优选小波函数的小波神经网络预报GPS卫星钟差     

王旭  柴洪洲  王昶  种洋 《测绘学报》2020,49(8):983-992

为了提高卫星钟差预报的精度,针对小波神经网络(WNN)模型未能根据实际情况选取合适的小波函数的问题,本文提出一种基于"Shannon熵-能量比"的优选小波函数的小波神经网络钟差预报模型。首先利用小波函数对钟差一次差分数据进行连续小波变换,得到变换后的小波系数。然后分别计算小波系数的能量值和Shannon熵值,将"Shannon熵-能量比"(SEE)作为最优小波函数选择的评价指标,以指导选择最适合的小波函数作为WNN模型的激活函数。最后利用优选的WNN模型对卫星钟差进行预报,对预报的结果进行对比分析。结果表明:该评价指标能够根据卫星钟差实际情况准确指导WNN模型选择合适的小波函数,提高WNN模型的预报精度和适用性,使该模型可以实现卫星钟差较高精度的预报。  相似文献   

滕州市努力加强地籍管理工作          下载免费PDF全文

常永民  刘冰 《山东国土资源》2009,25(6):50-51

地籍管理工作,是社会各界关注的焦点,涉及广大群众的切身利益。近年来,滕州市国土资源局不断加大地籍管理工作力度,提高工作水平和服务质量,充分发挥地籍信息优势,全面实行“对内以图管地,对外以证管地”工作机制,以产权管理为核心,以基础业务建设为重点,严把土地登记关,使地籍管理工作走上了规范化、制度化的轨道。  相似文献   

GPS高程拟合中剔除粗差的方法     

王昶  王旭  王彤 《测绘工程》2009,18(5):55-58,62

在GPS高程拟合中,粗差影响着整个拟合的精度,粗差剔除是GPS高程拟合中重要一步。文中提出一种循环泰勒多项式拟合法和F-T法的组合,通过与部分最小二乘平差法比较,发现这种方法不但有严谨的理论,有可行的应用价值,而且可以有效地剔除粗差。  相似文献   

基于VRML的三维地下管网信息系统的实现     

张小萍  瞿畅  王君泽 《测绘科学》2009,34(4)

针对目前广泛使用的地下管网系统在三维描述方面的欠缺,本文利用虚拟现实技术和VRML语言,构建了基于VRML的三维地下管网信息系统。这一系统的实现,用户可通过网络异地浏览地下管网的三维虚拟模型和查询相关数据信息,大大提高了工作效率和城市数字化管理水平。  相似文献   

An ANN–RTS smoother scheme for accurate INS/GPS integrated attitude determination     

Kai-Wei Chiang  Yung-Cheng Lin  Yun-Wen Huang  Hsiu-Wen Chang 《GPS Solutions》2009,13(3):199-208

Digital mobile mapping, the method that integrates digital imaging with direct geo-referencing, has developed rapidly over the past 15 years. The Kalman filter (KF) is considered an optimal estimation tool for real-time INS/GPS integrated kinematic positioning and orientation determination. However, the accuracy requirements of general mobile mapping applications cannot be easily achieved even when using the KF scheme. Therefore, this study proposes an intelligent scheme combining ANN and RTS backward smoother to overcome the limitations of KF and to enhance the overall accuracy of attitude determination for tactical grade and MEMS INS/GPS integrated systems.

Yun-Wen Huang (Corresponding author)Email:

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基于GIS的宁波市农业资源管理信息系统构建     

黄昌  董浙云  吴健平  杨同辉 《测绘与空间地理信息》2009,32(6):148-150

对在农业资源管理中应用GIS技术的必要性进行了论述,在了解了宁波市农业资源环境的特点以及用户需求的基础上,利用GIS的二次开发技术,对宁波市农业资源管理信息系统进行了构建与开发.  相似文献   

基于非稳态调和分析和长短时记忆神经网络的河口潮位短期预报混合模型     

徐晓武  陈永平  甘敏  刘畅  周宏杰 《海洋通报》2022,(4):401-410

河口潮汐过程受上游径流、外海潮波等因素影响,动力机制复杂,潮位预报难度大。本文提出了一种基于非稳态调和分析（NS＿TIDE）和长短时记忆（LSTM）神经网络的混合模型,对河口潮位进行12～48 h短期预报。该模型首先对河口实测潮汐数据进行非稳态调和分析,通过与实测资料对比得到分析误差的时序序列,并以此作为LSTM神经网络的输入数据,通过网络学习并预测未来12～48 h潮位预报误差,据此对NS＿TIDE的预测结果进行实时校正。利用该模型对2020年长江口潮位过程进行了预报检验,结果表明混合模型12 h、24 h、36 h和48 h短期水位预报的均方根误差（RMSE）相比NS＿TIDE模型至多分别降低了0.16 m、0.15 m、0.14 m和0.12 m;针对2020年南京站最高水位预测,NS＿TIDE模型预报误差为0.64 m,而混合模型预报误差仅为0.10 m。  相似文献   

Turbulent heat transfer in a tube fitted with serrated twist tape under rolling and pitching environments with applications to shipping machineries     

Shyy Woei Chang  Tong-Miin Liou  Kun-Tse Chen 《Ocean Engineering》2008,35(16):1569-1577

Turbulent heat transfer in a swinging tube with a serrated twist tape insert was experimentally examined to reveal the effects of swinging oscillations on heat transfer for such a swirl tube under sea-going conditions. This swirl tube swings about two orthogonal axes under single and compound rolling and pitching oscillations. A selection of Nusselt number (Nu) measurements illustrates the influences of swinging oscillations with and without buoyancy interaction on heat transfer performances. Single rolling or pitching oscillation with the swinging frequencies ranging from 0.333 to 1 Hz reduces heat transfer levels from the static references. Synergistic effects of compound rolling and pitching oscillations with either harmonic or non-harmonic rhythms improve heat transfer performances. Buoyancy effects in the swinging swirl tube elevate local Nu, but are weakened as the relative strength of swinging force increases. A set of heat transfer correlations is derived that permits the individual and interactive effects of single and compound swinging force effects with buoyancy interactions on the developed flow heat transfer value () to be quantified.  相似文献   

Reply to discussion on “Application of probabilistic neural network to design breakwater armor blocks” by Zekai Şen,Tarkan Erdik,Yavuz Karsavran     

Dookie Kim  Dong Hyawn Kim  Seongkyu Chang 《Ocean Engineering》2008,35(11-12):1284

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Propagation of a solitary wave over rigid porous beds   总被引：1，自引：0，他引：1  

Ching-Jer Huang  Mao-Lin Shen  Hsing-Han Chang 《Ocean Engineering》2008,35(11-12):1194-1202

The unsteady two-dimensional Navier–Stokes equations and Navier–Stokes type model equations for porous flows were solved numerically to simulate the propagation of a solitary wave over porous beds. The free surface boundary conditions and the interfacial boundary conditions between the water region and the porous bed are in complete form. The incoming waves were generated using a piston type wavemaker set up in the computational domain. Accuracy of the numerical model was verified by comparing the numerical results with the theoretical solutions. The main characteristics of the flow fields in both the water region and the porous bed were discussed by specifying the velocity fields. Behaviors of boundary layer flows in both fluid and porous bed regions were also revealed. Effects of different parameters on the wave height attenuation were studied and discussed. The results of this numerical model indicate that for the investigated incident wave as the ratio of the porous bed depth to the fluid depth exceeds 10, any further increase of the porous bed depth has no effect on wave height attenuation.  相似文献