单周期控制Boost—PFC基于Saber的设计与仿真

单周期控制策略简单可靠,动态响应速度快,能很好地抑制输入电压扰动和负载突变。本文阐述了单周期控制Boost—PFC的工作原理,对单周期控制Boost—PFC进行了基于Saber软件的CAD设计和仿真。仿真结果表明,单周期控制适用干Boost变换器,能够实现功率因数校正。     

TDR特性阻抗测试技术应用

当传输线的阻抗不连续时,将会产生多重反射,并破坏电路系统信号的完整性。通常使用时域反射计法（TDR）测量传输线的特性阻抗值。TDR法测试具有快速、简单、经济、实用、精度较高的特点。该测试方法又分为单端测量和差分测量两种,目前,单端测量的结果比较稳定,也较为常用。     

基于灰度共生矩阵的图像纹理特征提取分析

图像纹理作为一种重要的视觉手段,是图像中普遍存在而又难以描述的特征。目前常用的纹理特征提取的方法主要有统计方法、模型方法、信号处理方法和结构方法。灰度共生矩阵即为灰度级的空间相关矩阵,以其为基础的统计方法通过对矩阵统计量的求取较好地提取到了纹理特征,通过选取关键参数编程并进行仿真实现,分别求取了四个方向的灰度共生矩阵及其特征量来分析图像的纹理特征。     

RFID技术在电网资产全寿命周期管理应用模式探讨

为了配合电网企业建立RFID资产实物标识电子身份证系统,集成资产的实物流、信息流和价值流,实现账、卡、物相符一致,实现资产管理各阶段信息共享及开展资产全生命周期的跟踪管理,同时也为了提高电网设备的现代化管理水平,文章总结了多年来在电网设备RFID实物标识实施的切身体会,对RFID在国内外电力电网设备的应用方面进行了研究,重点对RFID技术在电网资产全寿命周期管理模式进行了探讨。     

人机界面可用性测试与评估研究综述

介绍并评述人机界面可用性的定义、可用性测试与评估的指标及方法。学术界对于可用性的内涵已基本达成共识,但大多针对不同界面选取不同的测试与评估指标及权重,测试与评估方法也大都停留于主观评价,还未能深入探讨用户与系统交互过程中的内在心理机制。     

基于统计阈值的Snort规则集动态产生的设计与实现

Snort作为开源的入侵检测系统,利用定义的静态规则集合实现对网络的入侵事件的检测。本文分析入侵检测系统的基本原理和模型,阐述Snort入侵检测系统部署到网络时,其静态规则集的配置方法,根据统计流量阈值和告警频率阈值动态产生动态规则集的方法,改进并提高了部署Snort应有的灵活性。     

基于DMT的1553B带宽扩展研究

由于传统的MIL-STD-1553B总线难以满足高速数据传输需求且更换现有总线代价过高,因此迫切需要在不影响现有基带通信的条件下升级1553B系统以提供高速通信接口。本文分析1553B的信道特性并据此选择频谱利用率高、抗频率选择性衰落的离散多音调制(DMT)作为扩展带宽的技术,基于离散多音调制,提出一个与现有通信相互兼容的扩展方案以显著提高传输速率,并对该方案涉及的关键技术进行介绍。     

Assessing terrestrial wildlife populations in the Toronto and Region Area of Concern

Beneficial use impairments (BUIs) under the Great Lakes Water Quality Agreement identify environmental issues requiring remedial action within the Great Lakes Areas of Concern (AOCs). We conducted this study to support the assessment of the wildlife component of BUI 3: degradation of fish and wildlife populations. We compared bird and amphibian (frogs and toads) data from the Toronto and Region Conservation Authority’s Terrestrial Long-term Monitoring Program in the Toronto and Region AOC to an adjacent, but otherwise similar, reference watershed, Duffins Creek. Twelve of 13 targets were met within the AOC for forest bird, wetland bird, meadow bird and amphibian populations based on averages of mean annual values at sites within the AOC that were within two standard deviations of averages at sites in the Duffins Creek reference watershed between 2008 and 2017. Even though wildlife populations within the AOC were within the normal range of variability expected from a reference watershed, they were often at lower levels than within the Duffins Creek reference watershed. In addition, forest bird and amphibian populations were negatively affected by urbanization within the AOC and meadow bird indices declined. We conclude that while wildlife populations within the AOC currently meet targets for BUI 3, they continue to be negatively impacted by numerous stressors that are primarily related to past and ongoing urbanization. Thus, continued restoration of wildlife habitat and protection of existing habitat within the AOC is highly recommended.     

Towards improving an Area of Concern: Main-channel habitat rehabilitation priorities for the Maumee River

The Maumee River watershed in the Laurentian Great Lakes Basin has been impacted by decades of pollution and habitat modification due to human settlement and development. As such, the lower 35 km of the Maumee River and several smaller adjacent watersheds comprising over 2000 km² were designated the Maumee Area of Concern (AOC) under the revised Great Lakes Water Quality Agreement in 1987. As part of pre-rehabilitation assessments in the Maumee AOC, we assessed fish and invertebrate communities in river km 24–11 of the Maumee River to identify: 1) areas that exhibit the highest biodiversity, 2) habitat characteristics associated with high biodiversity areas, 3) areas in need of protection from further degradation, and 4) areas that could feasibly be rehabilitated to increase biodiversity. Based on benthic trawl data, shallow water habitats surrounding large island complexes had the highest fish diversity and catch per unit effort (CPUE). Electrofishing displayed similar fish diversity and CPUE patterns across habitat types early in the study but yielded no discernable fish diversity or CPUE patterns towards the end of our study. Although highly variable among study sites, macroinvertebrate density was greatest in shallow water habitats <2.5 m and around large island complexes. Our results provide valuable baseline data that could act as a foundation for developing rehabilitation strategies in the lower Maumee River and for assessing the effectiveness of future aquatic habitat rehabilitation projects. In addition to increasing in-channel habitat, watershed-scale improvements of water quality might be necessary to ensure rehabilitation strategies are successful.     

数字证书在环保行业的应用分析

目前国家环保部正在开展的国家环境信息与统计能力建设项目中,采用数字证书为业务系统提供强身份认证服务。详细论述了数字证书在环保部的应用模式,指出了今后的工作方向,同时也指出了现有应用模式的不足之处。