基于信息扩散与自助法的旱灾风险评估模型──以安徽为例

旱灾风险管理是抗旱减灾的科学手段、干旱及旱灾研究的重要方向,定量评估旱灾风险是旱灾风险管理的核心内容。为降低各种不确定性因素影响下旱灾风险评估结果的误差,提高结果的可靠性,提出运用信息扩散法估计旱灾损失的超越概率,结合自助法的区间估计算法,建立基于信息扩散与自助法的灾害风险评估模型,用不同置信水平下旱灾损失对应超越概率的置信区间来反映旱灾风险。将该模型运用于安徽省农业易旱地区干旱灾害风险评估,计算并确定在置信水平为0.75时安徽省易旱地区的旱灾风险区间评估结果合理、可靠,可为抗旱规划提供科学的决策依据。     

Non-parametric MLE for Poisson species abundance models allowing for heterogeneity between species

The proper management of an ecological population is greatly aided by solid information about its species' abundances. For the general heterogeneous Poisson species abundance setting, we develop the non-parametric mle for the entire probability model, namely for the total number N of species and the generating distribution F for the expected values of the species' abundances. Solid estimation of the entire probability model allows us to develop generator-based measures of ecological diversity and evenness which have inferences over similar regions. Also, our methods produce a solid goodness-of-fit test for our model as well as a likelihood ratio test to examine if there is heterogeneity in the expected values of the species' abundances. These estimates and tests are examined, in detail, in the paper. In particular, we apply our methods to important data from the National Breeding Bird Survey and discuss how our methods can also be easily applied to sweep net sampling data. To further examine our methods, we provide simulations for several illustrative situations.     

Comparisons between air-transport models via bootstrapped significance tests

The bootstrap resampling method is used to help with the intercomparison of air transport models. Time-by-time analysis of variance and follow up simultaneous comparisons are proposed which do not rely on distributional assumptions for the predictions of the models and which allow errors to be postulated in the observed values of the phenomena under investigation. The techniques are demonstrated using some data from the APSIS experiment.     

A model of deforestation by human population interactions

A differential equation was employed in modelling deforestation by human population interactions to yield an explicit mathematical model. The theoretical relation and many possible models were applied to the grid cell data in Hiroshima Prefecture, and relative appropriateness of each model was evaluated by Akaike's information criterion (AIC) using raw data. Intensive further verification was executed bythe bootstrap method. It was demonstrated that the theoretical relation was in the best agreement among many other models in comparison.     

LONG TERM TRENDS OF ANNUAL AND MONTHLY PRECIPITATION IN JAPAN1

ABSTRACT: Long term trends in Japan's annual and monthly precipitation are investigated in this study. The statistical significance of a trend at a study site is assessed by the Mann‐Kendall (MK) test, and field significance of trends in climatic Regions II, III, and IV is evaluated using the bootstrap test preserving cross correlation. The practical significance of a trend is judged by a percentage change of the sample mean over an observation period. The field significance assessment demonstrates that annual precipitation in Region II did not show any significant change, but regional precipitation shifts occurred in different months. Precipitation significantly increased by 12.2 percent in May, while it significantly decreased by 12.0, 10.5, 15.6, and 19.7 percent, respectively, in April, September, October, and December. In Region III, annual precipitation declined by 11.8 percent, and monthly precipitation significantly decreased from September through January and in April, with the greatest decrease (38.2 percent) in December. In Region IV, significant reductions occurred in both annual precipitation (by 15.6 percent) and monthly precipitation from September through February and in June and July, with the worst reduction (44.7 percent) in December.     

武汉城市圈土地利用空间关联的碳排放效率及其收敛性分析

通过测算武汉城市圈土地利用空间关联的碳排放效率及其收敛性,为该城市群提供碳减排方案。通过运用结合Bootstrap技术的Malmquist指数方法测算了武汉城市圈土地利用空间关联的碳排放效率及其技术进步和技术效率,并对该效率做σ-收敛和β-收敛分析。研究发现该城市圈土地利用空间关联的碳排放效率在2010年前呈上升趋势,之后出现下降;究其原因,虽然技术进步是持续的,但是不足以弥补技术效率的不断降低;将武汉城市圈按照土地类型分为三类城市,收敛性分析发现它们均出现了不同程度的收敛,而且收敛于较高的碳排放水平。根据以上的分析结果,结合该城市圈的产业布局,提出了相应的减碳方案。     

大气污染物排放源清单不确定性定量分析方法及案例研究

大气污染物排放源清单由于在数据收集过程中存在的不可避免的监测误差、随机误差、关键数据缺乏以及数据代表性不足等因素而具有不确定性,而排放源清单的不确定性指的是人们对排放清单的真实值缺乏认识和了解.介绍了目前大气排放源清单定量不确定性方法框架,并使用电厂NO_x在线监测数据,通过实际案例量化排放源清单中的不确定性.结果表明:即使对被认为具有较高准确性的火电厂点源排放清单,案例中NO_x的排放源清单来自随机误差的不确定性在±15%左右.对排放源清单的不确定性量化有助于决策者确定污染物排放削减目标的可达性和科学制定大气污染物控制策略,指导排放源清单的改进和数据收集工作.同时,对我国排放源清单开发中不确定性分析提出建议.      

最近邻抽样回归模型在水环境预测中的应用

介绍了最近邻抽样回归模型(NNBR)进行单因子和多因子预测建模的基本思想和算法.该模型概念清晰,结构简单,不需对研究对象的相依形式和概率分布形式作假定,也不需估计太多的参数,是一类数据驱动的非参数预测模型,具有潜在的优势.通过水环境中的两个实例进行了预测应用,结果表明,预测效果较好,并与投影寻踪回归模型(PPR)进行了对比.     

Nonparametric MLE incorporation of heterogeneity and model testing into premarked cohort studies

We utilize mixture models and nonparametric maximum likelihood estimation to both develop a likelihood ratio test (lrt) for a common simplifying assumption and to allow heterogeneity within premarked cohort studies. Our methods allow estimation of the entire probability model and thus one can not only estimate many parameters of interest but one can also bootstrap from the estimated model to predict many things, including the standard deviations of estimators. Simulations suggest that our lrt has the appropriate protection for Type I error and often has good power. In practice, our lrt is important for determining the appropriateness of estimators and in examining if a simple design with only one capture period could be utilized for a future similar study.