对于光码分复用系统采用的光正交码容量及构造方法的讨论

介绍了等重对称、非对称和可变重对称、非对称光正交码的定义、容量的上界及求码的自相关函数和互相关函数的差分矩阵法，并对几种光正交码的容量进行了比较，对光正交码构造方法进行了讨论。     

Zk线性码的对称形式的MacWilliams恒等式

该文定义了Zk线性码的码字的对称重量计数公式,利用离散的Hadamard变换,建立了线性码与其对偶码之间的对称形式的MacWilliams恒等式。     

关于某些BCH码的不可检错误概率

本文研究了二元对称信道上，某些ＢＣＨ码的不可检错误概率。首先得到了几个重要的不等式。然后证明了纠正两个错误二进制本原ＢＣＨ码的扩展码是最佳检错码。     

自由空间光通信下对称Spinal码的性能分析

针对Spinal码不等差错保护性质而引起的差错控制性能不佳的问题,本文提出在自由空间光通信中采用对称Spinal码提高信息传输性能。通过反向编码过程提高传输速率、抗噪性能,降低误码率。并用迭代译码方式降低译码复杂度。仿真结果表明在大气湍流信道中,对称Spinal码比Spinal码在传输速率性能上有007～015 bit/s的提升;信噪比较高时,对称Spinal码相比于Spinal码具有更好的鲁棒性。码长较短时,对称Spinal码的误码率明显优于RS码、Polar码和Spinal码,误码率为1×10-4时,分别产生了05dB,175dB和04dB的增益。     

极大等重等距码结构的再分析

本文根据文[1]提出的极大等重等距码的概念,利用等重等距码窗口矩阵设计原理,对(n,4,m)极大等重等距码结构重新进行了分析.讨论了码重基本情形,对称情形与非对称情形等几类特殊结构类型,并组合了各种不同结构的极大等重等距码,其结果比较完整地解决了(n,4,m)极大等重等距码的结构等价类问题.     

极化码及性质

主要介绍了基于二元离散无记忆信道的极化码的构造以及相关性质。极化码不但能够在离散对称信道的条件下达到系统的对称容量,而且编译码的复杂度和码字长度几乎呈线性关系,即当码字长度为N时,其复杂度约为O（Nlog N）。最后讨论了极化码的应用以及研究热点。     

环Fp+vFp+v2Fp上线性码的各种重量计数器及其MacWilliams恒等式

首先给出了环R=F_p+vF_p+v²F_p上线性码及其对偶码的结构及其Gray象的性质.定义了环R上线性码的各种重量计数器并讨论了它们之间的关系,特别的,确定了该环上线性码与其对偶码之间关于完全重量计数器的MacWilliams恒等式,利用该恒等式,进一步建立了该环上线性码与其对偶码之间的一种对称形式的MacWilliams恒等式.最后,利用该对称形式的MacWilliams恒等式得到了该环上的Hamming重量计数器和Lee重量计数器的MacWilliams恒等式,利用不同的方法推广了文献[7]中的结果.     

等重对称光正交码的多址干扰

对异步系统中等重对称光正交码的多址性能进行分析。在不考虑热噪声、量子噪声和散弹噪声情况下，分别得到了码长、码重、判决门限、用户数和互相关值等对系统误码率的影响曲线。在Ｃｈｉｐ同步的情况下，得到了系统的误码率上限。我们发现系统的误码率受码长、码重，判决门限，用户数和相互相关值的影响。当上参量固定时，误码率分别随着码长，判决门限的增加而减小，随着用户数，码重，互相关值的增加而增加，其他三个参量固定时，     

非主理想环F_p+vF_p上线性码的MacWilliams恒等式

研究了环F-p+vF_p上线性码的结构,证明了互为对偶的线性码的Gray象仍是互为对偶的线性码.定义了环F_p+vF_p上码的Lee重量、Hamming重量和广义对称重量分布计数器的概念,利用域F_p上线性码和对偶码重量分布的关系及Gray映射的性质,给出了该环上线性码及其对偶码之间的各种重量分布的Macwilliam...     

等重对称光正交码的多址干扰

对异步系统中等重对称光正交码的多址性能进行了分析。在不考虑热噪声、量子噪声和散弹噪声的情况下 ,分别得到了码长、码重、判决门限、用户数和互相关值等对系统误码率的影响曲线。在 chip同步的情况下 ,得到了系统的误码率上限。我们发现系统的误码率受码长 ,码重 ,判决门限 ,用户数和互相关值的影响。当其它四个参量固定时 ,误码率分别随着码长 ,判决门限的增加而减小 ,随着用户数 ,码重 ,互相关值的增加而增加 ;其他三个参量固定时 ,误码率随着码重和判决门限的增加而减小。这可以作为对等重对称光正交码应用的参考     

Galerkin method for calculating valence-band wavefunctions in quantum-well structures using exact envelope theory

The ability to calculate accurately the valence-band structure in semiconductors is important in the design of quantum-well (QW) semiconductor devices. The Galerkin method for calculating accurate analytic approximations for multicomponent valence-band wavefunctions is computationally fast and efficient. The Galerkin method is, in fact, an improved version of an earlier Raleigh-Ritz-type variational method. In this paper, we remark that both the variational method and the more recently proposed Galerkin method are formulated such that they imply symmetrized boundary constraints at material interfaces, with the symmetrized nature of the constraints arising from neglecting the ordering of the operators. Burt's exact envelope-function theory for semiconductor microstructures has been used to demonstrate, however, that the commonly used symmetrized boundary constraints for material interfaces are unphysical. We therefore present a modified version of the Galerkin method that implicitly assumes physically reasonable, exact envelope-function boundary constraints. Simulations show that the modified Galerkin method successfully produces physical, semi-analytic results that are consistent with exact envelope theory.     

半导体激光器线阵光束扭转对称化的实验研究

利用双焦望远系统和扭转柱透镜系统实现了半导体激光器线阵(LD-bar)的扭转对称化，对称化后的光束在x和y两个方向的光束宽度、发散角和光束参量积接近相等，极大地改善了半导体激光器线阵光束的不对称性和像散特性，进行了以上变换的理论分析和实验研究。作为应用实例．用对称变换后的光束进行了抽运固体激光器的实验，激光器基模输出的效率比用不变换前的光束有明显提高。     

Calibration of Stokes and scattering matrix format polarimetric SARdata

It is shown that the assumptions about the backscatter and the polarimetric radar system for the two approaches described in J.D. Klein's (1992) and J.J. van Zyl's (1990) papers are equivalent. It is demonstrated that, to first order in the radar system crosstalk (i.e. neglecting terms of second order and above), an exact solution to the Stokes matrix format data calibration problem exists. It is shown that van Zyl's approach can give this first-order solution for appropriately symmetrized polarimetric radar data. Then it is shown how, if the data are properly symmetrized, van Zyl's approach can be used to calibrate both scattering matrix and Stokes matrix format data. These conclusions should be generally applicable to polarimetric imaging radar system data     

A fast method for nonlinear Schrodinger equation

The predictor-corrector split-step Fourier method (SSFM) is proposed for solving a nonlinear Schrodinger equation. In comparison with the symmetrized SSFM, the proposed method greatly decreases the relative error and increases the computing speed by /spl sim/2.8 to /spl sim/5.5 times at the same accuracy.     

Data volume reduction for single-look polarimetric imaging radardata

An 8-b quantization scheme to reduce the data volume for single-look complex scattering matrix data measured by polarimetric imaging radar systems is described. The scattering matrices are not symmetrized before compression, thereby retaining information about background noise and system effects. The data volume is reduced by a factor of 3.2. It is shown, with measured data, that the signal to quantization noise ratio for the compression scheme is more than 35 dB for the cross-polarized channels, and more than 45 dB for the copolarized channels     

三相全控桥整流装置的微机触发控制

介绍一种采用微机控制三相全控桥整流装置的方法．微机直接通过８２５３计数／定时器进行触发脉冲移相控制．同步信号实现数字化，使三相融发脉冲相位对称，从而保证了三相负载电流均衡，直流输出电压波形匀称平滑，减小了谐波电流对电网和负载的影响．电路结构简单可靠，抗干扰性强，优于模拟式触发器．     

Counterexamples to a Method for Identifying Hopf Bifurcations Without Eigenvalue Calculation

We give counterexamples to the numerical method for detecting Hopf bifurcations in electric power systems by singularity of a symmetrized Jacobian in Y. Zhou, V. Ajjarapu," A fast algorithm for identification and tracing of voltage and oscillatory stability margin boundaries", IEEE Proceedings, vol.93, no.5, May 2005, p.934-46. The counterexamples include some simple matrix examples and a single machine infinite bus power system     

基于色散渐减、非线性渐增原理的脉冲压缩

从理论上推导了色散渐减同时非线性渐增原理可以压缩脉冲的结论,并利用对称分步傅里叶方法研究了在不同色散渐减与非线性渐增比值下所得压缩脉冲的压缩比与基座性能,数值结果表明,非线性渐增原理最有利于脉冲压缩,而已有的基于色散渐减原理压缩脉冲的方法是压缩比最低的情况.通过和色散减渐方法压缩脉冲相比,表明利用非线性渐增方法可以在获得几乎相同的压缩比与更小的基座能量的同时将所需光纤长度缩短为原来的一半.