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Cleaner steelmaking using biomass: A novel ironmaking process
No full textInternational audienceThe iron-and steelmaking industry contributes significantly to greenhouse gas emissions because steel is produced in large quantities, and fossil coal is used as the energy source and reducing agent for this production. Substituting biogenic carbon from biomass for fossil coal could drastically reduce the contribution of the ironand steelmaking industry to global warming. Based on biomass, we propose a novel, breakthrough ironmaking process (BIORED), in which charcoal lumps and iron ore pellets are loaded at the top of a shaft reactor. CO, the reducing agent that converts iron oxide ore to metallic iron, is produced in situ by charcoal gasification. The exhaust gas mixture (CO-CO 2 ) is recycled for CO reuse and energy savings. The feasibility of such a process was investigated following a modeling approach that involves laboratory experiments. The results show that charcoal is devolatilized at the top and gasified at the bottom, whereas iron ore is reduced along the shaft, reaching a satisfactory metallization degree at the bottom. A specific experimental protocol was designed for the validation of the model, and the experimental results agreed with the computed results. The environmental performance of the BIORED-based steelmaking route was compared with that of the conventional route via life cycle assessment. The new route emits up to 8 times less CO 2 and has lower impacts on most of the other environmental categories
Weakly-sparse and strongly flip-flat classes of graphs are uniformly almost-wide
No full textInternational audienceIn this work we take a step towards characterising strongly flip-flat classes of graphs. Strong flip-flatness appears to be the analogue of uniform almost-wideness in the setting of dense classes of graphs. We prove that strongly flip-flat classes of graphs that are weakly sparse are indeed uniformly almost-wide
Epigenetic markers of lithium response in bipolar disorder: optimization of a Methylation-Sensitive High-Resolution Melting assay (MS-HRM) and relevance in combination with clinical factors
No full textInternational audienceLithium (Li) is the most frequently recommended first-line treatment in bipolar disorder (BD). Nevertheless, response to Li is highly variable between individuals and no clinical or biological biomarkers have been consistently associated to long-term response. We previously identified 3 differentially methylated regions (DMRs) that discriminated good from non-responders to Li. In this study, we validated 4 additional DMRs using Methylation Specific High-Resolution Melting (MS-HRM), a PCR-based low-cost method with easy transferability from bench to bedside. In 61 individuals with BD-I, we investigated associations between these 7 DMRs and Li response, alone or combined with demographic and clinical variables. Using 7 DMRs and 6 demographic and clinical variables, 90 % of the BD-I individuals were correctly classified according to their response status (AUC = 0.95). In particular, combining DNA methylation markers with clinical predictors improved the identification of non-responders (83 % correctly classified). This epigenetic signature might be useful in clinical practice especially as it is imperative to avoid exposing individuals to Li if they have a very low likelihood of response
The fluctuations of the outdoor temperature as a source of immaterial entropy production in energy conversion processes
No full textInternational audienceIn fluctuating outdoor conditions, adding a heat storage system between the energy conversion processes and the outdoor air, and employing it appropriately, helps to reduce primary energy consumption and, consequently, total entropy production. This combination is studied numerically for a heat pump heating a house in real winter conditions. Three strategies for using the heat storage are compared. One strategy uses no prediction of the upcoming outdoor temperature. The second assumes that it is at its lowest around dawn. The third uses exact prediction over 24 h. With reasonably sized heat storage, the first strategy reduces energy consumption by 2-4%, whereas the third reduces it by 5-7% thanks to using the heat storage at the coldest time of the day. The second strategy is almost as efficient, yet much more realistic.The entropy analysis of processes in fluctuating outdoor temperatures is conducted using the absolute upper limit of performance (i.e. the highest possible outdoor temperature) as a reference point. The entropy balance derived in this way reveals an unusual entropy production involving the outdoor temperature and the heat flux exchanged with the outdoor air. This production is not physical but immaterial. Its magnitude (up to 30% of the total entropy production) depends on the chosen strategy, which is an immaterial characteristic of the heat storage system. The results and formal derivations demonstrate that the entropy budget would be incomplete without this immaterial term.This robust analysis leads to a systemic interpretation of the role of heat storage.</p
(NHC-olefin)-nickel(0) nanoparticles: an efficient and selective catalyst for hydrogenation reactions at low temperature and pressure
No full textInternational audienceThe reduction of a NHC-cinnamyl nickel(II) organometallic complex through the use of different MeMgBr or MeMgCl reagents led to two types of NHC-olefin-coordinated nickel nanoparticles. Both of these unsupported nickel-NHC based nanomaterials behaved under hydrogen pressure as effective and selective catalysts operating at low temperature (≤ 80 °C), pressure (≤ 20 bar) and loading (≤ 6 mol%) for the reductions of broad scopes of alkenes, alkynes, imines and heterocycles, including a challenging tetra-substituted alkene. Among these two nickel-NHC nanocatalysts, the one generated with MeMgCl showed a significant high catalytic activity with high yields and could stand the comparison with Raney nickel and state-of-the-art nickel nanocatalysts. For example, by studying the hydrogenation of 1-phenylcyclohexene in ethanol at 60°C under 10 bar of H2, 3 mol% of this catalyst achieved the reaction within a single hour on a 5 mmol / 0.8 g substrate scale with a yield of 96%, a turnover number (TON) of 32 and a turnover frequency (TOF) of 32. Characterizations confirmed the coordination of the NHC-olefin ligands to the nickel nanoparticles, the reduced state of the nickel and the (poly-)crystallinity of the nanoparticles
Fast in-place accumulation
No full textInternational audienceThis paper deals with simultaneously fast and in-place algorithms for formulae where the result has to be linearly accumulated: some output variables are also input variables, linked by a linear dependency. Fundamental examples include the in-place accumulated multiplication of polynomials or matrices, C += AB (that is with only O(1) extra space). The difficulty is to combine in-place computations with fast algorithms: those usually come at the expense of (potentially large) extra temporary space, but with accumulation the output variables are not even available to store intermediate values. We first propose a novel automatic design of fast and in-place accumulating algorithms for any bilinear formulae (and thus for polynomial and matrix multiplication) and then extend it to any linear accumulation of a collection of functions. For this, we relax the in-place model to any algorithm allowed to modify its inputs, provided that those are restored to their initial state afterwards. This allows us to ultimately derive unprecedented in-place accumulating algorithms for fast polynomial multiplications and for Strassen-like matrix multiplications.We then consider the simultaneously fast and in-place computation of the Euclidean polynomial modular remainder R(X) ≡ A(X) mod B(X). Fast algorithms for this usually also come at the expense of a linear amount of extra temporary space. In particular, they require one to first compute and store the whole quotient Q(X) such that A = BQ+R. We here propose an *in-place* algorithm to compute the remainder only. If A and B have respective degree m+n and n, and M(k) denotes the complexity of a (not-in-place) algorithm to multiply two degree-k polynomials, our algorithm uses at most O((n/m) M(m) log(m)) arithmetic operations. In this particular case this is a factor log(n) more than the not-in-place algorithm. But if M(n) = Θ(n^{1+ε}) for some ε>0, then our algorithms do match the not-in-place complexity bound of O((n/m) M(m)). We also propose variants that compute – still in-place and with the same kind of complexity bounds – the over-place remainder A(X) ≡ A(X) mod B(X), the accumulated remainder R(X) += A(X) mod B(X) and the accumulated modular multiplication R(X) += A(X)C(X) mod B(X), that is multiplication in a polynomial extension of a finite field.To achieve this, we develop techniques for Toeplitz matrix operations, for generalized convolutions, short product and power series division and remainder whose output is also part of the input
Infinitely many saturated travelling waves for a degenerate Fisher-KPP equation not in divergence form
No full textInternational audienceWe consider an epidemic model with distributed-contacts. When the contact kernel concentrates, one formally reaches a very degenerate Fisher-KPP equation with a diffusion term that is not in divergence form. We make an exhaustive study of its travelling waves. For every admissible speed, there exist not only a unique non-saturated (smooth) wave but also infinitely many saturated (sharp) ones. Furthermore their tails may differ from what is usually expected. These results are thus in sharp contrast with their counterparts on related models
City Makers and the Politics of Urban Diversity Governance. Comparative Approaches from Europe and Asia
No full textInternational audienceThis open access book examines the rising challenges of managing diversity in European and Asian cities. It spotlights the roles of varied city makers - from urban leaders to migrant communities and civil society activists - in negotiating and transforming their city’s diversity governance. The book brings together the contributions of urban studies and migration studies scholars, which offer rich empirical analyses on various European and Asian cities, such as Paris, Singapore, Barcelona, and Guangzhou. Adopting a comparative lens, the book presents a decentered understanding of 'super-diverse' cities, examining shifts in urban policy-making within different geographical contexts, with distinct patterns of migration and diversification. By advancing urban comparison as a research tool, it contributes to the contemporary discussions on the local turn of migration and diversity policies
Direct numerical simulation of bubble cavitation at a wall in micro-gravity
No full textInternational audienceCryogenic tanks used in space applications face challenges due to propellant management, among which is phase change induced by a depressurization. Pool cavitation at the wall in pure methane under micro-gravity conditions is investigated, analyzing its impact on vapor creation and wall heat transfer. A compressible two-phase flow solver, including phase change and conjugate heat transfer, is used. After a validation with available experimental data for single bubble cavitation at the wall in micro-gravity, numerical simulations varying the depressurization amplitude and rate are carried out. Three distinct growth phases are put into evidence: an expansion-controlled phase, occurring within the depressurization time frame, and a transition phase leading to a diffusion-controlled growth where the bubble behaves as in a superheated liquid at constant pressure. Results allow to show the impact that compressible effects have on the phenomenon, and to demonstrate the importance of accounting for a nano-region at the contact line, strongly affecting the wall heat transfer
Modeling and correction of sensitivity thresholds determined by best EstimateThreshold (BET)
No full textInternational audienceThe r-Alternative Forced Choice (r-AFC) test is a test of discrimination in which the subject is presented with three samples, one of which is a test sample containing a nominated stimulus (test sample), the other being references. The subject is instructed to indicate the test sample. Taste and odor sensitivity thresholds are frequently determined using successive r-AFC tests with stimuli in increasing concentrations. The Best Estimate Threshold (BET) method consists in using successive 3-AFC with increasing concentrations to estimate sensitivity threshold. Then, the threshold is estimated using the geometrical mean of the highest concentration that caused an error and the concentration directly below it. However, a subject who feels no difference between the samples may give a correct answer by chance. It leads to consequent potential bias in the determination of the sensitivity thresholds. This paper aims to formalize and model the thresholds obtained in successive r-AFC in order to quantify the errors inherent in such protocols. It establishes that, when you assumed that the distribution of the true sensitivity threshold is known in the population, the threshold obtained by r-AFC can be modelled with a variable following a specific probability law. This paper presents the theory of this model, then illustrate it with simulations and application on a real dataset. An R package dedicated to these analyses, AFCR, was also created and is available on github (https://github.com/ChemoSens/AFCR). Therefore, sensory scientists could use the package as a help to set up their sensory protocol or-to analyze their own data