Little Swan (China)

This article proposes a solution to the challenge of achieving a reliable restart in sensorless permanent magnet synchronous motors transitioning from a three-phase six-switch inverter to a three-phase four-switch (TPFS) inverter due to faults. The proposed rotating restart method employs the injection of dual effective voltage vectors to synthesize the equivalent zero-voltage vector, under unbalanced capacitor voltage conditions in the TPFS inverter. This synthesis is achieved by incorporating the capacitor voltage offset into the duration calculation of the dual effective voltage vectors. Once the main power supply is restored, the dual effective voltage vectors are injected into the motor windings through the TPFS inverter, producing the short-circuit current influenced by the back electromotive force. The method utilizes the accumulated short-circuit current values to estimate the initial rotor position and speed, enabling a smooth and efficient rotating restart. This innovative method enhances the accuracy of rotor position and speed detection, reduces impulse current, and ensures the fault-tolerant operation of the system. The theoretical analysis is validated through experimental results, demonstrating the effectiveness and reliability of the proposed method.

Xylanase and β-xylosidase are the key enzymes for hemicellulose hydrolysis. To further improve hydrolysis efficacy, high temperature hydrolysis with thermostable hemicellulases showed promise. In this study, thermostable xylanase (Xyn) and β-xylosidase (XynB) genes from Pseudothermotoga thermarum were cloned and secretory expressed in Bacillu subtilis. Compared with Escherichia coli expression host, B. subtilis resulted in a 1.5 time increase of enzymatic activity for both recombinant enzymes. The optimal temperature and pH were 95°C and 6.5 for Xyn, and 95°C and 6.0 for XynB. Thermostability of both recombinant enzymes was observed between the temperature range of 75-85°C. Molecular docking analysis through AutoDock showed the involvement of Glu525, Asn526, Trp774 and Arg784 in Xyn-ligand interaction, and Val237, Lys238, Val761 and Asn76 in XynB-ligand interaction, respectively. The recombinant Xyn and XynB exhibited synergistic hydrolysis of beechwood xylan and pretreated lignocellulose, where Xyn and XynB pre-hydrolysis achieved a better improvement of pretreated lignocellulose hydrolysis by commercial cellulase. The observed stability of the enzymes at high temperature and the synergistic effect on lignocellulosic substrates suggested possible application of these enzymes in the field of saccharification process.

Passive micromixing can efficiently mix laminar flows through molecular and convective diffusion. Microstructures are expected to be efficient, easily integrated into micromixers, and suitable for micromixers over a wide range of Re. This paper presents the enhancement effects of the multiscale lateral microstructures on the flow field characteristics and mixing efficiency through numerical simulations at Re = 0.01–50. Inspired by the regulation of lateral microstructures on the local flow field, cross-scale staggered baffles (CSBs) were established and applied in typical passive micromixers. For low-Re conditions, the paired trapezoidal microstructures (PTMs) of the CSBs improved the mixing effect by increasing the local streamline tortuosity. For high-Re conditions, the PTMs of CSBs increased the number of expanding vortices in the microchannel, which could increase the size of the fluid interfaces, and an optimal mixing index with relatively little pressure drop was achieved. Moreover, the CSBs were applied to the serpentine curved channel, which caused large expanding vortices on the inner side of the curved channel, and then the state of the Dean vortices on the cross section of the curved channel changed. Therefore, compared with the conventional micromixer channel structure, lateral microstructures regulate the local flow field through the enhancement of the streamlines and the secondary flow effects, and lateral microstructures have great potential to improve the mixing efficiency over a wide range of Re.

Power transmission with HTS dc cables has the characteristics of high capacity, high efficiency, more compact size, and environmental friendly. It has become an alternative and revolutionary upgrade of the traditional dc power transmission. The self-acting limit function during its quenching for fault current is unique to HTS dc cables. Fault-current-limiting capability of the HTS DC cable in a line-commutated converter (LCC) HVDC system is therefore analyzed with HTS current-limiting features in different short-circuit situations to identify the HTS dc transmission system design and operation features and verification achieved with the HTS dc cable characteristics and parameters, especially the peak value of the fault currents in the LCC HVDC systems.