Factorizations of tropical and sign polynomials

In this text, we study factorizations of polynomials over the tropical hyperfield and the sign hyperfield, which we call tropical polynomials and sign polynomials, respectively. We classify all irreducible polynomials in either case. We show that tropical polynomials factor uniquely into irreducible factors, but that unique factorization fails for sign polynomials. We describe division algorithms for tropical and sign polynomials by linear terms that correspond to roots of the polynomials.     

A NOVEL INTEGER FREQUENCY OFFSET ESTIMATOR FOR OFDM

One of the principal disadvantages of Orthogonal Frequency Division Multiplexing （OFDM） is very sensitive to carrier frequency offset. The integer frequency offset has no effect on the orthogonality among the subcarriers, but it causes a circular shift and phase rotation of the received data symbols sequence, resulting in a Bit Error Rate（BER） of 0.5. In this paper, a novel integer frequency offset estimator for OFDM is derived based on maximum likelihood estimation technique and exploration of the differential relation between two consecutive OFDM data symbol sequences in frequency domain. Its performance is compared with the conventional method by computer simulations for the additive white Gaussian noise channel and a multipath fading channel. Simulation results show that the performance of the proposed estimator is better than the conventional estimator.     

正交频分复用系统的误码率分析

分析了正交频分复用(OFDM)系统的原理及实现方案上推导出了计算OFDM系统误码率的理论计算公式,构造了高斯白噪声信道模型,并用Matlab进行了OFDM仿真.结果表明,OFDM系统误码率的理论曲线与仿真结果相一致.     

InGaAsP／InP单片集成波长解复用器件

报道了基于二维凹面光栅的单片集成波长解复用器件，器件刻蚀在ＩｎＧａＡｓＰ／ＩｎＰ平板波导上，通过凹面光栅的色散作用实现不同波长光的分离，光的输入输出耦合由波阵列来完成，器件的工作波长在１．５μｍ附近，通道间隔约４．３ｎｍ。本文给出了器件的设计方法，制作工艺和初步测试结果。     

The Splitting Representation of Matrix and Matrix Equation over a Central Division Algebra

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Performance Comparison of WDM Systems with Different Duty Cycle

The performances of nonlinear WDM systems with different duty cycle are compared by means of numerical simulation.The numerical results show that the optical pulse with duty cycle of 0.5 is superior to the conventional NRZ modulation schene.The conclusion is different from that of some references.The reason is that inter symbol interference is not included in some references.In fact,inter symbol interference plays an important role in monlinear WDM system.Although the larger the duty cycle is,the stronger the effect of the cross-phase modulation and self-phase modulation on nonlinear WDM is however,the larger the duty cycle is ,the stronger the inter symbol interference is.     

移动数字电视中的信道估计分析

在提出信道模型的基础上,针对移动数字电视应用的OFDM信号特点,提出了几种当前比较受重视的信道估计算法,并对其应用范围及其优劣性作了详细阐述.     

玉竹花粉中造粉质体形成及增殖的超微结构研究

本文运用电子显微镜技术研究了玉竹花粉中造粉质体形成及增殖的超微结构特点，发现造粉质体在体积增加的过程中与内质网有密切关系，造粉质体除以分裂的形式进行增殖外可能还有其他的形式，分裂过程中在颈部出现分裂中的作用及其他可能的分裂机制进行了讨论。     

Spectrophotometric determination of nitrite with p-nitroaniline and 2-methyl-8-quinolinol in hexadecyl-trimethylammonium bromide solution

Nitrite ion at low concentrations is determined spectrophotometrically by diazotization of p-nitroaniline and coupling of the diazonium salt with 2-methyl-8-quinolinol. The resulting dye is solubilized in hexadecyltrimethylammonium bromide micelles. The molar absorptivity is 4.72 × 10⁴ l mol^-1 cm^-1, and the Sandell sensitivity is 9.7 × 10^-4 μg cm^-2. Some interferences are reported, and preconcentration by evaporation is evaluated. The solubility of hexadecyltrimethylammonium bromide in water was determined as a function of temperature; the Krafft point is 19.6°C. Salting-in of the surfactant by potassium nitrate is described.