صمد مرادی

The researched area is located around the city of Yasouj and is part of the Karun Bozorg basin. The main purpose of this study is to investigate the dominant structural characteristics and their effect on the discharge of springs and the control of underground water flow in their reservoir rocks. In this research, by using remote sensing data, GIS, ground observation data of water resources and analysis of discharge data using their recession curve, the relationship between structural factors on the frequency and discharge regime of representative springs was investigated. In the first step, a lineament map was prepared from satellite images and geological maps, and then the dependence of the location of the springs and their discharge regime with these structures was analyzed. The results showed that the occurrence of structural phenomena such as folds, faults, joints and fractures on the one hand and appropriate precipitation on the other hand, have created suitable conditions for the development of karst aquifers. The emergence of springs along the faults also shows the importance of the structural role in the region. These faults control the main directions of water flow in the karst basin, whereas the joints and fractures related to them play a role in the secondary directions of the flow. The analysis of fractures ishowed that the average opening of more than 20 mm and the slope of the bedding plane of about 50 degrees has facilitated the penetration and transfer of water in the catchment area of the springs

This paper deals with form-finding and free vibration analysis of a pre-stressed class-one triplex tensegrity structure. The form-finding is performed via a two-step procedure, the nodal coordinates connectivity matrix, and structural element force density determination. Accordingly, the possible states for the nodal coordinates and the structural force density of the triplex prism have been determined by trial and error (based on topology and member type knowledge) to satisfy the force density, and equilibrium matrices rank requirements. Based on different structural topologies, the equation of the motion in the frequency domain for free vibration analysis of the system is derived using the spectral element approach and dynamic shape functions. Simulations are provided for different system heights and the top-bottom aria ratios and compared with the FEM. The numerical simulations in the form of a comparative study of the natural frequencies of triplex tensegrity prism with different heights and cross-sections represent the system’s robustness with different topologies for single or multi-stage applications.

This paper presents a study concerning active vibration control of a smart flexible spacecraft during attitude maneuver using thrusters and reaction wheels (RW) in combination and piezoelectric (PZT) sensor/actuator patches. The large-angle maneuver and residual vibration of the spacecraft are controlled using an extended Lyapunov-based design (ELD) and strain rate feedback (SRF) theory for a two-mode mission. The single-axis fully coupled nolinear rigid-flexible dynamic of the system is derived applying a Lagrangian approach and Finite Element Method (FEM). The overall stability of the system including energetic terms covering a hub and two flexible appendages, torsional spring, RW, and PZT dynamics, has been proved and the control law has been derived accordingly. A pulse-width pulse-frequency (PWPF) modulation is used to alleviate the excitations of high-frequency flexible modes. However, due to the fast maneuver, there are still residual vibrations in the system. Hence, the SRF algorithm using PZT is applied to prepare further vibration suppression. A great feature of the proposed hybrid actuator system is the switching time of the thrusters and RW, which is based on total system energy. The numerical results for a flexible spacecraft with large-angle, agile, and precise maneuver requirements through a comparative study verify the merits of the proposed approach.

The free and forced vibration analysis of a rotating large flexible structure with a single crack is investigated using the Homotopy Perturbation Method (HPM). The crack is modeled with a torsional spring element on a structure that follows the Euler-Bernoulli theory. The nonlinear equations of motion of the co-rotational system considering centrifugal forces are derived using the calculus of variation and the Assumed Mode Method (AMM). Applying the Galerkin method, the spatial domain is extracted and the time domain is transformed into a second-order nonlinear differential equation. The results of time response, phase plane, and bifurcation diagrams for different functional parameters variations such as base angular velocity, crack position and stiffness have been analyzed. Moreover, it is shown that as the base angular velocity increases, a tensile force appears along the cracked structure axis, stiff it, and shifts the backbone to the right, this can highly affect the nonlinear features of the system.

This paper presents a study concerning active vibration control of a smart, flexible spacecraft during attitude maneuver using thrusters/ a reaction wheel and piezoelectric patches. The large-angle maneuver and residual vibration of the spacecraft are controlled utilizing an extended Lyapunov-based design (ELD) and strain rate feedback (SRF) theory. The single-axis fully coupled rigid-flexible dynamic of the system is derived applying a Lagrangian approach and Assumed Mode Method (AMM). The system's overall stability, including energetic terms covering a hub, two flexible appendages, PZT sensor/actuator, RW dynamics, and torsional spring, has been proved, and the control law has been derived accordingly. A pulse-width pulse-frequency (PWPF) modulation is used to alleviate the excitations of high-frequency flexible modes. However, due to the fast maneuver, there are still residual vibrations in the system. Hence, the SRF algorithm using PZT is applied to prepare further vibration suppression. The performance of the proposed extended controller is compared to the conventional Lyapunov and pole placement control algorithms. The numerical results for simultaneously large angle attitude and vibration control of a flexible spacecraft through a comparative study verify the merits of the proposed approach.

This paper presents advanced controllers for maneuver and vibration control of dynamic systems with rigid-flexible coordinates. Stability analysis of such a control system is one of the important issues. The control of flexible spacecrafts or flexible manipulators with rigid-flexible body dynamics has challenges that encourage designers to develop advanced controllers. Each of these control systems has some advantages and some disadvantages. The purpose of the present paper is to study various control design methods and to review the literature by addressing the weaknesses and strengths of existing techniques.

The high hillsides of the Tehran metropolis are prone to landslides due to the climatic conditions and the geological, geomorphological characteristics of the region. Therefore, it is vitally important that a landslide susceptibility map of the region be prepared. For this purpose, thematic layers including landslide inventory, lithology, slope, aspect, curvature, distance to stream, distance to fault, elevation, land use, and precipitation were used. Next, weighted raster thematic maps with assigned values for their classes were multiplied by the corresponding weights and combined to yield a simple map where each cell has a certain landslide susceptibility index (LSI) value. After reclassification, this represents the final susceptibility map of the study area. Finally the three maps were compared to assess the strength of the corresponding methods. In this study area, 74% of landslides occurred in highly or completely shaly units. Lithology, slope, distance to fault and distance to stream data layers were found to be important factors in the study area. The outcome of this comparison was the conclusion that the active landslide zones do not completely fit into the high and very high susceptibility classes. However, 99.6% of these landslide zones fall into the high and very high susceptibility zones of the bivariate statistics (WI) method, or 74.5% in the case of the analytic hierarchy process (AHP) method and 97.2% with the frequency ratio (FR) method. The results showed the WI and FR methods to give a more realistic picture of the actual distribution of landslide susceptibility than the AHP method.

This study examined students’ profiles regarding motivation orientations and tested whether profile groups differed on cognitive, affective and social outputs. Study was performed on Tabriz university students. The sample consisted of 370 students, which were randomly selected. The instrumentals employed in the study were The Academic Motivation Scale, Prosocial Goals, Classroom Attitudes and Learning Strategies Questionnaires. Hierarchical cluster analysis method, MANOVA and post Hoc Tests were used to determine the optimal cluster structure of students. The results revealed that 4 profiles: (a) students with high level of autonomous motivation (b) students with high level of interojected regulation and internal motivation, (c) students with high levels of both autonomous and controlled motivations and (d) students with low levels of both controlled and autonomous motivation but high levels of amotivation. In addition, it was found that students in the high autonomous/high controlled group reported the highest degree of cognitive, affective and social outputs.