Search results for "scale [mass]"
showing 10 items of 997 documents
Comparative study of initial stages of copper immersion deposition on bulk and porous silicon
2013
Initial stages of Cu immersion deposition in the presence of hydrofluoric acid on bulk and porous silicon were studied. Cu was found to deposit both on bulk and porous silicon as a layer of nanoparticles which grew according to the Volmer-Weber mechanism. It was revealed that at the initial stages of immersion deposition, Cu nanoparticles consisted of crystals with a maximum size of 10 nm and inherited the orientation of the original silicon substrate. Deposited Cu nanoparticles were found to be partially oxidized to Cu2O while CuO was not detected for all samples. In contrast to porous silicon, the crystal orientation of the original silicon substrate significantly affected the sizes, dens…
Optical determination and identification of organic shells around nanoparticles: application to silver nanoparticles
2013
We present a simple method to prove the presence of an organic shell around silver nanoparticles. This method is based on the comparison between optical extinction measurements of isolated nanoparticles and Mie calculations predicting the expected wavelength of the Localized Surface Plasmon Resonance of the nanoparticles with and without the presence of an organic layer. This method was applied to silver nanoparticles which seemed to be well protected from oxidation. Further experimental characterization via Surface Enhanced Raman Spectroscopy (SERS) measurements allowed to identify this protective shell as ethylene glycol. Combining LSPR and SERS measurements could thus give proof of both …
A hierarchical model for novel schemes of electrodialysis desalination
2019
Abstract A new hierarchical model for the electrodialysis (ED) process is presented. The model has been implemented into gPROMs Modelbuilder (PSE), allowing the development of a distributed-parameters simulation tool that combines the effectiveness of a semi-empirical modelling approach to the flexibility of a layered arrangement of modelling scales. Thanks to its structure, the tool makes possible the simulation of many different and complex layouts, requiring only membrane properties as input parameters (e.g. membrane resistance or salt and water permeability). The model has been validated against original experimental data obtained from a lab scale ED test rig. Simulation results concern…
Understanding teaching professionals' digital competence : What do PIAAC and TALIS reveal about technology-related skills, attitudes, and knowledge?
2021
In an ever-evolving technological landscape that challenges teaching professionals' digital competence, this study complements previous studies by providing an overall picture of teaching professionals' digital competence. We employed regression models on two large-scale assessment data sets on teachers from 11 countries—namely, the Teaching and Learning International Survey (TALIS; n = 50,800) and the Programme for the International Assessment of Adult Competencies (PIAAC; n = 2590)—to investigate through the theoretical lens of digital competence how teaching professionals' skills, attitudes and knowledge distribute and relate, and how they are associated with personal and contextual fact…
Specific heat of thin phonon cavities at low temperature: Very high values revealed by zeptojoule calorimetry
2022
The specific heat of phonon cavities is investigated in order to analyze the effect of phonon confinement on thermodynamic properties. The specific heat of freestanding very thin SiN membranes in the low-dimensional limit is measured down to very low temperatures (from 6 K to 50 mK). In the whole temperature range, we measured an excess specific heat orders of magnitude bigger than the typical value observed in amorphous solids. Below 1 K, a crossover in cp to a lower power law is seen, and the value of the specific heat of thinner membranes becomes larger than that of thicker ones demonstrating a significant contribution coming from the surface. We show that this high value of the specific…
Large scale modelling of photo-excitation processes in materials with application in organic photovoltaics
2019
La energía fotovoltaica a partir de materiales orgánicos representa una opción muy atractiva, en términos de costo y flexibilidad, para generar electricidad. Sin embargo, las bajas eficiencias alcanzadas hasta ahora limitan la producción de dispositivos fotovoltaicos a escala comercial. En el intento de superar las bajas eficiencias hoy en día se dedican considerables esfuerzos en la investigación y el diseño de materiales orgánicos así como de arquitecturas de dispositivos más eficientes. En particular esta tesis doctoral presenta un trabajo de carácter fundamental sobre los procesos de fotoexcitación en dispositivos optoelectrónicos orgánicos, donde se usan química teórica y modelización …
ESTIMATION OF OCEANIC PARTICULATE ORGANIC CARBON WITH MACHINE LEARNING
2020
Understanding and quantifying ocean carbon sinks of the planet is of paramount relevance in the current scenario of global change. Particulate organic carbon (POC) is a key biogeochemical parameter that helps us characterize export processes of the ocean. Ocean color observations enable the estimation of bio-optical proxies of POC (i.e. particulate backscattering coefficient, bbp) in the surface layer of the ocean quasi-synoptically. In parallel, the Argo program distributes vertical profiles of the physical properties with a global coverage and a high spatio-temporal resolution. Merging satellite ocean color and Argo data using a neural networkbased method has already shown strong potentia…
Analysis of Biomass Characteristics in MBR and MB-MBR Systems Fed with Synthetic Wastewater: Influence of a Gradual Salinity Increase
2014
The paper presents the results of a field gathering campaign carried out on two different pilot scale membrane bioreactor (MBR) systems, treating synthetic wastewater subject to a gradual increase of salinity. One was a conventional MBR system, while the other was a moving bed biofilm membrane bioreactor (MB-MBR), which combines suspended biomass and biofilm. Indeed, the presence of suspended carriers inside the bioreactor seems to give benefits due to the collisions between the circulating media and the membrane. The aim of the study was the comparison of two configurations in terms of biomass activity characterization and performance (pollutants removal and hydraulic behaviour). The resul…
Sensitivity of a mesoscale model to different convective parameterization schemes in a heavy rain event
2011
Abstract. The Valencia region, on the Mediterranean coast of the Iberian Peninsula, is propitious to heavy precipitation, especially the area encompassing the South of Valencia province and the North of the Alicante province. In October 2007 a torrential rain affected the aforementioned area, producing accumulated rainfall values greater than 400 mm in less than 24 h and flash-floods that caused extensive economic losses and human casualties. This rain event has been studied in numerical experiments using the Regional Atmospheric Modeling System. The present paper deals with the effect of using the different convective parameterizations (CP) currently implemented in the Regional Atmospheric…
A new mixed-mode fracture criterion for large-scale lattice models
2014
Abstract. Reasonable fracture criteria are crucial for the modeling of dynamic failure in computational lattice models. Successful criteria exist for experiments on the micro- and on the mesoscale, which are based on the stress that a bond experiences. In this paper, we test the applicability of these failure criteria to large-scale models, where gravity plays an important role in addition to the externally applied deformation. Brittle structures, resulting from these criteria, do not resemble the outcome predicted by fracture mechanics and by geological observations. For this reason we derive an elliptical fracture criterion, which is based on the strain energy stored in a bond. Simulation…