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Volume 16, Issue 2, 2009
Transactions on Chemistry and Chemical Engineering


Spectroscopic and Thermodynamic Studies of Interaction Between Dopamine and Cobalt(III) Schi -Base Complexe
 
        D.M. Boghaei (Professor)

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In this paper, the interactions of cobalt(III) tetradentate Schi -base complexes, [Co(3- MeO-salophen)]ClO4, (1), [Co(5-NO2-salophen)]ClO4, (2), and [Co(5-Br-salophen)]ClO4, (3), with dopamine, an important neurotransmitter, have been investigated. The formation and kinetic constants for complex formation of [Co(3-MeO-salophen)]ClO4, (1), with dopamine were determined spectrophotometrically in H2O/EtOH solution (4:1) at 30 C by using the Benesi-Hildbrand and Guggenheim equations, respectively. The stoichiometry has been found to be 1:1. The rate and equilibrium constants for the coordination of dopamine to [Co(3-MeO-salophen)]ClO4 were found to be 0.0053 min􀀀1 and 1600 dm3 mol􀀀1, respectively.

Keywords:
Cobalt(III) Schi -base complexes

    Dopamine
      Benesi-Hildbrand equation
        Guggenheim's method
          Neurotransmitter.


DFT Study of the Interaction of Thymine with Cu+ and Zn2+
 
        A. Fattahi (PhD.)
  • M. Shakorian Fard Jahromi [MSc.]

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Interaction of the DNA thymine base with Cu+ and Zn2+ was studied to explore: a) The metal binding energy (MIA) of thymine with Cu+ and Zn2+ and b) The possible correlation between charge transfer and MIAs. The gas-phase Cu+ and Zn2+ anities of thymine, as well as the Mulliken charges, on the complexed metal cations were both determined at the same computational level, including the density functional level and employing the hybrid B3LYP exchange correlation potential in connection with the 6-311++G (d

    p) basis set. All the molecular complexes were obtained by interaction between the most stable tautomer of thymine and two transition mono and divalent (Cu+, Zn2+) metal ions. To probe all possible binding sites, these two cations were placed around the thymine nucleobase and optimized. For both Cu+ and Zn2+, the complexes of thymine with O4 are the most stable structure. For complexes of thymine with mono cations (Li+, Na+, K+ and Cu+) and dications (Mg2+, Ca2+ and Zn2+), the results indicate a linear correlation between the transferred charge and metal binding energy. The results also indicate that the amount of charge transfer and bonding strength are the highest for the transion metal ions Cu+ and Zn2+, respectively.

    Keywords:
    Divalent cations
      Metal ion anity
        Thymine
          Metal complexation
            Charge transfer.


Superheated Water Extraction of Catechins from Green Tea Leaves: Modeling and Simulation
 
        I. Goodarznia (Professor)
  • A. Abdollahi Govar [MSc.]

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Catechins from fresh green tea leaves as potential sources of anticancer and antioxidant components were target materials in this work. Superheated water extraction, which is a kind of leaching operation, and solvent partition with chloroform and ethyl acetate were utilized to recover Catechins from tea leaves. Then, a mathematical model was developed to simulate the superheated water extraction of Catechins. The unsteady state mass balance of the solute in solid and superheated water phases led to two partial di erential equations. The model was solved numerically using a linear equilibrium relationship. The model parameters were predicted applying existing experimental correlations. An intraparticle di usion coecient was used as the model tuning parameter. The model is able to show the in uence of di erent process parameters, such as time of extraction, particle size and the ratio of water/leaves (v/w), on Catechin recovery.

Keywords:
Superheated extraction

    Modeling
      Mass transfer
        Di usion
          Catechins.


Application of Cyclic Steam Stimulation by Horizontal Wells in Iranian Heavy Oil Reservoirs
 
        R. Kharrat (PhD.)
  • S.D. Razavi [MSc.]

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In Iran, there are a number of heavy oil reservoirs whose importance is growing as the conventional resources deplete. This study concerns the numerical simulation of cyclic steam stimulation of one of the heavy oil reservoirs. Results are encouraging and should be tested by eld pilots. Heavy oil is characterized by its high viscosity. Thermal methods reduce viscosity and residual oil saturation to improve mobility and achieve an economical recovery. Cyclic Steam Stimulation (CSS) which has faster production, lower capital costs and lower pressure operations than steam- ooding is of great interest in thermal methods. Oil recovery with steam injection has been enhanced with horizontal wells by increasing sweep eciency, the contact area opened to ow, producible reserves, steam injectivity and also by decreasing the number of wells required so that higher oil production is reached. K-Field is one of the Iranian fractured heavy oil elds with low API of 7.24 and high viscosity of 2700 cp. Although steam injection in naturally fractured heavy oil reservoirs provides extremely challenging issues, it can be considered as a potentially e ective and ecient improved recovery method. In this study, using STARS, a thermal dual-porosity model was constructed based on the available measured data to study CSS. Comprehensive and comparative studies and a sensitivity analysis of various operational parameters were conducted in order to nd the optimum conditions for a high RF. This work shows that oil recovery could be improved from 0.66% by cold production to more than 10% by CSS during a 10 year period.

Keywords:
Heavy oil

    Enhanced oil recovery
      Thermal methods
        Steam injection
          Cyclic steam stimulation
            Horizontal well.


Production of Chitosan by Submerged Fermentation from Aspergillus niger
 
        V. Maghsoodi (PhD.)
  • J. Razavi [MSc.]
  • S. Yaghmaei [PhD.]

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The e ect of glucose concentration in submerged fermentation (SMF) on chitosan production by Aspergillus niger was investigated. A. niger, BBRC, 20004, from the Biochemical and Bioenvironmental Research Centre at Sharif University of Technology, Tehran, Iran, was grown in a Sabouro Dextrose media. Chitosan was extracted from the fungal mycelia using hot alkaline and acid treatment and after 12 days of cultivation, 0.8455 g chitosan /l of the fermentation medium was obtained. The content of glucose in the Sobouro Dextrose Broth media was also changed and the highest yield of chitosan 0.9121g/l was obtained in Sobouro Dextrose Broth media containing 8% glucose.

Keywords:
Chitosan

    Aspergillus niger
      Submerged fermentation
        Sabouro Dextrose Broth media; Glucose.


A New Eco-Friendly and Ecient Mesoporous Solid Acid Catalyst for the Alkylation of Phenols and Naphthols Under Microwave Irradiation and Solvent-Free Conditions
 
        F. Matloubi Moghaddam (PhD.)
  • M. Akhlaghi [MSc.]
  • L. Hojabri [MSc.]
  • M.G. Dekamin [MSc.]

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The catalytic activity of a mixture of ZnCl2: AlCl3 supported on silica gel was evaluated for the alkylation of phenols with benzyl alcohol, tret-butyl alcohol and styrene under microwave irradiation and solvent-free conditions. The catalyst preparation method, its characterization and reusability, were reported. The e ect of the phenol to benzyl alcohol ratio and the time of reaction on the phenol conversion and distribution of products was investigated. A conversion percentage up to 97% was achieved when hydroquinone was used. A selective ortho- directed alkylation for phenol, -naphthol and -naphthol was observed.

Keywords:
Mesoporous solid acid catalyst

    Alkylation
      Phenols
        Microwave irradiation
          Solvent free


Highly Ecient One-Pot Three-Component Mannich Reaction Under Solvent-Free Conditions
 
        M.R. Saidi (PhD.)
  • N. Azizi [MSc.]
  • F. Ebrahimi [MSc.]

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A mild and practically-convenient one-pot procedure for the direct Mannich reaction has been developed using a condensation of amines, aldehydes and unmodi ed ketones under solvent free conditions in the presence of ZnI2 with good to excellent yields. The present methodology o ers several advantages, such as excellent yields, simple procedures, short reaction times and milder conditions with very small amounts of catalyst. Furthermore, it is the rst time that the catalytic activity of several catalysts under solvent free conditions has been studied. It was found that both the diastereoselectivity and the rate of reaction were improved with various Lewis acids and metal oxides. However, the chiral catalysts, such as L-cystine, (-)-cinchonidine and L-proline, did not work well in terms of yield and diastereoselectivity under this condition.

Keywords:
Amine

    Aldehyde
      Catalyst
        Maanich reaction
          Solvent-free


An Improved Procedure for the Enrichment of Plasma F2-Isoprostanes Prior to Final Determination by GC-MS/NICI
 
        J. Nourooz-Zadeh (Professor)

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One of the most popular approaches to quantify oxidative injury is to measure lipid peroxidation products and, in particular, F2-isoprostanes (F2-IPs). F2-IPs is a group of prostaglandin F2-like compounds derived from the non-enzymatic oxidation of arachidonic acid. Of these, the 15-F2t-isoprostane (8-iso-PGF2 ) has received considerable attention, because it possesses adverse biological activities. Previous Gas Chromatographic-Mass Spectrometric (GC-MS) methods for measuring plasma F2-IPs from this laboratory involved two chromatography steps on C18 and NH2-cartridges. Problems may, however, arise with chromatography on C18 cartridges, as it can be time-consuming and losses may occur depending upon the pH and eciency of the sample loading. Therefore, it was decided that the C18 chromatography step be replaced with a single lipid partitioning step and the NH2-chromatography be simpli ed. In 70 plasma samples from healthy individuals, total (sum of free and esteri ed) 15-F2t-isoprostane concentrations ranged from 0.5 to 3.13 nM. This assay meets all prede ned method performances in terms of speci city and sensitivity. The improved method is suitable for the analysis of samples from larger clinical trials investigating the role of oxidant injury under conditions associated with oxidative stress. One of the most popular approaches to quantify oxidative injury is to measure lipid peroxidation products and, in particular, F2-isoprostanes (F2-IPs). F2-IPs is a group of prostaglandin F2-like compounds derived from the non-enzymatic oxidation of arachidonic acid. Of these, the 15-F2t-isoprostane (8-iso-PGF2 ) has received considerable attention, because it possesses adverse biological activities. Previous Gas Chromatographic-Mass Spectrometric (GC-MS) methods for measuring plasma F2-IPs from this laboratory involved two chromatography steps on C18 and NH2-cartridges. Problems may, however, arise with chromatography on C18 cartridges, as it can be time-consuming and losses may occur depending upon the pH and eciency of the sample loading. Therefore, it was decided that the C18 chromatography step be replaced with a single lipid partitioning step and the NH2-chromatography be simpli ed. In 70 plasma samples from healthy individuals, total (sum of free and esteri ed) 15-F2t-isoprostane concentrations ranged from 0.5 to 3.13 nM. This assay meets all prede ned method performances in terms of speci city and sensitivity. The improved method is suitable for the analysis of samples from larger clinical trials investigating the role of oxidant injury under conditions associated with oxidative stress.

Keywords:
F2-isoprostanes

    Lipid peroxidation
      Oxidative stress
        Gas chromatography-mass spectrometry.


Investigation and Selection of Suitable Layers in Bangestan Reservoir for Hydraulic Fracturing Operation
 
        S.R. Shadizadeh (PhD.)
  • B.A. Habibnia [PhD.]
  • R. Syllabee [PhD.]

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Hydraulic fracturing is a process applied to boreholes to improve the ability of uids (such as oil and gas) to ow to the hole and be recovered. Recent investigation has shown that fractures can play a major role in the productivity of low permeability formations. The Ahwaz oil eld is one of the largest in South West Iran. The Bangestan reservoir in this eld, with a suitable amount of oil in place and good rock reservoirs, has been selected for the present research work. The pressure pro le has been calculated in tight reservoirs in a few wells, for the purpose of hydraulic fracturing operation studies. In this work, the pore pressure was calculated by using the available eld data in the carbonated reservoir of the Ahwaz eld. The results indicate that the Ilam formation could be a good candidate for hydraulic fracturing.

Keywords:
Hydraulic fracturing

    Minimum horizontal stress
      Stress gradient
        Bangestan reservoir.


Mathematical Modeling of a Non-Catalytic Gas-Solid Reaction: Hematite Pellet Reduction with Syngas
 
        M.S. Valipour (PhD.)

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A mathematical model is developed to investigate the nonisothermal reduction of the hematite pellet with Syngas, namely is a mixture of hydrogen, water vapour, carbon dioxide and carbon monoxide gases. This model is based upon special application of the grain model and contains the interactions between Syngas and the hematite pellet as a re ection of the heat and mass transfer phenomena. Each grain is reduced as an un-reacted shrinking core model at three interfaces simultaneously. A concluded set of equations is solved using the nite volume approach as an implicit formulation. Finally, the model was applied to study the isothermal and non-isothermal reduction of the hematite pellet and investigate the e ects of Syngas characteristics, like gas utility ((CO+H2)/(CO2+H2O)) and gas ratio (H2/CO), on the rate of reduction.

Keywords:
Mathematical modeling

    Gas-solid reaction
      Direct reduction iron
        Hematite pellet
          Kinetics.