两子系统在周期切换连接下的振荡行为及其机理

研究了两非线性系统在周期切换连接下的分岔和混沌行为.通过局部分析,分别给出了两子系统参数空间诸如Fold分岔、Hopf分岔等临界条件,进而考虑两子系统存在不同稳态解时通过周期切换连接下的复合系统的分岔特性,给出了不同的周期振荡行为,并揭示了其相应的产生机理.指出系统轨迹可以由切换点分割成不同的部分,分别受两子系统的控制,而随参数的变化,切换点数目成倍增加,导致系统由倍周期分岔序列进入混沌.同时,在其演化过程中,虽然子系统定性保持不变,但由于切换导致的非光滑性,复合系统不仅仅表现为两子系统动力特性的简单连接,而是会产生各种分岔,导致诸如混沌等复杂振荡行为.     

OBS网络中基于优先级与突发包分割的偏射路由机制

为了有效地降低突发包的丢失率和保证OBS网络中不同优先级业务的服务质量,提出了一种基于优先级与突发包分割的偏射路由机制.当冲突发生时,首先基于突发包的优先级进行"竞争突发包头部分割或者原突发包尾部分割"处理;无冲突部分直接在事先预留的输出数据信道上处理,冲突部分的分割突发包根据参数可调的偏射路由机制被偏射到最佳偏射路径上.仿真结果表明,该机制能够有效地降低整个网络的丢包率和端到端的延时,并且得到高优先级突发包的丢失率和延时低于低优先级突发包.由此可知,基于优先级与突发包分割的偏射路由机制能够有效地解决突发包的冲突问题,从而提高整个OBS网络的性能.     

Effect of bounded noise on the chaotic motion of a Duffing Van der pol oscillator in a ϕ6 potential

This paper investigates the chaotic behavior of an extended Duffing Van der pol oscillator in a ϕ⁶ potential under additive harmonic and bounded noise excitations for a specific parameter choice. From Melnikov theorem, we obtain the conditions for the existence of homoclinic or heteroclinic bifurcation in the case of the ϕ⁶ potential is bounded, which are complemented by the numerical simulations from which we illustrate the bifurcation surfaces and the fractality of the basins of attraction. The results show that the threshold amplitude of bounded noise for onset of chaos will move upwards as the noise intensity increases, which is further validated by the top Lyapunov exponents of the original system. Thus the larger the noise intensity results in the less possible chaotic domain in parameter space. The effect of bounded noise on Poincare maps is also investigated.     

Synthesis of Platinum Nanoparticles-Decorated Poly(p-Phenylenediamine) Colloids with a High Performance for Methanol Electrocatalysis for Direct Methanol Fuel Cells

In this paper, the Pt/Poly(p-phenylenediamine) (Pt/PpPD) nanocomposite was synthesized via hydrothermal condition with H₂PtCl₆ as oxidant. The H₂PtCl₆ is an oxidant in formation process of PpPD and also played a role as the platinum source. The synthesis technique of this material is simple and the carrier material is low-cost. The spherical Pt nanoparticles which the diameter is about 50 nm are symmetrical dispersed on elliptical PpPD nanoparticles. The structure and morphologies of the composite were characterized with IR, Raman spectroscopy, XRD and scanning electron microscope. Electrocatalytic activity measurements shows the Pt/PpPD nanocomposite have good electrochemical performance for methanol fuel cells. The origin of good electrochemical performance for methanol of Pt/PpPD colloids is studied. The possible formation mechanism involved is also discussed.     

磷钨酸修饰活性炭载Pd催化剂的制备及对甲酸氧化的电催化性能简

通过水浴浸泡制备了磷钨酸(PWA)修饰的活性炭(PWA/C),再通过液相还原法将Pd沉积于PWA/C复合载体上制备了Pd-PWA/C催化剂. 采用X射线能量色散(EDS)谱、X射线衍射(XRD)谱、透射电子显微镜(TEM)和X射线光电子能谱(XPS)对产物进行表征. 结果表明,磷钨酸修饰活性炭不仅能有效降低Pd纳米粒子的粒径,而且与Pd纳米粒子间发生了强烈作用. 电化学测试结果显示,Pd-PWA/C催化剂对甲酸氧化的电催化活性和稳定性均远优于Pd/C催化剂,这是由于Pd与PWA/C间的强烈作用既能有效降低CO在催化剂上的吸附强度和吸附量,又能降低甲酸分解的速率,从而减弱CO的毒化作用.     

含取代噁唑结构的新型吡唑肟衍生物的合成与生物活性

为了发现具有良好生物活性的吡唑肟化合物,以唑螨酯为先导化合物,在吡唑肟中引入取代噁唑结构,设计并制备了20个未见文献报道的新型吡唑肟衍生物,利用1H NMR,13C NMR和元素分析确证了目标产物的结构.生物活性测试结果显示,部分目标化合物在500和100μg/mL浓度下对粘虫或蚜虫表现出优良的杀虫活性,其中5-(3-氟苯氧基)-1,3-二甲基-1H-吡唑-4-甲酰基-O-{[5-(4-氯苯基)噁唑-2-基]甲基}肟(9j)、5-(4-氟苯氧基)-1,3-二甲基-1H-吡唑-4-甲酰基-O-{[5-(4-氯苯基)噁唑-2-基]甲基}肟(9k)、5-(4-叔丁基苯氧基)-1,3-二甲基-1H-吡唑-4-甲酰基-O-{[5-(4-氯苯基)噁唑-2-基]甲基}肟(9r)和5-(4-甲氧基苯氧基)-1,3-二甲基-1H-吡唑-4-甲酰基-O-{[5-(4-氯苯基)噁唑-2-基]甲基}肟(9s)在浓度为100μg/mL时对粘虫的防治效果均达100%,5-(4-溴苯氧基)-1,3-二甲基-1H-吡唑-4-甲酰基-O-{[5-(4-氟苯基)噁唑-2-基]甲基}肟(9g)和9s在浓度为100μg/mL时对蚜虫的杀灭活性均为100%.此外,化合物9s在500μg/mL时对朱砂叶螨的防治效果为70%.     

从散射谱反演颗粒尺寸分布的测试方法改进

针对从散射谱反演颗粒尺寸分布测量中,由于衍射近似要求近前向取值而带来的反演噪声问题,提出了一种改进的方法.在Chin-Shifrin(C-S)积分变换反演中,插入一种调节函数使得噪声基本消失,又不至于影响反演谱的分布峰位置.对理想单分散颗粒群的模拟效果说明了该法的可行性.对以线阵CCD为接受器件的实验测量和反演结果显示...     

丙烷氧化脱氢不同硅基载体负载钒氧化物催化剂的TPSR表征

研究了钒负载不同氧化硅载体(Silica-gel,SBA-15,MCM-41,fumed-SiO2,Nano-SiO2)的丙烷氧化脱氢(ODH)催化剂的结构特征和催化性能,结合催化剂的程序升温表面反应(TPSR)的差热热重质谱(TG-DSC-MS)和原位紫外漫反射光谱(UV-vis DRS)等技术,研究钒在载体上的分散度和晶格氧的反应性。结果表明:负载型钒氧化物催化剂的活性取决于钒在不同硅基载体上的分散度,高度分散的隔离的四配位V5+是丙烷氧化脱氢的活性位。C3H6选择性主要与催化剂的平均孔径相关联,平均孔径越小,产物C3H6越易发生深度氧化。另外,不同氧化硅载体晶格氧与钒的结合强度对C3H6的选择性也产生影响,结合力较弱的V-O-Si中的晶格氧是丙烷氧化脱氢的燃烧位,且燃烧温度随晶格氧与钒、硅结合强度的减小而降低。而与钒结合力较强的V=O和V-O-V中的晶格氧是丙烷氧化脱氢的选择氧化位。硅基载体形貌和结构的不同导致负载型钒氧化物催化剂丙烷氧化脱氢活性和选择性发生差异。     

Bursting mechanism in a time-delayed oscillator with slowly varying external forcing

This paper investigates the generation of complex bursting patterns in the Duffing oscillator with time-delayed feedback. We present the bursting patterns, including symmetric fold–fold bursting and symmetric Hopf–Hopf bursting when periodic forcing changes slowly. We make an analysis of the system bifurcations and dynamics as a function of the delayed feedback and the periodic forcing. We calculate the conditions of fold bifurcation and Hopf bifurcation as well as its stability related to external forcing and delay. We also identify two regimes of bursting depending on the magnitude of the delay itself and the strength of time delayed coupling in the model. Our results show that the dynamics of bursters in delayed system are quite different from those in systems without any delay. In particular, delay can be used as a tuning parameter to modulate dynamics of bursting corresponding to the different type. Furthermore, we use transformed phase space analysis to explore the evolution details of the delayed bursting behavior. Also some numerical simulations are included to illustrate the validity of our study.