The quasi-static and dynamic tensile behaviors in electron beam welded（EBW） Ti-6Al-4V alloy were investigated at strain rates of 10-3 and 103 s-1,respectively,by materials test system（MTS） and reconstructive Hopki...The quasi-static and dynamic tensile behaviors in electron beam welded（EBW） Ti-6Al-4V alloy were investigated at strain rates of 10-3 and 103 s-1,respectively,by materials test system（MTS） and reconstructive Hopkinson bars apparatus.The microstructures of the base metal（BM） and the welded metal（WM） were observed with optical microscope.The fracture characteristics of the BM and WM were characterized with scanning electronic microscope.In Ti-6Al-4V alloy joint,the flow stress of WM is higher than that of BM,while the fracture strain of WM is less than that of BM at strain rates of 103 and 10-3 s-1,respectively.The fracture strain of WM has apparent improvement when the strain rate rises from 10-3 to 103 s-1,while the fracture strain of BM almost has no change.At the same time,the fracture mode of WM alters from brittle to ductile fracture,which causes improvement of the fracture strain of WM.展开更多
A scheme is presented for realizing an N-qubit quantum phase gate with trapped ions. Taking advantage of the virtual excitation of the vibrational mode, the qubit system undergoes a full-cycle of Rabi oscillation in t...A scheme is presented for realizing an N-qubit quantum phase gate with trapped ions. Taking advantage of the virtual excitation of the vibrational mode, the qubit system undergoes a full-cycle of Rabi oscillation in the selective symmetric Dicke subspace. The scheme only involves a single step and the operation is insensitive to thermal motion. Moreover, the scheme does not require individual addresing of the ions.展开更多
We investigate the generation and the evolution of continuous-variable(CV) entanglement from a laserdriven four-state atom inside a doubly resonant cavity under Raman excitation.Two transitions in the four-state atom ...We investigate the generation and the evolution of continuous-variable(CV) entanglement from a laserdriven four-state atom inside a doubly resonant cavity under Raman excitation.Two transitions in the four-state atom independently interact with the two cavity modes,while two other transitions are driven by coupling laser fields.By including the atomic relaxation as well as cavity losses,we show that the CV entanglement with large mean number of photons can be generated in our scheme.We also show that the intensity of the coupling laser fields can influence effectively the entanglement period of the cavity field.Different from the conventional resonant excitation scheme where zero one-photon detuning are required,it is found that the intensity and period of entanglement between the two cavity modes as well as the total mean photon number of the cavity field can be adjusted by properly modulating the frequency detuning.展开更多
Raman spectra of xLa203-（1-x）TeO2 （x=0, 0.05, 0.10, 0.15, 0.20, and 0.25） lanthanum tellurite glasses were measured and analyzed over the entire glass-forming region in an effort to quantitatively follow the struc...Raman spectra of xLa203-（1-x）TeO2 （x=0, 0.05, 0.10, 0.15, 0.20, and 0.25） lanthanum tellurite glasses were measured and analyzed over the entire glass-forming region in an effort to quantitatively follow the structural changes caused by lanthanum oxide variation. For the first time, systematic intensity measurements have been performed to elucidate the composition induced structural changes in tile high-frequency stretching vibration region and a possible mechanism was proposed. The network structure of the glasses is formed by mixing TeO4 trigonal bipyramid and Te03 trigonal pyramid units. The change of the lanthanum oxide content results in conversion of the TeO4 units to TeO3 units with a varying number of non-bridging oxygen atoms. Analysis of the Raman band contours in terms of vibrations due to different oxygen bridged trigonal bipyramid and trigonal pyramid tellurite structural units, allowed to calculate the relative amounts of the species involved in the structural changes with composition. The fraction of the terminal oxygen atoms has been estimated from the Raman intensities with the aid of a structural model concerning the structure of tellurite network systems. The simulation of the experimental density of lanthanum tellurite glasses with modifier content up to 25% revealed that the short range order building units assumed here are sufficient to account for the overall structure in these glasses.展开更多
文摘The quasi-static and dynamic tensile behaviors in electron beam welded（EBW） Ti-6Al-4V alloy were investigated at strain rates of 10-3 and 103 s-1,respectively,by materials test system（MTS） and reconstructive Hopkinson bars apparatus.The microstructures of the base metal（BM） and the welded metal（WM） were observed with optical microscope.The fracture characteristics of the BM and WM were characterized with scanning electronic microscope.In Ti-6Al-4V alloy joint,the flow stress of WM is higher than that of BM,while the fracture strain of WM is less than that of BM at strain rates of 103 and 10-3 s-1,respectively.The fracture strain of WM has apparent improvement when the strain rate rises from 10-3 to 103 s-1,while the fracture strain of BM almost has no change.At the same time,the fracture mode of WM alters from brittle to ductile fracture,which causes improvement of the fracture strain of WM.
基金Supported by the National Natural Science Foundation of China under Grant No.10974028the Doctoral Foundation of the Ministry of Education of China under Grant No.20093514110009the Natural Science Foundation of Fujian Province under Grant No.2009J06002
文摘A scheme is presented for realizing an N-qubit quantum phase gate with trapped ions. Taking advantage of the virtual excitation of the vibrational mode, the qubit system undergoes a full-cycle of Rabi oscillation in the selective symmetric Dicke subspace. The scheme only involves a single step and the operation is insensitive to thermal motion. Moreover, the scheme does not require individual addresing of the ions.
基金Supported by National Natural Science Foundation of China under Grant Nos.10704017,11074036 and 10874050National Fundamental Research Program of China Grant No.2007CB936300
文摘We investigate the generation and the evolution of continuous-variable(CV) entanglement from a laserdriven four-state atom inside a doubly resonant cavity under Raman excitation.Two transitions in the four-state atom independently interact with the two cavity modes,while two other transitions are driven by coupling laser fields.By including the atomic relaxation as well as cavity losses,we show that the CV entanglement with large mean number of photons can be generated in our scheme.We also show that the intensity of the coupling laser fields can influence effectively the entanglement period of the cavity field.Different from the conventional resonant excitation scheme where zero one-photon detuning are required,it is found that the intensity and period of entanglement between the two cavity modes as well as the total mean photon number of the cavity field can be adjusted by properly modulating the frequency detuning.
文摘Raman spectra of xLa203-（1-x）TeO2 （x=0, 0.05, 0.10, 0.15, 0.20, and 0.25） lanthanum tellurite glasses were measured and analyzed over the entire glass-forming region in an effort to quantitatively follow the structural changes caused by lanthanum oxide variation. For the first time, systematic intensity measurements have been performed to elucidate the composition induced structural changes in tile high-frequency stretching vibration region and a possible mechanism was proposed. The network structure of the glasses is formed by mixing TeO4 trigonal bipyramid and Te03 trigonal pyramid units. The change of the lanthanum oxide content results in conversion of the TeO4 units to TeO3 units with a varying number of non-bridging oxygen atoms. Analysis of the Raman band contours in terms of vibrations due to different oxygen bridged trigonal bipyramid and trigonal pyramid tellurite structural units, allowed to calculate the relative amounts of the species involved in the structural changes with composition. The fraction of the terminal oxygen atoms has been estimated from the Raman intensities with the aid of a structural model concerning the structure of tellurite network systems. The simulation of the experimental density of lanthanum tellurite glasses with modifier content up to 25% revealed that the short range order building units assumed here are sufficient to account for the overall structure in these glasses.
