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Good air quality is one of the prerequisites for stable urban economic growth and sustainable development. Air quality is influenced by a range of environmental elements. In this study, seven common air pollutants and six kinds of meteorological data in a major city in China are studied. In this urban setting, the air quality index will be estimated based on a Long Short-term Memory (LSTM)model. To improve prediction accuracy, the Random Forest (RF) method is adopted to choose important features and pass them to the LSTM model as input, an improved sparrow search algorithm (ISSA) is used to optimize the hyperparameters of the LSTM model. According to the experimental findings, the RF-ISSA-LSTM model demonstrates superior accuracy compared to both the basic LSTM model and the ISSA-LSTM fusion model. [ABSTRACT FROM AUTHOR]

In many countries, thunderstorms are the main contributor to hourly extreme precipitation (HEP). Prior studies have shown that the number of thunderstorms decreased steadily in whole country of China; however, HEP has increased significantly in several areas over the past half-century. The role of thunderstorms in changes in HEP occurrence remains largely unknown in China. In this study, for the first time, we used continuous 32-yr records of hourly precipitation and thunder, and the fifth-generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis (ERA5), to analyze changes in thunderstorms under various vertical wind shear (VWS) environments, and their contribution to HEP occurrence. The number of HEP events associated with thunderstorms (TD-HEP) increased significantly in southern China (SC) but decreased significantly in northeastern China (NEC) and east of the Tibetan Plateau (ETP). Weak VWS thunderstorms accounted for 69.1% of TD-HEP in SC. Changes in the most unstable convective available potential energy and precipitable water (PW) in SC favored an increase in weak-VWS thunderstorms, which resulted in an increase of 2.35 h per warm season in overall "station-mean" TD-HEP events from 1980 to 2011. As the major contributor to HEP in NEC, moderate VWS thunderstorms decreased by 0.37 h per warm season, due mainly to a reduction in PW, leading to a negative trend in TD-HEP events. Similarly, the decreasing TD-HEP occurrence on the ETP was due to a decrease of 1.12 h per warm season of moderate VWS thunderstorms. Studying the VWS environments of thunderstorms, and changes therein under a warming climate, can improve understanding of the changes in HEP in China. [ABSTRACT FROM AUTHOR]

As a vital means of transportation to alleviate urban traffic congestion, the metro vehicle has been developing rapidly in China during recent years. For the violent vibration and shock under the frequent switches between traction and braking conditions, higher requirements are put forward in the drive system. The dynamic performance of the traction motor and gearbox, which are the key elements in the drive system of the metro vehicle, is worthy of attention. Based on the classical vehicle–track coupled dynamics and the gear dynamics theory, a vertical–longitudinal dynamics model for a metro vehicle with frame-hung motors and gearboxes is developed in this paper. This model enables the consideration of some complicated excitations, such as external excitations (the track vertical irregularity) and internal excitations (the mesh stiffness and the dynamic transmission error). The established dynamics model is then validated by comparing the simulated results with the field test results in both time domain and time–frequency domain under traction conditions. Consequently, the established dynamics model is demonstrated to be capable of revealing the dynamic performance of the metro vehicle effectively, especially for the traction and transmission system in the entire vehicle vibration environment of a metro. In turn, the results indicate that the gear transmission has a great and lasting effect on the force state of the traction motors and gearboxes compared to its effect on the axle load transfer. [ABSTRACT FROM AUTHOR]

Phytophthora pini is a globally distributed plant pathogen of the Phytophthora genus. This fungus-like organism was recently associated with foliage blight and shoot dieback disease of Rhododendron pulchrum Sweet, which threaten the health of natural ecosystems and horticultural crops in China. Early and accurate detection of P. pini is critical for effective disease prevention and management. In this study, a new target gene Ppinihp1, which is a hypothetical protein, identified from the whole-genome sequence of P. pini was used to establish a conventional polymerase chain reaction (PCR) assay for the detection of this pathogen. PCR results were proved to be positive for P. pini , but negative for other Phytophthora , Pythium , fungal isolates and Bursaphelenchus species. The test was sensitive enough to detect 100 pg of P. pini purified genomic DNA in a 50 μL reaction mixture. P. pini was also detected in artificially inoculated R. pulchrum samples. Finally, this novel Ppinihp1- PCR-assay was able to detect P. pini in 15 of 40 soil samples collected from R. pulchrum fields in Jiangsu, China. This method established the specificity, sensitivity, accuracy and convenience for P. pini detection, offering a dependable tool for the rapid screening of Phytophthora root and stem rot in R. pulchrum. • A new target Ppinihp1 was identified from the whole-genome sequence for PCR detection of P.pini. [ABSTRACT FROM AUTHOR]