海洋平台桩腿周围局部冲刷及其对基础承载力的影响∗

在海洋平台桩靴基础安装施工过程中,容易发生穿透现象而导致破坏。业界建议可通过在桩靴周边加设向上的袖结构来抑制贯入时周围土体的回流,从而缓解穿透破坏。但这种袖结构的存在会导致局部冲刷,形成的冲刷坑会减小桩靴有效埋深,进而影响其使用期的承载力。通过一系列水槽试验,探讨了不同形式桩腿的面积比、开孔率、来流角度等因素对于冲刷坑形状的影响,进而开展了考虑冲刷坑影响的桩靴基础承载力数值计算,并与忽略最大冲刷深度以上土体的传统模型、假设冲刷坑为倒圆台状的简化模型计算结果进行了对比。主要研究结果如下：（1）加设圆形袖结构的桩腿引起的冲刷深度要比方形袖结构桩腿小,建议工程中采用面积比较小的圆形袖结构来缓解穿透破坏;（2）桩腿的面积比、开孔率、来流角度等因素对冲刷坑形状都存在影响。最大冲刷深度随着开孔率的增大而减小,当开孔率较大时,冲刷现象近似于群桩冲刷,出现随着冲刷角度的增大冲刷深度先增大后减小的现象;（3）当考虑冲刷坑对于桩靴承载力的影响时,简化模型能够合理反映冲刷坑对于桩靴基础承载力的影响。     

高压管汇磁致伸缩导波缺陷检测模拟研究

针对高压管汇导波缺陷检测问题,基于磁致伸缩效应,借助COMSOL有限元仿真软件,建立高压管汇直管段的导波缺陷检测模型,探究导波的激励条件及缺陷检测效果,分析不同参数对缺陷附近磁感应强度分布的影响。研究结果表明:在频率为10 kHz的正弦电流信号激励下,可产生沿管道轴向传播的T（0,1）模态导波,并能辨别缺陷处的回波信号。改变缺陷的尺寸参数时,缺陷附近的磁感应强度随着缺陷深度增加呈增大趋势,随轴向宽度增加呈减小趋势,不同形状的缺陷对应的磁感应强度存在一定的差异;改变激励条件,磁感应强度均随激励电流、激励频率的增加呈不断增加趋势。     

粉煤灰固定化絮凝剂填充床-鼓气工艺漂染污水处理研究

以粉煤灰固定化絮凝剂填充成絮凝过滤床 ,并组合成连续 -鼓气式五级絮凝过滤床污水处理系统。在吸附、絮凝、沉降、过滤和降解等协同作用下 ,污水流量为 2 5 L/h、鼓气量为 5 0 L/( L· h)、级数为 5时 ,处理水的悬浮物、色度、COD、氨氮、硫化物和苯胺的去除率分别为 99.0 %、91.8%、96.9%、95 %、96.9%、90 .6% ,p H=6.2～ 6.9,基本达到纺织染整工业污水 级排放标准     

热效应对焦煤甲烷解吸迟滞特征的影响研究*

为揭示煤中甲烷气体的储运机制,选取井下煤样研究不同温度条件下甲烷气体的等温吸附解吸实验。基于Langmuir模型、等量吸附热计算模型和解吸迟滞系数对实验数据进行分析,研究煤中甲烷气体解吸迟滞现象的热力学特征。结果表明:随温度升高,Langmuir模型得到的吸附常数均呈下降趋势;甲烷解吸迟滞现象明显,迟滞程度随温度升高缓慢下降;受解吸迟滞效应影响,相邻温度区间内吸附曲线的等量吸附热较为相近,不同温度区间内解吸曲线的等量吸附热高于吸附曲线,差异显著;解吸迟滞现象影响煤层甲烷含量预测的准确性,并且解吸曲线的热力学特征规律性较差。     

建筑企业韧性安全文化实证研究

为探讨韧性安全文化及其指标对建筑企业安全绩效的作用,将安全文化理论与韧性工程理论相结合,对建筑企业韧性安全文化指标进行分析;利用扎根理论和问卷调查方法对建筑企业相关人员进行数据收集,采用偏最小二乘估计结构方程模型（PLS-SEM）对数据进行分析。结果表明:最高管理层承诺、公正文化、学习文化、意识和不透明性、准备、适应性6个指标可用于评估韧性安全文化,其中公正文化、学习文化、准备及适应性具有显著的正向作用,最高管理层承诺、意识和不透明性具有负向作用;研究结果对建筑企业安全文化建设具有指导价值。     

换流站时钟及服务器对时异常故障分析

针对银川东换流站主时钟及服务器对时异常问题,通过对主时钟和服务器对时工作原理进行分析,提出了主时钟增加装置容错机制及内部时钟守时机制,服务器系统增加对时抗干扰机制的解决方案。应用结果表明:该方案有效提升了主时钟及服务器抗外部信号干扰的能力,大大提高了站内设备运行的稳定性。     

The capability of estuarine sediments to remove nitrogen: implications for drinking water resource in Yangtze Estuary

Water in the Yangtze Estuary is fresh most of the year because of the large discharge of Yangtze River. The Qingcaosha Reservoir built on the Changxing Island in the Yangtze Estuary is an estuarine reservoir for drinking water. Denitrification rate in the top 10 cm sediment of the intertidal marshes and bare mudflat of Yangtze Estuarine islands was measured by the acetylene inhibition method. Annual denitrification rate in the top 10 cm of sediment was 23.1 μmol m^?2 h^?1 in marshes (ranged from 7.5 to 42.1 μmol m^?2 h^?1) and 15.1 μmol m^?2 h^?1 at the mudflat (ranged from 6.6 to 26.5 μmol m^?2 h^?1). Annual average denitrification rate is higher at mashes than at mudflat, but without a significant difference (p?=?0.084, paired t test.). Taking into account the vegetation and water area of the reservoir, a total 1.42?×?10⁸ g N could be converted into nitrogen gas (N₂) annually by the sediment, which is 97.7 % of the dissolved inorganic nitrogen input through precipitation. Denitrification in reservoir sediment can control the bioavailable nitrogen level of the water body. At the Yangtze estuary, denitrification primarily took place in the top 4 cm of sediment, and there was no significant spatial or temporal variation of denitrification during the year at the marshes and mudflat, which led to no single factor determining the denitrification process but the combined effects of the environmental factors, hydrologic condition, and wetland vegetation.     

重金属污染土壤的植物修复技术与其他技术联用的进展与前景

随着工业和经济的发展,土壤重金属污染越来越严重,因此重金属污染土壤的修复迫在眉睫。植物修复技术因其经济、环保等优点已经成为国内外研究的热点,但存在修复植物稀少的问题。将其他技术与植物修复技术联用可能是突破植物修复这一局限性的关键举措之一。介绍了基因工程技术与植物修复技术联用的研究进展;总结了微生物技术与植物修复技术联用中植物根际促生细菌、菌根真菌的作用;概述了材料化学技术联合植物修复的应用现状,着重介绍了土壤改良剂和螯合剂的实际应用。最后对基因工程、微生物、材料化学等技术联合植物修复技术在研究和应用中的未来方向进行了前景展望,旨在为植物修复技术发展提供更多新的思路和参考。     

Do pilot free trade zones improve the green total factor productivity? Evidence from a quasi-natural experiment in China

China’s pilot free trade zone (PFTZ) is an important national strategy to achieve high-quality development, so it is necessary to discuss the effect of PFTZ implementation on green total factor productivity (GTFP). Based on the data from 279 cities in China from 2004 to 2018, this study takes the establishment of PFTZ as a quasi-natural experiment and uses the difference-in-differences (DID) method to systematically evaluate the effect of PFTZ on urban GTFP. The empirical results of this paper are shown as follows: Firstly, the construction of PFTZ has a significant effect on urban GTFP, and this effect has increased gradually over time. Secondly, the construction of PFTZ mainly promotes the urban GTFP by increasing the level of science and technology innovation, reducing government intervention and improving the level of human capital. Thirdly, the effect of PFTZ construction on GTFP is more pronounced in regions with earlier waves of PFTZ and in western regions where environmental concerns are higher. In addition, there is a significant positive linkage between the construction of the PFTZ and the Belt and Road Initiative to improve the urban GTFP. The findings of this paper enrich the relevant literature on PFTAs and sustainable development and provide a theoretical basis for further promotion of PFTZ construction.

     

Unveiling the recycling characteristics and trends of spent lithium-ion battery: a scientometric study

Environmental Science and Pollution Research - The recycling of spent lithium-ion batteries (LIBs) is both essential to sustainable resource utilization and environmental conservation. While spent...