Showing 4 results for Protection
M. Bakhshoodeh, H. Shafiei,
Volume 10, Issue 3 (10-2006)
Abstract
Evaluating different aspects of government policy in terms of their indirect and welfare effects has been always of interest. In this study, the effects of gauranteed purchasing policy on land under cultivation and yields of cotton, potatoes and onions were investigated in Fars province. For this purpose, a Nerlove model was applied to time series data of 1972-02 after testing their stationary to estimate the cultivated lands and yields functions of these products. The use of protection rates as explantory varrables is one of the interesting characteristic of such a model. Although the results were not similar for all the products, the indication is that the policy has not had significant influence on the land areas and yields of cotton, potatoes and onions. However, taking into account that the policy has been recentely commenced in Fars, and that the policy takes time to become effective, the policy may result in different outcomes in the long run.
Sh Mohammad Nejad Kiasari, M Safaee, Sh Nourozi, H Ahmadian, A Mataji,
Volume 13, Issue 48 (7-2009)
Abstract
Determination of suitable species is the most important factor in success of forestation in unfavorable conditions. One of the least costly and the shortest ways for introduction of adaptable species in an area is recognition of the plants that grow naturally. The objective in this study was to find out the effects of protection and water spreading operations on the quantitative improvement of Greek Juniper seedlings. In this study, the areas of water spreading station (Research station of Poshtkoh Water spreading) and an area in western section of water spreading station (an area as control) along the Poshtkoh watershed were chosen. The research was performed on counting of Greek Juniper (Juniper excelsa) in each of two areas. The ratio estimation method was used in a randomized systematic design in strips with the width of 50 meters and 200 meters apart for registration of qualitative parameters of Greek Juniper (Juniper excelsa). The total surface of areas was 600 ha and inventory with intensity of 16 percent has been done. This study showed that in spite of the less number of Greek juniper trees per ha in the station (0/104) in relation to the number of Greek juniper trees per hectare out of the station (0/666), the number of the Greek juniper seedlings in the station was eight times (8.34) more than the number of the Greek juniper seedlings out of the station. As to the effect of protection and water spreading operations on natural growth and increase of number of Greek Juniper seedlings in the station, forestation using this species in this area is recommended.
E. Jasemi Zargani, S. M. Kashefipour,
Volume 21, Issue 3 (11-2017)
Abstract
Spur dikes are the most common hydraulic structures for river bank protection. Since the construction of this structure causes higher velocities around it, this structure is exposed to erosion. Riprap around the structure nose is one of the most common and economic way to protect spur dike. The main aim of this study is to investigate the riprap stability in a mild 90 degrees bend. Experiments were conducted in a laboratory flume with a 90 degree bend. After specifying the critical spur dike along the bend, this spur and one before and one after it were protected by riprap. The variables were the length of the structure, spur space, riprap size, Froude number, and the amount of submergence, and 205 experiments were carried out in this flume. Finally an experimental equation was developed based on the flow and geometric parameters of submerged spur dike, which can be applied for designing the riprap size.
M. Dorosti, M. Shafai Bajestan, F. Amirsalari Maymani,
Volume 22, Issue 2 (9-2018)
Abstract
Scour around structures in the river is the most destructivr factor of these structures. Therefore, different methods have been studied to reduce it. A creation slot is one of these methods in the suitable position that can be modified to control the flow pattern scour. In this study, the effects of using two parallel chord rectangular slots in the single spur dike with the opening of the effective spur dike area of 10% and a ratio of a/b = 4 (a and b are the length and width of the slot) on two occasions were investigated, one near the bed (near the slot spur dike) and the other near the water surface (away from the nose of spur dike) on the pattern of erosion and sediment around the nose triangular spur dike in clear water conditions. In all experiments, flow depth and angle of the triangular spur dike installation angle were constant. The experiment was done in different hydraulic conditions (Froude number 0.287, 0.304, 0.322). Eventually the results of spur dike without slot (control experiments) were compared. The results showed the slot near the bed toward the slot near water surface and control experiments had a better performance in reducing the maximum depth of scour and deposition of sediments washed to the outer bank. The reduction of the maximum depth of scour at the slot near the bed in Froude numbers 0.287, 0.302 and 0.322, respectively, was compared to the control experiments , which were 23%, 13% and 24%, respectively, and then compared to the slot near the water surface, which was 60%, 40% and 32% respectively.
