Research Paper
Zoheir Saboohi
Volume 12, Issue 3 , September 2019, Pages 1-13
Abstract
In this paper, the design of a diffuser for a suction type subsonic wind tunnel equipped with three axial fans has been taken into account by CFD. The tunnel test section has a 140 cm height and 195cm width. For numerical modeling the axial fans that contains 10 rotor blades and 13 stator blades 3D modeling ...
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In this paper, the design of a diffuser for a suction type subsonic wind tunnel equipped with three axial fans has been taken into account by CFD. The tunnel test section has a 140 cm height and 195cm width. For numerical modeling the axial fans that contains 10 rotor blades and 13 stator blades 3D modeling to simulate the impeller have been used. The 3D modeling to simulate the impeller method provides an adequate means for simulating the swirl effects of air flow. The best geometrical characteristics have been selected for designing the optimal performance for the diffuser. The final design includes a circular diffuser which incorporates a 4 degree equivalent cone angle. This study also suggests that the circular scheme is superior to the triangular and fitted design aspect of the total pressure loss and the volumetric flow rate.
Research Paper
Saeed Zohoori; saeed shakhesi
Volume 12, Issue 3 , September 2019, Pages 15-30
Abstract
Using surface guided wave is one of the most reliable methods of structural health monitoring. Mostly the bulk wave is preferred for identification of internal defects, which is inefficient in localizing the surface cracks. In this paper the procedure of ultrasonic surface wave tomography for crack detection ...
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Using surface guided wave is one of the most reliable methods of structural health monitoring. Mostly the bulk wave is preferred for identification of internal defects, which is inefficient in localizing the surface cracks. In this paper the procedure of ultrasonic surface wave tomography for crack detection in an aluminum plate is investigated and applied for three cracks with the length of 4, 7 and 10 milimeters. Analytical equations and numerical simulations are used to extract dispersion curves as a means for selection of plate thickness and piezoelectric characteristics. Layout selection for transducers and providing numerical and experimental models are the next steps of inspection procedure. All the piezoelectric discs are actuated respectively. Meanwhile, other piezoelectric elements are used as sensors and their received signal is stored in both healthy and defected structures for both numerical and experimental models. Definition of signal difference criteria, signal reconstruction and tomogram generation are the last steps of the procedure presented in this paper.
Research Paper
Masoud Taefi Feijani; Abbas Alimohammadi Sarab; Mohammad Javad Valadan Zoej
Volume 12, Issue 3 , September 2019, Pages 31-42
Abstract
Forest Canopy Density Mapper is a method based on spectral indexes integration in forest canopy density classification. In this paper, a data integration procedure is used to improve the result. In this respect, SFIM method and spectral response algorithm is utilized without a bad effect on the spectral ...
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Forest Canopy Density Mapper is a method based on spectral indexes integration in forest canopy density classification. In this paper, a data integration procedure is used to improve the result. In this respect, SFIM method and spectral response algorithm is utilized without a bad effect on the spectral and radiometric properties of bands. In the following, Landsat images of Hyrcanian forests in the north of Iran were used to implement the conventional and improved methods. Also, the ground measurements including grass-land, thin forest, semi-dense forest and forest is utilized for evaluation. The result shows that the forest canopy density model is inefficient in the thin and semi-dense forests. Alternatively, the results in the dense forest and grass land is reliable. Additionally, the improvement of the proposed method in these two areas is clearly seen. It seems that a high resolution image should be used to improve the accuracy of the forest density classification in the semi-dense and thin forests.
Research Paper
Mohammadvali Arbabmir; Masoud Ebrahimi Kachoei
Volume 12, Issue 3 , September 2019, Pages 43-54
Abstract
In the last decades, the visual navigation system has been investigated by many researchers as an aided navigation system for Inertial Navigation System (INS) in the Unmanned Aerial Vehicles (UAV). In this research, for improving the INS errors a new approach based on feature tracking algorithm is used. ...
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In the last decades, the visual navigation system has been investigated by many researchers as an aided navigation system for Inertial Navigation System (INS) in the Unmanned Aerial Vehicles (UAV). In this research, for improving the INS errors a new approach based on feature tracking algorithm is used. In this approach, in order to estimate the feature points in the current image, the INS states, the feature points of the previous image and dynamic equations are used. Also, in this approach, for improving the estimation of terrain points, the outlier estimated feature points delete. Furthermore, in this article, for improving the altitude error, a barometer is used by the mentioned vision navigation system. The simulation results illustrate the desirable accuracy of the vision system and barometer observations in the update step of Extended Kalman Filter (EKF) and remarkable performance of integrated navigation system for calculating the UAV navigation parameters.
Research Paper
Mohammad Hosein Shafiei; negin vazirpour
Volume 12, Issue 3 , September 2019, Pages 55-61
Abstract
In this paper, the approach of discrete-time partial stabilization is employed to design a robust three-dimensional guidance law against maneuvering targets. In the partial stabilization method, the considered system is divided into two sub-systems which achieving to asymptotic stability is desirable ...
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In this paper, the approach of discrete-time partial stabilization is employed to design a robust three-dimensional guidance law against maneuvering targets. In the partial stabilization method, the considered system is divided into two sub-systems which achieving to asymptotic stability is desirable only for the first one. One of the advantages of this paper is to design a discrete-time guidance law even with limitations and difficulties in discrete-time Lyapunov theorem. The Lyapunov function has been chosen based on the physics of the guidance problem (making the rate of line of sight (LOS) rotation close to zero). In this paper, it is shown that there is no possibility for asymptotic stabilization of the guidance problem in the case of maneuvering targets. Thus, it has been sufficed to limit the rotation rate of LOS to a small value which will guarantee the missile hit to the target in a short time. Simulations results show the appropriate performance of the proposed guidance law.
Research Paper
investigating space radiation
Hamideh Daneshvar; Masoud Khoshsima; Abolfazl Dayyani
Volume 12, Issue 3 , September 2019, Pages 63-71
Abstract
One of the important issues to be considered in the design of space systems is the attention to the difference between the terrestrial and space environment. This issue changes the design and affects all subsystems of space systems. Radiation damage due to space radiation can cause disturbances in the ...
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One of the important issues to be considered in the design of space systems is the attention to the difference between the terrestrial and space environment. This issue changes the design and affects all subsystems of space systems. Radiation damage due to space radiation can cause disturbances in the functioning of space systems. In this paper, with a computational approach examines the most important radiation damage involving TID, DD and SEU in two satellites that have missions in LEO orbit. The calculations were performed using the OMERE software and finally, a comparison was made between different models for achieving different types of radiation damage.
