平流式二次沉淀池中异重流现象研究

通过对影响异重流形成因素的研究,发现在异重流的形成过程中进水污泥浓度对密度的影响远大于温度对密度的影响,二沉池的进水通常形成下层异重流.利用水力模型进行示踪试验,结果表明在平流式二沉池中存在明显的回流区.异重流对二沉池处理效果的影响有利有弊.     

王甫洲工程泄水闸围堰基础高喷防渗墙施工

王甫洲水利枢纽工程泄水闸施工围堰基础主要为砂卵石层，结构中密～密实，属较强～极强透水层。使用改制的ＢＺＫ—３Ａ 型喷灌机，大水量、大浆量、不分序连续施工，高压定喷构筑围堰基础防渗板墙。经围井开挖检查，钻孔及围井挖后抽水试验、泄水闸基坑开挖后的防渗效果分析表明，高喷防渗板墙厚度、墙体强度及墙体渗透系数均满足设计要求     

Evaluating Alternative Temporal Survey Designs for Monitoring Wetland Area and Detecting Changes Over Time in California

Evaluation of wetland extent and changes in extent is a foundation of many wetland monitoring and assessment programs. Probabilistic sampling and mapping provides a cost‐effective alternative to comprehensive mapping for large geographic areas. One unresolved challenge for probabilistic or design‐based approaches is how best to monitor both status (e.g., extent at a single point in time) and trends (e.g., changes in extent over time) within a single monitoring program. Existing wetland status and trends (S&T) monitoring programs employ fixed sampling locations; however, theoretical evaluation and limited implementation in other landscape monitoring areas suggest that alternative designs could increase statistical efficiency and overall accuracy. In particular, designs that employ both fixed and nonfixed sampling locations (alternately termed permanent and temporary samples), termed sampling with partial replacement (SPR), are considered to efficiently and effectively balance monitoring current status with detection of trends. This study utilized simulated sampling to assess the performance of fixed sampling locations, SPR, and strictly nonfixed designs for monitoring wetland S&T over time. Modeled changes in wetland density over time were used as inputs for sampling simulations. In contrast to previous evaluations of SPR, the results of this study support the use of a fixed sampling design and show that SPR may underestimate both S&T.     

Neutral modelling of agricultural landscapes by tessellation methods—Application for gene flow simulation

Neutral landscape models are not frequently used in the agronomical domain, whereas they would be very useful for studying given agro-ecological or physical processes. Contrary to ecological neutral landscape models, agricultural models have to represent and manage geometrical patches and thus should rely on tessellation methods. We present a three steps approach that aimed at simulating such landscapes. Firstly, we characterized the geometry of three real field patterns; secondly, we generated simulated field patterns with two tessellation methods attempting to control the value of some of the observed characteristics and, thirdly, we evaluated the simulated field patterns. For this evaluation, we considered that good simulated field patterns should capture characteristics of real landscapes that are important for the targeted agro-ecological process. Real landscapes and landscapes simulated using either a Voronoi or a rectangular tessellation were thus compared when used as input data within a gene flow model. The results showed that neither tessellation method captured field shapes correctly, thus leading to over or (small) under estimation of gene flow. The Voronoi tessellation, though, performed better than the rectangular tessellation. Possible research directions are proposed to improve the simulated patterns, including the use of post-processing, the control of cell orientation or the implementation of other tessellation techniques.     

盒形件拉深模CAD系统研究

此文介绍了作者自行开发的盒形件拉深模CAD系统的组成、功能以及编程中的若干技术问题。该系统人机对话界面友好,整个设计过程程序化程度高。系统运行时只需输入工件特征数据就可根据人机对话和菜单选项完成整个设计过程,最后输出工件图、毛坯图、排样图、工序图、模具零件图及总装图。     

双喷嘴矩形喷动床流体力学及脱硫性能的实验研究

针对半干法烟气脱硫方法,提出了一种新型的双喷嘴矩形喷动床半干法脱硫技术.在相同的静床层高度下,研究了最小喷动速度、最大喷动压降和喷动高度;在相同的Ca/S比、进气SO2浓度、进口温度、绝热饱和温差条件下,以消石灰为脱硫剂,研究了脱硫性能,并与传统柱锥形喷动床进行了比较.结果表明,矩形喷动床拥有更好的流动性能和脱硫率,得出了实验条件下矩形喷动床的最佳操作范围.     

矩形喷口射流火火焰轴向温度研究

随着我国能源结构低碳化的发展,天然气产业在我国得到进一步升级。在利用高压管道进行输运的过程中,因泄漏而引发的天然气火灾爆炸事故时有发生。实验以甲烷为燃料,研究不同开口特征下(长宽比n=1,2.25,4,9,16)矩形火源火焰中心轴线的温度分布。研究表明,火焰温度随热电偶相对位置的变化呈现出三段分布的规律。通过引入虚点源Z_0对经典羽流模型进行修正,发现不同长宽比下无量纲虚点源与火焰佛罗德数Fr_f呈现一定的函数关系,且无量纲温度在高度方向上仍呈现三段式分布。     

Some Interpolation Estimators in Environmental Risk Assessment for Spatially Misaligned Health Data

Ecological regression studies are widely used in geographical epidemiology to assess the relationships between health hazard and putative risk factors. Very often, health data are measured at an aggregate level because of confidentiality restrictions, while putative risk factors are measured on a different grid, i.e., independent (exposure) variable and response (counts) variable are spatially misaligned. To perform a regression of risk on exposure, one needs to realign the spatial support of the variables. Bayesian hierarchical models constitute a natural approach to the problem because of their ability to model the exposure field and the relationship between exposure and relative risk at different levels of the hierarchy, taking proper account of the variability induced by the covariate estimation. In the current paper, we propose two fully Bayesian solutions to the problem. The first one is based on the kernel-smoothing technique, while the second one is built on the tessellation of the study region. We illustrate our methods by assessing the relationship between exposure to uranium in drinkable waters and cancer incidence, in South Carolina (USA).     

Scale invariant measures of pattern intensity and grain: A simulation experiment

We propose new dimensionless and scale-invariant measures for detection of pattern intensity, defined as the level of aggregation of individuals regardless their kind, and pattern grain, the level of segregation among individuals of at least two different kinds in point-pattern spatial data using tessellation methodology. Both real and simulated data on spatial distribution of plants in ecological communities show that the proposed parameters can be considered fingerprints of particular point patterns. This approach allows definition of both pattern intensity and grain for any kind of tessellated plane in an operational way, rendering these available for quantification and testing.     

Improved SWAT Model Performance With Time-Dynamic Voronoi Tessellation of Climatic Input Data in Southern Africa1

Andersson, Jafet C.M., Alexander J.B. Zehnder, Bernhard Wehrli, and Hong Yang, 2012. Improved SWAT Model Performance with Time-Dynamic Voronoi Tessellation of Climatic Input Data in Southern Africa. Journal of the American Water Resources Association (JAWRA) 48(3): 480-493. DOI: 10.1111/j.1752-1688.2011.00627.x Abstract: In this study, we compared two approaches to obtain climatic time series for the Soil and Water Assessment Tool (SWAT), namely the conventional centroid method and time-dynamic Voronoi tessellation, and assessed the performance of SWAT in simulating discharge and smallholder maize yields in Southern Africa. Climatic time series were estimated with each method. The Voronoi method utilized all available precipitation and temperature data, but the centroid method used only 14.5 and 82.5%, respectively. After centroid processing, sub-basin time series were on average 42 and 63% incomplete, respectively. After Voronoi processing, all time series were complete. SWAT was fed with each climate dataset. Each model setup was independently calibrated and validated against discharge and maize yield. Similar model performance was obtained with both methods for yield. The root mean squared error during calibration was 0.26 and 0.27 t ha⁻¹ for the centroid and Voronoi methods, respectively (p-value: 0.80). However, daily discharge simulations improved significantly with the Voronoi method. The coefficient of determination increased from 0.24 to 0.39 in the calibration period (p-value: 9.6 × 10⁻¹³) and from 0.41 to 0.48 in the validation period (p-value: 3.1 × 10⁻³). The Voronoi method improved the simulation of the river flow regime. The largest improvements were obtained in data scarce situations, at high spatial and temporal resolution, and where the centroid method performed the worst.