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Due to their widespread use in engineering, hybrid nanofluids have been the primary focus of mathematical and physical research. Only the improvement of hybrid nanofluids’ variable heat conductivity and viscosity has been considered so far. Hybrid nanofluid flow across an inclined cylinder has many potential uses, including heat transfer and cooling in electrical devices, energy storage, refrigerants, and the automobile industry. Examining the effects of buoyant force, variable viscosity, variable thermal conductivity, mass suction, convective thermal conditions, and a magnetic field on the stagnation point flow of a Al₂O₃–Cu/H₂O hybrid nanofluid in an inclined cylinder is our objective in this work. In order to find solutions to boundary-condition flow-describing partial differential equations, we turn them into ordinary differential equations using similarity transformations. We achieve this by employing a numerical strategy known as the fourth-order Runge–Kutta technique, which incorporates shooting techniques. A graphical representation of the findings emphasizes the influence of many physical parameters on flow dynamics. In addition, we address the influence of drag force and rate of heat transfer on various elements, such as the Biot parameter, magnetic variable, viscosity variable, and thermal conductivity variable. The mixed convection and magnetic parameters cause the velocity profile to rise while the temperature profile falls. The research’s results elucidate the cause behind the rise in thermal contour of hybrid nanofluids, which is seen when there is an increment in thermal conductivity, radiation parameter, and Biot number. The heat transfer rate exhibits a significant increase of 36.87% in the aiding flow scenario when a 2.0 mass suction is applied in conjunction with a 0.01 hybrid nanofluid, as compared to the conventional fluid. In the scenario of opposing flow, the heat transfer rate exhibits a significant increase of 36.96% when compared to that of ordinary fluid. Heat transfer increases 43.00% when Rd increases from 0.1 to 0.5 for both assisting and opposing flow.

In this paper, we undertook a COVID-19 mathematical model with the social media impact in using of COVID-19 vaccination. For the mentioned study, we use fractals fractional order model to study the complex geometry behind the said dynamical systems. For the existence theory of such model, we used fixed point approach. Ulam–Hyers stability is also required in numerical findings. Some fundamental results such as basic reproductive number and equilibrium points are derived. Numerical analysis is performed to simulate the theoretical results. For the simulations purposes, a numerical scheme based on interpolation is developed. Various graphical presentations are given to demonstrate the results.

With the rapid development of urban rail transit, the environmental vibration and secondary noise induced by metro train operation have become increasingly serious, posing stricter requirements on the vibration and secondary noise of sensitive building office (SBO) and sensitive building school (SBS). To predict and control the vibrations and secondary noise in sensitive buildings along the metro line induced by metro train operations. A prediction method for the vibration and secondary noise of sensitive buildings along the metro line during metro train operation has been proposed. The sub-model of train-track system coupled dynamics and the sub-model of track-tunnel-soil-building system dynamics are included. The influence of metro train operation on the vibration and secondary noise of SBO and SBS is studied. The influence of the distance between the metro line and the building on the vibration and secondary noise of the sensitive building is discussed, and an effective control scheme of vibration and secondary noise is proposed. Results show that the vibration frequencies of the SBS and the SBO caused by the metro train operation are concentrated at about 8Hz and 63Hz. The vibration below the second floor of SBO caused by the metro train operation exceeds the limit, and the secondary noise below the third floor of SBS exceeds the limit. The secondary noise inside the building of each floor of SBO exceeded the limit. Using secondary noise to evaluate the environmental impact of metro train operations is more stringent than relying solely on vibration assessments. secondary noise is recommended in engineering to assess the impact of metro train operation on sensitive buildings along line. Combined with vibration, secondary noise and construction requirements, SBS and SBO are recommended to be no less than 72m and 74m away from the metro line, respectively.

This paper introduces a novel numerical method for investigating the dynamic stability of a flutter panel exposed to a supersonic gas flow and a fluctuating axial excitation force. Initially, the system equation of motion was derived using Lagrange’s equation, where the first two modes are coupled Mathieu–Hill equations with damping, constituting a system of linear second-order differential equations with periodically variable coefficients. Subsequently, a new numerical method was proposed to analyze the dynamic stability of coupled Mathieu–Hill equations with damping. This method involves breaking down an arbitrary parametric load into discrete segments to approximate the variable excitation function using a step function. The system responses of each segment are then accumulated in matrix form. The proposed numerical method proves particularly effective for dynamic systems whose parameters cannot be treated as small. In practical application, the method allows the construction of instability regions corresponding to natural frequencies, subharmonics, and combination frequencies. Dynamic stability diagrams were generated based on dynamic pressure ratio, air/panel density ratio, Mach number, panel thickness—length ratio, and excitation frequency. The results demonstrated general agreement with those obtained through Hsu’s perturbation method, however, our numerical results have proven more accurate. The paper concludes by offering suggestions for suppressing panel flutter through appropriate parameter combinations.

The research aims to explore seismic behaviors of a novel shuttle-shaped double-restrained buckling-restrained brace (SDR-BRB). To this end, three SDR-BRB specimens showing various restraining ratios were first prepared to conduct low-cycle cyclic loading tests to investigate their failure modes, hysteretic performance, and fatigue performance. Afterwards, the ABAQUS finite element (FE) model verified by experiments was established, and effects of multiple critical factors upon seismic behaviors of SDR-BRBs were discussed through parametric analysis. Finally, an improved dung beetle optimization (DBO) algorithm considering global optimization and local exploration was proposed by combining Tent chaotic mapping, adaptive T-distribution perturbation strategy, and Osprey optimization algorithm. Based on this algorithm, the parameter identification method was developed for the improved Bouc–Wen model of SDR-BRB. Results indicate that hysteretic curves of SDR-BRBs are plump and symmetrical, showing excellent energy-dissipation capacity and fatigue performance, and obvious strain-strengthening characteristics. The restraining ratio, core yield length, initial imperfection, and core diameter-thickness ratio have significant effects upon seismic behavior of SDR-BRBs, while the gap of the core and the external tube merely exerts a slight effect. As recommended, the restraining ratio should exceed 2.0, the diameter-thickness ratio need to be less than 15, and the gap should not be less than 2mm. The proposed parameter identification method for the restoring force model of SDR-BRB has high accuracy and agrees well with experimental and numerical results. It provides reference for applying SDR-BRBs to analyze elastoplastic seismic responses of a structural system.

Currently, the procedure for treating exposed comminuted mid-diaphyseal fractures in tibias consists of the use of an External Fixator (EF) linked by surgically placed screws, with the aim of repositioning and immobilizing the separate or quasi-separate parts of the bone and achieving the formation of the bony callus necessary for the regeneration of the tibia. Recent medical experiences show that the additional placement of an intramedullary rod improves the efficiency of the treatment, thus reducing the time of generation of the callus and the removal of the EF, minimizing the discomfort of the patient. In this work, the increase in stiffness provided by the intramedullary rod is quantified numerically to decrease the relative displacements between the two parts of the fractured bone. The three-dimensional modeling of an irregular body (bone) was analyzed in detail. The relative displacements between the bone and the rod, the proportions of stresses transmitted by the rod and the EF, and the connections between the bar elements and the solid elements were also investigated. A principal conclusion was an increase in the stiffness of the system by 90% on average and a reduction of relative displacements up to 20% of transverse, up to 45% longitudinal, and up to 75% torsional, for different variants of the position of the fixations, straight, and oblique fracture, and for various densities of bone, which allow validating the practical applications.

Skin cancer is one of the most common cancers, and is primarily caused by long-term exposure to ultraviolet (UV) radiation. Understanding these dynamics is critical for the development of effective preventive and treatment measures. In this study, we examined a mathematical model of skin cancer induced by UV rays, categorizing the total population into four compartments: susceptible $S(t)$, infected $I(t)$, recovered $R(t)$, and UV radiation $U(t)$. To solve the system of nonlinear differential equations and obtain a numerical solution for the SIRU model, we employed three semi-analytical methods: the differential transform method (DTM), Shehu transformation–Akbari–Ganjis–Pade approximation method (SAGPM), and higher-order inverse polynomial method (HOIPM). Each method was effective in providing highly accurate solutions with minimal computational effort. Compared to the $ode45$ solver, these semi-analytical methods have been validated for their accuracy, confirming their reliability and efficiency in solving complex real-world problems, leading to interesting findings. This study also investigated the impact of key parameters, offering valuable insights into the response and behavior of the skin cancer model under various conditions. These findings enhance our understanding of the dynamics of skin cancer.

In recent times, hybrid composite materials have gained prominence as a replacement for conventional composite materials due to their superior characteristics. This study centers on assessing the elastic and thermal properties of unidirectional hybrid composites composed of natural fibers and polymers. These composites are developed by combining banana and jute fibers in four varying weight proportions, which are then impregnated with epoxy resin. The resulting specimens are manufactured and subjected to testing according to ASTM standards. The empirical findings serve as a benchmark against which outcomes from numerical simulations and analytical techniques are validated. The numerical aspect involves the implementation of a finite element model using ANSYS software. This model is based on a three-dimensional micromechanical Representative Volume Element (RVE) with both square and hexagonal packing configurations. This approach encapsulates the hybrid fiber composite’s structural characteristics. Additionally, various analytical methods, such as the rule of hybrid mixture, Halpin–Tsai, and Lewis and Nielsen approaches, are employed to calculate the elastic and thermal properties of the hybrid composite material. Comparing the results, it is evident that the outcomes derived from finite element analysis closely correspond to the experimental data and analytical predictions. Particularly noteworthy is the reduction in longitudinal and transverse thermal conductivity of the hybrid composites by 32.95% and 48.57%, respectively, at the highest fiber content. These changes are influenced by parameters like fiber loading, void fraction, and the chosen RVE. This study underscores the efficacy of employing the homogenization technique through finite element analysis for the advanced prediction of material properties. In summary, hybrid composite materials exhibit promising potential, and this research offers valuable insights into their behavior under varying conditions.

Four point correlation functions for many electrons at finite temperature in periodic lattice of dimension d (≥1) are analyzed by the perturbation theory with respect to the coupling constant. The correlation functions are characterized as a limit of finite dimensional Grassmann integrals. A lower bound on the radius of convergence and an upper bound on the perturbation series are obtained by evaluating the Taylor expansion of logarithm of the finite dimensional Grassmann Gaussian integrals. The perturbation series up to second-order is numerically implemented along with the volume-independent upper bounds on the sum of the higher order terms in the 2-dimensional case.

The distribution function of hot carriers in state-of-the-art devices is insufficiently described using just the electric field or the average carrier energy as parameters. Still, the standard models to describe carrier transport in semiconductor devices, namely the drift-diffusion model and the energy-transport model rely on these assumptions. In this article we summarize our work on six moments transport models which allow an accurate characterization of the distribution function. Within this framework it is possible to selfconsistently model the scattering integral without resorting to the relaxation time approximation. In addition, hot electron processes such as impact ionization, which are difficult to model in lower order transport models, can be described accurately.

A computational analysis has been performed to study the flow instability of two-parallel wall motions in a Cuboidal enclosure incorporated by a cylinder under different radii sizes. A numerical methodology based on the Finite Volume Method (FVM) and a full Multigrid acceleration is utilized in this paper. Left and right parallel walls of the cavity are maintained driven and all the other walls completing the domain are motionless. Different radii sizes ($R=0.075$, 0.1, 0.125, 0.15 and 0.175) are employed encompassing descriptive Reynolds numbers that range three orders of magnitude 100, 400 and 800 for the steady state. The obtained results show positions $R=0.15$ and $R=0.175$ of the inner cylinder promote cell distortion. Also, when the radius equates to $R=0.15$, it may lead to the birth of tertiary cells at $\mathrm{\text{Re}}=400$ which are more developed for $\mathrm{\text{Re}}=800$. Thereafter, analysis of the flow evolution shows that with increasing Re beyond a certain critical value, the flow becomes unstable and undergoes a Hopf bifurcation. A nonuniform variation with the radius size of the inner cylinder is observed. Otherwise said, elongating the radius of the cylinder leads to decrease in the critical Reynolds number. Hence, the acceleration of the unsteadiness is realized. On the other hand, by further increasing Reynolds number more than the critical value from 1200 to 2100, we note that the kinetic energy is monotonously increasing with Reynolds number and a stronger motion in the velocity near the rear wall of the enclosure is observed. Furthermore, the symmetry of flow patterns observed in the steady state has been lost. Therefore, a systematic description of various effects illuminating the optimum geometrical parameters to achieve effective flow behavior in those systems has been successfully established through this paper.

In this study we derive a semi-linear Elliptic Partial Differential Equation (PDE) problem that models the static (zero voltage) behavior of a Josephson window junction. Iterative methods for solving this problem are proposed and their computer implementation is discussed. The preliminary computational results that are given, show the modeling power of our approach and exhibit its computational efficiency.

The accuracy of the lattice-Boltzmann method (LBM) is moderated by several factors, including Mach number, spatial resolution, boundary conditions, and the lattice mean free path. Results obtained with 3D lattices suggest that the accuracy of certain two-dimensional (2D) flows, such as Poiseuille and Couette flow, persist even when the mean free path between collisions is large, but that of the 3D duct flow deteriorates markedly when the mean free path exceeds the lattice spacing. Accuracy in general decreases with Knudsen number and Mach number, and the product of these two quantities is a useful index for the applicability of LBM to 3D low-Reynolds-number flow. The influence of boundary representations on LBM accuracy is captured by the proposed index, when the accuracy of the prescribed boundary conditions is consistent with that of LBM.

In this paper, a new type of honeycomb structure is proposed to enhance the energy absorption capacity for a honeycomb structure, and investigated its energy absorption efficiency (absorbed energy per unit volume) by finite element method (FEM). This model has small arc-shaped parts on the double cell wall, and can be manufactured by a similar way of standard honeycomb structures. Also, the proposed structure has large rigidity of plastic bending without increasing the mass. In this paper, effects of geometrical properties on the energy absorption characteristics are discussed.

This paper aims to study dynamic properties of loess. This study is helpful to the subject on how to avoid or decrease the seismic disasters on loess ground. Dynamic triaxial tests are carried out with saturated remoulded soil samples taken form loess sites in Xi'an, China. Dynamic stress and strain relationship as well as the rule of the accumulated residual strain are obtained from the test results. Linear relationship between accumulated residual strain and vibration circle under constant amplitude circular loading is presented. A hypothesis about the accumulated residual strain is proposed. 1D dynamic constitutive relationship model which can well describe the real relationship between dynamic stress and strain under irregular dynamic loading is established. Numerical program with this model is developed and an example is tested. Numerical results of hysteresis loop, accumulated residual strain, amplitude of dynamic stress and damping ratio show good agreement with test results. It is indicated that the hypothesis of accumulated residual strain and the 1D dynamic constitutive relationship model can accurately simulate the dynamic triaxial tests of saturated remoulded loess.

This paper deals with the temperature and rate-dependent elasto-viscoplasticity behaviour of a highly ductile acrylic adhesive and its effect on plastic bending of adhesively bonded sheet metals. Tensile lap shear tests of aluminium single-lap joints were performed at various temperature of 10-40°C at several tensile speeds. Based on the experimental results, a new constitutive model of temperature and rate-dependent elasto-viscoplasticity of the adhesive is presented. From V-bending experiments and the corresponding numerical simulation, it was found that the gull-wing bend is suppressed by high-speed forming at a lower temperature.

Single-wire flux-aided backing-submerged arc welding (FAB-SAW) technology has been widely used to weld thick steel plate due to its easy assembly and high heat input. The microstructure and property of welded joint are closely related to the thermal field of FAB-SAW process. In this research, the feature of thermal field for single-wire FAB-SAW was investigated. Based on the heat transfer mechanism, a three-dimensional transient model for thermal field was developed based on the influence of steel thickness, groove angle and ceramic backing. The temperature profile in single-wire FAB-SAW of D36 steel under different welding conditions was simulated by ANSYS. The characteristic of thermal field was analyzed and the influences of groove angle on temperature field for different plate thicknesses were discussed. The calculated geometries and dimensions of weld cross-section under different conditions show a good agreement with the experimental results. This newly built model can describe the thermal field accurately, which would be helpful to understanding the thermophysical mechanism of FAB-SAW and optimizing the welding process.

The work aims to explore the exponential rational function technique and the generalized Kudryashov procedure to investigate one of the most important equations which is the equation of cold bosonic atoms in a zig-zag optical lattice. The considered equation is reduced to a supreme equation by using the continuum approximation which describes the soliton’s dynamics with the implication pulse variables. The adopted techniques are accurate, simple, straightforward, and succinct to compute.

The bioconvection aspect for the rate type nanomaterial under dynamic of induced magnetic force has been numerically worked out. The Oldroyd-B nonlinear model is incorporated to inspect the interesting rheological dynamic of rate type classifications. Following nonlinear models, the relaxation and retardation features are observed. The numerical proposed data is fundamentally achieved via the shooting method. After developing the dimensionless problem expressions, the shooting numerical algorithm is followed for the computations. The physical onset of parameters is graphically listed with interesting applications. It is observed that a more strong induced magnetic field profile has been observed due to the presence of bio-convective Lewis number and Rayleigh number. An enriched profile of thermal phenomenon due to Grashof number is observed. The composed reflected outcomes present importance in thermal management systems, extrusion systems, plasma physics, chemical processes, nuclear systems, extrusion mechanism, biofuels, etc.

Hybrid nanofluids have unique characteristics that make them more useful than common heat transfer fluids. The potential applications can be found in applied thermal engineering, chemical engineering, hybrid powered engines, biomedical and mechanical engineering. Therefore, the analysis of SWCNTs–MWCNTs/C₂H₆O₂–H₂O with integrated effects of thermal radiations and perpendicular magnetic field is organized in this research. Thermal conductivity of C₂H₆O₂–H₂O is improved via Xue, Ota and Yamada thermal conductivity correlations. The mathematical problem is designed for two sheets and both the hybrid nanoliquid and the plates rotate in counter clockwise pattern. Mathematical treatment of the model is performed and the results were analyzed through graphical way. Keen observations of the results reveal that the fluid motion controlled by intensifying the magnetic field and higher density of SWCNTs–MWCNTs leads to optimum decrement. Further, the fluid movement is investigated optimum and slow for outward and inward plate movement, respectively. The temperature results for the parameters, especially the thermal radiations, showed that hybrid nanoliquid has the ability to store high thermal energy than common mono-nanoliquid, hence it would be suitable for future industrial applications. The parametric ranges are selected as $A_1=0.1$–1.7, ${\alpha }_1=0.1$–0.9, $M=1.0$–9.0 and $\mathrm{\Omega }=0.0$–20.0 for the study.