Virtual globes enable the combination of heterogeneous datasets for optimal routing analyses in transportation, environmental ecology, and construction engineering. In this study, considering the advantages of the hierarchical tiling structure and topography of virtual globes, we propose a tile‐based optimal routing method for large‐scale road networks in a virtual globe. This method designs a topographically preserved road‐network tile model by partitioning roads into tiles and constructs the road‐network pyramid from the bottom to the top. During construction, a TileArc is calculated and flagged as the shortest path in a tile. Based on the built road‐network pyramid carrying hierarchical TileArcs, a multi‐level and flexible shortest path query can be executed efficiently. The proposed method is implemented with large road networks with different road grades in a virtual globe. Experimental results verify its validity, efficiency, and exactness. Moreover, the length of the shortest path with surface distance is approximately 1.3 times longer than that with Euclidean distance. 相似文献
northeastern China is an important old industrial base in China. Mineral resources are the foundation of industry development. However, because of long-term exploitation of mineral resources in northeastern China, the mineral resources reserves decrease gradually and some mineral resources are nearly exhausted, which restricts revitalization and sustainable development of the northeast old industrial base. On the basis of the comprehensive analysis of development and utilization status of mineral resources and supply and demand situation of main mineral resources in northeastern China, the authors put forward countermeasures on main mineral resources sustainable supply in northeastern China. 相似文献
While evapotranspiration (ET) is normally measured as one hydrologic component, evaporation (E), and transpiration (T) result from different physical-biological processes. Using a two-source model, a trapezoid framework has been widely applied in recent years. The key to applying the trapezoid framework model is the determination of the dry/wet boundaries of the land surface temperature-fractional vegetation coverage trapezoid (LST-fc). Although algorithms have been developed to characterize the two boundaries, there remains a significant uncertainty near the wet boundary which scatters in a discrete and uneven manner. It is therefore difficult to precisely locate the wet boundary. To address this problem, a Wet Boundary Algorithm (WBA) was developed in this study with the algorithm applied in the region of Huang-Huai-Hai plain of China, using the Pixel Component Arranging and Comparing Algorithm (PCACA) to retrieve ET from MODerate-resolution Imaging Spectroradiometer (MODIS) Data. The eddy covariance (EC) measurements from Yucheng station was used to verify the modified model where the root mean square error (RMSE) of 17.8 W/m2, Bias of −7.2 W/m2 for latent heat flux (LE) simulation in 28 cloudless test days. The ratio of transpiration to evapotranspiration (T/ET) varied between 0.48 and 0.81 over the Huang-Huai-Hai plain. The spatial and temporal distribution of ET revealed that agriculture practices have a significant influence on the hydrological cycle, where crop growth promotes the magnitude of ET. Likewise, harvesting activities significantly reduce ET. The proposed WBA algorithm significantly reduces the uncertainty of the trapezoid ET model caused by wet edge positioning. The analysis of the impact of agricultural activities on ET provide a better understanding how human activities change the hydrological cycle at regional scales. 相似文献
As one of the methods to harvest and then reuse the traffic-induced mechanical energy or one of the materials to make specific piezoelectric sensors, the application of piezoelectric ceramic to the traffic engineering has drawn more and more attention in recent years. However, few studies have tried to install the piezoelectric ceramic especially piezoelectric patch in the unbound granular materials (UGMs) of pavement base or subbase layers, and then to investigate their coupling including the power generation characteristics of piezoelectric ceramic and the resilient behavior of UGMs under traffic loading. In this study, a special piezoelectric transducer in which the piezoelectric ceramic worked in a single 31-mode was made and it was installed in the UGMs sample. A series of resilient deformation tests based on a large-scale triaxial apparatus was performed to explore the effects of water content of UGMs, confining pressure, cyclic stress magnitude and initial deviatoric stress on the open-circuit voltage generated by piezoelectric patch, and the influences of power generation on the resilient modulus of UGMs. Test results show that the open-circuit voltage in saturated sample is larger than that in sample of optimum moisture condition. The increase in both confining pressure and cyclic stress magnitude lead to the increase in open-circuit voltage, while the influence of initial deviatoric stress is slight. However, the development patterns of open-circuit voltage over either confining pressure or cyclic stress magnitude are very different between the two water content conditions. The power generation by piezoelectric ceramic tends to lower the resilient modulus of UGMs. In general, the installation of piezoelectric ceramic in the UGMs of base or subbase layers is feasible, which provides another way to harvest the traffic-induced mechanical energy. The cyclic stress level should be the key factor influencing the power generation of piezoelectric ceramic, while the confining pressure and water content of UGMs would play minor but non-negligible roles.
