Iranian Journal of science and Technology (A: Siences)
Volume:39 Issue: 1, Winter 2015

In this paper, a new model based on kinetic theory of gases and longitude oscillations of metallic nanocluster on single carbon nanotube (CNT) in addition to phononvibrations of CNT on substrate is presented to describe the growth mechanism of ultra-long CNT in chemical vapor deposition (CVD).Interaction between CNT and catalyst is investigated by Lennard-Jones potential. Simulations demonstrate that metal nanocluster makes and keeps the carbon atoms at tip end reactive. So carbon nanotube can grow more than 1 cm. In addition, results show carbon nanotubes with larger diameter grow less owing to higher damping factors. Furthermore, effect of temperatureand type of catalyst on growth is discussed and it is shown thatthere is an optimum temperature and an optimum catalyst for growth process. Also, it is shown that the optimum temperature is changed by using different catalysts. Finally, effect of the partial pressure of decomposed hydrocarbons on the growth is also discussed. It is demonstrated that increasing partial pressure leads to the longest CNTs and influence of partial pressure on CNTs with smaller diameter is stronger. All results from the model are in good agreement with reported experimental results.

As benzimidazole ring is an important pharmacophore in modern drug discovery and benzimidazoles are very important intermediates in organic reactions, the preparation of benzimidazoles has gained considerable attention in recent years. Here, a comparative study on the synthesis of benzimidazoles from aromatic, aliphatic and heterocyclic carboxylic acid, benzonitrile and o-phenylenediamine under microwave irradiation and solvent-free conditions is catalyzed by alumina, silica gel and zeolite is presented. All the synthesized compounds are characterized by 1H-NMR, IR, Mass and CHNS analysis.

N-(diphenylphosphino)triethyl- and tributylammonium salts are introduced as easily prepared, cheap and stable ionic liquids that act as the condensing agent and media for the efficient esterification of acids with alcohols and phenols. This class of ionic liquids is immiscible with the ester products and thus allows simple and easy separation of the desired products from the reaction mixture.

This study investigated the effect of berberine on the hepatic dysfunction and histological damage induced by renal ischaemia/ reperfusion (I/R) at an early stage. There were four groups (n=7). In Ber+I/R group, rats received berberine (Ber; 15 mg/kg/day) orally for 7 days before induction of ischemia. I/R group received distilled water orally for 7 days. In sham and Ber+sham groups in which arteries were not occluded, distilled water and berberin (15 mg/kg/day) respectively were administered orally for 7 days before surgery. Renal ischemia was induced by occlusion of both renal arteries for 45 min followed by 24 h of reperfusion. Blood samples were collected for biochemical analysis, and finally liver samples were preserved for future histological examination. The renal ischaemic challenge resulted in major histological damage of the liver, which was associated with increased levels of creatinine, blood urea nitrogen (BUN), alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and alkaline phosphatase (ALK) during reperfusion period. In Ber+I/R group, the histological damage to the liver was improved along with increase in plasma creatinine, BUN, ALT, AST, LDH and ALK being smaller than those of the non-treated rats. Berberine exhibited a hepatoameliorative effect against renal ischemia/reperfusion-induced lesions.

Microbial demulsifiers represent a potentially important product for the petroleum industry due to their specific modes of action, relative ease of preparation, biodegradability and low toxicity. An extracellular demulsifier, capable of the rapid break up of model multiple water-crude oil emulsions was obtained from the bacterial isolate Ochrobactrum anthropi RIPI5-1. Demulsifying activity of the cell-free culture filtrate was not age dependent. The time course of demulsification by the whole culture and cell-free culture filtrate showed a similar pattern; the rate of demulsification was 5.21 h-1 and the emulsion half-life time (t1/2) was 5 h. The potential activity of the filtrate was also examined using a complex oilfield emulsion; demulsifying activity (DeI16) was calculated as 42%. Demulsifying activity of whole culture, cell-free culture filtrate and whole cells of strain RIPI5-1 was found to be associated with both the cell surface and extracellularly. Fractionation of the filtrate showed that demulsifying activity was a function of several compounds. The presence of various active demulsifying compounds may explain the ability of the filtrate to break up various crude oil emulsions and therefore represents a promising new technology.

The aim of present paper is to provide mathematical modelling for the two-dimensional MHD flow with induced magnetic field. The flaws in the already existing equations have been pointed out. The results of low magnetic Reynolds number approximation are recovered as a special case from the developed equations. As an example, the peristaltic flow for a couple stress fluid in a channel is considered. For the solution of the problem the governing equations are simplified under the realistic assumption of long wavelength. Exact solution of the problem is presented and some features of peristaltic motion have been discussed. It is observed that the applied magnetic field increases the pressure rise in the pumping region. However, the presence of applied electric field reduced it in that region. It is also found that the stream function is independent of applied electric field.

In this paper we consider a Petrovsky viscoelastic inverse source problem with memory term in the boundary condition. We obtain sufficient conditions on relaxation function and initial data for which the solutions of problem are asymptotically stable when the integral overdetermination tends to zero as time goes to infinity.

Biogeochemical investigation on S. orientalis, a flora growing on the soils derived from serpentinized dunite in the Forumad area, Sabzevar ophiolite has been conducted in order to examine the plant-soil relationship in chromite prospecting. Due to engagement of Cr in the chromite crystal structure and its non-essential role in the plant’s life cycle, Ni was used as pathfinder element in biogeochemical prospecting of chromite deposits. Quantitative estimation of Mn, Fe, Ca, Mg, K, Na, Cr, Ni and Co in soils and different plant organs of S. orientalis by using Atomic Absorption Spectroscopy (AAS) revealed that the leaf stem is the most reliable organ for ore prospecting in the Forumad area. Determination of bio-concentration factor (BCF) for Cr, Ni and Co in S. orientalis explicitly demonstrated that the flora adopts exclusion and accumulation mechanisms for Cr-Co and Ni, respectively. Current research signifies the excellent correlation between Cr and Ni (0.91) in host soil of the S. orientalis and the tendency of the plant to absorb Ni selectively enhances the chance of sampling the plant’s leaf as a biogeochemical medium for the exploration of new hidden mineral deposits in the Sabzevar ophiolite belt as well as the other similar settings.

Chaotic systems are nonlinear dynamic systems, the main feature of which is high sensitivity to initial conditions. To initiate a design process in fuzzy model, chaotic systems must first be represented by T-S fuzzy models. In this paper, a new fuzzy modeling method based on sector nonlinearity approach has been recommended for chaotic systems relating to initial condition variations using the interval type-2 Takagi–Sugeno (IT2 T-S) fuzzy model. Examining many famous chaotic systems, it can be seen that nonlinear terms in chaotic systems are composed of just one variable or more. In the process of constructing an IT2 T-S fuzzy model which represents the chaotic systems, authors will focus on nonlinear terms of the chaotic systems. The proposed interval type-2 Takagi-Sugeno fuzzy modeling method is employed for two kinds of nonlinear terms; at first, a uni-variable nonlinear term is presented and then a multi-variable one will be introduced. So, it will be shown how many famous chaotic systems are represented by IT2 T-S fuzzy model. Then the proposed approach is applied to Genesio-Tesi and Rossler systems. Numerical simulations are given to demonstrate the efficiency of the proposed method in MATLAB environment.

It is well known that if the coefficient matrix in a linear system is large and sparse or sometimes not readily available, then iterative solvers may become the only choice. The block solvers are an attractive class of iterative solvers for solving linear systems with multiple right-hand sides. In general, the block solvers are more suitable for dense systems with preconditioner. In this paper, we present a novel block LSMR (least squares minimal residual) algorithm for solving non-symmetric linear systems with multiple right-hand sides. This algorithm is based on the block bidiagonalization and LSMR algorithm and derived by minimizing the 2-norm of each column of normal equation. Then, we give some properties of the new algorithm. In addition, the convergence of the stated algorithm is studied. In practice, we also observe that the Frobenius norm of residual matrix decreases monotonically. Finally, some numerical examples are presented to show the efficiency of the new method in comparison with the traditional LSMR method.

The main purpose of this research paper is to compare Qiujiahe Formation (Є1q) and Longmaxi Formation (S1ln) in north Sichuan basin where shale gas exploration has not been fully researched, and hence represents the possibility of shale gas concentration under the complex geological conditions. Based on valid laboratorial analysis, there are optimistic prospects for Є1q and S1ln of research area for shale gas exploitation. For shale gas preservation, general geological settings as Paleozoic marine depositions of Є1q and S1ln are relatively favorable. Both formations possess the advantages in shale gas generation and preservation, respectively. However, Qiujiahe Formation (Є1q) can be a more favorable target for shale gas exploration.

Recently, in order to increase the efficiency of least squares method in numerical solution of ill-posed problems, the chain least squares method is presented in a recurrent process by Babolian et al. Despite the fact that the given method has many advantages in terms of accuracy and stability, it does not have any stopping criterion and has high computational cost. In this article, the attempt is to decrease the computational cost of chain least squares method by introducing the modified least squares method based on stopping criterion. Numerical results show that the modified method has high accuracy and stability and because of its low computational cost, it can be considered as an efficient numerical method.

In this paper, we introduce the notion of derivation on Krasner hyperrings as follows: the function d: R  R is a derivation on a Krasner hyperring R if for all x, y Ry x ) () (=) (y d x d y x d   and d (x  y) d (x)  y  x  d (y). Then, we investigate some fundamental properties of derivation on Krasner hyperings and prime Krasner hyperrings. Also, we introduce differential Krasner hyperingsand discuss some related properties.

Many astronomy studies are based on spectral measurements of the stars and heavenly bodies. In this paper, high-resolution spectrograph is designed to be used in the large astronomical telescope. By adding this system, the best use of large astronomical telescope such as national telescope change can be done. Spectrograph slit can be placed in the focal plane of astronomical telescope or the focused beam transferred with an optical system from the focal plane to the slit of spectrograph.