occur.     

分隔板形式对多爆震管间相互作用的影响分析

为研究共用喷管多爆震管间爆震流场的相互作用,以氢气和氧气混合物为例,对采用不同形式分隔板的共用喷管多爆震管间的相互作用过程进行了数值模拟,并对其性能进行了比较与分析。计算结果表明,采用斜分隔板能有效地减小多爆震管间的相互影响,并且加长分隔板长度可以进一步减小多爆震管间的相互影响,同时还可以通过控制分隔板的长度来控制折射激波到达上爆震管封闭端的时间。