The Experts below are selected from a list of 15237 Experts worldwide ranked by ideXlab platform
Andrew J Burton - One of the best experts on this subject based on the ideXlab platform.
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carbon fluxes storage and harvest removals through 60 years of stand development in red pine plantations and mixed hardwood stands in northern michigan usa
Forest Ecology and Management, 2015Co-Authors: Adam Gahagan, Christian P Giardina, John S King, Dan Binkley, Kurt S Pregitzer, Andrew J BurtonAbstract:Abstract The storage and flow of carbon (C) into and out of forests can differ under the influence of dominant tree species because of species-based variation in C production, decomposition, retention, and harvest-based export. Following abandonment of agricultural activities in the first half of the 20th century, many landscapes of the Great Lakes region (USA) were planted to red pine (Pinus resinosa) or naturally regenerated to northern hardwood species including sugar maple (Acer saccharum), red oak (Quercus rubra) and red maple (Acer rubrum). We located eight pairs of adjacent, similarly aged (∼60 yr) stands of planted red pine and naturally regenerated hardwood forests on previous agricultural fields. We found that the hardwood forests stored more C than pine stands (255 vs. 201 Mg C ha−1), with both storing substantially more than an adjacent area maintained as pasture (107 Mg C ha−1). The greater accumulation of C in the hardwood stands occurred mostly in living biomass. No significant differences for soil C (to 1 m depth) were found between forest types, despite significantly higher belowground inputs and aboveground litterfall in hardwood stands. Notably, both forest types had about 18% more soil C than the pasture, with O horizon C accounting for about one-third of the increase under trees. Forest type had no significant effect on estimated amount of exported C despite fairly large differences in projected end uses (solid wood products, land-fills, bioenergy). Using adjacent pasture as our baseline condition, we combined estimated on-site accumulation rates with estimates of exported C, and found that average total C sequestration rates were higher for hardwood (2.9 Mg C ha−1 yr−1) than red pine plots (2.3 Mg C ha−1 yr−1). The modeled potential contribution of exported C to these sequestration rate estimates did not differ between species, but the fate of modeled post-harvest off-site C may exert a large influence on sequestration rate estimates depending on Actual Displacement actions, including product longevity. These results show that tree species selection has the potential to impact C sequestration rates but effects vary by ecosystem component and could not be predicted from previous species effects studies.
Craig A Rogers - One of the best experts on this subject based on the ideXlab platform.
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engineering feasibility of induced strain actuators for rotor blade active vibration control
Journal of Intelligent Material Systems and Structures, 1995Co-Authors: Victor Giurgiutiu, Zaffir Chaudhry, Craig A RogersAbstract:Rotor blade vibration reduction based on Higher Harmonic Control—Individual Blade Control (HHC-IBC) principles is presented as a possible area of application of Induced Strain Actuation (ISA). Recent theoretical and experimental work on achieving HHC-IBC through conventional and ISA means is reviewed. Though the force-Displacement and power-energy estimates vary significantly, some common-base values are identified. Hence, a bench-mark specification for a tentative HHC-IBC device based on the aerodynamic servo-flap principle operated through ISA means is developed. Values for the invariant quantities of energy, power and force-Displacement product are identified, along with Actual Displacement and force values of practical interest. The implementation feasibility of this specification into an Actual ISA device is then discussed. It is shown that direct actuation is not feasible due to the large required length of the ISA device, resulting in excessive compressibility effects (Displacement loss and parasit...
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engineering feasibility of induced strain actuators for rotor blade active vibration control
Smart Structures and Materials 1994: Smart Structures and Intelligent Systems, 1994Co-Authors: Victor Giurgiutiu, Zaffir Chaudhry, Craig A RogersAbstract:Rotor blade vibration reduction based on higher harmonic control - individual blade control (HHC-IBC) principles is presented as a possible area of application of induced strain actuator (ISA). Recent theoretical and experimental work on achieving HHC-IBC through conventional and ISA means is reviewed. Though the force- Displacement and power-energy estimates vary significantly, some common-base values are identified. Hence, a benchmark specification for a tentative HHC-IBC device based on the aerodynamic servo-flap principle operated through ISA means is developed. Values for the invariant quantities of energy, power, and force-Displacement product are identified, along with Actual Displacement and force values of practical interest. The implementation feasibility of this specification into an Actual ISA device is then discussed. It is shown that direct actuation is not feasible due to the large required length of the ISA device, resulting in excessive compressibility effects (Displacement loss and parasitic strain energy). Indirect actuation through a Displacement amplifier was found to be more feasible, since it allows for matching the internal and external stiffness. A closed-form formula was developed for finding the optimal amplification gain for each required value of the closed- loop amplification ratio. Preliminary studies based on force, stroke, energy, and output power requirements show that available ISA stacks coupled with an optimally designed Displacement amplifier might meet the benchmark specifications.
Adam Gahagan - One of the best experts on this subject based on the ideXlab platform.
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carbon fluxes storage and harvest removals through 60 years of stand development in red pine plantations and mixed hardwood stands in northern michigan usa
Forest Ecology and Management, 2015Co-Authors: Adam Gahagan, Christian P Giardina, John S King, Dan Binkley, Kurt S Pregitzer, Andrew J BurtonAbstract:Abstract The storage and flow of carbon (C) into and out of forests can differ under the influence of dominant tree species because of species-based variation in C production, decomposition, retention, and harvest-based export. Following abandonment of agricultural activities in the first half of the 20th century, many landscapes of the Great Lakes region (USA) were planted to red pine (Pinus resinosa) or naturally regenerated to northern hardwood species including sugar maple (Acer saccharum), red oak (Quercus rubra) and red maple (Acer rubrum). We located eight pairs of adjacent, similarly aged (∼60 yr) stands of planted red pine and naturally regenerated hardwood forests on previous agricultural fields. We found that the hardwood forests stored more C than pine stands (255 vs. 201 Mg C ha−1), with both storing substantially more than an adjacent area maintained as pasture (107 Mg C ha−1). The greater accumulation of C in the hardwood stands occurred mostly in living biomass. No significant differences for soil C (to 1 m depth) were found between forest types, despite significantly higher belowground inputs and aboveground litterfall in hardwood stands. Notably, both forest types had about 18% more soil C than the pasture, with O horizon C accounting for about one-third of the increase under trees. Forest type had no significant effect on estimated amount of exported C despite fairly large differences in projected end uses (solid wood products, land-fills, bioenergy). Using adjacent pasture as our baseline condition, we combined estimated on-site accumulation rates with estimates of exported C, and found that average total C sequestration rates were higher for hardwood (2.9 Mg C ha−1 yr−1) than red pine plots (2.3 Mg C ha−1 yr−1). The modeled potential contribution of exported C to these sequestration rate estimates did not differ between species, but the fate of modeled post-harvest off-site C may exert a large influence on sequestration rate estimates depending on Actual Displacement actions, including product longevity. These results show that tree species selection has the potential to impact C sequestration rates but effects vary by ecosystem component and could not be predicted from previous species effects studies.
Victor Giurgiutiu - One of the best experts on this subject based on the ideXlab platform.
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engineering feasibility of induced strain actuators for rotor blade active vibration control
Journal of Intelligent Material Systems and Structures, 1995Co-Authors: Victor Giurgiutiu, Zaffir Chaudhry, Craig A RogersAbstract:Rotor blade vibration reduction based on Higher Harmonic Control—Individual Blade Control (HHC-IBC) principles is presented as a possible area of application of Induced Strain Actuation (ISA). Recent theoretical and experimental work on achieving HHC-IBC through conventional and ISA means is reviewed. Though the force-Displacement and power-energy estimates vary significantly, some common-base values are identified. Hence, a bench-mark specification for a tentative HHC-IBC device based on the aerodynamic servo-flap principle operated through ISA means is developed. Values for the invariant quantities of energy, power and force-Displacement product are identified, along with Actual Displacement and force values of practical interest. The implementation feasibility of this specification into an Actual ISA device is then discussed. It is shown that direct actuation is not feasible due to the large required length of the ISA device, resulting in excessive compressibility effects (Displacement loss and parasit...
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engineering feasibility of induced strain actuators for rotor blade active vibration control
Smart Structures and Materials 1994: Smart Structures and Intelligent Systems, 1994Co-Authors: Victor Giurgiutiu, Zaffir Chaudhry, Craig A RogersAbstract:Rotor blade vibration reduction based on higher harmonic control - individual blade control (HHC-IBC) principles is presented as a possible area of application of induced strain actuator (ISA). Recent theoretical and experimental work on achieving HHC-IBC through conventional and ISA means is reviewed. Though the force- Displacement and power-energy estimates vary significantly, some common-base values are identified. Hence, a benchmark specification for a tentative HHC-IBC device based on the aerodynamic servo-flap principle operated through ISA means is developed. Values for the invariant quantities of energy, power, and force-Displacement product are identified, along with Actual Displacement and force values of practical interest. The implementation feasibility of this specification into an Actual ISA device is then discussed. It is shown that direct actuation is not feasible due to the large required length of the ISA device, resulting in excessive compressibility effects (Displacement loss and parasitic strain energy). Indirect actuation through a Displacement amplifier was found to be more feasible, since it allows for matching the internal and external stiffness. A closed-form formula was developed for finding the optimal amplification gain for each required value of the closed- loop amplification ratio. Preliminary studies based on force, stroke, energy, and output power requirements show that available ISA stacks coupled with an optimally designed Displacement amplifier might meet the benchmark specifications.
Celal Batur - One of the best experts on this subject based on the ideXlab platform.
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precision tracking control of shape memory alloy actuators using neural networks and a sliding mode based robust controller
Smart Materials and Structures, 2003Co-Authors: Gangbing Song, V Chaudhry, Celal BaturAbstract:This paper presents a new approach to controlling shape memory alloy (SMA) actuators with hysteresis compensation by using a neural network feedforward controller and a sliding-mode based robust feedback controller. SMA actuators exhibit severe hysteresis, which is often responsible for position inaccuracy in a regulation or tracking system and may even cause instability in some cases. A single SMA wire actuator is used in this research. A testing system, which includes a wire stand, a linear bearing, a bias spring, a position sensor, a programmable current amplifier and a PC-based digital data acquisition and real-time control system, is used to test the SMA wire actuator in both open-and closed-loop fashions. The proposed control includes two major parts: a feedforward neural network controller, which is used to cancel or reduce the hysteresis, and a sliding-mode based robust feedback controller, which is employed to compensate uncertainties such as the error in hysteresis cancellation and ensures the system's stability. The feedforward neural network controller is designed based on the experimental results of open-loop testing of the wire actuator. With the proposed control, tests of the SMA actuator following sinusoidal commands with different frequencies and magnitudes are conducted. The experiments show that the Actual Displacement of the SMA actuator with the proposed control closely followed that of the desired sinusoidal command.
