基于PBLC算法的滑坡空间易发性分析

滑坡空间易发性统计模型的构建需要正样本(滑坡点)和负样本(非滑坡点)两类数据,但历史观测数据仅记录了正样本,而负样本的选取容易受到正样本污染,因为没有滑坡记录的地方也可能在过去或未来发生滑坡,从而导致模型的预测精度与稳定性受到影响。针对此问题,将前期提出的半监督学习算法PBLC(positive and background learning with constraints)应用于滑坡空间易发性分析,探讨其解决负样本污染问题的有效性。本文以粤东地区为研究区,选择高程、坡度、坡向、剖面曲率、距离道路最短距离、距离断层线最短距离、距水系最短距离、年平均降雨量、归一化植被指数和地理坐标共11个影响因子作为环境变量。结果表明,与传统的人工神经网络模型相比,基于PBLC算法的预测概率取值范围更为合理,预测结果更加稳定,且预测精度随背景样本数量增加而提高;粤东地区的滑坡灾害高易发区集中于北部和西南区域,坡度和高程是影响该地区滑坡易发性的主要因子。结果表明,半监督学习算法PBLC可以有效解决滑坡统计建模过程负样本污染的问题,提高模型预测精度。

超早期与早期手术对高血压脑出血患者的疗效比较

目的:分析超早期与早期手术对高血压脑出血患者的治疗效果。方法:将101例高血压脑出血患者随机分为早期组(50例)以及超早期组(51例),早期组患者从发病到手术时间为6~24 h,超早期组患者从发病到手术时间<6 h,比较两组患者的近期治疗效果。结果:超早期组手术治疗6个月后的优良率高于早期组(P<0.05),超早期组的脑水肿持续时间、术后脑残留血量、平均住院天数以及脑水肿体积均低于早期组(P<0.05)。结论:超早期手术治疗高血压脑出血患者的治疗效果优于早期手术治疗。

基于GIS的风暴潮灾害风险预警方法研究

风暴潮灾害是对沿海地区破坏性巨大的一种海洋灾害,风暴潮灾害监测预警是极为重要的减灾非工程措施。目前,国家海洋环境预报中心发布的风暴潮灾害预警主要是风暴潮增水预警,即增水值是多少,但风暴潮灾害事件的影响取决于风暴增水、增水发生时天文潮位、沿海地形、海堤高程及社会经济分布状况等多方面因素,仅有风暴增水的预警不能直观地预见灾害即将带来的影响。提出基于GIS对风暴潮灾害事件影响进行评估的监测预警方法,并以201604号台风"妮妲"为例进行了说明。首先,通过对天文潮和风暴增水预报获取目标区域潮位预报;然后,基于Flood Area构建风暴潮漫滩淹没模型,对风暴潮漫滩淹没进行仿真模拟;最后,结合淹没范围、深度和社会经济数据,评估风暴潮灾害事件可能导致的受灾人口数和GDP损失,基于风暴潮灾害风险进行预警分级,该方法可以为风暴潮灾害事件的应急管理提供决策支持。

20 000箱级LNG燃料集装箱船精度控制方案

精度管理是现代造船的重要课题,钢结构制造的精确性体现了船舶建造水平。文章以配备LNG燃料舱的20 000箱级集装箱船为例,简要分析了新型集装箱船精度控制存在的问题和难点,有针对性地提出了相应解决方案,制定了基于解决方案的控制标准以规范后续生产。研究和分析过程中应用了有限元计算、三维测量以及无余量模拟等手段与工具,遵循理论与实践相结合的思路,循序渐进,不断推进实物尺寸、计算结果、控制标准三者的有机统一,最终保证了控制标准切实可行,实现了实物尺寸精确性良好的预期目的。文章对超大型集装箱船所做的研究、分析和管理经验对领域内相关工作者具备一定的参考价值。

城市暴雨内涝综述:特征、机理、数据与方法

建成环境的高空间异质性与致灾过程的复杂性给城市暴雨内涝研究带来巨大的挑战,具体表现为模型代表性不够、计算效率低、基础数据和验证数据匮乏。以机器学习为代表的人工智能技术、高分遥感和互联网大数据的快速发展则为城市暴雨内涝研究提供了新的契机。论文结合人工智能、高分遥感和互联网大数据等新技术发展,从特征、机理、数据与方法4个维度对暴雨内涝的研究现状和发展趋势进行了系统总结,主要结论包括:(1)暴雨内涝具有短历时性、空间散布性、连锁性和突变性,其热点呈现空间上的动态迁移特征。(2)降雨时空特征和城市化程度决定暴雨内涝灾害的量级,地形条件尤其是微地形则决定发生位置和内涝频率。地形控制作用指数(topographic control index,TCI)对暴雨内涝发生位置具有良好的指示能力。(3)排水管网、高精度地形和不透水面分布是暴雨内涝模拟的关键基础数据;降雨过程的高时空变异性是暴雨内涝近实时预报预警的主要瓶颈,需要充分利用天气雷达观测提高其精准度;互联网众包大数据是获取高空间覆盖度暴雨内涝灾情信息的新途径,但也面临不同类型信息融合、提炼和质量控制的挑战。(4)结合水动力模拟与机器学习可建立兼具物理基础和计算效率的暴雨内涝模拟方法,是实现近实时模拟与快速预报预警的有效途径。

植保无人机投放螟黄赤眼蜂蜂球防治稻纵卷叶螟田间效果评价

研究植保无人机投放螟黄赤眼蜂防治稻纵卷叶螟的田间效果,为促进水稻病虫害绿色防控技术与统防统治相融合提供参考数据。在南宁市宾阳县古辣镇不丈垌的稻田设置2个放蜂区,采用植保无人机投放可降解球形放蜂器,每个球形放蜂器含2000头螟黄赤眼蜂,每次每667m^(2)投放4个球形放蜂器,共投放3次。放蜂前,放蜂区1、放蜂区2和对照区螟卵寄生率均为0,卷叶率分别为0.04%、0.05%和0.11%;3次放蜂后,放蜂区1、放蜂区2平均寄生率53.33%,防效分别为66.02%和70.87%,与农户自防区相比寄生率更高,防效更好。应用植保无人机投放螟黄赤眼蜂可有效控制稻纵卷叶螟田间为害率,提高卵寄生率,是稻纵卷叶螟的有效生物防治措施之一。

协同多时相波谱特征的不透水面信息级联提取

不透水面作为反应城市表征变化和区域城镇化的重要技术指标,其位置、图斑大小、空间分布等信息在地表水热循环和能量平衡等领域被广泛需求。传统方法大都基于单一时相信息提取不透水面,而忽略多时相所蕴含的丰富信息。因此,本文提出多时相信息融合的不透水面级联提取方法,利用Landsat-8 OLI遥感影像分析归一化植被指数(Normalized Difference Vegetation Index, NDVI)、改进的归一化水体指数(Modified Normalized Difference Water Index, MNDWI)和归一化建筑指数(Normalized Difference Building Index, NDBI)年内时序变化特点和典型地物间多时相波谱曲线的协同特征,并归纳不透水面多时相变化规律;再根据先验知识所获取的有效地表信息,进行多时相分级提取不透水面信息。此外,基于实地考察数据和同期2 m GF-1遥感影像屏幕数字化生成30 m不透水面图斑,进行精度验证、分析和对比单时相、四季相及多时相3种时序情况下的提取精度。结果表明:单时相提取不透水面总精度最低,四季相提取精度优于单时相,而多时相提取精度最高(精度可达93.66%,Kappa系数为0.81)。本方法在偏远城镇不透水面的有效识别中显露潜在优势,可为不透水面提取方法融合时序波谱特征提供新思路。

China’s urban expansion from 1990 to 2010 determined with satellite remote sensing

Based on the same data source of Landsat TM/ETM+ in 1990s,2000s and 2010s,all urban built-up areas in China are mapped mainly by human interpretation.Mapping results were checked and refined by the same analyst with the same set of criteria.The results show during the last 20 years urban areas in China have increased exponentially more than 2 times.The greatest area of urbanization changed from Northeastern provinces in 1990s to the Southeast coast of China in Jiangsu,Guangdong,Shandong,and Zhejiang in 2010s.Urban areas are mostly converted from croplands in China.Approximately 17750 km 2 croplands were converted into urban lands.Furthermore,the conversion from 2000 to 2010 doubled that from 1990 to 2000.During the 20 years,the most urbanized provinces are Jiangsu,Guangdong,Shandong and Zhejiang.We also analyzed built-up areas,gross domestic production (GDP) and population of 147 cities with a population of greater than 500000 in 2009.The result shows coastal cities and resource-based cities are with high economic efficiency per unit of built-up areas,resource-based cities have the highest population density,and the economic efficiency of most coastal provinces are lower than central provinces and Guangdong.The newly created urban expansion dataset is useful in many fields including trend analysis of urbanization in China;simulation of urban development dynamics;analysis of the relationship among urbanization,population growth and migration;studies of carbon emissions and climate change;adaptation of climate change;as well as land use and urban planning and management.

Mapping wetland changes in China between 1978 and 2008

Four wetland maps for all China have been produced,based on Landsat and CBERS-02B remote sensing data between 1978 and 2008 (1978,1990,2000 and 2008).These maps were mainly developed by manual interpretation and validated by substantial field investigation in 2009.Based on these maps,we analyzed the 2008 wetland distribution in China and discussed wetland changes and their drivers over the past 30 years.(i) There were about 324097 km 2 of wetlands in 2008,for which inland marshes or swamps were the most common wetland type (35%),with lakes (26%) second.Most of the wetlands were in Heilongjiang,Inner Mongolia,Qinghai and Tibet,occupying about 55% of the national wetland area.(ii) From 1978 to 2008,China's wetland area continually and significantly decreased,by about 33% based on changes in the wetland map.This was in sharp contrast to the increase in artificial wetlands,which increased by about 122%.Inland marshes accounted for the main loss of total wetlands from 1978 to 2000.From 2000 through 2008,riverine and lacustrine wetlands constituted the main wetland loss.Fortunately however,the rate of wetland loss decreased from 5523 to 831 km 2 /a.(iii) The change ratio of lost natural wetlands (including inland and coastal wetlands) to non-wetlands has decreased slightly over the past 30 years.From 1978 to 1990,nearly all natural wetlands (98%) lost were transformed into non-wetlands.However,the ratio declined to 86% from 1990 to 2000,and to 77% from 2000 to 2008.(iv) All Chinese provinces were divided into three groups according to patterns of wetland changes,which could relate to the driving forces of such changes.Tibet was completely different from other provinces,as it was one representative example in which there was a net wetland increase,because of global warming and decreased human activity since 1990.Increased economic development caused considerable wetland loss in most eastern provinces,and artificial wetlands increased.

Geographical characteristics of China’s wetlands derived from remotely sensed data

In this paper, we report the first wetland mapping of the entire China using Landsat enhanced thematic mapper plus (ETM+) data. These data were obtained from the Global Land Cover Facility at the University of Maryland spanning from 1999 to 2002. A total of 597 scenes of Landsat images were georeferenced and mosaiced. Manual image interpretation of satellite images was aided with elevation data, soil data, land cover/land use data and Google Earth. The minimum mapping unit is 10 pixel × 10 pixel, equivalent to 9 ha. The aim of our first round of mapping was only targeted at the boundary delineation of any type of wetland except those wetlands that are under agricultural use (i.e., paddy fields), which has already been well mapped by others. Our interpretation results indicate that a total of 359478 km2 of wetlands are of non-agricultural use. Among our preliminarily mapped wetland, 339353 km2 are inland wetland, 2786 km2 are non-agricultural artificial wetland, and 17609 km2 are coastal wetland. Because low-tide is rarely captured in satellite images, an under-estimation of coastal wetland is inevitable. We conducted some statistics based on our mapped wetlands and compared them with those previously obtained from a number of sources including a land cover/land use map made with satellite images during the late 1990s and early 2000s, a marshland map developed in approximately the same period, survey data of coastal wetland in early 1980s, and area data for approximately 400 larger patches of marshland in China compiled in 1996. Because some inconsistencies exist in the guidelines of those different wetland surveys, difference in area is expected. Some further comparison indicates that the wetland distributions derived from the preliminary wetland map are reasonable and more objective than other sources. The mapping process also indicated that the method adopted by us was efficient and cost-effective. We also found that in order to ensure comparability of the wetland maps developed at different times, a set of standard guidelines on the wetland categories to be mapped, and the mapping methods to be used must be well conceived, developed and effectively employed. We carried out some initial geographical analysis on the distribution of wetlands.

An improved Landsat Image Mosaic of Antarctica

A revised Landsat Image Mosaic of Antarctica (LIMA) is presented, using the 1073 multi-band scenes of the original Landsat-7 ETM+ LIMA image collection available at the United States Geological Survey (USGS: http://lima.usgs.gov/). Three improvements have been applied during the data processing: (1) DN saturation is adjusted by adopting a linear regression, which has a lower root mean square error than the ratio regression used by LIMA; (2) solar elevation angle is calculated using pixel-level latitude/longitude and the acquisition time and date of the central pixel of the scene, improving slightly upon the bilinear interpolation of the solar elevation angles of scene corners applied in LIMA; and (3) two additional image bands, Band 5 and Band 7, are sharpened using the panchromatic band (Band 8) and a Gram-Schmidt Spectral Sharpening algorithm to more easily distinguish snow, cloud and exposed rocks. The final planetary reflectance product is stored in 16-bit bands to preserve the full radiometric content of the scenes. A comparative statistical analysis among 12 sample regions indicates that the new mosaic has enhanced visual qualities, information entropy, and information content for land cover classification relative to LIMA.

Using a global reference sample set and a cropland map for area estimation in China

A technically transparent and freely available reference sample set for validation of global land cover mapping was recently established to assess the accuracies of land cover maps with multiple resolutions.This sample set can be used to estimate areas because of its equal-area hexagon-based sampling design.The capabilities of these sample set-based area estimates for cropland were investigated in this paper.A 30-m cropland map for China was consolidated using three thematic maps(cropland,forest and wetland maps)to reduce confusion between cropland and forest/wetland.We compared three area estimation methods using the sample set and the 30 m cropland map.The methods investigated were:(1)pixel counting from a complete coverage map,(2)direct estimation from reference samples,and(3)model-assisted estimation combining the map with samples.Our results indicated that all three methods produced generally consistent estimates which agreed with cropland area measured from an independent national land use dataset.Areas estimated from the reference sample set were less biased by comparing with a National Land Use Dataset of China(NLUD-C).This study indicates that the reference sample set can be used as an alternative source to estimate areas over large regions.