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.
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.
Other related fields
Zahra Dehghan bahabadi; Saeed Ghorbani Sehat
Volume 3, Issue 4 , March 2025, , Pages 101-130
Abstract
examines the extent of radioactive pollutant dispersion and radiation dose received due to hypothetical nuclear bomb explosion in central Iran using HYSPLIT and GDAS data, without considering chemical reactions. results indicate that the predominant direction of radioactive fallout is northeast, with ...
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examines the extent of radioactive pollutant dispersion and radiation dose received due to hypothetical nuclear bomb explosion in central Iran using HYSPLIT and GDAS data, without considering chemical reactions. results indicate that the predominant direction of radioactive fallout is northeast, with a minor amount towards southeast of explosion site. The spread of radioactive materials reaches approximately 300 kilometers from the explosion site within 12 hours, affecting Yazd province, southern regions of South Khorasan, and northern Kerman province. Additionally, dispersion and deposition of particles, as well as dose distribution, are highly dependent on local meteorological conditions. Initially, cloud grows significantly and reaches an altitude of 5,000 meters. Over time, particles settle over time , leading to greater deposition. peak concentration of deposited particles exceeds concentration of those dispersed, with maximum concentration and deposition occurring in northeastern area about 200 kilometers from explosion site, where radiation dose received by individuals exceeds 100 millisieverts. Furthermore, the total dose received by individuals on ground at 0 meter is higher than total dose received at altitudes of 0 to 100 meters. As time passes, density of radioactive cloud decreases, subsequently reducing radiation dose received by individuals. doses received by most individuals are significantly above permissible limits set by International Commission on Radiological Protection (ICRP). In terms of radioactivity, very few areas fall within the controlled zone, while most are classified as prohibited zones. emphasizes the importance of predicting and modeling dispersion of radioactive pollutants and demonstrates that instantaneous atmospheric conditions greatly influence accuracy of predictions.
Other related fields
Seyyed Mehdi Khoshfetrat; Mansur Hadadi; Mohammadreza Baezzat
Volume 3, Issue 4 , March 2025, , Pages 1-21
Abstract
Supercapacitors are gaining attention for their high-power density, long lifespan, and rapid charge-discharge capabilities (Especially its use in defense industries and military equipment). The performance of these devices heavily relies on their electrode materials. A nickel-based metal-organic framework ...
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Supercapacitors are gaining attention for their high-power density, long lifespan, and rapid charge-discharge capabilities (Especially its use in defense industries and military equipment). The performance of these devices heavily relies on their electrode materials. A nickel-based metal-organic framework (Ni-MOF) with a high specific surface area was synthesized to enhance energy storage. To improve electrical conductivity and capacitive properties, titanium carbide MXene (Ti3C2 MXene) and graphene (Gr) were incorporated into the MOF. This combination was deposited onto nickel foam (NF) via a hydrothermal method, which allowed for better surface area utilization by reducing aggregation between Gr and MXene layers and facilitating electrolyte transport through the conversion of graphene oxide to Gr. The inclusion of Ni-MOF also enhances the quasi-capacitive properties due to its electroactivity. The Ni-MOF/MXene/Gr/NF electrode achieved a specific capacitance of 845 F g⁻¹ in a 3 M KOH electrolyte, while the cathode (graphene aerogel integrated with activated carbon, C-GA/NF) exhibited a capacitance of 373.5 F g⁻¹. For the asymmetric supercapacitor configuration (Ni-MOF/MXene/Gr/NF‖C-GA/NF), a specific capacitance of 637 F g⁻¹, specific energy of 22.8 W h kg⁻¹, and specific power of 0.69 kW kg⁻¹ were recorded. Additionally, the device maintained 55.2% of its initial capacity after 5000 charge-discharge cycles at a current density of 8 A g⁻¹, indicating excellent stability and cycle life. Taken together, these features facilitate the use of this device in military and defense equipment.
Sound and acoustics (sound barriers, etc.)
Abbas Afshari; Reza Jafari Nia; Jaber Ragani Lamouki
Volume 3, Issue 4 , March 2025, , Pages 75-100
Abstract
This study presents a numerical analysis of a UAV propeller's aeroacoustic behavior under hovering conditions. The Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations for incompressible flow were solved using ANSYS Fluent, with turbulence modeled using the k-ω SST approach. Far-field noise ...
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This study presents a numerical analysis of a UAV propeller's aeroacoustic behavior under hovering conditions. The Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations for incompressible flow were solved using ANSYS Fluent, with turbulence modeled using the k-ω SST approach. Far-field noise prediction was performed employing the Ffowcs Williams-Hawkings (FW-H) acoustic equation. Static pressure contours revealed extensive low-pressure regions on the blade's upper surface, particularly near the leading edge at the tip, significantly contributing to both thrust generation and loading noise. Surface pressure fluctuations were most pronounced along the leading edge, diminishing toward the trailing edge, suggesting the leading edge as the primary broadband noise source due to turbulent interaction with preceding blades. Far-field analysis showed dominant tonal noise at 100 Hz and its harmonics, with higher-order blade passing frequencies exhibiting near-linear attenuation. Directivity patterns indicated negligible tonal noise at 0° and 15° (suction side) and 165° and 180° (wake side) polar angles, while broadband noise decreased and tonal noise intensified at 90°.
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