Iranian Journal of Biosystems Engineering
Year:2011 | Volume:42 | Issue:1|Papers Count:16

Soil compaction and moisture content are two of the factors that greatly influence variations in crop yield. Capacitance-based sensor is a sensitive device for estimating soil water content. In this method of soil moisture content measurement, soil acts as the dielectric of the capacitor. Throughout this research work, a capacitance-based moisture sensor that can measure the soil moisture content in a continuous manner, was developed and tested. The developed moisture sensor consisted of two parts namely: three electrodes and an electronic circuit. The electrodes are heat treated metallic terminals which with the needed heat treatment have become tough and their surfaces abrasion-resistant. These terminals are embedded in pieces of fiberglass. The excitation voltage of the electronic circuit was 12V with its output response being the frequency factor. The sensor was tested under static laboratory conditions, employing a silt clay loam type soil. The developed sensor was evaluated in filed conditions. An analysis of the results showed that the relationship between the soil water content and the output frequency could be presented through a quadratic. The error of the sensor was estimated as 1.55%. There was a significant correlation (R2=0.70) between the soil water content measured through the sensor, and that estimated through the gravimetric method. The results indicated that, the sensor output data, in addition to being influenced by soil moisture content, they were also affected by soil temperature.

This research presents a guidance-assistance system for agricultural swing machines. The new automatic steering system controls the vehicle based upon the position of the traces of the previous operation carried out on the field. For each image the trace of the tilled soil by seed drill is placed either on the center line, or on either side of the line. For traces coinciding with images' center line no correction would be needed and the guidance-assistant system can continue the command of sowing operation on the new path, otherwise the relative position of the trace is an indication of the need for steering wheel adjustment, as a result of which the tractor is guided either to the right or left so that the implement would be guided to work at the desired row spacing. The new system is a potential replacement for markers installed on the implement toolbar. The proposed system was evaluated at various conditions including different illumination intensities in laboratory, and on the filed. Filed tests were completed with three forward speeds and three steering angles for each output response of the electronic circuit. Distance Error (DE) and Response Time (RT) were found out for each forward speed and steering angle. Results indicated that various illuminations had not distorted the outcome of the proposed algorithm. RT decreased with increase in forward speed and steering angle. Effects of forward speed on DE were significant at 0.01p whereas the effect of steering angle on DE was not found out as non-significant. This suggests that it would be possible to assist the manual guidance of a planting unit carrying tractor through an automatic system equipped with a trace detecting camera.

Grading of agricultural products has always been a subject of research by scientists. One of the criteria to be chosen for grading of fruits is the fruit's level of ripeness. Different methods have been employed to assess the status of fruit ripeness some of which are destructive and others are not so. In this research, a noninvasive capacitive method was used to estimate the ripeness level in banana fruit. The relationship between levels of ripeness and dielectric constant were studied over the frequency range of 1 kHz to 10 MHz. Results revealed that the dielectric constant is severely influenced by the dimension and weight of the fruit. To eliminate the interfering effects of these parameters, a second model was proposed to predict the dielectric constant of banana fruit. This model is a function of equivalent dielectric constant, volume, effective length as well as width of the fruit. The dielectric constant showed a decrease with increase in the ripeness of the banana fruit. Since the decrease was more distinct at the 1 MHz, this frequency was employed to calibrate the system. The firmness was assessed also as a quality index and the relationship between dielectric constant and firmness also studied. The results of prediction were somehow acceptable with the correlation coefficient between the predicted vs. the real ripeness obtained as 0.853.

A prototype of a straw chopper, equipped with a discharge system was designed and fabricated in the Department of Mechanics of Agricultural Machinery, University of Tehran, Karaj, Iran. To test for the effective performance of the machine, the effects of such parameters as: drum speed (at three levels of: 400, 540, and 800 rpm), screen size (at two levels: 2.5 and 4 cm), and number of blades on each flange (4 and 8 blades), on power requirement for particle size reduction, chopping capacity, and straw particle size distribution were investigated. Based on the results, with increase in drum speed, power requirement as well as threshing capacity increased. There was no significant difference observed between drum speeds of 540 and 800 rpm as regards particle size distribution, while a speed of 400 rpm resulted in longer particles, therefore a drum speed range of 540 to 800 rpm was recommended. With decrease in screen openings' size, the power requirements increased while the threshing capacity decreasing. Screen size of 2.5 cm led to finer particles. With an increase in the number of blades on each flange, the power requirements decreased while the threshing capacity increasing. Since there was no significant difference observed between the numbers of the two sets of blades as regards particle size distribution, it is recommended that 8 blades be installed on each flange. The power requirement can thus be reduced and the cutting capacity increased.

Since threshing is one of the most sensitive rice post-harvest processing operations, this study was conducted to evaluate the threshing performance in axial - flow paddy thresher. Independent variables consisted of: drum speed at five levels (550, 650, 750 and 850 rpm), equivalent to peripheral velocities of: 14.67, 17.35, 20.01 and 22.37 m/s, respectively, paddy moisture content at two levels (16 and 20% w.b.) plus feed rate at two levels of: 12 and 20 kg/min. Dependent variables were: cracked, broken, and husked grains. The experiment was conducted as a split-split plot one based upon a Completely Randomized Design of three replications. With an increase in drum speed from 550 to 850 rpm, the mean cracked grain loss increased from 6.137 to 8.557% at 20% moisture content and 20 kg/min of feed rate. The loss increased from 8.797 to 18.077% at 16% moisture content and 12 kg/min of feed rate. With an increase in drum speed from 550 rpm to 850 rpm the broken and dehulled grain quantities changed from 0.713 to 1.173% and from 0.823% to 1.447% respectively. The trend indicates the necessity of threshing in higher seed moisture contents, higher drum speeds as well as feed rates.

Knowledge of physical properties of sunflower seed is essential for the design and development of such processing equipment as handling, separating, dehulling and storing. In this research, physical properties of sunflower seed, (Azargol variety as a case of study was investigated at various moisture contents (3-14% d.b) and in three categories of big, average and small sizes samples. The results revealed that the seed length is strongly correlated with its width and thickness. Also, there was a significant connection observed between width and thickness of seed; however there was no significant connection observed between dimentions and its mass. The results showed that mass, thousand grains mass, porosity and terminal velocity of sunflower seed linearly increased with increase in its moisture content from 3% to 14% in each of the size categories. In all sizes categories, the bulk density of sunflower seeds linearly decreased with increase in moisture content from 3 to 14%. In addition, the obtained results revealed that static coefficient of friction on some five studied surfaces increased linearly as moisture content increased from 3 to 14% for both cases of seed and kernel. The greatest value of static coefficient was found to occur on aluminum surface and for big size seeds, within the range of 0.42 to 0.45.

One of the new techniques applied in the drying process of food stuffs that can increase the drying rate, enhanced the product quality, and while decresing the costs of processing is an application of infrared radiational energy. In this study the thin layer drying process of button mushroom was modeled through an infrared applied drying method. Drying experiments with sliced samples of button mushroom were conducted at three radiation intensities of 0.22, 0.31 and 0.49 W cm-2 along with three inlet air velocities of 0.5, 0.7 and 1 m/s. During the drying process, weights of the samples were determined for a calculation of sample moisture contents. Drying curves were obtained using the experimental data with the standard models being then fitted to them. Fitted models were evaluated through an application of three parameters of coefficient of determination (R2), Chi-square (c2), as well as Root Mean Square Error (RMSE). The selected models were determined as Lewis, Page, Henderson & Pabis, Logarithmic, Logistic, Modified Page, Dual term, Second order, and Diffusivity. All the models led to proper results, but in total, the Logistic, with the biggest R2 and the smallest c2 along with RMSE (0.997, 0.0022 and 0.0049, respectively), ended up with the most appropriate results, and showed good agreement with the experimental data.

Agricultural crops and food materials exert frictional forces on agricultural machinery elements and on storage walls during their harvest, transportation, processing and storage. Coefficient of friction is an important parameter to be predetermined in designing equipments and evaluating processes. An assessment of the coefficient of friction for agricultural materials is usually done through simple equipments of low accuracy in which many errors are introduced during the process. The device that was designed and fabricated in this work measures coefficients of static and dynamic frictions for agricultural crops on different surfaces with high accuracy. While a box filled with sample material is being pulled on the frictional surface, the tensile force is measured by use of a load cell with the data saved in the memory of the device. Then a microcontroller estimates the static and dynamic coefficients of friction. To evaluate the performance of the device, some static and dynamic coefficients of friction were assessed for wheat and for peas on four different surfaces (glass, wood, galvanized as well as steel sheets) at three speed levels (0.05, 0.1 and 0.2 m/s). The results were then compared with the ones obtained from inclined plane method, under the same conditions. The data obtained from application of the designed device were close to those from the inclined plane, while the standard deviation of the results from inclined plane was up to 3.5 times that of the results obtained through the new device.

Large sums of fruits are annually wasted due to mechanical damage and bruise inflicted upon them during harvesting, handling, storage and packaging. The research which has been done to analyze the mentioned processes mostly used practical operational techniques with the results being applicable in certain defined conditions. The aim of this research was to develop computer models for an optimization and design of postharvest processes and equipment with a minimum incidence of bruise. Two experimental test series were conducted on Red Delicious variety of apple. The first test series were performed to determine the geometrical dimensions and mechanical properties of texture, as well as other parameters needed to attain accurate finite element models. The second ones were performed to determine pressure distribution in contact areas and to provide force-deformation data for validation and a comparison of results in simulation models. Mean curvature at the middle part of the apple fruit was found as 61.43 mm, that is 3.7 times larger than curvature at the top and lower parts of the fruit. Also, the mean failures of stress and strain were obtained 282, and 0.071 kPa, respectively. The simulation results revealed that there existed a significant difference between the results of elastic model and those of the experimental data, but there was no significant difference observed (at 1% level) between the elastoplastic model and the experimental data. Maximum compression load for Red Delicious variety of apple, using the simulation model was found equal to 32 N that well agreed with the other published research results.

With the aim of a determination of physical properties of date palm male flowers, as well as optimum flower detachment conditions, this study was carried out in two parts. In the first part of the study, the palm groves of Khuzestan Province were totally surveyed. “Ghanami” cultivar was in the end selected to be studied as the superior cultivar in the region. Drying up of the male flowers at 70°C in a standard oven and for 24 hours was found to be a rapid and appropriate method for moisture content determination. The final moisture contents of male flowers for red and green Ghanami cultivars, under normal conditions, were found out as 10 and 10.3 percent (w.b.) respectively. Results indicated that the force required for a detachment of an individual flower reaches its minimum at 2 days after opening of the spathe and when the inflorescence is dried under ambient conditions. At this time flower detachment mean force was estimated about 0.6 N for either of red and green Ghanami cultivars. After this time past the flower-strand joint becomes tougher with the passage of time, following a trap-like curve. Optimum thermal conditions for flower detachment were studied in the second part of the study. Results showed that 25oC (ambient temperature) led to a significant decrease in the time required to reach the minimum flower detachment force in comparison with the lower temperatures of 5 to -15oC. This time was 2 days, which is in match with that found in the early part of the study.

The effect of different juice extraction treatments on the qualitative properties of lime juice was investigated. Samples were selected from Jahromi lime variety and lime juice extracted by means of a screw type juice extraction device. The mechanical parameters of the helical juice extractor [screw velocity (270, 360 and 450 rpm), outlet pressure (minimum, medium vs. maximum)] and lime pretreatment parameters prior to juice extraction within five shapes (whole, half fruit, quarter, peeled vs. scraped lime) were taken as treatments. A factorial design was employed to find the effect of different treatments on some quality properties of the juice (limonin, physical stability, color, as well as peel oil content). The results indicated that rotation speed did not have any significant effect on brightness and on the amount of limonin. A lower level of peel oil content was resulted at a screw rotation speed of 360 rpm. The extents of oil (0.09%), limonin (8.33 ppm) and physical stability (79.76%) were lower for the case of peeled sample pretreatments. The higher brightness and less peel oil occurred at the medium pressure on residue while the highest physical stability was obtained when maximum pressure exerted on residue.

To study the potential of production of biogas, utilizing the wastes of rose distillation process, the wastes were mixed with cow manure at manure proportions of 5, 10, 15 and 20% and in temperatures at two levels of 35 and 45oC. The treatments were carried out using a 2×4 factorial design (a=0.05). The volumes of produced gas and generated methane were recorded daily and modeled as functions of time, using three mathematical models; namely: Gompertz, Logistic and Richards. The experimental results indicated that the treatment with 20% cow manure and at 45oC yielded the maximum cumulative gas production equal to 0.4268 m3/ (kg VS), while containing 72% methane. The mass reduction of available volatile compounds in this treatment was 81%. In general, the treatments mixed with higher proportions of cow manure reached their maximum level of daily gas productions in shorter periods of time. The results of mathematical modeling of the process indicated that Gompertz and Logistic models better fitted the experimental data with an R2 of over 94%.

The present research was carried out with the aim of site-specific nitrogen fertilizer management, through ASTER imagery. A 23 ha corn field in Pakdasht town in southern Tehran Province constituted the research area. Plant sampling was carried out simultaneous with the passing by of the satellite sensor over, throughout the farm. A total of 53 pixels were selected through systematic Randomized sampling method. Nitrogen content was determined through Kjeldahl method. Geometric correction was performed through RMS 0.2 pixels. To predict corn canopy nitrogen content, NDVI, MSAVI2, MCARI2 and MTVI2 indices were investigated. Results revealed that MTVI2 presented the highest correlation with a coefficient of R2=0.87. SAM approach as a supervised classification technique was performed to set apart different nitrogen levels. The overall accuracy was observed as 97.53% with a Kappa coefficient of 0.9669. Results of classification showed that, there were three nitrogen levels distinct on the farm namely: high nitrogen level (2.5-3% nitrogen content), medium (2-2.5% nitrogen content) vs. and low nitrogen level (1-2% nitrogen content). This indicates that 15.8%, 25.2% and 59% of the farm area had received high, medium vs. low nitrogen levels respectively. Based on high nitrogen variations observed in the experimental area, precision management of nitrogen fertilizer application is deemed economical and necessary.

Rhelogical properties of mucilage extracted from Garden cress (Lepidium sativum L.) seeds as influenced by gum concentration (0.4, 0.6, 0.8 and 1.0% w/w), temperature (5, 25 and 40oC), as well as pH (2.5, 4, 7 and 10) were investigated. Non-Newtonian shear thinning flow behavour was observed with the Power law model well describing the rheological behavior of the solutions. Increasing the solution concentrations increased the viscosity and pseudoplasticity while an increase in temperature resulted in a decrease in viscosity and pseudoplasticity. A marked dependence of viscosity on pH was also observed. As pH increased from 2.5 to 7, the viscosity increased whearas it started to decrease at pH 10. To study the structural aspects of the mucilage gum it was characterized through FT-IR with the results indicating that Garden cress seed gum contained carboxylic groups on the backbone of its polymer.

The possibility of fractional replacement of gelatin in pastille with either soluble, fractions or whole Persian gum and the effects of olibanum gum addition on some sensory and physical properties of pastille were evaluated. Findings revealed that Persian gum either alone or along with high levels of sucrose could not result in gelation, whereas its insoluble part addition led to some gelation. Moreover, with increase in the proportion of Persian gum plus its soluble fraction, the mechanical properties of: modulus of elasticity, tensile strength, elongation at break, and the work needed up to break point decreased, while the samples containing only the insoluble fraction yielded charateristics similar to the ordinary and common pastille. In terms of sensory evaluation, no significant differences were observed (P>0.05). With regard to olibanum gum addition, its presence in the formulations led to a significant improvement in mechanical properties. The results of sensory evaluation also indicated that the gelatin/olibanum containing pastilles were more desirable. The findings of this project clearly revealed the capabilities of olibanum powder and Persian gum as natural and organic ingredients in production of functional pastilles and as well the role of the latter in replacing of gelatin, by 40%.