This paper studied the microstructure evolution of a deformation-processed Cu-7Cr in situ composite prepared by thermo-mechanical processing. The longitudinal and transverse sectional microstructures were analyzed usi...This paper studied the microstructure evolution of a deformation-processed Cu-7Cr in situ composite prepared by thermo-mechanical processing. The longitudinal and transverse sectional microstructures were analyzed using an optical microscope and a scanning electronic microscope. In the longitudinal section, the initially randomly distributed Cr dendrites in the as-cast Cu-7Cr alloy were transformed into the fibres aligned parallel to the drawing axis;the Cr dendrites experienced breaking, flattening and rotating, lapping and merging, and homogenizing and refinement during thermo-mechanical processing. In the transverse section, the initially randomly distributed Cr dendrites in the as-cast Cu-7Cr alloy were changed into the curvy ribbon like fibres;the Cr dendrites underwent breaking, flattening and rotating, folding and twisting, and irregularizing and refinement during thermo-mechanical processing.展开更多
In AC microgrids(ACMG),hierarchical control is widely adopted,and conventionally,communication links are required between converters to transmit control instructions.However,establishing these communication links incr...In AC microgrids(ACMG),hierarchical control is widely adopted,and conventionally,communication links are required between converters to transmit control instructions.However,establishing these communication links increases system complexity and introduces communication delays.Consequently,there is an urgent need for highly integrated communication schemes in ACMG.Power and signal dual modulation(PSDM)offers an integrated communication solution that simultaneously modulates and transmits power and data in power electronic systems.In contrast,existing research primarily focuses on DC systems.In this paper,PSDM for cascaded H-Bridge multilevel inverters is proposed.The communication function is integrated into the power conversion process by modulating the data around the zero-crossing point of AC bus voltage,without interfering with power transmission.The harmonic effect and power losses introduced by this novel strategy in power transmission are further explored,offering theoretical guidance for designing DCAC PSDM systems.The proposed method has been implemented in an experimental platform of ACMG.The experimental results validated the proposed modulation scheme for full-duplex communication with a bit rate of 300bps.展开更多
Western architectura（ drawing techniques were introduced to China in the 1870s, when their importance was increasing（y recognized by the Chinese. The deve（opment of architectural drawing in the nation led to the di...Western architectura（ drawing techniques were introduced to China in the 1870s, when their importance was increasing（y recognized by the Chinese. The deve（opment of architectural drawing in the nation led to the dissemination of knowledge on engineering drawing and enhanced the integration of different theories of drawing from both China and the West. Based on the trans（ation of two western c（assica（ texts-Shi ）Cue （The See） and Qi Xiang Xian Zhen （The Engineer and Machinist＇s Drawing Book）-this study examines the technica（ development of architectural drawing in modern China.展开更多
Surface electromyography(sEMG)control interface is a common method for human-centered robotics.Researchers have frequently improved the recognition accuracy of sEMG through multichannel or high-precision signal acquis...Surface electromyography(sEMG)control interface is a common method for human-centered robotics.Researchers have frequently improved the recognition accuracy of sEMG through multichannel or high-precision signal acquisition devices.However,this increases the cost and complexity of the control system.Therefore,this study developed a control interface based on the sEMG enveloped signal for a collaborative wearable robot to improve the accuracy of sEMG recognition based on the time-domain(TD)features.Specifically,an acquisition device is developed to obtain the sEMG envelope signal,and 11 types of TD features are extracted from the sEMG envelope signal acquired from the upper limb.Furthermore,a dimension reduction method based on the correlation coefficient is proposed,transforming the 11-dimensional feature into a five-dimensional envelope feature set without decreasing the accuracy.Moreover,a recognition algorithm based on a neural network has also been proposed for gesture classification.Finally,the recognition accuracy of the proposed method,principal component analysis(PCA)feature set,and Hudgins TD feature set is compared,with their accuracy at 84.39%,72.44%,and 70.89%,respectively.Therefore,the results indicate that the envelope feature set performs better than the common gesture recognition method based on signal channel sEMG envelope signal.展开更多
文摘This paper studied the microstructure evolution of a deformation-processed Cu-7Cr in situ composite prepared by thermo-mechanical processing. The longitudinal and transverse sectional microstructures were analyzed using an optical microscope and a scanning electronic microscope. In the longitudinal section, the initially randomly distributed Cr dendrites in the as-cast Cu-7Cr alloy were transformed into the fibres aligned parallel to the drawing axis;the Cr dendrites experienced breaking, flattening and rotating, lapping and merging, and homogenizing and refinement during thermo-mechanical processing. In the transverse section, the initially randomly distributed Cr dendrites in the as-cast Cu-7Cr alloy were changed into the curvy ribbon like fibres;the Cr dendrites underwent breaking, flattening and rotating, folding and twisting, and irregularizing and refinement during thermo-mechanical processing.
基金supported in part by the National Natural Science Foundation of China under Grant 52350003in part by the Royal Society Research Grant(RG/R1/251624).
文摘In AC microgrids(ACMG),hierarchical control is widely adopted,and conventionally,communication links are required between converters to transmit control instructions.However,establishing these communication links increases system complexity and introduces communication delays.Consequently,there is an urgent need for highly integrated communication schemes in ACMG.Power and signal dual modulation(PSDM)offers an integrated communication solution that simultaneously modulates and transmits power and data in power electronic systems.In contrast,existing research primarily focuses on DC systems.In this paper,PSDM for cascaded H-Bridge multilevel inverters is proposed.The communication function is integrated into the power conversion process by modulating the data around the zero-crossing point of AC bus voltage,without interfering with power transmission.The harmonic effect and power losses introduced by this novel strategy in power transmission are further explored,offering theoretical guidance for designing DCAC PSDM systems.The proposed method has been implemented in an experimental platform of ACMG.The experimental results validated the proposed modulation scheme for full-duplex communication with a bit rate of 300bps.
文摘Western architectura（ drawing techniques were introduced to China in the 1870s, when their importance was increasing（y recognized by the Chinese. The deve（opment of architectural drawing in the nation led to the dissemination of knowledge on engineering drawing and enhanced the integration of different theories of drawing from both China and the West. Based on the trans（ation of two western c（assica（ texts-Shi ）Cue （The See） and Qi Xiang Xian Zhen （The Engineer and Machinist＇s Drawing Book）-this study examines the technica（ development of architectural drawing in modern China.
基金supported by the Fundamental Research Funds for the Central Universities,China(NS2020036 and NP2022304)the National Natural Science Foundation of China(52105103 and 52205018)the External Project of AECC Sichuan Gas Turbine Establishment(GJCZ-2020-0044).
文摘Surface electromyography(sEMG)control interface is a common method for human-centered robotics.Researchers have frequently improved the recognition accuracy of sEMG through multichannel or high-precision signal acquisition devices.However,this increases the cost and complexity of the control system.Therefore,this study developed a control interface based on the sEMG enveloped signal for a collaborative wearable robot to improve the accuracy of sEMG recognition based on the time-domain(TD)features.Specifically,an acquisition device is developed to obtain the sEMG envelope signal,and 11 types of TD features are extracted from the sEMG envelope signal acquired from the upper limb.Furthermore,a dimension reduction method based on the correlation coefficient is proposed,transforming the 11-dimensional feature into a five-dimensional envelope feature set without decreasing the accuracy.Moreover,a recognition algorithm based on a neural network has also been proposed for gesture classification.Finally,the recognition accuracy of the proposed method,principal component analysis(PCA)feature set,and Hudgins TD feature set is compared,with their accuracy at 84.39%,72.44%,and 70.89%,respectively.Therefore,the results indicate that the envelope feature set performs better than the common gesture recognition method based on signal channel sEMG envelope signal.
