Periodic solutions for a delay model of plankton allelopathy on time scales

In this paper, a delay model of plankton allelopathy is investigated. By using the coincidence degree theory, sufficient conditions for existence of periodic solutions are obtained. The presented criteria improve and extend previous results in the literature

Dynamic coupled vibration analysis of a large wind turbine gearbox transmission system

A lumped-parameter coupled nonlinear dynamic model for one large multi-stage wind turbine gearbox transmission system is established comprehensively including wind varying load, mesh stiffness, dynamic transmission error, gravity, and bearing nonlinear characteristics to obtain the gearbox dynamic response. The vibration differential equations of the drive-train are deduced through the Lagrange’s equation. On the basis of that, the dynamics of wind turbine gearbox is investigated by a Runge-Kutta numerical method that includes simultaneous internal and external excitations. The results show that the dynamic response of the partial component is mainly superposed by high-frequency component caused by the internal excitation and low-frequency component caused by the external excitation. In medium-speed stage and high-speed stage, the vibration amplitude has obvious fluctuation, and the multiple frequency and random frequency components become increasingly obvious with increasing rotational speed and eccentricity at gear and bearing positions. Axial vibrations of the system also have some fluctuation. The bearing has self-variable stiffness frequency, which should be avoided in engineering design stage. The study results provide a theoretical foundation for dynamical characteristics evaluation and dynamic optimization of a large wind turbine gearbox transmission system

The Quantitative Diagnosis Method of Rubbing Rotor System

The dynamics of the rubbing rotor system is analyzed by applying harmonic balance method. The relationship between harmonic components in the response of the rubbing rotor system and the dynamic stiffness matrix of the fault free rotor system is revealed, based on which a new model based method for rubbing identification is presented. By applying this method, the fault location and rubbing forces of the single rubbing rotor system can be identified by using vibration data of only two nodes, the rubbing locations and rubbing forces of the double rubbing rotor system can be identified by using vibration data of three nodes. The numerical simulations and experiments on the rotor test-rig are carried out to verify the efficiency of the present method

Cellular mechanisms of fibrin (ogen): insight from neurodegenerative diseases

Neurodegenerative diseases are prevalent and currently incurable conditions that progressively impair cognitive, behavioral, and psychiatric functions of the central or peripheral nervous system. Fibrinogen, a macromolecular glycoprotein, plays a crucial role in the inflammatory response and tissue repair in the human body and interacts with various nervous system cells due to its unique molecular structure. Accumulating evidence suggests that fibrinogen deposits in the brains of patients with neurodegenerative diseases. By regulating pathophysiological mechanisms and signaling pathways, fibrinogen can exacerbate the neuro-pathological features of neurodegenerative diseases, while depletion of fibrinogen contributes to the amelioration of cognitive function impairment in patients. This review comprehensively summarizes the molecular mechanisms and biological functions of fibrinogen in central nervous system cells and neurodegenerative diseases, including Alzheimer’s disease, Multiple Sclerosis, Parkinson’s disease, Vascular dementia, Huntington’s disease, and Amyotrophic Lateral Sclerosis. Additionally, we discuss the potential of fibrinogen-related treatments in the management of neurodegenerative disorders