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This paper presents a new rear-triggered vanadium-compensated 4H silicon carbide (4H-SiC) photoconductive semiconductor switch (PCSS) with aluminum nitride (AlN) anti-reflection coating on the back of PCSS device. Characteristics of PCSS are investigated by using semiconductor device simulation software Silvaco-TCAD. The switch substrates were doped with vanadium to make the substrates highly insulated. The on-state performance of the photoconductive switch was tested under pulsed light conditions with a wavelength of 532 nm and an optical power density of 6.8 MW/cm2 at a bias voltage of 2 kV. And the bias voltage was increased from 0 V to 10 kV in the absence of light trigger conditions, and its off-state characteristics were tested. Results show that the electric field strength between electrodes can be reduced by using rear-triggered structure, the switch breakdown voltage is over 80 kV DC, the maximum transient current is about 137 A, and the tail current almost disappears when the pulse light is turned off. In addition, the breakdown voltage of the rear-triggered PCSS to be higher than that of the front-triggered one. After adding AlN anti-reflection coating on the switch, the maximum transient of the switch and the optical utilization efficiency of laser energy are significantly improved, the maximum transient current of the switch was greatly improved from137 A to 150 A, which was increased by about 9.4 %. In addition, the effects of substrate thickness and optical power density on the switching performance were evaluated.

Dust particles from the Taklimakan Desert can be lofted vertically up to 10 km due to the unique topography and northeasterly winds associated with certain synoptic conditions. Then they can be transported horizontally to regions far downwind by westerlies. We combined data from the Multiangle Imaging Spectroradiometer (MISR) and the Cloud-Aerosol Lidar with Orthogonal Polarization to investigate the three-dimensional distribution of dust over the Taklimakan Desert and surrounding areas. During spring and summer, a dust belt with high aerosol optical depths (AOD) extends eastward from the Taklimakan Desert to the Loess Plateau along the Hexi Corridor and southward to the Tibetan Plateau. However, the dust extinction coefficients decrease rapidly from 0.340 km−1 near surface to 0.015 km−1 at 5 km in spring, while the extinction values vary within 0.100 ± 0.020 between the altitudes of 1.6 and 3.5 km and decrease to 0.023 km−1 at 5 km in summer, indicating that dust aerosol is relatively well mixed vertically. We further used MISR daily AOD to identify high- and low-dust days and then analyzed composite difference patterns of temperature, geopotential height, and wind between high- and low-dust days. It was found that although the synoptic situations of spring and summer are quite different, there are two common features: a strong anticyclonic wind anomaly over the Taklimakan at 500 hPa and an enhanced easterly wind over the Tarim Basin at 850 hPa for the two seasons. These conditions are favorable for dust entrainment from the dry desert surface, vertical lofting, and horizontal transport.

Nine bacterial strains isolated from root nodules of Astragalus sinicus were compared with 41 reference strains, including the type strains of the type species of the genera Rhizobium, Bradyrhizobium, and Agrobacterium, by performing a numerical analysis of 200 phenotype features. Representative strains belonging to different clusters were further compared with similar bacteria by using data from gel electrophoresis of whole-cell proteins, DNA G+C content data, and DNA-DNA hybridization data. The rhizobial strains isolated from nodules of A. sinicus constitute a distinct homology group that is quite different from previously described Rhizobium, Bradyrhizobium, and Agrobacterium species and from strains isolated from other Astragalus species. We propose the name Rhizobium huakuii sp. nov. for the strains isolated from A. sinicus. Type strain CCBAU 2609 (= 103) has been deposited in the Culture Collection of Beijing Agricultural University, Beijing, People's Republic of China.