Advanced Materials Research Vol. 978

Abstract: —In this paper, the effect of prey refuge on the dynamic consequences of the stage-structured predator-prey system with time delay are studied. The results indicate that the prey refuge play an important role in population dynamics, the extinction and coexistence of predator and prey population. The results show that the equilibrium density of immature and mature prey populations increase with increasing in prey refuge and the prey refuge has a clearly stabilizing effect on the predator-prey system with stage structure and time delay under a restricted set of conditions. The Data process is also analysized and obtained.

Abstract: Analyzed and studied the hydro-pneumatic buffer structure of railway vehicle, designed a new type of hydro-pneumatic buffer and established the detailed dynamics model. Calculated the static characteristic curve of hydro-pneumatic buffer with different compression rate and dynamic characteristic curve with different impact speed through the numerical simulation method. The simulation results shows that the biggest impedance force is 1836.3KN and buffer capacity reach 221.89KJ when impact velocity of the new hydro-pneumatic buffer is 5m/s.New hydro-pneumatic buffer can improve the speed of manipulating vehicle, reduce the longitudinal impact and vibration in the train and adapt to the needs of the trains.

Abstract: The adverse impact of the exhaust plume on the inner wall of the vertical launch box and the former friable lid of the adjacent launch box is a common phenomenon, which causes the deformation or damage of the launch container. By using the three-dimensional unsteady numerical simulation, discrete phase model and multicomponent model, the change of the pressure and temperature with time on many monitoring sites are analyzed. The results show that the pressure and the temperature on the edge of the inner wall significantly rise over time after 0.2s. The pressure on the centerline of the inner wall rises over time after 0.2s but the temperature gradually decreases. The maximum pressure on the former friable lid of the adjacent launch box peaks at 0.54s. The conclusion can be regarded as a theoretical reference for engineering application.

Abstract: Using biomechanical test system to reveal the kinematics parameters of instep shot in different heights in soccer players. Twelve healthy male college students voluntarily participated in this study. After digitizing the recording collected by camera, this study reached the following conclusion that (1) In instep front shot the lower the contact height with ball during kicking, the faster the ball velocity. Therefore, the author put forward a proposal that in order to obtain the faster ball velocity, the kicking ball point should be lower, and (2) the player can control the ball velocity, ball trajectory, and the time of technique by controlling the vertical distance between support leg and ball.

Abstract: In this paper, the study of the dynamics for the constant force polishing robot system is aimed, through the establishment of the dynamics equations for the end of the robot polishing. By comparing the before and the after installation of terminal buffer actuator force was verified by the experiment, the feasibility and stability constant of the system for the constant force polishing on the multi-robot are obtained.

Abstract: With the method of finite element, the sliding friction process of pressure plate and friction disc during clutch engagement was simulated to get temperature field and thermal deformation of the pressure plate. The law of temperature distribution on the pressure plate, which achieve from the simulation is same with the one measured by thermocouple. On this basis, analyzed the influence of pressure plate’s thermal deformation to torque transmission ability of clutch and put forward the structure design method of clutch pressure plate.

Abstract: The calculation of stress intensity factor (SIF) in fracture mechanics-based fatigue life prediction is mainly based on empirical formulas, the poor applicability of which limits the wide application of fatigue assessment based on crack propagation. This paper proposed a SIF calculation method for structures under wave loads. It was proved correct by comparing with the empirical formulas. Then, the method proposed was applied for the surface crack at weld toe of a connection between the column and brace of a semi-submersible platform. The predicted results showed that SIF ranges varied with wave loads, which were subjected to the effects of wave directions and frequencies. In addition, SIF ranges calculated by empirical formulas were very different from those of the proposed method. In order to accurately predict fatigue crack propagation life for ocean engineering structures, it is necessary to take the characters of wave loads into consideration. The proposed method in this paper may provide a reference.

Abstract: Numerical simulations have been done to investigate the effect of passive flow control on the flow separation and the strength of the shock wave of the NACA0012 airfoil with two types of the porous surface. It has also been discussed that which region the porous surface applied to will make better effect on the flow control. The results show that the B type of the porous surface, which has empty bottom, has effective control on the flow separation if applied to the region near behind the separation point, while the A type of the porous surface is useless. And both A and B porous surface have effect on the decreasing of the strength of the normal shock wave strength when the porosities have been applied to the region across the shock wave. And compared with A type porous surface, the effect of the control is better if B type porous surface is applied. The result has been concluded that the aerodynamic characteristics of the airfoil can be improved with B type of the porous surface. And the B type is worth to be used.

Abstract: Unsteady aerodynamics research is the foundation of aeroelastic analysis. How to effectively improve the aeroelastic computational efficiency,it is the key of current research on aeroelasticity now.Reduced order models are proposed as a powerful tool to solve this problem. Analyzed the three reduced-order models for Volterra ,Proper Orthogonal Decomposition and Harmonic Balance method ,their advantages and disadvantages were pointed out. The direction of the reduced order model in the future was Proposed and some suggest was given out for its application.

Abstract: The hatchway structure and operating mode were described according to the key technology of elevator safety device test tower. According to mounting structure of the ascending hatchway, the constraints of car-rail were proposed. According to constrains, the car-rail coupling dynamics models of moving and rotating were proposed at x-axis, y-axis and z-axis, and the vibration models were simplified to moving and rotating at z-axis. Based on simplified model, the dynamic characteristics of car were simulated when safety gear broken.