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The aim of this paper is to present a theoretical model to simulate the dynamic behavior of a spur gear, taking into account its ball bearings defects.

The proposed model is based on the implicit Newmark‐β with Newton‐Raphson numerical integration technique in order to analyze the impact of the worn bearings on the non linear dynamic behavior of one stage spur gear transmission system.

The dynamic behavior of spur gear is studied taking into account ball bearings defects thanks to the proposed model.

A new numerical model is proposed to simulate the dynamic behavior of rotating spur gear system taking into account both waviness and backlash defects.

The purpose of this paper is to study the influence of friction phenomenon generated by a disc brake on the dynamic behaviour of a one-stage spur gear.

A theoretical model is proposed and is based on both theories of Coulomb and Dahl in order to analyse the influence of disc brake friction phenomenon on the dynamic behaviour of one-stage spur gear transmission.

The influence of brake friction on the dynamic behaviour of the transmission is investigated using the proposed model and leads to observe higher vibration levels when the braking is occurring as well as the emergence of significant efforts at the gear teeth.

A new numerical model based on the implicit numerical integration technique of Newmark coupled with Newton-Raphson method is proposed to study the influence of friction phenomenon of a disc brake on the dynamic behaviour of one-stage spur gear.

The electromechanical planetary transmission system has the advantages of high transmission power and fast running speed, which is one of the important development directions in the future. However, during the operation of the electromechanical planetary transmission system, friction and other factors will lead to an increase in gear temperature and thermal deformation, which will affect the transmission performance of the system, and it is of great significance to study the influence of the temperature effect on the nonlinear dynamics of the electromechanical planetary system.

The effects of temperature change, motor speed, time-varying meshing stiffness, meshing damping ratio and error amplitude on the nonlinear dynamic characteristics of electromechanical planetary systems are studied by using bifurcation diagrams, time-domain diagrams, phase diagrams, Poincaré cross-sectional diagrams, spectra, etc.

The results show that when the temperature rise is less than 70 °C, the system will exhibit chaotic motion. When the motor speed is greater than 900r/min, the system enters a chaotic state. The changes in time-varying meshing stiffness, meshing damping ratio, and error amplitude will also make the system exhibit abundant bifurcation characteristics.

Based on the principle of thermal deformation, taking into account the temperature effect and nonlinear parameters, including time-varying meshing stiffness and tooth side clearance as well as comprehensive errors, a dynamic model of the electromechanical planetary gear system was established.

To accurately predict transient flow in homogeneous gas‐liquid mixtures in rigid and quasi‐rigid pipes, two mathematical models based on the gas‐fluid mass ratio are presented. The fluid pressure and velocity are considered as two principal dependent variables and the gas‐fluid mass ratio is assumed to be constant. By application of the conservation of mass and momentum laws, non‐linear hyperbolic systems of two differential equations are obtained and integrated numerically by a finite difference conservative scheme. The fluid density is defined by an expression averaging the two‐component densities where a polytropic process of the gaseous phase is admitted. The rigid model is deduced by neglecting the liquid compressibility and the pipe wall elasticity against the gas deformability. The quasi‐rigid model takes into account these two parameters. The effect of fluid compressibility on transient pressure behaviour is then analysed and confronted to the pipe wall elasticity. Numerical solutions are compared with numerical results available in literature and experiment developed in the laboratory. The results show that the pressure wave propagation is significantly influenced by the gas‐fluid mass ratio and the elasticity of the pipe wall. They indicate that the pipe elasticity and liquid compressibility may be neglected for great values of gas‐fluid mass ratio but not for the smaller ones.

The purpose of this paper is to investigate the use contexts of personal computing devices in multiple steps and conducts an in-depth analysis for the use context of smartphones. The determinants of use context changes of smartphones are investigated using the technology-to-performance chain model.

In steps 1 and 2, a diary study method and 2014-2015 Korea media panel research data provided by the Korea Information Society Development Institute are used. Correspondence analysis, χ² independence tests, and standardized residual analyses were conducted. In step 3, this study develops and validates a framework for use context changes using a survey method and structural equation modeling.

The results show that the use context of personal computing devices is represented differently and is clearly defined depending on the device used. Furthermore, the use context of smartphones has changed significantly because of the rapid growth of smartphone users and diverse usage patterns of smartphones. The research model results show that users expand the scope and frequency of smartphone use when they experience improved performance in everyday tasks and feel that smartphone content and functions could support everyday tasks better.

This study presents novel early stage research and presents empirical evidence and propositions in both exploratory and confirmatory ways. The main contribution of this study is to provide guidelines and general implications for other empirical studies on the use contexts of devices or information technology services.