Showing papers on "Shell (structure) published in 2014"
TL;DR: In this article, the authors used the generalized displacement field of the Carrera Unified Formulation (CUF), including the Zig-Zag (ZZ) effect given by the Murakami's function.
Abstract: The theoretical framework of the present manuscript covers the dynamic analysis of doubly-curved shell structures using the generalized displacement field of the Carrera Unified Formulation (CUF), including the Zig-Zag (ZZ) effect given by the Murakami’s function. The partial differential system of equations is solved by using the Generalized Differential Quadrature (GDQ) method. This numerical approach has been proven to be accurate, reliable and stable in several engineering applications. The current paper focuses on Functionally Graded (FG) doubly-curved shells and panels using various higher-order equivalent single layer theories, introduced and applied for the first time by the authors to completely doubly-curved shell structures, and different through-the-thickness volume fraction distributions, such as four-parameter power law, Weibull and exponential distributions. Moreover, the classic theory of mixtures is compared to the Mori–Tanaka scheme for the calculation of the mechanical properties of the materials. In particular, the numerical applications presented in this work are related to particular FG configurations in which it is possible to model a soft-core structure using a continuous variation of the mechanical properties of the materials at hand. The natural frequencies and mode shapes of several structures are presented and compared to numerical solutions taken from the literature.
224 citations
TL;DR: A magnetic energy functional is derived for an arbitrary curved thin shell on the assumption that the magnetostatic effects can be reduced to an effective easy-surface anisotropy; it can be used for solving both static and dynamic problems.
Abstract: A magnetic energy functional is derived for an arbitrary curved thin shell on the assumption that the magnetostatic effects can be reduced to an effective easy-surface anisotropy; it can be used for solving both static and dynamic problems. General static solutions are obtained in the limit of a strong anisotropy of both signs (easy-surface and easy-normal cases). It is shown that the effect of the curvature can be treated as the appearance of an effective magnetic field, which is aligned along the surface normal for the case of easy-surface anisotropy and is tangential to the surface for the case of easy-normal anisotropy. In general, the existence of such a field excludes the solutions that are strictly tangential or strictly normal to the surface. As an example, we consider static equilibrium solutions for a cone surface magnetization.
171 citations
TL;DR: In this article, the static and dynamic analyses of doubly-curved shells and panels of revolution resting on the Winkler-Pasternak elastic foundation using the generalized differential quadrature (GDQ) method are presented.
Abstract: This work presents the static and dynamic analyses of laminated doubly-curved shells and panels of revolution resting on the Winkler–Pasternak elastic foundation using the generalized differential quadrature (GDQ) method. The analyses are worked out considering the first-order shear deformation theory (FSDT) for the aforementioned moderately thick structural elements. The solutions are given in terms of generalized displacement components of points lying on the middle surface of the shell. Several types of shell structures such as doubly-curved and revolution shells, singly-curved and degenerate shells are considered in this paper. The main novelty of this paper is the application of the differential geometry within GDQ method to solve doubly-curved shells resting on the Winkler–Pasternak elastic foundation. The discretization of the differential system by means of the GDQ technique leads to a standard linear problem for the static analysis and to a standard linear eigenvalue problem for the dynamic analysis. In order to show the accuracy of this methodology, numerical comparisons between the present formulation and finite element solutions are presented. Very good agreement is observed. Finally, new results are presented to show effects of the Winkler modulus, the Pasternak modulus, and the inertia of the elastic foundation on the behavior of laminated doubly-curved shells.
141 citations
TL;DR: In this paper, the 3D vertically aligned carbon nanotube (CNT)/NiCo2O4 core/shell nanoarchitecture was built via a facile electrochemical deposition method followed by subsequent annealing in air.
Abstract: Three dimensional (3D) vertically aligned structures have attracted tremendous attention from scientists in many fields due to their unique properties. In this work, we have built the 3D vertically aligned carbon nanotube (CNT)/NiCo2O4 core/shell nanoarchitecture via a facile electrochemical deposition method followed by subsequent annealing in air. The morphology and structure have been in-depth characterized by SEM, TEM, XRD and Raman spectroscopy. Impressively, when used as the electrode material in a 6 M KOH electrolyte, the vertically aligned CNT/NiCo2O4 core/shell structures exhibit excellent supercapacitive performances, including high specific capacitance, excellent rate capability and good cycle stability. This is due to the unique 3D vertically aligned CNT/NiCo2O4 core/shell structures, which support high electron conductivity, large surface area of NiCo2O4 and fast ion/electron transport in the electrode and at the electrolyte–electrode interface. Furthermore, the synthesis strategy presented here can be easily extended to fabricate other metal oxides with a controlled core/shell structure, which may be a promising facile strategy for high performance supercapacitors, and even advanced Li-ion batteries.
137 citations
TL;DR: In this paper, the authors showed that core/shell colloidal quantum dots can replace their unshelled counterparts with a similar band gap as the active layer in a solar cell device, leading to an improvement in open circuit voltage from 0.42 to 0.66 V.
Abstract: Cation-exchange has been used to synthesize PbS/CdS core/shell colloidal quantum dots from PbS starting cores. These were then incorporated as the active material in solar cell test devices using a solution-based, air-ambient, layer-by-layer spin coating process. We show that core/shell colloidal quantum dots can replace their unshelled counterparts with a similar band gap as the active layer in a solar cell device, leading to an improvement in open circuit voltage from 0.42 to 0.66 V. This improvement is attributed to a reduction in recombination as a result of the passivating shell. However, this increase comes at the expense of short circuit current by creating a barrier for transport. To overcome this, we first optimize the shell thickness by varying the conditions for cation-exchange to form the thinnest shell layer possible that provides sufficient surface passivation. Next, ligand exchange with a combination of halide and bifunctional organic molecules is used in conjunction with the core/shell str...
123 citations
TL;DR: It is demonstrated that the hexagonal Yb/Er:NaGdF4 core size has a great impact on the completeness of the NaYF4 shell covering the core, which results in the intensification of upconversion luminescence of core-shell nanocrystals 10 000 times as high as that of the core-only ones.
Abstract: The purpose of the present work is to demonstrate that the hexagonal Yb/Er:NaGdF4 core size has a great impact on the completeness of the NaYF4 shell covering the core. With the increase of core size, the morphology of core–shell nanocrystals evolves from nanosphere to hexagonal nanoprism and finally to hexagonal nanoplate and, impressively, compared to that on the lateral faces of cores, the shell thickness on the top/bottom faces of cores becomes thinner. The shell growth mechanism is proposed to be the separate nucleation of the shell precursors followed by their ripening-mediated deposition on the cores. Based on this mechanism, controlling the thickness and completeness of the shell on the core can be easily realized by adopting appropriate size cores, which results in the intensification of upconversion luminescence of core–shell nanocrystals 10 000 times as high as that of the core-only ones. Generally, these new findings should be beneficial for designing and fabricating complex core–shell architecture and the understanding of structure-related properties of core–shell nanocrystals.
119 citations
TL;DR: In this article, it was found that the ZnO shell formed by a reaction of Na2S with ZnNPs followed by the formation of ZnS nano-crystals by the reaction of N2S and ZnCl2 at a later stage of the growth.
Abstract: ZnO nanoparticles were synthesized by co-precipitation with no capping agent followed by covering with ZnS using a solution-based chemical method at low temperature By variation of the solution concentrations it was found that the fully-covering ZnS shell forms by a reaction of Na2S with ZnO NPs followed by the formation of ZnS nano-crystals by the reaction of Na2S with ZnCl2 The mechanism that led to full coverage of the ZnO core is proposed to be the addition of ZnCl2 at a later stage of the growth which guarantees a continuous supply of Zn ions to the core surface Moreover, the ZnS nanocrystals that uniformly cover the ZnO NPs show no epitaxial relationship between the ZnO core and ZnS shell The slow atomic mobility at the low reaction temperature is attributed to the non-epitaxial uniform ZnS shell growth The rough surface of the ZnO grains provides initial nucleation positions for the growth of the ZnS shell nano-crystals The low growth temperature also inhibits the abnormal growth of ZnS grains and results in the homogeneous coverage of ZnS nano-crystals on the ZnO core surface The as-synthesized ZnO@ZnS core–shell nanoparticles were used as a photocatalyst to decompose Rose Bengal dye at three different pH values ZnO@ZnS core–shell nanoparticles perform as a more active photocatalyst at a pH of 4, while pure ZnO nanoparticles are more efficient at a pH of 7
110 citations
109 citations
TL;DR: In this article, a new 3-node triangular shell finite element, called the MITC3+ element, has been proposed, which is enriched by a cubic bubble function for the rotations.
105 citations
TL;DR: In this article, a three-dimensional vibration analysis of conical, cylindrical shells and annular plate structures with arbitrary elastic restraints is presented, and the exact solution is obtained by means of variational principle in conjunction with modified Fourier series which is composed of a standard Fourierseries and some auxiliary functions.
98 citations
TL;DR: In this article, the melting behavior of paraffin in a horizontal shell-and-tube type-storage unit is experimentally studied and three different values for the eccentricity from the center of the outer shell are investigated: e ǫ = 10, 20 and 30 mm besides the concentric geometry.
TL;DR: In this paper, a nonlinear mathematical model is derived using Green Lagrange type geometric nonlinearity in the framework of higher order shear deformation theory, all the nonlinear higher order terms are included in the mathematical model to achieve more general case.
Abstract: In this present article, large amplitude free vibration behaviour of doubly curved composite shell panels have been analysed using the nonlinear finite element method. The nonlinear mathematical model is derived using Green Lagrange type geometric nonlinearity in the framework of higher order shear deformation theory. In addition to that all the nonlinear higher order terms are included in the mathematical model to achieve more general case. The nonlinear governing equation of free vibrated curved panel is derived based on Hamilton׳s principle and solved numerically by using the direct iterative method. The developed mathematical model has been validated by comparing the responses with those available numerical results. Finally, some new numerical experimentation (orthotropicity ratio, stacking sequence, thickness ratio, amplitude ratio and support conditions) have been carried out to show the significance and the efficacy of the proposed mathematical model.
TL;DR: The results demonstrate the value of selecting from the diversity of BMC shell building blocks found in genomic sequence data for the construction of novel compartments and the use of these remarkably homogeneous shells for applications such as three-dimensional scaffolding and the construction
TL;DR: In this paper, the interaction of an incompressible Newtonian fluid with a linearly elastic Koiter shell whose motion is restricted to transverse displacements was analyzed and weak solutions exist as long as the magnitude of the displacement stays below some (possibly large) bound that rules out selfintersections of the shell.
Abstract: In this paper we analyse the interaction of an incompressible Newtonian fluid with a linearly elastic Koiter shell whosemotion is restricted to transverse displacements. The middle surface of the shell constitutes the mathematical boundary of the three-dimensional fluid domain. We show that weak solutions exist as long as the magnitude of the displacement stays below some (possibly large) bound that rules out selfintersections of the shell.
TL;DR: In this article, the free vibration analysis of composite laminated conical, cylindrical shells and annular plates with various boundary conditions based on the first order shear deformation theory, using the Haar wavelet discretization method, is presented.
TL;DR: In this paper, an isogeometric continuum shell formulation is proposed in which NURBS basis functions are used to construct the reference surface of the shell through-the-thickness behavior is interpolated using a higher-order B-spline which is in contrast to the standard continuum shell (solid-like shell) formulation where a linear Lagrange shape function is typically used in the thickness direction.
TL;DR: In this article, the Ritz minimum energy method, based on the use of the Principle of Virtual Displacements (PVD), is combined with refined Equivalent Single Layer (ESL) and Zig Zag (ZZ) shell models hierarchically generated by exploiting Carrera's Unified Formulation (CUF).
Patent•
10 Sep 2014
TL;DR: In this article, a magnetic hydrocyclone separation method and a magnetic cyclone separation device are described. But the method is not suitable for the application of water treatment, as it requires a large amount of power and power consumption.
Abstract: The invention discloses a magnetic hydrocyclone separation method and a magnetic hydrocyclone separation device. The magnetic hydrocyclone separation device comprises an inverted-cone boss cylindrical shell (1), centers of upper and lower ends of the inverted-cone boss cylindrical shell (1) are provided respectively with outlets (2,3), the side of the upper part is provided with a tangential inlet (4), an electrode bar (5) is arranged in the center of the inner cavity of the inverted-cone boss cylindrical shell (1), the electrode bar (5) is used as one electrode, the inverted-cone boss cylindrical shell (1) is used as the other corresponding electrode, an insulated wire (6) is wound on the inverted-cone boss cylindrical shell (1), and two ends of the insulated wire (6) are connected respectively to direct-current positive and negative electrodes so that a vertical magnetic field is formed. Water, waste water or sewage to be treated is input from the tangential inlet (4), flow and pressure are adjusted, and two separated materials are discharged from the outlets (2,3) in the centers of the upper and lower ends of the inverted-cone boss cylindrical shell (1). The magnetic hydrocyclone separation device has functions of flow rotation and magnetization, has good water treatment effects and a simple structure, is convenient for installation and use and widens an application range and efficacy of a hydrocyclone separation technology.
TL;DR: In this article, the large-amplitude (geometrically nonlinear) vibrations of rotating, laminated composite circular cylindrical shells subjected to radial harmonic excitation in the neighborhood of the lowest resonances are investigated.
Abstract: In this paper, the large-amplitude (geometrically nonlinear) vibrations of rotating, laminated composite circular cylindrical shells subjected to radial harmonic excitation in the neighborhood of the lowest resonances are investigated Nonlinearities due to large-amplitude shell motion are considered using the Donnell’s nonlinear shallow-shell theory, with account taken of the effect of viscous structure damping The dynamic Young’s modulus which varies with vibrational frequency of the laminated composite shell is considered An improved nonlinear model, which needs not to introduce the Airy stress function, is employed to study the nonlinear forced vibrations of the present shells The system is discretized by Galerkin’s method while a model involving two degrees of freedom, allowing for the traveling wave response of the shell, is adopted The method of harmonic balance is applied to study the forced vibration responses of the two-degrees-of-freedom system The stability of analytical steady-state solutions is analyzed Results obtained with analytical method are compared with numerical simulation The agreement between them bespeaks the validity of the method developed in this paper The effects of rotating speed and some other parameters on the nonlinear dynamic response of the system are also investigated
TL;DR: Light-induced changes in the magnetization of the normally light-insensitive KCoCr shell exhibit a new property resulting from the synergy between the core and shell of a coordination polymer heterostructure, giving direct evidence that the photomagnetic response of the shell is magnetomechanical in origin.
Abstract: Particles of formula Rb0.24Co[Fe(CN)6]0.74@K0.10Co[Cr(CN)6]0.70·nH2O with a light-responsive rubidium cobalt hexacyanoferrate (RbCoFe) core and a magnetic potassium cobalt hexacyanochromate (KCoCr) shell have been prepared and exhibit light-induced changes in the magnetization of the normally light-insensitive KCoCr shell, a new property resulting from the synergy between the core and shell of a coordination polymer heterostructure. A single batch of 135 ± 12 nm RbCoFe particles are used as seeds to generate three different core@shell samples, with KCoCr shell thicknesses of approximately 11, 23 and 37 nm, to probe the influence of the shell thickness over the particles’ morphology and structural and magnetic properties. Synchrotron powder X-ray diffraction reveals that structural changes in the shell accompany the charge transfer induced spin transition (CTIST) of the core, giving direct evidence that the photomagnetic response of the shell is magnetomechanical in origin. The depth to which the KCoCr she...
TL;DR: A universal relation between the surface strain and the oxygen adsorption energy is established based on which one can computationally screen and design core/shell nanoparticle catalysts for superior ORR activities.
Abstract: A computational strategy to design core/shell nanoparticle catalysts for oxygen reduction reactions (ORRs) is proposed based on multiscale modeling. Using a quantum mechanics/molecular mechanics (QM/MM) coupling method, we have studied the ORR on Pt–Cu core/shell nanoparticles with the size ranging from 3 to 8 nm. We have calculated the oxygen adsorption energy on the nanoparticle surface (a descriptor for ORR activity) as a function of the nanoparticle size and thickness of the Pt shell. We find that the Pt–Cu core/shell nanoparticles exhibit higher ORR activities than flat Pt(111) surfaces, consistent with experimental observations. We predict that the diameter of the core/shell nanoparticles should be larger than 7 nm to reach the peak of ORR activities. By examining the effects of ligand, quantum confinement, and surface strain, we confirm that the strain plays the dominant role on ORR activities for the core/shell nanoparticles. A universal relation between the surface strain and the oxygen adsorptio...
TL;DR: In this paper, the authors investigated the eccentricity from the center of the outer shell of a horizontal shell-and-tube type-storage system to understand the solidification behavior based on the transient temperature fields inside PCM.
TL;DR: In this article, the vibrational behavior of two joined cross-ply laminated conical shells is investigated and the natural frequencies and mode shapes are investigated, assuming trigonometric response in circumferential and series solution in meridional directions.
TL;DR: In this article, a 3D free vibration analysis of multilayered structures is proposed based on a layer-wise approach, the continuity of displacements and transverse shear/normal stresses is imposed at the interfaces between the layers of the structures.
Abstract: A 3D free vibration analysis of multilayered structures is proposed. An exact solution is developed for the differential equations of equilibrium written in general orthogonal curvilinear coordinates. The equations consider a geometry for shells without simplifications and allow the analysis of spherical shell panels, cylindrical shell panels, cylindrical closed shells and plates. The method is based on a layer-wise approach, the continuity of displacements and transverse shear/normal stresses is imposed at the interfaces between the layers of the structures. Results are given for multilayered composite and sandwich plates and shells. A free vibration analysis is proposed for a number of vibration modes, thickness ratios, imposed wave numbers, geometries and multilayer configurations embedding isotropic and orthotropic composite materials. These results can also be used as reference solutions for plate and shell 2D models developed for the analysis of multilayered structures.
TL;DR: In this article, a unified formulation for the free vibration analysis of open shells subjected to arbitrary boundary conditions and various geometric parameters such as subtended angle, conicity is presented, which can be readily applied to open shells with more complex boundaries such as point supports, nonuniform elastic restraints, partial supports and their combinations.
TL;DR: In this paper, the authors performed two-dimensional elemental mapping of shells of the bivalve Arctica islandica at a ∼3μm spatial resolution using electron microprobe.
TL;DR: In this paper, the Lagrange equations of the FG cylindrical shell are derived under the assumption of the nonlinear shallow-shell theory, and a semi-analytical approach, wherein the displacement fields are expanded by means of a double mixed series based on linear mode shape functions for the longitudinal, circumferential and radial variables, is proposed to characterize the non-linear response of the cylinrical shell.
Abstract: This paper addresses the nonlinear vibration problem of simply supported functionally graded (FG) cylindrical shells with embedded piezoelectric layers. The governing differential equations of motion of the FG cylindrical shell are derived using the Lagrange equations under the assumption of the Donnell׳s nonlinear shallow-shell theory. A semi analytical approach, wherein the displacement fields are expanded by means of a double mixed series based on linear mode shape functions for the longitudinal, circumferential and radial variables, is proposed to characterize the nonlinear response of the cylindrical shell. The large-amplitude response and amplitude frequency curves of the cylindrical shell are obtained by using the proposed approach. Finally, the effects of excitation force and applied voltage on the vibration behavior of the cylindrical shell are investigated.
TL;DR: In this paper, a shell size adjustable core-shell nano building block of SiO2@TiO2 using high refractive index materials of TiO2 as shell to coat colloidal NPs by one step approach was prepared.
Abstract: A shell size adjustable core–shell nano building block of SiO2@TiO2 using high refractive index materials of TiO2 as shell to coat SiO2 colloidal NPs by one step approach was prepared. Corresponding colloidal suspension of SiO2@TiO2 photonic crystals in propylene carbonate showed a highly adjustable structure color change with the high-refractive index upon applying of electric fields.
TL;DR: In this paper, the up-conversion performance of colloidal α-NaYF:Yb(3+), Tb-3+ doped nanocrystals was investigated.
Abstract: Lanthanide doped, up-converting nanoparticles have found considerable interest as luminescent probes in the field of bio-detection. Although the nanoparticles (NPs) have already been successfully applied for fluorescent bio-imaging and bio-assays, the efficiency of the up-conversion process seems to be the bottle-neck in rigorous applications. In this work, we have shown enhancement of the up-conversion in colloidal α-NaYF₄:Yb(3+), Tb(3+) doped nanocrystals owing to passivation of their surface. We have studied quantitatively the influence of the shell type (NaYF₄ and CaF₂), its thickness, as well as the shell deposition method (i.e. single thick shell vs. multi-layer shell) on the luminescent properties of the nanoparticles. The results showed that up to 40-fold up-conversion intensity enhancement may be obtained for the core-shell nanoparticles in comparison with the bare core nanoparticles, irrespective of the shell type and deposition method. Moreover, the suitability of the NaYF₄:Yb(3+), Tb(3+) core-shell NPs for multi-color emission and spectral multiplexing has been presented.
01 Aug 2014
TL;DR: A time‐ and space‐discrete geodesic calculus is developed that enables, for example, natural extrapolation of paths in shell space and transfer of large nonlinear deformations from one shell to another with applications in animation, geometric, and physical modeling.
Abstract: We prove both in the smooth and discrete setting that the Hessian of an elastic deformation energy results in a proper Riemannian metric on the space of shells modulo rigid body motions. Based on this foundation we develop a time- and space-discrete geodesic calculus. In particular we show how to shoot geodesics with prescribed initial data, and we give a construction for parallel transport in shell space. This enables, for example, natural extrapolation of paths in shell space and transfer of large nonlinear deformations from one shell to another with applications in animation, geometric, and physical modeling. Finally, we examine some aspects of curvature on shell space.