首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
长期盐水浸渍的水泥砂浆中的氯离子渗透   总被引:5,自引:0,他引:5  
研究了分别在NaCl和CaCl2·2H2O盐水溶液中浸渍7-730d的水泥砂浆试件受氯离子渗透的现象试验中,用染色法和滴定法先后测定了氯离子的渗透深度及其在渗透方向上的含量变化结果给出了渗透深度与水泥标号、水灰比、养护龄期、盐水溶液氯离子载体种类、氯离子浓度和试件浸渍时间等实验参数的关系,以及水泥砂浆的氯离子总含量和游离分量沿渗透方向的变化,并用滴定的结果对染色得到的分离子渗透深度进行了评价.  相似文献   

2.
制备工艺对SnO_2超细粉颗粒度的影响   总被引:3,自引:0,他引:3  
用液相沉淀法,在分析纯SnCl4·5H2O水溶液中滴加分析纯NH3含量为25%~28%的NH4OH水溶液,得到粒度为几个纳米至二十几个纳米的SnO2超细粉末;系统研究了SnCl4的浓度、滴加NH4OH水溶液的速度、干燥方法、煅烧温度及粉末中氯离子的含量对最终粉末颗粒度的影响规律,并探讨了影响机理  相似文献   

3.
针对实际工程应用中普通砂浆耐久性不足问题,研究了VAE乳胶粉对水泥砂浆耐久性改性效果,对不同聚合物含量(8%、9%、10%、11%和12%)的VAE乳胶粉改性砂浆通过收缩率、开裂性敏感度、抗渗性、耐氯盐腐蚀性和碳化实验,测试了收缩率、开裂总权值、渗水高度、透水压力、碳化深度以及氯离子渗透高度,结合扫描电镜实验,揭示了VAE乳胶粉对砂浆的微观改性机理。结果表明,VAE乳胶粉的加入显著提高了砂浆的抗渗透性。当聚合物含量为12%时,VAE乳胶粉砂浆的开裂总权值仅为普通水泥砂浆的55.1%,透水压力较普通水泥砂浆提高了78.6%,28 d碳化深度和氯离子渗透高度较普通水泥砂浆分别降低了36.8%、53.1%。VAE乳胶粉与砂浆中的骨料在浆体内部形成高黏结力的网状膜结构,填充改性砂浆的孔隙,使浆体内部更加密实,进而增强了改性砂浆的耐久性。  相似文献   

4.
利用电动势法测定了298.15K的电解质(KCl,NaCl,HCl,MgCl2和CaCl2)从水到葡萄糖水溶液物标准转移自由能。结果表明,所研究的每一电解质的标准转移自由能均随混合介质中葡萄糖的物质的量分数的增加而线性增大。此外,本文计算了水溶液中电解质-葡萄糖对相互作用的自由能参数。  相似文献   

5.
在恒温箱中测定了粉尘试样添加CaCl2或MgCl2和水玻璃后的含水率与环境温度、湿度、有效抑尘时间等因素之间的关系.研究结果表明:(1)当环境温度低于31℃,相对湿度高于60%,粉尘试样中CaCl2和水玻璃含量的质量分数分别达到20%和10%(MgCl2和水玻璃含量的质量分数为23%和11.5%)时,试样的含水率就能保持大于5%(质量分数);(2)当环境温度低于40℃,相对湿度高于50%,粉尘试样中CaCl2和水玻璃含量的质量分数分别达到26%和13%(MgCl2和水玻璃含量的质量分数为30%和15%)时,试样的含水率就能保持大于5%(质量分数);(3)CaCl2或MgCl2与水玻璃复合后,其粘尘功能进一步增强,而且其溶液的弱酸性得到进一步降低。  相似文献   

6.
为研究硅烷浸渍剂涂覆层数对不同龄期混凝土抗氯离子渗透性能的影响,采用了混凝土快速氯离子迁移系数法(RCM),研究了硅烷浸渍混凝土(两种配合比)抗氯离子渗透性能。试验结果表明,硅烷浸渍处理可以有效抑制氯离子在混凝土中的渗透,2层浸渍剂涂覆对混凝土氯离子渗透性抑制作用最为显著,两种配合比混凝土试件28 d氯离子扩散系数较未经硅烷浸渍试件分别降低了37.4%和37.6%。  相似文献   

7.
为研究PVA(聚乙烯醇)纤维掺量对不同龄期水泥砂浆氯离子扩散性能的影响规律,采用了快速氯离子迁移系数法(RCM),研究了PVA纤维水泥砂浆(7种配合比)抗氯离子渗透性能。分析了PVA纤维掺量与水泥砂浆孔隙率、电阻率的指标的关系,基于热传递方程建立氯离子扩散过程理论模型。结果表明,PVA纤维对水泥砂浆氯离子扩散系数有显著影响,改变了水泥砂浆的孔隙结构。28 d龄期,2%纤维掺量试件氯离子扩散系数和毛细孔率比不掺纤维试件分别降低24.1%和50.2%;PVA纤维水泥砂浆氯离子扩散系数与电阻率二者具有良好的线性负相关关系;PVA纤维掺量与水泥砂浆毛细孔率、气孔含量、电阻率之间有很好的相关性;桥面板中氯离子浓度与扩散系数成指数关系。  相似文献   

8.
关于烯烃与氯的水溶液加成机理之浅见杨菊仙(西南民族学院预科部)烯烃与氯气的水溶液的加成产物主要为氯代醇,即该加成好像在双键的两个碳上加上次氯酸的两个部分(OHδ-,Clδ+).为什么会有这样的结果呢?因为在氯的水溶液中含有一定分量的次氯酸:Cl2+H...  相似文献   

9.
用恒变形U形试件应力腐蚀试验、电化学极化和AES分析法研究了1Cr18Ni9Ti奥氏体不锈钢在室温H2S水溶液和90℃的H2Se+0.6mol/LNaCl水溶液中的应力腐蚀破裂,两种条件下都发现了台阶状的应力腐蚀裂纹。90℃时的破裂由〔Cl〕导致的阳极溶解机理控制,沿夹杂物/基体界面及轧制方向晶界的择优溶解导致台阶状裂纹。在室温无NaCl的H2S溶液中,破裂机理为氢致开裂,塑性变形造成的局部硬度增高可能是破裂的诱因。  相似文献   

10.
采用X射线衍射和分子动力学(MD)计算模拟等手段研究了67CdF2/33BaCl2玻璃(Ⅰ)和40CdF2/40BaF2/20CdCl2玻璃(Ⅱ)的结构。研究表明,在Ⅰ中Cd原子主要为6配位,Ⅱ中Cd原子主要为6或7配位。Cd—F的平均键长分别为231.6pm和230.4pm。在MD计算的玻璃中同时存在非桥F,桥F,3配位F和4配位F,几乎不存在不和Cd原子成键的游离F。弱的形成体阳离子和阴离子的连接较弱,Cd在大的阴离子空隙中的位置较松弛,体系随Cd含量增加稳定性下降。对混合卤化物玻璃的结构与形成的特点进行了讨论。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

14.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

15.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

16.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

17.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

18.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

19.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

20.
1 Rise of studies on climate change's effects on biodiversity
Until the 1980s, climate change and biodiversity were studied as two independent disciplines for more than a century. In 1992, the Ecological Society of America's annual report named climate change, biodiversity, and the sustainable ecological system as the three major global environmental issues of the twenty-first century [1].  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号