Showing papers by "University of Grenoble published in 2022"

Floating Weighting Factors ANN-MPC Based on Lyapunov Stability for Seven-Level Modified PUC Active Rectifier

Abstract: Despite being cost-effective, seven-level Modified Packed U-Cell (MPUC7) active rectifier tends to be unstable due to unequal dc-links. Thus, a multiobjective controller is required to stabilize voltages and currents besides preserving efficiency and power quality. While conventional finite-set model predictive control (FSMPC) can deal with the multiobjective problem, it cannot assure the system stability, and its weighing factors tuning significantly becomes tiresome as the number of objectives increases. This article presents a low-frequency adaptive FSMPC (AMPC) stabilized based on Lyapunov stability theory to overcome the design problems of FSMPC. AMPC handles four control objectives and a decoupled stability objective. The control objectives assure the standard performance of MPUC7 in terms of switching losses, d v /d t , THD, and capacitors ripple. The stability objective guarantees the rectifier reliability under unstable conditions. The weighting factors in AMPC are floating to tackle the tuning challenges where a radial basis function neural network controller (RBFC) adjusts their variations. RBFC is trained by a novel self-training method including particle swarm optimization (PSO) algorithm and some mathematical analyses without using any training data. Experimental and simulation tests also evaluate AMPC in different conditions to confirm its reliability in fulfilling the desired objectives.

Disentangling water, ion and polymer dynamics in an anion exchange membrane

Abstract: Semipermeable polymeric anion exchange membranes are essential for separation, filtration and energy conversion technologies including reverse electrodialysis systems that produce energy from salinity gradients, fuel cells to generate electrical power from the electrochemical reaction between hydrogen and oxygen, and water electrolyser systems that provide H2 fuel. Anion exchange membrane fuel cells and anion exchange membrane water electrolysers rely on the membrane to transport OH- ions between the cathode and anode in a process that involves cooperative interactions with H2O molecules and polymer dynamics. Understanding and controlling the interactions between the relaxation and diffusional processes pose a main scientific and critical membrane design challenge. Here quasi-elastic neutron scattering is applied over a wide range of timescales (100-103 ps) to disentangle the water, polymer relaxation and OH- diffusional dynamics in commercially available anion exchange membranes (Fumatech FAD-55) designed for selective anion transport across different technology platforms, using the concept of serial decoupling of relaxation and diffusional processes to analyse the data. Preliminary data are also reported for a laboratory-prepared anion exchange membrane especially designed for fuel cell applications.

Structural and rheological properties of meat analogues from Haematococcus pluvialis residue-pea protein by high moisture extrusion

Abstract: Meat analogues, a kind of healthy promising meat substitute, are gaining more and more attention due to its eco-friendly, personal satisfactory and low cost benefits. In this study, Haematococcus pluvialis residue (HPR) was used for preparing pea protein-based meat analogues by high moisture extrusion. Mixed raw material with HPR contents ranging from 10 g/100g to 40 g/100g can successfully be extruded under high moisture of 50 g/100g. The reddish color of HPR made the extrudates look like dried red meat. HPR could markedly improve the textural properties by loosening the layered and the fibrous structures of meat analogues. The fibrous degree of meat analogues with 10 g/100g (dry basis) HPR content reached the maximum (1.28 ± 0.05). Even though the HPR content increased to 40 g/100g (dry basis), the fibrous degree of meat analogues was 1.15 ± 0.03, which was higher than the extrudates without HPR (1.08 ± 0.05). The mechanism of forming meat analogues with better texture was mainly caused by the increased free water content and β-Sheet structure of extrudates after adding HPR. On the whole, HPR can be used as a raw material for high moisture extrusion to enhance the physical properties of meat analogues.

Structural and rheological properties of meat analogues from Haematococcus pluvialis residue-pea protein by high moisture extrusion

Abstract: Meat analogues, a kind of healthy promising meat substitute, are gaining more and more attention due to its eco-friendly, personal satisfactory and low cost benefits. In this study, Haematococcus pluvialis residue (HPR) was used for preparing pea protein-based meat analogues by high moisture extrusion. Mixed raw material with HPR contents ranging from 10 g/100g to 40 g/100g can successfully be extruded under high moisture of 50 g/100g. The reddish color of HPR made the extrudates look like dried red meat. HPR could markedly improve the textural properties by loosening the layered and the fibrous structures of meat analogues. The fibrous degree of meat analogues with 10 g/100g (dry basis) HPR content reached the maximum (1.28 ± 0.05). Even though the HPR content increased to 40 g/100g (dry basis), the fibrous degree of meat analogues was 1.15 ± 0.03, which was higher than the extrudates without HPR (1.08 ± 0.05). The mechanism of forming meat analogues with better texture was mainly caused by the increased free water content and β-Sheet structure of extrudates after adding HPR. On the whole, HPR can be used as a raw material for high moisture extrusion to enhance the physical properties of meat analogues.

Silicon-Germanium Avalanche Receivers With fJ/bit Energy Consumption

Abstract: Fast, low-noise and sensitive avalanche photo-receivers are needed for surging short-reach photonic applications. Limitations concerning bandwidth, throughput and energy consumption should be overcome. In this work, we comprehensively study the performance opportunities provided by avalanche p-i-n photodetectors with lateral silicon-germanium-silicon heterojunctions. Our aim is to circumvent the need for chip-bonded electronic amplifiers. In particular, we demonstrate that avalanche photodetectors based on silicon-germanium-silicon heterostructures yield reliable opto-electrical performances, with high gain-bandwidth products up to 480 GHz and low effective ionization ratios down to 0.15. Moreover, they improve power sensitivities for high-speed optical signals and have a low energy dissipation of only a few fJ per received information bit. These results pave the way for high-performing receivers for energy-aware data links, in next-generation short-distance data communications.

Enhanced NO2 gas sensing performance by hierarchical CuO–Co3O4 spheres

Abstract: Composite sensing materials with complex hierarchical structures exhibit better performance in chemiresistive sensors due to rich defects induced by the hierarchical structures. Herein, the hierarchical spheres assembled by CuO-Co3O4 nanowires were successfully prepared via the hydrothermal and sintering procedure. SEM, TEM, and XRD results revealed that the hierarchical structure was controllably constructed by adjusting the composition of the CuO and Co3O4. XPS confirmed that the hierarchical structure could promote the enrichment of lattice oxygen. The CuO-Co3O4 composite with hierarchical structure-based sensor demonstrates enhanced NO2 sensing performance. The detection range of the sensor is from 200 ppb to 100 ppm. For interfering gases such as CO, H2S, NH3, ethanol, toluene, and xylene, the sensor shows good selectivity. At the optimal operating temperature of 160 oC, the sensor response is 37.86% to 10 ppm NO2. At the same time, the sensor shows good response and recovery characteristics, with response and recovery time of 158 s and 738 s respectively. These enhanced sensing performances should be attributed to rich lattice oxygen with chemical activity induced by the hierarchical structure. The route of structure-induced lattice oxygen to improve sensing performance could provide some new ideas for the synthesis of high-performance composite sensing materials.

Enhanced NO2 Gas Sensing Performance by Hierarchical CuO-Co3O4 Spheres

Abstract: Composite sensing materials with complex hierarchical structures exhibit better performance in chemiresistive sensors due to rich defects induced by the hierarchical structures. Herein, the hierarchical spheres assembled by CuO-Co3O4 nanowires were successfully prepared via the hydrothermal and sintering procedure. SEM, TEM, and XRD results revealed that the hierarchical structure was controllably constructed by adjusting the composition of the CuO and Co3O4. XPS confirmed that the hierarchical structure could promote the enrichment of lattice oxygen. The CuO-Co3O4 composite with hierarchical structure-based sensor demonstrates enhanced NO2 sensing performance. The detection range of the sensor is from 200 ppb to 100 ppm. For interfering gases such as CO, H2S, NH3, ethanol, toluene, and xylene, the sensor shows good selectivity. At the optimal operating temperature of 160 oC, the sensor response is 37.86% to 10 ppm NO2. At the same time, the sensor shows good response and recovery characteristics, with response and recovery time of 158 s and 738 s respectively. These enhanced sensing performances should be attributed to rich lattice oxygen with chemical activity induced by the hierarchical structure. The route of structure-induced lattice oxygen to improve sensing performance could provide some new ideas for the synthesis of high-performance composite sensing materials.

Searches for Gravitational Waves from Known Pulsars at Two Harmonics in the Second and Third LIGO-Virgo Observing Runs

Abstract: We present a targeted search for continuous gravitational waves (GWs) from 236 pulsars using data from the third observing run of LIGO and Virgo (O3) combined with data from the second observing run (O2). Searches were for emission from the $l=m=2$ mass quadrupole mode with a frequency at only twice the pulsar rotation frequency (single harmonic) and the $l=2, m=1,2$ modes with a frequency of both once and twice the rotation frequency (dual harmonic). No evidence of GWs was found so we present 95\% credible upper limits on the strain amplitudes $h_0$ for the single harmonic search along with limits on the pulsars' mass quadrupole moments $Q_{22}$ and ellipticities $\varepsilon$. Of the pulsars studied, 23 have strain amplitudes that are lower than the limits calculated from their electromagnetically measured spin-down rates. These pulsars include the millisecond pulsars J0437\textminus4715 and J0711\textminus6830 which have spin-down ratios of 0.87 and 0.57 respectively. For nine pulsars, their spin-down limits have been surpassed for the first time. For the Crab and Vela pulsars our limits are factors of $\sim 100$ and $\sim 20$ more constraining than their spin-down limits, respectively. For the dual harmonic searches, new limits are placed on the strain amplitudes $C_{21}$ and $C_{22}$. For 23 pulsars we also present limits on the emission amplitude assuming dipole radiation as predicted by Brans-Dicke theory.

Implementation of hand hygiene in health-care facilities: results from the WHO Hand Hygiene Self-Assessment Framework global survey 2019

Abstract: Hand hygiene is at the core of effective infection prevention and control (IPC) programmes. 10 years after the development of the WHO Multimodal Hand Hygiene Improvement Strategy, we aimed to ascertain the level of hand hygiene implementation and its drivers in health-care facilities through a global WHO survey.From Jan 16 to Dec 31, 2019, IPC professionals were invited through email and campaigns to complete the online Hand Hygiene Self-Assessment Framework (HHSAF). A geospatial clustering algorithm selected unique health-care facilities responses and post-stratification weighting was applied to improve representativeness. Weighted median HHSAF scores and IQR were reported. Drivers of the HHSAF score were determined through a generalised estimation equation.3206 unique responses from 90 countries (46% WHO Member States) were included. The HHSAF score indicated an intermediate hand hygiene implementation level (350 points, IQR 248-430), which was positively associated with country income level and health-care facility funding structure. System Change had the highest score (85 points, IQR 55-100), whereby alcohol-based hand rub at the point of care has become standard practice in many health-care facilities, especially in high-income countries. Institutional Safety Climate had the lowest score (55 points, IQR 35-75). From 2015 to 2019, the median HHSAF score in health-care facilities participating in both HHSAF surveys (n=190) stagnated.Most health-care facilities had an intermediate level of hand hygiene implementation or higher, for which health-care facility funding and country income level were important drivers. Availability of resources, leadership, and organisational support are key elements to further improve quality of care and provide access to safe care for all.WHO, Geneva University Hospitals and Faculty of Medicine, and WHO Collaborating Center on Patient Safety, Geneva, Switzerland.

Embryo-scale epithelial buckling forms a propagating furrow that initiates gastrulation

Abstract: Cell apical constriction driven by actomyosin contraction forces is a conserved mechanism during tissue folding in embryo development. While much is now understood of the molecular mechanism responsible for apical constriction and of the tissue-scale integration of the ensuing in-plane deformations, it is still not clear if apical actomyosin contraction forces are necessary or sufficient per se to drive tissue folding. To tackle this question, we use the Drosophila embryo model system that forms a furrow on the ventral side, initiating mesoderm internalization. Past computational models support the idea that cell apical contraction forces may not be sufficient and that active or passive cell apico-basal forces may be necessary to drive cell wedging leading to tissue furrowing. By using 3D computational modelling and in toto embryo image analysis and manipulation, we now challenge this idea and show that embryo-scale force balance at the tissue surface, rather than cell-autonomous shape changes, is necessary and sufficient to drive a buckling of the epithelial surface forming a furrow which propagates and initiates embryo gastrulation.

The ‘bioeconomics vs bioeconomy’ debate: Beyond criticism, advancing research fronts

Abstract: The case for solving the environmental crisis through a bioeconomic transition is gaining momentum. However, aims and content of such a transition remain unclear, as this could target an economic sector, the analysis of economic activities, or society as a whole, especially in its relationship to the biosphere. This last possible object of transition – society – is where values, models and goals come into conflict. This study examines this controversy through the lens of the ‘bioeconomics vs bioeconomy’ debate, in which proponents of bioeconomics have raised an arsenal of critiques against what they consider the simplistic promises of public and private promoters of the bioeconomy. We discuss these critiques, which are mainly macro in scale and/or narrative-centred, and argue for a complementary research effort that supports transition initiatives. This research could take place on three fronts: better understanding bioeconomic systems, evaluating bioeconomic transitions, and identifying how to implement these transitions.

FFT-PEEC: A Fast Tool From CAD to Power Electronics Simulations

Abstract: A fast and general partial element equivalent circuit (PEEC) method based on the fast Fourier transform (FFT) is proposed for the first time. The numerical tool only requires common CAD data input files (e.g., $.\text{stl}$ format), then the discretization process is performed automatically by means of a fast voxelization technique based on ray intersection, thus, drastically reducing the human effort required to setup the model. The method allows for considering at the same time inductive and capacitive effects, and is focused on power electronics applications where propagation effects can be neglected, whereas all the other electromagnetic phenomena are considered. Specifically, the proposed method is particularly suited for problems where both electric and magnetic fields are equally important and, therefore, quasistatic approximations do not apply. An ad-hoc preconditioner which significantly speeds-up the solver is also proposed and, thanks to the FFT, both memory and computation time are significantly reduced, without the need of applying data compression. Both linear and nonlinear materials are considered by the proposed FFT-PEEC method. Sample implementation of the method is made publicly available.

Interactions of time delay and spatial diffusion induce the periodic oscillation of the vegetation system

Abstract: <p style='text-indent:20px;'>Empirical data exhibit a common phenomenon that vegetation biomass fluctuates periodically over time in ecosystem, but the corresponding internal driving mechanism is still unclear. Simultaneously, considering that the conversion of soil water absorbed by roots of the vegetation into vegetation biomass needs a period time, we thus introduce the conversion time into Klausmeier model, then a spatiotemporal vegetation model with time delay is established. Through theoretical analysis, we not only give the occurence conditions of stability switches for system without and with diffusion at the vegetation-existence equilibrium, but also derive the existence conditions of saddle-node-Hopf bifurcation of non-spatial system and Hopf bifurcation of spatial system at the coincidence equilibrium. Our results reveal that the conversion delay induces the interaction between the vegetation and soil water in the form of periodic oscillation when conversion delay increases to the critical value. By comparing the results of system without and with diffusion, we find that the critical value decreases with the increases of spatial diffusion factors, which is more conducive to emergence of periodic oscillation phenomenon, while spatial diffusion factors have no effects on the amplitude of periodic oscillation. These results provide a theoretical basis for understanding the spatiotemporal evolution behaviors of vegetation system.</p>

Hygromechanics of softwood cellulosic nanocomposite with intermolecular interactions at fiber-matrix interface investigated with molecular dynamics

Abstract: Intermolecular interactions at the fiber-matrix interface strongly affect the hygromechanical behavior and overall mechanical performance of hydrophilic cellulosic nanocomposites. The mechanics of a model interface consisting of cellulose and galactoglucomannan, inspired by the natural material wood, is investigated by molecular simulations over the full hydration range. With the increment of moisture content, the composite swells anisotropically and non-monotonically with an initial shrinkage. The interphase, a 1–2 nm thick region of matrix strongly influenced by the fiber, shows features of enrichment and ordered structure distinct from bulk. Pulling tests reveal the interfacial shear strength as a function of moisture content. The stick-slip behavior is explained by the strong correlation between the number of hydrogen bonds and the interfacial shear stress, suggesting the force rendered by a single hydrogen bond to be ∼140 pN. These insights shed light on the mechanics of interface and interphase, a topic of less attention yet critical for understanding the mechanical performance of fiber-reinforced composites.