Skip to content
Free planNo credit card requiredStart writing
AI for Research home
AI for Research home
Dashboard
Sign inGet started

Search 250 million research papers

Read the abstract, see who wrote it and who cites it, and get the citation in APA, MLA, Chicago or Harvard.

About 10,000 papers for “Spherical shell”

Spherical shell simulation.

Matthew C. Murphy (155130), John Huston III (492008), Clifford R. Jack Jr. (405793) et al. · Figshare · 2015

<p>a. A curl wave image calculated with traditional postprocessing methods is shown in the top-left panel, while one calculated with adaptive methods is shown in the top-right. Note the edge discontinuities in the image on the left compared with that on the right. The elastogram calculated with traditional postprocessing in the bottom-left panel shows a larger edge-related bias (3 voxels wide) as compared to the elastogram calculated with adaptive processing in the bottom-right (1 voxel wide). b. Using traditional postprocessing methods, 3 erosions are required to completely remove edge-related bias. c. Using adaptive methods, no edge-related bias is apparent.</p>

Cited by 0Open access

Hollow spherical shell manufacture

Thomas P O'Holleran · OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 2023

A process for making a hollow spherical shell of silicate glass composition in which an aqueous suspension of silicate glass particles and an immiscible liquid blowing agent is placed within the hollow spherical cavity of a porous mold. The mold is spun to reduce effective gravity to zero and to center the blowing agent, while being heated so as to vaporize the immiscible liquid and urge the water carrier of the aqueous suspension to migrate into the body of the mold, leaving a green shell compact deposited around the mold cavity. The green shell compact is then removed from the cavity, and is sintered for a time and a temperature sufficient to form a silicate glass shell of substantially homogeneous composition and uniform geometry.

Cited by 0Open access

Cooling a spherical nematic shell

Gaetano Napoli, Luigi Vergori · Physical review. E · 2021

Within the framework of Landau-de Gennes theory for nematic liquid crystals, we study the temperature-induced isotropic-nematic phase transition on a spherical shell under the assumption of degenerate tangential anchoring. Below a critical temperature, a thin layer of nematic coating a microscopic spherical particle exhibits nonuniform textures due to the geometrical frustration. We find the exact value of the critical threshold for the temperature and determine exactly the nematic textures at the transition by means of a weakly nonlinear analysis. The critical temperature is affected by the extrinsic curvature of the sphere, and the nematic alignment is consistent with the Poincaré-Hopf index theorem and experimental observations. The stability analysis of the bifurcate textures at the isotropic-nematic transition highlights that only the tetrahedral configuration is stable.

Cited by 0Open access

Multi-element spherical shell generation

Morrison, Andrew D. · NASA Technical Reports Server (NASA)

A nozzle assembly in a multi-element spherical shell generation system includes first and second side-by-side spaced apart nozzles and a web portion extending between and connecting the nozzles. The first nozzle has an inner orifice adapted to discharge a first filler material and an outer annular orifice separated from and defined in concentric relation about the inner orifice and adapted to discharge a first shell material. The second nozzle has an inner orifice adapted to discharge a second filler material and an outer annular orifice separated from and defined in concentric relation about the inner orifice and adapted to discharge a second shell material. A multi-element spherical shell can be formed through employment of the nozzle assembly by merger with one another after discharge from the outer orifices of the nozzles of a pair of adjacent annular streams of liquid or molten shell wall material of different compositions and encapsulation by the mixed shell wall materials of a common encapsulated core fluids also simultaneously discharged by the inner orifices nozzles. On the other hand, the pair of encapsulating streams of shell wall material can be of the same materials which merge together and encapsulate core fluids of different compositions which will merge together after discharge from the nozzles.

Cited by 0Open access

Dielectrophoresis: a spherical shell model

Ioan Turcu, Constantin Mihai Lucaciu · Journal of Physics A Mathematical and General · 1989

The complete algebraic expression in the effective dipole approximation for the dielectrophoretic force acting on a spherical object surrounded by a shell when placed in an alternating electric field is deduced. In the approximation of a thin shell of low conductivity the frequency dependence of the dielectrophoretic force is discussed revealing the contribution of the shell. The electric potential difference across the shell is also calculated.

Cited by 37

Thick-walled spherical shell problem

A. M. Artemov, Evgenii S. Baranovskii, A. A. Verlin et al. · Advanced Engineering Research (Rostov-on-Don) · 2021

Introduction. Cylindrical and spherical shells are extensively used in engineering. They face internal and/or external pressure and heat. Stresses and strains distribution in elastoplastic shells has been studied by many scientists. Numerous works involve the use of the von Mises yield conditions, maximum shear stress, maximum reduced stress. These condi- tions do not include the dependence on the first invariant of the stress tensor and the sign of the third invariant of the stress deviator. In some cases, it is possible to obtain numerical-analytical solutions for stresses, displacements and de- formations for bodies with spherical and cylindrical symmetry under axisymmetric thermal and force action. Materials and Methods. The problem on the state of a thick-walled elastoplastic shell is solved within the framework of the theory of small deformations. A plasticity condition is proposed, which takes into account the dependence of the stress tensor on three independent invariants, and also considers the sign of the third invariant of the stress deviator and translational hardening of the material. A disconnected thermoelastoplastic problem is being solved. To estimate the stresses in the region of the elastic state of a spherical shell, an equivalent stress is introduced, which is similar to the selected plasticity function. The construction of the stress vector hodograph is used as a method for verification of the stress state. Results. The problem has an analytical solution for linear plasticity functions. A solution is obtained when the strength- ening of the material is taken into account. Analytical and graphical relationships between the parameters of external action for the elastic or elastoplastic states of the sphere are determined. For a combined load, variants are possible when the plastic region is generated at the inner and outer boundaries of the sphere or between these boundaries. Discussion and Conclusions. The calculation results have shown that taking into account the plastic compressibility and the dependence of the plastic limit on temperature can have a significant impact on the stress and strain state of a hollow sphere. In this case, taking into account the first invariant of the stress tensor under the plasticity condition leads to the fact that not only the pressure drop between the outer and inner boundaries of the spherical shell, but the pressure values at these boundaries, can vary within a limited range. In this formulation of the problem, when there is only thermal action, the hollow sphere does not completely pass into the plastic state. The research results provide predicting the behavior of an object (a hollow sphere) that experiences centrally symmetric distributed power and thermal external influences.

Cited by 3Open access

Swimming through spherical shell buckling

Abderrahmane Djellouli · theses.fr (ABES) · 2017

Les micronageurs et parmi eux les microangeurs artificiels sont en général, limités à exister dans des écoulements dominés par des forces visqueses. Ces écoulements sont caractérisés par un bas nombre de Reynolds (Re). Cela impacte la stratégie de nage et plus particulièrement les séquences de forme possibles, qui doivent nécessairement être non-réciproques dans l'espace de déformation pour espérer induire un déplacement net non-nul. De plus, due aux forts effets de traînée, les vitesses de nage sont limités à des valeurs faibles.Dans cette thèse, on examine la possibilité d'utiliser un mécanisme de nage basé sur l'instabilité de flambage d'une sphère creuse. Cette instabilité est provoquée en soumettant la sphère à une onde de pression. La particularité de ce mécanisme est qu'il satisfait par construction la condition nécessaire de nage à bas Reynolds exposée précédemment. De plus, la rapidité de la déformation lors de l'instabilité pousse à prévoir l'apparition d'effets inertiels, et ce même à l'échelle microscopique.Une étude expérimentale a été conduite à l'échelle macroscopique dans le but de comprendre la dynamique de l'instabilité et son impact sur le fluide qui entoure la coque creuse. Ces expériences nous permettent de montrer qu'un déplacement net non-nul est produit pour tous les régimes d'écoulements.On met en évidence le rôle de paramètres géométriques, des propriétés du matériau composant la coque creuse et de la rhéologie du fluide sur l'efficacité de la nage.On montre l'existence d'un optimum de déplacement net pour des valeurs intermédiaires du nombre de Reynolds. Pour expliquer cela, on se sert de mesures de PIV résolues temporellement pour mettre en évidence la présence d'effets d'histoire non-triviaux qui augmentent le déplacement net.On dérive un simple modèle en se basant sur les observations expérimentales pour montrer que ce régime optimal de nage est atteignable pour des sphères microscopiques, ceci est possible grâce l'activation rapide de l'instabilité. Cette propriété permet aussi une excitation à haute fréquence en utilisant des ultrasons. Une étude d'échelle nous permet de prédire une vitesse de nage de 1 cm/s pour un micro-robot contrôlé à distance. Cet ordre de grandeur de vitesse est idéal pour des applications biologiques comme la distribution ciblée de médicaments.

Cited by 1Open access

The spherical shell nuclear model

H. A. Wilson · Proceedings of the Royal Society of London A Mathematical and Physical Sciences · 1952

Abstract It is found that the spherical shell nuclear model has new energy levels due to the interaction of the vibrations and the rotation. Each vibration level has a series of equally spaced levels belonging to it. The levels of aluminium 28 and silicon 28 are compared with the values predicted by the theory and good agreement is found.

Cited by 1

Thick-walled spherical shell problem

Bulletin of Miscellaneous Information (Royal Gardens Kew) · 2021

Introduction. Cylindrical and spherical shells are extensively used in engineering. They face internal and/or external pressure and heat. Stresses and strains distribution in elastoplastic shells has been studied by many scientists. Numerous works involve the use of the von Mises yield conditions, maximum shear stress, maximum reduced stress. These condi- tions do not include the dependence on the first invariant of the stress tensor and the sign of the third invariant of the stress deviator. In some cases, it is possible to obtain numerical-analytical solutions for stresses, displacements and de- formations for bodies with spherical and cylindrical symmetry under axisymmetric thermal and force action. Materials and Methods. The problem on the state of a thick-walled elastoplastic shell is solved within the framework of the theory of small deformations. A plasticity condition is proposed, which takes into account the dependence of the stress tensor on three independent invariants, and also considers the sign of the third invariant of the stress deviator and translational hardening of the material. A disconnected thermoelastoplastic problem is being solved. To estimate the stresses in the region of the elastic state of a spherical shell, an equivalent stress is introduced, which is similar to the selected plasticity function. The construction of the stress vector hodograph is used as a method for verification of the stress state. Results. The problem has an analytical solution for linear plasticity functions. A solution is obtained when the strength- ening of the material is taken into account. Analytical and graphical relationships between the parameters of external action for the elastic or elastoplastic states of the sphere are determined. For a combined load, variants are possible when the plastic region is generated at the inner and outer boundaries of the sphere or between these boundaries. Discussion and Conclusions. The calculation results have shown that taking into account the plastic compressibility and the dependence of the plastic limit on temperature can have a significant impact on the stress and strain state of a hollow sphere. In this case, taking into account the first invariant of the stress tensor under the plasticity condition leads to the fact that not only the pressure drop between the outer and inner boundaries of the spherical shell, but the pressure values at these boundaries, can vary within a limited range. In this formulation of the problem, when there is only thermal action, the hollow sphere does not completely pass into the plastic state. The research results provide predicting the behavior of an object (a hollow sphere) that experiences centrally symmetric distributed power and thermal external influences.

Cited by 0Open access

Wave fitting on a spherical shell

M. Tecpoyotl‐Torres, J. Almaguer-Medina, R. Castro-Sánchez et al. · 2004

We show the convenience of using the same concepts used on the data fitting on a pupil, Zernike polynomials on a discrete data set, for the data fitting on a spherical shell. Such a need arises on a broad range of problems that includes not only illumination, but also remote sensing, biology and others. We briefly discuss some direct applications.

Cited by 0

KONDO THEORY FOR SPHERICAL SHELL TECTONICS

Kazuhei Kikuchi · International Journal of Geomate · 2018

The buckling phenomenon of a flat or spherical shell lithosphere (tectonic plate) has been investigated in previous research.However, these studies do not give information regarding the curvature effect in the buckling phenomenon.Kondo applied Riemannian geometry to the yielding or buckling of curved materials.When the Riemannian manifold ( !dimensional manifold) with a nonzero Euler-Schouten curvature tensor is manifested in the enveloping manifold (Euclid space: !dimensional manifold), the included Riemannian manifold (dimension ! ) protrudes into the enveloping manifold (dimension ! ).The curvature effect for the buckling phenomenon of materials can be formulated by a force-balance equation from mechanics and the Euler-Schouten curvature tensor from differential geometry.In this paper, using the Euler-Schouten curvature tensor from differential geometry, the authors derive a formulation for the buckling phenomenon with the curvature effect for a spherical shell lithosphere as a buckling equation with high-order strain for lithosphere deformation.

Cited by 0Open access

Dynamic Analysis Of A Spherical Shell

Ufuk Kol · Istanbul Technical University Academic Open Archive (Istanbul Technical University) · 2010

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010

Cited by 0Open access

Scroll waves in spherical shell geometries

Raúl Chávez, Raymond Kapral, Guillaume Rousseau et al. · Chaos An Interdisciplinary Journal of Nonlinear Science · 2001

The evolution of scroll waves in excitable media with spherical shell geometries is studied as a function of shell thickness and outer radius. The motion of scroll wave filaments that are the locii of phaseless points in the medium and organize the wave pattern is investigated. When the inner radius is sufficiently large the filaments remain attached to both the inner and outer surfaces. The minimum size of the sphere that supports spiral waves and the maximum number of spiral waves that can be sustained on a sphere of given size are determined for both regular and random initial distributions. When the inner radius is too small to support spiral waves the filaments detach from the inner surface and form a curved filament connecting the two spiral tips in the surface. In certain parameter domains the filament is an arc of a circle that shrinks with constant shape. For parameter values close to the meandering border, the filament grows and collisions with the sphere walls lead to turbulent filament dynamics. (c) 2001 American Institute of Physics.

Cited by 21