宽覆盖锁相调频技术

本文侧重分析了自动频偏控制系统的工作原理,推导出环路方程,阐述了几种主要的特性。     

大动态PCM/FM信号的载波频率同步

针对大动态脉冲编码-频率调制（PCM/FM）遥测信号的载波频率同步,提出了基于快速傅里叶变换（FFT）及频谱重心的载波频率估计方法,并采用了频谱叠加及频谱截取的优化方法提高算法估计精度。相对于其他基于FFT的频率估计算法,频谱重心法有着更高的估计精度及更好的抗噪声性能,而且复杂度代价很小。仿真的均方误差结果表明,基于FFT长度为2 048和2块叠加以及保留信号99.9%能量的频谱截取方案有最好的估计性能。在最大多普勒频率、多普勒一阶变化率及二阶变化率分别为0.5倍、0.3倍及0.2倍符号率的大动态条件下,基于频谱重心法的二阶锁频环能够较好地完成载波频率跟踪。误码率曲线表明,经过频偏校正后的多符号非相干解调（MSD)性能与无频偏情况相比,无性能损失。     

FM 解调及AFC算法的VHDL设计实现

根据遥测中频PCM/FM信号的解调原理,介绍了FM解调及 自动频率控制（AFC）设计的理论架构和实现方法,通过理论分析、公式推导和Matlab仿真 等手段证明了方法的正确性,在此基础上完成VHDL程序设计,最后进行了仿真测试和实验验 证。仿真结果和实验结果证明了该实现方法的可行性。     

Profibus-DP网络的应用及故障分析处理——以涟源钢铁有限公司为例

文章简单介绍了Profibus-DP网络在笔者所在的涟源钢铁有限公司的使用情况,分析了几个典型案例,对在使用过程中发生的常见故障进行了分析并介绍了相应的处理方法。     

The wage gap between Francophones and Anglophones: a Canadian perspective, 1970–2000

Abstract. The wage gap between Francophone and Anglophone men from 1970 and 2000 fell by 25 percentage points within Quebec, but only by 10 points Canada‐wide, largely because the wages of Quebec Anglophones fell by 15 points relative to other Canadian Anglophones. Accordingly, the Canadian measure of the Francophone gap better reflects the changing welfare of Francophones than the Quebec measure. Over half of the reduction in the Canadian Francophone wage gap is explained by rising Francophone education levels. In Quebec, the declining number and relative wages of Anglophone workers is best explained by a falling demand for English‐speaking labour.     

中国铁路第六次大面积提速调图200 km/h速度级固定设施技术创新

比较国外和我国铁路既有线200 km/h提速技术,我国既有线时速200 km/h提速技术在推进自主创新、系统集成创新和引进、消化吸收再创新方面结出了丰硕成果,部分技术已达世界先进水平,其中200 km/h速度级固定设施技术创新成果,为第六次大面积提速调图提供了强大的技术支撑.     

The impacts of public news announcements on intraday implied volatility dynamics

We examine the responses of intraday option-implied volatilities to scheduled announcements of macroeconomic indicators. The increase in implied volatility around macroeconomic news announcements is more pronounced for puts than for calls and is stronger for announcements made during trading hours than for those made during nontrading hours. These effects are also more pronounced in the crisis and postcrisis periods than in the precrisis period. Monetary policy announcements have a more substantial impact on volatility than other announcements have, even after controlling for news surprise components. The impact appears to be greater for policy rate hikes than for policy rate cuts.     

调频锁相环路中分频器对调频的影响

本文详细分析了调频锁相环路中分频器的作用,给出了选择分频比的依据。     

Financial behaviours of consumers in credit counselling

Positive financial behaviours of consumers are examined using a national sample of consumers who use credit counselling services in the US from a behavioural economic perspective. The findings indicate that consumers in credit counselling may follow a hierarchical pattern in their financial behaviours, paying off debts and adjusting spending before considering saving. Consumers who are older, have a part‐time job (vs. the unemployed), and report a more secure retirement, a better family relationship, and a higher score of self‐evaluation of financial behaviours are likely to report more positive financial behaviours. Reporting more financial behaviours and a higher score of self‐evaluation of financial behaviours, along with several demographic and perception variables, tend to reduce financial stress and increase financial satisfaction among consumers who use credit counselling services.     

西门子S7—200替换S5序列PLC在鼓风机改造中的应用

福州祥坂污水处理厂有4台鼓风机,采用的是西门子的S5-101U序列PLC。由于SS序列PLC当前已处于淘汰状态,备件难以获得,并且价格昂贵,所以需要对鼓风机系统进行升级。考虑到相同品牌的兼容性,所以采用了主流的S7～200序列PLC进行改造。改造完成后,鼓风机达到了原系统的所有功能,并且在原基础上增加了远程监控和操作功能。使鼓风机子系统和全厂自动化得到了整合。