Gearboxes and similar machines containing rotating parts are complex systems with complicated structure and couplings. Generally they can be decomposed into more simple subsystems. These subsystems are usually rotating shafts with gears joined
by gear couplings and housing coupled with rotating shafts by bearings. The paper is aimed at the mathematical modelling of gearboxes with spur helical gears considered including their interior rotating shaft system and housing. The used bearing model
respects real number of rolling elements and roller contact forces acting between the journals and the outer housing. The model of a complete gearbox is created using the modal synthesis method. The kinematic transmission errors in gear couplings are viewed as sources of excitation. Vibration and noise analysis of the gearbox housing is performed by means of the created model. Four types of objective functions suitable for optimization from the radiated noise point of view are proposed. The presented methodology is applied to the simple test-gearbox. and Obsahuje seznam literatury
This article describes a technique for noise reduction of the differential bearings. Noise is excited by the mechanical looseness of the system and by the vibrations of the engine. The mathematical model enables the optimization of the radial stiffness of the differential bearings. A test rig has been designed for the simulation of the phenomenon outside the vehicle. Analytical software has been created that is capable of classifying the types of noise from the measured data. The optimal solution is tested on the rig at the end, thus proving that the technique works. and Obsahuje seznam literatury
We build the flows of non singular Morse-Smale systems on the 3-sphere from its round handle decomposition. We show the existence of flows corresponding to the same link of periodic orbits that are non equivalent. So, the link of periodic orbits is not in a 1-1 correspondence with this type of flows and we search for other topological invariants such as the associated dual graph.
Let X be a Banach space of analytic functions on the open unit disk and Γ a subset of linear isometries on X. Sufficient conditions are given for non-supercyclicity of Γ. In particular, we show that the semigroup of linear isometries on the spaces S^{p} (p>1), the little Bloch space, and the group of surjective linear isometries on the big Bloch space are not supercyclic. Also, we observe that the groups of all surjective linear isometries on the Hardy space H^{p} or the Bergman space L_{a}^{p} (1< p< ∞,p\neq 2) are not supercyclic., Abbas Moradi, Karim Hedayatian, Bahram Khani Robati, Mohammad Ansari., and Obsahuje seznam literatury
Background: Non-adherence to treatment in seniors with dementia is a frequent and potentially dangerous phenomenon in routine clinical practice which might lead to the inappropriate treatment of a patient, including the risk of intoxication. There might be different causes of non-adherence in patients with dementia: memory impairment, sensory disturbances, limitations in mobility, economical reasons limiting access to health care and medication. Non-adherence leads to serious clinical consequences as well as being a challenge for public health. Aim: to estimate prevalence of non-adherence in seniors with dementia and to study correlation between cognitive decline and non-adherence. Subjects and Methods: Prospective study, analyzing medical records of seniors with dementia admitted to the inpatient psychogeriatric ward in the Kromeriz mental hospital from January 2010 to January 2011. Cognitive decline measured by MMSE, prevalence of Non-adherence to treatment and reasons for patient Non-adherence were studied. Results: Non-adherence to any treatment was detected in 31.3% of seniors; memory impairment was the most common cause of non-adherence to treatment. Conclusion: In conclusion, non-adherence to treatment in the studied group of seniors with dementia correlates with the severity of cognitive impairment – a higher cognitive decline correlates with a higher risk of non-adherence to treatment. and J. Lužný, K. Ivanová, L. Juríčková