1,939 research outputs found
The Effect of Integrating Travel Time
This contribution demonstrates the potential gain for the quality of results
in a simulation of pedestrians when estimated remaining travel time is
considered as a determining factor for the movement of simulated pedestrians.
This is done twice: once for a force-based model and once for a cellular
automata-based model. The results show that for the (degree of realism of)
simulation results it is more relevant if estimated remaining travel time is
considered or not than which modeling technique is chosen -- here force-based
vs. cellular automata -- which normally is considered to be the most basic
choice of modeling approach.Comment: preprint of Pedestrian and Evacuation 2012 conference (PED2012)
contributio
The Inflection Point of the Speed-Density Relation and the Social Force Model
It has been argued that the speed-density digram of pedestrian movement has
an inflection point. This inflection point was found empirically in
investigations of closed-loop single-file pedestrian movement. The reduced
complexity of single-file movement does not only allow a higher precision for
the evaluation of empirical data, but it occasionally also allows analytical
considerations for micosimulation models. In this way it will be shown that
certain (common) variants of the Social Force Model (SFM) do not produce an
inflection point in the speed-density diagram if infinitely many pedestrians
contribute to the force computed for one pedestrian. We propose a modified
Social Force Model that produces the inflection point.Comment: accepted for presentation at conference Traffic and Granular Flow
201
Pedestrian Traffic: on the Quickest Path
When a large group of pedestrians moves around a corner, most pedestrians do
not follow the shortest path, which is to stay as close as possible to the
inner wall, but try to minimize the travel time. For this they accept to move
on a longer path with some distance to the corner, to avoid large densities and
by this succeed in maintaining a comparatively high speed. In many models of
pedestrian dynamics the basic rule of motion is often either "move as far as
possible toward the destination" or - reformulated - "of all coordinates
accessible in this time step move to the one with the smallest distance to the
destination". Atop of this rule modifications are placed to make the motion
more realistic. These modifications usually focus on local behavior and neglect
long-ranged effects. Compared to real pedestrians this leads to agents in a
simulation valuing the shortest path a lot better than the quickest. So, in a
situation as the movement of a large crowd around a corner, one needs an
additional element in a model of pedestrian dynamics that makes the agents
deviate from the rule of the shortest path. In this work it is shown, how this
can be achieved by using a flood fill dynamic potential field method, where
during the filling process the value of a field cell is not increased by 1, but
by a larger value, if it is occupied by an agent. This idea may be an obvious
one, however, the tricky part - and therefore in a strict sense the
contribution of this work - is a) to minimize unrealistic artifacts, as naive
flood fill metrics deviate considerably from the Euclidean metric and in this
respect yield large errors, b) do this with limited computational effort, and
c) keep agents' movement at very low densities unaltered
Characterizing correlations of flow oscillations at bottlenecks
"Oscillations" occur in quite different kinds of many-particle-systems when
two groups of particles with different directions of motion meet or intersect
at a certain spot. We present a model of pedestrian motion that is able to
reproduce oscillations with different characteristics. The Wald-Wolfowitz test
and Gillis' correlated random walk are shown to hold observables that can be
used to characterize different kinds of oscillations
Stochastic Transition Model for Discrete Agent Movements
We propose a calibrated two-dimensional cellular automaton model to simulate
pedestrian motion behavior. It is a v=4 (3) model with exclusion statistics and
random shuffled dynamics. The underlying regular grid structure results in a
direction-dependent behavior, which has in particular not been considered
within previous approaches. We efficiently compensate these grid-caused
deficiencies on model level.Comment: 8 pages, 4 figure
Dietary Diversity in Cambodian Garment Workers: The Role of Free Lunch Provision
The objective of this paper is to compare food consumption by Cambodian garment workers with and without access to a free model lunch provision through a factory-based canteen. Data from an exploratory randomised controlled trial were analysed. In total, 223 female Cambodian garment workers were allocated to an intervention arm (six-month lunch provision) or a control arm. Dietary intake on workdays was assessed by qualitative 24-h recalls at baseline and twice at follow-ups during the period of lunch provision using the Food and Agricultural Organization (FAO) guideline on assessing women´s dietary diversity. In total, 158 participants provided complete data on the dietary intake over workdays at all interviews. Lunch provision resulted in a more frequent consumption of dark green leafy vegetables (DGLV), vitamin A-rich fruits, other fruits, and oils and fats during lunch breaks. In contrast, flesh meats, legumes, nuts and seeds, as well as sweets, were eaten at a lower frequency. Except for a higher consumption rate of vitamin A-rich fruits and a lower intake frequency of sweets, lunch provision had a less clear impact on total 24-h intake from different food groups and was not associated with a higher women´s dietary diversity score (WDDS). A more gap-oriented design of the lunch sets taking into account underutilised foods and the nutritional status of the workers is recommended
Modeling the desired direction in a force-based model for pedestrian dynamics
We introduce an enhanced model based on the generalized centrifugal force
model. Furthermore, the desired direction of pedestrians is investigated. A new
approach leaning on the well-known concept of static and dynamic floor-fields
in cellular automata is presented. Numerical results of the model are presented
and compared with empirical data.Comment: 14 pages 11 figures, submitted to TGF'1
Zircon dissolution in a ductile shear zone, Monte Rosa granite gneiss, northern Italy
The sizes, distributions and shapes of zircon grains within variably deformed granite gneiss from the western Alps have been studied. Zircon shows numerous indicators of a metamorphic response in both the host gneiss and a 5 cm wide continuous ductile shear zone, within which the zircon grain sizes range from <1 µm to >50 µm. However, the very fine grain sizes are virtually absent from grain boundaries. Within this zone, zircons consistently have more rounded and embayed margins, which are interpreted as evidence of dissolution in response to fluid influx during shearing. Zircons are preferentially located near metamorphic muscovite in both the host gneiss and the shear zone and tend to show the poorest crystal shape, indicating that fluids linked to the formation and presence of muscovite may enhance both the crystallization of zircon and its subsequent dissolution. Larger zircon crystals typically show a brittle response to deformation when adjacent to phyllosilicates, with fractures consistently perpendicular to the (001) mica cleavage. The variety of metamorphic behaviour observed for zircon indicates that it may be highly reactive in sub-solidus mid-crustal metamorphic environments
Solving the Direction Field for Discrete Agent Motion
Models for pedestrian dynamics are often based on microscopic approaches
allowing for individual agent navigation. To reach a given destination, the
agent has to consider environmental obstacles. We propose a direction field
calculated on a regular grid with a Moore neighborhood, where obstacles are
represented by occupied cells. Our developed algorithm exactly reproduces the
shortest path with regard to the Euclidean metric.Comment: 8 pages, 4 figure
Quickest Paths in Simulations of Pedestrians
This contribution proposes a method to make agents in a microscopic
simulation of pedestrian traffic walk approximately along a path of estimated
minimal remaining travel time to their destination. Usually models of
pedestrian dynamics are (implicitly) built on the assumption that pedestrians
walk along the shortest path. Model elements formulated to make pedestrians
locally avoid collisions and intrusion into personal space do not produce
motion on quickest paths. Therefore a special model element is needed, if one
wants to model and simulate pedestrians for whom travel time matters most (e.g.
travelers in a station hall who are late for a train). Here such a model
element is proposed, discussed and used within the Social Force Model.Comment: revised version submitte
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