一种新型的MR隔震减振支座及其剪切性能试验研究

基于磁流变(MR)智能材料的减振器技术的研究可以为实现工程结构隔震减振自适应控制开辟一条新的途径。设计加工了一种新型的分体式MR隔震减振支座,并对该隔震减振支座的剪切性能进行了试验研究。新型MR隔震减振支座包含MR塑性体工作单元和MR弹性体工作单元,其中MR塑性体提供小位移工况时的刚度和阻尼,MR弹性体提供大位移工况时的刚度和阻尼。结果表明:新型MR隔震减振支座的剪切刚度随着工作电流强度的增大而增大,相较无电流工况,电流强度为2A时等效剪切刚度相对变化率可达到50%以上;无电流输入时支座中基体及普通填充橡胶仍可提供一定阻尼力,能够有效吸收振动能量,达到中高阻尼橡胶支座的性能;竖向压应力提高了新型MR隔震减振支座的剪切刚度;小位移时加载频率的降低对新型MR隔震减振支座的剪切刚度有增益效果。该新型MR隔震减振支座可以适用于震动荷载工况复杂多变,需要严格控制大位移变形的隔震结构物。     

循环温度荷载作用下饱和黏土的体积变形特性

采用温控三轴仪,研究了排水条件下温度循环引起的饱和黏土体积变化特性。试验结果表明,温度循环会使得土体产生不可恢复的体积变形,塑性体积应变的大小随温度循环周数的增加而增加,并逐渐趋于稳定值;若将经历过温度循环的土样重新加载到新的正常固结状态,后续温度循环中产生的塑性体积应变量值及发展规律与初始循环下的类似;同等温度增量下,体积应变的大小主要受超固结比OCR的影响,与应力水平无关。OCR越大,体积应变越小,随温度循环周数稳定的也越快。基于广义塑性理论,给出了热-力耦合作用下土体体积应变的计算模型。模型中考虑了温度塑性应变对屈服应力的硬化作用,根据屈服应力与前期固结应力之间的差异间接体现温度历史的影响,进而合理地模拟体积应变随温度循环周数的累积规律。利用所建立的模型对本文试验和文献中的数据进行了模拟,验证了模型的可靠性。     

As(III) adsorption onto Fe-impregnated food waste biochar: experimental investigation,modeling, and optimization using response surface methodology

Biochar derived from food waste was modified with Fe to enhance its adsorption capacity for As(III), which is the most toxic form of As. The synthesis of Fe-impregnated food waste biochar (Fe-FWB) was optimized using response surface methodology (RSM), and the pyrolysis time (1.0, 2.5, and 4.0 h), temperature (300, 450, and 600 °C), and Fe concentration (0.1, 0.3, and 0.5 M) were set as independent variables. The pyrolysis temperature and Fe concentration significantly influenced the As(III) removal, but the effect of pyrolysis time was insignificant. The optimum conditions for the synthesis of Fe-FWB were 1 h and 300 °C with a 0.42-M Fe concentration. Both physical and chemical properties of the optimized Fe-FWB were studied. They were also used for kinetic, equilibrium, thermodynamic, pH, and competing anion studies. Kinetic adsorption experiments demonstrated that the pseudo-second-order model had a superior fit for As(III) adsorption than the pseudo-first-order model. The maximum adsorption capacity derived from the Langmuir model was 119.5 mg/g, which surpassed that of other adsorbents published in the literature. Maximum As(III) adsorption occurred at an elevated pH in the range from 3 to 11 owing to the presence of As(III) as H₂AsO₃^? above a pH of 9.2. A slight reduction in As(III) adsorption was observed in the existence of bicarbonate, hydrogen phosphate, nitrate, and sulfate even at a high concentration of 10 mM. This study demonstrates that aqueous solutions can be treated using Fe-FWB, which is an affordable and readily available resource for As(III) removal.

     

Identification of iron and sulfate release processes during riverbank filtration using chemical mass balance modeling

Environmental Geochemistry and Health - Various hydrogeochemical processes can modify the quality of river water during riverbank filtration (RBF). Identifying the subsurface processes responsible...     

Short-term effect of temperature variation on the competition between PAOs and GAOs during acclimation period of an EBPR system

Sequencing batch reactor (SBR) for enhanced biological phosphorus removal (EBPR) processes was used to investigate the impact of the temperature shock on the competition between phosphorus-accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) in start-up stage. During the 34 days operation, SBR was set with temperature variation(0–5 d, 22±1°C; 6–13 d, 29±1°C; 14–34 d, 14±1°C). PAOs and GAOs were analyzed by fluorescent in situ hybridization (FISH), and intracellular polyphosphate granules were stained by Neisser-stain. The results showed that the influence of temperature shock on PAOs’ abundance was more serious than that on GAOs in the enriching process. Under sudden and substantially temperature variation, from 22±1°C to 29±1°C and then to 14±1°C, the domination of PAOs was deteriorated. After temperature shock, PAOs’ competitive advantages at low temperature that concluded in other study did not appear in our study. As mesophilic, GAOs (indicated by Alphaproteobacteria and Gammaproteobacteria) were more temperature adaptive and better grew and took the domination at 14±1°C in the end. In the competition process, organisms of tetrad forming organisms (TFOs)-like shape which were considered as typical GAOs, were observed. With the evidence of poly-P granules containing by Neisser-straining and result of FISH, these organisms of TFOs-like shape were better to be assumed as adaption state or a special self-protecting shape of PAOs.     

A/O交替运行钢渣基复合滤料生物滤池处理模拟生活污水脱氮除磷特性

利用两级钢渣基复合滤料生物滤池(SSMBF)构建厌氧/好氧(A/O)交替运行工艺系统.在单池HRT=2h,A/O交替周期48h,厌氧DO=0.2~0.5mg/L,好氧DO=3~5mg/L,T=23~27℃的运行条件下,考察了SSMBF系统对模拟生活污水(pH=6.8~7.5,COD=260~330mg/L,NH4+-N=35~40mg/L,PO43--P=9~11mg/L)的处理效果,分析了其氨氮和磷去除特性.结果表明,两级A/O交替SSMBF系统具有良好的生活污水处理能力,对氨氮、磷和COD的去除率分别为95%、40%~60%和83.3%,出水氨氮、磷和COD浓度分别为0.5mg/L?3~6mg/L和50mg/L.在厌氧/好氧交替周期为48h的工况下,SSMBF系统的氨氧化菌和聚磷菌分别可在10h和8h恢复最佳活性.SEM?EDS表征和污染物去除特性分析结果显示,A/O交替运行SSMBF系统充分发挥了钢渣基复合滤料的离子和碱度释放特性,通过聚磷菌的厌氧释磷效应,在厌氧SSMBF中诱导促进了生物-结晶协同除磷,结晶产物为以羟基磷灰石为主的磷酸盐化合物.     

铁矿区重金属污染对土壤微生物代谢活性的影响

以北京市密云水库上游某铁矿区为研究对象,利用比色法、微量热法对铁矿区内各采样点土壤酶活性及其微量热代谢活性指标进行分析,以探究不同区位重金属污染下土壤微生物代谢活性的变化. 结果表明:各采样点土壤中w(Cu)、w(Cd)、w(Zn)、w(Cr)均超过北京市土壤相应背景值. 在重金属污染程度较低的S6、S7、S8采样点,土壤脲酶、FDA酶(荧光素二乙酸脂酶)活性均较高,分别为0.64、1.22、0.64 mg/g和1.25、2.84、1.45 μg/g. 微量热代谢活性指标中,k (生长速率常数)在污染程度较低处的值均较高,而重度污染区域的S1、S4采样点的k为0. 相关性分析显示,k是反映微量热中代谢热活性的最具代表性指标. RDA(冗余度分析)结果显示,w(Cd)、w(TN)、w(AP)、w(TOC)、内梅罗污染指数及w(Cu)是影响k、P_m(最大热输出功率)的主要因素. Cd、Cu污染抑制了土壤微生物的代谢活性,不同代谢活性指标对重金属的敏感程度表现为k最强,P_m、脲酶活性、FDA酶活性次之.      

大鹏湾环境容量研究Ⅰ:自净能力模拟分析

在估算大鹏湾污染源强及统计海水污染物浓度的基础上,采用三维水动力模型及污染物扩散模型,模拟了大鹏湾的海水交换及污染物扩散过程,分析了大鹏湾海水交换与生化降解对自净能力的贡献.结果表明,大鹏湾潮差小,约为1m,潮流弱,污染物难于向湾外扩散,其物理自净能力差,湾内海水自净主要取决于生化降解.在吐露港海区与沙头角海区,污染排放较大,水深较小,海水难于交换,容易受到污染.     

湿式镁法烟气脱硫副产物MgSO4热解回收MgO

通过对MgSO4的热解研究为湿式镁法烟气脱硫副产物的综合利用探索适宜的热解条件.实验结果表明,在升温速率为20 ℃/min、热解温度为850℃、恒温时间为2.0 h的条件下,由无水MgSO4热解制得的MgO收率高达99.8％.由MgSO4·7H2O热解制得的MgO收率仅为72.1％.由此表明,干燥的MgSO4对热解更有利.     

中空柱状生物膜载体在处理工业废水工程中的应用

本文介绍新开发的一种在污水处理中的高科技产品一高效生物膜载体,通过对其在与其他处理方式各方面择比研究过程中的高找到其特点,推广新科技。