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- Li, Xiaogai, et al.
(författare)
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Personalization of human body models and beyond via image registration
- 2023
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Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Finite element human body models (HBMs) are becoming increasingly important numerical tools for traffic safety. Developing a validated and reliable HBM from the start requires integrated efforts and continues to be a challenging task. Mesh morphing is an efficient technique to generate personalized HBMs accounting for individual anatomy once a baseline model has been developed. This study presents a new image registration-based mesh morphing method to generate personalized HBMs. The method is demonstrated by morphing four baseline HBMs (SAFER, THUMS, and VIVA+ in both seated and standing postures) into ten subjects with varying heights, body mass indices (BMIs), and sex. The resulting personalized HBMs show comparable element quality to the baseline models. This method enables the comparison of HBMs by morphing them into the same subject, eliminating geometric differences. The method also shows superior geometry correction capabilities, which facilitates converting a seated HBM to a standing one, combined with additional positioning tools. Furthermore, this method can be extended to personalize other models, and the feasibility of morphing vehicle models has been illustrated. In conclusion, this new image registration-based mesh morphing method allows rapid and robust personalization of HBMs, facilitating personalized simulations.
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- Ferrari, S., et al.
(författare)
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Visualizing Vortex Clusters in the Wake of a High-Speed Train
- 2017
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Ingår i: 2017 IEEE INTERNATIONAL CONFERENCE ON SYSTEMS, MAN, AND CYBERNETICS (SMC). - 1062-922X. - 9781538616451 ; 2017-January, s. 683-688
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Konferensbidrag (refereegranskat)abstract
- Visualization of fluid flows at a high-Reynolds number (Re similar to 10(5)) presents difficulties for user comprehension due to density and ambiguous interactions between vortices. Prior work has used cluster-based reduced-order modelling (CROM) to analyze the wake of a High-Speed Train (HST) with Re = 86,000. In this paper, we present a novel surface visualization to convey the spatiotemporal changes undergone by clustered vortices in the HST wake. This visualization is accomplished through dimensional reduction of 3D volumetric vortices into 1D ridges, and physics-based feature tracking. The result is 3D surfaces visualizing the behavior of the vortices in the HST wake. Compared to conventional still-image representations, these surfaces allow the user to quickly compare and analyze the two shedding cycles identified via CROM. The spatiotemporal differences of the primary vortices in these shedding cycles provide analytic insight to influence the aerodynamics of the HST.
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| 4. |
- Iraeus, Johan, 1973, et al.
(författare)
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Comparison of Average Female and Male Active HBM Responses in Whole-Sequence Frontal Crash Simulations
- 2023
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; , s. 819-842
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Konferensbidrag (refereegranskat)abstract
- Active human body models (HBMs) are important enablers for the simulation of occupant kinematics in pre-crash manoeuvres in whole-sequence crash scenarios. Pre-crash kinematics as well as injury risks have been shown to vary with sex. In this study, an average-sized female version (F50) of the active M50 SAFER HBM was developed using parametric mesh morphing, complemented with scaling of the muscle cross-sectional area. The active F50 model was validated with respect to volunteer pre-crash kinematics in braking and evasive turning manoeuvres, for two different belt systems (standard/pre-tensioned). Overall, the active F50 model predictions were slightly on the compliant side, compared to the volunteer test data. However, quantitatively using the CORA method, the active F50 model showed good biofidelity (0.81/0.89) for the pre-crash braking manoeuvre and fair biofidelity (0.60/0.75) for the evasive turning manoeuvre. Whole-sequence, combined, pre-crash and in-crash simulations were run with the active F50 and M50 models. They revealed some differences between the models, for which the active F50 model showed lower upper body forward displacements, and higher pelvis displacements, for two crash configurations and belt systems, compared to the active M50 model. Overall, however, the differences were small between the two HBMs.
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| 5. |
- Kaiser, Eurika, et al.
(författare)
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Cluster-based reduced-order modelling of a mixing layer
- 2014
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Ingår i: Journal of Fluid Mechanics. - : Cambridge University Press (CUP). - 0022-1120 .- 1469-7645. ; 754, s. 365-414
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Tidskriftsartikel (refereegranskat)abstract
- We propose a novel cluster-based reduced-order modelling (CROM) strategy for unsteady flows. CROM combines the cluster analysis pioneered in Gunzburger’s group (Burkardt, Gunzburger & Lee, Comput. Meth. Appl. Mech. Engng, vol. 196, 2006a, pp. 337–355) and transition matrix models introduced in fluid dynamics in Eckhardt’s group (Schneider, Eckhardt & Vollmer, Phys. Rev. E, vol. 75, 2007, art. 066313). CROM constitutes a potential alternative to POD models and generalises the Ulam–Galerkin method classically used in dynamical systems to determine a finite-rank approximation of the Perron–Frobenius operator. The proposed strategy processes a time-resolved sequence of flow snapshots in two steps. First, the snapshot data are clustered into a small number of representative states, called centroids, in the state space. These centroids partition the state space in complementary non-overlapping regions (centroidal Voronoi cells). Departing from the standard algorithm, the probabilities of the clusters are determined, and the states are sorted by analysis of the transition matrix. Second, the transitions between the states are dynamically modelled using a Markov process. Physical mechanisms are then distilled by a refined analysis of the Markov process, e.g. using finite-time Lyapunov exponent (FTLE) and entropic methods. This CROM framework is applied to the Lorenz attractor (as illustrative example), to velocity fields of the spatially evolving incompressible mixing layer and the three-dimensional turbulent wake of a bluff body. For these examples, CROM is shown to identify non-trivial quasi-attractors and transition processes in an unsupervised manner. CROM has numerous potential applications for the systematic identification of physical mechanisms of complex dynamics, for comparison of flow evolution models, for the identification of precursors to desirable and undesirable events, and for flow control applications exploiting nonlinear actuation dynamics.
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| 9. |
- Larsson, Emma, 1991, et al.
(författare)
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Predicting occupant head displacements in evasive maneuvers; tuning and comparison of a rotational based and a translational based neck muscle controller
- 2023
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Ingår i: Frontiers in Bioengineering and Biotechnology. - 2296-4185. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Objective : Real-life car crashes are often preceded by an evasive maneuver, which can alter the occupant posture and muscle state. To simulate the occupant response in such maneuvers, human body models (HBMs) with active muscles have been developed. The aim of this study was to implement an omni-directional rotational head-neck muscle controller in the SAFER HBM and compare the bio-fidelity of the HBM with a rotational controller to the HBM with a translational controller, in simulations of evasive maneuvers. Methods : The rotational controller was developed using an axis-angle representation of head rotations, with x, y, and z components in the axis. Muscle load sharing was based on rotational direction in the simulation and muscle activity recorded in three volunteer experiments in these directions. The gains of the rotational and translational controller were tuned to minimize differences between translational and rotational head displacements of the HBM and volunteers in braking and lane change maneuvers using multi-objective optimizations. Bio-fidelity of the model with tuned controllers was evaluated objectively using CORrelation and Analysis (CORA). Results : The results indicated comparable performance for both controllers after tuning, with somewhat higher bio-fidelity for rotational kinematics with the translational controller. After tuning, good or excellent bio-fidelity was indicated for both controllers in the loading direction (forward in braking, and lateral in lane change), with CORA scores of 0.86−0.99 and 0.93−0.98 for the rotational and translational controllers, respectively. For rotational displacements, and translational displacements in the other directions, bio-fidelity ranged from poor to excellent, with slightly higher average CORA scores for the HBM with the translational controller in both braking and lane changing. Time-averaged muscle activity was within one standard deviation of time-averaged muscle activity from volunteers. Conclusion : Overall, the results show that when tuned, both the translational and rotational controllers can be used to predict the occupant response to an evasive maneuver, allowing for the inclusion of evasive maneuvers prior to a crash in evaluation of vehicle safety. The rotational controller shows potential in controlling omni-directional head displacements, but the translational controller outperformed the rotational controller. Thus, for now, the recommendation is to use the translational controller with tuned gains.
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| 10. |
- Leledakis, Alexandros, 1991, et al.
(författare)
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Influence of an Individualised Shoulder Belt Position for Diverse Occupant Anthropometries on Seatbelt Interaction in Frontal and Side Impacts
- 2023
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Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; , s. 639-664
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Konferensbidrag (refereegranskat)abstract
- This simulation study investigated the influence of individualised shoulder belt position on seatbelt interaction and occupant kinematics in two frontal and one far side impact, considering the variability of occupant anthropometry and sitting postures. Morphed Human Body Models, positioned as front passengers, were simulated in 132 setups. For every occupant, an individualised shoulder belt position configuration was created by changing the D-ring mounting location, aiming for a mid-shoulder belt fit. A “traditional belt” configuration was also tested, with the D-ring mounted on the B-pillar. The initial belt's placement over the occupant's shoulder was influential; however, it may not necessarily lead to an overall improved seatbelt interaction as a single parameter. Different occupants were associated with different seatbelt interaction challenges. Tall occupants with low Body Mass Index (BMI) were more likely to slide out of the shoulder belt, while short low-BMI occupants were more likely to submarine. The early torso to pelvis retention balance and the torso’s axial rotations were identified as the main mechanisms behind those observations. The study identified seatbelt interaction challenges for different occupant groups and could facilitate the analysis of additional changes in belt characteristics towards individualised occupant restraint systems.
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