略论发动机涡轮叶片的振动疲劳

针对发动机涡轮叶片的振动及振动疲劳破坏进行了理论分析。通过理论分析和实验，说明了叶片对抗振对疲劳的能力主要取决于性质及叶片的形式、表面状态，而与静强度无关。并对改进设计和工艺，充分挖掘材料潜力，加强对叶片防护，提出了建议和设想。     

Auto-normalization algorithm for robotic precision drilling system in aircraft component assembly

A novel approach is proposed to detect the normal vector to product surface in real time for the robotic precision drilling system in aircraft component assembly, and the auto-normalization algorithm is presented based on the detection system. Firstly, the deviation between the normal vector and the spindle axis is measured by the four laser displacement sensors installed at the head of the multi-function end effector. Then, the robot target attitude is inversely solved according to the auto-normalization algorithm. Finally, adjust the robot to the target attitude via pitch and yaw rotations about the tool center point and the spindle axis is corrected in line with the normal vector simultaneously. To test and verify the auto-normalization algorithm, an experimental platform is established in which the laser tracker is introduced for accurate measurement. The results show that the deviations between the corrected spindle axis and the normal vector are all reduced to less than 0.5°, with the mean value 0.32°. It is demonstrated the detection method and the auto-normalization algorithm are feasible and reliable.     

Identification of ground targets from sequential high-range-resolution radar signatures

An approach to identifying targets from sequential high-range-resolution (HRR) radar signatures is presented. In particular, a hidden Markov model (HMM) is employed to characterize the sequential information contained in multiaspect HRR target signatures. Features from each of the HRR waveforms are extracted via the RELAX algorithm. The statistical models used for the HMM states are formulated for application to RELAX features, and the expectation-maximization (EM) training algorithm is augmented appropriately. Example classification results are presented for the ten-target MSTAR data set.     

A knowledge-based architecture for planning military intelligence, surveillance, and reconnaissance

One of the most important objectives of military intelligence is to warn of potential or immediate threats. This paper investigates several related research issues. First, what kinds of data can military space provide, with which to watch, monitor, and analyze hostile forces? Second, what operational mechanisms can work to integrate military intelligence, surveillance, and reconnaissance? Third, how can a system architecture in support of intelligence operations be implemented for decision support and knowledge management? The paper investigates how research work can contribute a system concept with military space applications to national defense and security. It investigates the use of a geographical information system as a system platform for integrating the spatial database, attribute database, rule base, case base and knowledge repository as a knowledge-based decision support system. A hypothetical case showing how the system is implemented is presented.     

Methods to determine stress profile in ALT based on theoretical life models

With the recent products being more reliable,engineers cannot obtain enough failure or degradation information through the design period and even the product lifetime,therefore,accelerated life test(ALT)has become the most popular way to quantify the life characteristics of products.Test design is the most essential topic,such as testing duration,stress profile,data inference,etc.In this paper,a method and procedure based on theoretical life models is proposed to determine the accelerated stress profile.Firstly,the method for theoretical life calculation is put forward based on the main failure mechanism analysis and the theoretical life models.Secondly,the method is provided to determine the accelerated stress profile,including the method to determine the accelerated stress types and the stress range on the basis of the main failure mechanism analysis,the method to determine the acceleration factor and the accelerated stress level based on life quantitative calculation models,and the collaborative analysis method of the accelerated test time while taking the multiple failure mechanisms into consideration.Lastly,the actuator is taken as an example to describe the procedure of the method and the engineering applicability and the validity are verified.     

分布式非预混火焰传递函数的实验研究

非预混燃烧是动力设备和推进系统中常见的燃烧组织形式。为了理解非预混火焰的动力学特性、预测和控制其振荡燃烧现象,有必要获得其火焰传递函数。本文通过实验测量对分布式非预混火焰的传递函数进行了研究,实验对象为甲烷空气同心射流火焰。实验中使用双麦克风技术测量燃烧室出口速度脉动,作为传递函数的输入量;使用CH基自发荧光测量燃烧过程的放热率脉动,作为传递函数的输出量。搭建了卡塞格林光学测量系统,以提升放热率测量的空间分辨率,实现单点测量,进而得到一维分布式火焰传递函数。结果表明,在频域内,实验中测得的传递函数的幅值沿火焰轴向存在两个峰值,在幅值的峰谷处相位角有180°翻转,这是热斑以对流速度向下游传播,跨越火焰面时所造成的。     

Fabrication of Nanostructured Electroforming Copper Layer by Means of an Ultrasonic-assisted Mechanical Treatment

Electroformed copper layer with nanostructure is obtained using a subsequent mechanical treatment under the conditions of ultrasonic vibration according to the demand of high performance material in aeronautics. The microstructure of the electroformed copper layer is observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The tensile strength is evaluated with a tensile tester. It is found that bulk crystal of electroformed copper's surface layer is changed to nanocrystals (about 10 nm in size) after the ultrasonic-assisted mechanical treatment (UMT) but the whole monocrystalline structure still remains. The tensile strength exhibited by the new copper layer is two times better than the regular electroformed copper layer, while the fracture strain remains constant. In addition, the strengthening mechanism of UMT process is proved to be dislocation strengthening mechanism.     

An introduction to China FY3 radio occultation mission and its measurement simulation

GNSS (Global Navigation Satellite System) radio occultation mission for remote sensing of the Earth’s atmosphere will be performed by GNOS (GNSS Occultation Sounder) instrument on China FengYun-3 (FY3) 02 series satellites, the first of which FY3-C will be launched in the year 2013. This paper describes the FY3 GNOS mission and presents some results of measurement simulation. The key designed specifications of GNOS are also shown. The main objective of simulation is to provide scientific support for GNOS occultation mission on the FY3-C satellites. We used EGOPS software to simulate occultation measurements according to GNOS designed parameters. We analyzed the accuracy of retrieval profiles based on two typical occultation events occurring in China South–East area among total simulated events. Comparisons between the retrieval atmospheric profiles and background profiles show that GNOS occultation has high accuracy in the troposphere and lower stratosphere. The sensitivities of refractivity to three types of instrumental error, i.e. Doppler biases, clock stability and local multipath, were analyzed. The results indicated that the Doppler biases introduced by along-ray velocity error and GNOS clock error were the primary error sources for FY3-C occultation mission.     

浅析UNIX、LINUX、WindowsNT的存储管理

分析Unix、Linux和Windows NT几种操作系统中虚存管理的体系结构和运行机制,总结在目前主流操作系统虚存管理的实现中所采用的先进技术,如写时拷贝、映射文件、共享内存、懒惰算法、NUR算法等,并重点分析用户进程虚空间管理实现技术特点。     

基于Weka平台的辐射源数据挖掘研究

数据挖掘可以提高大规模数据集的有效利用,是电子侦察辐射源数据库深入开发的方向之一.通过对现有的数据挖掘算法进行归类分析,对不同算法的适用范围和处理效果进行分析比较,详细阐述了电子侦察辐射源数据挖掘过程的一般流程,并针对不同层级辐射源数据设计了基于Weka平台的挖掘模型.