1,3-双[3-(1-甲氧基-2-羟基丙氧基)丙基]封端聚硅氧烷的合成

以1,3-双[3-(1-甲氧基-2-羟基丙氧基)丙基]四甲基二硅氧烷和八甲基环四硅氧烷(D4)为原料,通过阳离子催化开环聚合制备了1,3-双(3-(1-甲氧基-2-羟基丙氧基)丙基)封端聚硅氧烷,研究了反应温度,反应时间,催化剂种类及加入量对于聚合反应的影响,结果表明,最佳反应条件为:反应温度65℃,反应时间24h,浓硫酸作为催化剂加入量为反应物质量的0.3%,此时反应拥有最高的转化率。通过红外光谱与核磁共振光谱对产物进行了表征。     

Effects of GC temperature and carrier gas flow rate on on‐line oxygen isotope measurement as studied by on‐column CO injection

Although deemed important to δ¹⁸O measurement by on‐line high‐temperature conversion techniques, how the GC conditions affect δ¹⁸O measurement is rarely examined adequately. We therefore directly injected different volumes of CO or CO–N₂ mix onto the GC column by a six‐port valve and examined the CO yield, CO peak shape, CO–N₂ separation, and δ¹⁸O value under different GC temperatures and carrier gas flow rates. The results show the CO peak area decreases when the carrier gas flow rate increases. The GC temperature has no effect on peak area. The peak width increases with the increase of CO injection volume but decreases with the increase of GC temperature and carrier gas flow rate. The peak intensity increases with the increase of GC temperature and CO injection volume but decreases with the increase of carrier gas flow rate. The peak separation time between N₂ and CO decreases with an increase of GC temperature and carrier gas flow rate. δ¹⁸O value decreases with the increase of CO injection volume (when half m/z 28 intensity is <3 V) and GC temperature but is insensitive to carrier gas flow rate. On average, the δ¹⁸O value of the injected CO is about 1‰ higher than that of identical reference CO. The δ¹⁸O distribution pattern of the injected CO is probably a combined result of ion source nonlinearity and preferential loss of C¹⁶O or oxygen isotopic exchange between zeolite and CO. For practical application, a lower carrier gas flow rate is therefore recommended as it has the combined advantages of higher CO yield, better N₂–CO separation, lower He consumption, and insignificant effect on δ¹⁸O value, while a higher‐than‐60 °C GC temperature and a larger‐than‐100 µl CO volume is also recommended. When no N₂ peak is expected, a higher GC temperature is recommended, and vice versa. Copyright © 2015 John Wiley & Sons, Ltd.     

考虑热应变的柔性并联空间机械臂动力学

研究考虑热应变的柔性并联空间机械臂动力学性态。用Jourdain速度变分原理建立各机械臂的动力学变分方程,在此基础上根据各物体之间的运动学约束关系,建立柔性多体系统的微分代数混合动力学方程。数值仿真结果表明,当温度升高时,机械臂的轴向约束力和中心刚体的质心运动速度均出现显著振荡,而适当减小温度变化率,可以有效地控制振幅。     

Attractors for Second-Order Evolution Equations with a Nonlinear Damping

We study long-time dynamics of abstract nonlinear second-order evolution equations with a nonlinear damping. Under suitable hypotheses we prove existence of a compact global attractor and finiteness of its fractal dimension. We also show that any solution is stabilized to an equilibrium and estimate the rate of the convergence which, in turn, depends on the behaviour at the origin of the function describing the dissipation. If the damping is bounded below by a linear function, this rate is exponential. Our approach is based on far reaching generalizations of the Ceron–Lopes theorem on asymptotic compactness and Ladyzhenskayas theorem on the dimension of invariant sets. An application of our results to nonlinear damped wave and plate equations allow us to obtain new results pertaining to structure and properties of global attractors for nonlinear waves and plates.     

The modified Casson＇s equation and its application to pipe flows of shear-thickening fluid

A few additional data from our previous experiments were plotted to emphasize the shear-thickening behavior of deoxy sickle erythrocyte (SS) suspension. A constitutive equation (named as FX equation) was developed and applied to a cylindrical pipe flow of a shear-thickening fluid. A blunt velocity profile and its volume flow rate were calculated. The flow was non-viscous (potential) in the central part of the pipe (i.e. the central core or the central plug-flow), and became more and more viscous towards the wall of the pipe after a specific radial distance, which was determined by a critical shear rate of (named as Fungs shear rate). Furthermore, combining the FX equation with the original Cassons equation, the author obtained a modified Cassons equation by introducing .The English text was polished by Yunming Chen.     

Dynamic compressive strength properties of aluminium foams. Part I—experimental data and observations

This study of the dynamic compressive strength properties of metal foams is in two parts. Part I presents data from an extensive experimental study of closed-cell Hydro/Cymat aluminium foam, which elucidates a number of key issues and phenomena. Part II focuses on modelling issues.The dynamic compressive response of the foam was investigated using a direct-impact technique for a range of velocities from 10 to . Elastic wave dispersion and attenuation in the pressure bar was corrected using a deconvolution technique.A new method of locating the point of densification in the nominal stress-strain curves of the foam is proposed, which provides a consistent framework for the definition of the plateau stress and the densification strain, both essential parameters of the ‘shock’ model in Part II. Data for the uniaxial, plastic collapse and plateau stresses are presented for two different average cell sizes of approximately 4 and 14 mm. They show that the plastic collapse strength of the foam changes significantly with compression rate. This phenomenon is discussed, and the distinctive roles of microinertia and ‘shock’ formation are described. The effects of compression rates on the initiation, development and distribution of cell crushing are also examined. Tests were carried out to examine the effects of density gradient and specimen gauge length at different rates of compression and the results are discussed. The origin of the conflicting conclusions in the literature on the correlation between nominal strain rate (ratio of the impact velocity V_i to the initial gauge length l_o of the specimen) and the dynamic strength of aluminium alloy foams is identified and explained.     

多功能Hopkinson压杆型试验装置的研制与应用

对传统的Hopkinson压杆试验装置进行了改进和完善，除了用于材料的动态压缩以外，还能进行动态拉伸、绝热剪切、裂纹扩展速度测定、动态断裂韧性测试等．本文介绍了几种试验方法的基本原理，并给出了试验结果．     

纤维复合材料的弹粘塑性行为体分比与应变率的影响

利用微观力学方法研究了纤维增复合材料的弹塑性行为，着重分析了纤维体分比和加载应变率对以金属基为主的复合材料应力－应变关系的影响。给出了不同体分比的Ｇｒａｐｈｉｔｅ／Ｔｉｔａｎｉｕｍ复合材料在不同常应变率下的应力－应变关系曲线，对这两种因素的影响进行了比较分析。     

Kinematic variables bridging discrete and continuum granular mechanics

It is known that there is wide, and at present, unbridgeable, gap between discrete and continuum granular mechanics. In this contribution, first, microscopic kinematic variables neglected in classical continuum granular mechanics are investigated based on the kinematics of discs in contact. Then, a kinematic variable called the averaged pure rotation rate (APR) is proposed for an assembly of circular discs of different sizes, which is then used to produce another two kinematic tensors with one equal to the deformation rate tensor and the other unifying the spin tensor and the APR. As an example, the kinematic variables are incorporated into the unified double-slip plasticity model. Finally, these theoretical analyses are verified using a two-dimensional discrete element method. The study shows that these kinematic variables can be used to bridge discrete and continuum granular mechanics.