181 research outputs found
Stein's method for dependent random variables occurring in Statistical Mechanics
We obtain rates of convergence in limit theorems of partial sums for
certain sequences of dependent, identically distributed random variables, which
arise naturally in statistical mechanics, in particular, in the context of the
Curie-Weiss models. Under appropriate assumptions there exists a real number
, a positive real number , and a positive integer such that
converges weakly to a random variable with
density proportional to . We develop Stein's method
for exchangeable pairs for a rich class of distributional approximations
including the Gaussian distributions as well as the non-Gaussian limit
distributions with density proportional to . Our
results include the optimal Berry-Esseen rate in the Central Limit Theorem for
the total magnetization in the classical Curie-Weiss model, for high
temperatures as well as at the critical temperature , where the
Central Limit Theorem fails. Moreover, we analyze Berry-Esseen bounds as the
temperature converges to one and obtain a threshold for the speed
of this convergence. Single spin distributions satisfying the
Griffiths-Hurst-Sherman (GHS) inequality like models of liquid helium or
continuous Curie-Weiss models are considered
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Data Science: History repeated? â The heritage of the Free and Open Source GIS community
[no abstract available
Rheology of gelling polymers in the Zimm model
In order to study rheological properties of gelling systems in dilute
solution, we investigate the viscosity and the normal stresses in the Zimm
model for randomly crosslinked monomers. The distribution of cluster topologies
and sizes is assumed to be given either by Erd\H os-R\'enyi random graphs or
three-dimensional bond percolation. Within this model the critical behaviour of
the viscosity and of the first normal stress coefficient is determined by the
power-law scaling of their averages over clusters of a given size with .
We investigate these Mark--Houwink like scaling relations numerically and
conclude that the scaling exponents are independent of the hydrodynamic
interaction strength. The numerically determined exponents agree well with
experimental data for branched polymers. However, we show that this traditional
model of polymer physics is not able to yield a critical divergence at the gel
point of the viscosity for a polydisperse dilute solution of gelation clusters.
A generally accepted scaling relation for the Zimm exponent of the viscosity is
thereby disproved.Comment: 9 pages, 2 figure
Systems Dynamics Modelling in Industrial Development Evaluation
The complexity of development processes makes it difficult to observe and interpret the impacts of policies. The authors demonstrate the use and benefits of system dynamics modelling (SDM) in impact evaluation of private sector development programmes. A system dynamics model was hereby specifically used to compare the observed post?intervention situation with a hypothetical non?intervention scenario. They used the model to construct an optimal mix of interventions that supports sustainable private sector development. They found that developing a system dynamics model and âgamingâ with it is an appropriate means to link the behaviour of the industrial system we observe to its structural elements. This supports the understanding of the impact of complex interventions in industrial systems and can be further useful to convey lessons learned from the evaluations of complex systemic interventions
More Greening, less Trashing
Die Umweltwirkungen der Globalisierung werden kontrovers diskutiert. Im Sinne einer eher optimistischen Sichtweise verfolgt die EuropĂ€ische Union die Strategie einer globalen Ăkologisierung der Wertschöpfungsketten. Das StichÂwort lautet Integrierte Produktpolitik. Doch inwieweit sind Hersteller aus EntÂwicklungslĂ€ndern in der Lage, hier mitzuhalten? Dies wird anhand des Beispiels der Elektronikindustrie diskutiert
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Videos for science communication and nature interpretation: The TIB|AV-Portal as resource
[no abstract available
Towards OSGeo Best Practices for Scientific Software Citation: Integration Options for Persistent Identifiers in OSGeo Project Repositories
As a contribution to the currently ongoing larger effort to establish Open Science as best practices in academia, this article focuses on the Open Source and Open Access tiers of the Open Science triad and community software projects. The current situation of research software development and the need to recognize it as a significant contribution to science is introduced in relation to Open Science. The adoption of the Open Science paradigms occurs at different speeds and on different levels within the various fields of science and crosscutting software communities. This is paralleled by the emerging of an underlying futuresafe technical infrastructure based on open standards to enable proper recognition for published articles, data, and software. Currently the number of journal publications about research software remains low in comparison to the amount of research code published on various software repositories in the WWW. Because common standards for the citation of software projects (containers) and versions of software are lacking, the FORCE11 group and the CodeMeta project recommending to establish Persistent Identifiers (PIDs), together with suitable metadata setss to reliably cite research software. This approach is compared to the best practices implemented by the OSGeo Foundation for geospatial community software projects. For GRASS GIS, a OSGeo project and one of the oldest geospatial open source community projects, the external requirements for DOI-based software citation are compared with the projects software documentation standards. Based on this status assessment, application scenarios are derived, how OSGeo projects can approach DOI-based software citation, both as a standalone option and also as a means to foster open access journal publications as part of reproducible Open Science
Recommended from our members
Towards OSGeo Best Practices for Scientific Software Citation: Integration Options for Persistent Identifiers fn OSGeo Project Repositories
As a contribution to the currently ongoing larger effort to establish Open Science as best practices in academia, this article focuses on the Open Source and Open Access tiers of the Open Science triad and community software projects. The current situation of research software development and the need to recognize it as a significant contribution to science is introduced in relation to Open Science. The adoption of the Open Science paradigms occurs at different speeds and on different levels within the various fields of science and crosscutting software communities. This is paralleled by the emerging of an underlying futuresafe technical infrastructure based on open standards to enable proper recognition for published articles, data, and software. Currently the number of journal publications about research software remains low in comparison to the amount of research code published on various software repositories in the WWW. Because common standards for the citation of software projects (containers) and versions of software are lacking, the FORCE11 group and the CodeMeta project recommending to establish Persistent Identifiers (PIDs), together with suitable metadata setss to reliably cite research software. This approach is compared to the best practices implemented by the OSGeo Foundation for geospatial community software projects. For GRASS GIS, a OSGeo project and one of the oldest geospatial open source community projects, the external requirements for DOI-based software citation are compared with the projects software documentation standards. Based on this status assessment, application scenarios are derived, how OSGeo projects can approach DOI-based software citation, both as a standalone option and also as a means to foster open access journal publications as part of reproducible Open Science
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