Statistical diagnosis and gross error test for semiparametric linear model     

Shijun Ding  Songlin Zhang  Weiping Jiang  Shouchun Wang 《地球空间信息科学学报》2013,16(4):296-302

This paper systematically studies the statistical diagnosis and hypothesis testing for the semiparametric linear regression model according to the theories and methods of the statistical diagnosis and hypothesis testing for parametric regression model. Several diagnostic measures and the methods for gross error testing are derived. Especially, the global and local influence analysis of the gross error on the parameter X and the nonparameter s are discussed in detail; at the same time, the paper proves that the data point deletion model is equivalent to the mean shift model for the semiparametric regression model. Finally, with one simulative computing example, some helpful conclusions are drawn.  相似文献   

Hyperspectral remote sensing analysis of short rotation woody crops grown with controlled nutrient and irrigation treatments     

Jungho Im  John R. Jensen  Mark Coleman  Eric Nelson 《国际地球制图》2013,28(4):293-312

Hyperspectral remote sensing research was conducted to document the biophysical and biochemical characteristics of controlled forest plots subjected to various nutrient and irrigation treatments. The experimental plots were located on the Savannah River Site near Aiken, SC. AISA hyperspectral imagery were analysed using three approaches, including: (1) normalized difference vegetation index based simple linear regression (NSLR), (2) partial least squares regression (PLSR) and (3) machine-learning regression trees (MLRT) to predict the biophysical and biochemical characteristics of the crops (leaf area index, stem biomass and five leaf nutrients concentrations). The calibration and cross-validation results were compared between the three techniques. The PLSR approach generally resulted in good predictive performance. The MLRT approach appeared to be a useful method to predict characteristics in a complex environment (i.e. many tree species and numerous fertilization and/or irrigation treatments) due to its powerful adaptability.  相似文献   

Localized versus wide-ranging effects of the post-Soviet wars in the Caucasus on agricultural abandonment     

《Global Environmental Change》2022

Wars are frequent and can affect land use substantially, but the effects of wars can vary greatly depending on their characteristics, such as intensity or duration. Furthermore, the spatial scale of the effects can differ. The effects of wars may be localized and thus close to conflict locations if direct mechanisms matter most (e.g., abandonment because active fighting precludes farming), or wide-ranging, e.g., farther away from conflict locations, if indirect mechanisms predominate (e.g., no access to agricultural inputs). Our goal was to quantify how the very different wars in the Caucasus region during post-Soviet times most likely affected agricultural abandonment at different scales. We analyzed data on conflict locations plus Landsat-derived land-cover data from 1987 to 2015, and applied matching statistics, difference-in-differences estimators, and logistic panel regressions. We examined the localized versus wide-ranging effects of the different wars on permanent agricultural abandonment and inferred to direct and indirect mechanisms that may have resulted in agricultural abandonment. While permanent agricultural abandonment was overall surprisingly limited across the Caucasus, up to one third of abandonment was most likely related to the wars. Among the wars, the war in Chechnya was by far the most intense and longest, but its effect on abandonment was similar to the less intense and relatively short war in Abkhazia. 47 % and 45 % of agricultural abandonment was related to each war, respectively. The reason was that the effect of the war in Chechnya was more localized, and abandonment occurred near conflict locations, in contrast to Abkhazia, where the effect was wide-ranging and abandonment occurred farther away from conflict locations. In contrast, the war in South Ossetia showed no significant effect on abandonment, and the war in Nagorno-Karabakh had the surprising pattern that abandonment was higher where no war had occurred. For each of the wars, abandonment was predominately related to the nearest conflict locations, but in Abkhazia additional conflict locations within 10 km further increased the probability of abandonment. We infer that the direct mechanisms of the war such as bombing, and active fighting most likely resulted in a localized effect close to conflict locations in Chechnya and in Nagorno-Karabakh. However, in Nagorno-Karabakh subsidies for new settlers after the war, (i.e., a positive wide-ranging effect), potentially reduced the amount of abandonment there. In contrast, negative wide-ranging effects such as refugee movements and post-war restrictions on their return is related to broad-scale abandonment in Abkhazia. In summary, permanent agricultural abandonment was not necessarily higher in a war with a high overall intensity. Instead, the effect of a given war varied in scale, and was related to the relative importance of direct and localized versus indirect and wide-ranging mechanisms, including postwar events and policies, which is likely the case for other wars, too.  相似文献   

基于Parsivel天气现象仪资料的郑州“7·20”罕见特大暴雨微物理特征分析     

周丹  周淑玲  田金华 《气象与环境科学》2022,45(1):93-101

基于2016-2018年ECMWF模式温度预报和浙江省72个国家基本站观测资料,根据温度日变化特征,采用K-近邻(KNN)回归算法进行误差订正,改进浙江省172 h精细化温度预报。在KNN回归算法中,将模式起报时刻的温度视作“背景”,由模式预报减去起报时刻温度消除“背景”影响,得到温度日变化曲线,通过温度日变化曲线构建差异指标,选取历史相似个例。根据历史相似个例的误差特征,对温度预报进行订正,得到改进的温度预报。检验结果表明,KNN方案的温度预报平均绝对误差较ECMWF和30 d滑动平均误差订正方案(OCF)的分别减小26.2%和5.2%;日最高和最低温度预报误差绝对值小于2℃,准确率较ECMWF的分别提高14.8%和4.3%,较OCF的分别提高3.0%和1.3%。KNN方案对地形复杂地区的温度预报改进效果更为明显,对冷空气活动和夏季高温等天气过程预报改善效果也较稳定。  相似文献   

海水热力学方程TEOS-10及其与海水状态方程EOS-80的比较     

孙永明  史久新  阳海鹏 《地球科学进展》2012,27(9):1014-1025

新的2010年海水热力学方程TEOS-10采用1990年国际温标以及考虑世界大洋海水组成空间差异的绝对盐度,与旧的1980年海水状态方程EOS-80相比,具有更高的准确度和更广的适用范围,能够直接计算包括熵、焓、热容量在内的旧方程无法计算的热力学变量,将给海洋学研究带来重要的影响。借助气候态平均数据计算的结果表明,新旧方程计算的密度之差,在全球大多数海域可超过10-2kg/m3。在赤道以北的太平洋和印度洋海域,包括中国东海和南海的深海区域,该差别尤为显著,在精度要求较高的研究中必须予以考虑。新方程对密度计算的这一修正主要归因于其首次提出的绝对盐度,考虑了包括中性溶质在内的所有溶质的作用,弥补了实用盐标的缺陷。新旧方程计算冰点等其他物理量也有相应的修正。应尽快推广应用TEOS-10以及绝对盐度,充分发挥其对海洋学发展的推动作用。  相似文献   

水稻土中重金属元素Cd、Pb的竞争吸附——以长株潭地区水稻土为例     

王岚  王亚平  许春雪  王苏明  杨理勤 《中国区域地质》2012,(4):601-607

对中国南方的3个水稻土样品进行了Cd、Pb单一离子和混合离子吸附特点的研究。结果表明,3个水稻土样品中Cd、Pb的吸附特点都相似,Langmuir等温方程可很好地描述Cd、Pb的吸附等温线。3个土壤样品中,有较高pH值和较低有机物、CEC浓度、粘土含量、高岭石含量的2个土壤样品对Cd、Pb有较大的吸附量,且其等温吸附拟合的最大吸附量（B）也较大。在两组分混合溶液中,尽管共存离子的存在影响了土壤对单一离子的吸附,同时土壤对Cd的吸附在一定程度上受影响的程度大,但3个土壤样品都表现出对Pb有强的吸附能力。在3个土壤样品中,Langmuir等温方程中Pb的健合能常数（K）都大于Cd的健合能常数（K）,混合溶液中的K值高于单一溶液的K值,表明2种金属离子对吸附位点的竞争提高了特定吸附位点的保持力,使金属离子在土壤中特定位点的吸附更加坚固。  相似文献   

不同覆盖物抑制铀尾矿氡析出的效果     

谭凯旋  胡寒桥  刘泽华  吕俊文  夏良树 《矿物学报》2012,32(2):233-237

对5种不同覆盖物（红土、砂、废石、砂与红土混合物、废石与红土混合物）降低铀尾矿氡析出的效果进行了现场实验研究。结果表明,不同覆盖物的效果存在较大差异,在相同覆盖厚度条件下,氡析出率降低系数是红土〉红土与废石混合物〉红土与砂混合物〉废石〉砂。表面氡析出率随覆盖物厚度增大而减小,氡析出率降低系数的对数与覆盖厚度成正比,所得到的各种覆盖物的拟合线性方程可用来评价覆盖效果。建立了各种覆盖物覆盖厚度估算的经验公式。综合考虑降氡效果、经济成本、生态环境效应,废石与红土混合物是该地区铀尾矿库最佳覆盖物。  相似文献   

三次拟合计算法测定土壤样品中的硫含量     

周小林  朱志雄 《贵州地质》2012,29(1):68-71

本方法采用三次拟合计算法处理土壤样品中硫含量的测试结果。试样采用传统的燃烧碘量法进行处理,在结果计算中使用三次拟合法处理测试结果,取得令人满意的效果。本方法的精密度为1.54%5.38%,方法检出限（3S）：0.005%,较好的满足土壤样品中硫的测试要求。  相似文献   

双误差回归模型在ICP-MS测定饮用水中锶的不确定度评定的简化应用     

郑松  况云所  赵平 《岩矿测试》2012,31(3):484-488

在计算电感耦合等离子体质谱法测定饮用水中锶的浓度(x)时,由于标准系列配制和仪器检测过程中信号(y)漂移产生的不确定度会传递给最终的计算结果。普通的一次或多次线性拟合结果不能真实地反映对于x、y值都含误差的数据拟合情况。文章对标准曲线进行了双误差回归计算,从双误差回归线性方程推导出校准曲线拟合过程产生不确定度的计算公式,建立了方法检出限与曲线拟合参数(x、y、曲线截距和斜率)及其相关不确定度之间的关系式,依据误差连续传递公式及不确定度分量计算公式简化了合成不确定度的表达式。从合成不确定度计算公式中可得出,水样中锶含量的浓度越低,其对应的不确定度越大;标准系列配制过程不细致、仪器灵敏度低,方法检出限越差,与实际测试情况符合。  相似文献   

Artificial neural networks and nonlinear regression techniques to assess the influence of slake durability cycles on the prediction of uniaxial compressive strength and modulus of elasticity for carbonate rocks   总被引：1，自引：0，他引：1  

S. Yagiz  E. A. Sezer  C. Gokceoglu 《国际地质力学数值与分析法杂志》2012,36(14):1636-1650

Understanding rock material characterizations and solving relevant problems are quite difficult tasks because of their complex behavior, which sometimes cannot be identified without intelligent, numerical, and analytical approaches. Because of that, some prediction techniques, like artificial neural networks (ANN) and nonlinear regression techniques, can be utilized to solve those problems. The purpose of this study is to examine the effects of the cycling integer of slake durability index test on intact rock behavior and estimate some rock properties, such as uniaxial compressive strength (UCS) and modulus of elasticity (E) from known rock index parameters using ANN and various regression techniques. Further, new performance index (PI) and degree of consistency (Cd) are introduced to examine the accuracy of generated models. For these purposes, intact rock dataset is established by performing rock tests including uniaxial compressive strength, modulus of elasticity, Schmidt hammer, effective porosity, dry unit weight, p‐wave velocity, and slake durability index tests on selected carbonate rocks. Afterward, the models are developed using ANN and nonlinear regression techniques. The concluding remark given is that four‐cycle slake durability index (I_d4) provides more accurate results to evaluate material characterization of carbonate rocks, and it is one of the reliable input variables to estimate UCS and E of carbonate rocks; introduced performance indices, both PI and Cd, may be accepted as good indicators to assess the accuracy of the complex models, and further, the ANN models have more prediction capability than the regression techniques to estimate relevant rock properties. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献