A probabilistic relaxation approach for matching road networks

Geospatial data matching is an important prerequisite for data integration, change detection and data updating. At present, crowdsourcing geospatial data are attracting considerable attention with its significant potential for timely and cost-effective updating of geospatial data and Geographical Information Science (GIS) applications. To integrate the available and up-to-date information of multi-source geospatial data, this article proposes a heuristic probabilistic relaxation road network matching method. The proposed method starts with an initial probabilistic matrix according to the dissimilarities in the shapes and then integrates the relative compatibility coefficient of neighbouring candidate pairs to iteratively update the initial probabilistic matrix until the probabilistic matrix is globally consistent. Finally, the initial 1:1 matching pairs are selected on the basis of probabilities that are calculated and refined on the basis of the structural similarity of the selected matching pairs. A process of matching is then implemented to find M:N matching pairs. Matching between OpenStreetMap network data and professional road network data shows that our method is independent of matching direction, successfully matches 1:0 (Null), 1:1 and M:N pairs, and achieves a robust matching precision of above 95%.     

不同螺距联合ASIR重建技术在COVID-19胸部低剂量CT扫描中的应用研究

目的:探讨2019冠状病毒病(COVID-19)患者使用大螺距联合自适应统计迭代重建技术行低剂量扫描的可行性,比较辐射剂量及图像质量的差异.方法:收集我院确诊为COVID-19的病例共91例作为低剂量组,同时选取同期于我院行新冠肺炎筛查的91例未确诊为COVID-19的患者作为常规剂量组.低剂量组使用大螺距扫描联合自适...     

A Pattern‐Based Approach for Matching Nodes in Heterogeneous Urban Road Networks

This article presents an approach to hierarchical matching of nodes in heterogeneous road networks in the same urban area. Heterogeneous road networks not only exist at different levels of detail (LoD), but also have different coordinate systems, leading to difficulties in matching and integrating them. To overcome these difficulties, a pattern‐based method was implemented. Based on the authors' previous work on detecting patterns of divided highways, complex road junctions, and strokes to eliminate the LoD effect of road networks, the proposed method extracts the local networks around each node in a road network and uses them as the matching units for the nodes. Second, the degree of shape similarity between the matching units is measured using a Minimum Road Edit Distance based on a transformation. Finally, the proposed method hierarchically matches the nodes in a road network using the Minimum Road Edit Distance and eliminates false matching nodes using M‐estimators. An experiment involving matching heterogeneous road networks with different LoDs and coordinate systems was carried out to verify the validity of the proposed method. The method achieves good and effective matching regardless of differences in LoDs and road‐network coordinate systems.     

无人机航测系统的海岛礁测绘应用研究

介绍了三型基于无人飞行器为平台的航测系统,分析了影响海岛区域无人机影像数据处理精度的因素,无人机航测系统在海岛区应用的技术特点。以该三型系统在我国某海岛区域进行了摄影作业,对实验数据质量、空中三角测量精度、正射影像精度等进行分析。实验结果表明,无人机低空航测系统在海岛区域大比例尺地形测绘或海图修测等领域具有良好的应用前景。     

Reconstructing the extraordinary palaeoflood events during 3200-2800 a BP in the upper reaches of Hanjiang River Valley,China

Palaeoflood hydrology study is a leading subject in global change study. Through field investigation in the upper reaches of Hanjiang River, palaeoflood slackwater deposits (SWD) were found in the bedrock gorges of the Yunxi reach. The results of field observation, laboratory analysis including particle-size distribution and magnetic susceptibility, and comparison with modern flood deposits, the SWD were identified as the most typical Holocene palaeoflood deposits of the Hanjiang River. By using stratigraphic correlation and OSL dating method, the palaeoflood event was dated to be 3200-2800 a BP at the turn from the middle to late Holocene. According to the palaeoflood peak stage and hydraulic parameters, the peak discharges of the palaeoflood were reconstructed as 48,830-51,710 m3/s by using the slope-area method. At same time, the flood peak discharges of 1983, 2005 and 2010 severe floods were reconstructed with the same method and hydraulic parameters in the same cross section. The error between the reconstructed and gauged discharges was 1.99%-4.21%. This showed that the reconstructed palaeoflood peak discharges were reliable. The flood peak discharge-frequency relationship at 10,000-year time scale was established by a combination of the gauged flood, historical flood and palaeoflood hydrological data. These results are very important for hydraulic engineering and flood mitigation on the Hanjiang River.     

Effects of UV-B radiation and different light repair conditions on the early development of the tetraspores of Chondrus ocellatus Holm

The effects of exposure to UV-B radiation,280-315 nm,and dark or dark repair conditions on the early development of Chondrus ocellatus Holm collected from Qingdao coast were studied under the laboratory condition.After being exposed to different doses [0,36,72,108,144 and 180 J/(m 2 · d)] of UV-B radiation,one treatment of tetraspores were put back to normal culture condition (PAR),the other treatment were put into dark condition to repair for 2 h.During the cultivation,the diameter of the tetraspores were recorded every 4 d till the 50th day when vertical branches formed in all treatments.Then at the 50th day,CPDs,phycoerythrin,chlorophyll a and MAAs (Palythine and asterina-330) were measured.The results showed that low doses UV-B radiation could significantly accelerate the growth rate of the tetraspores of C.ocellatus and the growth rate reduced gradually with UV-B radiation keep on increasing.The variation trend of both the phycoerythrin and chlorophyll a concentration reduced significantly ( P < 0.05) once given the UV-B radiation. Under UV-B stress,the CPDs were induced,and the concentrations of CPDs were significant low in dark repair groups.The data of MAAs analyzed by LC/MS in the tetraspores of C. ocellatus suggested that there were two MAAs formed (palythine and asterina-330) after UV-B radiation induced, and low dose of UV-B irradiation could significantly induced the concentration of MAAs.From the growth and development state of the tetraspores,negative effects of UV-B radiation on the dark repair groups were more serious than PAR.     

毛乌素沙地东南缘植被NDVI时空变化及其对气候因子的响应

了解植被生长对气候变化的响应是厘清生态系统动态关系的重点。基于1990—2018年气象数据和归一化植被指数（NDVI）,应用偏相关分析与地理探测器等方法,分析了在生长季,毛乌素沙地东南缘不同类型植被年均NDVI的变化趋势,探讨了年均气温与年总降水量对各类型植被的影响。结果表明：（1） 1990—2018年生长季研究区植被年均NDVI显著与极显著增加面积达97.9%,整体生态环境质量大幅度改善。2005年之前植被年均NDVI增速缓慢,此后以0.011·a^-1的速率发生了突变增加,其中灌丛类植被年均NDVI增长幅度最大。（2） 2000年为年总降水量与年均气温的趋势突变点,突变前年总降水量以-5.510 mm·a^-1的速率减少,此后以5.541 mm·a^-1的速率增加,且主要依赖于大雨雨量的增加;年均高温与年均低温在突变前上升速率分别为0.122 ℃·a^-1与0.230 ℃·a^-1,突变后,年均高温下降速率为-0.014 ℃·a^-1,而年均低温上升速率为0.022 ℃·a^-1。（3） 在植被年均NDVI缓慢增长阶段（1990—2005年）,年均低温对植被影响较大,与不同类型植被年均NDVI多呈显著正相关;在植被年均NDVI快速增长阶段（2006—2018年）,年总降水量与不同类型植被年均NDVI呈显著正相关,大降雨事件的频发使得降水量对于植被的生长起主导作用。年总降水量与年均气温尤其是年均低温的交互作用是促进植被生长的关键。     

青藏高原东部黄河切开若尔盖湖盆的沉积证据与年代研究

对青藏高原东部若尔盖盆地内外实地考察,在玛曲瓶颈段黄河二级阶地前沿陡坎,发现了含有古深湖相和古河床河漫滩相地层序列的典型沉积剖面。通过沉积物粒度特征分析和光释光(optically stimulated luminescence,OSL)测年,研究结果表明：① 剖面下部淡蓝灰色古深湖相沉积层为深水厌氧环境下形成的湖相沉积物,而覆盖其上的杂色卵石层夹淡黄橙色透镜状沙层则是古河床河漫滩相沉积物,指示了强动力流水作用过程。这2组地层的不整合接触关系,是黄河切开若尔盖湖盆导致古湖水外泄的直接证据。② 剖面古深湖相沉积层顶部和古滨浅湖相沉积层底部的OSL测年结果表明,古黄河在37 ka BP切开若尔盖湖盆,导致湖水外泄,35 ka BP湖水变浅消失,黄河沟通了若尔盖盆地水系。③ 晚更新世东昆仑大断裂强烈的新构造运动和37 ka 温暖湿润气候的综合影响使得尚处于玛曲断陷谷地草原的古黄河源溯源侵蚀加剧,由西向东在玛曲城南瓶颈段切开了若尔盖古湖盆,导致古湖水外泄,从而沟通了若尔盖湖盆的水系,使之成为黄河源。该研究结果对于深入理解青藏高原东北部河湖水系演变及黄河水系的形成具有重要的科学意义。     

北京市2006-2016绿色发展水平时空演变特征研究

绿色发展是实现全球可持续发展目标的重要途径。如何平衡经济发展与环境保护,已成为中国首都北京面临的巨大挑战,其研究成果与实践经验可以为其他城市的生态文明建设和绿色发展提供参考建议。本文以北京市2006-2016年的统计数据为基础,构建了北京市绿色发展评价体系,并运用投影寻踪模型和空间分析方法,分析了北京市绿色发展水平的时空演化特征,并进一步探讨了研究期间北京市绿色发展的主导因素。研究结果表明:(1)北京市绿色发展的总体水平和平均水平均呈现明显的上升趋势;(2)北京市各功能区绿色发展存在明显的空间差异,城市外区绿色水平明显高于内区;(3)生态环境以及消费水平是影响北京绿色发展的两个重要因素。