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Des mobilités déviantes et des mobilités acceptables ? Régulation et contrôle des pratiques de mobilité des ménages modestes par les politiques environnementales
No full textInternational audienc
Shape optimization of metastable states
No full textThe definition of metastable states is an ubiquitous task in the design and analysis of molecular simulation, and is a crucial input in a variety of acceleration methods for the sampling of long configurational trajectories. Although standard definitions based on local energy minimization procedures can sometimes be used, these definitions are typically suboptimal, or entirely inadequate when entropic effects are significant, or when the lowest energy barriers are quickly overcome by thermal fluctuations. In this work, we propose an approach to the definition of metastable states, based on the shape-optimization of a local separation of timescale metric directly linked to the efficiency of a class of accelerated molecular dynamics algorithms. To realize this approach, we derive analytic expressions for shape-variations of Dirichlet eigenvalues for a class of operators associated with reversible elliptic diffusions, and use them to construct a local ascent algorithm, explicitly treating the case of multiple eigenvalues. We propose two methods to make our method tractable in high-dimensional systems: one based on dynamical coarse-graining, the other on recently obtained low-temperature shape-sensitive spectral asymptotics. We validate our method on a benchmark biomolecular system, showcasing a significant improvement over conventional definitions of metastable states
Deriving Origin-Destination matrices from Aggregated Mobile Phone Data : a new insight on people's mobility
No full textInternational audienceTraditional household travel surveys are the main source of information to feed the transport models used for planning and evaluating transport policies, services and infrastructures. To bring complementary information, passive data such as Mobile Phone Data (MPD) have been considered as promising, as they are collected continuously and on larger samples. Unlike individual MPD, aggregated MPD avoids privacy concerns and can be collected over long periods of time, but it only provides the number of people in a given area during a given time interval and requires further processing for mobility management. This paper therefore proposes a theoretical framework for generating OD matrices from AMPD, using methods derived from traffic counts, thanks to an innovative analogy between these two data sources. To ensure proper data transformation, several algorithms are tested, first in a simulated case and then using real data in Rouen, France. The results demonstrate the potential of AMPD to generate high quality OD matrices on a continuous basis, coherent with expected values in the simulated case and the results of a household survey in the experimental case
Mind the gap: the interplay between genes and neighbourhood context on educational achievement
No full textInternational audienceThis article expands on previous research on gene-environment (GxE) effects on socio-economic status, by stepping beyond the family dimension and exploring how the neighbourhood context interacts with education linked genes in influencing educational achievement. While some evidence suggests that genetic links to education are more fully expressed in high socio-economic status families, other findings indicate that individuals with lower genetic predisposition for education benefit more from high socio-economic contexts. We argue that the neighbourhood environment may also play a role on the relationship between genes and education-related outcomes. We find evidence that living in socioeconomically advantaged neighbourhoods contributes to closing the gap between individuals characterized by high and low genetic predispositions towards educational achievement, with this effect primarily driven by influences on academic motivation, rather than cognitive skills. These findings emphasize that environmental contexts can shape the unfolding of genetic endowment and point to an important role of the neighbourhood in compensating for pre-existing disadvantage, thus contributing to improve chances of upward social mobility and to limit the reproduction of social inequalities in education over time
The Impact of Transience in the Interaction between Orographic Gravity Waves and Mean Flow
No full textInternational audienceAbstract A Lagrangian gravity wave parameterization [Multiscale Gravity Wave Model (MS-GWaM)] that allows for fully transient wave–mean-flow interaction and horizontal propagation is applied to orographic gravity waves for the first time. Both linear and nonlinear mountain waves are modeled in idealized simulations within the pseudoincompressible flow solver PincFlow. Two-dimensional flows over monochromatic orographies are considered, using MS-GWaM either in its fully transient implementation or in a steady-state implementation that represents classic mountain-wave parameterizations. Comparisons of wave-resolving simulations (not using MS-GWaM) and coarse-resolution simulations (using MS-GWaM) show that allowing for transience leads to a significantly more accurate forcing of the resolved mean flow. The parameterization is able to reproduce the transient forcing of linearly generated mountain waves that slowly propagate upward, in contrast to the instantaneous distribution of wave energy in classic parameterizations. At high altitudes, wave breaking induces a wind reversal that is captured by the transient parameterization but inhibited in steady-state simulations, due to the assumption of critical level formation. This shows that transience can have a substantial impact on the interaction between mountain waves and mean flow
Political Brinkmanship and Compromise
No full textWe study how do-or-die threats ending negotiations affect gridlock and welfare when twoopposing parties bargain. Failure to agree on a deal in any period implies a continuation of thenegotiation. However, under brinkmanship, agreement failure in any period may precipitate a crisis with a small chance. In equilibrium, such brinkmanship threats improve the probability of an agreement, but also increase the risk of crisis. Brinkmanship reduces welfare when one might think it is most needed: severe gridlock. In this case, despite this global welfare loss, a party has incentives to use brinkmanship strategically to obtain a favorable bargaining positio
Closing models, opening debates: theoretical uncertainty and the low-carbon transition
No full textQ50, C68, C5This study addresses a critical oversight in the Energy-Economy-Environment (E3) modeling landscape, where standard neoclassical assumptions-such as the causal primacy of savings over investment-have been taken as foundational. While the broader Computable General Equilibrium (CGE) field has rigorously examined the impact of "closure" choices on model outcomes, this issue has yet to be meaningfully integrated into E3 modeling, which is surprising given its implications for decarbonization policy. By constructing a stylized KLEM (Capital-Labour-Energy-Material) model and varying closure assumptions across pollution reduction targets, this work illustrates how E3 outcomes are highly contingent on model closure. These results suggest that the prevalent reliance on conventional neoclassical assumptions may produce an overly uniform view of decarbonization pathways, obscuring the potential diversity of policy effects. The study advocates for a systematic re-evaluation of closure options in E3 modeling to more accurately represent the complexity of the transition
El Niño and droughts in Southeast Asia: A stochastic-chaotic modeling approach
No full textInternational audienceThe El Niño-Southern Oscillation (ENSO) significantly impacts global weather, with strong El Niño events often linked to prolonged dry conditions in Southeast Asia. While some high-impact El Niño events have coincided with prolonged dry conditions, leading to droughts, the underlying causal mechanisms remain complex and inconsistent. In this study, we develop a minimal, datadriven model to quantify the conditions under which ENSO events amplify prolonged dry conditions risk in Southeast Asia. Unlike correlation-based approaches, our model identifies thresholds in sea surface temperatures and atmospheric patterns that increase the probability of prolonged dry conditions, highlighting both seasonal timing and intensity as critical factors. Our results show that when ENSO-induced anomalies exceed specific temperature and atmospheric thresholds, prolonged dry conditions probability rises significantly, aligning with observed historical droughts. Additionally, the model reveals periods where this link weakens due to competing regional climate factors, suggesting that certain conditions mitigate the typical ENSO-prolonged dry conditions connection. These findings provide a more nuanced understanding of ENSO-driven prolonged dry conditions variability, offering a probabilistic predictive framework with potential applications in climate adaptation, agricultural planning, and regional resource management. I. INTRODUCTIONEl Niño-Southern Oscillation (ENSO) is a naturally occurring climate phenomenon that affects weather patterns and precipitation across the globe [1]. ENSO is characterized by the cyclic warming and cooling of the tropical Pacific Ocean, which can lead to a wide range of impacts on global climate. El Niño (i.e. the positive phase of ENSO) which occurs when the sea surface temperature in the central and eastern Pacific is warmer than normal, is one of the most documented phases of ENSO [2].</div
A note on the complexity of the picker routing problem in multi-block warehouses and related problems
No full textInternational audienceThe Picker Routing Problem (PRP), which consists of finding a minimum-length tour between a set of storage locations in a warehouse, is one of the most important problems in the warehousing logistics literature. Despite its popularity, the tractability of the PRP in multi-block warehouses remains an open question. This technical note aims to fill this research gap by establishing that the problem is strongly NP-hard. As a corollary, the complexity status of other related problems is settled
Inequality Bands: Seventy-five years of measuring income inequality in Latin America
No full textInternational audienceDrawing on a comprehensive compilation of quantile shares and inequality measures for 34 countries, including over 5,600 estimated Gini coefficients, we review the measurement of income inequality in Latin America and the Caribbean over the last seven decades. We find that there is quite a bit of uncertainty regarding inequality levels for the same country/year combinations. Differences in inequality levels estimated from household surveys alone are present but they derive from differences in the construction of the welfare indicator, the unit of analysis, or the treatment of the data. With harmonized household surveys, the discrepancies are quite small. The range, however, expands significantly when to correct for undercoverage and underreporting especially at the top of the distribution inequality estimates come from some combination of surveys and administrative tax data. The range increases even further when survey-based income aggregates are scaled to achieve consistency not only with tax registries but with National Accounts. Since no single method to correct for underreporting at the top is fully convincing at present, we are left with (often wide) ranges, or bands, of inequality as our best summaries of inequality levels. Reassuringly, however, the dynamic patterns are generally robust across the bands. Although the evidence roughly until the 1970s is too fragmentary and difficult to compare, clearer patterns emerge for the last fifty years. The main feature is a broad inverted U curve, with inequality rising in most countries prior to and often during the 1990s, and falling during the early 21st century, at least until around 2015, when trends appear to diverge across countries. This pattern is broadly robust but features considerable variation in timing and magnitude depending on the country