Time-dependent global simulations of a thin accretion disc: the effects of magnetically-driven winds on thermal instability

According to the standard thin disc theory, it is predicted that the radiation-pressure-dominated inner region of a thin disc is thermally unstable, while observations suggest that it is common for a thin disc of more than 0.01 Eddington luminosity to be in a thermally stable state. Previous studies have suggested that magnetically driven winds have the potential to suppress instability. In this work, we implement one-dimensional global simulations of the thin accretion disc to study the effects of magnetically driven winds on thermal instability. The winds play a role in transferring the angular momentum of the disc and cooling the disc. When the mass outflow rate of winds is low, the important role of winds is to transfer the angular momentum and then shorten the outburst period. When the winds have a high mass outflow rate, they can calm down the thermal instability. We also explore the parameter space of the magnetic field strength and the mass loading parameter.Comment: 9 pages, 6 figures, accepted for publication in MNRA

Stability analysis and H ∞ control for hybrid complex dynamical networks with coupling delays

This paper formulates and studies a model of complex dynamical networks with switching topology and coupling delays. Based on the hybrid control and Lyapunov function, the stability and robust H control of such networks with impulsive and switching effects, which have not been studied before, are addressed with some criteria derived. Examples are given to illustrate the effectiveness of the theoretical results. Copyright © 2011 John Wiley & Sons, Ltd

Stability of internet-based control systems with uncertainties and multiple time-varying delays

In this paper, based on remote control and local control strategy, a class of hybrid multi-rate control models with uncertainties and multiple time-varying delays is formulated and their robust stability properties are investigated. By Lyapunov-Krasovskii functions and apply it to a descriptor model transformation, some new criteria of robust stability for such Internet-based control systems are established. Numerical example and simulation are given to illustrate the effectiveness of the theoretical results

Effects of Tai Chi on telomerase activity and gerotranscendence in middle aged and elderly adults in Chinese society

AbstractIntroductionTelomeres are DNA protein structures at the end of chromosomes and are linked to the physical aging process. The improvement of quality of life is closely associated with aerobic exercise, and the dynamic effects of exercise on physiology and psychology are evident with aging. Tai Chi is popularly practiced in China. However, findings on the effects of Tai Chi on telomerase activity (TA) in peripheral blood mononuclear cells, and gerotranscendence (GT), as well as the association of TA and GT with Tai Chi, have been inconsistent.PurposeThis study aims to assess TA in peripheral blood mononuclear cells, GT, and the associations between them. The associations among these variables are determined during six months of Tai Chi intervention among Chinese middle aged and elderly adults.MethodsTA assessment was obtained by TE-ELISA (human telomerase–enzyme linked immunosorbent assay), and GT was measured at the baseline level after six months of Tai Chi intervention.ResultsTA increased significantly in the Tai Chi group from 23.75 ± 3.78 u/mmol (pre-intervention) to 26.31 ± 2.93 u/mmol (after 6 months) (p < 0.05). Compared with the TA in the control group, the TA in the intervention group was statistically significant after six months (p < 0.05). Compared with the GT in the control group, the GT in the intervention group improved significantly after six months (p < 0.05). TA and GT had a positive correlation (r = 0.325, p < 0.01).ConclusionOur data illustrated that Tai Chi had a protective effect on TA and might improve the GT in Chinese middle aged and elderly adults. The TA increased with the increasing GT in Chinese middle aged and elderly adults