The enology characteristics were studied by three yeast strains of pure and mixed cultures of Saccharomyces cerevisiae QM, ZYFJQ and Hanseniaspora uvarum YQY with Cabernet sauvignon grape,respectively, while the commercial Saccharomyces cerevisiae RC212 was made as a control, in order to screen excellent yeast strains or the combination of those for the original wine. Chemical indices of the wines by three stiains were analyzed including ethanol, total acidity, volatile acidity and residual reducing sugar. Flavor compounds in wines and in must were extracted by dichloromethane and identified by GC–MS.The results showed that the chemical indices of the wine from selected strains could satisfy with the demand of Chinese national standard, and the volatiles were mainly the 2-phenylethanol, which shaped the main characteristics of wine aroma components. yeast strain QM and YQY got the best balance between acetate and alcohols. The best volatiles of wine was obtained from the mixed fermentations than from the pure or from the control ones. ndigenous yeast strains from grape played an important role on the types and amounts of flavor compounds in mixed culture fermentation. The yeasts could have potential applications to the original winemaking.
In recent years, the LLC (inductor–inductor–capacitor) DC transformer has been widely used in communication and computer power supply because of its advantages of zero voltage conduction of primary switch and zero current turn off concerning the output rectifier diode. To obtain higher transmission efficiency and make the LLC DC transformer always run at the optimal operating point, the switching frequency of the LLC DC transformer should work at the resonance frequency of the circuit. In actual conditions, the optimal operating frequency of the LLC DC transformer will be changed due to the influences of the working condition on the circuit parameters and the load change. Therefore, the LLC DC transformer controlled by the fixed frequency mode will not be in the best working condition. In this paper, an adaptive frequency tracking method is used to control the circuit; when the circuit parameters change, the LLC DC transformer can always be in the best working state. Then, the influence of circuit parameters such as output power and excitation inductor on the optimal working point of the LLC DC transformer is analyzed in detail. Finally, a 1 kW LLC resonant converter prototype is designed under laboratory conditions to verify the feasibility of the control strategy.
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