مجله پژوهش های مکانیک ماشین های کشاورزی
سال یازدهم شماره 4 (زمستان 1401)

Energy efficiency is in the production of agricultural and horticulture products. Due to the olives' compatibility in terms of resistance to water deficiency, olive cultivation has become popular in some parts of the country, including Ilam province. This study was conducted in 2019 with the aim of Economic Analysis Using the Cub-Douglas function of Production Olive in Ilam city. Information on the number of olive growers and yields was obtained from the Comprehensive Agricultural Data Structuring and Management System. The study included an economic analysis of olive production by analyzing human resources, electricity,  fossil fuels, chemical fertilizers and animal manure, pesticides, and water. The gross value,total production cost, interest-to-cost ratio, net profit (special profit), and gross profit of olive production were 17519366, 3928231, 3.46, 13591135, and 14669100 Tomans, respectively. The tensile strengths of manpower, gasoline, nitrogen fertilizer, livestock manure, water, and electricity were calculated to be 0.058, 0.01, 0.001, 0.038, 1.05, and 0.158, respectively. This study estimated APP and MPP of direct energies as higher than indirect energies. Average product productivity (APP) of renewable and non-renewable energy was obtained with coefficients of 1.046 and 1.252, respectively. Marginal physical product (MPP) of renewable and non-renewable energy was estimated with the coefficients of -0.735 and -0.026, respectively. The highest final product in Model 1 was water input. Direct energies' final productivity and average productivity were higher than indirect ones. Finally, due to the special profit and special profit obtained in this study, the economical production of olives is affordable.

Greenhouse drying is one of the drying methods that can dry large amounts of agricultural products simultaneously. All greenhouse dryer models use solar radiation energy. Greenhouse dryers are very similar in appearance to a greenhouse in that the air inside is  heated by solar radiation, and the desiccants are dried inside. Because a large part of Isfahan province has a dry climate and has 300 sunny days a year, there is a high potential for using this type of dryer. The performance of this dryer depends on the airflow characteristics and the geometry of the dryer chamber. Therefore, this study aims to predict the behavior of airflow inside the chamber of greenhouse dryers using computational fluid dynamics (CFD) for the climate of Isfahan. For this purpose, the effect of sunlight intensity and external geometry of the dryer on the speed, temperature, and air pressure inside the chamber was investigated by Ansys Fluent 18 software. This study evaluated four common types of geometries for greenhouse dryers. These four types of geometry include a greenhouse with a convex roof, a one-sided sloping roof, a double-sided sloping roof, and a greenhouse with a convex roof and vertical walls, respectively. The simulation results were validated by comparison with experimental results obtained from other researchers. The results showed that the greenhouse with a convex roof and vertical walls had the best performance in the uniformity of airflow velocity inside the dryer. Also, the best performance in the uniform air temperature distribution inside the dryer was related to the double-sided sloping roof and the greenhouse with a convex roof and vertical walls. The lowest air pressure inside the dryer chamber was associated with the geometry of the greenhouse with the convex roof.

In this study, an anaerobic digester with pneumatic digester (PMD) was designed to ferment lignocellulosic compounds of wheat and rice straw and was compared with mechanical digester (MD). Ultrasonic pretreatment was performed with time values of 30 min, acid concentration of 1.905 %v/v and bagasse load of 6%. Then acid hydrolysis was performed in 45 min, acid concentration of 2.04 %v/v and temperature of 148.4 °C. Then biomass was poured for fermentation in PMD and MD digesters and the fermentation process took place within 20 days and the sampling sequence was every 5 days. According to the results, the pneumatic digester was able to produce 38.66% more bioethanol than the mechanical digester. H2S, CO and O2 compounds were also measured during fermentation. In the pneumatic digester, the production of H2S and O2 was lower than in the mechanical digester, but the amount of CO production in the pneumatic digester was significantly higher. Also, the amount of produced compounds created 50 fermentation predicted days was examined by the neural network and compared with the actual results. According to the results, it is possible to predict the trend of changes in fermentation compounds by the neural network and make a definite decision to ferment the straw, wheat and rice compounds. Finally, it can be said that with the help of pneumatic digestion system, the amount of harmful compounds produced during the process can be controlled and the amount of bioethanol production can be increased.

Condition monitoring is one of the key elements in preventive maintenance. By using condition monitoring, maintenance can be programmed, or steps can be taken to prevent the side effects of a failure before its occurrence. With this definition, for failure detection, a deviation should occur in the base value of a parameter (such as temperature or vibrational behavior). Using this method is more economical than occurring a failure. By monitoring the condition of the tractor engine, we can take steps to reduce farm costs. In Iran, monitoring the conditions of tractors and their maintenance is underestimated and this is not performed based on the exact hour of operation. In this research, the lack of cleaning and servicing of the air filter (dirty filter) and the lack of appropriate valve clearance adjustment (low or high clearance) as independent variables were investigated on the sound level of the engine at the bottom of the cylinder head and cylinder block and also the engine's performance parameters, including exhaust temperature, fuel consumption, and opacity of exhaust gas. The tests were performed on an ITM285 tractor The results showed that both engine load and engine RPM have significant effects on engine exhaust gas opacity. While all factors have significant effects on fuel consumption. Moreover, the cleanliness of the air filter, the engine torque, and the engine RPM significantly affect the engine temperature. Engine load, engine speed, and valve clearance significantly affect the sound level of the engine cylinder head. Finally, the sound emitted from the engine block is significantly affected by engine speed.

The reason for drying is the long-term storage of food, minimizing the need for storage, packaging and reducing transportation costs. In this research, the aim is to use a combination of solar dryer with heat recovery system (MCHP) which, while storing energy, also makes temperature control possible. In the present study, the MCHP (Micro-scale Simultaneous Power and Heat Generation System) system consists of a single-cylinder diesel engine with a power of 4.5 hp and a maximum engine speed of 2,500 rpm, which runs on biodiesel fuel. The solar dryer also has a flat collector, inside which a heat exchanger is designed and built. A vacuum cleaner was used to direct hot air from the collector to the dryer chamber. The results showed that by increasing the gas valve (25%, 50%, 75% and 100%), the temperature of the exhaust gas before entering the heat exchanger increases. The second converter was designed and built in the collector. Outlet water temperature of the collector converter in different throttle positions (25%, 50%, 75% and 100%) respectively (37.5 ± 2.5, 43.3 ± 2.3, 49 ± 2 and 55 ± 2 ° degrees Celsius) was. Also, the drying time of barberry crop for temperature (70 ° C and a speed of 1.5 m / s) was shorter than the temperature and other velocities in this study.

Site-specific agriculture is a subset of precision agriculture that aims to increase productivity as well as the quantity and quality of crops based on measuring spatial variation, soil and plant characteristics, and consumption of inputs as variables in time and space. The first step to fulfill this goal is to locate the agricultural machine in the relevant place so that the desired operation can be performed accordingly. In the current research, a ground positioning device with sensors for measuring the steering angle and the number of rotations of the moving wheel of the tractor has been developed. The system was field-tested with local positioning without needing external servers, and the data were compared with the output values of a GNSS receiver. The experiments were performed on asphalt, plowed and uncultivated fields as well as in sunny and cloudy conditions. The statistical design was based on randomized completeblocks as a factorial test in 2 × 2 × 3 with four replications. According to the obtained results, the X and Y axes data of the GNSS receiver and self-tracking device showed a significant difference at the 1% and 5% levels, respectively. Changes in environmental factors, including sunny/cloudy and the ground surface conditions on both the X and Y axes, did notsignificantly affect positioning by the GNSS receiver and the self-tracker. The accuracy of the tracker system in the X direction was found to be 25 cm and for the GNSS receiver 250 cm, while in the Y direction, this was 50 cm and 140 cm for the GNSS receiver. As a result, the tracker system was more accurate on both the X and Y axes. In addition, path deviation distances obtained with the GNSS receiver and the self-tracking device were significantly different at the 1% probability level. The accuracy of determining the distance in the selftracking system was 60 cm, while with the GNSS receiver, it was 400 cm. In general, the performance of the self-tracking system in finding the optimal trajectory was more accurate than the conventional GNSS receiver (without DC correction).

Due to the economic value and the high cost of various inputs used to produce agricultural products, measuring their quality characteristics using non-destructive methods, is an important requirement. Among various non-destructive techniques, optical spectroscopy methods are more important because they are rapid and easy to use. In this research, visible/near-infrared (Vis-NIR) (400-900 nm) spectroscopy was used to predict the quality characteristics of Thomson oranges. Some physicochemical properties of oranges including dimensions, weight, volume weight, soluble solids content (SSC), acidity (TA), pH, as well as SSC/TA and BrimA indices were determined. Vis-NIR spectra were pre-processed using different smoothing and normalization methods and their combinations. The results showed that the Vis-NIR spectroscopy with median filter and multiplicative scatter correction (MSC) pre-processing methods can well predict SSC (rp = 0.983) and pH (rp = 0.972) of Thomson oranges. Moreover, this technique combined with median filter and MSC methods could predict TA (rp = 0.771) and BrimA index (rp = 0.865) of Thomson oranges with acceptable results. The SSC/TA index was also predicted with acceptable results using Vis-NIR spectroscopy combined with the median filter and MSC methods (rp = 0.829). Therefore, Vis-NIR spectroscopy as a non-destructive technique can be used for quality evaluation of Thomson oranges.

Rice is one of the most important summer crops that is harvested in recent years by combine harvesters with different mechanisms. In this study, the amount of quantitative and qualitative losses of Champa cultivar in Ramhormoz city was evaluated by different combines. This research was conducted in a randomized complete block design with the method of split plots. The main plots were the crop moisture at harvest time included three levels: 19-21 percent (M1), 21-23 percent (M2) and 23-53 percent (M3) and the secondary plots were the combine types included four levels: cereal combine, with raspbar thresher (C1), cereal combine, with spike type thresher (C2), rice combine, World model, with spike type thresher (C3) and rice combine, Chery model, with spike type thresher (C4).The results showed that quantitative and qualitative losses related to moisture were significant. In terms of moisture the lowest and highest total quantitative losses obtained in M2 with 3.60 percent and in M1 with 3.87 percent, respectively; and the lowest and highest total qualitative losses obtained in M3 with 1.37 percent, and in M1 with 3.01 percent, respectively. Also, all the different components of quantitative losses, except for the head section, as well as the various components of qualitative losses related to the type of combine were significant. In terms of total quantitative losses, the lowest and highest values were belonged to C3 with 2.97 percent and C1 with 4.83 percent, respectively, and in terms of qualitative total losses, the lowest and highest values were belonged to C4 with 1.32 percent and C1 with 3.99 percent, respectively.

An experiment was conducted during 2017-2018 and 2019-2020 (the land was followed between two intervals) as a split-split plot in a randomized complete block design with three replications to investigate the effect of using the no-tillage method in different residues and variable planting depth in rainfed conditions. In this experiment, the main plots were crop residue levels with two levels (1- retaining only standing stubble and 2- retaining all residues), and subplots were opener types (1- Narrow shovel, 2- wide shovel, and 3- disc opener), and sub-sub-plots were planting depths with two levels (4-6 cm and 6-8 cm). This study used common direct drilling employed in the Markazi province for rainfed wheat cultivation (Hamedan Machine Barzegar, Jeiran Sanat Arya, and Taka Companies). Conventional tillage and planting methods (moldboard plow+cultivator+deep seeder) were also considered controls in each subplot. The planting depth uniformity coefficient, horizontal seed distribution uniformity coefficient, field germination percentage, and crop yield were measured in all treatments. The results showed that the effect of opener type and planting depth on the yield was statistically significant (p<0.5). The effect of residue in two years of cultivation on yield and measured traits was  insignificant and confirmed that the effect on yield and measured factors was no different. The direct seeding technique demonstrated a lower yield, while the conventional planting method with a deep seeder using the conventional common opener had the highest yield. The uniformity coefficient of vertical seed distribution is statistically significant (p<0.01), which indicates that the type of furrow opener can be effective in seed depth placement. With increasing planting depth, seed germination percentage and grain yield decreased. The findings also showed that employing the direct drilling method while reducing operation time has saved the amount of fuel consumption by an average of 75% compared to the conventional cultivation methods.

Conservation tillage can be an alternative system to conventional tillage of irrigated wheat crops in Iran due to its potential for protecting soil and water resources and reducing production costs. Many studies in Iran have investigated the effect of different tillage methods on various factors, such as yield, soil physical properties, costs, etc., in irrigated wheat cultivation. All available studies were systematically reviewed to gain a better perspective on the impact of tillage methods on wheat yield in Iran, and their findings were analyzed by meta-analysis. All articles published in Iranian journals, final reports of research projects, and related articles presented at congresses and student dissertations were reviewed using standard keywords Then, the articles and reports published in this field with the criteria for entering the research were entered into the meta-analysis after quality control using a random model. Finally, 40 studies were selected to compare minimum tillage methods with conventional tillage, and 21 were selected to compare no-tillage with conventional tillage. The results showed that the effect size (SMD) in minimum tillage and non-tillage methods were -0.42 and -1.18, respectively, indicating the negative effect of these methods on yield. Reduced tillage methods significantly reduced wheat yield (-2.87%) compared to conventional tillage. Also, no-tillage significantly reduced yield (-8.2%) compared to conventional tillage. Minimum tillage methods did not have much effect on reducing wheat yield. It is suggested that one of the minimum tillage methods, including 1- Chiselpaker, 2- combined tiller (chisel plow equipped with rollers), 3- chisel plow + disc, and 4- disc according to the facilities and access of each area to these tools, replaced conventional tillage (moldboard plow + disc harrow + leveler).