Augmented Hammerstein model for the calibration of six‐port based dual band wireless receivers

Two architectures of concurrent dual‐band six‐port‐based receiver (SPR), which are modeled and calibrated using the augmented Hammerstein model (AHM) are proposed for the first time in this article. The receivers are based on six‐port junctions with one or two local oscillators (LO). The proposed single step calibration algorithms achieve the recovery of the two in‐phase (I₁ and I₂) and quadrature (Q₁ and Q₂) components of an RF signal with two frequency components (RF₁ and RF₂). Experimental validations have been performed to verify the performance of the proposed concurrent dual‐band receivers and to test the efficiency of the AHM based calibration algorithms. As a performance metric, the Error Vector Magnitude (EVM) has been measured to compare the transmitted and recovered baseband signals and to evaluate the performance and efficiency of the proposed calibration algorithms for the two receiver topologies. The IQ data has been recovered with EVMs no higher than 2% for the two LOs based receiver excited with a QAM modulated dual‐band RF signal. The single LO based receiver has been tested with a dual‐band LTE signal and the recovered IQ data exhibited EVMs no higher than 4%.     

Fuzzy chromatic co-occurrence matrices for tracking objects

Pattern Analysis and Applications - Tracking objects is an important field for many applications like driving assistance and video surveillance. Every tracking system should be able to track...     

Crystallographic Orientation in Pure and Aluminum-Doped Zinc Oxide Thin Films Prepared by Sol–Gel Technique

Novel sol–gel processes for the preparation of grain-oriented thin films of pure and aluminum-doped zinc oxide (AZO) are reported. Using various stabilizing ligands, oxide films with different degree of c -axis orientation could be prepared on amorphous substrates. The origin of orientation in sol–gel-derived ZnO and AZO films is investigated. The texture selection of ZnO films is independent of the heat-treatment schedule but sensitive to the precursor system. The electrical properties of the films do not depend significantly on the crystallographic orientation. The film visible transmittance remained higher than 90% even after vacuum annealing.     

Cotton fabric surface modification for improved UV radiation protection using sol–gel process

In this study, lightweight 100% cotton fabric was successfully modified by the sol–gel process to impart high ultraviolet radiation (UVR) scattering property to the fabric surface. Active ingredients were tetraethyl orthotitanate [Ti(OCH₂CH₃)₄] and tetraethyl orthosilicate [Si(OCH₂CH₃)₄]. The cotton fabric was padded with the nanosol solution, dried at 60°C, and cured at 150°C. Scanning electron microscopy showed continuous and uniform film on the fiber surface. Excellent UVR scattering was obtained with all treated fabrics. Increasing titania content in the nanosol solution leads to increased UVR protection. This is attributed to the increase of the refractive index of the film formed on the fabric surface. Excellent durability of the treatment was obtained, which indicates a good adhesion between the coating and the fabric surface. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 111–117, 2007.     

A New Approach in Optimizing the Induction Heating Process Using Flux Concentrators: Application to 4340 Steel Spur Gear

The beneficial effects of using flux concentrators during induction heat treatment process of spur gears made of 4340 high strength steel is demonstrated using 3D finite element model. The model is developed by coupling electromagnetic field and heat transfer equations and simulated by using Comsol software. Based on an adequate formulation and taking into account material properties and process parameters, the model allows calculating temperature distribution in the gear tooth. A new approach is proposed to reduce the electromagnetic edge effect in the gear teeth which allows achieving optimum hardness profile after induction heat treatment. In the proposed method, the principal gear is positioned in sandwich between two other gears having the same geometry that act as flux concentrators. The gap between the gear and the flux concentrators was optimized by studying temperature variation between the tip and root regions of gear teeth. Using the proposed model, it was possible identifying processing conditions that allow for quasi-uniform final temperature profile in the medium and high frequency conditions during induction hardening of spur gears.     

Multi‐walled carbon nanotubes as unexpected accelerators of chemical reactions

The influence of carbon nanotubes on various chemical reactions has been examined. These reactions include epoxy crosslinking, in situ polymerization of copolymers in the presence of carbon nanotubes and thermal degradation of a thermoplastic matrix. The various characterizations were based on different types of analyses, including differential scanning calorimetry, proton nuclear magnetic resonance, size exclusion chromatography and thermogravimetric analysis. In each case, we show that the presence of multi‐walled carbon nanotubes accelerates the process. © 2012 Society of Chemical Industry     

Removal of textile dyes from aqueous solutions by natural phosphate as a new adsorbent

The objective of this study was to investigate the ability of natural phosphate (NP) to remove textile dyes from aqueous solutions. The adsorption of methylene blue (MB) as a reference molecule for the adsorption studies of organic molecules, basic yellow 28 (BY 28) and reactive yellow 125 (RY 125) representatives of two families of textile dyes was studied in a batch mode. The experimental results show that NP can totally remove MB and BY 28, whereas a low adsorption affinity was found in the case of RY 125. The adsorption rate data were analysed using the pseudo-first order kinetics of Lagergren and the pseudo second order model to determine adsorption rate constants. The isotherms of adsorption data were analyzed by various adsorption isotherm models. The adsorption was temperature- and pH-dependent with a high adsorption capacity of MB and BY 28 in the basic range and a high adsorption of RY125 in an acidic range.