Showing 5 results for Rasoulian
Volume 12, Issue 1 (Number 1 - 2010)
Abstract
The European Corn Borer (ECB) is one of the most important insect pests of corn and some other crops such as rice in Iran. This pest is one of the most important hosts of the entomopathogenic fungus Beauveria bassiana, a well known fungal entomopathogen with high host range and considerable potential in insect pest control. In an isolate selection program of fungal isolates against ECB, ten isolates consisting of eight isolates from Iran and two from other countries were assayed using the dipping method on third instar larvae of ECB. Inoculum concentrations were 104, 105, 106, 107, and 108 conidia ml-1. For each concentration, 30 larvae were dipped into the conidial suspension for 30 secends. Control larvae were treated with distilled water containing 0.03 percent Tween-80 as surfactant. Each experiment was repeated three times. Results showed that BEH isolate which was isolated from the soil of insects living in the field, caused the highest mortality in larvae in comparison with other isolates with a mean of 57.67 percent mortality using 108 conidia ml-1. Other isolates, such as DEBI007 and EVIN I, were scored in the lower position with producing 53.43 and 42.67 percent mortality, respectively. EVIN II, DEBI002, and DEBI008 caused the lowest mortality in assayed larvae. A decrease in larval feeding was detectable a few days before death. Possible causes for the low mortality in isolates are discussed.
Farid Vakil-Tahami, Reza Hassannejad Qadim, Akbar Rasoulian,
Volume 14, Issue 16 (Forth Special Issue 2015)
Abstract
Nowadays, optimization is becoming one of the most important techniques in engineering and industry to provide competing products in design and manufacturing. Therefore, it is a necessity to search for optimum designs with productibility. In aerospace industry reducing weight and improving reliability of the products are major concerns. As regards the gearbox is one of the most important parts in the helicopter propulsion system, these objects should be more considered. However, most of the existing designs consider only one object, hence, it is vital to implement optimization techniques to include different objectives to improve the existing designs and provide optimum products. In this paper, optimum design parameters including module and face width of gears for the main gearbox of Sikorsky ASH-3D helicopter have been determined (modified) using single and multi-objective mixed discrete- continuous optimization method to minimize weight of the gearbox, increase the safety factor and reduce the difference between safety factors of different gears. The results show that the weight of the gears can be reduced by 27.24% comparing with the existing gearbox. The results of the multiobjective optimization have also been presented as Pareto front diagram wich can be used by the manufacturers to satisfy the prefered requiments.
Farid Vakil-Tahami, Akbar Rasoulian, Arash Mohammad Alizadeh Fard,
Volume 15, Issue 9 (11-2015)
Abstract
Creep behavior of butt-welded joints in pressurized steel pipes operating at high temperature is one of the major concerns in industry. The creep behavior of 1.25Cr0.5Mo weldment has been investigated in this paper. Three different layers: Base Metal (BM), Heat Affected Zone (HAZ) and Weld Metal (WM) have been considered and the creep behavior of each layer has been modeled using constitutive equations. Constitutive parameters have been determined using the results of uniaxial constant load creep tests. A numerical approach based on least square method has been used to calculate optimum values of the constitutive parameters. The results have been compared with those provided in the literature for different alloys and good agreement has been observed. Creep tests have been carried out at 30, 35, 40 and 50 MPa and temperature levels of 670, 700, 725, 750 and 800 °C. Specimens have been machined out from Base and Weld Metal. Since machining specimens with appropriate size from HAZ is impossible, a method is proposed to obtain constitutive parameters for this layer. This method is validated by comparing the constitutive parameters which have been calculated for WM with those obtained using creep tests. Micrographical and microhardness tests show that there are significant differences in the microstructure of the layers. Consequently, the creep behavior of layers is different. The results show that steady state creep strain rate for WM is higher than the rates for BM and HAZ; also at low stress levels, creep strain rate of HAZ is larger than BM.
F. Vakili-Tahami , M. Khoshravan , T. H. Smit, A. Rasoulian,
Volume 20, Issue 5 (May 2020)
Abstract
The intervertebral discs are of the most important body tissues that provides the required flexibility for the spine during daily activities. Due to the lamellar structure of the Annulus Fibrosus, that surrounds the central part of Nucleus Pulposus, it may show anisotropic behavior in carrying the applied loads. Therefore, this aspect was investigated using the experimental data that were obtained by confined compression relaxation tests on samples in three different directions: Axial, radial and circumferential. To obtain the experimental values of the permeability and aggregate modulus as material parameters, test data in three directions were fit to the constitutive equations that were based on the biphasic relaxation model. The results for the permeability and aggregate modulus in three directions show that the material parameters are almost independent of direction and therefore, it is concluded that AF can be treated as an isotropic material under the compressive loads.
F. Vakili-Tahami, M.r. Khoshravan, T. H.smit, A. Rasoulian,
Volume 20, Issue 10 (October 2020)
Abstract
One of the most important and active body tissues during daily life is the intervertebral disc that not only sustains the applied loads to the spine but also it provides the required flexibility for doing different activities. This tissue as an important factor to carry applied loads to the body is always subjected to possible damages. Hence, due to the improvements in medical sciences in treatment or replacing these damaged tissues, investigating the mechanical behavior of the intervertebral disc and assessing the damage level is a major concern for the researchers. For this purpose, different tests should be carried out but to simulate the behavior of the disc more accurately, it is necessary to ensure that the test conditions are as close as possible to the real ones in the body. Hence, the aim of this research is to develop a set of creep constitutive equations that are based on the experimental investigation of the effect of temperature on the creep behavior of the intervertebral disc. To do this, compressive creep tests were carried out on the goat intervertebral disc tissue and the permeability and aggregate modulus were obtained based on fitting the biphasic constitutive equations with the experimental data. Statistical analyses of the experimental data reveal the significant effect of the temperature on the values of both material parameters and the creep behavior of the intervertebral disc, so that with increasing temperature permeability increases and aggregate modulus decreases or vice versa.
