To improve the reconstruction image spatial resolutions of ultrasonic guided wave ray tomography, a sparse model, based on the differences between the inspected and original slowness of the ultrasonic guided waves propagating in the plate-like or pipe-like materials, is first proposed in this paper. Unlike the conventional ultrasonic guided wave tomography whose reconstruction image resolutions are limited by an underdetermined linear model, analyses show that our new model, although it is also underdetermined, can give the optimal solution of the reconstruction image when the constraints on the sparsity of the slowness difference distribution are valid. The reason for the validation of the sparse constraints on the corrosions of the materials is explained. Based on our new model, a least absolute shrinkage and selection operator (LASSO) approach to do the thickness change mapping of a structure health monitoring (SHM) application is then formulated. Analyses also show that the visible artifacts can be avoided using our method, and the spatial resolutions of reconstruction image by our approach can further be improved by increasing the number of grids in the calculation. The approach is validated by experimental work on an aluminum plate. It is also shown that compared to the conventional ray tomography, the presented method can achieve a relatively high spatial resolution, with good suppression of artifacts.

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Along with the continuous development of Ethernet technology based on optical fiber communication, the current trunk network of Distribution Automation System has been mostly built on optical network communication mode with the other methods playing the supplementary roles. No matter adopting the fiber optic communication module or the industrial Ethernet exchanger, the optical Ethernet could offer the reliable Ethernet reusable technology, which could dramatically improve the reliability and synchronization of the DA system by distributing the working bandwidth more efficiently and building independent communication virtual channels without adding the number of optic fibers.With its core functions of quick trouble diagnosis, isolating and recovering, the Feeder Automation System (FA) is one of the most important parts of Distribution Automation System (DA). The development of communication technology has brought the revolutionary effects to FA. First of all, the optical Ethernet could offer the channel multiplexing technology, which provides a separate channel for troubleshooting of FA as well as the communication channel for three normal remote functions of terminal units. It is brand new and different data communication processing mode compared with conventional one, which could dramatically improve the synchronization of data transmission and the reliability of FA system. Secondly, during the process of FA troubleshooting, the definition mode based on the fixed value down-installed is widely used. With the independent channel of FA, the terminal unit parameter could be customized and installed flexibly. The FA operation mode could be set according to the practical site situation. Namely, the FA system could be set flexibly as: the operation mode of voltage model, the operation mode of electric current model, the operation mode of reclosers and the operation mode of mixing models. The setting of these operation modes could be freely adjustable instead of being preset unchangeably in the factory, which makes it more convenient and practical to maintain the automation system. In view of the flexibility and particularity of rated load condition and operation configuration of DA, the online DTS of DA is proposed in this article to simulate the running situation on site to validate the validity of terminal configuration and rated-loading operation setting.

It is of great practical significance to analyze the hot issues, research frontiers, and trends concerning the relationship between air pollution and public health and to adopt reasonable strategies to control air pollution and prevent health hazards for follow-up research in this field. Unlike traditional literature reviews, this paper adopts a visual, flexible, and scientifically systematic approach to the analysis, which makes these analysis results more intuitive and comprehensive. Based on the core collection of the Web of Science and CNKI databases, this paper uses CiteSpace software to draw and comment on the maps of Chinese and English keywords, publishing time, author, country, and research institutions in this field. The results show the following: (1) The number of studies on the relationship between air pollution and health has increased year by year; researchers have formed sub cooperation networks, and the trend of cooperation and exchange has become more and more obvious in recent years; the impact of air pollution on health is a hot topic in the world. (2) Research hot topics mainly focus on the selection of air pollutants, health economic consequences of air pollution and the global burden of disease it causes, health indicators, research samples, which are gradually being refined, the synergistic governance of air pollution, and climate change. (3) The analysis of research frontiers and trends reveals that, first, the study of air pollutants in the English literature has undergone a refinement from nitrogen dioxide to fine particulate matter, and the sources of air pollutants in the Chinese literature have undergone changes in the petrochemical industry, indoor formaldehyde pollution, and haze. Second, atmospheric pollution has a significant negative impact on health, increasing the incidence of respiratory and cardiovascular diseases, and even causing death. Third, sustained exposure to pollution then causes greater damage to health and will be a key direction for future research. Fourth, the literature not only studies the correlation but also emphasizes the causal inference between air pollution and health and measures the economic costs associated with health. Finally, air pollution and climate change need to be governed synergistically. The article points out that the three areas of sustained pollution exposure, indirect consequences of negative health effects of air pollution, and air pollution and climate change may be the future focus of the field.

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