下穿隧道对地铁车站结构地震反应的影响研究*

针对下穿隧道对临近地铁车站地震反应的影响问题,本文采用数值模拟方法,基于 ABAQUS 平台建立了隧道下穿大开地铁车站的整体三维非线性数值分析模型,通过改变地震动类型和隧道与车站结构的交叉净距,从结构构件的破坏比和竖向变形等角度,定量分析了不同工况下隧道下穿对车站结构地震反应的影响,并与单体大开车站原型结构的地震反应进行了对比。研究表明：下穿隧道会增大地铁车站结构中柱和侧墙的破坏比(相应的最大增幅：中柱为 35%,侧墙为 26%);同时,底板的竖向变形显著增大,最大增幅达到 100%;随着交叉净距的增大, 中柱和侧墙地震反应减小,而底板竖向沉降有所增大;下穿隧道对车站结构地震反应的影响范围约为隧道直径的 3 倍。研究成果对隧道近距离穿越地铁车站结构的设计与分析具有一定的参考价值。     

Repercussions of COVID-19 pandemic on solid waste generation and management strategies

• Implication of COVID-19 on medical waste and MSW generation is studied. • Challenges and effective strategy of solid waste generation is reviewed. • 2.9 million tons of COVID-19 related medical waste has been generated until Sep. 22. • The pandemic has postponed policies related to the reduction of plastic use. • Blockade resulted in a significant drop in waste generation in some regions. It has been over ten months since the beginning of the 2019 coronavirus disease (COVID-2019), and its impact on solid waste management, especially medical waste, is becoming clearer. This study systematically reviews the potential influences of the COVID-19 pandemic on medical waste, personal protection equipment waste and municipal solid waste (MSW), and discusses the corresponding measures and policies of solid waste management in typical countries. The results show that the generation of medical waste from the pandemic increased significantly, with 18%‒425% growth. It is estimated that the daily output of COVID-19 medical waste increased from 200 t/d on Feb. 22 to over 29000 t/d at the end of September 2020 throughout the world. The use of personal protective equipment will continue to grow in the long-term, while the blockade and isolation measures greatly reduced the volume of commercial waste, especially for tourist cities, and part of this waste was transferred to household waste. Residents’ attitudes and behavior toward food waste have changed due to the COVID-19 pandemic. In response to the pandemic, international organizations and several countries have issued new policies and guidelines and adjusted their management strategies for medical waste and MSW treatment. The pandemic has brought specific challenges to the disposal capacity of medical waste worldwide. It has also brought about the stagnation of policies related to the reduction of plastic products and waste recycling. This study will provide some useful information for managers and governmental officials on effective solid waste management during and after the COVID-19 pandemic.     

大型污染场地修复过程中的问题探讨与工程实践

近年来,随着城市化进程的加快,城市遗留的大型污染场地土壤和地下水污染问题尤为突出,开发再利用过程中的环境与人体健康风险较高。大型污染场地具有分布范围广、占地面积大、污染情况复杂等特点,开发再利用过程中面临着重修复轻调查、修复技术类型单一、二次污染防控难度大等问题,在大型场地开发再利用问题分析的基础上,提出了基于绿色可持续修复理念的相应对策。以北京焦化厂为例,介绍了该场地在修复和开发再利用过程中通过开展场地补充调查、采用多技术集成修复、加强二次污染防控和建立公众参与机制等方面,开展绿色可持续修复的实践。     

“限塑令”政策有效性评估的实例分析

通过对上海市杨浦区3个居民小区"限塑令"实施前后塑料袋消费情况的调研.发现"限塑令"在一定程度上起到了塑料袋减量化的作用,但效果并不明显.其瓶颈在于我国当前对商品流通领域的控制能力非常薄弱,对非正规零售商约束力度不够、监管缺位,导致他们无视"限塑令"的规定,继续提供免费塑料袋,从而严重架空了"限塑令"的减量化效果.文章中提出了通过加强监管和处罚力度、培育社会参与机制,以及加大公众宣传活动等措施,消除"限塑令"的政策死角,以真正实现塑料购物袋消费减量化的目标.     

餐厨垃圾干式厌氧消化过程流变特性变化及其对反应器流场的影响

餐厨垃圾的有机组成是影响其干式厌氧消化性能的重要因素。以实际餐厨垃圾为研究对象,通过向其中投加馒头改变其有机组成,进而研究不同有机组成下物料厌氧消化过程中的流变特性变化及产甲烷特性。结果表明,不同有机组成物料的甲烷产气量与其粘度具有一定的负相关关系,表明物料流动性的提高有助于其产甲烷效率的提高。而物料流变特性的差异则主要可归因于TS、VS以及溶解性有机物释放的差异。物料的屈服应力与其TS、VS具有一定的线性相关关系。CFD模拟结果表明,随着厌氧消化的进行,反应器内流场逐渐变好,死区率降低,且死区率与物料TS质量分数、屈服应力及表观粘度呈正相关关系。因此,针对不同有机组成物料流变特性及反应器流场的不同需选取合适的搅拌策略,以实现搅拌效率与搅拌能耗之间的平衡。本研究结果可为优化干式厌氧消化反应器的运行提供参考。     

Droplet digital PCR is a cost-effective method for analyzing long cell-free DNA in maternal plasma: Application in preeclampsia

Objective

Long cell-free DNA (cfDNA) can be found in the plasma of pregnant women and cancer patients. We investigated if droplet digital PCR (ddPCR) can analyze such molecules for diagnostic purposes using preeclampsia as a model.

Method

Plasma samples from ten preeclamptic and sixteen normal pregnancies were analyzed. Two ddPCR assays targeting a single-copy gene, VCP, and one ddPCR assay targeting LINE-1 repetitive regions were used to measure the percentages of long cfDNA >533, 1001, and 170 bp, respectively. The LINE-1 assay was developed as guided by in silico PCR analyses to better differentiate preeclamptic and normal pregnancies.

Results

Preeclamptic patients had a significantly lower median percentage of long cfDNA than healthy pregnant controls, as determined by the LINE-1 170 bp assay (28.9% vs. 35.1%, p < 0.0001) and the VCP 533 bp assay (6.6% vs. 8.7%, p = 0.014). The LINE-1 assay provided a better differentiation than the VCP 533 bp assay (area under ROC curves, 0.94 vs. 0.79).

Conclusion

ddPCR is a cost-effective approach for unlocking diagnostic information carried by long cfDNA in plasma and may have applications for the detection of preeclampsia. Further longitudinal studies with larger cohorts are required to assess the clinical utility of this test.     

生态环境监测机构数据质量技术判断常见方法探讨

环境监测数据是客观评价环境质量状况、反映污染治理成效、实施环境管理与决策的基本依据。为了进一步加强环境监测过程管理,有效提高环境监测数据质量,以列举法对影响生态环境监测机构数据质量的样品采集、运输、交接和实验室分析等监测活动的各环节进行了技术分析,梳理总结了数据质量技术判断的常见方法,旨在为环境管理部门开展监督管理提供经验借鉴。同时,就进一步提高生态环境监测机构的监测数据质量提出了建议。     

What makes residents more willing to participate in source separation of waste masks under the COVID-19 pandemic?

Journal of Material Cycles and Waste Management - With the outbreak of the novel coronavirus (COVID-19), the generation of a large amount of medical waste brought a rude shock to the existing solid...     

水泥窑用低氮燃烧器燃烧特性的试验研究

基于水泥生产线NOx排放机理及控制方法,设计、研发了一种新型水泥窑用低氮燃烧器,并分析了天然气、煤制气及混合气的燃烧特性及其污染物的排放特性.结果表明:在过量空气系数α为1.2、二次风占比β为0.6时,新型低氮燃烧器燃烧天然气的效果较好,NOx排放量为53 mg/m3,CO排放量为22 mg/m3;在相同燃烧条件下,煤...     

热活化介孔水生苔藓植物化石对水溶液中Cd(Ⅱ)的去除效应

采用热活化技术改性上水石,探讨热活化前后上水石的特征变化和吸附能力,同时考察了热活化后上水石对Cd(Ⅱ)的吸附动力学、吸附热力学及吸附机理。结果表明:(1)热活化后上水石表面形成塌陷和界面缺陷,能提供更多的吸附活性位点来有效提高其吸附能力。(2)上水石经750℃热活化后,吸附量显著提高。其中,750℃热活化后的山东省、山西省上水石的最大吸附量分别为37.20、24.65mg/g。上水石对Cd(Ⅱ)的吸附更符合准二级动力学模型,表明吸附速率由化学吸附控制。Langmuir模型能更好拟合上水石对Cd(Ⅱ)的吸附,反映了该吸附过程是单层吸附。(3)热活化后上水石对Cd(Ⅱ)的吸附机理可归因于形成了CdCO_3、Cd(OH)_2和(Ca,Cd)CO_3的表面沉淀。