Une arme miracle contre le chômage ?:Une nouvelle évaluation des effets des allègements de charges sociales sur les bas salaires

La revue Économie et Statistique vient de faire paraître un article de Bruno Crépon et Rozenn Desplatz qui propose une nouvelle évaluation des effets des allègements de charges sociales sur les bas salaires. Selon cette étude, ceux-ci auraient provoqué, de 1994 à 1997, une augmentation de 460 000 du nombre d’emplois dans l’économie française. Ce chiffre est nettement supérieur aux estimations antérieures 1. Il est maintenant évoqué dans le débat public pour justifier la poursuite de la politique de baisse des charges sociales, comme axe central de la politique de l’emploi. Compte tenu de la complexité de l’article, la plupart des commentateurs se contentent de citer le chiffre tel quel : « Les experts ont parlé ». Mais quelle est la fiabilité de ce résultat ? Par quels mécanismes, ces emplois ont-ils été créés ? La réduction des cotisations sociales est-elle une arme miracle contre le chômage ? [Premier paragraphe]Bruno Crépon et Rozenn Deslpatz, Une nouvelle évaluation des effets des allègements de charges sociales sur les bas salaires, Economie et Statistique, n°348, 2001, 0336-145

critical relative indentation depth in carbon based thin films

Abstract The thin film hardness estimation by nanoindentation is influenced by substrate beyond a critical relative indentation depth (CRID). In this study we developed a methodology to identify the CRID in amorphous carbon film. Three types of amorphous carbon film deposited on silicon have been studied. The nanoindentation tests were carried out applying a 0.1–10 mN load range on a Berkovich diamond tip, leading to penetration depth-to-film thickness ratios of 8–100%. The work regained during unloading ( W e ) and the work performed during loading ( W t ) was estimated for each indentation. The trend of unload-to-load ratio ( W e / W t ) data as a function of depth has been studied. W e / W t depth profiles showed a sigmoid trend and the data were fitted by means of a Hill sigmoid equation. Using Hill sigmoid fit and a simple analytical method it is possible to estimate CRID of carbon based films

Development of W–SiO2 and Nb–TiO2 solar absorber coatings for combined heat and power systems at intermediate operation temperatures

Two new absorber coatings for mid-temperature operation (300–350 1C) in collectors for solar thermal electricity plants are presented in this study. The absorbers consist of two cermet layers of either W–SiO2 or Nb–TiO2, deposited on a molybdenum infrared reflector and coated with an antireflection layer of silicon oxide. The optimization of the optical performance was made in two steps. First, the layer structure was optimized in model calculations. The optical constants used in this modelling were derived directly from sputtered films of the cermet constituents using reflectance and transmittance measure- ments. The absorber coatings were then sputter-deposited using parameters from the modelling. The results show good agreement between modelled and sputtered optical performance evaluated as solar absorptance and thermal emittance at 350 1C. The optimal values reached for W–SiO2 was 0.91 in combination with 0.08 and 0.93 in combination with 0.09 for Nb–TiO2. The materials characterization from XRD, AES and TEM shows that the composite coatings contain nano-metal inclusions, meaning that they are cermet coatings. Scratch tests show that the coatings adhere well to the substrate of stainless steel. Temperature testing at 350 1C in vacuum for up to 1500 h shows that both coatings are stable under such conditions. Only a slight change occurs during the first 72 h that decreases the emittance but does not change the solar absorptance. ERDA confirms that there is no detectable level of ion migration between layers, only a small decrease in hydrogen content was observed, which indicates outgassing.Digespo projec

Wettability of graphitic materials and development of graphene layer as barriers to prevent the surface degradation induced by water.

Graphitic materials, thanks to the lamellar structure and chemical stability, are of particular interest to realize barriers against the degradation of surface properties induced by water. Many studies showed that water could be a source of degradation of surface properties. To develop a method to overcome the problem related to the deterioration of the surface it is fundamental to study the water- material interaction. For this reason, in this thesis, the water-surface interaction of graphitic- materials and the use of graphitic materials as impermeable barriers against water were explored. Different experimental set up were realized to study the liquid-gas-solid interaction, such as time evolution of the sessile water drop contact angle, captive bubble contact angle and contact angle measurements in a controlled atmosphere. Moreover, a method of deposition of protective graphene-based films using a Meyer rod to apply graphene-inks onto a surface was developed. To understand the intrinsic wettability of graphitic materials a detailed study of the gas-liquid-solid interactions of graphite was conducted in a wide range of experimental conditions. The surface chemical properties and morphology were studied by X-ray photoelectron spectroscopy (XPS), profilometry and atomic force microscopy(AFM), sessile drop contact angle, captive bubble and secondary emission microscopy (SEM). The results of the gas-liquid–surface interaction study indicated that HOPG surface was sensitive to experimental conditions like airborne contamination and the presence of gases. Similarly, a detailed study of the interaction of water with PDMS surface in various experimental conditions (in the air and immersed in water) were conducted. The findings showed that when PDMS was immersed in water, its surface changed. In fact, the volume of air bubbles in contact with the surface of PDMS increased by increasing immersion time in the water. The experimental results indicated that such dynamic evolution of the air bubbles was related to the rearrangement of surface polymer chains via the migration of the polar groups. This phenomenon induced a degradation of the surface properties of PDMS when it is immersed in water. When graphene monolayer was added to PDMS surface, it acted as a barrier against water, suppressing the dynamic evolution of the bubble. We studied the protective properties also of graphene-based films deposited on lead (Pb). We observed that Pb surface degradation occurred when Pb was in contact with a drop of water. The results showed that degradation of Pb surface in contact with water happened very rapidly but graphene-based films, in particular, graphene oxides films, were able to reduce degradation of the surface significantly

Characterisation of Gold Patterns on PDMS Substrates

We present a technique for metal patterning on PDMS without cracks and adhesion issues. The adhesion strength of the metal patterns is characterized by micro scratch tests to check the effect of surface treatments of plasma on PDMS. The elongation of PDMS is also calculated with the applied force using the micro scratch test

Analysis of Radiation Propagation inside a Hierarchical Solar Volumetric Absorber

none4The solar receiver is a critical component of concentrated solar power technology; it works as a heat exchanger, transforming the concentrated solar radiation into high-temperature heat. Volumetric receiver technologies, using air as a heat transfer fluid, are designed to reach higher temperatures than the current receiver technology, which is limited by material resistance and fluid instability. The higher temperature, up to 1200 K, could be used in high-temperature industrial processes or a high-temperature thermodynamic cycle. A correct radiation propagation is essential to develop their performances, reducing reflection and emission losses and promote the heat transfer to the fluid. In this study, the optical behaviour of a hierarchical volumetric receiver (HVR) developed in Bruno Kessler Foundation (FBK) has been studied using Monte Carlo ray tracing (MCRT) simulations. The simulations have been validated in an experimental setup that evaluates the light transmissivity of the HVR porous structure. Two different HVR structures are evaluated with MCRT simulations that use a real solar dish geometry to configure a complete concentrated solar power (CSP) plant. Results show that frontal and rear losses are, respectively, 12% and 3% of the incoming concentrated radiation. Inside the HVR, 15% of the incoming power is propagated trough the lateral void spaces. Therefore, the power spreading avoids the overconcentration of the centre of the focalized area. The HVR optical behaviour has been investigated, showing an optical efficiency of 85%.nonePratticò, Luca; Bartali, Ruben; Crema, Luigi; Sciubba, EnricoPratticò, Luca; Bartali, Ruben; Crema, Luigi; Sciubba, Enric

Effect of glass surface treatments on the deposition of highly transparent reduced graphene oxide films by dropcasting method

Transparent conductive materials are important in many applications such as flat panel displays, solar cells, touch screen and smartphones. Films today generally rely on indium tin oxide (ITO). However, indium is rare and its price is rising as demand soars. For this reason, reduced graphene oxide (RGO) is gaining deep interest for its potential to replace ITO to fabricate transparent conductive films. Unfortunately, obtaining well-dispersed RGO flakes is difficult and generally, toxic solvents and heat treatments are employed. In this work, we demonstrate a simple approach to produce reduced graphene oxide (RGO) thin films on glass substrate at room temperature by using a nontoxic solvent. The films RGO colloidal suspensions were deposited on simple and plasma treated glass substrates by drop casting. The results indicate that the transmittance and the conductivity of the films have a linear relationship with the films thickness deposited on the substrates. The conductivity of RGO films deposited on plasma treated glass is higher with respect to substrate without any grafted functional group. The best conductivity obtained for RGO depositions on piranha cleaned glass, treated in an ammonia plasma is 10.4Scm−1 and the transmittance is 70% at 550nm which are among the best results if compared to similar non annealed RGO films

Solar-thermal driven drying technologies for large-scale industrial applications: State of the art, gaps, and opportunities

Research and Innovation (R&I) on Large-scale Industrial Solar-thermal driven Drying technologies (LISDs) is one of the strategies required to transition to a low-carbon energy future. The objective for this work is to guide future R&I on LISDs by defining the state of the art, gaps, and opportunities. To provide a high-level perspective on the current state of solar drying research, results are presented from an analysis of the content relevant to LISDs found in 45 solar drying Review Articles published in journals over the past 25 years. A conclusion is that most of the existing solar drying research is not focused on LISDs. To build-on these existing 45 solar drying Review Articles, results are presented from an analysis of 30 Original Research Articles with significant content relevant to LISDs published over the past 5 years. A gap is identified in coupling existing or slightly modified solar thermal collectors with existing or slightly modified industrial drying technologies to create indirect LISDs. To facilitate formulating new coupling strategies, the drying characteristics most relevant to this coupling are described and four fundamental classes of industrial dryer technologies are defined based on the underlying heat transfer mechanism, which then impacts the appropriate collector choice. At their most fundamental level, many of the technologies needed to couple solar collectors and industrial dryers to create novel indirect LISDs are not unique to indirect LISDs, but rather can be generalized across a wide range of Solar Heat for Industrial Processes (SHIP) applications, and integration issues are discussed at a more fundamental SHIP level. The technical and economic characteristics of 19 existing LISDs installations throughout the world are presented, and potential and emerging areas discussed.This work was supported in part with funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731287 and by in-kind contributions from Orta Dogu Teknik Üniversitesi.Publisher's Versio

Hardness and Elastic Modulus of Neodymium-doped TiO2 films

In the present work the mechanical properties of titanium dioxide (TiO2) thin films doped with neodymium (Nd) were explored. TiO2Nd thin films were deposited by radiofrequency co-sputtering from a TiO2 and Nd targets. The chemistry was studied using Auger electron spectroscopy (AES). The mechanical properties were measured by nanoindentation. The results showed surprisingly that the incorporation of low concentration of Nd in an atomic ratio of 3.7% to Ti in the TiO2 matrix increase the hardness and elastic modulus of materials