Showing 8 results for Bahrami
S. Bahrami, M. Shahedi,
Volume 8, Issue 1 (spring 2004)
Abstract
In this study, the effects of quality and quantity of protein in flours with 95% and 70% extraction rates obtained from Mahdavi and Tajan wheat cultivars each baked at two different durations (100 and 75 sec.) and temperatures (210 and 250°C), after wrapping in polyethylene packages with 40µm thickness were investigated. All tests were carried out during 168 hours after packing and at 24h intervals.
Results indicated that bread staling was affected by wheat cultivar, flour extraction rate, and storage time. Bread prepared from Tajan flour had lower firmness and staleness than that prepared from Mahdavi. High bran content bread was firmer than that with lower bran content. Organoleptic tests indicated that bread baked with 95% flour and bread baked at high temperatures with short durations were not very acceptable.
A Vaezi, H Bahrami, H Sadeghi, M Mahdian,
Volume 13, Issue 49 (Water and Soil Science 2009)
Abstract
Proper evaluation of soil erodibility factor is very important in assessment of soil erosion. In this study, soil erodibility factor (K) was assessed in a zone, 900 km2 in area in Hashtrood, located in a semi-arid region in north west of Iran. Soil erodibility factor was measured at the unit plots under natural rainfall events in 36 different lands in the study area from March 2005 to March 2007. Results indicated that the measured soil erodibility factor K is on average 8.77 times lower than the nomograph-based values in the study area. To achieve a new nomograph, correlation between measured soil erodibility and soil physicochemical properties was studied. Based on the results, soil erodibility factor negatively correlated with coarse sand, clay, organic matter, lime, aggregate stability and permeability, while its correlation with very fine sand and silt was positive. Results of principal component analysis of soil properties and multi-regression analysis showed that the soil erodibility factor is significantly (R2 = 0.92, P < 0.001) related to soil permeability, aggregate stability, lime and coarse sand. A new nomograph with a R2 of 92% was developed based on these properties to easily estimate soil erodibility factor in the study area. The soil erodibility factor can be reliably estimated using the nomograph in all regions with the soil and rain properties similar to those in the study area.
R. Lalehzari, S. Boroomand-Nasa, M. Bahrami,
Volume 18, Issue 69 (fall 2014)
Abstract
Advance velocity is an important factor in surface irrigation system design and simulation. Volume balance is a simple model based on continuity equation used in surface irrigation design and management. In the past volume balance models, it is generally assumed that the upstream depth of surface water is constant and equal to normal depth. This initial assumption may cause significant errors in computing advance flow. In this paper, a modified volume balance (MVB) model is developed to predict the advance curve in furrow irrigation. In the suggested method the upstream surface, water depth is actual depth and variable in time. Predicted advance distance of VB, VB-ZI and MVB was compared to the observed data obtained for the three furrow lengths of 60, 80 and 90m. Evaluation indexes indicated that the modified volume balance equation is more accurate than the previous equations by RMSE 9.26, 7.37 and 6.76 respectively. Sensitivity analysis showed that the inlet discharge has the greatest effect on the model and the model is more sensitive to decreasing the discharge amount than to increasing it
A. Shabani, A. Jahanbazi, S. H. Ahmadi, M. M. Moghimi, M. Bahrami,
Volume 22, Issue 1 (Spring 2018)
Abstract
In this study, five infiltration models including Kostiakov, Kostiakov-Lewis, Philip, Soil Conservation Service (SCS) and Horton were fitted to the experimental data using the double rings, and the empirical coefficients of these models were determined. Infiltration experiments were conducted in the gravelly sandy loam soil under and between the olive and orange trees in Fasa city, Fars Province, Iran. The results showed that all five models were fitted accurately to the measured data. The accumulated infiltration under the trees was higher than those measured between two trees. Higher infiltration under the tree canopies was probably due to the higher soil organic matter, the lower soil bulk density, and the tree root channeling, which were more pronounced when compared to the small pores in these soils. Despite the positive effect of sand particles on soil infiltration, the big gravel occurrence in soil would decrease the cross section area of water flow path, thereby reducing the infiltration. Therefore, changing the land use and planting olive and orange trees in the gravel soils would increase the infiltration rate and consequently, decrease runoff and erosion rates in such soils.
M. Heydari, M. Bahrami Yarahmadi, M. Shafai Bejestan,
Volume 26, Issue 2 (ُSummer 2022)
Abstract
Bed shear stress is one of the most important hydraulic parameters to determine the amount of bed and suspended load and the bed and bank scouring in rivers. Bed shear stress depends on bedforms (ripples, dunes, and anti-dunes) in alluvial rivers. In this study, the effect of artificial ripple bedforms on bed shear stress has been investigated. Two types of uniform granulation with average sizes (d50) of 0.51 and 2.18 mm were used to roughen the surface of the artificial ripples. The bedform length and height were 20 and 4 cm, respectively. The angles of its upstream and downstream to the horizon were selected equal to 16.4 and 32 degrees, respectively. Different flow rates (Q= 10, 15, 20, 25, and 30 l/s) and different bed slopes (S= 0, 0.0001, 0.0005, 0.001, and 0.0015) were examined. The results showed that by increasing the particle size on the bed surface, total shear stress (tb ), grain-related bed-shear stress (t¢b ), and form-related bed-shear stress ( t²b ) increase. The value of tb , t¢b , and t²b in bed form roughened by sediment size of 2.18 mm were, on average, 22.38, 30.86, and 22.3% more than the bed form roughened by sediment size of 0.51 mm, respectively.
M.j Amiri, M. Bahrami, M. Mousavi Poor, A. Shabani,
Volume 26, Issue 4 (Winiter 2023)
Abstract
Class A pan evaporation method as one of the most common methods for reference evapotranspiration (ET0) estimation has been widely used in the world due to its simplicity, relatively low cost, and ability to estimate daily ET. In this study, the performance of 8 empirical methods consisting of Allen and Pruitt (1991), Cuenca (1989), Snyder (1992), modified Snyder, Pereira, et al. (1995), Orang (1998), Raghuwanshi and Wallender (1998), and FAO/56 were analyzed to estimate class A pan coefficient and ET0 at Fasa synoptic station located in Fars province. The calculated pan evaporation coefficients from the above equations were compared with measured pan evaporation coefficients which were obtained from the ratio of evapotranspiration calculated by the FAO-Penman-Monteith method to the rate of evaporation from the pan. The results showed that all empirical methods did not predict pan coefficient values well (R2 < 0.3 and NRMSE > 0.25). The comparison results between ET0 from empirical methods and ET0 obtained from FAO-Penman–Monteith indicated that the FAO/56 method had the best performance (R2 = 0.72 and NRMSE = 0.3). To increase the accuracy of empirical pan coefficient equations, these equations were modified with eight years (2007-2015) of meteorological data from the Fasa synoptic station and validated using two years of independent data (2015-2017). The results showed that the accuracy of all empirical models was improved and the Cuenca equation with NRMSE = 0.16 and R2= 0.63 was selected as the best equation for pan coefficient estimation and ET0 (R2 =0.85; NRMSE =0.18) in Fasa region. The sensitivity analysis revealed that the estimated pan coefficient is more sensitive to wind speed, followed by relative humidity, fetch distance, the slope of the saturation vapor pressure curve, sunshine hours, and air pressure. According to statistical results and sensitivity analysis, an equation was expanded for the Fasa region and other areas with the same climate.
M. Badzanchin, M. Bahrami Yarahmadi, M. Shafai Bejestan,
Volume 27, Issue 1 (Spring 2023)
Abstract
The formation of bed form in alluvial rivers due to sediment transport has a significant effect on the hydraulic parameters of the flow such as bed shear stress. The formation of the bed form and its shape and geometry depends on the bed shear stress. Therefore, the relationship between bed form and flow parameters (such as bed shear stress) is complicated. In the present study; the effect of dune bed forms with different heights on bed shear stress has been investigated. Artificial dunes made by sand-cement mortar with a length of 25 cm and heights of 1, 2, 3, and 4 cm were used. In the tests of this research, flow discharge of 10, 15, 20, 25, and 30 l/s and bed slopes of 0, 0.0001, 0.0005, 0.001, and 0.0015 were used. The results showed that with increasing the relative submergence and Δ/λ, the bed shear stress increased in dune-covered beds. The formation of the dune bed form and the increase in its height leads to an increase in the bed shear stress. The bed shear stress in dunes with a height of 1, 2, 3, and 4 cm was, on average, 39, 80, 141, and 146% more than in plane beds, respectively. Moreover, form shear stress for dunes with a height of 1, 2, 3, and 4 cm was, on average, 27.37, 43, 57.11, and 58.74% of the total shear stress, respectively.
L. Hashemi, S. M. Kashefipour, M. Ghomeshi, M. Bahrami Yarahmadi,
Volume 28, Issue 2 (Summer 2024)
Abstract
Local scour around bridge piers is one of the most significant factors for the bridges’ destruction. Therefore, it is necessary to investigate the scour depth around the bridge piers. The effect of the skew angle of the single-column pier group related to the flow direction in two different arrangements including 1×2 and 1×3 piers on the maximum scour depth around the pile group was investigated in this study. The experiments were carried out under steady flow conditions. The pier group was placed in the 1×2 arrangement at the skew angles of 0 to 90 degrees and in the 1×3 arrangement at the skew angles of 0 to 45 degrees. The results showed that increasing the skew angle of the pier group is almost ineffective on the maximum scour depth around the first pier. However, it has a great effect on the maximum scour depth, its temporal development, and the expansion of the scour hole around the second and third piers in different arrangements of the pier groups. The maximum scour depth of the pier group in both different arrangements occurred at a skew angle of 30 degrees, in the arrangement of 1×2 around the second pier and by 13.33% more than the first pier and in the arrangement of 1×3 around the third pier and by 21.57% more than the first pier.
