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This study introduces the results of preparing and testing a persistent current system including persistent current switch (PCS), large-scale HTS magnet, and joints. The transition state of PCS between superconductivity and normal was controlled by changing its temperature. The magnet with inductance of 2.5 H was excited to 136 A at 37 K and worked in persistent current mode. The joint resistance and magnetic field attenuation rate of the PCS system were calculated to be 1×10-6 Ω and 1.24 mT/h, respectively. If HTS magnets in machine are in persistent current mode, slip-ring just works at charging the magnet period. In the long run, by reducing working hours of the slip-ring, the HTS machine can be saved from frequent maintenance.

Vibration and noise are the key performance of marine propulsion motors. With the increase in the power level of marine propulsion motors, it is more and more important to study the vibration level and vibration isolation of marine propulsion motors. A 20 MW HTS motor (HTSM) with air-core stator and superconducting rotor is conceptually designed for marine electric propulsion in this study. Combined with the generation and transmission of the vibration, the full-band low-vibration design was carried out by the system acoustic design, the electromagnetic acoustic design, and the co-design of structure and electromagnetic from the perspective of excitation source and transmission path. A design method for low vibration design of HTSM was obtained, which can provide a reference for the follow-up development of large-capacity low-vibration HTSM.

The refined FEA model of Roebel transposed wires to analyze the stress and vibration of the HTS machines with air-core stators is unreasonable and needs more computing resources. The homogenization method based on representative unit cell (RUC) was used to equate the mechanical parameters and then simplify the model of the transposed wire in this study, the study process was as follows. First, the manufacturing process of the Roebel transposed wire was introduced. On this basis, an RUC consisting of repetitive microstructures along the length direction was used to establish the RUC of the wire. The FEA results showed that the mechanical parameters decreased with the increase in the thickness of its insulation and temperature. Especially, Young's modulus along the z-axis of the wire was less affected by the thickness of the insulation than that along the x-axis and the y-axis. Finally, tensile tests along the z-axis and modal analysis of the transposed wire were used to verify the homogenization method. The results showed that the first four-order bending modes and natural frequencies of the wire were consistent with the test results, and the errors were all within 5%.

Although very important, the mechanical properties of high-temperature superconducting (HTS) magnets are not as highly valued as their excellent electromagnetic performance such as high current transmitting and high magnetic density. The modal characteristics of HTS magnets under multi-physical loads may cause adverse structural responses, which may cast a negative impact on the electromagnetic performance of the magnets and even hinder the normal operation of the entire machine. To figure out the modal characteristics of the HTS magnets in the working environment, a series of analyses were conducted in this paper using Finite Element Analysis (FEA) and modal experimental methods. FEA models for an HTS motor magnet were established, and the accuracy of the models was verified with experimental data. Based on that, the influence of thermal and electromagnetic loads on the modal characteristics of the HTS magnet was further studied. The results indicate that electromagnetic loads hardly cause any changes in the modal frequency of the HTS magnets, but the thermal load can significantly reduce the modal frequency by 13.97%. This study provides an important basis for the design and vibration analysis of HTS motors in the future and supplements the research on the mechanical properties of HTS magnets.

Grapes (Vitis viniferaL.) are known for their deliciousness and health benefits. In the present study, the variations of physicochemical profiles and antioxidant activities of 25 grape varieties were evaluated. Among the varieties tested, glucose and fructose were the main sugars, and tartaric and malic acids were the main organic acids in all grapes. Shine Muscat was characterized as suitable for fresh eating due to its high sugar contents and low acid contents. While JintianMeigui had high sugar and anthocyanins contents, making it suitable for cultivation. Results showed that all grape fractions are sources of phenolic compounds and varied among cultivars. In general, regardless of cultivars, seed extracts showed the highest content of total phenolics and total proanthocyanidins contents, consistent with the observed higher antioxidant activities. Combining high-performance liquid chromatography (HPLC) and high-resolution tandem mass spectrometry (HRMS) technologies, a total of 28 phenolic components were preliminarily identified. The most abundant anthocyanins in skins were petunidin-3-glucoside and malvidin-3-glucoside, as well as catechin and epicatechin were the principal proanthocyanidins in seeds. Pearson correlation coefficient analysis showed the significant linear correlations between proanthocyanidins (catechin, epicatechin, proanthocyanidin A1, proanthocyanidin B1, proanthocyanidin B2, proanthocyanidin C1 and epicatechin-3-O-gallate) and antioxidant activities. However, further studies are needed to demonstrate and elucidate the health benefits of grapes for human nutrition as antioxidants. Overall, our results provided theoretical guidance for the further development and utilization of grapes.