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Active drag reduction (DR) of a square-back Ahmed body is experimentally studied based on machine learning or artificial intelligence (AI) control. The control system consists of four independently operated arrays of pulsed microjets, 25 pressure taps and an explorative downhill simplex method controller. Two strategies, i.e. asymmetric and symmetric actuations, are investigated, with 12 and 9 control parameters, respectively. Both achieve a DR by 13%, though with distinct flow physics and control mechanisms behind. A model linking the control parameters with the cost is developed based on Taylor expansion around the K-nearest neighbours of the smallest cost obtained from the AI control, resulting in a substantially reduced deviation between measured and predicted costs, especially when involving a large number of control parameters, compared with that based on Taylor expansion around the optimum cost. Sensitivity analysis, conducted based on the model, indicates that the control efficiency, i.e. the ratio of the power saving from DR to the total power consumption, may reach 55 and 78 for the symmetric and asymmetric strategies, respectively, given a 1–2% sacrifice on DR. This efficiency greatly exceeds that (26.5) obtained by Fan et al. (Fan et al. 2020 Phys. Fluids 32 , 125117. ( doi:10.1063/5.0033156 )), whose independent control parameters are only three.

As a novel X-ray focusing technology, lobster eye micro-pore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel (1979), the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we report on the first-light results from a flight experiment of the Lobster Eye Imager for Astronomy ($LEIA$), a pathfinder of the wide-field X-ray telescope of the Einstein Probe mission. The piggyback imager, launched in July 2022, has a mostly un-vignetted field of view of $18.6^\circ \times 18.6^\circ $. Its spatial resolution is in the range of 4$-$7 arcmin in FWHM and the focal spot effective area is 2$-$3 cm$^2$, both showing only mild fluctuations across the field of view. We present images of the Galactic center region, Sco X-1 and the diffuse Cygnus Loop nebular taken in snapshot observations over 0.5$-$4 keV. These are truly wide-field X-ray images of celestial bodies observed, for the first time, by a focusing imaging telescope. Initial analyses of the in-flight data show excellent agreement between the observed images and the on-ground calibration and simulations. The instrument and its characterization are briefly described, as well as the flight experiment. The results provide a solid basis for the development of the present and proposed wide-field X-ray missions using lobster eye MPO., Comment: 11 pages, 4 figures. Accepted for publication in Astrophysical Journal Letter

Considerable on-state impact ionization and off-state tunneling leakages are the two principal drawbacks of InAs/AlSb HEMTs, which have a small bandgap and type-II band lineup. This work introduced a wide-bandgap high-k Al2O3 between the gate metal and semiconductor surface and successfully demonstrated DC and RF performance of the InAs/AlSb metal–oxide–semiconductor HEMTs (MOS-HEMTs). An MOS-HEMT device with a 2.0 μm gate length yields DC performance of IDSS = 286 mA/mm and Gm = 495 mS/mm and RF performance of fT = 10.1 GHz and fMAX = 19.9 GHz. Compared with a conventional HEMT, gate leakage is reduced by one order and the marked dependence of drain current on gate bias in the deep subthreshold region is largely alleviated.

This paper puts forward to a new speed control method for the rapid development high-speed railway system. It receive information from track circuit, supervision speed curve, transponder and etc, deduce and calculate the speed value of dynamic expected, and calculate the real-time error. Then the closed-loop speed control system is used to realize the real-time control based on a multi-modal intelligent control algorithm that has been designed according to the real-time error. And make a simulation system to value it. The result shows it has good dynamic performance and reliable steady-state property. It is really a useful method to provide a advanced way for the train safer, faster and more comfort.

Mild cognitive impairment (MCI) and dementia in the elderly is increasing rapidly in the aging society. Studies reported the differences in gait characteristics between healthy elders and those who with MCI. Challenged with cognitively demanding task while walking will usually impaired gait performances in both groups of older adults (OAs). However, few study considered comparing gait changes under cognitive interferences of different constructs between two groups. Methods