Anna K Carlsson

Dynamic Kinematic Responses of Female Volunteers in Rear Impacts and Comparison to Previous Male Volunteer Tests

Objectives: The objective was to quantify dynamic responses of 50th percentile females in rear impacts and compare to those from similar tests with males. The results will serve as a basis for future work with models, criteria, and safety systems. Methods: A rear impact sled test series with 8 female volunteers was performed at velocity changes of 5 and 7 km/h. The following dynamic response corridors were generated for the head, T1 (first thoracic vertebra) and head relative to T1: (1) accelerations in posterior–anterior direction, (2) horizontal and vertical displacements, (3) angular displacements for 6 females close to the 50th percentile in size. Additionally, the head-to-head restraint distance and contact time and neck injury criterion (NIC) were extracted from the data set. These data were compared to results from previously performed male volunteer tests, representing the 50th percentile male, in equivalent test conditions. T-tests were performed with the statistical significance level of .05 to quantify the significance of the parameter value differences for the males and females. Results: At 7 km/h, the females showed 29 percent earlier head-to-head restraint contact time (p = .0072); 27 percent shorter horizontal rearward head displacement (p = .0017); 36 percent narrower head extension angle (p = .0281); and 52 percent lower NIC value (p = .0239) than the males in previous tests. This was mainly due to 35 percent shorter initial head-to-head restraint distance for the females (p = .0125). The peak head acceleration in the posterior–anterior direction was higher and occurred earlier for the females. Conclusions: The overall result indicated differences in the dynamic response for the female and male volunteers. The results could be used in developing and evaluating a mechanical and/or mathematical average-sized female dummy model for rear impact safety assessment. These models can be used as a tool in the design of protective systems and for further development and evaluation of injury criteria.

Motion of the head and neck of female and male volunteers in rear impact car-to-car impacts

Objectives: The objectives of this study were to quantify and compare dynamic motion responses between 50th percentile female and male volunteers in rear impact tests. These data are fundamental for developing future occupant models for crash safety development and assessment. Methods: High-speed video data from a rear impact test series with 21 male and 21 female volunteers at 4 and 8 km/h, originally presented in Siegmund et al. (1997), were used for further analysis. Data from a subset of female volunteers, 12 at 4 km/h and 9 at 8 km/h, were extracted from the original data set to represent the 50th percentile female. Their average height was 163 cm and their average weight was 62 kg. Among the male volunteers, 11 were selected, with an average height of 175 cm and an average weight of 73 kg, to represent the 50th percentile male. Response corridors were generated for the horizontal and angular displacements of the head, T1 (first thoracic vertebra), and the head relative to T1. T-tests were performed with the statistical significance level of .05 to quantify the significance of the differences in parameter values for the males and females. Results: Several differences were found in the average motion response of the male and female volunteers at 4 and 8 km/h. Generally, females had smaller rearward horizontal and angular motions of the head and T1 compared to the males. This was mainly due to shorter initial head-to–head restraint distance and earlier head-to–head restraint contact for the females. At 8 km/h, the female volunteers showed 12 percent lower horizontal peak rearward head displacement (P = .018); 22 percent lower horizontal peak rearward head relative to T1 displacement (P = .018); and 30 percent lower peak head extension angle (P = .001). The females also had more pronounced rebound motion. Conclusions: This study indicates that there may be characteristic differences in the head–neck motion response between 50th percentile males and females in rear impacts. The exclusive use of 50th percentile male rear impact dummies may thus limit the assessment and development of whiplash prevention systems that adequately protect both male and female occupants. The results of this study could be used in the development and evaluation of a mechanical and/or computational average-sized female dummy model for rear impact safety assessment. These models are used in the development and evaluation of protective systems. It would be of interest to make further studies into seat configurations featuring a greater head-to–head restraint distance.

Dynamic Responses of Female and Male Volunteers in Rear Impacts

Objectives: Whiplash injuries from vehicle collisions are common and costly. These injuries most frequently occur as a result of a rear impact and, compared to males, females have up to twice the risk of whiplash-associated disorders (WAD) resulting from vehicle crashes. The present study focuses on the differences in the dynamic response corridors of males and females in low-severity rear impacts. Methods: In this study, analysis of data from volunteer tests of females from previously published data has been performed. Corridors for the average female response were generated based on 12 volunteers exposed to a change of velocity of 4 km/h and 9 volunteers exposed to a change of velocity of 8 km/h. These corridors were compared to corridors for the average male response that were previously generated based on 11 male volunteers exposed to the same test conditions. Results: Comparison between the male and female data showed that the maximum x-acceleration of the head for the females occurred on average 10 ms earlier and was 29% higher during the 4 km/h test and 12 ms earlier and 9% higher during the 8 km/h test. Head-to-head restraint contact for the females occurred 14 ms earlier at 4 km/h and 11 ms earlier at 8 km/h compared to the males. For the same initial head-to-head restraint distance, head restraint contact occurred 11 and 7 ms earlier for the females than the males at 4 and 8 km/h, respectively. Furthermore, the calculated Neck Injury Criteria (NIC) values were similar for males and females at 4 km/h, whereas they were lower for females compared to the males at 8 km/h (3.2 and 4.0 m2/s2, respectively). Conclusions: The results of this study highlight the need to further investigate the differences in dynamic responses between males and females at low-severity impacts. Such data are fundamental for the development of future computer models and dummies for crash safety assessment. These models can be used not only as a tool in the design and development process of protective systems but also in the process of further evaluation and development of injury criteria.

ADSEAT – Adaptive seat to reduce neck injuries for female and male occupants

Neck injuries sustained in low severity vehicle crashes are of worldwide concern and the risk is higher for females than for males. The objective of the study was to provide guidance on how to evaluate protective performance of vehicle seat designs aiming to reduce the incidence of neck injuries for female and male occupants. The objective was achieved by reviewing injury risk, establishing anthropometric data of an average female, performing dynamic volunteer tests comprising females and males, and developing a finite element model, EvaRID, of an average female. With respect to injury criteria, it was concluded based on the tests that using NIC (with a lower threshold value) and Nkm (with reduced intercept values) for females would be a suitable starting point. Virtual impact simulations with seats showed that differences were found in the response of the BioRID II and EvaRID models, for certain seats.

Anthropometric Specifications, Development, and Evaluation of EvaRID—A 50th Percentile Female Rear Impact Finite Element Dummy Model

Objectives: Whiplash-associated disorders (WADs), or whiplash injuries, due to low-severity vehicle crashes are of great concern in motorized countries and it is well established that the risk of such injuries is higher for females than for males, even in similar crash conditions. Recent protective systems have been shown to be more beneficial for males than for females. Hence, there is a need for improved tools to address female WAD prevention when developing and evaluating the performance of whiplash protection systems. The objective of this study is to develop and evaluate a finite element model of a 50th percentile female rear impact crash test dummy. Methods: The anthropometry of the 50th percentile female was specified based on literature data. The model, called EvaRID (female rear impact dummy), was based on the same design concept as the existing 50th percentile male rear impact dummy, the BioRID II. A scaling approach was developed and the first version, EvaRID V1.0, was implemented. Its dynamic response was compared to female volunteer data from rear impact sled tests. Results: The EvaRID V1.0 model and the volunteer tests compared well until ∼250 ms of the head and T1 forward accelerations and rearward linear displacements and of the head rearward angular displacement. Markedly less T1 rearward angular displacement was found for the EvaRID model compared to the female volunteers. Similar results were received for the BioRID II model when comparing simulated responses with experimental data under volunteer loading conditions. The results indicate that the biofidelity of the EvaRID V1.0 and BioRID II FE models have limitations, predominantly in the T1 rearward angular displacement, at low velocity changes (7 km/h). The BioRID II model was validated against dummy test results in a loading range close to consumer test conditions (EuroNCAP) and lower severity levels of volunteer testing were not considered. Conclusions: The EvaRID dummy model demonstrated the potential of becoming a valuable tool when evaluating and developing seats and whiplash protection systems. However, updates of the joint stiffness will be required to provide better correlation at lower load levels. Moreover, the seated posture, curvature of the spine, and head position of 50th percentile female occupants needs to be established and implemented in future models.

Oscillatory photoemission cross section for alkali monolayer quantum well states

A strong oscillatory photon energy dependence, observed in the photon energy range between 5 and 26 eV, for the intensity of photoemission peaks due to quantum well states in Na and Cs monolayers on Cu(111) is ascribed to interference between the contributions to the outgoing photoelectron wave from the two tails of the quantum well state.

Real-world adjustments of driver seat and head restraint in Saab 9-3 vehicles

ABSTRACT Objective: Whiplash-associated disorder (WAD), commonly denoted whiplash injury, is a worldwide problem. These injuries occur at relatively low changes of velocity (typically <25 km/h) in impacts from all directions. Rear impacts, however, are the most common in the injury statistics. Females have a 1.5–3 times higher risk of whiplash injury than males.  Improved seat design is the prevailing means of increasing the protection of whiplash injury for occupants in rear impacts. Since 1997, more advanced whiplash protection systems have been introduced on the market, the Saab Active Head Restraint (SAHR) being one of the most prominent. The SAHR—which is height adjustable—is mounted to a pressure plate in the seatback by means of a spring-resisted link mechanism.  Nevertheless, studies have shown that seats equipped with reactive head restraints (such as the SAHR) have a very high injury-reducing effect for males (∼60–70%) but very low or no reduction effect for females. One influencing factor could be the position of the head restraint relative to the head, because a number of studies have reported that adjustable head restraints often are incorrectly positioned by drivers.  The aim was to investigate how female and male Saab drivers adjust the seat in the car they drive the most. Methods: The seated positions of drivers in stationary conditions have been investigated in a total of 76 volunteers (34 females, 42 males) who participated in the study. Inclusion criteria incorporated driving a Saab 9–3 on a regularly basis. Results: The majority of the volunteers (89%) adjusted the head restraint to any of the 3 uppermost positions and as many as 59% in the top position.  The average vertical distance between the top of the head and the top of the head restraint (offset) increase linearly with increasing statures, from an average of −26 mm (head below the head restraint) for small females to an average of 82 mm (head above the head restraint) for large males. On average, the offset was 23 mm for females, which is within a satisfactory range and in accordance with recommendations; the corresponding value for males was 72 mm.  The backset tended to be shorter among female volunteers (on average 27 mm) compared to the male volunteers (on average 44 mm). Moreover, the backset tended to increase with increasing statures. Conclusions: Incorrect adjustment of the head restraint cannot explain the large differences found between the sexes in the effectiveness of the SAHR system.

Fallolyckor bland gångtrafikanter

Malet med den har studien ar:  att sammanstalla och sprida kunskap om fotgangares fallolyckor (singelolyckor)  att kartlagga vad man vet om skadebilder, skademekanismer och toleransnivaer  att studera mojliga (passiva) atgarder for att reducera risken for allvarlig skada och dod  att foresla testmetoder Studien har fokuserat pa kroppsregionerna hoft, handled och huvud. Hoftfrakturer och huvudskador tillhor de allvarligaste skadorna som fotgangare kan raka ut for. Exempelvis har ungefar var tredje hoftfrakturpatient avlidit inom ett ar efter skadan. Handledsfrakturer ar mycket vanligt forekommande och drabbar foretradelsevis kvinnor >45 ar. Det finns potential att forebygga handledsfrakturer med hjalp av personskydd; daremot verkar underlaget inte ha nagon storre effekt pa skadeutfallet. Bade hoftfrakturer och huvudskador skulle dock forebyggas med hjalp av bade personskydd och/eller genom att installera stotdampande underlag i fotgangarnas trafikmiljo.

STRUCTURE CHANGES FOR Cu(111)/Li OBSERVED VIA DISCRETE QUANTUM WELL STATES

Via photoemission in the near UV from discrete quantum well states, four different types of atom rearrangements are observed for Cu(111)/Li. In the monolayer range a gradual energy shift reflects a gradual compression of the Li layer as more atoms are adsorbed. The onset of Li substitution and formation of a (2×2) structure when, at RT, monolayer Li coverage is exceeded is monitored via the appearance of a quantum well state characteristic of the new phase. A small energy shift indicates that, if it is cooled (170 K), the new structure is unstable with respect to Li adsorption. Finally, an energy downshift with increasing coverage observed for a state characteristic of 2 ML Li is ascribed to an increasing area for one-atomic-layer-high islands formed by Li atoms on top of the first full layer.