A new structure of microwave field effect transistor Dielectric Resonator Oscillator (DRO) working at 8.5GHz is presented with negative resistance theory and harmonic balance theory. In order to magnify the output power and enhance the load pulling, a Buffer Amplifier (BA) is designed after the DRO. The nonlinearity and linearity of this structure are analyzed and optimized with commercial software ADS. Then the properties of this structure are simulated with commercial software HFSS. Simulation results show that DRO co-integrated with BA a high output power of 13.426dBm, at an oscillation frequency of 8.5GHz.
Laser surface remelting experiments on Zn-4.0wt.%Cu hyperperitectic alloy have been performed on a 5kW CW CO2 laser with the scanning velocities between 6 and 1207mm/s. Microstructures in both longitudinal and transverse section of the molten pools have been analyzed by optical microscope and SEM technique, and the average composition in the molten pools has been measured by Electron Probe Microanalysis(EPMA). With the increasing of growth rate, the microstructures of Zn-4.0 wt.%Cu alloy change from planar interface to lamellar structures and then cellular structures, and finally to absolute stability planar interface at a growth rate of 562mm/s, which shows reasonable agreement with that predicted by M-S theory.
Laser Rapid Forming (LRF) is a new and advanced manufacture technology to accomplish near net shape metal components with high performance for use in the aerospace, defense and chemical processing industries. In this paper the close-range continuous photography is used to take side views on the cladding zone in order to disclose inherent characteristic of the laser rapid forming process. The vivid molten pool shape is obtained by adopting image partition technology since the not molten area is eliminated from the photos. It is found that the molten pool size depended essentially on the LRF process parameters. With introducing the metal powders into the focus spot of the laser beam, the molten pool retains a segment arc raised outward and the molten pool free surface inclines to the axis of laser beam. Further results show that the molten pool inclination plays an important role on the microstructure of the LRF components.
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