插件式GIS应用框架的设计与实现

应用框架已经成为软件开发中一种非常实用的编程规范和设计架构.采用了C#插件式应用开发,并利用ArcGISEngine提供的一套完备的嵌入式GIS组件库和工具库,完成了插件式GIS应用框架的核心即框架宿主程序及各功能插件的设计与实现,以及插件式GIS应用框架平台的设计与实现;采用了动态插件加载配置的开发技术优势,通过可视...     

Cascade optimization design of inter-satellite link enhanced with adaptability in future GNSS satellite networks

Inter-satellite communication and inter-satellite ranging are the foundation of autonomous navigation for satellite navigation systems. Due to cost limitations, it has been proposed in recent years to equip each satellite with one spot beam antenna, which points to different satellites according to a polling mechanism, resulting in an intermittently connected satellite network. This poses the problem of how to design the inter-satellite link (ISL) contact plan, which determines the evolution of network topology and has important effects on system performance. We propose a new framework for the ISL contact plan design in satellite navigation systems. Considering contact plan design as a multi-parameter and multi-objective optimization problem, the cascade optimization design (COD) is proposed as a method simple to implement and optimize the parameters of the contact plan. COD considers network load and geometry of satellites and has a good adaptability. In the proposed framework, both communication and measurement requirements are taken into account while the contact sequence and the slot length are optimized in two steps. Simulation results show that COD guarantees zero packet drops and achieves the least average delay with a selected network load. When the packet arrival rate is 0.45 packets/s, the packet drop ratio of COD is zero, while that of the traditional simulated annealing design (SAD) is 2.58%. The delay of COD is 22.97 s, which is only two-fifth of the SAD value of 58.77 s. At the same time, using COD the average autonomous navigation weighted dilution of precision decreases from 1.4408 to 0.9671. COD also has strong robustness and performance regardless of the onboard buffer size.     

导航接收机功率控制参数优化与性能分析

随着卫星导航接收机设计的越发复杂和先进,接收机功耗越来越高,对以电池供电为主的接收机来说是一个限制问题。功率控制技术是导航接收机实现低功耗行之有效的方法。对基本功率控制技术中的关键参数时间参数进行了优化分析,利用对锁相环进行暂态响应分析的方法,得出了最优的时间参数选取,同时进一步分析了功率控制对接收机性能的影响情况,为接收机在低功耗和性能之间的选择提供了参考。本文的结论可以直接指导接收机的功率控制设计。     

卫星导航接收机抗欺骗干扰方法研究

在分析各种可能的欺骗干扰方法的基础上,研究了欺骗干扰信号的特性,并从信号体制设计和接收机信号处理两个不同层面提出了一系列通用的抗欺骗措施,可直接用于关键民用基础设施GNSS接收机的抗欺骗设计。     

郑州市航空港区应急水源地数值模拟研究

在分析郑州市航空港区地质、水文地质条件的基础上,采用Visual Modflow软件对郑州市航空港区应急水源地进行了地下水数值模拟研究,通过对研究区的地下水流场与实测资料的识别与校正,建立地下水模型,并对不同的开采方案进行预测评价,为拟建水源地的科学运行提供了重要依据。     

小波分解与EMD在变形监测应用中的比较

为分析经验模式分解(Empirical Mode Decomposition, EMD)在GPS动态变形监测应用中的可行性和有效性,利用模拟数据和振动台的GPS实测数据分析比较了EMD和小波分析在信号去噪和多尺度分解上的能力.结果表明:EMD和小波均能较准确地提取结构振动信息,但当噪声较大时小波去噪和多尺度分解稳定性略优于EMD,而EMD则基于数据本身具有自适应性,不受小波基选择和分解层数的影响.     

Purification and characterization of novel κ-carrageenase from marine Tamlana sp. HC4

We isolated a bacterial strain (HC4) that is able to degrade κ-carrageenan from a live specimen of the red alga Hyalosiphonia caespitosa. With 16S rRNA gene sequencing, we identified the strain as Tamlana sp., and then purified an extracellular κ-carrageenase from a culture of Tamlana sp. HC4 by ammonium sulfate precipitation, Sephadex G-200 gel filtration chromatography, and DE-cellulose 52 anion-exchange chromatography. The purified enzyme yields a single band on SDS-PAGE with a molecular mass of 66.4 kDa. The optimal pH and temperature for κ-carrageenase activity are at 8.0 and 30°C, respectively. The enzyme is stable over the range of pH 7.2–8.6 below 45°C. The enzyme activity is strongly inhibited by Zn²⁺ and Cu²⁺ at 1 mmol/L. The enzyme-catalyzed reaction follows Michaelis-Menten kinetics with the Michaelis constant (K _m ) at 7.63 mg/ml. Analysis of the degradation products of the κ-carrageenase by ESI-MS and ¹³C-NMR spectroscopy indicates that the enzyme degrades κ-carrageenan down to the level of κ-neocarrabiose sulfate.     

一种利用增广参数Kalman滤波的GPS多路径效应处理方法

提出了一种基于增广参数Kalman滤波的多路径效应系统误差估计方法,将系统误差作为状态参数,并对其建立一阶AR模型,同时利用多路径重复性特性,更新多路径误差改正模型,在一定程度上解决了固定多路径误差模型随着时间推移重复性减小而有效性降低的问题,并利用16d实测数据例证了本方法具有一定的可行性和有效性。     

基于交叉证认的EMD滤波及其在GPS多路径效应中的应用

利用交叉证认的方法,提出一种新的基于EMD滤波去噪方法,并将其应用于GPS多路径效应的研究中。通过模拟实验及实测数据分析表明,该方法能够自适应地选择IMF中的信号层数,削弱随机噪声,合理地分离信号和噪声。利用该滤波方法去噪并建立具有重复性的多路径误差效应改正模型,可有效地削弱多路径效应的影响,进而提高GPS动态变形监测的精度。     

Topographic Mapping of Offshore Sandbank Tidal Flats Using the Waterline Detection Method: A Case Study on the Dongsha Sandbank of Jiangsu Radial Tidal Sand Ridges,China

The waterline detection method (WDM) based on satellite images is one of the most effective methods for constructing digital elevation models (DEMs) for tidal flats. The general practicability of the WDM has been demonstrated in previous studies for small areas. This article attempts to generate a DEM over a large offshore sandbank with a tidal flat area of more than 620 km² by integrating the conventional WDM with a hydraulic model and multitemporal satellite images. For illustration purposes, a case study was conducted at the Dongsha sandbank, one of the largest sandbanks among the radial tidal sand ridges of Jiangsu Province, China. In this study, 34 multitemporal satellite images acquired at different tidal phases in 2006 were analyzed to detect the waterlines. The water level at each satellite overpass moment was simulated by a south Yellow Sea hydraulic model, and discrete waterline points were combined with the corresponding water levels to produce a topographic map. Compared with the DEM produced during the same period by the airborne light detection and ranging (LiDAR) data, the DEM derived from WDM effectively contains the average height error within 47 cm, which is satisfactory. All of these findings may be useful for researchers and local authorities, as the findings could be used as a reference for sandbank evolution research or to support environmental management, coast protection, and storm forecasting.