The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Duncan J. Irschick - One of the best experts on this subject based on the ideXlab platform.
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Effects of temperature on Maximum Acceleration, deceleration and power output during vertical running in geckos.
Journal of Experimental Biology, 2006Co-Authors: Phillip Bergmann, Duncan J. IrschickAbstract:SUMMARY We studied performance and kinematics of the diurnal gekkonid lizard Phelsuma dubia while running vertically on a smooth surface at different temperatures. Trials were conducted at 5°C intervals from 15°C to 35°C. High-speed video recordings and digitization were used to obtain measures of instantaneous velocity, Acceleration, deceleration and mass-specific power output and maximal values for each were taken as performance measures. Kinematic variables were also obtained from high-speed video recordings and included stride length and duration, step (stance phase) length and duration, and duty factor. Maximal instantaneous velocity, Acceleration and deceleration increased by a factor of approximately 1.7 between 15°C and 25°C, and less so (∼1.2×) between 25°C and 35°C. Mass-specific power output was more temperature-sensitive, increasing 2.5× up to 25°C and a further 1.4× above that temperature. Stride length increased 1.5× over the entire temperature interval studied, while stride duration decreased by a factor of 1.9, suggesting that velocity is modulated by changes in both stride length and duration in P. dubia. Duty factor was not significantly influenced by temperature. Stride length was the only kinematic measure to be influenced by stride number, with second steps from a standstill being longer than first steps. We discuss the significance of velocity and Acceleration being affected in a similar manner by temperature, and that speed is modulated by both changes in stride length and duration.
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Effects of temperature on Maximum Acceleration, deceleration and power output during vertical running in geckos.
The Journal of experimental biology, 2006Co-Authors: Phillip Bergmann, Duncan J. IrschickAbstract:We studied performance and kinematics of the diurnal gekkonid lizard Phelsuma dubia while running vertically on a smooth surface at different temperatures. Trials were conducted at 5 degrees C intervals from 15 degrees C to 35 degrees C. High-speed video recordings and digitization were used to obtain measures of instantaneous velocity, Acceleration, deceleration and mass-specific power output and maximal values for each were taken as performance measures. Kinematic variables were also obtained from high-speed video recordings and included stride length and duration, step (stance phase) length and duration, and duty factor. Maximal instantaneous velocity, Acceleration and deceleration increased by a factor of approximately 1.7 between 15 degrees C and 25 degrees C, and less so (approximately 1.2x) between 25 degrees C and 35 degrees C. Mass-specific power output was more temperature-sensitive, increasing 2.5x up to 25 degrees C and a further 1.4x above that temperature. Stride length increased 1.5x over the entire temperature interval studied, while stride duration decreased by a factor of 1.9, suggesting that velocity is modulated by changes in both stride length and duration in P. dubia. Duty factor was not significantly influenced by temperature. Stride length was the only kinematic measure to be influenced by stride number, with second steps from a standstill being longer than first steps. We discuss the significance of velocity and Acceleration being affected in a similar manner by temperature, and that speed is modulated by both changes in stride length and duration.
Phillip Bergmann - One of the best experts on this subject based on the ideXlab platform.
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Effects of temperature on Maximum Acceleration, deceleration and power output during vertical running in geckos.
Journal of Experimental Biology, 2006Co-Authors: Phillip Bergmann, Duncan J. IrschickAbstract:SUMMARY We studied performance and kinematics of the diurnal gekkonid lizard Phelsuma dubia while running vertically on a smooth surface at different temperatures. Trials were conducted at 5°C intervals from 15°C to 35°C. High-speed video recordings and digitization were used to obtain measures of instantaneous velocity, Acceleration, deceleration and mass-specific power output and maximal values for each were taken as performance measures. Kinematic variables were also obtained from high-speed video recordings and included stride length and duration, step (stance phase) length and duration, and duty factor. Maximal instantaneous velocity, Acceleration and deceleration increased by a factor of approximately 1.7 between 15°C and 25°C, and less so (∼1.2×) between 25°C and 35°C. Mass-specific power output was more temperature-sensitive, increasing 2.5× up to 25°C and a further 1.4× above that temperature. Stride length increased 1.5× over the entire temperature interval studied, while stride duration decreased by a factor of 1.9, suggesting that velocity is modulated by changes in both stride length and duration in P. dubia. Duty factor was not significantly influenced by temperature. Stride length was the only kinematic measure to be influenced by stride number, with second steps from a standstill being longer than first steps. We discuss the significance of velocity and Acceleration being affected in a similar manner by temperature, and that speed is modulated by both changes in stride length and duration.
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Effects of temperature on Maximum Acceleration, deceleration and power output during vertical running in geckos.
The Journal of experimental biology, 2006Co-Authors: Phillip Bergmann, Duncan J. IrschickAbstract:We studied performance and kinematics of the diurnal gekkonid lizard Phelsuma dubia while running vertically on a smooth surface at different temperatures. Trials were conducted at 5 degrees C intervals from 15 degrees C to 35 degrees C. High-speed video recordings and digitization were used to obtain measures of instantaneous velocity, Acceleration, deceleration and mass-specific power output and maximal values for each were taken as performance measures. Kinematic variables were also obtained from high-speed video recordings and included stride length and duration, step (stance phase) length and duration, and duty factor. Maximal instantaneous velocity, Acceleration and deceleration increased by a factor of approximately 1.7 between 15 degrees C and 25 degrees C, and less so (approximately 1.2x) between 25 degrees C and 35 degrees C. Mass-specific power output was more temperature-sensitive, increasing 2.5x up to 25 degrees C and a further 1.4x above that temperature. Stride length increased 1.5x over the entire temperature interval studied, while stride duration decreased by a factor of 1.9, suggesting that velocity is modulated by changes in both stride length and duration in P. dubia. Duty factor was not significantly influenced by temperature. Stride length was the only kinematic measure to be influenced by stride number, with second steps from a standstill being longer than first steps. We discuss the significance of velocity and Acceleration being affected in a similar manner by temperature, and that speed is modulated by both changes in stride length and duration.
Timothy Paul Hutchinson - One of the best experts on this subject based on the ideXlab platform.
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Accelerations relevant to blunt trauma: theory and data
Industrial Health, 2015Co-Authors: Timothy Paul HutchinsonAbstract:Maximum Acceleration and the Head Injury Criterion (HIC) are both used as indicators of likely head injury severity. A dataset has previously been published of impacts of an instrumented missile on four ground surfaces having a layer of between 0 and 16 cm of sand. The dataset is compared with recently-developed theory that predicts power-function dependence of Maximum Acceleration and HIC on drop height. That prediction was supported by the data. The surfaces differed in respect of the exponents estimated.
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Dependence of the Head Injury Criterion and Maximum Acceleration on headform mass and initial velocity in tests simulating pedestrian impacts with vehicles
Journal of Biomechanical Engineering, 2013Co-Authors: Timothy Paul HutchinsonAbstract:Background. Impact testing of pedestrian headforms is usually conducted at one velocity and with one mass of headform, but real impacts occur at a range of velocities and masses. A method is proposed to predict the Head Injury Criterion (HIC) and similar quantities at other velocities from their values observed under test conditions. Method. The assumption is made that force during the impact is proportional to (x^c).[1 + (b/v)x?]. (The notation used is x = displacement, its differential x? = instantaneous velocity, m = mass of headform, and v = initial velocity.) This represents a spring that is nonlinear if c is not 1, with damping if b is not 0. This equation is not solved, but some properties of the solution are obtained. Results. It is shown that HIC is proportional to (m^p).(v^q), where the exponents are p = -1.5/(c+1) and q = (4c+1)/(c+1). Conclusion. Simple formulae are obtained for the dependence of HIC, Maximum Acceleration, and Maximum displacement on velocity and mass. These are relevant to many types of impact. Language: en
Marcus G Pandy - One of the best experts on this subject based on the ideXlab platform.
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Lower-limb joint mechanics during Maximum Acceleration sprinting.
The Journal of experimental biology, 2019Co-Authors: Anthony G Schache, Nicholas A.t. Brown, Adrian K M Lai, Kay M Crossley, Marcus G PandyAbstract:We explored how humans adjust the stance phase mechanical function of their major lower-limb joints (hip, knee, ankle) during Maximum Acceleration sprinting. Experimental data [motion capture and ground reaction force (GRF)] were recorded from eight participants as they performed overground sprinting trials. Six alternative starting locations were used to obtain a dataset that incorporated the majority of the Acceleration phase. Experimental data were combined with an inverse-dynamics-based analysis to calculate lower-limb joint mechanical variables. As forward Acceleration magnitude decreased, the vertical GRF impulse remained nearly unchanged whereas the net horizontal GRF impulse became smaller as a result of less propulsion and more braking. Mechanical function was adjusted at all three joints, although more dramatic changes were observed at the hip and ankle. The impulse from the ankle plantar-flexor moment was almost always larger than those from the hip and knee extensor moments. Forward Acceleration magnitude was linearly related to the impulses from the hip extensor moment (R 2=0.45) and the ankle plantar-flexor moment (R 2=0.47). Forward Acceleration magnitude was also linearly related to the net work done at all three joints, with the ankle displaying the strongest relationship (R 2=0.64). The ankle produced the largest amount of positive work (1.55±0.17 J kg-1) of all the joints, and provided a significantly greater proportion of the summed amount of lower-limb positive work as running speed increased and forward Acceleration magnitude decreased. We conclude that the hip and especially the ankle represent key sources of positive work during the stance phase of Maximum Acceleration sprinting.
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human ankle plantar flexor muscle tendon mechanics and energetics during Maximum Acceleration sprinting
Journal of the Royal Society Interface, 2016Co-Authors: Anthony G Schache, Nicholas A.t. Brown, Marcus G PandyAbstract:Tendon elastic strain energy is the dominant contributor to muscle–tendon work during steady-state running. Does this behaviour also occur for sprint Accelerations? We used experimental data and computational modelling to quantify muscle fascicle work and tendon elastic strain energy for the human ankle plantar flexors (specifically soleus and medial gastrocnemius) for multiple foot contacts of a maximal sprint as well as for running at a steady-state speed. Positive work done by the soleus and medial gastrocnemius muscle fascicles decreased incrementally throughout the maximal sprint and both muscles performed more work for the first foot contact of the maximal sprint (FC1) compared with steady-state running at 5 m s−1 (SS5). However, the differences in tendon strain energy for both muscles were negligible throughout the maximal sprint and when comparing FC1 to SS5. Consequently, the contribution of muscle fascicle work to stored tendon elastic strain energy was greater for FC1 compared with subsequent foot contacts of the maximal sprint and compared with SS5. We conclude that tendon elastic strain energy in the ankle plantar flexors is just as vital at the start of a maximal sprint as it is at the end, and as it is for running at a constant speed.
Cai Xia Yang - One of the best experts on this subject based on the ideXlab platform.
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local Maximum Acceleration based rotating machinery fault classification using knn
Electro Information Technology, 2019Co-Authors: Santosh Paudyal, Saifuddin Ahmed Atique, Cai Xia YangAbstract:Rotating machinery are continuously operated tools for power generation and mechanical applications. The smooth operation of these tools is fundamental in businesses to accomplish their profitability. The status of such machines can be monitored by continuously assessing their working parameters that aid to identify abnormal behaviors. Upon detection of abnormal behaviors, such machines can be early scheduled for maintenance. Conditioned Based Maintenance (CBM) is one such approach that continuously monitors the machine and recommends taking action before equipment fails. This approach uses monitoring parameters such as temperature, pressure, and vibration signals to minimize unnecessary breakdown and catastrophic failure. Vibration parameters based machine fault identification approach is one of the widely used methods in CBM. Various machine malfunctions can be predicted and detected based on energy at specific frequencies of vibration signals. Common faults such as unbalanced and misalignment are often identified by examining the operating frequencies and their harmonics. Based on machine malfunctions, the dominant differences are expected at these frequencies. Barring few dominating peaks, other peaks are not exactly located at harmonic speed, so it can be misleading to use information from only harmonic speed. Rather than just examining operating frequencies and their harmonics, we looked at the local peaks and identified their frequencies. The Acceleration amplitude at the operating speed and the local Maximum Acceleration amplitude are selected as a vibration feature for the fault classification. The proposed KNN classifier demonstrated its reliability with an accuracy of over 96% for the tested data set of 25 samples.
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EIT - Local Maximum Acceleration Based Rotating Machinery Fault Classification Using KNN
2019 IEEE International Conference on Electro Information Technology (EIT), 2019Co-Authors: Santosh Paudyal, Saifuddin Ahmed Atique, Cai Xia YangAbstract:Rotating machinery are continuously operated tools for power generation and mechanical applications. The smooth operation of these tools is fundamental in businesses to accomplish their profitability. The status of such machines can be monitored by continuously assessing their working parameters that aid to identify abnormal behaviors. Upon detection of abnormal behaviors, such machines can be early scheduled for maintenance. Conditioned Based Maintenance (CBM) is one such approach that continuously monitors the machine and recommends taking action before equipment fails. This approach uses monitoring parameters such as temperature, pressure, and vibration signals to minimize unnecessary breakdown and catastrophic failure. Vibration parameters based machine fault identification approach is one of the widely used methods in CBM. Various machine malfunctions can be predicted and detected based on energy at specific frequencies of vibration signals. Common faults such as unbalanced and misalignment are often identified by examining the operating frequencies and their harmonics. Based on machine malfunctions, the dominant differences are expected at these frequencies. Barring few dominating peaks, other peaks are not exactly located at harmonic speed, so it can be misleading to use information from only harmonic speed. Rather than just examining operating frequencies and their harmonics, we looked at the local peaks and identified their frequencies. The Acceleration amplitude at the operating speed and the local Maximum Acceleration amplitude are selected as a vibration feature for the fault classification. The proposed KNN classifier demonstrated its reliability with an accuracy of over 96% for the tested data set of 25 samples.