Approximation of the effective conductivity of ergodic media by periodization

 This paper is concerned with the approximation of the effective conductivity σ(A, μ) associated to an elliptic operator ∇ _xA (x,η)∇ _x where for xℝ ^d , d≥1, A(x,η) is a bounded elliptic random symmetric d×d matrix and η takes value in an ergodic probability space (X, μ). Writing A ^N (x, η) the periodization of A(x, η) on the torus T ^d _N of dimension d and side N we prove that for μ-almost all η

A subharmonic dynamical bifurcation during in vitro epileptiform activity

Epileptic seizures are considered to result from a sudden change in the synchronization of firing neurons in brain neural networks. We have used an in vitro model of status epilepticus (SE) to characterize dynamical regimes underlying the observed seizure-like activity. Time intervals between spikes or bursts were used as the variable to construct first-return interpeak or interburst interval plots, for studying neuronal population activity during the transition to seizure, as well as within seizures. Return maps constructed for a brief epoch before seizures were used for approximating the local system dynamics during that time window. Analysis of the first-return maps suggests that intermittency is a dynamical regime underlying the observed epileptic activity. This type of analysis may be useful for understanding the collective dynamics of neuronal populations in the normal and pathological brain.     

A New Algorithm for Digital Image Encryption Based on Chaos Theory

In recent decades, image encryption, as one of the significant information security fields, has attracted many researchers and scientists. However, several studies have been performed with different methods, and novel and useful algorithms have been suggested to improve secure image encryption schemes. Nowadays, chaotic methods have been found in diverse fields, such as the design of cryptosystems and image encryption. Chaotic methods-based digital image encryptions are a novel image encryption method. This technique uses random chaos sequences for encrypting images, and it is a highly-secured and fast method for image encryption. Limited accuracy is one of the disadvantages of this technique. This paper researches the chaos sequence and wavelet transform value to find gaps. Thus, a novel technique was proposed for digital image encryption and improved previous algorithms. The technique is run in MATLAB, and a comparison is made in terms of various performance metrics such as the Number of Pixels Change Rate (NPCR), Peak Signal to Noise Ratio (PSNR), Correlation coefficient, and Unified Average Changing Intensity (UACI). The simulation and theoretical analysis indicate the proposed scheme’s effectiveness and show that this technique is a suitable choice for actual image encryption.     

Computational simulation of variable magnetic force on heat characteristics of backward-facing step flow

Journal of Thermal Analysis and Calorimetry - The application of the nanofluid is highly increased due to its high heat rate in the attendance of the magnetic field. In current investigation, CFD...     

A new amino alcohol NpyNimineNamineOalcohol-donor ligand: coordination toward zinc(II) and cadmium(II) halides and enantioselective products

In the present work a new ligand, 2-(2-(phenyl(pyridin-2-yl)methyleneamino)ethylamino)ethanol (L), and its Zn(II) and Cd(II) complexes, [Zn(L)Br₂] (1), [Cd(L)Br₂] (2) and [Cd(L)I₂] (3), have been synthesized and characterized by elemental analysis, FT-IR, Raman and ¹H NMR spectroscopies as well as X-ray crystallography. All complexes are isostructural and their metal ions have distorted square pyramidal geometry with an MN₃X₂ (X: Br, I) environment. During the complexation process, the amine group of the ligand becomes a chiral center. In the solid-state, an R-configuration was observed in all three complexes. Furthermore, the molecules form intermolecular C–H?O, C–H?X and O–H?X (X: Br, I) hydrogen bonds in the solid-state.     

Expanding scissor-based UGV for large obstacles climbing

This research proposes a new extendable platform for an unmanned ground vehicle to overcome the obstacle climbing issue. The new platform is basically established on scissor mechanism principles which have been innovated to achieve long and rigid displacement. A couple of scissor mechanisms are embedded in the rover platform adjusting the mass center of rover respect to the rear and front wheels. Accordingly, it yields geometric control of the contact forces, which can simultaneously reduce the slip of the wheels and increase the performance of the obstacle climbing up. To demonstrate the performance of the proposed platform, the 3D kinematics is derived. Subsequently, the stick-slip Euler-Lagrange dynamics is derived and a three-level controller including the torque optimization is implemented to simulate the rover facing obstacles. Finally, without any hardware prototyping, the extendable rover is simulated and compared with a typical fixed-geometry rover to show the enhancement of the climbing ability by using the proposed concept. Moreover, controlling the normal contact forces of the wheels yields the slip reduction, which subsequently, increases the traction force.     

Multifunctional poly(amidoamine)-functionalized silica nanoparticles for epoxide-functionalized polyurethane and novolac resins crosslinking

Journal of Thermal Analysis and Calorimetry - Polyurethane and novolac resins functionalized with epoxide groups were cured by a multifunctional crosslinking agent decorated with amine functional...     

Entropy generation of nanomaterial through a tube considering swirl flow tools

Journal of Thermal Analysis and Calorimetry - The focus of the current investigation is on insertion of complex-shaped device for inducing swirl intensity. H2O-based copper oxide mixture was...     

Template synthesis of a rare 14-membered macrocyclic complex using cadmium(II) ion as a collector

Journal of Inclusion Phenomena and Macrocyclic Chemistry - In this work, a new macrocyclic cadmium complex, [Cd(ACE)I]2[CdI4] (1); ACE: 1,3,6,10,12,15-hexaazatricyclo[13.3.1.16,10]eicosane, was...     

Ferrofluid non-Darcy heat transfer involving second law analysis: an application of CVFEM

Journal of Thermal Analysis and Calorimetry - The non-Darcy heat transportation of the ferrofluid together with the entropy generation has been studied in a permeable zone under the role of...