فهرست مطالب majid rajaei

In some friction vibratory separators, the variations in the vertical forces and slip speed affect the damping rate and behavior of microslip and macroslip friction forces, leading to asymmetry in the force-displacement hysteresis loop diagram. High flexibility in modeling hysteresis loops and physical interpreting of its parameters is the advantage of the Iwan model. However, the effects of slip speed and changed vertical forces on the friction surfaces have not been included in the model. The present study aims to develop the generalized Iwan model by including the effects of slip speed and changed vertical forces on the friction surfaces for modeling the vibratory behavior of friction separators with asymmetric hysteresis. In experimental set-up, a friction separator made by passing a compressed polymer rope through spring is subjected to identification tests at different stimulation frequencies and amplitudes. Finally, the generalized Iwan model is updated to match its output with the results from tests using the genetic algorithm by optimizing the parameters

The purpose of this research was to determine the effects of biostimulats application on the yield and yield components of canola (Brassica napus L.) in a semi-arid region based on Amberje classification in Ilam province. The experiment was carried out as split plots arrangement based on randomized complete block design with three replications. The main plots were two irrigation regimes after evaporation of 80 and 140 mm from class-A evaporation pan and soil moisture compensation to the extent of field capacity in silty clay loam soil texture. The sub-plots were as 1- control (application of chemical fertilizers according to soil test), 2- compound 1 and L-amino acid (glycine, betaine and proline) spraying, 3- compound 1 and fertigation of 5 kg per hectare of humic acid in two stages (after the second irrigation and the beginning of shoot elongation) 4-compound 1 and spraying fulvic acid 5-compound 1 and spraying seaweed extract, 6-compound 1 and the co-application of treatments 2, 3 and 5. In all treatments, foliar spraying was done with a concentration of 5 per thousand at the late rosette stage and the beginning of flowering. Quantitative traits measured were seed yield, number of seeds per pod, number of pods per square meter, thousand grain weight and concentration of nutrient elements. Statistical analysis of data was done with SAS software and mean comparison was done with Duncan's test. The results showed that drought stress caused a significant decrease in yield and yield components, but the combined application of growth stimulants caused a significant increase in grain yield compared to the control. The amount of increase of grain yield without drought stress and under drought stress were 16.2% and 21.1%, respectively. These data indicated the greater effect of growth stimulants on increasing grain yield under drought stress than without drought stress. In normal condition, the application of amino acid significantly increased the grain yield by 14.4% compared to the control. In the condition of drought stress, the best results were obtained by combined application of growth stimulants. The application of growth stimulants improved the absorption of nutrient elements under drought stress. So, in the case of potassium, which is an important element in improving plant growth under drought stress, the application of fulvic acid had a significant effect on the increase of potassium concentration compared to the control, and its concentration increased from 2.9% to 3.8%. Also, the combined application of growth stimulants increased potassium concentration up to 3.6%. The results of this research showed the increase of drought tolerance and the improvement of canola growth with the combined application of growth stimulants.

Under salinity stress nitrogen and other plant nutrients uptake is reduced. In order to study the effect of nitrogen on growth and nutrient concentrations of Valencia orange grafted on lemon seedlings, a factorial experiment was carried out. The first factor was irrigation water salinity at four levels (0.86, 2, 4 and 6 dS m-1) and the second factor was nitrogen at five levels (50, 80, 120, 160 and 200 mg N kg-1 soil as ammonium sulfate). Salinity increased sodium and chloride ions concentration in plant leaf and roots to toxic levels and reduced the plant leaf and root dry weight. The highest level of salinity increased the sodium content in leaves and roots and also chlorine in leaves by 9, 5 and 20 times compared to salinity of 0.86, respectively. Although nitrogen had no significant effect on sodium concentration in plant leaves, at salinity levels of 2, 4 and 6 dS m-1, increasing the application of nitrogen from 50 to 200 mg kg-1 soil reduced 19, 16 and 18% of leaf chlorine and increased the corresponding dry weight of leaves by 117, 39 and 42%, respectively. Salinity decreased nitrogen, phosphorus, potassium, and micro nutrients concentration in plant leaf and in some cases reached them to sub optimal levels. In contrast, nitrogen alleviated this adverse effect by increasing the concentration of these elements in plant tissues. Based on the results, by taking into account of environmental considerations, nitrogen levels above the optimum limits can be used to reduce the adverse effects of salinity in saline conditions.

CMT process is a new developed gas metal arc welding (GMAW) process which has low dilution and heat input. This method is useful for expensive electrodes which are used in surfacing. In this research 1, 2 and 3 layer of flux cored Stellite 6 is deposited on A516-Grade 70. Same type of this steel with hard faced Stellite 6 is widely used in oil, gas and petrochemical industries especially where there is a need for wear and oxidation resistance at high temperatures. Chemical composition of layers is explored and the changes in dilution and iron content versus layer number and final thickness of deposited weld are investigated. Similar samples were prepared with conventional GMAW process for comparison. The results showed that heat affected zone (HAZ) in CMT samples are thinner and reduces by 28% which means less heat input in this process. In CMT process Dilution and weld penetration are 39% and 41% respectively less than conventional welding process. By using this method, the desired chemical composition is achievable with less number of thinner layers and leads to reduction of welding electrode consummation

The nonlinear system becomes an area with numerous investigations over the past decades. The conventional modal analysis could not be  applied on nonlinear continuous system which makes it impossible to construct the reduced order models and obtain system response based on limited number of measurement points. Nonlinear normal modes provide a useful tool for extending modal analysis to nonlinear systems but the extraction of nonlinear normal modes is cumbersome. In this research by neglecting the damping effect on response shape, the nonlinear joint in frictional beam is replaced by 3 order nonlinear spring. The equation of motion is solved using the method of multiple scales up to third super harmony which are neglected in most system identification practices. It is shown in an experimental test set-up, the general form of solution can regenerate observed response of any point and more important similar to linear system, the single mode would be sufficient in analysis when excitation frequency is close to resonant frequency.

Viscosity measurement could provide valuable information for melting and solidification base processes. In this paper a falling ball viscometer is used for measuring molten zinc viscosity. The molten metals are not transparent, some changes are done in the structure of conventional method for tracing ball movement. To solve this problem and in order to trace the movement of the ball (as a falling object) in the melt, a thin steel rod was connected to the ball. The displacement of the ball could then be evaluated from the rod end, which is outside the melt.Viscosity changes versus temperature is studied and as expected the viscosity of the liquid tends to decrease by increasing the temperature. In the beginning the rate of viscosity reduction was high (0.004 cP/°C) but then with increasing temperature the rate of viscosity reduction was decreased (0.0001 cP/°C). Molten zinc is a shear thinning fluid which means by increasing shear rate and mean speed of falling ball the viscosity of molten zinc would drop.