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The structure of aqueous solution surfactants, particularly the spacer group used to link the polar head groups, can significantly affect its surface activities and application properties. Herein, we designed and synthesized cationic gemini surfactants (i. e., CnDBH, n = 12, 14, 16, 18) with biphenyl and multiple amide groups as rigid spacer and characterized their structures using 1H NMR, 13C NMR, FT-IR and ESI-MS. Surface-active properties and micellization thermodynamics of CnDBH in aqueous solution were studied by surface tension and isothermal titration calorimetry at 298.2 K. Compared to the traditional surfactant of dodecyl dimethyl benzyl ammonium chloride (1227), the synthesized cationic gemini surfactants were found to have lower critical micelle concentrations (0.494–0.00711 mmol L−1) and excellent surface-tension-reducing abilities. The micellization process is thermodynamically spontaneous, exothermic and entropy-driven. Moreover, the cationic gemini surfactants show excellent foaming power and efficient emulsifying abilities for white-oil/water and toluene/water mixtures. Furthermore, they exhibit significant antimicrobial activities against Escherichia coli and Staphylococcus aureus. These excellent properties are attributed to the special molecular structure of CnDBH, in which the four amides is more easily form intermolecular and intramolecular hydrogen bonds, while the hydrophobic biphenyl group is in favour of pointing towards the micellar core in order to interact with the long hydrocarbon chains during the assembly process. Consequently, they can potentially be applicable in a variety of fields as highly efficient agents.

Electrolytic capacitor-less converters have the advantages of low cost, long life, high power density and high power factor. But the bus voltage is bound to fluctuate significantly with the greatly reduced electrolytic capacitor, causing damage to capacitor, switches, and motor. It’s necessary to suppress the fluctuation of bus voltage for a better performance. This paper presents a neural network-based bus voltage fluctuation suppression of electrolytic capacitor-less PMSM control system. The neural network is trained with the current speed status and margin of voltage to generate a dynamic reference speed that can reduce the power fluctuation on bus capacitor. It is verified that the bus voltage can be effectively suppressed compared to the non-optimized electrolytic capacitor-less model with only 4% of large electrolytic capacitor.

This paper presents a model-based SPMSM speed control strategy that takes into account the linear iron loss and minimizes the sum of copper loss and iron loss at steady state, while the motor has good dynamic performance. The strategy consists of three main regulators, a speed regulator based on improved fuzzy logic, a loss minimum regulator based on a modified SPMSM model and an optimal current regulator. Simulation results show that this strategy can effectively improve the steady-state efficiency of SPMSM and make the motor have a better dynamic performance compared with the speed control strategy without considering linear iron loss.

An efficient copper-catalyzed synthesis of substituted 2,4-diamino-1,3,5-triazines from 1,1-dibromoalkenes and biguanides under mild conditions has been developed. The reaction occurred in moderate to good yields and tolerated alkyl-, heterocyclic-, or aryl-substituted 1,1-dibromoalkenes containing functionalities such as nitriles, ethers, and halogens. Monosubstituted to tetrasubstituted biguanidines also afforded the desired products.