مجله پژوهش های مکانیک ماشین های کشاورزی
سال دوم شماره 1 (بهار و تابستان 1392)

Usually soybean is harvested in the cold season with high air relative humidity and possibility of rainfall. In this condition، the moisture content of soybean pod is high، so grain combine harvester can`t thresh and separate the bean from it s pod properly. Since the farmers should harvest and sell soybean on time and also they have to prepare land for the next cultivation، having a pre-threshing dryer unit which can reduce some moisture content of soybean pod in field، for proper working of combine is necessary. This study due to determination of thermal properties of soybean pod were done. The result are useful in fabrication of pre-threshing dryer on combine harvester. The thermal conductivity of soybean pod، was determined by method of conductivity prob. Each test were done in the moisture content rang of 14. 5، 21. 5، 25. 2 and 30. 5% (w. b.)، the temperature rang of 50، 150، 250، and 350 °C. The result of analysis of variance shows that thermal conductivity increased from 0. 038 W/m° C to 0. 338 W/m° C with increasing moisture content and temperature.

Importance of safflower as an oilseed crop, particularly due to fatty acid contents linoleic its world production has been focused. In the present study amount of moisture content in safflower seed at different ambient temperatures of 25, 40 and 60˚C were measured using gravimetric method. In order to run the experiments a controllable environmental chamber was used. The obtained E.M.C experimental values were employed to plot the isotherm curve at different environmental air temperatures. These data were also used to find the best fit E.M.C prediction equation. The data were fed to fourteen popular mathematical models namely: Caurie, Chung–Pfost, GAB, Halsey, Henderson, Kuhn, Modified BET, Modified Chung–Pfost, Modified Halsey, Modified Henderson, Modified Oswin, Modified Smith, Oswin and Peleg. The well known statistical factors such as coefficient of determination (), chi-square (), root of mean square error (RMSE) were calculated to validate the goodness of fit. The peleg model was selected as the best model for predicting the EMC at 25 and 40˚C temperatures level and the Oswin model was selected as the best model for predicting the EMC at 60˚C temperatures level. The results showed that increasing the environment temperature at a constant relative humidity, the equilibrium moisture content showed decreasing trend.

Volume determination of agricultural products is done in many reasons such as survey of quality and grading. In recent year’s use of nondestructive methods and fast machine vision have been discovered expanse and popularity by computer and digital cameras. This study tries for development and evaluation of the new image processing algorithm to error correction of natural perspective of imaging and cutting of similar elements and sum of their volume for volume estimation of product that in present study walnut was used. With this method some prevalent method such as weight of displaced water as reference method, geometric mean diameter and field of view surface to better evaluation of this method. The means of error of the geometric mean diameter, field of view surface and similar element method were 9.6%, 10.2% and 10.7%, respectively. The results showed in machine vision because of natural perspective of imaging, small objects (walnut) than larger ones produce more error for volume measurement.

Equipment and machinery used in Agricultural field produce sounds with wide spectrum. Therefore operators and other workers exposed to these sounds. In this study, effects of some factors on emitted noise of a Honda GXV 160 power lawn mower in three different distances were studied. The experiments were carried out based on a factorial statistical design in the form of randomized complete block design with four replications. Sound level measuring device and their establishment and set up were selected in which according to acquired data, the emitted noise level of power lawn mower could be calculated. The results showed that, there exists a significant relationship at 99% levels of probability between the levels of blade rotational speed and emitted noise. But no significant relationship was observed between the levels of collecting basket, operation type and emitted noise. Also results reveal the great sound level at operator’s ear position in comparison with other positions. According to permitted exposure noise level, the received noise level of operator was hazardous and using of hearing protection devices is mandatory. But the received noise level of other workers in field was not hazardous.

The process of tillagetool wearis the most important factorthat limitingtheuseful lifeand efficiencyof thesetools. This study aimed to investigatethe effects ofdepth and functioning level onchiselplowblade wear andidentify itscritical point. Experiments were conducted inclaysiltsoilsin12hectares. The depth and functional level was tested in 3 and 5 different levels, respectively. The resultsshowed thatdepth and functional level variables andtheir interactionhavea significant effectonthebladeedge andtipwear(P = 0.01). Mean comparisonshowed thatthe most wearrateis related toA1d3 (functioning level =12 hectaresanddepth= 25 cm). The results alsoshowed that thetip of thebladeisworn quicklyonthe firstworking day. The results showed that0.57% weight loss ofthe blade wasinthe first working dayand 0.42 %wears in thetenthhectares. Theresultsshowed that on thefourthday, plowoperationrate was 22 %less thanthe first day, and subsequently, thetractorfuel consumptionwas28%higher thanthe first dayof work.

Crop yield is influenced by seeding quality. In this study, some effective parameters on seeding quality have been surveyed. For this purpose, by use of split-split plot experiment, based on a randomized complete block design with three replications, effect of tillage method, planter type and travel speed on seeding quality indices like skip, single seeding, multiple seeding and seeding precision. Main plots were related to different tillage methods including; 1-mouldboard plow + one pass disk plow (T1), 2-mouldboard plow + two pass disk plow (T2) and 3-mouldboard plow + two pass disk plow + land leveler (T3). Sub plots were related to planter types including; 1- mechanical planter (P1) and 2-pneumatic planter (P2). Sub–sub plots were related planter travel speed including; 1- 4 km/h (S1), 2- 5.5 km/h (S2) and 3- 7 km/h (S3). Variance analysis showed that, tillage method had significant effect on all of the parameters except single seeding index and seeding precision. However, planter type and travel speed have significant effect on none of the parameters. Interaction between tillage method and planter type, have significant effect on all parameters except single seeding. With regard to seeding precision, the best treatment was T1P1 followed by T2P2. Therefore, using T2P1S3 treatment, speed and precision of seeding could be increased.

Determining the consumption patterns and presenting a model for that, apart from finding the amount of inputs and subsequently the energy consumption, provides the grounds for optimizing it, which would be dealt with in this study.The results revealed that total energy input and yield of garlic was 36616.78 MJ ha−1 and 14636.53 kg ha−1, respectively. Different functions between output and input energyies were fitted using regression analysis and curve estimation. Using Cobb-Douglas production function and with consider to statistical significance and expected signs of parameters the relationship between inputs and output energy was detemined. The results of econometric model estimation revealed that the regression coefficients of human labor, farmyard manure and seed energies were all statistically significant at 1% level. Durbin–Watson values were calculated as 2.138 indicating that there is no autocorrelation at the 1% significance level in the estimated model. The R2 value for this model was as 0.99.