UDu~T分解滤波算法及其应用

本文介绍UDU~T 分解滤波算法;用工程师容易理解的方法重新推导时间修正和量测修正滤波公式,并给出标准通用的UDU~T 分解滤波子程序。本算法子程序已实际用于工程估计器中。本算法具有高的数字稳定性。作为UDU~T 分解滤波算法理论和工程应用之间桥梁的本通用标准子程序具有良好性能,使用方便,极易推广应用。     

循环热处理工艺对熔模精铸钛铝基合金组织与性能的影响

循环热处理工艺主要是通过在回火过程中的不连续粗化反应细化合金的组织,循环次数和保温时间对循环热处理的效果有明显的影响。循环热处理工艺通过细化熔模精铸Ti-48Al-2Cr-2Nb合金的组织改善了其力学性能,经过循环热处理后合金的室温最大拉应变也达到了0.68%。对合金的室温拉伸断口分析可知,热处理后合金的室温拉伸断裂方式仍以穿层片断裂为主,没有出现明显的屈服。     

制造业IT生产力优化

分析了制造业企业在IT系统建设方面遇到的困境以及进行企业IT生产力优化的必要性,提出了企业进行IT生产力优化的基本方法体系,阐释了利用面向服务的架构(SOA)、开放组织架构框架(TOGAF)、ESB模式构建灵活稳健的企业IT架构的技术路线,并给出了针对制造业的解决方案参考模型。     

螺栓预紧方式工艺研究

采用液压拉伸螺栓预紧的方法,通过模拟某产品平台螺栓安装预紧的工艺试验研究,优选并确定了工艺的实际操作方法、步骤,以及所需要的工艺参数,为各种大型结构件的螺栓安装提供了技术支持。     

空间运输飞行器材料与制造技术需求分析

空间运输飞行器已经成为国际航天技术新的发展趋势,对材料和制造技术从两方面提出了新的需求:异形贮箱制造技术和热控材料与制造技术。本文对这两个问题进行了分析,结果表明:异形贮箱和热控硬件的材料与制造是制约空间运输飞行器发展的基础技术,必须在空间运输飞行器研制热潮之前先期突破。     

Hypothesis-test-based landcover change detection using multi-temporal satellite images – A comparative study

Remote sensing images and technologies have been widely applied to environmental monitoring, in particular landuse/landcover classification and change detection. However, the uncertainties involved in such applications have not been fully addressed. In this paper two hypothesis-test-based change detection methods, namely the bivariate joint distribution method and the conditional distribution method, are proposed to tackle the uncertainties in change detection by making decisions based on the desired level of significance. Both methods require a data set of class-dependent no-change pixels to form the basis for class-dependent hypothesis test. Using an exemplar study area in central Taiwan, performance of the proposed methods are shown to be significantly superior to two other commonly applied methods (the post-classification comparison and the image differencing methods) in terms of the overall change detection accuracies. The conditional distribution method takes into consideration the correlation between digital numbers of the pre- and post-images and the effect of the known pre-image digital number on the range of the post-image digital number, and therefore yields the highest change detection accuracy. It is also demonstrated that the class-dependent change detection is crucial for accurate landuse/landcover change detection.     

重庆机床集团新产品

近年来,重庆机床集团着眼于在高端技术市场跟进或超越,将滚、插、磨齿成套技术作为系统工程按模块化方式设计制造,确立产品朝着全数控、功能复合、柔性、自动化、安全性、网络化及绿色环保方向发展的战略目标,大力发展大型、精密、高速数控制齿装备.并充分发挥集团整体优势,打造从车床到齿轮加工机床的系列成套技术解决方案.     

运载火箭姿态系统自适应神经网络容错控制

针对运载火箭姿态系统跟踪问题,考虑干扰、执行器故障和模型不确定因素的影响,设计了一种基于自适应神经网络的非线性容错控制律。该控制算法结合了连续的终端滑模控制,径向基神经网络和自适应控制方法。首先,基于滑模控制理论,设计了一种快速终端滑模面,保证系统跟踪误差能够在有限时间收敛至零。然后,在终端滑模面基础上,提出了一种基于自适应径向基神经网络估计的终端滑模控制律。利用自适应参数的神经网络逼近系统参数并提高抗干扰性能,采用平滑连续控制策略消除了终端滑模中的颤动现象。通过李雅普诺夫的分析方法证明了闭环系统的收敛性和全局稳定性。采用数值仿真,验证了提出的基于自适应径向基神经网络的终端滑模控制律具有较好的跟踪性能和精度。     

Queuing theory application in imaging service analysis for small Earth observation satellites

The performance of Earth observation satellites is usually analyzed by real data or system simulation, which is accurate but not systematic. Modelling satellite service systems with queueing theory and analysing the performance statistics systematically will provide a useful guide in designing satellite systems. Earth observation satellites could be regarded as a two tandem server system with a finite buffer in between, providing two-stage service: image capture and image download service. In this paper, we introduce the queueing models for different service systems: the pure image capture service system, the two-stage service system with Poisson distribution download service, the pure download service system, and the two-stage system with general download service. Formulated solutions are given and some results are shown. From this work we can see queueing theory provides a good way to analyse the performance of small earth observation satellites, which is useful for system mission analysis and optimisation in design stage.