THE VERTEX AND EDGE PI INDICES OF GENERALIZED HIERARCHICAL PRODUCT OF GRAPHS

Tavakoli, M.,Rahbarnia, F. The Korean Society for Computational and Applied M 2013 Journal of applied mathematics & informatics Vol.31 No.3

Pattabiraman and Paulraja [K. Pattabiraman, P. Paulraja, Vertex and edge PI indices of the generalized hierarchical product of graphs, Discrete Appl. Math. 160 (2012) 1376- 1384] obtained exact formulas for the vertex and edge PI indices of generalized hierarchical product of graphs. The aim of this note is to improve the main results of this paper.

SOME NEW RESULTS ON IRREGULARITY OF GRAPHS

Tavakoli, M.,Rahbarnia, F.,Ashra, A.R. The Korean Society for Computational and Applied M 2014 Journal of applied mathematics & informatics Vol.32 No.5

Suppose G is a simple graph. The irregularity of G, irr(G), is the summation of imb(e) over all edges $uv=e{\in}G$, where imb(e) = |deg(u)-deg(v)|. In this paper, we investigate the behavior of this graph parameter under some old and new graph operations.

Optimization of triangular fins with/without longitudinal perforate for thermal performance enhancement

A. Shadlaghani,M. R. Tavakoli,M. Farzaneh,M. R. Salimpour 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.4

This study aimed at determining a suitable pattern to allow for a better design of the fins used in heat sinks. Flow was considered laminar and steady, and the studied heat transfer mechanism was forced convection. Considering a fixed fin volume, the shape of fin cross section and its dimensions were optimized to maximize the heat transfer rate in a given physical condition. Numerical results showed that at a constant fin base area, heat transfer rate was higher in a fin with a triangular cross section compared to the fins with rectangular or trapezoidal cross sections. Investigation of optimum dimensional ratio in triangular fins showed that an increased height/thickness ratio enhanced the heat transfer rate. The effect of vertical position of the longitudinal perforations with different cross sections but similar volume ratios on the thermal performance of triangular fins was also examined. Results showed that perforation enhanced the thermal performance of the fins. Perforations with square and circular cross sections had almost identical thermal performances and dissipated more heat compared to those with triangular perforations.

A new higher-order triangular plate bending element for the analysis of laminated composite and sandwich plates

M. Rezaiee-Pajand,F. Shahabian,F.H. Tavakoli 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.2

To analyze the bending and transverse shear effects of laminated composite plates, a thirteen nodes triangular element will be presented. The suggested formulations consider a parabolic variation of the transverse shear strains through the thickness. As a result, there is no need to use shear correction coefficients in computing the shear stresses. The proposed element can model both thin and thick plates without any problems, such as shear locking and spurious modes. Moreover, the effectiveness of w, n, as an independent degree of freedom, is concluded by the present study. To perform the accuracy tests, several examples will be solved. Numerical results for the orthotropic materials with different boundary conditions, shapes, number of layers, thickness ratios and fiber orientations will be presented. The suggested element calculates the deflections and stresses more accurate than those available in the literature.

Site effect microzonation of Babol, Iran

Tavakoli, H.R.,Amiri, M. Talebzade,Abdollahzade, G.,Janalizade, A. Techno-Press 2016 Geomechanics & engineering Vol.11 No.6

Extensive researches on distribution of earthquake induced damages in different regions have shown that geological and geotechnical conditions of the local soils significantly influence behavior of alluvial areas under seismic loading. In this article, the site of Babol city which is formed up of saturated fine alluvial soils is considered as a case study. In order to reduce the uncertainties associated with earthquake resistant design of structures in this area (Babol city), the required design parameters have been evaluated with consideration of site's dynamic effects. The utilized methodology combines experimental ground ambient noise analysis, expressed in terms of horizontal to vertical (H/V) spectral ratio, with numerical one-dimensional response analysis of soil columns using DEEPSOIL software. The H/V spectral analysis was performed at 60 points, experimentally, for the region in order to estimate both the fundamental period and its corresponding amplification for the ground vibration. The investigation resulted in amplification ratios that were greater than one in all areas. A good agreement between the proposed ranges of natural periods and alluvial amplification ratios obtained through the analytical model and the experimental microtremor studies verifies the analytical model to provide a good engineering reflection of the subterraneous alluviums.

Development of the Performance Based Plastic Design for Steel Moment Resistant Frame

M. Reza Banihashemi,A. R Mirzagoltabar,H. R Tavakoli 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.1

This paper presents the development of performance based plastic design (PBPD) method for steel moment frames withconsidering the gravity loads and P-Δ effects. In this method the design lateral forces are obtained from energy-work balanceequation by using pre-selected target drift and yield mechanism. For further improvement of PBPD method, some solutions arerepresented to precisely obtain the required moment of columns in order to prevent their yielding that leads to form undesirablemechanisms in the structure. In order to show more validity of PBPD method, two model frames, 5 and 10story, are designedbased on PBPD as well as elastic design method. The mentioned frames are evaluated by extensive nonlinear static pushoveranalysis and dynamic analysis. The results show that the frames designed by PBPD method reach the intended performanceobjectives in terms of yield mechanism and target drift levels. In contrast, the frame designed by Ed method experience largestory drifts due to flexural yielding of the columns. Since PBPD method is a direct design method, little or no evaluation areneeded after the initial design because the nonlinear behavior is built into the design process from the start.

Brønsted Acidic Ionic Liquids as Efficient Catalysts for Clean Synthesis of Carbamatoalkyl Naphthols

Tavakoli-Hoseini, Niloofar,Heravi, Majid M.,Bamoharram, Fatemeh F.,Davoodnia, Abolghasem Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.3

Under mild conditions and without any additional organic solvent, synthesis of carbamatoalkyl naphthols could be carried out in the present of two halogen-free Br${\phi}$nsted acidic ionic liquids, 3-methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate and N-(4-sulfonic acid)butylpyridinium hydrogen sulfate. A wide range of aromatic aldehydes easily undergo condensation with $\beta$-naphthol and methyl or benzyl carbamate to afford the desired products of good purity in excellent yields. The present methodology offers several advantages such as a simple procedure with an easy work-up, short reaction times, and excellent yields. The catalysts could be recycled and reused for several times without substantial reduction in their catalytic activities.

Comparing the generalized Hoek-Brown and Mohr-Coulomb failure criteria for stress analysis on the rocks failure plane

Mohammadi, M.,Tavakoli, H. Techno-Press 2015 Geomechanics & engineering Vol.9 No.1

Determination of mobilized shear strength parameters (that identify stresses on the failure plane) is required for analyzing the stability by limit equilibrium method. Generalized Hoek-Brown (GHB) and Mohr-Coulomb (MC) failure criteria are usually used for obtaining stresses on the plane of failure. In the present paper, the applicability of these criteria for determining the stresses on failure plane is investigated. The comparison is based on stresses on the real failure plane which are obtained from the Mohr stress circle. To do so, 18 sets of data (consist of principal stresses and angle of failure plane) presented in the literature are used. In addition, the values account for (VAF) and the root mean square error (RMSE) indices were calculated to check the determination performance of the obtained results. Values of VAF and RMSE for the normal stresses on the failure plane evaluated from MC are 49% and 31.5 where for GHB are 55% and 30.5, respectively. Also, for the shear stresses on failure plane, they are 74% and 36 for MC, 76% and 34.5 for GHB. Results show that the obtained stresses and angles of failure plane for each criterion differ from real ones, but GHB results are closer to the empirical results. Also, it is inferred that results are affected by the failure envelope not real failure plane. Therefore, obtained shear strength parameters are not mobilized. Finally, a multivariable regressed relation is presented for determining the stresses on the failure plane.

Taguchi Method Prediction of Effect of Processing Parameters on Nanoparticle Size in Chemical Vapor Condensation Process

A. Tavakoli,M. Sohrabi,A. Kargari,최철진 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.5

The Taguchi method has been applied to investigate the effect of various operating parameters such as decomposition temperature, bubbler temperature, carrier gas flow rate, precursor flow rate and pressure on particle size in the Chemical Vapor Condensation process. Also, the effect and contribution of each pertinent parameter on particle size and the interaction among them was determined by Taguchi analysis. It was observed that the decomposition temperature was the most significant process parameter affecting the particle size. Also, the predicted nanoparticle size was in good agreement with that found in the experiment. The Taguchi method has been applied to investigate the effect of various operating parameters such as decomposition temperature, bubbler temperature, carrier gas flow rate, precursor flow rate and pressure on particle size in the Chemical Vapor Condensation process. Also, the effect and contribution of each pertinent parameter on particle size and the interaction among them was determined by Taguchi analysis. It was observed that the decomposition temperature was the most significant process parameter affecting the particle size. Also, the predicted nanoparticle size was in good agreement with that found in the experiment.

Brønsted Acidic Ionic Liquids as Efficient Catalysts for Clean Synthesis of Carbamatoalkyl Naphthols

Niloofar Tavakoli-Hoseini,Majid M. Heravi,Fatemeh F. Bamoharram,Abolghasem Davoodnia 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.3

Under mild conditions and without any additional organic solvent, synthesis of carbamatoalkyl naphthols could be carried out in the present of two halogen-free Brønsted acidic ionic liquids, 3-methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate and N-(4-sulfonic acid)butylpyridinium hydrogen sulfate. A wide range of aromatic aldehydes easily undergo condensation with β-naphthol and methyl or benzyl carbamate to afford the desired products of good purity in excellent yields. The present methodology offers several advantages such as a simple procedure with an easy work-up, short reaction times, and excellent yields. The catalysts could be recycled and reused for several times without substantial reduction in their catalytic activities.