Gravity current is a phenomenon caused by density difference between two fluids and due to this phenomenon the fine sediments can be moved to the body dam and as a result causes for many serious problems for dam intake. Therefore, controlling the flow can reduce the potential problems. In this study a permeable obstacle was used to evaluate the performance of permeable obstacles for control of turbidity current. The variables were the porosity percentage of the obstacle and different concentrations of the currents. The gravity current discharges and concentrations were measured upstream and downstream of the obstacle. The results of the measured discharges showed that the obstacle efficiency in control of gravity current reduces with increasing porosity. The results of the measured concentrations also showed the same conclusion. The final results of the review sediment load and view similar trend was confirmed. After calculating water entrainment to the gravity current passing through the permeable obstacle, it was observed that with increasing porosity of permeable obstacle, the volume of water entrainment is reduced. Therefore it can be concluded due to lower volume of water entrainment, processing efficiency in controlling the gravity current using the permeable obstacle is reduced. Also, the maximum efficiency of the controlling the gravity current was measured about 73.2%.

Due to the high cost of construction of the dams, increasing the lifespan of this construction structure has been considered by water engineers. Sediments near the dam wall reduce the useful life of this structure. Constructing obstacles in the path of density currents be is one of the most widely used methods in controlling these sediments. In this study, the effect of permeable obstacles on density current head flux has been studied experimentally. The obstacles were made in the shape of trapezoid and were filled with sand particles with a diameter of one centimeter also salt were used to prepare the density current. In these experiments, the effect of inlet flow, flume slope and obstacle height on density current was investigated. Examining the variables of this study, it has been found that the reduction percentage of the density current head flux for the dimensionless ratio of height 1 is between 33.1 to 61%, for the dimensionless ratio of height 1.5 is between 43.2 to 63.3% and for the dimensionless ratio of height 2 is between 68.2 to It is 100%, also increasing the inlet flow ratio and flume slope increases the momentum of the current and thus reduces the efficiency of the obstacles. In addition, at the end, the density current head was modeled as linear and nonlinear regression.

Flood flow in rivers is often of density current type. Hence, recognizing and exploring these currents can solve some problems of sedimentation. In this study, the effect of porosity and the angle of permeable obstacles on the control and trapping of density current have been investigated in the laboratory. For this purpose, an expanded polystyrene (EPS) polymer was used with 1. 135 g/L density and average diameter of 1. 15 mm. The experiments were carried out with two concentrations (10 and 20%) and 5 porosity and 4 angles. The obstacles were made of palsy glass plates and two types of groove and cavity with 8. 2 mm width of the groove and the diameter of the cavity. The results showed that, with an increase in porosity ratio, the amount of trapping to optimum porosity decreases and then increases. The optimal porosity of the cavity and groove is 22 % and 19%, respectively. In experiments, the cavity trapping was observed more than the groove, in the concentrations of 10. 20% it was 0. 13 and 0. 14%, respectively. In addition, with the increase of the angle, the amount of trapping has reduced and its value was observed in the groove more than the cavity. The correlation coefficient in the grooves and cavities was 0. 996 and 0. 937, respectively. The major effect of obstacles, reducing velocity and slowing flow were identified as the average velocity in the cavity was 62. 3% higher than the groove. Accordingly, in the same conditions, the cavity obstacles have better performance than the groove obstacles.

This study explored the effect of porosity and installation angle, thickness (dimension) and second layer of permeable obstacles on density current control and trapping in the laboratory. For this purpose, an insoluble suspended polymer and two types of groove and cavity obstacles made from plexiglass sheets were selected. The experiments were conducted with two different concentrations, five different porosities, four different angles, four different thicknesses and two obstacle layers. The results showed that the optimum porosities for cavity and groove obstacles were 22 and 19%, respectively. In all experiments, the cavity trapping rates of 0.13% and 0.14% at 10% and 20% concentrations were higher than those of groove trapping. In addition, by increasing the angle, the rate of trapping decreased and its value was observed in the groove with the correlation coefficients of 0.995 and 0.981 compared to the cavity. The major effect of obstacles was found to be the flow deceleration where the average velocity in the cavity was obtained 3.62% higher than that in the groove. For the increased thickness with 10% porosity and groove type, the passage of materials from the obstacle further increased. By creating the second layer of obstacle, the passage of materials from the obstacle in the both groove and cavity increased, and the optimal distance of the second obstacle was 2.25 m from the first one.

Introduction: Density currents are often the main cause of sediment transport in deep water and reservoirs. To prevent sedimentation in critical locations of dams, various methods have been proposed, including placing obstacles in the path of these currents. Methods: In this study, the effect of discharge, inlet concentration, slope and height of trapezoidal permeable obstacle on the behavior of salt density current has been investigated experimentally. 72 experiments were performed with variable discharge of 0. 7, 1. 2 and 1. 7 liters per second and variable concentrations of 20 and 25 g/l, slope of 0. 5%, 1% and 1. 5% and obstacle height of 1, 1. 5 and 2 times the body of density current. The percentage of flux reduction was determined and the effect of other parameters was evaluated Findings: The results showed that the three parameters of slope, concentration and inlet discharge are the factors affecting the momentum and by increasing each of these parameters, the efficiency of obstacle with heights of 1 and 1. 5 times body density current decreases. In the case of obstacle with a height of 2 times the body, when the current collides with the obstacle, there is a lot of turbulence, which decreases the momentum of the current, and complete control is achieved. Conclusion: Thus, the average percentage of flux reduction for the dimensionless ratio of height 1 is about 38%, for the dimensionless ratio of height 1. 5 is about 52% and for the dimensionless ratio of height 2 is about 86%. Finally, linear and nonlinear regression of the average percentage of flux reduction head data was obtained.

Understanding and studying the river flooding, which in most cases is density current, can help to reduce adverse effects of sedimentation. To this end, the creation of obstacles in the bed of stream will be effective. In this paper, the effect of thickness (dimension) and the second layer of permeable obstacles on the control and trapping of density current is investigated experimentally. For this purpose, two types of groove and cavity obstacles with grooves and cavity diameters equal to 3 mm and made of plaque glass were used. Density currents were created by adding an insoluble, suspended polymer of expanded polystyrene with a mean diameter of 1. 15 mm and a density of 1. 155 g / l. The experiments utilized two different concentrations (10 and 20%), five different porosities, four different angles, four different thicknesses and two barrier layers. The results showed that the density current process with 10% porosity of the groove obstacle increased with increasing thickness. The second layer of obstacles have increased the material passage through both groove and cavity obstacles. This increase was recorded in the groove type of 1. 96 and the cavity type of 2. 34. Investigations showed that the optimal distance of the second obstacle from the first was 2. 25 meters. According to the results, under similar conditions, cavity obstacles always perform better than groove ones.

Detecting and preventing incidents with obstacles is a challenging problem. Most of the common obstacle detection techniques are currently sensor-based. Mobile robots like Small Unmanned Aerial Vehicles (UAVs) are not able to carry obstacle detection sensors such as radar; therefore, vision-based methods are considered, which can be divided into stereo and mono techniques. Mono methods are classified into two groups: Foreground-background separation, and brain-inspired methods. Brain-inspired methods are highly efficient in obstacle detection. A recent research in this field has focused on matching the Scale- Invariant Feature Transform (SIFT) points along with SIFT size-ratio factor and area-ratio of convex hulls in two consecutive frames to detect obstacles. However, this method is not able to distinguish between near and far obstacles nor the obstacles in a complex environment and, thus, is sensitive to wrong matched points. This paper aims to solve the aforementioned problems through using the distance-ratio of matched points. Then, every point is investigated for distinguishing between far and near obstacles. The results demonstrated the high efficiency of the proposed method in complex environments. The least achieved accuracy of the algorithm was 60.0%, and the overall accuracy was 79.0%.

Bushehr is one of the famous and historical ports. it has an important place in economy politics history and sailing of Iran and Persian gulf. in duration of Afsharieh Zandieh Qajar and even initial Pahlavi Bushehr port was not the largest port in Sothern iran but also considered as the most important and famous ports of Persian gulf. Near about 20 consulates from different countriesare located in the region. In 19 th century economy of Bushehr was basedon Business and commercial sailing. In crease in Bushehr commercial sailing in 19 th century resulted in forming a powerful commercial societythere in a way that great businessmen and capital owners migrated from different parts of iran and resded in bushehr. Despite of this prominent historical place in second half of 20th century bushehr dropped behind and left its place to rivals. As the moment it is considerd as the second class ports in Persian gulf. this research aims at exploring historical obstacles in development of bushehrand consequently the key question would be as: what are the historical obstaclers in deveploment of busheh? The main hypothesis in this study is weakness and degeneration of bushehr commercial society along with some other factores which ended in bushehr decline part. Obviously other factores will be also be studied in this research. Results show that bushrhr development dependes on resolving historical obstacles.

In this everchanging world, any policy - makersand expertshave been focused on the problems of employment and it"s complexities. It is obvious that the frame of country"s youth population and increasing work inquiries, requires more attention to this phenomenon. The fact is that, in due to change in traditional economies, in providing imployment and generating production, some temporary industrial projects, are not efficient. In other words, in today"s country situations, which have been most affected by external elements, to decfease the problem of unemployment, the new job opportunities should be defined and introduced to the society. In this paper, the focus woutd be on analysing the infrastructure obstacles facing the problems of country"s unemployment. Finally, with more attention to the different economic sectors with high potential, educational system and production development, the ways that can get rid of this crisis, will be presented.