多电平变换器SVPWH策略

论文针对多电平变换器的特点,介绍了基于两电平SVPWM、60°坐标系、虚空间矢量、神经网络以及虚坐标系等多种多电平变换器SVPWM的算法,分析这些算法的优缺点。     

Toward Meaningful Connectivity: Using Multilevel Communication Research to Reframe Digital Inequality

Digital inequality, or unequal access to the Internet and technologies that connect to it, has preoccupied communication scholars since the Internet's introduction into popular culture. The relationships between digital and broader social inequalities suggest that meaningful digital connectivity—that is, having the technical skills necessary to engage technology and mobilize information resources to address everyday needs—can empower socially disenfranchised individuals, families, and communities to address challenges related to those disparities. In this essay, we overview the arc of communication research on technology engagement and its consequences. On this foundation, we argue why multilevel research that accounts for individual‐, family‐, and community‐level influences on meaningful digital connectivity is the best path forward for research on digital inequality.     

1-Bit压缩感知盲重构算法

1-Bit压缩感知(CS)是压缩感知理论的一个重要分支。该领域中二进制迭代硬阈值(BIHT)算法重构精度高且一致性好,是一种有效的重构算法。该文针对BIHT算法重构过程需要信号稀疏度为先验信息的问题,提出一种稀疏度自适应二进制迭代硬阈值算法,简称为SABIHT算法。该算法修正了BIHT算法,首先通过自适应过程自动调节硬阈值参数,然后利用测试条件估计信号的稀疏度,最终实现不需要确切信号稀疏度的1-Bit压缩感知盲重构。理论分析和仿真结果表明,该算法较好地实现了未知信号稀疏度的精确重建,并且与BIHT算法相比重构精度及算法复杂度均相当。     

新的完备高斯整数序列的构造方法

该文提出了新的偶数周期的完备高斯整数序列构造方法。以整数集上的多电平完备序列为基础,并根据其周期的奇偶性,分别利用不同的组合和映射关系构造出完备高斯整数序列,所得到的完备高斯整数序列的周期等于或者2倍于多电平完备序列的周期。利用该方法可以得到新的完备高斯整数序列,从而实现了对现有完备高斯整数序列数量的扩展。     

基于模块化多电平换流器的新型高压变频器拓扑及其控制

为使煤矿设备高效利用能源,达到节能减排的目的,提出了基于模块化多电平换流器(Modular Multilevel Converter,MMC)的新型高压变频器。概述了其基本结构,分析了MMC拓扑及工作机制。以逆变侧为研究对象,建立MMC数学模型,采用建模排序法控制子模块电容电压稳定平衡,通过与不同调制算法对比,载波正负反相层叠脉冲宽度调制技术(POD-PWM)的优势得以凸显。以Matlab-Simulink及RT-Lab半实物仿真设备为实验平台,搭建上位机控制器,实验结果显示换流器运行正常、电容电压稳定平衡,输出电能质量高,谐波含量小,证明了提出的载波正负反相层叠与电压稳定平衡控制相结合的控制策略的可行性,并得出了实验条件下的最佳三角载波频率。     

隐通道识别技术研究

一、引言计算机的广泛应用,在促进了社会的进步,为人类创造了巨大的财富的同时,也带来了计算机系统的安全性问题。目前,这个问题已越来越成为关系国计民生的重要问题,也引起了人们的广泛关注。根据TC-SEC,开发具有B2级及以上的操作系统或数据库管理系统必须进行隐通道分析。隐通道分析的关键在于隐通道的识别,只有在隐通道标识出来后才能估算隐通道的带宽,并采取一些策略消除隐通道、限制隐通道的带宽或对隐通道审计。在一安全的计算机系统中,采用了自主存取控制和强制存取控制来限制信息只通过合法的通讯通道(如文件、共享内存和进程信号等)流     

基于离散正交小波变换的图象去噪方法

给出了一种基于离散正交小波变换的图象去噪方法,该方法通过二维离散小波变换将图象投影到小波变换域,通过对小波变换系数进行阈值处理实现二维图象的去噪,并用实验验证了该方法的有效性。     

基于二维阈值化与FCM相混合的图象快速分割方法

提出了一种将快速二维阈值化与模糊聚类相混合的图象分割方法,以进一步减少快速二维阈值分割中的噪声与错误分割。实验结果表明,利用这种方法分割信噪比较低的图象,能够在很短的时间内得到较为令人满意的分割结果。此外,本文还讨论了这一方法中隶属度函数的选取对分割结果的影响     

Time-domain writing architecture for multilevel RRAM cells resilient to temperature and process variations

The high potential of memristors as multilevel resistance devices is undermined by their highly non-linear behaviour and a strong dependency on different sources of variability (process, voltage, temperature…). Temperature fluctuations are specially harmful because small thermal variations may significantly modify the operation point of the device. For these reasons the circuitry required to accurately read or write multilevel devices is complex and area demanding, especially if multi-level storage is considered. This work addresses the problem of accurately writing a given resistance value in a memristive cell by using a time-domain architecture found on variable pulses. Temperature resiliency is achieved after performing an in depth analysis of the definition of the resistance levels in the presence of thermal variations. Furthermore, a calibration procedure has been conceived to make the writing circuitry resilient to device to device variations. Experimental results show that the proposed approach is valid for a wide temperature range.