Papers by Keyword: Fitting Function

Abstract: Under the different experimental condition of ignition energy, the variations of gas explosive limit were obtained. The explosive limit ranges from 4.86% to 16.72%, under the condition of high ignition energy of 450 J. The result is quite different from the theoretical explosion limit range from 5% to 16%, thus providing a new basis to effectively prevent the gas explosion accidents.

Abstract: To build a precise compressor model is a critical issue in the modeling and simulation of a turbocharged diesel engine. This paper proposes an exponential function for compressor flow model and a polynomial function for efficiency model. A case study of a compressor map for TCA88 turbocharger is implemented to verify the proposed model. Fitting results show that the compressor model performs in accordance with the manufacture compressor map. The compressor model can be applied to mean value models of turbocharged engines for non-linear control and state estimation.

Abstract: In this paper, the 3D model was built by the software Pro/E. Virtual Prototype analysis for the manipulator of punching machine was carried out by the software ADAMS. The force, torque and angular velocity were calculated respectively under the step5 driving function condition. Through analysis and comparison, the result shows that the working condition was better when the step5 function was applied. This laid the foundation of the manipulator driving programming.

Abstract: With the use of casing running tool (CRT), casing can be rotated and reciprocated at the same time with circulation of drilling fluid. Thus the flow in well bore was eccentric annular helical. Pressure exerted on casing was important for casing buckling analysis. A numerical model of eccentric annular helical flow of power law fluid was built in this paper. The relationship between average pressure gradient on pipe and some influence factors (pipe axial velocity, rotating angular velocity, drilling fluid circulation velocity, and axial coordination) was analyzed. Results showed that average pressure gradient caused by shear stress was only affected by average annular flow velocity, and it didn’t change along pipe length. Effect of rotating angular velocity on average pressure gradient on pipe was very small and could be negligible. A fitting function between average pressure gradient and average annular flow velocity was obtained in this end.

Abstract: As cement-based composite, concrete can be properly represented by three phases in microstructure: cement paste, aggregate as well as interfacial transition zone between them. As the matrix compositions of concrete, fracture properties of cement paste and mortar have great influence on fracture performance of concrete, and fracture energy is an important parameter for concrete non-linear fracture mechanics research. Therefore, three-point bending beams of cement paste and mortar with different sizes and strengths were tested. A complete load-deflection (P-δ) curve was directly obtained, and a fit was made for the tail of the P-δ curve using power and exponential function, respectively. And then the fitting results of the two function were compared. It was found that with the increase of specimen size the influence of tail curve on fracture energy is decrease，and considering the influence of tail curve, fracture energy of cement paste and mortar are size-independent. The discussion on the obtained results was made.