Spectrally‐Efficient Decode‐and‐Forward Scheme Based on Constellation Rotation

A spectrally‐efficient scheme is proposed for orthogonal decode‐and‐forward relaying. By utilizing constellation rotation, the scheme can achieve twice the spectral efficiency as that of the conventional one, with low implementation complexity. It can offer a full diversity order as well, whereas the loss in coding gain is less than 1 dB for practical environments.     

一种新的基于GPU实现的锥束CT正投影算法

锥束CT成像算法的正投影计算量大,消耗时间长.为此,本文提出了一种基于GPU实现的正投影加速算法.该算法在GPU的可编程管线中,通过纹理映射方法实现了圆轨迹锥束扫描模式下正投影计算.由于投影逐片并行计算,因此该算法具有较高的计算速率,且支持全浮点运算精度.在该正投影算法的基础上,本文还给出了三种算法优化方法.这些优化方法进一步提高了算法的执行效率.通过对Shepp-logan模型的正投影计算以及应用于迭代法进行三维图像重建等实验验证了本文算法的优点.     

Optimal selection of ARQ parameters in QAM channels

For a quadrature amplitude modulation (QAM) communication channel with forward error correction (FEC) and automatic repeat request (ARQ), the bit error rate (BER) is estimated as a function of the channel signal‐to‐noise ratio (SNR). A method is presented for trading off the number of allowed transmissions and the level of margin (or the line ARQ gain) applied to the channel SNR. The line ARQ gain maximizing the channel throughput is shown to be a sum of the channel SNR and some function of the bit load and FEC parameters. Using this result, we formulate a fast method of determining the optimum ARQ parameters at the actual channel conditions, based on their values at some reference conditions, the latter being either stored in the modem memory or pre‐calculated prior to channel initialization. The derivations are presented both for AWGN and slowly fading channel conditions. Copyright © 2004 John Wiley & Sons, Ltd.     

一个前向安全的代理签名方案的分析与改进

对一种已有的安全代理签名方案进行了安全性分析,指出它的不安全性.然后,改进了这个方案,并分析了新方案的安全性.     

Orthogonal-directional forward diffusion image inpainting and denoising model

In this paper, an orthogonal-directional forward diffusion Partial Differential Equation （PDE） image inpainting and denoising model which processes image based on variation problem is proposed. The novel model restores the damaged information and smoothes the noise in image simultaneously. The model is morphological invariant which processes image based on the geometrical property. The regularization item of it diffuses along and cross the isophote, and then the known image information is transported into the target region through two orthogonal directions. The cross isophote diffusion part is the TV （Total Variation） equation and the along isophote diffusion part is the inviscid Helmholtz vorticity equation. The equivalence between the Helmholtz equation and the inpainting PDEs is proved. The model with the fidelity item which is used in the whole image domain denoises while preserving edges. So the novel model could inpaint and denoise simultaneously. Both theoretical analysis and experiments have verified the validity of the novel model proposed in this paper.     

不同温度下半导体硅势垒的正向I-V特性曲线的汇聚特性

以正向电压为自变量,以正向电流的对数为应变量,以温度为参数得到的p-n结的I-V-(T)特性曲线在第一象限中近似汇聚于一点.汇聚点对应的电压近似等于半导体材料的禁带宽度.汇聚点可以用来获取任意温度下的I-V特性曲线.     

An algorithm for the selection of effective error correction coding in wireless networks based on a lookup table structure

In this paper, we propose an adaptive Forward Error Correction (FEC) coding algorithm at the Medium Access Control (MAC) layer used in wireless networks. Our algorithm is based on the lookup table architecture, including a distance lookup table and a bit error rate lookup table. These tables will store the best value of the FEC codes based on different distances and bit error rates. Because radio channels change over time, the bit error rate is always changing, or in the case of mobile nodes, when the transmission distance changes, the bit error rate also changes, so previously proposed algorithms take longer to find the optimal value of the FEC code for data transmission. Our proposed algorithm, however, is based on 2 lookup tables, and thus, it can always quickly select an optimal FEC code during early data transmissions and achieve high performance. We compare our algorithm with other methods based on performance metrics such as the recovery overhead of FEC codes, energy efficiency, and peak‐signal‐to‐noise ratio values in the case of image transmission. Our simulation indicates that the proposed algorithm achieves better performances and proves the correctness of the proposed lookup table architecture.     

硅薄膜太阳电池高效陷光结构的研究

利用严格耦合波分析方法和模式传输线理论,对硅薄膜太阳电池结合DBR（Distributed Bragg Reflector,分布布拉格反射器）和衍射光栅的叠层底部背反射器结构进行了优化设计。结果表明,光栅周期、光栅厚度和光栅宽度分别为0.5λg、0.18λg、0.48λg（λg为硅的带隙波长）以及对应的DBR中心波长为0.85μm时,太阳电池对光子的总吸收最强,且总吸收的提高主要来自于对长波光子的吸收增强,提高了薄膜太阳能电池对长波光子的陷光能力。     

江苏移动利用信令监测系统实现回拨业务分析

对网间互联互通中存在的回拨卡和回拨呼叫发生原理和业务特征进行了深入分析,详细说明了信令监测系统对于回拨呼叫行为的分析和统计。该分析有助于移动运营商有针对性拦截处理,减少异常欺诈业务对移动用户呼叫的影响。也对信令监测系统的深入分析应用有促进作用。     

一种同步整流有源箝位正激变换器的研究

提出一种同步整流有源箝位正激变换器。该变换器是在传统的同步整流有源箝位正激变换器的原边增加一个由箝位电容和电感构成的辅助网络得到。该辅助网络可以使变换器在全负载范围内更容易实现主开关管和辅助开关管的ZVS(Zero-Voltage Switching),副边采用自激式同步整流技术,能进一步提升变换器效率,适用于低压、大电流输出场合。详细分析了变换器的工作原理,搭建了一台8 V/100 W试验样机证明了理论分析的正确性。