A series of Dy（Gd）-based bulk amorphous alloy rods were prepared by water-cooled copper mold method. Thermal stability and structure of Dy-Gd-Co-Al alloys were investigated by differential scanning calorimetry and X...A series of Dy（Gd）-based bulk amorphous alloy rods were prepared by water-cooled copper mold method. Thermal stability and structure of Dy-Gd-Co-Al alloys were investigated by differential scanning calorimetry and X-ray diffraction, respectively. The results show that the Dy-Gd-Co-Al alloys have good glass-formation ability, and the Dy31Gd25Co20Al24 alloy can be readily cast into full glassy rods up to 5 mm in diameter. The glass-forming ability of multicomponent alloys was greatly dependent on their chemical interaction and the equivalent bond parameters among atoms such as equivalent electronegativity difference, equivalent atomic size parameter. The Dy （Gd）-based bulk amorphous alloys could be expected as potential functional materials.展开更多
Several works have been based on the study of thermal variations in biomass to derive more valuable products such as fuels capable of replacing oil in the event of a crisis or activated carbon used as an adsorbent mat...Several works have been based on the study of thermal variations in biomass to derive more valuable products such as fuels capable of replacing oil in the event of a crisis or activated carbon used as an adsorbent material, widely used in industry for the elimination of unwanted materials, both in liquid and gaseous environments. A study of thermal parameters such as: heating speed, retention time, drying temperature, carbonization temperature, particle size, was carried out with the aim of determining the characteristic factors of the carbonization of Polyethylene terephthalate (PET), sawdust (SC) and sawdust/polyethylene terephthalate (CPS) mixture. The results of the immediate analysis revealed a very low level of ash in PET (0.013%) compared to the level of ash in sawdust (2.9%), as well as a high level of fixed carbon (82.960%), which suggests the presence of mineral oxides and a significant carbon matrix unlike PET, which indicates a very significant organic matrix (essentially made up of organic matter) with the absence of mineral oxides. The study of thermal parameters showed the water loss from Sawdust (SC) and the Sawdust/Polyethylene terephthalate (CPS) mixture, an increase with temperature, unlike that of PET whose variation is essentially zero. Without heat treatment, sawdust alone contains approximately 7% water. The optimal drying temperature for this study is 110˚C for a stay of 24 hours. It appears that the largest mass losses for the PET samples are between 87.19% and 96.05%, followed by that of the mixture, between 47.33% and 64.37%. And the lowest are observed, those of sawdust (from 24.02% to 62.6%). However, here we can say that the influence of the mass is not great, given the slight difference between the losses by temperature. The results of the study of the influence of grain size showed that the differences are insignificant, even if we vary the diameter of the grains from simple to triple. To better minimize physical constraints such as the intragranular diffusibility of the volatile matter and the homogeneity of the temperature in the grains, 75 μm particles are found to be optimal for our study. It can be noted when studying the heating rate that the mass loss at the end of the reaction is approximately the same depending on each precursor material. However, it has been demonstrated that the heating rate strongly influences the nature of the reaction products both for volatile materials and for the solid residue as well as on the kinetic parameters of the chemical reaction. Furthermore, the variation in apparent density shows a decrease as a function of the increase in the residence time of the materials in the reactor. As the carbonization time increases, the apparent density decreases. We note, for the lignocellulosic material, that the apparent density stabilizes after 60 minutes.展开更多
This paper addresses the robust visual tracking of multi-feature points for a 3D manipulator with unknown intrinsic and extrinsic parameters of the vision system. This class of control systems are highly nonlinear con...This paper addresses the robust visual tracking of multi-feature points for a 3D manipulator with unknown intrinsic and extrinsic parameters of the vision system. This class of control systems are highly nonlinear control systems characterized as time-varying and strong coupling in states and unknown parameters. It is first pointed out that not only is the Jacobian image matrix nonsingular, but also its minimum singular value has a positive limit. This provides the foundation of kinematics and dynamics control of manipulators with visual feedback. Second, the Euler angle expressed rotation transformation is employed to estimate a subspace of the parameter space of the vision system. Based on the two results above, and arbitrarily chosen parameters in this subspace, the tracking controllers are proposed so that the image errors can be made as small as desired so long as the control gain is allowed to be large. The controller does not use visual velocity to achieve high and robust performance with low sampling rate of the vision system. The obtained results are proved by Lyapunov direct method. Experiments are included to demonstrate the effectiveness of the proposed controller.展开更多
In camera calibration,accurate estimation of homography matrix between the world coordinates of the calibration board and its image coordinates is a key step in high-precision calibration of intrinsic camera parameter...In camera calibration,accurate estimation of homography matrix between the world coordinates of the calibration board and its image coordinates is a key step in high-precision calibration of intrinsic camera parameters.The existing homography matrix estimation methods have problems such as dependence on thresholds,low computational efficiency,and initial model or sorting quality affecting results.In this paper,a homography matrix estimation method based on adaptive genetic algorithm was proposed.Firstly,a new circular grid calibration board was designed and the strategy of first sampling of data sets was optimized.Secondly,a mathematical model for the estimated homography matrix was established according to the adaptive genetic algorithm.Thereby the optimal homography matrix between the calibration board and its image was obtained.Finally,the intrinsic camera parameters were calculated based on Zhang’s calibration method.The experimental results show that compared with the results of three traditional estimation methods RANSAC,PROSAC,and LMEDS,the reprojection error of the images by our estimation method is reduced by about 4.11%-7.85%,11.94%-16.91%,and 10.19%-17.82%,respectively;and the average running time of the algorithm decreases by about 25.85%-37.47%,11.99%-22.71%,and 46.50%-53.35%,respectively.In addition,the homography matrix estimation method in this paper was applied to camera calibration.The results show that compared with the traditional estimation method,the average accuracy of the camera during the calibration process increases by about 5.48%,15.06%,and 11.47%,respectively;and the average calibration efficiency of the camera is improved by about 10.13%,5.71%,and 14.26%,respectively.The homography matrix estimation method proposed in this paper not only obtained reliable results,but also had certain value and significance in improving the estimation accuracy and calculation efficiency in camera calibration.展开更多
The phenomenon of induced transparency,characterized by a high quality(Q)factor,holds significant importance in the fields of high-precision sensing,energy storage and wave manipulation.Conventional transparency syste...The phenomenon of induced transparency,characterized by a high quality(Q)factor,holds significant importance in the fields of high-precision sensing,energy storage and wave manipulation.Conventional transparency systems are often constrained by the limited experimentally accessible parameter space and the lack of independent control over intrinsic parameters,thereby hindering advanced research on high-Q effects.Here we propose a virtualized coupled-oscillator system that enables reconfigurable induced transparency in the reflection spectrum.By virtually incorporating a pair of coupled oscillators into an individual acoustic meta-atom,we achieve the manipulation of induced transparency in a decoupled,wide-ranging,and elaborate manner.Exploiting the diverse evolutions across the intrinsic parameter space,we show experimentally a counter-intuitive increase in the Q-factor of the transparency window,which is attributed to the enhanced dissipation of the bright oscillator.Meanwhile,a constant group delay at the center frequency is observed accompanying this evolution.Our work demonstrates an intriguing platform as well as a novel strategy to engineer high-Q induced transparency phenomenon,and paves the way towards applications in programmable acoustic sensors,filters and slow-wave devices.展开更多
基金the financial support of the National Natural Science Foundation of China(No.50571054)
文摘A series of Dy（Gd）-based bulk amorphous alloy rods were prepared by water-cooled copper mold method. Thermal stability and structure of Dy-Gd-Co-Al alloys were investigated by differential scanning calorimetry and X-ray diffraction, respectively. The results show that the Dy-Gd-Co-Al alloys have good glass-formation ability, and the Dy31Gd25Co20Al24 alloy can be readily cast into full glassy rods up to 5 mm in diameter. The glass-forming ability of multicomponent alloys was greatly dependent on their chemical interaction and the equivalent bond parameters among atoms such as equivalent electronegativity difference, equivalent atomic size parameter. The Dy （Gd）-based bulk amorphous alloys could be expected as potential functional materials.
文摘Several works have been based on the study of thermal variations in biomass to derive more valuable products such as fuels capable of replacing oil in the event of a crisis or activated carbon used as an adsorbent material, widely used in industry for the elimination of unwanted materials, both in liquid and gaseous environments. A study of thermal parameters such as: heating speed, retention time, drying temperature, carbonization temperature, particle size, was carried out with the aim of determining the characteristic factors of the carbonization of Polyethylene terephthalate (PET), sawdust (SC) and sawdust/polyethylene terephthalate (CPS) mixture. The results of the immediate analysis revealed a very low level of ash in PET (0.013%) compared to the level of ash in sawdust (2.9%), as well as a high level of fixed carbon (82.960%), which suggests the presence of mineral oxides and a significant carbon matrix unlike PET, which indicates a very significant organic matrix (essentially made up of organic matter) with the absence of mineral oxides. The study of thermal parameters showed the water loss from Sawdust (SC) and the Sawdust/Polyethylene terephthalate (CPS) mixture, an increase with temperature, unlike that of PET whose variation is essentially zero. Without heat treatment, sawdust alone contains approximately 7% water. The optimal drying temperature for this study is 110˚C for a stay of 24 hours. It appears that the largest mass losses for the PET samples are between 87.19% and 96.05%, followed by that of the mixture, between 47.33% and 64.37%. And the lowest are observed, those of sawdust (from 24.02% to 62.6%). However, here we can say that the influence of the mass is not great, given the slight difference between the losses by temperature. The results of the study of the influence of grain size showed that the differences are insignificant, even if we vary the diameter of the grains from simple to triple. To better minimize physical constraints such as the intragranular diffusibility of the volatile matter and the homogeneity of the temperature in the grains, 75 μm particles are found to be optimal for our study. It can be noted when studying the heating rate that the mass loss at the end of the reaction is approximately the same depending on each precursor material. However, it has been demonstrated that the heating rate strongly influences the nature of the reaction products both for volatile materials and for the solid residue as well as on the kinetic parameters of the chemical reaction. Furthermore, the variation in apparent density shows a decrease as a function of the increase in the residence time of the materials in the reactor. As the carbonization time increases, the apparent density decreases. We note, for the lignocellulosic material, that the apparent density stabilizes after 60 minutes.
基金This work was supported by The National Science Foundation(No.60474009),Shu Guang Program(No.05SG48)Scientific Programm ofShanghai Education Committee(No.07zz90).
文摘This paper addresses the robust visual tracking of multi-feature points for a 3D manipulator with unknown intrinsic and extrinsic parameters of the vision system. This class of control systems are highly nonlinear control systems characterized as time-varying and strong coupling in states and unknown parameters. It is first pointed out that not only is the Jacobian image matrix nonsingular, but also its minimum singular value has a positive limit. This provides the foundation of kinematics and dynamics control of manipulators with visual feedback. Second, the Euler angle expressed rotation transformation is employed to estimate a subspace of the parameter space of the vision system. Based on the two results above, and arbitrarily chosen parameters in this subspace, the tracking controllers are proposed so that the image errors can be made as small as desired so long as the control gain is allowed to be large. The controller does not use visual velocity to achieve high and robust performance with low sampling rate of the vision system. The obtained results are proved by Lyapunov direct method. Experiments are included to demonstrate the effectiveness of the proposed controller.
基金supported by Anhui Province Key Research and Development Program(No.2022107020012).
文摘In camera calibration,accurate estimation of homography matrix between the world coordinates of the calibration board and its image coordinates is a key step in high-precision calibration of intrinsic camera parameters.The existing homography matrix estimation methods have problems such as dependence on thresholds,low computational efficiency,and initial model or sorting quality affecting results.In this paper,a homography matrix estimation method based on adaptive genetic algorithm was proposed.Firstly,a new circular grid calibration board was designed and the strategy of first sampling of data sets was optimized.Secondly,a mathematical model for the estimated homography matrix was established according to the adaptive genetic algorithm.Thereby the optimal homography matrix between the calibration board and its image was obtained.Finally,the intrinsic camera parameters were calculated based on Zhang’s calibration method.The experimental results show that compared with the results of three traditional estimation methods RANSAC,PROSAC,and LMEDS,the reprojection error of the images by our estimation method is reduced by about 4.11%-7.85%,11.94%-16.91%,and 10.19%-17.82%,respectively;and the average running time of the algorithm decreases by about 25.85%-37.47%,11.99%-22.71%,and 46.50%-53.35%,respectively.In addition,the homography matrix estimation method in this paper was applied to camera calibration.The results show that compared with the traditional estimation method,the average accuracy of the camera during the calibration process increases by about 5.48%,15.06%,and 11.47%,respectively;and the average calibration efficiency of the camera is improved by about 10.13%,5.71%,and 14.26%,respectively.The homography matrix estimation method proposed in this paper not only obtained reliable results,but also had certain value and significance in improving the estimation accuracy and calculation efficiency in camera calibration.
基金supported by the National Natural Science Foundation of China(Grant Nos.12104480 and 12104383)the National Natural Science Foundation of Beijing(Grant No.L233037)the IACAS Frontier Exploration Project(Grant No.QYTS202110)。
文摘The phenomenon of induced transparency,characterized by a high quality(Q)factor,holds significant importance in the fields of high-precision sensing,energy storage and wave manipulation.Conventional transparency systems are often constrained by the limited experimentally accessible parameter space and the lack of independent control over intrinsic parameters,thereby hindering advanced research on high-Q effects.Here we propose a virtualized coupled-oscillator system that enables reconfigurable induced transparency in the reflection spectrum.By virtually incorporating a pair of coupled oscillators into an individual acoustic meta-atom,we achieve the manipulation of induced transparency in a decoupled,wide-ranging,and elaborate manner.Exploiting the diverse evolutions across the intrinsic parameter space,we show experimentally a counter-intuitive increase in the Q-factor of the transparency window,which is attributed to the enhanced dissipation of the bright oscillator.Meanwhile,a constant group delay at the center frequency is observed accompanying this evolution.Our work demonstrates an intriguing platform as well as a novel strategy to engineer high-Q induced transparency phenomenon,and paves the way towards applications in programmable acoustic sensors,filters and slow-wave devices.
