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RTK-GPS��̬��λ���Ȳ����о� 总被引:1,自引:0,他引:1
??????RTK??GPS?????λ?????????????????????????????????????????3??????????????????????3?????????RTK??GPS???λ?????Ч????????????????????RTK??GPS?????????????????????RTK??GPS???λ??????????? 相似文献
104.
The transformation of nonlinear water waves over porous beds is studied by applying a numerical model based on Chen's [2006. Fully nonlinear Boussinesq-type equations for waves and currents over porous beds. Journal of Engineering Mechanics, 132:2, 220–230] Boussinesq-type equations for highly nonlinear waves on permeable beds. The numerical model uses a high-order time-marching solution and fourth-order finite-difference schemes for discretization of first-order spatial derivatives to obtain a computational accuracy consistent with the model equations. By forcing the wave celerity and spatial porous-damping rate of the linearized model to match the exact linear theory for horizontal porous bed over a prescribed range of relative depths, the values of the model parameters are optimally determined. Numerical simulations of the damped wave propagation over finite-thickness porous layer demonstrate the accuracy of both the numerical model and governing equations, which have been shown by prior theoretical analyses to be accurate for both nominal and thick porous layers. These simulations also elucidate on the significance of the higher-order porous-damping terms and the influence of the hydraulic parameters. Application of the model to the simulation of the wave field around a laboratory-scale submerged porous mound provides a measure of its capability, as well as useful insight into the scaling of the porous-resistance coefficients. For application to heterogeneous porous beds, the assumption of weak spatial variation of the porous resistance is examined using truncated forms of the governing equations. The results indicate that the complete set of Boussinesq-type equations is applicable to porous beds of nonhomogeneous makeup. 相似文献
105.
Huan-Xin Weng Ya-Chao Qin Xiang-Wei Sun Hailiang Dong Xiang-Hua Chen 《Estuarine, Coastal and Shelf Science》2007,73(3-4):501-509
Based on lab-culture experiments analyzing limitation and combination of iron and phosphorus on the growth of Cryptomonas sp. (Cryptophyceae), and the study of accumulation and release of Fe-bound P in sediment cores collected from the marine region of the Pearl River Estuary, China, reasons for the high frequency of phytoplankton bloom therein are discussed. Results show that the combined effect of Fe and P can obviously accelerate algal development, and the optimum culture conditions maintaining maximum growth rate are 0.05 μM Fe and 50 μM P. Cellular contents of Fe and P is consistent and the P:Fe molar ratio is 159:1. The optimum range of the P:Fe molar ratio in culture experiments for cell incubation is 500–1400. The vertical trends of total Fe and total P variations in sediments are parallel. Fe-bound P is the main species of inorganic sedimentary P. Through continuous leaching with agitation, 34–80% of exchangeable P and 4–23% of exchangeable Fe are concurrently released from the surficial sediments. This is a possible way by which nutrients are made available to phytoplankton. These factors might be responsible for a high frequency of harmful algal blooms in the Pearl River Estuary. 相似文献
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秦勃 《中国海洋大学学报(自然科学版)》1997,(4)
给出一种树型网络拓扑的语义描述方法及其拓扑简图的生成算法。该方法通过建立网络联接线路标识串集和网络设备连接标识串集,来构造网络设备的拓扑描述,并计算生成网络拓扑简图。 相似文献
109.
呼伦湖的近期扩张及其与全球气候变化的关系 总被引:10,自引:0,他引:10
通过近20多年湖泊水量平衡分析发现,湖泊水位变化主要由湖盆内径流补给量的丰枯决定。进一步分析揭示,呼伦湖地区乃至整个东北地区,本世纪以来随气温升高,随水有增加的趋势。降水增加导致入湖径流量,湖水位上升,呼伦湖本世纪以来的扩张与内蒙古东部地区其他内陆湖泊的变化一致,但这在我国乃至整个亚洲内陆干旱或半干旱区是独一无二的,为此成为这一地区气候变化的指示器。 相似文献
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