Search Results (22,661)

This study aims to improve the outlet temperature performance of a pneumatic heat-generating blower and investigate the influence of turbulence on the outlet temperature. Based on the heat generation mechanism and structural principle, mathematical models are developed for key components including the impeller and flow channel. The Kriging surrogate model and NSGA-II multi-objective genetic algorithm are adopted to optimize the aerodynamic performance responses of the impeller structural parameters. After comprehensive analysis, an optimal parameter combination is selected from the Pareto solution set for CFD numerical simulation. The results show that the optimization effectively improves the outlet temperature and turbulent kinetic energy distribution. The numerical results agree well with the optimization outcomes, verifying the reliability and accuracy of the proposed method. These findings provide a reference for the multi-physics coupled optimal design of blower blades. Full article

Given the therapeutic potential of bioactive cordycepin in medical and healthcare products, precision fermentation using an engineered strain of Aspergillus oryzae was performed to enhance cordycepin production. To understand and predict the dynamics of cell growth and cordycepin production in this fungal strain, mathematical modeling of submerged fermentation was applied. The effects of different nitrogen sources (yeast extract, peptone, (NH₄)₂SO₄, NH₄Cl, NaNO₃, and KNO₃) and carbon sources (glucose and cassava starch hydrolysate, CSH) on cell growth and cordycepin production were evaluated under submerged fermentation conditions. The results showed that organic nitrogen sources significantly enhanced biomass formation and cordycepin production compared with inorganic nitrogen sources. Among them, yeast extract provided the best performance, yielding the highest biomass (13.63–15.99 g/L) and cordycepin titer (1.24–1.72 g/L). In contrast, nitrate-based nitrogen sources supported cell growth but resulted in negligible cordycepin production. Under optimized conditions in a bioreactor, both glucose and CSH supported fungal growth, although CSH promoted higher biomass formation while glucose favored cordycepin biosynthesis. The kinetic model demonstrated that the growth of engineered A. oryzae was well described by the logistic growth model (R² > 0.88). The cordycepin production profiles were well fitted by the Luedeking–Piret model (R² > 0.99), indicating a mixed growth-associated product with kinetic constants α and β representing growth-associated and non-growth-associated production, respectively. Overall, the developed kinetic model provides a quantitative framework for describing cell growth, substrate utilization, and cordycepin formation, offering guidance for process optimization and scale-up of cordycepin production in engineered fungal systems. Full article

In this article, we introduce and investigate a novel class of graphs that are called Power Congruence Graph PCGs, which are defined over the vertex set V$=\{0,1,2,\dots ,n-1\}$ where two vertices $a,b\in V$ are adjacent if $a^k\equiv b^k(modm)$ for some modulus $m\in M_p$, where $M_p=\{p,p^2,\dots ,p^t\mid p^t<n\}$. We thoroughly characterize the structural features of these graphs, establishing that each PCG decomposes into a union of $d+1$ complete components, where $d={\displaystyle \frac{p-1}{gcd(k,p-1)}}$. The component sizes are explicitly given for n, p, and k. This decomposition highlights symmetry patterns in the component arrangement, emphasizing connectedness and structural balance. We derive key graph-theoretic metrics such as degree distribution, size, chromatic number, clique number and domination number. We also compute the adjacency and Laplacian matrices, as well as their spectra and associated graph energies to better understand the structural similarities and differences among PCGs with different exponents and prime moduli. This paper offers a systematic framework for comprehending power congruence based graph constructs, integrating number theory with structural and spectral graph theory and illustrating the natural symmetry that underpins these combinatorial structures. Full article

Conventional control strategies for battery energy storage systems (BESSs) fail to achieve symmetrical and coordinated control between the DC/DC and DC/AC conversion stages, resulting in unsatisfactory DC capacitor voltage fluctuation suppression and threatening the safe and stable operation of the system. To address this issue, this study proposes an improved model predictive control (MPC)-based control method that explicitly considers DC capacitor voltage fluctuation suppression. First, a dynamic mathematical model of the BESS is established by jointly considering its DC/DC and DC/AC energy conversion stages. The model is then discretized using the first-order forward Euler method to facilitate controller implementation. Second, the cost function of the proposed MPC-based control method is designed to simultaneously incorporate DC capacitor voltage fluctuation suppression and output current tracking errors on both the DC and AC sides. Finally, the switching states of the DC and AC converters are selected as the control set, and the optimal switching signals for the BESS are determined by optimizing the aforementioned cost function. Verification results demonstrate that, compared with traditional control strategies, the proposed strategy achieves more symmetrical stable and dynamic performance and reduces DC side capacitor voltage fluctuation by approximately 80%, thereby effectively ensuring the safe and stable operation of the system. Full article

The removal efficiency of wet scrubbers is governed by complex nonlinear interactions among operating parameters such as liquid level, airflow velocity, and dust concentration, making accurate real-time prediction challenging, which in turn leads to operational instability, increased energy consumption, and excessive emissions. To address this bottleneck, we first introduce multi-gene genetic programming (MGGP) to develop interpretable models quantifying multi-parameter coupling and predicting removal efficiency for PM₁, PM_2.5, PM₁₀, and TSP. Key input variables, including liquid level height, inlet airflow velocity, system pressure, and inlet dust concentration, were identified via correlation analysis. Explicit mathematical models were derived. Global sensitivity analysis using the elementary effect test (EET) identified inlet airflow velocity as most influential. Uncertainty quantification via quantile regression (QR) confirmed the model’s reliability with narrow prediction intervals and high coverage probabilities. MGGP offers a favorable balance of accuracy, generalization, and interpretability compared to extreme gradient boosting (XGBoost) and multiple nonlinear regression (MNR). Its explicit form quantifies parameter interactions, enabling efficient on-site monitoring with low computational cost. This study provides an interpretable prediction tool for intelligent wet scrubber operation, supporting cleaner production and refined control in complex industrial processes. Full article

Eddy-current inspection of anisotropic composites, such as aeronautical CFRP, demands models that ensure mathematical rigor, tensorial consistency, and clear energetic interpretation. This work presents a novel unified variational framework with a multiplicative tensor perturbation for the time-harmonic eddy-current problem in anisotropic media with defective regions. The formulation is posed in the natural spaces $H(\mathrm{curl};\Omega )\times H^1\left({\Omega }_c\right)$, and the well-posedness is established via the Lax–Milgram theorem under physically consistent assumptions on permeability and conductivity. The sesquilinear form admits a Hermitian decomposition that separates dissipative and reactive contributions, revealing the energetic structure of the weak formulation. Defects are modeled through multiplicative modifications of the baseline anisotropic conductivity tensor. This congruence-based approach preserves symmetry and positive definiteness, ensuring non-negative Joule losses and structural stability, allowing a modular representation of subsurface delamination, fiber breakage, conductive inclusions, and distributed porosity within a single tensorial framework. A central result of the present formulation is the reconstruction of the complex power functional from the evaluation of the weak form at the solution, showing that the active dissipated power and the magnetic reactive power arise directly from the same integral terms. Through the complex Poynting theorem, the quadratic form is linked to the internal complex power, establishing a direct connection between the variational formulation and measurable quantities such as probe impedance variations. Simulations of realistic layered CFRP configurations, including single- and multi-defect scenarios, confirm that, compared with additive perturbations, the multiplicative model provides enhanced energetic contrast, particularly in strongly anisotropic and interacting defect conditions. Agreement with experimental measurements, supported by a quantitative comparison of dissipated power variations obtained from controlled EC experiments, corroborates the physical relevance and robustness of the proposed complex power functional. Full article

This study develops an integrated mathematical model to investigate the interaction between tuberculosis (TB) transmission and childhood stunting, which is aligned with the United Nations Sustainable Development Goals (SDG 3). The population is structured into two age groups (0–5 years and ≥5 years), with stunting explicitly incorporated into the pediatric population to capture its potential influence on TB dynamics. The model is formulated as a system of ordinary differential equations and analyzed using equilibrium and stability analysis, with the basic reproduction number, R₀. The disease-free equilibrium is locally asymptotically stable when R₀ < 1, while an endemic equilibrium exists when R₀ > 1. Sensitivity analysis indicates that the transmission rate (β), progression rate from latent to active infection (σ), and recovery rate (γ) are the most influential parameters affecting R₀. These parameters are therefore selected as control variables in an optimal control framework to design effective intervention strategies. Numerical simulations show that the combined control strategy significantly reduces TB transmission, resulting in a reduction of more than 80% in active TB cases within a relatively short intervention period. The results suggest that integrated interventions targeting transmission, disease progression, and recovery are substantially more effective than single-measure strategies. This study provides a quantitative framework to support integrated public health policies addressing TB and childhood stunting simultaneously. Full article

Pectins are structurally complex plant polysaccharides whose functional properties strongly depend on molecular structure that may vary depending on the source of origin. The present study aimed to characterize and compare the hydrodynamic properties of pectins obtained from red and blackcurrants in semidilute and concentrated aqueous solutions. Pectins were extracted and analyzed using light scattering methods and rheology at 25 °C, 30 °C, 35 °C and 40 °C. The methodology used enabled the determination of the hydrodynamic properties of the pectins with changing temperature and concentration, and mathematical modeling was performed using the Kohlrausch–Williams–Watts model. The obtained samples differed in molecular structure, and these differences were reflected in the chain behavior in aqueous solution. The results indicate that even closely related botanical sources may yield pectins with significantly different functional properties. Hydrodynamic studies revealed that relaxation phenomena occurred in a similar manner for redcurrant pectin in the concentrated region and for blackcurrant pectin in the semidilute region (similar diffusion coefficients). Under shear flow conditions, blackcurrant pectin solutions behaved like Newtonian fluids, whereas redcurrant pectin exhibited complex, non-Newtonian behavior. Redcurrant pectin solutions also exhibited lower apparent viscosity values at concentrations comparable to those of blackcurrant pectin. The ability to scale apparent viscosity values indicated a unchanging friction mechanism in viscous flow, characteristic of semidilute and concentrated regions. Full article

Cervical cytology screening remains dependent on manual analysis, which is time-consuming and subject to variability. This study proposes a leakage-free hybrid deep learning framework for multiclass classification of cervical cells extracted from whole-slide Papanicolaou images. A fine-tuned DenseNet121 feature extractor was combined with three classifiers: Support Vector Machine (SVM), Stacked Extreme Learning Machine (SELM), and Cascaded Deep Forest (CDF). Experiments were conducted on the CRIC Cervix Collection dataset using slide-level data partitioning and group-aware stratified 7-fold cross-validation. Model comparison followed a paired non-parametric protocol (Friedman test with Wilcoxon post hoc and Holm correction). DenseNet121 + CDF achieved the highest cross-validation Accuracy (0.7370 ± 0.0357), significantly outperforming SVM (0.6644 ± 0.0287) and SELM (0.6431 ± 0.0471) (χ²(2) = 11.14, p = 0.0038; Kendall’s W = 0.79). Independent testing showed competitive generalization across models. These results support the statistical robustness of the Cascaded Deep Forest-based hybrid architecture for multiclass cervical cytology classification under realistic slide-level conditions. Full article

This paper investigates a nonlinear Bitsadze–Samarskii type boundary value problem for an elliptic-hyperbolic operator. First, we establish necessary and sufficient conditions for the unique solvability of the corresponding linear mixed-type problem using the abstract theory of correct restrictions and extensions of operators. Explicit solution formulas are obtained via Green’s function for the elliptic part and integral representations for the hyperbolic part. These results are then extended to a nonlinear mixed operator of power-law type by applying a bijective transformation that reduces the nonlinear problem to the linear case. The key condition for solvability is the continuity and invertibility of a functional coefficient in the boundary condition. Our work provides a systematic framework for handling non-standard boundary conditions in mixed-type problems and highlights the role of operator-theoretic methods in nonlinear settings. Full article

In this paper, considering the influence of high-temperature and high-pressure environments on the operating characteristics of rotary combined seals, a mathematical model of rotary composite seals is established based on the thermo-elastohydrodynamic lubrication theory. Furthermore, based on a static analysis of the composite seal and by using the deformation influence coefficient matrix method under the small deformation theory, the elastic deformation distribution of the composite seal under the action of oil film pressure is determined. Combined with the hydrodynamic lubrication equation, the energy equation for the temperature field, and the viscosity-temperature equation, the thermo-elastohydrodynamic lubrication model of the rotary composite seal is solved using the finite difference method, and the oil film thickness distribution and oil film pressure distribution during the operation of the composite seal are calculated. The results show that the sealing medium pressure has a significant effect on the sealing performance. In the axial direction, the oil film pressure first increases and then decreases, while remaining within a stable fluctuation range. Full article

Background: This exploratory study investigates whether STEM (science, technology, engineering, and mathematics) students’ increasing reliance on off-campus resources (e.g., online platforms, private tutors) reflects an authentic preference for autonomous learning or a compensatory response to perceived deficiencies in on-campus instruction. Methodology: Using a mixed-methods design, data were collected from 118 engineering and science students. A model was developed to examine the relationship between the intensity of student criticism and their declared preference for off-campus learning. Findings: The model revealed a significant negative relationship between the intensity of criticism and the preference for off-campus instruction. This suggests that for highly critical students, external resources function primarily as a compensatory mechanism for “needs frustration” rather than a preferred alternative. The results imply that these students continue to value the frontal model but find its current implementation insufficient to meet their pedagogical needs. Conclusion: These findings challenge the assumption that digital trends signify a voluntary abandonment of the classroom. Instead, reliance on external resources is positioned as a reactive, compensatory strategy. Higher education institutions should prioritize revitalizing frontal instruction through enhanced clarity and focus to reduce dependency on off-campus platforms and restore the value of the campus experience. Full article

This study explores an integrated multi-physics design approach for a high-speed Interior Permanent Magnet Synchronous Motor (IPMSM) optimized for marine diesel engine Exhaust Gas Recirculation (EGR) blower systems. To satisfy the rigorous operational demands of marine environments, an IPMSM with a rated output of 150 kW and a base speed of 9000 rpm was developed. The design validity was rigorously verified through a comprehensive multi-physics framework using the Finite Element Method (FEM), ensuring a balance between electromagnetic, thermal, and mechanical performance. The investigation established a mathematical model for the IPMSM driven by a Space Vector Pulse-Width Modulation (SVPWM) inverter, facilitating a detailed analysis of steady-state characteristics within the EGR system. To guarantee long-term reliability at high rotational speeds, the study performed an integrated thermal analysis based on precise electrical loss separation and a rotor-dynamic evaluation focusing on unbalanced vibration responses of the shaft. Finally, the proposed design was validated by integrating the IPMSM into a full-scale EGR blower system. Experimental evaluations across the entire operating range confirm that the integrated design successfully achieves the high power density and mechanical robustness required for marine diesel applications. Full article

As typical underactuated systems, overhead cranes are widely utilized in heavy-load transportation. However, their strong nonlinear coupling and underactuated characteristics complicate precise positioning and payload swing suppression. Furthermore, model uncertainties and external disturbances in practical environments increase control complexity and degrade system performance. To address these issues, this paper develops a trajectory tracking control scheme based on time delay estimation (TDE). Specifically, some transformations are made for the dynamic model and the TDE mechanism is used to estimate unknown nonlinear dynamics and external disturbances. Then, a sliding mode trajectory tracking controller, along with the TDE mechanism, is proposed for the trajectory tracking control and uncertainties estimation of the overhead crane system. Rigorous mathematical analysis is provided to demonstrate the asymptotic stability of the closed-loop system. Finally, simulation results verify the effectiveness of the proposed method in comparison with the existing control methods. Full article

The treatment of spent drilling fluids generated during the drilling of technological wells for uranium production represents an important engineering and environmental challenge associated with high energy consumption, significant waste generation, and the need for rational water use under arid regional conditions. Conventional phase separation methods based on gravitational settling and chemical–mechanical treatment are characterized by limited process controllability, long processing times, and increased consumption of reagents and energy. This study proposes an energy-efficient and reliable hydrodynamic technology for the treatment of spent drilling fluids based on the formation of controlled turbulent structures without the use of mechanical drives. The research object comprised spent drilling fluids (SDFs) generated during the drilling of technological wells for uranium production in the southern regions of the Republic of Kazakhstan and the Kyzylorda region. Experimental investigations were carried out using a laboratory–pilot hydrodynamic disperser with variations in velocity gradient, treatment time, flocculant dosage, and suspension flow rate. A mathematical model linking hydrodynamic process parameters with phase separation kinetics and energy characteristics was developed. Model calibration by weighted nonlinear least squares yielded a stable parameter set with 95% confidence intervals, and model validation demonstrated good agreement between calculated and experimental data (MAPE 8.4%; maximum relative error 11.8%). It was established that the use of a hydrodynamic disperser provides separation efficiency of up to 90–95% under optimal operating conditions while reducing specific energy consumption and maintaining stable repeated-cycle performance within the investigated operating window. Experimental results confirm that implementation of the hydrodynamic technology enables a reduction in sludge volume by 40–60%, recovery of up to 60–80% of process water, and a significant decrease in waste requiring transportation and disposal. The obtained results demonstrate the high environmental and resource-saving efficiency of the proposed technology and its suitability for scaling and industrial implementation at facilities drilling technological wells for uranium production. The developed hydrodynamic approach can be considered an effective engineering platform for creating energy-efficient and sustainable systems for drilling fluid treatment in regions with limited water resources and remote industrial infrastructure. Full article