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A B S T R A C T Viral noncoding (nc) RNAs have been shown to play important roles in viral life cycle. Many viruses employ different mechanism to produce ncRNAs. Here, we report that coronavirus infectious bronchitis virus (IBV) produces a novel ncRNA in virus-infected cells. This ncRNA consists of 563 nucleotides excluding a poly(A) tail, is mainly derived from the 3′-untranslated region of IBV genome, and contains a 63-nt-long of terminal leader sequence derived from the 5′ end of the viral genome. Using mutagenesis and reverse genetics, we reveal that this ncRNA is a subgenomic RNA generated by discontinuous transcription mechanism.

Leakage of stray current can cause serious problems by accelerating the corrosion process of a buried pipeline in the subway. A multi-physical finite element model of the DC-subway traction system was established in this study, and the dynamic process of the stray current corrosion on buried pipeline was calculated according to the real time traction conditions. In this study, the corrosion rate variation of stray current is evaluated, and the corrosion trend of stray current is quantitatively calculated. The model simulation shows that the stray current corrosion is significantly higher than other processes during the acceleration process of the subway locomotive. And the potential of the buried pipeline reaches a maximum value when an up-rush of traction current occurs. The corrosion is mainly concentrated in the anode region of the buried pipeline, and the closer the buried pipeline is to the rail the more serious the corrosion is. A corrosion experiment of N20 carbon steel was carried out and verified by finite element model. The results further show that the finite element model can quantitatively calculate and predict the mass loss of buried metal caused by stray current corrosion.

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Crack orientation plays a vital role in structural integrity analysis, which provides quantitative crack growth and structural failure information. Even though many structural health monitoring systems can detect crack location and length, only few methods are capable of detecting crack orientation. Recently, we have shown that an electromagnetically induced acoustic emission method can detect active defect with elastic waves. In this article, the ability of the electromagnetically induced acoustic emission method for finding the orientation of cracks is studied. Based on the freeelectron theory and electroplastic flow concept, the mechanism of electromagnetically induced acoustic emission effect will be explored at the microscopic level. By studying the energy exchange between the free electrons and the metallic dislocations, the total energy and the trajectory of drift electrons radiated during the electromagnetic loading can be evaluated theoretically. The Hilbert-Huang transform method is applied for extracting properties of the experimental electromagnetically induced acoustic emission signals. The results showed that the correlation coefficients between the original signals and the intrinsic mode function components, as well as the instantaneous frequency of the intrinsic mode function, depended on the crack orientations. Hence, experimental results and analysis confirm that the crack orientation can be monitored by the crack-induced intrinsic mode function extracted from the electromagnetically induced acoustic emission signals.

This study presents a modified one-side pitch-catch electromagnetic acoustic transducer (EMAT), the optimized design improves the horizontal static magnetic field excitation and helps to enhance the generation and reception of the Lamb wave. A coupling model is applied to characterise and analyse the new design in detail. The model indicates that the optimized magnetic field with an increased peak flux density compared to the traditional magnetic configuration of EMAT. As a result, the transduction efficiency of the one-side pitch-catch design is dramatically improved ingeneration and reception process. Experiments verify that a measurement system using the modified one-side pitch-catch design is improved by a factor of 3.3, when compared to conventional one-side pitch-catch design.INDEX TERMS EMAT, Lamb waves, magnetic circuit optimization, one-side pitch-catch.

Stray current directly affects the regular operation of electrical equipment and facilities in the subway DC traction power supply system. Therefore, it is worthwhile to study the stray current distribution characteristics during train operation and the quantitative corrosion of buried pipelines. This paper introduces the traction characteristics of power carriages and power wheelsets of subway vehicles into the DC traction process. A finite element model considering the dynamic distribution of stray current under the actual operation of subway vehicles is established. The interference characteristics of stray current and the contribution of power sources under the multiparticle model are analyzed. The rail insulation damage caused by long service time and the quantitative calculation of rail and buried pipeline corrosion is considered. The model results show that the stray current in the buried pipeline under the multiparticle model is more accurate and more suitable for the protection in the actual subway. The quantitative corrosion of the buried pipeline is stronger than the partial insulation damage environment when the rail is not insulated. The rail and buried pipeline corrosion at both ends of the insulation damage position is relatively severe. The stray current distribution model established in this paper gives full play to the solution advantages of the finite element method and provides a new idea for the quantitative calculation of buried pipeline corrosion.