235 research outputs found
Intermittency and the Slow Approach to Kolmogorov Scaling
From a simple path integral involving a variable volatility in the velocity
differences, we obtain velocity probability density functions with exponential
tails, resembling those observed in fully developed turbulence. The model
yields realistic scaling exponents and structure functions satisfying extended
self-similarity. But there is an additional small scale dependence for
quantities in the inertial range, which is linked to a slow approach to
Kolmogorov (1941) scaling occurring in the large distance limit.Comment: 10 pages, 5 figures, minor changes to mirror version to appear in PR
Monitoring ethnic minorities in the Netherlands
Item does not contain fulltextThe article first summarises the history of ethnic minority policy in the Netherlands and the development of the ‘ethnic minority’ and ‘allochthonous’ categories, which are peculiar in comparative perspective in emphasising socio-economic disadvantage as a constitutive dimension of minority status and in setting the minority question within the broader Dutch political principle of ‘pillarisation’. The article then examines the use of statistics in public policy, in a context where the national census has been discontinued since 1971, focusing more specifically on the case of education, where major statistical efforts have been devoted to identifying patterns of disadvantage and integration. Finally, the article briefly examines current debates on the situation of ethnic minorities in the Netherlands in the context of growing questioning of established Dutch models of minority policy.13 p
Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes
DOI:10.1787/011766488208This global screening study makes a first estimate of the exposure of the world's large port cities to coastal flooding due to storm surge and damage due to high winds. This assessment also investigates how climate change is likely to impact each port city's exposure to coastal flooding by the 2070s, alongside subsidence and population growth and urbanisation. The study provides a much more comprehensive analysis than earlier assessments, focusing on the 136 port cities around the world that have more than one million inhabitants in 2005. The analysis demonstrates that a large number of people are already exposed to coastal flooding in large port cities. Across all cities, about 40 million people (0.6% of the global population or roughly 1 in 10 of the total port city population in the cities considered here) are exposed to a 1 in 100 year coastal flood event. For present-day conditions (2005), the top ten cities in terms of exposed population are estimated to be Mumbai, Guangzhou, Shanghai, Miami, Ho Chi Minh City, Kolkata, Greater New York, Osaka-Kobe, Alexandria and New Orleans; almost equally split between developed and developing countries. When assets are considered, the current distribution becomes more heavily weighted towards developed countries, as the wealth of the cities becomes important. The top 10 cities in terms of assets exposed are Miami, Greater New York, New Orleans, Osaka-Kobe, Tokyo, Amsterdam, Rotterdam, Nagoya, Tampa-St Petersburg and Virginia Beach. These cities contain 60% of the total exposure, but are from only three (wealthy) countries: USA, Japan and the Netherlands. The total value of assets exposed in 2005 is across all cities considered here is estimated to be US3,000 billion; corresponding to around 5% of global GDP in 2005 (both measured in international USD)... Available at : http://www.oecd-ilibrary.org/environment/ranking-port-cities-with-high-exposure-and-vulnerability-to-climate-extremes_01176648820
Dynamical Organization around Turbulent Bursts
The detailed dynamics around intermittency bursts is investigated in
turbulent shell models. We observe that the amplitude of the high wave number
velocity modes vanishes before each burst, meaning that the fixed point in zero
and not the Kolmogorov fixed point determines the intermittency. The phases of
the field organize during the burst, and after a burst the field oscillates
back to the laminar level. We explain this behavior from the variations in the
values of the dissipation and the advection around the zero fixed point.Comment: 4 pages, REVTex, 3 figures in one ps-fil
Statistics of Dissipation and Enstrophy Induced by a Set of Burgers Vortices
Dissipation and enstropy statistics are calculated for an ensemble of
modified Burgers vortices in equilibrium under uniform straining. Different
best-fit, finite-range scaling exponents are found for locally-averaged
dissipation and enstrophy, in agreement with existing numerical simulations and
experiments. However, the ratios of dissipation and enstropy moments supported
by axisymmetric vortices of any profile are finite. Therefore the asymptotic
scaling exponents for dissipation and enstrophy induced by such vortices are
equal in the limit of infinite Reynolds number.Comment: Revtex (4 pages) with 4 postscript figures included via psfi
Inertial- and Dissipation-Range Asymptotics in Fluid Turbulence
We propose and verify a wave-vector-space version of generalized extended
self similarity and broaden its applicability to uncover intriguing, universal
scaling in the far dissipation range by computing high-order (\leq 20\/)
structure functions numerically for: (1) the three-dimensional, incompressible
Navier Stokes equation (with and without hyperviscosity); and (2) the GOY shell
model for turbulence. Also, in case (2), with Taylor-microscale Reynolds
numbers 4 \times 10^{4} \leq Re_{\lambda} \leq 3 \times 10^{6}\/, we find
that the inertial-range exponents (\zeta_{p}\/) of the order - p\/
structure functions do not approach their Kolmogorov value p/3\/ as
Re_{\lambda}\/ increases.Comment: RevTeX file, with six postscript figures. epsf.tex macro is used for
figure insertion. Packaged using the 'uufiles' utilit
Exact Resummations in the Theory of Hydrodynamic Turbulence: III. Scenarios for Anomalous Scaling and Intermittency
Elements of the analytic structure of anomalous scaling and intermittency in
fully developed hydrodynamic turbulence are described. We focus here on the
structure functions of velocity differences that satisfy inertial range scaling
laws , and the correlation of energy dissipation
. The goal is to understand the
exponents and from first principles. In paper II of this series
it was shown that the existence of an ultraviolet scale (the dissipation scale
) is associated with a spectrum of anomalous exponents that characterize
the ultraviolet divergences of correlations of gradient fields. The leading
scaling exponent in this family was denoted . The exact resummation of
ladder diagrams resulted in the calculation of which satisfies the
scaling relation . In this paper we continue our analysis and
show that nonperturbative effects may introduce multiscaling (i.e.
not being linear in ) with the renormalization scale being the infrared
outer scale of turbulence . It is shown that deviations from K41 scaling of
() must appear if the correlation of dissipation is
mixing (i.e. ). We derive an exact scaling relation . We present analytic expressions for for all
and discuss their relation to experimental data. One surprising prediction is
that the time decay constant of scales
independently of : the dynamic scaling exponent is the same for all
-order quantities, .Comment: PRE submitted, 22 pages + 11 figures, REVTeX. The Eps files of
figures will be FTPed by request to [email protected]
California Current System response to late Holocene climate cooling in southern California
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95512/1/grl24588.pd
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