基于饱和曲线法的地基沉降全过程预测

针对S形沉降时程特征,提出了饱和曲线预测模型。首先,证明了该模型与S形沉降曲线的特点是相吻合的,包括有界性、单调递增性、存在反弯点,同时考察了模型中各参数改变对结果的影响; 其次,阐述了待定参数的获取方法和沉降预测步骤; 最后,通过多个工程实例对沉降预测模型的合理性进行了研究。算例表明,饱和曲线预测模型可以有效地用于加载全过程的沉降预测,具有适应性较广、精度较高、稳定性好的特点。与双曲线法、指数曲线法、星野法、生长曲线法相比而言,本文提出的沉降预测模型可靠性较高,具有一定的工程价值和应用前景。     

非饱和抗剪强度指标c、φ值与含水率w的关系

非饱和土力学已经确认了基质吸力与非饱和土的强度指标有关,而基质吸力与含水率有着密切的关系。通过理论和三轴剪切试验分析,探讨了非饱和残积土抗剪强度指标c、φ与含水率ω变化的一般规律;同时结合已经推出的土水特征曲线关系,探讨抗剪强度指标c、φ与基质吸力μ的变化的一般规律。结果表明:随着非饱和土含水率ω增加、基质吸力μ的减小,黏聚力c有减少的趋势,内摩擦角φ变化不大。通过线性回归分析,黏聚力与含水率成半对数线性关系,黏聚力与基质吸力成线性关系。现有的非饱和土实用公式精确性较差,非饱和土抗剪强度指标有待进一步的研究与完善。     

应用心理学原理控制测量野外实习任务量

测量实习中的测量任务量的确定是关系到实习成败的关键因素,本文应用<心理学>的普遍原理并结合本校学生进行测量实习实际情况,通过<心理学>中关于注意、记忆、感知等思维的基本原理,以及对同学在不同时期时所学知识理解的问卷调查,并与教师完成任务量所用时间的比较.得到以教师所完成的工作量为参照,来探讨确定同学测量实习的最佳任务量的科学的方法.在教学实践中取得了良好的效果.     

软基处理中土方量的计算方法

本文在考虑地基沉降的基础上建立土方量计算模型,把土方量的计算分为两个构成要素,并结合现场沉降观测结果进行分析计算,从而计算出由于地基沉降而引起土方量的增加量,最终推导出堆载量的一个计算公式。     

How does carbon dioxide emission change with the economic development? Statistical experiences from 132 countries

Issues concerning what measures should be adopted to achieve a sustainable world with less carbon dioxide emission and in what magnitude should we reduce our emission have been on agenda in both international negotiations and countries’ policy making aimed at coping with potential global climate change. These issues cannot be easily addressed unless comprehensive understanding about the countries’ status quo as well as historical relationship between economic development and carbon dioxide emission are gained. In this paper, we examine the historical relationship between economic development and carbon dioxide emission; the ex ante restrictions on function forms and the poorly handled robustness issues rife in economics literature are synthetically addressed. Evidence from recent four decades indicates that per capita carbon dioxide emission first significantly and monotonously increase at low income level and flattens after per capita income reaches at about 22,000 $ (2005 constant price). We perform various robustness checks by employing different data sources, different model specifications and different econometric estimates. The captured development–emission relationship is robust. Our empirical results indicate factors such as urbanization, population density, trade, energy mix and economic environment impact the absolute level of carbon dioxide emission not the overall income elasticity structure of carbon dioxide emission.     

基于龚帕斯生长曲线的高填石路堤沉降规律分析

高填石路堤的沉降变形过程一般为从填石体施工期的瞬时变形到进一步的蠕变变形,其沉降变化规律与龚帕斯生长曲线变化规律相似,有着较为明显的出生、成长、成熟和衰老的阶段。通过对龚帕斯生长曲线模型的合理取值,可较好的利用该沉降分析模型来拟合和分析高填石路堤的沉降数据,并且可以反映出沉降的发展变化趋势,作出沉降预测。      

Using hydrologic and hydraulically derived geometric parameters of perennial rivers to determine minimum water requirements of ecological habitats (case study: Mazandaran Sea Basin—Iran)

This paper studies one of the most important problems of dry countries that are confronted with water deficit and the competition of rivals to allocate water. Some common methods have been investigated for computing the minimum water requirement to save a river's biological activity. After a discussion of the currently used method in Iran (the Tenant Method), the application of some other methods, which are known as Hydraulic and Hydrological Methods, is illustrated. The case study is a river in the northern part of Iran and this research addresses the critical situation of this river in near future regarding the planned anthropogenic alteration and its consequences. It has been shown that the application of environmental water allocation methods that have no background in a region could be misleading. The first proposed method is the Texas Method, in which flexibility in water allocation helps to develop an integrated river management paradigm in the study area. The second preferred method is a Hydraulic Method, by which the implementation of morphological parameters or flow geometrical properties could sustain physical habitat within an acceptable range in terms of depth, width, velocity, and bed shear stress. In the case study, the Maximum Curvature Method was superior to the Slope Method. The investigation revealed that using a widely recommended slope of 1 for the discharge‐wetted perimeter function can lead to an overestimated and unacceptable discharge. The Tenant Method in respect to minimum environmental flow requirement yielded the weakest result, and it has been illustrated that its application might impose irrecoverable shock to the ecosystem. The Flow Duration Curve Method (the Q₉₅ Method), in spite of its subjectivity, showed more compatibility with the river's condition in comparison with the Tenant Method. Copyright © 2011 John Wiley & Sons, Ltd.     

Automated registration of dense terrestrial laser-scanning point clouds using curves

This paper proposes an automatic method for registering terrestrial laser scans in terms of robustness and accuracy. The proposed method uses spatial curves as matching primitives to overcome the limitations of registration methods based on points, lines, or patches as primitives. These methods often have difficulty finding correspondences between the scanned point clouds of freeform surfaces (e.g., statues, cultural heritage). The proposed method first clusters visually prominent points selected according to their associated geometric curvatures to extract crest lines which describe the shape characteristics of point clouds. Second, a deformation energy model is proposed to measure the shape similarity of these crest lines to select the correct matching-curve pairs. Based on these pairs, good initial orientation parameters can be obtained, resulting in fine registration. Experiments were undertaken to evaluate the robustness and accuracy of the proposed method, demonstrating a reliable and stable solution for accurately registering complex scenes without good initial alignment.     

曲线弯曲识别与等高线簇结构化方法

提出基于曲线弯曲识别的等高线簇结构化方法,实现等高线簇中所蕴含的地形结构的提取。首先对基于Delau-nay三角网的曲线弯曲识别方法进行改进,包括伪弯曲的合并、弯曲基点的调整及小弯曲的删除方法;基于此,建立弯曲间的层次嵌套关系及平行相邻关系,实现曲线弯曲的识别方法;然后,根据单条等高线间的空间关系,对弯曲类型进行判断;结合曲线间的空间邻近度计算方法,将等高线簇中的成组弯曲进行提取;最后完成了地形结构的识别,实现了等高线簇的结构化。该方法不仅对地形中的山谷进行提取,并且提取出了其对称结构即山脊。试验结果与水系叠置显示,所提取出的地形结构基本合理,证明了该方法的有效性。     

Development of a robust runoff-prediction model by fusing the Rational Equation and a modified SCS-CN method

Abstract

The objective of this study is to develop a Modified Rational Equation (MoRE) that combines the advantages of the Rational Equation (e.g. simplicity and global acceptance) and those of the standard US Department of Agriculture (USDA) Soil Conservation Service (SCS) curve number (CN) method (e.g. easy parameterization and extensive verification across the world). Herein, the hypothesis is that the MoRE is more accurate, consistent and robust than the SCS-CN method and its improved versions in predicting runoff in watersheds with limited data. The MoRE was designed to have a simple structure that is described by four intrinsic parameters: CN, permanent wilting point, field capacity and saturation soil moisture, and does not include initial abstraction as a variable. An evaluation of 77 USDA small agricultural watersheds indicated that CN of the MoRE has different physical meanings from CN of the SCS-CN method. The MoRE (mean Nash-Sutcliffe coefficient, E > 0.73) performed better than the SCS-CN (mean E < 0.32) and the four improved models (mean E < 0.56) in reproducing the runoff of the study watersheds. Performance of all six models varied greatly between watersheds, as well as between events, but was independent of watershed drainage area. However, the model performances tend to be better for watersheds and/or events with a runoff-to-rainfall ratio of between 0.1 and 0.3 than for those with a ratio outside this range. The MoRE has the most consistent and robust performance.

Editor D. Koutsoyiannis; Associate editor I. Nalbantis

Citation Wang, X., Liu, T., and Yang, W., 2012. Development of a robust runoff-prediction model by fusing the rational equation and a modified SCS-CN method. Hydrological Sciences Journal, 57 (6), 1118–1140.