moslem namjoo

The extensive radiating surface of horn is an imperative part for amplifying the ultrasonic airborne waves generated for drying of foodstuffs. However, the radiation of high-intensity waves may lead to frequency shift, interaction of modes and reduced efficiency of ultrasonic system. Furthermore, the excitations may also be harmful to the transducer, horn and the joints. In this study, a finite element model is developed for the dynamic analysis of a cylindrical horn. In the modal analysis, the natural frequency of horn is found to be 19,498 Hz which is very close to the working frequency of the ultrasonic generator i.e., 20 kHz. At this frequency, the amplitude of non-beneficial longitudinal mode is negligible compared with that in main radial mode shape and there is no risk for interaction of modes. According to the harmonic analysis, the generated von Mises stresses in the horn are much lower than the endurance limit of constructing material and the horn can safely radiates the waves. The experimental data measured by a laser vibrometer are also used for validating the results of numerical simulation.

One of the old methods of butter production, which is still used in parts of Africa and the West of Asia, is the process of churning in the skin of a goat or deer that is half filled with milk or yogurt and air, which is beaten reciprocating. This type of butter production in the current research is mechanized and is called machine-type reciprocating butter churner (MRBC). This device is composed of chassis, churner, churn carrier, connector or crank, rotating wheel, driving system or power transmission and balance weights. In order to evaluate MRBC, the effect of churning amplitude (40, 60 and 80 cm), churning frequency (50, 61 and 72 cpm) and the churner volume (13.5 and 21.3 liters) on the butter yield was investigated. The results showed that the amplitude, frequency and churner volume had a significant effect on the butter yield at the level of 1%. Regardless of the churner volume, the minimum and maximum butter yield was obtained in the lowest and highest amplitude and frequency, respectively. The present study gives a general overview of the butter yield affected by machine mechanical parameters.

Recent research has proven that magnetic field application enhanced the percentage of germinated seed and shortened the period of seed germination. In present research in order to evaluation of the effect of magnetic field on seed germination and seedling growth indices of smooth leaf type parsley seeds and also the stability of magnetic properties on this seed, the quadrupole magnetic field was used. The experiment was conducted as factorial in a completely randomized design with three replications. Factors include; magnetic field intensity (150, 300 and 450 mT), time exposure (30, 60 and 90 min) and culture time (0, 7 and 14 days after the magnetic field application). The results of ANOVA showed the magnetic field had a significant effect on shoot length, fresh root weight and dry shoot weight (p≥0.01) and on fresh shoot weight (p≥0.05). Duration of the field application (time exposure), significantly affected on root length (p≥0.01). Culture time had a significant effect on root length, fresh root weight and dry shoot weight (p≥0.01) and also had a significant effect on other factors (p≥0.05). Culture time without delay after applying magnetic field (0 day) increased the root length and culture time at the 14 days after applying magnetic field increased the shoot length, fresh weight of root, fresh shoot weight, dry root weight and dry root weight. Our results suggest that magnetic field and culture time treatments can be used as a physical technique to improve the most of seedling growth indices of parsley seeds.

Design of new tools for pruning hedges cultivated with a shrub like wild privet can have a great impact on the quality of pruning and their appearance in parks. The movement of wild privet stalk during cutting is considered one of the issues of pruning when using common tools, which usually causes uneven pruning. In order to design a new pruning tool, it is necessary to know the shearing mechanical properties of the stalk, such as shear force, cutting energy and shear strength of the stalk. To determine them, a series of a series of experimental tests were performed. The parameters such as shear force, cutting energy, and shear strength were determined with two quasi-static and impact cutting methods in three cutting positions of the fifth, tenth, and fifteenth internode position. In the quasi-static cutting test, the stem samples were subjected to cutting with four cutting speeds of 5, 10, 15, and 20mm/min, and in the impact cutting test, the samples were subjected to cutting with four speeds of 1, 2, 3, and 4m/s. The average moisture content of the samples at the time of the experiment was measured at 75% on a wet basis. The results of quasi-static stalk cutting showed that cutting speed had a significant effect on the parameters of shear strength (P<0.01), and cutting energy (P<0.05), and the stalk cutting position had a significant effect on shear strength (P<0.05), and cutting energy (P<0.01).

Jiroft and Kahnuj, located south of Kerman province, are major areas of potato production in the Iran. According to the studies, in these areas semi-automatic horizontal rotating potato planter, automatic cup-chain potato planter and automatic cup-belt potato planter are used for mechanized potato cultivation. In this study, in order to evaluate the performance and determine the suitable planter in these areas, a factorial experiment with three types of conventional potato planters including two semi-automatic rows by horizontal rotating metering device, two-row automatic by cup-belt metering device and four-row automatic by cup-chain metering device. Three different values of 4, 5.5 and 7 km/h were considered for working speed. The results showed that the Semi-automatic potato planter and Cup-belt potato planter have the best operating indices such as feed quality and miss-planting index in the mentioned area and increasing the planter speed has harmful effects in feed quality and potato damaging. In most of the indices, the difference between the averages at speeds of 4 and 5.5 km/h was not significant and the speed of 5.5 km / h can be suggested as a suitable planting speed for all three workers in Jiroft and Kahnuj regions.

In low ambient temperatures the engine will have poor output torque and power generation at the first cycles of its performance, long start time and huge noxious emissions because of insufficient temperature and quality of air-fuel mixture and failure of flame to burn the charge. It is noted that any attempt to increase the charge temperature leads to better combustion conditions. By applying thin ceramic coating over the piston top surface and increasing the temperature of engine inner walls, more efficient combustion in shorter time can be provided for the engine. In current research, a transient thermal study is developed for simulating the engine performance under cold starting conditions and predicting the effect of insulating layer thickness on the charge temperature before ignition timing. The results demonstrate that the ceramic coating can provide higher temperature for piston crown and effectively improve the temperature of charge during the first cranking cycles of engine cold start stage.

In modern engines with higher compression ratios, severe pressures and non-uniform heating up is occurred for the engine parts. The piston as the most critical part among all automotive components has been the subject of numerous studies on calculation of temperature distribution, but thermal stress analyses are limited. In this study, the piston of gasoline engine XU7 which is widespread in Iran transport section is considered for thermo-mechanical investigation. A 3D linear static stress analysis is constructed in COSMOS Works to determine the stress distribution during the combustion stroke. The maximum normal stress takes place at the middle surface of the piston crown. The von Mises stress is found to be critical on upper parts of the pin-hole area. Effect of ceramic coating layer on stress distributions are evaluated and compared with results obtained for a traditional uncoated piston. According to the results, the maximum stress can be readily controlled by increasing the thickness of ceramic layer.

Owing to elastic and viscous characteristics embedded rubber compounds, the dissipated energy from periodic deformation is converted into heat generation and consequently, the tire may have different body temperatures for different operating conditions. In most performed investigations, just temperature distribution is considered and the mechanical behaviour of rubber parts which are highly temperature-dependent is ignored. In this study a 3D finite element model is used for evaluating the effects of loading conditions and rubber temperature on mechanical behaviour of tire. Comparing with related published works, the results of presented study have a great accuracy and can provide a comprehensive analysis to avoid the temperature related failure.

Uniform distribution of billets during planting operation by sugarcane billet planters is important from an economical view interms of amount of billets consumed and planting uniformity. Reduction in billets consumed in sugarcane planting results in lower costs of production. In this research a billet planter with capability of overlap planting pattern was desigend, developed, and field evaluated. Factors under consideration were filling percentage of metering device cupboards, under-overlapping, desired overlapping and, over-overlapping planting pattern as affected by planting forward speed (2, 3, and 4 km/h), sugarcane variety (CP69-1062 and CP57-614), and vertical angle of the metering device conveyor chain (25 and 30 degrees). Experiments were performed using a complete randomized design with three replications. Data obtained was analyzed in SPSS sofware to determine suitable chain angle, forward speed, and variety and their effect on planting uniformity. Results showed that planting speed had highest effect on filling percentage of metering device cupboards, under-overlapping, and desired overlapping. As speed increased, filling percentage and desired ovrlapping decreased and under-overlapping increased. Effect of chain angle and sugarcane variety on filling percentage of cupboards was significant. The best performance of the planter designed was obtained at a planting speed of 3 km/h for both varieties with a 25 degree conveyor chain angle.

Compaction under tractors tires is of special concern because the weight of these machines has increased dramatically in the last years. These machines and others associated with crop cultural practices weight enough to significantly compact the soil, especially if the soil is soft with high moisture content during tilling, planting, or harvesting. The stress distribution and the size and form of the tire-soil interface are decisive for the stress propagation in the soil profile. The finite element method is a very useful numerical tool in evaluating different effects of tire on the soil. The goals of this study are to model the response of a soft soil, in relation to tire pressure and axle load. To validate the model by comparison with measured responses in the literature for such a soil and develop the 2D symmetric multi-laminated model of a tractor tire interaction with soft soil and to verify the result with measured field response data reported in the literature. In this study we use a (2D) axisymmetric tire model for the numerical simulation of soil-tire interaction under different load and inflation pressure. The Maximum soil-tire pressure for 70 kpa inflation pressure and 15kN axel load was 83.7 kpa which were approximately 30% less than the stress at the tire contact patch in the field test as cited in the literature. Although in previous investigations with a 3D analysis the difference was 36%. Maximum vertical stress at contact area with 150kPa inflation pressure and 15 kN axel load was 98.6 kPa that was not significantly different than was 101 kPa reported with 3D analysis. In general, more accuracy in 2D compared than whit 3D analysis was obtained due to more accurate meshing in 2D analysis. This investigation shows that maximum stresses in tire occurred at the side wall. Results showed that a simple 2D axisymmetric model can show soil-tire stresses whit good accuracy.