12,688 research outputs found
Evaporation waves in superheated dodecane
We have observed propagating adiabatic evaporation waves in superheated liquid dodecane, C_(12)H_(26). Experiments were performed with a rapid decompression apparatus at initial temperatures of 180–300°C. Saturated dodecane in a tube was suddenly depressurized by rupturing a diaphragm. Motion pictures and still photographic images, and pressure and temperature data were obtained during the evaporation event that followed depressurization. Usually, a front or wave of evaporation started at the liquid free surface and propagated into the undisturbed regions of the metastable liquid. The evaporation wave front moved with a steady mean velocity but the front itself was unstable and fluctuating in character. At low superheats, no waves were observed until a threshold superheat was exceeded. At moderate superheats, subsonic downstream states were observed. At higher superheats, the downstream flow was choked, corresponding to a Chapman–Jouguet condition. At the most extreme superheat tested, a vapour content of over 90% was estimated from the measured data, indicating a nearly complete evaporation wave. Our results are interpreted by modelling the evaporation wave as a discontinuity, or jump, between a superheated liquid state and a two-phase liquid–vapour downstream state. Reasonable agreement is found between the model and observations; however, there is a fundamental indeterminacy that prevents the prediction of the observed wave speeds
Fracturing the optimal paths
Optimal paths play a fundamental role in numerous physical applications
ranging from random polymers to brittle fracture, from the flow through porous
media to information propagation. Here for the first time we explore the path
that is activated once this optimal path fails and what happens when this new
path also fails and so on, until the system is completely disconnected. In fact
numerous applications can be found for this novel fracture problem. In the
limit of strong disorder, our results show that all the cracks are located on a
single self-similar connected line of fractal dimension .
For weak disorder, the number of cracks spreads all over the entire network
before global connectivity is lost. Strikingly, the disconnecting path
(backbone) is, however, completely independent on the disorder.Comment: 4 pages,4 figure
Early Aspects at ICSE 2007: Workshop on Aspect-Oriented Requirements Engineering and Architecture Design
The “Early Aspects @ ICSE’07” is the 11th workshop in the series of Early Aspects workshops [1] which focuses on aspect identification during the requirements engineering and architecture derivation activities. The specific aim of the present workshop is twofold: (a) to initiate creation of an Early Aspects application demonstration and comparisons benchmark; and (b) to solicit submission of new
research
Ferromagnetic tendency at the surface of CE charge-ordered manganites
Most previous investigations have shown that the surface of a ferromagnetic
material may have antiferromagnetic tendencies. However, experimentally the
opposite effect has been recently observed: ferromagnetism appears in some
nano-sized manganites with a composition such that the antiferromagnetic
charge-ordered CE state is observed in the bulk. A possible origin is the
development of ferromagnetic correlations at the surface of these small
systems. To clarify these puzzling experimental observations, we have studied
the two-orbital double-exchange model near half-doping n=0.5, using open
boundary conditions to simulate the surface of either bulk or nano-sized
manganites. Considering the enhancement of surface charge density due to a
possible AO termination (A = trivalent/divalent ion composite, O = oxygen), an
unexpected surface phase-separated state emerges when the model is studied
using Monte Carlo techniques on small clusters. This tendency suppresses the CE
charge ordering and produces a weak ferromagnetic signal that could explain the
experimental observations.Comment: 8 pages, 5 figure
Collaboration networks from a large CV database: dynamics, topology and bonus impact
Understanding the dynamics of research production and collaboration may
reveal better strategies for scientific careers, academic institutions and
funding agencies. Here we propose the use of a large and multidisciplinar
database of scientific curricula in Brazil, namely, the Lattes Platform, to
study patterns of scientific production and collaboration. In this database,
detailed information about publications and researchers are made available by
themselves so that coauthorship is unambiguous and individuals can be evaluated
by scientific productivity, geographical location and field of expertise. Our
results show that the collaboration network is growing exponentially for the
last three decades, with a distribution of number of collaborators per
researcher that approaches a power-law as the network gets older. Moreover,
both the distributions of number of collaborators and production per researcher
obey power-law behaviors, regardless of the geographical location or field,
suggesting that the same universal mechanism might be responsible for network
growth and productivity.We also show that the collaboration network under
investigation displays a typical assortative mixing behavior, where teeming
researchers (i.e., with high degree) tend to collaborate with others alike.
Finally, our analysis reveals that the distinctive collaboration profile of
researchers awarded with governmental scholarships suggests a strong bonus
impact on their productivity.Comment: 8 pages, 8 figure
Ecological features of Terebellida fauna (Annelida, Polychaeta) from Ensenada de San Simón (NW Spain)
Ecological features of Terebellida (Annelida, Polychaeta) inhabiting the intertidal and subtidal soft-bottoms of Ensenada de San Simón (NW Spain) were analysed by means of quantitative sampling. A total of 4,814 specimens belonging to five families (Ampharetidae, Pectinariidae, Terebellidae, Trichobranchidae and Sabellariidae) and ten species were collected in a variety of substrata and depths. Ampharetidae was the numerically dominant family mostly due to the abundance of Ampharete finmarchica and Melinna palmata; these species accounted for up to 94% of the total Terebellida abundance. Intertidal areas colonised by the seagrasses Zostera marina L. and Z. noltii Hornem. One thousand eight hundred and thirty-two harboured low densities of Terebellida, whereas the deeper subtidal muddy bottoms showed high abundances of ampharetids. Multivariate analyses suggested that Terebellida assemblages are highly correlated with sediment composition
Cultivares de soja: Bahia safra 2011/12.
Grupo de maturaidade relativa, peso médio de sementes, semeadura, características botânicas e agronômicas, região de adaptação, reação a doenças de cultivares de soja convencionais (BRS Corisco, BRS Barreiras, BRS 313 [Tieta], BRS 314 Gabriela) e transgênica (BRS 315RR Lívia).bitstream/item/39936/1/Soja-BA2011-12-VE.pdf1 folder
LANDSAT and radar mapping of intrusive rocks in SE-Brazil
The feasibility of intrusive rock mapping was investigated and criteria for regional geological mapping established at the scale of 1:500,00 in polycyclic and polymetamorphic areas using the logic method of photointerpretation of LANDSAT imagery and radar from the RADAMBRASIL project. The spectral behavior of intrusive rocks, was evaluated using the interactive multispectral image analysis system (Image-100). The region of Campos (city) in northern Rio de Janeiro State was selected as the study area and digital imagery processing and pattern recognition techniques were applied. Various maps at the 2:250,000 scale were obtained to evaluate the results of automatic data processing
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