Utilisation de l'expérience de drainage à pas de pression multiples pour la détermination des fonctions hydrauliques du sol par la méthode inverse : résultats expérimentaux

La méthode de drainage à pas de pression multiples, combinée avec la méthode inverse, permet la détermination des fonctions hydrauliques du sol (têta(h) et K(h)) simultanément. Cependant, le choix des fonctions décrivant têta(h) et K(h) du sol est d'une importance capitale dans cette méthode. Les résultats expérimentaux montrent que le modèle de CAMPBELL (1974) dans sa version améliorée par HUTSON et CASS (1987) permet une description raisonnable du processus du drainage en fonction du temps et correspondant à des pas de pression croissants. Les courbes de rétention d'eau déduites des paramètres optimisés par la méthode inverse ont les mêmes allures que celles déterminées par la méthode standard (bac de sable et cellules à basses et hautes pressions). Ces résultats sont plus représentatifs de la réalité lorsque les paramètres têta(s) et K(s) sont fixes et égaux aux valeurs expérimentales, avec une précision sensiblement la même dans les cas d'optimisation, où têta(s) est fixe et têta(s) et K(s) fixes et égaux aux valeurs expérimentales; le premier cas où seulement le paramètre têta(s) est fixe est suggéré (il y a moins de paramètres à mesurer). (Résumé d'auteur

Utilisation de l'expérience de drainage à pas de pression multiples pour la détermination des fonctions hydrauliques du sol par la méthode inverse : présentation et évaluation de la méthode

L'optimisation des paramètres des fonctions décrivant les propriétés hydrauliques du sol têta(h) et K(h), basée sur les résultats de l'expérience de drainage interne à pas de pression multiples est une méthode prometteuse. En effet, cette dernière fournit suffisamment d'informations sur les propriétés hydrauliques essentielles d'un sol. Le modèle utilisé pour décrire les relations entre la teneur en eau volumique têta et la pression de l'eau h, d'une part, et entre la conductivité hydraulique K et h, d'autre part, est celui de CAMPBELL (1974) dans sa version améliorée par HUTSON et CASS (1987). Les résultats montrent que ce modèle décrit raisonnablement le processus du drainage en fonction du temps correspondant à des pas de pressions croissantes. La solution de la méthode d'identification des paramètres est unique tant que les valeurs assignées aux paramètres au départ sont proches (plus ou moins 20 %) de celles du sol étudié. L'effet d'une erreur expérimentale allant jusqu'à 10 % n'est pas significatif pour les résultats des paramètres optimisés. (Résumé d'auteur

The transformed-stationary approach: A generic and simplified methodology for non-stationary extreme value analysis

Statistical approaches to study extreme events require, by definition, long time series of data. In many scientific disciplines, these series are often subject to variations at different temporal scales that affect the frequency and intensity of their extremes. Therefore, the assumption of stationarity is violated and alternative methods to conventional stationary extreme value analysis (EVA) must be adopted. Using the example of environmental variables subject to climate change, in this study we introduce the transformed-stationary (TS) methodology for non-stationary EVA. This approach consists of (i) transforming a non-stationary time series into a stationary one, to which the stationary EVA theory can be applied, and (ii) reverse transforming the result into a non-stationary extreme value distribution. As a transformation, we propose and discuss a simple time-varying normalization of the signal and show that it enables a comprehensive formulation of non-stationary generalized extreme value (GEV) and generalized Pareto distribution (GPD) models with a constant shape parameter. A validation of the methodology is carried out on time series of significant wave height, residual water level, and river discharge, which show varying degrees of long-term and seasonal variability. The results from the proposed approach are comparable with the results from (a) a stationary EVA on quasi-stationary slices of non-stationary series and (b) the established method for non-stationary EVA. However, the proposed technique comes with advantages in both cases. For example, in contrast to (a), the proposed technique uses the whole time horizon of the series for the estimation of the extremes, allowing for a more accurate estimation of large return levels. Furthermore, with respect to (b), it decouples the detection of non-stationary patterns from the fitting of the extreme value distribution. As a result, the steps of the analysis are simplified and intermediate diagnostics are possible. In particular, the transformation can be carried out by means of simple statistical techniques such as low-pass filters based on the running mean and the standard deviation, and the fitting procedure is a stationary one with a few degrees of freedom and is easy to implement and control. An open-source MATLAB toolbox has been developed to cover this methodology, which is available at https://github.com/menta78/tsEva/ (Mentaschi et al., 2016)

Trends in heat and cold wave risks for the Italian Trentino-Alto Adige region from 1980 to 2018

Heat waves (HWs) and cold waves (CWs) can have considerable impact on people. Mapping risks of extreme temperature at local scale, accounting for the interactions between hazard, exposure, and vulnerability, remains a challenging task. In this study, we quantify risks from HWs and CWs for the Trentino-Alto Adige region of Italy from 1980 to 2018 at high spatial resolution. We use the Heat Wave Magnitude Index daily (HWMId) and the Cold Wave Magnitude Index daily (CWMId) as the hazard indicators. To obtain HWs and CW risk maps we combined the following: (i) occurrence probability maps of the hazard obtained using the zero-inflated Tweedie distribution (accounting directly for the absence of events for certain years), (ii) normalized population density maps, and (iii) normalized vulnerability maps based on eight socioeconomic indicators. The methodology allowed us to disentangle the contributions of each component of the risk relative to total change in risk. We find a statistically significant increase in HW hazard and exposure, while CW hazard remained stagnant in the analyzed area over the study period. A decrease in vulnerability to extreme temperature spells is observed through the region except in the larger cities where vulnerability increased. HW risk increased in 40 % of the region, with the increase being greatest in highly populated areas. Stagnant CW hazard and declining vulnerability result in reduced CW risk levels overall, except for the four main cities where increased vulnerability and exposure increased risk levels. These findings can help to steer investments in local risk mitigation, and this method can potentially be applied to other regions where there are sufficient detailed data.</p

Muscle Fatigue Analysis Using OpenSim

In this research, attempts are made to conduct concrete muscle fatigue analysis of arbitrary motions on OpenSim, a digital human modeling platform. A plug-in is written on the base of a muscle fatigue model, which makes it possible to calculate the decline of force-output capability of each muscle along time. The plug-in is tested on a three-dimensional, 29 degree-of-freedom human model. Motion data is obtained by motion capturing during an arbitrary running at a speed of 3.96 m/s. Ten muscles are selected for concrete analysis. As a result, the force-output capability of these muscles reduced to 60%-70% after 10 minutes' running, on a general basis. Erector spinae, which loses 39.2% of its maximal capability, is found to be more fatigue-exposed than the others. The influence of subject attributes (fatigability) is evaluated and discussed

An integrated approach for assessing flood impacts due to future climate and socio-economic conditions and the scope of adaptation in Europe

European Commission Seventh Framework Programm

The Wellesley News (06-10-1957)

https://repository.wellesley.edu/wcnews/1157/thumbnail.jp

Multisectoral partnerships and risk information

Knowing the increasing trends in natural disasters and losses, it is imperative to take action on disaster risks to improve resilience of European societies to natural hazards. The main goal, therefore, of the ENHANCE project is to develop and analyse innovative ways to manage natural hazard risks. The key is to develop new multi-sectoral partnerships (MSPs) that aim at reducing or redistributing risk, and increase resilience of societiesinfo:eu-repo/semantics/publishedVersio

African heritage sites threatened as sea-level rise accelerates

The African coast contains heritage sites of ‘Outstanding Universal Value’ that face increasing risk from anthropogenic climate change. Here, we generated a database of 213 natural and 71 cultural African heritage sites to assess exposure to coastal flooding and erosion under moderate (RCP 4.5) and high (RCP 8.5) greenhouse gas emission scenarios. Currently, 56 sites (20%) are at risk from a 1-in-100-year coastal extreme event, including the iconic ruins of Tipasa (Algeria) and the North Sinai Archaeological Sites Zone (Egypt). By 2050, the number of exposed sites is projected to more than triple, reaching almost 200 sites under high emissions. Emissions mitigation from RCP 8.5 to RCP 4.5 reduces the number of very highly exposed sites by 25%. These findings highlight the urgent need for increased climate change adaptation for heritage sites in Africa, including governance and management approaches, site-specific vulnerability assessments, exposure monitoring, and protection strategies