A Comparative Study on the Self Diffusion of N-Octadecane with Crystal and Amorphous Structure by Molecular Dynamics Simulation

The straight chain n-Mkanes and their mixture, which can be used as phase change materials （PCM） for ther- mal energy storage, have attracted much attention in recent years. We employ the molecular dynamics （MD） simulation to investigate their thermophysical properties, including self diffusion and melting of n-octadecane with crystal and amorphous structures. Our results show that, although the initial and melted structures of n-octadecane with crystal and amorphous are different, the melting behaviors of n-octadeeane judged by the self diffusion behavior are consistent. The MD simulation indicates that both the crystal and amorphous structures are effective for the property investigation of n-octadecane and the simulated conclusion can be used as reference for modeling the alkanes-based PCM system.     

相变材料微胶囊流体相变化过程流体内部流态的变化

相变材料是一种石蜡混合物,其主要成分为C_(19)H_(40),以该潜热相变材料作为芯物质,树脂为囊壁材料,制备成的微纳米胶囊流体。将其填充在水平矩形密闭容器内,在下表面加热,上表面冷却,其余各表面绝热的条件下,相变材料在发生相变化过程,对流体内部流动状态及温度分布进行了理论分析,并考察了不含有相变材料流体与含有相变材料的流体流动过程的差别.结果表明:相变化过程,降低了流体流动的速度,加大了流体在冷热板附近的温度梯度;矩形容器高度的增加,流体内部形成的涡数减少,对流越容易发生;热板温度的增加,在冷热板附近产生的温度梯度增加;流体质量浓度的增加,流体流速降低。     

HIRFL–CSR电子冷却装置上的横向电子束温度

从磁场中单电子的轨道运动方程出发,分析并推出了HIRFL-CSR电子冷却装置上的横向电子束温度,并得到了一些重要结论.     

HIRFL—CSR电子冷却系统

建议中的兰州重离子加速器冷却贮存环（ＨＩＲＦＬ－ＣＳＲ）拟采用电子冷却方法将重离子束冷却到３００ＭｅＶ／ｕ。最高电子能量为１６５ｋｅＶ，最大电子电流密度主０．２４４Ａ／ｃｍ＾２，叙述了ＣＳＲ电子冷却装置的初步方案。     

电子冷却

本文概述电子冷却原理及其国际现状。     

手性氨基醇（R）－2－氨基－1，1－二苯基－3－（2－萘基）－1－丙醇：制备及其对前手性酮硼烷还原的对映选择性催化作用

用丙二酸酯法合成了Ｎ－乙酰基－３－（２－萘基）－ＤＬ－α－丙氨酸乙酯３．３经酶法拆分，得光学活性的Ｄ－３，后者经盐酸水解、酯化后再与苯基溴化镁作用，制得标题化合物６。在０．５ｍｍｏｌ６存在下，用过量硼烷对一系列前手性酮还原，得到了相应的光学活性二级醇。对映体过量（ｅ．ｅ值）５７．０～１００％。     

MgO/SBA-15固体碱介孔材料的研制

结合浸渍和微波辐射技术，分别采用浸渍、浸渍-微波、微波辐射等方法将醋酸镁高分散在SBA-15上而成为MgO改性介孔固体碱材料。结果显示：使用不同负载方法以及含铝SBA-15为载体，均能使MgO均匀分散;负载量达到20%时，XRD法仍未检测到样品上有MgO的晶相。实验表明负载的MgO在载体上形成了多层重叠结构，产生较多的中强碱位，而在介孔分子筛中引入Al原子则有利于碱位的形成。     

超临界水中含碳酸根羟基磷灰石的快速连续合成

Carbonated hydroxyapatites(CHA) were rapidly and continuously synthesized in supercritical water by using a tubular reactor. The effects of reaction time and the ratio of PO₄^3-/CO₃^2- on the apatite structure were investigated by using XRD, FTIR and TEM. Results showed that 30 seconds were enough to produce fully crystalline CHA nano-rods, ca. 20×70 nm in size, at 380 ℃ and 24 MPa. When the ratio of PO₄^3-/CO₃^2- was not less than 1, the CO₃^2- ions mainly substituted for PO₄^3- in apatite structure; but CO₃^2- ions could react with Ca²⁺ to form CaCO₃ phase when the ratio of PO₄^3-/CO₃^2- was less than 1.