Boundary Integral Formulation of Frictionless Contact Problems Based on an Energetic Approach and Its Numerical Implementation by the Collocation BEM

A unified methodology to solve problems of frictionless unilateral contact as well as adhesive contact between linear elastic solids is presented. This methodology is based on energetic principles and is casted to a minimization problem of the total potential energy. Appropriate boundary integral forms of the energy are defined and the quadratic problem form of the contact problem is proposed. The problem is solved by the collocation boundary element method (BEM). To solve the quadratic problem two algorithms are developed, both being variants of the well-known conjugate gradient algorithm. The difference between them is given by the explicit construction or not of the quadratic-problem matrix. This matrix has the same physical meaning as the stiffness matrix commonly used in the context of the finite element method (FEM). Both symmetric and non-symmetric formulations of this matrix are presented and discussed, showing that the non-symmetric one provides more accurate results. The present procedure, in addition to its interest by itself, can also be extended to problems where dissipative phenomena take place such as friction, damage and plasticity. Essential steps of the numerical implementation are briefly presented and the numerical solutions of some standard problemsof frictionless contact are given and compared to those obtained by other well-known BEM and FEM procedures for contact problems.Junta de Andalucía TEP-4051European Social Fund TEP-4051Spanish Ministry of Science and Innovation MAT2009-14022Spanish Ministry of Economy and Competitiveness MAT2012-37387 MAT2015-71036-PEuropean Regional Development Fund MAT2012-37387 MAT2015-71036-PSpanish Ministry of Education AP2009-3968Stavros Niarchos Foundatio

Determinación de la humedad de suelo mediante regresión lineal múltiple con datos TerraSAR-X

Revista oficial de la Asociación Española de Teledetección[EN] The first five centimeters of soil form an interface where the main heat fluxes exchanges between the land surface and the atmosphere occur. Besides ground measurements, remote sensing has proven to be an excellent tool for the monitoring of spatial and temporal distributed data of the most relevant Earth surface parameters including soil’s parameters. Indeed, active microwave sensors (Synthetic Aperture Radar - SAR) offer the opportunity to monitor soil moisture (HS) at global, regional and local scales by monitoring involved processes. Several inversion algorithms, that derive geophysical information as HS from SAR data, were developed. Many of them use electromagnetic models for simulating the backscattering coefficient and are based on statistical techniques, such as neural networks, inversion methods and regression models. Recent studies have shown that simple multiple regression techniques yield satisfactory results. The involved geophysical variables in these methodologies are descriptive of the soil structure, microwave characteristics and land use. Therefore, in this paper we aim at developing a multiple linear regression model to estimate HS on flat agricultural regions using TerraSAR-X satellite data and data from a ground weather station. The results show that the backscatter, the precipitation and the relative humidity are the explanatory variables of HS. The results obtained presented a RMSE of 5.4 and a R2 of about 0.6[ES] Los primeros cinco centímetros del suelo forman una interfaz donde se producen los principales intercam-bios de flujos de calor entre la superficie terrestre y la atmósfera. La teledetección ha demostrado ser una excelente herramienta para el seguimiento de datos espacial y temporalmente distribuidos de las características sobresalientes de la superficie terrestre, incluidos los parámetros del suelo. Los sensores de microondas activos (Synthetic Aperture Radar- SAR) ofrecen la posibilidad de monitorizar la humedad de suelo (HS) a escala global, regional y local, mediante la modelación de los procesos involucrados. Diversos algoritmos de inversión han sido desarrollados para derivar información geofísica, como HS, a partir de información SAR. Muchos de ellos utilizan modelos electromagnéticos para simular el coeficiente de retrodispersión y se basan en técnicas estadísticas tales como redes neuronales, mé-todos de inversión y modelos de regresión. Estudios recientes han demostrado que las técnicas simples de regresión múltiple arrojan resultados aceptables. Las variables geofísicas implicadas en estas metodologías son descriptivas de la estructura del suelo, las características de las microondas y la cobertura del suelo. Por esto, en este trabajo se propone desarrollar un modelo de regresión lineal múltiple para estimar HS en zonas de llanura combinando datos de la misión satelital TerraSAR-X y datos de una estación meteorológica. La modelación propuesta involucra las variables hidrológicas que caracterizan las zonas de llanura, donde los movimientos verticales de agua en el suelo predominan sobre el escurrimiento horizontal. Los resultados obtenidos muestran que la retrodispersión, la precipitación y la hu-medad relativa del aire son las variables explicativas de HS. El modelo obtenido arrojó un RMSE de 5,4 y un R2 de 0,6.García, G.; Brogioni, M.; Venturini, V.; Rodriguez, L.; Fontanelli, G.; Walker, E.; Graciani, S.... (2016). Soil moisture estimation using multi linear regression with terraSAR-X data. Revista de Teledetección. (46):73-81. doi:10.4995/raet.2016.4024.SWORD73814

Stability and Electronic Properties of TiO2 Nanostructures With and Without B and N Doping

We address one of the main challenges to TiO2-photocatalysis, namely band gap narrowing, by combining nanostructural changes with doping. With this aim we compare TiO2's electronic properties for small 0D clusters, 1D nanorods and nanotubes, 2D layers, and 3D surface and bulk phases using different approximations within density functional theory and GW calculations. In particular, we propose very small (R < 0.5 nm) but surprisingly stable nanotubes with promising properties. The nanotubes are initially formed from TiO2 layers with the PtO2 structure, with the smallest (2,2) nanotube relaxing to a rutile nanorod structure. We find that quantum confinement effects - as expected - generally lead to a widening of the energy gap. However, substitutional doping with boron or nitrogen is found to give rise to (meta-)stable structures and the introduction of dopant and mid-gap states which effectively reduce the band gap. Boron is seen to always give rise to n-type doping while depending on the local bonding geometry, nitrogen may give rise to n-type or p-type doping. For under coordinated TiO2 surface structures found in clusters, nanorods, nanotubes, layers and surfaces nitrogen gives rise to acceptor states while for larger clusters and bulk structures donor states are introduced

The ZEUS Forward Plug Calorimeter with Lead-Scintillator Plates and WLS Fiber Readout

A Forward Plug Calorimeter (FPC) for the ZEUS detector at HERA has been built as a shashlik lead-scintillator calorimeter with wave length shifter fiber readout. Before installation it was tested and calibrated using the X5 test beam facility of the SPS accelerator at CERN. Electron, muon and pion beams in the momentum range of 10 to 100 GeV/c were used. Results of these measurements are presented as well as a calibration monitoring system based on a $^{60}$Co source.Comment: 38 pages (Latex); 26 figures (ps

Low pressure CO2 hydrogenation to methanol over gold nanoparticles activated on a CeOx/TiO2 Interface

Capture and recycling of CO2 into valuable chemicals such as alcohols could help mitigate its emissions into the atmosphere. Due to its inert nature, the activation of CO2 is a critical step in improving the overall reaction kinetics during its chemical conversion. Although pure gold is an inert noble metal and cannot catalyze hydrogenation reactions, it can be activated when deposited as nanoparticles on the appropriate oxide support. In this combined experimental and theoretical study, it is shown that an electronic polarization at the metal-oxide interface of Au nanoparticles anchored and stabilized on a CeOx/TiO2 substrate generates active centers for CO2 adsorption and its low pressure hydrogenation, leading to a higher selectivity toward methanol. This study illustrates the importance of localized electronic properties and structure in catalysis for achieving higher alcohol selectivity from CO2 hydrogenation.U.S. Department of Energy DE-AC02- 98CH10886, DE-AC02-05CH11231Brookhaven National Laboratory DE-SC001270

Observation of a New Ξb- Resonance

From samples of p p collision data collected by the LHCb experiment at √ s = 7 , 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5     fb − 1 , respectively, a peak in both the Λ 0 b K − and Ξ 0 b π − invariant mass spectra is observed. In the quark model, radially and orbitally excited Ξ − b resonances with quark content b d s are expected. Referring to this peak as Ξ b ( 6227 ) − , the mass and natural width are measured to be m Ξ b ( 6227 ) − = 6226.9 ± 2.0 ± 0.3 ± 0.2     MeV / c 2 and Γ Ξ b ( 6227 ) − = 18.1 ± 5.4 ± 1.8     MeV / c 2 , where the first uncertainty is statistical, the second is systematic, and the third, on m Ξ b ( 6227 ) − , is due to the knowledge of the Λ 0 b baryon mass. Relative production rates of the Ξ b ( 6227 ) − → Λ 0 b K − and Ξ b ( 6227 ) − → Ξ 0 b π − decays are also reported

High-performance hybrid oxide catalyst of manganese and cobalt for low-pressure methanol synthesis

Carbon dioxide capture and use as a carbon feedstock presents both environmental and industrial benefits. Here we report the discovery of a hybrid oxide catalyst comprising manganese oxide nanoparticles supported on mesoporous spinel cobalt oxide, which catalyses the conversion of carbon dioxide to methanol at high yields. In addition, carboncarbon bond formation is observed through the production of ethylene. We document the existence of an active interface between cobalt oxide surface layers and manganese oxide nanoparticles by using X-ray absorption spectroscopy and electron energy-loss spectroscopy in the scanning transmission electron microscopy mode. Through control experiments, we find that the catalyst&apos;s chemical nature and architecture are the key factors in enabling the enhanced methanol synthesis and ethylene production. To demonstrate the industrial applicability, the catalyst is also run under high conversion regimes, showing its potential as a substitute for current methanol synthesis technologies.open2