船载坞内无线标校监控系统的设计与实现

为提高船载测控设备的定轨精度,设备坞内标校期间,需要使用标校塔对测控设备的参数进行精确标定。通过对远程控制方式的比较和对控制对象的分析,采用ZigBee技术构建无线通信环境,并开发相应的硬件电路及控制软件,实现对标校设备/设施、仪器的远程监控。测试结果表明,构建的监控系统通信可靠、操作便捷,解决了人工保障模式下通信不畅、环境恶劣、效率低下等弊端,为高效、可靠地完成坞内标校工作做出了重要贡献。     

Numerical investigation on adiabatic film cooling effectiveness and heat transfer coefficient for effusion cooling over a transverse corrugated surface

Three-dimensional numerical computations are conducted to investigate the effects of the blowing ratio and corrugation geometry on the adiabatic film cooling effectiveness as well as the heat transfer coefficient over a transverse corrugated surface. It is noticeable that the adiabatic wall temperature on the wavy valley of the transverse corrugated surface is relatively lower than that on the wavy peak. Surface corrugation has a relatively obvious influence on the laterally-averaged adiabatic film cooling effectiveness in the region where the effusion film layer is developed, but has little influence in the front region. Compared to a flat surface, the transverse corrugated sur-face produces a smaller adiabatic film cooling effectiveness and a higher heat transfer coefficient ratio. The effusion cooling difference between the flat and corrugated surfaces behaves more obvi-ously under a small aspect ratio of the wavy corrugation.     

典型结构的高频响应研究

利用ＮＡＳＴＲＡＮ软件得到一简支梁从低频到高频的频响特性，研究了不同有限元网格划分对结构高频特性的影响，并通过ＳＥＡ法、有法元法以及解析解的对比揭示了ＳＥＡ法在高频响应预示中的有效性。然后以耦合梁为例，通过有限元法得到两个梁之间的能量传递，并进而得到ＳＥＡ所需的耦合损耗因子；将有限元计算结果和ＳＥＡ结果对比验证了该方法的有效性，以其建立一种用有限元法获得ＳＥＡ参数的新途径。此外，研究了集中质量和不     

双轴滚弯成形机成形过程与设计

通过分析板料双轴滚弯成形的变形机理，提出双轴滚弯成形有关参数的确定方法与滚轴设计的原则。     

转速的计算机测量与显示

本文介绍了一种实时测量和显示转速的方法，详细阐述了中断系统的硬件结构、ＩＮＴＥＬ８２－５３定时器／计数器的定时方法，并给出了递推算法的推导过程及Ｃ语言实现。     

C／C复合材料石墨化度的测定和评价

用Ｘ射线衍射方法对不同热处理温度下Ｃ／Ｃ复合材料石墨化度进行了测定，并对衍射峰进行了分峰处理。得出该材料由三种不同组元构成，即树脂炭，碳纤维和热解炭，求出各组元的石墨化度值及所占比例，进而得到试样的加权平均石墨化度。     

Novel passive localization algorithm based on double side matrix-restricted total least squares

In order to solve the bearings-only passive localization problem in the presence of erroneous observer position, a novel algorithm based on double side matrix-restricted total least squares (DSMRTLS) is proposed. First, the aforementioned passive localization problem is transferred to the DSMRTLS problem by deriving a multiplicative structure for both the observation matrix and the observation vector. Second, the corresponding optimization problem of the DSMRTLS problem without constraint is derived, which can be approximated as the generalized Rayleigh quotient minimization problem. Then, the localization solution which is globally optimal and asymptotically unbiased can be got by generalized eigenvalue decomposition. Simulation results verify the rationality of the approximation and the good performance of the proposed algorithm compared with several typical algorithms.     

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.     

Time-varying linear control for tiltrotor aircraft

Tiltrotor aircraft have three flight modes: helicopter mode, airplane mode, and transition mode. A tiltrotor has characteristics of highly nonlinear, time-varying flight dynamics and inertial/control couplings in its transition mode. It can transit from the helicopter mode to the airplane mode by tilting its nacelles, and an effective controller is crucial to accomplish tilting transition missions. Longitudinal dynamic characteristics of the tiltrotor are described by a nonlinear Lagrange-form model, which takes into account inertial/control couplings and aerodynamic interferences. Reference commands for airspeed velocity and attitude in the transition mode are calculated dynamically by visiting a command library which is founded in advance by analyzing the flight envelope of the tiltrotor. A Time-Varying Linear (TVL) model is obtained using a Taylor-expansion based online linearization technique from the nonlinear model. Subsequently, based on an optimal control concept, an online optimization based control method with input constraints considered is proposed. To validate the proposed control method, three typical tilting transition missions are simulated using the nonlinear model of XV-15 tiltrotor aircraft. Simulation results show that the controller can be used to control the tiltrotor throughout its operating envelop which includes a transition flight, and can also deal with vertical gust disturbances.     

缝道参数对多段翼型气动性能的影响

数值模拟研究缝道参数对着陆构型多段翼型气动性能的影响,采用有限体积法求解雷诺平均N-S(Navier-Stokes)方程,湍流模型采用S-A(Spalart-Allmaras)模型,给出了多段翼型升力系数与表面压力系数随各缝道参数的变化规律.计算结果表明:采用的计算模型可用于二维多段翼型的计算;缝道参数对多段翼型气动性能的影响显著,在各个缝道参数的变化范围内升力系数均存在最优值,适当的缝道参数可以抑制后翼上表面逆压梯度,消除后翼分离,并保持前翼尾迹不与后翼边界层相掺混,提高多段翼型的气动性能.