含硅的树枝状大分子的研究进展

树枝状大分子是一类具有规则的、高度支化的三维结构的高分子 ,含硅的树枝状大分子是以硅原子作为两代之间的支化点的树枝状大分子。本文主要综述了硅氧烷型、碳硅烷型、硅烷型树枝状大分子的合成方法及含硅的树状金属络合物的研究进展。     

Photon tunneling and transmittance resonance through a multi-layer structure with a left-handed material

This paper investigates the photon tunneling and transmittance resonance through a multi-layer structure including a left-handed material(LHM).An analytical expression for the transmittance in a five-layer structure is given by the analytical transfer matrix method.The transmittance is studied as a function of the refractive index and the width of the LHM layer.The perfect photon tunneling results from the multi-layer structure,especially from the relation between the magnitude of the refractive index and the width of the LHM layer and those of the adjoining layers.Photons may tunnel through a much greater distance in this structure.Transmittance resonance happens,the peaks and valleys appear periodically at the resonance thickness.For an LHM with inherent losses,the perfect transmittance is suppressed.     

差分吸收光谱CT诊断技术

提出了浓度场测量的差分吸收光谱层析技术,设计出一种由光源及控制系统、光学扫描测量系统和数据采集及处理系统三部分组成的典型差分吸收光谱层析诊断系统.采用改进的联合代数重建算法进行层析图像重建,数值模拟结果表明：在0°~180°视场范围内,在4个不同的投影方向获取投影数据的条件下,能有效地重建出待测场分布,其最大误差不大于5％,平均误差不大于1％.     

含有两个非临界点的强连通定向图的弧数

证明顶点数为$n\geq 4$,弧数为$m\geq {n-1 \choose 2}+3$的强连通定向
图$D$中存在两点$u^*$、!$v^*$,使得$D-u^*$和$D-v^*$都是强连通的, 并用例子说明这里所给的
关于弧数的下界是紧的.