冷凝换热表面超疏水复合涂层的制备及性能

针对目前促成滴状冷凝换热的超疏水表面造价昂贵、热导率低和综合性能差等问题,以可溶性聚四氟乙烯、改性石墨烯(C)、气相二氧化硅等为原料,通过共混法在不锈钢基材上制备了用于冷凝传热表面的高导热超疏水复合涂层,并对其耐腐蚀能力、导热系数、强度和蒸汽冷凝传热性能进行测试分析。结果表明,涂层的耐酸腐蚀性能、导热性能强于304不锈钢,当含3%的C时,导热系数为18.188W·(m·K)^-1,在20%硫酸浓度恒温30℃条件下腐蚀速率为0.201mg·(cm²·h)^-1,和基材结合强度达38MPa。SEM分析表明,涂层疏水性能与气相二氧化硅含量有关,且质量分数为10%时接触角达155°。冷凝实验表明常压蒸汽在涂层表面冷凝时传热系数达120k W·(m²·K)^-1,大于不锈钢表面近10倍,并得出其滴状冷凝不持久的原因。     

材料热工参数对混凝土箱梁横截面温度场的影响

为研究导热系数和比热容对混凝土箱梁横截面温度场的影响,总结了国内外文献中导热系数和比热容的取值范围,实测了某座混凝土桥的箱梁横截面温度日变化曲线,建立有限元模型开展参数分析。分析结果表明,随导热系数增大或比热容减小,顶板和腹板上部的温度日变化曲线峰值增大,峰值出现时间提前。材料热工参数对腹板下部和底板温度日变化曲线的影响可忽略。当导热系数介于1.0～2.0 W/(m·℃)或比热容介于800～1 000 J/(kg·℃)时,温度日变化曲线有限元计算值与实测值吻合较好。材料热工参数对横截面平均温度曲线最大值的影响可忽略,但对横截面竖向正温度梯度曲线影响较大。随导热系数或比热容增大,顶板和底板正温差减小,对腹板影响可忽略。比热容的影响小于导热系数。     

复合相变储能砂浆的制备及其性能研究

以工业石蜡为相变芯材,通过真空吸附法和硅酸钙外壳封装法制备石蜡/膨胀珍珠岩复合相变材料和复合相变储能砂浆.利用SEM和差示扫描量热法分析了石蜡/膨胀珍珠岩相变材料的形貌和蓄热能力,测试了复合相变储能砂浆的抗压强度、干表观密度、导热系数和三维条件下材料温度时间响应关系.结果表明,经硅酸钙外壳封装后石蜡/膨胀珍珠岩相变材料中石蜡的含量约为55.47%时,相变温度和相变潜热分别为35.59℃和96.77J/g;复合相变储能砂浆的28d抗压强度,干表观密度和导热系数分别为8.0MPa,1 678kg/m~3和0.46W·m~(-1)·K~(-1),在外界温度变化时,复合相变储能砂浆相对于传统砂浆材料具有升温和降温速度变化平缓,可用作保温砂浆.     

新型环氧树脂复合相变材料对沥青混合料调温性能影响

为解决相变材料用于沥青混合料热稳定性与力学性能不足的问题,采用环氧树脂与十五烷定形封装相变材料制备新型环氧树脂复合相变材料,并采用等体积替换法将其用于沥青混合料中。采用差示扫描量热仪(DSC)、热重分析仪(TG)与导热系数仪进行环氧树脂复合相变材料相变与热物特性测试分析;通过相变沥青混合料温度调控试验分析其调温性能与效果,并对相变沥青混合料路用性能进行验证。研究结果表明：环氧树脂复合相变材料相变焓值可达60 J/g以上,在180℃以内几乎不发生热损失,储热密度高、热稳定性良好;相变区间内表观比热容显著增大,升、降温过程中最大值分别为10.9和6.7 J/(g·℃);相变材料掺量(质量分数)越大温度调控效果越好;调温性能与混合料位置相关,相变沥青混合料最大调温温差和最大温度变化速率降低值随深度增大而增大;各掺量下相变沥青混合料均具有显著的调温效果,掺量小于4%时相变沥青混合料均可满足路用性能要求。     

预埋碳纤维发热线桥面升温性能影响因素分析

为研究预埋碳纤维发热线桥面的升温性能,使用有限元软件建立温度场模型,分析发热线间距、埋深、温度及沥青混凝土比热容、密度、导热系数对桥面铺装层升温效果的影响.结果表明:结构表面温度与发热线的间距及埋深呈负相关,在环境温度为-5℃,发热线间距、埋深分别为8和4 cm时,加热2 h后结构表面温度处于2.10～3.54℃之间,温度场分布均匀;发热线温度在30℃以上时,桥面温度均大于0℃,且桥面温度随发热线温度升高而近似线性增长;结构表面温度与沥青混凝土的比热容及密度呈负相关,但影响较弱;沥青混凝土导热系数自3 600 J·m~(-1)·h~(-1)·℃~(-1)提高至4 800 J·m~(-1)·h~(-1)·℃~(-1)时,桥面温度可提高86%.总之,结构表面温度与沥青混凝土的导热系数呈正相关关系,且受影响较大;发热线间距为8 cm、埋深为4 cm时,升温性能最佳.     

纳米TiO2 /石蜡复合乳状液相变材料的 制备与传热性能

蓄冷空调性能及制冷系数与相变材料密切相关.将石蜡复合乳状液作为分散介质,以纳米TiO_2粒子作为导热载体,采用低能乳化工艺微乳液转相法,制备出纳米TiO_2/石蜡复合乳状液相变材料,并对其分散稳定性、导热系数和蓄-放热循环稳定性进行了分析.研究结果表明:纳米TiO_2/石蜡复合乳状液相变材料的导热系数相对于纯石蜡乳状液的导热系数有明显提高,当纳米TiO_2粒子质量分数为0.15%时,纳米TiO_2/石蜡复合乳状液相变材料的导热系数比纯石蜡乳状液的导热系数提高了117.95%;TiO_2/石蜡乳状液固-液相变热循环过程中并无明显温度平台,而且其蓄-放热循环稳定性很好.该纳米TiO_2/石蜡复合乳状液相变材料有望应用于蓄冷空调,以提高蓄冷空调性能及制冷系数.     

相变蓄热材料导热系数对太阳能通风墙性能的影响

通过对相变蓄热型太阳能烟囱模型通风蓄放热变化过程的计算,分析比较不同相变蓄热墙导热系数对太阳能烟囱性能的影响.计算结果表明:吸热板最大表面温度随着相变蓄热墙导热系数的增大越接近相变蓄热墙的相变温度;蓄热阶段,入口平均风速随着相变蓄热墙导热系数的增大而减小;放热阶段,入口平均风速随着相变蓄热墙导热系数的增大反而越大;相变蓄热墙导热系数越大,蓄热型太阳能烟囱系统16 h的累计通风量越高,但在导热系数增大到0.66 W·(m·K)^-1后,再增大材料导热系数,累计通风量几乎不再增加.     

六水合氯化钙基相变材料对岩棉保温板储能和保温性能的影响

以岩棉板为载体,将自主研制的六水合氯化钙基相变储能材料均匀渗入到岩棉板,制备了六水合氯化钙基相变材料改性的岩棉/六水合氯化钙基保温墙板,研究了六水合氯化钙基相变材料对岩棉板储能隔热能力及其力学强度的影响.结果表明：相变材料加入赋予了岩棉吸热储能性能,使岩棉板保温性能得到提高.岩棉板对六水合氯化钙基相变材料的最大吸附量为30 wt.%,且该吸附量下的保温岩棉墙板显示出最大的比热容0.700 1 MJ/(m³·K).尽管该吸附量下复合板显示较大的导热系数0.089 1 W/(m·K),但其相应热扩散率却最小,为0.127 3 mm²/s.热温度测试表明该吸附量下室内最高温度降幅达到3.4℃,表明导热系数不是影响岩棉板保温性能的唯一因素,采用热扩散率评估其保温性能更为合理.SEM显示六水合氯化钙基相变材料黏附于岩棉纤维之间且形成了稳定的空间网格架构,有效提高了岩棉板的抗压强度.     

玉米芯骨料生态混凝土的物理和力学性能

基于多源固废开发玉米芯骨料生态混凝土，并对其物理和力学性能进行试验研究.结果表明：当玉米芯吸水量为其吸水率的80%时，生态混凝土强度最高，玉米芯中的水分可对水泥起到内养护作用；当玉米芯的体积分数为30%～50%时，生态混凝土的干密度为1 200～1 550 kg·m^-3、抗压强度为2.0～5.7 MPa、抗折强度为0.21～1.00 MPa、收缩应变为380×10^-6～590×10^-6;生态混凝土的弯曲分为弹性阶段、裂缝产生、裂缝扩展和破坏4个阶段，玉米芯颗粒在其中起到桥联作用，可约束裂缝的产生和扩展，所得生态混凝土的弯曲韧性为0.86～3.78 kN·mm.     

石蜡-酚醛-水泥相变砂浆的制备及性能分析

为了改善石蜡相变材料的封装效果和防火能力,利用不燃的酚醛树脂包裹石蜡制备出石蜡－酚醛复合胶囊,并利用石蜡-酚醛复合胶囊制备出水泥相变砂浆。实验结果显示,石蜡在常温范围内的相变热是20520 J·g-1,相变温度范围为27~38 ℃;石蜡－酚醛的相变热为4259 J·g-1,相变温度范围为18~30 ℃;相变砂浆的相变热为929 J·g-1,相变温度范围为20~29 ℃;相变砂浆的抗压强度、劈裂抗拉强度和粘结拉伸强度随着石蜡－酚醛胶囊掺量的增加而明显下降。工程应用表明,制备的相变砂浆在一定范围内具有较好的调节建筑室内温度,具有易存放、易施工、安全性高的特点     

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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