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Heat shock proteins (HSPs) consist of highly preserved stress proteins that are expressed in response to stress. Two studies were carried out to investigate whether HSP genes in hair follicles from beef calves can be suggested as indicators of heat stress (HS). In study 1, hair follicles were harvested from three male Hanwoo calves (aged 172.2 ± 7.20 days) on six dates over the period of 10 April to 9 August 2017. These days provided varying temperature–humidity indices (THIs). In study 2, 16 Hanwoo male calves (aged 169.6 ± 4.60 days, with a BW of 136.9 ± 6.23 kg) were maintained (4 calves per experiment) in environmentally controlled chambers. A completely randomized design with a 2 × 4 factorial arrangement involving two periods (thermoneutral: TN; HS) and four THI treatment groups (threshold: THI = 68 to 70; mild: THI = 74 to 76; moderate THI = 81 to 83; severe: THI = 88 to 90). The calves in the different group were subjected to ambient temperature (22°C) for 7 days (TN) and subsequently to the temperature and humidity corresponding to the target THI level for 21 days (HS). Every three days (at 1400 h) during both the TN and HS periods, the heart rate (HR) and rectal temperature (RT) of each individual were measured, and hair follicles were subsequently collected from the tails of each individual. In study 1, the high variation (P < 0.0001) in THI indicated that the external environment influenced the HS to different extents. The expression levels of the HSP70 and HSP90 genes at the high-THI level were higher (P = 0.0120, P = 0.0002) than those at the low-THI level. In study 2, no differences in the THI (P = 0.2638), HR (P = 0.2181) or RT (P = 0.3846) were found among the groups during the TN period, whereas differences in these indices (P < 0.0001, P < 0.0001 and P < 0.0001, respectively) were observed during the HS period. The expression levels of the HSP70 (P = 0.0010, moderate; P = 0.0065, severe) and HSP90 (P = 0.0040, severe) genes were increased after rapid exposure to heat-stress conditions (moderate and severe levels). We conclude that HSP gene expression in hair follicles provides precise and accurate data for evaluating HS and can be considered a novel indicator of HS in Hanwoo calves maintained in both external and climatic chambers.

In this study, the electromagnetic characteristics of the insulated (INS), non-insulated (NI), and metal-clad (MC) racetrack coils are examined in a time-varying magnetic field. The delay in the generation of induced current and the amount of induced current when the coils are exposed to the time-varying magnetic field have been thoroughly examined. Additionally, the electromagnetic stability of each test coil was investigated under an overcurrent condition in the presence of an external magnetic ripple field. We also performed an AC loss test to investigate the effects of an MC layer on the magnitude of the AC loss. Based on the test results, the feasibility of using an MC winding technique for developing a highly stable high-temperature superconducting wind turbine generator with an enhanced electromagnetic response was thoroughly examined

This paper investigates the quench and recovery characteristics of second-generation high-temperature superconducting GdBCO coated conductors (CC) with variously patterned stabilizers in over-current conditions. A chemical etching method was used to produce various patterns of stabilizer on GdBCO CC without degrading current-carrying capacity. From the results of the over-current testing of GdBCO CC tapes with variously patterned stabilizers, the tape that had stabilizer with longitudinally disconnected patterns exhibited higher voltage increase and slower recovery time than those that had continuity of stabilizers along the longitudinal direction, because the excessive heat and current could not be transferred through the stabilizers in the former. Overall, uniform heat and current distributions along the stabilizer of GdBCO CC are among the critical factors determining thermal and electrical stabilities of a GdBCO magnet in over-current conditions, especially when quench occurs.

In this paper, we propose the use of Cr-coated MgB2 wires to enhance the charging/discharging rates of the MgB2 magnet fabricated with a partial insulation (PI) winding technique that can provide a self-protecting feature to the magnet. The charging/discharging rates of the PI magnets with the Cr-coated MgB2 wires was approximately 10 times faster than that the magnets with un-coated wires. In addition, the self-protective behavior of the PI magnet with the Cr-coated wires was verified via over-current analysis. From the test results, the effectiveness of the proposed winding technique was verified for the development of self-protective MgB2 magnetic resonance imaging (MRI) magnets with rapid charging/discharging rates.

In this paper, we briefly review our recent progress on development of core technologies for 2G HTS NMR/MRI magnets at Korea University. To outperform the current state-of-art NMR/MRI magnet systems, we have developed the following technologies: 1) a REBCO-REBCO superconducting joint for operation of persistent current mode; 2) partial and grease-insulation winding techniques for self-protection of the HTS magnets; 3) pre-shimming to reduce the screening-current-induced-field; and 4) optimization of multi-width winding to minimize conductor consumption and volume of the HTS magnets. The test results demonstrated the feasibility of employing the developed techniques to achieve ultra-high-field and LHe-free 2G NMR/MRI magnets possessing self-protecting feature.