This study includes obstacle avoidance plan based on controlling the pitch angle – depth and the use of forward looking sonar for an Autonomous underwater vehicle (AUV). The forward looking sonar with vertical and horizontal scanning capability provides a measure of the distance and height of the obstacle to the guidance system. The guidance system determine the degree of vertical overlap of the obstacle with the sonar view window and using the dynamics of the device in the vertical channel, convert the angle of overlap to the rate of change of depth and thus the safe reference depth to avoid collision. Performing the optimal depth maneuver on the vertical plane leads to significant reduction in deviation from the main path and distance compared to conventional methods for bypassing the obstacle in the horizontal plane. This feature along with simple math makes it more attractive to use for devices with fast-dynamic. The results of the implementation in the context of a six-degree-of freedom model of an AUV indicate the proper performance of the proposed method of obstacle avoidance.

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.

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.

Hydraulic structures in some cases, cause to produce obstacles in path of the flow that create oscillating vortices in downstream of the obstacles. Vortices produce oscillating forces to the obstacle that are harmful for the stability of structure. In recent years this phenomenon is used to create clean energy. In this study, oscillation of an obstacle in the presence of a fixed obstacle at the upstream was examined. The experiments on triangular block were carried out under varying discharge and different upstream distances. The main objective of this study was to investigate the effect of parameters of velocity and upstream obstacle distance on the oscillation frequency. Using dimensional analysis, the dimensionless parameters of Strouhal number, Reynolds number and ratio of distance to diameter were obtained. The charts of the relationship of the Reynolds number and also the ratio of distance to diameter vs. the Strouhal numbers were plotted. Finally, a new relationship was presented using data analysis and spss20 software to estimate the Strouhal number. Verifying the proposed relation, confirmed a fairly good prediction of this relation.

Analysis of the inverse kinematics of redundant manipulators is one of the nesseccary tools in various robotic fields such as design, motion planning and control of these systems. Since, there is not an analytical solution for the inverse kinematics of several redundant manipulators, numerical approaches are needed to execute and investigate in this field. In this paper, combination of the neural networks, fuzzy systems and quadratic programming is used to obtain the joint variables. According to the proposed approach, seven neural networks are considered according to the each joint variable and by adaptation of the neural network’s weights, suitable configurations of the robot is determined to track a desired trajectory in the Cartesian space. Meanwhile, initial weights of the neural networks are obtained by fuzzy systems based on the vicinity of the endeffector to desired point and feasibility of the joint variables. Obstacle avoidance scheme is performed by investigation of the conditions including choosing the joint variables that involved in the equations of the arms constraints and determination of the most critical arm. In order to establish the constraints of the problem in the quadratic programming, realization of the Kun-Tucker conditions will be used. Evaluation of the proposed approach will be carried out on the PA-10 manipulator by simulation and analysis of the results.