A comprehensive approach to evaluating watershed models for predicting river flow regimes critical to downstream ecosystem services

Selection of strategies that help reduce riverine inputs requires numerical models that accurately quantify hydrologic processes. While numerous models exist, information on how to evaluate and select the most robust models is limited. Toward this end, we developed a comprehensive approach that helps evaluate watershed models in their ability to simulate flow regimes critical to downstream ecosystem services. We demonstrated the method using the Soil and Water Assessment Tool (SWAT), the Hydrological Simulation Program–FORTRAN (HSPF) model, and Distributed Large Basin Runoff Model (DLBRM) applied to the Maumee River Basin (USA). The approach helped in identifying that each model simulated flows within acceptable ranges. However, each was limited in its ability to simulate flows triggered by extreme weather events, owing to algorithms not being optimized for such events and mismatched physiographic watershed conditions. Ultimately, we found HSPF to best predict river flow, whereas SWAT offered the most flexibility for evaluating agricultural management practices.     

基于CvM算法的Nakagami衰落信道统计特性检验

Nakagami信道通过不同的衰落因子m可以仿真不同的信道衰落环境,仿真数据与实际测量值吻合度较高,在信道仿真领域得到广泛应用。然而,目前针对Nakagami信道模型的可信性研究较少,缺少科学的比对验证方法。根据典型Nakagami信道的一阶包络序列服从Nakagami分布这一信道统计特性,提出一种基于Cramer-von Mises （CvM）算法的拟合优度检验方法。使用“高斯+瑞利+直流”组合法建立Nakagami衰落信道模型,得到信道输出序列并从中提取包络序列。在此基础上,利用双样本CvM检验算法对包络序列的理论分布和实际分布进行拟合优度检验,实现对Nakagami信道模型的可信性评估。半实物仿真结果表明,与K-S检验、卡方检验和Z检验+卡方检验融合检验算法相比,CvM针对不同m下的Nakagami衰落信道均具有较好的识别性能,同时在可靠性和复杂度方面也具有优势,其对虚警概率为0.01以下的Nakagami衰落信道识别准确率达到92.6%,对样本长度为300 000以上的Nakagami衰落信道平均识别准确率达到96.4%,而当待检验信道为其他信道时,不存在误识别的情况。     

Residual analysis for ARCH(p)-time series

In this paper we provide consistency and distributional convergence results for functions of residuals from an ARCH(p)-time series. An application to a goodness-of-fit problem is also discussed.     

考虑测试与运行差别的软件可靠性增长模型

软件可靠性增长模型中测试阶段和操作运行阶段环境的不同导致了两个阶段故障检测率的不同．在随机过程类非齐次泊松过程（NHPP）中的经典模型G—O模型基础上,考虑运行剖面和测试剖面的不同,对测试阶段和操作运行阶段的故障检测率进行了转化,得到了较好的刻画测试阶段和操作阶段失效率差别的模型（TO—SRGM）．最后,通过实例用最小二乘法对此模型的参数进行了估计．实验结果表明,在某些失效数据集上TO—SRGM的拟和效果比G—O模型和PZ—SRGM好．     

基于EM算法和GOF的宽带分布式 目标检测算法

 针对K分布杂波背景下的宽带分布式目标检测问题,提出了一种基于期望最大化算法和拟合优度检测方法的检测算法.该算法利用期望最大化方法估计杂波参数,提高了估值精度.通过结合拟合优度检测有效利用了目标回波对杂波背景的干扰,并简要分析该算法的恒虚警率性.对仿真数据与实测数据的多个仿真结果表明,与传统的非相干积累方法及基于散射点密度的广义似然相比,该算法检测性能有明显的提高.     

Variability of waste copper slag concrete and its effect on the seismic safety of reinforced concrete building: A case study

Proven research output on the behavior of structures made of waste copper slag concrete can improve its utilization in the construction industry and thereby help to develop a sustainable built environment. Although numerous studies on waste copper slag concrete can be found in the published literature, no research has focused on the structural application of this type of concrete. In particular, the variability in the strength properties of waste copper slag concrete, which is required for various structural applications, such as limit state design formulation, reliability-based structural analysis, etc., has so far not attracted the attention of researchers. This paper quantifies the uncertainty associated with the compressive-, flexural- and split tensile strength of hardened concrete with different dosages of waste copper slag as fine aggregate. Best-fit probability distribution models are proposed based on statistical analyses of strength data generated from laboratory experiments. In addition, the paper presents a reliability-based seismic risk assessment of a typical waste copper slag incorporated reinforced concrete framed building, considering the proposed distribution model. The results show that waste copper slag can be safely used for seismic resistant structures as it results in an identical probability of failure and dispersion in the drift demand when compared with a conventional concrete building made of natural sand.     

某型坦克齿轮接触疲劳强度可靠性的Monte Carlo数值模拟

利用MonteCarlo技术与X^2检验,模拟和检验某型坦克传动箱主动齿轮接触应力与接触疲劳强度分布规律,表明接触应力服从正态分布,接触疲劳强度服从三参数威布尔分布。基于应力、强度分布规律的模拟结果,进一步由Monte Carlo方法模拟得到齿轮接触疲劳可靠度在0．99以上。Monte Carlo模拟计算精度取决于模拟次数,当模拟次数达到10^4时,可靠度的模拟误差小于10^-3。对随机参数的敏感性分析表明,影响接触疲劳可靠度的最主要的参数是节点区域系数ZH和材料的疲劳极限应力σHlim。提高齿轮加工精度和选用疲劳极限应力σHlim。较高的材料都会有利于提高坦克传动箱主动齿轮的接触疲劳可靠性。     

真空包装鸡肉早餐肠中细菌总数生长预测模型的拟合优度比较

为比较不同生长预测模型对真空包装鸡肉早餐肠中细菌总数生长情况的拟合效果,观察在不同贮藏温度（2～15 ℃）下,使用Baranyi、修正的Gompertz及修正的Logistic模型分别描述细菌总数随时间变化的情况,以及使用Arrhenius方程与平方根模型描述一级模型所得参数随温度变化的情况。通过计算各模型的评价参数（均方误差平方根RMSE、回归系数R2、赤池信息准则与贝叶斯信息准则）,参考模型所得特征值及货架期残差值,评价各模型的拟合优度,寻找最优组合。结果表明：Baranyi模型所得方程的评价参数最优,最大比生长速率（μmax）最大,所得产品货架期残差值较小;应用修正的Gompertz模型更有利于优化二级模型评价参数;而修正的Logistic模型拟合所得初始菌数N0值偏小,且将15 ℃贮藏组延滞时间λ计算为负值。因此Baranyi模型的拟合优度最高,其次为修正的Gompertz模型,最后为修正的Logistic模型。应用Arrhenius方程与平方根模型均能够成功拟合,但未能得出拟合更优者。     

基于经验似然的拟合优度检验及应用题

针对拟合优度检验的问题,本文关心的问题是如何构造一个合适的统计量,使检验在控制第一类错误的情况下尽量减少第二类错误的概率.经验似然在拟合优度上的应用是利用数据服从原假设分布的条件来找估计方程,并由此构造检验统计量.而且经验似然结合拟合优度检验应用到两总体检验上.     

加速可靠性增长模型研究

建立产品可靠性在环境应力水平和增长时间段上二维变化的加速可靠性增长模型,给出了模型参数的最小二乘估计(LSE)和模型的拟合优度检验方法,有效地解决不同应力水平产品平均故障间隔时间(MTBF)的转换难题,为加速可靠增长问题的解决提供了新的思路。最后用具体的算例,验证了模型的正确性。