227 research outputs found
Factors of subjective heat stress of urban citizens in contexts of everyday life
Heat waves and the consequent heat stress of urban populations have a growing relevance in urban risk management and strategies of urban adaptation to climate change. In this context, social science studies on subjective heat stress of urban citizens are a new emerging field. To contribute to the understanding of subjective heat stress and its major determinants in a daily life perspective, we conducted a questionnaire survey with 323 respondents in Karlsruhe, Germany, after a heat wave in July and August 2013. Statistical data analysis showed that heat stress is an issue permeating everyday activities. It was found that the subjective heat stress at home is lower than at work and in general. Subjective heat stress in general, at home, and at work was determined by the health impairments experienced during the heat and the feeling of being helplessly exposed to the heat. For heat stress at home, additionally characteristics of the residential building and the built environment played a role. Although the rate of implemented coping measures was rather high, coping measures showed no uniform effect for the subjective heat stress. The results furthermore show that coping with heat is performed within the scopes of action in daily life. We conclude that in terms of urban adaptation strategies, further research is needed to understand how various processes of daily social (work) life enable or limit individual coping and adaptation capacities and that communication strategies are important for building capacities to better cope with future heat waves
A mean-field kinetic lattice gas model of electrochemical cells
We develop Electrochemical Mean-Field Kinetic Equations (EMFKE) to simulate
electrochemical cells. We start from a microscopic lattice-gas model with
charged particles, and build mean-field kinetic equations following the lines
of earlier work for neutral particles. We include the Poisson equation to
account for the influence of the electric field on ion migration, and
oxido-reduction processes on the electrode surfaces to allow for growth and
dissolution. We confirm the viability of our approach by simulating (i) the
electrochemical equilibrium at flat electrodes, which displays the correct
charged double-layer, (ii) the growth kinetics of one-dimensional
electrochemical cells during growth and dissolution, and (iii) electrochemical
dendrites in two dimensions.Comment: 14 pages twocolumn, 17 figure
Phase field theory of polycrystalline solidification in three dimensions
A phase field theory of polycrystalline solidification is presented that is
able to describe the nucleation and growth of anisotropic particles with
different crystallographic orientation in three dimensions. As opposed with the
two-dimensional case, where a single orientation field suffices, in three
dimensions, minimum three fields are needed. The free energy of grain
boundaries is assumed to be proportional to the angular difference between the
adjacent crystals expressed here in terms of the differences of the four
symmetric Euler parameters. The equations of motion for these fields are
obtained from variational principles. Illustrative calculations are performed
for polycrystalline solidification with dendritic, needle and spherulitic
growth morphologies.Comment: 7 pages, 4 figures, submitted to Europhysics Letters on 14th
February, 200
Population dynamics of Agrobacterium vitis in two grapevine varieties during the vegetation period
In this work populations of Agrobacterium vitis were monitored within one year. Starting in the middle of May, the population density of A. vitis was screened every week in all parts of two-year-old MĂĽller-Thurgau and Riesling grapevines which were freed from A. vitis by thermotherapy and inoculated with A. vitis NW90. Every week, 5 plants of the two varieties were examined for A. vitis in new shoots, around the inoculation site, in one- and two-year-old parts of the stem, in the rootstock and in the roots. Beyond the inoculation site the A. vitis population density was too low for statistical evaluation of population dynamics. At the inoculation site a seasonal course of the A. vitis population was found in both grapevine varieties. The A. vitis population density was highest at the end of May, but little later it dropped to a low level during the sommer months. A second maximum of population density was determined in October which reached nearly the same value as in spring. Population density of A. vitis correlated to physiological changes of the grapevine plant during the vegetation period. Though the population dynamics of A. vitis followed parallel courses in both grapevine varieties, differences in the population density and in the onset of the autumn increase were determined. This could be attributed to physiological differences of the two varieties. The migration of pathogenic bacteria from the inoculation site to the roots took at least 15 weeks
Phase-Field Formulation for Quantitative Modeling of Alloy Solidification
A phase-field formulation is introduced to simulate quantitatively
microstructural pattern formation in alloys. The thin-interface limit of this
formulation yields a much less stringent restriction on the choice of interface
thickness than previous formulations and permits to eliminate non-equilibrium
effects at the interface. Dendrite growth simulations with vanishing solid
diffusivity show that both the interface evolution and the solute profile in
the solid are well resolved
Phase-Field Approach for Faceted Solidification
We extend the phase-field approach to model the solidification of faceted
materials. Our approach consists of using an approximate gamma-plot with
rounded cusps that can approach arbitrarily closely the true gamma-plot with
sharp cusps that correspond to faceted orientations. The phase-field equations
are solved in the thin-interface limit with local equilibrium at the
solid-liquid interface [A. Karma and W.-J. Rappel, Phys. Rev. E53, R3017
(1996)]. The convergence of our approach is first demonstrated for equilibrium
shapes. The growth of faceted needle crystals in an undercooled melt is then
studied as a function of undercooling and the cusp amplitude delta for a
gamma-plot of the form 1+delta(|sin(theta)|+|cos(theta)|). The phase-field
results are consistent with the scaling law "Lambda inversely proportional to
the square root of V" observed experimentally, where Lambda is the facet length
and V is the growth rate. In addition, the variation of V and Lambda with delta
is found to be reasonably well predicted by an approximate sharp-interface
analytical theory that includes capillary effects and assumes circular and
parabolic forms for the front and trailing rough parts of the needle crystal,
respectively.Comment: 1O pages, 2 tables, 17 figure
Resonant forcing of select degrees of freedom of multidimensional chaotic map dynamics
We study resonances of multidimensional chaotic map dynamics. We use the
calculus of variations to determine the additive forcing function that induces
the largest response, that is, the greatest deviation from the unperturbed
dynamics. We include the additional constraint that only select degrees of
freedom be forced, corresponding to a very general class of problems in which
not all of the degrees of freedom in an experimental system are accessible to
forcing. We find that certain Lagrange multipliers take on a fundamental
physical role as the efficiency of the forcing function and the effective
forcing experienced by the degrees of freedom which are not forced directly.
Furthermore, we find that the product of the displacement of nearby
trajectories and the effective total forcing function is a conserved quantity.
We demonstrate the efficacy of this methodology with several examples.Comment: 11 pages, 3 figure
Towards a quantitative phase-field model of two-phase solidification
We construct a diffuse-interface model of two-phase solidification that
quantitatively reproduces the classic free boundary problem on solid-liquid
interfaces in the thin-interface limit. Convergence tests and comparisons with
boundary integral simulations of eutectic growth show good accuracy for
steady-state lamellae, but the results for limit cycles depend on the interface
thickness through the trijunction behavior. This raises the fundamental issue
of diffuse multiple-junction dynamics.Comment: 4 pages, 2 figures. Better final discussion. 1 reference adde
Investigation of superstorm Sandy 2012 in a multi-disciplinary approach
At the end of October 2012, Hurricane Sandy moved from the Caribbean Sea into the Atlantic Ocean and entered the United States not far from New York. Along its track, Sandy caused more than 200 fatalities and severe losses in Jamaica, The Bahamas, Haiti, Cuba, and the US. This paper demonstrates the capability and potential for near-real-time analysis of catastrophes. It is shown that the impact of Sandy was driven by the superposition of different extremes (high wind speeds, storm surge, heavy precipitation) and by cascading effects. In particular the interaction between Sandy and an extra-tropical weather system created a huge storm that affected large areas in the US. It is examined how Sandy compares to historic hurricane events, both from a hydro-meteorological and impact perspective. The distribution of losses to different sectors of the economy is calculated with simple input-output models as well as government estimates. Direct economic losses are estimated about USD 4.2 billion in the Caribbean and between USD 78 and 97 billion in the US. Indirect economic losses from power outages is estimated in the order of USD 16.3 billion. Modelling sector-specific dependencies quantifies total business interruption losses between USD 10.8 and 15.5 billion. Thus, seven years after the record impact of Hurricane Katrina in 2005, Hurricane Sandy is the second costliest hurricane in the history of the United States
Multiscale Random-Walk Algorithm for Simulating Interfacial Pattern Formation
We present a novel computational method to simulate accurately a wide range
of interfacial patterns whose growth is limited by a large scale diffusion
field. To illustrate the computational power of this method, we demonstrate
that it can be used to simulate three-dimensional dendritic growth in a
previously unreachable range of low undercoolings that is of direct
experimental relevance.Comment: 4 pages RevTex, 6 eps figures; substantial changes in presentation,
but results and conclusions remain the sam
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