振动信号分析是轴承故障诊断中的重要技术手段之一。变转速工况下的滚动轴承振动信号是典型的非平稳信号,并且在转频变化较小的工况中还存在噪声干扰的问题,使传统的时频分析技术难以应用。为解决该问题,提出了一种基于经验最优包络(emp...振动信号分析是轴承故障诊断中的重要技术手段之一。变转速工况下的滚动轴承振动信号是典型的非平稳信号,并且在转频变化较小的工况中还存在噪声干扰的问题,使传统的时频分析技术难以应用。为解决该问题,提出了一种基于经验最优包络(empirical optimal envelope,EOE)的局部均值分解(local mean decomposition,LMD)和采用分段线性插值的计算阶次跟踪(computing order tracking,COT)算法相结合的故障诊断方法。首先,确定低通滤波器的截止频率和滤波阶数,对滚动轴承振动信号进行滤波,并对滤波后的包络信号进行COT,以获得角域平稳信号。然后,利用EOE_LMD对重采样后的平稳信号进行处理,得到若干乘积函数(product function,PF)分量。最后,通过计算各分量的信息熵和相关系数,选取合适的分量进行阶次分析,以判断变转速滚动轴承的故障类型。结果表明,该方法可以消除转速波动对故障特征提取的影响,在不同转速变化条件下对滚动轴承具有良好的故障诊断能力。展开更多
Background and Study Aim: Eosinophilic esophagitis (EoE) is a clinicopathological disease characterized by esophageal dysfunction and marked esophageal eosinophilic infiltration. It shows a marked increase in incidenc...Background and Study Aim: Eosinophilic esophagitis (EoE) is a clinicopathological disease characterized by esophageal dysfunction and marked esophageal eosinophilic infiltration. It shows a marked increase in incidence and prevalence and has been associated with gastroesophageal reflux disease (GERD). The aim of this work was to detect the prevalence of EoE in Egyptian adult patients presenting with upper gastrointestinal symptoms and to clarify its clinical pattern and the possibility of its overlap with GERD. Patients and Methods: The study included 91 adult patients presenting with various upper gastrointestinal symptoms. Upper gastrointestinal endoscopy was done and esophageal biopsies were taken. The presence of >15 eosinophils per high power field together with a history of intake of proton pump inhibitors for at least 3 weeks without improvement was used as prerequisite diagnostic criteria for EoE. Results: Classification of the patients was based on both endoscopic and histo-pathological findings. Accordingly, out of the 91 patients, 70 had GERD (76.9%);58 of them had erosive reflux disease (ERD) and 12 had endoscopically normal esophagus but with histopathological changes compatible with reflux esophagitis and were classified as non erosive reflux disease (NERD). Eighteen patients had normal endoscopic and histopathological esophagus (19.8%), and 3 patients had EoE (3.3%), with an overlap between ERD and EoE in one patient. The mean age of EoE patients was 41.6 ± 11.7 years. Two of them were males and one was a female. All of the 3 patients complained of dysphagia and none complained of heartburn. The endoscopists did not report any endoscopic findings characteristic of EoE. Conclusion: The prevalence of EoE is low in adult Egyptian patients presenting with upper gastrointestinal symptoms. Dysphagia is the main presenting symptom of EoE while heartburn is not characteristic of the disease. Normal esophagus endoscopically does not exclude EoE.展开更多
工业以太网是计算机革命带来的新型基础设施。工业4.0时代的到来,对工业以太网的拓展能力、集成能力和确定性通讯能力提出了更高的要求。针对传统的工业以太网在应用中遇到的网络结构不灵活、广播风暴风险等问题,从以太网交换机的工作...工业以太网是计算机革命带来的新型基础设施。工业4.0时代的到来,对工业以太网的拓展能力、集成能力和确定性通讯能力提出了更高的要求。针对传统的工业以太网在应用中遇到的网络结构不灵活、广播风暴风险等问题,从以太网交换机的工作原理出发,设计了一套新型的工业以太网网络架构,并命名为EOE(Ethernet Over Ethernet)。这种网络架构兼容传统的以太网架构和硬件设备,支持灵活多变的拓扑结构,从而为多网融合提供了技术基础。与此同时,加入了确定性通讯机制,从而确保根除网络风暴。展开更多
文摘振动信号分析是轴承故障诊断中的重要技术手段之一。变转速工况下的滚动轴承振动信号是典型的非平稳信号,并且在转频变化较小的工况中还存在噪声干扰的问题,使传统的时频分析技术难以应用。为解决该问题,提出了一种基于经验最优包络(empirical optimal envelope,EOE)的局部均值分解(local mean decomposition,LMD)和采用分段线性插值的计算阶次跟踪(computing order tracking,COT)算法相结合的故障诊断方法。首先,确定低通滤波器的截止频率和滤波阶数,对滚动轴承振动信号进行滤波,并对滤波后的包络信号进行COT,以获得角域平稳信号。然后,利用EOE_LMD对重采样后的平稳信号进行处理,得到若干乘积函数(product function,PF)分量。最后,通过计算各分量的信息熵和相关系数,选取合适的分量进行阶次分析,以判断变转速滚动轴承的故障类型。结果表明,该方法可以消除转速波动对故障特征提取的影响,在不同转速变化条件下对滚动轴承具有良好的故障诊断能力。
文摘Background and Study Aim: Eosinophilic esophagitis (EoE) is a clinicopathological disease characterized by esophageal dysfunction and marked esophageal eosinophilic infiltration. It shows a marked increase in incidence and prevalence and has been associated with gastroesophageal reflux disease (GERD). The aim of this work was to detect the prevalence of EoE in Egyptian adult patients presenting with upper gastrointestinal symptoms and to clarify its clinical pattern and the possibility of its overlap with GERD. Patients and Methods: The study included 91 adult patients presenting with various upper gastrointestinal symptoms. Upper gastrointestinal endoscopy was done and esophageal biopsies were taken. The presence of >15 eosinophils per high power field together with a history of intake of proton pump inhibitors for at least 3 weeks without improvement was used as prerequisite diagnostic criteria for EoE. Results: Classification of the patients was based on both endoscopic and histo-pathological findings. Accordingly, out of the 91 patients, 70 had GERD (76.9%);58 of them had erosive reflux disease (ERD) and 12 had endoscopically normal esophagus but with histopathological changes compatible with reflux esophagitis and were classified as non erosive reflux disease (NERD). Eighteen patients had normal endoscopic and histopathological esophagus (19.8%), and 3 patients had EoE (3.3%), with an overlap between ERD and EoE in one patient. The mean age of EoE patients was 41.6 ± 11.7 years. Two of them were males and one was a female. All of the 3 patients complained of dysphagia and none complained of heartburn. The endoscopists did not report any endoscopic findings characteristic of EoE. Conclusion: The prevalence of EoE is low in adult Egyptian patients presenting with upper gastrointestinal symptoms. Dysphagia is the main presenting symptom of EoE while heartburn is not characteristic of the disease. Normal esophagus endoscopically does not exclude EoE.
文摘工业以太网是计算机革命带来的新型基础设施。工业4.0时代的到来,对工业以太网的拓展能力、集成能力和确定性通讯能力提出了更高的要求。针对传统的工业以太网在应用中遇到的网络结构不灵活、广播风暴风险等问题,从以太网交换机的工作原理出发,设计了一套新型的工业以太网网络架构,并命名为EOE(Ethernet Over Ethernet)。这种网络架构兼容传统的以太网架构和硬件设备,支持灵活多变的拓扑结构,从而为多网融合提供了技术基础。与此同时,加入了确定性通讯机制,从而确保根除网络风暴。
