Effect of silica fume on the thaumasite form of sulfate attack on cement-based materials

Thaumasite form of sulfate attack(TSA) can be observed in cement containing limestone under sulfate condition at low temperature. Mixing with suitable mineral admixture could be a good choice to improve the TSA resistance performance of cement-based materials. We investigated the durability performance of limestone-cement mortars reinforced with silica fume(SF) in 5% MgSO_4 solution at 5 ℃. The mortars, which were immersed in aggressive condition, were prepared with 2%, 4%, 6%, 8%, and 10% cement replacement by SF at a fixed water-to-binder ratio. Appearance, compressive strength, change of length and mass and corrosion products were investigated to evaluate the TSA resistance performance of SF based specimens. The results showed that specimens in the absence of SF almost disintegrated. Increasing SF dosage can reduce the degree of deterioration of SF mortars in TSA environment. Mortar mixtures with more than 6% SF merely show slight degeneration in relation to macroscopic and microscopic tests and characterizations.     

早期养护条件对水泥石碳硫硅钙石型硫酸盐腐蚀的影响

研究了早期高湿度空气养护、水中标准养护及密封养护对水泥石碳硫硅钙石型硫酸盐腐蚀的影响。采用X射线衍射（XRD）、傅立叶转换红外光谱（FTIR）和扫描电子显微镜（SEM）等方法分析了水泥石经180 d硫酸盐侵蚀后的腐蚀产物。结果表明,早期高湿度空气养护,水泥石碳化生成的CaCO3填充于孔隙中,使表层结构更加致密,阻碍了SO4^2-等有害离子侵入,延缓了水泥石碳硫硅钙石型硫酸盐腐蚀过程。比较而言,早期密封养护,水泥水化不充分,水泥石内部缺陷相对较多,SO4^2-等有害离子容易侵入,水泥石碳硫硅钙石型硫酸盐腐蚀最为严重。     

Influence of curing duration on thaumasite formation of Portland-limestone cement pastes

Extensive researches have been carried out on the conventional sulfate attack, while it has been found that the thaumasite form of sulfate attack(TSA), sulfate attack at low temperature, has just been discovered and its mechanism is not well understood so far. In this study, the sulfate attack of cement paste incorporating 30% mass of limestone powder was investigated. After 20 ℃ water cured for 7, 14, and 28 days,respectively, 20 mm cube specimens were exposed in a 5% magnesium sulfate solution at(6 ±1) ℃ for periods up to 240 days. Their appearance change, compressive strength development were examined at different storage time, and selected paste samples were examined by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). The results indicate that all Portland-limstone cement pastes suffer from appearance deterioration to some extent. The compressive strength of cement paste initially increases and after 120 days decreases with increasing exposed period. In addition, the cement paste with short curing time is more susceptible to sulfate attack, which directly leads to the formation of non-binder thaumasite crystal accompanied by the formation of ettringite, gypsum and brucite, and becomes a white, mushy, and incohesive matrix. Additionally, the extent of sulfate attack is greater and the formation of thaumasite is observed earlier for shorter curing time.     

国内旅游卫星账户研究综述

十多年来我国在TSA理论研究和编制实践上已取得一定的成就,同时也存在一些值得关注的问题,如对TSA中部分关键概念的中文翻译不统一、部分地区编制的TSA没有严格遵从国际规范;未来我国TSA研究应在完善旅游统计调查制度的基础上,逐步将TSA纳入到国家、地区国民经济核算体系中。     

时空类比法及其在光脉冲传输中的应用

讨论了光传输问题研究中的时空类比法,给出了空间量和时间量以及相关公式的对应关系,在引入时流线和时流束的概念后,采用此法处理了肖冲在色散光纤中的传播问题,得到了有啁啾和无啁啾脉 展宽公式,给色散长度以严格的定义,并用时间ＡＢＣＤ矩阵法讨论了各种色散补偿问题。     

Use of different barium salts to inhibit the thaumasite form of sulfate attack in cement-based materials

We investigated the effects of different barium compounds on the thaumasite form of sulphate attack(TSA)resistance of cement-based materials when they were used as admixtures in mortars.Moreover,we analyzed the inhibition mechanisms within different types of barium salts,namely BaCO_3 and Ba(OH)_2,on the thaumasite formation.The controlcement mortar and mortars with barium salts to cement and limestone weight ratios of 0.5%,1.0%,and 1.5% were immersed in 5%(by weight)MgSO_4 solution at 5 ℃ to mimic TSA.Appearance,mass,and compressive strength of the mortar samples were monitored and measured to assess the generaldegradation extent of these samples.The products of sulphate attack were further analyzed by XRD,FTIR,and SEM,respectively.Experimentalresults show that different degradation extent is evident in allmortars cured in MgSO_4 solution.However,barium salts can greatly inhibit such degradation.Barium in hydroxide form has better effectiveness in protection against TSA than carbonate form,which may be due to their solubility difference in alkaline cement pore solution,and the presence of these barium compounds can reduce the degree of TSA by comparison with the almost completely decomposed controlsamples.     

港口吞吐量的马氏链 时序分析预测

通过比较分析时间序列分析（TSA）和马尔科夫链预测方法,研究港口吞吐量科学预测的新方法.组合温州港近20多年的历史吞吐量数据,分别采用TSA和马尔科夫链进行预测.将TSA与马尔科夫链校正模型相结合,进行港口吞吐量预测.结果表明,上述复合模型较之TSA模型平均预测精度提高50%,较之单一的马尔科夫链平均预测精度提高75%.根据吞吐量实际数据的验证结果,建立马氏链-时序分析预测模型.结果表明,该模型能够同时反映吞吐量序列的增长趋势和随机波动性,更符合港口吞吐量的实际变化情况.     

外加剂对混凝土TSA腐蚀的抑制作用

研究了掺加化学外加剂的水泥净浆试件在（5±2）℃、质量分数5%的硫酸镁溶液中浸泡300d的外观变化、强度发展及侵蚀产物,采用X射线衍射（XRD）、傅立叶转换红外光谱（FTIR）等方法分析了侵蚀产物的组成。结果表明：甲酸钙能延缓水泥石发生TSA腐蚀,但不能阻止TSA发生,在0.3%-0.7%范围内,随着甲酸钙掺量的增加,水泥石抗TSA腐蚀的能力增强。硝酸钡能有效抑制水泥石中碳硫硅钙石的生成,原因是硝酸钡能结合生成碳硫硅钙石所需的SO42-,从而降低了水泥石发生TSA腐蚀的程度。硝酸钡掺量在1%左右时,水泥石抗TSA性能较好。     

基于堆稀疏自编码神经网络的电网安全预判

为了满足安全裕度概念下电力系统暂态稳定评估的准确率和时效性,提出了基于深度学习的堆稀疏自编码神经网络(SSAEN)预判模型.首先尝试将母线时序电压数据构成的矩阵看作蕴含暂态运行机制的模式图,然后利用SSAEN逐层级地挖掘模式图的主导特征,并通过分析SSAEN的连接权重阐述了主导特征及其演变过程.最后通过Logistic分类器识别主导特征,预判未来时刻系统的稳定性.基于IEEE39系统仿真样本进行了实验,实验结果表明,SSAEN具有较高的准确度和预测速度,可为系统暂态失稳情况提供足够的安全时间裕度.     

聚硅酸金属盐处理含氟废水的实验研究

含氟工业废水危害大,处理困难,采用高效无机絮凝剂——聚硅硫酸金属盐能有效降低废水中的氟。对影响三种絮凝剂聚硅酸硫酸铝(PSAS)、聚硅酸硫酸铁(PSFS)和聚硅酸硫酸铁铝(PSFAS)絮凝效果的主要因素进行实验研究,并对絮凝机理进行了深入探讨。研究表明,pH值、絮凝剂用量、沉降时间和Fe(Al)/Si摩尔比对絮凝剂除氟率的影响很大。硅的加入能有效提高絮凝剂中有效成分Alb和Feb的含量,使絮凝效果大大提高。     

硫酸盐还原过程中氢分压的平衡与调节

采用两相厌氧工艺系统的产酸相反应器处理硫酸盐废水,通过连续流试验考察硫酸盐还原过程中分子氢的产生和去路．试验结果表明：在硫酸盐还原过程中,分子氢的产生者是产酸菌(AB)、产氢产乙酸菌(HPA)和利用脂肪酸的硫酸盐还原菌(ESRB);分子氢的消费者主要是利用氢的硫酸盐还原菌(HSRB)、产酸菌、产氢产乙酸菌和硫酸盐还原菌之间生物链式的协同代谢关系是维持系统低氢分压的前提．同时,揭示出在微生物的协同作用下,种间氢转移的途径和反应体系中氢分压的平衡与调节规律．     

硫酸铁及助凝剂处理上海合流污水试验研究

以硫酸铁为混凝剂配合不同的助凝剂，对上海合流一期污水中的污染物进行了混凝处理研究。采用了阳离子型聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、一种自制的有机高分子聚合物(AN)这3种有机物以及活化硅胶(AS)为助凝剂，研究了不同硫酸铁加入量以及多个硫酸铁加入量条件下各种助凝剂不同剂量时的混凝处理效果。研究结果表明，采用硫酸铁为混凝剂的处理工艺可以有效去除合流污水中的SS、COD．TP和PO4^3--P。     

上海合流一期污水混凝处理试验研究

以硫酸铝为混凝剂,对上海合流污水进行了混凝处理研究.实验采用阳离子型聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、一种自制的有机高分子聚合物(AN)以及活化硅胶(AS)作为助凝剂,研究了不同硫酸铝投加量以及硫酸铝剂量相同条件下各种助凝剂投加量的混凝处理效果.研究结果表明,采用硫酸铝为混凝剂的处理工艺可以有效去除合流污水中的SS、COD、TP和PO3-4 -P.同时PAM、PVA以及AN均有助凝作用,而AS助凝效果不明显.     

Quantification and control of restrictive ecological factors in acidogenic de-sulfate bioreactor

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硅胶担载硫酸铈催化合成乙酸丁酯

主要进行硅胶担载硫酸铈催化合成乙酸丁酯的研究。分别采用单因素实验法和正交实验法重点考察了酸醇摩尔比、催化剂担载量和反应时间等因素对乙酸转化率的影响,确定了其最佳工艺条件为:酸醇摩尔比1:1.4,催化剂担载量15%,反应时间50 min。在最佳工艺条件下,乙酸转化率分别为93.8     

附着型硫酸盐还原菌的分离及其定量检测

针对附着型硫酸盐还原菌(A-SRB)对管道和罐壁的腐蚀问题,应用Hungate厌氧技术对附着型硫酸盐还原菌进行分离、系统发育分析和定量检测研究.研究表明,在地面系统中的SRB菌里,附着型SRB菌占多数,该菌株主要分布在厚壁菌门梭菌纲(Clostridia)、变形菌门的γ-变形菌纲(Gammaproteobacteria)和δ-变形菌纲(Deltaproteobacteria),其中梭菌属(Clostridium)为优势菌属,附着型的硫酸盐还原菌的种类比较新颖.通过安装在管壁上的检测装置和绝迹稀释法(MPN)联用实现附着型SRB菌的定量检测,该技术已在油田生产中实际应用.     

生态因子对产酸脱硫反应器中硫酸盐去除率的影响

为探讨生态因子对产酸脱硫反应器中硫酸盐去除率的影响,采用产酸脱硫反应器作为硫酸盐还原单元,以食用红糖为碳源,硫酸钠为硫酸盐,通过一系列动态实验,研究了产酸相中生态因子pH、氧化还原电位(ORP)、碱度(ALK)以及COD/SO42-(C/S)对SO42-去除率的影响.在中温(34±1℃)条件下运行时,碱度为500~1 000 mg/L,pH值为6.0~7.0,氧化还原电位为-250~-410 mV,产酸脱硫反应器对硫酸盐的去除率最大.当进水C/S比小于2.0时,SO42-去除率小于81%;当进水C/S比为2.5~2.0时,SO42-去除率为90%~81%;当进水C/S比为大于2.5时,SO42-去除率为90%以上.随着C/S比的降低,SO42-的去除效果将有所降低.     

基于神经网络的建筑能耗混合预测模型

为了提升建筑能耗预测的精度、鲁棒性和泛化能力,提出树种算法（TSA）优化的径向基函数（RBF）神经网络与长短时记忆（LSTM）神经网络结合的混合预测模型. 采用基于自适应噪声的完全集成经验模态分解算法,将建筑能耗数据分解为1组本征模态函数（IMF）分量和1个残余分量,利用样本熵算法将各分量划分为高频分量和低频分量. 采用最小绝对收缩与选择算子（LASSO）方法进行特征选择. 分别利用TSA算法优化后的RBF模型与LSTM模型对低频分量和高频分量进行预测,并叠加重构得到最终预测结果. 模型评估结果表明,混合预测模型的精度为98. 72%. 相比于RBF、TSA-RBF、LSTM模型,所提模型的预测效果更好,且具有较强的鲁棒性和泛化能力,能够更为有效地用于建筑逐时电力能耗预测.     

超声辅助乙醇提取龙葵生物总碱的研究

通过正交试验确定传统乙醇溶液提取龙葵生物总碱的最佳提取条件,在此基础上,研究超声辅助乙醇提取龙葵生物总碱的工艺条件,并对提取物龙葵生物总碱进行了定性、定量分析.实验表明:超声辅助乙醇提取龙葵生物总碱,提取率略高于传统提取技术,可节省提取时间和外加能源.     

Effect of polymer-based grinding aid on sulfate attacking resistance of concrete

Influences of polymer-based grinding aid (PGA) on the damage process of concrete exposed to sulfate attack under dry-wet cycles were investigated. The mass loss, dynamic modulus of elasticity (E _rd), and S and Ca element contents of concrete specimens were measured. Scanning electron microscopy (SEM), mercury intrusion porosimetry(MIP), and X-ray diffractometry(XRD) were used to investigate the changing of microstructure of interior concrete. The results indicated that PGA was capable of reducing the mass loss and improving the sulfate attack resistance of concrete. X-ray fluorescence (XRF) analysis revealed that PGA delayed the transport process of sulfate ions and Ca ions. In addition, MIP analysis disclosed that the micropores of concrete with PGA increased in the fraction of 20–100 nm and decreased in the residues of 200 nm. Compared with the blank sample, concrete with PGA had more slender and well-organized hydration products, and no changes in hydration products ratio or type were observed.