Numerical and experimental investigation of nonlinear properties of rubber absorber in rail fastening

International audienceA nonlinear dynamic model of a rubber absorber in railway fastening systems is proposed, based on the superposition principle to simulate its nonlinear vibrational behavior. A dynamic experiment was carried out to obtain all model parameters. The accuracy of the model was supported by good agreement between measured and simulated results, and it should therefore be an effective mechanical tool for simulating and characterizing the nonlinear behavior of rubber absorbers in rail fastening systems at particular vibrational modes. Excitation frequency dependency and amplitude dependency of the nonlinear dynamic stiffness were also selected for further study. The results indicate that characteristics of the nonlinear dynamic stiffness are closely associated with both displacement amplitude and frequency, although frequency dependency is not as great as amplitude dependency

Investigation of transpiration cooling with local thermal non-equilibrium model: Effects of different thermal boundary conditions at the porous-fluid interface

In this study, the main stream coupled with a porous medium with local thermal non-equilibrium assumption is analyzed. The flow inside the porous material is modelled using the Darcy–Brinkman–Forchheimer equation and the incompressible Navier-Stokes equations are solved for the main stream. Several couple conditions between the main flow temperature and the temperatures of the solid matrix and coolant flow at the fluid/porous interface is calculated. The results show that the Model C assumes the main flow temperature equals the solid phase temperature and the main flow heat flux is all imposed on the solid phase gives the most reasonable answer

Effect of Cistanche deserticola Ma extract on memory of aged mice

Purpose: To assess the memory-enhancing effect of Cistanche deserticola Ma (Orobanchaceae) extract (CDME) on normal aged mice.Methods: An open-field test was used to study the effects of various doses of CDME on mouse locomotive activity. The mice were sacrificed following the locomotor test and the brain dissected to investigate the effects of CDME on catalase (CAT) and acetyl cholinesterase (AChE) activities in mouse brain tissue.Results: Compared with the control aged group, CDME (400 mg/kg) significantly reduced the total distance traveled (3312.5 ± 119.3 cm, p < 0.05), increased brain CAT activity (107.6 ± 11.8U/mg pro, p < 0.05), and inhibited brain AChE activity (0.89 ± 0.13 U/mg pro, p < 0.05) in CDME-exposed mice.Conclusion: The results show that CDME improves memory function in mice, probably by increasing the activity of CAT and decreasing AChE activity.Keywords: Cistanche deserticola Ma, Memory function, Catalase, Acetyl cholinesterase, Open-field tes

1-(2,4-Dinitro­phen­yl)-3,3-dinitro­azetidine

In the title compound, C9H7N5O8, the dihedral angle between the mean plane of the azetidine ring and that of the benzene ring is 26.1 (1)°; the planes of the two nitro groups of the azetidine ring are aligned at 88.7 (1)°

Design Change Model for Effective Scheduling Change Propagation Paths

Changes in requirements may result in the increasing of product development project cost and lead time, therefore, it is important to understand how requirement changes propagate in the design of complex product systems and be able to select best options to guide design. Currently, a most approach for design change is lack of take the multi-disciplinary coupling relationships and the number of parameters into account integrally. A new design change model is presented to systematically analyze and search change propagation paths. Firstly, a PDS-Behavior-Structure-based design change model is established to describe requirement changes causing the design change propagation in behavior and structure domains. Secondly, a multi-disciplinary oriented behavior matrix is utilized to support change propagation analysis of complex product systems, and the interaction relationships of the matrix elements are used to obtain an initial set of change paths. Finally, a rough set-based propagation space reducing tool is developed to assist in narrowing change propagation paths by computing the importance of the design change parameters. The proposed new design change model and its associated tools have been demonstrated by the scheduling change propagation paths of high speed train’s bogie to show its feasibility and effectiveness. This model is not only supportive to response quickly to diversified market requirements, but also helpful to satisfy customer requirements and reduce product development lead time. The proposed new design change model can be applied in a wide range of engineering systems design with improved efficiency