مجله پژوهش های مکانیک ماشین های کشاورزی
سال سوم شماره 1 (بهار و تابستان 1393)

Wheat as the most main food for the world and a strategic product has a major role in people's food supply. Average of wheat growing areas in Iran is 6.65 million hectares and more than 374 thousand hectares of wheat annually in Lorestan province is planted. In this study, conventional methods in the measurement of crop losses, John Deere and Behroozi-Lar method as proposed approaches was considered and the real waste of dry land wheat harvest, in 2011 in central part of the Khorramabad Township, in the center of Lorestan province, was measured. Using three Factors-factorial design, in field sampling, pre-harvest losses (normal), cutting platform Losses, unit pounding Losses, the unit separate and distinguishable Losses (end of combine) was measured and total farm losses were also determined. For statistical analysis of data, SPSS software was employed and for comparison of means, Duncan's test was used. The results showed that the average wheat harvest losses in Khorramabad has been 5.21% including 0.65% normal losses and 4./56% losses of combine.

Terminal velocity and drag coefficient are the most important aerodynamic properties of agricultural products like soya in the designing of machines and processing equipment. In this study, these properties were evaluated for three soybean varieties (Sahar, Viliyams and Dpx) and five moisture content levels (4, 8, 12, 16 and 20% d.b.). First, relation of the terminal velocity and the drag coefficient with the moisture content was mathematically formulated, and then, in fluidized bed dryer was practically investigated. The results showed, with the changing of the moisture content of three varieties (Sahar, Viliyams and DPX) from 4% to 20%, the terminal velocity of three varieties increased respectively from 4.42 to 5.1, 5.12 to 5.94 and 4.71 to 5.5 (m/s) while at the same moisture content the drag coefficient decreased from 0.45 to 0.389, 0.53 to 0.452 and 0.512 to 0.444. The diagrams of the terminal velocity and the drag coefficient revealed that the terminal velocity and the drag coefficient values have a linear relationship with the moisture content, but with increasing the moisture content, terminal velocity values increased whilist drag coefficient ones decreased.

Grain drills are the most common planting machines around the world. In this study, the effect of hopper gate opening was evaluated on a grain drill unit attached to a grease belt test stand at five levels and fluted wheel length at two levels on the bandwidth. Lateral, longitudinal and central uniformity parameters of seed distribution at four levels of sowing rates (120, 150, 180 and 210 kg per hectare) were also evaluated. Sowing rates and parameters were conducted separately in completely randomized designs and the data were analyzed based on 5 × 2 factorial treatments. The measurements of seed distribution uniformity were done using image processing technique. The highest coefficient of variation of bandwidth data occurred at 120 and 150 kg per hectare and their values were 42.81%, 33.19%, respectively. Comparison of treatment means showed no significant differences at 1% probability level for the interaction effect of groove length × tank gate opening for this parameter and lateral uniformity parameter in any of the tank gate opening and groove length levels. Comparison of treatment means indicated favorable results for longitudinal uniformity in all sowing rates, except for 120 kg, two levels of groove of seed distributors. Comparison of treatment means of groove length × tank gate opening interaction for central uniformity at 120 and 210 kg per hectare revealed significant differences at 5% probability level.

Use of nanocomposite active films in active packaging of agricultural products is one of the applications of nanotechnology in the agricultural industry to increase their storage time. In the present research, polyethylene-nanocomposite active films, C2T0.5 (2% nano-Clay and 0.5% nano-TiO2) and C4T0.5 (4% nano-Clay and 0.5% nano-TiO2) and also neat polyethylene film (C0T0) with melt mixing method were prepared. Then, in order to investigation of the structure of the produced nanocomposite films, the X-ray diffraction (XRD) test was used. Then, in order to find the effect of produced nanocomposite films over the shelf life of kiwifruit, some physical, mechanical and quality properties of this fruit were measured during storage time. Use of factorial experiment with Completely Randomized design, data was then analyzed. XRD results showed acceptable distribution of nanoparticles within the polymeric matrix of nanocomposite films with intercalated structure. In the study of different properties of kiwifruit, it was observed that samples packaged with active nanocomposite films compared to pure polyethylene films, had the lowest soluble solid content and pH and the highest moisture content and firmness. In the exploration of quality characteristics of kiwifruits, the highest rating in terms of color and appearance shape and total favorability for packaged samples with nanocomposite films were obtained. Thus, according to conditions of this research and results, in order to increase the shelf life of kiwifruit, the C2T0.5 nanocomposite film is recommended.

Wheat is one of the most important food staff in consumption pattern of each country. More than 50% of human energy is provided by bread in the developing countries. The aim of this study was to measure wheat losses during pre-harvest, harvest and post-harvest stages in Chaharmahal and Bakhtiari province of Iran in 2012. Wheat losses at harvest stages were measured for two wheat varieties; Sardari and Omid. Two models of John Deere combine (955 and 1055) were used. Samples of storage losses in home and industrial phases were gathered in 15, 30, 45, 60, 75 and 90 days. The data were analyzed by SAS software. For gathered data, Duncan’s multiple range tests were applied. The results showed that maximum and minimum losses occurred in Omid and Sardari varieties by John Deere 955 and John Deere 1055 combine as 6.08% (311.9 kg ha-1) and 3.46% (179.82kg ha-1), respectively. The maximum losses on post-harvest stage were 7.72% that 5.31% was in winnow stage (included useful losses, grain damage and non-useful) and about 2.41% related to storage losses.

The rapid removal of green skin and drying is an important stage of walnut in post harvesting process. The existence of Tanen in the walnut green skin which brings about fast oxidation, makes it dark and hard for removal. This would cause color change in walnut as well, resulting lower quality. In the present study, the mechanical properties of walnut skin was measured to determine required energy for shearing, crippling and penetrability process for the four most consuming genotypes (called K72، Z67، Pedro، Serr). Preliminary results led to innovation of a mechanism for skin removal and results showed an average of 93 percent success where rotational speed for wire heckle was 368 rpm, the distance of grasp cylinder was 12 mm and removal time was 60 seconds. The optimum reloading time was 15 seconds for 25 to 50 nuts (3-5 kg) and the machine capacity was obtained within 120-240 kg/hr.