Attitude stabilization of a pico-satellite by momentum wheel and magnetic coils

The three-axis active attitude control method with a momentum wheel and magnetic coils for a pico-satellite is considered. The designed satellite is a 2.5 kg class satellite stabilized to nadir pointing. The momentum wheel performs a pitch-axis momentum bias, nominally spinning at a particular rate. Three magnetic coils are mounted perpendicularly along the body axis for precise attitude control through the switch control mechanism. Momentum wheel start up control, damping control and attitude acquisition control are considered. Simulation results show that the proposed combined control laws for the pico-satellite is reliable and has an appropriate accuracy under different separation conditions. The proposed strategy to start up the wheel after separation from the launch vehicle shows that its pitch momentum wheel can start up successfully to its nominal speed from rest, and the attitude convergence can be completed within several orbits, depending on separation conditions.     

Optimal linear attitude estimators via geometric analysis

Three optimal linear attitude estimators are proposed for single-point real-time estimation of spacecraft attitude using a geometric approach. The final optimal attitude is represented by modified Rodrigues parameters (MRPs). After introducing incidental right-hand orthogonal coordinates for each pair of measured values, three error vectors are obtained by the use of dot or/and cross products. Corresponding optimality criteria are rigorously quadratic and unconstrained, which do not coincide with Wahba’s constrained criterion. The singularity, which occurs when the principal angle is close to π, can be easily avoided by one proper rotation. Numerical simulations show that the proposed three optimal linear estimators can provide a precision comparable with those complying with the Wahba optimality definition, and have faster computational speed than the famous quaternion estimator (QUEST).     

污染数据线性回归模型的贝叶斯估计

本文研究线性回归模型中响应变量受到另一随机变量序列污染时,模型参数和污染系数的估计问题.利用贝叶斯统计原理,给出了污染系数的贝叶斯区间估计及模型参数估计.     

A new relative efficiency in parameter estimation for linear model

A new relative efficiency of parameter estimation for generalized Gauss-Markov linear model was proposed. Its lower bound was also derived. Its properties were explored in comparison with three currently very popular relative efficiencies. The new relative efficiency not only reflects sensitively the error and loss caused by the substitution of the least square estimator for the best linear unbiased estimator, but also overcomes the disadvantage of weak dependence on the design matrix.     

混合系数线性模型的参数估计

将从整体数据出发,继续讨论a和b的估计,并且在系数矩阵呈病态的情况下,给出了可估函数c′d的最佳线性无偏估计。在系数矩阵趋于病态的时候,这里提出一种新的估计—局部Stein估计。这是在混合系数线性模型参数的Stein估计的基础上对LS估计的一种改进估计。     

模糊线性回归模型参数的最优线性相关估计

该文从预测值与观测值的偏差的角度给出了模糊线性回归模型参数的最优线性相关估计的概念。     

广义线性模型在线性约束下的参数估计

利用Lagrange乘数法导出了广义线性模型在线性约束下的回归参数的最小二乘估计,并讨论了它的性质.证明了当设计阵列满秩时,它在协方差阵意义下要优于无约束下的广义最小二乘估计.     

融合GPS/SINS的容积卡尔曼滤波智能车位置姿态估计方法

针对智能车在城市密集区域其全球定位系统(Global Positioning System,GPS)系统易受遮挡、干扰与多路径反射等因素影响,导致定位失灵和定位精度较低的问题,以及智能车位置姿态估计模型的非线性问题,提出了1种融合GPS/SINS的容积卡尔曼滤波智能车位置姿态估计方法。该方法将GPS和捷联惯导系统(Strap-down Inertial Navigation System,SINS)优势互补,构建以姿态误差、速度误差和位置误差等15维的系统状态方程,以GPS的位置/速度与SINS的位置/速度差值的6维系统观测方程,并采用容积卡尔曼滤波器对GPS和SINS的观测矢量进行有效关联与融合,估计并解算出车辆运动情况下的最优位置、速度、姿态参数。通过与GPS系统、SINS系统和基于扩展卡尔曼滤波的位姿估计方法仿真对比。结果表明,本文方法能给智能车提供精确可靠的车辆位姿参数。     

线性模型参数最小二乘估计唯一性的一个证明

对任意矩阵X,X(X′X)-X′与广义逆(X′X)-的选取无关,且有X=X(X′X)-X′X,X′=X′X(X′X)-X′.本文拓展了上述结果,证明了对任意正定阵V,X(X′V-1X)-X′V-1与广义逆(X′V-1X)-的选取无关,并有X=X(X′V-1X)-X′V-1X,X′=X′V-1X(X′V-1X)-X′.利用上述推广的结果,直接给出了广义线性模型中可估函数c′β的最小二乘估计c′β*的唯一性和无偏性的证明.     

Defining attitude for science educators

A distinct and complex definition of attitude is evolving within the literature. A mental readiness to respond and a correlational consistency between attitude and behavior—although controversial and in need of further study and analysis—remain viable subcomponents within the definition. Most agree that evaluation is the heartbeat of attitude. The impact of social influence on attitudes is becoming increasingly important. Attitudes are learned and not inherited.     

混合整数线性模型中方差因子Bayes估计实证分析

采用卫星在不同的历元时所得到的实际载波相位测量数据,得出载波相位在混合整数线性模型中的方差因子的Bayes估计结果,并根据其结果的大小,说明Bayes估计方法的可行性。     

力分解式动量方程实验仪研究

力分解式动量方程实验仪采用分体垂直射流机构、受力机构和测力机构的架构设计,规避了水平射流产生的原始误差,在保留原有实验特色下,增加了动量的定性与定量分析,并且将动量中的力拓展到力的合成与分解,能生动展现力的三角形法则和牛顿三大定律,将抽象物理概念形象、具体化,丰富了动量方程实验教学内容,增强了实验的创新性和趣味性。     

艾滋病态度量表在大学生群体中的修订

研究旨在采用Shrum艾滋病态度量表,修订适合中国大学生群体的测量工具。修订量表共19个项目,信效度良好,可作为我国大学生艾滋病态度的测评工具。研究发现,中国大学生艾滋病态度,在性别、学科和年级上不存显著差异。     

Computational estimation for numeracy

The importance of computational estimation is generally acknowledged. The widespread introduction of the hand-held calculator greatly increases its significance, particularly as a means of teaching number sense.The reason for its failure to be taught is traced to the multiplicity of methods used in estimation. Some agreed procedures are therefore suggested. These procedures have been developed in an unusual situation but are appropriate elsewhere. Detailed suggestions are made for estimating sums, differences, means, products, quotients and percentages.     

期望理论与职校生自信心的培养

应用期望理论培养学生的自信心应做到：向学生传递良好的期望,树立学生的自信心;帮助学生设立恰当的目标,增强他们的自信心;让学生享受成功的体验,强化自信心。以把他们培养成为一名自己满意、家长满意、教师满意的社会人。     

姿态运动模拟系统实习平台的应用

为了给大四学生提供更多的实习机会,结合实际科研项目,搭建了一套适合学生校内实习的姿态运动模拟实习平台。介绍了姿态运动模拟实习平台的总体结构和交流伺服系统的控制方案,其中包括硬件系统和控制软件。该实习平台人机界面友好、交互方便,具有完善的保护机制,使平台能够安全运行。姿态运动模拟实习平台能够帮助学生提高动手能力,增长工程实践经验,加深对相关课程的理解,在教学和科研中取得了良好的效果。     

Test-retest reliability estimates for eight dimensions of reading attitude

The Survey of Reading Attitudes was administered to a sample comprised of 68 intermediate-grade students from one elementary school in a large city school system for purposes of determining the reliability of the eight attitudinal dimensions which it measures. The test-retest interval was seven days. The following reliability estimates were obtained for the eight dimensions of reading attitude included in the Survey: Expressed Reading Difficulty. r_tt=.94; Reading as Direct Reinforcement, r_tt=.90; Reading as Enjoyment. r_tt=.95; Alternative Learning Modes. r_tt= 82; Reading Anxiety. r_tt=.84; Reading Group, r_tt=.91; Silent vs. Oral Reading, r_tt=90; and Comics, r_tt=.89.