Effects of hillslope topography on hydrological responses in a weathered granite mountain,Japan: comparison of the runoff response between the valley‐head and the side slope

To evaluate the effects of hillslope topography on storm runoff in a weathered granite mountain, discharge rate, soil pore water pressures, and water chemistry were observed on two types of hillslope: a valley‐head (a concave hillslope) and a side slope (a planar hillslope). Hydrological responses on the valley‐head and side slope reflected their respective topographic characteristics and varied with the rainfall magnitude. During small rainfall events (<35 mm), runoff from the side slope occurred rapidly relative to the valley‐head. The valley‐head showed little response in storm runoff. As rainfall amounts increased (35–60 mm), the valley‐head yielded a higher flow relative to the side slope. For large rainfall events (>60 mm), runoff from both hillslopes increased with rainfall, although that from the valley‐head was larger than that from the side slope. The differences in the runoff responses were caused by differences in the roles of lower‐slope soils and the convergence of the hillslope. During small rainfall events, the side slope could store little water; in contrast, all rainwater could be stored in the soils at the valley‐head hollow. As the amount of rainfall increased, the subsurface saturated area of the valley‐head extended from the bottom to the upper portion of the slope, with the contributions of transient groundwater via lateral preferential flowpaths due to the high concentration of subsurface water. Conversely, saturated subsurface flow did not contribute to runoff responses, and the subsurface saturated area at the side slope did not extend to the upper slope for the same storm size. During large rainfall events, expansion of the subsurface saturated area was observed in both hillslopes. Thus, differences in the concentration of subsurface water, reflecting hillslope topography, may create differences in the extension of the subsurface saturated area, as well as variability in runoff responses. Copyright © 2007 John Wiley & Sons, Ltd.     

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A J2‐plasticity model based on bounding surface concept

This article presents the development of a J₂ small strain plasticity model based on bounding surface concept, along with numerical examples to demonstrate model behaviors and identification of model parameter using laboratory test data. The model is motivated by the need for simulating permanent deformation accumulation of asphalt concrete mixtures, which leads to rutting in flexible pavements under repeated traffic loading. The proposed model accounts for the observation that rutting is mostly caused by shearing and takes advantage of the fact that bounding surface concept allows for the progressive accumulation of plastic deformation under constant amplitude loading condition. Analytical solutions are given for typical laboratory testing conditions. The model can be calibrated using repeated simple shear test data that are typically available for asphalt concrete mixtures. It is shown that the model is easy to use and provides a promising alternative for modeling permanent deformation accumulation in materials subjected to repetitive (cyclic) loading. Copyright © 2012 John Wiley & Sons, Ltd.     

统一硬化模型与下加载面模型的理论关系

Hashiguchi下加载面本构模型是国际上具有较大影响力的超固结土本构模型之一。因此,选取该模型进行理论和构建方法分析,并与UH模型进行对比。对比结果表明,Hashiguchi下加载面模型通过定义单一的数学公式来拟合超固结土内变量的变化规律,从而得到了超固结土应力−应变关系的公式;而统一硬化（unified hardening,简称UH）模型掌握了超固结土体的强度特性,因而能够更准确、合理地描述超固结土的应力−应变关系。相较于Hashiguchi下加载面本构模型,UH模型在理论上更为先进。同时,两个模型的试验预测与试验数据的对比也验证了UH模型在数值计算上的正确性与优越性。     

基于线黏弹性接触的落石冲击地面参量理论研究

落石与坡面或者防护结构接触过程中冲击参量随时间变化特征是描述落石碰撞过程的重要指标,对于揭示落石与坡面相互作用机制以及采取合理的防护措施具有重要的意义。在现有的相关设计规范中,并没有给出关于落石冲击力时程关系的计算方法,仅参照有关规范或经验方法确定一个落石最大冲击力值。为此,首先基于线黏弹性接触理论,建立落石冲击地面力学模型,根据位移-速度组合初始条件以及速度-加速度组合初始条件分别推导得到两种落石冲击特征参量理论解析解;然后基于 ANSYS/LS-DYNA 非线性动力学软件,建立落石冲击地面三维数值模型,研究球体落石冲击地面力学特点;最后将理论结果对比室内试验和已有的研究成果,得出以下结论：（1）Hertz 弹性接触理论结果中各参量变化在加载阶段和恢复阶段均呈现对称的趋势,速度、加速度初始条件下的落石冲击特征参量和动力有限元法非常接近,而位移-速度初始条件组合并不适用于研究落石冲击下的动力特征;（2）不同速度和下落高度下,落石最大冲击力值随落石下落高度和冲击速度的增大而增加,而落石冲击作用时间随下落高度和冲击速度的增加而减小;（3）计算结果得到的落石最大冲击力以及落石冲击作用时间与室内试验结果和已有成果相接近,相比室内试验和有限元结果的震荡性,此结果更能体现落石冲击力变化规律; （4）多种冲击速度下,对比不同方法得到的落石最大冲击力,可知计算结果均在各种冲击力计算结果的范围内,具有很好的可靠性。考虑到现有研究理论的不足,难以求解落石冲击力时程关系,求解结果丰富了落石碰撞理论,可以指导工程有关落石灾害的防护设计。     

无碰撞区跳频/时序列理论界与设计

跳频(时)序列分析与设计是跳频(时)扩频通信系统的核心技术.无碰撞区跳频序列是近年新出现的一个研究方向,现已成为通信领域的研究热点.对无碰撞区跳频序列的理论界及其设计进行深入研究,导出无碰撞区跳频序列的一些本质属性;讨论无碰撞区跳频序列集周期汉明相关函数的理论界,揭示几个理论界之间的关系,给出这些理论界等价的条件.提出最优无碰撞区跳频序列的一般构造方法.利用该构造方法,可以产生任意长度的最优无碰撞区跳频序列集.并且,任意一个最优无碰撞区跳频序列集,都可以由一般构造方法产生.     

非测绘专业《测量学》课程的教学改革探讨

本文以江西理工大学应用科学学院为背景,对非测绘专业《测量学》课程教学模式存在的问题进行详细剖析,并提出改革方案。     

A Study of the γ-ray and X-ray Radiations of BL Lac Objects

The X-ray and γ-ray flux densities of 18 γ-loud BL Lac objects as well as their average spectral indices of X-ray wave band (1 keV) and γ-ray wave band (>100 MeV) are collected, and the correlations among the various quantities are examined. The results indicate: (1) The X-ray flux density and the γ-ray flux density exhibit rather strong correlations in all the states, high, low or mediate. (2) Between the mean spectral indices in X-ray and γ-ray wave bands there is a comparatively intense anti-correlation. (3) Between the average spectral indices and the X-ray and γ- flux densities there is no evident correlation either in the high or the mediate state. (4) Between the average spectral index of γ-ray wave band and the flux density of X-rays in low state there is a rather strong anticorrelation. Between the mean spectral index of X-ray wave band and the γ-flux density in low state there also exists a weak correlation. The results of our analysis support the viewpoint that both the X-ray and γ-ray emissions of BL Lac objects come from the synchrotron radiation and synchrotron self Compton (SSC) radiation with one and the same distribution of relativistic electrons.     

地下水安全开采量的概念与评价方法研究

本文回顾了地下水安全开采量概念的产生与发展过程,综述了可持续开采量、允许开采量和安全开采量的内涵与差异,在此基础上,提出满足地下水的资源供给、生态环境维持、地质环境稳定和可持续开发利用能力4个功能条件下的地下水安全开采量概念.将安全开采量的评价方法分为单一约束型和耦合约束型两大类,提出一种基于水均衡和地下水动力学相结合的评价方法,并对安全开采量研究趋势进行了展望,为地下水的安全开采方案研究与动态管理提供技术支撑.     

论水土流失与土壤侵蚀及其有关概念的界定

水土流失、土壤侵蚀、水土保持等是水土保持学科和山区园土整治的常用概念，但长期以来对这些概念的解释可谓五花八门，即便正规教材、词（辞）典、知识性普及读物也是如此，这种状况极不利于山区水土流失防治工作的开展。本文在对土壤侵蚀过程、水土汉失内涵、土壤侵蚀量与流失量计量单元等关键性问题进行探析、并对现有国内外对这些概念的种种解释进行评述基础上，从水土保持的根本目的、特殊任务以及《水土保持法》的精神实质出发，按通俗性、大众性和可操作性的要求，对水土流失、土壤侵蚀、水土保持等基本概念进行了合理、可行的界定，得出了一些基本认识和体会，愿有助于山区水土流失防治工作的正常开展和水土保持学科的健康发展。