| 1. |
- Baumgartner, D., et al.
(författare)
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INFLUENCE OF HEAD ROTATIONAL ACCELERATION PULSE SHAPE ON BRAIN TISSUE STRAINS
- 2014
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Ingår i: Journal of Neurotrauma. - 0897-7151. ; 31:12
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Brain tolerance to rotational acceleration is relevant for understanding injury thresholds and development of injury mitigation techniques for automobiles and sporting events. This computational-modeling study outlined effects of head rotational acceleration pulse shape on strains within brain tissues. A detailed finite element model of the human skull and brain was developed and validated previously. The model was exercised using realistic rotational accelerations with different magnitude and duration characteristics, and the principal strain re- sponse was extracted for parietal cortex, hippocampus, thalamus, and hypothalamus. Rotational acceleration magnitude was varied to three levels: 3.6krad/s 2 (M1), 5.3krad/s 2 (M2), and 6.6krad/s 2 (M3). Duration was varied to 9msec (D1), 18msec (D2), and 27msec (D3). Hippocampus and hypothalamus sustained more strain than cortex and thalamus. With increasing acceleration magnitude from M1 to M2 and M2 to M3, strain in all brain regions was uniformly increased by 42% and 80%. However, strains demonstrated regionally dependent chan- ges with increasing duration (D1 to D3): 68%, 37%, 33% and 14% in parietal cortex, hippocampus, thalamus and hypothalamus, respec- tively. The trend was consistent for all acceleration magnitudes. This study demonstrated differing and independent effects of rotational acceleration magnitude and duration on strains within brain tissues during rotational acceleration. Magnitude has long been a correlate of injury severity and this study supports that finding in that increased acceleration magnitudes led to uniformly higher brain tissue strains (higher injury risk). However, rotational acceleration duration chan- ged the strain distribution within the brain, resulting in different injury risks in different brain regions. This finding is significant as changing strain distribution with different durations can manifest as different injury distributions within the brain and different neuropsychological outcomes following exposure to head rotational acceleration.
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| 2. |
- Shah, S.A., et al.
(författare)
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An experimental study on three-port measurements foracoustic characterization of a perforate
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Multiple analytical, experimental, and numerical studies have been carriedout on perforates to study their properties under operating conditions, resultingin varying hypothesis and models to predict their performance. Theongoing effort of providing experimental results using multiform test setups iscontinued in this study. Incorporating the three-port technique, the passiveacoustic response of a perforated plate is studied under acoustic excitationfrom three directions in presence of grazing flow and high-level excitation.Similar to the in-situ method, usage of the three-port technique has an advantageof being a direct method for impedance determination and is not boundby any boundary conditions traditionally considered in presence of grazingflow. Extending the observations of previous studies, a semi-empirical modelis determined for the real part of the transfer impedance of a perforate, wherethe characterisation of the determined impedance on the testing parameterslike the Strouhal number, particle velocity, flow velocity and shear numberis displayed.
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