Search results for "visual_art"
showing 10 items of 2987 documents
Capturing digital data of rock magnetic, gamma-ray and IR spectrometry for in-situ quality control and for the study of the physical–chemical regime …
2014
Abstract Residual kaolin deposits are operated on a worldwide basis. The majority of them is derived from chemical weathering of felsic rocks during the Cenozoic. This is true for the kaolin deposits on the western edge of the Bohemian Massif. Here this type of deposit provides industrial minerals for the ceramic industry in SE Germany. This raw material formed under tropical climatic conditions during the Miocene and Pliocene across a vast peneplain. Only within the Naab-Wondreb Depression, however, were economic accumulations preserved from erosion. Here near Tirschenreuth, kaolin has been mined since its discovery in 1830. The semi-consolidated regolith is composed of quartz and opaline …
Incorporation of trace metals Cu, Zn, and Cd into gypsum: Implication on their mobility and fate in natural and anthropogenic environments
2020
Abstract The coexistence of calcium (Ca2+), sulfate (SO42−) with trace metal cations (M(II)) can possibly lead to M(II)-gypsum coprecipitation and solid solution formation. However, gypsum's role in the fixation of M(II) is still largely unknown. This study investigated the precipitation of Ca2+ and SO42− in the presence of M(II) (i.e., Cu2+, Zn2+, or Cd2+) and the incorporation of the metal cations into the gypsum structure at different environmental conditions. Trace metals in two natural gypsum samples (Yunnan and Neimeng, China) and one hydrometallurgical byproduct gypsum sample from a Cu refinery were also assessed. X-ray diffraction, scanning electron microscopy-energy dispersive X-ra…
La Dernière Cène du réfectoire du monastère de Santa Cruz de Coimbra par Maître Hodart : considérations préalables sur la place d’une œuvre singulière
2018
Cet article a pour but de traiter d’une question qui hante l’historiographie de la Renaissance portugaise depuis longtemps. Le magnifique groupe de terre cuite grandeur nature représentant la Cène dans le réfectoire du monastère de Santa Cruz de Coimbra est aujourd’hui l’un des chefs-d’oeuvre du musée Machado de Castro de la ville, ainsi qu’encore une énigme. L’identité et le parcours du mystérieux maître Hodart, auquel quelques maigres sources permettent d’attribuer le groupe, restent l’objet de nombreuses spéculations. Ce texte se propose donc de situer cette oeuvre emblématique dans le concert plus large des arts européens du premier quart du XVIe siècle et de reconnaître des liens possi…
Optimization of the Surface Roughness Equation obtained by Al7136 End-Milling
2017
The aim of this paper is to optimize the regression equation of the surface roughness obtained by 7136 aluminium alloy machined by end-milling process. The surface roughness is dependent on certain process parameters, which can vary, causing in this way variations of the surface quality. The research method used in this paper is the experiment and the Taguchi design of experiment. The experiment was performed using an experimental stand, in which every step to get the purpose, is presented. The measurements were made using a portable surface roughness tester. In the first part of the paper the influence percentage of the involved parameters in the machining process, was determined. Then, a …
Surface finish generated in hard turning of quenched alloy steel parts using conventional and wiper ceramic inserts
2006
Abstract Significant progress has already been achieved in green manufacturing including dry and hard, often high-speed, machining technologies. For instance, the demand for higher productivity has resulted in the wider application of ceramic and PCBN tools with special multi-radii (wiper) geometry. This paper reports some important characteristics of the surface roughness produced in the turning of a hardened low-chromium alloy steel using mixed alumina–titanium carbon (TiC) ceramic cutting tools equipped with both conventional and wiper inserts. The characteristic geometrical features of surfaces obtained in both these turning operations have been assessed by means of representative two-d…
New Quadratic Self-Assembly of Double-Decker Phthalocyanine on Gold(111) Surface : From Macroscopic to Microscopic Scale
2018
Unveiling the self-organization mechanism of semiconducting organic molecules onto metallic surfaces is the first step to design hybrid devices in which the self-assembling is exploited to tailor magnetic properties. In this study, double-decker rare-earth phthalocyanines, namely, lutetium phthalocyanine (LuPc2), are deposited on Au(111) gold surface forming large-scale self-assemblies. Global and local experimental techniques, namely, grazing incidence X-ray diffraction and scanning tunneling microscopy, supplemented by density functional theory calculations with van der Waals corrections, give insight into the molecular structural arrangement of the thin film and the self organization at …
Noble-gas bubbles in metals: Molecular-dynamics simulations and positron states.
1987
A theoretical treatment of atomic structure and positron states in noble-gas bubbles in metals is presented. The Al-He and Cu-Kr systems are considered as specific examples. For large bubbles (radii above a few tens of angstroms) a calculational scheme is developed combining molecular-dynamics results for the metal--noble-gas interface with positron calculations. It is demonstrated that a positron is trapped at the surface of a noble-gas bubble, i.e., at the metal-gas interface. The annihilation rate with metal electrons is similar to that at a clean surface, while simultaneously there is a significant annihilation rate with gas-atom electrons. This enables relationships between the gas den…
Surface Anisotropy in the Expansion Behavior of Laminated Quasi-Isotropic Composites
1984
Mesure a l'aide d'un extensometre des deformations thermiques superficielles de deux materiaux stratifies resine epoxy-fibre de graphite. Les resultats dependent de la direction de mesure, l'anisotropie superficielle associee est inversement proportionnelle aux dimensions de l'echantillon et proportionnelle au rapport d'anisotropie d'une lamelle isolee. Comparaison avec la theorie des stratifications
Ridge-enhanced optical transmission through a continuous metal film
2004
Optical transmission through a continuous (without holes) metal film with a periodic structure of metal or dielectric ridges on one or both interfaces was numerically studied. The dependencies of the transmission on the ridge width and height as well as the ridge arrangements on the opposite interfaces were investigated in weak- and strong-coupling regimes. The transmission enhancement was shown to depend on the relative position of the ridge gratings on the opposite interfaces of a film, confirming the role of resonant tunneling processes involving states of the surface polariton Bloch modes.
Theory of positronium momentum spectra at metallic surfaces
1986
Theoretical calculations of momentum distributions of positronium (Ps) atoms ejected from clean metal surfaces are presented and compared with recent experimental results. The authors find that the momentum dependence of the Ps-forming interaction significantly affects the shape of the spectra. They also show that, within the model, the energy distribution of Ps atoms does not vary directly with the density of electronic states just outside the surface.