Journal Description
Symmetry
Symmetry
is an international, peer-reviewed, open access journal covering research on symmetry/asymmetry phenomena wherever they occur in all aspects of natural sciences. Symmetry is published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), CAPlus / SciFinder, Inspec, Astrophysics Data System, and other databases.
- Journal Rank: JCR - Q2 (Multidisciplinary Sciences) / CiteScore - Q1 (General Mathematics )
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.2 days after submission; acceptance to publication is undertaken in 3.5 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Testimonials: See what our editors and authors say about Symmetry.
Impact Factor:
2.7 (2022);
5-Year Impact Factor:
2.7 (2022)
Latest Articles
Results for Analytic Function Associated with Briot–Bouquet Differential Subordinations and Linear Fractional Integral Operators
Symmetry 2024, 16(6), 711; https://doi.org/10.3390/sym16060711 - 7 Jun 2024
Abstract
In this paper, we present a new class of linear fractional differential operators that are based on classical Gaussian hypergeometric functions. Then, we utilize the new operators and the concept of differential subordination to construct a convex set of analytic functions. Moreover, through
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In this paper, we present a new class of linear fractional differential operators that are based on classical Gaussian hypergeometric functions. Then, we utilize the new operators and the concept of differential subordination to construct a convex set of analytic functions. Moreover, through an examination of a certain operator, we establish several notable results related to differential subordination. In addition, we derive inclusion relation results by employing Briot–Bouquet differential subordinations. We also introduce a perspective study for developing subordination results using Gaussian hypergeometric functions and provide certain properties for further research in complex dynamical systems.
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(This article belongs to the Special Issue Symmetry in Geometric Theory of Analytic Functions)
Open AccessArticle
The Influence of Low-Frequency Oscillations on Trailing-Edge Tonal Noise with Symmetry Spanwise Source Regions
by
Zhangchen Song, Peiqing Liu, Hao Guo, Yifeng Sun and Shujie Jiang
Symmetry 2024, 16(6), 710; https://doi.org/10.3390/sym16060710 - 7 Jun 2024
Abstract
For noise reduction at a low-to-moderate Reynolds number, airfoil trailing-edge tonal noise has multiple prominent tones. Among these tones, secondary tones are greatly influenced by external disturbances such as oscillations commonly in the environment. In previous experiments, the spatial movement of sources was
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For noise reduction at a low-to-moderate Reynolds number, airfoil trailing-edge tonal noise has multiple prominent tones. Among these tones, secondary tones are greatly influenced by external disturbances such as oscillations commonly in the environment. In previous experiments, the spatial movement of sources was found to be related to an inherent high-frequency oscillation. Therefore, the spatial influence of external low-frequency oscillations was investigated in this study. By using tripping tapes to construct different symmetry source regions on the pressure side with side secondary tones, a transient spatial analysis of an NACA0012 airfoil at 2 degrees was performed by microphone arrays when a 10 Hz pressure oscillation was significant at 24 m/s. Temporally, this 10 Hz periodic strength change became more intense at a broader frequency bandwidth for a longer source region. Furthermore, a substantial time delay, significantly larger than the sound propagating time difference between microphones, was observed exclusively along the spanwise direction. This delay led to a periodic directivity pattern, particularly when two 0.2 m source regions were separated by a 0.2 m or 0.4 m tripping region. This low-frequency oscillation introduces an asymmetric transient switching pattern for symmetric spanwise source regions. Consequently, the response of airfoils to external oscillations in field tests should be considered.
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(This article belongs to the Special Issue Applications Based on Symmetry/Asymmetry in Fluid Mechanics)
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Intelligent Detection of Tunnel Leakage Based on Improved Mask R-CNN
by
Wenkai Wang, Xiangyang Xu and Hao Yang
Symmetry 2024, 16(6), 709; https://doi.org/10.3390/sym16060709 - 7 Jun 2024
Abstract
The instance segmentation model based on deep learning has addressed the challenges in intelligently detecting water leakage in shield tunneling. Due to the limited generalization ability of the baseline model, occurrences of missed detections, false detections, and repeated detections are encountered during the
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The instance segmentation model based on deep learning has addressed the challenges in intelligently detecting water leakage in shield tunneling. Due to the limited generalization ability of the baseline model, occurrences of missed detections, false detections, and repeated detections are encountered during the actual detection of tunnel water leakage. This paper adopts Mask R-CNN as the baseline model and introduces a mask cascade strategy to enhance the quality of positive samples. Additionally, the backbone network in the model is replaced with RegNetX to enlarge the model’s receptive field, and MDConv is introduced to enhance the model’s feature extraction capability in the edge receptive field region. Building upon these improvements, the proposed model is named Cascade-MRegNetX. The backbone network MRegNetX features a symmetrical block structure, which, when combined with deformable convolutions, greatly assists in extracting edge features from corresponding regions. During the dataset preprocessing stage, we augment the dataset through image rotation and classification, thereby improving both the quality and quantity of samples. Finally, by leveraging pre-trained models through transfer learning, we enhance the robustness of the target model. This model can effectively extract features from water leakage areas of different scales or deformations. Through instance segmentation experiments conducted on a dataset comprising 766 images of tunnel water leakage, the experimental results demonstrate that the improved model achieves higher precision in tunnel water leakage mask detection. Through these enhancements, the detection effectiveness, feature extraction capability, and generalization ability of the baseline model are improved. The improved Cascade-MRegNetX model achieves respective improvements of 7.7%, 2.8%, and 10.4% in terms of AP, AP0.5, and AP0.75 compared to the existing Cascade Mask R-CNN model.
Full article
(This article belongs to the Special Issue Symmetry, Finite Element Analysis, and Intelligent Sensing and Monitoring: Applications in Engineering)
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Method for the Trajectory Tracking Control of Unmanned Ground Vehicles Based on Chaotic Particle Swarm Optimization and Model Predictive Control
by
Mengtao Jin, Junmin Li and Te Chen
Symmetry 2024, 16(6), 708; https://doi.org/10.3390/sym16060708 - 7 Jun 2024
Abstract
The symmetry principle has significant guiding value in vehicle dynamics modeling and motion control. In complex driving scenarios, there are problems of low accuracy and large time delay in the trajectory tracking control of unmanned ground vehicles. In order to solve this problem
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The symmetry principle has significant guiding value in vehicle dynamics modeling and motion control. In complex driving scenarios, there are problems of low accuracy and large time delay in the trajectory tracking control of unmanned ground vehicles. In order to solve this problem and improve the motion control of unmanned ground vehicles, a vehicle coordination control method based on chaotic particle swarm optimization (CPSO) and model predictive control (MPC) algorithms is proposed. To achieve coordinated control of vehicle trajectory tracking and yaw stability, a model predictive controller was designed with the objective of minimizing trajectory tracking errors and yaw stability tracking errors. The required front wheel angle and yaw torque control variables were obtained by solving nonlinear constraint optimization. At the same time, considering the problems of low computational efficiency, high solving time, and local optimization in model predictive control, a chaotic particle swarm optimization algorithm is introduced to solve the optimization constraint problem within model predictive control, thereby effectively improving the computational efficiency and accuracy of the model predictive trajectory tracking controller. The results show that compared with MPC, the multi-objective function optimization solution time and vehicle lane changing time of CPSOMPC improved by 24.51% and 7.21%, respectively, which indicates the coordinated control method that combines the CPSO and MPC algorithms can effectively improve trajectory tracking performance while ensuring vehicle lateral stability.
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(This article belongs to the Special Issue Design Theory, Optimal Control and Intelligent Algorithms of Electric Vehicles and Intelligent Vehicles)
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Motion Control of Macro–Micro Linear Platform Based on Adaptive Fuzzy Active Disturbance Rejection Control
by
Mingyi Wang, Tianrun Kang, Kai Kang, Chengming Zhang and Liyi Li
Symmetry 2024, 16(6), 707; https://doi.org/10.3390/sym16060707 - 7 Jun 2024
Abstract
To ensure precise positioning of the macro–micro platform with a symmetrical structure, it is crucial to mitigate the impact of various perturbations, including disturbances, as well as complex factors such as external loads, electrical noise, and model parameter variations. This paper proposes a
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To ensure precise positioning of the macro–micro platform with a symmetrical structure, it is crucial to mitigate the impact of various perturbations, including disturbances, as well as complex factors such as external loads, electrical noise, and model parameter variations. This paper proposes a novel macro–micro master–slave control structure that incorporates adaptive fuzzy linear active disturbance rejection control (AFLADRC). The Kp and Kd parameters of the linear state error feedback (LSEF) are dynamically tuned and adjusted using fuzzy reasoning. This approach enhances the robustness of the system and simplifies the tuning process. In addition, this paper also analyzes the symmetry of the coupling effect between macro and micro, as the coupling will affect the motor force and the reaction potential of the motor. The macro–micro platform adopts a symmetric design; the macro stage is driven by a permanent magnet synchronous linear motor (PMLSM), and the micro stage is driven by a voice coil motor. Finally, we built the macro–micro linear motion experimental platform to verify the control effect of the proposed method by conducting trajectory tracking experiments and comparison experiments.
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(This article belongs to the Special Issue Symmetry/Asymmetry in Motor Control, Drives and Power Electronics)
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A Multi-Attribute Decision-Making Approach for International Shipping Operator Selection Based on Single-Valued Neutrosophic Power Hamy Mean Operators
by
Kecheng Zhang, Yawen Wang and Zhicheng Chen
Symmetry 2024, 16(6), 706; https://doi.org/10.3390/sym16060706 - 6 Jun 2024
Abstract
Maritime shipping is a crucial method of transporting goods internationally and is vital in supporting global trade. However, due to its global scope, the international shipping market is susceptible to political and economic disturbances. The recent escalation in the Israeli–Palestinian conflict has severely
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Maritime shipping is a crucial method of transporting goods internationally and is vital in supporting global trade. However, due to its global scope, the international shipping market is susceptible to political and economic disturbances. The recent escalation in the Israeli–Palestinian conflict has severely impacted the international shipping market, particularly in the tense Red Sea region. Previous research has neglected the significance of evaluating international shipping companies, particularly their origins, within their evaluation frameworks. A fuzzy multi-attribute decision-making (MADM) approach is necessary to address the complexity of evaluating shipping companies with unclear criteria and uncertain expert opinions. Symmetry is crucial in various mathematical fields, with recent applications in hesitant fuzzy sets (HFSs) and neutrosophic sets (NSs), which are frequently employed to solve complex MADM problems. The consideration of symmetry in decision-making processes can enhance the robustness and fairness of evaluations, ensuring a balanced and unbiased approach. The neutrosophic–hesitant fuzzy set (NHFS) considers both the uncertainty of membership degrees of elements (hesitancy in HFSs) and the performance of membership degrees in the true, false, and neutral aspects (the ternary relation in NSs). NHFSs can be seen as a generalization of HFSs and NSs, providing a flexible mathematical framework to more effectively describe and analyze the uncertainties, hesitancies, and fuzziness involved in MADM problems. This study presents single-valued neutrosophic power Hamy mean (SVNPHM) operators and single-valued neutrosophic weighted power Hamy mean (SVNWPHM) operators, which are derived from power aggregation operators (AOs) and the Hamy mean (HM), within the framework of single-valued neutrosophic sets (SVNS). Some properties were investigated via these operators. Furthermore, SVNWPHM operators were employed to address single-valued neutrosophic MADM issues. The proposed methodology was validated by conducting a case study on international shipping provider selection, showcasing the methodology’s relevance and efficiency.
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(This article belongs to the Section Mathematics)
Open AccessArticle
Existence of a Fixed Point and Convergence of Iterates for Self-Mappings of Metric Spaces with Graphs
by
Alexander J. Zaslavski
Symmetry 2024, 16(6), 705; https://doi.org/10.3390/sym16060705 - 6 Jun 2024
Abstract
In the present paper, under certain assumptions, we establish the convergence of iterates for self-mappings of complete metric spaces with graphs which are of a contractive type. The class of mappings considered in the paper contains the so-called cyclical mappings introduced by W.
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In the present paper, under certain assumptions, we establish the convergence of iterates for self-mappings of complete metric spaces with graphs which are of a contractive type. The class of mappings considered in the paper contains the so-called cyclical mappings introduced by W. A. Kirk, P. S. Srinivasan and P. Veeramani in 2003 and the class of monotone nonexpansive operators. Our results hold in the case of a symmetric graph.
Full article
(This article belongs to the Special Issue Fixed Point Theory and Its Applications Dedicated to the Memory of Professor William Arthur Kirk)
Open AccessArticle
A Coronal Loop Automatic Detection Method
by
Zhenhong Shang, Ziqi He and Runxin Li
Symmetry 2024, 16(6), 704; https://doi.org/10.3390/sym16060704 - 6 Jun 2024
Abstract
Coronal loops are bright, filamentary structures formed by thermal plasmas constrained by the sun’s magnetic field. Studying coronal loops provides insights into magnetic fields and their role in coronal heating processes. We propose a new automatic coronal loop detection method to optimize the
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Coronal loops are bright, filamentary structures formed by thermal plasmas constrained by the sun’s magnetic field. Studying coronal loops provides insights into magnetic fields and their role in coronal heating processes. We propose a new automatic coronal loop detection method to optimize the problem of existing algorithms in detecting low-intensity coronal loops. Our method employs a line-Gaussian filter to enhance the contrast between coronal loops and background pixels, facilitating the detection of low-intensity ones. Following the detection of coronal loops, each loop is extracted using a method based on approximate local direction. Compared with the classical automatic detection method, Oriented Coronal Curved Loop Tracing (OCCULT), and its improved version, OCCULT-2, the proposed method demonstrates superior accuracy and completeness in loop detection. Furthermore, testing with images from the Transition Region and Coronal Explorer (TRACE) at 173 Å, the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) at 193 Å, and the High-Resolution Coronal Imager (Hi-C) at 193 Å and 172 Å confirms the robust generalization capabilities of our method. Statistical analysis of the cross-section width of coronal loops shows that most of the loop widths are resolved in Hi-C images.
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(This article belongs to the Section Computer)
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The Deterioration of C-S-H Gel in a Severe Sulfate Environment
by
Wei Liao, Chunhua Lu and Zhongzi Xu
Symmetry 2024, 16(6), 703; https://doi.org/10.3390/sym16060703 - 6 Jun 2024
Abstract
Immersion tests with 5 wt.% Na2SO4 solution were carried out to investigate the deterioration of calcium silicate hydrate (C-S-H) gel in a sulfate environment. C-S-H gels with different Ca/(Si + Al) molar ratios were used for comparison. Particular attention was
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Immersion tests with 5 wt.% Na2SO4 solution were carried out to investigate the deterioration of calcium silicate hydrate (C-S-H) gel in a sulfate environment. C-S-H gels with different Ca/(Si + Al) molar ratios were used for comparison. Particular attention was paid to the changes in element composition and Si-O-Si chain structure of the C-S-H gel. The results show that the C-S-H gels with a low Ca/(Si + Al) ratio (0.8–1.0) and appropriate Si-O-Si chain length (14.8) presented better stability in a severe sulfate environment. The C-S-H gels with a higher Ca/(Si + Al) ratio (>2.0) were more sensitive to the attack of sulfate ions. Calcium ions dissolved rapidly during the immersion process, causing the loss of cohesive strength of the C-S-H gel, and then decomposed into fine particles. The C-S-H gel with a lower Ca/(Si + Al) ratio (about 1.1) rarely leached out calcium ions and maintained good micromorphology. The 29Si MAS-NMR results indicate that the Si-O-Si chains with too short or too long chain lengths will break and recombine under the attack of sulfate ions. The Si-O-Si chains with an appropriate chain length (14.8) maintained the stability of the structure of the C-S-H gel in a sulfate environment. These changes are closely related to the asymmetric layered structure of amorphous C-S-H gel. Partial calcium ions between the layers of the main chain structure of Si-O-Si are easily taken away by sulfate ions, leading to the structural instability of the C-S-H gel.
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(This article belongs to the Section Engineering and Materials)
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Results and Perspectives from the First Two Years of Neutrino Physics at the LHC by the SND@LHC Experiment
by
D. Abbaneo, S. Ahmad, R. Albanese, A. Alexandrov, F. Alicante, K. Androsov, A. Anokhina, T. Asada, C. Asawatangtrakuldee, M. A. Ayala Torres, C. Battilana, A. Bay, A. Bertocco, C. Betancourt, D. Bick, R. Biswas, A. Blanco Castro, V. Boccia, M. Bogomilov, D. Bonacorsi, W. M. Bonivento, P. Bordalo, A. Boyarsky, S. Buontempo, M. Campanelli, T. Camporesi, V. Canale, A. Castro, D. Centanni, F. Cerutti, M. Chernyavskiy, K.-Y. Choi, S. Cholak, F. Cindolo, M. Climescu, A. P. Conaboy, G. M. Dallavalle, D. Davino, P. T. de Bryas, G. De Lellis, M. De Magistris, A. De Roeck, A. De Rújula, M. De Serio, D. De Simone, A. Di Crescenzo, D. Di Ferdinando, R. Donà, O. Durhan, F. Fabbri, F. Fedotovs, M. Ferrillo, M. Ferro-Luzzi, R. A. Fini, A. Fiorillo, R. Fresa, W. Funk, F. M. Garay Walls, A. Golovatiuk, A. Golutvin, E. Graverini, A. M. Guler, V. Guliaeva, G. J. Haefeli, C. Hagner, J. C. Helo Herrera, E. van Herwijnen, P. Iengo, S. Ilieva, A. Infantino, A. Iuliano, R. Jacobsson, C. Kamiscioglu, A. M. Kauniskangas, E. Khalikov, S. H. Kim, Y. G. Kim, G. Klioutchnikov, M. Komatsu, N. Konovalova, S. Kuleshov, L. Krzempek, H. M. Lacker, O. Lantwin, F. Lasagni Manghi, A. Lauria, K. Y. Lee, K. S. Lee, S. Lo Meo, V. P. Loschiavo, S. Marcellini, A. Margiotta, A. Mascellani, F. Mei, A. Miano, A. Mikulenko, M. C. Montesi, F. L. Navarria, W. Nuntiyakul, S. Ogawa, N. Okateva, M. Ovchynnikov, G. Paggi, B. D. Park, A. Pastore, A. Perrotta, D. Podgrudkov, N. Polukhina, A. Prota, A. Quercia, S. Ramos, A. Reghunath, T. Roganova, F. Ronchetti, T. Rovelli, O. Ruchayskiy, T. Ruf, M. Sabate Gilarte, Z. Sadykov, M. Samoilov, V. Scalera, W. Schmidt-Parzefall, O. Schneider, G. Sekhniaidze, N. Serra, M. Shaposhnikov, V. Shevchenko, T. Shchedrina, L. Shchutska, H. Shibuya, S. Simone, G. P. Siroli, G. Sirri, G. Soares, J. Y. Sohn, O. J. Soto Sandoval, M. Spurio, N. Starkov, J. Steggemann, I. Timiryasov, V. Tioukov, F. Tramontano, C. Trippl, E. Ursov, A. Ustyuzhanin, G. Vankova-Kirilova, G. Vasquez, V. Verguilov, N. Viegas Guerreiro Leonardo, C. Vilela, C. Visone, R. Wanke, E. Yaman, Z. Yang, C. Yazici, C. S. Yoon, E. Zaffaroni, J. Zamora Saa and the SND@LHC Collaborationadd
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Symmetry 2024, 16(6), 702; https://doi.org/10.3390/sym16060702 - 6 Jun 2024
Abstract
After rapid approval and installation, the SND@LHC Collaboration was able to gather data successfully in 2022 and 2023. Neutrino interactions from νμs originating at the LHC IP1 were observed. Since muons constitute the major background for neutrino interactions, the muon flux
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After rapid approval and installation, the SND@LHC Collaboration was able to gather data successfully in 2022 and 2023. Neutrino interactions from νμs originating at the LHC IP1 were observed. Since muons constitute the major background for neutrino interactions, the muon flux entering the acceptance was also measured. To improve the rejection power of the detector and to increase the fiducial volume, a third Veto plane was recently installed. The energy resolution of the calorimeter system was measured in a test beam. This will help with the identification of νe interactions that can be used to probe charm production in the pseudo-rapidity range of SND@LHC (7.2 < η < 8.4). Events with three outgoing muons have been observed and are being studied. With no vertex in the target, these events are very likely from muon trident production in the rock before the detector. Events with a vertex in the detector could be from trident production, photon conversion, or positron annihilation. To enhance SND@LHC’s physics case, an upgrade is planned for HL-LHC that will increase the statistics and reduce the systematics. The installation of a magnet will allow the separation of νμ from
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(This article belongs to the Special Issue The Ring Tetralogy: What Did We Learn from the LHC and How We Will Use It)
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A Symmetric Fourth Party Logistics Routing Problem with Multiple Distributors in Uncertain Random Environments
by
Xinyu Gao, Xin Gao and Yang Liu
Symmetry 2024, 16(6), 701; https://doi.org/10.3390/sym16060701 - 6 Jun 2024
Abstract
Economic globalization and the rapid development of the Internet make logistics systems more and more diversified, people and enterprises have greatly increased their requirements for logistics systems, and fourth party logistics has received more and more attention from people and related enterprises. In
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Economic globalization and the rapid development of the Internet make logistics systems more and more diversified, people and enterprises have greatly increased their requirements for logistics systems, and fourth party logistics has received more and more attention from people and related enterprises. In order to further study the routing problem under uncertain stochastic environments, this paper considers the fourth party logistics routing problem from a single manufacturer to multiple distributors with uncertain times and random supplies under the complete information symmetry scenario and symmetric transportation volume decision space. Then, an uncertain stochastic programming model is established with the minimum total cost as its core objective, and the total transportation time, manufacturer’s supply, and distributor’s demand as constraints. In order to solve the optimal path of the above problems, this paper transforms the uncertain stochastic programming model into a classical mathematical programming model based on the distribution functions of uncertain time and random supply. Finally, two numerical examples are given to verify the effectiveness of the proposed model.
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(This article belongs to the Special Issue Symmetry Applications in Uncertain Differential Equations)
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Existence Results for Tempered-Hilfer Fractional Differential Problems on Hölder Spaces
by
Hussein A. H. Salem, Mieczysław Cichoń and Wafa Shammakh
Symmetry 2024, 16(6), 700; https://doi.org/10.3390/sym16060700 - 5 Jun 2024
Abstract
This paper considers a nonlinear fractional-order boundary value problem
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This paper considers a nonlinear fractional-order boundary value problem for , , , with appropriate integral boundary conditions on the Hölder spaces. Here, f is a real-valued function that satisfies the Hölder condition, and represents the tempered-Hilfer fractional derivative of order with parameter and type . The corresponding integral problem is introduced in the study of this issue. This paper addresses a fundamental issue in the field, namely the circumstances under which differential and integral problems are equivalent. This approach enables the study of differential problems using integral operators. In order to achieve this, tempered fractional calculus and the equivalence problem of the studied problems are introduced and studied. The selection of an appropriate function space is of fundamental importance. This paper investigates the applicability of these operators on Hölder spaces and provides a comprehensive rationale for this choice.
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(This article belongs to the Special Issue Symmetry in Differential Equations and Integral Operators)
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Research on Decomposition and Offloading Strategies for Complex Divisible Computing Tasks in Computing Power Networks
by
Ping He, Jiayue Cang, Huaying Qi and Hui Li
Symmetry 2024, 16(6), 699; https://doi.org/10.3390/sym16060699 - 5 Jun 2024
Abstract
With the continuous emergence of intelligent network applications and complex tasks for mobile terminals, the traditional single computing model often fails to meet the greater requirements of computing and network technology, thus promoting the formation of a new computing power network architecture, of
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With the continuous emergence of intelligent network applications and complex tasks for mobile terminals, the traditional single computing model often fails to meet the greater requirements of computing and network technology, thus promoting the formation of a new computing power network architecture, of ‘cloud, edge and end’ three-level heterogeneous computing. For complex divisible computing tasks in the network, task decomposition and offloading help to realize a distributed execution of tasks, thus reducing the overall running time and improving the utilization of fragmented resources in the network. However, in the process of task decomposition and offloading, there are problems, such as there only being a single method of task decomposition; that too large or too small decomposition granularity will lead to an increase in transmission delay; and the pursuit of low-delay and low-energy offloading requirements. Based on this, a complex divisible computing task decomposition and offloading scheme is proposed. Firstly, the computational task is decomposed into multiple task elements based on code partitioning, and then a density-peak-clustering algorithm with an improved adaptive truncation distance and clustering center (ATDCC-DPC) is proposed to cluster the task elements into subtasks based on the task elements themselves and the dependencies between the task elements. Secondly, taking the subtasks as the offloading objects, the improved Double Deep Q-Network subtask offloading algorithm (ISO-DDQN) is proposed to find the optimal offloading scheme that minimizes the delay and energy consumption. Finally, the proposed algorithms are verified by simulation experiments, and the scheme in this paper can effectively reduce the task delay and energy consumption and improve the service experience.
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(This article belongs to the Section Computer)
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Improving the Robustness of the Theil-Sen Estimator Using a Simple Heuristic-Based Modification
by
Artur Bal
Symmetry 2024, 16(6), 698; https://doi.org/10.3390/sym16060698 - 5 Jun 2024
Abstract
One of the most widely used robust regression methods for solving simple linear regression problems is the Theil-Sen (TS) estimator. This estimator has some notable advantages; however, it does not belong to the most robust estimation methods (called high-breakdown estimators) and is prone
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One of the most widely used robust regression methods for solving simple linear regression problems is the Theil-Sen (TS) estimator. This estimator has some notable advantages; however, it does not belong to the most robust estimation methods (called high-breakdown estimators) and is prone to outliers whose distribution is highly asymmetric with respect to the correct data points. This paper presents a modification of the TS estimator, the Robustified Theil-Sen (RTS) estimator. The new method uses a heuristic-based selection procedure to reduce the number of initial estimates of the regression function parameters computed with at least one outlier, thereby improving the regression results. The use of this heuristic procedure only slightly increases the computational time required for using the RTS estimator compared to the TS estimator. Preliminary results of two numerical experiments presented in the paper show that the RTS estimator outperforms other comparable estimators, i.e., the TS estimator and the repeated median estimator, in terms of robustness. The results presented also suggest that the breakpoint value (which is a measure of the robustness of estimators) of the RTS estimator is higher than the breakpoint value of the TS estimator and equal to the breakpoint value of the high-breakpoint estimators.
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(This article belongs to the Special Issue Symmetrical and Asymmetrical Distributions in Statistics and Data Science II)
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A Knowledge-Guided Multi-Objective Shuffled Frog Leaping Algorithm for Dynamic Multi-Depot Multi-Trip Vehicle Routing Problem
by
Yun Zhao, Xiaoning Shen and Zhongpei Ge
Symmetry 2024, 16(6), 697; https://doi.org/10.3390/sym16060697 - 5 Jun 2024
Abstract
Optimization algorithms have a wide range of applications in symmetry problems, such as graphs, networks, and pattern recognition. In this paper, a dynamic periodic multi-depot multi-trip vehicle routing model for scheduling test samples is constructed, which considers the differences in testing unit price
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Optimization algorithms have a wide range of applications in symmetry problems, such as graphs, networks, and pattern recognition. In this paper, a dynamic periodic multi-depot multi-trip vehicle routing model for scheduling test samples is constructed, which considers the differences in testing unit price and testing capacity of various agencies and introduces a cross-depot collaborative transport method. Both the cost and the testing time are minimized by determining the optimal sampling routes and testing agencies, subjecting to the constraints of vehicle capacity, number of vehicles, and delivery time. To solve the model, a knowledge-guided multi-objective shuffled frog leaping algorithm (KMOSFLA) is proposed. KMOSFLA adopts a convertible encoding mechanism to realize the diversified search in different search spaces. Three novel strategies are designed: the population initialization with historical information reuse, the leaping rule based on the greedy crossover and genetic recombination, and the objective-driven enhanced search. Systematic experimental studies are implemented. First, feasibility analyses of the model are carried out, where effectiveness of the cross-depot collaborative transport is validated and sensitivity analyses on two parameters (vehicle capacity and proportion of the third-party testing agencies) are performed. Then, the proposed algorithm KMOSFLA is compared with five state-of-the-art algorithms. Experimental results indicate that KMOSFLA can provide a set of non-dominated schedules with lower cost and shorter testing time in each scheduling period, which provides a reference for the dispatcher to make a final decision.
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(This article belongs to the Section Computer)
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Magneto Axisymmetric Vibration of FG-GPLs Reinforced Annular Sandwich Plates with an FG Porous Core Using DQM and a New Shear Deformation Theory
by
Aamna H. K. Al-Ali, Fatemah H. H. Al Mukahal and Mohammed Sobhy
Symmetry 2024, 16(6), 696; https://doi.org/10.3390/sym16060696 - 5 Jun 2024
Abstract
Based on the differential quadrature procedure (DQP), the vibrational response of functionally graded (FG) sandwich annular plates enhanced with graphene platelets (GPLs) and with an FG porous core is illustrated in this paper. The current annular plate is assumed to deform axisymmetrically and
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Based on the differential quadrature procedure (DQP), the vibrational response of functionally graded (FG) sandwich annular plates enhanced with graphene platelets (GPLs) and with an FG porous core is illustrated in this paper. The current annular plate is assumed to deform axisymmetrically and expose to a radial magnetic field. The Lorentz magnetic body force is deduced via Maxwell’s relations. The effective physical properties of the upper and lower layers of the sandwich plate are obtained by employing the Halpin–Tsai model. Our technique depends on a new four-unknown shear deformation theory to depict the displacements. In addition, the motion equations are established via Hamilton’s principle. The motion equations are solved by employing the DQP. In order to study the convergence of the DQ method, the minimum number of grid points needed for a converged solution is ascertained. In addition, the current theory’s outcomes are compared with those of previous higher-order theories. The effects of the porosity distribution type, porosity factor, GPLs distribution pattern, GPLs weight fraction, inner-to-outer radius ratio, outer radius-to-thickness ratio, magnetic field parameters, core thickness, and elastic substrate parameters on the nondimensional vibration frequencies are discussed.
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(This article belongs to the Section Mathematics)
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Open AccessArticle
The Influence of the Interface on the Micromechanical Behavior of Unidirectional Fiber-Reinforced Ceramic Matrix Composites: An Analysis Based on the Periodic Symmetric Boundary Conditions
by
Wei Yan, Shilun Shi, Longcheng Xiao, Xiulun Li and Jian Xu
Symmetry 2024, 16(6), 695; https://doi.org/10.3390/sym16060695 - 5 Jun 2024
Abstract
The long-term periodicity and uncontrollable interface properties during the preparation process for silicon carbide fiber reinforced silicon carbide-based composites (SiCf/SiC CMC) make it difficult to thoroughly investigate their mechanical damage behavior under complex loading conditions. To delve deeper into the influence
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The long-term periodicity and uncontrollable interface properties during the preparation process for silicon carbide fiber reinforced silicon carbide-based composites (SiCf/SiC CMC) make it difficult to thoroughly investigate their mechanical damage behavior under complex loading conditions. To delve deeper into the influence of the interface strength and toughness on the mechanical response of microscopic representative volume element (RVE) models under complex loading conditions, in this work, based on numerical simulation methods, a microscale representative volume element (RVE) with periodic symmetric boundary conditions for the material is constructed. The phase-field fracture theory and cohesive zone model are coupled to capture the brittle cracking of the matrix and the debonding behavior at the fiber/matrix interface. Simulation analysis is conducted for tensile, compressive, and shear loading as well as combined loading, and the validity of the model is verified based on the Chamis theory. Further investigation is conducted into the mechanical response behavior of the microscale RVE model under complex loading conditions in relation to the interface strength and interface toughness. The results indicate that under uniaxial loading, increasing the interface strength leads to a tighter bond between the fiber and matrix, suppressing crack initiation and propagation, and significantly increasing the material’s fracture strength. However, compared to the transverse compressive strength, increasing the interface strength does not continuously enhance the strength under other loading conditions. Meanwhile, under the condition of strong interface strength of 400 MPa, an increase in the interface toughness significantly increases the transverse compressive strength of the material. When it increases from 2 J/m2 to 20 J/m2, the transverse compressive strength increases by 28.49%. Under biaxial combined loading, increasing the interface strength significantly widens the failure envelope space under σ2-τ23 combined loading; with the transition from transverse compressive stress to tensile stress, the transverse shear strength shows a trend of first increasing and then decreasing, and when the ratio of transverse shear displacement to transverse tensile/compressive displacement is −1, it reaches the maximum. This study provides strong numerical support for the investigation of the interface properties and mechanical behavior of SiCf/SiC composites under complex loading conditions, offering important references for engineering design and material performance optimization.
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(This article belongs to the Special Issue Asymmetry and Symmetry in Dynamical Systems)
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Open AccessArticle
On Generalized Fibospinomials: Generalized Fibonacci Polynomial Spinors
by
Ece Gülşah Çolak, Nazmiye Gönül Bilgin and Yüksel Soykan
Symmetry 2024, 16(6), 694; https://doi.org/10.3390/sym16060694 - 5 Jun 2024
Abstract
Spinors are important objects in physics, which have found their place more and more after the discovery that particles have an intrinsic angular momentum shape and Cartan’s mathematical expression of this situation. Recent studies using special number sequences have also revealed a new
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Spinors are important objects in physics, which have found their place more and more after the discovery that particles have an intrinsic angular momentum shape and Cartan’s mathematical expression of this situation. Recent studies using special number sequences have also revealed a new approach to the use of spinors in mathematics and have provided a different perspective for spinor research that can be used as a source for future physics studies. The purpose of this work is to expand the generalized Fibonacci quaternion polynomials to the generalized Fibonacci polynomial spinors by associating spinors with quaternions, and to introduce and investigate a new polynomial sequence that can be used to benefit from the potential advantages of spinors in physical applications, and thus, to provide mathematical arguments, such as new polynomials, for studies using spinors and quaternions in quantum mechanics. Starting from this point of view, in this paper we introduce and investigate a new family of sequences called generalized Fibospinomials (or generalized Fibonacci polynomial spinors or Horadam polynomial spinors). Being particular cases, we use -Fibonacci and -Lucas polynomial spinors. We present Binet’s formulas, generating functions and the summation formulas for these polynomials. In addition, we obtain some special identities of these new sequences and matrices related to these polynomials. The importance of this study is that generalized Fibospinomials are currently the most generalized sequence in the literature when moving from Fibonacci quaternions to spinor structure, and that a wide variety of new spinor sequences can be obtained from this particular polynomial sequence.
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(This article belongs to the Special Issue Asymmetric and Symmetric Study on Number Theory and Cryptography)
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Covering-Based Intuitionistic Hesitant Fuzzy Rough Set Models and Their Application to Decision-Making Problems
by
Muhammad Kamraz Khan, Kamran, Muhammad Sajjad Ali Khan, Ahmad Aloqaily and Nabil Mlaiki
Symmetry 2024, 16(6), 693; https://doi.org/10.3390/sym16060693 - 4 Jun 2024
Abstract
In this paper, we present four categories of covering-based intuitionistic hesitant fuzzy rough set (CIHFRS) models using intuitionistic hesitant fuzzy -neighborhoods (IHF -neighborhoods) and intuitionistic hesitant fuzzy complementary -neighborhoods (IHFC -neighborhoods. Through theoretical analysis of covering-based IHFRS models, we
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In this paper, we present four categories of covering-based intuitionistic hesitant fuzzy rough set (CIHFRS) models using intuitionistic hesitant fuzzy -neighborhoods (IHF -neighborhoods) and intuitionistic hesitant fuzzy complementary -neighborhoods (IHFC -neighborhoods. Through theoretical analysis of covering-based IHFRS models, we propose the intuitionistic hesitant fuzzy TOPSIS (IHF-TOPSIS) technique for order of preference by similarity to an ideal solution, addressing multicriteria decision-making (MCDM) challenges concerning the assessment of IHF data. A compelling example aptly showcases the suggested approach. Furthermore, we address MCDM problems regarding the assessment of IHF information based on CIHFRS models. Through comparison and analysis, it is evident that addressing MCDM problems by assessing IHF data using CIHFRS models proves more effective than utilizing intuitionistic fuzzy data with CIFRS models or hesitant fuzzy information with CHFRS models. IHFS emerges as a unique and superior tool for addressing real-world challenges. Additionally, covering-based rough sets (CRSs) have been successfully applied to decision problems due to their robust capability in handling unclear data. In this study, by combining CRSs with IHFS, four classes of CIFRS versions are established using IHF -neighborhoods and IHFC -neighborhoods. A corresponding approximation axiomatic system is developed for each. The roughness and precision degrees of CBIHFRS models are specifically talked about. The relationship among these four types of IHFRS versions and existing related versions is presented based on theoretical investigations. A method for MCDM problems through IHF information, namely, IHF-TOPSIS, is introduced to further demonstrate its effectiveness and applicability. By conducting a comparative study, the effectiveness of the suggested approach is evaluated.
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(This article belongs to the Special Issue Fuzzy Covering Rough Set and Its Applications)
Open AccessArticle
Control of Three-Dimensional Natural Convection of Graphene–Water Nanofluids Using Symmetrical Tree-Shaped Obstacle and External Magnetic Field
by
Walid Aich, Inès Hilali-Jaghdam, Amnah Alshahrani, Chemseddine Maatki, Badr M. Alshammari and Lioua Kolsi
Symmetry 2024, 16(6), 692; https://doi.org/10.3390/sym16060692 - 4 Jun 2024
Abstract
This numerical investigation explores the enhanced control of the 3D natural convection (NC) within a cubic cavity filled with graphene–water nanofluids, utilizing a bottom-center-located tree-shaped obstacle and a horizontal magnetic field (MF). The analysis includes the effects of the Rayleigh number (Ra), the
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This numerical investigation explores the enhanced control of the 3D natural convection (NC) within a cubic cavity filled with graphene–water nanofluids, utilizing a bottom-center-located tree-shaped obstacle and a horizontal magnetic field (MF). The analysis includes the effects of the Rayleigh number (Ra), the solid volume fraction of graphene ( ), the Hartmann number (Ha), and the fins’ length (W). The results show complex flow patterns and thermal behavior within the cavity, indicating the interactive effects of nanofluid properties, the tree-shaped obstacle, and magnetic field effects. The MHD effects reduce the convection, while the addition of graphene improves the thermal conductivity of the fluid, which enhances the heat transfer observed with increasing Rayleigh numbers. The increase in the fins’ length on the heat transfer efficiency is found to be slightly negative, which is attributed to the complex interplay between the enhanced heat transfer surface area and fluid flow disruption. This study presents an original combination of non-destructive methods (magnetic field) and a destructive method (tree-shaped obstacle) for the control of the fluid flow and heat transfer characteristics in a 3D cavity filled with graphene–water nanofluids. In addition, it provides valuable information for optimizing heat transfer control strategies, with applications in electronic cooling, renewable energy systems, and advanced thermal management solutions. The application of a magnetic field was found to reduce the maximum velocity and total entropy generation by about 82% and 76%, respectively. The addition of graphene nanoparticles was found to reduce the maximum velocity by about 5.5% without the magnetic field and to increase it by 1.12% for Ha = 100. Varying the obstacles’ length from W = 0.2 to W = 0.8 led to a reduction in velocity by about 23.6%.
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(This article belongs to the Special Issue Symmetry in Thermal Fluid Sciences and Energy Applications)
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