基于System View的BPSK、QPSK与OQPSK仿真与分析

近几年,在卫星通信、移动通信等领域广泛应用相移键控。BPSK、QPSK和OQPSK是基本的相移键控。为了帮助初学者区分并学习这三种调制方式,文章介绍了BPSK、QPSK及OQPSK调制解调原理和基于System View的系统仿真设计,并对其仿真结果进行对比分析,使相移键控法更加形象具体,从而利于初学者深入理解。     

Highly accelerated aortic 4D flow MR imaging with variable-density random undersampling

Purpose

To investigate an effective time-resolved variable-density random undersampling scheme combined with an efficient parallel image reconstruction method for highly accelerated aortic 4D flow MR imaging with high reconstruction accuracy.

Materials and Methods

Variable-density Poisson-disk sampling (vPDS) was applied in both the phase-slice encoding plane and the temporal domain to accelerate the time-resolved 3D Cartesian acquisition of flow imaging. In order to generate an improved initial solution for the iterative self-consistent parallel imaging method (SPIRiT), a sample-selective view sharing reconstruction for time-resolved random undersampling (STIRRUP) was introduced. The performance of different undersampling and image reconstruction schemes were evaluated by retrospectively applying those to fully sampled data sets obtained from three healthy subjects and a flow phantom.

Results

Undersampling pattern based on the combination of time-resolved vPDS, the temporal sharing scheme STIRRUP, and parallel imaging SPIRiT, were able to achieve 6-fold accelerated 4D flow MRI with high accuracy using a small number of coils (N = 5). The normalized root mean square error between aorta flow waveforms obtained with the acceleration method and the fully sampled data in three healthy subjects was 0.04 ± 0.02, and the difference in peak-systolic mean velocity was − 0.29 ± 2.56 cm/s.

Conclusion

Qualitative and quantitative evaluation of our preliminary results demonstrate that time-resolved variable-density random sampling is efficient for highly accelerating 4D flow imaging while maintaining image reconstruction accuracy.     

用System View滤除伴音中的窄带噪声

有效滤除伴音中的噪声对提高节目播出质量是有帮助的。System View是一个功能强大的数字信号处理和通信系统设计的仿真软件，它提供了信号从时域到频域的转换和滤波器的设计工具，方便捕捉声音信号中的噪声频谱并通过设计合理的滤波器滤除噪声。本例说明使用System View软件滤除伴音信号中的窄带噪声的方法。     

一种嵌套、归属可变的综合报表设计

介绍了用PwerBuilder7.0和Oracle8i数据库开发一种灵活、多变的综合报表设计方案，解决了根据要求随时增加报表嵌套层次、调整嵌套项归属的技术性问题。经过神东公司总调度室的实际应用证明准确无误，具有一定的实际意义和参考价值。     

用ASP调用SQL Server的视图和存储过程

本文概述了用ASP调用SQLServer的视图和存储过程的一般方法     

Pseudoprime factorizations of integer matrices

We give a method of factoring integer matrices in View the MathML source" title="View the MathML source" align="absbottom" border="0" height=13 width="33"/> into components such that the factorization is not unique unless certain information is known. In Section 2, we introduce this method of factorization and provide theorems which establish its well-definedness. In Section 3, we construct a matrix in View the MathML source" title="View the MathML source" align="absbottom" border="0" height=17 width="57"/> as a product of specific types of matrices and establish an algorithm for factoring the result uniquely given an amount of information.     

Abel's method on summation by parts and theta hypergeometric series

Abel's lemma on summation by parts is reformulated to investigate systematically terminating theta hypergeometric series. Most of the known identities are reviewed and several new transformation and summation formulae are established. The authors are convinced by the exhibited examples that the iterating machinery based on the modified Abel lemma is powerful and a natural choice for dealing with terminating theta hypergeometric series.