Exact evaluation of laser linewidth requirements for optical PSKhomodyne communication systems with balanced PLL receivers

The power penalty induced by imperfect phase recovery in PSK homodyne communication systems with balanced phase-locked loop receivers are exactly evaluated. Optimum phase deviations between the mark-state and the space-state bits are used in this study. This study for the first time shows the imperfect-phase-recovery-induced power penalty as a function of laser linewidth with optimum phase deviations considered. It can be estimated from the theoretical result that an optimal balanced PLL receiver requires the laser linewidth as Δν⩽1.15×10^-6× (bit rate) in contrast to the previous reported one Δν⩽5.88×10^-6× (bit rate). We also point out here that the previously reported laser linewidth requirement was wrongly estimated     

Multiple negative-differential-resistance (MNDR) phenomena of ametal-insulator-semiconductor-insulator-metal (MISIM)-like structurewith step-compositioned InxGa1-xAs quantum wells

In this paper, a new multiple negative-differential-resistance (MNDR) device based on a metal-insulator-semiconductor-insulator-metal (MISIM)-like structure with step-compositional In_xGa_1-x As quantum wells has been fabricated and demonstrated. The interesting MNDR phenomena are found in the current-voltage (I-V) characteristics of this device. At room temperature, the triple switching behaviours and quadruple stable operation states are obtained. In addition, the sixfold switching behaviors and a staircase-shaped I-V characteristic are observed at -105°C. A sequential carrier accumulation at InGaAs subwells and the potential lowering process are used to qualitatively explain the interesting MNDR phenomena. From the experimental results, it is shown that the studied device has good potential in multiple-valued logic applications     

Multimode parameter extraction for multiconductor transmissionlines via single-pass FDTD and signal-processing techniques

We present two approaches to extract the broadband multimode parameters of guided wave structures from a single-pass finite-difference time-domain (FDTD) simulation. They include a two-dimensional (2-D) Fourier transform (FT) algorithm and a super-resolution estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm. Comparison is made to show the superiority of the super-resolution approach. As a typical application, a three-line coupled microstrip structure is studied. After a single-pass FDTD simulation, broadband multimode parameters such as propagation constants, modal-field templates, and modal impedances are extracted and verified against published data obtained by the spectral-domain method. The main feature of this parameter-extraction methodology is that it decouples the computational electromagnetics engine (in this case, the FDTD simulator) from the post-processing parameter-extraction algorithm, thus providing more flexibility and connectivity among the various simulation tools     

智能网的计算机技术

文章剖析了应用于智能网的计算机技术，阐述智能网和计算机技术的关系。     

最大熵重建的迭代凸I投影算法

本文探讨了用迭代凸Ｉ投影（ＩｔｅｒａｔｉｖｅＣｏｎｖｅｘＩ－Ｐｒｏｊｅｃｔｉｏｎ，ＩＣＩＰ）算法求解最大熵Ｘ－ＣＴ重建问题．其思路是将这个复杂问题转化为多个简单子问题，然后迭代地求解这种单约束子问题．理论证明，这种算法收敛并能收敛到问题的最大熵解．这种算法形式优美，仿真结果表明算法同时也是有效的．     

Design of finite-length metal-clad optical waveguide polarizer

The performance of optical metal-clad waveguide polarizers is analyzed in this paper with a view to optimizing the extinction ratio, a condition for which power of the TM mode is completely attenuated is identified here. In general, such a condition corresponding to an infinitely high extinction ratio can be met for a wide range of buffer layer thicknesses by selection of metal film thickness and polarizer length. When a very thick (e.g., semi-infinitely thick) metal film is used, the aforementioned condition can be met with a properly chosen buffer layer thickness and polarizer length. The numerical results show that all the polarizers designed here for realization of infinitely high extinction ratios have either quite low or reasonably acceptable attenuations for the TE mode     

一种漂移室定位子性能反常现象的研究

研究了一种漂移室定位子性能的反常现象,它关系到定位子的使用寿命．着重测量了暗电流和随机噪声与时间、高压及温度的关系.     

Determination of tyrosine traces by adsorption voltammetry of its copper (II) complex

The electrochemical behavior of the copper-tyrosine complex has been studied by linear-sweep adsorption voltammetry. In 0.02 mol/L Na₂HPO₄ buffer solution (pH=9.6), the complex can be adsorped on a hanging mercury drop electrode and reduced at a peak potential of about –0.42 V (vs. SCE). The secondary derivative peak height is linear proportional to the concentration of tyrosine in the range 1.0×10^–7–5.0×10^–5 mol/L. The detection limit is 5×10^–8 mol/L.Project supported by the Provincial Science Foundation of Shandong Province     

Ba（n，x）~（134）Cs，~（134）Ba（n，2n）~（133）Ba，

用中子活化法相对于５４Ｆｅ（ｎ，Ｐ）５４Ｍｎ反应，在１３．５０—１４．８０ＭｅＶ中子能区测量了Ｂａ（ｎ，ｘ）１３４Ｃｓ，１３４Ｂａ（ｎ，２ｎ）１３３Ｂａ，１４０Ｃｅ（ｎ，２ｎ）１３９Ｃｅ，１４２Ｃｅ（ｎ，２ｎ）１４１Ｃｅ和２３Ｎａ（ｎ，２ｎ）２２Ｎａ的反应截面．并将所测的结果和其他作者的结果进行了比较，中子能量是用９０Ｚｒ（ｎ，２ｎ）８９ｍ＋ｇＺｒ反应和９３Ｎｂ（ｎ，２ｎ）９２ｍＮｂ反应截面比法测定的。     

薄Si膜对基底表面粗糙度的影响

利用ＺＹＧＯ光学干涉测量仪，散射积分测量法观测了光学元件表面均方根粗糙度．详细分析了薄Ｓｉ膜对基底均方根粗糙度的影响，由此认为薄膜并不总是复制基底表面的粗糙度，结果出现了薄膜降低表面粗糙度的现象．提出了一定厚度范围的薄Ｓｉ膜的表面粗糙度存在着一个稳定值的新设想．