Search Results (33)

Modern power transmission systems are required to meet increasingly stringent demands, including a wide range of transmission ratios, compact dimensions, high precision, energy efficiency, reliability, and thermal stability under dynamic operating conditions. Among the solutions that satisfy these requirements, cycloidal reducers are particularly prominent, with their application continuously expanding in industrial robotics, computer numerical control (CNC) machines, and military and transportation systems, as well as in the satellite industry. However, as with all mechanical power transmissions, friction in the contact zones of load-carrying elements in cycloidal reducers leads to power losses and an increase in operating temperature, which in turn results in a range of adverse effects. These undesirable phenomena strongly depend on lubrication conditions, namely on the type and properties of the applied lubricant. Although manufacturers’ catalogs provide general recommendations for lubricant selection, they do not address the fundamental tribological mechanisms in the most heavily loaded contact pairs. At the same time, the available scientific literature reveals a significant lack of systematic and experimentally validated studies examining the influence of lubricant type on the energetic and thermal performance of cycloidal reducers. To address this identified research gap, this study presents an analytical and experimental investigation of the effects of different lubricant types—primarily greases and mineral oils—on the thermal stability and efficiency of cycloidal reducers. The results demonstrate that grease lubrication provides lower total power losses and a more stable thermal operating regime compared to oil lubrication, while oil film thickness analyses indicate that the most unfavorable lubrication conditions occur in the contact between the eccentric bearing rollers and the outer raceway. These findings provide valuable guidelines for engineers involved in cycloidal reducer design and lubricant selection under specific operating conditions, as well as deeper insight into the lubricant behavior mechanisms within critical contact zones. Full article

Metal powders have both a high specific energy and a high energy density, which explains their widespread use in energetic materials (propellants, explosives and pyrotechnics). Pyrotechnic compositions are used extensively for both civilian and military applications. However, the combustion of pyrotechnics remains challenging to understand or predict due to the diversity of the components and the wide range of parameters that affect their results. Therefore, ongoing research efforts worldwide aim to investigate the combustion mechanisms of pyrotechnic compositions to improve their performance. In this review, studies on the ignition and combustion mechanisms of four metal powders (Al, Mg, Fe and B) are discussed. Moreover, their use as fuel in pyrotechnic systems is reported, as well as the combustion performance and energy release of the pyrotechnic mixtures. Additionally, some mixtures composed of fluorinated oxidizers and Al, Mg and B are also presented. Thermal analysis methods such as DSC and TG are used to obtain the thermal behavior of the pyrotechnic compositions. Furthermore, parameters such as particle size and the equivalence ratio that affect the performance of pyrotechnic mixtures and those that remain little studied are reported in this review. Full article

Gigapascal ultra-high-strength steel holds significant applications in the energy and military sectors. Such steel is typically produced through quenching and tempering processes. However, during quenching, issues such as excessive internal stress often lead to significant deviations in flatness, thereby reducing product precision. This study adopts an approach integrating theoretical and practical methods to develop a control technology for achieving high flatness in gigapascal ultra-high-strength martensitic steel. Firstly, finite element simulation was employed to establish a temperature-phase transformation-stress coupling model for the quenching process of gigapascal martensitic steel. The study investigated the deformation behavior of steel plates under unilateral cooling, the influence of dynamic martensitic transformation on internal stress, and the effects of plate thickness and water ratio. This revealed how quenching process parameters affect the internal stress and deformation of steel plates. Based on theoretical calculations and considering on-site equipment conditions, industrial production line commissioning was conducted, which significantly reduced the quenching internal stress of gigapascal ultra-high-strength martensitic steel and greatly improved the flatness of the steel plates. The results surpassed those of international companies such as Sweden’s SSAB and other domestic enterprises, achieving an internationally leading level. Full article

Self-oscillating systems convert steady external stimuli into sustained motion, enabling diverse applications in robotics, energy absorption, optics, and logic. Inspired by the adhesion–detachment behavior of climbing plants, we propose a novel light-powered self-adhesion oscillator comprising an elastic strip–substrate structure and a weight suspended by a photo-responsive liquid crystal elastomer fiber. By integrating a nonlinear beam deformation model with Dugdale’s cohesive model, we develop a nonlinear dynamic framework to describe the self-adhesion behavior of the elastic strip. Quasi-static analysis reveals two distinct operating modes: a static mode and a self-adhesion mode. Under constant light exposure, the liquid crystal elastomer fiber undergoes light-induced contraction, increasing peeling force and triggering a sudden transition from adhesion-on to adhesion-off. Upon entering the adhesion-off state, the fiber recovers its contraction, leading to a sharp return to the adhesion-on state. This cycle sustains a four-stage oscillation: gradual peeling, abrupt adhesion-off, gradual adhering, and abrupt adhesion-on. Furthermore, we identify the critical conditions for initiating self-adhesion and demonstrate effective control over the oscillation period. The system exhibits key advantages including amplitude controllable oscillation, widely tunable frequency, well-defined motion trajectories, and structural simplicity. These characteristics suggest promising potential for applications in self-healing adhesion systems, rescue devices, military engineering, and beyond. Full article

Naval ships are of paramount importance to national security, culture, and naval operations. A primary challenge for naval authorities is to balance the imperatives of maritime dominance with the operational demands of achieving sufficient, sustainable reliability. Shaft generators (SGs) are crucial to the energy conversion systems on naval ships, functioning as part of the main power systems on board and providing both propulsion and power for various operational loads. In this sense, the design of shaft generators is an engineering element that has a major impact on the overall ship performance. The design process will be conducted within the MATLAB/Simulink environment, a platform that facilitates the study of the dynamic behaviors of the system through simulation. The increasing demand for efficiency, reliability, and sustainability in the military, along with the impact of emerging technologies, will further underscore the significance of shaft generators. Analyses carried out in MATLAB/Simulink demonstrate that the selection of the most suitable power system for naval ships is dictated by the system requirements and operational demands. The main construction is such that this work is the first of its kind in the field of shaft generator research for naval ships. Full article

The Multi-Objective Optimization Problem (MOOP) in Wireless Sensor Networks (WSNs) is a challenging issue that requires balancing multiple conflicting objectives, such as maintaining coverage, connectivity, and network lifetime all together. These objectives are important for a functioning WSN safety-critical applications, whether in environmental monitoring, military surveillance, or smart cities. To address these challenges, we propose a novel bio-inspired Bird Flocking Node Scheduling algorithm, which takes inspiration from the natural flocking behavior of birds migrating over long distance to optimize sensor node activity in a distributed and energy-efficient manner. The proposed algorithm integrates the Lyapunov function to maintain connected coverage while optimizing energy efficiency, ensuring service availability and reliability. The effectiveness of the algorithm is evaluated through extensive simulations, namely MATLAB R2018b simulator coupled with a Pareto front, comparing its performance with our previously developed BAT node scheduling algorithm. The results demonstrate significant improvements across key performance metrics, specifically, enhancing network coverage by 8%, improving connectivity by 10%, and extending network lifetime by an impressive 80%. These findings highlight the potential of bio-inspired Bird Flocking optimization techniques in advancing WSN dependability, making them more sustainable and suitable for real-world WSN safety-critical systems. Full article

Energy absorption capacity (EAC) is a parameter that expresses how much energy materials can store or dissipate under an external load or impact. EAC plays a critical role in understanding soil deformations and dynamic stability under impact loads (e.g., falling masses, projectile penetration, blast impacts, or vehicle collisions). Impact loads are sudden and high-accelerated forces that cause soils to deform rapidly and absorb energy differently. Understanding the EAC of soils under impact loads is critical for various geotechnical applications, particularly understanding soil behavior under blast loads, which is critical for military and civil structures, and the reinforcement of soils and design of protective structures that will be subjected to similar sudden impacts. This study aims to develop a novel experimental method and apparatus to evaluate the EAC of sandy soils under controlled laboratory conditions. A custom-designed test device was used to measure impact forces exerted by a metal sphere dropped from a fixed height onto soil samples with varying grain sizes (coarse, medium, and fine) and relative densities (40%, 70%, and 90%) under different moisture conditions (dry, optimum, and wet). The results showed that fine-grained sands exhibited the highest EAC, with absorbed energy values reaching 23.15 J, while coarse-grained sands under dense and saturated conditions exhibited the lowest capacity (22.05 J). An increase in moisture content from dry water content to optimum water content resulted in a moderate increase in energy absorption followed by a slight decrease under saturated conditions. Similarly, higher relative density marginally reduced energy absorption, reflecting reduced soil deformation at higher densities. The study introduces a potentially standardizable testing procedure for assessing soil impact response, providing valuable insights for geotechnical engineering applications, including soil stabilization, pavement design, and impact-resistant infrastructure. Full article

The objective of this study was to investigate the distribution of pyrolysis products and the chemical reaction kinetics of a novel composite, GO@CL-20. The GO@CL-20 composite powder was synthesized using a solvent–non-solvent method. The thermal decomposition process of GO@CL-20 was analyzed through thermogravimetric differential scanning calorimetry (TG-DSC). The results indicate that the incorporation of graphene oxide (GO) reduces the activation energy of the sample, thereby catalyzing the thermal decomposition process of the complex. Subsequently, single pulse shock tube experiments were conducted to assess ignition delay time distribution, from which corresponding data on pyrolysis product distribution for GO@CL-20 were obtained. The findings regarding ignition delay times demonstrate that adding GO decreases the energy within the complex system and mitigates its reactivity, consequently prolonging ignition delay times. An important carbon and nitrogen molecule, C₂N₂, was identified in the pyrolysis product distribution; notably, its yield increased progressively with higher concentrations of GO. Finally, mass transfer characteristics and sensitivity analyses for GO@CL-20 samples were performed using CHEMKIN software to preliminarily determine pyrolysis reaction pathways. The results reveal that incorporating GO can significantly alter the thermal decomposition behavior of the entire system; moreover, C₂N₂ exhibits a high cleavage rate along this reaction pathway—findings that align well with experimental observations. This study aims to enhance understanding of CL-20 and GO reaction kinetics—materials with extensive applications in military operations as well as aviation and aerospace—and provides valuable insights for propellant development. Full article

Veterans often face transportation barriers, but advances in technology enable real-world testing of shared autonomous electric vehicles as potential energy-efficient solutions. While previous research has assessed civilians’ perceptions of autonomous vehicles (AVs), veterans—due to unique military experiences and health conditions—represent a distinct demographic. This study investigates veterans’ perceptions of autonomous shuttles (ASs) to assess whether these innovations may foster sustainable transportation behaviors. Leveraging data from the Autonomous Vehicle User Perception Survey (AVUPS), this study assessed AS perceptions among 77 veterans across four Florida cities before and after exposure. Results indicated significant increases in intention to use and total acceptance and a decrease in perceived barriers, with no change in well-being. Urban veterans showed improvements across multiple subscales, while rural veterans only showed reduced perceived barriers. Those with initially low total acceptance scores demonstrated greater improvements, particularly in intention to use and perceived barriers. The analysis of survey items showed increased trust, greater willingness to multitask, improved safety perceptions, and reduced concerns about declining driving abilities and hesitations toward AVs, with the latter three items remaining significant after correction. Overall, AS exposure positively influenced veterans’ perceptions, and the results point to the potential of ASs as a sustainable transportation option for veterans. Full article

Li-ion batteries possess significant advantages like large energy density, fast recharge, and high reliability; hence, they are widely adopted in electric vehicles, portable electronics, and military and aerospace applications. Albeit having their merits, accurate battery modeling is subjected to problems like prior information on internal chemical reactions, complexity in problem formulation, a large number of unknown parameters, and the need for extensive experimentation. Hence, this article presents a reliable Spotted Hyena Optimizer (SHO) to determine the equivalent circuit parameters of lithium-ion (Li-ion) batteries. The methodology of the SHO is derived from the living and hunting tactics of spotted hyenas, and it is efficiently applied to solve the battery parameter estimation problem. Nine unknown battery model parameters of a Samsung INR 18650-25R are determined using this method. The model parameters estimated are endorsed for five different datasets with various discharge current values. Further, the effect of parameter range and its selection is also emphasized. Secondly, for validation, various performance metrics such as Integral Squared Error, mean best, mean worst, and Standard Deviation are evaluated to authenticate the superiority of the proposed parameter extraction. From the computed results, the SHO algorithm is able to explore the search area up to 89% in the case of larger search ranges. The chosen model and range of the SHO precisely predict the behavior of the proposed Li-ion battery, and the results are in accordance with the catalog data. Full article

With the rapid development of space–air–ground integrated networks (SAGIN), the synergy between the satellite and unmanned aerial vehicles (UAVs) in sensing environmental status information reveals substantial potential. In SAGIN, applications such as disaster response and military operations require fresh status information to respond effectively. The freshness of information, quantified by the age of information (AoI) metric, is crucial for an effective response. Therefore, it is urgent to investigate the AoI in real-time remote sensing systems leveraging satellite–UAV synergy. To this end, we first establish a comprehensive system model, corresponding to the satellite–UAV “multiscale explanation” synergy remote sensing system in SAGIN, in which we focus on the typical information transmission and fusion strategies of the system, the analysis framework of AoI, and the temporal evolution of AoI. Subsequently, the time-varying process of the system model is transformed into a corresponding finite-states continuous-time Markov chain, enabling a precise analysis of its stochastic behavior. By employing the stochastic hybrid system (SHS) approach, the moment generating functions (MGFs) and mean AoI, offering quantitative insights into the freshness of status information, are derived. Following this, a comparative analysis of AoI under different queuing disciplines, highlighting their respective performance characteristics, is conducted. Furthermore, considering transmit power and bandwidth constraints of the system, the AoI performances under full frequency reuse (FFR), and frequency division multiple access (FDMA) strategies are analyzed. The energy advantage and spectrum advantage associated with AoI are also examined to explore the superior AoI-related performance of the FFR strategy in SAGIN. Full article

Magnesium alloys show great promise in high-speed transport, aerospace, and military technology; however, their widespread adoption encounters challenges attributed to limitations such as poor plasticity and strength. This study examines the high-temperature deformation of semi-solid forged AZ91D magnesium alloy through a combination of experiments and simulations, with a focus on comprehending the influence of deformation conditions on dynamic recrystallization (DRX). The findings disclose that conspicuous signs of DRX manifest in the yield stress curve as strain increases. Additionally, decreasing the strain rate and temperature correlates with a reduction in both yield stress and peak strain, and the activation energy is 156.814 kJ/mol, while the critical strain and peak strain remain relatively consistent (${\epsilon }_{\mathrm{c}}=0.66208{\epsilon }_{\mathrm{p}}$). Microstructural changes during high-temperature deformation and the onset of DRX are thoroughly examined through experimental methods. Moreover, a critical strain model for DRX and a predictive model for the volume fraction of DRX were formulated. These equations and models, validated through a combination of experiments and simulations, serve as invaluable tools for predicting the mechanical behavior and microstructural evolution, which also establishes a foundation for accurately predicting the deformation behavior of this alloy. By analyzing the hot deformation characteristics and dynamic compression mechanism of the newly developed semi-solid forging AZ91D magnesium alloy, a numerical simulation model can be effectively established. This model objectively reflects the changes and distributions of stress, strain, and rheological velocity, providing a scientific basis for selecting subsequent plastic deformation process parameters and designing mold structures. Full article

Jute is an inherent lignocellulosic fiber, consisting of hemicellulose, α-cellulose, and lignin. Industrial ventilation, automotive composites, upholstery, carpets, military uniforms, hospital furnishings, and curtains necessitate the integration of flame-retardance properties into jute fibers. In this investigation, seven weave-structured jute fabrics were treated using an organophosphorus-based flame-retardant (FR) chemical (ITOFLAM CPN) and a crosslinking agent (KNITTEX CHN) by the pad–dry–cure method. The thermal stability, degradation and pyrolysis behavior of jute was measured using a thermogravimetric analyzer (TGA). Surface morphology and element distribution were scrutinized utilizing a scanning electron microscope (SEM) and an energy-dispersive spectrometer (EDS). The ATR-FTIR (Attenuated Total Reflection-Fourier Transform Infrared Spectrometer) technique has been employed for analyzing the composition of chemicals in the jute fabrics. According to the protocols specified in ISO 14184-1, free formaldehyde detection was carried out on the jute fabrics. The flame-retardance property was significantly improved on all of the jute fabrics after FR treatment. FTIR and SEM-EDS studies revealed the presence of FR chemical deposition on the surface of the jute fabrics. TGA analysis indicated that the fabrics treated with FR exhibited premature degradation, leading to the generation of more char compared to untreated samples. The jute fabrics specifically demonstrated a notable enhancement in residual mass, exceeding 50% after FR treatment. However, it is noteworthy that the FR-treated fabrics exhibited an elevated level of free formaldehyde content, surpassing the permissible limit of formaldehyde in textiles intended for direct skin contact. The residual mass loss percentage after ten washes of FR-treated fabrics remained in a range from 32% to 36%. Twill weave designed fabrics (FRD4 and FRD5) clearly showed a lower thermal degradation temperature than the other weaves used in this study. Full article

Metamaterials, recognized as advanced artificial materials endowed with distinctive properties, have found diverse applications in everyday life, military endeavors, and scientific research. Starting from monolayer metamaterials, multilayer ones are increasingly researched, especially in the field of electromagnetic wave absorption. In this article, we propose a multilayer metamaterial-absorber (MA) structure comprising two resonant layers crafted with copper and FR-4 dielectric. The presented multilayer MA structure exhibited an absorption greater than 90% in a frequency range from 4.84 to 5.02 GHz, with two maximum absorption peaks at 4.89 and 4.97 GHz. The bandwidth of the multilayer MA surpassed that of the individual single-layer MAs, with extension fractions reaching 360% and 257%, respectively. Through the simulation and calculation, the field distribution and equivalent circuit model elucidated that both individual magnetic resonances and their interplay contribute significantly to the absorption behavior of the multilayer MA. The absorption of the proposed multilayer MA structure was also investigated for the oblique incidence in the transverse electric (TE) and transverse magnetic (TM) modes. In the TE mode, the absorption intensity of two maximum peaks was maintained at over 93% up to an incident angle of 40 degrees and dropped to below 80% at an incident angle of 60 degrees. In the TM mode, the absorption was more stable and not significantly affected by the incident angle, ranging from 0 to 60 degrees. An absorption greater than 97% was observed when the incident angle increased from 0 to 60 degrees in the TM mode. Additionally, the approach in our work was further demonstrated by adding more resonant layers, making 3- and 4-layer structures. The results indicated that the absorption bandwidths of the 3- and 4-layer structures increased by 16% and 33%, respectively, compared to the bilayer structure. Furthermore, we analyzed the thermal distribution within the MA to understand the dissipation of absorbed electromagnetic energy. This research offers valuable insight into the augmented MA through a multilayer structure, presenting the implications for microwave applications like electromagnetic shielding, as well as in the design of MAs for terahertz devices and technologies, including emission and thermal imaging. These findings contribute to the advancement of knowledge in enhancing the absorption capabilities across various frequency ranges, expanding the potential applications of metamaterials. Full article

This paper deals with the analyses of batteries used in current military systems to power the electric drives of military vehicles. The article focuses on battery analyses based on operational data obtained from measurements rather than analyses of the chemical composition of the tested batteries. The authors of the article used their experience from the development test-laboratory of military technology. This article presents a comparative analysis of existing and promising technologies in the field of energy storage and buffering for military electric vehicles. The overview of these technologies, including the design, operating principles, advantages, and disadvantages, are briefly presented to produce theoretical comparative analyses. However, this article mainly focuses on the experimental verification of operational ability in varied conditions, as well as the comparison and analysis of these results. The main part of the article provides more experimental studies on technologies of energy storage and buffering using the results of several experiments conducted to demonstrate the behavior of each technology in different working conditions. The output parameters, as well as the state of charge of each technology’s samples, were surveyed in various temperatures and loading characteristics. The results presented in this paper are expected to be useful for optimizing the selection of energy storage and buffering solutions for military electric vehicles in different applications and functional environments. Full article