基于时间序列的深基坑支护结构变形预测

基坑工程由于受多种因素的影响．目前已成为岩土工程中的重点和难点。在基坑施工过程中,需要根据现场的实际工程地质条件及选择的支护型式、建筑物的安全等级．对支护结构的变形进行严格控制。时间序列分析主要是指采用参数模型对所观测到的有序的随机数据进行分析与处理的一种数据处理方法。通过现场量测的深基坑围护结构变形信息资料,对数据进行整理和分析．利用时间序列分析法对支护结构的变形作出预测,以保证基坑安全施工。     

基于MODIS时序NDVI主要农作物种植信息提取研究

农业在黄河三角洲地区占有重要地位,及时、准确地掌握该地区农作物分布信息对政府有关部门制定农业政策、指导农业生产具有十分重要的意义。时序植被指数能够反映农作物物候特征,帮助识别农作物类型,在农作物种植信息提取方面具有明显优势。论文选取2014年MOD09Q1时序遥感数据集,以黄河三角洲主要农作物为研究对象,利用Harmonic Analysis of NDVI Time-Series（Hants）滤波重构NDVI时序曲线,通过对比待分像元NDVI时序曲线与参考时序曲线的相似性,实现农作物种植信息提取。对分类结果进行面积统计和空间分布精度检验：冬小麦、棉花、玉米的面积提取精度分别达到96.8%、95.5%、85.1%,空间匹配总体精度达86.9%。结果表明该方法有效可行,能够为该地区农业监测提供技术基础。     

Is Scotland sustainable? A the series of indicators of sustainable development

Seven measures of sustainable development for Scotland are examined for the period 1980-1993. These measures are green net national product, genuine savings, ecological footprint, environmental space, human appropriation of net primary production, the index of sustainable economic welfare and the genuine progress indicator. Very different messages concerning sustainable development in Scotland emerge from these measures.     

The endowment effect,discounting and the environment

There is a considerable body of evidence showing that our preferences exhibit both reference dependence and loss aversion, a.k.a. the endowment effect. In this paper, we consider the implications of the endowment effect for discounting, with a special focus on discounting future improvements in the environment. We show that the endowment effect modifies the discount rate via (i) an instantaneous endowment effect and (ii) a reference-updating effect. Moreover we show that these two effects often combine to dampen the preference to smooth consumption over time. What this implies for discounting future environmental benefits may then depend critically on whether environmental quality is merely a factor of production of material consumption, or whether it is an amenity. On an increasing path of material consumption, dampened consumption smoothing implies a lower discount rate. But on a declining path of environmental quality and where we derive utility directly from environmental quality, it implies a higher discount rate. On non-monotonic paths, loss aversion specifically can give rise to substantial discontinuities in the discount rate.     

基于DFA的无定河径流长期变化趋势及持续性研究

河川径流量的变化对水资源的开发利用和国民经济的发展具有很大的影响。采用Ko1mogorov-Smirnov检验方法对无定河流域两个主要水文站赵石窑站和白家川站逐月径流量序列进行正态性检验,在此基础上运用DFA分析方法,估算两站时间序列的α标度指数,预测该流域径流量的未来变化趋势及其持续性,并采用随机重排法对估算结果进行了稳定性检验。分析结果显示:赵石窑和白家川两站径流时间序列的α标度指数分别为0.52和0.56,均大于0.5,径流时间序列表现为较强的长程依赖性,表明无定河流域在过去近50a内径流量的总体上呈下降趋势,在未来一段时间内,还将持续一段时间。对原时间序列随机重排后,两站月径流序列的α标度指数都变小,分别为0.48和0.49,接近于0.5,进一步证明原序列确实存在着标度不变性。研究结果对流域的水资源规划、管理与合理利用有帮助。     

Early Secondary Succession in Bottomland Hardwood Forests of Southeastern Virginia

Addressing the need for reference sites that permit wetland managers to evaluate the relative success of wetland restoration efforts, this project examines the early successional properties of a chronosequence of 17 forested wetlands that have been clear-cut and allowed to naturally revegetate. Ordinations performed on the data using CANOCO software indicated three general types of communities—one dominated by bald cypress (Taxodium distichum) and water tupelo (Nyssa aquatica), one dominated by black willow (Salix nigra), and one with a species composition similar to that of a mature stand of bottomland hardwoods. These divisions were correlated with the percentage of stems originating as coppice on stumps leftover from the clear-cut. In particular, the bottomland hardwood stands were regenerating predominantly as coppice, while the cypress/tupelo and black willow stands were regenerating primarily as seedlings. As indicated by the earlier development of overstory basal area, coppice sites were also regenerating much faster. The hydrology of a site also exhibited a strong impact on the rate of regeneration, with the semipermanently to permanently flooded portions of sites often exhibiting little or no regeneration. The results indicate that, because of the overwhelming reliance on coppice sprouts as the main source of stems and the concomitant enhanced rates of regeneration, certain vegetative parameters of clear-cut bottomland hardwood stands would not be effective benchmarks by which to judge the relative success of creation and restoration efforts.     

INTERVENTION ANALYSIS OF WATER QUALITY RECORDS1

The impoundment of the Kootenai River by Libby Dam caused changes in discharge and water quality in the river downstream from Lake Koocanusa. The changes observed downsteam were largely attributable to the depth of withdrawal from the reservoir and the reservoir's ability to store and mix various influent water masses. The preimpoundment and postimpoundment time series of discharge and six water quality variables were autocorrelated and exhibited strong seasonality. Intervention analysis, a technique employing Box-Jenkins time series models, was used to quantify the nature and magnitude of the changes in water quality after the construction of Libby Dam. The models were developed with data from June 1967 through February 1981 and were able to satisfactorily forecast riverine conditions from March 1981 through January 1982.     

MULTIFRACTAL SCALING OF DAILY RUNOFF TIME SERIES IN AGRICULTURAL WATERSHEDS1

Abstract: Multifractal scaling behavior of long-term records of daily runoff time series in 32 subwatersheds covering a wide range of sizes was examined. These subwatersheds were associated with four agricultural watersheds with different climates and topography. The empirical moment scaling curves obtained using the trace moment method showed that the runoff time series exhibited a multifractal behavior, which was valid over a time scale range from one day to about three years. The multi-fractal scaling of the runoff time series was well described by the Universal Multifractal Model. The spectral analysis (β < 1) and the order of fractional integration (H ⋍; 0) indicated that the runoff time series were conservative. The multifractal parameters, α (multifractal index) and C₁ (co-dimension), were reasonably close to each other for subwatersheds within each of the watersheds and were generally similar among the four watersheds. The α values of the four watersheds were 1.10 ± 0.13, 1.61 ± 0.06,1.61 ± 0.24, and 1.63 ± 0.19. The C₁ values of four watersheds were 0.19 ± 0.01, 0.17 ± 0.01, 0.17 ± 0.04, and 0.11 ± 0.02. The multifractal analyses provided useful insight into the runoff time series, especially the occurrence and distribution of extreme events.     

二次热解吸直接进样气相色谱法测定空气中苯系物

文章建立了空气中苯系物的分析方法,方法用Tenax TA吸附管吸附空气中苯系物,二次热解吸直接进毛细管气相色谱分析。该方法定性、定量准确,线性响应良好,回归方程的线性相关系数大于0．9991,相对标准偏差在2．1％～5．3％之间,加标回收率大于92％,具有良好的重现性。测定干扰小,检测灵敏度高,当采样体积1L时,平均解吸率在95％以上,苯系物的最低检出浓度可达0．5ug／m^3。本方法适合测定空气中低浓度的苯系物。     

苏州市空气质量的时间序列变化过程研究

城市空气质量水平是以空气质量指数(API)来表征的,API的时空变化可以反映城市空气质量的变化过程。文章以苏州市2002～2007年各月API值为研究对象,将其构成一组时间序列,采用时间序列理论中的小波分析原理和差分自回归滑动平均模型(ARIMA)原理对这组API序列进行趋势的辨识和数值预测,结果表明(1)苏州市近年来的空气质量水平不断提高,并将稳定保持在一个良好的水平上;(2)差分自回归滑动平均模型ARIMA(2,2,2)在拟合该地区API值时间尺度上的变化趋势效果较好,能够较好的预测苏州市月空气质量水平。