脱铝八面沸石的研究(Ⅳ)——异丙苯催化裂化

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。     

有常数出生率的传染病模型的定性分析

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。     

Contact effect in the dynamic electron transport of a two-probe mesoscopic conductor

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.     

巧用欧拉公式解题一例

题目 △ABC内有n个点,连同A、B、C共n 3个点,其中任意三点不共线,由这些点作互不重叠的小三角形,能作多少个?     

S_2N_2环夹心配合物的MO研究

根据ＭＡＤ－ＳＣＣ－ＥＨＭＯ法的计算结果,用衡量相对稳定性的三个指标：稳定化能、ＨＯＭＯ－ＬＵＭＯ能隙和重迭集居比较了无机环Ｓ２Ｎ２与有机环的夹心和半夹心配合物的相对稳定性,并用碎片分子轨道法讨论了Ｓ２Ｎ２环分子轨道与过渡金属ｄ轨道间的相互作用以及配合物的成键情况和电子结构．     

足球中的数学学问

你知道我们熟知的足球的结构吗?世界杯中用的是由边长相等的五边形和六边形缝合而成的多面体,有12个五边形和20个六边形总计32个平面围成,为什么是这样呢?下面我们用欧拉公式探讨这个问题.     

鱼腥草中癸酰乙醛含量的测定

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。     

Surface plasmon-polaritons on ultrathin metal films

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.     

赫芝的电磁波实验

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。