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In order to study the effects of subsidies targeted plan on Iran agricultural sector, a regional agricultural sector model is made. For this purpose, Iran is divided into 9 equal radar regions agro-climatologically. Then agricultural sector is modeled within 14 commodity groups and 23 production activities using positive mathematical programming (PMP) method and applying generalized maximum entropy (GME) approach. The results indicate that making subsidies targeted by increasing prices of inputs (irrigation water, fertility, pesticide and machinery), escalating energy prices for poultry and dairy farms and raising transportation cost, leads to decrease total surplus of agricultural sector, decrease in many crop and livestock activity levels in different regions, increase in prices, decrease in consumption and exports and increase in imports of some agricultural products. According to the results, if subsidies targeted policy is mixed with support payments to producers, dependent on amount of support payment, the social surplus of agricultural sector may decrease or increase. A support payment equal to 25 percent of production costs can compensate losses of producers due to targeted subsidies, transmit loss of social welfare to zero and decrease volatility of economic variables such as activity levels, price and quantity of consumption of commodity groups.  

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Prediction of spray droplet diameter distribution depends on the various parameters such as physical properties, fluid velocity, and discharge environment and injector geometry. The stage of forming droplets has a great variety in size and therefore will be predictable with a statistical approach. The maximum entropy principle is one of the most popular and best ways to predict the spray droplet size distribution along with the conservation equations. Due to some drawbacks in this model, the predicted results do not match well with the experimental data. It is suggested to improve the available energy source in the MEP model equation by numerical solution of flow inside the injector based on the CFD technique. This will enhance the calculation accuracy of the turbulent kinetic energy of the output spray. In fact, by using this sub-model in the maximum entropy model, the prediction accuracy of the spray characteristics is improved. Also, the requirement of the maximum entropy model to the experimental data as inputs has been reduced. By the present coupled model, the effect of spray upstream on the droplet size distribution can be considered with a good accuracy. The results show a close agreement with the available experimental data.

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Water is considered as the most important component, but a limiting input, for agricultural production in Iran. In the context of water resources management, due to the limited availability of water and high cost of supplying it to the users, improvement of water use productivity has been regarded as one of the most appropriate approaches to manage water demand. Various tools have been applied for water management policy in the context of preventing high levels of water deficit. In the present study, different policy scenarios related to water supply management are assessed. These include estimation of the impacts of each policy scenario on physical and economic productivity indices and employment, using positive mathematical programming methods and maximum entropy. This methodology was applied to water use in the Qazvin Plain, Iran. Results suggested that application of these policy scenarios not only decreased water consumption but also generated desirable social and economic effects. Results of the ranking showed that the policy of imposing tax on input generated the best results for the study area. However, it is admitted that selection of the best policy scenario is dependent on the weight that policy makers would select for various indicators.