The effects of parallel and angular butt designs with different gap widths on the microstructure and mechanical properties of the resultant magnesium joints in gas tungsten arc welding were investigated. The experimen...The effects of parallel and angular butt designs with different gap widths on the microstructure and mechanical properties of the resultant magnesium joints in gas tungsten arc welding were investigated. The experimental results displayed that the tensile strength of the joint made with angular butt joint and 0.3 ram-wide gap reached 266 MPa, the joint fractured through the heat-affected zone or base metal during tensile testing, and the microstructure examination showed that no macropore appeared in the fusion zone. However, macropores in diameter of larger than 200 micron occurred for other joint designs, the tensile strength of the resultant joints decreased, and the joints fractured through the fusion zone during tensile testing. The fracture surfaces were examined by scanning electron microscopy and the microhardness distribution in the joints was measured by using a Vickers microhardness tester.展开更多
We develop an improved design of thin gap chamber （TGC） simulation signal source. To further simulate the feature of TGC detector, a novel thought is proposed. The TGC source has 256 channels. Every channel can rand...We develop an improved design of thin gap chamber （TGC） simulation signal source. To further simulate the feature of TGC detector, a novel thought is proposed. The TGC source has 256 channels. Every channel can randomly output the signal in 25 ns. The design is based on true random number generator （TRNG）. Considering the electrical connection between the TGC source and the developing trigger electronics, the GFZ connector is used. The experimental results show that the improved TGC simulation signal source can uniformly output the random signal in every channel. The output noise is less than 3 mVrms.展开更多
A new kind of one-dimensional multilayer phononie heterostructure is constructed to obtain a broad acoustic omnidirectional reflection （ODR） band. The heterostructure is formed by combining finite periodic phononic ...A new kind of one-dimensional multilayer phononie heterostructure is constructed to obtain a broad acoustic omnidirectional reflection （ODR） band. The heterostructure is formed by combining finite periodic phononic crystals （PnCs） and Fibonacci （or Thue-Morse） quasiperiodic PnCs. From the numerical results performed by the transfer matrix method, it is found that the ODR bands can be enlarged obviously by using the combination of periodic and quasi-periodic PnCs. Moreover, an application of particle swarm optimization in designing and optimizing acoustic ODR bands is reported. With regards to different thickness ratios and periodic numbers in the heterostructure, we give some optimization examples and finally achieve phononic heterostructure with a very broad ODR bandwidth. The result provides a new approach to achieve broad acoustic ODR bandwidth, and will be applied in design of omnidirectional acoustic mirrors.展开更多
基金supported by the State Key Lab of Advanced Welding and Joining,Harbin Institute of Technology (Project No.09009)
文摘The effects of parallel and angular butt designs with different gap widths on the microstructure and mechanical properties of the resultant magnesium joints in gas tungsten arc welding were investigated. The experimental results displayed that the tensile strength of the joint made with angular butt joint and 0.3 ram-wide gap reached 266 MPa, the joint fractured through the heat-affected zone or base metal during tensile testing, and the microstructure examination showed that no macropore appeared in the fusion zone. However, macropores in diameter of larger than 200 micron occurred for other joint designs, the tensile strength of the resultant joints decreased, and the joints fractured through the fusion zone during tensile testing. The fracture surfaces were examined by scanning electron microscopy and the microhardness distribution in the joints was measured by using a Vickers microhardness tester.
基金Supported by the State Key Laboratory of Particle Detection and Electronicsthe National Natural Science Foundation of China under Grant No 11375179
文摘We develop an improved design of thin gap chamber （TGC） simulation signal source. To further simulate the feature of TGC detector, a novel thought is proposed. The TGC source has 256 channels. Every channel can randomly output the signal in 25 ns. The design is based on true random number generator （TRNG）. Considering the electrical connection between the TGC source and the developing trigger electronics, the GFZ connector is used. The experimental results show that the improved TGC simulation signal source can uniformly output the random signal in every channel. The output noise is less than 3 mVrms.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11304286,11274279 and 11174255the Scientific Research Fund of Zhejiang Provincial Education Department under Grant No Y201226257
文摘A new kind of one-dimensional multilayer phononie heterostructure is constructed to obtain a broad acoustic omnidirectional reflection （ODR） band. The heterostructure is formed by combining finite periodic phononic crystals （PnCs） and Fibonacci （or Thue-Morse） quasiperiodic PnCs. From the numerical results performed by the transfer matrix method, it is found that the ODR bands can be enlarged obviously by using the combination of periodic and quasi-periodic PnCs. Moreover, an application of particle swarm optimization in designing and optimizing acoustic ODR bands is reported. With regards to different thickness ratios and periodic numbers in the heterostructure, we give some optimization examples and finally achieve phononic heterostructure with a very broad ODR bandwidth. The result provides a new approach to achieve broad acoustic ODR bandwidth, and will be applied in design of omnidirectional acoustic mirrors.
