Showing papers on "Shell (structure) published in 2006"
INAF1
TL;DR: In this article, the authors presented the yield of solar metallicity stars with mass between 11 and 120 µm and quantified the relative contributions of the various components of the solar wind, the C convective shell and the explosive Ne/C burning.
Abstract: We present the
uk{Al}{26} and
uk{Fe}{60} yields produced by a generation of solar metallicity stars ranging in mass between 11 and 120\msun. We discuss the production sites of these $\gamma$ ray emitters and quantify the relative contributions of the various components. More specifically we provide the separate contribution of the wind, the C convective shell and the explosive Ne/C burning to the total
uk{Al}{26} yield per each stellar model in our grid. We provide the contributions of the He convective shell, the C convective shell and the explosive Ne/C burning to the
uk{Fe}{60} yield as well. From these computations we conclude that, at variance with current beliefs,
uk{Al}{26} is mainly produced by the explosive C/Ne burning over most of the mass interval presently analyzed while
uk{Fe}{60} is mainly produced by the C convective shell and the He convective shell.
364 citations
TL;DR: A new system that allows the catalytic activity of metal nanoparticles (Ag) by a thermodynamic transition that takes place within the carrier system to be modulated by volume transition over a wide range is presented.
Abstract: We present a new system that allows us to modulate the catalytic activity of metal nanoparticles (Ag) by a thermodynamic transition that takes place within the carrier system. Thermosensitive core−shell particles have been used as the carrier system in which the core consists of poly(styrene) (PS), whereas the shell consists of a poly(N-isopropylacrylamide) (PNIPA) network cross-linked by N,N‘-methylenebisacrylamide (BIS). Immersed in water, the shell of these particles is swollen. Heating the suspension above 32 °C leads to a volume transition within the shell that is followed by a marked shrinking of the network of the shell. The maximum degree of swelling can be adjusted by the degree of cross-linking. Silver nanoparticles with diameters ranging from 6.5 to 8.5 nm have been embedded into thermosensitive PNIPA networks with different cross-linking densities. The Ag nanoparticles do not influence the swelling and the shrinking of the network in the shell. The surface plasmon absorption band of the nanopa...
320 citations
TL;DR: Sublattice sensitivity of the images confirms that preferential growth takes place on the anion-terminated surfaces, which explains the three-dimensional "nanobullet" shape observed in the case of core/shell nanorods.
Abstract: Aberration-corrected Z-contrast scanning transmission electron microscopy of core/shell nanocrystals shows clear correlations between structure and quantum efficiency. Uniform shell coverage is obtained only for a graded CdS/ZnS shell material and is found to be critical to achieving near 100% quantum yield. The sublattice sensitivity of the images confirms that preferential growth takes place on the anion-terminated surfaces. This explains the three-dimensional "nanobullet" shape observed in the case of core/shell nanorods.
214 citations
TL;DR: A fiber-matrix constitutive model is employed and proposed that is able to account for the human cornea's mechanical behavior in healthy conditions or in the presence of keratoconus under increasing values of the intraocular pressure.
Abstract: The human cornea (the external lens of the eye) has the macroscopic structure of a thin shell, originated by the organization of collagen lamellae parallel to the middle surface of the shell. The lamellae, composed of bundles of collagen fibrils, are responsible for the experimentally observed anisotropy of the cornea. Anomalies in the fibril structure may explain the changes in the mechanical behavior of the tissue observed in pathologies such as keratoconus. We employ a fiber-matrix constitutive model and propose a numerical model for the human cornea that is able to account for its mechanical behavior in healthy conditions or in the presence of keratoconus under increasing values of the intraocular pressure. The ability of our model to reproduce the behavior of the human cornea opens a promising perspective for the numerical simulation of refractive surgery.
204 citations
TL;DR: In this paper, the authors presented linear thermal buckling and free vibration analysis for functionally graded cylindrical shells with clamped-clamped boundary condition based on temperature-dependent material properties.
196 citations
TL;DR: In this paper, multi-walled carbon nanotubes/snO2 (CNT/SnO2) core/shell nanostructures were synthesized by a simple wet-chemical method.
Abstract: Multi-walled carbon nanotubes/SnO2 (CNT/SnO2) core/shell nanostructures were synthesized by a simple wet-chemical method The thickness of the SnO2 shell was about 10 nm and the diameters of the SnO2 particles were 2–8 nm Sensors based on the core/shell heterostructures exhibited enhanced ethanol sensing properties The sensitivity to 50 ppm ethanol was up to 245, and the response time and recovery time were about 1 and 10 s, respectively In addition, the fluctuation of the sensitivity was less than ± 3% on remeasurement after 3 months These results indicate that the core/shell nanostructures are potentially new sensing materials for fabricating gas sensors
180 citations
TL;DR: The competing growth of a Pd shell on the {110} and {100} facets of Au nanorods (Au NRs) results in the disappearance of unstable facets and the formation of rectangularly shaped Pd/Au bimetallic nanorod that show only four stable side surfaces.
Abstract: In this letter, we report the competing growth of a Pd shell on the {110} and {100} facets of Au nanorods (Au NRs). This results in the disappearance of unstable {110} facets and the formation of rectangularly shaped Pd/Au bimetallic nanorods that show only four stable {100} side surfaces. The energy minimization to a more stable morphology is believed to be the driving force for the formation of the rectangular shape of the Pd shell.
178 citations
162 citations
TL;DR: In this article, the performance of seven popular density functionals (B3LYP, BLYP, BP86, mPW, OPBE, PBE, PW91) for describing the geometry and stability of the hydrogen bonds in DNA base pairs was investigated.
155 citations
Patent•
27 Oct 2006
TL;DR: In this article, the outer shell of a camera module is molded over and around the circuit element during a molding process to protect the circuit from exposure to the elements, which may substantially seal the circuit elements within the overmolded outer shell.
Abstract: A camera module (10) for a vision system of a vehicle includes a circuit element (12), a lens mounting element (14b, 14c), a lens assembly (14) and an outer shell or cover portion (16). The circuit element includes an imaging sensor and associated circuitry (12a). The lens assembly includes at least one optical element (14a) and the lens mounting element (14b, 14c) is attached to the circuit element (12) so as to provide an optical path through the optical element to the imaging sensor at the circuit element. The outer shell (16) is molded over and around the circuit element during a molding process to substantially encapsulate the circuit element within the outer shell. The module and method of making the module thus may substantially seal the circuit element within the overmolded outer shell to protect the circuit element from exposure to the elements. .
145 citations
TL;DR: In this paper, a two-dimensional boundary element method (BEM) is developed to simulate the water flow during the water impact of a horizontal circular cylinder, where a modal analysis is utilized for structural responses and the hydroelasticity.
TL;DR: In this article, a finite element methodology for evolution of cracks in thin shells using mid-surface displacement and director field discontinuities is presented, which is a variant of the one used in the extended finite element method.
TL;DR: In this paper, the shape evolution of small compound droplets at the exit of a core-shell system in the presence of a sufficiently strong electric field is studied both experimentally and theoretically.
Abstract: The shape evolution of small compound droplets at the exit of a core-shell system in the presence of a sufficiently strong electric field is studied both experimentally and theoretically. It is shown that the jetting effect at the tip of the shell nozzle does not necessarily cause entrainment of the core fluid, in which case the co-electrospinning process fails to produce core-shell nanofibers. The remedy lies in extending the core nozzle outside its shell counterpart by about half the radius of the latter. The results also show that the free charges migrate very rapidly from both fluids and their interface to the free surface of the shell. This reflects the fact that most of the prejetting evolution of the droplet can be effectively described in terms of the perfect conductor model, even though the fluids can be characterized as leaky dielectrics. The stress level at the core-shell interface is of the order of 5×103g∕(cms2), the relevant value in assessing the viability of viruses, bacteria, DNA molecule...
TL;DR: While the normalized shell radii are found to be independent of shielding, the shell occupation numbers are sensitive to screening and are quantitatively explained by an isotropic Yukawa model.
Abstract: Small three-dimensional strongly coupled charged particles in a spherical confinement potential arrange themselves in a nested shell structure. By means of experiments, computer simulations, and theoretical analysis, the sensitivity of their structural properties to the type of interparticle forces is explored. While the normalized shell radii are found to be independent of shielding, the shell occupation numbers are sensitive to screening and are quantitatively explained by an isotropic Yukawa model.
TL;DR: Swelling properties of doubly temperature sensitive core-shell microgels consisting of two thermosensitive polymers with lower critical solution temperatures (LCTS) at, respectively, 34 degrees C in the core and 44 degreesC in the shell have been investigated by SANS.
Abstract: Swelling properties of doubly temperature sensitive core-shell microgels consisting of two thermosensitive polymers with lower critical solution temperatures (LCTS) at, respectively, 34 degrees C in the core and 44 degrees C in the shell have been investigated by small-angle neutron scattering (SANS). A core-shell form factor has been employed to evaluate the structure, and the real space particle structure is expressed by radial density profiles. By this means, the influences of both shell/core mass composition and shell cross-linker content on the internal structure have been revealed at temperatures above, between, and below the LCSTs. Higher shell/core mass ratios lead to an increased expansion of the core at temperatures between the LCSTs, whereas a variation of cross-linker in the shell mainly effects the dimensions of the shell. The influence on the core structure was interpreted as resulting from an elastic force developed from the swollen shell. At temperatures below the core LCST, the core cannot swell to its native size (i.e., in the absence of a shell), because the maximum expanded shell network prohibits further swelling. Thus, depending on temperature, the shell either expands or compresses the core.
TL;DR: In this paper, the steady-state response of a functionally graded thick cylindrical shell subjected to thermal and mechanical loads is analyzed using the power series method, which is also valid for isotropic and fiber-reinforced shells.
TL;DR: Single-crystal NaCl core/nanoporous shell particles have been synthesized by evaporation-induced self-assembly and by variation of the hydrophobicity of the mesoporousshell, the release rates can be controlled by over 4 orders of magnitude.
Abstract: Single-crystal NaCl core/nanoporous shell particles have been synthesized by evaporation-induced self-assembly. By variation of the hydrophobicity of the mesoporous shell, we can control the release rates by over 4 orders of magnitude.
TL;DR: In this article, the analysis of functionally graded thick hollow cylinders under dynamic load is presented, where each subcylinder is considered as an isotropic layer and material properties in each layer are constant and functionally graded properties are resulted by suitable arrangement of layers in multilayer cylinder.
Patent•
13 Jun 2006
TL;DR: In this article, a curved shell with an opening at the apex of the shell is used to define a cavity for retaining a hearing device within the ear canal, where the shell can include a coating to retain the seal in the canal and/or to promote asparagine growth into the coating to fastenly retain the sealing.
Abstract: An embodiment provides a seal for retaining a hearing device within the ear canal comprising a curved shell having an opening at a shell apex portion. The shell defines a cavity for retention of a device component. An interior surface of a shell wall has a scalloped shape configured to distribute compressive forces applied to the shell perimeter such that when the shell is positioned in the canal, the shell wall conforms to the shape of the canal to maintain an acoustical seal between a shell exterior surface and the canal walls. The scalloped shape can be configured to produce a substantially constant amount of inward deformation of a shell wall independent of a force application point on a shell perimeter. The shell can include a coating to retain the seal in the canal and/or to promote asparagine growth into the coating to fastenly retain the seal in the canal.
TL;DR: In this article, closed-form formulations of two-dimensional higher-order shear deformation theories (HOSTs) for the free vibration analysis of simply supported cross-ply laminated composite and sandwich doubly curved shells are presented.
Abstract: Closed-form formulations of two-dimensional (2D) higher-order shear deformation theories (HOSTs) for the free vibration analysis of simply supported cross-ply laminated composite and sandwich doubly curved shells are presented. The formulation includes the Sander’s theory for doubly curved shells. Two of the HOSTs account for the effects of both transverse shear strains/stresses and the transverse normal strain/stress, while the third includes only the effects of transverse shear deformation. In these developments a realistic parabolic distribution of transverse shear strains through the shell thickness is assumed. The equations of motion are obtained using Hamilton’s principle. Solutions are obtained in closed-form using Navier’s technique and by solving the eigenvalue equations. Numerical results are presented for the natural frequencies of laminated composite and sandwich shallow shells. The closed-form solutions presented herein for laminated composite plates and shells are compared with the available...
Journal Article•
TL;DR: In this article, the shape of a grid shell is modelled using the dynamic relaxation algorithm to bypass the difficulty to predict the geometry of the final equilibrium state and the large rotations which occur during the erection process.
Abstract: The advantages of the use of glass fiber composites for grid shell are presented. The shape of grid shells results from a post-buckling state of tubes. To bypass the difficulty to predict the geometry of the final equilibrium state, the large rotations which occur during the erection process are modelled using the dynamic relaxation algorithm. This paper proposes an adaptation of this method for structures prestressed by bending through the development of a computer program. It includes the validation of this numerical tool through comparisons with a finite elements software. Then an application to the form-finding of a grid shell and the study of its stability under standard loading conditions will be presented. Finally the authors conclude on the technical and economic feasibility of this composite grid shell.
TL;DR: In this article, the static and dynamic instability characteristics of stiffened shell panels subjected to uniform in-plane harmonic edge loading are investigated, and the method of Hill's infinite determinant is applied to analyze the dynamic instability regions.
Abstract: The static and dynamic instability characteristics of stiffened shell panels subjected to uniform in-plane harmonic edge loading are investigated in this paper. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the shell panels and the stiffeners, respectively. As the usual formulation of degenerated beam element is found to overestimate the torsional rigidity, an attempt has been made to reformulate it in an efficient manner. Moreover, the new formulation for the beam element requires five degrees of freedom per node as that of shell element. The method of Hill's infinite determinant is applied to analyze the dynamic instability regions. Numerical results are presented through convergence and comparison with the published results from the literature. The effect of various parameters like shell geometry, stiffening scheme, static and dynamic load factors, stiffener size and position, and boundary conditions are considered in buckling and dynamic instability analysis of stiffened panels subjected to uniform in-plane harmonic loads along the boundaries.
TL;DR: Arguments based on Debye screening of interactions between like-charged particles help explain why core-shell clusters are stable despite possessing net electric charge.
Abstract: Electrostatic aggregation of oppositely charged silver and gold nanoparticles leads to the formation of core−shell clusters in which the shell is formed by the nanoparticles, which are in excess. Arguments based on Debye screening of interactions between like-charged particles help explain why these clusters are stable despite possessing net electric charge. The core−shell aggregates exhibit unusual optical properties with the resonance absorption of the shell particles enhanced by the particles in the core and that of the core suppressed by the shell. Experimental UV−vis absorption spectra are faithfully reproduced by Mie theory. The modeling allows for estimation of the numbers of particles forming the shell and of the shell's effective thickness. These theoretical predictions are substantiated by experiments using nanoparticles covered with different combinations of charged groups and performed at different values of pH.
TL;DR: In this paper, the buckling of a simply supported three-layer circular cylindrical shell under axial compressive load is studied, and the solution is expressed in terms of trigonometric functions that identically satisfy displacement type boundary conditions at the edges.
Abstract: Buckling of a simply supported three-layer circular cylindrical shell under axial compressive load is studied. The inner and outer layers of the shell are comprised of the same homogeneous and isotropic material, and the middle layer is made of an isotropic functionally graded (FG) material whose Young’s modulus varies either affinely or parabolically in the thickness direction from its value for the material of the inner layer to that of the outer layer. The solution is expressed in terms of trigonometric functions that identically satisfy displacement type boundary conditions at the edges. Buckling loads for different values of the geometric parameters and the variation in material parameters of the middle layer are computed. Numerical results show that buckling modes are symmetric in the circumferential coordinate, and the buckling load decreases with an increase in the radius to thickness ratio, and increases with an increase in the average value of Young’s modulus of the middle layer. The increase in the length to radius ratio has no effect on the buckling load, and it increases the axial wave number of the buckled shapes. r 2006 Elsevier Ltd. All rights reserved.
TL;DR: In this paper, a 4-node facet type quadrangular shell finite element based on a layerwise theory was developed for dynamic modeling of laminated structures with viscoelastic damping layers.
Abstract: This paper presents a 4-node facet type quadrangular shell finite element, based on a layerwise theory, developed for dynamic modelling of laminated structures with viscoelastic damping layers. The bending stiffness of the facet shell element is based on the Reissner–Mindlin assumptions and the plate theory is enriched with a shear locking protection adopting the MITC approach. The membrane component is corrected by using incompatible quadratic modes and the drilling degrees of freedom are introduced through a fictitious stiffness stabilization matrix. Linear static tests, using several pathological tests, showed good and convergent results. Dynamic analysis evaluation is provided by using two eigenproblems with exact analytical solution, as well as a conical sandwich shell with a closed-form analytical solution and a semi-analytical ring finite element solution. The applicability of the proposed finite element to viscoelastic core sandwich plates is assessed through experimental validation.
TL;DR: In this paper, the exact dynamic stiffness matrix for each segment is derived and used in the assembly of the complete structure dynamic stiffness matrices, and the natural frequencies of vibrations are found as the frequencies that cause this matrix to become singular.
Abstract: Axisymmetric shells are commonly used in all fields of engineering and their dynamic characteristics are of great importance in their overall performance. Segmented shells are shells that are built of several pieces that form together an axisymmetric shell with a joint axis. These can be cylindrical, conical or plate segments, which are connected to form a complete shell. In this research, the exact dynamic stiffness matrix for each segment is derived and used in the assembly of the complete structure dynamic stiffness matrix. Then the natural frequencies of vibrations are found as the frequencies that cause this matrix to become singular. Examples are given for the frequencies and modes of segmented shells made of conical, cylindrical, and plate segments.
TL;DR: The comparison between the model predictions and experimental measurements, indicates that the thin shell approximation is valid only for thickness to radius ratios up to 5% and that thick membranes obey non linear elastomer type constitutive laws.
TL;DR: In this paper, the dispersion of longitudinal waves in a single-walled armchair carbon nanotube was analyzed analytically using a non-local elastic cylindrical shell.
Abstract: This study deals with the dispersion of longitudinal waves in a single-walled armchair carbon nanotube, focusing on the effect of the microstructure of the carbon nanotube on the wave dispersion. To reveal the effect analytically, the carbon nanotube is modelled as a non-local elastic cylindrical shell in the study. The dynamic equation of the non-local elastic cylindrical shell is established and the corresponding dispersion relation of longitudinal waves is derived. These analytic results are verified via molecular dynamics simulations, based on the Terroff–Brenner potential, for the propagation of various longitudinal waves in three single-walled armchair carbon nanotubes. The molecular dynamics simulations indicate that the longitudinal wave dispersion predicted by the model of the non-local elastic cylindrical shell shows a good agreement with that of molecular dynamics simulations in a wide frequency range up to the terahertz region. They also show that both the microstructure of the carbon nanotube and the coupling between the longitudinal wave and the radial motion play an important role in the dispersion of longitudinal waves in a single-walled armchair carbon nanotube.
TL;DR: In this article, a geometrically non-linear solid shell element is proposed to analyze piezoelectric structures based on a variational principle of the Hu-Washizu type and includes six independent fields: displacements, electric potential, strains, electric field, mechanical stresses and dielectric displacements.
Abstract: This paper is concerned with a geometrically non-linear solid shell element to analyse piezoelectric structures. The finite element formulation is based on a variational principle of the Hu-Washizu type and includes six independent fields: displacements, electric potential, strains, electric field, mechanical stresses and dielectric displacements. The element has eight nodes with four nodal degrees of freedoms, three displacements and the electric potential. A bilinear distribution through the thickness of the independent electric field is assumed to fulfill the electric charge conservation law in bending dominated situations exactly. The presented finite shell element is able to model arbitrary curved shell structures and incorporates a 3D-material law. A geometrically non-linear theory allows large deformations and includes stability problems. Linear and non-linear numerical examples demonstrate the ability of the proposed model to analyse piezoelectric devices.
TL;DR: In this paper, aqueous solutions of 2M NaOH in the liquid state were modeled using empirical potential structure refinement which allows for the extraction of the ion-water and water-water correlations.
Abstract: Neutron diffraction with isotopic substitution has been used to investigate aqueous solutions of 2M NaOH in the liquid state. The data were modeled using empirical potential structure refinement which allows for the extraction of the ion-water and water-water correlations. The data show that the ion-water radial distribution functions are in accordance with those found by previous studies on NaOH solutions and follow a trend which is dependent on the concentration of the solute. In particular, the shape of the hydroxide hydration shell is found to be concentration independent, but the number of water molecules occupying this shell increases with dilution. Additionally, the water-water correlations show that there is still a measurable effect on water structure with the addition of ions at this concentration, as the second shell in the water oxygen radial distribution function is compressed relative to the first shell. The data are also used to discuss the recent claims that the published radial distribution functions of water are unreliable, showing that data taken at different neutron sources, with different diffraction geometry and systematic errors lead to the same structural information when analyzed via a realistic modeling regime.