加掺合料高性能混凝土早龄期收缩特性

采用新研制的智能型非接触式微位移传感器法对加掺合料高性能混凝土从成型后6h到3d龄期内的自生收缩和单面干燥条件下的总收缩进行试验研究,结果表明：掺入硅灰会略微增加混凝土早期自生收缩,而对早期干燥收缩影响不大;粉煤灰的掺入能大幅度地减小混凝土早期自生收缩,但使早期干燥收缩增加;磨细矿渣只有在掺量较多时才能明显降低早期自生收缩,却对早期干燥收缩不利。     

混凝土自收缩与干燥收缩的统一内因

为考察混凝土内部相对湿度与自收缩和干燥收缩的关系,实验测量了在表面密封(试件Ⅰ)和表面先密封后暴露于环境中(试件Ⅱ)2种干燥条件下早龄期混凝土试件的自由变形和内部温湿度变化规律。实验结果表明:在3 d龄期前,同处于密封状态的两试件的自由变形和内部温湿度变化相同;从3 d龄期开始,试件Ⅱ在水分散失作用下内部湿度下降明显大于试件Ⅰ,相应地,由于叠加了干燥收缩,其变形也明显大于试件Ⅰ的自收缩变形。这说明混凝土试件在近似相同的温度历程下,内部相对湿度与其湿度变形,可作为混凝土自收缩与干燥收缩的统一内因进行统一描述。     

超强吸水剂对混凝土早期内部相对湿度的影响

测定了高性能混凝土不同深度处早期湿度随时间的变化,探讨了不同掺量的超强吸水剂(SAP)对不同的外界温湿度条件、不同水灰比的高性能混凝土早期相对湿度的影响。结果表明,与未掺SAP的混凝土相比较,掺SAP混凝土的早期内部湿度有了明显的提高,其内部湿度分布均匀且随龄期的经时变化减小;而且随SAP掺量提高,效果继续增强,尤其是在干热环境以及低水灰比混凝土,SAP的作用更好。结论认为,SAP通过内部引水可以提高混凝土内部的含湿量,改善内部湿度梯度,能够为混凝土提供自养护。     

单面干燥条件下受约束高强混凝土的早期开裂研究

在单面干燥条件下应用自行研制的混凝土早期收缩应力测试仪及非接触式混凝土收缩变形测试仪测试了水灰比为0.26、0.40的高强混凝土的早期弹性模量和自由收缩变形,通过改进的环向约束试验观测了受约束试件内部的收缩应力及应力梯度,并在上述试验基础上研究了单面干燥条件下受约束高强混凝土的早期开裂趋势.结果表明,高强混凝土水灰比越小,单面干燥条件下的早期自由收缩变形、弹性模量、受约束状态下的内部收缩应力增长越快,干燥表面越容易发生塑性收缩开裂,早期开裂趋势越明显.     

单面干燥条件下受约束高强混凝土早期开裂研究

摘 要：本文在单面干燥条件下应用自行研制混凝土早期收缩应力测试仪及非接触式混凝土收缩变形测试仪测试了水灰比为0.26、0.40高强混凝土早期弹性模量、自由收缩变形,通过改进环向约束试验观测了受约束试件内部的收缩应力及应力梯度,并在上述试验基础上研究了单面干燥条件下受约束高强混凝土早期开裂趋势。结果表明,高强混凝土水灰比越小,单面干燥条件下早期自由收缩变形、弹性模量、受约束状态下内部收缩应力增长越快,干燥表面越易发生塑性收缩开裂,早期开裂趋势越明显。     

粉煤灰掺量对高性能混凝土收缩的影响

研究高性能混凝土的自生收缩和干燥收缩对于推广高性能混凝土在实际工程中的应用具有重要的理 论和现实意义．通过实验研究了不同掺量的粉煤灰对高性能混凝土的自生收缩和干燥收缩的影响．实验结 果表明,由于粉煤灰的滞后效应,用粉煤灰替代部分的水泥可以减少高性能混凝土的自生收缩和干燥收缩．     

列车气动效应作用下隧道衬砌混凝土水分传输理论研究

针对高速列车气动效应在铁路隧道衬砌混凝土表面产生的高速气流和空气低压作用,提出考虑列车气动效应的隧道衬砌混凝土水分传输和湿度场理论计算模型,并对气体流速和表面低压等关键影响因素进行分析。研究结果表明：高速气流加速混凝土表面水分交换速率并减薄水汽过渡层,表面低压作用降低环境中的水蒸气分压并增大混凝土表面与内部孔隙之间的压力梯度;混凝土表面风速越大、气压绝对值越低,其内部湿度下降越快;环境条件对混凝土湿度场的影响仅局限在混凝土表面一定范围内,环境风速和表面气压变化对混凝土内部湿度影响较小;在标准大气压条件下,当混凝土表面风速由5 m/s增大至15 m/s时,距离干燥面10 mm和30 mm处60 d龄期时相对湿度分别降低32.6%和3.9%;在环境风速为0 m/s条件下,当混凝土表面气压由80 kPa降低至50 kPa时,距离干燥面10 mm和30 mm处60 d龄期时混凝土相对湿度分别降低37.9%和3.8%。本文所提出的理论模型可较准确地描述上述因素对混凝土湿度变化的加速效应。     

真实环境下早龄期水工混凝土内部相对湿度实验研究

混凝土内部相对湿度是混凝土的重要性能参数之一.为了揭示实际工程中不同湿度状态下早龄期水工混凝土内部相对湿度的变化规律,在宜昌地区开展了高、低温季节真实环境下掺粉煤灰水工混凝土湿度实验,对比研究了6面包裹、5面包裹和6面裸露3种不同湿度交换状态下,水工混凝土立方体试件不同深度处的内部相对湿度变化规律.实验结果表明,高、低温季节下的水工混凝土内部相对湿度变化可分为两个阶段,即内部相对湿度在第一阶段维持为100%,在第二阶段缓慢下降;环境温度是影响水工混凝土内部相对湿度变化的重要因素,环境温度越高,水工混凝土内部相对湿度下降的越早且越快;由于水工混凝土的水胶比较高,水工混凝土内部相对湿度下降主要是水分向外界扩散引起,而由水化反应引起的内部相对湿度下降值基本可以忽略.     

大掺量粉煤灰混凝土干燥收缩性能

为了研究粉煤灰对混凝土收缩性能的影响并有效预测粉煤灰混凝土收缩发展的规律,对采用不同等级粉煤灰,且掺量分别为35%、40%、45%的粉煤灰混凝土的干燥收缩性能进行了研究,测试了各试件7～120 d的收缩值.结果表明:大掺量粉煤灰对混凝土的收缩有较好的抑制作用,且对后期收缩的抑制更为显著;Ⅰ级粉煤灰对混凝土收缩的抑制效果明显优于Ⅱ级粉煤灰.对收缩的时程曲线进行分析,发现其呈复合指数关系,并给出了考虑粉煤灰掺量影响的混凝土干燥收缩预测公式.     

密闭条件下UHPC的收缩性能试验研究

进行4组对比试验,研究密闭与非密闭条件下超高性能混凝土(Ultra-high performance concrete,UHPC)的收缩性能差异,分析不同钢纤维掺量、水胶比及粉煤灰掺量对密闭条件下UHPC自收缩和抗压强度的影响.研究结果表明,UHPC的自收缩和干燥收缩在早龄期阶段发展迅速,14d的自收缩值为114d自收缩值的80%~90%,6d后干燥收缩值不再增长;密闭条件下自收缩值占非密闭条件下总收缩值的82.8%,远大于干燥收缩值;随钢纤维掺量的增加,自收缩值随龄期的变化规律无显著变化,早龄期的自收缩值略微减小,抗压强度呈现先增大后减小的现象;增加粉煤灰掺量或水胶比可以减小自收缩值,但对抗压强度会产生削弱作用;粉煤灰的掺入改变了自收缩值随龄期的变化规律,并产生"滞后效应";基于试验结果对现有的UHPC自收缩预测模型进行了修正,修正后的预测模型可为工程设计提供参考.     

Markedness and its Interpretation in Language Use

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.     

Features of Women's language

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

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.     

Lower Paleozoic oil relationships within Williston Basin, Canada

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.     

低渗透非均质砂岩油藏启动压力梯度研究

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。     

On Tragic Consciousness In The Works By Ernest Hemingway

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.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the