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In PWM controlled variable rate spraying system, spraying quantities were regulated by fast switching solenoid valves. However, hydraulic impacts were generated by these fast switching solenoid valves in pipe system, which affected stabilities of spraying quantities and atomization characteristics. In order to study pressure changing regularities when solenoid valves operated, then to design a pressure controller to improve spraying qualities in PWM controlled variable rate spraying system, Fluent was used to simulate pressure characteristics in the pipe system and pressure curves were drawn under the following 3 working conditions, solenoid valve opening, closing, and switching continuously with 5 Hz frequency and 50% duty ratio. Related experiments were carried out to test real pressure signals in the pipe based on a PWM controlled variable rate spraying system. Relative errors between simulation results and experiment results were below 10%. Thus, this simulation model of PWM controlled variable rate spraying system in Fluent was reliable to simulate pressure characteristics in the pipe in other common working conditions, and which contributed to design pressure controller and to optimize the whole PWM controlled variable rate spraying system.

Grid-stiffened cylindrical shells are widely applied in aviation and aerospace engineering. Bearing capacities of grid-stiffened cylindrical shells will be reduced by local heating. In this study, numerical simulation method is applied to deduce the temperature distribution of the grid-stiffened cylindrical shells subjected to high power laser irradiation. Temperature dependent aluminum alloy properties are fully considered in the process of numerical simulation. Comparing to smooth thin-wall cylindrical shells, the effect of ribs size to temperature distribution is studied. As the material properties varying with temperature, the temperature rising rate is higher at the initial period when cylindrical shell is subjected to laser irradiation. The temperature rising rate gradually reduces with irradiation time increasing. Buckling analysis was performed to obtain the buckling bearing capacity and the effect of local heating on grid-stiffened cylindrical shells subjected to local heating.

With the rapid development of city, many large and medium-sized cities sprawl in urban space,triggering a series of socio-economic issues related to land-use. Based on RS and GIS, selected Kunming as study area for its typical representation of Yunnan plateau mountain cities, used the method of spatial quadrant orientation analysis, obtained the number and structure of construction land expansion in specific direction of study area in period of two different years, and calculated the intensity index and fractal dimensions of the urban expansion. Finally, according to local conditions, spatial expansion variations features of Kunming were analyzed systematically.