16 research outputs found
On the evaluation of global sea-salt aerosol models at coastal/orographic sites
Sea-salt aerosol global models are typically evaluated against concentration observations at coastal stations that are unaffected by local surf conditions and thus considered representative of open ocean conditions. Despite recent improvements in sea-salt source functions, studies still show significant model errors in specific regions. Using a multiscale model, we investigated the effect of high model resolution (0.1 degrees x 0.1 degrees vs. 1 degrees x 1.4 degrees) upon sea-salt patterns in four stations from the University of Miami Network: Baring Head, Chatam Island, and Invercargill in New Zealand, and Marion Island in the sub-antarctic Indian Ocean. Normalized biases improved from +63.7% to +3.3% and correlation increased from 0.52 to 0.84. The representation of sea/land interfaces, mesoscale circulations, and precipitation with the higher resolution model played a major role in the simulation of annual concentration trends. Our results recommend caution when comparing or constraining global models using surface concentration observations from coastal stations. (C) 2014 The Authors. Published by Elsevier Ltd.Postprint (published version
Scale-free static and dynamical correlations in melts of monodisperse and Flory-distributed homopolymers: A review of recent bond-fluctuation model studies
It has been assumed until very recently that all long-range correlations are
screened in three-dimensional melts of linear homopolymers on distances beyond
the correlation length characterizing the decay of the density
fluctuations. Summarizing simulation results obtained by means of a variant of
the bond-fluctuation model with finite monomer excluded volume interactions and
topology violating local and global Monte Carlo moves, we show that due to an
interplay of the chain connectivity and the incompressibility constraint, both
static and dynamical correlations arise on distances . These
correlations are scale-free and, surprisingly, do not depend explicitly on the
compressibility of the solution. Both monodisperse and (essentially)
Flory-distributed equilibrium polymers are considered.Comment: 60 pages, 49 figure
La campagne expérimentale FluxSAP 2010; mesures de climatologie en zone urbaine hétérogène
National audienc
Relations between cuticular hydrocarbon (HC) polymorphism, resistance against desiccation and breeding temperature; a model for HC evolution in D. melanogaster and D. simulans
Tendências no desenvolvimento de gases de proteção utilizados na soldagem MIG/MAG Trends in the development of protective gases used in GMAW welding
Este trabalho tem como objetivo apresentar uma revisĂŁo do estado da arte sobre os gases de proteção usados nos processos de soldagem a arco elĂ©trico, com ĂŞnfase na soldagem MIG/MAG do aço. SĂŁo apresentados os principais conceitos da fĂsica do arco e as propriedades relacionadas aos gases de proteção. O modelo de atmosfera ligeiramente oxidante para os gases de proteção Ă© discutido, sendo mostradas as formulações dos gases estudados em artigos cientĂficos e em patentes depositadas, bem como as reivindicações (vantagens) requeridas. TambĂ©m sĂŁo mencionados alguns poucos estudos usando adições de gases nĂŁo convencionais. Foi observado que no desenvolvimento de gases de proteção para soldagem MIG/MAG do aço predomina o modelo da formação de atmosfera ligeiramente oxidante. A maioria das formulações propostas envolve o uso de misturas binárias, ternárias e atĂ© quaternárias dos gases Ar, He, CO2 e O2. Em aplicações especĂficas, adições de N2 e H2 foram usadas. Neste sentido, pouca inovação foi identificada, sendo atribuĂdas possĂveis razões a este fato. A tendĂŞncia observada para o desenvolvimento de gases de proteção parece ser o uso de misturas ricas em gases inertes, com adições calibradas de elementos oxidantes, sempre atendendo a aplicações especĂficas.<br>This paper has as objective to present a state of the art review on the shielding gases used in the electric arc welding processes, with emphasis on GMAW welding of steel. There are shown the main concepts of arc physics and properties related to shielding gases. The model of slightly oxidizing atmosphere for shielding gases is discussed, and the formulations of the gases studied in scientific articles and in deposited patents, as well as the claims (benefits) required. It also mentions some few studies using additions of non-conventional gases. It was observed that for the development of shielding gases for the GMAW steel welding the model of slightly oxidizing atmosphere is predominant. Most of proposed formulations involve the use of binary, ternary or even quaternary mixtures of the gases Ar, He, CO2 and O2. For specific aplications, additions of N2 e H2 were used. In this meaning, few innovations were identified, and possible reasons were attributed. The trend observed for the development of shielding gases seems to be the use of mixtures rich in inert gases, with calibrated additions of oxidizing elements, always looking for specific applications