Showing 8 results for Akhavan
D. Lotfi, A. Hemmat, M. R. Akhavan Sarraf,
Volume 11, Issue 1 (spring 2007)
Abstract
For measuring draft force and drawbar power requirements for mounted implements, precise instruments such as three-point hitch dynamometers and tractor speed measurement devices are needed. In this research, a frame-type three-point hitch dynamometer was built and evaluated. Forces applied to dynamometer are measured by three separate load cells located on a frame which can be attached to tractor’s three-point hitch. Each dynamometer’s load cell measures load using a strain gauge bridge circuit. Each load cell was calibrated by applying a known load and measuring bridge circuit’s output voltage. Dynamometer was calibrated by the application of known forces and measuring the output voltage of the strain gauge bridges. The calibration showed a high degree of linearity between the applied forces and the bridge outputs (R2 = 0.996). The hysteresis effect between loading and unloading as well as the effect of the position of the applied forces from the longitudinal axis of the dynamometer was small. For measuring actual tractor speed, a fifth wheel equipped with an encoder shaft was designed and built. The calibration on tarmac and soil surfaces showed a highly linear relation between measured forward speed and output of encoder’s rotation (R2 =0.994). The errors in speed measurements at low speed in field and at high speed (up to 12.5 km/h) on tarmac surface were approximately 3 and 8%, respectively. The data acquisition system, not only could display the instantaneous force and speed, it could also show force-time and force-distance curves on the system’s monitor.
S. Akhavan, S. F. Mousavi, B. Mostafazadeh-Fard, A. Ghadami Firoz Abadi,
Volume 11, Issue 41 (fall 2007)
Abstract
To investigate yield and water use efficiency (WUE) of potato with tape and furrow irrigations, an experiment was performed at Hamadan Agricultural and Natural Resources Research Center (Ekbatan station) in 2004. The experiment was arranged in a split-plot experimental design based on completely randomized block with 3 replications of irrigation water amount as the main factor (75%, 100%, 125% of cumulative evaporation from class A pan) and sub-factor of irrigation method [including tapes in the middle of furrow ridge on soil surface (TD0), tapes in the middle of furrow ridge at the depth of 5 cm (TD5), tapes on the sides of furrow ridge on soil surface (TS0), and furrow irrigation (F)]. The results indicated that yield of potato increased with increasing water use. Regardless of irrigation method, maximum (32.51 ton/ha) and minimum (19.33 ton/ha) yield of potatoes was achieved with 125% and 75% irrigation water treatments, respectively. The lowest yield (21.35 ton/ha) was obtained in furrow irrigation and the highest yield (28.91 ton/ha) belonged to tape irrigation (TD5 treatment). The highest WUE (4.68 kg/m3) belonged to tape irrigation (TD5 treatment) and the lowest WUE (3.32 kg/m3) belonged to furrow irrigation (F). The difference in WUE between 75% and 100% irrigation water treatments was not significant. The highest WUE (4.49 kg/m3) was achieved in treatment 125%. Also, it is more economical to use irrigation water treatment of 125%, as compared with other irrigation water treatments.
A Akhavan, M Bahar, Gh Saeedi, M Lak,
Volume 13, Issue 47 (4-2009)
Abstract
To understand the role of relative humidity rate, host genotype, inoculation method and growth stage in epidemiology of bean common blight, two greenhouse experiments were carried out monitoring epiphytic population size of Xanthomonas axonopodis pv. phaseoli (Xap) and disease severity. The result showed significant differences among genotypes, inoculation methods and growth stages for epiphytic population size and sam effects except genotypes for disease severity. The epiphytic population size was significantly higher on spray inoculated Khomein cultivar of bean during flowering (R6). However, the relative humidity rates did not significantly affect population dynamics of epiphytic Xap and the disease severity. Two field experiments were also carried out to determine the effects of irrigation systems (furrow irrigation and overhead sprinkler irrigation), inoculation method, growth stage and their interactions on epiphytic population size of Xap and disease severity. The result showed that the epiphytic population size and disease severity were higher on spray inoculated plants irrigated with overhead sprinkler system during pods filling (R8). In this study, a significant positive correlation was found between epiphytic population size of Xap and bean common bacterial blight severity.
H Askarian, B Sharifnabi, M Olia, E Mahdikhani, A Akhavan,
Volume 13, Issue 47 (4-2009)
Abstract
Root knot nematodes (Meloidogyne spp.) cause yield loss in all countries, of which, M. javanica, is the most widespread species in Iran. In order to identify M. javanica, 100 infected root and soil samples of root knot nematode were collected from different regions of Kerman province. After purification of populations and identification of M. javanica based on morphological and morphometerical characters of females and second stage juveniles (J2), total DNA was extracted from eggs, J2 and female adults. Specific 670 and 1600 bp bands were amplified in all M. javanica populations using species-specific primer pairs including OPARjav / OPAFjav and Mjavf / Mjavr These specific bands could not be amplified in other species such as M. incognita and M. arenaria. It seems that, application of these species specific primers in comparison with morphological characters would be more applicable, leading to easier identification of M. javanica.
S Akhavan, J Abedi Koupaee, S.f Mousavi, K Abbaspour, M Afyuni, S.s Eslamian,
Volume 14, Issue 53 (fall 2010)
Abstract
Temporal and spatial distribution of water components in watersheds, estimation of water quality, and uncertainties
associated with these estimations are important issues in freshwater studies. In this study, Soil and Water Assessment
Tool (SWAT) model was used to estimate components of freshwater availability: blue water (surface runoff plus deep
aquifer recharge), green water flow (actual evapotranspiration) and green water storage (soil water), in Hamadan-Bahar
watershed. Also, the Sequential Uncertainty Fitting program (SUFI2) was used to calibrate and validate the SWAT
model and do the uncertainty analysis. Degree of uncertainty is calculated by R-factor and P-factor parameters. In this
paper, results of calibration and validation are given for the river monthly discharge. In most stations, especially in
outlet of the watershed (Koshkabad station), simulation of river discharge was satisfactory. Values of R-factor in
calibration of monthly runoff were 0.4-0.8. These small values show good calibration of runoff in this watershed.
Values of P-factor were 20-60%. These small values show high uncertainty in estimations. For most stations of the
watershed, lack of data on river-water withdrawal caused poor simulation of base-flow and therefore the P-factor values
were low. Nash-Sutcliff (NS) coefficient was 0.3-0.8 after calibration, which shows good model calibration of outlet.
This study provided good information on the components of freshwater availability at spatial (sub-basin) and temporal
(monthly) scales with 95% prediction uncertainty ranges. The results of uncertainty analysis of components of
freshwater availability show that uncertainty ranges of average monthly blue water are larger than the other
components, because of its sensitivity to more parameters.
S. Akhavan, A. Jodi Hameze Abad,
Volume 19, Issue 72 (summer 2015)
Abstract
Urmia Lake, located in north-west of Iran, has been exposed to various threats such as drought, construction of dams, land use changes and increased global temperature. Due to the importance of Urmia Lake, it is feasible to conduct different kinds of studies to identify the problems of its watershed. The main objective of this study was to evaluate SWAT program’s ability to simulate runoff in Urmia Lake watershed with an area of 52000 km2. The model was run for the 1980-1997 period. Calibration and validation periods were from 1980 to 1991 and from 1992 to 1997, respectively. The results of calibration for 10% and 85% of hydrometric stations were very good and suitable, respectively. Also, validation results for 25% and 45% of hydrometric stations were very good and suitable, respectively. These results show the high ability of SWAT model to simulate discharges in Urmia Lake watershed. Moreover, some factors influencing inflow to the lake in recent years were evaluated. The outcomes revealed that recent changes (dam cconstructions, climate change and land use change) in the watershed have caused inflow volume to the lake to decrease by 80%. So, if natural management conditions had prevailed in the watershed, the Lake’s conditions would have been much better.
Dr. S. Akhavan, N. Delavar, Dr. A. M. Mehnatkesh,
Volume 21, Issue 2 (Summer 2017)
Abstract
The aim of this study was to investigate the climate change impacts on some factors affecting rainfed wheat growth such as effective rainfall, planting date and length of growing season in four stations located in Chaharmahal and Bakhtiari province. Firstly, it is necessary to predict future (2046-2065) climatic conditions. For this purpose, the output of HADCM3 general circulation model was used under three scenarios of A1B, A2 and B1. The data were downscaled by LARS-WG model. After simulating the climatic parameters in mention period, the effective rainfall during the wheat growing season was calculated by Food and Agriculture Organization method. Also, the optimum planting date was defined according to the date of the first rain (at least 10 mm in case of continuing for next days). The wheat's growth stages were determined by Growing Degree Days method. The results indicated a rise in temperature for four stations. On average, it is expected that the annual temperature increase by 1.8°C compared with the baseline period (2010-1990). Total annual precipitation in Shahrekord, Koohrang and Borujen will decrease 2.2, 7.8 and 3.6 per cent respectively. About Lordegan it will increase by 2.7 per cent. Also, the results showed that in three stations of Shahrekord, Koohrang and Borujen, the amount of effective rainfall in November will increase compared to baseline, but in Lordegan it will reduce. So, in the first three stations, in most years, planting date was obtained earlier than baseline, but in Lordegan it was later than baseline. The Length of growing season will reduce in Shahrekord, Borujen and Lordegan stations, 12 days on average and in Koohrang about 13 days.
M. Heidarpour, Kimia Akhavan, N. Pourabdollah,
Volume 28, Issue 3 (Fall 2024)
Abstract
One of the ways to improve the characteristics of the hydraulic jump in the stilling basin is to use natural and artificial roughness. Recently, due to the advantages of immersed plates compared to other non-continuous artificial roughness, such as the smaller number of these and the vanes' ability to design their geometry and arrangement, it has been approached more. In this article, the effect of submerged vanes with three contact angles of 45°, 75°, and 90° has been investigated on the improvement of the characteristics of a hydraulic jump and its effect on parameters such as the depth ratio, relative length, energy loss rate, and bed shear force coefficient has been evaluated. The results of this research showed that the average effect of submerged vanes on reducing the depth ratio, jump length, and roller length compared to the classical mode is 9.4%, 24.6%, and 28.4%, respectively and the average relative energy loss is 5.5% compared to the classical state and maximum relative energy loss at the angle of 90 degrees of submerged vanes is 6.5%. Considering these results and other conditions such as ease of construction and use, stabilization, and reduction of economic costs among the available choices of sunken vanes, the angle of incidence of 75° is a suitable option for the optimal design of the stilling basin.
