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In this study, a 5-degrees-of-freedom dynamic model of variable lead preloaded single nut ball screw is proposed. The proposed model considers the effect of excitation amplitude, deflection angle, the number of balls, and the preload into consideration. Moreover, to study the effect of working parameters on nonlinear dynamics, bifurcation diagram, 3-D frequency spectrum, phase diagram and Poincaré section with different system parameters are shown in discussion section. The numerical analysis indicates that the system can exhibits different motion states, and the continuous frequency component can be observed. Moreover, a series of experiments are conducted to estimate the dynamic parameters and validate the proposed dynamic model.

Investigation of the dynamic characteristics of linear guideway is essential for enhancing structural performance of machine tools. However, few mechanical models are established for vibration analysis of linear guideway when it is subjected to complex external loads. In this paper, we presented a five degrees of freedom dynamic model for investigating nonlinear vibration behavior of linear guideway subjected to external periodic excitation. The idea of coordinate transformation is adopted for the easier derivations of piecewise restoring force function and equation of motion. The numerical simulation shows a wide variety of fascinating phenomena linked to vibration system with the effects from harmonic excitation frequency and amplitude, preload and mass of carriage. The multi-period, quasi-period and chaotic motions are observed by the characterization tools of bifurcation diagram and 3-D frequency spectrum. Moreover, the dynamic experiments are presented for verifying the proposed model. The analytical model developed here can be used for optimal design for high-precision linear guideway.

The thermal effect has a significant influence on the performance of angular contact ball bearings and thus affects the motion accuracy and stability of spindle-bearing system of computerized numerical control (CNC) lathe. In this paper, a comprehensive coupled CNC lathe spindle-bearing model considering the thermal effect is proposed to predict the dynamic characteristics of system. The spindle is modeled as Timoshenko’s beam by considering the centrifugal force and gyroscopic effects. The bearing is analyzed by a five degrees-of-freedom (DOF) quasi-static model considering the thermal effect in order to obtain the static deformations and thermal deformations of rolling bodies. The dynamic differential equation of system is established by the finite element method. Runge–Kutta integral method is used to solve the system equation numerically to study its nonlinear dynamic behaviors. The correctness of thermal model of CNC lathe spindle-bearing system is verified by testing the housing temperature. The simulation values of system response considering thermal effect or not are compared with the experimental results, which shows that the proposed model is feasible. Moreover, the effects of key parameters such as rotational speed, pulley eccentricity and bearing preload on the nonlinear characteristics of system are investigated. Single-periodic, multi-periodic, quasi-periodic and chaotic motions are observed by time history curve, 3-D frequency spectrum curve, phase diagram, Poincare section and bifurcation diagram under different operating conditions. The analytical model developed here can be also helpful to the design and optimization of CNC lathe spindle-bearing system.

Molecular mechanisms of peritoneal dialysis (PD) ultrafiltration failure, peritoneal neo-angiogenesis, and fibrosis remain to be determined. We aimed to determine the role of heparin-binding EGF-like growth factor (HB-EGF) inhibition on angiogenesis of peritoneal membrane in a PD rat model. 32 male Wistar rats were assigned into (1) control group; (2) uremic non-PD group: subtotal nephrectomy-induced uremic rats without PD; (3) uremic rats subjected to PD: uremic rats that were dialyzed with Dianeal® for 4 weeks; (4) CRM 197 group: dialyzed uremic rats were supplemented with CRM197, a specific HB-EGF inhibitor. Peritoneal transport function was examined by peritoneal equilibration test. Expression of HB-EGF and EGFR in peritoneal samples were examined by real-time PCR, immunohistochemical staining, and western blot. Progressive angiogenesis and fibrosis were observed in uremic PD rats, and there were associated with decreased net ultrafiltration (nUF), increased permeability of peritoneal membrane, and reduced expression of HB-EGF and EGFR protein and mRNA in uremic PD rats compared to uremic non-PD or control groups (both p