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ItemBiomechanics of locomotion during ground translation perturbations(Georgia Institute of Technology, 2023-02-23) Leestma, Jennifer K. ; Golyski, Pawel R. ; Smith, Courtney R. ; Sawicki, Gregory S. ; Young, AaronThe purpose of this data set is to enable the investigation of human balance and recovery strategies during perturbed walking. We performed a study where participants walked while being exposed to ground translation perturbations. We varied the magnitude, direction, and onset time of these perturbations while collecting various biomechanical outcome metrics.
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ItemMulti-Context, User-Independent, Real-Time Intent Recognition for Powered Lower-Limb Prostheses(Georgia Institute of Technology, 2023) Bhakta, Krishan ; Maldonado-Contreras, Jairo ; Camargo, Jonathan ; Zhou, Sixu ; Compton, William ; Herrin, Kinsey R. ; Young, AaronCommunity ambulation is a critical component in maintaining a healthy lifestyle but has numerous task demands that can be challenging for individuals with limb loss. In wearable robotics, specifically powered prostheses, a need exists to provide intuitive and seamless assistance to the user. We developed a user-independent and multi-context, intent recognition system that was deployed in real-time to an open-source knee and ankle powered prosthesis (OSL). The intent recognition system predicted user intent and environment attributes using embedded sensing and control. Eleven individuals with transfemoral amputation were recruited for this study, in which 7 individuals were used for real-time validation. Here, we proposed a hierarchical control framework in which the intelligent prosthesis would first predict locomotion mode and subsequently estimate an environmental variable (i.e., walking speed or slope). Two main conclusions were found: 1) the user-independent (IND) performance across mode, speed, and slope was not statistically different from user-dependent (DEP) models in real-time, even though the offline performance of the IND system was worse 2) IND walking speed estimates showed ~0.09 m/s average error and slope estimates showed ~0.95 deg average error, which provided acceptable performance for modulating ankle and knee assistance across multi-context scenarios. Our study suggests that intelligent controllers can generalize to individuals and can perform well in real-time. In addition, we made our training dataset and the developed machine learning models publicly available to an open-source repository. This approach provides novel prosthesis users with autonomous and task-dependent functionality across real-world walking tasks.
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ItemCharacterization of H2O vapor transport through Lunar Mare and Lunar Highland simulants at low pressures for in-situ resource utilization - Data Files(Georgia Institute of Technology, 2023) Farr, Tyler P. ; Jones, Brant M. ; Orlando, Thomas M. ; Loutzenhiser, Peter G.H2O(v) transport through packed beds of Lunar Mare and Lunar Highland simulants was examined for relevant in-situ resource utilization conditions to inform volatile H2O extraction from the lunar surface. Experiments were conducted with different packed beds at average bed pressures of 105 and 3,960 Pa at ~350K for different flow regimes in the range of 0.47 < < 20.7. A piecewise model was used to describe the transition between the advective flow regime to the Knudsen flow regime. Non-linear regression was used to determine a tortuosity shape factor of 2.6175 ± 0.0092 and 0.0937 ± 0.0008, a transition Knudsen number of 1.5984 and 4.0995, and a viscous flow permeability of 0.8238 ± 0.0010 × 10-12 m2 and 5.4805 ± 0.0061 × 10-12 m2 for the Lunar Mare simulant and Lunar Highland simulant, respectively. The resulting Knudsen diffusivities are 6.6530 ± 0.0018 cm2·s-1 and 18.9008 ± 0.0100 cm2·s-1, respectively. These results are necessary for informing the development of in-situ resource utilization technologies for the thermal extraction of H2O.
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ItemA Human Lower-Limb Biomechanics and Wearable Sensors Dataset During Cyclic and Non-Cyclic Activities(Georgia Institute of Technology, 2023) Scherpereel, Keaton ; Molinaro, Dean ; Inan, Omer ; Shepherd, Maxwell ; Young, AaronTasks of daily living are often sporadic, highly variable, and asymmetric. Analyzing these real-world non-cyclic activities is integral for expanding the applicability of exoskeletons, protheses, wearable sensing, and activity classification to real life, and could provide new insights into human biomechanics. Yet, currently available biomechanics datasets focus on either highly consistent, continuous, and symmetric activities, such as walking and running, or only a single specific non-cyclic task. To capture a more holistic picture of lower limb movements in everyday life, we collected data from 12 participants performing 20 non-cyclic activities (e.g. sit-to-stand, jumping, squatting, lunging, cutting) as well as 11 cyclic activities (e.g. walking, running) while kinematics (motion capture and IMUs), kinetics (force plates), and EMG were collected. This dataset provides normative biomechanics for a highly diverse range of activities and common tasks from a consistent set of participants and sensors.
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ItemExperimental characterization of extreme temperature granular flows for solar thermal energy transport and storage - supplementary data(Georgia Institute of Technology, 2022) Bagepallii, Malavika V. ; Jeong, Shin Young ; Brooks, Joshua ; Zhang, Zhuomin ; Ranjan, Devesh ; Loutzenhiser, Peter G.High-temperature, dense granular flows along an inclined plane were considered for solar thermal energy transport and storage with sintered bauxite particles. A series of experiments was performed for particle inlet temperatures of ~ 200, 400, 600, and 800 °C to understand the mechanisms of granular flows at extreme temperatures. Mass flow rates were measured using a load cell and free-surface velocities were measured and computed using particle image velocimetry. Surface temperatures were measured using infrared cameras. A significant decrease in steady-state particle mass flow rate was observed with increasing temperature due to changing flow properties. A decrease in bulk particle free-surface velocities was observed at higher temperatures. Free-surface velocity measurement error between experiments were within 20% of the average. The particle surface temperatures decreased from inlet to outlet with larger gradients at higher temperatures observed due to increasing convection and radiative heat losses. A decrease in temperature was observed along the side walls due to a decrease in particle velocities.
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ItemGeorgia Tech | Gen3 CSP Mechanical and Radiative Property Database(Georgia Institute of Technology, 2022) Loutzenhiser, Peter G. ; Ranjan, Devesh ; Zhang, Zhuomin ; Schrader, Andrew J. ; Pathikonda, Gokul ; Brooks, Joshua ; Bagepali, Malavika ; Chuyang, Chen ; Jeong, Shin Young ; Yarrington, Justin D.The focus of this work is to systematically characterize the heat transfer and flow properties for particulate (granular) flows at elevated temperatures up to 800 °C. This work is intended to address a serious gap within the field related to the understanding and modeling of particulate flow behavior and the related heat transfer at different temperatures, which directly correspond to the operating points of concentrated solar power applications that use particles for heat storage. These objectives will be accomplished using a combination of fundamental experimental measurements, modeling, and simplified flow experimentations over a range of temperatures. Ceramic sintered bauxite proppants will be used as a baseline for comparison with a range of other particles used for various applications. These results will be made available during the project to the research community to provide updated guidance and inputs to current modeling efforts to improve their results.
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ItemGranular Flow Experiments and Models Coupled with Temperature-Dependent Measured Properities for Solar Thermal Energy Transport and Storage Dataset(Georgia Institute of Technology, 2022) Bagepallii, Malavika V.Concentrated solar power is one of the most promising alternative sources of large- scale energy production with numerous applications including production of electricity, renewable fuel, and production of heat for industrial processes. High temperature granular media were characterized for solar thermal energy transport and storage. The characterization included three steps: (1) measurement of flow properties of granular media at different temperatures, including particle shape and size, elastic properties, coefficient of restitution, and coefficient of static friction; (2) performance of experiments using a range of temperatures in different flow geometries, including flow on incline plane and flow on stair geometry; and (3) assessment of flow and heat transfer models using the measured temperature dependent flow and thermophysical properties. The Lagrangian discrete element method was used to model granular flows and a Eulerian multiphase model was used for heat transfer modeling. The flow and heat transfer models were compared with experimental results to validate and inform the design of different solar particle heating receivers and reactors.
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ItemHigh-Temperature Granular Flow Experiments and Analysis along a Stair Geometry for Solar Particle Receiver Applications Dataset(Georgia Institute of Technology, 2022) Bagepallii, Malavika V. ; Jeong, Shin Young ; Brooks, Joshua ; Zhang, Zhuomin ; Ranjan, Devesh ; Loutzenhiser, Peter G.High-temperature, dense granular flows along a stair geometry were considered for application in concentrated solar receivers. A series of experiments was performed using sintered bauxite particles with inlet temperatures of ~600°C and ~800 °C. Mass flow rates were measured using a load cell. Changes in particle arial fraction was determined using high speed images and free-surface velocities were measured and computed using particle image velocimetry. Particle temperatures were measured using infrared cameras. Mass flow rate was steady during the experiment and did not change with temperature. Areal fraction decreased along the curtain flow direction due to increase in particle velocities. Particle velocities at curtain regions were in good agreement with theory. Average temperature decreased along the flow directions and were repeatable between experiments, with error within 1% deviation from the mean computed using a 95% confidence interval. Particle bed velocities at the stair geometry decreased with depth of layers due to shear forces from stagnant layers. The temperature of particle layers correlated well with velocities wherein inner, slow-moving layers were at lower temperatures compared to upper, fast-moving layers.
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ItemCharacterization of H2O Transport Through Johnson Space Center Number 1A Lunar Regolith Simulant at Low Pressure for In-situ Resource Utilization - Data File(Georgia Institute of Technology, 2021-02-04) Schieber, Garrett L. ; Jones, Brant M. ; Orlando, Thomas M. ; Loutzenhiser, Peter G.H2O transport through a packed bed of Johnson Space Center number 1A (JSC-1A) lunar regolith simulant was examined at relevant temperatures and pressures for in-situ resource utilization (ISRU) on the Moon. Experimentation was conducted over a range of pressures from 50 to 2,065 Pa at ~350 K, corresponding to Knudsen numbers of 0.3 < Kn < 11 and relevant towards ISRU technologies. A piecewise function was used to evaluate transition and Knudsen regime flows. The piecewise model utilized a Knudsen number that predicted the transition point between advective and Knudsen flows. A transition Knudsen number of 1.66 ± 0.61 and a tortuosity shape parameter of 0.736 ± 0.13 were determined from non-linear regression, and Knudsen diffusivities of 10.62 cm2·s-1, 10.40 cm2·s-1 and 9.04 cm2·s-1 for packed beds of JSC-1A with porosities of 0.388, 0.385, and 0.365, respectively. The experimental measurements, methodology, and modeling provide useful information for ISRU technologies involving the transport of volatiles (e.g., thermal extraction of H2O).
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ItemNumerical Analyses of High Temperature Dense, Granular Flows Coupled to High Temperature Flow Property Measurements for Solar Thermal Energy Storage Dataset(Georgia Institute of Technology, 2020-09-24) Yarrington, Justin D. ; Bagepalli, Malavika V. ; Pathikonda, Gokul ; Schrader, Andrew J. ; Zhang, Zhuomin ; Ranjan, Devesh ; Loutzenhiser, Peter G.High temperature particle flow properties necessary to predict granular flow behavior for solar thermal energy storage applications were measured and calculated for Carbobead CP 30/60 up to 800 °C. The measured properties included elastic and shear moduli, particle-particle coefficients of static sliding and rolling friction, and particle-particle coefficients of restitution. Poisson’s ratio was calculated with elastic and shear moduli. The flow properties were used as inputs for a numerical model using the discrete element method to examine granular flows along an inclined plane at high temperature. The flow behavior was strongly influenced by the coefficients of static friction, which impacted the particle residence time, shear effects from the side walls, and particle flow mass flux. An 8.7%, 15.6%, and 8.5% increase and 37.9% decrease in steady state mass flow rate was observed for 200 °C, 400 °C, 600 °C, and 800 °C, respectively, when compared to room temperature simulations. A 52%, 59%, and 33% decrease in the time to reach steady state was observed for 200 °C, 400 °C, and 600 °C, respectively, while a 53% increase in time was observed for 800 °C. A significant delay in the flow development at 800 °C was observed due to significantly higher frictional forces.