城市混凝土桥梁薄弱处分析

随着城市化进程的不断发展,包括高架桥、立交桥在内的大量混凝土桥梁在城市交通网络中扮演者极其重要的角色。但受环境侵蚀、交通量日益增加的影响,城市混凝土桥梁不可避免地出现一定损伤,严重甚至会导致桥梁倒塌等重大灾难事故。在分析城市混凝土桥梁的各种损伤及损伤演化过程的基础上提出运营桥梁薄弱处的概念。该薄弱处是指受环境侵蚀、材料老化、荷载变化等因素的影响,混凝土桥梁结构中最先发生破坏的构件或构件中的某一位置。对运营桥梁薄弱处的分析宜采用分析结构中各处的承载力下降及相应的荷载效应增加二者相结合的方法,通过比较获得桥梁中各处抗力与荷载效应最为接近的地方,即结构薄弱处。最后,总结了城市混凝土桥梁薄弱处分析研究的发展方向及亟待解决的关键技术。     

黑曲霉对弱酸性艳兰RAWL的吸附动力学和热力学研究

借助吸附等温线比较了不同pH以及完整细胞与单细胞壁染料生物的吸附性能差异,化学修饰研究了菌体表面不同官能团对染料吸附的贡献,考察了不同温度下染料生物的吸附动力学,并进行了模型拟合.结果表明,黑曲霉的染料吸附较好地符合Freundlich方程( R2 ＞0.99),低pH值有利于染料吸附;染料吸附不仅发生在细胞壁,细胞内部也可发生;表面氨基作为主要的吸附官能团,其质子化导致的菌体正电荷和染料负离子间的静电引力作用是染料吸附的重要机理;吸附动力学可用拟二级速率方程描述( R2 =0.999 9);吸附活化能 Ea=5.21 kJ/mol,表明吸附具一定的活化性.     

微碱解-厌氧水解-SBR好氧生化法处理有机磷农药废水

介绍了微碱解——厌氧水解——SBR好氧生化法处理有机磷农药废水的工艺流程、工艺参数和处理效果。废水处理设施运行结果：废水COD去除率平均为90.1%,BOD5去除率平均为94.2%,TP去除率平均为84.9%。     

渤海湾典型闸控入海河流水体N2O释放研究

为探究弱水动力条件下, 典型滨海地区水体N₂O释放通量及其主控因素, 于2019年7月和8月(夏季)和11月(冬季初期)对以大清河-独流减河-北大港湿地为代表的渤海湾弱水动力条件河流开展水样采集与分析工作.结果表明: N₂O浓度变化范围为0.4~184.5nmol/L, N₂O饱和度的变化范围为7.2%~2740%, 其中近90%的样品处于过饱和状态, 表明该研究区是潜在的N₂O释放源.N₂O水-气界面释放通量为-0.3~6.7μmol/(m²·h), 夏季水体N₂O的释放通量高于冬季.降雨前后N₂O浓度出现明显波动, 相同点位降雨前后N₂O浓度的变化值为-15.2~63.9nmol/L, 独流减河上游农业区N₂O浓度的平均增加量(22.1nmol/L)显著高于下游(1.3nmol/L), 降雨驱动了流域氮素的运移, 促进了水体N₂O释放.相关性分析表明, 水体N₂O的浓度受反应物浓度、水体盐度共同调控.通过计算得到该滨海地区弱水动力条件下河流N₂O的排放因子为0.0073, 表明气候变化委员会(IPCC)默认值0.0026可能低估了该地区间接N₂O释放.     

Protective effect of weak pulsed magnetic fields on early ontogeny of tugun Coregonus tugun (Pallas) under conditions of chronic oil pollution

The state of internal organs in tugun larvae was analyzed histologically in the intact (control) group, the group treated with a water-soluble oil fraction (WSOF) in fivefold excess over the maximum allowable concentration, and the group exposed in a weak pulsed magnetic field at the stage of hatching, prior to treatment with WSOF. Larvae of the second group had severe pathologies of inner organs that caused 100% mortality before the age of 15 days, but no pathomorphological changes in the organs of larvae and juvenile fish of the third group were revealed for up to 40 days. Probable causes of high resistance to the toxic agent in fish of the experimental group are discussed.     

基于泰沙基折减自重模型的隧道围岩压力的确定及验证

采用泰沙基折减自重模型,通过实例分别计算和分析了考虑内聚力和不考虑内聚力两种情况下的隧道竖向荷载大小及其与埋深的关系曲线,并与现场围岩压力测试结果进行比较,表明实测的隧道围岩最大压力值与模型计算结果相近,说明该模型适用于隧道围岩软弱破碎、风化不均的围岩压力的确定,从而为类似工程提供了借鉴。     

Response of the grain yield and quality of hybrid rice to weak light stress北大核心CSCD

In this study, three rice varieties, Byou268 (low light-sensitive type), Nei5you768 (intermediate type), and Yixiangyou1108 (low light-tolerant), were used as experimental materials to investigate the yield and quality responses of different rice varieties to low light stress under normal light (CK) and low light (SH). The results showed the following: (1) Compared with normal light, the decrease in Yixiangyou1108’s 1 000-grain weight, grain number per spike, and seed setting rate under low light treatment were much lower than those of Nei5you768 and Byou268. The yield decline of Yixiangyou1108 (46.5%) was significantly lower than that of Nei5you768 (56.5%) and Byou268 (69.8%). Yixiangyou1108 showed strong tolerance to low light stress in terms of 1 000-grain weight, seed setting rate, grain number per panicle, and yield. (2) Compared with normal light, the reduction in grain length and width of Yixiangyou1108 under low-light treatment was significantly greater than that of Byou268; however, the reduction in the length-width ratio did not reach a significant level. The amylose content and gel consistency of the rice were significantly reduced. The reduction in amylose content of Yixiangyou1108 (24.5%) was significantly lower than that of Nei5you768 (28.1%) and Byou268 (30.6%); however, the decrease in gel consistency of Yixiangyou1108 (14.7%) was significantly higher than that of Nei5you768 (9.8%) and Byou268 (8.1%). After low light treatment, the characteristic values of the RVA curve of rice changed. The peak viscosity and breakdown viscosity of Yixiangyou1108, Nei5you768, and Byou268 were significantly decreased, but the cold glue viscosity and setback viscosity were significantly increased, while there was no significant difference in the peak time and peak temperature. The response of 1 000-grain weight, grain number per spike, and seed setting rate under low light stress can be used as a yield index of rice breeding with low light tolerance; rice grain type, amylose, and gel consistency; and peak viscosity and hot paset viscosity in RVA characteristic values can be used as quality indexes of low-light-tolerant rice material breeding. © 2022 Science Press. All rights reserved.     

吸附相反应技术制备微弱光响应的多组分掺杂TiO2催化剂

利用弱光(紫外和可见)激发Ti O2光降解污染物是拓展多相光催化实际应用的关键之一.以吸附相反应技术为基础,利用N掺杂以及共掺杂两种方式制备多组分Ti O2光催化剂,并研究其在弱光下光降解甲基橙的过程.结合紫外可见漫反射光谱、X射线衍射、X射线电子能谱以及光致发光光谱等表征手段,探索焙烧温度、N掺杂量以及共掺杂对催化剂光吸收和可见光响应拓展的影响,进而研究弱光下催化剂活性的变化规律.结果发现,N掺杂可以显著增强催化剂的光吸收,从而显著提升其在弱紫外光下光降解甲基橙催化活性,所有N掺杂催化剂的活性均优于商用P25光催化剂.N掺杂对催化剂的可见光响应拓展作用不大,因而单一N掺杂后大部分催化剂在弱可见光下没有活性,仅5%N掺杂催化剂在900℃热处理后有微弱活性.N和Fe2O3二元耦合形成的共掺杂催化剂中,两者之间的协同作用既增强了复合光催化剂的光吸收,也显著拓展了催化剂的可见光响应,因而得到了在弱可见光下具有良好活性的复合光催化剂.     

基于薄弱环节的发动机加速贮存试验研究

对基于薄弱环节的发动机加速贮存试验的理论依据和发动机加速贮存试验的基本流程进行了介绍,在对发动机薄弱环节的确定方法和薄弱环节失效机理分析的基础上,提出了材料、部组件和整机层层递进的加速贮存试验方案和基于物理老化、化学老化和使用载荷验证的发动机加速贮存试验一体化设计方法.     

基于薄弱环节的整机加速因子计算

目的当薄弱环贮存寿命都服从指数分布或都服从形状参数相同的威布尔分布时,给出整机加速因子与薄弱环节加速因子关系的公式;若形状参数不同时,给出整机加速因子的取值范围。方法将各个薄弱环节做串联系统处理,利用不同可靠度时常应力和加速应力下系统贮存寿命的关系,计算整机加速因子或给出加速因子范围。结果基于不同薄弱环节数据,总结出整机加速因子或取值范围的计算方法。结论针对系统存在薄弱环节并且薄弱环节寿命服从一定的分布时,可以通过该方法计算出整机加速因子或加速因子的取值范围。