فهرست مطالب مسلم نامجو

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.

A robust numerical analysis was proposed for simulating the rebound velocity pendulum method for melon. For considered varieties (Zard-Eyvanekey and Sousky-Sabz varieties), the change in impact parameters (extracted from excitation by pendulum) was studied for five stages of ripening. With the melon ripeness, the rebound velocity, rebound height, relative rebound height, rebound angle, rebound energy and coefficient of restitution (velocity ratio) increased, while the absorbed energy decreased (from 37.6 to 27.9 MJ for Zard-Eyvanekey and from 38.5 to 27.9 MJ for Sousky-Sabz). The regression analysis showed a highly significant linear relationship (coefficient of determination, R² more than 0.8059) between impact parameters and five stages of ripening. So the results of the analysis are feasible in ripening detection and hence in the classification of the melon maturity.

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.

Cucumis melo includes a wide range of varieties. The acoustic is production, transmission and energy received form medium vibrations. Acoustic or sonic tests applies for grading productions, ripening determination of fruit firmness and sorting of broken eggs and so on in agriculture. Currently these methods are generalized for measuring non-spherical fruits properties. The primary objective of the present research was to investigate the effect of acoustic system variables such as impact places, impactor material type, pendulum angle and sound level meter position on acoustics response of two different melon varieties, including Zard-Eyvanekey and Sousky-Sabz. These results can be useful for designing acoustic implements related to agricultural products.

This research was conducted on 65 samples of Zard-Eyvanekey and Sousky-Sabz varieties (export varieties). A laboratory recording system used to acquire the acoustic impulse information that was comprised a mechanical excitement mechanism (an impactor such as pendulum), sound level meter, a lap-top computer and software to control the experimental setup and to analyze its results (Cool Edit Pro 2.0 Software), and melon-bed. The impactor consists of diameter and long copper rod 3 mm and 256 mm, respectively. The ball mass was 72.13 gram. The acoustic signal was sensed by a sound level meter (SLM) type 2270 B&K company Denmark. The samples locate on soft cushion for keeping because this bed prevents vibration distortion and causes free vibration. We consider three measurements on equator or mid-section of each fruit (approximately 120 degree) for diminishing inherent diversity of sample shapes. The sound level meter was placed at a distance of 2-5 mm from the fruit surface. The effects of sound level meter, impactor ball and pendulum angle on sound signals were investigated. The effects of other parameters were analyzed by factorial test in randomized complete plot by three replications for each sample. The treatments were 36 and 65 melons of each variety were selected.

The average samples peaks were 10576 and 28663 at 90 and 180 degrees respect to impact place, respectively. Other factors such as impactor ball type (steel), impact angle (70 degrees) and variety type (Zard-Eyvanekey) were constant. The resonance frequency was 123.05 Hz for both SLM position. The averages of peak sound pressure level were 55.29 and 52.38 dB at 90 and 180 degrees positions, respectively. It concluded that the change of sound pressure meter (SLM) position of 90 to 180 degree caused to increase sound pressure level but had no effect on reach the time to peak and resonance frequency. The effect of impactor ball material and impact angle of pendulum on recording signals approximately resemble up and did not state here. The factor levels were sound level meter position respect to impact place (two levels), impactor ball material (three levels) and impact angle of pendulum (three levels). We found that effect of sound level meter position; ball material and impact angle variables on sound pressure level values and interaction effect of sound level meter  impact angle on FFT magnitude was significant at 1% level in both varieties. None of the variables and interactions has effect on the resonance frequency in both varieties. It can be concluded from tables that resonance frequency was more suitable than sound pressure level and FFT magnitude in acoustic tests. The increment of angle caused to increase impact velocity because the length and mass of pendulum rod were constant. We can state the above conclusion about impact velocity (excitement velocity) too, e.g. the impact velocity (excitement velocity) had no effect on resonance frequency while it effected on sound pressure level and FFT magnitude. This conclusion coincides to others researchers.

The impactor ball, pendulum angle, sound level meter position and variety type factors did not showve significant effect on resonance frequency but they had significant effect on FFT magnitude and sound pressure meter. Because of the high pressure level and measurement easily, it was recommended the position 90 degrees of microphone respect to impact place for acoustics measurements. The maximum sound pressure levels were 54.43, 54.81 and 55.11dB for glass, steel and plastic, respectively. Other factors such as SLM position (180 degrees respect to impact), impact angle (70 degrees) and variety type (Zard-Eyvanekey) were constant. Because of receiving high pressure level from impact angle of 70 degrees respect to 20 and 45 degrees, it was recommended for acoustics measurements. It can be used the lower angles by considering the low background sound.

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.

Among various dissipating mechanisms, the viscoelastic effect of rubber material on creation of rolling resistance is responsible for 10-33% dissipation of supplied power at the tire/road interaction surface. So, evaluating this kind of loss is very essential in any analysis concerned with improving the fuel consumption of vehicles and resultantly energy savage. Hysteretic loss is a fraction of stored strain energy of tire which is dissipated during the rotational motion. In all related references and published articles, the hysteretic loss per revolution of tire is commonly considered as the rolling resistance. However, a reasonable approximation of stresses and strains time histories is very crucial for evaluating the amount of hysteretic loss. Based on the results of 3D static contact analysis, an efficient in-house program coded in Matlab is used for estimating the time variation of stress-strain cycles at different points of a rolling tire. Half the difference between maximum and minimum principal values of six stress and strain components can be used for evaluating the hysteretic loss during one revolution of a rolling tire. The results closely match the related experimental and numerical investigations.

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.