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利用国家级北斗连续运行基准站和省级区域北斗CORS站,基于国家卫星导航定位服务平台,通过改造和直接利用的方式,在华北平原构建了我国首个跨区域北斗分米级地基增强服务系统。经采用双频终端实地测试,该系统覆盖京津冀晋全部区域及内蒙古部分区域,采用GPS+北斗双模定位静态精度达到分米级,动态定位精度达到亚米级,单北斗模式定位精度略低,但仍在分米-亚米量级,极大地提高了我国北斗导航系统的高精度应用能力,拓宽了我国北斗民用导航的应用范围和领域,可满足高精度北斗实时导航、定位服务的应用需求。 相似文献
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The shape optimization of the 2-dimensional wing in ground effect (WIG) has been performed by the integration of CFD (computational fluid dynamics) and MOGA (multi-objective genetic algorithm). Because of the trade-off between the aerodynamic forces and the height stability, it is difficult to satisfy the design requirements of efficiency and stability at the same time. In this study, the lift coefficient, the lift-drag ratio and the static height stability are chosen as the objective functions to obtain the optimal wing profiles of a WIG craft. An NACA0015 airfoil is used for the baseline model; the aerodynamic characteristics of the base model are compared with that of the optimal solutions. The profile of the airfoil is constructed by four Bezier curves with fourteen control points resulting in the eighteen coordinates, which are adopted as the design variables. The optimal solutions of the multi-objective optimization are not unique but a set of the non-dominated optima: the Pareto frontiers or a Pareto set. As the results of the multi-objective optimization, the forty Pareto optima, which include high-lift, high-efficiency, and more stable airfoils on the edge of the 3-dimensional objective space, are obtained at thirty evolutions of the generation. 相似文献
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强夯密实处理块碎石填料试验研究 总被引:2,自引:0,他引:2
在高填方工程中,压实质量是工程成败的关键因素。强夯法所具有的优点,使其在许多地基处理工程中都有广泛的应用。某山区高填方工程,根据工程的实际需要,采用强夯法对山体爆破块碎石填料进行密实处理。为此,开展现场试验研究。首先对爆破的块碎石填料进行了颗粒分析试验和压实试验,分析其可填性和压实特征。按照试验参数和工序,分别进行了2000kNm、3000kNm单点夯试验;同时夯后进行了密实度试验、颗粒分析试验。由此,确定了合理的强夯施工参数。最后根据面层载荷试验的检测,以此确定的施工参数在该工程取得了良好的处理效果。 相似文献
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Huang Liren Zhao Chengkun Hu Huimmg Yang Guiye Cao XiangchunFirst Land Deformation Monitoring Center SSB Tianjin China Surveying Mapping Bureau of Tianjin Municipality Tianjin China 《中国地震研究》1994,(3)
In this paper,a study of the principal characteristics of the ground deformation disasters in the city of Tianjin caused by the Tangshan earthquake is based on the results from the recent remeasurements of the geodetic controlling network of Tianjin and from on-site investigations after the earthquake.These results show that only the ground deformation in the Ninghe and Hangu areas near the epicenter reflect directly the co-seismic crustal stress,while the serious ground deformation and the engineering earthquake damages in the urban districts of Tianjin are controlled to a great extent by the local engineering geological structures,showing a kind of secondary disaster.Several suggestions are also proposed in the paper concerning the counter-measures for reducing the earthquake damage in big cities. 相似文献
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Kalyani Chatterjea 《地球表面变化过程与地形》1994,19(7):585-607
The nature and rates of fluvial and slope processes change over time and space as urbanized areas replace forested land in Singapore. Storm-based and time-based data, from undisturbed rainforests, heavily disturbed construction sites, urban grass-covered slopes and an experimental plot, are collected to observe the impact of rainwater on the soil moisture conditions, surface microtopography, runoff generation, sediment movement, and ground lowering in the three different categories of land use. The undisturbed forested environment is characterized by high throughfall (58% of total rainfall) and frequent negative soil moisture suctions. The slow and unconcentrated overland flow during heavy storms is restricted by the forest floor microtopography. No rills develop. Ground lowering is recorded as 3·2–3·4 mm a?1. But sediment movement is episodic and suspended sediment concentrations in overland flow are 172–222 mg l?1. During urban construction, gully development is rapid on the bare slopes, runoff generation, voluminous, and sediment-laden discharges (5200–75498 mg l?1) lead to sediment plumes at channel mouths. Ground lowering rates are measured at 132·4 mm a?1. Once grass-covered, runoff carries less suspended sediment (800 mg l?1) and ground lowering rates are reduced, but depend on the condition of the cover, ranging from 0·2 to 8·2 mm a?1. As urban development continues, environments are altered both in time as well as spatially. 相似文献
70.
探地雷达图像的正演合成与偏移处理 总被引:8,自引:2,他引:8
本文讨论了射线追踪法实现二维地电断面的探地雷达图像的正演合成问题,其中包括二维地电断面的数字拟合、多层连续界面介质中高频电磁波的反射与透射统一的运动学边界方程;根据Huygen's-Fresnel原理导出了均匀介质中二维管状体模型的衍射雷达波的计算公式;给出了用射线追踪法合成的二维地电模型的探地雷达图像;用衍射波公式合成了二维管状模型的雷达图像,并与物理模拟作了比较.在此基础上,用Kirchhoff积分法对数字模拟与物理模拟记录的雷达图像作了偏移处理,并给出了实例. 相似文献