新疆呼图壁地下储气库的InSAR形变监测与模拟

利用TerraSAR-X卫星2013-08~2014-08的17景雷达影像,采用小基线集（small baseline subset,SBAS）InSAR技术获取呼图壁(HTB)地下储气库（underground gas storage,UGS）运行期间的地表形变序列,并结合UGS注（采）气井口的压力数据,采用多点源Mogi模型,对HTB UGS的形变场进行模拟。结果表明,整个UGS区域的形变特征为非连续分布,形变与注（采）气压力变化具有较好的相关性;注（采）气期间沿卫星视线向(LOS)的形变峰值分别为10 mm和-8 mm;采用自适应前向搜索法,基于多点源Mogi模型初步模拟注（采）气期间的形变过程,当UGS的注（采）气平均气压为18 MPa和15 MPa时,LOS的形变可达7 mm和-4 mm,地表形变的大小与注（采）气井口密度有关;UGS的储气分布呈非均匀状态,即地下气库结构复杂多变。     

BDS多路径效应特征及其对静态基线解精度的影响

为研究BDS载波相位多路径效应的特征,在强多路径环境下进行连续多天短基线静态数据采集,并计算双差观测值残差序列,分GEO、IGSO、MEO 3类卫星分析BDS多路径重复性,在此基础上研究多路径效应对BDS静态基线解精度的影响。结果表明,BDS多路径误差具有较强的重复性,其中GEO及IGSO卫星的多路径误差重复周期为1 d,MEO卫星的多路径误差重复周期为7 d;GEO卫星的多路径误差具有系统性偏移,但不是一个常数,而是随时间发生缓慢变化,因此长时间的静态观测并不能平滑该误差,从而导致在较强多路径环境下,BDS多路径误差对其静态解的影响可达cm级。     

环境损害鉴定评估的土壤基线确定方法

近年来,国内环境污染事故频繁发生,由此引发的环境损害问题日益严重。环境损害鉴定评估是中国推行的一项应对环境污染损害的重要环保举措,而基线则是确定损害的关键。基线确定作为损害评估与修复的重要组成部分,是科学评估的关键技术环节和重要前提,也是中国开展环境损害鉴定评估亟待解决的问题。总结国际上常用的4种基线确定方法：即历史数据法、参考点位法、环境标准法和模型推算法的优缺点及应用情况,探讨不同基线确定方法的具体工作步骤,并结合中国土壤环境研究工作积累与进展,提出中国土壤基线确定基本原则和推荐“4步法”工作程序,对中国开展土壤环境损害鉴定评估工作具有重要的理论意义和科学指导作用。     

基于凸壳构造技术的领海基点选取问题研究

领海基点的选取数量及其空间点位分布的不同,对海域划界结果有着重要的影响.在传统的领海基点选取工作中缺乏一种有效的用于检验选取方案优劣的数学模型,因而这一工作中存在着不确定性因素.为了解决这个问题,提出了利用最小凸包(凸壳)构造技术实现领海基点最优选取的思路和方法,并在此基础上对某群岛的领海基点选取方案作了实例分析.     

Boundaries Make a Difference: The Effects of Spatial and Temporal Parameters on Conservation Planning*

Conservation planning and resulting ecological target identification require selection of both a planning area boundary and temporal baseline or reference condition. We examined the effects that these selections can have on resulting amount and location of identified conservation targets. A gap analysis for California was conducted using five different sets of ecoregion boundaries to identify and compare existing conservation shortfalls in major land cover type representation in protected areas using a threshold of 30 percent per ecoregion per type as the minimum required for future ecological viability. Another gap analysis was run for a single ecoregion using two temporal baselines (current and pre-1900) for the land cover followed by a comparison of identified conservation needs. We found that the boundaries of different ecoregional schemes affected both the total area needed to meet the per ecoregion land cover conservation goals and the spatial location of underprotected land cover types. Choice of temporal baseline also had a significant effect on the establishment of conservation targets for the highly human-impacted Central Valley ecoregion. To meet the given conservation threshold using a historic rather than contemporary baseline, a substantial amount of restoration is required. The results can help identify areas of both conservation needs consensus and those that vary widely based on the chosen planning boundary, as well as aid in the selection of appropriate restoration targets in degraded ecosystems. Because all landscapes are continuous in nature and planning area boundaries are discrete, similar results are likely to be found in analyses conducted in other regions.     

Ranking spaces for predicting human movement in an urban environment

A city can be topologically represented as a connectivity graph, consisting of nodes representing individual spaces and links if the corresponding spaces are intersected. It turns out in the space syntax literature that some defined topological metrics can capture human movement rates in individual spaces. In other words, the topological metrics are significantly correlated to human movement rates, and individual spaces can be ranked by the metrics for predicting human movement. However, this correlation has never been well justified. In this paper, we study the same issue by applying the weighted PageRank algorithm to the connectivity graph or space–space topology for ranking the individual spaces, and find surprisingly that: (1) the PageRank scores are better correlated to human movement rates than the space syntax metrics, and (2) the underlying space–space topology demonstrates small world and scale free properties. The findings provide a novel justification as to why space syntax, or topological analysis in general, can be used to predict human movement. We further conjecture that this kind of analysis is no more than predicting a drunkard's walking on a small world and scale free network.     

Pesticides Removal by Filtration over Cactus Pear Leaves: A Cheap and Natural Method for Small‐Scale Water Purification in Semi‐Arid Regions

This study aims to examine the efficiency of Opuntia ficus‐indica for removing organochlorine pesticides from surface waters. Adsorption properties such as size, dose, and time of O. ficus‐indica for aldrin, dieldrin, and dichlorodiphenyltrichloroethane (DDT) were studied through stirring and column methods. Because of their high affinity and swelling characteristics, dried O. ficus‐indica was studied in stirring while fresh unpeeled O. ficus‐indica was applied in both stirring and column experiments and proved to be well‐suited to column application. Before removing pesticides, the column was flashed with distilled water eliminate the turbidity and smell from fresh unpeeled cactus. The removal of pesticides increased with an increasing adsorbent dose and decreased with adsorbent particle sizes. The optimum adsorbent dose is 10 g for dried and 15 g for fresh unpeeled O. ficus‐indica. The experimental results show that O. ficus‐indica possesses strong adsorption ability for aldrin, dieldrin, and DDT, and the adsorption isotherm data obeyed the Freundlich model. The results of our small‐scale experiments suggest a strong potential to develop local small‐scale water treatment units that can be used at the level of individual households or local communities, using a widely available adsorbent.     

HBCORS高精度参考框架获取策略分析

通过对HBCORS坐标联测方法、基线处理策略以及网平差策略进行研究,分析了HBCORS高精度参考框架建立的方法,为高精度区域参考框架的获取以及高精度GPS网数据处理提供了思路。     

GPS姿态测量中模糊度搜索方法的确定与比较

GPS载波相位观测值作为高精度观测量在姿态测量中得到广泛应用。姿态测量系统中,基线长度可以通过提前量测精确求得。作为约束条件,可以用于模糊度搜索,提高模糊度搜索效率和准确度。本文介绍了传统的LAMBDA方法,且在此基础上提出了附有基线长度约束的LAMBDA搜索方法,并比较了两者的搜索效率。     

The geographic distribution of small dams in Oregon using ecoregion and landform classification

Abstract

Small dams fragment river landscapes, disrupting channel connectivity and impacting water quality and quantity. Although they impound volumetrically less total water than large dams, the ubiquity of small dams suggests their cumulative impacts could be significant. Documenting the distribution and characteristics of small dams is necessary to understanding and mitigating their impacts. In this study, we compare datasets of small dams in Oregon, compile a new comprehensive dataset, and document geographic variations in small dam distributions between different ecoregions. We used Oregon Water Resources Department dam and Oregon Department of Fish and Wildlife fish passage barrier datasets to compare dam heights and contributing drainage areas between different ecoregions. Over 61% of Oregon’s land area is above one or more small dam. We highlight the location of Oregon’s small dams at valley margins, transition zones between flat plains and mountains, and areas of high population density. Given the hidden nature of small dams, evaluation of small dam impacts using public imagery is not effective. However, knowledge of small dam distributions given their association with landforms can aid in finding unrecorded dams, assessing approaches for evaluating their geomorphic impacts, and informing their management.