An interface‐enriched generalized finite element analysis for electromagnetic problems with non‐conformal discretizations

An interface‐enriched generalized finite element method is presented for analyzing electromagnetic problems involving highly inhomogeneous materials. To avoid creating conformal meshes within a complex computational domain and preparing multiple meshes during optimization, enriched vector basis functions are introduced over the finite elements that intersect the material interfaces to capture the normal derivative discontinuity of the tangential field component. These enrichment functions are directly constructed from a linear combination of the vector basis functions of the sub‐elements. Several numerical examples are presented to verify the method with analytical solutions and demonstrate its h‐refinement convergence rate. The proposed interface‐enriched generalized finite element method is shown to achieve the same level of accuracy as the standard finite element method based on conformal meshes. Two examples, involving multiple microvascular channels and circular inclusions of different radii, are analyzed to illustrate the capability of the proposed approach in handling complicated inhomogeneous geometries. Copyright © 2015 John Wiley & Sons, Ltd.     

Edge Coloring of Graphs with Applications in Coding Theory

In this paper,a new type of edge coloring of graphs together with an algorithm for such an edge coloring is presented to construct some columnweight three low-density parity-check(LDPC)codes whose Tanner graphs are free of 4-cycles.This kind of edge coloring is applied on some well-known classes of graphs such as complete graphs and complete bipartite graphs to generate some column-weight 3 LDPC codes having flexibility in terms of code length and rate.Interestingly,the constructed(3;k)-regular codes with regularities k=4;5;:::;22 have lengths n=12;20;26,35;48;57;70;88;104;117;140;155;176;204;228;247;280;301;330;having minimum block length compared to the best known similar codes in the literature.In addition to linear complexity of generating such parity-check matrices,they can be considered as the base matrices of some quasi-cyclic(QC)LDPC codes with maximum achievable girth 18,which inherit the low-complexity encoder implementations of QC-LDPC codes.Simulation results show that the QC-LDPC codes with large girth lifted from the constructed base matrices have good performances and outperform random codes,progressive edge growth LDPC codes,some finite fields and group rings based QC-LDPC codes and also have a close competition to the standard IEEE 802.16e(WiMAX)code.     

Locating a New Drainage Well by Optimization of a Back Propagation Model

Mine Water and the Environment - Geoelectric (GE) field data are usually interpreted using GE computer-codes. A back propagation (BP) ANN model is used to predict hydro-sedimentology (HS) well...     

Heating,microwave and UV irradiation effects on oxidative stability of Sardasht red grape (Vitis vinifera cultiv. Sardasht) seed oil

In the current study, for the first time, the oxidation stability of the extracted edible oil from Sardasht red grape at three different accelerated deteriorative conditions (oven, microwave and ultraviolet (UV) irradiation) was investigated. In this context, the peroxide value (PV), conjugated diene value (CDV), carbonyl value (CV), radical scavenging activity (RSA) and oil/oxidative stability indices, as well as fatty acid composition and total tocopherol content, were evaluated. Sardasht grape seed oil as a rich oil in unsaturated fatty acid (about 87%) contains linoleic acid in terms of the principal fatty acid (70.4 ± 1.8%). The excessive oxidative stability of crude oil can be correlated with the extreme content of natural antioxidants (tocopherols and tocotrienols). The findings showed that Sardasht red grape seed oil could be approached as new source of edible oil with acceptable oxidative stability.     

Sulfonic Acid-Functionalized Fe3O4 Reinforced Soluble Polyimide: Synthesis and Properties

In this study, a series of nanocomposite films based on an aromatic polyimide and sulfonic acid-functionalized magnetic nanoparticles was successfully prepared via an in situ technique. For this purpose, new soluble aromatic polyimide containing sulfone group as a polymeric matrix of the nanocomposites was synthesized. The surfaces of MNP were grafted with 3-mercaptopropyl trimethoxysilane. Then sulfonic acid-functionalized magnetic nanoparticle was obtained by oxidation of the thiol group. Effects of sulfonic acid-functionalized magnetic nanoparticles on thermal, tensile, and magnetic properties of the prepared nanocomposite films were studied. The magnetic nanoparticles containing the sulfonic acid groups could have strong intermolecular bond interactions between the hydroxyl groups of SO₃H and the sulfone and carbonyl groups of the polyimide matrix which caused the better dispersion of nanoparticle and exhibited superior mechanical properties, good magnetic properties, and high thermal stability.     

Nondestructive Evaluation of Welding Residual Stresses in Dissimilar Welded Pipes

This paper investigates the nondestructive capability of ultrasonic waves in residual stress evaluation of dissimilar welded pipes. Longitudinal critically refracted (L _CR ) waves are employed to measure the residual stresses in a pipe-pipe joint of stainless steel 304 and carbon steel A106. Measuring the acoustoelastic constant is usually accomplished through the tensile test which needs cutting the tested material to extract tensile test specimens. However, cutting the tested pipe to complement the nondestructive ultrasonic measurement was not considered here. Instead, a dissimilar welded plate with the same welding specification, joint geometry, thickness and the same dissimilar materials is used to extract tensile test samples. The measured acoustoelastic constant of the plate along with the measured time of flight of the L _CR wave on the pipe, are utilized for ultrasonic stress measurement. A finite element model of welding process validated by hole-drilling method is used to verify the ultrasonic results. The results show good agreement between finite element and ultrasonic measurements in the pipe measured without any destructive process.     

Novel nanocomposite based on reactive organoclay and photosensitive aliphatic–aromatic polyamide: Synthesis and characterization

Novel polyamide/organoclay nanocomposites were prepared through solution intercalation technique. Reactive organoclay was prepared using Cloisite‐Na⁺ and protonated form of 4,4′‐diaminodiphenylmethane via ion‐exchange reaction. New photosensitive aliphatic‐aromatic polyamide containing dibenzal acetone moiety was successfully synthesized through direct polycondensation. Flammability and thermal properties of the polyamide and corresponding nanocomposites were studied. Thermogravimetric analysis results indicated improved thermal stability of the nanocomposites compared to the neat polyamide. According to the microscale combustion calorimeter results, the peak heat release rate value has been decreased from 113 to 72 W/g by introducing 2 wt% of the organoclay in the polyamide matrix. POLYM. COMPOS., 36:1502–1509, 2015. © 2014 Society of Plastics Engineers