Dynamics modeling and simulation of mechanism with joint clearance

The existence of clearance in the joints of mechanisms system is inevitable.The movements of the real mechanism are deflection from the ideal mechanism due to the clearances and the motion accuracy is decreased.The effects of the hinge clearance on the crank and rocker mechanism system are studied.The system dynamics equation with clearance is presented.The contact dynamics model is established using the nonlinear equivalent spring-damp model and the friction effect is considered by using Coulomb friction model.Then the models are incorporated into ADAMS,and based on the model,large numbers numeric simulations are made.The regularity of contact forces in clearance are studied in detail.And the effects of clearance size,clearance friction on the mechanism dynamics characteristic are analyzed.The simulation results can predict the effects of clearance on the mechanism dynamics characteristic preferably.

Dynamic Modeling and Operations of a Heat-power Station System Based on Renewable Energy

The coexistence of pollution from coal-fired heating and inefficient utilization of renewable resources in northern China has raised great concern.Current studies on heat-power systems are primarily focused on traditional combined heat and power(CHP)systems and are limited to static energy flow analysis or the dynamic characteristics of a single system component.Hence,it is difficult to make full use of the complementary potential of electrical energy and heat energy.This paper proposes a heat-power station(HPS)system based on renewable energy for the purpose of utilizing the surplus renewable energy to generate heat and meet heating demands.The overall architecture of the HPS system is established and its operational principle and dynamic characteristics of both the electrical and heating components in the system are analyzed and dynamic mathematical models are also presented.In addition,a coordinated electro-thermal control method based on system characteristics is designed to ensure the normal operation of a HPS.Simulation results verify the effectiveness of the model and control in the case of renewables fuctuation and heat load variations.

Modeling and simulation of chemically reacting flows in gas-solid catalytic and non-catalytic processes

This paper gives an overview of the recent development of modeling and simulation of chemically react- ing flows in gas-solid catalytic and non-catalytic processes. General methodology has been focused on the Eulerian-Lagrangian description of particulate flows, where the particles behave as the catalysts or the reactant materials. For the strong interaction between the transport phenomena （i.e., momentum, heat and mass transfer） and the chemical reactions at the particle scale, a cross-scale modeling approach, i.e., CFD-DEM or CFD-DPM, is established for describing a wide variety of complex reacting flows in multiphase reactors, Representative processes, including fluid catalytic cracking （FCC）, catalytic conversion of syngas to methane, and coal pyrolysis to acetylene in thermal plasma, are chosen as case studies to demonstrate the unique advantages of the theoretical scheme based on the integrated particle-scale information with clear physical meanings, This type of modeling approach provides a solid basis for understanding the multiphase reacting flow problems in general.

Randomness in the Hybrid Modeling and Simulation of Insulin Secretion Pathways in Pancreatic Islets

Insulin secreted by pancreatic islet ˇ-cells is the principal regulating hormone of glucose metabolism.Disruption of insulin secretion may cause glucose to accumulate in the blood, and result in diabetes mellitus.Although deterministic models of the insulin secretion pathway have been developed, the stochastic aspect of this biological pathway has not been explored. The first step in this direction presented here is a hybrid model of the insulin secretion pathway, in which the delayed rectifying KCchannels are treated as stochastic events. This hybrid model can not only reproduce the oscillation dynamics as the deterministic model does, but can also capture stochastic dynamics that the deterministic model does not. To measure the insulin oscillation system behavior, a probability-based measure is proposed and applied to test the effectiveness of a new remedy.