Antenna Power Cutback Manipulation to Optimize Relay Power Allocation over MAMR Networks Employing Zero Forcing Scheme

Power allocation between relays and data streams is an important aspect of MIMO relay systems. Different methods are designed to consider weight matrices within relay channels. Commonly employed methods are based on linearly distributed multi antenna relay beamforming with match filter, zero forcing and MMSE techniques. This article proposes a cutback relay power allocation technique to design a suboptimal beamforming weight matrix by ZF–ZF method to decrease BER considerably at high SNRs. This method allocates the unused relay antenna power to others through the associated relay. This allows maximum workable power to increase; consequently the system performance is improved.     

Polystyrene-based composites and nanocomposites with reduced brominated-flame retardant

Polystyrene was melt blended with a halogen-based flame retardant (FR), hexabromocyclododecane, and a non-halogenated FR, triphenyl phosphate (TPP), in a twin-screw extruder. An organically modified montmorillonite (Cloisite 15A) was used to prepare FR polystyrene nanocomposites. The flammability properties and thermal stability of FR polystyrene composites and nanocomposites were investigated. X-ray diffraction analysis showed that the exfoliation structure of organically modified montmorillonite in polystyrene nanocomposites may be achieved by melt-compounding in a twin-screw extruder. Furthermore, a good dispersion of FRs and nanoparticles of organically modified montmorillonite was observed by energy dispersive X-ray analysis. Thermogravimetric analysis demonstrated that the thermal stability of FR nanocomposites enhanced in the presence of clay nanoparticles and antioxidant. The aim of this study was to reduce the FR level, especially in the brominated FRs. The good results obtained by the limiting oxygen index test showed high-performance flammability properties in the composites containing hexabromocyclododecane and TPP, resulted from the synergy effects between these two FRs. However, in spite of producing high thermal performance polystyrene nanocomposites and dispersing clay nanoparticles efficiently into the polystyrene matrix, the flame retardancy properties were deteriorated in the presence of clay nanoparticles. Therefore, the organically modified clay (Cloisite 15A) was not a good synergic compound to improve the flame retardancy of polystyrene nanocomposites.     

High energy and low emissions from catalytic combustion of crude oil

Combustion technology has been investigated to effectively and economically heat and power generation. A kinetic model of crude oil combustion in presence of CaO as a catalyst was developed. Effects of CaO mass yield (ppm) on three main parameters including combustion carbon conversion efficiency, reaction temperature, and combustion efficiency were investigated. Results showed that the CaO has a significant effect on the decrease of CO₂, which is the most important greenhouse gas. It also found that the carbon conversion efficiency decreases as the CaO increases, although it is not considerable.     

A fuzzy expert system to increase accuracy and precision in measurement system analysis

In this paper, we have presented the first proposal to apply measurement system analysis (MSA) in fuzzy environment. Nowadays, because the quality control techniques are applied a lot in manufacturing, research and development environments, many decisions are made in processes and equipment evaluation, control, and improvement. Besides, the philosophy of measurement system analysis (MSA) depends on measurement error which hides true process capability; therefore, it must be implemented prior to any process improvement activities to minimize the measurement errors. Since the capability of each quality system is related to the accuracy of its measurement system, this research develops a novel methodology to increase precision and accuracy of MSA. To do so analyzing measurement systems under fuzziness of indices are investigated to make the environment more realistic. In this article, not only fuzzy measurement system analysis with gauge repeatability and reproducibility (GR&R) index as a triangular fuzzy number is proposed, but a fuzzy measurement system analysis a fuzzy expert system is presented to make more reliable and appropriate decisions. At the end, the applicability of the proposed methodology has been demonstrated within a case study in automotive parts industry to show impact of uncertainty in the reality.     

An experimental approach for investigating low-level interturn winding faults in power transformers

Interturn faults are one of the most prevalent and potentially destructive electrical faults in power transformers. In spite of an extensive interturn fault detection literature, the issue still constitutes an open problem. The difficulty is mainly caused by lacking of enough information on the characteristic signatures associated with interturn faults which were not clearly brought out by the previous studies. This contribution is aimed at obtaining a better understanding of the physical behavior of the power transformers in the presence of interturn faults as well as extracting several features which would be useful to specify the transformers interturn faults. The approach keeps at disposal a 100 kVA distribution transformer on which interturn faults were imposed and an experimental setup consisting of an instrumentation system and suitable transducers which enables monitoring selected characteristics of the transformer. The paper examines the faulted transformer performance under various fault and transformer operating conditions. Unique characteristic fault-signatures derived from the experiments will provide an important basis for developing more reliable and sensitive methods to detect interturn faults on the transformer windings well before such faults lead to a catastrophic failure with serious damage to the windings.     

Resistance of wood pellets to low airflow

The pressure drop versus low airflow from 0.000117 to 0.1 m/s was measured across a fixed bed of wood pellets. Wood pellets were on average 6.2 mm in diameter and 12 mm in length. The moisture content of wood pellets ranged from 2.8% to 8.1%. Four equations, Darcy, Shedd, Hukill and Ergun representing flow versus static pressure drop for bulk granules were fitted to the experimental data. At airflows below 0.01 m/s, the predicted pressure drops using all four equations deviated from experimental data. This deviation was the largest for the Darcy equation and the smallest for Ergun equation. © 2011 Canadian Society for Chemical Engineering     

Effect of silicon carbide nanoparticles on the adhesion strength of steel–epoxy composite joints bonded with acrylic adhesives

This paper reports a study on the effect of silicon carbide nanoparticles on the adhesion strength of steel–glass/epoxy composite joints bonded with two-part structural acrylic adhesives. The introduction of nanosilicon carbide in the two-part acrylic adhesive led to a remarkable enhancement in the shear and tensile strength of the composite joints. The shear and tensile strengths of the adhesive joints increased with adding the filler content up to 1.5?wt%, after which decreased with adding more filler content. Also, addition of nanoparticles caused a reduction in the peel strength of the joints. DSC analysis revealed that Tg values of the adhesives rose with increase in the nanofiller content. The equilibrium water contact angle was decreased for adhesives containing nanoparticles. SEM micrographs revealed that addition of nanoparticles altered the fracture morphology from smooth to rough fracture surfaces.     

Adhesive strength of steel–epoxy composite joints bonded with structural acrylic adhesives filled with silica nanoparticles

This paper reports a study on the effect of silica nanoparticles on the adhesion strength of steel–glass/epoxy composite joints bonded with two-part structural acrylic adhesives. The introduction of nano-silica in the two-part acrylic adhesive led to a remarkable enhancement in the shear and tensile strength of the composite joints. The shear and tensile strengths of the adhesive joints increased with addition of the filler content up to 1.5 wt%, after which decreased with addition of more filler content. Also, addition of nanoparticles caused a reduction in the peel strength of the joints. Differential scanning calorimeter analysis revealed that T_g values of the adhesives rose with increasing the nanofiller content. The equilibrium water contact angle was decreased for adhesives containing nanoparticles. Scanning electron microscope micrographs revealed that addition of nanoparticles altered the fracture morphology from smooth to rough fracture surfaces.     

Fabrication of highly porous Pt coated nanostructured Cu-foam modified copper electrode and its enhanced catalytic ability for hydrogen evolution reaction

The nanoporous copper foam was prepared by electrochemical reduction of copper ion at the copper substrate. The as-prepared substrate was used as three-dimensional templates for preparation of Pt coated nanostructured Cu-foam by galvanic replacement of Cu with platinum by simply immersing the prepared nanoporous copper foam in a K₂PtCl₆ aqueous solution. The structure and nature of the fabricated Pt coated nanostructured Cu-foam was characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Pt coated nanostructured Cu-foam modified copper electrode exhibited remarkable electrocatalytic activity for the hydrogen evolution reaction. The effect of electrodeposition time during Cu-foam formation on the kinetic constants for hydrogen evolution reaction was comparatively investigated.     

Fabrication of platinum coated nanoporous gold film electrode: A nanostructured ultra low-platinum loading electrocatalyst for hydrogen evolution reaction

The electrolytic hydrogen evolution reaction (HER) on platinum coated nanoporous gold film (PtNPGF) electrode is demonstrated. The deposition of platinum occurred as a spontaneous redox process in which a copper layer, obtained by underpotential deposition, was oxidized by platinum ions, which were reduced and simultaneously deposited. The present method could provide a very low Pt-loading electrode and the results demonstrated that ultra thin Pt coating effected efficiently and behaved as the nanostructured Pt for electrocatalytic hydrogen evolution reaction. The loading of Pt was calculated as 4.2 × 10⁻³ μg cm⁻² for PtNPGF electrode. The current density at −0.4 V and −0.8 V vs. Ag/AgCl was as high as 0.66 A μg⁻¹ Pt and 3 A μg⁻¹ Pt, respectively and the j₀ was evaluated as 0.03 mA cm⁻² or 8 mA μg⁻¹ Pt. The results indicated that increasing electrode area had no catalytic effect, but the nanostructure nature of as-fabricated electrode and submonolayer deposition of copper resulted in electrocatalytic activity for PtNPGF electrode.