A Cause-Selecting Control Chart Method for Monitoring and Diagnosing Dependent Manufacturing Process Stages

Many industrial products are normally processed through multiple manufacturing process stages before it becomes a final product.Statistical process control techniques often utilize standard Shewhart control charts to monitor these process stages.If the process stages are independent,this is a meaningful procedure.However,they are not independent in many manufacturing scenarios.The standard Shewhart control charts can not provide the information to determine which process stage or group of process stages has caused the problems(i.e.,standard Shewhart control charts could not diagnose dependent manufacturing process stages).This study proposes a selective neural network ensemble-based cause-selecting system of control charts to monitor these process stages and distinguish incoming quality problems and problems in the current stage of a manufacturing process.Numerical results show that the proposed method is an improvement over the use of separate Shewhart control chart for each of dependent process stages,and even ordinary quality practitioners who lack of expertise in theoretical analysis can implement regression estimation and neural computing readily.     

A new stochastic model considering satellite clock interpolation errors in precise point positioning

Precise clock products are typically interpolated based on the sampling interval of the observational data when they are used for in precise point positioning. However, due to the occurrence of white noise in atomic clocks, a residual component of such noise will inevitable reside within the observations when clock errors are interpolated, and such noise will affect the resolution of the positioning results. In this paper, which is based on a twenty-one-week analysis of the atomic clock noise characteristics of numerous satellites, a new stochastic observation model that considers satellite clock interpolation errors is proposed. First, the systematic error of each satellite in the IGR clock product was extracted using a wavelet de-noising method to obtain the empirical characteristics of atomic clock noise within each clock product. Then, based on those empirical characteristics, a stochastic observation model was structured that considered the satellite clock interpolation errors. Subsequently, the IGR and IGS clock products at different time intervals were used for experimental validation. A verification using 179 stations worldwide from the IGS showed that, compared with the conventional model, the convergence times using the stochastic model proposed in this study were respectively shortened by 4.8% and 4.0% when the IGR and IGS 300-s-interval clock products were used and by 19.1% and 19.4% when the 900-s-interval clock products were used. Furthermore, the disturbances during the initial phase of the calculation were also effectively improved.     

翼型近尾迹流动的PIV研究—动力学机制

利用在线式互相关PIV(ParticleImageVelocimetry)系统,在低速风洞中对NACA0012翼型在雷诺数2.39×105,0°和4°攻角下的近尾迹流动进行了详细测量。实验结果表明,翼型近尾迹存在有序的涡街结构,涡街在尾缘处形成后,在向下游的迁移中,会经历一个发展壮大、失稳破碎的演化过程,流动从有序走向无序。翼型的近尾迹是一种以旋涡的运动学特性和动力学机制为主导的流动现象。本文着重探讨了翼型尾缘处的涡街形成机理,尾迹内的流动机制,以及近尾迹的流动稳定性。      

A permanently-acting NEA damage mitigation technique via the Yarkovsky effect

In the later stages of a combined mission of exploration and damage mitigation of a hazardous Near Earth Asteroid (NEA), sufficiently detailed tracking, orbit prediction, mass distribution, and physical properties data have been accumulated. It may be desirable to implement a “slow push” damage mitigation technique that is capable of altering the NEA orbit continuously and permanently. This possibility was suggested in a companion paper that outlined an archetypal exploration/mitigation mission to the NEA 99942 Apophis, which is achieved using a novel albedo change approach. The details and apparatus used in the albedo modification technique are described in the paper. We describe the design details and the constraints on particle size (to prevent electrostatic levitation and escape) and on the dispensing speed (to achieve the desired coverage zone and prevent particles from orbiting or escaping).     

激光频率波动对内差相干通信载波恢复性能的影响分析

搭建内差相干激光通信系统频率波动模型,对比分析BPSK和QPSK两种信号在不同频率波动条件下和Viterbi-Viterbi滤波器长度时的载波恢复性能.结果表明,当系统的工作状态稳定后,在激光频率波动幅度和波动频率较小时,两种信号的光信噪比损失平均值均小于0.5dB;随着波动幅度和波动频率的逐渐增大,Viterbi-V...     

一体化超燃冲压发动机初步设计计算模型

以总压恢复系数最大为目标，采用等激波强度和等激波角设计方法建立进气道模型；采用Ikawa“面积扩张因子”建立燃烧室模型；依据Edward方法初估尾喷管型面。在此基础上建立了一体化超燃冲压发动机进气道、隔离段、燃烧室及尾喷管计算模型，并对一体化设计的超燃冲压发动机模型进行了初步计算。     

先进复合材料成型工艺过程中的质量控制

介绍了先进复合材料的性能和工艺特点,着重从原材料质量控制、工艺过程质量控制和成品检验等方面阐述了研究先进复合材料成型工艺过程中的质量控制的意义。实践表明,加强先进复合材料成型工艺过程中的质量控制,对先进复合材料内部的质量进行全面监测控制,可有效地提高航天器复合材料的产品质量和可靠性。     

导弹垂直发射中二次流流场计算

本文应用Ｇｏｄｕｎｏｖ方法对导弹垂直发射系统的内流场进行了数值模拟，详细描述了导弹点火后二次流的形成及其对弹体的影响，为导弹的设计和发射系统的热防护提供参考。     

基于遗传算法的柔性机构形状变化综合优化研究

 实现机翼在不同的飞行状态下的最优气动外形是变弯度自适应机翼的一项关键技术。针对传统铰链机构会使机翼表面产生不连续变化而导致气流提早分离的问题,从全柔性机构实现连续平滑的形状变化的技术出发,以目标形状与实际形状的边界曲线之差最小为优化目标,采用遗传算法(GA)对柔性机构的拓扑、尺寸、形状进行了综合优化。在优化方法上,以二进制编码技术和实数编码技术为基础建立初始离散柔性机构的混合变量遗传算法模型,将其映射为有限元模型并进行了结构分析。在优化过程中引入了渐进结构优化(ESO)算法的思想,消除GA优化过程中产生的自由单元,改善了优化效率和分析结果。结合机翼前缘形状变化实例,基于MATLAB进行优化设计,并用ANSYS10.0对优化结果进行了机构的仿真分析。分析结果表明,所提出的方法合理、有效。     

求解可压缩流动的同位网格SIMPLE方法研究

在Rhie-Chou动量插值的基础上,推导了同位网格可压缩SIMPLE算法.经过无粘流超音速凸包算例和激波/湍流边界层干扰算例计算发现,如果对流项采用高阶有界HLPA格式,密度插值采用一阶迎风和中心差分的混合格式,这种算法能够很好地模拟凸包超音流的流动现象,在采用了新型GAO-YONG湍流模型后也能够较好地模拟激波/湍流边界层干扰.