An improved topographic correction model based on Minnaert

The uneven distribution of solar radiation due to topographic relief can significantly change the correlation between reflectance and other features such as biomass in rugged terrain regions. In this article, we use the transfer theory to improve the Minnaert approach. After comparing topographic correction methods for Landsat 8 Operational Land Imager (OLI) and EO-1 Advanced Land Imager (ALI) imagery acquired from the mountainous region in Beijing, China, we used visual inspection, statistical analysis, and correlation analysis to evaluate the algorithms and performance of the proposed Minnaert-E approach. The results indicate that corrections based on non-Lambertian methods have better performance than those based on the Lambertian assumption. The correction performances can be ranked as the Minnaert-E, followed by the Minnaert and the SCS+C corrections, and, finally, the C-HuangWei correction, which performed the worst. We found that the Minnaert-E approach can effectively weaken the influence of terrain relief on pixels and restore the true reflectance of the pixels in the relief area. Further analysis indicates that the Minnaert-E has a better effect on image processing where the slope gradient is restricted to less than 10° or between 30° and 43°.     

Development and evaluation of a DNA microarray assay for the simultaneous detection of nine harmful algal species in ship ballast and seaport waters

Rapid, high-throughput and reliable methods are urgently required to accurately detect and monitor harmful algae, which are responsible for algal blooms, such as red and green tides. In this study, we successfully developed a multiplex PCR-based DNA microarray method capable of detecting nine harmful algal species simultaneously, namely Alexandrium tamarense, Gyrodinium instriatum, Heterosigma akashiwo, Karenia mikimotoi, Prorocentrum donghaiense, Prorocentrum minimum, Ulva compressa, Ulva ohnoi and Ulva prolifera. This method achieved a limit of detection (LOD) of 0.5 ng of genomic DNA (orders of magnitude of the deci-nanogram range) in the tested algae cultures. Altogether, 230 field samples from ship ballast waters and seaport waters were used to evaluate the DNA microarray. The clinical sensitivity and specificity of the DNA microarray assay in detecting field samples were 96.4% and 90.9%, respectively, relative to conventional morphological methods. This indicated that this high-throughput, automatic, and specific method is well suited for the detection of algae in water samples.     

我国草地生态系统碳循环研究进展

文中首先分析了草地生态系统在碳循环研究中的地位和重要性,进而对我国草地生态系统碳循环的研究现状作了较为详尽的阐述,包括植物、凋落物、土壤三大碳库以及主要含碳温室气体通量等,对其主要研究结论进行了深入的剖析。同时提出了今后我国草地生态系统碳循环的重点研究方向和研究领域。     

The comparative study of multi‐site uncertainty evaluation method based on SWAT model

With the recent development of distributed hydrological models, the use of multi‐site observed data to evaluate model performance is becoming more common. Distributed hydrological model have many advantages, and at the same time, it also faces the challenge to calibrate over‐do parameters. As a typical distributed hydrological model, problems also exist in Soil and Water Assessment Tool (SWAT) parameter calibration. In the paper, four different uncertainty approaches – Particle Swarm Optimization (PSO) techniques, Generalized Likelihood Uncertainty Estimation (GLUE), Sequential Uncertainty Fitting algorithm (SUFI‐2) and Parameter Solution (PARASOL) – are taken to a comparative study with the SWAT model applied in Peace River Basin, central Florida. In our study, the observed river discharge data used in SWAT model calibration were collected from the three gauging stations at the main tributary of the Peace River. Behind these approaches, there is a shared philosophy; all methods seek out many parameter set to fit the uncertainties due to the non‐uniqueness in model parameter evaluation. On the basis of the statistical results of four uncertainty methods, difficulty level of each method, the number of runs and theoretical basis, the reasons that affected the accuracy of simulation were analysed and compared. Furthermore, for the four uncertainty method with SWAT model in the study area, the pairwise correlation between parameters and the distributions of model fit summary statistics computed from the sampling over the behavioural parameter and the entire model calibration parameter feasible spaces were identified and examined. It provided additional insight into the relative identifiability of the four uncertainty methods Copyright © 2014 John Wiley & Sons, Ltd.     

细沟形成对坡面产流产沙过程的影响

为探明细沟形成条件下不同土壤坡面水沙变化特性,利用室内模拟降雨试验,分析了塿土和黄绵土在细沟发育及已有细沟条件下的水沙过程变化规律。结果表明,塿土产流快,易形成细沟,细沟发育有明显的规律性,在坡面上呈平行状分布,细沟密度与坡度密切相关,细沟存在会延长产流时间;黄绵土产流慢,较难形成细沟,细沟发育随机性大。细沟发育对产流过程没有明显影响,土壤入渗快慢是两种土壤产流过程存在差异的主要原因。细沟发育程度加剧,会使塿土含沙量的增加速度加快,达到稳定含沙量的时间提前,坡面已有细沟只对稳定含沙量有明显影响,细沟密度增加会使稳定含沙量提高;黄绵土含沙量的变化主要取决于细沟发育过程中的随机性,当细沟侵蚀以崩塌作用为主时,含沙量会出现急剧增加,即使雨强较小,也会产生严重的土壤侵蚀。     

北京城市居民通勤时间变化及影响因素

以2005年和2010年两次问卷调查数据为基础,采用统计分析和地理信息系统技术对北京市区居民通勤时间变化进行了细致分析。研究结果显示,北京市区居民的通勤时间从2005年38分钟增加到2010年的43．6分钟,通勤时间增长冠著。通过比较城八区居民的平均通勤时间,发现内城居民的通勤状况有所改善,而城近郊区居民通勤状况则不乐观,通勤时间的变化存在明显的空间差异;而将社会经济属性不同的人群的通勤时间进行比较,也发现通勤时间变化和年龄、学历等因素关系更为密切。对通勤时间变化的影响因素研究表明,地铁建设等交通发展因素以及居民通勤方式的变化对居民通勤时间大幅增加影响显著,同时通过对典型就业集中区域和居住功能为主区域进行比较,发现城市规划中对不同区域功能定位也对居民的通勤时间变化产生显著影响。     

渭北２０１０年７月下旬区域性大暴雨天气过程分析

应用2008年7月1日08时-20时逐3hT639数值预报产品和高低空实况场资料,对2008年7月1日阳泉市的冰雹天气过程进行综合分析,结果表明：T639的24h形势预报场误差不大,但蒙古冷涡中心位置预报略偏北;应用其物理量预报场并结合阳泉本地冰雹的预报指标,能够较为准确的预报出该次大冰雹过程,说明T639数值预报产品对本地冰雹过程有一定的预报能力。     

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结合特征分量构建和面向对象方法提取高分辨率卫星影像阴影

针对高分辨率卫星影像,提出一种特征分量构建与面向对象结合的阴影提取方法。分析遥感阴影光谱特性,构建彩色不变特征C3、亮度特征I、主成分第一特征量PC1以及蓝色波段和近红外波段归一化比率特征RATIOb_nir,增强阴影信息。采用线性变换将几个特征分量Digital Number(DN)值归一化到相同范围,对这几个分量进行综合分析。以I和PC1分量为输入对影像进行多尺度分割,建立包括波段均值、标准差、最大差异等特征的规则集,实现面向对象的阴影信息提取。选取20幅QuickBird影像为例进行阴影提取实验,平均总体精度为97%,平均用户精度为96%,平均Kappa系数为0.94。实验结果表明,相对传统基于像素信息提取方法,本文方法提取阴影斑块完整,无破碎图斑;相对基于原始光谱的面向对象方法,本文方法提取精度更高。     

首都基础教育均衡性评价模型设计与实现

随着北京社会经济的快速发展、人口的快速增长以及人民生活水平的不断提高,人民群众对于优质教育教学资源的需求越来越强烈,而教育的公平性和均衡发展也受到了人民群众和政府越来越多的关注。基础教育的均衡发展更多的需要依靠教育主管部门的政策支持,而政策的制定又需要根据教育均衡发展的实际情况有针对性的制定,那么首先就要对首都基础教育的均衡情况进行分析。本文基于GIS技术和统计学方法,采用差异系数法,选取相关指标,建立首都基础教育均衡性评价模型,利用ArcEngine组件和.Net技术集成开发并实现模型,对首都基础教育均衡性、资源配置均衡性、教育质量均衡性做出评价,为教育决策部门提供决策支持。