For ship targets with complex motion,it is difficult for the traditional monostatic inverse synthetic aperture radar(ISAR)imaging to improve the cross-range resolution by increasing of accumulation time.In this paper,...For ship targets with complex motion,it is difficult for the traditional monostatic inverse synthetic aperture radar(ISAR)imaging to improve the cross-range resolution by increasing of accumulation time.In this paper,a distributed ISAR imaging algorithm is proposed to improve the cross-range resolution for the ship target.Multiple stations are used to observe the target in a short time,thereby the effect of incoherence caused by the complex motion of the ship can be reduced.The signal model of ship target with three-dimensional(3-D)rotation is constructed firstly.Then detailed analysis about the improvement of crossrange resolution is presented.Afterward,we propose the methods of parameters estimation to solve the problem of the overlap or gap,which will cause a loss of resolution and is necessary for subsequent processing.Besides,the compressed sensing(CS)method is applied to reconstruct the echoes with gaps.Finally,numerical simulations are presented to verify the effectiveness and the robustness of the proposed algorithm.展开更多
Traditionally,passenger comfort in vehicles is perceived as being most influenced by acceleration and jerk.Consequently,the current research primarily focuses on developing control algorithms to limit the maximum acce...Traditionally,passenger comfort in vehicles is perceived as being most influenced by acceleration and jerk.Consequently,the current research primarily focuses on developing control algorithms to limit the maximum acceleration and jerk of the vehicle in order to improve passenger comfort.However,naturalistic driving studies demonstrate that such simple characteristics are insufficient for accurately evaluating passenger comfort.This study identifies motion complexity as a key factor of passenger comfort.A series of naturalistic driving studies are conducted,during which passenger comfort is assessed using a 5-point Likert scale.Moreover,a real-time passenger comfort measurement based on electromyography(EMG)and stepwise regression is proposed to facilitate seamless data collection.Time-series features representing motion complexity are then introduced to better describe passenger comfort.Hierarchical regression confirms that simple characteristics of motion are insufficient to explain passenger comfort,and shows that the proposed motion complexity features have a substantial effect on passenger comfort.Finally,a machine learning-based real-time passenger comfort estimation method is developed according to the foregoing findings.Experimental results show that the proposed method can accurately estimate passenger comfort in real-time using only vehicle motion information.The findings of this study suggest that vehicle motion complexity should be considered in future passenger comfort studies.展开更多
An analytical study of the two degrees of freedom nonlinear dynamical system is presented. The internal motion of the system is separated and described by one fourth order differential equation. An approximate approac...An analytical study of the two degrees of freedom nonlinear dynamical system is presented. The internal motion of the system is separated and described by one fourth order differential equation. An approximate approach allows reducing the problem to the Duffing equation with adequate initial conditions. A novel idea for an effective study of nonlinear dynamical systems consisting in a concept of the socalled limiting phase trajectories is applied. Both qualitative and quantitative complex analyses have been performed. Important nonlinear dynamical transition type phenomena are detected are investigated analytically.展开更多
In this paper, the Steiner area formula and the polar moment of inertia were expressed during one-parameter closed planar homothetic inverse motions in complex plane. The Steiner point was defined when the rotation nu...In this paper, the Steiner area formula and the polar moment of inertia were expressed during one-parameter closed planar homothetic inverse motions in complex plane. The Steiner point was defined when the rotation number was different zero and it was called the Steiner normal when the rotation number was equal to zero. The fixed pole point was given with its components and its relation between Steiner point or Steiner normal was explained. The sagittal motion of a telescopic crane was considered as an example. This motion was described by a double hinge consisting of the fixed control panel of the telescopic crane and the moving arm of the telescopic crane. The theoretical concepts and results were applied for this motion.展开更多
The drift parameter estimation problem of the complex Ornstein-Uhlenbeck process driven by a complexα-stable motion is considered.Based on discrete observations,an estimator of the unknown drift parameter is construc...The drift parameter estimation problem of the complex Ornstein-Uhlenbeck process driven by a complexα-stable motion is considered.Based on discrete observations,an estimator of the unknown drift parameter is constructed by using the least squares method.Moreover,the strong consistency and the asymptotic distribution of the least squares estimator are derived under some assumptions.展开更多
In this paper, wave-body interactions under the effects of complex topography are investigated numerically by a two-phase incompressible Reynolds-Averaged Navier-Stokes(RANS) solver in OpenFOAM. A submerged bottom-sta...In this paper, wave-body interactions under the effects of complex topography are investigated numerically by a two-phase incompressible Reynolds-Averaged Navier-Stokes(RANS) solver in OpenFOAM. A submerged bottom-standing structure is distributed below the floating body, and the effects of the water depth and top width of the submerged structure on wave-body interactions are studied. The results show that the submerged structure can affect wave loads and roll motion. The vertical force can be amplified on the fixed body when the water depth of the submerged structure is smaller than half of the water depth of the body. The top width significantly affects the vertical force when the top width is smaller than the incident wave length and larger than the body width. For the free-rolling body, roll amplitude can be increased when the ratio of the incident wave length to the water depth of the submerged structure is large enough. On the resonance condition, roll amplitude is slightly reduced by the submerged structure. The effects of the top width on roll amplitude are remarkable when special conditions are fulfilled.展开更多
A complex number mode analysis approach is proposed for vibration reducing of structural flexible redundant manipulators by utilizing self motion. In the proposed approach, the self motion is evaluated to nullify th...A complex number mode analysis approach is proposed for vibration reducing of structural flexible redundant manipulators by utilizing self motion. In the proposed approach, the self motion is evaluated to nullify the modal exciting force of flexural motion, and the approach can be freely used when the degree of freedom of flexural motion is much greater than the available degree of reundancy. The availability and effectiveness of the proposed approach are demonstrated through numerical simulation with a four link spatial robotic manipulator possessing an end flexible link.展开更多
A minimum distortion direction prediction-based novel fast half-pixel motion vector search algorithm is proposed, which can reduce considerably the computation load of half-pixel search. Based on the single valley cha...A minimum distortion direction prediction-based novel fast half-pixel motion vector search algorithm is proposed, which can reduce considerably the computation load of half-pixel search. Based on the single valley characteristic of half-pixel error matching function inside search grid, the minimum distortion direction is predicted with the help of comparative results of sum of absolute difference(SAD) values of four integer-pixel points around integer-pixel motion vector. The experimental results reveal that, to all kinds of video sequences, the proposed algorithm can obtain almost the same video quality as that of the half-pixel full search algorithm with a decrease of computation cost by more than 66%.展开更多
基金supported by the National Natural Science Foundation of China(61871146)the Fundamental Research Funds for the Central Universities(FRFCU5710093720)。
文摘For ship targets with complex motion,it is difficult for the traditional monostatic inverse synthetic aperture radar(ISAR)imaging to improve the cross-range resolution by increasing of accumulation time.In this paper,a distributed ISAR imaging algorithm is proposed to improve the cross-range resolution for the ship target.Multiple stations are used to observe the target in a short time,thereby the effect of incoherence caused by the complex motion of the ship can be reduced.The signal model of ship target with three-dimensional(3-D)rotation is constructed firstly.Then detailed analysis about the improvement of crossrange resolution is presented.Afterward,we propose the methods of parameters estimation to solve the problem of the overlap or gap,which will cause a loss of resolution and is necessary for subsequent processing.Besides,the compressed sensing(CS)method is applied to reconstruct the echoes with gaps.Finally,numerical simulations are presented to verify the effectiveness and the robustness of the proposed algorithm.
基金Supported by National Natural Science Foundation of China(Grant No.52221005)Tsinghua-Toyota Joint Research Fund.
文摘Traditionally,passenger comfort in vehicles is perceived as being most influenced by acceleration and jerk.Consequently,the current research primarily focuses on developing control algorithms to limit the maximum acceleration and jerk of the vehicle in order to improve passenger comfort.However,naturalistic driving studies demonstrate that such simple characteristics are insufficient for accurately evaluating passenger comfort.This study identifies motion complexity as a key factor of passenger comfort.A series of naturalistic driving studies are conducted,during which passenger comfort is assessed using a 5-point Likert scale.Moreover,a real-time passenger comfort measurement based on electromyography(EMG)and stepwise regression is proposed to facilitate seamless data collection.Time-series features representing motion complexity are then introduced to better describe passenger comfort.Hierarchical regression confirms that simple characteristics of motion are insufficient to explain passenger comfort,and shows that the proposed motion complexity features have a substantial effect on passenger comfort.Finally,a machine learning-based real-time passenger comfort estimation method is developed according to the foregoing findings.Experimental results show that the proposed method can accurately estimate passenger comfort in real-time using only vehicle motion information.The findings of this study suggest that vehicle motion complexity should be considered in future passenger comfort studies.
文摘An analytical study of the two degrees of freedom nonlinear dynamical system is presented. The internal motion of the system is separated and described by one fourth order differential equation. An approximate approach allows reducing the problem to the Duffing equation with adequate initial conditions. A novel idea for an effective study of nonlinear dynamical systems consisting in a concept of the socalled limiting phase trajectories is applied. Both qualitative and quantitative complex analyses have been performed. Important nonlinear dynamical transition type phenomena are detected are investigated analytically.
文摘In this paper, the Steiner area formula and the polar moment of inertia were expressed during one-parameter closed planar homothetic inverse motions in complex plane. The Steiner point was defined when the rotation number was different zero and it was called the Steiner normal when the rotation number was equal to zero. The fixed pole point was given with its components and its relation between Steiner point or Steiner normal was explained. The sagittal motion of a telescopic crane was considered as an example. This motion was described by a double hinge consisting of the fixed control panel of the telescopic crane and the moving arm of the telescopic crane. The theoretical concepts and results were applied for this motion.
基金Key Natural Science Foundation of Anhui Education Commission,China(No.KJ2017A568)Natural Science Foundation of Anhui Province,China(No.1808085MA02)Natural Science Foundation of Bengbu University,China(No.2018CXY045)
文摘The drift parameter estimation problem of the complex Ornstein-Uhlenbeck process driven by a complexα-stable motion is considered.Based on discrete observations,an estimator of the unknown drift parameter is constructed by using the least squares method.Moreover,the strong consistency and the asymptotic distribution of the least squares estimator are derived under some assumptions.
基金supported by the National Key Research and Development Program of China under Grand No.2016YFB0200902supported by the Program for Guangdong Introducing Innovative and Entrepreneurial Teams under Grant No.2016ZT06D211
文摘In this paper, wave-body interactions under the effects of complex topography are investigated numerically by a two-phase incompressible Reynolds-Averaged Navier-Stokes(RANS) solver in OpenFOAM. A submerged bottom-standing structure is distributed below the floating body, and the effects of the water depth and top width of the submerged structure on wave-body interactions are studied. The results show that the submerged structure can affect wave loads and roll motion. The vertical force can be amplified on the fixed body when the water depth of the submerged structure is smaller than half of the water depth of the body. The top width significantly affects the vertical force when the top width is smaller than the incident wave length and larger than the body width. For the free-rolling body, roll amplitude can be increased when the ratio of the incident wave length to the water depth of the submerged structure is large enough. On the resonance condition, roll amplitude is slightly reduced by the submerged structure. The effects of the top width on roll amplitude are remarkable when special conditions are fulfilled.
文摘A complex number mode analysis approach is proposed for vibration reducing of structural flexible redundant manipulators by utilizing self motion. In the proposed approach, the self motion is evaluated to nullify the modal exciting force of flexural motion, and the approach can be freely used when the degree of freedom of flexural motion is much greater than the available degree of reundancy. The availability and effectiveness of the proposed approach are demonstrated through numerical simulation with a four link spatial robotic manipulator possessing an end flexible link.
文摘A minimum distortion direction prediction-based novel fast half-pixel motion vector search algorithm is proposed, which can reduce considerably the computation load of half-pixel search. Based on the single valley characteristic of half-pixel error matching function inside search grid, the minimum distortion direction is predicted with the help of comparative results of sum of absolute difference(SAD) values of four integer-pixel points around integer-pixel motion vector. The experimental results reveal that, to all kinds of video sequences, the proposed algorithm can obtain almost the same video quality as that of the half-pixel full search algorithm with a decrease of computation cost by more than 66%.
