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Search Results (1,003)

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Keywords = beam theory

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20 pages, 1086 KiB  
Article
A Higher-Order Theory for Nonlinear Dynamic of an FG Porous Piezoelectric Microtube Exposed to a Periodic Load
by Marwa F. S. Al Muhammadi, Fatemah H. H. Al Mukahal and Mohammed Sobhy
Mathematics 2024, 12(21), 3422; https://doi.org/10.3390/math12213422 (registering DOI) - 31 Oct 2024
Abstract
This paper investigates the nonlinear dynamic deflection, natural frequency, and wave propagation in functionally graded (FG) porous piezoelectric microscale tubes under periodic load, hygrothermal conditions, and an external electric field. The piezoelectric material used to make the smart microtubes has pores that may [...] Read more.
This paper investigates the nonlinear dynamic deflection, natural frequency, and wave propagation in functionally graded (FG) porous piezoelectric microscale tubes under periodic load, hygrothermal conditions, and an external electric field. The piezoelectric material used to make the smart microtubes has pores that may be smoothly changed or uniformly distributed over the tube wall. Here, three types of porosity distribution are taken into consideration. The nonlinear motion equations are constructed using a novel shear deformation beam theory and the modified couple stress theory (MCST). The nonlinear motion equations are solved using the fourth-order Runge–Kutta technique and the Galerkin approach. The effects of various geometric parameters, porosity distribution type, porosity factor, periodic load amplitude and frequency, material length scale parameter, moisture, and temperature on the nonlinear dynamic deflection, natural frequency, and wave frequency of FG porous piezoelectric microtubes are explored through a number of parametric investigations. Full article
10 pages, 639 KiB  
Article
Kondo Versus Fano in Superconducting Artificial High-Tc Heterostructures
by Gaetano Campi, Gennady Logvenov, Sergio Caprara, Antonio Valletta and Antonio Bianconi
Condens. Matter 2024, 9(4), 43; https://doi.org/10.3390/condmat9040043 - 31 Oct 2024
Abstract
Recently, the quest for high-Tc superconductors has evolved from the trial-and-error methodology to the growth of nanostructured artificial high-Tc superlattices (AHTSs) with tailor-made superconducting functional properties by quantum design. Here, we report the growth by molecular beam epitaxy (MBE) of a superlattice of [...] Read more.
Recently, the quest for high-Tc superconductors has evolved from the trial-and-error methodology to the growth of nanostructured artificial high-Tc superlattices (AHTSs) with tailor-made superconducting functional properties by quantum design. Here, we report the growth by molecular beam epitaxy (MBE) of a superlattice of Mott insulator metal interfaces (MIMIs) made of nanoscale superconducting layers of quantum confined-space charge in the Mott insulator La2CuO4 (LCO), with thickness L intercalated by normal metal La1.55Sr0.45CuO4 (LSCO) with period d. The critical temperature shows the superconducting dome with Tc as a function of the geometrical parameter L/d showing the maximum at the magic ratio L/d = 2/3 where the Fano–Feshbach resonance enhances the superconducting critical temperature. The normal state transport data of the samples at the top of the superconducting dome exhibit Planckian T-linear resistivity. For L/d > 2/3 and L/d < 2/3, the heterostructures show a resistance following Kondo universal scaling predicted by the numerical renormalization group theory for MIMI nanoscale heterostructures. We show that the Kondo temperature, TK, and the Kondo scattering amplitude, R0K, vanish at L/d = 2/3, while TK and R0K increase at both sides of the superconducting dome, indicating that the T-linear resistance regime competes with the Kondo proximity effect in the normal phase of MIMIs. Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
24 pages, 532 KiB  
Article
A Fast and Accurate Numerical Method for Solving Nonlinear Fourth-Order Boundary Value Problems in the Beam Theory
by Mohammad Ali Mehrpouya, Rezvan Salehi and Patricia J. Y. Wong
Axioms 2024, 13(11), 757; https://doi.org/10.3390/axioms13110757 (registering DOI) - 31 Oct 2024
Abstract
In this paper, an efficient computational discretization approach is investigated for nonlinear fourth-order boundary value problems using beam theory. We specifically deal with nonlinear models described by fourth-order boundary value problems. The proposed method is applied on three different types of problems, i.e., [...] Read more.
In this paper, an efficient computational discretization approach is investigated for nonlinear fourth-order boundary value problems using beam theory. We specifically deal with nonlinear models described by fourth-order boundary value problems. The proposed method is applied on three different types of problems, i.e., the problem when an elastic bearing is non-zero (Case I), the problem under homogeneous boundary conditions of the unknown function and its second derivative (Case II), and the problem with integral boundary conditions (Case III). Moreover, the convergence analysis of the proposed method is provided. Finally, illustrative examples are included to demonstrate the applicability and validity of the technique and the comparison is made with the existing methods to show the efficiency and accuracy of the proposed method. Full article
(This article belongs to the Special Issue Mathematical Modeling, Simulations and Applications)
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13 pages, 6109 KiB  
Review
Design and Characteristics of Photonic Crystal Resonators for Surface-Emitting Quantum Cascade Lasers
by Kazuaki Sakoda, Yuanzhao Yao, Naoki Ikeda, Yoshimasa Sugimoto, Takaaki Mano, Takashi Kuroda, Hirotaka Tanimura, Shigeyuki Takagi, Rei Hashimoto, Kei Kaneko, Tsutomu Kakuno, Shinji Ohkuma, Ryuichi Togawa, Tetsuya Miyagawa, Hiroshi Ohno and Shinji Saito
Photonics 2024, 11(11), 1024; https://doi.org/10.3390/photonics11111024 - 30 Oct 2024
Viewed by 208
Abstract
We present our recent development of the surface-emitting quantum cascade laser with a PC (photonic crystal) resonator and a strain-compensated MQW (multiple quantum well) active layer operating at around 4.3 μm. We describe the laser performance mainly from the viewpoint of the design [...] Read more.
We present our recent development of the surface-emitting quantum cascade laser with a PC (photonic crystal) resonator and a strain-compensated MQW (multiple quantum well) active layer operating at around 4.3 μm. We describe the laser performance mainly from the viewpoint of the design and analysis of the PC resonators, which include both numerical calculations by FEM (finite element method) and analytical calculations using the k·p perturbation theory and group theory. We analyze the resonance quality factor, overlap factor, extraction efficiency, and far-field pattern, and show how the output power and beam quality have been improved by the appropriate design of the PC resonator. Full article
(This article belongs to the Special Issue The Three-Decade Journey of Quantum Cascade Lasers)
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21 pages, 2782 KiB  
Article
The Method of the Natural Frequency of the Offshore Wind Turbine System Considering Pile–Soil Interaction
by Wei Li, Xiaojuan Li, Xufeng Zhao, Qian Yin, Mingxing Zhu and Le Yang
J. Mar. Sci. Eng. 2024, 12(11), 1912; https://doi.org/10.3390/jmse12111912 - 25 Oct 2024
Viewed by 330
Abstract
Accurately and efficiently evaluating the influence of pile–soil interaction on the overall natural frequency of wind turbines is one of the difficulties in current offshore wind power design. To improve the structural safety and reliability of the offshore wind turbine (OWT) systems, a [...] Read more.
Accurately and efficiently evaluating the influence of pile–soil interaction on the overall natural frequency of wind turbines is one of the difficulties in current offshore wind power design. To improve the structural safety and reliability of the offshore wind turbine (OWT) systems, a new closed-form solution method of the overall natural frequency of OWTs considering pile–soil interactions with highly effective calculations is established. In this method, Hamilton’s principle and the equivalent coupled spring model (ECS model) were firstly combined. In Hamilton’s theory, the Timoshenko beam assumption and continuum element theory considering the three-dimensional displacement field of soil were used to simulate the large-diameter monopile–soil interaction under lateral load in multilayer soil. Case studies were used to validate the proposed method’s correctness and efficiency. The results show that when compared with the data of 13 offshore wind projects reported in existing research papers, the difference between the overall natural frequency calculated by the proposed method and that reported in this study is within ±10%. This calculation method achieves the goal of convenient, fast and accurate prediction of the overall natural frequency of offshore wind systems. Full article
(This article belongs to the Special Issue Safety and Reliability of Ship and Ocean Engineering Structures)
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18 pages, 5282 KiB  
Article
Study on the Degradation Model of Service Performance in Railway Steel–Concrete Composite Beams Considering the Cumulative Fatigue of Steel Beams and Studs Based on Vehicle–Bridge Coupling Theory
by Ce Gao, Cheng Zhang and Bing Han
Buildings 2024, 14(11), 3391; https://doi.org/10.3390/buildings14113391 - 25 Oct 2024
Viewed by 325
Abstract
The steel–concrete composite beam, as a structural form that combines the advantages of steel and concrete, has been applied in railway engineering. However, with the increase in railway operation time, the degradation pattern of the service performance of steel–concrete composite bridges remains unclear. [...] Read more.
The steel–concrete composite beam, as a structural form that combines the advantages of steel and concrete, has been applied in railway engineering. However, with the increase in railway operation time, the degradation pattern of the service performance of steel–concrete composite bridges remains unclear. This paper proposes a method for calculating the long-term service performance of railway steel–concrete composite beams, considering the cumulative fatigue damage of steel beams and studs, based on the vehicle–bridge coupling theory and Miner’s linear cumulative damage criterion. The proposed method is validated using measured data from an in-service steel–concrete composite railway bridge with spans of 40 + 50 + 40 m. The calculated mid-span vertical displacement and the first two natural frequencies of the composite beam deviated from the measured results by only 2.1%, 7.7%, and 9.5%, respectively. The research results can provide a basis for extending the service life of composite beams and preventing the occurrence of safety accidents. Full article
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13 pages, 4542 KiB  
Article
A Study on the Influence of Hydraulic Compactor Reinforcement on the Force Law of an Independent Foundation Under a Column and Its Safety Standard
by Su Bu, Lishan Chen, Hailin Zhang and Zhe Qin
Buildings 2024, 14(11), 3331; https://doi.org/10.3390/buildings14113331 - 22 Oct 2024
Viewed by 529
Abstract
Due to the complexity of the actual geotechnical environment, the backfill compaction design theory and calculation method are not reflected in the current specification. Therefore, in order to investigate the effect of the hydraulic compactor on the foundation structure during the treatment of [...] Read more.
Due to the complexity of the actual geotechnical environment, the backfill compaction design theory and calculation method are not reflected in the current specification. Therefore, in order to investigate the effect of the hydraulic compactor on the foundation structure during the treatment of the backfill of an independent foundation under a column, the Menard formula was modified. At the same time, relying on an independent foundation project under a column in Jinan, the dynamic model of compactor tamping backfilling soil was established. The applicability of the calculation formula is verified by simulating the single-point multiple tamping on the backfill directly above the foundation tie beam, and the influence law of two factors, the thickness of the backfill and the tamping energy, on the force of the foundation tie beam is elucidated. The results show that after reaching the optimum number of tamping, the cumulative soil settlement and the effective reinforcement depth of tamping show a stable trend, and their simulation results are in good agreement with the analytical solution, which provides a supplement to the relevant safety standards. At this critical point, the force on the tie beams peaked and showed up and down fluctuations under the subsequent ramming action. The tamping action of the compactor has a significant effect on the structural forces within the effective reinforcement range, and there is a negative correlation between the magnitude of the structural forces and the thickness of the backfill. According to the numerical calculation results to choose the best construction programme, the on-site monitoring shows that under 42 KJ tamping energy and 1.5 m single backfilling thickness, the tie beam reinforcement stress reaches 18.5~55.5% of the specification warning value, which meets the safety standard. The research results of this paper can provide important guidance for the hydraulic tamping treatment of an independent foundation backfill project. Full article
(This article belongs to the Section Building Structures)
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17 pages, 11316 KiB  
Article
Experimental Study on the Flexural Performance of the Corrosion-Affected Simply Supported Prestressed Concrete Box Girder in a High-Speed Railway
by Hai Li, Yuanguang Qiu, Zhicheng Pan, Yiming Yang, Huang Tang and Fanjun Ma
Buildings 2024, 14(10), 3322; https://doi.org/10.3390/buildings14103322 - 21 Oct 2024
Viewed by 373
Abstract
Prestressed concrete box girders are commonly employed in the development of high-speed railway bridge constructions. The prestressed strands in the girder may corrode due to long-term chloride erosion, leading to the degradation of its flexural performance. To examine the flexural performance of corrosion-affected [...] Read more.
Prestressed concrete box girders are commonly employed in the development of high-speed railway bridge constructions. The prestressed strands in the girder may corrode due to long-term chloride erosion, leading to the degradation of its flexural performance. To examine the flexural performance of corrosion-affected simply supported prestressed concrete box girders, eight T-shaped mock-up beams related to the girders used in the construction of high-speed railway bridges were manufactured utilizing similarity theory. Seven of the beams underwent electrochemical accelerated corrosion, and then each beam was subjected to failure under the four-point load test method. Measurements recorded and analyzed in detail during the loading process included the following: crack propagation, crack width at various loads, crack load, ultimate load, deflection, and concrete strain of the mid-span section. The results demonstrate that a corrosion rate of just 8.31% has a considerable impact on the structural integrity of the beams, as evidenced by a pronounced reduction in flexural cracks and a tendency towards reduced reinforcement failure. Furthermore, the corrosive process has a detrimental effect on mid-span deflection, ductility, and ultimate flexural bearing capacity, which could have significant implications for bridge safety. This study provides valuable insights for the assessment of flexural performance and the development of appropriate maintenance strategies for corroded simply supported box girders in high-speed railways. Full article
(This article belongs to the Section Building Structures)
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15 pages, 3317 KiB  
Article
Holographic Multi-Notch Filters Recorded with Simultaneous Double-Exposure Contact Mirror-Based Method
by Bing-Han Zhuang, Sheng-Chun Hung, Kun-Huang Chen, Chien-Hung Yeh and Jing-Heng Chen
Photonics 2024, 11(10), 977; https://doi.org/10.3390/photonics11100977 - 18 Oct 2024
Viewed by 443
Abstract
This study presents a novel simultaneous double-exposure contact mirror-based method for fabricating holographic multi-notch filters with dual operational central wavelengths. The proposed method leverages coupled wave theory, the geometric relationships of K-vectors, and a reflection-type recording setup, incorporating additional reflecting mirrors to guide [...] Read more.
This study presents a novel simultaneous double-exposure contact mirror-based method for fabricating holographic multi-notch filters with dual operational central wavelengths. The proposed method leverages coupled wave theory, the geometric relationships of K-vectors, and a reflection-type recording setup, incorporating additional reflecting mirrors to guide the recording beams. To validate the approach, a holographic notch filter was fabricated using photopolymer recording materials, resulting in operational wavelengths of 531.13 nm and 633.01 nm. The measured diffraction efficiencies at these wavelengths were ηs = 52.35% and ηp = 52.45% for 531.13 nm, and ηs = 67.30% and ηp = 67.40% for 633.01 nm. The component’s performance was analyzed using s- and p-polarized spectral transmission intensities at various reconstruction angles, revealing polarization-independent characteristics under normal incidence and polarization-dependent behavior under oblique incidence. The study also explored the relationships between recording parameters, such as incident angle, wavelength, emulsion expansion, and dispersion. The findings demonstrate that the first operational central wavelength is primarily influenced by the recording wavelength, while the second is primarily determined by the incident angle, covering a range from visible light to near-infrared. This method offers significant potential for cost-effective, mass-produced filters in optoelectronic applications. Full article
(This article belongs to the Special Issue Advances in Holography and Its Applications)
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23 pages, 7087 KiB  
Article
Exponentially Graded Auxetic Structures: An Assessment of the Shear Correction Factor and Static Deflection
by Maria Amélia R. Loja and Joaquim I. Barbosa
Appl. Sci. 2024, 14(20), 9356; https://doi.org/10.3390/app14209356 - 14 Oct 2024
Viewed by 464
Abstract
This work aims to study the influence of the material and geometric parameters that characterize re-entrant hexagonal honeycomb auxetic structures in the maximum transverse static deflection of beams. In addition, this study considers the composition of the material through the thickness results from [...] Read more.
This work aims to study the influence of the material and geometric parameters that characterize re-entrant hexagonal honeycomb auxetic structures in the maximum transverse static deflection of beams. In addition, this study considers the composition of the material through the thickness results from the mixture of a metallic phase and one of four different selected ceramics, using the exponential volume fraction law. The first-order shear deformation theory within an equivalent single-layer approach is used to assess the material and geometric parameters’ influence on the structures’ deflection. Considering this theoretical approach, the impact of the material and geometric parameters on the shear correction factors, calculated for each specific case, is also analyzed. The results allow us to conclude how the shear correction factors and the structures’ maximum static deflection are affected by the re-entrant hexagonal honeycomb auxetic cells’ aspect ratios, by the angle associated with the direction of the inclined members of the hexagonal cells and the use of materials with differentiated Poisson’s ratios. Full article
(This article belongs to the Special Issue Computational Mechanics for Solids and Structures)
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30 pages, 35792 KiB  
Article
Research on the Structural Design of a Pressurized Cabin for Civil High-Speed Rotorcraft and the Multi-Dimensional Comprehensive Evaluation Method
by Yongjie Zhang, Tongxin Zhang, Jingpiao Zhou, Bo Cui and Fangyu Chen
Aerospace 2024, 11(10), 844; https://doi.org/10.3390/aerospace11100844 - 13 Oct 2024
Viewed by 464
Abstract
For civil high-speed rotorcraft designed to operate at specific cruising altitudes, this study proposes nine structural design schemes for pressurized cabins. These schemes integrate commonly used materials and processing technologies in the aviation industry with advanced PRSEUS (Pultruded Rod Stitched Efficient Unitized Structure) [...] Read more.
For civil high-speed rotorcraft designed to operate at specific cruising altitudes, this study proposes nine structural design schemes for pressurized cabins. These schemes integrate commonly used materials and processing technologies in the aviation industry with advanced PRSEUS (Pultruded Rod Stitched Efficient Unitized Structure) technology. An analysis of the structural composition reveals that frames constitute 8–19% of the total structural weight, while stringers and beams make up 15–50%, and skins account for 11–25%, with thicknesses ranging from 1.0 mm to 2.0 mm. The separating interface of the pressurized cabin contributes 4–29% of the total structural weight. The weight distribution of each component in the pressurized cabin structure varies significantly depending on the chosen materials and processing technologies. Utilizing the Analytic Hierarchy Process (AHP), along with Gray Relational Analysis (GRA) and Dempster–Shafer (D-S) evidence theory, this study compares the simulation results of the nine schemes across multiple dimensions. The findings indicate that the configuration combining 7075 aluminum alloy and T300 composite material has the greatest advantages in terms of the high structural reliability of the configuration, light weight, mature processing technology, and low production cost. This comprehensive evaluation method quantitatively analyzes the factors influencing the structural configuration design of the pressurized cabin for civil high-speed rotorcraft, offering a valuable reference for the design of similar structures in related fields. Full article
(This article belongs to the Section Aeronautics)
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16 pages, 4589 KiB  
Article
Theoretical Prediction and Safety Evaluation of Adjacent Pipeline Deformation Caused by Connecting Channel Excavation Reinforced with Freezing Method
by Jun Zhang, Jiguo Liu, Shuoren Fu and Zequn Hong
Appl. Sci. 2024, 14(20), 9274; https://doi.org/10.3390/app14209274 - 11 Oct 2024
Viewed by 433
Abstract
Underground excavation by freezing method can ensure the safety of the surrounding structures. The influence of excavation of a connecting channel between two tunnels by freezing method on adjacent pipelines is studied in this paper. Combined with field measurement, numerical simulation, and theoretical [...] Read more.
Underground excavation by freezing method can ensure the safety of the surrounding structures. The influence of excavation of a connecting channel between two tunnels by freezing method on adjacent pipelines is studied in this paper. Combined with field measurement, numerical simulation, and theoretical analysis, the stress and deformation law of the whole process of channel excavation by freezing method is studied. Based on Euler–Bernoulli beam theory prediction, the influence of temperature field and excavation parameters on the longitudinal deformation of pipeline is analyzed. The results show that the excavation rate significantly affects the pipeline settlement, and the settlement surges when the excavation rate exceeds 1.0 m/d. At the same time, the thick frozen soil wall formed by low freezing temperatures enhances the supporting ability and effectively reduces the formation disturbance and settlement. The study focuses on the influence of connecting channel excavation on the pipelines under uniform formation conditions, and puts forward the evaluation method of pipeline safety to provide a theoretical reference for engineering practice. Full article
(This article belongs to the Special Issue Effects of Temperature on Geotechnical Engineering)
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27 pages, 21355 KiB  
Article
Dynamic Response Characteristics and Pile Damage Identification of High-Piled Wharves under Dynamic Loading
by Xubing Xu, Xiaole Di, Yonglai Zheng, Anni Liu, Chenyu Hou and Xin Lan
Appl. Sci. 2024, 14(20), 9250; https://doi.org/10.3390/app14209250 - 11 Oct 2024
Viewed by 448
Abstract
In port dock engineering, high-piled wharves represent one of the primary structural forms. Damage to the foundation piles is a common issue, influenced by external loads such as impact forces during vessel berthing, slope deformations, and operational loads. This study focuses on the [...] Read more.
In port dock engineering, high-piled wharves represent one of the primary structural forms. Damage to the foundation piles is a common issue, influenced by external loads such as impact forces during vessel berthing, slope deformations, and operational loads. This study focuses on the Jungong Road Wharf in Shanghai, utilizing FLAC 3D version 6.0 to conduct dynamic calculations under ship impact loading. The dynamic responses of the structure were analyzed, and various internal forces were extracted during the impact event. By combining concrete cracking failure criteria and fatigue damage theories, the effects of ship collisions on the cracking damage of high-piled wharf structures under different scenarios were assessed. Additionally, the applicability of modal flexibility in high-piled wharf scenarios was evaluated through finite element simulations. The results indicate that the dynamic amplification factor caused by dynamic loading is approximately 1.5, underscoring the necessity of considering this effect in the design and impact analysis of high-piled wharves. The impact loading significantly influences the bending moments of the piles, with inclined piles showing the greatest sensitivity. When a designed ship model collides with the high-piled wharf structure at a speed of 0.2 m/s, the tensile stress in the inclined piles reaches 87% of the ultimate tensile strength of the reinforcement. The impact loading has a relatively minor effect on the axial forces of the piles, a limited influence on the bending moments of the beams, but a considerable impact on the axial forces of the beams. Berthing by oversized vessels and unexpected incidents can lead to more severe damage to high-piled wharf structures. In the finite element simulations, modal flexibility effectively identified the locations of damage, with greater changes in modal flexibility correlating with increased damage severity. Full article
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21 pages, 716 KiB  
Article
FedBeam: Reliable Incentive Mechanisms for Federated Learning in UAV-Enabled Internet of Vehicles
by Gangqiang Hu, Donglin Zhu, Jiaying Shen, Jialing Hu, Jianmin Han and Taiyong Li
Drones 2024, 8(10), 567; https://doi.org/10.3390/drones8100567 - 10 Oct 2024
Viewed by 574
Abstract
Unmanned aerial vehicles (UAVs) can be utilized as airborne base stations to deliver wireless communication and federated learning (FL) training services for ground vehicles. However, most existing studies assume that vehicles (clients) and UAVs (model owners) offer services voluntarily. In reality, participants (FL [...] Read more.
Unmanned aerial vehicles (UAVs) can be utilized as airborne base stations to deliver wireless communication and federated learning (FL) training services for ground vehicles. However, most existing studies assume that vehicles (clients) and UAVs (model owners) offer services voluntarily. In reality, participants (FL clients and model owners) are selfish and will not engage in training without compensation. Meanwhile, due to the heterogeneity of participants and the presence of free-riders and Byzantine behaviors, the quality of vehicles’ model updates can vary significantly. To incentivize participants to engage in model training and ensure reliable outcomes, this paper designs a reliable incentive mechanism (FedBeam) based on game theory. Specifically, we model the cooperation problem between model owners and clients as a two-layer Stackelberg game and prove the existence and uniqueness of the Stackelberg equilibrium (SE). For the cooperation among model owners, we formulate the problem as a coalition game and based on this, analyze and design a coalition formation algorithm to derive the Pareto optimal social utility. Additionally, to achieve reliable FL model updates, we design a weighted-beta (Wbeta) reputation update mechanism to incentivize FL clients to provide high-quality model updates. The experimental results show that compared to the baselines, the proposed incentive mechanism improves social welfare by 17.6% and test accuracy by 5.5% on simulated and real datasets, respectively. Full article
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16 pages, 29393 KiB  
Article
Switchable Dual-Wavelength Fiber Laser with Narrow-Linewidth Output Based on Parity-Time Symmetry System and the Cascaded FBG
by Kaiwen Wang, Bin Yin, Chao Lv, Yanzhi Lv, Yiming Wang, Hao Liang, Qun Wang, Shiyang Wang, Fengjie Yu, Zhong Zhang, Ziwang Li and Songhua Wu
Photonics 2024, 11(10), 946; https://doi.org/10.3390/photonics11100946 - 8 Oct 2024
Viewed by 708
Abstract
In this paper, a dual-wavelength narrow-linewidth fiber laser based on parity-time (PT) symmetry theory is proposed and experimentally demonstrated. The PT-symmetric filter system consists of two optical couplers (OCs), four polarization controllers (PCs), a polarization beam splitter (PBS), and cascaded fiber Bragg gratings [...] Read more.
In this paper, a dual-wavelength narrow-linewidth fiber laser based on parity-time (PT) symmetry theory is proposed and experimentally demonstrated. The PT-symmetric filter system consists of two optical couplers (OCs), four polarization controllers (PCs), a polarization beam splitter (PBS), and cascaded fiber Bragg gratings (FBGs), enabling stable switchable dual-wavelength output and single longitudinal-mode (SLM) operation. The realization of single-frequency oscillation requires precise tuning of the PCs to match gain, loss, and coupling coefficients to ensure that the PT-broken phase occurs. During single-wavelength operation at 1548.71 nm (λ1) over a 60-min period, power and wavelength fluctuations were observed to be 0.94 dB and 0.01 nm, respectively, while for the other wavelength at 1550.91 nm (λ2), fluctuations were measured at 0.76 dB and 0.01 nm. The linewidths of each wavelength were 1.01 kHz and 0.89 kHz, with a relative intensity noise (RIN) lower than −117 dB/Hz. Under dual-wavelength operation, the maximum wavelength fluctuations for λ1 and λ2 were 0.03 nm and 0.01 nm, respectively, with maximum power fluctuations of 3.23 dB and 2.38 dB. The SLM laser source is suitable for applications in long-distance fiber-optic sensing and coherent LiDAR detection. Full article
(This article belongs to the Special Issue Single Frequency Fiber Lasers and Their Applications)
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