Shell Model Research Articles

Hybrid-Trefftz Finite Element Model of Smart Doubly Curved Laminated Composite Shells

Abstract A novel smart hybrid-Trefftz finite element (HTFE) model has been developed for the analysis of smart doubly curved (DC) laminated composite shells integrated with a d_31 macro fiber composite (MFC) piezoelectric layer acting as the distributed actuator. The substrates of these smart shells include symmetric and antisymmetric spherical, paraboloid, and hyperboloid laminated shells. This HTFE model avoids the complex task of deriving the particular solutions for simultaneous governing partial differential equations (PDEs) of the element domain. The Trefftz functions here are constructed in straightforwardly manner from a finite number of free-field exact solutions of the homogeneous simultaneous governing PDEs of the element domain, without transforming them into a single governing equation. Exact solutions for the smart DC shells have also been derived here for validating the HTFE model. It is found that the HTFE model of smart DC shells accurately predicts the passive and active responses of the substrate DC laminated composite shells.

The influence of hardcore concept in the improvement of the beta decay calculation

This work investigates the impact of incorporating the hard-core concept in nuclear physics on theoretical beta decay calculations. The paper delves into the mathematical formalism employed to integrate this concept. Subsequently, it presents two sets of calculations for the beta decay chain within the [Formula: see text] nucleus using the shell model framework. A comparative analysis is conducted between the obtained results, along with a comparison to experimental data. This analysis aims to elucidate how the inclusion of the hard-core concept refines theoretical predictions for beta decay calculations.

Fast EEG/MEG BEM-based forward problem solution for high-resolution head models.

A fast BEM (boundary element method) based approach is developed to solve an EEG/MEG forward problem for a modern high-resolution head model. The method utilizes a charge-based BEM accelerated by the fast multipole method (BEM-FMM) with an adaptive mesh pre-refinement method (called b-refinement) close to the singular dipole source(s). No costly matrix-filling or direct solution steps typical for the standard BEM are required; the method generates on-skin voltages as well as MEG magnetic fields for high-resolution head models within 90 s after initial model assembly using a regular workstation. The forward method is validated by comparison against an analytical solution on a spherical shell model as well as comparison against a full h-refinement method on realistic 1M facet human head models, both of which yield agreement to within 5 % for the EEG skin potential and MEG magnetic fields. The method is further applied to an EEG source localization (inverse) problem for real human data, and a reasonable source dipole distribution is found.

Solar energetic particles injected inside and outside a magnetic cloud

Context. On 2022 January 20, the Energetic Particle Detector (EPD) on board Solar Orbiter measured a solar energetic particle (SEP) event showing unusual first arriving particles from the anti-Sun direction. Near-Earth spacecraft separated by 17° in longitude to the west of Solar Orbiter measured classic anti-sunward-directed fluxes. STEREO-A and MAVEN, separated by 18° to the east and by 143° to the west of Solar Orbiter, respectively, also observed the event, suggesting that particles spread over at least 160° in the heliosphere. Aims. The aim of the present study is to investigate how SEPs are accelerated and transported towards Solar Orbiter and near-Earth spacecraft, as well as to examine the influence of a magnetic cloud (MC) present in the heliosphere at the time of the event onset on the propagation of energetic particles. Methods. We analysed remote-sensing data, including flare, coronal mass ejection (CME), and radio emission to identify the parent solar source of the event. We investigated energetic particles, solar wind plasma, and magnetic field data from multiple spacecraft. Results. Solar Orbiter was embedded in a MC erupting on 16 January from the same active region as that related to the SEP event on 20 January. The SEP event is related to a M5.5 flare and a fast CME-driven shock of ∼1433 km s−1, which accelerated and injected particles within and outside the MC. Taken together, the hard SEP spectra, the presence of a Type II radio burst, and the co-temporal Type III radio burst being observed from 80 MHz that appears to emanate from the Type II burst, suggest that the shock is likely the main accelerator of the particles. Conclusions. Our detailed analysis of the SEP event strongly suggests that the energetic particles are mainly accelerated by a CME-driven shock and are injected into and outside of a previous MC present in the heliosphere at the time of the particle onset. The sunward-propagating SEPs measured by Solar Orbiter are produced by the injection of particles along the longer (western) leg of the MC still connected to the Sun at the time of the release of the particles. The determined electron propagation path length inside the MC is around 30% longer than the estimated length of the loop leg of the MC itself (based on the graduated cylindrical shell model), which is consistent with the low number of field line rotations.

Micromagnetic simulation of Nd–Fe–B grain with a dysprosium-containing shell

The effects of Dy-doped shell thickness on the magnetic properties and magnetization reversal behavior of a Nd–Fe–B grain have been systematically investigated using micromagnetic simulations based on a core–shell model. The Dy-containing shell can significantly enhance the coercivity of the model. Notably, when the shell thickness reaches 12 nm, the coercivity reaches its maximum value, and the nucleation sites shift from the core–shell interface to the grain corners. Ferromagnetic resonance spectra indicate that the low-frequency modes are associated with the nucleation sites, and the increased coercivity is related to the shift of the core–shell simultaneous resonance mode to higher frequency. In addition, we propose a multi-shell model to further enhance the coercivity by shifting the nucleation points. This approach of adjusting the nucleation sites can also be applied to improve the magnetic properties of other magnets.

Behavior of the dielectric and pyroelectric responses of ferroelectric fine‐grained ceramics

AbstractWe demonstrated the correlations between the specific temperature behavior of the colossal dielectric permittivity, unusual electro‐transport characteristics, and frequency dependences of the pyroelectric response of the fine‐grained ceramics prepared by the spark plasma sintering of the ferroelectric BaTiO3 nanoparticles. The temperature dependences of the electro‐resistivity indicate the frequency‐dependent transition in the electro‐transport mechanisms between the lower and higher conductivity states accompanied by the maximum in temperature dependence of the loss angle tangent. The pyroelectric thermal wave probing revealed the existence of the spatially inhomogeneous counter‐polarized ferroelectric states at the opposite surfaces of the ceramic sample. We described the temperature behavior of the colossal dielectric response and losses using the core−shell model for ceramic grains, effective medium approximation, and Maxwell−Wagner approach.

Shadow-based quantum subspace algorithm for the nuclear shell model

Shadow-based quantum subspace algorithm for the nuclear shell model

Prediction and optimization of composite shell with cutout under hydrostatic pressure via deep neural networks

Composite cylindrical shells with openings represent an innovative primary structural configuration for submersibles, effectively enhancing their structural performance and, consequently, their endurance capabilities. Under hydrostatic pressure conditions, it is essential to optimize the structural design parameters to improve the buckling load and static strength margins of composite cylindrical shells with openings. However, the stress state around openings is highly complex, making simulation and computational analysis challenging and time-intensive. Therefore, leveraging advanced computational methods to assist in structural design is imperative. This study presents an experimental study on the hydrostatic pressure bearing performance of filament-wound composite shells. Based on the experimental results, an accurate finite element method (FEM) model has been established. This study has developed a data-rich framework, generating a synthetic dataset of strength performance under hydrostatic pressure through 16,996 FEM analysis. Subsequently, machine learning (ML) models have been established to predict strength performance. This study presents the validation of the superiority of Deep Neural Network (DNN) models in predicting structural strength under hydrostatic pressure, and evaluates the prediction error. Additionally, for the first time, the DNN model is applied to estimate the structural performance under hydrostatic pressure, with optimization achieved through the integration of a genetic algorithm. The introducing of DNN greatly accelerates the computational speed compared to full FEM-based optimization procedures. By optimizing representative long and short shell models separately, it is demonstrated that ML-based optimization can replace full FEM-based procedures, facilitating preliminary structural design optimization and offering more efficient design solutions.

Riemannian Shape Optimization of Thin Shells Using Isogeometric Analysis

ABSTRACTIn this contribution, we consider the optimal shape design of thin elastic shell structures based on a linearized shell model of Koiter's type, whose shape can be described by a surface immersed in three‐dimensional Euclidean space. We regard the set of unparametrized immersions of the surface as an infinite‐dimensional Riemannian shape space and perform optimization in this setting using the Riemannian shape gradient. Nonuniform rational basis splines (NURBS) are employed to discretize the shell and numerically solve the underlying equations that govern its mechanical behavior via isogeometric analysis. By representing NURBS patches as B‐spline patches in real projective space, NURBS weights can also be incorporated into the optimization routine. We discuss the practical implementation of the method and demonstrate our approach on the compliance minimization of a half‐cylindrical shell under static load and fixed area constraint.

Exposing the dead-cone effect of jet quenching in QCD medium

Abstract When an energetic parton traverses the hot QCD medium it may suffer multiple scattering and lose its energy. The medium-induced gluon radiation for a massive quark will be suppressed relative to that of a light quark due to the dead-cone effect. The development of new declustering techniques of jet evolution makes a direct study of the dead-cone effect in the QCD medium possible for the first time. In this work, we compute the emission angle distribution of the charm-quark initiated splittings in $\rm D^0$ meson tagged jet and that of the light parton initiated splittings in an inclusive jet in p+p and Pb+Pb at $\rm 5.02$~TeV by utilizing the declustering techniques of jet evolution. The heavy quark propagation and indued energy loss in the QCD medium are simulated with the SHELL model based on the Langevin equation. By directly comparing the emission angle distributions of charm-quark-initiated splittings with those of light parton-initiated splittings at the same energy intervals of the initial parton, we provide insights into the fundamental splitting structure in A+A collisions， thereby exploring the possible exposure of the dead-cone effect in medium-induced radiation. We further investigate the case of the emission angle distributions normalized to the number of splittings and find the dead-cone effect will broaden the emission angle of the splitting and reduce the possibility to occur such splitting, therefore leading the massive parton to lose less energy. We also find the collisional energy loss mechanism has a negligible impact on the medium modification to the emission angle distribution of the charm-quark initiated splittings for $\rm D^0$-meson tagged jets. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd

Equivalent Layer and Single Layer Approaches to Modeling of Toroidal Sandwich Shells Using Carrera Unified Formulation*

Equivalent Layer and Single Layer Approaches to Modeling of Toroidal Sandwich Shells Using Carrera Unified Formulation*

A shear deformable shell model for dynamic performance of light-weight and advanced sport balls

The present study investigates the oscillation characteristics of a sport ball that is modeled as a doubly curved shell that is made of a nanocomposite material consisting of functionally graded graphene platelets and metal foams. The shell is immersed on a Kerr basis, which is an elastic foundation with three parameters. The organization of the pores and the dispersion of the graphene platelets throughout the thickness of the model are considered based on the stated functionality. The Halpin-Tsai and expanded rule of mixture micromechanical models are employed to determine the effective mechanical property values. Once the motion equations are established, the frequencies are derived using the analytical method, which is especially efficient for shells with simply supported edges. The investigation takes into account and deals with the effects of different influences on the natural frequencies. The results could serve as a benchmark for future research. Given the absence of comparable research in the existing literature, the findings of this study can serve as a standard for future investigations.

Unified vibration modeling of shell and plate structures with resonators

Unified vibration modeling of shell and plate structures with resonators

MESHING TRANSFERS IN AUTODESK INVENTOR

In order to improve the execution of drawings of gear elements in the Autodesk Inventor package, an approach to the presentation of geometric information in accordance with the requirements of current standards is proposed, based on the use of developed three-dimensional models of assembly units of gear elements in parametric shells. The basis for the development of the sketch geometry of parametric shells were the basic geometric parameters of the tooth crowns of the elements, since when making drawings of gear meshing elements, the images of the tooth crowns are made in violation of the requirements of current standards. In order to simplify the construction of drawings of gear elements in the Autodesk Inventor package, an algorithm was developed to provide geometric information through the developed three-dimensional models of the parametric shells of the gear crowns of their elements. That is, the geometric information is embedded in the parametric assembly units "gearing in shells". The algorithm is based on working with the parametric shells of the elements of the constituent units, where all the necessary geometric information is represented by a function of the main geometric parameters of real gear crowns. The method of parametric shells considers the issues of touching, implementation, methods of formation of such shells with detailed coverage of their properties and geometric parameters. The rigorous mathematical theory of parametric shells, which involves the joint processing of analytical and geometric information obtained on the basis of the geometry of the gear elements as forming elements, is characterized by generalization in approach and mathematical rigor. At the same time, the presence of toothed crowns of three-dimensional models of gear elements by meshing is ignored. The algorithm for simplified creation of gearing drawings involves making cuts based on sketches, adjusting contour lines and changing the properties of areas in accordance with the requirements of current standards. The library of parametric shells and the algorithm for creating working drawings of both elements and gearing are implemented in the educational process.

New approach for calculating nuclear binding energies of nickel isotopes 57-78Ni28 by using the Shell Model

Depending on the basic assumptions of the Shell Model and by using suitable potentials, we found a new formula to calculate the nuclear binding energies of nickel isotopes 57-78Ni28. This formula is related only to the mass number of these isotopes and the number of valence nucleons outside the closed core 56Ni28. When calculating the standard deviation of the experimental data from the theory, we found that our value is better than the value calculated by the Semi-Empirical Mass Formula; it is also better than that calculated by the Integrated Model and calculated by the Modified Integrated Model. This indicates that our inferred formula is better than the most important formulas previously used to calculate nuclear binding energies for our studied nuclei.

Analysis of the Phospholipid Transport Nanosystem Structure using Small Angle X-Ray Scattering

The structure of aqueous dispersions of phospholipid transport nanosystem (PhTNS) based on soybean phospholipids, developed at the Institute of Biomedical Chemistry (Moscow, Russia), was studied by the method of small-angle X-ray scattering. The PhTNS concentrations in water were 20, 25, 31.25, and 37.5%. The structural parameters of vesicles (inner radius, thicknesses of the regions of hydrophobic tails and polar heads) were determined in the “core multi shell model” approximation with variations in the scattering length densities of vesicle different parts, as well as the solution that was inside and outside the vesicle. A difference in the photon scattering length densities was detected between the solution volume and the inner region of the vesicle, due to the uneven maltose dissolution, which is part of PhTNS. With an almost constant thickness of the lipid bilayer, a decrease in the vesicle radius from ~150 to ~130 Å was observed with increasing concentration of the system which due to increasing osmotic pressure. The hydrophobic volume of vesicles was determined to be 7.45 × 106 Å3 at the lowest concentrations of 20% and 5.85 × 106 Å3 at the highest concentration of 37.5%.

Human Factors and AI in UAV Systems: Enhancing Operational Efficiency Through AHP and Real-Time Physiological Monitoring

Integrating Artificial Intelligence (AI) into Unmanned Aerial Vehicle (UAV) operations has advanced efficiency, safety, and decision-making. This study addresses critical gaps in UAV methods, including insufficient integration of human factors, operator variability, and the lack of systematic error analysis. To overcome these challenges, a novel approach combines the Analytic Hierarchy Process (AHP) with three core human factors models: the Observe-Orient-Decide-Act (OODA) loop, the Human Factors Analysis and Classification System (HFACS), and the SHELL model. An online survey was conducted across diverse UAV operator groups to prioritize critical factors within each model. Additionally, real-time monitoring of heart rate (HR), heart rate variability (HRV), and respiratory rate (RR) was conducted during UAV operations at various automation levels with different experience levels. Visualization through boxplots and percentage change matrices provided insights into operator stress and workload across automation levels. Integrating AHP findings and physiological data revealed significant differences in operator prioritization, highlighting the need for tailored AI-UAV strategies. This research combines survey data with real-time physiological monitoring, offering visions into optimizing human-AI interaction in UAV operations and providing a foundation for improving AI integration and operator strategies.

The variation after projection shell model

The variation after projection shell model

Vibration characteristics analysis of multi-layer composite cylindrical shell casing with different layer thickness ratios under external pressure using energy method

PurposeAero-engine casings commonly use composite cylindrical shell structures with excellent properties such as corrosion resistance and fatigue resistance. Still, their vibration behavior is relatively complex and may cause fatigue vibration damage, so it is essential to analyze the vibration characteristics of composite cylindrical shells. The purpose of this paper is to analyze the vibration characteristics of multilayer composite cylindrical shells subjected to external pressures and having different interlayer thickness ratios and provide some theoretical basis for the fatigue damage prediction of cylindrical shell casing to ensure the safety and stability of the engine during flight.Design/methodology/approachFirstly, the vibration differential equation with external pressure is established based on Soedel theory considering nonlinear effects, while four symmetric boundary conditions are chosen to constrain the cylindrical shell. Then the Rayleigh–Ritz method, which is more efficient and accurate in calculating large structural systems, is applied to solve the problem, and the theoretical model of three-layer cylindrical shell under external pressure is established. The accuracy of the model is verified by comparing the data with the specialized literature. Subsequently, the effects of different external pressures and different thickness-to-diameter ratios, different length-to-diameter ratios and different interlayer thickness percentages on the natural frequency of multilayer composite cylindrical shells were investigated by control variable analysis.FindingsThe conclusions obtained show that the external pressure increases the natural frequency of the cylindrical shell and that the frequency characteristics of the cylindrical shell vary for different boundary conditions. The effect of length-to-diameter ratio, thickness-to-diameter ratio and the percentage of the thickness of the intermediate layer on the natural frequency of the cylindrical shell are significantly increased under external pressure. Because the presence of external pressure increases the frequency of the cylindrical shell by about 70%, it has almost no effect on the frequency at the minimum number of circumferential waves, and the effect on the frequency at the maximum number of circumferential waves is reduced to about 50%. The frequencies in the SL-SL boundary condition are all in perfect agreement with the S-S boundary condition under the influence of different influencing factors.Originality/valueIn this paper, the effect of external pressure and the natural properties of the cylindrical shell under external pressure on the cylindrical shell’s frequency is considered, emphasizing the effect of different layer thickness ratios on the frequency. This paper aims to summarize the changing law between the natural frequency of the cylindrical shell itself and different design parameters during the flight pressure process. Reliable theoretical predictions are provided for analyzing the vibrational behavior of shells subjected to external pressures in aerospace, as well as a database for the practical production of cylindrical shells.

Natural frequencies and mode shapes for axisymmetric vibration of the shells of revolution using Carrera Unified Formulation

Here, natural frequencies and mode shapes for axisymmetric vibration of the composite laminate shells of revolution have been considered using the Unified Carrera Formulation (CUF) approach. For the first time, results of natural frequencies and mode shapes of complex geometry shells such as spherical, parabolic, elliptical, hyperbolic, catenoidal, toroidal and pseudospherical have been presented. Calculations have been done for the first, second, third, fourth and fifth order models and a comparison with the classical Timoshenko model. We consider thick, moderately thick, moderately thin and thin composite laminate shells. The higher-order layer-wise models of elastic composite multilayer shells of revolution are developed using the variational principle of virtual power for the 3-D linear anisotropic elastodynamics and generalized series in the thickness coordinates. The higher-order composite axisymmetric spherical, paraboloidal, elliptical, hyperbolic, catenoidal, toroidal and pseudo-spherical shell fixed at the ends are considered. Numerical calculations were performed using the computer algebra software Mathematica. The resulting equations have been used for theoretical analysis and calculation of the eigenvalues and eigenmodes of the higher-order shells of revolution used in science, engineering, and technology. The results of calculation can be used as benchmark examples for finite element analysis of the higher-order composite laminate shells.