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Zarei G.,Agricultural Engineering Research Institute | Homaee M.,Tarbiat Modares University | Liaghat A.M.,University of Tehran | Hoorfar A.H.,University of Tehran
Journal of Hydrology | Year: 2010

The objective of this study was to develop and verify a simple analytical model for one-dimensional non-steady upward flow from shallow and falling water table with minimum input data. Consequently, an analytical model was derived based on the Richards' equation with the Campbell's parametric retention model. This study proposes a model that uses the measurement of water table depth drawdown and some soil physical properties to estimate evaporation, instead of measuring evaporation rate itself. Nine relatively large lysimeters were packed with sandy loam, silty clay loam, and silty clay soil textures to obtain the data needed for evaluating the proposed model. The results indicate a reasonable agreement between the experimental data and the proposed model (root mean square error, RMSE = 2.11-4.22 mm/day). For the experimental period (64 days), however, there is some discrepancy between observation and simulation data. The reasons for this discrepancy may be attributed to vapor upward flow, evaporation which takes place from the lysimeters side gaps resulting from soil shrinkage and collapse of macropores resulting from soil packing. © 2009 Elsevier B.V. All rights reserved. Source


Tajeddin B.,Agricultural Engineering Research Institute
Polymers and Polymer Composites | Year: 2015

A viable solution for replacing petroleum-based materials is to combine petroleum and bioresources materials to produce biocomposites having the requisite properties for packaging applications. Although biocomposites have many applications in different purposes such as building construction and aircraft industries, their applications in the packaging engineering are still novel. Therefore, in this study, a biocomposite consisting of low-density polyethylene (LDPE), wheat straw (WS) and the compatibilizers Maleic Anhydride Polyethylene (MAPE) and Polyethylene Glycol (PEG) with molecular weights of 400 and 600, was produced based on the requirements of the packaging industry. By performing different mechanical tests such as tensile, flexure and impact, the effects of the compatibilizing agents was determined. The ratios of the matrix to the filling phase applied to the compound were 70/30, 60/40, 50/50, and 40/60, and the compatibilizers were used at the levels of 0, 7, and 10% respectively. The MAPE compatibilizer improved the tensile properties. The compatibilizer type had no effect on the impact strength properties of the biocomposites. The flexural strength of all compounds was higher than that of the control. Source


Karimi P.,SRI International | Qureshi A.S.,International Water Management Institute | Bahramloo R.,Agricultural Engineering Research Institute | Molden D.,SRI International
Agricultural Water Management | Year: 2012

Groundwater irrigation consumes considerable energy as well as water resources across the globe. Using a case study from Iran, this paper explores how enhanced farm water management can help in reducing groundwater exploitation and subsequently limiting energy consumption and the carbon footprint of the groundwater economy. Groundwater use for irrigated agriculture in Iran has increased vastly over the last three decades. We estimate that groundwater pumping consumes 20.5. billion. kWh electricity and 2 billion liters of diesel and contributes to 3.6% of the total carbon emission of the country. Thus there is an opportunity to reduce energy use and carbon emissions by pumping less water. However, groundwater use remains important for food security. To identify opportunities for water conservation within agricultural fields, the SWAP model was applied to simulate crop growth and field water balance for three major irrigated crops, i.e. wheat, maize, and sugar beet in the Gamasiab River Basin, one of the highest groundwater using irrigated areas of Iran. The model simulations showed that by adopting improved irrigation schedules and improving farm application efficiencies, water productivity will increase, and irrigation water withdrawals from groundwater can be reduced significantly with no reduction in yields. While these improvements may or may not result in water saving and retarding the ground water decline, depending on the fate of excess application, they will have significant water quality, energy, and carbon implications. Such reduction in irrigation application can result in 40% decline in energy consumption and subsequently carbon emission of groundwater use. © 2011 Elsevier B.V. Source


Mousavi Nezhad M.,University of Exeter | Javadi A.A.,University of Exeter | Abbasi F.,Agricultural Engineering Research Institute
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2011

Water flow is greatly influenced by the characteristics of the domain through which the process occurs. It is generally accepted that earth materials have extreme variations from point to point in space. Consequently, this heterogeneity results in high variation in hydraulic properties of soil. In order to develop an accurate predictive model for transport processes in soil, the effects of this variability should be considered. In this study a two-dimensional stochastic finite element flow model was developed for simulation of water flow through unsaturated soils. In this model, the stochastic partial differential governing equation of water flow, obtained from implementation of the perturbation-spectral stochastic method on classical Richard's equation, was solved using a finite element method in the space domain and a finite difference scheme in the time domain. The effective hydrological parameters embedded in the mathematical model depend on time derivatives of capillary tension head; this makes possible to consider the hysteresis due to large-scale variability of soil hydrological properties. The model is also capable of simulating infiltration and evaporation events and rapid change in the land surface boundary condition from one type event to another, based on a scheme used in the model for implementation of land surface boundary condition. The model was validated with the data obtained from a layered lysimeter test. The model was also used to simulate water flow under a long irrigation furrow. The results obtained with this model show better agreement with experimental measurements in comparison with a deterministic model. The possible reason for this agreement is that in the developed model, the influence of the variability of the properties of soil and effects of parameter hysteresis on water flow and water content redistribution are considered. © 2010 John Wiley & Sons, Ltd.. Source


Bagheri N.,Agricultural Engineering Research Institute | Bordbar M.,Islamic Azad University at Marvdasht
Agricultural Engineering International: CIGR Journal | Year: 2014

A descriptive survey research was undertaken in order to assess challenges facing agricultural mechanization development in Iran. The research population included agricultural mechanization experts, managers and specialists in private and governmental sections. Using proportional stratified sampling, a sample of 119 was constituted out of a total population of 809 based on the Cochran formula. Data were collected using questionnaire on which the statements were collected after literature review of research and interviews with mechanization specialists. The questionnaire was validated by a panel of experts and its reliability index was established by a Cronbach's coefficient. A pilot study was conducted with 30 questionnaires (not included in the sample population) to determine the reliability of the questionnaire. Computed Cronbach's alpha score was 75%, which indicated that the questionnaire was highly reliable. All survey data were analyzed using the Statistical Package for Social Sciences (SPSS 16.0). The results of factor analysis indicated that 69% of the variances of the challenges could be classified in seven groups, namely: programming, technical, infrastructural, managerial, economical, research and extension, and content area. From each group the most important challenges facing agricultural mechanization development in Iran include: inefficiency of subside payment methods for buying agricultural machinery, large number of time-worn agricultural machinery, incomplete collection of agricultural equipments for power generator machinery (tractor), slow trend of beneficiaries in accepting new technologies, financial weakness of agricultural beneficiaries, inefficiency of agricultural extension and education methods, and weakness of agricultural machinery producers and operators in protecting their guild benefits. Source

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