The essential requirements of the end-effector of large space manipulator are capabilities of misalignment tolerance and soft capture.According to these requirements,an end-effector prototype combining the tendon-shea...The essential requirements of the end-effector of large space manipulator are capabilities of misalignment tolerance and soft capture.According to these requirements,an end-effector prototype combining the tendon-sheath transmission system with steel cable snaring mechanism was manufactured.An analysis method based on the coordinate transformation and the projection of key points of the mechanical interface was proposed,and it was a guideline of the end-effector design.Furthermore,the tendon-sheath transmission system was employed in the capture subassembly to reduce the inertia of the capture mechanism and enlarge the capture space.The capabilities of misalignment tolerance and soft capture were validated through the dynamic simulation in ADAMS software.The results of the capture simulation and experiment show that the end-effector has outstanding capabilities of misalignment tolerance and soft capture.The translation misalignments in radial directions are±100 mm,and angular misalignments about pitch and yaw are±15°.展开更多
Due to the turbulent external business environment, the complexity of internal relations of the organization and the emergence of subversive IT roles, the business-IT alignment(BITA)has become increasingly difficult. ...Due to the turbulent external business environment, the complexity of internal relations of the organization and the emergence of subversive IT roles, the business-IT alignment(BITA)has become increasingly difficult. The unsuccessful realization of BITA will lead to the waste of organizational resources, the reduction of return on investment and eventually the loss of competitive advantage. In recent years, coevolution has received widespread attention due to its ability to describe the dynamic relationship between IT and business. Multiple principles such as quickening learning action loops and adopt suitable organizing principles for achieving business and IT coevolution(BITC) are obtained. However, the continuous BITC is still hard to be achieved because of the lack of complete BITC management. This paper focuses on the management process of the BITC and how to perform it gradually. A coevolution framework combines the enterprise architecture(EA) approach with the coevolution analysis is proposed, which contains the design of EA, the sensing and governance of the misalignment and the procedure of the EA misalignment prevention.The steps for the governance and prevention of misalignment are discussed in particular. Through comparison with the principles,characteristics and methods of coevolution in the literature, the proposed framework is evaluated. The results show that the proposed framework is effective for BITC implementation.展开更多
Orbital angular momentum(OAM)at radio frequency(RF)has attracted more and more attention as a novel approach of multiplexing a set of orthogonal OAM modes on the same frequency channel to achieve high spectral efficie...Orbital angular momentum(OAM)at radio frequency(RF)has attracted more and more attention as a novel approach of multiplexing a set of orthogonal OAM modes on the same frequency channel to achieve high spectral efficiency(SE).However,the precondition for maintaining the orthogonality among different OAM modes is perfect alignment of the transmit and receive uniform circular arrays(UCAs),which is difficult to be satisfied in practical wireless communication scenarios.Therefore,to achieve available multi-mode OAM broadband wireless communication,we first investigate the effect of oblique angles on the transmission performance of the multi-mode OAM broadband system in the non-parallel misalignment case.Then,we compare the UCA-based RF analog and baseband digital transceiver structures and corresponding beam steering schemes.Mathematical analysis and numerical simulations validate that the SE of the misaligned multi-mode OAM broadband system is quite low,while analog and digital beam steering(DBS)both can significantly improve the SE of the system.However,DBS can obtain higher SE than analog beam steering especially when the bandwidth and the number of array elements are large,which validates that the baseband digital transceiver with DBS is more suitable for multi-mode OAM broadband wireless communication systems in practice.展开更多
In order to present basic guidance for system calibration of split Hopkinson pressure bar(SHPB) with the special shape striker,wave characteristics and dynamic responses of SHPB under striker impact were analyzed.Stre...In order to present basic guidance for system calibration of split Hopkinson pressure bar(SHPB) with the special shape striker,wave characteristics and dynamic responses of SHPB under striker impact were analyzed.Stress generated by the special shape striker tends to have a half-sine waveform and has little wave dispersion during its propagation.Impact velocities of the special shape striker and peak values of generated stress still have linear relation but with a different coefficient from that of cylindrical strikers.From stress histories on the surfaces of the input bar impacted by the special shape striker off-axially and obliquely,it is found that the misalignment impacts usually trigger wave distortion and amplitude decrease,which can be used to identify the poor system adjustment.Finally,the system calibration of SHPB with the special shape striker can be classified into four steps:system adjustment,wave distortion identification,measurement calibration and transmission calibration,where the measurement calibration factor and transmission calibration factor are elaborated and redefined.展开更多
基金Project(2006AA04Z228) supported by National Hi-tech Research and Development Program of China
文摘The essential requirements of the end-effector of large space manipulator are capabilities of misalignment tolerance and soft capture.According to these requirements,an end-effector prototype combining the tendon-sheath transmission system with steel cable snaring mechanism was manufactured.An analysis method based on the coordinate transformation and the projection of key points of the mechanical interface was proposed,and it was a guideline of the end-effector design.Furthermore,the tendon-sheath transmission system was employed in the capture subassembly to reduce the inertia of the capture mechanism and enlarge the capture space.The capabilities of misalignment tolerance and soft capture were validated through the dynamic simulation in ADAMS software.The results of the capture simulation and experiment show that the end-effector has outstanding capabilities of misalignment tolerance and soft capture.The translation misalignments in radial directions are±100 mm,and angular misalignments about pitch and yaw are±15°.
文摘Due to the turbulent external business environment, the complexity of internal relations of the organization and the emergence of subversive IT roles, the business-IT alignment(BITA)has become increasingly difficult. The unsuccessful realization of BITA will lead to the waste of organizational resources, the reduction of return on investment and eventually the loss of competitive advantage. In recent years, coevolution has received widespread attention due to its ability to describe the dynamic relationship between IT and business. Multiple principles such as quickening learning action loops and adopt suitable organizing principles for achieving business and IT coevolution(BITC) are obtained. However, the continuous BITC is still hard to be achieved because of the lack of complete BITC management. This paper focuses on the management process of the BITC and how to perform it gradually. A coevolution framework combines the enterprise architecture(EA) approach with the coevolution analysis is proposed, which contains the design of EA, the sensing and governance of the misalignment and the procedure of the EA misalignment prevention.The steps for the governance and prevention of misalignment are discussed in particular. Through comparison with the principles,characteristics and methods of coevolution in the literature, the proposed framework is evaluated. The results show that the proposed framework is effective for BITC implementation.
基金supported by the Natural Science Basic Research Program of Shaanxi(2021JZ-18)the Natural Science Foundation of Guangdong Province of China(2021A1515010812)+1 种基金the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University(2021D04)the Fundamental Research Funds for Central Universities,and the Innovation Fund of Xidian University。
文摘Orbital angular momentum(OAM)at radio frequency(RF)has attracted more and more attention as a novel approach of multiplexing a set of orthogonal OAM modes on the same frequency channel to achieve high spectral efficiency(SE).However,the precondition for maintaining the orthogonality among different OAM modes is perfect alignment of the transmit and receive uniform circular arrays(UCAs),which is difficult to be satisfied in practical wireless communication scenarios.Therefore,to achieve available multi-mode OAM broadband wireless communication,we first investigate the effect of oblique angles on the transmission performance of the multi-mode OAM broadband system in the non-parallel misalignment case.Then,we compare the UCA-based RF analog and baseband digital transceiver structures and corresponding beam steering schemes.Mathematical analysis and numerical simulations validate that the SE of the misaligned multi-mode OAM broadband system is quite low,while analog and digital beam steering(DBS)both can significantly improve the SE of the system.However,DBS can obtain higher SE than analog beam steering especially when the bandwidth and the number of array elements are large,which validates that the baseband digital transceiver with DBS is more suitable for multi-mode OAM broadband wireless communication systems in practice.
基金Projects(50904079,50934006) supported by the National Natural Science Foundation of ChinaProject(2010CB732004) supported by the National Basic Research Program of China
文摘In order to present basic guidance for system calibration of split Hopkinson pressure bar(SHPB) with the special shape striker,wave characteristics and dynamic responses of SHPB under striker impact were analyzed.Stress generated by the special shape striker tends to have a half-sine waveform and has little wave dispersion during its propagation.Impact velocities of the special shape striker and peak values of generated stress still have linear relation but with a different coefficient from that of cylindrical strikers.From stress histories on the surfaces of the input bar impacted by the special shape striker off-axially and obliquely,it is found that the misalignment impacts usually trigger wave distortion and amplitude decrease,which can be used to identify the poor system adjustment.Finally,the system calibration of SHPB with the special shape striker can be classified into four steps:system adjustment,wave distortion identification,measurement calibration and transmission calibration,where the measurement calibration factor and transmission calibration factor are elaborated and redefined.
