3,413 research outputs found
Águas Subterrâneas em Cabo Verde - Qualidade da Água na Ilha de Santiago
Em Cabo Verde os recursos hídricos subterrâneos desempenham um papel fundamental, constituindo a
principal fonte de abastecimento de água para as populações de pequenos aglomerados urbanos.
O trabalho que se apresenta enquadra-se num estudo alargado de caracterização de águas subterrâneas; foi
efectuado nos seis concelhos da ilha de Santiago a maior do país, em captações do tipo poço, furo e galeria
destinadas ao abastecimento da população através de chafarizes e resulta de uma parceria entre o Instituto
Nacional de Gestão dos Recursos Hídricos de Cabo Verde (INGRH) e o Instituto Nacional de Saúde, Porto de
Portugal (INSA-Porto).
Com base nos dados obtidos, e no sentido de uma cooperação alargada, propõe-se a criação do
Observatório de Águas Subterrâneas nos Países Africanos de expressão Portuguesa
UV polymerization of room temperature ionic liquids for high temperature PEMs: Study of ionic moieties and crosslinking effects
The conductivity performance of commercial available room-temperature ionic liquids (RTILs) has been evaluated from room conditions up to 200oC as a function of relative humidity for their potential application in high temperature PEMs. In particular, ammonium and imidazolium based ionic liquids with different counterions and substituents have been investigated. On the basis of conductivity performance, the best RTILs have been selected for the preparation of all solid state ion conductive films by bulk photo-assisted radical polymerization. The goodness of the UV photopolymerization of the respective monomeric ionic liquids (MILs) with vinyl functionality as a function of divynilbenzene cross-linker content has been evaluated by TGA and FTIR analyses. Poly-ionic liquid (PIL) films have been successfully accomplished for polymerized H-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide upon exposure to 365 nm UV lamp with an intensity of 2.4 mW/cm2 for 15 min. Conductivity values above 1.1 S∙cm-1 at 200oC have been registered for pure poly[1-(3H-imidazolium)ethylene] bis(trifluoromethanesulfonyl)imide
Selecting Metrics to Evaluate Human Supervisory Control Applications
The goal of this research is to develop a methodology to select supervisory control metrics. This
methodology is based on cost-benefit analyses and generic metric classes. In the context of this research,
a metric class is defined as the set of metrics that quantify a certain aspect or component of a system.
Generic metric classes are developed because metrics are mission-specific, but metric classes are
generalizable across different missions. Cost-benefit analyses are utilized because each metric set has
advantages, limitations, and costs, thus the added value of different sets for a given context can be
calculated to select the set that maximizes value and minimizes costs. This report summarizes the
findings of the first part of this research effort that has focused on developing a supervisory control metric
taxonomy that defines generic metric classes and categorizes existing metrics. Future research will focus
on applying cost benefit analysis methodologies to metric selection.
Five main metric classes have been identified that apply to supervisory control teams composed
of humans and autonomous platforms: mission effectiveness, autonomous platform behavior efficiency,
human behavior efficiency, human behavior precursors, and collaborative metrics. Mission effectiveness
measures how well the mission goals are achieved. Autonomous platform and human behavior efficiency
measure the actions and decisions made by the humans and the automation that compose the team.
Human behavior precursors measure human initial state, including certain attitudes and cognitive
constructs that can be the cause of and drive a given behavior. Collaborative metrics address three
different aspects of collaboration: collaboration between the human and the autonomous platform he is
controlling, collaboration among humans that compose the team, and autonomous collaboration among
platforms. These five metric classes have been populated with metrics and measuring techniques from
the existing literature.
Which specific metrics should be used to evaluate a system will depend on many factors, but as a
rule-of-thumb, we propose that at a minimum, one metric from each class should be used to provide a
multi-dimensional assessment of the human-automation team. To determine what the impact on our
research has been by not following such a principled approach, we evaluated recent large-scale
supervisory control experiments conducted in the MIT Humans and Automation Laboratory. The results
show that prior to adapting this metric classification approach, we were fairly consistent in measuring
mission effectiveness and human behavior through such metrics as reaction times and decision
accuracies. However, despite our supervisory control focus, we were remiss in gathering attention
allocation metrics and collaboration metrics, and we often gathered too many correlated metrics that were
redundant and wasteful. This meta-analysis of our experimental shortcomings reflect those in the general
research population in that we tended to gravitate to popular metrics that are relatively easy to gather,
without a clear understanding of exactly what aspect of the systems we were measuring and how the
various metrics informed an overall research question
Mid-Infrared Imaging of NGC 6334 I
We present high-resolution (<0.5") mid-infrared Keck II images of individual
sources in the central region of NGC 6334 I. We compare these images to images
at a variety of other wavelengths from the near infrared to cm radio continuum
and speculate on the nature of the NGC 6334 I sources. We assert that the
cometary shape of the UCHII region here, NGC 6334 F, is due to a champagne-like
flow from a source on the edge of a molecular clump and not a due to a bow
shock caused by the supersonic motion of the UCHII region through the
interstellar medium. The mid-infrared emission in concentrated into an arc of
dust that define the boundary between the UCHII region and the molecular clump.
This dust arc contains a majority of the masers in the region. We discuss the
nature of the four near-infrared sources associated with IRS-I 1, and suggest
that one of the sources, IRS1E, is responsible for the heating and ionizing of
the UCHII region and the mid-infrared dust arc. Infrared source IRS-I 2, which
has been thought to be a circumstellar disk associated with a linear
distribution of methanol masers, is found not to be directly coincident with
the masers and elongated at a much different position angle. IRS-I 3 is found
to be a extended source of mid-infrared emission coming from a cluster of young
dusty sources seen in the near-infrared.Comment: Accepted for publication by the Astrophysical Journal, 27 pages, 9
figure
Reinforced SIL-1 micromembranes integrated on chip: APPLICATION to CO2 separation
A novel 4-step microfabrication process is proposed in this work to prepare arrays of c-oriented silicalite (SIL-1) micromembranes on customized silicon nitride (Si3Nx) microsieves. The arrays are integrated on chip and their overall porosity values can be tuned from 1.6% to 19.9%. A low stress Si3Nx microfabricated sieve has been used as support to reinforce via mechanical interlocking and to reduce the effects of the residual stress during membrane processing. The secondary hydrothermal growth over the Si3Nx microsieves also changes the SIL-1 chemistry, improving its affinity towards CO2 adsorption. As a result, the SIL-1/Si3Nx micromembranes integrated on chip facilitate the preferential permeation of CO2 in CO2/H2 mixtures, showing a maximum CO2/H2 separation factor of 16.9 and a CO2 permeance of 8.2×10-7 mol m-2 s-1 Pa-1 at ambient conditions
Sedimentological characteristics of ice-wedge polygon terrain in Adventdalen (Svalbard): environmental and climatic implications for the late Holocene
Ice wedges are widespread periglacial features in
the landscape of Adventdalen, Svalbard. The networks of ice
wedges have created areas with well-developed polygonal
terrains in the lowest fluvial terraces in this valley. We have
examined the sedimentological characteristics of the northern
and southern banks of the Advent river for palaeoenvironmental
purposes. The base of two sedimentary sections
reported radiocarbon dates of 3.3 and 3.9 ka BP, respectively.
The northern site is constituted by three very different
lithostratigraphical units, which suggests that their formation
should be related to different environmental and climate
conditions. By contrast, the southern section shows a
rather homogeneous composition, with no significant variations
in grain size and organic matter content. In both cases
the uppermost sediments are constituted by a thick aeolian
deposit. According to our data, warmer climate conditions
may have prevailed during the mid Holocene until 3.3 ka BP
with widespread peat formation in the valley bottom. Subsequently,
a period with alternating soil formation and aeolian
sedimentation took place from 3 to 2.5 ka BP, probably due
to increasing climatic severity. During the last millennium a
long-term cooling trend has favoured aeolian deposition in
the lowest part of Adventdalen.info:eu-repo/semantics/publishedVersio
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