Farhad Fani Saberi; Mansor Kabganian; Alireza Fazlyab; Abbas Ajorkar
Volume 9, Issue 1 , May 2016, , Pages 25-35
Abstract
In this paper, a robust attitude control algorithm is developed based on backstepping-sliding mode control for a satellite using four reaction wheels in a tetrahedron configuration. In this method, asymptotic stability of the proposed algorithm has been proven in the presence of reaction wheels dynamic ...
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In this paper, a robust attitude control algorithm is developed based on backstepping-sliding mode control for a satellite using four reaction wheels in a tetrahedron configuration. In this method, asymptotic stability of the proposed algorithm has been proven in the presence of reaction wheels dynamic model based on Lyapunov theory. Then, in order to evaluate the performance of the proposed algorithm, a low-cost real-time prossecor in the loop test bed is provided. The presented test bed is capable of real-time assessing the attitude backstepping-sliding mode control algorithm. In this test bed, real-time modeling of satellite dynamic, environmental disturbances and reaction wheels are achieved in a simulator computer and the proposed control algorithm performance is investigated by implementing it in an electronic control board of the prossecor in the loop test bed.
Hamed Arefkhani; Mehran Mehdi-Abadi; Seyed Mohammad Mehdi Dehghan
Volume 9, Issue 2 , September 2016, , Pages 25-34
Abstract
In this paper, magnetic spin control using Spin and B-dot control laws have been studied in a lab environment. Evaluation of this control laws is done by a "three degrees of freedom air-bearing simulator". Due to the inherent simulator limitations, laboratory test results are visible only on one axis. ...
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In this paper, magnetic spin control using Spin and B-dot control laws have been studied in a lab environment. Evaluation of this control laws is done by a "three degrees of freedom air-bearing simulator". Due to the inherent simulator limitations, laboratory test results are visible only on one axis. Therefore, to evaluate these three-axis laws precisely, evaluation modeling is discussed by comparing the simulator dynamic and kinematic equations with the results of laboratory experiments. After evaluation of the modeling process, simulation of three-axis control law is conducted. Since the validated model shares same basis with satellite model equations except the torque disturbances caused by the distance between the center of the mass and the center of the rotation, it can be assured that these control laws are suitable for three-axis control of a satellite. Test results indicate appropriate performance of control laws.
arman samadi; Masoud Ebrahimik; Hossein Jahanbakhsh
Volume 10, Issue 3 , December 2017, , Pages 25-39
Abstract
The main objective of this research is to improve the distribution of electrical potential on spacecraft surfaces by changing the surface coatings to reduce the risk of electrostatic discharge in the spacecraft. For this purpose, SPIS software, the EU standard software for modeling and simulating the ...
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The main objective of this research is to improve the distribution of electrical potential on spacecraft surfaces by changing the surface coatings to reduce the risk of electrostatic discharge in the spacecraft. For this purpose, SPIS software, the EU standard software for modeling and simulating the interaction of space plasma with the spacecraft is used. The spacecraft has 8 nodes, and each node is related to a particular substance. The simulations were compared with the variation in the materials of these nodes in terms of differential electric and floating potential. Investigating materials that differed in the differential electric potential of zero showed that they are conductive materials. In order to choose among several conductive materials, these materials were compared in terms of electric floating potential. Simulations on satellite surfaces showed an average of 11% improvement in the electrical potential on surfaces
space law
s. Hadi Mahmoudi; Rohollah Rohami; Hamid Heidaree
Volume 13, Issue 1 , March 2020, , Pages 25-38
Abstract
By incorporating provisions in Space Law documents, gateway for commercial space activities was opened. From the era of space treaties, commercial uses always are getting faster Due to the increasing of players and development of new technologies. Although the current framework does not comply with the ...
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By incorporating provisions in Space Law documents, gateway for commercial space activities was opened. From the era of space treaties, commercial uses always are getting faster Due to the increasing of players and development of new technologies. Although the current framework does not comply with the legal issues arising from rapid and ongoing process, the provisions of these instruments have so far been the basis for action by governments & Non-governmental Orgs. in carrying such activities. This paper assuming the need to further development of space law in terms of its commercial dimension, but intends to consider the possibility or refusal of commercial activities and the status of soft law through international cooperation and development of national space legislation to relative normality of space. An initial review indicates the prescription of these activities, despite the cessation of contractual normalization and existence of constraints derived from principles such as the prohibition of appropriation, the common heritage of mankind & equitable sharing.
Space systems design (spacecraft, satellites, space stations and their equipment)
Ghasem Heydari; Maryam Kiani; S. Hossein Pourtakdost; Mohammad Sayanjali
Volume 13, Issue 3 , September 2020, , Pages 25-38
Abstract
Halo orbits are of importance for observation and study of the space due to their specific characteristics including the orbital position and the periodic motion. In this regards, present paper has focused on optimal trajectory planning to transfer to halo orbits. To this aim, homotopy approach has been ...
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Halo orbits are of importance for observation and study of the space due to their specific characteristics including the orbital position and the periodic motion. In this regards, present paper has focused on optimal trajectory planning to transfer to halo orbits. To this aim, homotopy approach has been adopted for optimal trajectory design. This approach has improved the convergence rate and insensitivity of the problem to initial guess. The designed trajectory transfers a spacecraft orbiting the Earth to a Halo orbit around Lagrangian point L1 of the Earth-moon restricted three-body system. The propulsion system has been assumed to be low thrust with constant specific impulse. Homotopy approach has a broad domain of applicability and methods in which continuation method has been employed here among them. The optimal designed trajectory minimizes the fuel consumption via transforming solution of the minimum energy problem utilizing the homotopy approach. This approach simplifies solution of the complex problem of minimum fuel indeed.
Space systems design (spacecraft, satellites, space stations and their equipment)
Ramin Kamali Moghadam; Mohammad Taeibi Rahni; Salar Heyat Davoudian; Reinhard Miller
Volume 15, English Special Issue , May 2022, , Pages 25-33
Abstract
Superhydrophobic coatings can be made by creating a micro-sized structure on a surface providing super-repellent properties which has many applications in aerospace, defense, automotive, biomedical and engineering. Numerical simulation of drop dynamics and motion on a superhydrophobic surface helps us ...
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Superhydrophobic coatings can be made by creating a micro-sized structure on a surface providing super-repellent properties which has many applications in aerospace, defense, automotive, biomedical and engineering. Numerical simulation of drop dynamics and motion on a superhydrophobic surface helps us understand control and building surface textures and find optimum micro structured coatings of maximum hydrophobicity. In the present work, the dynamics of drops on superhydrophobic inclined micro-structured surfaces is studied, using a finite element method. Effect of microstructures on droplet behavior on a superhydrophobic surface is investigated using different microstructures. The governing equations and important dimensionless numbers are described and a numerical algorithm is introduced. The validation of the numerical algorithm is performed by simulation of drop motion attached to an inclined surface. In addition, droplet movement on the micro structured surface is numerically simulated on smooth and microstructure surfaces in the same conditions. Comparison of the results shows the effect of microstructure coating on the surface hydrophobicity properties.
Space systems design (spacecraft, satellites, space stations and their equipment)
Mostafa Jafarpanah; Hassan Naseh
Volume 14, Issue 4 , December 2021, , Pages 25-33
Abstract
The purpose of this paper is to present the cost estimation model for Cryogenic/Semi-Crogenic space propulsion systems. Therefore, the space propulsion system selection from fuel and oxidizer type aspect and achieving the maximum performance and minimum cost has been performed. Then, the fuel and oxidizer ...
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The purpose of this paper is to present the cost estimation model for Cryogenic/Semi-Crogenic space propulsion systems. Therefore, the space propulsion system selection from fuel and oxidizer type aspect and achieving the maximum performance and minimum cost has been performed. Then, the fuel and oxidizer pair samples based on the mass – energy specifications (engine weight- specific impulse) and engine operation cycle type with respect to the mission possibility has been determined. To this end, the algorithm for implementing and using the proposed cost estimation model has been designed. In this algorithm, the proposed cost estimation model is developed based on the existing cost estimation relationship and verified by comparing the existing models. Finally, the outputs in the algorithm are cost-performance (specific impulse) graph for the seven fuels and oxidizer pairwise, engine selection based on achieving maximum specific impulse and providing the design space searches for the cost and time optimization in the space projects.
Space subsystems design: (navigation, control, structure and…)
M. Navabi; Nazanin Safaei
Volume 13, Issue 4 , December 2020, , Pages 25-35
Abstract
Several novel control techniques have been created as a result of the diversity of researches which are conducted about the problem of satellite attitude control. There are always uncertainties in the problem of satellite attitude control in the space missions. Therefore, Adaptive control is a method ...
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Several novel control techniques have been created as a result of the diversity of researches which are conducted about the problem of satellite attitude control. There are always uncertainties in the problem of satellite attitude control in the space missions. Therefore, Adaptive control is a method which is taken into consideration. High computational volume is one of the problems of adaptive control technique. In this paper, a control technique which is based on optimization concepts is introduced for the problem of satellite angular velocity and attitude control. Also, it's developed based on the three-dimensional special orthogonal group, and it's not faced by a singularity problem. For comparison, the linear quadratic regulator (LQR) control technique is simulated. Finally, the results of the simulations show that the performance of the presented adaptive control technique is optimal, and this method is robust to inertia changes.
M. A. Sharifi; F. Samadzadegan; Saeed Saeed Farzaneh
Volume 2, Issue 2 , July 2009, , Pages 27-38
Abstract
Celestial positioning has been used for navigation purposes for many years. Stars as the extra-terrestrial benchmarks provide unique opportunity in absolute point positioning. However, astronomical field data acquisition and data processing of the collected data is very time-consuming. The advent of ...
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Celestial positioning has been used for navigation purposes for many years. Stars as the extra-terrestrial benchmarks provide unique opportunity in absolute point positioning. However, astronomical field data acquisition and data processing of the collected data is very time-consuming. The advent of the Global Positioning System (GPS) nearly made the celestial positioning system obsolete. The new satellite-based positioning system has been very popular since it is very efficient and convenient for many daily life applications. Nevertheless, the celestial positioning method is never replaced by satellite-based positioning in absolute point positioning sense.The invention of electro-optical devices at the beginning of the 21st century was really a rebirth in geodetic astronomy. Today, the digital cameras with relatively high geometric and radiometric accuracy has opened a new insight in satellite attitude determination and the study of the Earth’s surface geometry and physics of its interior, i.e., computation of astronomical coordinates and the vertical deflection components. In the automatic star detection, high precision and reliable in extraction of the star’s centers from the captured images and corresponding them with the astronomical coordinates is the most important point. In this article, the star’s centers are extracted by the advanced image processing technique with sub-pixel precision. Relating the parameters of the presented technique to star’s Mag is one of it’s exclusive properties
H. Bolandi; M. H. Ashtari; M. Esmaeilzadeh; M. Haghparast
Volume 6, Issue 3 , October 2013, , Pages 27-37
Abstract
In this paper predicting of position of satellite based on extended kalman filter with considering hardware implementation consideration and simultaneously maintaining desired accuracy is investigated. For this purpose, first, effective forces on orbital dynamic and nonlinear equation of orbital motion ...
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In this paper predicting of position of satellite based on extended kalman filter with considering hardware implementation consideration and simultaneously maintaining desired accuracy is investigated. For this purpose, first, effective forces on orbital dynamic and nonlinear equation of orbital motion are presented. In order to increasing accuracy of prediction in position of satellite, J2, J3 and J4 harmonics of potentialfunction of the earth are considered and future position of satellite is predicted using linearized dynamic model and applying EKF on this model. Here Measurement data are position and velocity vector of satellite which are extracted by GPS receivers. Since in this paper systematic satellite design is considered, scenario of “ON TIME” of GPS receivers based on power consumption considerations is discussed. Finally simulation results for a LEO satellite and comparing these results with STK results, shows accuracy of presented modeling and equations.
M. Navabi; M. R Akhlomadi
Volume 8, Issue 3 , October 2015, , Pages 27-40
Abstract
In this paper a nonlinear optimal control is suggested. Spacecraft intended to rendezvous and dock with the target is controlled by actuators to have a safe and stable course while satisfying requirements. The Nonlinear optimal controller is designed using nonlinear equations of relative position and ...
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In this paper a nonlinear optimal control is suggested. Spacecraft intended to rendezvous and dock with the target is controlled by actuators to have a safe and stable course while satisfying requirements. The Nonlinear optimal controller is designed using nonlinear equations of relative position and attitude of spacecraft for circular and elliptical orbits with and without reaction wheels. Cost function of the optimal control problem is expressed in the form of nonlinear quadratic regulator and control constraints are applied to the problem to gain controls in the allowable domain which is produced by the wheels. For the sake of robustness to the uncertainties as one of the most important element of the control design, nonlinear optimal control is derived using state dependent Riccatti equation based on analytical method of eigen vectors of Hamiltonian matrix. Simulation results show that this nonlinear control method achieves a good performance for rendezvous and docking problem.
Asad Saghari; Hadi Veysi; AmirReza Kosari
Volume 9, Issue 3 , December 2016, , Pages 27-36
Abstract
Orbital parameters are raised as one of the main inputs of electrical power subsystem and thermal control subsystem of a satellite. Some variables such as eclipse time, sun incidence angle to the panels, albedo and thermal radiation of Earth are dependent on satellite orbital features. In this paper, ...
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Orbital parameters are raised as one of the main inputs of electrical power subsystem and thermal control subsystem of a satellite. Some variables such as eclipse time, sun incidence angle to the panels, albedo and thermal radiation of Earth are dependent on satellite orbital features. In this paper, all of the parameters above are simulated using precise simulation methods within the satellite mission. That is, the process of optimal orbital design is performed with the aid of evolutionary optimization methods. This process is aimed at minimizing number of mission days that misses the assurance of satellite power supply in addition to minimizing thermal load exerted to satellite and also its standard deviation. At last, a pair of optimal solutions for two different configurations is compared.
H. Kazemi; Ali Akbar Golro
Volume 9, Issue 4 , April 2017, , Pages 27-37
Abstract
International regulations consist of rights and obligations of states in relation to space. States should respect the international obligations with all of their public and private sectors. Based on the 1967 outer space treaty, states should control and monitor natural and legal persons involved in space ...
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International regulations consist of rights and obligations of states in relation to space. States should respect the international obligations with all of their public and private sectors. Based on the 1967 outer space treaty, states should control and monitor natural and legal persons involved in space activity. They usually approve the required laws and regulations in their national law according to the international responsibilities in order to monitor their respective institutions. Monitoring space activities are on the basis of international law within the sovereignty of a country based on the regulatory environment for licensing space activities and establishing appropriate authority. Every state has its own mechanism for issuing the required licenses. However, there are common procedures to monitor space activities, such as launching in the international law, analyses monitoring space activities in national laws and regulations of some countries in comparative laws.
fatemeh Sadeghi-kia
Volume 10, Issue 1 , June 2017, , Pages 27-34
Abstract
This study focuses on the characteristics of plasma antennas for their application in space communication systems. Structural and functional characteristics of plasma antenna are presented to evaluate their capability of being used in space missions. Numerical and experimental analysis results of the ...
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This study focuses on the characteristics of plasma antennas for their application in space communication systems. Structural and functional characteristics of plasma antenna are presented to evaluate their capability of being used in space missions. Numerical and experimental analysis results of the plasma antenna show that the resonant frequency of the antenna is controllable by changing the applied power, thus allowing different transmitting frequencies with a single element. This property leads to the reduction of the antenna elements in a limited area and the simplification in the layout of onboard communication systems as well as a decrease in the interferences of the electromagnetic waves. Analysis of the circular array of plasma antenna shows a novel beam forming mechanism with a high directivity in the space.
Remote sensing
Masoud Taefi Feijani; Saeed Azadnejad; Masoud Moradi
Volume 14, Issue 2 , June 2021, , Pages 27-36
Abstract
Awareness of the trend of forest canopy density classification requires an operational exact model for forest crown classification. The preliminary challenge is the separation of the forest crown from other non-warlike vegetation coverings. In the following, previous attempts to improve the performance ...
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Awareness of the trend of forest canopy density classification requires an operational exact model for forest crown classification. The preliminary challenge is the separation of the forest crown from other non-warlike vegetation coverings. In the following, previous attempts to improve the performance of the FCD model, in this study, by adding the FCC index and the kernel, improved the average performance of the FCD model. The crown classification of Hyrcanian forests based on images of 1396 Landsat 8 was selected for implementation, evaluation, validation and analysis of the results. Improving the accuracy of the model is entirely sensible and even manual interpretation confirm it. The statistical analysis of the results also indicates a 10% and 24% increase in overall accuracy and kappa coefficient of the improved model compared to the initial model. Specifically, the accuracy of these two classes in the results of the improved model is about 13% and 7%, respectively.
communications
Mohammad Fathi; Javad Ranjbar
Volume 15, Issue 2 , June 2022, , Pages 27-41
Abstract
In emergency situations, where there is no possibility of using terrestrial-based or space-based telecommunication platforms or when there is a need for providing telecommunication services in remote, rural or hilly areas which are faced with lacking telecommunication infrastructures, typically using ...
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In emergency situations, where there is no possibility of using terrestrial-based or space-based telecommunication platforms or when there is a need for providing telecommunication services in remote, rural or hilly areas which are faced with lacking telecommunication infrastructures, typically using tethered balloon-based telecommunication technology is the best choice. Despite all the advantages of using this technology, small and limited coverage area is the biggest drawback of using tethered balloon platforms. In this paper, using a tethered balloon equipped with antenna pointing mechanism is proposed in order to, extend their small coverage area to a large region, in addition to benefit from inherent tethered balloons technology advantages. In this regard, dynamic and kinematic modeling of the proposed antenna pointing mechanism is discussed. In this research, the kinematic model is validated using RoboAnalyzer software and Robotics MATLAB toolbox. Antenna pointing mechanism provides the rotation ability for the antenna in two Azimuth and Elevation directions which increased the coverage area dramatically.
Space New Technologies
Pedram Hajipour; Roghieh Karimzadeh Baee; Houman Zarrabi; Roghayeh Doost; Leila Mohammadi
Volume 16, Issue 2 , June 2023, , Pages 27-42
Abstract
According to the technical specifications of the future generations of telecommunication (the fifth generation and later), which should provide new services with very high data rates in the minimum time and a wide coverage, as well as the exponential increase in traffic, the use of combined space-air ...
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According to the technical specifications of the future generations of telecommunication (the fifth generation and later), which should provide new services with very high data rates in the minimum time and a wide coverage, as well as the exponential increase in traffic, the use of combined space-air networks Land is essential. It should be noted that the management of this type of combined networks has major challenges in providing such services. Meanwhile, the intelligent management of resources in satellite-based hybrid networks will lead to increased capacity and improved service quality. For this purpose, in this article, a comprehensive review of the use of artificial intelligence in the field of satellite communications will be discussed. In the field of intelligent increase of capacity, various factors such as how to configure the network, how to allocate resources such as spectrum, energy and power will be investigated with consideration of intelligent interference management. Finally, in the field of service quality improvement, factors such as how to model and intelligently predict traffic, as well as how to deal with harmful environmental conditions, will be presented.
H. Bolandi; M. Haghparast; M. Abedi
Volume 5, Issue 1 , April 2012, , Pages 29-40
Abstract
A Fault Tolerant attitude control system has been designed in this paper, which provides abilities of fault detection, identification and recovery. For this purpose, nonlinear dynamics of satellite is modeled based on Takagi-Sugeno method, which enables us to extend advantages of linear adaptive observer ...
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A Fault Tolerant attitude control system has been designed in this paper, which provides abilities of fault detection, identification and recovery. For this purpose, nonlinear dynamics of satellite is modeled based on Takagi-Sugeno method, which enables us to extend advantages of linear adaptive observer for nonlinear dynamics of satellite. In the designed adaptive observer, occurrence of fault in satellite reaction wheels are estimated based on an adaptive law which provides abilities of fault detection and identification in these actuators. Also, a back stepping feedback linearization control law has been applied for recovery which uses estimated fault term provided by adaptive observer as a compensation term in control law. So, bounded error of attitude control has been guaranteed even in faulty conditions. Finally, fault detection, identification and recovery algorithms have been verified by simulation results.
space policy
Leila Mohammadi; Parvin Sojoodi; Mohammad Bod; saeed sheikhzadeh
Volume 16, Issue 4 , December 2023, , Pages 29-40
Abstract
The national information network is being implemented with the aim of providing the services needed by the people through internal infrastructure and independent of international internet platforms. Considering the geographical diversity of the country and in order to increase the reliability coefficient ...
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The national information network is being implemented with the aim of providing the services needed by the people through internal infrastructure and independent of international internet platforms. Considering the geographical diversity of the country and in order to increase the reliability coefficient and access penetration coefficient in the national information network and also due to the needs of future services, it is not possible to rely solely on fiber and the use of satellite communications will be unavoidable. At present, satellite communication has not reached a worthy position in the country's communication network and is limited to some applications such as banking, oil and gas etc. However, due to the development of broadband networks and the increasing need for high-speed data transmission and the increase in data volume, as well as creating social justice and increasing the speed of access, as well as the Internet penetration rate in the country in order to access various services, it is necessary to develop satellite communications to should be taken seriously. In this regard, an analysis of the market of several categories of services in Iran has been done so that the amount of gap in the amount of service provision and the amount of need to receive services can be seen.
Valiollah Ghaffari; Paknoosh Karimaghaee
Volume 11, Issue 1 , June 2018, , Pages 31-40
Abstract
Usually vehicles are equipped with guidance algorithm based on line of sight (LOS) angle. In this way, some measurements like target acceleration, LOS rate, and closing velocity are provided for the guidance algorithm. The noise effect on the guidance loop would be neglected when the variance of the ...
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Usually vehicles are equipped with guidance algorithm based on line of sight (LOS) angle. In this way, some measurements like target acceleration, LOS rate, and closing velocity are provided for the guidance algorithm. The noise effect on the guidance loop would be neglected when the variance of the measurement noise is small. However, the stability property and/or performance of the guidance loop may be effected when the measurement noise is considerable. In this paper, a suitable guidance law is proposed in the presence of measurement noise. Then, a numerical example is provided. The effectiveness of the proposed method in the simulation results is shown in comparison with the previous results.
Space New Technologies
Sadjad Samipour; Alireza Toloei; Vladimir Batrakoff
Volume 15, Issue 4 , December 2022, , Pages 31-43
Abstract
Development in the aerospace industry is linked to the continuous pursuit of lightweight designs. Open-architecture composite structures are a new and novel use of composites for minimal-weight component design. It is reasonable to use efficient and advanced techniques such as radial braiding in the ...
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Development in the aerospace industry is linked to the continuous pursuit of lightweight designs. Open-architecture composite structures are a new and novel use of composites for minimal-weight component design. It is reasonable to use efficient and advanced techniques such as radial braiding in the manufacturing of composite lattice tubular structures. In this article, an aerospace composite lattice tubular structure with a braided reinforcement system is studied. A method is developed to determine the parameters of the preform reinforcement. A new process has been created for the manufacture of lattice structures with a braided reinforcement system. A methodology has been developed for determining the technological parameters of radial braiding. A sample structure is manufactured and tested. Experimental studies of lattice structure samples were carried out in order to verify the methods for determining mechanical, structural, and technological parameters.
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.
Space Engineering
Mohammad N. Meibody; Hassan Naseh; Fathollah Ommi
Volume 12, Issue 4 , December 2019, , Pages 35-46
Abstract
Now, the required samples to achieve the specific precision of sensitivity analysis in design are performed based on trial and error methods. The purpose of this paper is to develop an approach for determining the number of the required sample to achieve the specific precision of sensitivity analysis. ...
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Now, the required samples to achieve the specific precision of sensitivity analysis in design are performed based on trial and error methods. The purpose of this paper is to develop an approach for determining the number of the required sample to achieve the specific precision of sensitivity analysis. Thus, in this paper, a new sensitivity analysis method is proposed based on the Progressive Latin hypercube Sampling (PLHS) and the convergence of the analysis results. For this purpose, a PLHS method has been developed. This cystic approach has led to a sensitivity analysis of accuracy, efficiency, and speed in a variety of models with a large number of large parameters and large changes. Sensitivity analysis has been performed on the design of a hydrazine monopropellant thruster catalyst bed model as a case study. The results of this study indicate that in the sensitivity analysis based on the PLHS, the minimum population required for sensitivity analysis with specified accuracy can be determined. This leads to lower processing costs in the sensitivity analysis process, especially in complex models.
Mohammad Hossein Tirandaz; Milad َAzimi
Volume 13, Issue 2 , June 2020, , Pages 37-50
Abstract
This paper aims to use H2 and H∞ norms to optimally place sensor/actuator patches on a flexible structure. Unlike most existing optimization methods, the proposed approach not only increases the norms of the controlled modes of the system but also it can reduce the system's spillover problems by ...
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This paper aims to use H2 and H∞ norms to optimally place sensor/actuator patches on a flexible structure. Unlike most existing optimization methods, the proposed approach not only increases the norms of the controlled modes of the system but also it can reduce the system's spillover problems by taking into account the residual modes and reducing systems H2 and H∞ norms. The residual vibration of the system is captured considering sandwich structures and the finite element analysis. In order to show the optimal placement effect of piezoelectric patches, the vibrational behavior of the closed-loop system is controlled using strain rate feedback controller. Numerical simulation is performed to study the debonding effects between the sandwich layers.
physiology and space medicine (astrobiology)
Ehsan Siami; Reza Mohammadi; Vajiheh Zarrinpour
Volume 15, Issue 1 , March 2022, , Pages 41-49
Abstract
This study evaluates the expression level of genes that change by pressure changes in astronautics and diving disorders such as decompression sickness. This study was performed on five skilled divers to analyze the expression level of TLR-2, HSP-72, IL-1b, NF-kB, and MPO genes that are responsible for ...
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This study evaluates the expression level of genes that change by pressure changes in astronautics and diving disorders such as decompression sickness. This study was performed on five skilled divers to analyze the expression level of TLR-2, HSP-72, IL-1b, NF-kB, and MPO genes that are responsible for pro-inflammatory conditions. In addition, the expression level of DRD4 and BNIP3 genes (Astronaut index genes that were previously measured in a spacecraft study on mice) was analyzed on native Iranian samples. Blood samples were taken half an hour after diving, RNA was extracted, and cDNA was synthesized. Then, real-time PCR was done. Based on the results obtained using the T-Student statistical method, it was found that the expression level of all genes except MPO and TLR-2 genes increased significantly after exposure to pressure changes and diving activities. These conditions can be a permanent effect after pressure changes and can be considered an indicator for healthy people under stress in diving and astronautics.
