On extremally disconnected topological groups

We introduce the notion of a partially selective ultrafilter and prove that (a) if G is an extremally disconnected topological group and p is a converging nonprincipal ultrafilter on G containing a countable discrete subset, then p is partially selective, and (b) the existence of a nonprincipal partially selective ultrafilter on a countable set implies the existence of a P-point in ω^∗. Thus it is consistent with ZFC that there is no extremally disconnected topological group containing a countable discrete nonclosed subset.     

Commutant Lifting Theorem for the Bergman Space

The central question of this paper is the one of finding the right analogue of the Commutant Lifting Theorem for the Bergman space L_a². We also analyze the analogous problem for weighted Bergman spaces L_a,α², − 1 < α < ∞.     

多进制数字调相系统分析与设计方法的探讨

对数字通信中MPSK系统的调制与解调问题进行了较为的分析，并以8PSK和循环码16PSK系统为例，阐述其调制器电路的逻辑设计方法。在此基础上给出了8PSK系统调制与解调的一种方案，讨论了循环码和自然二进制码16PSK系统的调制器的具体设计过程，该设计方法可应用于一般MPSK系统的逻辑设计。     

猜想M(2k,k+1)=3k-1+[(k-1)/2]的反例

Brualdi与Jung在[1]中研究了一类具有固定线和k的n×n矩阵上的最大跳跃数M(n,k),并提出猜想M(2k, k + 1) = 3k - 1 + [(k-1)/2].本文给出了这一猜想的两个反例．     

一种新型彩色三维光学成像系统

提出一种新型三维彩色光学数字成像系统。此系统利用投影结构光对现实世界中的物体进行数字化，同时得到对应的彩色纹理。详细介绍了系统的硬件设计和软件体系结构设计，得到物体彩色纹理的两种不同方法；直接获取和从编码条纹中提取，给出了用该系统得到的实验结果并简单评价了系统的性能。此系统在反求工程、影视制作、三维游戏制作、医学应用等方面有远大的应用前景。     

Luminescent properties of Ce in MSO4 (M: Ca, Sr and Ba) and the effect of Na co-doping

The optical properties of Ce³⁺ in CaSO₄, SrSO₄ and BaSO₄ are reported. The Ce³⁺ ion shows 4f⁰5d¹→²F_5/2,²F_7/2 luminescence in all three sulphates. Co-doping with Na⁺ does not change the local surrounding of the Ce³⁺ ion, but enhances the amount of Ce³⁺ ions built in. Under optical excitation, besides the typical Ce³⁺ doublet emission in the ultraviolet spectral region, band emission around 445 nm was observed. This band emission was not assigned to emission from a Ce³⁺ centre, but to emission from an impurity-trapped exciton. Under X-ray excitation, both Ce³⁺ emission and an emission band around 380 nm was observed. This band was assigned to emission from a self-trapped exciton.     

综合孔径微波辐射计二阶量化数字相关器研究

微波辐射计作为一种无源遥感器,在遥感技术领域有着巨大的应用前景.传统的微波辐射计的空间分辨率受到天线孔径的限制.综合孔径微波辐射计利用了干涉测量原理和复相关技术,是一种可以有效地提高空间分辨率的新型辐射计.本文针对综合孔径微波辐射计的数字相关器进行了深入研究,分析论证了二阶量化数字相关器的工作机理,并对采用该种相关器的系统的信噪比进行了分析.初步的试验验证结果证明了该方案的有效性.     

光漂白法制备有机聚合物非线性定向耦合器

研究了用光漂白的方法制备PMMA/DR1聚合物非线性定向耦合器,提出了一种容易的制备方法来得到要求的耦合长度.测量了材料的光学非线性对定向耦合器两臂透过率的影响.实验结果表明由于光学非线性,耦合器的耦合长度随着入射光强度的改变而发生变化.     

数据增值业务在DVB中的实现

首先对DVB标准作了简单介绍，然后讨论了在数字电视系统中实现增值业务，最后给出了一个实例。