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Producing realistic climate data with GANs
Get PDFThis paper investigates the potential of a Wasserstein Generative Adversarial Networks to produce realistic weather situations when trained from the climate of a general circulation model (GCM). To do so, a convolutional neural network architecture is proposed for the generator and trained on a synthetic climate database, computed using a simple 3 dimensional climate model: PLASIM.
The generator transforms a "latent space", defined by a 64 dimensional Gaussian distribution, into spatially defined anomalies on the same output grid as PLASIM. The analysis of the statistics in the leading empirical orthogonal functions shows that the generator is able to reproduce many aspects of the multivariate distribution of the synthetic climate. Moreover, generated states reproduce the leading geostrophic balance present in the atmosphere.
The ability to represent the climate state in a compact, dense and potentially nonlinear latent space opens new perspectives in the analysis and the handling of the climate. This contribution discusses the exploration of the extremes close to a given state and how to connect two realistic weather situations with this approach
CSI-aided Robust Neural-based Decoders
Get PDFIn this work, we investigate the design of neural based channel decoders for the Binary Asymmetric Channel (BAC), which exhibits robustness issues related to training/testing channel parameters mismatch. Rather than enforcing the independence of the trained model to the channel parameter as in our previous work, we show that providing even a coarse (possibly imperfect) quantized CSI to the decoder, allows to build a single robust neural decoder for all values of channel parameters
A Comodulation Analysis of Atmospheric Energy Injection Into the Ground Motion at InSight, Mars
Get PDFSeismic observations involve signals that can be easily masked by noise injection. For the
NASA Mars lander InSight, the atmosphere is a significant noise contributor, impeding the identification
of seismic events for two-thirds of a Martian day. While the noise is below that seen at even the quietest
sites on Earth, the amplitude of seismic signals on Mars is also considerably lower, requiring an
understanding and quantification of environmental injection at unprecedented levels. Mars’ ground
and atmosphere are a continuously coupled seismic system, and although atmospheric functions are of
distinct origins, the superposition of these noise contributions is poorly understood, making separation
a challenging task. We present a novel method for partitioning the observed signal into seismic and
environmental contributions. Atmospheric pressure and wind fluctuations are shown to exhibit temporal
cross-frequency coupling across multiple bands, injecting noise that is neither random nor coherent.
We investigate this through comodulation, quantifying the synchrony of the seismic motion, wind and
pressure signals. By working in the time-frequency domain, we discriminate between the different origins
of underlying processes and determine the site's environmental sensitivity. Our method aims to create a
virtual vault at InSight's landing site on Mars, shielding the seismometers with effective postprocessing
in lieu of a physical vault. This allows us to describe the environmental and seismic signals over a
sequence of sols, to quantify the wind and pressure injection and estimate the seismic content of possible
marsquakes with a signal-to-noise ratio that can be quantified in terms of environmental independence.
Finally, we exploit the relationship between the comodulated signals to identify their sources
Biodeterioration kinetics and microbial community organization on surface of cementitious materials exposed to anaerobic digestion conditions
Get PDFAnaerobic digestion is a process that can produce renewable energy through the fermentation of biodegradable biomass. Industrial anaerobic digestion tanks are usually made of concrete but the production of various aggressive compounds (CO2, NH4+ and volatile fatty acids) during the microbial fermentation leads to deterioration of the concrete structure. In addition, the formation of a microbial biofilm on the cementitious material surface could generate even more intense biodeterioration. The objective of this study is to gain a better understanding of the involvement of biofilm in the biodeterioration of cementitious materials during an anaerobic digestion process. More specifically, the study focuses on the heterogeneity of microbial populations within the biofilm and the reactive medium in anaerobic digestion. Laboratory scale anaerobic bioreactors mimicking the industrial anaerobic digestion medium were constructed and CEM I cement pastes were immersed in this medium for 2, 3, 4, 5, 10 and 15 weeks. The biodeterioration of the cement pastes was evaluated by determining the deteriorated thickness. The aggressive compounds in the medium were quantified. The biofilm attached to the surface of the cement pastes was analyzed using 16 s rRNA gene sequencing. To evaluate the heterogeneity of the biofilm, the growth of biofilm layers was successively caused to stall by using two distinct biofilm removal techniques. Three microbial fractions were defined: planktonic microorganisms, and the microorganisms within the biofilm that were loosely and strongly attached. The results showed that the planktonic lifestyle was more associated with microorganisms producing methane and consuming volatile fatty acids, while the biofilm was more associated with bacteria producing acids, mainly members of the Clostridium genus. A microbial community shift due to a reversible propionic acid accumulation during the first 5 weeks was also observed. In addition, no major differences were spotted between the loosely and strongly attached biomass, indicating homogeneity in the two layers of the biofilm. These results suggest that the biofilm could increase the biodeterioration of concrete since volatile fatty acids could be produced in massive quantities near the surface of the cement samples by the acidogenic microbial population more present within the biofilm
Nickel‐Decorated Silver Nanowires for Polymer‐Based Magnetoelectric Composite
Get PDFPolymer-based magnetoelectric composites are processed with an intrinsic piezoelectric poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) matrix and high-aspect-ratio magnetic nickel–decorated silver nanowires. These core/ shell wires are obtained by the polyol reduction of Ni2+ ions on high-aspect-ratio silver nanowires. Scanning electron microscopy and transmission electron microscopy analyses show a homogeneous and well-crystallized nickel layer. Magnetic properties of the intrinsic particles and their composites are measured and show a strong enhancement of the coercive field compared to spherical Ni nanopowders. They also show the existence of strong magnetic anisotropy in the composites. The composites processed with a small amount of metallic particles (0.3 vol%) allow the maintaining of the P(VDF-TrFE) crystalline phase and the ability of a macroscopic polarization. The latter is conducted under a 80 MV m−1 field, leading to a significant d33 (3.2 pC N−1). Thus, the magnetoelectric properties are analyzed and an important coupling coefficient αME equal to 1.8 V m−1 Oe−1 is measured
Advances in the Understanding of the Transfer of Saccharides through NF Membranes in the Presence of Electrolytes by Coupling Quantum Mechanics and Thermodynamic Methods
Get PDFDifferent studies have shown that the presence of electrolytes modifies the nanofiltration performances and that the variation of the neutral solute transfer is mainly governed by the modification of the solute properties. The objective of this work is to strengthen the understanding of the impact of the ion composition and to progress in the long-term objective for the prediction of the nanofiltration performances. The methodology is based on the comparison of the hydration properties obtained by experimental and theoretical approaches with the mass transfer of saccharides. The key role of the saccharide hydration number to understand the impact of the ionic composition on the saccharide transfer is clearly demonstrated. Moreover, it is established that the number of saccharide/cation interactions, which increases with the cation coordination number, is a key parameter to understand the mechanisms governing the impact of the nature of the cation on the saccharide mass transfer modification. Finally, correlations are obtained between the saccharide hydration number decrease and the variation of the saccharide radius calculated using a hydrodynamic model for different ionic compositions and operating modes (diffusion and filtration). From these results, it could be possible to evaluate the saccharide transfer for a given saccharide/electrolyte system transfe
Graphene oxide and reduced graphene oxide promote the effects of exogenous T3 thyroid hormone in the amphibian Xenopus laevis
Get PDFThe interest for graphene-based nanomaterials (GBMs) is growing worldwide as their properties allow the development of new innovative applications. In parallel, concerns are increasing about their potential adverse effects on the environment are increasing. The available data concerning the potential risk associated to exposure of aquatic organisms to these GBMs are still limited and little is known regarding their endocrine disruption potential. In the present study, the endocrine disruption potential of graphene oxide (GO) and reduced graphene oxide (rGO) was assessed using a T3-induced amphibian metamorphosis assay. The results indicated that GBMs potentiate the effects of exogenous T3 with a more marked effect of GO compared to rGO. T3 quantifications in the exposure media indicated adsorption of the hormone on GBMs, increasing its bioavailability for organisms because GBMs are accumulated in the gut and the gills of these amphibians. This study highlights that the tested GBMs do not disrupt the thyroid pathway in amphibians but indicates that adsorption properties of these nanomaterials may increase the bioavailability and the toxicity of other pollutants
Direct liquid injection chemical vapor deposition of ZrO2 films from a heteroleptic Zr precursor: Interplay between film characteristics and corrosion protection of stainless steel
Get PDFThe direct liquid injection chemical vapor deposition (DLI-CVD) of uniform and dense zirconium oxide (ZrO2) thin films applicable as corrosion protection coatings (CPCs) is reported. We present the entire development chain from the rational choice and thermal evaluation of the suitable heteroleptic precursor [Zr(OiPr)2(tbaoac)2] over the detailed DLI-CVD process design and finally benchmarking the CPC behavior using electrochemical impedance spectroscopy (EIS). For a thorough development of the growth process, the deposition temperature (Tdep) is varied in the range of 400 – 700 °C on Si(100) and stainless steel (AISI 304) substrates. Resulting thin films are thoroughly analyzed in terms of structure, composition, and morphology. Grazing incidence X-ray diffractometry (GIXRD) reveals an onset of crystallization at Tdep ≥ 500 °C yielding monoclinic and even cubic phase at low temperatures. At Tdep = 400 °C, isotropic growth of XRD amorphous material is shown to feature cubic crystalline domains at the interfacial region as revealed by electron diffraction. Corrosion results obtained through EIS measurements and further immersion tests revealed improved CPC characteristic for the 400 °C processed ZrO2 coatings compared to the ones deposited at Tdep ≥ 500 °C, yielding valuable insights into the correlation between growth parameter and CPC performance which are of high relevance for future exploration of CPCs
Oxidation and high-temperature radiative properties of the Kanthal Super ER intermetallic alloy
Get PDFThe oxidation resistance of receivers is a critical point in the development of plants using solar tower technology. Intermetallics in MoSiAl system present oxidation maximum temperature and creep resistance superior to the ones of the currently used Ni-based alloys. We followed here the oxidation resistance of such intermetallic exposed to different treatments in air: long-term oxidation (up to 700 h) at 1373 K, and for several cycles of 20 min in solar furnace. The normal spectral emissivity is measured up to 1640 K in air, and our main positive conclusion is this property is not degraded by the oxidation
An indicator to characterize hydrological alteration due to hydropeaking
Get PDFHydropeaking by hydroelectric facilities generates sudden changes in river flows and can affect the composition, abundance and structure of fish and invertebrate populations over long distances. To assess the level of hydrological alteration, as a factor of risk of biological impacts, a synthetic indicator was developed. Based on the analysis of 97 hydrometric stations and 1 575 years of unaltered flow data, rates of change in flow were calculated. Formulas representing the fastest natural variations, depending on the mean stream flow, the type of variation (increase or decrease) and the range of variation were established. Based on the analysis of 80 hydrometric stations and 491 years of flow data affected by hydropeaking, a method was developed to identify hydropeaks, essentially defined as variations with a rate of change greater than the maximum natural value computed using the formulas. A synthetic indicator differentiating five levels of hydrological alteration was developed using linear discriminant analysis based on five parameters characterizing hydropeaking regimes. Examples show that this indicator is sensitive to changes in the management of hydroelectric facilities and provides information on the spatial and temporal evolutions in hydropeaking regimes, including the progressive attenuation during downstream propagation