MTMD对高速铁路32m预应力混凝土简支箱梁竖向振动特性的影响分析

为降低京沪高速铁路苏州北站候车厅受桥梁振动的影响,拟在正线32m预应力混凝土简支箱梁内安装多重调频质量阻尼器(MTMD)。通过建立车—桥—MTMD竖向动力分析模型,分析MTMD对32m简支箱梁竖向振动特性的影响。计算结果表明,加装MTMD后,32m简支箱梁一阶竖向自振频率有所降低,32m简支箱梁的竖向振动响应明显减小。     

71 ℃试验法寿命外推结果的影响因素分析

目的 研究71 ℃试验法用于火工品贮存寿命外推结果的准确性。方法 采用对比分析的方法,对美军标和国军标中71 ℃试验法的寿命影响因素进行分析。结果 加速模型、试验条件和外推温度取值对火工品的寿命外推结果均有影响。结论 71 ℃试验法评估结果的准确性取决于使用场景是否正确,试验条件设置是否合理,贮存环境温度取值是否准确,并提出了71 ℃试验法的使用建议。     

Spectroscopic and molecular characterization of humic substances (HS) from soils and sediments in a watershed: comparative study of HS chemical fractions and the origins

Environmental Science and Pollution Research - Optical properties and molecular composition of humic substances (HS) can provide valuable information on the sources and the history of the...     

Ozonation effects on emerging micropollutants and effluent organic matter in wastewater: characterization using changes of three-dimensional HP-SEC and EEM fluorescence data

The degradation of effluent organic matter (EfOM) in a municipal wastewater treated by ozonation was characterized using the methods of high-performance size-exclusion chromatography (HP-SEC) and excitation/emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC). The removal of 40 diverse trace-level contaminants of emerging concern (CEC) present in the wastewater was determined as well. Ozonation caused a rapid decrease of the absorbance and fluorescence of the wastewater, which was associated primarily with the oxidation of high and low apparent molecular weight (AMW) EfOM fractions. PARAFAC analysis also showed that components C1 and C2 decreased prominently in these conditions. The EfOM fraction of intermediate molecular weight ascribable to a terrestrial humic-like component (C3) tended to be less reactive toward ozone. Relative changes of EEM fluorescence were quantified using F _max values of PARAFAC-identified components (∆F/F ⁰ _max). Unambiguous relationships between ∆F/F ⁰ _max values and the extent of the degradation of the examined CECs (∆C/C₀) were established. This allowed correlating main parameters of the ∆C/C₀ vs. ∆F/F ⁰ _max relationships with the rates of oxidation of these CECs. The results demonstrate the potential of online measurements of EEM fluorescence for quantitating effects of ozonation on EfOM and micropollutants in wastewater effluents.

     

膨胀石墨负载Co3O4催化过硫酸氢钾复合盐降解酸性橙Ⅱ的研究

以膨胀石墨(EG)作为Co3O4的载体,制备出应用于基于硫酸根自由基的高级氧化技术的非均相催化剂复合物——Co3O4/EG,并用其降解水中的偶氮染料酸性橙Ⅱ,同时考察了氧化剂投加量、催化剂投加量、温度等因素对降解性能的影响以及催化剂的稳定性.结果表明,Co3O4/EG具有很高的催化活性,在最佳条件下能在8 min内完全降解酸性橙Ⅱ,且具有很好的稳定性.     

利用截留数定量表征流速变化时DANPL驱替运移行为

SEAR(Surfactant-enhanced aquifer remediation)技术被用于修复DANPL,其修复机制分为增溶作用和驱替作用,其中驱替作用对于DNAPL的修复更为有效.多孔介质中DNAPL的驱替运移过程中,定量评价DNAPL的修复行为极为重要.本文利用多相流数值模型UTCHEM探究了流速对DNAPL驱替运移行为的影响.通过截留数定量评价流速变化时DNAPL的驱替行为,结果表明流速变化时,截留数能较准确描述驱替运移行为及流速变化时DNAPL的驱替效率.以截留数的两个分量毛管数和邦德数的比值定义的角度τ能够较准确预测不同流速条件下驱替作用过程中残留DNAPL的运移路径.     

Environmental fate and behavior of silver nanoparticles in natural estuarine systems

Silver nanoparticles (AgNPs) are widely used in many consumer products, whereas their environmental behaviors in natural aquatic systems remain unknown, especially in natural brackish media. Therefore, it is urgent to investigate the environmental fate of AgNPs in natural brackish waters. Here, we investigated the stability of citrate-coated AgNPs in natural brackish water collected from 6 different sites with distinct salinities in the Xinglinwan Reservoir, located in Xiamen City, southeast China. The obtained results showed that AgNP colloids remained stable in low-salinity waters, which was mainly determined by the effects of dissolved organic matter (DOM) promoting the stability of the nanoparticles. However, the environmental fate of AgNPs in high-salinity waters was dominated by the salinity or ionic strength, especially the free ion concentrations of Cl^?, SO₄^2?, or S^2?, resulting in rapid sedimentation and dissolution. In addition, both DOM and salinity contributed to the environmental behavior of AgNPs in moderate-salinity waters, ultimately resulting in either colloidal stability or sedimentation. Overall, these results may reveal that AgNPs remain relatively stable for a long period in low-salinity natural waters, and that the stability might gradually decrease as AgNPs are transferred from freshwaters through brackish waters and eventually end up in seawater along the bay. Our findings also further indicate that the toxicity and potential risks of AgNPs may present more serious threats to the environment and organisms in natural freshwaters than in natural estuarine systems or seawater.     

轻小型无人机遥感在高山峡谷区山地灾害应急监测中的应用∗

高山峡谷区频发的山地灾害易堵塞河道形成堰塞湖,对下游城镇和重要基础设施影响极为严重。复杂的地形地貌环境中无法找到合适起降场地、航线规划不准、操作复杂等因素极大地限制了专业级无人机遥感系统在该区域的应用。针对高山峡谷区山地灾害发生后观测数据获取困难局面,探索将轻小型无人机应用于灾害应急监测。以藏东南深切峡谷地区102滑坡群2#滑坡、古乡沟泥石流为例,介绍了轻小型无人机遥感数据快速采集流程。基于航测影像数据对灾害现场进行三维模型快速重建,并将建模结果与三维激光点云模型对比,验证方法的可行性和准确性。结果表明:应急条件下基于轻小型无人机的山地灾害三维模型精度在分米级,平面方向精度高于高程方向,最大误差率低于9.7%。作为一种数据快速获取方法,可将其应用到山地灾害应急监测领域。     

Impact of long-range transport and under-cloud scavenging on precipitation chemistry in East China

Introduction  

Two hundred twenty-five precipitation samples were collected at high- (summit, 1,534 m ASL) and low-elevation (base, 218 m ASL) sites between 2005 and 2008 in eastern China. The present work focused on the roles of long-range transport and under-cloud/boundary layer scavenging on chemical composition of precipitation collected at the two sites.