A wideband cavity-backed slot antenna operated in the ultra-high frequency （UHF） band is introduced. The antenna has a compact structure and low profile with the size ratio of the ground plane to the slot only 1.6：...A wideband cavity-backed slot antenna operated in the ultra-high frequency （UHF） band is introduced. The antenna has a compact structure and low profile with the size ratio of the ground plane to the slot only 1.6：1. The measured impedance bandwidth of VSWR≤3 achieves 85.3%, covering a frequency range from 390 MHz to 970 MHz. The measured gain is about 5.5-7.5 dB.展开更多
The stress-induced martensitic transformation and its relation with crack nucleation and propagation in CuNiAl shape memory alloy were investigated through in-situ tensile tests by SEM and TEM.The results indicated th...The stress-induced martensitic transformation and its relation with crack nucleation and propagation in CuNiAl shape memory alloy were investigated through in-situ tensile tests by SEM and TEM.The results indicated that the stress concentration ahead of the crack tip could induce formation of stacking faults and different types of martensites.TEM observations showed that the martensites could transform from one type to another and even reversely to the parent during loading.The micro-cracks nucleated along the martensite/parent interface and intersection between two martensites.When the crack propagated a certain distance,the stress concentration ahead of the crack tip was large enough to result in formation of slip bands,and in this condition the microcrack nucleated along slip bands more easily.展开更多
文摘A wideband cavity-backed slot antenna operated in the ultra-high frequency （UHF） band is introduced. The antenna has a compact structure and low profile with the size ratio of the ground plane to the slot only 1.6：1. The measured impedance bandwidth of VSWR≤3 achieves 85.3%, covering a frequency range from 390 MHz to 970 MHz. The measured gain is about 5.5-7.5 dB.
基金This work was supported by the National Major Basic Research Funds (G1990650) the National Natural Science Foundation of China (Grant No. 19891180).
文摘The stress-induced martensitic transformation and its relation with crack nucleation and propagation in CuNiAl shape memory alloy were investigated through in-situ tensile tests by SEM and TEM.The results indicated that the stress concentration ahead of the crack tip could induce formation of stacking faults and different types of martensites.TEM observations showed that the martensites could transform from one type to another and even reversely to the parent during loading.The micro-cracks nucleated along the martensite/parent interface and intersection between two martensites.When the crack propagated a certain distance,the stress concentration ahead of the crack tip was large enough to result in formation of slip bands,and in this condition the microcrack nucleated along slip bands more easily.
