Academic literature on the topic 'Head acceleration exposure'
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Journal articles on the topic "Head acceleration exposure"
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Basinas, Ioannis, Damien M. McElvenny, Neil Pearce, Valentina Gallo, and John W. Cherrie. "A Systematic Review of Head Impacts and Acceleration Associated with Soccer." International Journal of Environmental Research and Public Health 19, no. 9 (May 1, 2022): 5488. http://dx.doi.org/10.3390/ijerph19095488.
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Epidemiological studies of the neurological health of former professional soccer players are being undertaken to identify whether heading the ball is a risk factor for disease or premature death. A quantitative estimate of exposure to repeated sub-concussive head impacts would provide an opportunity to investigate possible exposure-response relationships. However, it is unclear how to formulate an appropriate exposure metric within the context of epidemiological studies. We have carried out a systematic review of the scientific literature to identify the factors that determine the magnitude of head impact acceleration during experiments and from observations during playing or training for soccer, up to the end of November 2021. Data were extracted from 33 experimental and 27 observational studies from male and female amateur players including both adults and children. There was a high correlation between peak linear and angular accelerations in the observational studies (p < 0.001) although the correlation was lower for the experimental data. We chose to rely on an analysis of maximum or peak linear acceleration for this review. Differences in measurement methodology were identified as important determinants of measured acceleration, and we concluded that only data from accelerometers fixed to the head provided reliable information about the magnitude of head acceleration from soccer-related impacts. Exposures differed between men and women and between children and adults, with women on average experiencing higher acceleration but less frequent impacts. Playing position appears to have some influence on the number of heading impacts but less so on the magnitude of the head acceleration. Head-to-head collisions result in high levels of exposure and thus probably risk causing a concussion. We concluded, in the absence of evidence to the contrary, that estimates of the cumulative number of heading impacts over a playing career should be used as the main exposure metric in epidemiological studies of professional players.
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Gellner, Ryan A., Eamon T. Campolettano, Eric P. Smith, and Steven Rowson. "Are specific players more likely to be involved in high-magnitude head impacts in youth football?" Journal of Neurosurgery: Pediatrics 24, no. 1 (July 2019): 47–53. http://dx.doi.org/10.3171/2019.2.peds18176.
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OBJECTIVEYouth football attracts approximately 3.5 million participants every year, but concern has recently arisen about the long-term effects of experiencing repetitive head accelerations from a young age due to participation in football. The objective of this study was to quantify total involvement in high-magnitude impacts among individual players in youth football practices. The authors explored the relationship between the total number of high-magnitude accelerations in which players were involved (experienced either by themselves or by other players) during practices and the number of high-magnitude accelerations players experienced.METHODSA local cohort of 94 youth football players (mean age 11.9 ± 1.5, mean body mass 50.3 ± 16.4 kg) from 4 different teams were recruited and outfitted with helmet-mounted accelerometer arrays. The teams were followed for one season each for a total of 128 sessions (practices, games, and scrimmages). All players involved in high-magnitude (greater than 40g) head accelerations were subsequently identified through analysis of practice film.RESULTSPlayers who experienced more high-magnitude accelerations were more likely to be involved in impacts associated with high-magnitude accelerations in other players. A small subset of 6 players (6%) were collectively involved in 230 (53%) high-magnitude impacts during practice, were involved in but did not experience a high-magnitude acceleration 78 times (21% of the 370 one-sided high-magnitude impacts), and experienced 152 (30%) of the 502 high-magnitude accelerations measured. Quarterbacks/running backs/linebackers were involved in the greatest number of high-magnitude impacts in practice and experienced the greatest number of high-magnitude accelerations. Which team a player was on was an important factor, as one team showed much greater head impact exposure than all others.CONCLUSIONSThis study showed that targeting the most impact-prone players for individualized interventions could reduce high-magnitude acceleration exposure for entire teams. These data will help to further quantify elevated head acceleration exposure and enable data-driven interventions that modify exposure for individual players and entire teams.
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Swenson, Abigail, Logan Miller, Jillian Urban, and Joel Stitzel. "Head Kinematics by Contact Scenarios in Youth Ice Hockey." Neurology 95, no. 20 Supplement 1 (November 16, 2020): S1.1—S1. http://dx.doi.org/10.1212/wnl.0000000000011045.
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ObjectiveThe objective of this pilot study was to characterize head impact exposure in a sample of youth boys' ice hockey using a novel instrumented mouthpiece, improving accuracy.BackgroundFrom 2010 to 2018 youth ice hockey saw a 15% increase in participation, despite growing concerns for concussion risk in contact sports. While contact sports with similar rates of concussion have been subjected to rigorous study, head impact exposure in youth ice hockey has been largely underexplored. Existing youth studies have utilized helmet-mounted sensors, which are associated with error due to poor coupling with the skull.Design/MethodsCustom mouthpieces containing a tri-axial accelerometer and gyroscope were fit to seven enrolled athletes, and monitored during practices and games throughout the season. Linear acceleration and rotational velocity of the head were recorded for 60 ms when 5 g was exceeded on any axis for at least 3 ms. Time-synchronized film was reviewed to identify the contact scenario and head contact. Summary statistics of kinematics were calculated by scenario and presence of head contact.ResultsA total of 465 events were recorded over 25 weeks. Of these events 25% involved head contact; 92% of all contact scenarios were board checks, falls, or ice checks. Events involving head contact (i.e., head impacts) had median [95th percentile] peak linear acceleration, rotational velocity, and angular acceleration of 8.1 [30.9] g, 7.9 [20.2] rad/s, and 614 [2673] rad/s2, respectively. Events not involving head contact had median [95th percentile] peak linear acceleration, rotational velocity, and angular acceleration of 6.6 [43.8] g, 6.5 [17.5] rad/s, and 455 [4115] rad/s2, respectively.ConclusionsThe majority of the recorded events could be classified as board checks, falls, or ice checks. Median peak kinematics were higher for head impacts than non-head impact events. In contrast, 95th percentile linear and angular accelerations were greater for impacts not involving head contact.
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Bellamkonda, Srinidhi, Samantha J. Woodward, Eamon Campolettano, Ryan Gellner, Mireille E. Kelley, Derek A. Jones, Amaris Genemaras, et al. "Head Impact Exposure in Practices Correlates With Exposure in Games for Youth Football Players." Journal of Applied Biomechanics 34, no. 5 (October 1, 2018): 354–60. http://dx.doi.org/10.1123/jab.2017-0207.
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This study aimed to compare head impact exposures between practices and games in football players ages 9 to 14 years, who account for approximately 70% of all football players in the United States. Over a period of 2 seasons, 136 players were enrolled from 3 youth programs, and 49,847 head impacts were recorded from 345 practices and 137 games. During the study, individual players sustained a median of 211 impacts per season, with a maximum of 1226 impacts. Players sustained 50th (95th) percentile peak linear acceleration of 18.3 (46.9) g, peak rotational acceleration of 1305.4 (3316.6) rad·s−2, and Head Impact Technology Severity Profile of 13.7 (24.3), respectively. Overall, players with a higher frequency of head impacts at practices recorded a higher frequency of head impacts at games (P < .001,r2 = .52), and players who sustained a greater average magnitude of head impacts during practice also recorded a greater average magnitude of head impacts during games (P < .001). The youth football head impact data quantified in this study provide valuable insight into the player exposure profile, which should serve as a key baseline in efforts to reduce injury.
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Lamond, Lindsey C., Jaclyn B. Caccese, Thomas A. Buckley, Joseph Glutting, and Thomas W. Kaminski. "Linear Acceleration in Direct Head Contact Across Impact Type, Player Position, and Playing Scenario in Collegiate Women's Soccer Players." Journal of Athletic Training 53, no. 2 (February 1, 2018): 115–21. http://dx.doi.org/10.4085/1062-6050-90-17.
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Context: Heading, an integral component of soccer, exposes athletes to a large number of head impacts over a career. The literature has begun to indicate that cumulative exposure may lead to long-term functional and psychological deficits. Quantifying an athlete's exposure over a season is a first step in understanding cumulative exposure. Objective: To measure the frequency and magnitude of direct head impacts in collegiate women's soccer players across impact type, player position, and game or practice scenario. Design: Cross-sectional study. Setting: National Collegiate Athletic Association Division I institution. Patients or Other Participants: Twenty-three collegiate women's soccer athletes. Main Outcome Measure(s): Athletes wore Smart Impact Monitor accelerometers during all games and practices. Impacts were classified during visual, on-field monitoring of athletic events. All direct head impacts that exceeded the 10g threshold were included in the final data analysis. The dependent variable was linear acceleration, and the fixed effects were (1) type of impact: clear, pass, shot, unintentional deflection, or head-to-head contact; (2) field position: goalkeeper, defense, forward, or midfielder; (3) playing scenario: game or practice. Results: Shots (32.94g ± 12.91g, n = 38; P = .02) and clears (31.09g ± 13.43g, n = 101; P = .008) resulted in higher mean linear accelerations than passes (26.11g ± 15.48g, n = 451). Head-to-head impacts (51.26g ± 36.61g, n = 13; P < .001) and unintentional deflections (37.40g ± 34.41g, n = 24; P = .002) resulted in higher mean linear accelerations than purposeful headers (ie, shots, clears, and passes). No differences were seen in linear acceleration across player position or playing scenario. Conclusions: Nonheader impacts, including head-to-head impacts and unintentional deflections, resulted in higher mean linear accelerations than purposeful headers, including shots, clears, and passes, but occurred infrequently on the field. Therefore, these unanticipated impacts may not add substantially to an athlete's cumulative exposure, which is a function of both frequency and magnitude of impact.
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Crisco, Joseph J., Bethany J. Wilcox, Jason T. Machan, Thomas W. McAllister, Ann-Christine Duhaime, Stefan M. Duma, Steven Rowson, Jonathan G. Beckwith, Jeffrey J. Chu, and Richard M. Greenwald. "Magnitude of Head Impact Exposures in Individual Collegiate Football Players." Journal of Applied Biomechanics 28, no. 2 (May 2012): 174–83. http://dx.doi.org/10.1123/jab.28.2.174.
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The purpose of this study was to quantify the severity of head impacts sustained by individual collegiate football players and to investigate differences between impacts sustained during practice and game sessions, as well as by player position and impact location. Head impacts (N = 184,358) were analyzed for 254 collegiate players at three collegiate institutions. In practice, the 50th and 95th percentile values for individual players were 20.0 g and 49.5 g for peak linear acceleration, 1187 rad/s2 and 3147 rad/s2 for peak rotational acceleration, and 13.4 and 29.9 for HITsp, respectively. Only the 95th percentile HITsp increased significantly in games compared with practices (8.4%, p = .0002). Player position and impact location were the largest factors associated with differences in head impacts. Running backs consistently sustained the greatest impact magnitudes. Peak linear accelerations were greatest for impacts to the top of the helmet, whereas rotational accelerations were greatest for impacts to the front and back. The findings of this study provide essential data for future investigations that aim to establish the correlations between head impact exposure, acute brain injury, and long-term cognitive deficits.
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DiGuglielmo, Daniella M., Mireille E. Kelley, Mark A. Espeland, Zachary A. Gregory, Tanner D. Payne, Derek A. Jones, Tanner M. Filben, Alexander K. Powers, Joel D. Stitzel, and Jillian E. Urban. "The Effect of Player Contact Characteristics on Head Impact Exposure in Youth Football Games." Journal of Applied Biomechanics 37, no. 2 (April 1, 2021): 145–55. http://dx.doi.org/10.1123/jab.2020-0145.
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To reduce head impact exposure (HIE) in youth football, further understanding of the context in which head impacts occur and the associated biomechanics is needed. The objective of this study was to evaluate the effect of contact characteristics on HIE during player versus player contact scenarios in youth football. Head impact data and time-synchronized video were collected from 4 youth football games over 2 seasons in which opposing teams were instrumented with the Head Impact Telemetry (HIT) System. Coded contact characteristics included the player’s role in the contact, player speed and body position, contact height, type, and direction, and head contact surface. Head accelerations were compared among the contact characteristics using mixed-effects models. Among 72 instrumented athletes, 446 contact scenarios (n = 557 impacts) with visible opposing instrumented players were identified. When at least one player had a recorded impact, players who were struck tended to have higher rotational acceleration than players in striking positions. When both players had a recorded impact, lighter players and taller players experienced higher mean head accelerations compared with heavier players and shorter players. Understanding the factors influencing HIE during contact events in football may help inform methods to reduce head injury risk.
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Kelley, Mireille E., Joeline M. Kane, Mark A. Espeland, Logan E. Miller, Alexander K. Powers, Joel D. Stitzel, and Jillian E. Urban. "Head impact exposure measured in a single youth football team during practice drills." Journal of Neurosurgery: Pediatrics 20, no. 5 (November 2017): 489–97. http://dx.doi.org/10.3171/2017.5.peds16627.
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OBJECTIVEThis study evaluated the frequency, magnitude, and location of head impacts in practice drills within a youth football team to determine how head impact exposure varies among different types of drills.METHODSOn-field head impact data were collected from athletes participating in a youth football team for a single season. Each athlete wore a helmet instrumented with a Head Impact Telemetry (HIT) System head acceleration measurement device during all preseason, regular season, and playoff practices. Video was recorded for all practices, and video analysis was performed to verify head impacts and assign each head impact to a specific drill. Eleven drills were identified: dummy/sled tackling, install, special teams, Oklahoma, one-on-one, open-field tackling, passing, position skill work, multiplayer tackle, scrimmage, and tackling drill stations. Generalized linear models were fitted to log-transformed data, and Wald tests were used to assess differences in head accelerations and impact rates.RESULTSA total of 2125 impacts were measured during 30 contact practices in 9 athletes (mean age 11.1 ± 0.6 years, mean mass 44.9 ± 4.1 kg). Open-field tackling had the highest median and 95th percentile linear accelerations (24.7g and 97.8g, respectively) and resulted in significantly higher mean head accelerations than several other drills. The multiplayer tackle drill resulted in the highest head impact frequency, with an average of 0.59 impacts per minute per athlete, but the lowest 95th percentile linear accelerations of all drills. The front of the head was the most common impact location for all drills except dummy/sled tackling.CONCLUSIONSHead impact exposure varies significantly in youth football practice drills, with several drills exposing athletes to high-magnitude and/or high-frequency head impacts. These data suggest that further study of practice drills is an important step in developing evidence-based recommendations for modifying or eliminating certain high-intensity drills to reduce head impact exposure and injury risk for all levels of play.
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Tierney, Gregory, Daniel Weaving, James Tooby, Marwan Al-Dawoud, Sharief Hendricks, Gemma Phillips, Keith A. Stokes, Kevin Till, and Ben Jones. "Quantifying head acceleration exposure via instrumented mouthguards (iMG): a validity and feasibility study protocol to inform iMG suitability for the TaCKLE project." BMJ Open Sport & Exercise Medicine 7, no. 3 (September 2021): e001125. http://dx.doi.org/10.1136/bmjsem-2021-001125.
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Instrumented mouthguards (iMGs) have the potential to quantify head acceleration exposures in sport. The Rugby Football League is looking to deploy iMGs to quantify head acceleration exposures as part of the Tackle and Contact Kinematics, Loads and Exposure (TaCKLE) project. iMGs and associated software platforms are novel, thus limited validation studies exist. The aim of this paper is to describe the methods that will determine the validity (ie, laboratory validation of kinematic measures and on-field validity) and feasibility (ie, player comfort and wearability and practitioner considerations) of available iMGs for quantifying head acceleration events in rugby league. Phase 1 will determine the reliability and validity of iMG kinematic measures (peak linear acceleration, peak rotational velocity, peak rotational acceleration), based on laboratory criterion standards. Players will have three-dimensional dental scans and be provided with available iMGs for phase 2 and phase 3. Phase 2 will determine the on-field validity of iMGs (ie, identifying true positive head acceleration events during a match). Phase 3 will evaluate player perceptions of fit (too loose, too tight, bulky, small/thin, held mouth open, held teeth apart, pain in jaw muscles, uneven bite), comfort (on lips, gum, tongue, teeth) and function (speech, swallowing, dry mouth). Phase 4 will evaluate the practical feasibility of iMGs, as determined by practitioners using the system usability scale (preparing iMG system and managing iMG data). The outcome will provide a systematic and robust assessment of a range of iMGs, which will help inform the suitability of each iMG system for the TaCKLE project.
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Randjelovic, Danijela, and Miroslav Pavlovic. "The effect of acceleration on color vision." Vojnosanitetski pregled 75, no. 6 (2018): 623–31. http://dx.doi.org/10.2298/vsp160622288r.
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Background/Aim. Over 80% of all information a pilot receives during the flight is visual with color perception being one of the most important visual functions for managing an aircraft. The reception of color is of high significance in aviation due to the importance of signal tracking on instrument panels as well as the importance of visual stimulus and environment signs. There is no sufficient number of papers and studies that deal with this issue, although recent studies have shown that the connection between acceleration and color perception exists. The aim of this study was to demonstrate the correlation between pilot exposure to +Gz acceleration in human centrifuge and color perception before and after acceleration exposure. Methods. Subjects of the study were 40 military pilots, aged 35?45, with 10 and 20 years of flying experience. Pilots were exposed to +Gz acceleration (inertial force acts from head to feet) in the human centrifuge for pilot training with accelerations of +2Gz, +5.5Gz up to +7Gz. The tests focused on color perception before and after the exposure to the acceleration. Results. Out of 40 pilots examined for color vision, in 35 (87.50%) had normal results in color identification before and after +Gz; 5.00% (2 subjects) had two mistakes ? reading number 5 instead of number 3, which falls within the normal trichomes, and reading number 16 instead of number 26. Three subjects (7.50%) gave their answers slower than the accepted response time. After the +7Gz exposure, 34 (85%) persons had normal results in color identification, 2 (5%) subjects made three mistakes ? at numbers 5, 74 and 26; one (2.50%) pilot made four mistakes on numbers 5, 7, 74 and 26; 7.50% (3 pilots) of the subjects identified colors slower. Conclusion. Color perception in pilots is unstable on high +Gz accelerations. Exposure to +5.5Gz acceleration does not lead to significant changes in color perception, while exposure to +7Gz acceleration showed a significant percentage of reversible disturbance in color perception which lasted for 10 minutes.
Dissertations / Theses on the topic "Head acceleration exposure"
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Rowson, Steven. "Head Acceleration Experienced by Man: Exposure, Tolerance, and Applications." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/37605.
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Between 1.6 and 3.8 million sports-related concussions are sustained by persons living in the United States annually. While sports-related concussion was once considered to only result in immediate neurocognitive impairment and symptoms that are transient in nature, recent research has correlated long-term neurodegenerative effects with a history of sports-related concussion. Increased awareness and current media attention have contributed to concussions becoming a primary health concern. Although much research has been performed investigating the biomechanics of concussion, little is understood about the biomechanics that cause concussion in humans. The research presented in this dissertation investigates human tolerance to head acceleration using methods that pair biomechanical data collected from human volunteers with clinical data. Head impact exposure and injury risk are quantified and presented.
In contrast to the publicly available data on the safety of automobiles, consumers have no analytical mechanism to evaluate the protective performance of football helmets. With this in mind, the Summation of Tests for the Analysis of Risk (STAR) evaluation system was developed to evaluate the impact performance of footballs helmets and provide consumers with information about helmet safety. The STAR evaluation system was designed using real world data that relate impact exposure to injury risk.Ph. D.
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(10725504), Xiaoyu Ji. "EFFECTS ON SEED-BASED RESTING STATE FMRI OF ONE SEASON OF EXPOSURE TO MIDDLE SCHOOL AND HIGH SCHOOL FOOTBALL SUBCONCUSSIVE HEAD ACCELERATIONS." Thesis, 2021.
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Young football players are hypothesized to experience damage to the brain and brain
function from repeated subconcussive head acceleration events (HAEs) during practices and
games. Such damage may cause delayed cognitive and mental problems. Resting state
fMRI (rs-fMRI) is an effective non-invasive method to detect alterations in brain functional
connectivity. Seed-based rsfMRI analysis using the central node of the default mode network
(DMN) as the seed is a common approach to measuring intrinsic changes of the DMN,
accepted as a key network in brain function. Seed-based rs-fMRI analysis of the DMN
was used to explore how age, HAE intensity, and HAE counts influence brain connectivity in
youth athletes (ages 12-18). Middle school and high school football players and peer controls
were studied using rs-fMRI before and after one season of competition. An identifiability
matrix was generated from the seed-based connectivity matrix, allowing measurement of
similarity between pre-season and post-season functional connectivity. The consistency of
seed-based brain functional connectivity we observed across the season of play for players
has no statistically significant difference from controls. The identifiability matrix exhibited
no relation to the number and magnitude of any subset of HAEs experienced which rejected
our hypothesis. Another finding is that high school football players exhibited the largest
percentage increase in identification from middle school football players in the somatomotor
network over other resting-state networks.
Book chapters on the topic "Head acceleration exposure"
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Lepage, Christian, Inga K. Koerte, Vivian Schultz, Michael J. Coleman, and Martha E. Shenton. "Traumatic brain injury." In New Oxford Textbook of Psychiatry, edited by John R. Geddes, Nancy C. Andreasen, and Guy M. Goodwin, 464–74. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198713005.003.0047.
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Traumatic brain injury (TBI) results from blunt trauma, acceleration–deceleration forces, rotational forces, or blast exposure to the head. The injury involves a heterogenous pattern of focal and/or diffuse axonal injury, leading to a wide range of symptoms. The severity of the injury covers the spectrum from mild to moderate to severe, with severe injury leading to possible coma and even death. The range of symptoms, the variability in treatment options, and the prognosis of TBI, as well as the psychosocial implications, make it a complex injury that often calls upon the services of neurosurgeons, neurologists, psychiatrists, psychologists, and rehabilitation specialists to help patients achieve the best possible outcome. This chapter aims to provide an overview of TBI that includes the classification, epidemiology, aetiology, pathophysiology, clinical symptoms, long-term outcome, diagnostic implications, and differential diagnosis, as well as possible treatment options and future directions for research.
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Baecker, Ronald M. "Security." In Computers and Society. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198827085.003.0013.
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Throughout history, humanity has invented valuable technologies and ways to organize society. These innovations are typically accompanied by risks. Fire cooks food, and also provides heat on cold nights. Yet, when left unchecked, fire can cause huge damage as well as loss of life. Cities enabled new forms of community and commerce. However, they brought us more thievery, and made it easier for epidemics to spread. The automobile allowed a separation of locales for work and residence; trucks allowed goods to be shipped long distances. But vehicular accidents have caused far greater injury and loss of life than did mishaps with horses and mules. Information technology, like other technologies, has potential for good and for harm. In the first six chapters, we introduced aspects of human activity, such as education, medicine, and government, in which IT has been transformative and mostly positive. The next three chapters examine areas in which the negatives of IT are dominant, in which risks seem everywhere. This chapter focuses on security. IT security flaws are exploited by outsiders for personal or political gain. In Chapter 8 we shall look at safety, where the risks are often injury or loss of life. In Chapter 9, we shall look at privacy, where the risks are exposure of private, confidential, and even sensitive information. Security is the attribute of a computer system that ensures that it can continue to function properly after an attack. Attacks against computer systems happen routinely now, are in the news almost every week, and are accelerating in numbers and in impact. Damage to both individuals and organizations—financial losses, chaos, and deteriorating morale— is severe. We shall provide a primer on the multitude of ways computer systems, from large networks to mobile phones, can be ‘hacked’ so that they no longer function properly. We shall define the most common kinds of destructive software, often called malware. We will discuss large-scale data breaches, which now happen frequently and expose the personal data of millions to billions of people. The word hackers refers to individuals who disrupt digital technologies and thereby damage the functioning of an institution or a society.
Conference papers on the topic "Head acceleration exposure"
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Brown, Brandon A., Ray W. Daniel, Valeta Carol Chancey, and Tyler F. Rooks. "Parametric Evaluation of Head Center of Gravity Acceleration Error From Rigid Body Kinematics Assumptions Used in Environmental Sensors." In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-69334.
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Abstract Environmental sensors (ES) are a proposed way to identify potentially concussive events using Rigid Body Kinematics (RBK) to get motion at the head CG. This study systematically investigated the extent that errors in RBK assumptions including sensor orientation (SO), head CG position (HCGP), and exposure severity contribute to errors in sensor readings of predicted peak resultant linear acceleration (PRLA) at the head CG. Simulated sensor readings were defined by idealized representations of head motion [extension, lateral bending and axial rotation] using a half sine pulse for linear and angular acceleration. Peak magnitudes of linear acceleration ranged from 12.5 to 100 Gs and peak magnitudes of angular acceleration ranged from 1250 to 10000 rad/s/s. Durations of linear and angular accelerations ranged between 5 and 30 ms. Simulated HCGP variations ranged from −10% to 10% radius of the head (assumed to be a sphere) in each direction and SO variations ranged from −20 to 20 degrees about each axis. True head CG response was calculated using zero error for SO and HCGP. Mean (+/− standard deviation) of calculated errors for maximum percent error (MaxPE) of a given head exposure was 30.3% (+/−9.71). 50% and 38% of all simulated exposures had MaxPE associated with maximum SO and HCGP offset, respectively. MaxPE was likely due to user error, ES form factor, and anthropometric variation.
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Ott, Kyle, Liming Voo, Andrew Merkle, Alexander Iwaskiw, Alexis Wickwire, Brock Wester, and Robert Armiger. "Experimental Determination of Pressure Wave Transmission to the Brain During Head-Neck Blast Tests." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14834.
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Traumatic Brain Injury (TBI) has been the termed the “signature injury” in wounded soldiers in recent military operations [1]. Evidence has shown a strong association between TBI and blast loading to the head due to exposure to explosive events [2, 3]. Head injury mechanisms in a primary blast environment remain elusive and are the subject of much speculation and hypotheses. However, brain injury mechanisms have traditionally been attributed to either a direct impact or a rapid head acceleration or deceleration. Extensive research has been performed regarding the effects of blunt trauma and inertial loading on head injuries [4, 5]. Direct impacts to the head can largely be described based on linear acceleration measurements that correlate to skull fracture and focal brain injuries [6]. Computational head modeling of blunt impact events has shown that the linear acceleration response correlates well with increases in brain pressure [7]. Intracranial pressure, therefore, has been one of the major quantities investigated for correlation to blast induced TBI injury mechanisms [8–14].
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Van Ee, Chris, Barbara Moroski-Browne, David Raymond, Kirk Thibault, Warren Hardy, and John Plunkett. "Evaluation and Refinement of the CRABI-6 Anthropomorphic Test Device Injury Criteria for Skull Fracture." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12973.
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Only sparse experimental pediatric tissue tolerance data are available for the development of pediatric surrogates and associated injury reference values. The objective of this study is to improve the efficacy of the CRABI series anthropometric test devices by increasing the foundational data used for head injury and skull fracture. To accomplish this, this study evaluated and refined the CRABI-6 injury assessment reference values (IARV) associated with skull fracture by correlating the test device response with the detailed fracture results of 50 infant cadaver drop studies reported by Weber in 1984 and 1985. Using the CRABI-6 test device, four 82-cm height free fall impacts were performed onto each of four different impact surfaces: concrete, carpet, 2-cm foam mat, and an 8-cm thick camel hair blanket. Average and standard deviation of peak head linear acceleration and HIC36 (Head Injury Criteria) were computed for each impact surface. The average CRABI impact response was mapped to the Weber fracture outcomes for corresponding impact surfaces and logistic regression was performed to define a skull fracture risk curve based on exposure. The 5%, 25%, 50%, 75%, and 95% risk for skull fracture correlated with a CRABI-6 peak linear head acceleration of 50, 70, 82, 94, and 114 g’s and a HIC36 of 87, 214, 290, 366 and 493, respectively. This study made use of the most extensive set of controlled infant cadaver head impact and fracture data currently available. Previous head IARVs for the CRABI-6 are given by Melvin (1995) and by Klinich et al. (2002). Based on a review of pediatric tissue experiments, scaling of adult and child dummy IARVs, and sled tests, Melvin suggested a HIC22 of 390 and a limit on peak head acceleration of 50 g’s. Klinich et al. reported the results of three reconstructions of airbag-related infant head injuries and three additional reconstructions not associated with head injury. They estimated the 50% risk of minor skull fracture to be 85 g’s and 220 HIC15. These previously reported estimates appear to be in agreement with the results reported from this study for CRABI-6 IARV of 50% risk of skull fracture at 82 g’s and 290 HIC36.
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Tan, X. Gary, and Amit Bagchi. "Computational Analysis for Validation of Blast Induced Traumatic Brain Injury and Protection of Combat Helmet." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-87689.
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Current understanding of blast wave transmission and mechanism of primary traumatic brain injury (TBI) and the role of helmet is incomplete thus limiting the development of protection and therapeutic measures. Combat helmets are usually designed based on costly and time consuming laboratory tests, firing range, and forensic data. Until now advanced medical imaging and computational modeling tools have not been adequately utilized in the design and optimization of combat helmets. The goal of this work is to develop high fidelity computational tools, representative virtual human head and combat helmet models that could help in the design of next generation helmets with improved blast and ballistic protection. We explore different helmet configurations to investigate blast induced brain biomechanics and understand the protection role of helmet by utilizing an integrated experimental and computational method. By employing the coupled Eulerian-Lagrangian fluid structure interaction (FSI) approach we solved the dynamic problem of helmet and head under the blast exposure. Experimental shock tube tests of the head surrogate provide benchmark quality data and were used for the validation of computational models. The full-scale computational NRL head-neck model with a combat helmet provides physical quantities such as acceleration, pressure, strain, and energy to blast loads thus provides a more complete understanding of the conditions that may contribute to TBI. This paper discusses possible pathways of blast energy transmission to the brain and the effectiveness of helmet systems at blast loads. The existing high-fidelity image-based finite element (FE) head model was applied to investigate the influence of helmet configuration, suspension pads, and shell material stiffness. The two-phase flow model was developed to simulate the helium-air shock wave interaction with the helmeted head in the shock tube. The main contribution was the elucidation of blast wave brain injury pathways, including wave focusing in ocular cavities and the back of head under the helmet, the effect of neck, and the frequency spectrum entering the brain through the helmet and head. The suspension material was seen to significantly affect the ICP results and energy transmission. These findings can be used to design next generation helmets including helmet shape, suspension system, and eye protection.
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Hinz, Brandon J., Matthew V. Grimm, Karim H. Muci-Ku¨chler, and Shawn M. Walsh. "Comparative Study of the Dynamic Response of Different Materials Subjected to Compressed Gas Blast Loading." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64395.
Full textAbstract:
Understanding the dynamic response of materials under blast and impact loading is of interest for both military and civilian applications. In the case of blast loading, the mitigation characteristics of materials employed in personal protective equipment (PPE) is of particular importance. Without adequate protection, exposure of the head to blast waves may result in or contribute to brain tissue damage leading to traumatic brain injury (TBI). The development of simple but representative laboratory experiments that can be used to study the mechanical response of different materials and/or material combinations to blast loading could be very useful for the design of PPE such as helmets. This paper presents a basic experimental setup that can be conveniently used to perform such studies using small scale compressed gas blasts. An open end shock tube is employed to generate the blasts used to load flat plate samples placed in a special rigid holder. Acceleration time histories at selected locations in the sample are used to generate data to compare the dynamic response and blast mitigation effectiveness of different specimens. High speed schlieren video is used to correlate the arrival of the shock wave and air flow that follows with the motion of the test sample.
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Liu, Xiaofeng, and Joseph Katz. "Measurements of Pressure Distribution in a Cavity Flow by Integrating the Material Acceleration." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56373.
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In turbulence research, the velocity-pressure-gradient tensor in the Reynolds stress transport equation is critical for understanding and modeling of turbulence. Pressure is also of fundamental importance in understanding and modeling of cavitation. Motivated by the lack of experimental tools to measure the instantaneous pressure distribution away from boundaries, the paper introduces a non-intrusive method for simultaneously measuring the instantaneous velocity and pressure distribution over a sample area. The technique utilizes four exposure PIV to measure the distribution of material acceleration, and integrating it to obtain the pressure distribution. If necessary, e.g., for cavitation research, a reference pressure at a single point is also required. Two cameras and perpendicularly polarized Nd:Yag lasers are used for recording four exposures on separate frames. Images 1 and 3 are used for measuring the first velocity distribution, whereas images 2 and 4 give the second velocity map. The material acceleration is calculated from the velocity difference in sample areas shifted relative to each other according to the local velocity. Averaged omni-directional integration of the material acceleration over the entire flow field, while avoiding regions dominated by viscous diffusion, provides the pressure distribution. To improve the accuracy of the acceleration measurement, cross-correlation of the corresponding image correlation maps is implemented in areas with high velocity gradient. Applications of these procedures to synthetic flows show that the standard deviation of the measured instantaneous pressure from the theoretical value is about 2%. The system has been used to measure the instantaneous pressure and velocity distributions of a 2D cavity flow field in a water tunnel. Three pressure transducers mounted at different locations on the wall are being used for comparison and calibration. Detailed measurements of acceleration, vorticity and pressure distributions within the cavity shear layer indicate that the cavity shear layer flow exhibits highly unsteady behavior due to the self-excited oscillation.
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Kebschull, Scott A., and R. Michael Van Auken. "Development of Vehicle Safety Rating Systems and Application to Off-Road Vehicles." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-12178.
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Abstract The first vehicle safety rating systems were the US National Highway Traffic Safety Administration’s New Car Assessment Program (NCAP), started in 1979, and the Australasian NCAP, started in 1992. These systems were investigated in order to determine the methods used to develop them and the characteristics that make them scientifically valid. In addition, a proposed safety rating system for All-Terrain Vehicles (ATVs) and Side by Side Vehicles (SSVs) was compared to the automotive NCAP systems in order to determine its scientific validity. The literature related to the history and development of the original NCAP safety rating systems was reviewed. The proposed safety rating system for ATVs was also reviewed and comparisons with the original NCAP systems were made. The original NCAP systems have been based on correlations between the measured acceleration of the head and chest and actual injury outcome probabilities. These systems also were intentionally restricted to providing comparisons between vehicles of similar mass. Based on this premise, criteria for the establishment of a vehicle safety rating system have been developed with the aim to ensure that such a system has validity and provides ratings that are based on scientifically established correlations between objectively and repeatably measured values and desirable safety outcomes. The proposed safety rating system for ATVs and SSVs that was not developed following this method was found to have no basis in known relationships between the test outcomes and injury probabilities. Although the proposed safety rating system for ATVs and SSVs was found to be unacceptable, a methodology for developing a safety rating system that would meet the criteria is proposed. The methodology would involve collecting real-world injury and exposure data and correlations with measurable vehicle characteristics. This correlation could then lead to the development of scientifically valid safety rating systems for ATVs and SSVs.
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Sezgin, Jean-Gabriel, and Junichiro Yamabe. "Tensile and Fatigue Failure of 17-4 PH Martensitic Stainless Steels in Presence of Hydrogen Depending on Frequency and Heat Treatment." In ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21122.
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Abstract Slow-strain-rate tensile (SSRT) and fatigue-life tests were carried out on 17-4PH martensitic stainless steel with an ultimate tensile strength (UTS) of ∼ 1 GPa. The specimens were precharged by exposure to hydrogen gas at pressures of 35 MPa or 100 MPa at 270°C for 200 h. The SSRT tests used smooth axisymmetric specimens made of two grades of 17-4PH (H1150 and H900) differing by the UTS due to their thermal history. No degradation of the UTS was observed for both H1150 and H900 grades. However, the relative reduction in area (RRA) was 0.31 for H1150 or 0.11 for H900, translating a difference in their hydrogen sensitivity. Both grades presented different fracture-surface morphologies: a mixture of quasi-cleavage (QC) and intergranular (IG) facets for H1150 and cleavage (C) facets for H900. Circumferentially-notched axisymmetric specimens made of H1150 were used for the fatigue-life tests in the [10−3 Hz;10 Hz] frequency range. Our previous study on low-alloy steels with UTS of around 950 MPa demonstrates that the fatigue life of a circumferentially-notched specimen with a sharp notch can be successfully predicted from the fatigue crack growth (FCG) property following the Paris law. This study used the same specimen geometry and a BCC steel with a similar UTS value; hence, the FCG behavior was investigated from the fatigue-life test of the notched specimen. As a result, the degradation of fatigue lives attributed to the FCG acceleration was observed in presence of hydrogen. A FCG acceleration ratio bounded to 30 was observed in the high-cycle regime, accompanied by QC facets. A FCG acceleration ratio bounded to ∼100 was observed in the low-cycle regime, accompanied by QC and IG facets. A FCG model accounting for the interaction of elementary mechanisms was proposed and succeeded in predicting the FCG acceleration ratio observed on H1150. This model was also successfully applied to a low-alloy steel with a comparable UTS (1002 MPa) tested in gaseous hydrogen.
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Reid, M., J. Punch, B. Rodgers, T. Galkin, T. Stenberg, O. Rusanenc, E. Elonen, M. Vile`n, and K. Va¨keva¨inen. "Prolonged Steady-State Exposure of Printed Wiring Boards Under Conditions of Temperature Humidity and Bias." In ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ipack2005-73353.
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Ionic migration has been the subject of intensive study, both theoretical and experimental, over the past 40 years. It is known as a reliability concern for printed wiring boards (PWBs) in high density microelectronic packaging and power electronic packaging. Ionic migration is an electrochemical phenomena that occurs primarily under normal ambient conditions: i.e. when the local temperatures and current densities are low enough to allow moisture on the surface. Standardised test 85°C/85%RH is typically used for accelerating and predicting ionic migration failure, however, the possibility of moisture condensation — a prerequisite for ionic migration — at a relatively high temperature and low relative humidity is unlikely. In order to assess more realistic and less thermally severe environments, this work examines prolonged steady state exposure of PWBs. Steady-state conditions of 90%RH at 30°C under a bias of 5V DC were tested over a 210 day period with continuous in-situ monitoring of dendritic growth. Investigative techniques were conducted to evaluate the migration development on the PWBs after testing using optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). This paper will demonstrate that steady-state thermal humidity bias (THB) tests appear to provide ionic migration behaviour similar in service conditions, however, do not demonstrate the dramatic failure associated with ionic migration.
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Shah, Alok S., Brian D. Stemper, Narayan Yoganandan, and Barry S. Shender. "Quantification of Shockwave Transmission Through the Cranium Using an Experimental Model." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14356.
Full textAbstract:
Studies have hypothesized mechanisms for brain injury resulting from exposure to blast waves. Theories include shockwaves increasing fluid pressure within brain tissue by transmitting through bones and blood vessels 1, indirect brain tissue damage due to ischemia from pulmonary blast injury 2, and formation of mechanical stresses that can result in tissue distortion 3. Mechanical damage to brain tissue can occur due to skull flexure resulting in loads typically seen in impact-induced injury 4 or axonal shearing/stretching, due to linear or rotational accelerations resulting in Diffuse Axonal Injury (DAI) 5. Despite several investigations it remains unclear whether direct propagation of the shockwave through the cranium can deform brain tissue and result in mechanically-induced injury 6. Finite element 7, 8 and animal 9, 10 models provide information on mechanisms and outcomes of blast-induced mTBI (mild traumatic brain injury). However, validations of FEM studies were limited due to the paucity of high rate material properties. Animal tests were designed to understand mechanisms of shockwave transmission but most did not report intracranial pressures. Understanding blast injury mechanisms requires a better delineation of shockwave energy transfer through the head and the influence of factors including region-specific differences, and mechanical properties of brain simulant. A Post Mortem Human Subjects (PMHS) model was used in this study to examine these factors and provide an understanding of shockwave transmission through the tissues of the human head.