Monitoring early-age acoustic emission of cement paste and fly ash paste

In this study, a combined approach of several monitoring techniques was applied to allow correlations between the AE activity and related processes such as shrinkage and settlement evolution, capillary pressure and temperature development in fresh cementitious media. AE parameters related to frequency, energy, and cumulative activity which exhibit sensitivity to the particle size distribution of cement paste are compared with inert fly ash (FA) leading to isolation of the mechanical sources from the chemical ones. Characterization of the origin of different processes occurring in cement paste during hydration is complex. Although acoustic emission (AE) monitoring has been used before, a qualitative relation between the microstructural formation or other early-age processes and the number or parameters of AE signals has not been established. The high sensitivity of AE enables the recording of elastic waves within the cementitious material, allowing the detection of even low-intensity activities

Monitoring of fresh concrete curing by combined NDT techniques

Ensuring the quality of fresh concrete and suitable curing conditions substantially reduces the possibility of future failure to perform as designed. However, the most reliable examination for concrete is mechanical testing after hardening. In order to obtain better control on the process from very early age, this study describes a combined approach of several monitoring techniques. Acoustic emission is used to record the numerous events occurring during the first hours when concrete is in liquid form as well as later when hardening takes place and drying shrinkage cracking is exhibited. In addition, pressure sensors follow the development of capillary pressure in the matrix and indicate the moment of air entry into the system. Settlement and shrinkage, measured both non-contact by digital image correlation and conventionally, as well as temperature shed light into the complex processes occurring into fresh concrete and help to verify the sources of AE. The final aim is to develop a methodology to assess the quality of the fresh concrete from an early age, to possibly project to the final mechanical properties and to ensure a proper service life

Volcans de la Chaîne des Puys (Massif Central, France) : point sur la chronologie Vasset-Kilian-Pariou-Chopine

ThermoluminescenceInternational audienceLa compilation des datations radiocarbone de bois carbonisés par leurs déferlantes basales, complétée par des observations téphrochronologiques, permet d'avancer que le puy Chopine, il y a environ 9700 ans, a précédé le Vasset et le Kilian, tous deux péné-contemporains, vers 9400-9300 ans. Les produits du Nouveau Pariou sont recouverts par ceux d'un volcan trachytique, probablement le Kilian. Sous les produits explosifs initiaux du Nouveau Pariou (faciès "Traversin"), les trachytes à amphibole qui avaient été attribués au Kilian, sont vraisemblablement une forme méconnue des trachytes de la phase acide du Pariou lui-même. L'ordre chronologique des éruptions serait donc : Chopine/Pariou/?Vasset?/Kilian, la position du Vasset, hypothétique, restant à confirme

Meeting Couple and Coparenting Relationship Needs of Foster Caregivers: Perceptions of Georgia Child Welfare County Directors

Foster caregivers face many unique challenges that may cause strain on their couple/coparenting relationships. Though foster caregivers receive training to help them navigate certain challenges of fostering, there is a lack of resources dedicated to supporting their couple/coparenting relationships. In the study described in this article, we examined the perceptions of Georgia Division of Family and Children Services (DFCS) county directors regarding potential effects of providing healthy marriage and relationship education (HMRE) to foster caregivers. Findings suggest that DFCS directors are in favor of providing HMRE to foster parents but that barriers to doing so must be addressed

Projection of snowfall extremes in the French Alps as a function of elevation and global warming level

Following the projected increase in extreme precipitation, an increase in extreme snowfall may be expected in cold regions, e.g. for high latitudes or at high elevations. By contrast, in low/medium elevation areas, the probability to experience rainfall instead of snowfall is generally projected to increase due to warming conditions. In mountainous areas, despite the likely existence of these contrasted trends according to elevation, changes in extreme snowfall with warming remain poorly quantified. This paper assesses projected changes in heavy and extreme snowfall, i.e. in mean annual maxima and 100-year return levels, in the French Alps as a function of elevation and global warming level using a recent methodology based on non-stationary extreme value models. This methodology is applied to an ensemble of 20 adjusted GCM-RCM pairs from the EURO-CORDEX experiment under the scenario RCP8.5. available for each of the 23 massifs of the French Alps from 1951 to 2100, and every 300 m of elevations. Results are provided as relative or absolute changes computed w.r.t. current climate conditions, at the massif scale and averaged over all available massifs. Overall, mean annual maxima are projected to decrease below 3000 m and increase above 3600 m, while 100-year return levels are projected to decrease below 2400 m and increase above 3300 m. At elevations in between, values are on average projected to increase until +3 &deg;C of global warming, and then decrease. At +4 &deg;C, average relative changes in mean annual maxima and 100-year return levels respectively vary from &minus;26 % (&minus;7 kg m&minus;2) and &minus;15 % (&minus;11 kg m&minus;2) at 900 m, to +3 % (+3 kg m&minus;2) and +8 % (+13 kg m&minus;2) at 3600 m. Finally, for each global warming level, we compute the elevation threshold that separates contrasted trends, i.e. where the average relative change equals zero. This elevation threshold is projected to rise between +1.5 &deg;C and +4 &deg;C: from 3000 m to 3350 m for mean annual maxima, and from 2600 m to 3000 m for 100-year return levels. These results have implications for the management of risks related to extreme snowfall.</p

Pitfalls and improvements in the joint inference of heteroscedasticity and autocorrelation in hydrological model calibration

Residual errors of hydrological models are usually both heteroscedastic and autocorrelated. However, only a few studies have attempted to explicitly include these two statistical properties into the residual error model and jointly infer them with the hydrological model parameters. This technical note shows that applying autoregressive error models to raw heteroscedastic residuals, as done in some recent studies, can lead to unstable error models with poor predictive performance. This instability can be avoided by applying the autoregressive process to standardized residuals. The theoretical analysis is supported by empirical findings in three hydrologically distinct catchments. The case studies also highlight strong interactions between the parameters of autoregressive residual error models and the water balance parameters of the hydrological model. ©2013. American Geophysical Union. All Rights Reserved.Guillaume Evin, Dmitri Kavetski, Mark Thyer, and George Kuczer

Development and evaluation of a method to identify potential release areas of snow avalanches based on watershed delineation

Snow avalanches are a prevalent threat in mountain territories. Large-scale mapping of avalanche-prone terrain is a prerequisite for land-use planning where historical information about past events is insufficient. To this aim, the most common approach is the identification of potential release areas (PRAs) followed by numerical avalanche simulations. Existing methods for identifying PRAs rely on terrain analysis. Despite their efficiency, they suffer from (i) a lack of systematic evaluation on the basis of adapted metrics and past observations over large areas and (ii) a limited ability to distinguish PRAs corresponding to individual avalanche paths. The latter may preclude performing numerical simulations corresponding to individual avalanche events, questioning the realism of resulting hazard assessments. In this paper, a method that accurately identifies individual snow avalanche PRAs based on terrain parameters and watershed delineation is developed, and confusion matrices and different scores are proposed to evaluate it. Comparison to an extensive cadastre of past avalanche limits from different massifs of the French Alps used as ground truth leads to true positive rates (recall) between 80 % and 87 % in PRA numbers and between 92.4 % and 94 % in PRA areas, which shows the applicability of the method to the French Alps context. A parametric study is performed, highlighting the overall robustness of the approach and the most important steps/choices to maximize PRA detection, among which the important role of watershed delineation to identify the right number of individual PRAs is highlighted. These results may contribute to better understanding avalanche hazard in the French Alps. Wider outcomes include an in-depth investigation of the issue of evaluating automated PRA detection methods and a large data set that could be used for additional developments, and to benchmark existing and/or new PRA detection methods.</p