The use of driving simulation for vehicle design and driver perception studies is expanding rapidly. This is largely because simulation saves engineering time and costs, and can be used for studies of road and traffic safety. How applicable driving simulation is to the real world is unclear however, because analyses of perceptual criteria carried out in driving simulation experiments are controversial. On the one hand, recent data suggest that, in driving simulators with a large field of view, longitudinal speed can be estimated correctly from visual information. On the other hand, recent psychophysical studies have revealed an unexpectedly important contribution of vestibular cues in distance perception and steering, prompting a re-evaluation of the role of visuo-vestibular interaction in driving simulation studies.Vehicle driving implies perception and control of selfmotion at a greater range of velocities than locomotion by walking. It is often considered to be a task dominated by visual information. However, it is well-established that other sensory information, such as that provided by the vestibular and PROPRIOCEPTIVE (see Glossary) channels, also contributes to the perception and control of selfmotion. Motivated by a recent renewed interest in the role and function of these non-visual sensory modalities, we aim in this review to re-evaluate the role of visuovestibular interactions in driving simulation experiments, and to assess how applicable driving simulation is to the real world for studies of vehicle dynamics or driver behaviour.In 1938 Gibson [1] proposed a psychophysical theory of perception for automobile-driving, defining a 'terrain of field of space' for the driver, with the car considered as a tool of locomotion and the driver aiming to drive in the middle of a 'field of safe travel'. In 1950 he described the visual perception of space [2] based on visual depth, distance or orientation stimulus variables. OPTIC FLOW, one of the most important visual cues he proposed, is defined as the visual motion experienced as a result of walking or driving, and it is thought to play a dominant role in the control of heading [3] and collision detection [4 -7]. However, regarding the control of the direction of movement in natural environments (i.e. walking), there is still disagreement over whether the structure of the flow [8,9] or the visual EGOCENTRIC DIRECTION per se [10,11] is the dominant source of information. It is not clear either whether the same strategies used for natural locomotion apply to driving situations where displacements occur at higher velocities. Interestingly, a new point of view on these controversial issues was recently provided by experiments performed in driving simulators [12]. However, Gibson's original theory also included a definition of the perceptual field of the car itself, bringing to the driver kinaesthetic and tactile cues. These ideas were applied to driving simulation from the early 1980s [13][14][15], and since then many simulator experiments have been carried out for...
One of the ways that we perceive shape is through seeing motion. Visual motion may be actively generated (for example, in locomotion), or passively observed. In the study of the perception of three-dimensional structure from motion, the non-moving, passive observer in an environment of moving rigid objects has been used as a substitute for an active observer moving in an environment of stationary objects; this 'rigidity hypothesis' has played a central role in computational and experimental studies of structure from motion. Here we show that this is not an adequate substitution because active and passive observers can perceive three-dimensional structure differently, despite experiencing the same visual stimulus: active observers' perception of three-dimensional structure depends on extraretinal information about their own movements. The visual system thus treats objects that are stationary (in an allocentric, earth-fixed reference frame) differently from objects that are merely rigid. These results show that action makes an important contribution to depth perception, and argue for a revision of the rigidity hypothesis to incorporate the special case of stationary objects.
Porous carbon fiber materials are used as effective insulators in many applications where high temperatures are involved. In particular, they are used as the substrate of ablative thermal protection materials for atmospheric entry systems. In this application and in many other industrial uses, quantifying the permeability of porous materials is needed to compute the flow rate of gases through them, under certain environmental conditions. In this work, direct simulation Monte Carlo (DSMC) simulations are used to compute permeability of several fibrous substrates to high temperature gases. The actual porous geometry of the materials is digitized using X-ray microtomography. Numerical results at various pressures and Knudsen numbers are compared with experimental data published in the literature. The method confirms that the pressure dependence of effective gas permeability is well represented by the Klinkenberg formulation.The method is validated by showing close agreement between measurements of permeability from simulations and experimental investigations. Four carbon fiber materials with different microstructures are investigated. We show that the permeability strongly depends on the pore size distribution, as well as on 20 ing the Boltzmann equation. It was originally proposed for rarefied and transitional flows but has since been applied to near-continuum and continuum flows.DSMC can provide an accurate model for the entire boundary layer including the flow within the microstructure, where the size of the fibers may approach the mean-free-path of the flow. As the permeability of a porous material is a 25 function of the distribution of its micropores, in this paper, the computational domain for DSMC simulations is obtained from three-dimensional (3D) images
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