The two-way mass transfer behavior between solvent and non-solvent is a key factor effecting on the pore size and size distribution of 3-D scaffolds formed by ScCO2induced phase separation process. The mathematical model of the mass transfer related to this process is presented on the basis of the model developed by Reuvers. By means of the composition paths calculated by this model in the ternary phase diagram, the pore size and size distribution of PLLA 3-D scaffolds are analyzed under different conditions (solution concentrations, CO2pressures and temperatures).The calculated results are verified by experiment. The results show that the pore size of the PLLA 3-D scaffolds increases with the decrease of solution concentration and increase of the CO2pressure and temperature.
The supercritical fluid impinging technology combined with fluidized bed (SFIT-FB) process is a novel technique to prepare microcapsules. The process was performed using ultra-fine glass beads as the core particle and paraffin the coating material. The influences of operation parameters, including the pressure and the temperature of mixing vessel and the impinging distance on the microcapsule morphology, size distribution and coating rate were investigated. The microcapsule characteristics could be controlled by adjusting the operation conditions. A number of techniques were used for the characterisation of the microcapsules. A scanning electron microscope (SEM) was used to examine the morphology of particle surface. A laser particle size analyzer (LPSA) was used to measure the particle size distribution, and differential scanning calorimeter (DSC) measurements were conducted to determine the apparent coating rates of microcapsules. The advantages of SFIT lies in enhancing the mass transfer and heat transfer, which prevent particles agglomeration.
This paper mainly study the Space Vector Pulse Width Modulation (SVPWM) algorithm of AC motor control system, Vector control strategy of the SVPWM voltage source inverter fed AC motor studied. In order to testify the correctness of the control strategy, simulation method is proposed to modify the motor speed and realize a simple and high performance speed control system. This system has been implemented on dynamic simulated tool simulation of MATLAB software in AC motor. Results show that the method gives satisfying rotor speed in the whole speed range and can improve the control precision.
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