Risk Assessment of Cyclist Falls in Snowy and lcy Conditions

Experience and key data suggest that snow and ice lead to increased numbers of cyclist falls during the winter months. Reliable in-depth data concering the extent and characteristics of this issue are currently not available in most countries. In Germany, this is due to the high level of under-reporting in official statistics, particularly for incidents involving only one bicyclist. In combination with the lack of knowledge on exposure this causes difficulties to quantify risks for cyclist falls. This study addresses these gaps. lt aims at quantifying the risk of single bicycle accidents in inclement weather conditions. This study focusses on icy and snowy conditions as these are of relevance for the risk to fall. Cyclists are particularly affected by slippery icy and snowy road conditions; these might exist in clear, cloudy, or foggy weather, in situations with high or low humidity and with higher or lower wind speed. Variables from official weather data are purposefully combined in this study to identify time periods with snow or ice on the roads and to allow for the comparison of those with all other time periods ('other weather''). We address the above-mentioned problems of exposure and underreporting by using multiple data sources for quantifying the risk of falls. This approach allows to compute clear risk ratios for icy/snowy and the other weather conditions and thus contributes to the scarce and fragmented literature that has generated such values so far. [from Background, AIM

Numerische Methoden zur Berechnung von Druckverteilungen und zur Identifikation von Luftlagem

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Numerical comparison of hybridized discontinuous Galerkin and finite volume methods for incompressible flow

A numerical comparison of a hybridizable discontinuous Galerkin method proposed by Nguyen et al. and the well established finite volume method of second order in space represented by the icoFoam and simpleFoam solver of OpenFOAM is given. The hybridizable discontinuous Galerkin method has been reformulated as Picard iteration, hybridized and implemented from scratch. The methods are introduced and four numerical standard simulations are used in order to benchmark and evaluate the solver - the Taylor-Green vortex, the 180 degrees fence case as well as a two-dimensional stationary and non-stationary DFG benchmark. The numerical examples suggests hybridized discontinuous Galerkin methods are a competitive alternative to finite volume solvers for incompressible fluid simulations due to high accuracy and better stability properties

Analysis of optimal boundary control of the Boussinesq approximation

A revised version was published as Preprint 10-2008.In the present paper we complement the work in preprint 15-03 of the Inst. of Mathematics of the TU Berlin (also published in ZAMM 86(2006)6) with presenting the analytical framework for general optimal boundary control problems of the Boussinesq approximation. We prove existence of optimal controls, use results of H. Gajewski to prove existence and uniqueness of solutions to state and the adjoint system, and derive first order necessary as well as second order sufficient optimality conditions

Analysis of optimal boundary control of the Boussinesq approximation

This preprint is a revised version of Preprint 38-2007.In the present paper we complement a recent applied work with presenting the analytical framework for general optimal boundary control problems of the Boussinesq approximation. We prove existence of optimal controls, use results of Gajewski (1975) to prove existence and uniqueness of solutions to state and the adjoint system, and derive first order necessary as well as second order sufficient optimality conditions

A Multispecies Pedestrian Model based on a 3d multiphase incompressible fluid flow model

The idea to simulate pedestrian flow by the application of fluid dynamics equations has a certain history in that field. This approach is based on the application of partial differential equations, which makes it a macroscopic method. The need to simulate several different species of pedestrians is a need from the start, which has not been matched very well by numerical simulations of macroscopic type. The basis of the description of non dense pedestrian movement by incompressible fluid flow models consists in the introduction of an empty phase as a species of a multiphase system of distinct phases