We present models designed to represent the evolution of microstructure and crystallographic texture during recrystallization. For engineering applications the models are tied to a finite element approach. A connectio...We present models designed to represent the evolution of microstructure and crystallographic texture during recrystallization. For engineering applications the models are tied to a finite element approach. A connection to the deformed microstructure is established by dislocation theory of work hardening and Taylor type texture simulations. For temporal and spatial resolution a modified cellular automaton model was developed. A fast statistical approach for prediction of recrystallization kinetics and texture development discrete in time is presented. Predictions of the models are compared with experimental data.展开更多
Visual sensors are used to measure the relative state of the chaser spacecraft to the target spacecraft during close range ren- dezvous phases. This article proposes a two-stage iterative algorithm based on an inverse...Visual sensors are used to measure the relative state of the chaser spacecraft to the target spacecraft during close range ren- dezvous phases. This article proposes a two-stage iterative algorithm based on an inverse projection ray approach to address the relative position and attitude estimation by using feature points and monocular vision. It consists of two stages： absolute orienta- tion and depth recovery. In the first stage, Umeyama＇s algorithm is used to fit the three-dimensional （3D） model set and estimate the 3D point set while in the second stage, the depths of the observed feature points are estimated. This procedure is repeated until the result converges. Moreover, the effectiveness and convergence of the proposed algorithm are verified through theoreti- cal analysis and mathematical simulation.展开更多
Isothermal recovery in the macroscopic length of homogeneously deformed specimens of amorphous poly(ethylene terephthalate) (PET) film sample uniaxially drawn at 69 degrees C to the draw ratios lambda(0) = 1.26-2.20 w...Isothermal recovery in the macroscopic length of homogeneously deformed specimens of amorphous poly(ethylene terephthalate) (PET) film sample uniaxially drawn at 69 degrees C to the draw ratios lambda(0) = 1.26-2.20 were studied at temperatures around the glass transition temperature (T-g = 73 degrees C). Experimental results indicate that the length recovery look place in two distinct steps: a fast first step (fast relaxation) followed by a slow second step (slow relaxation). The relaxation processes were accompanied by the reversion of trans-conformers (1340 cm(-1)) to gauche, and the dichroic function of the 1340 cm(-1) band characterizing the segmental orientation along the chain direction decreased to a very low value at the end of the fast relaxation. This fact led us to assign the fast relaxation as the segmental orientation while the slow relaxation as relaxation of the global chain orientation. It was found that the slow relaxation follows a single exponential function, with relaxation times strongly dependent on the temperature resembling the glass transition process. The fast relaxation does not follow a single exponential decay, presumably a distribution of relaxation times is involved.展开更多
In this study,typical microstructural characteristics of a metastableβTi alloy(Ti–5Al–5Mo–5V–3Cr–1Fe)forged in a dual-phase region(strain of 54%at 820℃)were investigated in detail by the combined use of X-ray d...In this study,typical microstructural characteristics of a metastableβTi alloy(Ti–5Al–5Mo–5V–3Cr–1Fe)forged in a dual-phase region(strain of 54%at 820℃)were investigated in detail by the combined use of X-ray diff raction,energy dispersive spectroscopy,electron channeling contrast imaging and electron backscatter diff raction techniques.Results show that the microstructure of the forged alloy is composed of bulkαgrains,αplates andβmatrix.The bulkαgrains correspond to retained primaryαphase(αp,average grain size^2.4μm),while theαplates are secondaryαphase(αs,width^70 nm)precipitated from theβmatrix during air cooling.During forging,theβmatrix experiences dynamic recovery with many subgrains and signifi cant orientation gradients formed.Analyses of the orientation relationship between theαandβphases show that the Burgers orientation relationship is not maintained between someα_p andβphases,which should be related to thermal deformation-induced changes of their orientations.In contrast,all of theαs plates are found to maintain well the Burgers orientation relationship with theβphase.展开更多
Through reviewing the development history of tight oil and gas in China,summarizing theoretical understandings in exploration and development,and comparing the geological conditions and development technologies object...Through reviewing the development history of tight oil and gas in China,summarizing theoretical understandings in exploration and development,and comparing the geological conditions and development technologies objectively in China and the United States,we clarified the progress and stage of tight oil and gas exploration and development in China,and envisaged the future development orientation of theory and technology,process methods and development policy.In nearly a decade,relying on the exploration and development practice,science and technology research and management innovation,huge breakthroughs have been made.The laws of formation,distribution and accumulation of tight oil and gas have been researched,the development theories such as"multi-stage pressure drop"and"man-made reservoirs"have been established,and several technology series have been innovated and integrated.These technology series include enrichment regions selection,well pattern deployment,single well production and recovery factor enhancement,and low cost development.As a result,both of reserves and production of tight oil and gas increase rapidly.However,limited by the sedimentary environment and tectonic background,compared with North America,China’s tight oil and gas reservoirs are worse in continuity,more difficult to develop and poorer in economic efficiency.Moreover,there are still some gaps in reservoir identification accuracy and stimulating technology between China and North America.In the future,Chinese oil and gas companies should further improve the resource evaluation method,tackle key technologies such as high-precision 3D seismic interpretation,man-made reservoir,and intelligent engineering,innovate theories and technologies to enhance single well production and recovery rate,and actively endeavor to get the finance and tax subsidy on tight oil and gas.展开更多
文摘We present models designed to represent the evolution of microstructure and crystallographic texture during recrystallization. For engineering applications the models are tied to a finite element approach. A connection to the deformed microstructure is established by dislocation theory of work hardening and Taylor type texture simulations. For temporal and spatial resolution a modified cellular automaton model was developed. A fast statistical approach for prediction of recrystallization kinetics and texture development discrete in time is presented. Predictions of the models are compared with experimental data.
基金Program for Changjiang Scholars and Innovative Research Team in University (IRT0520)Ph.D.Programs Foundation of Ministry of Education of China (20070213055)
文摘Visual sensors are used to measure the relative state of the chaser spacecraft to the target spacecraft during close range ren- dezvous phases. This article proposes a two-stage iterative algorithm based on an inverse projection ray approach to address the relative position and attitude estimation by using feature points and monocular vision. It consists of two stages： absolute orienta- tion and depth recovery. In the first stage, Umeyama＇s algorithm is used to fit the three-dimensional （3D） model set and estimate the 3D point set while in the second stage, the depths of the observed feature points are estimated. This procedure is repeated until the result converges. Moreover, the effectiveness and convergence of the proposed algorithm are verified through theoreti- cal analysis and mathematical simulation.
基金This work was supported by the National Key Projects for Fundamental Research, "Macromolecular Condensed State", of Ministry of Science and Technology of China.
文摘Isothermal recovery in the macroscopic length of homogeneously deformed specimens of amorphous poly(ethylene terephthalate) (PET) film sample uniaxially drawn at 69 degrees C to the draw ratios lambda(0) = 1.26-2.20 were studied at temperatures around the glass transition temperature (T-g = 73 degrees C). Experimental results indicate that the length recovery look place in two distinct steps: a fast first step (fast relaxation) followed by a slow second step (slow relaxation). The relaxation processes were accompanied by the reversion of trans-conformers (1340 cm(-1)) to gauche, and the dichroic function of the 1340 cm(-1) band characterizing the segmental orientation along the chain direction decreased to a very low value at the end of the fast relaxation. This fact led us to assign the fast relaxation as the segmental orientation while the slow relaxation as relaxation of the global chain orientation. It was found that the slow relaxation follows a single exponential function, with relaxation times strongly dependent on the temperature resembling the glass transition process. The fast relaxation does not follow a single exponential decay, presumably a distribution of relaxation times is involved.
基金financially supported by the Technology Innovation and Application Demonstration Project of Chongqing(Grant No.cstc2018jszx-cyzdX0080)the Fundamental and Cutting-Edge Research Plan of Chongqing(Grant No.cstc2018jcyjAX0299)。
文摘In this study,typical microstructural characteristics of a metastableβTi alloy(Ti–5Al–5Mo–5V–3Cr–1Fe)forged in a dual-phase region(strain of 54%at 820℃)were investigated in detail by the combined use of X-ray diff raction,energy dispersive spectroscopy,electron channeling contrast imaging and electron backscatter diff raction techniques.Results show that the microstructure of the forged alloy is composed of bulkαgrains,αplates andβmatrix.The bulkαgrains correspond to retained primaryαphase(αp,average grain size^2.4μm),while theαplates are secondaryαphase(αs,width^70 nm)precipitated from theβmatrix during air cooling.During forging,theβmatrix experiences dynamic recovery with many subgrains and signifi cant orientation gradients formed.Analyses of the orientation relationship between theαandβphases show that the Burgers orientation relationship is not maintained between someα_p andβphases,which should be related to thermal deformation-induced changes of their orientations.In contrast,all of theαs plates are found to maintain well the Burgers orientation relationship with theβphase.
基金Supported by the China National Science and Technology Major Project(2016ZX05015,2016ZX05047,2017ZX05001).
文摘Through reviewing the development history of tight oil and gas in China,summarizing theoretical understandings in exploration and development,and comparing the geological conditions and development technologies objectively in China and the United States,we clarified the progress and stage of tight oil and gas exploration and development in China,and envisaged the future development orientation of theory and technology,process methods and development policy.In nearly a decade,relying on the exploration and development practice,science and technology research and management innovation,huge breakthroughs have been made.The laws of formation,distribution and accumulation of tight oil and gas have been researched,the development theories such as"multi-stage pressure drop"and"man-made reservoirs"have been established,and several technology series have been innovated and integrated.These technology series include enrichment regions selection,well pattern deployment,single well production and recovery factor enhancement,and low cost development.As a result,both of reserves and production of tight oil and gas increase rapidly.However,limited by the sedimentary environment and tectonic background,compared with North America,China’s tight oil and gas reservoirs are worse in continuity,more difficult to develop and poorer in economic efficiency.Moreover,there are still some gaps in reservoir identification accuracy and stimulating technology between China and North America.In the future,Chinese oil and gas companies should further improve the resource evaluation method,tackle key technologies such as high-precision 3D seismic interpretation,man-made reservoir,and intelligent engineering,innovate theories and technologies to enhance single well production and recovery rate,and actively endeavor to get the finance and tax subsidy on tight oil and gas.
