Cyclotrimerization of nitriles catalyzed by Li<Subscript>3</Subscript>N

Nitriles were unexpectedly trimerized into s-triazines or amino-pyrimidines in high yields in the presence of catalytic amount of Li3N, resulting in a simple, solvent-free and easy-to-scale-up one-pot way to synthesize s-triazines and 4-amino-pyrimidines with high yield.     

MPLS自治系统中基于人工蜘蛛的重路由研究

提出了将一个MPLS自治网络按照自然界中蜘蛛网的形式转化为逻辑上的人工蜘蛛网络的思想,对网络内每个节点赋予了坐标,从而可以方便地对网络进行区域划分以及区域内寻路.在此基础上,提出了基于人工蜘蛛的动态分布式重路由算法(DDRAAS),以及改进的DDRAAS算法来实现MPLS网络中的快速重路由,通过仿真试验与传统的重路由算法作了比较,表明改进的DDRAAS算法在快速重路由方面具有较好的效果.     

宽带卫星网微波副载波光调制系统方案

为简化星上光调制过程和星间光路由,基于宽带卫星网的特点,利用微波副载波对激光的直接调制,提出了一种新型星上光调制技术方案,建立了系统分析模型,给出了具体的相关实现技术。该方案引入了“目标卫星流”聚合、交换的技术和副载波频率重用的新概念,有效减轻了卫星的处理负荷,提高了系统在微波层和光层对频谱资源的利用效率。仿真结果表明,通过实施波长控制技术和增加光调制指数等措施,可以有效提高系统载噪比。     

FDTD modeling of transient scattering by subsurface targets

In this paper, a two-dimensional (2-D) finitedifference time-domain method (FDTD) scheme is used to simulate the transient scattering characteristics of buried objects, which are modeled by columns of arbitrary permittivities, conductivities, and sizes. The FDTD soil is modeled by isotropic, homogeneous and lossy media. The standing-traveling wave boundary condition (STWBC) that can simplify calculation and save CPU storage is used for modeling physical absorbers inside the FDTD computational dornairL Reflection of electromagnetic pulses incident on a layered medium and transient scattering by the ground and an underground airsqu are cylinder are computed. These results verify the validity of the FDTD scheme by comparisons with those shown in some references. Numerical results presented in the final part of this paper are desirable and meaningful, explicitly distinguishing echo waves stemming from the ground and the buried ohjects.     

Synthesis and crystal structure of tetranuclear zinc benzoate

A tetranuclear zinc benzoate Zr4O(C6H5CO2)6 was synthesized and characterized by X-ray single crystal determination. It crystallizes in cubic, space group Ia-3d. Its crystal cell is very large, α=4.10063(18)nm, V=68.953(5)nm^3 and Z=48. The structure is composed of discrete Zr4O(C6H5CO2)6 molecules. In each molecule, four zinc atoms are held together by a central oxygen atom, which results in the formation of a regular tetrahedron. All benzoate ligands coordinate to zinc atoms in a bidentate bridging mode. Each zinc atom is in a slightly distorted tetrahedral geometry, coordinated by three benzoate oxygen atoms and the central oxygen atom. The intermolecular interactions result in the formation of a three-dimensional supramolecular framework, with non-intersecting parallel channels.     

《春秋左传》中"无(有)以"

从句型变换的角度来看,位于动词前和句末的两种“无(有)以”结构,它们二者因在句中所处的位置不同而产生了分化。     

Generalized solutions to the Benjamin-Ono equations in sense of Colombeau

This paper discusses the existence and uniqueness of the generalized solution in the sense of Colombeau to the Benjamin-Ono (B-O) equation and the relationship between the new generalized solution and the classical solution.     

"无乐之乐,乐之至也"--陶渊明"性不解音"解读

史载陶渊明"性不解音",其实陶渊明对音乐的深刻理解是不拘泥于具体的曲调、音符,而只寻音乐的真谛的.他去掉琴的弦、徵,手抚素琴,独与宇宙精神相往来,追求的正是"乐之至"的"无乐之乐".     

南极无冰区古气候与冰盖进退历史研究进展

环南极洲无冰区就是随着气候变暖、冰川后退而出现,是研究南极乃至全球的自然环境演化历史的理想场所。本文主要介绍了国内外学者在恢复无冰区古气候、古环境演变与冰盖进退历史方面所采用的主要手段和方法,并着重论述了近几年关于南极半岛、西南极和东南极环海岸一带无冰区的冰川作用历史与古气候研究成果,指出了目前研究中所存在的问题,提出了以后研究中所要解决的问题。     

图的圆色数等于其色数的充分条件

图G的圆色数xc（G）（也称为星色数）是图的色数的一种推广,给出了图的圆色数等于其色数的一些充分条件。