Search results for "Honeycomb"
showing 10 items of 33 documents
Efficient finite difference formulation of a geometrically nonlinear beam element
2021
The article is focused on a two-dimensional geometrically nonlinear formulation of a Bernoulli beam element that can accommodate arbitrarily large rotations of cross sections. The formulation is based on the integrated form of equilibrium equations, which are combined with the kinematic equations and generalized material equations, leading to a set of three first-order differential equations. These equations are then discretized by finite differences and the boundary value problem is converted into an initial value problem using a technique inspired by the shooting method. Accuracy of the numerical approximation is conveniently increased by refining the integration scheme on the element lev…
Momentum-space structure of surface states in a topological semimetal with a nexus point of Dirac lines
2016
Three-dimensional topological semimetals come in different variants, either containing Weyl points or Dirac lines. Here we describe a more complicated momentum-space topological defect where several separate Dirac lines connect with each other, forming a momentum-space equivalent of the real-space nexus considered before for helium-3. Close to the nexus the Dirac lines exhibit a transition from type I to type II lines. We consider a general model of stacked honeycomb lattices with the symmetry of Bernal (AB) stacked graphite and show that the structural mirror symmetries in such systems protect the presence of the Dirac lines, and also naturally lead to the formation of the nexus. By the bu…
Highly textured boron/nitrogen co-doped TiO2 with honeycomb structure showing enhanced visible-light photoelectrocatalytic activity
2020
International audience; In this work, we report a novel photocatalyst based on boron and nitrogen co-doped TiO2 rutile (1 1 0) honeycomb structures. The photocatalyst has been prepared by simultaneously oxidizing and doping a Ti-foil substrate at 750 degrees C. The unit cell volume and the crystallite size of grown TiO2 films were measured by Rietveld refinement analysis. The co-doping by boron and nitrogen was achieved simultaneously with the oxidation of the titanium, resulting in a rutile (1 1 0) textured TiO2 film. X-ray photoelectron spectroscopy analysis revealed the presence of Ti-O-N and Ti-O-B-N bonds, and the presence of crystal defects in the lattice was detected and displayed by…
Two-Dimensional Carbon: A Review of Synthesis Methods, and Electronic, Optical, and Vibrational Properties of Single-Layer Graphene
2019
Graphite has been widely used by humans for a large part of their history. Nevertheless, it has only recently been possible to isolate its basic unit: carbon atoms arranged in a honeycomb structure on a single plane, namely graphene. Since its discovery, many techniques have been developed and improved to properly synthesize graphene and its derivatives which are part of the novel class of two-dimensional materials. These advanced materials have imposed themselves in nanotechnology thanks to some outstanding physical properties due to their reduced dimensions. In the case of graphene, its reduced dimension gives rise to a high electrical mobility, a large thermal conductivity, a high mechan…
On critical properties of the Berry curvature in the Kitaev honeycomb model
2019
We analyse the Kitaev honeycomb model, by means of the Berry curvature with respect to Hamiltonian parameters. We concentrate on the ground-state vortex-free sector, which allows us to exploit an appropriate Fermionisation technique. The parameter space includes a time-reversal breaking term which provides an analytical headway to study the curvature in phases in which it would otherwise vanish. The curvature is then analysed in the limit in which the time-reversal-symmetry-breaking perturbation vanishes. This provides remarkable information about the topological phase transitions of the model. The Berry curvature in itself exhibits no singularities at criticality, nevertheless it distingui…
Synthesis, Structure, and Magnetic Properties of [(S)-[PhCH(CH3)N(CH3)3]][Mn(CH3CN)2/3Cr(ox)3]·(CH3CN)_(solvate), a 2D Chiral Magnet Containing a Qua…
2008
The synthesis, structure, and magnetic properties of a novel oxalate-based bimetallic magnet obtained by using the chiral (S)-trimethyl-(1-phenyl-ethyl)-ammonium, ((S)-[PhCH(CH3)N(CH3)3](+)), cation as template is reported. This compound can be formulated as [(S)-[PhCH(CH3)N(CH3)3]][Mn(CH3CN)2/3Cr(ox)3] x (CH3CN)_(solvate), and it crystallizes in the chiral trigonal space group P3. It shows a distorted two-dimensional honeycomb structure formed by Mn(II) and Cr(III) ions connected through oxalate anions with [(S)-[PhCH(CH3)N(CH3)3](+) cations and solvent molecules intercalated between the oxalate layers. Two-thirds of the Mn(II) ions of the honeycomb anionic network are heptacoordinated. Th…
An ultrathin suspended hydrophobic porous membrane for high-efficiency water desalination
2017
Abstract An ultrathin highly fluorinated porous membrane was designed for a large production of desalted water at very low energy consumption. Imprinting water droplets were used through a low thermally conductive tetra-fluoroethylene (TFE)/2,2,4-trifluoro-5-tri-fluorometoxy-1,3-dioxol (TIT) (HYFLON AD 60) solution and the generated porous nanofilm was suspended onto a polyethersulfone (PES) honeycomb texture. The very tiny fluorinated thickness together with a large number of small-shaped pores provided the membrane for enhanced anti-wetting surface properties, extremely reduced resistance to water vapor transfer and outstanding thermal efficiency. Fine materials structure-transport relati…
Out-of-plane elastic constants of curved cell walls honeycombs
2021
International audience; The work describes the out-of-plane properties of a curved wall honeycomb structure evaluated using analytical models and finite elements techniques. Out-of-plane properties are calculated using a theoretical approach based on energy theorems and validated using a fullscale<br>finite element technique to simulate transverse shear tests. The effects of the curvature of the walls and the depth of the honeycomb cells on the out-of-plane elastic constants are evaluated and excellent agreement is observed between theoretical and numerical models. These curved cell wall honeycombs feature specific (i.e., relative density weighted) highly tailorable upper shear bounds tha…
Exploring the diversity of listeria monocytogenes biofilm architecture by high-throughput confocal laser scanning microscopy and the predominance of …
2015
ABSTRACT Listeria monocytogenes is involved in food-borne illness with a high mortality rate. The persistence of the pathogen along the food chain can be associated with its ability to form biofilms on inert surfaces. While most of the phenotypes associated with biofilms are related to their spatial organization, most published data comparing biofilm formation by L. monocytogenes isolates are based on the quantitative crystal violet assay, which does not give access to structural information. Using a high-throughput confocal-imaging approach, the aim of this work was to decipher the structural diversity of biofilms formed by 96 L. monocytogenes strains isolated from various environments. Pr…
Was heißt wie? Ansatz und Glossar zu Befundung und Verständnis in der HRCT der Lunge
1996
In HRCT reports multiple different, often synonymous, German and English terms are used. The variety of terms impede understanding and acceptance of HRCT. Purpose of this paper is to present a scheme, which is based on the anatomic landmarks (secondary lobule), and the density of pathologic changes, as well as a glossary from the German HRCT-literature, including suitable terms, definitions, synonyms and English terms. Low attenuation changes include emphysemas, air-filled cavities (bullae, cysts, cavitations, honeycombing) and bronchial dilatation, changes with increased density consist of diffuse (ground glass opacity, consolidation) and focal processes (reticular and nodular densities). …