共查询到20条相似文献，搜索用时 31 毫秒
1.
地图目标的形状在地图制图综合、空间查询等研究中发挥着重要作用。地图建筑物形状的识别与分类作为建筑物轮廓化简与典型化的基础,一直是制图综合研究的热点问题。目前,主要的建筑物形状识别方法主要依赖对建筑物轮廓的描述,对建筑物等地图面状要素的形态特征有较强的依赖性,通常只在应对特定类型的规则轮廓或直角化轮廓时能发挥较好的效果,对于形状不规则或复杂的情况识别不佳。本文提出一种AlexNet支持下的地图建筑物形状分类方法,将矢量地图中建筑物数据的形状分类问题,转化为建筑物栅格图像的分类问题,通过完成卷积神经网络的图形分类实现建筑物的形状识别。该方法首先结合空间认知规律提出一系列典型建筑物形状类型,然后利用矢量-栅格转换的方法从OSM数据采样单体建筑物栅格图像,通过人工标识获得建筑物形状分类训练样本,训练AlexNet卷积神经网络分类模型,最后利用训练好的模型对大比例尺建筑物数据进行智能形状分类与识别。本文利用北京、香港2个城市的OSM建筑物数据作为样本训练建筑物形状分类模型,并在广州部分城区的OSM建筑物数据上进行验证。相较传统形状相似性度量方法,本文提出的方法对实验区建筑物的识别分类总体查全率提高了2.48%,达到92.32%,对于较为复杂的形状（如T形、十字形）识别也具有更高的精度,查准率分别提高了13.83%和24.53%。实验结果表明本文提出的方法对建筑物形状分类的效果有明显提升,能够实现常见建筑物形状的有效分类,为下一步的建筑物化简、典型化等综合操作打下了基础。 相似文献
2.
针对缝洞型低渗碳酸盐油藏,建立考虑启动压力梯度和动边界共同影响的三重介质低渗透油藏非线性非稳态渗流模型.鉴于数学模型的非线性和非齐次性,通过引入新定义的压力(量纲一)线性化压力扩散方程,应用Laplace变换和Duhamel原理结合Stehfest数值反演对模型进行求解,获得三重介质低渗油藏产量递减典型曲线,在产量递减双对数图上出现3个递减阶段和2个相对平缓稳定阶段;分析启动压力梯度、溶洞窜流系数、基质窜流系数、裂缝弹性储容比和溶洞弹性储容比与基质弹性储容比之比等敏感参数对产量(量纲一)的影响规律.计算分析表明,启动压力梯度越大,中后期产量递减曲线下降幅度越大.通过绘制的产量递减曲线图版,可以预测缝洞型低渗透碳酸盐岩油藏未来产量的变化. 相似文献
3.
针对多项式拟合模型系数矩阵中部分元素是某一自变量的函数的特点,根据Partial EIV模型的解算思想,将系数矩阵中自变量的函数作为随机元素提取,顾及泰勒展开的二阶项,由协方差传播律计算自变量函数的协因数阵进行平差解算。实验结果表明,系数矩阵的元素不再是单独的自变量时,使用该算法可以得到与已有非线性总体最小二乘方法相近的参数结果,从构造随机向量权阵的角度提供了一种新的解算方法。 相似文献
4.
A generalized limit equilibrium method for the solution of active earth pressure on a retaining wall
In this paper, a generalized limit equilibrium method of solving the active earth pressure problem behind a retaining wall is proposed. Differing from other limit equilibrium methods, an arbitrary slip surface shape without any assumptions of pre-defined shapes is needed in the current framework, which is verified to find the most probable failure slip surface. Based on the current computational framework, numerical comparisons with experiment, discrete element method and other methods are carried out. In addition, the influences of the inclination of the wall, the soil cohesion, the angle of the internal friction of the soil, the slope inclination of the backfill soil on the critical pressure coefficient of the soil, the point of application of the resultant earth pressure and the shape of the slip surface are also carefully investigated. The results demonstrate that limit equilibrium solution from predefined slip plane assumption, including Coulomb solution, is a special case of current computational framework. It is well illustrated that the current method is feasible to evaluate the characteristics of earth pressure problem. 相似文献
5.
嵇昆浦 《大地测量与地球动力学》2019,39(12):1304-1309
利用平差参数间合理的先验信息能够显著提高解的精度。在病态总体最小二乘模型的基础上,引入等式约束条件,建立等式约束病态总体最小二乘模型,构建该模型的约束正则化准则,并根据拉格朗日极值法导出参数的迭代解及方差-协方差阵,最后以数值算例和病态测边网算例验证公式的正确性。结果表明,新方法通过正则化准则能改善法矩阵的病态性,且遵从EIV准则顾及系数阵的误差,同时还考虑参数间合理的先验信息,其解的精度得到显著提升。 相似文献
6.
The key concept of spectrum response estimation with commercial software, such as the SESAM software tool, typically includes two main steps: finding a suitable loading spectrum and computing the response amplitude operators (RAOs) subjected to a frequency-specified wave component. In this paper, we propose a nontraditional spectrum response estimation method that uses a numerical representation of the retardation functions. Based on estimated added mass and damping matrices of the structure, we decompose and replace the convolution terms with a series of poles and corresponding residues in the Laplace domain. Then, we estimate the power density corresponding to each frequency component using the improved periodogram method. The advantage of this approach is that the frequency-dependent motion equations in the time domain can be transformed into the Laplace domain without requiring Laplace-domain expressions for the added mass and damping. To validate the proposed method, we use a numerical semi-submerged pontoon from the SESAM. The numerical results show that the responses of the proposed method match well with those obtained from the traditional method. Furthermore, the estimated spectrum also matches well, which indicates its potential application to deep-water floating structures. 相似文献
7.
《中国海洋大学学报(英文版)》2017,(4)
The key concept of spectrum response estimation with commercial software,such as the SESAM software tool,typically includes two main steps:finding a suitable loading spectrum and computing the response amplitude operators(RAOs) subjected to a frequency-specified wave component.In this paper,we propose a nontraditional spectrum response estimation method that uses a numerical representation of the retardation functions.Based on estimated added mass and damping matrices of the structure,we decompose and replace the convolution terms with a series of poles and corresponding residues in the Laplace domain.Then,we estimate the power density corresponding to each frequency component using the improved periodogram method.The advantage of this approach is that the frequency-dependent motion equations in the time domain can be transformed into the Laplace domain without requiring Laplace-domain expressions for the added mass and damping.To validate the proposed method,we use a numerical semi-submerged pontoon from the SESAM.The numerical results show that the responses of the proposed method match well with those obtained from the traditional method.Furthermore,the estimated spectrum also matches well,which indicates its potential application to deep-water floating structures. 相似文献
8.
基于再分析资料ERA5的对流层延迟估计方法及精度评估 总被引：1，自引：0，他引：1
提出基于再分析资料ERA5的天顶对流层延迟计算方法,使用中国大陆构造环境监测网络提供的26个GNSS测站2017年全年数据,评估由该方法计算的天顶对流层延迟的精度,并与前一代再分析资料ERA-Interim的计算结果进行对比分析。结果显示,ERA5计算的天顶对流层延迟均方根误差比ERA-Interim计算结果低,表明新一代产品的精度有明显提升。 相似文献
9.
采用数值分析理论讨论方阵奇异性判别的方法,针对平面四参数坐标转换模型法方程系数矩阵病态性的问题,提出中心化坐标与缩小误差方程系数相结合的方法,有效改善了法方程系数矩阵的结构与病态性,获取到稳定可靠的转换参数。通过理论与实例分析,验证了该方法简单可行,为区域工程测量中平面坐标转换提供了参考。 相似文献
10.
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11.
Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank in these vehicles is partially filled, it is essential to be able to evaluate the fluid dynamic loads on tank perimeter. Different geometric shapes such as rectangular, cylindrical, elliptical, spherical and circular conical have been suggested for ship storage tanks by previous researchers. In this paper a numerical model is developed based on incompressible and inviscid fluid motion for the liquid sloshing phenomenon. The coupled BEM-FEM is used to solve the governing equations and nonlinear free surface boundary conditions. The results are validated for rectangular container using data obtained for a horizontal periodic sway motion. Using the results of this model a new arrangement of trapezoidal shapes with quadratic sidewalls is suggested for tanker ship storage panels. The suggested geometric shape not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing effects more efficiently than the existing geometric shapes. 相似文献
12.
《中国海洋大学学报(英文版)》2015,(6)
For modal parameter estimation of offshore structures, one has to deal with two challenges: 1) identify the interested frequencies, and 2) reduce the number of false modes. In this article, we propose an improved method of modal parameter estimation by reconstructing a new signal only with interested frequencies. The approach consists of three steps: 1) isolation and reconstruction of interested frequencies using FFT filtering, 2) smoothness of reconstructed signals, and 3) extraction of interested modal parameters in time domain. The theoretical improvement is that the frequency response function(FRF) of filtered signals is smoothed based on singular value decomposition technique. The elimination of false modes is realized by reconstructing a block data matrix of the eigensystem realization algorithm(ERA) using the filtered and smoothed signals. The advantage is that the efficiency of the identification process of modal parameters will be improved greatly without introducing any false modes. A five-DOF mass-spring system is chosen to illustrate the procedure and demonstrate the performance of the proposed scheme. Numerical results indicate that interested frequencies can be isolated successfully using FFT filtering, and unexpected peaks in auto spectral density can be removed effectively. In addition, interested modal parameters, such as frequencies and damping ratios, can be identified properly by reconstructing the Hankel matrix with a small dimension of ERA, even the original signal has measurement noises. 相似文献
13.
《中国海洋大学学报(英文版)》2019,(6)
This paper proposes a new method for data assimilation of the surface radial current observed by High Frequency ground wave radar and optimization of the bottom friction coefficient. In this method, the shallow water wave equation is introduced into the cost function of the multigrid three-dimensional variation data assimilation method as the weak constraint term, the surface current and the bottom friction coefficient are defined as the analytical variables, and the high spatiotemporal resolution surface radial flow observed by the high-frequency ground wave radar is used to optimize the surface current and bottom friction coefficient. This method can effectively consider the spatiotemporal correlation of radar data and extract multiscale information from surface radial flow data from long waves to short waves. Introducing the shallow water wave equation into the cost function as a weak constraint condition can adjust both the momentum and mass fields simultaneously to obtain more reasonable analysis information. The optimized bottom friction coefficient is introduced into the regional ocean numerical model to carry out numerical experiments. The test results show that the bottom friction coefficient obtained by this method can effectively improve the accuracy of the numerical simulation of sea surface height in the offshore area and reduce the simulation error. 相似文献
14.
三角形形状因子对地壳形变计算精度的影响 总被引：11，自引：5，他引：6
引入三角形内切圆半径与外接圆半径之比值作为三角形形状因子，讨论利用三角形法计算应变分量的精度与三角形形状因子之间的关系。设计一种涵盖所有三角形形状的方法，计算分析了用三角形法计算应变分量精度的分布。研究表明：当三角形形状因子达到0．36时，计算得到的应变分量均方差，一般不会超过位移数据均方差的3倍；而当三角形形状因子小于0．1时，计算得到的应变分量均方差会陡然增大，这样的三角形一般不适合用于应变分量的计算。在利用GPS观测站组成三角形计算地应变时，建议所组成的三角形形状因子的阈值应取为0．1～0．36。 相似文献
15.
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16.
?????????С???????????????????????????????????????????????????в?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????÷??????????????????Schaffrin & Wieser???????????????????? 相似文献
17.
在非等间距GM(1,1)模型中,系数矩阵中有无误差的常数项和有误差的随机项,并且系数矩阵与观测向量误差同源,即系数矩阵与观测向量中有相同的元素存在,这些相同元素应该有相同的改正数,为此本文推导了一种适合非等间距GM(1,1)模型求解的总体最小二乘算法。同时,考虑到非等间距GM(1,1)模型中存在病态问题时影响总体最小二乘计算结果的稳定性,提出对系数矩阵常数列乘以某一常数的方法,以改善病态问题。 相似文献
18.
高时空分辨率的气温栅格数据是多种地学模型和气候模型的重要输入。山区地形复杂,气温空间异质性强,如何获取高时空分辨率的山区地表气温数据一直是研究热点与难点。本文选择地形复杂的河北省张家口市作为试验区,基于局部薄盘样条函数对ERA5再分析日均近地表气温（2 m高度）进行空间插值,并利用随机森林算法,结合少量气象站观测气温数据、地形地表参数数据构建日均气温订正模型和气温逐时化模型,实现空间分辨率由0.1 °（约11 km）到30 m的逐时气温降尺度,最后将该模型拓展应用于其他时间与区域,检验本文发展的降尺度方法在没有站点观测数据条件下的时空移植性。结果显示,本文降尺度方法得到的高时空分辨率山区气温数据精度较高,1月均方根误差（RMSE）平均值为2.4 ℃,明显优于气象站点插值结果,且气温相对高低的空间分布更为合理、纹理更加丰富;将该方法应用到其他时间与区域的RMSE平均值分别为2.9 ℃与2.5 ℃,均小于再分析资料直接插值所产生的误差。研究结果总体表明,在气象站点较少甚至没有时,可利用本文方法通过ERA5再分析气温准确获取复杂地形条件下的山区高时空分辨率气温数据。 相似文献
19.
《中国海洋大学学报(英文版)》2021,20(5)
Marine geological disasters occurred frequently in the deep-water slope area of the northern South China Sea, especially submarine landslides, which caused serious damage to marine facilities. The cyclic elastoplastic model that can describe the cyclic stress-strain response characteristic for soft clay, is embedded into the coupled Eulerian-Lagrangian(CEL) algorithm of ABAQUS by means of subroutine interface technology. On the basis of CEL technique and undrained cyclic elastoplastic model, a method for analyzing the dynamic instability process of marine slopes under the action of earthquake load is developed. The rationality for cyclic elastoplastic constitutive model is validated by comparing its calculated results with those of von Mises model built in Abaqus. The dynamic instability process of slopes under different conditions are analyzed. The results indicate that the deformation accumulation of soft clay have a significant effect on the dynamic instability process of submarine slopes under earthquake loading. The cumulative deformation is taken into our model and this makes the calculated final deformation of the slope under earthquake load larger than the results of conventional numerical method. When different contact conditions are used for analysis, the smaller the friction coefficient is, the larger the deformation of slopes will be. A numerical analysis method that can both reflect the dynamic properties of soft clay and display the dynamic instability process of submarine landslide is proposed, which could visually predict the topographies of the previous and post failure for submarine slope. 相似文献
20.
关于非球形粒子光散射的T-矩阵数值计算方法的研究 总被引：1，自引：0，他引：1
首先介绍了无规取向轴对称非球形粒子光散射的T－矩阵数值方法。然后，进一步研究了T－矩阵计算的收敛问题，提出了一种新的关于无规取向无吸收非线形散射物体的物理收敛方法，我们研究了椭球粒子的收敛问题，结果表明我们的数值方法和T－矩阵计算程序是有效的， 收敛精度与粒子的尺度和形状有很强的依赖性，在一定的条件下，我们的物理收敛速度优于NASA Mishchenko的数学收敛速序。 相似文献