Current Issue : July - September Volume : 2016 Issue Number : 3 Articles : 4 Articles
This research aims to deepen the understanding of the interaction mechanisms between\nmicrowave and matter in a metal-ceramic system based on in situ synchrotron radiation computed\ntomography. A special internal ââ?¬Å?core-shellââ?¬Â microstructure was discovered for the first time and used\nas an indicator for the interaction mechanisms between microwave and matter. Firstly, it was proved\nthat the microwave magnetic field acted on metal particles by way of inducing an eddy current in\nthe surface of the metal particles, which led to the formation of a ââ?¬Å?core-shellââ?¬Â microstructure in the\nmetal particles. On this basis, it was proposed that the ceramic particles could change the microwave\nfield and open a way for the microwave, thereby leading to selective heating in the region around the\nceramic particles, which was verified by the fact that all the ââ?¬Å?core-shellââ?¬Â microstructure was located\naround ceramic particles. Furthermore, it was indicated that the ceramic particles would gather\nthe microwaves, and might lead to local heating in the metal-ceramic contact region. The focusing\nof the microwave was proved by the quantitative analysis of the evolution rate of the ââ?¬Å?core-shellââ?¬Â\nmicrostructure in a different region. This study will help to reveal the microwave-matter interaction\nmechanisms during microwave sintering....
In this work the study, design, development and experimental results of a new microwave\nexcitation signal generating circuit are presented. New design of this circuit is based\non the method of direct digital synthesis. The results of theoretical calculations and\nexperimental researches show that the new design not only has a high precision, but\nalso has an improvement in the spectral characteristics of the output signal. Range\nof generated output frequencies is expanded, that leads to the possibility of detuning\nthe frequency of the neighboring resonance of spectral line and adjust the C-field in\nquantum frequency standard. Experimental research of the metrological characteristics\nof the quantum frequency standard on the atoms of caesium with a new functional unit\nshowed an improvement in the daily frequency stability....
We simulated the microwave sintering of ZnO by 3D modelling. A large-size Al-doped ZnO (AZO) green ceramic compact was\nprepared by slurry casting. Through studying the microwave and electric hybrid sintering of the green compact, a relative density of\nup to 98.1% could be obtained by starting microwave heating at 1200âË?Ë?C and increasing the power 20 min later to 4kW for an AZO\nceramic target measuring 120 Ã?â?? 240 Ã?â?? 12 mm. The resistivity of AZO targets sintered with microwave assistance was investigated.\nThe energy consumption of sintering could be greatly reduced by this heating method. Until now, few studies have been reported\non the microwave and electric hybrid sintering of large-size AZO ceramic targets. This research can aid in developing sintering\ntechnology for large-size high-quality oxide ceramic targets....
The paper introduces the principles, simulation results, and hardware implementation of ultrawideband (UWB) noise radar for\nobtaining tomographic images of various scenarios of rotating cylindrical objects using independent and identically distributed\nUWB noise waveforms. A UWB noise radar was designed to transmit multiple UWB random noise waveforms over the 3ââ?¬â??5GHz\nfrequency range and to measure the backward scattering data for the validation of the theoretical analysis and numerical simulation\nresults. The reconstructed tomographic images of the rotating cylindrical objects based on experimental results are seen to be in\ngood agreement with the simulation results, which demonstrates the capability of UWB noise radar for complete two-dimensional\ntomographic image reconstruction of various shaped metallic and dielectric target objects....
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