常用预测方法应用分析

本文针对GM（1，1）的预测方法，介绍了其原息模型、新息模型和等维新息模型的建摸方法，比较分析了基于GM（1，1）的各种预测模型应用的可靠性问题。     

扩展分形在SAR图像特定尺寸目标检测中的应用

介绍了扩展分形(Extended fractal)技术在合成孔径雷达(SAR)图像特定尺寸目标检测中的应用。与传统的检测特征相比，扩展分形特征不仅可以依靠时比度从背景中识别目标，而且对目标物体的尺寸敏感。文中对扩展分形的定义以及扩展分形的均值和方差进行了分析，表明了扩展分形对目标尺寸和对比度的敏感特性。在扩展分形定义中，通过比较不同的能量增长间隔比值对扩展分形均值和方差的影响，确定了最优能量增长间隔比值，将扩展分形技术用于对实测SAR图像中特定尺寸目标检测，得到了良好的识别效果。实验表明，扩展分形技术对特定尺寸的目标具有很好的检测性能。     

主电桥预移相模型恒温热线(膜)流速计动态响应方程的解析解

对主电桥预移相恒温热线(膜)流速计动态响应方程调节元参量的解析解,及利用本线路模型理论,设计新型 HWFA 的若干原则作了阐述。根据这些原则研制的IFA-900型智能流速计系统,革除了传统 HWFA 所必需的三个调节参量,使用简单,操作方便;频带宽,稳定性好,动态性能有重大改进;软件功能强,智能化功能多,自动化程度有很大提高。     

基于可编程逻辑器件的增量式编码器信号 去抖方法的实现

在伺服系统中,实时、准确地获得编码器反馈信号对伺服闭环控制至关重要.从增量式编码器的结构原理出发,分析引起其输出信号抖动的可能原因.根据D触发器逻辑功能,设计了一种基于可编程逻辑器件的增量式编码器信号去抖方法.实验结果表明,该方法能有效滤除信号的边沿抖动和干扰毛刺.     

应用端部效应改善的LS+NN模型进行日长变化预报

现有ΔLOD(Delta Length-Of-Day,日长变化)预报模式在进行周期项与残差项拟合分离时,通常没有考虑LS(Least Squares,最小二乘)拟合序列的端部效应,预报精度难以取得较大提高。针对端部效应现象,首先采用时间序列分析模型在ΔLOD序列两端进行数据延拓,构成一个新序列,然后用新序列求得LS外推模型系数,再结合LS外推模型和NN(Neural Network,神经网络)对原始ΔLOD序列进行预测。算例表明,在ΔLOD序列两端增加延拓数据,能有效改善LS拟合序列的端部效应;端部效应改善的LS+NN模型的预报精度明显优于常规LS+NN模型,精度最大提高了17.86%。该方法不仅适用于LS+NN模型,也适用于LS外推模型与其他模型的组合。     

中继卫星系统地面云存储架构设计

针对中继卫星系统日益增长的海量数据存储需求,探索将云技术应用于中继卫星地面存储系统中,研究并设计了适用于中继卫星系统的分布式云存储的体系架构.该架构通过分布式存储和存储虚拟化技术,对存储资源进行了整合,将分布在不同地理位置上的存储网络,集合成一个大规模广域云存储系统,可提供整体存储和访问的功能,并实现对数据的高效“存”、“取”、“管”.与传统NAS(Network Attached Storage,网络附加存储)架构分析比较,该架构从系统扩展性、可靠性和服务性等多个方面均更加具有优势,能够适应日益增长的中继卫星系统海量数据存储需求,解决中继卫星系统中大容量数据存储的瓶颈.     

Two-Dimensional Modal Curvature for Damage Detection in Plates

Mode shape has become a hotspot of vibration-based damage detection in plates.Two-dimensional(2D)modal curvature(MC2D),derived from mode shapes,is a prevailing physical quantity used to indicate damage.Unfortunately,the physical mechanism of MC2 Dfor characterizing damage in plates has not been clarified to date.In contrast,one-dimensional(1D)modal curvature(MC1D)has explicit physical mechanism to portray damage in beams.Unresolved physical mechanism of MC2 Dseverely hampers its applications for damage identification in plates.To address this deficiency,the clarification mechanism of MC2 Dis investigated to identify damage.With the clarified mechanism,numerical and experimental cases are used to demonstrate the effectiveness of MC2 Din detecting damage in plates.     

Global characteristics of ionospheric electric fields and disturbances during the first hours of magnetic storms

The ionospheric plasma density can be significantly disturbed during magnetic storms. In the conventional scenario of ionospheric storms, the negative storm phases with plasma density decreases are caused by neutral composition changes, and the positive storm phases with plasma density increases are often related to atmospheric gravity waves. However, recent studies show that the global redistribution of the ionospheric plasma is dominated primarily by electric fields during the first hours of magnetic storms. In this paper, we present the measurements of ionospheric disturbances by the DMSP satellites and GPS network during the magnetic storm on 6 April 2000. The DMSP measurements include the F region ion velocity and density at the altitude of ∼840 km, and the GPS receiver network provides total electron content (TEC) measurements. The storm-time ionospheric disturbances show the following characteristics. The plasma density is deeply depleted in a latitudinal range of ∼20° over the equatorial region in the evening sector, and the depletions represent plasma bubbles. The ionospheric plasma density at middle latitudes (20°–40° magnetic latitudes) is significantly increased. The dayside TEC is increased simultaneously over a large latitudinal range. An enhanced TEC band forms in the afternoon sector, goes through the cusp region, and enters the polar cap. All the observed ionospheric disturbances occur within 1–5 h from the storm sudden commencement. The observations suggest that penetration electric fields play a major role in the rapid generation of equatorial plasma bubbles and the simultaneous increases of the dayside TEC within the first 2 h during the storm main phase. The ionospheric disturbances at later times may be caused by the combination of penetration electric fields and neutral wind dynamo process.     

混合小推力航天器轨道保持高性能滑模控制

针对采用太阳帆、太阳电混合小推力推进的航天器，研究了其在日心悬浮轨道的保持控制问题。为解决已有控制方法中未综合考虑内部未建模动态和外部未知扰动的问题，以及进一步提高系统控制性能，设计了一种高性能滑模控制策略。首先，考虑模型不确定性，建立了混合小推力航天器在日心悬浮轨道柱面坐标系的动力学方程；其次，基于改进型条件积分滑模面和径向基（RBF）神经网络设计了控制律，结合自适应方法在线估计不确定参数；接着，将求取的虚拟控制量在推进剂最优条件下转换成实际控制量，即太阳帆姿态角和太阳电推进力；最后，数值仿真验证了上述设计方法提高了系统鲁棒性，减小了轨道位置超调，并且混合推进相比于单一太阳帆推进，在更短收敛时间内控制精度提高了4个数量级，相比于单一太阳电推进，一年可以节省约89.6%的推进剂。     

COMPARISON OF THE EXPERIMENTAL AND COMPUTATIONAL STUDY ON THE EFFECTS OF VORTEX CONTROL BY DEFLECTING FLAPS ON A HIGHLY SWEPT DELTA WING

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