107 research outputs found
Mutual Information for Explainable Deep Learning of Multiscale Systems
Timely completion of design cycles for complex systems ranging from consumer
electronics to hypersonic vehicles relies on rapid simulation-based
prototyping. The latter typically involves high-dimensional spaces of possibly
correlated control variables (CVs) and quantities of interest (QoIs) with
non-Gaussian and possibly multimodal distributions. We develop a
model-agnostic, moment-independent global sensitivity analysis (GSA) that
relies on differential mutual information to rank the effects of CVs on QoIs.
The data requirements of this information-theoretic approach to GSA are met by
replacing computationally intensive components of the physics-based model with
a deep neural network surrogate. Subsequently, the GSA is used to explain the
network predictions, and the surrogate is deployed to close design loops.
Viewed as an uncertainty quantification method for interrogating the surrogate,
this framework is compatible with a wide variety of black-box models. We
demonstrate that the surrogate-driven mutual information GSA provides useful
and distinguishable rankings on two applications of interest in energy storage.
Consequently, our information-theoretic GSA provides an "outer loop" for
accelerated product design by identifying the most and least sensitive input
directions and performing subsequent optimization over appropriately reduced
parameter subspaces.Comment: 27 pages, 8 figures. Added additional example
Sediment discharge in the Scheldt estuary
The environmental effects of erosion, movement and deposition of sediment can be serious. The variation in drainage basin and precipitation characteristics results in significant differences in the quantity of fluvial sediment. This difference requires the manager of the navigable waterways in Flanders (Administration of Waterways and Marine Affairs, AWZ) to monitor the suspended sediment transport at the upstream boundaries of its territory. This monitoring network provides sediment data that can be used to (1) evaluate the effects of landmanagement practices that will reduce erosion rates, (2) determine the morphological effects of riverbed enlargment measures, (3) estimate the quantities to be dredged (4) fulfill the monitoring aspects of the EU Water Framework Directive, (5) enlarge the knowledge of the watersystem and (6) provide basic information for treatment of dredging material. The approach consists of a continuous hourly monitoring method completed with topographical cross section measurements, measurements of turbidity samples, calibration of the turbidity monitor and correlation between local turbidity and cross section turbidity. Finally sediment transport is calculated from turbidity and validated discharge measurements. Sediment data were collected at eight stations from 1999. Data for 1999 and 2000 were published in the annual report. Data collection at different locations and processing of sediment samples will continue. All data will be published in annual data-reports and in the future on the internet
Advanced EFL learners' beliefs about language learning and teaching: a comparison between grammar, pronunciation, and vocabulary
This paper reports on the results of a study exploring learners’ beliefs on the learning and teaching of English grammar, pronunciation and vocabulary at tertiary level. While the importance of learners’ beliefs on the acquisition process is generally recognized, few studies have focussed on and compared learners’ views on different components of the language system. A questionnaire containing semantic scale and Likert scale items probing learners’ views on grammar, pronunciation and vocabulary was designed and completed by 117 native speakers of Dutch in Flanders, who were studying English at university. The analysis of the responses revealed that (i) vocabulary was considered to be different from grammar and pronunciation, both in the extent to which an incorrect use could lead to communication breakdown and with respect to the learners’ language learning strategies, (ii) learners believed in the feasibility of achieving a native-like proficiency in all three components, and (iii) in-class grammar, pronunciation and vocabulary exercises were considered to be useful, even at tertiary level. The results are discussed in light of pedagogical approaches to language teaching
Description of a strain from an atypical population of Aspergillus parasiticus that produces aflatoxins B only, and the impact of temperature on fungal growth and mycotoxin production
In this study, an atypical strain of Aspergillus parasiticus is described. This strain, reported from Portuguese almonds, was named Aspergillus parasiticus B strain. The strain is herein characterised at the morphological and physiological levels, and compared with the typical A. parasiticus strain and other similar species in section Flavi. Previously published morphological and molecular data support that the B strain is very closely related to the A. parasiticus type strain. However, while A. parasiticus typically produces aflatoxins B and G, B strain produces aflatoxins B only. Furthermore, this atypical strain showed to differ from the typical strain in the fact that higher growth (colony diameter) and strain. This strain can become a major food safety concern in colder regions where the typical A. parasiticus strains are not well adapted.NORTE-07-0124-FEDER-000028PEst-OE/EQB/LA0023/2013PEst-OE/AGR/UI0690/201
Simple methodology for the quantitative analysis of fatty acids in human red blood cells
In the last years, there has been an increasing
interest in evaluating possible relations between fatty acid
(FA) patterns and the risk for chronic diseases. Due to the
long life span (120 days) of red blood cells (RBCs), their
FA profile reflects a longer term dietary intake and was
recently suggested to be used as an appropriate biomarker
to investigate correlations between FA metabolism and diseases.
Therefore, the aim of this work was to develop and
validate a simple and fast methodology for the quantification
of a broad range of FAs in RBCs using gas chromatography
with flame ionization detector, as a more common
and affordable equipment suitable for biomedical and
nutritional studies including a large number of samples. For
this purpose, different sample preparation protocols were
tested and compared, including a classic two-step method
(Folch method) with modifications and different one-step methods, in which lipid extraction and derivatization were
performed simultaneously. For the one-step methods, different
methylation periods and the inclusion of a saponification
reaction were evaluated. Differences in absolute FA
concentrations were observed among the tested methods,
in particular for some metabolically relevant FAs such as
trans elaidic acid and eicosapentaenoic acid. The one-step
method with saponification and 60 min of methylation time
was selected since it allowed the identification of a higher
number of FAs, and was further submitted to in-house validation.
The proposed methodology provides a simple, fast
and accurate tool to quantitatively analyse FAs in human
RBCs, useful for clinical and nutritional studies.This work received financial support from the
European Union (FEDER funds through COMPETE) and National
Funds (FCT, Fundação para a Ciência e Tecnologia) through project
PTDC/SAU-ENB/116929/2010 and EXPL/EMS-SIS/2215/2013.
ROR acknowledges PhD scholarship SFRH/BD/97658/2013 attributed
by FCT (Fundação para a Ciência e Tecnologia).info:eu-repo/semantics/publishedVersio
Determination of chlorinated solvents in industrial water and wastewater by DAI–GC–ECD
A very simple and quick analytical method, based on direct aqueous injection, for determination of halogenated solvents in refinery water and wastewater, is described. There is a need to determine halogenated solvents in refinery water streams, because they may originate from several processes. There is also a need to develop methods enabling VOX to be determined in samples containing oil fractions. The method described enables simultaneous determination of 26 compounds with low detection limits (sub-μg L−1) and excellent precision, especially for highly halogenated solvents. The matrix effects of four types of sample were evaluated—the method seemed to be relatively insensitive to variations in matrix composition. Deuterated 1,2-dichloroethane was used as internal standard and surrogate compound in quantitative analysis; application of isotopically labelled compounds is rarely reported when non-mass spectrometric detectors are used for analysis. Analysis of real samples showed that the most frequently detected compounds were dichloromethane and 1,2-dichloroethane
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