Advanced materials (nano materials, absorbents, adhesives, lubricants, fire retardants, etc.)
Hamidreza Hatami; Nader Ghobadi; Dariush mehrparvar; Mohammad Farokhzadi
Volume 2, Issue 4 , December 2024, , Pages 1-15
Abstract
In this work, an attempt was made to prepare thin layers of nanostructured cadmium selenide (CdSe) based on a simple solution method of chemical bath deposition (CBD), which commercially has an accessible precursor. In the chemical solution bath layering method, manufacturing factors play a significant ...
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In this work, an attempt was made to prepare thin layers of nanostructured cadmium selenide (CdSe) based on a simple solution method of chemical bath deposition (CBD), which commercially has an accessible precursor. In the chemical solution bath layering method, manufacturing factors play a significant role and determine the characteristics of the final product. In this research, the effect of an important factor, the concentration of primary solutions of selenium and cadmium ions, which is one of the most important factors in the formation of cadmium selenide, and it will be observed that the change in the concentration of these metal and non-metal ions strongly affects the type of electronic structure of the material. In comparison with the sputtering methods, in the chemical solution deposition method, there is a high control in the formation of solid deposits with different combinations of metal and non-metal binary compounds. Changing the selenide ionconcentration changes the size of the energy band gap. It has been observed that the energy gap increases with the increase of selenide non-metal ion concentration.
Defense mechanics/navigation/control/...
sariyeh Moghtader Arbat sofla; A.H. Mazinan; M.J Mahmoodabadi
Volume 3, Issue 1 , May 2024, , Pages 48-65
Abstract
In recent years, due to the widespread use of nonlinear under-actuated systems, many efforts have been made to design a controller compatible with these systems. In fact, the defect in stimulation is done in order to reduce the number of system acctuators, in order to lighten the mechanism and reduce ...
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In recent years, due to the widespread use of nonlinear under-actuated systems, many efforts have been made to design a controller compatible with these systems. In fact, the defect in stimulation is done in order to reduce the number of system acctuators, in order to lighten the mechanism and reduce the cost of production. Such applications require a high degree of precision and innovation in control and sustainability.This paper proposes an optimal adaptive control method for the stabilization of under-actuated fourth-order balls and beam system, which is a classical example of inherently unstable systems. The basic structure for this controller is the feedback linearization (FBL) technique, while a sliding surface is applied using the sliding mod along with an adaptive method to calculate the interest coefficients. In addition, the control coefficients are optimized using the hummingbird algorithm by considering two opposing objective functions. Finally, the effectiveness of the proposed method for controlling the nonlinear ball and beam system is investigated. The results of the simulations show the high efficiency of the proposed method compared to similar works.
Sound and acoustics (sound barriers, etc.)
Abbas Afshari; Jaber Ragani Lamouki
Volume 2, Issue 4 , December 2024, , Pages 78-93
Abstract
In recent decades, the use of drones as part of urban and regional transport infrastructure, as well as military applications, has developed extensively. Contrarily, their high aerodynamic noise is one of the serious challenges to obtaining a certificate of airworthiness for these flying devices. The ...
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In recent decades, the use of drones as part of urban and regional transport infrastructure, as well as military applications, has developed extensively. Contrarily, their high aerodynamic noise is one of the serious challenges to obtaining a certificate of airworthiness for these flying devices. The most important source of noise in multi-rotors, airplanes, and propeller drones with electric motors or even turboprop engines is the noise caused by propellers. In the present study, to learn more about the mechanisms affecting the propeller's noise at low Reynolds numbers and to investigate the sensitivity of the noise to the propeller rotational speed and the polar angle of its propagation, the far-field noise of a drone propeller has been evaluated experimentally. The results show that the propeller's noise includes tonal and broadband noise, so that at low frequencies, the largest propeller tonal noise occurs at the blade pass frequency, and its harmonics are still visible up to high frequencies. On the other hand, the broadband components of noise predominate in the medium and high-frequency ranges. The increase in propeller rotational speed has led to an increase in the amplitude of both the tonal and broadband noise spectrum, so that the values of the overall sound pressure level and the noise spectra of the propeller at the first blade pass frequency have increased with the increment of the propeller speed. Finally, the results showed that broadband noise has a higher sensitivity to the polar angle of sound propagation than tonal noise.
Maintenance and repair of the engine, wing and body of unmanned aerial vehicles/technology/construction/...
davood moosavian; Morteza Ahmadi Nohedani
Volume 3, Issue 1 , May 2024, , Pages 1-18
Abstract
A new method for cooling the combustion chamber walls, it is cooled by the bidirectional vortex Flow. Combustion stability, reducing the temperature of the combustion chamber walls and reduces losses and increase efficiency and uniformity are the properties of the vortex combustion engine. In similar ...
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A new method for cooling the combustion chamber walls, it is cooled by the bidirectional vortex Flow. Combustion stability, reducing the temperature of the combustion chamber walls and reduces losses and increase efficiency and uniformity are the properties of the vortex combustion engine. In similar circumstances the volume of flame the vortex engine is greater than the volume of flame at common axial engine. However; temperature of the Wall of the combustion chamber of the vortex engines less than temperature of the Wall of the combustion chamber of the engine Axial. Because cooled by the external vortex. In this study, was carried out Simulation and Numerical Solution the combustion chamber a special vortex engine in conditions single phase gaseous to fuel hydrogen and oxidant oxygen and assuming incompressible flow and irrespective of effect nozzle In order to simplify for review conditions governing on flow the combustion chamber. Examination of the streamlines shows a forced vortex in the center of the core and a free vortex around the core. The simulation results show that the pitch of the Stream lines near the roof is very small and the intensity of the flow rotation is high, which causes the maximum mixing of fuel and oxidizer. The flame is surrounded by an external vortex. In the simulated chamber, by increasing the distance from the edge of the stairs to the ceiling, the mixing and combustion will increase, and as a result, we will have an increase in the temperature of the wall.
IT and cyber warfare (encryption and data security, penetration and disruption in information networks, radars, dealing with hackers, etc.)
Farhad Sadeghi; majid zarie
Volume 2, Issue 4 , December 2024, , Pages 16-38
Abstract
This article aims at the improvement of Synthetic Aperture Radar (SAR) resolution by using a Matched Filter (MF) based on the Fractional Fourier Transform (FrFT) that has been called a Matched Slope Filter (MSF). Generally, the received SAR signals are processed by well-known algorithms to extract the ...
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This article aims at the improvement of Synthetic Aperture Radar (SAR) resolution by using a Matched Filter (MF) based on the Fractional Fourier Transform (FrFT) that has been called a Matched Slope Filter (MSF). Generally, the received SAR signals are processed by well-known algorithms to extract the final image, such as the Chirp Scaling Algorithm (CSA) and the Range Doppler Algorithm (RDA). Implementing a Matched Filter (MF) that aims at compressing the received signal in the range and azimuth directions is a principal part of these algorithms to deliver target positioning and high resolution. Because the transmitted signal by SARs has often been Linear Frequency Modulated (LFM), the received echo from the targets in the range direction is the LFM. On the other hand, there is always a chirp signal in the azimuth orientation. Thus, this paper proposes the Matched on Slope Filter to improve the compression of the azimuth signals. It's clear the proposed method has been adopted for LFM signal compression in the range direction also. The evaluation results show that our method that uses the FrFT in the time-frequency domain for implementing a Matched Slope Filter enhances the resultant azimuth resolution and reduces the sidelobe level compared to the other frequency-based method.
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