硫化天然橡胶物理松弛时间的测量

硫化天然橡胶物理松弛时间的测量裘怿明刘从伟时锋傅政（青岛化工学院橡胶工程学院青岛２６６０４２）关键词硫化天然橡胶，应力松弛速率，数值计算方法，曲线拟合高分子热运动的特点之一是存在松弛现象，通常，人们描述高分子材料的松驰速度采用松驰时间τ［１］．实际...     

理想气体任意过程最高和最低温度的计算方法

给出理想气体任意过程最高和最低温度的三种计算方法，用p-V图中的直线过程、圆过程、椭圆过程为例，计算该过程最高、最低温度的状态。     

A nonconvex dissipative system and its applications (II)

This paper presents exact solutions in terms of implicit functions and hyperbolic functions to a nonconvex dissipative system, controlled by a Duffing–van der Pol nonlinear equation with a fifth-order nonlinearity. Applications to the complex Ginzburg–Landau equation are illustrated and several classes of uniformly translating solutions are obtained accordingly. Part of the work was announced at the International Conference on Complementarity, Duality, and Global Optimization in Science and Engineering, Virginia Tech. University, Blacksburg, Virginia, August 15–17, 2005. This work is supported by NSF Grant CCF–0514768.     

khintchine不等式中最佳常数的一个注记

最近文[1]给出了Khintchine不等式中的最佳常数。设Rademacher函数r_n(t)=sign(sin2~nπt),n=1,2,…,则当p≥3时成立着     

One-pot synthesis of spring-like superstructures consisting of layered tin(IV) hydrogen phosphate nanodisks

Spring-like superstructures consisting of layered tin(IV) hydrogen phosphate nanodisks can be obtained via a one-pot solvothermal reaction of tin tetrachloride and phosphoric acid in ethanol. These superstructures are active anode materials for the lithium-ion battery.     

Dynamics of A Damping Oscillator with Impact and Impulsive Excitation

There exist many types of external excitations that make the damping oscillator with impact have complex dynamics. In this study, both external impulsive excitation and impact are considered to construct a vibro-impact system. The fixed time pulse (impulsive excitation) and the state pulse (impact) lead to the complex and interesting dynamics. The conditions of the existence and stability of four kinds of periodic solutions are investigated, and the bifurcations of period-(1, 0) and period-(1, 1) solutions are analytically studied. Numerical simulations on periodic solutions and bifurcation diagrams are shown by the illustrative example.     

羟烷基壳聚糖制备及应用研究进展

壳聚糖是由甲壳素通过脱乙酰作用得到的一种天然高分子多糖,具有良好的生物相容性、抗菌性、无毒和可生物降解等优点,但壳聚糖水溶性差限制了其在很多方面的应用。为克服壳聚糖在水溶性上的不足,利用壳聚糖结构中氨基和羟基上的活泼氢进行化学改性以引进羟烷基等亲水性基团成为重要手段。本文主要对壳聚糖羟烷基化改性的方法及羟烷基壳聚糖在医药、水处理和组织工程材料等领域的研究和应用现状进行介绍,并对羟烷基壳聚糖未来的发展趋势进行了展望。     

Synchronization transition in gap-junction-coupled leech neurons

Real neurons can exhibit various types of firings including tonic spiking, bursting as well as silent state, which are frequently observed in neuronal electrophysiological experiments. More interestingly, it is found that neurons can demonstrate the co-existing mode of stable tonic spiking and bursting, which depends on initial conditions. In this paper, synchronization in gap-junction-coupled neurons with co-existing attractors of spiking and bursting firings is investigated as the coupling strength gets increased. Synchronization transitions can be identified by means of the bifurcation diagram and the correlation coefficient. It is illustrated that the coupled neurons can exhibit different types of synchronization transitions between spiking and bursting when the coupling strength increases. In the course of synchronization transitions, an intermittent synchronization can be observed. These results may be instructive to understand synchronization transitions in neuronal systems.     

羧基化多壁碳纳米管分散固相萃取/气相色谱-质谱法测定茶青中18种多氯联苯

建立了超声提取、分散固相萃取净化结合气相色谱-质谱(GC-MS)同时检测茶青中18种多氯联苯(PCBs)的方法。样品经正己烷-丙酮(1∶1,体积比)超声提取,通过甲苯溶剂置换后,用羧基化多壁碳纳米管(MWCNTs-COOH)和N-丙基乙二胺(PSA)吸附剂净化,在GC-MS选择离子监测模式下进行测定,以保留时间和特征离子丰度比定性,基质匹配标准溶液外标法定量。优化了气相色谱-质谱条件,考察了提取溶剂及吸附剂种类和用量、提取时间和净化时间对分析结果的影响。在最优实验条件下,18种PCBs在5～500μg/kg范围内线性关系良好,相关系数不低于0. 999 8;在5、10、100μg/kg加标水平下,平均回收率为92. 3%～111%,相对标准偏差(n=6)为1. 2%～7. 9%;方法检出限为0. 5～1. 4μg/kg,定量下限均为5μg/kg。该法操作简单、快速准确、灵敏度高、样品净化效果好,可用于茶青中18种PCBs的同时检测。     

Supermolecule density functional calculations on the water exchange of aquated Al(III) species in aqueous solution

Supermolecule density functional calculations suggest the dissociative (D) mechanism for the water exchange of aquated Al(iii) species in aqueous solution and the calculated results agree well with experimental data.