双金属氰化物催化二氧化碳与环氧丙烷聚合

研究了双金属氰化配合物(DMC)催化剂催化二氧化碳(CO2)与环氧丙烷(PO)的共聚及PO的均聚反应,考察了DMC催化剂的诱导现象。结果表明,共聚时DMC催化的诱导期比均聚短,尤其是在低CO2压力(1.0MPa)下更明显,诱导期由均聚时的45min缩短为共聚时的15min。共聚时诱导期随CO2压力升高而增加,当反应压力由1.0MPa升高至7.0MPa时,诱导期由15min增至40min。PO与CO2共聚时的引发现象不同于PO均聚:共聚引发时温度和压力突然异常升高并迅速降低至引发前的状态,而均聚引发时温度突然升高后逐渐下降。由此可知CO2能促进DMC催化剂的活化。     

Detection and analysis of paraffin oil adulteration in coconut oil using fiber optic long period grating sensor

A fiber optic sensing system for the detection of adulteration of coconut oil by paraffin oil is experimentally demonstrated. The sensing mechanism is based on the sensitive dependence of the resonance peaks of a long period grating (LPG) on the changes of the refractive index of the environmental medium surrounding the cladding surface of the grating. The wavelength shift of the attenuation bands of the LPG was measured with the sensor immersed in a mixture of paraffin oil and pure coconut oil in different proportions. Detection limit of adulteration was found to be 3% for coconut oil-paraffin oil binary mixture.     

Controlling of symmetric and asymmetric mode coupling in long-period fiber gratings singe-side induced by long-pulse CO2 laser

We report a simple fabricating approach to control the mode couplings in long-period fiber gratings (LPFGs) through side exposing fiber to long-pulse-10.6-μm laser from a cheap, internally modulated CO₂ tube. By tuning focused-spot size on fibers, not only circularly symmetric mode coupling but also asymmetric mode couplings can be effectively achieved. Simulation of mode profiles in grating cross-section with Finite Element Method (FEM), and LPFG-cladding etching experiment with hydrofluoric acid (HF), support our explanation that asymmetric mode coupling in LPFGs depends on local refractive-index (RI) change within an azimuthally thin cladding layer, resulted from large-spot method induced deep melt flow on fiber surface during CO₂ laser irradiation.     

Analysis of statistical nature of electrical breakdown time delay in nitrogen at 6.6 mbar pressure in presence of positive ions and N(4S) atoms

On the basis of the mean value of electrical breakdown time delay and the standard deviation of electrical breakdown time delay σ dependence on the afterglow period τ, the mechanisms which dominantly influence to breakdown initiation in nitrogen were separated. It was shown that the positive ions formed in mutual collision of long‐lived metastable molecules have a dominant role in breakdown initiation for τ values up to 70 ms. The metastable molecules were derived from previous breakdown and discharge. In this case σ ≪ t_d and the total time delay t_d is approximately equal to formative time t_f which decreases in value with the increase of overvoltage. When positive ions have a dominant role in the breakdown initiation the Gaussian distribution describes data of t_d ≈ t_f very well. For τ > 1 s, N (⁴S) atoms formed in previous breakdown and discharge, have a dominant role in the breakdown initiation. Then, σ ≈ and Laue's distribution, which is valid for statistical time delay t_s, describes t_d data very well (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Duffing单边碰撞系统的混沌鞍合并激变

以典型的Duffing单边碰撞系统为研究对象,对系统中的混沌鞍进行了细致的分析.研究表明,系统的混沌鞍同样存在合并激变,合并激变是由连接两个混沌鞍的周期鞍的稳定流形与不稳定流形相切所诱发,相切使得边界上的混沌鞍与内部的混沌鞍发生碰撞而突然合并为一个较大的边界混沌鞍.混沌鞍的合并激变行为最终会诱导混沌吸引子的合并激变发生. 关键词： Duffing碰撞系统 混沌鞍 周期鞍 稳定与不稳定流形     

Mock period functions in higher level cases

Generalizing the results of Bringmann, Diamantis and Raum [3] we investigate a generating series of non-critical values which can be interpreted as a mock period function and prove that non-critical values can be encoded into a sesquiharmonic Maass form in higher level cases. Moreover we prove Eichler–Shimura-type isomorphism for the space of period polynomials and for that of mock period functions in level p   with p∈{2,3}$p\in \{2,3\}$.     

Symmetric period solutions with prescribed minimal period for even autonomous semipositive Hamiltonian systems

We study some monotonicity and iteration inequality of the Maslov-type index i-1of linear Hamiltonian systems.As an application we prove the existence of symmetric periodic solutions with prescribed minimal period for first order nonlinear autonomous Hamiltonian systems which are semipositive,even,and superquadratic at zero and infinity.This result gives a positive answer to Rabinowitz’s minimal period conjecture in this case without strictly convex assumption.We also give a different proof of the existence of symmetric periodic solutions with prescribed minimal period for classical Hamiltonian systems which are semipositive,even,and superquadratic at zero and infinity which was proved by Fei,Kim and Wang in 2001.     

带有脉冲药物治疗策略的SIA模型的全局稳定性

根据艾滋病的传播特点,建立了带有脉冲药物治疗策略的感染年龄结构SIA模型,得到了控制疾病传播的基本再生数R_O(p,T),并讨论了无病平衡态的全局稳定性.     

二元超晶格弹性应力的能带理论计算

根据量子能带理论 ,采用经验赝势方法 ,对 (Pb) n/ (Bi) n,(Al) n/ (As) n 的假想简立方二元超晶格结构的弹性应力进行了计算 .结果表明弹性应力随超晶格周期λ的增加而迅速升高至一定大小后趋于稳定 ,且只有在周期较小时才同过渡金属氮化物超晶格硬度随周期的变化的趋势定性一致 ,为超晶格硬度随周期的变化提供了一种可能的解释     

Period doubling toward chaos in a driven magnetic macrospin

The Landau-Lifshitz-Gilbert equation is analyzed in the case of a configuration involving easy plane isotropy under the influence of a sinusoidally oscillating magnetic field and a demagnetizing field. Through the use of numerical techniques, chaotic behavior is found and analyzed. By reducing the system to a discrete map (numerically), bifurcation diagrams for the system are computed. The system is found to exhibit a period doubling cascade route to chaos, and it obeys certain convergence rules for chaotic transitions outlined by Feigenbaum. A connection is drawn between the route to chaos and the geometry of the system, and comparisons are made with similar systems. Within the chaotic regime, windows of arbitrarily large period are suspected to exist, and explicitly illustrated and discussed for a period three window.