降雨诱发浅层冻土区边坡土剥落颗粒流模拟:以G214线典型冻土区路基边坡为例

为明确降雨诱发浅层冻土区边坡土剥落机理,以G214线典型冻土区路基边坡为例,基于颗粒流和等效降雨法,模拟不同坡度和冲刷速度下边坡坡面土的剥落过程,从边坡形态、颗粒运移规律、力链演化规律和剥落量等方面详细进行探究。结果表明:浅层冻土区边坡土受到雨水冲刷后,仅在坡面浅层部位出现坑槽,并提出边坡形态系数(τ)来定量化表征边坡形态的凹凸程度。边坡形态总体变化态势可概括为:笔直平坦(1.0≤τ<1.40)、粗糙不整(1.40≤τ<1.50)和凹凸不平(1.50≤τ)。土颗粒间接触力演化主要发生在降雨冲刷作用初期,冲刷过程中接触力演化特征并不明显。随循环次数增加,冲刷速度越大接触数量总体越少,但最终稳定状态下的接触数量近乎相同。此外,边坡浅层土在冻融循环作用下结构疏松是导致冻土区坡面土易被雨水冲刷剥落和坡面易形成冲沟的本质原因。

基于社会需求为导向的统计软件教学改革

统计软件已经成为大数据时代背景下数据分析的重要工具。通过对以社会需求为导向的统计软件教学方法、教学过程进行探讨,以期为推动统计软件的教学进一步提高提供一定的借鉴意义。

Estimation and test of restricted linear EV model with nonignorable missing covariates

This paper deals with estimation and test procedures for restricted linear errors-invariables(EV) models with nonignorable missing covariates. We develop a restricted weighted corrected least squares(WCLS) estimator based on the propensity score, which is fitted by an exponentially tilted likelihood method. The limiting distributions of the proposed estimators are discussed when tilted parameter is known or unknown. To test the validity of the constraints,we construct two test procedures based on corrected residual sum of squares and empirical likelihood method and derive their asymptotic properties. Numerical studies are conducted to examine the finite sample performance of our proposed methods.