87 research outputs found
Wave-front phase retrieval in transmission electron microscopy via ptychography
No full textThere are many different strategies that allow the solving of the well-known phase problem corresponding to the loss of phase information during a physical measurement. In microscopy, and, in particular, in transmission electron microscopy, most of these strategies focus on the retrieval of high-resolution information with the importance of lower resolution data often overlooked. Ptychography offers a means to investigate such data. Ptychography is a robust diffractive imaging technique with fast convergence for phase retrieval but, until now, has not been applied at the nanoscale. In this paper, we use the ptychographical iterative engine to retrieve the phase change at the exit plane of metallic nanoparticles using a conventional transmission electron microscope. Ptychographical reconstructions yielded images with a phase resolution of π/10 and a spatial resolution of 1 nm. These results stand as a first step toward aberration-free lensless imaging. The technique lends itself to be an alternative to off-axis electron holography or focal series reconstructio
Law & Economics Perspectives on Electricity Regulation
No full textThis paper first reviews some of the main contributions of the new institutional economics to the analysis of the process of competitive transformation of network industries. It shows that neoinstitutional analysis is complementary to the microeconomics of rational pricing, since it accounts for the decisive role of an institutional framework adapted to new transactions. It emphasizes the importance of the political reform process, which draws on the conditions of attractiveness and feasibility to define an initial reorganization of property rights in these industries. The paper then analyzes in this light some of the main challenges ahead for electricity regulation: the question of investment in generation capacities and the link to long term contracts, the regulation of wholesale market power, the support to Renewable Energy Sources for Electricity (RES-E) and the design of new regulatory authorities.Electricity Markets; New Institutional Economics; Law & Economics
Biogeochemical redox proxies in sediments from Dotternhausen during the Toarcian (Early Jurassic)
No full textAuthor contributions:
The lead author is Angela L. Coe. Measurements were performed by Stephan M. Harding, with supervision of Angela L. Coe and Anthony S. Cohen. Measurements were gathered, processed and analysed by Itzel Ruvalcaba Baroni
Biogeochemical redox proxies in sediments from Yorkshire during the Toarcian (Early Jurassic)
No full textAuthor contributions:
The lead author is Angela L. Coe. Measurements were performed by Stephan M. Harding, with supervision of Angela L. Coe and Anthony S. Cohen. Measurements were gathered, processed and analysed by Itzel Ruvalcaba Baroni
Turbulence, Inequality, and Cheap Steel
No full textIron and steel production grew dramatically in the U.S. when mass production technologies for steel were adopted in the 1860s. According to new measures presented in this study, earnings inequality rose within the iron and steel industries about 1870, perhaps because technological uncertainty led to gambles and turbulence. Firms made a variety of technological choices and began formal research and development. Professional associations and journals for mechanical engineers and chemists appeared. A national market replaced local markets for iron and steel. An industrial union replaced craft unions. As new ore sources and cheap water transportation were introduced, new plants along the Great Lakes outcompeted existing plants elsewhere. Because new iron and steel plants in the 1870s were larger than any U.S. plants had ever been, cost accounting appeared in the industry and grew in importance. Uncertainty explains the rise in inequality better than a skill bias account, according to which differences among individuals generate greater differences in wages. Analogous issues of inequality come up with respect to recent information technology.technological change, Bessemer steel, technological uncertainty, turbulence, inequality, innovation
Analysis of the viscoelastic deformation behaviour of continuous fibre-reinforced polymers subjected to the automotive painting process
No full textThe automotive industry has developed an interest in manufacturing structural parts from continuous fibre-reinforced polymers because legislation is becoming more strict on the permissible CO2 emission of newly produced vehicles. Additional requirements on the level of recyclability has raised the question if composite materials with a thermoplastic matrix in particular can be utilised in the body structure. From the perspective of cost sensitivity, the conventional automotive manufacturing chain has to remain as it is and requires the body structure to pass through the automotive paint shop and subjects all structural elements to significant hygrothermal loading. The objective of this research is to analyse the deformation behaviour of continuous fibre-reinforced thermoplastics subjected to hygrothermal loading characteristic for the automotive painting process.Studying the theory behind viscoelastic problems revealed that numerical solutions to the integral form of the linear viscoelastic constitutive equations often pose a problem regarding computational memory usage because of the importance of strain history. Utilising a recursive formulation of the constitutive equations eliminated this problem and identified the required material parameters for the numerical model. Thermal expansion, hygroscopic shrinkage, polymer-chemical effects, and stress relaxation were the four phenomena that governed the deformation. Measurements with a dilatometer, a micrometer, and an analytical scale yielded quantitative results about hygrothermal expansion. Thermogravimetric analysis provided information on the moisture diffusion and dynamic mechanical analysis quantified the stress relaxation behaviour. Quasi-static tensile tests confirmed the linearity of the viscoelasticity and digital image correlation supplied the major Poisson’s ratio.A finite element model has been developed that implements hygrothermal expansion and takes into account orthotropic linear viscoelastic behaviour by means of a material user subroutine. Adopting a sequential uncoupled simulation approach allowed the prediction of heat transfer, moisture diffusion, and stress distribution. A semi-numerical simulation approach enabled the calculation of the expansion of symmetric balanced laminates through classical laminate theory whilst taking into account the time- and temperature-dependency of the mechanical properties computed with a micromechanical model created for special orthotropic laminae. Sensitivity studies justified the usage of one-dimensional heat transfer- and moisture diffusion simulations. Moreover, mesh- and time step convergence studies revealed the sensitivity of the simulation to these parameters.Dilatometer experiments with dry- and moisture saturated multi-directional specimens confirmed the correct calculation of hygrothermal expansion. Increasing in complexity, measuring the out-of-plane deformation of a clamped unidirectional tensile specimen subjected to a temperature profile that resembles the most severe thermal loading found in the automotive painting process confirmed a satisfactory agreement between the numerical results and the experimental data. Geometric compensation for the thermal expansion of the fixture and choosing graphite as construction material kept the thermal expansion of the fixture to a minimum. Components with the geometry of the roof bow that is currently in series production for the BMW 7 Series were manufactured by a thermoforming method to allow validation of the simulation with complex geometry. A proper agreement between the predicted deformation behaviour by the semi-numerical simulation and the optical measurements of the dry- and moisture saturated roof bows with various multi-directional lay-ups validated the functioning of the developed simulation.Aerospace Engineerin
Biogeochemical redox proxies in sediments from Schandelah during the Toarcian (Early Jurassic)
No full textAuthor contributions:
The sampling was led by Bas van de Schootbrugge and measurements performed by Nina Papadomanolaki, with supervision of Niels A. G. M. van Helmond and Caroline P. Slomp. Measurements were gathered, processed and analysed by Itzel Ruvalcaba Baroni
Les Fondations Françaises Et La Tutelle De L'Etat
No full textDocument written in the framework of the conference "Légitimité et fonctions des fondations en Europe et aux Etats-Unis." This conference was organised in 2004 in Paris by the Fondation Mattei Dogan, the Social Science Research Council, and the Russell Sage Foundation, under the patronage of M. J.P. Raffarin, French Prime Minister. The author (Sous-directeur des affaires politiques et de la vie associative au ministère français de l'intérieur) analyses the relationship between the foundation sector and the French State
Selective adhesion of Bacillus cereus spores on heterogeneously wetted silicon nanowires
No full textISI Document Delivery No.: 556ZPTimes Cited: 1Cited Reference Count: 33Galopin, Elisabeth Piret, Gaelle Szunerits, Sabine Lequette, Yannick Faille, Christine Boukherroub, RabahCentre National de la Recherche Scientifique (CNRS); Nord-Pas-de Calais; Agence Nationale de la Recherche[ANR-07-PNRA-009-01 InterSpore]We gratefully acknowledge the Centre National de la Recherche Scientifique (CNRS) and the Nord-Pas-de Calais region for support. We are grateful to G. Ronse, A. Ronse. and M. Clarisse from INRA for technical assistance provided for biological sample preparation. This work has been partially financed by the Agence Nationale de la Recherche under the Programme National de Recherche en Alimentation et Nutrition Humaine, project ANR-07-PNRA-009-01 InterSpore.Amer chemical socWashingtonBoukherroub, R (reprint author), CNRS, IRI, USR 3078, Parc Haute Borne,50 Ave Halley,BP 70478, F-59658 Villeneuve Dascq, [email protected] audienceThe article reports on the selective adhesion of Bacillus cereus spores oil patterned and heterogeneously wetted superhydrophobic silicon nanowires surfaces. Superhydrophilic patterns on superhydrophobic silicon nanowire (SiNW) surfaces were prepared by a standard optical lithography technique. Exposure of the patterned surface to a suspension of B. cercus spores in water led to their specific adsorption in superhydrophobic areas. Comparable results were obtained on a patterned hydrophobic/hydrophilic flat silicon (Si) surface even though at higher concentration of spores wits observed on the hydrophobic areas, its compared to the superhydrophobic regions of the SiNW substrate, The surfaces were characterized using scanning electron microscopy (SEM), fluorescence spectroscopy, and contact angle measurements
The comparison of different stress measurements in determining the stress profile of a near-surface low-stress hard-rock mine
No full textMeasuring rock stress is a difficult process, especially in the Stjernøya Nepheline-Syenite mine in Northern Norway. The complex nature and topography of the shallow deposit makes it difficult to conduct industry standard tests. Therefore, this thesis aims at answering how different stress measurement techniques and their results compare to each other in a shallow low-stress hard-rock mine. To do this, an elaborate laboratory work is done to find a relation between stress (UCS) and acoustic properties and velocities of the nepheline syenite. Using that information, a similar combination of tests is done in the field, namely a flat jack test and acoustic velocity measurements with a hammer and geophones. To give further insight in the gathered field-data, visual classification methods, like RMR are done to verify and aid the tests and the results. The laboratory tests gave more insight in the relation between stress and acoustic velocity. There exists a positive, somewhat logarithmic relation between confining pressure and velocity through the sample, until the end of the elastic domain. Depending on the sample, this becomes more apparent after an initial loading phase between 0 and 10-20 MPa. In this low-stress zone, the wave arrival times could not be accurately observed and tend to give very low results. This problem translated to the field. Despite the flat-jack provided an understandable vertical pressure of 9.8 MPa, the acoustic measurements in the field did not always coincide with this pressure, according to the laboratory relationship, generally giving lower velocities than expected. However, a relation between rock quality and wave-velocity could also be present, as the cracks in the heterogeneous rock could heavily influence acoustic velocity. Therefore, this research concludes that both the flat jack and the acoustic investigative methods have their use in understanding the stress-profile of the shallow deposit. Given the low stresses in the mine, the acoustical investigative method could not be used directly to measure stress, but it can be used as a control for the flat jack tests and have use in monitoring of the rock wall.Applied Earth Sciences | European Mining Cours
- …
