Universal spaces for asymptotic dimension

We construct a universal space for the class of proper metric spaces of bounded geometry and of given asymptotic dimension. As a consequence of this result, we establish coincidence of asymptotic dimension with asymptotic inductive dimension.     

Topological Simplicity of a Certain LF-Algebra

We show that the LF-algebra considered by Akkar and Nacir in [1] is topologically simple.     

Tesla变压器型电子束加速器初步实验

 介绍了一种Tesla变压器型的强流电子束加速器。当变压器初级输入20kV左右的电压时，加速器二极管输出电压500kV，电流9kA，信号脉宽大约50ns，该装置具有结构简单，安装方便，运行可靠等特点。     

300kVA高温超导变压器电流引线漏热损耗的测量

电流引线是高温超导变压器的主要外部漏热来源,它的漏热量直接影响了超导变压器的经济性能,因此,引线的设计与漏热测量一直备受关注。文中构建了一个实验方案,运用量热法测量低压引线的漏热,并将试验结果与仿真预期值进行了对比和分析,从而验证了仿真设计的正确性。     

Electrostatic calculation of the substituent effect: an efficient test on isolated molecules

The energy of a disubstituted molecule has often been approximated by simple electrostatic formulas that represent the substituents as poles or dipoles. Herein, we test this approach on a new model system that is more direct and more efficient than testing on acid-base properties. The energies of 27 1,4-derivatives of bicyclo[2.2.2]octane were calculated within the framework of the density functional theory at the B3LYP/6-311+G(d,p) level; interaction of the two substituents was evaluated in terms of isodesmic homodesmotic reactions. This interaction energy, checked previously on some experimental gas-phase acidities, was considered to be accurate and served as reference to test the electrostatic approximation. This approximation works well in the qualitative sense as far as the sign and the order of magnitude are concerned: beginning with the strongest interaction between two poles, a weaker interaction between pole and dipole, and the weakest between two dipoles. However, all the electrostatic calculations yield energies that are too small, particularly for weak interaction, and this fundamental defect is not remedied by some possible improvements. In particular, variation of the effective permittivity would require a physically impossible value less than unity. The explanation must lie in a more complex distribution of electron density than anticipated in the electrostatic model. It also follows that possible conclusions about the transmission of substituent effects "through space" have little validity.     

分子诱导效应指数与链烷烃的沸点

利用基团的诱导效应指数，首次提出了分子的诱导效应指数的概念，并定义了 链烷烃的有效碳链长度NC＝（MIs,N/MIb,N)·N，式中MIs,N,MIb,N分别为直链和支 链异构体的分子诱导效应指数。研究结果表明，链烷烃的沸点Tb(℃）与NC关系是 ：1n(806.5-Tb)=6.9824-0.11431NC^2/3     

Basicity and structure of 5-hydroxybenzimidazoles in nitromethane

Examination of the acid-base properties of 5-hydroxybenzimidazoles has shown them to exist in nitromethane as the 5-hydroxy-tautomers. Substituents in the 2-position have a predominantly inductive effect on the basicity of the 3-nitrogen, rationalized as in other nitrogen heterocycles by the proximity of the substituents to the reaction center.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. The Research Institute for Intermediates and Dyes, 103787 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 421–425, February, 1992.     

Operator Semigroup Compactifications

A weakly continuous, equicontinuous representation of a semitopological semigroup on a locally convex topological vector space gives rise to a family of operator semigroup compactifications of , one for each invariant subspace of . We consider those invariant subspaces which are maximal with respect to the associated compactification possessing a given property of semigroup compactifications and show that under suitable hypotheses this maximality is preserved under the formation of projective limits, strict inductive limits and tensor products.

     

Graded PZT ceramics for piezoelectric transformers

In the present study two types of the synthesized Pb(Zr_1−xTi_x)O₃ (PZT) powders differing in Zr/Ti ratio were used to prepare the spatially inhomogeneous (i.e., graded) structure. A position-dependent chemical composition was expected to cause the property gradient. Disk-shaped compacts were prepared in a way such that two different orientations of the radial gradients were formed. The solid state sintering under pressure was utilized to prepare ceramics. Simultaneous thermal analysis was used to study thermal behavior of the ceramic powders. Graded PZT ceramics were characterized using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. It was also characterized in terms of its dielectric properties by both bridge technique and the impedance spectroscopy. On the basis of graded PZT ceramics the disk-shaped radial mode piezoelectric transformer was developed and fabricated.