长江三角洲蓝图重绘的基础科学问题:进展与未来研究     

汪亚平  贾建军  杨阳  周亮  冯威  高建华  魏稳  李占海  史本伟  高抒 《海洋科学》2019,43(10):2-12

在全球气候变化和人类活动影响加剧的背景下,作为河口海岸重要子系统的三角洲正在发生快速变化。长江三角洲地处长江入东海交汇处,是中国最重要的经济核心区之一,对邻近区域乃至整个长江经济带经济社会发展都起着重要作用。由于全球变暖、海面上升和强烈人类活动引发了三角洲系统状态转换,因此以往基于恒定系统状态而获得的有关长江三角洲的认识已不能满足未来需求,迫切需要对未来海面变化、极端事件、流域与河口工程影响下的三角洲物质循环条件、物理过程、地貌冲淤演化、源-汇格局调整等科学问题进行深入研究。在三角洲系统行为、未来演化趋势的预测能力建设中,应重视从海面到海底的综合立体观测系统的发展,以获取关键数据;基于三角洲系统的时、空演化特征,建立三角洲本征态和衍生态的谱系理论。未来需针对系统状态转换而调整原先的经济社会发展模式,以便保护自然资源、重建生态系统,更好地支撑长江经济带发展,重绘长江三角洲发展蓝图。  相似文献   

LED光色对欧洲舌齿鲈幼鱼抗氧化能力和消化能力的影响   总被引：1，自引：0，他引：1  

代明允  任纪龙  费凡  魏平平  马贺  高东奎  宋昌斌  喻胜  刘鹰 《海洋科学》2019,43(4):16-21

作者利用循环水养殖实验系统,研究了红、绿、白、黄、蓝5种光色对欧洲舌齿鲈(Dicentrarchus labrax)幼鱼抗氧化能力和消化能力的影响。结果表明,红光组的欧洲舌齿鲈幼鱼超氧化物歧化酶(SOD)活力显著高于其他光色组(P0.05),而绿、白、黄和蓝光色组的SOD活力没有显著性差异;红光组的还原型谷胱甘肽(GSH)含量显著高于其他光色组(P0.05),绿、白光组与黄、蓝光组的GSH含量之间有显著性差异(P0.05);红光组过氧化氢酶(CAT)活力显著高于其他光色组(P0.05),白光组的CAT活力显著低于其他光色组(P0.05)。黄光组的胃蛋白酶活力显著高于红、绿、白光组(P0.05),绿光组的胃蛋白酶活力显著低于其他光色组(P0.05);红、绿、蓝光组的淀粉酶活力要显著高于白、黄光组(P0.05),红、绿、蓝光组的淀粉酶活力没有显著性差异,黄、白光组的淀粉酶活力没有显著性差异;白光组纤维素酶活力显著高于其他光色组(P0.05),绿光组的纤维素酶活力显著高于红、蓝光组(P0.05),黄光组的纤维素酶活力和绿、红、蓝光组没有显著性差异。因此,欧洲舌齿鲈在红光下养殖,其体内的抗氧化能力强,能有效应对氧化应激,而在黄光或红光下养殖其消化能力更强。  相似文献   

一种基于定位和姿态数据确定试验船质心的方法     

孙文川  刘维国  卫鑫  吴延军 《海洋测绘》2019,39(2):30-33

针对试验舰质心确定困难问题,提出了一种基于定位和姿态数据的试验舰质心确定方法。通过建立试验舰姿态与传感器中心诱导升沉的关系,推导出了试验舰锚泊状态下质心在船固坐标系中位置的解算模型。实验结果表明,采用本方法进行试验舰质心确定不需添测深仪以外的设备,确定的试验舰质心具有较高的精度,能明显地提高舰载无人飞行器惯导对准效率。  相似文献   

捷联式海洋重力数据的小波阈值滤波     

韦建成  肖云  王利  孟宁  邹嘉盛 《大地测量与地球动力学》2019,39(11):1132-1136

基于捷联式海洋重力测量数据，对比不同小波、阈值及施加方式对滤波效果的影响。结果表明，db6、db7、db8、db9、db10、sym6、sym7、sym8、sym9、sym10、coif3、coif4和coif5小波较适用于海洋重力测量，小波分解层次可取至8层或9层，采用史坦无偏风险阈值滤波效果较好；小波分解至第8、9层时，阈值滤波结果与截止频率为0.005 Hz和0.003 3 Hz的Butterworth低通滤波器的滤波结果吻合较好，但小波阈值滤波结果更加平滑，两者差值的RMSE在0.25 mGal以内，且小波阈值滤波更容易分解出噪声成分，可以更有效地消除重力畸变。  相似文献   

Mapping 3D visibility in an urban street environment from mobile LiDAR point clouds     

Yi Zhao  Jianping Wu  Song Shu  Handong Liang  Min Liu 《地理信息系统科学与遥感》2020,57(6):797-812

ABSTRACT

Visibility determination is a key requirement in a wide range of national and urban applications, such as national security, landscape management, and urban design. Mobile LiDAR point clouds can depict the urban built environment with a high level of details and accuracy. However, few three-dimensional visibility approaches have been developed for the street-level point-cloud data. Accordingly, an approach based on mobile LiDAR point clouds has been developed to map the three-dimensional visibility at the street level. The method consists of five steps: voxelization of point-cloud data, construction of lines-of-sight, construction of sectors of sight, construction of three-dimensional visible space, and calculation of volume index. The proposed approach is able to automatically measure the volume of visible space and openness at any viewpoint along a street. This approach has been applied to three study areas. The results indicated that the proposed approach enables accurate simulation of visible space as well as high-resolution (1 m × 1 m) mapping of the visible volume index. The proposed approach can make a contribution to the improvement of urban planning and design processes that aim at developing more sustainable built environments.  相似文献   

基于低空无人机倾斜摄影测量在农村房屋不动产登记权籍调查中的应用     

刘敏  张启超  赵彬  李智慧 《测绘与空间地理信息》2020,(1):181-183

低空无人机倾斜摄影测量技术可以快速获取实景三维影像,具有可量测、现实感逼真、纹理清晰等特点。该技术应用于农村房屋不动产登记权籍调查中,减少了外业实地丈量的工作量,克服了不通视房屋拐点量边的困难,可快速生成数字线划图,通过三维不动产模型可以查看测量三维数据,解决了外业调查耗时费力、界址边丈量人为误差等问题。  相似文献   

遗传算法优化的BP神经网络卫星钟差预报          下载免费PDF全文

孙鹏超  魏东平  孙碧娟 《天文学报》2020,61(6):67

针对BP (Back Propagation)神经网络模型预测卫星钟差中权值和阈值的最优化问题, 提出了基于遗传算法优化的BP神经网络卫星钟差短期预报模型, 给出了遗传算法优化BP神经网络的基本思想、具体方法和实施步骤. 为验证该优化模型的有效性和可行性, 利用北斗卫星导航系统(BeiDou navigation satellite system, BDS)卫星钟差数据进行钟差预报精度分析, 并将其与灰色模型(GM(1,1))和BP神经网络模型预报的结果比较分析. 结果表明: 该模型在短期钟差预报中具有较好的精度, 优于GM(1,1)模型和BP神经网络模型.  相似文献   

Two-stage permutation tests for determining homogeneity within a spatial cluster     

Qiliang Liu  Wenkai Liu  Min Deng  Yaolin Liu 《International journal of geographical information science》2019,33(9):1718-1738

The discovery of spatial clusters formed by proximal spatial units with similar non-spatial attribute values plays an important role in spatial data analysis. Although several spatial contiguity-constrained clustering methods are currently available, almost all of them discover clusters in a geographical dataset, even though the dataset has no natural clustering structure. Statistically evaluating the significance of the degree of homogeneity within a single spatial cluster is difficult. To overcome this limitation, this study develops a permutation test approach Specifically, the homogeneity of a spatial cluster is measured based on the local variance and cluster member permutation, and two-stage permutation tests are developed to determine the significance of the degree of homogeneity within each spatial cluster. The proposed permutation tests can be integrated into the existing spatial clustering algorithms to detect homogeneous spatial clusters. The proposed tests are compared with four existing tests (i.e., Park’s test, the contiguity-constrained nonparametric analysis of variance (COCOPAN) method, spatial scan statistic, and q-statistic) using two simulated and two meteorological datasets. The comparison shows that the proposed two-stage permutation tests are more effective to identify homogeneous spatial clusters and to determine homogeneous clustering structures in practical applications.  相似文献   

Species Abundance Distribution Patterns of a Toona ciliata Community in Xingdoushan Nature Reserve     

WANG Yang  ZHU Shengjie  LI Jie  HE Xiuling  JIANG Xiongbo  ZHANG Min 《资源与生态学报(英文版)》2019,10(5):494-503

With the goal of model fitting species abundance distribution patterns of the tree, shrub and herb layers of the natural Toona ciliata community in Xingdoushan Nature Reserve, Enshi Autonomous Prefecture, Hubei Province, we used the data collected from the field survey and employed different ecological niche models. The models tested were the broken stick model (BSM), the overlapping niche model (ONM) and the niche preemption model (NPM), as well as three statistic models, the log-series distribution model (LSD), the log-normal distribution model (LND) and the Weibull distribution model (WDM). To determine the fitted model most suitable to each layer, the fitting effects were judged by criteria of the lowest value of Akaike Information Criterion (AIC), Chi-square and the K-S values with no significant difference (P>0.05) between the theoretical predictions and observed species abundance distribution values. The result showed: (1) The fitting suitability and goodness of fit of the tree, shrub and herb layers by using the three ecological niche models were ranked as: NPM>BSM>ONM. Of the three statistical models, by accepting the fitting results of the three layers, WDM was the best fitting model, followed by LND. By rejecting the fitting tests of the herb layer, LSD had the worst fitting effect. The goodness of the statistical models was ranked as: WDM>LND>LSD. In general, the statistical models had better fitting results than the ecological models. (2) T. ciliata was the dominant species of the tree layer. The species richness and diversity of the herb layer were much higher than those of either the tree layer or the shrub layer. The species richness and diversity of the shrub layer were slightly higher than those of the tree layer. The community evenness accorded to the following order: herb>shrub>tree. Considering the fitting results of the different layers, different ecological niche models or statistical models with optimal goodness of fit and ecological significance can be given priority to in studying the species abundance distribution patterns of T. ciliata communities.  相似文献   

Solubilities,Densities,Refractive Indices of Aqueous Ternary Systems PEG400-NaCl/KCl-H₂O at 298 K          下载免费PDF全文

YU Xu-dong  LI Mao-lan  WANG Lin  HUANG Qin  ZHENG Hong  ZHENG Qiu-feng  LIU Min  ZENG Ying 《盐湖研究》2019,27(2):40-45

Phase equilibria for the NaCl/KCl-PEG400-H_2 O aqueous ternary systems at 298 K were studied using an isothermal dissolution method. In addition,the densities and refractive indices were determined. The corresponding phase diagrams,as well as the density vs. composition and refractive index vs.composition diagrams,were plotted. Results revealed that over the entire PEG400 composition range studied at 298 K only 1 liquid phase was obtained,without the formation of a biphase region. The phase diagrams of these 2 systems consist of 1 homogeneous area with unsaturated liquid( L) and an equilibrium area containing the solid phase of NaCl/KCl and the saturated liquid phase( S + L). The solubility of NaCl/KCl decreases with the addition of PEG400 at 298 K.  相似文献