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Predicting the aerodynamic phenomena in a train-tunnel system is important for increasing the speed of railway trains. Among these phenomena, many studies have focused on the effects of pressure; however, only a few studies have examined the effects of flow velocity. When designing train roof equipment such as a pantograph and an aerodynamic braking unit, it is necessary to estimate the flow velocity while considering the influence of the boundary layer developed on the train roof. Until now, numerical simulations using a one-dimensional model have been utilized to predict the flow velocity around a train traveling through a tunnel; however, the influence of the boundary layer cannot be taken into consideration in these simulations. For this purpose, the authors have previously proposed a simple calculation method based on a steady incompressible tunnel flow model that can take into account the influence of the boundary layer, but this method could not incorporate the unsteadiness of the flow velocity. Therefore, in this study, the authors extend the previous simple calculation method such that it can be used for an unsteady incompressible tunnel flow. The authors compare the calculation results obtained from the extended method with the results of a model experiment and a field test to confirm its effectiveness.

It is necessary to obtain the aerodynamic force coefficients of the train on the embankment for the assessment of the running safety in a crosswind. In general, wind tunnel tests are conducted using the static train model on the embankment model. In this paper, the influence of the airflow condition and the distance from the upstream end of the embankment model to the train model on the aerodynamic force coefficients is investigated. In the wind tunnel tests, the side force coefficients (CS) reached their maximum values at a yaw angle of 50° in smooth flow while they reached their maximum values at a yaw angle of 90° in atmospheric boundary layer (ABL) flow. Large-eddy simulation (LES) was made on the flow around the train model on the embankment, and it was found that CS became larger as the upstream embankment length became smaller owing to the vortex generated near the upstream end of the embankment at the yaw angle of 50°. LES on the flow around the embankment model showed that the distance over which the flow field was affected by this vortex was 16 times the height of the embankment model in smooth flow, and it was 12 times in ABL flow at the yaw angle of 50°.

A pantograph mounted on a high-speed train roof is exposed to high-speed air flow while traveling, and lift force is generated in the pantograph. To ensure high current collecting performance of the pantograph, it is important to appropriately adjust the lift force generated in the pantograph. The flow velocity along the roof of a train has a significant influence on the lift force. In this study, we proposed a simple calculation method that enabled us to easily calculate the flow on the train roof in a tunnel using a personal computer. To validate the effectiveness of the proposed method, model experiments were carried out and calculation and experimental results were compared. Furthermore, the influence of hydraulic friction coefficients on train roof flow velocity was examined using the proposed method, which was not time consuming.

In flowering plants, the tapetum, the innermost layer of the anther, provides both nutrient and lipid components to developing microspores, pollen grains, and the pollen coat. Though the programmed cell death of the tapetum is one of the most critical and sensitive steps for fertility and is affected by various environmental stresses, its regulatory mechanisms remain mostly unknown. Here we show that autophagy is required for the metabolic regulation and nutrient supply in anthers and that autophagic degradation within tapetum cells is essential for postmeiotic anther development in rice. Autophagosome-like structures and several vacuole-enclosed lipid bodies were observed in postmeiotic tapetum cells specifically at the uninucleate stage during pollen development, which were completely abolished in a retrotransposon-insertional OsATG7 (autophagy-related 7)-knockout mutant defective in autophagy, suggesting that autophagy is induced in tapetum cells. Surprisingly, the mutant showed complete sporophytic male sterility, failed to accumulate lipidic and starch components in pollen grains at the flowering stage, showed reduced pollen germination activity, and had limited anther dehiscence. Lipidomic analyses suggested impairment of editing of phosphatidylcholines and lipid desaturation in the mutant during pollen maturation. These results indicate a critical involvement of autophagy in a reproductive developmental process of rice, and shed light on the novel autophagy-mediated regulation of lipid metabolism in eukaryotic cells.