Regionalization of Flood Data Using Probability Distributions and Their Parameters

The U. S. Geological survey recently used the method of residuals to delineate seven flood regions for the State of Kentucky. As an alternative approach, the FASTCLUS clustering procedure of the Statistical Analysis system (SAS) is used in this study to delineate five to six cluster regions in conjunction with statistical properties of the AMF series, like the coefficient of variation as estimated using method of L-moments, LCV, the parameters of the EVl and GEV flood frequency distributions, and the specific mean annual flood, QSP. For both cluster and USGS flood regions, regionalized flood frequency growth curves are developed and their performance evaluated using Monte Carlo simulation techniques. Flood regions are.then evaluated and compared ·using trends in the hydrological characteristics of important.variables, performance of the regionalized flood frequency growth curves, discriminant analysis and regression equations relating flood quantiles to watershed physical characteristics. Results show that the cluster regions are more distinguishable in terms of their flood characteristics than the USGS regions. The.regionalized flood frequency growth curves of the EVl and GEV model are more distinct for the cluster regions than the USGS regions, although their performance in terms of bias and RMSE are comparable. The standard errors associated with the regression equations, developed for predicting the EVl and GEV flood quantiles, are similar for cluster and USGS regions

Measurement of the generalized spin polarizabilities of the neutron in the low-Q2Q^2 region

International audienceUnderstanding the nucleon spin structure in the regime where the strong interaction becomes truly strong poses a challenge to both experiment and theory. At energy scales below the nucleon mass of about 1 GeV, the intense interaction among the quarks and gluons inside the nucleon makes them highly correlated. Their coherent behaviour causes the emergence of effective degrees of freedom, requiring the application of non-perturbative techniques such as chiral effective field theory1. Here we present measurements of the neutron’s generalized spin polarizabilities that quantify the neutron’s spin precession under electromagnetic fields at very low energy-momentum transfer squared down to 0.035 GeV2. In this regime, chiral effective field theory calculations2,3,4 are expected to be applicable. Our data, however, show a strong discrepancy with these predictions, presenting a challenge to the current description of the neutron’s spin properties