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 In this paper, the generation of the second harmonic due to the propagation of a short laser pulse in a low-density cold plasma in the presence of a Wiegler magnetic field is investigated with respect to successive collisions and reflections. Using a non-magnetic isotropic plasma, only odd harmonics can be produced. Tthe nonlinear Lorentz forces can be strengthened, which creates a transverse gradient in the electron number density, which is one of the factors producing even harmonics Next, using the perturbation theory, the components of the first and second harmonic electric field are calculated up to the first order of perturbation, and the effect of successive reflections on the amplitude of the first and second harmonic electric field, as well as the reflected power efficiency of the second harmonic, is investigated, and conclusions are drawn by analyzing the desired relationships and drawing the desired graphs.. Finally, the behavior of the harmonic field amplitude for zeroth and first order perturbation in the plasma blade is investigated for different cases and their changes are plotted in terms of different parameters and the results and optimal conditions for different applications are discussed and suggestions are made. This technology can revolutionize laser systems, electronic warfare, advanced radars, and aerospace defense in the near future. Its combination with nonlinear plasmas and the Wiggler magnetic field allows the generation and guidance of electromagnetic waves that can be effective in countering modern threats such as hypersonic missiles, stealth drones, and hostile space systems.

Abstract This article examines the design of active isolators using the optimal algorithm (LQR). For this purpose, the dynamic model of the satellite launch vehicle as 6 degrees of freedom has been considered. Because the satellite carrier structure has a shell with reinforced ribs and stringers, Stiffness Calculation Methods(SCM) for reinforced shells were used. Also, to calculate the final frequency of the system, the equations of motion obtained from the dynamic model of the satellite launch vehicle were used. For damp vibrations generated with a vibration amplitude of less than 100 Hz, no method in the research conducted has been proposed. In this research, for the first time, a combined system of passive and active isolators to damp vibrations introduced into the energy supply block was used. The results of the present study show that combining these two systems improves the performance of each of the passive and active systems.In this combination, according to the results obtained by this system, vibrations with a vibration amplitude of less than 50 Hz are damped by up to 88 percent, and vibrations on the energy supply block with a vibration amplitude between 50 and 500 Hz by up to 96 percent are damped.