مجله پژوهش های مکانیک ماشین های کشاورزی
سال یازدهم شماره 2 (تابستان 1401)

Among agricultural activities, working and driving with farm tractors in open weather is very hard and lead to fatigue and especial burnout. The objective of this study was to evaluate the job satisfaction and mental health of farm tractor drivers besides their hope in different weather conditions of Fars province. From tractor drivers in the central region of Fars, 115tractor drivers were selected as the statistical sample. The required information was gathered via different questionnaires related to job satisfaction, mental health, and hope. To analyze the data, we used SPSS/18 and Mann-Whitney U test (α= 0.05). The results showed that the indicators of hope, mental health and job satisfaction of medium age people were higher than those of in young and older people. One of the reasons for this result is that medium age people had a higher range of income. The regression analysis showed a positive and significant relationship between income and job satisfaction for young people. There were significant differences in the hope and job satisfaction between different ages and working experiences (P<0.05), but there was no difference in the mental health of a different group of drivers (P>0.05). Considering the drivers' suitable level of hope and mental health, their job satisfaction should be improved by increasing income levels.

The porous materials in hot water dryers are used in industry because they increase heat transfer. In these cases, the thermal performance of the heat channels is greatly influenced by the arrangement of the porous material inside the duct. Therefore, the aim of this study, which was performed by simulation method by Ansys Fluent 16 software, is to improve heat transfer in hot water dryers using new geometries of porous materials. For this purpose, the effect of 5 different types of geometry for porous material (with equal volumes) at 5 different dimensional heights of metal foam (1, 0.8, 0.6, 0.4, and 0.2) and the effect of two different pore diameters (0.1 and 0.05 cm) were evaluated on the  hydrodynamic and heat transfer indices including average Nu number and performance evaluation criteria (PEC). The porous material was considered aluminum alloy with a thermal conductivity of 40 W / m2K and a porosity of 0.95 throws a thermal sink. The results showed that using porous materials in the heat channel increased the Nu number and heat transfer. Also, increasing the pore diameter in porous materials increased the Nu number. The highest PEC number was related to the case where the pore diameter and the height of the porous material are equal to 0.1 and 0.2 cm, respectively.

This study aims to analyze the efficiency and technological gap ratio of rice fields in Rasht. Data from 531 farmers were used for the research. This information was obtained in 2018 using the cluster sampling method proportional to the size of the population. The sample farms were divided into small, medium, and large groups using cluster analysis to avoid the bias caused by differences in farmers' characteristics and decision-making behaviors. In this study, the data envelopment analysis (DEA) model was used to estimate the technical efficiency relative to the group boundary, and the metafrontier method was used for estimating the technological gap ratio (TGR). The results showed that the average group technical efficiency for small, medium, and large farms was 85.2%, 88.3%, and 89.1%, respectively. In other words, using a certain amount of production inputs, these units produce, on average, about 85%, 88%, and 89% of the amount of products that could be produced using the current amount of input and the available technology level. In addition, estimating the technical efficiency based on the metafrontier function showed that the technical gap between the best farmer and other farmers was minimum in the large farm group and was maximum in the small farm group. The technological gap ratio for the above three groups is 0.80, 0.82, and 0.90, respectively. Therefore, large farms have better technical performance and a higher technological gap ratio than small and medium farms.

Renewable energies have become a popular alternative to fossil fuels as they can avoid environmental pollution such as air pollution. One of the renewable energies that can be harnessed to meet our energy needs is solar energy. Salinity gradient solar ponds are an effective way to collect and store solar radiation, making them an attractive alternative to photovoltaic systems for applications requiring low-grade heat. The pond is filled with salt and water to form three zones: upper, non-convective, and lower convective zones. An experimental unit is constructed to observe the behavior of a salinity gradient solar pond. The parameters, such as temperature and salinity value of water in the solar pond, are examined as part of the maintenance and stability of the pond. Results showed the existence of the three zones in the pond fruitfully. The highest temperature of the solar pond to be built in Shahr-e-kord was 31.4°C.

Greenhouse culture is one of the agriculture sector's production methods that is highly dependent on energy. Therefore, if the efficiency of greenhouse heating systems is improved, it will have sound effects on the energy consumption of the greenhouse sector in the country. In this study, to determine the efficiency of fuel consumption of conventional heating systems in greenhouses, data were taken in 6 greenhouses in Alborz province. For this purpose, the thermal requirements of greenhouses were calculated. Then climate suitability graphs were drawn. For determining fuel efficiency, in addition to recording thermal images in the greenhouse, the status of exhaust gases such as CO, CO2, HC, O2, and NOx was recorded in the greenhouse. The results showed that the greenhouses in Alborz province need to heat for 6 months. The average efficiencies of the burners used in the greenhouses were 85%. The pollution of heating systems in these areas also showed that the percentage of CO and CO2 gases were 0.06 and 3.085 in greenhouses, respectively. HC and NOx pollutants were 9.1 and 13.36 ppm, respectively. Factors such as using non-standard heating systems and improper installation of heating systems were the most important factors in creating these pollutants.

Ethylene, with the chemical formula C2H4, is called the aging hormone; in addition to being able to ripen the fruit, it sometimes leads to a decline in the quality of many fruits, including apples. This study examines the effect of four types of ethylene adsorbents prepared in paper sheets with zeolite, biochar, nano clay, and LDH (bilayer hydroxides) coatings on the shelf life and quality characteristics of ―Red delicious‖ apples were investigated. BET and SEM tests were performed to evaluate the porosity of the absorbent paper cavities. The results of these tests showed that all four papers have porous particles and are capable of absorbing gas. Also, to evaluate the durability and quality characteristics, three apples and three grams of each adsorbent were placed in polyvinyl packages along with the control treatment, sealed with a vacuum device, and stored in the refrigerator. Qualitative characteristics of these apples, including weight loss percentage, soluble solids content (TSS), titratable acidity (TA), fruit firmness, and pH were measured every 7 days until the end of 35 days of storage. A completely randomized statistical design based on the factorial test in three replications and SPSS statistical software were used to analyze the data. A comparison of means shows that after 35 days of storage, zeolite adsorbent has the best results in maintaining quality characteristics and increasing shelf life. Minimum weight loss (0.74%), highest fruit firmness (2.1 N / m2 ), lowest TSS (14.2%), lowest TA (0.17), and pH (4.53) were obtained for zeolite treatment. Therefore, using paper adsorbents to absorb ethylene from the environment around the apple and thus increase its shelf life is effective, but the zeolite treatment and then LDH treatment were the most effective.

Sedimentation chambers can be used in harvesters equipped with a suction and pneumatic conveying system, such as a chickpea harvester. Innovation in the traditional structure of conventional single-suction chambers and optimal design of these chambers can enhance the product sedimentation efficiency and decrease the energy consumption of these chambers. In this study, the effect of side fans on the sedimentation efficiency and airflow required by comparing a conventional single-suction chamber and an innovative design including a conventional single-suction chamber equipped with two lateral fans was evaluated. Also, the air velocity distributions, pressure inside the chamber, and the pods movement path were investigated for a comprehensive understanding of the variations. A hot wire anemometer and differential pressure gauge were used to measure the velocity and pressure of airflow in different parts of the chamber. The chamber was made of Plexiglas, and a fast imaging method was used to navigate the pea pods. The results showed that using auxiliary fans enhanced the sedimentation efficiency by 14.7% and reached 94.7 %. Moreover, the required chamber airflow was decreased by 35.7%. The internal pressure drop of the chamber was reduced.

Adopting new technologies has been one of the most important concerns of experts in variousfields from the past until now. Although the rapid advancement of technology is effective inincreasing productivity, the challenges of accepting new technology by the target communitymust also be considered. Electronic technologies are one of the most important things that cansignificantly impact the agricultural industry. Despite many types of research for confirmingtheir effectiveness, the level of acceptance has not been acceptable. This study aims toidentify and rank the factors affecting the adoption of technology in agriculture, and thestatistical population includes 50 active experts in agricultural companies. This studyidentified and ranked the effective factors in accepting new technologies by presenting amodel. Also, software Smart PLS has been used for factor analysis, and method FANP hasbeen used for ranking the indicators. Based on the results, the factors of acceptance culture,economic factors, education and promotion, efficiency, and individual characteristics wereranked first to fifth, respectively. Therefore, using the social power of the government,providing government facilities, and investing in educational and extension issues are themost important factors that can provide the basis for turning traditional agriculture intoindustry.

To study six types of planters for chickpea cultivation, an experiment was performed using strip plots in the form of a design with completely randomized blocks with four replications in the 2021-2022 crop year in the research farm of Bu-Ali-Sina University in Hamadan. In this plan, the parameters of fracture percentage, planting depth, uniformity of distribution, seed fall, seed germination percentage, and effective field capacity were measured. The planting machine was examined in a working width of 1.5 meters with two factors progress speed and type of planter. The forward speed was tested at two levels of 4, and 6 km/h, and the type of planter were tested at six levels: V-shaped, U-shaped, inverted T, V-shaped, two-plate, crossshaped, and tulip-shaped. The overall purpose of this study was to introduce the best planter for growing chickpeas for direct sowing machines in Iran, to develop technical knowledge of the application of some planting methods, to introduce new distributions that reduce failure rates, and to eliminate traditional methods of the past. The results showed that the crusader has a significant advantage at the level of %5 in the four parameters studied. Compared to the other five types of planters, cross-planting increased the uniformity of planting depth by %7, uniformity of seed length distances by %23, and germination percentage by %2.3 compared to other planters. Also, increasing the growth rate did not significantly affect the parameters of fracture percentage, uniformity of planting depth, and uniformity of seed longitudinal distances but caused a significant decrease in seed germination percentage and a significant increase in field capacity.

Greenhouse dryers absorb sunlight directly through the transparent coating on the roof of the greenhouse structure. Absorption of pleasant radiation in these dryers is done only from the side where there is sunlight, and it is not possible to absorb pleasant radiation from the opposite side. The purpose of this study is to use a solar parabolic collector to reflect pleasant light on the other side of the dryer to increase the dryer efficiency. For this purpose, the effect of using linear parabolic and point parabolic pleasant collectors and the effect of solar radiation intensity, representing different hours of the day and month in Isfahan, on the speed and temperature of the air inside the chamber of four types of  common greenhouse dryers were evaluated by computational fluid dynamics method. The behavior of hot air flow insidethe dryer was simulated using ANSYS fluent 18 commercial software. The results showed that using solar collectors in greenhouse dryers increased the speed and temperature of the air inside the dryer. Although the point parabolic collector created more localized hot spots in the dryer than the linear parabolic collector, the linear parabolic collector produced a more uniform speed and temperature than the point parabolic collector. Overall, the fourth type ofdryer with a linear parabolic collector had the best performance among the simulated dryers.