Effects of communication efficiency and exit capacity on fundamental diagrams for pedestrian motion in an obscure tunnel|a particle system approach

Fundamental diagrams describing the relation between pedestrians speed and density are key points in understanding pedestrian dynamics. Experimental data evidence the onset of complex behaviors in which the velocity decreases with the density and different logistic regimes are identified. This paper addresses the issue of pedestrians transport and of fundamental diagrams for a scenario involving the motion of pedestrians escaping from an obscure tunnel. % via a simple one--dimensional particle system model. We capture the effects of the communication efficiency and the exit capacity by means of two thresholds controlling the rate at which particles (walkers, pedestrians) move on the lattice. Using a particle system model, we show that in absence of limitation in communication among pedestrians we reproduce with good accuracy the standard fundamental diagrams, whose basic behaviors can be interpreted in terms of the exit capacity limitation. When the effect of a limited communication ability is considered, then interesting non--intuitive phenomena occur. Particularly, we shed light on the loss of monotonicity of the typical speed--density curves, revealing the existence of a pedestrians density optimizing the escape. We study both the discrete particle dynamics as well as the corresponding hydrodynamic limit (a porous medium equation and a transport (continuity) equation). We also point out the dependence of the effective transport coefficients on the two thresholds -- the essence of the microstructure information

Weak solutions to Allen-Cahn-like equations modelling consolidation of porous media

We study the weak solvability of a system of coupled Allen--Cahn--like equations resembling cross--diffusion which is arising as a model for the consolidation of saturated porous media. Besides using energy like estimates, we cast the special structure of the system in the framework of the Leray--Schauder fixed point principle and ensure this way the local existence of strong solutions to a regularised version of our system. Furthermore, weak convergence techniques ensure the existence of weak solutions to the original consolidation problem. The uniqueness of global-in-time solutions is guaranteed in a particular case. Moreover, we use a finite difference scheme to show the negativity of the vector of solutions.}{Weak solutions; cross--diffusion system; energy method; Leray--Schauder fixed point theorem; finite differences; consolidation of porous medi

A multiscale Galerkin approach for a class of nonlinear coupled reaction–diffusion systems in complex media

AbstractA Galerkin approach for a class of multiscale reaction–diffusion systems with nonlinear coupling between the microscopic and macroscopic variables is presented. This type of models are obtained e.g. by upscaling of processes in chemical engineering (particularly in catalysis), biochemistry, or geochemistry. Exploiting the special structure of the models, the functions spaces used for the approximation of the solution are chosen as tensor products of spaces on the macroscopic domain and on the standard cell associated to the microstructure. Uniform estimates for the finite dimensional approximations are proven. Based on these estimates, the convergence of the approximating sequence is shown. This approach can be used as a basis for the numerical computation of the solution

Thrački konjanik

Today, mobile devices have become an integral part of their possessor’s life. Learning using mobile devices has the advantage of receiving educational content at the moment when it is actually needed, or when the learner feels like s/he is able to study. Moreover, mobile devices used in education can augment the learning experience by delivering further information to the learner, depending on the learner’s context. However, there are still challenges to overcome in order to achieve a widespread adoption of mobile learning. One of these is the high cost of delivering educational content over wireless networks, especially when multimedia content is transmitted. This research proposes a solution that predicts the learner’s economic behaviour and takes it into account when delivering educational multimedia content. A mechanism for reducing the cost of the educational content delivery over wireless networks is also presented

Does an aromatic chloride substitute position influence the aggregation properties of direct dyes?

Dyes ions have a tendency to self-associate in aqueous solutions. The main factors influencing aggregation are dye concentration, electrolyte concentration, and temperature. In the present work, the influence of the chloride position in the dye structure on the dye aggregation was investigated. The molecular aggregation has been studied spectrophotometrically in aqueous solutions as a function of dye concentration (10'6 -s- 10"3 mol/L). As the concentration increases, different changes were observed in the dyes UV-vis spectra indicating that the molecules are beginning to aggregate. The shapes of the obtained spectra were totally different as the position of the chloride was changed in the dye molecule

Experimental study of the interaction of one local anesthetic with a cellulose type support

The extent of the adsorption of a local anesthetic (Bupivacaine) on a pharmaceutical adsorbent, namely microcrystalline cellulose (MCC) suspended in aqueous solution was investigated spectrophotometrically at three different temperatures. The equilibrium adsorption contact times were determined for all the temperatures and were found around 90 minutes. Adsorption isotherms have been analyzed by the Freundlich and Langmuir models. The obtained results indicated that the Freundlich isotherms presented the highest correlation coefficients, and thus they describe better the adsorption of the studied drug on MCC

Colour expression in the Cielab colour scale of new stilbene dyes

Using the well known CIELAB colour space parameters: lightness (L*), redness (a*), yellowness (b*), chroma (C*) and hue angle (h°) relative to the standard illuminants D65 (natural day light), A (tungsten light), and the standard 10° observer, the colour expression of two new symmetrical direct disazo-stilbene dyes was performed. The colour differences AEab* and AECMC were calculated against one standard, indicating a high colouring power of the both disazo-stilbene dyes. The studied dyes were synthesized using 4,4'- diaminostilbene-2,2'-disulphonic acid as middle eco-friendly component and 2-methyl-Nacetoacetanilide and 5-acetoacetylaminobenzimidazolone as coupling components respectively

Efficient removal of methylene blue from colored wastewater using magnetite/carbon nanocomposite

In this work, a new nanocomposite based on activated carbon and magnetite (PM) was synthesized and characterized by the most indicated and modern methods. The obtained magnetite/carbon nanocomposite was tested as adsorbent for the removal of Methylene Blue (MB) from colored wastewater. In ortder to elucidate the adsorption mechanism, kinetic and thermodynamic studies were carried out. The high adsorption capacity of the synthesized nanocomposite was highlighted by regeneration and reuse studies in consecutive adsorption/desorption cycles