مجله پژوهش های مکانیک ماشین های کشاورزی
سال پنجم شماره 2 (پاییز و زمستان 1395)

One of the most important issues in the management of production is how to select the best option for each production activity, so that the time and cost of production are minimized and the quality is simultaneously maximized. Considering a large number of activities and possible options for them, this choice does not have a unique solution and can be used the utility function and assign weights to time, cost and quality in order to select the best answer from those obtained. Since in reality a vast amount of uncertainty can be observed, an effective management necessitates dealing with these uncertainty issues. In this study, a fuzzy math model for a chain of activities is suggested to determine the best practical method employed by the milk production process. In order to achieve this goal, fuzzy alpha cut was employed to manage the risk of these series of activities. Accordingly, Non-dominated Sorting Genetic Algorithm-II (NSGA-II) with fuzzy inputs was used and the best method of implementation for each activity of milk production process from the starting point of cows birth to the ending point of removing these cows from the herd was introduced.

Due to the limitation of water land and energy resources, prepared research aimed at finding the most suitable solar energy absorption system was designed for use in greenhouses so, the greenhouses were built an area 10m2 in Izeh city in Khuzestan province.
Common system of heating greenhouses in addition, four other systems including: solar water heater, water wall, stone bed and phase-change material. Each was implement in a greenhouse and the research was conducted during six months.
Technical factors including functional safety, useful life, reliability, ease of maintenance and repairs beside of economic and environmental factors have been investigated, finally, the method of Analytic Hierarchy process (AHP) was used to introduce the best system.
The result showed that the solar water heater system has had higher cost and energy absorption also lower average time to repair and phase-change material method has had the least failure frequency. The analytic hierarchy determined aquatic wall as the most appropriate system and thence the solar water heater. Although solar water heater consumes less fuel but it has more cost, lower sale services, failure frequency and repeating accident rate more than water wall. This method can be in the first place by reducing cost and improving after – sale services. In last place of the traditional method shows that it was not suitable and it’s use should be revised.

The goal of the present study was to study the effect of mixer speed on biogas compounds produced from semi-industrial biogas plant. The biogas was produced with slurry made by combination of 41% cow manure, 56% municipal waste and 3% kitchen waste with adding 2.38% NaOH and 3.75% H2O2 as the chemical pretreatment. Then, the effect of mixer rotation speed on mixing quality of the slurry was linked to the anaerobic microbial communities and some of physical and chemical parameters of the slurry. The results showed that by increasing the rotation speed from 60rpm to 100rpm, the amounts of CH4 and CO within the biogas compound increased by 6.6% and 71.7%, and the amounts of H2S and O2 decreased by 4% and 5.5%, respectively. This was due to decrease in the chemical oxygen demand (COD) and total volatile solids (TVS) of the slurry by 3.6% and 3.9%, respectively because of an increase in the anaerobic microbial communities by 3.7%. Furthermore, the same trend existed between the CH4 and anaerobic microbial communities of the slurry that was similar to the COD and TVS decreasing trends.

This study was aimed to investigate the effect of the differential lock on the drive wheel slip and fuel consumption rates for the three tractors made in Iran (ITM399 4WD-ITM285 4WD-ITM285 2WD). In this study, the factors were tillage depth at two levels (20 and 30 cm) and differential lock (use and non-use of differential lock). The experiments were carried out in randomized complete blocks with three replications separately for each tractor. The experiments were conducted in the same conditions and at the Shahrekord university field. Analysis of factors effects were obtained by measuring the parameters of drive wheels slip, fuel consumption of the tractor and the time of way. The results showed that using of differential lock during moldboard plow in all tractors caused to reduce of fuel consumption and the time of way. The use of differential lock had significant effect on the driving wheel slip of tractor, so much with using of differential lock the average of rear right wheel slip 15.57 % and the rear left wheel slip 25.64 reduced. Base on the results of this study, with increasing in plowing depth the driving wheels slip, fuel consumption and the time of way for all tractors increased. ITM285 4WD tractor in 4WD condition had the best and in 2WD had the worst performance comparing to other two tractors.

Diseases caused by vibration are considered one of the most important occupational diseases. In order to prevent major problems in terms of occupational health and safety for tractor drivers, identify and limit the amplitude of vibration sources are necessary. In this study, a number of factors affecting the Seat Effective Amplitude Transmissibility (SEAT) of three tractors, Goldoni 341, Massey Ferguson 285 and John Deere 3140, had been evaluated. Research factors were including type of route, gear ratios and engine speed. Accordingly, a factorial experiment based on randomized complete block was designed with three replications. The results of this study showed that the levels of type of route, gear ratio and engine speed for all three tractors have been significant at the 1% level. However, the changes in engine speed related to gear ratio showed a more even trend in SEAT. Tractors showed different behaviors on the types of route, so that the plowed route in Goldoni and John Deere tractors had the highest value of SEAT in comparison with other routes (paved roads and rural roads). However, the opposite trend was observed in Massey Ferguson. The maximum and minimum range of SEAT with 98.2 and 22.6 for Goldoni and John Deere tractors were achieved, respectively.

Qualitative grading and classification of rice are one of the factors affecting the appearance quality and customer satisfaction. The objective of this study was to develop an accurate algorithm for diagnosing three important qualitative indices of rice including percentage of broken grains, percentage of chalky grains and degree of milling. Some rice samples of a variety namely 'AliKazemi' were provided from Rice Research Institute of Iran. After questioning expert persons, three quantitative levels (Low, Medium and High) were defined. Each of the 270 samples of rice grains were photographed under identical conditions. Afterwards, image quality improvement, rice image segmentation and textural, color and size features identification were performed using Matlab Software and image processing methods. In development of fuzzy inference model for the product pricing, the Mamdani inference system was applied and defuzzification process was done using Center of Area defuzzifier. Results indicated that the average accuracy of the image processing algorithm in detecting percentage of broken grains, percentage of chalky grains and degree of milling was respectively equal to 95.2%, 90.74% and 98.99%. The decisions made by the fuzzy model were consistent with the expert’s judgment in 95.2% of the cases. This technic can be good alternative to manually which takes less time and more accurately assess the characteristics of the product key.