A Comparison Study Between Pre-Equalization Schemes for Single and Multi Carrier Modulation Systems

In this paper, frequency domain pre-equalization (Pre-FDE) is developed for broadband cyclic prefix-code division multiple access (CP-CDMA) as a single carrier transmission scheme, and for multi carrier-CDMA (MC-CDMA) and orthogonal frequency division multiplexing (OFDM) as multi carrier transmission schemes. A comparison study is held between these schemes and the traditional equalization schemes. Experimental results show that pre-equalization improves significantly the performance of the single and multi carrier communication systems with a very low complexity at the receiver. The comparative study between MIMO pre-equalization for single carrier systems and for multi carrier systems shows that MIMO pre-equalization for single carrier systems outperforms that for multi carrier systems in terms of bit error rate (BER) performance since single carrier transmission has more frequency diversity than multi carrier transmission in the uncoded case.     

Synthesis, characterization and evaluation of nano-zirconium vanadate ion exchanger by using three different preparation techniques

Sol-gel, homogeneous precipitation and hydrothermal synthesis are three different preparation techniques have been used as an attempt to synthesize nano-zirconium vanadate with properties suitable to be used as ion exchangers. The impact of the synthetic preparation variables such as the reactant concentrations, reaction temperature and reaction time on the ion exchange capacity of the produced ion exchanger has been considered for each preparation technique. One sample from each preparation technique having the largest ion exchange capacity has been selected to be physically and chemically characterized using various analytical techniques such as XRD, TGA, DSC, pH titration, FTIR and SEM in order to determine the properties of the ion exchanger produced from each technique. For all the studied ZrV samples it can be presumed that they have the ion exchange affinity sequences for alkali metal ions K > Na > Li, the order for the alkaline earth metals is Ba > Ca > Mg and their affinity for radioactive metals follow Cs > Sr. Moreover, the prepared materials are of high thermal and radiation stabilities. Also they have high chemical stabilities toward wide concentration ranges of acid, basic as well as polar solvents. It has been deduced from the X-ray analysis that ZrV produced from the sol-gel technique has an amorphous structural. While those produced from the homogeneous precipitation and hydrothermal synthesis techniques, in the nano-scale have semi-crystalline structural. Furthermore, SEM confirms that particle size of the all studied prepared ZrV samples have nano-diameters of range 50-60 nm. Specific surface area of the three different prepared ion exchangers are found to be equal to 187, 192 and 320 m²/g for sol-gel, homogeneous precipitation and hydrothermal, respectively. A tentative structural formula of Zr(OH)₂(HVO₄)₂·2H₂O has been proposed for all studied samples on the basis of on FTIR, DSC and TGA results.     

Filtering approaches to accelerated consensus in diffusion sensor networks

The main objective in distributed sensor networks is to reach agreement or consensus on values acquired by the sensors. A common methodology to approach this problem is using the iterative and weighted linear combination of those values to which each sensor has access. Different methods to compute appropriate weights have been extensively studied, but the resulting iterative algorithm still requires many iterations to provide a fairly good estimate of the consensus value. In this paper, different accelerating consensus approaches based on adaptive and non‐adaptive filtering techniques are studied and applied on the problem of acoustic source localization using the adaptive projected subgradient method. A comparative simulation study shows that the non‐adaptive polynomial filters based on Newton's interpolating polynomials and semi‐definite programming can provide more accelerated consensus and better estimation accuracy than adaptive filters evaluated using constrained affine projection algorithm or stochastic gradient algorithm provided that the network topology is known beforehand. Copyright © 2013 John Wiley & Sons, Ltd.     

Corrosion of Zinc in acetic acid derivatives: Glycollic,mercaptoacetic and cyanoacetic acids and glycine

The corrosion behaviour of zinc in glycollic, mercaptoacetic and cyanoacetic acids and glycine was studied by weight loss, pH-monitoring and polarization measurements. The rate of corrosion was found to be a first order with respect to hydrogen ion activity and strongly dependent of the acid type. The abnormal behaviour in cyanoacetic acid at < 0.5 M was attributed to the hydrolysis of the acid during the corrosion and formation of malonic acid as confirmed by FT-IR spectroscopy. Morphological investigation of the corroded surfaces showed localized corrosion in cyanoacetic and glycollic acids which increased as the acid concentration or corrosion time increased. The FT-IR analysis indicated also the formation of zinc glycollate and zinc thioglycollate as the corrosion products of zinc in glycollic and mercaptoacetic acids, respectively (Scheme 1a+b).     

Physico-analytical Studies on Salicylaldehyde Thiosemicarbazone Complexes

In this study the complexes of salicylaldehyde thiosemicarbazone with Pd, Cu and Ru were prepared. The prepared complexes were characterized by spectroscopic, element and thermal analyses and D.C. conductivity measurement. The antimicrobial activity of all the prepared compounds against gram-positive, gram-negative and fungi was studied. From these studies, it has been obtained that the ligand is bonded to the metals through O, N and S, but to palladium in [Pd(H2L2)]Cl2 only through N and O. Biological studies confirm that the organic effect on both gram-positive and gram-negative bacteria is very weak and their complexes have no effect on fungi, but Cu-complex has strong influence on both types of bacteria.     

Raman spectroscopic study of CdS,PVA composite films

A new material, which can be used in solar energy utilization, is obtained here by adding different weights of poly(vinyl alcohol) (PVA) to the semiconducting material CdS. The effect of this addition was studied by using FT‐Raman spectrometer (based on 1500 mW Nd : YAG laser at 1064 nm), UV–Vis‐IR (190–800 nm) spectrophotometer, and X‐ray diffractometer. Our experimental results indicated the appearance of several new Raman bands, which have not existed in both CdS and PVA. Some of the bands which are already existing in the Raman spectra of PVA showed an unexpected systematic increase in their intensities after the addition of CdS to the matrix. On the other hand, some of the new Raman bands appeared in special concentrations of PVA only, whereas some of the Raman bands of CdS were found to disappear after adding PVA. Finally, shifts in some bands associated with random increase in their intensities after adding PVA to CdS was detected in the FT‐Raman analysis. The experimental evidence given here might be attributed to the occurrence of new bonds, indicating that the produced mixture is a new material. The assignment of the new bands as well as an interpretation of the obtained variations is given here. Our X‐ray diffraction data confirmed the interpretation introduced here. Moreover, the UV–Vis spectra confirmed the existence of new absorption bands in the Visible region. The I‐V characteristic curve was measured for a selected concentration of the new composite material, showing a remarkable increase in the values of the conduction current of about two orders of magnitude as compared with the pure PVA material. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1984–1992, 2004     

Measurement of thermophysical properties of polyester cured with styrene in the range 300–450 K

A pulse method for the simultaneous determination of thermal diffusivity, α, specific heat capacity, C_p, and thermal conductivity, λ, are measured for a series of curing of polyester and styrene in the presence of 10, 20, and 30% carbon black in the temperature range 300–450 K. The results show a dependence of the above-mentioned properties on temperature and composition. The mechanism of heat transfer through the specimens is also discussed. © 1993 John Wiley & Sons, Inc.     

Synthesis of poly(methylmethacrylate)/montmorillonite nanocomposites via in situ intercalative suspension and emulsion polymerization

Summary Na-montmorillonite (MMT) with cation exchange capacity (CEC) of 90 mEq/100g was converted to MMT-CTAB and MMT-CPC forms by the intercalation of Cetyltrimethylammonium bromide (CTAB) and Cetylpyridinium chloride (CPC), respectively. The intercalation of these surfactants onto the basal space of the montmorillonite was evidenced by fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD). The intercalation of the CPC expanded the basal space from 12.19 A^o to 21.47 A^o while in case of CTAB it was expanded to 19.35 A^o only. The (MMT-CPC) was subsequently used as a host for the preparation of PMMA nanocomposites via intercalative suspension and emulsion polymerization of methylmethacrylate (MMA) using benzoyl peroxide (BPO) and potassium persulphate (PPS) individually and simultaneously. The use of BPO and PPS together invoked better exfoliation but the yield did not change appreciably in comparison with using either of the initiators alone. Different structures were obtained with the variation of the preparation conditions; exfoliated and intercalated nanocomposites which were characterized by XRD, transmission electron microscope (TEM), thermal gravimetric analysis (TGA), and differential scanning calorimeter (DSC). The resultant nanocomposites exhibited improved thermal stability relative to the equivalent macrocomposites. No glass transition temperature (Tg) could be detected for the prepared nanocomposites which was assumed to result from the restricted molecular motion of the polymer chains.     

Anodic behaviour of tin in maleic acid solution and the effect of some inorganic inhibitors

The anodic behaviour of a tin electrode in maleic acid solutions was investigated by potentiodynamic and chronopotentiometric methods. Measurements were conducted under different experimental conditions. The results demonstrated that the polarization curves exhibit active/passive transition. In active regions, tin dissolves as Sn²⁺ which is subsequently oxidized to Sn⁴⁺ and the dissolution process is controlled partly by diffusion of the solution species. The passivity is due to the presence of thin film of SnO₂ on the anode surface formed by dehydration of precipitated Sn(OH)₄. The active dissolution of tin increases with increasing acid concentration, temperature and scan rate. The potential transients showed that the passivation time decreases with increasing applied current density. The effect of adding increasing concentrations of CrO₄²⁻, MoO₄²⁻ and NO₂⁻ ions on the anodic behaviour of tin in maleic acid was studied. These ions inhibit the active dissolution of tin and promote the attainment of passivity. The extent of these changes depends upon the type and concentration of the inhibitor.     

Induced electrodeposition of tungsten with nickel from acidic citrate electrolyte

Induced electrodeposition of Ni–W alloys was carried out onto steel substrates from acidic citrate baths (pH 4.5) under different conditions of concentration of electrolyte, current density and temperature. Bright and highly adherent Ni–W deposits were successfully obtained with a relatively high cathodic current efficiency CCE (80–85%). The CCE increases greatly with increasing pH and Ni²⁺ ion content in the bath. The W% in the alloy deposits is in the range of 4–20 wt% depending on the operating condition. The W content in the deposit was found to increase with an increase in Ni²⁺ ion content, pH and temperature. The surface morphology was examined by scanning electron microscopy while the structure of the alloy was examined by X-ray diffraction analysis.