Showing papers by "Bu-Ali Sina University published in 2010"

Comparative analysis of energy absorption and deformations of thin walled tubes with various section geometries

Abstract: In this paper, deformations and energy absorption capacity of thin walled tubes with various section shapes (circular, square, rectangular, hexagonal, triangular, pyramidal and conical) are investigated both experimentally and numerically. The tubes have the same volume, height, average section area, thickness and material and are subjected under axial quasi static loading. The results of simulations are in good agreement with the experimental data and show that the section geometry has considerable effect on the energy absorption. The circular tube has the most energy absorption capacity and the most average force among all investigated sections. Since the maximum force is concerned in impact events, pyramidal and conical tubes are recommended, due to their uniform load–displacement curves and therefore, less difference between the maximum and the average forces.

Evaluation of Reference Crop Evapotranspiration Equations in Various Climates

Abstract: Evapotranspiration is one of the most important elements for quantifying available water since it generally constitutes the largest component of the terrestrial water cycle. This study evaluated four models (Makkink, Turc, Priestley–Taylor and Hargreaves) commonly used to estimate monthly reference crop evapotranspiration (ETo) values. The main aim of this study was to determine the model used to estimate ETo with small data requirements and high accuracy for twelve synoptic stations in four climates of Iran. The results showed that the Turc model was the best suited model in estimating ETo for cold humid and arid climates. The Hargreaves model turned out to be the most precise model under warm humid and semi-arid climatic conditions. In contrast, the Makkink model presented the poorest estimates in all of the climates exception for cold humid environment. In cold humid climate, the Hargreaves model was the least accurate model in estimating ETo. In general, the results obtained from this study revealed very clearly that the Makkink and Priestley–Taylor models estimated ETo values less accurately than Turc and Hargreaves models for the all climates.

The molecular basis for stress-induced acquisition of somatic embryogenesis.

Abstract: Somatic embryogenesis (SE) has been studied as a model system for understanding of molecular events in the physiology, biochemistry, and biology areas occurring during plant embryo development. Stresses are also the factors that have been increasingly recognized as having important role in the induction of SE. Plant growth regulators such as 2,4-dichlorophenoxyacetic acid (2,4-D), ABA, ethylene, and high concentrations of 2,4-D are known as stress-related substances for acquisition of embryogenic competence by plant cells. Gene expression analysis in both the proteome and transcriptome levels have led to the identification and characterization of some stress-related genes and proteins associated with SE. This review focuses on the molecular basis for stress-induced acquisition of SE.

Estimation of daily pan evaporation using artificial neural network and multivariate non-linear regression.

Abstract: Measurement of evaporation (E) rate from various natural surfaces is known as the key element in any hydrological cycle and hydrometeorological studies. Due to the shortage of pan evaporation (EP) data, the estimation of EP for such studies seems necessary. The main aim of this paper was to estimate daily EP using artificial neural network (ANN) and multivariate non-linear regression (MNLR) methods in semi-arid region of Iran. Five different ANN and MNLR models comprising various combinations of daily meteorological variables, that is, relative humidity (RH), air temperature (T), solar radiation (SR), wind speed (U) and precipitation (P) were developed to evaluate degree of effect of each of these variables on EP. The comparison of models estimates showed that the ANN 5 model characterized by Delta-Bar-Delta learning algorithm and Sigmoid activation function which uses all input parameters (T, U, SR, RH, P) performed best in prediction of daily EP. The sensitivity analysis revealed that the estimated EP data are more sensitive to T and U, respectively. A comparison of the model performance between ANN and MNLR models indicated that ANN method presents the best estimates of daily EP.

Dynamic scheduling in flexible job shop systems by considering simultaneously efficiency and stability

Abstract: Scheduling for the flexible job shop is very important in the fields of production management and combinatorial optimization. However, it is quite difficult to achieve an optimal solution to this problem in medium and actual size problems with traditional optimization approaches owing to the high computational complexity. In this paper, dynamic scheduling in flexible job shop is considered. The dynamic status intensifies the complexity of this problem. Nevertheless, there are many industries which have a dynamic status. Two objectives are considered to make a balance between efficiency and stability of the schedules. A multi-objective mathematical model for the considered problem is developed. Since the problem is well known as NP-hard, a meta-heuristic algorithm based on the genetic algorithm is developed. Numerical experiments are used to evaluate the performance and efficiency of the proposed algorithm. The experimental results show that the proposed algorithm is capable to achieve the optimal solutions for the small size problems and near optimal solutions for the medium size problems.

Analytic approximate solutions for unsteady boundary-layer flow and heat transfer due to a stretching sheet by homotopy analysis method

Abstract: In this work, the homotopy analysis method is applied to study the unsteady boundary-layer flow and heat transfer due to a stretching sheet. The analytic solutions of the system of nonlinear ordinary differential equations are constructed in the series form. The convergence of the obtained series solutions is carefully analyzed. The velocity and temperature profiles are shown and the influence of non-dimensional parameter on the heat transfer is discussed in detail. The validity of our solutions is verified by the numerical results.

Evaluation of Class A Pan Coefficient Models for Estimation of Reference Crop Evapotranspiration in Cold Semi-Arid and Warm Arid Climates

Abstract: Evapotranspiration and evaporation measurements are important parameters for many agricultural activities such as water resource management and environmental studies. There are several models which can determine pan coefficient (KPan), using wind speed, relative humidity and fetch length conditions. This paper analyses seven exiting pan models to estimate KPan values for two different climates of Iran. Monthly mean reference crop evapotranspiration (ET0) was calculated according to the pan-ET0 model. The results showed that estimated pan coefficients by majority of the suggested models were not statistically accurate to be used in the pan-ET0 conversion method. However, for the cold semi-arid climate condition, the best KPan models for estimation of ET0 were Orang and Raghuwanshi–Wallender, respectively. Also, the Snyder and Orang models were best fitted models for warm arid climate, respectively. The mean annual value of KPan, determined by Penman–Monteith FAO 56 (PMF-56) standard model for warm arid sites, was approximately 32% higher than the corresponding value in the cold semi-arid climate. Similarly, the mean annual ET0 in the warm arid sites was 66% higher, compared to the ET0 of the cold semi-arid sites. These types of warm arid and semi-arid climates are found widely throughout the world.

3-Methyl-1-Sulfonic acid imidazolium chloride as a new, efficient and recyclable catalyst and solvent for the preparation of N-sulfonyl imines at room temperature

Abstract: New Bronsted acidic ionic liquid, 3-methyl-1-sulfonic acid imidazolium chloride {[Msim]Cl} was used as an efficient, green and reusable catalyst and solvent for the synthesis of N-sulfonyl imines via the condensation of sulfonamides with aldehydes as well as isatin. The reactions proceeded at room temperature and the title compounds were obtained in high to excellent yields and in relatively short reaction times.

A Compromise Programming Model to Integrated Urban Water Management

Abstract: Integrated urban water management is an important and critical matter in every city and country. Many objectives and criteria such as satisfaction of the urban water consumers, the national benefits and social hazards must be considered in the integrated urban water management. So the integrated urban water management can be considered as a multi-objective problem. In this paper, a mathematical model which uses the compromise programming model is presented to optimize this multi-objective problem. Three famous objectives involving water distribution cost, leakage water and social satisfaction level are considered. To evaluate the performance and efficiency of the proposed model, Hamedan potable water network is chosen as a case study. Results show that the proposed model is capable to present effective solutions for the considered problem. So the proposed mathematical model can be used as an efficient tool for the integrated urban water management in every urban area.

Trityl chloride as an efficient organic catalyst for the synthesis of 1-amidoalkyl-2-naphtols in neutral media at room temperature

Abstract: A highly efficient and simple procedure for the preparation of 1-amidoalkyl-2-naphthols via one-pot three-component condensation reaction of 2-naphthol, arylaldehydes and acetonitrile (Ritter type reaction) in the presence of catalytic amount of trityl chloride at room temperature is described The reactions proceed in high yields and in relatively short reaction times

A reliable treatment of a homotopy analysis method for two-dimensional viscous flow in a rectangular domain bounded by two moving porous walls

Abstract: This study investigates the problem of laminar, isothermal, incompressible and viscous flow in a rectangular domain bounded by two moving porous walls, which enable the fluid to enter or exit during successive expansions or contractions. The basic equations governing the flow are reduced to a highly nonlinear ordinary differential equation. This equation is solved analytically by using the homotopy analysis method (HAM). The analytic solutions of non-linear differential equation are constructed in the series form. The convergence of the obtained series solutions is carefully analyzed. The convergence analysis elucidates that the homotopy perturbation method (HPM) does not give the accurate results for the large values of the permeation Reynolds number Re. Graphical results are presented to investigate the influence of the nondimensional wall dilation rate α and permeation Reynolds number on the velocity, normal pressure distribution and wall shear stress. It is noted that the behavior of the HAM solution for the velocity, normal pressure distribution and wall shear stress is in good agreement with the numerical solution.

Using Differential Transform Method and Padé Approximant for Solving MHD Flow in a Laminar Liquid Film from a Horizontal Stretching Surface

Abstract: The purpose of this study is to approximate the stream function and temperature distribution of the MHD flow in a laminar liquid film from a horizontal stretching surface. In this paper DTM-Pade method was used which is a combination of differential transform method (DTM) and Pade approximant. The DTM solutions are only valid for small values of independent variables. Comparison between the solutions obtained by the DTM and the DTM-Pade with numerical solution (fourth-order Runge–Kutta) revealed that the DTM-Pade method is an excellent method for solving MHD boundary-layer equations.

Soil water availability for plants as quantified by conventional available water, least limiting water range and integral water capacity.

Abstract: There are different approaches to define the soil available water (SAW) for plants. The objectives of this study are to evaluate the SAW values of 12 arable soils from Hamadan province (western Iran) calculated by plant available water (PAW), least limiting water range (LLWR) and integral water capacity (IWC) approaches and to explore their relations with Dexter’s index of soil physical quality (i.e., S-value). Soil water retention and mechanical resistance were determined on the intact samples which were taken from the 5–10 cm layer. For calculation of LLWR and IWC, the van Genuchten-Mualem model was fitted to the observed soil water retention data. Two matric suctions (h) of 100 and 330 cm were used for the field capacity (FC). There were significant differences (P < 0.01) between the SAW values calculated by PAW100, PAW330, LLWR100, LLWR330 and IWC. The highest (i.e., 0.210 cm3 cm−3) and the lowest (i.e., 0.129 cm3 cm−3) means of SAW were calculated for the IWC and LLWR330, respectively. The upper limit of LLWR330 for all of the soils was h of 330 cm, and that of LLWR100 (except for one soil that was air-filled porosity of 0.1 cm3 cm−3) was h of 100 cm. The lower limit of LLWR330 and LLWR100 for five soils was h of 15,000 cm and for seven soils was mechanical resistance of 2 MPa. The IWC values were smaller than those of LLWR100 for two soils, equal to those of LLWR100 for three soils and greater than those of LLWR100 for the rest. There is, therefore, a tendency to predict more SAW using the IWC approach than with the LLWR approach. This is due to the chosen critical soil limits and gradual changes of soil limitations vs. water content in the IWC calculation procedure. Significant relationships of SAW with bulk density or relative bulk density were found but not with the clay and organic matter contents. Linear relations between IWC and LLWR100 or LLWR330 were found as: IWC = −0.0514 + 1.4438LLWR100, R2 = 0.83; and IWC = −0.0405 + 2.0465LLWR330, R2 = 0.84, respectively (both significant at P < 0.01). Significant relationships were obtained between the SAW values and S indicating the suitability of the index S to explain the availability of soil water for plants even when complicated approaches like IWC are considered. Overall, the results demonstrate the importance of the choice of the approach to be used and its critical limits in the estimation of the soil available water to plants.