Heat control
Mohamad Reza Nasresfahani; Mohamad Nasresfahani; hossein Nazemi; mojtaba forghani; hadi gorabi
Abstract
One of the most common methods to increase the adhesion of aluminum surfaces is the use of anodized coatings. However, if we heat the manufactured products before adhering due to the hydration of the anodized coating, cracking and morphological changes, the adhesive capacity will be severely reduced. ...
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One of the most common methods to increase the adhesion of aluminum surfaces is the use of anodized coatings. However, if we heat the manufactured products before adhering due to the hydration of the anodized coating, cracking and morphological changes, the adhesive capacity will be severely reduced. As part of the research presented in this study, methods such as non- sealing of the anodize, primer application before heating the coating, sandblasting before and after the anodizing coating, and use of FPL (Forest Products Laboratory) replacement coating have been used to investigate the adhesive behavior of the coating. According to the results, not sealing the anodized coating and priming it before heating will increase the adhesiveness of the coating in all cases. Sandblasting after coating had no significant effect on adhesion. Sandblasting before anodizing improves adhesion by altering the texture of roughness and morphology. FPL can also be used to replace anodized coatings. They were less sensitive to heating and storage
Masoud Hekmatfar; Mirsaman Pishvaee
Abstract
One of the main issues in the arrangement of equipment in multi-layered satellites includes placing the equipment in each layer separately. In the arrangement of equipment on surfaces, the non-overlap constraint has always been a challenge, especially for parts that do not have a circular cross-section. ...
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One of the main issues in the arrangement of equipment in multi-layered satellites includes placing the equipment in each layer separately. In the arrangement of equipment on surfaces, the non-overlap constraint has always been a challenge, especially for parts that do not have a circular cross-section. This paper presents a robust flexible programming model (RFPM) for placing equipment in different layers and considering uncertainty for placement of cubic equipment. Comparing the output of the proposed model with previous studies in this field shows that the efficiency of the model has increased significantly to meet the limitations of non-overlapping between equipment. Eventually, it is expected that this research can cover the existing gaps in this field and by observing other limitations such as stability and thermal limitations, moments of inertia and center of gravity, it will reduce the design time in the conceptual and preliminary phase and ultimately reduce the overall dimensions of the satellite, which has always been one of the main goals of designers.
Electric power
Mohammad Zarei-Jelyani; Mohammad Mohsen Loghavi; Mohsen Babaiee; Rahim Eqra; Masood Masoumi
Abstract
In recent years, extensive research has been focused on the key materials of vanadium redox flow batteries (VRFBs) to improve the power and energy density. In a VRFB system, the ion-exchange membrane is an important component, because it is used to separate the positive and negative electrolytes and ...
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In recent years, extensive research has been focused on the key materials of vanadium redox flow batteries (VRFBs) to improve the power and energy density. In a VRFB system, the ion-exchange membrane is an important component, because it is used to separate the positive and negative electrolytes and to allow the transfer of ions. Nafion membrane is now widely used in VRFBs due to its high proton conductivity and remarkable chemical stability. In the present study, the Nafion 117 membrane was subjected to acid-heat pretreatment for utilizing in VRFBs. Three-cell stacks of VRFB were assembled using bare and pretreated membranes, and their performances were evaluated during charge/discharge cycles. The results indicate that acid and heat pretreatment on the Nafion 117 membrane improves the VRFB energy density up to 30%. In addition, the average discharge voltage, which is one of the key parameters in the VRFB performance, is increased from 3.57 V (for the bare membrane) to 3.9 V (for the pretreated membrane). This helps to reduce the weight of the VRFB stack as well as the cost of the battery manufacturing. On the other hand, the acid and heat pretreatment of the membrane improves the energy and voltage efficiencies of VRFB from 66.9% and 76.8% to 73% and 87%, respectively
Mona Zahednamazi; Alireza Toloei; Reza Ghasemi
Abstract
One of the best attitude sensors for space applications is the star sensor. This sensor determines the attitude using stars in the field of view. One of the main advantages of this sensor is attitude initialization using lost-in-space star identification algorithms. This paper presents a new lost-in-space ...
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One of the best attitude sensors for space applications is the star sensor. This sensor determines the attitude using stars in the field of view. One of the main advantages of this sensor is attitude initialization using lost-in-space star identification algorithms. This paper presents a new lost-in-space star identification algorithm based on Hausdorff distance. Using Hausdorff distance, two different identification algorithms have been proposed, and their results have been compared. The first approach is designed based on pivot star, and the second approach uses the segmentation of the celestial sphere. The performance of these two approaches has been investigated using the simulation of 200 random directions of the star sensor in different magnitudes. The results show the approach of the pivot star has a better performance, and its identification rate is 93.5% at the magnitude of 6. Also, the identification time of the Hausdorff algorithm has been compared with the pyramid algorithm and some geometric algorithms. The results show that the Hausdorff identification algorithm has the shortest identification time which makes it suitable for real-time applications
Flight dynamics
Ali Jafarian; Saeed Sarkheil; Vahab Haghighat
Abstract
In this paper, the computational fluid dynamics simulation of a tactical aerostat is conducted and the longitudinal static coefficients of the aerostat are evaluated. In this simulation, Fluent software and Spalart- Allmaras turbulent model are used. First, in order to validate the numerical method and ...
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In this paper, the computational fluid dynamics simulation of a tactical aerostat is conducted and the longitudinal static coefficients of the aerostat are evaluated. In this simulation, Fluent software and Spalart- Allmaras turbulent model are used. First, in order to validate the numerical method and the applied turbulent model, a famous airship hull is simulated and the drag coefficient at zero angle of attack is compared with the references and the CD0 is in very good agreement with references. Then, the designed aerostat is simulated in the angle attack of )-10 to 30( degrees then the pressure, Y+ contours and the streamlines around the aerostat are presented. Furthermore, the aerodynamic longitudinal coefficients are calculated for 5 and 20 m/s. The results show that the aerodynamic coefficients do not vary significantly with the change of velocity and the pitch moment coefficient about the nose of the designed aerostat has a negative slope. Finally, Comparing the pitch moment coefficient of the designed aerostat with two American and Korean aerostats indicate that, the designed aerostat has more static stability.
Material science
Maedeh sadat Zoei; S. Javid Mirahmadi; Mojtaba Forghani; mohammad chiani; Saeed Asghari
Abstract
Thermal barrier coatings (TBCs), are advanced ceramic systems that are usually applied to the surface of hot industrial parts to improve equipment performance at higher temperatures. During each thermal cycle, due to the mismatch in the coefficients of thermal expansion of TBC layers, these layers expand ...
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Thermal barrier coatings (TBCs), are advanced ceramic systems that are usually applied to the surface of hot industrial parts to improve equipment performance at higher temperatures. During each thermal cycle, due to the mismatch in the coefficients of thermal expansion of TBC layers, these layers expand and contract unbalanced. The resulting thermal stresses cause the nucleation and growth of microcracks in the TBC system. After several hundreds of thermal cycles, the microcracks eventually combine and form a relatively large crack that causes spallation and separation of the coating, exposing the parts to high temperatures and ultimately leading to catastrophic failure of the entire equipment. The creation of self-healing capability provides the ability to repair cracks spontaneously. In this article, various types of technologies for achieving self-healing in YSZ thermal barrier coatings and the structure and properties of the resulting coatings have been introduced and reviewed. After extracting the technologies of applying self-healing thermal barrier coating and comparing them with each other, it is possible to obtain coatings with self-healing properties according to the needs of each industry and then determined the proper composition of the self-healing coating, the proper thickness of the self-healing coating layer, the proper arrangement of the self-healing coating layer and the parameters of the coating process
control
mahyar madani esfahani; aref aghamolaie; Taleb Abdollahi; Saeed shamaghdari
Abstract
In this paper, a satellite attitude control system (SACS) based on tube-based robust model predictive control (TMPC) methodology is designed which is robust to bounded disturbances. All Euler angles and their derivatives are ensured not to deviate more than a determined limit under those disturbances ...
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In this paper, a satellite attitude control system (SACS) based on tube-based robust model predictive control (TMPC) methodology is designed which is robust to bounded disturbances. All Euler angles and their derivatives are ensured not to deviate more than a determined limit under those disturbances with known bounds. It is conducted based on the concept of the minimal robust positive invariant (mRPI) set. Actuators and Euler variables constraints could be considered in the SACS. The dynamics are guaranteed to be robustly stable. Given that the satellite dynamics consists of a great number of states, it is not possible to implement a TMPC scheme on the SACS in real-time. The number of satellite system states in this article is 6. Which has practically increased the volume of calculations. In order to solve this challenge, the proposed solution of tube estimation is presented to reduce the volume of satellite calculations. With this estimation, the process of increasing the volume of computations for tube-based robust predictive control design for satellite is stopped. For the desired system, simulation has been done in the presence of uncertain and limited disturbance. The results show satellite attitude control by reducing the amount of computation when designing a tube-based robust Model predictive control.
adel Pourtaghi Marzrood; Arezoo Esmaeili; adel Pourtaghi marzrood; Moharram Shameli
Abstract
Backflow is a phenomenon that occurs due to the increase of upstream pressure compared to downstream pressure. In converging-diverging nozzles, by increasing the outlet pressure compared to the design pressure, the phenomenon of backflow is observed in the divergent part, which causes a decrease in the ...
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Backflow is a phenomenon that occurs due to the increase of upstream pressure compared to downstream pressure. In converging-diverging nozzles, by increasing the outlet pressure compared to the design pressure, the phenomenon of backflow is observed in the divergent part, which causes a decrease in the output velocity and thrust. In this paper, a converging- diverging nozzle with suitable expansion ratio for vacuum condition is selected and the propellant flow, which is considered as butane in this research, is simulated by finite volume method for output pressure equal to vacuum pressure and atmospheric pressure conditions. It has seen that in the atmospheric pressure, backflow occurs in the nozzle in order to determine the appropriate expansion ratio for the nozzle operating in atmospheric pressure, the flow inside the nozzle is simulated for the different expansion ratios and the average outlet axial velocity at the output of theses nozzles is obtained. According to the results, the most suitable expansion ratio of the surface has the highest average axial velocity. Also, to verify the obtained results from finite element simulation, four nozzles with different surface expansion ratios were manufactured and the thrust force obtained from experimental test on the measuring stand with equivalent results obtained from the simulations were compared
Control
Ali Foroutan; alireza safa
Abstract
The gyroscope system is an attractive nonlinear system that is used in various industries such as the military, aerospace, navigation, etc. Considering the importance and applications of the non-linear system of the gyroscope, the design of the control system for the operation of the gyroscope system ...
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The gyroscope system is an attractive nonlinear system that is used in various industries such as the military, aerospace, navigation, etc. Considering the importance and applications of the non-linear system of the gyroscope, the design of the control system for the operation of the gyroscope system is indispensable. Most systems in the real world have nonlinear dynamics, and it is inevitable to avoid the destructive effects of noise and unpredictable external disturbances. Nonlinear uncertainties in gyroscope dynamics, noise, and unpredictable external disturbances are major challenges in controller design. The model-free control is developed for this system. Particularly, the sliding mode controller is widely used in the control of non-linear systems due to its robustness to system dynamic uncertainties and system disturbances. In this paper, the dynamic behavior of the nonlinear gyroscope system is analyzed then a sliding mode controller based on the neural network is used to control the gyroscope system. The stability of the nonlinear gyroscope system is proved using Lyapunov's theory. The nonlinear model of the gyroscope is simulated in Simulink MATLAB to investigate the behavior of the proposed control method and compare it with other controller's methods, so the efficiency of the proposed control method in the control of the nonlinear gyroscope system is investigated
Propulsion
Nooredin Ghadiri Massoom; alireza rajabi; mohamad ali amirifar; Zahra Amirsardari; Akram Dourani; majid kamranifar
Abstract
In this paper, the effects of different weight percentage of iridium (Ir) nanoparticles loadings on performance parameters of hydrazine catalyst and monopropellant thruster have been studied. Nanoparticles of iridium with different contents of 10 wt%, 20 wt%, and 30 wt% has been coated on gamma-alumina ...
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In this paper, the effects of different weight percentage of iridium (Ir) nanoparticles loadings on performance parameters of hydrazine catalyst and monopropellant thruster have been studied. Nanoparticles of iridium with different contents of 10 wt%, 20 wt%, and 30 wt% has been coated on gamma-alumina of 1 to 2 mm size for decomposition of hydrazine during some various steps of calcination. These catalysts then have been tested in a 1 N thruster. The tests were conducted using a scenario of different stages of steady and pulsating fires of different times and duty cycles. The test results showed that catalyst loss was minimum with 30 wt% of iridium nanoparticles loading. Despite of this, there were no meaningful difference between other parameters such as pressure roughness, thrust, specific impulse, and catalyst crushing. The results showed a good value of characteristic velocity. All parameter values of three type of catalysts were in the expected and desired range
Material science
maryam salvatifar
Abstract
One of the most serious problems of the industrialized world is heavy metal contamination. As a heavy metal, lead has very harmful effects on human health even in small amounts. Therefore, removing it from water is one of the most important challenges in public health system. Microorganism application ...
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One of the most serious problems of the industrialized world is heavy metal contamination. As a heavy metal, lead has very harmful effects on human health even in small amounts. Therefore, removing it from water is one of the most important challenges in public health system. Microorganism application is very useful and safe in this field. Creatures living on Earth are constantly under the influence of gravity, and if it changes, they will be affected by a unique shock. Such a change has effects on the structure and function of cells by interfering with biochemical pathways and gene expression. Investigating these changes, in addition to maintaining the health of astronauts, will also be useful for improving the quality of human life on earth. In this study, the efficiency of Lactobacillus acidophilus ATCC 4356 bacteria in the bioremoval of lead from aqueous solution was investigated in microgravity and Mars gravity conditions. The results showed a decrease in lead concentration after 24-hour treatment by 82.1% under microgravity conditions, 79.6% under simulated Mars gravity conditions and 70.6% under natural Earth gravity conditions. Therefore, by reducing the gravity, it is possible to increase the efficiency of L. acidophilus in the bioremoval of lead metal
control
Milad Kamzan; Mana Ghanifar; AmirAli Nikkhah; Jafar Roshanian; Mohammad Teshnehlab
Abstract
In this article, a new closed-loop algorithm is presented to generate an optimal angular trajectory for a given satellite to reach the desired final point. Using the capabilities of artificial neural networks, this algorithm can find the best trajectory to reach the final setpoints based on the dynamic ...
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In this article, a new closed-loop algorithm is presented to generate an optimal angular trajectory for a given satellite to reach the desired final point. Using the capabilities of artificial neural networks, this algorithm can find the best trajectory to reach the final setpoints based on the dynamic behavior of the system and the preset controller capability by using the desired final values of the trajectory and the values of the system state variables at each simulation time. In the presence of external disturbances, this closed-loop intelligent trajectory generation algorithm shows advanced adaptive performance, which allows it to develop the best alternative trajectory to achieve the final setpoint and return the system to the main trajectory. Despite the fact that this algorithm is able to restore the main trajectory, it is also capable of preventing unreasonable control efforts by considering the control properties of the system. This intelligent algorithm of angular path generation shows high accuracy and effective performance after simulations are performed in the MATLAB software environment with predefined external disturbances.
Telecommunication
Hossein Eskandari; Razieh Narimani; Elham Hosseini
Abstract
In this paper a waveguide antenna to create a saddle shaped pattern for remote sensing satellite applications has been introduced, and a method to excite a waveguide as feeding X-band antenna with the aim of achieving circular polarization has been presented. With the use of a circular microstrip probe, ...
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In this paper a waveguide antenna to create a saddle shaped pattern for remote sensing satellite applications has been introduced, and a method to excite a waveguide as feeding X-band antenna with the aim of achieving circular polarization has been presented. With the use of a circular microstrip probe, the mode inside the cylindrical waveguide is stimulated in such a way that the antenna has circular polarization with only one feeding input, and in addition, the input impedance of the antenna is fifty ohms. To achieve the saddle-shaped pattern, plus-shaped guides have been used. These guides are printed as microstrips on the Rogers 5880 substrate. The innovation of this article is in the simultaneous use of directional elements to create a saddle-shaped pattern and a circular probe to create circular polarization in order to design a suitable antenna for LEO remote sensing satellites. After simulation, the antenna was fabricated and tested. The test results show that the antenna has a real gain of more than 3 dBi at angles of θ = ±65. The axial ratio of the antenna is less than 3 dB in the working frequency for θ values between ±50, which shows that the antenna has a desired circular polarization in this θ angle range.
Material science
shahab khameneh asl; reza golzarian; behnam salahimehr; ali fardi
Abstract
The use of thermal knives as holding mechanism and non-explosive release in the field of space mechanisms has always been considered. In these mechanisms, the use of materials with high melting points and low weight, as well as the possibility of production on a small scale is a major challenge. Therefore, ...
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The use of thermal knives as holding mechanism and non-explosive release in the field of space mechanisms has always been considered. In these mechanisms, the use of materials with high melting points and low weight, as well as the possibility of production on a small scale is a major challenge. Therefore, the use of platinum / alumina catalysts can be a good solution to the leading problems in this field.The purpose of this paper is to prepare a high specific surface alumina base using the process of anodizing aluminum and coating it with platinum particles. Thus, the present study consists of two stages; In the first stage, aluminum is anodized in oxalic acid solution and its parameters are optimized in order to achieve aluminum nanotubes with various diameters and wall thicknesses, as well as the applied voltage, electrolyte concentration and anodizing conditions. In the next step, platinum nanoparticles were precipitated in different amounts using metal salt and suitable solvent using electrochemical method. The results showed that the obtained nanowires have a diameter of about 200 nm and a length of several micrometers. All samples were mechanically polished and it was shown that the aluminum anode oxide membranes were completely filled with a combination of metals. Also, the performed analyzes showed that the obtained nanowires are stable inside the membrane
Space engineering
Roya Sanaie; Pouya Talebinejad; Seyed Mohammadjavad Tabatabiee; Mahdi Fakoor
Abstract
The solar array ,one of the main parts of the satellite's electrical power subsystem, is responsible for providing the required electrical power for the satellite during the mission. Micrometeorites and small space debris are considered serious risk for the satellite mission. Due to the number of satellites ...
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The solar array ,one of the main parts of the satellite's electrical power subsystem, is responsible for providing the required electrical power for the satellite during the mission. Micrometeorites and small space debris are considered serious risk for the satellite mission. Due to the number of satellites in orbit, space debris is increasing. The impact of micrometeorites or orbital debris on the solar panels of the satellite can damage the internal structure of the panel, which causes a drop in the electrical power of the satellite. In this article, along with the numerical and geometrical simulation of the solar panels of the MEO communication satellite, an algorithm based on the direct random impact of micrometeorites and orbital debris on the solar panels has been presented, and their damage rate has been calculated. The size of meteorites and space debris is determined based on the average size of the particles in the earth's orbit. After summarizing the collision results, the redundant solar panel has been simulated based on the minimum and maximum damage to compensate for the satellite power loss. The results show that the redundant solar panel can compensate the loss of satellite power after the collision and estimate the extent of damage as soon as possible
dynamics
Masoud Dehnad; Morteza Farhid; Samira Mazhari Anvar
Abstract
In this article, a fault tolerant control based on a virtual actuator is used for the maneuvering of low earth orbit satellites that are subject to the loss of the effectiveness and additive actuator faults as well as natural disturbances such as atmospheric drag, earth's gravity, solar radiation and ...
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In this article, a fault tolerant control based on a virtual actuator is used for the maneuvering of low earth orbit satellites that are subject to the loss of the effectiveness and additive actuator faults as well as natural disturbances such as atmospheric drag, earth's gravity, solar radiation and third body. In the approach used, there is no need for a separate unit to detect, isolate and identify the error. The main feature of this approach is to provide the same performance for the nominal system and the faulty system since the actuator faults and disturbances are hide from the nominal controller due to placing a virtual actuator between the faulty plant and the nominal controller.For the purpose of satellite maneuvering, using Kepler's orbital dynamics, which is affected only by the Earth's gravity, the desired second orbit parameters are calculated. In addition, orbital dynamics based on six modified orbital elements have been used, which avoids singularities. Then, using the desired orbit parameters, the relative motion elements are calculated and used in the control laws. To demonstrate the effectiveness of the control method, a maneuvering scenario of a satellite with Kepler's orbital dynamics that affected by natural disturbances and the actuator faults, is simulated for 42 days. The satellite has an effective cross-sectional area of 0.56 m2, and an actuator fault is occurred since the 32nd day. The results show higher performances the proposed method compared with conventional controllers like LQR.
control
Sevil M. Sadigh; Hossein Behesgti
Abstract
In this paper, a passive fault tolerant control method is proposed for the satellite attitude tracking in the presence of external disturbances, the inertia matrix uncertainties, and reaction wheel faults. To achieve this goal, a modified fast terminal sliding model approach is used due to its robustness ...
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In this paper, a passive fault tolerant control method is proposed for the satellite attitude tracking in the presence of external disturbances, the inertia matrix uncertainties, and reaction wheel faults. To achieve this goal, a modified fast terminal sliding model approach is used due to its robustness against the un-modeled uncertainties and being suitable for the nonlinear system model. The sliding surface variable is chosen to avoid singularity, converge to zero in a finite time, and also reduce the Chatting phenomenon. The stability and finite time convergence of the attitude variables are also demonstrated by the extended Lyapunov method. In order to increase the accuracy of the designed controller, the dynamic model of the mentioned actuators is considered. Finally, in order to evaluate the performance of the proposed method, the simulation is performed on a satellite with four reaction wheels under the mentioned conditions. The results show that the proposed method can maintain the stability of the system despite the occurrence of actuator faults, and it makes the state variables converge to the desired trajectories in a finite time and also produce chattering-free control signals.
Amirreza Kosari; Elahe Khatoonabadi; Aida Kazemi; reza amjadifard; Vahid Bohlouri
Abstract
This paper investigates solar activities and its phenomena from the perspective of risks on the functioning of urban infrastructures, industrial systems and economic structure affected by such phenomena. Also, according to the existing analyzes and results, the basic requirements to prevent the severity ...
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This paper investigates solar activities and its phenomena from the perspective of risks on the functioning of urban infrastructures, industrial systems and economic structure affected by such phenomena. Also, according to the existing analyzes and results, the basic requirements to prevent the severity of the resulting injuries have been introduced. Space weather events can cause disruptions in the power grid, telecommunications and radio communications, airlines, railways, and in addition cause damage to pipelines, oil and mining industry, and aviation each of these cases it is examined as an economic infrastructure in this paper. Also, the effect of these phenomena in damage and dysfunction in satellites that are used for global positioning, telecommunications and weather forecasting has been investigated. Considering the importance of the items mentioned in this article, an attempt has been made to investigate the research done in some other countries regarding the impact of space weather phenomena on socio-economic systems and to study the disruptions and failures caused by this impacts in the industries and socio-economic infrastructures of the society. This studies can help in the formation of the necessary fields and preventive actions in facing the dangers of space weather in order to lead the scientific community to investigate similar cases in the country in order to create management arrangements and related technological
control
Hossein Ghadiri; Reza Esmaelzadeh; Reza Zardashti
Abstract
Generally, the determination methods of the satellite orientation are known as attitude determination and attitude estimation. The attitude determination solution of the satellite leads to the Wahba problem. Therefore, at least two independent measurement vectors and two corresponding reference vectors ...
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Generally, the determination methods of the satellite orientation are known as attitude determination and attitude estimation. The attitude determination solution of the satellite leads to the Wahba problem. Therefore, at least two independent measurement vectors and two corresponding reference vectors are needed to apply the Wahba problem. These input vectors aren't accurate due to sensor noises, misalignment, and low-order approximations. However, these uncertainties aren't considered in the classic Wahba problem directly. In this case, the estimation error of the Wahba problem depends on the input vectors' accuracy. Hence, modeling error and measurement noise are modeled using Interval analysis. Then, the attitude determination problem is transformed from a single-objective problem to a multi-objective robust optimization problem. Since solving the multi-objective problem with heuristic solvers such as NSGA II is time-consuming, the multi-objective problem was solved using the min-max optimization algorithm. The attitude determination error with the proposed method is reduced (7 times) compared to the quaternion method, and its dependence on the accuracy of the input vectors is reduced (200 times). In fact, while reducing the mean attitude error, the algorithm robustness has increased compared to the uncertainties in the input vectors. Using the min-max algorithm has reduced the execution time of the algorithm (about 600 times) compared to the NSGA II algorithm and is suitable for real-time applications. Based on the results, the proposed method has narrower bounds, so that the mean square error (RMS) is decreased by more than 50% over the q-method.
Remote Sensing
Tayebe Managhebi; Akram JafarAghaee
Abstract
Forest biomass is one of the most important parameters in the ecosystem changes assessment and global carbon cycle modelling. In the other hand, the forest height is an effective parameter in the allometric equations which are used for biomass estimation. In this research, the effect of two physical ...
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Forest biomass is one of the most important parameters in the ecosystem changes assessment and global carbon cycle modelling. In the other hand, the forest height is an effective parameter in the allometric equations which are used for biomass estimation. In this research, the effect of two physical factors forest height and forest density, will be evaluated in the applicability of the four common inversion algorithms for forest height estimation based on the polarimetric Interferometry SAR (PolInSAR) technique. The applicability of the digital elevation model (DEM) differencing, volume coherence amplitude, hybrid and three-stage methods are studied for different forest height and forest density by using simulated polarimetric interferometric SAR data in L-band. The experimental results of the forest height estimation in simulated data with a density of 100 to 900 trees per hectare and a height of 10 to 18 meters show that the results of the hybrid method show high sensivity to changes in both height and density. The root mean square of error was 5.8, 5.6, 3.2 and 4 m for data with variable height and 11.6, 6.7, 5.8 and 5.3 m for data with different densities, respectively.
Structure
Saeed Ahmadpour Kasgari
Abstract
Paying attention to the increasing use of metal-polymer composites in aerial and space structures and their economic efficiency, it is possible to achieve a more economical and high-quality connection by determining the appropriate parameters. The purpose of this article is to calculate the optimal parameters ...
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Paying attention to the increasing use of metal-polymer composites in aerial and space structures and their economic efficiency, it is possible to achieve a more economical and high-quality connection by determining the appropriate parameters. The purpose of this article is to calculate the optimal parameters for the friction stir welding (FSW) process to properly join aluminum to polymer. Polycarbonate sheets and aluminum alloy sheets, widely used materials in the aerospace industry, were employed for FSW. Initially, a traditional FSW was conducted without additional material. Subsequently, for two samples, a layer of epoxy glue was placed between the two sheets, followed by FSW. On the second sample, a restorative FSW was performed with a 10 mm comb stirrer head. The results indicated that the most optimal condition was a spindle speed of 1400 r/min and a welding speed of 50 mm/min, particularly for the sample with epoxy glue and repair welding. Traditional FSW showed flaws, while FSW with adhesive displayed fewer defects. Repair welding significantly influenced the FSW joint, enhancing the cleanliness of the macroscopic appearance of the weld surface. In the tensile test, it was observed that the tensile strength of the repair weld exceeded that of the joint welded by two traditional methods and with glue. Microscopic results revealed more holes in FSW with two traditional methods and with glue, gradually reducing defects during repair welding.
control
Marzieh Afkhami; simin Alibani; Hossein Forouzan; Mohammad ali Asnafi
Abstract
One of the key subsystems in satellites is the attitude determination, and the sun sensor is one of the most common sensors in this field. Today, due to the increasing development of satellites, the need to increase the accuracy of satellite subsystems seems very necessary. In this paper, the design ...
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One of the key subsystems in satellites is the attitude determination, and the sun sensor is one of the most common sensors in this field. Today, due to the increasing development of satellites, the need to increase the accuracy of satellite subsystems seems very necessary. In this paper, the design of a sun sensor made with an optimized slit in the entire field of view is examined. In this sensor, two orthogonal linear detectors are used, on top of each of the detectors, an optimal gap perpendicular to the detectors is required at an optimal distance according to the field of view. Due to the light passing through the optimized slits and its effect on the detectors and the slit, a peak can be seen in the output of the detectors, which according to the location of the peak, the angle of the incoming light can be calculated with high accuracy. The sun sensor made in Shiraz Mechanics Research Institute has an absolute error (2 sigma) of 0.14 in the 50 degrees of field of view
Space engineering
Hamed Sheikhbahaee; Farkhondeh Saliminezhad; Seyed Alireza Ghorashi; Saeed Hajialigol
Abstract
Ion mobility spectroscopy (IMS), as one of the detection methods based on the ionization of mineral, organic, and chemical substances, has been used efficiently for many years in manned and robotic space missions. The space applications of these instruments include environmental monitoring of spacecraft ...
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Ion mobility spectroscopy (IMS), as one of the detection methods based on the ionization of mineral, organic, and chemical substances, has been used efficiently for many years in manned and robotic space missions. The space applications of these instruments include environmental monitoring of spacecraft and identification of organic and mineral substances in samples collected from space. In this method, warm-up is required for the cleanup and transport of ions in the drift area of the detector cell. Considering the need to miniaturize and optimize the necessary power of space detectors, the experimental investigation of the thermal gradient and factors affecting warm-up time is essential. For conducting the experimental thermal analysis of the IMS cell, micropumps, desorber, and temperature recording equipment such as a temperature control system, data logger, thermocouple sensors, monitoring system, and resistance temperature detector have been used. In this research, by experimentally investigating the warm-up time and thermal gradient in the IMS cell in different modes and several target temperatures, the main factors have been determined. The results showed that the oscillating air flow inside the IMS cell can reduce the warm-up time and the temperature gradient. Finally, several suggestions for better thermal efficiency are presented.
Zahra Khaji; Mahdi Fakoor; Saeed Shakhesi
Abstract
The design of space operations must be done carefully. Because the smallest mistake in the design and construction of the spacecraft causes heavy financial losses. Electronic boards are one of the most important components of electronic systems in any operation. These boards must continue to operate ...
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The design of space operations must be done carefully. Because the smallest mistake in the design and construction of the spacecraft causes heavy financial losses. Electronic boards are one of the most important components of electronic systems in any operation. These boards must continue to operate under the applied loading. Strong levels of random vibrations can cause damage and fracture in electronic boards. The random vibration field applied to the electronic board can be modeled by mixed-mode I/II loading. Solder joints are very sensitive components of satellites. Fracture of electronic packages often occurs due to cracking in the joint between the electronic board and the solder under mixed-mode I/II loading. In this research, a new fracture criterion based on the maximum tangential stress is presented to predict the fracture for the interfacial crack between the electronic board and the solder. Based on the presented criterion, the direction and moment of crack initiation are predicted for the interfacial crack between isotropic and orthotropic materials. In this way, the fracture limit curve can be drawn. By comparing the presented criterion with the available experimental data, it can be concluded that the presented criterion has sufficient validity to evaluate the prediction of fracture in interfacial cracks between isotropic and orthotropic materials.
Material science
Yaser Vahidshad; caren abrinia; Peyman aalimehr
Abstract
This research focused on investigating additive manufacturing factors using Selective Laser Melting (SLM) with maraging grade 300 steel powder via Taguchi method. The main objectives were to explore the influence of process parameters and achieve optimal levels. Experiments were exactly designed with ...
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This research focused on investigating additive manufacturing factors using Selective Laser Melting (SLM) with maraging grade 300 steel powder via Taguchi method. The main objectives were to explore the influence of process parameters and achieve optimal levels. Experiments were exactly designed with the assistance of Mini-Tab software. The study specifically targeted scanning speed, hatch distance, layer thickness, and scanning strategy for fabricating tensile samples. Comprehensive characterization using optical and scanning electron microscopes examined mechanical and microstructural properties. The analysis revealed that the optimal levels for achieving desirable results were as follows: scanning speed of 100 mm/s, layer thickness of 20 microns, hatch distance of 0.15 mm, and implementing the Stripe scanning strategy in the XY direction. The output results showed significant findings, with a final tensile strength of 951 MPa, porosity measured at 0.4%, and an impressive relative density of 99.6%. In conclusion, this research provides valuable insights into optimizing the selective laser melting process with maraging grade 300 steel, offering crucial knowledge about effective process parameters for obtaining optimal mechanical and microstructural properties in the additive manufacturing of tensile samples.
