Abstract: This application provides a resonant conversion system, including a controller and a resonant conversion circuit. The resonant conversion circuit includes a high frequency chopper circuit, a resonant cavity, a transformer, and a rectification filter network, and the high frequency chopper circuit includes switches S1 and S2. The controller is configured to: detect a bridge arm midpoint voltage VSW, and determine based on the VSW a current threshold signal used to indicate a current threshold; detect a resonant current on a primary side of the transformer, and compare the resonant current with the current threshold signal to control on/off of the switch S1 or S2 based on the second electrical signal, so that the system operates in an inductive mode to ensure zero voltage switching of the switch, while operating in a state close to a capacitive mode to maximize the use of a gain region.

Abstract: A heparin skeleton synthase originates from Neisseria animaloris, with an amino acid sequence as shown in SEQ ID NO.2 and a nucleotide sequence of the coding gene as shown in SEQ ID NO.1. Its recombinant expression level is 6.8 times that of the existing heparin skeleton synthase KfiA from Escherichia coli K5, and total enzyme activity per fermentation liquor is 5.22 times that of the heparin skeleton synthase KfiA. The heparin skeleton synthase mutants obtained through site-directed mutagenesis of the sites No. 16, No. 25, No. 30, No. 111, No. 165, and No. 172 in the amino acid sequence of the said heparin skeleton synthase all have high expression levels.

Abstract: A portable intrinsically-safe device for acquiring vibration signal comprises a vibration signal acquisition unit, a signal processing unit, a signal storage unit and an intrinsically-safe power source, wherein the vibration signal acquisition unit is connected to the signal storage unit through the signal processing unit; the intrinsically-safe power source supplies power for all the units; the signal processing unit and the signal storage unit are integrally packaged in an intrinsically safe manner. The device solves the vibration signal acquisition from a large portable electromechanical equipment, providing a powerful data information for equipment status monitoring and failure analysis. Particularly, intrinsically safe design satisfies the test requirements when the portable equipment is under a complex and harsh environment of a coal mine well. The device is easy to mount, low in power consumption, easy to control, flexible to use and wide in range of application.