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Head-Mounted Displays
Published in Cary R. Spitzer, Uma Ferrell, Thomas Ferrell, Digital Avionics Handbook, 2017
The human head weighs approximately 9–10 lb and sits atop the spinal column (Figure 16.15). The occipital condyles on the base of the skull mate to the superior articular facets of the first cervical vertebra (C1, or the Atlas).93 These two small oblong mating surfaces on either side of the spinal column are the pivot points for the head.
Finite element brain deformation in adolescent soccer heading
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Colin M. Huber, Declan A. Patton, Jalaj Maheshwari, Zhou Zhou, Svein Kleiven, Kristy B. Arbogast
The KTH model is a detailed and parameterized FE model, which has been previously described in detail (Kleiven 2007). The model includes the scalp, skull, brain, meninges, cerebrospinal fluid, parasagittal bridging veins, and a simplified neck based on the anatomy of a 50th percentile male human head. Brain tissue was modeled using a nonlinearly elastic 2nd order Ogden model coupled with broad spectrum viscoelasticity. The model has been extensively validated with post-mortem human subject experimental data (Kleiven 2006). In an objective assessment of brain deformation modeling accuracy compared with post-mortem human subject data, the KTH model outperformed other major head models (Miller et al. 2017). The brain-skull interaction was modified to a tied contact defined between the cerebrospinal fluid and brain and dura mater tied to the skull to run simulations using high-performance computing (Alvarez et al. 2014). The skull was approximated to be rigid, and the time histories of linear and angular acceleration from each soccer header were prescribed to the head center of gravity of the model.
Optimized deployment of anchors based on GDOP minimization for ultra-wideband positioning
Published in Journal of Spatial Science, 2022
Chuanyang Wang, Yipeng Ning, Jian Wang, Longping Zhang, Jun Wan, Qimin He
In practical applications, the anchors are usually placed installed on the indoor ceiling or wall. Meanwhile, the tag is mounted on the human body or on the helmet which is worn on the human head. To ensure the signal propagation, the positioning configuration will be restricted. The elevations angles of anchors relative to the tag should be as positive as possible. Because of the constraints on the relative position of anchors and tag, the configuration with the theoretical lowest GDOP” is not applicable for indoor positioning, for instance, the regular polyhedrons. Furthermore, in UWB positioning, the ranging measurements are performed based on the two-way ranging (TWR) by determining the time of flight (TOF) of signals travelling between the anchor and tag. The signal round-trip time (RTT) without a common time reference is estimated in the positioning system and the error due to imperfect synchronization is effectively reduced. Thus, we can optimize the deployment of anchors based on the lowest GDOP’.
Modeling of head injuries induced by golf ball impacts
Published in Mechanics of Advanced Materials and Structures, 2019
There have been continuous efforts to understand the mechanisms of head injuries induced by golf ball impacts, especially for children (e.g., [9], [16], [17]). For example, an early survey by Nicholas et al. [15] found that contusion is the major head injury related to golf ball impacts. Also, a traumatic basal subarachnoid hemorrhage caused by a high-speed golf ball impact was investigated by Watanabe-Suzuki et al. [18] through a case study of a 50-year-old male. In addition, a number of computational studies have been conducted to investigate such head injuries. A finite element (FE) model of a golf ball striking on a human head was proposed by Lee and Wang [11], where the stress and energy flow patterns were evaluated for various striking velocities, ball falling angles, and impact locations. Katagiri et al. [13] simulated the forehead impact by a golf ball using a FE head model and a three-layer FE model for the golf ball. They implemented a stress-based skull fracture criterion. More recently, Pearce and Young [19] studied the impact of a golf ball on a human head with a short duration, where the intracranial pressure (ICP) in the brain was evaluated using a FE head and neck model. In all of these computational studies, only a human head model or a human head and neck model was considered. Since the impact-induced motion of a human head depends on the support of not only the neck but also the other parts of the human body below the neck, the use of a full human body model can better represent the impact of a golf ball on a human head, even though employing a head model or a head-neck model simplifies simulations.