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The special daytime echoes, which present the V‐shaped echo pattern between 90–180 km ranges in the range‐time‐intensity (RTI) plot, were occasionally recorded by the Hainan coherent scatter phased array radar (HCOPAR) located at the low latitude of China. Four cases with distinct echo traces are presented to display the common characteristics of the V‐shaped echoes. They usually occur between 10:00–15:00 LT in the daytime with the enhanced top frequency and blanketing frequency of Es layer (ftEs and fbEs). Their left/right wings present negative/positive Doppler velocity. A case on 16 August 2015 was investigated by the joint observation of the HCOPAR, the Hainan Digisonde, and a scintillation receiver. The echo spectra show that the V‐shaped echoes were backscattered from the type 2 irregularities. The formation of the V‐shaped echo pattern was due to the leakage of the antenna sidelobe for the very intense scatter from Es layer. The irregularities were found traveling westward with the velocity of 41.12 ± 2.08 m/s. While the occurrence of the intense irregularities, there were periodic peaks appearing on the ftEs and fbEs curves, and the maximum ftEs‐fbEs reached 10.31 MHz. At the same time, the strong ionospheric scintillation event was recorded by the scintillation receiver. The wind shear is considered to produce the sharp density gradient in the Es plasma and then induce the gradient drift instability. The large‐scale gravity waves have the possibility to induce the E‐region wind shear.

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Simulation of pedestrian evacuation from a room with multi-exit and asymmetrical pedestrian layout is presented based on an improved dynamic parameter model in this paper. The computation and the count-area of imaginary distance are improved based on the Max-Min evacuation path selection of actual and imaginary distance in order to reduce evacuation imbalance caused by the asymmetry of pedestrian layout. An imbalance coefficient is introduced to describe the asymmetry of pedestrian layout. The effects of pedestrian layout asymmetry on the evacuation time are analyzed respectively from fixed and unfixed pedestrian initialization site. The simulation results of the improved and original models are compared and analyzed, and the improved model can effectively reduce evacuation imbalance. Simulation results show that under normal evacuation condition with considerring reasonable pedestrian and jam around exits, evacuation time is hardly affected by pedestrian and exit layout and depends mainly on cognition coefficient, total width of exits and pedestrian initialization amount.

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