نشریه مهندسی بیوسیستم ایران
سال چهل و دوم شماره 2 (پاییز و زمستان 1390)

The use of plant fibers in producing different industrial products has attracted the attention of many researchers. Plant fibers, in comparison with industrial ones, are degraded faster in nature and are more environments friendly. One of the major conventional uses of plant fibers is the production of traditional ropes which are subjected to tensile forces. However, the traditional ropes bear rough surfaces, working with which becomes a difficult task. By reducing the lignin content of the fibers and their coverage them with polymeric materials, their surface roughness will be moderated. In this research, mechanical properties of the ropes, prepared from either raw or polymeric treated fibers, including tensile strength, modulus of elasticity and strain under tensile loads were assessed. The distributions of stress and strain within the ropes were modeled in ANSYS using solid mechanical equations. The maximum tensile force supported by the ropes prepared from 10 single raw fibers was 172N which was increased to 400N by reducing their lignin content and while having them covered with PVA resin. Moduli of elasticity for these ropes were found out as 600 and 250 MPa, respectively. The distribution models for stress and strain within the ropes revealed that the rupture point occurred at a point with a distance of about 25% of the length of the rope, away from the fixed end of the rope. The practical tensile test indicated a verification of these findings too.

A suitable option for manufacture of packing materials is the use of clay and silver nano particles. These materials help create optimal relative impermeable quality, in addition to other features being improved. Moisture-packed bread by use of these materials prevent water vapor loss and therefore reduce the level of bread becoming stale. In this study, seven types of nano-films with different percentages of silver and clay content were tested for the passage of water vapor quality. The level of permeability of the material was evaluated through a measurement of p packaged bread moisture content. At the end, the data were analyzed using software SPSS (Duncan test), and compared with control (with no nano particles inclusion). The results suggested a reduction of 3.1 to 4.9 times of water vapor permeability due to nano film's use. Packaged bread moisture increased about 14 to 25 percent and this in turn reduced bread staling between 40 to 60 percent. Nano-films, especially nano films including nano silver, proved to reduce permeablity moisture. The rate of bread staling was reduced significantly by being maintained at 0.01 level. From among the films, nano-silver film with 2 percent of silver (S2) was recognized as the most appropriate one.

Savojbolagh is the main region of hydroponic greenhouse agriculture in Iran and is of the capacity to produce the highest in greenhouse production strawberry. The aims followed in this study were to calculate the energy use pattern and determine the relationship between energy input in greenhouse strawberry production and its yield through a linear programming model as based on Data Envelopment Analysis (DEA). Technical efficiency of greenhouses were calculated and target input energies optimized. Results indicated that greenhouse strawberry production consumed a total energy of 800 GJ ha-1 with a specific energy of 12.5 MJ kg-1calculated. Linear Regression Analysis indicated that the impacts of diesel fuel, fertilizer, electricity and human labour were significant on yield. These effective inputs were assumed as inputs while yield as an output in the model of DEA and the technical efficiency of a greenhouse (in input oriented variable return to scale model) estimated. Energy technical efficiency of strawberry producing greenhouses was estimated as 0.93 and the maximum possible contribution to the total energy savings was estimated 61% that could come from diesel fuel saving. A determination of real and target energy inputs in inefficient greenhouses revealed that 16% of resources could be saved by raising the performance of these greenhouses to their highest possible level.

Efficient energy use in agriculture sector is one of the prerequisites to sustainable agriculture, because it allows financial savings, fossil resources preservation along with decreasing trend of air pollution. This research was conducted at the Agricultural Research Field of Zanjan University to determine the level of input energy in different tillage systems in forage maize production when in rotation with canola and to investigate the impact of different tillage systems on growth indices. The study was planned as a split-block design with three tillage systems as main plots and three cultivation systems as sub plots and in four replications. The tillage treatments were: moldboard plow+disk (A1); cyclo-tiller (A2); and minimum-till (A3) the cultivation treatments being: cultivator with furrower (B1); cultivator without furrower with the tendency of the cutting share towards inside (B2); cultivator without furrower with the tendency of the cutting share towards outside (B3). For a comparison of energy consumption, the variabls of: forward speed, tillage time and fuel consumption for each plot were calculated. All the three methods of tillage were carried out at same soil moisture level and crop residues conditions. The energy consumption in the three treatments were recorded as 1990.6, 1157.2 and 558.7 MJ ha-1 respectively showing significant differences, in terms of energy consumption, among the main treatments. Also the interaction of tillage and cultivation was significant at a 5% probability level. Finally, according to the obtained results, minimum-till method is suggested 10 to be employed in the study area.

One method of seed placement into the soil as regards no-till system is the use of punch planting by which one can plant through a considerable depth of surface residue. The study was conducted using a 23 split-plot experimental design of three replications. The factors considered were two types of plantes (conventional planter vs. hinging pneumatic Punch Planter) and three levels of wheat residue (0, 30 and 60 %). Field study was conducted to compare the effects of type of planter and wheat residue on indices of corn planting. The analysis of the obtained data indicated that types of planter and different levels of wheat residue exert meaningful effects on miss, quality of feed and precision indices. Furthermore, results show that by augment of wheat residue, miss and precision indices are increased while the quality of feed index follows a descending trend. These factors do not exert any significant effects on multiple index. Also the results showed that different levels of wheat residue lay significant effects on emergence rate, shoot and root height, shoot and root dry weight, vigour Seed 1and 2 and as well on relative growth rate indices. The types of planter have significant effects on emergence rate; root height and on root dry weight. The most appropriate performance of a hinging pneumatic punch planter is finally recommended in a field that is under the coverage of 30% residue.

To design the equipment and facilities for preservation, storage and processing of pomegranate, it is necessary to know the specific heat and thermal conductivity of the fruit components. The specific heat of exocarp, mesocarp and of seeds of pomegranate were assessed at three moisture content levels (30, 50 and 76% for seed and mesocarp; 15, 35 and 52% for exocarp) and at four temperature levels (3, 8, 13 and 18˚C). Also, the thermal conductivity of the components were measured at three moisture content levels (25, 50 and 73% for seed, 20,40 and 60% for mesocarp and 15, 35 and 52% for exocarp) as well as at three temperature levels (5, 13 and 18˚C). The mixture method was employed for measuring the specific heat. The thermal conductivity of the exocarp and mesocarp were determined through prob and hot wire methods, respectively. The specific heat of the components were increased linearly from 1.127 to 2.789 kJ/kg˚C for seed, 0.931 to 3.066 kJ/kg˚C for mesocarp and 1.516 to 3.411 kJ/kg˚C for exocarp with an increasing trend in moisture content and in temperature. Also, the thermal conductivities of the components increased from 0.15 to 0.42 W/m˚C for seed, 0.15 to 0.41 W/m˚C for mesocarp and 0.13 to 0.37 W/m˚C for exocrap with increase in the experimental range of the variables. The specific heat and thermal conductivity of the components were significantly affected by the moisture content and temperature. The specific heat and thermal conductivity of the pomegranate components were estimated as a function of temperature and moisture content using regression models of high coefficients of determination (R2).

Thin layer drying behavior of sweet lemon slice was experimentally investigated in a convective type dryer and the mathematical modeling performed, using thin layer drying models given in literature. Drying experiments were conducted at inlet drying air temperatures of 40, 50, 60, 70 and 80 ºC; two slice thicknesses of 3 and 6 mm, and, at one drying air velocity of 0.5 m/s with three replications in each treatment. Page model was employed (according to their coefficients of correlation) to estimate the drying curves. The effects of drying air temperature on the model constants and coefficients were evaluated through a non-linear regression technique. The accuracy of the model was estimated according to three statistical parameters of: coefficient of determination (R2), Chi-square (χ2) and Root Mean Square Error (RMSE). Results indicated that Page model could satisfactorily describe the drying curve of sweet lemon slices with R2=0.99812, (χ2) =0.0000518 and RMSE=0.003912 for a thickness of 3 mm while R2=0.997776, (χ2) =0.0000715 and RMSE=0.0082232 for a thickness of 6 mm. Moisture transfer from the slices was described by applying Fick’s diffusion model. The effective diffusivity coefficient values changed from 8.04×10-9to 7.63×10-8 m2/s for the range of temperatures considered. An Arrhenius relation with an activation energy value of 28.53 kJ/mol and the diffusivity constant of 5.01×10-4 m2/s for a thickness of 3 mm, while 39.46 kJ/mol along with a diffusivity constant of 9.37×10-4 m2/s for a slice thickness of 6 mm, were obtained, indicating the effect of drying air temperature and slice thickness on the diffusivity parameter.

Agricultural products are affected by static and dynamic forces at different stages of harvesting, handling and processing. In most cases, the damages are inflicted upon raw products. In the present study the mechanical properties of tomato fruits were found out for two cultivars (Super Bta and Petoerly Ch), during 4 periods of time (1, 5, 10 and 15 days past harvest), and at two levels of fruit sizes (small and medium). Statistical analysis was performed in the form of a split-plot arrangement in time with a completely randomized design of 10 replications. The effect of time past harvest was significant on the exerted force and deformation at bioyield points. Rate of deformation and rate of force at biologic yield points were found out to be greater for petoerly Ch than for super Bta variety. Also, the effect of variety was significant on deformation at rupture point. Tomatoes with of the small size were found to be tougher than the medium ones. Smaller size fruits are tougher and need less force to rupture. Also, significant differences were observed between different size fruits for the following parameters: maximum force, maximum deformation, deformation at rupture point and force at bioyield point. At one day past harvest petoerly variety was found to be of more strength, in ui-naxial loading, than super Bta, as compared with other points of time.

Optimum working life of tractor and farm machinery employed in potato production in Hamadan Province was assessed through Data Envelopment Analysis. An input oriented model was applied to determine the optimized machinery system. In this model inputs were the lifetime of tractor as well as seven involved machines including moldboard plow, potato planter, chemical fertilizer spreader, tractor mounted sprayer, furrower, potato haulm cutter and potato digger, while outputs were: yield (kg ha-1), economic return (kg thousand Rials-1) and energy (kg MJ-1) as productivity indices of potato cultivation. Results revealed that 38% of farms were inefficient. They, due to old machinery, cannot be economically efficient and are spending extra energy. On the other side, efficient farms, through an employment of optimized new machinery pay less maintenance cost and can produce more economically with a less energy spending. Also, analysis showed that the utmost mechanization employed on the farms is the use of tractor and moldboard plow. If inefficient farms use suitable mechanization systems, they can raise to even a duplicate level, their economic return by raising their energy productivity (up to 70%) and improving the yield.

The effect of Xanthan hydrocolloid (0.1 and 0.5% W/W of flour) on physical and sensory properties of the fresh and stored Barbary bread were studied. Effects of hydrocolloids on physical properties of baked bread were determined by different tests of: penetration, colorimetry (Hunter values) of crust and Differential Scanning Colorimetry (DSC). Sensory evaluation also was carried out for determining the overall acceptability of the bread samples. All the experiments, except colorimetry, were carried out on the first, second and fourth days after baking. With an addition of Xanthan, physical and overall acceptability of the bread were improved. Xanthan gum increased dough consistency, water absorption, dough developing time as well as the softening index. Furthermore, it increased yellowness and lightness indexes of the crust and softness of the crumb in the bread experimental samples. The bread samples containing Xanthan gum at 0.5% level showed the highest quality accompanied by the least unfavorable change during their storage time.

Response surface methodology was applied to determine the optimum processing conditions that lead to maximum water loss, weight reduction and minimum solid gain as well as water activity during osmotic dehydration of carrots. Temperature (30-50ºC), processing time (120-240 min), glucose syrup DE=42 (30-50% w/w) and salt (5-15%) concentrations were the factors investigated with respect to water loss (WL), Weight Reduction (WR), Solid Gain (SG), and water activity (aw). Experiments were arranged according to Central Composite Rotatable Design with these four factors each at three different levels, including central and axial points. Experiments were conducted with constant agitation rate of 200 rpm and solution to sample ratio of 10:1 (w/w). With respect to water loss, solid gain, weight reduction and water activity, both linear and quadratic effects of variables were found to be significant (p<0.001). For each response, second order polynomial models were developed using Multiple Linear Regression Analysis. Analysis of Variance (ANOVA) was performed to check the adequacy and accuracy of the fitted models. The optimal conditions for maximum water loss and weight reduction as well as minimum solid gain and water activity correspond to temperature of 30 ºC, glucose syrup concentration of 43.315%, salt concentration of 5%, time of 227.19 min to obtain water loss of 66.97 (g/100 g fresh sample), weight reduction of 62.52 (g/100 g fresh sample), solid gain of 4.475 (g/100 g fresh sample) and water activity of 0.789.

The physico-chemical characteristics and physiological qualities of palm (Phoenix dactylifera) fruit strongly depend on the storage conditions. Storage environment and packaging type are the factors most influencing on the quality of dates during their storage. Date fruits were packed within an aerobic atmosphere, vacuumed in PA/PE pouches and stored at different temperatures (-20, 4, 25 and 40 ºC). Throughout the study, the effect of packaging type, storage temperatures as well as storage time on physical properties of the fruits were investigated. The samples were evaluated for color indices (L*,a*, b*) and as well for textural parameters (gumminess and chewiness) on a monthly basis, and during storage for a duration period of up to 6 months. Results demonstrated that the storage temperatures, storage time and packaging type greatly (p < 0.01) affect all the physical parameters (color indices, guminess, chewiness) during storage. The color index values (L*, a*, b*) of dates stored at 40 ºC were lower than those of the other date fruits. L*,a* and b* indices of atmospheric packed dates were higher than those of the vacuum packed samples. The gumminess and chewiness were higher in the dates stored at 40 ºC within all packaging types within the sixth month. An increase of gumminess and chewiness was detected for all the samples throughout the storage period. However, it was noted that the increase was significantly greater at 40 ºC as compared with those at the other storage temperatures.