The advancement of autonomous driving technologies necessitates the development of sophisticated object detection systems capable of integrating heterogeneous sensor data to overcome the inherent limitations of unimodal approaches. While multi-modal fusion strategies offer promising solutions, they confront significant challenges such as data alignment complexities in early fusion and computational burdens coupled with overfitting risks in deep fusion methodologies. To address these issues, we propose a Multi-modal Multi-class Late Fusion (MMLF) framework that operates at the decision level. This late-fusion strategy preserves the architectural integrity of individual detectors and facilitates the flexible integration of diverse modalities. A key innovation of our approach is the incorporation of an evidence-theoretic uncertainty quantification mechanism, based on Dempster-Shafer theory, which provides a mathematically grounded confidence measure. Comprehensive offline evaluations on the KITTI benchmark dataset demonstrate the effectiveness of our framework, showing substantial performance improvements across multiple metrics (including 2D detection, 3D detection, and bird’s-eye view tasks) while simultaneously achieving significant reductions in uncertainty estimates—by approximately 77% for cars, 76% for pedestrians, and 67% for cyclists. These results collectively enhance both the reliability and interpretability of object detection outcomes. This work provides a versatile and scalable solution for multi-modal object detection that effectively addresses critical challenges in autonomous driving applications.
Free-space optical (FSO) communication systems face significant challenges from atmospheric turbulence, which induces time-correlated fading and burst errors that critically affect link reliability. This paper presents a comprehensive end-to-end CCSDS O3K simulation platform with detailed atmospheric channel and pointing error modeling, enabling realistic performance evaluation. The atmospheric channel model follows ITU-R P.1622-1 recommendations and incorporates amplitude scintillation with temporal correlation using Ornstein–Uhlenbeck processes, while the pointing error model captures beam misalignment effects inherent in satellite optical links. Through extensive Monte Carlo simulations, we investigate the impact of coherence time, and interleaving depth on system performance. Results show that deeper interleaving significantly improves reliability under realistic channel conditions, providing valuable design guidance for CCSDS-compliant optical communication systems. This study does not propose new algorithms or protocols; rather, it delivers the first end-to-end CCSDS-compliant simulation framework under realistically modeled turbulence and pointing errors. Accordingly, the results offer meaningful reference value and practical benchmarks for inter-satellite optical communication research and system design.
With the continuous progress of UAV technology and the rapid development of mobile edge computing (MEC), the UAV-assisted MEC system has shown great application potential in special fields such as disaster rescue and emergency response. However, traditional deep reinforcement learning (DRL) decision-making methods suffer from limitations such as difficulty in balancing multiple objectives and training convergence when making mixed action space decisions for UAV path planning and task offloading. This article innovatively proposes a hybrid decision framework based on the improved Dynamic Adaptive Genetic Optimization Algorithm (DAGOA) and soft actor–critic with hierarchical action decomposition, an uncertainty-quantified critic ensemble, and adaptive entropy temperature, where DAGOA performs an effective search and optimization in discrete action space, while SAC can perform fine control and adjustment in continuous action space. By combining the above algorithms, the joint optimization of drone path planning and task offloading can be achieved, improving the overall performance of the system. The experimental results show that the framework offers significant advantages in improving system performance, reducing energy consumption, and enhancing task completion efficiency. When the system adopts a hybrid decision framework, the reward score increases by a maximum of 153.53% compared to pure deep reinforcement learning algorithms for decision-making. Moreover, it can achieve an average improvement of 61.09% on the basis of various reinforcement learning algorithms such as proposed SAC, proximal policy optimization (PPO), deep deterministic policy gradient (DDPG), and twin delayed deep deterministic policy gradient (TD3).
Sayani Sarkar, Sima Shafaei, Trishtanya S. Jones
et al.
Deployment of Unmanned Aerial Vehicles (UAVs) continues to expand rapidly across a wide range of applications, including environmental monitoring, precision agriculture, and disaster response. Despite their increasing ubiquity, UAVs remain inherently vulnerable to security threats due to resource-constrained hardware, energy limitations, and reliance on open wireless communication channels. These factors render traditional cryptographic solutions impractical, thereby necessitating the development of lightweight, UAV-specific security mechanisms. This review article presents a comprehensive analysis of lightweight encryption techniques and key management strategies designed for energy-efficient and secure UAV communication. Special emphasis is placed on recent cryptographic advancements, including the adoption of the ASCON family of ciphers and the emergence of post-quantum algorithms that can secure UAV networks against future quantum threats. Key management techniques such as blockchain-based decentralized key exchange, Physical Unclonable Function (PUF)-based authentication, and hierarchical clustering schemes are evaluated for their performance and scalability. To ensure comprehensive protection, this review introduces a multilayer security framework addressing vulnerabilities from the physical to the application layer. Comparative analysis of lightweight cryptographic algorithms and multiple key distribution approaches is conducted based on energy consumption, latency, memory usage, and deployment feasibility in dynamic aerial environments. Unlike design- or implementation-focused studies, this work synthesizes existing literature across six interconnected security dimensions to provide an integrative foundation. Our review also identifies key research challenges, including secure and efficient rekeying during flight, resilience to cross-layer attacks, and the need for standardized frameworks supporting post-quantum cryptography in UAV swarms. By highlighting current advancements and research gaps, this study aims to guide future efforts in developing secure communication architectures tailored to the unique operational constraints of UAV networks.
The adaptability of conductive rubber in SO2/salt spray environment was studied by using graphene-filled conductive fluoroether rubber and alloy nickel powder-filled conductive silicone rubber in“SO2/salt spray” test. The macro morphology，Shore A hardness，tensile strength，elongation at break，tear strength and volume resistivity were tested to analyze the influence of the “SO2/salt spray” environment on the properties of conductive rubber. The results show before the test，the Shore A hardness of conductive fluoroether rubber and conductive silicone rubber are equivalent，the tensile strength of conductive fluoroether rubber is higher than that of conductive silicone rubber，and the volume resistivity is lower than that of conductive silicone rubber. After 8 cycles of “SO2/salt spray” test，the macro morphology of conductive fluoroether rubber does not change，Shore A hardness decreases by 3，tensile strength increases by 0.8 MPa（5%），elongation at break decreases by 18%， the volume resistivity increases by 2.1 Ω·cm（65.8%）and there is no change in tear strength；while the conductive silicone rubber has obvious corrosion，with green corrosion products appeared on the surface，Shore A hardness gradually decreases，and the tensile strength decreases by 1.2 MPa（16.4%），the elongation at break decreases by 2%，the volume resistivity decreases by 3.00 Ω·cm（52.4%）and there is no change in tear strength. The analysis of the comprehensive performances obtained by the study shows that the adaptability of conductive fluoroether rubber in “SO2/salt spray” environment is superior to that of conductive silicone rubber.
Vacuum chambers providing a low pressure environment similar to the vacuum environment in low earth orbit have been used for the testing of plasma thrusters. A signi!cant proportion of research on the effects of vacuum facility on plasma thrusters has focused on the effects of background pressure and plume expansion; however, the electrical interaction of the conductive chamber walls with the plasma thrusters needs to be explored further. In this study, the operation of a prototype Hall thruster, HK40, was investigated to understand the effects of wiring configuration of the thruster-cathode-chamber system. During the tests, the thruster was operated in two different grounding configurations. A resistance analogy regarding the changes in the electrical potentials and measured currents was introduced. The calculated thrust and efficiency values of the two configurations were compared. This study shows that the current extracted from the emitter surface of the cathode, along with the cathode-to- ground voltage can be used to estimate the thrust and thruster efficiency. In addition, the theoretical predictions were compared with the values based on the measurements made with an in-house-built inverted pendulum type thrust stand. The presented results show that the thrust and efficiency values are predicted with 3.4% and 8.3% uncertainty, respectively.
Technology, Motor vehicles. Aeronautics. Astronautics
This paper uses high-order approximate coupling (HOAC) dynamics equations for the hub–beam system with segmented active constrained layer damping treatment (SACLD). To improve the damping characteristics of traditional active constrained layer damping (ACLD), the viscoelastic damping layer, and the piezoelectric constraining layer are cut at the same position. The damping characteristics of the structure are enhanced by increasing the shear strain of the viscoelastic damping layer. The finite element method is used to discretize the SACLD beam. The discontinuity of the SACLD beam element-to-element displacement achieves the notch. Based on the theory of rigid–flexible coupling dynamics, the dynamic responses of the SACLD rotating beam under different cases are studied. The results show that the segmentation method is not always effective. A SACLD beam provides better vibration suppression than an ACLD beam only when appropriate material and dimensional parameters are used. The influences of base-layer thickness, piezoelectric constraining layer thickness, viscoelastic damping-layer thickness, angular velocity, the viscoelastic damping-layer loss factor, and control gains on the vibration of the rotating flexible beam with SACLD treatment are also discussed.
Ghazanfar Mehdi, Sara Bonuso, Maria Grazia De Giorgi
Re-ignition of aeroengines under high altitude conditions is of great importance to the safety and use of lean-burn flame. This study is focused on the experimental and numerical characterization of flow dynamics and flame re-ignition in a rectangular burner. A ring-needle type plasma actuator was considered and run by high-voltage (HV) nanopulsed plasma generator. The electrical power delivered to the fluid and an optimal value of reduced electric field (E<sub>N</sub>) was calculated considering non-reactive flow. Smoke flow visualizations using a high-speed camera and proper orthogonal decomposition (POD) were performed to recognize the most dominant flow structures. Experimental results revealed the transport effects due to plasma discharge, such as the induced flow, that could have a strong impact on the recirculation zone near the corners of combustor, improving the mixing performance and reducing the ignition delay time. Two different numerical tools (ZDPlasKin and Chemkin) were used to investigate the ignition characteristics. ZDPlasKin calculated the thermal effect and the plasma kinetic of nanopulsed plasma discharge at the experimentally measured E<sub>N</sub>. Finally, based on the output of ZDPlasKin, Chemkin estimated the flame ignition at low pressure and low temperature conditions. It was noticed that time required to achieve the maximum flame temperature with plasma actuation is significantly less than the auto-ignition time (‘clean case’, simulation result of the model without considering the plasma effect). Maximum reduction in ignition time was observed at inlet pressure 1 bar (3.5 × 10<sup>−5</sup> s) with respect to the clean case (1.1 × 10<sup>−3</sup> s). However, as the inlet pressure is reduced, the ignition delay time was increased. At 0.6 bar flame ignition occurred in clean case at 0.0048 s and at 0.0022 s in presence of the plasma actuation, a further decrease of the pressure up to 0.4 bar leads the ignition at 0.0027 s and 0.0063 s in clean and plasma actuation, respectively.
Currently, unmanned aerial vehicles (UAVs) are widely used due to their low cost and flexibility. In particular, they are used in remote sensing as airborne platforms for various instruments. Here, we investigate the capability of a conical scanning radar operated as a scatterometer mounted on a high-altitude UAV to perform sea surface wind retrieval based on an appropriate geophysical model function (GMF). Increasing the maximum altitude of the wind retrieval method’s applicability is an important problem for UAV or manned aircraft scatterometers. For this purpose, we consider the possibility of increasing the method’s maximum altitude by applying a semicircular scheme for azimuth normalized radar cross section (NRCS) sampling instead of a whole 360° circular scheme. We developed wind retrieval algorithms for both semicircular and circular NRCS sampling schemes and evaluated them using Monte Carlo simulations. The simulations showed that the semicircular scheme for azimuth NRCS sampling enables twice the maximum altitude for wind retrieval compared to a 360° circular scheme. At the same time, however, the semicircular scheme requires approximately three times the number of integrated NRCS samples in each azimuth sector to provide equivalent wind retrieval accuracy. Nonetheless, our results confirm that the semicircular azimuth NRCS sampling scheme is well-suited for wind retrieval, and any wind retrieval errors are within the typical range for scatterometer wind recovery. The obtained results can be used for enhancing existing UAV and aircraft radars, and for the development of new remote sensing systems.
Soil erosion monitoring is a pivotal exercise at macro through micro landscape levels, which directly informs environmental management at diverse spatial and temporal scales. The monitoring of soil erosion can be an arduous task when completed through ground-based surveys and there are uncertainties associated with the use of large-scale medium resolution image-based digital elevation models for estimating erosion rates. LiDAR derived elevation models have proven effective in modeling erosion, but such data proves costly to obtain, process, and analyze. The proliferation of images and other geospatial datasets generated by unmanned aerial systems (UAS) is increasingly able to reveal additional nuances that traditional geospatial datasets were not able to obtain due to the former’s higher spatial resolution. This study evaluated the efficacy of a UAS derived digital terrain model (DTM) to estimate surface flow and sediment loading in a fluvial aggregate excavation operation in Waukesha County, Wisconsin. A nested scale distributed hydrologic flow and sediment loading model was constructed for the UAS point cloud derived DTM. To evaluate the effectiveness of flow and sediment loading generated by the UAS point cloud derived DTM, a LiDAR derived DTM was used for comparison in consonance with several statistical measures of model efficiency. Results demonstrate that the UAS derived DTM can be used in modeling flow and sediment erosion estimation across space in the absence of a LiDAR-based derived DTM.
Artur Gustavo Slongo, André Luís da Silva, Deniel Desconzi Moraes
et al.
During the last decade, the world faced the mass insertion of small satellites in the space technology scenario. Every year, the number of micro and nanosatellites launched increases and gets more attention from players in the space market. Despite the lack of a national launcher, the Brazilian Space Program is known for some successful development in the last century, including its space assets, such as a privileged launch site near the equator, a family of flight proven and reliable sounding rockets for suborbital flights and microgravity experiments and universities with established small satellites programs. Thereby, the present work proposes a modification of the Brazilian VSB-30 sounding rocket in order to allow the launch and insertion in low Earth orbit (LEO) of small satellites fulfilling the gap of a national launcher. It also presents a CubeSat orbital decay simulation and orbital insertion simulation with the modified rocket launched from the Alcântara Launch Center as a matter of verifying the potential of national missions using this modified launcher.
Technology, Motor vehicles. Aeronautics. Astronautics
The design of aircraft and engine components hinges on the use of computer aided design (CAD) models and the subsequent geometry-based analyses for evaluation of the quality of a concept. However, the generation (and variation) of CAD models to include radical or novel design solutions is a resource intense modelling effort. While approaches to automate the generation and variation of CAD models exist, they neglect the capture and representation of the product’s design rationale—what the product is supposed to do. The design space exploration approach Function and Geometry Exploration (FGE) aims to support the exploration of more functionally and geometrically different product concepts under consideration of not only geometrical, but also teleological aspects. The FGE approach has been presented and verified in a previous presentation. However, in order to contribute to engineering design practice, a design method needs to be validated through application in industrial practice. Hence, this publication reports from a study where the FGE approach has been applied by a design team of a Swedish aerospace manufacturers in a conceptual product development project. Conceptually different alternatives were identified in order to meet the expected functionality of a guide vane (GV). The FGE was introduced and applied in a series of workshops. Data was collected through participatory observation in the design teams by the researchers, as well as interviews and questionnaires. The results reveal the potential of the FGE approach as a design support to: (1) Represent and capture the design rationale and the design space; (2) capture, integrate and model novel solutions; and (3) provide support for the embodiment of novel concepts that would otherwise remain unexplored. In conclusion, the FGE method supports designers to articulate and link the design rationale, including functional requirements and alternative solutions, to geometrical features of the product concepts. The method supports the exploration of alternative solutions as well as functions. However, scalability and robustness of the generated CAD models remain subject to further research.
We seek to ascertain and understand source terms that drive thermoacoustic instability and acoustic radiation. We present a new theory based on the decomposition of the Navier-Stokes equations coupled with the mass fraction equations. A series of solutions are presented via the method of the vector Green’s function. We identify both combustion-combustion and combustion-aerodynamic interaction source terms. Both classical combustion noise theory and classical Rayleigh criterion are recovered from the presently developed more general theory. An analytical spectral prediction method is presented, and the two-point source terms are consistent with Lord Rayleigh’s instability model. Particular correlations correspond to the source terms of Lighthill, which represent the noise from turbulence and additional terms for the noise from reacting flow.
In order to realize the acquisition and storage of underwater acoustic signals for aiming at the requirements of multi-channel, low power consumption and small volume for underwater receiver extension of sonar system, a multi-channel signal acquisition and storage system based on FPGA and STM32 with variable number of working channels and sampling frequency is designed, in which the system is consisted of 8 pieces, 8 channel and 24 bits high dynamic range Δ-Σ ADS1278 ADC chip to synchronous multi-channel analog signal acquisition. FPGA, as the acquisition sequence and logic control, reads and collates the ADC chip data and writes it into the internal high-capacity FIFO, and adds corresponding operations according to the characteristics of FIFO in an application. SMT32 single-chip microcomputer reads the FIFO data through the high-speed SPI interface with FPGA and writes the multi-channel data into the high-capacity SD card. The testing results have verified that the system has characteristics such as stable and reliable, easy configuration, low power consumption, can guarantee the multichannel data serial transmission, storage, accurate, up to 64 analog signals at the same time the real-time collection and storage, top 20 kHz sampling rate, the system total power of the system of about 3W, data rates up to 100 Mb/s, fully meet the needs of underwater sound acquisition system.
In order to study the influence of the equal-life curve models on DFR, the fitting accuracies of Gerber model and Goodman model for high-cycle fatigue data were compared with six typical aviation materials．The formula of DFR based on Gerber model and the expression of corrosion conversion coefficient <i>C</i><sub>C</sub> were derived， pre-corrosion fatigue tests for 0 h, 6 h, 12 h, 24 h, 36 h, and 72 h of 2024-T3 aluminum alloy (surface anodizing) were carried out，and the fatigue fracture of pre-corrosion for 72 hours was analyzed. The results show that Goodman model is suitable for brittle materials while Gerber model is suitable for ductile materials. As the pre-corrosion time increases, the DFR of 2024-T3 aluminum alloy decreases．The DFR based on Gerber model are 84.251 MPa, 84.721 MPa, 79.683 MPa, 80.745 MPa, 77.026 MPa and 74.996 MPa respectively, and the <i>C</i><sub>C</sub> is 1.006, 0.946, 0.958, 0.914 and 0.890，the fitting curve of the DFR with the pre-corrosion time is $ DFR=84.251{\left[ {\lg \left( {t + 10} \right)} \right]^{ - 0.15578}}$. It is found that when <i>N</i><sub>95/95</sub> > 10<sup>5</sup>, the DFR method based on Gerber model can give full play to the fatigue performance of ductile materials．Corrosion pits produced by pre-corrosion and inclusions in materials can accelerate the formation and expansion of fatigue cracks, but DFR of the anodized specimens is decreased in a corrosive environment compared with the bare materials.
Yahya Zefri, Achraf ElKettani, Imane Sebari
et al.
Being sustainable, clean, and eco-friendly, photovoltaic technology is considered as one of the most hoped solutions face to worldwide energetic challenges. Morocco joins this context with the inauguration of numerous clean energy projects. However, one key factor in making photovoltaic installations a profitable investment are regular and effective inspections in order to detect occurred defects. Unmanned aerial vehicles (UAV) are increasingly used in various inspection fields. In this respect, this work focuses on the use of thermal and visual imagery taken by UAV in the inspection of photovoltaic installations. Visual and thermal images of photovoltaic modules, obtained by UAV, from different installations, and with different acquisition conditions and parameters, were exploited to generate orthomosaics for inspection purposes. The methodology was tested on a dataset we have acquired by a mission in Rabat (Morocco), and also on external datasets acquired in Switzerland. As final results, several visual defects were detected in visual RGB and thermal orthomosaics, such as cracks, soiling, and hotspots. In addition, a procedure of semi-automatic hotspots’ extraction was also developed and is presented within this work. On the other side, various tests were conducted on the influence of some acquisition and processing parameters (images’ overlap, the ground sampling distance, the flying height, the use of ground control points, the internal camera parameters’ optimization) on the detection of defects and the quality of visual and thermal generated orthomosaics. In the end, the potential of UAV thermal and visual imagery in the inspection of photovoltaic installations was discussed in function of various parameters. On the basis of the discussion feedback, UAV were concluded as advantageous tools within the thematic of this project, which proves the necessity of their implementation in this context.
The article focuses on the study of the specific application of eddy-current probes (ECP) to monitor the parameters of dispersed media. To do this, a three-dimensional finite element model of the wear particles ECP was constructed in Ansys Maxwell 2015. The analysis of the the radial displacement of particles in the cross section of ECP with the help of the Sergei Korolyov supercomputer was carried out. It was found that the non-uniformity of electromagnetic field displacement of a particle from the axis to the periphery of the ECP results in three-fold increase of the insertion parameter. The deviation of the insertion parameters depends mainly on the geometrical position of the particle in the sectional plane of the sensor and it is weakly dependent on the frequency of the exciting field and particle size. On the basis of the established dependency we propose an ECP structure that allows mitigating the influence of the radial displacement of particles on the output signal of the ECP.
The article is addressed to the analysis of the trajectory parameters and videos obtained during the flight experiment at the launch of meteo-rocket MMP-06 with the purpose to determine major parameters of motion of a round parachute at subsonic speeds in the range of altitudes from 0 to 40 km. The data analysis showed that the trajectory of the parachute represents spiral "stretched" by the wind in the horizontal direction and disturbed by random factors of a non-stationary flow around the parachute. The main parameters of the trajectory are obtained according to the experimental data. Only qualitative analysis of spiral motion paths for round parachutes may be found in the publications on parachute subjects. This article presents the quantitative characteristics of this process.