基于超短基线的GPS测姿算法研究

针对超短基线下姿态测量结果稳定性差及可靠性低的问题,提出一种更加可靠稳定的基于超短基线的全球定位系统（global positioning system,GPS）姿态测量算法。构建了扩展卡尔曼滤波（extended Kalman filtering,EKF）模型,并对扩展卡尔曼滤波模型中测量噪声矩阵采用基于卫星高度角模型,得出比较准确的浮点模糊度;联立了载波双差观测方程和伪距双差观测方程,并采用改进模糊度最小二乘去相关平差法（modified least-squares ambiguity decorrelation adjustment algorithm,M-LAMBDA）进行快速模糊度固定解算;利用了滤波法进行姿态解算。实验结果表明,与其他测姿算法相比,该算法可适用于超短基线,能够提高姿态结果的稳定性与可靠性,在基线为20 cm静态环境中,该算法模型航向角的误差方差为0.1左右,航向角的绝对误差为2°左右。在基线为20 cm动态环境中,该算法模型航向角的误差方差为2左右,姿态角的绝对误差为3°左右。     

Cooperative localization against GPS signal loss in multiple UAVs flight

Based on multiple unmanned aerial vehicles(UAVs) flight at a constant altitude,a fault-tolerant cooperative localization algorithm against global positioning system(GPS) signal loss due to GPS receiver malfunction is proposed.Contrast to the traditional means with single UAV,the proposed method is based on the use of inter-UAV relative range measurements against GPS signal loss and more suitable for the small-size and low-cost UAV applications.Firstly,for re-localizing an UAV with a malfunction in its GPS receiver,an algorithm which makes use of any other three healthy UAVs in the cooperative flight as the reference points for re-localization is proposed.Secondly,by using the relative ranges from the faulty UAV to the other three UAVs,its horizontal location can be determined after the GPS signal is lost.In order to improve an accuracy of the localization,a Kalman filter is further exploited to provide the estimated location of the UAV with the GPS signal loss.The Kalman filter calculates the variance of observations in terms of horizontal dilution of positioning(HDOP) automatically.Then,during each discrete computing time step,the best reference points are selected adaptively by minimizing the HDOP.Finally,two simulation examples in Matlab/Simulink environment with five UAVs in cooperative flight are shown to evaluate the effectiveness of the proposed method.     

电极参数对电凝并式空气净化装置净化颗粒物的影响

研究了一种新型高压高频(HV-HF)电凝并式空气净化系统,进行了电极参数的变化对该电凝并装置净化颗粒物效果的实验研究。实验结果表明:电凝并装置存在最佳的交直流电压之间的匹配。最佳匹配值为直流电压12kV,交流电压440V。粒径小于1μm的颗粒物,其净化效果受电极参数的影响较明显,粒径大于1μm的颗粒物,在不同的电极参数下净化效果差别不大。     

An analysis of single point positioning with real-time internet-based precise GPS data

Single Point Positioning (SPP) is currently capable of providing position accuracy of several meters. To obtain a better accuracy, the Differential GPS (DGPS) method must be applied. For large-scale applications such as aerial survey and mapping, however,the requirement of a base station(s) in conventional DGPS often become problematic in practice due to the increased operational cost and complexity. Recently a concept of Global Differential GPS (GDGPS) has attracted increasing interests among the GPS communities. GDGPS has the same user's implementation as SPP,but its accuracy is augmented by the globally or regionally distributed precise GPS data currently including precise satellite orbit and clock corrections. The major advantage of GDGPS lies in two aspects: system simplicity at the user's end, and globally consistent positioning accuracy. This paper presents GDGPS positioning results using the precise GPS data generated by the Natural Resources Canada (NRCan). NRCan's precise data can be retrieved real-time from Internet base on Virtual Private Network (VPN) and Multicast technology. The packet delay and Packet Loss Rate (PLR) of multicasting over Intemet will first be investigated.The total latency of precise GPS data as well as the position accuracyof GDGPS will then be analyzed. The numerical results have shown that a meter to half-meter level accuracy is obtainable based on epoch-by-epoch data processing. With phase-smoothed code observations, the positioning accuracy can be further improved.     

室内绿化的配置格局与审美作用

该文结合环境艺术设计专业的室内设计基础课的教学实践,对室内绿化的设计及配置提出了较系统的理论依据。     

D-R卫星定位算法数字接收机实现方案

D R卫星定位算法可以在只观测 3颗卫星的条件下实现用户的三维定位以及授时、授频功能。讨论了利用该算法实现定位的用户接收机的方案。对定位接收机数字处理部分进行了较细致的讨论。对用户进行定位所需的测量量的提取方法作了深入的分析。提出了D R定位算法的一种在工程上容易实现的方案     

室内新风空气净化系统微生物多样性研究

对济南市历城区使用不同时间的新风空气净化系统滤膜样本的细菌多样性进行检测，分析室内新风系统潜在的微生物二次污染风险。采集使用6至12个月的新风系统中超细玻璃纤维空气滤膜积累的微生物为样本，进行16S rDNA扩增子测序分析。结果显示：变形菌门、厚壁菌门、放线菌门和拟杆菌门为优势菌门，优势属有副球菌属、鞘氨醇单胞菌属、芽孢杆菌属、甲基杆菌属、双歧杆菌属等；随着滤膜使用时间的增加，优势菌门之间的相对丰度比例变化不明显，但总丰度呈现上升趋势，表明该地区室内空气微生物丰富且群落结构长期变化不大；使用12个月的样本中特别富含莱茵海默氏菌属、乳杆菌属和不动杆菌属，且条件致病菌奥斯陆莫拉氏菌的相对丰度较高，表明该地区的室内新风系统使用12个月时存在微生物二次污染风险。研究结果对居民防控室内空气二次污染起指导作用。     

破损燃料定位系统探测器缺陷分析及改进

本文介绍了破损燃料定位系统及探测器的工作原理,对于因探测器导致系统不可用的故障类型进行统计分类,分析故障原因及系统的设计缺陷并进行针对性的改进。通过新旧探测器的对比和新型标定工具进行测试,验证了改进后探测器性能优于旧型号探测器,提高了破损燃料定位系统的可靠性。     

Strategies for 4-D regional modeling of water vapour using GPS

Global Positioning System (GPS) signals experience ranging errors due to propagation through the neutral atmosphere. These range delays consist of a hydrostatic component, dependent on air pressure and temperature, and a wet delay dependent on water vapour pressure and temperature.Range delays arising from the hydrostatic component can be computed with accuracies of a few millimeters using existing models, provided that surface barometric or meteorological data are available. By using a regional network of GPS reference stations, it is possible to recover estimates of the Slant Wet Delay to all satellites in view. Observations of the Slant Wet Delay (SWD) can be used to model the vertical and horizontal structure of water vapour over a local area. These techniques are based on a tomographic approach using the SWD as input observables, where 4-D models of the wet refractivity may be derived. This method allows improved resolution of water vapour estimates for precise positioning applications and assimilation into Numerical Weather Predictions (NWP). In this paper we present strategies for real-time modeling of wet refractivity, with simulations and preliminary results of data processing for a regional GPS network in Southern California.     

Oxidative damages to DNA by indoor PM10s: Their relationships with trace element compositions

Plasmid DNA assay and ICP-MS analysis were conducted in order to investigate the bioreactivity of inhalable particles (PM10) and the relationship between bioreactivity and trace element compositions of PM10 in Beijing air. A total of four PM10 samples were carefully selected to represent the indoor and corresponding outdoor environments: one from urban smoker's home, two from non-smoker's homes, and the other from the outdoor. In general, the oxidative damage by indoor PM10 was slightly higher than that of outdoor. Among the four sets of samples, the PM10 from the smoker's home had a lowest TD50 (toxic dose of PM10 causing 50% DNA to be damaged), being 100 μg·mL-1, suggesting the highest bioreactivity. The heavy metals are believed to be the main reason for oxidative damage to plasmid DNA. The ICP-MS analysis combined with the DNA assay showed that the water-soluble zinc levels had better relationship with TD50 values than other elements, implying that water-soluble zinc might play an important role in the damage of DNA. It is concluded that the PM10 in smoker's home had the highest level of water-soluble zinc as well as the lowest TD50 (highest bioreactivity). Iron is considered to be one of the most bioreactive elements, but it will cause little damage to plasmid DNA, probably because iron is mainly in water-insoluble state in Beijing PM10.