Documents published in Scipedia

• MTNet: Multi-Task Underwater Image Enhancement Method Based on Retinex

  Y. Song, X. Deng, H. Shao

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (2), 18

  
  

  Abstract

  Underwater images play a critical role in underwater exploration and related tasks. However, due to light attenuation and other underwater factors, underwater images often suffer from color distortion and low contrast, which to some extent limit the efficiency and safety of underwater exploration. To meticulously address these issues and enhance the accuracy and reliability of underwater exploration, this paper proposes a multi-task underwater image enhancement method based on Retinex theory. This method divides the underwater image enhancement task into several sub-tasks, including image decomposition, color correction, detail reconstruction, and illumination adjustment. Specialized sub-networks— DecomNet, DecolorNet, and DelightNet—are designed to specifically address these problems, thereby alleviating color distortion, enhancing image details, and improving contrast. Experiments conducted on several publicly underwater image datasets indicate that the quality of underwater images is significantly improved after enhancement with the proposed method, compared to other representative underwater image processing techniques. For example, on the real-world dataset Underwater Image Enhancement Benchmark, the MSE, Structural Similarity Index Measure, and Peak signal-to-noise ratio scores achieved were 453.480, 0.901, and 25.145, respectively. This study holds significant implications for underwater exploration, with potential applications in the fields of marine research and underwater archaeology.OPEN ACCESS Received: 03/11/2024 Accepted: 27/12/2024 Published: 20/04/2025

  Abstract
  Underwater images play a critical role in underwater exploration and related tasks. However, due to light attenuation and other underwater factors, underwater images often [...]

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• Study and Optimization of Energy Absorption Characteristics of Windowed Multi-Cell Thin-Walled Conical Tube under the Axial Loading

  T. Wei, X. Lin, X. Zhou, C. Kou, S. Zeng

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (2), 17

  
  

  Abstract

  Conical tubes have attracted significant attention due to their more stable deformation mode and lower initial peak load compared to non-conical tubes under axial load. Firstly, based on LS-DYNA software and a multiobjective optimization algorithm, simulations of the conical tube structure under axial load were conducted to determine the optimal dimensions of the conical tube. Then, based on the optimal unicellular conical tube structure, the energy absorption characteristics of the windowed multicell conical tube structures with horizontal and vertical partitions and square holes were designed, and a predictive expression for the mean load was proposed based on the simulation data. Finally, the results show that the optimal dimensions of the mono-cell conical tube are ϕ= 10° and t = 1.29 mm, while the optimal dimensions of the windowed multi-cell conical tube structure are four transverse split panels (v= 4), four vertical split panels (n= 4), and four holes (k = 4). Compared to the unicellular conical tube, the energy absorption efficiency of the windowed multi-cell conical tube has increased by 70.06%, while the initial peak load has decreased by 23.60%. Furthermore, both simulation and experimental results show that the predictive expression for the mean load of the windowed multicell conical tube exhibits good universality and reliability. The research results provide a new design concept for thin-walled conical tube energy absorption boxes.OPEN ACCESS Received: 24/07/2024 Accepted: 09/12/2024 Published: 20/04/2025

  Abstract
  Conical tubes have attracted significant attention due to their more stable deformation mode and lower initial peak load compared to non-conical tubes under axial load. Firstly, [...]

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• Efficient Analytic Technique for Fractional Fourth-Order Cubic Nonlinear Schrodinger Equation

  A. Hagag, Z. Alqahtani, A. Arafa

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (2), 16

  
  

  Abstract

  This paper presents an advanced analytical solution for the fractional fourth-order dispersive cubic nonlinear Schrödinger equation (DNLS), a model significant for engineering applications in optical fiber systems, quantum mechanics, and plasma physics. This work leverages the qhomotopy analysis transform method (q-HATM) to address the challenges in modeling complex, nonlinear wave propagation in engineering and physics applications involving fractional dynamics. By providing highly accurate, convergent solutions, this method allows engineers and scientists to model memory effects and higher-order dispersions more effectively in systems like optical waveguides and plasma waves. The demonstrated accuracy and convergence of q-HATM establish it as a practical tool for researchers aiming to solve complex wave propagation problems, advancing both theoretical understanding and real-world engineering solutions in nonlinear optics, quantum fields, and other areas requiring precise modeling of wave interactions.OPEN ACCESS Received: 25/10/2024 Accepted: 05/03/2025 Published: 20/04/2025

  Abstract
  This paper presents an advanced analytical solution for the fractional fourth-order dispersive cubic nonlinear Schrödinger equation (DNLS), a model significant for engineering [...]

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• PCB Defect Detection Algorithm Combining Cascaded-Wise Residual and Dynamic Sparse Attention

  W. FAN, J. Peng, S. Lan

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (2), 15

  
  

  Abstract

  Detecting defects is crucial to ensuring the quality of printed circuit board (PCB) products. Due to the diminutive nature of surface defects on PCBs, current detection algorithms struggle to extract small defect features accurately, leading to a propensity for missed detections. To tackle these challenges, we propose a PCB defect detection algorithm that builds upon the YOLOv7 algorithm with enhancements. Firstly, we integrate the proposed CREC module into the backbone network to enhance the capture of local features about minor defects. Secondly, we propose the integration of a multi-scale feature fusion module, SPPB, within the head network to selectively activate channels or positions related to minor defects in the feature map, thereby enhancing the accuracy of local feature extraction for minor defects. Subsequently, the algorithm is endowed with higher efficiency in learning small defect features with the help of a new loss function, MPNWD. Finally, a small target detection layer P2 is added to enrich the contextual information in order to facilitate the algorithm to understand the relationship between small defects and their surrounding regions. Experimental results demonstrate the effectiveness of the enhanced YOLOv7 algorithm in testing the PCB_DATASET defect dataset, achieving a detection accuracy (mAP) of 99.3%, surpassing YOLOv7 by 5.4%, and outperforming other algorithms in terms of detection accuracy.OPEN ACCESS Received: 24/07/2024 Accepted: 19/11/2024 Published: 20/04/2025

  Abstract
  Detecting defects is crucial to ensuring the quality of printed circuit board (PCB) products. Due to the diminutive nature of surface defects on PCBs, current detection algorithms [...]

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• Investigation of Load Sharing Factor of the Fixed-Setting Face-Milled Curvilinear Cylindrical Gear by Finite Element Method

  X. Zhang, Y. Dong, B. Gan

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (1), 13

  
  

  Abstract

  The fixed-setting face-milled curvilinear cylindrical gear (FSC gear) is a type of parallel-axis gear characterized by a circular arc-shape tooth in the longitudinal direction, with contact impressions on the tooth surface that can be adjusted through the manufacturing process. The finite element method is employed to investigate the effects of various gear parameters on the load-sharing factor (LSF) of FSC-gears. Initially, a sensitivity analysis was conducted to enhance the accuracy of the finite element model for FSC gear drives. Secondly, the accuracy of the finite element model was validated by the Hertzian contact theory. Furthermore, the correctness of the finite element method for determining the LSF was validated based on American Gear Manufacturers Association standards (AGMA). In this study, the effects of assembly errors, tooth modification, driving torque, cutter radius, and contact pattern size on LSF are investigated by numerical examples. The results show that the precise LSF can be determined without intentionally increasing the element density of the subsurface of the tooth surface. Compared with the AGMA standard, the finite element method offers advantages in calculating the LSF of any non-standard gear. The influence of the milling cutter radius and the tooth surface contact pattern size on the LSF can be neglected.OPEN ACCESS Received: 11/08/2024 Accepted: 21/11/2024 Published: 07/04/2025

  Abstract
  The fixed-setting face-milled curvilinear cylindrical gear (FSC gear) is a type of parallel-axis gear characterized by a circular arc-shape tooth in the longitudinal direction, [...]

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• Optimal Control Strategies for COVID-19 Epidemic Management: A Mathematical Modeling Approach Using the SEIQR Framework

  R. Ramalingam, A. Gnanaprakasam, S. Boulaaras

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (1), 12

  
  

  Abstract

   T he COVID-19 pandemic has necessitated the development of robust mathematical models to understand and mitigate its impact. This study presentsacompartmentalmodel for the IndianpandemicCOVID-19 dynamics, incorporating key compartments such as susceptible, exposed, infected, quarantined, and recovered populations. The positivity and boundednessofsolutionsarerigorously analyzed to ensure that the model remains biologically meaningful over time. A detailed exploration of the basic reproduction number R0 is conducted using the next-generation matrix approach, identifying it as a pivotal threshold parameter dictating disease dynamics. Theequilibriaof thesystem, includingthe Disease-Free Equilibrium (DFE) and the Endemic Equilibrium (EE), are derived and analyzed for their stability properties. The local stability of the DFE is established for R0 < 1, while conditions for the existence and stability of the EE are explored for R0 > 1. Additionally, the study employs Lyapunov functions to assess the global stability of equilibria, ensuring the robustness of the proposed model under varying initial conditions. T he Pontryagin’s Maximum Principle is utilized to derive optimal con trol strategies, focusing on minimizing the number of infections and optimizing interventions such as vaccination, treatment, and quarantine measures like wearing a face mask and hand washing. Numerical simula tions validate the theoretical findings, providing critical insights into the effectiveness of various control measures. This comprehensive framework contributes to the mathematical understanding of COVID-19 dynamics and offers valuable guidance for public health decision-making.

  Abstract
   T he COVID-19 pandemic has necessitated the development of robust mathematical models to understand and mitigate its impact. This study presentsacompartmentalmodel for [...]

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• The Influence of Specific Heat Ratio on the Flow Characteristics of Over-Expanded Single Expansion Ramp Nozzles

  Z. Wang, T. Yu, Y. Guo, R. Liu, Y. Yu

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (1), 11

  
  

  Abstract

  The flow field in the over-expanded single expansion ramp nozzle (SERN) demonstrates pronounced flow separation, intricate interactions involving intersecting and reflecting shocks, and mutual interference between shocks and boundary layers. Discrepancies arising from cold flow experiments vs. actual operational conditions introduce a notable influence of the specific heat ratio (γ ) on shock angles and shock/boundary layer interactions, thereby impacting the entire flow field. In this study, the differences between the cold flow conditions inside the nozzle and the actual operating conditions are found through numerical simulations, and the effects of γ on the shock structure and the shock/boundary layer interactions in an over-expanded SERN are investigated. Results indicated that cold flow experiments inadequately represented the authentic flow dynamics within the nozzle. Under varying nozzle pressure ratios (NPR) and γ conditions, the two-dimensional (2D) flow field structure of the over-expanded SERN exhibited diverse configurations of separated shock structures, encompassing Mach reflections, regular reflections, and triangular shock waves. Furthermore, alterations in γ influenced the movement of separation and reattachment points, induced pressure variations, and potentially triggered a transition in flow separation patterns. The changes in NPR and γ also modified the position and scale of the separation region, with an augmented NPR intensifying this effect. Moreover, the smaller values of γ were likely to lead to flow separation, separation pattern transitions, and changes in the structure of the separated shock waves. Compared with the 2D case, the three-dimensional outcomes indicated that the separated shock structure on the symmetry plane remained consistent, whereas that away from the symmetry plane contracted inward. The interaction patterns of the separated shocks on the ramp and flap also changed.OPEN ACCESS Received: 23/07/2024 Accepted: 07/11/2024 Published: 07/04/2025

  Abstract
  The flow field in the over-expanded single expansion ramp nozzle (SERN) demonstrates pronounced flow separation, intricate interactions involving intersecting and reflecting [...]

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• Effectiveness Heat Transfer of CombinedConvectionFlowAg-TiO2-GOWater Casson Ternary Hybrid Nanofluids in Magneto-Hydrodynamic Medium

  M. Alotaibi, M. Shqair, M. Swalmeh, A. Hagag

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (1), 10

  
  

  Abstract

  The chief target of this existing study is to demonstrate and discuss the problem behaviors of ternary hybrid nanofluid (HNF) flow across a vertical sheet. The boundary layer through a Casson medium and magneto-hydrodynamics effects were considered. Besides that, the constant wall temperature boundary conditions were also subjected to the present problem. The non-dimensional dominant equations for the considered problem are studied numerically, and the Keller box method (KBM) is meticulously chosen because of its suitability and accuracy. The outcome linear system of equations was programmed via MATLAB command software. The impact of magnetic, Casson ternary (HNFs), and mixed convection coefficients on the interested physical quantities in this study were obtained as results on the type figures and tables. These work outcomes agree with earlier work outcomes. The outcome linear system of equations was programmed via MATLAB command software. The effects of magnetic, Casson, nanoparticle (NPs) volume fraction, and mixed convection parameters on Nusselt number (Nu), local skin friction, temperature profiles, and velocity profiles were obtained as results from the type figures and tables. As an important result, the parameters enhanced the heat transfer, velocity, and friction when adding (NPs), so the ternary (HNFs) studied in the present study became an efficient fluid. These current work outcomes are in excellent agreement with earlier work outcomes.OPEN ACCESS Received: 10/10/2024 Accepted: 07/01/2025 Published: 07/04/2025

  Abstract
  The chief target of this existing study is to demonstrate and discuss the problem behaviors of ternary hybrid nanofluid (HNF) flow across a vertical sheet. The boundary layer [...]

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• Effects of Fan Installation on Ventilation in Indoor Sports Halls: A Numerical Simulation Study

  Y. Xiao, X. Wu

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (1), 9

  
  

  Abstract

  In this study, numerical simulations were conducted to investigate the changes in air circulation after the installation of fans in a large indoor sports hall. It was found that optimizing the arrangement of fans and the settings for doors and windows can significantly enhance air convection, improve the distribution of airflow, and increase the thermal comfort of athletes. The combination of natural ventilation systems with mechanical fans can further improve air quality and energy efficiency. These findings can provide practical recommendations for the design of sports halls, which are crucial for improving athletes’ performance and comfort, as well as enhancing the experience of spectators and other users. The analysis results indicate that in Model 2, the average wind speed of Scheme 7 is 1.6% higher than that of Scheme 5, 11.5% higher than that of Scheme 6, and 34.3% higher than that of Scheme 8. Therefore, Schemes 7 and 5 are identified as the optimal solutions for Model 2. When comparing the optimal solutions of both models, it was found that the average wind speed of Scheme 7 is 1.6% higher than that of Scheme 5, and 12% higher than that of Scheme 1, making Scheme 7 the overall optimal solution.OPEN ACCESS Received: 17/07/2024 Accepted: 31/10/2024 Published: 07/04/2025

  Abstract
  In this study, numerical simulations were conducted to investigate the changes in air circulation after the installation of fans in a large indoor sports hall. It was found [...]

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• An Application for Pair Sum Modulo Labeling in Cryptography

  P. Amudha, J. Jayapriya

  Rev. int. métodos numér. cálc. diseño ing. (2025). Vol. 41, (1), 8

  
  

  Abstract

   In the dynamic realmof cybersecurity, it is important to create a strong cryptographic technique to protect sensitive data against advanced threats. This paper introduces an innovative encryption and decryp tion technique leveraging graph theory and matrix algebra, especially through the use of pair sum modulo (PSM) labeling of graphs, adjacency matrices, and self-invertible matrices. The PSM labeling for a simple undirected graph G(VG, EG)with |VG| = p and |EG| = q, is an 1-1 map FG:VG → {±1,±2,...,±p}, and there is an induced edge labeling bijective function gG:EG → {0,1,2,...,(q − 1)} such that gG (uv) = [FG(u)+FG(v)](mod q) is distinct for each edge uv. A graph that satisfies PSM labeling is known as a PSM graph. Building on recent developments in graph labeling and matrix applications in cryp tography, our method enhances security. It improves resistance to brute force attacks by utilizing a large key space. Additionally, it leverages the complexity of matrix inversion to make cryptanalysis more difficult. The amalgamation of these mathematical groundworks reinforces the entropy and resistance to bit-flipping, thereby stimulating the ciphertext against statistical and cryptanalytic threats. We utilize the core principles of PSM labeling andalgorithmicencryptionmethods,asdefinedinpriorresearch, to develop an innovative cryptographic algorithm. The sustainability of the proposed method is verified through a thorough evaluation of its encryption efficacy, computational complexity, and a comparative study with existing cryptographic techniques. This work not only contributes to a new approach to the cryptographic domain but also opens avenues for further research into the integration of advanced mathematical structures in encryption algorithms.

  Abstract
   In the dynamic realmof cybersecurity, it is important to create a strong cryptographic technique to protect sensitive data against advanced threats. This paper introduces [...]

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