HTRB600级高强钢筋高温下的力学性能

为研究600 MPa级高强钢筋高温下的力学性能,对HTRB600级热处理高强钢筋进行高温下的拉伸试验,分别测得其在20,200,300,400,500,600,700及800℃高温下的弹性模量、比例极限、屈服强度、极限强度及应力-应变曲线.试验结果表明:HTRB600级高强钢筋高温下屈服强度、极限强度、比例极限与弹性模量均随着温度的升高而显著降低.500℃时其高温下的弹性模量、比例极限、屈服强度与极限强度降低为不足常温下的50%,800℃时已不足常温下的10%.高温下HTRB600级高强钢筋应力-应变曲线随温度的升高逐渐趋于圆滑,当温度达到200℃时,屈服台阶就已消失.600 MPa级钢筋高温下屈服强度和极限强度的降低程度明显大于其他钢筋500 MPa以下强度的钢筋.最后提出了适用于HTRB600级高强钢筋的高温下应力-应变曲线简化计算模型.     

高温作用后石灰岩受压破裂过程的声发射试验研究

利用声发射测试和单轴压缩试验相结合的方法,研究了河南焦作矿区的石灰岩在100~800 °C高温压缩破坏条件下的声发射过程,结合不同温度下石灰岩的力学性质,分析不同声发射参数条件下石灰岩在不同受力阶段的声发射特点.结果表明：在高温作用下石灰岩出现了明显的声发射现象;石灰岩峰值应力随着作用温度的升高而不断降低,800 °C以后,峰值应力较600 °C时降幅达50%,但是峰值应变随着作用温度的升高而变化不明显;在400 °C以前,声发射振铃累计数均值随着温度的升高而增加,400 °C后随着温度的升高而不断降低;在600~800 °C时,试样呈现出明显的塑性破坏特征,高温致使石灰岩劣化,声发射试验中,振铃累计数大幅度降低,应力与应变和声发射特征参数变化规律较吻合.     

高温后轻质多孔混凝土力学性能试验

通过高温后轻质加气混凝土的力学性能试验,测得了抗压强度、弹性模量和峰值应变与温度的关系.试验表明:高温后轻质加气混凝土的抗压强度在100℃时略微提高,到300℃时逐渐下降,超过300℃时,强度变化不明显;在100℃以内,弹性模量基本保持不变,超过100℃后,弹性模量不断减小,与温度成线性关系;随着温度的升高,峰值应变逐渐增大,呈直线上升趋势.最后分析了不同温度下的应力-应变曲线,提出了高温后轻质加气混凝土的本构模型.     

加载速率对不同温度状态石灰岩力学性能影响的试验研究

借助美国MTS810电液伺服材料试验机和高温炉,对常温和600℃两种温度状态下石灰岩试件进行不同加载速率下的单轴压缩试验,得到石灰岩力学性能随加载速率的变化规律。结果表明:常温时,石灰岩岩样在3×10-4~3×10-3 mm/s的低应变率范围内,加载速率对峰值应力和弹性模量影响不大,在加载速率为3×10-3~3×10-1 mm/s的区段内,峰值应力和弹性模量均呈明显上升趋势;600℃时,峰值应力和弹性模量随加载速率增加变化不大。常温时,不同加载速率下石灰岩岩样均为竖向劈裂破坏,且在3×10-3~3×10-1 mm/s的加载速率区段中,随加载速率的增加,劈裂面逐渐增多;600℃时,石灰岩岩样在不同加载速率下均为剪切破坏。     

温度作用对石灰岩的热学与力学性能影响

温度作用对石灰岩性能的影响在液化天然气储存、核工程建设、地下煤气及地热资源开发等工程中均有涉及,为了研究石灰岩在不同温度环境下的热学及力学性能,通过自主研发的力-温度同步施加试验装置,对石灰岩进行了从常温至高温300℃以及从常温至低温-165℃的变温加载耦合试验。通过原位补偿方法,将温度与力引起的应变输出分离,进而得到石灰岩的线膨胀系数(CLTE)及其随温度的变化规律。通过加载试验,建立不同温度下的应力-应变关系曲线,进而得到石灰岩的弹性模量随温度的变化规律。试验结果表明:温度从0℃降温到-165℃时,石灰岩的线膨胀系数平均下降了86%,弹性模量下降了10%。当温度为30～300℃时,石灰岩的线膨胀系数平均提高了58%,弹性模量则增加了60%。     

高温及冻融后蒸压轻质混凝土力学性能研究

为研究蒸压轻质混凝土结构在高温-冻融耦合作用下力学性能的变化情况,将不同高温处理后的蒸压轻质混凝土试件经过冻融循环试验后进行静态力学性能试验,研究了不同温度、不同冻融方法对蒸压轻质混凝土试件抗压强度、弹性模量、应力应变关系、能量吸收的影响。试验结果表明,蒸压轻质混凝土试件经高温与冻融循环耦合作用后,随着处理温度增加,其抗压强度减小,弹性模量降低,塑性提高,应力应变曲线变平缓,峰值应力减小,峰值应变增加,能量吸收减小,盐冻冻融循环相较于水冻冻融循环对高温处理后试件的力学性能劣化影响更大,使得试件破坏所需吸收的能量更小。     

国产Q550高强钢高温力学性能试验研究

通过稳态拉伸法对国产Q550高强钢高温力学性能进行试验研究,得到20~800℃下钢材的试验现象、力学性能参数、应力-应变关系曲线,并将所得试验结果与国内外相关规范和研究成果对比.试验表明:不同温度下试件破坏时表面及断口形貌区别明显;300℃后随着温度升高,弹性模量、屈服强度、极限强度下降,应力-应变关系曲线的弹性段和强化段缩短,下降段趋于平缓.450℃内高温对断后伸长率影响不大,此后随温度升高断后伸长率急剧增大.现有钢材高温力学性能参数模型对国产Q550高强钢并不适用.因此,分别采用多项式模型和美国国家标准与技术研究院的钢材高温通用材料模型进行拟合,得到高温下Q550高强钢力学性能参数的数学模型.     

不同冷却方式下ALC高温劣化损伤试验研究

为研究不同冷却方式下ALC在高温处理后性能劣化损伤情况,通过对不同温度、不同冷却方式处理后的ALC试件进行超声无损检测试验、静态力学性能试验、毛细吸水试验的方法研究了温度、冷却方式对其质量损失率、纵波波速、抗压强度、弹性模量、应力应变关系、能量耗散、毛细吸水性的影响。研究结果表明：ALC内各种水化产物受热分解,水分消散,体积膨胀,微裂隙增加,纵波波速减小,抗压强度减小,弹性模量降低,塑性提高,峰值应变增加,能量耗散不断提高,最大毛细吸水量增大;其应力-应变曲线的形状与普通混凝土相似,都经历了压密阶段、弹塑性阶段、破坏阶段、残余阶段。喷淋冷却试件相对于自然冷却试件在300℃前损伤较小,性能劣化程度较低,300~600℃时劣化损伤明显增大,毛细吸水性增长显著,600~800℃时不同冷却方式对ALC性能影响逐渐减小。可见,不同的冷却方式对高温处理后ALC有一定的影响,但随着温度升高,影响逐渐降低。     

高温遇水冷却石灰岩力学与声学性质研究

以石灰岩为研究对象,对加温遇水冷却后的岩样进行轴向压缩试验和声波测试,研究不同高温遇水冷却岩样的表观形态和力学性质的变化情况,分析力学与声学性质的关系。研究结果表明:随温度升高,高温遇水冷却干燥后岩样的颜色逐渐变浅,700℃时变为灰白色;峰值强度整体上呈减小趋势;当从常温升至500℃时,峰值应变逐渐增大,弹性模量和变形模量逐渐减小;高于500℃时,随温度升高,峰值应变先减小后增大,弹性模量和变形模量先增大后减小;随温度变化,弹性模量、峰值强度与纵波声波波速、横波声波波速间均呈现出良好的相关性。     

高温荷载耦合作用下地聚物砂浆损伤模型研究

为研究高温对地聚物砂浆的力学性能与导热性能的影响，以温度为变量设置了25℃、200℃、400℃、600℃、800℃这5种温度进行常规导热试验和单轴压力试验。试验获取了导热系数、应力-应变全曲线、抗压强度、峰值应变、切线模量等参数指标，并对不同高温作用后的地聚物砂浆进行了SEM和XRD试验，深入分析了不同温度对其力学性能与导热性能的影响规律，并建立了地聚物砂浆高温损伤模型。结果表明：（1）随着温度的升高，地聚物砂浆的导热系数呈现逐渐下降的趋势，温度为200℃时，相比于其他温度的导热系数下降幅度明显；（2）高温使地聚物砂浆的力学性能随温度的升高不断降低，并且随着温度升高，高温劣化作用越来越显著，使强度迅速下降；（3）高温会导致地聚物砂浆内部裂缝逐渐增多、C-S-H胶凝物质减少，在温度为600℃时C-S-H胶凝物质基本消失，800℃发生固相反应生成钙铝黄长石且砂浆内部细小裂缝转变为贯通型大裂缝；（4）建立了地聚物砂浆高温损伤模型。     

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.     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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