16,632 research outputs found
A stochastic design rainfall generator based on copulas and mass curves
The use of design storms can be very useful in many hydrological and hydraulic practices. In this study, the concept of a copula-based secondary return period in combination with the concept of mass curves is used to generate point-scale design storms. The analysis is based on storms selected from the 105 year rainfall time series with a 10 min resolution, measured at Uccle, Belgium. In first instance, bivariate copulas and secondary return periods are explained, together with a focus on which couple of storm variables is of highest interest for the analysis and a discussion of how the results might be affected by the goodness-of-fit of the copula. Subsequently, the fitted copula is used to sample storms with a predefined secondary return period for which characteristic variables such as storm duration and total storm depth can be derived. In order to construct design storms with a realistic storm structure, mass curves of 1st, 2nd, 3rd and 4th quartile storms are developed. An analysis shows that the assumption of independence between the secondary return period and the internal storm structure could be made. Based on the mass curves, a technique is developed to randomly generate an intrastorm structure. The coupling of both techniques eventually results in a methodology for stochastic design storm generation. Finally, its practical usefulness for design studies is illustrated based on the generation of a set of statistically identical design storm and rainfall-runoff modelling
Surface stress of Ni adlayers on W(110): the critical role of the surface atomic structure
Puzzling trends in surface stress were reported experimentally for Ni/W(110)
as a function of Ni coverage. In order to explain this behavior, we have
performed a density-functional-theory study of the surface stress and atomic
structure of the pseudomorphic and of several different possible 1x7
configurations for this system. For the 1x7 phase, we predict a different, more
regular atomic structure than previously proposed based on surface x-ray
diffraction. At the same time, we reproduce the unexpected experimental change
of surface stress between the pseudomorphic and 1x7 configuration along the
crystallographic surface direction which does not undergo density changes. We
show that the observed behavior in the surface stress is dominated by the
effect of a change in Ni adsorption/coordination sites on the W(110) surface.Comment: 14 pages, 3 figures Published in J. Phys.: Condens. Matter 24 (2012)
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An investigation of some thermal and mechanical properties of a low-density phenolic-nylon ablation material Final report
Thermal and mechanical properties of phenolic nylon ablation material
The limits of filopodium stability
Filopodia are long, finger-like membrane tubes supported by cytoskeletal
filaments. Their shape is determined by the stiffness of the actin filament
bundles found inside them and by the interplay between the surface tension and
bending rigidity of the membrane. Although one might expect the Euler buckling
instability to limit the length of filopodia, we show through simple energetic
considerations that this is in general not the case. By further analyzing the
statics of filaments inside membrane tubes, and through computer simulations
that capture membrane and filament fluctuations, we show under which conditions
filopodia of arbitrary lengths are stable. We discuss several in vitro
experiments where this kind of stability has already been observed.
Furthermore, we predict that the filaments in long, stable filopodia adopt a
helical shape
Introduction
Published in cooperation with the American Bar Association Section of Dispute Resolutio
Developing the MRI (Mediation Receptivity Index)
Published in cooperation with the American Bar Association Section of Dispute Resolutio
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