水平摆钟控自动标定装置     

叶传潜 《大地测量与地球动力学》1992,(3)

本文介绍了水银胀盒钟控自动标定装置。该装置采用脉冲式标定形式,具有定时起标,到位自停等功能,能在无人值守下自动按预置状态完成标定的全过程。文中还介绍了随迹标定法,该方法的应用使倾斜观测具有连续的灵敏度监测。  相似文献   

一种纳米纯AgI气溶胶的制备方法 及其成冰核活性的检测     

杨绍忠  陈跃 《气象》2018,44(3):442-448

将100mg纯AgI粉末置于一个气氛炉的汽化管内加热到1600℃使之汽化,再利用高压空气将气态AgI爆冲到一个容积为2m~3的金属容器里,骤冷后形成AgI气溶胶。用碳支持膜对形成的AgI气溶胶粒子自然沉降取样,然后用X射线衍射仪和电镜检测其成分和粒子尺度。检测表明:粉末状纯AgI经汽化—冷凝产生的气溶胶其成分仍为纯AgI,粒子尺度在0.84～34.6nm,峰值直径约为2.17nm。为了验证产生的纳米纯AgI气溶胶在冰核化中是否具有成冰核活性,用15L混合云室分别在云室中有冷雾和无冷雾两种条件下定量注入纳米纯AgI气溶胶,检测了它们在不同温度下的成冰核效率,检测结果是:在云室中有-10℃冷雾时,成核率为1.1×10~(11)个·g~(-1),在云室中-10℃无冷雾时,成核率约为3.4×10~(10)个·g~(-1)。  相似文献   

利用时域有限差分方法计算雷电水平电场     

田瑞敏  张华明 《气象科技》2018,46(5):875-879

雷电水平电场是计算电力架空线雷电感应过电压的重要参数,为了准确获得该参数值,本文利用时域有限差分方法(FDTD)对不同地面电导率情况以及距雷电回击通道不同距离处的雷电水平电场进行了计算和分析,结果表明:(1)地面电导率均匀情况下,地面电导率越大,计算距离越近,雷电水平电场波形愈加接近模式输入的电流波形,这与雷电水平电场中的辐射场分量较小有关,而增大地面电导率或者增加计算距离都会导致计算结果变小甚至波形出现双极性的特征;(2)地面电导率水平分层情况下,计算得到的雷电水平电场受上层土壤的电导率影响更大,但是下层不同电导率的土壤一定程度上改变了土壤整体的等效电导率,使得计算结果与均匀电导率情况下有所差别。  相似文献   

X波段双偏振雷达垂直指向法标定的应用     

蔡康龙  李兆明  俞小鼎  何镜文  戴春容 《气象科技》2018,46(5):880-885

垂直指向法标定是双偏振雷达的差分反射率因子ZDR标定有效方法的一种,可以订正ZDR测量误差,提高雷达数据的质量。本文基于双发双收模式的X波段双线偏振天气雷达系统,通过分析雷达硬件系统和垂直指向法标定的数据,诊断了观测数值的一些质量问题,初步判断是方位旋转关节损坏而导致ZDR的数值在某一固定区域上出现较大偏差。更换新的方位旋转关节后,对比处理问题前后的垂直指向标定数据证明能有效解决此问题。最后,经过多次试验分析表明,当垂直指向法标定在回波强度为25.5~30.5dB之间的中等范围稳定的层状云降水情况下使用时,其标定的数据能有效订正系统ZDR偏移量。  相似文献   

基于空-谱先验条件随机场的高分辨率遥感影像变化检测方法     

吕鹏远  钟燕飞  赵济  张良培 《南京气象学院学报》2018,10(1):123-130

高空间分辨率遥感影像能够提供丰富的空间细节信息,使利用遥感影像进行精细变化检测成为可能.为充分挖掘高分辨率影像中的光谱、空间信息,本文提出一种基于影像空-谱先验信息的条件随机场（Conditional Random Field based on Spectral-Spatial Prior,SSPCRF）模型,该方法使用显著性检测方式自动提供先验光谱-空间样本信息,提高一元势能构建精度,有效缓解一元势能构建不准确导致的推理过程中的误差传递问题,并在二元势能中综合考虑标记场与观察影像的空间上下文信息以保持变化地物轮廓信息.最后,使用基于消息传递机制的推理方法将模型进行全局优化.在2组高分辨率影像数据集上的实验结果表明该方法能够提供较精确的初始变化检测信息,使得在减少变化检测结果中虚警点的同时保持变化地物细节信息.  相似文献   

区域自动气象站风向风速传感器检测仪设计与应用     

魏明明  刘禹杉  章允昊 《气象科技》2018,46(4):659-664

为了解决区域自动气象站的风向传感器、风速传感器的检测难题,设计出一种新型便携式风向风速传感器检测仪。该检测仪通过上位机软件和单片机来实现智能检测和控制等功能,工作时由单片机对步进电机驱动器编程可控制步进电机的精确定位,进而精确控制风向传感器的转动角度或风速传感器的转动速度,将传感器输出值与步进电机的标准值进行对比,最终实现自动化检测风向传感器、风速传感器计量性能的目的。通过与现有检测方法对比,结果显示其精确度更高,稳定性更好;该检测仪体积小、重量轻、操作简单便于携带、集合了风向检测功能和风速检测功能;能有效地解决野外区域自动气象站的现场检测难题。  相似文献   

Mapping spatiotemporal patterns of events using social media: a case study of influenza trends     

Yizhao Gao  Anand Padmanabhan  Junjun Yin  Guofeng Cao 《International journal of geographical information science》2018,32(3):425-449

Tracking spatial and temporal trends of events (e.g. disease outbreaks and natural disasters) is important for situation awareness and timely response. Social media, with increasing popularity, provide an effective way to collect event-related data from massive populations and thus a significant opportunity to dynamically monitor events as they emerge and evolve. While existing research has demonstrated the value of social media as sensors in event detection, estimating potential time spans and influenced areas of an event from social media remains challenging. Challenges include the unstable volumes of available data, the spatial heterogeneity of event activities and social media data, and the data sparsity. This paper describes a systematic approach to detecting potential spatiotemporal patterns of events by resolving these challenges through several interrelated strategies: using kernel density estimation for smoothed social media intensity surfaces; utilizing event-unrelated social media posts to help map relative event prevalence; and normalizing event indicators based on historical fluctuation. This approach generates event indicator maps and significance maps explaining spatiotemporal variations of event prevalence to identify space-time regions with potentially abnormal event activities. The approach has been applied to detect influenza activity patterns in the conterminous US using Twitter data. A set of experiments demonstrated that our approach produces high-resolution influenza activity maps that could be explained by available ground truth data.  相似文献   

Automatic change detection in lane-level road networks using GPS trajectories   总被引：1，自引：0，他引：1  

Xue Yang  Kathleen Stewart  Zhen Dong  Xia Zhang  Qingquan Li 《International journal of geographical information science》2018,32(3):601-621

Lane-level road network updating is crucial for urban traffic applications that use geographic information systems contributing to, for example, intelligent driving, route planning and traffic control. Researchers have developed various algorithms to update road networks using sensor data, such as high-definition images or GPS data; however, approaches that involve change detection for road networks at lane level using GPS data are less common. This paper presents a novel method for automatic change detection of lane-level road networks based on GPS trajectories of vehicles. The proposed method includes two steps: map matching at lane level and lane-level change recognition. To integrate the most up-to-date GPS data with a lane-level road network, this research uses a fuzzy logic road network matching method. The proposed map-matching method starts with a confirmation of candidate lane-level road segments that use error ellipses derived from the GPS data, and then computes the membership degree between GPS data and candidate lane-level segments. The GPS trajectory data is classified into successful or unsuccessful matches using a set of defuzzification rules. Any topological and geometrical changes to road networks are detected by analysing the two kinds of matching results and comparing their relationships with the original road network. Change detection results for road networks in Wuhan, China using collected GPS trajectories show that these methods can be successfully applied to detect lane-level road changes including added lanes, closed lanes and lane-changing and turning rules, while achieving a robust detection precision of above 80%.  相似文献   

青海省柴达木地区钾肥生产企业粉尘、噪声主要职业病危害的调查分析     

萨如丽 《盐湖研究》2018,26(3):64-69

青海是我国资源较为丰富的省份,钾盐资源的开发及钾肥生产在国内占有重要地位。随着青海高原地区盐湖钾肥产业的迅速发展,相关部门对该行业职业卫生、职业病防治工作日渐重视。通过大量的现场数据收集、整理,对青海高原地区盐湖钾肥行业作业人员面临的职业病危害因素、健康安全等相关问题进行了总结和分析,提出了有针对性的防范措施。  相似文献   

Understanding spatial structures and organizational patterns of city networks in China: A highway passenger flow perspective   总被引：6，自引：2，他引：4  

Wei Chen  Weidong Liu  Wenqian Ke  Nyuying Wang 《地理学报(英文版)》2018,28(4):477-494

The use of multi-perspective and multi-scalar city networks has gradually developed into a range of critical approaches to understand spatial interactions and linkages. In particular, road linkages represent key characteristics of spatial dependence and distance decay, and are of great significance in depicting spatial relationships at the regional scale. Therefore, based on highway passenger flow data between prefecture-level administrative units, this paper attempted to identify the functional structures and regional impacts of city networks in China, and to further explore the spatial organization patterns of the existing functional regions, aiming to deepen our understanding of city network structures and to provide new cognitive perspectives for ongoing research. The research results lead to four key conclusions. First, city networks that are based on highway flows exhibit strong spatial dependence and hierarchical characteristics, to a large extent spatially coupled with the distributions of major megaregions in China. These phenomena are a reflection of spatial relationships at regional scales as well as core-periphery structure. Second, 19 communities that belong to an important type of spatial configuration are identified through community detection algorithm, and we suggest they are correspondingly urban economic regions within urban China. Their spatial metaphors include the administrative region economy, spatial spillover effects of megaregions, and core-periphery structure. Third, each community possesses a specific city network system and exhibits strong spatial dependence and various spatial organization patterns. Regional patterns have emerged as the result of multi-level, dynamic, and networked characteristics. Fourth, adopting a morphology-based perspective, the regional city network systems can be basically divided into monocentric, dual-nuclei, polycentric, and low-level equilibration spatial structures, while most are developing monocentrically.  相似文献