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We study dynamics of spiral waves under a uniform periodic temporal forcing in an excitable medium. With a specific combination of frequency and amplitude of the external periodic forcing, a resonance drift of a spiral wave occurs along a straight line, and it is accompanied by a complicated ‘flower-like' motion on each side of this bifurcate boundary line. It is confirmed that the straight-line drift frequency of spiral waves is not locked to the nature rotation frequency as the forcing amplitude expends are further verified numerically for a simplified kinematical the range of the spiral wave frequency. These results model. 相似文献
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热解石墨平台石墨炉原子化器在环境分析中测定镉的应用 总被引:2,自引:1,他引:1
本文探讨了热解石墨平台对环境标准物质和海水的测定,比较了基体改进剂钯(0.5mgml~(-1))和抗坏血酸(10mg ml~(-1))的实验特征量值和理论特征量值,选择了最佳实验条件。本文还介绍了环境标准物质的无标准分析的可能性。 相似文献
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Spiral dynamics controlled by a weakly localized pacing around the spiral tip is investigated. Numerical simulations show two distinct characteristics when the pacing is applied with the weak amplitude for suitable frequencies: for a rigidly .rotating spiral, a transition from rigid rotation to meandering motion is observed, and for unstable spiral waves, spiral breakup can be prevented. Successfully preventing spiral breakup is relevant to the modulation of the tip trajectory induced by a localized pacing. 相似文献
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In this paper, the evolution of the pattern transition induced by the vortical electric field (VEF) is investigated. Firstly, a scheme is suggested to generate the VEF by changing the spatial magnetic field. Secondly, the VEF is imposed on the whole medium, and the evolutions of the spiral wave and the spatiotemporal chaos are investigated by using the numerical simulation. The result confirms that the drift and the breakup of the spiral wave and the new net-like pattern are observed when different polarized fields are imposed on the whole medium respectively. Finally, the pattern transition induced by the polarized field is discussed theoretically. 相似文献
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红色荧光材料Sr_3Ti_2O_7:Pr的合成及性能 总被引:1,自引:0,他引:1
首次合成了红色荧光材料Sr_3Ti_2O_7:Pr,经过对样品激发、发射光谱、XRD的分析,讨论了具有Ruddlesden-Popper相的Sr_3Ti_2O_7:Pr样品中存在的SrO晶面缺陷对荧光性能的影响,得出SrO层的存在使Pr~(3+)所处的晶体场强度增大、对称性下降,宇称选律部分解禁,同时使Pr-Ti间距减少,由此导致了电荷迁移态(CTS)下降,其激发与发射光谱强度比SrTiO_3:Pr约大20倍. 相似文献
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A conservation equation for topological charges of phase singularities (scroll and spiral waves) in excitable media is given. It provides some topological properties of scroll (spiral) waves: for example, the topological charge of the generated or annihilated spiral pair must be opposite. Additionally, we obtain another equation on scroll waves, which shows that singular filaments of scroll waves occur on a set of one-dimensional curves which may be either closed loops or infinite lines. 相似文献
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