Thickness Of Spherical Shell Research Articles

Persistent currents of ultrarelativistic plasma-encased endofullerene molecules entrapping a H atom

In this work, for the first time in the relevant literature, the persistent currents (PC) and induced magnetic fields (IMF) of an endofullerene molecule entrapping a hydrogen atom, under spherical confinement, are investigated. The endofullerene molecule is enclosed within a spherical region and embedded in a plasma environment. The plasma environment is depicted with the more general exponential cosine screened Coulomb potential, and its relevant effects are analyzed by considering plasma screening parameters. The relevant model for endohedral confinement is the Woods–Saxon confinement potential, which is compatible with experimental data. The effects of various forms of C n are thoroughly elucidated via the analysis of the confinement depth, spherical shell thickness, the inner radius, and the smoothing parameters. To find the bound states in the spherically confined endofullerene, the decoupling of the second-order Dirac equation for the large and small components of the radial atomic wave functions is considered. The Dirac equation with the interaction potential is solved numerically by using the Runge–Kutta–Fehlberg method via the decoupling formalism. The influence of spin orientations on the PC and IMF is also elucidated. The effects of spherical confinement, plasma shielding, and the structural properties of the fullerene on the PC and IMF are thoroughly viewed. Moreover, under given physical conditions, the optimal ranges of these effects are determined.

Reconstruction of indoor gamma-ray background spectrum for HPGe detectors

Background reconstruction stands as a critical technique for diverse domains, such as signal isolation for gamma spectroscopy, pre-testing of radiation shielding designs, and environmental monitoring. Traditional methods aim to seek the optimal intensity of the background source under a fixed spatial distribution. However, their efficacy is often constrained due to the limited number of variable parameters, resulting in inadequate degrees of freedom and suboptimal performance. This paper introduces an innovative method for background reconstruction, aiming to overcome the limitations of existing approaches. The proposed technique involves the simultaneous adjustment of both intensities and shell thicknesses of a series of monoenergetic sources, modeled as spherical shells. The reconstructed spectrum is conceptualized as a superposition of simulated spectra from these sources, with the optimized parameters being the intensity and thickness of each source. The objective is to minimize the disparity in regions of interest (ROIs) between reconstructed and target spectra through a multivariate nonlinear optimization process, incorporating distinct weight factors for each ROI. The efficacy of the proposed method is validated using a simulation-generated theoretical spectrum. Results demonstrate successful reconstruction, with a high overall concordance between reconstructed and target spectra, showcasing reliability of the method. Subsequently, the method is applied to the reconstruction of an experimental spectrum, and a comparative analysis with a fixed spherical shell thickness method reveals the superior agreement of our proposed method with the experimental spectra.

Robust Amino-Functionalized Mesoporous Silica Hollow Spheres Templated by CO2 Bubbles.

Hollow-structured mesoporous silica has wide applications in catalysis and drug delivery due to its high surface area, large hollow space, and short diffusion mesochannels. However, the synthesis of hollow structures usually requires sacrificial templates, leading to increased production costs and environmental problems. Here, for the first time, amino-functionalized mesoporous silica hollow spheres were synthesized by using CO2 gaseous bubbles as templates. The assembly of anionic surfactants, co-structure directing agents, and inorganic silica precursors around CO2 bubbles formed the mesoporous silica shells. The hollow silica spheres, 200–400 nm in size with 20–30 nm spherical shell thickness, had abundant amine groups on the surface of the mesopores, indicating excellent applications for CO2 capture, Knoevenagel condensation reaction, and the controlled release of Drugs.

Investigation on energy efficiency of rolling triboelectric nanogenerator using cylinder-cylindrical shell dynamic model

The triboelectric nanogenerator (TENG) technology is rapidly becoming a promising candidate for harvesting wave energy from the ocean. In this paper, through an in-depth analysis of the working principle of spherical TENGs, for the first time, a dynamic model of this structure is proposed based on a cylinder-cylindrical shell configuration, and integrated into TENGs electric model. We verified the assumption that the motion of internal ball of the spherical TENGs is a small oscillation by comparing the V-Q-x relationship with experiments. The model reveals the influence of structural/material parameters, such as the radius of inner ball, density of material, and thickness of the shell on the energy output of TENGs. The results show that the change of the radius of the inner ball plays the dominant role on the power output with the other two parameters affecting the power output level of the TENG to varying degrees. These structural/material parameters can be combined to optimize and increase the output performance of spherical TENGs. • The structural/material dynamic model of spherical triboelectric nanogenerator (TENG) is established. • The influence of structural/material parameters on power output is investigated. • The change of inner ball radius has a dominant influence on the power output. • The thickness of spherical shell and material density has also impact on the power output.

Effective thermal conductivity modeling of hollow nanosphere packing structures

Nanoporous insulating materials are of importance for applications such as energy-efficient buildings, energy storage and savings, and cryogenic engineering. Recent progress on manufacturing technology has enabled the fabrication of ordered nanostructures to be practical, providing a possibility to fabricate high-performance insulation materials. In this work, three kinds of nanoporous insulating materials with regular geometric structures and controllable thermal conductivities, including a simple cubic packing, a face-centered cubic packing, and a cubic array of intersecting spheres packing of uniform-sized hollow nanospheres, were designed. The effective thermal conductivity models of each packing structure were developed according to the assumption of one-dimensional heat transfer, in which the following factors including material types, size of the hollow nanosphere packing structure (e.g., sphere size, spherical shell thickness, contact ratio), gas pressure, the rarefaction effect of gas and the mean free path of phonons were considered. The developed models of the hollow nanosphere packing structures were validated by the experimental results from the literature. It is found that the effective thermal conductivity can be lowered to ~ 0.01 W/(m⋅K) by tuning the packing style and size of hollow nanosphere packing structures in the room environment, showing excellent thermal insulation performance. The work provides a new strategy for the design of super-insulation materials.

An Exact and Practical Analyzing Model for Radial Vibration of Piezoelectric Spherical Transducers With Arbitrary Wall Thickness.

The piezoelectric spherical transducers have attracted extensive attention in hydroacoustics and health monitoring. However, most reported piezoelectric spherical transducers are merely analyzed by the thin spherical shell theory, which is unsuitable for the gradually increased spherical shell thickness. Therefore, it is necessary to develop the radial vibration theory of the piezoelectric spherical transducer with arbitrary wall thickness. Herein, an exact analyzing model for the radial vibration of the piezoelectric spherical transducer with arbitrary wall thickness is proposed. The radial displacement and electric potential for radial vibration of the piezoelectric spherical transducer are precisely given, and then, the electromechanical equivalent circuit is obtained. Based on the electromechanical equivalent circuit, the resonance/antiresonance frequency equations of piezoelectric spherical transducers in the radial vibration are obtained. Besides, the relationship between performance parameters and wall thicknesses is discussed. The wall thickness has a significant influence on the performance parameters of the spherical transducer. The accuracy of the theory is validated by comparing the results with the experiment and finite element analysis.

The photocatalytic redox properties of polymeric carbon nitride nanocages (PCNCs) with mesoporous hollow spherical structures prepared by a ZnO-template method

Abstract The polymeric carbon nitride nanocages (PCNCs) with mesoporous hollow spherical structures and a spherical shell thickness of ca 50 nm have been successfully prepared via an ZnO-template method, in which the ZnO@PCN core-shell structures were fabricated by simple calcination of ZnO nanospheres and deposited melamine, followed by sequential treatment with hydrochloric acid and aqueous ammonia for thorough removal of ZnO templates and residual Zn2+ ions. The as-prepared pure PCNCs were characterized by various physico-chemical techniques combined with the photocatalytic oxidation reaction of rhodamine B in aqueous solution and the photocatalytic hydrogen evolution reaction under visible light irradiation. The photocatalytic evaluation results indicate that the PCNCs catalysts show higher activity for both photocatalytic reactions than the bulk PCN catalysts prepared by conventional calcination method. The characterization results have shown that the enhanced photocatalytic properties of PCNCs catalysts are mainly attributed to their larger specific surface area, more mesoporous in the range of 2–50 nm, lower band gap energy, higher visible light absorbance and more efficient electron-hole separation in the shell of hollow spherical nanocages than those of bulk PCN. Moreover, the PCNCs catalysts with hollow spherical structures exhibit an excellent reusability in both photocatalytic reactions.

Preparation of hollow silver-polymer microspheres with a hierarchical structure for SERS

The Surface-enhanced Raman scattering (SERS) effect on the surface of metal conductors can significantly improve the sensitivity of molecular detection. Therefore, it is widely used in the field of chemical sensors. The nanostructure of the metal surface strongly influences the strength of the SERS by adsorption and surface electric field. Herein, we combine microfluidic technology with electroless silver plating to produce hollow microspheres with different wall thicknesses. The microspheres have a diameter of 400 μm and a spherical shell thickness of 40–100 μm. The spherical shell has a porous structure formed by phase separation, on which nanosilver particles can be deposited. The silver-polymer hybrid microspheres can adsorb dyes in aqueous solution and produce significant SERS effects, and the Raman signal enhancement factors can be up to 7.11 × 1011. Computational simulations and experimental results show that the Raman enhancement effect is related to the distance between the silver particles on the surface and the hollow structure of the microspheres.

Opening reinforcement design and buckling of spherical shell subjected to external pressure

This paper focuses on spherical shells with openings and reinforcement under uniform external pressure. To reduce the local weakening and buckling effects of the openings on these spherical pressure shells, the opening reinforcement parameters were optimized to minimize the buckling instability. According to the result of the optimization, two laboratory-scale models were manufactured and tested. The geometry, spherical shell thickness, wall thickness, buckling load, and final collapsed mode were measured for each spherical shell with an opening; the material properties of the corresponding sheets were also measured. The buckling behavior of a simulated spherical shell with an opening was demonstrated numerically according to experimental data. Numerical calculations involved considering the real geometrical shape, average values of parameters, and elastic-plastic modeling of true stress–strain curves. Moreover, the effects of initial geometrical imperfections on the critical load of the simulated spherical shell were analyzed numerically. The scanning model was calculated according to deterministic imperfections obtained from measured geometrical shapes. The theoretical model was calculated according to the equivalent geometrical imperfection valued as the first buckling mode of linear buckling. The results of the experimental and numerical investigations were compared in tables and figures.

Synthesis of porous Cr2O3 hollow microspheres via a facile template-free approach

Porous Cr2O3 hollow microspheres assembled by nanoparticles have been successfully synthesized by thermal decomposition of a precursor which was prepared via a mild template-free hydrothermal approach. The average dimensions of these Cr2O3 hollow microspheres were about 2.2µm in diameter and 130nm in thickness of spherical shell. The structures and morphologies of the synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). Moreover, the formation mechanism of the Cr2O3 precursor hollow structure was suggested to be an inside-out formation mechanism process through tracking the morphology evolution with different reaction times.

An ideal nano-porous insulation material: Design, modeling and numerical validation

Based on the mechanisms of conductive heat transfer in nano-porous insulation materials, such as suppressed gaseous heat conduction at micro- and nanoscale, and low volume fraction of solid, a nano-porous material of hollow spherical pellets packing stack is designed. Its effective thermal conductivity is derived based on one-dimensional steady-state heat conduction, which is validated and improved by numerical simulation. Analysis on geometrical parameters, thermodynamic parameters and solid thermal conductivity indicates that the designed nano-porous material has the excellent thermal insulation performance. Decreasing the spherical shell thickness and the contact area can efficiently lower the effective thermal conductivity of material. Conductive heat transfer trough solid spherical shell has significant impact on the effective thermal conductivity of material. Under the same conditions, hollow spheres packed in line has the lowest effective thermal conductivity of about 0.01 W m−1 K−1, if properly designed.

Template-free microwave-assisted synthesis of ZnO hollow microspheres and their application in gas sensing

We report a facile template-free microwave-assisted approach to synthesize ZnO hollow microspheres. Field emission scanning electron microscopic and transmission electron microscopic results revealed that the average dimensions of these hollow microspheres were about 4 μm in diameter and 400 nm in thickness of spherical shell. Interestingly, the “hollowness” of these ZnO spheres could be adjusted by varying the microwave irradiation time. Moreover, various distinct ZnO structures could be obtained by simply changing the amounts of trisodium citrate dihydrate. On the basis of these results, a possible formation mechanism was proposed. Gas sensors were fabricated based on as-prepared hollow spheres, and their gas sensing properties were tested for response to ethanol and methanol.

Accurate determination of dose‐point‐kernel functions close to the origin using Monte Carlo simulations

Dose-point-kernel (DPK) functions are used extensively for the dosimetry of gamma and beta emitters in many physical problems. These functions are usually obtained from Monte Carlo simulations where the energy deposited in concentric spherical shells around a point source is tallied. The energy scored in a spherical shell divided by the shell mass is taken as the dose at some effective radius R(eff) of the shell. The effective radius R(eff), defined as the distance of a hypothetical zero-thickness scoring region from the source, can be evaluated in different ways for a finite thickness scoring region. For a shell thickness that is very small compared to the distance from the origin, this exact evaluation method becomes unimportant and the arithmetic mean is usually an accurate estimator for R(eff). However, accurately determining R(eff) can be problematic for the innermost regions when the radial dose function D(r) varies considerably over the finite spherical shell thickness. In this work, a new method for determining R(eff) is introduced which yields consistent results for any shell thickness, thus improving on previous Monte Carlo calculations for DPKs at or near the origin. Dimensionless DPK functions for monoenergetic electrons were reevaluated using EGSnrc with an emphasis on accuracy and consistency near the origin using our new method for determining R(eff). These improved functions were implemented in a software code to calculate the DPKs for an exhaustive list of 546 beta emitters, thus extending the compilation from previous works.