bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Temperature and Water Vapor Content on Microstructure, Mechanical Properties and Corrosion Behavior of C/C-SiC Composites
Authors: Wei Yanbin , Ye Zhiyong , Wang Yalei , Xiong Xiang , Liu Zaidong , Wang Jinming , Li Tongqi
Published: December 2024

Carbon-fiber-reinforced carbon and silicon carbide (C/C-SiC) composites were prepared using chemical vapor infiltration (CVI) combined with reactive melt infiltration (RMI). The microstructure and flexural properties of C/C-SiC composites after oxidation in different temperature water vapor environments were studied. The results indicate that the difficulty of oxidation in water vapor can be ranked from easy to difficult in the following order: carbon fiber (CF), pyrolytic carbon (PyC), and ceramic phase. The surface CFs become cone-shaped under corrosion. PyC has a slower oxidation rate and lower degree of oxidation compared to CF. The SiO2 layer formed by the oxidation of SiC and residual Si was insufficient to fully cover the surface of CFs and PyC. As the temperature increased, the oxide film thickened, but the corrosion degree of CF and PyC intensified, and the flexural performance continuously deteriorated. The flexural strength of C/C-SiC composites was 271.86 MPa at room temperature. Their strength retention rates were all higher than 92.19% after water vapor corrosion at 1000 °C, still maintaining the “pseudoplastic” fracture characteristics. After water vapor corrosion at 1200 °C, the CFs inside the composites sustained more severe damage, with a strength retention rate as low as 48.75%. The fracture mode was also more inclined towards brittle fracture.
Transformations in the Ti-6Al-4V Alloy Studied Using Dilatometry Supported by Acoustic Emission
Authors: Łazarska Małgorzata , Musiał Janusz , Tański Tomasz , Ranachowski Zbigniew
Published: December 2024

This paper presents the results of research on the kinetics of transformations in the two-phase (α + β) Ti-6Al-4V alloy. The transformation start and end temperatures during heating at different rates were determined using a dilatometer. A modified dilatometer was employed, equipped with an acoustic emission measurement apparatus and software enabling the assessment of sample dimensional changes during heating and cooling. The results were obtained in the form of dilatometric curves. Additionally, the occurrence of the transformation was confirmed by acoustic emission signals. In the study of the Ti-6Al-4V alloy, acoustic emission refers to the application of this non-destructive technique to monitor the alloy’s behavior during thermal processes. As the temperature increased, regardless of the heating rate, the α→β transformation was observed to occur after exceeding 900 °C. Within the transformation range, acoustic emission signals were recorded. Moreover, it was found that the applied research methods enabled the identification of signal components originating from the transformation. The application of acoustic methods in the analysis of phase transformations opens new possibilities for their use in industry.
Numerical Analysis of the Influence of Air Flow Rate on the Development of the Porous Structure of Activated Carbons Prepared from Macadamia Nut Shells
Authors: Kwiatkowski Mirosław , Zhang Guojie
Published: December 2024

This paper presents the numerical analysis of the influence of air flow rate on the porous structure development of activated carbons prepared from macadamia nut shells. The analyses based on nitrogen and carbon dioxide isotherms were carried out by the new numerical clustering-based adsorption analysis method. Therefore, it was possible to evaluate the porous structure with high precision and reliability. In particular, the results obtained showed that activated carbon prepared at an air flow rate of 700 cm3/min has the highest adsorption capacity with respect to this adsorbate, but with surface heterogeneity. On the other hand, numerical analysis based on carbon dioxide adsorption isotherms showed that the activated carbon with the highest adsorption capacity towards carbon dioxide is the sample obtained at an air flow rate of 500 cm3/min. The analyses conducted have shown that too high an air flow rate causes a violent oxidation reaction, leading to uncontrolled burning of the carbonaceous substance and destruction of the structure of the smallest micropores.
Study on Properties of Additive Manufacturing Ta10W Alloy Laser-Welded Joints
Authors: Zhen Rui , Li Liqun , Gong Yunhao , Gong Jianfeng , Huang Yichen , Chang Shuai
Published: December 2024

This investigation focuses on Selective Laser Melting (SLM)-fabricated thin-walled Ta10W alloy components. Given the inherent limitations of SLM in producing large-scale, complex components in a single operation, laser welding was investigated as a viable secondary processing method for component integration. The study addresses the critical issue of weldability in additively manufactured tantalum-tungsten alloys, which frequently exhibit internal defects due to process imperfections. Comprehensive analyses were conducted on weldability, microstructural evolution, texture intensity, and mechanical properties for welds oriented along both traveling and building directions. Results demonstrate that welds oriented along the traveling direction exhibit superior performance characteristics, including enhanced tensile strength, increased yield strength, improved elongation, and reduced texture intensity compared to building direction welds. Notably, grain orientation alignment between the weld zone and base material was observed consistently in both directional configurations.
Crown Ether-Grafted Graphene Oxide-Based Materials—Synthesis, Characterization and Study of Lithium Adsorption from Complex Brine
Authors: Knapik Ewa , Rotko Grzegorz , Piotrowski Marcin , Marszałek Marta
Published: December 2024

Direct lithium extraction from unconventional resources requires the development of effective adsorbents. Crown ether-containing materials have been reported as promising structures in terms of lithium selectivity, but data on adsorption in real, highly saline brines are scarce. Crown ether-grafted graphene oxides were synthesized using 2-hydroxymethyl-12-crown-4, hydroxy-dibenzo-14-crown-4 and epichlorohydrin as a source of anchoring groups. The obtained carbonaceous materials were used to prepare chitosan–polyvinyl alcohol composites. The prepared materials (and intermediate products) were characterized using FTIR, XRD, Raman spectroscopy and SEM-EDS methods. Adsorption tests were performed in a pure diluted LiCl solution ([Li] = 200 mg/kg) as well as in a real, highly saline oilfield brine ([Li] ≈ 220 mg/kg), and the distribution coefficients (Kd) were determined. The obtained results show that Kd in pure LiCl solution was in the range of 0.9–75.6, while in brine it was in the range of 0.2–2.3. The study indicates that the high affinity for lithium in pure LiCl solution is mostly associated with the non-selective interaction of lithium ions with the graphene oxide matrix (COOH groups). It was also shown that the application of dibenzo-14-crown-4 moiety to graphene oxide modification groups increases the affinity of the composite material for lithium ions compared to an analogous material containing 12-crown-4-ether groups.
Study on the Dynamic Fracture Properties of Defective Basalt Fiber Concrete Materials Under a Freeze–Thaw Environment
Authors: Pei Guangzhao , Xiao Dingjun , Zhang Miaomiao , Jiang Jiajie , Xie Jiping , Li Xiongzi , Guo Junbo
Published: December 2024

This study examines the crack resistance of basalt-fiber-reinforced concrete (BFRC) materials subjected to freeze–thaw cycles (FTCs). We utilized a φ50 mm Split Hopkinson Pressure Bar (SHPB) apparatus alongside numerical simulations to carry out impact compression tests at a velocity of 5 m/s on BFRC specimens that experienced 0, 10, 20, and 30 FTCs. Additionally, we investigated the effects of basalt fiber (BF) orientation position and length on stress intensity factors. The results reveal that with an increasing number of FTCs, the dynamic crack propagation speed of BFRC with a prefabricated crack inclined at 0° rises from 311.84 m/s to 449.92 m/s, while its pure I fracture toughness decreases from 0.6266 MPa·m0.5 to 0.4902 MPa·m0.5. For BFRC specimens with a prefabricated crack inclination of 15°, the dynamic crack propagation speed increases from 305.81 m/s to 490.02 m/s, accompanied by a reduction in mode I fracture toughness from 0.3901 MPa·m0.5 to 0.2867 MPa·m0.5 and mode II fracture toughness from 0.6266 MPa·m0.5 to 0.4902 MPa·m0.5. In the case of a prefabricated crack inclination of 28.89°, the dynamic crack propagation speed rises from 436.10 m/s to 494.28 m/s, while its pure mode II fracture toughness decreases from 1.1427 MPa·m0.5 to 0.7797 MPa·m0.5. Numerical simulations indicate that fibers positioned ahead of the crack tip—especially those that are longer, located closer to the crack tip, and oriented more perpendicularly—significantly reduce the mode I stress intensity factor. However, these fibers have a minimal impact on reducing the mode II stress intensity factor. The study qualitatively and quantitatively analyzes the crack resistance of basalt-fiber-reinforced concrete in relation to freeze–thaw cycles and the fibers ahead of the crack tip, offering insights into the fiber reinforcement effects within the concrete matrix.
Assessment of Corrosion and Cavitation Resistance of Laser Remelted GX40CrNiSi25-20 Cast Stainless Steel
Authors: Mitelea Ion , Bordeașu Ilare , Cosma Daniela , Buzdugan Dragoș , Crăciunescu Corneliu Marius , Uțu Ion Dragoș
Published: December 2024

This paper explores the enhancement of cavitation and corrosion resistance in cast stainless steel through laser beam surface remelting. The influence of laser treatment on material properties was assessed by analyzing the microstructure using optical microscopy, electron microscopy, and X-ray diffraction. Cavitation erosion was evaluated in tap water using an ultrasonic vibration setup, following ASTM G32—2016 standards. Results show that local remelting of the surface with a laser beam causes a reduction in material loss and cavitation erosion rate. Potentiodynamic polarization tests revealed a significant improvement in corrosion resistance, indicated by a reduced corrosion current density in the laser-treated surface. The observed improvements in cavitation and corrosion resistance are attributed to microstructural hardening, characterized by grain refinement and a uniform, homogeneous structure with finely dispersed, small precipitate particles.
Annealing Effect on Linear and Ultrafast Nonlinear Optical Properties of Bi2Te3 Thin Films
Authors: Zhang Tengfei , Wei Shenjin , Song Xiaoxiao , Zhang Shubo , Li Yaopeng , Zou Yiyun , Wang Ying , Li Menghan , Jiang Ying , Wang Junhua , Hu Ertao , Li Jing
Published: December 2024

In recent years, the fabrication of materials with large nonlinear optical coefficients and the investigation of methods to enhance nonlinear optical performance have been in the spotlight. Herein, the bismuth telluride (Bi2Te3) thin films were prepared by radio-frequency magnetron sputtering and annealed in vacuum at various temperatures. The structural and optical properties were characterized and analyzed using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and UV/VIS/NIR spectrophotometry. The third-order optical nonlinearities of Bi2Te3 thin films were investigated using the Z-scan technique, employing a 100 fs pulse width at an 800 nm wavelength. It is found that the crystallinity and the average grain size of the films increase with the annealing temperature. Meanwhile, the extinction coefficient of the annealed films increased, accompanied by a redshift in the optical bandgap. All samples exhibit pronounced saturable absorption and self-focusing behaviors. The nonlinear absorption coefficient and nonlinear refractive index of Bi2Te3 films annealed at 300 °C were found to be 2.44 times and 1.85 times higher than those of the as-deposited films, respectively. These findings demonstrate that annealing treatment is an effective approach to tuning the crystalline structure and linear optical properties of Bi2Te3 films while simultaneously enhancing their nonlinear optical performance.
Development on Light and Thin Broadband Sound Absorption Structure Based on Unequal-Cross-Section Microperforated Plate Series Connection
Authors: Jv Xin , Wu Jinwu , Mao Qibo , Li Qi , Zhang Tianhang
Published: December 2024

The sound absorption structure of a microperforated plate has many advantages and has great potential in the field of noise control. In order to solve the problem of broadband sound absorption of microperforated plates, a series acoustic structure of microperforated plates of unequal cross-section was designed based on the traditional microperforated plate series acoustic structure. Compared with the traditional series structure, the sudden change of cross-section increases the sound energy dissipation and greatly improves the sound absorption performance. Through the analysis of its parameters, when the overall thickness of the structure is 20 mm, its sound absorption coefficient is above 0.5 in the frequency range of 1000–3450 Hz; there are three formants, and the sound absorption coefficients corresponding to the three formants reach 1. This study provides new ideas and methods for the design of broadband acoustic structures.
Corrosion Properties of Cold-Sprayed Cr3C2-25(Ni20Cr) Coatings After Heat Treatment
Authors: Scendo Mieczysław , Żórawski Wojciech
Published: December 2024

The corrosion resistance of a Cr3C2-25(Ni20Cr) cermet coating applied to an Al7075 substrate (Cr3C2-25(Ni20Cr)/Al7075) was investigated. The coating was produced using a cold spraying (CS) method. The main aim of the research was to determine the effect of heat treatment on the properties of cermet coatings on the Al7075 substrate. The mechanical properties of the Cr3C2-25(Ni20Cr)/Al7075 composite were assessed through microhardness (HV) measurements. The surface morphology and microstructure of the specimens were examined using a scanning electron microscope (SEM). Electrochemical testing in an acidic chloride solution was employed to evaluate the corrosion behavior of the materials. The cermet coating effectively protected the Al7075 substrate from the aggressive corrosive environment. Heat treatment homogenized the structure of the cermet coating, eliminating microcracks and pores on the Cr3C2-25(Ni20Cr)/Al7075 surface. Notably, annealing at 300 °C in air significantly enhanced the corrosion resistance of the cermet coating. The corrosion rate was reduced by more than five times compared to the non-heat-treated Cr3C2-25(Ni20Cr)/Al7075 coating.
The Influence of the Strain Rate on Texture Formation During the Plane Strain Compression of AZ80 Magnesium Alloy
Authors: Ji Yebeen , Yun Jimin , Kim Kibeom , Lee Tae Hee , Kim Kwonhoo
Published: December 2024

Controlling microstructure and texture development is a key approach to improving the formability of magnesium alloys. In this study, the effects of the strain rate and initial texture on the texture evolution of magnesium alloys during high-temperature processing are investigated. The plane strain compression of three types of AZ80 magnesium alloys with different initial textures was assessed at 723 K and a train rate of 0.0005 s−1. Work softening was consistently observed in the stress–strain curves of all samples. However, the peak stress varied depending on the initial texture, with lower peak stress observed under conditions favoring prismatic slip. Under these conditions, the activation of non-basal slip suppressed the formation of basal texture. The texture shifted and developed parallel to the transverse direction when prismatic slip was dominant. In contrast, the activation of pyramidal slip led to the formation of a basal texture tilted by 25° from the (0001) plane. The effects of recrystallization and grain boundary migration on texture development were minimal. This study contributes to understanding the texture development mechanisms in magnesium alloys and provides insights into improving their workability and ductility through texture modification.
Effect of Heat Treatment on the Microstructure and Property of Metastable β Titanium Alloy
Authors: Tang Jiafeng , Luo Hengjun , Wu Biliu , Liu Wenhao , Rong Yu , Chen Danyang , Qin Yulin , Zhang Ning , Hao Fang , Deng Hao , Chen Longqing , Zhu Jun , Yin Ming
Published: December 2024

TB18 is a newly developed high-strength metastable β-titanium alloy, commonly used in aerospace structural materials, which demands high mechanical performance. By altering the alloy’s microstructure, heat treatment can affect its mechanical characteristics. The alloy was solution treated for one to four hours at 870 °C in order to examine the impact of solution treatment duration. Using X-ray diffraction (XRD) and scanning electron microscopy (SEM), the effects of solution treatment time on the β-phase grain size and its effect on stress distribution during tensile testing were examined. The findings showed that stress concentration during the tensile process was successfully decreased by refining the β-phase grain size. Sample solutions treated for two hours at 870 °C were then aged at various temperatures (510 °C, 520 °C, 530 °C, and 540 °C) to examine the impact of aging temperature. While the mass proportion of the α-phase first climbed and subsequently declined, reaching its maximum at 530 °C, the size of the α-phase increased monotonically as the aging temperature increased. The varies of mass fraction is associated with how the aging temperature affects α-phase nucleation. Tensile studies on TB18 alloy aged at various temperatures showed that while the alloy’s ductility reduced, its strength increased as the aging temperature rose. The Hall-Petch relationship explains this tendency.
Mechanical Properties of Concrete Mixes with Selectively Crushed Wind Turbine Blade: Comparison with Raw-Crushing
Authors: Revilla-Cuesta Víctor , Espinosa Ana B. , Serrano-López Roberto , Skaf Marta , Manso Juan M.
Published: December 2024

The glass fiber-reinforced polymer (GFRP) materials of wind turbine blades can be recovered and recycled by crushing, thereby solving one of the most perplexing problems facing the wind energy sector. This process yields selectively crushed wind turbine blade (SCWTB), a novel waste that is almost exclusively composed of GFRP composite fibers that can be revalued in terms of their use as a raw material in concrete production. In this research, the fresh and mechanical performance of concrete made with 1.5%, 3.0%, 4.5%, and 6.0% SCWTB is studied. Once incorporated into concrete mixes, SCWTB waste slightly reduced slumps due to the large specific surface area of the fibers, and the stitching effect of the fibers on mechanical behavior was generally adequate, as scanning electron microscopy demonstrated good fiber adhesion within the cementitious matrix. Thus, despite the increase in the content of water and plasticizers when adding this waste to preserve workability, the compressive strength only decreased in the long term with the addition of 6.0% SCWTB, a value of 45 MPa always being reached at 28 days; Poisson’s coefficient remained constant from 3.0% SCWTB; splitting tensile strength was maintained at around 4.7 MPa up to additions of 3.0% SCWTB; and the flexural strength of mixes containing 6.0% and 1.5% SCWTB was statistically equal, with a value near 6.1 MPa. Furthermore, all mechanical properties of the concrete except for flexural strength were improved with additions of SCWTB compared to raw crushed wind turbine blade, which apart from GFRP composite fibers contains approximately spherical polymer and balsa wood particles. Flexural strength was conditioned by the proportion of fibers, their dimensions, and their strength, which were almost identical for both waste types. SCWTB would be preferable for applications in which compression stresses predominate.
Durability of Wood–Cement Composites with Modified Composition by Limestone and Stabilised Spruce Chips
Authors: Melichar Tomáš , Dufka Amos , Dvořák Karel , Bayer Patrik , Vasas Silvestr , Novakova Iveta , Schwarzova Ivana , Bydžovský Jiří
Published: December 2024

Limestone (LS) and stabilised secondary spruce chips (SCs) utilisation in wood–cement composites is still an unexplored area. Therefore, the main objective of the research presented here is the assessment of the long-term behaviour of cement-bonded particleboards (CBPs) modified by LS and SCs. Cement (CE) was replaced by 10% of LS, and spruce chips by 7% of SCs. The test specimens were stored in a laboratory and exterior environment (Middle Europe) for up to 2 years. The density, strength, and modulus of elasticity were evaluated after 28 days, and then in 6-month periods. The hygroscopicity was analysed separately. The mineralogical composition and microstructure were analysed due to possible LS participation during hydration. SC synergic behaviour in CBPs was also studied. After 2 years, the microstructure of the CBP was more compact, and denser. Strong carbonatation contributes to the improvement of CBP properties. The products of carbonatation were present in both the matrix and wood chips. The hydration of the matrix was almost finished. LS has a positive effect on the matrix microstructure development. LS acts both as an active component participating in the formation of the cement matrix structure and as an inert microfiller, synergic with hydration products. SCs have a positive effect on the hygroscopic behaviour of CBPs and slightly negative effect on the tensile strength.
Convergence of Implicit Iterative Processes for Semigroups of Nonlinear Operators Acting in Regular Modular Spaces
Authors: Kozlowski Wojciech M.
Published: December 2024

This paper focuses on one-parameter semigroups of ρ-nonexpansive mappings Tt:C→C, where C is a subset of a modular space Xρ, the parameter t ranges over [0,+∞), and ρ is a convex modular with the Fatou property. The common fixed points of such semigroups can be interpreted as stationary points of a dynamic system defined by the semigroup, meaning they remain unchanged during the transformation Tt at any given time t. We demonstrate that, under specific conditions, the sequence {xk} generated by the implicit iterative process xk+1=ckTtk+1(xk+1)+(1−ck)xk is ρ-convergent to a common fixed point of the semigroup. Our findings extend existing convergence results for semigroups of operators, from Banach spaces to a broader class of regular modular spaces.
A Finite Representation of Durational Action Timed Automata Semantics
Authors: Bouzenada Ahmed , Saidouni Djamel Eddine , Díaz Gregorio
Published: December 2024

Durational action timed automata (daTAs) are state transition systems like timed automata (TAs) that capture information regarding the concurrent execution of actions and their durations using maximality-based semantics. As the underlying semantics of daTAs are infinite due to the modeling of time progress, conventional model checking techniques become impractical for systems specified using daTAs. Therefore, a finite abstract representation of daTA behavior is required to enable model checking for such system specifications. For that, we propose a finite abstraction of the underlying semantics of a daTA-like region abstraction of timed automata. In addition, we highlight the unique benefits of daTAs by illustrating that they enable the verification of properties concerning concurrency and action duration that cannot be verified using the traditional TA model. We demonstrate mathematically that the number of states in durational action timed automata becomes significantly smaller than the number of states in timed automata as the number of actions increases, confirming the efficiency of daTAs in modeling behavior with action durations.
A Lightweight Malware Detection Model Based on Knowledge Distillation
Authors: Miao Chunyu , Kou Liang , Zhang Jilin , Dong Guozhong
Published: December 2024

The extremely destructive nature of malware has become a major threat to Internet security. The research on malware detection techniques has been evolving. Deep learning-based malware detection methods have achieved good results by using large-scale, pre-trained models. However, these models are complex, have large parameters, and require a large amount of hardware resources and have a high inference time cost when applied. To address this challenge, this paper proposes DistillMal, a new method for lightweight malware detection based on knowledge distillation, which improves performance by using a student network to learn valuable cueing knowledge from a teacher network to achieve a lightweight model. We conducted extensive experiments on two new datasets and showed that the student network model’s performance is very close to that of the original model and the outperforms it on some metrics. Our approach helps address the resource constraints and computational challenges faced by traditional deep learning large models. Our research highlights the potential of using knowledge distillation to develop lightweight malware detection models.
Solvability of Some Elliptic Equations with a Nonlocal Boundary Condition
Authors: Aitzhanov Serik , Koshanov Bakytbek , Kuntuarova Aray
Published: December 2024

In this work, we study a nonlocal boundary value problem for a quasilinear elliptic equation. Using the method of regularization and parameter continuation, we prove the existence and uniqueness of a regular solution to the nonlocal boundary value problem, i.e., a solution that possesses all generalized derivatives in the sense of S. L. Sobolev, which are involved in the corresponding equation.
Modeling and Analysis of Thermoelastic Damping in a Piezoelectro-Magneto-Thermoelastic Imperfect Flexible Beam
Authors: Alneamy Ayman M. , Guha Sayantan , Tharwan Mohammed Y.
Published: December 2024

This research addresses the phenomena of thermoelastic damping (TED) and frequency shift (FS) of a thin flexible piezoelectro-magneto-thermoelastic (PEMT) composite beam. Its motion is constrained by two linear flexible springs attached to both ends. The novelty behind the proposed study is to mimic the uncertainties during the fabrication of the beam. Therefore, the equation of motion was derived utilizing the linear Euler–Bernoulli theory accounting for the flexible boundary conditions. The beam’s eigenvalues, mode shapes, and the effects of the thermal relaxation time (t1), the dimensions of the beam, the linear spring coefficients (KL0 and KLL), and the critical thickness (CT) on both TED and FS of the PEMT beam were investigated numerically employing the Newton–Raphson method. The results show that the peak value of thermoelastic damping (Qpeak−1) and the frequency shift (Ω) of the beam increase as t1 escalates. Another observation was made for the primary fundamental mode, where an increase in the spring coefficient KLL leads to a further increase in Ω. On the other hand, the opposite trend is noted for the higher modes. Indeed, the results show the possibility of using the proposed design in a variety of applications that involve damping dissipation.
Bioconvective Flow Characteristics of NEPCM–Water Nanofluid over an Inclined Cylinder in Porous Medium: An Extended Darcy Model Approach
Authors: Das Bikash , Ahmed Sahin , Zueco Joaquín
Published: December 2024

Bioconvection phenomena play a pivotal role in diverse applications, including the synthesis of biological polymers and advancements in renewable energy technologies. This study develops a comprehensive mathematical model to examine the effects of key parameters, such as the Lewis number (Lb), Peclet number (Pe), volume fraction (φ), and angle of inclination (α), on the flow and heat transfer characteristics of a nanofluid over an inclined cylinder embedded in a non-Darcy porous medium. The investigated nanofluid comprises nano-encapsulated phase-change materials (NEPCMs) dispersed in water, offering enhanced thermal performance. The governing non-linear partial differential equations are transformed into dimensionless ordinary differential equations using similarity transformations and solved numerically via the Network Simulation Method (NSM) and an implicit Runge–Kutta method implemented through the bvp4c routine in MATLAB R2021a. Validation against the existing literature confirms the accuracy and reliability of the numerical approach, with strong convergence observed. Quantitative analysis reveals that an increase in the Peclet number reduces the shear stress at the cylinder wall by up to 18% while simultaneously enhancing heat transfer by approximately 12%. Similarly, the angle of inclination (α) significantly boosts heat transmission rates. Additionally, higher Peclet and Lewis numbers, along with greater nanoparticle volume fractions, amplify the density gradient of microorganisms, intensifying the bioconvection process by nearly 15%. These findings underscore the critical interplay between bioconvection and transport phenomena, providing a framework for optimizing bioconvection-driven heat and mass transfer systems. The insights from this investigation hold substantial implications for industrial processes and renewable energy technologies, paving the way for improved efficiency in applications such as thermal energy storage and advanced cooling systems.
Nonlinear Adaptive Optimal Control Design and Implementation for Trajectory Tracking of Four-Wheeled Mecanum Mobile Robots
Authors: Chen Yung-Hsiang
Published: December 2024

This study proposes a nonlinear adaptive optimal control method, the adaptive H2 control method, applied to the trajectory tracking problem of the wheeled mobile robot (WMR) with four-wheel mecanum wheels. From the perspective of solving mathematical problems, finding an analytical adaptive control solution that satisfies the adaptive H2 performance criterion for the trajectory tracking problem of the WMR with four-wheel mecanum wheels is an extremely challenging task due to the high complexity of the dynamic system. To analytically derive the control law and adaptive control law for this trajectory tracking problem, a proportional-derivative (PD) type transformation is employed to formalize the trajectory tracking error dynamics between the WMR and the desired trajectory (DT). Based on an in-depth analysis of the trajectory tracking error dynamics, a closed-form adaptive control law is analytically derived from the highly complex nonlinear dynamic system equations. This control law provides a solution to the trajectory tracking problem of the WMR while satisfying the adaptive H2 performance criterion. The proposed adaptive nonlinear control method offers a simple control structure and advantages such as improved energy efficiency. Finally, simulations and experimental implementations were conducted to verify the performance of the proposed adaptive H2 control method and the H2 control method in tracking the DT. The results demonstrate that, compared to the H2 control method, the adaptive H2 control method exhibits superior trajectory tracking performance, particularly in the presence of significant model uncertainties.
Sustainable Design Factors and Solutions Analysis and Assessment for the Graphic Design Industry: A Hybrid Fuzzy AHP–Fuzzy MARCOS Approach
Authors: Lin Chia-Liang
Published: December 2024

Within the realm of graphic design sustainability, selecting appropriate solutions has become a crucial strategic decision for organizations aiming to optimize their operations. This paper presents a novel hybrid multi-criteria decision-making (MCDM) approach, integrating a fuzzy analytical hierarchy process (FAHP) and fuzzy measurement alternatives and ranking according to compromise solution (FMARCOS). Evaluation criteria for graphic design sustainability are determined through consultation with experts, with their judgments expressed using linguistic terms based on fuzzy numbers. Criteria weights are calculated using FAHP, and the ranking and selection of the optimal potential solution are determined using FMARCOS. Subsequently, sensitivity analysis of the criteria weights is conducted to validate the results. Findings indicate that the integrated FAHP and FMARCOS model provides a robust and adaptable assessment framework for graphic design sustainability, enabling companies to navigate complexities strategically and effectively. The key contribution of this research is its emphasis on a systematic and objective model, offering practical insights relevant to the industry. It also serves as a valuable benchmark for future research in similar fields.
Summed Series Involving 1F2 Hypergeometric Functions
Authors: Straton Jack C.
Published: December 2024

Summation of infinite series has played a significant role in a broad range of problems in the physical sciences and is of interest in a purely mathematical context. In a prior paper, we found that the Fourier–Legendre series of a Bessel function of the first kind JNkx and modified Bessel functions of the first kind INkx lead to an infinite set of series involving F21 hypergeometric functions (extracted therefrom) that could be summed, having values that are inverse powers of the eight primes 1/2i3j5k7l11m13n17o19p multiplying powers of the coefficient k, for the first 22 terms in each series. The present paper shows how to generate additional, doubly infinite summed series involving F21 hypergeometric functions from Chebyshev polynomial expansions of Bessel functions, and trebly infinite sets of summed series involving F21 hypergeometric functions from Gegenbauer polynomial expansions of Bessel functions. That the parameters in these new cases can be varied at will significantly expands the landscape of applications for which they could provide a solution.
Improved Genetic Algorithm for Solving Robot Path Planning Based on Grid Maps
Authors: Zhu Jie , Pan Dazhi
Published: December 2024

Aiming at some shortcomings of the genetic algorithm to solve the path planning in a global static environment, such as a low efficiency of population initialization, slow convergence speed, and easy-to-fall-into the local optimum, an improved genetic algorithm is proposed to solve the path planning problem. Firstly, the environment model is established by using the grid method; secondly, in order to overcome the difficulty of a low efficiency of population initialization, a population initialization method with directional guidance is proposed; finally, in order to balance the global and local optimization searching and to speed up the solution speed, the proposed non-common point crossover operator, range mutation operator, and simplification operator are used in combination with the one-point crossover operator and one-point mutation operator in the traditional genetic algorithm to obtain an improved genetic algorithm. In the simulation experiment, Experiment 1 verifies the effectiveness of the population initialization method proposed in this paper. The success rates in Map 1, Map 2, Map 3, and Map 4 were 56.3854%, 55.851%, 34.1%, and 24.1514%, respectively, which were higher than the two initialization methods compared. Experiment 2 verifies the effectiveness of the genetic algorithm (IGA) improved in this paper for path planning. In four maps, the path planning is compared with the five algorithms and the shortest distance is achieved in all of them. The two experiments show that the improved genetic algorithm in this paper has advantages in path planning.
Analyzing Sample Size in Information-Theoretic Models
Authors: Bernal-Casas D. , Oller J. M.
Published: December 2024

In this paper, we delve into the complexities of information-theoretic models, specifically focusing on how we can model sample size and how it affects our previous findings. This question is fundamental and intricate, posing a significant intellectual challenge to our research. While previous studies have considered a fixed sample size, this work explores other possible alternatives to assess its impact on the mathematical approach. To ensure that our framework aligns with the principles of quantum theory, specific conditions related to sample size must be met, as they are inherently linked to information quantities. The arbitrary nature of sample size presents a significant challenge in achieving this alignment, which we thoroughly investigate in this study.
The Impact of Digital Economy Development on Regional Income Gaps: A Perspective on Multidimensional Inequality Decomposition and Threshold Effects
Authors: Ruan Jing , Zou Lu , Liu Ruiqi , Pan Hongyun
Published: December 2024

This paper investigates the impact of digital economy development on regional income gaps within provinces in China, focusing on the underlying mechanisms and multidimensional threshold effects. Using provincial panel data from 2011 to 2021, this study finds that the relationship between digital economy development and income gaps follows a U-shape, initially reducing the gap and later widening it. This analysis identifies internet penetration and digital transaction growth as key contributors to multidimensional inequality in digital economy development. Moreover, moderate levels of multidimensional inequality in digital economy development enhance its positive effect on narrowing regional income gaps, while excessive multidimensional inequality may diminish or even reverse this effect. These findings highlight the importance of managing multidimensional inequality to maximize digital economies’ potential for fostering more balanced regional development.
Low-Light Image Enhancement Integrating Retinex-Inspired Extended Decomposition with a Plug-and-Play Framework
Authors: Zhao Chenping , Yue Wenlong , Wang Yingjun , Wang Jianping , Luo Shousheng , Chen Huazhu , Wang Yan
Published: December 2024

Images captured under low-light conditions often suffer from serious degradation due to insufficient light, which adversely impacts subsequent computer vision tasks. Retinex-based methods have demonstrated strong potential in low-light image enhancement. However, existing approaches often directly design prior regularization functions for either illumination or reflectance components, which may unintentionally introduce noise. To address these limitations, this paper presents an enhancement method by integrating a Plug-and-Play strategy into an extended decomposition model. The proposed model consists of three main components: an extended decomposition term, an iterative reweighting regularization function for the illumination component, and a Plug-and-Play refinement term applied to the reflectance component. The extended decomposition enables a more precise representation of image components, while the iterative reweighting mechanism allows for gentle smoothing near edges and brighter areas while applying more pronounced smoothing in darker regions. Additionally, the Plug-and-Play framework incorporates off-the-shelf image denoising filters to effectively suppress noise and preserve useful image details. Extensive experiments on several datasets confirm that the proposed method consistently outperforms existing techniques.
Analysis of Block Adaptive Type-II Progressive Hybrid Censoring with Weibull Distribution
Authors: Singh Kundan , Tripathi Yogesh Mani , Wang Liang , Wu Shuo-Jye
Published: December 2024

The estimation of unknown model parameters and reliability characteristics is considered under a block adaptive progressive hybrid censoring scheme, where data are observed from a Weibull model. This censoring scheme enhances experimental efficiency by conducting experiments across different testing facilities. Point and interval estimates for parameters and reliability assessments are derived using both classical and Bayesian approaches. The existence and uniqueness of maximum likelihood estimates are established. Consequently, reliability performance and differences across different testing facilities are analyzed. In addition, a Metropolis–Hastings sampling algorithm is developed to approximate complex posterior computations. Approximate confidence intervals and highest posterior density credible intervals are obtained for the parametric functions. The performance of all estimators is evaluated through an extensive simulation study, and observations are discussed. A cancer dataset is analyzed to illustrate the findings under the block adaptive censoring scheme.
Considering a Classical Upper Bound on the Frobenius Number
Authors: Williams Aled , Haijima Daiki
Published: December 2024

In this paper, we study the (classical) Frobenius problem, namely the problem of finding the largest integer that cannot be represented as a nonnegative integer combination of given, relatively prime, (strictly) positive integers (known as the Frobenius number). The main contribution of this paper are observations regarding a previously known upper bound on the Frobenius number where, in particular, we observe that a previously presented argument features a subtle error, which alters the value of the upper bound. Despite this, we demonstrate that the subtle error does not impact upon on the validity of the upper bound, although it does impact on the upper bounds tightness. Notably, we formally state the corrected result and additionally compare the relative tightness of the corrected upper bound with the original. In particular, we show that the updated bound is tighter in all but only a relatively “small” number of cases using both formal techniques and via Monte Carlo simulation techniques.
Generalized Type-2 Fuzzy Approach for Parameter Adaptation in the Whale Optimization Algorithm
Authors: Amador-Angulo Leticia , Castillo Oscar , Melin Patricia , Geem Zong Woo
Published: December 2024

An enhanced whale optimization algorithm (WOA) through the implementation of a generalized type-2 fuzzy logic system (GT2FLS) is outlined. The initial idea is to improve the efficacy of the original WOA using a GT2FLS to find the optimal values of the r→1 and r→2 parameters of the WOA, for the case of optimizing mathematical functions. In the WOA algorithm, r→1 is a variable that affects the new position of the whale in the search space, in this case, affecting the exploration, and r→2 is a variable that has an effect on finding the local optima, which is an important factor for the exploration. The efficiency of a fuzzy WOA with a GT2FLS (FWOA-GT2FLS) is highlighted by presenting the excellent results of the case study of the benchmark function optimization. A relevant analysis and comparison with a bio-inspired algorithm based on artificial bees is also presented. Statistical tests and comparisons with other bio-inspired algorithms and the initial WOA, with type-1 FLS (FWOA-T1FLS) and interval type-2 FLS (FWOA-IT2FLS), are presented. For each of the methodologies, the metric for evaluation is the average of the minimum squared errors.
Solution of a Nonlinear Integral Equation Arising in the Moment Approximation of Spatial Logistic Dynamics
Authors: Nikolaev Mikhail , Nikitin Alexey , Dieckmann Ulf
Published: December 2024

We investigate a nonlinear integral equation derived through moment approximation from the individual-based representation of spatial logistic dynamics. The equation describes how the densities of pairs of individuals represented by points in continuous space are expected to equilibrate under spatially explicit birth–death processes characterized by constant fecundity with local natal dispersal and variable mortality determined by local competition. The equation is derived from a moment hierarchy truncated by a moment closure expressing the densities of triplets as a function of the densities of pairs. Focusing on results for individuals inhabiting two-dimensional habitats, we explore the solvability of the equation by introducing a dedicated space of functions that are integrable up to a constant. Using this function space, we establish sufficient conditions for the existence of solutions of the equation within a zero-centered ball. For illustration and further insights, we complement our analytical findings with numerical results.
Crude Oil Futures Price Forecasting Based on Variational and Empirical Mode Decompositions and Transformer Model
Authors: Huang Linya , Yang Xite , Lai Yongzeng , Zou Ankang , Zhang Jilin
Published: December 2024

Crude oil is a raw and natural, but nonrenewable, resource. It is one of the world’s most important commodities, and its price can have ripple effects throughout the broader economy. Accurately predicting crude oil prices is vital for investment decisions but it remains challenging. Due to the deficiencies neglecting residual factors when forecasting using conventional combination models, such as the autoregressive moving average and the long short-term memory for prediction, the variational mode decomposition (VMD)-empirical mode decomposition (EMD)-Transformer model is proposed to predict crude oil prices in this study. This model integrates a second decomposition and Transformer model-based machine learning method. More specifically, we employ the VMD technique to decompose the original sequence into variational mode filtering (VMF) and a residual sequence, followed by using EMD to decompose the residual sequence. Ultimately, we apply the Transformer model to predict the decomposed modal components and superimpose the results to produce the final forecasted prices. Further empirical test results demonstrate that the proposed quadratic decomposition composite model can comprehensively identify the characteristics of WTI and Brent crude oil futures daily price series. The test results illustrate that the proposed VMD–EMD–Transformer model outperforms the other three models—long short-term memory (LSTM), Transformer, and VMD–Transformer in forecasting crude oil prices. Details are presented in the empirical study part.
Classical Gasses with Singular Densities
Authors: Di Persio Luca , Kondratiev Yuri , Vardanyan Viktorya
Published: December 2024

We investigate classical continuous systems characterized by singular velocity distributions, where the corresponding Radon measures are defined over the entire space with infinite mass. These singular distributions are used to model particle velocities in systems where traditional velocity distributions do not apply. As a result, the particle positions in such systems no longer conform to conventional configurations in physical space. This necessitates the development of novel analytical tools to understand the underlying models. To address this, we introduce a new conceptual framework that redefines particle configurations in phase space, where each particle is represented by its spatial position and a velocity vector. The key idea is the construction of the Plato space, which is designed to represent idealized particle configurations where the total velocity remains bounded within any compact subset of phase space. This space serves as a crucial bridge to the space of vector-valued discrete Radon measures, where each measure captures the velocity distribution over the entire system. Given the inherent complexity of analyzing infinite-dimensional spaces, we tackle the problem by reformulating it onto a finite-dimensional configuration space. This is achieved by decomposing the infinite space into smaller, more manageable components. A central tool in this reformulation is the K-transform, which is pivotal in enabling harmonic analysis of the space. The K-transform allows us to represent the system in terms of components that are more amenable to analysis, thus simplifying the study of the system’s dynamics. Furthermore, we extend previous results in the study of correlation functions by developing correlation measures tailored for these vector-valued Radon measures. These generalized functions provide deeper insights into the correlations between particle positions and velocities, expanding the range of analysis to systems with singular velocity distributions. Through this approach, we develop a robust mathematical framework that sheds light on the structure and dynamics of complex particle systems, especially those characterized by singular velocity distributions. Our results offer a new perspective on systems with non-traditional velocity distributions, advancing the theory and methodology of particle systems in both classical and modern contexts.