聚芳醚酮环状低聚物的基质辅助激光解吸电离质谱表征

采用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)技术分别对2种合成的聚芳醚酮环状低聚物进行了分析研究 ,并讨论了低聚物中不同聚合度离子组分的分布规律。实验结果表明MALDI-TOF-MS是分析环状低聚物直观、准确、快速的分析工具。     

甲壳素色谱柱富集—快速吸光光度法测定环境试样中痕量铁

研究了甲壳素色谱柱富集Fe(Ⅱ)-磺基水杨酸-十八烷基二甲基氨基乙酸的红紫色缔合物,用磺基水杨酸洗脱后,在分光光度计上直接测定洗脱液的吸光度,方法快速,简单、富集倍数高,用于环境水样中痕量铁的测定,结果令人满意。     

Enantioselective epoxidation of terminal olefins by chiral dioxirane

[see reaction]. This paper describes an enantioselective epoxidation of terminal olefins using chiral ketone 3 as catalyst and Oxone as oxidant. Up to 85% ee has been obtained.     

塑化剂迁移量测定和迁移模型研究进展

综述国内外塑化剂迁移量测定和迁移模型研究进展,从创新实验测定方法和实验误差分析的角度简要评述了迁移量测定的研究成果;从数学模型的角度对微分方程模型、统计模型和计算机模拟3类重要迁移模型进行评述。最后指出,测定实验和迁移模型相结合来研究塑化剂迁移问题是未来一个值得重视的方法。     

塑性全量理论的变分不等式模式及其无迭代解

变分不等式是解决一类带单侧约束的定常力学问题的有效数学工具.本文就弹塑性全量理论构造了等价的变分不等式模式,解除了弹塑性问题本构约束的不等式关系,比一般能量形式的描述更为简洁.它便于计算,具有可靠的数学依据,可以用二次规划法求解.计算时无需分级加载迭代,一步即可得收敛解.     

A new class of penalized NCP-functions and its properties

In this paper, we consider a class of penalized NCP-functions, which includes several existing well-known NCP-functions as special cases. The merit function induced by this class of NCP-functions is shown to have bounded level sets and provide error bounds under mild conditions. A derivative free algorithm is also proposed, its global convergence is proved and numerical performance compared with those based on some existing NCP-functions is reported.     

Hierarchical structures in a turbulent pipe flow

A hierarchical structure (HS) analysis (β-test and γ-test) is applied to a fully developed turbulent pipe flow. Velocity signals are measured at two cross sections in the pipe and at a series of radial locations from the pipe wall. Particular attention is paid to the variation of turbulent statistics at wall units 10<y⁺<3000. It is shown that at all locations the velocity fluctuations satisfy the She–Leveque hierarchical symmetry (Phys. Rev. Lett. 72 (1994) 336). The measured HS parameters, β and γ, are interpreted in terms of the variation of fluid structures. Intense anisotropic fluid structures generated near the wall appear to be more singular than the most intermittent structures in isotropic turbulence and appear to be more outstanding compared to the background fluctuations; this yields a more intermittent velocity signal with smaller γ and β. As turbulence migrates into the logarithmic region, small-scale motions are generated by an energy cascade and large-scale organized structures emerge which are also less singular than the most intermittent structures of isotropic turbulence. At the center, turbulence is nearly isotropic, and β and γ are close to the 1994 She–Leveque predictions. A transition is observed from the logarithmic region to the center in which γ drops and the large-scale organized structures break down. We speculate that it is due to the growing eddy viscosity effects of widely spread turbulent fluctuations in a similar way as in the breakdown of the Taylor vortices in a turbulent Couette–Taylor flow at high Reynolds numbers.     

A semi-algebraic approach for asymptotic stability analysis

This paper deals with the problem of computing Lyapunov functions for asymptotic stability analysis of autonomous polynomial systems of differential equations. We propose a new semi-algebraic approach by making advantage of the local property of the Lyapunov function as well as its derivative. This is done by first constructing a semi-algebraic system and then solving this semi-algebraic system in an adaptive way. Experiment results show that our semi-algebraic approach is more efficient in practice, especially for low-order systems.