1,705 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 design concept of the 6-degree-of-freedom hydraulic shaker at ESTEC
The European Space Agency (ESA) has decided to extend its test facilities at the European Space and Technology Center (ESTEC) at Noordwijk, The Netherlands, by implementing a 6-degree-of-freedom hydraulic shaker. This shaker will permit vibration testing of large payloads in the frequency range from 0.1 Hz to 100 Hz. Conventional single axis sine and random vibration modes can be applied without the need for a configuration change of the test set-up for vertical and lateral excitations. Transients occurring during launch and/or landing of space vehicles can be accurately simulated in 6-degrees-of-freedom. The performance requirements of the shaker are outlined and the results of the various trade-offs, which are investigated during the initial phase of the design and engineering program are provided. Finally, the resulting baseline concept and the anticipated implementation plan of the new test facility are presented
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
Sub 20 nm Short Channel Carbon Nanotube Transistors
Carbon nanotube field-effect transistors with sub 20 nm long channels and
on/off current ratios of > 1000000 are demonstrated. Individual single-walled
carbon nanotubes with diameters ranging from 0.7 nm to 1.1 nm grown from
structured catalytic islands using chemical vapor deposition at 700 degree
Celsius form the channels. Electron beam lithography and a combination of HSQ,
calix[6]arene and PMMA e-beam resists were used to structure the short channels
and source and drain regions. The nanotube transistors display on-currents in
excess of 15 microA for drain-source biases of only 0.4 Volt.Comment: Nano Letters in pres
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
Extrachromosomal Circular DNA: Current Knowledge and Implications for CNS Aging and Neurodegeneration
Optimized Protocol for Proportionate CNS Cell Retrieval as a Versatile Platform for Cellular and Molecular Phenomapping in Aging and Neurodegeneration
Efficient purification of viable neural cells from the mature CNS has been historically challenging due to the heterogeneity of the inherent cell populations. Moreover, changes in cellular interconnections, membrane lipid and cholesterol compositions, compartment-specific biophysical properties, and intercellular space constituents demand technical adjustments for cell isolation at different stages of maturation and aging. Though such obstacles are addressed and partially overcome for embryonic premature and mature CNS tissues, procedural adaptations to an aged, progeroid, and degenerative CNS environment are underrepresented. Here, we describe a practical workflow for the acquisition and phenomapping of CNS neural cells at states of health, physiological and precocious aging, and genetically provoked neurodegeneration. Following recent, unprecedented evidence of post-mitotic cellular senescence (PoMiCS), the protocol appears suitable for such de novo characterization and phenotypic opposition to classical senescence. Technically, the protocol is rapid, efficient as for cellular yield and well preserves physiological cell proportions. It is suitable for a variety of downstream applications aiming at cell type-specific interrogations, including cell culture systems, Flow-FISH, flow cytometry/FACS, senescence studies, and retrieval of omic-scale DNA, RNA, and protein profiles. We expect suitability for transfer to other CNS targets and to a broad spectrum of engineered systems addressing aging, neurodegeneration, progeria, and senescence
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
Scanning spreading resistance microscopy of two-dimensional diffusion of boron implanted in free-standing silicon nanostructures
B implants of 1keV, 1×10¹⁵at.cm⁻² into 125-nm-wide, free-standing Si nanostructures have been characterized using scanning spreading resistancemicroscopy following a 0s, 1050°Canneal in N₂. A curved diffusion front has been observed. B in the center of the ridge diffuses further than at the sides. A similar effect has been observed in SUPREM-IV simulations. It is attributed to a reduction in transient enhanced diffusion close to the vertical surfaces due to recombination of ion-implantation-induced excess Si self-interstitials
Experimental study of pedestrian flow through a bottleneck
In this work the results of a bottleneck experiment with pedestrians are
presented in the form of total times, fluxes, specific fluxes, and time gaps. A
main aim was to find the dependence of these values from the bottleneck width.
The results show a linear decline of the specific flux with increasing width as
long as only one person at a time can pass, and a constant value for larger
bottleneck widths. Differences between small (one person at a time) and wide
bottlenecks (two persons at a time) were also found in the distribution of time
gaps.Comment: accepted for publication in J. Stat. Mec
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