As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a typical rotary ...As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a typical rotary forming technology, and the upper and lower rolls have different radii and speeds. To quickly predict the three-dimensional stresses and eliminate fishtail defect, an improved strip layer method is developed, in which the asymmetry of the upper and lower rolls, non-uniform deformation and stress, as well as the asymmetrical spread on the end surface are considered. The deformation zone is divided into a certain number of layers and strips along the thickness and width, respectively. The transverse displacement model is constructed by polynomial function, in order to increase the computation speed greatly. From the metal plastic mechanics principle, the three-dimensional stress models are established. The genetic algorithm is used for optimization calculation in an industrial experiment example. The results show that the rolling pressure, the normal stresses, the upper and lower friction stress distributions are not similar with those of a general plate rolling. There are two relative maximum values in rolling pressure distribution. The upper and lower longitudinal friction stresses change direction nearby the upper and lower neutral points, respectively. The fishtail profile of spread on the end surface is predicted satisfactorily. The reduction could be helpful to eliminate fishtail defect. The large cylindrical shell rolling example illustrates the calculation results acquired rapidly are good agreements with the finite element simulation and experimental values of previous study. A highly effective and reliable three-dimensional simulation method is proposed for large cylindrical shell rolling and other asymmetrical rolling.展开更多
The common-reflection-surface (CRS) stacking is a new seismic imaging method, which only depends on seismic three parameters and near-surface velocity instead of macro-velocity model. According to optimized three para...The common-reflection-surface (CRS) stacking is a new seismic imaging method, which only depends on seismic three parameters and near-surface velocity instead of macro-velocity model. According to optimized three parameters obtained by CRS stacking, we derived an analytical relationship between three parameters and migration velocity field, and put forward CRS gather migration velocity modeling method, which realize velocity estimation by optimizing three parameters in CRS gather. The test of a sag model proved that this method is more effective and adaptable for velocity modeling of a complex geological body, and the accuracy of velocity analysis depends on the precision of optimized three parameters.展开更多
To solve the potential inversion problem of the coupled system for one-way wave equations, the absorbing boundary conditions in the lateral direction are derived. The difference schemes are constructed and a layer str...To solve the potential inversion problem of the coupled system for one-way wave equations, the absorbing boundary conditions in the lateral direction are derived. The difference schemes are constructed and a layer stripping method is proposed. Some numerical experiments are presented.展开更多
Thispaperintroduces materialandstructureofthe hydrogenation reactors, and analysesthe problems presentin use of hydrogenation reactors. Main factors which can lead to stoppingworkof reactors, are hydrogen attack, hyd...Thispaperintroduces materialandstructureofthe hydrogenation reactors, and analysesthe problems presentin use of hydrogenation reactors. Main factors which can lead to stoppingworkof reactors, are hydrogen attack, hydrogen embrittlement, temper embrittlement andstripsof overlap weldinglayer,andsomeproposalsare putforward forsafeoperation ofre actors. Finallyitissuggested thatitbe notenough only by advancing the reactor material,and adoptingthe new design and structureof reactorisimperative.展开更多
A new static induction thyristor （SITH） with a strip anode region and p- buffer layer structure （SAP-B） has been successfully designed and fabricated. This structure is composed of a p- buffer layer and lightly do...A new static induction thyristor （SITH） with a strip anode region and p- buffer layer structure （SAP-B） has been successfully designed and fabricated. This structure is composed of a p- buffer layer and lightly doped n- regions embedded in the p＋-emitter. Compared with the conventional structure of a buffed-gate with a diffused source region （DSR buffed-gate）, besides the simple fabrication process, the forward blocking voltage of this SITH has been increased to 1600 V from the previous value of 1000 V, the blocking gain increased from 40 to 70, and the turn-offtime decreased from 0.8 to 0.4μs.展开更多
基金Supported by National Science and Technology Major Project of China(Grant No.2011ZX04002-101)National Science and Technology Support Plan of China(Grant No.2011BAF15B02)National Natural Science Foundation of China(Grant No.51305388)
文摘As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a typical rotary forming technology, and the upper and lower rolls have different radii and speeds. To quickly predict the three-dimensional stresses and eliminate fishtail defect, an improved strip layer method is developed, in which the asymmetry of the upper and lower rolls, non-uniform deformation and stress, as well as the asymmetrical spread on the end surface are considered. The deformation zone is divided into a certain number of layers and strips along the thickness and width, respectively. The transverse displacement model is constructed by polynomial function, in order to increase the computation speed greatly. From the metal plastic mechanics principle, the three-dimensional stress models are established. The genetic algorithm is used for optimization calculation in an industrial experiment example. The results show that the rolling pressure, the normal stresses, the upper and lower friction stress distributions are not similar with those of a general plate rolling. There are two relative maximum values in rolling pressure distribution. The upper and lower longitudinal friction stresses change direction nearby the upper and lower neutral points, respectively. The fishtail profile of spread on the end surface is predicted satisfactorily. The reduction could be helpful to eliminate fishtail defect. The large cylindrical shell rolling example illustrates the calculation results acquired rapidly are good agreements with the finite element simulation and experimental values of previous study. A highly effective and reliable three-dimensional simulation method is proposed for large cylindrical shell rolling and other asymmetrical rolling.
基金State Natural Science Foundation of China (49894190-024).
文摘The common-reflection-surface (CRS) stacking is a new seismic imaging method, which only depends on seismic three parameters and near-surface velocity instead of macro-velocity model. According to optimized three parameters obtained by CRS stacking, we derived an analytical relationship between three parameters and migration velocity field, and put forward CRS gather migration velocity modeling method, which realize velocity estimation by optimizing three parameters in CRS gather. The test of a sag model proved that this method is more effective and adaptable for velocity modeling of a complex geological body, and the accuracy of velocity analysis depends on the precision of optimized three parameters.
文摘To solve the potential inversion problem of the coupled system for one-way wave equations, the absorbing boundary conditions in the lateral direction are derived. The difference schemes are constructed and a layer stripping method is proposed. Some numerical experiments are presented.
文摘Thispaperintroduces materialandstructureofthe hydrogenation reactors, and analysesthe problems presentin use of hydrogenation reactors. Main factors which can lead to stoppingworkof reactors, are hydrogen attack, hydrogen embrittlement, temper embrittlement andstripsof overlap weldinglayer,andsomeproposalsare putforward forsafeoperation ofre actors. Finallyitissuggested thatitbe notenough only by advancing the reactor material,and adoptingthe new design and structureof reactorisimperative.
基金supported by the Scientific and Technological Development Plan of Lanzhou City of China(No.2009-1-1).
文摘A new static induction thyristor （SITH） with a strip anode region and p- buffer layer structure （SAP-B） has been successfully designed and fabricated. This structure is composed of a p- buffer layer and lightly doped n- regions embedded in the p＋-emitter. Compared with the conventional structure of a buffed-gate with a diffused source region （DSR buffed-gate）, besides the simple fabrication process, the forward blocking voltage of this SITH has been increased to 1600 V from the previous value of 1000 V, the blocking gain increased from 40 to 70, and the turn-offtime decreased from 0.8 to 0.4μs.
