1,324 research outputs found
Influence of secondary phases during annealing on re-crystallization of CuInSe2 electrodeposited films
Electrodeposited CuInSe2 thin films are of potential importance, as light absorber material, in the next generation of photovoltaic cells as long as we can optimize their annealing process to obtain dense and highly crystalline films. The intent of this study was to gain a basic understanding of the key experimental parameters governing the structuralâtextural-composition evolution of thin films as function of the annealing temperature via X-ray diffraction, scanning/transmission electron microscopy and thermal analysis measurements. The crystallization of the electrodeposited CuInSe2 films, with the presence of Se and orthorhombic Cu2âxSe (o-Cu2âxSe) phases, occurs over two distinct temperature ranges, between 220 °C and 250 °C and beyond 520 °C. Such domains of temperature are consistent with the melting of elemental Se and the binary CuSe phase, respectively. The CuSe phase forming during annealing results from the reaction between the two secondary species o-Cu2âxSe and Se (o-Cu2âxSe+Seâ2 CuSe) but can be decomposed into the cubic ÎČ-Cu2âxSe phase by slowing down the heating rate. Formation of liquid CuSe beyond 520°C seems to govern both the grain size of the films and the porosity of the substrateâCuInSe2 film interface. A simple model explaining the competitive interplay between the film crystallinity and the interface porosity is proposed, aiming at an improved protocol based on temperature range, which will enable to enhance the film crystalline nature while limiting the interface porosity
Une analyse empirique des dĂ©cisions en matiĂšre dâantidumping aux Ătats-Unis
Les firmes amĂ©ricaines, qui deviennent la proie des firmes Ă©trangĂšres faisant du dumping sur le marchĂ© amĂ©ricain, rĂ©clament que ces derniĂšres soient soumises Ă une rĂ©glementation. Jouissant des pleins pouvoirs qui leur sont confĂ©rĂ©s par le corps lĂ©gislatif, les lĂ©gislateurs mettent en application des lois antidumping pour contrer de telles pratiques. Toutefois, la prĂ©sence dâasymĂ©trie dans lâinformation entre le corps lĂ©gislatif et les firmes domestiques, Ă laquelle sâajoute le pouvoir discrĂ©tionnaire de lâorganisme de rĂ©glementation qui est sensĂ© rĂ©duire cette asymĂ©trie, pourraient rendre captifs les membres de cet organisme. Nous examinons la possibilitĂ© dâune rĂ©glementation captive dans le contexte de lâapplication des lois antidumping amĂ©ricaines.U.S. firms seek regulation against foreign firms that are alleged to have dumped their goods in the U.S. market, preying on domestic firms. Regulators, empowered by the legislative body, administer antidumping laws to counter such practices. However, due to informational asymmetries that exist between the legislative body and domestic firms, and because of the discretionary power of the regulatory body, which is supposed to bridge this information gap, regulators may be captured. We examine the possibility of regulatory capture in the context of the administration of the U.S. Antidumping law
Une analyse empirique des dĂ©cisions en matiĂšre dâantidumping aux Ătats-Unis
U.S. firms seek regulation against foreign firms that are alleged to have dumped their goods in the U.S. market, preying on domestic firms. Regulators, empowered by the legislative body, administer antidumping laws to counter such practices. However, due to informational asymmetries that exist between the legislative body and domestic firms, and because of the discretionary power of the regulatory body, which is supposed to bridge this information gap, regulators may be captured. We examine the possibility of regulatory capture in the context of the administration of the U.S. Antidumping law. Les firmes amĂ©ricaines, qui deviennent la proie des firmes Ă©trangĂšres faisant du dumping sur le marchĂ© amĂ©ricain, rĂ©clament que ces derniĂšres soient soumises Ă une rĂ©glementation. Jouissant des pleins pouvoirs qui leur sont confĂ©rĂ©s par le corps lĂ©gislatif, les lĂ©gislateurs mettent en application des lois antidumping pour contrer de telles pratiques. Toutefois, la prĂ©sence dâasymĂ©trie dans lâinformation entre le corps lĂ©gislatif et les firmes domestiques, Ă laquelle sâajoute le pouvoir discrĂ©tionnaire de lâorganisme de rĂ©glementation qui est sensĂ© rĂ©duire cette asymĂ©trie, pourraient rendre captifs les membres de cet organisme. Nous examinons la possibilitĂ© dâune rĂ©glementation captive dans le contexte de lâapplication des lois antidumping amĂ©ricaines.
Public Good Overprovision by a Manipulative Provider
We study contracting between a public good provider and users with private valuations of the good. We show that, once the provider extracts the users' private information, she benefits from manipulating the collective information received from all users when communicating with them. We derive conditions under which such manipulation determines the direction of distortions in public good provision. If the provider is non-manipulative, the public good is always underprovided, whereas overprovision occurs with a manipulative provider. With overprovision, not only high-valuation users, but also low-valuation users may obtain positive rentsâusers may prefer facing a manipulative provider.Peer Reviewe
Incentivizing High Quality Crowdwork
We study the causal effects of financial incentives on the quality of
crowdwork. We focus on performance-based payments (PBPs), bonus payments
awarded to workers for producing high quality work. We design and run
randomized behavioral experiments on the popular crowdsourcing platform Amazon
Mechanical Turk with the goal of understanding when, where, and why PBPs help,
identifying properties of the payment, payment structure, and the task itself
that make them most effective. We provide examples of tasks for which PBPs do
improve quality. For such tasks, the effectiveness of PBPs is not too sensitive
to the threshold for quality required to receive the bonus, while the magnitude
of the bonus must be large enough to make the reward salient. We also present
examples of tasks for which PBPs do not improve quality. Our results suggest
that for PBPs to improve quality, the task must be effort-responsive: the task
must allow workers to produce higher quality work by exerting more effort. We
also give a simple method to determine if a task is effort-responsive a priori.
Furthermore, our experiments suggest that all payments on Mechanical Turk are,
to some degree, implicitly performance-based in that workers believe their work
may be rejected if their performance is sufficiently poor. Finally, we propose
a new model of worker behavior that extends the standard principal-agent model
from economics to include a worker's subjective beliefs about his likelihood of
being paid, and show that the predictions of this model are in line with our
experimental findings. This model may be useful as a foundation for theoretical
studies of incentives in crowdsourcing markets.Comment: This is a preprint of an Article accepted for publication in WWW
\c{opyright} 2015 International World Wide Web Conference Committe
Bimanual coordination in stroke recovery: Kinematic analysis provides open leads to individualize upper limb rehabilitation
Climatic and palaeoceanographic changes during the Pliensbachian (Early Jurassic) 2 inferred from clay mineralogy and stable isotope (C-O) geochemistry (NW Europe)
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Available online 17 January 2017The Early Jurassic was broadly a greenhouse climate period that was punctuated by short
warm and cold climatic events, positive and negative excursions of carbon isotopes, and
episodes of enhanced organic matter burial. Clay minerals from Pliensbachian sediments
recovered from two boreholes in the Paris Basin, are used here as proxies of detrital supplies,
runoff conditions, and palaeoceanographic changes. The combined use of these minerals with
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stable isotope data (C-O) from bulk carbonates and organic matter allows palaeoclimatic
reconstructions to be refined for the Pliensbachian. Kaolinite/illite ratio is discussed as a
reliable proxy of the hydrological cycle and runoff from landmasses. Three periods of
enhanced runoff are recognised within the Pliensbachian. The first one at the SinemurianPliensbachian
transition shows a significant increase of kaolinite concomitant with the
negative carbon isotope excursion at the so-called Sinemurian Pliensbachian Boundary Event
(SPBE). The Early/Late Pliensbachian transition was also characterised by more humid
conditions. This warm interval is associated with a major change in oceanic circulation during
the Davoei Zone, likely triggered by sea-level rise; the newly created palaeogeography,
notably the flooding of the London-Brabant Massif, allowed boreal detrital supplies, including
kaolinite and chlorite, to be exported to the Paris Basin. The last event of enhanced runoff
occurred during the late Pliensbachian (Subdonosus Subzone of the Margaritatus Zone),
which occurred also during a warm period, favouring organic matter production and
preservation. Our study highlights the major role of the London Brabant Massif in influencing
oceanic circulation of the NW European area, as a topographic barrier (emerged lands) during
periods of lowstand sea-level and its flooding during period of high sea-level. This massif was
the unique source of smectite in the Paris Basin. Two episodes of smectite-rich sedimentation
(âsmectite eventsâ), coincide with regressive intervals, indicating emersion of the London
Brabant Massif and thus suggesting that an amplitude of sea-level change high enough to be
linked to glacio-eustasy. This mechanism is consistent with sedimentological and
geochemical evidences of continental ice growth notably during the Latest Pliensbachian
(Spinatum Zone), and possibly during the Early Pliensbachian (late Jamesoni/early Ibex
Zones).The study was supported by the âAgence Nationale pour la Gestion des DĂ©chets Radioactifsâ (AndraââFrench National Radioactive Waste Management Agency)
Market Power and Collusion on Interconnection Phone Market in Tunisia : What Lessons from International Experiences
We try in this paper to characterize the state of mobile phone market in Tunisia. Our study is based on a survey of foreign experience (Europe) in detecting collusive behavior and a comparison of the critical threshold of collusion between operators in developing countries like Tunisia. The market power is estimated based on the work of Parker Roller (1997) and the assumption of "Balanced Calling Pattern". We use then the model of Friedman (1971) to compare the critical threshold of collusion. We show that the "conduct parameter" measuring the intensity of competition is not null during the period 1993-2011. Results show also that collusion is easier on the Tunisian market that on the Algerian, Jordanian, or Moroccan one
Mercury in the Black Sea:New Insights From Measurements and Numerical Modeling
Redox conditions and organic matter control marine methylmercury (MeHg) production. The Black Sea is the world's largest and deepest anoxic basin and is thus ideal to study Hg species along the extended redox gradient. Here we present new dissolved Hg and MeHg data from the 2013 GEOTRACES MEDBlack cruise (GN04_leg2) that we integrated into a numerical 1-D model, to track the fate and dynamics of Hg and MeHg. Contrary to a previous study, our new data show highest MeHg concentrations in the permanently anoxic waters. Observed MeHg/Hg percentage (range 9-57%) in the anoxic waters is comparable to other subsurface maxima in oxic open-ocean waters. With the modeling we tested for various Hg methylation and demethylation scenarios along the redox gradient. The results show that Hg methylation must occur in the anoxic waters. The model was then used to simulate the time evolution (1850-2050) of Hg species in the Black Sea. Our findings quantify (1) inputs and outputs of Hg-T (similar to 31 and similar to 28 kmol yr(-1)) and MeHgT (similar to 5 and similar to 4 kmol yr(-1)) to the basin, (2) the extent of net demethylation occurring in oxic (similar to 1 kmol yr(-1)) and suboxic water (similar to 6 kmol yr(-1)), (3) and the net Hg methylation in the anoxic waters of the Black Sea (similar to 11 kmol yr(-1)). The model was also used to estimate the amount of anthropogenic Hg (85-93%) in the Black Sea
Size-dependent spinodal and miscibility gaps for intercalation in nano-particles
Using a recently-proposed mathematical model for intercalation dynamics in
phase-separating materials [Singh, Ceder, Bazant, Electrochimica Acta 53, 7599
(2008)], we show that the spinodal and miscibility gaps generally shrink as the
host particle size decreases to the nano-scale. Our work is motivated by recent
experiments on the high-rate Li-ion battery material LiFePO4; this serves as
the basis for our examples, but our analysis and conclusions apply to any
intercalation material. We describe two general mechanisms for the suppression
of phase separation in nano-particles: (i) a classical bulk effect, predicted
by the Cahn-Hilliard equation, in which the diffuse phase boundary becomes
confined by the particle geometry; and (ii) a novel surface effect, predicted
by chemical-potential-dependent reaction kinetics, in which
insertion/extraction reactions stabilize composition gradients near surfaces in
equilibrium with the local environment. Composition-dependent surface energy
and (especially) elastic strain can contribute to these effects but are not
required to predict decreased spinodal and miscibility gaps at the nano-scale
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