Pub Date : 2024-08-21DOI: 10.1016/j.dt.2024.08.009
Chen Tao, Chong Ji, Xin Wang, Juan Gu, Yuting Wang, Changxiao Zhao
Liquid-filled containers (LFC) are widely used to store and transport petroleum, chemical reagents, and other resources. As an important target of military strikes and terrorist bombings, LFC are vulnerable to blast waves and fragments. To explore the protective effect of polyurea elastomer on LFC, the damage characteristics of polyurea coated liquid-filled container (PLFC) under the combined loading of blast shock wave and fragments were studied experimentally. The microstructure of the polyurea layer was observed by scanning electron microscopy, and the fracture and self-healing phenomena were analyzed. The simulation approach was used to explain the combined blast- and fragments-induced on the PLFC in detail. Finally, the effects of shock wave and fragment alone and in combination on the damage of PLFC were comprehensively compared. Results showed that the polyurea reduces the perforation rate of the fragment to the LFC, and the self-healing phenomenon could also reduce the liquid loss rate inside the container. The polyurea reduces the degree of depression in the center of the LFC, resulting in a decrease in the distance between adjacent fragments penetrating the LFC, and an increase in the probability of transfixion and fracture between holes. Under the close-in blast, the detonation shock wave reached the LFC before the fragment. Polyurea does not all have an enhanced effect on the protection of LFC. The presence of internal water enhances the anti-blast performance of the container, and the hydrodynamic ram (HRAM) formed by the fragment impacting the water aggravated the plastic deformation of the container. The combined action has an enhancement effect on the deformation of the LFC. The depth of the container depression was 27% higher than that of the blast shock wave alone; thus, it cannot be simply summarized as linear superposition.
{"title":"Characterization of combined blast- and fragments-induced synergetic damage in polyurea coated liquid-filled container","authors":"Chen Tao, Chong Ji, Xin Wang, Juan Gu, Yuting Wang, Changxiao Zhao","doi":"10.1016/j.dt.2024.08.009","DOIUrl":"https://doi.org/10.1016/j.dt.2024.08.009","url":null,"abstract":"Liquid-filled containers (LFC) are widely used to store and transport petroleum, chemical reagents, and other resources. As an important target of military strikes and terrorist bombings, LFC are vulnerable to blast waves and fragments. To explore the protective effect of polyurea elastomer on LFC, the damage characteristics of polyurea coated liquid-filled container (PLFC) under the combined loading of blast shock wave and fragments were studied experimentally. The microstructure of the polyurea layer was observed by scanning electron microscopy, and the fracture and self-healing phenomena were analyzed. The simulation approach was used to explain the combined blast- and fragments-induced on the PLFC in detail. Finally, the effects of shock wave and fragment alone and in combination on the damage of PLFC were comprehensively compared. Results showed that the polyurea reduces the perforation rate of the fragment to the LFC, and the self-healing phenomenon could also reduce the liquid loss rate inside the container. The polyurea reduces the degree of depression in the center of the LFC, resulting in a decrease in the distance between adjacent fragments penetrating the LFC, and an increase in the probability of transfixion and fracture between holes. Under the close-in blast, the detonation shock wave reached the LFC before the fragment. Polyurea does not all have an enhanced effect on the protection of LFC. The presence of internal water enhances the anti-blast performance of the container, and the hydrodynamic ram (HRAM) formed by the fragment impacting the water aggravated the plastic deformation of the container. The combined action has an enhancement effect on the deformation of the LFC. The depth of the container depression was 27% higher than that of the blast shock wave alone; thus, it cannot be simply summarized as linear superposition.","PeriodicalId":10986,"journal":{"name":"Defence Technology","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142189173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-21DOI: 10.1016/j.dt.2024.08.015
Kangning Yin, Xinhui Ji, Yan Wang, Zhiguo Wang
Federated learning (FL) is a distributed machine learning paradigm for edge cloud computing. FL can facilitate data-driven decision-making in tactical scenarios, effectively addressing both data volume and infrastructure challenges in edge environments. However, the diversity of clients in edge cloud computing presents significant challenges for FL. Personalized federated learning (pFL) received considerable attention in recent years. One example of pFL involves exploiting the global and local information in the local model. Current pFL algorithms experience limitations such as slow convergence speed, catastrophic forgetting, and poor performance in complex tasks, which still have significant shortcomings compared to the centralized learning. To achieve high pFL performance, we propose FedCLCC: Federated Contrastive Learning and Conditional Computing. The core of FedCLCC is the use of contrastive learning and conditional computing. Contrastive learning determines the feature representation similarity to adjust the local model. Conditional computing separates the global and local information and feeds it to their corresponding heads for global and local handling. Our comprehensive experiments demonstrate that FedCLCC outperforms other state-of-the-art FL algorithms.
{"title":"FedCLCC: A personalized federated learning algorithm for edge cloud collaboration based on contrastive learning and conditional computing","authors":"Kangning Yin, Xinhui Ji, Yan Wang, Zhiguo Wang","doi":"10.1016/j.dt.2024.08.015","DOIUrl":"https://doi.org/10.1016/j.dt.2024.08.015","url":null,"abstract":"Federated learning (FL) is a distributed machine learning paradigm for edge cloud computing. FL can facilitate data-driven decision-making in tactical scenarios, effectively addressing both data volume and infrastructure challenges in edge environments. However, the diversity of clients in edge cloud computing presents significant challenges for FL. Personalized federated learning (pFL) received considerable attention in recent years. One example of pFL involves exploiting the global and local information in the local model. Current pFL algorithms experience limitations such as slow convergence speed, catastrophic forgetting, and poor performance in complex tasks, which still have significant shortcomings compared to the centralized learning. To achieve high pFL performance, we propose FedCLCC: Federated Contrastive Learning and Conditional Computing. The core of FedCLCC is the use of contrastive learning and conditional computing. Contrastive learning determines the feature representation similarity to adjust the local model. Conditional computing separates the global and local information and feeds it to their corresponding heads for global and local handling. Our comprehensive experiments demonstrate that FedCLCC outperforms other state-of-the-art FL algorithms.","PeriodicalId":10986,"journal":{"name":"Defence Technology","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142189172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-19DOI: 10.1016/j.dt.2024.08.011
Hang Zhou, Hujun Li, Zhen Wang, Dongming Yan, Wenxin Wang, Guokai Zhang, Zirui Cheng, Song Sun, Mingyang Wang
The compression and energy absorption properties of foam geopolymers increase stress wave attenuation under explosion impacts, reducing the vibration effect on the structure. Explosion tests were conducted using several composite structure models, including a concrete lining structure (CLS) without foam geopolymer and six foam geopolymer composite structures (FGCS) with different backfill parameters, to study the dynamic response and wave dissipation mechanisms of FGCS under explosive loading. Pressure, strain, and vibration responses at different locations were synchronously tested. The damage modes and dynamic responses of different models were compared, and how wave elimination and energy absorption efficiencies were affected by foam geopolymer backfill parameters was analyzed. The results showed that the foam geopolymer absorbed and dissipated the impact energy through continuous compressive deformation under high strain rates and dynamic loading, reducing the strain in the liner structure by 52% and increasing the pressure attenuation rate by 28%. Additionally, the foam geopolymer backfill reduced structural vibration and liner deformation, with the FGCS structure showing 35% less displacement and 70% less acceleration compared to the CLS. The FGCS model with thicker, less dense foam geopolymer backfill, having more pores and higher porosity, demonstrated better compression and energy absorption under dynamic impact, increasing stress wave attenuation efficiency. By analyzing the stress wave propagation and the compression characteristics of the porous medium, it was concluded that the stress transfer ratio of FGCS-ρ-579 was 77% lower than that of CLS, and the transmitted wave energy was 90% lower. The results of this study provide a scientific basis for optimizing underground composite structure interlayer parameters.
{"title":"Experimental investigation on the anti-detonation performance of composite structure containing foam geopolymer backfill material","authors":"Hang Zhou, Hujun Li, Zhen Wang, Dongming Yan, Wenxin Wang, Guokai Zhang, Zirui Cheng, Song Sun, Mingyang Wang","doi":"10.1016/j.dt.2024.08.011","DOIUrl":"https://doi.org/10.1016/j.dt.2024.08.011","url":null,"abstract":"The compression and energy absorption properties of foam geopolymers increase stress wave attenuation under explosion impacts, reducing the vibration effect on the structure. Explosion tests were conducted using several composite structure models, including a concrete lining structure (CLS) without foam geopolymer and six foam geopolymer composite structures (FGCS) with different backfill parameters, to study the dynamic response and wave dissipation mechanisms of FGCS under explosive loading. Pressure, strain, and vibration responses at different locations were synchronously tested. The damage modes and dynamic responses of different models were compared, and how wave elimination and energy absorption efficiencies were affected by foam geopolymer backfill parameters was analyzed. The results showed that the foam geopolymer absorbed and dissipated the impact energy through continuous compressive deformation under high strain rates and dynamic loading, reducing the strain in the liner structure by 52% and increasing the pressure attenuation rate by 28%. Additionally, the foam geopolymer backfill reduced structural vibration and liner deformation, with the FGCS structure showing 35% less displacement and 70% less acceleration compared to the CLS. The FGCS model with thicker, less dense foam geopolymer backfill, having more pores and higher porosity, demonstrated better compression and energy absorption under dynamic impact, increasing stress wave attenuation efficiency. By analyzing the stress wave propagation and the compression characteristics of the porous medium, it was concluded that the stress transfer ratio of FGCS-ρ-579 was 77% lower than that of CLS, and the transmitted wave energy was 90% lower. The results of this study provide a scientific basis for optimizing underground composite structure interlayer parameters.","PeriodicalId":10986,"journal":{"name":"Defence Technology","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-19DOI: 10.1016/j.dt.2024.08.012
Zübeyde Özkan, Uğur Gökmen, Sema Bilge Ocak
Functionally graded composite/hybrid materials (FGCM/FGHCM) were produced by adding BC, TiO, and BC+TiO ceramic materials at various ratios (0–50%) into the AA6082 matrix. The analysis of the damage caused by Co ions' (1.173–1.1332 MeV) on the material was examined using the SRIM/TRIM Monte Carlo simulation software. In the simulation, the following data regarding the atoms of the target materials were obtained: ion distribution, target ionization, total displacements, surface binding energy, lattice binding energy, and displacement energy. Among the studied four materials, the one with the highest ion range value was found to be AA6082 with 8550 Å. TiO was found to be the reinforcement material that reduced the ion range the most in the material. Due to its high binding energy, BC reinforced AA6082+(0–50%) BC FGCM was found to have the least vacancy with 4782/ion.
通过在 AA6082 基体中添加不同比例（0-50%）的 BC、TiO 和 BC+TiO 陶瓷材料，制备了功能分级复合材料/混合材料（FGCM/FGHCM）。使用 SRIM/TRIM Monte Carlo 仿真软件分析了 Co 离子（1.173-1.1332 MeV）对材料造成的破坏。在模拟过程中，获得了目标材料原子的以下数据：离子分布、目标电离、总位移、表面结合能、晶格结合能和位移能。在所研究的四种材料中，离子范围值最高的是 AA6082，为 8550 Å。由于结合能较高，BC 增强 AA6082+（0-50%）BC FGCM 的空位最少，为 4782 个/离子。
{"title":"Damage analysis caused by 60Co ions in functionally graded materials","authors":"Zübeyde Özkan, Uğur Gökmen, Sema Bilge Ocak","doi":"10.1016/j.dt.2024.08.012","DOIUrl":"https://doi.org/10.1016/j.dt.2024.08.012","url":null,"abstract":"Functionally graded composite/hybrid materials (FGCM/FGHCM) were produced by adding BC, TiO, and BC+TiO ceramic materials at various ratios (0–50%) into the AA6082 matrix. The analysis of the damage caused by Co ions' (1.173–1.1332 MeV) on the material was examined using the SRIM/TRIM Monte Carlo simulation software. In the simulation, the following data regarding the atoms of the target materials were obtained: ion distribution, target ionization, total displacements, surface binding energy, lattice binding energy, and displacement energy. Among the studied four materials, the one with the highest ion range value was found to be AA6082 with 8550 Å. TiO was found to be the reinforcement material that reduced the ion range the most in the material. Due to its high binding energy, BC reinforced AA6082+(0–50%) BC FGCM was found to have the least vacancy with 4782/ion.","PeriodicalId":10986,"journal":{"name":"Defence Technology","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142189175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-14DOI: 10.1016/j.dt.2024.08.004
Zhihai Dong, Ye Tian, Long Zhang, Tong Jiang, Dafeng Wang, Yunlong Chang, Donggao Chen
Titanium alloy has the advantages of high strength, strong corrosion resistance, excellent high and low temperature mechanical properties, etc., and is widely used in aerospace, shipbuilding, weapons and equipment, and other fields. In recent years, with the continuous increase in demand for medium-thick plate titanium alloys, corresponding welding technologies have also continued to develop. Therefore, this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys, mainly covering traditional arc welding, high-energy beam welding, and other welding technologies. Among many methods, narrow gap welding, hybrid welding, and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys. Finally, the development trend of deep penetration welding technology for medium-thick plate titanium alloys is prospected.
{"title":"Research status of high efficiency deep penetration welding of medium-thick plate titanium alloy: A review","authors":"Zhihai Dong, Ye Tian, Long Zhang, Tong Jiang, Dafeng Wang, Yunlong Chang, Donggao Chen","doi":"10.1016/j.dt.2024.08.004","DOIUrl":"https://doi.org/10.1016/j.dt.2024.08.004","url":null,"abstract":"Titanium alloy has the advantages of high strength, strong corrosion resistance, excellent high and low temperature mechanical properties, etc., and is widely used in aerospace, shipbuilding, weapons and equipment, and other fields. In recent years, with the continuous increase in demand for medium-thick plate titanium alloys, corresponding welding technologies have also continued to develop. Therefore, this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys, mainly covering traditional arc welding, high-energy beam welding, and other welding technologies. Among many methods, narrow gap welding, hybrid welding, and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys. Finally, the development trend of deep penetration welding technology for medium-thick plate titanium alloys is prospected.","PeriodicalId":10986,"journal":{"name":"Defence Technology","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142189178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-13DOI: 10.1016/j.dt.2024.08.002
Xinwei Wang, Xiaohua Gao, Lei Wang, Xichao Su, Junhong Jin, Xuanbo Liu, Zhilong Deng
Combat effectiveness of unmanned aerial vehicle (UAV) formations can be severely affected by the mission execution reliability. During the practical execution phase, there are inevitable risks where UAVs being destroyed or targets failed to be executed. To improve the mission reliability, a resilient mission planning framework integrates task pre- and re-assignment modules is developed in this paper. In the task pre-assignment phase, to guarantee the mission reliability, probability constraints regarding the minimum mission success rate are imposed to establish a multi-objective optimization model. And an improved genetic algorithm with the multi-population mechanism and specifically designed evolutionary operators is used for efficient solution. As in the task-reassignment phase, possible trigger events are first analyzed. A real-time contract net protocol-based algorithm is then proposed to address the corresponding emergency scenario. And the dual objective used in the former phase is adapted into a single objective to keep a consistent combat intention. Three cases of different scales demonstrate that the two modules cooperate well with each other. On the one hand, the pre-assignment module can generate high-reliability mission schedules as an elaborate mathematical model is introduced. On the other hand, the re-assignment module can efficiently respond to various emergencies and adjust the original schedule within a millisecond. The corresponding animation is accessible at bilibili.com/video/BV12t421w7EE for better illustration.
{"title":"Resilient multi-objective mission planning for UAV formation: A unified framework integrating task pre- and re-assignment","authors":"Xinwei Wang, Xiaohua Gao, Lei Wang, Xichao Su, Junhong Jin, Xuanbo Liu, Zhilong Deng","doi":"10.1016/j.dt.2024.08.002","DOIUrl":"https://doi.org/10.1016/j.dt.2024.08.002","url":null,"abstract":"Combat effectiveness of unmanned aerial vehicle (UAV) formations can be severely affected by the mission execution reliability. During the practical execution phase, there are inevitable risks where UAVs being destroyed or targets failed to be executed. To improve the mission reliability, a resilient mission planning framework integrates task pre- and re-assignment modules is developed in this paper. In the task pre-assignment phase, to guarantee the mission reliability, probability constraints regarding the minimum mission success rate are imposed to establish a multi-objective optimization model. And an improved genetic algorithm with the multi-population mechanism and specifically designed evolutionary operators is used for efficient solution. As in the task-reassignment phase, possible trigger events are first analyzed. A real-time contract net protocol-based algorithm is then proposed to address the corresponding emergency scenario. And the dual objective used in the former phase is adapted into a single objective to keep a consistent combat intention. Three cases of different scales demonstrate that the two modules cooperate well with each other. On the one hand, the pre-assignment module can generate high-reliability mission schedules as an elaborate mathematical model is introduced. On the other hand, the re-assignment module can efficiently respond to various emergencies and adjust the original schedule within a millisecond. The corresponding animation is accessible at bilibili.com/video/BV12t421w7EE for better illustration.","PeriodicalId":10986,"journal":{"name":"Defence Technology","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142189176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-10DOI: 10.1016/j.dt.2024.08.007
Guijun Wang, Yanqing Wu, Kun Yang, Quanzhi Xia, Fenglei Huang
The interfacial structure has an important effect on the mechanical properties and safety of the energetic material. In this work, a mesostructure model reflecting the real internal structure of PBX is established through image digital modeling and vectorization processing technology. The microscopic molecular structure model of PBX is constructed by molecular dynamics, and the interface bonding energy is calculated and transferred to the mesostructure model. Numerical simulations are used to study the influence of the interface roughness on the dynamic compression and impact ignition response of PBX, and to regulate and optimize the mechanical properties and safety of the explosive to obtain the optimal design of the surface roughness of the explosive crystal. The results show that the critical hot spot density of PBX ignition under impact loading is 0.68 mm. The improvement of crystal surface roughness can improve the mechanical properties of materials, but at the same time it can improve the impact ignition sensitivity and reduce the safety of materials. The optimal friction coefficient range for the crystal surface that satisfies both the mechanical properties and safety of PBX is 0.06–0.12. This work can provide a reference basis for the formulation design and production processing of energetic materials.
{"title":"Optimization of mechanical and safety properties by designing interface characteristics within energetic composites","authors":"Guijun Wang, Yanqing Wu, Kun Yang, Quanzhi Xia, Fenglei Huang","doi":"10.1016/j.dt.2024.08.007","DOIUrl":"https://doi.org/10.1016/j.dt.2024.08.007","url":null,"abstract":"The interfacial structure has an important effect on the mechanical properties and safety of the energetic material. In this work, a mesostructure model reflecting the real internal structure of PBX is established through image digital modeling and vectorization processing technology. The microscopic molecular structure model of PBX is constructed by molecular dynamics, and the interface bonding energy is calculated and transferred to the mesostructure model. Numerical simulations are used to study the influence of the interface roughness on the dynamic compression and impact ignition response of PBX, and to regulate and optimize the mechanical properties and safety of the explosive to obtain the optimal design of the surface roughness of the explosive crystal. The results show that the critical hot spot density of PBX ignition under impact loading is 0.68 mm. The improvement of crystal surface roughness can improve the mechanical properties of materials, but at the same time it can improve the impact ignition sensitivity and reduce the safety of materials. The optimal friction coefficient range for the crystal surface that satisfies both the mechanical properties and safety of PBX is 0.06–0.12. This work can provide a reference basis for the formulation design and production processing of energetic materials.","PeriodicalId":10986,"journal":{"name":"Defence Technology","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142189180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SiC aerogel presents several advantageous features like lightweight and high temperature resistance when applied as microwave absorbing material. In this paper, SiC aerogel was prepared eventually followed by the sol-gel and carbonization reduction process. The results showed that the effective electromagnetic microwave absorption capacity of SiC aerogel was highly increased after being pyrolyzed at 1500 °C, which presented a minimum reflection loss value of −57.80 dB at 3.10 mm and 9.86 GHz. Besides, the electromagnetic parameters of SiC aerogel with different paraffin ratios were discussed as well as the varying electromagnetic microwave absorption performances. The minimum reflection loss value first rose then fell as the SiC/paraffin ratio increased, which demonstrated the importance of SiC content. This study establishes the theoretical foundation for the subsequent functional application of SiC aerogel.
{"title":"Preparation and microwave absorption performance of SiC aerogel via sol-gel and carbonization reduction process","authors":"Xinli Ye, Pengyi Xu, Hao Yu, Shan Li, Xiaomin Ma, Wei Xu, Junxiong Zhang","doi":"10.1016/j.dt.2024.08.006","DOIUrl":"https://doi.org/10.1016/j.dt.2024.08.006","url":null,"abstract":"SiC aerogel presents several advantageous features like lightweight and high temperature resistance when applied as microwave absorbing material. In this paper, SiC aerogel was prepared eventually followed by the sol-gel and carbonization reduction process. The results showed that the effective electromagnetic microwave absorption capacity of SiC aerogel was highly increased after being pyrolyzed at 1500 °C, which presented a minimum reflection loss value of −57.80 dB at 3.10 mm and 9.86 GHz. Besides, the electromagnetic parameters of SiC aerogel with different paraffin ratios were discussed as well as the varying electromagnetic microwave absorption performances. The minimum reflection loss value first rose then fell as the SiC/paraffin ratio increased, which demonstrated the importance of SiC content. This study establishes the theoretical foundation for the subsequent functional application of SiC aerogel.","PeriodicalId":10986,"journal":{"name":"Defence Technology","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142189177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Additive Manufacturing (AM) can provide customized parts that conventional techniques fail to deliver. One important parameter in AM is the quality of the parts, as a result of the material extrusion 3D printing (3D-P) procedure. This can be very important in defense-related applications, where optimum performance needs to be guaranteed. The quality of the Polyetherimide 3D-P specimens was examined by considering six control parameters, namely, infill percentage, layer height, deposition angle, travel speed, nozzle, and bed temperature. The quality indicators were the root mean square (q) and average (a) roughness, porosity, and the actual to nominal dimensional deviation. The examination was performed with optical profilometry, optical microscopy, and micro-computed tomography scanning. The Taguchi design of experiments was applied, with twenty-five runs, five levels for each control parameter, on five replicas. Two additional confirmation runs were conducted, to ensure reliability. Prediction equations were constructed to express the quality indicators in terms of the control parameters. Three modeling approaches were applied to the experimental data, to compare their efficiency, i.e., Linear Regression Model (LRM), Reduced Quadratic Regression Model, and Quadratic Regression Model (QRM). QRM was the most accurate one, still the differences were not high even considering the simpler LRM model.
{"title":"Critical quality indicators of high-performance polyetherimide (ULTEM) over the MEX 3D printing key generic control parameters: Prospects for personalized equipment in the defense industry","authors":"Nectarios Vidakis, Markos Petousis, Constantine David, Nektarios K. Nasikas, Dimitrios Sagris, Nikolaos Mountakis, Mariza Spiridaki, Amalia Moutsopoulou, Emmanuel Stratakis","doi":"10.1016/j.dt.2024.08.001","DOIUrl":"https://doi.org/10.1016/j.dt.2024.08.001","url":null,"abstract":"Additive Manufacturing (AM) can provide customized parts that conventional techniques fail to deliver. One important parameter in AM is the quality of the parts, as a result of the material extrusion 3D printing (3D-P) procedure. This can be very important in defense-related applications, where optimum performance needs to be guaranteed. The quality of the Polyetherimide 3D-P specimens was examined by considering six control parameters, namely, infill percentage, layer height, deposition angle, travel speed, nozzle, and bed temperature. The quality indicators were the root mean square (q) and average (a) roughness, porosity, and the actual to nominal dimensional deviation. The examination was performed with optical profilometry, optical microscopy, and micro-computed tomography scanning. The Taguchi design of experiments was applied, with twenty-five runs, five levels for each control parameter, on five replicas. Two additional confirmation runs were conducted, to ensure reliability. Prediction equations were constructed to express the quality indicators in terms of the control parameters. Three modeling approaches were applied to the experimental data, to compare their efficiency, i.e., Linear Regression Model (LRM), Reduced Quadratic Regression Model, and Quadratic Regression Model (QRM). QRM was the most accurate one, still the differences were not high even considering the simpler LRM model.","PeriodicalId":10986,"journal":{"name":"Defence Technology","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142189179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-30DOI: 10.1016/j.dt.2024.07.014
Jiqing Luo, Husheng Fang, Yue Zhong, Jing Zhang, Shengli Song
In this paper, the fixed-time time-varying formation of heterogeneous multi-agent systems (MASs) based on tracking error observer under denial-of-service (DoS) attacks is investigated. Firstly, the dynamic pinning strategy is used to reconstruct the communication channel for the system that suffers from DoS attacks to prevent the discontinuous transmission information of the communication network from affecting MASs formation. Then, considering that the leader state is not available to each follower under DoS attacks, a fixed-time distributed observer without velocity information is constructed to estimate the tracking error between followers and the leader. Finally, adaptive radial basis function neural network (RBFNN) is used to approximate the unknown ensemble disturbances in the system, and the fixed-time time-varying formation scheme is designed with the constructed observer. The effectiveness of the proposed control algorithm is demonstrated by the numerical simulation.
本文研究了在拒绝服务（DoS）攻击下，基于跟踪误差观测器的异构多代理系统（MAS）的定时时变形成。首先，采用动态销钉策略为遭受 DoS 攻击的系统重建通信信道，防止通信网络传输信息不连续影响 MAS 的形成。然后，考虑到在 DoS 攻击下每个跟随者无法获得领导者的状态，构建了一个没有速度信息的固定时间分布式观测器来估计跟随者与领导者之间的跟踪误差。最后，使用自适应径向基函数神经网络（RBFNN）来近似系统中的未知集合干扰，并利用构建的观测器设计定时时变编队方案。数值仿真证明了所提控制算法的有效性。
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