权值动态分配的GFSINS多角速度加权平均融合算法

针对单一角速度算法解算精度不高,提出将最优加权平均法应用于GFSINS角速度解算中。针对实际应用中各种算法无法准确获取到角速度解算误差方差的情况,给出了一种对方差进行实时估计,再基于最优权值分配原则来动态分配权值的加权融合算法;对积分法、开方法、微分法和对数法四种角速度算法进行了有效融合,并完成了仿真。仿真结果表明,即使精度最低的积分法参与加权融合,也能进一步提高融合精度,同时还验证了加权平均法在系统角速度解算中的有效性,融合后,角速度精度比对数法提高了一倍。     

对"联邦滤波器理论研究"一文的商榷

讨论了联邦滤波信息分配原则，指出了《中国惯性技术学报》第10卷第6期“联邦滤波器理论研究”一中有关信息分配的一些问题，说明采用该献所述方法，主滤波器和各个子滤波器估计均不是最优的，并在GPs姿态测量系统中利用实测数据进行了仿真研究。结果表明信息分配因子选择不当将造成联邦滤波器估计性能下降。     

分布式自适应多传感器多目标跟踪算法

为了有效提高复杂环境下的船舶多目标跟踪系统的跟踪性能,提出了一种分布式自适应多传感器多目标跟踪算法。针对分布式融合结构设计了一种在线估计的自适应分配信息系数的方法,将自适应分配算法和动态权值分配算法相结合,实现在线自适应权值分配算法,以解决融合航迹误差低和不稳定性问题。对系统进行建模与分析,对提出的分布式自适应多传感器多目标跟踪算法进行了公式推导。通过仿真表明,改进的自适应算法估计精度提高了20%,同时该方法能够提高多目标跟踪系统稳健性。     

多机械臂搬运同一物体的协调动态载荷分配

针对多机械臂共同搬运同一物体形成闭运动链的协调系统,研究了多机械臂协调动态载荷分配存在冗余情况下的实时性分配方法文中提出了“应集中惯性质量棒”的概念,进而根据各机械臂的承载能力,采用线性加权的方法发展了一种操作物体质心处零内力的载荷分配原则。最后给出了系统载荷分配的解析表达式,有效地解决了多机械臂搬运同一物体时其动态载荷分配的实时性问题。     

基于遗传算法优化神经网络的多源信息融合室内定位方法

为了解决复杂室内环境中单一定位技术误差较大的问题,提出了一种基于遗传算法优化BP神经网络的多源信息融合室内定位方法。首先利用Wi Fi定位结果约束地磁匹配范围进行组合定位,降低误匹配率;再采用遗传算法寻找网络全局最优解对BP神经网络的初始权值和阈值进行优化,提升网络精度并加快收敛;使用优化后的网络对组合定位结果和推算定位结果向真实位置坐标方向训练融合,得到最优定位结果。数据显示,经遗传算法优化后BP神经网络预测均方误差降低了约75%,融合定位精度较单一定位方式定位精度平均提升约47%。结果表明,所提的方法可有效提升定位精度,具有更优的定位性能。     

基于H∞滤波的变权多通道数据融合方法研究

在对多通道定位数据进行数据融合中，采用H∞滤波可有效地解决各传感器数据误差模型不确定的滤波和状态估计问题。但由于数据采样时刻及精度的不一致性，对于多通道数据的融合应采用变权融合方式，以提高融合后数据的可靠性。该由此给出了一种基于H∞滤波的变权数据融合计算方法，通过对实测实时数据的仿真计算表明，其方法具有很好的实用性。     

基于UKF的INS/GNSS/CNS组合导航最优数据融合方法

为了提高INS/GNSS/CNS组合系统的导航精度,提出了一种基于UKF的多传感器最优数据融合方法。该方法具有两层融合结构,第一层中,GNSS和CNS分别通过两个局部UKF滤波器与INS组合,以并行的方式获得INS/GNSS和INS/CNS子系统的局部最优状态估值;第二层中,根据线性最小方差准则推导出一种矩阵加权数据融合算法,对局部状态估值进行融合,获取系统状态的全局最优估计。提出的方法无需采用方差上界技术对局部状态进行去相关处理,克服了联邦卡尔曼滤波(FKF)及其优化形式存在的缺陷。仿真结果表明,相比于FKF,提出方法的导航精度可至少提高36.4%;相比于UKF-FKF,其导航精度也可至少提高21.0%。     

基于熵权法修正的生土建筑安全性评价研究

传统的生土建筑安全性评价标准受主观因素影响较大,评价结果往往有一定的偏差。相比于现有方法,熵权法因其严谨的数学意义,可避免权重赋予时的主观性,提高评价的客观性。为此,在现有方法的基础上,本文提出了熵权法修正的生土建筑安全性评价方法。该方法以地基基础、上部承重结构、围护结构为3个二级评价指标,并向下细分为多个三级指标,建立层次分析法评价模型,计算确定权重值;运用熵权法对层次分析法所确定的权重进行修正,进一步得到修正后的多层次评价模型,实现对生土建筑安全性的客观综合评估。利用修正后的模型对长安区某生土建筑安全性进行评价,实例结果表明,所提出的评价方法有效地融合了专家经验与熵权法客观性的优点,可实现对生土建筑更为准确的安全性评估。     

多探头星敏感器星图融合姿态确定精度

针对多探头星敏感器星图融合姿态确定精度问题做了研究。首先提出多探头星敏感器星图融合方法;其次在此基础上以三个探头为例,推导了三探头星敏感器星图融合姿态确定误差协方差矩阵公式;然后利用协方差椭球对该协方差矩阵的性质做了详细分析,明确了探头间构型、星图融合参考系选择以及各探头星点选取等因素对星图融合姿态确定精度的影响关系;仿真结果表明,最优构型的多探头星敏感器通过星图融合可输出同精度的三轴姿态,并且光轴精度较单探头星敏感器提升了30%。研究成果对多探头星敏感器的工程研制具有理论指导意义。     

多尺度递归融合估计在组合导航系统中的应用

多尺度递归融合估计是对多传感器系统进行的基于尺度的融合估计算法.利用小波变换中多尺度分析的思想,构造出多尺度动态模型,利用该模型对粗尺度上的状态估计值进行修正,递归获得最细尺度上基于全局测量值的最优估计值,该估计值是方差最小意义下的最优估计.将此算法应用于SINS/GPS组合导航系统中,仿真结果表明,应用该算法能取得较好的效果,获得了比仅在单一尺度上进行kaIman融合估计更好的结果,有效地提高了组合导航系统的精度.     

An aspect ratio agglomeration multigrid for unstructured grids

A robust aspect ratio‐based agglomeration algorithm to generate high quality of coarse grids for unstructured and hybrid grids is proposed in this paper. The algorithm focuses on multigrid techniques for the numerical solution of Euler and Navier–Stokes equations, which conform to cell‐centered finite volume special discretization scheme, combines vertex‐based isotropic agglomeration and cell‐based directional agglomeration to yield large increases in convergence rates. Aspect ratio is used as fusing weight to capture the degree of cell convexity and give an indication of cell stretching. Agglomeration front queue is established to propagate inward from the boundaries, which stores isotropic vertex and also high‐stretched cell marked with different flag according to aspect ratio. We conduct the present method to solve Euler and Navier–Stokes equations on unstructured and hybrid grids and compare the results with single grid as well as MGridGen, which shows that the present method is efficient in reducing computational time for large‐scale system equations. Copyright © 2013 John Wiley & Sons, Ltd.     

一种描述结构面剖面线粗糙度的新方法

采用法向矢量单位圆描述结构面剖面线粗糙度,从各微分段的角度关系阐述粗糙度,进而将二维问题转化为一维问题处理并提出"角度粗糙度"的概念。考虑到各微分段的实际长度对粗糙度的贡献,采用加权均值与加权方差定量描述角度粗糙度; 角度粗糙度越大表明该剖面越粗糙。对规则剖面线与不规则剖面线采用"角度粗糙度"进行描述,所得结果跟已有的剖面线粗糙性表征方法相比,二者具有较好的一致性,表明新方法评价的正确性与可行性。     

Accurate Reconstruction of Porous Materials via Stochastic Fusion of Limited Bimodal Microstructural Data

Porous materials such as sandstones have important applications in petroleum engineering and geosciences. An accurate knowledge of the porous microstructure of such materials is crucial for the understanding of their physical properties and performance. Here, we present a procedure for accurate reconstruction of porous materials by stochastically fusing limited bimodal microstructural data including limited-angle X-ray tomographic radiographs and 2D optical micrographs. The key microstructural information contained in the micrographs is statistically extracted and represented using certain lower-order spatial correlation functions associated with the pore phase, and a probabilistic interpretation of the attenuated intensity in the tomographic radiographs is developed. A stochastic procedure based on simulated annealing that generalizes the widely used Yeong–Torquato framework is devised to efficiently incorporate and fuse the complementary bimodal imaging data for accurate microstructure reconstruction. The information content of the complementary microstructural data is systematically investigated using a 2D model system. Our procedure is subsequently applied to accurately reconstruct a variety of 3D sandstone microstructures with a wide range of porosities from limited X-ray tomographic radiographs and 2D optical micrographs. The accuracy of the reconstructions is quantitatively ascertained by directly comparing the original and reconstructed microstructures and their corresponding clustering statistics.     

Autonomous gauge for blast impulse determination close to explosive charges

This paper reports on a new gauge for blast impulse determination close to explosive charges. The gauge is based on the autonomous data recorder g-rec developed at the Ernst-Mach-Institute for data acquisition in harsh environments. Combined with an acceleration sensor these data recorders allow for the direct determination of the momentum transferred to an object by a blast wave even in the immediate vicinity of the explosive charge. From this the blast impulse can be determined. Using autonomous electronics distinct advantages are gained compared to classical passive momentum traps. The paper summarizes the properties of the g-rec recorder and describes the setup of the autonomous momentum trap in detail. Numerical simulations are presented which illustrate the gauge performance and its limitations. Tests with 1 kg charges demonstrate the feasibility of the approach. Good agreement was found between simulations and tests. The application range of the gauges is determined by the measurement range of the built-in acceleration sensor and its overall dimensions and weight. The present configuration is designed for distances between \(\sim \)0.3 and 1 m from charges between several 100 g and several kilograms. Data were successfully collected down to reduced distances of 0.25 m/kg\(^{1/3}\). Minor changes in gauge dimensions, weight, or measurement range enable the gauges to be deployed at even closer distances.     

Weight functions for a surface semi-elliptical crack in a finite thickness plate

Weight functions for the surface and the deepest point of a semi-elliptical crack in a finite thickness plate were derived from a general weight function and two references stress intensity factors. The weight functions were validated against finite element data by comparison of stress intensity factors calculated for several linear and non-linear stress fields. Differences were less than 2% for the surface point and 5% for the deepest point. The final weight functions are given in closed forms suitable for computer numerical integration. The weight functions appear to be particularly suitable for fatigue crack growth prediction of semi-elliptical cracks and fracture analysis of such cracks in complex stress fields.     

油液分析多技术集成的特征与信息融合

在对油液分析多技术集成的特征进行描述的基础，构造了一种油液分析多技术集成的信息融合模型，并且结合ＹＺＢ－１油液分析软件包的开发，     

不同装药战斗部壳体对水中兵器的爆炸威力

通过对裸炸药和带壳战斗部在无限水域中水下爆炸的实验研究,对比分析了炸药的冲击波峰值压力、比冲击波能、比气泡能、总比能量及相对比总能量等爆炸特性参数。结果表明:不同装药爆炸后峰值压力从大到小分别是热塑梯黑铝、熔梯黑铝、复合PBX、TNT,其他对比参数从大到小分别是复合PBX、熔梯黑铝、热塑梯黑铝、TNT;带壳战斗部爆炸后比冲击波能、比气泡能、总比能量相对裸炸药均有不同程度的下降,其中总比能量分别比裸炸药减少25%、21%、15%和15%;战斗部壳体对水中兵器爆炸的比冲击波能、比气泡能及总比能量的影响较为显著。因此,研究水中兵器爆炸威力必须考虑战斗部壳体因素,不能简化。研究成果对于战斗部水下爆炸威力考核有一定的借鉴意义。     

A micro-aerodynamic decelerator based on permeable surfaces of nanofiber mats

This work deals with nonwoven permeable light mats made of submicron-diameter nanofibers. The nanofibers were obtained through electrospinning of polymer solutions. The mats were positioned on light pyramid-shaped frames. These platforms fell freely through the air, apex down, at a constant velocity. The drag of such passive airborne platforms is of significant interest in a number of modern aerodynamics applications including, for example, dispersion of "smart dust" carrying various chemical and thermal sensors, dispersion of seeds, as well as movement of small organisms with bristle appendages. In the present work, drag is measured using the free fall method supplemented by extensive flow visualization. The effects of platform weight, average nanofiber diameter, and porosity of the nonwoven mats on the drag force are studied. The results are compared to data for the corresponding impermeable structures that are covered with plastic wrap. The data are presented in the form of standard dependencies of drag coefficient on the Reynolds number of the structure. It was found that permeable platforms with holes on the order of several microns (which is about ten times the diameter of the nanofibers) are essentially impermeable for airflow.     

Elongational properties and molecular structure of polyethylene melts

Summary The viscosity and the recoverable strain in the steady state of elongation have been measured on several polyethylenes of different molecular structures. The elongational viscosity as a function of tensile stress runs through a more or less pronounced maximum in the nonlinear range whereas in the linear range the Trouton viscosity is reached. For low density polyethylenes it could be demonstrated that the maximum of the steady-state elongational viscosity and the elasticity expressed by the steady-state compliances in shear and tension sensitively increase if the molecular weight distribution is broadened by the addition of high molecular weight components. A variation of the weight average molecular weight does only shift the elongational viscosity curve but leaves its shape unchanged. Two of the four high density polyethylenes investigated do not show a maximum of the steady-state elongational viscosity, for the others it is less pronounced than in the case of low density polyethylenes. The influence of branching on the elongational behaviour of polyethylene melts in the steady-state and the transient region is qualitatively discussed.With 11 figures and 4 tables     

Rheological characterization of highly branched poly(ethyleneterephthalate)

Linear and highly branched poly(ethyleneterephthalate) samples were synthesized and characterized in terms of intrinsic viscosity, molecular weight and melt viscosity over a wide range of shear rates at several temperatures, in the range from 265° to 295 °C. Linear samples exhibited Newtonian behavior over a wide range of shear rates, while the branched ones became shear thinning at relatively low shear rates. Our experimental data, as well as data previously reported, were found to be described by a proposed correlation between the melt viscosity ratio and a branching index. Moreover, the activation energy for melt flow was found for the highly branched samples to be a little higher than that of the linear samples.