Showing papers by "University of Tabriz published in 2003"
TL;DR: In this article, it was shown that acid red 14 (AR14) can be photocatalytically degraded using TiO 2 suspensions irradiated by a UV-C lamp (30 W).
Abstract: Acid Red 14 (AR14), commonly used as a textile dye, could be photocatalytically degraded using TiO 2 suspensions irradiated by a UV-C lamp (30 W). The experiments showed that TiO 2 and UV light had a negligible effect when they were used on their own. The semi-log plot of dye concentration versus time was linear, suggesting first order reaction ( K =1.41×10 −2 min −1 ). The effects of some parameters such as pH, the amount of TiO 2 and initial dye concentration were also examined. The photodegradation of AR14 was enhanced by the addition of proper amount of hydrogen peroxide, but it was inhibited by ethanol. From the inhibitive effect of ethanol it was deducted that hydroxyl radicals played a significant role in the photodegradation of dye, but a direct oxidation by positive holes was probably not negligible. Accordingly, it could be stated that the complete removal of color, after selecting optimal operational parameters could be achieved in a relatively short time, about 3.5 h.
820 citations
TL;DR: In this article, the decolorization of orange II by the D.C. electrocoagulation (EC) method has been studied and the optimum operating range for each of these operating variables was experimentally determined.
355 citations
TL;DR: The results indicated the utility of the sequential path model for determining the interrelationships among grain yield and related traits in maize.
Abstract: Knowledge of interrelationships between grain yield and its contributing components will improve the efficiency of breeding programs through the use of appropriate selection indices. Previous path analyses studies in maize (Zea mays L.) treated yield components as first-order variables. The present study, based on evaluation of 90 experimental maize hybrids (comprising one diallel and one line x tester set) at two locations in India, utilizes a sequential path model for analysis of genetic associations among grain yield and its related traits by ordering the various variables in first-, second-, and third-order paths on the basis of their maximum direct effects and minimal collinearity. The sequential path model showed distinct advantages over the conventional path model in discerning the actual effects of different predictor variables. Two first-order variables, namely 100-grain weight and total number of kernels per ear, revealed highest direct effects on total grain weight (p = 0.74 and p = 0.78, respectively), while ear length, ear diameter, number of kernel rows, and number of kernels per row were found to fit as second-order variables. All direct effects were found to be significant, as indicated by bootstrap analysis. Test for the goodness-of-fit revealed that the sequential path model provided better fit to various datasets analyzed in the study. Correlations between the predicted values of various response variables in the second season dataset based on the path coefficients of the first season were high, except for ear length and number of kernels per row. The applicability of the model has been confirmed through analysis of two additional datasets during 2000. The results indicated the utility of the sequential path model for determining the interrelationships among grain yield and related traits in maize.
209 citations
TL;DR: In this paper, the efficiency of anodized aluminum wire as a new fiber for solid phase microextraction (SPME) was investigated and the optimum conditions for the preparation and conditioning of fibers and the extraction of analytes from gaseous samples were obtained.
Abstract: The efficiency of anodized aluminum wire was investigated as a new fiber for solid-phase microextraction (SPME). Aluminum wires were anodized by direct current in a solution of sulfuric acid at room temperature and were conditioned at 300 °C for 30 min. These fibers were used for the extraction of some aliphatic alcohols, BTEX, and petroleum products from gaseous samples. The extracted analytes were transferred to a GC injector using an (in-house-designed) SPME syringe that also allowed for an easy change of SPME fibers. The results obtained prove the ability of anodized aluminum wire as a new fiber for sampling of organic compounds from gaseous samples. This behavior is due most probably to the porous layer of aluminum oxide, which is formed on the metal surfaces. In this work, the optimum conditions for the preparation and conditioning of fibers and the extraction of analytes from gaseous samples were obtained. In the optimum conditions, one fiber was used in several equal analyses and the relative stan...
205 citations
TL;DR: A series of rare-earth iron borates having general formula LnFe 3 (BO 3 ) 4 (Ln =Y, La-Nd, Sm-Ho) were prepared and their magnetic properties have been investigated by the magnetic susceptibility, specific heat, and 57 Fe Mossbauer spectrum measurements.
147 citations
TL;DR: In this article, the preparation and characterization of polyaniline and polyvinyl alcohol composites is described, and the electrical conductivity of the films increased with an increasing amount of aniline to a high value of 2.5 S cm −1.
139 citations
TL;DR: In this paper, a CoPCNF-modified glassy carbon electrode was studied by cyclic voltammetry; the modified electrode shows one pair of peaks with a surface-confined characteristic in 0.5 M KNO3 as supporting electrolyte.
120 citations
TL;DR: Dithizone (diphenylthiocarbazone) was used as a complexing agent in cloud point extraction for the first time and applied for selective preconcentration of trace amounts of silver as mentioned in this paper.
118 citations
TL;DR: In this paper, the synthesis of linear-dendritic thermoreversible hydrogel copolymers was achieved via two procedures: an esterification step using thionylchloride and pyridine, and a second procedure using dicyclohexyl carbodiimide (DHCD) and Pyridine.
109 citations
TL;DR: In this paper, a rechargeable battery of the type Zn/ZnCl2, NH4Cl/polyaniline (PAn)-reticulated vitreous carbon was successfully prepared based on a PAn modified electrode.
108 citations
TL;DR: A reference-flux-generating method is followed and an approximate equation is derived using numerical techniques in order to obtain the reference flux from the torque to achieve the maximum torque per flux (MTPF).
Abstract: A permanent-magnet synchronous machine (PMSM) can be controlled using the direct torque control (DTC) technique in three different ways, i.e., by controlling flux, reactive torque and rotor d-axis current. Frequently, the DTC technique controls the speed of the motor by controlling stator flux with the aim of obtaining an optimal torque. A varying flux, proportional to the torque, may be used instead of a fixed flux, resulting in a maximum torque per ampere or maximum torque per flux (MTPF). In this paper, a reference-flux-generating method is followed to achieve the MTPF. An approximate equation is then derived using numerical techniques in order to obtain the reference flux from the torque. This equation is then applied to the DTC control system in order to obtain the reference flux. The control scheme has been verified by simulation and tests on a salient-pole permanent-magnet synchronous motor.
TL;DR: In this article, the binodal curves were described using a three-parameter equation, and the tie lines were satisfactorily described using the Othmer−Tobias and Bancroft equations.
Abstract: Liquid−liquid equilibrium data of poly(ethylene glycol) 6000 + potassium citrate + water have been measured at (25, 30, and 35) °C. The binodal curves were described using a three-parameter equation, and the tie lines were satisfactorily described using the Othmer−Tobias and Bancroft equations.
TL;DR: In this paper, the cloud point methodology was successfully used to preconcentrate trace amounts of Co and Ni as a prior step to their determination by flame atomic absorption spectrometry.
Abstract: Cloud point methodology was successfully used to preconcentrate trace amounts of Co and Ni as a prior step to their determination by flame atomic absorption spectrometry. 1-Nitroso-2-naphthol and polyethylene glycol-p-nonylphenylether (PONPE 7.5) are used as hydrophobic ligand and nonionic surfactant, respectively. Optimization was performed of the variables effecting complexation and phase separation. Additionally, the influence of viscosity on the analytical signal was investigated. Under the experimental conditions used, preconcentration of only 10 mL of sample in the presence of 0.075% (v/v) PONPE 7.5 permitted the detection of 1.09 µg L−1 of Ni and 1.22 µg L−1 of Co with enhancement factors of 29 and 27 for Ni and Co, respectively. The relative standard deviations (n=5) at concentrations of 80 and 50 µg L−1 for Co and Ni were 2.53 and 2.89%, respectively. Good recoveries in the range of 96–105% were obtained for spiked samples. The effect of different interferent species was studied. The proposed method was applied to the determination of Ni and Co in different water samples.
TL;DR: The calculated rate constants indicate that degradation rate of PVA solutions decreases with increasing of solution concentration, and viscosity increases and it causes a reduction in the cavitation efficiency thus, the rate of degradation will be decreased.
TL;DR: A sensitive spectrofluorimetric method with a linear range of 0.1-2 microg ml(-1) and a detection limit was developed and applied satisfactorily to the determination of ibuprofen in pharmaceutical preparations.
TL;DR: In this paper, the electrocatalytic oxidation of methanol at a glassy carbon electrode modified by a thin film of poly(o-aminophenol) (PoAP) containing Pt, Pt-Ru and Pt-Sn microparticles has been investigated using cyclic voltammetry as analytical technique and 0.10m perchloric acid as supporting electrolyte.
Abstract: The electrocatalytic oxidation of methanol at a glassy carbon electrode modified by a thin film of poly(o-aminophenol) (PoAP) containing Pt, Pt-Ru and Pt-Sn microparticles has been investigated using cyclic voltammetry as analytical technique and 0.10 M perchloric acid as supporting electrolyte. It has been shown that the presence of PoAP film increases considerably the efficiency of deposited Pt microparticles toward the oxidation of methanol. The catalytic activity of Pt particles is further enhanced when Ru or specially Sn is co-deposited in the polymer film. The effects of various parameters such as the thickness of polymer film, concentration of methanol, medium temperature as well as the long term stability of modified electrodes have also been investigated.
TL;DR: In this paper, a solution casting method was used for modification of quartz crystal with a thin layer of polyvinylpyrrolidone (PVP) for determination of ammonia and a number of short chain primary aliphatic amines in atmospheric media.
Abstract: Polyvinylpyrrolidone (PVP) modified quartz crystal microbalance (QCM) has been used for determination of ammonia and a number of short chain primary aliphatic amines in atmospheric media. A solution casting method was used for modification of quartz crystal with a thin layer of PVP. Determination was based on frequency shifts due to adsorption of the compounds at the surface of the modified electrode. The frequency shifts were found to be linear against the concentration of analyte in the range between 0.5 and 30 mg l−1 with correlation coefficients of above 0.9903. The sensitivity factors in the range of 7.5–48.2 Hz/mg l−1 was obtained. A storage period of over 5 months proved no loss in sensitivity and performance. Among some possible interference tested, no major interference was involved in the performance of the sensor except for water vapor, which may be resolved by drying the samples prior to injection.
TL;DR: An enzymatic method for the synthesis of a water-soluble, conducting poly( o -toluidine) (POT) in the presence of sulfonated polystyrene (SPS) is presented in this article.
TL;DR: In this article, the response mechanism of the conducting polymer to a selection of gases and vapors was investigated using two techniques, measurement of conductance and mass changes using a four-point probe method, and a X-ray fluorescence (XRF) device, respectively.
Abstract: Blends of the conducting polymer, polypyrrole (PPy), and in the insulating host polymers, polyvinyl acetate (PVAc), polystyrene (PS), and polyvinyl chloride (PVC) resin, have been prepared chemically. Threshold conductivities occur at about 5% for PPy in blends with host polymers. The characterizations of these blends were done by FTIR, UV-visible, differential scanning calorimetric (DSC), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). The products of the blends have electrical conductivity comparable to PPy and mechanical properties similar to hosting polymers. The response mechanism of the conducting blends to a selection of gases and vapors was investigated using two techniques, measurement of conductance and mass changes using a four-point probe method, and a X-ray fluorescence (XRF) device, respectively. These responses of blends to toxic gases and vapors are more well explained. Prepared films were exposed to hydrogen halides (HCl, HBr, and HI), hydrogen cyanide, halogens (Cl 2 , Br 2 , and I 2 ), monochloroacetic acid (MCAA), 1-3-5 trichloromethyl benzene (TCMB), methylbenzyl bromide (MBB), bromoacetone (BA), and cyanogen bromide (CB). The changes of conductivity of polymers frequently observed are partly due to one stage in the two-stage sorption, perhaps involving the swelling of the polymer, then diffusion gases into polymer chains. The swelling of polymers is a slow process, therefore, preswelled polymer films tend to decrease the response times of blends with respect to gases.
TL;DR: In this paper, stable isotope (S, O, H, and C) studies were performed to determine the origin of the ore-forming solutions, and their important components (e.g. sulfur and carbon).
TL;DR: A nickel pentacyanonitrosylferrate (NiPCNF) film modified/Al electrode prepared by a simple and rapid electroless dipping procedure was used for the mediated oxidation of sulfite as discussed by the authors.
01 Aug 2003
TL;DR: In this paper, an experimental study was conducted to determine the performance and exhaust emission characteristics of an automotive direct injection dual-fuelled diesel engine, where natural gas was used such that 65 per cent of engine brake power was supplied from compressed natural gas and the rest from diesel fuel.
Abstract: An experimental study was conducted to determine the performance and exhaust emission characteristics of an automotive direct injection dual-fuelled diesel engine. Natural gas was used such that 65 per cent of engine brake power was supplied from compressed natural gas and the rest was supplied from diesel fuel. The objective of this work is to investigate the possibility of decreasing exhaust emission with the lowest performance sacrifice. At part loads, a dual-fuelled engine inevitably suffers from lower thermal efficiency and higher carbon monoxide (CO) emission. This is mainly due to leaner mixture and incomplete combustion, which is a consequence of the smaller amount of pilot fuel. To resolve these problems, the e ects of cooled exhaust gas recirculation (EGR) were investigated. The experimental results show that the application of EGR, at higher loads with 10 per cent EGR and at part loads with 15 per cent EGR, can considerably reduce NOx and other exhaust emissions such as unburned hydroca...
TL;DR: A new approach for developing a cloud-point extraction-flame atomic absorption spectrometric method has been described and used for the determination of cobalt and the effect of the water concentration in the final diluted methanolic surfactant solution on the analytical signal was investigated.
Abstract: A new approach for developing a cloud-point extraction-flame atomic absorption spectrometric method has been described and used for the determination of cobalt. In this approach, water was removed from the final diluted surfactant rich phase obtained in cloud-point extraction procedure. The results indicated that removing water from this phase increased the enhancement factor by 4-fold. 1-(2-Pyridylazo)-2-naphthol (PAN) and octylphenoxypolyethoxyethanol (Triton X-114) were used as a hydrophobic ligand and a nonionic surfactant, respectively. The chemical variables affecting the preconcentration step were optimized. The effect of the water concentration in the final diluted methanolic surfactant solution on the analytical signal was investigated. The results showed that the analytical signal decreased by 30% and 52% in 15% and 25% water concentrations in methanol, respectively. An enhancement factor of 115 was obtained for cobalt extracted from only 10 ml of a sample. The detection limit obtained under the optimal condition was 0.38 μg l-1. The proposed procedure was applied to the determination of cobalt in urine samples.
TL;DR: In this article, a range of Zn efficient and inefficient genotypes of rice (Oryza sativa L.), wheat (Triticum aestivum L. and Triticum durum L.) and rye (Secale cereale L.) were investigated to examine shoot and root growth response to bicarbonate and high pH at different Zn levels.
Abstract: A range of Zn efficient and inefficient genotypes of rice (Oryza sativa L.), wheat (Triticum aestivum L. and Triticum durum L.) and rye (Secale cereale L.) were investigated to examine shoot and root growth response to bicarbonate and high pH at different Zn levels. The treatment of bicarbonate was 10 mM as NaHCO3, high pH was 8.0 buffered with HEPES, and three Zn levels included without addition of Zn (deficient Zn), with 0.5 and 1.0 μM Zn (moderate Zn), and 1.5 and 3.5 μM (high Zn) for rice and wheat or rye, respectively. For rice, shoot and root growth of Zn-inefficient genotypes was strongly inhibited, whereas root length of Zn-efficient genotypes was considerably enhanced by bicarbonate. High pH had much less effect on reduced root growth of the Zn-inefficient rice genotypes and enhanced root length of the Zn-efficient genotypes, as compared with bicarbonate. Responses of plants to bicarbonate at different Zn levels showed that under deficient or moderate Zn supply conditions, root dry weight and length were significantly increased for the Zn-efficient rice genotypes, but were decreased for the Zn-inefficient rice genotypes grown with bicarbonate. At high Zn supply, however, root elongation of the Zn-efficient rice genotypes and of the Zn-inefficient genotypes was enhanced. In contrast to rice, either bicarbonate or high pH had little effects on shoot and root growth for all the Zn-efficient and Zn-inefficient wheat genotypes except for Dagdas (Zn-efficient) at moderate Zn levels. Decreased root growth due to bicarbonate treatment was observed only in the Zn-efficient rye. Root lengths of all the wheat and rye genotypes except for Kunduru (Zn-inefficient) were reduced by high pH but not affected by bicarbonate. At deficient Zn levels, shoot growth was reduced by bicarbonate for both Zn-efficient rye and inefficient wheat genotypes. Root lengths was reduced due to bicarbonate for the Zn-inefficient wheat genotype at deficient and high Zn, but not at moderate Zn levels. The results imply that Zn efficiency in rice is closely associated with plant tolerance to bicarbonate relative to root growth, and bicarbonate tolerance and Zn efficiency might be developed simultaneously in lowland rice.
TL;DR: In this article, a new structure for a 4-bit full optical analog to digital converter (A/D) using Kerr-like nonlinear two-port ring resonator is presented.
TL;DR: In this article, two predictive models of the effective thermal conductivity of porous food were developed (Krischer and Maxwell models), and the results were in good agreement with the experimental data.
Abstract: The modelling of heat transfer within materials with high porosity is complicated by evaporation-condensation phenomena. The aim of this work is to develop a model for apparent thermal conductivity in these products. The effective thermal conductivity of a porous food model (sponge) having 0–60% moisture contents and 0.59–0.94 porosity was measured by a line-source heat probe system in the range −35 to 25 °C. Two predictive models of the effective thermal conductivity of porous food were developed (Krischer and Maxwell models). The effective thermal conductivity predicted by Krischer model were in good agreement with the experimental data. Also, it was shown that the model including the effect of evaporation-condensation phenomena in addition to heat conduction was useful to predict the effective thermal conductivity of sponges.
TL;DR: In this article, the efficiency of polyaniline (PANI) coated gold wire as a fiber of solid-phase microextraction (SPME) was investigated for the extraction of phenol and 4-chlorophenol from gaseous samples and headspace of aqueous samples.
Abstract: The efficiency of polyaniline (PANI) coated gold wire as a fiber of solid-phase microextraction (SPME) was investigated for the extraction of phenol and 4-chlorophenol from gaseous samples and headspace of aqueous samples. Polymerization and extraction time, sample humidity, temperature, salt addition, sample pH and stirring speed were optimized. Extraction at room temperature for 80 min in the presence of 8 g NaCl at constant stirring speed yields maximum efficiency. Using the proposed microsolid phase as an efficient sampling device and capillary gas chromatography with flame ionization detection, reliable determination of these compounds at parts-per-billion and parts-per-million concentrations was achieved for the extraction from gaseous samples and headspace (HS) of aqueous samples, respectively. The calibration graphs were linear for both methods. The proposed method was successfully applied to the determination of phenol and 4-chlorophenol in real sample such as petrochemical sewage.
TL;DR: In this paper, dissymmetric tetradentate Schiff base ligands, containing a mixed donor set of NSNO were prepared by the reaction of aminothioether pyridine with the appropriate salicylaldehyde and characterized by FTIR, 1 H and 13 C NMR and elemental analysis methods.
14 Dec 2003
TL;DR: In this paper, a 50-kVA three-phase distribution transformer is modeled using the finite element (FE) method and its losses are estimated under rated frequency and load and also under nonlinear loads.
Abstract: Transformers are normally designed and built for utilizing at rated frequency and perfect sinusoidal load current. Supplying non-linear loads by transformer leads to higher losses, early fatigue of insulation, premature defectiveness and reduction of the useful life of the transformer. To prevent these problems, rated capacity of transformers supplying non-linear loads must be reduced. In this paper, a 50-kVA three-phase distribution transformer is modeled using the finite element (FE) method and its losses are estimated under rated frequency and load and also under nonlinear loads. An equivalent rating of the transformer is estimated based on the harmonic loss factor and it is compared to the recommended standard rating. This comparison shows that the estimation of derating of the transformer supplying non-linear loads using the standard recommendations is acceptable, but it is slightly conservative.
TL;DR: In this paper, the synthesis of N2O3 macrocyclic ligand 8,9,18,19-tetrahydro-7H,17H-dibenzo[f,o][1,5, 9,13] dioxadiazacyclohexadecin-18-ol (L=2) and preparation of complexes NiLX2 (X=Cl, Br, I, ClO4) and NiLXY (X =Cl, B, I and Y=ClO4).