published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy

This thesis comprehends a series of nonlinear numerical studies with the finite element software's LS-Dyna and Impetus AFEA. The main focus lies on a comparative crash analysis of an aluminium beam profile which the company Sapa technology has used during their crash analysis. The aluminium profile has the characteristic of having different thickness over span ratios within the profile. This characteristic provided the opportunity to conduct a performance investigation of shell and solid elements with finite element analysis. Numerical comparisons were made between shell and solid elements where measurable parameters such as internal energy, simulation times, buckling patterns and material failures were compared to physical tests conducted prior to this thesis by Sapa technology. The performance investigation of shell and solid elements was initiated by creating models of the aluminium profile for general visualization and to facilitate the meshing of surfaces. The meshing procedure was considered to be an important factor of the analysis. The mesh quality and element orientations were carefully monitored in order to achieve acceptable results when the models were compared to physical tests. Preliminary simulations were further conducted in order to obtain a clear understanding of software parameters when performing crash simulations in LS-Dyna and Impetus AFEA. The investigated parameters were element formulations and material models. A general parameter understanding facilitated in the selection of parameters for actual simulations, where material failure and damage models were used. In conclusion, LS-Dyna was observed to provide a bigger internal energy absorption during the crushing of the beam with longer simulation times for solid elements when compared to shell elements. Impetus AFEA did on the other hand provide results close to physical test data with acceptable simulation times when compared to physical tests. The result difference obtained from the FE-software's in relation to physical crash experiments were considered to be varied but did indicate that shell elements were efficient enough for the specific profile during simulations with LS-Dyna. Impetus AFEA proved that the same time to be numerically efficient for energy approximations with solid elements refined with the third polynomial.

In this study, we capture the moderating effect of aggressive driving behavior while assessing the influence of a comprehensive set of variables on injury severity. In doing so, we are able to account for the indirect effects of variables on injury severity through their influence on aggressive driving behavior, as well as the direct effect of variables on injury severity. The methodology used in this study to accommodate the moderating effect of aggressive driving behavior takes the form of two models – one for aggressive driving and another for injury severity. These are appropriately linked to obtain the indirect and direct effects of variables. The data for estimation is obtained from the National Motor Vehicle Crash Causation Study (NMVCCS). From an empirical standpoint, we consider a fine age categorization until 20 years of age when examining age effects on aggressive driving behavior and injury severity. There are several important results from the empirical analysis. Young drivers (especially novice drivers between 16-17 years of age), drivers who are not wearing seat belt, under the influence of alcohol, not having a valid license, and driving a pickup are found to be most likely to behave aggressively. Situational, vehicle, and roadway factors such as young drivers traveling with young passengers, young drivers driving an SUV or a pick-up truck, driving during the morning rush hour, and driving on roads with high speed limits are also found to trigger aggressive driving behavior. In terms of vehicle occupants, the safest situation from a driver injury standpoint is when there are 2 or more passengers in the vehicle, at least one of whom is above the age of 20 years. These and many other results are discussed, along with implications of the result for graduated driving licensing (GDL) programs. / text

The overall aim was to elucidate the effects of vehicle passengers on young drivers. This generated two specific aims and four papers. The first aim was to investigate the crash risk for young drivers with passengers and to establish whether such accidents involve any special circumstances compared to those that occur without passengers. This goal was achieved by analysing accident and exposure data from two registers. The second objective was to analyse the group processes that develop between four young men in a vehicle and to ascertain how those interactions affect driving behaviour. Those issues were addressed by performing an observational study of twelve young men driving an instrumented vehicle in real traffic with and without passengers. The interactions between the vehicle occupants were video and audio recorded, and the driving behaviour was registered in various ways. The results show that drivers with passengers have a lower crash risk compared to those driving alone regardless of the driver’s age, although this effect is weaker for young drivers (especially males) than for other age groups. Compared to driving alone, driving with passengers for young drivers is more extensively associated with single-vehicle crashes that occur at night, on weekends, and in rural areas on roads with higher speed limits, and it leads to more severe outcomes. It has also been found that the passengers sometimes try to induce the young drivers to act in either safer or more dangerous ways, although the drivers very often resist urging and coaxing from their passengers. Cohesion is another factor that affect the driver-passenger group: a high level of cohesion, especially task cohesion, is associated with a low number of unsafe driving actions. Consequently, it seems that the presence of passengers is not enough to ensure safe driving—substantial group cohesion is also necessary for such behaviour. / Det övergripande syftet med denna avhandling var att studera passagerares effekt på unga förare, vilket genererade två delsyften och fyra delarbeten. Det första delsyftet var att undersöka olycksrisken för unga förare med passagerare och att ta reda på om dessa olyckor skedde under några speciella omständigheter. För att få svar på syftet gjordes en registerstudie där olycks- och exponeringsdata från två olika register analyserades. Det andra delsyftet var att analysera de grupprocesser som utvecklas mellan fyra unga män i en bil och att studera hur dessa interaktioner påverkar körbeteendet. Detta undersöktes med en observationsstudie där tolv unga män fick köra en instrumenterad bil i verklig trafik, både med och utan passagerare. Interaktionerna som uppstod i bilen spelades in med hjälp av videokameror och mikrofoner och körbeteendet registrerades med olika mätinstrument. Resultatet visar att förare med passagerare har en lägre olycksrisk jämfört med förare utan passagerare oavsett förarens ålder. Denna effekt är inte lika stark för unga förare (speciellt inte unga män) som den är för övriga åldersgrupper. Unga förares olyckor med passagerare är också mer vanligt förekommande under speciella omständigheter. Jämfört med olyckor utan passagerare sker de i större utsträckning under nattetid, under veckoslut, i tätbebyggt område, på vägar med hög hastighetsbegränsning, de är oftare singelolyckor och de får mer allvarliga konsekvenser. Vidare visar resultaten att passagerare ibland, på olika sätt, försöker få den unga föraren att köra på ett annat sätt än vad de gör vilket kan betyda ett säkrare eller ett mer trafikfarligt beteende. Det verkar dock som att förarna oftast står emot dessa övertalningsförsök och förolämpningar. En annan faktor som påverkar gruppen är kohesion: en hög grad av kohesion, speciellt uppgiftskohesion, visar sig leda till färre trafikfarliga körbeteenden. Med andra ord verkar det som att blotta närvaron av passagerare inte räcker för att få ett säkert körbeteende; det behövs även en betydande grad av kohesion.

This thesis presents the results of an investigation into the failure detection problem. We consider the specific case of the Quality of Service (QoS) of crash failure detection. In contrast to previous work, we address the crash failure detection problem when the monitored target is resilient and recovers after failure. To the best of our knowledge, this is the first work to provide an analysis of crash-recovery failure detection from the QoS perspective. We develop a probabilistic model of the behavior of a crash-recovery target, i.e. one which has the ability to recover from the crash state. We show that the fail-free run and the crash-stop run are special cases of the crash-recovery run with mean time to failure (MTTF) approaching to infinity and mean time to recovery (MTTR) approaching to infinity, respectively. We extend the previously published QoS metrics to allow the measurement of the recovery speed, and the definition of the completeness property of a failure detector. Then, the impact of the dependability of the crash-recovery target on the QoS bounds for such a crash-recovery failure detector is analyzed using general dependability metrics, such as MTTF and MTTR, based on an approximate probabilistic model of the two-process failure detection system. Then according to our approximate model, we show how to estimate the failure detector’s parameters to achieve a required QoS, based on Chen et al.’s NFD-S algorithm analytically, and how to execute the configuration procedure of this crash-recovery failure detector. In order to make the failure detector adaptive to the target’s crash-recovery behavior and enable the autonomy of the monitoring procedure, we propose two types of recovery detection protocols. One is a reliable recovery detection protocol, which can guarantee to detect each occurring failure and recovery by adopting persistent storage. The other is a lightweight recovery detection protocol, which does not guarantee to detect every failure and recovery but which reduces the system overhead. Both of these recovery detection protocols improve the completeness without reducing the other QoS aspects of a failure detector. In addition, we also demonstrate how to estimate the inputs, such as the dependability metrics, using the failure detector itself. In order to evaluate our analytical work, we simulate the following failure detection algorithms: the simple heartbeat timeout algorithm, the NFD-S algorithm and the NFDS algorithm with the lightweight recovery detection protocol, for various values of MTTF and MTTR. The simulation results show that the dependability of a recoverable monitored target could have significant impact on the QoS of such a failure detector. This conforms well to our models and analysis. We show that in the case of reasonable long MTTF, the NFD-S algorithm with the lightweight recovery detection protocol exhibits better QoS than the NFD-S algorithm for the completeness of a crash-recovery failure detector, and similarly for other QoS metrics.

nforme final de Seminario para optar al grado de Licenciada en Lengua y Literatura Hispánica con mención en Literatura / En este primer capítulo nos proponemos mostrar un panorama general acerca de la ciencia ficción (en adelante CF) y las problemáticas que pueden desprenderse de ella, para así tener una base sobre la cual instalar nuestros análisis personales de diferentes novelas del género. La primera parte del Seminario de Grado el curso se enfocó en abordar lo que más adelante expondremos, es decir, la historia del género, su definición, y sus distintas manifestaciones en subgéneros; para lo cual leímos y vimos varias o bras que resultan representativas de la CF. Además, se dedicó tiempo a procesar la bibliografía con la que trabajaremos, y a discutir distintos aspectos de la misma. Así, durante la segunda parte del curso, enfocada a la producción de nuestros informes fin ales, pudimos aplicar y ampliar lo visto en clases en función de la obra que cada uno decidió analizar. Antes de comenzar, es pertinente mencionar un suceso que tomó lugar tras asistir al primer encuentro de seminario de grado: nos enteramos de que todos manejamos un nivel de inglés que nos permite leer en el idioma. Este aspecto resultó relevante, pues la gran mayoría de las obras y bibliografía de ciencia ficción es producida por angloparlantes. Luego de llegar un acuerdo común, el profesor guía decidió reestructurar el programa del curso, en función de incluir textos actuales que carecen de traducciones. Tal decisión impactó nuestro paso por el seminario, pues el espectro de posibilidades para elegir nuestro objeto de estudio se vio favorablemente ampliado.

The stock market crash of 1929 stands today as the largest decline in market value in the history of the United States. Consequently, the event destroyed the wealth of thousands of American families and institutions. On October 28th and 29th, the United States stock market fell 11.3 percent and 12.4 percent respectively, marking the beginning of a down market that lasted over three years, the time period known today as the Great Depression. This paper empirically analyzes the effects felt by each individual industry sector in the crash of 1929, identifying gross and abnormal returns over three major days in the crash. I then compare my findings to previous literature and economic theories, analyzing which sector returns were expected and which were abnormal.

Ethnic/racial minorities in the United States are overrepresented in fatalities from motor vehicle crashes (MVC). Growing evidence indicates that there are differences among racial/ethnic groups in risk of involvement in fatal crashes. Based on previous research, numerous factors may be involved in high racial/ethnic fatality rates from MVCs, including failure to use safety equipment, driving while under the influence of alcohol/drug, red light running, and speeding. Using data from the Office of the Chief Medical Examiner (OCME) and the FR300P Police Crash Report, this project explores differences in variables associated with traffic safety behavior and traffic law obedience between non-White and White road users (drivers, passengers, and pedestrians). Results indicate that there is a significant association between race/ethnicity and driving while under the influence of alcohol/drugs (DUI). Those endeavoring to develop more effective traffic safety prevention and education programs may consider the effect of social/cultural factors in future efforts.

Purpose. This research study on automobile collision in Virginia amongst fifteen to nineteen (15-19) year olds looked into the trend analysis over a five (5) year period of 2000 to 2004. Trend analysis is usually done for aggregates of all injuries—either intentional or unintentional injuries, or both. The primary objective of this research study was to examine the trend in hospitalization rates and mortality rates for males and females independently. It further looked into the trend, if any, in hospitalization rates, mortality rates, and case-fatality rates, for both males and females combined. The different Tables illustrate the extent and the impact of automobile collision in terms of demographics and characteristics of hospitalizations, types of hospitalizations, hospitalization rates, mortality rates and case-fatality rates among this age group.Methods: An investigation was carried out in a case control manner of 2353 cases using data from the Virginia Department of Health-Division of Injury Prevention & Violence on automobile collision amongst 15-19 year olds, from 2000 to 2004, a (5) five year period. Hospitalization data were obtained from Virginia Health Information, coded in line with International Classification of Diseases, 9th revision (ICD-9); external cause of injury (E)-codes. Mortalityldeath rates and case fatality rates were calculated using U.S. Census Bureau, Census 2000 for Virginia's population data. Frequency distribution analysis was done with SPSS 14.0, data entry using M.S. Excel, while rate ratio and confidence intervals for hospitalization rates, mortality rates were calculated. Linear trend was analyzed for hospitalization rates, mortality rates and case-fatality rates, using Chi square statistics test for significance. Geographical Information System (GIs) methods were used to display counties in Virginia.Results: Out of 2353 cases of automobile collision in Virginia, amongst 15-19 year olds, from 2000 to 2004, the demographic did not changed much. Males were fairly distributed over the five year period, while automobile collision characteristics showed that 2142 cases (91%) were more likely to be hospitalized on an emergency basis, with males having a higher percentage, fifty-nine (59%) percent, and forty (40%)percent for females. (Table 1 & 2). The hospitalization rates were higher for males than females, with rate ratio (RR>1) greater than one over the five years of study (Table 3). Mortality rates showed increase rates for males, over the five year of study (RR>1.5) (Table 4). Test for linear trend in hospitalization rates (Chi. Sq.=14.127, p-value ≤ 0.001) were significant for both males and females. Mortality rates test for trend were also significant for both males and females. (Chi Sq. = 377.0, p-value ≤ 0.001). Case-fatality rates trend test were significant for both males and females. (Chi sq. = 11.580, p value ≤ 0.001). The trend in hospitalization, mortality and case-fatality rates, showed a decrease over the five year of study.Conclusion: Given the impact of injuries in ,the U.S., mainly automobile collisions, it is socially beneficial to continue research, intervention and prevention programs in this area, particularly directed and targeted to this population - Healthy People 2010 objectives.

Title: Biomechanical reflection of the cervicocranial part during frontal impact Objectives: The aim of the work was to analyze in which parameters differs ATD from human participant during frontal impact. Characterize the head movement, compare maximal post impact head speed between ATD and human volunteers and defereneces between volunteer with eye control and without. Methods: Measuring was done with 8 volunteers and ATD (Manikin, 50th percentile man). For each volunteer were done two measurements, first without eye control and second with eye control. ATD was measured twice. It was recorded by Qualisys system, specifically by three optical cameras, on crash simulator. Results were processed in Qualisys Track Manager. There were tracked three markers, two on the body - forehead, shoulder and one on the sledge. Results: Results showed that speed of the head depends on eye control. Volunteer without eye control had higher post impact speed of head (4,94 m/s) than ATD (3,67 m/s) and volunteer with eye contact (3,19 m/s). Quite the same result was observed in change of distance between head and sledge after impact. There was higher value for volunteer without eye contact than for ATD. Keywords: Whiplash, frontal impact, Qualisys, crash simulator, cervicocranial part