开源技术在高校WebGIS课程教学中的应用探讨     

邢华桥  于明洋  孟飞  仇培元  刘建涛 《地理空间信息》2022,20(3):140-143

WebGIS课程是GIS专业课程建设的重要分支,其教学实践对GIS本科人才培养与就业具有重要作用.首先分析了WebGIS课程的特点,指出开源GIS技术能有效促进高校学生科研能力和创新思维的培养;然后对现有的开源GIS软件与技术进行了总结,并以山东建筑大学地理信息科学专业的《网络GIS设计与实现》教学课程与课程设计为例,...  相似文献   

十八世纪我国长江下游等地区的气候   总被引：9，自引：1，他引：8  

龚高法  张丕远  张瑾瑢 《地理研究》1983,2(2):20-33

关于1500-1900年小冰期气候问题是历史时期气候变化研究中的一个重要课题.本文根据我国晴雨录、古代天气日记、诗文等历史文献资料来讨论小冰期中一个相对温暖时期(十八世纪)的气候.研究表明,这个时期冬季(12-2月)平均气温比现在低1.0℃(杭州、苏州)到1.5℃(南京).但其间还有10年以上时间尺度的起伏波动,在温暖时段,冬季平均气温仍比现在低0.5-1.6℃,在寒冷时段,冬季平均气温比现在低2.1-2.4℃.但十八世纪大部分时期春季反比现在暖些.对湿润状况分析表明,十八世纪长江中下游地区比现代潮湿,反映了当时大气环流与今有较大差别.杭州古风向记录(1723-1769年)分析表明,当时盛行风向与现在不同:冬季西北风频率比现在多,春秋盛行东北风时间比现在长,频率比现在多.  相似文献   

TDC-GPX在卫星激光测距中的应用   总被引：1，自引：0，他引：1  

朱威  王培源  李欣  林强 《大地测量与地球动力学》2011,31(Z1):174-177

利用高精度时间测量芯片TDC-GPX以提高卫星激光测距系统中的时间测量精度,再结合FPGA的大规模数字集成设计,从而提高了卫星激光测距系统的测量精度.  相似文献   

网络数据流分析方法   总被引：2，自引：0，他引：2  

罗莎  朱威  王培源  邹彤  郭唐永 《大地测量与地球动力学》2011,31(Z1):146-148,151

介绍网络数据流中最主要的数据流挖掘技术.  相似文献   

原子钟的发展与应用     

沈基玲  郭唐永  王培源 《大地测量与地球动力学》2007,27(Z1):122-125

介绍原子钟的原理、发展状况和应用，并比较它们的主要功能。  相似文献   

COMBINED EFFECTS OF TEMPERATURE, IRRADIANCE AND SALINITY ON GROWTH OF DIATOM SKELETONEMA COSTATUM   总被引：2，自引：0，他引：2  

Yan Tian  Zhou Mingjiang  Qian Peiyuan 《中国海洋湖沼学报》2002,20(3):237-243

3-factor experiment was used to study the combined effects of temperature, irradiance and salinity on the growth of an HAB species diatomSkeletonema costatum (Grev.) Cleve. The results showed that temperature (12, 19, 25, 32 °C), irradiance (0.02, 0.08, 0.3, 1.6)×10¹⁶ quanta/(s·cm²)) and salinity (10, 18, 25, 30, 35) significantly influenced the growth of this species. There were interactive effects between any two of and among all three physical factors on the growth. In the experiment, the most optimal growth condition forS. costatum was temperature of 25°C, salinity of 18–35 and irradiance of 1.6×10¹⁶ quanta/(s·cm²). The results indicatedS. costatum could divide at higher rate and were more likely to bloom under high temperature and high illumination from spring to fall. It was able to distribute widely in ocean and estuary due to its adaptation to a wide range of salinities. This study was supported by the PREPP and National Key Basic Research Project (2001CB4097) NNSFC No. 39950001, 20177023, 49576301, 49906007 and KZCX2-206.  相似文献   

Competition Among Dinoflagellate Alexandrium Tam—arense, Raphidophyte Heterosigma Carterae and Diatom Skeletonema Costatum under Combinations ofTwo Temperatures and Five Salinities     

颜天周名江  钱培元 《中国海洋湖沼学报》2003,21(3):245-250

Competition among HAB (Harmful Algal Bloom) species Dinoflagellate Alexandrium tamarense, Raphidophyte Heterosigma carterae, and Diatom Skeletonema costatum was studied in the laboratory. Experiments with these three major HAB species under combinations of different salinities (10, 18, 25, 30, 35) and temperatures (19℃, 25℃) were carried out. The results showed that S. costatum successfully competed with the other two species at salinities of 18, 25,30, and 35 at temperatures of 19℃ and 25℃. However, H. carterae showed its advantage at low salinity of 10 and became the single dominant species at salinity 10 and 25℃. A. tamarense could not compete successfully with the other two species especially at low salinities. However, it could remain at low density in the presence of higher densities of other algae.  相似文献   

Improved precise point positioning in the presence of ionospheric scintillation   总被引：2，自引：2，他引：0  

Xiaohong Zhang  Fei Guo  Peiyuan Zhou 《GPS Solutions》2014,18(1):51-60

Ionospheric disturbances can be detrimental to accuracy and reliability of GNSS positioning. We focus on how ionospheric scintillation induces significant degradation to Precise Point Positioning (PPP) and how to improve the performance of PPP during ionospheric scintillation periods. We briefly describe these problems and give the physical explanation of highly correlated phenomenon of degraded PPP estimates and occurrence of ionospheric scintillation. Three possible reasons can contribute to significant accuracy degradation in the presence of ionospheric scintillation: (a) unexpected loss of lock of tracked satellites which greatly reduces the available observations and considerably weakens the geometry, (b) abnormal blunders which are not properly mitigated by positioning programs, and (c) failure of cycle slip detection algorithms due to the high rate of total electronic content. The latter two reasons are confirmed as the major causes of sudden accuracy degradation by means of a comparative analysis. To reduce their adverse effect on positioning, an improved approach based on a robust iterative Kalman filter is adopted to enhance the PPP performance. Before the data enter the filter, the differential code biases are used for GNSS data quality checking. Any satellite whose C1–P1 and P1–P2 biases exceed 10 and 30 m, respectively, will be rejected. Both the Melbourne–Wubbena and geometry-free combination are used for cycle slip detection. But the thresholds are set more flexibly when ionospheric conditions become unusual. With these steps, most of the outliers and cycle slips can be effectively detected, and a first PPP estimation can be carried out. Furthermore, an iterative PPP estimator is utilized to mitigate the remaining gross errors and cycle slips which will be reflected in the posterior residuals. Further validation tests based on extensive experiments confirm our physical explanation and the new approach. The results show that the improved approach effectively avoids a large number of ambiguity resets which would otherwise be necessary. It reduces the number of re-parameterized phase ambiguities by approximately half, without scarifying the accuracy and reliability of the PPP solution.  相似文献   

基于联合主题特征的网络新闻文本蕴含环境污染事件检测     

黄宗财  仇培元  陆锋  吴升 《地球信息科学学报》2019,21(10):1510-1517

网络新闻文本在环境污染事件感知方面具有重要的应用价值。然而,由于环境污染事件的“多米诺效应”,网络新闻文本往往存在对多类型污染事件的混合描述,现有事件检测方法容易导致文本分类错误。本文提出一种基于联合主题特征的网络新闻文本蕴含环境污染事件检测方法,通过兼顾环境网络新闻文本的全局特征和主题分布特征来改善检测分类效果。该方法采用词频-逆文档频率向量对文档进行全局特征表示,并结合文档的主题分布特征向量,构建联合主题特征向量作为监督分类模型的输入,实现环境污染事件检测。实验结果表明,使用联合主题特征的支持向量机方法进行事件类别检测平均F1值相较于全局特征提高15%,相较于主题特征提高36%。本文提出的网络新闻文本蕴含环境污染事件检测方法可支持污染事件类型检测和影响信息抽取,有助于环境污染事件的时空统计与变化趋势预测。  相似文献   

互联网文本蕴含道路交通信息抽取的模式匹配方法     

仇培元  张恒才  陆锋 《地球信息科学学报》2015,17(4):416-422

互联网页面和社交网络文本中蕴含丰富的道路交通信息,是其他交通信息采集平台的有效补充。然而,自然语言文本形式的交通信息多以线性参考或地标方位描述交通事件空间位置,且大量存在事件元素缺失或隐含现象,对交通信息的自动化抽取有着较大影响。考虑到交通信息的自然语言表达方式虽然自由随意,但表达模式相对固定,提出一种从互联网文本中抽取道路交通信息的模式匹配方法。首先,基于道路交通事件描述的语言特征构建模式库;然后,以特征词词性序列的形式表达互联网文本和抽取模式,利用DTW距离度量序列相似度,实现抽取模式匹配;最后,在匹配抽取模式和填补规则指导下获取结构化的道路交通信息。由上海市城市交通相关门户网站和微博客平台的实验过程显示,本文所提出的模式匹配方法,抽取道路交通信息的准确率和召回率分别达到90%和80%以上,表明该方法能有效抽取互联网文本蕴含的道路交通信息,且实现过程相对简单,易于扩展,具有可用性。  相似文献