共查询到19条相似文献，搜索用时 733 毫秒
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从亥姆霍兹方程出发，导出了自聚焦光纤中传导模在圆柱坐标系中的场分布形式，并给出了几个低阶模的分布图。 相似文献
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从亥姆霍兹方程出发，导出了自聚焦光纤中传导模在圆柱坐标系中的场分布形式，并给出了几个低阶模的分布图。 相似文献
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翁兴涛 《武汉测绘科技大学学报》1994,19(4):367-370
从求解柱坐标内亥姆霍兹方程出发，导出了类透镜介质传导模的特征参量、场分布状态及传播常数，求出了入射激光束和导模之间的耦合系数，并讨论了它们的物理意义。 相似文献
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本文详细地叙述和分析了Ｎｉ００２因瓦水准标尺模板研制的整个过程，包括冲孔模的研制模板的冲裁，模板及标尺全分划刻划误差的检验，并由此推算出喷漆复制精度和模板的精度。文中，特别指出了冲孔模冲头间距误差正负号的的排列对标尺检验结构的影响，并在初中得取了验证。 相似文献
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本文对用于地图更新系统的几种自动匹配及变化探测方法进行了探讨，其中ＧＩＳ数据库不同以信的无控像更新法采用的是从矢量数据集提取模片，并将模片与新的栅格影像相匹配。 相似文献
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在对车型识别去噪和边缘检测进行分析的基础上，提出了一种基于反对称小波的检测方法。首先采用尺度间相关性和尺度内相位法进行有效去噪，然后检测变换模极大值，并进行有效区分保留真正边缘模极大值，最后进行相关恢复处理得到比较清晰的车型边缘。结果表明，该方法提高了车型边缘检测的准确性和车型识别率，具有很好的应用前景。 相似文献
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本文根据地图质量模糊评判的数学模建建立起一个计算机地图质量评判与管理系统，它克服了人工评定地图质量的主观性和随意性，使地图质量评定定量化、标准化。用系统对部分地形图编绘质量进行了评判，所得结果令人满意。 相似文献
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影像特征的表示和描述是计算机视觉中的重要内容。本文给出了基于小波变换的影像特征检测算法，从理论上说明了利用不同分辨率上小波变换系数的模值描述特征强度的合理性。 相似文献
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Antennas that are located on or near the boundary between two electrically different media, such as air and earth, or seawater and rock, are used as prospective tools for remote sensing and geophysical exploration. As an example, this letter examines the electromagnetic (EM) response of a metallic object that is submerged in a conducting layer of seawater that is situated between an infinite half-space of air and a seabed of lower electrical conductivity. When the source and the object are at some distance away in the water, the primary EM propagation mode is on the interfaces because the surface waves are less attenuated than those following the direct or reflected propagation paths. The simulation tool that predicts the performances of the EM detection system uses the method-of-moments integral equation technique. The method is validated and applied to calculate the scattered fields from a submerged perfectly conducting cylinder. The numerical results are then compared with experimental data that are obtained by towing a steel cylinder through an impressed field that is produced by a horizontal electric source. 相似文献
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本文结合三角测量的实例对误差传播定律一些应用问题进行了讨论,指出当只有一个独立的观测值时,和函数与倍数函数运用误差传播定律不会出现悖论;采用数学中更为复杂的恒等函数关系式中不同的算式求解相同观测值的函数值,运用误差传播定律也不会出现悖论。如果在测量工作中有多余的直接观测值,就需用平差后的间接观测值按协方差传播律来计算,这样数学中相等的函数关系才能得到同样的函数中误差结果。 相似文献
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在利用近地表遥感探测方法对地表信息进行反演时，地表状态的不同会导致电磁波传播方式不同，进而决定了所采取的遥感探测方式、探测波长及探测手段的不同。因此，地表状态的识别是进行近地表遥感反演的前提和基础，其识别的准确率也决定了反演结果的准确度。本文提供了一种改进LBP（local binary pattern）和HSV颜色直方图相结合的地表状态识别算法，通过改进阈值的LBP算法和HSV颜色直方图提取特征向量并建立判别条件，最后利用K邻近算法对测试样本与训练样本进行特征匹配，得到识别结果。将野外采集的411张图片多粗随机分组为训练样本和测试样本，结果表明206张测试样本的分类正确率都达98.7%以上，证明了本文算法的有效性。 相似文献
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针对传统地图制作门槛高、传播效率低的弊端,提出了一种新的地图形式——微地图,以适应自媒体时代对地图的要求。给出了微地图的定义、特点及其与传统地图的区别,阐释了微地图系统的功能。微地图作为传统地图的有益补充,将以其小、快、灵的特点成为面向"草根"阶层的地图。 相似文献
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The purpose of this work is to determine whether spatial modeling can be used to model the spread of the Black Death. The study is limited to models for the propagation of the disease in Sweden in 1350. Geographic data of Swedish water bodies and medieval road networks, historical data on the population in Swedish parishes, including their medieval boundaries, along with historical notes and disease characteristics, were used to build alternative models for spatial distribution. Three different models are presented: one radial, one cost‐based and one combining network analysis and radial propagation. Simulations were made to depict different scenarios on the spread of the disease, as well as the drastic changes in the overall population of Sweden, over a couple of hundred years. For purpose of validation the population decrease estimated in each parish is compared with independent historical documents. Results from model scenarios are visualized in maps of propagation, animated video sequences and a web map service. Our analyses clearly demonstrate the power of spatial analysis and geographic information systems to describe, model and visualize epidemiologic processes in space and time. 相似文献
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轨道误差传播研究在空间碰撞风险分析、任务规划等空间态势感知领域具有重要作用。轨道误差常用误差协方差矩阵表达,其传播方式主要有线性传播模型与非线性传播模型两种。线性传播模型通过状态转移矩阵外推初始协方差矩阵,计算快速,但因将高度非线性化的轨道动力学问题线性化描述,导致传播精度随时间快速降低。非线性传播模型精度高但计算慢,难以进行大规模碎片群的轨道误差传播。在轨道误差传播特性分析的基础上,提出了一种获得较为真实的空间碎片轨道预报误差的方法,分3步进行:初始协方差矩阵的构建、初始轨道协方差线性传播以及基于实测数据对轨道预报协方差的动态校正。经大量案例统计分析,结果表明,校正后的轨道预报协方差,相较于线性传播结果,精度提高了60%以上,可服务于空间碰撞风险分析等高精度空间任务。 相似文献
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GIS中直线元内插点精度及对误差带的影响 总被引：1，自引：0，他引：1
基于误差传播定律，考虑参数r误差影响，推导了线元内插点的精度计算公式，讨论内插点精度对线元误差带的影响，并对影响的结果进行了分析，得到了一些有益的结论。 相似文献
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Understanding the interplay between bus,metro, and cab ridership dynamics in Shenzhen,China 
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下载免费PDF全文 Mengxue Yue Chaogui Kang Clio Andris Kun Qin Yu Liu Qingxiang Meng 《Transactions in GIS》2018,22(3):855-871
The most common mass transit modes in metropolitan cities include buses, subways, and taxicabs, each of which contribute to an interconnected complex network that delivers urban dwellers to their destinations. Understanding the intertwined usages of these three transit modes at different places and time allows for better sensing of urban mobility and the built environment. In this article, we leverage a comprehensive data collection of bus, metro, and taxicab ridership from Shenzhen, China to unveil the spatio‐temporal interplay between different mass transit modes. To achieve this goal, we develop a novel spectral clustering framework that imposes spatio‐temporal similarities between mass transit mode usage in urban space and differentiates urban spaces associated with distinct ridership patterns of mass transit modes. Five resulting categories of urban spaces are identified and interpreted with auxiliary knowledge of the city's metro network and land‐use functionality. In general, different categorized urban spaces are associated with different accessibility levels (such as high‐, medium‐, and low‐ranked) and different urban functionalities (such as residential, commercial, leisure‐dominant, and home–work balanced). The results indicate that different mass transit modes cooperate or compete based on demographic and socioeconomic attributes of the underlying urban environments. Our proposed analytical framework provides a novel and effective way to explore the mass transit system and the functional heterogeneity in cities. It demonstrates great potential for assisting policymakers and municipal managers in optimizing public transportation facility allocation and city‐wide daily commuting distribution. 相似文献