Magnetic resonance angiography at 0.3 T using MS-325

Preliminary results on MS-325 versus ProHance enhanced magnetic resonance angiography (MRA) at low field strength in a rabbit model are reported. MS-325-enhanced images were acquired in vivo and compared with pre-contrast as well as conventional contrast-enhanced images. Visual image quality observations correlated with measurements of signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). While published in vitro data show 7-fold greater relaxivity for MS-325 compared with conventional contrast agents, we observed an even greater effect here due, presumably, to better matching of the longer vascular lifetime with longer scan time in this study. In addition, overall vessel clarity improved significantly throughout all the phases of the experiment in MS-325-enhanced images when compared with conventional contrast-enhanced images.     

Δ∑模数转换器中数字抽取滤波器的设计

抽取滤波器是过采样模数转换器中的重要组成部分。低字率、高采样频率的数字调制信号被转换成高字率、奈奎斯特频率采样的信号。该文介绍了应用于不同过采样率的通用数字抽取滤波器的设计,适用于一阶到七阶的Δ∑调制器,输入字长从1bit到32bit。设计和实现了一个过采样率为256的数字抽取滤波器,应用于三阶级联的Δ∑调制器。该抽取滤波器包括:级联积分梳状滤波器、补偿滤波器和一个窄带有限冲击响应半带滤波器。滤波器系数都采用CSD(Canonic SignedDigit)码实现。多级多采样率信号处理电路被用来实现补偿和半带滤波。整个滤波器经过了FPGA验证,输出正弦波的信噪比达到了110dB。     

基于先验信息辅助的8PSK信号信噪比估计

基于最大似然序列估计准则,提出了3种先验信息辅助的8PSK调制信号的信噪比估计方法.与现有硬判决辅助的信噪比估计方法进行了比较,解决了现有方法在低信噪比时估计误差较大的问题.分析了3种方法在Turbo均衡系统中初始迭代以及迭代进行过程中的性能,根据不同的迭代次数,在不同的方法之间进行切换会提高信噪比的估计精度,并降低计算复杂度.新方法只需要利用很少的数据符号就能得到准确的结果,并且能适用较大的信噪比范围.     

Hybrid Taguchi-Immune Algorithm for the thermal unit commitment

In this paper, a Hybrid Taguchi-Immune Algorithm (HTIA) is presented to deal with the unit commitment problem. HTIA integrates the Taguchi method and the Traditional Immune Algorithm (TIA), providing a powerful global exploration capability. The Taguchi method (TM) is incorporated in the crossover operations in order to select the better gene for achieving crossover consequently, enhancing the TIA. It has been widely used in experimental designs for problems with multiple parameters. The effectiveness and efficiency of HTIA are demonstrated by presenting several cases, and the results are compared with previous publications. Our results show that the proposed method is feasible, robust, and more effective than many other previously developed computation algorithms.     

Fast Small Offshore Target Detection Based on Object Region Characteristic

A fast object detection method based on object region dissimilarity and 1-D AGADM (one dimensional average gray absolute difference maximum) between object and background is proposed for real-time defection of small offshore targets.Then computational complexity,antinoise performance,the signal-to-noise ratio (SNR) gain between original images and their results as a function of SNR of original images and receiver operating characteristic (ROC) curve are analyzed and compared with those existing methods of small target detection such as two dimensional average gray absolute difference maximum (2-D AGADM),median contrast filter algorithm and multi-level filter algorithm.Experimental results and theoretical analysis have shown that the proposed method has faster speed and more adaptability to small object shape and also yields improved SNR performance.     

基于特征子空间的最小二乘恒模算法

最小二乘恒模算法(lscma)是阵列信号处理中广泛使用的一种能全局收敛且稳定性强的算法,但是当低信噪比的情况下它的收敛性和输出信干噪比会明显下降。本文在信号子空间特征值分解的基础上进行权值迭代,提出一种基于特征子空间的最小二乘恒模算法(eb-lscm)。经过实验仿真该算法的收敛性要强于lscma算法。     

中巴地球资源一号卫星多光谱扫描图象质量评价

基于中国资源卫星应用中心提供的中巴地球资源一号卫星红外多光谱扫描仪（IRMSS）4个波段零级图象数据，首先综合运用各种有效方法进行了图象预处理（包括错位纠正、辐射校正、去噪声、清晰化、几何精校正等），然后在此基础上选择图象信噪比、地面分解力、清晰度、辐射精度、反差等5个指标对图象进行了全面的质量评价。研究分析表明，中巴地球资源一号卫生IRMSS图象某些波段的清晰度和反差稍好于TM，但在图象信噪比、地面分解力、清晰度等方面与TM相比尚有差距；通过图象灰度平衡、清晰化和数据融合等处理，中巴地球资源一号卫生IRMSS数据仍有很大的图象改善空间，并在国土资源调查、城市规划等诸多领域有着广阔的应用前景。     

电力线通信中提高信噪比方法的探讨

分析了电力线通信噪声的机理与特点，介绍了抑制噪声、提高信噪比的方法并给出了相应的应用实例。     

非线性交调的频率问题的数学模型

对无线电通信工程领域中常见的非线性交调的频率设计问题给出了一个数学模型。此模型所给的方法由于是基于实验基础，即只需测量给定系统在一些确定输入信号时的响应，而不需具体了解非线性物理结构，因此具有实用价值。     

具有信噪比处理增益的有源降噪系统性能分析

传统的有源降噪（ANC）系统的待抵消噪声中不包含有用信号，噪声希望被完全抵消；但在某些特殊的应用场合里，特别是对引入新的声场极度敏感的舰艇环境，待抵消噪声（主要是舰艇自噪声）中包含有目标信号（有用信号），噪声被降低的同时，希望信号被保留，这就是具有信噪比处理增益的有源降噪系统。本文给出了这种系统的物理模型，提出了针对该系统的“信噪比处理增益”和“信号失真度”概念，并进行了数理分析和仿真实验。研究表明：该系统能够降低噪声，但是信号会失真，影响该系统性能的最主要因素是参考输入端信噪比的大小。也就是说，只要合理设计参考噪声的拾取方式，该系统能够用于抵消舰艇自噪声，在获得较高的信噪比处理增益的同时，保持较低的信号失真度。