Aerospace Defense

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 (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.

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 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°.

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 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.

Abstract The spread of fake news on social networks has become a serious challenge in the fields of information and cybersecurity, particularly in the realm of passive defense. Early detection of such news can play a crucial role in improving cybersecurity and controlling the dissemination of misinformation. This paper presents a novel approach that uses the correlation between headlines and news content to identify fake news. Using deep neural networks, the headline and body of news articles are analyzed as two independent components, and their correlation is measured. We fine-tuned two BERT language models on the headline and body text as the two constituent parts of the news to determine whether there is a correlation between the news headline and body text. The results showed that this approach to fake news can enhance model accuracy compared to similar models.

Abstract Cobalt ferrite with a spinel structure is an important magnetic material.‌ These materials have interesting electrical and magnetic properties with high thermal and chemical stability. In this study, ferritic compound CO1-xMgxFe2O4 was prepared with different values of X 0.0, 0.2, 0.4, 0.6 and 0.8 using a sol-gel combustion method. The crystalline structure of the prepared samples was studied using an X-ray diffraction device (XRD). The particle Morphology was studied using scanning electronic microscope (SEM). The magnetic properties of the samples were investigated by a VSM Magnetized Magnetometer device. Also, the photocatalytic activity of nanostructures prepared for the destruction of organic contamination was studied using ultraviolet-spectrometer spectroscopy. The powder diffusion pattern showed that the produced powders had a spinel crystal structure and no impurities were observed. Investigating the magnetic properties of the samples showed that, by increasing the amount of magnesium, the nature of the sample varies from hard to soft ferromagnetic. Photocatalytic results showed that these materials are capable of destroying organic colors in the presence of visible light.

Abstract The radar receiver protector is one of the important components in the radar system. It prevents the receiver from noise and powerful Electromagnetic wave. In this paper, the simulations are done for different structures of the radar receiver protector using COMSOL software in the X-band frequency.The simulation selected structure is based on the WR90 waveguide structure. In this simulation, parameters such as reflection and transmission coefficients, as well as the maximum field intensity created within different radar receiver protector structures, have been investigated. The studied structures include iris-diaphragms-pairs, posts-and-diaphragms, truncated-cones-and-diaphragms, Dumbell-pointed-post-tunable, Dumbell-pointed-post, and Dumbell structures.



The simulation results show that the internal structure of the waveguide has an important parameter on the filtration performance, the frequency selection and intensity modes created on the tips of the electrodes. Dumbell-pointed-posts-tunable among the investigated structures due to the frequency modes and high intensity of the electric field at the tip of the electrodes, it is superior to other structures.

Abstract In this study, has been investigated the effects of key parameters, including coolant flow velocity and temperature, heat flux, and fin angle, on heat transfer performance. For this purpose, a concave parabolic fin has been used with angles of 0, 45, and 90 degrees relative to the coolant flow (air), flow velocity (between 1 and 2.5 m/s), and heat flux of 18.5 and 4.6 kW/m2. Due to its high thermal conductivity, the fin material has been selected aluminum. Results reveal that the parabolic fin's sharp-tip and curvature not only reduce its weight and volume compared to a triangular fin but also improve flow uniformity and thermal contact area. This leads to reduced pressure drop and thermal stresses, ultimately enhancing fin durability. The parabolic fin’s sharp end further minimizes vortex formation and variations in the heat transfer coefficient, and as flow velocity increases, the average heat transfer coefficient rises. Moreover, the analysis shows that changes in the angle between the fluid flow and fin alignment have minimal impact on fin efficiency, with pressure drop primarily influenced by flow velocity. The lowest pressure drop occurs at a flow angle of zero degrees. Additional, findings indicate that while an increase in flow velocity substantially raises pressure drop, changes in fin angle and heat flux have less pronounced effects. At zero-degree flow alignment, the minimal cross-sectional resistance of the fin results in the lowest observed pressure drop.