Impact of Thermal Aging on the Microstructure Evolution and Mechanical Properties of Lanthanum-Doped Tin-Silver-Copper Lead-Free Solders

The authors would like to thank Ste´phanie Blanc (Electrical Engineer at Schlumberger) for her useful contribution to the project, Claude Guyomard and Olivier Naegelen (Arts et Me´tiers ParisTech) for the die design and sample casting, respectively, and Jean-Marc Raulot for his enriching discussions.An extensive study is made to analyze the impact of pure lanthanum on the microstructure and mechanical properties of Sn-Ag-Cu (SAC) alloys at high temperatures. Different compositions are tested; the temperature applied for the isothermal aging is 150 C, and aging times of 10 h, 25 h, 50 h, 100 h, and 200 h are studied. Optical microscopy with cross-polarized light is used to follow the grain size, which is refined from 8 mm to 1 mm for as-cast samples and is maintained during thermal aging. Intermetallic compounds (IMCs) present inside the bulk Sn matrix affect the mechanical properties of the SAC alloys. Due to high-temperature exposure, these IMCs grow and hence their impact on mechanical properties becomes more significant. This growth is followed by scanning electron microscopy, and energy-dispersive spectroscopy is used for elemental mapping of each phase. A significant refinement in the average size of IMCs of up to 40% is identified for the as-cast samples, and the coarsening rate of these IMCs is slowed by up to 70% with no change in the interparticle spacing. Yield stress and tensile strength are determined through tensile testing at 20 C for as-cast samples and after thermal aging at 150 C for 100 h and 200h. Both yield stress and tensile strength are increased by up to 20% by minute lanthanum doping

Achieving the Dispatchability of Distribution Feeders through Prosumers Data Driven Forecasting and Model Predictive Control of Electrochemical Storage

We propose and experimentally validate a control strategy to dispatch the operation of a distribution feeder interfacing heterogeneous prosumers by using a grid-connected battery energy storage system (BESS) as a controllable element coupled with a minimally invasive monitoring infrastructure. It consists in a two-stage procedure: day-ahead dispatch planning, where the feeder 5-minute average power consumption trajectory for the next day of operation (called \emph{dispatch plan}) is determined, and intra-day/real-time operation, where the mismatch with respect to the \emph{dispatch plan} is corrected by applying receding horizon model predictive control (MPC) to decide the BESS charging/discharging profile while accounting for operational constraints. The consumption forecast necessary to compute the \emph{dispatch plan} and the battery model for the MPC algorithm are built by applying adaptive data driven methodologies. The discussed control framework currently operates on a daily basis to dispatch the operation of a 20~kV feeder of the EPFL university campus using a 750~kW/500~kWh lithium titanate BESS.Comment: Submitted for publication, 201

Del positivismo a los mecanismos generativos : el programa de investigación pionero de Raymond Boudon

Este artículo compara brevemente dos tradiciones de investigación: la del empirismo y la de los mecanismos generativos. Además, recuerda también brevemente los argumentos del empirismo epistemológico y su justificación filosófica, cuya expresión paradigmática es el positivismo. El artículo examina, pues, las críticas que se han dirigido contra esta tradición y expone los principios de la estrategia de los mecanismos generativos en sociología limitándose a las investigaciones de Boudon, que son las más representativas de esta orientación metodológica.This paper briefly compares two research traditions: empiricism and generative mechanisms. Moreover, it briefly recalls the arguments of empiricist epistemology and its philosophical justification, whose paradigmatic expression is positivism. The paper then examines the criticisms that have been addressed against this trend and sets out the principles of the generative mechanisms strategy in sociology by focusing on several studies by Boudon which are the most representative of this methodological orientation.Aquest article compara breument dues tradicions de recerca: la de l'empirisme i la dels mecanismes generatius. A més, també recorda breument els arguments de l'empirisme epistemològic i la seva justificació filosòfica, l'expressió paradigmàtica de la qual és el positivisme. L'article examina, doncs, les crítiques que s'han adreçat contra aquesta tradició i exposa els principis de l'estratègia dels mecanismes generatius en sociologia limitant-se a les investigacions de Boudon, que són les més representatives d'aquesta orientació metodològica

Changes in Antioxidant Enzymes Activity and Oxidative Damage in Four Argania spinosa Ecotypes Under Water Stress Conditions

_Argania spinosa_ L. Skell, a tree endemic of Morocco, grows in semiarid and arid areas. Biochemical response to drought in four ecotypes of the _A. spinosa_ was compared. Choice of ecotypes was based on evident differences in geographical features in south-west Morocco: two coastal ecotypes (Essaouira and Agadir) and two paralittorale ecotypes (Aoulouz and Lakhssas). Lipid peroxidation (malonyldialdehyde (MDA)), content of endogenous hydrogen peroxide (H2O2) and antioxidant enzyme system (Catalase (CAT), Ascorbate peroxidase (APX), Total peroxidase (POD) and Polyphenoloxidase (PPO) were measured in control (100% relative humidity (RH) at field capacity (FC)) and water-stressed plants (50 and 25% RH at FC). For all ecotypes, drought stress significantly increased the contents of MDA and H2O2 and an ecotype effect was noted. According Two-way ANOVA analysis, the ecotype x watering regime interaction was highly significant. We found an increase in the activities of the four ROS-scavenging enzymes and an ecotype effect was noted. Ecotype x watering regime interaction shows that only the CAT and APX activities were significant. Highest values of POD and PPO activities were found in both paralittorale ecotypes. Increase in antioxidant enzyme activities appears to be an adaptive response to restore the reactive oxygen species in their homeostasis. The four study ecotypes were separated by two discriminant functions obtained by canonical discriminant analysis. Coastal ecotypes are separated from the paralittorale ecotypes mainly by POD and PPO activities and MDA content

Fluorescent cell segmentation and classification

During image acquisition and processing of cellular micrographs for high throughput automated analysis, one commonly encountered problem is segmentation of multiple overlapping cells. In addition, to further classify the cells based on shape information, segmentation should preserve the boundary structures of the cells. In this paper, we combine the distance transform with the marker based watershed algorithm to effectively segment Saccharomyces Cerevisiae cells, fluorescently labeled at their outermost yeast boundaries. This algorithm uses the adaptive threshold to magnify and outline the cell boundaries, adopts the distance transform to turn the position information of pixels to grey level information, and then relies on the watershed algorithm to realize the search and segmentation of the adhesion border of the cells. For classification, invariant features, such as Hu moments, are extracted from segmented cell boundaries. The invariant features enable recognition of objects from imagery in a manner that is independent of scale, position, and orientation. The algorithm was tested on a set of 20 images and produced an average of 90% segmentation rate, and Hu moments with the use of a Multi-Layer Perceptron demonstrated their efficiency with an average of 95% classification rate. We conclude from this data that the currently designed algorithm is robust for classifying fluorescent yeast cells, and it may potentially be applied to more diverse biological samples