基于平面压入技术研究焊接接头单轴应力-应变关系

目的 获取异种金属焊接接头母材和热影响区局部拉伸应力-应变关系。方法 对压水堆机组蒸汽发生器接管安全端异种金属焊接接头(20MND 5-INCONEL 52-Z2 CND 18.12控氮)进行研究,通过金相检验和显微硬度测试,研究DMWJ母材、热影响区、焊缝熔合线位置的金相组织和维氏硬度分布。采用等直圆棒拉伸试验获得DMWJ低合金钢(20MND 5)母材的应力-应变关系,采用基于能量等效理论的平面压入技术获得DMWJ低合金钢母材、热影响区和焊缝局部材料应力-应变关系。结果 DMWJ材料组织、力学性能不均匀,等直圆棒拉伸试验得到的低合金钢母材拉伸应力-应变关系与平面压入技术测得结果较为吻合。结论 基于能量等效理论的平面压入技术可精确测得DMWJ低合金钢母材、热影响区和焊缝局部材料应力-应变关系,对压水堆核电站DMWJ在役检测及结构完整性评价具有重要意义。     

基于流域演化的泥石流敏感性分析

基于泥石流来源于某些处于特殊演化阶段的分支小流域的理论,分析了面积高程曲线及其参数与泥石流活动的关系。面积高程曲线积分值S表征流域内松散固体物质量,S/2对应的相对高差比值K表征流域源地面积在不同高程的分布,以S和K为参数提出泥石流敏感性分析思路。针对汶川县主要公路(都汶公路和省道303)沿线泥石流敏感性分析,在Arcgis、Matlab等软件的支持下,基于震前1:50 000地形数据,计算了研究区泥石流流域的S和K。根据计算结果,初步判定了各流域的地貌发育阶段,以及流域源地汇水区的高程位置。并根据震后泥石流实际活动情况,对于S小于0.5但又属于震后频发型,或者S值大于0.5但其面积较大且分支较多泥石流沟,进行了次一级子流域的面积高程值计算,判定其易发生泥石流具体源地。最后,根据流域面积高程值S得出了研究区泥石流敏感性分级图,分析结果基本反应了地貌演化对泥石流发生能力的潜在影响。     

常温低基质厌氧氨氧化反应器启动及其稳定性

以上向流生物滤池为反应器,以实验室内氧化沟回流污泥为接种污泥,采用先培育好氧生物膜,后转为厌氧环境培育厌氧氨氧化生物膜的方式,成功实现了常温低基质浓度下厌氧氨氧化反应器的启动。控制反应器进水pH为7.50～7.80,NH4+-N为30～40 mg/L,NO2--N为35～50 mg/L,温度为20～25℃。224 d以后,反应器启动成功。在稳定运行阶段,出水亚硝氮和氨氮的平均浓度分别为1.4 mg/L和4.6 mg/L,平均去除率分别为95.3%和90.1%,去除比例为1～1.8∶1,主要集中在1.4～1.5∶1,亚硝氮和氨氮去除的容积负荷分别为104.2 mg/(L.d)和146.0 mg/(L.d)。     

河流近域土地利用格局与水质相关性分析——以巢湖流域为例

以河流近域土地利用构成与水环境质量间定量关系为研究对象，基于巢湖流域40个水质监测断面和320个河流近域作用区，运用GIS空间分析功能计算不同尺度作用区内土地利用构成，借助相关分析、冗余分析(RDA)等数理统计手段，分析土地利用构成与水质指数间的相关关系；并分析和比较了流域内山区和平原地区土地利用构成与水质之间关系。结果表明，巢湖流域近河道地区土地利用构成对各水质指数有重要影响，且受地形因素影响。其中，建设用地对河流水质恶化具有明显作用；河流沿岸林地布局能显著改善水质，尤其是对氨氮和高锰酸盐指数敏感；耕地面积变化与水质相关性不显著。RDA冗余分析证实了不同尺度下的土地利用类型对水环境影响具有尺度效应。研究成果对巢湖流域水环境管理具有重要的实际指导意义，并为同类研究提供借鉴     

塔山水库蓝藻暴发的成因及控制

简述了塔山水库蓝藻暴发的过程及成因。指出 ,由于水库的营养物质增多、水质恶化 ,在不利的水文、气象 (高温、光照充足、微风 )等条件下 ,导致蓝藻暴发。提出了相应的控制对策     

天津市中心城区空气污染物时间变化规律的研究

根据空气质量标准，分析了SO2、NO2和PM103项污染物不同季节，不同时期，不同时段变化规律、达标状况以及为制定相应的防治措施提供参考依据。     

Science with Society in the Anthropocene

Interdisciplinary scientific knowledge is necessary but not sufficient when it comes to addressing sustainable transformations, as science increasingly has to deal with normative and value-related issues. A systems perspective on coupled human–environmental systems (HES) helps to address the inherent complexities. Additionally, a thorough interaction between science and society (i.e., transdisciplinarity = TD) is necessary, as sustainable transitions are sometimes contested and can cause conflicts. In order to navigate complexities regarding the delicate interaction of scientific research with societal decisions these processes must proceed in a structured and functional way. We thus propose HES-based TD processes to provide a basis for reorganizing science in coming decades.     

Anthropogenic impacts on suspended sediment load in the Upper Yangtze river

Climate change and human disturbance drive catchment erosion and increase riverine sediment load sensitively in small and medium-sized watersheds. This is not always true in large basins, where aggregation and buffering effects have dampen the ability to determine the driving forces of sedimentation. Even though there are significant responses to sedimentation in large river basins, it is difficult to get a precise quantitative assessment of specific drivers. This paper develops a methodology to identify driving forces that change suspended sediment load in the Upper Yangtze river. Annual runoff and sediment load data from 1954 to 2005 at the Yichang gauging station in the Upper Yangtze basin, daily precipitation data from 60 meteorological stations, and survey data on reservoir sediment were collected for the study. Sediment load/rainfall erosivity (S/R), is a new proxy indicator introduced to reflect human activities. Since the mid-1980s, S/R in the Upper Yangtze has dramatically declined from 0.21 to 0.03 (×10¹⁰ t ha h MJ⁻¹ mm⁻¹), indicating that human activity has played a key role in the decline of the suspended sediment load. Before the mid-1980s, a higher average S/R is attributed to large-scale deforestation and land reclamation. A significant sediment decrease occurred from 1959 to 1961 during an extreme drought condition, and an increase in sedimentation in 1998 coincided with an extreme flood event, which was well recorded in the S/R curve. This indicates that the S/R proxy is able to distinguish anthropogenic from climate impacts on suspended sediment load, but is not necessarily indicatory in extreme climate events. In addition, typical drivers of riverine sediment load variation including soil conservation projects, reservoirs construction, and land use/cover change are discussed.     

Application of an enzyme-linked immunosorbent assay for the detection of clenbuterol residues in swine urine and feeds

The present study outlines applications of an enzyme-linked immunosorbent assay (ELISA) for the analysis of clenbuterol residues. Antisera were raised from rabbits immunized with diazotized clenbuterol-bovine serum albumin (BSA) conjugate. The assay was specific to clenbuterol with a half-maximum inhibition concentration (IC₅₀) of 1.8 ng/mL and 2.5 ng/mL in blank swine urine and phosphate buffer solution, respectively. The assay had high cross-reactivity (86%) with mabuterol, but low with other adrenergic agonists and antagonists. The average recovery of clenbuterol, as measured with the ELISA, ranged from 90% to 112% in swine urine samples and from 86% to 95% in feeds, respectively. This new assay was compared with commercial ELISA test kits. An excellent correlation (r ² = 0.98) between the two methods and satisfactory recoveries suggest that the new assay can be suitable for the determination of clenbuterol residues in real samples. The assay was used to analyze clenbuterol residues in 103 swine urine samples and 68 feed samples collected from northern China. Approximately 50% of the urine samples and 25% of the feed samples analyzed were found positive (concentration of clenbuterol ≥ 1 ppb). The results indicate that clenbuterol was misused in some of the areas surveyed.