Effect of Al2O3/water nanofluid on performance of parallel flow heat exchangers

Journal of Thermal Analysis and Calorimetry - A comprehensive experimental investigation is intended to survey consequence of nanofluid on performance of sundry parallel flow heat exchangers with...     

Application of Fe–graphene Oxide Nanocomposite to Improve SERS Intensity of Polyaromatic Hydrocarbons

Optics and Spectroscopy - Raman spectroscopy is used to provide a structural finger-print by which molecules can be identified. SERS technique offers many orders of magnitude enhancement in initial...     

Kinetics of nonisothermal reduction and carburization of WO3─NiO nano-composite powders by CO─CO2

The kinetics of simultaneous reduction and carburization of WO₃─NiO nanocomposite powders by CO/CO₂ was studied using a nonisothermal thermogravimetric analysis. The experiments were carried out at heating rates between 5 and 15°C/min, showing that the thermochemical processes can be divided into four steps, each dominated by a reaction, as following: NiO → Ni, WO₃ → WO₂, WO₂ → W, and W → WC. The apparent activation energy for each step was obtained based on the Flynn-Wall-Ozawa isoconversional method for the individual steps, and the kinetic model was assessed by fitting master plots of various kinetic models for these steps at different heating rates. The Avrami-Erofeev kinetic model was found to fit to the third and fourth steps and main part of the first, and the geometric contracting model fitted the best for the second step. Changing the heating rate did not affect the master plots of the third step. However, for the first step, increasing the heating rate made the Avrami-Erofeev model the best-fitting correlation and also for the second step the matching model changed at the highest heating rate (15°C/min) from a two-dimensional contracting model (cylindrical particles) to a three-dimensional contracting model (spherical particles).     

Interaction of Molybdenum(VI) with Methyliminodiacetic Acid at Different Ionic Strengths by Using Parabolic,Extended Debye-Hückel and Specific Ion Interaction Models

The main aim of this research is to study the complexation of molybdenum(VI) with methyliminodiacetic acid in NaClO₄ aqueous solutions at pH = 6.00 and ionic strengths (0.1<I/mol⋅dm⁻³<1.0) at 25 °C by using potentiometric and UV spectrophotometric measurements in order to obtain thermodynamic stability constants at I=0 mol⋅dm⁻³. A comparison with previous literature data was made for the stability constants, though few data were available. The stability constants data have been analyzed and interpreted by using extended Debye-Hückel theory, specific ion interaction theory and parabolic model. Finally it might be concluded that parabolic model applies better for this complexation reaction.     

Effect of magnetic field on the impurity binding energy of the excited states in spherical quantum dot

The effect of external magnetic field on the excited state energies in a spherical quantum dot was studied. The impurity energy and binding energy were calculated using the variational method within the effective mass approximation and finite barrier potential. The results showed that by increasing the magnetic field, the energy would be increased. The results obtained by this method were compared with the previous investigations.     

Complexation of Dioxovanadium(V) with D-(-)-Quinic Acid at Different Ionic Strengths Using Different Models Based on the Debye-Hückel Theory

The complex formation reaction between the dioxovanadium(V) cation $\mathrm{VO}_{2}^{+}$ and D-(-)-quinic acid {(1R,3R,4S,5R)-(-)-1,3,4,5-tetrahydroxycyclohexane-1-carboxylic acid} has been studied in aqueous solutions. The UV data and the values of the derived conditional stability constants are presented and discussed in the light of one stoichiometric model for the reaction at T=298?K and different ionic strengths (0.10 to 1.00)?mol?dm^?3 of sodium chloride. Speciation diagrams and dissociation constants were obtained on the basis of UV spectroscopic measurements and potentiometric titrations, respectively. Our results show that one complex species, VO₂L, exists in solution in the pH range of about 1.00 to 3.00. The parabolic, Specific Ion Interaction Theory (SIT), and extended Debye-Hückel type (EDH) models successfully describe the ionic strength dependence of the stability constants. A comparison with literature data is also reported.     

Classification of skew‐Hadamard matrices of order 32 and association schemes of order 31

Using a backtracking algorithm along with an essential change to the rows of representatives of known 13 710 027 equivalence classes of Hadamard matrices of order 32, we make an exhaustive computer search feasible and show that there are exactly 6662 inequivalent skew‐Hadamard matrices of order 32. Two skew‐Hadamard matrices are considered SH ‐equivalent if they are similar by a signed permutation matrix. We determine that there are precisely 7227 skew‐Hadamard matrices of order 32 up to SH ‐equivalence. This partly settles a problem posed by Kim and Solé. As a consequence, we provide the classification of association schemes of order 31.     

The approximation method for calculation of the exponents of the gluon distribution, λ g , and the structure function, λ S ,at low x

We present a set of formulas using the solution of the QCD Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equation to extract of the exponents of the gluon distribution, λ _g , and structure function, λ _S , from the Regge-like behavior at low x. The exponents are found to be independent of x and to increase linearly with lnQ ² and are compared with the most data from the H1 Collaboration. We also calculated the structure function F ₂(x,Q ²) and the gluon distribution G(x,Q ²) at low x assuming the Regge-like behavior of the gluon distribution function at this limit and compared them with an NLO-QCD fit to theH1 data, two-Pomeron fit, multipole Pomeron exchange fit, and MRST (A.D. Martin, R.G. Roberts, W.J. Stirling, and R.S. Thorne), DL (A. Donnachie and P.V. Landshoff), and NLO GRV (M. Glük, E. Reya, and A. Vogt) fit results. The text was submitted by the authors in English.     

Substituent effect on the tautomerism of 5-acetyl-2-methoxydihydropyrimidines: experimental NMR and computational DFT studies

Some selected 5-acetyl-2-methoxydihydropyrimidines (DHPMs) are synthesized and the electronic effect of the substituent on the 4-position of the heterocyclic ring on the ratio of the possible tautomeric forms is investigated using dynamic NMR experiments. The results of this study indicate that these compounds coexist in two tautomeric 1,4- and 3,4-forms in the solution and their tautomeric ratios depend on the electronic nature of the additional substituent on the 4-phenyl substituent, the nature of solvent used for NMR study and also on the temperature. B3LYP/6–31 ++G** computational studies in the gas and solution phases elucidate the effect of the additional substituent on the phenyl ring on the structural, electronic and bonding characteristics of the tautomeric forms in these compounds. Furthermore, solvation of these DHPMs determines the relative stabilities of the two tautomers in the solution phase, which cannot be probed by model solvents adopted in SCRF calculations.