An integrated package for drought monitoring,prediction and analysis to aid drought modeling and assessment

Due to severe drought events and disastrous impacts in recent decades, substantial efforts have been devoted recently to drought monitoring, prediction and risk analysis for aiding drought preparedness plans and mitigation measures. Providing an overview of these aspects of drought research, this study presents an integrated R package and illustrates a wide range of its applications for drought modeling and assessment based on univariate and multivariate drought indices for both operational and research purposes. The package also includes statistical prediction of drought in a probabilistic manner based on multiple drought indicators, which serves as a baseline for drought prediction. The univariate and multivariate drought risk analysis of drought properties and indices is also presented. Finally, potential extensions of this package are also discussed. The package is provided freely to public to aid drought early warning and management.     

IBI and CA Model based Extraction of Urban Built\|up Areaand Its Application：A Case Study in Shanghai

At present,the automatic extraction of urban built\|up area is still a problem.Taking Shanghai city as an example,this research uses the binary image,which was derived from an IBI(index\|based built\|up index)image,as the geographical cellular automaton initial input data.This was then imported to the extended cellular automata model for further processing.After a series of processing such as thresholding,corrosion and connectivity test,the urban built\|up area was simulated and can be extracted.Based on this method,the urban built\|up area of Shanghai in five different years between 1987 and 2015 was extracted using multi\|temporal Landsat images of Shanghai.In addition,the urban growth intensity index,the concentric buffers analysis and radar chart analysis were calculated and used to analysis spatiotemporal pattern of Shanghai urban expansion in the 28 study years.The result shows that the built\|up area of Shanghai was expanded from 195 km² in 1987 to 1759 km² in 2015,which is eight times as large as that in 1987.In the period between 1987 and 2002,the urban built\|up area expanded mainly along the North\|South axis of the Huangpu River.However,after 2002 the expansion rate was increased more quickly,and the direction of the expansion was shifted to an east to west direction.Generally speaking,Shanghai has experienced a rapid urban expansion in the recent three decades.     

SAR影像海洋表面溢油检测方法与实现

海洋是地球的重要组成部分,它为人类提供了丰富的物质和宝贵的资源,每年海洋都承受着不同程度的侵害,其中油类污染是给海洋造成巨大危害的污染之一。而油类污染又主要来源于轮船破裂漏油以及油井平台或海底输油管道爆炸等。每次事故造成的直接经济损失达几百万至上千万不等,所以对海上溢油进行监测具有重要的意义。选用Envisat的ASAR数据进行海上溢油检测,介绍并分析了SAR图像溢油检测的一般步骤及其实现方法,通过采用单一阈值分割法、最大熵分割法和非监督分类法对影像进行目标检测,从而粗略地将影像区分为前景区域与背景区域,并结合影像的纹理特征进行分类。在纹理特征选取过程中,通过人工选取部分溢油区与非溢油区作为感兴趣区,在感兴趣区上分别统计SAR影像常用的纹理特征,并结合不同目标检测的结果以及原始影像进行基于BP神经网络的分类,得到了良好的效果。最后展望了SAR图像海洋溢油检测的发展方向。     

A Piecewise Grey System Model for Study the Effects of Anthropogenic Activities on Karst Hydrological Processes

Sustainable groundwater development must rely on a good understanding of hydrological processes, especially under effects of anthropogenic activities. This paper develops a piecewise analysis based on grey system model for study effects of anthropogenic activities on hydrological processes. The time series of precipitation and spring discharge were segmented into three time periods depending on whether variations are due to climate variation: the predevelopment stage, the transition stage, and the new equilibrium stage. Then we modeled hydrological process of the predevelopment stage and new equilibrium stage by the grey system model. By comparing the model results, we can quantify the effects of human activities on hydrological processes. We applied the model to Liulin Springs China. The results indicated that the hydraulic response time of the spring discharge to precipitation from the predevelopment stage to the new equilibrium stage, ranges from less than 1 year to up to 4 years. The results revealed that human activities slow the groundwater flow. GM (1,N) models of Liulin Springs discharge showed that the driving coefficients of precipitation to the spring discharge decreased from 0.012272 in the predevelopment stage to 0.007753 in the new equilibrium stage, which means that groundwater recharge ability has reduced about 36.82 %. Human activities in Liulin Springs have drastically changed the groundwater system. Piecewise grey system model is a robust method for hydrological process simulation.     

白洋淀气候变化及对生态系统的影响

根据1955年-2010年白洋淀地区气象数据及生态资料,研究了气候变化对白洋淀湿地生态系统的影响,以期为白洋淀湿地保护和可持续发展提供依据。结果表明:近56年来,白洋淀地区的气温总体呈现上升趋势,且在2007年达到最高值,而降水量、平均风速和日照时数均呈现下降趋势,其中1996年以后的降水量均低于56年的平均降水量。白洋淀地区降水量和年最高水位呈明显的正相关关系,平均气温和水域面积的变化趋势则相反。水位、水域面积的变化以及人类活动等因素影响了白洋淀水质和生物多样性以及不同土地利用类型的分配比例。     

Treatment of textile dye effluent using a self-made positively charged nanofiltration membrane

A self-made positively charged nanofi ltration(NF)membrane was used to treat textile dye effluent to generate water for reuse,and the factors affecting nanofi ltration process such as operating pressure,feed flow and membrane cleaning were investigated.With an applied pressure of 1.0 MPa and a feed flow of 40 L/h,this NF membrane has a removal of 93.3% for CODcr and a reduction of approximately 51.0% in TDS,salinity and conductivity achieving the chroma removal of 100%.The permeate obtained through this membrane is suitable for recycling.Moreover,the membrane could be reused after being cleaned with 1% NaOH solution.     

微晶化加工含钾页岩的实验研究

采用自行研制的设备WJH-1微晶化加工含钾页岩,对产品进行分时段采样,运用激光粒度分析仪、比表面积仪、SEM和XRD对其粒度分布、比表面积、形貌、成分和晶体结构进行了表征,利用等球直径分析了物料d50,d97等粒度分布的变化及图表法分析比表面积和晶格参数的变化.结果表明:d50,d97随时间呈指数下降,在前1.5h减小幅度最大,d50下降幅度达到80.07%,d97下降幅度为79.68%;比表面积先增加后降低,然后又缓慢增加;选用四次多项式对比表面积与能耗的关系进行拟合,拟合效果良好;矿物晶体发生晶格畸变,结晶度降低,加工过程具有微晶化效果.     

Use of flow-normalization to evaluate nutrient concentration and flux changes in Lake Champlain tributaries, 1990–2009

The U.S. Geological Survey evaluated 20 years of total phosphorus (P) and total nitrogen (N) concentration data for 18 Lake Champlain tributaries using a new statistical method based on weighted regressions to estimate daily concentration and flux histories based on discharge, season, and trend as explanatory variables. The use of all the streamflow discharge values for a given date in the record, in a process called “flow-normalization”, removed the year-to-year variation due to streamflow and generated a smooth time series from which trends were calculated. This approach to data analysis can be of great value to evaluations of the success of restoration efforts because it filters out the large random fluctuations in the flux that are due to the temporal variability in streamflow. Results for the full 20 years of record showed a mixture of upward and downward trends for concentrations and yields of P and N. When the record was broken into two 10-year periods, for many tributaries, the more recent period showed a reversal in N from upward to downward trends and a similar reversal or reduction in magnitude of upward trends for P. Some measures of P and N concentrations and yields appear to be related to intensity of agricultural activities, point-source loads of P, or population density. Total flow-normalized P flux aggregated from the monitored tributaries showed a decrease of 30 metric tons per year from 1991 to 2009, which is about 15% of the targeted reduction established by the operational management plan for the Lake Champlain Basin.     

影响岩质路堑边坡表层土稳定性因素的敏感度分析

针对渝怀铁路鱼嘴车站岩质路堑植被边坡,采用直剪切试验获得边坡表层绿色防护层的物理力学参数。在此基础上,选取5个影响边坡表层土稳定性的因素(坡度、土层厚度、重度、粘聚力、内摩擦角),采用数学及数理统计的方法进行敏感度分析,得出各影响因素的敏感度顺序为内摩擦角>坡度>重度>土层厚度>粘聚力,分析表明绿色防护层的内摩擦角是控制其稳定性的主控因素。