也论化学元素周期表的形成和发展

In the time order, the author proposes that the discovery and development of the periodic table of chemical elements are divided into four stages:point→1D→2D→3D. This article cites the main historical facts and documents available to unscramble the above four stages, which will facilitate the teaching and scientific research of the periodic table.     

相变微胶囊型吸热剂MPCM-2的制备及其控热效果

以十二水合磷酸氢二钠为芯材,乙基纤维素为壁材,采用原位聚合工艺制备了相变微胶囊型吸热剂MPCM-2,其结构和性能经IR、 DSC、TG和粒度分析表征。结果表明：MPCM-2的相变温度为43.34和58.77 ℃,总相变焓值为144.82 J·g^-1,包裹率为67.5%; MPCM颗粒中径为57.26 μm,同时,MPCM-2应用于深水固井水泥浆体系可实现对水化热及水化温升的有效控制。     

Radiation energy flux of Dirac field of static spherically symmetric black holes

By the statistical entropy of the Dirac field of the static spherically symmetric black hole, the result is obtained that the radiation energy flux of the black hole is proportional to the quartic of the temperature of its event horizon. That is, the thermal radiation of the black hole always satisfies the generalised Stenfan--Boltzmann law. The derived generalised Stenfan--Boltzmann coefficient is no longer a constant. When the cut-off distance and the thin film thickness are both fixed, it is a proportional coefficient related to the space--time metric near the event horizon and the average radial effusion velocity of the radiation particles from the thin film. Finally, the radiation energy fluxes and the radiation powers of the Schwarzschild black hole and the Reissner--Nordstrõm black hole are derived, separately.     

乙酰基亚甲基三苯基胂在有机合成中应用的研究

Trippett等和Ramirez等曾报导乙酰基甲基三苯基膦与苯甲醛在苯或四氢呋喃中,需要长时间回流方能反应,而在相似条件下与酮根本不起反应。 本文报导乙酰基亚甲基三苯基胂不仅可在温和条件下与多种取代的苯甲醛反应,且可与苯乙酮、环乙酮一步反应,产率中平到优良。     

导数光谱法快速测定混合稀土中的钕

光度法单一稀土的测定主要依靠4/电子的跃迁及其受配位场或环境影响后的超灵敏光谱^[1~6],钕与钛铁试剂络合后使其特征峰增强约4倍^[2]可用于测定钕。我们发现此络合物在紫外区尚有二强吸收峰,镧、铈、错、钕、钐、钇的峰位均相同,且摩尔吸光系数很接近,因而可用以代替称量测定总稀土(在255nm)。为提高灵敏度与消除干扰,我们用其三阶导数光谱测钕。据此拟定的快速测定钕法曾试用于合成样及实物,均获得满意的结果。     

活性炭吸附ICP-MS同时测定地球化学样品中的金和银

建立了用活性炭对地球化学样品中痕量金、银进行预富集的新方法.结果表明当消解液中硫脲浓度大于0.2％时,活性炭能对溶液中金和硫脲还原后的痕量银进行吸附富集.而Cu、Fe、Co、Ni、Pb、Zn、Bi和Sb等常见阳离子不被吸附,吸附完的活性炭经碳化、灰化、浸取后用ICP-MS同时测定,通过测定3个国家标准物质评价方法的准确度,结果与标准值吻合.该法准确度高、检出限低,且方便快速.     

Some problems of second method of Lyapunov. In discrete systems

The geometric properties of the solution set of Lyapunov equation of linear time-invariant discrete system are discussed. Furthermore, the stabitility of piecewise linear discrete systems is studied and some sufficient conditions are obtained for the asymptotical stability of piecewise linear discrete systems in which each sub-system is stable. The results are applied to second order piecewise linear systems.Supported by the National Natural Science Foundation of China.     

离散系统Lyapunov第二方法的一些问题

本文讨论线性时不变离散系统Lyapunov方程解集的几何性质以及分段线性离散系统的稳定性,得出每个子系统都是稳定的分段线性离散系统渐近稳定的一些充分条件,并把这些结果应用于二阶分段线性系统.     

Barriola-Vilenkin黑洞Dirac场的广义Stefan-Boltzmann定律

利用薄膜模型研究Barriola-Vilenkin黑洞的热辐射,得到了黑洞的热辐射满足广义Stefan-Boltzmann定律的结论,导出的广义Stefan-Boltzmann系数不再是一个恒量,当截断距离以及薄膜厚度取定后,它是一个与黑洞视界附近的时空度规以及辐射粒子的径向平均泻流速率有关的比例系数.得到的Barriola-Vilenkin黑洞视界附近Dirac场的辐射能通量与薄层膜内辐射粒子的径向平均泻流速率成正比,与黑洞的质量平方成反比。     

SOME PROBLEMS OF SECOND METHOD OF LYAPUNOV. IN DISCRETE SYSTEMS

The geometrk, properties of the solution set of Lyapunov equation of linear time invariant discrete system are discussed. Furthermore, the stabitility of piecewise linear discrete systems is studied and some sufficient conditions are obtained for the asymptotical stability of piecewise linear discrete systems in which each sub-system is stable. The results are applied to second order piecewise linear systems.