The Experts below are selected from a list of 5874 Experts worldwide ranked by ideXlab platform
Aftab E Patla - One of the best experts on this subject based on the ideXlab platform.
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effects of head immobilization on the coordination and control of head and body reorientation and translation during steering
Experimental Brain Research, 2001Co-Authors: Mark A Hollands, K L Sorensen, Aftab E PatlaAbstract:Changing the direction of locomotion involves lateral translation of the body in addition to body reorientation to align with the new travel direction. We designed this study to investigate the CNS control of these postural adjustments. The specific aims of the study were: first, to test the hypothesis that anticipatory head movements towards the new travel path are proactively contRolled by the CNS to provide a stable frame of reference for body reorientation and, second, to investigate the relative contribution of foot placement and other mechanisms to the control of lateral body translation during steering. We achieved these aims by carrying out a comprehensive biomechanical analysis of participants performing a steering paradigm and observing the effects of immobilizing the head (by fixing it to the trunk) on postural control and the sequencing of body segment reorientation. Participants performed a task whereby they were visually cued to change their direction of walking by 30° or 60°, left or right, at the midpoint of a 9-m path. The temporal sequence of body reorientation was consistent with previous findings that the head starts to turn in the direction of travel before the rest of the body. Translation of the centre of mass (COM) in the new travel direction was achieved both through alternate placement of the contralateral foot prior to the turn step and use of a hip strategy to control the body pendulum during swing. Immobilizing the head resulted in the following significant changes: earlier onset of trunk yaw with respect to cue delivery, later trunk Roll onset and a reduction in trunk Roll Amplitude. These results provide valuable information regarding the biomechanics of steering and support the hypothesis that aligning the head with motor or locomotor goals using vision provides the CNS with a stable frame of reference, independent of gaze, that can be used to control the repositioning of the body in space.
Mark A Hollands - One of the best experts on this subject based on the ideXlab platform.
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effects of head immobilization on the coordination and control of head and body reorientation and translation during steering
Experimental Brain Research, 2001Co-Authors: Mark A Hollands, K L Sorensen, Aftab E PatlaAbstract:Changing the direction of locomotion involves lateral translation of the body in addition to body reorientation to align with the new travel direction. We designed this study to investigate the CNS control of these postural adjustments. The specific aims of the study were: first, to test the hypothesis that anticipatory head movements towards the new travel path are proactively contRolled by the CNS to provide a stable frame of reference for body reorientation and, second, to investigate the relative contribution of foot placement and other mechanisms to the control of lateral body translation during steering. We achieved these aims by carrying out a comprehensive biomechanical analysis of participants performing a steering paradigm and observing the effects of immobilizing the head (by fixing it to the trunk) on postural control and the sequencing of body segment reorientation. Participants performed a task whereby they were visually cued to change their direction of walking by 30° or 60°, left or right, at the midpoint of a 9-m path. The temporal sequence of body reorientation was consistent with previous findings that the head starts to turn in the direction of travel before the rest of the body. Translation of the centre of mass (COM) in the new travel direction was achieved both through alternate placement of the contralateral foot prior to the turn step and use of a hip strategy to control the body pendulum during swing. Immobilizing the head resulted in the following significant changes: earlier onset of trunk yaw with respect to cue delivery, later trunk Roll onset and a reduction in trunk Roll Amplitude. These results provide valuable information regarding the biomechanics of steering and support the hypothesis that aligning the head with motor or locomotor goals using vision provides the CNS with a stable frame of reference, independent of gaze, that can be used to control the repositioning of the body in space.
J G Kherian - One of the best experts on this subject based on the ideXlab platform.
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on Roll hydrodynamics of fpso s fitted with bilge keels and riser balcony
ASME 2011 30th International Conference on Ocean Offshore and Arctic Engineering, 2011Co-Authors: R Van T Veer, F Fathi, J G KherianAbstract:The topic of this paper is the Roll motion prediction of ship-shaped FPSO’s, designed for continuous operation at site location. The maximum Roll Amplitude is a critical operability parameter which is difficult to predict accurately due to the nonlinear Roll damping associated with the appendages. This paper contributes to the understanding of Roll damping physics through model test results, CFD simulations and potential flow predictions. The model tests discussed concern two different Floating Production, Storage and Offloading (FPSO) units, designed by SBM as spread-moored units for operation offshore Brazil. The relevant Roll damping appendages are the bilge keels on both sides and the submerged riser balcony on one side of the vessel. In particular the riser balcony complicates the motion prediction and was a main reason for the model tests and CFD investigation. The results presented focus on Roll motion prediction in the frequency domain.Copyright © 2011 by ASME
Shuqi Wang - One of the best experts on this subject based on the ideXlab platform.
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the effects of Roll motion of the floating platform on hydrodynamics performance of horizontal axis tidal current turbine
Journal of Marine Science and Technology, 2017Co-Authors: Shuqi Wang, Jianhua Zhang, Liang ZhangAbstract:Under the condition of actual sea state, hydrodynamic characteristics of floating horizontal-axis turbine are related to wave characteristics and floating carrier motion responses. We recently published the hydrodynamic performance and axial damping coefficient of the horizontal-axis tidal current turbine influenced by surge motion in constant inflow using CFD simulation (Zhang et al. Renew Energy 74:796–802, 2015). Encouraged by this result, this paper uses sliding mesh to analyze the hydrodynamic characteristics in uniform stream when the turbine is forced to Roll and studies influences of different Roll frequency, Roll Amplitude, and tip speed ratio on turbine’s performance. Roll-damping coefficient and added mass coefficient can be derived by torque almanacs curve of Rolling turbine by the least square method. Results show that the turbine axial load, Roll moment, and energy utilization ratio will fluctuate in Roll motion; the more Roll frequency and Roll Amplitude, and the more load and moment wave Amplitude of momentary value. The crest value occurs in the balance position of Rolling, while the Amplitude of oscillation depends on the angular speed of Rolling and rotating speed of the turbine. The frequency and Amplitude of the Roll have little impact on damping coefficient, but rotational speed of the turbine has positive impact on this coefficient. Results of this study can provide data to study motion response of floating carrier for floating tidal current turbine system and check the structural design and control of the electric output.
Fuat Alarcin - One of the best experts on this subject based on the ideXlab platform.
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internal model control using neural network for ship Roll stabilization
Journal of Marine Science and Technology, 2007Co-Authors: Fuat AlarcinAbstract:In this paper, a neural network (NN) based on internal model control (IMC) is developed to adjust control parameters for Roll motions of a container ship. ContRoller architecture, which combines neural network with internal model control, has been outlined and its effectiveness demonstrated on the container ship Roll stabilizer. The control signal error is used with back-propagation algorithm to update the weights of the neural contRoller. In conclusion, the neural network based on internal model control systems are analyzed, and compared to classical PID control results. As can be seen from numerical results, the NN based on IMC is implemented successfully to reduce Roll Amplitude.
