Search

Permanent magnet synchronous motors (PMSMs) have been employed in the direct drive traction system of locomotives as the traction motor. Due to the unique traction structure of the direct drive system, complicated excitations such as track irregularity and harmonic torque have a direct effect on the dynamic performance of the motor and other key components of the locomotive. However, the dynamic characteristics under this effect and influencing law have not been revealed completely. This paper develops a dynamics model of a locomotive with direct drive traction system which enables considering the electromechanical coupling effect between the vehicle subsystem and the PMSM control subsystem. The nonlinearity of the wheel–rail contact and flexible transmission coupling are taken into account in this model. By using this model, the dynamic responses of the locomotive are analysed under electrical and mechanical excitations. The results indicate that the harmonic components in the electrical subsystem have considerable effects on the key components of the locomotive, such as the wheelsets and the motors. It can also cause resonance in the mechanical transmission system when the locomotive is operating at a specific speed. This resonance can be eliminated by adopting the harmonic suppression algorithm. [ABSTRACT FROM AUTHOR]

Antibiotic resistance poses a significant threat to the public health domain. A favorable platform for generating and disseminating antibiotic-resistant genes (ARGs) and antibiotic-resistant bacteria (ARB) is provided by landscaped fish ponds created by urbanization. This research delved into the effects exerted by different concentrations of specific antibiotics, namely tetracycline and ciprofloxacin, on the microbial community composition present in water samples obtained from a landscape pond. Additionally, we analyzed the abundance of ARGs and the class 1 integron-integrase gene (intI1), and identified potential hosts of ARGs. The results indicated that the consistent administration of antibiotics significantly influenced the microbial community structure, resulting in variations within both bacterial communities and functionalities. Furthermore, the absolute quantities of ARGs, including tetA, tetC, qnrA, and qnrS, as well as the integrase gene intI1, exhibited augmentation in response to varying types and concentrations of antibiotics. Notably, the regular input of low concentrations of antibiotics produced higher levels of abundance of ARGs than the regular input of higher concentrations of antibiotics. The use of different types of antibiotics led to diverse host bacteria structures. [ABSTRACT FROM AUTHOR]

Pregnant women and children sometimes had to undergo chest computed tomography (CT) scans during the Corona Virus Disease 2019 (COVID-19) pandemic. This study estimated the fetal and pediatric doses from chest CT scans. Organ doses and effective doses were calculated using the VirtualDose-CT software. Two groups of computational human phantoms, pregnant females and pediatric patients were used in this study. The results of doses normalized to volumetric CT Dose Index (CTDIvol) can be used universally for other dosimetry studies. Based on our calculations and international survey data of CTDIvol, fetal absorbed doses from COVID-19-related chest CT were found to be 0.04–0.36, 0.05–0.44 and 0.07–0.61 mGy for 3, 6 and 9 months of pregnancy, respectively. When the scan range is extended to the abdominal region, fetal doses increase by almost 4-fold. Effective doses for COVID-19-related chest CT were 1.62–13.77, 1.58–13.46, 1.57–13.33 and 1.29–10.98 mSv for the newborn, 1-, 5- and 10-y-old children, respectively. In addition, the effects of specific axial scan ranges exceeding the thorax region were evaluated. Although doses from chest CT scans are small, such data allow radiologists and patients to be informed of the dose levels and ways to avoid unnecessary radiation. [ABSTRACT FROM AUTHOR]