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以脉冲微型反应技术研究了脱铝八面沸石对异丙苯的催化裂化行为,并与反应条件下表面酸性进行了关联。样品裂化活性随骨架Si/Al比增加呈山峰形变化,Si/Al=5.38时最大;反应条件下酸中心数随脱铝深度增加却单调降低。动力学数据表明,样品裂化反应速度常数与强质子酸中心数随骨架Si/Al比增加具有平行的山峰形变化规律,Si/Al比为8.87附近的样品最高。 相似文献
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Based on the self-consistent electron dynamic transport theory for multi-probe mesoscopic systems, we calculate the distribution of internal potential, charge density, and ac conductance of a two-probe mesoscopic conductor with wide trapezoid reservoirs, and study the contact effect. The results show that including the contact effect can make a significant difference to the frequency-dependent electron transport properties. In the nonzero frequency case, the internal potential and the charge density are complex with extremely small imaginary parts. Importantly, the imaginary part of the charge density gives rise to a real ac conductance (admittance), which corresponds to the charge-relaxation resistance. 相似文献
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本文对有常数出生率的传染病模型,运用定性分析方法,分析了唯一正平衡点的拓扑结构.运用Liapunov第二方法,论证了正平衡点的稳定性.并运用DuLac函数法,得出该系统不存在极限环的结论。进而为研究该传染病的发生流行,传播及成为地方病等提供了充分的理论依据。 相似文献
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We discuss the surface plasmon-polaritons used for ultrathin metal films with the aid of linear response theory and make comparisons with the known result given by Economou E N. In this paper we consider transverse electromagnetic fields and assume that the electromagnetic field in the linear response formula is the induced field due to the current of the electrons. It satisfies the Maxwell equation and thus we replace the current (charge) term in the Maxwell equation with the linear response expectation value. Finally,taking the external field to be zero,we obtain the dispersion relation of the surface plasmons from the eigenvalue equation. In addition,the charge-density and current-density in the z direction on the surface of ultrathin metal films are also calculated. The results may be helpful to the fundamental understanding of the complex phenomenon of surface plasmon-polaritons. 相似文献
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本文中所谈到的“振动器”与本期“电磁波的辐射和接收”一文中所谈到的“赫芝偶极子”原理上是一个东西,赫芝当时使用的设备是“振动器”,而分析其辐射的特性时,则将它画成偶极子。两者的原理是一样的—将振荡迴路的电容器张开。但在“振动器”上的电流是衰减振荡,它是自由振荡,当产生高频振荡时,并没有高频电源连在上边,这是因为赫芝当时还没有高频电源;而“偶极子”上的电流通常都设为等幅振荡,是由高频电源供给的。它们的等效线路都是L、C串连。自由振荡时,迴路不接入电源(火花间隙在放电时等于接通的导线),强迫振荡时,间隙处用高频电源来代替,这是唯一的区别。 相似文献
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鱼腥草中癸酰乙醛含量的测定 总被引:5,自引:0,他引:5
以2^n-溴-3,3′-二甲基-4′-羟基-5,5′-二羧基羟基品红酮为Cu^2 的显色剂,分光光度法间接地测定了鱼腥草中有效成分之一癸酰乙醛的含量。 相似文献