An improved approach to model ionospheric delays for single-frequency Precise Point Positioning

PPP with low-cost, single-frequency receivers has been receiving increasing interest in recent years because of its large amount of possible users. One crucial issue in single-frequency PPP is the mitigation of ionospheric delays which cannot be removed by combining observations on different frequencies. For this purpose, several approaches have been developed, such as, the approach using ionospheric model corrections with proper weight, the GRAPHIC (Group and Phase Ionosphere Calibration) approach, and the method to model ionospheric delays over a station with a low polynomial or stochastic process. From our investigation on the stochastic characteristics of the ionospheric delay over a station, it cannot be precisely represented by either a deterministic model in the form of a low-order polynomial or a stochastic process for each satellite, because of its strong irregular spatial and temporal variations. Therefore, a novel approach is developed accordingly in which the deterministic representation is further refined by a stochastic process for each satellite with an empirical model for its power density. Furthermore, ionospheric delay corrections from a constructed model using GNSS data are also included as pseudo-observations for a better solution. A large data set collected from about 200 IGS stations over one month in 2010 is processed with the new approach and several commonly adopted approaches for validation. The results show its significant improvements in terms of positioning accuracy and convergence time with a negligible extra processing time, which is also demonstrated by data collected with a low-cost, handheld, single-frequency receiver.     

Improvement of the ADEOS-II/GLI sun-glint algorithm using concomitant microwave scatterometer-derived wind data

The tendency of over-estimation of sun-glint reflectance was found in GLI satellite ocean color data, after applying the traditional sun-glint model of Cox and Munk together with objective analysis wind data. ADEOS-II has provided a good opportunity to improve the glint model using data measured by GLI and SeaWinds, both onboard the satellite. With the help of simultaneous wind measurements achieved by SeaWinds, the Cox and Munk model is re-evaluated using GLI measurements to obtain a new relationship between the surface mean square slope and wind. The new model was found to be very close to the Cox and Munk under moderate wind speed but is much different under calm condition, where it shows similarity to the result reported by Ebuchi and Kizu. It also improves the ocean color data availability and the precision of sun-glint reflectance, based on the evaluation result of the generated Level 3 data products.     

基于简化误差修正的卫星姿态确定算法

针对典型的星敏感器/陀螺姿态卫星确定算法运算复杂这一问题,提出了一种基于简化误差修正的星敏感器/陀螺卫星姿态确定算法.通过对陀螺角速度进行简化修正,减少了滤波器的状态变量,降低滤波器的复杂性.仿真结果表明：该算法在保证姿态确定精度的条件下,能够减少运算量,提高算法的实时性.     

端板法翼型实验的数据处理与洞壁干扰修正方法

 用端板法测量气动力数据时,端板附近有自由涡拖出。通过实验观察假设了端板翼型实验的涡系模型。由涡系模型可计算出机翼加端板后的有效展弦比,再按举力线理论可将实验结果转换成二维(翼型)数据;按镜象法也可作升力洞壁干扰修正。对于端板法中间剖面的测压结果亦应作二维转换和洞壁干扰修正,方法类似。经过这样的数据处理后,翼型数据准确可靠。     

我国财政赤字的经济增长效应实证分析

理论研究表明,财政赤字对经济增长的作用要取决于客观经济状况,在我国目前现实国情下,财政赤字是否具有经济增长效应关系到我国未来的财政政策措施与取向。本文尝试运用最新发展的时间序列经济计量方法对改革开放以来的财政赤字与经济增长之间关系进行实证分析,借以为我国积极的财政政策提供理论分析与实证检验的依据。     

多智能体协同视觉SLAM技术研究进展

多智能体的协同视觉SLAM系统在地面机器人或空中飞行器梯队中应用得越来越广泛。由于不同的智能体之间会交换或共享信息,协同视觉SLAM系统不同于应用在单个智能体上的典型的视觉SLAM系统,具有更好的鲁棒性、准确性和高效性。阐述了多智能体协同视觉SLAM的发展历史和现有的研究方法,描述了协同视觉SLAM系统实现所涉及的关键技术,包括协同姿态估计和地图构建,以及新兴的分布式架构。此外,对多智能体协同视觉SLAM技术的发展趋势进行了展望。     

力均衡式余度电液伺服系统的优化设计

 本文论述了驱动同一负载的余度电液伺服系统的优化设计问题。基于解耦理论提出多通道系统的均衡技术,以此来消除通道间力的纷争,其结论非常便于工程实现。     

壁压法低速风洞洞壁干扰修正

 对于低速风洞中大模型、大迎角以及一般具有分离流的情况,本文采用壁压测量用影响函数法计算了洞壁干扰,并进行了实验验证.计算与实验表明,本文的计算是可靠的提供的曲线数据可供实际使用。     

电传系统设计研究

研究了纵向电传系统前向指令回路非线性校正、过载指令的设计和综合、C*反馈回路的设计、调参规律的选取、校正网络特征、闭环系统稳定性、闭环系统相位补偿以及放宽静安定度补偿方法等,并对伺服弹性回路和人-机耦合回路的综合设计进行了研讨。     

无陀螺飞行器姿态和角速度确定

通过预测滤波方法研究了利用矢量观测确定无陀螺飞行姿态和角速度的方法。给出的观测滤波法在一定的二次型优化准则下，对飞行器姿态和名义姿态运动模型的等效角速度误差可同时进行实时估计，能够准确跟踪敏感器的测量，有效减小模型误差的影响，数值仿真结果验证了算法的优越性。