Mutual coupling compensation of linear antenna array using evolutionary optimization technique

This paper presents an optimization-based approach to compensate for the mutual coupling effect and to reduce the sidelobe level (SLL) of the normalized radiation pattern by optimizing the current excitation amplitude of the antenna array elements. Due to the mutual coupling effect, the SLL of the radiation pattern is increased, and thereby, the field pattern of the antenna array is severely degraded. This causes interference with other communication systems working at the same frequency. Toward the compensation of the mutual coupling effect and reduction of SLL, the Cat swarm optimization (CSO) algorithm is employed, and the excitation amplitudes of the antenna elements are optimized. In this regard, optimizing the cost function is defined by introducing the impedance factor (IF), calculated by using the self-impedance and mutual impedance of the antenna elements. The proposed method for the synthesis of a mutually coupled linear antenna array is less expensive, simpler to use, and more effective. Array sets of 4, 6, 8, and 10 elements are considered for optimization.     

Fabrication and Microstructure of Micro and Nano Silicon Carbide Reinforced Copper Metal Matrix Composites/Nanocomposites

Silicon - This study investigates the influence of micro and nano silicon carbide on properties of copper matrix composites/nanocomposites containing up to 4 wt% of reinforcement...     

Entropy generation on unsteady stagnation-point Casson nanofluid flow past a stretching sheet in a porous medium under the influence of an inclined magnetic field with homogeneous and heterogeneous reactions

This study explores the entropy generation analysis on unsteady nonlinear radiative ethylene glycol-based Casson nanofluid flow near stagnation point towards a stretching sheet through a porous medium. Analysis has been accomplished in the presence of an inclined magnetic field, heat generation, homogeneous–heterogeneous reactions, and viscous dissipation with velocity slip and convective boundary conditions. The nondimensional governing equations are solved by the shooting technique with the help of the RK45 method. We have experimented with copper and silver nanoparticles and a comparative analysis has been highlighted for both copper and silver nanofluids. Numerical outcomes are executed by the MATLAB built-in bvp4c function. The consequences of the experiment for various pertinent flow parameters are portrayed by graphs and tables for both the Ag- and Cu-Casson nanofluids. Results reveal that the enhancement of nanoparticles volume fraction accelerates temperature but it slows down concentration and velocity distributions. Higher values of the Eckert number boost velocity and temperature but reduce skin friction coefficient and Nusselt number. Enhancement of the Brinkman number boosts up entropy generation but it slows down Bejan's number. The results of the model can be applied in the movement of biological fluids, separation of biomolecules, glass manufacturing, paper production, food processing, crude oil purification, polymer drag reduction, and cooling atomic reactors.     

Effect of Stress Relief Annealing on Microstructure & Mechanical Properties of Welded Joints Between Low Alloy Carbon Steel and Stainless Steel

Metallurgical and Materials Transactions A - Two types of welded joints were prepared using low alloy carbon steel and austenitic stainless steel as base materials. In one variety, buttering...     

Current Situation and Prospect of Nanometrology and its Standardization in Indonesia

As one of the emerging technologies in Indonesia, nanotechnology requires comprehensive studies of supporting infrastructures as well as the regulation that will underpin the quality of nanoproducts or nanoservices. Nanometrology is one of the most important supporting infrastructures for development of nanotechnology. This article reviews the importance of nanometrology and its standardization within the context of nanotechnology development in Indonesia. Current situation of nanotechnology development, relevant standards availability, necessity for new standards, nanometrology development and future goals have been explained. This article contributes novel insights about nanotechnology and nanometrology developments and may help the regulation body to make the policy.     

Poly(N‐[4H‐1,2,4‐triazol‐4‐yl]acrylamide) with different ratio of poly(vinyl chloride) composite membrane for liquid phase sensing of alcohol

Functionalized polymer membranes have been used as sensor materials for fabrication of electronic tongue. Here, we report the synthesis and characterization of a novel poly(N‐[4H‐1,2,4‐triazol‐4‐yl]acrylamide) (PNTA) for liquid phase aliphatic alcohol sensing in the form of membranes prepared after blending with poly(vinyl chloride) (PVC). Three PNTA‐PVC based membranes were prepared for sensing of six aliphatic alcohols. Polymer membranes were characterized by spectroscopic techniques. Polar groups on PNTA molecules contribute to the alcohol sensing characteristics. The membrane electric potential, generated by the interaction between membrane surface and aqueous aliphatic alcohols, was monitored with the developed multi‐channel electrode based prototype sensing system (MEBPSS). The polymer membranes showed distinct and repeatable response patterns toward different aliphatic alcohols. Among them PNTA‐PVC12 membrane showed maximum discrimination ability due to the PNTA molecules on the membrane surface with highest charge density as ascertained from field emission scanning electron microscopic studies. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44675.     

New block copolymers. 1. Synthesis and characterization of an (a–b)n type block copolymer

A new (A–B)_n type block copolymer has been synthesized by polycondensation of acidchloride terminated poly(ethylene-terephthalate) with amine-terminated butadiene acrylonitrile rubber (ATBN). The acid chloride terminated poly(ethylene-terephthalate) was synthesized by reacting terephthaloyl chloride with ethylene glycol using N,N-dimethyl formamide as the solvent. The resulting polymer was characterized by nitrogen analysis, IR and NMR spectroscopy. The solubility characteristics, solution viscosity behaviour, crystallinity, and phase characteristics of the polymer have been studied.     

Preparation and in vitro evaluation of novel cross‐linked chondroitin sulphate nanoparticles by aluminium ions for encapsulation of green tea flavonoids

Chondroitin sulphate is a sulphated glycosaminoglycan biopolymer composed over 100 individual sugars. Chondroitin sulphate nanoparticles (NPs) loaded with catechin were prepared by an ionic gelation method using AlCl₃ and optimised for polymer and cross‐linking agent concentration, curing time and stirring speed. Zeta potential, particle size, loading efficiency, and release efficiency over 24 h (RE₂₄ %) were evaluated. The surface morphology of NPs was investigated by scanning electron microscopy and their thermal behaviour by differential scanning calorimetric. Antioxidant effect of NPs was determined by chelating activity of iron ions. The cell viability of mesenchymal stem cells was determined by 3‐[4, 5‐dimethylthiazol‐2‐yl]‐2, 5‐diphenyl tetrazolium bromide assay and the calcification of osteoblasts was studied by Alizarin red staining. The optimised NPs showed particle size of 176 nm, zeta potential of −20.8 mV, loading efficiency of 93.3% and RE₂₄ % of 80.6%. The chatechin loaded chondroitin sulphate NPs showed 70‐fold more antioxidant activity, 3‐fold proliferation effect and higher calcium precipitation in osteoblasts than free catechin.Inspec keywords: nanoparticles, encapsulation, biomedical materials, particle size, nanofabrication, nanomedicine, electrokinetic effects, cellular biophysics, polymer blends, molecular biophysics, molecular configurations, biochemistry, curing, surface morphology, scanning electron microscopy, differential scanning calorimetry, dyes, precipitationOther keywords: in vitro evaluation, cross‐linked chondroitin sulphate nanoparticles, aluminium ions, nanoparticles, green tea flavonoids, sulphated glycosaminoglycan biopolymer, sugars, catechin, ionic gelation method, cross‐linking agent concentration, curing time, size 176 nm, time 24 h, calcium precipitation, 3‐fold proliferation effect, antioxidant activity, chatechin loaded chondroitin sulphate NPs, Alizarin red staining, osteoblasts, calcification, 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyl tetrazolium bromide assay, mesenchymal stem cells, cell viability, chelating activity, differential scanning calorimetry, thermal behaviour, scanning electron microscopy, surface morphology, release efficiency, loading efficiency, particle size, zeta potential, stirring speed     

Design and fabrication of screen printed microheater

Microsystem Technologies - This paper presents the design and fabrication of a low-cost series microheater which works on the principle of Joule heating. The conducting silver-ink (LOCTITE ECI 1010...     

Removal of Ions and Acidity from Acid Mine Water Using Transformed Fly Ash

Fly ash obtained from a coal combustion thermal electric power plant was reacted with NaOH at 100 °C for 24 h to synthesize zeolite. Shaker flasks experiments were conducted to assess whether fly ash or fly ash zeolite (FAZ) could be used to treat acidic mine water. The FAZ was used to treat the mine water at doses of 5–60 g/L; the FAZ increased pH from 2.76 to as high as 7.51 and removed most of the Ca and Mg hardness and acidity from the mine water, though it did not affect sulphate concentrations. The cation exchange capacity of the FAZ was regenerated using NaCl. After six regeneration/reuse cycles, the FAZ was less effective but still capable of increasing pH and removing substantial hardness. In contrast, fly ash was not effective in removing hardness or acidity, and instead released ions into the mine water.