Roos bound for skew cyclic codes in Hamming and rank metric

In this paper, a Roos like bound on the minimum distance for skew cyclic codes over a general field is provided. The result holds in the Hamming metric and in the rank metric. The proofs involve arithmetic properties of skew polynomials and an analysis of the rank of parity-check matrices. For the rank metric case, a way to arithmetically construct codes with a prescribed minimum rank distance, using the skew Roos bound, is also given. Moreover, some examples of MDS codes and MRD codes over finite fields are built, using the skew Roos bound.     

All-optical clock frequency divider using Fabry-Perot laser diode based on the dynamical period-one oscillation

We propose and experimentally demonstrate a frequency divider implemented by an optically injected Fabry-Perot laser diode (FP-LD) based on the nonlinear dynamical period-one oscillation. Injected by optical pulses, the FP-LD will oscillate in unstable dynamical period-one (P1) oscillation. Through changing the injected strength, emitting wavelength and bias current of the FP-LD, the oscillating frequencies of the P1 state can be varied. Once one of the harmonic frequencies is adjusted to match the repetition frequency of injected optical clock pulse, the P1 oscillation will be locked, and then a divided clock at the fundamental frequency of the P1 oscillation can be generated. By utilizing this divider, we can achieve the optical clock frequency division of divide-by-two, -three and -four in a wide input frequency range, for instance, of 9.0 to 20.0 GHz for divide-by-two. The influence of injected optical power on the timing jitter of the divided clock is also investigated. It is expected that this frequency divider can be applied to high frequency division exceeding 100 GHz due to its fast P1 oscillation.     

An image encryption scheme based on irregularly decimated chaotic maps

An image encryption scheme provides means for securely transmitting images over public channels. In this work, we propose a robust shuffling–masking image encryption scheme based on chaotic maps. The shuffling phase permutes square blocks of bytes using a 3-dimensional chaotic cat map coupled with a zigzag scanning procedure. The masking phase then scrambles b-byte blocks of the shuffled image with combined outputs of three 1-dimensional chaotic skew tent maps, in such a way that the masking of every block is influenced by all previously masked blocks. Empirical results show that while the suggested scheme has good running speed, it generates ciphered images that exhibit (i) random-like behavior, (ii) almost flat histograms, (iii) almost no adjacent pixel correlation, (iv) information entropy close to the ideal theoretical value. Furthermore, this scheme has a large key space, strong sensitivity to the secret key, and is robust against differential attacks. On the basis of these results, this scheme can be regarded as secure and reliable scheme for use in secure communication applications.     

A constructive solution to a problem of ranking tournaments

A tournament is an oriented complete graph. The problem of ranking tournaments was firstly investigated by P. Erd?s and J. W. Moon. By probabilistic methods, the existence of ?? ?? unrankable” tournaments was proved. On the other hand, they also mentioned the problem of explicit constructions. However, there seems to be only a few of explicit constructions of such tournaments. In this note, we give a construction of many such tournaments by using skew Hadamard difference sets which have been investigated in combinatorial design theory.     

The skew Schubert polynomials

We obtain a tableau definition of the skew Schubert polynomials named by Lascoux, which are defined as flagged double skew Schur functions. These polynomials are in fact Schubert polynomials in two sets of variables indexed by 321-avoiding permutations. From the divided difference definition of the skew Schubert polynomials, we construct a lattice path interpretation based on the Chen–Li–Louck pairing lemma. The lattice path explanation immediately leads to the determinantal definition and the tableau definition of the skew Schubert polynomials. For the case of a single variable set, the skew Schubert polynomials reduce to flagged skew Schur functions as studied by Wachs and by Billey, Jockusch, and Stanley. We also present a lattice path interpretation for the isobaric divided difference operators, and derive an expression of the flagged Schur function in terms of isobaric operators acting on a monomial. Moreover, we find lattice path interpretations for the Giambelli identity and the Lascoux–Pragacz identity for super-Schur functions. For the super-Lascoux–Pragacz identity, the lattice path construction is related to the code of the partition which determines the directions of the lines parallel to the y-axis in the lattice.     

Skew CR Submanifolds of a Sasakian Manifold

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1024位6相时钟MOS图像传感器

介绍一种采用６相时钟电路的１０２４位ＭＯＳ图像传感器，其像元中心距为１５μｍ，移位寄存器采用５管动态无比电路，功耗小于０．５ｍＷ，且与位数无关。器件光敏面上沉积了ＳｉＯ２增透膜，提高了光电转换效率。给出了该器件光电参数测试结果。     

基于电吸收调制器的高速时钟信号的提取

对高速光时分复用系统中(2×10 Gb/s)基于电吸收调制器(EAM)的注入光电混合振荡器的时钟提取方法进行了实验验证. 实验证明,光电混合振荡器必须保证一定的增益才能提取出时钟,在此基础上,无论光电混合振荡器内或外的光功率的增加,将增加提取时钟的幅度,减小提取时钟的时间抖动.当偏置电压一定时,射频幅度增加,则电吸收调制器的窗口变窄,提取时钟幅度增大,抖动减小.     

基于FPGA的高频时钟的分频和分配设计

介绍了为PET(正电子发射断层扫描仪)的前端电子学模块提供时间基准而设计的一种新型高频时钟扇出电路。该电路利用FPGA芯片来实现对高频时钟的分频与分配，并用LVDS传输标准对生成的多路时钟信号进行传输，从而最大程度地减少了输出各路时钟之间的延时偏差，同时利用低压差分信号的传输特性增强了信号的抗干扰能力。文章给出了采用VHDL语言编写的时钟电路程序代码。     

采用相邻采样求和的突发模式相位插值型CDR

提出了一种具有良好抑制输入数据抖动性能的突发模式相位插值型时钟数据恢复电路。在传统相位插值型电路结构的基础上,在采样保持电路与相位插值电路之间加入一级求和电路,理论分析和仿真结果表明,恢复时钟相位变化受输入数据抖动的影响明显减小。电路基于1.1 V SMIC 40 nm 1P8M CMOS工艺搭建,其数据率为6.25 Gb/s,消耗功耗为6.7 mW,版图面积为0.35 mm²。