Search results for " Stab"
showing 10 items of 1773 documents
An Ultrahigh CO2-Loaded Silicalite-1 Zeolite: Structural Stability and Physical Properties at High Pressures and Temperatures
2018
[EN] We report the formation of an ultrahigh CO2-loaded pure-SiO2, silicalite-1 structure at high pressure (0.7 GPa) from the interaction of empty zeolite and fluid CO, medium. The CO2-filled structure was characterized in situ by means of synchrotron powder X-ray diffraction. Rietveld refinements and Fourier recycling allowed the location of 16 guest carbon dioxide molecules per unit cell within the straight and sinusoidal channels of the porous framework to be analyzed. The complete filling of pores by CO, molecules favors structural stability under compression, avoiding pressure-induced amorphization below 20 GPa, and significantly reduces the compressibility of the system compared to th…
Performance of a thermoelectric module based on n-type (La0.12Sr0.88)0.95TiO3-δ and p-type Ca3Co4-xO9+δ
2020
Here, we present the performance of a thermoelectric (TE) module consisting of n-type (La0.12Sr0.88)0.95TiO3 and p-type Ca3Co4-xO9+δ materials. The main challenge in this investigation was operation of TE module in different atmosphere conditions, since n-type has its optimum TE-performance at reducing, while p-type at oxidizing conditions. The TE module was exposed to two different atmospheres and demonstrated higher stability in N2 atmosphere than in air. The maximum electrical power output decreased after 40 h when the hot side was exposed to N2 at 600 °C, while only 1 h at 400 °C in ambient air was enough to oxidize (La0.12Sr0.88)0.95TiO3 followed by a reduced electrical power output. T…
Theoretical and experimental study of the structural stability ofTbPO4at high pressures
2010
We have performed a theoretical and experimental study of the structural stability of terbium phosphate at high pressures. Theoretical ab initio total-energy and lattice-dynamics calculations together with x-ray diffraction experiments have allowed us to completely characterize a phase transition at {approx}9.8 GPa from the zircon to the monazite structure. Furthermore, total-energy calculations have been performed to check the relative stability of 17 candidate structures at different pressures and allow us to propose the zircon {yields} monazite {yields} scheelite {yields} SrUO{sub 4}-type sequence of stable structures with increasing pressure. In this sequence, sixfold P coordination is …
High-pressure theoretical and experimental study of HgWO4
2011
HgWO 4 at ambient pressure is characterized using a combination of ab initio calculations, X-ray diffraction and Raman scattering measurements. The effect of low pressure and temperature on the structural stability is analysed. Extending our ab initio study to the range of higher pressures, a sequence of stable phases up to 30GPa is proposed. © 2011 Taylor & Francis.
Pattern formation in clouds via Turing instabilities
2020
Pattern formation in clouds is a well-known feature, which can be observed almost every day. However, the guiding processes for structure formation are mostly unknown, and also theoretical investigations of cloud patterns are quite rare. From many scientific disciplines the occurrence of patterns in non-equilibrium systems due to Turing instabilities is known, i.e. unstable modes grow and form spatial structures. In this study we investigate a generic cloud model for the possibility of Turing instabilities. For this purpose, the model is extended by diffusion terms. We can show that for some cloud models, i.e special cases of the generic model, no Turing instabilities are possible. However,…
Triphenylmethyl and triphenylsilyl based molecular glasses for photonic applications
2015
Triphenylmethyl and triphenylsilyl structural fragments can be used to obtain glass forming, solution processable materials from polar chromophore molecules. Large number of compounds has been synthesized taking advantage of this approach, making it possible to identify some structure-property relations. Regarding the non-linear optical (NLO) properties of the given materials it is evident that triphenylmethyl groups help shielding unwanted NLO efficiency limiting dipolar interactions between polar chromophores in solid films. Chromophore stacking is still observed for compounds with large dipole momentum values. The glass transition temperatures of the compounds increase with the molecular…
Transitive partially hyperbolic diffeomorphisms on 3-manifolds
2005
Abstract The known examples of transitive partially hyperbolic diffeomorphisms on 3-manifolds belong to 3 basic classes: perturbations of skew products over an Anosov map of T 2 , perturbations of the time one map of a transitive Anosov flow, and certain derived from Anosov diffeomorphisms of the torus T 3 . In this work we characterize the two first types by a local hypothesis associated to one closed periodic curve.
Quantum Relaxation Time in Asymmetric Bistable Potential
2010
Quantum tunneling effect occurs often in condensed matter physics, examples are JJs, heteronanostructures, etc.. The tunneling effect plays an important role in the nonlinear relaxation time from a metastable state in an open quantum system, interacting with a thermal bath. Symmetrical and asymmetric bistable systems are good quantum model systems for analysis of the "superconducting quantum bits" and decoherence phenomena. To obtain very long coherence times in the presence of interaction between the qubit and the noisy environment is one of the greatest challenges of physics. The inf1uence of the environment in quantum tunneling has been in the focus of intense research over the last year…
A new solver for incompressible non-isothermal flows in natural and mixed convection over unstructured grids
2022
Abstract In the present paper we propose a new numerical methodology for the solution of 2D non-isothermal incompressible flows for natural and mixed convection in irregular geometries. The governing equations are the Incompressible Navier-Stokes Equations and the Energy Conservation Equation. Fluid velocity and temperature are coupled in the buoyancy term of the momentum equations according to the Oberbeck–Boussinesq approximation. The governing equations are discretized over unstructured triangular meshes satisfying the Delaunay property. Thanks to the Oberbeck–Boussinesq hypothesis, the flow and energy problems are solved in an uncoupled way, and two fractional time step procedures are s…
Immediate implants following tooth extraction. A systematic review
2012
Objectives: The aim of this article is to review the current state of immediate implants, with their pros and contras, and the clinical indications and contraindications. Material and Methods: An exhaustive literature search has been carried out in the COCHRANE library and MEDLINE electronic databases from 2004 to November 2009. Randomized clinical trials and clinical trials focused on single implants placed in fresh extraction sockets were included and compared. A meta-analysis could not be performed due to heterogeneity of the data. Results: Twenty studies out of 135 articles from the initial search were finally included, which summed up a total of 1139 immediate implants with at least a …