Dissertations / Theses on the topic 'Helmets'

This thesis examines surface finishes and tinning on Archaic period (7th-5th c. BC) Greek helmets. Experiments are designed to review and further understanding of what comprises evidence of tinning on low-tin archaeological bronzes and to investigate the efficacy of common and non-destructive methods for its detection. Methods examined include SEM, XRD and neutron diffraction. Problems related to composition analysis are identified and the thesis offers new data on the corrosion profiles of low tin bronzes, which adds to current understanding. A ternary diagram to aid interpretation of compositional data is proposed. This thesis also provides new data on the manufacturing and development of the Corinthian and Illyrian type helmets.

Plusieurs études ont montré que dans les accidents réels, la vitesse d’impact de la tête n’est que rarement normale à la surface et présente une composante tangentielle non négligeable. Aucune norme, à l’heure actuelle ne propose de choc oblique avec enregistrement de l’accélération en translation et en rotation de la fausse tête. Un aspect essentiel de cette recherche a été d’aborder les descriptions d’accidents réels impliquant un motocycliste et un véhicule afin d’évaluer les conditions aux limites de la tête juste avant impact, en termes de vecteur vitesse et de localisation d’impact. Cette étude a permis d’établir le vecteur vitesse possible et de l’angle d’impact de la tête du motocycliste en situation. Une méthode de test pour évaluer le casque a été proposée. Les tests d'impact obliques, sont effectués avec une vitesse d’impact de 8.5 m/s sur une enclume inclinée de 45° permettant la rotation autour de l’axe Y X et Z. Les accélérations 6-D sont implémentés dans le modèle SUFEHM afin d’extraire la déformation axonal maximale et le risque lésionnel. Cette fusion de la méthode expérimentale et numérique donne un avantage par rapport aux normes conventionnelles, tant en termes de conditions d’impact qu’en termes de critère de blessure de la tête
It is well know that in case of accident the head does not only impact perpendicularly to the impacted structure but presents an oblique impact condition. However none of the today helmet standards do integrate oblique impacts with the recording of the dummy head rotational acceleration. An essential aspect of the present research is to simulate real world accident and to compute the victim’s kinematic in order to extract the head impact conditions. In collaboration with University Florence (Italy) 19 cases were considered and it was shown that the head impact velocity vector presents a significative angle. A novel helmet test method has been proposed. Helmeted headfoml is impacting a 45° inclined anvil at a speed of 8.5 m/s and the 6D acceleration versus time curves are introduced into an existing head FEM in order to compute the axon strains and to derive the brain injury risk

The purpose of this study was to examine the differences between international certification standards for ice hockey helmets. The American Society for Testing and Materials (ASTM), Canadian Standards Association (CSA) and International Organization Standards (ISO) protocols were compared. Only the impact testing methods at ambient temperatures were examined. Four helmet models, currently available to consumers, were used for testing. No significant differences (p $<$ 0.05) were found between the standards in a rank order comparison. Further analysis of differences, with peak linear accelerations separated by impact locations showed significant differences (p $<$ 0.05) between all standards, at five of the six defined impact sites, with no differences being found between standards at the rear site. Post-hoc pairwise multiple comparisons also showed significant performance differences (p $<$ 0.05) between helmet models.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
Includes bibliographical references (leaf 30).
The study of aerodynamics is very important in the world of cycling. Wind tunnel research is conducted on most of the equipment that is used by a rider and is a critical factor in the advancement of the sport. However, to date, a comprehensive study of time-trial helmets has not been performed. This thesis presents aerodynamic data for the most commonly used time-trial helmets in professional cycling. The helmets were tested at a sweep of yaw angles, from 0⁰ to 15⁰, in increments of 5⁰. The helmets were tested at three head angle positions at each yaw angle in order to best mimic actual riding conditions. A control road helmet was used to serve as a comparative tool. In order to maintain manufacturer confidentiality, the helmets were all randomly assigned variables. Thus, the thesis presents ranges of benefit and drag numbers, but does not rank by helmet name. The testing results showed that aerodynamic helmets offer drag reduction over a standard road helmet. The best and the worst performing helmets are all more aerodynamic than a road helmet.
by Stephanie Sidelko.
S.B.

The widespread use of vehicles has led to an increase in traffic accidents. In these accidents, motorcyclists are exposed to more risks because they are more vulnerable than car drivers. With the development of technology, manufacturers have increased their work on vehicle security systems. Advancements in these studies which are being applied in daily life resulted in a reduction of risks in accidents. In this thesis, Zero-Power Fall Detection System is developed for smart helmets, which is a safety system for motorcycles. Since the lifetime of electronic devices has become one of the most important features of today, the aim of this study is to design a self-sustainable fall detection system that consumes as low power as possible. First, the system is designed with Piezoelectric Wake-up Circuits, a microcontroller unit with bluetooth low energy communication and a self-sustainable battery management system with high efficiency power recovery. Then, a fall detection algorithm is designed to send a message to a smartphone, tablet or etc. through bluetooth low energy connection when hazardous situations are detected. Based on this algorithm, the software of the system is prepared. Finally, field tests have been carried out and according to the results, it has been shown that the fall detection system developed is functional and has a very low power consumption.

Thesis (M.S.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains ix, 117 p. : ill. Includes abstract. Includes bibliographical references (p. 99-105).

This study evaluated the mechanical durability of ice hockey helmets for multiple impacts at defined energy levels. A monorail drop testing apparatus was used to conduct controlled impact tests according to the CSA standard (CAN/CSA-Z262.1-M90). Five ice hockey helmet models were tested, for a total sample of 45 helmets. All helmets were impacted up to 50 times at each of in four different locations (i.e. front, right side, back, and crown), at one of 40, 50 or 60 J of kinetic energies. In general, by increasing the impact energy, the impact acceleration attenuation properties of the helmets was decreased significantly (from 4% to 80%). Although all the helmets meet the CSA standards, attenuation properties were found to be substantially reduced beyond three repeated impacts and above 40 J impact energy. In particular, all helmets showed effective multiple impact attenuation properties at the crown, front, and rear sites; however, poor multiple impact attenuation durability was evident at the side.

Based on accident reports, oblique head impacts associated with rotational acceleration occur frequently in cycling. Rotational acceleration stimulates brain tissue strain resulting in mild to severe brain injuries. Current bicycle helmet standards test for linear acceleration, but not for rotational acceleration. The proposed standard (EN13087-11) by the European Committee for Standardization (CEN) and the Angular Launched Impact (ALI) protocol are oblique test protocols which impart rotational acceleration to the head at three impact locations (Front_Y, Lateral_X and Lateral_Z). The CEN proposed standard drops the helmeted headform vertically onto a 45° steel anvil, while the ALI protocol launches the headform at an angle of 45° towards the steel surface. The CEN proposed standard may represent a cyclist falling vertically onto a curb, angled surface or motor vehicle. The ALI represents a cyclist skidding or falling over the handlebars and have been described as frequent-accident cases in the literature. Both protocols represent unique falling events in cycling which elicit distinct rotational head responses. The purpose of this study was to compare the dynamic head response and brain tissue deformation between the two oblique test protocols on two common types of cycling helmets (PVC shell-PU liner and ABS shell-EPS liner). The study revealed that falling vertically onto a curb, angled surface or motor vehicle (CEN proposed standard), resulted in a greater rotational head response and brain tissue deformation, compared to frequent-accident events of skidding or falling over the handlebars (ALI protocol). Linear and rotational acceleration were significantly less on the PVC shell-PU liner compared to the ABS shell-EPS liner on both oblique test protocols. Distinct impact vectors associated with unique falling events in cycling create different rotational head responses and brain tissue deformation. Helmet standards should consider incorporating oblique testing methods, to manage mild and severe brain injuries associated with frequent falling events in cycling.

Youth and varsity football helmets are currently designed similarly and tested to the same impact standards from the National Operating Committee on Standards for Athletic Equipment (NOCSAE). Youth players have differences in anthropometry, physiology, impact exposure, and potentially injury tolerance that should be considered in future youth-specific helmets and standards. This thesis begins by investigating the current standards and relating them to on-field data. The standard drop tests represented the most severe on-field impacts, and the performance of the youth and varsity helmet did not differ. There likely is not a need for a youth-specific standard as the current standard has essentially eliminated the catastrophic head injuries it tests for. As more is known about concussion, standards specific to the youth population can be developed. The second portion of this thesis compares the impact performance between 8 matched youth and varsity helmet models, using linear acceleration, rotational acceleration, and concussion correlate. It was found that helmet performance did not differ between the youth and varsity helmets, likely attributed to testing to the same standard. The final portion of this feature is aimed at advancing STAR for youth and varsity football helmets by including linear and rotational head kinematics. For varsity helmets, an adult surrogate is used for impact tests which are weighted based on on-field data collected from collegiate football players. For youth helmets, a youth surrogate is used and tests are weighted based on data collected from youth players.
Master of Science

Mestrado em Engenharia Mecânica
Neste trabalho efetua-se uma avaliação do desempenho de um capacete rodoviário já comercializado e aprovado pela maioria das normas de segurança atuais. Este desempenho é avaliado através da reprodução fidedigna de impactos semelhantes aos que ocorrem comumente em acidentes reais, onde ambos os movimentos, translacionais e rotacionais estão presentes. Duas validações foram realizadas por comparação com resultados experimentais: uma relativa ao modelo constitutivo do poliestireno expandido, que integra a camada de absorção de energia do capacete e outra relativa aos valores das acelerações do centro de gravidade da cabeça após os impactos definidos pela norma de segurança ECE R22. Após validação, um impacto oblíquo foi simulado e os resultados foram comparados com os valores limites de traumatismo craniano, a fim de prever as lesões na cabeça resultantes de acelerações rotacionais, não previstas na norma referida. A partir desta comparação, concluiu-se que lesões cerebrais, tais como concussão e lesão axonal difusa podem ocorrer mesmo com um capacete rodoviário que foi aprovado pela maioria das normas atuais, e apenas replicando um impacto que vulgarmente é observado em colisões reais. As mesmas lesões foram previstas após avaliação das lesões num impacto da norma ECE R22 com uma cabeça biomecânica modelada em elementos finitos. As conclusões apontam para uma recomendação assertiva no sentido de que os efeitos decorrentes de desacelerações rotacionais devem também ser contemplados pelas normas de segurança vigentes e que os procedimentos de teste actuais devem ser melhorados, especialmente a cabeça de teste, a qual não é capaz de prever lesões, para promover a segurança entre os motociclistas.
In this work it is carried out the performance assessment of a motorcycle helmet, approved by the majority of current standards and already placed on the market. The evaluation is based on accurate reproduction of impacts that are similar to the ones that commonly occur in real crashes, where both motions, translational and rotational are considered. The numerical framework is validated against two di erent set of experimental results. The first concerns the constitutive model of the expanded polystyrene, the material responsible for energy absorption during impact; the second related to the head's centre of mass acceleration after the impacts de ned in the European ECE R22 standard. Both were validated against experimental data. Doing so, an oblique impact was simulated and the results were compared against head injury thresholds in order to predict the resultant head injuries. From this comparison, it was concluded that brain injuries such as concussion and di use axonal injury can occur even with a helmet that was approved by the majority of the helmet standards, that unfortunately do not contemplate rotational components of acceleration. The same lesions were predicted after assessing injuries resulting from an impact de ned by the ECE R22 standard with a biomechanical FE head model. At the end, conclusion points out a strong recommendation on the necessity of including rotational motion in forthcoming motorcycle helmet standards and improving the the actual test procedures, especially the test headform, which is not able to predict lesions, to improve the safety between the motorcyclists.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 136-139). Also available in electronic version. Access restricted to campus users.

This thesis reports on a design study, conducted for an advanced composite helmet shell for helicopter pilots. The helmet shell is expected to provide a level of protection against low velocity impacts with its weight criteria. Therefore, ergonomy, light weight, and the ability to withstand low velocity impact became the main issues for this study. For this purpose, an experimental program has been developed including low velocity impact tests on specimens. The drop height, drop weight, specimen stacking sequences and size were constant parameters. Test specimens were produced using the plate size of 220x220 mm having different thicknesses. Specimen materials were aramid, carbon, and a hybrid form of these two. Thus, the parameters of the study were specimen thickness and the material types. The impact tests are carried out on a specially designed test rig. The design decisions are made in accordance with the results of the experiments. In compliance with the lightweight and manufacturing criteria, the hybrid specimen was selected helmet shell. For the purpose of ergonomy a geometric design was also conducted from headfrom sizes of Turkish Army by using 3D design software. After specifying the composite material, manufactured helmet shell was tested in another test rig according to the ANSI Z90.1.1992. For the requirement of the acceleration level 300g, the helmet shell design was found to be successful at seven different and critical impact points.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 51-53).
American football is notorious for being a high impact sport. There exists an especially high amount of danger to each player's brain, created in part by gameplay, but also from the helmets worn by the athletes. Football helmet pads were comparatively investigated, in order to find a better alternative that can lower the amount of acceleration on the brain. A new pad system was introduced that allows for the force to be dissipated horizontally, through use of a dashpot-like center, also employing a foam shell to assist in the vertical energy dissipation. The pad currently used, along with the new dashpot system were further tested inside helmet shells on a head form drop test, and compared to the national standards that regulate athletic equipment.
by Christine Elizabeth Labaza.
S.B.

Motorbike riders are among the most vulnerable road users. The improvement of the protection offered by motorcycle helmets through use of non-conventional energy absorbing materials could significantly reduce the number of motorcyclists’ fatalities. This thesis investigates the coupling of hexagonal aluminium honeycomb with polymeric foams for the design of innovative and safer motorbike helmets. The compressive behaviour and energy absorption properties of two layered foam-honeycomb composites are assessed experimentally. The experiments include quasi-static and impact compressive tests. Experimental outcomes show an increase of the energy absorbed by the two-layered materials with respect to the one provided by foams currently used for the manufacturing of helmets, tested under the same conditions. A finite element model representing the two-layered materials is also proposed. The model is validated against the experimental results. An accurate reproduction of the experiments is attained. A commercially available helmet is then modified to accommodate aluminium honeycombs in the energy absorbing liner, and standard tests are performed. The investigation includes also the testing of unmodified helmets, presenting same geometry and material properties of the prototypes. The experiments consist of impacts against a flat and kerbstone surfaces, as prescribed by standards. The dynamical responses of the prototypes and their commercial counterparts are compared. It is found that for impacts against the kerbstone anvil, the prototypes offer a noticeable reduction of the accelerations transmitted to the head, compared to the commercial helmets. For impacts against the flat surface, commercial helmets generally provide better protection to the head, which highlights a non optimum design of the prototype helmet and the limitations of using aluminium honeycombs as reinforcement materials. Experimental findings are later used to validate a finite element model of the prototype, where the two-layered model presented in this thesis is implemented. Numerical results are in good agreement with experimental findings.

The massive number of injuries sustained in trafficaccidents is a growing problem worldwide, especially indeveloping countries. In 1998, more than one million peoplewere killed in traffic accidents worldwide, while about tentimes as many people were injured. Injuries to the centralnervous system and in particular to the headare especiallycritical to human life. This thesis contains five researchpapers looking at head injuries and head protection, proposingnew and more efficient ways of protecting the head, especiallyin traffic accidents.

In order to define the national dimensions of the patternsof injuries incurred in motorcycle and moped accidents inSweden, a statistical survey was performed on data spanning a13-year period (Paper A). In Sweden, 27,100 individualsreceived in-patient care for motorcycle and moped accidentinjuries between 1987 and 1999. The motorcycle and moped injuryrate reduced in the second half of the study period, so toowere the total number of days of treatment per year. Males hadeight times the incidence of injuries of females. Head injurieswere the single most frequent diagnosis, followed by fracturesof the lower limbs. Concussion was the most frequent headinjury. These statistics clearly show the need for better headinjury prevention systems.

According to the statistics, the most common type of impactto the head in motorcycle and moped accidents is an obliqueimpact. Oblique impacts generate rotations of the head, whichare a common cause of the most severe head injuries. Thereforea new test rig was constructed to reproduce oblique impacts toa helmeted dummy head, simulating those occurring in real lifeaccidents (Paper B). The new test rig was shown to provideuseful data at speeds of up to 50 km/h and with impact anglesvarying from purely tangential to purely radial. Thisinnovative test rig appears to provide an accurate method formeasuring accelerations in oblique impacts to helmets.

When testing the performances of motorcycle helmets,discrepancies are usually seen in the test results. In order toevaluate these discrepancies, the finite element method (FEM)was used for simulations of a few oblique helmet impacts (PaperC). Amongthe parameters studied, the coefficients of frictionbetween the impacting surface and the helmet and between thehead and the helmet had the most significant influence on therotational accelerations. Additionally, a thinner andconsequently also weaker shell and a weaker liner, providedbetter protection for the impacts studied.

Since there are no generally accepted global injurythresholds for oblique impacts to the human head, a study wasdesigned to propose new injury tolerances accounting for bothtranslations and rotations of the head (Paper D). In thatstudy, FE models of (a) a human head, (b) a Hybrid III dummyhead, and (c) the experimental helmet were used. Differentcriteria were proposed for different impact scenarios. Both thetranslational and the rotational effects were found to beimportant when proposing a predictor equation for the strainlevels experienced by the human brain in simulated impacts tothe head.

In order to reduce the level of head injuries in society andto better understand helmet impacts from different aspect, aballistic impact was also studied (Paper E). The effects ofdifferent helmet shell stiffness and different angles ofimpacts were simulated. In this study, the same FE head modelfrom Paper D was used, however here it was protected with amodel of a composite ballistic helmet. It was concluded thatthe helmet shell should be stiff enough to prevent the insideof the shell from striking the skull, and that the strainsarising in the brain tissue were higher for some obliqueimpacts than for purely radial ones.

In conclusion, this thesis describes the injury pattern ofmotorcycle and moped accidents in Sweden. This thesis showsthat the injuries sustained from these accidents can bereduced. In order to study both translational as well asrotational impacts, a new laboratory test rig was designed. Byusing the finite element method, it is possible to simulaterealistic impacts to the head and also to predict how severehead injuries may potentially be prevented.

Mild traumatic brain injury in snowsports is a prevalent concern. With as many as 130,000 hospitalized injuries in the U.S. associated with snowsports in 2017, head injury constitutes about 28% and is the main cause of fatality. Studies have found that a combination of rotational and linear velocities is the most mechanistic way to model brain injury, but despite decades of research, the biomechanical mechanisms remain largely unknown. However, evidence suggests a difference in concussion tolerance may exist between athlete populations. To improve the ability to predict and therefore reduce concussions, we need to understand the impact conditions associated with head impacts across various sports. There is limited research on the conditions associated with head impacts in snowsports. These head impacts often occur on an angled slope, creating a normal and tangential linear velocity component. Additionally, the impact surface friction in a snowsport environment is highly variable, but could greatly influence the rotational kinematics of head impact. Currently helmet testing standards don't consider these rotational kinematics, or varying friction conditions that potentially occur in real-world scenarios. The purpose of this study is to investigate the head impact conditions in a snowsport environment to inform laboratory testing and evaluate snow helmet design. We determined head impact conditions through video analysis to determine the impact locations, mechanism of fall, and the kinematics pre-impact. We used these data to develop a test protocol that evaluates snowsport helmets in a realistic manner. Ultimately, the results from this research will provide snowsport participants unbiased impact data to make informed helmet purchases, while concurrently providing a realistic test protocol that allows for design interventions to reduce the risk of injury.
Master of Science
Mild traumatic brain injury in snowsports is a prevalent concern. With as many as 130,000 hospitalized injuries in the U.S. associated with snowsports in 2017, head injury constitutes about 28% and is the main cause of fatality. Studies have found that a combination of rotational and linear velocities is the most mechanistic way to model brain injury, but despite decades of research, the biomechanical mechanisms remain largely unknown. However, evidence suggests a difference in concussion tolerance may exist between athlete populations. To improve the ability to predict and therefore reduce concussions, we need to understand the impact conditions associated with head impacts across various sports. There is limited research on the conditions associated with head impacts in snowsports. These head impacts often occur on an angled slope, creating a normal and tangential linear velocity component. Additionally, the impact surface friction in a snowsport environment is highly variable, but could greatly influence the rotational kinematics of head impact. Currently helmet testing standards don't consider these rotational kinematics, or varying friction conditions that potentially occur in real-world scenarios. The purpose of this study is to investigate the head impact conditions in a snowsport environment to inform laboratory testing and evaluate snow helmet design. We determined head impact conditions through video analysis to determine the impact locations, mechanism of fall, and the kinematics pre-impact. We used these data to develop a test protocol that evaluates snowsport helmets in a realistic manner. Ultimately, the results from this research will provide snowsport participants unbiased impact data to make informed helmet purchases, while concurrently providing a realistic test protocol that allows for design interventions to reduce the risk of injury.

Introduction: Concussions in American Football are of a major concern due to highly reported injury rates. The importance of properly designed helmets have shown effect in reducing the risk of injuries, such as skull fractures. However, they are not as effective in reducing the risk of concussion. Helmets designed are required to pass standards and regulations for them to be allowed within the football leagues. The current test methods evaluate linear impacts, but lack evaluations of oblique impacts which are believed to cause concussions. Several test methods have been suggested, but little is known regarding how they compare. Objective: The purpose of this study was to compare three different test methods for evaluating helmet performance, utilizing finite element simulation. Three different helmet models were used for comparison, evaluating head kinematics. The helmet models were additionally ranked from best to worst based on their performances. Method: Three test methods, linear impactor, 45° angled linear impactor, and a drop test onto a 45° angled plate were simulated with three different open source helmet models. Simulations were conducted with one impact velocity at three impact locations. The influence of the interaction between helmet and head was also evaluated by altering the friction coefficient. Results: The test methods showed different results depending on helmet models, impact locations, and kinematics evaluated. Similarly, rankings of the helmets were varied based on methods and impact location. Little difference was observed after lowering the friction coefficient in majority of cases. The linear and angular acceleration for the drop side impact were mostly affected. Conclusion: Further evaluations of the test methods and comparison to real impacts is required to evaluate what method resembles head impacts best. Lowered friction coefficient had an effect for the drop impacts, but minor effect for other test methods

The purpose of this study was to investigate whether ice hockey facial protectors can decrease overall head acceleration during blunt impacts as well as to identify if attenuation differences exist between visors and cages. Commercial models of three cages and three visors were assessed. Blunt impacts were simulated permitting the measurement of peak accelerations (PA) within the surrogate head form. Results indicated that indeed face protectors in combination with helmets substantially reduced PA during blunt impacts within threshold safety limits (below 300 g's). In general, cages showed lower PA than visors (p=0.004). Differences between models were also observed during repeated impacts and impact site (p=0.0001, p=0.007). In conclusion, this study demonstrates that facial protectors function beyond their role in preventing facial injuries, complementing the role of the helmet in attenuating head deceleration during impact. Consequently, the utilization of facial protectors may reduce the severity and incidence of mTBI.

Although cycling offers many health and environmental benefits, it is not an activity free of injury risk. Increases in cycling popularity in the United States over the past 15 years have been paralleled by a 120% growth in cycling-related hospital admissions, with injuries to the head among the most common and debilitating injuries. Bicycle helmets can reduce head injury risk and are presently required to meet safety standard certification criteria specifying a minimal level of acceptable impact protection. However, the conditions surrounding cyclist head impacts are thought to be much more complex than the test conditions prescribed in standards and have important implications related to mechanisms of injury. The overarching aim of this dissertation was thus to investigate the protective capabilities of bicycle helmets in the context of real-world impact conditions and relevant head injury mechanisms. This aim was achieved through a series of studies, the objectives of which were to: compare helmet impact performance across standards impact testing and more realistic, oblique impact testing; to probe how changing boundary conditions of oblique impact testing may influence helmet test outcomes; to use this knowledge to inform the development of an objective helmet evaluation protocol reflective of realistic impact conditions and related head injury risks; and finally, to enhance the body of knowledge pertaining to cyclist head impact conditions via advanced helmet damage reconstruction techniques. The compilation of results across these studies serves to enhance cyclist safety by stimulating improved helmet evaluation and design while simultaneously providing objective, biomechanical data to consumers, enabling them to make safety-based purchasing decisions.
Doctor of Philosophy
Although cycling offers many health and environmental benefits and is increasing in popularity in the United States, it is not always a perfectly safe activity. The number of cycling-related hospital admissions in the US has been increasing over the past 15 years. Cyclists often sustain head injuries from crashes, which can be particularly debilitating. Fortunately, wearing a helmet can protect against head injuries during a crash. Bicycle helmets are presently designed around safety standards that drop a helmeted dummy head onto a horizontal anvil and require the helmet to limit the force on the head to acceptable levels. However, standards tests overly simplify how cyclists actually hit their head during a crash and are consequently unable to assess how well helmets protect against common brain injuries like concussion. The overarching goal of this research was to evaluate how effectively bicycle helmets protect cyclists from concussion in realistic impact scenarios. Several studies were conducted to achieve this goal. Their individual objectives were to: compare how bicycle helmets reduce impact forces associated with standards tests versus more realistic, angled impact tests; to understand how changing constraints of an angled impact setup influences helmet effectiveness; to develop an unbiased evaluation protocol for bicycle helmets based on realistic cyclist crash scenarios and concussion risk assessment; and finally, to further explore how cyclists impact their head in real-world crashes using advanced techniques for reconstructing bicycle helmet damage from actual accidents. All of these studies lead to improved cyclist safety by stimulating improved helmet evaluation and design, while also providing consumers with information on how protective their helmets are.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2000.
Includes bibliographical references (leaves [58]-[61]).
The participation of women in the building sector is an exception rather than a rule. Inmost countries of the world the building industry is almost exclusively the domain of men. In India a large number of women are actively involved in the construction process itself. According to 1993-94 Statistics, the construction sector in India provided employment to 6% (5.9 million) of all employed women, constituting about 20% of the total workers in the industry. In spite of their large numbers, women construction workers are seen as secondary/ temporary workers with seldom any opportunities for training, upward mobility, wage guarantees, fringe benefits or social protections. My research has been an exploration and an inquiry of this widely observed phenomena of women construction workers and how it operates from the perspectives of the various role players in the industry, namely, the workers, contractors, intermediaries etc. The purpose is to map the existing know ledge base on the role of women workers and to identify from this mapping key issues that need to be critically examined if opportunities for women in the industry are to be enhanced. The idea has been to make vivid the experience that women have on a construction site and draw from their account implications, issues and problems that one needs to address while formulating a public policy and modifying the practice. The construction industry remains one of the least researched industries in India. There is very little research published or reliable data on numbers, working and socio-economic conditions and the position of women workers within the construction industry. Through my research I attempt to create a knowledge base and fill the lacuna in the existing literature on the subject and contribute towards a "different" understanding of the role of women workers in the construction industry.
by Sabina Suri.
S.M.

Modern sport helmets have been effective in reducing catastrophic head injuries such as skull fracture and subdural hematoma; yet, the high prevalence of minor traumatic brain injuries (mTBI) is an unresolved public health concern. Consequently, there is a need for greater scrutiny in a helmet's ability to mitigate collision forces that may correspond to mTBI risk. Current safety standards primarily assess a helmet's ability to minimize the whole head's peak acceleration during blunt impacts. Absent are dynamic measures local to the impact site itself due to the technical challenge to spatial map high impact force magnitudes with high temporal resolution. Inclusion of the latter measures may enhance the functional assessment of helmets. Thus, the aim of this research was to develop a localized impact mapping system (LIMS) for placement between the helmet and head interface and then to utilize the LIMS to evaluate the mechanical behaviour of various padding foams and helmets during controlled headform drop and projectile collision tests. Interposed between the helmet shell/padding and head surface, this LIMS consists of an array of discrete, thin force sensors connected to a compact signal conditioner and high speed data acquisition digital recorder. A first study demonstrated the feasibility of the LIMS to accurately capture impact events in terms of both force magnitude and temporal response. The results of this initial study demonstrated that the system could capture impact forces with acceptable error (~5%) and high correlation (0.97) between measures of global force and the sensor array. Furthermore, the LIMS demonstrated the ability to capture impact "footprints" that functionally differentiated material properties of density and temperature. A second study incorporated the LIMS as part of a standard controlled surrogate headform drop test for blunt impacts. The LIMS performed equally well on the curved cranial surface geometry of the headform and was able to differentiate unique impact contact distribution patterns based on the ice hockey helmet model's shell and padding configurations, including identification of high focal force concentrations (>16 MPa) during side impact. Of note, global head impact acceleration measures did not correspond to the magnitude of localized contact forces (R-square=0.22), but did correspond to net global contact force (R-square=0.98). A third study used the LIMS between a Hybrid III surrogate headform and an ice hockey helmet during controlled puck projectile collisions. The LIMS was effective at capturing local force distributions dynamics for short impact events lasting 2-4 ms, and again was able to distinguish between varied helmet model's padding materials and installed configurations. Five helmet models were subject to highly localized puck impact at two different velocities (V1=24.2 m/s, V2=33.3 m/s). At V2, peak contact pressures, averaged across all helmet models, were nearly double (393 N/cm^2) those recorded at the same location during vertical drop testing (201 N/cm^2). Again, linear acceleration data did not discern these differences in localized pressures. In summary, this novel testing approach provides an instrument for the assessment of helmet design and material properties on local impact dynamics, and demonstrates merit as an industrial and research tool to enhance head protection.
Les casques de sport modernes ont été efficaces pour réduire les traumatismes crâniens sévères tels que les fractures du crâne et les hématomes sous-duraux. Malgré tout, la prévalence élevée des lésions cérébrales traumatiques mineures reste un problème de santé publique non résolu. Par conséquence, il existe un besoin important pour un examen plus approfondi de la capacité des casques à atténuer les forces de collision qui pourraient correspondre à un risque de traumatisme cérébral mineur. Les normes actuelles évaluent principalement l'efficacité des casques à minimiser les accélérations maximales de la tête lors d'impacts contondants. L'absence de mesures dynamiques locales, plus précisément au site d'impact, est surtout dû au défi technique qui est d'insérer des matrices sensorielles avec une haute résolution temporelle. Le développement de cette dernière technique de mesure pourrait améliorer l'évaluation fonctionnelle des casques en général. Ainsi, l'objectif principal de cette recherche était de développer un système de cartographie d'impact local (CIL) tout en permettant l'insertion de ce système entre le casque et la tête, et ainsi, utiliser le CIL afin d'évaluer les caractéristiques mécaniques de differentes mousses de rembourrage et différents casques au cours de chute et de collision contrôlée sur une fausse tête. Interposé entre la calotte/rembourrage et la surface de la tête, ce CIL est constitué d'un réseau de capteurs de force discrets, minces, connectés à une grande vitesse d'acquisition de données numériques. Une première étude a démontré la faisabilité d'utiliser le CIL pour capturer avec précision des événements d'impact en termes d'amplitude et de force ainsi que la réponse temporelle. Par ailleurs, le CIL a démontré la capacité de capturer les «empreintes» d'impact et de différencier fonctionnellement divers matériaux en mousse et des densités. Une deuxième étude a intégré le CIL dans le cadre d'une norme d'essai contrôlé de fausse tête de substitution lors de chute sur objets contondants. Le CIL s'est révélé tout aussi précis sur la géométrie de la surface crânienne courbe et a été en mesure de différencier les modèles uniques d'impact de contact de distribution basé sur le modèle de coque des casques de hockey et de configurations de remplissage, y compris l'identification de concentrations élevées de force de contact (>16 MPa). Fait à noter, l'impact global des mesures d'accélération de la tête ne correspond pas nécessairement à l'ampleur des forces d'intervention (R-square=0.22). Une troisième étude a utilisé le CIL entre une fausse tête de substitution Hybrid III et un casque de hockey sur glace lors de collisions de projectiles. Le CIL est efficace pour capturer des distributions locales de forces dynamiques lors d'événements de moins de 4 ms, et encore une fois a été en mesure de faire la distinction entre les matériaux de rembourrage des modèles de casques variés. En résumé, cette approche de test innovatrice s'est avérée être un instrument précis pour l'évaluation de la conception du casque et des propriétés des matériaux sur la dynamique d'impact local, et démontre le mérite d'un outil industriel et de recherche visant à améliorer la protection de la tête.

The purpose of this research was to identify the design characteristics and attitudes that impact the use of snowboarding helmets and to test statistically a proposed conceptual framework for identifying perceived importance of functional, expressive, aesthetic, and regulatory (FEAR) needs of snowboarding helmets for current snowboarders. Data for this study was collected online. The final sample was composed of 391 participants, which represented a 13.67% response rate. Multiple comparisons were used to examine mean differences among the FEAR variables, as well as attitudes toward helmet use. A multiple linear regression was used to test four proposed hypotheses. The results of hypotheses revealed that there was an impact between attitudes toward helmet use and perceived importance of functional needs, but this relationship depended on the level of expressive needs, aesthetic needs, and helmet usage. The typical impact of functional needs on attitudes toward helmet use was positive (slope = .013) when all variables were at their respective means (Hypothesis 1). Hypothesis 2 tested to see if there was an impact between attitudes toward helmet use and perceived importance of expressive needs, but again, this relationship depended on the level of functional needs and helmet usage. The typical impact of expressive needs on attitudes toward helmet use was positive (slope = .014) when all variables were at their respective means. Similarly, the impact between attitudes toward helmet use and the perceived importance of aesthetic needs was dependent on the level of functional needs and helmet usage. The impact of aesthetic needs on attitudes toward helmet use was typically negative (slope = -.012) when all variables were at their respective means (Hypothesis 3). Finally, Hypothesis 4 looked at the impact between attitudes toward helmet use and the perceived importance of regulatory needs. Unlike the other three hypotheses, this relationship did not depend on any other variables. The impact of regulatory needs on attitudes toward helmet use was positive, and the strength of association was .010. Although hypothesis 1-3 were substantially supported, and hypothesis 4 was fully supported, from a statistical point of view, the interaction effects between the independent variables (i.e., FEA needs) and the covariate (i.e., helmet usage) limit the findings, so we can not really state that the hypotheses were supported. However, based on information obtained from the respondents in this study, the application of a FEAR needs assessment of snowboarding helmets could help to enhance the overall performance of snowboarders. In other words, the improvement of helmet functionality, expressive qualities, aesthetic attributes and regulatory needs would provide a more enjoyable snow activity to participants. Thus, the conceptual framework of the perceived importance of FEAR needs would be acceptable to understand the attitudes toward helmet use among snowboarders.
Ph. D.

This is an examination of a neglected class of relations that have become more common after the Cold War, those between the United Nations and sub-State insurgent groups. This relationship has changed significantly after the end of the Cold War, both in the nature and frequency of the United Nations' response, and in the character of the insurgents that are addressed. Observing a strong influence of realism in both the motivations of insurgent actions and in the determinants and constraints of United Nations security initiatives, this study hypothesises that the predominant determinant of the effectiveness of United Nations-insurgent interactions is an essential concurrence in their approaches to the interaction. The research design develops an analytical framework of approach indicators to test the validity of this hypothesis across a range of United Nations-insurgent interactions. Those interactions chosen for analysis are Mediation; Peacekeeping, including Monitoring Ceasefires, Humanitarian Peacekeeping; and Disarmament and Demobilisation; and Election Monitoring. United Nations interactions with contemporary insurgent movements - the FMLN, the Khmer Rouge, the Bosnian Serbs, Renamo, the USC-SNA, the Contras, and Unita - are chosen according to their operational viability in order to fully test the hypothesised relationship. The general support for the hypothesis revealed by the analysis suggests important conclusions for the planning and conduct of United Nations initiatives, which are increasingly being called on since the Cold War to intervene in civil wars.

During the development process of a product, tests are typically conducted to ensure the quality of the features of the product before it is made available to the public. The scope of this project was to find a realistic and reliable way to test components in a Multi-Directional Impact Protection System (MIPS) in fully mounted helmets. The reason for this type of testing is to ensure that all components included in the Brain Protection System (BPS) hold up over time in daily use. Therefore, the goal with this project was to design and build a new test machine that could simulate the long-term effects of material fatigue on the MIPS BPS. The machine was able to shake a head with a helmet attached to it to simulate the lifecycle use of a helmet in a shorter time span. The motion of the machine was powered by a stepper motor who is connected to a rocker arm, that transfers a rotational motion to a linear motion, heaving a plate with the head attached to it. The motor is controlled by an Arduino which receives signals from a control panel that enables adjustments to the number of cycles that the machine runs. This report describes the main components, design and function of the machine.
Under produktutvecklingsprocesser genomförs tester för att säkerställa produktens olika kvaliteter innan den görs tillgänglig för allmänheten. Syftet med detta projekt var att hitta ett realistiskt och pålitligt sätt att testa komponenter i ett MIPS (Multi-Directional Impact Protection System) i fullt monterade hjälmar. Anledningen till denna typ av testning är att säkerställa att alla komponenter som ingår i Brain Protection System (BPS) håller över tid vid daglig användning. Målet var därför att skapa en ny testmaskin för att simulera de långsiktiga effekterna av förslitning på komponenterna i MIPS BPS. Maskinen kan skaka ett huvud med en hjälm fäst på för att simulera användningen under en hel livscykel hos en hjälm. Maskinen drivs av en stegmotor som är ansluten till en vipparm, vilken i sin tur överför rotationsrörelsen till en linjär rörelse som lyfter plattan med huvudet. Motorn styrs av en Arduino som tar emot signaler från kontrollpanelen vilket möjliggör justeringar av antalet cykler som maskinen kör. Denna rapport redogör för maskinens huvudsakliga komponenter, konstruktion och funktion.

The most common diagnoses after bicycle accidents are head injuries and fractures on arms and legs. At two of three injured cyclists, head injuries are the primary cause of death and bicycle helmets are a good protection against these injuries. Because the brain is very fragile, even a moderate hit can cause a serious injury. Arms and legs can often be treated, while brain damage could be a permanent disability. The main goal of this paper is to find out what makes students at Linköping University wear a bicycle helmet. The specific aim of this paper is to find out why students at Linköping University do not wear a bicycle helmet when they are cycling. The paper is divided into a literature review and a case study. The literature review delivers an insight into the road traffic safety system and the contributing factors that influence road traffic safety. It covers research analysis of experts about human behavior and gives an overview of relevant facts and figures concerning cycling within Sweden as well as within the European Union. The case study is a survey carried out at Linköping University. The method used is paper questionnaire with the target group of students at Linköping University. The result of the questionnaire is that more information regarding bicycle helmets and cycling as such, bicycle helmets for free or at least for reduced prices and to somehow change the attitudes towards bicycle helmets is important to increase the number of students wearing a bicycle helmet at Linköping University. As the most important reasons for not wearing a bicycle helmet, practical problems due to having no opportunity to fix the bicycle helmet secure to the bicycle, the fear of negative appearance and the discomfort of wearing a bicycle helmet have been mentioned. To increase the usage of bicycle helmets measures like increasing the awareness, reducing the helmet price or providing extra features with the helmet, based on the results of the literature review and the questionnaire, are suggested at the end of this paper.

Athletes competing in contact sports commonly wear intra-oral dental mouthguards. Data are sparse concerning the influence of a mouthguard on breathing during exercise. We compared VE and VO2 during submaximal and maximal exercise on a skating treadmill (TM) while wearing an intra-oral dental mouthguard. Female varsity hockey players (n = 12) performed two skating tests on a TM with and without a mouthguard (WIPSS Jaw-Joint Protecto(TM)). The players wore the mouthguard during hockey practices prior to collection of ventilation data on the treadmill. Also, the players completed a questionnaire that examined their perceptions of the mouthguard in terms of ventilation, comfort and performance. A 10-point rating scale was used for this evaluation. Two performance tests on the skating treadmill examined the effect of the mouthguard on submaximal and maximal aerobic exercise. The subjects skated for 4 min at 2 submaximal velocities (14 and 16 km·h-1 ) separated by 5 min of passive recovery. A VO2 max test followed the submaximal tests and commenced at 18 km·h-1 with the velocity increasing by 1 km·h-1 every minute until volitional fatigue. VE, VO2, VCO 2 and RER were analyzed using a Sensor Medics 2900 metabolic cart. Two-way (2 conditions x 3 velocities) repeated measures ANOVAs were used to examine differences in VE, VO2 and HR. Ventilation was unchanged when skating at the two submaximal velocities. VO2 max was 48.8 ml·kg-1·min-1 using the intra-oral mouthguard and was 52.4 ml·kg-1·min -1 without a mouthguard. VE max was 108.5 L·min -1 using the intra-oral mouthguard and was 114.1 L·min -1 without a mouthguard. The results showed that VE max and VO2 max were lower using the mouthguard compared to the no mouthguard condition.

Віртуальна реальність (VR) - це штучний світ, створений спеціальними технічними пристроями, за допомогою яких людина може потрапити у цифровий світ. Головна відмінність віртуальної реальності - максимальний вплив на почуття людини - зір, слух, дотик.

[EN] Predicting thermal comfort perceived during wearing protective clothing is important especially for the head as it is one of the most sensitive body parts to heat. Since helmets typically induce an additional thermal insulation that impairs the heat dissipation from the head, a special attention should be drawn to a heat strain leading to a decrease of the cognitive performance and to adverse health effects. Thermal manikins allow systematic analysis of the heat and mass transfer properties of protective clothing. However, this methodology does not provide sufficient information about the local and the whole body human physiological response in different cases of use. The prediction of the physiological state of the body is provided by a thermophysiological model. However, they are not capable of accounting for complex heat and mass exchange processes at the skin surface when the clothing is worn. Thermal devices could measure the overall effect of these processes when wearing the given actual gear and being exposed to the surrounding environment. Several attempts to couple thermal manikins with physiological models have been undertaken, however, the partial coupling of a body part manikin with a physiological model has not been addressed so far. Hence, the aim of this work was to develop a novel thermophysiological human head simulator for headgear evaluation based on the coupling of a thermal head manikin with a thermophysiological model. This method would be able to realistically reproduce the effect of clothing on the heat and mass transfer from the head's skin to the environment. A thermal head manikin with a dedicated segmentation for headgear testing was evaluated for the thermophysiological human head simulator. This head manikin showed consistent when compared to previously published data of a less segmented head manikin and the more detailed investigation of the local heat transfer at head brought additional information regarding the contribution of the local design characteristics of the headgear to the overall heat exchange. The thermal head manikin was evaluated in the most demanding scenarios according to the human physiology. It was possible to consistently define four head parts, namely, forehead, cranial, face and neck parts. When heterogeneous surface temperature distribution was applied on the head manikin, the gradients between head parts could compromise the precision of skin temperature prediction at forehead and face. The passive heating and cooling responsiveness of the head manikin did not present any limitation for simulating sudden temperature step changes. However, when the manikin heating and cooling processes were modulated by the PI control with default settings, the time needed to reach the temperature set point was larger than the time required by the human physiology. The thermophysiological model was validated for prediction of global and local skin temperatures by comparing simulations against human experimental data in a wide range of conditions. The physiological model showed a good precision in general when predicting core and mean skin temperature. A reduced precision was observed for some local skin temperatures. Finally, the thermal head manikin and the physiological model were coupled to build up the thermophysiological head simulator. The comparison of the prediction of the coupled system with human experimental data in several scenarios showed a good agreement for rectal and mean skin temperatures. However, some greater discrepancy was observed for forehead temperature in exposures in which participants were exercising in warm environments. The representation of the human sweat evaporation could be affected by a reduced evaporation efficiency and manikin sweat dynamics. The industry will benefit from this thermophysiological human head simulator, which will lead to the development of helmet designs with enhanced thermal comfort, and therefore, with higher acceptance by users
[ES] Poder predecir el confort térmico durante el uso de indumentaria de protección es muy relevante especialmente en el caso de la cabeza, ya que es una de las partes más sensibles del cuerpo al calor. Los cascos y otros elementos de protección frente a impactos incorporan un aislamiento adicional que di-ficulta la disipación de calor en la cabeza. Los maniquís térmicos permiten analizar de manera sistemática las propiedades de transferencia de calor y humedad de la indumentaria de protección. Sin embargo, esta metodología no permite inferir la respuesta fisiológica del usuario cuando utiliza la prenda. Existen modelos termofisiológicos que permiten predecir la respuesta térmica humana pero presentan algunas limitaciones cuando se representan los procesos de transferencia de calor y humedad a través de la ropa. En este caso, un maniquí térmico podría cuantificar el intercambio real de calor que se pro-duce con el ambiente térmico cuando se viste una determinada prenda. Existen experiencias en las que un maniquí de cuerpo completo ha sido acoplado con un modelo termofisiológico. Sin embargo, el acoplamiento de un maniquí que representa únicamente una parte del cuerpo con un modelo de la fisiología humana no ha sido llevado a cabo hasta ahora. Por lo tanto, el objetivo de este trabajo ha sido desarrollar una nueva metodología para evaluar cascos y equipos de protección para la cabeza basándose en el acoplamiento de un maniquí térmico de cabeza con un modelo fisiológico. Un maniquí térmico de cabeza ha sido evaluado para ser acoplado con un modelo termofisiológico. Sus medidas fueron consistentes con resultados anteriormente publicados realizados con un maniquí en menos seccionado. Este nuevo maniquí introdujo información adicional sobre la contribución en particular de las distintas características de diseño del casco al intercambio de calor global. El maniquí térmico de cabeza fue evaluado en los escenarios más extremos identificados para la fisiología humana. Se pudo identificar cuatro partes en el sistema acoplado, frente, cráneo, cara y cuello. En el caso de simular una distribución heterogénea de temperatura, los gradientes generados entre las diferentes partes podrían comprometer la precisión en la predicción de la temperatura de la piel en la frente y la cara. La capacidad pasiva de calentamiento y enfriamiento del maniquí de cabeza no supuso ninguna limitación para simular los cambios súbitos de temperatura de la piel pero cuando el control PI del maniquí moduló los procesos de calentamiento y enfriamiento, el tiempo necesario para alcanzar la temperatura de consigna fue mayor que el tiempo de reacción observado en la fisiología humana. Las predicciones de temperatura obtenidas con el modelo de la fisiología humana fueron validadas mediante la comparación con datos humanos experimentales. En general, el modelo mostró buena precisión para la predicción de la temperatura interna y la temperatura media de la piel. Sin embargo, la precisión observada fue menor para la predicción de algunas temperaturas locales. El maniquí térmico de cabeza y el modelo termofisiológico fueron acoplados. La comparación de las predicciones del sistema acoplado con datos humanos experimentales en diferentes escenarios mostró concordancia para la temperatura rectal y media de la piel. No obstante, se observó una mayor discrepancia en la predicción de la temperatura de la frente si se comparaba las simulaciones obtenidas con el modelo por sí solo y con el sistema acoplado en escenarios en los que los participantes realizaban actividad física ambientes cálidos. La representación de la evaporación del sudor humano en el sistema acoplado podría estar condicionada por una menor eficiencia en la evaporación y la respuesta dinámica de la sudoración del maniquí. La industria se podrá beneficiar de este sistema para avanzar en el desarrollo de nuevos productos que proporcionen
[CAT] Poder predir el confort tèrmic durant l'ús d'indumentària de protecció es especialment rellevant en el cas del cap, ja que és una de les parts més sensibles del cos a la calor. Els cascs incorporen un aïllament adicional que dificulta la dissipació de la calor al cap. Aquest fet és particularment dramàtic quan l'estrès tèrmic afecta negativament a la funció cognitiva i té efectes negatius sobre la salut. Els maniquins tèrmics permeten analitzar de manera sistemàtica les propietats tèrmiques de la indumentària de protecció. No obstant, aquesta metodologia no permet inferir la resposta fisiològica de l'usuari quan utilitza la indumentària. En l'actualitat existixen models matemàtics que permeten predir l'estat fisiològic del cos humà però presenten algunes limitacions quan es tracta de simular els complexos processos de transferència de calor i humitat que ocorren amb roba. En aquest cas, un maniquí tèrmic podria quantificar l'intercanvi real de calor que es produïx en l'ambient tèrmic quan es porta una determinada roba. Existixen experiències prèvies en les que un maniquí de cos complet ha sigut acoblat en un model de la fisiologia humana. No obstant, l'acoblament d'un maniquí que representa únicament una part del cos en un model de la fisiologia humana no ha sigut dut a terme fins ara. Per tant, l'objectiu d'aquest treball es desenvolupar una nova metodologia per a evaluar cascs i indumentària de protecció per al cap basada en l'acoblament d'un maniquí tèrmic de cap amb un model fisiològic. Un maniquí tèrmic de cap ha sigut valorat per a ser acoplat en un model de la fisiologia humana. Les mesures del maniquí van ser consistents amb els resultats publicats en maniquís menys seccionats. Aquest maniquí tèrmic de cap introduix informació adicional sobre la contribució particular de les dife-rents característiques del disseny dels cascs a l'intercanvi de calor global. El maniquí tèrmic de cap ha sigut valorat en els escenaris més extrems identificats per la fisiologia hu-mana. Es van poder identificar quatre parts al sistema acoblat, front, crani, cara i coll. En el cas de simular una distribució heterogènia de temperatura en la superfície del maniquí de cap, els gradients generats entre les diferents parts podria comprometre la precisió en la predicció de la temperatura de la pell en el front i la cara. La capacitat passiva de calfament i refredament del maniquí de cap no va suposar ninguna limitació per simular els canvis sobtats de temperatura de la pell observats en la fisiologia humana. No obstant, quant el control PI del maniquí modulà els processos de calfament i refredament, el temps necessari per alcançar la temperatura de consigna va ser major que el temps de reacció observat en la fisiologia humana. Les prediccions de temperatura obtingudes en el model de la fisiologia humana previst per formar part del sistema acoblat van ser validades amb dades humanes experimentals. En general, el model va mostrar una bona precisió en la predicció de la temperatura interna i la temperatura mitjana de la pell. No obstant, la precisió va ser menor en la predicció de las temperaturas locals. El maniquí tèrmic de cap i el model de la fisiologia humana van ser acoblats. La comparació de les prediccions del sistema acoblat amb dades humanes experimentals mostraren concordança en el cas de la temperatura rectal i mitjana de la pell. No obstant, s'observà una major discrepància en la predicció de la temperatura del front quant es comparaven les simulacions obtingudes en el model per sí mateix i el sistema acoblat en escenaris en els quals els participants realitzaven activitat física en am-bients càlids. La representació de l'evaporament del suor humà en el sistema acoblat podria estar con-dicionada per una menor eficiència en l'evaporament. La indústria es podra beneficiar d'aquest sistema per a avançar en el desenvolupament de nous productes que proporcione
Martínez Guillamón, N. (2016). Multi-sector thermophysiological head simulator for headgear research [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61487
TESIS

The main causes of human Traumatic Brain Injuries (TBIs) in war zones are ballistic impacts and blast waves. While understanding the mechanism of TBI and the brain injury thresholds are in urgent needs, efficiency of helmets as injury protective is not well-examined. To address these gaps, this study investigates the impact of ballistic helmets and padding systems on the biomechanical responses of the brain under dynamic ballistics and blasts loads. A nonlinear human head-neck finite element modeling procedure has been employed for the analysis. The results are examined against de-facto standard experimental data. The response of the finite element head model (FEHM) in terms of biomechanical parameters of the brain has been examined to measure the influence of padding system materials on the level of the loads transferred to the head. The results show when a bullet hits the front of the helmet vertically, the brain experiences the highest amount of stresses in comparisons with other impact orientations. Also, low stiffness foams cause less amount of load to be transferred to the head, indicating the importance of the mechanical properties of the padding system in helmet design. Parametric studies have also been carried out to examine the efficiency of the helmet under various blast situations and intensities by varying standoff distances and orientation angles of the FEHM. The results indicate that the protected heads experience lower accelerations, and stresses than unprotected heads. In general it was found that the performance of the helmet depends on the extent of the coverage of the head by helmet. To examine the influence of the entire human body in comparison with the only head model, the torso and attached to the head was modeled and the responses of the brain to equivalent loadings were examined. In general for the first few milliseconds of the assault on the head, biomechanical parameters of the brain remain independent of the torso. However, one can iv see the body influence as times goes by. As a conclusion one can rely on the results of the head and neck model to be credible enough for brain injury analysis.

Product testing and development are essential parts in sports and for the athletes in their quest to reach the podium. Manufacturers of sports equipment often use basic test methods which do not test the equipment in a sports specific way. Much of the equipment used by world-class athletes is chosen based only on subjective tests and the athletes’ feelings. One short term aim was therefore to develop test methods for objective tests of sports equipment that also tested the equipment in a sports  specific  way.  Another  aim  was  to  integrate  mechanics  and  simulations  to  enhance  the understanding of the test results. The more long term aims are to contribute to increased theoretical knowledge regarding test methods for sports equipment and to contribute to the development of test  methods  to  create  new  and  better  sports  equipment.  Experimental  tests  combined  with simulations  can  give  valuable  information  to  improve  the  performance  and  safety  of  sports equipment. Three studies dealt with the issue of objective yet sport specific test methods for sports equipment. The main methodological advancement is the modification of established test methods together  with  conventional  mechanics  calculations.  New  test  devices  and  methodologies  are proposed for alpine ski helmets and cross-country ski poles. Suggestions are given for improved test setups as well as theoretical simulation are introduced for glide tests of skis. The results show how sport   specific   test   methodologies   together   with   theoretical   calculations   can   improve   the objectiveness and relevance when testing sports equipment. However, the collected and used data require high precision to obtain high accuracy in the simulations. High data accuracy can be an issue in field measurements but also due to manufacturers not disclosing key material data. Still, the used methods  and  calculations  in  this  thesis  produce  relevant  and  reliable  results  which  can  be implemented to accurate evaluations of different sports equipment. Even though it has not been a first priority aim in this work, the results from the alpine helmet study have been used by helmet manufacturers to design new helmets with increased safety properties. This further show how an objective and sport specific test approach together with theoretical simulation can improve sports equipment and in the longer perspective, also the athletes’ performances.

QC 20140423

Sports engineering can be considered as the bridge between the knowledge of sports science and the principles of engineering and has an important role not only in improving the athletic performance, but also in increasing the safety of the athletes. Testing and optimization of sports equipment and athletic performance are essential for supporting athletes in their quest to reach the podium. However, most of the equipment used by world-class athletes is chosen based only on subjective tests and the athletes’ feelings. Consequently, one of the aims of this thesis was to combine mechanics and mathematics to develop new objective test methods for sports equipment. Another objective was to investigate the possibility to accurately track and analyse cross-country skiing performance by using a real-time locating system. A long term aim is the contribution to increased knowledge about objective test and analysis methods in sports. The main methodological advancements are the modification of established test methods for sports equipment and the implementation of spline-interpolated measured positioning data to evaluate cross-country skiing performance. The first two papers show that it is possible to design objective yet sport specific test methods for different sports equipment. New test devices and methodologies are proposed for alpine ski helmets and cross-country ski poles. The third paper gives suggestions for improved test setups and theoretical simulations are introduced for glide tests of skis. It is shown, it the fourth paper, that data from a real-time locating system in combination with a spline model offers considerable potential for performance analysis in cross-country sprint skiing. In the last paper, for the first time, propulsive power during a cross-country sprint skiing race is estimated by applying a power balance model to spline-interpolated measured positioning data, enabling in-depth analyses of power output and pacing strategies in cross-country skiing. Even though it has not been a first priority aim in this work, the results from the first two papers have been used by manufacturers to design new helmets with increased safety properties and cross-country ski poles with increased force transfer properties. In summary, the results of this thesis demonstrate the feasibility of using mechanics and mathematics to increase the objectiveness and relevance when analysing sports equipment and athletic performance.

QC 20160927

Introdução: Acidentes com ciclistas podem ser bastante sérios especialmente pela possibilidade de trauma cranioencefálico grave. Métodos: O objetivo desse trabalho foi estimar a prevalência do uso de capacetes por ciclistas nos finais de semana e feriados na cidade de Porto Alegre. Durante os finais de semana e feriados da primavera de 2007, foi realizado um estudo transversal. 969 ciclistas foram incluídos na amostra. Este estudo foi aprovado pelo Comitê de Ética do Grupo de Pesquisa e Pós-Graduação do Hospital de Clínicas de Porto Alegre. Resultados: A prevalência do uso de capacetes pelos ciclistas foi de 5,6% (IC 95% 4,5 a 7,5). Os ciclistas mais jovens (idade ≤ 20 anos) tiveram uma prevalência menor do uso do capacete, quando comparados à observada entre os demais ciclistas (idade > 20 anos), (P< 0,001; 2,1% vs. 7,8%, respectivamente). Discussão: Embora esse estudo tenha sido realizado em fins de semana e feriados, quando se espera que a prevalência do uso do capacete seja maior, nós encontramos somente 5,6% dos ciclistas utilizando esse equipamento de proteção. Medidas educativas e iniciativas que reduzam o preço de tais equipamentos poderiam trazer benefícios consideráveis para a saúde dessa população.
Introduction: Accidents involving cyclists can be very serious, especially due to the possibility of severe traumatic brain injury. Methods: The objective of this work was estimate the prevalence of helmet use among cyclists in weekends and holidays in the city of Porto Alegre. During the spring of 2007 we conducted a cross-sectional study involving 969 cyclists. The survey was carried out during weekends and holidays on 20 randomly distributed observation sites around the city. The Ethics Committee of the Research and Pos-Graduation Group of Hospital de Clínicas de Porto Alegre approved this study. Results: The observed prevalence of helmet use was 5.6% (IC 95% 4.5 a 7.5). Younger cyclists (age ≤ 20 years) had a lower prevalence of helmet use than that observed among older cyclists (age > 20 years), (P< 0.001; 2.1% vs. 7.8%, respectively). Discussion: Although this study was carried out on weekends and holidays, when the prevalence of helmet use was expected to be higher, we found only 5.6% of cyclist using this protective device. Educational measures and incentives to reduce the price of such equipment could bring considerable benefits to the safety and health of cyclists in this population.

International organisations such as the World Health Organisation highlight the road crash problem in less motorised (or developing, or low income) countries like those in Southeast Asia and recommend the adoption of Western road safety measures. However, there are many differences between highly motorised and less motorised countries which raise questions about how successfully Western road safety knowledge and expertise can be transferred.----- A review of the statistical information on road crashes shows a great deal of uncertainty about both the scale and likely trajectory of road fatalities globally, in less motorised countries and in Asia. It is generally agreed, however, that Asia accounts for around half of all road fatalities, and analysis of the limited available data shows both that Southeast Asia is not an atypical region of Asia in road safety terms, and that Thailand and Vietnam are not atypical of Southeast Asian countries.----- A literature review of recommended practice approaches to road safety transfer in Asia shows that there are many economic, institutional, social and cultural factors which potentially influence the success of transfer. The review also shows that there is no coherent, comprehensive approach which either conceptualises these factors and their relationship to transfer outcomes, or uses an analysis of these factors to plan or modify transfer. To address this gap, this thesis develops a 'road safety space' model as a tool for conceptualisation and analysis, based on a biological metaphor which views the transfer of road safety measures from one context to another as analogous to the transfer of a species into a new ecological space. The road safety space model explicitly considers economic, institutional, social and cultural factors (from specific to broad) which influence the particular road safety issue which a particular road safety transfer effort seeks to address. A central contention of this thesis is that the road safety space model is both a feasible and useful tool to improve the process of road safety transfer to less motorised countries. Road safety space analysis is seen to have a role in a broader process of selection of road safety measures for transfer, along with knowledge of how the measures are considered to operate.----- The research reported in this thesis is comprised of three studies. Study 1 reviewed evaluations of road safety transfer to Thailand and Vietnam. Studies 2 and 3 were case studies of road safety transfer to Thailand and Vietnam respectively.----- Study 1 was an analysis of existing evaluations of road safety transfer to Thailand and Vietnam. The aims were to analyse the evaluations for their consideration of contextual factors, as described in the road safety space model, and to discuss whether the road safety space model assisted in understanding the reasons for success or failure of transfer. However, very few such evaluations exist, and those that were found generally lacked information on whether contextual factors were considered. This indicated the need for a more detailed, in-depth qualitative investigation of particular cases of road safety transfer, in order to investigate the feasibility and utility of the road safety space model.----- Two case studies (Study 2 and Study 3) were conducted to test whether the road safety space approach was both feasible and useful as a means of improving road safety transfer efforts. Study 2 was a case study of the development and implementation in Thailand of a road safety education program for school children, which involved the transfer of Western research and techniques. The transfer agents (i.e. those who effected the road safety transfer) were Australian consultants working for the Australian Road Research Board (ARRB). The transfer was funded by the World Bank and managed by the Thai Ministry of Education (MOE). Study 3 was a case study of the development and implementation of a motorcycle helmet wearing program in Vietnam, which involved the transfer of Western knowledge, techniques and technology. The transfer agents were staff of Asia Injury (AI), a non-government organisation (NGO), and the program was funded initially by a charitable fund, with the intention of becoming self-funding through operation of a helmet factory.----- The case studies employed background research into existing information on economic, institutional, social and cultural factors relevant to the road safety issues (road use behaviour of school children in Thailand and motorcycle helmet purchase and wearing in Vietnam), and collected data through interviews with key informants, analysis of secondary sources and observations. This information was used to derive the road safety space for each road safety issue, to identify the road safety space recognised and addressed by the transfer agents (ARRB and AI), and to determine which factors they missed, or were aware of but took no action on. The focus of this analysis was on the processes used in transfer, not on the road safety outcomes of transfer, although these provided information on the processes as well. Available evaluation information was used to draw links between the omissions and the success of the transfer processes. It was noted that information on how the transferred measures operate should come from a road safety space analysis in the originating country, although this raised questions about selection of country and time (when the measure was first introduced, or in its maturity).----- The feasibility and utility of the road safety space model were discussed. It was clear that the model provided information on the cases which was missed by the transfer agents. The questions examined next were whether this information could have been obtained from an exercise conducted before the transfer had commenced, whether the required effort and cost justified the potential benefits, and whether the information on the road safety space could have been useful for the transfer agents. Comparisons between the road safety spaces for the two cases showed some areas of commonality, e.g. perceptions of police corruption, but also many differences. It was considered likely that some broad factors could be generic, and the possibility was mooted that less motorised countries share issues with police enforcement. This requires further research, however, and at this stage it is better to treat each road safety space as a unique combination of contextual factors influencing the road safety issue of interest.----- It is concluded that the road safety space model is feasible if used in such a way as to minimise the research involved, and useful, although the degree of utility needs to be further explored in a prospective study. The limitation introduced by restricting informants to those who could speak English are discussed. An approach using road safety space analysis is recommended, emphasising analysis of the country to which the road safety measure is being transferred, supplemented by analysis of the originating country road safety space. Gaps in knowledge are identified for further research and development, in particular the theoretical and practical understanding of road use behaviours and their modification in less motorised countries in Southeast Asia. Elaboration of the model is also recommended, to take into account the influence of the type of measure transferred, the role of the transfer agent, the area of road safety (education, engineering or enforcement), and the time dimension (the time which might be needed for a transfer to show its effects).----- The findings of this research are likely to be applicable to road safety transfer in other less motorised regions of the world, however prospective testing is needed. They may also be relevant to issues of transfer for areas other than road safety, in particular public health and traffic engineering, where similar economic, institutional, social and cultural issues come together.

International organisations such as the World Health Organisation highlight the road crash problem in less motorised (or developing, or low income) countries like those in Southeast Asia and recommend the adoption of Western road safety measures. However, there are many differences between highly motorised and less motorised countries which raise questions about how successfully Western road safety knowledge and expertise can be transferred.----- A review of the statistical information on road crashes shows a great deal of uncertainty about both the scale and likely trajectory of road fatalities globally, in less motorised countries and in Asia. It is generally agreed, however, that Asia accounts for around half of all road fatalities, and analysis of the limited available data shows both that Southeast Asia is not an atypical region of Asia in road safety terms, and that Thailand and Vietnam are not atypical of Southeast Asian countries.----- A literature review of recommended practice approaches to road safety transfer in Asia shows that there are many economic, institutional, social and cultural factors which potentially influence the success of transfer. The review also shows that there is no coherent, comprehensive approach which either conceptualises these factors and their relationship to transfer outcomes, or uses an analysis of these factors to plan or modify transfer. To address this gap, this thesis develops a 'road safety space' model as a tool for conceptualisation and analysis, based on a biological metaphor which views the transfer of road safety measures from one context to another as analogous to the transfer of a species into a new ecological space. The road safety space model explicitly considers economic, institutional, social and cultural factors (from specific to broad) which influence the particular road safety issue which a particular road safety transfer effort seeks to address. A central contention of this thesis is that the road safety space model is both a feasible and useful tool to improve the process of road safety transfer to less motorised countries. Road safety space analysis is seen to have a role in a broader process of selection of road safety measures for transfer, along with knowledge of how the measures are considered to operate.----- The research reported in this thesis is comprised of three studies. Study 1 reviewed evaluations of road safety transfer to Thailand and Vietnam. Studies 2 and 3 were case studies of road safety transfer to Thailand and Vietnam respectively.----- Study 1 was an analysis of existing evaluations of road safety transfer to Thailand and Vietnam. The aims were to analyse the evaluations for their consideration of contextual factors, as described in the road safety space model, and to discuss whether the road safety space model assisted in understanding the reasons for success or failure of transfer. However, very few such evaluations exist, and those that were found generally lacked information on whether contextual factors were considered. This indicated the need for a more detailed, in-depth qualitative investigation of particular cases of road safety transfer, in order to investigate the feasibility and utility of the road safety space model.----- Two case studies (Study 2 and Study 3) were conducted to test whether the road safety space approach was both feasible and useful as a means of improving road safety transfer efforts. Study 2 was a case study of the development and implementation in Thailand of a road safety education program for school children, which involved the transfer of Western research and techniques. The transfer agents (i.e. those who effected the road safety transfer) were Australian consultants working for the Australian Road Research Board (ARRB). The transfer was funded by the World Bank and managed by the Thai Ministry of Education (MOE). Study 3 was a case study of the development and implementation of a motorcycle helmet wearing program in Vietnam, which involved the transfer of Western knowledge, techniques and technology. The transfer agents were staff of Asia Injury (AI), a non-government organisation (NGO), and the program was funded initially by a charitable fund, with the intention of becoming self-funding through operation of a helmet factory.----- The case studies employed background research into existing information on economic, institutional, social and cultural factors relevant to the road safety issues (road use behaviour of school children in Thailand and motorcycle helmet purchase and wearing in Vietnam), and collected data through interviews with key informants, analysis of secondary sources and observations. This information was used to derive the road safety space for each road safety issue, to identify the road safety space recognised and addressed by the transfer agents (ARRB and AI), and to determine which factors they missed, or were aware of but took no action on. The focus of this analysis was on the processes used in transfer, not on the road safety outcomes of transfer, although these provided information on the processes as well. Available evaluation information was used to draw links between the omissions and the success of the transfer processes. It was noted that information on how the transferred measures operate should come from a road safety space analysis in the originating country, although this raised questions about selection of country and time (when the measure was first introduced, or in its maturity).----- The feasibility and utility of the road safety space model were discussed. It was clear that the model provided information on the cases which was missed by the transfer agents. The questions examined next were whether this information could have been obtained from an exercise conducted before the transfer had commenced, whether the required effort and cost justified the potential benefits, and whether the information on the road safety space could have been useful for the transfer agents. Comparisons between the road safety spaces for the two cases showed some areas of commonality, e.g. perceptions of police corruption, but also many differences. It was considered likely that some broad factors could be generic, and the possibility was mooted that less motorised countries share issues with police enforcement. This requires further research, however, and at this stage it is better to treat each road safety space as a unique combination of contextual factors influencing the road safety issue of interest.----- It is concluded that the road safety space model is feasible if used in such a way as to minimise the research involved, and useful, although the degree of utility needs to be further explored in a prospective study. The limitation introduced by restricting informants to those who could speak English are discussed. An approach using road safety space analysis is recommended, emphasising analysis of the country to which the road safety measure is being transferred, supplemented by analysis of the originating country road safety space. Gaps in knowledge are identified for further research and development, in particular the theoretical and practical understanding of road use behaviours and their modification in less motorised countries in Southeast Asia. Elaboration of the model is also recommended, to take into account the influence of the type of measure transferred, the role of the transfer agent, the area of road safety (education, engineering or enforcement), and the time dimension (the time which might be needed for a transfer to show its effects).----- The findings of this research are likely to be applicable to road safety transfer in other less motorised regions of the world, however prospective testing is needed. They may also be relevant to issues of transfer for areas other than road safety, in particular public health and traffic engineering, where similar economic, institutional, social and cultural issues come together.

For everyday cycling, one needs to carry rainproof clothing just for the case of unexpected downpours. In the present research, we present a concept for a helmet which is automatically rainproof when the rain starts. When the sun comes out, the helmet is breathable again even before it completely dries up. This functionality is provided by active hydrogel meshes. Hydrogel meshes offer great advantages due to their ability to change the aperture size with swelling and deswelling. In our current work, we present the design and modeling steps for hydrogel-layered active meshes which use (i) swelling and deswelling in hydrated state and (ii) swelling starting from the dry state. The main goal is to close the air openings of a bicycle helmet when rain starts as an automatic rainproofing. This can be achieved through the swelling of the hydrogel pNiPAAM-co-chlorophyllin in the meshes, which leads to closing when hydrated. At the same time, the light-sensitive behavior leads to opening of the apertures under direct sun exposure, i.e. when the sun appears again after the rain. We present the steps of modeling and design using the Normalized Extended Temperature-Expansion-Model (NETEM) to perform simulations in Abaqus. The model is capable of describing both the swelling of the hydrogel under light stimulus and the volume change due to hydration. It is based on the analogy between free swelling and thermal expansion and defined for nonlinear displacements. We also discuss the fabrication process of hydrogel-layered fibers and challenges in their application and simulation. As a proof of concept for hydrogel-layered meshes, we show preliminary experimental results of a poly(acrylamide)/poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAAm/PAMPS) hydrogel with semi-interpenetrated network (SIPN) structure and its swelling capacities on a mesh. Starting from the active hydrogel meshes as presented in the current work, the next step can be smart textiles that harness the power of hydrogels: the adaptation to combinations of stimuli - like humidity, temperature and brightness - that define environments.

The horseracing industry currently lacks media attention. Studies have indicated the sport’s viewing and gambling declination over the decades. While popular televised sports such as football and baseball maintain a modernized entertainment culture through high-definition wireless streaming, horseracing remains in the 'binocular era'. An idea is introduced and a solution is analyzed to establish a foothold for horseracing in contemporary entertainment and inspire a developing fan base. EquiSight LLC desires wireless telemetry within the form factor of a jockey's helmet to meet these ends. The system devised must function while satisfying safety regulations. Individual component decisions are justified in addition to safety and quality tests. Current technology restricts bandwidth and data transfer rate. Standard-and high-definition possibilities and implications are discussed. Analog and digital transmission systems are evaluated and a preference justification is developed. A reliable power source and integration technique are chosen. Environmental, space, and range constraints are considered. Two-way audio communication between the jockey and trainer is described. In summary, a compact solution for EquiSight LLC is presented and its design choices are reviewed. The proposed system, implemented within a $3000 budget, will attract new fans, reignite interest, and provide a fairness and/or outcome judging tool.