江淮丘陵区塘坝灌溉能力估算及其演变特征

鉴于塘坝工程在江淮丘陵区蓄水灌溉中的重要作用,通过对塘坝工程与作物种植结构发展历程的综合分析,提出了基于水量供需平衡分析的塘坝灌区灌溉能力概念及其计算模型,定量评估了江淮丘陵区不同年代的塘坝灌溉能力,揭示了塘坝灌溉能力的动态演变特征。研究结果表明:江淮丘陵区全区塘坝灌溉能力在20世纪60年代达到峰值后,70～90年代呈显著下降趋势,至21世纪初有所回升。研究结果可为江淮丘陵区塘坝发展规划与灌溉制度的制定提供理论依据与技术支撑,具有重要实际指导意义。     

印尼地区嵌岩灌注桩竖向承载特性现场试验

为更加深入研究不同竖向荷载作用下大直径嵌岩灌注桩的承载特性与荷载传递规律,以印尼地区某工程为依托,对3根直径为800 mm的嵌岩灌注桩进行单桩竖向抗压静载试验与桩身应力测试。试验结果表明:3根试桩的Q-s曲线均为缓变型,沉降量均不超过17 mm,回弹率较大,介于54.8%~70.9%之间,残余沉降较小,承载力较高,均满足设计要求。桩身轴力随桩顶荷载的增加逐渐增大,随深度逐渐递减;桩侧摩阻力的发挥具有异步性,随着荷载的增大,桩侧摩阻力逐渐发挥,在嵌岩段桩侧摩阻力最大,但仍未充分发挥;桩端阻力随桩顶荷载的增加近似呈线性增大,在最大荷载作用下,桩端阻力占比约55%,表现出摩擦端承桩的特性。研究结果对国内桩基规范的完善以及当地桩基规范的制订具有较重要的意义。     

NH3·H2O对桂林地区红黏土工程特性的影响试验研究

为研究氮肥污染对桂林红黏土物理力学性质的影响,使用氨水(NH₃·H₂O)溶液对具有代表性的桂林雁山红黏土进行浸泡,考虑氨水质量分数(0,4.5%,9.0%,13.5%,18.0%)和养护时间(1,7,14 d)双因子因素,通过室内试验,分析氨水污染对桂林雁山红黏土物理力学性质的影响规律。试验结果表明:随着氨水质量分数及养护时间的增加,桂林雁山红黏土的质量、含水率、相对密度和液塑限均增大,压缩模量减小,土体压缩性增强;碱-土作用是引起红黏土物理力学性质发生变化的主要原因,其相互作用导致红黏土颗粒间的胶结物被溶解后又重新生成絮状物,使其原本稳定的结构状态发生改变。     

考虑多因素作用下的RC梁抗力时空退化模型

为研究钢筋混凝土结构锈蚀后的力学性能和抗力退化规律,基于RC梁加速锈蚀试验结果,首先综合考虑均匀锈蚀和点蚀同时发生的影响,对钢筋截面面积的时变模型进行分析,其次探讨裂缝宽度与氯离子扩散系数及RC梁抗力的关系,随后考虑受拉主筋锈蚀不均衡的影响,对结构抗力计算模型进行讨论,最后基于材料性能和结构尺寸的空间变异性,建立RC梁抗力时空退化模型,并对桥梁服役100 a后的抗力进行预测.研究发现:当考虑各参数的空间变异性时,不考虑裂缝影响得到的抗力值比考虑裂缝影响得到的抗力值高了9.91%;考虑各参数空间变异性时的抗力值比不考虑时下降了14.68%;适当的选取波动系数和单元尺寸对考虑结构各参数的空间变异性十分重要;潮汐区和浪溅区环境下结构的剩余抗力分别为初始抗力的43.23%和36.45%,较海岸线大气区环境下的抗力值分别下降了6.73%和21.35%,因此在结构服役期间,应尽量做好防腐措施,减少氯离子侵蚀对结构耐久性的破坏.     

High precision frequency measurement based on the characteristic of the fuzzy area

The phase difference change is random in the discrete fuzzy area by considering the limit of device resolution, which the device can not stably capture, and the precision of the measured value only reaches the level of ns, but the phase difference change in the concentrated fuzzy area is step by step, and the device can stably capture the change of ps. By using the fuzzy area conversion technology, a high precision frequency measurement is designed. Through computer control and frequency synthesis,the discrete fuzzy area is converted to the concentrated fuzzy area, the ps stability properties of phase difference change on the border of the concentrated fuzzy area is used, the precision can be improved two or three orders of magnitude, and the high precision measurement in a wide range is achieved.     

Fast method for SAR echo simulation of a three-dimensional ground scene

Due to huge calculation of SAR echo simulation of a three-dimensional (3D) ground scene, a fast simulation method is proposed. First, the data of a 3D ground scene are fractionally interpolated based on the Fractional Brownian Motion (FBM) model. Second, the data interpolated are divided into lots of small facets whose precision meets the simulation requirement, the backscattering coefficients of the small facets are calculated. Third, the shaded area is judged by the comparison method of overlook angles. Three parallel levels are analyzed and the kernel function is designed. Finally, the computing method of reduction adding and external thread are also utilized under the framework of GPU in order to get high efficiency. With the methods mentioned above, the imaging result of experimental DEM data verifies the validity and superiority of the proposed method.     

1951—2013年周口地区降水时空变化特征研究

为了研究区域降水的时空演变规律,根据周口地区28个雨量站1951—2013年的月降水量实测资料,利用经验正交函数(EOF)分析法、Mann-Kendall检验法及Morlet小波分析法,分析了周口地区63年来降水的空间分布、时间系数变化特征和时间序列的趋势性、突变性及周期性。结果表明,周口地区降水的空间分布有3种模式:全市丰(枯)一致型、南丰(枯)北枯(丰)型和东丰(枯)西枯(丰)型,其中全市丰(枯)一致型为周口地区降水的主要分布模式,其中1966年的全市降水偏枯和2003年的全市降水偏丰最为典型;周口地区降水量由东南向西北逐渐减小,各站点降水趋势变化不一,西南部呈下降趋势,中北部呈上升趋势,降水总体呈下降趋势;区域整体降水在1997年发生了突变,整体降水周期性变化明显,存在时间尺度为21 a的变化周期。研究结果可为周口地区的农业生产以及旱涝预警和减灾防灾提供理论支撑。     

Groundwater impact of open cut coal mine and an assessment methodology: A case study in NSW

Large scale open cut coal mining operations have significant impacts to groundwater in surrounding areas in both active and post-mining phases. The prediction of water inflows into a surface mine excavation is one of the many components involved in mine design phase. Groundwater performance also reacts to mining activities from the operational, economic and safety implications perspective. Under NSW planning legislation, as part of the comprehensive risk assessment, a groundwater impact assessment has to be conducted for a coal project to predict and mitigate the impacts in consideration of the government requirements. In this paper, the groundwater assessment modelling of mine pits was discussed in predicting of groundwater inflows and reviewing analytical and numerical approaches. A methodology of groundwater impact assessment for an open cut mine in NSW with a three-dimensional groundwater flow model Modflow Surfact demonstrated its functions in simulating the project's impacts on the groundwater regime. The key findings with mitigations are discussed and recommended in the paper to reduce impacts on groundwater and fulfil regulation requirements in NSW.     

内陆干旱区实施最严格水资源管理的关键技术研究——以新疆呼图壁河流域为典型示范区

以最严格水资源管理理念为前提,从最严格水资源管理下的区域水资源综合模拟、水资源管理分配,以及典型研究区流域水资源监测框架核心技术及考核指标的评价体系这4个方面,研究内陆干旱区实施最严格水资源管理的关键技术,且以天山北坡中段呼图壁河流域为典型示范区,揭示流域内水资源的供需规律,建立适应内陆干旱区的最严格水资源管理制度,为实现区域水资源的可持续利用以及支撑区域经济社会的可持续发展提供科学依据和决策建议,为干旱区贯彻和落实最严格水资源管理制度提供科技支撑。     

Structural variability and its relation to edaphic attributes of mangroves in the south‐west coast of India

We estimated the tree structural variables (density, frequency and basal area) of true mangroves and soil variables like particle size distribution, carbon, available nitrogen and phosphorus, sulphur, nutrient cations (K, Na, Ca, Mg) of Cochin mangroves and examined the relationship between vegetation and environment. The study sites were classified as seaward fringe, riverine and interior. Of the thirteen true mangrove species present, Avicennia officinalis, Sonneratia caseolaris and Excoecaria agallocha showed higher Importance Value Index. The mean stem density varied from 80 to 25,000 no./ha and basal area from 0.1 to 39.68 m²/ha. Seaward mangroves showed maximum stand basal area and biomass production while riverine exhibited maximum density. Maturity Index value of Cochin mangroves revealed a very low degree of structural maturity. Interior mangroves were characterized by silty soil with higher nutrient concentrations. Principal component analysis of soil data revealed that the major factors influencing mangrove vegetation were soil texture, nutrients, salinity and oxidation–reduction potential. The stem density and basal area of different species correlated highly with soil nutrients and texture (p < .001) while salinity showed negative correlations with vegetation characteristics. The data generated in the study would be fundamental in site‐specific management and conservation efforts of these degrading mangroves.