基于无人机高光谱数据的玉米叶面积指数估算

无人机高光谱遥感是低成本、高精度获取精细尺度农作物生物物理参数和生物化学参数的新型手段,以此快速反演叶面积指数（Leaf Area Index, LAI）对作物长势评价、产量预测具有重要意义。以山东禹城市玉米为研究对象,利用PROSAIL辐射传输模型模拟玉米冠层反射率获取LAI特征响应波段结合相关性定量分析获取对LAI变化最为敏感的波段,并以此计算6种植被指数（Vegetation Index,VI）,利用6种回归模型分别对单一特征波段和VI进行反演建模,以实测LAI评定模型精度。研究表明,光谱反射率中516、636、702、760和867 nm等波段对LAI变化最为敏感,以此建立的单一特征波段反演模型预测LAI精度R2为0.44~0.58;RMSE为0.16~0.18,其中636 nm建立的模型(LAI=21.86exp(-29.47R₆₃₆))相比其他反演模型预测精度较高（R2=0.58,RMSE=0.16）;6种植被指数与LAI高度相关,相关性系数R ²为0.85~0.86,以此建立的反演模型相比单一特征波段反演模型精度有所提高,R2为0.66~0.72,RMSE为0.12~0.14;其中mNDVI构建的LAI估算模型（LAI=exp(2.76~1.77/mNDVI))精度最高（R2=0.72,RMSE=0.13）。无人机高光谱遥感是快速、无损监测农作物生长信息的有效手段,为指导精细化尺度作物管理提供依据。     

长春百年城市土地利用空间结构演变特征研究

综合集成SPOT5、TM遥感影像,大比例尺地形图、城市现状图、城市规划图、历史地图等空间数据建立了一种"面向对象分割"的信息提取方法重建长春1905年、1932年、1954年、1976年、1990年和2004年共6期城市土地利用空间分类信息.利用分形模型、空间集聚模型、空间圈层结构模型分析长春百年来城市土地利用空间结构演变特征.结果表明:"面向对象分割"的多源源空间信息集成下的系列城市土地利用分类信息提取方法在提高信息提取效率、分类精度以及进一步的空间分析定位精度方面具有较好的效果.     

A hybrid message passing/shared memory parallelization of the adaptive integral method for multi-core clusters

A hybrid message passing and shared memory parallelization technique is presented for improving the scalability of the adaptive integral method (AIM), an FFT based algorithm, on clusters of identical multi-core processors. The proposed hybrid MPI/OpenMP parallelization scheme is based on a nested one-dimensional (1-D) slab decomposition of the 3-D auxiliary regular grid and the associated AIM calculations: If there are M processors and T cores per processor, the scheme (i) divides the regular grid into M slabs and MT sub-slabs, (ii) assigns each slab/sub-slab and the associated operations to one of the processors/cores, and (iii) uses MPI for inter-processor data communication and OpenMP for intra-processor data exchange. The MPI/OpenMP parallel AIM is used to accelerate the solution of the combined-field integral equation pertinent to the analysis of time-harmonic electromagnetic scattering from perfectly conducting surfaces. The scalability of the scheme is investigated theoretically and verified on a state-of-the-art multi-core cluster for benchmark scattering problems. Timing and speedup results on up to 1024 quad-core processors show that the hybrid MPI/OpenMP parallelization of AIM exhibits better strong scalability (fixed problem size speedup) than pure MPI parallelization of it when multiple cores are used on each processor.     

服务质量敏感型空间信息服务引擎设计

为避免基于速率控制的TCP友好拥塞控制策略在调整多媒体流的发送速率时变化波动较大的问题,提出一种新的改进策略——延迟预警算法,通过在发送端设置延迟预警信号,对TFRC流的发送速率进行调整,使其在与TCP流的竞争中变得更加平滑。仿真实验结果表明,该算法能够有效改善TFRC的性能,具有良好TCP友好性及速率平滑性。     

一种基于Lucene改进的全文检索工具包

基于Lucene实现了一种改进的全文检索引擎工具包ELucene。它引入了索引配置文件,可针对不同应用背景来灵活定制索引的细节;提供了定时自动更新索引的功能;通过动态多态机制实现了支持多种索引数据源的功能;ELucene内部设计了引擎基础对象类,并以静态对象的方式运行来避免频繁读取索引文件带来的性能损失。面向检索,提供了检索请求类和检索响应类来分别封装用户的查询要求和查询结果集,并设计实现了一些实用的查询输入和输出处理的方法。基于ELucene的元数据搜索系统已成功应用到“国家科学数据共享工程：地球系统科学数据共享网”中。     

Simulating canopy temperature for modelling heat stress in cereals

Crop models must be improved to account for the effects of heat stress events on crop yields. To date, most approaches in crop models use air temperature to define heat stress intensity as the cumulative sum of thermal times (TT) above a high temperature threshold during a sensitive period for yield formation. However, observational evidence indicates that crop canopy temperature better explains yield reductions associated with high temperature events than air temperature does. This study presents a canopy level energy balance using Monin–Obukhov Similarity Theory (MOST) with simplifications about the canopy resistance that render it suitable for application in crop models and other models of the plant environment. The model is evaluated for a uniform irrigated wheat canopy in Arizona and rainfed maize in Burkina Faso. No single variable regression relationships for key explanatory variables were found that were consistent across sowing dates to explain the deviation of canopy temperature from air temperature. Finally, thermal times determined with simulated canopy temperatures were able to reproduce thermal times calculated with observed canopy temperature, whereas those determined with air temperatures were not.     

Monitoring of forest virtual water in Hunan Province,China, based on HJ-CCD remote-sensing images and pattern analysis

Virtual water has become an important part of global water supply and demand and has led to the globalization of water. Virtual water research most mainly focused on the field of agriculture. Minimal attention has been devoted to forest virtual water (FVW). To our knowledge, no research on the monitoring and analysis of FVW through remote-sensing technology has been conducted. In this study, based on object-oriented technology and through the use of 30 scenes from multi-temporal Chinese HJ-CCD images, we monitored FVW in Hunan Province, China, in 2010 and analysed the pattern of FVW. Results showed that the amount of FVW is large and greater than that of entity water. Hunan Province had 5.83 × 10¹¹m³ FVW in 2010, which was 3.09 times the amount of agriculture and livestock. FVW was thrice as large as the total entity water, 4.07 times the amount of surface water, and 14.57 times the amount of underground water in Hunan Province. The distribution of FVW in Hunan Province is uneven and presents a trend that gradually increases from northeast to southwest; nevertheless, the trend is reasonable and in favour of alleviating and optimizing the pattern of water resources. Our analysis indicated that we need to improve the cognition of virtual water and pay due attention to FVW from the perspective of water management and allocation. Our results also indicated that forest and woody products are water intensive. An efficient method of balancing FVW and other uses of water is thus required; control and management of water consumption in forests should also be implemented under the condition of protecting the environment. For China, woody forest products should be mainly imported to improve water-use efficiency and relieve the shortage of water. Meanwhile, remote-sensing technology is a useful tool, and Chinese HJ-CCD images are an important data source for the estimation of FVW.     

基于GIS技术的市区级环境事故应急处置系统

阐述了市区级环境事故应急处置系统的一般特点、处置工作内容与功能需求以及信息需求,这些需求需要GIS技术来满足。因此,探讨了GIS技术应用于环境事故应急处置时所能发挥的重要作用,并以张家口市环境事故应急处置系统为简单实例,介绍了GIS技术在环境管理中的部分实际应用。最后对GIS在市区级环境事故应急处置中的应用前景提出了一些看法。     

SWATShare – A web platform for collaborative research and education through online sharing,simulation and visualization of SWAT models

Hydrologic models for a particular watershed or a region are created for addressing a specific research or management problem, and most of the models do not get reused after the project is completed. Similarly, multiple models may exist for a particular geographic location from different researchers or organizations. To avoid the duplication of efforts, and enable model reuse and enhancement through collaborative efforts, a prototype cyberinfrastructure, called SWATShare, is developed for sharing, execution and visualization of Soil and Water Assessment Tool (SWAT). The objective of this paper is to present the software architecture, functional capabilities and implementation of SWATShare as a collaborative environment for hydrology research and education using the models published and shared in the system. Besides the capability of publishing, sharing, discovery and downloading of SWAT models, some of the functions in SWATShare such as model calibration are supported by providing access to high performance computing resources including the XSEDE and cloud. Additionally, SWATShare can create dynamic spatial and temporal plots of model outputs at different scales. SWATShare can also be used as an educational tool within a classroom setting for comparing the hydrologic processes under different geographic and climatic settings. The utility of SWATShare for collaborative research and education is demonstrated by using three case studies. Even though this paper focuses on the SWAT model, the system’s architecture can be replicated for other models as well.     

等高线树构建及高保真DEM构建

研究正负地貌等高线（含未闭合等高线）的空间关系。首先将未闭合等高线分为完全开放等高线和贴边等高线,分别进行自动闭合处理。然后使用多边形叠加分析的方法判断闭合等高线之间的关系,构建等高线树。通过对等高线树结构的遍历,获取格网点高程值的上下界,将上下界输入到高精度曲面建模区域优化控制方法进行约束优化控制模拟,能保证模拟结果的回放等高线与原始等高线的最大距离不超过一个栅格的宽度。最后对高斯合成曲面和扫描矢量化等高线两个实例进行论证。