مجله پژوهش های مکانیک ماشین های کشاورزی
سال دهم شماره 1 (بهار 1400)

Shear strength is one of the critical properties of soil that affects the interaction of machine and soil. Wetting-drying cycles change the structure the soil (due to frequent surface irrigation) and affects the shear strength parameters of the soil. Therefore, the effect of this process on the shear strength parameters of coarse-textured soil (sandy loam) is studied. In this study, large soil samples were prepared and some of them were subjected to 5 wettingdrying cycle. After that, the large soil samples with/without wetting and drying cycles were compressed under three loads (0, 100 or 200 kPa) at two water contents (0.9 plastic limit; PL and 1.1PL). Then three samples were prepared for direct shear tests. The results showed that the increase in water contents will increase bulk density and cohesion, and reduce the internal friction angle. Compressing the soil after wetting and drying process resulted in an increase in bulk density and cohesion, and reduction in internal friction angle. These changes were due to clay particles mobility and sedimentation among larger particles as well as developing water films among aggregates during wetting.

Using screw presses is a method for extracting oil, from oilseeds, which requires a low initial investment. Since most of the edible oil supplied through importation, it is important to promote the production methods to reduce the rate of imports. In this research, the Kern Kraft-KK20F screw press, made by Kern Kraft Company, with a capacity of 20 kg/hr and 2kW power, was evaluated for extracting oil from sesame seeds. A factorial experiment was carried out in a completely randomized design to evaluate the effect of grain heating, helical rotational speed, and nozzle size on oil extraction efficiency. In this experiment, heating at four levels of 40, 60, 80, and 100 ° C, helical rotational speed at three levels of 30, 40, and 50 rpm, and nozzle diameter size at three levels of 10, 12, and 15 mm were studied. The results of the analysis of variance showed that the effect of all factors on oil extraction efficiency is significant. Comparison of the mean of the main factors by Duncan's new multiple range test at the level of 5% showed that the highest efficiency was obtained at a heating temperature of 100 ° C, the rotational speed of 40 rpm, and nozzle diameter of 10 mm. Finally, a quadratic regression was suggested to predict oil extraction efficiency.

Despite the dangers of agricultural pesticides for human, animals, and the environment, spraying is the main way to control weeds, pests, and plant diseases. The size of particle and uniformity of toxin distribution during spraying time are two of the most influencing factors in the spraying quality. To achieve this, it is necessary to study the effect of various factors on the behavior and movement pattern of toxin particles from the time of spraying until the moment of settling on the plant. Using experimental method, is the most common method for assessing the quality of spraying. In this research, using ANSYS R17.1 software computational fluid dynamics (CFD) method was used to simulate the fluid behavior as an alternative to the experimental method. Therefore, the effect of three types of Tee Jet nozzles of 0-21, 0-110, and 110-04 with various pressure levels of 2, 3, and 4 bar were evaluated. A factorial experiment with 3 replications in a completely randomized design and Duncan's test were applied to compare the means of treatments. The data from simulation and experimental results demonstrated that the best nozzle in terms of uniform volume distribution of particles was sprayer nozzle 110/03 which has the best spraying uniformity in the three pressure levels studied compared to other nozzles. Comparing the spray angle results revealed that the maximum difference between the experimental method and the simulation was only 8%. Finally, it was concluded that computational fluid dynamics modeling is an appropriate method for predicting the behavior of toxin particles during the spray from the nozzle.

Controlling the humidity and temperature inside the greenhouse is an effective way of plant growth that could be done in different ways. The humidity and temperature of the greenhouse environment could be controlled by the fogging system. A uniform humidity in the greenhouse could be achieved by investigating the effect of various factors on the fluid flow behavior when leaves the spray nozzle. In this study, the effect of three types of BD power fuel injector nozzles (made in Taiwan) in various numbers of 0.03, 0.04, and 0.05 in three pressure levels of 20, 40, and 60 bar on the pattern of fog spray in the environment, spray angle, and spray uniformity was examined. Both methods of experimental and computational fluid dynamics modeling used in this study. For experimental examinations, the greenhouse of Yasuj Airport was used. For evaluation of experimental examinations, a factorial experiment in randomized complete block design with 3 replications was used and to compare the means of treatments Duncan's test was used. To solve the governing equations of flow such as continuity and momentum in the modeling method, FLUENT software is used. The results from experimental study showed that there is a significant association between pressure and nozzle type on the spray angle (P<0.01). The highest fluid spraying was observed in the outlet center of the nozzle, and by moving away from the center of the nozzle the amount of fluid settling was reduced. In this type of sprayer, the best spraying quality was obtained at a pressure of 40 bar. The results from simulation of particle velocity showed that at the pressure of 20 bar, the trend of velocity changes is V-shaped. In the center of the nozzles the velocity of the particles was maximum and then decreased as the particles move towards the sides. Any increments in pressure led to spraying non-uniformity and phenomenon of elongation. However, both simulation and experimental results were matched appropriately.

The drying process is one of the most important and effective steps in the post-harvest processing of paddy, which is effective in improving the quality of its conversion to white rice and decrement the percentage of cracks created in the grain. In the present study, aimed to reduce energy consumption in the process of paddy drying and also to eliminate the adverse effects of fixed bed dryers in rice mills, a solar rotary dryer was designed and built. The main rotating tank of the device was made of a mesh plate and covered by a fixed cylinder made of galvanized sheets. The mesh plate distributes and passes air evenly in different directions and reduces the moisture content of the paddy. An electric motor of 0.75 hp was used to ensure the rotational motion of the main tank of the device. In this regard, the effect of a rotary solar dryer on reducing moisture content and the number of cracks created in paddy of Hashemi cultivar, and also the effect of airspeed on reducing its humidity were investigated. The paddies were dried at a temperature range of 43 to 46 ° C with a rotary dryer. The crack development response in the product was investigated with initial humidity of 11, 14, and 16% water-based. The stress crack index (SCI) was used to quantify the stress cracks created in paddy grains. The results obtained from the number of cracks index in rice grains showed that the solar rotary dryer has acceptable performance and the solar collector can provide the desired temperature conditions for drying rice paddy (43 to 46 degrees Celsius). Studies on the amount of stress crack index of paddy and its comparison with the stress crack index of paddy dried with batch dryer showed that drying paddy by rotary method significantly decreases the crack in brown rice.

Investigating the state of penetration resistance of sugarcane fields and identifying the affecting factors is a very critical issue. In this regard, a broad range of methods can be applied. In this study, effective models and algorithms were explored using two decision tree algorithms (CART and CHAID). After introducing the variables of soil depth, the number of traffics, soil moisture, soil texture, forward speed, and age of the plant as predictor variables of the decision tree as well as soil cone index as a dependent variable, the two algorithms were entered. The algorithms were evaluated using two statistical indicators of coefficient of determination (R2) and absolute mean error (MAE). Based on the two statistical indices, the CART tree model with R2= 0.952 and MAE= 0.504 had better performance in predicting penetration resistance of soil in sugarcane fields which presented as a proposed algorithm to Amir Kabir agro-Industry. The results of the model showed that the tree decision-making method can predict the penetration resistance of soil with high precision using effective variables. Moreover, given the simple interpretation of the decision tree and the comprehensibility of the rules for extracting it for agricultural and agro-industrial experts, it can be used at various levels.

Wheat is the most important crop and nutrient in the human consumption pattern. So that more than 50% of the required nutritional energy in Iran is provided by bread wheat. Harvesting is one of the most important stages of crop production. During 2017-2018 crop year, the present research was carried out to determine the cost and income of combine owners and to evaluate the profitability of using combine harvesters in line with profitability indices. In this regard, 49 combine harvesters including conventional combine JD 955, JD 1055, CLASS S 68 and NEW Holland TC 5080 combine were investigated in agricultural farms in 5 city of Ardabil provinces, Iran. To find out if the assumption is proved, we used partial budgeting technique including net present value, economic and non-economic test for substitution of harvesters under minimum, mean and maximum harvesting condition and marginal rate of return (MRR). The highest effective field and capacity was for NEW Holland TC 5080 which were 1.16 ha hr-1 and 5.14 ton hr-1 respectively. Economic analysis revealed that JD-955 combine, compared to the other combines, had the lowest cost and highest profits. MRR for replacement of JD 955 combine, instead of other combines was estimated more than 60.63%. In highest harvesting capacity, New-Holland (TC 5080) combine was more profitable. MRR for replacement of New-Holland (TC 5080) combine was at the high rate of 64.70%. Finally, it was revealed that in an average sustainable yield John-Deer (JD 955) combine and in maximum sustainable yield New-Holland (TC-5080) combine recommended for Ardebil province farmer.

In this study, the ability of the near infrared interactance (NIR) spectrometry for nondestructive assessment and prediction of the sugar content of the roots of sugar beet were studied. Additionally, the effect of spectral pre-processing methods on the accuracy of multivariate predictor models was assessed. In this regard, the spectrometry of sugar beet samples was performed in the interactance measurement mode within the spectral range of 350-2500 nm using a contact probe. For this purpose, at first skin spectroscopy was performed in 3 desired areas and then the samples were cut vertically and finally spectroscopy was performed in these three areas. The results show that spectroscopy could be used to measure the amount of sugar in beets. Regions of the main absorbance peaks on NIR spectra of the intact and peeled sugar beets were the same. Therefore, the effect of chemical compounds of sugar beet skin can be ignored to identify internal compounds with nondestructive NIR spectroscopy. Additionally, sugar content of the product can be measured without the need to cut it. Prediction of the sugar content of intact samples with the PLS model based on SG + D2, is the the most accurate prediction method. Thus, SG+D2 preprocessing (rc =0.87, RMSEC = 0.90, rp = 0.95, RMSEP = 0.55) is suitable for predicting the amount of SC with the highes accuracy rate (SDR= 3.20). Finally, a system was designed based on the developed model with the ability to measure the grade of the product in a nondestructive way. This system can be used to process the facilities of sugar beet as well as research on breeding of sugar beet in breeding Institutes.