温度梯度对热致型形状记忆聚合物板力学性能的影响

形状记忆聚合物作为一种新型的智能材料,由于质量轻、成本低以及变形回复率大等优势,已经在航空、医学等领域得到广泛应用。当前对于热致型形状记忆聚合物力学行为的研究,大都集中在整体变温的情况下,随着应用环境的越来越广泛,温度梯度对材料力学性能的影响效果越发重要。本文在均匀应力的假设下,给出材料在不同初始和传热条件下的温度梯度分布情况,结合传热学和热致型形状记忆聚合物相变理论本构模型,分别讨论了不同温度梯度对存储应变、弹性模量等力学性能的影响,通过理论分析和实验数据对比验证了模型正确性。本文研究可为不同导热情况下,对热致型形状记忆聚合物力学行为监测提供思路,也为形状记忆聚合物的进一步工程应用提供理论依据。     

Shock oscillation in highly underexpanded jets

The oscillatory motions of shocks in highly underexpanded jets with nozzle pressure ratios of 5.60, 7.47, 9.34, and11.21 are quantitatively studied by using large eddy simulation. Two types of shock oscillations are observed: one is the Mach disk oscillation in the streamwise direction and the other is the shock oscillation in the radial direction. It is found that the Mach disk moves quickly in the middle of the oscillatory region but slowly at the top or bottom boundaries. The oscillation cycles of Mach disk are the same for different cases, and are all dominated by an axisymmetric mode of 5.298 k Hz. For the oscillation in the radial direction, the shocks oscillate more toward the jet centerline but less in the jet shear layer, and the oscillation magnitude is an increasing function of screech amplitude. The cycles of the radial shock oscillation switch randomly between the two screech frequencies for the first two cases. However, the oscillation periodicity is more complex for the jets with high nozzle pressure ratios of 9.34 and 11.21 than for the jets with the low nozzle pressure ratios of 5.6 and 7.47. In addition, the shock oscillation characteristics are also captured by coarse mesh and Smagorinsky model,but the coarse mesh tends to predict a slower and weaker shock oscillation.     

物理问题中神奇的临界条件 — — — 共速

: 临界问题是诸多物理问题中很值得重视的一类. 解决临界问题的关键是找出临界条件. 仔细关注一下 诸多的临界问题之后, 会有一个很有意思的发现, 就是“ 共速”是许多临界问题中的临界条件.     

应用实例在高等代数教学中的作用

针对学生难以理解高等代数中的基本概念,在高等代数的教学过程中,结合具体教学内容加入一些应用实例帮助学生更好的理解相关概念和体会数学的广泛应用.以讲述矩阵特征值和特征向量为例,除讲解基本概念和计算方法外,结合自己的研究工作介绍了人口模型和传染病模型,给学生展示了特征值和特征向量应用的例子,使得学生对特征值和特征向量有了更深入的理解.     

含苯并噻唑砌块的2,4,6-三取代嘧啶衍生物的合成及抗肿瘤活性评价(英文)

为了寻找高效的抗肿瘤药物,设计并合成了一系列含苯并噻唑砌块的2,4,6-三取代嘧啶衍生物.采用噻唑蓝(MTT)法对目标化合物在人类四种癌细胞[EC-109(人食管癌细胞)、MGC-803(人胃癌细胞)、PC-3(人前列腺癌细胞)、Hep G-2(人肝癌细胞)]、GES-1(人正常胃黏膜上皮细胞)和HEEC(人正常食管细胞)中进行抗肿瘤活性评价,结果显示部分化合物对MGC-803和PC-3细胞表现出中度至强效的抗肿瘤活性.其中2-(((4-(4-(吡啶-2-基)哌嗪-1-基)-6-(三氟甲基)嘧啶-2-基)硫基)甲基)苯并[d]噻唑(13h)和2-(((4-(4-(嘧啶-2-基)哌嗪-1-基)-6-(三-氟甲基)嘧啶-2-基)硫代)甲基)苯并[d]噻唑(13i)对PC-3表现出比较好的抗肿瘤活性, IC50值分别3.82和2.29μmol/L,且化合物13h和13i对GES-1的细胞增值毒性明显小于阳性对照5-氟尿嘧啶.     

新型1,3-二取代酞嗪酮类衍生物的合成及抗肿瘤活性研究

为了寻找高效低毒的抗肿瘤药物,设计并合成新型的1,3位取代酞嗪酮类化合物.采用噻唑蓝(MTT)法对目标化合物在MCF-7(人乳腺癌细胞)、PC-3(人前列腺癌细胞)、SW-620(人结肠癌细胞)和HGC-27(人胃癌细胞)四种人类癌细胞的抗增殖活性进行评价.结果显示大部分化合物具有较好的抗增殖活性.其中,2-(4-(4-溴苯基)-1-氧代酞嗪-2(1H)-基)-N-(2-氟苯基)乙酰胺(5g)对MCF-7细胞的抗增殖活性较好,IC50值为6.01μmol/L,为抗肿瘤药物的研究提供了思路.     

A principle to correlate extreme values of excess thermodynamic functions with partial molar quantities

Excess thermodynamic properties are widely used quantitatively for fluids. It was found that at constant temperature and pressure a molar excess quantity of a mutually miscible binary mixture at the extreme points equals the excess partial molar quantities of the two components, i.e.F_(1)~E = F_(2)~E = F_(m)~E , forming a triple cross point. The relationship is hold for properties such as en-thalpy, entropy, Gibbs free energy, and volume, and is applicable for excess functions with multi extreme points. Solutions at extreme points can be referred to as special mixtures. Particularly fora special mixture of Gibbs free energy, activity coefficients of the two components are identical.     

Particle path tracking method in two- and three-dimensional continuously rotating detonation engines

The particle path tracking method is proposed and used in two-dimensional（2D） and three-dimensional（3D） numerical simulations of continuously rotating detonation engines（CRDEs）. This method is used to analyze the combustion and expansion processes of the fresh particles, and the thermodynamic cycle process of CRDE. In a 3D CRDE flow field, as the radius of the annulus increases, the no-injection area proportion increases, the non-detonation proportion decreases, and the detonation height decreases. The flow field parameters on the 3D mid annulus are different from in the 2D flow field under the same chamber size. The non-detonation proportion in the 3D flow field is less than in the 2D flow field. In the 2D and 3D CRDE, the paths of the flow particles have only a small fluctuation in the circumferential direction. The numerical thermodynamic cycle processes are qualitatively consistent with the three ideal cycle models, and they are right in between the ideal F–J cycle and ideal ZND cycle. The net mechanical work and thermal efficiency are slightly smaller in the 2D simulation than in the 3D simulation. In the 3D CRDE, as the radius of the annulus increases, the net mechanical work is almost constant, and the thermal efficiency increases. The numerical thermal efficiencies are larger than F–J cycle, and much smaller than ZND cycle.     

红外光谱法研究聚苯乙烯磺酰氯树脂功能基团的均一性

利用380FTIR型红外光谱研究了聚苯乙烯与氯磺酸在不同时间及投料比条件下的氯磺化反应。以1 601.5 cm-1苯环特征峰作为内标峰,1 377.4与3 476.8 cm-1处的磺酰氯和磺酸特征峰作为参比峰,以朗伯-比耳定律为理论依据,利用红外光谱法测定了特征频率强度A,将 A_{1 377.4}和A_{3 476.8}与A_{1 601.5}进行比较,并以A_{1 377.4}∶A_{3 476.8}的大小表示聚苯乙烯磺酰氯树脂均一性的高低。结果表明：(1)当反应1 h之后A_{1 377.4}∶A_{3 476.8}随时间的延长而增大。(2)在投料比为1∶1之前,A3 476.8∶A_{1 601.5}随投料比的增大而增大,之后则随投料比的增大而减小,同时出现了磺酰氯吸收峰且A_{1 377.4}∶A_{1 601.5}随投料比逐渐增大,在4∶1之后A_{1 377.4}∶A_{1 601.5}与A_{3 476.8}∶A_{1 601.5}呈现稳定。在一步法反应条件下,当投料比为4∶1时,反应5 h,可获得均一性较好的聚苯乙烯磺酰氯树脂 (磺酰氯的担载量为4.0 mmol·g-1)。结果证明红外光谱法可方便、快捷地检测聚苯乙烯磺酰氯树脂的均一性,具有一定的实用性及推广性。     

介绍一种测量表面间分子作用力的仪器:表面力仪

研究分子间或分子聚集体间的相互作用是认识物质构筑规律、了解物质从微观到宏观各种物理化学性质以及探索生命奥秘的基础,长期以来科学家们梦寐以求能够直接测量分子(或分子聚集体)间的作用力.表面力仪(Surface Force Apparatus,常简写为SFA)就是一种直接测定两个微小表面间分子相互作用力与他们间距离关系的精密仪器.