Temperature at Horizon in de Sitter Spacetime

It is found that there is no period in the imaginary Beltrami-time of the de Sitter spacetime with Beltrami metric and that the `surface-gravity' in view of inertial observers in de Sitter spacetime is zero! They show that the horizon might be at zero temperature in de Sitter spacetime and that the thermal property of the horizon in the de Sitter spacetime with a static metric should be analogous to that of the Rindler horizon in Minkowski spacetime.Comment: 7 pages, 1 figur

On Beltrami Model of de Sitter Spacetime

Based on some important properties of $dS$ space, we present a Beltrami model ${\cal B}_\Lambda$ that may shed light on the observable puzzle of $dS$ space and the paradox between the special relativity principle and cosmological principle. In ${\cal B}_\Lambda$, there are inertial-type coordinates and inertial-type observers. Thus, the classical observables can be defined for test particles and light signals. In addition, by choosing the definition of simultaneity the Beltrami metric is transformed to the Robertson-Walker-like metric. It is of positive spatial curvature of order $\Lambda$. This is more or less indicated already by the CMB power spectrum from WMAP and should be further confirmed by its data in large scale.Comment: 4 page

Snyder's Model -- de Sitter Special Relativity Duality and de Sitter Gravity

Between Snyder's quantized space-time model in de Sitter space of momenta and the \dS special relativity on \dS-spacetime of radius $R$ with Beltrami coordinates, there is a one-to-one dual correspondence supported by a minimum uncertainty-like argument. Together with Planck length $\ell_P$, $R\simeq (3/\Lambda)^{1/2}$ should be a fundamental constant. They lead to a dimensionless constant $g{\sim\ell_PR^{-1}}=(G\hbar c^{-3}\Lambda/3)^{1/2}\sim 10^{-61}$. These indicate that physics at these two scales should be dual to each other and there is in-between gravity of local \dS-invariance characterized by $g$. A simple model of \dS-gravity with a gauge-like action on umbilical manifolds may show these characters. It can pass the observation tests and support the duality.Comment: 32 page

Anion-exchange synthesis of thermoelectric layered SnS0.1Se0.9-xTex nano/microstructures in aqueous solution; complexity and carrier concentration

Nanostructured SnS0.1Se0.9-xTex (x = 0.02, 0.05, 0.08) quaternary chalcogenides have been controllably synthesised via a facile solution-processable anion-exchange method. All the products exist as “flower-like” architectures assembled from individual nano/microplates that are each hundreds of nanometers in thickness and several micrometers in lateral size. This morphology is essentially preserved from the original SnS starting material. Spark plasma sintering (SPS) not only consolidates the as-prepared powder samples, but also eliminates secondary phases, leading to pellets of phase-pure SnS0.1Se0.9-xTex solid solution members. The electrical conductivity of SnS0.1Se0.88Te0.02 is significantly enhanced over the Te-free material in the low-temperature range, achieving a peak value of ≈5760 S m-1 at 373 K, which is ≈41% higher than SnS0.1Se0.9 at the same temperature. Also possessing a high Seebeck coefficient, SnS0.1Se0.88Te0.02 exhibits a maximum power factor (ca. 0.54 mW m-1 K-2) at 423 K. The thermoelectric performance of SnS0.1Se0.9-xTex has been optimised through modifying the Te concentration, leading to a peak ZT of ≈0.43 for SnS0.1Se0.88Te0.02 at 773 K. This robust, scalable and surfactant-free approach paves the way to engineer increasingly complex (in this case, quaternary) metal chalcogenides controllably in aqueous solution

The mechanism of inhibiting swelling deformation and slope instability of expansive soils by replacement method

Za padine od ekspanzivnih tala, zamjena glinom koja ne nabrekne je uvijek najučinkovitija mjera. Ipak, još uvijek postoje neriješeni problemi u načinu zamjene, uključujući kako odrediti optimalnu debljinu zamjene i da li dolazi do nestabilnosti padina ekspanzivnih tala. U ovom je radu primijenjen "Stress Path Triaxial Testing System" (GDS) za istraživanje troosnog omjera izdizanja. Predložen je troosni model omjera izdizanja za ekspanzivna tla i taj je model razvijen u ABAQUSu. Nanesena je zamjenska glina različite debljine pri ispitivanju padina sastavljenih od čvrstog, srednjeg i slabog ekspanzivnog tla. Provedena je i analiza osjetljivosti primjenom metode konačnih elemenata. Za padinu od čvrstog ekspanzivnog tla s prirodnim sadržajem vlage od 27,5 % faktor sigurnosti bez zamjene glinom bio je 0,73. Faktor sigurnosti bio je 0,85; 1,08 i 1,33 uz odgovarajuću debljinu zamjene od 1 m, 2 m i 3 m. Rezultati su potvrdili da se metodom zamjene može ne samo spriječiti izdizanje ekspanzivnih tala već se može i odgovarajuće poboljšati stabilnost padine. Uz to, različitim debljinama zamjene mogu se postići različiti omjeri povećanja faktora sigurnosti padine. Rastući omjer se nelinearno promijenio. Konačno, pokazan je mehanički mehanizam učinaka smanjenja metodom zamjene na nestabilnost padine od ekspanzivnog tla. Rezultati istraživanja mogu pružiti teoretsku osnovu za praktično inženjerstvo u tretiranju opasnosti od izdizanja kod padina od ekspanzivnog tla.For expansive soils slope, replacement with non-swelling clay is always the most vital treatment measure. However, there are still many unsolved problems in the replacement method, including how to determine the optimal replacement thickness, and whether there was inhibition effect on slope instability of expansive soils. In this study, a "Stress Path Triaxial Testing System" (GDS) has been applied for exploring triaxial swelling rate. It proposed a triaxial swelling rate model for expansive soils, and this model was secondary developed and embedded in ABAQUS. Different thicknesses of replacement clay have been applied in treating slopes composed by strong, medium and weak expansive soil respectively. Sensitivity analysis also has been carried out with finite element method. For the strong expansive soil slope with natural moisture content 27,5 %, the safety coefficient without clay replacement was 0,73. The safety coefficient was 0,85; 1,08 and 1,33 with the replacement thickness of 1 m, 2 m and 3 m, respectively. The results validated that the replacement method could not only effectively inhibit the swelling of expansive soils, but also correspondingly improve the slope stability. In addition, the different replacement thicknesses could bring varied increasing rate of slope safety coefficient. The increasing rate was nonlinearly changed. Finally, it demonstrated the mechanical mechanism of inhibiting effects from existing replacement method on slope instability of expansive soils. The research results are able to provide theoretical basis for practical engineering. It could be conductive to treating swelling danger from expansive soil slope