Statistical modeling of the space–time relation between wind and significant wave height

Many marine activities, such as designing ocean structures and planning marine operations, require the characterization of sea-state climate. This study investigates the statistical relationship between wind and sea states, considering its spatiotemporal behavior. A transfer function is established between wind fields over the North Atlantic (predictors) and the significant wave height (predictand) at three locations: southwest of the French coast (Gironde), the English Channel, and the Gulf of Maine. The developed method considers both wind seas and swells by including local and global predictors. Using a fully data-driven approach, the global predictors' spatiotemporal structure is defined to account for the non-local and non-instantaneous relationship between wind and waves. Weather types are constructed using a regression-guided clustering method, and the resulting clusters correspond to different wave systems (swells and wind seas). Then, in each weather type, a penalized linear regression model is fitted between the predictor and the predictand. The validation analysis proves the models skill in predicting the significant wave height, with a root mean square error of approximately 0.3 m in the three considered locations. Additionally, the study discusses the physical insights underlying the proposed method.</p

Intramolecular Epistasis and the Evolution of a New Enzymatic Function

Atrazine chlorohydrolase (AtzA) and its close relative melamine deaminase (TriA) differ by just nine amino acid substitutions but have distinct catalytic activities. Together, they offer an informative model system to study the molecular processes that underpin the emergence of new enzymatic function. Here we have constructed the potential evolutionary trajectories between AtzA and TriA, and characterized the catalytic activities and biophysical properties of the intermediates along those trajectories. The order in which the nine amino acid substitutions that separate the enzymes could be introduced to either enzyme, while maintaining significant catalytic activity, was dictated by epistatic interactions, principally between three amino acids within the active site: namely, S331C, N328D and F84L. The mechanistic basis for the epistatic relationships is consistent with a model for the catalytic mechanisms in which protonation is required for hydrolysis of melamine, but not atrazine

Stochastic prediction of wave impact kinematics and loads for ship appendages

International audienceA stochastic approach is implemented to address the problem of a marine structure exposed to water wave impacts. The focus is on (i) the average frequency of wave impacts, and (ii) the related probability distribution of impact kinematic variables. The wave field is assumed to be Gaussian. The seakeeping motions of the considered body are taken into account in the analysis. The coupling of the stochastic model with a water entry model is demonstrated through the case study of a foil exposed to wave impacts

Statistical modeling of the space-time relation between wind and significant wave height

Many marine activities, such as designing ocean structures and planning marine operations, require the characterization of sea state climate. This study investigates the statistical relationship between wind and sea states, considering its spatiotemporal behavior. A transfer function is established between wind fields over the North Atlantic (predictors) and the significant wave height (predictand) in a location in the Bay of Biscay off the French coast. The developed method takes into consideration both wind seas and swells by including local and global predictors. The global predictors’ spatiotemporal structure is defined to account for the non-local and non-instantaneous relationship between wind and waves, using a fully data-driven approach. Weather types are constructed using a regression guided-clustering method, and the resulting clusters correspond to different wave systems (swells and wind seas). Then, in each weather type, a penalized linear regression model is fitted between the predictor and the predictand. The validation analysis proves the model’s skill in predicting the significant wave height (RMSE = 0.27m); furthermore, the interpretability of the model is discussed

Rate law model to better understand the influence of process parameters during toluene photocatalytic degradation in indoor air conditions

International audienc

Cherry Carnival parade float, ca. 1960

Float with two white pillars travelling down Main St with three women on it. Royalty

Photocatalytic oxidation of several mixtures of indoor air pollutants by a commercialized stand-alone device

International audienc

Photocatalytic oxidation of several mixtures of indoor air pollutants by a commercialized stand-alone device

International audienc