重叠滤波多音系统的频偏性能分析及优化

重叠滤波多音(O-FMT)是针对滤波多音(FMT)系统频谱利用率低的缺点而根据超奈奎斯特(FTN)概念引入子载波重叠得到的方案。鉴于O-FMT系统在频偏环境下的性能缺陷，理论分析了频偏对系统信号各部分的影响，比较了O-FMT与正交频分复用（OFDM）系统的抗频偏性能。针对频偏性能优化问题，提出了基于最佳线性无偏估计（BLUE）的改进盲估计算法，设计了基于频域滤波器系数的内嵌结构进行频偏补偿。仿真实验表明，O-FMT相比OFDM具有更好的抗频偏能力，改进的盲估计算法估计值精度更高，抗干扰、抗衰落能力更强，设计的频偏补偿结构可以使系统获得更好的性能。     

卷接包集控系统网络结构的规划分析

为解决绵阳卷烟厂卷包生产过程中存在的设备自控关联性差、连锁方式难以改变、分散的设备与生产运行难以监控、生产管理模式难以满足柔性化生产等问题,引进了卷包集控系统,并对该系统的三层网络结构进行了规划设计、对比分析。通过改变三个网络层次之间的连接方式、网络拓扑结构,使卷接包生产因集控系统网络故障引起的停机时间降到最低。应用效果表明,改进后的网络结构有利于缩小网络规模,控制网络风险,保证数据交换,避免I/O整体失控,有效提高了通信网络的安全性和稳定性及网络资源的利用率。     

一种改进的CPFSK信号频率估计方法

针对突发信号解调中多普勒频偏大的问题，提出了一种改进的连续相位移频键控信号(CPFSK)频率估计方法。首先接收信号平方运算使信号的调制指数加倍，再通过一次离散傅里叶变换(DFT)，用搜索信号平方谱谱峰的方法实现突发信号频率估计。仿真实验表明，在低信噪比条件下，该算法的频率估计精度比经典的相位差频率估计算法提高了20%；该算法与广泛用于高动态突发信号的频率插值估计算法相比，同道干扰信道下信干比改善可达4 dB，DFT长度缩短约1/3。     

试论烟草卷烟机械设备的维修

随着当前科学技术的发展,在烟草检验机械设备研发的过程中,也在向着高速度以及智能化的方向进行研发。对于烟草卷烟机械设备行业来讲,在发展的过程中,针对维修工的要求也在随之提升。所以为了能够保证烟草卷烟机的设备维修工作的相关需求得到满足,需要就当前烟草卷烟机械设备维修工作进行深入探讨。     

Measuring the effectiveness of US monetary policy during the COVID-19 recession

The COVID-19 recession that started in March 2020 led to an unprecedented decline in economic activity across the globe. To fight this recession, policy makers in central banks engaged in expansionary monetary policy. This paper asks whether the measures adopted by the US Federal Reserve (Fed) have been effective in boosting real activity and calming financial markets. To measure these effects at high frequencies, we propose a novel mixed frequency vector autoregressive (MF-VAR) model. This model allows us to combine weekly and monthly information within a unified framework. Our model combines a set of macroeconomic aggregates such as industrial production, unemployment rates, and inflation with high-frequency information from financial markets such as stock prices, interest rate spreads, and weekly information on the Fed's balance sheet size. The latter set of high-frequency time series is used to dynamically interpolate the monthly time series to obtain weekly macroeconomic measures. We use this setup to simulate counterfactuals in absence of monetary stimulus. The results show that the monetary expansion caused higher output growth and stock market returns, more favorable long-term financing conditions and a depreciation of the US dollar compared with a no-policy benchmark scenario.     

张力控制系统在变频造纸设备中的应用研究

张力控制在变频造纸设备中的应用是造纸业的控制难题。本文构建了变频造纸设备张力控制系统模型,通过张力检测装置采集张力值,经PLC接收和判定,最终组成了直接张力控制系统,有效地保证了张力的恒定。同时采用Simulink工具箱,模拟和分析了Matlab软件环境下张力控制系统的仿真运行,最终证实了张力控制系统在变频造纸设备应用中的可行性,为张力控制系统的后续研究与发展指明了方向。     

检测机构仪器设备档案管理初探

阐述了检测机构如何根据《实验室资质认定评审准则》要求,确定仪器设备档案的归档范围、归档内容,并通过建立实验室管理系统使仪器设备档案管理实现数字化、网络化,还对仪器设备档案的归档流程等内容进行了探讨。     

变频器内建PLC在上料机改造中的应用

结合青海百通公司的高炉情况,设计出了上料机改造方案。介绍了台达变频器在高炉卷扬调速系统中的应用情况,给出了电气原理图、注意事项和常见故障处理。实际应用的良好效果验证了该系统的稳定性和可靠性。     

地方高校大型分析测试仪器的管理和使用——以榆林学院为例

本文以榆林学院为例,从地方高校大型分析测试仪器设备发展中呈现出的特点以及存在的问题出发,在提高大型仪器设备的利用率和使用效益等方面进行了分析探讨。     

The impact of reverse logistics process coordination on third party relationship quality: A moderated mediation model for multichannel retailers in the fashion industry

Multichannel retailing is a widely adopted strategy in the fashion industry. Companies in this industry find it a source of competitive advantage to invest in reverse logistics infrastructure. However, limited empirical studies investigate the enablers of the relationship quality between the retailers and their reverse logistics service providers. This study quantifies the impact of reverse logistics process coordination between retailers and logistics service providers on relationship quality. Moreover, it tests the mediating role of reverse logistics service quality and the moderating role of conflict frequency in this relationship. Data were collected through a survey using a purposive sample of 241 retail store managers from the fashion retail industry of Pakistan. For this purpose, a self-administered questionnaire was developed using a five-point Likert Scale to gauge the responses. Conditional process analysis was used to evaluate the moderated mediation model. The findings showed a significant positive impact of reverse logistics process coordination on the relationship quality with a logistics service provider, a significant positive mediation effect of reverse logistics service quality, and a significant moderation effect of conflict frequency on the indirect relationship. However, conflict frequency, contrary to the hypothesis in the study, strengthened the indirect relationship. Furthermore, the moderation effect of conflict frequency on the direct relationship was insignificant. This study will help managers better understand the best practices leading to effective management of reverse logistics processes, particularly product returns.