Simulation study of driver stress and performance to an unexpected event

Abstract In this paper, we study the effect of unexpected behaviour of a Driving Assistance System (DAS) on the driver, during a common task of driving in a virtual environment. The considered system is an electrical steering, which allows drivers to reduce efforts needed to handle the steering wheel during cornering manoeuvres. A failure of such system could produce a sudden and permanent loss of steering assistance and make the steering wheel more difficult to turn. The objective of this study is to determine how this event will affect the driver's performance, particularly in terms of stress and visual performance. At last, drivers are able to adapt to this kind of event if it occurs before entering a curve. Moreover, an increase of muscle stiffness has been observed during lane change manoeuvres, which provide a more robust control of the steering wheel to external perturbations. At last drivers are able to manage a sudden increase of stress. The experiment was conducted on the ULTIMATE dynamic driving simulator developed by the Technical Centre for Simulation of RENAULT. The simulator has been fitted with a new steering force feedback system improving dynamical performance. This simulator upgrade and assessment methodology will be presented in more details in this paper. The driver behaviour was studied through questionnaires to assess the stress produced by the different situations. Detection and/or recognition of objects in the virtual scene give cues on the DAS failure effects on the driver's visual attention. In order to quantify the drivers' performance, objective indicators such as steering reversal rate, steering entropy and time-to-lane-crossing were also used. In spite of the unexpected steering event, all drivers have achieved their driving task, without leaving the road. Results show an increase of stress for drivers when the unexpected event occurs. We also notice an alteration of the visual performance revealed by drivers' difficulties to recognize critical objects in the environment. This study suggests that high-performance driving simulators may be valuable to assess the effects of safety-critical events on driving performance. Résumé Dans cet article, nous étudions l'effet sur le conducteur d'un comportement inattendu d'un système d'aide à la conduite (DAS) et ceci lors d'une tâche de conduite ordinaire en environnement virtuel. Le système retenu est une direction assistée électrique qui permet au conducteur de réduire les efforts nécessaires à produire pour le maniement du volant en virage. Une défaillance d'un tel système peut produire une perte soudaine et permanente d'assistance et rendre ainsi le volant plus difficile à tourner. L'objectif de cette étude est de déterminer l'impact de ce type d'évènement sur les performances du conducteur. Seront considérés en particulier la performance visuelle et la production de stress. Il a été constaté que lorsque cet évènement apparaît avant l'entrée en virage, les conducteurs sont capables de s'y adapter. De plus, une augmentation de la raideur des muscles du bras a été observée lors de manoeuvres de changement de file, ce qui rend le contrôle du volant plus robuste à des perturbations extérieures. Enfin, il semble que les conducteurs sont capables de gérer un stress soudain et de courte durée. L'expérimentation a été réalisée sur le simulateur de conduite dynamique ULTIMATE développé au Centre Technique de Simulation de RENAULT. Le simulateur s'est vu doté d'un nouveau restituteur d'effort pour le volant, offrant des performances dynamiques supérieures au précédent restituteur. L'installation et la validation de ce nouveau matériel sera présentée dans de plus amples détails. Le comportement des conducteurs a été étudié au travers de questionnaires afin d'évaluer la production de stress lors des différentes situations. La détection et/ou la reconnaissance d'objets dans la scène virtuelle procure des indices quant aux effets sur l'attention visuelle du conducteur de la défaillance du système d'assistance. Dans le but de quantifier la performance de conduite, des indicateurs tels que le Steering Reversal Rate, le Steering Entropy et le Time-to-Line-Crossing ont été utilisés. Malgré que l'évènement soit inattendu, tous les conducteurs ont réussi à terminer leur tâche de conduite sans quitter la route. Les résultats montrent une augmentation du stress lorsque cet évènement apparaît. Remarquons aussi l'altération de l'attention visuelle des conducteurs de part leur difficulté à reconnaître les objets de l'environnement. Cette étude suggère que les simulateurs de conduite à hautes performances autorisent l'évaluation des effets sur la performance de conduite d'évènements critiques en termes de sécurité

Evidence for the Role of Horizontal Transfer in Generating pVT1, a Large Mosaic Conjugative Plasmid from the Clam Pathogen, Vibrio tapetis

The marine bacterium Vibrio tapetis is the causative agent of the brown ring disease, which affects the clam Ruditapes philippinarum and causes heavy economic losses in North of Europe and in Eastern Asia. Further characterization of V. tapetis isolates showed that all the investigated strains harbored at least one large plasmid. We determined the sequence of the 82,266 bp plasmid pVT1 from the CECT4600T reference strain and analyzed its genetic content. pVT1 is a mosaic plasmid closely related to several conjugative plasmids isolated from Vibrio vulnificus strains and was shown to be itself conjugative in Vibrios. In addition, it contains DNA regions that have similarity with several other plasmids from marine bacteria (Vibrio sp., Shewanella sp., Listonella anguillarum and Photobacterium profundum). pVT1 contains a number of mobile elements, including twelve Insertion Sequences or inactivated IS genes and an RS1 phage element related to the CTXphi phage of V. cholerae. The genetic organization of pVT1 underscores an important role of horizontal gene transfer through conjugative plasmid shuffling and transposition events in the acquisition of new genetic resources and in generating the pVT1 modular organization. In addition, pVT1 presents a copy number of 9, relatively high for a conjugative plasmid, and appears to belong to a new type of replicon, which may be specific to Vibrionaceae and Shewanelleacae

Introduction: Human ecology in the Himalaya

Knowledge of human adaptation in the Himalayas has developed more slowly than that for other world mountain systems. At the same time, the opening of the region to research has focused attention toward description in a “natural history” mode until quite recently. Where these studies have addressed issues of adaptation they have tended to do so more as a heuristic tool rather than in terms of contributing to the development of adaptive perspectives from a uniquely Himalayan vantage point. The contributions to this special issue suggest some of Himalayan cultural ecology's new themes as it more directly assumes a truly processual approach that incorporates the individual and domestic dimensions of adaptation within historical and social contexts .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44482/1/10745_2004_Article_BF00889710.pd

Observations relatives à la biologie et la nidification de quelques abeilles sauvages psammophiles d’intérêt en Wallonie. 2. Observations estivales et automnales

info:eu-repo/semantics/publishe

Observations relatives à la biologie et à la nidification de quelques abeilles sauvages psammophiles d’intérêt en Wallonie: 1. Observations printanières

info:eu-repo/semantics/publishe

Shape transition during nest digging in ants

Nest building in social insects is among the collective processes that show highly conservative features such as basic modules (chambers and galleries) or homeostatic properties. Although ant nests share common characteristics, they exhibit a high structural variability, of which morphogenesis and underlying mechanisms remain largely unknown. We conducted two-dimensional nest-digging experiments under homogeneous laboratory conditions to investigate the shape diversity that emerges only from digging dynamics and without the influence of any environmental heterogeneity. These experiments revealed that, during the excavation, a morphological transition occurs because the primary circular cavity evolves into a ramified structure through a branching process. Such a transition is observed, whatever the number of ants involved, but occurs more frequently for a larger number of workers. A stochastic model highlights the central role of density effects in shape transition. These results indicate that nest digging shares similar properties with various physical, chemical, and biological systems. Moreover, our model of morphogenesis provides an explanatory framework for shape transitions in decentralized growing structures in group-living animals

Phylogenetic and Functional Diversity of Microbial Communities Associated with Subsurface Sediments of the Sonora Margin, Guaymas Basin

Subsurface sediments of the Sonora Margin (Guaymas Basin), located in proximity of active cold seep sites were explored. The taxonomic and functional diversity of bacterial and archaeal communities were investigated from 1 to 10 meters below the seafloor. Microbial community structure and abundance and distribution of dominant populations were assessed using complementary molecular approaches (Ribosomal Intergenic Spacer Analysis, 16S rRNA libraries and quantitative PCR with an extensive primers set) and correlated to comprehensive geochemical data. Moreover the metabolic potentials and functional traits of the microbial community were also identified using the GeoChip functional gene microarray and metabolic rates. The active microbial community structure in the Sonora Margin sediments was related to deep subsurface ecosystems (Marine Benthic Groups B and D, Miscellaneous Crenarchaeotal Group, Chloroflexi and Candidate divisions) and remained relatively similar throughout the sediment section, despite defined biogeochemical gradients. However, relative abundances of bacterial and archaeal dominant lineages were significantly correlated with organic carbon quantity and origin. Consistently, metabolic pathways for the degradation and assimilation of this organic carbon as well as genetic potentials for the transformation of detrital organic matters, hydrocarbons and recalcitrant substrates were detected, suggesting that chemoorganotrophic microorganisms may dominate the microbial community of the Sonora Margin subsurface sediments