The microstructure in the weld metals for HQ130+QJ63 high strength steels, which are welded by Ar CO 2 gas shielded metal arc welding, was analyzed by means of microscope and scan electron microscope (SEM). The rela...The microstructure in the weld metals for HQ130+QJ63 high strength steels, which are welded by Ar CO 2 gas shielded metal arc welding, was analyzed by means of microscope and scan electron microscope (SEM). The relative content of different microstructure was evaluated with XQF 2000 micro image analyzer. The effect of acicular ferrite content on the impact toughness was also studied. The test results indicated that the main microstructure in the weld metals of HQ130+QJ63 high strength steels is acicular ferrite and a few pro eutectic ferrite on the boundary of original austenite grain. Near the fusion zone there are columnar grains whose direction coefficient (X) is 3 22, but the microstructure in the center of the weld metal is isometric grain, whose direction coefficient X=1 In order to avoid welding crack and improve welding technology the weld heat input should be strictly controlled in 10-16 kJ/cm. Thus, the main microstructure in the weld metals is fine acicular ferrite and the content of pro eutectic ferrite is limited. The impact toughness in the weld metals of HQ130+QJ63 steels can be ensured and can meet the requirements for application in engineering and machinery.展开更多
On January 20, 2010, the award ceremony for the First Olympus Confocal Micro Imaging Competition China was held in Beijing. After rounds of judging and competition, 16 photos finally won the prize.The First Olympus Co...On January 20, 2010, the award ceremony for the First Olympus Confocal Micro Imaging Competition China was held in Beijing. After rounds of judging and competition, 16 photos finally won the prize.The First Olympus Confocal MicroImaging Competition China Award Ceremony was organized by Sciencenet.展开更多
The hydrodynamics and locomotion mechanism of Euglena Gracilis(E.Gracilis)is investigated using microscopic shadow imaging and micro particle image velocimetry(MicroPIV).Three distinct locomotion modes were observed:t...The hydrodynamics and locomotion mechanism of Euglena Gracilis(E.Gracilis)is investigated using microscopic shadow imaging and micro particle image velocimetry(MicroPIV).Three distinct locomotion modes were observed:translation,spin,and left/right turn.Since the flagellum was not possible to image,the strokes were identified by evaluating the flow field around the protist.The flow field information is obtained using a phase-separated PIV evaluation,which uses a histogram-thresholding based dynamic masking approach.The temporal resolution of the experiment was sufficient to identify the sequence of two modes,translation and spin,and the stroke-pulling frequency.The flow field result during a stroke is compared with existing Stokeslet dipole theories and flow disturbance decay with distance is investigated.The results indicate that the organism has a complex locomotion technique that allows the change of direction,axial orientation and propulsion.展开更多
基金Sponsored by National Key Fundamental Research Development Project(G1998061513)
文摘The microstructure in the weld metals for HQ130+QJ63 high strength steels, which are welded by Ar CO 2 gas shielded metal arc welding, was analyzed by means of microscope and scan electron microscope (SEM). The relative content of different microstructure was evaluated with XQF 2000 micro image analyzer. The effect of acicular ferrite content on the impact toughness was also studied. The test results indicated that the main microstructure in the weld metals of HQ130+QJ63 high strength steels is acicular ferrite and a few pro eutectic ferrite on the boundary of original austenite grain. Near the fusion zone there are columnar grains whose direction coefficient (X) is 3 22, but the microstructure in the center of the weld metal is isometric grain, whose direction coefficient X=1 In order to avoid welding crack and improve welding technology the weld heat input should be strictly controlled in 10-16 kJ/cm. Thus, the main microstructure in the weld metals is fine acicular ferrite and the content of pro eutectic ferrite is limited. The impact toughness in the weld metals of HQ130+QJ63 steels can be ensured and can meet the requirements for application in engineering and machinery.
文摘On January 20, 2010, the award ceremony for the First Olympus Confocal Micro Imaging Competition China was held in Beijing. After rounds of judging and competition, 16 photos finally won the prize.The First Olympus Confocal MicroImaging Competition China Award Ceremony was organized by Sciencenet.
文摘The hydrodynamics and locomotion mechanism of Euglena Gracilis(E.Gracilis)is investigated using microscopic shadow imaging and micro particle image velocimetry(MicroPIV).Three distinct locomotion modes were observed:translation,spin,and left/right turn.Since the flagellum was not possible to image,the strokes were identified by evaluating the flow field around the protist.The flow field information is obtained using a phase-separated PIV evaluation,which uses a histogram-thresholding based dynamic masking approach.The temporal resolution of the experiment was sufficient to identify the sequence of two modes,translation and spin,and the stroke-pulling frequency.The flow field result during a stroke is compared with existing Stokeslet dipole theories and flow disturbance decay with distance is investigated.The results indicate that the organism has a complex locomotion technique that allows the change of direction,axial orientation and propulsion.
