四种α-取代丙酸酯在环糊精气相色谱固定相上的手性拆分机理

计算了4种α-取代丙酸酯衍生物在β-环糊精衍生物气相色谱固定相上手性分离过程中的热力学参数,对手性拆分机理进行了探讨。实验结果显示随着温度的升高,样品的容量因子、手性选择因子和分离度都在逐渐降低。热力学参数表明,4种α-取代丙酸酯在固定相上的色谱保留及手性识别都为焓驱动过程,氢键力没有在手性识别中起到决定作用,而样品的母体结构和取代基团的性质则对手性识别有较大的影响。样品在固定相上的手性分离效率的驱动力主要来自于其对映异构体与固定相之间作用力的能量差异。     

分形最新进展与力学中的分形

分形在力学领域中的应用已很普遍,从微结构的位错分布、局部剪切场到地壳的运动和变形都已观察到分形的行为和分形结构.本文概述了分形理论的最新进展及在力学中的应用.给出了微结构、混沌与分形的关联及塑性、局部剪切的分形模型.进而讨论了损伤断裂的分形描述以及分形熵与热力学.     

工艺应力模拟技术中的热相似律

分析了热处理及焊接的热过程，从热传导的基本方程及边界条件出发，结合不同工艺过程的特点，提出了用光弹法模拟整体淬火热应力，表面淬火热应力和焊接过程热应力及残余应力的热相似律。     

高压下硝基甲烷分子温度的密度泛函计算

用密度泛函理论在B3LYP/6-311++G(2d,2P)计算水平上对硝基甲烷分子进行了结构优化、频率和热化学分析.发现:在相同温度条件下改变压强,分子熵函数产生了改变,当温度和压强条件相同时,对于不同物质熵函数的改变是相同的.以热力学理论中麦克斯韦关系为基础,通过计算等温过程中分子的熵函数对压强的变化率,用数值拟合方法得到不同压强条件下分子温度的表达式:T=T0+(1-B)[18.3858+0.5392P]V0,式中T0、V0分别表示分子系统初态的温度和体积,T、V分别表示系统在末态的温度和体积,B是体积的压缩比.在选定参数的情况下该表达式可以计算不同压强条件下CHNO含能材料的分子温度.同时,以硝基甲烷为验证,选取基本参数V0和B,计算其在C-J条件对应的爆压14GPa下,分子温度为3461K,对应爱因斯坦温度,相当于3228cm-1的能量,在实验中该能量足以激发硝基甲烷分子内振动能量重新分配过程,有可能激发C-N键的红外振动而引起单分子分解反应的发生.因此,此表达式可用于预测含能材料撞击点火过程单分子分解可能的反应通道.     

基于(火积)耗散率最小的T-Y形肋片构形优化

基于构形理论,以导热和对流换热总(火积)耗散率最小为优化目标,对T-Y形肋片进行构形优化,得到同时考虑导热和对流换热(火积)耗散性能的T-Y形肋片最优构形。结果表明:存在最佳单元级直肋和中部空腔高度和长度比使得T-Y形肋片无量纲当量热阻取得二次最小值。增大肋片高度和长度比和肋片占比有助于提高T-Y形肋片整体传热性能。T-Y形肋片与T形肋片相比,T-Y形肋片二次最小无量纲当量热阻降低32.33%,此时T-Y形肋片温度梯度场更均匀,整体传热性能得到明显提高。     

利用自发布里渊散射测量液体声速

为了克服共振干涉法在液体的热力学声速和高频声速测量方面精度不高的问题, 本文建立了一种基于自发布里渊散射原理的测定液体声速的实验装置. 利用法布里-珀罗干涉仪对散射光进行扫描滤波, 数据采集卡结合光子计数器对散射光进行探测, 设计了一种散射光信息采集分析方法. 该实验方法有效的解决了传统布里渊散射方法中信号失真的问题, 显著地提升了液体声速测量精度. 对308.6–906.2 MHz内298.15 K饱和液相CCl₄声速进行了测量, 测量结果与文献值具有较好一致性. 利用法布里-珀罗干涉仪周期性扫描的滤波原理, 通过在测量得到的布里渊频移上加减整数倍个自由波谱区, 得到了更大频率的波谱信息, 进而设计一种测定介质高频声速的方法. 对CCl₄在5406.1–5521.0 MHz频段内的声速进行了测量. 实验结果显示, CCl₄的热力学声速随频率无明显变化, 而高频声速随频率的增大呈增大趋势且远大于热力学声速, 证实CCl₄具有色散现象.     

反常磁矩对弱磁场弱相互作用费米气体热力学性质的影响

考虑费米子的反常磁矩, 运用赝势法和热力学理论, 导出弱磁场中弱相互作用费米气体自由能的解析式, 以此为基础给出高温和低温情况下系统热力学性质, 分析反常磁矩对热力学性质的影响机理. 研究表明: 反常磁矩对热力学性质的影响与温度相关, 而且这种影响随温度的上升在低温区是增大的, 在高温区是减小的; 对于系统的化学势、内能, 反常磁矩加强了磁场的影响, 弱化了相互作用的影响; 对于系统的热容量, 反常磁矩在低温区使其减小, 在高温区使其增加.     

煤气化废渣基活性炭吸附对二甲苯动力学与热力学研究

本文以固体废弃物煤气化废渣(CGR)为原料,采用两阶段酸处理与CO_2活化制得煤气化废渣基活性炭(CGR-AC)。选用CGR-AC为吸附剂,系统考察了模拟精对苯二甲酸(PTA)精制工艺产生的含对二甲苯(PX)废水在不同温度下的吸附过程。结果表明,CGR-AC吸附PX的过程在热力学上符合Freundlich方程,且ΔH0,ΔG0,是一个自发的、吸热的物理吸附过程;在动力学上符合准二阶动力学模型,说明该吸附过程可能存在吸附剂与吸附质之间的电子共享与交换。     

烷基链工程对两亲有机半导体热力学性能影响的研究

Due to their special polar structure, amphiphilic molecules are simple to process, low in cost and excellent in material properties. Thus, they can be widely applied in the preparation of functional film materials and bionics related to cell membranes. Therefore, amphiphilic organic semiconductor materials are receiving increasing attention in research and industrial fields. The structure of organic amphiphilic semiconductor molecules usually consists of three functional parts: a hydrophilic group, a hydrophobic group, and a linking group between them. The adjustment of their correlation to achieve the target performance is particularly important and needs experimental discussion regarding synthetic methodologies. In this work, we focused on the engineering of a substituent alkyl-chain, and an amphiphilic functional molecule (benzo[b]benzo[4, 5] thieno[2, 3-d]thiophene, named C_nPA-BTBT, n = 3–11) was proposed and synthesized. This molecule links the hydrophobic semiconductor backbone and hydrophilic polar group through alkyl chains of different lengths. Fundamental properties were investigated by nuclear magnetic resonance (NMR) and ultraviolet-visible spectroscopy (UV-Vis) to conform the structure and the band gap properties of the designed organic semiconductor. Thermodynamic features were investigated by thermogravimetric analysis (TGA) and corresponding differential thermal gravity (DTG), which indicate that the functional molecule C_nPA-BTBT (n = 3–11) has a great stability in ambient conditions. Moreover, the results show that the binding ability of the amphiphilic molecule to water molecules was regulated by the odd-even alternating effect of the alkyl chain and the intramolecular coupling with BTBT. Furthermore, differential scanning calorimetry (DSC) and polarized optical microscopy (POM) were used to study the material properties in detail. As the length of the alkyl chain increased, the functional molecule C_nPA-BTBT (n = 3–11) gradually changed from "hard" species with no thermodynamic changes to a transition one with a pair of thermodynamic peaks, and eventually to a "soft" one as a typical liquid crystal with clear observation of Maltese-cross spherulites. The cooling and freezing points were further studied, and the values and trends of their enthalpy and corresponding temperature fluctuated and alternated due to the volume effect, odd-even alternating effect, flexibility, and other functions of the alkyl chain. Three molecular models were proposed according to the thermodynamic study results, namely the brick-like model, transition model, and liquid crystal model. This work presents in-depth discussion on material structure and corresponding thermodynamic properties, and it is an experimental basis for the design, synthesis, optimization, and screening of target performance materials.