基于MATLAB的FIR数字低通滤波器分析和设计

以FIR数字低通滤波器为例,详细分析时域卷积运算和频域加权算法的物理意义.并利用MATLAB的声音处理函数作为数据接口,利用多媒体播放器作为交互界面,利用MATLAB的FDATool作为滤波器设计工具,设计一组语音低通滤波器,通过对比滤波前后的语音效果,可加深对数字信号处理的认识.     

基于决策树和bloom filter的包过滤防火墙

分析了基于链表的包过滤防火墙的性能和特点,针对其不足,将决策树和Bloom Filter引入到包过滤防火墙中,并对其中涉及到的算法和步骤的开销进行了分析.分析表明,这种方法可以有效提高包过滤防火墙的性能.     

邮件服务器中基于地址的一种电子邮件过滤方法

互联网是一个无政府世界，有些人利用电子邮件肆意散发邮件广告，导致很多人的邮箱垃圾成堆；有些人利用电子邮件制造邮件炸弹，要么使电子邮件服务器瘫痪，要么使别人无法正常使用电子信箱；还有更坏的人利用电子邮箱传播电脑病毒．本文针对UNIX系统中的邮件服务器，阐述了通过使用Sendmail配置邮件中继域文件relay-domains和Ac-cess文件防止邮件攻击的技术．     

Dating in the time of “relational filter bubbles”: exploring imaginaries,perceptions and tactics of Italian dating app users

ABSTRACT

In this paper, we address algorithmic imaginary, perception and tactics of Italian dating apps users. Little attention has hitherto been devoted to the ways in which the algorithms employed by mobile dating platforms (to rate users, to manage user visibility, to arrange results) might contrast, or enhance, people’s homophily. Our goal is to explore whether and how mobile dating algorithms modify the perception of what we define as “relational filter bubbles”; and whether, and how, users believe dating algorithms reshape (extend or limit) the heterogeneity of their intimate interactions. The paper builds on literature addressing online dating, the datafication of society, the rise of the so-called quantified self, and of the algorithmic culture. We organized 4 focus groups involving Italian dating apps users, who reported a variety of sexual orientations and of dating apps usage. Overall, while dating apps’ algorithms operate in an opaque way, participants developed an “algorithmic imaginary”. Moreover, they appreciate the role of mobile dating apps in reinforcing their relational homophily (their tendency to like people that are “similar” to them), whilst, at the same time, mainly using these apps for increasing the diversity of their intimate interactions in terms of extending their preexisting networks.     

一种概率密度的中值滤波算法

提出了一种新的图象噪声消除算法,该方法可以快速有效地去除图象中的脉冲噪声,并保留图象的细节.该算法主要通过利用象素点的值在滤波窗口出现的概率密度信息,进行噪声的判定及滤波过程的介绍,对本算法进行了分析仿真,结果表明该算法去除噪声与保留细节的效果好,且运算速度较快.     

自适应信号分解实验装置

用开关电容滤波器和锁相环构成的二阶自适应带通滤波器,运用锁相环原理为开关电容滤波器提供时钟信号,使其带通滤波中心频率将跟随输入信号频率变化,克服了传统滤波器带通中心频率不易改变的缺点。实验结果表明,该滤波器较好地实现了自适应带通滤波的功能,可用于教学和科研中周期信号的分解。     

WPT-based modal control on distributed structures with MRF-04K damper

The magnetorheological (MR) fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this paper, a novel modal controller using wavelet packet transform (WPT) is proposed for the vibration control of distributed structures. In the proposed control system, the WPT method is utilized to decompose the acceleration measurement and select the modes containing most of the WPT energy component as the dominant modes. Then, a modal controller is designed to control the dominant modes and the optimal active control force is solved. Finally, Clipped-optimal con- trol law is adopted to determine the voltage applied to each MR damper. A Kalman-filter observer, which estimates the full controlled modal states from local accelerometer feedbacks, is designed for rendering the controller to be more applicable to distributed structures with a large number of degrees of freedom. A numerical example of a stadium roof structure installed with MRF-04K damper is presented. The effectiveness of the controller is evaluated under both Tianjin and El Centro earthquake excitations. The superior performance and adaptability of the controller for versatile loading conditions are demonstrated through the comparison with traditional truncated modal controller.     

降低循环水场循环水浊度新方法探究

针对循环水浊度偏高问题,分析造成悬浮物、浊度升高的原因,通过增加隔油池排泥反洗实验,探究降低循环水浊度的新方法,评价排泥反洗中试装置中,浅层压力式过滤罐与滤池降低浊度的效果对比,在加药和不加药两种情况下,浊度和去除率的情况。     

O-200kPa气动控制信号检测系统的设计

为检测气动执行器常用控制信号0-200kPa气压,设计了基于MSP430单片机和压阻式压力传感器MPX2200的气压检测系统．阐述了检测系统的软硬件设计,给出了MPX2200恒流源电路和放大倍数可调的两级放大电路,介绍了软件设计中的标度变换、分段插值和中值滤波方法．该系统在电路设计上选用仪用放大器、单片机自带AD转换器,所用元器件少、功耗低、精度高,可广泛应用于智能化、低功耗化的气动执行机构及其元器件的设计中．     

无人直升机旋翼转速控制器设计

针对无人机的特殊性以及对电机动态性能的要求,设计了一种以ARM芯片LPC2148为核心的旋翼转速控制器。首先分析了直升机的飞行特点以及原旋翼转速控制器的不足,设计基于EKF和矢量控制的新旋翼转速控制器,并对扩展卡尔曼滤波法和矢量控制的模块进行说明,且给出了MATLAB仿真结果,验证了控制系统的正确性。