无线环境下失真和时限感知的视频分组调度机制

现有无线分组调度算法一般以最大化系统吞吐量或者保证用户之间公平性为目标。然而,不同视频分组之间存在着重要性差异,使得传统的内容无关调度算法不适用于无线视频传输。充分发掘视频分组之间存在的重要性差异并准确衡量视频分组的传输失真,能够在资源受限的无线环境下更合理地分配资源,提高视频传输质量。该文首先提出一种分组级别视频传输失真衡量模型,用于预测视频分组丢失对视频质量的影响,然后考虑分组时限的影响,提出分组级别的时限扩展模型。在此基础上,利用正交频分复用(OFDM)技术在无线资源(时域、频域及功率)分配上的灵活性,提出一种基于梯度的失真和时限感知调度算法。仿真结果表明该文所提出的调度算法相对于传统内容无关算法最大有4.3 dB的平均峰值信噪比(PSNR)增益。     

硅烷偶联剂对太阳电池铝浆性能的影响及分析

在晶体硅太阳电池制造过程中,铝电极是通过丝网印刷-烘干-烧结制成的。该过程中铝电极膜层与传送网带发生相对摩擦,易导致铝膜表面产生划痕、起灰。重点研究了添加不同质量分数w(硅烷偶联剂)(0.5%~3.0%)对铝浆有机载体的表面张力、铝膜表面划痕、起灰、导电性能的影响规律。结果表明:当w(硅烷偶联剂)为2.5%时,有机载体的表面张力可从约30mN/m降低至25.69mN/m,提高了铝粉颗粒之间以及铝膜与硅片之间的黏附作用,从而减少划痕和灰化,进而可使铝电极的接触电阻由0.60?降低至0.19?。     

Bandwidth allocation and admission control scheme based on Nash bargaining solution for WiMAX systems

Development of fair and efficient bandwidth allocation and admission control schemes is one of the key issues in the design of IEEE 802.16 broadband wireless access systems in time division multiple access (TDMA) mode. In this article, the problem of bandwidth allocation and admission control is formulated as a Nash bargaining model. The nash bargaining solution (NBS) derived from the cooperative game is adopted to maximize the spectrum utilization. Analysis and simulation results show that there is a unique Pareto optimal bandwidth allocation solution by using NBS among various flows. Furthermore, maximum utility of the system can also be maintained by using the admission control policy with different number of connections and variable channel qualities. The total throughput of the proposed scheme is close to the maximal one, while significantly improving fairness compared to the existing solutions.     

A nonlinear model for fractal image coding

After a very promising start, progress in fractal image coding has been relatively slow recently. Most improvements have been concentrating on better adaptive coding algorithms and on search strategies to reduce the encoding time. Very little has been-done to challenge the linear model of the fractal transformations used so far in practical applications. In this paper, we explain why effective nonlinear transformations are not easy to find and propose a model based on conformal mappings in the geometric domain that are a natural extension of the affine model. Our compression results show improvements over the linear model and support the hope that a deeper understanding of the notion of self-similarity would further advance fractal image coding.     

Closed-form solutions for one-dimensional inhomogeneous anisotropicmedium in a special case. II. Inverse scattering problem

For pt. I see ibid., vol.45, no.5, p.936, 1997. An analytical method is presented for the inverse scattering problem of a one-dimensional (1-D) inhomogeneous anisotropic medium in a special case. Using the closed-form formulations for the reflection coefficients derived in the first part of this paper, reconstruction formulas are obtained for the wave impedance profiles, permittivity profiles or permeability profiles of the anisotropic medium, all of which are given in closed form. In the meantime, a partial inverse scattering method for the electric parameters at the interface of the medium with free space is also investigated by using a Wedtzel-Kramers-Brillouin (WKB) approximation. Numerical examples show the validity of the methods     

Er-doped glass ridge-waveguide amplifiers fabricated with a collimated sputter deposition technique

We report a new fabrication process for Er-doped glass ridge waveguides. The process does not require etching of an Er-doped film in defining the lateral dimension of a waveguide, but involves a liftoff process using polyimide as a sacrificial layer. An Er-doped soda-lime silicate glass film (1.5 /spl mu/m thick) was deposited at 350/spl deg/C using a collimated sputtering technique. Conventional sputtering techniques have been known to be incompatible with a liftoff process. The collimated sputtering, however, allowed us easy liftoff of Er-doped films, and produced well-defined ridges with smooth surface profiles. A 1.7-cm-long waveguide thus fabricated shows a 1.55-/spl mu/m signal enhancement of 15.4 dB with a 980-nm pump power of 40 mW. This enhancement fully compensates for both Er absorption and waveguide losses, and results in a gain of 7.2 dB.     

具有监控功能的数码相机的研制

本文介绍了一种具有监控功能的数码相机的研制,包括其中的硬件设计和软件设计,该数码相机具有一般相机的基本功能。还具有监控功能,满足了一些实践应用场合的需要。     

微斑光电流谱和光反射谱的自动测量系统

叙述了为测量半导体光电器件的光电流谱和光反射谱所构成的自动测量系统及其数据处理方法。     

增镀光学薄膜改善DFB激光器的光谱特性

利用增镀光学薄膜的方法,有效地将原来处于双模工作的１．３μｍＤＦＢ激光器变为单模工作的激光器．选择的增镀膜层起到了抑制边模的作用．从而改变了激光器的模式特性．实验表明,增镀光学薄膜技术可望成为改善ＤＦＢ激光器单模成品率的一种辅助方法     

计算多芯片多基片模块稳态热场的层次模型

提出的层次模型将包括多芯片多基片模块的复杂热场模拟 ,分解为有确定耦合关系的形状简单的层次单元的热场计算 ,通过迭代将分区计算结果连成模块的热场 .在计算一个层次单元 (芯片、基片或底座 )的热场时 ,将其所在的层次单元 (母层次单元 )的上表面温度 ,作为该层次单元下表面的边界条件 ,而把它上表面上的层次单元 (子层次单元 )的下表面的向下热流作为置于它上表面的等效热源 .通过芯片→基片→底座→基片→芯片→基片…的几轮迭代就可收敛到正确值 .提出的层次单元间的耦合强度 (即每轮计算中 ,母层次单元上表面的温度改变不是全部 ,而是部分用于