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In situ photoluminescence system for studying surface passivation in silicon heterojunction solar cells
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Vibrational mode assignment of finite temperature infrared spectra using the AMOEBA polarizable force field †
No full textInternational audienceThe calculation of infrared spectra by molecular dynamics simulations based on the AMOEBA polarizable force field has recently been demonstrated [Semrouni et al., J. Chem. Theory Comput., 2014, 10, 3190]. While this approach allows access to temperature and anharmonicity effects, band assignment requires additional tools, which we describe in this paper. The Driven Molecular Dynamics approach, originally developed by Bowman, Kaledin et al. [Bowman et al. J. Chem. Phys., 2003, 119, 646, Kaledin et al. J. Chem. Phys., 2004, 121, 5646] has been adapted and associated with AMOEBA. Its advantages and limitations are described. The IR spectrum of the Ac-Phe-Ala-NH 2 model peptide is analyzed in detail. In addition to differentiation of conformations by reproducing frequency shifts due to non-covalent interactions, DMD allows visualizing the temperature-dependent vibrational modes
La dynamique des dispositifs d’action collective entre firmes : Le cas des méta-organisations dans le secteur pétrolier
No full textInternational audienceOur paper studies collective action between firms from the perspective of devices. To do so, we use the concepts of meta-organizations and partial organizations that were developed by Ahrne and Brunsson (2008, 2010). We conduct a case study of the oil and gas sector and show that while literature has expected these devices to retreat due to globalization and weakening of States and collective negotiations, they actually remain a powerful mean of collective action between firms. Notably, firms widely use these devices to deal with CSR and sustainable development issues, in relation with all the different stakeholders. From a strategic standpoint, these collective action devices allow firms to manage reputational effects and weak signals coming from the environment, as well as to neutralize conflicts with stakeholders. From the institutional standpoint, the invention of new organizational forms since the 1960s – business thematic and multi-stakeholder metaorganizations – occurred in a dynamics of institutional complementarity. Indeed, these devices rely on one another and complete each other, therefore allowing firms to develop a broad range of collective strategies.L’article étudie l’action collective des entreprises sous l’angle des dispositifs. Pour analyser ces derniers, il utilise les concepts de méta-organisation et d’organisation partielle mis en avant par Ahrne et Brunsson (2008 ; 2010). S’appuyant sur le cas d’un secteur, celui du pétrole, il montre que contrairement à ce qui avait été anticipé en raison de la globalisation et de l’affaiblissement des États et de la négociation collective, ces dispositifs continuent à être utilisés à grande échelle par les entreprises, notamment pour traiter les questions de responsabilité sociale et de développement durable en relation avec les différentes parties-prenantes. En effet, sur le plan stratégique, ces dispositifs d’action collective permettent de gérer les effets de réputation des entreprises, les signaux faibles venant de l’environnement et le désamorçage des conflits avec les parties prenantes. Sur le plan institutionnel, l’invention de nouvelles formes de dispositifs depuis les années 1960 – les méta-organisations corporatives thématiques et multi-parties-prenantes – s’est faite dans une dynamique de complémentarité, les dispositifs s’appuyant les uns sur les autres et se complétant pour permettre aux entreprises une large gamme de stratégies collectives
Quantitative measurement of permeabilization of living cells by terahertz attenuated total reflection
No full textInternational audienceUsing Attenuated Total Reflection imaging technique in the terahertz domain, we demonstrate non-invasive, non-staining real time measurements of cytoplasm leakage during permeabilization of epithelial cells by saponin. The terahertz signal is mostly sensitive to the intracellular protein concentration in the cells, in a very good agreement with standard bicinchoninic acid protein measurements. It opens the way to in situ real time dynamics of protein content and permeabilization in live cells
Reasoning about Computational Systems using Abella
No full textInternational audienceWe present a tutorial on the Abella theorem prover that is designed to reason about relational specifications in higher-order abstract syntax
Managing Base of the Pyramid as a Business Opportunity : A Longitudinal Field Study
No full textIn the last decade a growing articulation of the business strategy of the firms with somespecific global societal challenge in line with its core activities has been observed. Thischange provides both a need and an opportunity for Base of the Pyramid (BoP) activities tomigrate from their preserved status within the Corporate Social responsibility (CSR)department to business operations. We explore the successive steps associated with thischange at Schneider Electric through a longitudinal case study. The newly adopted businessstrategy of the firm clearly facilitates the change in the mindsets all through the company.Still the need for adapting the management systems remains pending. A key finding thatemerges from our analysis is to instill interactive processes through an organizational changeand a strong commitment on the commercial purpose of the BoP activities. We also highlightthat BoP activities cannot be directly transferred to operational entities withoutsimultaneously identifying which of the functional department will be in charge of providingthe corresponding management systems and support such longer-term investments
Influence of impurities on Cr3+ luminescence properties in Brazilian emerald and alexandrite
No full textInternational audienceEmerald and alexandrite, the chromiferous varieties of beryl, Be3Al2[Si6O18], and chrysoberyl, BeAl2O4, respectively, are, as gems, of high economical and technological interest. The Cr3+ properties in natural beryl and chrysoberyl samples have been studied by mainly photoluminescence technique and electron paramagnetic resonance (EPR) as a function of Cr content (50–11370 ppm) as well as impurities, such as Fe and V. In emeralds, the Cr3+ crystal field value is linked to the Cr content and decreases when Cr increases. In chrysoberyl with low Cr content, the vanishing of Cr3+ emission from Cr3+ ions located on the inversion-symmetry site suggests a competition between Cr and V regarding chemical substitution. The Fe3+ ion substitutes efficiently on the mirror-symmetry site, with a strong impact on the Cr3+ lifetime on this site
Sub-Threshold Startup Charge Pump using Depletion MOSFET for a low-Voltage Harvesting Application
No full textInternational audienceThis paper presents a fully integrated CMOS start-up circuit for a low voltage battery-less harvesting application. The proposed topology is based on a step-up charge pump using depletion transistors instead of enhancement transistors. With this architecture, we can obtain a self-starting voltage below the enhancement transistor's threshold due to its normally-on operation. The key advantages are the CMOS compatibility, inductor-less solution and no extra post-fabrication processing. The topology has been simulated in 0.18µm technology using a transistor-level model and has been compared to the traditional charge pump structure. The depletion-based voltage doubler charge pump enables operation from an input voltage as low as 250mV compared to 400mV in an enhancement-based one. The proposed topology can also achieve other conversion ratios such as 1:-1 inverter or 1:N step-up. Keywords— DC-DC converter, charge pump, low-voltage startup, depletion MOSFET, energy harvesting interface, thermo-energy generator
The deployment of BEV and FCEV in 2015
No full textIn Europe the transport sector contributes about 25% of total GHG emissions, 75% of which come from road transport. Contrarily to industrial emissions road emissions have increased over the period 1990-2015 in OECD countries: California (+26%), Germany (0%), France (+12%), Japan (+2%), Denmark (+30%). The number of registered vehicles on road in these countries amounts respectively to: California (33 million), Germany (61.5 million), France (38 million), Japan (77 million), Denmark (4 million). Even if these numbers are not expected to grow in the future this calls for major programs to reduce the corresponding GHG emissions in order to achieve the global GHG targets for 2050. The benefits from these programs will spread out to non OECD countries in which road emissions are bound to increase. Programs to promote zero emissions vehicles (ZEV) effectively started in the 2000’s through public private partnerships involving government agencies, manufacturers, utilities and fuel companies. These partnerships provided subsidies for R&D, pilot programs and infrastructure. Moreover, technical norms for emissions, global requirements for the portfolio of sales for manufacturers, rebates on the purchasing price for customers as well as various perks (driving bus lanes, free parking, etc.) are now in place. These multiple policy instruments constitute powerful incentives to orient the strategies of manufacturers and to stimulate the demand for ZEV. The carbon tax on the distribution of fossil fuels, whenever it exists, remains low and, at this stage, cannot be considered as an important driving force. The cases studies reveal important differences for the deployment of battery electric vehicle (BEV) versus fuel cell electric vehicle (FCEV). BEV is leading the game with a cheaper infrastructure investment cost and a lower cost for vehicle. The relatively low autonomy makes BEV mostly suited for urban use, which is a large segment of the road market. The current level of BEV vehicles on roads starts to be significant with California (70,000), Germany (25,000), France (31,000), Japan (608,000) Denmark (3,000), but they remain very low relative to the targets for 2020: California (1.5 million), Germany (1 million), France (2 million), Japan (0.8-1.1 million for ZEV new registrations), Denmark (0.25 million). The developments and efficiency gains in battery technology along with subsidies for battery charging public stations are expected to facilitate the achievement of the growth. The relative rates of equipment (number of publicly available stations / number of BEV) provide indirect evidence on the effort made in the different countries: California (3%), Germany (12%), France (28%), Japan (11%), and Denmark (61%). In some countries public procurement plays a significant role. In France Autolib (publicly available cars in towns) represents a large share of the overall BEV deployment (12%), and the government recently announced a 50% target for low emissions in all public vehicles new equipment. FCEV is still in an early deployment stage due to a higher infrastructure investment cost and a higher cost for vehicle. The relatively high autonomy combined with speed refueling make FCEV mostly suited for long distance and interurban usage. At present there are only a very limited numbers of HRS deployed: California (28), Germany (15), France (6), Japan (31), Japan (7), Denmark (7), and only a few units of H2 vehicles on road: California (300), Germany (125), France (60), Japan (7), Denmark (21). However, a detailed analysis of the current road maps suggests that FCEV has a large potential. Targets for the 2025-2030 horizons are significant in particular in Germany (4% in 2030), Denmark (4.5% in 2025) and Japan (15-20% for ZEV new registrations in 2020). The California ARB has recently redefined its program (subsidies and mandates) to provide higher incentives for FCEV. France appears to focus on specialized regional submarkets to promote FCEV (such as the use of H2 range extending light utility vehicles). The financing of the H2 infrastructure appears as a bottleneck for FCEV deployment. Roadmaps address this issue through progressive geographical expansion (clusters) and a high level of public subsidies hydrogen refueling station (HRS) in particular in all countries except France. At this stage of BEV and FCEV do not appear as direct competitors; they address distinct market segments. Unexpected delays in the development of infrastructure in FCEV, possible breakthroughs in battery technology, and the promotion of national champions may change the nature of this competition, making it more intense in the future
Importing SMT and Connection proofs as expansion trees
No full textInternational audienceDifferent automated theorem provers reason in various deductive systems and, thus, produce proof objects which are in general not compatible. To understand and analyze these objects, one needs to study the corresponding proof theory, and then study the language used to represent proofs, on a prover by prover basis. In this work we present an implementation that takes SMT and Connection proof objects from two different provers and imports them both as expansion trees. By representing the proofs in the same framework, all the algorithms and tools available for expansion trees (compression , visualization, sequent calculus proof construction, proof checking, etc.) can be employed uniformly. The expansion proofs can also be used as a validation tool for the proof objects produced