Morphological,rheological, and mechanical properties of ethylene propylene diene monomer/carboxylated styrene-butadiene rubber/multiwall carbon nanotube nanocomposites

Abstract

A hybrid nanocomposite based on ethylene propylene diene monomer/carboxylated styrene-butadiene rubber (EPDM/XSBR) blend with different concentrations (0–7 phr) of multiwall carbon nanotube (MWCNT) was prepared on a two-roll mill. The role of grafted maleic anhydride (EPDM-g-MA) as compatibilizer and the effect of different concentrations of MWCNT on mechanical properties, morphology, rheological and curing characteristics of nanocomposites were investigated. The curing behavior of the prepared nanocomposites was studied using a rheometer. Also, the microstructure of nanocomposites was observed using TEM. By increasing the MWCNT concentration in the compatible blends, the curing time and scorch time of the blends decreased, while the maximum and minimum torque increased. Failure surface morphology studies showed that the existence of EPDM-g-MAH compatibilizer improved the distribution of MWCNT within the polymer matrix and uniform distribution of MWCNT with a small amount of aggregation was obtained. On the other hand, the presence of MWCNT in the matrix led to a sharper surface of the fracture. Also, mechanical properties such as modulus, tensile strength, hardness, fatigue, resilience and elongation-at-break for compatible EPDM/XSBR nanocomposite showed better results than those for incompatible composite.     

A Study of Downward Sets with p-Functions

In this paper, we study downward sets and increasing functions in a topological vector space and their similarities to the convex sets and convex functions. It will be shown that a very special increasing function, namely, the p-function, can give a geometric interpretation for separating downward sets from outside points. Also, this function can be used to approximate topical functions in the framework of abstract convexity.     

A Catalytic Route to Pyrrole Derivatives via Copper‐catalyzed Multicomponent Reaction

A novel approach for the synthesis of pyrrole derivatives has been reported. The reactions starting from terminal alkynes, carbodiimides, and malononitrile using CuI, DBU, and TBPAc in anhydrous MeCN afforded the functionalized pyrroles in acceptable yields. Alkyl‐, aryl‐, and heteroaromatic terminal alkynes were tolerated. Carbodiimides could be symmetrical and unsymmetrical substrates with aryl or alkyl substituents. The reaction exhibited a good regioselectivity when unsymmetrical carbodiimides were employed.     

Evaluating the modulated gradient model in large eddy simulation of channel flow with OpenFOAM

Recently, a new family of subgrid-scale (SGS) models, termed as gradient-based models, has been introduced to calculate the SGS stresses in large eddy simulation (LES). In the present work, the modulated gradient model (MGM) was implemented in the OpenFOAM package, and the pimpleFoam solver was improved to be adopted with non-eddy viscosity models. The MGM is a new, nonlinear model that uses the local equilibrium hypothesis to assess the SGS kinetic energy and the velocity gradient tensor to calculate the relative weight of the different components of the SGS stress tensor. To evaluate the accuracy of the MGM along with the modified pimpleFoam solver, a turbulent channel flow was simulated at the three different frictional Reynolds numbers of 180, 395 and 590. Furthermore, the results were compared with direct numerical simulation data, as well as the numerical results obtained by the established SGS models such as the dynamic Smagorinsky model (DSM). A suitable accuracy for the first- and second-order turbulence parameters was reported. Moreover, it was demonstrated that MGM is computationally efficient compared to the DSM in treating channel flow.     

One-pot,three-component synthesis and in vitro antibacterial evaluation of novel 3-amino-N-benzyl-1-aryl-1H-benzo[f]chromene-2-carboxamide derivatives

A series of novel 3-amino-N-benzyl-1-aryl-1H-benzo[f]chromene-2-carboxamides have been synthesized by the reaction of N-benzyl-2-cyanoacetamide with 2-naphthol and aromatic aldehydes in the presence of piperidine as a base. The chemical structures of all the compounds were confirmed by spectroscopic methods as well as elemental analysis. In addition, the antibacterial activities of some target compounds against Gram-negative and Gram-positive bacteria in vitro were determined. Among these compounds, 4b, 4c, 4h and 4i exhibited antibacterial effects. The advantages of the present work reaction are clean reaction, metal-free transition, environmentally friendly approach to prepare different benzo[f]chromene-2-carboxamide derivatives, good yields, low cost, readily available starting materials and in addition does not need cumbersome procedure.     

An adaptive quality of service channel borrowing algorithm for cellular networks

A multimedia call consists of three main sub‐streams (i.e. video, audio and data) each with its own distinct quality of service (QoS) requirements (e.g. packet loss rate, delay tolerance, and jitter). These requirements constitute a specific fixed QoS level. In contrast to static approaches, we propose an adaptive QoS platform in which each sub‐stream declares a preset range of acceptable QoS levels (e.g. maximum, acceptable, minimum) instead of just a single level. This range of QoS levels is pre‐defined in a user‐defined profile (UDP). In this paper, we propose a channel borrowing algorithm based on such adaptive QoS platform. In our proposed algorithm, an acceptor cell that has used all its channels can borrow from any neighbouring (donor) cell as long as this donor cell has some channels available after satisfying a minimum QoS (minQ) level defined in the UDP. A donor cell that is assigning QoS levels (to calls under its coverage) higher than the minQ levels will declare those channels as available for borrowing by other acceptor cells. The criteria for choosing the free channel include not only the number of free channels, but also the QoS levels in the donor cell. The criteria are also extended to include the effect of channel locking on the number of free channels, and the QoS levels on the locked cells. The algorithm is not triggered unless it does not cause any call dropping in either the donor cell, or the cells affected by call blocking. In the meantime, the call blocking rate is significantly decreased while the offered load increases. Copyright © 2003 John Wiley & Sons, Ltd.     

An efficient synthesis of 3,4-dihydropyrimidin-2(1H)-ones catalyzed by molten [Et3NH][HSO4]

A simple ammonium salt of sulfuric acid in molten state was used as a cheap and mild acidic ionic liquid for efficient synthesis of 3,4-dihydropyrimidin-2(1H)-ones in good to excellent yields.     

Farkas-Type Theorems and Applications: From IPH Functions to ICR Functions

Abstract

Some versions of Farkas-type theorems for systems of inequalities consisting of Increasing and Positively Homogeneous (IPH) functions are established. Applying these results, we establish Farkas-type theorems for the systems involving Increasing and Coradiant (ICR) functions as well. As an application, we apply these results to solve constrained IPH and ICR optimization problems with unconstrained counterparts.