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A common assumption in the analysis of swashplate type axial piston machines (APMs) is to consider the relative rotation between the piston and cylinder block almost equal to the shaft speed. While this effect has been observed experimentally and confirmed by simplified models, an in-depth study and confirmation of the causes has never been undertaken. To address this, the presented work performs a simulation study of the piston and slipper spin in APMs. For this purpose, this work first develops a strongly coupled simulation model considering the displacing action of the machine coupled - with asynchronous time stepping - with the detailed simulation of its lubricating interfaces. The proposed approach accounts for the dynamics of the floating bodies in these machines, the ball-socket friction which couples the dynamic of each piston and slipper, and the impact on the fluid-structure induced cavitation and mixed lubrication in their tribological interfaces. As a consequence, the mutual interaction between the slipper-swash plate interface and the piston-cylinder interface of the APM is taken into account. After validating this model on a reference commercial unit, the impacts of the operating parameters (such as instantaneous displacement, pressure and shaft speed) and of the ball socket friction on the behavior of the machine are explored. It can be observed from the simulation results that the relative piston rotary motion in the cylinder bore varies with the operating conditions and the swashplate angle is one of the most influential parameters. • A novel piston machine simulation tool that considers coupled physics across multiple lubricating interfaces. • Ball joint friction modeling and coupled piston and slipper dynamics. • Numerical analysis of piston spin at various operating conditions using the proposed fully coupled model. [ABSTRACT FROM AUTHOR]

The understanding of the power loss contributions of each loss source is essential for an effective development of swash plate type axial piston pump. However, it is difficult to obtain the assessment of the power loss distribution due to the lack of methodologies that allow an independent evaluation of each source. This paper addresses this challenge using the most recent simulation methods. It describes the determination of each source, along with the corresponding loss of performance, and the principle of their prediction during the design phase. It also reports the validation of the simulation model by comparing the simulated dynamic displacement chamber pressure and the solid body temperature distribution with measurements obtained from a special pump prototype. This proposed virtual assessment of power loss contributions is demonstrated on a commercial hydraulic unit and the detailed results are reported in this paper. [ABSTRACT FROM AUTHOR]

In lieu of reliable scaling rules, hydraulic pump and motor manufacturers pay a high monetary and temporal price for attempting to expand their production lines by scaling their existing units to other sizes. The challenge is that the lubricating interfaces, which are the key elements in determining the performance of a positive displacement machine, are not easily scalable. This article includes an analysis of the size-dependence of these units with regard to the significant physical phenomena describing the behavior of their three most critical lubricating interfaces. These phenomena include the non-isothermal elastohydrodynamic effects in the fluid domain, and the heat transfer and thermal elastic deflection in the solid domain. The performance change due to size variation is found to be unavoidable and explained through fundamental physics. The results are demonstrated using a numerical fluid–structure–thermal interaction model over a wide range of unit sizes. Based on the findings, a guide to scaling swashplate-type axial piston machines such as to uphold their efficiency is proposed. [ABSTRACT FROM AUTHOR]

The changes of local field potentials (LFP, mainly gamma rhythm and theta rhythm) in the brain are closely related to learning and memory formation. Reduced gamma rhythm (20–50 Hz) and theta rhythm (4–10 Hz) has been observed in the progression of Alzheimer's disease (AD), but it is not clear whether it is related to cognition in AD. Here, we investigated behaviorally driven gamma rhythm and theta rhythm in APP/PS1 mice, and optogenetically stimulated GABAergic neurons in the brain to better understand the relationship between the changes of LFP, cognition, and cellular pathologies. Optogenetically driving GABAergic neurons rescued memory formation in a water maze task and normalized theta and gamma rhythm in the EEG. Furthermore, the optogenetic stimulation alleviated neuroinflammation and levels of amyloid-β (Aβ)1–42 fragments, and induced autophagy. GABA blockers also reversed the normalization of theta and gamma rhythms in the brain by optogenetic stimulation. The results demonstrate that stimulation of GABAergic interneurons not only rescues LFP rhythms and memory formation, but furthermore activates autophagy and reduces neuroinflammation, which have beneficial additional effects such as clearing amyloid. This is a proof of concept for a novel therapeutic approach to AD treatment. • Activating GABAergic interneurons in the hippocampus has therapeutic effects. • The memory impairment in these mice is reversed. • EEG Theta and Gamma is normalized. • And β-amyloid levels are reduced via autophagy. [ABSTRACT FROM AUTHOR]