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Purpose - The purpose of this paper is to focus on the machine design and control strategy of the permanent magnet synchronous generator (PMSG) system, especially utilized in variable speed applications, in order to stabilize the output voltage on the dc link over a wide speed range. Design/methodology/approach - Different ac/dc power converter topologies are comparatively studied, each with an accordingly designed PMSG, so as to investigate the influence of the armature winding inductance as well as the relationship between the PMSG and power converter topologies. Findings - Pulse width modulation (PWM) rectifier is preferable for the said application due to its good performance and controllability. Moreover, by employing the PWM rectifier, relatively large inductance of the PMSG is considered for both short-circuit current reduction and field regulation. Originality/value - Field-regulating control is realized with a space vector PWM (SVPWM) rectifier, which can weaken the PMSG magnetic field during high-speed operation, while even properly enhance the field at low speed, ensuring a small change of the PMSG output voltage and a stable dc voltage. [ABSTRACT FROM AUTHOR]

Background: Centrifuge training is an important method of improving the hypergravity tolerance of pilots, cosmonauts, and Chinese astronauts. However, the concomitants of tension or anxiety often impede training. Guided imagery (CI), a mind-body relaxation technique, pro-vides a behavioral and cognitive means whereby individuals are able to exert control over the focus of attention. This study aims to investigate the immediate effects of CI for reducing stress in centrifuge training. Methods: There were 12 healthy young men who were randomly as-signed to a GI group or music group. We measured changes in heart rate during centrifuge training, in heart rate variability before and after cen-trifuge training, and also evaluated relaxation and anxiety in three phases: before intervention, after intervention, and following centrifuge training. Results: The change in the pattern of anxiety was different in the two groups over the three phases. Anxiety (measured by State Anxi-ety Inventory) in the GI group changed from 31.7 ± 5.9 to 26.8 ± 2.6 and 27.8 ± 4.1, whereas for the music group this changed from 32.2 ± 7.6 to 31.2 ± 8.3 and 26.8 ± 6.8. During centrifuge training, the maxi-mal HR for the GI group (101.2 ± 8.8) was lower than that of the music group (123.0 ± 19.1). In addition CI showed a decrease in low fre-quency (LF, 0.04-0.15 Hz) components and an increase in high frequency (HF, 0.15-0.4 Hz) components before and after centrifuge training. Conclusion: GI was capable of decreasing tension, anxiety, and sympathetic nervous system activity pre-or post-centrifugation. [ABSTRACT FROM AUTHOR]