考虑土体刚度衰减的地面堆载对既有隧道影响

地面临时堆载可能会使周围土体产生明显的沉降变形,进而对城市地下空间中的邻近既有隧道产生不利影响。理论解析法是评估地表超载对既有隧道影响的有效方法。目前的理论解析分析方法一般假定土体刚度沿既有隧道轴线方向为一定值,忽略了地面堆载引发的土体刚度衰减的影响。基于两阶段分析法提出了考虑纵向土体刚度衰减的地面堆载引发既有隧道变形计算模型。既有隧道被假定为搁置在Winkler地基上的Euler-Bernoulli梁。利用邓肯-张模型对地表堆载引发的土体非线性响应进行评估,并结合现场实测数据对模型的适用性进行验证。研究成果可为合理评估地表堆载对既有隧道的影响提供依据。     

Conversion of polyhydroxybutyrate (PHB) to methyl crotonate for the production of biobased monomers

Within the concept of the replacement of fossil with biobased resources, bacterial polyhydroxybutyrate (PHB) can be obtained from volatile fatty acids (VFAs) from agro‐food waste streams and used as an intermediate toward attractive chemicals. Here we address a crucial step in this process, the conversion of PHB to methyl crotonate (MC), which can be converted via cross‐metathesis with ethylene to methyl acrylate and propylene, two important monomers for the plastics industry. The conversion of PHB to MC proceeds via a thermolysis of PHB to crotonic acid (CA), followed by an esterification to MC. At pressures below 18 bar, the thermolysis of PHB to CA is the rate‐determining step, where above 18 bar, the esterification of CA to MC becomes rate limiting. At 200°C and 18 bar, a full conversion and 60% selectivity to MC is obtained. This conversion circumvents processing and application issues of PHB as a polymer and allows PHB to be used as an intermediate to produce biobased chemicals. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42462.     

Nanocrystalline Bi2O3–B2O3– (MoO3 or V2O5) glass-ceramic systems for organic pollutants degradation

Fixation of photocatalyst in glass matrix would solve the problem of photocatalyst recovery. In this study, the system 30 Bi₂O₃, 20 B₂O₃ and 50 (MoO₃ or V₂O₅), was used for the preparation and stabilization of the photoactive phases of both bismuth molybdate β-Bi₂Mo₂O₉ and monoclinic–scheelite BiVO₄ in a glassy matrix. Proper heat-treatment schedule, based on differential thermal analysis (DTA) results, has been applied to improve the crystallinity of the prepared glass–ceramics. The applied heat-treatment program showed a significant effect on the size of the formed crystals, especially in samples with molybdenum content. For instance, one-step heat-treatment (500°C/2 h) improves the crystallinity of the material than two-step heat-treatment (355°C/1 h+400°C/2 h). It was also noticed that the amount of glassy matrix relative to crystalline part in case of vanadium-contained samples is much more than that in the corresponding molybdenum-contained samples. The prepared samples were used for the degradation of Red SPD Cotton dye in order to assess their photocatalytic activity. All molybdenum contained samples showed a promising photocatalytic activity. On contrary, vanadium-contained samples were inactive suggesting that most of photoactive crystals are in the bulk of materials.     

二氧化锰/石墨烯臭氧催化氧化甲苯反应性能

采用一步水热合成法,在180℃,12 h条件下制备了30%二氧化锰/石墨烯(MnO2/G)复合材料。实验结果表明:MnO2均匀且较为牢固地锚定于石墨烯表面,同时MnO2的沉积阻止了多层石墨烯的复合,从而使得复合物具有较大的比表面积。相同条件下,MnO2/石墨烯相较于单纯MnO2或石墨烯具有很好的臭氧催化氧化甲苯性能,这可以归结于MnO2和石墨烯间的协同催化作用。     

微生物异化铁对环境污染的治理机理研究

随着科学技术的不断发展微生物以及微生物金属矿物组成的多界相体系对于地下环境中污染物的治理,受到了越来越多的重视。在多界相体系中结合表面Fe（ II）对污染物进行还原降解。另外,多界相体系中,针铁矿浓度,电子递体,还原机制, pH、温度和碳源都会成为反应体系的影响因素。总之通过深入研究微生物异化铁在环境污染治理中的作用机制,以便为未来环境的治理及修复提供更为充分的理论依据。     

影响甲磺酰菌唑在土壤中降解因素的研究

建立了超高效液相色谱检测土壤中甲磺酰菌唑的方法。对贵州、广西、山东三个地区土壤中甲磺酰菌唑的降解进行了研究,探讨了土壤中主要因素:含水率、微生物、温度、药剂质量分数以及p H值对甲磺酰菌唑降解的影响。结果表明:在本实验条件下,微生物越多、环境温度越高、p H值越大、含水率越多和质量分数越大,甲磺酰菌唑的降解速率越快。     

环氧复合材料压力法降解及其纤维的回收利用

研究了压力法组合溶剂法一步降解环氧碳纤维复合材料的工艺,测试了降解产物成分与特性并探索了回收碳纤维再利用的可能性。利用红外光谱分析确定了其断键形式主要为醚键断裂,利用气相色谱-质谱联用分析确定了降解产物主要是丙烷和2-戊酮。利用扫描电子显微镜(SEM)表征了纤维表面树脂粘附少,再制备复合材料的界面结合良好。纤维力学性能测试确定了所回收的碳纤维仍具有良好的力学性能。复合材料力学性能测试确定了其性能损失小。研究表明,使用该方法降解效率高,回收纤维单丝拉伸强度保留率高,具有很好的运用前景。     

硬脂酸锰改性LDPE降解材料的研究

将维生素C、聚乙二醇1000和交联淀粉作为降解剂按一定配比加入到低密度聚乙烯(LDPE)基体中,采用不同用量的硬脂酸锰与上述LDPE降解材料制取薄膜并进行老化试验,用红外光谱、扫描电镜和力学性能分析研究了硬脂酸锰对LDPE降解材料热氧降解性和光降解性的影响。结果表明:当加入0.4%的硬脂酸锰时,LDPE的光和氧化降解性增强,降解过程中产生大量羰基,材料质量减少,其断面出现孔洞,可促使LDPE进一步完全降解。     

2.5维机织复合材料疲劳寿命预测

对2.5维机织复合材料进行了静力分析,在受拉伸载荷的情况下将其视为经纱层和纬纱层组合而成的层合板。以单向板疲劳寿命预测为基础,考虑到疲劳加载过程中刚度退化导致的应力重新分配,采用Miner理论对其拉-拉疲劳寿命进行预测,且对该方法进行了试验验证,为预测2.5维机织复合材料的疲劳寿命提供了一种途径。     

Fenton氧化工艺降解废水中3,4-二氯三氟甲苯

该文利用Fenton法降解水中农药中间体3,4-二氯三氟甲苯(3,4-DCBTE)。为评估Fenton法处理3,4-DCBTE时的降解特性,对初始p H,H2O2/Fe2+投加比率和温度Fenton等不同反应参数及Fenton法氧化3,4-DCBTE的降解产物进行了研究。结果表明在H2O2投加量为2.67 g/L、温度为20℃、H2O2/Fe2+配比为15、p H为3的最优条件下反应2 h,3,4-DCBTE去除率高达93.1%。结合数据进一步分析,推测3,4-DCBTE最终被氧化生成氯苯。