Burnishing experiments with different burnishing parameters were performed on a computer numerical control milling machine to characterize the surface roughness of an aluminum alloy during burnishing.The chaos theory ...Burnishing experiments with different burnishing parameters were performed on a computer numerical control milling machine to characterize the surface roughness of an aluminum alloy during burnishing.The chaos theory was employed to investigate the nonlinear features of the burnishing system.The experimental results show that the power spectrum is broadband and continuous,and the Lyapunov exponentλis positive,proving that burnishing has chaotic characteristics.The chaotic characteristic parameter,the correlation dimension D,is sensitive to the time behavior of the system and is used to establish the corresponding relationship with the surface roughness.The correlation dimension was the largest,when the surface roughness was the smallest.Furthermore,when the correlation dimension curve decreases,the roughness curve increases.The correlation dimension and surface roughness exhibit opposite variation trends.The higher the correlation dimension,the lower the surface roughness.The surface roughness of the aluminum alloy can be characterized online by calculating the correlation dimension during burnishing.展开更多
Objective of the study: This study aimed at characterizing output features of the higher-order motor control centers (hoMCCs), including secondary (premotor cortex [Pre] and supplementary motor area [SMA]) and associa...Objective of the study: This study aimed at characterizing output features of the higher-order motor control centers (hoMCCs), including secondary (premotor cortex [Pre] and supplementary motor area [SMA]) and association (prefrontal cortex [PFC]) motor regions to the primary motor cortex (M1) during graded force tasks. It is well known that one of the major roles of the primary motor cortex (M1) is controlling motor output such as muscle force. However, it is unclear how the hoMCCs interact with M1 in regulating voluntary muscle contractions. Methods: fMRI data was acquired during graded force tasks and fMRI-based effective connectivity (EC) and muscle force analyses were performed to study the relationship between hoMCCs-M1 effective connectivity and voluntarily exerted handgrip force. Results: The results show that there is a consistent information flow from the hoMCCs to M1 under all force conditions, suggesting a hierarchical control mechanism in the brain in regulating voluntary muscle force. Only the premotor cortex exhibited a significant role in mediating the level of force production through its EC with M1 but that role diminished when the exerted force was high, suggesting perhaps a ceiling and/or fatigue effect on the EC. A flip in the direction of EC from the primary sensory cortex (S1) to the hoMCCs (PFC, SMA, and Pre) at lower force levels while at higher forces EC was observed from the hoMCCs to S1. Conclusion: The hoMCCs regulate M1 output to produce desired voluntary muscle force. Only the Pre-to-M1 connectivity strength directly correlates with the force level especially from low to moderate levels. The hoMCCs are involved in modulating higher force production likely by strengthening M1 output and downgrad<span style="font-size:12px;line-height:102%;font-family:Verdana;">ing</span><span style="font-size:12px;line-height:102%;font-family:Verdana;"> inhibition from S1 to M1.</span>展开更多
A simple quasi-distributed fiber sensing interrogation system based on random speckles is proposed for weak fiber Bragg gratings(WFBGs) in this work. Without using tunable lasers or spectrometers, a piece of multimode...A simple quasi-distributed fiber sensing interrogation system based on random speckles is proposed for weak fiber Bragg gratings(WFBGs) in this work. Without using tunable lasers or spectrometers, a piece of multimode fiber is applied to interrogate the WFBGs relying on the wavelength sensitivity of speckles. Instead of the CCD sensor, an InGaAs quadrant detector serves as the receiver to capture the fast-changing speckle patterns. A supervised deep learning algorithm of the multilayer perceptron architecture is implemented to process speckle data and to interrogate temperature changes or dynamic strains. The proposed demodulation system is experimentally demonstrated for WFBGs with 0.1% reflectivity.The experimental results demonstrate that the new system is capable of measuring temperature change with an accuracy of 1℃ and achieving dynamic frequency of 100 Hz. This speckle-based interrogation system paves a new way for distributed WFBGs sensing with a simple design.展开更多
A resonator fiber optic gyro with the light time-division input and multiplexing output(TDM-RFOG)in the clockwise(CW)and counterclockwise(CCW)directions is proposed.The light time-division input in the CW and CCW dire...A resonator fiber optic gyro with the light time-division input and multiplexing output(TDM-RFOG)in the clockwise(CW)and counterclockwise(CCW)directions is proposed.The light time-division input in the CW and CCW directions can effectively suppress the backscattering induced noise.The TDM-RFOG is implemented with the 2×2 Mach–Zehnder interferometer(MZI)optical switch.The response time of the fiber ring resonator is analyzed,and it is demonstrated by experiments that light time-division input in the CW and CCW directions can reduce the backscattering induced noise.The suppression effectiveness of backscattering induced noise in the TDM-RFOG is determined by the extinction ratio of the optical switch,so a closed loop is designed to adjust the phase shift difference between the two arms of the MZI optical switch to control the extinction ratio.The method using two arms of the MZI optical switch with twin 90°polarization-axis rotated splices is proposed to make the extinction ratio along both slow and fast axes greater than-70 d B.展开更多
以一个方便方法创造现实主义的 3D 树模型是在由于树结构的多样化和吸藏做的比赛设计和电影的挑战。为快树建模的当前的基于大意、基于图象的途径实际上有限制,速度,和他们通常包括复杂参数调整,它把困难带到新手。在这份报纸,我们...以一个方便方法创造现实主义的 3D 树模型是在由于树结构的多样化和吸藏做的比赛设计和电影的挑战。为快树建模的当前的基于大意、基于图象的途径实际上有限制,速度,和他们通常包括复杂参数调整,它把困难带到新手。在这份报纸,我们在场没有参数调整,为快速产生各种各样的 3D 树的一个简单方法从凭手画的图案当模特儿。在二幅输入图象上,用户拉代表主要树枝和一棵树的王冠剪影的击。系统自动地以高速度生产一棵 3D 树。首先,二架 2D 骨骼从击,和类似于输入图案的 3D 树结构被造被树枝检索从 2D 骨骼造。小树枝基于自我类似和角度限制在勾略的 2D 王冠剪影以内被产生。这个系统在许多例子上被表明。它维持一棵树的主要特征:主要树枝结构和王冠形状,和罐头为树模拟和设计被用作一个方便工具。展开更多
基金National Natural Science Foundation of China(Grant Nos.52175194,52105215,52075047)Zhejiang Provincial Natural Science Foundation of China(LR23E050002)+1 种基金Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.RF-A2019008)Key Laboratory of E&M(Zhejiang University of Technology),Ministry of Education&Zhejiang Province(Grant No.EM2021120103)。
文摘Burnishing experiments with different burnishing parameters were performed on a computer numerical control milling machine to characterize the surface roughness of an aluminum alloy during burnishing.The chaos theory was employed to investigate the nonlinear features of the burnishing system.The experimental results show that the power spectrum is broadband and continuous,and the Lyapunov exponentλis positive,proving that burnishing has chaotic characteristics.The chaotic characteristic parameter,the correlation dimension D,is sensitive to the time behavior of the system and is used to establish the corresponding relationship with the surface roughness.The correlation dimension was the largest,when the surface roughness was the smallest.Furthermore,when the correlation dimension curve decreases,the roughness curve increases.The correlation dimension and surface roughness exhibit opposite variation trends.The higher the correlation dimension,the lower the surface roughness.The surface roughness of the aluminum alloy can be characterized online by calculating the correlation dimension during burnishing.
文摘Objective of the study: This study aimed at characterizing output features of the higher-order motor control centers (hoMCCs), including secondary (premotor cortex [Pre] and supplementary motor area [SMA]) and association (prefrontal cortex [PFC]) motor regions to the primary motor cortex (M1) during graded force tasks. It is well known that one of the major roles of the primary motor cortex (M1) is controlling motor output such as muscle force. However, it is unclear how the hoMCCs interact with M1 in regulating voluntary muscle contractions. Methods: fMRI data was acquired during graded force tasks and fMRI-based effective connectivity (EC) and muscle force analyses were performed to study the relationship between hoMCCs-M1 effective connectivity and voluntarily exerted handgrip force. Results: The results show that there is a consistent information flow from the hoMCCs to M1 under all force conditions, suggesting a hierarchical control mechanism in the brain in regulating voluntary muscle force. Only the premotor cortex exhibited a significant role in mediating the level of force production through its EC with M1 but that role diminished when the exerted force was high, suggesting perhaps a ceiling and/or fatigue effect on the EC. A flip in the direction of EC from the primary sensory cortex (S1) to the hoMCCs (PFC, SMA, and Pre) at lower force levels while at higher forces EC was observed from the hoMCCs to S1. Conclusion: The hoMCCs regulate M1 output to produce desired voluntary muscle force. Only the Pre-to-M1 connectivity strength directly correlates with the force level especially from low to moderate levels. The hoMCCs are involved in modulating higher force production likely by strengthening M1 output and downgrad<span style="font-size:12px;line-height:102%;font-family:Verdana;">ing</span><span style="font-size:12px;line-height:102%;font-family:Verdana;"> inhibition from S1 to M1.</span>
基金supported by the National Key Research and Development Program of China(No.2021YFC3340400)Key Laboratory of Medical Electronics and Digital Health of Zhejiang Province(No.MEDH202209)+1 种基金Natural Science Foundation of Zhejiang Province(No.LY22F050004)Zhejiang Xinmiao Talents Program(No.2022R409043).
文摘A simple quasi-distributed fiber sensing interrogation system based on random speckles is proposed for weak fiber Bragg gratings(WFBGs) in this work. Without using tunable lasers or spectrometers, a piece of multimode fiber is applied to interrogate the WFBGs relying on the wavelength sensitivity of speckles. Instead of the CCD sensor, an InGaAs quadrant detector serves as the receiver to capture the fast-changing speckle patterns. A supervised deep learning algorithm of the multilayer perceptron architecture is implemented to process speckle data and to interrogate temperature changes or dynamic strains. The proposed demodulation system is experimentally demonstrated for WFBGs with 0.1% reflectivity.The experimental results demonstrate that the new system is capable of measuring temperature change with an accuracy of 1℃ and achieving dynamic frequency of 100 Hz. This speckle-based interrogation system paves a new way for distributed WFBGs sensing with a simple design.
基金supported by the Shanghai Aerospace Science and Technology Innovation Fund(No.SAST2015076)。
文摘A resonator fiber optic gyro with the light time-division input and multiplexing output(TDM-RFOG)in the clockwise(CW)and counterclockwise(CCW)directions is proposed.The light time-division input in the CW and CCW directions can effectively suppress the backscattering induced noise.The TDM-RFOG is implemented with the 2×2 Mach–Zehnder interferometer(MZI)optical switch.The response time of the fiber ring resonator is analyzed,and it is demonstrated by experiments that light time-division input in the CW and CCW directions can reduce the backscattering induced noise.The suppression effectiveness of backscattering induced noise in the TDM-RFOG is determined by the extinction ratio of the optical switch,so a closed loop is designed to adjust the phase shift difference between the two arms of the MZI optical switch to control the extinction ratio.The method using two arms of the MZI optical switch with twin 90°polarization-axis rotated splices is proposed to make the extinction ratio along both slow and fast axes greater than-70 d B.
基金Acknowledgements This work was supported in part by the National Natural Science Foundation of China (Grant Nos. 60970093, 60902078, 6117210, and 61072151) by Natural Science Foundation of Beijing (4112061), and by the Scientific Research Foundation for the Returned Overseas Chinese Scholars of State Education Ministry of China.
文摘以一个方便方法创造现实主义的 3D 树模型是在由于树结构的多样化和吸藏做的比赛设计和电影的挑战。为快树建模的当前的基于大意、基于图象的途径实际上有限制,速度,和他们通常包括复杂参数调整,它把困难带到新手。在这份报纸,我们在场没有参数调整,为快速产生各种各样的 3D 树的一个简单方法从凭手画的图案当模特儿。在二幅输入图象上,用户拉代表主要树枝和一棵树的王冠剪影的击。系统自动地以高速度生产一棵 3D 树。首先,二架 2D 骨骼从击,和类似于输入图案的 3D 树结构被造被树枝检索从 2D 骨骼造。小树枝基于自我类似和角度限制在勾略的 2D 王冠剪影以内被产生。这个系统在许多例子上被表明。它维持一棵树的主要特征:主要树枝结构和王冠形状,和罐头为树模拟和设计被用作一个方便工具。