Approach to performance optimisation in frequency-weighted memory network pattern classifiers

The performance of memory network pattern classifiers based on a feature frequency-weighting scheme can suffer from an inappropriate arbitrary choice of zero-frequency component in the computation of discriminant functions. This letter assesses the effect of optimising this factor, emphasising the value of optimisation in pairwise class discrimination, which is of particular relevance in the design of efficient hierarchical classifier architectures.     

Microcontroller implementation of direct torque control

The switching frequency of a conventional direct torque control (DTC) strategy which is based on hysteresis controllers results in a variable switching frequency which depends on the mechanical speed, stator flux, stator voltage, and the hysteresis band of the comparator. In this paper, a DTC scheme using space vector modulator (SVM) and fuzzy logic controller (FLC) is suggested. A comparison with the classical DTC is presented. The suggested control strategy guarantees very good dynamic and steady state characteristics with low sampling rate and a constant switching frequency. The experimental results are presented to validate the scheme. Copyright © 2005 John Wiley & Sons Ltd.     

Electrical double-layer capacitors: evaluation of ageing phenomena during cycle life testing

This paper represents an assessment of the main ageing phenomena in electrical double-layer capacitors (EDLCs). In this study the cycle life of the EDLC cells with a rated capacitance of 1,600 F has been investigated at different ambient temperatures and current rates. From the experimental results we can observe that the impact of the high ambient temperature is significant on the cycle life of the cells. Moreover, the results also show the negative impact of the current rate. The internal resistance tests showed that the increase of the resistance is much higher than the decrease of the capacitance. Thus, the ageing of the EDLC during cycling was clearly non-linear. Further the EIS measurements indicated the higher increase of the imaginary part of the impedance at low frequencies during cycling, which indicates the capacitance fade.     

Synthesis and characterization of chitosan-coated magnetite nanoparticles using a modified wet method for drug delivery applications

Abstract

Immobilizing various chemical functionalities on the surfaces of magnetite nanoparticles extends these applications without affecting the overall magnetic properties of the coated nanoparticles. In this study, magnetite nanoparticles have been prepared in the presence of chitosan using a simple modified wet method. Composition, morphology and magnetic properties of the chitosan-coated nanoparticles were investigated. Results showed the formation of coating with various thicknesses on the surfaces of the superparamagnetic nanoparticles. This in turn reduced the magnetization of the nanoparticles to some extent. The least particle size obtained in the presence of chitosan was 10?nm.     

Radiation synthesis of hydrogels based on carboxymethyl cellulose and its application in removal of pollutants from wastewater

Synthesis of carboxymethyl cellulose‐g‐methacrylic acid/acrylamide Poly(CMC/MAAc:AAm) hydrogel was carried out using direct radiation copolymerization technique at ambient temperature. The gel (%) increased with increasing the content of AAm till level off at Poly(CMC/MAAc:AAm) (1/50:50 wt%) hydrogel and the swelling behavior found to be increased with increasing MAAc content in the hydrogel composition up to Poly(CMC/MAAc:AAm) (1/60:40 wt%). The grafting yield, grafting ratio, swelling behavior, and the thermal stability of Poly(CMC/MAAc:AAm) binary system are higher than those reported in our previous study by the same author which described the individual grafting of acrylamide (AAm) and methacrylic acid (MAAc) with different concentration onto carboxymethyl cellulose (CMC) using direct radiation grafting technique. The swelling kinetics and diffusion mechanism indicate that the water penetration obey non‐Fickian transport mechanism. The characterization of the prepared hydrogel was evaluated using Fourier transform infrared, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The analyses by different analytical tools confirmed the successful grafting of both MAAc and AAm onto CMC. The adsorption capacity of Poly(CMC/MAAc:AAm) (1/60:40 wt%) hydrogel toward metal ions such as Cu⁺² and Co⁺², dyes such as acid blue dye and methyl green have been investigated. J. VINYL ADDIT. TECHNOL., 25:E35–E43, 2019. © 2017 Society of Plastics Engineers     

Utility of Zinc (Lignin/Silica/Fatty Acids) Complex Driven From Rice Straw as Antioxidant and Activator in Rubber Composites

This article presents a method to precipitate zinc (lignin/silica/fatty acids) complex (Zn LSF complex) from the black liquor of pulped rice straw and studying the efficiency of it as green activator and antioxidant in natural rubber composites. The results obtained revealed that the investigated zinc complex has dual function as activator and antioxidant in natural rubber composites. This evaluation was supported by physico‐mechanical properties of the vulcanizates which showed a considerable improvement of rheometric characteristics, tensile strength, strain at break, hardness, Young's modulus, thermal oxidative aging, and thermal stability of NR composites. The composite loaded with 7 phr of Zn LSF complex as activator exhibited the best mechanical properties in comparison with the same concentrations of control activator zinc stearate. Also, results revealed that Zn LSF complex is efficient as antioxidant in NR vulcanizates compared conventional antioxidants, namely polymerized 2,2,4‐trimethyl‐1,2‐dihydroquinoline. POLYM. ENG. SCI., 59:E196–E205, 2019. © 2018 Society of Plastics Engineers     

Mechanical properties of gamma‐irradiated styrene‐butadiene rubber/acid‐treated vermiculite clay/maleic anhydride nanocomposites

Nanoparticle vermiculite (VMT) clay was prepared by treatment with hydrochloric acid. Styrene‐butadiene rubber (SBR) nanocomposites were prepared by mixing different contents (2.5, 5, 7.5, and 10 phr) of untreated (VMT) and acid‐treated (DVMT) vermiculite clay, respectively. In addition, different contents (3, 7, and 10 phr) of maleic anhydride (MA) as compatibilizer were mixed via direct melt compounding in internal mixer. The effect of gamma irradiation, VMT clay, and MA contents on the mechanical properties was studied. The acid‐treated VMT clay was characterized by x‐ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FT‐IR) spectroscopy. Meanwhile, the SBR/VMT composites, SBR/DVMT, and SBR/DVMT/MA nanocomposites were characterized via crosslinking density and tensile mechanical testing and FT‐IR spectroscopic analysis. The results indicated that good yield of nanoparticle vermiculite was achieved when the acid treatment was carried out for 120 h. In addition, the results showed that the presence of DVMT clay improved the chemical bonding in the SBR nanocomposites and hence their mechanical properties. The highest improvement was obtained when the contents of DVMT clay, MA, and irradiation dose were 10 phr, 3 phr, and 100 kGy, respectively. POLYM. ENG. SCI., 59:355–364, 2019. © 2018 Society of Plastics Engineers     

Diglycidyl ether of bisphenol A/chitosan‐graft‐polyaniline composites with electromagnetic interference shielding properties: Synthesis,characterization, and curing kinetics

Conducting filler based on chitosan and grafted polyaniline (Ch‐g‐PANI) was prepared with different grafting ratios and used as fillers for polyester powder coating system. Differential scanning calorimetry is applied to study the effect of Ch‐g‐PANI on the curing of the polyester powder coating. The activation energy calculated by isoconversional Kissinger method was increased by either increasing the Ch‐g‐PANI content or the content of polyaniline in the filler, suggesting the contribution of the filler in the curing reactions. The cured samples were characterized using FTIR and TG analyses. Thermogravimetric analysis showed that the total thermal stability was enhanced upon the filler addition as detected from the values of integral procedural decomposition temperature. Furthermore, a dielectric study showed that the dielectric constant and loss were increased upon increasing of the filler. Vogel–Fulcher–Tammann equation was well‐fitted when used to examine the dependence of α‐relaxation on the temperature and the dielectrically calculated T_g values were comparable to that measured by DSC. The shielding effectiveness toward microwaves was enhanced by increasing the filler content. POLYM. ENG. SCI., 59:372–381, 2019. © 2018 Society of Plastics Engineers